Sample records for kaiser crater suggest
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Investigating Mars: Kaiser Crater Dunes
2018-02-01
This VIS image of the floor of Kaiser Crater contains several sand dune shapes and sizes. The "whiter" material is the hard crater floor surface. Kaiser Crater is located in the southern hemisphere in the Noachis region west of Hellas Planitia. Kaiser Crater is just one of several large craters with extensive dune fields on the crater floor. Other nearby dune filled craters are Proctor, Russell, and Rabe. Kaiser Crater is 207 km (129 miles) in diameter. The dunes are located in the southern part of the crater floor. The Odyssey spacecraft has spent over 15 years in orbit around Mars, circling the planet more than 71,000 times. It holds the record for longest working spacecraft at Mars. THEMIS, the IR/VIS camera system, has collected data for the entire mission and provides images covering all seasons and lighting conditions. Over the years many features of interest have received repeated imaging, building up a suite of images covering the entire feature. From the deepest chasma to the tallest volcano, individual dunes inside craters and dune fields that encircle the north pole, channels carved by water and lava, and a variety of other feature, THEMIS has imaged them all. For the next several months the image of the day will focus on the Tharsis volcanoes, the various chasmata of Valles Marineris, and the major dunes fields. We hope you enjoy these images! Orbit Number: 39910 Latitude: -46.9063 Longitude: 19.8112 Instrument: VIS Captured: 2010-12-13 11:17 https://photojournal.jpl.nasa.gov/catalog/PIA22264
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Investigating Mars: Kaiser Crater Dunes
2018-01-31
This VIS image of the floor of Kaiser Crater contains a large variety of sand dune shapes and sizes. The "whiter" material is the hard crater floor surface. Kaiser Crater is located in the southern hemisphere in the Noachis region west of Hellas Planitia. Kaiser Crater is just one of several large craters with extensive dune fields on the crater floor. Other nearby dune filled craters are Proctor, Russell, and Rabe. Kaiser Crater is 207 km (129 miles) in diameter. The dunes are located in the southern part of the crater floor. The Odyssey spacecraft has spent over 15 years in orbit around Mars, circling the planet more than 71,000 times. It holds the record for longest working spacecraft at Mars. THEMIS, the IR/VIS camera system, has collected data for the entire mission and provides images covering all seasons and lighting conditions. Over the years many features of interest have received repeated imaging, building up a suite of images covering the entire feature. From the deepest chasma to the tallest volcano, individual dunes inside craters and dune fields that encircle the north pole, channels carved by water and lava, and a variety of other feature, THEMIS has imaged them all. For the next several months the image of the day will focus on the Tharsis volcanoes, the various chasmata of Valles Marineris, and the major dunes fields. We hope you enjoy these images! Orbit Number: 35430 Latitude: -46.8699 Longitude: 19.4731 Instrument: VIS Captured: 2009-12-09 14:09 https://photojournal.jpl.nasa.gov/catalog/PIA22263
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Investigating Mars: Kaiser Crater Dunes
2018-02-02
This is a false color image of Kaiser Crater. In this combination of filters "blue" typically means basaltic sand. This VIS image crosses 3/4 of the crater and demonstrates how extensive the dunes are on the floor of Kaiser Crater. Kaiser Crater is located in the southern hemisphere in the Noachis region west of Hellas Planitia. Kaiser Crater is just one of several large craters with extensive dune fields on the crater floor. Other nearby dune filled craters are Proctor, Russell, and Rabe. Kaiser Crater is 207 km (129 miles) in diameter. The dunes are located in the southern part of the crater floor. The THEMIS VIS camera contains 5 filters. The data from different filters can be combined in multiple ways to create a false color image. These false color images may reveal subtle variations of the surface not easily identified in a single band image. The Odyssey spacecraft has spent over 15 years in orbit around Mars, circling the planet more than 71,000 times. It holds the record for longest working spacecraft at Mars. THEMIS, the IR/VIS camera system, has collected data for the entire mission and provides images covering all seasons and lighting conditions. Over the years many features of interest have received repeated imaging, building up a suite of images covering the entire feature. From the deepest chasma to the tallest volcano, individual dunes inside craters and dune fields that encircle the north pole, channels carved by water and lava, and a variety of other feature, THEMIS has imaged them all. For the next several months the image of the day will focus on the Tharsis volcanoes, the various chasmata of Valles Marineris, and the major dunes fields. We hope you enjoy these images! Orbit Number: 66602 Latitude: -47.0551 Longitude: 19.446 Instrument: VIS Captured: 2016-12-18 21:42 https://photojournal.jpl.nasa.gov/catalog/PIA22265
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Investigating Mars: Kaiser Crater Dunes
2018-01-29
This VIS image of Kaiser Crater shows a region of the dunes with varied appearances. The different dune forms developed due to different amounts of available sand, different wind directions, and the texture of the crater floor. The dune forms change from the bottom to the top of the image - large long connected dunes, to large individual dunes, to the very small individual dunes at the top of the image. Kaiser Crater is located in the southern hemisphere in the Noachis region west of Hellas Planitia. Kaiser Crater is just one of several large craters with extensive dune fields on the crater floor. Other nearby dune filled craters are Proctor, Russell, and Rabe. Kaiser Crater is 207 km (129 miles) in diameter. The dunes are located in the southern part of the crater floor. The Odyssey spacecraft has spent over 15 years in orbit around Mars, circling the planet more than 71,000 times. It holds the record for longest working spacecraft at Mars. THEMIS, the IR/VIS camera system, has collected data for the entire mission and provides images covering all seasons and lighting conditions. Over the years many features of interest have received repeated imaging, building up a suite of images covering the entire feature. From the deepest chasma to the tallest volcano, individual dunes inside craters and dune fields that encircle the north pole, channels carved by water and lava, and a variety of other feature, THEMIS has imaged them all. For the next several months the image of the day will focus on the Tharsis volcanoes, the various chasmata of Valles Marineris, and the major dunes fields. We hope you enjoy these images! Orbit Number: 17686 Latitude: -46.6956 Longitude: 19.8394 Instrument: VIS Captured: 2005-12-09 13:25 https://photojournal.jpl.nasa.gov/catalog/PIA22261
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Investigating Mars: Kaiser Crater Dunes
2018-01-24
This VIS image of Kaiser Crater shows individual dunes and where the dunes have coalesced into longer dune forms. The addition of sand makes the dunes larger and the intra-dune areas go from sand-free to complete coverage of the hard surface of the crater floor. With a continued influx of sand the region will transition from individual dunes to a sand sheet with surface dune forms. Kaiser Crater is located in the southern hemisphere in the Noachis region west of Hellas Planitia. Kaiser Crater is just one of several large craters with extensive dune fields on the crater floor. Other nearby dune filled craters are Proctor, Russell, and Rabe. Kaiser Crater is 207 km (129 miles) in diameter. The dunes are located in the southern part of the crater floor. The Odyssey spacecraft has spent over 15 years in orbit around Mars, circling the planet more than 69000 times. It holds the record for longest working spacecraft at Mars. THEMIS, the IR/VIS camera system, has collected data for the entire mission and provides images covering all seasons and lighting conditions. Over the years many features of interest have received repeated imaging, building up a suite of images covering the entire feature. From the deepest chasma to the tallest volcano, individual dunes inside craters and dune fields that encircle the north pole, channels carved by water and lava, and a variety of other feature, THEMIS has imaged them all. For the next several months the image of the day will focus on the Tharsis volcanoes, the various chasmata of Valles Marineris, and the major dunes fields. We hope you enjoy these images! Orbit Number: 1423 Latitude: -46.9573 Longitude: 18.6192 Instrument: VIS Captured: 2002-04-10 16:44 https://photojournal.jpl.nasa.gov/catalog/PIA22173
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Investigating Mars: Kaiser Crater Dunes
2018-01-23
Kaiser Crater is located in the southern hemisphere in the Noachis region west of Hellas Planitia. Kaiser Crater is just one of several large craters with extensive dune fields on the crater floor. Other nearby dune filled craters are Proctor, Russell, and Rabe. Kaiser Crater is 207 km (129 miles) in diameter. The dunes are located in the southeastern part of the crater floor. Most of the individual dunes in Kaiser Crater are barchan dunes. Barchan dunes are crescent shaped with the points of the crescent pointing downwind. The sand is blown up the low angle side of the dune and then tumbles down the steep slip face. This dune type forms on hard surfaces where there is limited amounts of sand. Barchan dunes can merge together over time with increased sand in the local area. The Odyssey spacecraft has spent over 15 years in orbit around Mars, circling the planet more than 69000 times. It holds the record for longest working spacecraft at Mars. THEMIS, the IR/VIS camera system, has collected data for the entire mission and provides images covering all seasons and lighting conditions. Over the years many features of interest have received repeated imaging, building up a suite of images covering the entire feature. From the deepest chasma to the tallest volcano, individual dunes inside craters and dune fields that encircle the north pole, channels carved by water and lava, and a variety of other feature, THEMIS has imaged them all. For the next several months the image of the day will focus on the Tharsis volcanoes, the various chasmata of Valles Marineris, and the major dunes fields. We hope you enjoy these images! Orbit Number: 1036 Latitude: -46.7795 Longitude: 20.2075 Instrument: VIS Captured: 2002-03-09 20:07 https://photojournal.jpl.nasa.gov/catalog/PIA22172
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Investigating Mars: Kaiser Crater Dunes
2018-01-30
At the top of this VIS image crescent shaped dunes are visible. As the dunes approach a break in elevation the forms change to connect the crescents together forming long aligned dune forms. Kaiser Crater is located in the southern hemisphere in the Noachis region west of Hellas Planitia. Kaiser Crater is just one of several large craters with extensive dune fields on the crater floor. Other nearby dune filled craters are Proctor, Russell, and Rabe. Kaiser Crater is 207 km (129 miles) in diameter. The dunes are located in the southern part of the crater floor. The Odyssey spacecraft has spent over 15 years in orbit around Mars, circling the planet more than 71,000 times. It holds the record for longest working spacecraft at Mars. THEMIS, the IR/VIS camera system, has collected data for the entire mission and provides images covering all seasons and lighting conditions. Over the years many features of interest have received repeated imaging, building up a suite of images covering the entire feature. From the deepest chasma to the tallest volcano, individual dunes inside craters and dune fields that encircle the north pole, channels carved by water and lava, and a variety of other feature, THEMIS has imaged them all. For the next several months the image of the day will focus on the Tharsis volcanoes, the various chasmata of Valles Marineris, and the major dunes fields. We hope you enjoy these images! Orbit Number: 34157 Latitude: -46.9336 Longitude: 18.9272 Instrument: VIS Captured: 2009-08-26 18:49 https://photojournal.jpl.nasa.gov/catalog/PIA22262
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Bedrock Outcrops in Kaiser Crater
2017-03-13
This enhanced-color image from NASA Mars Reconnaissance Orbiter shows a patch of well-exposed bedrock on the floor of Kaiser Crater. The wind has stripped off the overlying soil, and created grooves and scallops in the bedrock. The narrow linear ridges are fractures that have been indurated, probably by precipitation of cementing minerals from groundwater flow. The rippled dark blue patches consist of sand. The map is projected here at a scale of 25 centimeters (9.8 inches) per pixel. [The original image scale is 25.3 centimeters (9.9 inches) per pixel (with 1 x 1 binning); objects on the order of 76 centimeters (29.9 inches) across are resolved.] North is up. http://photojournal.jpl.nasa.gov/catalog/PIA21559
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Achieving Kaiser Permanente Quality
McHugh, Matthew D.; Aiken, Linda H.; Eckenhoff, Myra E.; Burns, Lawton R.
2015-01-01
Background The Kaiser Permanente model of integrated health delivery is highly regarded for high quality and efficient health care. Efforts to reproduce Kaiser’s success have mostly failed. One factor that has received little attention and that could explain Kaiser’s advantage is its commitment to and investment in nursing as a key component of organizational culture and patient-centered care. Purpose The aim of this study was to investigate the role of Kaiser’s nursing organization in promoting quality of care. Methodology This was a cross-sectional analysis of linked secondary data from multiple sources, including a detailed survey of nurses, for 564 adult, general acute care hospitals from California, Florida, Pennsylvania, and New Jersey in 2006–2007. We used logistic regression models to examine whether patient (mortality and failure-to-rescue) and nurse (burnout, job satisfaction, and intent-to-leave) outcomes in Kaiser hospitals were better than in non-Kaiser hospitals. We then assessed whether differences in nursing explained outcomes differences between Kaiser and other hospitals. Finally, we examined whether Kaiser hospitals compared favorably with hospitals known for having excellent nurse work environments — Magnet hospitals. Findings Patient and nurse outcomes in Kaiser hospitals were significantly better compared with non-Magnet hospitals. Kaiser hospitals had significantly better nurse work environments, staffing levels, and more nurses with bachelor’s degrees. Differences in nursing explained a significant proportion of the Kaiser outcomes advantage. Kaiser hospital outcomes were comparable to Magnet hospitals, where better outcomes have been largely explained by differences in nursing. Implications An important element in Kaiser’s success is its investment in professional nursing, which may not be evident to systems seeking to achieve Kaiser’s advantage. Our results suggest that a possible strategy for achieving outcomes like Kaiser
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Kaiser captures spirit of games.
Herreria, J
1998-01-01
With a multi-media campaign, Kaiser Permanente blitzed its market area by becoming a sponsor of the Nike World Masters Games. The advertising campaign promoted Kaiser as the exclusive health care sponsor. Company officials are counting on this campaign to leverage the health care institution's commitment to the community. In addition to the advertising, Kaiser searched for local athletes to represent its "play the sports for life" theme. As part of a promotion to award 200 athlete sponsorships to the Games, Kaiser's own master athletes were invited to tell their stories. Some of the members shared stories about such topics as experiencing an accident, receiving assistance from a Kaiser physician and incorporating a lifestyle of sport for rehabilitation. From the hundreds of letters received, two members and one employee were selected for the television spots. The sporting event reinforces Kaiser's philosophy of fitness-oriented lifestyles among its members. The Nike World Masters Games are the largest participatory multi-sport competition in the world, gathering together more than 25,000 men and women from more than 100 countries.
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Questioning the claims from Kaiser
Talbot-Smith, Alison; Gnani, Shamini; Pollock, Allyson M; Gray, Denis Pereira
2004-01-01
Background: The article by Feachem et al, published in the BMJ in 2002, claimed to show that, compared with the United Kingdom (UK) National Health Service (NHS), the Kaiser Permanente healthcare system in the United States (US) has similar healthcare costs per capita, and performance that is considerably better in certain respects. Aim: To assess the accuracy of Feachem et al's comparison and conclusions. Method: Detailed re-examination of the data and methods used and consideration of the 82 letters responding to the article. Results: Analyses revealed four main areas in which Feachem et al's methodology was flawed. Firstly, the populations of patients served by Kaiser Permanente and by the NHS are fundamentally different. Kaiser's patients are mainly employed, significantly younger, and significantly less socially deprived and so are healthier. Feachem et al fail to adjust adequately for these factors. Secondly, Feachem et al have wrongly inflated NHS costs by omitting substantial user charges payable by Kaiser members for care, excluding the costs of marketing and administration, and deducting the surplus from Kaiser's costs while underestimating the capital charge element of the NHS budget and other costs. They also used two methods of converting currency, the currency rate and a health purchasing power parity conversion. This is double counting. Feachem et al reported that NHS costs were 10% less per head than Kaiser. Correcting for the double currency conversion gives the NHS a 40% cost advantage such that per capita costs are $1161 and $1951 for the NHS and Kaiser, respectively. Thirdly, Feachem et al use non-standardised data for NHS bed days from the Organisation for Economic Cooperation and Development, rather than official Department of Health bed availability and activity statistics for England. Leaving aside the non-comparability of the population and lack of standardisation of the data, the result is to inflate NHS acute bed use and underestimate the
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Kaiser Permanente Northwest's Center for Health Research was created to study health maintenance organizations by scientists were recruited from a variety of fields to study a range of health and medical care issues.
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Frederik Kaiser (1808-1872) and the Modernisation of Dutch Astronomy
NASA Astrophysics Data System (ADS)
van der Heijden, Petra
Frederik Kaiser was the director of Leiden Observatory from 1837 until his death in 1872. Educated by his German-born uncle Johan Frederik Keyser (1766-1823), who was a proficient amateur astronomer, Kaiser proved to be a real observational talent. Despite the poor conditions in which he worked, his observations soon rivalled with the best in the world. Kaiser's contributions to astronomical practice include the foundation of a new, completely up-to-date observatory building in Leiden, and the introduction of statistics and precision measurements in daily practice at the observatory. Moreover he was the author of several bestselling books on popular astronomy. Kaiser had an extensive correspondence with colleagues all over Europe, mostly in Germany. Correpondents include Airy, Argelander, Von Auwers, Bessel, Encke, John Herschel, LeVerrier, Von Littrow, Schumacher, Otto W. Struve, as well as several geodesists and instrument makers. Preliminary research indicates that Frederik Kaiser played a crucial role in the revival of Dutch astronomy in the second half of the 19th century. This project aims at analysing and explaining Kaiser's activities in science, institutionalisation and popularisation, in the context of national and international developments in 19th-century astronomy and scientific culture.
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2016-12-21
the lineated material on the crater floor. It is necessary to distinguish secondary craters from the primary impacts that we rely upon to estimate the ages of Martian surfaces. The large number of small craters clustered together here is typical of crater rays elsewhere on Mars and suggests that these are indeed, secondary impact craters. http://photojournal.jpl.nasa.gov/catalog/PIA14450
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Simultaneous impact and lunar craters
NASA Technical Reports Server (NTRS)
Oberbeck, V. R.
1972-01-01
The existence of large terrestrial impact crater doublets and crater doublets that have been inferred to be impact craters on Mars suggests that simultaneous impact of two or more bodies can occur at nearly the same point on planetary surfaces. An experimental study of simultaneous impact of two projectiles near one another shows that doublet craters with ridges perpendicular to the bilateral axis of symmetry result when separation between impact points relative to individual crater diameter is large. When separation is progressively less, elliptical craters with central ridges and peaks, and circular craters with deep round bottoms are produced. These craters are similar in structure to many of the large lunar craters. Results suggest that the simultaneous impact of meteoroids near one another may be an important mechanism for the production of central peaks in large lunar craters.
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2002-12-04
With a location roughly equidistant between two of the largest volcanic constructs on the planet, the fate of the approximately 50 km 31 mile impact crater in this image from NASA Mars Odyssey was sealed. It has been buried to the rim by lava flows. The MOLA context image shows pronounced flow lobes surrounding the crater, a clear indication of the most recent episode of volcanism that could have contributed to its infilling. Breaches in the rim are clearly evident in the image and suggest locations through which lavas could have flowed. These openings appear to be limited to the west side of the crater. Other craters in the area are nearly obliterated by the voluminous lava flows, further demonstrating one of the means by which Mars renews its surface. The MOLA context image shows pronounced flow lobes surrounding the crater, a clear indication of the most recent episode of volcanism that could have contributed to its infilling. Breaches in the rim are clearly evident in the image and suggest locations through which lavas could have flowed. These openings appear to be limited to the west side of the crater. Other craters in the area are nearly obliterated by the voluminous lava flows, further demonstrating one of the means by which Mars renews its surface. http://photojournal.jpl.nasa.gov/catalog/PIA04018
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Federal Register 2010, 2011, 2012, 2013, 2014
2010-11-18
... Fabricated Products, LLC; Kaiser Aluminum- Greenwood Forge Division; Currently Known As Contech Forgings, LLC..., South Carolina; Amended Certification Regarding Eligibility To Apply or Worker Adjustment Assistance In... Labor issued a Certification of Eligibility to Apply for Worker Adjustment Assistance on October 2, 2009...
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Crater studies: Part A: lunar crater morphometry
Pike, Richard J.
1973-01-01
Morphometry, the quantitative study of shape, complements the visual observation and photointerpretation in analyzing the most outstanding landforms of the Moon, its craters (refs. 32-1 and 32-2). All three of these interpretative tools, which were developed throughout the long history of telescopic lunar study preceding the Apollo Program, will continue to be applicable to crater analysis until detailed field work becomes possible. Although no large (>17.5 km diameter) craters were examined in situ on any of the Apollo landings, the photographs acquired from the command modules will markedly strengthen results of less direct investigations of the craters. For morphometry, the most useful materials are the orbital metric and panoramic photographs from the final three Apollo missions. These photographs permit preparation of contour maps, topographic profiles, and other numerical data that accurately portray for the first time the surface geometry of lunar craters of all sizes. Interpretations of craters no longer need be compromised by inadequate topographic data. In the pre-Apollo era, hypotheses for the genesis of lunar craters usually were constructed without any numerical descriptive data. Such speculations will have little credibility unless supported by accurate, quantitative data, especially those generated from Apollo orbital photographs. This paper presents a general study of the surface geometry of 25 far-side craters and a more detailed study of rim-crest evenness for 15 near-side and far-side craters. Analysis of this preliminary sample of Apollo 15 and 17 data, which includes craters between 1.5 and 275 km in diameter, suggests that most genetic interpretations of craters made from pre-Apollo topographic measurements may require no drastic revision. All measurements were made from topographic profiles generated on a stereoplotter at the Photogrammetric Unit of the U.S. Geological Survey, Center of Astrogeology, Flagstaff, Arizona.
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2006-10-10
Several craters were formed on the rim of this large crater. The movement of material downhill toward the floor of the large crater has formed interesting patterns on the floors of the smaller craters
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Crater gradation in Gusev crater and Meridiani Planum, Mars
Grant, J. A.; Arvidson, R. E.; Crumpler, L.S.; Golombek, M.P.; Hahn, B.; Haldemann, A.F.C.; Li, R.; Soderblom, L.A.; Squyres, S. W.; Wright, S.P.; Watters, W.A.
2006-01-01
The Mars Exploration Rovers investigated numerous craters in Gusev crater and Meridiani Planum during the first ???400 sols of their missions. Craters vary in size and preservation state but are mostly due to secondary impacts at Gusev and primary impacts at Meridiani. Craters at both locations are modified primarily by eolian erosion and infilling and lack evidence for modification by aqueous processes. Effects of gradation on crater form are dependent on size, local lithology, slopes, and availability of mobile sediments. At Gusev, impacts into basaltic rubble create shallow craters and ejecta composed of resistant rocks. Ejecta initially experience eolian stripping, which becomes weathering-limited as lags develop on ejecta surfaces and sediments are trapped within craters. Subsequent eolian gradation depends on the slow production of fines by weathering and impacts and is accompanied by minor mass wasting. At Meridiani the sulfate-rich bedrock is more susceptible to eolian erosion, and exposed crater rims, walls, and ejecta are eroded, while lower interiors and low-relief surfaces are increasingly infilled and buried by mostly basaltic sediments. Eolian processes outpace early mass wasting, often produce meters of erosion, and mantle some surfaces. Some small craters were likely completely eroded/buried. Craters >100 m in diameter on the Hesperian-aged floor of Gusev are generally more pristine than on the Amazonian-aged Meridiani plains. This conclusion contradicts interpretations from orbital views, which do not readily distinguish crater gradation state at Meridiani and reveal apparently subdued crater forms at Gusev that may suggest more gradation than has occurred. Copyright 2006 by the American Geophysical Union.
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Crater gradation in Gusev crater and Meridiani Planum, Mars
NASA Astrophysics Data System (ADS)
Grant, J. A.; Arvidson, R. E.; Crumpler, L. S.; Golombek, M. P.; Hahn, B.; Haldemann, A. F. C.; Li, R.; Soderblom, L. A.; Squyres, S. W.; Wright, S. P.; Watters, W. A.
2006-01-01
The Mars Exploration Rovers investigated numerous craters in Gusev crater and Meridiani Planum during the first ~400 sols of their missions. Craters vary in size and preservation state but are mostly due to secondary impacts at Gusev and primary impacts at Meridiani. Craters at both locations are modified primarily by eolian erosion and infilling and lack evidence for modification by aqueous processes. Effects of gradation on crater form are dependent on size, local lithology, slopes, and availability of mobile sediments. At Gusev, impacts into basaltic rubble create shallow craters and ejecta composed of resistant rocks. Ejecta initially experience eolian stripping, which becomes weathering-limited as lags develop on ejecta surfaces and sediments are trapped within craters. Subsequent eolian gradation depends on the slow production of fines by weathering and impacts and is accompanied by minor mass wasting. At Meridiani the sulfate-rich bedrock is more susceptible to eolian erosion, and exposed crater rims, walls, and ejecta are eroded, while lower interiors and low-relief surfaces are increasingly infilled and buried by mostly basaltic sediments. Eolian processes outpace early mass wasting, often produce meters of erosion, and mantle some surfaces. Some small craters were likely completely eroded/buried. Craters >100 m in diameter on the Hesperian-aged floor of Gusev are generally more pristine than on the Amazonian-aged Meridiani plains. This conclusion contradicts interpretations from orbital views, which do not readily distinguish crater gradation state at Meridiani and reveal apparently subdued crater forms at Gusev that may suggest more gradation than has occurred.
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2017-06-01
This image from NASA's Mars Reconnaissance Orbiter shows an elongated depression from three merged craters. The raised rims and ejecta indicate that these are impact craters rather than collapse or volcanic landforms. The pattern made by the ejecta and the craters suggest this was a highly oblique (low angle to the surface) impact, probably coming from the west. There may have been three major pieces flying in close formation to make this triple crater. https://photojournal.jpl.nasa.gov/catalog/PIA21652
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Secondary craters on Europa and implications for cratered surfaces.
Bierhaus, Edward B; Chapman, Clark R; Merline, William J
2005-10-20
For several decades, most planetary researchers have regarded the impact crater populations on solid-surfaced planets and smaller bodies as predominantly reflecting the direct ('primary') impacts of asteroids and comets. Estimates of the relative and absolute ages of geological units on these objects have been based on this assumption. Here we present an analysis of the comparatively sparse crater population on Jupiter's icy moon Europa and suggest that this assumption is incorrect for small craters. We find that 'secondaries' (craters formed by material ejected from large primary impact craters) comprise about 95 per cent of the small craters (diameters less than 1 km) on Europa. We therefore conclude that large primary impacts into a solid surface (for example, ice or rock) produce far more secondaries than previously believed, implying that the small crater populations on the Moon, Mars and other large bodies must be dominated by secondaries. Moreover, our results indicate that there have been few small comets (less than 100 m diameter) passing through the jovian system in recent times, consistent with dynamical simulations.
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Observation of the Kaiser Effect Using Noble Gas Release Signals
DOE Office of Scientific and Technical Information (OSTI.GOV)
Bauer, Stephen J.
The Kaiser effect was defined in the early 1950s (Kaiser 1953) and was extensively reviewed and evaluated by Lavrov (2002) with a view toward understanding stress estimations. The Kaiser effect is a stress memory phenomenon which has most often been demonstrated in rock using acoustic emissions. During cyclic loading–unloading–reloading, the acoustic emissions are near zero until the load exceeds the level of the previous load cycle. Here, we sought to explore the Kaiser effect in rock using real-time noble gas release. Laboratory studies using real-time mass spectrometry measurements during deformation have quantified, to a degree, the types of gases releasedmore » (Bauer et al. 2016a, b), their release rates and amounts during deformation, estimates of permeability created from pore structure modifications during deformation (Gardner et al. 2017) and the impact of mineral plasticity upon gas release. We found that noble gases contained in brittle crystalline rock are readily released during deformation.« less
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Observation of the Kaiser Effect Using Noble Gas Release Signals
Bauer, Stephen J.
2017-10-24
The Kaiser effect was defined in the early 1950s (Kaiser 1953) and was extensively reviewed and evaluated by Lavrov (2002) with a view toward understanding stress estimations. The Kaiser effect is a stress memory phenomenon which has most often been demonstrated in rock using acoustic emissions. During cyclic loading–unloading–reloading, the acoustic emissions are near zero until the load exceeds the level of the previous load cycle. Here, we sought to explore the Kaiser effect in rock using real-time noble gas release. Laboratory studies using real-time mass spectrometry measurements during deformation have quantified, to a degree, the types of gases releasedmore » (Bauer et al. 2016a, b), their release rates and amounts during deformation, estimates of permeability created from pore structure modifications during deformation (Gardner et al. 2017) and the impact of mineral plasticity upon gas release. We found that noble gases contained in brittle crystalline rock are readily released during deformation.« less
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75 FR 43885 - Proposed Amendment of Class E Airspace; Kaiser/Lake Ozark, MO
Federal Register 2010, 2011, 2012, 2013, 2014
2010-07-27
...-0604; Airspace Docket No. 10-ACE-5] Proposed Amendment of Class E Airspace; Kaiser/Lake Ozark, MO...: This action proposes to amend Class E airspace for the Kaiser/ Lake Ozark, MO, area. Additional... for the Kaiser/Lake Ozark, MO area, to accommodate SIAPs at Camdenton Memorial Airport, Camdenton, MO...
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Energy Assessment Helps Kaiser Aluminum Save Energy and Improve Productivity
DOE Office of Scientific and Technical Information (OSTI.GOV)
None
2008-07-01
The Kaiser Aluminum plant in Sherman, Texas, adjusted controls and made repairs to a furnace for a simple payback of 1 month. Kaiser adopted DOE's Process Heating Assessment and Survey Tool (PHAST) software as the corporate diagnostic tool and has used it to evaluate process heating systems at five other aluminum plants.
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Povilaitis, R Z; Robinson, M S; van der Bogert, C H; Hiesinger, Harald; Meyer, H M; Ostrach, Lillian
2017-01-01
The global population of lunar craters >20 km in diameter was analyzed by Head et al., (2010) to correlate crater distribution with resurfacing events and multiple impactor populations. The work presented here extends the global crater distribution analysis to smaller craters (5–20 km diameters, n = 22,746). Smaller craters form at a higher rate than larger craters and thus add granularity to age estimates of larger units and can reveal smaller and younger areas of resurfacing. An areal density difference map generated by comparing the new dataset with that of Head et al., (2010) shows local deficiencies of 5–20 km diameter craters, which we interpret to be caused by a combination of resurfacing by the Orientale basin, infilling of intercrater plains within the nearside highlands, and partial mare flooding of the Australe region. Chains of 5–30 km diameter secondaries northwest of Orientale and possible 8–22 km diameter basin secondaries within the farside highlands are also distinguishable. Analysis of the new database indicates that craters 57–160 km in diameter across much of the lunar highlands are at or exceed relative crater densities of R = 0.3 or 10% geometric saturation, but nonetheless appear to fit the lunar production function. Combined with the observation that small craters on old surfaces can reach saturation equilibrium at 1% geometric saturation (Xiao and Werner, 2015), this suggests that saturation equilibrium is a size-dependent process, where large craters persist because of their resistance to destruction, degradation, and resurfacing.
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Relative age of Camelot crater and crater clusters near the Apollo 17 landing site
Lucchitta, B.K.
1979-01-01
Topographic profiles and depth-diameter ratios from the crater Camelot and craters of the central cluster in the Apollo 17 landing area suggest that these craters are of the same age. Therefore, layers that can be recognized in the deep-drill core and that can be identified as ejecta deposits from Camelot or from the cluster craters should yield similar emplacement ages. ?? 1979.
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NASA Astrophysics Data System (ADS)
Fassett, Caleb I.; Crowley, Malinda C.; Leight, Clarissa; Dyar, M. Darby; Minton, David A.; Hirabayashi, Masatoshi; Thomson, Bradley J.; Watters, Wesley A.
2017-06-01
Examining the topography of impact craters and their evolution with time is useful for assessing how fast planetary surfaces evolve. Here, new measurements of depth/diameter (d/D) ratios for 204 craters of 2.5 to 5 km in diameter superposed on Mercury's smooth plains are reported. The median d/D is 0.13, much lower than expected for newly formed simple craters ( 0.21). In comparison, lunar craters that postdate the maria are much less modified, and the median crater in the same size range has a d/D ratio that is nearly indistinguishable from the fresh value. This difference in crater degradation is remarkable given that Mercury's smooth plains and the lunar maria likely have ages that are comparable, if not identical. Applying a topographic diffusion model, these results imply that crater degradation is faster by a factor of approximately two on Mercury than on the Moon, suggesting more rapid landform evolution on Mercury at all scales.
Plain Language SummaryMercury and the Moon are both airless bodies that have experienced numerous impact events over billions of years. These impacts form <span class="hlt">craters</span> in a geologic instant. The question examined in this manuscript is how fast these <span class="hlt">craters</span> erode after their formation. To simplify the problem, we examined <span class="hlt">craters</span> of a particular size (2.5 to 5 km in diameter) on a particular geologic terrain type (volcanic smooth plains) on both the Moon and Mercury. We then measured the topography of hundreds of <span class="hlt">craters</span> on both bodies that met these criteria. Our results <span class="hlt">suggest</span> that <span class="hlt">craters</span> on Mercury become shallower much more quickly than <span class="hlt">craters</span> on the Moon. We estimate that Mercury's topography erodes at a rate at least a factor of two faster than the Moon's.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA09369&hterms=block+chain&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dblock%2Bchain','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA09369&hterms=block+chain&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dblock%2Bchain"><span>Rayed Gratteri <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2006-01-01</p> <p><p/> [figure removed for brevity, see original site] Click on image for larger version <p/> This HiRISE image covers the western portion of the primary cavity of Gratteri <span class="hlt">crater</span> situated in the Memnonia Fossae region. Gratteri <span class="hlt">crater</span> is one of five definitive large rayed <span class="hlt">craters</span> on Mars. Gratteri <span class="hlt">crater</span> has a diameter of approximately 6.9 kilometers. <span class="hlt">Crater</span> rays are long, linear features formed from the high-velocity ejection of blocks of material that re-impact the surface in linear clusters or chains that appear to emanate from the main or primary cavity. Such <span class="hlt">craters</span> have been long recognized as the 'brightest' and 'freshest' <span class="hlt">craters</span> on the Moon. However, Martian rays differ from lunar rays in that they are not 'bright,' but best recognized by their thermal signature (at night) in 100 meter/pixel THEMIS thermal infrared images. The HiRISE image shows that Gratteri <span class="hlt">crater</span> has well-developed and sharp <span class="hlt">crater</span> morphologic features with no discernable superimposed impact <span class="hlt">craters</span>. The HiRISE sub-image shows that this is true for the ejecta and <span class="hlt">crater</span> floor up to the full resolution of the image. Massive slumped blocks of materials on the <span class="hlt">crater</span> floor and the 'spur and gully' morphology with the <span class="hlt">crater</span> wall may <span class="hlt">suggest</span> that the subsurface in this area may be thick and homogenous. Gratteri <span class="hlt">crater</span>'s ejecta blanket (as seen in THEMIS images) can be described as 'fluidized,' which may be <span class="hlt">suggestive</span> of the presence of ground-ice that may have helped to 'liquefy' the ejecta as it was deposited near the <span class="hlt">crater</span>. Gratteri's ejecta can be observed to have flowed in and around obstacles including an older, degraded <span class="hlt">crater</span> lying immediately to the SW of Gratteri's primary cavity. <p/> Image PSP_001367_1620 was taken by the High Resolution Imaging Science Experiment (HiRISE) camera onboard the Mars Reconnaissance Orbiter spacecraft on November 10, 2006. The complete image is centered at -17.7 degrees latitude, 199.9 degrees East longitude. The range to the target site was 257.1 km</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA04410.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA04410.html"><span><span class="hlt">Crater</span> Wall and Floor</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2003-02-18</p> <p>The impact <span class="hlt">crater</span> observed in this NASA Mars Odyssey image taken in Terra Cimmeria <span class="hlt">suggests</span> sediments have filled the <span class="hlt">crater</span> due to the flat and smooth nature of the floor compared to rougher surfaces at higher elevations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://epi.grants.cancer.gov/pharm/pharmacoepi_db/kp-mcp.html','NCI'); return false;" href="https://epi.grants.cancer.gov/pharm/pharmacoepi_db/kp-mcp.html"><span><span class="hlt">Kaiser</span> Permanente Medical Care Programs (KP-MCP)</span></a></p> <p><a target="_blank" href="http://www.cancer.gov">Cancer.gov</a></p> <p></p> <p></p> <p>The Division of Research within KP-MCP conducts, publishes, and disseminates high-quality epidemiologic and health services research to improve the health and medical care of <span class="hlt">Kaiser</span> Permanente members and the society at large.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014DokPh..59..214K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014DokPh..59..214K"><span>A new class of weight and WA systems of the Kravchenko-<span class="hlt">Kaiser</span> functions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kravchenko, V. F.; Pustovoit, V. I.; Churikov, D. V.</p> <p>2014-05-01</p> <p>A new class of weight and WA-systems of the Kravchenko-<span class="hlt">Kaiser</span> functions which showed its efficiency in various physical applications is proposed and substantiated. This publication consists of three parts. In the first the Kravchenko-<span class="hlt">Kaiser</span> weight functions are constructed on basis of the theory of atomic functions (AFs) and the <span class="hlt">Kaiser</span> windows for the first time. In the second part new constructions of analytic WA-systems of the Kravchenko-<span class="hlt">Kaiser</span> functions are costructed. In the third part their applications to problems of weight averaging of the difference frequency signals are considered. The numerical experiment and the physical analysis of the results for concrete physical models confirmed their efficiency. This class of functions can find wide physical applications in problems of digital signal processing, restoration of images, radar, radiometry, radio astronomy, remote sensing, etc.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.sciencedirect.com/science/article/pii/S0019103509003753','USGSPUBS'); return false;" href="http://www.sciencedirect.com/science/article/pii/S0019103509003753"><span>Impact <span class="hlt">craters</span> on Titan</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Wood, Charles A.; Lorenz, Ralph; Kirk, Randy; Lopes, Rosaly; Mitchell, Karl; Stofan, Ellen; ,</p> <p>2010-01-01</p> <p>Five certain impact <span class="hlt">craters</span> and 44 additional nearly certain and probable ones have been identified on the 22% of Titan's surface imaged by Cassini's high-resolution radar through December 2007. The certain <span class="hlt">craters</span> have morphologies similar to impact <span class="hlt">craters</span> on rocky planets, as well as two with radar bright, jagged rims. The less certain <span class="hlt">craters</span> often appear to be eroded versions of the certain ones. Titan's <span class="hlt">craters</span> are modified by a variety of processes including fluvial erosion, mass wasting, burial by dunes and submergence in seas, but there is no compelling evidence of isostatic adjustments as on other icy moons, nor draping by thick atmospheric deposits. The paucity of <span class="hlt">craters</span> implies that Titan's surface is quite young, but the modeled age depends on which published <span class="hlt">crater</span> production rate is assumed. Using the model of Artemieva and Lunine (2005) <span class="hlt">suggests</span> that <span class="hlt">craters</span> with diameters smaller than about 35 km are younger than 200 million years old, and larger <span class="hlt">craters</span> are older. <span class="hlt">Craters</span> are not distributed uniformly; Xanadu has a <span class="hlt">crater</span> density 2-9 times greater than the rest of Titan, and the density on equatorial dune areas is much lower than average. There is a small excess of <span class="hlt">craters</span> on the leading hemisphere, and <span class="hlt">craters</span> are deficient in the north polar region compared to the rest of the world. The youthful age of Titan overall, and the various erosional states of its likely impact <span class="hlt">craters</span>, demonstrate that dynamic processes have destroyed most of the early history of the moon, and that multiple processes continue to strongly modify its surface. The existence of 24 possible impact <span class="hlt">craters</span> with diameters less than 20 km appears consistent with the Ivanov, Basilevsky and Neukum (1997) model of the effectiveness of Titan's atmosphere in destroying most but not all small projectiles.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70037384','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70037384"><span>Impact <span class="hlt">craters</span> on Titan</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Wood, C.A.; Lorenz, R.; Kirk, R.; Lopes, R.; Mitchell, Ken; Stofan, E.</p> <p>2010-01-01</p> <p>Five certain impact <span class="hlt">craters</span> and 44 additional nearly certain and probable ones have been identified on the 22% of Titan's surface imaged by Cassini's high-resolution radar through December 2007. The certain <span class="hlt">craters</span> have morphologies similar to impact <span class="hlt">craters</span> on rocky planets, as well as two with radar bright, jagged rims. The less certain <span class="hlt">craters</span> often appear to be eroded versions of the certain ones. Titan's <span class="hlt">craters</span> are modified by a variety of processes including fluvial erosion, mass wasting, burial by dunes and submergence in seas, but there is no compelling evidence of isostatic adjustments as on other icy moons, nor draping by thick atmospheric deposits. The paucity of <span class="hlt">craters</span> implies that Titan's surface is quite young, but the modeled age depends on which published <span class="hlt">crater</span> production rate is assumed. Using the model of Artemieva and Lunine (2005) <span class="hlt">suggests</span> that <span class="hlt">craters</span> with diameters smaller than about 35 km are younger than 200 million years old, and larger <span class="hlt">craters</span> are older. <span class="hlt">Craters</span> are not distributed uniformly; Xanadu has a <span class="hlt">crater</span> density 2-9 times greater than the rest of Titan, and the density on equatorial dune areas is much lower than average. There is a small excess of <span class="hlt">craters</span> on the leading hemisphere, and <span class="hlt">craters</span> are deficient in the north polar region compared to the rest of the world. The youthful age of Titan overall, and the various erosional states of its likely impact <span class="hlt">craters</span>, demonstrate that dynamic processes have destroyed most of the early history of the moon, and that multiple processes continue to strongly modify its surface. The existence of 24 possible impact <span class="hlt">craters</span> with diameters less than 20 km appears consistent with the Ivanov, Basilevsky and Neukum (1997) model of the effectiveness of Titan's atmosphere in destroying most but not all small projectiles. ?? 2009 Elsevier Inc.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA21754.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA21754.html"><span>Juling <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2017-08-25</p> <p>This high-resolution image of Juling <span class="hlt">Crater</span> on Ceres reveals, in exquisite detail, features on the rims and <span class="hlt">crater</span> floor. The <span class="hlt">crater</span> is about 1.6 miles (2.5 kilometers) deep and the small mountain, seen left of the center of the <span class="hlt">crater</span>, is about 0.6 miles (1 kilometers) high. The many features indicative of the flow of material <span class="hlt">suggest</span> the subsurface is rich in ice. The geological structure of this region also generally <span class="hlt">suggests</span> that ice is involved. The origin of the small depression seen at the top of the mountain is not fully understood but might have formed as a consequence of a landslide, visible on the northeastern flank. Dawn took this image during its extended mission on August 25, 2016, from its low-altitude mapping orbit at a distance of about 240 miles (385 kilometers) above the surface. The center coordinates of this image are 36 degrees south latitude, 167 degrees east longitude. Juling is named after the Sakai/Orang Asli spirit of the crops from Malaysia. NASA's Dawn spacecraft acquired this picture on August 24, 2016. The image was taken during Dawn's extended mission, from its low altitude mapping orbit at about 240 miles (385 kilometers) above the surface. The center coordinates of this image are 38 degrees south latitude, 165 degrees east longitude. https://photojournal.jpl.nasa.gov/catalog/PIA21754</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017Icar..295..140X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017Icar..295..140X"><span>Ray <span class="hlt">craters</span> on Ganymede: Implications for <span class="hlt">cratering</span> apex-antapex asymmetry and surface modification processes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xu, Luyuan; Hirata, Naoyuki; Miyamoto, Hideaki</p> <p>2017-10-01</p> <p>As the youngest features on Ganymede, ray <span class="hlt">craters</span> are useful in revealing the sources of recent impactors and surface modification processes on the satellite. We examine <span class="hlt">craters</span> with D > 10 km on Ganymede from images obtained by the Voyager and Galileo spacecraft to identify ray <span class="hlt">craters</span> and study their spatial distributions. Furthermore, we carefully select images of appropriate solar and emission angles to obtain unbiased ray <span class="hlt">crater</span> densities. As a result, we find that the density of large ray <span class="hlt">craters</span> (D > 25 km) on the bright terrain exhibits an apex-antapex asymmetry, and its degree of asymmetry is much lower than the theoretical estimation for ecliptic comets. For large <span class="hlt">craters</span> (D > 25 km), ecliptic comets ought to be less important than previously assumed, and a possible explanation is that nearly isotropic comets may play a more important role on Ganymede than previously thought. We also find that small ray <span class="hlt">craters</span> (10 km < D < 25 km) on the bright terrain and ray <span class="hlt">craters</span> (D > 10 km) on the dark terrain show no apex-antapex asymmetry. We interpret that the distribution difference between the terrain types comes from preferential thermal sublimation on the dark terrain, while the distribution difference between large and small ray <span class="hlt">craters</span> <span class="hlt">suggests</span> that rays of small <span class="hlt">craters</span> are more readily erased by some surface modification processes, such as micrometeorite gardening.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010M%26PS...45..638B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010M%26PS...45..638B"><span>Rampart <span class="hlt">craters</span> on Ganymede: Their implications for fluidized ejecta emplacement</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Boyce, Joseph; Barlow, Nadine; Mouginis-Mark, Peter; Stewart, Sarah</p> <p>2010-04-01</p> <p>Some fresh impact <span class="hlt">craters</span> on Ganymede have the overall ejecta morphology similar to Martian double-layer ejecta (DLE), with the exception of the <span class="hlt">crater</span> Nergal that is most like Martian single layer ejecta (SLE) <span class="hlt">craters</span> (as is the terrestrial <span class="hlt">crater</span> Lonar). Similar <span class="hlt">craters</span> also have been identified on Europa, but no outer ejecta layer has been found on these <span class="hlt">craters</span>. The morphometry of these <span class="hlt">craters</span> <span class="hlt">suggests</span> that the types of layered ejecta <span class="hlt">craters</span> identified by Barlow et al. (2000) are fundamental. In addition, the mere existence of these <span class="hlt">craters</span> on Ganymede and Europa <span class="hlt">suggests</span> that an atmosphere is not required for ejecta fluidization, nor can ejecta fluidization be explained by the flow of dry ejecta. Moreover, the absence of fluidized ejecta on other icy bodies <span class="hlt">suggests</span> that abundant volatiles in the target also may not be the sole cause of ejecta fluidization. The restriction of these <span class="hlt">craters</span> to the grooved terrain of Ganymede and the concentration of Martian DLE <span class="hlt">craters</span> on the northern lowlands <span class="hlt">suggests</span> that these terrains may share key characteristics that control the development of the ejecta of these <span class="hlt">craters</span>. In addition, average ejecta mobility (EM) ratios indicate that the ejecta of these bodies are self-similar with <span class="hlt">crater</span> size, but are systematically smaller on Ganymede and Europa. This may be due to the effects of the abundant ice in the crusts of these satellites that results in increased ejection angle causing ejecta to impact closer to the <span class="hlt">crater</span> and with lower horizontal velocity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA03785.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA03785.html"><span><span class="hlt">Cratered</span> terrain in Terra Meridiani</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2002-05-23</p> <p>This region of Terra Meridiani, imaged by NASA Mars Odyssey, shows an old, heavily degraded channel that appears to terminate abruptly at the rim of a 10 km diameter <span class="hlt">crater</span>, <span class="hlt">suggesting</span> that the impact <span class="hlt">crater</span> was created after the channel was formed.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_1");'>1</a></li> <li class="active"><span>2</span></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_2 --> <div id="page_3" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_1");'>1</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li class="active"><span>3</span></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="41"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFM.P31C0545K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFM.P31C0545K"><span>Gully formation in terrestrial simple <span class="hlt">craters</span>: Meteor <span class="hlt">Crater</span>, USA and Lonar <span class="hlt">Crater</span>, India</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kumar, P.; Head, J. W.; Kring, D. A.</p> <p>2007-12-01</p> <p>Geomorphic features such as gullies, valley networks, and channels on Mars have been used as a proxy to understand the climate and landscape evolution of Mars. Terrestrial analogues provide significant insight as to how the various exogenic and endogenic processes might contribute to the evolution of these martian landscapes. We describe here a terrestrial example from Meteor <span class="hlt">Crater</span>, which shows a spectacular development of gullies throughout the inner wall in response to rainwater precipitation, snow melting and groundwater discharge. As liquid water has been envisaged as one of the important agents of landscape sculpturing, Meteor <span class="hlt">Crater</span> remains a useful landmark, where planetary geologists can learn some lessons. We also show here how the lithology and structural framework of this <span class="hlt">crater</span> controls the gully distribution. Like many martian impact <span class="hlt">craters</span>, it was emplaced in layered sedimentary rocks with an exceptionally well-developed centripetal drainage pattern consisting of individual alcoves, channels and fans. Some of the gullies originate from the rim crest and others from the middle <span class="hlt">crater</span> wall, where a lithologic transition occurs. Deeply incised alcoves are well-developed on the soft sandstones of the Coconino Formation exposed on the middle <span class="hlt">crater</span> wall, beneath overlying dolomite. In general, the gully locations are along <span class="hlt">crater</span> wall radial fractures and faults, which are favorable locales of groundwater flow and discharge; these structural discontinuities are also the locales where the surface runoff from rain precipitation and snow melting can preferentially flow, causing degradation. Like martian <span class="hlt">craters</span>, channels are well developed on the talus deposits and alluvial fans on the periphery of the <span class="hlt">crater</span> floor. In addition, lake sediments on the <span class="hlt">crater</span> floor provide significant evidence of a past pluvial climate, when groundwater seeped from springs on the <span class="hlt">crater</span> wall. Caves exposed on the lower <span class="hlt">crater</span> level may point to percolation of surface runoff</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA21454.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA21454.html"><span>A Dragonfly-Shaped <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2017-02-10</p> <p>The broader scene for this image is the fluidized ejecta from Bakhuysen <span class="hlt">Crater</span> to the southwest, but there's something very interesting going on here on a much smaller scale. A small impact <span class="hlt">crater</span>, about 25 meters in diameter, with a gouged-out trench extends to the south. The ejecta (rocky material ejected from the <span class="hlt">crater</span>) mostly extends to the east and west of the <span class="hlt">crater</span>. This "butterfly" ejecta is very common for <span class="hlt">craters</span> formed at low impact angles. Taken together, these observations <span class="hlt">suggest</span> that the <span class="hlt">crater</span>-forming impactor came in at a low angle from the north, hit the ground and ejected material to the sides. The top of the impactor may have sheared off ("decapitating" the impactor) and continued downrange, forming the trench. We can't prove that's what happened, but this explanation is consistent with the observations. Regardless of how it formed, it's quite an interesting-looking "dragonfly" <span class="hlt">crater</span>. The map is projected here at a scale of 50 centimeters (19.69 inches) per pixel. [The original image scale is 55.7 centimeters (21.92 inches) per pixel (with 2 x 2 binning); objects on the order of 167 centimeters (65.7 inches) across are resolved.] North is up. http://photojournal.jpl.nasa.gov/catalog/PIA21454</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19770054896&hterms=conversion+rate&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dconversion%2Brate%2527','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19770054896&hterms=conversion+rate&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dconversion%2Brate%2527"><span>Relative <span class="hlt">crater</span> production rates on planets</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hartmann, W. K.</p> <p>1977-01-01</p> <p>The relative numbers of impacts on different planets, estimated from the dynamical histories of planetesimals in specified orbits (Wetherill, 1975), are converted by a described procedure to <span class="hlt">crater</span> production rates. Conversions are dependent on impact velocity and surface gravity. <span class="hlt">Crater</span> retention ages can then be derived from the ratio of the <span class="hlt">crater</span> density to the <span class="hlt">crater</span> production rate. The data indicate that the terrestrial planets have <span class="hlt">crater</span> production rates within a factor ten of each other. As an example, for the case of Mars, least-squares fits to <span class="hlt">crater</span>-count data <span class="hlt">suggest</span> an average age of 0.3 to 3 billion years for two types of channels. The age of Olympus Mons is discussed, and the effect of Tharsis volcanism on channel formation is considered.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009APS..DFD.PK009C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009APS..DFD.PK009C"><span>Granular <span class="hlt">Crater</span> Formation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Clark, Abe; Behringer, Robert; Brandenburg, John</p> <p>2009-11-01</p> <p>This project characterizes <span class="hlt">crater</span> formation in a granular material by a jet of gas impinging on a granular material, such as a retro-rocket landing on the moon. We have constructed a 2D model of a planetary surface, which consists of a thin, clear box partially filled with granular materials (sand, lunar and Mars simulants...). A metal pipe connected to a tank of nitrogen gas via a solenoid valve is inserted into the top of the box to model the rocket. The results are recorded using high-speed video. We process these images and videos in order to test existing models and develop new ones for describing <span class="hlt">crater</span> formation. A similar set-up has been used by Metzger et al.footnotetextP. T. Metzger et al. Journal of Aerospace Engineering (2009) We find that the long-time shape of the <span class="hlt">crater</span> is consistent with a predicted catenary shape (Brandenburg). The depth and width of the <span class="hlt">crater</span> both evolve logarithmically in time, <span class="hlt">suggesting</span> an analogy to a description in terms of an activated process: dD/dt = A (-aD) (D is the <span class="hlt">crater</span> depth, a and A constants). This model provides a useful context to understand the role of the jet speed, as characterized by the pressure used to drive the flow. The box width also plays an important role in setting the width of the <span class="hlt">crater</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930043867&hterms=barlow&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dbarlow','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930043867&hterms=barlow&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dbarlow"><span>The Martian impact <span class="hlt">cratering</span> record</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Strom, Robert G.; Croft, Steven K.; Barlow, Nadine G.</p> <p>1992-01-01</p> <p>A detailed analysis of the Martian impact <span class="hlt">cratering</span> record is presented. The major differences in impact <span class="hlt">crater</span> morphology and morphometry between Mars and the moon and Mercury are argued to be largely the result of subsurface volatiles on Mars. In general, the depth to these volatiles may decrease with increasing latitude in the southern hemisphere, but the base of this layer may be at a more or less constant depth. The Martial crustal dichotomy could have been the result of a very large impact near the end of the accretion of Mars. Monte Carlo computer simulations <span class="hlt">suggest</span> that such an impact was not only possible, but likely. The Martian highland <span class="hlt">cratering</span> record shows a marked paucity of <span class="hlt">craters</span> less than about 30 km in diameter relative to the lunar highlands. This paucity of <span class="hlt">craters</span> was probably the result of the obliteration of <span class="hlt">craters</span> by an early period of intense erosion and deposition by aeolian, fluvial, and glacial processes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017RAA....17...24J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017RAA....17...24J"><span>Physical properties of lunar <span class="hlt">craters</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Joshi, Maitri P.; Bhatt, Kushal P.; Jain, Rajmal</p> <p>2017-02-01</p> <p> diameter are perhaps formed by the impact of meteorites that have very high density but small diameter with a conical shape. Based on analysis of the data selected for the current investigation, we further found that out of 339 <span class="hlt">craters</span>, 100 (29.5%) <span class="hlt">craters</span> exist near the equator, 131 (38.6%) are in the northern hemisphere and 108 (31.80%) are in the southern hemisphere. This <span class="hlt">suggests</span> the Moon is heavily <span class="hlt">cratered</span> at higher latitudes and near the equatorial zone.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20030018897&hterms=geology&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dgeology','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20030018897&hterms=geology&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dgeology"><span>Geology of Lofn <span class="hlt">Crater</span>, Callisto</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Greeley, Ronald; Heiner, Sarah; Klemaszewski, James E.</p> <p>2001-01-01</p> <p>Lofn <span class="hlt">crater</span> is a 180-km-diameter impact structure in the southern <span class="hlt">cratered</span> plains of Callisto and is among the youngest features seen on the surface. The Lofn area was imaged by the Galileo spacecraft at regional-scale resolutions (875 m/pixel), which enable the general geology to be investigated. The morphology of Lofn <span class="hlt">crater</span> <span class="hlt">suggests</span> that (1) it is a class of impact structure intermediate between complex <span class="hlt">craters</span> and palimpsests or (2) it formed by the impact of a projectile which fragmented before reaching the surface, resulting in a shallow <span class="hlt">crater</span> (even for Callisto). The asymmetric pattern of the rim and ejecta deposits <span class="hlt">suggests</span> that the impactor entered at a low angle from the northwest. The albedo and other characteristics of the ejecta deposits from Lofn also provide insight into the properties of the icy lithosphere and subsurface configuration at the time of impact. The "target" for the Lofn impact is inferred to have included layered materials associated with the Adlinda multiring structure northwest of Loh and ejecta deposits from the Heimdall <span class="hlt">crater</span> area to the southeast. The Lofn impact might have penetrated through these materials into a viscous substrate of ductile ice or possibly liquid water. This interpretation is consistent with models of the current interior of Callisto based on geophysical information obtained from the Galileo spacecraft.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1995Metic..30Q.567R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1995Metic..30Q.567R"><span>Meteor <span class="hlt">Crater</span> (Barringer Meteorite <span class="hlt">Crater</span>), Arizona: Summary of Impact Conditions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Roddy, D. J.; Shoemaker, E. M.</p> <p>1995-09-01</p> <p>-field rock and meteorite ejecta parameters, 13) Inferred and estimated cloud-rise and fall-out conditions, 14) Late-stage meteorite falls after impact, 15) Estimated damage effect ranges, 16) Erosion of <span class="hlt">crater</span> and ejecta blanket, 17) New topographic and digital maps of <span class="hlt">crater</span> and ejecta blanket, 18) Other. (<span class="hlt">Suggestions</span> are welcome) This compilation will contain expanded discussions of new data as well as revised interpretations of existing information. For example in Item 1, we <span class="hlt">suggest</span> the impacting body most likely formed during a collision in the main asteroid belt that fragmented the iron-nickel core of an asteroid some 0.5 billion years ago. The fragments remained in space until about 50,000+/-3000 yrs ago, when they were captured by the Earth's gravitational field. In Item 3, the trajectory of the impacting body is interpreted by EMS as traveling north-northwest at a relatively low impact angle. The presence of both shocked meteorite fragments and melt spherules indicate the meteorite had a velocity in the range of about 13 to 20 km/s, probably in the lower part of this range [4]. In Item 4, the coherent meteorite diameter is estimated to have been 45 to 50 m with a mass of 300,000 to 400,000 tons, i.e., large enough to experience less than 1% in both mass ablation and velocity deceleration. During this time, minor flake-off of the meteorite's exterior produced a limited number of smaller fragments that followed the main mass to the impact site but at greatly reduced velocities. In Item 6, we estimate the kinetic energy of impact to be in the range of 20 to 40 Mt depending on the energy coupling functions used and corrections for angle of oblique impact. At impact, terrain conditions were about as we see them today, a gently rolling plain with outcrops of Moenkopi and a meter or so of soil cover. In Item 18, EMS estimates production of a Meteor <span class="hlt">Crater</span>-size event should occur on the continents about every 50,000 years; interestingly, this is the age of Meteor <span class="hlt">Crater</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050167021','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050167021"><span>Alluvial Fans on Dunes in <span class="hlt">Kaiser</span> <span class="hlt">Crater</span> <span class="hlt">Suggest</span> Niveo-Aeolian and Denivation Processes on Mars</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bourke, M. C.</p> <p>2005-01-01</p> <p>On Earth, cold region sand dunes often contain inter-bedded sand, snow, and ice. These mixed deposits of wind-driven snow, sand, silt, vegetal debris, or other detritus have been termed Niveo-aeolian deposits. These deposits are often coupled with features that are due to melting or sublimation of snow, called denivation features. Snow and ice may be incorporated into dunes on Mars in three ways. Diffusion of water vapour into pore spaces is the widely accepted mechanism for the accretion of premafrost ice. Additional mechanisms may include the burial by sand of snow that has fallen on the dune surface or the synchronous transportation and deposition of snow, sand and ice. Both of these mechanisms have been reported for polar dunes on Earth. Niveo-aeolian deposits in polar deserts on Earth have unique morphologies and sedimentary structures that are generally not found in warm desert dunes. Recent analysis of MOC-scale data have found evidence for potential niveo-aeolian and denivation deposits in sand dunes on Mars.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19790055292&hterms=gravity+anomaly&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dgravity%2Banomaly','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19790055292&hterms=gravity+anomaly&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dgravity%2Banomaly"><span>Lunar Bouguer gravity anomalies - Imbrian age <span class="hlt">craters</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Dvorak, J.; Phillips, R. J.</p> <p>1978-01-01</p> <p>The Bouguer gravity of mass anomalies associated with four Imbrian age <span class="hlt">craters</span>, analyzed in the present paper, are found to differ considerably from the values of the mass anomalies associated with some young lunar <span class="hlt">craters</span>. Of the Imbrian age <span class="hlt">craters</span>, only Piccolomini exhibits a negative gravity anomaly (i.e., a low density region) which is characteristic of the young <span class="hlt">craters</span> studied. The Bouguer gravity anomalies are zero for each of the remaining Imbrian age <span class="hlt">craters</span>. Since, Piccolomini is younger, or at least less modified, than the other Imbrian age <span class="hlt">craters</span>, it is <span class="hlt">suggested</span> that the processes responsible for the post-impact modification of the Imbrian age <span class="hlt">craters</span> may also be responsible for removing the negative mass anomalies initially associated with these features.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..14.5200D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..14.5200D"><span>Experimental impact <span class="hlt">crater</span> morphology</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dufresne, A.; Poelchau, M. H.; Hoerth, T.; Schaefer, F.; Thoma, K.; Deutsch, A.; Kenkmann, T.</p> <p>2012-04-01</p> <p> failure planes ("terraces") in the outer, near-surface region of the <span class="hlt">crater</span>. We <span class="hlt">suggest</span> that these differences are due to a reduction in tensile strength in pore-space saturated sandstone. Linking morphological characteristics to impact conditions might provide a tool to help reconstruct impact conditions in small, more strength- than gravity-dominated impact <span class="hlt">craters</span> in nature. Findings in small-scale experiments can aid the identification of particular structures in the field, such as spallation induced uplift of strata outside of the <span class="hlt">crater</span> margins.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27342446','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27342446"><span>Investing in Obesity Treatment: <span class="hlt">Kaiser</span> Permanente's Approach to Chronic Disease Management.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Tsai, Adam G; Histon, Trina; Donahoo, W Troy; Hashmi, Shahid; Murali, Sameer; Latare, Peggy; Oliver, Lajune; Slovis, Jennifer; Grall, Sarah; Fisher, David; Solomon, Loel</p> <p>2016-09-01</p> <p><span class="hlt">Kaiser</span> Permanente, an integrated health care delivery system in the USA, takes a "whole systems" approach to the chronic disease of obesity that begins with efforts to prevent it by modifying the environment in communities and schools. Aggressive case-finding and substantial investment in intensive lifestyle modification programs target individuals at high risk of diabetes and other weight-related conditions. <span class="hlt">Kaiser</span> Permanente regions are increasingly standardizing their approach when patients with obesity require treatment intensification using medically supervised diets, prescription medication to treat obesity, or weight loss surgery.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA21753.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA21753.html"><span>Juling and Kupalo <span class="hlt">Craters</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2017-08-17</p> <p>This region on Ceres, located in the vicinity of Toharu <span class="hlt">Crater</span>, presents two small <span class="hlt">craters</span>: Juling at top (12 miles, 20 kilometers in diameter) and Kupalo at bottom (16 miles, 26 kilometers in diameter). Both <span class="hlt">craters</span> are relatively young, as indicated by their sharp rims. These features are located at about the same latitude (about 38 degrees south) as Tawals <span class="hlt">Crater</span> and show similar <span class="hlt">crater</span> shapes and rugged terrain. These features may reflect the presence of ice below the surface. Subtle bright features can be distinguished in places. These likely were excavated by small impacts and landslides along the slopes of the <span class="hlt">crater</span> rims. This <span class="hlt">suggests</span> that a different type of material, likely rich in salts, is present in the shallow subsurface. Juling is named after the Sakai/Orang Asli spirit of the crops from Malaysia, and Kupalo gets its name from the Russian god of vegetation and of the harvest. NASA's Dawn spacecraft acquired this picture on August 24, 2016. The image was taken during Dawn's extended mission, from its low altitude mapping orbit at about 240 miles (385 kilometers) above the surface. The center coordinates of this image are 38 degrees south latitude, 165 degrees east longitude. https://photojournal.jpl.nasa.gov/catalog/PIA21753</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017M%26PS...52..493H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017M%26PS...52..493H"><span>Martian <span class="hlt">cratering</span> 11. Utilizing decameter scale <span class="hlt">crater</span> populations to study Martian history</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hartmann, W. K.; Daubar, I. J.</p> <p>2017-03-01</p> <p>New information has been obtained in recent years regarding formation rates and the production size-frequency distribution (PSFD) of decameter-scale primary Martian <span class="hlt">craters</span> formed during recent orbiter missions. Here we compare the PSFD of the currently forming small primaries (P) with new data on the PSFD of the total small <span class="hlt">crater</span> population that includes primaries and field secondaries (P + fS), which represents an average over longer time periods. The two data sets, if used in a combined manner, have extraordinary potential for clarifying not only the evolutionary history and resurfacing episodes of small Martian geological formations (as small as one or few km2) but also possible episodes of recent climatic change. In response to recent discussions of statistical methodologies, we point out that <span class="hlt">crater</span> counts do not produce idealized statistics, and that inherent uncertainties limit improvements that can be made by more sophisticated statistical analyses. We propose three mutually supportive procedures for interpreting <span class="hlt">crater</span> counts of small <span class="hlt">craters</span> in this context. Applications of these procedures support <span class="hlt">suggestions</span> that topographic features in upper meters of mid-latitude ice-rich areas date only from the last few periods of extreme Martian obliquity, and associated predicted climate excursions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19830035018&hterms=clay+viscosity&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dclay%2Bviscosity','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19830035018&hterms=clay+viscosity&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dclay%2Bviscosity"><span>Experimental simulation of impact <span class="hlt">cratering</span> on icy satellites</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Greeley, R.; Fink, J. H.; Gault, D. E.; Guest, J. E.</p> <p>1982-01-01</p> <p><span class="hlt">Cratering</span> processes on icy satellites were simulated in a series of 102 laboratory impact experiments involving a wide range of target materials. For impacts into homogeneous clay slurries with impact energies ranging from five million to ten billion ergs, target yield strengths ranged from 100 to 38 Pa, and apparent viscosities ranged from 8 to 200 Pa s. Bowl-shaped <span class="hlt">craters</span>, flat-floored <span class="hlt">craters</span>, central peak <span class="hlt">craters</span> with high or little relief, and <span class="hlt">craters</span> with no relief were observed. <span class="hlt">Crater</span> diameters increased steadily as energies were raised. A similar sequence was seen for experiment in which impact energy was held constant but target viscosity and strength progressively decreases. The experiments <span class="hlt">suggest</span> that the physical properties of the target media relative to the gravitationally induced stresses determined the final <span class="hlt">crater</span> morphology. <span class="hlt">Crater</span> palimpsests could form by prompt collapse of large central peak <span class="hlt">craters</span> formed in low target strength materials. Ages estimated from <span class="hlt">crater</span> size-frequency distributions that include these large <span class="hlt">craters</span> may give values that are too high.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA04032&hterms=ports+World&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dports%2BWorld','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA04032&hterms=ports+World&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dports%2BWorld"><span>Palos <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2002-01-01</p> <p><p/> [figure removed for brevity, see original site] <p/>Palos <span class="hlt">Crater</span> has been <span class="hlt">suggested</span> as a future landing site for Mars Missions. This <span class="hlt">crater</span> has a channel called Tinto Vallis, which enters from the south. This site was <span class="hlt">suggested</span> as a landing site because it may contain lake deposits. Palos <span class="hlt">Crater</span> is named in honor of the port city in Spain from which Christopher Columbus sailed on his way to the New World in August of 1492. The floor of Palos <span class="hlt">Crater</span> appears to be layered in places providing further evidence that this site may in fact have been the location of an ancient lake.<p/>Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.<p/>NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.<p/></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70171435','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70171435"><span>Recharge from a subsidence <span class="hlt">crater</span> at the Nevada test site</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Wilson, G. V.; Ely, D.M.; Hokett, S. L.; Gillespie, D. R.</p> <p>2000-01-01</p> <p>Current recharge through the alluvial fans of the Nevada Test Site (NTS) is considered to be negligible, but the impact of more than 400 nuclear subsidence <span class="hlt">craters</span> on recharge is uncertain. Many of the <span class="hlt">craters</span> contain a playa region, but the impact of these playas has not been addressed. It was hypothesized that a <span class="hlt">crater</span> playa would focus infiltration through the surrounding coarser-grained material, thereby increasing recharge. <span class="hlt">Crater</span> U5a was selected because it represented a worst case for runoff into <span class="hlt">craters</span>. A borehole was instrumented for neutron logging beneath the playa center and immediately outside the <span class="hlt">crater</span>. Physical and hydraulic properties were measured along a transect in the <span class="hlt">crater</span> and outside the <span class="hlt">crater</span>. Particle-size analysis of the 14.6 m of sediment in the <span class="hlt">crater</span> and morphological features of the <span class="hlt">crater</span> <span class="hlt">suggest</span> that a large ponding event of ≈63000 m3 had occurred since <span class="hlt">crater</span> formation. Water flow simulations with HYDRUS-2D, which were corroborated by the measured water contents, <span class="hlt">suggest</span> that the wetting front advanced initially by as much as 30 m yr−1 with a recharge rate 32 yr after the event of 2.5 m yr−1Simulations based on the measured properties of the sediments <span class="hlt">suggest</span> that infiltration will occur preferentially around the playa perimeter. However, these sediments were shown to effectively restrict future recharge by storing water until removal by evapotranspiration (ET). This work demonstrated that subsidence <span class="hlt">craters</span> may be self-healing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.P23C2741W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.P23C2741W"><span>Using THEMIS thermal infrared observations of rays from Corinto <span class="hlt">crater</span> to study secondary <span class="hlt">crater</span> formation on Mars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Williams, J. P.</p> <p>2017-12-01</p> <p>Corinto <span class="hlt">crater</span> (16.95°N, 141.72°E), a 13.8 km diameter <span class="hlt">crater</span> in Elysium Planitia, displays dramatic rays in Mars Odyssey's Thermal Emission Imaging System (THEMIS) nighttime infrared imagery where high concentrations of secondary <span class="hlt">craters</span> have altered the thermophysical properties of the martian surface. The THEMIS observations provide a record of secondary <span class="hlt">crater</span> formation in the region and ray segments are identified up to 2000 km ( 145 <span class="hlt">crater</span> radii) distance [1][2]. Secondary <span class="hlt">craters</span> are likely to have the largest influence on model surfaces ages between 0.1 to a few Myr as there is the potential for one or two sizeable <span class="hlt">craters</span> to project secondary <span class="hlt">craters</span> onto those surfaces and thus alter the <span class="hlt">crater</span> size-frequency distribution (CSFD) with an instantaneous spike in <span class="hlt">crater</span> production [3]. Corinto <span class="hlt">crater</span> is estimated to be less than a few Ma [4] placing the formation of its secondaries within this formative time period. Secondary <span class="hlt">craters</span> superposed on relatively young impact <span class="hlt">craters</span> that predate Corinto provide observations of the secondary <span class="hlt">crater</span> populations. <span class="hlt">Crater</span> counts at 520 and 660 km distance from Corinto (38 and 48 <span class="hlt">crater</span> radii respectively), were conducted. Higher <span class="hlt">crater</span> densities were observed within ray segments, however secondary <span class="hlt">craters</span> still influenced the CSFD where ray segments were not apparent, resulting in steepening in the CSFD. Randomness analysis confirms an increase in clustering as diameters decrease <span class="hlt">suggesting</span> an increasing fraction of secondary <span class="hlt">craters</span> at smaller diameters, both within the ray and outside. The counts demonstrate that even at nearly 50 <span class="hlt">crater</span> radii, Corinto secondaries still influence the observed CSFD, even outside of any obvious rays. <span class="hlt">Crater</span> populations used to derive model ages on many geologically young regions on Mars, such as glacial and periglacial landforms related to obliquity excursions that occur on 106 - 107 yr cycles, should be used cautiously and analyzed for any evidence, either morphologic or</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4867502','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4867502"><span>High-pressure minerals in eucrite <span class="hlt">suggest</span> a small source <span class="hlt">crater</span> on Vesta</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Pang, Run-Lian; Zhang, Ai-Cheng; Wang, Shu-Zhou; Wang, Ru-Cheng; Yurimoto, Hisayoshi</p> <p>2016-01-01</p> <p>High-pressure minerals in meteorites are important records of shock events that have affected the surfaces of planets and asteroids. A widespread distribution of impact <span class="hlt">craters</span> has been observed on the Vestan surface. However, very few high-pressure minerals have been discovered in Howardite-Eucrite-Diogenite (HED) meteorites. Here we present the first evidence of tissintite, vacancy-rich clinopyroxene, and super-silicic garnet in the eucrite Northwest Africa (NWA) 8003. Combined with coesite and stishovite, the presence of these high-pressure minerals and their chemical compositions reveal that solidification of melt veins in NWA 8003 began at a pressure of >~10 GPa and ceased when the pressure dropped to <~8.5 GPa. The shock temperature in the melt veins exceeded 1900 °C. Simulation results show that shock events that create impact <span class="hlt">craters</span> of ~3 km in diameter (subject to a factor of 2 uncertainty) are associated with sufficiently high pressures to account for the occurrence of the high-pressure minerals observed in NWA 8003. This indicates that HED meteorites containing similar high-pressure minerals should be observed more frequently than previously thought. PMID:27181381</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20000113023&hterms=sedimentation+channels&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dsedimentation%2Bchannels','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20000113023&hterms=sedimentation+channels&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dsedimentation%2Bchannels"><span>Gale <span class="hlt">Crater</span>: An Amazonian Impact <span class="hlt">Crater</span> Lake at the Plateau/Plain Boundary</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cabrol, N. A.; Grin, E. A.</p> <p>1998-01-01</p> <p> sedimentary material that can originate both from drainage of the regional subsurface aquifer, and/or from surface flood. The central deposit shows three main levels: (a) the current <span class="hlt">crater</span> floor (north of Gale), (b) an ancient level about 200 rn higher (south of Gale), and (c) the massive terraced deposits. A <span class="hlt">crater</span> statistics on the 15,400 kM2 area of the <span class="hlt">crater</span> floor and deposit [3,41 gave: 259+/-112.4 <span class="hlt">craters</span>, most of them partly embayed in the sedimentary deposit, and all inferior to 5-km diameter. For superimposed <span class="hlt">crater</span> population only, the result is 194+/-112. The deduced relative ages ranges from Early to Middle Amazonian. The population of <span class="hlt">craters</span> are comparable for the three levels, implying that the last sedimentation/erosion episode on Gale was recent and affected the whole <span class="hlt">crater</span>. The streamlined morphology of the border of the deposit, the layering, the channels, and the terraces are compatible with a significant fluvio-lacustrine history of the site. Multiple levels may <span class="hlt">suggest</span> different episodes, but the common statistical age of the three levels shows that the last episode involved the whole <span class="hlt">crater</span>. The origin of the lake water in Gale may have varied in time. Three major contributions have been proposed: (a) the drainage of the regional underground aquifer by Gale <span class="hlt">crater</span> over an area of 110-km radius around the <span class="hlt">crater</span> which would have provided approximately 1,600 cubic km of water, (b), surface drainage entering Gale by the south and north rims. In the south, a 250-km long system originates in the <span class="hlt">cratered</span> uplands in a Noachian <span class="hlt">crater</span> material plain (Nc), and crosses Hesperian and Amazonian <span class="hlt">crater</span> material plains (AHc) northward [1]. Several fluvial systems originate in the Aeolis Mensae, east of Gale. They may had two functions in time: to recharge, the underground aquifer in the region of Gale, and to supply surface water in the <span class="hlt">crater</span> by overspilling the northern rim, and (c) surface floods that originated from the rising of the water level in the</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_1");'>1</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li class="active"><span>3</span></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_3 --> <div id="page_4" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li class="active"><span>4</span></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="61"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006DPS....38.3015B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006DPS....38.3015B"><span>Interior and Ejecta Morphologies of Impact <span class="hlt">Craters</span> on Ganymede</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Barlow, Nadine G.; Klaybor, K.; Katz-Wigmore, J.</p> <p>2006-09-01</p> <p>We are utilizing Galileo SSI imagery of Ganymede to classify impact <span class="hlt">crater</span> interior and ejecta morphologies. Although we are in the early stages of compiling our Catalog of Impact <span class="hlt">Craters</span> on Ganymede, some interesting trends are beginning to emerge. Few <span class="hlt">craters</span> display obvious ejecta morphologies, but 68 <span class="hlt">craters</span> are classified as single layer ejecta and 3 as double layer ejecta. We see no obvious correlation of layered ejecta morphologies with terrain or latitude. All layered ejecta <span class="hlt">craters</span> have diameters between 10 and 40 km. Sinuosity ("lobateness") and ejecta extent ("ejecta mobility ratio") of Ganymede layered ejecta <span class="hlt">craters</span> are lower than for martian layered ejecta <span class="hlt">craters</span>. This <span class="hlt">suggests</span> less mobility of ejecta materials on Ganymede, perhaps due to the colder temperatures. Interior structures being investigated include central domes, peaks, and pits. 57 dome <span class="hlt">craters</span>, 212 central peak <span class="hlt">craters</span>, and 313 central pit <span class="hlt">craters</span> have been identified. Central domes occur in 50-100 km diameter <span class="hlt">craters</span> while peaks are found in <span class="hlt">craters</span> between 20 and 50 km and central pit <span class="hlt">craters</span> range between 29 and 74 km in diameter. The Galileo Regio region displays higher concentrations of central dome and central pit <span class="hlt">craters</span> than other regions we have investigated. 67% of central pit <span class="hlt">craters</span> studied to date are small pits, where the ratio of pit diameter to <span class="hlt">crater</span> diameter is <0.2. <span class="hlt">Craters</span> containing the three interior structures preferentially occur on darker terrain units, <span class="hlt">suggesting</span> that an ice-silicate composition is more conducive to interior feature formation than pure ice alone. Results of this study have important implications not only for the formation of specific interior and ejecta morphologies on Ganymede but also for analogous features associated with Martian impact <span class="hlt">craters</span>. This research is funded through NASA Outer Planets Research Program Award #NNG05G116G to N. G. Barlow.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22136537-large-crater-asteroid-steins-really-impact-crater','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22136537-large-crater-asteroid-steins-really-impact-crater"><span>IS THE LARGE <span class="hlt">CRATER</span> ON THE ASTEROID (2867) STEINS REALLY AN IMPACT <span class="hlt">CRATER</span>?</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Morris, A. J. W.; Price, M. C.; Burchell, M. J., E-mail: m.j.burchell@kent.ac.uk</p> <p></p> <p>The large <span class="hlt">crater</span> on the asteroid (2867) Steins attracted much attention when it was first observed by the Rosetta spacecraft in 2008. Initially, it was widely thought to be unusually large compared to the size of the asteroid. It was quickly realized that this was not the case and there are other examples of similar (or larger) <span class="hlt">craters</span> on small bodies in the same size range; however, it is still widely accepted that it is a <span class="hlt">crater</span> arising from an impact onto the body which occurred after its formation. The asteroid (2867) Steins also has an equatorial bulge, usually consideredmore » to have arisen from redistribution of mass due to spin-up of the body caused by the YORP effect. Conversely, it is shown here that, based on catastrophic disruption experiments in laboratory impact studies, a similarly shaped body to the asteroid Steins can arise from the break-up of a parent in a catastrophic disruption event; this includes the presence of a large <span class="hlt">crater</span>-like feature and equatorial bulge. This <span class="hlt">suggests</span> that the large <span class="hlt">crater</span>-like feature on Steins may not be a <span class="hlt">crater</span> from a subsequent impact, but may have arisen directly from the fragmentation process of a larger, catastrophically disrupted parent.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ISPAr62W1...23B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ISPAr62W1...23B"><span>Small <span class="hlt">Craters</span> and Their Diagnostic Potential</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bugiolacchi, R.</p> <p>2017-07-01</p> <p>I analysed and compared the size-frequency distributions of <span class="hlt">craters</span> in the Apollo 17 landing region, comprising of six mare terrains with varying morphologies and <span class="hlt">cratering</span> characteristics, along with three other regions allegedly affected by the same secondary event (Tycho secondary surge). I propose that for the smaller <span class="hlt">crater</span> sizes (in this work 9-30 m), a] an exponential curve of power -0.18D can approximate Nkm-2 <span class="hlt">crater</span> densities in a regime of equilibrium, while b] a power function D-3 closely describes the factorised representation of <span class="hlt">craters</span> by size (1 m). The saturation level within the Central Area <span class="hlt">suggests</span> that c] either the modelled rates of <span class="hlt">crater</span> erosion on the Moon should be revised, or that the Tycho event occurred much earlier in time than the current estimate. We propose that d] the size-frequency distribution of small secondary <span class="hlt">craters</span> may bear the signature (in terms of size-frequency distribution of debris/surge) of the source impact and that this observation should be tested further.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.2240K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.2240K"><span>Why do complex impact <span class="hlt">craters</span> have elevated <span class="hlt">crater</span> rims?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kenkmann, Thomas; Sturm, Sebastian; Krueger, Tim</p> <p>2014-05-01</p> <p>Most of the complex impact <span class="hlt">craters</span> on the Moon and on Mars have elevated <span class="hlt">crater</span> rims like their simple counterparts. The raised rim of simple <span class="hlt">craters</span> is the result of (i) the deposition of a coherent proximal ejecta blanket at the edge of the transient cavity (overturned flap) and (ii) a structural uplift of the pre-impact surface near the transient cavity rim during the excavation stage of <span class="hlt">cratering</span> [1]. The latter occurs either by plastic thickening or localized buckling of target rocks, as well as by the emplacement of interthrust wedges [2] or by the injection of dike material. Ejecta and the structural uplift contribute equally to the total elevation of simple <span class="hlt">crater</span> rims. The cause of elevated <span class="hlt">crater</span> rims of large complex <span class="hlt">craters</span> [3] is less obvious, but still, the rim height scales with the final <span class="hlt">crater</span> diameter. Depending on <span class="hlt">crater</span> size, gravity, and target rheology, the final <span class="hlt">crater</span> rim of complex <span class="hlt">craters</span> can be situated up to 1.5-2.0 transient <span class="hlt">crater</span> radii distance from the <span class="hlt">crater</span> center. Here the thickness of the ejecta blanket is only a fraction of that occurring at the rim of simple <span class="hlt">craters</span>, e.g. [4], and thus cannot account for a strong elevation. Likewise, plastic thickening including dike injection of the underlying target may not play a significant role at this distance any more. We started to systematically investigate the structural uplift and ejecta thickness along the rim of complex impact <span class="hlt">craters</span> to understand the cause of their elevation. Our studies of two lunar <span class="hlt">craters</span> (Bessel, 16 km diameter and Euler, 28 km diameter) [5] and one unnamed complex martian <span class="hlt">crater</span> (16 km diameter) [6] showed that the structural uplift at the final <span class="hlt">crater</span> rim makes 56-67% of the total rim elevation while the ejecta thickness contributes 33-44%. Thus with increasing distance from the transient cavity rim, the structural uplift seems to dominate. As dike injection and plastic thickening are unlikely at such a distance from the transient cavity, we propose that</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018Geomo.306..128X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018Geomo.306..128X"><span>Hailar <span class="hlt">crater</span> - A possible impact structure in Inner Mongolia, China</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xiao, Zhiyong; Chen, Zhaoxu; Pu, Jiang; Xiao, Xiao; Wang, Yichen; Huang, Jun</p> <p>2018-04-01</p> <p>Hailar <span class="hlt">crater</span>, a probable impact structure, is a circular depression about 300 m diameter in Inner Mongolia, northeast China. With broad elevated rims, the present rim-to-floor depth is 8-20 m. Regional geological background and geomorphological comparison <span class="hlt">suggest</span> that this feature is likely not formed by surface processes such as salt diapir, karst, aeolian, glacial, or volcanic activity. Its unique occurrence in this region and well-preserved morphology are most consistent with it being a Cenozoic impact <span class="hlt">crater</span>. Two field expeditions in 2016 and 2017 investigated the origin of this structure, recognizing that (1) no additional <span class="hlt">craters</span> were identified around Hailar <span class="hlt">crater</span> in the centimeter-scale digital topography models that were constructed using a drone imaging system and stereo photogrammetry; (2) no bedrock exposures are visible within or adjacent to the <span class="hlt">crater</span> because of thick regolith coverage, and only small pieces of angular unconsolidated rocks are present on the <span class="hlt">crater</span> wall and the gently-sloped <span class="hlt">crater</span> rim, <span class="hlt">suggesting</span> recent energetic formation of the <span class="hlt">crater</span>; (3) most samples collected from the <span class="hlt">crater</span> have identical lithology and petrographic characteristics with the background terrain, but some <span class="hlt">crater</span> samples contain more abundant clasts and silicate hydrothermal veins, indicating that rocks from depths have been exposed by the <span class="hlt">crater</span>; (4) no shock metamorphic features were found in the samples after thin section examinations; and (5) a systematic sample survey and iron detector scan within and outside of the <span class="hlt">crater</span> found no iron-rich meteorites larger than 2 cm in size in a depth of 30 cm. Although no conclusive evidence for an impact origin is found yet, Hailar <span class="hlt">crater</span> was most likely formed by an impact based on its unique occurrence and comparative geomorphologic study. We <span class="hlt">suggest</span> that drilling in the <span class="hlt">crater</span> center is required to verify the impact origin, where hypothesized melt-bearing impactites may be encountered.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009LPI....40.1379K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009LPI....40.1379K"><span>Ring-Mold <span class="hlt">Craters</span> on Lineated Valley Fill, Lobate Debris Aprons, and Concentric <span class="hlt">Crater</span> Fill on Mars: Implications for Near-Surface Structure, Composition, and Age.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kress, A.; Head, J. W.</p> <p>2009-03-01</p> <p>Analysis of ring-mold <span class="hlt">crater</span> populations on lineated valley fill, lobate debris aprons, and concentric <span class="hlt">crater</span> fill on Mars and of ice-impact experiments <span class="hlt">suggest</span> <span class="hlt">crater</span>-count-derived ages may be erroneously old.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26684505','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26684505"><span>Weathering Profiles in Phosphorus-Rich Rocks at Gusev <span class="hlt">Crater</span>, Mars, <span class="hlt">Suggest</span> Dissolution of Phosphate Minerals into Potentially Habitable Near-Neutral Waters.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Adcock, Christopher T; Hausrath, Elisabeth M</p> <p>2015-12-01</p> <p>Abundant evidence indicates that significant surface and near-surface liquid water has existed on Mars in the past. Evaluating the potential for habitable environments on Mars requires an understanding of the chemical and physical conditions that prevailed in such aqueous environments. Among the geological features that may hold evidence of past environmental conditions on Mars are weathering profiles, such as those in the phosphorus-rich Wishstone-class rocks in Gusev <span class="hlt">Crater</span>. The weathering profiles in these rocks indicate that a Ca-phosphate mineral has been lost during past aqueous interactions. The high phosphorus content of these rocks and potential release of phosphorus during aqueous interactions also make them of astrobiological interest, as phosphorus is among the elements required for all known life. In this work, we used Mars mission data, laboratory-derived kinetic and thermodynamic data, and data from terrestrial analogues, including phosphorus-rich basalts from Idaho, to model a conceptualized Wishstone-class rock using the reactive transport code CrunchFlow. Modeling results most consistent with the weathering profiles in Wishstone-class rocks <span class="hlt">suggest</span> a combination of chemical and physical erosion and past aqueous interactions with near-neutral waters. The modeling results also indicate that multiple Ca-phosphate minerals are likely in Wishstone-class rocks, consistent with observations of martian meteorites. These findings <span class="hlt">suggest</span> that Gusev <span class="hlt">Crater</span> experienced a near-neutral phosphate-bearing aqueous environment that may have been conducive to life on Mars in the past. Mars-Gusev <span class="hlt">Crater</span>-Wishstone-Reactive transport modeling-CrunchFlow-Aqueous interactions-Neutral pH-Habitability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010Icar..207..248S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010Icar..207..248S"><span>The formation of floor-fractured <span class="hlt">craters</span> in Xanthe Terra</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sato, Hiroyuki; Kurita, Kei; Baratoux, David</p> <p>2010-05-01</p> <p>Floor-fractured <span class="hlt">craters</span> (FFC) are a peculiar form of degradation of impact <span class="hlt">craters</span> defined by the presence of crevice networks and mesas affecting <span class="hlt">crater</span> floors. They are preferentially distributed near chaotic terrains and outflow channels. The scope of this paper is to present a detailed systematic analysis of FFC at Xanthe Terra. FFC morphologies in this region are classified into five types making a picture of different stages of the same degradation process. FFC are geographically intermixed with un-fractured normal <span class="hlt">craters</span> (non-FFC). Young <span class="hlt">craters</span> are less prone to show this type of degradation, as <span class="hlt">suggested</span> by fresh ejecta layer with preserved <span class="hlt">crater</span> floor. Size distributions of FFC and non-FFC indicate that larger <span class="hlt">craters</span> are preferentially fractured. Careful examinations of the <span class="hlt">crater</span> floor elevations reveal that the crevices often extend deeper than the original <span class="hlt">crater</span> cavity. Furthermore, an onset depth for the formation of FFC is evidenced from the difference of spatial distributions between FFC and non-FFC. Roof-collapsed depressions observed in the same region have been also documented and their characteristics <span class="hlt">suggest</span> the removal of subsurface material at depth from about 1200 to 4000 m. These observations taken together <span class="hlt">suggest</span> a subsurface zone of volume deficit at depth from 1 to 2 km down to several kilometers responsible for FFC formation. Then a scenario of FFC formations is presented in the context of groundwater discharge events at the late Hesperian. This scenario involves two key processes, Earth fissuring and piping erosion, known to occur with rapid groundwater migrations on Earth.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19740047045&hterms=genetic+data+analysis&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dgenetic%2Bdata%2Banalysis','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19740047045&hterms=genetic+data+analysis&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dgenetic%2Bdata%2Banalysis"><span>Multivariate analyses of <span class="hlt">crater</span> parameters and the classification of <span class="hlt">craters</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Siegal, B. S.; Griffiths, J. C.</p> <p>1974-01-01</p> <p>Multivariate analyses were performed on certain linear dimensions of six genetic types of <span class="hlt">craters</span>. A total of 320 <span class="hlt">craters</span>, consisting of laboratory fluidization <span class="hlt">craters</span>, <span class="hlt">craters</span> formed by chemical and nuclear explosives, terrestrial maars and other volcanic <span class="hlt">craters</span>, and terrestrial meteorite impact <span class="hlt">craters</span>, authenticated and probable, were analyzed in the first data set in terms of their mean rim crest diameter, mean interior relief, rim height, and mean exterior rim width. The second data set contained an additional 91 terrestrial <span class="hlt">craters</span> of which 19 were of experimental percussive impact and 28 of volcanic collapse origin, and which was analyzed in terms of mean rim crest diameter, mean interior relief, and rim height. Principal component analyses were performed on the six genetic types of <span class="hlt">craters</span>. Ninety per cent of the variation in the variables can be accounted for by two components. Ninety-nine per cent of the variation in the <span class="hlt">craters</span> formed by chemical and nuclear explosives is explained by the first component alone.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19720046652&hterms=2441&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3D%2526%25232441','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19720046652&hterms=2441&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3D%2526%25232441"><span>Regional variations in degradation and density of Martian <span class="hlt">craters</span>.</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mcgill, G. E.; Wise, D. U.</p> <p>1972-01-01</p> <p>Martian <span class="hlt">craters</span> visible on Mariner 6 and 7 imagery show a spectrum of topographic types from very fresh to highly degraded. A method of numerical scoring of rim, wall, and floor is proposed to yield a degradation number to classify each <span class="hlt">crater</span>. Plots of degradation class vs density of large <span class="hlt">craters</span> are similar for all four regions studied, whereas similar plots for small <span class="hlt">craters</span> show marked differences between regions. The data <span class="hlt">suggest</span> general continuity of <span class="hlt">crater</span> formation and degradation, along with locally sporadic formation and/or degradation of the smallest <span class="hlt">craters</span> classified. Deucalionis Regio, with an excess of fresh, small <span class="hlt">craters</span>, experienced an episode of small <span class="hlt">crater</span> formation (or nondegradation) most recently; Margaritifer Sinus was similarly disturbed at some more remote time. Meridiani Sinus and Hellespontus-Noachis show little or no sign of excess fresh, small <span class="hlt">craters</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA01516&hterms=gardening&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dgardening','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA01516&hterms=gardening&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dgardening"><span><span class="hlt">Cratering</span> and Grooved Terrain on Ganymede</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1979-01-01</p> <p>This color picture as acquired by Voyager 1 during its approach to Ganymede on Monday afternoon (the 5th of March). At ranges between about 230 to 250 thousand km. The image shows detail on the surface with a resolution of four and a half km. This picture is just south of PIA001515 (P21161) and shows more <span class="hlt">craters</span>. It also shows the two distinctive types of terrain found by Voyager, the darker ungrooved regions and the lighter areas which show the grooves or fractures in abundance. The most striking features are the bright ray <span class="hlt">craters</span> which havE a distinctly 'bluer' color appearing white against the redder background. Ganymede's surface is known to contain large amounts of surface ice and it appears that these relatively young <span class="hlt">craters</span> have spread bright fresh ice materials over the surface. Likewise, the lighter color and reflectivity of the grooved areas <span class="hlt">suggests</span> that here too, there is cleaner ice. We see ray <span class="hlt">craters</span> with all sizes of ray patterns, ranging from extensive systems of the <span class="hlt">crater</span> in the northern part of this picture, which has rays at least 300-500 kilometers long, down to <span class="hlt">craters</span> which have only faint remnants of bright ejecta patterns. This variation <span class="hlt">suggests</span> that, as on the Moon, there are processes which act to darken ray material, probably 'gardening' by micrometeoroid impact. JPL manages and controls the Voyager project for NASA's Office of Space Science.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29771861','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29771861"><span>Vincristine-associated Neuropathy With Antifungal Usage: A <span class="hlt">Kaiser</span> Northern California Experience.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Nikanjam, Mina; Sun, Aida; Albers, Mark; Mangalindin, Kristine; Song, Eyun; Vempaty, Hyma; Sam, Danny; Capparelli, Edmund V</p> <p>2018-05-16</p> <p>The dose-limiting toxicity for vincristine is peripheral neuropathy which can be potentiated with concurrent usage of azole antifungals. The current retrospective study assessed the incidence of concurrent vincristine and azole antifungal usage to determine if it led to increased neurotoxicity for the <span class="hlt">Kaiser</span> Northern California pediatric acute lymphoblastic leukemia (ALL) and Hodgkin lymphoma patient population. Data were obtained from the electronic medical record (2007 to 2014). In total, 130 subjects received at least one dose of vincristine for ALL or Hodgkin lymphoma (median age 9, 88% ALL, 58% male, 47% Caucasian). Thirty one percent of patients received concurrent antifungal usage (fluconazole, 78%; voriconazole, 10%; fluconazole/voriconazole, 12%); however, concurrent antifungal usage accounted for <15% of vincristine doses. Grade 2 or greater neuropathy occurred in 51% of patients; grade 3 neuropathy was present in 8% of patients. No difference in the incidence of grade 2 or greater neuropathy was observed with the concurrent use of antifungal therapy (P=0.35), sex (P=0.59), type of cancer (P=0.41), ethnicity (P=0.29), or age (P=0.39), but was higher with increasing amount of vincristine doses (P=0.004). These results <span class="hlt">suggest</span> that concurrent azole antifungal usage with vincristine for patients with ALL and Hodgkin lymphoma was low in the <span class="hlt">Kaiser</span> Northern California population and limited usage as needed may be reasonable and safe.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016cosp...41E1981V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016cosp...41E1981V"><span>Identification of <span class="hlt">craters</span> on Moon using <span class="hlt">Crater</span> Density Parameter</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vandana, Vandana</p> <p>2016-07-01</p> <p>Lunar <span class="hlt">craters</span> are the most noticeable features on the face of the moon. They take up 40.96% of the lunar surface and, their accumulated area is approximately three times as much as the lunar surface area. There are many myths about the moon. Some says moon is made of cheese. The moon and the sun chase each other across the sky etc. but scientifically the moon are closest and are only natural satellite of earth. The orbit plane of the moon is tilted by 5° and orbit period around the earth is 27-3 days. There are two eclipse i.e. lunar eclipse and solar eclipse which always comes in pair. Moon surface has 3 parts i.e. highland, Maria, and <span class="hlt">crater</span>. For <span class="hlt">crater</span> diagnostic <span class="hlt">crater</span> density parameter is one of the means for measuring distance can be easily identity the density between two <span class="hlt">craters</span>. <span class="hlt">Crater</span> size frequency distribution (CSFD) is being computed for lunar surface using TMC and MiniSAR image data and hence, also the age for the selected test sites of mars is also determined. The GIS-based program uses the density and orientation of individual <span class="hlt">craters</span> within LCCs (as vector points) to identify potential source <span class="hlt">craters</span> through a series of cluster identification and ejection modeling analyses. JMars software is also recommended and operated only the time when connected with server but work can be done in Arc GIS with the help of Arc Objects and Model Builder. The study plays a vital role to determine the lunar surface based on <span class="hlt">crater</span> (shape, size and density) and exploring affected <span class="hlt">craters</span> on the basis of height, weight and velocity. Keywords: Moon; <span class="hlt">Crater</span>; MiniSAR.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19780033374&hterms=Two+planets+moon&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DTwo%2Bplanets%2Bmoon.','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19780033374&hterms=Two+planets+moon&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DTwo%2Bplanets%2Bmoon."><span>Moon-Mercury - Relative preservation states of secondary <span class="hlt">craters</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Scott, D. H.</p> <p>1977-01-01</p> <p>Geologic studies including mapping of the Kuiper quadrangle of Mercury <span class="hlt">suggest</span> that secondary <span class="hlt">craters</span> are much better preserved than those on the moon. Factors which may account for the apparent differences between lunar and Mercurian secondary <span class="hlt">crater</span> morphology include: (1) the rapid isostatic adjustment of the parent <span class="hlt">crater</span>, (2) different impact fluxes of the two planets, (3) the greater concentration of Mercurian secondaries around impact areas, and (4) differences in <span class="hlt">crater</span> ejection velocities. It has been shown that the ejection velocities on Mercury are about 50% greater than those on the moon at equivalent ranges. This may account for morphologically enhanced secondary <span class="hlt">craters</span>, and may explain their better preservation with time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoRL..43.7424X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoRL..43.7424X"><span>The self-secondary <span class="hlt">crater</span> population of the Hokusai <span class="hlt">crater</span> on Mercury</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xiao, Zhiyong; Prieur, Nils C.; Werner, Stephanie C.</p> <p>2016-07-01</p> <p>Whether or not self-secondaries dominate small <span class="hlt">crater</span> populations on continuous ejecta deposits and floors of fresh impact <span class="hlt">craters</span> has long been a controversy. This issue potentially affects the age determination technique using <span class="hlt">crater</span> statistics. Here the self-secondary <span class="hlt">crater</span> population on the continuous ejecta deposits of the Hokusai <span class="hlt">crater</span> on Mercury is unambiguously recognized. Superposition relationships show that this population was emplaced after both the ballistic sedimentation of excavation flows and the subsequent veneering of impact melt, but it predated the settlement and solidification of melt pools on the <span class="hlt">crater</span> floor. Fragments that formed self-secondaries were launched via impact spallation with large angles. Complex <span class="hlt">craters</span> on the Moon, Mercury, and Mars probably all have formed self-secondaries populations. Dating young <span class="hlt">craters</span> using <span class="hlt">crater</span> statistics on their continuous ejecta deposits can be misleading. Impact melt pools are less affected by self-secondaries. Overprint by subsequent <span class="hlt">crater</span> populations with time reduces the predominance of self-secondaries.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRB..120.6141S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRB..120.6141S"><span>Scaling multiblast <span class="hlt">craters</span>: General approach and application to volcanic <span class="hlt">craters</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sonder, I.; Graettinger, A. H.; Valentine, G. A.</p> <p>2015-09-01</p> <p>Most volcanic explosions leave a <span class="hlt">crater</span> in the surface around the center of the explosions. Such <span class="hlt">craters</span> differ from products of single events like meteorite impacts or those produced by military testing because they typically result from multiple, rather than single, explosions. Here we analyze the evolution of experimental <span class="hlt">craters</span> that were created by several detonations of chemical explosives in layered aggregates. An empirical relationship for the scaled <span class="hlt">crater</span> radius as a function of scaled explosion depth for single blasts in flat test beds is derived from experimental data, which differs from existing relations and has better applicability for deep blasts. A method to calculate an effective explosion depth for nonflat topography (e.g., for explosions below existing <span class="hlt">craters</span>) is derived, showing how multiblast <span class="hlt">crater</span> sizes differ from the single-blast case: Sizes of natural caters (radii and volumes) are not characteristic of the number of explosions, nor therefore of the total acting energy, that formed a <span class="hlt">crater</span>. Also, the <span class="hlt">crater</span> size is not simply related to the largest explosion in a sequence but depends upon that explosion and the energy of that single blast and on the cumulative energy of all blasts that formed a <span class="hlt">crater</span>. The two energies can be combined to form an effective number of explosions that is characteristic for the <span class="hlt">crater</span> evolution. The multiblast <span class="hlt">crater</span> size evolution has implications on the estimates of volcanic eruption energies, indicating that it is not correct to estimate explosion energy from <span class="hlt">crater</span> size using previously published relationships that were derived for single-blast cases.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA22371.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA22371.html"><span>Bonestell <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2018-04-17</p> <p>Bonestell <span class="hlt">Crater</span> is a relatively young <span class="hlt">crater</span> located in Acidalia Planitia. The grooved surface of the ejecta blanket is evident in this VIS image. Dust blown into the <span class="hlt">crater</span> and the downslope movement of fine materials from the rim are slowly modifying the <span class="hlt">crater</span> features. Orbit Number: 71230 Latitude: 36.398 Longitude: 329.708 Instrument: VIS Captured: 2018-01-04 05:31 https://photojournal.jpl.nasa.gov/catalog/PIA22371</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.P41F1979T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.P41F1979T"><span>Lunar <span class="hlt">Cratering</span> Chronology: Calibrating Degree of Freshness of <span class="hlt">Craters</span> to Absolute Ages</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Trang, D.; Gillis-Davis, J.; Boyce, J. M.</p> <p>2013-12-01</p> <p>The use of impact <span class="hlt">craters</span> to age-date surfaces of and/or geomorphological features on planetary bodies is a decades old practice. Various dating techniques use different aspects of impact <span class="hlt">craters</span> in order to determine ages. One approach is based on the degree of freshness of primary-impact <span class="hlt">craters</span>. This method examines the degradation state of <span class="hlt">craters</span> through visual inspection of seven criteria: polygonality, <span class="hlt">crater</span> ray, continuous ejecta, rim crest sharpness, satellite <span class="hlt">craters</span>, radial channels, and terraces. These criteria are used to rank <span class="hlt">craters</span> in order of age from 0.0 (oldest) to 7.0 (youngest). However, the relative decimal scale used in this technique has not been tied to a classification of absolute ages. In this work, we calibrate the degree of freshness to absolute ages through <span class="hlt">crater</span> counting. We link the degree of freshness to absolute ages through <span class="hlt">crater</span> counting of fifteen <span class="hlt">craters</span> with diameters ranging from 5-22 km and degree of freshness from 6.3 to 2.5. We use the Terrain Camera data set on Kaguya to count <span class="hlt">craters</span> on the continuous ejecta of each <span class="hlt">crater</span> in our sample suite. Specifically, we divide the <span class="hlt">crater</span>'s ejecta blanket into quarters and count <span class="hlt">craters</span> between the rim of the main <span class="hlt">crater</span> out to one <span class="hlt">crater</span> radii from the rim for two of the four sections. From these <span class="hlt">crater</span> counts, we are able to estimate the absolute model age of each main <span class="hlt">crater</span> using the Craterstats2 tool in ArcGIS. Next, we compare the degree of freshness for the <span class="hlt">crater</span> count-derived age of our main <span class="hlt">craters</span> to obtain a linear inverse relation that links these two metrics. So far, for <span class="hlt">craters</span> with degree of freshness from 6.3 to 5.0, the linear regression has an R2 value of 0.7, which corresponds to a relative uncertainty of ×230 million years. At this point, this tool that links degree of freshness to absolute ages cannot be used with <span class="hlt">craters</span> <8km because this class of <span class="hlt">crater</span> degrades quicker than larger <span class="hlt">craters</span>. A graphical solution exists for correcting the degree of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA03490.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA03490.html"><span>Meteor <span class="hlt">Crater</span>, AZ</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2002-03-12</p> <p>The Barringer Meteorite <span class="hlt">Crater</span> (also known as "Meteor <span class="hlt">Crater</span>") is a gigantic hole in the middle of the arid sandstone of the Arizona desert. A rim of smashed and jumbled boulders, some of them the size of small houses, rises 50 m above the level of the surrounding plain. The <span class="hlt">crater</span> itself is nearly a 1500 m wide, and 180 m deep. When Europeans first discovered the <span class="hlt">crater</span>, the plain around it was covered with chunks of meteoritic iron - over 30 tons of it, scattered over an area 12 to 15 km in diameter. Scientists now believe that the <span class="hlt">crater</span> was created approximately 50,000 years ago. The meteorite which made it was composed almost entirely of nickel-iron, <span class="hlt">suggesting</span> that it may have originated in the interior of a small planet. It was 50 m across, weighed roughly 300,000 tons, and was traveling at a speed of 65,000 km per hour. This ASTER 3-D perspective view was created by draping an ASTER bands 3-2-1image over a digital elevation model from the US Geological Survey National Elevation Dataset. This image was acquired on May 17, 2001 by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA's Terra satellite. With its 14 spectral bands from the visible to the thermal infrared wavelength region, and its high spatial resolution of 15 to 90 meters (about 50 to 300 feet), ASTER will image Earth for the next 6 years to map and monitor the changing surface of our planet. http://photojournal.jpl.nasa.gov/catalog/PIA03490</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.loc.gov/pictures/collection/hh/item/ca1870.photos.034184p/','SCIGOV-HHH'); return false;" href="https://www.loc.gov/pictures/collection/hh/item/ca1870.photos.034184p/"><span>20. Photocopy of drawing (1961 mechanical drawing by <span class="hlt">Kaiser</span> Engineers) ...</span></a></p> <p><a target="_blank" href="http://www.loc.gov/pictures/collection/hh/">Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey</a></p> <p></p> <p></p> <p>20. Photocopy of drawing (1961 mechanical drawing by <span class="hlt">Kaiser</span> Engineers) ELECTRICAL LAYOUTS FOR VEHICLE SUPPORT BUILDING, SHEET E-2 - Vandenberg Air Force Base, Space Launch Complex 3, Vehicle Support Building, Napa & Alden Roads, Lompoc, Santa Barbara County, CA</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li class="active"><span>4</span></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_4 --> <div id="page_5" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li class="active"><span>5</span></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="81"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA04448.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA04448.html"><span>Cydonia <span class="hlt">Craters</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2003-03-22</p> <p>In this image from NASA Mars Odyssey, eroded mesas and secondary <span class="hlt">craters</span> dot the landscape in an area of Cydonia Mensae. The single oval-shaped <span class="hlt">crater</span> displays a butterfly ejecta pattern, indicating that the <span class="hlt">crater</span> formed from a low-angle impact.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009Icar..203...77S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009Icar..203...77S"><span>Machine cataloging of impact <span class="hlt">craters</span> on Mars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stepinski, Tomasz F.; Mendenhall, Michael P.; Bue, Brian D.</p> <p>2009-09-01</p> <p>This study presents an automated system for cataloging impact <span class="hlt">craters</span> using the MOLA 128 pixels/degree digital elevation model of Mars. <span class="hlt">Craters</span> are detected by a two-step algorithm that first identifies round and symmetric topographic depressions as <span class="hlt">crater</span> candidates and then selects <span class="hlt">craters</span> using a machine-learning technique. The system is robust with respect to surface types; <span class="hlt">craters</span> are identified with similar accuracy from all different types of martian surfaces without adjusting input parameters. By using a large training set in its final selection step, the system produces virtually no false detections. Finally, the system provides a seamless integration of <span class="hlt">crater</span> detection with its characterization. Of particular interest is the ability of our algorithm to calculate <span class="hlt">crater</span> depths. The system is described and its application is demonstrated on eight large sites representing all major types of martian surfaces. An evaluation of its performance and prospects for its utilization for global surveys are given by means of detailed comparison of obtained results to the manually-derived Catalog of Large Martian Impact <span class="hlt">Craters</span>. We use the results from the test sites to construct local depth-diameter relationships based on a large number of <span class="hlt">craters</span>. In general, obtained relationships are in agreement with what was inferred on the basis of manual measurements. However, we have found that, in Terra Cimmeria, the depth/diameter ratio has an abrupt decrease at ˜38°S regardless of <span class="hlt">crater</span> size. If shallowing of <span class="hlt">craters</span> is attributed to presence of sub-surface ice, a sudden change in its spatial distribution is <span class="hlt">suggested</span> by our findings.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA01515&hterms=gardening&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dgardening','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA01515&hterms=gardening&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dgardening"><span>Bright Ray <span class="hlt">Craters</span> in Ganymede's Northern Hemisphere</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1979-01-01</p> <p>GANYMEDE COLOR PHOTOS: This color picture as acquired by Voyager 1 during its approach to Ganymede on Monday afternoon (the 5th of March). At ranges between about 230 to 250 thousand km. The images show detail on the surface with a resolution of four and a half km. This picture is of a region in the northern hemisphere near the terminator. It shows a variety of impact structures, including both razed and unrazed <span class="hlt">craters</span>, and the odd, groove-like structures discovered by Voyager in the lighter regions. The most striking features are the bright ray <span class="hlt">craters</span> which have a distinctly 'bluer' color appearing white against the redder background. Ganymede's surface is known to contain large amounts of surface ice and it appears that these relatively young <span class="hlt">craters</span> have spread bright fresh ice materials over the surface. Likewise, the lighter color and reflectivity of the grooved areas <span class="hlt">suggests</span> that here, too, there is cleaner ice. We see ray <span class="hlt">craters</span> with all sizes of ray patterns, ranging from extensive systems of the <span class="hlt">crater</span> in the southern part of this picture, which has rays at least 300-500 kilometers long, down to <span class="hlt">craters</span> which have only faint remnants of bright ejects patterns (such as several of the <span class="hlt">craters</span> in the southern half of PIA01516; P21262). This variation <span class="hlt">suggests</span> that, as on the Moon, there are processes which act to darken ray material, probably 'gardening' by micrometeoroid impact. JPL manages and controls the Voyager project for NASA's Office of Space Science.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19780060127&hterms=TNT&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DTNT','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19780060127&hterms=TNT&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DTNT"><span>Tabular comparisons of the Flynn Creek impact <span class="hlt">crater</span>, United States, Steinheim impact <span class="hlt">crater</span>, Germany and Snowball explosion <span class="hlt">crater</span>, Canada</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Roddy, D. J.</p> <p>1977-01-01</p> <p>A tabular outline of comparative data is presented for 340 basic dimensional, morphological, and structural parameters and related aspects for three <span class="hlt">craters</span> of the flat-floored, central uplift type, two of which are natural terrestrial impact <span class="hlt">craters</span> and one is a large-scale experimental explosion <span class="hlt">crater</span>. The three <span class="hlt">craters</span> are part of a general class, in terms of their morphology and structural deformation that is represented on each of the terrestrial planets including the moon. One of the considered <span class="hlt">craters</span>, the Flynn Creek <span class="hlt">Crater</span>, was formed by a hypervelocity impact event approximately 360 m.y. ago in what is now north central Tennessee. The impacting body appears to have been a carbonaceous chondrite or a cometary mass. The second <span class="hlt">crater</span>, the Steinheim <span class="hlt">Crater</span>, was formed by an impact event approximately 14.7 m.y. ago in what is now southwestern Germany. The Snowball <span class="hlt">Crater</span> was formed by the detonation of a 500-ton TNT hemisphere on flat-lying, unconsolidated alluvium in Alberta, Canada.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.loc.gov/pictures/collection/hh/item/ca1870.photos.034182p/','SCIGOV-HHH'); return false;" href="https://www.loc.gov/pictures/collection/hh/item/ca1870.photos.034182p/"><span>18. Photocopy of drawing (1961 architectural drawing by <span class="hlt">Kaiser</span> Engineers) ...</span></a></p> <p><a target="_blank" href="http://www.loc.gov/pictures/collection/hh/">Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey</a></p> <p></p> <p></p> <p>18. Photocopy of drawing (1961 architectural drawing by <span class="hlt">Kaiser</span> Engineers) FLOOR PLAN, ELEVATIONS, AND SCHEDULE FOR VEHICLE SUPPORT BUILDING, SHEET A-1 - Vandenberg Air Force Base, Space Launch Complex 3, Vehicle Support Building, Napa & Alden Roads, Lompoc, Santa Barbara County, CA</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.loc.gov/pictures/collection/hh/item/ca1870.photos.034183p/','SCIGOV-HHH'); return false;" href="https://www.loc.gov/pictures/collection/hh/item/ca1870.photos.034183p/"><span>19. Photocopy of drawing (1961 piping drawing by <span class="hlt">Kaiser</span> Engineers) ...</span></a></p> <p><a target="_blank" href="http://www.loc.gov/pictures/collection/hh/">Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey</a></p> <p></p> <p></p> <p>19. Photocopy of drawing (1961 piping drawing by <span class="hlt">Kaiser</span> Engineers) PIPING PLANS AND DETAILS FOR VEHICLE SUPPORT BUILDING, SHEET P-1 - Vandenberg Air Force Base, Space Launch Complex 3, Vehicle Support Building, Napa & Alden Roads, Lompoc, Santa Barbara County, CA</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.B23A2053A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.B23A2053A"><span>Numerical simulation of turbulent flows over <span class="hlt">crater</span>-like obstacles: application to Gale <span class="hlt">crater</span>, landing site of the Curiosity rover</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Anderson, W.; Day, M. D.</p> <p>2017-12-01</p> <p>Mars is a dry planet with a thin atmosphere. Aeolian processes - wind-driven mobilization of sediment and dust - are the dominant mode of landscape variability on the dessicated landscapes of Mars. <span class="hlt">Craters</span> are common topographic features on the surface of Mars, and many <span class="hlt">craters</span> on Mars contain a prominent central mound (NASA's Curiosity rover was landed in Gale <span class="hlt">crater</span>, with the rover journeying across an inner plan and towards Gale's central mound, Aeolus Mons). These mounds are composed of sedimentary fill, and, therefore, they contain rich information on the evolution of climatic conditions on Mars embodied in the stratigraphic "layering" of sediments. Many other <span class="hlt">craters</span> no longer house a mound, but contain sediment and dust from which dune fields and other features form. Using density-normalized large-eddy simulations, we have modeled turbulent flows over <span class="hlt">crater</span>-like topographies that feature a central mound. Resultant datasets <span class="hlt">suggest</span> a deflationary mechanism wherein vortices shed from the upwind <span class="hlt">crater</span> rim are realigned to conform to the <span class="hlt">crater</span> profile via stretching and tilting. This insight was gained using three-dimensional datasets (momentum, vorticity, and turbulent stresses) retrieved from LES, and assessment of the relative influence of constituent terms responsible for the sustenance of mean vorticity. The helical, counter-rotating vortices occupy the inner region of the <span class="hlt">crater</span>, and, therefore, are argued to be of great importance for aeolian morphodynamics in the <span class="hlt">crater</span> (radial katabatic flows are also important to aeolian processes within the <span class="hlt">crater</span>).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70012258','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70012258"><span>Morphology of Lonar <span class="hlt">Crater</span>, India: Comparisons and implications</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Fudali, R.F.; Milton, D.J.; Fredriksson, K.; Dube, A.</p> <p>1980-01-01</p> <p>Lonar <span class="hlt">Crater</span> is a young meteorite impact <span class="hlt">crater</span> emplaced in Deccan basalt. Data from 5 drillholes, a gravity network, and field mapping are used to reconstruct its original dimensions, delineate the nature of the pre-impact target rocks, and interpret the emplacement mode of the ejecta. Our estimates of the pre-erosion dimensions are: average diameter of 1710 m; average rim height of 40 m (30-35 m of rim rock uplift, 5-10 m of ejected debris); depth of 230-245 m (from rim crest to <span class="hlt">crater</span> floor). The <span class="hlt">crater</span>'s circularity index is 0.9 and is unlikely to have been lower in the past. There are minor irregularities in the original <span class="hlt">crater</span> floor (present sediment-breccia boundary) possibly due to incipient rebound effects. A continuous ejecta blanket extends an average of 1410 m beyond the pre-erosion rim crest. In general, 'fresh' terrestrial <span class="hlt">craters</span>, less than 10 km in diameter, have smaller depth/diameter and larger rim height/diameter ratios than their lunar counterparts. Both ratios are intermediate for Mercurian <span class="hlt">craters</span>, <span class="hlt">suggesting</span> that <span class="hlt">crater</span> shape is gravity dependent, all else being equal. Lonar demonstrates that all else is not always equal. Its depth/diameter ratio is normal but, because of less rim rock uplift, its rim height/diameter ratio is much smaller than both 'fresh' terrestrial and lunar impact <span class="hlt">craters</span>. The target rock column at Lonar consists of one or more layers of weathered, soft basalt capped by fresh, dense flows. Plastic deformation and/or compaction of this lower, incompetent material probably absorbed much of the energy normally available in the <span class="hlt">cratering</span> process for rim rock uplift. A variety of features within the ejecta blanket and the immediately underlying substrate, plus the broad extent of the blanket boundaries, <span class="hlt">suggest</span> that a fluidized debris surge was the dominant mechanism of ejecta transportation and deposition at Lonar. In these aspects, Lonar should be a good analog for the 'fluidized <span class="hlt">craters</span>' of Mars. ?? 1980 D. Reidel</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/of/1982/0457/report.pdf','USGSPUBS'); return false;" href="https://pubs.usgs.gov/of/1982/0457/report.pdf"><span>Volcanotectonic history of <span class="hlt">Crater</span> Flat, southwestern Nevada, as <span class="hlt">suggested</span> by new evidence from drill hole USW-VH-1 and vicinity</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Carr, W.J.</p> <p>1982-01-01</p> <p>New evidence for a possible resurgent dome in the caldera related to eruption of the Bullfrog Member of the <span class="hlt">Crater</span> Flat Tuff has been provided by recent drilling of a 762-meter (2,501-foot) hole in central <span class="hlt">Crater</span> Flat. Although no new volcanic units were penetrated by the drill hole (USW-VH-1), the positive aeromagnetic anomaly in the vicinity of the drill hole appears to result in part from the unusually thick, densely welded tuff of the Bullfrog. Major units penetrated include alluvium, basalt of <span class="hlt">Crater</span> Flat, Tiva Canyon and Topopah Spring Members of the Paintbrush Tuff, and Prow Pass and Bullfrog Members of the <span class="hlt">Crater</span> Flat Tuff. In addition, the drill hole provided the first subsurface hydrologic information for the area. The water table in the hole is at about 180 meters (600 feet), and the temperature gradient appears slightly higher than normal for the region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70020209','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70020209"><span>Impact <span class="hlt">cratering</span> through geologic time</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Shoemaker, E.M.; Shoemaker, C.S.</p> <p>1998-01-01</p> <p>New data on lunar <span class="hlt">craters</span> and recent discoveries about <span class="hlt">craters</span> on Earth permit a reassessment of the bombardment history of Earth over the last 3.2 billion years. The combined lunar and terrestrial <span class="hlt">crater</span> records <span class="hlt">suggest</span> that the long-term average rate of production of <span class="hlt">craters</span> larger than 20 km in diameter has increased, perhaps by as much as 60%, in the last 100 to 200 million years. Production of <span class="hlt">craters</span> larger than 70 km in diameter may have increased, in the same time interval, by a factor of five or more over the average for the preceding three billion years. A large increase in the flux of long-period comets appears to be the most likely explanation for such a long-term increase in the <span class="hlt">cratering</span> rate. Two large <span class="hlt">craters</span>, in particular, appear to be associated with a comet shower that occurred about 35.5 million years ago. The infall of cosmic dust, as traced by 3He in deep sea sediments, and the ages of large <span class="hlt">craters</span>, impact glass horizons, and other stratigraphic markers of large impacts seem to be approximately correlated with the estimated times of passage of the Sun through the galactic plane, at least for the last 65 million years. Those are predicted times for an increased near-Earth flux of comets from the Oort Cloud induced by the combined effects of galactic tidal perturbations and encounters of the Sun with passing stars. Long-term changes in the average comet flux may be related to changes in the amplitude of the z-motion of the Sun perpendicular to the galactic plane or to stripping of the outer Oort cloud by encounters with large passing stars, followed by restoration from the inner Oort cloud reservoir.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA21414.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA21414.html"><span>Hakumyi <span class="hlt">Crater</span> from LAMO</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2017-07-20</p> <p>This close-up view of Hakumyi <span class="hlt">crater</span>, as seen by NASA's Dawn spacecraft, provides insight into the origin of the small <span class="hlt">crater</span> and lobe-shaped flow next to its southern rim. The sharp edges of these features indicate they are relatively recent with respect to the more subdued Hakumyi, which is 43 miles (70 kilometers) wide. The lobate flow ends in a tongue-shaped deposit. A more discrete feature slightly west (left) of the large lobe-shaped flow <span class="hlt">suggests</span> an ancient or partially developed lobe. These kinds of flow features, which typically are found at high latitudes on Ceres, are expressions of what is termed "mass wasting," meaning the downslope movement of material. This process is initiated by slumping or detachment of material from <span class="hlt">crater</span> rims. Here the process seems to have been triggered by small <span class="hlt">craters</span> whose remnant shapes can be discerned at the top of each flow. Dawn took this image from its low-altitude mapping orbit, or LAMO, at a distance of about 240 miles (385 kilometers) above the surface. The center coordinates of this image are 52 degrees North latitude and 26 degrees east longitude. https://photojournal.jpl.nasa.gov/catalog/PIA21414</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.P33B4033B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.P33B4033B"><span>Modeling Low Velocity Impacts: Predicting <span class="hlt">Crater</span> Depth on Pluto</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bray, V. J.; Schenk, P.</p> <p>2014-12-01</p> <p>The New Horizons mission is due to fly-by the Pluto system in Summer 2015 and provides the first opportunity to image the Pluto surface in detail, allowing both the appearance and number of its <span class="hlt">crater</span> population to be studied for the first time. Bray and Schenk (2014) combined previous <span class="hlt">cratering</span> studies and numerical modeling of the impact process to predict <span class="hlt">crater</span> morphology on Pluto based on current understanding of Pluto's composition, structure and surrounding impactor population. Predictions of how the low mean impact velocity (~2km/s) of the Pluto system will influence <span class="hlt">crater</span> formation is a complex issue. Observations of secondary <span class="hlt">cratering</span> (low velocity, high angle) and laboratory experiments of impact at low velocity are at odds regarding how velocity controls depth-diameter ratios: Observations of secondary <span class="hlt">craters</span> show that these low velocity <span class="hlt">craters</span> are shallower than would be expected for a hyper-velocity primary. Conversely, gas gun work has shown that relative <span class="hlt">crater</span> depth increases as impact velocity decreases. We have investigated the influence of impact velocity further with iSALE hydrocode modeling of comet impact into Pluto. With increasing impact velocity, a projectile will produce wider and deeper <span class="hlt">craters</span>. The depth-diameter ratio (d/D) however has a more complex progression with increasing impact velocity: impacts faster than 2km/s lead to smaller d/D ratios as impact velocity increases, in agreement with gas-gun studies. However, decreasing impact velocity from 2km/s to 300 m/s produced smaller d/D as impact velocity was decreased. This <span class="hlt">suggests</span> that on Pluto the deepest <span class="hlt">craters</span> would be produced by ~ 2km/s impacts, with shallower <span class="hlt">craters</span> produced by velocities either side of this critical point. Further simulations to investigate whether this effect is connected to the sound speed of the target material are ongoing. The complex relationship between impact velocity and <span class="hlt">crater</span> depth for impacts occurring between 300m/s and 10 km/s <span class="hlt">suggests</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19970023492','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19970023492"><span>Impact <span class="hlt">Cratering</span> Calculations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ahrens, Thomas J.</p> <p>1997-01-01</p> <p>Understanding the physical processes of impact <span class="hlt">cratering</span> on planetary surfaces and atmospheres as well as collisions of finite-size self-gravitating objects is vitally important to planetary science. The observation has often been made that <span class="hlt">craters</span> are the most ubiquitous landform on the solid planets and the satellites. The density of <span class="hlt">craters</span> is used to date surfaces on planets and satellites. For large ringed basin <span class="hlt">craters</span> (e.g. Chicxulub), the issue of identification of exactly what 'diameter' transient <span class="hlt">crater</span> is associated with this structure is exemplified by the arguments of Sharpton et al. (1993) versus those of Hildebrand et al. (1995). The size of a transient <span class="hlt">crater</span>, such as the K/T extinction <span class="hlt">crater</span> at Yucatan, Mexico, which is thought to be the source of SO,-induced sulfuric acid aerosol that globally acidified surface waters as the result of massive vaporization of CASO, in the target rock, is addressed by our present project. The impact process excavates samples of planetary interiors. The degree to which this occurs (e.g. how deeply does excavation occur for a given <span class="hlt">crater</span> diameter) has been of interest, both with regard to exposing mantle rocks in <span class="hlt">crater</span> floors, as well as launching samples into space which become part of the terrestrial meteorite collection (e.g. lunar meteorites, SNC's from Mars). Only in the case of the Earth can we test calculations in the laboratory and field. Previous calculations predict, independent of diameter, that the depth of excavation, normalized by <span class="hlt">crater</span> diameter, is d(sub ex)/D = 0.085 (O'Keefe and Ahrens, 1993). For Comet Shoemaker-Levy 9 (SL9) fragments impacting Jupiter, predicted excavation depths of different gas-rich layers in the atmosphere, were much larger. The trajectory and fate of highly shocked material from a large impact on the Earth, such as the K/T bolide is of interest. Melosh et al. (1990) proposed that the condensed material from the impact upon reentering the Earth's atmosphere induced. radiative</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19720040039&hterms=history+theory&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dhistory%2Btheory','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19720040039&hterms=history+theory&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dhistory%2Btheory"><span>Martian <span class="hlt">cratering</span>. II - Asteroid impact history.</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hartmann, W. K.</p> <p>1971-01-01</p> <p>This paper considers the extent to which Martian <span class="hlt">craters</span> can be explained by considering asteroidal impact. Sections I, II, and III of this paper derive the diameter distribution of hypothetical asteroidal <span class="hlt">craters</span> on Mars from recent Palomar-Leiden asteroid statistics and show that the observed Martian <span class="hlt">craters</span> correspond to a bombardment by roughly 100 times the present number of Mars-crossing asteroids. Section IV discusses the early bombardment history of Mars, based on the capture theory of Opik and probable orbital parameters of early planetesimals. These results show that the visible <span class="hlt">craters</span> and surface of Mars should not be identified with the initial, accreted surface. A backward extrapolation of the impact rates based on surviving Mars-crossing asteroids can account for the majority of Mars <span class="hlt">craters</span> over an interval of several aeons, indicating that we see back in time no further than part-way into a period of intense bombardment. An early period of erosion and deposition is thus <span class="hlt">suggested</span>. Section V presents a comparison with results and terminology of other authors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20170003184&hterms=moon&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dmoon','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20170003184&hterms=moon&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dmoon"><span>Secondary <span class="hlt">Crater</span>-Initiated Debris Flow on the Moon</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Martin-Wells, K. S.; Campbell, D. B.; Campbell, B. A.; Carter, L. M.; Fox, Q.</p> <p>2016-01-01</p> <p>In recent work, radar circular polarization echo properties have been used to identify "secondary" <span class="hlt">craters</span> without distinctive secondary morphologies. Because of the potential for this method to improve our knowledge of secondary <span class="hlt">crater</span> population-in particular the effect of secondary populations on <span class="hlt">crater</span>- derived ages based on small <span class="hlt">craters</span>-it is important to understand the origin of radar polarization signatures associated with secondary impacts. In this paper, we utilize Lunar Reconnaissance Orbiter Camera photographs to examine the geomorphology of secondary <span class="hlt">craters</span> with radar circular polarization ratio enhancements. Our investigation reveals evidence of dry debris flow with an impact melt component at such secondary <span class="hlt">craters</span>. We hypothesize that these debris flows were initiated by the secondary impacts themselves, and that they have entrained blocky material ejected from the secondaries. By transporting this blocky material downrange, we propose that these debris flows (rather than solely ballistic emplacement) are responsible for the tail-like geometries of enhanced radar circular polarization ratio associated with the secondary <span class="hlt">craters</span> investigated in this work. Evidence of debris flow was observed at both clustered and isolated secondary <span class="hlt">craters</span>, <span class="hlt">suggesting</span> that such flow may be a widespread occurrence, with important implications for the mixing of primary and local material in <span class="hlt">crater</span> rays.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009RMxAC..35...19B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009RMxAC..35...19B"><span>Analytical Model for Mars <span class="hlt">Crater</span>-Size Frequency Distribution</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bruckman, W.; Ruiz, A.; Ramos, E.</p> <p>2009-05-01</p> <p>We present a theoretical and analytical curve that reproduces essential features of the frequency distributions vs. diameter of the 42,000 impact <span class="hlt">craters</span> contained in Barlow's Mars Catalog. The model is derived using reasonable simple assumptions that allow us to relate the present <span class="hlt">craters</span> population with the <span class="hlt">craters</span> population at each particular epoch. The model takes into consideration the reduction of the number of <span class="hlt">craters</span> as a function of time caused by their erosion and obliteration, and this provides a simple and natural explanation for the presence of different slopes in the empirical log-log plot of number of <span class="hlt">craters</span> (N) vs. diameter (D). A mean life for martians <span class="hlt">craters</span> as a function of diameter is deduced, and it is shown that this result is consistent with the corresponding determination of <span class="hlt">craters</span> mean life based on Earth data. Arguments are given to <span class="hlt">suggest</span> that this consistency follows from the fact that a <span class="hlt">crater</span> mean life is proportional to its volumen. It also follows that in the absence of erosions and obliterations, when <span class="hlt">craters</span> are preserved, we would have N ∝ 1/D^{4.3}, which is a striking conclusion, since the exponent 4.3 is larger than previously thought. Such an exponent implies a similar slope in the extrapolated impactors size-frequency distribution.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA18384.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA18384.html"><span>Large, Fresh <span class="hlt">Crater</span> Surrounded by Smaller <span class="hlt">Craters</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2014-05-22</p> <p>The largest <span class="hlt">crater</span> associated with a March 2012 impact on Mars has many smaller <span class="hlt">craters</span> around it, revealed in this image from the High Resolution Imaging Science Experiment HiRISE camera on NASA Mars Reconnaissance Orbiter.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.loc.gov/pictures/collection/hh/item/ca1870.photos.034181p/','SCIGOV-HHH'); return false;" href="https://www.loc.gov/pictures/collection/hh/item/ca1870.photos.034181p/"><span>17. Photocopy of drawing (1961 civil engineering drawing by <span class="hlt">Kaiser</span> ...</span></a></p> <p><a target="_blank" href="http://www.loc.gov/pictures/collection/hh/">Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey</a></p> <p></p> <p></p> <p>17. Photocopy of drawing (1961 civil engineering drawing by <span class="hlt">Kaiser</span> Engineers) SITE PLAN, PLOT PLAN, AND LOCATION MAP FOR VEHICLE SUPPORT BUILDING, SHEET C-1 - Vandenberg Air Force Base, Space Launch Complex 3, Vehicle Support Building, Napa & Alden Roads, Lompoc, Santa Barbara County, CA</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=deferred+AND+maintenance&pg=6&id=EJ299870','ERIC'); return false;" href="https://eric.ed.gov/?q=deferred+AND+maintenance&pg=6&id=EJ299870"><span>The Dilemma of Campus Upkeep: An Interview with Harvey <span class="hlt">Kaiser</span>.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Christian, Roslyn Stewart</p> <p>1984-01-01</p> <p>Deferred maintenance is reaching crisis proportion on many campuses. An overview of this priority for governing boards and a look at how trustees should be involved is presented in an interview of Harvey <span class="hlt">Kaiser</span>, vice president for facilities administration at Syracuse University. (Author/MLW)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21090018','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21090018"><span><span class="hlt">Kaiser</span> Permanente's performance improvement system, Part 1: From benchmarking to executing on strategic priorities.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Schilling, Lisa; Chase, Alide; Kehrli, Sommer; Liu, Amy Y; Stiefel, Matt; Brentari, Ruth</p> <p>2010-11-01</p> <p>By 2004, senior leaders at <span class="hlt">Kaiser</span> Permanente, the largest not-for-profit health plan in the United States, recognizing variations across service areas in quality, safety, service, and efficiency, began developing a performance improvement (PI) system to realizing best-in-class quality performance across all 35 medical centers. MEASURING SYSTEMWIDE PERFORMANCE: In 2005, a Web-based data dashboard, "Big Q," which tracks the performance of each medical center and service area against external benchmarks and internal goals, was created. PLANNING FOR PI AND BENCHMARKING PERFORMANCE: In 2006, <span class="hlt">Kaiser</span> Permanente national and regional continued planning the PI system, and in 2007, quality, medical group, operations, and information technology leaders benchmarked five high-performing organizations to identify capabilities required to achieve consistent best-in-class organizational performance. THE PI SYSTEM: The PI system addresses the six capabilities: leadership priority setting, a systems approach to improvement, measurement capability, a learning organization, improvement capacity, and a culture of improvement. PI "deep experts" (mentors) consult with national, regional, and local leaders, and more than 500 improvement advisors are trained to manage portfolios of 90-120 day improvement initiatives at medical centers. Between the second quarter of 2008 and the first quarter of 2009, performance across all <span class="hlt">Kaiser</span> Permanente medical centers improved on the Big Q metrics. The lessons learned in implementing and sustaining PI as it becomes fully integrated into all levels of <span class="hlt">Kaiser</span> Permanente can be generalized to other health care systems, hospitals, and other health care organizations.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li class="active"><span>5</span></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_5 --> <div id="page_6" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li class="active"><span>6</span></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="101"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19870006229','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19870006229"><span><span class="hlt">Cratering</span> mechanics</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ivanov, B. A.</p> <p>1986-01-01</p> <p>Main concepts and theoretical models which are used for studying the mechanics of <span class="hlt">cratering</span> are discussed. Numerical two-dimensional calculations are made of explosions near a surface and high-speed impact. Models are given for the motion of a medium during <span class="hlt">cratering</span>. Data from laboratory modeling are given. The effect of gravitational force and scales of <span class="hlt">cratering</span> phenomena is analyzed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050170016','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050170016"><span>Martian Central Pit <span class="hlt">Craters</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hillman, E.; Barlow, N. G.</p> <p>2005-01-01</p> <p>Impact <span class="hlt">craters</span> containing central pits are rare on the terrestrial planets but common on icy bodies. Mars is the exception among the terrestrial planets, where central pits are seen on <span class="hlt">crater</span> floors ( floor pits ) as well as on top of central peaks ( summit pits ). Wood et al. [1] proposed that degassing of subsurface volatiles during <span class="hlt">crater</span> formation produced central pits. Croft [2] argued instead that central pits might form during the impact of volatile-rich comets. Although central pits are seen in impact <span class="hlt">craters</span> on icy moons such as Ganymede, they do show some significant differences from their martian counterparts: (a) only floor pits are seen on Ganymede, and (b) central pits begin to occur at <span class="hlt">crater</span> diameters where the peak ring interior morphology begins to appear in terrestrial planet <span class="hlt">craters</span> [3]. A study of <span class="hlt">craters</span> containing central pits was conducted by Barlow and Bradley [4] using Viking imagery. They found that 28% of <span class="hlt">craters</span> displaying an interior morphology on Mars contain central pits. Diameters of <span class="hlt">craters</span> containing central pits ranged from 16 to 64 km. Barlow and Bradley noted that summit pit <span class="hlt">craters</span> tended to be smaller than <span class="hlt">craters</span> containing floor pits. They also noted a correlation of central pit <span class="hlt">craters</span> with the proposed rings of large impact basins. They argued that basin ring formation fractured the martian crust and allowed subsurface volatiles to concentrate in these locations. They favored the model that degassing of the substrate during <span class="hlt">crater</span> formation was responsible for central pit formation due to the preferential location of central pit <span class="hlt">craters</span> along these basin rings.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA06865&hterms=Football&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DFootball','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA06865&hterms=Football&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DFootball"><span>'Endurance <span class="hlt">Crater</span>' Overview</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2004-01-01</p> <p><p/> This overview of 'Endurance <span class="hlt">Crater</span>' traces the path of the Mars Exploration Rover Opportunity from sol 94 (April 29, 2004) to sol 205 (August 21, 2004). The route charted to enter the <span class="hlt">crater</span> was a bit circuitous, but well worth the extra care engineers took to ensure the rover's safety. On sol 94, Opportunity sat on the edge of this impressive, football field-sized <span class="hlt">crater</span> while rover team members assessed the scene. After traversing around the 'Karatepe' region and past 'Burns Cliff,' the rover engineering team assessed the possibility of entering the <span class="hlt">crater</span>. Careful analysis of the angles Opportunity would face, including testing an Earth-bound model on simulated martian terrain, led the team to decide against entering the <span class="hlt">crater</span> at that particular place. Opportunity then backed up before finally dipping into the <span class="hlt">crater</span> on its 130th sol (June 5, 2004). The rover has since made its way down the <span class="hlt">crater</span>'s inner slope, grinding, trenching and examining fascinating rocks and soil targets along the way. The rover nearly made it to the intriguing dunes at the bottom of the <span class="hlt">crater</span>, but when it got close, the terrain did not look safe enough to cross.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018SoSyR..52....1I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018SoSyR..52....1I"><span>Size-Frequency Distribution of Small Lunar <span class="hlt">Craters</span>: Widening with Degradation and <span class="hlt">Crater</span> Lifetime</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ivanov, B. A.</p> <p>2018-01-01</p> <p>The review and new measurements are presented for depth/diameter ratio and slope angle evolution during small ( D < 1 km) lunar impact <span class="hlt">craters</span> aging (degradation). Comparative analysis of available data on the areal <span class="hlt">cratering</span> density and on the <span class="hlt">crater</span> degradation state for selected <span class="hlt">craters</span>, dated with returned Apollo samples, in the first approximation confirms Neukum's chronological model. The uncertainty of <span class="hlt">crater</span> retention age due to <span class="hlt">crater</span> degradational widening is estimated. The collected and analyzed data are discussed to be used in the future updating of mechanical models for lunar <span class="hlt">crater</span> aging.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFM.V51H..06B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFM.V51H..06B"><span><span class="hlt">Crater</span> Floor and Lava Lake Dynamics Measured with T-LIDAR at Pu`u`O`o <span class="hlt">Crater</span>, Hawai`i</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brooks, B. A.; Kauahikaua, J. P.; Foster, J. H.; Poland, M. P.</p> <p>2007-12-01</p> <p>We used a near-infrared (1.2 micron wavelength) tripod-based scanning LiDAR system (T-LIDAR) to capture <span class="hlt">crater</span> floor and lava lake dynamics in unprecedented detail at P`u`u `O`o <span class="hlt">crater</span> on Kilauea volcano, Hawai`i. In the ~40 days following the June 17-19 intrusion/eruption, Pu`u `O`o <span class="hlt">crater</span> experienced substantial deformation comprising 2 collapse events bracketing rapid filling of the <span class="hlt">crater</span> by a lava lake. We surveyed the <span class="hlt">crater</span> floor with centimeter-scale spot-spacings from 3 different vantage points on July 13 and from one vantage point on July 24. Data return was excellent despite heavy fume on July 24 that obscured nearly all of the <span class="hlt">crater</span> features, including the walls and floor. We formed displacement fields by aligning identical features from different acquisition times in zones on the relatively stable <span class="hlt">crater</span> walls. From July 13, over a period of several hours, we imaged ~2 m of differential lava lake surface topography from the upwelling (eastern) to downstream (western) portion of the flowing lava lake. From July 13 to July 24, the lava lake level dropped by as much as 20 meters in a zone confined by flanking levees. Our results confirm the utility of T-LiDAR as a new tool for detailed volcano geodesy studies and <span class="hlt">suggest</span> potential applications in volcano hazards monitoring.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22235538','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22235538"><span><span class="hlt">Kaiser</span> Permanente's performance improvement system, Part 4: Creating a learning organization.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Schilling, Lisa; Dearing, James W; Staley, Paul; Harvey, Patti; Fahey, Linda; Kuruppu, Francesca</p> <p>2011-12-01</p> <p>In 2006, recognizing variations in performance in quality, safety, service, and efficiency, <span class="hlt">Kaiser</span> Permanente leaders initiated the development of a performance improvement (PI) system. <span class="hlt">Kaiser</span> Permanente has implemented a strategy for creating the systemic capacity for continuous improvement that characterizes a learning organization. Six "building blocks" were identified to enable <span class="hlt">Kaiser</span> Permanente to make the transition to becoming a learning organization: real-time sharing of meaningful performance data; formal training in problem-solving methodology; workforce engagement and informal knowledge sharing; leadership structures, beliefs, and behaviors; internal and external benchmarking; and technical knowledge sharing. Putting each building block into place required multiple complex strategies combining top-down and bottom-up approaches. Although the strategies have largely been successful, challenges remain. The demand for real-time meaningful performance data can conflict with prioritized changes to health information systems. It is an ongoing challenge to teach PI, change management, innovation, and project management to all managers and staff without consuming too much training time. Challenges with workforce engagement include low initial use of tools intended to disseminate information through virtual social networking. Uptake of knowledge-sharing technologies is still primarily by innovators and early adopters. Leaders adopt new behaviors at varying speeds and have a range of abilities to foster an environment that is psychologically safe and stimulates inquiry. A learning organization has the capability to improve, and it develops structures and processes that facilitate the acquisition and sharing of knowledge.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19930000991','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19930000991"><span>Paradigm lost: Venus <span class="hlt">crater</span> depths and the role of gravity in <span class="hlt">crater</span> modification</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sharpton, Virgil L.</p> <p>1992-01-01</p> <p>Previous to Magellan, a convincing case had been assembled that predicted that complex impact <span class="hlt">craters</span> on Venus were considerably shallower than their counterparts on Mars, Mercury, the Moon, and perhaps even Earth. This was fueled primarily by the morphometric observation that, for a given diameter (D), <span class="hlt">crater</span> depth (d) seems to scale inversely with surface gravity for the other planets in the inner solar system. The unpredicted depth of fresh impact <span class="hlt">craters</span> on Venus argues against a simple inverse relationship between surface gravity and <span class="hlt">crater</span> depth. Factors that could contribute to deep <span class="hlt">craters</span> on Venus include (1) more efficient excavation on Venus, possibly reflecting rheological effects of the hot venusian environment; (2) more melting and efficient removal of melt from the <span class="hlt">crater</span> cavity; and (3) enhanced ejection of material out of the <span class="hlt">crater</span>, possibly as a result of entrainment in an atmosphere set in motion by the passage of the projectile. The broader issue raised by the venusian <span class="hlt">crater</span> depths is whether surface gravity is the predominant influence on <span class="hlt">crater</span> depths on any planet. While inverse gravity scaling of <span class="hlt">crater</span> depths has been a useful paradigm in planetary <span class="hlt">cratering</span>, the venusian data do not support this model and the terrestrial data are equivocal at best. The hypothesis that planetary gravity is the primary influence over <span class="hlt">crater</span> depths and the paradigm that terrestrial <span class="hlt">craters</span> are shallow should be reevaluated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17213500','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17213500"><span>Breaching the security of the <span class="hlt">Kaiser</span> Permanente Internet patient portal: the organizational foundations of information security.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Collmann, Jeff; Cooper, Ted</p> <p>2007-01-01</p> <p>This case study describes and analyzes a breach of the confidentiality and integrity of personally identified health information (e.g. appointment details, answers to patients' questions, medical advice) for over 800 <span class="hlt">Kaiser</span> Permanente (KP) members through KP Online, a web-enabled health care portal. The authors obtained and analyzed multiple types of qualitative data about this incident including interviews with KP staff, incident reports, root cause analyses, and media reports. Reasons at multiple levels account for the breach, including the architecture of the information system, the motivations of individual staff members, and differences among the subcultures of individual groups within as well as technical and social relations across the <span class="hlt">Kaiser</span> IT program. None of these reasons could be classified, strictly speaking, as "security violations." This case study, thus, <span class="hlt">suggests</span> that, to protect sensitive patient information, health care organizations should build safe organizational contexts for complex health information systems in addition to complying with good information security practice and regulations such as the Health Insurance Portability and Accountability Act (HIPAA) of 1996.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA21561.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA21561.html"><span>A Closer Look at Holden <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2017-03-15</p> <p>Holden <span class="hlt">Crater</span> in southern Margaritifer Terra displays a series of finely layered deposits on its floor. The layered deposits are especially well exposed in the southwestern section of the <span class="hlt">crater</span> where erosion by water flowing through a breach in the <span class="hlt">crater</span> rim created spectacular outcrops. In this location, the deposits appear beneath a cap of alluvial fan materials (tan to brown in this image). Within the deposits, individual layers are nearly flat-lying and can be traced for hundreds of meters to kilometers. Information from the CRISM instrument on the Mars Reconnaissance Orbiter <span class="hlt">suggests</span> that at least some of these beds contain clays. By contrast, the beds in the overlying alluvial fan are less continuous and dip in varying directions, showing less evidence for clays. Collectively, the characteristics of the finely bedded deposits <span class="hlt">suggest</span> they may have been deposited into a lake on the <span class="hlt">crater</span> floor, perhaps fed by runoff related to formation of the overlying fans. The map is projected here at a scale of 25 centimeters (9.8 inches) per pixel. [The original image scale is 25.9 centimeters (10.2 inches) per pixel (with 1 x 1 binning); objects on the order of 78 centimeters (30.7 inches) across are resolved.] North is up. http://photojournal.jpl.nasa.gov/catalog/PIA21561</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/10630183','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/10630183"><span>Breast cancer genetics and managed care. The <span class="hlt">Kaiser</span> Permanente experience.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kutner, S E</p> <p>1999-12-01</p> <p>In 1996, with evolution of the science of cancer genetics and the advent of commercially available BRCA1 and later BRCA2 testing, <span class="hlt">Kaiser</span> Permanente began to apply these advances in clinical practice. Recommendations for referral to genetic counseling were developed in 1997 as the Clinical Practice Guidelines for Referral for Genetic Counseling for Inherited Susceptibility for Breast and Ovarian Cancer. Implementation of these guidelines with associated protocols in <span class="hlt">Kaiser</span> Permanente's Northern California Region has occupied the ensuing years and includes dissemination of the high-risk guidelines for breast and ovarian cancer, dissemination of patient and physician educational materials on the breast cancer guidelines, monthly classes and taped healthphone messages for patients, interactive videoconferencing for physicians, a training seminar for medical geneticists who will counsel patients at risk, publication of articles on breast cancer and genetic risk in health plan member- and physician-directed magazines, identification and training of clinical specialists and supporting clinicians to care for patients before and after counseling, individual counseling and testing of patients and families, and development of a data registry. Implementing the guidelines helped us communicate the uncertainty surrounding breast cancer testing, and we were obliged to learn more about ethical, legal, societal, and insurance controversies surrounding genetic testing. Given the lack of effective prevention for breast or ovarian cancer and the difficulty of treatment, the appropriate use of genetics in patient care is essential. In the near future, we will see the need for cancer genetics to become an integral part of practice throughout the spectrum of health care. We at <span class="hlt">Kaiser</span> Permanente feel that the breast cancer guideline project is the first step in this process.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150019437','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150019437"><span>The Degradational History of Endeavour <span class="hlt">Crater</span>, Mars</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Grant, J. A.; Parker, T. J.; Crumpler, L. S.; Wilson, S. A.; Golombek, M. P.; Mittlefehldt, D. W.</p> <p>2015-01-01</p> <p>Endeavour <span class="hlt">crater</span> (2.28 deg S, 354.77 deg E) is a Noachian-aged 22 km-diameter impact structure of complex morphology in Meridiani Planum. The degradation state of the <span class="hlt">crater</span> has been studied using Mars Reconnaissance Orbiter and Opportunity rover data. Exposed rim segments rise approximately 10 m to approximately 100 m above the level of the embaying Burns Formation and the <span class="hlt">crater</span> is 200-500 m deep with the southern interior wall exposing over approximately 300 m relief. Both pre-impact rocks (Matijevic Formation) and Endeavour impact ejecta (Shoemaker Formation) are present at Cape York, but only the Shoemaker crops out (up to approximately 140 m) along the rim segment from Murray Ridge to Cape Tribulation. Study of pristine complex <span class="hlt">craters</span> Bopolu and Tooting, and morphometry of other martian complex <span class="hlt">craters</span>, enables us to approximate Endeavour's pristine form. The original rim likely averaged 410 m (+/-)200 m in elevation and a 250-275 m section of ejecta ((+/-)50-60 m) would have composed a significant fraction of the rim height. The original <span class="hlt">crater</span> depth was likely between 1.5 km and 2.2 km. Comparison between the predicted original and current form of Endeavour <span class="hlt">suggests</span> approximately 100-200 m rim lowering that removed most ejecta in some locales (e.g., Cape York) while thick sections remain elsewhere (e.g., Cape Tribulation). Almost complete removal of ejecta at Cape York and minimal observable offset across fractures indicates current differences in rim relief are not solely due to original rim relief. Rim segments are embayed by approximately 100-200 m thickness of plains rocks outside the <span class="hlt">crater</span>, but thicker deposits lie inside the <span class="hlt">crater</span>. Ventifact textures confirm ongoing eolian erosion with the overall extent difficult to estimate. Analogy with degraded Noachian-aged <span class="hlt">craters</span> south of Endeavour, however, <span class="hlt">suggests</span> fluvial erosion dominated rim degradation in the Noachian and was likely followed by approximately 10s of meters modification by alternate</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19810041820&hterms=evolution+rock&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Devolution%2Brock','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19810041820&hterms=evolution+rock&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Devolution%2Brock"><span>Infrared and radar signatures of lunar <span class="hlt">craters</span> - Implications about <span class="hlt">crater</span> evolution</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Thompson, T. W.; Cutts, J. A.; Shorthill, R. W.; Zisk, S. H.</p> <p>1980-01-01</p> <p>Geological models accounting for the strongly <span class="hlt">crater</span> size-dependent IR and radar signatures of lunar <span class="hlt">crater</span> floors are examined. The simplest model involves the formation and subsequent 'gardening' of an impact melt layer on the <span class="hlt">crater</span> floor, but while adequate in accounting for the gradual fading of IR temperatures and echo strengths in <span class="hlt">craters</span> larger than 30 km in diameter, it is inadequate for smaller ones. It is concluded that quantitative models of the evolution of rock populations in regoliths and of the interaction of microwaves with regoliths are needed in order to understand <span class="hlt">crater</span> evolutionary processes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19870043241&hterms=Mexico+sonora&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DMexico%2Bsonora','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19870043241&hterms=Mexico+sonora&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DMexico%2Bsonora"><span>Radar characteristics of small <span class="hlt">craters</span> - Implications for Venus</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Greeley, Ronald; Christensen, Philip R.; Mchone, John F.</p> <p>1987-01-01</p> <p>Shuttle radar images (SIR-A) of volcanic and impact <span class="hlt">craters</span> were examined to assess their appearance on radar images. Radar characteristics were determined for (1) nine maarlikie <span class="hlt">craters</span> in the Pinacate volcanic field, Sonora, Mexico; (2) the caldera of Cerro Volcan Quemado, in the Bolivian Andes; (3) Talemzane impact <span class="hlt">crater</span>, Algeria; and (4) Al Umchaimin, a possible impact structure in Iraq. SIR-A images were compared with conventional photographs and with results from field studies. Consideration was then given to radar images available for Venus, or anticipated from the Magellan mission. Of the criteria ordinarily used to identify impact <span class="hlt">craters</span>, some can be assessed with radar images and others cannot be used; planimetric form, expressed as circularity, and ejecta-block distribution can be assessed on radar images, but rim and floor elevations relative to the surrounding plain and disposition of rim strata are difficult or impossible to determine. It is concluded that it will be difficult to separate small impact <span class="hlt">craters</span> from small volcanic <span class="hlt">craters</span> on Venus using radar images and is <span class="hlt">suggested</span> that it will be necessary to understand the geological setting of the areas containing the <span class="hlt">craters</span> in order to determine their origin.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA10947&hterms=slump&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dslump','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA10947&hterms=slump&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dslump"><span>Oudemans <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2008-01-01</p> <p><p/> This image of the interior of Oudemans <span class="hlt">Crater</span> was taken by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) at 1800 UTC (1:00 p.m. EDT) on October 2, 2006, near 9.8 degrees south latitude, 268.5 degrees east longitude. CRISM's image was taken in 544 colors covering 0.36-3.92 micrometers, and shows features as small as 20 meters (66 feet) across. <p/> Oudemans <span class="hlt">Crater</span> is located at the extreme western end of Valles Marineris in the Sinai Planum region of Mars. The <span class="hlt">crater</span> measures some 124 kilometers (77 miles) across and sports a large central peak. <p/> Complex <span class="hlt">craters</span> like Oudemans are formed when an object, such as an asteroid or comet, impacts the planet. The size, speed and angle at which the object hits all determine the type of <span class="hlt">crater</span> that forms. The initial impact creates a bowl-shaped <span class="hlt">crater</span> and flings material (known as ejecta) out in all directions along and beyond the margins of the bowl forming an ejecta blanket. As the initial <span class="hlt">crater</span> cavity succumbs to gravity, it rebounds to form a central peak while material along the bowl's rim slumps back into the <span class="hlt">crater</span> forming terraces along the inner wall. If the force of the impact is strong enough, a central peak forms and begins to collapse back into the <span class="hlt">crater</span> basin, forming a central peak ring. <p/> The uppermost image in the montage above shows the location of CRISM data on a mosaic taken by the Mars Odyssey spacecraft's Thermal Emission Imaging System (THEMIS). The CRISM data was taken inside the <span class="hlt">crater</span>, on the northeast slope of the central peak. <p/> The lower left image is an infrared false-color image that reveals several distinctive deposits. The center of the image holds a ruddy-brown deposit that appears to correlates with a ridge running southwest to northeast. Lighter, buff-colored deposits occupy low areas interspersed within the ruddy-brown deposit. The southeast corner holds small hills that form part of the central peak complex. <p/> The lower right image shows spectral</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015DPS....4731001K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015DPS....4731001K"><span>Geologic Conditions Required for the Fluvial Erosion of Titan’s <span class="hlt">Craters</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kinser, Rebeca; Neish, Catherine; Howard, Alan; Schenk, Paul; Bray, Veronica</p> <p>2015-11-01</p> <p>In comparison to other icy satellites, Titan has a small number of impact <span class="hlt">craters</span> on its surface. This <span class="hlt">suggests</span> that it has a young surface and/or erosional processes that remove <span class="hlt">craters</span> from its surface. The set of geological conditions on Titan that would allow <span class="hlt">craters</span> to become unrecognizable by orbiting spacecraft such as Cassini is unclear. Initial results <span class="hlt">suggest</span> that not all geologic conditions would allow for complete degradation of impact <span class="hlt">craters</span> on Titan. Using a landscape evolution model, we explored a larger parameter space to determine the conditions under which a representative 40 km <span class="hlt">crater</span> on Titan would be eroded. We focused on varying the values of parameters such as bedrock and regolith erodibility, sediment grain size, the weathering rate of the regolith, and whether or not the regolith was saturated with liquid hydrocarbons. We found that only after changing the saturation state of the regolith mid-way through the simulation was it possible to completely erode the <span class="hlt">crater</span>. Since there are few <span class="hlt">craters</span> on Titan, this <span class="hlt">suggests</span> that during Titan’s geological history there may have been varying quantities of liquid on its surface. Titan is known to have a dense atmosphere, not unlike that of the Earth, that could allow for surface liquids to vary under a changing climate. The erosion rate could then also vary as a direct result of changing climatic conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016DPS....4850605B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016DPS....4850605B"><span>Floor-fractured <span class="hlt">craters</span> on Ceres and implications for interior processes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Buczkowski, Debra; Schenk, Paul M.; Scully, Jennifer E. C.; Park, Ryan; Preusker, Frank; Raymond, Carol; Russell, Christopher T.</p> <p>2016-10-01</p> <p>Several of the impact <span class="hlt">craters</span> on Ceres have patterns of fractures on their floors. These fractures appear similar to those found within a class of lunar <span class="hlt">craters</span> referred to as Floor-Fractured <span class="hlt">Craters</span> (FFCs) [Schultz, 1976].Lunar FFCs are characterized by anomalously shallow floors cut by radial, concentric, and/or polygonal fractures, and have been classified into <span class="hlt">crater</span> classes, Types 1 through 6, based on their morphometric properties [Schultz, 1976; Jozwiak et al, 2012, 2015]. Models for their formation have included both floor uplift due to magmatic intrusion below the <span class="hlt">crater</span> or floor shallowing due to viscous relaxation. However, the observation that the depth versus diameter (d/D) relationship of the FFCs is distinctly shallower than the same association for other lunar <span class="hlt">craters</span> supports the hypotheses that the floor fractures form due to shallow magmatic intrusion under the <span class="hlt">crater</span> [Jozwiak et al, 2012, 2015].FFCs have also been identified on Mars [Bamberg et al., 2014]. Martian FFCs exhibit morphological characteristics similar to the lunar FFCs, and analyses <span class="hlt">suggest</span> that the Martian FCCs also formed due to volcanic activity, although heavily influenced by interactions with groundwater and/or ice.We have cataloged the Ceres FFCs according to the classification scheme designed for the Moon. Large (>50 km) Ceres FFCs are most consistent with Type 1 lunar FFCs, having deep floors, central peaks, wall terraces, and radial and/or concentric fractures. Smaller <span class="hlt">craters</span> on Ceres are more consistent with Type 4 lunar FFCs, having less-pronounced floor fractures and a v-shaped moats separating the wall scarp from the <span class="hlt">crater</span> interior.An analysis of the d/D ratio for Ceres <span class="hlt">craters</span> shows that, like lunar FFCs, the Ceres FFCs are anomalously shallow. This <span class="hlt">suggests</span> that the fractures on the floor of Ceres FFCs may be due the intrusion of a low-density material below the <span class="hlt">craters</span> that is uplifting their floors. While on the Moon and Mars the intrusive material is hypothesized</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19750027106&hterms=future+implications&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dfuture%2Bimplications','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19750027106&hterms=future+implications&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dfuture%2Bimplications"><span><span class="hlt">Cratering</span> on Mars. I - <span class="hlt">Cratering</span> and obliteration history. II Implications for future <span class="hlt">cratering</span> studies from Mariner 4 reanalysis</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chapman, C. R.</p> <p>1974-01-01</p> <p>It is pointed out that Mars is especially well adapted to statistical studies of <span class="hlt">crater</span> morphologies for deciphering its geological history. A framework for understanding planetary geomorphological histories from the diameter-frequency relations of different morphological classes of <span class="hlt">craters</span> described by Chapmam et al. (1970) is extended in order to understand Martian <span class="hlt">cratering</span>, erosional, and depositional history. The <span class="hlt">cratering</span>-obliteration history derived is compared with global interpretations considered by Hartman (1973) and Soderblom et al. (1974). An idealized dust-filling model is employed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017CG....105...81L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017CG....105...81L"><span>Large <span class="hlt">Crater</span> Clustering tool</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Laura, Jason; Skinner, James A.; Hunter, Marc A.</p> <p>2017-08-01</p> <p>In this paper we present the Large <span class="hlt">Crater</span> Clustering (LCC) tool set, an ArcGIS plugin that supports the quantitative approximation of a primary impact location from user-identified locations of possible secondary impact <span class="hlt">craters</span> or the long-axes of clustered secondary <span class="hlt">craters</span>. The identification of primary impact <span class="hlt">craters</span> directly supports planetary geologic mapping and topical science studies where the chronostratigraphic age of some geologic units may be known, but more distant features have questionable geologic ages. Previous works (e.g., McEwen et al., 2005; Dundas and McEwen, 2007) have shown that the source of secondary impact <span class="hlt">craters</span> can be estimated from secondary impact <span class="hlt">craters</span>. This work adapts those methods into a statistically robust tool set. We describe the four individual tools within the LCC tool set to support: (1) processing individually digitized point observations (<span class="hlt">craters</span>), (2) estimating the directional distribution of a clustered set of <span class="hlt">craters</span>, back projecting the potential flight paths (<span class="hlt">crater</span> clusters or linearly approximated catenae or lineaments), (3) intersecting projected paths, and (4) intersecting back-projected trajectories to approximate the local of potential source primary <span class="hlt">craters</span>. We present two case studies using secondary impact features mapped in two regions of Mars. We demonstrate that the tool is able to quantitatively identify primary impacts and supports the improved qualitative interpretation of potential secondary <span class="hlt">crater</span> flight trajectories.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19930000980','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19930000980"><span>A history of the Lonar <span class="hlt">crater</span>, India: An overview</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Nayak, V. K.</p> <p>1992-01-01</p> <p>The origin of the circular structure at Lonar, India, described variously as cauldron, pit, hollow, depression, and <span class="hlt">crater</span>, has been a controversial subject since the early nineteenth century. A history of its origin and other aspects from 1823 to 1990 are overviewed. The structure in the Deccan Trap Basalt is nearly circular with a breach in the northeast, 1830 m in diameter, 150 m deep, with a saline lake in the <span class="hlt">crater</span> floor. Over the years, the origin of the Lonar structure has risen from volcanism, subsidence, and cryptovolcanism to an authentic meteorite impact <span class="hlt">crater</span>. Lonar is unique because it is probably the only terrestrial <span class="hlt">crater</span> in basalt and is the closest analog with the Moon's <span class="hlt">craters</span>. Some unresolved questions are <span class="hlt">suggested</span>. The proposal is made that the young Lonar impact <span class="hlt">crater</span>, which is less than 50,000 years old, should be considered as the best <span class="hlt">crater</span> laboratory analogous to those of the Moon, be treated as a global monument, and preserved for scientists to comprehend more about the mysteries of nature and impact <span class="hlt">cratering</span>, which is now emerging as a fundamental ubiquitous geological process in the evolution of the planets.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA03829&hterms=DIRT&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DDIRT','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA03829&hterms=DIRT&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DDIRT"><span>Impact <span class="hlt">Crater</span> with Peak</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2002-01-01</p> <p>(Released 14 June 2002) The Science This THEMIS visible image shows a classic example of a martian impact <span class="hlt">crater</span> with a central peak. Central peaks are common in large, fresh <span class="hlt">craters</span> on both Mars and the Moon. This peak formed during the extremely high-energy impact <span class="hlt">cratering</span> event. In many martian <span class="hlt">craters</span> the central peak has been either eroded or buried by later sedimentary processes, so the presence of a peak in this <span class="hlt">crater</span> indicates that the <span class="hlt">crater</span> is relatively young and has experienced little degradation. Observations of large <span class="hlt">craters</span> on the Earth and the Moon, as well as computer modeling of the impact process, show that the central peak contains material brought from deep beneath the surface. The material exposed in these peaks will provide an excellent opportunity to study the composition of the martian interior using THEMIS multi-spectral infrared observations. The ejecta material around the <span class="hlt">crater</span> can is well preserved, again indicating relatively little modification of this landform since its initial creation. The inner walls of this approximately 18 km diameter <span class="hlt">crater</span> show complex slumping that likely occurred during the impact event. Since that time there has been some downslope movement of material to form the small chutes and gullies that can be seen on the inner <span class="hlt">crater</span> wall. Small (50-100 m) mega-ripples composed of mobile material can be seen on the floor of the <span class="hlt">crater</span>. Much of this material may have come from the walls of the <span class="hlt">crater</span> itself, or may have been blown into the <span class="hlt">crater</span> by the wind. The Story When a meteor smacked into the surface of Mars with extremely high energy, pow! Not only did it punch an 11-mile-wide <span class="hlt">crater</span> in the smoother terrain, it created a central peak in the middle of the <span class="hlt">crater</span>. This peak forms kind of on the 'rebound.' You can see this same effect if you drop a single drop of milk into a glass of milk. With <span class="hlt">craters</span>, in the heat and fury of the impact, some of the land material can even liquefy. Central peaks like the one</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li class="active"><span>6</span></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_6 --> <div id="page_7" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active"><span>7</span></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="121"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA21402.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA21402.html"><span>Inamahari <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2017-04-13</p> <p>Inamahari <span class="hlt">Crater</span> on Ceres, the large well-defined <span class="hlt">crater</span> at the center of this image, is one of the sites where scientists have discovered evidence for organic material. The <span class="hlt">crater</span>, 42 miles (68 kilometers) in diameter, presents other interesting attributes. It has a polygonal shape and an association with another <span class="hlt">crater</span> of similar size and geometry called Homshuk (center right), although the latter appears eroded and is likely older. Future studies of Inamahari <span class="hlt">crater</span> and surroundings may help uncover the mechanisms involved in the exposure of organic material onto Ceres' surface. Inamahari was named for a pair of male and female deities from the ancient Siouan tribe of South Carolina, invoked for a successful sowing season. Homshuk refers to the spirit of corn (maize) from the Popoluca peoples of southern Mexico. Inamahari is located at 14 degrees north latitude, 89 degrees east longitude. This picture was taken by NASA's Dawn on September 25, 2015 from an altitude of about 915 miles (1,470 kilometers). It has a resolution of 450 feet (140 meters) per pixel. https://photojournal.jpl.nasa.gov/catalog/PIA21402</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70047182','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70047182"><span>Ancient impact and aqueous processes at Endeavour <span class="hlt">Crater</span>, Mars</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Squyres, S. W.; Arvidson, R. E.; Bell, J.F.; Calef, F.J.; Clark, B. C.; Cohen, B. A.; Crumpler, L.A.; de Souza, P. A.; Farrand, W. H.; Gellert, Ralf; Grant, J.; Herkenhoff, K. E.; Hurowitz, J.A.; Johnson, J. R.; Jolliff, B.L.; Knoll, A.H.; Li, R.; McLennan, S.M.; Ming, D. W.; Mittlefehldt, D. W.; Parker, T.J.; Paulsen, G.; Rice, M.S.; Ruff, S.W.; Schröder, C.; Yen, A. S.; Zacny, K.</p> <p>2012-01-01</p> <p>The rover Opportunity has investigated the rim of Endeavour <span class="hlt">Crater</span>, a large ancient impact <span class="hlt">crater</span> on Mars. Basaltic breccias produced by the impact form the rim deposits, with stratigraphy similar to that observed at similar-sized <span class="hlt">craters</span> on Earth. Highly localized zinc enrichments in some breccia materials <span class="hlt">suggest</span> hydrothermal alteration of rim deposits. Gypsum-rich veins cut sedimentary rocks adjacent to the <span class="hlt">crater</span> rim. The gypsum was precipitated from low-temperature aqueous fluids flowing upward from the ancient materials of the rim, leading temporarily to potentially habitable conditions and providing some of the waters involved in formation of the ubiquitous sulfate-rich sandstones of the Meridiani region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050174579','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050174579"><span>Distant Secondary <span class="hlt">Craters</span> and Age Constraints on Young Martian Terrains</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>McEwen, A.; Preblich, B.; Turtle, E.; Studer, D.; Artemieva, N.; Golombek, M.; Hurst, M.; Kirk, R.; Burr, D.</p> <p>2005-01-01</p> <p>Are small (less than approx. 1 km diameter) <span class="hlt">craters</span> on Mars and the Moon dominated by primary impacts, by secondary impacts of much larger primary <span class="hlt">craters</span>, or are both primaries and secondaries significant? This question is critical to age constraints for young terrains and for older terrains covering small areas, where only small <span class="hlt">craters</span> are superimposed on the unit. If the martian rayed <span class="hlt">crater</span> Zunil is representative of large impact events on Mars, then the density of secondaries should exceed the density of primaries at diameters a factor of 1000 smaller than that of the largest contributing primary <span class="hlt">crater</span>. On the basis of morphology and depth/diameter measurements, most small <span class="hlt">craters</span> on Mars could be secondaries. Two additional observations (discussed below) <span class="hlt">suggest</span> that the production functions of Hartmann and Neukum predict too many primary <span class="hlt">craters</span> smaller than a few hundred meters in diameter. Fewer small, high-velocity impacts may explain why there appears to be little impact regolith over Amazonian terrains. Martian terrains dated by small <span class="hlt">craters</span> could be older than reported in recent publications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA15382.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA15382.html"><span>Successive Formation of Impact <span class="hlt">Craters</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2012-02-16</p> <p>This image from NASA Dawn spacecraft shows two overlapping impact <span class="hlt">craters</span> on asteroid Vesta. The rims of the <span class="hlt">craters</span> are both reasonably fresh but the larger <span class="hlt">crater</span> must be older because the smaller <span class="hlt">crater</span> cuts across the larger <span class="hlt">crater</span> rim.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA15591.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA15591.html"><span>Canuleia <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2012-04-24</p> <p>This image from NASA Dawn spacecraft of asteroid Vesta shows Canuleia <span class="hlt">crater</span>, a large, irregularly shaped <span class="hlt">crater</span>. Other interesting features of Canuleia include the diffuse bright material that is both inside and outside of its rim.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20150005819&hterms=AGEs&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DAGEs','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20150005819&hterms=AGEs&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DAGEs"><span>Small Rayed <span class="hlt">Crater</span> Ejecta Retention Age Calculated from Current <span class="hlt">Crater</span> Production Rates on Mars</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Calef, F. J. III; Herrick, R. R.; Sharpton, V. L.</p> <p>2011-01-01</p> <p>Ejecta from impact <span class="hlt">craters</span>, while extant, records erosive and depositional processes on their surfaces. Estimating ejecta retention age (Eret), the time span when ejecta remains recognizable around a <span class="hlt">crater</span>, can be applied to estimate the timescale that surface processes operate on, thereby obtaining a history of geologic activity. However, the abundance of sub-kilometer diameter (D) <span class="hlt">craters</span> identifiable in high resolution Mars imagery has led to questions of accuracy in absolute <span class="hlt">crater</span> dating and hence ejecta retention ages (Eret). This research calculates the maximum Eret for small rayed impact <span class="hlt">craters</span> (SRC) on Mars using estimates of the Martian impactor flux adjusted for meteorite ablation losses in the atmosphere. In addition, we utilize the diameter-distance relationship of secondary <span class="hlt">cratering</span> to adjust <span class="hlt">crater</span> counts in the vicinity of the large primary <span class="hlt">crater</span> Zunil.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19730013046&hterms=vehicle+identification&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dvehicle%2Bidentification','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19730013046&hterms=vehicle+identification&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dvehicle%2Bidentification"><span>Artificial lunar impact <span class="hlt">craters</span>: Four new identifications, part I</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Whitaker, E. A.</p> <p>1972-01-01</p> <p>The Apollo 16 panoramic camera photographed the impact locations of the Ranger 7 and 9 spacecraft and the S-4B stage of the Apollo 14 Saturn launch vehicle. Identification of the Ranger <span class="hlt">craters</span> was very simple because each photographed its target point before impact. Identification of the S-4B impact <span class="hlt">crater</span> proved to be a simple matter because the impact location, as derived from earth-based tracking, displayed a prominent and unique system of mixed light and dark rays. By using the criterion of a dark ray pattern, a reexamination of the Apollo 14 500 mm Hasselblad sequence taken of the Apollo 13 S-4B impact area was made. This examination quickly led to the discovery of the ray system and the impact <span class="hlt">crater</span>. The study of artificial lunar impact <span class="hlt">craters</span>, ejecta blankets, and ray systems provides the long-needed link between the various experimental terrestrial impact and explosion <span class="hlt">craters</span>, and the naturally occurring impact <span class="hlt">craters</span> on the moon. This elementary study shows that lunar impact <span class="hlt">crater</span> diameters are closely predictable from a knowledge of the energies involved, at least in the size range considered, and <span class="hlt">suggests</span> that parameters, such as velocity, may have a profound effect on <span class="hlt">crater</span> morphology and ejecta blanket albedo.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70032023','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70032023"><span>Survey of TES high albedo events in Mars' northern polar <span class="hlt">craters</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Armstrong, J.C.; Nielson, S.K.; Titus, T.N.</p> <p>2007-01-01</p> <p>Following the work exploring Korolev <span class="hlt">Crater</span> (Armstrong et al., 2005) for evidence of <span class="hlt">crater</span> interior ice deposits, we have conducted a survey of Thermal Emission Spectroscopy (TES) temperature and albedo measurements for Mars' northern polar <span class="hlt">craters</span> larger than 10 km. Specifically, we identify a class of <span class="hlt">craters</span> that exhibits brightening in their interiors during a solar longitude, Ls, of 60 to 120 degrees, roughly depending on latitude. These <span class="hlt">craters</span> vary in size, latitude, and morphology, but appear to have a specific regional association on the surface that correlates with the distribution of subsurface hydrogen (interpreted as water ice) previously observed on Mars. We <span class="hlt">suggest</span> that these <span class="hlt">craters</span>, like Korolev, exhibit seasonal high albedo frost events that indicate subsurface water ice within the <span class="hlt">craters</span>. A detailed study of these <span class="hlt">craters</span> may provide insight in the geographical distribution of the ice and context for future polar missions. Copyright 2007 by the American Geophysical Union.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19770066431&hterms=gravity+anomaly&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dgravity%2Banomaly','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19770066431&hterms=gravity+anomaly&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dgravity%2Banomaly"><span>The nature of the gravity anomalies associated with large young lunar <span class="hlt">craters</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Dvorak, J.; Phillips, R. J.</p> <p>1977-01-01</p> <p>The negative Bouguer anomalies (i.e., mass deficiencies) associated with four young lunar <span class="hlt">craters</span> are analyzed. Model calculations based on generalizations made from studies of terrestrial impact structures <span class="hlt">suggest</span> that the major contribution to the Bouguer anomaly for these lunar <span class="hlt">craters</span> is due to a lens of brecciated material confined within the present <span class="hlt">crater</span> rim crest and extending vertically to at least a depth of one-third the <span class="hlt">crater</span> rim diameter. Calculations also reveal a systematic variation in the magnitude of the mass deficiencies with the cube of the <span class="hlt">crater</span> diameter.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19840011716','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19840011716"><span>Centrifuge impact <span class="hlt">cratering</span> experiment 5</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1984-01-01</p> <p>Transient crates motions, <span class="hlt">cratering</span> flow fields, crates dynamics, determining impact conditions from total <span class="hlt">crater</span> welt, centrifuge quarter-space <span class="hlt">cratering</span>, and impact <span class="hlt">cratering</span> mechanics research is documented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014acm..conf..564V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014acm..conf..564V"><span><span class="hlt">Craters</span> on comets</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vincent, J.; Oklay, N.; Marchi, S.; Höfner, S.; Sierks, H.</p> <p>2014-07-01</p> <p>This paper reviews the observations of <span class="hlt">crater</span>-like features on cometary nuclei. ''Pits'' have been observed on almost all cometary nuclei but their origin is not fully understood [1,2,3,4]. It is currently assumed that they are created mainly by the cometary activity with a pocket of volatiles erupting under a dust crust, leaving a hole behind. There are, however, other features which cannot be explained in this way and are interpreted alternatively as remnants of impact <span class="hlt">craters</span>. This work focusses on the second type of pit features: impact <span class="hlt">craters</span>. We present an in-depth review of what has been observed previously and conclude that two main types of <span class="hlt">crater</span> morphologies can be observed: ''pit-halo'' and ''sharp pit''. We extend this review by a series of analysis of impact <span class="hlt">craters</span> on cometary nuclei through different approaches [5]: (1) Probability of impact: We discuss the chances that a Jupiter Family Comet like 9P/Tempel 1 or the target of Rosetta 67P/Churyumov-Gerasimenko can experience an impact, taking into account the most recent work on the size distribution of small objects in the asteroid Main Belt [6]. (2) <span class="hlt">Crater</span> morphology from scaling laws: We present the status of scaling laws for impact <span class="hlt">craters</span> on cometary nuclei [7] and discuss their strengths and limitations when modeling what happens when a rocky projectile hits a very porous material. (3) Numerical experiments: We extend the work on scaling laws by a series of hydrocode impact simulations, using the iSALE shock physics code [8,9,10] for varying surface porosity and impactor velocity (see Figure). (4) Surface processes and evolution: We discuss finally the fate of the projectile and the effects of the impact-induced surface compaction on the activity of the nucleus. To summarize, we find that comets do undergo impacts although the rapid evolution of the surface erases most of the features and make <span class="hlt">craters</span> difficult to detect. In the case of a collision between a rocky body and a highly porous</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GeoRL..4411311H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GeoRL..4411311H"><span><span class="hlt">Crater</span> Lake Controls on Volcano Stability: Insights From White Island, New Zealand</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hamling, Ian J.</p> <p>2017-11-01</p> <p>Many volcanoes around the world host summit <span class="hlt">crater</span> lakes but their influence on the overall stability of the edifice remains poorly understood. Here I use satellite radar data acquired by TerraSAR-X from early 2015 to July 2017 over White Island, New Zealand, to investigate the interaction of the <span class="hlt">crater</span> lake and deformation of the surrounding edifice. An eruption in April 2016 was preceded by a period of uplift within the <span class="hlt">crater</span> floor and drop in the lake level. Modeling of the uplift indicates a shallow source located at ˜100 m depth in the vicinity of the <span class="hlt">crater</span> lake, likely coinciding with the shallow hydrothermal system. In addition to the drop in the lake level, stress changes induced by the inflation <span class="hlt">suggest</span> that the pressurization of the shallow hydrothermal system helped promote failure along the edge of the <span class="hlt">crater</span> lake which collapsed during the eruption. After the eruption, and almost complete removal of the <span class="hlt">crater</span> lake, large areas of the <span class="hlt">crater</span> wall and lake edge began moving downslope at rates approaching 400 mm/yr. The coincidence between the rapid increase in the displacement rates and removal of the <span class="hlt">crater</span> lake <span class="hlt">suggests</span> that the lake provides a physical control on the stability of the surrounding edifice.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA16710.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA16710.html"><span>Layers with Carbonate Content Inside McLaughlin <span class="hlt">Crater</span> on Mars</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2013-01-20</p> <p>This view of layered rocks on the floor of McLaughlin <span class="hlt">Crater</span> shows sedimentary rocks that contain spectroscopic evidence for minerals formed through interaction with water. A combination of clues <span class="hlt">suggests</span> this <span class="hlt">crater</span> once held a lake fed by groundwater.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA03909&hterms=textural+features&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dtextural%2Bfeatures','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA03909&hterms=textural+features&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dtextural%2Bfeatures"><span>Poynting <span class="hlt">Crater</span> Ejecta</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2002-01-01</p> <p>[figure removed for brevity, see original site] (Released 30 July 2002) Located roughly equidistant between two massive volcanoes, the approximately 60 km Poynting <span class="hlt">Crater</span> and its ejecta have experienced an onslaught of volcanic activity. Pavonis Mons to the south and Ascraeus Mons to the north are two of the biggest volcanoes on Mars. They have supplied copious amounts of lava and presumably, ash and tephra to the region. This THEMIS image captures evidence for these volcanic materials. The rugged mound of material that dominates the center of the image likely is ejecta from Poynting <span class="hlt">Crater</span> just 40 km to the west (see MOLA context image). The textural features of this mound are surprisingly muted, giving the appearance that the image is out of focus or has atmospheric obscuration. But the surrounding terrain shows clear textural details and the mound itself displays tiny <span class="hlt">craters</span> and protruding peaks that demonstrate the true clarity of the image. One conclusion is that the ejecta mound is covered by a mantle of material that could be related to its proximity to the big volcanoes. The tephra and ash deposits produced by these volcanoes could easily accumulate to a thickness that would bury any textural details that originally existed on the ejecta mound. In contrast, the lava flows that lap up to the base of the mound show clear textural details, indicating that they came after the eruptive activity that mantled the ejecta mound. Given the fact that any ejecta material is preserved at all <span class="hlt">suggests</span> that the impact that produced Poynting <span class="hlt">Crater</span> postdated the major construction phase of the volcanoes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA04454.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA04454.html"><span>Flooded <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2003-04-04</p> <p>This image from NASA Mars Odyssey spacecraft shows a flooded <span class="hlt">crater</span> in Amazonis Planitia. This <span class="hlt">crater</span> has been either flooded with mud and or lava. The fluid then ponded up, dried and formed the surface textures we see today.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA13738.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA13738.html"><span>Doublet <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2010-12-22</p> <p>This image from NASA Mars Odyssey is of a doublet <span class="hlt">crater</span> located in Utopia Planitia, near the Elysium Volcanic region. Doublet <span class="hlt">craters</span> are formed by simultaneous impact of a meteor that broke into two pieces prior to hitting the surface.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050172168','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050172168"><span>Hydrothermal Alteration at Lonar <span class="hlt">Crater</span>, India and Elemental Variations in Impact <span class="hlt">Crater</span> Clays</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Newsom, H. E.; Nelson, M. J.; Shearer, C. K.; Misra, S.; Narasimham, V.</p> <p>2005-01-01</p> <p>The role of hydrothermal alteration and chemical transport involving impact <span class="hlt">craters</span> could have occurred on Mars, the poles of Mercury and the Moon, and other small bodies. We are studying terrestrial <span class="hlt">craters</span> of various sizes in different environments to better understand aqueous alteration and chemical transport processes. The Lonar <span class="hlt">crater</span> in India (1.8 km diameter) is particularly interesting being the only impact <span class="hlt">crater</span> in basalt. In January of 2004, during fieldwork in the ejecta blanket around the rim of the Lonar <span class="hlt">crater</span> we discovered alteration zones not previously described at this <span class="hlt">crater</span>. The alteration of the ejecta blanket could represent evidence of localized hydrothermal activity. Such activity is consistent with the presence of large amounts of impact melt in the ejecta blanket. Map of one area on the north rim of the <span class="hlt">crater</span> containing highly altered zones at least 3 m deep is shown.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1996M%26PS...31..433C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1996M%26PS...31..433C"><span>Discovering research value in the Campo del Cielo, Argentina, meteorite <span class="hlt">craters</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cassidy, William A.; Renard, Marc L.</p> <p>1996-07-01</p> <p>The Campo del Cielo meteorite <span class="hlt">crater</span> field in Argentina contains at least 20 small meteorite <span class="hlt">craters</span>, but a recent review of the field data and a remote sensing study <span class="hlt">suggest</span> that there may be more. The fall occurred ˜4000 years ago into a uniform loessy soil, and the <span class="hlt">craters</span> are well enough preserved so that some of their parameters of impact can be determined after excavation. The <span class="hlt">craters</span> were formed by multi-ton fragments of a type IA meteoroid with abundant silicate inclusions. Relative to the horizontal, the angle of infall was ˜9°. Reflecting the low angle of infall, the <span class="hlt">crater</span> field is elongated with apparent dimensions of 3 × 18.5 km. The largest <span class="hlt">craters</span> are near the center of this ellipse. This <span class="hlt">suggests</span> that when the parent meteoroid broke apart, the resulting fragments diverged from the original trajectory in inverse relation to their masses and did not undergo size sorting due to atmospheric deceleration. The major axis of the <span class="hlt">crater</span> field as we know it extends along N63°E, but the azimuths of infall determined by excavation of <span class="hlt">Craters</span> 9 and 10 are N83.5°E and N75.5°E, respectively. This <span class="hlt">suggests</span> that the major axis of the <span class="hlt">crater</span> field is not yet well determined. The three or four largest <span class="hlt">craters</span> appear to have been formed by impacts that disrupted the projectiles, scattering fragments around the outsides of the <span class="hlt">craters</span> and leaving no large masses within them; these are relatively symmetrical in shape. Other <span class="hlt">craters</span> are elongated features with multi-ton masses preserved within them and no fragmentation products outside. There are two ways in which field research on the Campo del Cielo <span class="hlt">crater</span> field is found to be useful. (1) Studies exist that have been used to interpret impact <span class="hlt">craters</span> on planetary surfaces other than the Earth. This occurrence of a swarm of projectiles impacting at known angles and similar velocities into a uniform target material provides an excellent field site at which to test the applicability of those studies. (2) Individual</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA04049&hterms=sputnik&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dsputnik','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA04049&hterms=sputnik&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dsputnik"><span>Impact <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2002-01-01</p> <p><p/> [figure removed for brevity, see original site] <p/>Today marks the 45th anniversary of the dawn of the Space Age (October 4, 1957). On this date the former Soviet Union launched the world's first satellite, Sputnik 1. Sputnik means fellow traveler. For comparison Sputnik 1 weighed only 83.6 kg (184 pounds) while Mars Odyssey weighs in at 758 kg (1,671 pounds).<p/>This scene shows several interesting geologic features associated with impact <span class="hlt">craters</span> on Mars. The continuous lobes of material that make up the ejecta blanket of the large impact <span class="hlt">crater</span> are evidence that the <span class="hlt">crater</span> ejecta were fluidized upon impact of the meteor that formed the <span class="hlt">crater</span>. Volatiles within the surface mixed with the ejecta upon impact thus creating the fluidized form. Several smaller impact <span class="hlt">craters</span> are also observed within the ejecta blanket of the larger impact <span class="hlt">crater</span> giving a relative timing of events. Layering of geologic units is also observed within the large impact <span class="hlt">crater</span> walls and floor and may represent different compositional units that erode at variable rates. Cliff faces, dissected gullies, and heavily eroded impact <span class="hlt">craters</span> are observed in the bottom half of the image at the terminus of a flat-topped plateau.<p/>Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.<p/>NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA08457.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA08457.html"><span>Filled <span class="hlt">Craters</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2006-05-11</p> <p>This MOC image shows adjacent impact <span class="hlt">craters</span> located north-northwest of the Acheron Fossae region of Mars. The two <span class="hlt">craters</span> are of similar size and formed by meteor impacts. However, one is much more filled than the other, indicating that it is older</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active"><span>7</span></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_7 --> <div id="page_8" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="141"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA03849.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA03849.html"><span>Spallanzani <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2002-07-17</p> <p>The <span class="hlt">craters</span> on Mars display a variety of interior deposits, one of which is shown in this image from NASA Mars Odyssey. Spallanzani <span class="hlt">Crater</span> is located far enough south that it probably experiences the seasonal growth and retreat of the south polar cap.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70019214','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70019214"><span>The phanerozoic impact <span class="hlt">cratering</span> rate: Evidence from the farside of the Moon</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>McEwen, A.S.; Moore, Johnnie N.; Shoemaker, E.M.</p> <p>1997-01-01</p> <p>The relatively recent (< 1 b.y.) flux of asteroids and comets forming large <span class="hlt">craters</span> on the Earth and Moon may be accurately recorded by <span class="hlt">craters</span> with bright rays on the Moon's farside. Many previously unknown farside rayed <span class="hlt">craters</span> are clearly distinguished in the low-phase-angle images returned by the Clementine spacecraft. Some large rayed <span class="hlt">craters</span> on the lunar nearside are probably significantly older than 1 Ga; rays remain visible over the maria due to compositional contrasts long after soils have reached optical maturity. Most of the farside crust has a more homogeneous composition and only immature rays are visible. The size-frequency distribution of farside rayed <span class="hlt">craters</span> is similar to that measured for Eratosthenian <span class="hlt">craters</span> (up to 3.2 b.y.) at diameters larger than 15 km. The areal density of farside rayed <span class="hlt">craters</span> matches that of a corrected tabulation of nearside Copernican <span class="hlt">craters</span>. Hence the presence of bright rays due to immature soils around large <span class="hlt">craters</span> provides a consistent time-stratigraphic basis for defining the base of the Copernican System. The density of large <span class="hlt">craters</span> less than ???3.2 b.y. old is ???3.2 times higher than that of large farside rayed <span class="hlt">craters</span> alone. This observation can be interpreted in two ways: (1) the average <span class="hlt">cratering</span> rate has been constant over the past 3.2 b.y. and the base of the Copernican is ???1 Ga, or (2) the <span class="hlt">cratering</span> rate has increased in recent geologic time and the base of the Copernican is less than 1 Ga. We favor the latter interpretation because the rays of Copernicus (800-850 m.y. old) appear to be very close to optical maturity, <span class="hlt">suggesting</span> that the average Copernican <span class="hlt">cratering</span> rate was ???35% higher than the average Eratosthenian rate. Other lines of evidence for an increase in the Phanerozoic (545 Ga) <span class="hlt">cratering</span> rate are (1) the densities of small <span class="hlt">craters</span> superimposed on Copernicus and Apollo landing sites, (2) the rates estimated from well-dated terrestrial <span class="hlt">craters</span> (??? 120 m.y.) and from present-day astronomical</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/5480441-observations-kaiser-effect-under-multiaxial-stress-states-implications-its-use-determining-situ-stress','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/5480441-observations-kaiser-effect-under-multiaxial-stress-states-implications-its-use-determining-situ-stress"><span>Observations of the <span class="hlt">Kaiser</span> effect under multiaxial stress states: Implications for its use in determining in situ stress</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Holcomb, D.J.</p> <p>1993-10-08</p> <p>Experimental tests of the <span class="hlt">Kaiser</span> effect, the stress-history dependence of acoustic emission production, show that interactions between principal stresses cannot be ignored as is commonly done when trying to use the <span class="hlt">Kaiser</span> effect to determine in situ stress. Experimental results obtained under multiaxial stress states are explained in terms of a qualitative model. The results show that the commonly-used technique of loading uniaxially along various directions to determine stress history must be reevaluated as it cannot be justified in terms of the laboratory experiments. One possible resolution of the conflict between laboratory and field results is that the <span class="hlt">Kaiser</span> effectmore » phenomenon observed in cores retrieved from the earth is not the same phenomenon as is observed in rock loaded under laboratory conditions.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19810013459','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19810013459"><span>An investigation of the <span class="hlt">cratering</span>-induced motions occurring during the formation of bowl-shaped <span class="hlt">craters</span>. [using high explosive charges as the <span class="hlt">cratering</span> source</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Piekutowski, A. J.</p> <p>1980-01-01</p> <p>The effects of the dynamic processes which occur during <span class="hlt">crater</span> formation were examined using small hemispherical high-explosive charges detonated in a tank which had one wall constructed of a thick piece of clear plexiglas. <span class="hlt">Crater</span> formation and the motions of numerous tracer particles installed in the <span class="hlt">cratering</span> medium at the medium-wall interface were viewed through the wall of this quarter-space tank and recorded with high-speed cameras. Subsequent study and analysis of particle motions and events recorded on the film provide data needed to develop a time-sequence description of the formation of a bowl-shaped <span class="hlt">crater</span>. Tables show the dimensions of <span class="hlt">craters</span> produced in a quarter-space tank compared with dimensions of <span class="hlt">craters</span> produced in normal half-space tanks. <span class="hlt">Crater</span> growth rate summaries are also tabulated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA05739&hterms=marte&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dmarte','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA05739&hterms=marte&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dmarte"><span>Marte Valles <span class="hlt">Crater</span> 'Island'</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2004-01-01</p> <p><p/>10 April 2004 Marte Valles is an outflow channel system that straddles 180oW longitude between the region south of Cerberus and far northwestern Amazonis. The floor of the Marte valleys have enigmatic platy flow features that some argue are formed by lava, others <span class="hlt">suggest</span> they are remnants of mud flows. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows an island created in the middle of the main Marte Valles channel as fluid---whether lava or mud---flowed past two older meteor impact <span class="hlt">craters</span>. The <span class="hlt">craters</span> are located near 21.5oN, 175.3oW. The image covers an area about 3 km (1.9 mi) across. Sunlight illuminates the scene from the lower left.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA19263.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA19263.html"><span>Crumpled <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2015-03-30</p> <p>It is no secret that Mercury's surface is scarred by abundant tectonic deformation, the vast majority of which is due to the planet's history of cooling and contraction through time. Yet Mercury is also heavily <span class="hlt">cratered</span>, and hosts widespread volcanic plains. So it's perhaps unsurprising that these three types of landform often intersect-literally-as shown in this scene. Here, an unnamed <span class="hlt">crater</span>, about 7.5 km (4.7 mi.) in diameter was covered, and almost fully buried, by lava. At some point after, compression of the surface formed scarps and ridges in the area that, when they reached the buried <span class="hlt">crater</span>, came to describe its curved outline. Many arcuate ridges on Mercury formed this way. In this high-resolution view, we can also see the younger, later population of smaller <span class="hlt">craters</span> that pock-mark the surface. http://photojournal.jpl.nasa.gov/catalog/PIA19263</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70012357','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70012357"><span>Goat paddock cryptoexplosion <span class="hlt">crater</span>, Western Australia</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Harms, J.E.; Milton, D.J.; Ferguson, J.; Gilbert, D.J.; Harris, W.K.; Goleby, B.</p> <p>1980-01-01</p> <p>Goat Paddock, a <span class="hlt">crater</span> slightly over 5 km in diameter (18??20??? S, 126??40???E), lies at the north edge of the King Leopold Range/Mueller Range junction in the Kimberley district, Western Australia (Fig. 1). It was noted as a geological anomaly in 1964 during regional mapping by the Bureau of Mineral Resources, Geology and Geophysics and the Geological Survey of Western Australia. The possibility of its being a meteorite impact <span class="hlt">crater</span> has been discussed1, although this <span class="hlt">suggestion</span> was subsequently ignored2. Two holes were drilled by a mining corporation in 1972 to test whether kimberlite underlay the structure. Here we report the findings of five days of reconnaissance in August 1979 which established that Goat Paddock is a cryptoexplosion <span class="hlt">crater</span> containing shocked rocks and an unusually well exposed set of structural features. ?? 1980 Nature Publishing Group.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014Icar..239..186B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014Icar..239..186B"><span>Martian Low-Aspect-Ratio Layered Ejecta (LARLE) <span class="hlt">craters</span>: Distribution, characteristics, and relationship to pedestal <span class="hlt">craters</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Barlow, Nadine G.; Boyce, Joseph M.; Cornwall, Carin</p> <p>2014-09-01</p> <p>Low-Aspect-Ratio Layered Ejecta (LARLE) <span class="hlt">craters</span> are a unique landform found on Mars. LARLE <span class="hlt">craters</span> are characterized by a <span class="hlt">crater</span> and normal layered ejecta pattern surrounded by an extensive but thin outer deposit which terminates in a sinuous, almost flame-like morphology. We have conducted a survey to identify all LARLE <span class="hlt">craters</span> ⩾1-km-diameter within the ±75° latitude zone and to determine their morphologic and morphometric characteristics. The survey reveals 140 LARLE <span class="hlt">craters</span>, with the majority (91%) located poleward of 40°S and 35°N and all occurring within thick mantles of fine-grained deposits which are likely ice-rich. LARLE <span class="hlt">craters</span> range in diameter from the cut-off limit of 1 km up to 12.2 km, with 83% being smaller than 5 km. The radius of the outer LARLE deposit displays a linear trend with the <span class="hlt">crater</span> radius and is greatest at higher polar latitudes. The LARLE deposit ranges in length between 2.56 and 14.81 <span class="hlt">crater</span> radii in average extent, with maximum length extending up to 21.4 <span class="hlt">crater</span> radii. The LARLE layer is very sinuous, with lobateness values ranging between 1.45 and 4.35. LARLE <span class="hlt">craters</span> display a number of characteristics in common with pedestal <span class="hlt">craters</span> and we propose that pedestal <span class="hlt">craters</span> are eroded versions of LARLE <span class="hlt">craters</span>. The distribution and characteristics of the LARLE <span class="hlt">craters</span> lead us to propose that impact excavation into ice-rich fine-grained deposits produces a dusty base surge cloud (like those produced by explosion <span class="hlt">craters</span>) that deposits dust and ice particles to create the LARLE layers. Salts emplaced by upward migration of water through the LARLE deposit produce a surficial duricrust layer which protects the deposit from immediate removal by eolian processes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA14954.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA14954.html"><span>Fresh Dark Ray <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2011-10-15</p> <p>The <span class="hlt">crater</span> on asteroid Vesta shown in this image from NASA Dawn spacecraft was emplaced onto the ejecta blanket of two large twin <span class="hlt">craters</span>. Commonly, rays from impact <span class="hlt">craters</span> are brighter than the surrounding surface.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA03907&hterms=pluton&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dpluton','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA03907&hterms=pluton&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dpluton"><span>Pandora Fretum <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2002-01-01</p> <p>[figure removed for brevity, see original site] (Released 26 July 2002) Another in a series of <span class="hlt">craters</span> with unusual interior deposits, this THEMIS image shows an unnamed <span class="hlt">crater</span> in the southern hemisphere Pandora Fretum region near the Hellas Basin. <span class="hlt">Craters</span> with eroded layered deposits are quite common on Mars but the crusty textured domes in the center of the image make this <span class="hlt">crater</span> more unusual. Looking vaguely like granitic intrusions, there erosional style is distinct from the rest of the interior deposit which shows a very obvious layered morphology. While it is unlikely that the domes are granite plutons, it is possible that they do represent some other shallowly emplaced magmatic intrusion. More likely still is that variations in induration of the layered deposit allow for variations in the erosional morphology. Note how the surface of the <span class="hlt">crater</span> floor in the northernmost portion of the image has a texture similar to that of the domes. This may represent an incipient form of the erosion that has produced the domes but has not progressed as far. An analysis of other <span class="hlt">craters</span> in the area may shed light on the origin of the domes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19950017405','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19950017405"><span>Small <span class="hlt">craters</span> on the meteoroid and space debris impact experiment</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Humes, Donald H.</p> <p>1995-01-01</p> <p>Examination of 9.34 m(exp 2) of thick aluminum plates from the Long Duration Exposure Facility (LDEF) using a 25X microscope revealed 4341 <span class="hlt">craters</span> that were 0.1 mm in diameter or larger. The largest was 3 mm in diameter. Most were roughly hemispherical with lips that were raised above the original plate surface. The <span class="hlt">crater</span> diameter measured was the diameter at the top of the raised lips. There was a large variation in the number density of <span class="hlt">craters</span> around the three-axis gravity-gradient stabilized spacecraft. A model of the near-Earth meteoroid environment is presented which uses a meteoroid size distribution based on the <span class="hlt">crater</span> size distribution on the space end of the LDEF. An argument is made that nearly all the <span class="hlt">craters</span> on the space end must have been caused by meteoroids and that very few could have been caused by man-made orbital debris. However, no chemical analysis of impactor residue that will distinguish between meteoroids and man-made debris is yet available. A small area (0.0447 m(exp 2)) of one of the plates on the space end was scanned with a 200X microscope revealing 155 <span class="hlt">craters</span> between 10 micron and 100 micron in diameter and 3 <span class="hlt">craters</span> smaller than 10 micron. This data was used to extend the size distribution of meteoroids down to approximately 1 micron. New penetration equations developed by Alan Watts were used to relate <span class="hlt">crater</span> dimensions to meteoroid size. The equations <span class="hlt">suggest</span> that meteoroids must have a density near 2.5 g/cm(exp 3) to produce <span class="hlt">craters</span> of the shape found on the LDEF. The near-Earth meteoroid model <span class="hlt">suggests</span> that about 80 to 85 percent of the 100 micron to 1 mm diameter <span class="hlt">craters</span> on the twelve peripheral rows of the LDEF were caused by meteoroids, leaving 15 to 20 percent to be caused by man-made orbital debris.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008P%26SS...56.1992S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008P%26SS...56.1992S"><span>GT-57633 catalogue of Martian impact <span class="hlt">craters</span> developed for evaluation of <span class="hlt">crater</span> detection algorithms</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Salamunićcar, Goran; Lončarić, Sven</p> <p>2008-12-01</p> <p><span class="hlt">Crater</span> detection algorithms (CDAs) are an important subject of the recent scientific research. A ground truth (GT) catalogue, which contains the locations and sizes of known <span class="hlt">craters</span>, is important for the evaluation of CDAs in a wide range of CDA applications. Unfortunately, previous catalogues of <span class="hlt">craters</span> by other authors cannot be easily used as GT. In this paper, we propose a method for integration of several existing catalogues to obtain a new <span class="hlt">craters</span> catalogue. The methods developed and used during this work on the GT catalogue are: (1) initial screening of used catalogues; (2) evaluation of self-consistency of used catalogues; (3) initial registration from three different catalogues; (4) cross-evaluation of used catalogues; (5) additional registrations and registrations from additional catalogues; and (6) fine-tuning and registration with additional data-sets. During this process, all <span class="hlt">craters</span> from all major currently available manually assembled catalogues were processed, including catalogues by Barlow, Rodionova, Boyce, Kuzmin, and our previous work. Each <span class="hlt">crater</span> from the GT catalogue contains references to <span class="hlt">crater(s</span>) that are used for its registration. This provides direct access to all properties assigned to <span class="hlt">craters</span> from the used catalogues, which can be of interest even to those scientists that are not directly interested in CDAs. Having all these <span class="hlt">craters</span> in a single catalogue also provides a good starting point for searching for <span class="hlt">craters</span> still not catalogued manually, which is also expected to be one of the challenges of CDAs. The resulting new GT catalogue contains 57,633 <span class="hlt">craters</span>, significantly more than any previous catalogue. From this point of view, GT-57633 catalogue is currently the most complete catalogue of large Martian impact <span class="hlt">craters</span>. Additionally, each <span class="hlt">crater</span> from the resulting GT-57633 catalogue is aligned with MOLA topography and, during the final review phase, additionally registered/aligned with 1/256° THEMIS-DIR, 1/256° MDIM and 1/256° MOC</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMEP53B1731R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMEP53B1731R"><span>Monturaqui meteorite impact <span class="hlt">crater</span>, Chile: A field test of the utility of satellite-based mapping of ejecta at small <span class="hlt">craters</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rathbun, K.; Ukstins, I.; Drop, S.</p> <p>2017-12-01</p> <p>Monturaqui <span class="hlt">Crater</span> is a small ( 350 m diameter), simple meteorite impact <span class="hlt">crater</span> located in the Atacama Desert of northern Chile that was emplaced in Ordovician granite overlain by discontinuous Pliocene ignimbrite. Ejecta deposits are granite and ignimbrite, with lesser amounts of dark impact melt and rare tektites and iron shale. The impact restructured existing drainage systems in the area that have subsequently eroded through the ejecta. Satellite-based mapping and modeling, including a synthesis of photographic satellite imagery and ASTER thermal infrared imagery in ArcGIS, were used to construct a basic geological interpretation of the site with special emphasis on understanding ejecta distribution patterns. This was combined with field-based mapping to construct a high-resolution geologic map of the <span class="hlt">crater</span> and its ejecta blanket and field check the satellite-based geologic interpretation. The satellite- and modeling-based interpretation <span class="hlt">suggests</span> a well-preserved <span class="hlt">crater</span> with an intact, heterogeneous ejecta blanket that has been subjected to moderate erosion. In contrast, field mapping shows that the <span class="hlt">crater</span> has a heavily-eroded rim and ejecta blanket, and the ejecta is more heterogeneous than previously thought. In addition, the erosion rate at Monturaqui is much higher than erosion rates reported elsewhere in the Atacama Desert. The bulk compositions of the target rocks at Monturaqui are similar and the ejecta deposits are highly heterogeneous, so distinguishing between them with remote sensing is less effective than with direct field observations. In particular, the resolution of available imagery for the site is too low to resolve critical details that are readily apparent in the field on the scale of 10s of cm, and which significantly alter the geologic interpretation. The limiting factors for effective remote interpretation at Monturaqui are its target composition and <span class="hlt">crater</span> size relative to the resolution of the remote sensing methods employed. This</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19920003687','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19920003687"><span>Degradation studies of Martian impact <span class="hlt">craters</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Barlow, N. G.</p> <p>1991-01-01</p> <p>The amount of obliteration suffered by Martian impact <span class="hlt">craters</span> is quantified by comparing measurable attributes of the current <span class="hlt">crater</span> shape to those values expected for a fresh <span class="hlt">crater</span> of identical size. <span class="hlt">Crater</span> diameters are measured from profiles obtained using photoclinometry across the structure. The relationship between the diameter of a fresh <span class="hlt">crater</span> and a <span class="hlt">crater</span> depth, floor width, rim height, central peak height, etc. was determined by empirical studies performed on fresh Martian impact <span class="hlt">craters</span>. We utilized the changes in <span class="hlt">crater</span> depth and rim height to judge the degree of obliteration suffered by Martian impact <span class="hlt">craters</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19890001447','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19890001447"><span><span class="hlt">Crater</span> ejecta morphology and the presence of water on Mars</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Schultz, P. H.</p> <p>1987-01-01</p> <p>The possible effects of projectile, target, and environment on the <span class="hlt">cratering</span> process is reviewed. It is <span class="hlt">suggested</span> that contradictions in interpreting Martian <span class="hlt">crater</span> ejecta morphologies reflect over simplifying the process as a singular consequence of buried water. It seem entirely possible that most ejecta facies could be produced without the presence of liquid water. However, the combination of extraordinary ejecta fluidity, absence of secondaries, and high ejection angles all would point to the combined effects of atmosphere and fluid rich substrates. Moreover, recent experiments revealing the broad scour zone associated with rapid vapor expansion may account for numerous <span class="hlt">craters</span> in the circumpolar regions with subtle radial grooving extending 10 <span class="hlt">crater</span> radii away with faint distal ramparts. Thus certain <span class="hlt">crater</span> ejecta morphologies may yet provide fundamental clues for the presence of unbound water.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20000031463&hterms=cold+chain&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dcold%2Bchain','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20000031463&hterms=cold+chain&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dcold%2Bchain"><span><span class="hlt">Cratering</span> on Titan: A Pre-Cassini Perspective</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lorenz, R. D.</p> <p>1997-01-01</p> <p>The NASA-ESA Cassini mission, comprising a formidably instrumented orbiter and parachute-borne probe to be launched this October, promises to reveal a <span class="hlt">crater</span> population on Titan that has been heretofore hidden by atmospheric haze. This population on the largest remaining unexplored surface in the solar system will be invaluable in comparative planetological studies, since it introduces evidence of the atmospheric effects of <span class="hlt">cratering</span> on an icy satellite. Here, I highlight some impact features we may hope to find and could devote some modeling effort toward. Titan in a Nutshell: Radius= 2575 km. Density= 1880 kg/cubic m consistent with rock-ice composition. Surface pressure = 1.5 bar. Surface gravity = 1.35 m/square s Atmosphere -94% N2 6% CH, Surface temperature = 94K Tropopause temperature = 70K at 40 km alt. Probable liquid hydrocarbon deposits exist on or near the surface.Titan in a Nutshell: Radius= 2575 km. Density= 1880 kg/cubic m consistent with rock-ice composition. Surface pressure = 1.5 bar. Surface gravity = 1.35 m/square s; Atmosphere about 94% N2 6% CH, Surface temperature = 94K Tropopause temperature = 70K at 40 km alt. Probable liquid hydrocarbon deposits exist on or near the surface. Titan is comparable to Callisto and Ganymede for strength/gravity, Mars/Earth/Venus for atmospheric interaction, and Hyperion, Rhea, and Iapetus for impactor distribution. The leading/trailing asymmetry of <span class="hlt">crater</span> density from heliocentric impactors is expected to be about 5-6, in the absence of resurfacing. Any Saturnocentric impactor population is likely to alter this. In particular the impact disruption of Hyperion is noted; because of the 3:4 orbital resonance with Titan, fragments from the proto-Hyperion breakup would have rapidly accreted onto Titan. Titan's resurfacing history is of course unknown. The disruption of impactors into fragments that individually create small <span class="hlt">craters</span> is expected to occur. A crude estimate <span class="hlt">suggests</span> a maximum separation of about 2 km</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1997LPICo.922...31L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1997LPICo.922...31L"><span><span class="hlt">Cratering</span> on Titan: A Pre-Cassini Perspective</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lorenz, R. D.</p> <p>1997-01-01</p> <p>The NASA-ESA Cassini mission, comprising a formidably instrumented orbiter and parachute-borne probe to be launched this October, promises to reveal a <span class="hlt">crater</span> population on Titan that has been heretofore hidden by atmospheric haze. This population on the largest remaining unexplored surface in the solar system will be invaluable in comparative planetological studies, since it introduces evidence of the atmospheric effects of <span class="hlt">cratering</span> on an icy satellite. Here, I highlight some impact features we may hope to find and could devote some modeling effort toward. Titan in a Nutshell: Radius= 2575 km. Density= 1880 kg/cubic m consistent with rock-ice composition. Surface pressure = 1.5 bar. Surface gravity = 1.35 m/square s Atmosphere -94% N2 6% CH, Surface temperature = 94K Tropopause temperature = 70K at 40 km alt. Probable liquid hydrocarbon deposits exist on or near the surface.Titan in a Nutshell: Radius= 2575 km. Density= 1880 kg/cubic m consistent with rock-ice composition. Surface pressure = 1.5 bar. Surface gravity = 1.35 m/square s; Atmosphere about 94% N2 6% CH, Surface temperature = 94K Tropopause temperature = 70K at 40 km alt. Probable liquid hydrocarbon deposits exist on or near the surface. Titan is comparable to Callisto and Ganymede for strength/gravity, Mars/Earth/Venus for atmospheric interaction, and Hyperion, Rhea, and Iapetus for impactor distribution. The leading/trailing asymmetry of <span class="hlt">crater</span> density from heliocentric impactors is expected to be about 5-6, in the absence of resurfacing. Any Saturnocentric impactor population is likely to alter this. In particular the impact disruption of Hyperion is noted; because of the 3:4 orbital resonance with Titan, fragments from the proto-Hyperion breakup would have rapidly accreted onto Titan. Titan's resurfacing history is of course unknown. The disruption of impactors into fragments that individually create small <span class="hlt">craters</span> is expected to occur. A crude estimate <span class="hlt">suggests</span> a maximum separation of about 2 km</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010cosp...38..532S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010cosp...38..532S"><span>Method for evaluation of laboratory <span class="hlt">craters</span> using <span class="hlt">crater</span> detection algorithm for digital topography data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Salamunićcar, Goran; Vinković, Dejan; Lončarić, Sven; Vučina, Damir; Pehnec, Igor; Vojković, Marin; Gomerčić, Mladen; Hercigonja, Tomislav</p> <p></p> <p>In our previous work the following has been done: (1) the <span class="hlt">crater</span> detection algorithm (CDA) based on digital elevation model (DEM) has been developed and the GT-115225 catalog has been assembled [GRS, 48 (5), in press, doi:10.1109/TGRS.2009.2037750]; and (2) the results of comparison between explosion-induced laboratory <span class="hlt">craters</span> in stone powder surfaces and GT-115225 have been presented using depth/diameter measurements [41stLPSC, Abstract #1428]. The next step achievable using the available technology is to create 3D scans of such labo-ratory <span class="hlt">craters</span>, in order to compare different properties with simple Martian <span class="hlt">craters</span>. In this work, we propose a formal method for evaluation of laboratory <span class="hlt">craters</span>, in order to provide objective, measurable and reproducible estimation of the level of achieved similarity between these laboratory and real impact <span class="hlt">craters</span>. In the first step, the section of MOLA data for Mars (or SELENE LALT for Moon) is replaced with one or several 3D-scans of laboratory <span class="hlt">craters</span>. Once embedment was done, the CDA can be used to find out whether this laboratory <span class="hlt">crater</span> is similar enough to real <span class="hlt">craters</span>, as to be recognized as a <span class="hlt">crater</span> by the CDA. The CDA evaluation using ROC' curve represents how true detection rate (TDR=TP/(TP+FN)=TP/GT) depends on the false detection rate (FDR=FP/(TP+FP)). Using this curve, it is now possible to define the measure of similarity between laboratory and real impact <span class="hlt">craters</span>, as TDR or FDR value, or as a distance from the bottom-right origin of the ROC' curve. With such an approach, the reproducible (formally described) method for evaluation of laboratory <span class="hlt">craters</span> is provided.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014M%26PS...49.2175F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014M%26PS...49.2175F"><span>Shock metamorphism and impact melting in small impact <span class="hlt">craters</span> on Earth: Evidence from Kamil <span class="hlt">crater</span>, Egypt</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fazio, Agnese; Folco, Luigi; D'Orazio, Massimo; Frezzotti, Maria Luce; Cordier, Carole</p> <p>2014-12-01</p> <p>Kamil is a 45 m diameter impact <span class="hlt">crater</span> identified in 2008 in southern Egypt. It was generated by the hypervelocity impact of the Gebel Kamil iron meteorite on a sedimentary target, namely layered sandstones with subhorizontal bedding. We have carried out a petrographic study of samples from the <span class="hlt">crater</span> wall and ejecta deposits collected during our first geophysical campaign (February 2010) in order to investigate shock effects recorded in these rocks. Ejecta samples reveal a wide range of shock features common in quartz-rich target rocks. They have been divided into two categories, as a function of their abundance at thin section scale: (1) pervasive shock features (the most abundant), including fracturing, planar deformation features, and impact melt lapilli and bombs, and (2) localized shock features (the least abundant) including high-pressure phases and localized impact melting in the form of intergranular melt, melt veins, and melt films in shatter cones. In particular, Kamil <span class="hlt">crater</span> is the smallest impact <span class="hlt">crater</span> where shatter cones, coesite, stishovite, diamond, and melt veins have been reported. Based on experimental calibrations reported in the literature, pervasive shock features <span class="hlt">suggest</span> that the maximum shock pressure was between 30 and 60 GPa. Using the planar impact approximation, we calculate a vertical component of the impact velocity of at least 3.5 km s-1. The wide range of shock features and their freshness make Kamil a natural laboratory for studying impact <span class="hlt">cratering</span> and shock deformation processes in small impact structures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA21410.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA21410.html"><span>Yalode <span class="hlt">Crater</span> on Ceres</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2017-06-28</p> <p>Yalode <span class="hlt">crater</span> is so large -- at 162 miles, 260 kilometers in diameter -- that a variety of vantage points is necessary to understand its geological context. This view of the northern portion of Yalode is one of many images NASA's Dawn spacecraft has taken of this <span class="hlt">crater</span>. The large impact that formed the <span class="hlt">crater</span> likely involved a lot of heat, which explains the relatively smooth <span class="hlt">crater</span> floor punctuated by smaller <span class="hlt">craters</span>. A couple of larger <span class="hlt">craters</span> in Yalode have polygonal shapes. This type of <span class="hlt">crater</span> shape is frequently found on Ceres and may be indicative of extensive underground fractures. The larger <span class="hlt">crater</span> to the right of center in this image is called Lono (12 miles, 20 kilometers in diameter) and the one below it is called Besua (11 miles, 17 kilometers). Some of the small <span class="hlt">craters</span> are accompanied by ejecta blankets that are more reflective than their surroundings. The strange Nar Sulcus fractures can be seen in the bottom left corner of the picture. Linear features seen throughout the image may have formed when material collapsed above empty spaces underground. These linear features include linear chains of <span class="hlt">craters</span> called catenae. Dawn took this image on September 27, 2015, from 915 miles (1,470 kilometers) altitude. The center coordinates of this image are 32 degrees south latitude and 300 degrees east longitude. Yalode gets its name from a goddess worshipped by women at the harvest rites in the Dahomey culture of western Africa. Besua takes its name from the Egyptian grain god, and Lono from the Hawaiian god of agriculture. https://photojournal.jpl.nasa.gov/catalog/PIA21410</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_8 --> <div id="page_9" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="161"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA04678&hterms=under+armor&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dunder%2Barmor','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA04678&hterms=under+armor&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dunder%2Barmor"><span>Pedestal <span class="hlt">Crater</span> and Yardangs</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2003-01-01</p> <p>MGS MOC Release No. MOC2-444, 6 August 2003<p/>This April 2003 Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a small meteor impact <span class="hlt">crater</span> that has been modified by wind erosion. Two things happened after the <span class="hlt">crater</span> formed. First, the upper few meters of surface material into which the meteor impacted was later eroded away by wind. The <span class="hlt">crater</span> ejecta formed a protective armor that kept the material under the ejecta from been blown away. This caused the <span class="hlt">crater</span> and ejecta to appear as if standing upon a raised platform--a feature that Mars geologists call a <i>pedestal <span class="hlt">crater</span>.</i> Next, the pedestal <span class="hlt">crater</span> was buried beneath several meters of new sediment, and then this material was eroded away by wind to form the array of sharp ridges that run across the pedestal <span class="hlt">crater</span>'s surface. These small ridges are known as <i>yardangs</i>. This picture is illuminated by sunlight from the upper left; it is located in west Daedalia Planum near 14.6oS, 131.9oW.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA00088.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA00088.html"><span>Venus - Stein Triplet <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>1996-01-29</p> <p>NASA Magellan synthetic aperture radar SAR imaged this unique triplet <span class="hlt">crater</span>, or <span class="hlt">crater</span> field during orbits 418-421 on Sept. 21, 1990. The three <span class="hlt">craters</span> appear to have relatively steep walls. http://photojournal.jpl.nasa.gov/catalog/PIA00088</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA22462.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA22462.html"><span>A New Impact <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2018-05-29</p> <p>NASA's Mars Reconnaissance Orbiter (MRO) keeps finding new impact sites on Mars. This one occurred within the dense secondary <span class="hlt">crater</span> field of Corinto <span class="hlt">Crater</span>, to the north-northeast. The new <span class="hlt">crater</span> and its ejecta have distinctive color patterns. Once the colors have faded in a few decades, this new <span class="hlt">crater</span> will still be distinctive compared to the secondaries by having a deeper cavity compared to its diameter. https://photojournal.jpl.nasa.gov/catalog/PIA22462</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1992Metic..27R.276P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1992Metic..27R.276P"><span>Meteorite Sterlitamak -- A New <span class="hlt">Crater</span> Forming Fall</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Petaev, M. I.</p> <p>1992-07-01</p> <p> recovered at a depth of ~12 m. This sample is a 50 x 45 x 28 cm block with front, rear and two adjoining lateral surfaces covered by regmaglypts and thick (~0.5 mm) fusion crust. The other two surfaces are very rough, contain no regmaglypts, and have a thinner fusion crust. The preimpact shape of the meteorite may be approximately modeled as a slab ~100 x 100 x 28 cm. An estimate of the projectile mass was made based on the <span class="hlt">crater</span> dimensions. From the relationships between <span class="hlt">crater</span> diameter and projectile mass determined for the Sikhote-Alin <span class="hlt">craters</span>, the impact mass of the Sterlitamak meteorite is estimated at ~1 ton (Petaev, 1992). A separate estimate, based on <span class="hlt">cratering</span> energy, yields a total mass of ~1.5 tons (Ivanov, Petaev, 1992). A comparison of the estimated projectile mass and the weight and morphology of the individual recovered <span class="hlt">suggests</span> a fragmentation of the projectile in the atmosphere and the formation of the <span class="hlt">crater</span> by the impact of an agglomeration of individuals. The other fragments of the projectile are still in the <span class="hlt">crater</span>. REFERENCES Ivanov B.A., Petaev M.I. (1992) Lunar Planet. Sci. (abstract), 23, 573-574. Petaev M.I. (1992) Astron. Vestnik, #4, in press (in Russian) (English translation is named Solar System Research). Petaev M.I., Kisarev Yu.L., Mustafin Sh.A., Shakurov R.K., Pavlov A.V., Ivanov B.A. (1991) Lunar Planet. Sci. (abstract), 22, 1059-1060</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA04436&hterms=block+chain&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dblock%2Bchain','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA04436&hterms=block+chain&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dblock%2Bchain"><span><span class="hlt">Crater</span> Chains</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2003-01-01</p> <p><p/> [figure removed for brevity, see original site] <p/>The large <span class="hlt">crater</span> at the top of this THEMIS visible image has several other <span class="hlt">craters</span> inside of it. Most noticeable are the <span class="hlt">craters</span> that form a 'chain' on the southern wall of the large <span class="hlt">crater</span>. These <span class="hlt">craters</span> are a wonderful example of secondary impacts. They were formed when large blocks of ejecta from an impact crashed back down onto the surface of Mars. Secondaries often form radial patterns around the impact <span class="hlt">crater</span> that generated them, allowing researchers to trace them back to their origin.<p/>Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.<p/>NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.<p/>Image information: VIS instrument. Latitude 19.3, Longitude 347.5 East (12.5 West). 19 meter/pixel resolution.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA08783&hterms=duck&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dduck','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA08783&hterms=duck&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dduck"><span>'Victoria <span class="hlt">Crater</span>' from 'Duck Bay'</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2006-01-01</p> <p><p/> NASA's Mars rover Opportunity edged 3.7 meters (12 feet) closer to the top of the 'Duck Bay' alcove along the rim of 'Victoria <span class="hlt">Crater</span>' during the rover's 952nd Martian day, or sol (overnight Sept. 27 to Sept. 28), and gained this vista of the <span class="hlt">crater</span>. The rover's navigation camera took the seven exposures combined into this mosaic view of the <span class="hlt">crater</span>'s interior. This <span class="hlt">crater</span> has been the mission's long-term destination for the past 21 Earth months. <p/> The far side of the <span class="hlt">crater</span> is about 800 meters (one-half mile) away. The rim of the <span class="hlt">crater</span> is composed of alternating promontories, rocky points towering approximately 70 meters (230 feet) above the <span class="hlt">crater</span> floor, and recessed alcoves, such as Duck Bay. The bottom of the <span class="hlt">crater</span> is covered by sand that has been shaped into ripples by the Martian wind. The rocky cliffs in the foreground have been informally named 'Cape Verde,' on the left, and 'Cabo Frio,' on the right. <p/> Victoria <span class="hlt">Crater</span> is about five times wider than 'Endurance <span class="hlt">Crater</span>,' which Opportunity spent six months examining in 2004, and about 40 times wider than 'Eagle <span class="hlt">Crater</span>,' where Opportunity first landed. The great lure of Victoria is an expectation that the thick stack of geological layers exposed in the <span class="hlt">crater</span> walls could reveal the record of past environmental conditions over a much greater span of time than Opportunity has read from rocks examined earlier in the mission. <p/> This view is presented as a cylindrical projection with geometric seam correction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/477742','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/477742"><span><span class="hlt">Kaiser</span> Permanente/Sandia National health care model. Phase I prototype final report. Part 1 - model overview</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Edwards, D.; Yoshimura, A.; Butler, D.</p> <p>1996-11-01</p> <p>This report describes the results of a Cooperative Research and Development Agreement between Sandia National Laboratories and <span class="hlt">Kaiser</span> Permanente Southern California to develop a prototype computer model of <span class="hlt">Kaiser</span> Permanente`s health care delivery system. As a discrete event simulation, SimHCO models for each of 100,000 patients the progression of disease, individual resource usage, and patient choices in a competitive environment. SimHCO is implemented in the object-oriented programming language C++, stressing reusable knowledge and reusable software components. The versioned implementation of SimHCO showed that the object-oriented framework allows the program to grow in complexity in an incremental way. Furthermore, timing calculationsmore » showed that SimHCO runs in a reasonable time on typical workstations, and that a second phase model will scale proportionally and run within the system constraints of contemporary computer technology. This report is published as two documents: Model Overview and Domain Analysis. A separate <span class="hlt">Kaiser</span>-proprietary report contains the Disease and Health Care Organization Selection Models.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA15660.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA15660.html"><span><span class="hlt">Crater</span> Impacts on Vesta</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2012-05-10</p> <p>This graphic shows the global distribution of <span class="hlt">craters</span> that hit the giant asteroid Vesta, based on data from NASA Dawn mission. The yellow circles indicate <span class="hlt">craters</span> of 2 miles or wider, with the size of the circles indicating the size of the <span class="hlt">crater</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA21915.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA21915.html"><span>Kokopelli <span class="hlt">Crater</span> on Ceres</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2017-12-14</p> <p>This image obtained by NASA's Dawn spacecraft shows a field of small <span class="hlt">craters</span> next to Kokopelli <span class="hlt">Crater</span>, seen at bottom right in this image, on dwarf planet Ceres. The small <span class="hlt">craters</span> overlay a smooth, wavy material that represents ejecta from nearby Dantu <span class="hlt">Crater</span>. The small <span class="hlt">craters</span> were formed by blocks ejected in the Dantu impact event, and likely from the Kokopelli impact as well. Kokopelli is named after the fertility deity who presides over agriculture in the tradition of the Pueblo people from the southwestern United States. The <span class="hlt">crater</span> measures 21 miles (34 kilometers) in diameter. Dawn took this image during its first extended mission on August 11, 2016, from its low-altitude mapping orbit, at about 240 miles (385 kilometers) above the surface. The center coordinates of this image are 20 degrees north latitude, 123 degrees east longitude. https://photojournal.jpl.nasa.gov/catalog/PIA21915</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19940016252&hterms=origin+military&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dorigin%2Bmilitary','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19940016252&hterms=origin+military&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dorigin%2Bmilitary"><span>Named Venusian <span class="hlt">craters</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Russell, Joel F.; Schaber, Gerald G.</p> <p>1993-01-01</p> <p>Schaber et al. compiled a database of 841 <span class="hlt">craters</span> on Venus, based on Magellan coverage of 89 percent of the planet's surface. That database, derived from coverage of approximately 98 percent of Venus' surface, has been expanded to 912 <span class="hlt">craters</span>, ranging in diameter from 1.5 to 280 km. About 150 of the larger <span class="hlt">craters</span> were previously identified by Pioneer Venus and Soviet Venera projects and subsequently formally named by the International Astronomical Union (IAU). Altogether, the <span class="hlt">crater</span> names submitted to the IAU for approval to date number about 550, a little more than half of the number of <span class="hlt">craters</span> identified on Magellan images. The IAU will consider more names as they are submitted for approval. Anyone--planetary scientist or layman--may submit names; however, candidate names must conform to IAU rules. The person to be honored must be deceased for at least three years, must not be a religious figure or a military or political figure of the 19th or 20th century, and, for Venus, must be a woman. All formally and provisionally approved names for Venusian impact <span class="hlt">craters</span>, along with their latitude, longitude, size, and origin of their name, will be presented at LPSC and will be available as handouts.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1997LPI....28..631I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1997LPI....28..631I"><span>Block oscillation model for impact <span class="hlt">crater</span> collapse</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ivanov, B. A.; Kostuchenko, V. N.</p> <p>1997-03-01</p> <p>Previous investigations of the impact <span class="hlt">crater</span> formation mechanics have shown that the late stage, a transient cavity collapse in a gravity field, may be modeled with a traditional rock mechanics if one ascribes very specific mechanical properties of rock in the vicinity of a <span class="hlt">crater</span>: an effective strength of rock needed is around 30 bar, and effective angle of internal friction below 5 deg. The rock media with such properties may be supposed 'temporary fluidized'. The nature of this fluidization is now poorly understood; an acoustic (vibration) nature of this fluidization has been <span class="hlt">suggested</span>. This model now seems to be the best approach to the problem. The open question is how to implement the model (or other possible models) in a hydrocode for numerical simulation of a dynamic <span class="hlt">crater</span> collapse. We study more relevant models of mechanical behavior of rocks during <span class="hlt">cratering</span>. The specific of rock deformation is that the rock media deforms not as a plastic metal-like continuum, but as a system of discrete rock blocks. The deep drilling of impact <span class="hlt">craters</span> revealed the system of rock blocks of 50 m to 200 m in size. We used the model of these block oscillations to formulate the appropriate rheological law for the subcrater flow during the modification stage.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19850015222&hterms=centrifuge&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dcentrifuge','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19850015222&hterms=centrifuge&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dcentrifuge"><span>Centrifuge Impact <span class="hlt">Cratering</span> Experiments</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Schmidt, R. M.; Housen, K. R.; Bjorkman, M. D.</p> <p>1985-01-01</p> <p>The kinematics of <span class="hlt">crater</span> growth, impact induced target flow fields and the generation of impact melt were determined. The feasibility of using scaling relationships for impact melt and <span class="hlt">crater</span> dimensions to determine impactor size and velocity was studied. It is concluded that a coupling parameter determines both the quantity of melt and the <span class="hlt">crater</span> dimensions for impact velocities greater than 10km/s. As a result impactor radius, a, or velocity, U cannot be determined individually, but only as a product in the form of a coupling parameter, delta U micron. The melt volume and <span class="hlt">crater</span> volume scaling relations were applied to Brent <span class="hlt">crater</span>. The transport of melt and the validity of the melt volume scaling relations are examined.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19870014075','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19870014075"><span><span class="hlt">Crater</span> ejecta morphology and the presence of water on Mars</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Schultz, Peter H.</p> <p>1987-01-01</p> <p>The purpose of this contribution is to review the possible effects of projectile, target, and environment on the <span class="hlt">cratering</span> process. The discussion presented <span class="hlt">suggests</span> that contradictions in interpreting Martian <span class="hlt">crater</span> ejecta morphologies reflect oversimplifying the process as a singular consequence of buried water. It seem entirely possible that most ejecta facies could be produced without the presence of liquid water. However, the combination of extraordinary ejecta fluidity, absence of secondaries, and high ejection angles all would point to the combined effects of atmosphere and fluid rich substrates. Moreover, recent experiments revealing the broad scour zone associated with rapid vapor expansion may account for numerous <span class="hlt">craters</span> in the circum-polar regions with subtle radial grooving extending 10 <span class="hlt">crater</span> radii away with faint distal ramparts. Thus certain <span class="hlt">crater</span> ejecta morphologies may yet provide fundamental clues for the presence of unbound water.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/FR-2010-10-28/pdf/2010-27268.pdf','FEDREG'); return false;" href="https://www.gpo.gov/fdsys/pkg/FR-2010-10-28/pdf/2010-27268.pdf"><span>75 FR 66302 - Establishment of Class E Airspace; <span class="hlt">Kaiser</span>/Lake Ozark, MO</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collection.action?collectionCode=FR">Federal Register 2010, 2011, 2012, 2013, 2014</a></p> <p></p> <p>2010-10-28</p> <p>... Class E airspace for the <span class="hlt">Kaiser</span>/Lake Ozark, MO, area to accommodate Area Navigation (RNAV) Standard Instrument Approach Procedures (SIAP) at Camdenton Memorial Airport, Camdenton, MO. The FAA is taking this action to enhance the safety and management of Instrument Flight Rule (IFR) operations at the airport...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/imap/2790/pdf/i2790.pdf','USGSPUBS'); return false;" href="https://pubs.usgs.gov/imap/2790/pdf/i2790.pdf"><span><span class="hlt">Crater</span> Lake revealed</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Ramsey, David W.; Dartnell, Peter; Bacon, Charles R.; Robinson, Joel E.; Gardner, James V.</p> <p>2003-01-01</p> <p>Around 500,000 people each year visit <span class="hlt">Crater</span> Lake National Park in the Cascade Range of southern Oregon. Volcanic peaks, evergreen forests, and <span class="hlt">Crater</span> Lake’s incredibly blue water are the park’s main attractions. <span class="hlt">Crater</span> Lake partially fills the caldera that formed approximately 7,700 years ago by the eruption and subsequent collapse of a 12,000-foot volcano called Mount Mazama. The caldera-forming or climactic eruption of Mount Mazama drastically changed the landscape all around the volcano and spread a blanket of volcanic ash at least as far away as southern Canada.Prior to the climactic event, Mount Mazama had a 400,000 year history of cone building activity like that of other Cascade volcanoes such as Mount Shasta. Since the climactic eruption, there have been several less violent, smaller postcaldera eruptions within the caldera itself. However, relatively little was known about the specifics of these eruptions because their products were obscured beneath <span class="hlt">Crater</span> Lake’s surface. As the <span class="hlt">Crater</span> Lake region is still potentially volcanically active, understanding past eruptive events is important to understanding future eruptions, which could threaten facilities and people at <span class="hlt">Crater</span> Lake National Park and the major transportation corridor east of the Cascades.Recently, the lake bottom was mapped with a high-resolution multibeam echo sounder. The new bathymetric survey provides a 2m/pixel view of the lake floor from its deepest basins virtually to the shoreline. Using Geographic Information Systems (GIS) applications, the bathymetry data can be visualized and analyzed to shed light on the geology, geomorphology, and geologic history of <span class="hlt">Crater</span> Lake.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006M%26PS...41.1509S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006M%26PS...41.1509S"><span>Martian subsurface properties and <span class="hlt">crater</span> formation processes inferred from fresh impact <span class="hlt">crater</span> geometries</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stewart, Sarah T.; Valiant, Gregory J.</p> <p>2006-10-01</p> <p>The geometry of simple impact <span class="hlt">craters</span> reflects the properties of the target materials, and the diverse range of fluidized morphologies observed in Martian ejecta blankets are controlled by the near-surface composition and the climate at the time of impact. Using the Mars Orbiter Laser Altimeter (MOLA) data set, quantitative information about the strength of the upper crust and the dynamics of Martian ejecta blankets may be derived from <span class="hlt">crater</span> geometry measurements. Here, we present the results from geometrical measurements of fresh <span class="hlt">craters</span> 3-50 km in rim diameter in selected highland (Lunae and Solis Plana) and lowland (Acidalia, Isidis, and Utopia Planitiae) terrains. We find large, resolved differences between the geometrical properties of the freshest highland and lowland <span class="hlt">craters</span>. Simple lowland <span class="hlt">craters</span> are 1.5-2.0 times deeper (≥5σo difference) with >50% larger cavities (≥2σo) compared to highland <span class="hlt">craters</span> of the same diameter. Rim heights and the volume of material above the preimpact surface are slightly greater in the lowlands over most of the size range studied. The different shapes of simple highland and lowland <span class="hlt">craters</span> indicate that the upper ˜6.5 km of the lowland study regions are significantly stronger than the upper crust of the highland plateaus. Lowland <span class="hlt">craters</span> collapse to final volumes of 45-70% of their transient cavity volumes, while highland <span class="hlt">craters</span> preserve only 25-50%. The effective yield strength of the upper crust in the lowland regions falls in the range of competent rock, approximately 9-12 MPa, and the highland plateaus may be weaker by a factor of 2 or more, consistent with heavily fractured Noachian layered deposits. The measured volumes of continuous ejecta blankets and uplifted surface materials exceed the predictions from standard <span class="hlt">crater</span> scaling relationships and Maxwell's Z model of <span class="hlt">crater</span> excavation by a factor of 3. The excess volume of fluidized ejecta blankets on Mars cannot be explained by concentration of ejecta through</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA00472&hterms=created+halo&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dcreated%2Bhalo','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA00472&hterms=created+halo&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dcreated%2Bhalo"><span>Venus - Impact <span class="hlt">Crater</span> 'Jeanne</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1991-01-01</p> <p>This Magellan full-resolution image shows Jeanne <span class="hlt">crater</span>, a 19.5 kilometer (12 mile) diameter impact <span class="hlt">crater</span>. Jeanne <span class="hlt">crater</span> is located at 40.0 degrees north latitude and 331.4 degrees longitude. The distinctive triangular shape of the ejecta indicates that the impacting body probably hit obliquely, traveling from southwest to northeast. The <span class="hlt">crater</span> is surrounded by dark material of two types. The dark area on the southwest side of the <span class="hlt">crater</span> is covered by smooth (radar-dark) lava flows which have a strongly digitate contact with surrounding brighter flows. The very dark area on the northeast side of the <span class="hlt">crater</span> is probably covered by smooth material such as fine-grained sediment. This dark halo is asymmetric, mimicking the asymmetric shape of the ejecta blanket. The dark halo may have been caused by an atmospheric shock or pressure wave produced by the incoming body. Jeanne <span class="hlt">crater</span> also displays several outflow lobes on the northwest side. These flow-like features may have formed by fine-grained ejecta transported by a hot, turbulent flow created by the arrival of the impacting object. Alternatively, they may have formed by flow of impact melt.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1991Icar...89..384F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1991Icar...89..384F"><span>Stickney-forming impact on PHOBOS - <span class="hlt">Crater</span> shape and induced stress distribution</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fujiwara, A.</p> <p>1991-02-01</p> <p>The results of the present simplified modeling of the size and rim shape of the Phobos <span class="hlt">crater</span> Stickney, together with the impact-generated stress patterns on the surface of the <span class="hlt">crater</span>, account for the general features observed and <span class="hlt">suggest</span>, on the basis of some of the P-waves' surface stress pattern, that a region of higher tensile stress may have occurred in the vicinity of 0 deg latitude and 270 deg W. The correlation of this pattern with the focusing of groove patterns that occurs on the trailing side of Phobos is <span class="hlt">suggested</span> to demonstrate a connection between these grooves and the Stickney <span class="hlt">crater</span>-forming impact.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4690707','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4690707"><span><span class="hlt">Kaiser</span> Permanente National Hand Hygiene Program</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Barnes, Sue; Barron, Dana; Becker, Linda; Canola, Teresa; Salemi, Charles</p> <p>2004-01-01</p> <p>Objective: Hand hygiene has historically been identified as an important intervention for preventing infection acquired in health care settings. Recently, the advent of waterless, alcohol-based skin degermer and elimination of artificial nails have been recognized as other important interventions for preventing infection. Supplied with this information, the National Infection Control Peer Group convened a KP Hand Hygiene Work Group, which, in August 2001, launched a National Hand Hygiene Program initiative titled “Infection Control: It’s In Our Hands” to increase compliance with hand hygiene throughout the <span class="hlt">Kaiser</span> Permanente (KP) organization. Design: The infection control initiative was designed to include employee and physician education as well as to implement standard hand hygiene products (eg, alcohol degermers), eliminate use of artificial nails, and monitor outcomes. Results: From 2001 through September 2003, the National KP Hand Hygiene Work Group coordinated implementation of the Hand Hygiene initiative throughout the KP organization. To date, outcome monitoring has shown a 26% increase in compliance with hand hygiene as well as a decrease in the number of bloodstream infections and methycillin-resistant Staphylococcus aureus (MRSA) infections. As of May 2003, use of artificial nails had been reduced by 97% nationwide. Conclusions: Endorsement of this Hand Hygiene Program initiative by KP leadership has led to implementation of the initiative at all medical centers throughout the KP organization. Outcome indicators to date <span class="hlt">suggest</span> that the initiative has been successful; final outcome monitoring will be completed in December 2003. PMID:26704605</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Icar..273..224S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Icar..273..224S"><span>Mini-RF and LROC observations of mare <span class="hlt">crater</span> layering relationships</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stickle, A. M.; Patterson, G. W.; Cahill, J. T. S.; Bussey, D. B. J.</p> <p>2016-07-01</p> <p>The lunar maria cover approximately 17% of the Moon's surface. Discerning discrete subsurface layers in the mare provides some constraints on thickness and volume estimates of mare volcanism. Multiple types of data and measurement techniques allow probing the subsurface and provide insights into these layers, including detailed examination of impact <span class="hlt">craters</span>, mare pits and sinuous rilles, and radar sounders. Unfortunately, radar sounding includes many uncertainties about the material properties of the lunar surface that may influence estimates of layer depth and thickness. Because they distribute material from depth onto the surface, detailed examination of impact ejecta blankets provides a reliable way to examine deeper material using orbital instruments such as cameras, spectrometers, or imaging radars. Here, we utilize Miniature Radio Frequency (Mini-RF) data to investigate the scattering characteristics of ejecta blankets of young lunar <span class="hlt">craters</span>. We use Circular Polarization Ratio (CPR) information from twenty-two young, fresh lunar <span class="hlt">craters</span> to examine how the scattering behavior changes as a function of radius from the <span class="hlt">crater</span> rim. Observations across a range of <span class="hlt">crater</span> size and relative ages exhibit significant diversity within mare regions. Five of the examined <span class="hlt">craters</span> exhibit profiles with no shelf of constant CPR near the <span class="hlt">crater</span> rim. Comparing these CPR profiles with LROC imagery shows that the magnitude of the CPR may be an indication of <span class="hlt">crater</span> degradation state; this may manifest differently at radar compared to optical wavelengths. Comparisons of radar and optical data also <span class="hlt">suggest</span> relationships between subsurface stratigraphy and structure in the mare and the block size of the material found within the ejecta blanket. Of the examined <span class="hlt">craters</span>, twelve have shelves of approximately constant CPR as well as discrete layers outcropping in the subsurface, and nine fall along a trend line when comparing shelf-width with thickness of subsurface layers. These</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_9 --> <div id="page_10" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="181"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA04030.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA04030.html"><span><span class="hlt">Crater</span> in Cydonia</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2002-12-16</p> <p>This image shows the dissected interior of a <span class="hlt">crater</span> in the Cydonia region of Mars. The flat-topped buttes and mesas in the northern portion of the image were once a continuous layer of material that filled the <span class="hlt">crater</span>. Since deposition, the material has been disturbed and dissected. The process that causes such landforms is not well known, but likely involves frozen subsurface water that may have found its way to the surface. The surfaces on the mesas are not rough, <span class="hlt">suggesting</span> that the whole scene is mantled with fine dust, masking the details that may give clues to whether surface water was involved at some point in the past. Small recent channels can be seen in the lower left. This is an indication of relatively recent small-scale surface activity, which has been could have been volcanic, fluvial, or some process involving subsurface volatiles (ice). http://photojournal.jpl.nasa.gov/catalog/PIA04030</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19940026526','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19940026526"><span>Morphology correlation of <span class="hlt">craters</span> formed by hypervelocity impacts</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Crawford, Gary D.; Rose, M. Frank; Zee, Ralph H.</p> <p>1993-01-01</p> <p>Dust-sized olivine particles were fired at a copper plate using the Space Power Institute hypervelocity facility, simulating micrometeoroid damage from natural debris to spacecraft in low-Earth orbit (LEO). Techniques were developed for measuring <span class="hlt">crater</span> volume, particle volume, and particle velocity, with the particle velocities ranging from 5.6 to 8.7 km/s. A roughly linear correlation was found between <span class="hlt">crater</span> volume and particle energy which <span class="hlt">suggested</span> that micrometeoroids follow standard hypervelocity relationships. The residual debris analysis showed that for olivine impacts of up to 8.7 km/s, particle residue is found in the <span class="hlt">crater</span>. By using the Space Power Institute hypervelocity facility, micrometeoroid damage to satellites can be accurately modeled.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19770044544&hterms=surface+density&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dsurface%2Bdensity','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19770044544&hterms=surface+density&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dsurface%2Bdensity"><span>Phobos - Surface density of impact <span class="hlt">craters</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Thomas, P.; Veverka, J.</p> <p>1977-01-01</p> <p>Revised <span class="hlt">crater</span> counts for Phobos are presented which are based on uniform Mariner 9 imagery and Duxbury's (1974) map of the satellite. The contiguous portion of the satellite's surface on which all <span class="hlt">craters</span> down to the limiting resolution of 0.2 to 0.3 km in diameter would be expected to be identified is delineated and found to contain 87 identifiable <span class="hlt">craters</span> larger than 0.2 km in diameter. Analysis of the <span class="hlt">crater</span> size distribution shows that the surface appears to be saturated for <span class="hlt">craters</span> exceeding 1 km in diameter but the <span class="hlt">crater</span> counts definitely fall below the saturation curve for smaller <span class="hlt">craters</span>. Reasons for this fall-off are considered, and it is noted that too few <span class="hlt">craters</span> are visible in Mariner 9 images of Deimos to permit meaningful <span class="hlt">crater</span> counts on that satellite's surface. It is concluded that, contrary to a previous assertion, the surfaces of Phobos and Deimos are not known to be saturated with <span class="hlt">craters</span> larger than 0.2 km in diameter.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19790055295&hterms=functional+structure&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dfunctional%2Bstructure','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19790055295&hterms=functional+structure&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dfunctional%2Bstructure"><span>Lunar <span class="hlt">crater</span> volumes - Interpretation by models of impact <span class="hlt">cratering</span> and upper crustal structure</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Croft, S. K.</p> <p>1978-01-01</p> <p>Lunar <span class="hlt">crater</span> volumes can be divided by size into two general classes with distinctly different functional dependence on diameter. <span class="hlt">Craters</span> smaller than approximately 12 km in diameter are morphologically simple and increase in volume as the cube of the diameter, while <span class="hlt">craters</span> larger than about 20 km are complex and increase in volume at a significantly lower rate implying shallowing. Ejecta and interior volumes are not identical and their ratio, Schroeters Ratio (SR), increases from about 0.5 for simple <span class="hlt">craters</span> to about 1.5 for complex <span class="hlt">craters</span>. The excess of ejecta volume causing the increase, can be accounted for by a discontinuity in lunar crust porosity at 1.5-2 km depth. The diameter range of significant increase in SR corresponds with the diameter range of transition from simple to complex <span class="hlt">crater</span> morphology. This observation, combined with theoretical rebound calculation, indicates control of the transition diameter by the porosity structure of the upper crust.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JGRE..123..763C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JGRE..123..763C"><span>An Assessment of Regional Variations in Martian Modified Impact <span class="hlt">Crater</span> Morphology</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Craddock, Robert A.; Bandeira, Lourenço.; Howard, Alan D.</p> <p>2018-03-01</p> <p>Impact <span class="hlt">craters</span> on Mars have been extensively modified by ancient geologic processes that may have included rainfall and surface runoff, snow and ice, denudation by lava flows, burial by eolian material, or others. Many of these processes can leave distinct signatures on the morphometry of the modified impact <span class="hlt">crater</span> as well as the surrounding landscape. To look for signs of potential regional differences in <span class="hlt">crater</span> modification processes, we conducted an analysis of different morphometric parameters related to modified impact <span class="hlt">craters</span> located in the Margaritifer Sinus, Sinus Sabaeus, Iapygia, Mare Tyrrhenum, Aeolis, and Eridania quadrangles, including depth, <span class="hlt">crater</span> wall slope, <span class="hlt">crater</span> floor slope, the curvature between the interior wall and the <span class="hlt">crater</span> floor slope, and the curvature between the interior wall and surrounding landscape. A Welch's t test analysis comparing these parameters shows that fresh impact <span class="hlt">craters</span> (Type 4) have consistent morphologies regardless of their geographic location examined in this study, which is not unexpected. Modified impact <span class="hlt">craters</span> both in the initial (Type 3) and terminal stages (Type 1) of modification also have statistically consistent morphologies. This would <span class="hlt">suggest</span> that the processes that operated in the late Noachian were globally ubiquitous, and that modified <span class="hlt">craters</span> eventually reached a stable <span class="hlt">crater</span> morphology. However, <span class="hlt">craters</span> preserved in advanced (but not terminal) stages of modification (Type 2) have morphologies that vary across the quadrangles. It is possible that these variations reflect spatial differences in the types and intensity of geologic processes that operated during the Noachian, implying that the ancient climate also varied across regions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.9655H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.9655H"><span>How old is Autolycus <span class="hlt">crater</span>?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hiesinger, Harald; Pasckert, Jan Henrik; van der Bogert, Carolyn H.; Robinson, Mark S.</p> <p>2016-04-01</p> <p>Accurately determining the lunar <span class="hlt">cratering</span> chronology is prerequisite for deriving absolute model ages (AMAs) across the lunar surface and throughout the Solar System [e.g., 1]. However, the lunar chronology is only constrained by a few data points over the last 1 Ga and there are no calibration data available between 1 and 3 Ga and beyond 3.9 Ga [2]. Rays from Autolycus and Aristillus cross the Apollo 15 landing site and presumably transported material to this location [3]. [4] proposed that at the Apollo 15 landing site about 32% of any exotic material would come from Autolycus <span class="hlt">crater</span> and 25% would come from Aristillus <span class="hlt">crater</span>. [5,6] proposed that the 39Ar-40Ar age of 2.1 Ga derived from three petrologically distinct, shocked Apollo 15 KREEP basalt samples, date Autolycus <span class="hlt">crater</span>. Grier et al. [7] reported that the optical maturity (OMAT) characteristics of these <span class="hlt">craters</span> are indistinguishable from the background values despite the fact that both <span class="hlt">craters</span> exhibit rays that were used to infer relatively young, i.e., Copernican ages [8,9]. Thus, both OMAT characteristics and radiometric ages of 2.1 Ga and 1.29 Ga for Autolycus and Aristillus, respectively, <span class="hlt">suggest</span> that these two <span class="hlt">craters</span> are not Copernican in age. [10] interpreted newer U-Pb ages of 1.4 and 1.9 Ga from sample 15405 as the formation ages of Aristillus and Autolycus. If Autolycus is indeed the source of the dated exotic material collected at the Apollo 15 landing site, than performing <span class="hlt">crater</span> size frequency distribution (CSFD) measurements for Autolycus offers the possibility to add a new calibration point to the lunar chronology, particularly in an age range that was previously unconstrained. We used calibrated and map-projected LRO NAC images to perform CSFD measurements within ArcGIS, using <span class="hlt">Crater</span>Tools [11]. CSFDs were then plotted with <span class="hlt">Crater</span>Stats [12], using the production and chronology functions of [13]. We determined ages of 3.72 and 3.85 Ga for the interior (Ai1) and ejecta area Ae3, which we</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014P%26SS...96...71M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014P%26SS...96...71M"><span>Impact <span class="hlt">cratering</span> experiments in brittle targets with variable thickness: Implications for deep pit <span class="hlt">craters</span> on Mars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Michikami, T.; Hagermann, A.; Miyamoto, H.; Miura, S.; Haruyama, J.; Lykawka, P. S.</p> <p>2014-06-01</p> <p>High-resolution images reveal that numerous pit <span class="hlt">craters</span> exist on the surface of Mars. For some pit <span class="hlt">craters</span>, the depth-to-diameter ratios are much greater than for ordinary <span class="hlt">craters</span>. Such deep pit <span class="hlt">craters</span> are generally considered to be the results of material drainage into a subsurface void space, which might be formed by a lava tube, dike injection, extensional fracturing, and dilational normal faulting. Morphological studies indicate that the formation of a pit <span class="hlt">crater</span> might be triggered by the impact event, and followed by collapse of the ceiling. To test this hypothesis, we carried out laboratory experiments of impact <span class="hlt">cratering</span> into brittle targets with variable roof thickness. In particular, the effect of the target thickness on the <span class="hlt">crater</span> formation is studied to understand the penetration process by an impact. For this purpose, we produced mortar targets with roof thickness of 1-6 cm, and a bulk density of 1550 kg/m3 by using a mixture of cement, water and sand (0.2 mm) in the ratio of 1:1:10, by weight. The compressive strength of the resulting targets is 3.2±0.9 MPa. A spherical nylon projectile (diameter 7 mm) is shot perpendicularly into the target surface at the nominal velocity of 1.2 km/s, using a two-stage light-gas gun. <span class="hlt">Craters</span> are formed on the opposite side of the impact even when no target penetration occurs. Penetration of the target is achieved when <span class="hlt">craters</span> on the opposite sides of the target connect with each other. In this case, the cross section of <span class="hlt">crater</span> somehow attains a flat hourglass-like shape. We also find that the <span class="hlt">crater</span> diameter on the opposite side is larger than that on the impact side, and more fragments are ejected from the <span class="hlt">crater</span> on the opposite side than from the <span class="hlt">crater</span> on the impact side. This result gives a qualitative explanation for the observation that the Martian deep pit <span class="hlt">craters</span> lack a raised rim and have the ejecta deposit on their floor instead. <span class="hlt">Craters</span> are formed on the opposite impact side even when no penetration</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA00472.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA00472.html"><span>Venus - Impact <span class="hlt">Crater</span> Jeanne</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>1996-11-20</p> <p>This full-resolution image from NASA Magellan spacecraft shows Jeanne <span class="hlt">crater</span>, a 19.5 kilometer (12 mile) diameter impact <span class="hlt">crater</span>. Jeanne <span class="hlt">crater</span> is located at 40.0 degrees north latitude and 331.4 degrees longitude. The distinctive triangular shape of the ejecta indicates that the impacting body probably hit obliquely, traveling from southwest to northeast. The <span class="hlt">crater</span> is surrounded by dark material of two types. The dark area on the southwest side of the <span class="hlt">crater</span> is covered by smooth (radar-dark) lava flows which have a strongly digitate contact with surrounding brighter flows. The very dark area on the northeast side of the <span class="hlt">crater</span> is probably covered by smooth material such as fine-grained sediment. This dark halo is asymmetric, mimicking the asymmetric shape of the ejecta blanket. The dark halo may have been caused by an atmospheric shock or pressure wave produced by the incoming body. Jeanne <span class="hlt">crater</span> also displays several outflow lobes on the northwest side. These flow-like features may have formed by fine-grained ejecta transported by a hot, turbulent flow created by the arrival of the impacting object. Alternatively, they may have formed by flow of impact melt. http://photojournal.jpl.nasa.gov/catalog/PIA00472</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA12328.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA12328.html"><span><span class="hlt">Crater</span> with Exposed Layers</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2017-01-17</p> <p>On Earth, geologists can dig holes and pull up core samples to find out what lies beneath the surface. On Mars, geologists cannot dig holes very easily themselves, but a process has been occurring for billions of years that has been digging holes for them: impact <span class="hlt">cratering</span>. Impact <span class="hlt">craters</span> form when an asteroid, meteoroid, or comet crashes into a planet's surface, causing an explosion. The energy of the explosion, and the resulting size of the impact <span class="hlt">crater</span>, depends on the size and density of the impactor, as well as the properties of the surface it hits. In general, the larger and denser the impactor, the larger the <span class="hlt">crater</span> it will form. The impact <span class="hlt">crater</span> in this image is a little less than 3 kilometers in diameter. The impact revealed layers when it excavated the Martian surface. Layers can form in a variety of different ways. Multiple lava flows in one area can form stacked sequences, as can deposits from rivers or lakes. Understanding the geology around impact <span class="hlt">craters</span> and searching for mineralogical data within their layers can help scientists on Earth better understand what the walls of impact <span class="hlt">craters</span> on Mars expose. http://photojournal.jpl.nasa.gov/catalog/PIA12328</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.P41D2864R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.P41D2864R"><span>Impact <span class="hlt">Craters</span>: Size-Dependent Degration Rates</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ravi, S.; Mahanti, P.; Meyer, H. M.; Robinson, M. S.</p> <p>2017-12-01</p> <p>From superposition relations, Shoemaker and Hackman (1) devised the lunar geologic timescale with Copernican and Eratosthenian as the most recent periods. Classifying <span class="hlt">craters</span> into the two periods is key to understanding impactor flux and regolith maturation rates over the last 3 Ga. Both Copernican and Eratosthenian <span class="hlt">craters</span> exhibit crisp morphologies (sharp rims, steep slopes), however, only the former exhibit high reflectance rays and ejecta (1). Based on the Optical Maturity Parameter (OMAT; 2), Grier et al. (3) classified 50 fresh <span class="hlt">craters</span> (D >20 km) into 3 categories - young (OMAT >0.22), intermediate, and old (OMAT <0.16). In our previous work, Copernican <span class="hlt">craters</span> (D > 10) were identified (4) from a catalogue of 11,875 <span class="hlt">craters</span> (5). In this work; we compare two size ranges (D: 5 km - 10 km and 10 km to 15 km) of 177 Copernican <span class="hlt">craters</span> based on the average OMAT, measured near the <span class="hlt">crater</span> rim (3). OMAT is measured at the <span class="hlt">crater</span> rim (as opposed to further away from the <span class="hlt">crater</span>) to minimize the influence of spatial variation of OMAT (6) in our investigation. We found that OMAT values are typically lower for smaller <span class="hlt">craters</span> (5km < D < 10km) in comparison to larger <span class="hlt">craters</span> (10km < D < 15km). However, when compared against morphological freshness (as determined by d/D for simpler <span class="hlt">craters</span>), the smaller <span class="hlt">craters</span> were fresher (higher d/D value). Since the OMAT value decreases with age, <span class="hlt">craters</span> with higher d/D value (morphologically fresher) should have higher OMAT, but this is not the case. We propose that quicker loss of OMAT (over time) for smaller <span class="hlt">craters</span> compared to decrease in d/D with <span class="hlt">crater</span> ageing, is responsible for the observed decreased OMAT for smaller <span class="hlt">craters</span>. (1) Shoemaker and Hackman, 1962 (2) Lucey et al., 2000 (3) Grier et al., 2001 (4) Ravi et al., 2016 (5) Reinhold et al., 2015 (6) Mahanti et al., 2016</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014Icar..243..337S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014Icar..243..337S"><span>Occurrence and mechanisms of impact melt emplacement at small lunar <span class="hlt">craters</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stopar, Julie D.; Hawke, B. Ray; Robinson, Mark S.; Denevi, Brett W.; Giguere, Thomas A.; Koeber, Steven D.</p> <p>2014-11-01</p> <p>Using observations from the Lunar Reconnaissance Orbiter Camera (LROC), we assess the frequency and occurrence of impact melt at simple <span class="hlt">craters</span> less than 5 km in diameter. Nine-hundred-and-fifty fresh, randomly distributed impact <span class="hlt">craters</span> were identified for study based on their maturity, albedo, and preservation state. The occurrence, frequency, and distribution of impact melt deposits associated with these <span class="hlt">craters</span>, particularly ponded melt and lobate flows, are diagnostic of melt emplacement mechanisms. Like larger <span class="hlt">craters</span>, those smaller than a few kilometers in diameter often exhibit ponded melt on the <span class="hlt">crater</span> floor as well as lobate flows near the <span class="hlt">crater</span> rim crest. The morphologies of these deposits <span class="hlt">suggest</span> gravity-driven flow while the melt was molten. Impact melt deposits emplaced as veneers and ;sprays;, thin layers of ejecta that drape other <span class="hlt">crater</span> materials, indicate deposition late in the <span class="hlt">cratering</span> process; the deposits of fine sprays are particularly sensitive to degradation. Exterior melt deposits found near the rims of a few dozen <span class="hlt">craters</span> are distributed asymmetrically around the <span class="hlt">crater</span> and are rare at <span class="hlt">craters</span> less than 2 km in diameter. Pre-existing topography plays a role in the occurrence and distribution of these melt deposits, particularly for <span class="hlt">craters</span> smaller than 1 km in diameter, but does not account for all observed asymmetries in impact melt distribution. The observed relative abundance and frequency of ponded melt and flows in and around simple lunar <span class="hlt">craters</span> increases with <span class="hlt">crater</span> diameter, as was previously predicted from models. However, impact melt deposits are found more commonly at simple lunar <span class="hlt">craters</span> (i.e., those less than a few kilometers in diameter) than previously expected. Ponded melt deposits are observed in roughly 15% of fresh <span class="hlt">craters</span> smaller than 300 m in diameter and 80% of fresh <span class="hlt">craters</span> between 600 m and 5 km in diameter. Furthermore, melt deposits are observed at roughly twice as many non-mare <span class="hlt">craters</span> than at mare <span class="hlt">craters</span>. We</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920033269&hterms=slump&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dslump','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920033269&hterms=slump&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dslump"><span>Terrace width variations in complex Mercurian <span class="hlt">craters</span> and the transient strength of <span class="hlt">cratered</span> Mercurian and lunar crust</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Leith, Andrew C.; Mckinnon, William B.</p> <p>1991-01-01</p> <p>The effective cohesion of the <span class="hlt">cratered</span> region during <span class="hlt">crater</span> collapse is determined via the widths of slump terraces of complex <span class="hlt">craters</span>. Terrace widths are measured for complex <span class="hlt">craters</span> on Mercury; these generally increase outward toward the rim for a given <span class="hlt">crater</span>, and the width of the outermost major terrace is generally an increasing function of <span class="hlt">crater</span> diameter. The terrace widths on Mercury and a gravity-driven slump model are used to estimate the strength of the <span class="hlt">cratered</span> region immediately after impact (about 1-2 MPa). A comparison with the previous study of lunar complex <span class="hlt">craters</span> by Pearce and Melosh (1986) indicates that the transient strength of <span class="hlt">cratered</span> Mercurian crust is no greater than that of the moon. The strength estimates vary only slightly with the geometric model used to restore the outermost major terrace to its precollapse configuration and are consistent with independent strength estimates from the simple-to-complex <span class="hlt">crater</span> depth/diameter transition.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA03469&hterms=falling+meteors&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dfalling%2Bmeteors','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA03469&hterms=falling+meteors&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dfalling%2Bmeteors"><span>Fresh Impact <span class="hlt">Crater</span> and Rays in Tharsis</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2002-01-01</p> <p> from the <span class="hlt">crater</span>--immediately adjacent to the <span class="hlt">crater</span> rim in the picture on the right (above, B)--is not continuously connected to the larger pattern of rays. Asymmetries in <span class="hlt">crater</span> form and ejecta patterns are generally believed to occur when the impact is oblique to the surface. The offset of the <span class="hlt">crater</span> from the center of the rays <span class="hlt">suggests</span> that the meteor struck at an angle, most likely from the bottom/lower right (south/southeast). The strange geometry of the rays is quite different from that seen for rays associated with impact <span class="hlt">craters</span> on the Moon and other airless bodies; one possible explanation is that they resulted from disruption of dust on the martian surface by winds generated by the shock wave as the meteor plunged through the martian atmosphere before it struck the ground.<p/>Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050167173','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050167173"><span>The Explorer's Guide to Impact <span class="hlt">Craters</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chuang, F.; Pierazzo, E.; Osinski, G.</p> <p>2005-01-01</p> <p>Impact <span class="hlt">cratering</span> is a fundamental geologic process of our solar system. It competes with other processes, such as plate tectonics, volcanism, fluvial, glacial and eolian activity, in shaping the surfaces of planetary bodies. In some cases, like the Moon and Mercury, impact <span class="hlt">craters</span> are the dominant landform. On other planetary bodies impact <span class="hlt">craters</span> are being continuously erased by the action of other geological processes, like volcanism on Io, erosion and plate tectonics on the Earth, tectonic and volcanic resurfacing on Venus, or ancient erosion periods on Mars. The study of <span class="hlt">crater</span> populations is one of the principal tools for understanding the geologic history of a planetary surface. Among the general public, impact <span class="hlt">cratering</span> has drawn wide attention through its portrayal in several Hollywood movies. Questions that are raised after watching these movies include: How do scientists learn about impact <span class="hlt">cratering</span>? , and What information do impact <span class="hlt">craters</span> provide in understanding the evolution of a planetary surface? Fundamental approaches used by scientists to learn about impact <span class="hlt">cratering</span> include field work at known terrestrial <span class="hlt">craters</span>, remote sensing studies of <span class="hlt">craters</span> on various solid surfaces of solar system bodies, and theoretical and laboratory studies using the known physics of impact <span class="hlt">cratering</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/120860','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/120860"><span>Site support program plan for ICF <span class="hlt">Kaiser</span> Hanford Company, Revision 1</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>NONE</p> <p>1995-10-01</p> <p>This document is the general administrative plan implemented by the Hanford Site contractor, ICF <span class="hlt">Kaiser</span> Hanford Company. It describes the mission, administrative structure, projected staffing, to be provided by the contractor. The report breaks out the work responsibilities within the different units of the company, a baseline schedule for the different groups, and a cost summary for the different operating units.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70031393','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70031393"><span>Geology of five small Australian impact <span class="hlt">craters</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Shoemaker, E.M.; Macdonald, F.A.; Shoemaker, C.S.</p> <p>2005-01-01</p> <p>Here we present detailed geological maps and cross-sections of Liverpool, Wolfe Creek, Boxhole, Veevers and Dalgaranga <span class="hlt">craters</span>. Liverpool <span class="hlt">crater</span> and Wolfe Creek Meteorite <span class="hlt">Crater</span> are classic bowlshaped, Barringer-type <span class="hlt">craters</span>, Liverpool was likely formed during the Neoproterozoic and was filled and covered with sediments soon thereafter. In the Cenozoic, this cover was exhumed exposing the <span class="hlt">crater</span>'s brecciated wall rocks. Wolfe Creek Meteorite <span class="hlt">Crater</span> displays many striking features, including well-bedded ejecta units, <span class="hlt">crater</span>-floor faults and sinkholes, a ringed aeromagnetic anomaly, rim-skirting dunes, and numerous iron-rich shale balls. Boxhole Meteorite <span class="hlt">Crater</span>, Veevers Meteorite <span class="hlt">Crater</span> and Dalgaranga <span class="hlt">crater</span> are smaller, Odessa-type <span class="hlt">craters</span> without fully developed, steep, overturned rims. Boxhole and Dalgaranga <span class="hlt">craters</span> are developed in highly follated Precambrian basement rocks with a veneer of Holocene colluvium. The pre-existing structure at these two sites complicates structural analyses of the <span class="hlt">craters</span>, and may have influenced target deformation during impact. Veevers Meteorite <span class="hlt">Crater</span> is formed in Cenozoic laterites, and is one of the best-preserved impact <span class="hlt">craters</span> on Earth. The <span class="hlt">craters</span> discussed herein were formed in different target materials, ranging from crystalline rocks to loosely consolidated sediments, containing evidence that the impactors struck at an array of angles and velocities. This facilitates a comparative study of the influence of these factors on the structural and topographic form of small impact <span class="hlt">craters</span>. ?? Geological Society of Australia.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17782143','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17782143"><span>Impact <span class="hlt">crater</span> densities on volcanoes and coronae on venus: implications for volcanic resurfacing.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Namiki, N; Solomon, S C</p> <p>1994-08-12</p> <p>The density of impact <span class="hlt">craters</span> on large volcanoes on Venus is half the average <span class="hlt">crater</span> density for the planet. The <span class="hlt">crater</span> density on some classes of coronae is not significantly different from the global average density, but coronae with extensive associated volcanic deposits have lower <span class="hlt">crater</span> densities. These results are inconsistent with both single-age and steady-state models for global resurfacing and <span class="hlt">suggest</span> that volcanoes and coronae with associated volcanism have been active on Venus over the last 500 million years.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018Icar..306..214S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018Icar..306..214S"><span>Relaxed impact <span class="hlt">craters</span> on Ganymede: Regional variation and high heat flows</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Singer, Kelsi N.; Bland, Michael T.; Schenk, Paul M.; McKinnon, William B.</p> <p>2018-05-01</p> <p>Viscously relaxed <span class="hlt">craters</span> provide a window into the thermal history of Ganymede, a satellite with copious geologic signs of past high heat flows. Here we present measurements of relaxed <span class="hlt">craters</span> in four regions for which suitable imaging exists: near Anshar Sulcus, Tiamat Sulcus, northern Marius Regio, and Ganymede's south pole. We describe a technique to measure apparent depth, or depth of the <span class="hlt">crater</span> with respect to the surrounding terrain elevation. Measured relaxation states are compared with results from finite element modeling to constrain heat flow scenarios [see companion paper: Bland et al. (2017)]. The presence of numerous, substantially relaxed <span class="hlt">craters</span> indicates high heat flows-in excess of 30-40 mW m-2 over 2 Gyr, with many small (<10 km in diameter) relaxed <span class="hlt">craters</span> indicating even higher heat flows. <span class="hlt">Crater</span> relaxation states are bimodal for some equatorial regions but not in the region studied near the south pole, which <span class="hlt">suggests</span> regional variations in Ganymede's thermal history.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70196308','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70196308"><span>Relaxed impact <span class="hlt">craters</span> on Ganymede: Regional variation and high heat flows</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Singer, Kelsi N.; Bland, Michael T.; Schenk, Paul M.; McKinnon, William B.</p> <p>2018-01-01</p> <p>Viscously relaxed <span class="hlt">craters</span> provide a window into the thermal history of Ganymede, a satellite with copious geologic signs of past high heat flows. Here we present measurements of relaxed <span class="hlt">craters</span> in four regions for which suitable imaging exists: near Anshar Sulcus, Tiamat Sulcus, northern Marius Regio, and Ganymede's south pole. We describe a technique to measure apparent depth, or depth of the <span class="hlt">crater</span> with respect to the surrounding terrain elevation. Measured relaxation states are compared with results from finite element modeling to constrain heat flow scenarios [see companion paper: Bland et al. (2017)]. The presence of numerous, substantially relaxed <span class="hlt">craters</span> indicates high heat flows—in excess of 30–40 mW m−2 over 2 Gyr, with many small (<10 km in diameter) relaxed <span class="hlt">craters</span> indicating even higher heat flows. <span class="hlt">Crater</span> relaxation states are bimodal for some equatorial regions but not in the region studied near the south pole, which <span class="hlt">suggests</span> regional variations in Ganymede's thermal history.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA16630.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA16630.html"><span>Dark <span class="hlt">Crater</span> Rims</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2013-01-03</p> <p>These mosaic images from NASA Dawn mission show how dark, carbon-rich materials tend to speckle the rims of smaller <span class="hlt">craters</span> or their immediate surroundings on the giant asteroid Vesta; Numisia <span class="hlt">Crater</span> is shown at left.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_10 --> <div id="page_11" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="201"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012ttt..work...22N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012ttt..work...22N"><span><span class="hlt">Crater</span> topography on Titan: Implications for landscape evolution</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Neish, C.; Kirk, R.; Lorenz, R.; Bray, V.; Schenk, P.; Stiles, B.; Turtle, E.; Cassini Radar Team</p> <p>2012-04-01</p> <p>Unique among the icy satellites, Titan’s surface shows evidence for extensive modification by fluvial and aeolian erosion, which act to change the topography of its surface over time. Quantifying the extent of this landscape evolution is difficult, since the original, ‘non-eroded’ surface topography is generally unknown. However, fresh <span class="hlt">craters</span> on icy satellites have a well-known shape and morphology, which has been determined from extensive studies on the airless worlds of the outer solar system (Schenk et al., 2004). By comparing the topography of <span class="hlt">craters</span> on Titan to similarly sized, pristine analogues on airless bodies, we can obtain one of the few direct measures of the amount of erosion that has occurred on Titan. Cassini RADAR has imaged >30% of the surface of Titan, and more than 60 potential <span class="hlt">craters</span> have been identified in this data set (Wood et al., 2010; Neish and Lorenz, 2012). Topographic information for these <span class="hlt">craters</span> can be obtained from a technique known as ‘SARTopo’, which estimates surface heights by comparing the calibration of overlapping synthetic aperture radar (SAR) beams (Stiles et al., 2009). We present topography data for several <span class="hlt">craters</span> on Titan, and compare the data to similarly sized <span class="hlt">craters</span> on Ganymede, for which topography has been extracted from stereo-derived digital elevation models (Bray et al., 2012). We find that the depths of <span class="hlt">craters</span> on Titan are generally within the range of depths observed on Ganymede, but several hundreds of meters shallower than the average (Fig. 1). A statistical comparison between the two data sets <span class="hlt">suggests</span> that it is extremely unlikely that Titan’s <span class="hlt">craters</span> were selected from the depth distribution of fresh <span class="hlt">craters</span> on Ganymede, and that is it much more probable that the relative depths of Titan are uniformly distributed between ‘fresh’ and ‘completely infilled’. This is consistent with an infilling process that varies linearly with time, such as aeolian infilling. Figure 1: Depth of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA22378.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA22378.html"><span>Bamberg <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2018-04-26</p> <p>Today's VIS image shows the western rim of Bamberg <span class="hlt">Crater</span>. The complex nature of the rim is one indication of the relative youth of this <span class="hlt">crater</span> in relation to it's surrounding. Many gullies dissect this rim. Orbit Number: 71254 Latitude: 39.6224 Longitude: 356.451 Instrument: VIS Captured: 2018-01-06 05:00 https://photojournal.jpl.nasa.gov/catalog/PIA22378</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19850047917&hterms=dg&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Ddg','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19850047917&hterms=dg&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Ddg"><span>The scaling of complex <span class="hlt">craters</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Croft, S. K.</p> <p>1985-01-01</p> <p>The empirical relation between the transient <span class="hlt">crater</span> diameter (Dg) and final <span class="hlt">crater</span> diameter (Dr) of complex <span class="hlt">craters</span> and basins is estimated using cumulative terrace widths, central uplift diameters, continuous ejecta radii, and transient <span class="hlt">crater</span> reconstructions determined from lunar and terrestrial impact structures. The ratio Dg/Dr is a power law function of Dr, decreasing uniformly from unity at the diameter of the simple-complex <span class="hlt">crater</span> morphology transition to about 0.5 for large multiring basins like Imbrium on the moon. The empirical constants in the Dg/Dr relation are interpreted physically to mean that the position of the final rim relative to the transient <span class="hlt">crater</span>, and hence the extent of collapse, is controlled or greatly influenced by the properties of the zone of dissociated material produced by the impact shock. The continuity of the Dg/Dr relation over the entire spectrum of morphologic types from complex <span class="hlt">craters</span> to multiring basins implies that the rims of all these structures form in the same tectonic environment despite morphologic differences.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA04904&hterms=Northeast&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DNortheast','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA04904&hterms=Northeast&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DNortheast"><span>Exhuming <span class="hlt">Crater</span> in Northeast Arabia</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2003-01-01</p> <p>MGS MOC Release No. MOC2-563, 3 December 2003<p/>The upper crust of Mars is layered, and interbedded with these layers are old, filled and buried meteor impact <span class="hlt">craters</span>. In a few places on Mars, such as Arabia Terra, erosion has re-exposed some of the filled and buried <span class="hlt">craters</span>. This October 2003 Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows an example. The larger circular feature was once a meteor <span class="hlt">crater</span>. It was filled with sediment, then buried beneath younger rocks. The smaller circular feature is a younger impact <span class="hlt">crater</span> that formed in the surface above the rocks that buried the large <span class="hlt">crater</span>. Later, erosion removed all of the material that covered the larger, buried <span class="hlt">crater</span>, except in the location of the small <span class="hlt">crater</span>. This pair of martian landforms is located near 17.6oN, 312.8oW. The image covers an area 3 km (1.9 mi) wide and is illuminated from the lower left.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19890049148&hterms=mass+wasting&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dmass%2Bwasting','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19890049148&hterms=mass+wasting&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dmass%2Bwasting"><span>Concentric <span class="hlt">crater</span> fill on Mars - An aeolian alternative to ice-rich mass wasting</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zimbelman, J. R.; Clifford, S. M.; Williams, S. H.</p> <p>1989-01-01</p> <p>Concentric <span class="hlt">crater</span> fill, a distinctive martian landform represented by a concentric pattern of surface undulations confined within a <span class="hlt">crater</span> rim, has been interpreted as an example of ice-enhanced regolith creep at midlatitudes (e.g., Squyres and Carr, 1986). Theoretical constraints on the stability and mobility of ground ice limit the applicability of an ice-rich soil in effectively mobilizing downslope movement at latitudes poleward of + or - 30 deg, where concentric <span class="hlt">crater</span> fill is observed. High-resolution images of concentric <span class="hlt">crater</span> fill material in the Utopia Planitia region (45 deg N, 271 deg W) show it to be an eroded, multiple-layer deposit. Layering should not be preserved if the <span class="hlt">crater</span> fill material moved by slow deformation throughout its thickness, as envisioned in the ice-enhanced creep model. Multiple layers are also exposed in the plains material surrounding the <span class="hlt">craters</span>, indicating a recurrent depositional process that was at least regional in extent. Mantling layers are observed in high-resolution images of many other locations around Mars, <span class="hlt">suggesting</span> that deposition occurred on a global scale and was not limited to the Utopia Planitia region. It is <span class="hlt">suggested</span> that an aeolian interpretation for the origin and modification of concentric <span class="hlt">crater</span> fill material is most consistent with morphologic and theoretical constraints.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.P43C2115B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.P43C2115B"><span>Floor-Fractured <span class="hlt">Craters</span> on Ceres and Implications for Internal Composition and Processes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Buczkowski, D.; Schenk, P.; Scully, J. E. C.; Park, R. S.; Preusker, F.; Raymond, C. A.; Russell, C. T.</p> <p>2016-12-01</p> <p>Several of the impact <span class="hlt">craters</span> on Ceres have patterns of fractures on their floors. These fractures appear similar to those found within a class of lunar <span class="hlt">craters</span> referred to as Floor-Fractured <span class="hlt">Craters</span> (FFCs) [1]. Lunar FFCs are characterized by anomalously shallow floors cut by radial, concentric, and/or polygonal fractures, and have been classified into <span class="hlt">crater</span> classes, Types 1 through 6, based on their morphometric properties [1,2]. Models for their formation have included both floor uplift due to magmatic intrusion below the <span class="hlt">crater</span> or floor shallowing due to viscous relaxation. However, the observation that the depth versus diameter (d/D) relationship of the FFCs is distinctly shallower than the same association for other lunar <span class="hlt">craters</span> supports the hypotheses that the floor fractures form due to shallow magmatic intrusion under the <span class="hlt">crater</span> [2]. We have cataloged the Ceres FFCs according to the classification scheme designed for the Moon. Large (>50 km) Ceres FFCs are most consistent with Type 1 lunar FFCs, having deep floors, central peaks, wall terraces, and radial and/or concentric fractures. Smaller <span class="hlt">craters</span> on Ceres are more consistent with Type 4 lunar FFCs, having less-pronounced floor fractures and v-shaped moats separating the wall scarp from the <span class="hlt">crater</span> interior. An analysis of the d/D ratio for Ceres <span class="hlt">craters</span> shows that, like lunar FFCs, the Ceres FFCs are anomalously shallow. This <span class="hlt">suggests</span> that the fractures on the floor of Ceres FFCs may be due the intrusion of a low-density material below the <span class="hlt">craters</span> that is uplifting their floors. While on the Moon the intrusive material is hypothesized to be silicate magma, this is unlikely for Ceres. However, a cryovolcanic extrusive edifice has been identified on Ceres [3], <span class="hlt">suggesting</span> that cryomagmatic intrusions could be responsible for the formation of the Ceres FFCs. References: [1] Schultz P. (1976) Moon, 15, 241-273 [2] Jozwiak L.M. et al (2015) JGR 117, doi: 10.1029/2012JE004134 [3] Ruesch O. et al (2016</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005P%26SS...53.1496V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005P%26SS...53.1496V"><span>How much material do the radar-bright <span class="hlt">craters</span> at the Mercurian poles contain?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vilas, Faith; Cobian, Paul S.; Barlow, Nadine G.; Lederer, Susan M.</p> <p>2005-12-01</p> <p>The depth-to-diameter (d/D) ratios were determined for 12 <span class="hlt">craters</span> located near the Mercurian north pole that were identified by Harmon et al. (2001, Icarus 149) as having strong depolarized radar echos. We find that the mean d/D value of these radar-bright <span class="hlt">craters</span> is {2}/{3} the mean d/D value of the general population of non-radar-bright <span class="hlt">craters</span> in the surrounding north polar region. Previous studies, however, show no difference between d/D values of Mercurian polar and equatorial <span class="hlt">crater</span> populations, <span class="hlt">suggesting</span> that no terrain softening which could modify <span class="hlt">crater</span> structure exists at the Mercurian poles (Barlow et al., 1999, 194, Icarus 141). Thus, the change in d/D is governed by a change in <span class="hlt">crater</span> depth, probably due to deposition of material inside the <span class="hlt">crater</span>. The volume of infilling material, including volatiles, in the radar-bright <span class="hlt">craters</span> is significantly greater than predicted by proposed mechanisms for the emplacement of either water ice or sulfur.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20020051084','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20020051084"><span>Impact <span class="hlt">Cratering</span> Calculations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ahrens, Thomas J.</p> <p>2002-01-01</p> <p>Many Martian <span class="hlt">craters</span> are surrounded by ejecta blankets which appear to have been fluidized forming lobate and layered deposits terminated by one or more continuous distal scarps, or ramparts. One of the first hypotheses for the formation of so-called rampart ejecta features was shock-melting of subsurface ice, entrainment of liquid water into the ejecta blanket, and subsequent fluidized flow. Our work quantifies this concept. Rampart ejecta found on all but the youngest volcanic and polar regions, and the different rampart ejecta morphologies are correlated with <span class="hlt">crater</span> size and terrain. In addition, the minimum diameter of <span class="hlt">craters</span> with rampart features decreases with increasing latitude indicating that ice laden crust resides closer to the surface as one goes poleward on Mars. Our second goal in was to determine what strength model(s) reproduce the faults and complex features found in large scale gravity driven <span class="hlt">craters</span>. Collapse features found in large scale <span class="hlt">craters</span> require that the rock strength weaken as a result of the shock processing of rock and the later <span class="hlt">cratering</span> shear flows. In addition to the presence of molten silicate in the intensely shocked region, the presence of water, either ambient, or the result of shock melting of ice weakens rock. There are several other mechanisms for the reduction of strength in geologic materials including dynamic tensile and shear induced fracturing. Fracturing is a mechanism for large reductions in strength. We found that by incorporating damage into the models that we could in a single integrated impact calculation, starting in the atmosphere produce final <span class="hlt">crater</span> profiles having the major features found in the field measurements (central uplifts, inner ring, terracing and faulting). This was accomplished with undamaged surface strengths (0.1 GPa) and in depth strengths (1.0 GPa).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA04017.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA04017.html"><span>Trouvelot <span class="hlt">Crater</span> Deposit</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2002-12-04</p> <p>Like many of the <span class="hlt">craters</span> in the Oxia Palus region of Mars, Trouvelot <span class="hlt">Crater</span>, shown in this NASA Mars Odyssey image, hosts an eroded, light-toned, sedimentary deposit on its floor. Compared with the much larger example in Becquerel <span class="hlt">Crater</span> to the NE, the Trouvelot deposit has been so eroded by the scouring action of dark, wind-blown sand that very little of it remains. Tiny outliers of bright material separated from the main mass attest to the once, more really extensive coverage by the deposit. A similar observation can be made for White Rock, the best known example of a bright, <span class="hlt">crater</span> interior deposit. The origin of the sediments in these deposits remains enigmatic but they are likely the result of fallout from ash or dust carried by the thin martian atmosphere. http://photojournal.jpl.nasa.gov/catalog/PIA04017</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70032716','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70032716"><span>Degradation of Victoria <span class="hlt">crater</span>, Mars</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Grant, J. A.; Wilson, S.A.; Cohen, B. A.; Golombek, M.P.; Geissler, P.E.; Sullivan, R.J.; Kirk, R.L.; Parker, T.J.</p> <p>2008-01-01</p> <p>The ???750 m diameter and ???75 m deep Victoria <span class="hlt">crater</span> in Meridiani Planum, Mars, is a degraded primary impact structure retaining a ???5 m raised rim consisting of 1-2 m of uplifted rocks overlain by ???3 m of ejecta at the rim crest. The rim is 120-220 m wide and is surrounded by a dark annulus reaching an average of 590 m beyond the raised rim. Comparison between observed morphology and that expected for pristine <span class="hlt">craters</span> 500-750 m across indicates that the original, pristine <span class="hlt">crater</span> was close to 600 m in diameter. Hence, the <span class="hlt">crater</span> has been erosionally widened by ???150 m and infilled by ???50 m of sediments. Eolian processes are responsible for most <span class="hlt">crater</span> modification, but lesser mass wasting or gully activity contributions cannot be ruled out. Erosion by prevailing winds is most significant along the exposed rim and upper walls and accounts for ???50 m widening across a WNW-ESE diameter. The volume of material eroded from the <span class="hlt">crater</span> walls and rim is ???20% less than the volume of sediments partially filling the <span class="hlt">crater</span>, indicating eolian infilling from sources outside the <span class="hlt">crater</span> over time. The annulus formed when ???1 m deflation of the ejecta created a lag of more resistant hematite spherules that trapped <10-20 cm of darker, regional basaltic sands. Greater relief along the rim enabled meters of erosion. Comparison between Victoria and regional <span class="hlt">craters</span> leads to definition of a <span class="hlt">crater</span> degradation sequence dominated by eolian erosion and infilling over time. Copyright 2008 by the American Geophysical Union.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFM.P23B1374K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFM.P23B1374K"><span>Cataloging of <span class="hlt">Craters</span> on Enceladus</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Karpes, B. A.; Stoddard, P. R.</p> <p>2008-12-01</p> <p>The surface of Saturn's satellite Enceladus is unique in terms of the amount of geologic activity that is taking place on what many had once assumed would be a cold and dead icy moon. Instead of a cold, <span class="hlt">cratered</span> surface we have found a surface scarred with signs of tectonic activity in the form of numerous long rifts and fractures and we have seen cryovolcanic activity emanating from the south polar region. Using mostly Cassini images (a few of the map images are from Voyager), we are currently in the process of creating a comprehensive catalog of <span class="hlt">craters</span> that, we believe, will be an invaluable tool in aiding our understanding of this enigmatic moon. The catalog will give the location of all <span class="hlt">craters</span> measuring at least one-half degree (~2.2 km) in diameter. In addition to location and size, the catalog will also note deformation of the <span class="hlt">craters</span>, both in terms of rifting and ellipticity. The deformations can give us insight to the tectonic history (i.e. many of the <span class="hlt">craters</span> show post impact rifting) as well as giving us a further tool to study tectonic stresses across the surface. Areas of differing resolution are highlighted as they are an important limiting factor in determining <span class="hlt">crater</span> densities. It is for this reason that <span class="hlt">crater</span> sizes of one-half degree were chosen as they are more identifiable in lower resolution areas than <span class="hlt">craters</span> that are much smaller. We intend to study <span class="hlt">crater</span> distribution and have so far noted high <span class="hlt">crater</span> densities between 216° W and 144° W and between 10° S and 10° N approximately centered around 180° longitude (the antipode to the sub-Saturnian point). In addition to our study of <span class="hlt">crater</span> distribution we believe this catalog, upon completion, will be useful in the study of surface processes and surface heating of Enceladus.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1913417L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1913417L"><span>Spectral Clustering of Hermean <span class="hlt">craters</span> hollows</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lucchetti, Alice; Pajola, Maurizio; Cremonese, Gabriele; Carli, Cristian; Marzo, Giuseppe; Roush, Ted</p> <p>2017-04-01</p> <p>The Mercury Dual Imaging System (MDIS, Hawkins et al., 2007) onboard NASA MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) spacecraft, provided high-resolution images of "hollows", i.e. shallow, irregular, rimless, flat-floored depressions with bright interiors and halos, often found on <span class="hlt">crater</span> walls, rims, floors and central peaks (Blewett et al., 2011, 2013). The formation mechanism of these features was <span class="hlt">suggested</span> to be related to the depletion of subsurface volatiles (Blewett et al., 2011, Vaughan et al., 2012). To understand the hollows' mineralogical composition, which can provide new insights on Mercury's surface characterization, we applied a spectral clustering method to different <span class="hlt">craters</span> where hollows are present. We chose, as first test case, the 20 km wide Dominici <span class="hlt">crater</span> due to previous multiple spectral detection (Vilas et al., 2016). We used the MDIS WAC dataset covering Dominici <span class="hlt">crater</span> with a scale of 935 m/pixel through eight filters, ranging from 0.433 to 0.996 μm. First, the images have been photometrically corrected using the Hapke parameters (Hapke et al., 2002) derived in Domingue et al. (2015). We then applied a statistical clustering over the entire dataset based on a K-means partitioning algorithm (Marzo et al., 2006). This approach was developed and evaluated by Marzo et al. (2006, 2008, 2009) and makes use of the Calinski and Harabasz criterion (Calinski, T., Harabasz, J., 1974) to identify the intrinsically natural number of clusters, making the process unsupervised. The natural number of ten clusters was identified and spectrally separates the Dominici surrounding terrains from its interior, as well as the two hollows from their edges. The units located on the brightest part of the south wall/rim of Dominici <span class="hlt">crater</span> clearly present a wide absorption band between 0.558 and 0.828 μm. Hollows surrounding terrains typically present a red slope in the VNIR with a possible weak absorption band centered at 0.748 </p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006APS..4CF.F1005A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006APS..4CF.F1005A"><span>Polar <span class="hlt">Crater</span> Deposits as a Probe for Ancient Climate Change on Mars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Armstrong, John</p> <p>2006-10-01</p> <p>Dynamical studies of the Martian orbit <span class="hlt">suggest</span> a planet that has undergone extreme orbital change. How has this affected the planet's climate? Is there a record of this orbit-induced climate change written in the geology that is expressed on the surface? If so, such a record would provide insight into Mars' climate history, and shed light on the types of habitats for life that may have existed in the past. We are exploring how the current seasonal polar caps interact with polar <span class="hlt">craters</span> in an effort to identify modification that can be linked to the proximity of the polar cap. Ice deposits within the <span class="hlt">craters</span> are evident in both thermal spectra and imagery from Mars orbiters. We have linked these ice deposits to morphological deposits that can be identified in other <span class="hlt">craters</span> that are further from the pole. These deposits may act as a probe of the variations <span class="hlt">suggested</span> by orbital calculations, as well as provide an indicator of the extent of the sub-surface ice table. We will present preliminary results from a sample of northern <span class="hlt">craters</span>, and explain how this can be extended to southern <span class="hlt">craters</span>, and possibly mid-latitude <span class="hlt">craters</span>, in an effort to understand more fully the martian climate through time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA14611.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA14611.html"><span>Line of <span class="hlt">Craters</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2012-06-04</p> <p>NASA Cassini spacecraft takes a close look at a row of <span class="hlt">craters</span> on Saturn moon Tethys during the spacecraft April 14, 2012, flyby of the moon. Three large <span class="hlt">craters</span> are visible along the terminator between day and night on Tethys.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA12935.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA12935.html"><span>Fresh Copernican <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2009-12-21</p> <p>A subset of NAC Image M112162602L showing landslides bottom covering impact melt on the floor top of a fresh Copernican-age <span class="hlt">crater</span> at the edge of Oceanus Procellarum and west of Balboa <span class="hlt">crater</span> taken by NASA Lunar Reconnaissance Orbiter.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19910013673','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19910013673"><span>Martian impact <span class="hlt">craters</span>: Continuing analysis of lobate ejecta sinuosity</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Barlow, Nadine G.</p> <p>1990-01-01</p> <p>The lobate ejecta morphology surrounding most fresh Martian impact <span class="hlt">craters</span> can be quantitatively analyzed to determine variations in ejecta sinuosity with diameter, latitude, longitude, and terrain. The results of such studies provide another clue to the question of how these morphologies formed: are they the results of vaporization of subsurface volatiles or caused by ejecta entrainment in atmospheric gases. Kargel provided a simple expression to determine the degree of non-circularity of an ejecta blanket. This measure of sinuosity, called 'lobateness', is given by the ratio of the ejecta perimeter to the perimeter of a circle with the same area as that of the ejecta. The Kargel study of 538 rampart <span class="hlt">craters</span> in selected areas of Mars led to the <span class="hlt">suggestion</span> that lobateness increased with increasing diameter, decreased at higher latitude, and showed no dependence on elevation or geologic unit. Major problems with the Kargel analysis are the limited size and distribution of the data set and the lack of discrimination among the different types of lobate ejecta morphologies. Bridges and Barlow undertook a new lobateness study of 1582 single lobe (SL) and 251 double lobe (DL) <span class="hlt">craters</span>. The results are summarized. These results agree with the finding of Kargel that lobateness increases with increasing diameter, but found no indication of a latitude dependence for SL <span class="hlt">craters</span>. The Bridges and Barlow study has now been extended to multiple lobe (ML) <span class="hlt">craters</span>. Three hundred and eighty ML <span class="hlt">craters</span> located across the entire Martian surface were studied. ML <span class="hlt">craters</span> provide more complications to lobateness studies than do SL and DL <span class="hlt">craters</span> - in particular, the ejecta lobes surrounding the <span class="hlt">crater</span> are often incomplete. Since the lobateness formula compares the perimeter of the ejecta lobe to that of a circle, the analysis was restricted only to complete lobes. The lobes are defined sequentially starting with the outermost lobe and moving inward.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70190499','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70190499"><span>Viscous relaxation of Ganymede's impact <span class="hlt">craters</span>: Constraints on heat flux</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Bland, Michael T.; Singer, Kelsi N.; McKinnon, William B.; Schenk, Paul M.</p> <p>2017-01-01</p> <p>Measurement of <span class="hlt">crater</span> depths in Ganymede’s dark terrain have revealed substantial numbers of unusually shallow <span class="hlt">craters</span> indicative of viscous relaxation [see companion paper: Singer, K.N., Schenk, P. M., Bland, M.T., McKinnon, W.B., (2017). Relaxed impact <span class="hlt">craters</span> on Ganymede: Regional variations and high heat flow. Icarus, submitted]. These viscously relaxed <span class="hlt">craters</span> provide insight into the thermal history of the dark terrain: the rate of relaxation depends on the size of the <span class="hlt">crater</span> and the thermal structure of the lithosphere. Here we use finite element simulations of <span class="hlt">crater</span> relaxation to constrain the heat flux within the dark terrain when relaxation occurred. We show that the degree of viscous relaxation observed cannot be achieved through radiogenic heating alone, even if all of the relaxed <span class="hlt">craters</span> are ancient and experienced the high radiogenic fluxes present early in the satellite’s history. For <span class="hlt">craters</span> with diameter ≥ 10 km, heat fluxes of 40–50 mW m-2−2"> can reproduce the observed <span class="hlt">crater</span> depths, but only if the fluxes are sustained for ∼1 Gyr. These <span class="hlt">craters</span> can also be explained by shorter-lived “heat pulses” with magnitudes of ∼100 mW m-2−2"> and timescales of 10–100 Myr. At small <span class="hlt">crater</span> diameters (4 km) the observed shallow depths are difficult to achieve even when heat fluxes as high as 150 mW m-2−2"> are sustained for 1 Gyr. The extreme thermal conditions required to viscously relax small <span class="hlt">craters</span> may indicate that mechanisms other than viscous relaxation, such as topographic degradation, are also in play at small <span class="hlt">crater</span> diameters. The timing of the relaxation event(s) is poorly constrained due to the sparsity of adequate topographic information, though it likely occurred in Ganymede’s middle history (neither recently, nor shortly after satellite formation). The consistency between the timing and magnitude of the heat fluxes derived here and those inferred from other tectonic features <span class="hlt">suggests</span> that a single event</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017Icar..296..275B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017Icar..296..275B"><span>Viscous relaxation of Ganymede's impact <span class="hlt">craters</span>: Constraints on heat flux</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bland, Michael T.; Singer, Kelsi N.; McKinnon, William B.; Schenk, Paul M.</p> <p>2017-11-01</p> <p>Measurement of <span class="hlt">crater</span> depths in Ganymede's dark terrain have revealed substantial numbers of unusually shallow <span class="hlt">craters</span> indicative of viscous relaxation [see companion paper: Singer, K.N., Schenk, P. M., Bland, M.T., McKinnon, W.B., (2017). Relaxed impact <span class="hlt">craters</span> on Ganymede: Regional variations and high heat flow. Icarus, submitted]. These viscously relaxed <span class="hlt">craters</span> provide insight into the thermal history of the dark terrain: the rate of relaxation depends on the size of the <span class="hlt">crater</span> and the thermal structure of the lithosphere. Here we use finite element simulations of <span class="hlt">crater</span> relaxation to constrain the heat flux within the dark terrain when relaxation occurred. We show that the degree of viscous relaxation observed cannot be achieved through radiogenic heating alone, even if all of the relaxed <span class="hlt">craters</span> are ancient and experienced the high radiogenic fluxes present early in the satellite's history. For <span class="hlt">craters</span> with diameter ≥ 10 km, heat fluxes of 40-50 mW m-2 can reproduce the observed <span class="hlt">crater</span> depths, but only if the fluxes are sustained for ∼1 Gyr. These <span class="hlt">craters</span> can also be explained by shorter-lived "heat pulses" with magnitudes of ∼100 mW m-2 and timescales of 10-100 Myr. At small <span class="hlt">crater</span> diameters (4 km) the observed shallow depths are difficult to achieve even when heat fluxes as high as 150 mW m-2 are sustained for 1 Gyr. The extreme thermal conditions required to viscously relax small <span class="hlt">craters</span> may indicate that mechanisms other than viscous relaxation, such as topographic degradation, are also in play at small <span class="hlt">crater</span> diameters. The timing of the relaxation event(s) is poorly constrained due to the sparsity of adequate topographic information, though it likely occurred in Ganymede's middle history (neither recently, nor shortly after satellite formation). The consistency between the timing and magnitude of the heat fluxes derived here and those inferred from other tectonic features <span class="hlt">suggests</span> that a single event caused both Ganymede's tectonic deformation and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA03832&hterms=knife&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dknife','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA03832&hterms=knife&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dknife"><span>Galle <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2002-01-01</p> <p>(Released 19 June 2002) The Science This image is of part of Galle <span class="hlt">Crater</span>, located at 51.9S, 29.5W. This image was taken far enough south and late enough into the southern hemisphere fall to catch observe water ice clouds partially obscuring the surface. The most striking aspect of the surface is the dissected layered unit to the left in the image. Other areas also appear to have layering, but they are either more obscured by clouds or are less well defined on the surface. The layers appear to be mostly flat lying and layer boundaries appear as topographic lines would on a map, but there are a few areas where it appears that these layers have been deformed to some level. Other areas of the image contain rugged, mountainous terrain as well as a separate pitted terrain where the surface appears to be a separate unit from the mountains and the layered terrain. The Story Galle <span class="hlt">Crater</span> is officially named after a German astronomer who, in 1846, was the first to observe the planet Neptune. It is better known, however, as the 'Happy Face <span class="hlt">Crater</span>.' The image above focuses on too small an area of the <span class="hlt">crater</span> to see its beguiling grin, but you can catch the rocky line of a 'half-smile' in the context image to the right (to the left of the red box). While water ice clouds make some of the surface harder to see, nothing detracts from the fabulous layering at the center left-hand edge of the image. If you click on the above image, the scalloped layers almost look as if a giant knife has swirled through a landscape of cake frosting. These layers, the rugged, mountains near them, and pits on the surface (upper to middle section of the image on the right-hand side) all create varying textures on the <span class="hlt">crater</span> floor. With such different features in the same place, geologists have a lot to study to figure out what has happened in the <span class="hlt">crater</span> since it formed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA22147.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA22147.html"><span>Investigating Mars: Rabe <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2017-12-21</p> <p>This is a false color image of Rabe <span class="hlt">Crater</span>. In this combination of filters "blue" typically means basaltic sand. This VIS image crosses the entire <span class="hlt">crater</span> and demonstrates how extensive the dunes are on the floor of Rabe <span class="hlt">Crater</span>. Rabe <span class="hlt">Crater</span> is 108 km (67 miles) across. <span class="hlt">Craters</span> of similar size often have flat floors. Rabe <span class="hlt">Crater</span> has some areas of flat floor, but also has a large complex pit occupying a substantial part of the floor. The interior fill of the <span class="hlt">crater</span> is thought to be layered sediments created by wind and or water action. The pit is eroded into this material. The eroded materials appear to have stayed within the <span class="hlt">crater</span> forming a large sand sheet with surface dune forms as well as individual dunes where the <span class="hlt">crater</span> floor is visible. The dunes also appear to be moving from the upper floor level into the pit. The THEMIS VIS camera contains 5 filters. The data from different filters can be combined in multiple ways to create a false color image. These false color images may reveal subtle variations of the surface not easily identified in a single band image. The Odyssey spacecraft has spent over 15 years in orbit around Mars, circling the planet more than 69000 times. It holds the record for longest working spacecraft at Mars. THEMIS, the IR/VIS camera system, has collected data for the entire mission and provides images covering all seasons and lighting conditions. Over the years many features of interest have received repeated imaging, building up a suite of images covering the entire feature. From the deepest chasma to the tallest volcano, individual dunes inside <span class="hlt">craters</span> and dune fields that encircle the north pole, channels carved by water and lava, and a variety of other feature, THEMIS has imaged them all. For the next several months the image of the day will focus on the Tharsis volcanoes, the various chasmata of Valles Marineris, and the major dunes fields. We hope you enjoy these images! Orbit Number: 67013 Latitude: -43.2572 Longitude: 34</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_11 --> <div id="page_12" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="221"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29938148','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29938148"><span>Mineralogical Diversity and Geology of Humboldt <span class="hlt">Crater</span> Derived Using Moon Mineralogy Mapper Data.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Martinot, M; Besse, S; Flahaut, J; Quantin-Nataf, C; Lozac'h, L; van Westrenen, W</p> <p>2018-02-01</p> <p>Moon Mineralogy Mapper (M 3 ) spectroscopic data and high-resolution imagery data sets were used to study the mineralogy and geology of the 207 km diameter Humboldt <span class="hlt">crater</span>. Analyses of M 3 data, using a custom-made method for M 3 spectra continuum removal and spectral parameters calculation, reveal multiple pure crystalline plagioclase detections within the Humboldt <span class="hlt">crater</span> central peak complex, hinting at its crustal origin. However, olivine, spinel, and glass are observed in the <span class="hlt">crater</span> walls and rims, <span class="hlt">suggesting</span> these minerals derive from shallower levels than the plagioclase of the central peak complex. High-calcium pyroxenes are detected in association with volcanic deposits emplaced on the <span class="hlt">crater</span>'s floor. Geologic mapping was performed, and the age of Humboldt <span class="hlt">crater</span>'s units was estimated from <span class="hlt">crater</span> counts. Results <span class="hlt">suggest</span> that volcanic activity within this floor-fractured <span class="hlt">crater</span> spanned over a billion years. The felsic mineralogy of the central peak complex region, which presumably excavated deeper material, and the shallow mafic minerals (olivine and spinel) detected in Humboldt <span class="hlt">crater</span> walls and rim are not in accordance with the general view of the structure of the lunar crust. Our observations can be explained by the presence of a mafic pluton emplaced in the anorthositic crust prior to the Humboldt-forming impact event. Alternatively, the excavation of Australe basin ejecta could explain the observed mineralogical detections. This highlights the importance of detailed combined mineralogical and geological remote sensing studies to assess the heterogeneity of the lunar crust.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JGRE..123..612M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JGRE..123..612M"><span>Mineralogical Diversity and Geology of Humboldt <span class="hlt">Crater</span> Derived Using Moon Mineralogy Mapper Data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Martinot, M.; Besse, S.; Flahaut, J.; Quantin-Nataf, C.; Lozac'h, L.; van Westrenen, W.</p> <p>2018-02-01</p> <p>Moon Mineralogy Mapper (M3) spectroscopic data and high-resolution imagery data sets were used to study the mineralogy and geology of the 207 km diameter Humboldt <span class="hlt">crater</span>. Analyses of M3 data, using a custom-made method for M3 spectra continuum removal and spectral parameters calculation, reveal multiple pure crystalline plagioclase detections within the Humboldt <span class="hlt">crater</span> central peak complex, hinting at its crustal origin. However, olivine, spinel, and glass are observed in the <span class="hlt">crater</span> walls and rims, <span class="hlt">suggesting</span> these minerals derive from shallower levels than the plagioclase of the central peak complex. High-calcium pyroxenes are detected in association with volcanic deposits emplaced on the <span class="hlt">crater</span>'s floor. Geologic mapping was performed, and the age of Humboldt <span class="hlt">crater</span>'s units was estimated from <span class="hlt">crater</span> counts. Results <span class="hlt">suggest</span> that volcanic activity within this floor-fractured <span class="hlt">crater</span> spanned over a billion years. The felsic mineralogy of the central peak complex region, which presumably excavated deeper material, and the shallow mafic minerals (olivine and spinel) detected in Humboldt <span class="hlt">crater</span> walls and rim are not in accordance with the general view of the structure of the lunar crust. Our observations can be explained by the presence of a mafic pluton emplaced in the anorthositic crust prior to the Humboldt-forming impact event. Alternatively, the excavation of Australe basin ejecta could explain the observed mineralogical detections. This highlights the importance of detailed combined mineralogical and geological remote sensing studies to assess the heterogeneity of the lunar crust.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EPSC....9..454R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EPSC....9..454R"><span>The Variability of <span class="hlt">Crater</span> Identification Among Expert and Community <span class="hlt">Crater</span> Analysts</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Robbins, S. J.; Antonenko, I.; Kirchoff, M. R.; Chapman, C. R.; Fassett, C. I.; Herrick, R. R.; Singer, K.; Zanetti, M.; Lehan, C.; Huang, D.; Gay, P.</p> <p>2014-04-01</p> <p>Statistical studies of impact <span class="hlt">crater</span> populations have been used to model ages of planetary surfaces for several decades [1]. This assumes that <span class="hlt">crater</span> counts are approximately invariant and a "correct" population will be identified if the analyst is skilled and diligent. However, the reality is that <span class="hlt">crater</span> identification is somewhat subjective, so variability between analysts, or even a single analyst's variation from day-to-day, is expected [e.g., 2, 3]. This study was undertaken to quantify that variability within an expert analyst population and between experts and minimally trained volunteers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA05281&hterms=swiss+cheese&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dswiss%2Bcheese','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA05281&hterms=swiss+cheese&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dswiss%2Bcheese"><span>Exhuming South Polar <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2004-01-01</p> <p>7 February 2004 The large, circular feature in this image is an old meteor impact <span class="hlt">crater</span>. The <span class="hlt">crater</span> is larger than the 3 kilometers-wide (1.9 miles-wide) Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image, thus only part of the <span class="hlt">crater</span> is seen. The bright mesas full of pits and holes--in some areas resembling swiss cheese--are composed of frozen carbon dioxide. In this summertime view, the mesa slopes and pit walls are darkened as sunlight causes some of the ice to sublime away. At one time in the past, the <span class="hlt">crater</span> shown here may have been completely covered with carbon dioxide ice, but, over time, it has been exhumed as the ice sublimes a little bit more each summer. The <span class="hlt">crater</span> is located near 86.8oS, 111.6oW. Sunlight illuminates this scene from the upper left.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA20252.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA20252.html"><span><span class="hlt">Craters</span> - False Color</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2016-02-04</p> <p>The THEMIS camera contains 5 filters. The data from different filters can be combined in multiple ways to create a false color image. This image captured by NASA 2001 Mars Odyssey spacecraft shows a group of unnamed <span class="hlt">craters</span> north of Fournier <span class="hlt">Crater</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000DPS....32.5803G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000DPS....32.5803G"><span>Constraining the Age of Martian Polar Strata by <span class="hlt">Crater</span> Counts</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Grier, J. A.; Hartmann, W. K.; Berman, D. C.; Goldman, E. B.; Esquerdo, G. A.</p> <p>2000-10-01</p> <p>Mars Global Surveyor images are capable of giving good counts on <span class="hlt">craters</span> down to about D 11 m. We studied 70 north polar images covering 2513 km2, mostly at latitudes 79-86 degrees, detecting a few probable impact <span class="hlt">craters</span> and placing upper limits from non-detections in other frames. From these data we conclude that impact <span class="hlt">craters</span> in the diameter range 11 m < D < 88 m indicate a survival lifetime of <span class="hlt">craters</span> and <span class="hlt">crater</span>-like topography in the north polar regions of < a few hundred Ka. The <span class="hlt">crater</span> counts <span class="hlt">suggest</span> a much flatter slope in the diameter distribution of the young polar laminae than found in the production function on young, low-latitude lava surfaces, confirming the rapid obliteration of smaller <span class="hlt">craters</span> even in recent geologic time (Plaut et al. 1988). To obliterate small <span class="hlt">craters</span>, if vertical relief on the order of 30 m is completely blanketed and removed in < 500,000 yrs, then an inferred upper limit on the sediment deposition rate is 6 x 10-5 meters/year or 60 μ /y. These results are consistent with models which call for enhanced dust deposition at the poles due to a process whereby dust particles act as condensation nuclei for winter ice and are preferentially dropped out of the polar atmosphere. Pollack et al. (1979) calculated polar deposition at 300 μ /y. Our age results are also consistent with Herkenhoff and Plaut (2000) who sought <span class="hlt">craters</span> of D > 300 m on Viking images of the north cap and derived the same age, < 100,000 years. They used the same logic to infer a higher deposition limit of 1200 μ /y. The measured north polar deposition rates are one to three orders of magnitude above the 1 to 4 μ /y <span class="hlt">suggested</span> at lower latitudes (Hartmann 1966, 1971; Matijevic et al. 1997). References: Hartmann 1966, Icarus 5:406; Hartmann 1971, Icarus 15: 410; Herkenhoff and Plaut 2000, Icarus 144: 243; Matijevic et al. 1997, Science 278:1765; Pollack et al. 1977, J. Geophys. Res. 84: 2929; Plaut et al. 1988 Icarus 75 :357.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017DPS....4930104W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017DPS....4930104W"><span>Compositional Variations of Titan's Impact <span class="hlt">Craters</span> Indicates Active Surface Erosion</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Werynski, Alyssa; Neish, Catherine; Le Gall, Alice; Janssen, Michael A.</p> <p>2017-10-01</p> <p>Titan’s crust is assumed to be mostly water-ice. However, the surface composition is not well constrained due to its thick atmosphere. Based on infrared and radiometry data, the surface appears enriched in organics, with only few areas showing evidence of exposed water-ice. Regions of water-ice enrichment include the rims and ejecta blankets of impact <span class="hlt">craters</span>. This study utilizes these geologic features to examine compositional variations across Titan’s surface, and their subsequent modification due to erosional processes.Sixteen <span class="hlt">craters</span> and their ejecta blankets were mapped on a Cassini RADAR mosaic. These features were selected because they are some of the best preserved <span class="hlt">craters</span> on Titan. Composition was inferred from Cassini’s Visual and Infrared Mapping Spectrometer (VIMS) and 2-cm emissivity data from the Cassini radiometer. With VIMS, different compositional units were inferred from their reflectivity at specific wavelengths. With the emissivity data, high values <span class="hlt">suggest</span> more organic-rich material, while lower values indicate strong volume scattering. Areas with low emissivity have been interpreted to be water-ice rich, as water-ice is a favorable medium for volume scattering.Results show fresher, well-preserved <span class="hlt">craters</span> in the dunes regions have a low emissivity indicative of water-ice, and a VIMS spectrum consistent with an unknown material, possibly a mixture of water-ice and organics. As these <span class="hlt">craters</span> erode over time, the VIMS spectra remain the same but the emissivity increases. Well-preserved <span class="hlt">craters</span> in the mid-latitude plains show VIMS spectra and emissivity values consistent with water-ice. As these plain <span class="hlt">craters</span> degrade, the VIMS spectra remain the same, but the emissivity increases. The differing VIMS signatures <span class="hlt">suggest</span> more mixing with organics during the <span class="hlt">cratering</span> event in the organic-rich dunes than the plains. The changes in emissivity over time are consistent with organic infilling of subsurface fractures in both regions, with limited</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19940016195&hterms=gravity+anomaly&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dgravity%2Banomaly','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19940016195&hterms=gravity+anomaly&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dgravity%2Banomaly"><span>Modelling the gravity and magnetic field anomalies of the Chicxulub <span class="hlt">crater</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Aleman, C. Ortiz; Pilkington, M.; Hildebrand, A. R.; Roest, W. R.; Grieve, R. A. F.; Keating, P.</p> <p>1993-01-01</p> <p>The approximately 180-km-diameter Chicxulub <span class="hlt">crater</span> lies buried by approximately 1 km of sediment on the northwestern corner of the Yucatan Peninsula, Mexico. Geophysical, stratigraphic and petrologic evidence support an impact origin for the structure and biostratigraphy <span class="hlt">suggests</span> that a K/T age is possible for the impact. The <span class="hlt">crater</span>'s location is in agreement with constraints derived from proximal K/T impact-wave and ejecta deposits and its melt-rock is similar in composition to the K/T tektites. Radiometric dating of the melt rock reveals an age identical to that of the K/T tektites. The impact which produced the Chicxulub <span class="hlt">crater</span> probably produced the K/T extinctions and understanding the now-buried <span class="hlt">crater</span> will provide constraints on the impact's lethal effects. The outstanding preservation of the <span class="hlt">crater</span>, the availability of detailed gravity and magnetic data sets, and the two-component target of carbonate/evaporites overlying silicate basement allow application of geophysical modeling techniques to explore the <span class="hlt">crater</span> under most favorable circumstances. We have found that the main features of the gravity and magnetic field anomalies may be produced by the <span class="hlt">crater</span> lithologies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70188371','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70188371"><span>Subsurface volatile content of martian double-layer ejecta (DLE) <span class="hlt">craters</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Viola, Donna; McEwen, Alfred S.; Dundas, Colin M.; Byrne, Shane</p> <p>2017-01-01</p> <p>Excess ice is widespread throughout the martian mid-latitudes, particularly in Arcadia Planitia, where double-layer ejecta (DLE) <span class="hlt">craters</span> also tend to be abundant. In this region, we observe the presence of thermokarstically-expanded secondary <span class="hlt">craters</span> that likely form from impacts that destabilize a subsurface layer of excess ice, which subsequently sublimates. The presence of these expanded <span class="hlt">craters</span> shows that excess ice is still preserved within the adjacent terrain. Here, we focus on a 15-km DLE <span class="hlt">crater</span> that contains abundant superposed expanded <span class="hlt">craters</span> in order to study the distribution of subsurface volatiles both at the time when the secondary <span class="hlt">craters</span> formed and, by extension, remaining today. To do this, we measure the size distribution of the superposed expanded <span class="hlt">craters</span> and use topographic data to calculate <span class="hlt">crater</span> volumes as a proxy for the volumes of ice lost to sublimation during the expansion process. The inner ejecta layer contains <span class="hlt">craters</span> that appear to have undergone more expansion, <span class="hlt">suggesting</span> that excess ice was most abundant in that region. However, both of the ejecta layers had more expanded <span class="hlt">craters</span> than the surrounding terrain. We extrapolate that the total volume of ice remaining within the entire ejecta deposit is as much as 74 km3 or more. The variation in ice content between the ejecta layers could be the result of (1) volatile preservation from the formation of the DLE <span class="hlt">crater</span>, (2) post-impact deposition in the form of ice lenses; or (3) preferential accumulation or preservation of subsequent snowfall. We have ruled out (2) as the primary mode for ice deposition in this location based on inconsistencies with our observations, though it may operate in concert with other processes. Although none of the existing DLE formation hypotheses are completely consistent with our observations, which may merit a new or modified mechanism, we can conclude that DLE <span class="hlt">craters</span> contain a significant quantity of excess ice today.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA21591.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA21591.html"><span>Secondary <span class="hlt">Craters</span> in Bas Relief</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2017-04-17</p> <p>NASA's Mars Reconnaissance Orbiter (MRO) captured this region of Mars, sprayed with secondary <span class="hlt">craters</span> from 10-kilometer Zunil <span class="hlt">Crater</span> to the northwest. Secondary <span class="hlt">craters</span> form from rocks ejected at high speed from the primary <span class="hlt">crater</span>, which then impact the ground at sufficiently high speed to make huge numbers of much smaller <span class="hlt">craters</span> over a large region. In this scene, however, the secondary <span class="hlt">crater</span> ejecta has an unusual raised-relief appearance like bas-relief sculpture. How did that happen? One idea is that the region was covered with a layer of fine-grained materials like dust or pyroclastics about 1 to 2 meters thick when the Zunil impact occurred (about a million years ago), and the ejecta served to harden or otherwise protect the fine-grained layer from later erosion by the wind. https://photojournal.jpl.nasa.gov/catalog/PIA21591</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA22144.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA22144.html"><span>Investigating Mars: Rabe <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2017-12-18</p> <p>The majority of the dune field in Rabe <span class="hlt">Crater</span> consists of a sand sheet with dune forms on the surface. The sand sheet is where a thick layer of sand has been concentrated. As continued winds blow across the sand surface it creates dune forms. The depth of the sand sheet prevents excavation to the <span class="hlt">crater</span> floor and the dune forms all appear connected. Rabe <span class="hlt">Crater</span> is 108 km (67 miles) across. <span class="hlt">Craters</span> of similar size often have flat floors. Rabe <span class="hlt">Crater</span> has some areas of flat floor, but also has a large complex pit occupying a substantial part of the floor. The interior fill of the <span class="hlt">crater</span> is thought to be layered sediments created by wind and or water action. The pit is eroded into this material. The eroded materials appear to have stayed within the <span class="hlt">crater</span> forming a large sand sheet with surface dune forms as well as individual dunes where the <span class="hlt">crater</span> floor is visible. The dunes also appear to be moving from the upper floor level into the pit. The Odyssey spacecraft has spent over 15 years in orbit around Mars, circling the planet more than 69000 times. It holds the record for longest working spacecraft at Mars. THEMIS, the IR/VIS camera system, has collected data for the entire mission and provides images covering all seasons and lighting conditions. Over the years many features of interest have received repeated imaging, building up a suite of images covering the entire feature. From the deepest chasma to the tallest volcano, individual dunes inside <span class="hlt">craters</span> and dune fields that encircle the north pole, channels carved by water and lava, and a variety of other feature, THEMIS has imaged them all. For the next several months the image of the day will focus on the Tharsis volcanoes, the various chasmata of Valles Marineris, and the major dunes fields. We hope you enjoy these images! Orbit Number: 58024 Latitude: -43.6954 Longitude: 34.8236 Instrument: VIS Captured: 2015-01-12 09:48 https://photojournal.jpl.nasa.gov/catalog/PIA22144</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19930005204','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19930005204"><span>Low-emissivity impact <span class="hlt">craters</span> on Venus</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Weitz, C. M.; Elachi, C.; Moore, H. J.; Basilevsky, A. T.; Ivanov, B. A.; Schaber, G. G.</p> <p>1992-01-01</p> <p>An analysis of 144 impact <span class="hlt">craters</span> on Venus has shown that 11 of these have floors with average emissivities lower than 0.8. The remaining <span class="hlt">craters</span> have emissivities between 0.8 and 0.9, independent of the specific backscatter cross section of the <span class="hlt">crater</span> floors. These 144 impact <span class="hlt">craters</span> were chosen from a possible 164 <span class="hlt">craters</span> with diameters greater than 30 km as identified by researchers for 89 percent of the surface of Venus. We have only looked at <span class="hlt">craters</span> below 6053.5 km altitude because a mineralogical change causes high reflectivity/low emissivity above the altitude. We have also excluded all <span class="hlt">craters</span> with diameters smaller than 30 km because the emissivity footprint at periapsis is 16 x 24 km and becomes larger at the poles.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AGUFMED51A0004P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AGUFMED51A0004P"><span>The Explorer's Guide to Impact <span class="hlt">Craters</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pierazzo, E.; Osinski, G.; Chuang, F.</p> <p>2004-12-01</p> <p>Impact <span class="hlt">cratering</span> is a fundamental geologic process of our solar system. It competes with other processes, such as plate tectonics, volcanism, or fluvial, glacial and eolian activity, in shaping the surfaces of planetary bodies. In some cases, like the Moon and Mercury, impact <span class="hlt">craters</span> are the dominant landform. On other planetary bodies impact <span class="hlt">craters</span> are being continuously erased by the action of other geological processes, like volcanism on Io, erosion and plate tectonics on the Earth, tectonic and volcanic resurfacing on Venus, or ancient erosion periods on Mars. The study of <span class="hlt">crater</span> populations is one of the principal tools for understanding the geologic history of a planetary surface. Among the general public, impact <span class="hlt">cratering</span> has drawn wide attention through its portrayal in several Hollywood movies. Questions that are raised after watching these movies include: ``How do scientists learn about impact <span class="hlt">cratering</span>?'', and ``What information do impact <span class="hlt">craters</span> provide in understanding the evolution of a planetary surface?'' Fundamental approaches used by scientists to learn about impact <span class="hlt">cratering</span> include field work at known terrestrial <span class="hlt">craters</span>, remote sensing studies of <span class="hlt">craters</span> on various solid surfaces of solar system bodies, and theoretical and laboratory studies using the known physics of impact <span class="hlt">cratering</span>. We will provide students, science teachers, and the general public an opportunity to experience the scientific endeavor of understanding and exploring impact <span class="hlt">craters</span> through a multi-level approach including images, videos, and rock samples. This type of interactive learning can also be made available to the general public in the form of a website, which can be addressed worldwide at any time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.9649I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.9649I"><span>Reading the Magnetic Patterns in Earth complex impact <span class="hlt">craters</span> to detect similarities and cues from some Nectarian <span class="hlt">craters</span> of the Moon</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Isac, Anca; Mandea, Mioara; Purucker, Michael</p> <p>2013-04-01</p> <p>Most of the terrestrial impact <span class="hlt">craters</span> have been obliterated by other terrestrial geological processes. Some examples however remain. Among them, complex <span class="hlt">craters</span> such as Chicxculub, Vredefort, or the outsider Bangui structure (proposed but still unconfirmed as a result of an early Precambrian large impact) exert in the total magnetic field anomaly global map (WDMAM-B) circular shapes with positive anomalies which may <span class="hlt">suggest</span> the circularity of a multiring structure. A similar pattern is observed from the newest available data (global spherical model of the internal magnetic field by Purucker and Nicolas, 2010) for some Nectarian basins as Moscovienese, Mendel-Rydberg or Crissium. As in the case of Earth's impacts, the positive anomalies appear near the basin center and inside the first ring, this distribution being strongly connected with <span class="hlt">crater</span>-forming event. Detailed analysis of largest impact <span class="hlt">craters</span> from Earth and Moon --using a forward modeling approach by means of the Equivalent Source Dipole method--evaluates the shock impact demagnetization effects--a magnetic low--by reducing the thickness of the pre-magnetized lithosphere due to the excavation process (the impact <span class="hlt">crater</span> being shaped as a paraboloid of revolution). The magnetic signature of representative early Nectarian <span class="hlt">craters</span>, Crissium, as well as Earth's complex <span class="hlt">craters</span>, defined by stronger magnetic fields near the basin center and/or inside the first ring, might be a consequence of the shock remanent magnetization of the central uplift plus a thermoremanent magnetization of the impact melt in a steady magnetizing field generated by a former active dynamo. In this case, ESD method is not able to obtain a close fit of the forward model to the observation altitude map or model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017Icar..298...64Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017Icar..298...64Z"><span>Evidence for self-secondary <span class="hlt">cratering</span> of Copernican-age continuous ejecta deposits on the Moon</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zanetti, M.; Stadermann, A.; Jolliff, B.; Hiesinger, H.; van der Bogert, C. H.; Plescia, J.</p> <p>2017-12-01</p> <p><span class="hlt">Crater</span> size-frequency distributions on the ejecta blankets of Aristarchus and Tycho <span class="hlt">Craters</span> are highly variable, resulting in apparent absolute model age differences despite ejecta being emplaced in a geologic instant. <span class="hlt">Crater</span> populations on impact melt ponds are a factor of 4 less than on the ejecta, and <span class="hlt">crater</span> density increases with distance from the parent <span class="hlt">crater</span> rim. Although target material properties may affect <span class="hlt">crater</span> diameters and in turn <span class="hlt">crater</span> size-frequency distribution (CSFD) results, they cannot completely reconcile <span class="hlt">crater</span> density and population differences observed within the ejecta blanket. We infer from the data that self-secondary <span class="hlt">cratering</span>, the formation of impact <span class="hlt">craters</span> immediately following the emplacement of the continuous ejecta blanket by ejecta from the parent <span class="hlt">crater</span>, contributed to the population of small <span class="hlt">craters</span> (< 300 m diameter) on ejecta blankets and must be taken into account if small <span class="hlt">craters</span> and small count areas are to be used for relative and absolute model age determinations on the Moon. Our results indicate that the cumulative number of <span class="hlt">craters</span> larger than 1 km in diameter per unit area, N(1), on the continuous ejecta blanket at Tycho <span class="hlt">Crater</span>, ranges between 2.17 × 10-5 and 1.0 × 10-4, with impact melt ponds most accurately reflecting the primary <span class="hlt">crater</span> flux (N(1) = 3.4 × 10-5). Using the <span class="hlt">cratering</span> flux recorded on Tycho impact melt deposits calibrated to accepted exposure age (109 ± 1.5 Ma) as ground truth, and using similar <span class="hlt">crater</span> distribution analyses on impact melt at Aristarchus <span class="hlt">Crater</span>, we infer the age of Aristarchus <span class="hlt">Crater</span> to be ∼280 Ma. The broader implications of this work <span class="hlt">suggest</span> that the measured <span class="hlt">cratering</span> rate on ejecta blankets throughout the Solar System may be overestimated, and caution should be exercised when using small <span class="hlt">crater</span> diameters (i.e. < 300 m on the Moon) for absolute model age determination.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA21152.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA21152.html"><span>Palikir <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2016-10-27</p> <p>Today's VIS image is of Palikir <span class="hlt">Crater</span> in Terra Sirenum. The inner rim of the <span class="hlt">crater</span> is dissected with numerous gullies. In higher resolution images from other imagers these gullies are the location of changing linea, which appear to grow and retreat as seasons change. Orbit Number: 65311 Latitude: -41.6177 Longitude: 202.206 Instrument: VIS Captured: 2016-09-03 13:12 http://photojournal.jpl.nasa.gov/catalog/PIA21152</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA20092.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA20092.html"><span>Central Pit <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2015-11-13</p> <p><span class="hlt">Crater</span> floors can have a range of features, from flat to a central peak or a central pit. This image from NASA 2001 Mars Odyssey spacecraft shows an unnamed <span class="hlt">crater</span> in Terra Sabaea has a central pit. This unnamed <span class="hlt">crater</span> in Terra Sabaea has a central pit. The different floor features develop do due several factors, including the size of the impactor, the geology of the surface material and the geology of the materials at depth. Orbit Number: 60737 Latitude: 22.3358 Longitude: 61.2019 Instrument: VIS Captured: 2015-08-23 20:13 http://photojournal.jpl.nasa.gov/catalog/PIA20092</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA21911.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA21911.html"><span>Emesh <span class="hlt">Crater</span> on Ceres</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2017-11-02</p> <p>This image taken by NASA's Dawn spacecraft shows Emesh, a <span class="hlt">crater</span> on Ceres. Emesh, named after the Sumerian god of vegetation and agriculture, is 12 miles (20 kilometers) wide. Located at the edge of the Vendimia Planitia, the floor of this <span class="hlt">crater</span> is asymmetrical with terraces distributed along the eastern rim. Additionally, this image shows many subtle linear features that are likely the surface expressions of faults. These faults play a big role in shaping Ceres' <span class="hlt">craters</span>, leading to non-circular <span class="hlt">craters</span> such as Emesh. To the left of Emesh in this view, a much older <span class="hlt">crater</span> of similar size has mostly been erased by impacts and their ejecta. Dawn took this image on May 11, 2016, from its low-altitude mapping orbit, at a distance of about 240 miles (385 kilometers) above the surface. The center coordinates of this image are 11 degrees north latitude, 158 degrees east longitude. https://photojournal.jpl.nasa.gov/catalog/PIA21911</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA01039&hterms=water+meter&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dwater%2Bmeter','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA01039&hterms=water+meter&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dwater%2Bmeter"><span>Evidence for Recent Liquid Water on Mars: Channeled Aprons in a Small <span class="hlt">Crater</span> within Newton <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2000-01-01</p> <p>[figure removed for brevity, see original site] <p/>Newton <span class="hlt">Crater</span> is a large basin formed by an asteroid impact that probably occurred more than 3 billion years ago. It is approximately 287 kilometers (178 miles) across. The picture shown here (top) highlights the north wall of a specific, smaller <span class="hlt">crater</span> located in the southwestern quarter of Newton <span class="hlt">Crater</span> (above). The <span class="hlt">crater</span> of interest was also formed by an impact; it is about 7 km (4.4 mi) across, which is about 7 times bigger than the famous Meteor <span class="hlt">Crater</span> in northern Arizona in North America.<p/>The north wall of the small <span class="hlt">crater</span> has many narrow gullies eroded into it. These are hypothesized to have been formed by flowing water and debris flows. Debris transported with the water created lobed and finger-like deposits at the base of the <span class="hlt">crater</span> wall where it intersects the floor (bottom center top image). Many of the finger-like deposits have small channels indicating that a liquid--most likely water--flowed in these areas. Hundreds of individual water and debris flow events might have occurred to create the scene shown here. Each outburst of water from higher upon the <span class="hlt">crater</span> slopes would have constituted a competition between evaporation, freezing, and gravity.<p/>The individual deposits at the ends of channels in this MOC image mosaic were used to get a rough estimate of the minimum amount of water that might be involved in each flow event. This is done first by assuming that the deposits are like debris flows on Earth. In a debris flow, no less than about 10% (and no more than 30%) of their volume is water. Second, the volume of an apron deposit is estimated by measuring the area covered in the MOC image and multiplying it by a conservative estimate of thickness, 2 meters (6.5 feet). For a flow containing only 10% water, these estimates conservatively <span class="hlt">suggest</span> that about 2.5 million liters (660,000 gallons) of water are involved in each event; this is enough to fill about 7 community-sized swimming pools or</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017Icar..288...69H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017Icar..288...69H"><span>Spatial distribution of impact <span class="hlt">craters</span> on Deimos</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hirata, Naoyuki</p> <p>2017-05-01</p> <p>Deimos, one of the Martian moons, has numerous impact <span class="hlt">craters</span>. However, it is unclear whether <span class="hlt">crater</span> saturation has been reached on this satellite. To address this issue, we apply a statistical test known as nearest-neighbor analysis to analyze the <span class="hlt">crater</span> distribution of Deimos. When a planetary surface such as the Moon is saturated with impact <span class="hlt">craters</span>, the spatial distribution of <span class="hlt">craters</span> is generally changed from random to more ordered. We measured impact <span class="hlt">craters</span> on Deimos from Viking and HiRISE images and found (1) that the power law of the size-frequency distribution of the <span class="hlt">craters</span> is approximately -1.7, which is significantly shallower than those of potential impactors, and (2) that the spatial distribution of <span class="hlt">craters</span> over 30 m in diameter cannot be statistically distinguished from completely random distribution, which indicates that the surface of Deimos is inconsistent with a surface saturated with impact <span class="hlt">craters</span>. Although a <span class="hlt">crater</span> size-frequency distribution curve with a slope of -2 is generally interpreted as indicating saturation equilibrium, it is here proposed that two competing mechanisms, seismic shaking and ejecta emplacement, have played a major role in erasing <span class="hlt">craters</span> on Deimos and are therefore responsible for the shallow slope of this curve. The observed <span class="hlt">crater</span> density may have reached steady state owing to the obliterations induced by the two competing mechanisms. Such an occurrence indicates that the surface is saturated with impact <span class="hlt">craters</span> despite the random distribution of <span class="hlt">craters</span> on Deimos. Therefore, this work proposes that the age determined by the current <span class="hlt">craters</span> on Deimos reflects neither the age of Deimos itself nor that of the formation of the large concavity centered at its south pole because <span class="hlt">craters</span> should be removed by later impacts. However, a few of the largest <span class="hlt">craters</span> on Deimos may be indicative of the age of the south pole event.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_12 --> <div id="page_13" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="241"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19750050844&hterms=geologic+time+scale&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dgeologic%2Btime%2Bscale','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19750050844&hterms=geologic+time+scale&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dgeologic%2Btime%2Bscale"><span>Processes of lunar <span class="hlt">crater</span> degradation - Changes in style with geologic time</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Head, J. W.</p> <p>1975-01-01</p> <p>Relative age schemes of <span class="hlt">crater</span> degradation are calibrated to radiometric dates obtained from lunar samples, changes in morphologic features are analyzed, and the style and rate of lunar surface degradation processes are modeled in relation to lunar geologic time. A comparison of radiometric age scales and the relative degradation of morphologic features for <span class="hlt">craters</span> larger than about 5 km in diameter shows that <span class="hlt">crater</span> degradation can be divided into two periods: Period I, prior to about 3.9 billion years ago and characterized by a high meteoritic influx rate and the formation of large multiringed basins, and Period II, from about 3.9 billion years ago to the present and characterized by a much lower influx rate and a lack of large multiringed basins. Diagnostic features for determining the relative ages of <span class="hlt">craters</span> are described, and <span class="hlt">crater</span> modification processes are considered, including primary impacts, lateral sedimentation, proximity weathering, landslides, and tectonism. It is <span class="hlt">suggested</span> that the fundamental degradation of early Martian <span class="hlt">craters</span> may be associated with erosional and depositional processes related to the intense bombardment characteristics of Period I.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20170002466','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20170002466"><span>Evolution of Circular Polarization Ratio (CPR) Profiles of Kilometer-scale <span class="hlt">Craters</span> on the Lunar Maria</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>King, I. R.; Fassett, C. I.; Thomson, B. J.; Minton, D. A.; Watters, W. A.</p> <p>2017-01-01</p> <p>When sufficiently large impact <span class="hlt">craters</span> form on the Moon, rocks and unweathered materials are excavated from beneath the regolith and deposited into their blocky ejecta. This enhances the rockiness and roughness of the proximal ejecta surrounding fresh impact <span class="hlt">craters</span>. The interior of fresh <span class="hlt">craters</span> are typically also rough, due to blocks, breccia, and impact melt. Thus, both the interior and proximal ejecta of fresh <span class="hlt">craters</span> are usually radar bright and have high circular polarization ratios (CPR). Beyond the proximal ejecta, radar-dark halos are observed around some fresh <span class="hlt">craters</span>, <span class="hlt">suggesting</span> that distal ejecta is finer-grained than background regolith. The radar signatures of <span class="hlt">craters</span> fade with time as the regolith grows.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70012224','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70012224"><span>Low-velocity impact <span class="hlt">craters</span> in ice and ice-saturated sand with implications for Martian <span class="hlt">crater</span> count ages.</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Croft, S.K.; Kieffer, S.W.; Ahrens, T.J.</p> <p>1979-01-01</p> <p>We produced a series of decimeter-sized impact <span class="hlt">craters</span> in blocks of ice near 0oC and -70oC and in ice-saturated sand near -70oC as a preliminary investigation of <span class="hlt">cratering</span> in materials analogous to those found on Mars and the outer solar satellites. <span class="hlt">Crater</span> diameters in the ice-saturated sand were 2 times larger than <span class="hlt">craters</span> in the same energy and velocity range in competent blocks of granite, basalt and cement. <span class="hlt">Craters</span> in ice were c.3 times larger. Martian impact <span class="hlt">crater</span> energy versus diameter scaling may thus be a function of latitude. -from Authors</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA08784&hterms=duck&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dduck','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA08784&hterms=duck&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dduck"><span>'Victoria <span class="hlt">Crater</span>' from 'Duck Bay' (Stereo)</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2006-01-01</p> <p><p/> [figure removed for brevity, see original site] Figure 1 <p/> [figure removed for brevity, see original site] Figure 2 <p/> NASA's Mars rover Opportunity edged 3.7 meters (12 feet) closer to the top of the 'Duck Bay' alcove along the rim of 'Victoria <span class="hlt">Crater</span>' during the rover's 952nd Martian day, or sol (overnight Sept. 27 to Sept. 28), and gained this vista of the <span class="hlt">crater</span>. The rover's navigation camera took the seven exposures combined into this mosaic view of the <span class="hlt">crater</span>'s interior. This <span class="hlt">crater</span> has been the mission's long-term destination for the past 21 Earth months. <p/> The far side of the <span class="hlt">crater</span> is about 800 meters (one-half mile) away. The rim of the <span class="hlt">crater</span> is composed of alternating promontories, rocky points towering approximately 70 meters (230 feet) above the <span class="hlt">crater</span> floor, and recessed alcoves, such as Duck Bay. The bottom of the <span class="hlt">crater</span> is covered by sand that has been shaped into ripples by the Martian wind. The rocky cliffs in the foreground have been informally named 'Cape Verde,' on the left, and 'Cabo Frio,' on the right. <p/> Victoria <span class="hlt">Crater</span> is about five times wider than 'Endurance <span class="hlt">Crater</span>,' which Opportunity spent six months examining in 2004, and about 40 times wider than 'Eagle <span class="hlt">Crater</span>,' where Opportunity first landed. The great lure of Victoria is an expectation that the thick stack of geological layers exposed in the <span class="hlt">crater</span> walls could reveal the record of past environmental conditions over a much greater span of time than Opportunity has read from rocks examined earlier in the mission. <p/> The stereo-anaglyph view presented here is a cylindrical projection with geometric seam correction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19770038698&hterms=relationship+form&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Drelationship%2Bform','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19770038698&hterms=relationship+form&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Drelationship%2Bform"><span>Landform degradation on Mercury, the moon, and Mars - Evidence from <span class="hlt">crater</span> depth/diameter relationships</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Malin, M. C.; Dzurisin, D.</p> <p>1977-01-01</p> <p><span class="hlt">Craters</span> on Mercury, the moon, and Mars were classified into two groups, namely, fresh and degraded <span class="hlt">craters</span>, on the basis of qualitative visual degradation as revealed by degree of rim crispness, terraced interior walls, slumping from <span class="hlt">crater</span> walls, etc., and the depth/diameter relationship of <span class="hlt">craters</span> was studied. Lunar and Mercurian <span class="hlt">crater</span> populations indicate the existence of terrain-correlated degradational phenomena. The depth/diameter relations for Mercury and the moon display remarkably similar forms, <span class="hlt">suggesting</span> similar degrees of landform degradation. Depth/diameter curves display a break in slope, dividing two distinct <span class="hlt">crater</span> populations. Mars <span class="hlt">craters</span> show few of the trends of those of Mercury and the moon. The depth/diameter curve has no definite break in slope, though there is considerable depth variation. The role of nonballistic degradation in connection with the early formation of large expanses of intercrater plains is discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920019775&hterms=graduation+rates&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dgraduation%2Brates','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920019775&hterms=graduation+rates&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dgraduation%2Brates"><span>Styles of <span class="hlt">crater</span> gradation in Southern Ismenius Lacus, Mars: Clues from Meteor <span class="hlt">Crater</span>, Arizona</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Grant, J. A.; Schultz, P. H.</p> <p>1992-01-01</p> <p>Impact <span class="hlt">craters</span> on the Earth and Mars provide a unique opportunity to quantify the gradational evolution of instantaneously created landforms in a variety of geologic settings. Unlike most landforms, the initial morphology associated with impact <span class="hlt">craters</span> on both planets is uncomplicated by competition between construction and degradation during formation. Furthermore, pristine morphologies are both well-constrained and similar to a first order. The present study compares styles of graduation at Meteor <span class="hlt">Crater</span> with those around selected <span class="hlt">craters</span> (greater than 1-2 km in diameter) in southern Ismenius Lacus. Emphasis is placed on features visible in images near LANDSAT TM resolution (30-50 m/pixel) which is available for both areas. In contrast to Mars, vegetation on the Earth can modify gradation, but appears to influence overall rates and styles by 2X-3X rather than orders of magnitude. Further studies of additional <span class="hlt">craters</span> in differing settings will refine the effects of this and other factors (e.g., substrate). Finally, by analogy with results from other terrestrial gradational surfaces this study should help provide constraints on climate over <span class="hlt">crater</span> histories.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5554037','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5554037"><span>Crack Identification in CFRP Laminated Beams Using Multi-Resolution Modal Teager–<span class="hlt">Kaiser</span> Energy under Noisy Environments</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Xu, Wei; Cao, Maosen; Ding, Keqin; Radzieński, Maciej; Ostachowicz, Wiesław</p> <p>2017-01-01</p> <p>Carbon fiber reinforced polymer laminates are increasingly used in the aerospace and civil engineering fields. Identifying cracks in carbon fiber reinforced polymer laminated beam components is of considerable significance for ensuring the integrity and safety of the whole structures. With the development of high-resolution measurement technologies, mode-shape-based crack identification in such laminated beam components has become an active research focus. Despite its sensitivity to cracks, however, this method is susceptible to noise. To address this deficiency, this study proposes a new concept of multi-resolution modal Teager–<span class="hlt">Kaiser</span> energy, which is the Teager–<span class="hlt">Kaiser</span> energy of a mode shape represented in multi-resolution, for identifying cracks in carbon fiber reinforced polymer laminated beams. The efficacy of this concept is analytically demonstrated by identifying cracks in Timoshenko beams with general boundary conditions; and its applicability is validated by diagnosing cracks in a carbon fiber reinforced polymer laminated beam, whose mode shapes are precisely acquired via non-contact measurement using a scanning laser vibrometer. The analytical and experimental results show that multi-resolution modal Teager–<span class="hlt">Kaiser</span> energy is capable of designating the presence and location of cracks in these beams under noisy environments. This proposed method holds promise for developing crack identification systems for carbon fiber reinforced polymer laminates. PMID:28773016</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017Geomo.296...11M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017Geomo.296...11M"><span>Snow-avalanche impact <span class="hlt">craters</span> in southern Norway: Their morphology and dynamics compared with small terrestrial meteorite <span class="hlt">craters</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Matthews, John A.; Owen, Geraint; McEwen, Lindsey J.; Shakesby, Richard A.; Hill, Jennifer L.; Vater, Amber E.; Ratcliffe, Anna C.</p> <p>2017-11-01</p> <p>This regional inventory and study of a globally uncommon landform type reveals similarities in form and process between <span class="hlt">craters</span> produced by snow-avalanche and meteorite impacts. Fifty-two snow-avalanche impact <span class="hlt">craters</span> (mean diameter 85 m, range 10-185 m) were investigated through field research, aerial photographic interpretation and analysis of topographic maps. The <span class="hlt">craters</span> are sited on valley bottoms or lake margins at the foot of steep avalanche paths (α = 28-59°), generally with an easterly aspect, where the slope of the final 200 m of the avalanche path (β) typically exceeds 15°. <span class="hlt">Crater</span> diameter correlates with the area of the avalanche start zone, which points to snow-avalanche volume as the main control on <span class="hlt">crater</span> size. Proximal erosional scars ('blast zones') up to 40 m high indicate up-range ejection of material from the <span class="hlt">crater</span>, assisted by air-launch of the avalanches and impulse waves generated by their impact into water-filled <span class="hlt">craters</span>. Formation of distal mounds up to 12 m high of variable shape is favoured by more dispersed down-range deposition of ejecta. Key to the development of snow-avalanche impact <span class="hlt">craters</span> is the repeated occurrence of topographically-focused snow avalanches that impact with a steep angle on unconsolidated sediment. Secondary <span class="hlt">craters</span> or pits, a few metres in diameter, are attributed to the impact of individual boulders or smaller bodies of snow ejected from the main avalanche. The process of <span class="hlt">crater</span> formation by low-density, low-velocity, large-volume snow flows occurring as multiple events is broadly comparable with <span class="hlt">cratering</span> by single-event, high-density, high-velocity, small-volume projectiles such as small meteorites. Simple comparative modelling of snow-avalanche events associated with a <span class="hlt">crater</span> of average size (diameter 85 m) indicates that the kinetic energy of a single snow-avalanche impact event is two orders of magnitude less than that of a single meteorite-impact event capable of producing a <span class="hlt">crater</span> of similar size</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.S43B0844B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.S43B0844B"><span>Mineralogical control on thermal damage and the presence of a thermal <span class="hlt">Kaiser</span> effect during temperature-cycling experiments</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Browning, J.; Daoud, A.; Meredith, P. G.; Mitchell, T. M.</p> <p>2017-12-01</p> <p>Volcanic and geothermal systems are in part controlled by the mechanical and thermal stresses acting on them and so it is important to understand the response of volcanic rocks to thermo-mechanical loading. One such response is the well-known `<span class="hlt">Kaiser</span> stress-memory' effect observed under cyclic mechanical loading. By contrast, the presence of an analogous `<span class="hlt">Kaiser</span> temperature-memory effect' during cyclic thermal loading has received little attention. We have therefore explored the possibility of a <span class="hlt">Kaiser</span> temperature-memory effect using three igneous rocks of different composition, grain size and origin; Slaufrudalur Granophyre (SGP), Nea Kameni Andesite (NKA) and Seljadalur Basalt (SB). We present results from a series of thermal stressing experiments in which acoustic emissions (AE) were recorded contemporaneously with changing temperature. Samples of each rock were subjected to both a single heating and cooling cycle to a maximum temperature of 900 °C and multiple heating/cooling cycles to peak temperatures of 350°C, 500°C, 700°C and 900 °C (all at a constant rate of 1°C/min on heating and a natural cooling rate of <1°C/min). Porosity, permeability and P-wave velocity measurements were made on each sample both before and after thermal treatment. We use the onset of AEs as a proxy for the onset of thermal cracking. This clearly demonstrates the presence of a <span class="hlt">Kaiser</span> temperature-memory effect in SGP, but not in either NKA and SB. We further find that the vast majority of thermal crack damage is generated upon cooling in the finer grained materials (NKA and SB), but that substantial thermal crack damage is generated during heating in the coarser grained SGP. The total amount of crack damage generated due to heating or cooling is dependent on the mineral composition and, most importantly, the grain size and arrangement, as well as the maximum temperature to which the rock is exposed. Knowledge of thermal stress history and the presence of a <span class="hlt">Kaiser</span> temperature</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19930005117','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19930005117"><span>Bright <span class="hlt">crater</span> outflows: Possible emplacement mechanisms</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chadwick, D. John; Schaber, Gerald G.; Strom, Robert G.; Duval, Darla M.</p> <p>1992-01-01</p> <p>Lobate features with a strong backscatter are associated with 43 percent of the impact <span class="hlt">craters</span> cataloged in Magellan's cycle 1. Their apparent thinness and great lengths are consistent with a low-viscosity material. The longest outflow yet identified is about 600 km in length and flows from the 90-km-diameter <span class="hlt">crater</span> Addams. There is strong evidence that the outflows are largely composed of impact melt, although the mechanisms of their emplacement are not clearly understood. High temperatures and pressures of target rocks on Venus allow for more melt to be produced than on other terrestrial planets because lower shock pressures are required for melting. The percentage of impact <span class="hlt">craters</span> with outflows increases with increasing <span class="hlt">crater</span> diameter. The mean diameter of <span class="hlt">craters</span> without outflows is 14.4 km, compared with 27.8 km for <span class="hlt">craters</span> with outflows. No <span class="hlt">craters</span> smaller than 3 km, 43 percent of <span class="hlt">craters</span> in the 10- to 30-km-diameter range, and 90 percent in the 80- to 100-km-diameter range have associated bright outflows. More melt is produced in the more energetic impact events that produce larger <span class="hlt">craters</span>. However, three of the four largest <span class="hlt">craters</span> have no outflows. We present four possible mechanisms for the emplacement of bright outflows. We believe this 'shotgun' approach is justified because all four mechanisms may indeed have operated to some degree.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA15121.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA15121.html"><span>Vesta <span class="hlt">Cratered</span> Landscape: Double <span class="hlt">Crater</span> and <span class="hlt">Craters</span> with Bright Ejecta</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2011-11-23</p> <p>This image from NASA Dawn spacecraft is dominated by a double <span class="hlt">crater</span> which may have been formed by the simultaneous impact of a binary asteroid. Binary asteroids are asteroids that orbit their mutual center of mass.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA20696.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA20696.html"><span>Shadowed <span class="hlt">Craters</span> on Ceres</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2016-07-08</p> <p>At the poles of Ceres, scientists have found <span class="hlt">craters</span> that are permanently in shadow (indicated by blue markings). Such <span class="hlt">craters</span> are called "cold traps" if they remain below about minus 240 degrees Fahrenheit (minus 151 degrees Celsius). These shadowed <span class="hlt">craters</span> may have been collecting ice for billions of years because they are so cold. This image was created using data from NASA's Dawn spacecraft. http://photojournal.jpl.nasa.gov/catalog/PIA20696</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19780057835&hterms=TNT&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DTNT','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19780057835&hterms=TNT&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DTNT"><span><span class="hlt">Cratering</span> motions and structural deformation in the rim of the Prairie Flat multiring explosion <span class="hlt">crater</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Roddy, D. J.; Ullrich, G. W.; Sauer, F. M.; Jones, G. H. S.</p> <p>1977-01-01</p> <p><span class="hlt">Cratering</span> motions and structural deformation are described for the rim of the Prairie Flat multiring <span class="hlt">crater</span>, 85.5 m across and 5.3 m deep, which was formed by the detonation of a 500-ton TNT surface-tangent sphere. The terminal displacement and motion data are derived from marker cans and velocity gages emplaced in drill holes in a three-dimensional matrix radial to the <span class="hlt">crater</span>. The integration of this data with a detailed geologic cross section, mapped from deep trench excavations through the rim, provides a composite view of the general sequence of motions that formed a transiently uplifted rim, overturned flap, inverted stratigraphy, downfolded rim, and deformed strata in the <span class="hlt">crater</span> walls. Preliminary comparisons with laboratory experimental <span class="hlt">cratering</span> and with numerical simulations indicate that explosion <span class="hlt">craters</span> of the Prairie Flat-type generated by surface and near-surface energy sources tend to follow predictable motion sequences and produce comparable structural deformation. More specifically, central uplift and multiring impact <span class="hlt">craters</span> with morphologies and structures comparable to Prairie Flat are inferred to have experienced similar deformational histories of the rim, such as uplift, overturning, terracing, and downfolding.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA03859.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA03859.html"><span>Iturralde <span class="hlt">Crater</span>, Bolivia</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2002-09-17</p> <p>NASA scientists will venture into an isolated part of the Bolivian Amazon to try and uncover the origin of a 5 mile (8 kilometer) diameter <span class="hlt">crater</span> there known as the Iturralde <span class="hlt">Crater</span>. Traveling to this inhospitable forest setting, the Iturralde <span class="hlt">Crater</span> Expedition 2002 will seek to determine if the unusual circular <span class="hlt">crater</span> was created by a meteor or comet. Organized by Dr. Peter Wasilewski of NASA's Goddard Space Flight Center, Greenbelt, Md., the Iturralde <span class="hlt">Crater</span> Expedition 2002 will be led by Dr. Tim Killeen of Conservation International, which is based in Bolivia. Killeen will be assisted by Dr. Compton Tucker of Goddard. The team intends to collect and analyze rocks and soil, look for glass particles that develop from meteor impacts and study magnetic properties in the area to determine if the Iturralde site was indeed created by a meteor. This image was acquired on June 29, 2001 by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA's Terra satellite. With its 14 spectral bands from the visible to the thermal infrared wavelength region, and its high spatial resolution of 15 to 90 meters (about 50 to 300 feet), ASTER will image Earth for the next 6 years to map and monitor the changing surface of our planet. http://photojournal.jpl.nasa.gov/catalog/PIA03859</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA22142.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA22142.html"><span>Investigating Mars: Rabe <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2017-12-14</p> <p>This VIS image of Rabe <span class="hlt">Crater</span> is dominated by the extensive dunes that cover the <span class="hlt">crater</span> floor. To the top of the image part of the pit is visible, as well as a small peninsula that has been eroded into the upper level floor materials. On the upper elevation on the side left of the peninsula the dunes cascade onto the lower pit elevation. There is also a slight arc to the dunes on the pit floor due to how the peninsula changed the wind pattern. Rabe <span class="hlt">Crater</span> is 108 km (67 miles) across. <span class="hlt">Craters</span> of similar size often have flat floors. Rabe <span class="hlt">Crater</span> has some areas of flat floor, but also has a large complex pit occupying a substantial part of the floor. The interior fill of the <span class="hlt">crater</span> is thought to be layered sediments created by wind and or water action. The pit is eroded into this material. The eroded materials appear to have stayed within the <span class="hlt">crater</span> forming a large sand sheet with surface dune forms as well as individual dunes where the <span class="hlt">crater</span> floor is visible. The dunes also appear to be moving from the upper floor level into the pit. The Odyssey spacecraft has spent over 15 years in orbit around Mars, circling the planet more than 69000 times. It holds the record for longest working spacecraft at Mars. THEMIS, the IR/VIS camera system, has collected data for the entire mission and provides images covering all seasons and lighting conditions. Over the years many features of interest have received repeated imaging, building up a suite of images covering the entire feature. From the deepest chasma to the tallest volcano, individual dunes inside <span class="hlt">craters</span> and dune fields that encircle the north pole, channels carved by water and lava, and a variety of other feature, THEMIS has imaged them all. For the next several months the image of the day will focus on the Tharsis volcanoes, the various chasmata of Valles Marineris, and the major dunes fields. We hope you enjoy these images! Orbit Number: 52206 Latitude: -43.6573 Longitude: 34.9551 Instrument: VIS Captured: 2013</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA22141.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA22141.html"><span>Investigating Mars: Rabe <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2017-12-13</p> <p>Dunes cover the majority of this image of Rabe <span class="hlt">Crater</span>. As the dunes are created by wind action the forms of the dunes record the wind direction. Dunes will have a long low angle component and a short high angle side. The steep side is called the slip face. The wind blows up the long side of the dune. In this VIS image the slip faces are illuminated more than the longer side. In this part of the <span class="hlt">crater</span> the winds were generally moving from the lower right corner of the image towards the upper left. Rabe <span class="hlt">Crater</span> is 108 km (67 miles) across. <span class="hlt">Craters</span> of similar size often have flat floors. Rabe <span class="hlt">Crater</span> has some areas of flat floor, but also has a large complex pit occupying a substantial part of the floor. The interior fill of the <span class="hlt">crater</span> is thought to be layered sediments created by wind and or water action. The pit is eroded into this material. The eroded materials appear to have stayed within the <span class="hlt">crater</span> forming a large sand sheet with surface dune forms as well as individual dunes where the <span class="hlt">crater</span> floor is visible. The dunes also appear to be moving from the upper floor level into the pit. The Odyssey spacecraft has spent over 15 years in orbit around Mars, circling the planet more than 69000 times. It holds the record for longest working spacecraft at Mars. THEMIS, the IR/VIS camera system, has collected data for the entire mission and provides images covering all seasons and lighting conditions. Over the years many features of interest have received repeated imaging, building up a suite of images covering the entire feature. From the deepest chasma to the tallest volcano, individual dunes inside <span class="hlt">craters</span> and dune fields that encircle the north pole, channels carved by water and lava, and a variety of other feature, THEMIS has imaged them all. For the next several months the image of the day will focus on the Tharsis volcanoes, the various chasmata of Valles Marineris, and the major dunes fields. We hope you enjoy these images! Orbit Number: 35105 Latitude: -43</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70010404','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70010404"><span>Moon-Mercury: Relative preservation states of secondary <span class="hlt">craters</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Scott, D.H.</p> <p>1977-01-01</p> <p>Geologic mapping of the Kuiper quadrangle of Mercury and other geologic studies of the planet indicate that secondary <span class="hlt">craters</span> are much better preserved than those on the moon around primary <span class="hlt">craters</span> of similar size and morphology. Among the oldest recognized secondary <span class="hlt">craters</span> on the moon associated with <span class="hlt">craters</span> 100 km across or less are those of Posidonius, Atlas and Plato; these <span class="hlt">craters</span> have been dated as middle to late Imbrian in age. Many <span class="hlt">craters</span> on Mercury with dimensions, morphologies and superposed <span class="hlt">crater</span> densities similar to these lunar <span class="hlt">craters</span> have fields and clusters of fresher appearing secondary <span class="hlt">craters</span>. The apparent differences between secondary-<span class="hlt">crater</span> morphology and parent <span class="hlt">crater</span> may be due in part to: (1) rapid isostatic adjustment of the parent <span class="hlt">crater</span>; (2) different impact fluxes between the two planets; and (or) (3) to the greater concentration of Mercurian secondaries around impact areas, thereby accentuating <span class="hlt">crater</span> forms. Another factor which may contribute to the better state of preservation of Mercurian secondaries relative to the moon is the difference in <span class="hlt">crater</span> ejecta velocities on both bodies. These velocities have been calculated for fields of secondary <span class="hlt">craters</span> at about equal ranges from lunar and Mercurian parent <span class="hlt">craters</span>. Results show that ejection velocities of material producing most of the secondary <span class="hlt">craters</span> are rather low (<1 km/s) but velocities on Mercury are about 50% greater than those on the moon for equivalent ranges. Higher velocities may produce morphologically enhanced secondary <span class="hlt">craters</span> which may account for their better preservation with time. ?? 1977.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018Icar..305..314S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018Icar..305..314S"><span><span class="hlt">Crater</span> relaxation on Titan aided by low thermal conductivity sand infill</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schurmeier, Lauren R.; Dombard, Andrew J.</p> <p>2018-05-01</p> <p>Titan's few impact <span class="hlt">craters</span> are currently many hundreds of meters shallower than the depths expected. Assuming these <span class="hlt">craters</span> initially had depths equal to that of similar-size fresh <span class="hlt">craters</span> on Ganymede and Callisto (moons of similar size, composition, and target lithology), then some process has shallowed them over time. Since nearly all of Titan's recognized <span class="hlt">craters</span> are located within the arid equatorial sand seas of organic-rich dunes, where rain is infrequent, and atmospheric sedimentation is expected to be low, it has been <span class="hlt">suggested</span> that aeolian infill plays a major role in shallowing the <span class="hlt">craters</span>. Topographic relaxation at Titan's current heat flow was previously assumed to be an unimportant process on Titan due to its low surface temperature (94 K). However, our estimate of the thermal conductivity of Titan's organic-rich sand is remarkably low (0.025 W m-1 K-1), and when in thick deposits, will result in a thermal blanketing effect that can aid relaxation. Here, we simulate the relaxation of Titan's <span class="hlt">craters</span> Afekan, Soi, and Sinlap including thermal effects of various amounts of sand inside and around Titan's <span class="hlt">craters</span>. We find that the combination of aeolian infill and subsequent relaxation can produce the current <span class="hlt">crater</span> depths in a geologically reasonable period of time using Titan's current heat flow. Instead of needing to fill completely the missing volume with 100% sand, only ∼62%, ∼71%, and ∼97%, of the volume need be sand at the current basal heat flux for Afekan, Soi, and Sinlap, respectively. We conclude that both processes are likely at work shallowing these <span class="hlt">craters</span>, and this finding contributes to why Titan overall lacks impact <span class="hlt">craters</span> in the arid equatorial regions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA21920.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA21920.html"><span>Juling <span class="hlt">Crater</span>'s Floor</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2018-03-14</p> <p>This view from NASA's Dawn mission shows the floor of Ceres' Juling <span class="hlt">Crater</span>. The <span class="hlt">crater</span> floor shows evidence of the flow of ice and rock, similar to rock glaciers in Earth's polar regions. Dawn acquired the picture with its framing camera on Aug. 30, 2016. https://photojournal.jpl.nasa.gov/catalog/PIA21920</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018P%26SS..153..120B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018P%26SS..153..120B"><span>Rock spatial densities on the rims of the Tycho secondary <span class="hlt">craters</span> in Mare Nectaris</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Basilevsky, A. T.; Michael, G. G.; Kozlova, N. A.</p> <p>2018-04-01</p> <p>The aim of this work is to check whether the technique of estimation of age of small lunar <span class="hlt">craters</span> based on spatial density of rock boulders on their rims described in Basilevsky et al. (2013, 2015b) and Li et al. (2017) for the <span class="hlt">craters</span> < 1 km in diameter is applicable to the larger <span class="hlt">craters</span>. The work presents the rock counts on the rims of four <span class="hlt">craters</span> having diameters 1000, 1100, 1240 and 1400 m located in Mare Nectaris. These <span class="hlt">craters</span> are secondaries of the primary <span class="hlt">crater</span> Tycho, whose age was found to be 109 ± 4 Ma (Stoffler and Ryder, 2001) so this may be taken as the age of the four <span class="hlt">craters</span>, too. Using the dependence of the rock spatial densities at the <span class="hlt">crater</span> rims on the <span class="hlt">crater</span> age for the case of mare <span class="hlt">craters</span> (Li et al., 2017) our measured rock densities correspond to ages from ∼100 to 130 Ma. These estimates are reasonably close to the given age of the primary <span class="hlt">crater</span> Tycho. This, in turn, <span class="hlt">suggests</span> that this technique of <span class="hlt">crater</span> age estimation is applicable to <span class="hlt">craters</span> up to ∼1.5 km in diameter. For the four considered <span class="hlt">craters</span> we also measured their depth/diameter ratios and the maximum angles of the <span class="hlt">crater</span> inner slopes. For the considered <span class="hlt">craters</span> it was found that with increasing <span class="hlt">crater</span> diameter, the depth/diameter ratios and maximum angles of internal slopes increase, but the values of these parameters for specific <span class="hlt">craters</span> may deviate significantly from the general trends. The deviations probably result from some dissimilarities in the primary <span class="hlt">crater</span> geometries, that may be due to <span class="hlt">crater</span> to <span class="hlt">crater</span> differences in characteristics of impactors (e.g., in their bulk densities) and/or differences in the mechanical properties of the target. It may be possible to find secondaries of <span class="hlt">crater</span> Tycho in the South pole area and, if so, they may be studied to check the specifics and rates of the rock boulder degradation in the lunar polar environment.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <div id="page_14" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="261"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA21908.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA21908.html"><span>Axomama <span class="hlt">Crater</span> on Ceres</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2017-10-06</p> <p>This image from NASA's Dawn spacecraft highlights Axomama <span class="hlt">Crater</span>, the small <span class="hlt">crater</span> shown to the right of center. It is 3 miles (5 kilometers) in diameter and located just inside the western rim of Dantu <span class="hlt">Crater</span>. Axomama is one of the newly named <span class="hlt">craters</span> on Ceres. Its sharp edges indicate recent emplacement by a small impact. This picture also shows details on the floor of Dantu, which comprises most of the image. The many fractures and the central pit (see also PIA20303) are reminiscent of Occator <span class="hlt">Crater</span> and could point to a similar formation history, involving activity driven by the presence of liquid water in the subsurface. Axomama is named after the Incan goddess of potato, or "Potato-mother." NASA's Dawn spacecraft acquired this picture during its extended mission on July 24, 2016, from its low altitude mapping orbit at about 240 miles (385 kilometers) above the surface. The center coordinates of this image are 24 degrees north latitude, 131 degrees east longitude. https://photojournal.jpl.nasa.gov/catalog/PIA21908</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19800067530&hterms=factoring&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dfactoring','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19800067530&hterms=factoring&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dfactoring"><span>Ganymede - A relationship between thermal history and <span class="hlt">crater</span> statistics</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Phillips, R. J.; Malin, M. C.</p> <p>1980-01-01</p> <p>An approach for factoring the effects of a planetary thermal history into a predicted set of <span class="hlt">crater</span> statistics for an icy satellite is developed and forms the basis for subsequent data inversion studies. The key parameter is a thermal evolution-dependent critical time for which <span class="hlt">craters</span> of a particular size forming earlier do not contribute to present-day statistics. An example is given for the satellite Ganymede and the effect of the thermal history is easily seen in the resulting predicted <span class="hlt">crater</span> statistics. A preliminary comparison with the data, subject to the uncertainties in ice rheology and impact flux history, <span class="hlt">suggests</span> a surface age of 3.8 x 10 to the 9th years and a radionuclide abundance of 0.3 times the chondritic value.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012ttt..work...24S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012ttt..work...24S"><span>Titan's Impact <span class="hlt">Cratering</span> Record: Erosion of Ganymedean (and other) <span class="hlt">Craters</span> on a Wet Icy Landscape</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schenk, P.; Moore, J.; Howard, A.</p> <p>2012-04-01</p> <p>We examine the <span class="hlt">cratering</span> record of Titan from the perspective of icy satellites undergoing persistent landscape erosion. First we evaluate whether Ganymede (and Callisto) or the smaller low-gravity neighboring icy satellites of Saturn are the proper reference standard for evaluating Titan’s impact <span class="hlt">crater</span> morphologies, using topographic and morphometric measurements (Schenk, 2002; Schenk et al. (2004) and unpublished data). The special case of Titan’s largest <span class="hlt">crater</span>, Minrva, is addressed through analysis of large impact basins such as Gilgamesh, Lofn, Odysseus and Turgis. Second, we employ a sophisticated landscape evolution and modification model developed for study of martian and other planetary landforms (e.g., Howard, 2007). This technique applies mass redistribution principles due to erosion by impact, fluvial and hydrological processes to a planetary landscape. The primary advantage of our technique is the possession of a limited but crucial body of areal digital elevation models (DEMs) of Ganymede (and Callisto) impact <span class="hlt">craters</span> as well as global DEM mapping of Saturn’s midsize icy satellites, in combination with the ability to simulate rainfall and redeposition of granular material to determine whether Ganymede <span class="hlt">craters</span> can be eroded to resemble Titan <span class="hlt">craters</span> and the degree of erosion required. References: Howard, A. D., “Simulating the development of martian highland landscapes through the interaction of impact <span class="hlt">cratering</span>, fluvial erosion, and variable hydrologic forcing”, Geomorphology, 91, 332-363, 2007. Schenk, P. "Thickness constraints on the icy shells of the galilean satellites from impact <span class="hlt">crater</span> shapes". Nature, 417, 419-421, 2002. Schenk, P.M., et al. "Ages and interiors: the <span class="hlt">cratering</span> record of the Galilean satellites". In: Jupiter: The Planet, Satellites, and Magnetosphere, Cambridge University Press, Cambridge, UK, pp. 427-456, 2004.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20030067009&hterms=TURTLES&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DTURTLES','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20030067009&hterms=TURTLES&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DTURTLES"><span>Numerical Simulations of Silverpit <span class="hlt">Crater</span> Collapse</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Collins, G. S.; Ivanov, B. A.; Turtle, E. P.; Melosh, H. J.</p> <p>2003-01-01</p> <p>The Silverpit <span class="hlt">crater</span> is a recently discovered, 60-65 Myr old complex <span class="hlt">crater</span>, which lies buried beneath the North Sea, about 150 km east of Britain. High-resolution images of Silverpit's subsurface structure, provided by three-dimensional seismic reflection data, reveal an inner-<span class="hlt">crater</span> morphology similar to that expected for a 5-8 km diameter terrestrial <span class="hlt">crater</span>. The <span class="hlt">crater</span> walls show evidence of terrace-style slumping and there is a distinct central uplift, which may have produced a central peak in the pristine <span class="hlt">crater</span> morphology. However, Silverpit is not a typical 5-km diameter terrestrial <span class="hlt">crater</span>, because it exhibits multiple, concentric rings outside the main cavity. External concentric rings are normally associated with much larger impact structures, for example Chicxulub on Earth, or Orientale on the Moon. Furthermore, external rings associated with large impacts on the terrestrial planets and moons are widely-spaced, predominantly inwardly-facing, asymmetric scarps. However, the seismic data show that the external rings at Silverpit represent closely-spaced, concentric faultbound graben, with both inwardly and outwardly facing fault-scarps. This type of multi-ring structure directly analogous to the Valhalla-type multi-ring basins found on the icy satellites. Thus, the presence and style of the multiple rings at Silverpit is surprising given both the size of the <span class="hlt">crater</span> and its planetary setting. A further curiosity of the Silverpit structure is that the external concentric rings appear to be extensional features on the West side of the <span class="hlt">crater</span> and compressional features on the East side. The <span class="hlt">crater</span> also lies in a local depression, thought to be created by postimpact movement of a salt layer buried beneath the <span class="hlt">crater</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA07041&hterms=tale&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dtale','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA07041&hterms=tale&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dtale"><span>A Tale of 3 <span class="hlt">Craters</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2004-01-01</p> <p><p/> 11 November 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image captures some of the complexity of the martian upper crust. Mars does not simply have an impact-<span class="hlt">cratered</span> surface, it's upper crust is a <span class="hlt">cratered</span> volume. Over time, older <span class="hlt">craters</span> on Mars have been eroded, filled, buried, and in some cases exhumed and re-exposed at the martian surface. The crust of Mars is layered to depths of 10 or more kilometers, and mixed in with the layered bedrock are a variety of ancient <span class="hlt">craters</span> with diameters ranging from a few tens of meters (a few tens of yards) to several hundred kilometers (more than one or two hundred miles). <p/> The picture shown here captures some of the essence of the layered, <span class="hlt">cratered</span> volume of the upper crust of Mars in a very simple form. The image shows three distinct circular features. The smallest, in the lower right quarter of the image, is a meteor <span class="hlt">crater</span> surrounded by a mound of material. This small <span class="hlt">crater</span> formed within a layer of bedrock that once covered the entire scene, but today is found only in this small remnant adjacent to the <span class="hlt">crater</span>. The intermediate-sized <span class="hlt">crater</span>, west (left) of the small one, formed either in the next layer down--that is, below the layer in which the small <span class="hlt">crater</span> formed--or it formed in some layers that are now removed, but was big enough to penetrate deeply into the rock that is near the surface today. The largest circular feature in the image, in the upper right quarter of the image, is still largely buried. It formed in layers of rock that are below the present surface. Erosion has brought traces of its rim back to the surface of Mars. This picture is located near 50.0oS, 77.8oW, and covers an area approximately 3 km (1.9 mi) across. Sunlight illuminates this October 2004 image from the upper left.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5012121','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5012121"><span>Spectral properties of Titan's impact <span class="hlt">craters</span> imply chemical weathering of its surface</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Barnes, J. W.; Sotin, C.; MacKenzie, S.; Soderblom, J. M.; Le Mouélic, S.; Kirk, R. L.; Stiles, B. W.; Malaska, M. J.; Le Gall, A.; Brown, R. H.; Baines, K. H.; Buratti, B.; Clark, R. N.; Nicholson, P. D.</p> <p>2015-01-01</p> <p>Abstract We examined the spectral properties of a selection of Titan's impact <span class="hlt">craters</span> that represent a range of degradation states. The most degraded <span class="hlt">craters</span> have rims and ejecta blankets with spectral characteristics that <span class="hlt">suggest</span> that they are more enriched in water ice than the rims and ejecta blankets of the freshest <span class="hlt">craters</span> on Titan. The progression is consistent with the chemical weathering of Titan's surface. We propose an evolutionary sequence such that Titan's <span class="hlt">craters</span> expose an intimate mixture of water ice and organic materials, and chemical weathering by methane rainfall removes the soluble organic materials, leaving the insoluble organics and water ice behind. These observations support the idea that fluvial processes are active in Titan's equatorial regions. PMID:27656006</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70186309','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70186309"><span>Impact <span class="hlt">crater</span> outflows on Venus: Morphology and emplacement mechanisms</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Chadwick, D. John; Schaber, Gerald G.</p> <p>1993-01-01</p> <p>Many of the 932 impact <span class="hlt">craters</span> discovered by the Magellan spacecraft at Venus are associated with lobate flows that originate at or near the <span class="hlt">crater</span> rim. They extend for several to several hundred kilometers from the <span class="hlt">crater</span>, and they commonly have a strong radar backscatter. A morphologic study of all identifiable <span class="hlt">crater</span> outflows on Venus has revealed that many individual flows each consist of two areas, defined by distinct morphologic features. These two areas appear to represent two stages of deposition for each flow. The part of the flow that is generally deposited closest to the <span class="hlt">crater</span> tends to be on the downrange side of the <span class="hlt">crater</span>, flows in the downrange direction, and it is interpreted to be a late-stage ejecta. In many cases, this proximal part of the flow is too thin to completely bury the large blocks in subjacent ejecta deposits. Dendritic channels, present in many proximal flows, appear to have drained liquid from the proximal part in the downhill direction, and they debouch to feed the outer part of the flows. This distal part flows downhill, fills small grabens, and is ponded by ridges, behavior that mimics that of volcanic lava flows. The meandering and dendritic channels and the relation of the distal flows to topography strongly <span class="hlt">suggest</span> that the distal portion is the result of coalescence and slow drainage of impact melt from the proximal portion. Impact melt forms a lining to the transient <span class="hlt">crater</span> and mixes turbulently with solid clasts, and part of this mixture may be ejected to form the proximal part of the flow during the excavation stage of <span class="hlt">crater</span> development. A statistical study of the Venusian <span class="hlt">craters</span> has revealed that, in general, large <span class="hlt">craters</span> produced by impacts with relatively low incidence angles to the surface are more likely to produce flows than small <span class="hlt">craters</span> produced by higher-angle impacts. The greater flow production and downrange focusing of the proximal flows with decreasing incidence angle indicate a strong control of the flows</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20170002467','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20170002467"><span><span class="hlt">Crater</span> Morphometry and <span class="hlt">Crater</span> Degradation on Mercury: Mercury Laser Altimeter (MLA) Measurements and Comparison to Stereo-DTM Derived Results</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Leight, C.; Fassett, C. I.; Crowley, M. C.; Dyar, M. D.</p> <p>2017-01-01</p> <p>Two types of measurements of Mercury's surface topography were obtained by the MESSENGER (MErcury Surface Space ENvironment, GEochemisty and Ranging) spacecraft: laser ranging data from Mercury Laser Altimeter (MLA) [1], and stereo imagery from the Mercury Dual Imaging System (MDIS) camera [e.g., 2, 3]. MLA data provide precise and accurate elevation meaurements, but with sparse spatial sampling except at the highest northern latitudes. Digital terrain models (DTMs) from MDIS have superior resolution but with less vertical accuracy, limited approximately to the pixel resolution of the original images (in the case of [3], 15-75 m). Last year [4], we reported topographic measurements of <span class="hlt">craters</span> in the D=2.5 to 5 km diameter range from stereo images and <span class="hlt">suggested</span> that <span class="hlt">craters</span> on Mercury degrade more quickly than on the Moon (by a factor of up to approximately 10×). However, we listed several alternative explanations for this finding, including the hypothesis that the lower depth/diameter ratios we observe might be a result of the resolution and accuracy of the stereo DTMs. Thus, additional measurements were undertaken using MLA data to examine the morphometry of <span class="hlt">craters</span> in this diameter range and assess whether the faster <span class="hlt">crater</span> degradation rates proposed to occur on Mercury is robust.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19920001715','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19920001715"><span>Impact <span class="hlt">cratering</span> calculations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ahrens, Thomas J.; Okeefe, J. D.; Smither, C.; Takata, T.</p> <p>1991-01-01</p> <p>In the course of carrying out finite difference calculations, it was discovered that for large <span class="hlt">craters</span>, a previously unrecognized type of <span class="hlt">crater</span> (diameter) growth occurred which was called lip wave propagation. This type of growth is illustrated for an impact of a 1000 km (2a) silicate bolide at 12 km/sec (U) onto a silicate half-space at earth gravity (1 g). The von Misses crustal strength is 2.4 kbar. The motion at the <span class="hlt">crater</span> lip associated with this wave type phenomena is up, outward, and then down, similar to the particle motion of a surface wave. It is shown that the <span class="hlt">crater</span> diameter has grown d/a of approximately 25 to d/a of approximately 4 via lip propagation from Ut/a = 5.56 to 17.0 during the time when rebound occurs. A new code is being used to study partitioning of energy and momentum and <span class="hlt">cratering</span> efficiency with self gravity for finite-sized objects rather than the previously discussed planetary half-space problems. These are important and fundamental subjects which can be addressed with smoothed particle hydrodynamic (SPH) codes. The SPH method was used to model various problems in astrophysics and planetary physics. The initial work demonstrates that the energy budget for normal and oblique impacts are distinctly different than earlier calculations for silicate projectile impact on a silicate half space. Motivated by the first striking radar images of Venus obtained by Magellan, the effect of the atmosphere on impact <span class="hlt">cratering</span> was studied. In order the further quantify the processes of meteor break-up and trajectory scattering upon break-up, the reentry physics of meteors striking Venus' atmosphere versus that of the Earth were studied.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011PhDT.........6R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011PhDT.........6R"><span>Planetary Surface Properties, <span class="hlt">Cratering</span> Physics, and the Volcanic History of Mars from a New Global Martian <span class="hlt">Crater</span> Database</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Robbins, Stuart James</p> <p></p> <p>Impact <span class="hlt">craters</span> are arguably the primary exogenic planetary process contributing to the surface evolution of solid bodies in the solar system. <span class="hlt">Craters</span> appear across the entire surface of Mars, and they are vital to understanding its crustal properties as well as surface ages and modification events. They allow inferences into the ancient climate and hydrologic history, and they add a key data point for the understanding of impact physics. Previously available databases of Mars impact <span class="hlt">craters</span> were created from now antiquated datasets, automated algorithms with biases and inaccuracies, were limited in scope, and/or complete only to multikilometer diameters. This work presents a new global database for Mars that contains 378,540 <span class="hlt">craters</span> statistically complete for diameters D ≳ 1 km. This detailed database includes location and size, ejecta morphology and morphometry, interior morphology and degradation state, and whether the <span class="hlt">crater</span> is a secondary impact. This database allowed exploration of global <span class="hlt">crater</span> type distributions, depth, and morphologies in unprecedented detail that were used to re-examine basic <span class="hlt">crater</span> scaling laws for the planet. The inclusion of hundreds of thousands of small, approximately kilometer-sized impacts facilitated a detailed study of the properties of nearby fields of secondary <span class="hlt">craters</span> in relation to their primary <span class="hlt">crater</span>. It also allowed the discovery of vast distant clusters of secondary <span class="hlt">craters</span> over 5000 km from their primary <span class="hlt">crater</span>, Lyot. Finally, significantly smaller <span class="hlt">craters</span> were used to age-date volcanic calderas on the planet to re-construct the timeline of the last primary eruption events from 20 of the major Martian volcanoes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA22146.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA22146.html"><span>Investigating Mars: Rabe <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2017-12-20</p> <p>This is a false color image of Rabe <span class="hlt">Crater</span>. In this combination of filters "blue" typically means basaltic sand. Rabe <span class="hlt">Crater</span> is 108 km (67 miles) across. <span class="hlt">Craters</span> of similar size often have flat floors. Rabe <span class="hlt">Crater</span> has some areas of flat floor, but also has a large complex pit occupying a substantial part of the floor. The interior fill of the <span class="hlt">crater</span> is thought to be layered sediments created by wind and or water action. The pit is eroded into this material. The eroded materials appear to have stayed within the <span class="hlt">crater</span> forming a large sand sheet with surface dune forms as well as individual dunes where the <span class="hlt">crater</span> floor is visible. The dunes also appear to be moving from the upper floor level into the pit. The THEMIS VIS camera contains 5 filters. The data from different filters can be combined in multiple ways to create a false color image. These false color images may reveal subtle variations of the surface not easily identified in a single band image. The Odyssey spacecraft has spent over 15 years in orbit around Mars, circling the planet more than 69000 times. It holds the record for longest working spacecraft at Mars. THEMIS, the IR/VIS camera system, has collected data for the entire mission and provides images covering all seasons and lighting conditions. Over the years many features of interest have received repeated imaging, building up a suite of images covering the entire feature. From the deepest chasma to the tallest volcano, individual dunes inside <span class="hlt">craters</span> and dune fields that encircle the north pole, channels carved by water and lava, and a variety of other feature, THEMIS has imaged them all. For the next several months the image of the day will focus on the Tharsis volcanoes, the various chasmata of Valles Marineris, and the major dunes fields. We hope you enjoy these images! Orbit Number: 52231 Latitude: -43.6665 Longitude: 34.2627 Instrument: VIS Captured: 2013-09-22 14:29 https://photojournal.jpl.nasa.gov/catalog/PIA22146</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA22148.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA22148.html"><span>Investigating Mars: Rabe <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2017-12-22</p> <p>This is a false color image of Rabe <span class="hlt">Crater</span>. In this combination of filters "blue" typically means basaltic sand. Rabe <span class="hlt">Crater</span> is 108 km (67 miles) across. <span class="hlt">Craters</span> of similar size often have flat floors. Rabe <span class="hlt">Crater</span> has some areas of flat floor, but also has a large complex pit occupying a substantial part of the floor. The interior fill of the <span class="hlt">crater</span> is thought to be layered sediments created by wind and or water action. The pit is eroded into this material. The eroded materials appear to have stayed within the <span class="hlt">crater</span> forming a large sand sheet with surface dune forms as well as individual dunes where the <span class="hlt">crater</span> floor is visible. The dunes also appear to be moving from the upper floor level into the pit. The THEMIS VIS camera contains 5 filters. The data from different filters can be combined in multiple ways to create a false color image. These false color images may reveal subtle variations of the surface not easily identified in a single band image. The Odyssey spacecraft has spent over 15 years in orbit around Mars, circling the planet more than 69000 times. It holds the record for longest working spacecraft at Mars. THEMIS, the IR/VIS camera system, has collected data for the entire mission and provides images covering all seasons and lighting conditions. Over the years many features of interest have received repeated imaging, building up a suite of images covering the entire feature. From the deepest chasma to the tallest volcano, individual dunes inside <span class="hlt">craters</span> and dune fields that encircle the north pole, channels carved by water and lava, and a variety of other feature, THEMIS has imaged them all. For the next several months the image of the day will focus on the Tharsis volcanoes, the various chasmata of Valles Marineris, and the major dunes fields. We hope you enjoy these images! Orbit Number: 67144 Latitude: -43.5512 Longitude: 34.5951 Instrument: VIS Captured: 2017-02-01 12:57 https://photojournal.jpl.nasa.gov/catalog/PIA22148</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA22145.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA22145.html"><span>Investigating Mars: Rabe <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2017-12-19</p> <p>This is a false color image of Rabe <span class="hlt">Crater</span>. In this combination of filters "blue" typically means basaltic sand. Rabe <span class="hlt">Crater</span> is 108 km (67 miles) across. <span class="hlt">Craters</span> of similar size often have flat floors. Rabe <span class="hlt">Crater</span> has some areas of flat floor, but also has a large complex pit occupying a substantial part of the floor. The interior fill of the <span class="hlt">crater</span> is thought to be layered sediments created by wind and or water action. The pit is eroded into this material. The eroded materials appear to have stayed within the <span class="hlt">crater</span> forming a large sand sheet with surface dune forms as well as individual dunes where the <span class="hlt">crater</span> floor is visible. The dunes also appear to be moving from the upper floor level into the pit. The THEMIS VIS camera contains 5 filters. The data from different filters can be combined in multiple ways to create a false color image. These false color images may reveal subtle variations of the surface not easily identified in a single band image. The Odyssey spacecraft has spent over 15 years in orbit around Mars, circling the planet more than 69000 times. It holds the record for longest working spacecraft at Mars. THEMIS, the IR/VIS camera system, has collected data for the entire mission and provides images covering all seasons and lighting conditions. Over the years many features of interest have received repeated imaging, building up a suite of images covering the entire feature. From the deepest chasma to the tallest volcano, individual dunes inside <span class="hlt">craters</span> and dune fields that encircle the north pole, channels carved by water and lava, and a variety of other feature, THEMIS has imaged them all. For the next several months the image of the day will focus on the Tharsis volcanoes, the various chasmata of Valles Marineris, and the major dunes fields. We hope you enjoy these images! Orbit Number: 51157 Latitude: -43.6787 Longitude: 34.3985 Instrument: VIS Captured: 2013-06-26 05:33 https://photojournal.jpl.nasa.gov/catalog/PIA22145</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA22140.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA22140.html"><span>Investigating Mars: Rabe <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2017-12-12</p> <p>In this VIS image of the floor of Rabe <span class="hlt">Crater</span> the step down into the pit is visible in the sinuous ridges on the left side of the image. The appearance of the exposed side of the cliffs does not look like a volcanic, difficult to erode material, but rather an easy to erode material such as layered sediments. Rabe <span class="hlt">Crater</span> is 108 km (67 miles) across. <span class="hlt">Craters</span> of similar size often have flat floors. Rabe <span class="hlt">Crater</span> has some areas of flat floor, but also has a large complex pit occupying a substantial part of the floor. The interior fill of the <span class="hlt">crater</span> is thought to be layered sediments created by wind and or water action. The pit is eroded into this material. The eroded materials appear to have stayed within the <span class="hlt">crater</span> forming a large sand sheet with surface dune forms as well as individual dunes where the <span class="hlt">crater</span> floor is visible. The dunes also appear to be moving from the upper floor level into the pit. The Odyssey spacecraft has spent over 15 years in orbit around Mars, circling the planet more than 69000 times. It holds the record for longest working spacecraft at Mars. THEMIS, the IR/VIS camera system, has collected data for the entire mission and provides images covering all seasons and lighting conditions. Over the years many features of interest have received repeated imaging, building up a suite of images covering the entire feature. From the deepest chasma to the tallest volcano, individual dunes inside <span class="hlt">craters</span> and dune fields that encircle the north pole, channels carved by water and lava, and a variety of other feature, THEMIS has imaged them all. For the next several months the image of the day will focus on the Tharsis volcanoes, the various chasmata of Valles Marineris, and the major dunes fields. We hope you enjoy these images! Orbit Number: 34456 Latitude: -43.7164 Longitude: 34.4056 Instrument: VIS Captured: 2009-09-20 09:38 https://photojournal.jpl.nasa.gov/catalog/PIA22140</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19910013683','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19910013683"><span>Martian <span class="hlt">crater</span> counts on Elysium Mons</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mcbride, Kathleen; Barlow, Nadine G.</p> <p>1990-01-01</p> <p>Without returned samples from the Martian surface, relative age chronologies and stratigraphic relationships provide the best information for determining the ages of geomorphic features and surface regions. <span class="hlt">Crater</span>-size frequency distributions of six recently mapped geological units of Elysium Mons were measured to establish their relative ages. Most of the <span class="hlt">craters</span> on Elysium Mons and the adjacent plains units are between 500 and 1000 meters in diameter. However, only <span class="hlt">craters</span> 1 km in diameter or larger were used because of inadequate spatial resolution of some of the Viking images and to reduce probability of counting secondary <span class="hlt">craters</span>. The six geologic units include all of the Elysium Mons construct and a portion of the plains units west of the volcano. The surface area of the units studied is approximately 128,000 sq km. Four of the geologic units were used to create <span class="hlt">crater</span> distribution curves. There are no <span class="hlt">craters</span> larger than 1 km within the Elysium Mons caldera. <span class="hlt">Craters</span> that lacked raised rims, were irregularly shaped, or were arranged in a linear pattern were assumed to be endogenic in origin and not counted. A <span class="hlt">crater</span> frequency distribution analysis is presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013JGRE..118.2439L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JGRE..118.2439L"><span>Sequence of infilling events in Gale <span class="hlt">Crater</span>, Mars: Results from morphology, stratigraphy, and mineralogy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Le Deit, Laetitia; Hauber, Ernst; Fueten, Frank; Pondrelli, Monica; Rossi, Angelo Pio; Jaumann, Ralf</p> <p>2013-12-01</p> <p><span class="hlt">Crater</span> is filled by sedimentary deposits including a mound of layered deposits, Aeolis Mons. Using orbital data, we mapped the <span class="hlt">crater</span> infillings and measured their geometry to determine their origin. The sediment of Aeolis Mons is interpreted to be primarily air fall material such as dust, volcanic ash, fine-grained impact products, and possibly snow deposited by settling from the atmosphere, as well as wind-blown sands cemented in the <span class="hlt">crater</span> center. Unconformity surfaces between the geological units are evidence for depositional hiatuses. <span class="hlt">Crater</span> floor material deposited around Aeolis Mons and on the <span class="hlt">crater</span> wall is interpreted to be alluvial and colluvial deposits. Morphologic evidence <span class="hlt">suggests</span> that a shallow lake existed after the formation of the lowermost part of Aeolis Mons (the Small yardangs unit and the mass-wasting deposits). A suite of several features including patterned ground and possible rock glaciers are <span class="hlt">suggestive</span> of periglacial processes with a permafrost environment after the first hundreds of thousands of years following its formation, dated to ~3.61 Ga, in the Late Noachian/Early Hesperian. Episodic melting of snow in the <span class="hlt">crater</span> could have caused the formation of sulfates and clays in Aeolis Mons, the formation of rock glaciers and the incision of deep canyons and valleys along its flanks as well as on the <span class="hlt">crater</span> wall and rim, and the formation of a lake in the deepest portions of Gale.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.P31A2802H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.P31A2802H"><span>Between Two Lakes: Opportunities for the Inception of Life in Gale <span class="hlt">Crater</span>, Mars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Heydari, E.; Calef, F.; Schroeder, J.; van Beek, J.; Parker, T. J.; Rowland, S. K.; Fairén, A. G.; Hallet, B.</p> <p>2017-12-01</p> <p>Many lakes may have existed in Gale <span class="hlt">crater</span>, Mars. Five years of investigations by the Curiosity Rover has revealed clear sedimentological evidence for the presence of at least two in the rover's landing ellipse. They are here named the first lake and the last lake. The first lake formed soon after the formation of the <span class="hlt">crater</span> and was previously introduced by Grotzinger et al. (2015). Water rushed into the <span class="hlt">crater</span> from its northern rim inundating the <span class="hlt">crater</span> quickly. Physical evidence for the presence of the first lake includes 300 m of mudstone of the Murray formation exposed in the foothills of Mt. Sharp. Abundance of fine-grained lithologies, dominance of laminations, absence of features <span class="hlt">suggestive</span> of sedimentation in shallow-waters, and the lack of indicators of an ice-covered lake, all <span class="hlt">suggest</span> that the Murray formation was deposited at the bottom of a lake that was kilometers deep and was not frozen. The first lake eventually dried up and about 3 km of sediments whose characteristics are known only from orbital images filled Gale <span class="hlt">crater</span> (Malin and Edgett, 2000). A sediment-filled Gale <span class="hlt">crater</span> was later exhumed from its margins, leading to the emergence of Mt. Sharp at the <span class="hlt">crater</span> center. Afterwards, water flowed into the <span class="hlt">crater</span>, this time from the south, forming a100 m - 200 m deep lake in the vicinity of the landing ellipse: the last lake. The evidence for the last lake is sedimentological record of two to three river deltas preserved in the Rugged Terrain Unit. These deltas prograded rapidly from south to north depositing a 5 m-thick layer over all previously deposited strata. The first lake established the potential conditions for life to begin in Gale <span class="hlt">crater</span>. They continued until the last lake dried up and Mars became permanently cold. The duration is not well known, but it may have endured for millions of years. Sedimentological evidence provided by the Curiosity rover <span class="hlt">suggests</span> that multitude of opportunities existed for the inception of life between the two</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://connection.ebscohost.com/c/articles/9710051096/secrets-wabar-craters','USGSPUBS'); return false;" href="http://connection.ebscohost.com/c/articles/9710051096/secrets-wabar-craters"><span>Secrets of the Wabar <span class="hlt">craters</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Wynn, Jeffrey C.; Shoemaker, Eugene M.</p> <p>1997-01-01</p> <p>Focuses on the existence of <span class="hlt">craters</span> in the Empty Quarter of Saudi Arabia created by the impact of meteors in early times. Mars Pathfinder and Mars Global Surveyor's encounter with impact <span class="hlt">craters</span>; Elimination of <span class="hlt">craters</span> in the Earth's surface by the action of natural elements; Impact sites' demand for careful scientific inspections; Location of the impact sites.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19940023803','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19940023803"><span>Some implications of large impact <span class="hlt">craters</span> and basins on Venus for terrestrial ringed <span class="hlt">craters</span> and planetary evolution</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mckinnon, W. B.; Alexopoulos, J. S.</p> <p>1994-01-01</p> <p>Approximately 950 impact <span class="hlt">craters</span> have been identified on the surface of Venus, mainly in Magellan radar images. From a combination of Earth-based Arecibo, Venera 15/1, and Magellan radar images, we have interpreted 72 as unequivocal peak-ring <span class="hlt">craters</span> and four as multiringed basins. The morphological and structural preservation of these <span class="hlt">craters</span> is high owing to the low level of geologic activity on the venusian surface (which is in some ways similar to the terrestrial benthic environment). Thus these <span class="hlt">craters</span> should prove crucial to understanding the mechanics of ringed <span class="hlt">crater</span> formation. They are also the most direct analogs for <span class="hlt">craters</span> formed on the Earth in Phanerozoic time, such as Chicxulub. We summarize our findings to date concerning these structures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JGRE..123..113S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JGRE..123..113S"><span><span class="hlt">Crater</span> Mound Formation by Wind Erosion on Mars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Steele, L. J.; Kite, E. S.; Michaels, T. I.</p> <p>2018-01-01</p> <p>Most of Mars' ancient sedimentary rocks by volume are in wind-eroded sedimentary mounds within impact <span class="hlt">craters</span> and canyons, but the connections between mound form and wind erosion are unclear. We perform mesoscale simulations of different <span class="hlt">crater</span> and mound morphologies to understand the formation of sedimentary mounds. As <span class="hlt">crater</span> depth increases, slope winds produce increased erosion near the base of the <span class="hlt">crater</span> wall, forming mounds. Peak erosion rates occur when the <span class="hlt">crater</span> depth is ˜2 km. Mound evolution depends on the size of the host <span class="hlt">crater</span>. In smaller <span class="hlt">craters</span> mounds preferentially erode at the top, becoming more squat, while in larger <span class="hlt">craters</span> mounds become steeper sided. This agrees with observations where smaller <span class="hlt">craters</span> tend to have proportionally shorter mounds and larger <span class="hlt">craters</span> have mounds encircled by moats. If a large-scale sedimentary layer blankets a <span class="hlt">crater</span>, then as the layer recedes across the <span class="hlt">crater</span> it will erode more toward the edges of the <span class="hlt">crater</span>, resulting in a crescent-shaped moat. When a 160 km diameter mound-hosting <span class="hlt">crater</span> is subject to a prevailing wind, the surface wind stress is stronger on the leeward side than on the windward side. This results in the center of the mound appearing to "march upwind" over time and forming a "bat-wing" shape, as is observed for Mount Sharp in Gale <span class="hlt">crater</span>.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_14 --> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018P%26SS..151...85L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018P%26SS..151...85L"><span>Geological mapping of lunar highland <span class="hlt">crater</span> Lalande: Topographic configuration, morphology and <span class="hlt">cratering</span> process</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Bo; Ling, Zongcheng; Zhang, Jiang; Chen, Jian; Liu, ChangQing; Bi, Xiangyu</p> <p>2018-02-01</p> <p>Highland <span class="hlt">crater</span> Lalande (4.45°S, 8.63°W; D = 23.4 km) is located on the PKT area of the lunar near side, southeast of the Mare Insularum. It is a complex <span class="hlt">crater</span> in Copernican era and has three distinguishing features: high silicic anomaly, the highest Th abundance and special landforms on its floor. There are some low-relief bulges on the left of Lalande's floor with regular circle or ellipse shapes. They are ∼250-680 m wide and ∼30-91 m high with maximum flank slopes >20°. There are two possible scenarios for the formation of these low-relief bulges which are impact melt products or young silicic volcanic eruptions. We estimated the absolute model ages of the ejecta deposits, several melt ponds and the hummocky floor and determined the ratio of diameter and depth of the <span class="hlt">crater</span> Lalande. In addition, we found some similar bugle features within other Copernican-aged <span class="hlt">craters</span> and there were no volcanic source vents on Lalande's floor. Thus, we hypothesized that these low-relief bulges were most consistent with an origin of impact melts during the <span class="hlt">crater</span> formation instead of small and young volcanic activities occurring on the floor. Based on Kaguya Terrain Camera (TC) ortho-mosaic and Digital Terrain Model (DTM) data produced by TC imagery in stereo, geological units and some linear features on the floor and wall of Lalande have been mapped. Eight geological units are organized by <span class="hlt">crater</span> floor units: hummocky floor, central peak and low-relief bulges; and <span class="hlt">crater</span> wall units: terraced walls, channeled and veneered walls, interior walls, mass wasting areas, blocky areas, and melt ponds. These geological units and linear features provided us a chance to understand some details of the <span class="hlt">cratering</span> process and elevation differences on the floor. We proposed that subsidence due to melt cooling, late-stage wall collapse and rocks uplifted from beneath the surface could be the possible causes of the observed elevation differences on Lalande's floor.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20170001959','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20170001959"><span>Investigating Evolved Compositions Around Wolf <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Greenhagen, B. T.; Cahill, J. T. S.; Jolliff, B. L.; Lawrence, S. J.; Glotch, T. D.</p> <p>2017-01-01</p> <p>Wolf <span class="hlt">crater</span> is an irregularly shaped, approximately 25 km <span class="hlt">crater</span> in the south-central portion of Mare Nubium on the lunar nearside. While not previously identified as a lunar "red spot", Wolf <span class="hlt">crater</span> was identified as a Th anomaly by Lawrence and coworkers. We have used data from the Lunar Reconnaissance Orbiter (LRO) to determine the area surrounding Wolf <span class="hlt">crater</span> has composition more similar to highly evolved, non-mare volcanic structures than typical lunar crustal lithology. In this presentation, we will investigate the geomorphology and composition of the Wolf <span class="hlt">crater</span> and discuss implications for the origin of the anomalous terrain.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA02937.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA02937.html"><span>Heavily <span class="hlt">Cratered</span> Terrain at South Pole</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2000-08-05</p> <p>NASA Mariner 10 photo reveals a heavily <span class="hlt">cratered</span> terrain on Mercury with a prominent scrap extending several hundred kilometers across the upper left. A <span class="hlt">crater</span>, nested in a larger <span class="hlt">crater</span>, is at top center.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/FR-2010-10-04/pdf/2010-24772.pdf','FEDREG'); return false;" href="https://www.gpo.gov/fdsys/pkg/FR-2010-10-04/pdf/2010-24772.pdf"><span>75 FR 61246 - <span class="hlt">Kaiser</span> Federal Financial Group, Inc., Covina, CA; Approval of Conversion Application</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collection.action?collectionCode=FR">Federal Register 2010, 2011, 2012, 2013, 2014</a></p> <p></p> <p>2010-10-04</p> <p>... DEPARTMENT OF THE TREASURY Office of Thrift Supervision [AC-51: OTS No. H-4729] <span class="hlt">Kaiser</span> Federal Financial Group, Inc., Covina, CA; Approval of Conversion Application Notice is hereby given that on September 28, 2010, the Office of Thrift Supervision approved the application of K-Fed Mutual Holding...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014DPS....4641310H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014DPS....4641310H"><span>Modeling the Provenance of <span class="hlt">Crater</span> Ejecta</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Huang, Ya-Huei; Minton, David A.</p> <p>2014-11-01</p> <p>The <span class="hlt">cratering</span> history of the Moon provides a way to study the violent early history of our early solar system. Nevertheless, we are still limited in our ability to interpret the lunar <span class="hlt">cratering</span> history because the complex process of generation and subsequent transportation and destruction of impact melt products is relatively poorly understood. Here we describe a preliminary model for the transport of datable impact melt products by <span class="hlt">craters</span> over Gy timescales on the lunar surface. We use a numerical model based on the Maxwell Z-model to model the exhumation and transport of ejecta material from within the excavation flow of a transient <span class="hlt">crater</span>. We describe our algorithm for rapidly estimating the provenance of ejecta material for use in a Monte Carlo <span class="hlt">cratering</span> code capable of simulating lunar <span class="hlt">cratering</span> over Gy timescales.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA22139.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA22139.html"><span>Investigating Mars: Rabe <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2017-12-11</p> <p>Rabe <span class="hlt">Crater</span> is 108 km (67 miles) across. <span class="hlt">Craters</span> of similar size often have flat floors. Rabe <span class="hlt">Crater</span> has some areas of flat floor, but also has a large complex pit occupying a substantial part of the floor. The interior fill of the <span class="hlt">crater</span> is thought to be layered sediments created by wind and or water action. The pit is eroded into this material. The eroded materials appear to have stayed within the <span class="hlt">crater</span> forming a large sand sheet with surface dune forms as well as individual dunes where the <span class="hlt">crater</span> floor is visible. The dunes also appear to be moving from the upper floor level into the pit. In this VIS image the rim of the pit is visible near the top of the image. The Odyssey spacecraft has spent over 15 years in orbit around Mars, circling the planet more than 69000 times. It holds the record for longest working spacecraft at Mars. THEMIS, the IR/VIS camera system, has collected data for the entire mission and provides images covering all seasons and lighting conditions. Over the years many features of interest have received repeated imaging, building up a suite of images covering the entire feature. From the deepest chasma to the tallest volcano, individual dunes inside <span class="hlt">craters</span> and dune fields that encircle the north pole, channels carved by water and lava, and a variety of other feature, THEMIS has imaged them all. For the next several months the image of the day will focus on the Tharsis volcanoes, the various chasmata of Valles Marineris, and the major dunes fields. We hope you enjoy these images! Orbit Number: 17074 Latitude: -43.6954 Longitude: 34.66 Instrument: VIS Captured: 2005-10-20 04:05 https://photojournal.jpl.nasa.gov/catalog/PIA22139</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70001158','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70001158"><span><span class="hlt">Crater</span> dimensions from apollo data and supplemental sources</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Pike, R.J.</p> <p>1976-01-01</p> <p>A catalog of <span class="hlt">crater</span> dimensions that were compiled mostly from the new Apollo-based Lunar Topographic Orthophotomaps is presented in its entirety. Values of <span class="hlt">crater</span> diameter, depth, rim height, flank width, circularity, and floor diameter (where applicable) are tabulated for a sample of 484 <span class="hlt">craters</span> on the Moon and 22 <span class="hlt">craters</span> on Earth. Systematic techniques of mensuration are detailed. The lunar <span class="hlt">craters</span> range in size from 400 m to 300 km across and include primary impact <span class="hlt">craters</span> of the main sequence, secondary impact <span class="hlt">craters</span>, craterlets atop domes and cones, and dark-halo <span class="hlt">craters</span>. The terrestrial <span class="hlt">craters</span> are between 10 m and 22.5 km in diameter and were formed by meteorite impact. ?? 1976 D. Reidel Publishing Company.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017P%26SS..144...32S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017P%26SS..144...32S"><span>Geomorphic investigation of <span class="hlt">craters</span> in Alba Mons, Mars: Implications for Late Amazonian glacial activity in the region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sinha, Rishitosh K.; Vijayan, S.</p> <p>2017-09-01</p> <p>Evidence for mid-high latitude glacial episodes existing within the Late Amazonian history of Mars has been reported from analysis of variety of glacial/periglacial landforms and their stratigraphic relationships. In this study, using the Context Camera (CTX) images, we have surveyed the interior of <span class="hlt">craters</span> within the Alba Mons region of Mars (30°-60°N; 80°-140°W) to decipher the presence of ice-related flow features. The primary goals of this study are to (1) <span class="hlt">suggest</span> from observations that the flow features identified in the interior of Alba Mons <span class="hlt">craters</span> have flow characteristic possibly different from concentric <span class="hlt">crater</span> fill (CCF) landforms and (2) interpret the extent of glacial activity that led to formation of flow features with respect to previously described mid-latitude ice-related landforms. Our geomorphic investigation revealed evidence for the presence of tongue-like or lobate shaped ice-related flow feature from the interior of ∼346 <span class="hlt">craters</span> in the study region. The presence of ring-mold <span class="hlt">crater</span> morphologies and brain-terrain texture preserved on the surface of flow features <span class="hlt">suggests</span> that they are possibly formed of near-surface ice-rich bodies. We found that these flow features tend to form inside both the smaller (<5 km) and larger (>5 km) diameter <span class="hlt">craters</span> emplaced at a wide range of elevation (from ∼ -3.3 km to 6.1 km). The measurement of overall length and flow direction of flow features is <span class="hlt">suggestive</span> that they are similar to pole-facing small-scale lobate debris apron (LDA) formed inside <span class="hlt">craters</span>. <span class="hlt">Crater</span> size-frequency distribution of these small-scale LDAs reveals a model age of ∼10-100 Ma. Together with topographic and geomorphic observations, orientation measurements, and distribution within the study region, we <span class="hlt">suggest</span> that the flow features (identified as pole-facing small-scale LDAs in the interior of <span class="hlt">craters</span>) have flow characteristic possibly different from CCF landforms. Our observations and findings support the results of previous</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19870046817&hterms=Workers+india&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DWorkers%2Bindia','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19870046817&hterms=Workers+india&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DWorkers%2Bindia"><span>Tektite-like bodies at Lonar <span class="hlt">Crater</span>, India - Implications for the origin of tektites</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Murali, A. V.; Zolensky, M. E.; Blanchard, D. P.</p> <p>1987-01-01</p> <p>Homogeneous dense glass bodies (both irregular and splash form) with high silica contents (about 67 pct SiO2) occur in the vicinity of Lonar <span class="hlt">Crater</span>, India. Their lack of microlites and mineral remnants and their uniform chemical composition virtually preclude a volcanic origin. They are similar to tektites reported in the literature. While such a close association of tektite-like bodies with impact <span class="hlt">craters</span> is already known (Aouelloul <span class="hlt">Crater</span>, Mauritania; Zhamanshin <span class="hlt">Crater</span>, U.S.S.R.), the tektite-like bodies at Lonar <span class="hlt">Crater</span> are unique in that they occur in an essentially basaltic terrain. Present geochemical data are consistent with these high silica glass bodies being impact melt products of two-thirds basalt and one-third local intertrappean sediment (chert). The tektite-like bodies of the impact <span class="hlt">craters</span> Lonar, Zhamanshin, and Aouelloul are generally similar. Strong terrestrial geochemical signatures reflect the target rock REE patterns and abundance ratios and demonstrate their terrestrial origin resulting from meteorite impact, as has been <span class="hlt">suggested</span> by earlier workers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008epsc.conf..237K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008epsc.conf..237K"><span>Young populations of small <span class="hlt">craters</span> on Mars: A case study.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kreslavsky, M.</p> <p>2008-09-01</p> <p> have flat floors due to infill with loose material (only a few <span class="hlt">craters</span> have pristine bowl-shaped floors). Thus, the most prominent process of <span class="hlt">crater</span> modification is deposition of loose wind-transported material (sand and dust). However, the total number of recognisable <span class="hlt">craters</span> with partly buried rims is small; it looks like the accumulation of sand and dust effectively fills depressions only, while the total accumulation is modest. This <span class="hlt">suggests</span> that the number of obliterated <span class="hlt">craters</span> is small, especially among larger <span class="hlt">craters</span>. Clustering due to atmospheric break-up Some <span class="hlt">craters</span> in the population form more or less tight clusters. These clusters are formed due to the break-up of projectiles in the atmosphere [1]. The morphology of overlapping <span class="hlt">craters</span> is perfectly consistent with simultaneous impacts of fragments of the same projectile. The largest cluster contains 44 <span class="hlt">craters</span> and reaches ~400 m in size, which is noticeably greater than predicted for the atmospheric break-up in [1] (~50 m) and observed for 20 impacts that have occurred during the last decade [2] (<100 m, [1]). The largest cluster(s) can be a superposition of two clusters formed by different projectiles, or the separation of the fragments can be greater due to periods of higher atmospheric pressure in the recent past. For the purposes of age estimates each cluster should be considered as a single impact event. I ran a "clustering" algorithm, which repeatedly searches for the tightest pair of <span class="hlt">craters</span> and replaces it with an "effective" <span class="hlt">crater</span> with diameter Deff = (D1 3+D2 3)1/3 located between the original <span class="hlt">craters</span>. The process was stopped when the separation between <span class="hlt">craters</span> in the tightest pair reached 40 m. This limit was consistently deduced from: (1) visual comparison of plots of frequency distributions of the nearest-neighbourdistance for the actual population and simulated purely random spatial scattering; (2) application of the "clustering" algorithm to purely random simulations and comparison of the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JVGR..339...41A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JVGR..339...41A"><span>Compound maar <span class="hlt">crater</span> and co-eruptive scoria cone in the Lunar <span class="hlt">Crater</span> Volcanic Field (Nevada, USA)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Amin, Jamal; Valentine, Greg A.</p> <p>2017-06-01</p> <p>Bea's <span class="hlt">Crater</span> (Lunar <span class="hlt">Crater</span> Volcanic Field, Nevada, USA) consists of two coalesced maar <span class="hlt">craters</span> with diameters of 440 m and 1050 m, combined with a co-eruptive scoria cone that straddles the northeast rim of the larger <span class="hlt">crater</span>. The two <span class="hlt">craters</span> and the cone form an alignment that parallels many local and regional structures such as normal faults, and is interpreted to represent the orientation of the feeder dyke near the surface. The maar formed among a dense cluster of scoria cones; the cone-cluster topography resulted in <span class="hlt">crater</span> rim that has a variable elevation. These older cones are composed of variably welded agglomerate and scoria with differing competence that subsequently affected the shape of Bea's <span class="hlt">Crater</span>. Tephra ring deposits associated with phreatomagmatic maar-forming eruptions are rich in basaltic lithics derived from < 250 m depth, with variable contents of deeper-seated ignimbrite lithic clasts, consistent with ejection from relatively shallow explosions although a diatreme might extend to deeper levels beneath the maar. Interbedding of deposits on the northeastern cone and in the tephra ring record variations in the magmatic volatile driven and phreatomagmatic eruption styles in both space and time along a feeder dike.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA19304.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA19304.html"><span><span class="hlt">Craters</span> Near Nilokeras Scopulus</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2015-03-04</p> <p>This image from NASA Mars Reconnaissance Orbiter of <span class="hlt">craters</span> near Nilokeras Scopulus shows two pits partially filled with lumpy material, probably trapped dust that blew in from the atmosphere. This image shows two pits partially filled with lumpy material, probably trapped dust that blew in from the atmosphere. The pits themselves resemble impact <span class="hlt">craters</span>, but they are part of a chain of similar features aligned with nearby faults, so they could be collapse features instead. Note also the tracks left by rolling boulders at the bottom of the <span class="hlt">craters</span>. Nilokeras Scopulus is the name for the cliff, about 756 kilometers long, in the northern hemisphere of Mars where these <span class="hlt">craters</span> are located. It was named based on an albedo (brightness) feature mapped by astronomer E. M. Antoniadi in 1930. http://photojournal.jpl.nasa.gov/catalog/PIA19304</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA19439.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA19439.html"><span>Five New <span class="hlt">Crater</span> Names for Mercury</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2015-04-29</p> <p>Five previously unnamed <span class="hlt">craters</span> on Mercury now have names. MESSENGER's Education and Public Outreach (EPO) team led a contest that solicited naming <span class="hlt">suggestions</span> from the public via a competition website. In total, 3,600 contest entries were received and a semi-final list of 17 names were submitted to the International Astronomical Union (IAU) for consideration. The IAU selected the final five <span class="hlt">crater</span> names, keeping with the convention that Mercury's <span class="hlt">craters</span> are named after those who have made significant contributions to the humanities. And the winners are: Carolan: (83.8° N, 31.7° E) Named for Turlough O'Carolan, the Irish musician and composer (1670-1738) Enheduanna: (48.3° N, 326.2° E) Named for the author and poet from ancient Mesopotamia Karsh (35.6° S, 78.9° E) Named for Yousuf Karsh, twentieth century Armenian-Canadian portrait photographer Kulthum (50.7° N, 93.5° E) Named for Umm Kulthum, twentieth century Egyptian singer, songwriter, and actress Rivera: (69.3° N, 32.4° E) Named for Diego Rivera, twentieth century Mexican painter and muralist http://photojournal.jpl.nasa.gov/catalog/PIA19439</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19830035017&hterms=geologic+time+scale&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dgeologic%2Btime%2Bscale','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19830035017&hterms=geologic+time+scale&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dgeologic%2Btime%2Bscale"><span><span class="hlt">Cratering</span> time scales for the Galilean satellites</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Shoemaker, E. M.; Wolfe, R. F.</p> <p>1982-01-01</p> <p>An attempt is made to estimate the present <span class="hlt">cratering</span> rate for each Galilean satellite within the correct order of magnitude and to extend the <span class="hlt">cratering</span> rates back into the geologic past on the basis of evidence from the earth-moon system. For collisions with long and short period comets, the magnitudes and size distributions of the comet nuclei, the distribution of their perihelion distances, and the completeness of discovery are addressed. The diameters and masses of cometary nuclei are assessed, as are <span class="hlt">crater</span> diameters and <span class="hlt">cratering</span> rates. The dynamical relations between long period and short period comets are discussed, and the population of Jupiter-crossing asteroids is assessed. Estimated present <span class="hlt">cratering</span> rates on the Galilean satellites are compared and variations of <span class="hlt">cratering</span> rate with time are considered. Finally, the consistency of derived <span class="hlt">cratering</span> time scales with the <span class="hlt">cratering</span> record of the icy Galilean satellites is discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA13611.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA13611.html"><span>Fresh <span class="hlt">Crater</span> with Gullies</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2010-11-12</p> <p>The <span class="hlt">crater</span> shown in this image from NASA Mars Reconnaissance Orbiter has very few <span class="hlt">craters</span> superposed on it, which attests to its youth. It also has very steep slopes and a sharp rim; more evidence of its young age.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA08785&hterms=duck&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dduck','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA08785&hterms=duck&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dduck"><span>'Victoria <span class="hlt">Crater</span>' from 'Duck Bay' (Polar Projection)</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2006-01-01</p> <p><p/> NASA's Mars rover Opportunity edged 3.7 meters (12 feet) closer to the top of the 'Duck Bay' alcove along the rim of 'Victoria <span class="hlt">Crater</span>' during the rover's 952nd Martian day, or sol (overnight Sept. 27 to Sept. 28), and gained this vista of the <span class="hlt">crater</span>. The rover's navigation camera took the seven exposures combined into this mosaic view of the <span class="hlt">crater</span>'s interior. This <span class="hlt">crater</span> has been the mission's long-term destination for the past 21 Earth months. <p/> The far side of the <span class="hlt">crater</span> is about 800 meters (one-half mile) away. The rim of the <span class="hlt">crater</span> is composed of alternating promontories, rocky points towering approximately 70 meters (230 feet) above the <span class="hlt">crater</span> floor, and recessed alcoves, such as Duck Bay. The bottom of the <span class="hlt">crater</span> is covered by sand that has been shaped into ripples by the Martian wind. The rocky cliffs in the foreground have been informally named 'Cape Verde,' on the left, and 'Cabo Frio,' on the right. <p/> Victoria <span class="hlt">Crater</span> is about five times wider than 'Endurance <span class="hlt">Crater</span>,' which Opportunity spent six months examining in 2004, and about 40 times wider than 'Eagle <span class="hlt">Crater</span>,' where Opportunity first landed. The great lure of Victoria is an expectation that the thick stack of geological layers exposed in the <span class="hlt">crater</span> walls could reveal the record of past environmental conditions over a much greater span of time than Opportunity has read from rocks examined earlier in the mission. <p/> This view is presented as a polar projection with geometric seam correction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA08786&hterms=duck&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dduck','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA08786&hterms=duck&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dduck"><span>'Victoria <span class="hlt">Crater</span>' from 'Duck Bay' (Vertical Projection)</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2006-01-01</p> <p><p/> NASA's Mars rover Opportunity edged 3.7 meters (12 feet) closer to the top of the 'Duck Bay' alcove along the rim of 'Victoria <span class="hlt">Crater</span>' during the rover's 952nd Martian day, or sol (overnight Sept. 27 to Sept. 28), and gained this vista of the <span class="hlt">crater</span>. The rover's navigation camera took the seven exposures combined into this mosaic view of the <span class="hlt">crater</span>'s interior. This <span class="hlt">crater</span> has been the mission's long-term destination for the past 21 Earth months. <p/> The far side of the <span class="hlt">crater</span> is about 800 meters (one-half mile) away. The rim of the <span class="hlt">crater</span> is composed of alternating promontories, rocky points towering approximately 70 meters (230 feet) above the <span class="hlt">crater</span> floor, and recessed alcoves, such as Duck Bay. The bottom of the <span class="hlt">crater</span> is covered by sand that has been shaped into ripples by the Martian wind. The rocky cliffs in the foreground have been informally named 'Cape Verde,' on the left, and 'Cabo Frio,' on the right. <p/> Victoria <span class="hlt">Crater</span> is about five times wider than 'Endurance <span class="hlt">Crater</span>,' which Opportunity spent six months examining in 2004, and about 40 times wider than 'Eagle <span class="hlt">Crater</span>,' where Opportunity first landed. The great lure of Victoria is an expectation that the thick stack of geological layers exposed in the <span class="hlt">crater</span> walls could reveal the record of past environmental conditions over a much greater span of time than Opportunity has read from rocks examined earlier in the mission. <p/> This view is presented as a vertical projection with geometric seam correction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017DPS....4910003B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017DPS....4910003B"><span>What Really Happened to Earth's Older <span class="hlt">Craters</span>?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bottke, William; Mazrouei, Sara; Ghent, Rebecca; Parker, Alex</p> <p>2017-10-01</p> <p>Most assume the Earth’s <span class="hlt">crater</span> record is heavily biased, with erosion/tectonics destroying older <span class="hlt">craters</span>. This matches expectations, but is it actually true? To test this idea, we compared Earth’s <span class="hlt">crater</span> record, where nearly all D ≥ 20 km <span class="hlt">craters</span> are < 650 Myr old, to the Moon’s. Here lunar <span class="hlt">crater</span> ages were computed using a new method employing LRO-Diviner temperature data. Large lunar rocks have high thermal inertia and remain warm through the night relative to the regolith. Analysis shows young <span class="hlt">craters</span> with numerous meter-sized fragments are easy to pick out from older <span class="hlt">craters</span> with eroded fragments. Moreover, an inverse relationship between rock abundance (RA) and <span class="hlt">crater</span> age exists. Using measured RA values, we computed ages for 111 rocky <span class="hlt">craters</span> with D ≥ 10 km that formed between 80°N and 80°S over the last 1 Gyr.We found several surprising results. First, the production rate of D ≥ 10 km lunar <span class="hlt">craters</span> increased by a factor of 2.2 [-0.9, +4.4; 95% confidence limits] over the past 250 Myr compared to the previous 750 Myr. Thus, the NEO population is higher now than it has been for the last billion years. Second, the size and age distributions of lunar and terrestrial <span class="hlt">craters</span> for D ≥ 20 km over the last 650 Myr have similar shapes. This implies that <span class="hlt">crater</span> erasure must be limited on stable terrestrial terrains; in an average sense, for a given region, the Earth either keeps all or loses all of its D ≥ 20 <span class="hlt">craters</span> at the same rate, independent of size. It also implies the observed deficit of large terrestrial <span class="hlt">craters</span> between 250-650 Myr is not preservation bias but rather reflects a distinctly lower impact flux. We predict 355 ± 86 D ≥ 20 km <span class="hlt">craters</span> formed on Earth over the last 650 Myr. Only 38 ± 6 are known, so the ratio, 10.7 ± 3.1%, is a measure of the Earth’s surface that is reasonably stable to large <span class="hlt">crater</span> formation over 650 Myr. If erosion had dominated, the age distribution of terrestrial <span class="hlt">craters</span> would be strongly skewed toward</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150021036','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150021036"><span>Processes Modifying <span class="hlt">Cratered</span> Terrains on Pluto</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Moore, J. M.</p> <p>2015-01-01</p> <p>The July encounter with Pluto by the New Horizons spacecraft permitted imaging of its <span class="hlt">cratered</span> terrains with scales as high as approximately 100 m/pixel, and in stereo. In the initial download of images, acquired at 2.2 km/pixel, widely distributed impact <span class="hlt">craters</span> up to 260 km diameter are seen in the near-encounter hemisphere. Many of the <span class="hlt">craters</span> appear to be significantly degraded or infilled. Some <span class="hlt">craters</span> appear partially destroyed, perhaps by erosion such as associated with the retreat of scarps. Bright ice-rich deposits highlight some <span class="hlt">crater</span> rims and/or floors. While the <span class="hlt">cratered</span> terrains identified in the initial downloaded images are generally seen on high-to-intermediate albedo surfaces, the dark equatorial terrain informally known as Cthulhu Regio is also densely <span class="hlt">cratered</span>. We will explore the range of possible processes that might have operated (or still be operating) to modify the landscape from that of an ancient pristinely <span class="hlt">cratered</span> state to the present terrains revealed in New Horizons images. The sequence, intensity, and type of processes that have modified ancient landscapes are, among other things, the record of climate and volatile evolution throughout much of the Pluto's existence. The deciphering of this record will be discussed. This work was supported by NASA's New Horizons project.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA20340.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA20340.html"><span>A Young, Fresh <span class="hlt">Crater</span> in Hellespontus</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2016-01-14</p> <p>This image from NASA Mars Reconnaissance Orbiter spacecraft is of a morphologically fresh and simple impact <span class="hlt">crater</span> in the Hellespontus region. At 1.3 kilometers in diameter, this unnamed <span class="hlt">crater</span> is only slightly larger than Arizona's Barringer (aka Meteor) <span class="hlt">Crater</span>, by about 200 meters. Note the simple bowl shape and the raised <span class="hlt">crater</span> rim. Rock and soil excavated out of the <span class="hlt">crater</span> by the impacting meteor -- called ejecta -- forms the ejecta deposit. It is continuous for about one <span class="hlt">crater</span> radius away from the rim and is likely composed of about 90 percent ejecta and 10 percent in-place material that was re-worked by both the impact and the subsequently sliding ejecta. The discontinuous ejecta deposit extends from about one <span class="hlt">crater</span> radius outward. Here, high velocity ejecta that was launched from close to the impact point -- and got the biggest kick -- flew a long way, landed, rolled, slid, and scoured the ground, forming long tendrils of ejecta and v-shaped ridges. http://photojournal.jpl.nasa.gov/catalog/PIA20340</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_15 --> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1995Metic..30..578S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1995Metic..30..578S"><span>Impact <span class="hlt">Crater</span> Identified on the Navajo Nation Near Chinle, Arizona</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shoemaker, E. M.; Roddy, D. J.; Moore, C. B.; Pfeilsticker, R.; Curley, C. L.; Dunkelman, T.; Kuerzel, K.; Taylor, M.; Shoemaker, C.; Donnelly, P.</p> <p>1995-09-01</p> <p> the <span class="hlt">crater</span> was scoured down to the Jeddito-Chinle contact across the center of the <span class="hlt">crater</span>. Some of the Chinle was excavated by impact south of the center, as seen in the trench in the south wall. The original <span class="hlt">crater</span> walls slope inward about 30 degrees on the east and west sides, about 20 degrees on the north, and about 45 degrees on the south. Beds are dragged up along the east, west, and south walls, but not along the north wall. The deformation is restricted to within about 0.5 m of the wall. From the asymmetry of shape and deformation in the walls, we believe that the impacting body struck at an oblique angle and was traveling from north to south. A small, magnetic, iron oxide fragment, about 1 mm across, was collected from material excavated from the south <span class="hlt">crater</span> wall area. Analyses of this fragment by electron microprobe detected a significant nickel concentration of 5%. Two senior Navajo women (70-80 year age range) independently remember this <span class="hlt">crater</span> as being much deeper during their childhood and both <span class="hlt">suggest</span> that the impact was witnessed 3 to 4 generations ago. Interestingly, many persons in the Navajo community thought that this <span class="hlt">crater</span> was of impact origin. Additional work is planned, including a broader aerial search for other possible impact sites.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007M%26PS...42.1995K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007M%26PS...42.1995K"><span>Coupled effects of impact and orogeny: Is the marine Lockne <span class="hlt">crater</span>, Sweden, pristine?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kenkmann, T.; Kiebach, F.; Rosenau, M.; Raschke, U.; Pigowske, A.; Mittelhaus, K.; Eue, D.</p> <p></p> <p>Our current understanding of marine-impact <span class="hlt">cratering</span> processes is partly inferred from the geological structure of the Lockne <span class="hlt">crater</span>. We present results of a mapping campaign and structural data indicating that this <span class="hlt">crater</span> is not pristine. In the western part of the <span class="hlt">crater</span>, pre-impact, impact, and post-impact rocks are incorporated in Caledonian thrust slices and are subjected to folding and faulting. A nappe outlier in the central <span class="hlt">crater</span> depression is a relic of the Caledonian nappe cover that reached a thickness of more than 5 km. The overthrusted <span class="hlt">crater</span> is gently deformed. Strike of strata and trend of fold axes deviate from standard Caledonian directions (northeast-southwest). Radially oriented <span class="hlt">crater</span> depressions, which were previously regarded as marine resurge gullies formed when resurging seawater erosively cut through the <span class="hlt">crater</span> brim, are interpreted to be open synclines in which resurge deposits were better preserved.The presence of the impact structure influenced orogenesis due to morphological and lithological anomalies of the <span class="hlt">crater</span>: i) a raised <span class="hlt">crater</span> brim zone acted as an obstacle during nappe propagation, (ii) the occurrence of a central <span class="hlt">crater</span> depression caused downward sagging of nappes, and (iii) the lack of an appropriate detachment horizon (alum shale) within the <span class="hlt">crater</span> led to an enhanced mechanical coupling and internal deformation of the nappe and the overthrusted foreland. Preliminary results of 3-D-analogue experiments <span class="hlt">suggest</span> that a circular high-friction zone representing the <span class="hlt">crater</span> locally hinders nappe propagation and initiates a circumferentially striking ramp fault that delineates the <span class="hlt">crater</span>. Crustal shortening is also partitioned into the <span class="hlt">crater</span> basement and decreases laterally outward. Deformation of the foreland affected the geometry of the detachment and could be associated with the activation of a deeper detachment horizon beneath the <span class="hlt">crater</span>. Strain gradients both vertically and horizontally result in non-plane strain deformation</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140004932','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140004932"><span>LU60645GT and MA132843GT Catalogues of Lunar and Martian Impact <span class="hlt">Craters</span> Developed Using a <span class="hlt">Crater</span> Shape-based Interpolation <span class="hlt">Crater</span> Detection Algorithm for Topography Data</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Salamuniccar, Goran; Loncaric, Sven; Mazarico, Erwan Matias</p> <p>2012-01-01</p> <p>For Mars, 57,633 <span class="hlt">craters</span> from the manually assembled catalogues and 72,668 additional <span class="hlt">craters</span> identified using several <span class="hlt">crater</span> detection algorithms (CDAs) have been merged into the MA130301GT catalogue. By contrast, for the Moon the most complete previous catalogue contains only 14,923 <span class="hlt">craters</span>. Two recent missions provided higher-quality digital elevation maps (DEMs): SELENE (in 1/16° resolution) and Lunar Reconnaissance Orbiter (we used up to 1/512°). This was the main motivation for work on the new <span class="hlt">Crater</span> Shape-based interpolation module, which improves previous CDA as follows: (1) it decreases the number of false-detections for the required number of true detections; (2) it improves detection capabilities for very small <span class="hlt">craters</span>; and (3) it provides more accurate automated measurements of <span class="hlt">craters</span>' properties. The results are: (1) LU60645GT, which is currently the most complete (up to D>=8 km) catalogue of Lunar <span class="hlt">craters</span>; and (2) MA132843GT catalogue of Martian <span class="hlt">craters</span> complete up to D>=2 km, which is the extension of the previous MA130301GT catalogue. As previously achieved for Mars, LU60645GT provides all properties that were provided by the previous Lunar catalogues, plus: (1) correlation between morphological descriptors from used catalogues; (2) correlation between manually assigned attributes and automated measurements; (3) average errors and their standard deviations for manually and automatically assigned attributes such as position coordinates, diameter, depth/diameter ratio, etc; and (4) a review of positional accuracy of used datasets. Additionally, surface dating could potentially be improved with the exhaustiveness of this new catalogue. The accompanying results are: (1) the possibility of comparing a large number of Lunar and Martian <span class="hlt">craters</span>, of e.g. depth/diameter ratio and 2D profiles; (2) utilisation of a method for re-projection of datasets and catalogues, which is very useful for <span class="hlt">craters</span> that are very close to poles; and (3) the extension of the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001Icar..153...71R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001Icar..153...71R"><span>The Compensation State of Intermediate Size Lunar <span class="hlt">Craters</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Reindler, Lucas; Arkani-Hamed, Jafar</p> <p>2001-09-01</p> <p>The compensation state of 49 intermediate size (120 to 600 km diameter) lunar <span class="hlt">craters</span> are investigated using the most recent spherical harmonic models of the lunar topography and gravity, truncated at degree n=110. The total mass anomalies per unit area (i.e., the lateral variations of the vertically integrated density perturbations per unit area) within an otherwise uniform crust of 60 km thickness are determined such that, together with the surface topography, give rise to the model gravity anomalies. Crustal thicknesses of 40 and 80 km are also considered, but the general results of this study are not significantly affected. Excess mass anomalies are obtained by subtracting from the total mass anomalies the mass anomalies that are required for the isostatic compensation of the surface topography. The excess mass anomaly of a <span class="hlt">crater</span> denotes its particular state of compensation. Dependencies of the excess mass anomalies on <span class="hlt">crater</span> location, size, and age are investigated, but in general few discernable trends are evident. Although the vast majority of <span class="hlt">craters</span> indicate some compensation, no correlation exists between age or size and the state of compensation. Roughly 16% of the <span class="hlt">craters</span> show no compensation, and in some cases have mass deficiencies most likely due to the shock fractured bedrock: the breccia lens of lower density. The crust in these regions was likely cold and rigid enough at the time of impact to rigidly support the stress caused by <span class="hlt">crater</span> excavation. These features are seen throughout different geological periods, demonstrating that the lunar crust cooled quickly and strengthened soon after formation. A comparison of the compensation state of <span class="hlt">craters</span> Apollo, Korolev, and Hertzsprung <span class="hlt">suggests</span> that the thermal and mechanical properties of the crust prior to impact had an appreciable effect on the compensation, and that crustal thickness may be the single most important factor controlling the compensation of intermediate size <span class="hlt">craters</span>. The</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70013801','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70013801"><span><span class="hlt">Cratering</span> history of Miranda: Implications for geologic processes</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Plescia, J.B.</p> <p>1988-01-01</p> <p>Miranda's surface is divisible into <span class="hlt">cratered</span> terrain and coronae. The <span class="hlt">cratered</span> terrain is the most heavily <span class="hlt">cratered</span> of the terrains and presumably is the oldest. The frequency of <span class="hlt">craters</span> in the <span class="hlt">cratered</span> terrain is variable and related to position on the satellite. The coronae are also variably <span class="hlt">cratered</span>. Elsinore and Arden Coronae have similar <span class="hlt">crater</span> frequencies and may have formed simultaneously. They are of intermediate agompared to the <span class="hlt">cratered</span> terrain and to Inverness Corona, which is the youngest major terrain. Graben formation appears to have occured both before and after the formation of the coronae reflecting periods of global expansion. Miranda's surfaces are, in general, the least <span class="hlt">cratered</span> and therefore inferred to be the youngest within the Uranian system. ?? 1988.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.P32A..01E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.P32A..01E"><span>Curiosity's field site in Gale <span class="hlt">Crater</span>, Mars, in context</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Edgett, K. S.; Malin, M. C.</p> <p>2011-12-01</p> <p>NASA's Mars rover, Curiosity, is anticipated to land in Gale <span class="hlt">Crater</span> in August 2012. Gale is a 155 km-diameter impact <span class="hlt">crater</span> adjacent to the ancient crustal "north-south dichotomy boundary." It contains a mound of layered rock (of yet-unknown proportions of clastic sediment, tephra, and chemical precipitates) ˜5 km-high that was eroded by fluvial, eolian, and mass-movement processes. The stratigraphy includes erosional unconformities representing periods when new impact <span class="hlt">craters</span> formed and streams cut canyons into layered rock. The majority of known impact sites on Earth are <span class="hlt">craters</span> that were filled and buried in sediment; examples occur under the Chesapeake Bay and beneath the Chicago O'Hare Airport. The upper crust of Mars, with its relative lack of tectonism, is almost entirely a layered, <span class="hlt">cratered</span> volume of filled, buried, and complexly-interbedded <span class="hlt">craters</span> and fluvial systems. Some of these have been exhumed or partly exhumed; some, like Gale, were once filled with extensive rock layers that were eroded to form mounds or mesas. Landforms all across Arabia Terra show that similar materials were also deposited between <span class="hlt">craters</span>. Gale is of the family of Mars <span class="hlt">craters</span> that were filled and buried (or nearly so). The highest elevation on the Gale mound exceeds the <span class="hlt">crater</span>'s north rim by ˜2 km and is within 500 m of the highest point on the south rim. Many similar <span class="hlt">craters</span> occur in Arabia Terra; these are instructive as some contain mounds, others have mesas or buttes or other erosional expressions. <span class="hlt">Craters</span> within 10s to a few 100s of km of each other typically contain very different materials, as exhibited by varied erosional expression, bedding style, and layer thickness. This <span class="hlt">suggests</span> that the depositional environments, sources, and physical properties of the deposited material differed from place to place and time to time, even in neighboring settings. The Curiosity site in Gale has the potential to illuminate processes that acted locally and globally on early Mars. In</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70037501','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70037501"><span>The sedimentology and dynamics of <span class="hlt">crater</span>-affiliated wind streaks in western Arabia Terra, Mars and Patagonia, Argentina</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Rodriguez, J.A.P.; Tanaka, K.L.; Yamamoto, A.; Berman, D.C.; Zimbelman, J.R.; Kargel, J.S.; Sasaki, S.; Jinguo, Y.; Miyamoto, H.</p> <p>2010-01-01</p> <p>Wind streaks comprise recent aeolian deposits that have been extensively documented on Venus, Earth and Mars. Martian wind streaks are among the most abundant surface features on the planet and commonly extend from the downwind margins of impact <span class="hlt">craters</span>. Previous studies of wind streaks emerging from <span class="hlt">crater</span> interior deposits <span class="hlt">suggested</span> that the mode of emplacement was primarily related to the deposition of silt-sized particles as these settled from plumes. We have performed geologic investigations of two wind streaks clusters; one situated in western Arabia Terra, a region in the northern hemisphere of Mars, and another in an analogous terrestrial site located in southern Patagonia, Argentina, where occurrences of wind streaks emanate from playas within maar <span class="hlt">craters</span>. In both these regions we have identified bedforms in sedimentary deposits on <span class="hlt">crater</span> floors, along wind-facing interior <span class="hlt">crater</span> margins, and along wind streaks. These observations indicate that these deposits contain sand-sized particles and that sediment migration has occurred via saltation from <span class="hlt">crater</span> interior deposits to wind streaks. In Arabia Terra and in Patagonia wind streaks initiate from <span class="hlt">crater</span> floors that contain lithic and evaporitic sedimentary deposits, <span class="hlt">suggesting</span> that the composition of wind streak source materials has played an important role in development. Spatial and topographic analyses <span class="hlt">suggest</span> that regional clustering of wind streaks in the studied regions directly correlates to the areal density of <span class="hlt">craters</span> with interior deposits, the degree of proximity of these deposits, and the <span class="hlt">craters</span>' rim-to-floor depths. In addition, some (but not all) wind streaks within the studied clusters have propagated at comparable yearly (Earth years) rates. Extensive saltation is inferred to have been involved in its propagation based on the studied terrestrial wind streak that shows ripples and dunes on its surface and the Martian counterpart changes orientation toward the downslope direction where it</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19980008049','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19980008049"><span>Scaling Impact-Melt and <span class="hlt">Crater</span> Dimensions: Implications for the Lunar <span class="hlt">Cratering</span> Record</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cintala , Mark J.; Grieve, Richard A. F.</p> <p>1997-01-01</p> <p>The consequences of impact on the solid bodies of the solar system are manifest and legion. Although the visible effects on planetary surfaces, such as the Moon's, are the most obvious testimony to the spatial and temporal importance of impacts, less dramatic chemical and petrographic characteristics of materials affected by shock abound. Both the morphologic and petrologic aspects of impact <span class="hlt">cratering</span> are important in deciphering lunar history, and, ideally, each should complement the other. In practice, however, a gap has persisted in relating large-scale <span class="hlt">cratering</span> processes to petrologic and geochemical data obtained from lunar samples. While this is due in no small part to the fact that no Apollo mission unambiguously sampled deposits of a large <span class="hlt">crater</span>, it can also be attributed to the general state of our knowledge of <span class="hlt">cratering</span> phenomena, particularly those accompanying large events. The most common shock-metamorphosed lunar samples are breccias, but a substantial number are impact-melt rocks. Indeed, numerous workers have called attention to the importance of impact-melt rocks spanning a wide range of ages in the lunar sample collection. Photogeologic studies also have demonstrated the widespread occurrence of impact-melt lithologies in and around lunar <span class="hlt">craters</span>. Thus, it is clear that impact melting has been a fundamental process operating throughout lunar history, at scales ranging from pits formed on individual regolith grains to the largest impact basins. This contribution examines the potential relationship between impact melting on the Moon and the interior morphologies of large <span class="hlt">craters</span> and peaking basins. It then examines some of the implications of impact melting at such large scales for lunar-sample provenance and evolution of the lunar crust.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/4008567-high-explosive-crater-studies-tuff','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/4008567-high-explosive-crater-studies-tuff"><span>HIGH EXPLOSIVE <span class="hlt">CRATER</span> STUDIES: TUFF</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Murphey, B.F.</p> <p>1961-04-01</p> <p>Spherical charges of TNT, each weighing 256 pounds, were exploded at various depths in tuff to determine apparent <span class="hlt">crater</span> dimensions in a soft rock. No <span class="hlt">craters</span> were obtained for depths of burst equal to or greater than 13.3 feet. It was deduced that rock fragments were sufficiently large that charges of greater magnitude should be employed for <span class="hlt">crater</span> experiments intended as models of nuclear explosions. (auth)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29886860','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29886860"><span>Diagnosing the <span class="hlt">Kaiser</span>: Psychiatry, Wilhelm II and the Question of German War Guilt The William Bynum Prize Essay 2016.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Freis, David</p> <p>2018-07-01</p> <p>After his abdication in November 1918, the German emperor Wilhelm II continued to haunt the minds of his people. With the abolition of the lese-majesty laws in the new republic, many topics that were only discussed privately or obliquely before could now be broached openly. One of these topics was the mental state of the exiled <span class="hlt">Kaiser</span>. Numerous psychiatrists, physicians and laypeople published their diagnoses of Wilhelm in high-circulation newspaper articles, pamphlets, and books shortly after the end of the war. Whether these diagnoses were accurate and whether the <span class="hlt">Kaiser</span> really was mentally ill became the issue of a heated debate.This article situates these diagnoses of Wilhelm II in their political context. The authors of these diagnoses - none of whom had met or examined Wilhelm II in person - came from all political camps and they wrote with very different motives in mind. Diagnosing the exiled <span class="hlt">Kaiser</span> as mentally ill was a kind of exorcism of the Hohenzollern rule, opening the way for either a socialist republic or the hoped-for rule of a new leader. But more importantly, it was a way to discuss and allocate political responsibility and culpability. Psychiatric diagnoses were used to exonerate both the Emperor (for whom the treaty of Versailles provided a tribunal as war criminal) and the German nation. They were also used to blame the <span class="hlt">Kaiser</span>'s entourage and groups that had allegedly manipulated the weak-willed monarch. Medical concepts became a vehicle for a debate on the key political questions in interwar Germany.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014DPS....4641303B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014DPS....4641303B"><span>Small-Scale Spectral and Color Analysis of Ritchey <span class="hlt">Crater</span> Impact Materials</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bray, Veronica; Chojnacki, Matthew; McEwen, Alfred; Heyd, Rodney</p> <p>2014-11-01</p> <p>Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) analysis of Ritchey <span class="hlt">crater</span> on Mars has allowed identification of the minerals uplifted from depth within its central peak as well as the dominant spectral signature of the <span class="hlt">crater</span> fill materials which surround it. However, the 18m/px resolution of CRISM prevents full analysis of the nature of small-scale dykes, mega breccia blocks and finer scale <span class="hlt">crater</span>-fill units. We extend our existing CRISM-based compositional mapping of the Ritchey <span class="hlt">crater</span> interior to sub-CRISM pixel scales with the use of High Resolution Imaging Science Experiment (HiRISE) Color Ratio Products (CRPs). These CRPs are then compared to CRISM images; correlation between color ratio and CRISM spectral signature for a large bedrock unit is defined and used to <span class="hlt">suggest</span> similar composition for a smaller unit with the same color ratio. Megabreccia deposits, angular fragments of rock in excess of 1 meter in diameter within a finer grained matrix, are common at Ritchey. The dominant spectral signature from each megabreccia unit varies with location around Ritchey and appears to reflect the matrix composition (based on texture and albedo similarities to surrounding rocks) rather than clast composition. In cases where the breccia block size is large enough for CRISM analysis, many different mineral compositions are noted (low calcium pyroxene (LCP) olivine (OL), alteration products) depending on the location. All block compositions (as inferred from CRPs) are observed down to the limit of HiRISE resolution. We have found a variety of dyke compositions within our mapping area. Correlation between CRP color and CRISM spectra in this area <span class="hlt">suggest</span> that large 10 m wide) dykes within LCP-bearing bedrock close to the <span class="hlt">crater</span> center tend to have similar composition to the host rock. Smaller dykes running non-parallel to the larger dykes are inferred to be OL-rich <span class="hlt">suggesting</span> multiple phases of dyke formation within the Ritchey <span class="hlt">crater</span> and its bedrock.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA15093.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA15093.html"><span>Topography of Gale <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2011-11-21</p> <p>Color coding in this image of Gale <span class="hlt">Crater</span> on Mars represents differences in elevation. The vertical difference from a low point inside the landing ellipse for NASA Mars Science Laboratory yellow dot to a high point on the mountain inside the <span class="hlt">crater</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA04930.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA04930.html"><span>Clouds Near Mie <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2003-12-13</p> <p>Mie <span class="hlt">Crater</span>, a large basin formed by asteroid or comet impact in Utopia Planitia, lies at the center of this Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) red wide angle image. The <span class="hlt">crater</span> is approximately 104 km (65 mi) across. To the east and southeast (toward the lower right) of Mie, in this 5 December 2003 view, are clouds of dust and water ice kicked up by local dust storm activity. It is mid-winter in the northern hemisphere of Mars, a time when passing storms are common on the northern plains of the red planet. Sunlight illuminates this image from the lower left; Mie <span class="hlt">Crater</span> is located at 48.5°N, 220.3°W. Viking 2 landed west/southwest of Mie <span class="hlt">Crater</span>, off the left edge of this image, in September 1976. http://photojournal.jpl.nasa.gov/catalog/PIA04930</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA15519.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA15519.html"><span>Large Subdued and Small Fresh <span class="hlt">Craters</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2012-03-27</p> <p>This image from NASA Dawn spacecraft shows many large subdued <span class="hlt">craters</span> that have smaller, younger <span class="hlt">craters</span> on top of them on asteroid Vesta. There are two large subdued <span class="hlt">craters</span> in the center of the image, which have very degraded and rounded rims.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/1016194','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/1016194"><span>Unusual bacterioplankton community structure in ultra-oligotrophic <span class="hlt">Crater</span> Lake</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Urbach, Ena; Vergin, Kevin L.; Morse, Ariel</p> <p>2001-01-01</p> <p>The bacterioplankton assemblage in <span class="hlt">Crater</span> Lake, Oregon (U.S.A.), is different from communities found in other oxygenated lakes, as demonstrated by four small subunit ribosomal ribonucleic acid (SSU rRNA) gene clone libraries and oligonucleotide probe hybridization to RNA from lake water. Populations in the euphotic zone of this deep (589 m), oligotrophic caldera lake are dominated by two phylogenetic clusters of currently uncultivated bacteria: CL120-10, a newly identified cluster in the verrucomicrobiales, and ACK4 actinomycetes, known as a minor constituent of bacterioplankton in other lakes. Deep-water populations at 300 and 500 m are dominated by a different pair of uncultivated taxa: CL500-11, a novel cluster in the green nonsulfur bacteria, and group I marine crenarchaeota. b-Proteobacteria, dominant in most other freshwater environments, are relatively rare in <span class="hlt">Crater</span> Lake (<=16% of nonchloroplast bacterial rRNA at all depths). Other taxa identified in <span class="hlt">Crater</span> Lake libraries include a newly identified candidate bacterial division, ABY1, and a newly identified subcluster, CL0-1, within candidate division OP10. Probe analyses confirmed vertical stratification of several microbial groups, similar to patterns observed in open-ocean systems. Additional similarities between <span class="hlt">Crater</span> Lake and ocean microbial populations include aphotic zone dominance of group I marine crenarchaeota and green nonsulfur bacteria. Comparison of <span class="hlt">Crater</span> Lake to other lakes studied by rRNA methods <span class="hlt">suggests</span> that selective factors structuring <span class="hlt">Crater</span> Lake bacterioplankton populations may include low concentrations of available trace metals and dissolved organic matter, chemistry of infiltrating hydrothermal waters, and irradiation by high levels of ultraviolet light.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/11878353','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/11878353"><span><span class="hlt">Cratering</span> rates on the Galilean satellites.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zahnle, K; Dones, L; Levison, H F</p> <p>1998-12-01</p> <p>We exploit recent theoretical advances toward the origin and orbital evolution of comets and asteroids to obtain revised estimates for <span class="hlt">cratering</span> rates in the jovian system. We find that most, probably more than 90%, of the <span class="hlt">craters</span> on the Galilean satellites are caused by the impact of Jupiter-family comets (JFCs). These are comets with short periods, in generally low-inclination orbits, whose dynamics are dominated by Jupiter. Nearly isotropic comets (long period and Halley-type) contribute at the 1-10% level. Trojan asteroids might also be important at the 1-10% level; if they are important, they would be especially important for smaller <span class="hlt">craters</span>. Main belt asteroids are currently unimportant, as each 20-km <span class="hlt">crater</span> made on Ganymede implies the disruption of a 200-km diameter parental asteroid, a destruction rate far beyond the resources of today's asteroid belt. Twenty-kilometer diameter <span class="hlt">craters</span> are made by kilometer-size impactors; such events occur on a Galilean satellite about once in a million years. The paucity of 20-km <span class="hlt">craters</span> on Europa indicates that its surface is of order 10 Ma. Lightly <span class="hlt">cratered</span> surfaces on Ganymede are nominally of order 0.5-1.0 Ga. The uncertainty in these estimates is about a factor of five. Callisto is old, probably more than 4 Ga. It is too heavily <span class="hlt">cratered</span> to be accounted for by the current flux of JFCs. The lack of pronounced apex-antapex asymmetries on Ganymede may be compatible with <span class="hlt">crater</span> equilibrium, but it is more easily understood as evidence for nonsynchronous rotation of an icy carapace. c 1998 Academic Press.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70027122','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70027122"><span>Marine-target <span class="hlt">craters</span> on Mars? An assessment study</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Ormo, J.; Dohm, J.M.; Ferris, J.C.; Lepinette, A.; Fairen, A.G.</p> <p>2004-01-01</p> <p>Observations of impact <span class="hlt">craters</span> on Earth show that a water column at the target strongly influences lithology and morphology of the resultant <span class="hlt">crater</span>. The degree of influence varies with the target water depth and impactor diameter. Morphological features detectable in satellite imagery include a concentric shape with an inner <span class="hlt">crater</span> inset within a shallower outer <span class="hlt">crater</span>, which is cut by gullies excavated by the resurge of water. In this study, we show that if oceans, large seas, and lakes existed on Mars for periods of time, marine-target <span class="hlt">craters</span> must have formed. We make an assessment of the minimum and maximum amounts of such <span class="hlt">craters</span> based on published data on water depths, extent, and duration of putative oceans within "contacts 1 and 2," <span class="hlt">cratering</span> rate during the different oceanic phases, and computer modeling of minimum impactor diameters required to form long-lasting <span class="hlt">craters</span> in the seafloor of the oceans. We also discuss the influence of erosion and sedimentation on the preservation and exposure of the <span class="hlt">craters</span>. For an ocean within the smaller "contact 2" with a duration of 100,000 yr and the low present <span class="hlt">crater</span> formation rate, only ???1-2 detectable marine-target <span class="hlt">craters</span> would have formed. In a maximum estimate with a duration of 0.8 Gyr, as many as 1400 <span class="hlt">craters</span> may have formed. An ocean within the larger "contact 1-Meridiani," with a duration of 100,000 yr, would not have received any seafloor <span class="hlt">craters</span> despite the higher <span class="hlt">crater</span> formation rate estimated before 3.5 Gyr. On the other hand, with a maximum duration of 0.8 Gyr, about 160 seafloor <span class="hlt">craters</span> may have formed. However, terrestrial examples show that most marine-target <span class="hlt">craters</span> may be covered by thick sediments. Ground penetrating radar surveys planned for the ESA Mars Express and NASA 2005 missions may reveal buried <span class="hlt">craters</span>, though it is uncertain if the resolution will allow the detection of diagnostic features of marine-target <span class="hlt">craters</span>. The implications regarding the discovery of marine-target <span class="hlt">craters</span> on</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/4045338-high-explosive-crater-studies-desert-alluvium','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/4045338-high-explosive-crater-studies-desert-alluvium"><span>HIGH EXPLOSIVE <span class="hlt">CRATER</span> STUDIES: DESERT ALLUVIUM</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Murphey, B.F.</p> <p>1961-05-01</p> <p><span class="hlt">Crater</span> dimensions were determined for 23 explosions of 256-pound spherical TNT charges buried in desert alluvium. As opposed to previous work covering depths of burst as great as 6 feet, the work presented in this report extends knowledge of apparent <span class="hlt">crater</span> radius and depth to depths of burst as great as 30 feet. Optimum depth of burst for apparent <span class="hlt">crater</span> radius was near 10 feet and for apparent <span class="hlt">crater</span> depth near 8 feet. Surface motion photography illustrated a very great slowing down of the surface motion between depths of burst of 9.5 and 15.9 feet. <span class="hlt">Crater</span> contours, profiles, snd overheadmore » photographs are presented as illustrations. (auth)« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20030111111&hterms=TURTLES&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DTURTLES','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20030111111&hterms=TURTLES&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DTURTLES"><span>Numerical Simulations of Silverpit <span class="hlt">Crater</span> Collapse</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Collins, G. S.; Turtle, E. P.; Melosh, H. J.</p> <p>2003-01-01</p> <p>The Silverpit <span class="hlt">crater</span> is a recently discovered, 60-65 Myr old complex <span class="hlt">crater</span>, which lies buried beneath the North Sea, about 150 km east of Britain. High-resolution images of Silverpit's subsurface structure, provided by three-dimensional seismic reflection data, reveal an inner-<span class="hlt">crater</span> morphology similar to that expected for a 5-8 km diameter terrestrial <span class="hlt">crater</span>. The <span class="hlt">crater</span> walls show evidence of terracestyle slumping and there is a distinct central uplift, which may have produced a central peak in the pristine <span class="hlt">crater</span> morphology. However, Silverpit is not a typical 5-km diameter terrestrial <span class="hlt">crater</span>, because it exhibits multiple, concentric rings outside the main cavity. External concentric rings are normally associated with much larger impact structures, for example Chicxulub on Earth, or Orientale on the Moon. Furthermore, external rings associated with large impacts on the terrestrial planets and moons are widely-spaced, predominantly inwardly-facing, asymmetric scarps. However, the seismic data show that the external rings at Silverpit represent closely-spaced, concentric fault-bound graben, with both inwardly and outwardly facing faults-carps. This type of multi-ring structure is directly analogous to the Valhalla-type multi-ring basins found on the icy satellites. Thus, the presence and style of the multiple rings at Silverpit is surprising given both the size of the <span class="hlt">crater</span> and its planetary setting.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA03794.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA03794.html"><span>Reuyl <span class="hlt">Crater</span> Dust Avalanches</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2002-06-04</p> <p>The rugged, arcuate rim of the 90 km <span class="hlt">crater</span> Reuyl dominates this NASA Mars Odyssey image. Reuyl <span class="hlt">crater</span> is at the southern edge of a region known to be blanketed in thick dust based on its high albedo brightness and low thermal inertia values.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12554552','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12554552"><span>Internet infrastructures and health care systems: a qualitative comparative analysis on networks and markets in the British National Health Service and <span class="hlt">Kaiser</span> Permanente.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Séror, Ann C</p> <p>2002-12-01</p> <p>The Internet and emergent telecommunications infrastructures are transforming the future of health care management. The costs of health care delivery systems, products, and services continue to rise everywhere, but performance of health care delivery is associated with institutional and ideological considerations as well as availability of financial and technological resources. to identify the effects of ideological differences on health care market infrastructures including the Internet and telecommunications technologies by a comparative case analysis of two large health care organizations: the British National Health Service and the California-based <span class="hlt">Kaiser</span> Permanente health maintenance organization. A qualitative comparative analysis focusing on the British National Health Service and the <span class="hlt">Kaiser</span> Permanente health maintenance organization to show how system infrastructures vary according to market dynamics dominated by health care institutions ("push") or by consumer demand ("pull"). System control mechanisms may be technologically embedded, institutional, or behavioral. The analysis <span class="hlt">suggests</span> that telecommunications technologies and the Internet may contribute significantly to health care system performance in a context of ideological diversity. The study offers evidence to validate alternative models of health care governance: the national constitution model, and the enterprise business contract model. This evidence also <span class="hlt">suggests</span> important questions for health care policy makers as well as researchers in telecommunications, organizational theory, and health care management.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017P%26SS..148...12K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017P%26SS..148...12K"><span>Characteristics of small young lunar impact <span class="hlt">craters</span> focusing on current production and degradation on the Moon</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kereszturi, Akos; Steinmann, Vilmos</p> <p>2017-11-01</p> <p>Analysing the size-frequency distribution of very small lunar <span class="hlt">craters</span> (sized below 100 m including ones below 10 m) using LROC images, spatial density and related age estimations were calculated for mare and terra terrains. Altogether 1.55 km2 area was surveyed composed of 0.1-0.2 km2 units, counting 2784 <span class="hlt">craters</span>. The maximal areal density was present at the 4-8 m diameter range at every analysed terrain <span class="hlt">suggesting</span> the bombardment is areally relatively homogeneous. Analysing the similarities and differences between various areas, the mare terrains look about two times older than the terra terrains using <100 m diameter <span class="hlt">craters</span>. The calculated ages ranged between 13 and 20 Ma for mare, 4-6 Ma for terra terrains. Substantial fluctuation (min: 936 <span class="hlt">craters</span>/km2, max: 2495 <span class="hlt">craters</span>/km2) was observed without obvious source of nearby secondaries or fresh ejecta blanket produced fresh <span class="hlt">crater</span>. Randomness analysis and visual inspection also <span class="hlt">suggested</span> no secondary <span class="hlt">craters</span> or ejecta blanket from fresh impact could contribute substantially in the observed heterogeneity of the areal distribution of small <span class="hlt">craters</span> - thus distant secondaries or even other, poorly known resurfacing processes should be considered in the future. The difference between the terra/mare ages might come only partly from the easier identification of small <span class="hlt">craters</span> on smooth mare terrains, as the differences were observed for larger (30-60 m diameter) <span class="hlt">craters</span> too. Difference in the target hardness could more contribute in this effect. It was possible to separate two groups of small <span class="hlt">craters</span> based on their appearance: a rimmed thus less eroded, and a rimless thus more eroded one. As the separate usage of different morphology groups of <span class="hlt">craters</span> for age estimation at the same area is not justifiable, this was used only for comparison. The SFD curves of these two groups showed characteristic differences: the steepness of the fresh <span class="hlt">craters</span>' SFD curves are similar to each other and were larger than the isochrones. The</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19820038852&hterms=projectile+motion&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dprojectile%2Bmotion','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19820038852&hterms=projectile+motion&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dprojectile%2Bmotion"><span>Calculational investigation of impact <span class="hlt">cratering</span> dynamics - Material motions during the <span class="hlt">crater</span> growth period</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Austin, M. G.; Thomsen, J. M.; Ruhl, S. F.; Orphal, D. L.; Schultz, P. H.</p> <p>1980-01-01</p> <p>The considered investigation was conducted in connection with studies which are to provide a better understanding of the detailed dynamics of impact <span class="hlt">cratering</span> processes. Such an understanding is vital for a comprehension of planetary surfaces. The investigation is the continuation of a study of impact dynamics in a uniform, nongeologic material at impact velocities achievable in laboratory-scale experiments conducted by Thomsen et al. (1979). A calculation of a 6 km/sec impact of a 0.3 g spherical 2024 aluminum projectile into low strength (50 kPa) homogeneous plasticene clay has been continued from 18 microseconds to past 600 microseconds. The <span class="hlt">cratering</span> flow field, defined as the material flow field in the target beyond the transient cavity but well behind the outgoing shock wave, has been analyzed in detail to see how applicable the Maxwell Z-Model, developed from analysis of near-surface explosion <span class="hlt">cratering</span> calculations, is to impact <span class="hlt">cratering</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA10006&hterms=duck+hazard&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dduck%2Bhazard','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA10006&hterms=duck+hazard&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dduck%2Bhazard"><span>At Bright Band Inside Victoria <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2007-01-01</p> <p><p/> A layer of light-toned rock exposed inside Victoria <span class="hlt">Crater</span> in the Meridiani Planum region of Mars appears to mark where the surface was at the time, many millions of years ago, when an impact excavated the <span class="hlt">crater</span>. NASA's Mars Exploration Rover Opportunity drove to this bright band as the science team's first destination for the rover during investigations inside the <span class="hlt">crater</span>. <p/> Opportunity's left front hazard-identification camera took this image just after the rover finished a drive of 2.25 meters (7 feet, 5 inches) during the rover's 1,305th Martian day, or sol, (Sept. 25, 2007). The rocks beneath the rover and its extended robotic arm are part of the bright band. <p/> Victoria <span class="hlt">Crater</span> has a scalloped shape of alternating alcoves and promontories around the <span class="hlt">crater</span>'s circumference. Opportunity descended into the <span class="hlt">crater</span> two weeks earlier, within an alcove called 'Duck Bay.' Counterclockwise around the rim, just to the right of the arm in this image, is a promontory called 'Cabo Frio.'</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19940016309&hterms=missing&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dmissing','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19940016309&hterms=missing&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dmissing"><span>The missing impact <span class="hlt">craters</span> on Venus</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Speidel, D. H.</p> <p>1993-01-01</p> <p>The size-frequency pattern of the 842 impact <span class="hlt">craters</span> on Venus measured to date can be well described (across four standard deviation units) as a single log normal distribution with a mean <span class="hlt">crater</span> diameter of 14.5 km. This result was predicted in 1991 on examination of the initial Magellan analysis. If this observed distribution is close to the real distribution, the 'missing' 90 percent of the small <span class="hlt">craters</span> and the 'anomalous' lack of surface splotches may thus be neither missing nor anomalous. I think that the missing <span class="hlt">craters</span> and missing splotches can be satisfactorily explained by accepting that the observed distribution approximates the real one, that it is not <span class="hlt">craters</span> that are missing but the impactors. What you see is what you got. The implication that Venus crossing impactors would have the same type of log normal distribution is consistent with recently described distribution for terrestrial <span class="hlt">craters</span> and Earth crossing asteroids.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018Icar..308..209W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018Icar..308..209W"><span>Modeling concentric <span class="hlt">crater</span> fill in Utopia Planitia, Mars, with an ice flow line model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Weitz, N.; Zanetti, M.; Osinski, G. R.; Fastook, J. L.</p> <p>2018-07-01</p> <p>Impact <span class="hlt">craters</span> in the mid-latitudes of Mars are commonly filled to variable degrees with some combination of ice, dust, and rocky debris. Concentric surface features visible in these <span class="hlt">craters</span> have been linked to debris transportation and glacial and periglacial processes. Concentric <span class="hlt">crater</span> fill (CCF) observed today are interpreted to be the remains of repeated periods of accumulation and sublimation during the last tens to hundreds of million years. Previous work <span class="hlt">suggests</span> that during phases of high obliquity, ice accumulates in <span class="hlt">crater</span> interiors and begins to flow down steep <span class="hlt">crater</span> slopes, slowly filling the <span class="hlt">crater</span>. During times of low obliquity ice is protected from sublimation through a surface debris layer consisting of dust and rocky material. Here, we use an ice flow line model to understand the development of concentric <span class="hlt">crater</span> fill. In a regional study of Utopia Planitia <span class="hlt">craters</span>, we address questions about the influence of <span class="hlt">crater</span> size on the CCF formation process, the time scales needed to fill an impact <span class="hlt">crater</span> with ice, and explore commonly described flow features of CCF. We show that observed surface debris deposits as well as asymmetric flow features can be reproduced with the model. Using surface mass balance data from global climate models and a credible obliquity scenario, we find that <span class="hlt">craters</span> less than 80 km in diameter can be entirely filled in less than 8 My, beginning as recently as 40 Ma ago. Uncertainties in input variables related to ice viscosity do not change the overall behavior of ice flow and the filling process. We model CCF for the Utopia Planitia region and find subtle trends for <span class="hlt">crater</span> size versus fill level, <span class="hlt">crater</span> size versus sublimation reduction by the surface debris layer, and <span class="hlt">crater</span> floor elevation versus fill level.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20130009717','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20130009717"><span>Evidence for a Global Martian Soil Composition Extends to Gale <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Yen, A. S.; Gellert, R.; Clark, B. C.; Ming, D. W.; King, P. L.; Schmidt, M. E.; Leshin, L.; Morris, R. V.; Squyres, S. W.; Campbell, J. L.</p> <p>2013-01-01</p> <p>The eolian bedform within Gale <span class="hlt">Crater</span> referred to as "Rocknest" was investigated by the science instruments of the Curiosity Mars rover. Physical, chemical and mineralogical results are consistent with data collected from soils at other landing sites, <span class="hlt">suggesting</span> a globally-similar composition. Results from the Curiosity payload from Rocknest should be considered relevant beyond a single, localized region with Gale <span class="hlt">Crater</span>, providing key insights into planetary scale processes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016DPS....4822304M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016DPS....4822304M"><span>Quantifying Slope Effects and Variations in <span class="hlt">Crater</span> Density across a Single Geologic Unit</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Meyer, Heather; Mahanti, Prasun; Robinson, Mark; Povilaitis, Reinhold</p> <p>2016-10-01</p> <p>Steep underlying slopes (>~5°) significantly increase the rate of degradation of <span class="hlt">craters</span> [1-3]. As a result, the density of <span class="hlt">craters</span> is less on steeper slopes for terrains of the same age [2, 4]. Thus, when age-dating a planetary surface, an area encompassing one geologic unit of constant low slope is chosen. However, many key geologic units, such as ejecta blankets, lack sufficient area of constant slope to derive robust age estimates. Therefore, accurate age-dating of such units requires an accurate understanding of the effects of slope on age estimates. This work seeks to determine if the observed trend of decreasing <span class="hlt">crater</span> density with increasing slopes [2] holds for <span class="hlt">craters</span> >1 km and to quantify the effect of slope for <span class="hlt">craters</span> of this size, focusing on the effect of slopes over the kilometer scale. Our study focuses on the continuous ejecta of Orientale basin, where we measure <span class="hlt">craters</span> >1 km excluding secondaries that occur as chains or clusters. Age-dating via <span class="hlt">crater</span> density measurements relies on uniform <span class="hlt">cratering</span> across a single geologic unit. In the case of ejecta blankets and other impact related surfaces, this assumption may not hold due to the formation of auto- secondary <span class="hlt">craters</span>. As such, we use LRO WAC mosaics [5], <span class="hlt">crater</span> size-frequency distributions, absolute age estimates, a 3 km slope map derived from the WAC GLD100 [6], and density maps for various <span class="hlt">crater</span> size ranges to look for evidence of non-uniform <span class="hlt">cratering</span> across the continuous ejecta of Orientale and to determine the effect of slope on <span class="hlt">crater</span> density. Preliminary results <span class="hlt">suggest</span> that <span class="hlt">crater</span> density does decrease with increasing slope for <span class="hlt">craters</span> >1 km in diameter though at a slower rate than for smaller <span class="hlt">craters</span>.References: [1] Trask N. J. and Rowan L. C. (1967) Science 158, 1529-1535. [2] Basilevsky (1976) Proc. Lunar Sci. Conf. 7th, p. 1005-1020. [3] Pohn and Offield (1970) USGS Prof. Pap., 153-162. [4] Xiao et al. (2013) Earth and Planet. Sci. Lett., 376, pgs. 1-11. doi:10.1016/j.epsl.2013</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA22143.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA22143.html"><span>Investigating Mars: Rabe <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2017-12-15</p> <p>This VIS image provides another instance where the topography of the upper floor material affects the winds and dune formation. At the edges of the dune field, the dunes become smaller and more separated, revealing the harder surface that the dunes are moving across. Rabe <span class="hlt">Crater</span> is 108 km (67 miles) across. <span class="hlt">Craters</span> of similar size often have flat floors. Rabe <span class="hlt">Crater</span> has some areas of flat floor, but also has a large complex pit occupying a substantial part of the floor. The interior fill of the <span class="hlt">crater</span> is thought to be layered sediments created by wind and or water action. The pit is eroded into this material. The eroded materials appear to have stayed within the <span class="hlt">crater</span> forming a large sand sheet with surface dune forms as well as individual dunes where the <span class="hlt">crater</span> floor is visible. The dunes also appear to be moving from the upper floor level into the pit. The Odyssey spacecraft has spent over 15 years in orbit around Mars, circling the planet more than 69000 times. It holds the record for longest working spacecraft at Mars. THEMIS, the IR/VIS camera system, has collected data for the entire mission and provides images covering all seasons and lighting conditions. Over the years many features of interest have received repeated imaging, building up a suite of images covering the entire feature. From the deepest chasma to the tallest volcano, individual dunes inside <span class="hlt">craters</span> and dune fields that encircle the north pole, channels carved by water and lava, and a variety of other feature, THEMIS has imaged them all. For the next several months the image of the day will focus on the Tharsis volcanoes, the various chasmata of Valles Marineris, and the major dunes fields. We hope you enjoy these images! Orbit Number: 57843 Latitude: -43.3482 Longitude: 34.6454 Instrument: VIS Captured: 2014-12-28 12:37 https://photojournal.jpl.nasa.gov/catalog/PIA22143</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006epsc.conf..625P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006epsc.conf..625P"><span>An assessment of <span class="hlt">crater</span> erosional histories on the Earth and Mars using digital terrain models.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Paul, R. L.; Muller, J.-P.; Murray, J. B.</p> <p></p> <p>The research will examine quantitatively the geomorphology of both Terrestrial and Martian <span class="hlt">craters</span>. The erosional and sub-surface processes will be investigated to understand how these affect a <span class="hlt">crater</span>'s morphology. For example, the Barringer <span class="hlt">crater</span> in Arizona has an unusual shape. The Earth has a very high percentage of water both in the atmosphere as clouds or rain and under the surface. The presence of water will therefore affect a <span class="hlt">crater</span>'s formation and its subsequent erosional modification. On Mars there is little or no water present currently, though recent observations <span class="hlt">suggest</span> there may be near-surface ice in some areas. How do <span class="hlt">craters</span> formed in the Martian environment therefore differ from Terrestrial ones? How has the structure of Martian <span class="hlt">craters</span> changed in areas of possible fluvial activity? How does the surface material affect <span class="hlt">crater</span> formation? How does the Earth's fluvial activity affect a <span class="hlt">crater</span>'s evolution? At present, four measurements of circularity have been used to describe a <span class="hlt">crater</span> (Murray & Guest, 1972). These parameters will be re-examined to see how effectively they describe Terrestrial and Martian <span class="hlt">craters</span> using high resolution DTMs which were not available at the time of the original study. The model described by Forsberg-Taylor et al. 2004, and others will also be applied to results obtained from the chosen <span class="hlt">craters</span> to assess how effectively these <span class="hlt">craters</span> are described. Both hypsometric curves and hydrological analysis will be used to assess <span class="hlt">crater</span> evolution. A suitable criterion for the selection of Terrestrial and Martian <span class="hlt">craters</span> is essential for this type of research. Terrestrial <span class="hlt">craters</span> have been selected in arid or semi-arid terrain with <span class="hlt">crater</span> diameters larger than one kilometre. <span class="hlt">Craters</span> less than five million years old would be ideal. However, this was too restrictive and so a variety of <span class="hlt">crater</span> ages have had to be used. Eight terrestrial <span class="hlt">craters</span> have been selected in arid or semi-arid areas for study, using the Earth Impact Database and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APS..DFDR35001A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..DFDR35001A"><span>Modeling turbulent flows in the atmospheric boundary layer of Mars: application to Gale <span class="hlt">crater</span>, Mars, landing site of the Curiosity rover</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Anderson, William; Day, Kenzie; Kocurek, Gary</p> <p>2016-11-01</p> <p>Mars is a dry planet with a thin atmosphere. Aeolian processes - wind-driven mobilization of sediment and dust - are the exclusive mode of landscape variability on Mars. <span class="hlt">Craters</span> are common topographic features on the surface of Mars, and many <span class="hlt">craters</span> on Mars contain a prominent central mound (NASA's Curiosity rover was landed in Gale <span class="hlt">crater</span>). Using density-normalized large-eddy simulations, we have modeled turbulent flows over <span class="hlt">crater</span>-like topographies that feature a central mound. We have also run one simulation of flow over a digital elevation map of Gale <span class="hlt">crater</span>. Resultant datasets <span class="hlt">suggest</span> a deflationary mechanism wherein vortices shed from the upwind <span class="hlt">crater</span> rim are realigned to conform to the <span class="hlt">crater</span> profile via stretching and tilting. This was accomplished using three-dimensional datasets (momentum and vorticity) retrieved from LES. As a result, helical vortices occupy the inner region of the <span class="hlt">crater</span> and, therefore, are primarily responsible for aeolian morphodynamics in the <span class="hlt">crater</span>. We have also used the immersed-boundary method body force distribution to compute the aerodynamic surface stress on the <span class="hlt">crater</span>. These results <span class="hlt">suggest</span> that secondary flows - originating from flow separation at the <span class="hlt">crater</span> - have played an important role in shaping landscape features observed in <span class="hlt">craters</span> (including the dune fields observed on Mars, many of which are actively evolving). None.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1917367A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1917367A"><span>Modeling turbulent flows in the atmospheric boundary layer of Mars: application to Gale <span class="hlt">crater</span>, Mars, landing site of the Curiosity rover</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Anderson, William</p> <p>2017-04-01</p> <p>Mars is a dry planet with a thin atmosphere. Aeolian processes - wind-driven mobilization of sediment and dust - are the exclusive mode of landscape variability on Mars. <span class="hlt">Craters</span> are common topographic features on the surface of Mars, and many <span class="hlt">craters</span> on Mars contain a prominent central mound (NASA's Curiosity rover was landed in Gale <span class="hlt">crater</span>). Using density-normalized large-eddy simulations, we have modeled turbulent flows over <span class="hlt">crater</span>-like topographies that feature a central mound. We have also run one simulation of flow over a digital elevation map of Gale <span class="hlt">crater</span>. Resultant datasets <span class="hlt">suggest</span> a deflationary mechanism wherein vortices shed from the upwind <span class="hlt">crater</span> rim are realigned to conform to the <span class="hlt">crater</span> profile via stretching and tilting. This was accomplished using three-dimensional datasets (momentum and vorticity) retrieved from LES. As a result, helical vortices occupy the inner region of the <span class="hlt">crater</span> and, therefore, are primarily responsible for aeolian morphodynamics in the <span class="hlt">crater</span>. We have also used the immersed-boundary method body force distribution to compute the aerodynamic surface stress on the <span class="hlt">crater</span>. These results <span class="hlt">suggest</span> that secondary flows - originating from flow separation at the <span class="hlt">crater</span> - have played an important role in shaping landscape features observed in <span class="hlt">craters</span> (including the dune fields observed on Mars, many of which are actively evolving).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/11539331','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/11539331"><span>Surface expression of the Chicxulub <span class="hlt">crater</span></span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pope, K O; Ocampo, A C; Kinsland, G L; Smith, R</p> <p>1996-06-01</p> <p>Analyses of geomorphic, soil, and topographic data from the northern Yucatan Peninsula, Mexico, confirm that the buried Chicxulub impact <span class="hlt">crater</span> has a distinct surface expression and that carbonate sedimentation throughout the Cenozoic has been influenced by the <span class="hlt">crater</span>. Late Tertiary sedimentation was mostly restricted to the region within the buried <span class="hlt">crater</span>, and a semicircular moat existed until at least Pliocene time. The topographic expression of the <span class="hlt">crater</span> is a series of features concentric with the <span class="hlt">crater</span>. The most prominent is an approximately 83-km-radius trough or moat containing sinkholes (the Cenote ring). Early Tertiary surfaces rise abruptly outside the moat and form a stepped topography with an outer trough and ridge crest at radii of approximately 103 and approximately 129 km, respectively. Two discontinuous troughs lie within the moat at radii of approximately 41 and approximately 62 km. The low ridge between the inner troughs corresponds to the buried peak ring. The moat corresponds to the outer edge of the <span class="hlt">crater</span> floor demarcated by a major ring fault. The outer trough and the approximately 62-km-radius inner trough also mark buried ring faults. The ridge crest corresponds to the topographic rim of the <span class="hlt">crater</span> as modified by postimpact processes. These interpretations support previous findings that the principal impact basin has a diameter of approximately 180 km, but concentric, low-relief slumping extends well beyond this diameter and the eroded <span class="hlt">crater</span> rim may extend to a diameter of approximately 260 km.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018Icar..302..104S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018Icar..302..104S"><span>Ceres and the terrestrial planets impact <span class="hlt">cratering</span> record</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Strom, R. G.; Marchi, S.; Malhotra, R.</p> <p>2018-03-01</p> <p>Dwarf planet Ceres, the largest object in the Main Asteroid Belt, has a surface that exhibits a range of <span class="hlt">crater</span> densities for a <span class="hlt">crater</span> diameter range of 5-300 km. In all areas the shape of the <span class="hlt">craters</span>' size-frequency distribution is very similar to those of the most ancient heavily <span class="hlt">cratered</span> surfaces on the terrestrial planets. The most heavily <span class="hlt">cratered</span> terrain on Ceres covers ∼15% of its surface and has a <span class="hlt">crater</span> density similar to the highest <span class="hlt">crater</span> density on <1% of the lunar highlands. This region of higher <span class="hlt">crater</span> density on Ceres probably records the high impact rate at early times and indicates that the other 85% of Ceres was partly resurfaced after the Late Heavy Bombardment (LHB) at ∼4 Ga. The Ceres <span class="hlt">cratering</span> record strongly indicates that the period of Late Heavy Bombardment originated from an impactor population whose size-frequency distribution resembles that of the Main Belt Asteroids.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70073409','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70073409"><span>HiRISE observations of new impact <span class="hlt">craters</span> exposing Martian ground ice</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Dundas, Colin M.; Byrne, Shane; McEwen, Alfred S.; Mellon, Michael T.; Kennedy, Megan R.; Daubar, Ingrid J.; Saper, Lee</p> <p>2014-01-01</p> <p>Twenty small new impact <span class="hlt">craters</span> or clusters have been observed to excavate bright material inferred to be ice at mid and high latitudes on Mars. In the northern hemisphere, the <span class="hlt">craters</span> are widely distributed geographically and occur at latitudes as low as 39°N. Stability modeling <span class="hlt">suggests</span> that this ice distribution requires a long-term average atmospheric water vapor content around 25 precipitable microns, more than double the present value, which is consistent with the expected effect of recent orbital variations. Alternatively, near-surface humidity could be higher than expected for current column abundances if water vapor is not well-mixed with atmospheric CO2, or the vapor pressure at the ice table could be lower due to salts. Ice in and around the <span class="hlt">craters</span> remains visibly bright for months to years, indicating that it is clean ice rather than ice-cemented regolith. Although some clean ice may be produced by the impact process, it is likely that the original ground ice was excess ice (exceeding dry soil pore space) in many cases. Observations of the <span class="hlt">craters</span> <span class="hlt">suggest</span> small-scale heterogeneities in this excess ice. The origin of such ice is uncertain. Ice lens formation by migration of thin films of liquid is most consistent with local heterogeneity in ice content and common surface boulders, but in some cases nearby thermokarst landforms <span class="hlt">suggest</span> large amounts of excess ice that may be best explained by a degraded ice sheet.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA04516&hterms=polygons&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dpolygons','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA04516&hterms=polygons&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dpolygons"><span>Polygons on <span class="hlt">Crater</span> Floor</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2003-01-01</p> <p>MGS MOC Release No. MOC2-357, 11 May 2003<p/>This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) picture shows a pattern of polygons on the floor of a northern plains impact <span class="hlt">crater</span>. These landforms are common on <span class="hlt">crater</span> floors at high latitudes on Mars. Similar polygons occur in the arctic and antarctic regions of Earth, where they indicate the presence and freeze-thaw cycling of ground ice. Whether the polygons on Mars also indicate water ice in the ground is uncertain. The image is located in a <span class="hlt">crater</span> at 64.8oN, 292.7oW. Sunlight illuminates the scene from the lower left.<p/></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19880037987&hterms=hey&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dhey','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19880037987&hterms=hey&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dhey"><span>Zhamanshin and Aouelloul - <span class="hlt">Craters</span> produced by impact of tektite-like glasses?</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>O'Keefe, John A.</p> <p>1987-01-01</p> <p>It is shown that the enhanced abundance of siderophile elements and chromium in tektite-like glasses from the two impact <span class="hlt">craters</span> of Zhamanshin and Aouelloul cannot be explained as a result of contamination of the country rock by meteorites nor, probably, comets. The pattern is, however, like that found in certain Australasian tektites, and in Ivory Coast tektites. It is concluded, in agreement with earlier <span class="hlt">suggestions</span> by Campbell-Smith and Hey, that these <span class="hlt">craters</span> were formed by the impact of large masses of tektite-like glass, of which the glasses which were studied are fragments. It follows that it is necessary, in considering an impact <span class="hlt">crater</span>, to bear in mind that the projectile may have been a glass.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1987Metic..22..219O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1987Metic..22..219O"><span>Zhamanshin and Aouelloul - <span class="hlt">Craters</span> produced by impact of tektite-like glasses?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>O'Keefe, John A.</p> <p>1987-09-01</p> <p>It is shown that the enhanced abundance of siderophile elements and chromium in tektite-like glasses from the two impact <span class="hlt">craters</span> of Zhamanshin and Aouelloul cannot be explained as a result of contamination of the country rock by meteorites nor, probably, comets. The pattern is, however, like that found in certain Australasian tektites, and in Ivory Coast tektites. It is concluded, in agreement with earlier <span class="hlt">suggestions</span> by Campbell-Smith and Hey, that these <span class="hlt">craters</span> were formed by the impact of large masses of tektite-like glass, of which the glasses which were studied are fragments. It follows that it is necessary, in considering an impact <span class="hlt">crater</span>, to bear in mind that the projectile may have been a glass.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA01454&hterms=first+moon+landing&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dfirst%2Bmoon%2Blanding','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA01454&hterms=first+moon+landing&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dfirst%2Bmoon%2Blanding"><span>Moon/Mars Landing Commemorative Release: Gusev <span class="hlt">Crater</span> and Ma'adim Vallis</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1998-01-01</p> <p><p/> On July 20, 1969, the first human beings landed on the Moon. On July 20, 1976, the first robotic lander touched down on Mars. This July 20th-- 29 years after Apollo 11 and 22 years since the Viking 1 Mars landing-- we take a look forward toward one possible future exploration site on the red planet.<p/>One of the advantages of the Mars Global Surveyor Mars Orbiter Camera (MOC) over its predecessors on the Viking and Mariner spacecraft is resolution. The ability to see<i>-- resolve--</i>fine details on the martian surface is key to planning future landing sites for robotic and, perhaps, human explorers that may one day visit the planet.<p/>At present, NASA is studying potential landing sites for the Mars Surveyor landers, rovers, and sample return vehicles that are scheduled to be launched in 2001, 2003, and 2005. Among the types of sites being considered for these early 21st Century landings are those with 'exobiologic potential'--that is, locations on Mars that are in some way related to the past presence of water.<p/>For more than a decade, two of the prime candidates <span class="hlt">suggested</span> by various Mars research scientists are Gusev <span class="hlt">Crater</span> and Ma'adim Vallis. Located in the martian southern <span class="hlt">cratered</span> highlands at 14.7o S, 184.5o W, Gusev <span class="hlt">Crater</span> is a large, ancient, meteor impact basin that--after it formed--was breached by Ma'adim Vallis.<p/>Viking Orbiter observations provided some evidence to <span class="hlt">suggest</span> that a fluid--most likely, water--once flowed through Ma'adim Vallis and into Gusev <span class="hlt">Crater</span>. Some scientists have <span class="hlt">suggested</span> that there were many episodes of flow into Gusev <span class="hlt">Crater</span> (as well as flow out of Gusev through its topographically-lower northwestern rim). Some have also indicated that there were times when Ma'adim Vallis, also, was full of water such that it formed a long, narrow lake.<p/>The possibility that water flowed into Gusev <span class="hlt">Crater</span> and formed a lake has led to the <span class="hlt">suggestion</span> that the materials seen on the floor of this <span class="hlt">crater</span>--smooth-surfaced deposits</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/6576626-calvin-impact-crater-its-associated-oil-production-cass-county-michigan','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/6576626-calvin-impact-crater-its-associated-oil-production-cass-county-michigan"><span>The Calvin impact <span class="hlt">crater</span> and its associated oil production, Cass County, Michigan</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Milstein, R.L.</p> <p>1996-01-01</p> <p>The Calvin impact <span class="hlt">crater</span> is an isolated, nearly circular subsurface structure of Late Ordovician age in southwestern Michigan. The <span class="hlt">crater</span> is defined by 110 oil and gas test wells, has a diameter of 6.2 km, and consists of a central dome exhibiting 415 m of structural uplift, an annular depression, and an encircling anticlinal rim. Exploration and development of three Devonian oil fields associated wit this structure provide all available subsurface data. All oil production is from the Middle Devonian Traverse Limestone, with the exception of one well producing from the Middle Devonian Sylvania Sandstone. This study models the grossmore » morphology of the Calvin structure using multiple tools and compares the results to known impact <span class="hlt">craters</span>. Combined results of reflection seismic, gravity, magnetic, and resistivity data, as well as organized relationships between stratigraphic displacement and structural diameters observed in complex impact <span class="hlt">craters</span>, <span class="hlt">suggest</span> the Calvin structure is morphologically similar to recognized complex impact <span class="hlt">craters</span> in sedimentary targets. In addition, individual quartz grains recovered from the Calvin structure exhibit decorated shock lamellae, Boehm lamellae, rhombohederal cleavage, and radiating concussion fractures. Based on the available data, I conclude the Calvin structure is a buried complex impact <span class="hlt">crater</span> and that the trapping and reservoir characteristics of the associated Calvin 20, Juno Lake, and Calvin 28 oil fields are resultant of the <span class="hlt">craters</span> morphology.« less</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/425743-calvin-impact-crater-its-associated-oil-production-cass-county-michigan','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/425743-calvin-impact-crater-its-associated-oil-production-cass-county-michigan"><span>The Calvin impact <span class="hlt">crater</span> and its associated oil production, Cass County, Michigan</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Milstein, R.L.</p> <p>1996-12-31</p> <p>The Calvin impact <span class="hlt">crater</span> is an isolated, nearly circular subsurface structure of Late Ordovician age in southwestern Michigan. The <span class="hlt">crater</span> is defined by 110 oil and gas test wells, has a diameter of 6.2 km, and consists of a central dome exhibiting 415 m of structural uplift, an annular depression, and an encircling anticlinal rim. Exploration and development of three Devonian oil fields associated wit this structure provide all available subsurface data. All oil production is from the Middle Devonian Traverse Limestone, with the exception of one well producing from the Middle Devonian Sylvania Sandstone. This study models the grossmore » morphology of the Calvin structure using multiple tools and compares the results to known impact <span class="hlt">craters</span>. Combined results of reflection seismic, gravity, magnetic, and resistivity data, as well as organized relationships between stratigraphic displacement and structural diameters observed in complex impact <span class="hlt">craters</span>, <span class="hlt">suggest</span> the Calvin structure is morphologically similar to recognized complex impact <span class="hlt">craters</span> in sedimentary targets. In addition, individual quartz grains recovered from the Calvin structure exhibit decorated shock lamellae, Boehm lamellae, rhombohederal cleavage, and radiating concussion fractures. Based on the available data, I conclude the Calvin structure is a buried complex impact <span class="hlt">crater</span> and that the trapping and reservoir characteristics of the associated Calvin 20, Juno Lake, and Calvin 28 oil fields are resultant of the <span class="hlt">craters</span> morphology.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA09924&hterms=duck+hazard&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dduck%2Bhazard','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA09924&hterms=duck+hazard&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dduck%2Bhazard"><span>Opportunity's First Dip into Victoria <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2007-01-01</p> <p><p/> NASA's Mars Exploration Rover Opportunity entered Victoria <span class="hlt">Crater</span> during the rover's 1,291st Martian day, or sol, (Sept. 11, 2007). The rover team commanded Opportunity to drive just far enough into the <span class="hlt">crater</span> to get all six wheels onto the inner slope, and then to back out again and assess how much the wheels slipped on the slope. The driving commands for the day included a precaution for the rover to stop driving if the wheels were slipping more than 40 percent. Slippage exceeded that amount on the last step of the drive, so Opportunity stopped with its front pair of wheels still inside the <span class="hlt">crater</span>. The rover team planned to assess results of the drive, then start Opportunity on an extended exploration inside the <span class="hlt">crater</span>. <p/> This wide-angle view taken by Opportunity's front hazard-identification camera at the end of the day's driving shows the wheel tracks created by the short dip into the <span class="hlt">crater</span>. The left half of the image looks across an alcove informally named 'Duck Bay' toward a promontory called 'Cape Verde' clockwise around the <span class="hlt">crater</span> wall. The right half of the image looks across the main body of the <span class="hlt">crater</span>, which is 800 meters (half a mile) in diameter.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA00462.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA00462.html"><span>Venus - Multiple-Floored, Irregular Impact <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>1996-09-26</p> <p>NASA' sMagellan imaged this multiple-floored, irregular impact <span class="hlt">crater</span> at latitude 16.4 degrees north, longitude 352.1 degrees east, during orbits 481 and 482 on 27 September 1990. This <span class="hlt">crater</span>, about 9.2 kilometers in maximum diameter, was formed on what appears to be a slightly fractured, radar-dark (smooth) plain. The abundant, low viscosity flows associated with this <span class="hlt">cratering</span> event have, however, filled local, fault-controlled troughs (called graben). These shallow graben are well portrayed on this Magellan image but would be unrecognizable but for their coincidental infilling by the radar-bright <span class="hlt">crater</span> flows. This fortuitous enhancement by the <span class="hlt">crater</span> flows of fault structures that are below the resolution of the Magellan synthetic aperture radar is providing the Magellan Science Team with valuable geologic information. The flow deposits from the <span class="hlt">craters</span> are thought to consist primarily of shock melted rock and fragmented debris resulting from the nearly simultaneous impacts of two projectile fragments into the hot (800 degrees Fahrenheit) surface rocks of Venus. The presence of the various floors of this irregular <span class="hlt">crater</span> is interpreted to be the result of crushing, fragmentation, and eventual aerodynamic dispersion of a single entry projectile during passage through the dense Venusian atmosphere. http://photojournal.jpl.nasa.gov/catalog/PIA00462</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050201861','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050201861"><span>Mars Exploration Rover Field Observations of Impact <span class="hlt">Craters</span> at Gusev <span class="hlt">Crater</span> and Meridiani Planum and Implications for Climate Change</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Golombek, M.; Grant, J. A.; Crumpler, L. S.</p> <p>2005-01-01</p> <p>The Mars Exploration Rovers have provided a field geologist's perspective of impact <span class="hlt">craters</span> in various states of degradation along their traverses at Gusev <span class="hlt">crater</span> and Meridiani Planum. This abstract will describe the <span class="hlt">craters</span> observed and changes to the <span class="hlt">craters</span> that constrain the erosion rates and the climate [l]. Changes to <span class="hlt">craters</span> on the plains of Gusev argue for a dry and desiccating environment since the Late Hesperian in contrast to the wet and likely warm environment in the Late Noachian at Meridiani in which the sulfate evaporites were deposited in salt-water playas or sabkhas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19780057844&hterms=statistics+levels&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dstatistics%2Blevels','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19780057844&hterms=statistics+levels&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dstatistics%2Blevels"><span>Interpreting statistics of small lunar <span class="hlt">craters</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Schultz, P. H.; Gault, D.; Greeley, R.</p> <p>1977-01-01</p> <p>Some of the wide variations in the <span class="hlt">crater</span>-size distributions in lunar photography and in the resulting statistics were interpreted as different degradation rates on different surfaces, different scaling laws in different targets, and a possible population of endogenic <span class="hlt">craters</span>. These possibilities are reexamined for statistics of 26 different regions. In contrast to most other studies, <span class="hlt">crater</span> diameters as small as 5 m were measured from enlarged Lunar Orbiter framelets. According to the results of the reported analysis, the different <span class="hlt">crater</span> distribution types appear to be most consistent with the hypotheses of differential degradation and a superposed <span class="hlt">crater</span> population. Differential degradation can account for the low level of equilibrium in incompetent materials such as ejecta deposits, mantle deposits, and deep regoliths where scaling law changes and catastrophic processes introduce contradictions with other observations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA02425.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA02425.html"><span>Young <span class="hlt">Craters</span> on Smooth Plains</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2000-01-15</p> <p>This image, from NASA Mariner 10 spacecraft which launched in 1974, shows young <span class="hlt">craters</span> superposed on smooth plains. Larger young <span class="hlt">craters</span> have central peaks, flat floors, terraced walls, and radial ejecta deposits.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19890011921','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19890011921"><span>The <span class="hlt">cratering</span> record in the inner solar system: Implications for earth</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Barlow, N. G.</p> <p>1988-01-01</p> <p>Internal and external processes have reworked the Earth's surface throughout its history. In particular, the effect of meteorite impacts on the early history of the earth is lost due to fluvial, aeolian, volcanic and plate tectonic action. The <span class="hlt">cratering</span> record on other inner solar system bodies often provides the only clue to the relative <span class="hlt">cratering</span> rates and intensities that the earth has experienced throughout its history. Of the five major bodies within the inner solar system, Mercury, Mars, and the Moon retain scars of an early episode of high impact rates. The heavily <span class="hlt">cratered</span> regions on Mercury, Mars, and the Moon show <span class="hlt">crater</span> size-frequency distribution curves similar in shape and <span class="hlt">crater</span> density, whereas the lightly <span class="hlt">cratered</span> plains on the Moon and Mars show distribution curves which, although similar to each other, are statistically different in shape and density from the more heavily <span class="hlt">cratered</span> units. The similarities among <span class="hlt">crater</span> size-frequency distribution curves for the Moon, Mercury, and Mars <span class="hlt">suggest</span> that the entire inner solar system was subjected to the two populations of impacting objects but Earth and Venus have lost their record of heavy bombardment impactors. Thus, based on the <span class="hlt">cratering</span> record on the Moon, Mercury, and Mars, it can be inferred that the Earth experienced a period of high <span class="hlt">crater</span> rates and basin formation prior to about 3.8 BY ago. Recent studies have linked mass extinctions to large terrestrial impacts, so life forms were unable to establish themselves until impact rates decreased substantially and terrestrial conditions became more benign. The possible periodicity of mass extinctions has led to the theory of fluctuating impact rates due to comet showers in the post heavy bombardment period. The active erosional environment on the Earth complicates attempts to verify these showers by erasing geological evidence of older impact <span class="hlt">craters</span>. The estimated size of the impactor purportedly responsible for the Cretaceous-Tertiary mass</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhDT........28V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhDT........28V"><span>Expanded <span class="hlt">Craters</span> on Mars: Implications for Shallow, Mid-latitude Excess Ice</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Viola, Donna</p> <p></p> <p>Understanding the age and distribution of shallow ice on Mars is valuable for interpreting past and present climate conditions, and has implications on habitability and future in situ resource utilization. Many ice-related features, such as lobate debris aprons and concentric <span class="hlt">crater</span> fill, have been studied using a range of remote sensing techniques. Here, I explore the distribution of expanded <span class="hlt">craters</span>, a form of sublimation thermokarst where shallow, excess ice has been destabilized and sublimated following an impact event. This leads to the collapse of the overlying dry regolith to produce the appearance of diameter widening. The modern presence of these features <span class="hlt">suggests</span> that excess ice has remained preserved in the terrain immediately surrounding the <span class="hlt">craters</span> since the time of their formation in order to maintain the surface. High-resolution imagery is ideal for observing thermokarst features, and much of the work described here will utilize data from the Context Camera (CTX) and High Resolution Imaging Science Experiment (HiRISE) on the Mars Reconnaissance Orbiter (MRO). Expanded <span class="hlt">craters</span> tend to be found in clusters that emanate radially from at least four primary <span class="hlt">craters</span> in Arcadia Planitia, and are interpreted as secondary <span class="hlt">craters</span> that formed nearly simultaneously with their primaries. <span class="hlt">Crater</span> age dates of the primaries indicate that the expanded secondaries, as well as the ice layer into which they impacted, must be at least tens of millions of years old. Older double-layer ejecta <span class="hlt">craters</span> in Arcadia Planitia commonly have expanded <span class="hlt">craters</span> superposed on their ejecta - and they tend to be more expanded (with larger diameters) in the inner ejecta layer. This has implications on the formation mechanisms for <span class="hlt">craters</span> with this unique ejecta morphology. Finally, I explore the distribution of expanded <span class="hlt">craters</span> south of Arcadia Planitia and across the southern mid-latitudes, along with scalloped depressions (another form of sublimation thermokarst), in order to identify</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19940011922','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19940011922"><span>Galileo SSI lunar observations: Copernican <span class="hlt">craters</span> and soils</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mcewen, A. S.; Greeley, R.; Head, James W.; Pieters, C. M.; Fischer, E. M.; Johnson, T. V.; Neukum, G.</p> <p>1993-01-01</p> <p>The Galileo spacecraft completed its first Earth-Moon flyby (EMI) in December 1990 and its second flyby (EM2) in December 1992. Copernican-age <span class="hlt">craters</span> are among the most prominent features seen in the SSI (Solid-State Imaging) multispectral images of the Moon. The interiors, rays, and continuous ejecta deposits of these youngest <span class="hlt">craters</span> stand out as the brightest features in images of albedo and visible/1-micron color ratios (except where impact melts are abundant). <span class="hlt">Crater</span> colors and albedos (away from impact melts) are correlated with their geologic emplacement ages as determined from counts of superposed <span class="hlt">craters</span>; these age-color relations can be used to estimate the emplacement age (time since impact event) for many Copernican-age <span class="hlt">craters</span> on the near and far sides of the Moon. The spectral reflectivities of lunar soils are controlled primarily by (1) soil maturity, resulting from the soil's cumulative age of exposure to the space environment; (2) steady-state horizontal and vertical mixing of fresh crystalline materials ; and (3) the mineralogy of the underlying bedrock or megaregolith. Improved understanding of items (1) and (2) above will improve our ability to interpret item (3), especially for the use of <span class="hlt">crater</span> compositions as probes of crustal stratigraphy. We have examined the multispectral and superposed <span class="hlt">crater</span> frequencies of large isolated <span class="hlt">craters</span>, mostly of Eratosthenian and Copernican ages, to avoid complications due to (1) secondaries (as they affect superposed <span class="hlt">crater</span> counts) and (2) spatially and temporally nonuniform regolith mixing from younger, large, and nearby impacts. <span class="hlt">Crater</span> counts are available for 11 mare <span class="hlt">craters</span> and 9 highlands <span class="hlt">craters</span> within the region of the Moon imaged during EM1. The EM2 coverage provides multispectral data for 10 additional <span class="hlt">craters</span> with superposed <span class="hlt">crater</span> counts. Also, the EM2 data provide improved spatial resolution and signal-to-noise ratios over the western nearside.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMEP41B1838B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMEP41B1838B"><span>Physical Modeling of Flow Over Gale <span class="hlt">Crater</span>, Mars: Laboratory Measurements of Basin Secondary Circulations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bristow, N.; Blois, G.; Kim, T.; Anderson, W.; Day, M. D.; Kocurek, G.; Christensen, K. T.</p> <p>2017-12-01</p> <p>Impact <span class="hlt">craters</span>, common large-scale topographic features on the surface of Mars, are circular depressions delimited by a sharp ridge. A variety of <span class="hlt">crater</span> fill morphologies exist, <span class="hlt">suggesting</span> that complex intracrater circulations affect their evolution. Some large <span class="hlt">craters</span> (diameter > 10 km), particularly at mid latitudes on Mars, exhibit a central mound surrounded by circular moat. Foremost among these examples is Gale <span class="hlt">crater</span>, landing site of NASA's Curiosity rover, since large-scale climatic processes early in in the history of Mars are preserved in the stratigraphic record of the inner mound. Investigating the intracrater flow produced by large scale winds aloft Mars <span class="hlt">craters</span> is key to a number of important scientific issues including ongoing research on Mars paleo-environmental reconstruction and the planning of future missions (these results must be viewed in conjunction with the affects of radial katabatibc flows, the importance of which is already established in preceding studies). In this work we consider a number of <span class="hlt">crater</span> shapes inspired by Gale morphology, including idealized <span class="hlt">craters</span>. Access to the flow field within such geometrically complex topography is achieved herein using a refractive index matched approach. Instantaneous velocity maps, using both planar and volumetric PIV techniques, are presented to elucidate complex three-dimensional flow within the <span class="hlt">crater</span>. In addition, first- and second-order statistics will be discussed in the context of wind-driven (aeolian) excavation of <span class="hlt">crater</span> fill.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.4085L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.4085L"><span>Are pre-<span class="hlt">crater</span> mounds gas-inflated?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Leibman, Marina; Kizyakov, Alexandr; Khomutov, Artem; Dvornikov, Yury; Babkina, Elena; Arefiev, Stanislav; Khairullin, Rustam</p> <p>2017-04-01</p> <p>Gas-emission <span class="hlt">craters</span> (GEC) on Yamal peninsula, which occupied minds of researches for the last couple of years since first discovered in 2014, appeared to form on the place of specifically shaped mounds. There was a number of hypotheses involving pingo as an origin of these mounds. This arouse an interest in mapping pingo thus marking the areas of GEC formation risk. Our field research allows us to <span class="hlt">suggest</span> that remote-sensing-based mapping of pingo may result in mix up of mounds of various origin. Thus, we started with classification of the mounds based on remote-sensing, field observations and survey from helicopter. Then we compared indicators of mounds of various classes to the properties of pre-<span class="hlt">crater</span> mounds to conclude on their origin. Summarizing field experience, there are three main mound types on Yamal. (1) Outliers (remnant hills), separated from the main geomorphic landform by erosion. Often these mounds comprise polygonal blocks, kind of "baydzherakh". Their indicators are asymmetry (short gentle slope towards the main landform, and steep slope often descending into a small pond of thermokarst-nivation origin), often quadrangle or conic shape, and large size. (2) Pingo, appear within the khasyrei (drain lake basin); often are characterized by open cracks resulting from expansion of polygonal network formed when re-freezing of lake talik prior to pingo formation; old pingo may bear traces of collapse on the top, with depression which differs from the GEC by absence of parapet. (3) Frost-heave mounds (excluding pingo) may form on deep active layer, reducing due to moss-peat formation and forming ice lenses from an active layer water, usually they appear in the drainage hollows, valley bottoms, drain-lake basins periphery. These features are smaller than the first two types of mounds. Their tops as a rule are well vegetated. We were unable to find a single or a set of indicators unequivocally defining any specific mound type, thus indicators of pre-<span class="hlt">crater</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017Icar..287..187R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017Icar..287..187R"><span><span class="hlt">Craters</span> of the Pluto-Charon system</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Robbins, Stuart J.; Singer, Kelsi N.; Bray, Veronica J.; Schenk, Paul; Lauer, Tod R.; Weaver, Harold A.; Runyon, Kirby; McKinnon, William B.; Beyer, Ross A.; Porter, Simon; White, Oliver L.; Hofgartner, Jason D.; Zangari, Amanda M.; Moore, Jeffrey M.; Young, Leslie A.; Spencer, John R.; Binzel, Richard P.; Buie, Marc W.; Buratti, Bonnie J.; Cheng, Andrew F.; Grundy, William M.; Linscott, Ivan R.; Reitsema, Harold J.; Reuter, Dennis C.; Showalter, Mark R.; Tyler, G. Len; Olkin, Catherine B.; Ennico, Kimberly S.; Stern, S. Alan; New Horizons Lorri, Mvic Instrument Teams</p> <p>2017-05-01</p> <p>NASA's New Horizons flyby mission of the Pluto-Charon binary system and its four moons provided humanity with its first spacecraft-based look at a large Kuiper Belt Object beyond Triton. Excluding this system, multiple Kuiper Belt Objects (KBOs) have been observed for only 20 years from Earth, and the KBO size distribution is unconstrained except among the largest objects. Because small KBOs will remain beyond the capabilities of ground-based observatories for the foreseeable future, one of the best ways to constrain the small KBO population is to examine the <span class="hlt">craters</span> they have made on the Pluto-Charon system. The first step to understanding the <span class="hlt">crater</span> population is to map it. In this work, we describe the steps undertaken to produce a robust <span class="hlt">crater</span> database of impact features on Pluto, Charon, and their two largest moons, Nix and Hydra. These include an examination of different types of images and image processing, and we present an analysis of variability among the <span class="hlt">crater</span> mapping team, where <span class="hlt">crater</span> diameters were found to average ± 10% uncertainty across all sizes measured (∼0.5-300 km). We also present a few basic analyses of the <span class="hlt">crater</span> databases, finding that Pluto's <span class="hlt">craters</span>' differential size-frequency distribution across the encounter hemisphere has a power-law slope of approximately -3.1 ± 0.1 over diameters D ≈ 15-200 km, and Charon's has a slope of -3.0 ± 0.2 over diameters D ≈ 10-120 km; it is significantly shallower on both bodies at smaller diameters. We also better quantify evidence of resurfacing evidenced by Pluto's <span class="hlt">craters</span> in contrast with Charon's. With this work, we are also releasing our database of potential and probable impact <span class="hlt">craters</span>: 5287 on Pluto, 2287 on Charon, 35 on Nix, and 6 on Hydra.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20170007522&hterms=ross&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAuthor-Name%26N%3D0%26No%3D10%26Ntt%3DWill%2Bross','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20170007522&hterms=ross&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAuthor-Name%26N%3D0%26No%3D10%26Ntt%3DWill%2Bross"><span><span class="hlt">Craters</span> of the Pluto-Charon System</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Robbins, Stuart J.; Singer, Kelsi N.; Bray, Veronica J.; Schenk, Paul; Lauer, Todd R.; Weaver, Harold A.; Runyon, Kirby; Mckinnon, William B.; Beyer, Ross A.; Porter, Simon; <a style="text-decoration: none; " href="javascript:void(0); " onClick="displayelement('author_20170007522'); toggleEditAbsImage('author_20170007522_show'); toggleEditAbsImage('author_20170007522_hide'); "> <img style="display:inline; width:12px; height:12px; " src="images/arrow-up.gif" width="12" height="12" border="0" alt="hide" id="author_20170007522_show"> <img style="width:12px; height:12px; display:none; " src="images/arrow-down.gif" width="12" height="12" border="0" alt="hide" id="author_20170007522_hide"></p> <p>2016-01-01</p> <p>NASA's New Horizons flyby mission of the Pluto-Charon binary system and its four moons provided humanity with its first spacecraft-based look at a large Kuiper Belt Object beyond Triton. Excluding this system, multiple Kuiper Belt Objects (KBOs) have been observed for only 20 years from Earth, and the KBO size distribution is unconstrained except among the largest objects. Because small KBOs will remain beyond the capabilities of ground-based observatories for the foreseeable future, one of the best ways to constrain the small KBO population is to examine the <span class="hlt">craters</span> they have made on the Pluto-Charon system. The first step to understanding the <span class="hlt">crater</span> population is to map it. In this work, we describe the steps undertaken to produce a robust <span class="hlt">crater</span> database of impact features on Pluto, Charon, and their two largest moons, Nix and Hydra. These include an examination of different types of images and image processing, and we present an analysis of variability among the <span class="hlt">crater</span> mapping team, where <span class="hlt">crater</span> diameters were found to average +/-10% uncertainty across all sizes measured (approx.0.5-300 km). We also present a few basic analyses of the <span class="hlt">crater</span> databases, finding that Pluto's <span class="hlt">craters</span>' differential size-frequency distribution across the encounter hemisphere has a power-law slope of approximately -3.1 +/- 0.1 over diameters D approx. = 15-200 km, and Charon's has a slope of -3.0 +/- 0.2 over diameters D approx. = 10-120 km; it is significantly shallower on both bodies at smaller diameters. We also better quantify evidence of resurfacing evidenced by Pluto's <span class="hlt">craters</span> in contrast with Charon's. With this work, we are also releasing our database of potential and probable impact <span class="hlt">craters</span>: 5287 on Pluto, 2287 on Charon, 35 on Nix, and 6 on Hydra.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009M%26PS...44...43O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009M%26PS...44...43O"><span>Layered ejecta <span class="hlt">craters</span> and the early water/ice aquifer on Mars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Oberbeck, V. R.</p> <p>2009-03-01</p> <p>A model for emplacement of deposits of impact <span class="hlt">craters</span> is presented that explains the size range of Martian layered ejecta <span class="hlt">craters</span> between 5 km and 60 km in diameter in the low and middle latitudes. The impact model provides estimates of the water content of <span class="hlt">crater</span> deposits relative to volatile content in the aquifer of Mars. These estimates together with the amount of water required to initiate fluid flow in terrestrial debris flows provide an estimate of 21% by volume (7.6 × 107 km3) of water/ice that was stored between 0.27 and 2.5 km depth in the crust of Mars during Hesperian and Amazonian time. This would have been sufficient to supply the water for an ocean in the northern lowlands of Mars. The existence of fluidized <span class="hlt">craters</span> smaller than 5 km diameter in some places on Mars <span class="hlt">suggests</span> that volatiles were present locally at depths less than 0.27 km. Deposits of Martian <span class="hlt">craters</span> may be ideal sites for searches for fossils of early organisms that may have existed in the water table if life originated on Mars.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018LPICo2047.6109H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018LPICo2047.6109H"><span>The Nonrandom Distribution of Interior Landforms for 100-km Diameter <span class="hlt">Craters</span> on Mercury <span class="hlt">Suggests</span> Regional Variations in Near-Surface Mechanical Properties</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Herrick, R. R.</p> <p>2018-05-01</p> <p>There is great diversity of appearance in the interiors of 100-km diameter <span class="hlt">craters</span>. The spatial distribution of interior landforms is clustered and nonrandom, but does not clearly correlate with Mercury's surface geology patterns.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19920001654','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19920001654"><span>Characteristics of ejecta and alluvial deposits at Meteor <span class="hlt">Crater</span>, Arizona and Odessa <span class="hlt">Craters</span>, Texas: Results from ground penetrating radar</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Grant, J. A.; Schultz, P. H.</p> <p>1991-01-01</p> <p>Previous ground penetrating radar (GRP) studies around 50,000 year old Meteor <span class="hlt">Crater</span> revealed the potential for rapid, inexpensive, and non-destructive sub-surface investigations for deep reflectors (generally greater than 10 m). New GRP results are summarized focusing the shallow sub-surfaces (1-2 m) around Meteor <span class="hlt">Crater</span> and the main <span class="hlt">crater</span> at Odessa. The following subject areas are covered: (1) the thickness, distribution, and nature of the contact between surrounding alluvial deposits and distal ejecta; and (2) stratigraphic relationships between both the ejecta and alluvium derived from both pre and post <span class="hlt">crater</span> drainages. These results support previous conclusions indicating limited vertical lowering (less than 1 m) of the distal ejecta at Meteor <span class="hlt">Crater</span> and allow initial assessment of the gradational state if the Odessa <span class="hlt">craters</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70010158','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70010158"><span>Lonar Lake, India: An impact <span class="hlt">Crater</span> in basalt</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Fredriksson, K.; Dube, A.; Milton, D.J.; Balasundaram, M.S.</p> <p>1973-01-01</p> <p>Discovery of shock-metamorphosed material establishes the impact origin of Lonar <span class="hlt">Crater</span>. Coarse breccia with shatter coning and microbreccia with moderately shocked fragments containing maskelynite were found in drill holes through the <span class="hlt">crater</span> floor. Trenches on the rim yield strongly shocked fragments in which plagioclase has melted and vesiculated, and bombs and spherules of homogeneous rock melt. As the only known terrestrial impact <span class="hlt">crater</span> in basalt, Lonar <span class="hlt">Crater</span> provides unique opportunities for comparison with lunar <span class="hlt">craters</span>. In particular, microbreccias and glass spherules from Lonar <span class="hlt">Crater</span> have close analogs among the Apollo specimens.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70037266','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70037266"><span>Geology of the Selk <span class="hlt">crater</span> region on Titan from Cassini VIMS observations</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Soderblom, J.M.; Brown, R.H.; Soderblom, L.A.; Barnes, J.W.; Jaumann, R.; Le Mouélic, Stéphane; Sotin, Christophe; Stephan, K.; Baines, K.H.; Buratti, B.J.; Clark, R.N.; Nicholson, P.D.</p> <p>2010-01-01</p> <p> in the lee of Selk <span class="hlt">crater</span> by fluid flow. Vestigial circular outlines in this feature just east of Selk's ejecta blanket <span class="hlt">suggest</span> that this might be a remnant of an ancient, <span class="hlt">cratered</span> crust. Evidently the southern margin of the feature has sufficient relief to prevent the encroachment of dunes from the Belet dune field. We conclude that this feature either represents a relatively high-viscosity, fluidized-ejecta flow (a class intermediate to ejecta blankets and long venusian-style ejecta flows) or a streamlined upland remnant that formed downstream from the <span class="hlt">crater</span> by erosive fluid flow from the west-northwest. ?? 2010 Elsevier Inc.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19930020183','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19930020183"><span>Interplanetary meteoroid debris in LDEF metal <span class="hlt">craters</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Brownlee, D. E.; Joswiak, D.; Bradley, J.; Hoerz, Friedrich</p> <p>1993-01-01</p> <p>We have examined <span class="hlt">craters</span> in Al and Au LDEF surfaces to determine the nature of meteoroid residue in the rare cases where projectile material is abundantly preserved in the <span class="hlt">crater</span> floor. Typical <span class="hlt">craters</span> contain only small amounts of residue and we find that less than 10 percent of the <span class="hlt">craters</span> in Al have retained abundant residue consistent with survival of a significant fraction (greater than 20 percent) of the projectile mass. The residue-rich <span class="hlt">craters</span> can usually be distinguished optically because their interiors are darker than ones with little or no apparent projectile debris. The character of the meteoroid debris in these <span class="hlt">craters</span> ranges from thin glass liners, to thick vesicular glass containing unmelted mineral fragments, to debris dominated by unmelted mineral fragments. In the best cases of meteoroid survival, unmelted mineral fragments preserve both information on projectile mineralogy as well as other properties such as nuclear tracks caused by solar flare irradiation. The wide range of the observed abundance and alteration state of projectile residue is most probably due to differences in impact velocity. The <span class="hlt">crater</span> liners are being studied to determine the composition of meteoroids reaching the Earth. The compositional types most commonly seen in the <span class="hlt">craters</span> are: (1) chondritic (Mg, Si, S, Fe in approximately solar proportions), (2) Mg silicate. amd (3) iron sulfide. These are also the most common compositional types of extraterrestrial particle types collected in the stratosphere. The correlation between these compositions indicates that vapor fractionation was not a major process influencing residue composition in these <span class="hlt">craters</span>. Although the biases involved with finding analyzable meteoroid debris in metal <span class="hlt">craters</span> differ from those for extraterrestrial particles collected in and below the atmosphere, there is a common bias favoring particles with low entry velocity. For <span class="hlt">craters</span> this is very strong and probably all of the metal <span class="hlt">craters</span> with abundant</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19930005181','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19930005181"><span>Impact <span class="hlt">craters</span> on Venus: An overview from Magellan observations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Schaber, G. G.; Strom, R. G.; Moore, H. J.; Soderblom, L. A.; Kirk, R. L.; Chadwick, D. J.; Dawson, D. D.; Gaddis, L. R.; Boyce, J. M.; Russell, J.</p> <p>1992-01-01</p> <p>Magellan has revealed an ensemble of impact <span class="hlt">craters</span> on Venus that is unique in many important ways. We have compiled a database describing 842 <span class="hlt">craters</span> on 89 percent of the planet's surface mapped through orbit 2578 (the <span class="hlt">craters</span> range in diameter from 1.5 to 280 km). We have studied the distribution, size-frequency, morphology, and geology of these <span class="hlt">craters</span> both in aggregate and, for some <span class="hlt">craters</span>, in more detail. We have found the following: (1) the spatial distribution of <span class="hlt">craters</span> is highly uniform; (2) the size-density distribution of <span class="hlt">craters</span> with diameters greater than or equal to 35 km is consistent with a 'production' population having a surprisingly young age of about 0.5 Ga (based on the estimated population of Venus-crossing asteroids); (3) the spectrum of <span class="hlt">crater</span> modification differs greatly from that on other planets--62 percent of all <span class="hlt">craters</span> are pristine, only 4 percent volcanically embayed, and the remainder affected by tectonism, but none are severely and progressively depleted based on size-density distribution extrapolated from larger <span class="hlt">craters</span>; (4) large <span class="hlt">craters</span> have a progression of morphologies generally similar to those on other planets, but small <span class="hlt">craters</span> are typically irregular or multiple rather than bowl shaped; (5) diffuse radar-bright or -dark features surround some <span class="hlt">craters</span>, and about 370 similar diffuse 'splotches' with no central <span class="hlt">crater</span> are observed whose size-density distribution is similar to that of small <span class="hlt">craters</span>; and (6) other features unique to Venus include radar-bright or -dark parabolic arcs opening westward and extensive outflows originating in <span class="hlt">crater</span> ejecta.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20090014052&hterms=mass+wasting&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dmass%2Bwasting','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20090014052&hterms=mass+wasting&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dmass%2Bwasting"><span>Degradation of Victoria <span class="hlt">Crater</span>, Mars</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wilson, Sharon A.; Grant, John A.; Cohen, Barbara A.; Golombek, Mathew P.; Geissler, Paul E.; Sullivan, Robert J.; Kirk, Randolph L.; Parker, Timothy J.</p> <p>2008-01-01</p> <p>The $\\sim$750 m diameter and $\\sim$75 m deep Victoria <span class="hlt">crater</span> in Meridiani Planum, Mars, presents evidence for significant degradation including a low, serrated, raised rim characterized by alternating alcoves and promontories, a surrounding low relief annulus, and a floor partially covered by dunes. The amount and processes of degradation responsible for the modified appearance of Victoria <span class="hlt">crater</span> were evaluated using images obtained in situ by the Mars Exploration Rover Opportunity in concert with a digital elevation model created using orbital HiRISE images. Opportunity traversed along the north and northwest rim and annulus, but sufficiently characterized features visible in the DEM to enable detailed measurements of rim relief, ejecta thickness, and wall slopes around the entire degraded, primary impact structure. Victoria retains a 5 m raised rim consisting of 1-2 m of uplifted rocks overlain by 3 m of ejecta at the rim crest. The rim is $\\sim$120 to 220 m wide and is surrounded by a dark annulus reaching an average of 590 m beyond the raised rim. Comparison between observed morphology and that expected for pristine <span class="hlt">craters</span> 500 to 750 m across indicate the original, pristine <span class="hlt">crater</span> was close to 600 m in diameter. Hence, the <span class="hlt">crater</span> has been erosionally widened by approximately 150 m and infilled by about 50 m of sediments. Eolian processes are responsible for modification at Victoria, but lesser contributions from mass wasting or other processes cannot be ruled out. Erosion by prevailing winds is most significant along the exposed rim and upper walls and accounts for $\\sim$50 m widening across a WNW-ESE diameter. The volume of material eroded from the <span class="hlt">crater</span> walls and rim is $\\sim$20% less than the volume of sediments partially filling the <span class="hlt">crater</span>, indicating eolian infilling from sources outside the <span class="hlt">crater</span> over time. The annulus formed when $\\sim$1 m deflation of the ejecta created a lag of more resistant hematite spherules that trapped darker, regional</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA19766.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA19766.html"><span><span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2015-09-03</p> <p>This relatively young <span class="hlt">crater</span> is located on the northern plains of Arcadia Planitia. Orbit Number: 60388 Latitude: 61.6777 Longitude: 228.91 Instrument: VIS Captured: 2015-07-26 03:01 http://photojournal.jpl.nasa.gov/catalog/PIA19766</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20100003189','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20100003189"><span>Creation of High Resolution Terrain Models of Barringer Meteorite <span class="hlt">Crater</span> (Meteor <span class="hlt">Crater</span>) Using Photogrammetry and Terrestrial Laser Scanning Methods</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Brown, Richard B.; Navard, Andrew R.; Holland, Donald E.; McKellip, Rodney D.; Brannon, David P.</p> <p>2010-01-01</p> <p>Barringer Meteorite <span class="hlt">Crater</span> or Meteor <span class="hlt">Crater</span>, AZ, has been a site of high interest for lunar and Mars analog <span class="hlt">crater</span> and terrain studies since the early days of the Apollo-Saturn program. It continues to be a site of exceptional interest to lunar, Mars, and other planetary <span class="hlt">crater</span> and impact analog studies because of its relatively young age (est. 50 thousand years) and well-preserved structure. High resolution (2 meter to 1 decimeter) digital terrain models of Meteor <span class="hlt">Crater</span> in whole or in part were created at NASA Stennis Space Center to support several lunar surface analog modeling activities using photogrammetric and ground based laser scanning techniques. The dataset created by this activity provides new and highly accurate 3D models of the inside slope of the <span class="hlt">crater</span> as well as the downslope rock distribution of the western ejecta field. The data are presented to the science community for possible use in furthering studies of Meteor <span class="hlt">Crater</span> and impact <span class="hlt">craters</span> in general as well as its current near term lunar exploration use in providing a beneficial test model for lunar surface analog modeling and surface operation studies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Icar..273..164K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Icar..273..164K"><span>Geomorphologic mapping of the lunar <span class="hlt">crater</span> Tycho and its impact melt deposits</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Krüger, T.; van der Bogert, C. H.; Hiesinger, H.</p> <p>2016-07-01</p> <p>Using SELENE/Kaguya Terrain Camera and Lunar Reconnaissance Orbiter Camera (LROC) data, we produced a new, high-resolution (10 m/pixel), geomorphological and impact melt distribution map for the lunar <span class="hlt">crater</span> Tycho. The distal ejecta blanket and <span class="hlt">crater</span> rays were investigated using LROC wide-angle camera (WAC) data (100 m/pixel), while the fine-scale morphologies of individual units were documented using high resolution (∼0.5 m/pixel) LROC narrow-angle camera (NAC) frames. In particular, Tycho shows a large coherent melt sheet on the <span class="hlt">crater</span> floor, melt pools and flows along the terraced walls, and melt pools on the continuous ejecta blanket. The <span class="hlt">crater</span> floor of Tycho exhibits three distinct units, distinguishable by their elevation and hummocky surface morphology. The distribution of impact melt pools and ejecta, as well as topographic asymmetries, support the formation of Tycho as an oblique impact from the W-SW. The asymmetric ejecta blanket, significantly reduced melt emplacement uprange, and the depressed uprange <span class="hlt">crater</span> rim at Tycho <span class="hlt">suggest</span> an impact angle of ∼25-45°.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70178874','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70178874"><span><span class="hlt">Cratering</span> on Ceres: Implications for its crust and evolution</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Hiesinger, H.; Marchi, S.; Schmedemann, N.; Schenk, P.; Pasckert, J. H.; Neesemann, A.; O'Brien, D. P.; Kneissl, T.; Ermakov, A.; Fu, R.R.; Bland, M. T.; Nathues, A.; Platz, T.; Williams, D.A.; Jaumann, R.; Castillo-Rogez, J. C.; Ruesch, O.; Schmidt, B.; Park, R.S.; Preusker, F.; Buczkowski, D.L.; Russell, C.T.; Raymond, C.A.</p> <p>2016-01-01</p> <p>Thermochemical models have predicted that Ceres, is to some extent, differentiated and should have an icy crust with few or no impact <span class="hlt">craters</span>. We present observations by the Dawn spacecraft that reveal a heavily <span class="hlt">cratered</span> surface, a heterogeneous <span class="hlt">crater</span> distribution, and an apparent absence of large <span class="hlt">craters</span>. The morphology of some impact <span class="hlt">craters</span> is consistent with ice in the subsurface, which might have favored relaxation, yet large unrelaxed <span class="hlt">craters</span> are also present. Numerous <span class="hlt">craters</span> exhibit polygonal shapes, terraces, flowlike features, slumping, smooth deposits, and bright spots. <span class="hlt">Crater</span> morphology and simple-to-complex <span class="hlt">crater</span> transition diameters indicate that the crust of Ceres is neither purely icy nor rocky. By dating a smooth region associated with the Kerwan <span class="hlt">crater</span>, we determined absolute model ages (AMAs) of 550 million and 720 million years, depending on the applied chronology model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA00420&hterms=mass+wasting&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dmass%2Bwasting','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA00420&hterms=mass+wasting&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dmass%2Bwasting"><span><span class="hlt">Crater</span> Moreux</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1997-01-01</p> <p>Color image of part of the Ismenius Lacus region of Mars (MC-5 quadrangle) containing the impact <span class="hlt">crater</span> Moreux (right center); north toward top. The scene shows heavily <span class="hlt">cratered</span> highlands in the south on relatively smooth lowland plains in the north separated by a belt of dissected terrain, containing flat-floored valleys, mesas, and buttes. This image is a composite of Viking medium-resolution images in black and white and low-resolution images in color. The image extends from latitude 36 degrees N. to 50 degrees N. and from longitude 310 degrees to 340 degrees; Lambert conformal conic projection. The dissected terrain along the highlands/lowlands boundary consists of the flat-floored valleys of Deuteronilus Mensae (on left) and Prontonilus Mensae (on right) and farther north the small, rounded hills of knobby terrain. Flows on the mensae floors contain striae that run parallel to valley walls; where valleys meet, the striae merge, similar to medial moraines on glaciers. Terraces within the valley hills have been interpreted as either layered rocks or wave terraces. The knobby terrain has been interpreted as remnants of the old, densely <span class="hlt">cratered</span> highland terrain perhaps eroded by mass wasting.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19870008162','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19870008162"><span>Zhamanshin meteor <span class="hlt">crater</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Florenskiy, P. V.; Dabizha, A. I.</p> <p>1987-01-01</p> <p>A historical survey and geographic, geologic and geophysical characteristics, the results of many years of study of the Zhamanshin meteor <span class="hlt">crater</span> in the Northern Aral region, are reported. From this data the likely initial configuration and cause of formation of the <span class="hlt">crater</span> are reconstructed. Petrographic and mineralogical analyses are given of the brecciated and remelted rocks, of the zhamanshinites and irgizite tektites in particular. The impact melting, dispersion and quenching processes resulting in tektite formation are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1992Metic..27...21M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1992Metic..27...21M"><span>Impact <span class="hlt">craters</span> - Are they useful?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Masaitis, V. L.</p> <p>1992-03-01</p> <p>Terrestrial impact <span class="hlt">craters</span> are important geological and geomorphological objects that are significant not only for scientific research but for industrial and commercial purposes. The structures may contain commercial minerals produced directly by thermodynamic transformation of target rocks (including primary forming ores) controlled by some morphological, structural or lithological factors and exposed in the <span class="hlt">crater</span>. Iron and uranium ores, nonferrous metals, diamonds, coals, oil shales, hydrocarbons, mineral waters and other raw materials occur in impact <span class="hlt">craters</span>. Impact morphostructures may be used for underground storage of gases or liquid waste material. Surface <span class="hlt">craters</span> may serve as reservoirs for hydropower. These ring structures may be of value to society in other ways. Scientific investigation of them is especially important in comparative planetology, terrestrial geology and in other divisions of the natural sciences.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120009640','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120009640"><span>Brightening and Volatile Distribution Within Shackleton <span class="hlt">Crater</span> Observed by the LRO Laser Altimeter.</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Smith, D. E.; Zuber, M. T.; Head, J. W.; Neumann, G. A.; Mazarico, E.; Torrence, M. H.; Aharonson, O.; Tye, A. R.; Fassett, C. I.; Rosengurg, M. A.; <a style="text-decoration: none; " href="javascript:void(0); " onClick="displayelement('author_20120009640'); toggleEditAbsImage('author_20120009640_show'); toggleEditAbsImage('author_20120009640_hide'); "> <img style="display:inline; width:12px; height:12px; " src="images/arrow-up.gif" width="12" height="12" border="0" alt="hide" id="author_20120009640_show"> <img style="width:12px; height:12px; display:none; " src="images/arrow-down.gif" width="12" height="12" border="0" alt="hide" id="author_20120009640_hide"></p> <p>2012-01-01</p> <p>Shackleton <span class="hlt">crater</span>, whose interior lies largely in permanent shadow, is of interest due to its potential to sequester volatiles. Observations from the Lunar Orbiter Laser Altimeter onboard the Lunar Reconnaissance Orbiter have enabled an unprecedented topographic characterization, revealing Shackleton to be an ancient, unusually well-preserved simple <span class="hlt">crater</span> whose interior walls are fresher than its floor and rim. Shackleton floor deposits are nearly the same age as the rim, <span class="hlt">suggesting</span> little floor deposition since <span class="hlt">crater</span> formation over 3 billion years ago. At 1064 nm the floor of Shackleton is brighter than the surrounding terrain and the interiors of nearby <span class="hlt">craters</span>, but not as bright as the interior walls. The combined observations are explainable primarily by downslope movement of regolith on the walls exposing fresher underlying material. The relatively brighter <span class="hlt">crater</span> floor is most simply explained by decreased space weathering due to shadowing, but a 1-mm-thick layer containing approx 20% surficial ice is an alternative possibility.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA03961&hterms=Butterfly&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DButterfly','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA03961&hterms=Butterfly&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DButterfly"><span>Small Impact <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2005-01-01</p> <p><p/> 22 June 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a small impact <span class="hlt">crater</span> with a 'butterfly' ejecta pattern. The butterfly pattern results from an oblique impact. Not all oblique impacts result in an elliptical <span class="hlt">crater</span>, but they can result in a non-radial pattern of ejecta distribution. The two-toned nature of the ejecta -- with dark material near the <span class="hlt">crater</span> and brighter material further away -- might indicate the nature of subsurface materials. Below the surface, there may be a layer of lighter-toned material, underlain by a layer of darker material. The impact throws these materials out in a pattern that reflects the nature of the underlying layers. <p/> <i>Location near</i>: 3.7oN, 348.2oW <i>Image width</i>: 3 km (1.9 mi) <i>Illumination from</i>: lower left <i>Season</i>: Northern Autumn</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA01090&hterms=Top+secrets&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DTop%2Bsecrets','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA01090&hterms=Top+secrets&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DTop%2Bsecrets"><span>Khensu <span class="hlt">Crater</span> on Ganymede</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1997-01-01</p> <p>The dark-floored <span class="hlt">crater</span>, Khensu, is the target of this image of Ganymede. The solid state imaging camera on NASA's Galileo spacecraft imaged this region as it passed Ganymede during its second orbit through the Jovian system. Khensu is located at 2 degrees latitude and 153 degrees longitude in a region of bright terrain known as Uruk Sulcus, and is about 13 kilometers (8 miles) in diameter. Like some other <span class="hlt">craters</span> on Ganymede, it possesses an unusually dark floor and a bright ejecta blanket. The dark component may be residual material from the impactor that formed the <span class="hlt">crater</span>. Another possibility is that the impactor may have punched through the bright surface to reveal a dark layer beneath.<p/>Another large <span class="hlt">crater</span> named El is partly visible in the top-right corner of the image. This <span class="hlt">crater</span> is 54 kilometers (34 miles) in diameter and has a small 'pit' in its center. <span class="hlt">Craters</span> with such a 'central pit' are common across Ganymede and are especially intriguing since they may reveal secrets about the structure of the satellite's shallow subsurface.<p/>North is to the top-left of the picture and the sun illuminates the surface from nearly overhead. The image covers an area about 100 kilometers (62 miles) by 86 kilometers (54 miles) across at a resolution of 111 meters (370 feet) per picture element. The image was taken on September 6, 1996 by the solid state imaging (CCD) system on NASA's Galileo spacecraft.<p/>The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).<p/>This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA01176&hterms=Dark+web&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DDark%2Bweb','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA01176&hterms=Dark+web&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DDark%2Bweb"><span>Europa's Pwyll <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1998-01-01</p> <p>This view of the Pwyll impact <span class="hlt">crater</span> on Jupiter's moon Europa taken by NASA's Galileo spacecraft shows the interior structure and surrounding ejecta deposits. Pwyll's location is shown in the background global view taken by Galileo's camera on December 16, 1997. Bright rays seen radiating from Pwyll in the global image indicate that this <span class="hlt">crater</span> is geologically young. The rim of Pwyll is about 26 kilometers (16 miles) in diameter, and a halo of dark material excavated from below the surface extends a few kilometers beyond the rim. Beyond this dark halo, the surface is bright and numerous secondary <span class="hlt">craters</span> can be seen. The closeup view of Pwyll, which combines imaging data gathered during the December flyby and the flyby of February 20, 1997, indicates that unlike most fresh impact <span class="hlt">craters</span>, which have much deeper floors, Pwyll's <span class="hlt">crater</span> floor is at approximately the same level as the surrounding background terrain.<p/>North is to the top of the picture and the sun illuminates the surface from the northeast. This closeup image, centered at approximately 26 degrees south latitude and 271 degrees west longitude, covers an area approximately 125 by 75 kilometers (75 by 45 miles). The finest details that can be discerned in this picture are about 250 meters (800 feet) across. This image was taken on at a range of 12,400 kilometers (7,400 miles), with the green filter of Galileo's solid state imaging system.<p/>The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).<p/>This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://www.jpl.nasa.gov/ galileo.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA09928&hterms=duck+hazard&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dduck%2Bhazard','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA09928&hterms=duck+hazard&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dduck%2Bhazard"><span>Inside Victoria <span class="hlt">Crater</span> for Extended Exploration</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2007-01-01</p> <p><p/> After a finishing an in-and-out maneuver to check wheel slippage near the rim of Victoria <span class="hlt">Crater</span>, NASA's Mars Exploration Rover Opportunity re-entered the <span class="hlt">crater</span> during the rover's 1,293rd Martian day, or sol, (Sept. 13, 2007) to begin a weeks-long exploration of the inner slope. <p/> Opportunity's front hazard-identification camera recorded this wide-angle view looking down into and across the <span class="hlt">crater</span> at the end of the day's drive. The rover's position was about six meters (20 feet) inside the rim, in the 'Duck Bay' alcove of the <span class="hlt">crater</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA10077&hterms=duck+hazard&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dduck%2Bhazard','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA10077&hterms=duck+hazard&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dduck%2Bhazard"><span>Opportunity at Work Inside Victoria <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2007-01-01</p> <p><p/> NASA Mars Exploration Rover Opportunity used its front hazard-identification camera to capture this wide-angle view of its robotic arm extended to a rock in a bright-toned layer inside Victoria <span class="hlt">Crater</span>. <p/> The image was taken during the rover's 1,322nd Martian day, or sol (Oct. 13, 2007). <p/> Victoria <span class="hlt">Crater</span> has a scalloped shape of alternating alcoves and promontories around the <span class="hlt">crater</span>'s circumference. Opportunity descended into the <span class="hlt">crater</span> two weeks earlier, within an alcove called 'Duck Bay.' Counterclockwise around the rim, just to the right of the arm in this image, is a promontory called 'Cabo Frio.'</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.P11A2500F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.P11A2500F"><span>The curious history of Tethys as evidenced by irregular <span class="hlt">craters</span> and variable tectonism</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ferguson, S. N.; Rhoden, A.; Nayak, M.; Asphaug, E. I.</p> <p>2017-12-01</p> <p>At first glance, the surface of Saturn's moon Tethys appears dominated by <span class="hlt">craters</span> and its large canyon system, Ithaca Chasma. However, high-resolution Cassini imagery reveals a surface rife with curious geologic features, perhaps indicative of non-heliocentric impact populations and, potentially, a history of tectonic activity. We mapped three regions on Tethys to survey the diversity of features present on the surface, determine <span class="hlt">crater</span> counts for each region, map and analyze fracture patterns, and identify constraints on the impactor populations. One study region is just south and west of the Odysseus impact basin (R1), and the other two regions sit slightly west of Ithaca Chasma (R2 and R3). The regions were imaged at average resolutions of 200m/pix, which is adequate to identify <span class="hlt">craters</span> down to D=1km. Of 1200 total <span class="hlt">craters</span> counted, we have identified 195 elliptical <span class="hlt">craters</span> and 28 polygonal <span class="hlt">craters</span>. Elliptical <span class="hlt">craters</span> likely form from slow, oblique impacts, whereas polygonal <span class="hlt">craters</span> are indicative of underlying tectonic structure. We identified 605 small <span class="hlt">craters</span>, D=1-2km, across the three regions; we find that R1 has many more 1-10 km <span class="hlt">craters</span> than R2 and R3. We also mapped 367 linear features. The median and range of orientations of the linear features vary across the regions. Despite their proximity, the orientations of lineations in R2 and R3 are not consistent with the orientation of Ithaca Chasma. This could be <span class="hlt">suggestive</span> of different epochs of tectonic activity on Tethys. When compared with R2 and R3, R1 has more small <span class="hlt">craters</span>, more lineations, and a preferred orientation of lineations that is distinct from the other two regions. Possible causes for a larger population of small <span class="hlt">craters</span> in R1 include secondary <span class="hlt">craters</span> from Odysseus and oblique impacts from debris ejected from Tethys' co-orbital moons, which should create many more 1km <span class="hlt">craters</span> in R1 than the other regions. Due to the oblique impact angles predicted for incoming co-orbital debris, these impacts</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70012230','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70012230"><span>Small impact <span class="hlt">craters</span> in the lunar regolith - Their morphologies, relative ages, and rates of formation</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Moore, H.J.; Boyce, J.M.; Hahn, D.A.</p> <p>1980-01-01</p> <p>Apparently, there are two types of size-frequency distributions of small lunar <span class="hlt">craters</span> (???1-100 m across): (1) <span class="hlt">crater</span> production distributions for which the cumulative frequency of <span class="hlt">craters</span> is an inverse function of diameter to power near 2.8, and (2) steady-state distributions for which the cumulative frequency of <span class="hlt">craters</span> is inversely proportional to the square of their diameters. According to theory, cumulative frequencies of <span class="hlt">craters</span> in each morphologic category within the steady-state should also be an inverse function of the square of their diameters. Some data on frequency distribution of <span class="hlt">craters</span> by morphologic types are approximately consistent with theory, whereas other data are inconsistent with theory. A flux of <span class="hlt">crater</span> producing objects can be inferred from size-frequency distributions of small <span class="hlt">craters</span> on the flanks and ejecta of <span class="hlt">craters</span> of known age. <span class="hlt">Crater</span> frequency distributions and data on the <span class="hlt">craters</span> Tycho, North Ray, Cone, and South Ray, when compared with the flux of objects measured by the Apollo Passive Seismometer, <span class="hlt">suggest</span> that the flux of objects has been relatively constant over the last 100 m.y. (within 1/3 to 3 times of the flux estimated for Tycho). Steady-state frequency distributions for <span class="hlt">craters</span> in several morphologic categories formed the basis for estimating the relative ages of <span class="hlt">craters</span> and surfaces in a system used during the Apollo landing site mapping program of the U.S. Geological Survey. The relative ages in this system are converted to model absolute ages that have a rather broad range of values. The range of values of the absolute ages are between about 1/3 to 3 times the assigned model absolute age. ?? 1980 D. Reidel Publishing Co.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.P53E2187S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.P53E2187S"><span>Geomorphological Evidence for Pervasive Ground Ice on Ceres from Dawn Observations of <span class="hlt">Craters</span> and Flows.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schmidt, B. E.; Chilton, H.; Hughson, K.; Scully, J. E. C.; Russell, C. T.; Sizemore, H. G.; Nathues, A.; Platz, T.; Bland, M. T.; Schenk, P.; Hiesinger, H.; Jaumann, R.; Byrne, S.; Schorghofer, N.; Ammannito, E.; Marchi, S.; O'Brien, D. P.; Sykes, M. V.; Le Corre, L.; Capria, M. T.; Reddy, V.; Raymond, C. A.; Mest, S. C.; Feldman, W. C.</p> <p>2015-12-01</p> <p>Five decades of observations of Ceres' albedo, surface composition, shape and density <span class="hlt">suggest</span> that Ceres is comprised of both silicates and tens of percent of ice. Historical <span class="hlt">suggestions</span> of surficial hydrated silicates and evidence for water emission, coupled with its bulk density of ~2100 kg/m3 and Dawn observations of young <span class="hlt">craters</span> containing high albedo spots support this conclusion. We report geomorphological evidence from survey data demonstrating that evaporative and fluid-flow processes within silicate-ice mixtures are prevalent on Ceres, and indicate that its surface materials contain significant water ice. Here we highlight three classes of features that possess strong evidence for ground ice. First, ubiquitous scalloped and "breached" <span class="hlt">craters</span> are characterized by mass wasting and by the recession of <span class="hlt">crater</span> walls in asymmetric patterns; these appear analogous to scalloped terrain on Mars and protalus lobes formed by mass wasting in terrestrial glaciated regions. The degradation of <span class="hlt">crater</span> walls appears to be responsible for the nearly complete removal of some <span class="hlt">craters</span>, particularly at low latitudes. Second, several high latitude, high elevation <span class="hlt">craters</span> feature lobed flows that emanate from cirque-shaped head walls and bear strikingly similar morphology to terrestrial rock glaciers. These similarities include lobate toes and indications of furrows and ridges consistent with ice-cored or ice-cemented material. Other lobed flows persist at the base of <span class="hlt">crater</span> walls and mass wasting features. Many flow features evidently terminate at ramparts. Third, there are frequent irregular domes, peaks and mounds within <span class="hlt">crater</span> floors that depart from traditional <span class="hlt">crater</span> central peaks or peak complexes. In some cases the irregular domes show evidence for high albedo or activity, and thus given other evidence for ice, these could be due to local melt and extrusion via hydrologic gradients, forming domes similar to pingos. The global distribution of these classes of features</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA03490&hterms=pollution+rims&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dpollution%2Brims','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA03490&hterms=pollution+rims&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dpollution%2Brims"><span>Meteor <span class="hlt">Crater</span>, AZ</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2002-01-01</p> <p>The Barringer Meteorite <span class="hlt">Crater</span> (also known as 'Meteor <span class="hlt">Crater</span>') is a gigantic hole in the middle of the arid sandstone of the Arizona desert. A rim of smashed and jumbled boulders, some of them the size of small houses, rises 50 m above the level of the surrounding plain. The <span class="hlt">crater</span> itself is nearly a 1500 m wide, and 180 m deep. When Europeans first discovered the <span class="hlt">crater</span>, the plain around it was covered with chunks of meteoritic iron - over 30 tons of it, scattered over an area 12 to 15 km in diameter. Scientists now believe that the <span class="hlt">crater</span> was created approximately 50,000 years ago. The meteorite which made it was composed almost entirely of nickel-iron, <span class="hlt">suggesting</span> that it may have originated in the interior of a small planet. It was 50 m across, weighed roughly 300,000 tons, and was traveling at a speed of 65,000 km per hour. This ASTER 3-D perspective view was created by draping an ASTER bands 3-2-1image over a digital elevation model from the US Geological Survey National Elevation Dataset.<p/>This image was acquired on May 17, 2001 by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA's Terra satellite. With its 14 spectral bands from the visible to the thermal infrared wavelength region, and its high spatial resolution of 15 to 90 meters (about 50 to 300 feet), ASTER will image Earth for the next 6 years to map and monitor the changing surface of our planet.<p/>ASTER is one of five Earth-observing instruments launched December 18,1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of Economy, Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, California, is the U.S. Science team leader; Bjorn Eng of JPL is the project manager. ASTER is the only high resolution imaging sensor on Terra. The Terra mission is part of NASA's Earth Science Enterprise, along</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19780060124&hterms=Nuclear+explosion&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DNuclear%2Bexplosion','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19780060124&hterms=Nuclear+explosion&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DNuclear%2Bexplosion"><span>Application of high explosion <span class="hlt">cratering</span> data to planetary problems</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Oberbeck, V. R.</p> <p>1977-01-01</p> <p>The present paper deals with the conditions of explosion or nuclear <span class="hlt">cratering</span> required to simulate impact <span class="hlt">crater</span> formation. Some planetary problems associated with three different aspects of <span class="hlt">crater</span> formation are discussed, and solutions based on high-explosion data are proposed. Structures of impact <span class="hlt">craters</span> and some selected explosion <span class="hlt">craters</span> formed in layered media are examined and are related to the structure of lunar basins. The mode of ejection of material from impact <span class="hlt">craters</span> is identified using explosion analogs. The ejection mode is shown to have important implications for the origin of material in <span class="hlt">crater</span> and basin deposits. Equally important are the populations of secondary <span class="hlt">craters</span> on lunar and planetary surfaces.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140000236','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140000236"><span>Pyroclastic Deposits in the Floor-fractured <span class="hlt">Crater</span> Alphonsus</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Allen, Carlton C.; Donaldson-Hanna, Kerri L.; Pieters, Carle M.; Moriarty, Daniel P.; Greenhagen, Benjamin T.; Bennett, Kristen A.; Kramer, Georgiana Y.; Paige, David A.</p> <p>2013-01-01</p> <p>Alphonsus, the 118 km diameter floor-fractured <span class="hlt">crater</span>, is located immediately east of Mare Nubium. Eleven pyroclastic deposits have been identified on the <span class="hlt">crater</span>'s floor. Early telescopic spectra <span class="hlt">suggest</span> that the floor of Alphonsus is noritic, and that the pyroclastic deposits contain mixtures of floor material and a juvenile component including basaltic glass. Head and Wilson contend that Nubium lavas intruded the breccia zone beneath Alphonsus, forming dikes and fractures on the <span class="hlt">crater</span> floor. In this model, the magma ascended to the level of the mare but cooled underground, and a portion broke thru to the surface in vulcanian (explosive) eruptions. Alternatively, the erupted material could be from a source unrelated to the mare, in the style of regional pyroclastic deposits. High-resolution images and spectroscopy from the Moon Mineralogy Mapper (M3), Diviner Lunar Radiometer, and Lunar Reconnaissance Orbiter Camera Narrow Angle Camera (NAC) provide data to test these formation models. Spectra from M3 confirm that the <span class="hlt">crater</span> floor is primarily composed of noritic material, and that the Nubium lavas are basaltic. Spectra from the three largest pyroclastic deposits in Alphonsus are consistent with a minor low- Ca pyroxene component in a glass-rich matrix. The centers of the 2 micron absorption bands have wavelengths too short to be of the same origin as the Nubium basalts. Diviner Christiansen feature (CF) values were used to estimate FeO abundances for the <span class="hlt">crater</span> floor, Nubium soil, and pyroclastic deposits. The estimated abundance for the <span class="hlt">crater</span> floor (7.5 +/- 1.4 wt.%) is within the range of FeO values for Apollo norite samples. However, the estimated FeO abundance for Nubium soil (13.4 +/- 1.4 wt.%) is lower than those measured in most mare samples. The difference may reflect contamination of the mare soil by highland ejecta. The Diviner-derived FeO abundance for the western pyroclastic deposit is 13.8 +/- 3.3 wt.%. This is lower than the values for mare soil</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/491508','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/491508"><span><span class="hlt">Kaiser</span> Permanente-Sandia National Health Care Model: Phase 1 prototype final report. Part 2 -- Domain analysis</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Edwards, D.; Yoshimura, A.; Butler, D.</p> <p></p> <p>This report describes the results of a Cooperative Research and Development Agreement between Sandia National Laboratories and <span class="hlt">Kaiser</span> Permanente Southern California to develop a prototype computer model of <span class="hlt">Kaiser</span> Permanente`s health care delivery system. As a discrete event simulation, SimHCO models for each of 100,000 patients the progression of disease, individual resource usage, and patient choices in a competitive environment. SimHCO is implemented in the object-oriented programming language C{sup 2}, stressing reusable knowledge and reusable software components. The versioned implementation of SimHCO showed that the object-oriented framework allows the program to grow in complexity in an incremental way. Furthermore, timingmore » calculations showed that SimHCO runs in a reasonable time on typical workstations, and that a second phase model will scale proportionally and run within the system constraints of contemporary computer technology.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015P%26SS..117...45I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015P%26SS..117...45I"><span>Landing site selection for Luna-Glob mission in <span class="hlt">crater</span> Boguslawsky</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ivanov, M. A.; Hiesinger, H.; Abdrakhimov, A. M.; Basilevsky, A. T.; Head, J. W.; Pasckert, J.-H.; Bauch, K.; van der Bogert, C. H.; Gläser, P.; Kohanov, A.</p> <p>2015-11-01</p> <p>Boguslawsky <span class="hlt">crater</span> (72.9°S, 43.3°E, ~100 km in diameter) is a primary target for the Luna-Glob mission. The <span class="hlt">crater</span> has a morphologically smooth (at the resolution of WAC images), flat, and horizontal floor, which is about 55-60 km in diameter. Two ellipses were selected as specific candidate landing areas on the floor: the western ellipse is centered at 72.9°S, 41.3°E and the eastern ellipse is centered at 73.9°S, 43.9°E. Both ellipses represent areas from which Earth is visible during the entire year of 2016 and lack permanently shadowed areas. Boguslawsky <span class="hlt">crater</span> is located on or near the rim of the South Pole-Aitken basin, which provides the unique possibility to sample some of the most ancient rocks on the Moon that probably pre-date the SPA impact event. The low depth/diameter ratio of Boguslawsky <span class="hlt">suggests</span> that the <span class="hlt">crater</span> has been partly filled after its formation. Although volcanic flooding of the <span class="hlt">crater</span> cannot be ruled out, the more likely process of filling of Boguslawsky is the emplacement of ejecta from nearby and remote large <span class="hlt">craters</span>/basins. Three morphologically distinctive units are the most abundant within the selected landing ellipses: rolling plains (rpc), flat plains (fp), and ejecta from <span class="hlt">crater</span> Boguslawsky-D (ejf), which occurs on the eastern wall of Boguslawsky. The possible contribution of materials from unknown sources makes the flat and rolling plains less desirable targets for landing. In contrast, ejecta from Boguslawsky-D represents local materials re-distributed by the Boguslawsky-D impact from the wall onto the floor of Boguslawsky. Thus, this unit, which constitutes about 50% of the eastern landing ellipse, represents a target of clearer provenance and a higher scientific priority.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20080041020','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20080041020"><span>Geologic Mapping of the Martian Impact <span class="hlt">Crater</span> Tooting</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mouginis-Mark, Peter; Boyce, Joseph M.</p> <p>2008-01-01</p> <p>Tooting <span class="hlt">crater</span> is approximately 29 km in diameters, is located at 23.4 deg N, 207.5 deg E and is classified as a multi-layered ejecta <span class="hlt">crater</span>. Tooting <span class="hlt">crater</span> is a very young <span class="hlt">crater</span>, with an estimated age of 700,000 to 2M years. The <span class="hlt">crater</span> formed on virtually flat lava flows within Amazonis Planitia where there appears to have been no major topographic features prior to the impact, so that we can measure ejecta thickness and cavity volume. In the past 12 months, the authors have: published their first detailed analysis of the geometry of the <span class="hlt">crater</span> cavity and the distribution of the ejecta layers; refined the geologic map of the interior of Tooting <span class="hlt">crater</span> through mapping of the cavity at a scale of 1:1100K; and continued the analysis of an increasing number of high resolution images obtained by the CTX and HiRISE instruments. Currently the authors seek to resolve several science issues that have been identified during this mapping, including: what is the origin of the lobate flows on the NW and SW rims of the <span class="hlt">crater</span>?; how did the ejecta curtain break apart during the formation of the <span class="hlt">crater</span>, and how uniform was the emplacement process for the ejecta layers; and, can we infer physical characteristics about the ejecta? Future study plans include the completion of a draft geologic map of Tooting <span class="hlt">crater</span> and submission of it to the U.S. Geological survey for a preliminary review, publishing a second research paper on the detailed geology of the <span class="hlt">crater</span> cavity and the distribution of the flows on the <span class="hlt">crater</span> rim, and completing the map text for the 1:100K geologic map description of units at Tooting <span class="hlt">crater</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JGRE..123..445I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JGRE..123..445I"><span>Wind-Eroded <span class="hlt">Crater</span> Floors and Intercrater Plains, Terra Sabaea, Mars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Irwin, Rossman P.; Wray, James J.; Mest, Scott C.; Maxwell, Ted A.</p> <p>2018-02-01</p> <p>Ancient impact <span class="hlt">craters</span> with wind-eroded layering on their floors provide a record of resurfacing materials and processes on early Mars. In a 54 km Noachian <span class="hlt">crater</span> in Terra Sabaea (20.2°S, 42.6°E), eolian deflation of a friable, dark-toned layer up to tens of meters thick has exposed more resistant, underlying light-toned material. These layers differ significantly from strata of similar tone described in other regions of Mars. The light-toned material has no apparent internal stratification, and visible/near-infrared spectral analysis <span class="hlt">suggests</span> that it is rich in feldspar. Its origin is ambiguous, as we cannot confidently reject igneous, pyroclastic, or clastic alternatives. The overlying dark-toned layer is probably a basaltic siltstone or sandstone that was emplaced mostly by wind, although its weak cementation and inverted fluvial paleochannels indicate some modification by water. Negative-relief channels are not found on the <span class="hlt">crater</span> floor, and fluvial erosion is otherwise weakly expressed in the study area. Small impacts onto this <span class="hlt">crater</span>'s floor have exposed deeper friable materials that appear to contain goethite. Bedrock outcrops on the <span class="hlt">crater</span> walls are phyllosilicate bearing. The intercrater plains contain remnants of a post-Noachian thin, widespread, likely eolian mantle with an indurated surface. Plains near Hellas-concentric escarpments to the north are more consistent with volcanic resurfacing. A 48 km <span class="hlt">crater</span> nearby contains similar dark-over-light outcrops but no paleochannels. Our findings indicate that dark-over-light stratigraphy has diverse origins across Mars and that some dark-toned plains with mafic mineralogy are not of igneous origin.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19730050944&hterms=ghosts&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dghosts','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19730050944&hterms=ghosts&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dghosts"><span>Moon - 'Ghost' <span class="hlt">craters</span> formed during Mare filling.</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cruikshank, D. P.; Hartmann, W. K.; Wood, C. A.</p> <p>1973-01-01</p> <p>This paper discusses formation of 'pathological' cases of <span class="hlt">crater</span> morphology due to interaction of <span class="hlt">craters</span> with molten lavas. Terrestrial observations of such a process are discussed. In lunar maria, a number of small impact <span class="hlt">craters</span> (D less than 10 km) may have been covered by thin layers of fluid lavas, or formed in molten lava. Some specific lunar examples are discussed, including unusual shallow rings resembling experimental <span class="hlt">craters</span> deformed by isostatic filling.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUSM.U33A..08K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUSM.U33A..08K"><span>Impact-generated Hydrothermal Activity at the Chicxulub <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kring, D. A.; Zurcher, L.; Abramov, O.</p> <p>2007-05-01</p> <p>Borehole samples recovered from PEMEX exploration boreholes and an ICDP scientific borehole indicate the Chicxulub impact event generated hydrothermal alteration throughout a large volume of the Maya Block beneath the <span class="hlt">crater</span> floor and extending across the bulk of the ~180 km diameter <span class="hlt">crater</span>. The first indications of hydrothermal alteration were observed in the <span class="hlt">crater</span> discovery samples from the Yucatan-6 borehole and manifest itself in the form of anhydrite and quartz veins. Continuous core from the Yaxcopoil-1 borehole reveal a more complex and temporally extensive alteration sequence: following a brief period at high temperatures, impact- melt-bearing polymict breccias and a thin, underlying unit of impact melt were subjected to metasomatism, producing alkali feldspar, sphene, apatite, and magnetite. As the system continued to cool, smectite-series phyllosilicates appeared. A saline solution was involved. Stable isotopes <span class="hlt">suggest</span> the fluid was dominated by a basinal brine created mostly from existing groundwater of the Yucatan Peninsula, although contributions from down-welling water also occurred in some parts of the system. Numerical modeling of the hydrothermal system <span class="hlt">suggests</span> circulation occurred for 1.5 to 2.3 Myr, depending on the permeability of the system. Our understanding of the hydrothermal system, however, is still crude. Additional core recovery projects, particularly into the central melt sheet, are needed to better evaluate the extent and duration of hydrothermal alteration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1610635H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1610635H"><span>An in-depth study of Marcia <span class="hlt">Crater</span>, Vesta</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hiesinger, Harald; Ruesch, Ottaviano; Williams, David A.; Nathues, Andreas; Prettyman, Thomas H.; Tosi, Frederico; De Sanctis, M. Christina; Scully, Jennifer E. C.; Schenk, Paul M.; Aileen Yingst, R.; Denevi, Bret W.; Jaumann, Ralf; Raymond, Carol A.; Russell, Chris T.</p> <p>2014-05-01</p> <p>After visiting the second most massive asteroid Vesta from July 2011 to September 2012, the Dawn spacecraft is now on its way to asteroid Ceres. Dawn observed Vesta with three instruments: the German Framing Camera (FC), the Italian Visible and InfraRed mapping spectrometer (VIR), and the American Gamma Ray and Neutron Detector (GRaND) [1]. Marcia <span class="hlt">crater</span> (190°E, 10°N; 68 x 58 km) is the largest of three adjacent impact structures: Marcia (youngest), Calpurnia, and Minucia (oldest). It is the largest well-preserved post-Rheasilvia impact <span class="hlt">crater</span>, shows a complex geology [2], is young [2], exhibits evidence for gully-like mass wasting [3], contains the largest location of pitted terrain [4], has smooth impact melt ponds [5], shows enhanced spectral pyroxene signatures on its inner walls [2], and has low abundances of OH and H in comparison to the surrounding low-albedo terrain [6, 7]. Geophysically, the broad region of Marcia and Calpurnia <span class="hlt">craters</span> is characterized by a higher Bouguer gravity, indicating denser material [9]. Williams et al. [2] have produced a detailed geologic map of Marcia <span class="hlt">crater</span> and the surrounding terrain. They identified several units within Marcia <span class="hlt">crater</span>, including bright <span class="hlt">crater</span> material, pitted terrain, and smooth material. Units outside Marcia, include undivided <span class="hlt">crater</span> ejecta material, bright lobate material, dark lobate material, and dark <span class="hlt">crater</span> ray material [2]. Because of its extensive ejecta and fresh appearance, the Marcia impact defines a major stratigraphic event, postdating the Rheasilvia impact [2]. However, the exact age of Marcia <span class="hlt">crater</span> is still under debate. Compositionally, Marcia <span class="hlt">crater</span> is characterized by higher iron abundances, which were interpreted as more basaltic-eucrite-rich materials <span class="hlt">suggesting</span> that this region has not been blanketed by diogenitic materials from large impact events [10, 11]. Using FC data, [13] identified "gray material" associated with the ejecta blanket of Marcia <span class="hlt">crater</span>. This material is characterized</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70035986','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70035986"><span>Columbus <span class="hlt">crater</span> and other possible groundwater-fed paleolakes of Terra Sirenum, Mars</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Wray, J.J.; Milliken, R.E.; Dundas, C.M.; Swayze, G.A.; Andrews-Hanna, J. C.; Baldridge, A.M.; Chojnacki, M.; Bishop, J.L.; Ehlmann, B.L.; Murchie, S.L.; Clark, R.N.; Seelos, F.P.; Tornabene, L.L.; Squyres, S. W.</p> <p>2011-01-01</p> <p>Columbus <span class="hlt">crater</span> in the Terra Sirenum region of the Martian southern highlands contains light-toned layered deposits with interbedded sulfate and phyllosilicate minerals, a rare occurrence on Mars. Here we investigate in detail the morphology, thermophysical properties, mineralogy, and stratigraphy of these deposits; explore their regional context; and interpret the <span class="hlt">crater</span>'s aqueous history. Hydrated mineral-bearing deposits occupy a discrete ring around the walls of Columbus <span class="hlt">crater</span> and are also exposed beneath younger materials, possibly lava flows, on its floor. Widespread minerals identified in the <span class="hlt">crater</span> include gypsum, polyhydrated and monohydrated Mg/Fe-sulfates, and kaolinite; localized deposits consistent with montmorillonite, Fe/Mg-phyllosilicates, jarosite, alunite, and crystalline ferric oxide or hydroxide are also detected. Thermal emission spectra <span class="hlt">suggest</span> abundances of these minerals in the tens of percent range. Other <span class="hlt">craters</span> in northwest Terra Sirenum also contain layered deposits and Al/Fe/Mg-phyllosilicates, but sulfates have so far been found only in Columbus and Cross <span class="hlt">craters</span>. The region's intercrater plains contain scattered exposures of Al-phyllosilicates and one isolated mound with opaline silica, in addition to more common Fe/Mg-phyllosilicates with chlorides. A Late Noachian age is estimated for the aqueous deposits in Columbus, coinciding with a period of inferred groundwater upwelling and evaporation, which (according to model results reported here) could have formed evaporites in Columbus and other <span class="hlt">craters</span> in Terra Sirenum. Hypotheses for the origin of these deposits include groundwater cementation of <span class="hlt">crater</span>-filling sediments and/or direct precipitation from subaerial springs or in a deep (???900 m) paleolake. Especially under the deep lake scenario, which we prefer, chemical gradients in Columbus <span class="hlt">crater</span> may have created a habitable environment at this location on early Mars. ?? 2011 by the American Geophysical Union.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19890008969','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19890008969"><span>Absolute ages from <span class="hlt">crater</span> statistics: Using radiometric ages of Martian samples for determining the Martian <span class="hlt">cratering</span> chronology</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Neukum, G.</p> <p>1988-01-01</p> <p>In the absence of dates derived from rock samples, impact <span class="hlt">crater</span> frequencies are commonly used to date Martian surface units. All models for absolute dating rely on the lunar <span class="hlt">cratering</span> chronology and on the validity of its extrapolation to Martian conditions. Starting from somewhat different lunar chronologies, rather different Martian <span class="hlt">cratering</span> chronologies are found in the literature. Currently favored models are compared. The differences at old ages are significant, the differences at younger ages are considerable and give absolute ages for the same <span class="hlt">crater</span> frequencies as different as a factor of 3. The total uncertainty could be much higher, though, since the ratio of lunar to Martian <span class="hlt">cratering</span> rate which is of basic importance in the models is believed to be known no better than within a factor of 2. Thus, it is of crucial importance for understanding the the evolution of Mars and determining the sequence of events to establish an unambiguous Martian <span class="hlt">cratering</span> chronology from <span class="hlt">crater</span> statistics in combination with clean radiometric ages of returned Martian samples. For the dating goal, rocks should be as pristine as possible from a geologically simple area with a one-stage emplacement history of the local formation. A minimum of at least one highland site for old ages, two intermediate-aged sites, and one very young site is needed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA15083.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA15083.html"><span>Dark Material Associated with and between <span class="hlt">Craters</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2011-11-18</p> <p>This image from NASA Dawn spacecraft shows areas of dark material which are both associated with impact <span class="hlt">craters</span> and between these <span class="hlt">craters</span> on asteroid Vesta. Dark material is seen cropping out of the rims and sides of the larger <span class="hlt">craters</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20020011680','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20020011680"><span>Impact <span class="hlt">Cratering</span> Calculations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ahrens, Thomas J.</p> <p>2001-01-01</p> <p>We examined the von Mises and Mohr-Coulomb strength models with and without damage effects and developed a model for dilatancy. The models and results are given in O'Keefe et al. We found that by incorporating damage into the models that we could in a single integrated impact calculation, starting with the bolide in the atmosphere produce final <span class="hlt">crater</span> profiles having the major features found in the field measurements. These features included a central uplift, an inner ring, circular terracing and faulting. This was accomplished with undamaged surface strengths of approximately 0.1 GPa and at depth strengths of approximately 1.0 GPa. We modeled the damage in geologic materials using a phenomenological approach, which coupled the Johnson-Cook damage model with the CTH code geologic strength model. The objective here was not to determine the distribution of fragment sizes, but rather to determine the effect of brecciated and comminuted material on the <span class="hlt">crater</span> evolution, fault production, ejecta distribution, and final <span class="hlt">crater</span> morphology.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20170001795&hterms=extinction&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dextinction','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20170001795&hterms=extinction&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dextinction"><span>Periodic Impact <span class="hlt">Cratering</span> and Extinction Events Over the Last 260 Million Years</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Rampino, Michael R.; Caldeira, Ken</p> <p>2015-01-01</p> <p>The claims of periodicity in impact <span class="hlt">cratering</span> and biological extinction events are controversial. Anewly revised record of dated impact <span class="hlt">craters</span> has been analyzed for periodicity, and compared with the record of extinctions over the past 260 Myr. A digital circular spectral analysis of 37 <span class="hlt">crater</span> ages (ranging in age from 15 to 254 Myr ago) yielded evidence for a significant 25.8 +/- 0.6 Myr cycle. Using the same method, we found a significant 27.0 +/- 0.7 Myr cycle in the dates of the eight recognized marine extinction events over the same period. The cycles detected in impacts and extinctions have a similar phase. The impact <span class="hlt">crater</span> dataset shows 11 apparent peaks in the last 260 Myr, at least 5 of which correlate closely with significant extinction peaks. These results <span class="hlt">suggest</span> that the hypothesis of periodic impacts and extinction events is still viable.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.P43A2871F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.P43A2871F"><span>Investigations of Ceres's <span class="hlt">Craters</span> with Straightened Rim</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Frigeri, A.; De Sanctis, M. C.; Ammannito, E.; Raponi, A.; Formisano, M.; Ciarniello, M.; Magni, G.; Combe, J. P.; Marchi, S.; Raymond, C. A.; Schwartz, S. J.</p> <p>2017-12-01</p> <p>Dwarf planet Ceres hosts some geological features that are unique in the solar system because its composition, rich in aqueously-altered silicates, is usually found on full-size planets, whereas its mean radius is smaller than most natural satellites in the solar system. For example, the local high-albedo, carbonate-rich areas or faculaeare specific to Ceres; also, the absence of big impact <span class="hlt">crater</span> structures is key to understand the overall mechanical behaviour of the Cerean crust. After the first findings of water ice occurring in the shadowed areas of <span class="hlt">craters</span> on Ceres by the NASA/Dawn mission (1, 2), we analyzed the morphology of <span class="hlt">craters</span> looking for features similar to the ones where the water ice composition has been detected analyzing the data from the VIR spectrometer (3). These <span class="hlt">craters</span> fall outside of the family of polygonal <span class="hlt">craters</span> which are mainly related to regional or global scale tectonics (4). We analyzed the morphology on the base of the global mosaic, the digital terrain model derived by using the stereo photogrammetry method and the single data frames of the Framing Camera. Our investigation started from <span class="hlt">crater</span> Juling, which is characterized by a portion of the rim which forms a straight segment instead of a portion of a circle. This linear <span class="hlt">crater</span> wall is also steep enough that it forms a cliff that is in the shadowed area in all images acquired by Dawn. Very smooth and bright deposits lay at the foot of this <span class="hlt">crater</span>-wall cliff. Then, we identified several other <span class="hlt">craters</span>, relatively fresh, with radius of 2 to 10 kilometers, showing one or two sectors of the <span class="hlt">crater</span>-rim being truncated by a mass-wasting process, probably a rockfall. Our first analysis show that in the selected <span class="hlt">craters</span>, the truncated sectors are always in the north-eastern sector of the rim for the <span class="hlt">craters</span> in the southern hemisphere. Conversely, the <span class="hlt">craters</span> on the northern hemisphere exhibit a truncated rim in their south-eastern sector. Although a more detailed analysis is mandatory</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRE..122.2685S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRE..122.2685S"><span>Impact <span class="hlt">Crater</span> Morphology and the Structure of Europa's Ice Shell</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Silber, Elizabeth A.; Johnson, Brandon C.</p> <p>2017-12-01</p> <p>We performed numerical simulations of impact <span class="hlt">crater</span> formation on Europa to infer the thickness and structure of its ice shell. The simulations were performed using iSALE to test both the conductive ice shell over ocean and the conductive lid over warm convective ice scenarios for a variety of conditions. The modeled <span class="hlt">crater</span> depth-diameter is strongly dependent on the thermal gradient and temperature of the warm convective ice. Our results indicate that both a fully conductive (thin) shell and a conductive-convective (thick) shell can reproduce the observed <span class="hlt">crater</span> depth-diameter and morphologies. For the conductive ice shell over ocean, the best fit is an approximately 8 km thick conductive ice shell. Depending on the temperature (255-265 K) and therefore strength of warm convective ice, the thickness of the conductive ice lid is estimated at 5-7 km. If central features within the <span class="hlt">crater</span>, such as pits and domes, form during <span class="hlt">crater</span> collapse, our simulations are in better agreement with the fully conductive shell (thin shell). If central features form well after the impact, however, our simulations <span class="hlt">suggest</span> that a conductive-convective shell (thick shell) is more likely. Although our study does not provide a firm conclusion regarding the thickness of Europa's ice shell, our work indicates that Valhalla class multiring basins on Europa may provide robust constraints on the thickness of Europa's ice shell.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19940011723','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19940011723"><span>Martian <span class="hlt">crater</span> degradation by eolian processes: Analogy with the Rio Cuarto <span class="hlt">Crater</span> Field, Argentina</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Grant, J. A.; Schultz, P. H.</p> <p>1993-01-01</p> <p>Numerous degraded and rimless <span class="hlt">craters</span> occur across broad areas of the Martian surface that are mantled by thick, unconformable deposits. These regions include Arabia, Mesogaea, Electris, Tempe, the interior and surface to the northwest of Isidis Basin, southern Ismenius Lacus, and the polar layered terrains. Occurrence of the deposits and low regional thermal inertias indicate that at least some accumulated fine-grained sediment (effective particle diameters of 0.1-0.5 mm or coarse silt to medium sand) to a thickness of 100's to 1000's of meters. Most unconformable deposits experienced some eolian modification that may be recent in some locales. Despite the presence of these deposits, simple eolian deposition appears incapable of creating the numerous degraded and rimless <span class="hlt">craters</span> occurring within their limits. Nevertheless, terrestrial analyses of the Rio Cuario <span class="hlt">craters</span> formed into loessoid deposits demonstrates that eolian redistribution of fine-grained sediment in and around <span class="hlt">craters</span> produces degraded morphologies that are analogous to some found in mantled regions on Mars.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150001344','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150001344"><span>The Geology of the Marcia Quadrangle of Asteroid Vesta: Assessing the Effects of Large, Young <span class="hlt">Craters</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Williams, David A.; Denevi, Brett W.; Mittlefehldt, David W.; Mest, Scott C.; Schenk, Paul M.; Yingst, R. Aileen; Buczowski, Debra L.; Scully, Jennifer E. C.; Garry, W. Brent; McCord, Thomas B.; <a style="text-decoration: none; " href="javascript:void(0); " onClick="displayelement('author_20150001344'); toggleEditAbsImage('author_20150001344_show'); toggleEditAbsImage('author_20150001344_hide'); "> <img style="display:inline; width:12px; height:12px; " src="images/arrow-up.gif" width="12" height="12" border="0" alt="hide" id="author_20150001344_show"> <img style="width:12px; height:12px; display:none; " src="images/arrow-down.gif" width="12" height="12" border="0" alt="hide" id="author_20150001344_hide"></p> <p>2014-01-01</p> <p>We used Dawn spacecraft data to identify and delineate geological units and landforms in the Marcia quadrangle of Vesta as a means to assess the role of the large, relatively young impact <span class="hlt">craters</span> Marcia (approximately 63 kilometers diameter) and Calpurnia (approximately 53 kilometers diameter) and their surrounding ejecta field on the local geology. We also investigated a local topographic high with a dark-rayed <span class="hlt">crater</span> named Aricia Tholus, and the impact <span class="hlt">crater</span> Octavia that is surrounded by a distinctive diffuse mantle. <span class="hlt">Crater</span> counts and stratigraphic relations <span class="hlt">suggest</span> that Marcia is the youngest large <span class="hlt">crater</span> on Vesta, in which a putative impact melt on the <span class="hlt">crater</span> floor ranges in age between approximately 40 and 60 million years (depending upon choice of chronology system), and Marcia's ejecta blanket ranges in age between approximately 120 and 390 million years (depending upon choice of chronology system). We interpret the geologic units in and around Marcia <span class="hlt">crater</span> to mark a major Vestan time-stratigraphic event, and that the Marcia Formation is one of the geologically youngest formations on Vesta. Marcia <span class="hlt">crater</span> reveals pristine bright and dark material in its walls and smooth and pitted terrains on its floor. The smooth unit we interpret as evidence of flow of impact melts and (for the pitted terrain) release of volatiles during or after the impact process. The distinctive dark ejecta surrounding <span class="hlt">craters</span> Marcia and Calpurnia is enriched in OH- or H-bearing phases and has a variable morphology, <span class="hlt">suggestive</span> of a complex mixture of impact ejecta and impact melts including dark materials possibly derived from carbonaceous chondrite-rich material. Aricia Tholus, which was originally interpreted as a putative Vestan volcanic edifice based on lower resolution observations, appears to be a fragment of an ancient impact basin rim topped by a dark-rayed impact <span class="hlt">crater</span>. Octavia <span class="hlt">crater</span> has a <span class="hlt">cratering</span> model formation age of approximately 280-990 million years based on counts</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA02433.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA02433.html"><span>Scarps Confined to <span class="hlt">Crater</span> Floors</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2000-01-15</p> <p>This image, from NASA Mariner 10 spacecraft which launched in 1974, shows several scarps, which appear to be confined to <span class="hlt">crater</span> floors. The scarp in the <span class="hlt">crater</span> at the upper left of the image has been diverted by the central peaks.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AGUFM.V51C1497H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AGUFM.V51C1497H"><span>Tempest in Vailulu'u <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hart, S. R.; Staudigel, H.; Koppers, A.; Young, C.; Baker, E.</p> <p>2005-12-01</p> <p>The summit <span class="hlt">crater</span> of the Samoan submarine volcano, Vailulu'u, has been actively erupting since 2001. Based on water chemistry, CTD and temperature logger data from 2000 and 2001, we formulated a model for the hydrothermal system in the <span class="hlt">crater</span> involving a tidally-modulated "breathing" (Staudigel et al., 2004). During low stands of internal waves (exterior to the <span class="hlt">crater</span>), the <span class="hlt">crater</span> exhales warm buoyant hydrothermal water that forms a "halo" around the <span class="hlt">crater</span> rich in Mn, 3He, and particulates. During "high tides", cold dense external water is inhaled into the <span class="hlt">crater</span> through the three breaches, and cascades to the <span class="hlt">crater</span> floor. In April 2005, we used the HURL PISCES V submersible to deploy various temperature and particulate loggers and current meters in and around the <span class="hlt">crater</span>; these were retrieved by Pisces V in July 2005. In addition, continuous CTD profiling was carried out over 12 hour tidal cycles at one location inside, and one outside, the <span class="hlt">crater</span>. The accumulated data set fully reinforces our "breathing" model. An ADCP, deployed for 93 days in the NW breach at 752m, showed dominant easterly inflow currents and westerly outflow currents, with maximum velocities of approximately 25 cm/s. The flows were coherent for distances up to 50-60m above the ADCP; the mean inflow velocity and azimuth (20-40 m interval above the ADCP) was 7 cm/s due east; the mean outflow velocity and azimuth was 5 cm/s at 260 degrees. Mean inflows were consistently colder than outflows (5.00 C vs 5.20 C); the maximum observed range in temperature was 1.1 C, correlated with peak flow velocities. The coldest inflows would require very large regional internal wave amplitudes, up to 50-100 meters. A 2-D acoustic current meter was deployed on top of the west <span class="hlt">crater</span> rim summit (582m) for 90 days, and in the S breach (697m) for 4 days. The summit flows are presumed to represent the regional scale currents; these were largely from the SW quadrant, with typical velocities of 8-15 cm/s, and peaks to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1761941','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1761941"><span>Internet Infrastructures and Health Care Systems: a Qualitative Comparative Analysis on Networks and Markets in the British National Health Service and <span class="hlt">Kaiser</span> Permanente</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p></p> <p>2002-01-01</p> <p>Background The Internet and emergent telecommunications infrastructures are transforming the future of health care management. The costs of health care delivery systems, products, and services continue to rise everywhere, but performance of health care delivery is associated with institutional and ideological considerations as well as availability of financial and technological resources. Objective To identify the effects of ideological differences on health care market infrastructures including the Internet and telecommunications technologies by a comparative case analysis of two large health care organizations: the British National Health Service and the California-based <span class="hlt">Kaiser</span> Permanente health maintenance organization. Methods A qualitative comparative analysis focusing on the British National Health Service and the <span class="hlt">Kaiser</span> Permanente health maintenance organization to show how system infrastructures vary according to market dynamics dominated by health care institutions ("push") or by consumer demand ("pull"). System control mechanisms may be technologically embedded, institutional, or behavioral. Results The analysis <span class="hlt">suggests</span> that telecommunications technologies and the Internet may contribute significantly to health care system performance in a context of ideological diversity. Conclusions The study offers evidence to validate alternative models of health care governance: the national constitution model, and the enterprise business contract model. This evidence also <span class="hlt">suggests</span> important questions for health care policy makers as well as researchers in telecommunications, organizational theory, and health care management. PMID:12554552</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014acm..conf..357M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014acm..conf..357M"><span>Asteroid families from <span class="hlt">cratering</span>: Detection and models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Milani, A.; Cellino, A.; Knežević, Z.; Novaković, B.; Spoto, F.; Paolicchi, P.</p> <p>2014-07-01</p> <p>A new asteroid families classification, more efficient in the inclusion of smaller family members, shows how relevant the <span class="hlt">cratering</span> impacts are on large asteroids. These do not disrupt the target, but just form families with the ejecta from large <span class="hlt">craters</span>. Of the 12 largest asteroids, 8 have <span class="hlt">cratering</span> families: number (2), (4), (5), (10), (87), (15), (3), and (31). At least another 7 <span class="hlt">cratering</span> families can be identified. Of the <span class="hlt">cratering</span> families identified so far, 7 have >1000 members. This imposes a remarkable change from the focus on fragmentation families of previous classifications. Such a large dataset of asteroids believed to be <span class="hlt">crater</span> ejecta opens a new challenge: to model the <span class="hlt">crater</span> and family forming event(s) generating them. The first problem is to identify which <span class="hlt">cratering</span> families, found by the similarity of proper elements, can be formed at once, with a single collision. We have identified as a likely outcome of multiple collisions the families of (4), (10), (15), and (20). Of the ejecta generated by <span class="hlt">cratering</span>, only a fraction reaches the escape velocity from the surviving parent body. The distribution of velocities at infinity, giving to the resulting family an initial position and shape in the proper elements space, is highly asymmetric with respect to the parent body. This shape is deformed by the Yarkovsky effect and by the interaction with resonances. All the largest asteroids have been subjected to large <span class="hlt">cratering</span> events, thus the lack of a family needs to be interpreted. The most interesting case is (1) Ceres, which is not the parent body of the nearby family of (93). Two possible interpretations of the low family forming efficiency are based on either the composition of Ceres with a significant fraction of ice, protected by a thin crust, or with the larger escape velocity of ~500 m/s.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.P43B3985H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.P43B3985H"><span>The Global Contribution of Secondary <span class="hlt">Craters</span> on the Icy Satellites</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hoogenboom, T.; Johnson, K. E.; Schenk, P.</p> <p>2014-12-01</p> <p>At present, surface ages of bodies in the Outer Solar System are determined only from <span class="hlt">crater</span> size-frequency distributions (a method dependent on an understanding of the projectile populations responsible for impact <span class="hlt">craters</span> in these planetary systems). To derive accurate ages using impact <span class="hlt">craters</span>, the impactor population must be understood. Impact <span class="hlt">craters</span> in the Outer Solar System can be primary, secondary or sesquinary. The contribution of secondary <span class="hlt">craters</span> to the overall population has recently become a "topic of interest." Our objective is to better understand the contribution of dispersed secondary <span class="hlt">craters</span> to the small <span class="hlt">crater</span> populations, and ultimately that of small comets to the projectile flux on icy satellites in general. We measure the diameters of obvious secondary <span class="hlt">craters</span> (determined by e.g. irregular <span class="hlt">crater</span> shape, small size, clustering) formed by all primary <span class="hlt">craters</span> on Ganymede for which we have sufficiently high resolution data to map secondary <span class="hlt">craters</span>. Primary <span class="hlt">craters</span> mapped range from approximately 40 km to 210 km. Image resolution ranges from 45 to 440 m/pixel. Bright terrain on Ganymede is our primary focus. These resurfaced terrains have relatively low <span class="hlt">crater</span> densities and serve as a basis for characterizing secondary populations as a function of primary size on an icy body for the first time. Although focusing on Ganymede, we also investigate secondary <span class="hlt">crater</span> size, frequency, distribution, and formation, as well as secondary <span class="hlt">crater</span> chain formation on icy satellites throughout the Saturnian and Jovian systems principally Rhea. We compare our results to similar studies of secondary <span class="hlt">cratering</span> on the Moon and Mercury. Using Galileo and Voyager data, we have identified approximately 3,400 secondary <span class="hlt">craters</span> on Ganymede. In some cases, we measured <span class="hlt">crater</span> density as a function of distance from a primary <span class="hlt">crater</span>. Because of the limitations of the Galileo data, it is necessary to extrapolate from small data sets to the global population of secondary <span class="hlt">craters</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/of/1959/0108/report.pdf','USGSPUBS'); return false;" href="https://pubs.usgs.gov/of/1959/0108/report.pdf"><span>Impact mechanics at Meteor <span class="hlt">Crater</span>, Arizona</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Shoemaker, Eugene Merle</p> <p>1959-01-01</p> <p>Meteor Crator is a bowl-shaped depression encompassed by a rim composed chiefly of debris stacked in layers of different composition. Original bedrock stratigraphy is preserved, inverted, in the debris. The debris rests on older disturbed strata, which are turned up at moderate to steep angles in the wall of the <span class="hlt">crater</span> and are locally overturned near the contact with the debris. These features of Meteor <span class="hlt">Crater</span> correspond closely to those of a <span class="hlt">crater</span> produced by nuclear explosion where depth of burial of the device was about 1/5 the diameter of the resultant <span class="hlt">crater</span>. Studies of <span class="hlt">craters</span> formed by detonation of nuclear devices show that structures of the <span class="hlt">crater</span> rims are sensitive to the depth of explosion scaled to the yield of the device. The structure of Meteor <span class="hlt">Crater</span> is such as would be produced by a very strong shock originating about at the level of the present <span class="hlt">crater</span> floor, 400 feet below the original surface. At supersonic to hypersonic velocity an impacting meteorite penetrates the ground by a complex mechanism that includes compression of the target rocks and the meteorite by shock as well as hydrodynamic flow of the compressed material under high pressure and temperature. The depth of penetration of the meteorite, before it loses its integrity as a single body, is a function primarily of the velocity and shape of the meteorite and the densities and equations of state of the meteorite and target. The intensely compressed material then becomes dispersed in a large volume of breccia formed in the expanding shock wave. An impact velocity of about 15 km/sec is consonant with the geology of Meteor <span class="hlt">Crater</span> in light of the experimental equation of state of iron and inferred compressibility of the target rocks. The kinetic energy of the meteorite is estimated by scaling to have been from 1.4 to 1.7 megatons TNT equivalent.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.P44B..04G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.P44B..04G"><span>Evolution of Lunar <span class="hlt">Crater</span> Ejecta Through Time: Influence of <span class="hlt">Crater</span> Size on the Record of Dynamic Processes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ghent, R. R.; Tai Udovicic, C.; Mazrouei, S.; Bottke, W. F., Jr.</p> <p>2017-12-01</p> <p>The bombardment history of the Moon holds the key to understanding important aspects of the evolution of the Solar System at 1AU. It informs our thinking about the rates and chronology of events on other planetary bodies and the evolution of the asteroid belt. In previous work, we established a quantitative relationship between the ages of lunar <span class="hlt">craters</span> and the rockiness of their ejecta. That result was based on the idea that <span class="hlt">crater</span>-forming impacts eject rocks from beneath the regolith, instantaneously emplacing a deposit with characteristic initial physical properties, such as rock abundance. The ejecta rocks are then gradually removed and / or covered by a combination of mechanical breakdown via micrometeorite bombardment, emplacement of regolith fines due to nearby impacts, and possibly rupture due to thermal stresses. We found that ejecta rocks, as detected by the Lunar Reconnaissance Orbiter Diviner thermal radiometer disappear on a timescale of 1 Gyr, eventually becoming undetectable by the Diviner instrument against the ambient background rock abundance of the regolith.The "index" <span class="hlt">craters</span> we used to establish the rock abundance—age relationship are all larger than 15 km (our smallest index <span class="hlt">crater</span> is Byrgius A, at 18.7 km), and therefore above the transition diameter between simple and complex <span class="hlt">craters</span> (15-20 km). Here, we extend our analysis to include <span class="hlt">craters</span> smaller than the transition diameter. It is not obvious a priori that the initial ejecta properties of simple and complex <span class="hlt">craters</span> should be identical, and therefore, that the same metrics of <span class="hlt">crater</span> age can be applied to both populations. We explore this issue using LRO Diviner rock abundance and a high-resolution optical maturity dataset derived from Kaguya multiband imager VIS/NIR data to identify young <span class="hlt">craters</span> to 5 km diameter. We examine the statistical properties of this population relative to that of the NEO population, and interpret the results in the context of our recently documented evidence</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19820048255&hterms=clay+viscosity&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dclay%2Bviscosity','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19820048255&hterms=clay+viscosity&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dclay%2Bviscosity"><span>Impact <span class="hlt">cratering</span> experiments in Bingham materials and the morphology of <span class="hlt">craters</span> on Mars and Ganymede</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Fink, J. H.; Greeley, R.; Gault, D. E.</p> <p>1982-01-01</p> <p>Results from a series of laboratory impacts into clay slurry targets are compared with photographs of impact <span class="hlt">craters</span> on Mars and Ganymede. The interior and ejecta lobe morphology of rampart-type <span class="hlt">craters</span>, as well as the progression of <span class="hlt">crater</span> forms seen with increasing diameter on both Mars and Ganymede, are equalitatively explained by a model for impact into Bingham materials. For increasing impact energies and constant target rheology, laboratory <span class="hlt">craters</span> exhibit a morphologic progression from bowl-shaped forms that are typical of dry planetary surfaces to <span class="hlt">craters</span> with ejecta flow lobes and decreasing interior relief, characteristic of more volatile-rich planets. A similar sequence is seen for uniform impact energy in slurries of decreasing yield strength. The planetary progressions are explained by assuming that volatile-rich or icy planetary surfaces behave locally in the same way as Bingham materials and produce ejecta slurries with yield strenghs and viscosities comparable to terrestrial debris flows. Hypothetical impact into Mars and Ganymede are compared, and it is concluded that less ejecta would be produced on Ganymede owing to its lower gravitational acceleration, surface temperature, and density of surface materials.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018Icar..301...26B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018Icar..301...26B"><span>Lobate impact melt flows within the extended ejecta blanket of Pierazzo <span class="hlt">crater</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bray, Veronica J.; Atwood-Stone, Corwin; Neish, Catherine D.; Artemieva, Natalia A.; McEwen, Alfred S.; McElwaine, Jim N.</p> <p>2018-02-01</p> <p>Impact melt flows are observed within the continuous and discontinuous ejecta blanket of the 9 km lunar <span class="hlt">crater</span> Pierazzo, from the <span class="hlt">crater</span> rim to more than 40 km away from the center of the <span class="hlt">crater</span>. Our mapping, fractal analysis, and thermal modeling <span class="hlt">suggest</span> that melt can be emplaced ballistically and, upon landing, can become separated from solid ejecta to form the observed flow features. Our analysis is based on the identification of established melt morphology for these in-ejecta flows and supported by fractal analysis and thermal modeling. We computed the fractal dimension for the flow boundaries and found values of D = 1.05-1.17. These are consistent with terrestrial basaltic lava flows (D = 1.06-1.2) and established lunar impact melt flows (D = 1.06-1.18), but inconsistent with lunar dry granular flows (D = 1.31-1.34). Melt flows within discontinuous ejecta deposits are noted within just 1.5% of the mapping area, <span class="hlt">suggesting</span> that the surface expression of impact melt in the extended ejecta around <span class="hlt">craters</span> of this size is rare, most likely due to the efficient mixing of melts with solid ejecta and local target rocks. However, if the ejected fragments (both, molten and solid) are large enough, segregation of melt and its consequent flow is possible. As most of the flows mapped in this work occur on <span class="hlt">crater</span>-facing slopes, the development of defined melt flows within ejecta deposits might be facilitated by high <span class="hlt">crater</span>-facing topography restricting the flow of ejecta soon after it makes ground contact, limiting the quenching of molten ejecta through turbulent mixing with solid debris. Our study confirms the idea that impact melt can travel far beyond the continuous ejecta blanket, adding to the lunar regolith over an extensive area.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19930000978','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19930000978"><span>What can we learn about impact mechanics from large <span class="hlt">craters</span> on Venus?</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mckinnon, William B.; Alexopoulos, J. S.</p> <p>1992-01-01</p> <p>More than 50 unequivocal peak-ring <span class="hlt">craters</span> and multiringed impact basins have been identified on Venus from Earth-based Arecibo, Venera 15/16, and Magellan radar images. These ringed <span class="hlt">craters</span> are relatively pristine, and so serve as an important new dataset that will further understanding of the structural and rheological properties of the venusian surface and of impact mechanics in general. They are also the most direct analogues for <span class="hlt">craters</span> formed on the Earth in Phanerozoic time. Finite-element simulations of basin collapse and ring formation were undertaken in collaboration with V. J. Hillgren (University of Arizona). These calculations used an axisymmetric version of the viscoelastic finite element code TECTON, modeled structures on the scale of Klenova or Meitner, and demonstrated two major points. First, viscous flow and ring formation are possible on the timescale of <span class="hlt">crater</span> collapse for the sizes of multiringed basins seen on Venus and heat flows appropriate to the plant. Second, an elastic lithosphere overlying a Newtonian viscous asthenosphere results mainly in uplift beneath the <span class="hlt">crater</span>. Inward asthenospheric flow mainly occurs at deeper levels. Lithospheric response is dominantly vertical and flexural. Tensional stress maxima occur and ring formation by normal faulting is predicted in some cases, but these predicted rings occur too far out to explain observed ring spacings on Venus (or on the Moon). Overall, these estimates and models <span class="hlt">suggest</span> that multiringed basin formation is indeed possible at the scales observed on Venus. Furthermore, due to the strong inverse dependence of solid-state viscosity on stress, the absence of Cordilleran-style ring faulting in <span class="hlt">craters</span> smaller than Meitner or Klenova makes sense. The apparent increase in viscosity of shock-fluidized rock with <span class="hlt">crater</span> diameter, greater interior temperatures accessed by larger, deeper <span class="hlt">craters</span>, and decreased non-Newtonian viscosity associated with larger <span class="hlt">craters</span> may conspire to make the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017APS..DFDG39010B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017APS..DFDG39010B"><span>Investigating large-scale secondary circulations within impact <span class="hlt">crater</span> topographies in a refractive index-matched facility</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Blois, Gianluca; Kim, Taehoon; Bristow, Nathan; Day, Mackenzie; Kocurek, Gary; Anderson, William; Christensen, Kenneth</p> <p>2017-11-01</p> <p>Impact <span class="hlt">craters</span>, common large-scale topographic features on the surface of Mars, are circular depressions delimited by a sharp ridge. A variety of <span class="hlt">crater</span> fill morphologies exist, <span class="hlt">suggesting</span> that complex intracrater circulations affect their evolution. Some large <span class="hlt">craters</span> (diameter >10 km), particularly at mid latitudes on Mars, exhibit a central mound surrounded by circular moat. Foremost among these examples is Gale <span class="hlt">crater</span>, landing site of NASA's Curiosity rover, since large-scale climatic processes early in in the history of Mars are preserved in the stratigraphic record of the inner mound. Investigating the intracrater flow produced by large scale winds aloft Mars <span class="hlt">craters</span> is key to a number of important scientific issues including ongoing research on Mars paleo-environmental reconstruction and the planning of future missions (these results must be viewed in conjunction with the affects of radial katabatibc flows, the importance of which is already established in preceding studies). In this work we consider a number of <span class="hlt">crater</span> shapes inspired by Gale morphology, including idealized <span class="hlt">craters</span>. Access to the flow field within such geometrically complex topography is achieved herein using a refractive index matched approach. Instantaneous velocity maps, using both planar and volumetric PIV techniques, are presented to elucidate complex three-dimensional flow within the <span class="hlt">crater</span>. In addition, first- and second-order statistics will be discussed in the context of wind-driven (aeolian) excavation of <span class="hlt">crater</span> fill.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19940011749','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19940011749"><span>Confirmation of saturation equilibrium conditions in <span class="hlt">crater</span> populations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hartmann, William K.; Gaskell, Robert W.</p> <p>1993-01-01</p> <p>We have continued work on realistic numerical models of <span class="hlt">cratered</span> surfaces, as first reported at last year's LPSC. We confirm the saturation equilibrium level with a new, independent test. One of us has developed a realistic computer simulation of a <span class="hlt">cratered</span> surface. The model starts with a smooth surface or fractal topography, and adds primary <span class="hlt">craters</span> according to the cumulative power law with exponent -1.83, as observed on lunar maria and Martian plains. Each <span class="hlt">crater</span> has an ejecta blanket with the volume of the <span class="hlt">crater</span>, feathering out to a distance of 4 <span class="hlt">crater</span> radii. We use the model to test the levels of saturation equilibrium reached in naturally occurring systems, by increasing <span class="hlt">crater</span> density and observing its dependence on various parameters. In particular, we have tested to see if these artificial systems reach the level found by Hartmann on heavily <span class="hlt">cratered</span> planetary surfaces, hypothesized to be the natural saturation equilibrium level. This year's work gives the first results of a <span class="hlt">crater</span> population that includes secondaries. Our model 'Gaskell-4' (September, 1992) includes primaries as described above, but also includes a secondary population, defined by exponent -4. We allowed the largest secondary from each primary to be 0.10 times the size of the primary. These parameters will be changed to test their effects in future models. The model gives realistic images of a <span class="hlt">cratered</span> surface although it appears richer in secondaries than real surfaces are. The effect of running the model toward saturation gives interesting results for the diameter distribution. Our most heavily <span class="hlt">cratered</span> surface had the input number of primary <span class="hlt">craters</span> reach about 0.65 times the hypothesized saturation equilibrium, but the input number rises to more than 100 times that level for secondaries below 1.4 km in size.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA04212&hterms=polygons&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dpolygons','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA04212&hterms=polygons&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dpolygons"><span>Polygons and <span class="hlt">Craters</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2005-01-01</p> <p><p/> 3 September 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows polygons enhanced by subliming seasonal frost in the martian south polar region. Polygons similar to these occur in frozen ground at high latitudes on Earth, <span class="hlt">suggesting</span> that perhaps their presence on Mars is also a sign that there is or once was ice in the shallow subsurface. The circular features are degraded meteor impact <span class="hlt">craters</span>. <p/> <i>Location near</i>: 72.2oS, 310.3oW <i>Image width</i>: width: 3 km (1.9 mi) <i>Illumination from</i>: upper left <i>Season</i>: Southern Spring</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA12167.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA12167.html"><span>Oblique View of Victoria <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2009-08-12</p> <p>This image of Victoria <span class="hlt">Crater</span> in the Meridiani Planum region of Mars was taken by the High Resolution Imaging Science Experiment HiRISE camera on NASA Mars Reconnaissance Orbiter at more of a sideways angle than earlier orbital images of this <span class="hlt">crater</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20090041760','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20090041760"><span>Processing Images of <span class="hlt">Craters</span> for Spacecraft Navigation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cheng, Yang; Johnson, Andrew E.; Matthies, Larry H.</p> <p>2009-01-01</p> <p>A <span class="hlt">crater</span>-detection algorithm has been conceived to enable automation of what, heretofore, have been manual processes for utilizing images of <span class="hlt">craters</span> on a celestial body as landmarks for navigating a spacecraft flying near or landing on that body. The images are acquired by an electronic camera aboard the spacecraft, then digitized, then processed by the algorithm, which consists mainly of the following steps: 1. Edges in an image detected and placed in a database. 2. <span class="hlt">Crater</span> rim edges are selected from the edge database. 3. Edges that belong to the same <span class="hlt">crater</span> are grouped together. 4. An ellipse is fitted to each group of <span class="hlt">crater</span> edges. 5. Ellipses are refined directly in the image domain to reduce errors introduced in the detection of edges and fitting of ellipses. 6. The quality of each detected <span class="hlt">crater</span> is evaluated. It is planned to utilize this algorithm as the basis of a computer program for automated, real-time, onboard processing of <span class="hlt">crater</span>-image data. Experimental studies have led to the conclusion that this algorithm is capable of a detection rate >93 percent, a false-alarm rate <5 percent, a geometric error <0.5 pixel, and a position error <0.3 pixel.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018Icar..302..537F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018Icar..302..537F"><span>Planetary boundary layer and circulation dynamics at Gale <span class="hlt">Crater</span>, Mars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fonseca, Ricardo M.; Zorzano-Mier, María-Paz; Martín-Torres, Javier</p> <p>2018-03-01</p> <p>The Mars implementation of the Planet Weather Research and Forecasting (PlanetWRF) model, MarsWRF, is used here to simulate the atmospheric conditions at Gale <span class="hlt">Crater</span> for different seasons during a period coincident with the Curiosity rover operations. The model is first evaluated with the existing single-point observations from the Rover Environmental Monitoring Station (REMS), and is then used to provide a larger scale interpretation of these unique measurements as well as to give complementary information where there are gaps in the measurements. The variability of the planetary boundary layer depth may be a driver of the changes in the local dust and trace gas content within the <span class="hlt">crater</span>. Our results show that the average time when the PBL height is deeper than the <span class="hlt">crater</span> rim increases and decreases with the same rate and pattern as Curiosity's observations of the line-of-sight of dust within the <span class="hlt">crater</span> and that the season when maximal (minimal) mixing is produced is Ls 225°-315° (Ls 90°-110°). Thus the diurnal and seasonal variability of the PBL depth seems to be the driver of the changes in the local dust content within the <span class="hlt">crater</span>. A comparison with the available methane measurements <span class="hlt">suggests</span> that changes in the PBL depth may also be one of the factors that accounts for the observed variability, with the model results pointing towards a local source to the north of the MSL site. The interaction between regional and local flows at Gale <span class="hlt">Crater</span> is also investigated assuming that the meridional wind, the dynamically important component of the horizontal wind at Gale, anomalies with respect to the daily mean can be approximated by a sinusoidal function as they typically oscillate between positive (south to north) and negative (north to south) values that correspond to upslope/downslope or downslope/upslope regimes along the <span class="hlt">crater</span> rim and Mount Sharp slopes and the dichotomy boundary. The smallest magnitudes are found in the northern <span class="hlt">crater</span> floor in a region that</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA06088&hterms=landslide&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dlandslide','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA06088&hterms=landslide&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dlandslide"><span><span class="hlt">Crater</span> Landslide</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2006-01-01</p> <p><p/> [figure removed for brevity, see original site] Context image for PIA06088 <span class="hlt">Crater</span> Landslide <p/> This landslide occurs in an unnamed <span class="hlt">crater</span> southeast of Millochau <span class="hlt">Crater</span>. <p/> Image information: VIS instrument. Latitude -24.4N, Longitude 87.5E. 17 meter/pixel resolution. <p/> Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. <p/> NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA00420.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA00420.html"><span><span class="hlt">Crater</span> Moreux</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>1998-06-08</p> <p>Color image of part of the Ismenius Lacus region of Mars (MC-5 quadrangle) containing the impact <span class="hlt">crater</span> Moreux (right center); north toward top. The scene shows heavily <span class="hlt">cratered</span> highlands in the south on relatively smooth lowland plains in the north separated by a belt of dissected terrain, containing flat-floored valleys, mesas, and buttes. This image is a composite of Viking medium-resolution images in black and white and low-resolution images in color. The image extends from latitude 36 degrees N. to 50 degrees N. and from longitude 310 degrees to 340 degrees; Lambert conformal conic projection. The dissected terrain along the highlands/lowlands boundary consists of the flat-floored valleys of Deuteronilus Mensae (on left) and Prontonilus Mensae (on right) and farther north the small, rounded hills of knobby terrain. Flows on the mensae floors contain striae that run parallel to valley walls; where valleys meet, the striae merge, similar to medial moraines on glaciers. Terraces within the valley hills have been interpreted as either layered rocks or wave terraces. The knobby terrain has been interpreted as remnants of the old, densely <span class="hlt">cratered</span> highland terrain perhaps eroded by mass wasting. http://photojournal.jpl.nasa.gov/catalog/PIA00420</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA21799.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA21799.html"><span>Investigating Mars: Russell <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2017-08-01</p> <p>This image shows individual dunes on the floor of Russell <span class="hlt">Crater</span>. These dunes are in the southern part of the dune field. Russell <span class="hlt">Crater</span> is located in Noachis Terra. A spectacular dune ridge and other dune forms on the <span class="hlt">crater</span> floor have caused extensive imaging. The Odyssey spacecraft has spent over 15 years in orbit around Mars, circling the planet more than 69000 times. It holds the record for longest working spacecraft at Mars. THEMIS, the IR/VIS camera system, has collected data for the entire mission and provides images covering all seasons and lighting conditions. Over the years many features of interest have received repeated imaging, building up a suite of images covering the entire feature. From the deepest chasma to the tallest volcano, individual dunes inside <span class="hlt">craters</span> and dune fields that encircle the north pole, channels carved by water and lava, and a variety of other feature, THEMIS has imaged them all. For the next several months the image of the day will focus on the Tharsis volcanoes, the various chasmata of Valles Marineris, and the major dunes fields. We hope you enjoy these images! https://photojournal.jpl.nasa.gov/catalog/PIA21799</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014acm..conf...88C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014acm..conf...88C"><span><span class="hlt">Cratering</span> statistics on asteroids: Methods and perspectives</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chapman, C.</p> <p>2014-07-01</p> <p><span class="hlt">Crater</span> size-frequency distributions (SFDs) on the surfaces of solid-surfaced bodies in the solar system have provided valuable insights about planetary surface processes and about impactor populations since the first spacecraft images were obtained in the 1960s. They can be used to determine relative age differences between surficial units, to obtain absolute model ages if the impactor flux and scaling laws are understood, to assess various endogenic planetary or asteroidal processes that degrade <span class="hlt">craters</span> or resurface units, as well as assess changes in impactor populations across the solar system and/or with time. The first asteroid SFDs were measured from Galileo images of Gaspra and Ida (cf., Chapman 2002). Despite the superficial simplicity of these studies, they are fraught with many difficulties, including confusion by secondary and/or endogenic <span class="hlt">cratering</span> and poorly understood aspects of varying target properties (including regoliths, ejecta blankets, and nearly-zero-g rubble piles), widely varying attributes of impactors, and a host of methodological problems including recognizability of degraded <span class="hlt">craters</span>, which is affected by illumination angle and by the ''personal equations'' of analysts. Indeed, controlled studies (Robbins et al. 2014) demonstrate <span class="hlt">crater</span>-density differences of a factor of two or more between experienced <span class="hlt">crater</span> counters. These inherent difficulties have been especially apparent in divergent results for Vesta from different members of the Dawn Science Team (cf. Russell et al. 2013). Indeed, they have been exacerbated by misuse of a widely available tool (Craterstats: hrscview.fu- berlin.de/craterstats.html), which incorrectly computes error bars for proper interpretation of cumulative SFDs, resulting in derived model ages specified to three significant figures and interpretations of statistically insignificant kinks. They are further exacerbated, and for other small-body <span class="hlt">crater</span> SFDs analyzed by the Berlin group, by stubbornly adopting</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA04412&hterms=Freedom&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DFreedom','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA04412&hterms=Freedom&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DFreedom"><span>Freedom <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2003-01-01</p> <p><p/> [figure removed for brevity, see original site] <p/>Freedom <span class="hlt">crater</span>, located in Acidalia Planitia, exhibits a concentric ring pattern in its interior, <span class="hlt">suggesting</span> that there has been some movement of these materials towards the center of the <span class="hlt">crater</span>. Slumping towards the center may have been caused by the presence of ground ice mixed in with the sediments. The origin for the scarps on the western edge of the interior deposit is unknown.<p/>Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.<p/>NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.<p/>Image information: VIS instrument. Latitude 43.3, Longitude 351.3 East (8.7 West). 19 meter/pixel resolution.<p/></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA06318&hterms=reading&qs=N%3D0%26Ntk%3DTitle%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dreading','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA06318&hterms=reading&qs=N%3D0%26Ntk%3DTitle%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dreading"><span>Reading 'Endurance <span class="hlt">Crater</span>'</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2004-01-01</p> <p>[figure removed for brevity, see original site] Figure 1 <p/> This image shows the area inside 'Endurance <span class="hlt">Crater</span>' that the Mars Exploration Rover Opportunity has been examining. The rover is investigating the distinct layers of rock that make up this region. Each layer is defined by subtle color and texture variations and represents a separate chapter in Mars' history. The deeper the layer, the further back in time the rocks were formed. Scientists are 'reading' this history book by systematically studying each layer with the rover's scientific instruments. So far, data from the rover indicate that the top layers are sulfate-rich, like the rocks observed in 'Eagle <span class="hlt">Crater</span>.' This implies that water processes were involved in forming the materials that make up these rocks. <p/> In figure 1, the layer labeled 'A' in this picture contains broken-up rocks that most closely resemble those of 'Eagle <span class="hlt">Crater</span>.' Layers 'B,C and D' appear less broken up and more finely laminated. Layer 'E,' on the other hand, looks more like 'A.' At present, the rover is examining layer 'D.' <p/> So far, data from the rover indicates that the first four layers consist of sulfate-rich, jarosite-containing rocks like those observed in Eagle <span class="hlt">Crater</span>. This implies that water processes were involved in forming the materials that make up these rocks, though the materials themselves may have been laid down by wind. <p/> This image was taken by Opportunity's navigation camera on sol 134 (June 9, 2004).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010E%26PSL.294..230H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010E%26PSL.294..230H"><span>Martian <span class="hlt">Cratering</span> 10. Progress in use of <span class="hlt">crater</span> counts to interpret geological processes: Examples from two debris aprons</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hartmann, William K.; Werner, Stephanie C.</p> <p>2010-06-01</p> <p>Recent controversies about systems of <span class="hlt">crater</span>-count dating have been largely resolved, and with continuing refinements, <span class="hlt">crater</span> counts will offer a fundamental geological tool to interpret not only ages, but also the nature of geological processes altering the surface of Mars. As an example of the latter technique, we present data on two debris aprons east of Hellas. The aprons show much shorter survival times of small <span class="hlt">craters</span> than do the nearby contiguous plains. The order-of-magnitude depths of layers involved in the loss process can be judged from the depths of the affected <span class="hlt">craters</span>. We infer that ice-rich layers in the top tens of meters of both aprons have lost <span class="hlt">crater</span> topography within the last few 10 8 yr, probably due to flow or sublimation of ice-rich materials. Mantling by ice-rich deposits, associated with climate change cycles of obliquity change, has probably also affected both the aprons and the plains. The <span class="hlt">crater</span>-count tool thus adds chronological and vertical dimensional information to purely morphological studies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA21870.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA21870.html"><span><span class="hlt">Crater</span> Rim Layers, Rubble, and Gullies</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2017-08-07</p> <p>This observation from NASA's Mars Reconnaissance Orbiter shows a close view of the rim and upper wall of an impact <span class="hlt">crater</span> on the Martian surface. The layers in enhanced color are exposed subsurface strata that are relatively resistant to erosion. Boulder-like rubble beyond the <span class="hlt">crater</span> rim is scattered down the wall of the <span class="hlt">crater</span> (down-slope is toward the lower left of the image). Another feature of interest to Mars scientists is a large gully roughly 100 meters across. These gullies may have formed when water from melted ice on the <span class="hlt">crater</span> walls, or from groundwater within the walls, assisted in transporting eroding material downslope. https://photojournal.jpl.nasa.gov/catalog/PIA21870</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018Icar..300..227T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018Icar..300..227T"><span><span class="hlt">Cratering</span> efficiency on coarse-grain targets: Implications for the dynamical evolution of asteroid 25143 Itokawa</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tatsumi, Eri; Sugita, Seiji</p> <p>2018-01-01</p> <p>Remote sensing observations made by the spacecraft Hayabusa provided the first direct evidence of a rubble-pile asteroid: 25143 Itokawa. Itokawa was found to have a surface structure very different from other explored asteroids; covered with coarse pebbles and boulders ranging at least from cm to meter size. The cumulative size distribution of small circular depressions on Itokawa, most of which may be of impact origin, has a significantly shallower slope than that on the Moon; small <span class="hlt">craters</span> are highly depleted on Itokawa compared to the Moon. This deficiency of small circular depressions and other features, such as clustered fragments and pits on boulders, <span class="hlt">suggest</span> that the boulders on Itokawa might behave like armor, preventing <span class="hlt">crater</span> formation: the ;armoring effect;. This might contribute to the low number density of small <span class="hlt">crater</span> candidates. In this study, the <span class="hlt">cratering</span> efficiency reduction due to coarse-grained targets was investigated based on impact experiments at velocities ranging from ∼ 70 m/s to ∼ 6 km/s using two vertical gas gun ranges. We propose a scaling law extended for <span class="hlt">cratering</span> on coarse-grained targets (i.e., target grain size ≳ projectile size). We have found that the <span class="hlt">crater</span> efficiency reduction is caused by energy dissipation at the collision site where momentum is transferred from the impactor to the first-contact target grain, and that the armoring effect can be classified into three regimes: (1) gravity scaled regime, (2) reduced size <span class="hlt">crater</span> regime, or (3) no apparent <span class="hlt">crater</span> regime, depending on the ratio of the impactor size to the target grain size and the ratio of the impactor kinetic energy to the disruption energy of a target grain. We found that the shallow slope of the circular depressions on Itokawa cannot be accounted for by this new scaling law, <span class="hlt">suggesting</span> that obliteration processes, such as regolith convection and migration, play a greater role in the depletion of circular depressions on Itokawa. Based on the new extended</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.P31E..06C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.P31E..06C"><span>Impact <span class="hlt">Cratering</span> Processes as Understood Through Martian and Terrestrial Analog Studies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Caudill, C. M.; Osinski, G. R.; Tornabene, L. L.</p> <p>2016-12-01</p> <p>Impact ejecta deposits allow an understanding of subsurface lithologies, volatile content, and other compositional and physical properties of a planetary crust, yet development and emplacement of these deposits on terrestrial bodies throughout the solar system is still widely debated. Relating relatively well-preserved Martian ejecta to terrestrial impact deposits is an area of active research. In this study, we report on the mapping and geologic interpretation of 150-km diameter Bakhuysen <span class="hlt">Crater</span>, Mars, which is likely large enough to have produced a significant volume of melt, and has uniquely preserved ejecta deposits. Our mapping supports the current formation hypothesis for Martian <span class="hlt">crater</span>-related pitted material, where pits are likened to collapsed degassing features identified at the Ries and Haughton terrestrial impact structures. As hot impact melt-bearing ejecta deposits are emplaced over volatile-saturated material during <span class="hlt">crater</span> formation, a rapid degassing of the underlying layer results in lapilli-like fluid and gas flow pipes which may eventually lead to collapse features on the surface. At the Haughton impact structure, degassing pipes are related to <span class="hlt">crater</span> fracture and fault systems; this is analogous to structure and collapse pits mapped in Bakhuysen <span class="hlt">Crater</span>. Based on stratigraphic superposition, surface and flow texture, and morphological and thermophysical mapping of Bakhuysen, we interpret the top-most ejecta unit to be likely melt-bearing and analogous to terrestrial impact deposits (e.g., Ries suevites). Furthermore, we <span class="hlt">suggest</span> that Chicxulub is an apt terrestrial comparison based on its final diameter and the evidence of a ballistically-emplaced and volatile-entrained initial ejecta. This is significant as Bakhuysen ejecta deposits may provide insight into larger impact structures where limited exposures make studies difficult. This supports previous work which <span class="hlt">suggests</span> that given similarities in volatile content and subsurface stratigraphy</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27021613','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27021613"><span>Searching for the Source <span class="hlt">Crater</span> of Nakhlite Meteorites.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kereszturi, A; Chatzitheodoridis, E</p> <p>2016-11-01</p> <p>We surveyed the Martian surface in order to identify possible source <span class="hlt">craters</span> of the nakhlite Martian meteorites. We investigated rayed <span class="hlt">craters</span> that are assumed to be younger than 11 Ma, on lava surfaces with a solidification age around 1.2 Ga. An area of 17.3 million km 2 Amazonian lava plains was surveyed and 53 rayed <span class="hlt">craters</span> were identified. Although most of them are smaller than the threshold limit that is estimated as minimum of launching fragments to possible Earth crossing trajectories, their observed size frequency distribution agrees with the expected areal density from <span class="hlt">cratering</span> models characteristic for <span class="hlt">craters</span> that are less than few tens of Ma old. We identified 6 <span class="hlt">craters</span> larger than 3 km diameter constituting the potentially best source <span class="hlt">craters</span> for nakhlites. These larger candidates are located mostly on a smooth lava surface, and in some cases, on the earlier fluvial-like channels. In three cases they are associated with fluidized ejecta lobes and rays - although the rays are faint in these <span class="hlt">craters</span>, thus might be older than the other <span class="hlt">craters</span> with more obvious rays. More work is therefore required to accurately estimate ages based on ray system for this purpose. A more detailed search should further link remote sensing Martian data with the in-situ laboratory analyses of Martian meteorites, especially in case of high altitude, steep terrains, where the <span class="hlt">crater</span> rays seems to rarely survive several Ma.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19920001566','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19920001566"><span>Styles of <span class="hlt">crater</span> gradation in Southern Ismenius Lacus, Mars</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Grant, J. A.; Schultz, P. H.</p> <p>1991-01-01</p> <p>Preserved morphology around selected impact <span class="hlt">craters</span> together with results from study of long term gradational evolution are used to assess processes responsible for <span class="hlt">crater</span> modification in southern Ismenius Lacus. Results are compared with the gradational styles of selected terrestrial <span class="hlt">craters</span>. Although most <span class="hlt">craters</span> in the region display complex primary morphologies, some first order comparisons with the gradational styles around simple terrestrial <span class="hlt">craters</span> may be valid. Nearly complete high resolution coverage provides a basis for studying morphologic features at scales comparable to those observed in LANDSAT TM images of terrestrial <span class="hlt">craters</span>. It is concluded that the relative importance of gradational processes differs around the terrestrial and Martian <span class="hlt">craters</span> considered here: Martian rimless morphologies are produced by mass wasting, eolian deposition/erosion, and limited fluvial incisement resulting in downwasting and significant backwasting of <span class="hlt">crater</span> walls.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19780057836&hterms=Two+planets+moon&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DTwo%2Bplanets%2Bmoon.','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19780057836&hterms=Two+planets+moon&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DTwo%2Bplanets%2Bmoon."><span>The effects of target characteristics on fresh <span class="hlt">crater</span> morphology - Preliminary results for the moon and Mercury</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cintala, M. J.; Wood, C. A.; Head, J. W.</p> <p>1977-01-01</p> <p>The results are reported of an analysis of the characteristics of fresh <span class="hlt">crater</span> samples occurring on the two major geologic units on the moon (maria and highlands) and on Mercury (smooth plains and <span class="hlt">cratered</span> terrain). In particular, the onset diameters and abundances of central peaks and terraces are examined and compared for both geologic units on each planet in order to detect any variations that might be due to geologic unit characteristics. The analysis of lunar <span class="hlt">crater</span> characteristics is based on information provided in the LPL Catalog of Lunar <span class="hlt">Craters</span> of Wood and Andersson (1977). The Mercurian data set utilized is related to a program involving the cataloguing of Mercurian <span class="hlt">craters</span> visible in Mariner 10 photography. It is concluded that the characteristics of the substrate have exerted a measurable influence on the occurrence of central peaks, terraces, and scallops in flash <span class="hlt">crater</span> samples. Therefore, in order to compare the morphologic characteristics of fresh <span class="hlt">crater</span> populations between planets, an analysis of possible substrate-related differences must first be undertaken for each planet under consideration. It is <span class="hlt">suggested</span> that large variations in gravity do not produce major variations in <span class="hlt">crater</span> wall failure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA22303.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA22303.html"><span>Yuty <span class="hlt">Crater</span> Ejecta</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2018-03-26</p> <p>Off the image to the right is Yuty <span class="hlt">Crater</span>, located between Simud and Tiu Valles. The <span class="hlt">crater</span> ejcta forms the large lobes along the right side of this VIS image. This type of ejecta was created by surface flow rather than air fall. It is thought that the near surface materials contained volatiles (like water) which mixed with the ejecta at the time of the impact. Orbit Number: 68736 Latitude: 22.247 Longitude: 325.213 Instrument: VIS Captured: 2017-06-12 17:57 https://photojournal.jpl.nasa.gov/catalog/PIA22303</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018Icar..305...33K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018Icar..305...33K"><span>Usability of small impact <span class="hlt">craters</span> on small surface areas in <span class="hlt">crater</span> count dating: Analysing examples from the Harmakhis Vallis outflow channel, Mars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kukkonen, S.; Kostama, V.-P.</p> <p>2018-05-01</p> <p>The availability of very high-resolution images has made it possible to extend <span class="hlt">crater</span> size-frequency distribution studies to small, deca/hectometer-scale <span class="hlt">craters</span>. This has enabled the dating of small and young surface units, as well as recent, short-time and small-scale geologic processes that have occurred on the units. Usually, however, the higher the spatial resolution of space images is, the smaller area is covered by the images. Thus the use of single, very high-resolution images in <span class="hlt">crater</span> count age determination may be debatable if the images do not cover the studied region entirely. Here we compare the <span class="hlt">crater</span> count results for the floor of the Harmakhis Vallis outflow channel obtained from the images of the ConTeXt camera (CTX) and High Resolution Imaging Science Experiment (HiRISE) aboard the Mars Reconnaissance Orbiter (MRO). The CTX images enable <span class="hlt">crater</span> counts for entire units on the Harmakhis Vallis main valley, whereas the coverage of the higher-resolution HiRISE images is limited and thus the images can only be used to date small parts of the units. Our case study shows that the <span class="hlt">crater</span> count data based on small impact <span class="hlt">craters</span> and small surface areas mainly correspond with the <span class="hlt">crater</span> count data based on larger <span class="hlt">craters</span> and more extensive counting areas on the same unit. If differences between the results were founded, they could usually be explained by the regional geology. Usually, these differences appeared when at least one <span class="hlt">cratering</span> model age is missing from either of the <span class="hlt">crater</span> datasets. On the other hand, we found only a few cases in which the <span class="hlt">cratering</span> model ages were completely different. We conclude that the <span class="hlt">crater</span> counts using small impact <span class="hlt">craters</span> on small counting areas provide useful information about the geological processes which have modified the surface. However, it is important to remember that all the <span class="hlt">crater</span> counts results obtained from a specific counting area always primarily represent the results from the counting area-not the whole</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009M%26PS...44..985K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009M%26PS...44..985K"><span>The Carancas meteorite impact <span class="hlt">crater</span>, Peru: Geologic surveying and modeling of <span class="hlt">crater</span> formation and atmospheric passage</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kenkmann, T.; Artemieva, N. A.; Wünnemann, K.; Poelchau, M. H.; Elbeshausen, D.; Núñez Del Prado, H.</p> <p>2009-08-01</p> <p>The recent Carancas meteorite impact event caused a worldwide sensation. An H4-5 chondrite struck the Earth south of Lake Titicaca in Peru on September 15, 2007, and formed a <span class="hlt">crater</span> 14.2 m across. It is the smallest, youngest, and one of two eye-witnessed impact <span class="hlt">crater</span> events on Earth. The impact violated the hitherto existing view that stony meteorites below a size of 100 m undergo major disruption and deceleration during their passage through the atmosphere and are not capable of producing <span class="hlt">craters</span>. Fragmentation occurs if the strength of the meteoroid is less than the aerodynamic stresses that occur in flight. The small fragments that result from a breakup rain down at terminal velocity and are not capable of producing impact <span class="hlt">craters</span>. The Carancas <span class="hlt">cratering</span> event, however, demonstrates that meter-sized stony meteoroids indeed can survive the atmospheric passage under specific circumstances. We present results of a detailed geologic survey of the <span class="hlt">crater</span> and its ejecta. To constrain the possible range of impact parameters we carried out numerical models of <span class="hlt">crater</span> formation with the iSALE hydrocode in two and three dimensions. Depending on the strength properties of the target, the impact energies range between approximately 100-1000 MJ (0.024- 0.24 t TNT). By modeling the atmospheric traverse we demonstrate that low cosmic velocities (12- 14 kms-1) and shallow entry angles (<20°) are prerequisites to keep aerodynamic stresses low (<10 MPa) and thus to prevent fragmentation of stony meteoroids with standard strength properties. This scenario results in a strong meteoroid deceleration, a deflection of the trajectory to a steeper impact angle (40-60°), and an impact velocity of 350-600 ms-1, which is insufficient to produce a shock wave and significant shock effects in target minerals. Aerodynamic and <span class="hlt">crater</span> modeling are consistent with field data and our microscopic inspection. However, these data are in conflict with trajectories inferred from the analysis of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1996LPI....27..473G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1996LPI....27..473G"><span>The Group of Macha <span class="hlt">Craters</span> in Western Yakutia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gurov, E. P.</p> <p>1996-03-01</p> <p>The group of Macha <span class="hlt">craters</span> is placed in the marginal part of Aldan Anteclise in Macha river basin, the left tributary of Lena river. Coordinates of the <span class="hlt">craters</span>: 60 degrees 06 minutes N, 117 degrees 35 minutes E. The Macha <span class="hlt">craters</span> were discovered by aerovisual observations of Aldan Shield and Aldan Anteclise during the impact <span class="hlt">craters</span> search in this region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19860035476&hterms=copernicus&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dcopernicus','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19860035476&hterms=copernicus&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dcopernicus"><span>The nature of <span class="hlt">crater</span> rays - The Copernicus example</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Pieters, C. M.; Adams, J. B.; Smith, M. O.; Mouginis-Mark, P. J.; Zisk, S. H.</p> <p>1985-01-01</p> <p>It is pointed out that <span class="hlt">crater</span> rays are filamentous, generally high-albedo features which emanate nearly radially from young impact structures. An investigation has been conducted of the physical and chemical properties of a single lunar ray system for Copernicus <span class="hlt">crater</span> with the objective to achieve a better understanding of the nature of <span class="hlt">crater</span> rays, taking into account questions regarding the local or foreign origin of ray material. A combination of data is considered, giving attention to spectral reflectance (for composition), radar (for physical properties), and images (for photogeologic context). The <span class="hlt">crater</span> Copernicus was selected because of its well-developed ray system, the <span class="hlt">crater</span>'s relative youth, and the compositional contrast between the target material of Copernicus <span class="hlt">crater</span> and the material on which many rays were emplaced.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001Icar..149...37H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001Icar..149...37H"><span>Martian <span class="hlt">Cratering</span> 7: The Role of Impact Gardening</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hartmann, William K.; Anguita, Jorge; de la Casa, Miguel A.; Berman, Daniel C.; Ryan, Eileen V.</p> <p>2001-01-01</p> <p>Viking-era researchers concluded that impact <span class="hlt">craters</span> of diameter D<50 m were absent on Mars, and thus impact gardening was considered negligible in establishing decameter-scale surface properties. This paper documents martian <span class="hlt">crater</span> populations down to diameter D˜11 m and probably less on Mars, requiring a certain degree of impact gardening. Applying lunar data, we calculate cumulative gardening depth as a function of total <span class="hlt">cratering</span>. Stratigraphic units exposed since Noachian times would have experienced tens to hundreds of meters of gardening. Early Amazonian/late Hesperian sites, such as the first three landing sites, experienced cumulative gardening on the order of 3-14 m, a conclusion that may conflict with some landing site interpretations. Martian surfaces with less than a percent or so of lunar mare <span class="hlt">crater</span> densities have negligible impact gardening because of a probable cutoff of hypervelocity impact <span class="hlt">cratering</span> below D˜1 m, due to Mars' atmosphere. Unlike lunar regolith, martian regolith has been affected, and fines removed, by many processes. Deflation may have been a factor in leaving widespread boulder fields and associated dune fields, observed by the first three landers. Ancient regolith provided a porous medium for water storage, subsurface transport, and massive permafrost formation. Older regolith was probably cemented by evaporites and permafrost, may contain interbedded sediments and lavas, and may have been brecciated by later impacts. Growing evidence <span class="hlt">suggests</span> recent water mobility, and the existence of duricrust at Viking and Pathfinder sites demonstrates the cementing process. These results affect lander/rover searches for intact ancient deposits. The upper tens of meters of exposed Noachian units cannot survive today in a pristine state. Intact Noachian deposits might best be found in cliffside strata, or in recently exhumed regions. The hematite-rich areas found in Terra Meridiani by the Mars Global Surveyor are probably examples of the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA21215.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA21215.html"><span>Cracks in a <span class="hlt">Crater</span> Ice</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2016-12-07</p> <p>Many impact <span class="hlt">craters</span> on Mars were filled with ice in past climates. Sometimes this ice flows or slumps down the <span class="hlt">crater</span> walls into the center and acquires concentric wrinkles as a result. This image shows an example of this. There are other ways that scientists know the material in the <span class="hlt">crater</span> is icy. Surface cracks that form polygonal shapes cover the material in the <span class="hlt">crater</span>. They are easy to see in this spring-time image because seasonal frost hides inside the cracks, outlining them in bright white. These cracks form because ice within the ground expands and contracts a lot as it warms and cools. Scientists can see similar cracks in icy areas of the Earth and other icy locations on Mars. If you look closely, you'll see small polygons inside larger ones. The small polygons are younger and the cracks shallower while the large ones are outlined with cracks that penetrate more deeply. http://photojournal.jpl.nasa.gov/catalog/PIA21215</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19780031470&hterms=Astronaut+training&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DAstronaut%2Btraining','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19780031470&hterms=Astronaut+training&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DAstronaut%2Btraining"><span>Nevada Test Site <span class="hlt">craters</span> used for astronaut training</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Moore, H. J.</p> <p>1977-01-01</p> <p><span class="hlt">Craters</span> produced by chemical and nuclear explosives at the Nevada Test Site were used to train astronauts before their lunar missions. The <span class="hlt">craters</span> have characteristics suitable for reconnaissance-type field investigations. The Schooner test produced a <span class="hlt">crater</span> about 300 m across and excavated more than 72 m of stratigraphic section deposited in a fairly regular fashion so that systematic observations yield systematic results. Other features common on the moon, such as secondary <span class="hlt">craters</span> and glass-coated rocks, are present at Schooner <span class="hlt">crater</span>. Smaller explosive tests on Buckboard Mesa excavated rocks from three horizontal alteration zones within basalt flows so that the original sequence of the zones could be determined. One <span class="hlt">crater</span> illustrated the characteristics of <span class="hlt">craters</span> formed across vertical boundaries between rock units. Although the exercises at the Nevada Test Site were only a small part of the training of the astronauts, voice transcripts of Apollo missions 14, 16, and 17 show that the exercises contributed to astronaut performance on the moon.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007DPS....39.5006O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007DPS....39.5006O"><span>The Lack of Small <span class="hlt">Craters</span> on Eros is not due to the Yarkovsky Effect</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>O'Brien, David P.; Greenberg, R.</p> <p>2007-10-01</p> <p>Eros approaches saturation for <span class="hlt">craters</span> larger than 200 m in diameter, but is significantly depleted in smaller <span class="hlt">craters</span> [1]. It has been <span class="hlt">suggested</span> that this could reflect a paucity of small impactors in the main belt, due to their removal by the Yarkovsky effect [1,2]. Here we present the results of a self-consistent collisional and dynamical evolution model for the main belt and NEAs, along with a model for the evolution of asteroid <span class="hlt">crater</span> populations, that show that Eros' lack of small <span class="hlt">craters</span> is not likely due to the depletion of small impactors by the Yarkovsky effect, or any other depletion mechanism. To produce a main-belt size distribution that is suitably depleted in small impactors to match Eros' small <span class="hlt">crater</span> population requires a more extreme size-dependent removal rate than the Yarkovsky effect and Poynting-Robertson drag can provide. Using such an extreme removal rate introduces a wave into the model main-belt size distribution that propagates to large sizes, and is inconsistent with the observed main-belt population. Similarly, it introduces a wave in the model NEA population that is inconsistent with the observed NEAs. Eros is not alone in showing a depletion of small <span class="hlt">craters</span>. Recent observations of the asteroid Itokawa by the Hyabusa spacecraft show relatively few <span class="hlt">craters</span>, and Yarkovsky depletion of small impactors has again been <span class="hlt">suggested</span> as a possible explanation [3]. Our work shows that a substantial depletion of small impactors from the main belt would have consequences at large sizes, inconsistent with observations of the actual main-belt and NEA size distributions. Other explanations for the depletion of small <span class="hlt">craters</span> on asteroid surfaces must be explored [eg. 4,5]. References: [1] Chapman (2002), Icarus 155, p.104. [2] Bell (2001), LPSC XXXII, no.1964. [3] Saito (2006), Science 312, p.1341. [4] Richardson (2004), Science 306, p.1526. [5] Greenberg (2003), DPS 35, no.24.06.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19920001658','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19920001658"><span>Igneous intrusion models for floor fracturing in lunar <span class="hlt">craters</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wichman, R. W.; Schultz, P. H.</p> <p>1991-01-01</p> <p>Lunar floor-fractured <span class="hlt">craters</span> are primarily located near the maria and frequently contain ponded mare units and dark mantling deposits. Fracturing is confined to the <span class="hlt">crater</span> interior, often producing a moat-like feature near the floor edge, and <span class="hlt">crater</span> depth is commonly reduced by uplift of the <span class="hlt">crater</span> floor. Although viscous relaxation of <span class="hlt">crater</span> topography can produce such uplift, the close association of modification with surface volcanism supports a model linking floor fracture to <span class="hlt">crater</span>-centered igneous intrusions. The consequences of two intrusion models for the lunar interior are quantitatively explored. The first model is based on terrestrial laccoliths and describes a shallow intrusion beneath the <span class="hlt">crater</span>. The second model is based on cone sheet complexes where surface deformation results from a deeper magma chamber. Both models, their fit to observed <span class="hlt">crater</span> modifications and possible implications for local volcanism are described.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA10230&hterms=duck&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dduck','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA10230&hterms=duck&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dduck"><span>'Lyell' Panorama inside Victoria <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2008-01-01</p> <p><p/> During four months prior to the fourth anniversary of its landing on Mars, NASA's Mars Exploration Rover Opportunity examined rocks inside an alcove called 'Duck Bay' in the western portion of Victoria <span class="hlt">Crater</span>. The main body of the <span class="hlt">crater</span> appears in the upper right of this stereo panorama, with the far side of the <span class="hlt">crater</span> lying about 800 meters (half a mile) away. Bracketing that part of the view are two promontories on the <span class="hlt">crater</span>'s rim at either side of Duck Bay. They are 'Cape Verde,' about 6 meters (20 feet) tall, on the left, and 'Cabo Frio,' about 15 meters (50 feet) tall, on the right. The rest of the image, other than sky and portions of the rover, is ground within Duck Bay. <p/> Opportunity's targets of study during the last quarter of 2007 were rock layers within a band exposed around the interior of the <span class="hlt">crater</span>, about 6 meters (20 feet) from the rim. Bright rocks within the band are visible in the foreground of the panorama. The rover science team assigned informal names to three subdivisions of the band: 'Steno,' 'Smith,' and 'Lyell.' <p/> This view combines many images taken by Opportunity's panoramic camera (Pancam) from the 1,332nd through 1,379th Martian days, or sols, of the mission (Oct. 23 to Dec. 11, 2007). Images taken through Pancam filters centered on wavelengths of 753 nanometers, 535 nanometers and 432 nanometers were mixed to produce an approximately true-color panorama. Some visible patterns in dark and light tones are the result of combining frames that were affected by dust on the front sapphire window of the rover's camera. <p/> Opportunity landed on Jan. 25, 2004, Universal Time, (Jan. 24, Pacific Time) inside a much smaller <span class="hlt">crater</span> about 6 kilometers (4 miles) north of Victoria <span class="hlt">Crater</span>, to begin a surface mission designed to last 3 months and drive about 600 meters (0.4 mile).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AGUFM.P51B1199S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AGUFM.P51B1199S"><span>Comparison of Topographic Profiles Across Venus' Coronae and <span class="hlt">Craters</span>: Implications for Corona Origin Hypothesis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stoddard, P. R.; Jurdy, D. M.</p> <p>2006-12-01</p> <p>Venus' surface hosts nearly 1000 unambiguous impact <span class="hlt">craters</span>, ranging in diameter from 1.5 to 280 km. Although the majority of these are pristine, slightly less than 200 have been modified by either volcanic or tectonic activity or both. In addition, numerous researchers have identified hundreds of ring-like features of varying morphology, termed "coronae." These have typically been thought of as having a diapiric or volcanic origin. Recently, however, based on the circular to quasi-circular nature of coronae, an alternative origin - impact - has been proposed. We compare the profiles across agreed-upon <span class="hlt">craters</span> to several coronae that have been <span class="hlt">suggested</span> as impact sites. For each feature, 36 profiles (taken every ten degrees) are aligned and then averaged together. For Mead, Cleopatra, Meitner, and Isabella <span class="hlt">craters</span>, the profiles display the typical rim and basin structure expected for <span class="hlt">craters</span>, but for Klenova <span class="hlt">crater</span> the average is more domal, with only a few of the individual profiles looking <span class="hlt">crater</span>-like. Among the "contested" coronae, the average profiles for Eurynome, Maya, and C21 appear <span class="hlt">crater</span>-like, albeit with more variation among the individual profiles than seen in the agreed-upon <span class="hlt">craters</span>. Anquet has a rim-and-basin structure, but unlike typical <span class="hlt">craters</span>, the basin is elevated above the surrounding plains. Acrea appears to be a small hill in a large depression, again with a high degree of variability among the profiles. Ninhursag is clearly domal, and cannot be taken as a <span class="hlt">crater</span>. A summary of the variability of the profiles - where 100% correlation would indicate perfect circular symmetry - indicates that, with the exception of Klenova, those features universally agreed-upon as <span class="hlt">craters</span> have the highest correlation percentages - all at or above 80%. The disputed features are not as circular, although C21 is close. Based on this analysis, we conclude that Klenova has been mischaracterized as an impact <span class="hlt">crater</span>, and that C21 and some other features previously</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-GSFC_20171208_Archive_e001873.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-GSFC_20171208_Archive_e001873.html"><span>Tycho <span class="hlt">Crater</span>'s Peak</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2011-06-29</p> <p>NASA image release June 30, 2011 On June 10, 2011, NASA's Lunar Reconnaissance Orbiter captured a dramatic sunrise view of Tycho <span class="hlt">crater</span>. A very popular target with amateur astronomers, Tycho is located at 43.37°S, 348.68°E, and is about 51 miles (82 km) in diameter. The summit of the central peak is 1.24 miles (2 km) above the <span class="hlt">crater</span> floor. The distance from Tycho's floor to its rim is about 2.92 miles (4.7 km). Tycho <span class="hlt">crater</span>'s central peak complex, shown here, is about 9.3 miles (15 km) wide, left to right (southeast to northwest in this view). › More information and related images › NASA's LRO website Credit: NASA Goddard/Arizona State University NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA20036.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA20036.html"><span>The Youngest <span class="hlt">Crater</span> on Charon?</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2015-10-29</p> <p>NASA's New Horizons scientists have discovered a striking contrast between one of the fresh <span class="hlt">craters</span> on Pluto's largest moon Charon and a neighboring <span class="hlt">crater</span> dotting the moon's Pluto-facing hemisphere. The <span class="hlt">crater</span>, informally named Organa, caught scientists' attention as they were studying New Horizons' highest-resolution infrared compositional scan of Charon. Organa and portions of the surrounding material ejected from it show infrared absorption at wavelengths of about 2.2 microns, indicating that the <span class="hlt">crater</span> is rich in frozen ammonia -- and, from what scientists have seen so far, unique on Pluto's largest moon. The infrared spectrum of nearby Skywalker <span class="hlt">crater</span>, for example, is similar to the rest of Charon's <span class="hlt">craters</span> and surface, with features dominated by ordinary water ice. This composite image is based on observations from the New Horizons Ralph/LEISA instrument made at 10:25 UT (6:25 a.m. EDT) on July 14, 2015, when New Horizons was 50,000 miles (81,000 kilometers) from Charon. The spatial resolution is 3 miles (5 kilometers) per pixel. The LEISA data were downlinked Oct. 1-4, 2015, and processed into a map of Charon's 2.2 micron ammonia-ice absorption band. Long Range Reconnaissance Imager (LORRI) panchromatic images used as the background in this composite were taken about 8:33 UT (4:33 a.m. EDT) July 14 at a resolution of 0.6 miles (0.9 kilometers) per pixel and downlinked Oct. 5-6. The ammonia absorption map from LEISA is shown in green on the LORRI image. The region covered by the yellow box is 174 miles across (280 kilometers). http://photojournal.jpl.nasa.gov/catalog/PIA20036</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Icar..266...44S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Icar..266...44S"><span>Geomorphology of Lowell <span class="hlt">crater</span> region on the Moon</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Srivastava, N.; Varatharajan, I.</p> <p>2016-03-01</p> <p>Surface topography, surface morphology and <span class="hlt">crater</span> chronology studies have been carried out for the Lowell <span class="hlt">crater</span> region (occupying ∼198 × 198 km2 in the northwestern quadrant of the Orientale basin) using Kaguya TC-DTM, LRO-WAC data, and Chandrayaan-1 M3-750 nm image, to characterize and date Lowell impact event and to identify and assess the geological importance of the Lowell <span class="hlt">crater</span> and effect of pre-existing geological conditions on the present day appearance of Lowell <span class="hlt">crater</span>. The Lowell <span class="hlt">crater</span> has been found to be polygonal in shape with an average diameter of 69.03 km. Its average rim height and depth from pre-existing surface are 1.02 km and 2.82 km respectively. A prominent central peak with average height of 1.77 km above the <span class="hlt">crater</span> floor is present, which could have exposed undifferentiated mantle rocks. The peak exhibits a pronounced ;V; shaped slumped zone on the eastern side and a distinct ;V; shaped depression in the adjacent region on the <span class="hlt">crater</span> floor. Several other peculiarities noticed and mapped here include W-E asymmetry in the degree of slumping of the walls and height of the topographic rim, N-S asymmetry in the proximal ejecta distribution with most of the material lying in the northern direction, concentration of exterior melt pools in the northeastern direction only, presence of several cross cutting pre-existing lineaments on the <span class="hlt">crater</span> walls, presence of a superposed rayed <span class="hlt">crater</span> on the eastern wall, and a geologically interesting resurfaced unit, which could be an outcome of recent volcanic activity in the region. It has been inferred that the Lowell <span class="hlt">crater</span> formed due to impact of a ∼5.7 km diameter bolide in the Montes Rook region. The impact occurred at an angle of ∼30-45° from the S-SW direction. The age of the Lowell <span class="hlt">crater</span> has been estimated as 374 ± 28 Ma, therefore it is a Younger Copernican <span class="hlt">crater</span> consistent with the possibility expressed by McEwen et al. (McEwen, A.S., et al. [1993]. J. Geophys. Res. 98(E9), 17207</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012LPI....43.2579H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012LPI....43.2579H"><span>Investigation of Secondary <span class="hlt">Craters</span> in the Saturnian System</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hoogenboom, T.; Schenk, P.; White, O. L.</p> <p>2012-03-01</p> <p>To derive accurate ages using impact <span class="hlt">craters</span>, the impact source must be determined. We investigate secondary <span class="hlt">crater</span> size, frequency, distribution, formation, and <span class="hlt">crater</span> chain formation on icy satellites throughout the Jupiter and Saturn systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19760006915','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19760006915"><span>A size-frequency study of large Martian <span class="hlt">craters</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Woronow, A.</p> <p>1975-01-01</p> <p>The log normal frequency distribution law was used to analyze the <span class="hlt">crater</span> population on the surface of Mars. Resulting data show possible evidence for the size frequency evolution of <span class="hlt">crater</span> producing bodies. Some regions on Mars display excessive depletion of either large or small <span class="hlt">craters</span>; the most likely causes of the depletion are considered. Apparently, eolian sedimentation has markedly altered the population of the small <span class="hlt">craters</span> south of -30 deg latitude. The general effects of <span class="hlt">crater</span> obliteration in the Southern Hemisphere appear to be confined to diameters of less than 20 km. A strong depletion of large <span class="hlt">craters</span> in a large region just south of Deuteronilus Mensae, and in a small region centered at 35 deg latitude and 10 deg west longitude, may indicate locations of subsurface ice.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19910048874&hterms=joseph+campbell&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Djoseph%2Bcampbell','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19910048874&hterms=joseph+campbell&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Djoseph%2Bcampbell"><span>Impact <span class="hlt">craters</span> on Venus - Initial analysis from Magellan</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Phillips, Roger J.; Arvidson, Raymond E.; Boyce, Joseph M.; Campbell, Donald B.; Guest, John E.</p> <p>1991-01-01</p> <p>The general features of impact <span class="hlt">craters</span> are described emphasizing two aspects: the effect of the atmosphere on <span class="hlt">crater</span> and ejecta morphology and the implications of the distribution and appearance of the <span class="hlt">craters</span> for the volcanic and tectonic resurfacing history of Venus. Magellan radar images reveal 135 <span class="hlt">craters</span> about 15 km in diameter containing central peaks, multiple central peaks, and peak rings. <span class="hlt">Craters</span> smaller than 15 km exhibit multiple floors or appear in clusters. Surface flows of material initially entrained in the atmosphere are characterized. Zones of low radar albedo originated from deformation of the surface by the shock or pressure wave associated with the incoming meteoroid surround many <span class="hlt">craters</span>. A spectrum of surface ages on Venus ranging from 0 to 800 million years indicates that Venus must be a geologically active planet.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ISPAr42.3..865L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ISPAr42.3..865L"><span>Remote Sensing Observations and Numerical Simulation for Martian Layered Ejecta <span class="hlt">Craters</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, L.; Yue, Z.; Zhang, C.; Li, D.</p> <p>2018-04-01</p> <p>To understand past Martian climates, it is important to know the distribution and nature of water ice on Mars. Impact <span class="hlt">craters</span> are widely used ubiquitous indicators for the presence of subsurface water or ice on Mars. Remote sensing observations and numerical simulation are powerful tools for investigating morphological and topographic features on planetary surfaces, and we can use the morphology of layered ejecta <span class="hlt">craters</span> and hydrocode modeling to constrain possible layering and impact environments. The approach of this work consists of three stages. Firstly, the morphological characteristics of the Martian layered ejecta <span class="hlt">craters</span> are performed based on Martian images and DEM data. Secondly, numerical modeling layered ejecta are performed through the hydrocode iSALE (impact-SALE). We present hydrocode modeling of impacts onto targets with a single icy layer within an otherwise uniform basalt crust to quantify the effects of subsurface H2O on observable layered ejecta morphologies. The model setup is based on a layered target made up of a regolithic layer (described by the basalt ANEOS), on top an ice layer (described by ANEOS equation of H2O ice), in turn on top of an underlying basaltic crust. The bolide is a 0.8 km diameter basaltic asteroid hitting the Martian surface vertically at a velocity of 12.8 km/s. Finally, the numerical results are compared with the MOLA DEM profile in order to analyze the formation mechanism of Martian layered ejecta <span class="hlt">craters</span>. Our simulations <span class="hlt">suggest</span> that the presence of an icy layer significantly modifies the <span class="hlt">cratering</span> mechanics, and many of the unusual features of SLE <span class="hlt">craters</span> may be explained by the presence of icy layers. Impact <span class="hlt">cratering</span> on icy satellites is significantly affected by the presence of subsurface H2O.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19800039557&hterms=depression+mexico&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Ddepression%2Bmexico','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19800039557&hterms=depression+mexico&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Ddepression%2Bmexico"><span>Endogenic <span class="hlt">craters</span> on basaltic lava flows - Size frequency distributions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Greeley, R.; Gault, D. E.</p> <p>1979-01-01</p> <p>Circular <span class="hlt">crater</span> forms, termed collapse depressions, which occur on many basalt flows on the earth have also been detected on the moon and Mars and possibly on Mercury and Io. The admixture of collapse <span class="hlt">craters</span> with impact <span class="hlt">craters</span> would affect age determinations of planetary surface units based on impact <span class="hlt">crater</span> statistics by making them appear anomalously old. In the work described in the present paper, the techniques conventionally used in planetary <span class="hlt">crater</span> counting were applied to the determination of the size range and size frequency distribution of collapse <span class="hlt">craters</span> on lava flows in Idaho, California, and New Mexico. Collapse depressions range in size from 3 to 80 m in diameter; their cumulative size distributions are similar to those of small impact <span class="hlt">craters</span> on the moon.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004JGRE..109.6005W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004JGRE..109.6005W"><span>Distribution, morphology, and origins of Martian pit <span class="hlt">crater</span> chains</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wyrick, Danielle; Ferrill, David A.; Morris, Alan P.; Colton, Shannon L.; Sims, Darrell W.</p> <p>2004-06-01</p> <p>Pit <span class="hlt">craters</span> are circular to elliptical depressions found in alignments (chains), which in many cases coalesce into linear troughs. They are common on the surface of Mars and similar to features observed on Earth and other terrestrial bodies. Pit <span class="hlt">craters</span> lack an elevated rim, ejecta deposits, or lava flows that are associated with impact <span class="hlt">craters</span> or calderas. It is generally agreed that the pits are formed by collapse into a subsurface cavity or explosive eruption. Hypotheses regarding the formation of pit <span class="hlt">crater</span> chains require development of a substantial subsurface void to accommodate collapse of the overlying material. <span class="hlt">Suggested</span> mechanisms of formation include: collapsed lava tubes, dike swarms, collapsed magma chamber, substrate dissolution (analogous to terrestrial karst), fissuring beneath loose material, and dilational faulting. The research described here is intended to constrain current interpretations of pit <span class="hlt">crater</span> chain formation by analyzing their distribution and morphology. The western hemisphere of Mars was systematically mapped using Mars Orbiter Camera (MOC) images to generate ArcView™ Geographic Information System (GIS) coverages. All visible pit <span class="hlt">crater</span> chains were mapped, including their orientations and associations with other structures. We found that pit chains commonly occur in areas that show regional extension or local fissuring. There is a strong correlation between pit chains and fault-bounded grabens. Frequently, there are transitions along strike from (1) visible faulting to (2) faults and pits to (3) pits alone. We performed a detailed quantitative analysis of pit <span class="hlt">crater</span> morphology using MOC narrow angle images, Thermal Emission Imaging System (THEMIS) visual images, and Mars Orbiter Laser Altimeter (MOLA) data. This allowed us to determine a pattern of pit chain evolution and calculate pit depth, slope, and volume. Volumes of approximately 150 pits from five areas were calculated to determine volume size distribution and regional</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.P12B..04K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.P12B..04K"><span>An upper limit on Early Mars atmospheric pressure from small ancient <span class="hlt">craters</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kite, E. S.; Williams, J.; Lucas, A.; Aharonson, O.</p> <p>2012-12-01</p> <p>Planetary atmospheres brake, ablate, and disrupt small asteroids and comets, filtering out small hypervelocity surface impacts and causing fireballs, airblasts, meteors, and meteorites. Hypervelocity <span class="hlt">craters</span> <1 km diameter on Earth are typically caused by irons (because stones are more likely to break up), and the smallest hypervelocity <span class="hlt">craters</span> near sea-level on Earth are ~20 m in diameter. 'Zap pits' as small as 30 microns are known from the airless moon, but the other airy worlds show the effects of progressively thicker atmospheres:- the modern Mars atmosphere is marginally capable of removing >90% of the kinetic energy of >240 kg iron impactors; Titan's paucity of small <span class="hlt">craters</span> is consistent with a model predicting atmospheric filtering of <span class="hlt">craters</span> smaller than 6-8km; and on Venus, <span class="hlt">craters</span> below ~20 km diameter are substantially depleted. Changes in atmospheric CO2 concentration are believed to be the single most important control on Mars climate evolution and habitability. Existing data requires an early epoch of massive atmospheric loss to space; <span class="hlt">suggests</span> that the present-day rate of escape to space is small; and offers only limited evidence for carbonate formation. Existing evidence has not led to convergence of atmosphere-evolution models, which must balance poorly understood fluxes from volcanic degassing, surface weathering, and escape to space. More direct measurements are required in order to determine the history of CO2 concentrations. Wind erosion and tectonics exposes ancient surfaces on Mars, and the size-frequency distribution of impacts on these surfaces has been previously <span class="hlt">suggested</span> as a proxy time series of Mars atmospheric thickness. We will present a new upper limit on Early Mars atmospheric pressure using the size-frequency distribution of 20-100m diameter ancient <span class="hlt">craters</span> in Aeolis Dorsa, validated using HiRISE DTMs, in combination with Monte Carlo simulations of the effect of paleo-atmospheres of varying thickness on the <span class="hlt">crater</span> flux. These</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA07169&hterms=night+shift&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dnight%2Bshift','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA07169&hterms=night+shift&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dnight%2Bshift"><span><span class="hlt">Crater</span> At Night</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2004-01-01</p> <p><p/> [figure removed for brevity, see original site] <p/> This nighttime IR image is dominated by a large <span class="hlt">crater</span>. The <span class="hlt">crater</span> no longer has any visible ejecta, and retains only it's rim - seen here as a varigated black/gray semi-circle surrounding a brighter floor. The smaller <span class="hlt">craters</span> in the image have bright rings representing their rocky rims. This <span class="hlt">crater</span> is located just south of Syrtis Major. <p/> Image information: IR instrument. Latitude 2.8, Longitude 76.4 East (283.6 West). 100 meter/pixel resolution. <p/> Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. <p/> NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA21802.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA21802.html"><span>Investigating Mars: Russell <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2017-08-04</p> <p>This image shows the western part of the dune field on the floor of Russell <span class="hlt">Crater</span>. Russell <span class="hlt">Crater</span> is located in Noachis Terra. A spectacular dune ridge and other dune forms on the <span class="hlt">crater</span> floor have caused extensive imaging. The Odyssey spacecraft has spent over 15 years in orbit around Mars, circling the planet more than 69000 times. It holds the record for longest working spacecraft at Mars. THEMIS, the IR/VIS camera system, has collected data for the entire mission and provides images covering all seasons and lighting conditions. Over the years many features of interest have received repeated imaging, building up a suite of images covering the entire feature. From the deepest chasma to the tallest volcano, individual dunes inside <span class="hlt">craters</span> and dune fields that encircle the north pole, channels carved by water and lava, and a variety of other feature, THEMIS has imaged them all. For the next several months the image of the day will focus on the Tharsis volcanoes, the various chasmata of Valles Marineris, and the major dunes fields. We hope you enjoy these images! Orbit Number: 33970 Latitude: -54.3831 Longitude: 12.3712 Instrument: VIS Captured: 2009-08-11 09:20 https://photojournal.jpl.nasa.gov/catalog/PIA21802</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA21806.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA21806.html"><span>Investigating Mars: Russell <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2017-08-09</p> <p>This image shows the central part of the dune field on the floor of Russell <span class="hlt">Crater</span>. Russell <span class="hlt">Crater</span> is located in Noachis Terra. A spectacular dune ridge and other dune forms on the <span class="hlt">crater</span> floor have caused extensive imaging. The Odyssey spacecraft has spent over 15 years in orbit around Mars, circling the planet more than 69000 times. It holds the record for longest working spacecraft at Mars. THEMIS, the IR/VIS camera system, has collected data for the entire mission and provides images covering all seasons and lighting conditions. Over the years many features of interest have received repeated imaging, building up a suite of images covering the entire feature. From the deepest chasma to the tallest volcano, individual dunes inside <span class="hlt">craters</span> and dune fields that encircle the north pole, channels carved by water and lava, and a variety of other feature, THEMIS has imaged them all. For the next several months the image of the day will focus on the Tharsis volcanoes, the various chasmata of Valles Marineris, and the major dunes fields. We hope you enjoy these images! Orbit Number: 34856 Latitude: -54.5757 Longitude: 12.8629 Instrument: VIS Captured: 2009-10-23 08:04 https://photojournal.jpl.nasa.gov/catalog/PIA21806</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA21798.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA21798.html"><span>Investigating Mars: Russell <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2017-07-31</p> <p>This image shows a slice of the floor of Russell <span class="hlt">Crater</span>. Russell <span class="hlt">Crater</span> is located in Noachis Terra. The spectacular dune ridge and other dune forms on the <span class="hlt">crater</span> floor have caused extensive imaging. The Odyssey spacecraft has spent over 15 years in orbit around Mars, circling the planet more than 69,000 times. It holds the record for longest working spacecraft at Mars. THEMIS, the IR/VIS camera system, has collected data for the entire mission and provides images covering all seasons and lighting conditions. Over the years many features of interest have received repeated imaging, building up a suite of images covering the entire feature. From the deepest chasma to the tallest volcano, individual dunes inside <span class="hlt">craters</span> and dune fields that encircle the north pole, channels carved by water and lava, and a variety of other feature, THEMIS has imaged them all. For the next several months the image of the day will focus on the Tharsis volcanoes, the various chasmata of Valles Marineris, and the major dunes fields. We hope you enjoy these images! Orbit Number: 6354 Latitude: -54.6188 Longitude: 12.9816 Instrument: VIS Captured: 2003-05-21 14:24 https://photojournal.jpl.nasa.gov/catalog/PIA21798</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EPSC...10..284O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EPSC...10..284O"><span>Polygonal <span class="hlt">Craters</span> on Dwarf-Planet Ceres</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Otto, K. A.; Jaumann, R.; Krohn, K.; Buczkowski, D. L.; von der Gathen, I.; Kersten, E.; Mest, S. C.; Preusker, F.; Roatsch, T.; Schenk, P. M.; Schröder, S.; Schulzeck, F.; Scully, J. E. C.; Stepahn, K.; Wagner, R.; Williams, D. A.; Raymond, C. A.; Russell, C. T.</p> <p>2015-10-01</p> <p>With approximately 950 km diameter and a mass of #1/3 of the total mass of the asteroid belt, (1) Ceres is the largest and most massive object in the Main Asteroid Belt. As an intact proto-planet, Ceres is key to understanding the origin and evolution of the terrestrialplanets [1]. In particular, the role of water during planet formation is of interest, because the differentiated dwarf-planet is thought to possess a water rich mantle overlying a rocky core [2]. The Dawn space craft arrived at Ceres in March this year after completing its mission at (4) Vesta. At Ceres, the on-board Framing Camera (FC) collected image data which revealed a large variety of impact <span class="hlt">crater</span> morphologies including polygonal <span class="hlt">craters</span> (Figure 1). Polygonal <span class="hlt">craters</span> show straight rim sections aligned to form an angular shape. They are commonly associated with fractures in the target material. Simple polygonal <span class="hlt">craters</span> develop during the excavation stage when the excavation flow propagates faster along preexisting fractures [3, 5]. Complex polygonal <span class="hlt">craters</span> adopt their shape during the modification stage when slumping along fractures is favoured [3]. Polygonal <span class="hlt">craters</span> are known from a variety of planetary bodies including Earth [e.g. 4], the Moon [e.g. 5], Mars [e.g. 6], Mercury [e.g. 7], Venus [e.g. 8] and outer Solar System icy satellites [e.g. 9].</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA20339.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA20339.html"><span>Erosion and Deposition in Schaeberle <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2016-01-14</p> <p>Schaeberle <span class="hlt">Crater</span> is a large, heavily-infilled <span class="hlt">crater</span> with many interesting features. This image NASA Mars Reconnaissance Orbiter spacecraft shows a window into the <span class="hlt">crater</span> fill deposit, showcasing eroding bedrock and aeolian landforms. This pit is located near the geometric center of our image, making it a central pit <span class="hlt">crater</span>. Central pit <span class="hlt">craters</span> are thought to form from impact melt draining through subsurface cracks in the deepest part of the <span class="hlt">crater</span> shortly following impact. A closeup image shows light-toned bedrock and a small cliff that appears to be weathering away. Below the cliff there are several different types of aeolian features, including ripples and transverse aeolian ridges (TAR). The sand that forms the small, bluish ripples may be weathering out of the cliff face, in contrast to the larger, light-toned TAR which are thought to be currently inactive. More of the TAR are visible in another closeup image. In this case, they are clearly covered by a dark, ripple-covered sand sheet. We have only imaged this location once, so it is impossible to determine whether or not the sand sheet is blowing in the wind. But due to repeated HiRISE imaging in other areas, active dunes are now known to be common across Mars and we can reasonably speculate that these dunes are moving, too. http://photojournal.jpl.nasa.gov/catalog/PIA20339</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20090033478','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20090033478"><span><span class="hlt">Cratering</span> Equations for Zinc Orthotitanate Coated Aluminum</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hyde, James; Christiansen, Eric; Liou, Jer-Chyi; Ryan, Shannon</p> <p>2009-01-01</p> <p>The final STS-125 servicing mission (SM4) to the Hubble Space Telescope (HST) in May of 2009 saw the return of the 2nd Wide Field Planetary Camera (WFPC2) aboard the shuttle Discovery. This hardware had been in service on HST since it was installed during the SM1 mission in December of 1993 yielding one of the longest low Earth orbit exposure times (15.4 years) of any returned space hardware. The WFPC2 is equipped with a 0.8 x 2.2 m radiator for thermal control of the camera electronics (Figure 1). The space facing surface of the 4.1 mm thick aluminum radiator is coated with Z93 zinc orthotitanate thermal control paint with a nominal thickness of 0.1 0.2 mm. Post flight inspections of the radiator panel revealed hundreds of micrometeoroid/orbital debris (MMOD) impact <span class="hlt">craters</span> ranging in size from less than 300 to nearly 1000 microns in diameter. The Z93 paint exhibited large spall areas around the larger impact sites (Figure 2) and the <span class="hlt">craters</span> observed in the 6061-T651 aluminum had a different shape than those observed in uncoated aluminum. Typical hypervelocity impact <span class="hlt">craters</span> in aluminum have raised lips around the impact site. The <span class="hlt">craters</span> in the HST radiator panel had suppressed <span class="hlt">crater</span> lips, and in some cases multiple <span class="hlt">craters</span> were present instead of a single individual <span class="hlt">crater</span>. Humes and Kinard observed similar behavior after the WFPC1 post flight inspection and assumed the Z93 coating was acting like a bumper in a Whipple shield. Similar paint behavior (spall) was also observed by Bland2 during post flight inspection of the International Space Station (ISS) S-Band Antenna Structural Assembly (SASA) in 2008. The SASA, with similar Z93 coated aluminum, was inspected after nearly 4 years of exposure on the ISS. The multi-<span class="hlt">crater</span> phenomena could be a function of the density, composition, or impact obliquity angle of the impacting particle. For instance, a micrometeoroid particle consisting of loosely bound grains of material could be responsible for creating the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA22255.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA22255.html"><span>Icy Layers in <span class="hlt">Craters</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2018-02-20</p> <p>In this image from NASA's Mars Reconnaissance Rover (MRO) we can see the edge of a mound of ice in one of these mid-latitude <span class="hlt">craters</span>. Some of it has already been removed, so we can see layering that used to be in the <span class="hlt">crater</span>'s interior. Scientists use ice deposits like these to figure out how the climate has changed on Mars. Another upside of recognizing this ice is that future astronauts will have plenty of drinking water. Scientists now realize that ice is very common on the Martian surface. It often fills up <span class="hlt">craters</span> and valleys in the mid-latitudes in older climates, although when it's covered in dust it can be hard to recognize. Today the climate on Mars makes this ice unstable and some of it has evaporated away. https://photojournal.jpl.nasa.gov/catalog/PIA22255</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA20192.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA20192.html"><span>Kupalo <span class="hlt">Crater</span> from LAMO</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2016-01-12</p> <p>This image from NASA's Dawn spacecraft shows Kupalo <span class="hlt">Crater</span>, one of the youngest <span class="hlt">craters</span> on Ceres. The <span class="hlt">crater</span> has bright material exposed on its rim and walls, which could be salts. Its flat floor likely formed from impact melt and debris. Kupalo, which measures 16 miles (26 kilometers) across and is located at southern mid-latitudes, is named for the Slavic god of vegetation and harvest. Kupalo was imaged earlier in Dawn's science mission at Ceres -- during Survey orbit (see PIA19624) and from the high altitude mapping orbit, or HAMO (see PIA20124). Dawn took this image on Dec. 21 from its low-altitude mapping orbit (LAMO) at an approximate altitude of 240 miles (385 kilometers) above Ceres. The image resolution is 120 feet (35 meters) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA20192</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA06085&hterms=cloud+technology&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dcloud%2Btechnology','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA06085&hterms=cloud+technology&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dcloud%2Btechnology"><span><span class="hlt">Crater</span> Clouds</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2006-01-01</p> <p><p/> [figure removed for brevity, see original site] Context image for PIA06085 <span class="hlt">Crater</span> Clouds <p/> The <span class="hlt">crater</span> on the right side of this image is affecting the local wind regime. Note the bright line of clouds streaming off the north rim of the <span class="hlt">crater</span>. <p/> Image information: VIS instrument. Latitude -78.8N, Longitude 320.0E. 17 meter/pixel resolution. <p/> Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. <p/> NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA04448&hterms=Butterfly&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DButterfly','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA04448&hterms=Butterfly&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DButterfly"><span>Cydonia <span class="hlt">Craters</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2003-01-01</p> <p><p/> [figure removed for brevity, see original site] <p/>Eroded mesas and secondary <span class="hlt">craters</span> dot the landscape in this area of the Cydonia Mensae region. The single oval-shaped <span class="hlt">crater</span> displays a 'butterfly' ejecta pattern, indicating that the <span class="hlt">crater</span> formed from a low-angle impact.<p/>Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.<p/>NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.<p/>Image information: VIS instrument. Latitude 32.9, Longitude 343.8 East (16.2 West). 19 meter/pixel resolution.<p/></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018Icar..299...68T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018Icar..299...68T"><span>A depth versus diameter scaling relationship for the best-preserved melt-bearing complex <span class="hlt">craters</span> on Mars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tornabene, Livio L.; Watters, Wesley A.; Osinski, Gordon R.; Boyce, Joseph M.; Harrison, Tanya N.; Ling, Victor; McEwen, Alfred S.</p> <p>2018-01-01</p> <p>We use topographic data to show that impact <span class="hlt">craters</span> with pitted floor deposits are among the deepest on Mars. This is consistent with the interpretation of pitted materials as primary <span class="hlt">crater</span>-fill impactite deposits emplaced during <span class="hlt">crater</span> formation. Our database consists of 224 pitted material <span class="hlt">craters</span> ranging in size from ∼1 to 150 km in diameter. Our measurements are based on topographic data from the Mars Orbiter Laser Altimeter (MOLA) and the High-Resolution Stereo Camera (HRSC). We have used these <span class="hlt">craters</span> to measure the relationship between <span class="hlt">crater</span> diameter and the initial post-formation depth. Depth was measured as maximum rim-to-floor depth, (dr), but we also report the depth measured using other definitions. The database was down-selected by refining or removing elevation measurements from ;problematic; <span class="hlt">craters</span> affected by processes and conditions that influenced their dr/D, such as pre-impact slopes/topography and later overprinting <span class="hlt">craters</span>. We report a maximum (deepest) and mean scaling relationship of dr = (0.347 ± 0.021)D0.537 ± 0.017 and dr = (0.323 ± 0.017)D0.538 ± 0.016, respectively. Our results <span class="hlt">suggest</span> that significant variations between previously-reported MOLA-based dr vs. D relationships may result from the inclusion of <span class="hlt">craters</span> that: 1) are influenced by atypical processes (e.g., highly oblique impact), 2) are significantly degraded, 3) reside within high-strength regions, and 4) are transitional (partially collapsed). By taking such issues into consideration and only measuring <span class="hlt">craters</span> with primary floor materials, we present the best estimate to date of a MOLA-based relationship of dr vs. D for the least-degraded complex <span class="hlt">craters</span> on Mars. This can be applied to <span class="hlt">crater</span> degradation studies and provides a useful constraint for models of complex <span class="hlt">crater</span> formation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA01008&hterms=Adobe+Photoshop&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DAdobe%2BPhotoshop','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA01008&hterms=Adobe+Photoshop&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DAdobe%2BPhotoshop"><span>Big <span class="hlt">Crater</span> as Viewed by Pathfinder Lander</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1997-01-01</p> <p>The 'Big <span class="hlt">Crater</span>' is actually a relatively small Martian <span class="hlt">crater</span> to the southeast of the Mars Pathfinder landing site. It is 1500 meters (4900 feet) in diameter, or about the same size as Meteor <span class="hlt">Crater</span> in Arizona. Superimposed on the rim of Big <span class="hlt">Crater</span> (the central part of the rim as seen here) is a smaller <span class="hlt">crater</span> nicknamed 'Rimshot <span class="hlt">Crater</span>.' The distance to this smaller <span class="hlt">crater</span>, and the nearest portion of the rim of Big <span class="hlt">Crater</span>, is 2200 meters (7200 feet). To the right of Big <span class="hlt">Crater</span>, south from the spacecraft, almost lost in the atmospheric dust 'haze,' is the large streamlined mountain nicknamed 'Far Knob.' This mountain is over 450 meters (1480 feet) tall, and is over 30 kilometers (19 miles) from the spacecraft. Another, smaller and closer knob, nicknamed 'Southeast Knob' can be seen as a triangular peak to the left of the flanks of the Big <span class="hlt">Crater</span> rim. This knob is 21 kilometers (13 miles) southeast from the spacecraft.<p/>The larger features visible in this scene - Big <span class="hlt">Crater</span>, Far Knob, and Southeast Knob - were discovered on the first panoramas taken by the IMP camera on the 4th of July, 1997, and subsequently identified in Viking Orbiter images taken over 20 years ago. The scene includes rocky ridges and swales or 'hummocks' of flood debris that range from a few tens of meters away from the lander to the distance of South Twin Peak. The largest rock in the nearfield, just left of center in the foreground, nicknamed 'Otter', is about 1.5 meters (4.9 feet) long and 10 meters (33 feet) from the spacecraft.<p/>This view of Big <span class="hlt">Crater</span> was produced by combining 6 individual 'Superpan' scenes from the left and right eyes of the IMP camera. Each frame consists of 8 individual frames (left eye) and 7 frames (right eye) taken with different color filters that were enlarged by 500% and then co-added using Adobe Photoshop to produce, in effect, a super-resolution panchromatic frame that is sharper than an individual frame would be.<p/>Mars Pathfinder is the second in NASA</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_23 --> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1997DPS....29.1403W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1997DPS....29.1403W"><span>Ganymede Impact <span class="hlt">Crater</span> Morphology as Revealed by Galileo</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Weitz, C. M.; Head, J. W.; Pappalardo, R.; Chapman, C.; Greeley, R.; Helfenstein, P.; Neukum, G.; Galileo SSI Team</p> <p>1997-07-01</p> <p>We have used the Galileo G1, G2, G7, and G8 images to study the morpholo- gy and degradation of impact <span class="hlt">craters</span> on Ganymede. Results from the G1 and G2 data showed three types of degradation states: pristine, partially degraded, and heavily degraded. With the more recent G7 and G8 images, there are now several other distinct <span class="hlt">crater</span> morphologies that we have identified. Enki Catena is about 120 km in length and consists of 13 attached impact <span class="hlt">craters</span>. The six <span class="hlt">craters</span> in the chain that impacted onto the bright terrain have visible bright ejecta while those that impacted onto the dark terrain have barely visible ejecta. Kittu <span class="hlt">crater</span> is about 15 km in diameter and it has a bright central peak surrounded by a bright floor and hummocky wall material. The <span class="hlt">crater</span> rim in the north is linear in appearance at the location that corresponds to the boundary between the groove terrain and the adjacent dark terrain, indicating structural control by the underlying topography. The dark rays that are easily seen in the Voyager images are barely visible in the Galileo image. Neith <span class="hlt">crater</span> has a central fractured dome surrounded by a jagged central ring, smoother outer ejecta facies, and less prominent outer rings. Achelous <span class="hlt">crater</span> and its neighbor, which were imaged at low sun angle to show topography, have smooth floors and subdued pedestal ejecta. Nicholson Regio has tectonically disrupted <span class="hlt">craters</span> on the groove and fractured terrains while the surrounding smoother dark terrain has numerous degrad- ed <span class="hlt">craters</span> that may indicate burial by resurfacing or by regolith development.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014cosp...40E1298I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014cosp...40E1298I"><span>Spatial and size-frequency distributions of boulders on the floor of <span class="hlt">crater</span> Boguslawsky, the primary target of the Luna-Glob mission.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ivanov, Mikhail; Head, James; Hiesinger, Harald; Bazilevskiy, Alexander; Hendrik Pasckert, Jan; Bauch, Karin</p> <p></p> <p><span class="hlt">Crater</span> Boguslawsky (73S, 44E) is the primary target for the lander-oriented Russian mission Luna-Glob. The rocky surfaces represent serious threats to landers. We have conducted a survey of the NAC images seeking for the rocky sites on the floor and assessing quantitative parameters of the size-frequency distributions (SFD) of boulders. Two <span class="hlt">craters</span> on the Boguslawsky floor show abundant boulders in their surroundings. In the vicinity of <span class="hlt">Crater</span> 1 (73.0S, 42.0E, 405 m), we have counted 9,000 rock fragments (1-13 m) at a radial distance <670 m outside the <span class="hlt">crater</span> rim. The mean density of boulders in this zone is 76 rocks/10,000 m2. Boulders are arranged in elongated ray-like clusters. Shallow grooves (tracks) are associated with some larger boulders; the visible depth of the tracks is 0.3-0.5 m. There are 3,200 boulders (1-8 m) around <span class="hlt">Crater</span> 4 (72.6S 44.9E, 340 m) at a radial distance <500 m outside the <span class="hlt">crater</span> rim; the mean density is 52 rocks/10,000 m2. The spatial distribution of boulders around <span class="hlt">Crater</span> 4 is similar to that at <span class="hlt">Crater</span> 1, but no tracks are associated with boulders at <span class="hlt">Crater</span> 4. The mean density of boulders around <span class="hlt">Crater</span> 4 is 30% less than that at <span class="hlt">Crater</span> 1, which <span class="hlt">suggests</span> that <span class="hlt">Crater</span> 4 is 30-50 Ma older than <span class="hlt">Crater</span> 1 [Basilevsky et al., 2013]. The lack of boulder tracks in the vicinity of <span class="hlt">Crater</span> 4 implies that a layer of regolith 0.3-0.5 m thick has been reworked during this time interval. A slope of -4.37 characterizes the SFD of boulders around <span class="hlt">Crater</span> 1, whereas the SFD of boulders around <span class="hlt">Crater</span> 4 has a slope of -5.54. These differences in slope indicate the preferential destruction of the larger rock fragments and <span class="hlt">suggest</span> that up to 90% of boulders in the diameter range 8-12 m are fragmented into smaller pieces during the 30-50 Ma time span.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004EOSTr..85..378N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004EOSTr..85..378N"><span><span class="hlt">Cratering</span> in Marine Environments and on Ice</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Newsom, Horton E.</p> <p>2004-09-01</p> <p>Since the discovery of plate tectonics, impact <span class="hlt">cratering</span> is arguably the most significant geologic process now recognized as an important process on Earth. Impacts into ice, another main topic covered in this book, may be important on other worlds. Large numbers of impact <span class="hlt">craters</span> that formed in marine environments on Earth have only been discovered in the last 10 years. Twenty-five <span class="hlt">craters</span> that formed in marine environments have been documented, according to the first chapter of this book, although none are known that excavated oceanic crust. The papers in <span class="hlt">Cratering</span> in Marine Environments and on Ice will whet your appetite for the exciting and ambitious range of topics implied by the title, which stems from a conference in Svalbard, Norway, in September 2001. This book provides a flavor of the rapidly advancing and diverse field of impact <span class="hlt">cratering</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007MSAIS..11..124M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007MSAIS..11..124M"><span>Analysis of impact <span class="hlt">craters</span> on Mercury's surface.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Martellato, E.; Cremonese, G.; Marzari, F.; Massironi, M.; Capria, M. T.</p> <p></p> <p>The formation of a <span class="hlt">crater</span> is a complex process, which can be analyzed with numerical simulations and/or observational methods. This work reports a preliminary analysis of some <span class="hlt">craters</span> on Mercury, based on the Mariner 10 images. The physical and dynamical properties of the projectile may not derive from the knowledge of the <span class="hlt">crater</span> alone, since the size of an impact <span class="hlt">crater</span> depends on many parameters. We have calculated the diameter of the projectile using the scaling law of Schmidt and Housen (\\citep{SandM87}). It is performed for different projectile compositions and impact velocities, assuming an anorthositic composition of the surface. The melt volume production at the initial phases of the <span class="hlt">crater</span> formation is also calculated by the experimental law proposed by O'Keefe and Ahrens (\\citep{OA82}), giving the ratio between melt and projectile mass.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920018008&hterms=SIG&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DSIG','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920018008&hterms=SIG&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DSIG"><span>Meteoroid and debris special investigation group; status of 3-D <span class="hlt">crater</span> analysis from binocular imagery</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sapp, Clyde A.; See, Thomas H.; Zolensky, Michael E.</p> <p>1992-01-01</p> <p>During the 3 month deintegration of the LDEF, the M&D SIG generated approximately 5000 digital color stereo image pairs of impact related features from all space exposed surfaces. Currently, these images are being processed at JSC to yield more accurate feature information. Work is currently underway to determine the minimum number of data points necessary to parametrically define impact <span class="hlt">crater</span> morphologies in order to minimize the man-hour intensive task of tie point selection. Initial attempts at deriving accurate <span class="hlt">crater</span> depth and diameter measurements from binocular imagery were based on the assumption that the <span class="hlt">crater</span> geometries were best defined by paraboloid. We made no assumptions regarding the <span class="hlt">crater</span> depth/diameter ratios but instead allowed each <span class="hlt">crater</span> to define its own coefficients by performing a least-squares fit based on user-selected tiepoints. Initial test cases resulted in larger errors than desired, so it was decided to test our basic assumptions that the <span class="hlt">crater</span> geometries could be parametrically defined as paraboloids. The method for testing this assumption was to carefully slice test <span class="hlt">craters</span> (experimentally produced in an appropriate aluminum alloy) vertically through the center resulting in a readily visible cross-section of the <span class="hlt">crater</span> geometry. Initially, five separate <span class="hlt">craters</span> were cross-sectioned in this fashion. A digital image of each cross-section was then created, and the 2-D <span class="hlt">crater</span> geometry was then hand-digitized to create a table of XY position for each <span class="hlt">crater</span>. A 2nd order polynomial (parabolic) was fitted to the data using a least-squares approach. The differences between the fit equation and the actual data were fairly significant, and easily large enough to account for the errors found in the 3-D fits. The differences between the curve fit and the actual data were consistent between the caters. This consistency <span class="hlt">suggested</span> that the differences were due to the fact that a parabola did not sufficiently define the generic <span class="hlt">crater</span> geometry</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017MsT.........23D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017MsT.........23D"><span>Structural Evolution of Martin <span class="hlt">Crater</span> Thaumasia Planum, Mars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dolan, Daniel J.</p> <p></p> <p>A detailed structural map of the central uplift of Martin <span class="hlt">Crater</span> in western Thaumasia Planum, Mars, reveals highly folded and fractured geology throughout the 15-km diameter uplift. The stratigraphy in the central uplift of the <span class="hlt">crater</span> has been rotated to near vertical dip and imaged by high-definition cameras aboard the Mars Reconnaissance Orbiter (MRO). These unique factors allow individual geologic beds in Martin <span class="hlt">Crater</span> to be studied and located across the length of the uplift. Bedding in Martin <span class="hlt">Crater</span> primarily strikes SSE-NNW and dips near vertically. Many units are separated by a highly complex series of linear faults, creating megablocks of uplifted material. Faulting is dominantly left-slip in surface expression and strikes SW-NE, roughly perpendicular to bedding, and major fold axes plunge toward the SW. Coupled with infrared imagery of the ejecta blanket, which shows an "exclusion zone" northeast of the <span class="hlt">crater</span>, these structural indicators provide strong support for a low-angle impactor (approximately 10-20°) originating from the northeast. Acoustic fluidization is the prevailing theoretical model put forth to explain complex <span class="hlt">crater</span> uplift. The theory predicts that uplifted megablocks in <span class="hlt">craters</span> are small, discrete, separated and highly randomized in orientation. However, megablocks in Martin <span class="hlt">Crater</span> are tightly interlocked and often continuous in lithology across several kilometers. Thus, the model of acoustic fluidization, as it is currently formulated, does not appear to be supported by the structural evidence found in Martin <span class="hlt">Crater</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70016574','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70016574"><span>Impact <span class="hlt">craters</span> on Venus: Initial analysis from Magellan</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Phillips, R.J.; Arvidson, R. E.; Boyce, J.M.; Campbell, D.B.; Guest, J.E.; Schaber, G.G.; Soderblom, L.A.</p> <p>1991-01-01</p> <p>Magellan radar images of 15 percent of the planet show 135 <span class="hlt">craters</span> of probable impact origin. <span class="hlt">Craters</span> more than 15 km across tend to contain central peaks, multiple central peaks, and peak rings. Many <span class="hlt">craters</span> smaller than 15 km exhibit multiple floors or appear in clusters; these phenomena are attributed to atmospheric breakup of incoming meteoroids. Additionally, the atmosphere appears to have prevented the formation of primary impact <span class="hlt">craters</span> smaller than about 3 km and produced a deficiency in the number of <span class="hlt">craters</span> smaller than about 25 km across. Ejecta is found at greater distances than that predicted by simple ballistic emplacement, and the distal ends of some ejecta deposits are lobate. These characteristics may represent surface flows of material initially entrained in the atmosphere. Many <span class="hlt">craters</span> are surrounded by zones of low radar albedo whose origin may have been deformation of the surface by the shock or pressure wave associated with the incoming meteoroid. <span class="hlt">Craters</span> are absent from several large areas such as a 5 million square kilometer region around Sappho Patera, where the most likely explanation for the dearth of <span class="hlt">craters</span> is volcanic resurfacing, There is apparently a spectrum of surface ages on Venus ranging approximately from 0 to 800 million years, and therefore Venus must be a geologically active planet.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA03912.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA03912.html"><span>Frosted <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2002-08-05</p> <p>This image from NASA Mars Odyssey spacecraft displays a frosted <span class="hlt">crater</span> in the Martian northern hemisphere. It was taken during the northern spring, when the CO2 ice cap starts to sublimate and recede.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70011077','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70011077"><span>Martian planetwide <span class="hlt">crater</span> distributions: Implications for geologic history and surface processes</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Soderblom, L.A.; Condit, C.D.; West, R.A.; Herman, B.M.; Kreidler, T.J.</p> <p>1974-01-01</p> <p> thin mantle. Because this belt is also coincident with the latitutde of maximum solar insolation (periapsis occurs near summer solstice), we <span class="hlt">suggest</span> that this band arises from the asymmetrical global wind patterns at the surface and that the band probably follows the latitude of maximum heating which migrates north and south from 25??N to 25??S within the unmantled terrain on a 50,000 year timescale. The population of intermediate-sized <span class="hlt">craters</span> (4-10 km diameter) appears unaffected by the eolian mantles, at least within the ??45?? latitudes. Hence the local density of these <span class="hlt">craters</span> is probably a valid indicator of the relative age of surfaces generated during the period since the uplands were intensely bombarded and eroded. It now appears that the impact fluxes at Mars and the moon have been roughly the same over the last 4 b.y. because the oldest postaccretional, mare-like surfaces on Mars and the moon display about the same <span class="hlt">crater</span> density. If so, the nearness of Mars to the asteroid belt has not generated a flux 10 to 25 times greater than the lunar flux. Whereas the lunar maria show a variation of about a factor of three in <span class="hlt">crater</span> density from the oldest to the youngest major units, analogous surfaces on Mars show a variation between 30 and 50. This implies that periods of active eolian erosion, tectonic evolution, volcanic eruption, and possibly fluvial modification have been scattered throughout Martian history since the formation and degradation of the martian uplands and not confined to small, ancient or recent, epochs. These processes are surely active on the planet today. ?? 1974.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JGRE..123..131K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JGRE..123..131K"><span>Timing and Distribution of Single-Layered Ejecta <span class="hlt">Craters</span> Imply Sporadic Preservation of Tropical Subsurface Ice on Mars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kirchoff, Michelle R.; Grimm, Robert E.</p> <p>2018-01-01</p> <p>Determining the evolution of tropical subsurface ice is a key component to understanding Mars's climate and geologic history. Study of an intriguing <span class="hlt">crater</span> type on Mars—layered ejecta <span class="hlt">craters</span>, which likely form by tapping subsurface ice—may provide constraints on this evolution. Layered ejecta <span class="hlt">craters</span> have a continuous ejecta deposit with a fluidized-flow appearance. Single-layered ejecta (SLE) <span class="hlt">craters</span> are the most common and dominate at tropical latitudes and therefore offer the best opportunity to derive new constraints on the temporal evolution of low-latitude subsurface ice. We estimate model formation ages of 54 SLE <span class="hlt">craters</span> with diameter (<fi>D</fi>) ≥ 5 km using the density of small, superposed <span class="hlt">craters</span> with <fi>D</fi> < 1 km on their continuous ejecta deposits. These model ages indicate that SLE <span class="hlt">craters</span> have formed throughout the Amazonian and at a similar rate expected for all Martian <span class="hlt">craters</span>. This <span class="hlt">suggests</span> that tropical ice has remained at relatively shallow depths at least where these <span class="hlt">craters</span> formed. In particular, the presence of equatorial SLE <span class="hlt">craters</span> with <fi>D</fi> 1 km indicates that ice could be preserved as shallow as 100 m or less at those locations. Finally, there is a striking spatial mixing in an area of highlands near the equator of layered and radial (lunar-like ballistic) ejecta <span class="hlt">craters</span>; the latter form where there are insufficient concentrations of subsurface ice. This implies strong spatial heterogeneity in the concentration of tropical subsurface ice.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1917147L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1917147L"><span>Formation (and dating) of small impact <span class="hlt">craters</span> on Earth as an analogue for Mars (Ilumetsa <span class="hlt">Craters</span> Estonia)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Losiak, Anna; Jõeleht, Argo; Plado, Juri; Szyszka, Mateusz; Wild, Eva Maria; Bronikowska, Malgorzata; Belcher, Claire; Kirsimäe, Kalle; Steier, Peter</p> <p>2017-04-01</p> <p><span class="hlt">Crater</span>-strewn-fields are present on planetary bodies with an atmosphere such as Earth and Mars, but the process of their formation is still not fully understood. For example, a recent discovery of small pieces of impact-produced-charcoal within the ejecta blanket of 100 m in diameter Kaali <span class="hlt">crater</span> (Losiak et al. 2016) may <span class="hlt">suggest</span> existence of very local ( 10 cm thick layer in the distance of 10 m from the rim), short lived ( hours) thermal anomalies ( 300°C) in the ejecta blanket of even small <span class="hlt">craters</span>. Ilumetsa in SE Estonia is an atypical example of <span class="hlt">crater</span>-strewn-field consisting of only two relatively large, rimmed structures with diameters of 75-80 m (Ilumetsa Large: IL) and 50 m (Ilumetsa Small: IS) with true depths of about 8 and 3.5 m, respectively (Plado 2012 MAPS). Structures were previously dated by the 14C analysis of gyttja from the bottom of IL (Liiva et al. 1979 Eesti Loodus) to be 7170-6660 cal. BP. About 600 years older age (7570-7320 cal. BC: Raukas et al. 2001, MAPS) was proposed based on dated layer of peat in which glassy spherules, interpreted as dissipated melt or condensed vapor (however their chemical composition was not reported). Ilumetsa is listed as a proven meteorite impact in the Earth Impact Database, but neither remnants of the projectile nor other identification criteria (e.g., PDFs) have been found up to this point. The aim of this study was to search for possible impact related charcoals in order to determine the size and extend of thermal anomalies around small impact <span class="hlt">craters</span>, as well as to determine how this atypical strew field was formed. Additionally, we hoped to determine/confirm the age of those structures. We have found charcoal in a similar geological setting as in Kaali Main <span class="hlt">crater</span> in both Ilumetsa structures. The calibrated (95,4% probability) time ranges of four dated samples from IL and one sample of IS span the time interval from 7670-6950 cal. BP (consistent with previous dating). One sample from IS is younger (4830</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA22186.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA22186.html"><span>Depressions and Channels on the Floor of Lyot <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2017-12-12</p> <p>Lyot <span class="hlt">Crater</span> (220-kilometers in diameter) is located in the Northern lowlands of Mars. The <span class="hlt">crater</span>'s floor marks the lowest elevation in the Northern Hemisphere as seen in this image from NASA's Mars Reconnaissance Orbiter (MRO). On the <span class="hlt">crater</span>'s floor, we see a network of channels. connecting a series of irregular shaped pits. These resemble terrestrial beaded streams, which are common in the Arctic regions of Earth and develop from uneven permafrost thawing. If terrestrial beaded streams are a good analog, these landforms <span class="hlt">suggest</span> liquid water flow in the past. If not then these pits may result from the process of sublimation and would indicate pockets of easily accessible near-surface ground ice, which might have potentially preserved evidence of past habitability. The map is projected here at a scale of 25 centimeters (9.8 inches) per pixel. [The original image scale is 12.2 centimeters (9.8 inches) per pixel (with 1 x 1 binning); objects on the order of 93 centimeters (36.6 inches) across are resolved.] North is up. https://photojournal.jpl.nasa.gov/catalog/PIA22186</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20030066704&hterms=Molas&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DMolas','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20030066704&hterms=Molas&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DMolas"><span><span class="hlt">Craters</span> on Mars: Global Geometric Properties from Gridded MOLA Topography</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Garvin, J. B.; Sakimoto, S. E. H.; Frawley, J. J.</p> <p>2003-01-01</p> <p>Impact <span class="hlt">craters</span> serve as natural probes of the target properties of planetary crusts and the tremendous diversity of morphological expressions of such features on Mars attests to their importance for deciphering the history of crustal assembly, modification, and erosion. This paper summarizes the key findings associated with a five year long survey of the three-dimensional properties of approx. 6000 martian impact <span class="hlt">craters</span> using finely gridded MOLA topography. Previous efforts have treated representative subpopulations, but this effort treats global properties from the largest survey of impact features from the perspective of their topography ever assimilated. With the Viking missions of the mid-1970 s, the most intensive and comprehensive robotic expeditions to any Deep Space location in the history of humanity were achieved, with scientifically stunning results associated with the morphology of impact <span class="hlt">craters</span>. The relationships illustrated and <span class="hlt">suggest</span> that martian impact features are remarkably sensitive to target properties and to the local depositional processes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3104824','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3104824"><span>The <span class="hlt">Kaiser</span> Permanente Northwest Cardiovascular Risk Factor Management Program: A Model for All</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Joyce, Jodi S; Fetter, Martina M; Klopfenstein, Dean H; Nash, Michael K</p> <p>2005-01-01</p> <p>Proof of the effectiveness of preventive measures that reduce established risk traits for atherothrombotic disorders has spurred attempts to systematically apply these interventions among susceptible populations. One such attempt is the Cardiovascular Risk Factor Management (CVRFM) Program, launched in 2003 to optimize clinical management and outcomes for 75,000 <span class="hlt">Kaiser</span> Permanente Northwest Region (KPNW) members with atherosclerotic cardiovascular disease (CVD) or hypertension. The CVRFM Program is a centralized, multidisciplinary, proactive telephone-based clinical management intervention consisting of an “outreach” call, an interview, a mailed individualized care plan and information packet, regular follow-up (including protocolized medication management) and—when “goal status” is achieved—transfer of the patient to a maintenance plan. Quarterly evaluation of effectiveness entailed measurement of a range of clinical, utilization, and member satisfaction outcomes. Results by the fourth quarter were outstanding: For example, >98% of participants with coronary disease or diabetes had LDL cholesterol testing, >90% of coronary patients received aspirin or statin treatment, 99% were “extremely” or “very” satisfied with the program, and reductions were observed in the number of hospitalizations and visits to the emergency department and clinic. Mathematical models predict a decrease in myocardial infarctions and cardiovascular mortality within two years after implementing the program, the underlying principles of which should yield similar improvement in other <span class="hlt">Kaiser</span> Permanente (KP) Regions and in other health care organizations. PMID:21660155</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA03832.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA03832.html"><span>Galle <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2002-06-26</p> <p>This image from NASA Mars Odyssey spacecraft shows part of Galle <span class="hlt">Crater</span>. It was taken far enough south and late enough into the southern hemisphere fall to observe water ice clouds partially obscuring the surface.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA03812.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA03812.html"><span>Maunder <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2002-06-17</p> <p>This image taken by NASA Mars Odyssey spacecraft shows a portion of Maunder <span class="hlt">Crater</span> with a number of interesting features including a series of barchan dunes that are traveling from right to left and gullies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA12952.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA12952.html"><span><span class="hlt">Crater</span> Wall in Van de Graaff</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2010-02-11</p> <p>This image taken NASA Lunar Reconnaissance Orbiter shows the wall of <span class="hlt">crater</span> Van de Graaff C, where brighter material is exposed by more active processes associated with steeper slopes, recent small <span class="hlt">craters</span>, and even individual rolling boulders.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA00479.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA00479.html"><span>Venus - Complex <span class="hlt">Crater</span> Dickinson in NE Atalanta Region</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>1996-11-26</p> <p>This Magellan image is centered at 74.6 degrees north latitude and 177.3 east longitude, in the northeastern Atalanta Region of Venus. The image is approximately 185 kilometers (115 miles) wide at the base and shows Dickinson, an impact <span class="hlt">crater</span> 69 kilometers (43 miles) in diameter. The <span class="hlt">crater</span> is complex, characterized by a partial central ring and a floor flooded by radar-dark and radar-bright materials. Hummocky, rough-textured ejecta extend all around the <span class="hlt">crater</span>, except to the west. The lack of ejecta to the west may indicate that the impactor that produced the <span class="hlt">crater</span> was an oblique impact from the west. Extensive radar-bright flows that emanate from the <span class="hlt">crater</span>'s eastern walls may represent large volumes of impact melt, or they may be the result of volcanic material released from the subsurface during the <span class="hlt">cratering</span> event. http://photojournal.jpl.nasa.gov/catalog/PIA00479</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA22035.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA22035.html"><span>Investigating Mars: Moreux <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2017-11-22</p> <p>This image of Moreux <span class="hlt">Crater</span> shows the western floor of the <span class="hlt">crater</span> and the multitude of sand dunes that are found on the floor of the <span class="hlt">crater</span>. A large sand sheet with surface dunes forms is located at the top of the image, and smaller individual dunes stretch from the bottom of the sand sheet to the bottom of the image. In this false color image sand dunes are "blue". Moreux <span class="hlt">Crater</span> is located in northern Arabia Terra and has a diameter of 138 kilometers. The THEMIS VIS camera contains 5 filters. The data from different filters can be combined in multiple ways to create a false color image. These false color images may reveal subtle variations of the surface not easily identified in a single band image. The Odyssey spacecraft has spent over 15 years in orbit around Mars, circling the planet more than 69000 times. It holds the record for longest working spacecraft at Mars. THEMIS, the IR/VIS camera system, has collected data for the entire mission and provides images covering all seasons and lighting conditions. Over the years many features of interest have received repeated imaging, building up a suite of images covering the entire feature. From the deepest chasma to the tallest volcano, individual dunes inside <span class="hlt">craters</span> and dune fields that encircle the north pole, channels carved by water and lava, and a variety of other feature, THEMIS has imaged them all. For the next several months the image of the day will focus on the Tharsis volcanoes, the various chasmata of Valles Marineris, and the major dunes fields. We hope you enjoy these images! Orbit Number: 10384 Latitude: 41.841 Longitude: 44.087 Instrument: VIS Captured: 2004-04-17 10:07 https://photojournal.jpl.nasa.gov/catalog/PIA22035</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA00854.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA00854.html"><span>Antum <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>1998-03-26</p> <p>The left image is an airbrush map of the surface of Ganymede from NASA Voyager data. The small square shows the location of Antum <span class="hlt">crater</span>, target of the image from NASA Galileo spacecraft on the right.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_24 --> <div id="page_25" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="481"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19940011827','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19940011827"><span>Implications of <span class="hlt">crater</span> distributions on Venus</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kaula, W. M.</p> <p>1993-01-01</p> <p>The horizontal locations of <span class="hlt">craters</span> on Venus are consistent with randomness. However, (1) randomness does not make <span class="hlt">crater</span> counts useless for age indications; (2) consistency does not imply necessity or optimality; and (3) horizontal location is not the only reference frame against which to test models. Re (1), the apparent smallness of resurfacing areas means that a region on the order of one percent of the planet with a typical number of <span class="hlt">craters</span>, 5-15, will have a range of feature ages of several 100 My. Re (2), models of resurfacing somewhat similar to Earth's can be found that are also consistent and more optimal than random: i.e., resurfacing occurring in clusters, that arise and die away in lime intervals on the order of 50 My. These agree with the observation that there are more areas of high <span class="hlt">crater</span> density, and fewer of moderate density, than optimal for random. Re (3), 799 <span class="hlt">crater</span> elevations were tested; there are more at low elevations and fewer at high elevations than optimal for random: i.e., 54.6 percent below the median. Only one of 40 random sets of 799 was as extreme.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA04011&hterms=5S&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3D5S','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA04011&hterms=5S&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3D5S"><span>Proctor <span class="hlt">Crater</span> Dunes</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2002-01-01</p> <p><p/> [figure removed for brevity, see original site] <p/>This image, located near 30E and 47.5S, displays sand dunes within Proctor <span class="hlt">Crater</span>. These dunes are composed of basaltic sand that has collected in the bottom of the <span class="hlt">crater</span>. The topographic depression of the <span class="hlt">crater</span> forms a sand trap that prevents the sand from escaping. Dune fields are common in the bottoms of <span class="hlt">craters</span> on Mars and appear as dark splotches that lean up against the downwind walls of the <span class="hlt">craters</span>. Dunes are useful for studying both the geology and meteorology of Mars. The sand forms by erosion of larger rocks, but it is unclear when and where this erosion took place on Mars or how such large volumes of sand could be formed. The dunes also indicate the local wind directions by their morphology. In this case, there are few clear slipfaces that would indicate the downwind direction. The crests of the dunes also typically run north-south in the image. This dune form indicates that there are probably two prevailing wind directions that run east and west (left to right and right to left).<p/>Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.<p/>NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA01402&hterms=spiders&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dspiders','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA01402&hterms=spiders&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dspiders"><span>Mannann'an <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1998-01-01</p> <p>This composite view taken by NASA's Galileo spacecraft shows the rim and interior of the impact <span class="hlt">crater</span>, Mannann'an, on Jupiter's moon, Europa. A high resolution image (20 meters per picture element) was combined with lower resolution (80 meters per picture element) color images taken through violet, green and near-infrared filters, to produce this synthetic color composite image. The color data can be used to distinguish between regions of purer (clean) and more contaminated (dirty) ice on the surface, and also offers information on the size of the ice grains. The reddish brown material is thought to be dirty ice, while the bluish areas inside the <span class="hlt">crater</span> are purer ice. The <span class="hlt">crater</span> rim is on the left at the boundary between the reddish brown material and the gray material.<p/>The high resolution data show small features inside the <span class="hlt">crater</span>, including concentric fractures and a spider-like set of fractures near the right (east) edge of the image. For a more regional perspective, the Mannann'an <span class="hlt">crater</span> can be seen as a large circular feature with bright rays in the lower left corner of a regional image from Galileo's first orbit of Jupiter in June 1996.<p/>North is to the top of the picture and the Sun illuminates the scene from the east (right). The image, centered at 3 degrees north latitude and 240 degrees west longitude, covers an area approximately 18 by 4 kilometers (11 by 2.5 miles). The finest details that can be discerned in this picture are about 40 meters (44 yards) across. The images were taken by the spacecraft's onboard solid state imaging camera when Galileo flew by Europa on March 29th, 1998 at a distance of 1,934 kilometers (1,200 miles).<p/>The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).<p/>This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AGUFM.P23A0184B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AGUFM.P23A0184B"><span>Machine Identification of Martian <span class="hlt">Craters</span> Using Digital Elevation Data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bue, B.; Stepinski, T. F.</p> <p>2005-12-01</p> <p>Impact <span class="hlt">craters</span> are among the most studied features on Martian surface. Their importance stems from the worth of information that a detailed analysis of their number and morphology can bring forth. Because building manually a comprehensive dataset of <span class="hlt">craters</span> is a laborious process, there have been many previous attempts to develop an automatic, image-based <span class="hlt">crater</span> identifier. The resulting identifiers suffer from low efficiency and remain in an experimental stage. We have developed a DEM-based, fully autonomous <span class="hlt">crater</span> identifier that takes an arbitrarily large Martian site as an input and produces a catalog of <span class="hlt">craters</span> as an output. Using the topography data we calculate a topographic profile curvature that is thresholded to produce a binary image, pixels having maximum negative curvature are labeled black, the remaining pixels are labeled white. The black pixels outline <span class="hlt">craters</span> because <span class="hlt">crater</span> rims are the most convex feature in the Martian landscape. The Hough Transform (HT) is used for an actual recognition of <span class="hlt">craters</span> in the binary image. The image is first segmented (without cutting the <span class="hlt">craters</span>) into a large number of smaller images using the ``flood" algorithm that identifies basins. This segmentation makes possible the application of highly inefficient HT to large sites. The identifier is applied to a 106 km2 site located around the Herschel <span class="hlt">crater</span>. According to the Barlow catalog, this site contains 485 <span class="hlt">craters</span> >5 km. Our identifier finds 1099 segments, 628 of them are classified as <span class="hlt">craters</span> >5 km. Overall, there is an excellent agreement between the two catalogs, although the specific statistics are still pending due to the difficulties in recalculating the MDIM 1 coordinate system used in the Barlow catalog to the MDIM 2.1 coordinate system used by our identifier.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.P53A2172B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.P53A2172B"><span>Mapping Ejecta Thickness Around Small Lunar <span class="hlt">Craters</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brunner, A.; Robinson, M. S.</p> <p>2016-12-01</p> <p>Detailed knowledge of the distribution of ejecta around small ( 1 km) <span class="hlt">craters</span> is still a key missing piece in our understanding of <span class="hlt">crater</span> formation. McGetchin et al. [1] compiled data from lunar, terrestrial, and synthetic <span class="hlt">craters</span> to generate a semi-empirical model of radial ejecta distribution. Despite the abundance of models, experiments, and previous field and remote sensing studies of this problem, images from the 0.5 m/pixel Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Camera (NAC) [2] provides the first chance to quantify the extent and thickness of ejecta around kilometer scale lunar <span class="hlt">craters</span>. Impacts excavate fresh (brighter) material from below the more weathered (darker) surface, forming a relatively bright ejecta blanket. Over time space weathering tends to lower the reflectance of the ejected fresh material [3] resulting in the fading of albedo signatures around <span class="hlt">craters</span>. Relatively small impacts that excavate through the high reflectance immature ejecta of larger fresh <span class="hlt">craters</span> provide the means of estimating ejecta thickness. These subsequent impacts may excavate material from within the high reflectance ejecta layer or from beneath that layer to the lower-reflectance mature pre-impact surface. The reflectance of the ejecta around a subsequent impact allows us to categorize it as either an upper or lower limit on the ejecta thickness at that location. The excavation depth of each <span class="hlt">crater</span> found in the ejecta blanket is approximated by assuming a depth-to-diameter relationship relevant for lunar simple <span class="hlt">craters</span> [4, e.g.]. Preliminary results [Figure] show that this technique is valuable for finding the radially averaged profile of the ejecta thickness and that the data are roughly consistent with the McGetchin equation. However, data from <span class="hlt">craters</span> with asymmetric ejecta blankets are harder to interpret. [1] McGetchin et al. (1973) Earth Planet. Sci. Lett., 20, 226-236. [2] Robinson et al. (2010) Space Sci. Rev., 150, 1-4, 81-124. [3] Denevi et al</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3997327','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3997327"><span><span class="hlt">Crater</span> lake cichlids individually specialize along the benthic–limnetic axis</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Kusche, Henrik; Recknagel, Hans; Elmer, Kathryn Rebecca; Meyer, Axel</p> <p>2014-01-01</p> <p>A common pattern of adaptive diversification in freshwater fishes is the repeated evolution of elongated open water (limnetic) species and high-bodied shore (benthic) species from generalist ancestors. Studies on phenotype-diet correlations have <span class="hlt">suggested</span> that population-wide individual specialization occurs at an early evolutionary and ecological stage of divergence and niche partitioning. This variable restricted niche use across individuals can provide the raw material for earliest stages of sympatric divergence. We investigated variation in morphology and diet as well as their correlations along the benthic-limnetic axis in an extremely young Midas cichlid species, Amphilophus tolteca, endemic to the Nicaraguan <span class="hlt">crater</span> lake Asososca Managua. We found that A. tolteca varied continuously in ecologically relevant traits such as body shape and lower pharyngeal jaw morphology. The correlation of these phenotypes with niche <span class="hlt">suggested</span> that individuals are specialized along the benthic-limnetic axis. No genetic differentiation within the <span class="hlt">crater</span> lake was detected based on genotypes from 13 microsatellite loci. Overall, we found that individual specialization in this young <span class="hlt">crater</span> lake species encompasses the limnetic-as well as the benthic macro-habitat. Yet there is no evidence for any diversification within the species, making this a candidate system for studying what might be the early stages preceding sympatric divergence. A common pattern of adaptive diversification in freshwater fishes is the repeated evolution of open water (limnetic) species and of shore (benthic) species. Individual specialization can reflect earliest stages of evolutionary and ecological divergence. We here demonstrate individual specialization along the benthic–limnetic axis in a young adaptive radiation of <span class="hlt">crater</span> lake cichlid fishes. PMID:24772288</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19940011795','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19940011795"><span>A first-order model for impact <span class="hlt">crater</span> degradation on Venus</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Izenberg, Noam R.; Arvidson, Raymond E.; Phillips, Roger J.</p> <p>1993-01-01</p> <p>A first-order impact <span class="hlt">crater</span> aging model is presented based on observations of the global <span class="hlt">crater</span> population of Venus. The total population consists of 879 <span class="hlt">craters</span> found over the approximately 98 percent of the planet that has been mapped by the Magellan spacecraft during the first three cycles of its mission. The model is based upon three primary aspects of venusian impact <span class="hlt">craters</span>: (1) extended ejecta deposits (EED's); (2) <span class="hlt">crater</span> rims and continuous ejecta deposits; and (3) <span class="hlt">crater</span> interiors and floors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AGUFM.P34B..02S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AGUFM.P34B..02S"><span>Robust System for Automated Identification of Martian Impact <span class="hlt">Craters</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stepinski, T. F.; Mendenhall, M. P.</p> <p>2006-12-01</p> <p>Detailed analysis of the number and morphology of impact <span class="hlt">craters</span> on Mars provides the worth of information about the geologic history of its surface. Global catalogs of Martian <span class="hlt">craters</span> have been compiled (for example, the Barlow catalog) but they are not comprehensive, especially for small <span class="hlt">craters</span>. Existing methods for machine detection of <span class="hlt">craters</span> from images suffer from low efficiency and are not practical for global surveys. We have developed a robust two-stage system for an automated cataloging of <span class="hlt">craters</span> from digital topography data (DEM). In the first stage an innovative <span class="hlt">crater</span>-finding transform is performed on a DEM to identify centers of potential <span class="hlt">craters</span>, their extents, and their basic characteristics. This stage produces a preliminary catalog. In the second stage a machine learning methods are employed to eliminate false positives. Using the MOLA derived DEMs with resolution of 1/128 degrees/pixel, we have applied our system to six ~ 106 km2 sites. The system has identified 3217 <span class="hlt">craters</span>, 43% more than are present in the Barlow catalog. The extra finds are predominantly small <span class="hlt">craters</span> that are most difficult to account for in manual surveys. Because our automated survey is DEM-based, the resulting catalog lists <span class="hlt">craters</span>' depths in addition to their positions, sizes, and measures of shape. This feature significantly increases the scientific utility of any catalog generated using our system. Our initial calculations yield a training set that will be used to identify <span class="hlt">craters</span> over the entire Martian surface with estimated accuracy of 95%. Moreover, because our method is pixel-based and scale- independent, the present training set may be used to identify <span class="hlt">craters</span> in higher resolution DEMs derived from Mars Express HRSC images. It also can be applied to future topography data from Mars and other planets. For example, it may be utilized to catalog <span class="hlt">craters</span> on Mercury and the Moon using altimetry data to be gathered by Messenger and Lunar Reconnaissance Orbiter</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA21800.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA21800.html"><span>Investigating Mars: Russell <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2017-08-02</p> <p>This image shows individual dunes on the floor of Russell <span class="hlt">Crater</span>, as well as larger dunes created by individual dunes coalescing . These dunes are in the western part of the dune field. Russell <span class="hlt">Crater</span> is located in Noachis Terra. A spectacular dune ridge and other dune forms on the <span class="hlt">crater</span> floor have caused extensive imaging. The Odyssey spacecraft has spent over 15 years in orbit around Mars, circling the planet more than 69000 times. It holds the record for longest working spacecraft at Mars. THEMIS, the IR/VIS camera system, has collected data for the entire mission and provides images covering all seasons and lighting conditions. Over the years many features of interest have received repeated imaging, building up a suite of images covering the entire feature. From the deepest chasma to the tallest volcano, individual dunes inside <span class="hlt">craters</span> and dune fields that encircle the north pole, channels carved by water and lava, and a variety of other feature, THEMIS has imaged them all. For the next several months the image of the day will focus on the Tharsis volcanoes, the various chasmata of Valles Marineris, and the major dunes fields. We hope you enjoy these images! Orbit Number: 26372 Latitude: -54.372 Longitude: 12.5481 Instrument: VIS Captured: 2007-11-24 17:16 https://photojournal.jpl.nasa.gov/catalog/PIA21800</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA21804.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA21804.html"><span>Investigating Mars: Russell <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2017-08-07</p> <p>This image shows the central part of the dune field on the floor of Russell <span class="hlt">Crater</span>. The large ridge "bends" about 60 degrees from parallel to the right side of the image to angle towards the upper left corner. Russell <span class="hlt">Crater</span> is located in Noachis Terra. A spectacular dune ridge and other dune forms on the <span class="hlt">crater</span> floor have caused extensive imaging. The Odyssey spacecraft has spent over 15 years in orbit around Mars, circling the planet more than 69000 times. It holds the record for longest working spacecraft at Mars. THEMIS, the IR/VIS camera system, has collected data for the entire mission and provides images covering all seasons and lighting conditions. Over the years many features of interest have received repeated imaging, building up a suite of images covering the entire feature. From the deepest chasma to the tallest volcano, individual dunes inside <span class="hlt">craters</span> and dune fields that encircle the north pole, channels carved by water and lava, and a variety of other feature, THEMIS has imaged them all. For the next several months the image of the day will focus on the Tharsis volcanoes, the various chasmata of Valles Marineris, and the major dunes fields. We hope you enjoy these images! Orbit Number: 34232 Latitude: -54.4921 Longitude: 12.9013 Instrument: VIS Captured: 2009-09-01 23:04 https://photojournal.jpl.nasa.gov/catalog/PIA21804</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA08185.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA08185.html"><span><span class="hlt">Cratered</span> Crescent</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2006-05-25</p> <p>Quiet and cold, a crescent Tethys floats above the nearly edge-on rings of Saturn. The only surface features visible on Tethys 1,071 kilometers, or 665 miles across from this distance are a few impact <span class="hlt">craters</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1998P%26SS...46..323G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1998P%26SS...46..323G"><span>The group of Macha <span class="hlt">craters</span> in western Yakutia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gurov, E. P.; Gurova, E. P.</p> <p>1998-02-01</p> <p>The group of Macha impact <span class="hlt">craters</span> in western Yakutia is represented by five crateriform structures from 60 to 300 m in diameter. The <span class="hlt">craters</span> were formed in sandy strata of the Quaternary period and in underlying sedimentary rocks of Late Proterozoic ages. Shock metamorphic effects including planar features in quartz were established in the rocks from the <span class="hlt">craters</span>. The age of the <span class="hlt">craters</span> is 7315 ± 80 yr. The nature of the projectiles is not totally clear, although they might be iron meteoritic.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19920009568','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19920009568"><span>Planetary <span class="hlt">cratering</span> mechanics</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Okeefe, John D.; Ahrens, Thomas J.</p> <p>1992-01-01</p> <p>To obtain a quantitative understanding of the <span class="hlt">cratering</span> process over a broad range of conditions, we have numerically computed the evolution of impact induced flow fields and calculated the time histories of the major measures of <span class="hlt">crater</span> geometry (e.g., depth diameter, lip height ...) for variations in planetary gravity (0 to 10 exp 9 cm/sq seconds), material strength (0 to 140 kbar), thermodynamic properties, and impactor radius (0.05 to 5000 km). These results were fit into the framework of the scaling relations of Holsapple and Schmidt (1987). We describe the impact process in terms of four regimes: (1) penetration; (2) inertial; (3) terminal; and (4) relaxation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/of/1984/0114/report.pdf','USGSPUBS'); return false;" href="https://pubs.usgs.gov/of/1984/0114/report.pdf"><span>Stratigraphic and volcano-tectonic relations of <span class="hlt">Crater</span> Flat Tuff and some older volcanic units, Nye County, Nevada</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Carr, W.J.; Byers, F.M.; Orkild, Paul P.</p> <p>1984-01-01</p> <p>The <span class="hlt">Crater</span> Flat Tuff is herein revised to include a newly recognized lowest unit, the Tram Member, exposed at scattered localities in the southwest Nevada Test Site region, and in several drill holes in the Yucca Mountain area. The overlying Bullfrog and Prow Pass Members are well exposed at the type locality of the formation near the southeast edge of <span class="hlt">Crater</span> Flat, just north of U.S. Highway 95. In previous work, the Tram Member was thought to be the Bullfrog Member, and therefore was shown as Bullfrog or as undifferentiated <span class="hlt">Crater</span> Flat Tuff on published maps. The revised <span class="hlt">Crater</span> Flat Tuff is stratigraphically below the Topopah Spring Member of the Paintbrush Tuff and above the Grouse Canyon Member of the Belted Range Tuff, and is approximately 13.6 m.y. old. Drill holes on Yucca Mountain and near Fortymile Wash penetrate all three members of the <span class="hlt">Crater</span> Flat as well as an underlying quartz-poor unit, which is herein defined as the Lithic Ridge Tuff from exposures on Lithic Ridge near the head of Topopah Wash. In outcrops between Calico Hills and Yucca Flat, the Lithic Ridge Tuff overlies a Bullfrog-like unit of reverse magnetic polarity that probably correlates with a widespread unit around and under Yucca Flat, referred to previously as <span class="hlt">Crater</span> Flat Tuff. This unit is here informally designated as the tuff of Yucca Flat. Although older, it may be genetically related to the <span class="hlt">Crater</span> Flat Tuff. Although the rocks are poorly exposed, geophysical and geologic evidence to date <span class="hlt">suggests</span> that (1) the source of the <span class="hlt">Crater</span> Flat Tuff is a caldera complex in the <span class="hlt">Crater</span> Flat area between Yucca Mountain and Bare Mountain, and (2) there are at least two cauldrons within this complex--one probably associated with eruption of the Tram, the other with the Bullfrog and Prow Pass Members. The complex is named the <span class="hlt">Crater</span> Flat-Prospector Pass caldera complex. The northern part of the Yucca Mountain area is <span class="hlt">suggested</span> as the general location of the source of pre-<span class="hlt">Crater</span> Flat tuffs, but a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA15143.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA15143.html"><span>Fresh Impact <span class="hlt">Craters</span> on Asteroid Vesta</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2011-12-06</p> <p>This image combines two separate views of the giant asteroid Vesta obtained by NASA Dawn spacecraft. The fresh impact <span class="hlt">craters</span> in this view are located in the south polar region, which has been partly covered by landslides from the adjacent <span class="hlt">crater</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA14132.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA14132.html"><span>Opportunity Beside a Small, Young <span class="hlt">Crater</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2011-06-02</p> <p>NASA Mars Exploration Rover Opportunity captured this view of a wee <span class="hlt">crater</span>, informally named Skylab, along the rover route. Based on the estimated age of the area sand ripples, the <span class="hlt">crater</span> was likely formed within the past 100,000 years.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930062613&hterms=neither+deep+shallow&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dneither%2Bdeep%2Bshallow','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930062613&hterms=neither+deep+shallow&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dneither%2Bdeep%2Bshallow"><span>Shallow and deep fresh impact <span class="hlt">craters</span> in Hesperia Planum, Mars</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mouginis-Mark, Peter J.; Hayashi, Joan N.</p> <p>1993-01-01</p> <p>The depths of 109 impact <span class="hlt">craters</span> about 2-16 km in diameter, located on the ridged plains materials of Hesperia Planum, Mars, have been measured from their shadow lengths using digital Viking Orbiter images (orbit numbers 417S-419S) and the PICS computer software. On the basis of their pristine morphology (very fresh lobate ejecta blankets, well preserved rim crests, and lack of superposed impact <span class="hlt">craters</span>), 57 of these <span class="hlt">craters</span> have been selected for detailed analysis of their spatial distribution and geometry. We find that south of 30 deg S, <span class="hlt">craters</span> less than 6.0 km in diameter are markedly shallower than similar-sized <span class="hlt">craters</span> equatorward of this latitude. No comparable relationship is observed for morphologically fresh <span class="hlt">craters</span> greater than 6.0 km diameter. We also find that two populations exist for older <span class="hlt">craters</span> less than 6.0 km diameter. When <span class="hlt">craters</span> that lack ejecta blankets are grouped on the basis of depth/diameter ratio, the deeper <span class="hlt">craters</span> also typically lie equatorward of 30 S. We interpret the spatial variation in <span class="hlt">crater</span> depth/diameter ratios as most likely due to a poleward increase in volatiles within the top 400 m of the surface at the times these <span class="hlt">craters</span> were formed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70010635','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70010635"><span>Coesite from Wabar <span class="hlt">crater</span>, near Al Hadida, Arabia</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Chao, E.C.T.; Fahey, J.J.; Littler, J.</p> <p>1961-01-01</p> <p>The third natural occurrence of coesite, the high pressure polymorph of silica, is found at the Wabar meteorite <span class="hlt">crater</span>, Arabia. The Wabar <span class="hlt">crater</span> is about 300 feet in diameter and about 40 feet deep. It is the smallest of three <span class="hlt">craters</span> where coesite has been found.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EPSC...11..658M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EPSC...11..658M"><span>Experimental Investigation of the Formation of Complex <span class="hlt">Craters</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Martellato, E.; Dörfler, M. A.; Schuster, B.; Wünnemman, K.; Kenkmann, T.</p> <p>2017-09-01</p> <p>The formation of complex impact <span class="hlt">craters</span> is still poorly understood, because standard material models fail to explain the gravity-driven collapse at the observed size-range of a bowl-shaped transient <span class="hlt">crater</span> into a flat-floored <span class="hlt">crater</span> structure with a central peak or ring and terraced rim. To explain such a collapse the so-called Acoustic Fluidization (AF) model has been proposed. The AF assumes that heavily fractured target rocks surrounding the transient <span class="hlt">crater</span> are temporarily softened by an acoustic field in the wake of an expanding shock wave generated upon impact. The AF has been successfully employed in numerous modeling studies of complex <span class="hlt">crater</span> formation; however, there is no clear relationship between model parameters and observables. In this study, we present preliminary results of laboratory experiments aiming at relating the AF parameters to observables such as the grain size, average wave length of the acoustic field and its decay time τ relative to the <span class="hlt">crater</span> formation time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA19288.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA19288.html"><span>Filled <span class="hlt">Crater</span> and Scallops</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2015-01-28</p> <p>In this observation from NASA Mars Reconnaissance Orbiter made for a study of ancient <span class="hlt">craters</span>, we see the <span class="hlt">craters</span> filled with smooth material that has subsequently degraded into scallops. These formations might be possibly due to ground ice sublimation. High resolution can help to estimate any differences in roughness on the smoother main mantle and in the eroded hollows. With the enhanced color swath, we might be able to view composition variations of the material. http://photojournal.jpl.nasa.gov/catalog/PIA19288</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_25 --> <div class="footer-extlink text-muted" style="margin-bottom:1rem; text-align:center;">Some links on this page may take you to non-federal websites. 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