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Sample records for large meteorite impacts

  1. Meteoritic material at five large impact craters

    NASA Technical Reports Server (NTRS)

    Palme, H.; Janssens, M.-J.; Takahashi, H.; Anders, E.; Hertogen, J.

    1978-01-01

    The paper analyzes the meteoritic material at five multikilometer craters: Clearwater (Lac a l'Eau Claire) East and West (22 and 32 km), Manicouagan (70 km) and Mistastin (28 km), all in Canada; and Lake Bosumtwi (10.5 km), Ghana, which is associated with Ivory Coast tektites. Radiochemical neutron activation analysis is applied to 16 crater samples for the siderophile trace elements Ir, Os, Pd, Ni, Ge, and Re, which are depleted to varying degrees in the earth's crust but are abundant in all meteorites except achondrites. It is found that only two samples, both from Clearwater, exhibit a strong meteoritic signal. The remaining ones fall within or slightly above the range for terrestrial rocks, and therefore at best contain only small meteoritic components. Clearwater East is the first terrestrial impact crater to be associated with a stony meteorite (a C1 or C2 chondrite).

  2. Large Meteorite Impacts and Planetary Evolution

    NASA Technical Reports Server (NTRS)

    1997-01-01

    The present volume of abstracts of conference papers discusses topics associated with the role of meteorite impacts on the Earth, the moon, and Titan. Particular attention is given to the description of the impact damage and the description of the actual craters. Attention is also given to the Sudbury structure, and the Chicxulub crater. Mineralogical, geophysical, petrographic, seismic and image data are described and discussed.

  3. International Conference on Large Meteorite Impacts and Planetary Evolution

    NASA Technical Reports Server (NTRS)

    1992-01-01

    The papers that were accepted for the International Conference on Large Meteorite Impacts and Planetary Evolution, 31 Aug. - 2 Sep. 1992, are presented. One of the major paper topics was the Sudbury project.

  4. Large Meteorite Impacts and Planetary Evolution

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Topics considered include: Petrography, geochemistry and geochronology; impact-induced hydrothermal base metal mineralization; nickel-and platinum group element -enriched quartz norite in the latest jurassic morokweng impact structure, south Africa; extraterrestrial helium trapped in fullerenes in the sudbury; synthetic aperture radar characteristics of a glacially modified meltsheet; the chicxulub seismic experiment; chemical compositions of chicxulub impact breccias; experimental investigation of the chemistry of vaporization of targets in relation to the chicxulub impact; artificial ozone hole generation following a large meteoroid impact into an oceanic site; three dimensional modeling of impactite bodies of popigai impact crater, Russia.

  5. Methane production by large iron meteorite impacts on early Earth

    NASA Astrophysics Data System (ADS)

    Sekine, Yasuhito; Sugita, Seiji; Kadono, Toshihiko; Matsui, Takafumi

    2003-07-01

    The continuous existence of life on the Earth is thought to have begun around 4 Ga, which is near the end of the heavy bombardment period. Impacts of asteroids and comets may have produced and delivered organic matter on the Hadean Earth. However, the nature of those processes has not been understood well yet. In this paper, we propose a new process of organic synthesis induced by asteroid impacts. We consider the effect of impact vapor condensates reentering the Earth's early atmosphere. Vapor condensates produced by a large-scale impact are dispersed around the globe and reenter the atmosphere at very high speed. The reentering condensates are heated and decelerated by the friction with the atmosphere and form a ``hot condensate layer'' around the globe. We calculate the temperature and atmospheric pressure of the hot condensate layer as a function of time. A Fischer-Tropsch reaction on the surface of the reentering iron and nickel condensates will lead to efficient methane production. The reaction rate of Fischer-Tropsch catalysis is estimated based on a kinetic model. Calculation results indicate that the amount of methane produced by the impact of an iron meteorite with a diameter of 10 km at 15 km sec-1 of velocity reaches ~1012-1013 kg. Some of the methane formed by this process is photodissociated to HCN and organic aerosols. The amount of the resulting HCN is estimated to be ~1010-1012 kg. This is 103-104 times the preimpact inventory of HCN on the Earth, which is maintained by UV radiation and electric discharge in a mildly reducing (i.e., CO-CO2 dominant) atmosphere. Such an episodic increase in the organic inventory on the surface of the early Earth may have played an important role in the origin of life.

  6. LSU scientists discover evidence of large meteorite impacts on the early earth

    NASA Technical Reports Server (NTRS)

    Lowe, Donald R.; Byerly, Gary R.

    1988-01-01

    Recent discoveries by scientists at Lousiana State University are examined which may provide a window through which early planetary accretion is viewed and studied and the role of large meteorite impacts on the evolution of life and the earth's surface evaluated.

  7. Meteoritic Microfossils in Eltanin Impact Deposits

    NASA Technical Reports Server (NTRS)

    Kyte, Frank T.; Gersonde, Rainer; Kuhn, Gerhard

    2006-01-01

    We report the unique occurrence of microfossils composed largely of meteoritic ejecta particles from the late Pliocene (2.5 Ma) Eltanin impact event. These deposits are unique, recording the only known km-sized asteroid impact into a deep-ocean (5 km) basin. First discovered as in Ir anomaly in sediment cores that were collected in 1965, the deposits contain nun-sized shock-melted asteroidal material, unmelted meteorite fragments (named the Eltanin meteorite), and trace impact spherules. Two oceanographic expeditions by the FS Polarstern in 1995 and 2001 explored approximately 80,000 sq-km. of the impact region, mapping the distribution of meteoritic ejecta, disturbance of seafloor sediments by the impact, and collected 20 new cores with impact deposits in the vicinity of the Freeden Seamounts (57.3S, 90.5W). Analyses of sediment cores show that the impact disrupted sediments on the ocean floor, redepositing them as a chaotic jumble of sediment fragments overlain by a sequence of laminated sands, silts and clays deposited from the water column. Overprinted on this is a pulse of meteoritic ejecta, likely transported ballistically, then settled through the water column. At some localities, meteoritic ejecta was as much as 0.4 to 2.8 g/cm2. This is the most meteorite-rich locality known on Earth.

  8. Exotic minerals in 3,500 million year old rocks: Evidence for large meteorite impacts

    NASA Technical Reports Server (NTRS)

    Byerly, G. R.; Lowe, D. R.; Asaro, F.

    1988-01-01

    A relatively small area of mountainous terrain in southern Africa provides scientists from all over the world a look at what the surface of the earth was like three and a half billion years ago. The Barberton Mountains lie astride the borders of the Republic of South Africa, Mozambique, and the Kingdom of Swaziland. The discovery of several widely distributed deposits that were likely formed by major terrestrial impacts of large extraterrestrial bodies during this early period of earth's history is reported. The Barberton impact deposits are being studied by electron microscopy. The impact deposits were examined for minerals that show the effects of shock metamorphism or compositions unusual in terrestrial rocks.

  9. Meteoritic Microfossils In Eltanin Impact Deposits

    NASA Astrophysics Data System (ADS)

    Kyte, F. T.; Wollenburg, J.; Gersonde, R.; Kuhn, G.

    2006-12-01

    Introduction: We report the unique occurrence of microfossils composed largely of meteoritic ejecta particles from the late Pliocene (2.5 Ma) Eltanin impact event. These deposits are unique, recording the only known km- sized asteroid impact into a deep-ocean (5 km) basin. First discovered as in Ir anomaly in sediment cores that were collected in 1965, the deposits contain mm-sized shock-melted asteroidal material, unmelted meteorite fragments (named the Eltanin meteorite), and trace impact spherules. Two oceanographic expeditions by the FS Polarstern in 1995 and 2001 explored 80,000 square km of the impact region, mapping the distribution of meteoritic ejecta, disturbance of seafloor sediments by the impact, and collected 20 new cores with impact deposits in the vicinity of the Freeden Seamounts (57.3S, 90.5W). Analyses of sediment cores show that the impact disrupted sediments on the ocean floor, redepositing them as a chaotic jumble of sediment fragments overlain by a sequence of laminated sands, silts and clays deposited from the water column. Overprinted on this is a pulse of meteoritic ejecta, likely transported ballistically, then settled through the water column. At some localities, meteoritic ejecta was as much as 5 to 50 kg per square meter. This is the most meteorite-rich locality known on Earth. Results: Two cores were taken in a basin near the top of the Freeden Seamounts at a water depth of 2.7 km. Sediments in this shallow basin are compositionally different than those at all other sites as they contain abundant calcareous microfossils. In deeper water sites (4 to 5 km depth), higher pressures and CO2 concentrations cause dissolution of calcite and sediments contain siliceous (opal) microfossils or are barren. An exception to this is a few sites in the immediate vicinity of the seamounts that contain calcareous sediments that flowed off the seamounts after being disturbed by the impact. At the top of the seamounts, sediments with meteoritic ejecta

  10. Cosmogenic Nuclides Study of Large Iron Meteorites

    NASA Astrophysics Data System (ADS)

    Hutzler, A.; Smith, T.; Rochette, P.; Bourles, D. L.; Leya, I.; Gattacceca, J.

    2014-09-01

    Six large iron meteorites were selected (Saint-Aubin, Mont-Dieu, Caille, Morasko, Agoudal, and Gebel Kamil). We measured stable and radiogenic cosmogenic nuclides, to study pre-atmospheric size, cosmic-ray exposure ages and terrestrial ages.

  11. Amino Acid Degradation after Meteoritic Impact Simulation

    NASA Technical Reports Server (NTRS)

    Bertrand, M.; Westall, F.; vanderGaast, S.; Vilas, F.; Hoerz, F.; Barnes, G.; Chabin, A.; Brack, A.

    2008-01-01

    Amino acids are among the most important prebiotic molecules as it is from these precursors that the building blocks of life were formed [1]. Although organic molecules were among the components of the planetesimals making up the terrestrial planets, large amounts of primitive organic precursor molecules are believed to be exogenous in origin and to have been imported to the Earth via micrometeorites, carbonaceous meteorites and comets, especially during the early stages of the formation of the Solar System [1,2]. Our study concerns the hypothesis that prebiotic organic matter, present on Earth, was synthesized in the interstellar environment, and then imported to Earth by meteorites or micrometeorites. We are particularly concerned with the formation and fate of amino acids. We have already shown that amino acid synthesis is possible inside cometary grains under interstellar environment conditions [3]. We are now interested in the effects of space conditions and meteoritic impact on these amino acids [4-6]. Most of the extraterrestrial organic molecules known today have been identified in carbonaceous chondrite meteorites [7]. One of the components of these meteorites is a clay with a composition close to that of saponite, used in our experiments. Two American teams have studied the effects of impact on various amino acids [8,9]. [8] investigated amino acids in saturated solution in water with pressure ranges between 5.1 and 21 GPa and temperature ranges between 412 and 870 K. [9] studied amino acids in solid form associated with and without minerals (Murchison and Allende meteorite extracts) and pressure ranges between 3 and 30 GPa. In these two experiments, the amino acids survived up to 15 GPa. At higher pressure, the quantity of preserved amino acids decreases quickly. Some secondary products such as dipeptides and diketopiperazins were identified in the [8] experiment.

  12. The first large meteorite impact structure discovered in the Middle East: Jebel Waqf as Suwwan, Jordan

    NASA Astrophysics Data System (ADS)

    Salameh, E.; Khoury, H.; Reimold, W. U.; Schneider, W.

    2008-10-01

    Triggered by re-evaluation of a 1960s report on the regional geology of the northeastern border region of Jordan and following Landsat satellite image investigation, a 5.5 km diameter, complex, circular structure was discovered in the central eastern region of the Kingdom of Jordan. Initial ground truthing revealed complex geological structures involving Upper Cretaceous and Paleogene strata, and including a prominent outer rim rising up to 60 m above the surrounding plain, an intermediate ring of up to 20 m elevation within a ring syncline, and a central zone of stratigraphically uplifted sedimentary strata characterized by intense macroscopic (folding and faulting, widespread cataclasis) and locally mesoscopic (cataclasis) deformation. Ten sites with shatter cone development in fine-grained sandstone or limestone have been mapped to date, mostly in the outer parts of the central uplifted area. This finding confirms that the Jebel Waqf as Suwwan structure was formed as the result of the impact of an extraterrestrial projectile. Search for impactdiagnostic micro-deformation has been rather unsuccessful: only 1 quartz grain with both planar deformation features and planar fractures has been detected in a sandstone sample to date. The overall majority of the approximately 70 samples investigated by micropetrographic analysis consist of extremely fine-grained chert, siltstone, or marly limestone. Cataclasis is widespread in chert and limestone, also on the micro-scale. Considering the severely limited amount of characteristic impact microdeformation, and the stratigraphic situation within the central uplift, it is likely that a relatively deep level of the central uplift is currently exposed. The extensive drainage demonstrated for this region supports the conclusion that this impact structure could be quite deeply eroded—especially as its geology involves some relatively soft lithologies (marls, limestones). The age of this impact event is at present poorly

  13. Meteoritic material at four Canadian impact craters

    NASA Astrophysics Data System (ADS)

    Wolf, R.; Woodrow, A.; Grieve, R. A. F.

    1980-07-01

    Eleven impact melt and six basement rock samples from four craters were analyzed by neutron activation for Au, Co, Cr, Fe, Ge, Ir, Ni, Os, Pd, Re and Se. Wanapitei Lake, Ontario: the impact melts show uniform enrichments corresponding to 1-2% C1-chondrite material. Interelement ratios (Co/Cr, Ni/Cr, Ni/Ir) suggest that the impacting body was a C1-, C2-, or LL-chondrite. Nicholson Lake, North West Territory: Ni, Cr and Co are distinctly more enriched than Ir and Au which tentatively suggests an olivine-rich achondrite (nakhlite or ureilite). Gow Lake, Saskatchewan and Mistastin, Labrador: small enrichments in Ir and Ni; both the low Ir/Ni ratios and low Cr content suggest iron meteorites, but the signals are too weak for conclusive identification. A tentative comparison of meteoritic signatures at 10 large, greater than or equal to 4 km craters and their presumed celestial counterparts (13 Apollo and Amor asteroids) shows more irons and achondrites among known projectile types, and a preponderance of S-type objects, having no known meteoritic equivalent, among asteroids. It is not yet clear that these differences are significant, in view of the tentative nature of the crater identifications and the limited statistics.

  14. Meteoritic material at four Canadian impact craters

    NASA Technical Reports Server (NTRS)

    Wolf, R.; Woodrow, A. B.; Grieve, R. A. F.

    1980-01-01

    Eleven impact melt and six basement rock samples from four craters were analyzed by neutron activation for Au, Co, Cr, Fe, Ge, Ir, Ni, Os, Pd, Re and Se. Wanapitei Lake, Ontario: the impact melts show uniform enrichments corresponding to 1-2% C1-chondrite material. Interelement ratios (Co/Cr, Ni/Cr, Ni/Ir) suggest that the impacting body was a C1-, C2-, or LL-chondrite. Nicholson Lake, North West Territory: Ni, Cr and Co are distinctly more enriched than Ir and Au which tentatively suggests an olivine-rich achondrite (nakhlite or ureilite). Gow Lake, Saskatchewan and Mistastin, Labrador: small enrichments in Ir and Ni; both the low Ir/Ni ratios and low Cr content suggest iron meteorites, but the signals are too weak for conclusive identification. A tentative comparison of meteoritic signatures at 10 large, greater than or equal to 4 km craters and their presumed celestial counterparts (13 Apollo and Amor asteroids) shows more irons and achondrites among known projectile types, and a preponderance of S-type objects, having no known meteoritic equivalent, among asteroids. It is not yet clear that these differences are significant, in view of the tentative nature of the crater identifications and the limited statistics.

  15. Impact ages of meteorites: A synthesis

    NASA Astrophysics Data System (ADS)

    Bogard, D.

    1995-05-01

    Isotopic ages of meteorites that indicate chronometer resetting due to impact heating are . Most of the ages were obtained by the 39Ar-40Ar technique, but several Rb-Sr, Pb-Pb, and Sm-Nd ages also suggest some degree of impact resetting. Considerations of experimental data on element diffusion in silicates suggest that various isotopic chronometers ought to differ in their ease of resetting during shock heating in the order K-Ar (easiest), Rb-Sr, Pb-Pb, and Sm-Nd, which is approximately the order observed in meteorites. Partial rather than total chronometer resetting by impacts appears to be the norm; consequently, interpretation of the event age is not always straightforward. Essentially all 39Ar-40Ar ages of eucrites and howardites indicate partial to total resetting in the relatively narrow time interval of 3.44.1 Ga ago (1 Ga = l09 years). Several disturbed Rb-Sr ages appear consistent with this age distribution. This grouping of ages and the brecciated nature of many eucrites and all howardites argues for a large-scale impact bombardment of the HED parent body during the same time period that the Moon received its cataclysmic bombardment. Other meteorite parent bodies such as those of mesosiderites, some chondrites, and HE irons also may have experienced this bombardment. These data suggest that the early bombardment was not lunar specific but involved much of the inner Solar System, and may have been caused by breakup of a larger planetismal. Although a few chondrites show evidence of age resetting ˜3.5-3.9 Ga ago, most impact ages of chondrites tend to fall below 1.3 Ga in age. A minimum of ˜4 impact events, including events at 0.3, 0.5, 1.2, and possibly 0.9 Ga appear to be required to explain the younger ages of H, L, and LL chondrites, although additional events are possible. Most L chondrites show evidence of shock, and the majority of 39Ar40Ar ages of L chondrites fall near 0.5 Ga. The L chondrite parent body apparently experienced a major impact at

  16. Mercurian impact ejecta: Meteorites and mantle

    NASA Astrophysics Data System (ADS)

    Gladman, B.; Coffey, J.

    2009-03-01

    We have examined the fate of impact ejecta liberated from the surface of Mercury due to impacts by comets or asteroids, in order to study 1) meteorite transfer to Earth, and 2) reaccumulation of an expelled mantle in giant-impact scenarios seeking to explain Mercury’s large core. In the context of meteorite transfer during the last 30 Myr, we note that Mercury’s impact ejecta leave the planet’s surface much faster (on average) than other planets in the solar system because it is the only planet where impact speeds routinely range from 5 to 20 times the planet’s escape speed; this causes impact ejecta to leave its surface moving many times faster than needed to escape its gravitational pull. Thus, a large fraction of Mercurian ejecta may reach heliocentric orbit with speeds sufficiently high for Earth-crossing orbits to exist immediately after impact, resulting in larger fractions of the ejecta reaching Earth as meteorites. We calculate the delivery rate to Earth on a time scale of 30 Myr (typical of stony meteorites from the asteroid belt) and show that several percent of the high-speed ejecta reach Earth (a factor of 2-3 less than typical launches from Mars); this is one to two orders of magnitude more efficient than previous estimates. Similar quantities of material reach Venus. These calculations also yield measurements of the re-accretion time scale of material ejected from Mercury in a putative giant impact (assuming gravity is dominant). For Mercurian ejecta escaping the gravitational reach of the planet with excess speeds equal to Mercury’s escape speed, about one third of ejecta reaccretes in as little as 2 Myr. Thus collisional stripping of a silicate proto-Mercurian mantle can only work effectively if the liberated mantle material remains in small enough particles that radiation forces can drag them into the Sun on time scale of a few million years, or Mercury would simply re-accrete the material.

  17. Why Meteorites

    NASA Astrophysics Data System (ADS)

    Heikal, M. Th. S.

    2014-09-01

    The present work is focused on the characteristic features of meteorites, different types and their composition, world distribution, the global effects of large meteorite impacts through the geologic eras, economic aspects and environmental assessments.

  18. The Meteoritic Component in Impact Deposits

    NASA Technical Reports Server (NTRS)

    Kyte, Frank T.

    2003-01-01

    This proposal requested support for a broad-based research program designed to understand the chemical and mineralogical record of accretion of extraterrestrial matter to the Earth. The primary goal of this research is to study the accretion history of the Earth, to understand how this accretion history reflects the long-term flux of comets, asteroids, and dust in the inner solar system and how this flux is related to the geological and biological history of the Earth. This goal is approached by seeking out the most significant projects that can be attacked utilizing the expertise of the PI and potential collaborators. The greatest expertise of the PI is the analysis of meteoritic components in terrestrial sediments. This proposal identifies three primary areas of research, involving impact events in the early Archean (3.2 Ga), the late Eocene (35 Ma) and the late Pliocene (2 Ma). In the early Archean we investigate sediments that contain the oldest recorded impacts on Earth. These are thick spherule beds, three of which were deposited within 20 m.y. If these are impact deposits the flux of objects to Earth at this time was much greater than predicted by current models. Earlier work used Cr isotopes to prove that one of these contain extraterrestrial matter, from a projectile with Cr isotopes similar to CV chondrites. We planned to expand this work to other spherule beds and to search for additional evidence of other impact events. With samples from D. Lowe (Stanford Univ.) the PI proposed to screen samples for high Ir and Cr so that appropriate samples can be provided to A. Shukolyukov for Cr-isotopic analyses. This work was expected to provide evidence that at least one interval in the early Archean was a period of intense bombardment and to characterize the composition of objects accreted. The late Eocene is also a period of intense bombardment with multiple spherule deposits and two large craters. Farley et al. (1998) demonstrated an increased (3)He flux to

  19. High resolution Osmium isotopes in deep-sea ferromanganese crusts reveal a large meteorite impact in the Central Pacific at 12 ± 4 ka (Invited)

    NASA Astrophysics Data System (ADS)

    Sharma, M.; Chen, C.; Jackson, B. P.; Abouchami, W.

    2009-12-01

    Ferromanganese crusts grow by incorporating metals from ambient seawater and are shown to be faithful recorders of ocean paleochemistry. We studied a well-dated crust (VA 13/2) from the Central Pacific with the aim to provide a high resolution record of glacial-interglacial variations in the seawater Os isotope composition. The uppermost 1.5 mm section of the crust was sampled at every 50 μ m with an 8 mm diameter drill-bit that was mounted on a high precision lathe. This corresponds to a time resolution of 4 ka for the first 550 μ m and of 8 ka for the rest on the basis of 230Thexcess dating. Surprisingly, the Os contents and isotope ratios in the crust appear to be compromised between 50 and 100 μ m by contact with a source that is highly enriched in Os but with low 187Os\\188Os ratio. The depth corresponds to an age of 12 ± 4 ka and in comparison to a background seawater isotope ratio of 0.93-1.02, at this time the crust shows an isotope ratio of 0.24 suggesting input of meteorite derived Os. We prepared a thick-section of the crust to investigate whether the Os signal is associated with the presence of extraterrestrial (ET) particles. We found using optical microscopy and LA-ICP-MS that there are no large ET particles and that the Os enrichment of the crust is confined to within 100 μ m of the surface. This suggests that the crust received meteorite-derived Os as extremely small particles. Investigations of surface scrapes of other crusts in the vicinity of VA 13/2 helped us define a large area in the Pacific with 187Os\\188Os ratios lower than that estimated for the ambient seawater. We infer that the Central Pacific was a site of deposition of Os resulting from dust cloud following a meteorite impact at 12 ± 4 ka that suppressed the 187Os\\188Os ratios of the crusts. Using the distribution of the Fe-Mn crusts whose surface-scrapes display 187Os\\188Os ratios much less than ambient seawater (0.9 or less) we find that the meteorite could be up to 100 m in

  20. Meteorites

    NASA Astrophysics Data System (ADS)

    Jenniskens, Peter

    2015-08-01

    Meteorites have long been known to offer a unique window into planetary formation processes at the time of solar system formation and into the materials that rained down on Earth at the time of the origin of life. Their material properties determine the impact hazard of Near Earth Asteroids. Some insight into how future laboratory studies of meteorites and laboratory astrophysics simulations of relevant physical processes can help address open questions in these areas and generate new astronomical observations, comes from what was learned from the recent laboratory studies of freshly fallen meteorites. The rapid recovery of Almahata Sitta (a polymict Ureilite), Sutter's Mill (a CM chondrite regolith breccia), Novato (an L6 chondrite), and Chelyabinsk (an LL5 chondrite) each were followed by the creation of a meteorite consortium, which grew to over 50 researchers in the case of Chelyabinsk. New technologies were used to probe the organic content of the meteorites as well as their magnetic signatures, isotopic abundances, trapped noble gasses, and cosmogenic radio nucleides, amongst others. This has resulted in fascinating insight into the nature of the Ureilite parent body, the likely source region of the CM chondrites in the main asteroid belt, and the collisional environment of the CM parent body. This work has encouraged follow-up in the hope of catching more unique materials. Rapid response efforts are being developed that aim to recover meteorites as pristinely as possible from falls for which the approach orbit was measured. A significant increase in the number of known approach orbits for different meteorite types will help tie meteorite types to their asteroid family source regions. Work so far suggests that future laboratory studies may recognize multiple source regions for iron-rich ordinary chondrites, for example. Hope is that these source regions will give insight into the material properties of impacting asteroids. At least some future laboratory

  1. Survivability of Meteorite Projectiles - Results from Impact Experiments

    NASA Technical Reports Server (NTRS)

    Bland, P. A.; Cintala, M. J.; Hoerz, F.; Cressey, G.

    2001-01-01

    An experimental impact study investigating the fragmentation of various projectiles, including meteorite, at speeds up to 1.8 km/s. The results have implications for the survivability of meteorites impacting planetary and asteroidal surfaces. Additional information is contained in the original extended abstract.

  2. Modeling Meteorite Impacts: What We Know and What We Would Like to Know

    NASA Astrophysics Data System (ADS)

    Melosh, H. J.

    2003-01-01

    Meteorite impacts can be studied by computer simulation: Large meteorite impacts are among those phenomena that are either too large or too dangerous to study experimentally. Although impacts have affected the formation and surfaces of nearly every body in the solar system, we are limited to observing the results of past events. Investigation of impact processes is thus divided into observational studies of the traces of past impacts, small-scale analogue laboratory experiments and, most recently, detailed computer modeling. Computer models offer the possibility of studying craters at all scales, provided we completely understand the physics of the process and possess enough computer power to simulate the features of interest.

  3. Meteor Crater (Barringer Meteorite Crater), Arizona: Summary of Impact Conditions

    NASA Astrophysics Data System (ADS)

    Roddy, D. J.; Shoemaker, E. M.

    1995-09-01

    Meteor Crater in northern Arizona represents the most abundant type of impact feature in our Solar System, i.e., the simple bowl-shaped crater. Excellent exposures and preservation of this large crater and its ejecta blanket have made it a critical data set in both terrestrial and planetary cratering research. Recognition of the value of the crater was initiated in the early 1900's by Daniel Moreau Barringer, whose 27 years of exploration championed its impact origin [1]. In 1960, Shoemaker presented information that conclusively demonstrated that Meteor Crater was formed by hypervelocity impact [2]. This led the U.S. Geological Survey to use the crater extensively in the 1960-70's as a prime training site for the Apollo astronauts. Today, Meteor Crater continues to serve as an important research site for the international science community, as well as an educational site for over 300,000 visitors per year. Since the late 1950's, studies of this crater have presented an increasingly clearer view of this impact and its effects and have provided an improved view of impact cratering in general. To expand on this data set, we are preparing an upgraded summary on the Meteor Crater event following the format in [3], including information and interpretations on: 1) Inferred origin and age of the impacting body, 2) Inferred ablation and deceleration history in Earth's atmosphere, 3) Estimated speed, trajectory, angle of impact, and bow shock conditions, 4) Estimated coherence, density, size, and mass of impacting body, 5) Composition of impacting body (Canyon Diablo meteorite), 6) Estimated kinetic energy coupled to target rocks and atmosphere, 7) Terrain conditions at time of impact and age of impact, 8) Estimated impact dynamics, such as pressures in air, meteorite, and rocks, 9) Inferred and estimated material partitioning into vapor, melt, and fragments, 10) Crater and near-field ejecta parameters, 11) Rock unit distributions in ejecta blanket, 12) Estimated far

  4. Martian soil component in impact glasses in a Martian meteorite.

    PubMed

    Rao, M N; Borg, L E; McKay, D S; Wentworth, S J

    1999-11-01

    Chemical compositions of impact melt glass veins, called Lithology C (Lith C) in Martian meteorite EET79001 were determined by electron microprobe analysis. A large enrichment of S, and significant enrichments of Al, Ca, and Na were observed in Lith C glass compared to Lithology A (Lith A). The S enrichment is due to mixing of plagioclase- enriched Lith A material with Martian soil, either prior to or during impact on Mars. A mixture of 87% Lith A, 7% plagioclase, and 6% Martian soil reproduces the average elemental abundances observed in Lith C. Shock melting of such a mixture of plagioclase-enriched, fine-grained Lith A host rock and Martian soil could yield large excesses of S (observed in this study) and Martian atmospheric noble gases (found by Bogard et al., 1983) in Lith C. These mixing proportions can be used to constrain the elemental abundance of phosphorus in Martian soil.

  5. Dating the Moon-forming impact event with asteroidal meteorites

    NASA Astrophysics Data System (ADS)

    Bottke, W. F.; Vokrouhlický, D.; Marchi, S.; Swindle, T.; Scott, E. R. D.; Weirich, J. R.; Levison, H.

    2015-04-01

    The inner solar system’s biggest and most recent known collision was the Moon-forming giant impact between a large protoplanet and proto-Earth. Not only did it create a disk near Earth that formed the Moon, it also ejected several percent of an Earth mass out of the Earth-Moon system. Here, we argue that numerous kilometer-sized ejecta fragments from that event struck main-belt asteroids at velocities exceeding 10 kilometers per second, enough to heat and degas target rock. Such impacts produce ~1000 times more highly heated material by volume than do typical main belt collisions at ~5 kilometers per second. By modeling their temporal evolution, and fitting the results to ancient impact heating signatures in stony meteorites, we infer that the Moon formed ~4.47 billion years ago, which is in agreement with previous estimates.

  6. Seismic detectability of meteorite impacts on Europa

    NASA Astrophysics Data System (ADS)

    Tsuji, Daisuke; Teanby, Nicholas

    2016-04-01

    Europa, the second of Jupiter's Galilean satellites, has an icy outer shell, beneath which there is probably liquid water in contact with a rocky core. Europa, may thus provide an example of a sub-surface habitable environment so is an attractive object for future lander missions. In fact, the Jupiter Icy Moon Explorer (JUICE) mission has been selected for the L1 launch slot of ESA's Cosmic Vision science programme with the aim of launching in 2022 to explore Jupiter and its potentially habitable icy moons. One of the best ways to probe icy moon interiors in any future mission will be with a seismic investigation. Previously, the Apollo seismic experiment, installed by astronauts, enhanced our knowledge of the lunar interior. For a recent mission, NASA's 2016 InSight Mars lander aims to obtain seismic data and will deploy a seismometer directly onto Mars' surface. Motivated by these works, in this study we show how many meteorite impacts will be detected using a single seismic station on Europa, which will be useful for planning the next generation of outer solar system missions. To this end, we derive: (1) the current small impact flux on Europa from Jupiter impact rate models; (2) a crater diameter versus impactor energy scaling relation for ice by merging previous experiments and simulations; (3) scaling relations for seismic signals as a function of distance from an impact site for a given crater size based on analogue explosive data obtained on Earth's icy surfaces. Finally, resultant amplitudes are compared to the noise level of a likely seismic instrument (based on the NASA InSight mission seismometers) and the number of detectable impacts are estimated. As a result, 0.5-3.0 local/regional small impacts (i.e., direct P-waves through the ice crust) are expected to be detected per year, while global-scale impact events (i.e., PKP-waves refracted through the mantle) are rare and unlikely to be detected by a short duration mission. We note that our results are

  7. The meteorite impact-induced tsunami hazard.

    PubMed

    Wünnemann, K; Weiss, R

    2015-10-28

    When a cosmic object strikes the Earth, it most probably falls into an ocean. Depending on the impact energy and the depth of the ocean, a large amount of water is displaced, forming a temporary crater in the water column. Large tsunami-like waves originate from the collapse of the cavity in the water and the ejecta splash. Because of the far-reaching destructive consequences of such waves, an oceanic impact has been suggested to be more severe than a similar-sized impact on land; in other words, oceanic impacts may punch over their weight. This review paper summarizes the process of impact-induced wave generation and subsequent propagation, whether the wave characteristic differs from tsunamis generated by other classical mechanisms, and what methods have been applied to quantify the consequences of an oceanic impact. Finally, the impact-induced tsunami hazard will be evaluated by means of the Eltanin impact event.

  8. The Origin and Impact History of Lunar Meteorite Yamato 86032

    NASA Technical Reports Server (NTRS)

    Yamaguchi, A.; Takeda, H.; Nyquist, L. E.; Bogard, D. D.; Ebihara, M.; Karouji, Y.

    2004-01-01

    Yamato (Y) 86032 is a feldspathic lunar highland breccia having some characteristics of regolith breccia. The absence of KREEP components in the matrix in Y86032 indicates that these meteorites came from a long distance from Mare Imbrium, perhaps from the far-side of the moon. One ferroan anorthosite (FAN) clast in Y86032 has a very old Ar-Ar age of approximately 4.35-4.4 Ga. The negative Nd of this clast may suggest a direct link with the primordial magma ocean. The facts indicate that Y86032 contains components derived from a protolith of the original lunar crust. Detailed petrologic characterization of each component in this breccia is essential to understand the early impact history and origin of the lunar highland crust. We made a large slab (5.2 x 3.6 cm x 3-5 mm) of Y86032 to better understand the relationship of various lithologies and their petrologic origin.

  9. Spherule Beds 3.47-3.24 Billion Years Old in the Barberton Greenstone Belt, South Africa: A Record of Large Meteorite Impacts and Their Influence on Early Crustal and Biological Evolution

    NASA Technical Reports Server (NTRS)

    Lowe, Donald R.; Byerly, Gary R.; Kyte, Frank T.; Shukolyukov, Alexander; Asaro, Frank; Krull, Alexander

    2003-01-01

    Four layers, S1-S4, containing sand-sized spherical particles formed as a result of large meteorite impacts, occur in 3.47-3.24 Ga rocks of the Barberton Greenstone Belt, South Africa. Ir levels in S3 and S4 locally equal or exceed chondritic values but in other sections are at or only slightly above background. Most spherules are inferred to have formed by condensation of impact-produced rock vapor clouds, although some may represent ballistically ejected liquid droplets. Extreme Ir abundances and heterogeneity may reflect element fractionation during spherule formation, hydraulic fractionation during deposition, and/or diagenetic and metasomatic processes. Deposition of S1, S2, and S3 was widely influenced by waves and/or currents interpreted to represent impact-generated tsunamis, and S1 and S2 show multiple graded layers indicating the passage of two or more wave trains. These tsunamis may have promoted mixing within a globally stratified ocean, enriching surface waters in nutrients for biological communities. S2 and S3 mark the transition from the 300-million-year-long Onverwacht stage of predominantly basaltic and komatiitic volcanism to the late orogenic stage of greenstone belt evolution, suggesting that regional and possibly global tectonic reorganization resulted from these large impacts. These beds provide the oldest known direct record of terrestrial impacts and an opportunity to explore their influence on early life, crust, ocean, and atmosphere. The apparent presence of impact clusters at 3.26-3.24 Ga and approx. 2.65-2.5 Ga suggests either spikes in impact rates during the Archean or that the entire Archean was characterized by terrestrial impact rates above those currently estimated from the lunar cratering record.

  10. Spherule beds 3.47-3.24 billion years old in the Barberton Greenstone Belt, South Africa: a record of large meteorite impacts and their influence on early crustal and biological evolution.

    PubMed

    Lowe, Donald R; Byerly, Gary R; Kyte, Frank T; Shukolyukov, Alexander; Asaro, Frank; Krull, Alexandra

    2003-01-01

    Four layers, S1-S4, containing sand-sized spherical particles formed as a result of large meteorite impacts, occur in 3.47-3.24 Ga rocks of the Barberton Greenstone Belt, South Africa. Ir levels in S3 and S4 locally equal or exceed chondritic values but in other sections are at or only slightly above background. Most spherules are inferred to have formed by condensation of impact-produced rock vapor clouds, although some may represent ballistically ejected liquid droplets. Extreme Ir abundances and heterogeneity may reflect element fractionation during spherule formation, hydraulic fractionation during deposition, and/or diagenetic and metasomatic processes. Deposition of S1, S2, and S3 was widely influenced by waves and/or currents interpreted to represent impact-generated tsunamis, and S1 and S2 show multiple graded layers indicating the passage of two or more wave trains. These tsunamis may have promoted mixing within a globally stratified ocean, enriching surface waters in nutrients for biological communities. S2 and S3 mark the transition from the 300-million-year-long Onverwacht stage of predominantly basaltic and komatiitic volcanism to the late orogenic stage of greenstone belt evolution, suggesting that regional and possibly global tectonic reorganization resulted from these large impacts. These beds provide the oldest known direct record of terrestrial impacts and an opportunity to explore their influence on early life, crust, ocean, and atmosphere. The apparent presence of impact clusters at 3.26-3.24 Ga and approximately 2.65-2.5 Ga suggests either spikes in impact rates during the Archean or that the entire Archean was characterized by terrestrial impact rates above those currently estimated from the lunar cratering record.

  11. Environmental Effects of Small Meteorite Impact in Unconsolidated Sediments — Case of Iron Meteorite Shower in Morasko, Poland

    NASA Astrophysics Data System (ADS)

    Szczuciński, W.; Pleskot, K.; Makohonienko, M.; Tjallingii, R.; Apolinarska, K.; Cerbin, S.; Goslar, T.; Nowaczyk, N.; Rzodkiewicz, M.; Słowiński, M.; Woszczyk, M.; Brauer, A.

    2016-08-01

    We show record of environmental consequences of mid-Holocene small meteorite impact. It is based on sedimentological, geochemical and biological indicators studied in lake deposits, which revealed relatively small extent of the impact effects.

  12. The Tissint Martian meteorite as evidence for the largest impact excavation.

    PubMed

    Baziotis, Ioannis P; Liu, Yang; DeCarli, Paul S; Melosh, H Jay; McSween, Harry Y; Bodnar, Robert J; Taylor, Lawrence A

    2013-01-01

    High-pressure minerals in meteorites provide clues for the impact processes that excavated, launched and delivered these samples to Earth. Most Martian meteorites are suggested to have been excavated from 3 to 7 km diameter impact craters. Here we show that the Tissint meteorite, a 2011 meteorite fall, contains virtually all the high-pressure phases (seven minerals and two mineral glasses) that have been reported in isolated occurrences in other Martian meteorites. Particularly, one ringwoodite (75 × 140 μm(2)) represents the largest grain observed in all Martian samples. Collectively, the ubiquitous high-pressure minerals of unusually large sizes in Tissint indicate that shock metamorphism was widely dispersed in this sample (~25 GPa and ~2,000 °C). Using the size and growth kinetics of the ringwoodite grains, we infer an initial impact crater with ~90 km diameter, with a factor of 2 uncertainty. These energetic conditions imply alteration of any possible low-T minerals in Tissint.

  13. Where's the Beaverhead beef?. [meteorite impact structure

    NASA Technical Reports Server (NTRS)

    Hargraves, R. B.

    1992-01-01

    Only rare quartz grains with single-set planar (1013) deformation features (PDF's) are present in breccia dikes found in association with uniformly oriented shatter cones that occur over an area 8 x 25 km. This suggests that the Beaverhead shocked rocks come from only the outer part of the central uplift of what must have been a large (greater than 100 km diameter) complex impact structure. An impact event of this magnitude on continental crust (thought to have occurred in late Precambrian or ealy Paleozoic time) could be expected to punctuate local geologic history. Furthermore, although it may now be covered, its scar should remain despite all the considerable subsequent erosion/deposition and tectonism since the impact. The following are three large-scale singularities or anomalies that may reflect the event and mark its source. (1) The Lemhi Arch is a major structural uplift that occurred in late Proterozoic-early Paleozoic time in East Central Idaho and caused the erosion of at least 4 km of sedimentary cover. This may be directly related to the impact. (2) Of the many thrust sheets comprising the Cordilleran belt, the Cabin plate that carries the shocked rocks is unique in that it alone intersected the crystalline basement. It also now marks the apex of the Southwest Montana Recess in the Sevier front. The basement uplift remaining from the impact may have constituted a mechanical obstacle to the advancing thrust sheets in Cretaceous time, causing the recess. (3) What could be interpreted as a roughly circular aeromagnetic anomaly approx. 70 km in diameter can be discerned in the state aeromagnetic map centered about 20 km southeast of Challis, Idaho, in the Lost River range. It is in approximately the right place, and ignoring the possibility that the anomalies have diverse causes and the circular pattern is coincidental, it may mark what remains of the buried central uplift structure.

  14. Experimental studies of oblique impact. [of meteorites on planetary surfaces

    NASA Technical Reports Server (NTRS)

    Gault, D. E.; Wedekind, J. A.

    1978-01-01

    Meteoritic materials most probably impact planetary bodies along oblique trajectories inclined less than 45 deg above their surfaces. Laboratory studies of hypervelocity impacts against rock and particulate media are presented that indicate important effects of obliquity on crater size, shape, and ejecta distribution. The effects are particularly important to crater size-frequency analyses and geologic interpretations of crater formations. Impacts at shallow incidence, which are not uncommon, lead to ricochet of the impacting object accompanied with some entrained excavated materials at velocities only slightly reduced from the pre-impact value.

  15. The meteorite component of Apollo 16 noritic impact melt breccias

    NASA Astrophysics Data System (ADS)

    Korotev, Randy L.

    Noritic melt rocks (alias LKFM and VHA) from Apollo 16 have concentrations of Ni approximately three to five times those of impact melt rocks of similar composition from other lunar landing sites. The melt rock associated with Apollo 16 dimict breccias has the highest mean concentration of Ni of any lunar rock type (1150 µg/g in 11 samples). The Ni is contained in Fe-Ni metal that is dissimilar in composition to metal from ordinary chondrites in having a lower Ni concentration (6%) and lower Ni/Co ratio (17). It also has Ir/Ni and Ir/Au ratios of about one-half and one-third those of chondrites. The metal in the noritic impact melts is the carrier of the siderophile element signature of ancient meteorite group 1H. The composition of the Fe-Ni metal is dissimilar to that of chondrites because it derives from metal-rich meteorites, probably irons, that created the impact melts 3.9 Ga ago. The metal from these iron meteorites dominates the siderophile element concentrations of polymict samples at Apollo 16. Models that attempt to estimate indigenous concentrations of Ni and Co in Apollo 16 materials overestimate their abundance by assuming that the meteoritic component has chondritic ratios of Ir to Ni and Co. The type-2 melt (VHA) associated with the dimict breccias and the type-1 melt (Apollo 16 LKFM) were most likely produced by impact of two related iron meteoroids that impacted near the Apollo 16 site. The type-2 melt found in samples from station 7 is probably from the same impact as that producing the dimict breccias, although it could represent the impact of a third, related iron.

  16. Comet nongravitational forces and meteoritic impacts

    NASA Technical Reports Server (NTRS)

    Matese, John J.; Whitman, Patrick G.; Whitmire, Daniel P.

    1992-01-01

    We have considered those comets whose original orbits have been determined to be hyperbolic when only planetary perturbations are accounted for. It is found that formally unbound incident trajectories correlate most confidently with orbits that have small perihelion distances and move in a retrograde sense relative to planetary motion. Arguments are presented that these results are not due to measurement error or to selection effects. We conclude that the phenomenon is attributable to enhanced volatility leading to abnormally large nongravitational forces. Since the effect is absent in the prograde small-perihelia population, increased insolation is not the sole explanation. It is suggested that the significance of the retrograde correlation is connected with a larger energy of relative motion between retrograde comets and a population of prograde ecliptic meteoroids which impact the comet mantle exposing the underlying volatiles. The subsequent enhanced outgassing is the cause of the larger nongravitational forces.

  17. Survivability and reactivity of glycine and alanine in early oceans: effects of meteorite impacts.

    PubMed

    Umeda, Yuhei; Fukunaga, Nao; Sekine, Toshimori; Furukawa, Yoshihiro; Kakegawa, Takeshi; Kobayashi, Takamichi; Nakazawa, Hiromoto

    2016-01-01

    Prebiotic oceans might have contained abundant amino acids, and were subjected to meteorite impacts, especially during the late heavy bombardment. It is so far unknown how meteorite impacts affected amino acids in the early oceans. Impact experiments were performed under the conditions where glycine was synthesized from carbon, ammonia, and water, using aqueous solutions containing (13)C-labeled glycine and alanine. Selected amino acids and amines in samples were analyzed with liquid chromatography-mass spectrometry (LC/MS). In particular, the (13)C-labeled reaction products were analyzed to distinguish between run products and contaminants. The results revealed that both amino acids survived partially in the early ocean through meteorite impacts, that part of glycine changed into alanine, and that large amounts of methylamine and ethylamine were formed. Fast decarboxylation was confirmed to occur during such impact processes. Furthermore, the formation of n-butylamine, detected only in the samples recovered from the solutions with additional nitrogen and carbon sources of ammonia and benzene, suggests that chemical reactions to form new biomolecules can proceed through marine impacts. Methylamine and ethylamine from glycine and alanine increased considerably in the presence of hematite rather than olivine under similar impact conditions. These results also suggest that amino acids present in early oceans can contribute further to impact-induced reactions, implying that impact energy plays a potential role in the prebiotic formation of various biomolecules, although the reactions are complicated and depend upon the chemical environments as well.

  18. Experimental simulation of marine meteorite impacts: Implications for astrobiology

    NASA Astrophysics Data System (ADS)

    Umeda, Y.; Suga, H.; Sekine, T.; Kobayashi, T.; Furukawa, Y.; Kakegawa, T.

    2016-12-01

    Early oceans on planets which had liquid water (e.g. Earth, Mars) might have contained certain amounts of organic compounds such as amino acids, and were subjected to meteorite impacts, especially during the late heavy bombardment (LHB). Therefore, it is necessary to know chemical reactions and products of amino acids in aqueous solution under shock conditions in order to elucidate the prebiotic chemistry and evolution of amino acids through marine meteorite impacts. In our study, we performed shock recovery experiments in order to simulate shock reactions of marine meteorite impacts among olivine as meteorite components and water and amino acids as oceanic components (Umeda et al., 2016). The analytical results on shocked products in the recovered sample showed (i) the formation of carbon-rich substances derived from amino acids and (ii) morphological changes of olivine to fiber and features of lumpy surfaces affected by hot water. These results suggest that marine meteorite impacts might be able to occur the formation of carbon-rich substances from amino acids and the interaction between minerals and water. Hereafter, we will conduct more detailed analyses to investigate the chemical bonding and the chemical composition of carbon-rich substances as the experimental product from amino acids by Scanning Transmission X-ray Microscopy (STXM) and to identify the morphological change of olivine by Scanning Transmission Electron Microscope (STEM). These informations such as the chemical bonding and the composition of carbon-rich substances may be useful to make the reaction and the transformation of amino acids under shock conditions clear in more detail. As a further implication, carbon-rich substances have been also found in solar system (e.g. comets, meteorites) as important materials related to origin of life, although the origin (precursors) and the formation mechanism (what kinds of reactions) of them are still unknown well. If carbon-rich substances between

  19. Reactivity and survivability of glycolaldehyde in simulated meteorite impact experiments.

    PubMed

    McCaffrey, V P; Zellner, N E B; Waun, C M; Bennett, E R; Earl, E K

    2014-02-01

    Sugars of extraterrestrial origin have been observed in the interstellar medium (ISM), in at least one comet spectrum, and in several carbonaceous chondritic meteorites that have been recovered from the surface of the Earth. The origins of these sugars within the meteorites have been debated. To explore the possibility that sugars could be generated during shock events, this paper reports on the results of the first laboratory impact experiments wherein glycolaldehyde, found in the ISM, as well as glycolaldehyde mixed with montmorillonite clay, have been subjected to reverberated shocks from ~5 to >25 GPa. New biologically relevant molecules, including threose, erythrose and ethylene glycol, were identified in the resulting samples. These results show that sugar molecules can not only survive but also become more complex during impact delivery to planetary bodies.

  20. Laboratory Simulations of Martian Meteorite Impacts and Their Seismic Signatures

    NASA Astrophysics Data System (ADS)

    Kedar, S.; Richardson, J. E.; Harvey, N. E.; Perry, D. C.; Bowling, T. J.; Kanamori, H.; Webb, F.; Li, M.; Garnero, E. J.

    2012-12-01

    Recent satellite images have revealed that meteorites regularly impact the Martian surface. Such impacts provide a constant background of planet-wide seismicity, and add a substantial number of seismic sources to an otherwise seismically quiet planet, with a natural quake rate estimated to be ~1000 times lower than on Earth. This is a potentially rich and relatively unexplored source of seismic activity that may be used to answer fundamental questions about the planet's internal structure, such as the size and nature of the core, the composition and layering of the mantle, and the planets crustal thickness and variability. Determining whether meteoritic impacts can be used as seismic sources for studying the Martian interior depends directly upon two fundamental parameters: (1) the rate of transfer of momentum to the elastic medium as defined by an impact's source-time function (or its power spectrum); and (2) the efficiency with which the kinetic energy of the impacting body is transferred to seismic energy. However, uncertainty of the impact source time function, combined with the wide range of impact seismic efficiency factors observed in various settings, makes it very difficult to determine the efficacy of natural impacts for seismic exploration. To overcome these challenges, we have begun a campaign combining impact laboratory experiments and numerical simulations with the goal of determining how well the observed meteoritic impact distribution on Mars can be used to resolve the Martian interior structure. To simulate the seismic signals expected from meteorite impacts on the Martian surface, we carried out a series of high velocity impact experiments at the NASA Ames Vertical Gun Range (AVGR) facility. The experiments spanned a variety of projectile impact velocities and angles, and were carried out in near vacuum conditions to mimic Martian atmospheric conditions. Seismic sensors were embedded in target material analogous to the Martian surface and were

  1. The Survival of Meteorite Organic Compounds with Increasing Impact Pressure

    NASA Technical Reports Server (NTRS)

    Cooper, George; Horz, Friedrich; Oleary, Alanna; Chang, Sherwood; DeVincenzi, Donald L. (Technical Monitor)

    2000-01-01

    The majority of carbonaceous meteorites studied today are thought to originate in the asteroid belt. Impacts among asteroidal objects generate heat and pressure that may have altered or destroyed pre-existing organic matter in both targets and projectiles to a greater or lesser degree depending upon impact velocities. Very little is known about the shock related chemical evolution of organic matter relevant to this stage of the cosmic history of biogenic elements and compounds. The present work continues our study of the effects of shock impacts on selected classes of organic compounds utilizing laboratory shock facilities. Our approach was to subject mixtures of organic compounds, embedded in a matrix of the Murchison meteorite, to a simulated hypervelocity impact. The molecular compositions of products were then analyzed to determine the degree of survival of the original compounds. Insofar as results associated with velocities < 8 km/sec may be relevant to impacts on planetary surfaces (e.g., oblique impacts, impacts on small outer planet satellites) or grain-grain collisions in the interstellar medium, then our experiments will be applicable to these environments as well.

  2. Analysis of a crater-forming meteorite impact in Peru

    NASA Astrophysics Data System (ADS)

    Brown, P.; ReVelle, D. O.; Silber, E. A.; Edwards, W. N.; Arrowsmith, S.; Jackson, L. E.; Tancredi, G.; Eaton, D.

    2008-09-01

    The fireball producing a crater-forming meteorite fall near Carancas, Peru, on 15 September 2007 has been analyzed using eyewitness, seismic, and infrasound records. The meteorite impact, which produced a crater of 13.5 m diameter, is found to have released of order 1010 J of energy, equivalent to ~2-3 tons of TNT high explosives based on infrasonic measurements. Our best fit trajectory solution places the fireball radiant at an azimuth of 82° relative to the crater, with an entry angle from the horizontal of 63°. From entry modeling and infrasonic energetics constraints, we find an initial energy for the fireball to be in the 0.06-0.32 kton TNT equivalent. The initial velocity for the meteoroid is restricted to be below 17 km/s from orbit considerations alone, while modeling suggests an even lower best fit velocity close to 12 km/s. The initial mass of the meteoroid is in the range of 3-9 tons. At impact, modeling suggests a final end mass of order a few metric tons and impact velocity in the 1.5-4 km/s range. We suggest that the formation of such a substantial crater from a chondritic mass was the result of the unusually high strength (and corresponding low degree of fragmentation in the atmosphere) of the meteoritic body. Additionally, the high altitude of the impact site (3800 m.a.s.l) resulted in an almost one order of magnitude higher impact speed than would have been the case for the same body impacting close to sea level.

  3. Kinetic Damage from Meteorites

    NASA Technical Reports Server (NTRS)

    Cooke, William; Brown, Peter; Matney, Mark

    2017-01-01

    A Near Earth object impacting into Earth's atmosphere may produce damaging effects at the surface due to airblast, thermal pulse, or kinetic impact in the form of meteorites. At large sizes (greater than many tens of meters), the damage is amplified by the hypersonic impact of these large projectiles moving with cosmic velocity, leaving explosively produced craters. However, much more common is simple "kinetic" damage caused by the impact of smaller meteorites moving at terminal speeds. As of this date a handful of instances are definitively known of people or structures being directly hit and/or damaged by the kinetic impact of meteorites. Meteorites known to have struck humans include the Sylacauga, Alabama fall (1954) and the Mbale meteorite fall (1992). Much more common is kinetic meteorite damage to cars, buildings, and even a post box (Claxton, Georgia - 1984). Historical accounts indicate that direct kinetic damage by meteorites may be more common than recent accounts suggest (Yau et al., 1994). In this talk we will examine the contemporary meteorite flux and estimate the frequency of kinetic damage to various structures, as well as how the meteorite flux might affect the rate of human casualties. This will update an earlier study by Halliday et al (1985), adding variations expected in meteorite flux with latitude (Le Feuvre and Wieczorek, 2008) and validating these model predictions of speed and entry angle with observations from the NASA and SOMN fireball networks. In particular, we explore the physical characteristics of bright meteors which may be used as a diagnostic for estimating which fireballs produce meteorites and hence how early warning of such kinetic damage may be estimated in advance through observations and modeling.

  4. Kinetic Damage from Meteorites

    NASA Technical Reports Server (NTRS)

    Cooke, William; Brown, Peter; Matney, Mark

    2017-01-01

    A Near Earth object impacting into Earth's atmosphere may produce damaging effects at the surface due to airblast, thermal pulse, or kinetic impact in the form of meteorites. At large sizes (>many tens of meters), the damage is amplified by the hypersonic impact of these large projectiles moving with cosmic velocity, leaving explosively produced craters. However, much more common is simple "kinetic" damage caused by the impact of smaller meteorites moving at terminal speeds. As of this date a handful of instances are definitively known of people or structures being directly hit and/or damaged by the kinetic impact of meteorites. Meteorites known to have struck humans include the Sylacauga, Alabama fall (1954) and the Mbale meteorite fall (1992). Much more common is kinetic meteorite damage to cars, buildings, and even a post box (Claxton, Georgia - 1984). Historical accounts indicate that direct kinetic damage by meteorites may be more common than recent accounts suggest (Yau et al., 1994). In this talk we will examine the contemporary meteorite flux and estimate the frequency of kinetic damage to various structures, as well as how the meteorite flux might affect the rate of human casualties. This will update an earlier study by Halliday et al (1985), adding variations expected in meteorite flux with latitude (Le Feuvre and Wieczorek, 2008) and validating these model predictions of speed and entry angle with observations from the NASA and SOMN fireball networks. In particular, we explore the physical characteristics of bright meteors which may be used as a diagnostic for estimating which fireballs produce meteorites and hence how early warning of such kinetic damage may be estimated in advance through observations and modelling.

  5. Meteorites

    NASA Astrophysics Data System (ADS)

    Zanda, Brigitte; Rotaru, Monica; Hewins, Translated by Roger

    2001-07-01

    1. The harder they fall C. Perron; 2. Stones fallen from the sky U. Marvin; 3. Impact craters P. Thomas; 4. Cretaceous Park R. Rocchia, E. Robin and H. Leroux; 5. Like no rock on Earth B. Zanda, M. Christophe Michel Lévy, M. Bourot Denise and C. Caillet Komorowski; 6. Little planets D. Benest; 7. The Sound and the Fury J.-P. Bibring; 8. Signed carbon F. Robert, M. Festou and F. Raulin; 9. A stormy nebula R. Hewins; 10. The age of the solar system G. Manhès; 11. Galactic fossils E. Zinner; 12. Leafing through the past two centuries... P. Pellas; Glossary; Acknowledgements; Illustration credits.

  6. The Effect of Meteorite Impacts on the Elements Essential for Life

    NASA Astrophysics Data System (ADS)

    Osinski, G. R.; Cockell, C. S.; Lindgren, P.; Parnell, J.

    2010-04-01

    We explore the question: what is the effect of meteorite impact events on the concentration and distribution of elements essential for life? The results for carbonates suggest that there may not be a major loss of these elements during meteorite impact events.

  7. Nd-isotopic evidence for the origin of the Sudbury complex by meteoritic impact

    NASA Technical Reports Server (NTRS)

    Faggart, B. E.; Basu, A. R.; Tatsumoto, M.

    1985-01-01

    A Neodymium isotopic investigation was undertaken in order to determine the possibility that the Sudbury geological structure in Ontario, Canada was formed by meteoritic impact. Conclusive evidence points to the melting of crustal rocks by way of meteoritic impact in the forming of the Sudbury structure.

  8. Cometary and meteorite swarm impact on planetary surfaces

    SciTech Connect

    O'Keefe, J.D.; Ahrens, T.J.

    1982-08-10

    The velocity flow fields, energy partitioning, and ejecta distributions resulting from impact of porous (fragmented) icy cometary nuclei with silicate planetary surfaces at speeds from 5 to 45 km/s are different than those resulting from the impact of solid ice or silicate meteorites. The impact of 1 g/cm/sup 3/ ice spheres onto an atmosphereless anorthosite planetary surface cratering flows that appear similar to those induced by normal density anorthosite meteorite impact. Both of these impactors lead to deep transient crater cavities for final crater diameters less than approx.1 to approx.10 km and for escape velocities < or approx. =10/sup 5/ cm/s. Moreover the fraction of internal energy partitioned into the planetary surface at the cratering site is 0.6 for both ice and anorthosite impactors at 15 km/s. As the assumed density of the hypothetical cometary nucleus or fragment cloud from a nucleus decreases to 0.01 g/cm/sup 3/, the fraction of the impact energy partitioned into planetary surface energy decreases to less than 0.01, and the flow field displays a toroidal behavior in which the apparent source of the flow appears to emanate from a disc or ringlike region rather than from a single point, as in the explosive cratering case. The edges of the crater region are in several cases depressed and flow downward, whereas the center of the crater region is uplifted. Moreover, the resultant postimpact particle velotity flow in some cases indicates the formation of concentric ridges, a central peak, and a distinct absence of a deep transient cavity. In contrast, transient cavities are a ubiquitous feature of nearly all previous hypervelocity impact calculations.

  9. Earth's Largest Meteorite Impact Craters discovered in South America?

    NASA Astrophysics Data System (ADS)

    Kellndorfer, J. M.; Schmidt-Falkenberg, H.

    2014-12-01

    Novel analysis of high resolution InSAR-based digital elevation data from the year 2001 Shuttle Radar Topography Mission combined with a recently produced dataset of pan-tropical vegetation height from ALOS-1 SAR and IceSAT/GLAS Lidar estimates led to the quasi-bald-Earth discovery of four sizable near-perfect circle arcs in South America under dense tropical forests ranging in length from 216 km to 441 km. Terrain elevation profiles of cross-sections across the arcs show a distinct vertical rising and falling in elevations of hundreds of meters over a horizontal distance of tens of kilometers. It is hypothesized that these sizable arcs and associated rim-like topographic terrain features are remnants of huge meteorite impact craters with diameters ranging from 770 km to 1,310 km, thus forming potentially the largest known impact carter structures discovered on Earth today. The potential impact crater rim structures are located north of the eastern Amazon River, in the coastal region of Recife and Natal, and in the Brazilian, Bolivian and Paraguayan border region encompassing the Pantanal. Elevation profiles, hillshades and gray-shaded elevation maps were produced to support the geomorphologic analysis. It is also speculated whether in three of the four potential impact craters, central uplift domes or peaks, which are typical for complex impact crater structures can be identified. The worlds largest iron ore mining area of Carajás in Para, Brazil, falls exactly in the center of the largest hypothesized circular impact crater showing topographic elevations similar to the rim structure discovered 655 km to the north-north-west. Based on the topographic/geomorphologic driven hypothesis, geologic exploration of these topographic features is needed to test whether indeed meteorite impact craters could be verified, what the more exact ellipsoidal shapes of the potential impact craters might be, and to determine when during geologic times the impacts would have taken

  10. Early Impact History and Dynamical Origin of Differentiated Meteorites and Asteroids

    NASA Astrophysics Data System (ADS)

    Scott, E. R. D.; Keil, K.; Goldstein, J. I.; Asphaug, E.; Bottke, W. F.; Moskovitz, N. A.

    Differentiated asteroids and igneous meteorites present numerous challenges to our understanding of the impact and dynamical evolution of asteroids and meteorite parent bodies. Igneous meteorites, including irons, achondrites, and stony-iron meteorites, testify to the prior existence of ~100 differentiated bodies. Destruction of these bodies by hypervelocity impact over 4 G.y. would have required numerous giant impacts, although this is inconsistent with the preservation of Vesta's basaltic crust and the lack of differentiated asteroid families. We review recent advances in elucidating the early chronology of meteorites, spectroscopic observations of likely differentiated asteroids, petrological studies of differentiated meteorites, impact disruption of differentiated planetesimals during accretion, and dynamical scenarios for capturing material into the asteroid belt. Together, these advances suggest a new paradigm in which planetesimals accreted rapidly in the inner solar system and were melted by 26Al less than 2 m.y. after the formation of calcium-aluminum-rich inclusions (CAIs). While molten they were disrupted by grazing hit-and-run impacts during the accretion of planetesimals. Later, when still hot, the survivors were disrupted by hypervelocity impacts. Impact debris from the differentiated bodies was transferred from the newly formed terrestrial planet region to stable orbits in the asteroid belt. This evolutionary history leaves many questions unanswered but suggests new paths for future exploration of the asteroid belt and petrological and isotopic studies of meteorites.

  11. Laboratory experiments on the impact disruption of iron meteorites at temperature of near-Earth space

    NASA Astrophysics Data System (ADS)

    Katsura, Takekuni; Nakamura, Akiko M.; Takabe, Ayana; Okamoto, Takaya; Sangen, Kazuyoshi; Hasegawa, Sunao; Liu, Xun; Mashimo, Tsutomu

    2014-10-01

    Iron meteorites and some M-class asteroids are generally understood to be fragments that were originally part of cores of differentiated planetesimals or part of local melt pools on primitive bodies. The parent bodies of iron meteorites may have formed in the terrestrial planet region, from which they were then scattered into the main belt (Bottke, W.F., Nesvorný, D., Grimm, R.E., Morbidelli, A., O'Brien, D.P. [2006]. Nature 439, 821-824). Therefore, a wide range of collisional events at different mass scales, temperatures, and impact velocities would have occurred between the time when the iron was segregated and the impact that eventually exposed the iron meteorites to interplanetary space. In this study, we performed impact disruption experiments of iron meteorite specimens as projectiles or targets at room temperature to increase understanding of the disruption process of iron bodies in near-Earth space. Our iron specimens (as projectiles or targets) were almost all smaller in size than their counterparts (as targets or projectiles, respectively). Experiments of impacts of steel specimens were also conducted for comparison. The fragment mass distribution of the iron material was different from that of rocks. In the iron fragmentation, a higher percentage of the mass was concentrated in larger fragments, probably due to the ductile nature of the material at room temperature. The largest fragment mass fraction f was dependent not only on the energy density but also on the size d of the specimen. We assumed a power-law dependence of the largest fragment mass fraction to initial peak pressure P0 normalized by a dynamic strength, Y, which was defined to be dependent on the size of the iron material. A least squares fit to the data of iron meteorite specimens resulted in the following relationship: f∝∝d, indicating a large size dependence of f. Additionally, the deformation of the iron materials in high-velocity shots was found to be most significant when the

  12. The preservation of the Agoudal impact crater, Morocco, under a landslide: Indication of a genetic link between shatter cones and meteorite fragments

    NASA Astrophysics Data System (ADS)

    Nachit, Hassane; Abia, El Hassan; Bonadiman, Costanza; Di Martino, Mario; Vaccaro, Carmela

    2017-10-01

    Geological studies and tomographic profiles of a locality nearby the Agoudal village (Morocco) showed the presence of a single impact crater, 500-600 m diameter, largely hidden by a limestone block, 220 m long and 40 m deep. The site was interpreted as a landslide that followed the fall of a cosmic body. The Agoudal impact crater was not affected by intense erosion. The lack of an evident impact structure, as well as the sporadic distribution of impactites and their limited occurrence, can be explained by a complex geological framework and by recent tectonics. The latter is the result of the sliding of limestone block, which hides almost two-thirds of the crater's depression, and the oblique fall of the meteoroid on sloping ground. In addition, some impact breccia dikes sharply cut the host rock in the Agoudal impact structure. They do not show any genetic relationship with tectonics or hydrothermal activity, nor are they related to any karst or calcrete formations. Altogether, the overlapping of the meteorite strewn field (11 km long and 3 km wide) with the area of occurrence of shatter cones and impact breccias, together with the presence of meteorite fragments (shrapnel) ejected from the crater, the presence of shatter cones contaminated by products of iron meteorites and the presence of impact breccias that contain meteorite fragments of the same chemical composition of the Agoudal meteorite indicate that the fall of this meteorite can be responsible for the formation of the impact structure.

  13. Meteorite impacts on ancient oceans opened up multiple NH3 production pathways.

    PubMed

    Shimamura, Kohei; Shimojo, Fuyuki; Nakano, Aiichiro; Tanaka, Shigenori

    2017-05-10

    A recent series of shock experiments by Nakazawa et al. starting in 2005 (e.g. [Nakazawa et al., Earth Planet. Sci. Lett., 2005, 235, 356]) suggested that meteorite impacts on ancient oceans would have yielded a considerable amount of NH3 to the early Earth from atmospheric N2 and oceanic H2O through reduction by meteoritic iron. To clarify the mechanisms, we imitated the impact events by performing multi-scale shock technique-based ab initio molecular dynamics in the framework of density functional theory in combination with multi-scale shock technique (MSST) simulations. Our previous simulations with impact energies close to that of the experiments revealed picosecond-order rapid NH3 production during shock compression [Shimamura et al., Sci. Rep., 2016, 6, 38952]. It was also shown that the reduction of N2 took place with an associative mechanism as seen in the catalysis of nitrogenase enzymes. In this study, we performed an MSST-AIMD simulation to investigate the production by meteorite impacts with higher energies, which are closer to the expected values on the early Earth. It was found that the amount of NH3 produced further increased. We also found that the increased NH3 production is due to the emergence of multiple reaction mechanisms at increased impact energies. We elucidated that the reduction of N2 was not only attributed to the associative mechanism but also to a dissociative mechanism as seen in the Haber-Bosch process and to a mechanism through a hydrazinium ion. The emergence of these multiple production mechanisms capable of providing a large amount of NH3 would support the suggestions from recent experiments much more strongly than was previously believed, i.e., shock-induced NH3 production played a key role in the origin of life on Earth.

  14. Raman spectroscopy of shocked gypsum from a meteorite impact crater

    NASA Astrophysics Data System (ADS)

    Brolly, Connor; Parnell, John; Bowden, Stephen

    2017-07-01

    Impact craters and associated hydrothermal systems are regarded as sites within which life could originate on Earth, and on Mars. The Haughton impact crater, one of the most well preserved craters on Earth, is abundant in Ca-sulphates. Selenite, a transparent form of gypsum, has been colonized by viable cyanobacteria. Basement rocks, which have been shocked, are more abundant in endolithic organisms, when compared with un-shocked basement. We infer that selenitic and shocked gypsum are more suitable for microbial colonization and have enhanced habitability. This is analogous to many Martian craters, such as Gale Crater, which has sulphate deposits in a central layered mound, thought to be formed by post-impact hydrothermal springs. In preparation for the 2020 ExoMars mission, experiments were conducted to determine whether Raman spectroscopy can distinguish between gypsum with different degrees of habitability. Ca-sulphates were analysed using Raman spectroscopy and results show no significant statistical difference between gypsum that has experienced shock by meteorite impact and gypsum, which has been dissolved and re-precipitated as an evaporitic crust. Raman spectroscopy is able to distinguish between selenite and unaltered gypsum. This shows that Raman spectroscopy can identify more habitable forms of gypsum, and demonstrates the current capabilities of Raman spectroscopy for the interpretation of gypsum habitability.

  15. Coesite and stishovite in a shocked lunar meteorite, Asuka-881757, and impact events in lunar surface.

    PubMed

    Ohtani, E; Ozawa, S; Miyahara, M; Ito, Y; Mikouchi, T; Kimura, M; Arai, T; Sato, K; Hiraga, K

    2011-01-11

    Microcrystals of coesite and stishovite were discovered as inclusions in amorphous silica grains in shocked melt pockets of a lunar meteorite Asuka-881757 by micro-Raman spectrometry, scanning electron microscopy, electron back-scatter diffraction, and transmission electron microscopy. These high-pressure polymorphs of SiO(2) in amorphous silica indicate that the meteorite experienced an equilibrium shock-pressure of at least 8-30 GPa. Secondary quartz grains are also observed in separate amorphous silica grains in the meteorite. The estimated age reported by the (39)Ar/(40)Ar chronology indicates that the source basalt of this meteorite was impacted at 3,800 Ma ago, time of lunar cataclysm; i.e., the heavy bombardment in the lunar surface. Observation of coesite and stishovite formed in the lunar breccias suggests that high-pressure impact metamorphism and formation of high-pressure minerals are common phenomena in brecciated lunar surface altered by the heavy meteoritic bombardment.

  16. Formation of a small impact structure discovered within the Agoudal meteorite strewn field, Morocco

    NASA Astrophysics Data System (ADS)

    Lorenz, C. A.; Ivanova, M. A.; Artemieva, N. A.; Sadilenko, D. A.; Chennaoui Aoudjehane, H.; Roschina, I. A.; Korochantsev, A. V.; Humayun, M.

    2015-01-01

    A relic impact structure was recognized within the strewn field of the Agoudal iron meteorite. The heavily eroded structure has preserved shatter cones in a limestone basement, and remnants of autochthonous and allochthonous breccias. Fragments of iron incorporated into the allochthonous breccia have a chemical composition (Ni = 5.16 wt%, Ir = 0.019 ppm) similar to that of the Agoudal meteorite, supporting a syngenetic origin of the strewn field and the impact structure. The total recovered mass of Agoudal meteorite fragments is estimated at approximately 500 kg. The estimated size of the SE-NW-oriented strewn field is 6 × 2 km. Model calculations with minimal preatmospheric size show that a similar meteorite strewn field plus one small crater with observed shock effects could be formed by fragmentation of a meteoroid approximately 1.4 m in diameter with an impact angle of approximately 60° from the horizontal. However, the most probable is an impact of a larger, 3-4 m diameter meteoroid, resulting a strewn field with approximately 10 craters, 10-30 m in diameter each, plus numerous meteorite fragments. The calculated scattering area of meteorite shrapnel ejected from these impact craters could completely cover the observed strewn field of the Agoudal meteorite.

  17. Microdeformations at the Contact Zones of the Morasko Iron Meteorite with Surrounding Sediments — Likely Evidence of Meteorite Impact

    NASA Astrophysics Data System (ADS)

    Duczmal-Czernikiewicz, A.; Muszyński, A.

    2016-08-01

    Deformed or crushed grain clasts in the sediments around the meteorite fragments clearly indicate the meteorite fall. A small range of the observed microstructures in the deformation zones can only be the result of a small meteorite fall.

  18. Martian Meteorite Chronology and Effects of Impact Metamorphism (Invited)

    NASA Astrophysics Data System (ADS)

    Bouvier, A.; Blichert-Toft, J.; Albarede, F.

    2009-12-01

    Martian (SNC) meteorites provide important clues to processes of alteration or shock at the surface of the planet as many of them contain secondary phases and/or high-pressure assemblages, which are the products of aqueous alteration and impact events, respectively. They include gabbros (shergottites), pyroxenites (nakhlites), and dunites (chassignites), and a single orthopyroxenite, ALH 84001. Pb-Pb isotope systematics of Martian meteorites favor three groups of formation ages: 4.3 Ga for depleted shergottites, 4.1 Ga for ALH 84001 and intermediate and enriched shergottites, and 1.3 Ga for nakhlites and Chassigny [1]. This contrasts with the young mineral isochron ages obtained by Ar-Ar dating or phosphate-based chronometers (e.g., U-Pb, Sm-Nd). In addition to Pb-Pb isotope systematics [1], we have obtained preliminary Sm-Nd and Lu-Hf mineral isochron data for the shergottite NWA 480 and find an age of ~345 Ma in contrast to its ~4.1 Ga Pb-Pb age. For the nakhlites MIL 03346 and Yamato-000593, we find Sm-Nd and Lu-Hf ages at ~1335 Ma, consistent with their ~1.3 Ga Pb-Pb age. Hence, all shergottites unambiguously show evidence of resetting events, which is not the case for nakhlites. We interpret the young ages indicated by shergottite Rb-Sr, Sm-Nd, Lu-Hf, and U-Pb internal isochrons as recent resetting by fluids, impacts, or both. Internal isochrons date the last closure, whether initial cooling or late resetting, of the chronometric system in coexisting minerals. Problems arise in part because the carriers of the parent and daughter nuclides have been wrongly assigned to major rather than accessory minerals, and in part because, with the exception of the Pb-Pb chronometer, the rock samples have been strongly leached and, hence, the parent and daughter nuclides became fractionated in the process. The Rb-Sr, U-Pb, Sm-Nd, and Lu-Hf mineral isochrons of shergottites show young age clusters around 180, 350, 475, and 575 Ma. Each cluster of young mineral isochron ages

  19. Variations in impact effects among IIIE iron meteorites

    NASA Astrophysics Data System (ADS)

    Breen, John P.; Rubin, Alan E.; Wasson, John T.

    2016-09-01

    Group-IIIE iron meteorites can be ordered into four categories reflecting increasing degrees of shock alteration. Weakly shocked samples (Armanty, Colonia Obrera, Coopertown, Porto Alegre, Rhine Villa, Staunton, and Tanokami Mountain) have haxonite within plessite, unrecrystallized kamacite grains containing Neumann lines or possessing the ɛ structure, and sulfide inclusions typically consisting of polycrystalline troilite with daubréelite exsolution lamellae. The only moderately shocked sample is NWA 4704, in which haxonite has been partially decomposed to graphite; the majority of the kamacite in NWA 4704 is recrystallized, and its sulfide inclusions were partly melted. Strongly shocked samples (Cachiyuyal, Kokstad, and Paloduro) contain graphite and no haxonite, suggesting that pre-existing haxonite fully decomposed. Also present in these rocks are recrystallized kamacite and melted troilite. Residual heat from the impact caused annealing and recrystallization of kamacite as well as the decomposition of haxonite into graphite. Severely shocked samples (Aliskerovo and Willow Creek) have sulfide-rich assemblages consisting of fragmental and subhedral daubréelite crystals, 1-4 vol% spidery troilite filaments, and 30-50 vol% low-Ni kamacite grains, some of which contain up to 6.0 wt% Co; haxonite in these inclusions has fully decomposed to graphite. The wide range of impact effects in IIIE irons is attributed to one or more major collision(s) on the parent asteroid that affected different group members to different extents depending on their proximity to the impact point.

  20. Effects of meteorite impacts on the atmospheric evolution of Mars.

    PubMed

    Pham, Lê Binh San; Karatekin, Ozgür; Dehant, Véronique

    2009-01-01

    Early in its history, Mars probably had a denser atmosphere with sufficient greenhouse gases to sustain the presence of stable liquid water at the surface. Impacts by asteroids and comets would have played a significant role in the evolution of the martian atmosphere, not only by causing atmospheric erosion but also by delivering material and volatiles to the planet. We investigate the atmospheric loss and the delivery of volatiles with an analytical model that takes into account the impact simulation results and the flux of impactors given in the literature. The atmospheric loss and the delivery of volatiles are calculated to obtain the atmospheric pressure evolution. Our results suggest that the impacts alone cannot satisfactorily explain the loss of significant atmospheric mass since the Late Noachian (approximately 3.7-4 Ga). A period with intense bombardment of meteorites could have increased the atmospheric loss; but to explain the loss of a speculative massive atmosphere in the Late Noachian, other factors of atmospheric erosion and replenishment also need to be taken into account.

  1. Traces of Catastrophe: A Handbook of Shock-Metamorphic Effects in Terrestrial Meteorite Impact Structures

    NASA Technical Reports Server (NTRS)

    French, Bevan M.

    1998-01-01

    This handbook of Shock-Metamorphic Effects in Terrestrial Meteorite Impact Structures emphasizes terrestrial impact structures, field geology, and particularly the recognition and petrographic study of shock-metamorphic effects in terrestrial rocks. Individual chapters include: 1) Landscapes with Craters: Meteorite Impacts, Earth, and the Solar System; 2) Target Earth: Present, Past and Future; 3) Formation of Impact Craters; 4) Shock-Metamorphic Effects in Rocks and Minerals; 5) Shock-Metamorphosed Rocks (Impactities) in Impact Structures; 6) Impact Melts; 7) How to Find Impact Structures; and 8) What Next? Current Problems and Future Investigations.

  2. Nucleobase and amino acid formation through impacts of meteorites on the early ocean

    NASA Astrophysics Data System (ADS)

    Furukawa, Yoshihiro; Nakazawa, Hiromoto; Sekine, Toshimori; Kobayashi, Takamichi; Kakegawa, Takeshi

    2015-11-01

    The emergence of life's building blocks on the prebiotic Earth was the first crucial step for the origins of life. Extraterrestrial delivery of intact amino acids and nucleobases is the prevailing hypothesis for their availability on prebiotic Earth because of the difficulties associated with the production of these organics from terrestrial carbon and nitrogen sources under plausible prebiotic conditions. However, the variety and amounts of these intact organics delivered by meteorites would have been limited. Previous shock-recovery experiments have demonstrated that meteorite impact reactions could have generated organics on the prebiotic Earth. Here, we report on the simultaneous formation of nucleobases (cytosine and uracil) found in DNA and/or RNA, various proteinogenic amino acids (glycine, alanine, serine, aspartic acid, glutamic acid, valine, leucine, isoleucine, and proline), non-proteinogenic amino acids, and aliphatic amines in experiments simulating reactions induced by extraterrestrial objects impacting on the early oceans. To the best of our knowledge, this is the first report of the formation of nucleobases from inorganic materials by shock conditions. In these experiments, bicarbonate was used as the carbon source. Bicarbonate, which is a common dissolved carbon species in CO2-rich atmospheric conditions, was presumably the most abundant carbon species in the early oceans and in post-impact plumes. Thus, the present results expand the possibility that impact-induced reactions generated various building blocks for life on prebiotic Earth in large quantities through the use of terrestrial carbon reservoirs.

  3. Reconciling Impact Evidence and Meteorite Strewnfield in Agoudal (Morocco): Field, Geomorphology and Geophysical Evidences

    NASA Astrophysics Data System (ADS)

    Rochette, P.; Chennaoui Aoudjehane, H.; El Kerni, H.; Quesnel, Y.; Uehara, M.; Aboulharis, M.; Hutzler, A.; Bourles, D.

    2014-09-01

    We present a synthesis of the field observations, magnetic and electromagnetic geophysical prospection, and ongoing measurements to discuss the likelyhood that the Agoudal impact and meteorite strewnfield are the same event, dated within Pleistocene.

  4. Transient High-Temperature Processing of Silicates in Fulgurites as Analogues for Meteorite and Impact Melts

    NASA Astrophysics Data System (ADS)

    Parnell, J.; Thackrey, S.; Muirhead, D. K.; Wright, A. J.

    2008-03-01

    A fulgurite from the Sahara yielded petrographic data valuable as an analogue for highly reduced meteorite and impact melts, including iron silicide formation, devolatilization features, zircon melting and extreme melt heterogeneity.

  5. Properties of Ejecta Blanket Deposits Surrounding Morasko Meteorite Impact Craters (Poland)

    NASA Astrophysics Data System (ADS)

    Szokaluk, M.; Muszyński, A.; Jagodziński, R.; Szczuciński, W.

    2016-08-01

    Morasko impact craters are a record of the fall of a meteorite into the soft sediments. The presented results illustrate the geological structure of the area around the crater as well as providing evidence of the occurrence of ejecta blanket.

  6. The Impact of International Scientific Teams on Investigations of Yugoslavian Meteorites

    NASA Astrophysics Data System (ADS)

    Kolomejceva-Jovanovic, L.

    2008-10-01

    Investigations of scientific heritage is very important for every country. The evidence concerning the meteorites which have fallen upon the territory of former Yugoslavia can be a nice example. The samples of Yugoslav meteorites can be found in the biggest world museums of natural history (in Washington, Moscow, Vienna, Paris, Budapest, Berlin, Prague and London). In such a way scientists engaged in the area of meteorites, cosmochemistry, cosmic mineralogy, astrochemistry, astrophysics and other multidisciplinary scientific branches have the possibility to study these meteorites. The huge impact on the study of Yugoslav meteorites is given by international teams from Institute of Physics (Belgrade), Joint Institute for Nuclear Investigations (Dubna, Russia), Naturhistorisches Museum (Vienna, Austria), Institute of Geochemistry and Analytical Chemistry (Moscow, Russia) and Museum of Natural History (Belgrade).

  7. Lunar formation. Dating the Moon-forming impact event with asteroidal meteorites.

    PubMed

    Bottke, W F; Vokrouhlický, D; Marchi, S; Swindle, T; Scott, E R D; Weirich, J R; Levison, H

    2015-04-17

    The inner solar system's biggest and most recent known collision was the Moon-forming giant impact between a large protoplanet and proto-Earth. Not only did it create a disk near Earth that formed the Moon, it also ejected several percent of an Earth mass out of the Earth-Moon system. Here, we argue that numerous kilometer-sized ejecta fragments from that event struck main-belt asteroids at velocities exceeding 10 kilometers per second, enough to heat and degas target rock. Such impacts produce ~1000 times more highly heated material by volume than do typical main belt collisions at ~5 kilometers per second. By modeling their temporal evolution, and fitting the results to ancient impact heating signatures in stony meteorites, we infer that the Moon formed ~4.47 billion years ago, which is in agreement with previous estimates. Copyright © 2015, American Association for the Advancement of Science.

  8. The Wells Creek Meteorite Impact Site and Changing Views on Impact Cratering

    NASA Astrophysics Data System (ADS)

    Ford, J. R. H.; Orchiston, Wayne; Clendening, Ron

    2012-11-01

    Wells Creek is a confirmed meteorite impact site in Tennessee, USA. The Wells Creek structure was first noticed by railroad surveyors around 1855 and brought to the attention of J.M. Safford, Tennessee's State Geologist. He included an insert in the 1869 Geologic Map of Tennessee, which is the first known map to include the structure. The origin of the Wells Creek structure was controversial, and was interpreted as being either the result of volcanic steam explosion or meteorite impact. It was only in the 1960s that Wilson and Stearns were able to state that the impact hypothesis was preferred. Evidence for a Wells Creek meteorite impact includes drill core results, extreme brecciation and shatter cones, while a local lack of volcanic material is telling. Just to the north of the Wells Creek Basin are three small basins that Wilson concluded were associated with the Wells Creek impact event, but evidence regarding the origin of the Austin, Indian Mound and Cave Spring Hollow sites is not conclusive.

  9. Identification of Meteoritic Components in Terrestrial Impact Craters and Their Ejecta

    NASA Astrophysics Data System (ADS)

    Koeberl, C.

    2007-12-01

    The geochemistry and cosmochemistry of impacts (i.e., of impact craters and impact processes) is a rapidly developing research area that encompasses such wide-ranging topics as the simple chemical characterization of the various rock types involved (target rocks, impact breccias, melt rocks, etc.), the identification of extraterrestrial components in impact ejecta, the determination of the impactor (projectile) composition, and the determination of the causes of environmental changes from chemolithostratigraphic analyses. The recognition of geological structures and ejecta layers on Earth as being of impact origin requires the detection of either shock metamorphic effects in minerals and rocks, and/or the presence of a meteoritic component in these rocks. In addition, ejecta layers that formed from meteorite impacts can be found and confirmed by geochemical studies aimed at confirming the presence of an extraterrestrial component. In the absence of actual meteorite fragments, it is necessary to chemically search for traces of meteoritic material that is mixed in with the target rocks in breccias and melt rocks. Meteoritic components have been identified for just about 45 impact structures, out of the more than 170 impact structures that have so far been identified on Earth. The presence of a meteoritic component can be verified by measuring abundances and interelement ratios of siderophile elements, especially the platinum group elements (PGE), which are much more abundant in meteorites than in terrestrial upper crustal rocks. Often the content of the element iridium is measured as a proxy for all PGEs, because it can be measured with the best detection limit of all PGEs by neutron activation analysis, but taken out of context, small Ir anomalies alone have little diagnostic power. More reliable results can be achieved by measuring whole suites of elements, for example, the PGEs, which also avoids some of the ambiguities that result if only moderately siderophile

  10. An Antarctic iron meteorite contains preterrestrial impact-produced diamond and lonsdaleite

    NASA Astrophysics Data System (ADS)

    Clarke, R. S.; Appleman, D. E.; Ross, D. R.

    1981-06-01

    The discovery of diamond and lonsdaleite inclusions in an iron meteorite recovered from Allan Hills, Antarctica, which are attributed to preterrestrial impact is reported. ALHA 77283, a 10.5-kg carbon-rich octahedrite of chemical group IA similar in composition and structure to the Canyon Diablo meteorite, was found to contain troilite-graphite-schreibersite-cohenite inclusions containing unusually hard protrusions identified as carbonado-type diamond-lonsdaleite nodules. Metallographic examination of polished sections of the meteorite revealed a well developed heat-altered zone over most of the sample edge, which indicates that the meteorite was ablatively decelerated upon atmospheric entry and landed softly. Metallographic changes indicative of shock loading as well as the presence of the diamond and lonsdaleite were thus concluded to have been produced before atmospheric entry, but after Widmanstaetten pattern formation, most likely at the time of parent body break-up or subsequent collisions in space.

  11. A tungsten isotope approach to search for meteoritic components in terrestrial impact rocks

    NASA Astrophysics Data System (ADS)

    Moynier, Frederic; Koeberl, Christian; Quitté, Ghylaine; Telouk, Philippe

    2009-08-01

    The identification of meteorite impact structures on Earth is based on two main criteria: the presence of shock-metamorphic effects in the crater rock ejecta and/or the confirmation of an extraterrestrial (meteoritic) component in breccias or melt rocks. For the latter, both high elemental abundances of siderophile elements (especially the platinum group elements) with corresponding meteoritic inter-element ratios and the osmium (Os) and chromium (Cr) isotopic signatures characteristic of meteorites have been used successfully. Inspired by earlier suggestions of a meteoritic component in Archean rocks based on tungsten (W) isotope anomalies, here we explore the possible use of 182W, which has been produced by the decay of now extinct 182Hf ( T1/2 = 8.9 Ma), as a tracer of meteoritic component in terrestrial material. Each group of meteorites has W isotopic compositions that are distinct from each other and from the terrestrial crust. 182W has already been used to try to identify the impactor at the K/T boundary by analyzing the sediments and Ni-rich spinel. In the present study, we broaden the field of investigation by choosing a different approach, namely analyzing a variety of known impact rocks. We measured the W isotope composition in four samples from different impact structures (Gardnos, Norway; Morokweng, South Africa; Vredefort, South Africa; Ries, Germany) as well as in two samples from a distal ejecta layer (K-T boundary samples from Gams, Austria, and Berwind Canyon, USA). All these samples are unambiguously impact-produced and in several of those materials a meteoritic component has unequivocally been identified by other geochemical proxies. In all these samples, the isotopic composition of W is identical with analytical error to that of the Earth's continental crust, and no 182W anomalies are present, even in the samples containing a significant (percent level) meteoritic component. Therefore, we conclude that, in contrast to the Cr or Os isotopes, W

  12. Geological and geochemical record of 3400-million-year-old terrestrial meteorite impacts

    NASA Technical Reports Server (NTRS)

    Lowe, Donald R.; Byerly, Gary R.; Asaro, Frank; Kyte, Frank T.

    1989-01-01

    Beds of sand-sized spherules in the 3400-million-year-old Fig Tree Group, Barberton Greenstone belt, South Africa, formed by the fall of quenched liquid silicate droplets into a range of shallow- to deep-water depositional environments. The regional extent of the layers, their compositional complexity, and lack of included volcanic debris suggest that they are not products of volcanic activity. The layers are greatly enriched in iridium and other platinum group elements in roughly chondritic proportions. Geochemical modeling based on immobile element abundances suggests that the original average spherule composition can be approximated by a mixture of fractionated tholeiitic basalt, komatiite, and CI carbonaceous chondrite. The spherules are thought to be the products of large meteorite impacts on the Archean earth.

  13. Tracing the effects of an enormous meteorite impact 3 billion years ago

    NASA Astrophysics Data System (ADS)

    Wendel, JoAnna

    2014-07-01

    The most well-known and popularized meteorite impact occurred 65 million years ago and left behind the Chicxulub crater, a feature more than 110 miles in diameter. Dust kicked up by the impact, which lingered in the atmosphere for years, may have helped kill all the nonavian dinosaurs along with three quarters of the world's plant and animal species.

  14. An historical perspective on the suspected meteorite impact sites of Tennessee. 2: The Howell Structure

    NASA Astrophysics Data System (ADS)

    Ford, J. R. H.; Orchiston, Wayne; Clendening, Ron

    2015-03-01

    The Howell Structure is a suspected meteorite impact site in Tennessee, USA, and came to the attention of geologists during the 1930s. It was first investigated by Born and Wilson in 1937, and the few subsequent investigations that have occurred at this extensively eroded site have revealed the presence of breccias and the possible existence of shatter cones. However, cores drilled in the 1960s have recently been analyzed, and these provide evidence of shock metamorphism, suggesting that the Howell Structure is the eroded scar of a meteorite impact.

  15. Educating the Public about Meteorites and Impacts through Virtual Field Trips and Classroom Experience Boxes

    NASA Astrophysics Data System (ADS)

    Ashcraft, Teresa; Hines, R.; Minitti, M.; Taylor, W.; Morris, M. A.; Wadhwa, M.

    2014-01-01

    With specimens representing over 2,000 individual meteorites, the Center for Meteorite Studies (CMS) at Arizona State University (ASU) is home to the world's largest university-based meteorite collection. As part of our mission to provide educational opportunities that expand awareness and understanding of the science of meteoritics, CMS continues to develop new ways to engage the public in meteorite and space science, including the opening of a new Meteorite Gallery, and expansion of online resources through upgrades to the CMS website, meteorites.asu.edu. In 2008, CMS was the recipient of a philanthropic grant to improve online education tools and develop loanable modules for educators. These modules focus on the origin of meteorites, and contain actual meteorite specimens, media resources, a user guide, and lesson plans, as well as a series of engaging activities that utilize hands-on materials geared to help students develop logical thinking, analytical skills, and proficiency in STEM disciplines. In 2010, in partnership with the ASU NASA Astrobiology Institute team, CMS obtained a NASA EPOESS grant to develop Virtual Field Trips (VFTs) complemented by loanable “Experience Boxes” containing lesson plans, media, and hands-on objects related to the VFT sites. One VFT-Box pair focuses on the record of the oldest multicellular organisms on Earth. The second VFT-Box pair focuses on the Upheaval Dome (UD) structure, a meteorite impact crater in Utah’s Canyonlands National Park. UD is widely accepted as the deeply eroded remnant of a ~5 kilometer impact crater (e.g. Kriens et al., 1999). The alternate hypothesis that the Dome was formed by the upwelling of salt from a deposit underlying the region (e.g. Jackson et al., 1998) makes UD an ideal site to learn not only about specific scientific principles present in the Next Generation Science Standards, but also the process of scientific inquiry. The VFTs are located on an interactive website dedicated to VFTs, vft

  16. Nanoindenting the Chelyabinsk Meteorite to Learn about Impact Deflection Effects in Asteroids

    NASA Astrophysics Data System (ADS)

    Moyano-Cambero, Carles E.; Pellicer, Eva; Trigo-Rodríguez, Josep M.; Williams, Iwan P.; Blum, Jürgen; Michel, Patrick; Küppers, Michael; Martínez-Jiménez, Marina; Lloro, Ivan; Sort, Jordi

    2017-02-01

    The Chelyabinsk meteorite is a highly shocked, low porosity, ordinary chondrite, probably similar to S- or Q-type asteroids. Therefore, nanoindentation experiments on this meteorite allow us to obtain key data to understand the physical properties of near-Earth asteroids. Tests at different length scales provide information about the local mechanical properties of the minerals forming this meteorite: reduced Young’s modulus, hardness, elastic recovery, and fracture toughness. Those tests are also useful to understand the potential to deflect threatening asteroids using a kinetic projectile. We found that the differences in mechanical properties between regions of the meteorite, which increase or reduce the efficiency of impacts, are not a result of compositional differences. A low mean particle size, attributed to repetitive shock, can increase hardness, while low porosity promotes a higher momentum multiplication. Momentum multiplication is the ratio between the change in momentum of a target due to an impact, and the momentum of the projectile, and therefore, higher values imply more efficient impacts. In the Chelyabinsk meteorite, the properties of the light-colored lithology materials facilitate obtaining higher momentum multiplication values, compared to the other regions described for this meteorite. Also, we found a low value of fracture toughness in the shock-melt veins of Chelyabinsk, which would promote the ejection of material after an impact and therefore increase the momentum multiplication. These results are relevant to the growing interest in missions to test asteroid deflection, such as the recent collaboration between the European Space Agency and NASA, known as the Asteroid Impact and Deflection Assessment mission.

  17. Abstracts for the International Workshop on Meteorite Impact on the Early Earth

    NASA Technical Reports Server (NTRS)

    1990-01-01

    This volume contains abstracts that were accepted for presentation at the International Workshop on Meteorite Impact on the Early Earth, September 21-22, 1990, in Perth, Western Australia. The effects these impacts had on the young Earth are emphasized and a few of the topics covered are as follows: impact induced hot atmosphere, crater size and distribution, late heavy bombardment, terrestrial mantle and crust, impact damage, continental growth, volcanism, climate catastrophes, shocked quartz, and others.

  18. Abstracts for the International Workshop on Meteorite Impact on the Early Earth

    SciTech Connect

    Not Available

    1990-09-01

    This volume contains abstracts that were accepted for presentation at the International Workshop on Meteorite Impact on the Early Earth, September 21-22, 1990, in Perth, Western Australia. The effects these impacts had on the young Earth are emphasized and a few of the topics covered are as follows: impact induced hot atmosphere, crater size and distribution, late heavy bombardment, terrestrial mantle and crust, impact damage, continental growth, volcanism, climate catastrophes, shocked quartz, and others.

  19. Soil Components in Heterogeneous Impact Glass in Martian Meteorite EETA79001

    NASA Technical Reports Server (NTRS)

    Schrader, C. M.; Cohen, B. A.; Donovan, J. J.; Vicenzi, E. P.

    2010-01-01

    Martian soil composition can illuminate past and ongoing near-surface processes such as impact gardening [2] and hydrothermal and volcanic activity [3,4]. Though the Mars Exploration Rovers (MER) have analyzed the major-element composition of Martian soils, no soil samples have been returned to Earth for detailed chemical analysis. Rao et al. [1] suggested that Martian meteorite EETA79001 contains melted Martian soil in its impact glass (Lithology C) based on sulfur enrichment of Lithology C relative to the meteorite s basaltic lithologies (A and B) [1,2]. If true, it may be possible to extract detailed soil chemical analyses using this meteoritic sample. We conducted high-resolution (0.3 m/pixel) element mapping of Lithology C in thin section EETA79001,18 by energy dispersive spectrometry (EDS). We use these data for principal component analysis (PCA).

  20. Probing Mars' interior using seismic signals from small high-frequency meteorite impacts

    NASA Astrophysics Data System (ADS)

    Teanby, Nicholas A.; Wookey, James

    2014-11-01

    In 2016 NASA will launch the InSight Discovery-class mission to Mars. This is the first geophysics-led planetary mission and will provide a wealth of new information about Mars’ interior and sub-surface. Instruments include two seismometers, a heat probe, and environmental sensors. Science return from the seismometers will critically depend on the occurrence of natural seismic sources, of which meteorite impacts will play a key role. Seismic recording of impact events will also allow the current cratering rate to be estimated, providing important new constraints on crater-based chronologies.In a recent study it was found that large globally detectable events require impacts to produce craters of order 100m in diameter (Teanby and Wookey, 2011). Such events are rare and only a few such events are predicted during the InSight mission. Here we extend this study to consider the much more frequent smaller events. While not producing as much seismic energy, these small events are much more numerous, as evidenced by recent observations of over 200 new impact craters (Dauber et al, 2013). Therefore, the probability of a small impact happening close to the InSight landing site is much higher. Importantly, these local events will not suffer as much crustal attenuation as distant events so may in fact be more detectable. They will also have a much higher frequency content, providing important information on the Mars' crustal structure.We calculate the seismic amplitudes from small impacts using ray tracing calibrated by impacts recorded on the Earth and Moon, allowing us to determine the number of events that will be detectable with InSight's seismometers. In particular, we focus on the short period seismometer, which is ideally suited to studying their higher frequency content.Daubar, I. J.; McEwen, A. S.; Byrne, S.; Kennedy, M. R. & Ivanov, B. (2013), 'The current martian cratering rate', Icarus 225, 506-516.Teanby, N. A. & Wookey, J. (2011), 'Seismic detection of

  1. Coesite and stishovite in a shocked lunar meteorite, Asuka-881757, and impact events in lunar surface

    PubMed Central

    Ohtani, E.; Ozawa, S.; Miyahara, M.; Ito, Y.; Mikouchi, T.; Kimura, M.; Arai, T.; Sato, K.; Hiraga, K.

    2011-01-01

    Microcrystals of coesite and stishovite were discovered as inclusions in amorphous silica grains in shocked melt pockets of a lunar meteorite Asuka-881757 by micro-Raman spectrometry, scanning electron microscopy, electron back-scatter diffraction, and transmission electron microscopy. These high-pressure polymorphs of SiO2 in amorphous silica indicate that the meteorite experienced an equilibrium shock-pressure of at least 8–30 GPa. Secondary quartz grains are also observed in separate amorphous silica grains in the meteorite. The estimated age reported by the 39Ar/40Ar chronology indicates that the source basalt of this meteorite was impacted at 3,800 Ma ago, time of lunar cataclysm; i.e., the heavy bombardment in the lunar surface. Observation of coesite and stishovite formed in the lunar breccias suggests that high-pressure impact metamorphism and formation of high-pressure minerals are common phenomena in brecciated lunar surface altered by the heavy meteoritic bombardment. PMID:21187434

  2. Experimental Simulation of Shock Reequilibration of Fluid Inclusions During Meteorite Impact

    NASA Technical Reports Server (NTRS)

    Madden, M. E. Elwood; Hoerz, R. J.; Bodnar, R. J.

    2003-01-01

    Fluid inclusions are microscopic volumes of fluid trapped within minerals as they precipitate. Fluid inclusions are common in terrestrial minerals formed under a wide array of geological settings from surface evaporite deposits to kimberlite pipes. While fluid inclusions in terrestrial rocks are the rule rather than the exception, only few fluid inclusion-bearing meteorites have been documented. The rarity of fluid inclusions in meteoritic material may be explained in two ways. First, it may reflect the absence of fluids (water?) on meteorite parent bodies. Alternatively, fluids may have been present when the rock formed, but any fluid inclusions originally trapped on the parent body were destroyed by the extreme P-T conditions meteorites often experience during impact events. Distinguishing between these two possibilities can provide significant constraints on the likelihood of life on the parent body. Just as textures, structures, and compositions of mineral phases can be significantly altered by shock metamorphism upon hypervelocity impact, fluid inclusions contained within component minerals may be altered or destroyed due to the high pressures, temperatures, and strain rates associated with impact events. Reequilibration may occur when external pressure-temperature conditions differ significantly from internal fluid isochoric conditions, and result in changes in fluid inclusion properties and/or textures. Shock metamorphism and fluid inclusion reequilibration can affect both the impacted target material and the meteoritic projectile. By examining the effects of shock deformation on fluid inclusion properties and textures we may be able to better constrain the pressure-temperature path experienced by shocked materials and also gain a clearer understanding of why fluid inclusions are rarely found in meteoritic samples.

  3. Mass Estinctions Caused by Large Bolide Impacts

    SciTech Connect

    Lavarez, Luis W.

    1987-01-01

    In this talk, I will describe the wealth of evidence that has forced my colleagues and me to conclude that the great mass extinctions, 65 million years ago, were caused by a large bolide impact on the earth. Bolide is a new word to most people, and it means any piece of solar system debris, such as a meteorite, asteroid, or comet nucleus. As I will show, the bolide responsible for the extinction of most of the then existing species, including the dinosaurs, was about 10 kilometers in diameter.

  4. Oblique impact: A process for providing meteorite samples of other planets

    NASA Technical Reports Server (NTRS)

    Okeefe, J. D.; Ahrens, T. J.

    1986-01-01

    Cratering flow calculations for a series of oblique to normal impacts of silicate projectiles onto a silicate halfspace were carried out to determine whether the gas produced upon shock vaporizing both projectile and planetary material could entrain and accelerate surface rocks and thus provide a mechanism for propelling SNC meteorites from the Martian surface. The difficult constraints that the impact origin hypothesis for SNC meteorites has to satisfy are that these meteorites are lightly to moderately shocked and yet were accelerated to speeds in excess of the Martian escape velocity. Two dimensional finite difference calculations demonstrate that at highly probable impact velocities, vapor plume jets are produced at oblique impact angles of 25 deg to 60 deg and have speeds as great as 20 km/sec. These plumes flow nearly parallel to the planetary surface. It is shown that upon impact of projectiles having radii of 0.1 to 1 km, the resulting vapor jets have densities of 0.1 to 1 g/cu.cm. These jets can entrain Martian surface rocks and accelerate them to velocities 5 km/sec. It is suggested that this mechanism launches SNC meteorites to Earth.

  5. The Chiemgau Meteorite Impact And Tsunami Event (Southeast Germany): First Osl Dating

    NASA Astrophysics Data System (ADS)

    Liritzis, I.; Zacharias, N.; Polymeris, G. S.; Kitis, G.; Ernstson, K.; Sudhaus, D.; Neumair, A.; Mayer, W.; Rappenglück, M. A.; Rappenglück, B.

    A more exact dating of the Chiemgau meteorite impact in Bavaria, southeast Germany, that produced a large strewn field of more than 80 craters sized between a few meters and several hundred meters, may provide the indispensable fundament for evaluating its cultural implications and thus enable an extraordinary case study. A straightforward answer has not yet been provided due to e.g. scarce existence of diagnostic material, lack of specialised micromorphologists, absence of absolute dating data etc. Here we report on a first OSL dating applied to a catastrophic impact layer that features both impact ejecta and tsunami characteristics attributed to proposed falls of projectiles into Lake Chiemsee in the impact event. The OSL dating was conducted on a quartzite cobble and four sediment samples collected from an excavated archaeological stratigraphy at Lake Chiemsee that comprised also the impact layer. In a first approach the analyses were based on the assumption of zero luminescence resetting clock from the induced impact shock for the quartzite cobble, and a solar bleaching of tsunamigenerated sediments. Optically Stimulated Luminescence (OSL) was applied using the Single Aliquot Regeneration (SAR) protocol and relevant reliability criteria. For sediments the beta-TL method was also applied. Reported ages fall around the beginning of 2nd millennium BC. Special attention is given to the peculiar situation of OSL dating of material that may have been exposed to impact shock of strongly varying intensity, to excavation, ejection and ejecta emplacement, the latter overprinted by and mixed with tsunami transport processes resulting in possibly very complex bleaching scenarios largely differing from the original assumptions.

  6. Meteorite impact ejecta - Dependence of mass and energy lost on planetary escape velocity

    NASA Technical Reports Server (NTRS)

    Okeefe, J. D.; Ahrens, T. J.

    1977-01-01

    The amounts of material and energy which escape a planet in a meteorite impact event is calculated as functions of impact and escape velocities. Results are obtained from the computed flow induced by the impact of iron and gabbroic anorthosite spheres onto a half-space of anorthosite at impact velocities of 5 to 45 km/sec. The impact-induced flows were determined by a numerical method using the mass, momentum, and energy conservation relations in finite-difference approximation, within an Eulerian computational grid. The impact velocities at which ejecta losses equal meteorite mass gains are found to be approximately 20, 35, and 45 km/sec for anorthosite objects and approximately 25, 35, and 40 km/sec for iron objects striking anorthosite surfaces for the gravity fields of the moon, Mercury and Mars.

  7. Meteoritic Ablation Debris from the Transantarctic Mountains: Evidence for a Tunguska-like Impact over Antarctica

    NASA Astrophysics Data System (ADS)

    van Ginneken, M.; Folco, L.; Perchiazzi, N.; Rochette, P.; Bland, P. A.

    2010-03-01

    Meteorite Ablation Spheres were found in Antarctica. They are likely paired with particles from two coeval dust layers from Dome F and Dome C ice cores. Continental scale distribution of the MAS can be explained by a Tunguska-like impact event.

  8. Bosumtwi impact structure, Ghana: Geochemistry of impactites and target rocks, and search for a meteoritic component

    NASA Astrophysics Data System (ADS)

    Dai, Xiongxin; Boamah, Daniel; Koeberl, Christian; Reimold, Wolf Uwe; Irvine, Gordon; McDonald, Iain

    2005-10-01

    Major and trace element data, including platinum group element abundances, of representative impactites and target rocks from the crater rim and environs of the Bosumtwi impact structure, Ghana, have been investigated for the possible presence of a meteoritic component in impact-related rocks. A comparison of chemical data for Bosumtwi target rocks and impactites with those for Ivory Coast tektites and microtektites supports the interpretation that the Bosumtwi structure and Ivory Coast tektites formed during the same impact event. High siderophile element contents (compared to average upper crustal abundances) were determined for target rocks as well as for impactites. Chondrite-normalized (and iron meteorite-normalized) abundances for target rocks and impactites are similar. They do not, however, allow the unambiguous detection of the presence, or identification of the type, of a meteoritic component in the impactites. The indigenous siderophile element contents are high and possibly related to regional gold mineralization, although mineralized samples from the general region show somewhat different platinum-group element abundance patterns compared to the rocks at Bosumtwi. The present data underline the necessity of extensive target rock analyses at Bosumtwi, and at impact structures in general, before making any conclusions regarding the presence of a meteoritic component in impactites.

  9. Were Ocean Impacts an Important Mechanism to Deliver Meteoritic Organic Matter to the Early Earth? Some Inferences from Eltanin

    NASA Technical Reports Server (NTRS)

    Kyte, Frank T.; Gersonde, Rainer; Kuhn. Gerhard

    2002-01-01

    Several workers have addressed the potential for extraterrestrial delivery of volatles, including water and complex organic compounds, to the early Earth. For example, Chyba and Sagan (1992) argued that since impacts would destroy organic matter, most extraterrestrial organics must be delivered in the fine-fractions of interplanetary dust. More recent computer simulations (Pierazzo and Chyba, 1999), however, have shown that substantial amounts of amino acids may survive the impacts of large (km-sized) comets and that this may exceed the amounts derived from IDPs or Miller-Urey synthesis in the atmosphere. Once an ocean developed on the early Earth, impacts of small ,asteroids and comets into deep-ocean basins were potentially common and may have been the most likely events to deliver large amounts of organics. The deposits of the late Pliocene impact of the Eltanin asteroid into the Bellingshausen Sea provide the only record of a deep-ocean (approx. 5 km) impact that can be used to constrain models of these events. This impact was first discovered in 1981 as an Ir anomaly in sediment cores collected by the USNS Eltanin in 1965 (Kyte et al., 1981). In 1995, Polarstem expedition ANT XII/4 made the first geological survey of the suspected impact region. Three sediment cores sampled around the San Martin seamounts (approx. 57.5S, 91 W) contained well-preserved impact deposits that include disturbed ocean sediments and meteoritic impact ejecta (Gersonde et al., 1997). The latter is composed of shock- melted asteroidal materials and unmelted meteorites. In 2001, the FS Polarstem returned to the impact area during expedition ANT XVIII/5a. At least 16 cores were recovered that contain ejecta deposits. These cores and geophysical data from the expedition can be used to map the effects of the impact over a large region of the ocean floor.

  10. Were Ocean Impacts an Important Mechanism to Deliver Meteoritic Organic Matter to the Early Earth? Some Inferences from Eltanin

    NASA Technical Reports Server (NTRS)

    Kyte, Frank T.; Gersonde, Rainer; Kuhn. Gerhard

    2002-01-01

    Several workers have addressed the potential for extraterrestrial delivery of volatles, including water and complex organic compounds, to the early Earth. For example, Chyba and Sagan (1992) argued that since impacts would destroy organic matter, most extraterrestrial organics must be delivered in the fine-fractions of interplanetary dust. More recent computer simulations (Pierazzo and Chyba, 1999), however, have shown that substantial amounts of amino acids may survive the impacts of large (km-sized) comets and that this may exceed the amounts derived from IDPs or Miller-Urey synthesis in the atmosphere. Once an ocean developed on the early Earth, impacts of small ,asteroids and comets into deep-ocean basins were potentially common and may have been the most likely events to deliver large amounts of organics. The deposits of the late Pliocene impact of the Eltanin asteroid into the Bellingshausen Sea provide the only record of a deep-ocean (approx. 5 km) impact that can be used to constrain models of these events. This impact was first discovered in 1981 as an Ir anomaly in sediment cores collected by the USNS Eltanin in 1965 (Kyte et al., 1981). In 1995, Polarstem expedition ANT XII/4 made the first geological survey of the suspected impact region. Three sediment cores sampled around the San Martin seamounts (approx. 57.5S, 91 W) contained well-preserved impact deposits that include disturbed ocean sediments and meteoritic impact ejecta (Gersonde et al., 1997). The latter is composed of shock- melted asteroidal materials and unmelted meteorites. In 2001, the FS Polarstem returned to the impact area during expedition ANT XVIII/5a. At least 16 cores were recovered that contain ejecta deposits. These cores and geophysical data from the expedition can be used to map the effects of the impact over a large region of the ocean floor.

  11. Simulated meteorite impacts and volcanic explosions: Ejecta analyses and planetary implications

    NASA Technical Reports Server (NTRS)

    Gratz, A. J.; Nellis, W. J.

    1992-01-01

    Past cratering studies have focused primarily on crater morphology. However, important questions remain about the nature of crater deposits. Phenomena that need to be studied include the distribution of shock effects in crater deposits and crater walls; the origin of mono- and polymict breccia; differences between local and distal ejecta; deformation induced by explosive volcanism; and the production of unshocked, high-speed ejecta that could form the lunar and martian meteorites found on the Earth. To study these phenomena, one must characterize ejecta and crater wall materials from impacts produced under controlled conditions. New efforts at LLNL simulate impacts and volcanism and study resultant deformation. All experiments use the two-stage light-gas gun facility at LLNL to accelerate projectiles to velocities of 0.2 to 4.3 km/s, including shock pressures of 0.9 to 50 GPa. We use granite targets and novel experimental geometries to unravel cratering processes in crystalline rocks. We have thus far conducted three types of simulations: soft recovery of ejecta, 'frozen crater' experiments, and an 'artificial volcano. Our ejecta recovery experiments produced a useful separation of impactites. Material originally below the projectile remained trapped there, embedded in the soft metal of the flyer plate. In contrast, material directly adjacent to the projectile was jetted away from the impact, producing an ejecta cone that was trapped in the foam recovery fixture. We find that a significant component of crater ejecta shows no signs of strong shock; this material comes from the near-surface 'interference zone' surrounding the impact site. This phenomenon explains the existence of unshocked meteorites on the Earth of lunar and martian origin. Impact of a large bolide on neighboring planets will produce high-speed, weakly shocked ejecta, which may be trapped by the Earth's gravitational field. 'Frozen crater' experiments show that the interference zone is highly

  12. Meteoritic ablation debris from the Transantarctic Mountains: Evidence for a Tunguska-like impact over Antarctica ca. 480 ka ago

    NASA Astrophysics Data System (ADS)

    van Ginneken, M.; Folco, L.; Perchiazzi, N.; Rochette, P.; Bland, P. A.

    2010-04-01

    Aggregates of microscopic spherules broadly similar in texture and composition to cosmic spherules or meteorite ablation spheres were discovered within the ˜ 1 Ma-old Transantarctic Mountain micrometeorite traps at Miller Butte, Victoria Land, Antarctica. Mineralogical and geochemical data obtained by means of field emission-scanning electron microscopy, electron microprobe analyses, synchrotron X-ray diffraction, and magnetization measurements show that they consist of a porous aggregate of quench-textured spherules, with individual spherules ranging from less than 1 to 65 µm in diameter. Spherule types include porphyritic olivine plus magnesioferrite spherules, dendritic magnesioferrite spherules, barred and feathered olivine spherules, and cryptocrystalline spherules. In contrast to the textural variations, the bulk composition of the individual spherules is fairly homogeneous and broadly chondritic. Likewise olivine has a nearly homogeneous composition Fa 16.3 ± 2.7 . Olivine and magnesioferrite are characterized by high NiO contents (2.72 ± 1.6 and 4.68 ± 0.68 wt.%, respectively), as typically observed in ablation debris and meteorite fusion crusts. The bulk composition of the aggregates is similar to the fusion crust of ordinary and carbonaceous chondrites. We interpret the spherulitic aggregates as meteorite ablation debris formed during the atmospheric entry of a large meteorite of ordinary or carbonaceous chondritic composition. Comparison with the available literature data shows that the ablation debris found at Miller Butte is most likely paired with the extraterrestrial dust found in a ˜ 480 ka-old ice layer in the EPICA-Dome C and Dome Fuji ice cores (East Antarctic ice sheet), thereby documenting a continental-scale distribution of ablation debris associated with a major meteoritic impact event which occurred ˜ 480 ka ago. Based on estimates of the projectile mass (> 10 8 kg) and numerical simulation of small-scale impacts from literature, we

  13. Meteorite - Impact Melt Mixing: PGE and Re-Os Evidence from the Morokweng Impact, South Africa

    NASA Astrophysics Data System (ADS)

    Hart, R.; Andreoli, M.; Cloete, M.; McDonald, I.; Carlson, R. W.; Tredoux, M.

    2001-12-01

    Preserved within the 870m thick impact melt sheet of the 144 Ma Morokweng impact structure, South Africa (1,2) are small (mm-cm) inclusions that are interpreted to be remnants of the impactor. Inclusions are disseminated throughout the melt sheet and consist of ultramafic silicate clasts with segregations of Ni-rich sulfides and oxides. The silicate component in the inclusions displays remnant fabric and, where unaltered, has mineral compositions consistent with ordinary chondrites (3). The sulfide-oxide component of the inclusions is Ni-rich, has high PGE contents (Ir = 16.7 x chondrite) and fractionated PGE ratios compared to chondrites and to the bulk impact melt which reflects the signature of the ordinary chondrite impactor (4). Specifically, the oxides show depletion in Pd, while the sulfide is slightly enriched in Rh and Pt and strongly enriched in Pd relative to Ir and Ru. Significantly, Ru and Ir (the high temperature PGE's) are not fractionated from one another. Initial Os isotopic compositions of the inclusion sulfides and oxides (0.1335 - 0.1358) are slightly more radiogenic than found in the melt rock (0.1301 - 0.1324), but both are substantially less radiogenic than a sample of the basement granite (0.259). The 1/Os vs 187Os/188Os correlation displayed by the bulk melt rocks is consistent with the presence of 1-3 wt% chondritic impactor in the crustal melt. The more radiogenic Os found in the inclusion minerals indicates that the inclusions contain a larger crustal PGE component than the melt rock. Though Os concentration is well correlated with Os isotopic composition in the melt rock, Re concentration is not. Thus, simple binary mixing between crustal melt and meteorite cannot explain the Re-Os systematics. The Re-Os and PGE fractionation observed in inclusion minerals suggests that meteorite-impact melt mixing occurred first through chemical exchange between oxidized melt and reduced, metal or sulfur-rich, impactor. Lithophile elements (e.g. Fe

  14. Possible relationship between the Farmington meteorite and a seismically detected swarm of meteoroids impacting the moon

    NASA Technical Reports Server (NTRS)

    Oberst, Jurgen

    1989-01-01

    The Farmington ordinary L5 chondrite with its uniquely short cosmic-ray exposure age of less than 25,000 years may have been a member of a large meteoroid swarm which was detected by the Apollo seismic network when it encountered the moon in June 1975. The association implies that the parent body of the Farmington meteorite was in an earth-crossing orbit at the time the swarm was formed. This supports the idea that at least some meteorites are derived from the observable population of earth-crossing asteroids.

  15. Anomalous Enstatite Meteorites Queen Alexandra Range 94204 and Pairs: The Perplexing Question of Impact Melts or Partial Melt Residues, Either way, Unrelated to Yamato 793225

    NASA Astrophysics Data System (ADS)

    van Niekerk, D.; Keil, K.

    2012-03-01

    QUE 94204 and its seven pairs are anomalous enstatite meteorites that may either be impact melt products, or partial melt residues. We explore the petrology of these meteorites and present new findings.

  16. Geomagnetic field intensity recorded after impact in the Ries meteorite crater, Germany

    NASA Astrophysics Data System (ADS)

    Koch, Stephan A.; Gilder, Stuart A.; Pohl, Jean; Trepmann, Claudia

    2012-04-01

    We carried out palaeointensity experiments on 45 samples collected throughout the ca. 15 Ma Ries crater (Germany) to test whether meteorite impacts can influence the geodynamo. A Thellier-Thellier procedure with alteration, tail and additivity checks yields a weighted average palaeointensity of 19.1 ± 1.1 μT from 15 samples that pass stringent data selection criteria. The corresponding virtual dipole moment of 3.2 ± 0.2 × 1022 Am2 is relatively low, but indistinguishable from the global palaeointensity database between 20 and 10 Ma. Our results suggest that either the energy released during the Ries meteorite impact event was too low to affect the geodynamo, the Ries impact lithologies cooled too fast to record any effect, or the time averaged by the impact lithologies was long enough to record secular variation, but that the geodynamo was remarkably stable over that time.

  17. Evidence for coeval Late Triassic terrestrial impacts from the Rochechouart (France) meteorite crater

    NASA Astrophysics Data System (ADS)

    Gilder, S. A.; Carporzen, L.

    2006-12-01

    High temperature impact melt breccias from the Rochechouart (France) meteorite crater record a magnetization component with antipodal, normal and reverse polarities. The corresponding paleomagnetic pole for this component lies between the 220 Ma and 210 Ma reference poles on the Eurasian apparent polar wander path, consistent with the 214 ± 8 Ma ^{40} Ar/ ^{39} Ar age of the crater [Kelley and Spray, 1997]. Late Triassic tectonic reconstructions of the Eurasian and North American plates place this pole within 95 % confidence limits of the paleomagnetic pole from the Manicouagan (Canada) meteorite impact crater, which is dated at 214 ± 1 Ma [Hodych and Dunning, 1992]. Together, these observations reinforce the hypothesis of Spray et al. [1998] for a Late Triassic, multiple meteorite impact event on Earth. References: Hodych, J. P., and G. R. Dunning (1992), Did the Manicouagan impact trigger end-of-Triassic mass extinction?, Geology, 20, 51-54. Kelley, S. P., and J. G. Spray (1997), A late Triassic age for the Rochechouart impact structure, France, Meteor., 32, 629-636. Spray, J. G., S. P. Kelley, and D. B. Rowley (1998), Evidence for a late Triassic multiple impact event on Earth, Nature, 392, 171-173.

  18. Enhancing Magnetic Interpretation Towards Meteorite Impact Crater at Bukit Bunuh, Perak, Malaysia

    NASA Astrophysics Data System (ADS)

    Nur Amalina, M. K. A.; Nordiana, M. M.; Saad, Rosli; Saidin, Mokhtar

    2017-04-01

    Bukit Bunuh is the most popular area of suspected meteorite impact crater. In the history of meteorite impact hitting the earth, Bukit Bunuh has complex crater of a rebound zone of positive magnetic anomaly value. This study area was located at Lenggong, Perak of peninsular Malaysia. The crater rim extended 5 km outwards with a clear subdued zone and immediately surround by a positive magnetic residual crater rim zone. A recent study was done to enhance the magnetic interpretation towards meteorite impact crater on this study area. The result obtained is being correlated with boreholes data to determine the range of local magnetic value. For the magnetic survey, the equipment used is Geometric G-856 Proton Precision magnetometers with the aids of other tools such as compass and GPS. In advance, the using of proton precision magnetometer causes it able in measures the magnetic fields separately within interval of second. Also, 18 boreholes are accumulated at study area to enhance the interpretation. The additional boreholes data had successfully described the structure of the impact crater at Bukit Bunuh in detailed where it is an eroded impact crater. Correlations with borehole records enlighten the results acquired from magnetic methods to be more reliable. A better insight of magnetic interpretation of Bukit Bunuh impact crater was done with the aid of geotechnical methods.

  19. Laser-Ablation ICP-MS Analyses of Meteoritic Metal Grains in Lunar Impact-Melt Breccias

    NASA Technical Reports Server (NTRS)

    Korotev, R. L.; Jolliff, B. L.; Campbell, A. J.; Humayun, M.

    2003-01-01

    Lunar impact-melt breccias contain metal grains from the meteorites that formed the breccias. Because the breccias contain clastic material that may derive from older breccias, metal grains from earlier impacts may be present, too. The large subset of moderately mafic (8 - 12% FeO), KREEP-rich ("LKFM") melt breccias is particularly important because: (1) these are the melt breccias most likely to have been produced in basin-forming impacts, (2) it is from these breccias that many of the approx. 3.9 Gyr ages that are so common in lunar samples derive, (3) the breccias contain large proportions of FeNi metal, more than 1% in some types of Apollo 16 breccias, and (4) the metal potentially provides information about the impactors causing the apparent cataclysm at 3.9 Gyr.

  20. Laser-Ablation ICP-MS Analyses of Meteoritic Metal Grains in Lunar Impact-Melt Breccias

    NASA Technical Reports Server (NTRS)

    Korotev, R. L.; Jolliff, B. L.; Campbell, A. J.; Humayun, M.

    2003-01-01

    Lunar impact-melt breccias contain metal grains from the meteorites that formed the breccias. Because the breccias contain clastic material that may derive from older breccias, metal grains from earlier impacts may be present, too. The large subset of moderately mafic (8 - 12% FeO), KREEP-rich ("LKFM") melt breccias is particularly important because: (1) these are the melt breccias most likely to have been produced in basin-forming impacts, (2) it is from these breccias that many of the approx. 3.9 Gyr ages that are so common in lunar samples derive, (3) the breccias contain large proportions of FeNi metal, more than 1% in some types of Apollo 16 breccias, and (4) the metal potentially provides information about the impactors causing the apparent cataclysm at 3.9 Gyr.

  1. The Agoudal (High Atlas Mountains, Morocco) shatter cone conundrum: A recent meteorite fall onto the remnant of an impact site

    NASA Astrophysics Data System (ADS)

    Chennaoui Aoudjehane, Hasnaa; El Kerni, Houda; Reimold, Wolf Uwe; Baratoux, David; Koeberl, Christian; Bouley, Sylvain; Aoudjehane, Mohamed

    2016-08-01

    Associations between impact structures and meteorite occurrences are rare and restricted to very young structures. Meteorite fragments are often disrupted in the atmosphere, and in most cases, meteorite falls that have been decelerated by atmospheric drag do not form a crater. Furthermore, meteorites are rapidly weathered. In this context, the finding of shatter cones in Jurassic marly limestone in the same location as a recent (105 ± 40 ka) iron meteorite fall near the village of Agoudal (High Atlas Mountains, Morocco) is enigmatic. The shatter cones are the only piece of evidence of a meteorite impact in the area. The overlap of a meteorite strewn field with the area of occurrence of shatter cones led previous researchers to consider that the meteorite fall was responsible for the formation of shatter cones in the context of formation of one or several small (<100 m) impact craters that had since been eroded. Shatter cones are generally not reported in association with subkilometer-diameter impact craters. Here, we present new field observations and an analysis of the distribution and characteristics of shatter cones, breccia, and meteorites in the Agoudal area. Evidence for local deformation not related to the structural High Atlas tectonics has been observed, such as a vertical to overturned stratum trending N150-N160. New outcrops with exposures of shatter cones are reported and extend the previously known area of occurrence. The area of in situ shatter cones (~0.15 km2) and the strewn field of meteorites are distinct, although they show some overlap. The alleged impact breccia is revealed as calcrete formations. No evidence for a genetic relationship between the shatter cones and the meteorites can be inferred from field observations. The extent of the area where in situ shatter cones and macrodeformation not corresponding to Atlas tectonic deformation are observed suggest that the original diameter of an impact structure could have been between at least 1

  2. Age of Lunar Meteorite LAP02205 and Implications for Impact-Sampling of Planetary Surfaces

    NASA Technical Reports Server (NTRS)

    Nyquist, L. E.; Shih, C.-Y.; Reese, Y.; Bogard, D. D.

    2005-01-01

    We have measured the age of lunar meteorite LAP02205 by the Rb-Sr and Ar-Ar methods. Sm-Nd analyses are in progress. The Rb-Sr and Ar-Ar ages indicate a crystallization age of approx. 3 Ga. Comparing the ages of LAP02205 and other lunar mare basaltic meteorites to mare surface ages based on the density of impact craters shows no significant bias in impact- sampling of lunar mare surfaces. Comparing the isotopic and geochemical data for LAP02205 to those for other lunar mare basalts suggests that it is a younger variant of the type of volcanism that produced the Apollo 12 basalts. Representative impact-sampling of the lunar surface

  3. Ar-40-Ar-39 Age of an Impact-Melt Lithology in Lunar Meteorite Dhofar 961

    NASA Technical Reports Server (NTRS)

    Cohen, Barbara; Frasl, Barbara; Jolliff, Brad; Korotev, Randy; Zeigler, Ryan

    2016-01-01

    The Dhofar 961 lunar meteorite was found in 2003 in Oman. It is texturally paired with Dhofar 925 and Dhofar 960 (though Dhofar 961 is more mafic and richer in incompatible elements). Several lines of reasoning point to the South Pole-Aitken Basin (SPA) basin as a plausible source (Figure 2): Mafic character of the melt-breccia lithic clasts consistent the interior of SPA, rules out feldspathic highlands. Compositional differences from Apollo impact-melt groups point to a provenance that is separated and perhaps far distant from the Procellarum KREEP Terrane SPA "hot spots" where Th concentrations reach 5 ppm and it has a broad "background" of about 2 ppm, similar to lithic clasts in Dhofar 961 subsamples If true, impact-melt lithologies in this meteorite may be unaffected by the Imbrium-forming event that is pervasively found in our Apollo sample collection, and instead record the early impact history of the Moon.

  4. The Fractionation of Highly Siderophile Elements (HSE) in Impact Melts and the Determination of the Meteoritic Components

    NASA Astrophysics Data System (ADS)

    Schmidt, G.; Palme, H.; Kratz, K. L.

    1995-09-01

    Lunar highland rocks contain an excess of siderophile elements, which has been attributed to meteoritic influx after the formation of the lunar crust [1-4]. Siderophile element enrichment has subsequently become a standard method for the identification of terrestrial impact craters. Janssens et al. [5], Grieve [6] and Palme et al. [7] have shown the dominant role of impact melt as the main carrier of meteoritic material at large terrestrial impact craters. This has been demonstrated at Clearwater East [8], Lappajarvi [9-11], Saaksjarvi [12], Brent [6] and Rochechouart [5]. The amount of projectile material incorporated in impact melt sheets is generally low (<1%). The highest recorded is 8% at East Clearwater, where the siderophiles are carried in a sulphide phase. In other cases, searches for siderophile anomalies at some impact structure have been largely unsuccessful. Melt bearing mixed breccias (suevitic melt) and fall-back sediments have been found to be free of meteoritic components in Brent, Lappajarvi and Ries samples [6,9,12-14]. However, from approximately 130 craters which are currently known on Earth only four clearly identified chondrites have been found as projectiles of large craters [15,16]. In this study we analyzed twenty-two impact melt samples (10 g) from Saaksjarvi (Finland), Mien and Dellen (Sweden) impact craters for Os, Re, Ir, Ru, Rh, Pd and Au by a slightly modified version of the fire assay neutron activation method using nickel sulphide as the collector [13,14]. All samples were obtained from the collection of the University of Munster. Only fresh, nearly fragment-free, fine grained samples without any sign of alteration were selected for chemical studies. All samples have been described previously [17]. The INAA procedure involved two irradiations: a short irradiation for Rh and a long irradiation for the other elements. Impact melts from Saaksjarvi are highly enriched in PGEs. The flat siderophile pattern suggests that the meteoritic

  5. Accretion timescale and impact history of Mars deduced from the isotopic systematics of martian meteorites

    SciTech Connect

    Borg, Lars E.; Brennecka, Gregory A.; Symes, Steven J. K.

    2015-12-12

    large scale mantle reservoirs formed during planetary differentiation associated with magma ocean solidification, the age determined here implies that magma ocean solidification occurred several tens of millions of years after the beginning of the Solar System. Recent thermal models, however, suggest that Mars-sized bodies cool rapidly in less than similar to 5 Ma after accretion ceases, even in the presence of a thick atmosphere. In assuming these models are correct, an extended period of accretion is necessary to provide a mechanism to keep portions of the martian mantle partially molten until 4504 Ma. Late accretional heating of Mars could either be associated with protracted accretion occurring at a quasi-steady state or alternatively be associated with a late giant impact. If this scenario is correct, then accretion of Mars-sized bodies takes up to 60 Ma and is likely to be contemporaneous with the core formation and possibly the onset of silicate differentiation. This further challenges the concept that isotopic equilibrium is attained during primordial evolution of planets, and may help to account for geochemical evidence implying addition of material into planetary interiors after core formation was completed.

  6. Accretion timescale and impact history of Mars deduced from the isotopic systematics of martian meteorites

    NASA Astrophysics Data System (ADS)

    Borg, Lars E.; Brennecka, Gregory A.; Symes, Steven J. K.

    2016-02-01

    High precision Sm-Nd isotopic analyses have been completed on a suite of 11 martian basaltic meteorites in order to better constrain the age of silicate differentiation on Mars associated with the formation of their mantle sources. These data are used to evaluate the merits and disadvantages of various mathematical approaches that have been employed in previous work on this topic. Ages determined from the Sm-Nd isotopic systematics of individual samples are strongly dependent on the assumed Nd isotopic composition of the bulk planet. This assumption is problematic given differences observed between the Nd isotopic composition of Earth and chondritic meteorites and the fact that these materials are both commonly used to represent bulk planetary Nd isotopic compositions. Ages determined from the slope of 146Sm-142Nd whole rock isochrons are not dependent on the assumed 142Nd/144Nd ratio of the planet, but require the sample suite to be derived from complementary, contemporaneously-formed reservoirs. In this work, we present a mathematical expression that defines the age of formation of the source regions of such a suite of samples that is based solely on the slope of a 143Nd-142Nd whole rock isochron and is also independent of any a priori assumptions regarding the bulk isotopic composition of the planet. This expression is also applicable to mineral isochrons and has been used to successfully calculate 143Nd-142Nd model crystallization ages of early refractory solids as well as lunar samples. This permits ages to be obtained using only Nd isotopic measurements without the need for 147Sm/144Nd isotope dilution determinations. When used in conjunction with high-precision Nd isotopic measurements completed on martian meteorites this expression yields an age of formation of the martian basaltic meteorite source regions of 4504 ± 6 Ma. Because the Sm-Nd model ages for the formation of martian source regions are commonly interpreted to record the age at which large scale

  7. Impact cratering as a major process in planet formation: Projectile identification of meteorite craters

    NASA Astrophysics Data System (ADS)

    Schmidt, G.; Kratz, K.

    2009-12-01

    Ancient surfaces of solid planets show that impact cratering is a major process in planet formation. Understanding origin and influence of impactors on the chemical composition of planets (core, mantle and crust) it is important to know the relative abundances of highly siderophile elements (Os, Ir, Ru, Pt, Rh, Pd) in the silicate mantle and crust of planets and meteorites. Refractory highly siderophile elements, such as Os and Ir, are abundant in most meteorites but depleted in crustal rocks (low target/meteorite ratios) and thus the most reliable elements for projectile identification. However, target/meteorite ratios are high if target rocks consist of mantle rocks. In such cases elements are enriched in impactites due to relatively high abundances (ng/g level) in target rocks to make the identification of projectile types difficult (e.g., Gardnos impact structure in Norway). The Ru/Ir ratio is the most reliable key ratio that rules out Earth primitive upper mantle (PUM) derived refractory highly siderophile element components in impactites. The well established Ru/Ir ratio of the Earth mantle of 2.0 ± 0.1 (e.g. Schmidt and Kratz 2004) is significantly above the chondritic ratios varying from 1.4 to 1.6. On Earth Rh/Ir, Ru/Ir, Pd/Ir, and Pt/Os derived from PUM match the ratios of group IV irons with fractionated trace element patterns. The question raise if HSE in mantle rocks are added to the accreting Earth by a late bombardment of pre-differentiated objects or the cores of these objects (magmatic iron meteorites as remnants of the first planetesimals, e.g. Kleine et al. 2009) or some unsampled inner solar system materials from the Mercury-Venus formation region, not sampled through meteorite collections (Schmidt 2009). The PGE and Ni systematics of the upper continental crust (UCC) closely resembles group IIIAB iron meteorites with highly fractionated refractory trace element patterns, pallasites, and the evolved suite of Martian meteorites (representing

  8. Meteorite Impact-Induced Rapid NH3 Production on Early Earth: Ab Initio Molecular Dynamics Simulation.

    PubMed

    Shimamura, Kohei; Shimojo, Fuyuki; Nakano, Aiichiro; Tanaka, Shigenori

    2016-12-14

    NH3 is an essential molecule as a nitrogen source for prebiotic amino acid syntheses such as the Strecker reaction. Previous shock experiments demonstrated that meteorite impacts on ancient oceans would have provided a considerable amount of NH3 from atmospheric N2 and oceanic H2O through reduction by meteoritic iron. However, specific production mechanisms remain unclear, and impact velocities employed in the experiments were substantially lower than typical impact velocities of meteorites on the early Earth. Here, to investigate the issues from the atomistic viewpoint, we performed multi-scale shock technique-based ab initio molecular dynamics simulations. The results revealed a rapid production of NH3 within several picoseconds after the shock, indicating that shocks with greater impact velocities would provide further increase in the yield of NH3. Meanwhile, the picosecond-order production makes one expect that the important nitrogen source precursors of amino acids were obtained immediately after the impact. It was also observed that the reduction of N2 proceeded according to an associative mechanism, rather than a dissociative mechanism as in the Haber-Bosch process.

  9. Evidence for a Meteoritic Component in Impact Melt Rock from the Chicxulub Structure

    NASA Technical Reports Server (NTRS)

    Koeberl, Christian; Sharpton, Virgil L.; Schuraytz, Benjamin C.; Shirey, Steven B.; Blum, Joel D.; Marin, Luis E.

    1994-01-01

    The Chicxulub structure in Yucatan, Mexico, has recently been recognized as a greater then 200-km-diameter multi-ring impact crater of K-T boundary age. Crystalline impact melt rocks and breccias from within the crater, which have compositions similar to those of normal continental crustal rocks and which show shock metamorphic effects, have been studied for trace element and Re-Os isotope compositions. Re-Os isotope systematics allow the sensitive and selective determination of an extraterrestrial component in impact-derived rocks. A melt rock sample shows elevated iridium concentrations, an osmium concentration of 25 ppb, and a low Os-187/Os-188 ratio of 0.113, which are incompatible with derivation from the continental crust. Even though the Os-187/Os-188 ratio is slightly lower than the range so far measured in meteorites, a mantle origin seems unlikely for mass balance reasons and because the cratering event is unlikely to have excavated mantle material. The data support the hypothesis of a heterogeneously distributed meteoritic component in the Chicxulub melt rock. A sample of impact glass from the Haitian K-T boundary at Beloc yielded about 0.1 ppb osmium and an Os-187/0s-188 ratio of 0.251, indicating the presence of a small meteoritic component in the impact ejecta as well.

  10. The Rock Elm meteorite impact structure, Wisconsin: Geology and shock-metamorphic effects in quartz

    USGS Publications Warehouse

    French, B.M.; Cordua, W.S.; Plescia, J.B.

    2004-01-01

    The Rock Elm structure in southwest Wisconsin is an anomalous circular area of highly deformed rocks, ???6.5 km in diameter, located in a region of virtually horizontal undeformed sedimentary rocks. Shock-produced planar microstructures (PMs) have been identified in quartz grains in several lithologies associated with the structure: sandstones, quartzite pebbles, and breccia. Two distinct types of PMs are present: P1 features, which appear identical to planar fractures (PFs or cleavage), and P2 features, which are interpreted as possible incipient planar deformation features (PDFs). The latter are uniquely produced by the shock waves associated with meteorite impact events. Both types of PMs are oriented parallel to specific crystallographic planes in the quartz, most commonly to c(0001), ??112??2, and r/z101??1. The association of unusual, structurally deformed strata with distinct shock-produced microdeformation features in their quartz-bearing rocks establishes Rock Elm as a meteorite impact structure and supports the view that the presence of multiple parallel cleavages in quartz may be used independently as a criterion for meteorite impact. Preliminary paleontological studies indicate a minimum age of Middle Ordovician for the Rock Elm structure. A similar age estimate (450-400 Ma) is obtained independently by combining the results of studies of the general morphology of complex impact structures with estimated rates of sedimentation for the region. Such methods may be applicable to dating other old and deeply eroded impact structures formed in sedimentary target rocks.

  11. Meteorite Impact-Induced Rapid NH3 Production on Early Earth: Ab Initio Molecular Dynamics Simulation

    NASA Astrophysics Data System (ADS)

    Shimamura, Kohei; Shimojo, Fuyuki; Nakano, Aiichiro; Tanaka, Shigenori

    2016-12-01

    NH3 is an essential molecule as a nitrogen source for prebiotic amino acid syntheses such as the Strecker reaction. Previous shock experiments demonstrated that meteorite impacts on ancient oceans would have provided a considerable amount of NH3 from atmospheric N2 and oceanic H2O through reduction by meteoritic iron. However, specific production mechanisms remain unclear, and impact velocities employed in the experiments were substantially lower than typical impact velocities of meteorites on the early Earth. Here, to investigate the issues from the atomistic viewpoint, we performed multi-scale shock technique-based ab initio molecular dynamics simulations. The results revealed a rapid production of NH3 within several picoseconds after the shock, indicating that shocks with greater impact velocities would provide further increase in the yield of NH3. Meanwhile, the picosecond-order production makes one expect that the important nitrogen source precursors of amino acids were obtained immediately after the impact. It was also observed that the reduction of N2 proceeded according to an associative mechanism, rather than a dissociative mechanism as in the Haber-Bosch process.

  12. Meteorite Impact-Induced Rapid NH3 Production on Early Earth: Ab Initio Molecular Dynamics Simulation

    PubMed Central

    Shimamura, Kohei; Shimojo, Fuyuki; Nakano, Aiichiro; Tanaka, Shigenori

    2016-01-01

    NH3 is an essential molecule as a nitrogen source for prebiotic amino acid syntheses such as the Strecker reaction. Previous shock experiments demonstrated that meteorite impacts on ancient oceans would have provided a considerable amount of NH3 from atmospheric N2 and oceanic H2O through reduction by meteoritic iron. However, specific production mechanisms remain unclear, and impact velocities employed in the experiments were substantially lower than typical impact velocities of meteorites on the early Earth. Here, to investigate the issues from the atomistic viewpoint, we performed multi-scale shock technique-based ab initio molecular dynamics simulations. The results revealed a rapid production of NH3 within several picoseconds after the shock, indicating that shocks with greater impact velocities would provide further increase in the yield of NH3. Meanwhile, the picosecond-order production makes one expect that the important nitrogen source precursors of amino acids were obtained immediately after the impact. It was also observed that the reduction of N2 proceeded according to an associative mechanism, rather than a dissociative mechanism as in the Haber-Bosch process. PMID:27966594

  13. The Environmental Effect of Meteoritic Impacts on Early Mars with a Versatile 3-D Global Climate Model

    NASA Astrophysics Data System (ADS)

    Turbet, M.; Forget, F.; Svetsov, V.; Tran, H.; Hartmann, J.-M.; Karatekin, O.; Gillmann, C.; Popova, O.; Head, J.

    2017-10-01

    We simulated the environmental effect of meteoritic impacts with a 3-D Global Climate Model to explore if they could trigger the warm conditions and the precipitation rates required to explain the formation of the Martian valley networks.

  14. The Flynn Creek Meteorite Impact Site and Changing Views on Impact Cratering

    NASA Astrophysics Data System (ADS)

    Ford, J. R. H.; Orchiston, Wayne; Clendening, Ron

    2013-07-01

    Flynn Creek is one of two confirmed meteorite impact sites in Tennessee, USA. The first published mention of the Flynn Creek Structure was by J.M. Safford, Tennessee's State Geologist, in his Geology of Tennessee (1869). Subsequently, the site was investigated briefly in the 1920s and 1930s, but it was only in the 1960s following the founding of the United States Geological Survey's Astrogeological Studies Group as a lead-up to manned lunar exploration that Flynn Creek assumed international importance. This was because it was seen as the best terrestrial analog of a 'typical lunar crater'. As a result, CALTECH graduate student D.J. Roddy used Flynn Creek as the focus of his Ph.D. research, under the supervision of the Group's leader, Gene Shoemaker. After graduating, Roddy continued to conduct on-going investigations at this site up until the time of his death in 2002. Roddy's research has provided a wealth of information regarding the formation and structural features of the Flynn Creek site and shown that the crater was formed during Middle to Late Devonian times as a result of a shallow marine impact. Impact folding and faulting and subsequent uplift and erosion led to the formation of a system of caves at Flynn Creek that is unique among US impact sites.

  15. Evidence for a meteoritic component in impact melt rock from the Chicxulub structure

    NASA Astrophysics Data System (ADS)

    Koeberl, Christian; Sharpton, Virgil L.; Schuraytz, Benjamin C.; Shirey, Steven B.; Blum, Joel D.; Marin, Luis E.; Koeberl, Christian

    1994-03-01

    The Chicxulub structure in Yucatan, Mexico, has recently been recognized as a greater than 200-km diameter multi-ring impact crater of K-T boundary age. Crystalline impact melt rocks and breccias from within the crater, which have compositions similar to those of normal continental crustal rocks and which show shock metamorphic effects, have been studied for trace element and Re-Os isotope compositions. A melt rock sample shows elevated iridium concentrations, an osmium concentration of 25 ppb, and a low Os-187/Os-188 ratio of 0.113, which are incompatible with derivation from the continental crust. Even though the Os-187/Os-188 ratio is slightly lower than the range so far measured in meteorites, a mantle origin seems unlikely for mass balance reasons and because the cratering event is unlikely to have excavated mantle material. The data support the hypothesis of a heterogeneously distributed meteoritic component in the Chicxulub melt rock.

  16. 3D Global Climate Modelling of the environmental effect of meteoritic impacts on Early Mars

    NASA Astrophysics Data System (ADS)

    Turbet, Martin; Forget, Francois; Gillmann, Cedric; Karatekin, Ozgur; Svetsov, Vladimir; Popova, Olga; Wallemacq, Quentin

    2016-10-01

    There are now robust evidences that liquid water flowed on ancient Mars: dry river beds and lakes, hydrated sedimentary minerals and high erosion rates. Climate models that consider only CO2/H2O as greenhouse gases have been unable yet to produce warm climates suitable for liquid water on Early Mars, given the lower solar luminosity at that time. It has been suggested that the warm conditions required to explain the formation of the 3.8 Gyrs old valley networks could have been transient and produced in response to the meteoritic impacts that occured during the contemporaneous Late Heavy Bombardment (LHB). This scenario is appealing because, in a predominately cold climate, the ice tends to accumulate preferentially in the regions where the rivers were sculpted ('Icy Highlands' scenario). This would be a very efficient mechanism of recharge of the valley network water sources between two impact-induced melting events.Using the LMD Global Climate Model (LMD-GCM) designed for flexible (from cold & dry to warm & wet) conditions, we explored the environmental effect of LHB impact events of various sizes on Early Mars. Our main result is that, whatever the initial impact-induced temperatures and water vapor content injected, warm climates cannot be stable and are in fact short-lived (lifetime of ~ 5 martian years/bar of H2O injected). Moreover, we will give preliminar estimates of the amount of rainfall/snowmelt that can be produced after impact events depending on their size, following three different approaches:1) For large impact events (Dimpactor < 50km, N ~ 40) we initialize the LMD-GCM with warm/moist conditions prescribed with simple scaling laws and assuming energy conservation.2) For moderate-size events (5km < Dimpactor < 50km, N ~ 3x103) we use the SOVA hydrocode for short-term modelling of impact cratering. It provides us with post-impact temperature fields, injection of volatiles, ejecta and dust distribution that serve as input for the LMD-GCM.3

  17. Trilogy possible meteorite impact crater at Bukit Bunuh, Malaysia using 2-D electrical resistivity imaging

    NASA Astrophysics Data System (ADS)

    Jinmin, M.; Rosli, S.; Nordiana, M. M.; Mokhtar, S.

    2017-07-01

    Bukit Bunuh situated in Lenggong (Perak) is one of Malaysia's most important areas for archeology that revealed many traces of Malaysia's prehistory. Geophysical method especially 2-D electrical resistivity imaging method is non-destructive which is applied in geo-subsurface study for meteorite impact. The study consists of two stages which are regional and detail study with a total of fourteen survey lines. The survey lines were conducted using Pole-dipole array with 5 m minimum electrode spacing. The results of each stage are correlated and combined to produce detail subsurface resistivity distribution of the study area. It shows that the area consists of two main layers which are overburden and granitic bedrock. The first layer is overburden mix with boulders with resistivity value of 10-800 Ωm while the second layer is granitic bedrock with resistivity value of >1500 Ωm. This study also shows few spotted possibility of uplift (rebound) due to the high impact which suspected from meteorite. A lot of fracture were found within the survey area which could be one of the effect of meteorite impact. The result suggest that Bukit Bunuh is under layer by a complex crater with diameter of crater rim is approximately 5-6 km.

  18. Petrology and geochemistry of feldspathic impact-melt breccia Abar al' Uj 012, the first lunar meteorite from Saudi Arabia

    NASA Astrophysics Data System (ADS)

    Mészáros, Marianna; Hofmann, Beda A.; Lanari, Pierre; Korotev, Randy L.; Gnos, Edwin; Greber, Nicolas D.; Leya, Ingo; Greenwood, Richard C.; Jull, A. J. Timothy; Al-Wagdani, Khalid; Mahjoub, Ayman; Al-Solami, Abdulaziz A.; Habibullah, Siddiq N.

    2016-10-01

    Abar al' Uj (AaU) 012 is a clast-rich, vesicular impact-melt (IM) breccia, composed of lithic and mineral clasts set in a very fine-grained and well-crystallized matrix. It is a typical feldspathic lunar meteorite, most likely originating from the lunar farside. Bulk composition (31.0 wt% Al2O3, 3.85 wt% FeO) is close to the mean of feldspathic lunar meteorites and Apollo FAN-suite rocks. The low concentration of incompatible trace elements (0.39 ppm Th, 0.13 ppm U) reflects the absence of a significant KREEP component. Plagioclase is highly anorthitic with a mean of An96.9Ab3.0Or0.1. Bulk rock Mg# is 63 and molar FeO/MnO is 76. The terrestrial age of the meteorite is 33.4 ± 5.2 kyr. AaU 012 contains a 1.4 × 1.5 mm2 exotic clast different from the lithic clast population which is dominated by clasts of anorthosite breccias. Bulk composition and presence of relatively large vesicles indicate that the clast was most probably formed by an impact into a precursor having nonmare igneous origin most likely related to the rare alkali-suite rocks. The IM clast is mainly composed of clinopyroxenes, contains a significant amount of cristobalite (9.0 vol%), and has a microcrystalline mesostasis. Although the clast shows similarities in texture and modal mineral abundances with some Apollo pigeonite basalts, it has lower FeO and higher SiO2 than any mare basalt. It also has higher FeO and lower Al2O3 than rocks from the FAN- or Mg-suite. Its lower Mg# (59) compared to Mg-suite rocks also excludes a relationship with these types of lunar material.

  19. Hematite formed from pyroxene on Mars by meteoritic impact

    NASA Technical Reports Server (NTRS)

    Morris, Richard V.; Bell, James F., III; Lauer, H. V., Jr.

    1994-01-01

    In earlier work, we showed using Mossbauer data that the mineralogy of iron-bearing phases in impact melt rocks from Manicouagan Crater (Quebec, Canada) is to a first approximation hematite and pyroxene. The visible and near-IR reflectivity data for these impact melt rocks show a continuous trend in band position from approximately 850 to approximately 1000 nm, which corresponds to the positions for the hematite and pyroxene endmembers, respectively. The oxidation is thought to occur shortly after the impact when oxidizing vapors and/or solutions reacted with the impact melt which was below its solidus temperature but still relatively hot. The reflectance data have important implications for Mars because band positions which occur between approximately 850 and 1000 nm bands observed for Mars can be attributed to hematite-pyroxene assemblages and not necessarily to different ferric mineralogy. Because oxidation of impact melt rocks at Manicouagan is thought to occur subsolidus, precursors for the hematite include oxides such as magnetite and ilmenite and silicates such as pyroxene and olivine. To determine if the Manicouagan impact-melt rocks are related to each other by simple thermal subsolidus oxidation, we calcined in air a relatively unoxidized Manicouagan impact-melt rock (MAN-74-608A). Previous work has shown that np-Hm (nanophase hematite) particles can be derived by calcination of iron-bearing silicates.

  20. Maskelynite in asteroidal, lunar and planetary basaltic meteorites: An indicator of shock pressure during impact ejection from their parent bodies

    NASA Astrophysics Data System (ADS)

    Rubin, Alan E.

    2015-09-01

    Maskelynite is a diaplectic glass that forms from plagioclase at shock pressures of ∼20-30 GPa, depending on the Ca concentration. The proportion of maskelynite-rich samples in a basaltic meteorite group correlates with the parent-body escape velocity and serves as a shock indicator of launching conditions. For eucrites (basalts widely presumed to be from Vesta; vesc = 0.36 km s-1), ∼5% of the samples are maskelynite rich. For the Moon (vesc = 2.38 km s-1), ∼30% of basaltic meteorites are maskelynite rich. For Mars (vesc = 5.03 km s-1), ∼93% of basaltic meteorites are maskelynite rich. In contrast, literature data show that maskelynite is rare (∼1%) among mare basalts and basaltic fragments in Apollo 11, 12, 15 and 17 soils (which were never ejected from the Moon). Angrites are unbrecciated basaltic meteorites that are maskelynite free; they were ejected at low-to-moderate shock pressures from an asteroid smaller than Vesta. Because most impacts that eject materials from a large (⩾100 km) parent body are barely energetic enough to do that, a collision that has little more than the threshold energy required to eject a sample from Vesta will not be able to eject identical samples from the Moon or Mars. There must have been relatively few impacts, if any, that launched eucrites off their parent body that also imparted shock pressures of ∼20-30 GPa in the ejected rocks. More-energetic impacts were required to launch basalts off the Moon and Mars. On average, Vesta ejecta were subjected to lower shock pressures than lunar ejecta, and lunar ejecta were subjected to lower shock pressures than martian ejecta. H and LL ordinary chondrites have low percentages of shock-stage S5 maskelynite-bearing samples (∼1% and ∼4%, respectively), probably reflecting shock processes experienced by these rocks on their parent asteroids. In contrast, L chondrites have a relatively high proportion of samples containing maskelynite (∼11%), most likely a result of

  1. Plasma and collision processes of hypervelocity meteorite impact in the prehistory of life

    NASA Astrophysics Data System (ADS)

    Managadze, G.

    2010-07-01

    A new concept is proposed, according to which the plasma and collision processes accompanying hypervelocity impacts of meteorites can contribute to the arising of the conditions on early Earth, which are necessary for the appearance of primary forms of living matter. It was shown that the processes necessary for the emergence of living matter could have started in a plasma torch of meteorite impact and have continued in an impact crater in the case of the arising of the simplest life form. It is generally accepted that planets are the optimal place for the origin and evolution of life. In the process of forming the planetary systems the meteorites, space bodies feeding planet growth, appear around stars. In the process of Earth's formation, meteorite sizes ranged from hundreds and thousands of kilometres. These space bodies consisted mostly of the planetesimals and comet nucleus. During acceleration in Earth's gravitational field they reached hypervelocity and, hitting the surface of planet, generated powerful blowouts of hot plasma in the form of a torch. They also created giant-size craters and dense dust clouds. These bodies were composed of all elements needed for the synthesis of organic compounds, with the content of carbon being up to 5%-15%. A new idea of possible synthesis of the complex organic compounds in the hypervelocity impact-generated plasma torch was proposed and experimentally confirmed. A previously unknown and experimentally corroborated feature of the impact-generated plasma torch allowed a new concept of the prehistory of life to be developed. According to this concept the intensive synthesis of complex organic compounds arose during meteoritic bombardment in the first 0.5 billion years at the stage of the planet's formation. This most powerful and destructive action in Earth's history could have played a key role and prepared conditions for the origin of life. In the interstellar gas-dust clouds, the synthesis of simple organic matter could

  2. Accretion timescale and impact history of Mars deduced from the isotopic systematics of martian meteorites

    DOE PAGES

    Borg, Lars E.; Brennecka, Gregory A.; Symes, Steven J. K.

    2015-12-12

    which large scale mantle reservoirs formed during planetary differentiation associated with magma ocean solidification, the age determined here implies that magma ocean solidification occurred several tens of millions of years after the beginning of the Solar System. Recent thermal models, however, suggest that Mars-sized bodies cool rapidly in less than similar to 5 Ma after accretion ceases, even in the presence of a thick atmosphere. In assuming these models are correct, an extended period of accretion is necessary to provide a mechanism to keep portions of the martian mantle partially molten until 4504 Ma. Late accretional heating of Mars could either be associated with protracted accretion occurring at a quasi-steady state or alternatively be associated with a late giant impact. If this scenario is correct, then accretion of Mars-sized bodies takes up to 60 Ma and is likely to be contemporaneous with the core formation and possibly the onset of silicate differentiation. This further challenges the concept that isotopic equilibrium is attained during primordial evolution of planets, and may help to account for geochemical evidence implying addition of material into planetary interiors after core formation was completed.« less

  3. Age and effects of the Odessa meteorite impact, western Texas, USA

    NASA Astrophysics Data System (ADS)

    Holliday, Vance T.; Kring, David A.; Mayer, James H.; Goble, Ronald J.

    2005-12-01

    The Odessa meteorite craters (Texas, United States) include a main crater (˜160 m diameter, ˜30 m deep) plus four smaller meteorite craters. The main crater was sampled by coring (to 22 m depth) to better understand its origin and history. Dating by optically stimulated luminescence indicates that it was produced immediately prior to ca. 63.5 ± 4.5 ka. Sediment filling the crater includes impact breccias produced at the time of impact; wind-dominated silts with minor amounts of pond sediments deposited ca. 63.5 ka, probably just after the impact, and ca. 53 ± 2 ka; wind-dominated silt ca. 38 ± 1.7 ka; and playa muds with a wind-blown silt component younger than 36 ka. The environment was arid or semiarid at the time of impact based on characteristics of soils on the surrounding landscape. The impact caused severe damage within 2 km and produced >1000 km/hr winds and thermal pulse. Animals within a 1 1.5-km-diameter area were probably killed. This is only the second well-dated Pleistocene hypervelocity impact crater in North America.

  4. Meteorite Impacts and Planetary Habitability: The Good, the Bad, and the Ugly

    NASA Astrophysics Data System (ADS)

    Osinski, G. R.

    2012-12-01

    It is now widely accepted that meteorite impacts negatively affect life on a planet, as evidenced by the deleterious effects associated with the formation of the Chicxulub impact structure, Mexico, 65 Myr. ago and its link to the Cretaceous-Paleogene mass extinction event. This impact event had a profound affect on the evolution of life on Earth by ending the age of the dinosaurs and paving the way for mammals to ascend to dominance. In terms of the origin of life, despite the controversy over when exactly life appeared on Earth, it is likely that it did so during one of the harshest, most inhospitable times in Earth history: the Late Heavy Bombardment Period ~4.0-3.8 Ga. During this time, asteroid and comet impacts were ~10-20 times as frequent as they are at the present day. This may seem counterintuitive until one considers that these cataclysmic, initially destructive impact events may also have had beneficial effects with respect to life. This contribution will present a synthesis of information concerning the role that meteorite impacts may have played in the origin and evolution of life on Earth and, by analogy, with other planetary bodies throughout the Universe. It will hopefully be demonstrated that impact events do not just frustrate life, but that impact craters, once formed, may represent protected niches where life can survive and evolve and, potentially, where life may have originated. It is proposed that the geological, biological, and environmental changes known to be caused by an impact allow for the formulation of key cross-cutting hypotheses concerning the potential deleterious and beneficial effects of meteorite impact events. Most notably, it is proposed that impact events produce new, unique habitats for life and, therefore, can have an overall positive effect on planetary habitability. Habitats include: 1) impact-generated hydrothermal systems, which could provide habitats for thermophilic and hyperthermophilic microorganisms, 2) impact

  5. Chiral changes of simple amino acids in early Earth's ocean by meteorite impacts: Experimental simulations

    NASA Astrophysics Data System (ADS)

    Takase, A.; Sekine, T.; Furukawa, Y.; Kakegawa, T.

    2012-12-01

    It has been recognized that meteorite impacts on early Earth ocean may have contributed significantly for molecules related to the origin of life to originate and evolve. We have already established the formation of simple biomolecules from inorganic materials through oceanic impacts that may have occurred at late heavy bombardment. These simple molecules including amino acids need to be subjected to further developments to initiate life on the Earth. The chirality of terrestrial amino acids constructing proteins is only L-type. In order to make clear the the point that biomolecules are formed by oceanic impacts of meteorites, it wll be crucial to determine how they select the chirality. In order to investigate the basic chemistry on chirality of simple amino acids, we tried to simulate experimentally the chiral change of some amino acids present in ocean at that time under shock loading. Each aqueous solution (0.1 M) of L- and D-valine was prepared and used as mixtures of olivine powders and solutions in sealed steel containers. We performed shock recovery experiments at an impact condition where samples were compressed at ~5 GPa. The analytical results of shock recovered solutions indicate that valine survives significantly (~10%) and that L- and D-valines transform partially to D- and L-valine, respectively. The transformation rate varied with the chemical species present in solutions. These results imply that meteorite impacts as well as the surrounding conditions play important roles to control the chirality of simple amino acids that may have been formed at that time.

  6. The convincing identification of terrestrial meteorite impact structures: What works, what doesn't, and why

    NASA Astrophysics Data System (ADS)

    French, Bevan M.; Koeberl, Christian

    2010-01-01

    In the geological sciences it has only recently been recognized how important the process of impact cratering is on a planetary scale, where it is commonly the most important surface-modifying process. On the Moon and other planetary bodies that lack an appreciable atmosphere, meteorite impact craters are well preserved, and they can commonly be recognized from morphological characteristics, but on Earth complications arise as a consequence of the weathering, obliteration, deformation, or burial of impact craters and the projectiles that formed them. These problems made it necessary to develop diagnostic criteria for the identification and confirmation of impact structures on Earth. Diagnostic evidence for impact events is often present in the target rocks that were affected by the impact. The conditions of impact produce an unusual group of melted, shocked, and brecciated rocks, some of which fill the resulting crater, and others which are transported, in some cases to considerable distances from the source crater. Only the presence of diagnostic shock-metamorphic effects and, in some cases, the discovery of meteorites, or traces thereof, is generally accepted as unambiguous evidence for an impact origin. Shock deformation can be expressed in macroscopic form (shatter cones) or in microscopic forms (e.g., distinctive planar deformation features [PDFs] in quartz). In nature, shock-metamorphic effects are uniquely characteristic of shock levels associated with hypervelocity impact. The same two criteria (shock-metamorphic effects or traces of the impacting meteorite) apply to distal impact ejecta layers, and their presence confirms that materials found in such layers originated in an impact event at a possibly still unknown location. As of 2009 about 175 impact structures have been identified on Earth based on these criteria. A wide variety of shock-metamorphic effects has been identified, with the best diagnostic indicators for shock metamorphism being features

  7. Fossil Meteorite Unearthed From Crater

    NASA Astrophysics Data System (ADS)

    Martel, L. M. V.

    2006-06-01

    A team of scientists lead by Wolf Maier (University of Quebec, Canada and University of Pretoria, South Africa and soon at University of Western Australia, Perth) and Marco Andreoli (University of the Witwatersrand and South African Nuclear Energy Corp.) and colleagues who also hail from Canada, South Africa, the United Kingdom, and the United States, have announced the discovery of a 25-centimeter-wide chondritic meteorite unearthed from the 145-million-year-old Morokweng impact crater in South Africa. Found within the crater's impact melt sheet about 770 meters (half a mile) down a drilling borehole, the hefty meteorite's existence would seem improbable given its low chance of surviving the high shock pressures and temperatures normally associated with large impact events. Its unusual composition could mean it is a sample from a previously unknown part of the LL chondrite parent body or maybe it is from an entirely different asteroid population than other known meteorites.

  8. Impact melting of the largest known enstatite meteorite: Al Haggounia 001, a fossil EL chondrite

    NASA Astrophysics Data System (ADS)

    Rubin, Alan E.

    2016-09-01

    Al Haggounia 001 and paired specimens (including Northwest Africa [NWA] 2828 and 7401) are part of a vesicular, incompletely melted, EL chondrite impact melt rock with a mass of ~3 metric tons. The meteorite exhibits numerous shock effects including (1) development of undulose to weak mosaic extinction in low-Ca pyroxene; (2) dispersion of metal-sulfide blebs within silicates causing "darkening"; (3) incomplete impact melting wherein some relict chondrules survived; (4) vaporization of troilite, resulting in S2 bubbles that infused the melt; (5) formation of immiscible silicate and metal-sulfide melts; (6) shock-induced transportation of the metal-sulfide melt to distances >10 cm (7) partial resorption of relict chondrules and coarse silicate grains by the surrounding silicate melt; (8) crystallization of enstatite in the matrix and as overgrowths on relict silicate grains and relict chondrules; (9) crystallization of plagioclase from the melt; and (10) quenching of the vesicular silicate melt. The vesicular samples lost almost all of their metal during the shock event and were less susceptible to terrestrial weathering; in contrast, the samples in which the metal melt accumulated became severely weathered. Literature data indicate the meteorite fell ~23,000 yr ago; numerous secondary phases formed during weathering. Both impact melting and weathering altered the meteorite's bulk chemical composition: e.g., impact melting and loss of a metal-sulfide melt from NWA 2828 is responsible for bulk depletions in common siderophile elements and in Mn (from alabandite); weathering of oldhamite caused depletions in many rare earth elements; the growth of secondary phases caused enrichments in alkalis, Ga, As, Se, and Au.

  9. Chemical and mineralogical size segregation in the impact disruption of anhydrous stone meteorites

    SciTech Connect

    Flynn, G.J.; Durda, D.D.

    2005-02-02

    We performed impact disruption experiments on pieces from eight different anhydrous chondritic meteorites - four weathered ordinary chondrite finds from North Africa (NWA791, NWA620, NWA869 and MOR001), three almost unweathered ordinary chondrite falls (Mbale, Gao, and Saratov), and an almost unweathered carbonaceous chondrite fall (Allende). In each case the impactor was a small (1/8 or 1/4 in) aluminum sphere fired at the meteorite target at {approx} 5 km/s, comparable to the mean collision speed in the main-belt. Some of the {approx}5 to {approx} 150 {micro}m debris from each disruption was collected in aerogel capture cells, and the captured particles were analyzed by in situ synchrotron-based X-ray fluorescence. For each meteorite, many of the smallest particles (< 10 {micro}m up to 35 {micro}m in size, depending on the meteorite) exhibit very high Ni/Fe ratios compared to the Ni/Fe ratios measured in the larger particles (> 45 {micro}m), a composition consistent with the smallest debris being dominated by matrix material while the larger debris is dominated by fragments from olivine chondrules. These results may explain why the {approx} 10 {micro}m interplanetary dust particles (IDPs) collected from the Earth's stratosphere are C-rich and volatile-rich compared to the presumed solar nebula composition. The {approx} 10 {micro}m IDPs may simply sample the matrix of an inhomogeneous parent body, structurally and mineralogically similar to the chondritic meteorites, which are inhomogeneous assemblages of compact, strong, C- and volatile-poor chondrules that are distributed in a more porous, C- and volatile-rich matrix. In addition, these results may explain why the micrometeorites, which are {approx} 50 {micro}m to millimeters in size, recovered from the polar ices are Ni- and S-poor compared to chondritic meteorites, since these polar micrometeorites may preferentially sample fragments from the Ni- and S-poor olivine chondrules. These results indicate that the

  10. Shock remagnetization associated with meteorite impact at planetary surfaces

    NASA Technical Reports Server (NTRS)

    Wasilewski, P. J.

    1973-01-01

    The stages of a cratering event are considered together with four distinct magnetization volumes, taking into account the jetted material, the ejecta, the impact melt, and shock-compressed material which remains in situ. Shock classifications are discussed along with mineralogical aspects of shock remagnetization, the behavior of iron sulfides, defect cubic spinels, ilmenite-hematite series, the Fe-Ti-O system, alloys phases, and silicates. Remagnetization mechanisms considered include a first order reversible crystallographic transition in bcc iron-nickel, a second order Curie point transition in fcc iron-nickel, shock-induced anisotropy, and shock melting of iron containing silicates. Experimental results are reported together with a hypothetical crater model.

  11. Confirmation of a meteoritic component in impact-melt rocks of the Chesapeake Bay impact structure, Virginia, USA - Evidence from osmium isotopic and PGE systematics

    USGS Publications Warehouse

    Lee, S.R.; Horton, J.W.; Walker, R.J.

    2006-01-01

    The osmium isotope ratios and platinum-group element (PGE) concentrations of impact-melt rocks in the Chesapeake Bay impact structure were determined. The impact-melt rocks come from the cored part of a lower-crater section of suevitic crystalline-clast breccia in an 823 m scientific test hole over the central uplift at Cape Charles, Virginia. The 187Os/188Os ratios of impact-melt rocks range from 0.151 to 0.518. The rhenium and platinum-group element (PGE) concentrations of these rocks are 30-270?? higher than concentrations in basement gneiss, and together with the osmium isotopes indicate a substantial meteoritic component in some impact-melt rocks. Because the PGE abundances in the impact-melt rocks are dominated by the target materials, interelemental ratios of the impact-melt rocks are highly variable and nonchondritic. The chemical nature of the projectile for the Chesapeake Bay impact structure cannot be constrained at this time. Model mixing calculations between chondritic and crustal components suggest that most impact-melt rocks include a bulk meteoritic component of 0.01-0.1% by mass. Several impact-melt rocks with lowest initial 187Os/188Os ratios and the highest osmium concentrations could have been produced by additions of 0.1%-0.2% of a meteoritic component. In these samples, as much as 70% of the total Os may be of meteoritic origin. At the calculated proportions of a meteoritic component (0.01-0.1% by mass), no mixtures of the investigated target rocks and sediments can reproduce the observed PGE abundances of the impact-melt rocks, suggesting that other PGE enrichment processes operated along with the meteoritic contamination. Possible explanations are 1) participation of unsampled target materials with high PGE abundances in the impact-melt rocks, and 2) variable fractionations of PGE during syn- to post-impact events. ?? The Meteoritical Society, 2006.

  12. Early impact event and fluid activity on H chondrite parent body registered in the Pułtusk meteorite

    NASA Astrophysics Data System (ADS)

    Krzesinska, Agata

    2015-04-01

    Impact is one of the most important processes affecting asteroids, but it is neglected as a source for heat of these bodies. Recent modeling work show, however, that impact into warm planetesimals is able to cause global-scale temperature increase to the point of melting of silicates [1]. An obvious consequence of this fact is that the impact activity in early evolution of asteroids may promote formation of melt and its differentiation. H chondrites provide some lines of evidence for an early, 4.4 Ga impact event on their parent body. The event resulted in formation of heavily shocked and melted H chondrites with old gas retention ages [2, 3], including Portales Valley, an unique metal-rich breccia [e.g. 4]. The impact led also, very likely, to unmixing of silicate and metal-sulfide melts and to formation of silicate-iron non-magmatic IIE meteorites [5]. Additional evidence for this event, and for melting it caused, may come from highly equilibrated and recrystallized fragments of the Pułtusk meteorite containing vein-like metal accumulations [6]. In the Pułtusk, vein-like metal accumulations are kamacite-rich, and basically depleted in sulfides. They form many tendrils into the equilibrated, well recrystallized chondritic rock. Marked feature of the chondritic rock at the contact with accumulations is presence of unusually large phosphate and feldspar grains. The minerals bear record of crystallization from melt. Both vein-like metal accumulations and chondritic rock record, however, slow cooling rate. Phopshates are in the meteorite represented by merrillite and apatite, predominantly intergrown with each other. Merrillite poikilitically encloses silicate grains. It is probably of magmatic origin, since it contains detectable amount of potassium and high content of sodium. Apatite contains varying concentrations of chlorine, fluorine and missing structural component. Content of Cl and F are negatively correlated and both elements are heterogeneously distributed

  13. Origin of the Sudbury Complex by meteoritic impact: Neodymium isotopic evidence

    USGS Publications Warehouse

    Faggart, B.E.; Basu, A.R.; Tatsumoto, M.

    1985-01-01

    Samarium-neodymium isotopic data on whole rocks and minerals of the Sudbury Complex in Canada gave an igneous crystallization age of 1840 ?? 21 ?? 106 years. The initial epsilon neodymium values for 15 whole rocks are similar to those for average upper continental crust, falling on the crustal trend of neodymium isotopic evolution as defined by shales. The rare earth element concentration patterns of Sudbury rocks are also similar to upper crustal averages. These data suggest that the Sudbury Complex formed from melts generated in the upper crust and are consistent with a meteoritic impact.

  14. The Shaw meteorite - History of a chondrite consisting of impact-melted and metamorphic lithologies

    NASA Technical Reports Server (NTRS)

    Taylor, G. J.; Keil, K.; Berkley, J. L.; Lange, D. E.; Fodor, R. V.

    1979-01-01

    Three intermingled lithologies are identified in the Shaw L-group chondrite: a light-colored lithology with a poikilitic texture, consisting of olivine and augite crystals surrounded by larger orthopyroxene grains; a dark-colored lithology containing remnant chondrules and exhibiting a microgranular texture; and a gray lithology which appears to be intermediate between the other two. Contrary to published opinions, the Shaw meteorite contains normal L-group chondrite abundances of metal and troilite, though these phases are irregularly distributed. The lithological analyses suggest that 4.52 Byr ago an impact took place on the L-group chondrite parent object of Shaw.

  15. The 1993 Zimbabwe impact crater and meteorite expedition

    NASA Astrophysics Data System (ADS)

    Reimold, W. U.; Master, S.; Koeberl, C.; Robertson, D.

    1994-07-01

    In September 1993 our expedition visited four strucutres in Zimbabwe that had been selected because of circular outlines or because of unusual aeromagnetic anomalies. The first one, the 1.1-km-diameter Thuli structure was identified as a well-preserved volcanic caldera formed by a series of basaltic, gabbroic, and dioritic instrusions. Preliminary results of magnetic traverses are consistent with the model of a volcanic pipe. The 600- and 800-m-wide Save craters near the Mozambican border closely resemble young, well-preserved impact craters such as the Pretoria Saltpan crater in South Africa. However, detailed geological traverses revealed only volcanic rocks intruded into sandstone forming the sharp rim crests. The Mucheka region is the site of the most prominent aeromagnetic anomaly in Zimbabwe. In the absence of any exposures other than Archean basement, the cause of this anomaly is still unknown. None of the basement rock specimens obtained yielded any evidence for shock metamorphism. In 1985 German geologists reportedly noted a circular structure in the Highbury area on Landsat images. An approximately 25-km-wide circular structure is visible on a SPOT satellite image as well. The regional geological map revealed the presence of a slight elevation near the center of this otherwise flat area. The flat floor of this structure is formed by fertile soils overlying locally exposed Deweras arkose and metadolomites, in turn surrounded by hills of Lomagundi sandstones and slates. Near the geographical center a small hill of sandstone and quartzite was indeed detected. Reconnaissance sampling in 'rim' and 'central uplift' provided several specimens with significant numbers of quartz grains with single or multiple sets of planar deformation features (PDFs). A strongly hematized sample from the 'central uplift' contains shocked quartz and relics of glass.

  16. Systematic chemical variations in large 3AB iron meteorites: Clues to core crystallization

    NASA Technical Reports Server (NTRS)

    Haack, H.; Scott, E. R. D.; Rubio, G. S.; Gutierrez, D. F.; Lewis, C. F.; Wasson, J. T.; Brooks, R. R.; Guo, X.; Ryan, D. E.; Holzbecher, J.

    1993-01-01

    Analysis of numerous individual iron meteorites have shown that fractional crystallization of iron cores result in variations in chemical concentration of the solid core which span several orders of magnitude. The magnitude and direction of the resulting spatial gradients in the core can provide clues to the physical nature of the core crystallization process. We have analyzed suites of samples from three large 3AB irons (Cape York, 58t; Chupaderos, 24t; Morito, 10t) in order to estimate local chemical gradients. Initial results for the concentrations of Ge, Pd, Pt (Massey group), Ir, Au, As, Co, Os, and Rh (Dalhouse group), and P (Arizona group) show significant ranges among the Cape York and Chupaderos samples and marginally significant ranges among the Morito samples. Measurements of Au, Ir, Co, Ni, Cu, Ga, As, W, Re (from UCLA) and Ni and Co (Arizona group) are in progress. We find a spatial Ir gradient in Chupaderos with a magnitude similar to the one reported for Agpalilik (Cape York iron) by Esbensen et al.

  17. Meteorite impact ejecta: dependence of mass and energy lost on planetary escape velocity.

    PubMed

    O'keefe, J D; Ahrens, T J

    1977-12-23

    The calculated energy efficiency of mass ejection for iron and anorthosite objects striking an anorthosite planet at speeds of 5 to 45 kilometers per second decreases with increasing impact velocity at low escape velocities. At escape velocities of >10(5) and >2 x 10(4) centimeters per second, respectively, the slower impactors produce relatively less ejecta for a given impact energy. The impact velocities at which ejecta losses equal meteorite mass gains are found to be approximately 20, 35, and 45 kilometers per second for anorthosite objects and approximately 25, 35, and 40 kilometers per second for iron objects striking anorthosite surfaces for the gravity fields of the moon, Mercury, and Mars.

  18. A Review of Lunar Meteorite Impact-Melt Clast Compositions and Ages

    NASA Technical Reports Server (NTRS)

    Cohen, Barbara A.

    2008-01-01

    One of the important outstanding goals of lunar science is understanding the bombardment history of the Moon and calibrating the impact flux curve for extrapolation to the Earth and other terrestrial planets. Obtaining a sample from a carefully-characterized interior melt sheet or ring massif is a reliable way to tell a single crater's age. A different but complementary approach is to use extensive laboratory characterization (microscopic, geochemical, isotopic) of float samples to understand the integrated impact history of a region. Both approaches have their merits and limitations. In essence, the latter is the approach we have used to understand the impact history of the Feldspathic Highland Terrain (FHT) as told by lunar feldspathic meteorites.

  19. First finding of impact melt in the IIE Netschaëvo meteorite

    NASA Astrophysics Data System (ADS)

    Roosbroek, N.; Pittarello, L.; Greshake, A.; Debaille, V.; Claeys, P.

    2016-02-01

    About half of the IIE nonmagmatic iron meteorites contain silicate inclusions with a primitive to differentiated nature. The presence of preserved chondrules has been reported for two IIE meteorites so far, Netschaëvo and Mont Dieu, which represent the most primitive silicate material within this group. In this study, silicate inclusions from two samples of Netschaëvo were examined. Both silicate inclusions are characterized by a porphyritic texture dominated by clusters of coarse-grained olivine and pyroxene, set in a fine-grained groundmass that consists of new crystals of olivine and a glassy appearing matrix. This texture does not correspond to the description of the previously examined pieces of Netschaëvo, which consist of primitive chondrule-bearing angular clasts. Detailed petrographic observations and geochemical analyses suggest that the investigated samples of Netschaëvo consist of quenched impact melt. This implies that Netschaëvo is a breccia containing metamorphosed and impact-melt rock (IMR) clasts and that collisions played a major role in the formation of the IIE group.

  20. Meteorite crater impact study: a new way to study seismology at school with exciting experiments, and an example of meteorite astroblema in France (Rochechouart)

    NASA Astrophysics Data System (ADS)

    Carrer, Diane; Berenguer, Jean-Luc; MacMurray, Andrew

    2016-04-01

    The InSIGHT mission to Mars (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) supported by NASA, IPGP and CNES, is a great opportunity for teachers and pupils to study the Red planet, but also to study other fields of geology at school, such as seismology. With our pupils, we are following the InSight mission and we look forward to analyze seismic data registered by the SEIS seismometer , once it will be available (the InSight mission will launch in 2018 from California, and will land to Mars in 2018 or 2019). As this mission needs meteorite impacts to generate seismic waves ( to discover the Martian interior structure) , we've decided to model those meteorite strikes in the classroom. With our pupils, we've modeled meteorite impact craters with different impactors , such as tennis balls, baseballs, or pingpong balls, and used an analogue substratum made by flour and cocoa. Then, we kept on going our geophysical investigation , studying several parameters. For instance, we've studied the link between size of impactor and size of crater , the link between mass of impactor and Crater Formation, and the link between velocity of impactor and crater formation. In this geophysical approach , potential energy and kinetic energy can be introduced in terms of energy transfer as the impactor falls ( calculation of the velocity of impact and plotting that against crater diameter using v = (2gh)1/2). For each crater formation made in class by students, we have registered seismological data thanks to Audacity software, and study the seismic signal propagation. This exemple of hands-on activity with pupils, and its wide range of geophysical calculation shows how we can do simple experiment modeling meteorite crater impact and exploit registered seismological data at school. We've finaly focused our work with the very famous example of the astroblema of Rochechouart in the South-west of France ( crater formation : - 214 My) , in which it's easy to

  1. Siberian Meteorite Chelyabinsk

    NASA Astrophysics Data System (ADS)

    Marov, Mikhail Ya.

    On the February 15, 2013, in 9 (h) 20 (m) LT, a spectacular phenomenon - large meteorite fall - was observed over Chelyabinsk city in Siberia, Russia. Basically, this rather routine astronomical event (though largest for the recent one hundred years) attracted great attention because occurred in the well populated area and affected environment and people. The phenomenon has been well documented and numerous fragments of the fall collected, the largest one excavated from Chebarcul lake amounting 560 kg. The meteorite was called Chelyabinsk. It was observed as very bright bolide of 18 m in size which was exploded and mostly destroyed at the heights between 23 and 29 km and formed a powerful bow shock responsible for destructions when reaching the ground. Energy release at the explosion was estimated 300 to 500 Kt of TNT. The pieces collected brought evidence that Chelyabinsk is the stony meteorite classified as typical ordinary chondrite of LL type of the 5th petrological class. Morphology and isotopic composition of the meteorite’s matter allowed us to reconstruct its history and to conclude that it represents a fragment of much larger asteroid-type body of the age close to the solar system origin and experienced a number of collisions, including the very early one during the first 30 million years after formation, which resulted to melted phase in the structure of the main matrix. The study of meteorites gives us unique opportunity to penetrate deep in the fundamental cosmochemical aspects of the solar system origin and also provide unique information concerning the processes of its thermal and dynamical early evolution. The new data contribute to the study. Besides, Chelyabinsk meteorite fall brought new important evidence that Earth is vulnerable to space hazards and raised warning how to protect our planet from asteroid-comet impacts.

  2. Confirmation of a meteoritic component in impact-melt rocks of the Chesapeake Bay impact structure, Virginia, USA - Evidence from osmium isotopic and PGE systematics

    NASA Astrophysics Data System (ADS)

    Lee, Seung Ryeol; Horton, J. Wright; Walker, Richard J.

    2006-06-01

    The osmium isotope ratios and platinum-group element (PGE) concentrations of impact-melt rocks in the Chesapeake Bay impact structure were determined. The impact-melt rocks come from the cored part of a lower-crater section of suevitic crystalline-clast breccia in an 823 m scientific test hole over the central uplift at Cape Charles, Virginia. The 187Os/188Os ratios of impact-melt rocks range from 0.151 to 0.518. The rhenium and platinum-group element (PGE) concentrations of these rocks are 30-270× higher than concentrations in basement gneiss, and together with the osmium isotopes indicate a substantial meteoritic component in some impact-melt rocks. Because the PGE abundances in the impact-melt rocks are dominated by the target materials, interelemental ratios of the impact-melt rocks are highly variable and nonchondritic. The chemical nature of the projectile for the Chesapeake Bay impact structure cannot be constrained at this time. Model mixing calculations between chondritic and crustal components suggest that most impact-melt rocks include a bulk meteoritic component of 0.01-0.1% by mass. Several impact-melt rocks with lowest initial 187Os/188Os ratios and the highest osmium concentrations could have been produced by additions of 0.1%-0.2% of a meteoritic component. In these samples, as much as 70% of the total Os may be of meteoritic origin. At the calculated proportions of a meteoritic component (0.01-0.1% by mass), no mixtures of the investigated target rocks and sediments can reproduce the observed PGE abundances of the impact-melt rocks, suggesting that other PGE enrichment processes operated along with the meteoritic contamination. Possible explanations are 1) participation of unsampled target materials with high PGE abundances in the impact-melt rocks, and 2) variable fractionations of PGE during syn- to post-impact events.

  3. Silicon Carbide from the Canyon Diablo Meteorite and the Ewing Impact Structure

    NASA Astrophysics Data System (ADS)

    Leung, I. S.; Winston, R.; Abbott, D. H.

    2004-05-01

    One hundred years ago, Henri Moissan reported his discovery of silicon carbide (SiC) in the Canyon Diablo Meteorite. Since then, other researchers tried, but failed to replicate his findings. In our study of highly oxidized samples of the Canyon Diablo Meteorite, we found two carbon nodules, respectively 1 cm and 2 cm in size; the latter is no longer in the matrix which had disintegrated into rust. We found several SiC crystals in these nodules. Most of them show color zoning, planar deformation features (PDFs), black inclusions and black rims. The X-ray diffraction pattern of a 60-micron crystal showed a 6H polytype structure for the host in addition to a weak lattice, related to that of the host by a 2-degree rotation about the a-axis. We believe that the weak lattice was derived from the PDFs. We also report here the first find of SiC from deep sea sediments on the rim of the Ewing Impact Crater, located near the Equator at about 10 degrees east of the longitude of Hawaii. The SiC crystals also contain PDFs. An X-ray diffraction study showed 6H structure for the host, and 15R structure for the PDFs. Thus, 15R seems to be the high-pressure phase, a potentially useful marker for shock deformation events. Implications of our study are as follows. (1) Because all occurrences of terrestrial SiC are associated with kimberlites, SiC found at impact sites might have originated from space, or, by transformation of terrestrial materials by impact mechanisms. (2) The extreme sturdiness of SiC might enable it to resist alteration, long after other impact markers have decomposed. (3) Hence, SiC crystals, with or without PDFs, though small in size and few in number, might provide clues for deciphering possible relationships between impact events and global extinction of species.

  4. The mechanics of large meteoroid impacts in the earth's oceans

    NASA Technical Reports Server (NTRS)

    Melosh, H. J.

    1982-01-01

    The sequence of events subsequent to the impact of a large meteoroid in an ocean differs in several respects from an impact on land. Even if the meteoroid is large enough to produce a crater on the sea floor (that is, larger than a few km in diameter), the presence of water affects the character of the early-time events. The principal difference between land and oceanic impacts is the expansion of shock-vaporized water following an oceanic impact. A steam explosion follows the meteoroid's deposition of energy in the target. Shocked water expands from an initial pressure of 3 to 6 Mbar for 20-30 km/second impacts, ejecting water vapor and dust from the vaporized meteoroid several hundred km into the atmosphere. The violent vapor plume thus formed may explain how dust with a dominantly meteoritic composition can be dispersed to form a world-wide dust layer, as required by the Alvarez hypothesis.

  5. The resonant orbit of the Lost City meteorite

    NASA Technical Reports Server (NTRS)

    Williams, J. G.

    1975-01-01

    An integration of the long-period perturbations of Jupiter and Saturn on the orbit of the Lost City meteorite shows that the average nodal rate of the meteorite was nearly the same as the nodal rates of Jupiter and Saturn. This near equality of rates led to a large resonant variation in the inclination of the meteorite's orbit with a period on the order of 1 million years. The resonance makes the orbital evolution too sensitive to the deficiencies of the perturbation calculations and to the values of the elements at impact to allow definitive calculations. It is shown that an orbit similar to the meteorite's orbit can spend approximately 88% of its time with an eccentricity too small to allow for intersections with the earth's orbit. The ordinary cosmic ray exposure age of the Lost City meteorite does not suggest that its collisional lifetime was unusual, but the role of resonances in determining the lifetime of typical meteorites is unknown.

  6. Large spinel grains in a CM chondrite (Acfer 331): Implications for reconstructions of ancient meteorite fluxes

    NASA Astrophysics Data System (ADS)

    BjäRnborg, Karolina; Schmitz, Birger

    2013-02-01

    By dissolving 30-400 kg of marine limestone in HCl and HF acid, our group has previously recovered common relict chromite grains (approximately 63-250 μm) from ordinary chondritic micrometeorites that fell on ancient sea floors, up to 500 Myr old. Here, we evaluate if CM group carbonaceous chondritic material, which makes up an important fraction of the micrometeorite flux today, contains analogous grains that can be searched for in acid residues. We dissolved 8 g of CM2 meteorite Acfer 331 in HF, which yielded a characteristic assemblage of both transparent Mg-Al- and opaque Cr-spinels >28 μm. We find on average 4.6 and 130 Mg-Al-spinel grains per gram in the 63-250 and 28-63 μm size fractions, respectively. These grains are mostly pink or colorless, and often characterized by heterogeneous Cr-content. Black, opaque Cr-spinel grains are absent from the >63 μm fraction, but in the 28-63 μm fraction we find approximately 65 such grains per gram meteorite. The individual grains have a characteristic composition, with heterogeneous major element compositions (e.g., 44.4-61.7 wt% Cr2O3), but narrow ranges for maximum TiO2 (0.6-1.6 wt%) and V2O3 (0.5-1.0 wt%) concentrations. The content of spinel grains in the 28-63 μm fraction of CM meteorites appears comparable at the order of magnitude level with the content of >63 μm sized chromite grains in fossil L-chondrites from Ordovician limestone. Our approach of recovering meteoritic spinel from sediment may thus be extended to include CM meteorites, but the smaller size fraction of the acid residues should be searched.

  7. Turkish meteor surveillance systems and network: Impact craters and meteorites database

    NASA Astrophysics Data System (ADS)

    Unsalan, O.; Ozel, M. E.; Derman, I. E.; Terzioglu, Z.; Kaygisiz, E.; Temel, T.; Topoyan, D.; Solmaz, A.; Yilmaz Kocahan, O.; Esenoglu, H. H.; Emrahoglu, N.; Yilmaz, A.; Yalcinkaya, B. O.

    2014-07-01

    In our project, we aim toward constructing Turkish Meteor Surveillance Systems and Network in Turkey. For this goal, video observational systems from SonotaCo (Japan) were chosen. Meteors are going to be observed with the specific cameras, their orbits will be calculated by the software from SonotaCo, and the places where they will be falling / impacting will be examined by field trips. The collected meteorites will be investigated by IR-Raman Spectroscopic techniques and SEM-EDX analyses in order to setup a database. On the other hand, according to our Prime Ministry Ottoman Archives, there are huge amounts of reports of falls for the past centuries. In order to treat these data properly, it is obvious that processing systems should be constructed and developed.

  8. Iridium Concentrations and Abundances of Meteoritic Ejecta from the Eltanin Impact in Sediment Cores from Polarstern Expedition ANT XII/4

    NASA Technical Reports Server (NTRS)

    Kyte, Frank T.

    2002-01-01

    The abundances of meteoritic ejecta from the Eltanin asteroid impact have been examined in several sediment cores recovered by the FS Polarstern during expedition ANT XII/4 using elemental concentrations of iridium and weights of coarse ejecta debris. Three cores with well-preserved impact deposits, PS204-1, PS2708-1, and PS2709-1, each contain Ir and ejecta fluences similar to those found in USNS Eltanin core E13-4. Small Ir anomalies and traces of ejecta were found in cores PS2706-1 and PS2710-1, but since these cores lack well-defined deposits, these are considered to be reworked and not representative of the fallout. No evidence of ejecta was found in cores PS2802-1 and PS2705-1. These results confirm earlier speculation that the Eltanin impact resulted in deposits of ejecta with up to 1 gram/sq centimeter of depris over a wide area of the ocean floor. However, there are sill large uncertainties over the actual regional or global extent of this unique sediment deposit.

  9. Iridium Concentrations and Abundances of Meteoritic Ejecta from the Eltanin Impact in Sediment Cores from Polarstern Expedition ANT XII/4

    NASA Technical Reports Server (NTRS)

    Kyte, Frank T.

    2002-01-01

    The abundances of meteoritic ejecta from the Eltanin asteroid impact have been examined in several sediment cores recovered by the FS Polarstern during expedition ANT XII/4 using elemental concentrations of iridium and weights of coarse ejecta debris. Three cores with well-preserved impact deposits, PS204-1, PS2708-1, and PS2709-1, each contain Ir and ejecta fluences similar to those found in USNS Eltanin core E13-4. Small Ir anomalies and traces of ejecta were found in cores PS2706-1 and PS2710-1, but since these cores lack well-defined deposits, these are considered to be reworked and not representative of the fallout. No evidence of ejecta was found in cores PS2802-1 and PS2705-1. These results confirm earlier speculation that the Eltanin impact resulted in deposits of ejecta with up to 1 gram/sq centimeter of depris over a wide area of the ocean floor. However, there are sill large uncertainties over the actual regional or global extent of this unique sediment deposit.

  10. Health impacts of large dams

    SciTech Connect

    Lerer, L.B.; Scudder, T.

    1999-03-01

    Large dams have been criticized because of their negative environmental and social impacts. Public health interest largely has focused on vector-borne diseases, such as schistosomiasis, associated with reservoirs and irrigation projects. Large dams also influence health through changes in water and food security, increases in communicable diseases, and the social disruption caused by construction and involuntary resettlement. Communities living in close proximity to large dams often do not benefit from water transfer and electricity generation revenues. A comprehensive health component is required in environmental and social impact assessments for large dam projects.

  11. Meteorites on Mars

    NASA Technical Reports Server (NTRS)

    Flynn, G. J.; Mckay, D. S.

    1988-01-01

    Four types of meteoritic material should be found on Mars: (1) micrometeorites, many of which will survive atmospheric entry unmelted, which should fall relatively uniformly over the planet's surface, (2) ablation products from larger meteorites which ablate, break up and burn up in the Mars atmosphere, (3) debris from large, crater forming objects, which, by analogy to terrestrial and lunar impact events, will be concentrated in the crater ejecta blankets (except for rare, large events, such as the proposed C-T event on earth, which can distribute debris on a planetary scale), and (4) debris from the early, intense bombardment, which, in many areas of the planet, may now be incorporated into rocks by geologic processes subsequent to the intense bombardment era. To estimate the extent of meteoritic addition to indigenous Martian material, the meteoritic flux on Mars must be known. It is estimated that the overall flux is twice that for the Moon and 1.33 that for Earth. For small particles, whose orbital evolution is dominated by Poynting Robertson drag, the flux at Mars can be estimated from the Earth flux. The smaller Martian gravitational enhancement as well as the decrease in the spatial density of interplanetary dust with increasing heliocentric distance should reduce the flux of small particles at Mars to about 0.33 times the flux at Earth. Because of the smaller planetary cross-section the total infalling mass at Mars is then estimated to be 0.09 time the infalling mass in the micrometeorite size range at Earth.

  12. Impact of prebiotic synthesis and diagenesis on the distribution, stereochemistry, and stable isotope composition of amino acids in carbonaceous meteorites

    NASA Astrophysics Data System (ADS)

    Engel, Michael H.

    2013-09-01

    Simulation experiments for prebiotic synthesis result in racemic mixtures (D/L = 1.0) for protein and non-protein amino acids, irrespective of the composition of the precursor gas mixtures or the energy sources employed. It is therefore not surprising that it was commonly assumed that if amino acids in carbonaceous meteorites were formed by similar reactions they would also be racemic. Engel and Nagy1 and more recently Glavin et al.2 have shown that protein amino acids in carbonaceous meteorites often exhibit a moderate to strong L-amino acid excess (D/L ˂ 1.0). Engel3 hypothesized that this extraterrestrial L-excess might be the precursor material from which life as we know it originated. Stable isotope analysese.g 4 confirmed that the L-amino acid excess in meteorites was indigenous rather than the result of contamination subsequent to impact on Earth. A key question that arises is that since there are no known mechanisms for the direct prebiotic synthesis of amino acids with an L-enantiomer excess, how did these compounds come to exist in carbonaceous meteorites? It has been proposed5 and references therein that a series of diagenetic reactions subsequent to synthesis are responsible for the L-enantiomer excess. In this paper, this hypothesis is further explored with respect to explaining the range of D/L values for amino acids in the various types of carbonaceous meteorites as well as in different stones of the same meteorite. Possible effects of diagenesis on the stable isotope compositions of these compounds are also addressed.

  13. Compositions of large metal nodules in mesosiderites - Links to iron meteorite group IIIAB and the origin of mesosiderite subgroups

    NASA Technical Reports Server (NTRS)

    Hassanzadeh, Jamshid; Rubin, Alan E.; Wasson, John T.

    1990-01-01

    The compositions of large metal nodules in 12 mesosiderites, ranging from 3 mm to 4 cm in minimum dimensions and from 10 to 200 mg/g in silicate content, were analyzed by neutron activation; also analyzed were two additional samples (Pennyweight Point and Murchison Downs) which were originally designated iron meteorites but were later classified as Mes nodules. It was found that mesosiderites subgroups classified on the basis of metal composition are virtually the same as those based on silicate composition. The general covariation of the silicate and the metal compositional characteristics suggests that these features were established in the same process or in linked processes. A mesosiderite formation model is proposed.

  14. End-Cretaceous extinction in Antarctica linked to both Deccan volcanism and meteorite impact via climate change

    PubMed Central

    Petersen, Sierra V.; Dutton, Andrea; Lohmann, Kyger C.

    2016-01-01

    The cause of the end-Cretaceous (KPg) mass extinction is still debated due to difficulty separating the influences of two closely timed potential causal events: eruption of the Deccan Traps volcanic province and impact of the Chicxulub meteorite. Here we combine published extinction patterns with a new clumped isotope temperature record from a hiatus-free, expanded KPg boundary section from Seymour Island, Antarctica. We document a 7.8±3.3 °C warming synchronous with the onset of Deccan Traps volcanism and a second, smaller warming at the time of meteorite impact. Local warming may have been amplified due to simultaneous disappearance of continental or sea ice. Intra-shell variability indicates a possible reduction in seasonality after Deccan eruptions began, continuing through the meteorite event. Species extinction at Seymour Island occurred in two pulses that coincide with the two observed warming events, directly linking the end-Cretaceous extinction at this site to both volcanic and meteorite events via climate change. PMID:27377632

  15. The Impact and Oxidation Survival of Selected Meteoritic Compounds: Signatures of Asteroid Organic Material on Planetary Surfaces

    NASA Technical Reports Server (NTRS)

    Cooper, George; Horz, Fred; Oleary, Alanna; Chang, Sherwood

    2013-01-01

    Polar, non-volatile organic compounds may be present on the surfaces (or near surfaces) of multiple Solar System bodies. If found, by current or future missions, it would be desirable to determine the origin(s) of such compounds, e.g., asteroidal or in situ. To test the possible survival of meteoritic compounds both during impacts with planetary surfaces and under subsequent (possibly) harsh ambient conditions, we subjected known meteoritic compounds to relatively high impact-shock pressures and/or to varying oxidizing/corrosive conditions. Tested compounds include sulfonic and phosphonic acids (S&P), polyaromatic hydrocarbons (PAHs) amino acids, keto acids, dicarboxylic acids, deoxy sugar acids, and hydroxy tricarboxylic acids (Table 1). Meteoritic sulfonic acids were found to be relatively abundant in the Murchison meteorite and to possess unusual S-33 isotope anomalies (non mass-dependent isotope fractionations). Combined with distinctive C-S and C-P bonds, the S&P are potential signatures of asteroidal organic material.

  16. End-Cretaceous extinction in Antarctica linked to both Deccan volcanism and meteorite impact via climate change.

    PubMed

    Petersen, Sierra V; Dutton, Andrea; Lohmann, Kyger C

    2016-07-05

    The cause of the end-Cretaceous (KPg) mass extinction is still debated due to difficulty separating the influences of two closely timed potential causal events: eruption of the Deccan Traps volcanic province and impact of the Chicxulub meteorite. Here we combine published extinction patterns with a new clumped isotope temperature record from a hiatus-free, expanded KPg boundary section from Seymour Island, Antarctica. We document a 7.8±3.3 °C warming synchronous with the onset of Deccan Traps volcanism and a second, smaller warming at the time of meteorite impact. Local warming may have been amplified due to simultaneous disappearance of continental or sea ice. Intra-shell variability indicates a possible reduction in seasonality after Deccan eruptions began, continuing through the meteorite event. Species extinction at Seymour Island occurred in two pulses that coincide with the two observed warming events, directly linking the end-Cretaceous extinction at this site to both volcanic and meteorite events via climate change.

  17. End-Cretaceous extinction in Antarctica linked to both Deccan volcanism and meteorite impact via climate change

    NASA Astrophysics Data System (ADS)

    Petersen, Sierra V.; Dutton, Andrea; Lohmann, Kyger C.

    2016-07-01

    The cause of the end-Cretaceous (KPg) mass extinction is still debated due to difficulty separating the influences of two closely timed potential causal events: eruption of the Deccan Traps volcanic province and impact of the Chicxulub meteorite. Here we combine published extinction patterns with a new clumped isotope temperature record from a hiatus-free, expanded KPg boundary section from Seymour Island, Antarctica. We document a 7.8+/-3.3 °C warming synchronous with the onset of Deccan Traps volcanism and a second, smaller warming at the time of meteorite impact. Local warming may have been amplified due to simultaneous disappearance of continental or sea ice. Intra-shell variability indicates a possible reduction in seasonality after Deccan eruptions began, continuing through the meteorite event. Species extinction at Seymour Island occurred in two pulses that coincide with the two observed warming events, directly linking the end-Cretaceous extinction at this site to both volcanic and meteorite events via climate change.

  18. Excess of L-Alanine in Amino Acids Synthesized in a Plasma Torch Generated by a Hypervelocity Meteorite Impact Reproduced in the Laboratory

    NASA Technical Reports Server (NTRS)

    Managadze, George G.; Engle, Michael H.; Getty, Stephanie A.; Wurz, Peter; Brinckerhoff, William B.; Shokolov, Anatoly; Sholin, Gennady; Terent'ev, Sergey A.; Chumikov, Alexander E.; Skalkin, Alexander S

    2016-01-01

    We present a laboratory reproduction of hypervelocity impacts of a carbon containing meteorite on a mineral substance representative of planetary surfaces. The physical conditions of the resulting impact plasma torch provide favorable conditions for abiogenic synthesis of protein amino acids: We identified glycine and alanine, and in smaller quantities serine, in the produced material. Moreover, we observe breaking of alanine mirror symmetry with L excess, which coincides with the bioorganic world. Therefore the selection of L-amino acids for the formation of proteins for living matter could have been the result from plasma processes occurring during the impact meteorites on the surface. This indicates that the plasma torch from meteorite impacts could play an important role in the formation of biomolecular homochirality. Thus, meteorite impacts possibly were the initial stage of this process and promoted conditions for the emergence of a living matter.

  19. Excess of L-alanine in amino acids synthesized in a plasma torch generated by a hypervelocity meteorite impact reproduced in the laboratory

    NASA Astrophysics Data System (ADS)

    Managadze, George G.; Engel, Michael H.; Getty, Stephanie; Wurz, Peter; Brinckerhoff, William B.; Shokolov, Anatoly G.; Sholin, Gennady V.; Terent'ev, Sergey A.; Chumikov, Alexander E.; Skalkin, Alexander S.; Blank, Vladimir D.; Prokhorov, Vyacheslav M.; Managadze, Nina G.; Luchnikov, Konstantin A.

    2016-10-01

    We present a laboratory reproduction of hypervelocity impacts of a carbon containing meteorite on a mineral substance representative of planetary surfaces. The physical conditions of the resulting impact plasma torch provide favorable conditions for abiogenic synthesis of protein amino acids: We identified glycine and alanine, and in smaller quantities serine, in the produced material. Moreover, we observe breaking of alanine mirror symmetry with L excess, which coincides with the bioorganic world. Therefore the selection of L-amino acids for the formation of proteins for living matter could have been the result from plasma processes occurring during the impact meteorites on the surface. This indicates that the plasma torch from meteorite impacts could play an important role in the formation of biomolecular homochirality. Thus, meteorite impacts possibly were the initial stage of this process and promoted conditions for the emergence of a living matter.

  20. Jadeite in Chelyabinsk meteorite and the nature of an impact event on its parent body

    PubMed Central

    Ozawa, Shin; Miyahara, Masaaki; Ohtani, Eiji; Koroleva, Olga N.; Ito, Yoshinori; Litasov, Konstantin D.; Pokhilenko, Nikolay P.

    2014-01-01

    The Chelyabinsk asteroid impact is the second largest asteroid airburst in our recorded history. To prepare for a potential threat from asteroid impacts, it is important to understand the nature and formational history of Near-Earth Objects (NEOs) like Chelyabinsk asteroid. In orbital evolution of an asteroid, collision with other asteroids is a key process. Here, we show the existence of a high-pressure mineral jadeite in shock-melt veins of Chelyabinsk meteorite. Based on the mineral assemblage and calculated solidification time of the shock-melt veins, the equilibrium shock pressure and its duration were estimated to be at least 3–12 GPa and longer than 70 ms, respectively. This suggests that an impactor larger than 0.15–0.19 km in diameter collided with the Chelyabinsk parent body at a speed of at least 0.4–1.5 km/s. This impact might have separated the Chelyabinsk asteroid from its parent body and delivered it to the Earth. PMID:24852082

  1. Jadeite in Chelyabinsk meteorite and the nature of an impact event on its parent body.

    PubMed

    Ozawa, Shin; Miyahara, Masaaki; Ohtani, Eiji; Koroleva, Olga N; Ito, Yoshinori; Litasov, Konstantin D; Pokhilenko, Nikolay P

    2014-05-22

    The Chelyabinsk asteroid impact is the second largest asteroid airburst in our recorded history. To prepare for a potential threat from asteroid impacts, it is important to understand the nature and formational history of Near-Earth Objects (NEOs) like Chelyabinsk asteroid. In orbital evolution of an asteroid, collision with other asteroids is a key process. Here, we show the existence of a high-pressure mineral jadeite in shock-melt veins of Chelyabinsk meteorite. Based on the mineral assemblage and calculated solidification time of the shock-melt veins, the equilibrium shock pressure and its duration were estimated to be at least 3-12 GPa and longer than 70 ms, respectively. This suggests that an impactor larger than 0.15-0.19 km in diameter collided with the Chelyabinsk parent body at a speed of at least 0.4-1.5 km/s. This impact might have separated the Chelyabinsk asteroid from its parent body and delivered it to the Earth.

  2. Mechanical properties of several Fe-Ni meteorites

    SciTech Connect

    Mulford, Roberta N; El - Dasher, Bassem

    2010-10-28

    The strength and elastic constants of meteorites are of increasing interest as predictions of meteorite impacts on earth come within the realm of possibility. In addition, meteorite impacts on extraterrestrial bodies provide an excellent sampling tool for evaluation of planetary compositions and properties. Fe-Ni meteorites provide a well-defined group of materials of fairly uniform composition. Iron-nickel meteorites exhibit a unique lamellar microstructure, a Widmanstatten structure, consisting of small regions with steep-iron-nickel composition gradients. This microstructure is found in the Fe-Ni system only in meteorites, and is believed to arise as a result of slow cooling in a planetary core or other large mass. Meteorites with compositions consisting of between 5 and 17% nickel in iron are termed 'octahedrite,' and further characterized according to the width of the Ni-poor kamacite bands; 'fine,' (0.2-0.5 mm) 'medium,' (0.5-1.3 mm) and 'coarse,' (1.5-3.3 mm). Many meteorites have inclusions and structures indicating that the material has been shocked at some point early in its evolution. Several Iron-nickel meteorites have been examined using Vickers and spherical indentation, x-ray fluorescence, and EBSD. Direct observation of mechanical properties in these highly structured materials provides a valuable supplement to bulk measurements, which frequently exhibit large variation in dynamic properties, even within a single sample. Previous studies of the mechanical properties of a typical iron-nickel meteorite, a Diablo Canyon specimen, indicated that the strength of the composite was higher by almost an order of magnitude than values obtained from laboratory-prepared specimens. Additional meteorite specimens have been examined to establish a range of error on the previously measured yield, to determine the extent to which deformation upon re-entry contributes to yield, and to establish the degree to which the strength varies as a function of microstructure.

  3. The 45th Annual Meteoritical Society Meeting

    NASA Technical Reports Server (NTRS)

    Jones, P. (Compiler); Turner, L. (Compiler)

    1982-01-01

    Impact craters and shock effects, chondrite formation and evolution, meteorites, chondrules, irons, nebular processes and meteorite parent bodies, regoliths and breccias, antarctic meteorite curation, isotopic studies of meteorites and lunar samples, organics and terrestrial weathering, refractory inclusions, cosmic dust, particle irradiations before and after compaction, and mineralogic studies and analytical techniques are discussed.

  4. Are large time differences in meteorite formation real. [cosmochronological dating and nucleosynthetic ratios

    NASA Technical Reports Server (NTRS)

    Cameron, A. G. W.

    1973-01-01

    Considerations are given concerning the interpretation of the results of two types of cosmochronological dating in order to examine the validity of the conclusions inferred from these results that the time intervals between the formation of various meteorite samples are very great. It is theorized that the isotopic differences between Angra dos Reis and other basaltic achondrites may be due to real fluctuations between the relative abundances of s-process and r-process nucleosynthesis products at a level delta about 0.001.

  5. Comparison of Os and Cr Isotopic Methods for the Detection of Meteoritic Components in Impact Melt Rocks from the Morokweng and Vredefort Impact Structures, South Africa

    NASA Technical Reports Server (NTRS)

    Koeberl, Christian; Peucker-Ehrenbrink, Bernhard; Reimold, Wolf Uwe; Shukolyukov, Alex; Lugmair, Guenter W.

    2000-01-01

    The verification of an extraterrestrial component in impact-derived melt rocks or breccias can be of diagnostic value to provide confirming evidence for an impact origin of a geological structure. Geochemical methods are used to determine the presence of the traces of such a component. In the absence of actual meteorite fragments, it is necessary to search for traces of meteoritic material that is mixed in with the target rocks in breccias and melt rocks. Meteoritic components have been identified for just over 40 impact structures (out of more than 160 known on Earth), which reflects also the detail in which these structures were studied. The identification of a meteoritic component can be achieved by determining the concentrations and interelement ratios of siderophile elements, especially the platinum group elements (PGE), which are several orders of magnitude more abundant in meteorites than in terrestrial upper crustal rocks. The usage of platinum group element abundances and ratios avoids some of the ambiguities that may result if only common siderophile elements (e.g., Cr, Co, Ni) are considered. However, problems may arise if the target rocks have high abundances of siderophile elements, or if the siderophile element concentrations in the impactites are very low. In such cases, the Os and Cr isotopic systems have recently been used for establishing the presence of a meteoritic component in a number of impact melt rocks and breccias. In the past it was attempted to use PGE data to determine the type or class of meteorite for the impactor, but these attempts were not always successful. It is difficult to decide between chondrite types based on PGE abundances, which has led to conflicting identifications for a number of impact structures. Clearly, the identification of a meteoritic component in impactites is not a trivial problem. In this study, we are using a combination of trace element (PGE) analyses and the results from both, Os and Cr isotopic studies, to

  6. Comparison of Os and Cr Isotopic Methods for the Detection of Meteoritic Components in Impact Melt Rocks from the Morokweng and Vredefort Impact Structures, South Africa

    NASA Technical Reports Server (NTRS)

    Koeberl, Christian; Peucker-Ehrenbrink, Bernhard; Reimold, Wolf Uwe; Shukolyukov, Alex; Lugmair, Guenter W.

    2000-01-01

    The verification of an extraterrestrial component in impact-derived melt rocks or breccias can be of diagnostic value to provide confirming evidence for an impact origin of a geological structure. Geochemical methods are used to determine the presence of the traces of such a component. In the absence of actual meteorite fragments, it is necessary to search for traces of meteoritic material that is mixed in with the target rocks in breccias and melt rocks. Meteoritic components have been identified for just over 40 impact structures (out of more than 160 known on Earth), which reflects also the detail in which these structures were studied. The identification of a meteoritic component can be achieved by determining the concentrations and interelement ratios of siderophile elements, especially the platinum group elements (PGE), which are several orders of magnitude more abundant in meteorites than in terrestrial upper crustal rocks. The usage of platinum group element abundances and ratios avoids some of the ambiguities that may result if only common siderophile elements (e.g., Cr, Co, Ni) are considered. However, problems may arise if the target rocks have high abundances of siderophile elements, or if the siderophile element concentrations in the impactites are very low. In such cases, the Os and Cr isotopic systems have recently been used for establishing the presence of a meteoritic component in a number of impact melt rocks and breccias. In the past it was attempted to use PGE data to determine the type or class of meteorite for the impactor, but these attempts were not always successful. It is difficult to decide between chondrite types based on PGE abundances, which has led to conflicting identifications for a number of impact structures. Clearly, the identification of a meteoritic component in impactites is not a trivial problem. In this study, we are using a combination of trace element (PGE) analyses and the results from both, Os and Cr isotopic studies, to

  7. Impact history of the Chelyabinsk meteorite: Electron microprobe and LA-ICP-MS study of sulfides and metals

    NASA Astrophysics Data System (ADS)

    Andronikov, A. V.; Andronikova, I. E.; Hill, D. H.

    2015-12-01

    Electron microprobe and LA-ICP-MS study of sulfides and metals from two fragments of the LL5 Chelyabinsk meteorite were conducted. The fragments are impact breccias, one fragment contains both chondritic and shock vein lithologies, and the other contains shock-darkened chondritic clasts and vesicular impact melts. The chondritic lithology and shock veins display very similar opaque mineral compositions. The mineral compositions in the impact-melt breccias are distinctly different. The brecciated state of the Chelyabinsk meteorite suggests strong involvement of shock-related processes during the evolution of the parent body. Multiple heavy impact events occurred on the parent asteroid and on the Chelyabinsk meteoroid itself over the time period from ca. 4.5 Ga until ca. 1.2 Ma. The shock veins were produced in situ on the parent body. The impact-melt breccias could have formed because of the dramatic impact to the parent LL-chondrite body that could be partly disintegrated. The fragment containing shock-darkened chondritic clasts and vesicular impact melt lithologies preserves a record of melting, volatilization, partial degassing, and quenching of the molten material. The abundance and size (up to 1 mm) of the vesicles suggest that the impact melt must have been buried at some depth after formation. After impact and subsequent melting occurred, the impact-induced pressure on the shallow asteroid interior was released that caused "boiling" of volatiles and generation of S-rich bubbles. Such an impact excavated down to depths of the body generating multiple fragments with complicated histories. These fragments reaccumulated into a gravitational aggregate and formed the parental meteoroid for the Chelyabinsk meteorite.

  8. Large enantiomeric excesses in primitive meteorites and the diverse effects of water in cosmochemical evolution

    PubMed Central

    Pizzarello, Sandra; Schrader, Devin L.; Monroe, Adam A.; Lauretta, Dante S.

    2012-01-01

    Carbonaceous chondrites are meteoritic fragments of asteroids that avoided the geological reprocessing of larger planets and allow laboratory probing of early solar-nebula materials. Among these, Renazzo-type (CR) chondrites found in Antarctica appear remarkably pristine and are distinguished by abundant organic materials and water-soluble molecules such as amino acids and ammonia. We present a comprehensive analysis of the organic composition of selected CR meteorites of different petrographic classification and compare compounds’ abundance and distribution as they may relate to asteroidal aqueous processing and concomitant evolution of the mineral phases. We found that several CR compounds such as amino acids and sugar alcohols are fully represented in stones with no or minimal water exposure indicating a formation that, if solar, preceded parent body processes. The most pristine CRs also revealed natal enantiomeric excesses (ee) of up to 60%, much larger than ever recorded. However, aqueous alteration appears to affect CR soluble organic composition and abundances, in particular some diastereomeric amino acids may gauge its extent by the consequent racemization of their ee. PMID:22778439

  9. Large enantiomeric excesses in primitive meteorites and the diverse effects of water in cosmochemical evolution.

    PubMed

    Pizzarello, Sandra; Schrader, Devin L; Monroe, Adam A; Lauretta, Dante S

    2012-07-24

    Carbonaceous chondrites are meteoritic fragments of asteroids that avoided the geological reprocessing of larger planets and allow laboratory probing of early solar-nebula materials. Among these, Renazzo-type (CR) chondrites found in Antarctica appear remarkably pristine and are distinguished by abundant organic materials and water-soluble molecules such as amino acids and ammonia. We present a comprehensive analysis of the organic composition of selected CR meteorites of different petrographic classification and compare compounds' abundance and distribution as they may relate to asteroidal aqueous processing and concomitant evolution of the mineral phases. We found that several CR compounds such as amino acids and sugar alcohols are fully represented in stones with no or minimal water exposure indicating a formation that, if solar, preceded parent body processes. The most pristine CRs also revealed natal enantiomeric excesses (ee) of up to 60%, much larger than ever recorded. However, aqueous alteration appears to affect CR soluble organic composition and abundances, in particular some diastereomeric amino acids may gauge its extent by the consequent racemization of their ee.

  10. Large thallium isotopic variations in iron meteorites and evidence for lead-205 in the early solar system

    NASA Astrophysics Data System (ADS)

    Nielsen, Sune G.; Rehkämper, Mark; Halliday, Alex N.

    2006-05-01

    Lead-205 decays to 205Tl with a half-life of 15 Myr and should have been present in the early solar system according to astrophysical models. However, despite numerous attempts, Tl isotopic measurements of meteorites have been unable to demonstrate convincingly its former presence. Here, we report large (˜5‰) variations in Tl isotope composition in metal and troilite fragments from a range of iron meteorites that were determined at high precision using multiple collector inductively coupled plasma mass spectrometry. The Tl isotopic compositions of seven metal samples of the IAB iron meteorites Toluca and Canyon Diablo define a correlation with 204Pb/ 203Tl. When interpreted as an isochron, this corresponds to an initial 205Pb/ 204Pb ratio of (7.4 ± 1.0) × 10 -5. Alternative explanations for the correlation, such as mixing of variably mass-fractionated meteorite components or terrestrial contamination are harder to reconcile with independent constraints. However, troilite nodules from Toluca and Canyon Diablo contain Tl that is significantly less radiogenic than co-existing metal with isotope compositions that are variable and decoupled from 204Pb/ 203Tl. These effects are similar to those recently reported by others for Fe and Ni isotopes in iron meteorite sulfides and appear to be the result of kinetic stable isotope fractionation during diffusion. Though it cannot conclusively be shown that the metal fragments are unaffected by the secondary processes that disturbed the troilites, mass balance modeling indicates that the alteration of the troilites is unlikely to have significantly affected the Tl isotope compositions of the co-existing metals. It is therefore reasonable to conclude that the IAB metal isochron is a product of the in situ decay of 205Pb. If the I-Xe ages of IAB silicate inclusions record the same event as the 205Pb- 205Tl chronometer then crystallization of the IAB metal was probably completed between 10 and 20 Myr after the condensation of

  11. Metal/sulfide-silicate intergrowth textures in EL3 meteorites: Origin by impact melting on the EL parent body

    NASA Astrophysics Data System (ADS)

    van Niekerk, Deon; Keil, Klaus

    2011-10-01

    We document the petrographic setting and textures of Fe,Ni metal, the mineralogy of metallic assemblages, and the modal mineral abundances in the EL3 meteorites Asuka (A-) 881314, A-882067, Allan Hills 85119, Elephant Moraine (EET) 90299/EET 90992, LaPaz Icefield 03930, MacAlpine Hills (MAC) 02635, MAC 02837/MAC 02839, MAC 88136, Northwest Africa (NWA) 3132, Pecora Escarpment 91020, Queen Alexandra Range (QUE) 93351/QUE 94321, QUE 94594, and higher petrologic type ELs Dar al Gani 1031 (EL4), Sayh al Uhaymir 188 (EL4), MAC 02747 (EL4), QUE 94368 (EL4), and NWA 1222 (EL5). Large metal assemblages (often containing schreibersite and graphite) only occur outside chondrules and are usually intergrown with silicate minerals (euhedral to subhedral enstatite, silica, and feldspar). Sulfides (troilite, daubréelite, and keilite) are also sometimes intergrown with silicates. Numerous authors have shown that metal in enstatite chondrites that are interpreted to have been impact melted contains euhedral crystals of enstatite. We argue that the metal/sulfide-silicate intergrowths in the ELs we studied were also formed during impact melting and that metal in EL3s thus does not retain primitive (i.e., nebular) textures. Likewise, the EL4s are also impact-melt breccias. Modal abundances of metal in the EL3s and EL4s range from approximately 7 to 30 wt%. These abundances overlap or exceed those of EL6s, and this is consistent either with pre-existing heterogeneity in the parent body or with redistribution of metal during impact processes.

  12. Osmium isotope and highly siderophile element constraints on ages and nature of meteoritic components in ancient lunar impact rocks

    NASA Astrophysics Data System (ADS)

    Fischer-Gödde, Mario; Becker, Harry

    2012-01-01

    The concentrations of highly siderophile elements (HSE: Re, Os, Ir, Ru, Pt, Rh, Pd, Au) and 187Os/188Os isotope compositions have been determined for 67 subsamples of six lunar impact rocks from the Apollo 14, 16 and 17 landing sites, and the lunar meteorite Dar al Gani (DaG) 400 using inductively coupled plasma mass spectrometry (ICP-MS) and negative thermal ionization mass spectrometry (N-TIMS). We report the first Re-Os isochron age on a lunar impact melt rock. 187Re-187Os isotope systematics for Apollo 16 sample 67935 define an isochron age of 4.21 ± 0.13 Ga (MSWD = 1.5), which is interpreted to reflect localized partitioning processes between solid metal-liquid metal as this rock melted. The new age adds further constraints on the significance of pre-4.0 Ga basin forming impacts on the Moon and possible mixing of ancient impactor compositions in lunar impact rocks. Linear correlations displayed by subsamples of a given impact rock in plots of HSE versus Ir concentrations are explained by dilution processes through essentially HSE-free anorthositic lunar crustal target rocks or binary mixing between a high HSE meteoritic end-member and a low HSE end-member composition. Slope-derived HSE ratios and 187Os/188Os of the meteoritic component in granulitic impactites 67915, 67955 and 79215 are similar to slightly volatile element depleted carbonaceous chondrites. Suprachondritic ratios of Ru/Ir, Pt/Ir, Rh/Ir, and Pd/Ir for Apollo 14 impact melt rock 14310 are similar to ratios observed for other Apollo 14 samples and Apollo 17 poikilitic impact melt rocks. Apollo 16 poikilitic and subophitic impact melt rocks 60315 and 67935 show slightly subchondritic Os/Ir and suprachondritic ratios of 187Os/188Os, Ru/Ir, Pt/Ir, Rh/Ir, Pd/Ir and Au/Ir. Their strongly fractionated HSE compositions are similar to some members of the IVA iron meteorite group and provide further evidence for an iron meteorite impactor component in Apollo 16 impact melt rocks. The range of chondritic

  13. The enigmatic Zerelia twin-lakes (Thessaly, Central Greece): two potential meteorite impact Craters

    NASA Astrophysics Data System (ADS)

    Dietrich, V. J.; Lagios, E.; Reusser, E.; Sakkas, V.; Gartzos, E.; Kyriakopoulos, K.

    2013-09-01

    Two circular permanent lakes of 150 and 250 m diameter and 6-8 m depth to an unconsolidated muddy bottom occur 250 m apart from each other in the agricultural fields SW of the town of Almiros (Thessaly, central Greece). The age of the lakes is assumed to be Late Pliocene to Early Holocene with a minimum age of approx. 7000 yr BP. The abundant polymict, quartz-rich carbonate breccia and clasts with a clay rich matrix in the shallow embankments of the lakes show weak stratification but no volcanic structures. The carbonate clasts and particles often display spheroidal shapes and consist of calcite aggregates with feathery, arborescent, variolitic to micro-sparitic textures and spheroidal fabrics, recrystallized and deformed glass-shaped fragments, calcite globules in quartz; thus indications of possible carbonate melting, quenching and devitrification. The carbonatic matrix includes small xenomorphic phases, such as chromspinel, zircon with blurred granular and skeletal textures, skeletal rutile and ilmenite, which are interpreted as relicts of partial melting and quenching under high temperatures of 1240-1800 °C. Only a few quartz fragments exhibit indistinct planar fractures. In several cases they include exotic Al-Si- and sulfur bearing Fe-phases, < 1-10 μm as globules. The modeled "Residual Gravity" profiles through the lakes indicate negative gravity anomalies of bowl-type structures down to 150 m for the eastern lake and down to 250 m for the larger western lake. Several hypotheses can be drawn upon to explain the origin of these enigmatic twin-lakes: (a) Maar-type volcanic craters; (b) hydrothermal or CO2/hydrocarbon gas explosion craters; (c) and (d) doline holes due to karstification; or (e) small meteorite impact craters, the latter being a plausible explanation due to geologic, petrologic, and geophysical evidence. The morphology and dimensions of the lakes as well as the density contrast tomography of the bedrock favor a meteorite impact hypothesis of a

  14. Fullerenes in Allende Meteorite

    NASA Technical Reports Server (NTRS)

    Becker, L.; Bada, J. L.; Winans, R. E.; Bunch, T. E.

    1994-01-01

    The detection of fullerenes in deposits from meteor impacts has led to renewed interest in the possibility that fullerenes are present in meteorites. Although fullerenes have not previously been detected in the Murchison and Allende meteorites, the Allende meteorite is known to contain several well-ordered graphite particles which are remarkably similar in size and appearance to the fullerene-related structures carbon onions and nanotubes. We report that fullerenes are in fact present in trace amounts in the Allende meteorite. In addition to fullerenes, we detected many polycyclic aromatic hydrocarbons (PAHs) in the Allende meteorite, consistent with previous reports. In particular, we detected benzofluoranthene and corannulene (C20H10), five-membered ring structures which have been proposed as precursors to the formation of fullerene synthesis, perhaps within circumstellar envelopes or other sites in the interstellar medium.

  15. Fullerenes in Allende Meteorite

    NASA Technical Reports Server (NTRS)

    Becker, L.; Bada, J. L.; Winans, R. E.; Bunch, T. E.

    1994-01-01

    The detection of fullerenes in deposits from meteor impacts has led to renewed interest in the possibility that fullerenes are present in meteorites. Although fullerenes have not previously been detected in the Murchison and Allende meteorites, the Allende meteorite is known to contain several well-ordered graphite particles which are remarkably similar in size and appearance to the fullerene-related structures carbon onions and nanotubes. We report that fullerenes are in fact present in trace amounts in the Allende meteorite. In addition to fullerenes, we detected many polycyclic aromatic hydrocarbons (PAHs) in the Allende meteorite, consistent with previous reports. In particular, we detected benzofluoranthene and corannulene (C20H10), five-membered ring structures which have been proposed as precursors to the formation of fullerene synthesis, perhaps within circumstellar envelopes or other sites in the interstellar medium.

  16. Self-consistent modelling of Mercury’s exosphere by sputtering, micro-meteorite impact and photon-stimulated desorption

    NASA Astrophysics Data System (ADS)

    Wurz, P.; Whitby, J. A.; Rohner, U.; Martín-Fernández, J. A.; Lammer, H.; Kolb, C.

    2010-10-01

    A Monte-Carlo model of exospheres ( Wurz and Lammer, 2003) was extended by treating the ion-induced sputtering process, photon-stimulated desorption, and micro-meteorite impact vaporisation quantitatively in a self-consistent way starting with the actual release of particles from the mineral surface of Mercury. Based on available literature data we established a global model for the surface mineralogy of Mercury and from that derived the average elemental composition of the surface. This model serves as a tool to estimate densities of species in the exosphere depending on the release mechanism and the associated physical parameters quantitatively describing the particle release from the surface. Our calculation shows that the total contribution to the exospheric density at the Hermean surface by solar wind sputtering is about 4×10 7 m -3, which is much less than the experimental upper limit of the exospheric density of 10 12 m -3. The total calculated exospheric density from micro-meteorite impact vaporisation is about 1.6×10 8 m -3, also much less than the observed value. We conclude that solar wind sputtering and micro-meteorite impact vaporisation contribute only a small fraction of Mercury's exosphere, at least close to the surface. Because of the considerably larger scale height of atoms released via sputtering into the exosphere, sputtered atoms start to dominate the exosphere at altitudes exceeding around 1000 km, with the exception of some light and abundant species released thermally, e.g. H 2 and He. Because of Mercury's strong gravitational field not all particles released by sputtering and micro-meteorite impact escape. Over extended time scales this will lead to an alteration of the surface composition.

  17. Strain Memory of the Verwey Transition and its Application for Estimating Pressures in Meteorite Impact Craters

    NASA Astrophysics Data System (ADS)

    Carporzen, L.; Gilder, S. A.

    2009-12-01

    We studied the effects of stress on the Verwey transition for pure, stoichiometric, synthetic multi-domain magnetite and for natural multi-domain magnetite having both relatively low and high degrees of oxidation. Low temperature measurements of the magnetic moments were carried out after pressure release. Our results unambiguously show an increase in the Verwey transition temperature with increasing pressure that ranges from 1 K/GPa for stoichiometric magnetite to 3 K/GPa for highly oxidized magnetite for pressures up to ca. 5 GPa where the effect seems to saturate. The transition width broadens with increasing stress for stoichiometric magnetite, and then becomes less broad as oxidation increases until the width is invariant with respect to stress for highly oxidized magnetite. Heat treatment to 700°C does not appreciably reverse the effect, which could make the Verwey transition suitable for use as a geobarometer. Application of this potential geobarometer to the basement rocks of the Vredefort meteorite impact crater shows that most of the Archean magnetite has experienced pressures exceeding 5 GPa.

  18. Reported sulfate mineral in lunar meteorite PCA 02007 is impact glass

    NASA Astrophysics Data System (ADS)

    Gross, Juliane; Treiman, Allan H.; Harlow, George E.

    2017-01-01

    A grain of light-blue sulfate material was reported in the lunar highlands regolith meteorite PCA 02007 (Satterwhite and Righter 2013). Allocated grains of that material are, in fact, aluminosilicate glass with a chemical composition like that of the bulk meteorite and other lunar highlands regoliths. The calcium sulfate detected in PCA 02007 was likely a surface coating, and reasonably of Antarctic (not lunar) origin.

  19. Foundations of Forensic Meteoritics

    NASA Astrophysics Data System (ADS)

    Treiman, A. H.

    1992-07-01

    , soil) adhering to a meteorite are samples of the actual physical environment in which the meteorite rested. Adhesion may derive from chemical cementation (incl. rust from the meteorite), biologic activity (incl. desert varnish?), or impact processes [2]. Given the wide diversity of geological materials and processes on the Earth, adhering geological materials may be useful forensic tools. For instance, fall in a volcanic terrane may be inconsistent with adhering sediments of clean quartz sand. Biologic matter on meteorites includes animal and vegetable matter mixed with the adhering geological materials, lichens and other plants growing in place, and purposefully attached animal matter (e.g. insect eggs). The most useful biological data may be provided by pollen, which can often be referred unambiguously to genera and species of plants. For example, sediments adhering to meteorites from the central Nullabor Plain (W. Australia) are different from sediments from the Plain's margin in S. Australia. Sediment on meteorites from the central Nullabor (e.g. Mundrabilla) lacks quartz sand and consists almost entirely of clay-sized particles, consistent with derivation from the local saprolitic soil. Sediment on meteorites from the eastern Nullabor (e.g. Hughes and Cook, S.A.) contains a significant fraction of quartz sand, 1/4- to 1/2-mm grains, probably blown from the Great Victoria Desert to the north and northwest. However, sedimentologic data alone may be misleading. For instance, sediments adhering to Nuevo Mercurio stones (H5; Zacatecas, Mexico) are clay-sized and lack coarser material. But sediment on Nuevo Mercurio (b), a ureilite found in the Nuevo Mercurio strewn field, consists of quartz sand and clay pellets, 1/4 to 1/2 mm diameter. Clearly, local environments may affect the character of sediment adhering to a meteorite, and careful detailed study may be required to determine whether a meteorite has been transported. I am grateful to R. Farrell and D. New for

  20. Non-destructive elemental analysis of large meteorite samples by prompt gamma-ray neutron activation analysis with the internal mono-standard method.

    PubMed

    Latif, Sk A; Oura, Y; Ebihara, M; Nakahara, H

    2013-11-01

    Prompt gamma-ray neutron activation analysis (PGNAA) using the internal mono-standard method was tested for its applicability to analyzing large solid samples including irregularly shaped meteorite samples. For evaluating the accuracy and precision of the method, large quantities of the Geological Survey of Japan standardized rock powders (JB-1a, JG-1a, and JP-1) were analyzed and 12 elements (B, Na, Mg, Al, Cl, K, Ca, Ti, Mn, Fe, Sm, and Gd) were determined by using Si as an internal standard element. Analytical results were mostly in agreement with literature values within 10 %. The precision of the method was also shown to be within 10 % (1σ) for most of these elements. The analytical procedure was then applied to four stony meteorites (Allende, Kimble County, Leedey, Lake Labyrinth) and four iron meteorites (Canyon Diablo, Toluca (Mexico), Toluca (Xiquipilco), Squaw Creek) consisting of large chunks or single slabs. For stony meteorites, major elements (Mg, Al, Si, S, Ca, and Ni), minor elements (Na and Mn) and trace element (B, Cl, K, Ti, Co, and Sm) were determined with adequate accuracy. For iron meteorites, results for the Co and Ni mass fractions determined are all consistent with corresponding literature values. After the analysis, it was confirmed that the residual radioactivity remaining in the sample after PGNAA was very low and decreased down to the background level. This study shows that PGNAA with the internal mono-standard method is highly practical for determining the elemental composition of large, irregularly shaped solid samples including meteorites.

  1. Target Earth: evidence for large-scale impact events.

    PubMed

    Grieve, R A

    1997-05-30

    Unlike the Moon, the Earth has retained only a small sample of its population of impact structures. Currently, over 150 impact structures are known and there are 15 instances of impact known from the stratigraphic record, some of which have been correlated with known impact structures. The terrestrial record is biased toward younger and larger structures on the stable cratonic areas of the crust, because of the effects of constant surface renewal on the Earth. The high level of endogenic geologic activity also affects the morphology and morphometry of terrestrial impact structures; although, the same general morphologic forms that occur on the other terrestrial planets can be observed. A terrestrial cratering rate of 5.6 +/- 2.8 x 10(-15) km-1 a-1 for structures > or = 20 km in diameter can be derived, which is equivalent to that estimated from astronomical observations. Although there are claims to the contrary, the overall uncertainties in the ages of structures in the impact record preclude the determination of any periodicity in the record. Small terrestrial impact structures are the result of the impact of iron or stony iron bodies, with weaker stony and icy bodies being crushed on atmospheric passage. At larger structures (>1 km), trace element geochemistry suggests that approximately 50% of the impact flux is from chondritic bodies, but this may be a function of the signal:noise ratio of the meteoritic tracer elements. Evidence for impact in the stratigraphic record is both chemical and physical. Although currently small in number, there are indications that more evidence will be forthcoming with time. Such searches for evidence of impact have been stimulated by the chemical and physical evidence of the involvement of impact at the K/T boundary. There will, however, be problems in differentiating geochemically the signal of even relatively large impact events from the background cosmic flux of every day meteoritic debris. Even with these biases and

  2. Petrogenesis of the SNC (shergottites, nakhlites, chassignites) meteorites - Implications for their origin from a large dynamic planet, possibly Mars

    NASA Astrophysics Data System (ADS)

    Smith, M. R.; Laul, J. C.; Ma, M.-S.; Huston, T.; Verkouteren, R. M.; Lipschutz, M. E.; Schmitt, R. A.

    1984-02-01

    Comprehensive chemical data are presented on the shergottites Shergotty, Zagami, Allan Hills (ALHA) 77005, and the new member Elephant Moraine (EETA) 79001 using results of sequential instrumental and radiochemical neutron activation analysis. The close relationship of the Antarctic shergotites indicates that ALHA 77005 is a residual source produced by incongruent melting of a source similar in bulk composition to EETA 79001A and that EETA 79001B and the interstitial phases in EETA 79001A are the melts produced by such melting episodes. The large ion lithophile LIL) trace element abundanced of the shergottites require variable but extensive degrees of nomodal melting of isotopically constrained parent sources. The SNG sources are consistent with their derivation by extensive fractionation of a primitive magma initially produced from a source having chondritic refractory LIL trace element abundances. Petrogenetic and age relationships among SNC meteorites suggest a single complex-provenance on a dynamic planet not unlike earth, probably Mars.

  3. Petrogenesis of the SNC (shergottites, nakhlites, chassignites) meteorites - Implications for their origin from a large dynamic planet, possibly Mars

    NASA Technical Reports Server (NTRS)

    Smith, M. R.; Laul, J. C.; Ma, M. S.; Huston, T.; Verkouteren, R. M.; Lipschutz, M. E.; Schmitt, R. A.

    1984-01-01

    Comprehensive chemical data are presented on the shergottites Shergotty, Zagami, Allan Hills (ALHA) 77005, and the new member Elephant Moraine (EETA) 79001 using results of sequential instrumental and radiochemical neutron activation analysis. The close relationship of the Antarctic shergotites indicates that ALHA 77005 is a residual source produced by incongruent melting of a source similar in bulk composition to EETA 79001A and that EETA 79001B and the interstitial phases in EETA 79001A are the melts produced by such melting episodes. The large ion lithophile LIL) trace element abundanced of the shergottites require variable but extensive degrees of nomodal melting of isotopically constrained parent sources. The SNG sources are consistent with their derivation by extensive fractionation of a primitive magma initially produced from a source having chondritic refractory LIL trace element abundances. Petrogenetic and age relationships among SNC meteorites suggest a single complex-provenance on a dynamic planet not unlike earth, probably Mars.

  4. Vesiculation, melt formation, noble gas/nitrogen behaviour, and impact chronology on a planetary regolith : the case of Benccubbin (CB) meteorite

    NASA Astrophysics Data System (ADS)

    Marty, B.; Turner, G.; Kelley, S. P.

    2008-12-01

    The Benccubbin meteorite is a member of the CB peculiar meteorite family, which all have reduced silicates, metal zoning, solar Ni/Co and large enrichments in 15N, that have been regarded as relics of their very primitive character. However, these meteorites also show tugsten isotopic ratios suggesting metal differentiation events several Ma after start of solar system formation. The Benccubbin mineralogy is best explained as being an heterogeneous planetary regolith containing clasts of different origins (e.g., CO, CI chondrules and clasts, silicates of unknown origin). This meteorite presents evidence of having been impacted, such as melt, temperature gradient recorded at the silicate/metal interface, and textures indicative of rapid cooling. Notably, Benccubbin contains vesicles in several phases : partially molten silicate clasts and CO chondrules, impact melt, and the so-called bubble grains 1. We have analysed several Benccubbin mineral and metal phases for N and noble gas isotopes and abundances by both laser fusion and vacuum crushing. 15N-rich nitrogen (d15N up to +1,000 per mil) is ubiquituous, particularly inside vesicles, and is associated with noble gases. Notably, N and noble gases appear to have largely exchanged between silicate and vesicles, reaching locally equilibrium partitioning. Gases are still released after extensive crushing up to 4,000 strokes, in contrast to the case of MORB glasses and suggesting a foam-like, decompression structure of the impacted melt. N and Ar correlate well, showing that the N solubility was comparable to that of Ar and therefore that the redox conditions were above IW, according to 2. From the N content of the glass, we estimate that it equilibrated with a vapor plume in which the pressure of nitrogen was ~300 Bar. Radiogenic 40Ar is present inside the vesicles, showing that the vesiculation event was not an early process. Ar-Ar dating of Benccubbin suggests involvement in an impact around 4.2 Ga. In contrast to

  5. Mass and Size Frequency Distribution of the Impact Debris from Disruption of Chondritic Meteorites

    NASA Technical Reports Server (NTRS)

    VanVeghten, T. W.; Flynn, G. J.; Durda, D. D.; Hart, S.; Asphaug, E.

    2003-01-01

    Since direct observation of the collision of asteroids in space is not always convenient for earthbound observers, we have undertaken simulations of these collisions using the NASA Ames Vertical Gun Range (AVGR). To simulate the collision of asteroids in space, and aluminum projectiles with velocities ranging from approx.1 to approx.6 km/sec were fired at 70g to approx.200 g fragments of chondritic meteorites. The target meteorite was placed in an evacuated chamber at the AVGR. Detectors, usually four, were set up around the target meteorite. These detectors consisted of aerogel and aluminum foil of varying thickness. The aerogel's purpose was to catch debris after the collision, and the aluminum foil.s purpose was to show the size of the debris particles through the size of the holes in the aluminum foil. Outside the chamber, a camera was set up to record high-speed film of the collision. This camera recorded at either 500 frames per second or 1000 frames per second. Three different types of targets were used for these tests. The first were actual meteorites, which varied in mineralogical composition, density, and porosity. The second type of target was a Hawaiian basalt, consisting of olivine phenocrysts in a porous matrix, which we thought might be similar to the chondritic meteorites, thus providing data for comparison. The final type was made out of Styrofoam. The Styrofoam was thought to simulate very low-density asteroids and comets.

  6. Search for a meteoritic component at the Beaverhead impact structure, Montana

    NASA Technical Reports Server (NTRS)

    Lee, Pascal; Kay, Robert W.

    1992-01-01

    The Beaverhead impact structure, in southwestern Montana, was identified recently by the presence of shatter cones and impactites in outcrops of Proterozoic sandstones of the Belt Supergroup. The cones occur over an area greater than 100 sq km. Because the geologic and tectonic history of this region is long and complex, the outline of the original impact crater is no longer identifiable. The extent of the area over which shatter cones occur suggests, however, that the feature may have been at least 60 km in diameter. The absence of shatter cones in younger sedimentary units suggests that the impact event occurred in late Precambrian or early Paleozoic time. We have collected samples of shocked sandstone from the so-called 'Main Site' of dark-matrix breccias, and of impact breccias and melts from the south end of Island Butte. The melts, occurring often as veins through brecciated sandstone, exhibit a distinctive fluidal texture, a greenish color, and a cryptocrystalline matrix, with small inclusions of deformed sandstone. Samples of the same type, along with country rock, were analyzed previously for major- and trace-element abundances. It was found that, although the major-element composition as relatively uniform, trace-element composition showed variations between the melt material and the adjacent sandstone. These variations were attributed to extensive weathering and hydrothermal alteration. In a more specific search for a possible meteoritic signature in the breccia and the melt material we have conducted a new series of trace-element analyses on powders of our own samples by thermal neutron activation analysis. Our results indicate that Ir abundances in the breccia, the melts, and the adjacent sandstone clasts are no greater than about 0.1 ppb, suggesting no Ir enrichment of the breccia or the melts relative to the country rock. However, both the breccia and the melt material exhibit notable enrichments in Cr (8- and 10-fold), in U (9- and 5-fold), and in

  7. Predicted detection rates of regional-scale meteorite impacts on Mars with the InSight short-period seismometer

    NASA Astrophysics Data System (ADS)

    Teanby, N. A.

    2015-08-01

    In 2016 NASA will launch the InSight discovery-class mission, which aims to study the detailed internal structure of Mars for the first time. Short- and long-period seismometers form a major component of InSight's payload and have the potential to detect seismic waves generated by meteorite impacts. Large globally detectable impact events producing craters with diameters of ∼ 100 m have been investigated previously and are likely to be rare (Teanby, N.A., Wookey, J. [2011]. Phys. Earth Planet. Int. 186, 70-80), but smaller impacts producing craters in the 0.5-20 m range are more numerous and potentially occur sufficiently often to be detectable on regional scales (≲1000 km). At these distances, seismic waves will have significant high frequency content and will be suited to detection with InSight's short-period seismometer SEIS-SP. In this paper I estimate the current martian crater production function from observations of new craters (Malin, M.C. et al. [2006]. Science 314, 1573-1577; Daubar, I.J. et al. [2013]. Icarus 225, 506-516), model results (Williams, J.P., Pathare, A.V., Aharonson, O. [2014]. Icarus 235, 23-36), and standard isochrons (Hartmann, W.K. [2005]. Icarus 174, 294-320). These impact rates are combined with an empirical relation between impact energy, source-receiver distance, and peak seismogram amplitude, derived from a compilation of seismic recordings of terrestrial and lunar impacts, chemical explosions, and nuclear tests. The resulting peak seismogram amplitude scaling law contains significant uncertainty, but can be used to predict impact detection rates. I estimate that for a short-period instrument, with a noise spectral density of 10-8 ms-2 Hz-1/2 in the 1-16 Hz frequency band, approximately 0.1-30 regional impacts per year should be detectable with a nominal value of 1-3 impacts per year. Therefore, small regional impacts are likely to be a viable source of seismic energy for probing Mars' crustal and upper mantle structure. This is

  8. Carbonates in fractures of Martian meteorite Allan Hills 84001: petrologic evidence for impact origin

    NASA Technical Reports Server (NTRS)

    Scott, E. R.; Krot, A. N.; Yamaguchi, A.

    1998-01-01

    Carbonates in Martian meteorite Allan Hills 84001 occur as grains on pyroxene grain boundaries, in crushed zones, and as disks, veins, and irregularly shaped grains in healed pyroxene fractures. Some carbonate disks have tapered Mg-rich edges and are accompanied by smaller, thinner and relatively homogeneous, magnesite microdisks. Except for the microdisks, all types of carbonate grains show the same unique chemical zoning pattern on MgCO3-FeCO3-CaCO3 plots. This chemical characteristic and the close spatial association of diverse carbonate types show that all carbonates formed by a similar process. The heterogeneous distribution of carbonates in fractures, tapered shapes of some disks, and the localized occurrence of Mg-rich microdisks appear to be incompatible with growth from an externally derived CO2-rich fluid that changed in composition over time. These features suggest instead that the fractures were closed as carbonates grew from an internally derived fluid and that the microdisks formed from a residual Mg-rich fluid that was squeezed along fractures. Carbonate in pyroxene fractures is most abundant near grains of plagioclase glass that are located on pyroxene grain boundaries and commonly contain major or minor amounts of carbonate. We infer that carbonates in fractures formed from grain boundary carbonates associated with plagiociase that were melted by impact and dispersed into the surrounding fractured pyroxene. Carbonates in fractures, which include those studied by McKay et al. (1996), could not have formed at low temperatures and preserved mineralogical evidence for Martian organisms.

  9. Carbonates in fractures of Martian meteorite Allan Hills 84001: petrologic evidence for impact origin

    NASA Technical Reports Server (NTRS)

    Scott, E. R.; Krot, A. N.; Yamaguchi, A.

    1998-01-01

    Carbonates in Martian meteorite Allan Hills 84001 occur as grains on pyroxene grain boundaries, in crushed zones, and as disks, veins, and irregularly shaped grains in healed pyroxene fractures. Some carbonate disks have tapered Mg-rich edges and are accompanied by smaller, thinner and relatively homogeneous, magnesite microdisks. Except for the microdisks, all types of carbonate grains show the same unique chemical zoning pattern on MgCO3-FeCO3-CaCO3 plots. This chemical characteristic and the close spatial association of diverse carbonate types show that all carbonates formed by a similar process. The heterogeneous distribution of carbonates in fractures, tapered shapes of some disks, and the localized occurrence of Mg-rich microdisks appear to be incompatible with growth from an externally derived CO2-rich fluid that changed in composition over time. These features suggest instead that the fractures were closed as carbonates grew from an internally derived fluid and that the microdisks formed from a residual Mg-rich fluid that was squeezed along fractures. Carbonate in pyroxene fractures is most abundant near grains of plagioclase glass that are located on pyroxene grain boundaries and commonly contain major or minor amounts of carbonate. We infer that carbonates in fractures formed from grain boundary carbonates associated with plagiociase that were melted by impact and dispersed into the surrounding fractured pyroxene. Carbonates in fractures, which include those studied by McKay et al. (1996), could not have formed at low temperatures and preserved mineralogical evidence for Martian organisms.

  10. Making an Impact with Public Outreach Activities on Asteroids, Comets, and Meteorites

    NASA Astrophysics Data System (ADS)

    White, V.; Gurton, S.; Berendsen, M.; Dusenbery, P.

    2010-12-01

    The Night Sky Network is a collaboration of close to 350 astronomy clubs across the US that actively engage in public outreach within their communities. Since 2004, the Astronomical Society of the Pacific has been creating outreach ToolKits filled with carefully crafted sets of physical materials designed to help these volunteer clubs explain the wonders of the night sky to the public. The effectiveness of the ToolKit activities and demonstrations is the direct result of a thorough testing and vetting process. Find out how this iterative assessment process can help other programs create useful tools for both formal and informal educators. The current Space Rocks Outreach ToolKit focuses on explaining asteroids, comets, and meteorites to the general public using quick, big-picture activities that get audiences involved. Eight previous ToolKits cover a wide range of topics from the Moon to black holes. In each case, amateur astronomers and the public helped direct the development the activities along the way through surveys, focus groups, and active field-testing. The resulting activities have been embraced by the larger informal learning community and are enthusiastically being delivered to millions of people across the US and around the world. Each ToolKit is delivered free of charge to active Night Sky Network astronomy clubs. All activity write-ups are available free to download at the website listed here. Amateur astronomers receive frequent questions from the public about Earth impacts, meteors, and comets so this set of activities will help them explain the dynamics of these phenomena to the public. The Space Rocks ToolKit resources complement the Great Balls of Fire museum exhibit produced by Space Science Institute’s National Center for Interactive Learning and scheduled for release in 2011. NSF has funded this national traveling exhibition and outreach ToolKit under Grant DRL-0813528.

  11. Meteorite Linked to Rock at Meridiani

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This meteorite, a basalt lava rock nearly indistinguishable from many Earth rocks, provided the first strong proof that meteorites could come from Mars. Originally weighing nearly 8 kilograms (17.6 pounds), it was collected in 1979 in the Elephant Moraine area of Antarctica. The side of the cube at the lower left in this image measures 1 centimeter (0.4 inches).

    This picture shows a sawn face of this fine-grained gray rock. (The vertical stripes are saw marks.) The black patches in the rock are melted rock, or glass, formed when a large meteorite hit Mars near the rock. The meteorite impact probably threw this rock, dubbed 'EETA79001,' off Mars and toward Antarctica on Earth. The black glass contains traces of martian atmosphere gases.

    The Mars Exploration Rover Opportunity has discovered that a rock dubbed 'Bounce' at Meridiani Planum has a very similar mineral composition to this meteorite and likely shares common origins. Bounce itself is thought to have originated outside the area surrounding Opportunity's landing site; an impact or collision likely threw the rock away from its primary home.

  12. Meteorite Linked to Rock at Meridiani

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This meteorite, a basalt lava rock nearly indistinguishable from many Earth rocks, provided the first strong proof that meteorites could come from Mars. Originally weighing nearly 8 kilograms (17.6 pounds), it was collected in 1979 in the Elephant Moraine area of Antarctica. The side of the cube at the lower left in this image measures 1 centimeter (0.4 inches).

    This picture shows a sawn face of this fine-grained gray rock. (The vertical stripes are saw marks.) The black patches in the rock are melted rock, or glass, formed when a large meteorite hit Mars near the rock. The meteorite impact probably threw this rock, dubbed 'EETA79001,' off Mars and toward Antarctica on Earth. The black glass contains traces of martian atmosphere gases.

    The Mars Exploration Rover Opportunity has discovered that a rock dubbed 'Bounce' at Meridiani Planum has a very similar mineral composition to this meteorite and likely shares common origins. Bounce itself is thought to have originated outside the area surrounding Opportunity's landing site; an impact or collision likely threw the rock away from its primary home.

  13. Impact ejection of lunar meteorites and the age of Giordano Bruno

    NASA Astrophysics Data System (ADS)

    Fritz, Jörg

    2012-11-01

    Based on literature data from lunar meteorites and orbital observations it is argued that the lunar crater Giordano Bruno (22 km ∅) formed more than 1 Ma ago and probably ejected the lunar meteorites Yamato 82192/82193/86032 at 8.5 ± 1.5 Ma ago from the Th-poor highlands of the Moon. The efficiency and time scale to deliver 3He-rich lunar material into Earth’s sediments is discussed to assess the temporal relationship between the Giordano Bruno cratering event and a 1 Ma enduring 3He-spike which is observed in 8.2 Ma old sediments on Earth.

  14. Meteorite impact, cryptoexplosion, and shock metamorphism - A perspective on the evidence at the K/T boundary

    NASA Technical Reports Server (NTRS)

    Sharpton, V. L.; Grieve, R. A. F.

    1990-01-01

    A perspective on the evidence of a major impact event at the K/T boundary is proposed using field and laboratory studies of terrestrial impact craters. Recent assertions that diagnostic indications of shock metamorphism are also produced in volcanic environments are challenged. A general geological framework of impact structures is developed and the issue of volcanically induced shock metamorphism is examined. Cryptoexplosion is addressed by assessing the geology of two structures: the Slate Islands and Manson, which are often cited by advocates of an internal origin for shock metamorphism as volcanic structures. It is concluded that the link between shock metamorphism and meteorite impact is now established beyond reasonable doubt. The occurrence and worldwide distribution of shocked minerals at the K/T boundary is considered to be the conclusive evidence for a major impact event.

  15. Meteoritic Zircon.

    PubMed

    Marvin, U B; Klein, C

    1964-11-13

    Zircon (ZrSiO(5)) has been identified as an accessory mineral in the Vaca Muerta mesosiderite and in the troilite nodules of the Toluca iron meteorite. The occurrence in Vaca Muerta is a new discovery confirmned by electron-probe nmicroanalysis of a grain in a polished section of the meteorite. Our identification of zircon in Toluca substantiates an occurrence in this meteorite reported in 1895 by Laspeyres and Kaiser.

  16. Multibeam Mapping of Cretaceous-Paleogene Meteorite Impact Deposits on the Campeche Escarpment, YUCATÁN , MÉXICO

    NASA Astrophysics Data System (ADS)

    Gwiazda, R.; Paull, C. K.; Caress, D. W.; Rebolledo-Vieyra, M.; Fucugauchi, J. U.; Canales, I.; Sumner, E. J.; Tubau Carbonell, X.; Lundsten, E. M.; Anderson, K.

    2013-12-01

    The Chicxulub crater in the Yucatán Peninsula, México, at the Cretaceous-Paleogene (K-Pg) boundary, is believed to have been created by the impact of a meteorite ~65 million years ago. Ejecta from the impact were deposited beyond the crater site and are now buried under >1 km of Cenozoic carbonate sediments. Outcrops of the ejecta are believed to be exposed on the Campeche escarpment, which is the dramatically steep northern edge of the Yucatán Peninsula. A seafloor-mapping cruise aboard the R/V Falkor, equipped with Kongsberg EM302 30 kHz and EM710 70-100 kHz multibeam sonars, was conducted in March 2013 to produce a detailed map of the escarpment. Surveys were conducted along the escarpment face for 612 km, targeting the water depth range between 400 m and the escarpment base at ≤ 3,700 m. Segments with two distinctive reliefs are observed in the escarpment face: The first type of relief is a continuous slope over the entire surveyed depth, with numerous v-shaped gullies and intervening ridges. In contrast, the second type of relief is characterized by slopes of 5° above ~2-2.5 km depth with an abrupt change to 25° slopes below. As many as 80 submarine canyons are present along this relief. The canyons are topped with semicircular amphitheaters of gentler slopes above ~2-2.5 km but rimmed with 500 m high cliffs on the steep slope section below. The steep cliffs appear free from sediment drape and can be traced laterally for large segments of the escarpment, suggesting that these are horizontal units with outcropping strata. The location of the K-Pg boundary on the escarpment can be inferred from its identification on DSDP Leg 17 Site 86, drilled on a terrace at 1,462 m depth, and 200 m from the edge of the escarpment, and on DSDP Leg 17 Site 94, drilled in 1,793 m depth, 5.5 km from the edge of the platform. Based on the biostratigraphy of core cuttings recovered from both boreholes the base of the Tertiary in Site 86 is placed at between 2,016 and 2,081 m

  17. Antarctic meteorites

    NASA Astrophysics Data System (ADS)

    Cassidy, W. A.; Rancitelli, L. A.

    1982-04-01

    An abundance of meteorites has been discovered on two sites in the Antarctic which may assist in the study of the origins of meteorites and the history of the solar system. Characteristics particular to those meteorites discovered in this region are explained. These specimens, being well preserved due to the climate, have implications in the study of the cosmic ray flux through time, the meteoroid complex in space, and cosmic ray exposure ages. Implications for the study of the Antarctic, particularly the ice flow, are also discussed. Further discoveries of meteorites in this region are anticipated.

  18. The Shergotty consortium and SNC meteorites - An overview

    NASA Technical Reports Server (NTRS)

    Laul, J. C.

    1986-01-01

    The key up-to-date findings on the Shergotty and other SNC meteorites are summarized. The Martian origin of these meteorites is strongly suggested by the evidence of trapped noble gases and nitrogen compositions in glasses of the EETA 79001 meteorite, which compare well with the results of the Martian atmosphere investigation by the Viking spacecraft. Age-dating and exposure scenarios suggest two possibilities for the ejection of SNC meteorites: (1) ejection as a large (larger than 6 m) body by a single impact on Mars and then multiple breakup in the asteroidal belt, at about 11 Myr for Chassigny and nakhlites, at 2.5 Myr for Shergotty, Zagami and ALHA 77005, and at 0.6 Myr for EETA 79001; and (2) ejection of small (less than 0.5 m) objects by multiple impacts on the Martian terrain at 11, 2.5, and 0.6 Myr, with no breakup in space.

  19. Proceedings of a Workshop on Antarctic Meteorite Stranding Surfaces

    SciTech Connect

    Cassidy, W.A.; Whillans, I.M.

    1990-08-01

    The discovery of large numbers of meteorites on the Antarctic Ice Sheet is one of the most exciting developments in polar science in recent years. The meteorites are found on areas of ice called stranding surfaces. Because of the sudden availability of hundreds, and then thousands, of new meteorite specimens at these sites, the significance of the discovery of meteorite stranding surfaces in Antarctica had an immediate and profound impact on planetary science, but there is also in this discovery an enormous, largely unrealized potential to glaciology for records of climatic and ice sheet changes. The glaciological interest derives from the antiquity of the ice in meteorite stranding surfaces. This exposed ice covers a range of ages, probably between zero and more than 500,000 years. The Workshop on Antarctic Meteorite Stranding Surfaces was convened to explore this potential and to devise a course of action that could be recommended to granting agencies. The workshop recognized three prime functions of meteorite stranding surfaces. They provide: (1) A proxy record of climatic change (i.e., a long record of climatic change is probably preserved in the exposed ice stratigraphy); (2) A proxy record of ice volume change; and (3) A source of unique nonterrestrial material.

  20. Proceedings of a Workshop on Antarctic Meteorite Stranding Surfaces

    NASA Technical Reports Server (NTRS)

    Cassidy, W. A. (Editor); Whillans, I. M. (Editor)

    1990-01-01

    The discovery of large numbers of meteorites on the Antarctic Ice Sheet is one of the most exciting developments in polar science in recent years. The meteorites are found on areas of ice called stranding surfaces. Because of the sudden availability of hundreds, and then thousands, of new meteorite specimens at these sites, the significance of the discovery of meteorite stranding surfaces in Antarctica had an immediate and profound impact on planetary science, but there is also in this discovery an enormous, largely unrealized potential to glaciology for records of climatic and ice sheet changes. The glaciological interest derives from the antiquity of the ice in meteorite stranding surfaces. This exposed ice covers a range of ages, probably between zero and more than 500,000 years. The Workshop on Antarctic Meteorite Stranding Surfaces was convened to explore this potential and to devise a course of action that could be recommended to granting agencies. The workshop recognized three prime functions of meteorite stranding surfaces. They provide: (1) A proxy record of climatic change (i.e., a long record of climatic change is probably preserved in the exposed ice stratigraphy); (2) A proxy record of ice volume change; and (3) A source of unique nonterrestrial material.

  1. Cat Mountain: A meteoritic sample of an impact-melted chondritic asteroid

    NASA Technical Reports Server (NTRS)

    Kring, David A.

    1993-01-01

    Although impact cratering and collisional disruption are the dominant geologic processes affecting asteroids, samples of impact melt breccias comprise less than 1 percent of ordinary chondritic material and none exist among enstatite and carbonaceous chondrite groups. Because the average collisional velocity among asteroids is sufficiently large to produce impact melts, this paucity of impact-melted material is generally believed to be a sampling bias, making it difficult to determine the evolutionary history of chondritic bodies and how impact processes may have affected the physical properties of asteroids (e.g., their structural integrity and reflectance spectra). To help address these and related issues, the first petrographic description of a new chondritic impact melt breccia sample, tentatively named Cat Mountain, is presented.

  2. The Meteoritical Bulletin, No. 98, September 2010

    NASA Astrophysics Data System (ADS)

    Weisberg, Michael K.; Smith, Caroline; Herd, Christopher; Haack, Henning; Yamaguchi, Akira; Chennaoui Aoudjehane, Hasnaa; Welzenbach, Linda; Grossman, Jeffrey N.

    2010-09-01

    This issue of The Meteoritical Bulletin reports information on 1103 meteorites including 281 non-Antarctic meteorites (Table 1) and 822 Antarctic meteorites (Table 2). Reported in full written descriptions are three falls. Full descriptions are also given for three shergottites, two ungrouped irons, a primitive achondrite, an olivine diogenite, and a lunar meteorite. One iron, Gebel Kamil, was found in and around the Kamil impact crater. Also reported is a new dense collection area in Tunisia. Tables list a wide variety of meteorites including chondrites, ureilites, irons, acapulcoites, and HEDs. Antarctic meteorites reported in this edition include meteorites recovered by ANSMET (US), CHINARE (China), KOREAMET (Korea), and the NIPR (Japan) meteorite recovery programs.

  3. Initial Results on the Meteoritic Component of new Sediment Cores Containing Deposits of the Eltanin Impact Event

    NASA Technical Reports Server (NTRS)

    Kyte, Frank T.; Gersonde, Rainer; Kuhn, Gerhard

    2002-01-01

    The late Pliocene impact of the Eltanin asteroid is the only known asteroid impact in a deep- ocean (-5 km) basin . This was first discovered in 1981 as an Ir anomaly in sediment cores collected by the USNS Eltanin in 1965. In 1995, Polarstern expedition ANT XII/4 made the first geological survey of the suspected impact region. Three sediment cores sampled around the San Martin seamounts (approx. 57.5 S, 91 W) contained well-preserved impact deposits that include disturbed ocean sediments and meteoritic impact ejecta. The latter is composed of shock-melted asteroidal materials and unmelted meteorites. In 2001, the FS Polarstern returned to the impact area during expedition ANT XVIIU5a. At least 16 cores were recovered that contain ejecta deposits. These cores and geophysical data from the expedition can be used to map the effects of the impact over a region of about 80,000 square km. To date we have measured Ir concentrations in sediments from seven of the new cores and preliminary data should be available for a few more by the time of the meeting. Our initial interpretation of these data is that there is a region in the vicinity of the San Martin Seamounts comprising at least 20,000 square km in which the average amount of meteoritic material deposited was more than 1 g per square cm. This alone is enough material to support a 500 m asteroid. Beyond this is a region of about 60,000 square km, mostly to the north and west, where the amount of ejecta probably averages about 0.2 g per square cm. Another 400 km to the east, USNS Eltanin core E10-2 has about 0.05 g per square cm, so we know that ejecta probably occurs across more than a million square km of ocean floor. A key to future exploration of this impact is to find evidence of the ejecta at more sites distant from the seamounts. We currently have almost no data from regions to the west or south of the San Martin seamounts.

  4. Initial Results on the Meteoritic Component of new Sediment Cores Containing Deposits of the Eltanin Impact Event

    NASA Technical Reports Server (NTRS)

    Kyte, Frank T.; Gersonde, Rainer; Kuhn, Gerhard

    2002-01-01

    The late Pliocene impact of the Eltanin asteroid is the only known asteroid impact in a deep- ocean (-5 km) basin . This was first discovered in 1981 as an Ir anomaly in sediment cores collected by the USNS Eltanin in 1965. In 1995, Polarstern expedition ANT XII/4 made the first geological survey of the suspected impact region. Three sediment cores sampled around the San Martin seamounts (approx. 57.5 S, 91 W) contained well-preserved impact deposits that include disturbed ocean sediments and meteoritic impact ejecta. The latter is composed of shock-melted asteroidal materials and unmelted meteorites. In 2001, the FS Polarstern returned to the impact area during expedition ANT XVIIU5a. At least 16 cores were recovered that contain ejecta deposits. These cores and geophysical data from the expedition can be used to map the effects of the impact over a region of about 80,000 square km. To date we have measured Ir concentrations in sediments from seven of the new cores and preliminary data should be available for a few more by the time of the meeting. Our initial interpretation of these data is that there is a region in the vicinity of the San Martin Seamounts comprising at least 20,000 square km in which the average amount of meteoritic material deposited was more than 1 g per square cm. This alone is enough material to support a 500 m asteroid. Beyond this is a region of about 60,000 square km, mostly to the north and west, where the amount of ejecta probably averages about 0.2 g per square cm. Another 400 km to the east, USNS Eltanin core E10-2 has about 0.05 g per square cm, so we know that ejecta probably occurs across more than a million square km of ocean floor. A key to future exploration of this impact is to find evidence of the ejecta at more sites distant from the seamounts. We currently have almost no data from regions to the west or south of the San Martin seamounts.

  5. Meteorite falls in Africa

    NASA Astrophysics Data System (ADS)

    Khiri, Fouad; Ibhi, Abderrahmane; Saint-Gerant, Thierry; Medjkane, Mohand; Ouknine, Lahcen

    2017-10-01

    The study of meteorites provides insight into the earliest history of our solar system. From 1800, about the year meteorites were first recognized as objects falling from the sky, until December 2014, 158 observed meteorite falls were recorded in Africa. Their collected mass ranges from 1.4 g to 175 kg with the 1-10 kg cases predominant. The average rate of African falls is low with only one fall recovery per 1.35-year time interval (or 0.023 per year per million km2). This African collection is dominated by ordinary chondrites (78%) just like in the worldwide falls. The seventeen achondrites include three Martian meteorite falls (Nakhla of Egypt, Tissint of Morocco and Zagami of Nigeria). Observed Iron meteorite falls are relatively rare and represent only 5%. The falls' rate in Africa is variable in time and in space. The number of falls continues to grow since 1860, 80% of which were recovered during the period between 1910 and 2014. Most of these documented meteorite falls have been recovered from North-Western Africa, Eastern Africa and Southern Africa. They are concentrated in countries which have a large surface area and a large population with a uniform distribution. Other factors are also favorable for observing and collecting meteorite falls across the African territory, such as: a genuine meteorite education, a semi-arid to arid climate (clear sky throughout the year most of the time), croplands or sparse grasslands and possible access to the fall location with a low percentage of forest cover and dense road network.

  6. Meteorites, Microfossils and Exobiology

    NASA Technical Reports Server (NTRS)

    Hoover, Richard B.

    1997-01-01

    The discovery of evidence for biogenic activity and possible microfossils in a Martian meteorite may have initiated a paradigm shift regarding the existence of extraterrestrial microbial life. Terrestrial extremophiles that live in deep granite and hydrothermal vents and nanofossils in volcanic tuffs have altered the premise that microbial life and microfossils are inconsistent with volcanic activity and igneous rocks. Evidence for biogenic activity and microfossils in meteorites can no longer be dismissed solely because the meteoritic rock matrix is not sedimentary. Meteorite impact-ejection and comets provide mechanisms for planetary cross-contamination of biogenic chemicals, microfossils, and living microorganisms. Hence, previously dismissed evidence for complex indigenous biochemicals and possible microfossils in carbonaceous chondrites must be re-examined. Many similar, unidentifiable, biological-like microstructures have been found in different carbonaceous chondrites and the prevailing terrestrial contaminant model is considered suspect. This paper reports the discovery of microfossils indigenous to the Murchison meteorite. These forms were found in-situ in freshly broken, interior surfaces of the meteorite. Environmental Scanning Electron Microscope (ESEM) and optical microscopy images indicate that a population of different biological-like forms are represented. Energy Dispersive Spectroscopy reveals these forms have high carbon content overlaying an elemental distribution similar to the matrix. Efforts at identification with terrestrial microfossils and microorganisms were negative. Some forms strongly resemble bodies previously isolated in the Orgueil meteorite and considered microfossils by prior researchers. The Murchison forms are interpreted to represent an indigenous population of the preserved and altered carbonized remains (microfossils) of microorganisms that lived in the parent body of this meteorite at diverse times during the past 4.5 billion

  7. Meteoritic Matter on Fracture Surfaces of Shocked Fossils (Shattered Belemnites) from the Nördlinger Ries Impact Structure, Southern Germany

    NASA Astrophysics Data System (ADS)

    Buchner, E.; Schmieder, M.

    2015-09-01

    We report on the surprising discovery of meteoritic matter on fracture surfaces of shattered belemnites from limestone target rocks of the Nördlinger Ries crater. The crucial element ratios might indicate an iron meteoritic Ries projectile.

  8. Dangerous Near-Earth Asteroids and Meteorites

    NASA Astrophysics Data System (ADS)

    Mickaelian, A. M.; Grigoryan, A. E.

    2015-07-01

    The problem of Near-Earth Objects (NEOs; Astreoids and Meteorites) is discussed. To have an understanding on the probablity of encounters with such objects, one may use two different approaches: 1) historical, based on the statistics of existing large meteorite craters on the Earth, estimation of the source meteorites size and the age of these craters to derive the frequency of encounters with a given size of meteorites and 2) astronomical, based on the study and cataloging of all medium-size and large bodies in the Earth's neighbourhood and their orbits to estimate the probability, angles and other parameters of encounters. Therefore, we discuss both aspects and give our present knowledge on both phenomena. Though dangerous NEOs are one of the main source for cosmic catastrophes, we also focus on other possible dangers, such as even slight changes of Solar irradiance or Earth's orbit, change of Moon's impact on Earth, Solar flares or other manifestations of Solar activity, transit of comets (with impact on Earth's atmosphere), global climate change, dilution of Earth's atmosphere, damage of ozone layer, explosion of nearby Supernovae, and even an attack by extraterrestrial intelligence.

  9. The Cantarell Breccia System, Southern Gulf Of Mexico: Structural Evolution And Support For An Origin Relarted To The Chixculub Meteorite Impact

    NASA Astrophysics Data System (ADS)

    Ricoy, V.

    2003-04-01

    The Upper Cretaceous within the Campeche Basin, southern Gulf of Mexico hosts a world class petroleum system. Cantarell is the most important reservoir that consists of a complex brecciated carbonate reservoir deposited at or around the Cretaceous-Tertiary boundary. Previous sedimentological studies suggests that the Upper Cretaceous Carbonate breccias found in the Cantarell oilfield system and through the Bay of Campeche, were the result of a catastrophic shelf collapse event triggered by the Chixculub meteorite impact. This work presents new evidence from structural and stratigraphic interpretation of 3D seismic and 2D lines which gives light to features that support the platform collapse model. The reservoir consists of thick (up to 300 m), heterogeneous, monomyctic and polymictic breccias developed at the K-T boundary, and widely distributed throughout the Campeche Basin. The timing, internal architecture, widespread deposition and distance to the platform margin source (over 30 kms) of the breccia unit, combined with a contorted irregular seismic reflector near the base of the Cretaceous carbonate platform, suggests that the geological processes accountable for the emplacement of the breccias relates to the massive catastrophic collapse of the Cretaceous platform as a result of the Chixculub meteorite impact. Structural interpretation of the 3D seismic data, together with well stratigraphic markers unraveled a complex Oligocene-Miocene structural deformation history of the Cantarell field, which resulted in several discrete reservoir blocks partitioned by a complex array of thrusts, normal and reverse faults. It is proposed that the structural deformation of the area controlled to a large extent the distribution of the reservoir properties found in the Cantarell area. This idea is tested using the structural model matched against the well log porosity data.

  10. High Temperature and High Pressure Mixtures of Iron Oxides from the Impact Event at the Bee Bluff Crypto-Meteorite Impact Crater of South Texas

    NASA Astrophysics Data System (ADS)

    Graham, R. A.

    2012-10-01

    Disturbed geology within a several km diameter surface area of sedimentary Carrizo Sandstone near Uvalde, Texas, indicates the presence of a partially buried meteorite impact crater. Identification of its impact origin is supported by detailed studies but quartz grains recovered from distances of about100 km from the structure also show planar deformation features (PDFs). While PDFs are recognized as uniquely from impact processes, quantitative interpretation requires extension of Hugoniot materials models to more realistic grain-level, mixture models. Carrizo sandstone is a porous mixture of fine quartz and goethite. At impact pressures of tens of GPa, goethite separates into hematite and water vapor upon release of impact pressure. Samples from six different locations up to 50 km from the impact site preserve characteristic features resulting from mixtures of goethite, its water vapor, hematite and quartz. Spheroids resulting from local radial acceleration of mixed density, hot products are common at various sites. Local hydrodynamic instabilities cause similar effects.

  11. Meteorite Fractures and Scaling for Atmospheric Entry

    NASA Astrophysics Data System (ADS)

    Bryson, Kathryn L.; Ostrowski, Daniel R.

    2016-10-01

    We are attempting to understand the behavior of asteroids entering the atmosphere in order to help quantify the impact hazard. The strength of meteorites plays a critical role in determining the outcome of their impact events. Our objective is to scale fracture parameters in meteorites to their parent body.In this study over a thousand meteorite fragments in the Natural History Museums of Vienna and London (mostly hand-sized, some 40 or 50 cm across) were examined and fracture patterns in selected fragments were imaged. We identified six kinds of fracturing behavior. The density and length of the observed fractures were measured in hand specimens and thin sections. We assume that fracturing follows the Weibull distribution, where fractures are assumed to be randomly distributed through the target and the likelihood of encountering a fracture increases with distance. The images collected of the six fracture behaviors provide a two-dimensional view of the fractures. A relationship exists between the distributions of measured trace length and actual fracture size, where the slope of a log-log plot of trace length vs fracture density is proportional to α, the shape parameter. The value for α is unclear and a large range in α has been determined from light curve data. α can be used to scale strengths from the meteorite to the larger parent body.The majority of the meteorite fractures imaged displayed no particular sensitivity to meteorite texture. A value of α of 0.185 has been determined for a chondrite with a fracture pattern that shows no sensitivity to meteorite texture and has no point of origin. This study will continue to examine additional meteorites with similar fracture patterns along with the other 5 patterns to see if there is a correlation between fracture pattern and α. This may explain the variations in α determined from fireball data. Values of α will be used in models created by the Asteroid Threat Assessment Project to try to determine the

  12. Meteorite Fractures and Scaling for Asteroid Atmospheric Entry

    NASA Astrophysics Data System (ADS)

    Bryson, K.; Ostrowski, D. R.

    2016-12-01

    We are attempting to understand the behavior of asteroids entering the atmosphere in order to help quantify the impact hazard. The strength of meteorites plays a critical role in determining the outcome of their impact events. Our objective is to scale fracture parameters in meteorites to their parent body. In this study >1000 meteorite fragments in the Natural History Museums of Vienna and London were examined and fracture patterns in selected fragments were imaged. We identified six kinds of fracturing behavior. The density and length of the observed fractures were measured in hand specimens and thin sections. We assume that fracturing follows the Weibull distribution, where fractures are assumed to be randomly distributed through the target and the likelihood of encountering a fracture increases with distance. The images collected of the six fracture behaviors provide a two-dimensional view of the fractures. A relationship exists between the distributions of measured trace length and actual fracture size, where the slope of a log-log plot of trace length vs fracture density is proportional to α, the shape parameter. The value for α is unclear and a large range in α has been determined from light curve data. α can be used to scale strengths from the meteorite to the larger parent body. The majority of the meteorite fractures imaged displayed no particular sensitivity to meteorite texture. Values of α have been determined for an intial set of meteorite samples. This study will continue to examine additional meteorites including all six fractures patterns to see if there is a correlation between fracture pattern and α. This may explain the variations in α determined from fireball data. Values of α will be used in models created by the Asteroid Threat Assessment Project to try to determine the behavior of asteroids entering the atmosphere and quantify their impact hazard.

  13. Cosmochemical Studies: Meteorites and their Parent Asteroids

    NASA Technical Reports Server (NTRS)

    Wasson, John T.

    2003-01-01

    This a final technical report that focuses on cosmochemical studies of meteorites and their parent asteroids. The topics include: 1) Formation of iron meteorites and other metal rich meteorites; 2) New perspectives on the formation of chondrules; and 3) Consequences of large aerial bursts. Also a list of seven papers that received significant support from this research are included.

  14. Heterogeneous mineral assemblages in martian meteorite Tissint as a result of a recent small impact event on Mars

    NASA Astrophysics Data System (ADS)

    Walton, E. L.; Sharp, T. G.; Hu, J.; Filiberto, J.

    2014-09-01

    occur within 1.2 s in larger volumes of melt (1 mm2). The apparent variation in shock pressure recorded by variable mineral assemblages within and around shock melts in Tissint is consistent with a shock pulse on the order of 10-20 ms combined with a longer duration of post-shock cooling and complex thermal history. This implies that the impact on Mars that shocked and ejected Tissint at ∼1 Ma was not exceptionally large.

  15. Oxygen Isotopes in Meteorites

    NASA Astrophysics Data System (ADS)

    Clayton, R. N.

    2003-12-01

    Oxygen isotope abundance variations in meteorites are very useful in elucidating chemical and physical processes that occurred during the formation of the solar system (Clayton, 1993). On Earth, the mean abundances of the three stable isotopes are 16O: 99.76%, 17O: 0.039%, and 18O: 0.202%. It is conventional to express variations in abundances of the isotopes in terms of isotopic ratios, relative to an arbitrary standard, called SMOW (for standard mean ocean water), as follows:The isotopic composition of any sample can then be represented by one point on a "three-isotope plot," a graph of δ17O versus δ18O. It will be seen that such plots are invaluable in interpreting meteoritic data. Figure 1 shows schematically the effect of various processes on an initial composition at the center of the diagram. Almost all terrestrial materials lie along a "fractionation" trend; most meteoritic materials lie near a line of "16O addition" (or subtraction). (4K)Figure 1. Schematic representation of various isotopic processes shown on an oxygen three-isotope plot. Almost all terrestrial materials plot along a line of "fractionation"; most primitive meteoritic materials plot near a line of "16O addition." The three isotopes of oxygen are produced by nucleosynthesis in stars, but by different nuclear processes in different stellar environments. The principal isotope, 16O, is a primary isotope (capable of being produced from hydrogen and helium alone), formed in massive stars (>10 solar masses), and ejected by supernova explosions. The two rare isotopes are secondary nuclei (produced in stars from nuclei formed in an earlier generation of stars), with 17O coming primarily from low- and intermediate-mass stars (<8 solar masses), and 18O coming primarily from high-mass stars (Prantzos et al., 1996). These differences in type of stellar source result in large observable variations in stellar isotopic abundances as functions of age, size, metallicity, and galactic location ( Prantzos

  16. Shock effects in meteorites

    NASA Technical Reports Server (NTRS)

    Stoeffler, D.; Bischoff, A.; Buchwald, V.; Rubin, A. E.

    1988-01-01

    The impacts that can occur between objects on intersecting solar system orbits can generate shock-induced deformations and transformations, creating new mineral phases or melting old ones. These shock-metamorphic effects affect not only the petrography but the chemical and isotopic properties and the ages of primordial meteoritic materials. A fuller understanding of shock metamorphism and breccia formation in meteorites will be essential not only in the study of early accretion, differentiation, and regolith-evolution processes, but in the characterization of the primordial composition of the accreted material itself.

  17. Hf-W, Sm-Nd, and Rb-Sr isotopic evidence of late impact fractionation and mixing of silicates on iron meteorite parent bodies

    NASA Astrophysics Data System (ADS)

    Snyder, Gregory A.; Lee, Der-Chuen; Ruzicka, Alex M.; Prinz, Martin; Taylor, Lawrence A.; Halliday, Alex N.

    2001-03-01

    We report the first Sm-Nd and Rb-Sr isotopic analyses of silicate inclusions in four IIE iron meteorites: Miles, Weekeroo Station A and B, and Watson. We also report the Hf-W isotopic composition of a silicate inclusion from Watson and 182W/ 184W of the host FeNi metal in all four IIEs. The host metal in Watson has a negative ɛW value (-2.21±0.24), similar to or higher than other iron meteorites [1,35] and consistent with segregation of metal from silicate early in solar system history. However, the large silicate inclusion in the Watson IIE iron yielded a chondritic ɛW value (-0.50±0.55), thus indicating a lack of equilibration with the FeNi host within the practical lifetime of activity of the parent 182Hf (˜50 Ma). One of the silicate inclusions in Miles is roughly chondritic in major-element composition, has a present-day ɛNd of +10.3, relatively non-radiogenic 87Sr/ 86Sr (0.714177±13), and a TCHUR age of 4270 Ma. Two silicate inclusions from Weekeroo Station and one from Watson exhibit fractionated Sm/Nd and Rb/Sr ratios, and more radiogenic 87Sr/ 86Sr (0.731639±12 to 0.791852±11) and non-radiogenic ɛNd values (-5.9 to -13.4). The silicate inclusion in Watson has a TCHUR age of 3040 Ma, in agreement with previously determined 4He and 40Ar gas retention ages, indicative of a late thermal event. A later event is implied for the two silicate inclusions in Weekeroo Station, which yield indistinguishable TCHUR ages of 698 and 705 Ma. Silicate inclusions in IIE iron meteorites formed over a period of 3 billion yr by impacts, involving an H-chondrite parent body and an FeNi metal parent body. The LILE-enriched nature of some of these silicates suggests several stages of melting, mixing, and processing. However, there is little evidence to suggest that the silicates in the IIE irons were ever in equilibrium with the host FeNi metal.

  18. Search for a meteoritic component in impact-melt rocks from the Lonar crater, India - Evidence from osmium isotope systematics

    NASA Astrophysics Data System (ADS)

    Schulz, T.; Luguet, A.; Koeberl, C.

    2013-12-01

    Introduction: The Lonar crater in western India (Maharashtra) is a bowl-shaped simple impact structure of 1830 m diameter and a depth of 120 m below the rim crest. The crater formed 0.656 × 0.081 Ma ago on the 65 Ma old basaltic lava flows of the Deccan Traps (Jourdan et al. 2010) and is one of the few terrestrial impact structures to have formed in basaltic host-rocks. In the absence of actual meteorite fragments, the impact origin of this structure was supported by the identification of a variety of shock metamorphic features (e.g. Fredriksson et al. 1973). However, clear indications of an extraterrestrial component in impactites based on geochemical studies are absent or remained ambiguous so far (e.g. Osae et al. 2005). As the Os isotope tool has the potential to provide firm constraints on the presence or absence of even very small (<<1%) contributions of meteoritic matter to impactite lithologies (e.g. Koeberl et al. 2002), we conduct a detailed Os isotope study of a variety of unshocked host-basalts (target rocks) and impactites (impact-melt rocks) from the Lonar crater. Samples and Method: All samples analyzed in this study were collected in 2000 and 2001 and were geochemically characterized by Osae et al. (2005). Osmium (and additional PGE) analyses were performed on about 2 g whole rock powders, which were spiked with a mixed 190Os,185Re,191Ir,194Pt tracer, and digested via high pressure Asher using inverse aqua regia. Osmium solvent extraction and microdistillation were performed as described by Cohen and Waters (1996). Osmium isotopic compositions were measured using a TRITON N-TIMS at the Department of Lithospheric Research in Vienna. Results and Discussion: Osmium data on seven target and nine impact melt rocks reveal 187Os/188Os ratios ranging from ~0.38 to ~2.23 for the target rocks and from ~0.22 to ~0.59 for the nine analyzed impact melt rocks, whereas Os concentrations range from ~7.1 to ~31.6 ppt and ~7.2 to ~134 ppt, respectively. Although in

  19. A statistical dynamical study of meteorite impactors: A case study based on parameters derived from the Bosumtwi impact event

    NASA Astrophysics Data System (ADS)

    Galiazzo, M. A.; Bazsó, Á.; Huber, M. S.; Losiak, A.; Dvorak, R.; Koeberl, C.

    2013-11-01

    The study of meteorite craters on Earth provides information about the dynamic evolution of bodies within the Solar System. the Bosumtwi crater is a well studied, 10.5 km in diameter, ca. 1.07 Myr old impact structure located in Ghana. (Koeberl et al., 1997a). The impactor was ˜ 1 km in diameter, an ordinary chondrite and struck the Earth with an angle between 30o and 45o (Artemieva et al., 2004) from the horizontal. We have used a two phase backward integration to constrain the most probable parent region of the impactor. We find that the most likely source region is a high inclination object from the Middle Main Belt.

  20. Geochemical comparison of impact glasses from lunar meteorites ALHA81005 and MAC88105 and Apollo 16 regolith 64001

    SciTech Connect

    Delano, J.W. )

    1991-11-01

    Most glasses that occur in lunar highland regolith are quenched droplets of impact melt. The chemical compositions of these glasses are equivalent, in the absence of volatile losses, to the original target materials. The compositional range of impact glasses in a regolith reflects the chemical diversity that existed throughout the region up to the time of system closure (e.g., breccia formation). Since these glasses are a product of widespread and random sampling, both in terms of space and time, they can be used for geochemical exploration of the Moon. The major-element compositions of impact glasses occurring in three samples of lunar feldspathic regolith (ALHA81005; MAC88105; Apollo 16 64001) have been determined by electron microprobe. The glass populations among these three unrelated samples are compositionally distinct. While most of the impact glasses within each of these three samples are compositionally similar to the regolith in which they are found, up to 40% of the impact glasses are different. Some of the compositionally exotic glasses were ballistically transported from other areas of the Moon and thereby provide information about the compositional range of regoliths that exist elsewhere. Since the geological setting of the Apollo 16 region is well known compared to the source areas of the lunar meteorites, the Apollo 16 glasses provide a ground truth for interpretations.

  1. History of meteorites from the moon collected in antarctica.

    PubMed

    Eugster, O

    1989-09-15

    In large asteroidal or cometary impacts on the moon, lunar surface material can be ejected with escape velocities. A few of these rocks were captured by Earth and were recently collected on the Antarctic ice. The records of noble gas isotopes and of cosmic ray-produced radionuclides in five of these meteorites reveal that they originated from at least two different impact craters on the moon. The chemical composition indicates that the impact sites were probably far from the Apollo and Luna landing sites. The duration of the moon-Earth transfer for three meteorites, which belong to the same fall event on Earth, lasted 5 to 11 million years, in contrast to a duration of less than 300,000 years for the two other meteorites. From the activities of cosmic ray-produced radionuclides, the date of fall onto the Antarctic ice sheet is calculated as 70,000 to 170,000 years ago.

  2. History of meteorites from the moon collected in Antarctica

    NASA Astrophysics Data System (ADS)

    Eugster, O.

    1989-09-01

    In large asteroidal or cometary impacts on the moon, lunar surface material can be ejected with escape velocities. A few of these rocks were captured by earth and were recently collected on the Antarctic ice. The records of noble gas isotopes and of cosmic ray-produced radio-nuclides in five of these meteorites reveal that they originated from at least two different impact craters on the moon. The chemical composition indicates that the impact sites were probably far from the Apollo and Luna landing sites. The duration of the moon-earth transfer for three meteorites, which belong to the same fall event on earth, lasted 5 to 11 million years, in contrast to a duration of less than 300,000 years for the two other meteorites. From the activities of cosmic ray-produced radionuclides, the date of fall onto the Antarctic ice sheet is calculated as 70,000 to 170,000 years ago.

  3. From meteorites to evolution and habitability of planets

    NASA Astrophysics Data System (ADS)

    Véronique, Dehant; Doris, Breuer; Philippe, Claeys; Vinciane, Debaille; Johan, De Keyser; Emmanuelle, Javaux; Steven, Goderis; Özgur, Karatekin; Tilman, Spohn; Ann Carine, Vandaele; Frank, Vanhaecke; Tim, Van Hoolst; Valérie, Wilquet

    2012-11-01

    The evolution of planets is driven by the composition, structure, and thermal state of their internal core, mantle, lithosphere, and crust, and by interactions with a possible ocean and/or atmosphere. A planet's history is a long chronology of events with possibly a sequence of apocalyptic events in which asteroids, comets and their meteorite offspring play an important role. Large meteorite impacts on the young Earth could have contributed to the conditions for life to appear, and similarly large meteorite impacts could also create the conditions to erase life or drastically decrease biodiversity on the surface of the planet. Meteorites also contain valuable information to understand the evolution of a planet through their gas inclusion, their composition, and their cosmogenic isotopes. This paper addresses the evolution of the terrestrial bodies of our Solar System, in particular through all phenomena related to meteorites and what we can learn from them. This includes our present understanding of planet formation, their interior, their atmosphere, and the effects and relations of meteorites with respect to these reservoirs. It brings further insight into the origin and sustainability of life on planets, including Earth. Particular attention is devoted to Earth and Mars, as well as to planets and satellites possessing an atmosphere (Earth, Mars, Venus, and Titan) or a subsurface ocean (e.g., Europa), because those are the best candidates for hosting life. Though the conditions on the planets Earth, Mars, and Venus were probably similar soon after their formation, their histories have diverged about 4 billion years ago. The search for traces of life on early Earth serves as a case study to refine techniques/environments allowing the detection of potential habitats and possible life on other planets. A strong emphasis is placed on impact processes, an obvious shaper of planetary evolution, and on meteorites that document early Solar System evolution and witness the

  4. The Isli-Agoudal meteorite strewnfield

    NASA Astrophysics Data System (ADS)

    Nachit, Hassane; Ibhi, Abderrahmane; Vaccaro, Carmela

    2014-01-01

    New meteorite prospections at different places in the region of Imilchil showed that (1) besides the Ataxite of Tasraft, all the other collected specimens belong to the same and only IIAB iron mother meteorite; (2) the strewnfield of the meteorite has a length of about 38 km along the north-south direction; (3) the small crater of Agoudal as well as the impact crater of Isli are situated on a parallel north-south axis, if not taken together with the strewnfield of the Imilchil meteorite; (4) these two structures might be the result of the fall of the single common mother meteorite of the IIAB type.

  5. Unprecedented Evidence for Large Scale Heterogeneous Nucleation of Polar Stratospheric Clouds, Likely by Nanometer-Sized Meteoritic Particles

    NASA Astrophysics Data System (ADS)

    Engel, I.; Pitts, M. C.; Luo, B.; Hoyle, C. R.; Zobrist, B.; Jacot, L.; Poole, L. R.; Grooss, J.; Weigel, R.; Borrmann, S.; Ebert, M.; Duprat, J.; Peter, T.

    2012-12-01

    Recent observations cast serious doubts on our understanding of the processes responsible for polar stratospheric cloud (PSC) formation. PSCs play crucial roles in polar ozone chemistry by hosting heterogeneous reactions and by removal of reactive nitrogen through sedimenting nitric acid trihydrate (NAT) particles. An extensive field campaign took place in the Arctic during the winter 2009/2010 within the European Union project RECONCILE, complemented by measurements from the spaceborne CALIOP (Cloud-Aerosol LIdar with Orthogonal Polarization) instrument. Through trajectory and microphysical box model calculations, we analyzed CALIOP data from the RECONCILE winter to investigate the nucleation of PSC particles in detail. One significant finding was that liquid/NAT mixture PSCs were prevalent in late December 2009, a period during which no ice PSCs were observed, and temperatures were higher by 6 K than required for homogeneous ice freezing at the onset of PSC formation. These NAT particles must have formed through some non-ice nucleation mechanism, which runs counter to the widely held view that the only efficient NAT nuclei were ice crystals formed by homogeneous freezing of STS droplets. Furthermore, in mid-January 2010, a large region of the Arctic vortex cooled below the frost point, leading to widespread synoptic-scale ice PSCs, unusual for the Arctic. Our modeling studies indicate that a match with the CALIOP data calls for new heterogeneous nucleation mechanisms for both NAT and ice particles, namely freezing on nanometer-sized, solid nuclei immersed in the liquid stratospheric aerosols. Number concentrations of non-volatile particles were measured in situ during RECONCILE by means of the heated channel of the condensation nuclei (CN) counter COPAS on board of the high-flying aircraft Geophysica. 60-80 % of all CN survived heating to 250 °C. Offline Environmental Scanning Electron Microscopy and Energy Dispersive X-Ray Analysis of RECONCILE impactor samples

  6. Osmium isotope evidence for a large Late Triassic impact event

    PubMed Central

    Sato, Honami; Onoue, Tetsuji; Nozaki, Tatsuo; Suzuki, Katsuhiko

    2013-01-01

    Anomalously high platinum group element concentrations have previously been reported for Upper Triassic deep-sea sediments, which are interpreted to be derived from an extraterrestrial impact event. Here we report the osmium (Os) isotope fingerprint of an extraterrestrial impact from Upper Triassic chert successions in Japan. Os isotope data exhibit a marked negative excursion from an initial Os isotope ratio (187Os/188Osi) of ∼0.477 to unradiogenic values of ∼0.126 in a platinum group element-enriched claystone layer, indicating the input of meteorite-derived Os into the sediments. The timing of the Os isotope excursion coincides with both elevated Os concentrations and low Re/Os ratios. The magnitude of this negative Os isotope excursion is comparable to those found at Cretaceous–Paleogene boundary sites. These geochemical lines of evidence demonstrate that a large impactor (3.3–7.8 km in diameter) produced a global decrease in seawater 187Os/188Os ratios in the Late Triassic. PMID:24036603

  7. Osmium isotope evidence for a large Late Triassic impact event.

    PubMed

    Sato, Honami; Onoue, Tetsuji; Nozaki, Tatsuo; Suzuki, Katsuhiko

    2013-01-01

    Anomalously high platinum group element concentrations have previously been reported for Upper Triassic deep-sea sediments, which are interpreted to be derived from an extraterrestrial impact event. Here we report the osmium (Os) isotope fingerprint of an extraterrestrial impact from Upper Triassic chert successions in Japan. Os isotope data exhibit a marked negative excursion from an initial Os isotope ratio ((187)Os/(188)Osi) of ~0.477 to unradiogenic values of ~0.126 in a platinum group element-enriched claystone layer, indicating the input of meteorite-derived Os into the sediments. The timing of the Os isotope excursion coincides with both elevated Os concentrations and low Re/Os ratios. The magnitude of this negative Os isotope excursion is comparable to those found at Cretaceous-Paleogene boundary sites. These geochemical lines of evidence demonstrate that a large impactor (3.3-7.8 km in diameter) produced a global decrease in seawater (187)Os/(188)Os ratios in the Late Triassic.

  8. Unmelted meteoritic debris in the Late Pliocene iridium anomaly - Evidence for the ocean impact of a nonchondritic asteroid

    NASA Technical Reports Server (NTRS)

    Kyte, F. T.; Brownlee, D. E.

    1985-01-01

    Ir-bearing particles have been recovered from two piston cores in the Antarctic Basin in the southeastern Pacific. In core E13-3, the particles closely correspond to the Late Pliocene Ir anomaly and have a fluence of about 100 mg/cm sq. In core E13-4, 120 km to the southwest, the particle fluence is about 4 mg/cm sq. Particles with diameters from 0.5 to 4 mm contain at least 35 percent of the Ir in this horizon. Three types of particles have been identified: (1) vesicular, (2) basaltic, and (3) metal. The vesicular particles appear to be shock-melted debris derived from the oceanic impact of a howarditic asteroid containing a minor metal component. These particles have recrystallized from a melt and impact into the ocean has resulted in the incorporation of Na, K, Cl, and radiogenic Sr from the ocean water target. The basaltic clasts appear to be unmelted fragments of the original asteroid which may have separated from the main body prior to impact. Combined vesicular and basaltic particles are believed to have formed by collisions in the debris cloud. Estimates of the diameter of the projectile range from 100 to 500 m. By many orders of magnitude, this is the most massive achondrite sampled by a single meteorite fall.

  9. Unmelted meteoritic debris in the Late Pliocene iridium anomaly - Evidence for the ocean impact of a nonchondritic asteroid

    NASA Technical Reports Server (NTRS)

    Kyte, F. T.; Brownlee, D. E.

    1985-01-01

    Ir-bearing particles have been recovered from two piston cores in the Antarctic Basin in the southeastern Pacific. In core E13-3, the particles closely correspond to the Late Pliocene Ir anomaly and have a fluence of about 100 mg/cm sq. In core E13-4, 120 km to the southwest, the particle fluence is about 4 mg/cm sq. Particles with diameters from 0.5 to 4 mm contain at least 35 percent of the Ir in this horizon. Three types of particles have been identified: (1) vesicular, (2) basaltic, and (3) metal. The vesicular particles appear to be shock-melted debris derived from the oceanic impact of a howarditic asteroid containing a minor metal component. These particles have recrystallized from a melt and impact into the ocean has resulted in the incorporation of Na, K, Cl, and radiogenic Sr from the ocean water target. The basaltic clasts appear to be unmelted fragments of the original asteroid which may have separated from the main body prior to impact. Combined vesicular and basaltic particles are believed to have formed by collisions in the debris cloud. Estimates of the diameter of the projectile range from 100 to 500 m. By many orders of magnitude, this is the most massive achondrite sampled by a single meteorite fall.

  10. Dynamical properties measurements for asteroid, comet and meteorite material applicable to impact modeling and mitigation calculations

    SciTech Connect

    Furnish, M.D.; Boslough, M.B.; Gray, G.T. III; Remo, J.L.

    1994-07-01

    We describe methods for measuring dynamical properties for two material categories of interest in understanding large-scale extraterrestrial impacts: iron-nickel and underdense materials (e.g. snow). Particular material properties measured by the present methods include Hugoniot release paths and constitutive properties (stress vs. strain). The iron-nickel materials lend themselves well to conventional shock and quasi-static experiments. As examples, a suite of experiments is described including six impact tests (wave profile compression/release) over the stress range 2--20 GPa, metallography, quasi-static and split Hopkinson pressure bar (SHPB) mechanical testing, and ultrasonic mapping and sound velocity measurements. Temperature sensitivity of the dynamic behavior was measured at high and low strain rates. Among the iron-nickel materials tested, an octahedrite was found to have behavior close to that of Armco iron under shock and quasi-static conditions, while an ataxite exhibited a significantly larger quasi-static yield strength than did the octahedrite or a hexahedrite. The underdense materials pose three primary experimental difficulties. First, the samples are friable; they can melt or sublimate during storage, preparation and testing. Second, they are brittle and crushable; they cannot withstand such treatment as traditional machining or launch in a gun system. Third, with increasing porosity the calculated Hugoniot density becomes rapidly more sensitive to errors in wave time-of-arrival measurements. Carefully chosen simulants eliminate preservation (friability) difficulties, but the other difficulties remain. A family of 36 impact tests was conducted on snow and snow simulants at Sandia, yielding reliable Hugoniot and reshock states, but limited release property information. Other methods for characterizing these materials are discussed.

  11. If a Meteorite of Martian Sandstone Hit You on the Head Would You Recognize It?

    NASA Astrophysics Data System (ADS)

    Ashley, G. M.; Delaney, J. S.

    1999-03-01

    Martian meteorites are igneous but Mars is Earthlike with sediments, igneous and maybe sedimentary rocks. Sedimentary meteorites should occur in proportion to the igneous/sedimentary ratio. Sedimentary meteorites would impact climatology and the search for life on Mars.

  12. Search for a meteoritic component in drill cores from the Bosumtwi impact structure, Ghana: Platinum group element contents and osmium isotopic characteristics

    NASA Astrophysics Data System (ADS)

    McDonald, Iain; Peucker-Ehrenbrink, Bernhard; Coney, Louise; Ferrière, Ludovic; Reimold, Wolf Uwe; Koeberl, Christian

    An attempt was made to detect a meteoritic component in both crater-fill (fallback) impact breccias and fallout suevites (outside the crater rim) at the Bosumtwi impact structure in Ghana. Thus far, the only clear indication for an extraterrestrial component related to this structure has been the discovery of a meteoritic signature in Ivory Coast tektites, which formed during the Bosumtwi impact event. Earlier work at Bosumtwi indicated unusually high levels of elements that are commonly used for the identification of meteoritic contamination (i.e., siderophile elements, including the platinum group elements [PGE]) in both target rocks and impact breccias from surface exposures around the crater structure, which does not allow unambiguous verification of an extraterrestrial signature. The present work, involving PGE abundance determinations and Os isotope measurements on drill core samples from inside and outside the crater rim, arrives at the same conclusion. Despite the potential of the Os isotope system to detect even small amounts of extraterrestrial contribution, the wide range in PGE concentrations and Os isotope composition observed in the target rocks makes the interpretation of unradiogenic, high-concentration samples as an impact signature ambiguous.

  13. Meteorite craters

    NASA Technical Reports Server (NTRS)

    Ivanov, B. A.; Bazilevskiy, A. T.

    1986-01-01

    The origin and formation of various types of craters, both on the Earth and on other planetary bodies, are discussed. Various models are utilized to depict various potential causes of the types and forms of meteorite craters in our solar system, and the geological structures are also discussed.

  14. Methane Emission from the Murchison Meteorite Induced by Ultraviolet Radiation and its Potential Impact on the Martian Atmosphere

    NASA Astrophysics Data System (ADS)

    Keppler, F.; Vigano, I.; McLeod, A.; Ott, U.; Roeckmann, T.

    2011-12-01

    might have important implications for our understanding of the generation of methane on Mars because meteoritic material (mostly micrometeorites resembling in composition the CM meteorites) containing a few percent organic matter is estimated to reach the Martian surface at high rates (Flynn and McKay, 1990), resulting in Martian soil that contains large amounts of meteoritic debris. Thus our results provide an explanation for a potentially significant contribution to Martian atmospheric methane but may also explain some local sources and seasonal variations such as the recently observed methane plumes (Mumma et al. 2009). Court, R.W., Sephton, M.A. (2009) Earth and Planetary Science Letters 288, 382-385. Formisano, V. et al. (2004). Science 306, 1758-1761. Flynn, G.J., McKay, D.S., (1990). J. Geophys. Res.-Solid 95, 14,497-14,509. Lefèvre, F., Forget, F., (2009) Nature 460, 720-723. Krasnopolsky, V.A. et al. (2004) Icarus 172, 537-547. Mumma, M. J. et al. (2003) Bull. Am. Astron. Soc. 35, 937. Mumma, M.J. et al. (2009) Science 323, 1041-1045. Schuerger, A.C. et al. (2011) Icarus 213, 393-403.

  15. Detection of a meteoritic component in ivory coast tektites with rhenium-osmium isotopes.

    PubMed

    Koeberl, C; Shirey, S B

    1993-07-30

    Measurement of rhenium (Re) and osmium (Os) concentrations and Os isotopic compositions in Ivory Coast tektites (natural glasses with upper crustal compositions that are ejected great distances during meteorite impact) and rocks from the inferred source crater, Lake Bosumtwi, Ghana, show that these tektites incorporate about 0.6 percent of a meteoritic component. Analysis of elemental abundances of noble metals alone gives equivocal results in the detection of meteoritic components because the target rocks already have relatively large amounts of noble metals. The Re-Os system is ideally suited for the study of meteorite impacts on old continental crust for three reasons. (i) The isotopic compositions of the target rocks and the meteoritic impactor are significantly different. (ii) Closed-system mixing of target rocks and meteorites is linear on Re-Os isochron diagrams, which thus permits identification of the loss of Re or Os. (iii) Osmium isotopic compositions are not likely to be altered during meteorite impact even if Re and Os are lost.

  16. Detection of a meteoritic component in Ivory Coast tektites with rhenium-osmium isotopes

    NASA Astrophysics Data System (ADS)

    Koeberl, Christian; Shirey, Steven B.

    1993-07-01

    Measurement of rhenium (Re) and osmium (Os) concentrations and Os isotopic compositions in Ivory Coast tektites (natural glasses with upper crustal compositions that are ejected great distances during meteorite impact) and rocks from the inferred source crater, Lake Bosumtwi, Ghana, show that these tektites incorporate about 0.6 percent of a meteoritic component. Analysis of elemental abundances of noble metals alone gives equivocal results in the detection of meteoritic components because the target rocks already have relatively large amounts of noble metals. The Re-Os system is ideally suited for the study of meteorite impacts on old continental crust for three reasons. The isotopic compositions of the target rocks and the meteoritic impactor are significantly different. Closed-system mixing of target rocks and meteorites is linear on Re-Os isochron diagrams, which thus permits identification of the loss of Re or Os. Osmium isotopic compositions are not likely to be altered during meteorite impact even if Re and Os are lost.

  17. Meteorites for K-12 Classrooms: NASA Meteorite Educational Materials

    NASA Astrophysics Data System (ADS)

    Lindstrom, M.; Allen, J.

    1995-09-01

    The fall of a new meteorite is an event that catches the interest of the public in matters of science. The threat of a huge impact like last year's comet Shoemaker-Levy 9 gives us all reason to evaluate such potential risks. NASA's meteorite educational materials use our natural interest in rocks from space to present classroom activities on planetary science. The meteorite educational package includes a meteorite sample disk, a teachers's guide and a slide set. The sample disk is a lucite disk containing chips of six different kinds of meteorites (3 chondrites, achondrite, iron, stony-iron). EXPLORING METEORITE MYSTERIES is a teacher's guide with background information and 19 hands-on or heads-on activities for grades 4-12. It was prepared in a partnership of planetary scientists and teachers. The slide set consists of 48 slides with captions to be used with the activities. The materials will be available in Fall 1995. Teachers may obtain a loan of the whole package from NASA Teacher Resource Centers; researchers may borrow them from the JSC meteorite curator. The booklet is available separately from the same sources, and the slide set will be available from NASA CORE. EXPLORING METEORITE MYSTERIES is an interdisciplinary planetary science unit which teaches basic science concepts and techniques together with math, reading, writing and social studies The activities are done in a variety of different teaching styles which emphasize observation, experimentation and critical thinking. The activities are ideal for middle schools where teaming makes interdisciplinary units desireable, but most of the activities can be easily modified for grade levels from upper elementary through high school. Meteorites are a natural subject for interdisciplinary teaching because their study involves all fields of science and offers fascinating historical accounts and possibilities for creative expression. Topics covered in EXPLORING METEORITE MYSTERES are centered around basic

  18. Meteorite infall as a function of mass - Implications for the accumulation of meteorites on Antarctic ice

    NASA Technical Reports Server (NTRS)

    Huss, Gary R.

    1990-01-01

    Antarctic meteorites are considerably smaller, on average, than those recovered elsewhere in the world, and seem to represent a different portion of the mass distribution of infalling meteorites. When an infall rate appropriate to the size of Antarctic meteorites is used (1000 meteorites 10 grams or larger/sq km/1 million years), it is found that direct infall can produce the meteorite accumulations found on eight ice fields in the Allan Hills region in times ranging from a few thousand to nearly 200,000 years, with all but the Allan Hills Main and Near Western ice fields requiring less than 30,000 years. Meteorites incorporated into the ice over time are concentrated on the surface when the ice flows into a local area of rapid ablation. The calculated accumulation times, which can be considered the average age of the exposed ice, agree well with terrestrial ages for the meteorites and measured ages of exposed ice. Since vertical concentration of meteorites through removal of ice by ablation is sufficient to explain the observed meteorite accumulations, there is no need to invoke mechanisms to bring meteorites from large areas to the relatively small blue-ice patches where they are found. Once a meteorite is on a bare ice surface, freeze-thaw cycling and wind break down the meteorite and remove it from the ice. The weathering lifetime of a 100-gram meteorite on Antarctic ice is on the order of 10,000 + or - 5,000 years.

  19. Impacts and Ophiolites: A Way to Recognize Large Terrestrial Impact Basins?

    NASA Astrophysics Data System (ADS)

    Olds, E. P.

    2015-12-01

    That Chicxulub Crater is located on ~35 km thick continental crust is apparently inconsistent with oceanic crustal/upper mantle geochemical signatures detected globally in the KT boundary impact layer [1-5 and unpublished Cr isotope data from the Yin lab at UC Davis] since introduction of the Alvarez hypothesis [6]. Apparent excavation and ejection of mafic/ultramafic target rock by the KT boundary impact might imply an additional KT impact site involving oceanic lithosphere. We speculate: 1) The Greater Antilles island chain ophiolite belt marks the rim of a ~700 km diameter impact basin, deformed and dismembered from an originally circular form by at least 50 million years of left lateral shear on the North American-Caribbean transform plate boundary; 2) Other ophiolite segments may similarly mark rims of large impact basins deformed to greater or lesser extent by, and serving as strain markers for, relative plate motions over geologic time; 3) The Greater Antilles/Chicxulub and Sulu Sea Basin/Spratly Island cases may constitute doublet craters of similar size ratio and separation distance; 4) Plate boundaries may be formed or modified by such impacts. Problems include: 1) The KT fireball layer should be tens of cm thick rather than a few mm thick [8-9]; 2) Impact basins of this size/scale are not expected in the Phanerozoic/Proterozoic [10]; References: [1] DePaolo D. J. et al. 1983. EPSL 64:356-373. [2] Hildebrand A. R. and Boynton W. V. 1988, LPI Contributions 673:78-79. [3] Hildebrand A. R. and Boynton W. V.. 1990. Science 248:843-847. [4] Montanari A. et al. 1983. Geology 11:668. [5] Bohor B. F. et al. 1989. Meteoritics 24:253. [6] Alvarez L. W. et al. 1980 Science 208:1095-1108. [7][8] Grieve R.A.F. and Cintala M.J. 1992 Meteoritics 27: 526-538. [9] Pierazzo E. et al. 1997 Icarus 127/2:408-423. [10] Ivanov B.A. et al. 2002 Asteroids III 89-101

  20. Magnetic classification of meteorites

    NASA Astrophysics Data System (ADS)

    Rochette, P.; Sagnotti, L.; Consolmagno, G.; Denise, M.; Folco, L.; Gattacceca, J.; Osete, M.; Pesonen, L.

    2003-04-01

    Magnetic susceptibility (X) provides a versatile rapid and non destructive way to quantify the amount of magnetic minerals (FeNi metal, magnetic oxides and sulfides) on large volume of material. As petrological studies of meteorites suggest that this parameter should be quite discriminant, we assembled a database of measurements on about 1200 stony meteorites from various European collections: Helsinki, Madrid, Moscou, Paris, Prague, Roma, Siena, Vatican, and other smaller collections. From 1 to >20 pieces and 1 to >100 cc per meteorite allow to define a representative mean value, using a large coil (8 cm) Kappabridge. For ordinary chondrites, it appears that weathering is responsible for a systematic bias toward low X for Antarctic (Frontier Mountain) and non Antarctic (mainly from Sahara) finds. Once only falls are considered a quite narrow range of X is observed for a given class, with no effect of petrological grade except for LL. This does not support suggested decrease of metal amount with metamorphism for L chondrites. High grade LLs (heated above 400°C) develop the weakly magnetic antitaenite-tetrataenite phases during slow cooling, explaining the difference with low grade taenite-bearing LLs. Once a few % of outliers are excluded, well defined means for H and L are observed with no overlap at 2 s.d.; this agrees with the lack of overlap on metal amount. For non ordinary chondrites and achondrites, weakly magnetic classes are HED, Aubrites and SNC (below LL), strongly ones are E (above H) and Ureilites (in the L-H range), while C chondrites are spread in the whole range, again with each class showing restricted variation. Outliers appeared to be in most cases either misclassified meteorites or misindentified samples, based on petrographic and microprobe investigations of thin sections from outlying samples. It appears that systematic magnetic screening of large collections is an efficient way to detect erroneous sample identification, due to exchange with

  1. Mechanical Properties of Fe-Ni Meteorites

    NASA Astrophysics Data System (ADS)

    Roberta, Mulford; El Dasher, B.

    2010-10-01

    Iron-nickel meteorites exhibit a unique lamellar microstructure, Widmanstatten patterns, consisting of small regions with steep-iron-nickel composition gradients.1,2 The microstructure arises as a result of extremely slow cooling in a planetary core or other large mass. Mechanical properties of these structures have been investigated using microindentation, x-ray fluorescence, and EBSD. Observation of local mechanical properties in these highly structured materials supplements bulk measurements, which can exhibit large variation in dynamic properties, even within a single sample. 3 Accurate mechanical properties for meteorites may enable better modeling of planetary cores, the likely origin of these objects. Appropriate values for strength are important in impact and crater modeling and in understanding the consequences of observed impacts on planetary crusts. Previous studies of the mechanical properties of a typical iron-nickel meteorite, a Diablo Canyon specimen, indicated that the strength of the composite was higher by almost an order of magnitude than values obtained from laboratory-prepared specimens.4 This was ascribed to the extreme work-hardening evident in the EBSD measurements. This particular specimen exhibited only residual Widmanstatten structures, and may have been heated and deformed during its traverse of the atmosphere. Additional specimens from the Canyon Diablo fall (type IAB, coarse octahedrite) and examples from the Muonionalusta meteorite and Gibeon fall ( both IVA, fine octahedrite), have been examined to establish a range of error on the previously measured yield, to determine the extent to which deformation upon re-entry contributes to yield, and to establish the degree to which the strength varies as a function of microstructure. 1. A. Christiansen, et.al., Physica Scripta, 29 94-96 (1984.) 2. Goldstein and Ogilvie, Geochim Cosmochim Acta, 29 893-925 (1965.) 3. M. D. Furnish, M.B. Boslough, G.T. Gray II, and J.L. Remo, Int. J. Impact Eng

  2. Relationships among basaltic lunar meteorites

    NASA Technical Reports Server (NTRS)

    Lindstrom, Marilyn M.

    1991-01-01

    During the past two years four meteorites of dominantly mare basalt composition were identified in the Japanese and US Antarctic collections. Basalts represent a much higher proportion of the lunar meteorites than is expected from photogeologic mapping of mare and highland regions. Also, the basaltic lunar meteorites are all described as VLT mare basalt, which is a relatively uncommon type among returned lunar samples. The significance of the basaltic meteorites to the understanding of the lunar crust depends on the evaluation of possible relationships among the individual meteorites. None of the specimens are paired meteorites. They differ from each other in petrography and composition. It is important to determine whether they might be paired ejecta which were ejected from the same mare region by the same impact. The question of paired ejecta must be addressed using a combination of exposure histories and petrographic/compositional characteristics. It is possible that the basaltic lunar meteorites are paired ejecta from the same region of the Moon. However, the relationships among them are more complicated than the basaltic breccias being simply brecciated mare gabbros.

  3. Thermal and impact histories of reheated group IVA, IVB, and ungrouped iron meteorites and their parent asteroids

    NASA Astrophysics Data System (ADS)

    Yang, J.; Goldstein, J. I.; Scott, E. R. D.; Michael, J. R.; Kotula, P. G.; Pham, T.; McCoy, T. J.

    2011-09-01

    cause of reheating. Cooling over years rather than hours precludes shock during the impacts that exposed the irons to cosmic rays. If the reheated irons that we studied are representative, the IVA irons may have been shocked soon after they cooled below 200 °C at 4.5 Gyr in an impact that created a rubblepile asteroid with fragments from diverse depths. The primary cooling rates of the IVA irons and the proposed early history are remarkably consistent with the Pb-Pb ages of troilite inclusions in two IVA irons including the oldest known differentiated meteorite (Blichert-Toft et al. 2010).

  4. Methane Retention by Rocks Following Simulated Meteorite Impacts: Implications for Mars

    NASA Astrophysics Data System (ADS)

    McMahon, S.; Parnell, J.; Burchell, M.; Blamey, N. J. F.

    2012-03-01

    A high-velocity impact was simulated in the laboratory and methane-retention in the crater quantified by mass spectrometry. The results are consistent with the possibility that impact events could store methane in the martian crust.

  5. Proposal of a Spatial Decision Support System architecture to estimate the consequences and costs of small meteorites impacts

    NASA Astrophysics Data System (ADS)

    Garbolino, E.; Michel, P.

    2011-11-01

    On a frequency, depending on their size, small celestial bodies enter into the Earth atmosphere and collide with our planet. On a daily basis, the size is likely to be about 20 cm, while for monthly events the largest it may be is about 1 m. The last significant witnessed event occurred in 1908 in the Siberian area of the Tunguska. The forest was devastated over an area of 2000 km2. According to recent estimates, this kind of event could occur with a frequency of one per hundred to thousand years. Since the last century, the demography and the urbanisation have significantly increased. Although the probability that such an event occurs over a populated area remains small, if this happened, it could cause significant damages (industrial, shopping centres, recreational places, etc.). From the analysis of the data on meteorites that have impacted the Earth, of the orbital and size properties of small threatening bodies as well as their potential impact outcome, this paper proposes a methodology to estimate the damage resulting from the impact of objects of given sizes. The considered sizes are up to the maximum threshold for local damages (less than a hundred metres in diameter) on some given territory. This approach is based on an initial definition phase of collision scenarios. Then, a second phase consisting of the accurate modelling of the territory, taking into account the land-use, the spatial distribution of the populations and goods, and the characterisation of the biophysical vulnerability of the stakes using thresholds of dangerous phenomena (overpressures). The third phase is related to the impact simulation on the territory, the estimation of the stakes potentially exposed and the costs of the destruction. The aim of this paper is to make a demonstration of principle, using as a study case the city of Nice that benefits from a complete database of infrastructures.

  6. Microfossils in Carbonaceous Meteorites

    NASA Technical Reports Server (NTRS)

    Hoover, Richard B.

    2009-01-01

    Microfossils of large filamentous trichomic prokaryotes have been detected during in-situ investigations of carbonaceous meteorites. This research has been carried out using the Field Emission Scanning Electron Microscope (FESEM) to examine freshly fractured interior surfaces of the meteorites. The images obtained reveal that many of these remains are embedded in the meteorite rock matrix. Energy Dispersive X-Ray Spectroscopy (EDS) studies establish that the filamentous microstructures have elemental compositions consistent with the meteorite matrix, but are often encased within carbon-rich electron transparent sheath-like structures infilled with magnesium sulfate. This is consistent with the taphonomic modes of fossilization of cyanobacteria and sulphur bacteria, since the life habits and processes of these microorganisms frequently result in distinctive chemical biosignatures associated with the properties of their cell-walls, trichomes, and the extracellular polymeric substances (EPS) of the sheath. In this paper the evidence for biogenicity presented includes detailed morphological and morphometric data consistent with known characteristics of uniseriate and multiseriate cyanobacteria. Evidence for indigeneity includes the embedded nature of the fossils and elemental compositions inconsistent with modern biocontaminants.

  7. Microfossils in Carbonaceous Meteorites

    NASA Technical Reports Server (NTRS)

    Hoover, Richard B.

    2009-01-01

    Microfossils of large filamentous trichomic prokaryotes have been detected during in-situ investigations of carbonaceous meteorites. This research has been carried out using the Field Emission Scanning Electron Microscope (FESEM) to examine freshly fractured interior surfaces of the meteorites. The images obtained reveal that many of these remains are embedded in the meteorite rock matrix. Energy Dispersive X-Ray Spectroscopy (EDS) studies establish that the filamentous microstructures have elemental compositions consistent with the meteorite matrix, but are often encased within carbon-rich electron transparent sheath-like structures infilled with magnesium sulfate. This is consistent with the taphonomic modes of fossilization of cyanobacteria and sulphur bacteria, since the life habits and processes of these microorganisms frequently result in distinctive chemical biosignatures associated with the properties of their cell-walls, trichomes, and the extracellular polymeric substances (EPS) of the sheath. In this paper the evidence for biogenicity presented includes detailed morphological and morphometric data consistent with known characteristics of uniseriate and multiseriate cyanobacteria. Evidence for indigeneity includes the embedded nature of the fossils and elemental compositions inconsistent with modern biocontaminants.

  8. High resolution seismic imaging at the Odessa (TX) meteorite impact site: the ground-impact geohazard and integration with magnetic gradiometry and time-domain electromagnetics

    NASA Astrophysics Data System (ADS)

    Soule, D.; Everett, M.

    2007-05-01

    Comet and asteroid bombardment along with impact crater formation has occurred continuously throughout Earth's history. The greatest impact-related geohazard is due to moderate sized impactors which represent the worst-case trade-off between frequency of occurrence, difficulty of mitigation, and severity of environmental destruction. Impacts in this size range pose a significant regional threat to densely populated areas. The primary objective of this research is to evaluate the ground-impact geohazard via high resolution seismic imaging of the remnants of a moderate-sized impact event, namely that associated with the 50 ka Odessa (TX) Group IAB iron meteorite. We provide high-resolution subsurface images of the 150-m diameter crater, the outcropping crater rim, the ejecta blanket, and the surrounding plain. The subsurface images are analyzed in terms of the deformation and thrusting of the underlying Cretaceous limestone and shale strata and the likely environmental effects caused by the impact. The analysis will build upon and extend our previous geophysical investigations based on magnetic gradiometry and time-domain electromagnetic data.

  9. International Workshop on Antarctic Meteorites

    NASA Technical Reports Server (NTRS)

    Annexstad, J. O.; Schultz, L.; Waenke, H.

    1986-01-01

    Topics addressed include: meteorite concentration mechanisms; meteorites and the Antarctic ice sheet; iron meteorites; iodine overabundance in meteorites; entrainment, transport, and concentration of meteorites in polar ice sheets; weathering of stony meteorites; cosmic ray records; radiocarbon dating; element distribution and noble gas isotopic abundances in lunar meteorites; thermoanalytical characterization; trace elements; thermoluminescence; parent sources; and meteorite ablation and fusion spherules in Antarctic ice.

  10. Comparison of petrophysical properties of impactites for four meteoritic impact structures

    NASA Astrophysics Data System (ADS)

    Popov, Y.; Mayr, S.; Romushkevich, R.; Burkhardt, H.; Wilhelm, H.

    2014-05-01

    We reanalyzed and compared unique data sets, which we obtained in the frame of combined petrophysical and geothermal investigations within scientific drilling projects on four impact structures: the Puchezh-Katunki impact structure (Vorotilovo borehole, Russia), the Ries impact structure (Noerdlingen-73 borehole, Germany), the Chicxulub impact structure (ICDP Yaxcopoil-1 borehole, Mexico), and the Chesapeake impact structure (ICDP-USGS-Eyreville borehole, USA). For a joined interpretation, we used the following previously published data: thermal properties, using the optical scanning technique, and porosities, both measured on densely sampled halfcores of the boreholes. For the two ICDP boreholes, we also used our previously published P-wave velocities measured on a subset of cores. We show that thermal conductivity, thermal anisotropy, porosity, and velocity can be correlated with shock metamorphism (target rocks of the Puchezh-Katunki and Ries impact structures), and confirm the absence of shock metamorphism in the samples taken from megablocks (Chicxulub and Chesapeake impact structure). The physical properties of the lithic impact breccias and suevites are influenced mainly by their impact-related porosity. Physical properties of lower porosity lithic impact breccias and suevites are also influenced by their chemical composition. These data allow for a distinction between different types of breccias due to differences concerning the texture and chemistry and the different amounts of melt and rock clasts.

  11. Identification of minerals and meteoritic materials via Raman techniques after capture in hypervelocity impacts on aerogel

    SciTech Connect

    Burchell, M J; Mann, J; Creighton, J A; Kearsley, A; Graham, G A; Esposito, A P; Franchi, I A; Westphal, A J; Snead, C

    2004-10-04

    For this study, an extensive suite of mineral particles analogous to components of cosmic dust were tested to determine if their Raman signatures can be recognized after hypervelocity capture in aerogel. The mineral particles were mainly of greater than 20 micrometers in size and were accelerated onto the silica aerogel by light gas gun shots. It was found that all the individual minerals captured in aerogel could be subsequently identified using Raman (or fluorescent) spectra. The beam spot size used for the laser illumination was of the order of 5 micrometers, and in some cases the captured particles were of a similar small size. In some samples fired into aerogel there was observed a shift in the wavenumbers of some of the Raman bands, a result of the trapped particles being at quite high temperatures due to heating by the laser. Temperatures of samples under laser illumination were estimated from the relative intensities of Stokes and anti-Stokes Raman bands, or, in the case of ruby particles, from the wavenumber of fluorescence bands excited by the laser. It was found that the temperature of particles in aerogel varied greatly, dependent upon laser power and the nature of the particle. In the worst case, some particles were shown to have temperatures in the 500-700 C range at a laser power of about 3 mW at the sample. However most of the mineral particles examined at this laser power had temperatures below 200 C. This is sufficiently low a temperature not to damage most materials expected to be found captured in aerogel in space. In addition, selected meteorite samples were examined to obtain Raman signatures of their constituent minerals and were then shot into aerogel. It was possible to find several Raman signatures after capture in aerogel and obtain a Raman map of a whole grain in situ in the aerogel. Finally, a Raman analysis was carried out of a particle captured in aerogel in space and carbonaceous material identified. In general therefore it is

  12. Evidence for a major meteorite impact on the earth 34 million years ago - Implication for Eocene extinctions

    NASA Astrophysics Data System (ADS)

    Ganapathy, R.

    1982-05-01

    A deep-sea core from the Caribbean contains a layer of sediment highly enriched in meteoritic iridium. This layer underlies a layer of North American microtekites dated at 34.4 million years ago and coincides with the extinction of five major species of Radiolaria. It is suggested that a massive, chemically undifferentiated meteorite collided with the earth, producing the tektites and leading to extinctions 34 millions years ago.

  13. Meteoritic trace element toxification and the terminal Mesozoic mass extinction

    SciTech Connect

    Dickson, S.M.; Erickson, D.J. III

    1985-01-01

    Calculations of trace element fluxes to the earth associated with 5 and 10 kilometer diameter Cl chondrites and iron meteorites are presented. The data indicate that the masses of certain trace elements contained in the bolide, such as Fe, Co, Ni, Cr, Pb, and Cu, are as large as or larger than the world ocean burden. The authors believe that this pulse of trace elements was of sufficient magnitude to perturb the biogeochemical cycles operative 65 million years ago, a probably time of meteorite impact. Geochemical anomalies in Cretaceous-Tertiary boundary sediments suggest that elevated concentrations of trace elements may have persisted for thousands of years in the ocean. Through direct exposure and bioaccumulation, many trophic levels of the global food chain, including that of the dinosaurs, would have been adversely affected by these meteoritic trace elements. The trace element toxification hypothesis may account for the selective extinction of both marine and terrestrial species in the enigmatic terminal Mesozoic event.

  14. I-Xe structure of ILAFEGH 009 and shallowater: Evidence for early formation and rapid cooling of impact-derived enstatite meteorites

    NASA Technical Reports Server (NTRS)

    Kehm, K.; Nichols, R. H., Jr.; Hohenberg, C. M.; Mccoy, T. J.; Keil, K.

    1993-01-01

    Enstatite meteorites have proven to be ideal samples for past studies of the I-Xe system. This work focuses on two enstatite meteorites that were formed by impact processes. Ilafegh 009 is a clast-free impact melt rock from the EL chondrite parent body. The Shallowater aubrite likely formed when a fully molten planetesimal collided with a solid planetesimal, mixing fragments of the solid planetesimal into the enstatite mantle of the molten planetesimal. A complex three-stage cooling history resulted from this mixing and later break-up and reassembly of the parent body. The present study indicates that the I-Xe structure of these two meteorites resulted from in situ decay of live I-129 and that both experienced xenon closure of the iodine host phase at approximately the same time. I-Xe cooling rates are consistent with the cooling rates derived from mineralogic and petrologic studies of these objects. The similarities in ages suggest that the region of the nebula in which enstatite parent bodies formed must have experienced an intense early bombardment.

  15. The Role of Meteorite Impacts in Creating a Habitable Early Mars

    NASA Astrophysics Data System (ADS)

    Osinski, G. R.; Caudill, C.; Cockell, C. S.; Pontefract, A.; Sapers, H. M.; Simpson, S.; Svensson, M.; Tornabene, L. L.

    2017-10-01

    Impact craters may have provided conditions suitable for the emergence of life on Mars through the production of substrates for prebiotic chemistry and through the production of habitats for the emergence and subsequent survival of microbial life.

  16. The Lawn Hill annulus: An Ordovician meteorite impact into water-saturated dolomite

    NASA Astrophysics Data System (ADS)

    Darlington, Vicki; Blenkinsop, Tom; Dirks, Paul; Salisbury, Jess; Tomkins, Andrew

    2016-12-01

    The Lawn Hill Impact Structure (LHIS) is located 250 km N of Mt Isa in NW Queensland, Australia, and is marked by a highly deformed dolomite annulus with an outer diameter of 18 km, overlying low metamorphic grade siltstone, sandstone, and shale, along the NE margin of the Georgina Basin. This study provides detailed field observations from sections of the Lawn Hill annulus and adjacent areas that demonstrate a clear link between the deformation of the dolomite and the Lawn Hill impact. 40Ar-39Ar dating of impact-related melt particles provides a time of impact in the Ordovician (472 ± 8 Ma) when the Georgina Basin was an active depocenter. The timing and stratigraphic thickness of the dolomite sequence in the annulus suggest that there was possibly up to 300 m of additional sedimentary rocks on top of the currently exposed Thorntonia Limestone at the time of impact. The exposed annulus is remarkably well preserved, with preservation attributed to postimpact sedimentation. The LHIS has an atypical crater morphology with no central uplift. The heterogeneous target materials at Lawn Hill were probably low-strength, porous, and water-saturated, with all three properties affecting the crater morphology. The water-saturated nature of the carbonate unit at the time of impact is thought to have influenced the highly brecciated nature of the annulus, and restricted melt production. The impact timing raises the possibility that the Lawn Hill structure may be a member of a group of impacts resulting from an asteroid breakup that occurred in the mid-Ordovician (470 ± 6 Ma).

  17. Structural effects of meteorite impact on basalt: Evidence from Lonar crater, India

    NASA Astrophysics Data System (ADS)

    Kumar, P. Senthil

    2005-12-01

    Lonar crater is a simple, bowl-shaped, near-circular impact crater in the ˜65 Myr old Deccan Volcanic Province in India. As Lonar crater is a rare terrestrial crater formed entirely in basalt, it provides an excellent opportunity to study the impact deformation in target basalt, which is common on the surfaces of other terrestrial planets and their satellites. The present study aims at documenting the impact deformational structures in the massive basalt well exposed on the upper crater wall, where the basalt shows upward turning of the flow sequence, resulting in a circular deformation pattern. Three fracture systems (radial, concentric, and conical fractures) are exposed on the inner crater wall. On the fracture planes, plumose structures are common. Uplift and tilting of the basalt sequence and formation of the fractures inside the crater are clearly related to the impact event and are different from the preimpact structures such as cooling-related columnar joints and fractures of possible tectonic origin, which are observed outside the crater. Slumping is common throughout the inner wall, and listric faulting displaces the flows in the northeastern inner wall. The impact structures of Lonar crater are broadly similar to those at other simple terrestrial craters in granites and clastic sedimentary rocks and even small-scale experimental craters formed in gabbro targets. As Lonar crater is similar to the strength-controlled laboratory craters, impact parameters could be modeled for this crater, provided maximum depth of fracture formation would be known.

  18. Meteorite and meteoroid: New comprehensive definitions

    USGS Publications Warehouse

    Rubin, A.E.; Grossman, J.N.

    2010-01-01

    Meteorites have traditionally been defined as solid objects that have fallen to Earth from space. This definition, however, is no longer adequate. In recent decades, man-made objects have fallen to Earth from space, meteorites have been identified on the Moon and Mars, and small interplanetary objects have impacted orbiting spacecraft. Taking these facts and other potential complications into consideration, we offer new comprehensive definitions of the terms "meteorite,""meteoroid," and their smaller counterparts: A meteoroid is a 10-??m to 1-m-size natural solid object moving in interplanetary space. A micrometeoroid is a meteoroid 10 ??m to 2 mm in size. A meteorite is a natural, solid object larger than 10 ??m in size, derived from a celestial body, that was transported by natural means from the body on which it formed to a region outside the dominant gravitational influence of that body and that later collided with a natural or artificial body larger than itself (even if it is the same body from which it was launched). Weathering and other secondary processes do not affect an object's status as a meteorite as long as something recognizable remains of its original minerals or structure. An object loses its status as a meteorite if it is incorporated into a larger rock that becomes a meteorite itself. A micrometeorite is a meteorite between 10 ??m and 2 mm in size. Meteorite- "a solid substance or body falling from the high regions of the atmosphere" (Craig 1849); "[a] mass of stone and iron that ha[s] been directly observed to have fallen down to the Earth's surface" (translated from Cohen 1894); "[a] solid bod[y] which came to the earth from space" (Farrington 1915); "A mass of solid matter, too small to be considered an asteroid; either traveling through space as an unattached unit, or having landed on the earth and still retaining its identity" (Nininger 1933); "[a meteoroid] which has reached the surface of the Earth without being vaporized" (1958

  19. Amino acid survival in large cometary impacts

    NASA Astrophysics Data System (ADS)

    Pierazzo, E.; Chyba, C. F.

    1999-11-01

    A significant fraction of the Earth's prebiotic volatile inventory may have been delivered by asteroidal and cometary impacts during the period of heavy bombardment. The realization that comets are particularly rich in organic material seemed to strengthen this suggestion. Previous modeling studies, however, indicated that most organics would be entirely destroyed in large comet and asteroid impacts. The availability of new kinetic parameters for the thermal degradation of amino acids in the solid phase made it possible to readdress this question. We present the results of new high-resolution hydrocode simulations of asteroid and comet impact coupled with recent experimental data for amino acid pyrolysis in the solid phase. Differences due to impact velocity as well as projectile material have been investigated. Effects of angle of impacts were also addressed. The results suggest that some amino acids would survive the shock heating of large (kilometer-radius) cometary impacts. At the time of the origins of life on Earth, the steady-state oceanic concentration of certain amino acids (like aspartic and glutamic acid) delivered by comets could have equaled or substantially exceeded that due to Miller-Urey synthesis in a carbon dioxide-rich atmosphere. Furthermore, in the unlikely case of a grazing impact (impact angle around 5 degrees from the horizontal) an amount of some amino acids comparable to that due to the background steady-state production or delivery would be delivered to the early Earth.

  20. Study of the Transformation of Meteoritic Organics during Hypervelocity Impacts in Support of Characterisation of Exogenous Organic Matter on the Surface of Icy Satellites

    NASA Astrophysics Data System (ADS)

    Zaitsev, Maxim; Gerasimov, Mikhail; Ivanova, Marina; Lorenz, Cyril; Aseev, Sergey; Korochantsev, Alexander

    The main goal of the planned missions to Jupiter's Galilean satellites Ganymede or Europa is the search for extraterrestrial life which can be reviled by characterization of surface organics at the landing site. Planets and satellites are exposed for steady meteoritic and cometary bombardment which delivers exogenous organic species. The exogenous organic matter on the satellites surfaces can be represented by both unaltered organic matter of meteorites and comets, and by organic matter which is synthesized from organic and/or mineral components of falling bodies during the impacts. Adequate interpretation of volatile organic compounds (VOCs) on the surface of Ganymede or Europa must take into account the presence of exogenous organic matter described above. The quantitative composition of exogenous organics is difficult to predict because it depends on the frequency of meteoritic/cometary bombardment, conditions and efficiency of organic synthesis in water mantle below the ice crust, speed of the ice crust renovation, and other factors. However, the qualitative composition of exogenous organics can be described through the study of organic matter in different classes of meteorites and products of their shock-evaporative transformation. We have carried out comparative studies of VOCs - products of pyrolysis of carbonaceous chondrites and condensed products of their high-temperature transformation in simulated shock-induced evaporation by pulse laser. We have investigated VOCs in samples of carbonaceous CM2 and CO3 chondrites (Murchison and Kainsaz respectively) and in condensed products of their high-temperature evaporation in neutral (helium) atmosphere using pyrolytic gas chromatography coupled with mass spectrometry (Pyr-GC/MS) [1, 2]. Condensates contained the same hydrocarbons that we extracted at 460(°) C from the bulk samples of meteorites (aliphatic, alicyclic and aromatic hydrocarbons) but sufficiently larger amount of nitrogen-containing compounds

  1. Two Shatter-Coned NWA Meteorites

    NASA Astrophysics Data System (ADS)

    McHone, J. F.; Shoemaker, C.; Killgore, M.; Killgore, K.

    2012-03-01

    Shatter cones are found in target rocks at more than 70 terrestrial impact sites and are regarded as reliable field criteria for meteoroid impact events. Shatter cones are now seen in chondritic meteorites and indicate early collision events.

  2. Demagnetization of Martian Crust by Large Impacts

    NASA Astrophysics Data System (ADS)

    Mohit, P. S.; Arkani-Hamed, J.

    2001-12-01

    The magnetic anomaly map of Mars derived from Mars Global Surveyor magnetic data shows no magnetic signature inside large basins such as Hellas, Argyre and Isidis, but it does show some appreciable anomalies over the immediate surroundings of these basins. This implies that the large impacts that produced these giant basins demagnetized the entire crust beneath the basins. To investigate the extent of the impact effects, we first assess the excavation by determining the crustal thickness beneath the basins under the assumption that the observed gravity anomaly arises from the surface topography and the undulation of the crust-mantle interface. Using the resulting crustal structure, we then model the neighboring small magnetic anomalies to determine the degradation of crustal magnetization as a function of distance from the impact site. This provides a means to constrain the extent of the shock effects and the initial temperature distribution immediately after the impact. The impacts have generated shock pressures of about 3 GPa at the edge of the basins, implying that shock was a major factor in the demagnetization of the crust beneath the basins. The magnetic effects of the initial shock wave and the heat resulting from isentropic decompression following the impact are then investigated. We also modeled the thermal evolution of the crust beneath the basins and possible remagnetization of small source bodies in the surroundings to establish that the impacts occurred in the absence of the core field.

  3. Meteorite regolithic breccias

    NASA Technical Reports Server (NTRS)

    Bunch, T. E.; Rajan, R. S.

    1988-01-01

    In addition to endogenic processes such as heating and aqueous activity, meteorite parent bodies were subjected also to exogenic processing brought about by the impact of the other solar-system objects. Such impacts can produce a variety of effects, ranging from shock metamorphism of individual mineral grains to production of breccias; i.e., rocks consisting of mixtures of disparate lithic units. The present paper reviews recent studies of such breccias, which have generated significant information about the accretional growth of parent bodies, as well as their evolution, composition, stratigraphy, and geological processing.

  4. Dynamic fracture by large extraterrestrial impacts as the origin of shatter cones.

    PubMed

    Sagy, Amir; Reches, Ze'ev; Fineberg, Jay

    2002-07-18

    A large impact by a comet or meteorite releases an enormous amount of energy, which evaporates, melts and fractures the surrounding rocks. Distinctive features of such impacts are 'shatter cones', deformed rocks characterized by hierarchical striated features. Although such features have been used for decades as unequivocal fingerprints of large-body impacts, the process by which shatter cones form has remained enigmatic. Here we show that the distinctive shatter-cone striations naturally result from nonlinear waves (front waves) that propagate along a fracture front. This explains the observed systematic increase of striation angles with the distance from the impact. Shatter-cone networks, typically spanning many scales, can be understood as hierarchical bifurcations of the fracture front, which is generated by the immense energy flux carried by the initial, impact-generated, shock waves. Our quantitative predictions based on this theory are supported by field measurements at the Kentland and Vredefort impact sites. These measurements indicate that shatter cones near to the impact site were formed by fractures propagating at nearly the Rayleigh wave speed of the host rocks, whereas the furthest shatter cones observed (about 40 km from the impact site) were formed by fronts moving more slowly. These results provide insight into impact dynamics as well as dissipative mechanisms in solids subjected to sudden, extremely intense fluxes of energy.

  5. Ni/S/Cl systematics and the origin of impact-melt glasses in Martian meteorite Elephant Moraine 79001

    NASA Astrophysics Data System (ADS)

    Schrader, Christian M.; Cohen, Barbara A.; Donovan, John J.; Vicenzi, Edward P.

    2016-04-01

    Martian meteorite Elephant Moraine A79001 (EET 79001) has received considerable attention for the unusual composition of its shock melt glass, particularly its enrichment in sulfur relative to the host shergottite. It has been hypothesized that Martian regolith was incorporated into the melt or, conversely, that the S-enrichment stems from preferential melting of sulfide minerals in the host rock during shock. We present results from an electron microprobe study of EET 79001 including robust measurements of major and trace elements in the shock melt glass (S, Cl, Ni, Co, V, and Sc) and minerals in the host rock (Ni, Co, and V). We find that both S and major element abundances can be reconciled with previous hypotheses of regolith incorporation and/or excess sulfide melt. However, trace element characteristics of the shock melt glass, particularly Ni and Cl abundances relative to S, cannot be explained either by the incorporation of regolith or sulfide minerals. We therefore propose an alternative hypothesis whereby, prior to shock melting, portions of EET 79001 experienced acid-sulfate leaching of the mesostasis, possibly groundmass feldspar, and olivine, producing Al-sulfates that were later incorporated into the shock melt, which then quenched to glass. Such activity in the Martian near-surface is supported by observations from the Mars Exploration Rovers and laboratory experiments. Our preimpact alteration model, accompanied by the preferential survival of olivine and excess melting of feldspar during impact, explains the measured trace element abundances better than either the regolith incorporation or excess sulfide melting hypothesis does.

  6. Fast delivery of meteorites to Earth after a major asteroid collision.

    PubMed

    Heck, Philipp R; Schmitz, Birger; Baur, Heinrich; Halliday, Alex N; Wieler, Rainer

    2004-07-15

    Very large collisions in the asteroid belt could lead temporarily to a substantial increase in the rate of impacts of meteorites on Earth. Orbital simulations predict that fragments from such events may arrive considerably faster than the typical transit times of meteorites falling today, because in some large impacts part of the debris is transferred directly into a resonant orbit with Jupiter. Such an efficient meteorite delivery track, however, has not been verified. Here we report high-sensitivity measurements of noble gases produced by cosmic rays in chromite grains from a unique suite of fossil meteorites preserved in approximately 480 million year old sediments. The transfer times deduced from the noble gases are as short as approximately 10(5) years, and they increase with stratigraphic height in agreement with the estimated duration of sedimentation. These data provide powerful evidence that this unusual meteorite occurrence was the result of a long-lasting rain of meteorites following the destruction of an asteroid, and show that at least one strong resonance in the main asteroid belt can deliver material into the inner Solar System within the short timescales suggested by dynamical models.

  7. Distributional Impacts of Large Dams in China

    NASA Astrophysics Data System (ADS)

    Bao, X.

    2010-12-01

    Dams on a river are believed to have heterogeneous impacts to the upstream, local and downstream areas. Generally, irrigation dams will bring benefits to the downstream by facilitating more irrigation, while it will bring negative impacts to upstream due to inundation or no impact to local area as a combination result of population dislocation and economic benefits. This paper checked the impacts of large dams (above 100 meters) on the upstream, downstream and local area, using 2000-2008 county level data in China. Robust heterogeneous impacts of different categories of dams (mainly dams serving for irrigation, hydropower, or other purposes) were found on different areas, using IV regression approaches. Dams higher than 100 meters are significantly and heterogeneously impacting agricultural production, urban employment and rural per capita income. Its beneficial impact on agriculture production is significant for downstream especially in continuous drought years. But its impacts on social welfare indicators, such as primary school enrollment and hospital beds, are not heterogeneously different across regions.

  8. Asteroid, Meteor, Meteorite

    NASA Astrophysics Data System (ADS)

    Martel, L. M. V.

    2010-04-01

    Almahata Sitta is the name identifying the collection of meteorite remnants of the first observed fall of a tracked asteroid, 2008 TC3. Ground-based observatories, orbiting satellites, a pilot of a commercial airline flight, and eyewitnesses of the fireball in the Nubian Desert of northern Sudan all observed evidence of the spectacular events on October 6, 2008. The first meteorites were recovered two months later in Sudan by students and staff from the University of Khartoum (Sudan) led by Dr. Muawia Shaddad and further guided by Dr. Peter Jenniskens of the SETI Institute and NASA Ames Research Center (Mt. View, California). A session at the 41st Lunar and Planetary Science Conference held March 1-5, 2010 focused on ureilitic asteroids and insights from Almahata Sitta, and forms the basis for this article. Rather than discuss the results of each of the talks and posters presented at the conference, I highlight what makes the impact, recovery, and characterization of the ureilite meteorite fragments so outstanding.

  9. Environmental effects of large impacts on Mars.

    PubMed

    Segura, Teresa L; Toon, Owen B; Colaprete, Anthony; Zahnle, Kevin

    2002-12-06

    The martian valley networks formed near the end of the period of heavy bombardment of the inner solar system, about 3.5 billion years ago. The largest impacts produced global blankets of very hot ejecta, ranging in thickness from meters to hundreds of meters. Our simulations indicated that the ejecta warmed the surface, keeping it above the freezing point of water for periods ranging from decades to millennia, depending on impactor size, and caused shallow subsurface or polar ice to evaporate or melt. Large impacts also injected steam into the atmosphere from the craters or from water innate to the impactors. From all sources, a typical 100-, 200-, or 250-kilometers asteroid injected about 2, 9, or 16 meters, respectively, of precipitable water into the atmosphere, which eventually rained out at a rate of about 2 meters per year. The rains from a large impact formed rivers and contributed to recharging aquifers.

  10. Chips off of asteroid 4 Vesta - Evidence for the parent body of basaltic achondrite meteorites

    NASA Technical Reports Server (NTRS)

    Binzel, Richard P.; Xu, Shui

    1993-01-01

    For more than two decades, asteroid 4 Vesta has been debated as the source for the eucrite, diogenite, and howardite classes of basaltic achondrite meteorites. Its basaltic achondrite spectral properties are unlike those of other large main-belt asteroids. Telescopic measurements have revealed 20 small main-belt asteroids that have distinctive optical reflectance spectral features similar to those of Vesta and eucrite and diogenite meteorites. Twelve have orbits that are similar to Vesta's and were previously predicted to be dynamically associated with Vesta. Eight bridge the orbital space between Vesta and the 3:1 resonance, a proposed source region for meteorites. These asteroids are most probably multikilometer-sized fragments excavated from Vesta through one or more impacts. The sizes, ejection velocities of 500 meters per second, and proximity of these fragments to the 3:1 resonance establish Vesta as a dynamically viable source for eucrite, diogenite, and howardite meteorites.

  11. Insights to Meteorites and Impact Processes provided by Advanced EBSD Analysis

    NASA Astrophysics Data System (ADS)

    Palasse, Laurie; Berlin, Jana; Goran, Daniel; Tagle, Roald; Hamers, Maartje; Assis Fernandes, Vera; Deutsch, Alexander; Schulte, Peter; Salge, Tobias

    2013-04-01

    Electron backscatter diffraction (EBSD) is a powerful analytical technique for assessing the petrographic texture of rocks and the crystallographic orientation of minerals therein using a scanning electron microscope (SEM). Innovations in EBSD technology include colour-coded forescattered electron (FSE) images, high resolution and highly sensitive EBSD detectors, together with advanced EDS integration. It allows to accurately identify and discriminate different phases, and to investigate microstructures related to shock metamorphism. As an example, shocked carbonates and shocked quartz reveal a complex thermal history during post-shock cooling. (A) EBSD studies of calcite ejecta particles from the Chicxulub impact event, at the K-Pg boundary of El Guayal, Mexico (~520 km SW of the Chicxulub crater centre) display various microstructures [1] and spherulitic calcite ejecta particles reveal a fibre texture of elongated crystals with a preferred orientation. This indicates the presence of carbonate melts which were ejected at T>1240°C and P>40 bar from upper target lithologies and crystallized at cooling rates of ~100´s °C/s [2]. The calcite particles of El Guayal and the K/Pg boundary of La Lajilla (~1000 km W of the crater centre) show distinct microstructures represented by unoriented, equiaxed crystals with random orientation distribution. It documents recrystallization upon impact induced thermal stress at T>550°C during prolonged atmospheric transport. (B) Combined EBSD, FSE and cathodoluminescence (CL) studies of semi-amorphous shocked quartz of Chicxulub, Ries and Popigai impactites, reveal various microstructures. Colour-coded FSE imaging reveal recrystallized/deformed bands in Ries and Popigai samples indicative of planar deformation features. EBSD studies of Popigai allow to distinguish twinned Qz, α-Qz and α-cristobalite along the transition zone between shocked gneiss clast and impact melt. Recrystallized Qz grains are associated with amorphous SiO2

  12. Comparison of lunar rocks and meteorites: Implications to histories of the moon and parent meteorite bodies

    NASA Technical Reports Server (NTRS)

    Prinz, M.; Fodor, R. V.; Keil, K.

    1977-01-01

    There are many similarities between lunar samples and stone meteorites. Lunar samples, especially from the highlands, indicate that they have been affected by complex and repeated impact processes. Similar complex and repeated impact processes have also been operative on the achondritic and chondritic meteorites. Similarities between lunar and meteoritic rocks are discussed as follows: (1) Monomict and polymict breccias occur in lunar rocks, as well as in achondritic and chondritic meteorites, having resulted from complex and repeated impact processes; (2) Chondrules are present in lunar meteorites, as well as in a few achondritic and most chondritic meteorites. They apparently crystallized spontaneously from molten highly supercooled droplets which may have formed from impact melts or, perhaps, volcanic processes (as well as from the solar nebula, in the case of meteoritic chondrites); (3) Lithic fragments vary from little modified (relative to the apparent original texture) to partly or completely melted and recrystallized lithic fragments. Their detailed study allows conclusions to be drawn about their parent rock types and their origin, thereby gaining insight into preimpact histories of lunar and meteoritic breccias. There is evidence that cumulate rocks were involved in the early history of both moon and parent meteorite bodies.

  13. Public health impact of large airports.

    PubMed

    Passchier, W; Knottnerus, A; Albering, H; Walda, I

    2000-01-01

    Large airports with the related infrastructure, businesses and industrial activities affect the health of the population living, travelling and working in the surroundings of or at the airport. The employment and contributions to economy from the airport and related operations are expected to have a beneficial effect, which, however, is difficult to quantify. More pertinent data are available on the, largely negative, health effects of environmental factors, such as air and soil pollution, noise, accident risk, and landscape changes. Information on the concurrent and cumulative impact of these factors is lacking, but is of primary relevance for public health policy. A committee of the Health Council of The Netherlands recently reviewed the data on the health impact of large airports. It was concluded that, generally, integrated health assessments are not available. Such assessments, as part of sustainable mobility policy, should accompany the further development of the global aviation system.

  14. Lithium in tektites and impact glasses: Implications for sources, histories and large impacts

    NASA Astrophysics Data System (ADS)

    Magna, T.; Deutsch, A.; Mezger, K.; Skála, R.; Seitz, H.-M.; Mizera, J.; Řanda, Z.; Adolph, L.

    2011-04-01

    Lithium (Li) abundances and isotope compositions were determined in a representative suite of tektites (moldavites, Muong Nong-type tektites and an australite, Ivory Coast tektites and bediasites), impact-related glasses (Libyan Desert Glass, zhamanshinites and irghizites), a glass fragment embedded in the suevite from the Ries impact crater and sedimentary materials in order to test a possible susceptibility of Li to fractionation during hypervelocity impact events and to de-convolve links to their potential parental sources. The overall data show a large spread in Li abundance (4.7-58 ppm Li) and δ 7Li values (-3.2‰ to 26.0‰) but individual groups of tektites and impact glasses have distinctive Li compositions. Most importantly, any significant high-temperature Li isotope fractionation can be excluded by comparing sedimentary lithologies from central Europe with moldavites. Instead, we suggest that Li isotope compositions in tektites and impact-related glasses are probably diagnostic of the precursor materials and their pre-impact geological histories. The Muong Nong-type tektites and australite specimen are identical in terms of Li concentrations and δ 7Li and we tentatively endorse their common origin in a single impact event. Evidence for low-temperature Rayleigh fractionation, which must have operated prior to impact-induced melting and solidification, is provided for a subset of Muong Nong-type tektites. Although Li isotope variations in most tektites are broadly similar to those of the upper continental crust, Libyan Desert Glass carries high δ 7Li ⩾24.7‰, which appears to mirror the previous fluvial history of parental material that was perhaps deposited in lacustrine environment or coastal seawater. Lithium isotopes in impact-related glasses from the Zhamanshin crater define a group distinct from all other samples and point to melting of chemically less evolved mafic lithologies, which is also consistent with their major and trace element

  15. Experimental investigation into the effects of meteoritic impacts on the spectral properties of phyllosilicates on Mars

    NASA Astrophysics Data System (ADS)

    Gavin, P.; Chevrier, V.; Ninagawa, K.; Gucsik, A.; Hasegawa, S.

    2013-01-01

    Phyllosilicates have been identified in some of the most highly cratered Noachian terrains on Mars. To study the effects of such impacts on the properties of phyllosilicates, we experimentally shocked six phyllosilicate minerals relevant to the Martian surface: montmorillonite, nontronite, kaolinite, prehnite, chlorite, and serpentine. The shock-treated samples were analyzed with X-ray diffraction (XRD), near- and mid-infrared (NIR and MIR) spectroscopy, Raman spectroscopy, cathodoluminescence (CL), and the shock pressures and temperatures in some were modeled using Autodyn modeling software. XRD data show that the structure of each mineral, except prehnite, underwent partial structural deformation or amorphization. We also found that while the NIR spectra of shocked samples were very similar to that of the original sample, the MIR spectra changed significantly. This may explain some of the discrepancies between CRISM/OMEGA data (NIR) and TES/THEMIS (MIR) observations of phyllosilicates on Mars. Quartz was identified as a secondary phase in the XRD of shocked chlorite.

  16. Terrestrial Ages of Antarctic Meteorites- Update 1999

    NASA Technical Reports Server (NTRS)

    Nishiizumi, Kunihiko; Welten, K. C.; Caffee, Marc W.

    1999-01-01

    We are continuing our ongoing study of cosmogenic nuclides in Antarctic meteorites. In addition to the studies of exposure histories of meteorites, we study terrestrial ages and pairing of Antarctic meteorites and desert meteorites. Terrestrial ages of Antarctic meteorites provide information on meteorite accumulation mechanisms, mean weathering lifetimes, and influx rates. The determination of Cl-36(half-life=3.01 x 10(exp 5) y) terrestrial ages is one of our long-term on-going projects, however, in many instances neither Cl-36 or C-14 (5,730 y) yields an accurate terrestrial age. Using Ca-14 (1.04 x 10(exp 5) y) for terrestrial age determinations solves this problem by filling the c,ap in half-life between 14-C and Cl-36 ages. We are now applying the new Ca-41- Cl-36 terrestrial age method as well as the Cl-36-Be-10 method to Antarctic meteorites. Our measurements and C-14 terrestrial age determinations by the University of Arizona group are always complementary. We have measured Cl-36 in over 270 Antarctic meteorites since our previous compilation of terrestrial ages. Since a large number of meteorites have been recovered from many different icefields in Antarctica, we continue to survey the trends of terrestrial ages for different icefields. We have also measured detailed terrestrial ages vs. sample locations for Allan Hills, Elephant Moraine, and Lewis Cliff Icefields, where meteorites have been found with very long ages. The updated histograms of terrestrial ages of meteorites from the Allan Hills Main Icefield and Lewis Cliff Icefield are shown. These figures include C-14 ages obtained by the University of Arizona group. Pairs of meteorites are shown as one object for which the age is the average of all members of the same fall. The width of the bars represents 70,000 years, which was a typical uncertainty for Cl-36 ages. We reduced the uncertainty of terrestrial age determinations to approx. 40,000 years by using pairs of nuclides such as Ca-41-Cl-36 or Cl

  17. Meteorite and meteoroid: New comprehensive definitions

    NASA Astrophysics Data System (ADS)

    Rubin, Alan E.; Grossman, Jeffrey N.

    2010-01-01

    Meteorites have traditionally been defined as solid objects that have fallen to Earth from space. This definition, however, is no longer adequate. In recent decades, man-made objects have fallen to Earth from space, meteorites have been identified on the Moon and Mars, and small interplanetary objects have impacted orbiting spacecraft. Taking these facts and other potential complications into consideration, we offer new comprehensive definitions of the terms ``meteorite,''``meteoroid,'' and their smaller counterparts: A meteoroid is a 10-μm to 1-m-size natural solid object moving in interplanetary space. A micrometeoroid is a meteoroid 10μm to 2mm in size. A meteorite is a natural, solid object larger than 10μm in size, derived from a celestial body, that was transported by natural means from the body on which it formed to a region outside the dominant gravitational influence of that body and that later collided with a natural or artificial body larger than itself (even if it is the same body from which it was launched). Weathering and other secondary processes do not affect an object's status as a meteorite as long as something recognizable remains of its original minerals or structure. An object loses its status as a meteorite if it is incorporated into a larger rock that becomes a meteorite itself. A micrometeorite is a meteorite between 10μm and 2mm in size.Meteorite-``a solid substance or body falling from the high regions of the atmosphere'' (Craig 1849); ``[a] mass of stone and iron that ha[s] been directly observed to have fallen down to the Earth's surface'' (translated from Cohen 1894); ``[a] solid bod[y] which came to the earth from space'' (Farrington 1915); ``A mass of solid matter, too small to be considered an asteroid; either traveling through space as an unattached unit, or having landed on the earth and still retaining its identity'' (Nininger 1933); ``[a meteoroid] which has reached the surface of the Earth without being vaporized'' (1958

  18. Abstracts for the 54th Annual Meeting of the Meteoritical Society

    NASA Technical Reports Server (NTRS)

    1991-01-01

    Abstracts of the papers presented at 54th Annual Meeting of the Meteoritic Society are compiled. The following subject areas are covered: Antarctic meteorites; nebula and parent body processing; primary and secondary SNC parent planet processes; enstatite chondrites and aubrites; achondrite stew; refractory inclusions; meteorite exposure ages and sizes; interstellar/meteorite connections; lunar origins, processes and meteorites; craters, cratering and tektites; cretaceous-tertiary impact(s); IDPs (LDEF, stratosphere, Greenland and Antarctica); chondrules; and chondrites.

  19. Large Impact Features on Icy Galilean Satellites

    NASA Technical Reports Server (NTRS)

    Moore, J. M.; Schenk, P. M.; Korycansky, D. G.

    2017-01-01

    Impact crater morphology can be a very useful tool for probing planetary interiors, but nowhere in the solar system is a greater variety of crater morphologies observed (Fig. 1) than on the large icy Galilean satellites Ganymede and Callisto [e.g., 1- 3]. As on the rocky terrestrial planets, impact crater morphology becomes more complex with increasing size on these satellites. With increasing size, however, these same craters become less like their counterparts on the rocky planets. Several impact landforms and structures (multiring furrows, palimpsests, and central domes, for example), have no obvious analogs on any other planets. Further, several studies [e.g., 4-6] have drawn attention to impact landforms on Europa which are unusual, even by Galilean satellite standards. These radical differences in morphology suggest that impact into icy lithospheres that are mechanically distinct from silicate lithospheres may be responsible. As such, large impact structures may be important probes of the interiors of these bodies over time [e.g., 7]. The first goal of this work is to integrate and correlate the detailed morphologic and morphometric measurements and observations of craters on icy Galilean satellites [e.g., 4, 8-12] with new detailed mapping of these structures from Galileo high-resolution images. As a result, we put forward a revised crater taxonomy for Ganymede and Callisto in order to simplify the nonuniform impact crater nomenclature cluttering the literature. We develop and present an integrated model for the development of these unusual crater morphologies and their implications for the thermal evolution of these bodies.

  20. Rediscovery of Polish meteorites

    NASA Astrophysics Data System (ADS)

    Tymiński, Z.; Stolarz, M.; Żołądek, P.; Wiśniewski, M.; Olech, A.

    2016-01-01

    The total number of Polish registered meteorites (by July 2016) including the meteoritical artifacts as Czestochowa Raków I and II is 22. Most of them are described by the pioneer of Polish Meteoritics Jerzy Pokrzywnicki who also identified the meteorite fall locations. In recent years prospectors found impressive specimens of known Polish meteorites such as Morasko: 34 kg, 50 kg, 164 kg, 174 kg and 261 kg or Pultusk: 1578 g, 1576 g, 1510 g, 610 g and 580 g expanding and determining precisely the known meteorite strewn fields.

  1. Guide to the US collection of antarctic meteorites 1976-1988 (everything you wanted to know about the meteorite collection). Antarctic Meteorite Newsletter, Volume 13, Number 1

    NASA Technical Reports Server (NTRS)

    Score, Roberta; Lindstrom, Marilyn M.

    1990-01-01

    The state of the collection of Antarctic Meteorites is summarized. This guide is intended to assist investigators plan their meteorite research and select and request samples. Useful information is presented for all classified meteorites from 1976 to 1988 collections, as of Sept. 1989. The meteorite collection has grown over 13 years to include 4264 samples of which 2754 have been classified. Most of the unclassified meteorites are ordinary chondrites because the collections have been culled for specimens of special petrologic type. The guide consists of two large classification tables. They are preceded by a list of sample locations and important notes to make the tables understandable.

  2. The SNC Meteorites

    NASA Astrophysics Data System (ADS)

    Varela, M. E.

    2014-10-01

    The SNC (Shergotty-Nakhla-Chassigny) group, are achondritic meteorites. Of all SNC meteorites recognized up to date, shergottites are the most abundant group. The petrographic study of Shergotty began several years ago when Tschermak, (1872) identified this rock as an extraterrestrial basalt. Oxygen isotopes in SNC meteorites indicate that these rocks are from a single planetary body (Clayton and Mayeda, 1983). Because the abundance patterns of rare gases trapped in glasses from shock melts (e.g., Pepin, 1985) turned out to be very similar to the Martian atmosphere (as analyzed by the Viking landers, Owen, 1976), the SNC meteorites are believed to originate from Mars (e.g. McSween, 1994). Possibly, they were ejected from the Martian surface either in a giant impact or in several impact events (Meyer 2006). Although there is a broad consensus for nakhlites and chassignites being -1.3Ga old, the age of the shergottites is a matter of ongoing debates. Different lines of evidences indicate that these rocks are young (180Ma and 330-475Ma), or very old (> 4Ga). However, the young age in shergottites could be the result of a resetting of these chronometers by either strong impacts or fluid percolation on these rocks (Bouvier et al., 2005-2009). Thus, it is important to check the presence of secondary processes, such as re-equilibration or pressure-induce metamorphism (El Goresy et al., 2013) that can produce major changes in compositions and obscure the primary information. A useful tool, that is used to reconstruct the condition prevailing during the formation of early phases or the secondary processes to which the rock was exposed, is the study of glass-bearing inclusions hosted by different mineral phases. I will discuss the identification of extreme compositional variations in many of these inclusions (Varela et al. 2007-2013) that constrain the assumption that these objects are the result of closed-system crystallization. The question then arises whether these

  3. Assessment of the long-term risk of a meteorite impact on a hypothetical Canadian nuclear fuel waste disposal vault deep in plutonic rock

    SciTech Connect

    Wuschke, D.M.; Whitaker, S.H.; Goodwin, B.W.; Rasmussen, L.R.

    1995-12-31

    Canada has conducted an extensive research program on the safe disposal of nuclear fuel waste. The program has focused on disposal of used fuel in durable containers in an engineered facility or ``vault``, 500 to 1,000 m deep in plutonic rock of the Canadian Shield. This paper describes an assessment of the long-term radiological risk to a critical group, resulting from a meteorite impact on a hypothetical reference disposal vault. The authors assume the critical group is a small rural community which, sometime after the impact, moves to the area contaminated by nuclear fuel waste exposed by the impact. The estimated risk is compared to a risk criterion established by Canada`s nuclear regulatory agency.

  4. Searching for Meteorites

    NASA Image and Video Library

    This lesson combines a series of activities to provide students with an understanding of how meteorites can unlock answers to the early history of the solar system and how meteorites and their big ...

  5. Meteorite Falls in Morocco

    NASA Astrophysics Data System (ADS)

    Chennaoui Aoudjehane, H.

    2016-08-01

    The number of meteorite falls reported in Morocco since 2000 is highest than any other place compared to the other countries in the world, that call into question the efficiency of the randomly meteorite falls on Earth.

  6. The missing large impact craters on Ceres

    NASA Astrophysics Data System (ADS)

    Marchi, S.; Ermakov, A. I.; Raymond, C. A.; Fu, R. R.; O'Brien, D. P.; Bland, M. T.; Ammannito, E.; de Sanctis, M. C.; Bowling, T.; Schenk, P.; Scully, J. E. C.; Buczkowski, D. L.; Williams, D. A.; Hiesinger, H.; Russell, C. T.

    2016-07-01

    Asteroids provide fundamental clues to the formation and evolution of planetesimals. Collisional models based on the depletion of the primordial main belt of asteroids predict 10-15 craters >400 km should have formed on Ceres, the largest object between Mars and Jupiter, over the last 4.55 Gyr. Likewise, an extrapolation from the asteroid Vesta would require at least 6-7 such basins. However, Ceres' surface appears devoid of impact craters >~280 km. Here, we show a significant depletion of cerean craters down to 100-150 km in diameter. The overall scarcity of recognizable large craters is incompatible with collisional models, even in the case of a late implantation of Ceres in the main belt, a possibility raised by the presence of ammoniated phyllosilicates. Our results indicate that a significant population of large craters has been obliterated, implying that long-wavelength topography viscously relaxed or that Ceres experienced protracted widespread resurfacing.

  7. Extraterrestrial Amino Acids in the Almahata Sitta Meteorite

    NASA Astrophysics Data System (ADS)

    Callahan, Michael; Aubrey, A.; Bada, J. L.; Dworkin, J. P.; Elsila, J. E.; Glavin, D. P.; Parker, E.; Jenniskens, P.

    2009-09-01

    The recovery of meteorite fragments from the 2008 TC3 asteroid impact, collectively named Almahata Sitta, revealed a rare, anomalous polymict ureilite containing large carbonaceous grains (Jenniskens et al. 2009). Here we report the first amino acid analysis of a meteorite from an F-type asteroid as part of the Almahata Sitta meteorite sample analysis consortium. A single fragment (piece #4, 1.2 grams) was crushed to a powder, and separate 0.1 g aliquots of the same meteorite were carried through identical hot-water extraction, acid hydrolysis and desalting procedures at NASA Goddard Space Flight Center and the Scripps Institution of Oceanography. The o-phthaldialdehyde/N-acetyl-L-cysteine amino acid derivatives in the extracts were analyzed by high performance liquid chromatography with UV fluorescence detection and time-of-flight mass spectrometry. Analyses of the meteorite extracts revealed a complex distribution of two- to six-carbon aliphatic amino acids with abundances ranging from 0.5 to 69 parts-per-billion (ppb). Glycine was the most abundant amino acid detected, however, since this protein amino acid is a common terrestrial contaminant, we are currently unable to rule out at least a partial terrestrial source. However, the D/L ratio of alanine in the meteorite was racemic, suggesting that very little terrestrial amino acid contamination. Several non-protein amino acids that are rare in the biosphere were also identified in the meteorite above background levels including D,L-4-amino-2-methybutyric acid (65 ± 8 ppb), D-isovaline (1.3 ± 0.1 ppb), L-isovaline (1.4 ± 0.1 ppb), and α-aminoisobutryic acid (7.1 ± 5.8 ppb). The abundance of isovaline and AIB are 1000 times lower than the abundances found in the CM2 meteorite Murchison while D,L-4-amino-2-methybutyric acid is similar. The very low amino acid abundances and the presence of several amino acid decomposition products including methylamine, ethylamine, and isopropylamine are consistent with

  8. Impact Cratering Physics al Large Planetary Scales

    NASA Astrophysics Data System (ADS)

    Ahrens, Thomas J.

    2007-06-01

    Present understanding of the physics controlling formation of ˜10^3 km diameter, multi-ringed impact structures on planets were derived from the ideas of Scripps oceanographer, W. Van Dorn, University of London's, W, Murray, and, Caltech's, D. O'Keefe who modeled the vertical oscillations (gravity and elasticity restoring forces) of shock-induced melt and damaged rock within the transient crater immediately after the downward propagating hemispheric shock has processed rock (both lining, and substantially below, the transient cavity crater). The resulting very large surface wave displacements produce the characteristic concentric, multi-ringed basins, as stored energy is radiated away and also dissipated upon inducing further cracking. Initial calculational description, of the above oscillation scenario, has focused upon on properly predicting the resulting density of cracks, and, their orientations. A new numerical version of the Ashby--Sammis crack damage model is coupled to an existing shock hydrodynamics code to predict impact induced damage distributions in a series of 15--70 cm rock targets from high speed impact experiments for a range of impactor type and velocity. These are compared to results of crack damage distributions induced in crustal rocks with small arms impactors and mapped ultrasonically in recent Caltech experiments (Ai and Ahrens, 2006).

  9. Mapping the Iron Oxidation State in Martian Meteorites

    NASA Technical Reports Server (NTRS)

    Martin, A. M.; Treimann, A. H.; Righter, K.

    2017-01-01

    Several types of Martian igneous meteorites have been identified: clinopyroxenites (nakhlites), basaltic shergottites, peridotitic shergottites, dunites (chassignites) and orthopyroxenites [1,2]. In order to constrain the heterogeneity of the Martian mantle and crust, and their evolution through time, numerous studies have been performed on the iron oxidation state of these meteorites [3,4,5,6,7,8,9]. The calculated fO2 values all lie within the FMQ-5 to FMQ+0.5 range (FMQ representing the Fayalite = Magnetite + Quartz buffer); however, discrepancies appear between the various studies, which are either attributed to the choice of the minerals/melts used, or to the precision of the analytical/calculation method. The redox record in volcanic samples is primarily related to the oxidation state in the mantle source(s). However, it is also influenced by several deep processes: melting, crystallization, magma mixing [10], assimilation and degassing [11]. In addition, the oxidation state in Martian meteorites is potentially affected by several surface processes: assimilation of sediment/ crust during lava flowing at Mars' surface, low temperature micro-crystallization [10], weathering at the surface of Mars and low temperature reequilibration, impact processes (i.e. high pressure phase transitions, mechanical mixing, shock degassing and melting), space weathering, and weathering on Earth (at atmospheric conditions different from Mars). Decoding the redox record of Martian meteorites, therefore, requires large-scale quantitative analysis methods, as well as a perfect understanding of oxidation processes.

  10. Asteroid Geophysics and Quantifying the Impact Hazard

    NASA Technical Reports Server (NTRS)

    Sears, D.; Wooden, D. H.; Korycanksy, D. G.

    2015-01-01

    Probably the major challenge in understanding, quantifying, and mitigating the effects of an impact on Earth is understanding the nature of the impactor. Of the roughly 25 meteorite craters on the Earth that have associated meteorites, all but one was produced by an iron meteorite and only one was produced by a stony meteorite. Equally important, even meteorites of a given chemical class produce a wide variety of behavior in the atmosphere. This is because they show considerable diversity in their mechanical properties which have a profound influence on the behavior of meteorites during atmospheric passage. Some stony meteorites are weak and do not reach the surface or reach the surface as thousands of relatively harmless pieces. Some stony meteorites roll into a maximum drag configuration and are strong enough to remain intact so a large single object reaches the surface. Others have high concentrations of water that may facilitate disruption. However, while meteorite falls and meteorites provide invaluable information on the physical nature of the objects entering the atmosphere, there are many unknowns concerning size and scale that can only be determined by from the pre-atmospheric properties of the asteroids. Their internal structure, their thermal properties, their internal strength and composition, will all play a role in determining the behavior of the object as it passes through the atmosphere, whether it produces an airblast and at what height, and the nature of the impact and amount and distribution of ejecta.

  11. A post-stishovite SiO2 polymorph in the meteorite Shergotty: implications for impact events.

    PubMed

    Sharp, T G; El Goresy, A; Wopenka, B; Chen, M

    1999-05-28

    Transmission electron microscopy and electron diffraction show that the martian meteorite Shergotty, a shocked achondrite, contains a dense orthorhombic SiO2 phase similar to post-stishovite SiO2 with the alpha-PbO2 structure. If an SiO2 mineral exists in Earth's lower mantle, it would probably occur in a post-stishovite SiO2 structure. The presence of such a high-density polymorph in a shocked sample indicates that post-stishovite SiO2 structures may be used as indicators of extreme shock pressures.

  12. The Mbale meteorite shower

    NASA Technical Reports Server (NTRS)

    Jenniskens, Peter; Betlem, Hans; Betlem, Jan; Barifaijo, Erasmus; Schluter, Thomas; Hampton, Craig; Laubenstien, Matthias; Kunz, Joachim; Heusser, Gerd

    1994-01-01

    On 1992 August 14 at 12:40 UTC, an ordinary chondrite of type L5/6 entered the atmosphere over Mbale, Uganda, broke up, and caused a strewn field of size 3 x 7 km. Shortly after the fall, an expedition gathered eye witness accounts and located the position of 48 impacts of masses between 0.19 and 27.4 kg. Short-lived radionuclide data were measured for two specimens, one of which was only 12 days after the fall. Subsequent recoveries of fragements has resulted in a total of 863 mass estimates by 1993 October. The surfaces of all fragments contain fusion crust. The meteorite shower caused some minor inconveniences. Most remarkably, a young boy was hit on the head by a small specimen. The data interpreted as to indicate that the meteorite had an initial mass between 400-1000 kg (most likely approximately 1000 kg) and approached Mbale from AZ = 185 +/- 15, H = 55 +/- 15, and V(sub infinity) = 13.5 +/- 1.5/s. Orbital elements are given. Fragmentation of the initial mass started probably above 25 km altitude, but the final catastrophic breakup occurred at an altitude of 10-14 km. An estimated 190 +/- 40 kg reached the Earth's surface minutes after the final breakup of which 150 kg of material has been recovered.

  13. The Mbale meteorite shower

    NASA Astrophysics Data System (ADS)

    Jenniskens, P.; Betlem, H.; Betlem, J.; Barifaijo, E.; Schluter, T.; Hampton, C.; Laubenstein, M.; Kunz, J.; Heusser, G.

    1994-03-01

    On 1992 August 14 at 12:40 UTC, an ordinary chondrite of type L5/6 entered the atmosphere over Mbale, Uganda, broke up, and caused a strewn field of size 3 x 7 km. Shortly after the fall, an expedition gathered eye witness accounts and located the position of 48 impacts of masses between 0.19 and 27.4 kg. Short-lived radionuclide data were measured for two specimens, one of which was only 12 days after the fall. Subsequent recoveries of fragements has resulted in a total of 863 mass estimates by 1993 October. The surfaces of all fragments contain fusion crust. The meteorite shower caused some minor inconveniences. Most remarkably, a young boy was hit on the head by a small specimen. The data interpreted as to indicate that the meteorite had an initial mass between 400-1000 kg (most likely approximately 1000 kg) and approached Mbale from AZ = 185 +/- 15, H = 55 +/- 15, and Vinfinity = 13.5 +/- 1.5/s. Orbital elements are given. Fragmentation of the initial mass started probably above 25 km altitude, but the final catastrophic breakup occurred at an altitude of 10-14 km. An estimated 190 +/- 40 kg reached the Earth's surface minutes after the final breakup of which 150 kg of material has been recovered.

  14. Shock Experiments on Basalt - Ferric Sulfate Mixes at 21 GPa & 49 GPa and their Relevance to Martian Meteorite Impact Glasses

    NASA Technical Reports Server (NTRS)

    Rao, M. N.; Ross, D. K.; See, T. H.; Nyquist, L. E.; Sutton, S.; Asimow, P.

    2013-01-01

    Large abundance of Martian atmospheric gases and neutron-induced isotopic excesses as well as Rb-Sr isotopic variations determined in some impact glasses in basaltic shergottites (e.g., Shergotty #DBS, Zagami #H1 and EET79001 #27, #8 and #104) provide definitive evidence for the occurrence of a Martian regolith component in their constituent mineral assemblages. Some of these glass-es, known as gas-rich impact-melts (GRIM), contain numerous micron-sized iron sulfide blebs along with minor amounts of iron sulfate particulates. As these GRIM glasses contain a Martian regolith component and as iron sulfates (but not sulfides) are found to occur abundantly on the Mars surface, we suggested that the sulfide blebs in GRIMs were likely generated by shock-reduction of the parental iron sulfate bearing regolith material that had been incorporated into the cavities/crevices of basaltic host rock prior to the impact event on Mars. To test whether the sulfates could be reduced to sulfides by impact shock, we carried out laboratory shock experiments on a basalt plus ferric sulfate mixture at 49 GPa at the Caltech Shock Wave Laboratory and at 21 GPa at Johnson Space Center (JSC) Experimental Impact Laboratory. The experimental details and the preliminary results for the Caltech 49 GPa experiment were presented at LPSC last year. Here, we report the results for the 21 GPa experiment at JSC and compare these results to obtain further insight into the mechanism of the bleb formation in the GRIM glasses.

  15. Connecting Lunar Meteorites to Source Terrains on the Moon

    NASA Technical Reports Server (NTRS)

    Jolliff, B. L.; Carpenter, P. K.; Korotev, R. L.; North-Valencia, S. N.; Wittmann, A.; Zeigler, R. A.

    2014-01-01

    The number of named stones found on Earth that have proven to be meteorites from the Moon is approx. 180 so far. Since the Moon has been mapped globally in composition and mineralogy from orbit, it has become possible to speculate broadly on the region of origin on the basis of distinctive compositional characteristics of some of the lunar meteorites. In particular, Lunar Prospector in 1998 [1,2] mapped Fe and Th at 0.5 degree/pixel and major elements at 5 degree/pixel using gamma ray spectroscopy. Also, various multispectral datasets have been used to derive FeO and TiO2 concentrations at 100 m/pixel spatial resolution or better using UV-VIS spectral features [e.g., 3]. Using these data, several lunar meteorite bulk compositions can be related to regions of the Moon that share their distinctive compositional characteristics. We then use EPMA to characterize the petrographic characteristics, including lithic clast components of the meteorites, which typically are breccias. In this way, we can extend knowledge of the Moon's crust to regions beyond the Apollo and Luna sample-return sites, including sites on the lunar farside. Feldspathic Regolith Breccias. One of the most distinctive general characteristics of many lunar meteorites is that they have highly feldspathic compositions (Al2O3 approx. 28% wt.%, FeO <5 wt.%, Th <1 ppm). These compositions are significant because they are similar to a vast region of the Moon's farside highlands, the Feldspathic Highlands Terrane, which are characterized by low Fe and Th in remotely sensed data [4]. The meteorites provide a perspective on the lithologic makeup of this part of the Moon, specifically, how anorthositic is the surface and what, if any, are the mafic lithic components? These meteorites are mostly regolith breccias dominated by anorthositic lithic clasts and feldspathic glasses, but they do also contain a variety of more mafic clasts. On the basis of textures, we infer these clasts to have formed by large impacts

  16. Large-scale thermal events in the solar nebula: evidence from Fe,Ni metal grains in primitive meteorites

    PubMed

    Meibom; Desch; Krot; Cuzzi; Petaev; Wilson; Keil

    2000-05-05

    Chemical zoning patterns in some iron, nickel metal grains from CH carbonaceous chondrites imply formation at temperatures from 1370 to 1270 kelvin by condensation from a solar nebular gas cooling at a rate of approximately 0.2 kelvin per hour. This cooling rate requires a large-scale thermal event in the nebula, in contrast to the localized, transient heating events inferred for chondrule formation. In our model, mass accretion through the protoplanetary disk caused large-scale evaporation of precursor dust near its midplane inside of a few astronomical units. Gas convectively moved from the midplane to cooler regions above it, and the metal grains condensed in these parcels of rising gas.

  17. Chondrules in Apollo 14 samples - Implications for the origin of chondritic meteorites.

    NASA Technical Reports Server (NTRS)

    King, E. A., Jr.; Carman, M. F.; Butler, J. C.

    1972-01-01

    Chondrules have been observed in several breccia samples returned by the Apollo 14 mission. These lunar chondrules are believed to have formed during a large impact event, perhaps the one that formed the Imbrian Basin. This suggests that some meteoritic chondrules are also formed by impact processes such as crystallization after shock melting and abrasion and diffusion in base-surge and fall-back deposits generated by impacts on planetary surfaces.

  18. The missing large impact craters on Ceres

    USGS Publications Warehouse

    Marchi, S.; Ermakov, A.; Raymond, C.A.; Fu, R.R.; O'Brien, D.P.; Bland, Michael; Ammannito, E.; De Sanctis, M.C.; Bowling, Tim; Schenk, P.; Scully, J.E.C.; Buczkowski, D.L.; Williams, D.A.; Hiesinger, H.; Russell, C.T.

    2016-01-01

    Asteroids provide fundamental clues to the formation and evolution of planetesimals. Collisional models based on the depletion of the primordial main belt of asteroids predict 10–15 craters >400 km should have formed on Ceres, the largest object between Mars and Jupiter, over the last 4.55 Gyr. Likewise, an extrapolation from the asteroid Vesta would require at least 6–7 such basins. However, Ceres’ surface appears devoid of impact craters >~280 km. Here, we show a significant depletion of cerean craters down to 100–150 km in diameter. The overall scarcity of recognizable large craters is incompatible with collisional models, even in the case of a late implantation of Ceres in the main belt, a possibility raised by the presence of ammoniated phyllosilicates. Our results indicate that a significant population of large craters has been obliterated, implying that long-wavelength topography viscously relaxed or that Ceres experienced protracted widespread resurfacing.

  19. The missing large impact craters on Ceres.

    PubMed

    Marchi, S; Ermakov, A I; Raymond, C A; Fu, R R; O'Brien, D P; Bland, M T; Ammannito, E; De Sanctis, M C; Bowling, T; Schenk, P; Scully, J E C; Buczkowski, D L; Williams, D A; Hiesinger, H; Russell, C T

    2016-07-26

    Asteroids provide fundamental clues to the formation and evolution of planetesimals. Collisional models based on the depletion of the primordial main belt of asteroids predict 10-15 craters >400 km should have formed on Ceres, the largest object between Mars and Jupiter, over the last 4.55 Gyr. Likewise, an extrapolation from the asteroid Vesta would require at least 6-7 such basins. However, Ceres' surface appears devoid of impact craters >∼280 km. Here, we show a significant depletion of cerean craters down to 100-150 km in diameter. The overall scarcity of recognizable large craters is incompatible with collisional models, even in the case of a late implantation of Ceres in the main belt, a possibility raised by the presence of ammoniated phyllosilicates. Our results indicate that a significant population of large craters has been obliterated, implying that long-wavelength topography viscously relaxed or that Ceres experienced protracted widespread resurfacing.

  20. The missing large impact craters on Ceres

    PubMed Central

    Marchi, S.; Ermakov, A. I.; Raymond, C. A.; Fu, R. R.; O'Brien, D. P.; Bland, M. T.; Ammannito, E.; De Sanctis, M. C.; Bowling, T.; Schenk, P.; Scully, J. E. C.; Buczkowski, D. L.; Williams, D. A.; Hiesinger, H.; Russell, C. T.

    2016-01-01

    Asteroids provide fundamental clues to the formation and evolution of planetesimals. Collisional models based on the depletion of the primordial main belt of asteroids predict 10–15 craters >400 km should have formed on Ceres, the largest object between Mars and Jupiter, over the last 4.55 Gyr. Likewise, an extrapolation from the asteroid Vesta would require at least 6–7 such basins. However, Ceres' surface appears devoid of impact craters >∼280 km. Here, we show a significant depletion of cerean craters down to 100–150 km in diameter. The overall scarcity of recognizable large craters is incompatible with collisional models, even in the case of a late implantation of Ceres in the main belt, a possibility raised by the presence of ammoniated phyllosilicates. Our results indicate that a significant population of large craters has been obliterated, implying that long-wavelength topography viscously relaxed or that Ceres experienced protracted widespread resurfacing. PMID:27459197

  1. Large meteoroid's impact damage: review of available impact hazard simulators

    NASA Astrophysics Data System (ADS)

    Moreno-Ibáñez, M.; Gritsevich, M.; Trigo-Rodríguez, J. M.

    2016-01-01

    The damage caused by meter-sized meteoroids encountering the Earth is expected to be severe. Meteor-sized objects in heliocentric orbits can release energies higher than 108 J either in the upper atmosphere through an energetic airblast or, if reaching the surface, their impact may create a crater, provoke an earthquake or start up a tsunami. A limited variety of cases has been observed in the recent past (e.g. Tunguska, Carancas or Chelyabinsk). Hence, our knowledge has to be constrained with the help of theoretical studies and numerical simulations. There are several simulation programs which aim to forecast the impact consequences of such events. We have tested them using the recent case of the Chelyabinsk superbolide. Particularly, Chelyabinsk belongs to the ten to hundred meter-sized objects which constitute the main source of risk to Earth given the current difficulty in detecting them in advance. Furthermore, it was a detailed documented case, thus allowing us to properly check the accuracy of the studied simulators. As we present, these open simulators provide a first approximation of the impact consequences. However, all of them fail to accurately determine the caused damage. We explain the observed discrepancies between the observed and simulated consequences with the following consideration. The large amount of unknown properties of the potential impacting meteoroid, the atmospheric conditions, the flight dynamics and the uncertainty in the impact point itself hinder any modelling task. This difficulty can be partially overcome by reducing the number of unknowns using dimensional analysis and scaling laws. Despite the description of physical processes associated with atmospheric entry could be still further improved, we conclude that such approach would significantly improve the efficiency of the simulators.

  2. Exposure histories of the lunar meteorites - MAC88104, MAC88105, Y791197, and Y86032

    NASA Technical Reports Server (NTRS)

    Vogt, S.; Herzog, G. F.; Fink, D.; Klein, J.; Middleton, R.; Dockhorn, B.; Korschinek, G.; Nolte, E.

    1991-01-01

    Four lunar meteorites were analyzed for the cosmogenic radionuclides Be-10, Al-26, Cl-36, and Ca-41. Histories of exposure to cosmic rays were modelled in terms of two-stage irradiations, each with a long first stage on the moon, lasting a time T sub 2pi greater than 5 Ma at a burial depth d sub 2pi(g/sq cm), followed by a second stage in space, i.e., the transit time between the moon and the earth, lasting a time T sub 4pi (Ma) in a body of typical metereological size. It is inferred that the production rate is of the order of 5/Ma and the arrival rate worldwide is about 3,000,000 meteorites/Ma. It is concluded that each impact event large enough to produce lunar meteorites sends a large number of them to the earth.

  3. Synchroneity of the K-T oceanic mass extinction and meteorite impact: Blake Nose, western North Atlantic

    USGS Publications Warehouse

    Norris, R.D.; Huber, B.T.; Self-Trail, J.

    1999-01-01

    A 10-cm-thick layer of green spherules occurs precisely at the biostratigraphic boundary between the Cretaceous and Paleogene (K-T boundary) at Ocean Drilling Program Site 1049 (lat 30??08???N, long 76??06???W). The spherulitic layer contains abundant rock fragments (chalk, limestone, dolomite, chert, mica books, and schist) as well as shocked quartz, abundant large Cretaceous planktic foraminifera, and rounded clasts of clay as long as 4 mm interpreted as altered tektite glass probably derived from the Chicxulub impact structure. Most of the Cretaceous foraminifera present above the spherule layer are not survivors since small specimens are conspicuously rare compared to large individuals. Instead, the Cretaceous taxa in Paleocene sediments are thought to be reworked. The first Paleocene planktic foraminifera and calcareous nannofossil species are recorded immediately above the spherule bed, the upper part of which contains an iridium anomaly. Hence, deposition of the impact ejecta exactly coincided with the biostratigraphic K-T boundary and demonstrates that the impact event was synchronous with the evolutionary turnover in the oceans. These results are consistent with a reanalysis of the biostratigraphy of the K-T boundary stratotype, which argues that shallow-marine K-T boundary sections are not biostratigraphically more complete than deep-sea K-T boundary sites.

  4. Isotopic, optical, and trace element properties of large single SiC grains from the Murchison meteorite

    NASA Technical Reports Server (NTRS)

    Virag, Alois; Wopenka, Brigitte; Amari, Sachiko; Zinner, Ernst; Anders, Edward; Lewis, Roy S.

    1992-01-01

    Ion probe mass spectrometry is used to analyze 41 large SiC grains from the Murchison CM2 chondrite, ranging up to 15 x 26 microns, for the isotopic compositions of C, N, Mg, and Si, and the concentrations of Al, Ti, V, Fe, Zr, and Ba. The majority were found to have large isotopic anomalies. Only two grains, characterized by extremely heavy carbon, give evidence for fossil Mg-26. On the basis of C and Si isotopic composition, 29 of the grains fall into three compact clusters, presumably from three discrete sources. The clustering of coarse-grained SiC stands in sharp contrast to the quasi-continuous distribution of finer-grained SiC and suggests that the top 0.1 percent of the mass distribution is a distinct population. The C and N isotopic compositions of the anomalous grains are not very diagnostic, being consistent with H-burning in the CNO cycle. The Si-isotopic compositions qualitatively show the signature of neutron capture in He-burning shells of highly evolved stars.

  5. Interpretation of Wild 2 Dust Fine Structure: Comparison of Stardust Aluminium Foil Craters to the Three-Dimensional Shape of Experimental Impacts by Artificial Aggregate Particles and Meteorite Powders

    SciTech Connect

    Kearsley, A T; Burchell, M J; Price, M C; Graham, G A; Wozniakiewicz, P J; Cole, M J; Foster, N J; Teslich, N

    2009-12-10

    New experimental results show that Stardust crater morphology is consistent with interpretation of many larger Wild 2 dust grains being aggregates, albeit most of low porosity and therefore relatively high density. The majority of large Stardust grains (i.e. those carrying most of the cometary dust mass) probably had density of 2.4 g cm{sup -3} (similar to soda-lime glass used in earlier calibration experiments) or greater, and porosity of 25% or less, akin to consolidated carbonaceous chondrite meteorites, and much lower than the 80% suggested for fractal dust aggregates. Although better size calibration is required for interpretation of the very smallest impacting grains, we suggest that aggregates could have dense components dominated by {micro}m-scale and smaller sub-grains. If porosity of the Wild 2 nucleus is high, with similar bulk density to other comets, much of the pore-space may be at a scale of tens of micrometers, between coarser, denser grains. Successful demonstration of aggregate projectile impacts in the laboratory now opens the possibility of experiments to further constrain the conditions for creation of bulbous (Type C) tracks in aerogel, which we have observed in recent shots. We are also using mixed mineral aggregates to document differential survival of pristine composition and crystalline structure in diverse fine-grained components of aggregate cometary dust analogues, impacted onto both foil and aerogel under Stardust encounter conditions.

  6. Terrestrial and exposure histories of Antarctic meteorites

    NASA Technical Reports Server (NTRS)

    Nishiizumi, K.

    1986-01-01

    Records of cosmogenic effects were studied in a large suite of Antarctic meteorites. The cosmogenic nuclide measurements together with cosmic ray track measurements on Antartic meteorites provide information such as exposure age, terrestrial age, size and depth in meteoroid or parent body, influx rate in the past, and pairing. The terrestrail age is the time period between the fall of the meteorite on the Earth and the present. To define terrestrial age, two or more nuclides with different half-lives and possibly noble gases are required. The cosmogenic radionuclides used are C-14, Kr-81, Cl-36, Al-26, Be-10, Mn-53, and K-40.

  7. Microfossils in CI and CO Carbonaceous Meteorites

    NASA Technical Reports Server (NTRS)

    Hoover, Richard B.; Rozanov, Alexei Y.; Jerman, Gregory; Costen, James

    2003-01-01

    Secondary and backscatter electron images and x-ray spectral data of selected CI (Alais, Orgueil, and Tagish Lake) and CO3 (Rainbow and Dar a1 Gani 749) carbonaceous meteorites have recently been obtained using Field Emission and Environmental Scanning Electron Microscopes These studies indicate the presence of a large assemblage of biomarkers and complex lithified and carbonized remains of bodies that we interpret as indigenous microfossils. We discuss the meteorites, provide images of many of the biogenic forms found embedded in the freshly fractured meteorite surfaces.

  8. Microfossils in CI and CO Carbonaceous Meteorites

    NASA Technical Reports Server (NTRS)

    Hoover, Richard B.; Rozanov, Alexei Y.; Jerman, Gregory; Costen, James

    2003-01-01

    Secondary and backscatter electron images and x-ray spectral data of selected CI (Alais, Orgueil, and Tagish Lake) and CO3 (Rainbow and Dar a1 Gani 749) carbonaceous meteorites have recently been obtained using Field Emission and Environmental Scanning Electron Microscopes These studies indicate the presence of a large assemblage of biomarkers and complex lithified and carbonized remains of bodies that we interpret as indigenous microfossils. We discuss the meteorites, provide images of many of the biogenic forms found embedded in the freshly fractured meteorite surfaces.

  9. An Adulterated Martian Meteorite

    NASA Astrophysics Data System (ADS)

    Taylor, G. J.

    1999-07-01

    Martian meteorite, Elephant Moraine EETA79001, is composed of two distinct rock types. Scientists have thought that both formed from magmas, hence are igneous rocks and contain important information about the interior of Mars, the nature of lava flows on its surface, and the timing of igneous events on Mars. All that is now open to question, as a group of investigators at Lockheed Martin Space Operations and the Johnson Space Center led by David Mittlefehldt (Lockheed) has shown that one of the rock types making up EETA79001, designated lithology A, is almost certainly a melted mixture of other rocks. Mittlefehldt and coworkers suggest that formation by impact melting is the most likely explanation for the chemical and mineralogical features seen in the rock. If confirmed by other investigations, this may change the way we view the igneous evolution of Mars.

  10. Ecological catastrophe in connection with the impact of the Kaali Meteorite about 800-400 BC on the island of Saaremaa, Estonia

    NASA Astrophysics Data System (ADS)

    Veski, Siim; Heinsalu, Atko; Kirsimäe, Kalle; Poska, Anneli; Saarse, Leili

    2001-10-01

    A sequence of peat enriched with impact ejecta (allochthonous minerals and iridium) from Piila bog, 6 km away from the Kaali impact crater (island of Saaremaa, Estonia), was examined using pollen, radiocarbon, loss-on-ignition, and x-ray diffraction analyses to date and assess the environmental effect of the impact. The vegetation in the surroundings of the Piila bog before the Kaali impact was a fen surrounded by forest in natural conditions. Significant changes occur in pollen accumulation and composition of pollen in the depth interval 170-178 cm, which contains above background values of iridium (up to 0.53 ppb). Two samples from the basal silt layer inside the main crater at Kaali contain 0.8 ppb of iridium, showing that iridium was present in the impact ejecta. The impact explosion swept the surroundings clean of forest shown by the threefold decrease in the total pollen influx (especially tree pollen influx), increase in influx and diversity of herb taxa, and the relative dominance of pine. Increased input of mineral matter measured by loss-on-ignition and the composition mineral matter (increased input of allochthonous minerals) together with an extensive layer of charcoal and wood stumps in Piila bog at the same depth interval points to an ecological catastrophe, with local impact-induced wildfires reaching at least 6 km northwest of the epicenter. The disappearance of cereals in the pollen record suggests that farming, cultivation and possibly human habitation in the region ceased for a period of ~100 years. The meteorite explosion at Kaali ranged between the effects of Hiroshima and Tunguska. The age of the Kaali impact event is placed between 800-400 b.c. based on radiocarbon dating of the peat enriched with impact ejecta in the Piila bog.

  11. Meteorites at Meridiani Planum provide evidence for significant amounts of surface and near-surface water on early Mars

    USGS Publications Warehouse

    Fairen, Alberto G.; Dohm, James M.; Baker, Victor R.; Thompson, Shane D.; Mahaney, William C.; Herkenhoff, Kenneth E.; Rodriguez, J. Alexis P.; Davila, Alfonso F.; Schulze-Makuch, Dirk; El Maarry, M. Ramy; Uceda, Esther R.; Amils, Ricardo; Miyamoto, Hirdy; Kim, Kyeong J.; Anderson, Robert C.; McKay, Christopher P.

    2011-01-01

    Six large iron meteorites have been discovered in the Meridiani Planum region of Mars by the Mars Exploration Rover Opportunity in a nearly 25 km-long traverse. Herein, we review and synthesize the available data to propose that the discovery and characteristics of the six meteorites could be explained as the result of their impact into a soft and wet surface, sometime during the Noachian or the Hesperian, subsequently to be exposed at the Martian surface through differential erosion. As recorded by its sediments and chemical deposits, Meridiani has been interpreted to have undergone a watery past, including a shallow sea, a playa, an environment of fluctuating ground water, and/or an icy landscape. Meteorites could have been encased upon impact and/or subsequently buried, and kept underground for a long time, shielded from the atmosphere. The meteorites apparently underwent significant chemical weathering due to aqueous alteration, as indicated by cavernous features that suggest differential acidic corrosion removing less resistant material and softer inclusions. During the Amazonian, the almost complete disappearance of surface water and desiccation of the landscape, followed by induration of the sediments and subsequent differential erosion and degradation of Meridiani sediments, including at least 10–80 m of deflation in the last 3–3.5 Gy, would have exposed the buried meteorites. We conclude that the iron meteorites support the hypothesis that Mars once had a denser atmosphere and considerable amounts of water and/or water ice at and/or near the surface.

  12. Nitrogen isotopic compositions of iron meteorites

    NASA Technical Reports Server (NTRS)

    Prombo, Carol A.; Clayton, Robert N.

    1993-01-01

    Iron meteorites analyzed in this study have nitrogen concentrations 70 microg/g or less and delta N-15 from -90 to +150 percent. Although the iron meteorites have a large range of delta N-15, most have values more negative than -50 percent. The nitrogen isotopic compositions were established by cosmochemical processes and were little modified by fractional crystallization or other chemical processes within the parent bodies. The data do not suggest the existence of a well-mixed solar nebular reservoir for nitrogen, as was already inferred from data from stony meteorites. The range of greater than 1100 percent observed for delta N-15 in bulk meteorites is probably too large to be accounted for by physical and chemical mass-dependent fractionation processes in the solar nebula, and thus reflects nebular inhomogeneities of nucleosynthetic origin.

  13. Finding Shatter Cones in Meteorites from the Natural History Museum Vienna Collection

    NASA Astrophysics Data System (ADS)

    Ferrière, L.; Brandstätter, F.; Koeberl, C.

    2013-09-01

    New findings of shatter cones in a few meteorites from the Natural History Museum Vienna as well as other impact metamorphism features are presented. Their occurrence in meteorites records hypervelocity collisions in the solar system.

  14. Meteorite transport—Revisited

    NASA Astrophysics Data System (ADS)

    Wisdom, Jack

    2017-08-01

    Meteorites are delivered from the asteroid belt by way of chaotic zones (Wisdom 1985a). The dominant sources are believed to be the chaotic zones associated with the ν6 secular resonance, the 3:1 mean motion resonance, and the 5:2 mean motion resonance. Though the meteorite transport process has been previously studied, those studies have limitations. Here I reassess the meteorite transport process with fewer limitations. Prior studies have not been able to reproduce the afternoon excess (the fact that approximately twice as many meteorites fall in the afternoon as in the morning) and suggested that the afternoon excess is an observational artifact; here it is shown that the afternoon excess is in fact consistent with the transport of meteorites by way of chaotic zones in the asteroid belt. By studying models with and without the inner planets it is found that the inner planets significantly speed up the transport of meteorites.

  15. Metal-saturated sulfide assemblages in NWA 2737: Evidence for impact-related sulfur devolatilization in Martian meteorites

    NASA Astrophysics Data System (ADS)

    Lorand, Jean-Pierre; Barrat, Jean-Alix; Chevrier, Vincent; Sautter, Violaine; Pont, Sylvain

    2012-11-01

    Abstract-NWA 2737, a Martian <span class="hlt">meteorite</span> from the Chassignite subclass, contains minute amounts (0.010 ± 0.005 vol%) of metal-saturated Fe-Ni sulfides. These latter bear evidence of the strong shock effects documented by abundant Fe nanoparticles and planar defects in Northwest Africa (NWA) 2737 olivine. A Ni-poor troilite (Fe/S = 1.0 ± 0.01), sometimes Cr-bearing (up to 1 wt%), coexists with micrometer-sized taenite/tetrataenite-type native Ni-Fe alloys (Ni/Fe = 1) and Fe-Os-Ir-(Ru) alloys a few hundreds of nanometers across. The troilite has exsolved flame-like pentlandite (Fe/Fe + Ni = 0.5-0.6). Chalcopyrite is almost lacking, and no pyrite has been found. As a hot desert find, NWA 2737 shows astonishingly fresh sulfides. The composition of troilite coexisting with Ni-Fe alloys is completely at odds with Chassigny and Nahkla sulfides (pyrite + metal-deficient monoclinic-type pyrrhotite). It indicates strongly reducing crystallization conditions (close to IW), several log units below the fO2 conditions inferred from chromites compositions and accepted for Chassignites (FMQ-1 log unit). It is proposed that reduction in sulfides into base and precious metal alloys is operated via sulfur degassing, which is supported by the highly resorbed and denticulated shape of sulfide blebs and their spongy textures. Shock-related S degassing may be responsible for considerable damages in magmatic sulfide structures and sulfide assemblages, with concomitant loss of magnetic properties as documented in some other Martian <span class="hlt">meteorites</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFMGP23A0994K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFMGP23A0994K"><span>Electromagnetic depth sounding in the Earth's crust: Survey and modeling of the effects of a <span class="hlt">meteorite</span> <span class="hlt">impact</span> on the conductivity structure in Southern Germany</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kerch, J.; Bahr, K.</p> <p>2010-12-01</p> <p>More than 14 million years ago a <span class="hlt">meteorite</span> hit Bavaria and left a huge hole where the Swabian and the Franconian Jura meet in Southern Germany. The <span class="hlt">impact</span> clearly changed the earth’s surface but what happened in the depth? How deep did the earth got shaken by the <span class="hlt">impact</span>? And did it affect the crustal conductor? The anisotropy of the crustal conductor in Southern Germany manifests itself in a magnetotelluric phase split. The results of two earlier magnetotelluric surveys in the area, which show a decreased phase split within the crater compared to outside it, indicate a breach in the crustal conductor underneath the crater due to the <span class="hlt">impact</span>. In order to base the modeling on more solid ground new magnetotelluric data from 14 sites in the region was acquired between June and September 2010 to fill the gaps in the existing data about the area. A simultaneous study on the sediments that filled the crater due to the formation of a lake which does not exist anymore shall contribute some new information on the conductivity of the upper layers. The question arises if it is maybe even possible to identify the direction of the <span class="hlt">impact</span> with the method. Additionally to a renewed magnetotelluric analysis, geomagnetic depth sounding (GDS) will be used to gain new insights and further improve the model to explain the findings.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA06012.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA06012.html"><span>Hills in Arctic Canada with <span class="hlt">Impact</span> Origin</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2004-06-02</p> <p>While most hills and mountains on Earth originate from tectonic motions or volcanism, Earth also has some examples of hills that originated from <span class="hlt">impacts</span> of <span class="hlt">large</span> <span class="hlt">meteorites</span>, the predominant origin for hills and mountains on the Moon.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20000040793','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20000040793"><span>Antarctic <span class="hlt">Meteorite</span> Newsletter</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lindstrom, Marilyn</p> <p>2000-01-01</p> <p>This newsletter contains something for everyone! It lists classifications of about 440 <span class="hlt">meteorites</span> mostly from the 1997 and 1998 ANSMET (Antarctic Search for <span class="hlt">Meteorites</span>) seasons. It also gives descriptions of about 45 <span class="hlt">meteorites</span> of special petrologic type. These include 1 iron, 17 chondrites (7 CC, 1 EC, 9 OC) and 27 achondrites (25 HED, UR). Most notable are an acapoloite (GRA98028) and an olivine diogenite (GRA98108).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19770050274&hterms=Fluorine&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DFluorine','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19770050274&hterms=Fluorine&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DFluorine"><span>Fluorine in <span class="hlt">meteorites</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Allen, R. O., Jr.; Clark, P. J.</p> <p>1977-01-01</p> <p>Microanalysis using a resonant nuclear reaction was used to measure F concentrations in USGS standard rocks and 21 <span class="hlt">meteorites</span>. The F appears to be a moderately depleted element, but there were significant variations within each sample. Measurements on separated metal phases suggest that about 20% of <span class="hlt">meteoritic</span> F is in the metal or in a phase closely associated with it. Simultaneous measurements of F, Mg, Na, Al and Si in the nonmagnetic fractions of <span class="hlt">meteorites</span> suggest plagioclase as a F containing phase.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20080026075','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20080026075"><span>Antarctic <span class="hlt">Meteorite</span> Newsletter, Volume 29, Number 1</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Satterwhite, Cecilia (Editor); Righter, Kevin (Editor)</p> <p>2006-01-01</p> <p>This newsletter contains classifications for 597 new <span class="hlt">meteorites</span> from the 2003 and 2004 ANtarctic Search for <span class="hlt">METeorites</span> (ANSMET) seasons. They include samples from the Cumulus Hills, Dominion Range, Grosvenor Mountains, LaPaz Icefield, MacAlpine Hills, and the Miller Range. Macroscopic and petrographic descriptions are given for 25 of the new <span class="hlt">meteorites</span>: 1 acapulcoite/Iodranite, 1 howardite, 1 diogenite, 2 eucrites, 1 enstatite chondrite, four L3 and two H3 chondrites, 2 CM, 3 CK and 1 CV chondrites, three R chondrites, and four <span class="hlt">impact</span> melt breccias (with affinities for H and L). Likely the most interesting sample announced in this newsletter is LAP04840, with affinity to R chondrites. This <span class="hlt">meteorite</span> contains approximately 15% horneblende, and has mineral compositional ranges and oxygen isotopic values similar to those of R chondrites. The presence of an apparently hydrous phase in this petrologic grade 6 chondrite is very unusual, and should be of great interest to many meteoriticists.</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('http://hdl.handle.net/2060/20170000781','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20170000781"><span>Brachinite-Like Clast in the Kaidun <span class="hlt">Meteorite</span>: First Report of Primitive Achondrite Material</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Higashi, K.; Hasegawa, H.; Mikouchi, T.; Zolensky, M. E.</p> <p>2017-01-01</p> <p>Kaidun is a brecciated <span class="hlt">meteorite</span> containing many different types of <span class="hlt">meteorites</span>. It is composed of carbonaceous, enstatite, ordinary and R chondrites with smaller amounts of basaltic achondrites, <span class="hlt">impact</span> melt products and unknown [1, 2]. Because of the multiple components and high abundance of carbonaceous chondrites, the Kaidun parent body was probably a <span class="hlt">large</span> C-type asteroid in order to have accumulated clasts of many unrelated asteroids, and thus Kaidun contains previously unknown materials[1]. It has been suggested that the Kaidun parent body trawled through different regions of the solar system [3], but the formation of Kaidun <span class="hlt">meteorite</span> is still uncertain. In this abstract, we report the first discovery of a brachinite-like clast in Kaidun.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19880021189','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19880021189"><span>Antarctic <span class="hlt">Meteorite</span> Newsletter, Volume 11, Number 2, August 1988</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1988-01-01</p> <p>Presented are classifications and descriptions of a <span class="hlt">large</span> number of <span class="hlt">meteorites</span> which include the last samples from the 1984 collection and the first samples from the 1987 collection. There is a particularly good selection of <span class="hlt">meteorites</span> of special petrologic type in the 1987 collection. The achondrites include aubrites, ureilites, howardites, eucrites, and a diogenite. The howardites are particularly notable because of their size and previous scarcity in the Antarctic collection. Noteworthy among the 7 irons and 3 mesosiderities are 2 anamolous irons and 2 <span class="hlt">large</span> mesosiderites. The carbonaceous chondrites include good suites of C2 and C4 <span class="hlt">meteorites</span>, and 2 highly equilibrated carbonaceous chondrites tentatively identified as C5 and C6 <span class="hlt">meteorites</span>. Also included are surveys of numerous <span class="hlt">meteorites</span> for Al-26 and thermoluminescence. These studies provide information on the thermal and radiation histories of the <span class="hlt">meteorites</span> and can be used as measures of their terrestrial ages.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23971552','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23971552"><span>Solution of the α-potential mystery in the γ process and its <span class="hlt">impact</span> on the Nd/Sm ratio in <span class="hlt">meteorites</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Rauscher, Thomas</p> <p>2013-08-09</p> <p>The 146Sm/144Sm ratio in the early solar system has been constrained by Nd/Sm isotope ratios in <span class="hlt">meteoritic</span> material. Predictions of 146Sm and 144Sm production in the γ process in massive stars are at odds with these constraints, and this is partly due to deficiencies in the prediction of the reaction rates involved. The production ratio depends almost exclusively on the (γ,n)/(γ,α) branching at 148Gd. A measurement of 144Sm(α,γ)148Gd at low energy had discovered considerable discrepancies between cross-section predictions and the data. Although this reaction cross section mainly depends on the optical α+nucleus potential, no global optical potential has yet been found that can consistently describe the results of this and similar α-induced reactions at the low energies encountered in astrophysical environments. The untypically <span class="hlt">large</span> deviation in 144Sm(α,γ) and the unusual energy dependence can be explained, however, by low-energy Coulomb excitation, which is competing with compound nucleus formation at very low energies. Considering this additional reaction channel, the cross sections can be described with the usual optical potential variations, compatible with findings for (n, α) reactions in this mass range. Low-energy (α, γ) and (α, n) data on other nuclei can also be consistently explained in this way. Since Coulomb excitation does not affect α emission, the 148Gd(γ,α) rate is much higher than previously assumed. This leads to very small 146Sm/144Sm stellar production ratios, in even more pronounced conflict with the <span class="hlt">meteorite</span> data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMED51D..05B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMED51D..05B"><span>Vigie-Ciel : a french citizen network to study meteors and <span class="hlt">meteorites</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bouley, S.; Zanda, B.; Colas, F.; Vaubaillon, J.; Marmo, C.; Vernazza, P.; Gattacceca, J.</p> <p>2013-12-01</p> <p>Vigie Ciel is a french citizen network supported by the Muséum National d'Histoire Naturelle (MNHN) and the Université Paris-Sud (UPsud). It is based on the scientific FRIPON program developed by Paris Observatory (Fireball Recovery and Planetary Inter Observation Network) which has for main goal to (i) determine the source region(s) of the various <span class="hlt">meteorite</span> classes, (ii) collect both fresh and rare <span class="hlt">meteorite</span> types and (iii) perform scientific outreach. This will be achieved by building the densest camera network in the world, based on state of the art technologies and associated with a participative network for <span class="hlt">meteorite</span> recovery. We propose to install a network of 100 digital cameras covering the entire French territory to compute <span class="hlt">impact</span> locations with accuracy of the order of one kilometer. Considering that there are 5 to 25 falls over France per year (~15 on average), during the same time, we will observe ~50 falls out of which we realistically expect to find 10 <span class="hlt">meteorites</span>. Our project is original in several ways. (i) It is inter-disciplinary, involving experts in <span class="hlt">meteoritics</span>, asteroidal science as well as fireball observation and dynamics. It will thus create new synergies between prominent institutions and/or laboratories, namely between MNHN, Paris Observatory and Université Paris-Sud in the Parisian region; and between CEREGE and LAM in the Provence region. Overall, scientists from over 25 laboratories will be involved, covering a mix of scientific disciplines and all the regions of France. (ii) It will generate a <span class="hlt">large</span> body of data, feeding databases of interest to several disciplines (e.g. bird migration, variations of the luminosity of the brightest stars, observation of space debris, meteorology...). (iii) It will for the first time involve the general public (including schools) in the search for the <span class="hlt">meteorite</span> falls, thus boosting the interest in <span class="hlt">meteorite</span> and asteroid related science.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1995Metic..30R.561P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1995Metic..30R.561P"><span>Edward P. Henderson and the Development of <span class="hlt">Meteoritics</span> at the Smithsonian Institution, 1929-1965</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Plotkin, H.</p> <p>1995-09-01</p> <p>Ed Henderson's long career as Curator of <span class="hlt">Meteorites</span> at the U.S. National Museum (1929-1965) had a tremendous <span class="hlt">impact</span> on the development of <span class="hlt">meteoritics</span>. As a result of his tenure, the Museum's collection of <span class="hlt">meteorites</span> grew to become arguably the largest and finest in the world, and the Smithsonian became one of the world's leading centers for their study. During Henderson's administration, his ability to acquire <span class="hlt">meteorites</span> was due partially to the availability of the Roebling Fund, but more importantly it was due to his extraordinary resourcefulness, his single-mindedness of purpose, his intuitive grasp of new directions in <span class="hlt">meteoritics</span>, and his ability to make many influential friends who became staunch supporters of the Museum. His early efforts, however, were <span class="hlt">largely</span> shaped by his relationship with two remarkable men: Harvey Nininger, the world's first full-time self-employed meteoriticist, and Stuart Perry, a Michigan newspaper publisher and vice president of the Associated Press who developed a strong interest in collecting and studying <span class="hlt">meteorites</span>. Henderson's love for <span class="hlt">meteorites</span> and for the Smithsonian collection took him to Europe, the Philippines, the former Soviet Union, and Australia, where he aggressively hunted for <span class="hlt">meteorites</span> and tektites, or arranged for purchases or exchanges. As well, he routinely contacted the owners of newly fallen <span class="hlt">meteorites</span> to see if he could obtain material from them. Frequently he travelled to some remote spot to negotiate with the owner for a purchase. Sometimes this involved days of haggling, but Henderson was very good at this; he was a born trader. Post-WWII advances in atomic physics and related fields completely transformed <span class="hlt">meteoritics</span>. A new breed of scientist arose, who viewed <span class="hlt">meteorites</span> as keys which could be used to unlock the mysteries of the origin and evolution of the Solar System. Henderson generously provided these scientists with specimens from the Smithsonian's collection for their research. Although his training</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19740018174','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19740018174"><span>Magnetism in <span class="hlt">meteorites</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Herndon, J. M.; Rowe, M. W.</p> <p>1974-01-01</p> <p>An overview is presented of magnetism in <span class="hlt">meteorites</span>. A glossary of magnetism terminology followed by discussion of the various techniques used for magnetism studies in <span class="hlt">meteorites</span> are included. The generalized results from use of these techniques by workers in the field are described. A brief critical analysis is offered.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012M%26PS...47..929P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012M%26PS...47..929P"><span>The Old Woman, California, IIAB iron <span class="hlt">meteorite</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Plotkin, Howard; Clarke, Roy S.; McCoy, Timothy J.; Corrigan, Catherine M.</p> <p>2012-05-01</p> <p>The Old Woman <span class="hlt">meteorite</span>, discovered in March 1976 by two prospectors searching for a fabled lost Spanish gold mine in mountains ˜270 km east of Los Angeles, has achieved the status of a legend among <span class="hlt">meteorite</span> hunters and collectors. The question of the ownership of the 2753 kg group IIAB <span class="hlt">meteorite</span>, the second largest ever found in the United States (34°28'N, 115°14'W), gave rise to disputes involving the finders, the Bureau of Land Management, the Secretary of the Department of the Interior, the State of California, the California members of the U.S. Congress, various museums in California, the Smithsonian Institution, and the Department of Justice. Ultimately, ownership of the <span class="hlt">meteorite</span> was transferred to the Smithsonian under the powers of the 1906 Antiquities Act, a ruling upheld in a U.S. District Court and a U.S. Court of Appeals. After additional debate, the Smithsonian removed a <span class="hlt">large</span> cut for study and curation, and for disbursement of specimens to qualified researchers. The main mass was then returned to California on long-term loan to the Bureau of Land Management's Desert Discovery Center in Barstow. The Old Woman <span class="hlt">meteorite</span> litigation served as an important test case for the ownership and control of <span class="hlt">meteorites</span> found on federal lands. The Old Woman <span class="hlt">meteorite</span> appears to be structurally unique in containing both hexahedral and coarsest octahedral structures in the same mass, unique oriented schreibersites within hexahedral areas, and polycrystalline parent austenite crystals. These structures suggest that different portions of the <span class="hlt">meteorite</span> may have transformed via different mechanisms upon subsolidus cooling, making the <span class="hlt">large</span> slices of Old Woman promising targets for future research.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19980019921','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19980019921"><span>Lunar <span class="hlt">Meteorite</span> Queen Alexandra Range 93069 and the Iron Concentration of the Lunar Highlands Surface</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Korotev, Randy L.; Jolliff, Bradley L.; Rockow, Kaylynn M.</p> <p>1996-01-01</p> <p>Lunar <span class="hlt">meteorite</span> Queen Alexandra Range 93069 is a clast-rich, glassy-matrix regolith breccia of ferroan, highly aluminous bulk composition. It is similar in composition to other feldspathic lunar <span class="hlt">meteorites</span> but differs in having higher concentrations of siderophile elements and incompatible trace elements. Based on electron microprobe analyses of the fusion crust, glassy matrix, and clasts, and instrumental neutron activation analysis of breccia fragments, QUE 93069 is dominated by nonmare components of ferroan, noritic- anorthosite bulk composition. Thin section QUE 93069,31 also contains a <span class="hlt">large</span>, <span class="hlt">impact</span>-melted, partially devitrified clast of magnesian, anorthositic-norite composition. The enrichment in Fe, Sc, and Cr and lower Mg/Fe ratio of lunar <span class="hlt">meteorites</span> Yamato 791197 and Yamato 82192/3 compared to other feldspathic lunar <span class="hlt">meteorites</span> can be attributed to a small proportion (5-10%) of low-Ti mare basalt. It is likely that the non- mare components of Yamato 82192/3 are similar to and occur in similar abundance to those of Yamato 86032, with which it is paired. There is a significant difference between the average FeO concentration of the lunar highlands surface as inferred from the feldspathic lunar <span class="hlt">meteorites</span> (mean: approx. 5.0%; range: 4.3-6.1 %) and a recent estimate based on data from the Clementine mission (3.6%).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19740029965&hterms=organic+inorganic+compounds&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dorganic%2Binorganic%2Bcompounds','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19740029965&hterms=organic+inorganic+compounds&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dorganic%2Binorganic%2Bcompounds"><span>Organic compounds in <span class="hlt">meteorites</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Anders, E.; Hayatsu, R.; Studier, M. H.</p> <p>1973-01-01</p> <p>The problem of whether organic compounds originated in <span class="hlt">meteorites</span> as a primary condensate from a solar gas or whether they were introduced as a secondary product into the <span class="hlt">meteorite</span> during its residence in a parent body is examined by initially attempting to reconstruct the physical conditions during condensation (temperature, pressure, time) from clues in the inorganic matrix of the <span class="hlt">meteorite</span>. The condensation behavior of carbon under these conditions is then analyzed on the basis of thermodynamic calculations, and compounds synthesized in model experiments on the condensation of carbon are compared with those actually found in <span class="hlt">meteorites</span>. Organic compounds in <span class="hlt">meteorites</span> seem to have formed by catalytic reactions of carbon monoxide, hydrogen, and ammonia in the solar nebula at 360 to 400 K temperature and about 3 to 7.6 microtorr pressure. The onset of these reactions was triggered by the formation of suitable catalysts (magnetite, hydrated silicates) at these temperatures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19740029965&hterms=organic+compounds&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dorganic%2Bcompounds','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19740029965&hterms=organic+compounds&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dorganic%2Bcompounds"><span>Organic compounds in <span class="hlt">meteorites</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Anders, E.; Hayatsu, R.; Studier, M. H.</p> <p>1973-01-01</p> <p>The problem of whether organic compounds originated in <span class="hlt">meteorites</span> as a primary condensate from a solar gas or whether they were introduced as a secondary product into the <span class="hlt">meteorite</span> during its residence in a parent body is examined by initially attempting to reconstruct the physical conditions during condensation (temperature, pressure, time) from clues in the inorganic matrix of the <span class="hlt">meteorite</span>. The condensation behavior of carbon under these conditions is then analyzed on the basis of thermodynamic calculations, and compounds synthesized in model experiments on the condensation of carbon are compared with those actually found in <span class="hlt">meteorites</span>. Organic compounds in <span class="hlt">meteorites</span> seem to have formed by catalytic reactions of carbon monoxide, hydrogen, and ammonia in the solar nebula at 360 to 400 K temperature and about 3 to 7.6 microtorr pressure. The onset of these reactions was triggered by the formation of suitable catalysts (magnetite, hydrated silicates) at these temperatures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/653368','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/653368"><span><span class="hlt">Meteoritic</span> event recorded in Antarctic ice</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Harvey, R.P.; Dunbar, N.W.; McIntosh, W.C.; Esser, R.P.; Nishiizumi, Kuni; Taylor, S.; Caffee, M.W.</p> <p>1998-07-01</p> <p>During systematic sampling of volcanic ash (tephra) layers at a well-known Antarctic <span class="hlt">meteorite</span> collection site (the Allan Hills main ice field), a band of unusually dark and rounded (many spheroidal) particles was discovered. This debris layer (BIT-58) extends parallel to the stratigraphy of the ice established from the tephra bands, apparently marking a single depositional event. The shapes, internal texture, major element composition, and levels of cosmogenic nuclides of particles from within BIT-58 all strongly suggest that this material represents ablation debris from the passage of a <span class="hlt">large</span> H-group ordinary chondrite. Preliminary cosmogenic isotope dating suggests an age of 2.8 Ma, implying that the East Antarctic ice sheet has been stable since that time. The relationship of the Bit-58 layer to known <span class="hlt">impact</span> events is not clear.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JPhCS.712a2097M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JPhCS.712a2097M"><span>Weathering and precipitation after <span class="hlt">meteorite</span> <span class="hlt">impact</span> of Ni, Cr, Fe, Ca and Mn in K-T boundary clays from Stevns Klint</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Miyano, Yumiko; Yoshiasa, Akira; Tobase, Tsubasa; Isobe, Hiroshi; Hongu, Hidetomo; Okube, Maki; Nakatsuka, Akihiko; Sugiyama, Kazumasa</p> <p>2016-05-01</p> <p>Ni, Cr, Fe, Ca and Mn K-edge XANES and EXAFS spectra were measured on K-T boundary clays from Stevns Klint in Denmark. According to XANES spectra and EXAFS analyses, the local structures of Ni, Cr and Fe in K-T boundary clays is similar to Ni(OH)2, Cr2O3 and FeOOH, respectively. It is assumed that the Ni, Cr and Fe elements in <span class="hlt">impact</span> related glasses is changing into stable hydrate and oxide by the weathering and diagenesis at the surface of the Earth. Ca in K-T boundary clays maintains the diopside-like structure. Local structure of Ca in K-T clays seems to keep information on the condition at <span class="hlt">meteorite</span> <span class="hlt">impact</span>. Mn has a local structure like MnCO3 with divalent state. It is assumed that the origin on low abundant of Mn in the Fe-group element in K-T clays was the consumption by life activity and the diffusion to other parts.</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><span class="hlt">Meteorite</span> Sterlitamak -- A New Crater 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>The Sterlitamak <span class="hlt">meteorite</span> fell on May 17, 1990 at 23h20m local time (17h20m GMT) and formed a crater in a field 20 km westward of the town of Sterlitamak (Petaev et al., 1991). Many witnesses in South Bashkiria saw a very bright fireball (up to -5 magnitude) moving from south to north at a ~45 degree angle to the horizon. Witnesses located ~2 km from the crater observed the fireball glowing right up to the time of <span class="hlt">impact</span>, after which several explosions were heard. The crater was found on May 19. From witnesses' reports, the fresh crater was 4.5-5 m in depth and had sheer walls ~3 m in height below which was a conical talus surface with a hole in the center. The crater itself was surrounded by a continuous rim 60-70 cm in thickness and by radial ejecta. Our field team arrived at the crater on May 23, six days after its formation. We found the crater in rather good condition except for partial collapse of the rim, material from which had filled in the crater up to ~3 m from the surface. The western wall of the crater was composed of well-preserved brown loam with shale- like parting dipping 25-30 degrees away from the crater center. A <span class="hlt">large</span> slip block of autogenic breccia was observed along the eastern crater wall. An allogenic breccia composed of a mixture of brown loam and black soil was traced to the depth of ~5 m from the surface. Outside the rim, the crater ejecta formed an asymmetric continuous blanket and distinct radial rays. The southern rays were shorter and thicker than the northern and eastern rays. About 2 dozen <span class="hlt">meteorite</span> fragments, from several grams to several hundred grams in weight, were recovered in the crater vicinity. A search for other <span class="hlt">meteorite</span> fragments or individuals at distances up to 1 km southward from the crater was unsuccessful. Two partly encrusted fragments (3 and 6 kg) with clear Widmanstatten pattern on a broken surface were found at a depth of ~8 m during crater excavation. In May of 1991 a 315-kg partly fragmented individual was</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040056006&hterms=main+belt+location&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dmain%2Bbelt%2Blocation','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040056006&hterms=main+belt+location&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dmain%2Bbelt%2Blocation"><span>Tracing <span class="hlt">Meteorites</span> to Their Sources Through Asteroid Spectroscopy</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Binzel, R. P.</p> <p>2004-01-01</p> <p>The goal of tracing <span class="hlt">meteorites</span> to their main-belt sources is seemingly impossible given the inherent uncertainties in relating astronomical remote sensing measurements of asteroids to laboratory measurements of <span class="hlt">meteorites</span>. What's more, the chaotic routes for delivery of <span class="hlt">meteorites</span> would seem to be sufficient to mask any trace of their points of origin. Yet reasonably compelling links can be made for the origin for two <span class="hlt">meteorite</span> types: highly reduced enstatite achondrites (aubrites) appear to have a source from the inner most edge of the main-belt known as the Hungaria region; reduced basaltic achondrite howardite-eucrite-diogenite (HED) <span class="hlt">meteorites</span> are plausibly derived from the <span class="hlt">large</span> asteroid 4 Vesta. Beyond these specific examples, we seek to find additional evidence to more thoroughly pinpoint original locations for the much wider range of <span class="hlt">meteorite</span> types and the oxidation environments they sample. A discussion on Near Earth asteroids along with CCD visible and near-infrared spectra observations are presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040088818&hterms=Ferrous&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DFerrous','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040088818&hterms=Ferrous&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DFerrous"><span>An abiotic origin for hydrocarbons in the Allan Hills 84001 martian <span class="hlt">meteorite</span> through cooling of magmatic and <span class="hlt">impact</span>-generated gases</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Shock, E. L.</p> <p>2000-01-01</p> <p>Thermodynamic calculations of metastable equilibria were used to evaluate the potential for abiotic synthesis of aliphatic and polycyclic aromatic hydrocarbons (PAHs) in the martian <span class="hlt">meteorite</span> Allan Hills (ALH) 84001. The calculations show that PAHs and normal alkanes could form metastably from CO, CO2, and H2 below approximately 250-300 degrees C during rapid cooling of trapped magmatic or <span class="hlt">impact</span>-generated gases. Depending on temperature, bulk composition, and oxidation-reduction conditions, PAHs and normal alkanes can form simultaneously or separately. Moreover, PAHs can form at lower H/C ratios, higher CO/CO2 ratios, and higher temperatures than normal alkanes. Dry conditions with H/C ratios less than approximately 0.01-0.001 together with high CO/CO2 ratios also favor the formation of unalkylated PAHs. The observed abundance of PAHs, their low alkylation, and a variable but high aromatic to aliphatic ratio in ALH 84001 all correspond to low H/C and high CO/CO2 ratios in magmatic and <span class="hlt">impact</span> gases and can be used to deduce spatial variations of these ratios. Some hydrocarbons could have been formed from trapped magmatic gases, especially if the cooling was fast enough to prevent reequilibration. We propose that subsequent <span class="hlt">impact</span> heating(s) in ALH 84001 could have led to dissociation of ferrous carbonates to yield fine-grain magnetite, formation of a CO-rich local gas phase, reduction of water vapor to H2, reequilibration of the trapped magmatic gases, aromatization of hydrocarbons formed previously, and overprinting of the synthesis from magmatic gases, if any. Rapid cooling and high-temperature quenching of CO-, H2-rich <span class="hlt">impact</span> gases could have led to magnetite-catalyzed hydrocarbon synthesis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/11543519','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/11543519"><span>An abiotic origin for hydrocarbons in the Allan Hills 84001 martian <span class="hlt">meteorite</span> through cooling of magmatic and <span class="hlt">impact</span>-generated gases.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zolotov MYu; Shock, E L</p> <p>2000-05-01</p> <p>Thermodynamic calculations of metastable equilibria were used to evaluate the potential for abiotic synthesis of aliphatic and polycyclic aromatic hydrocarbons (PAHs) in the martian <span class="hlt">meteorite</span> Allan Hills (ALH) 84001. The calculations show that PAHs and normal alkanes could form metastably from CO, CO2, and H2 below approximately 250-300 degrees C during rapid cooling of trapped magmatic or <span class="hlt">impact</span>-generated gases. Depending on temperature, bulk composition, and oxidation-reduction conditions, PAHs and normal alkanes can form simultaneously or separately. Moreover, PAHs can form at lower H/C ratios, higher CO/CO2 ratios, and higher temperatures than normal alkanes. Dry conditions with H/C ratios less than approximately 0.01-0.001 together with high CO/CO2 ratios also favor the formation of unalkylated PAHs. The observed abundance of PAHs, their low alkylation, and a variable but high aromatic to aliphatic ratio in ALH 84001 all correspond to low H/C and high CO/CO2 ratios in magmatic and <span class="hlt">impact</span> gases and can be used to deduce spatial variations of these ratios. Some hydrocarbons could have been formed from trapped magmatic gases, especially if the cooling was fast enough to prevent reequilibration. We propose that subsequent <span class="hlt">impact</span> heating(s) in ALH 84001 could have led to dissociation of ferrous carbonates to yield fine-grain magnetite, formation of a CO-rich local gas phase, reduction of water vapor to H2, reequilibration of the trapped magmatic gases, aromatization of hydrocarbons formed previously, and overprinting of the synthesis from magmatic gases, if any. Rapid cooling and high-temperature quenching of CO-, H2-rich <span class="hlt">impact</span> gases could have led to magnetite-catalyzed hydrocarbon synthesis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040088818&hterms=prevent+volcanic+eruption&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dprevent%2Bvolcanic%2Beruption','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040088818&hterms=prevent+volcanic+eruption&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dprevent%2Bvolcanic%2Beruption"><span>An abiotic origin for hydrocarbons in the Allan Hills 84001 martian <span class="hlt">meteorite</span> through cooling of magmatic and <span class="hlt">impact</span>-generated gases</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Shock, E. L.</p> <p>2000-01-01</p> <p>Thermodynamic calculations of metastable equilibria were used to evaluate the potential for abiotic synthesis of aliphatic and polycyclic aromatic hydrocarbons (PAHs) in the martian <span class="hlt">meteorite</span> Allan Hills (ALH) 84001. The calculations show that PAHs and normal alkanes could form metastably from CO, CO2, and H2 below approximately 250-300 degrees C during rapid cooling of trapped magmatic or <span class="hlt">impact</span>-generated gases. Depending on temperature, bulk composition, and oxidation-reduction conditions, PAHs and normal alkanes can form simultaneously or separately. Moreover, PAHs can form at lower H/C ratios, higher CO/CO2 ratios, and higher temperatures than normal alkanes. Dry conditions with H/C ratios less than approximately 0.01-0.001 together with high CO/CO2 ratios also favor the formation of unalkylated PAHs. The observed abundance of PAHs, their low alkylation, and a variable but high aromatic to aliphatic ratio in ALH 84001 all correspond to low H/C and high CO/CO2 ratios in magmatic and <span class="hlt">impact</span> gases and can be used to deduce spatial variations of these ratios. Some hydrocarbons could have been formed from trapped magmatic gases, especially if the cooling was fast enough to prevent reequilibration. We propose that subsequent <span class="hlt">impact</span> heating(s) in ALH 84001 could have led to dissociation of ferrous carbonates to yield fine-grain magnetite, formation of a CO-rich local gas phase, reduction of water vapor to H2, reequilibration of the trapped magmatic gases, aromatization of hydrocarbons formed previously, and overprinting of the synthesis from magmatic gases, if any. Rapid cooling and high-temperature quenching of CO-, H2-rich <span class="hlt">impact</span> gases could have led to magnetite-catalyzed hydrocarbon synthesis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19820024357&hterms=Allan&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DAllan','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19820024357&hterms=Allan&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DAllan"><span>The Allan Hills icefield and its relationship to <span class="hlt">meteorite</span> concentration</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Annexstad, J. O.</p> <p>1982-01-01</p> <p>The Allan Hills icefield is described by as a limited icefield that has <span class="hlt">large</span> concentrations of <span class="hlt">meteorites</span>. The <span class="hlt">meteorites</span> appear to be concentrated on the lower limb of an ice monocline with other finds scattered throughout the field. In an attempt to understand the mechanisms of <span class="hlt">meteorite</span> concentration, a triangulation chain was established across the icefield. This chain is composed of 20 stations, two of which are on bedrock, and extends westward from the Allan Hills a distance of 15 kilometers. The triangulation chain and its relationship to the <span class="hlt">meteorite</span> concentrations is shown.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004GeCoA..68.2379F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004GeCoA..68.2379F"><span>Extensive <span class="hlt">impact</span> melting on the H-chondrite parent asteroid during the cataclysmic bombardment of the early solar system: Evidence from the achondritic <span class="hlt">meteorite</span> Dar al Gani 896</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Folco, Luigi; Bland, Philip A.; D'Orazio, Massimo; Franchi, Ian A.; Kelley, Simon P.; Rocchi, Sergio</p> <p>2004-05-01</p> <p>DaG 896 is an olivine-rich microporphyritic rock of komatiitic composition. Both the olivine composition (Fa 17.5±2.1, [Mn/Mg] = 0.0061) and the bulk oxygen isotopic composition (δ 17O = +2.55, δ 18O = +3.50) indicate that DaG 896 is a sample of the H-chondrite parent body. The bulk chemistry shows an H-chondritic distribution of lithophile elements, whereas chalcophile and siderophile elements are strongly depleted, indicating formation through whole-rock melting (or nearly so) of H-chondrite material, nearly complete loss of the metal plus sulfide component, and crystallization without significant igneous fractionation. Superheated, severely shocked chondritic relics (˜10 vol%), typically in the form of corroded lithic fragments <100 μm in size intimately distributed within the igneous lithology, indicate that melting was triggered by a highly energetic <span class="hlt">impact</span>, which possibly induced shock pressures of ˜80-100 GPa. The relatively young 3.704 ± 0.035 Ga 40Ar- 39Ar crystallization age is consistent with the <span class="hlt">impact</span> melting origin, as magmatism in the asteroid belt was active only in the first hundred million years of solar system history. Based on textural data and thermodynamic crystallization modelling, we infer that DaG 896 crystallized from a liquidus temperature of ˜1630°C under relatively slow cooling rates (˜10°C h -1) to ˜1300°C, before quenching. The two-stage cooling history indicates that a reasonable formation environment might be a dike intruding cooler basement below a crater floor. Metal-silicate fractionation may have been accomplished, at least at the centimeter-scale of the studied <span class="hlt">meteorite</span> sample, through differential acceleration of immiscible liquids of different density during the intense flow regimes associated with the excavation and modification stages of the cratering mechanism. Alternatively, DaG 896 may represent a surface sample of a differentiated melt body at the floor of an <span class="hlt">impact</span> crater, as gravitational settling</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GeCoA.208..198G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GeCoA.208..198G"><span>Effective radium-226 concentration in <span class="hlt">meteorites</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Girault, Frédéric; Perrier, Frédéric; Moreira, Manuel; Zanda, Brigitte; Rochette, Pierre; Teitler, Yoram</p> <p>2017-07-01</p> <p>The analysis of noble gases in <span class="hlt">meteorites</span> provides constraints on the early solar system and the pre-solar nebula. This requires a better characterization and understanding of the capture, production, and release of noble gases in <span class="hlt">meteorites</span>. The knowledge of transfer properties of noble gases for each individual <span class="hlt">meteorite</span> could benefit from using radon-222, radioactive daughter of radium-226. The radon-222 emanating power is commonly quantified by the effective radium-226 concentration (ECRa), the product of the bulk radium-226 concentration and of the emanation coefficient E, which represents the probability of one decaying radium-226 to inject one radon-222 into the free porous network. Owing to a non-destructive, high-sensitivity accumulation method based on long photomultiplier counting sessions, we are now able to measure ECRa of <span class="hlt">meteorite</span> samples, which usually have mass smaller than 15 g and ECRa < 0.5 Bq kg-1. We report here the results obtained from 41 different <span class="hlt">meteorites</span>, based on 129 measurements on 70 samples using two variants of our method, showing satisfactory repeatability and a detection limit below 10-2 Bq kg-1 for a sample mass of 1 g. While two <span class="hlt">meteorites</span> remain below detection level, we obtain for 39 <span class="hlt">meteorites</span> heterogeneous ECRa values with mean (min-max range) of ca. 0.1 (0.018-1.30) Bq kg-1. Carbonaceous chondrites exhibit the largest ECRa values and eucrites the smallest. Such values are smaller than typical values from most terrestrial rocks, but comparable with those from Archean rocks (mean of ca. 0.18 Bq kg-1), an end-member of terrestrial rocks. Using uranium concentration from the literature, E is inferred from ECRa for all the <span class="hlt">meteorite</span> samples. Values of E for <span class="hlt">meteorites</span> (mean 40 ± 4%) are higher than E values for Archean rocks and reported values for lunar and Martian soils. Exceptionally <span class="hlt">large</span> E values likely suggest that the 238U-226Ra pair would not be at equilibrium in most <span class="hlt">meteorites</span> and that uranium and/or radium are most</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/scitech/biblio/5538614','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5538614"><span><span class="hlt">Impact</span> performance of <span class="hlt">large</span> scale electromagnetic launchers</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Fahrenthold, E.P. . Dept. of Mechanical Engineering)</p> <p>1991-01-01</p> <p>This paper reports on the development of high performance electromagnetic launchers and associated pulsed power supplies which has led to the aerodynamic and structural design of new projectile types. The <span class="hlt">impact</span> performance of monolithic railgun projectiles between one and four kilograms in mass has been estimated using Lagrangian hydrocode simulations at velocities up to three kilometers per second. The simulation predictions are within expected bounds, based on existing correlations of experimental measurements on cylindrical projectiles of equivalent mass.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016E%26PSL.437...57S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016E%26PSL.437...57S"><span>Siderophile elements in brecciated HED <span class="hlt">meteorites</span> and the nature of projectile materials in HED <span class="hlt">meteorites</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shirai, N.; Okamoto, C.; Yamaguchi, A.; Ebihara, M.</p> <p>2016-03-01</p> <p>Petrological, mineralogical and geochemical studies were performed on five brecciated HED <span class="hlt">meteorites</span> (ALH 76005, EET 92003, LEW 85300, LEW 87026 and GRO 95633) in order to elucidate the nature of impactors on the HED parent body. Some brecciated HED <span class="hlt">meteorites</span> contain exotic materials such as FeNi-metal grains with low Co/Ni ratios (ALH 76005, EET 92003 and GRO 95633) and carbonaceous chondrite clasts (LEW 85300) in a clastic and/or <span class="hlt">impact</span> melt matrix. Such exotic materials were incorporated during brecciation. Platinum group element (PGE) abundances vary significantly (CI × 0.002-0.05), but are higher than those of pristine rocks from the HED parent body. The PGE ratios for the five HED <span class="hlt">meteorites</span> are inconsistent with each other, implying that the impactor components of each HED <span class="hlt">meteorites</span> are different from each other. The various PGE ratios are consistent with those for metals from chondrites and iron <span class="hlt">meteorites</span>, and carbonaceous chondrites. This study provides the evidence that IAB and IVA iron <span class="hlt">meteorites</span>, and carbonaceous chondrites (CM, CO, CV, CK, CB and CR), ordinary chondrites (L and H) and enstatite chondrite (EL) are candidates of the impactor materials on the HED parent body. It is highly probable that significant amounts of siderophile elements were incorporated into the inner solar system objects like the HED parent body from both chondritic materials and differentiated materials like iron <span class="hlt">meteorites</span> during heavy bombardment. The HED <span class="hlt">meteorites</span> in this study and metals from mesosiderite have different Pd/Ir ratios, probably implying that HED <span class="hlt">meteorites</span> and mesosiderites formed either at distinct settings on one common parent body or on similar parent bodies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19860019348','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19860019348"><span>Radiocarbon datings of Yamato <span class="hlt">meteorites</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kigoshi, K.; Matsuda, E.</p> <p>1986-01-01</p> <p>The terrestrial ages of five Yamato <span class="hlt">Meteorites</span> were measured by the content of cosmic-ray-produced carbon-14. Three Yamato <span class="hlt">Meteorites</span> Y-74013, Y-74097, and Y-74136, which are all diogenites, were found at sites from one to two kilometers apart from each other. Evidence is presented for these three <span class="hlt">meteorites</span> being a single <span class="hlt">meteorite</span>. Also presented is a method adopted in the experimental procedure which includes a check for modern carbon contamination in the <span class="hlt">meteorites</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012M%26PS...47..927M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012M%26PS...47..927M"><span><span class="hlt">Meteorites</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>McCall, G. Joseph H.</p> <p>2012-05-01</p> <p>The article by Fairén et al. (2011) is very interesting to me, as not only have I published, albeit very cursorily, on the occurrence of <span class="hlt">meteorites</span> on Mars (McCall 2005, 2011, 2012; McCall et al. 2006), but I was the author (McCall 1965) of the description of the Mount Padbury mesosiderite cited by Schröder et al. (2010) in their description of the four stony <span class="hlt">meteorites</span> also found by the Opportunity rover. I have given my reasons elsewhere for thinking these are not mesosiderites (McCall 2012), but are likely differentiated stony <span class="hlt">meteorites</span> of a hitherto unknown type.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19720060466&hterms=chromium+spinel&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dchromium%2Bspinel','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19720060466&hterms=chromium+spinel&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dchromium%2Bspinel"><span>The mineralogy of <span class="hlt">meteorites</span>.</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mason, B.</p> <p>1972-01-01</p> <p>Of particular interest among minerals recently discovered in <span class="hlt">meteorites</span> are five phosphate minerals, three of them unknown in terrestrial rocks; a chromium nitride and a silicon oxynitride; lonsdaleite and chaoite, new polymorphs of carbon; ringwoodite and majorite, the spinel and garnet analogs of olivine and pyroxene, respectively; a number of calcium- and aluminum-rich silicates in the Allende <span class="hlt">meteorite</span>, a type III carbonaceous chondrite which fell in 1969; and several alkali-rich silicates found as inclusions in iron <span class="hlt">meteorites</span>. Knowledge of the compositional range of the common minerals olivine, pyroxene, and plagioclase has also been greatly increased by recent researches.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20080026035','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20080026035"><span>Asteroid-<span class="hlt">Meteorite</span> Links: The Vesta Conundrum(s)</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.; Binzel, R.; Bogard, D.; Hiroi, T.; Mittlefehldt, D. W.; Nyquist, L.; Rivkin, A.; Takeda, H.</p> <p>2006-01-01</p> <p>Although a direct link between the HED <span class="hlt">meteorites</span> and the asteroid 4 Vesta is generally acknowledged, several issues continue to be actively examined that tie Vesta to early processes in the solar system. Vesta is no longer the only basaltic asteroid in the Main belt. In addition to the Vestoids of the Vesta family, the small asteroid Magnya is basaltic but appears to be unrelated to Vesta. Similarly, diversity now identified in the collection of basaltic <span class="hlt">meteorites</span> requires more than one basaltic parent body, consistent with the abundance of differentiated parent bodies implied by iron <span class="hlt">meteorites</span>. The timing of the formation of the Vestoids (and presumably the <span class="hlt">large</span> crater at the south pole of Vesta) is unresolved. Peaks in Ar-Ar dates of eucrites suggest this <span class="hlt">impact</span> event could be related to a possible late heavy bombardment at least 3.5 Gyr ago. On the other hand, the optically fresh appearance of both Vesta and the Vestoids requires either a relatively recent resurfacing event or that their surfaces do not weather in the same manner thought to occur on other asteroids such as the ordinary chondrite parent body. Diversity across the surface of Vesta has been observed with HST and there are hints of compositional variations (possibly involving minor olivine) in near-infrared spectra.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6496223','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6496223"><span>Mass extinctions caused by <span class="hlt">large</span> bolide <span class="hlt">impacts</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Alvarez, L.W.</p> <p>1987-07-01</p> <p>Evidence indicates that the collision of Earth and a <span class="hlt">large</span> piece of Solar System derbris such as a meteoroid, asteroid or comet caused the great extinctions of 65 million years ago, leading to the transition from the age of the dinosaurs to the age of the mammals.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014Icar..237..116R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014Icar..237..116R"><span>Chelyabinsk <span class="hlt">meteorite</span> explains unusual spectral properties of Baptistina Asteroid Family</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Reddy, Vishnu; Sanchez, Juan A.; Bottke, William F.; Cloutis, Edward A.; Izawa, Matthew R. M.; O'Brien, David P.; Mann, Paul; Cuddy, Matthew; Le Corre, Lucille; Gaffey, Michael J.; Fujihara, Gary</p> <p>2014-07-01</p> <p> melts are rare in <span class="hlt">meteorites</span> is that high <span class="hlt">impact</span> velocities (V > 10 km/s) are needed to generate the necessary shock pressures and temperatures (e.g., Pierazzo, E., Melosh, H.J. [1998]. Hydrocode modeling of oblique <span class="hlt">impacts</span>: The fate of the projectile. In: Origin of the Earth and Moon, Proceedings of the Conference. LPI Contribution No. 957) unless the target material is highly porous. Nearly all asteroid <span class="hlt">impacts</span> within the main belt are at ∼5 km/s (Bottke, W.F., Nolan, M.C., Greenberg, R., Kolvoord, R.A. [1994]. Collisional lifetimes and <span class="hlt">impact</span> statistics of near-Earth asteroids. In: Tucson, Gehrels T. (Ed.), Hazards Due to Comets and Asteroids. The University of Arizona Press, Arizona, pp. 337-357), which prevents them from producing much <span class="hlt">impact</span> melt unless they are highly porous. However, shock darkening is an equally efficient process that takes place at much lower <span class="hlt">impact</span> velocities (∼2 km/s) and can cause the observed spectral effects. Spectral effects of shock darkening and <span class="hlt">impact</span> melt are identical. The parent asteroid of BAF was either a member of the Flora family or had the same basic composition as the Floras (LL Chondrite). The shock pressures produced during the <span class="hlt">impact</span> event generated enough <span class="hlt">impact</span> melt or shock blackening to alter the spectral properties of BAF, but keep the BAF composition <span class="hlt">largely</span> unchanged. Collisional mixing of shock blackened/<span class="hlt">impact</span> melt and LL5 chondritic material could have created the Baptistina Asteroid Family with composition identical to those of the Floras, but with subdued absorption bands. Shock darkening and <span class="hlt">impact</span> melt play an important role in altering the spectral and albedo properties of ordinary chondrites and our work confirms earlier work by Britt and Pieters (Britt, D.T., Pieters, C.M. [1994]. Geochimica et Cosmochimica Acta 58, 3905-3919).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20020051091','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20020051091"><span>A IAB-Complex Iron <span class="hlt">Meteorite</span> Containing Low-Ca Clinopyroxene: Northwest Africa 468 and its Relationship to Iodranites and Formation by <span class="hlt">Impact</span> Melting</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Rubin, Alan E.; Kallemeyn, Gregory W.; Wasson, John T.</p> <p>2002-01-01</p> <p>Northwest Africa 468 (NWA 468) is a new ungrouped, silicate-rich member of the IAB complex of nonmagmatic iron <span class="hlt">meteorites</span>. The silicates contain relatively coarse (approximately 300 micron-size) grains of low-Ca clinopyroxene with polysynthetic twinning and inclined extinction. Low-Ca clinopyroxene is indicative of quenching from high temperatures (either from protoenstatite in a few seconds or high-temperature clinoenstatite in a few hours). It seems likely that NWA 468 formed by <span class="hlt">impact</span> melting followed by rapid cooling to less than or equal to 660 C. After the loss of a metal-sulfide melt from the silicates, sulfide was reintroduced, either from <span class="hlt">impact</span>-mobilized FeS or as an S2 vapor that combined with metallic Fe to produce FeS. The O-isotopic composition (delta O-17 = -1.39 %) indicates that the precursor material of NWA 468 was a metal-rich (e.g., CR) carbonaceous chondrite. Lodranites are similar in bulk chemical and O-isotopic composition to the silicates in NWA 468; the MAC 88177 lodranite (which also contains low-Ca clinopyroxene) is close in bulk chemical composition. Both NWA 468 and MAC 88177 have relatively low abundances of REE (rare earth elements) and plagiophile elements. Siderophiles in the metal-rich areas of NWA 468 are similar to those in the MAC 88177 whole rock; both samples contain low Ir and relatively high Fe, Cu and Se. Most unweathered lodranites contain approximately 20 - 38 wt. % metallic Fe-Ni. These rocks may have formed in an analogous manner to NWA 468 (i.e., by <span class="hlt">impact</span> melting of metal-rich carbonaceous-chondrite precursors) but with less separation of metal-rich melts from silicates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014HyInt.224..143L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014HyInt.224..143L"><span>Minerals of a soil developed in the <span class="hlt">meteoritic</span> crater of Carancas, Peru, and evidences of phase changes on the <span class="hlt">impact</span> event</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Loayza, María L. Cerón; Cabrejos, Jorge A. Bravo</p> <p>2014-01-01</p> <p>We report studies about the phase transformations in the soil of the Carancas <span class="hlt">meteoritic</span> crater located in an inhabited area near the town of Carancas, in the Region of Puno, about 1,300 km southeast of Lima, Peru. The studies by energy dispersive X-ray fluorescence, X-ray diffractometry and transmission Mössbauer spectroscopy (at RT and 77 K) reveal that the sample consists mainly of quartz, albite and impactites such as coesite and stishovite (SiO2) that have experienced phase metamorphism or alterations, related to high pressures and temperatures, forming their corresponding polymorphs. The occurrence of these phases, with high content of SiO2, in the soil of the crater strengthens the hypothesis of its origin by metamorphism induced by <span class="hlt">impact</span>; we observed also a magnetic sextet on the Mössbauer pattern, assigned to the Fe3 + in hematite, and three paramagnetic doublets, two of them associated with structural Fe3 + and Fe2 + cations, respectively, in illite and/or montmorillonite, and a third one due to an unidentified Fe3 + site.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013HyInt.tmp..139L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013HyInt.tmp..139L"><span>Minerals of a soil developed in the <span class="hlt">meteoritic</span> crater of Carancas, Peru, and evidences of phase changes on the <span class="hlt">impact</span> event</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Loayza, María L. Cerón; Cabrejos, Jorge A. Bravo</p> <p>2013-04-01</p> <p>We report studies about the phase transformations in the soil of the Carancas <span class="hlt">meteoritic</span> crater located in an inhabited area near the town of Carancas, in the Region of Puno, about 1,300 km southeast of Lima, Peru. The studies by energy dispersive X-ray fluorescence, X-ray diffractometry and transmission Mössbauer spectroscopy (at RT and 77 K) reveal that the sample consists mainly of quartz, albite and impactites such as coesite and stishovite (SiO2) that have experienced phase metamorphism or alterations, related to high pressures and temperatures, forming their corresponding polymorphs. The occurrence of these phases, with high content of SiO2, in the soil of the crater strengthens the hypothesis of its origin by metamorphism induced by <span class="hlt">impact</span>; we observed also a magnetic sextet on the Mössbauer pattern, assigned to the Fe3 + in hematite, and three paramagnetic doublets, two of them associated with structural Fe3 + and Fe2 + cations, respectively, in illite and/or montmorillonite, and a third one due to an unidentified Fe3 + site.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70027161','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70027161"><span>Luminescence dating of the Wabar <span class="hlt">meteorite</span> craters, Saudi 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>Prescott, J.R.; Robertson, G.B.; Shoemaker, C.; Shoemaker, E.M.; Wynn, J.</p> <p>2004-01-01</p> <p>Luminescence dating has been used to find the age of <span class="hlt">meteorite</span> <span class="hlt">impact</span> craters at Wabar (Al Hadida) in Saudi Arabia. The luminescence characteristics of the shocked material were determined. Using a variety of luminescence dating techniques applied to impactite formed by the <span class="hlt">meteorite</span>, and to the underlying sand, the age is found to be 290 ± 38 years. A comparison is made with two possible historically recorded ages. An <span class="hlt">impact</span> as young as this has implications for the assessment of hazards from the <span class="hlt">impact</span> on Earth of small <span class="hlt">meteorites</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20020054184&hterms=Ice+Age&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DIce%2BAge','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20020054184&hterms=Ice+Age&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DIce%2BAge"><span>Concentrating Antarctic <span class="hlt">Meteorites</span> on Blue ice Fields: The Frontier Mountain <span class="hlt">Meteorite</span> Trap</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sandford, Scott A.; DeVincenzi, D. (Technical Monitor)</p> <p>2002-01-01</p> <p>The collection of <span class="hlt">meteorites</span> in Antarctica has greatly stimulated advancement in the field of <span class="hlt">meteoritics</span> by providing the community with significant numbers of rare and unique <span class="hlt">meteorites</span> types and by yielding <span class="hlt">large</span> numbers of <span class="hlt">meteorites</span> that sample older infall epochs (Grady et al., 1998). The majority of Antarctic <span class="hlt">meteorites</span> are found on blue ice fields, where they are thought to be concentrated by wind and glacial drift (cf. Cassidy et al., 1992). The basic "ice flow model" describes the concentration of <span class="hlt">meteorites</span> by the stagnation or slowing of ice as it moves against a barrier located in a zone with low snow accumulation. However, our limited knowledge of the details of the actual concentration mechanisms prevents establishing firm conclusions concerning the past <span class="hlt">meteorite</span> flux from the Antarctic record (Zolensky, 1998). The terrestrial ages of Antarctic <span class="hlt">meteorites</span> indicate that their concentration occurs on time scales of tens to hundreds of thousands of years (Nishiizumi et al., 1989). It is a challenge to measure a mechanism that operates so slowly, and since such time scales can span more than one glacial epoch one cannot assume that the snow accumulation rates, ice velocities and directions, etc. that are measured today are representative of those extant over the age of the trap. Testing the basic "ice flow model" therefore requires the careful measurement of <span class="hlt">meteorite</span> locations, glacialogical ice flow data, ice thicknesses, bedrock and surface topology, ice ablation and snow accumulation rates, and mass transport by wind over an extended period of time in a location where these quantities can be interpreted in the context of past glacialogical history.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19810047270&hterms=antimony&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dantimony','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19810047270&hterms=antimony&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dantimony"><span>Antimony in iron <span class="hlt">meteorites</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Willis, J.</p> <p>1981-01-01</p> <p>Sb concentrations determined by radiochemical neutron activation analysis in 60 iron <span class="hlt">meteorites</span> range from 0.2 ng/g to 36 microg/g. The <span class="hlt">meteorites</span> with the highest Sb concentrations are those of the nonmagmatic groups IAB and IIICD, while <span class="hlt">meteorites</span> with the lowest Sb concentrations are found in groups IVA and IVB. In all groups Sb is positively correlated with Ni; slopes on log Sb vs log Ni plots decrease with increasing Ni. This decrease may reflect an increasing tendency to avoid schreibersite during the analysis of high-Ni <span class="hlt">meteorites</span> because Sb partitions strongly into schreibersite. It is found that schreibersite from New Westville is enriched in Cr, Ni, Ge, As, Sb, and Au and depleted in Fe, Co, Ir; the Sb content in schreibersite is 540 times higher than the bulk metal value.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19870061224&hterms=mass+extinction+currently&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dmass%2Bextinction%2Bcurrently','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19870061224&hterms=mass+extinction+currently&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dmass%2Bextinction%2Bcurrently"><span>Mass extinction caused by <span class="hlt">large</span> bolide <span class="hlt">impacts</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Alvarez, Luis W.</p> <p>1987-01-01</p> <p>A history and development status assessment is presented for the hypothesis that the great extinction of living species 65 million years ago, at the boundary between the Tertiary and Cretaceous geological ages, was due to the collision of a meteoroid, asteroid, or comet with the earth. The initial, deeply suggestive indication of the extraterrestial origin of the extinction-initiating mechanism was the detection of an exceptionally high concentration of iridium at the stratigraphic position of the extinction. Detailed computer modeling of the atmospheric effect of such a bolide <span class="hlt">impact</span> has shown that the earth would have first grown intensely cold during a period of darkness due to particulate debris clouds in the upper atmosphere, followed by an enormous increase in global temperatures as the debris cleared, created by the persistence of greenhouse-effect gases; this heating would have been especially lethal to numerous forms of life.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19870061224&hterms=Extraterrestial+life&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DExtraterrestial%2Blife','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19870061224&hterms=Extraterrestial+life&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DExtraterrestial%2Blife"><span>Mass extinction caused by <span class="hlt">large</span> bolide <span class="hlt">impacts</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Alvarez, Luis W.</p> <p>1987-01-01</p> <p>A history and development status assessment is presented for the hypothesis that the great extinction of living species 65 million years ago, at the boundary between the Tertiary and Cretaceous geological ages, was due to the collision of a meteoroid, asteroid, or comet with the earth. The initial, deeply suggestive indication of the extraterrestial origin of the extinction-initiating mechanism was the detection of an exceptionally high concentration of iridium at the stratigraphic position of the extinction. Detailed computer modeling of the atmospheric effect of such a bolide <span class="hlt">impact</span> has shown that the earth would have first grown intensely cold during a period of darkness due to particulate debris clouds in the upper atmosphere, followed by an enormous increase in global temperatures as the debris cleared, created by the persistence of greenhouse-effect gases; this heating would have been especially lethal to numerous forms of life.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70035620','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70035620"><span><span class="hlt">Meteorites</span> at Meridiani Planum provide evidence for significant amounts of surface and near-surface water on early 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>Fairen, A.G.; Dohm, J.M.; Baker, V.R.; Thompson, S.D.; Mahaney, W.C.; Herkenhoff, K. E.; Rodriguez, J.A.P.; Davila, A.F.; Schulze-Makuch, D.; El Maarry, M.R.; Uceda, E.R.; Amils, R.; Miyamoto, H.; Kim, K.J.; Anderson, R.C.; McKay, C.P.</p> <p>2011-01-01</p> <p>Six <span class="hlt">large</span> iron <span class="hlt">meteorites</span> have been discovered in the Meridiani Planum region of Mars by the Mars Exploration Rover Opportunity in a nearly 25km-long traverse. Herein, we review and synthesize the available data to propose that the discovery and characteristics of the six <span class="hlt">meteorites</span> could be explained as the result of their <span class="hlt">impact</span> into a soft and wet surface, sometime during the Noachian or the Hesperian, subsequently to be exposed at the Martian surface through differential erosion. As recorded by its sediments and chemical deposits, Meridiani has been interpreted to have undergone a watery past, including a shallow sea, a playa, an environment of fluctuating ground water, and/or an icy landscape. <span class="hlt">Meteorites</span> could have been encased upon <span class="hlt">impact</span> and/or subsequently buried, and kept underground for a long time, shielded from the atmosphere. The <span class="hlt">meteorites</span> apparently underwent significant chemical weathering due to aqueous alteration, as indicated by cavernous features that suggest differential acidic corrosion removing less resistant material and softer inclusions. During the Amazonian, the almost complete disappearance of surface water and desiccation of the landscape, followed by induration of the sediments and subsequent differential erosion and degradation of Meridiani sediments, including at least 10-80m of deflation in the last 3-3.5Gy, would have exposed the buried <span class="hlt">meteorites</span>. We conclude that the iron <span class="hlt">meteorites</span> support the hypothesis that Mars once had a denser atmosphere and considerable amounts of water and/or water ice at and/or near the surface. ?? The <span class="hlt">Meteoritical</span> Society, 2011.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1991SSRv...56...13J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1991SSRv...56...13J"><span>Chronology of SNC <span class="hlt">meteorites</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jagoutz, E.</p> <p>1991-04-01</p> <p>A model is presented for the geochemical evolution of Mars which is constrained by the isotope systematics of Pb, Nd, and Sr determined for SCN <span class="hlt">meteorites</span>. The young magmatic crystallization ages of SCNs may indicate that these <span class="hlt">meteorites</span> do in fact stem from Mars. Internal ages of U-Pb and Pb-Pb systematics strongly suggest that they are the result of two magmatic processes. In addition, shock metamorphism is implied from observed petrographic shock features.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19870029377&hterms=chromium&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dchromium','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19870029377&hterms=chromium&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dchromium"><span>Chromium isotopic anomalies in the Allende <span class="hlt">meteorite</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Papanastassiou, D. A.</p> <p>1986-01-01</p> <p>Abundances of the chromium isotopes in terrestrial and bulk <span class="hlt">meteorite</span> samples are identical to 0.01 percent. However, Ca-Al-rich inclusions from the Allende <span class="hlt">meteorite</span> show endemic isotopic anomalies in chromium which require at least three nucleosynthetic components. <span class="hlt">Large</span> anomalies at Cr-54 in a special class of inclusions are correlated with <span class="hlt">large</span> anomalies at Ca-48 and Ti-50 and provide strong support for a component reflecting neutron-rich nucleosynthesis at nuclear statistical equilibrium. This correlation suggests that materials from very near the core of an exploding massive star may be injected into the interstellar medium.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19870029377&hterms=Chromium&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DChromium','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19870029377&hterms=Chromium&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DChromium"><span>Chromium isotopic anomalies in the Allende <span class="hlt">meteorite</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Papanastassiou, D. A.</p> <p>1986-01-01</p> <p>Abundances of the chromium isotopes in terrestrial and bulk <span class="hlt">meteorite</span> samples are identical to 0.01 percent. However, Ca-Al-rich inclusions from the Allende <span class="hlt">meteorite</span> show endemic isotopic anomalies in chromium which require at least three nucleosynthetic components. <span class="hlt">Large</span> anomalies at Cr-54 in a special class of inclusions are correlated with <span class="hlt">large</span> anomalies at Ca-48 and Ti-50 and provide strong support for a component reflecting neutron-rich nucleosynthesis at nuclear statistical equilibrium. This correlation suggests that materials from very near the core of an exploding massive star may be injected into the interstellar medium.</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('http://adsabs.harvard.edu/abs/2003mia..book.....C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003mia..book.....C"><span><span class="hlt">Meteorites</span>, Ice, and Antarctica</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.</p> <p>2003-08-01</p> <p>Bill Cassidy led <span class="hlt">meteorite</span> recovery expeditions in the Antarctic for fifteen years and his searches have resulted in the collection of thousands of <span class="hlt">meteorite</span> specimens from the ice. This personal account of his field experiences on the U.S. Antarctic Search for <span class="hlt">Meteorites</span> Project reveals the influence the work has had on our understanding of the moon, Mars and the asteroid belt. Cassidy describes the hardships and dangers of fieldwork in a hostile environment, as well as the appreciation he developed for its beauty. William Cassidy is Emeritus Professor of Geology and Planetary Science at the University of Pittsburgh. He initiated the U.S. Antarctic Search for <span class="hlt">Meteorites</span> (ANSMET) nroject and led <span class="hlt">meteorite</span> recovery expeditions in Antarctica in1976. His name is found attached to a mineral (cassidyite), on the map of Antarctica (Cassidy Glacier), and in the Catalog of Asteroids (3382 Cassidy). Profiled in "American Men of Science," and "Who's Who in America," he is also a recipient of The Antarctic Service Medal from the United States and has published widely in Science, <span class="hlt">Meteoritics</span> and Planetary Science, and The Journal of Geophysical Research.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21969535','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21969535"><span>Combining <span class="hlt">meteorites</span> and missions to explore Mars.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>McCoy, Timothy J; Corrigan, Catherine M; Herd, Christopher D K</p> <p>2011-11-29</p> <p>Laboratory studies of <span class="hlt">meteorites</span> and robotic exploration of Mars reveal scant atmosphere, no evidence of plate tectonics, past evidence for abundant water, and a protracted igneous evolution. Despite indirect hints, direct evidence of a martian origin came with the discovery of trapped atmospheric gases in one <span class="hlt">meteorite</span>. Since then, the study of martian <span class="hlt">meteorites</span> and findings from missions have been linked. Although the <span class="hlt">meteorite</span> source locations are unknown, <span class="hlt">impact</span> ejection modeling and spectral mapping of Mars suggest derivation from small craters in terrains of Amazonian to Hesperian age. Whereas most martian <span class="hlt">meteorites</span> are young (< 1.3 Ga), the spread of whole rock isotopic compositions results from crystallization of a magma ocean > 4.5 Ga and formation of enriched and depleted reservoirs. However, the history inferred from martian <span class="hlt">meteorites</span> conflicts with results from recent Mars missions, calling into doubt whether the igneous histor y inferred from the <span class="hlt">meteorites</span> is applicable to Mars as a whole. Allan Hills 84001 dates to 4.09 Ga and contains fluid-deposited carbonates. Accompanying debate about the mechanism and temperature of origin of the carbonates came several features suggestive of past microbial life in the carbonates. Although highly disputed, the suggestion spurred interest in habitable extreme environments on Earth and throughout the Solar System. A flotilla of subsequent spacecraft has redefined Mars from a volcanic planet to a hydrologically active planet that may have harbored life. Understanding the history and habitability of Mars depends on understanding the coupling of the atmosphere, surface, and subsurface. Sample return that brings back direct evidence from these diverse reservoirs is essential.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3228422','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3228422"><span>Combining <span class="hlt">meteorites</span> and missions to explore Mars</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>McCoy, Timothy J.; Corrigan, Catherine M.; Herd, Christopher D. K.</p> <p>2011-01-01</p> <p>Laboratory studies of <span class="hlt">meteorites</span> and robotic exploration of Mars reveal scant atmosphere, no evidence of plate tectonics, past evidence for abundant water, and a protracted igneous evolution. Despite indirect hints, direct evidence of a martian origin came with the discovery of trapped atmospheric gases in one <span class="hlt">meteorite</span>. Since then, the study of martian <span class="hlt">meteorites</span> and findings from missions have been linked. Although the <span class="hlt">meteorite</span> source locations are unknown, <span class="hlt">impact</span> ejection modeling and spectral mapping of Mars suggest derivation from small craters in terrains of Amazonian to Hesperian age. Whereas most martian <span class="hlt">meteorites</span> are young (< 1.3 Ga), the spread of whole rock isotopic compositions results from crystallization of a magma ocean > 4.5 Ga and formation of enriched and depleted reservoirs. However, the history inferred from martian <span class="hlt">meteorites</span> conflicts with results from recent Mars missions, calling into doubt whether the igneous histor y inferred from the <span class="hlt">meteorites</span> is applicable to Mars as a whole. Allan Hills 84001 dates to 4.09 Ga and contains fluid-deposited carbonates. Accompanying debate about the mechanism and temperature of origin of the carbonates came several features suggestive of past microbial life in the carbonates. Although highly disputed, the suggestion spurred interest in habitable extreme environments on Earth and throughout the Solar System. A flotilla of subsequent spacecraft has redefined Mars from a volcanic planet to a hydrologically active planet that may have harbored life. Understanding the history and habitability of Mars depends on understanding the coupling of the atmosphere, surface, and subsurface. Sample return that brings back direct evidence from these diverse reservoirs is essential. PMID:21969535</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017M%26PS...52.1014R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017M%26PS...52.1014R"><span>The <span class="hlt">Meteoritical</span> Bulletin, No. 103</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ruzicka, Alex; Grossman, Jeffrey; Bouvier, Audrey; Agee, Carl B.</p> <p>2017-05-01</p> <p><span class="hlt">Meteoritical</span> Bulletin 103 contains 2582 <span class="hlt">meteorites</span> including 10 falls (Ardón, Demsa, Jinju, Križevci, Kuresoi, Novato, Tinajdad, Tirhert, Vicência, Wolcott), with 2174 ordinary chondrites, 130 HED achondrites, 113 carbonaceous chondrites, 41 ureilites, 27 lunar <span class="hlt">meteorites</span>, 24 enstatite chondrites, 21 iron <span class="hlt">meteorites</span>, 15 primitive achondrites, 11 mesosiderites, 10 Martian <span class="hlt">meteorites</span>, 6 Rumuruti chondrites, 5 ungrouped achondrites, 2 enstatite achondrites, 1 relict <span class="hlt">meteorite</span>, 1 pallasite, and 1 angrite, and with 1511 from Antarctica, 588 from Africa, 361 from Asia, 86 from South America, 28 from North America, and 6 from Europe. Note: 1 <span class="hlt">meteorite</span> from Russia was counted as European. The complete contents of this bulletin (244 pages) are available on line. Information about approved <span class="hlt">meteorites</span> can be obtained from the <span class="hlt">Meteoritical</span> Bulletin Database (MBD) available on line at <url href="http://www.lpi.usra.edu/meteor/">http://www.lpi.usra.edu/meteor/.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19930000961','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19930000961"><span><span class="hlt">Large</span> <span class="hlt">impacts</span> in the Baltic shield with special attention to the Uppland structure</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Henkel, H.; Lilljequist, R.</p> <p>1992-01-01</p> <p>Within the Baltic Shield several very <span class="hlt">large</span> structures have been identified and are suspected to be of <span class="hlt">meteorite</span> <span class="hlt">impact</span> origin. Some of these deeply eroded circular features are presented with special attention to the Uppland structure, where several indications point toward an <span class="hlt">impact</span> origin in the mid-Proterozoic. The structures exceed 100 km in diameter and the topographic expression is inferior or absent. An arcuate arrangement of lithologies occurs around the margin of the structures and the central regions show conform magnetic and positive gravity anomalies. The Uppland structure is approximately 320 km in diameter as expressed by morphological, geological, and geophysical concentric patterns. The central part is topographically remarkably flat and is characterized by an unusual irregular fracture pattern. A subcircular central tonalite with density of 2.81 Mg(sup -3) gives a positive gravity anomaly of 35 mgal and the gravimetric profile is very similar to that of Manicouagan and Vredefort. The tonalite constitutes a huge antiform, 80 km in diameter, probably representing a 12-km structural uplift of infracrustal rocks. The flancs of the tonalite are characterized by recrystallized pseudotachylitic breccia dykes and breccia zones. Around the central parts amphibolite-grade metamorphic rocks appear as <span class="hlt">large</span> fragments within a fine-grained granite interpreted as a thermally annealed melt rock. Several occurrences of breccia dykes and breccia-bearing melts have been identified about 100 km from the gravimetric center of the structure. <span class="hlt">Impact</span>-related ore deposits are located around the margin of the structure and are interpreted as preexisting downfaulted iron formations, and deposits formed from remobilization of these preimpact occurrences. The so-called ball ores are interpreted to have formed by fluid injection similar to the formation of breccia dykes. The extensive hydrothermal alteration along the outer margin of the structure have created extreme soda</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016LPICo1921.6063G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016LPICo1921.6063G"><span>The Vredefort Pseudotachylytes: A Centennial Reappraisal of S. J. Shand (1916). Shaken, not Stirred by <span class="hlt">Meteorite</span> <span class="hlt">Impacting</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Garde, A. A.; Klausen, M. B.</p> <p>2016-08-01</p> <p>The famous pseudotachylytes in theVredefort Dome were formed by <span class="hlt">impact</span>-induced seismic shaking, a common but overlooked deformation process in terrestrial cratering. Seismic shaking is a fundamental geophysical process and well-known from the moon.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20170000498','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20170000498"><span>Asteroid 2008 TC3 Breakup and <span class="hlt">Meteorite</span> Fractions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Goodrich, C.; Jenniskens, P.; Shaddad, M. H.; Zolensky, M. E.; Fioretti, A. M.</p> <p>2017-01-01</p> <p>The recovery of <span class="hlt">meteorites</span> from the <span class="hlt">impact</span> of asteroid 2008 TC3 in the Nubian Desert of Sudan on October 7, 2008, marked the first time <span class="hlt">meteorites</span> were collected from an asteroid observed in space by astronomical techniques before <span class="hlt">impacting</span>. Search teams from the University of Khartoum traced the location of the strewn field and collected about 660 <span class="hlt">meteorites</span> in four expeditions to the fall region, all of which have known fall coordinates. Upon further study, the Almahata Sitta <span class="hlt">meteorites</span> proved to be a mixed bag of mostly ureilites (course grained, fine grained, and sulfide-metal assemblages), enstatite chondrites (EL3-6, EH3, EH5, breccias) and ordinary chondrites (H5-6, L4-5). One bencubbinite-like carbonaceous chondrite was identified, as well as one unique Rumuruti-like chondrite and an Enstatite achondrite. New analysis: The analysed <span class="hlt">meteorites</span> so far suggest a high 30-40 percent fraction of non-ureilites among the recovered samples, but that high fraction does not appear to be in agreement with the <span class="hlt">meteorites</span> in the University of Khartoum (UoK) collection. Ureilites dominate the <span class="hlt">meteorites</span> that were recovered by the Sudanese teams. To better understand the fraction of recovered materials that fell to Earth, a program has been initiated to type the <span class="hlt">meteorites</span> in the UoK collection in defined search areas. At this meeting, we will present some preliminary results from that investigation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004psrd.reptE..87M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004psrd.reptE..87M"><span><span class="hlt">Meteorite</span> Shower in Park Forest, Illinois</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Martel, L. M. V.</p> <p>2004-08-01</p> <p>Steven Simon (University of Chicago) and seven colleagues from the University of Chicago, the Planetary Studies Foundation, Harper College, Pacific Northwest National Lab, and the Field Museum in Chicago have classified the <span class="hlt">meteorite</span> fragments that fell on Chicago's southern suburbs on the night of March 26, 2003. Described as ".. the most densely populated region to be hit by a <span class="hlt">meteorite</span> shower in modern times," the village of Park Forest is at the center of the strewnfield and fortuitously also happens to be home to the Simon family, who answered scores of phone calls from neighboring <span class="hlt">meteorite</span> finders. No injuries were reported though plenty of roofs, windows, walls, and cars were hit, and the police department took individual fusion-crusted fragments into custody as evidence. Its chemical and mineralogical compositions establish the Park Forest <span class="hlt">meteorite</span> as an L5 chondrite, one of the most primitive groups of known <span class="hlt">meteorites</span>. It is a strongly shocked monomict breccia (a term applied to a breccia made of one kind of rock) with light-colored clasts in a very dark matrix. The team measured cosmic radionuclides in Park Forest and found nearly zero cobalt-56 and high cobalt-60, values that indicate a <span class="hlt">large</span> preatmospheric mass. They estimate the meteoroid was at least 900 kilograms and possibly as <span class="hlt">large</span> as 7000 kilograms before it broke apart in the atmosphere, of which only about 30 kilograms of fragments have been recovered.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1994Metic..29..757M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1994Metic..29..757M"><span>What we have learned about Mars from SNC <span class="hlt">meteorites</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>McSween, Harry Y., Jr.</p> <p>1994-11-01</p> <p> lithosphere, but it is in isotopic equilibrium with the atmosphere and has been since 1.3 Ga. The isotopically heavy atmosphere/hydrosphere composition deduced from these rocks reflects a loss process more severe than current atmospheric evolution models, and the occurence of carbonates in SNC <span class="hlt">meteorites</span> suggest that they, rather than scapolite or hydrous carbonates, are the major crustal sink for CO2. Weathering products in SNC <span class="hlt">meteorites</span> support the idea of limited alteration of the lithosphere by small volumes of saline, CO2-bearing water. Atmospheric composition and evolution are further constrained by noble gases in these <span class="hlt">meteorites</span>, although Xe and Kr isotopes suggest different origins for the atmosphere. Planetary ejection of these rocks has promoted an advance in the understanding of <span class="hlt">impact</span> physics, which has been accomplished by a model involving spallation during <span class="hlt">large</span> cratering events. Ejection of all the SNC <span class="hlt">meteorites</span> (except ALH84001) in one or two events may provide a plausible solution to most constraints imposed by chronology, geochemistry, and cosmic ray exposure, although problems remain with this scenario; ALH84001 may represent older martian crust sampled during a separate <span class="hlt">impact</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950035631&hterms=hydrosphere&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dhydrosphere','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950035631&hterms=hydrosphere&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dhydrosphere"><span>What we have learned about Mars from SNC <span class="hlt">meteorites</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mcsween, Harry Y., Jr.</p> <p>1994-01-01</p> <p> lithosphere, but it is in isotopic equilibrium with the atmosphere and has been since 1.3 Ga. The isotopically heavy atmosphere/hydrosphere composition deduced from these rocks reflects a loss process more severe than current atmospheric evolution models, and the occurence of carbonates in SNC <span class="hlt">meteorites</span> suggest that they, rather than scapolite or hydrous carbonates, are the major crustal sink for CO2. Weathering products in SNC <span class="hlt">meteorites</span> support the idea of limited alteration of the lithosphere by small volumes of saline, CO2-bearing water. Atmospheric composition and evolution are further constrained by noble gases in these <span class="hlt">meteorites</span>, although Xe and Kr isotopes suggest different origins for the atmosphere. Planetary ejection of these rocks has promoted an advance in the understanding of <span class="hlt">impact</span> physics, which has been accomplished by a model involving spallation during <span class="hlt">large</span> cratering events. Ejection of all the SNC <span class="hlt">meteorites</span> (except ALH84001) in one or two events may provide a plausible solution to most constraints imposed by chronology, geochemistry, and cosmic ray exposure, although problems remain with this scenario; ALH84001 may represent older martian crust sampled during a separate <span class="hlt">impact</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950035631&hterms=overlap+differentiation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Doverlap%2Bdifferentiation','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950035631&hterms=overlap+differentiation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Doverlap%2Bdifferentiation"><span>What we have learned about Mars from SNC <span class="hlt">meteorites</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mcsween, Harry Y., Jr.</p> <p>1994-01-01</p> <p> lithosphere, but it is in isotopic equilibrium with the atmosphere and has been since 1.3 Ga. The isotopically heavy atmosphere/hydrosphere composition deduced from these rocks reflects a loss process more severe than current atmospheric evolution models, and the occurence of carbonates in SNC <span class="hlt">meteorites</span> suggest that they, rather than scapolite or hydrous carbonates, are the major crustal sink for CO2. Weathering products in SNC <span class="hlt">meteorites</span> support the idea of limited alteration of the lithosphere by small volumes of saline, CO2-bearing water. Atmospheric composition and evolution are further constrained by noble gases in these <span class="hlt">meteorites</span>, although Xe and Kr isotopes suggest different origins for the atmosphere. Planetary ejection of these rocks has promoted an advance in the understanding of <span class="hlt">impact</span> physics, which has been accomplished by a model involving spallation during <span class="hlt">large</span> cratering events. Ejection of all the SNC <span class="hlt">meteorites</span> (except ALH84001) in one or two events may provide a plausible solution to most constraints imposed by chronology, geochemistry, and cosmic ray exposure, although problems remain with this scenario; ALH84001 may represent older martian crust sampled during a separate <span class="hlt">impact</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015IAUGA..2253637M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015IAUGA..2253637M"><span>Organic Molecules in <span class="hlt">Meteorites</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Martins, Zita</p> <p>2015-08-01</p> <p>Carbonaceous <span class="hlt">meteorites</span> are primitive samples from the asteroid belt, containing 3-5wt% organic carbon. The exogenous delivery of organic matter by carbonaceous <span class="hlt">meteorites</span> may have contributed to the organic inventory of the early Earth. The majority (>70%) of the <span class="hlt">meteoritic</span> organic material consist of insoluble organic matter (IOM) [1]. The remaining <span class="hlt">meteoritic</span> organic material (<30%) consists of a rich organic inventory of soluble organic compounds, including key compounds important in terrestrial biochemistry [2-4]. Different carbonaceous <span class="hlt">meteorites</span> contain soluble organic molecules with different abundances and distributions, which may reflect the extension of aqueous alteration or thermal metamorphism on the <span class="hlt">meteorite</span> parent bodies. Extensive aqueous alteration on the <span class="hlt">meteorite</span> parent body may result on 1) the decomposition of α-amino acids [5, 6]; 2) synthesis of β- and γ-amino acids [2, 6-9]; 3) higher relative abundances of alkylated polycyclic aromatic hydrocarbons (PAHs) [6, 10]; and 4) higher L-enantiomer excess (Lee) value of isovaline [6, 11, 12].The soluble organic content of carbonaceous <span class="hlt">meteorites</span> may also have a contribution from Fischer-Tropsch/Haber-Bosch type gas-grain reactions after the <span class="hlt">meteorite</span> parent body cooled to lower temperatures [13, 14].The analysis of the abundances and distribution of the organic molecules present in <span class="hlt">meteorites</span> helps to determine the physical and chemical conditions of the early solar system, and the prebiotic organic compounds available on the early Earth.[1] Cody and Alexander (2005) GCA 69, 1085. [2] Cronin and Chang (1993) in: The Chemistry of Life’s Origin. pp. 209-258. [3] Martins and Sephton (2009) in: Amino acids, peptides and proteins in organic chemistry. pp. 1-42. [4] Martins (2011) Elements 7, 35. [5] Botta et al. (2007) MAPS 42, 81. [6] Martins et al. (2015) MAPS, in press. [7] Cooper and Cronin (1995) GCA 59, 1003. [8] Glavin et al. (2006) MAPS. 41, 889. [9] Glavin et al. (2011) MAPS 45, 1948. [10</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010M%26PS...45.1340P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010M%26PS...45.1340P"><span>The preservation of fossil biomarkers during <span class="hlt">meteorite</span> <span class="hlt">impact</span> events: Experimental evidence from biomarker-rich projectiles and target rocks</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Parnell, John; Bowden, Stephen; Lindgren, Paula; Burchell, Mark; Milner, Daniel; Price, Mark; Baldwin, Emily C.; Crawford, Ian A.</p> <p>2010-08-01</p> <p>A Devonian siltstone from Orkney, Scotland, shows survival of biomarkers in high-velocity <span class="hlt">impact</span> experiments. The biomarkers were detected in ejecta fragments from experiments involving normal incidence of steel projectiles at 5-6kms-1, and in projectile fragments from <span class="hlt">impact</span> experiments into sand and water at 2-5kms-1. The associated peak shock pressures were calculated to be in the range of 110-147GPa for <span class="hlt">impacts</span> of the steel projectiles into the siltstone target, and hydrocode simulations are used to show the variation of peak pressure with depth in the target and throughout the finite volume projectiles. Thermally sensitive biomarker ratios, including ratios of hopanoids and steranes, and the methylphenanthrene ratio, showed an increase in thermal maturity in the ejecta, and especially the projectile, fragments. Measurement of absolute concentrations of selected biomarkers indicates that changes in biomarker ratios reflect synthesis of new material rather than selective destruction. Their presence in ejecta and projectile fragments suggests that fossil biomarkers may survive hypervelocity <span class="hlt">impacts</span>, and that experiments using biomarker-rich rock have high potential for testing survival of organic matter in a range of <span class="hlt">impact</span> scenarios.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017P%26SS..142...48W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017P%26SS..142...48W"><span><span class="hlt">Meteorites</span> from Phobos and Deimos at Earth?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wiegert, P.; Galiazzo, M. A.</p> <p>2017-08-01</p> <p>We examine the conditions under which material from the martian moons Phobos and Deimos could reach our planet in the form of <span class="hlt">meteorites</span>. We find that the necessary ejection speeds from these moons (900 and 600 m/s for Phobos and Deimos respectively) are much smaller than from Mars' surface (5000 m/s). These speeds are below typical <span class="hlt">impact</span> speeds for asteroids and comets (10-40 km/s) at Mars' orbit, and we conclude that delivery of <span class="hlt">meteorites</span> from Phobos and Deimos to the Earth can occur.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4757754','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4757754"><span>A potential hidden layer of <span class="hlt">meteorites</span> below the ice surface of Antarctica</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Evatt, G. W.; Coughlan, M. J.; Joy, K. H.; Smedley, A. R. D.; Connolly, P. J.; Abrahams, I. D.</p> <p>2016-01-01</p> <p>Antarctica contains some of the most productive regions on Earth for collecting <span class="hlt">meteorites</span>. These small areas of glacial ice are known as <span class="hlt">meteorite</span> stranding zones, where upward-flowing ice combines with high ablation rates to concentrate <span class="hlt">large</span> numbers of englacially transported <span class="hlt">meteorites</span> onto their surface. However, <span class="hlt">meteorite</span> collection data shows that iron and stony-iron <span class="hlt">meteorites</span> are significantly under-represented from these regions as compared with all other sites on Earth. Here we explain how this discrepancy may be due to englacial solar warming, whereby <span class="hlt">meteorites</span> a few tens of centimetres below the ice surface can be warmed up enough to cause melting of their surrounding ice and sink downwards. We show that <span class="hlt">meteorites</span> with a high-enough thermal conductivity (for example, iron <span class="hlt">meteorites</span>) can sink at a rate sufficient to offset the total annual upward ice transport, which may therefore permanently trap them below the ice surface and explain their absence from collection data. PMID:26882053</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NatCo...710679E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatCo...710679E"><span>A potential hidden layer of <span class="hlt">meteorites</span> below the ice surface of Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Evatt, G. W.; Coughlan, M. J.; Joy, K. H.; Smedley, A. R. D.; Connolly, P. J.; Abrahams, I. D.</p> <p>2016-02-01</p> <p>Antarctica contains some of the most productive regions on Earth for collecting <span class="hlt">meteorites</span>. These small areas of glacial ice are known as <span class="hlt">meteorite</span> stranding zones, where upward-flowing ice combines with high ablation rates to concentrate <span class="hlt">large</span> numbers of englacially transported <span class="hlt">meteorites</span> onto their surface. However, <span class="hlt">meteorite</span> collection data shows that iron and stony-iron <span class="hlt">meteorites</span> are significantly under-represented from these regions as compared with all other sites on Earth. Here we explain how this discrepancy may be due to englacial solar warming, whereby <span class="hlt">meteorites</span> a few tens of centimetres below the ice surface can be warmed up enough to cause melting of their surrounding ice and sink downwards. We show that <span class="hlt">meteorites</span> with a high-enough thermal conductivity (for example, iron <span class="hlt">meteorites</span>) can sink at a rate sufficient to offset the total annual upward ice transport, which may therefore permanently trap them below the ice surface and explain their absence from collection data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26882053','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26882053"><span>A potential hidden layer of <span class="hlt">meteorites</span> below the ice surface of Antarctica.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Evatt, G W; Coughlan, M J; Joy, K H; Smedley, A R D; Connolly, P J; Abrahams, I D</p> <p>2016-02-16</p> <p>Antarctica contains some of the most productive regions on Earth for collecting <span class="hlt">meteorites</span>. These small areas of glacial ice are known as <span class="hlt">meteorite</span> stranding zones, where upward-flowing ice combines with high ablation rates to concentrate <span class="hlt">large</span> numbers of englacially transported <span class="hlt">meteorites</span> onto their surface. However, <span class="hlt">meteorite</span> collection data shows that iron and stony-iron <span class="hlt">meteorites</span> are significantly under-represented from these regions as compared with all other sites on Earth. Here we explain how this discrepancy may be due to englacial solar warming, whereby <span class="hlt">meteorites</span> a few tens of centimetres below the ice surface can be warmed up enough to cause melting of their surrounding ice and sink downwards. We show that <span class="hlt">meteorites</span> with a high-enough thermal conductivity (for example, iron <span class="hlt">meteorites</span>) can sink at a rate sufficient to offset the total annual upward ice transport, which may therefore permanently trap them below the ice surface and explain their absence from collection data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21138163','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21138163"><span><span class="hlt">Meteorites</span>: messengers from the early solar system.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hofmann, Beda A</p> <p>2010-01-01</p> <p><span class="hlt">Meteorites</span> are fragments from solar system bodies, dominantly asteroids. A small fraction is derived from the Moon and from Mars. These rocks tell a rich history of the early solar system and range from solids little changed since the earliest phases of solid matter condensation in the solar nebula (chondrites) to material representing asteroidal metamorphism and melting, <span class="hlt">impact</span> processes on the Moon and even aqueous alteration near the surface of Mars. <span class="hlt">Meteorites</span> are very rare. Currently many <span class="hlt">meteorites</span> result from searches in Antarctica and the hot deserts of North Africa and Arabia. The present high find rate likely represents a unique short-term event, asking for a careful management of this scarce scientific resource.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016LPICo1921.6028B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016LPICo1921.6028B"><span>Discovery of Possible <span class="hlt">Meteoritic</span> Matter on Shatter Cones — 2. Clearwater East <span class="hlt">Impact</span> Structure, Québec, Canada</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Buchner, E.; Schmieder, M.</p> <p>2016-08-01</p> <p>In the frame of the “Shatter Cone Coatings Project,” we investigated shatter cones from the Clearwater East <span class="hlt">impact</span> structure that contain several Fe-Ni-Co metal and metal oxide particles (kamacite and taenite) and a sulfide particle (troilite?).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011JCos...13.3743H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011JCos...13.3743H"><span><span class="hlt">Meteoritics</span> and cosmology among the Aboriginal cultures of Central Australia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hamacher, Duane W.</p> <p>2011-03-01</p> <p>The night sky played an important role in the social structure, oral traditions, and cosmology of the Arrernte and Luritja Aboriginal cultures of Central Australia. A component of this cosmology relates to meteors, <span class="hlt">meteorites</span>, and <span class="hlt">impact</span> craters. This paper discusses the role of <span class="hlt">meteoritic</span> phenomena in Arrernte and Luritja cosmology, showing not only that these groups incorporated this phenomenon in their cultural traditions, but that their oral traditions regarding the relationship between meteors, <span class="hlt">meteorites</span> and <span class="hlt">impact</span> structures suggests the Arrernte and Luritja understood that they are directly related.</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('http://adsabs.harvard.edu/abs/2007M%26PS...42.1763H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007M%26PS...42.1763H"><span>Mineralogy, petrology, and shock history of lunar <span class="hlt">meteorite</span> Sayh al Uhaymir 300: A crystalline <span class="hlt">impact</span>-melt breccia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hudgins, J. A.; Walton, E. L.; Spray, J. G.</p> <p></p> <p>Sayh al Uhaymir (SaU) 300 comprises a microcrystalline igneous matrix (grain size <10 μm), dominated by plagioclase, pyroxene, and olivine. Pyroxene geothermometry indicates that the matrix crystallized at ˜1100 °C. The matrix encloses mineral and lithic clasts that record the effects of variable levels of shock. Mineral clasts include plagioclase, low- and high-Ca pyroxene, pigeonite, and olivine. Minor amounts of ilmenite, FeNi metal, chromite, and a silica phase are also present. A variety of lithic clast types are observed, including glassy <span class="hlt">impact</span> melts, <span class="hlt">impact</span>-melt breccias, and metamorphosed <span class="hlt">impact</span> melts. One clast of granulitic breccia was also noted. A lunar origin for SaU 300 is supported by the composition of the plagioclase (average An95), the high Cr content in olivine, the lack of hydrous phases, and the Fe/Mn ratio of mafic minerals. Both matrix and clasts have been locally overprinted by shock veins and melt pockets. SaU 300 has previously been described as an anorthositic regolith breccia with basaltic components and a granulitic matrix, but we here interpret it to be a polymict crystalline <span class="hlt">impact</span>-melt breccia with an olivine-rich anorthositic norite bulk composition. The varying shock states of the mineral and lithic clasts suggest that they were shocked to between 5-28 GPa (shock stages S1-S2) by <span class="hlt">impact</span> events in target rocks prior to their inclusion in the matrix. Formation of the igneous matrix requires a minimum shock pressure of 60 GPa (shock stage >S4). The association of maskelynite with melt pockets and shock veins indicates a subsequent, local 28-45 GPa (shock stage S2-S3) excursion, which was probably responsible for lofting the sample from the lunar surface. Subsequent fracturing is attributed to atmospheric entry and probable breakup of the parent meteor.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013M%26PS...48..270B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013M%26PS...48..270B"><span><span class="hlt">Meteorites</span> from meteor showers: A case study of the Taurids</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brown, Peter; Marchenko, Valerie; Moser, Danielle E.; Weryk, Robert; Cooke, William</p> <p>2013-02-01</p> <p>We propose that the Taurid meteor shower may contain bodies able to survive and be recovered as <span class="hlt">meteorites</span>. We review the expected properties of <span class="hlt">meteorite</span>-producing fireballs, and suggest that end heights below 35 km and terminal speeds below 10 km s-1 are necessary conditions for fireballs expected to produce <span class="hlt">meteorites</span>. Applying the meteoroid strength index (PE criteria) of Ceplecha and McCrosky (1976) to a suite of 33 photographically recorded Taurid fireballs, we find a <span class="hlt">large</span> spread in the apparent meteoroid strengths within the stream, including some very strong meteoroids. We also examine in detail the flight behavior of a Taurid fireball (SOMN 101031) and show that it has the potential to be a (small) <span class="hlt">meteorite</span>-producing event. Similarly, photographic observations of a bright, potential Taurid fireball recorded in November of 1995 in Spain show that it also had <span class="hlt">meteorite</span>-producing characteristics, despite a very high entry velocity (33 km s-1). Finally, we note that the recent Maribo <span class="hlt">meteorite</span> fall may have had a very high entry velocity (28 km s-1), further suggesting that survival of <span class="hlt">meteorites</span> at Taurid-like velocities is possible. Application of a numerical entry model also shows plausible survival of <span class="hlt">meteorites</span> at Taurid-like velocities, provided the initial meteoroids are fairly strong and <span class="hlt">large</span>, both of which are characteristics found in the Taurid stream.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1995Metic..30R.544M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1995Metic..30R.544M"><span>Metallographic Cooling Rates of IAB Iron <span class="hlt">Meteorites</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Meibom, A.; Haack, H.; Jensen, S. K.; Ulff-Moller, F.; Rasmussen, K. L.</p> <p>1995-09-01</p> <p>Non-metals can play an important role for the diffusion-controlled growth of the Widmanstatten structure in iron <span class="hlt">meteorites</span>. The presence of P significantly changes the diffusivity and equilibrium concentration of Ni in kamacite and taenite [1,2], and the effects of P have therefore been included in metallographic cooling rate calculations for many years. The presence of C probably increases the diffusivity of Ni in taenite up to a factor of two, which is considerably smaller than the effect of P that increases the Ni diffusivity by up to a factor of 10 [3,1]. On the other hand, C partitions strongly into taenite leaving kamacite essentially C-free (<10 micrograms/g [4]) and significantly reduces the equilibrium Ni-concentration in taenite [5]. Therefore, the effect of C should be included in metallographic cooling rate calculations of C-rich iron <span class="hlt">meteorites</span> [6]. IAB iron <span class="hlt">meteorites</span> have much higher bulk C-concentrations than most other iron <span class="hlt">meteorites</span> and the metallic phases of the IAB irons were probably saturated with C soon after kamacite nucleation commenced. Since C is expected to decrease the solubility of P in taenite [7] we have based our cooling rate estimate of Toluca (IAB) on the Fe-Ni-C system rather than the Fe-Ni-P system. Previous metallographic cooling rates determined for IAB irons, including the effect of P, are low (1-10 degrees C/My [8] and 30-70 degrees C/My [9]). Fractional crystallization of S-rich cores [10, 11] and <span class="hlt">impact</span> generated melt pools [12] have been proposed as origins of the IAB iron <span class="hlt">meteorites</span>. Since we expect melt pools near the surface to have cooled significantly faster than the core of a differentiated parent body, the metallographic cooling rates may be used to discriminate between the two models. We have performed thermodynamic calculations on the C-saturated Fe-Ni-C-system at temperatures above 400 degrees C [13]. The results agree with earlier experimental work [5] and indicate that C, to the same degree as P, reduces the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20130010162&hterms=Breccia&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DBreccia','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20130010162&hterms=Breccia&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DBreccia"><span>The Galim LL/EH Polymict Breccia: Evidence for <span class="hlt">Impact</span>-Induced Exchange Between Reduced and Oxidized <span class="hlt">Meteoritic</span> Material</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Rubin, Alan E.</p> <p>1997-01-01</p> <p>Galim is a polymict breccia consisting of a heavily shocked (shock stage S6) LL6 chondrite, Galim (a), and an <span class="hlt">impact</span>-melted EH chondrite, Galim (b). Relict chondrules in Galim (b) served as nucleation sites for euhedral enstatite grains crystallizing from the <span class="hlt">impact</span> melt. Many of the reduced phases typical of EH chondrites (e.g., Si-bearing metallic Fe-Ni; Ti-bearing troilite) are absent. Galim (b) was probably shock-melted while in contact with a more oxidized source, namely, Galim (a); during this event, Si was oxidized from the metal and Ti was oxidized from troilite. Galim (a) contains shock veins and recrystallized, unzoned olivine. The absence of evidence for reduction in Galim (a) may indicate that the amount of LL material greatly exceeded that of EH material; shock metamorphism may have taken place on the LL parent body. Shock-induced redox reactions such as those inferred for the Galim breccia appear to be restricted mainly to asteroids because the low-end tail of their relative-velocity distribution permits mixing of intact disparate materials (including accretion of projectiles of different oxidation states), whereas the peak of the distribution leads to high equilibration shock pressures (allowing <span class="hlt">impact</span>-induced exchange between previously accreted, disequilibrated materials). Galim probably formed by a two-stage process: (I) accretion to the LL parent body of an intact EH projectile at low relative velocities, and (2) shock metamorphism of the assemblage by the subsequent <span class="hlt">impact</span> of another projectile at significantly higher relative velocities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20130010162&hterms=eH&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DeH%2527','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20130010162&hterms=eH&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DeH%2527"><span>The Galim LL/EH Polymict Breccia: Evidence for <span class="hlt">Impact</span>-Induced Exchange Between Reduced and Oxidized <span class="hlt">Meteoritic</span> Material</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Rubin, Alan E.</p> <p>1997-01-01</p> <p>Galim is a polymict breccia consisting of a heavily shocked (shock stage S6) LL6 chondrite, Galim (a), and an <span class="hlt">impact</span>-melted EH chondrite, Galim (b). Relict chondrules in Galim (b) served as nucleation sites for euhedral enstatite grains crystallizing from the <span class="hlt">impact</span> melt. Many of the reduced phases typical of EH chondrites (e.g., Si-bearing metallic Fe-Ni; Ti-bearing troilite) are absent. Galim (b) was probably shock-melted while in contact with a more oxidized source, namely, Galim (a); during this event, Si was oxidized from the metal and Ti was oxidized from troilite. Galim (a) contains shock veins and recrystallized, unzoned olivine. The absence of evidence for reduction in Galim (a) may indicate that the amount of LL material greatly exceeded that of EH material; shock metamorphism may have taken place on the LL parent body. Shock-induced redox reactions such as those inferred for the Galim breccia appear to be restricted mainly to asteroids because the low-end tail of their relative-velocity distribution permits mixing of intact disparate materials (including accretion of projectiles of different oxidation states), whereas the peak of the distribution leads to high equilibration shock pressures (allowing <span class="hlt">impact</span>-induced exchange between previously accreted, disequilibrated materials). Galim probably formed by a two-stage process: (I) accretion to the LL parent body of an intact EH projectile at low relative velocities, and (2) shock metamorphism of the assemblage by the subsequent <span class="hlt">impact</span> of another projectile at significantly higher relative velocities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19860019356','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19860019356"><span>Thermoluminescence and Antarctic <span class="hlt">meteorites</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sears, D. W. G.; Hasan, F. A.</p> <p>1986-01-01</p> <p>The level of natural thermoluminescence (TL) in <span class="hlt">meteorites</span> is the result of competition between build-up, due to exposure to cosmic radiation, and thermal decay. Antarctic <span class="hlt">meteorites</span> tend to have lower natural TL than non-Antarctic <span class="hlt">meteorites</span> because of their generally larger terrestrial ages. However, since a few observed falls have low TL due to a recent heating event, such as passage within approximately 0.7 astronomical units of the Sun, this could also be the case for some Antarctic <span class="hlt">meteorites</span>. Dose rate variations due to shielding, heating during atmospheric passage, and anomalous fading also cause natural TL variations, but the effects are either relatively small, occur infrequently, or can be experimentally circumvented. The TL sensitivity of <span class="hlt">meteorites</span> reflects the abundance and nature of the feldspar. Thus intense shock, which destroys feldspar, causes the TL sensitivity to decrease by 1 to 2 orders of magnitude, while metamorphism, which generates feldspar through the devitrification of glass, causes TL sensitivity to increase by a factor of approximately 10000. The TL-metamorphism relationship is particularly strong for the lowest levels of metamorphism. The order-disorder transformation in feldspar also affect the TL emission characteristics and thus TL provides a means of paleothermometry.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19970041155','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19970041155"><span>Antarctic <span class="hlt">Meteorite</span> Newsletter. Volume 20</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lindstrom, Marilyn M.; Satterwhite, Cecilia E.</p> <p>1997-01-01</p> <p>The availability of 116 new <span class="hlt">meteorites</span> from the 1994-1996 collections is announced. There are 4 special chondrites, 2 carbonaceous chondrites, and 1 achondrite among the new <span class="hlt">meteorites</span>. Also included is a redescription of Lodranite GRA95209.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015M%26PS...50.1661R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015M%26PS...50.1661R"><span>The <span class="hlt">Meteoritical</span> Bulletin, No. 101</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ruzicka, Alex; Grossman, Jeffrey; Bouvier, Audrey; Herd, Christopher D. K.; Agee, Carl B.</p> <p>2015-09-01</p> <p><span class="hlt">Meteoritical</span> Bulletin 101 contains 2639 <span class="hlt">meteorites</span> accepted by the Nomenclature Committee in 2012, including 1 fall (Battle Mountain), with 2308 ordinary chondrites, 156 carbonaceous chondrites, 63 HED achondrites, 17 relict <span class="hlt">meteorites</span>, 16 Rumuruti chondrites, 15 enstatite chondrites, 15 ureilites, 10 iron <span class="hlt">meteorites</span>, 9 lunar <span class="hlt">meteorites</span>, 9 primitive achondrites, 8 ungrouped achondrites, 7 mesosiderites, 4 Martian <span class="hlt">meteorites</span>, and 2 Pallasites, and with 1812 from Antarctica, 437 from Asia, 301 from Africa, 43 from South America, 21 from Europe (including Russia), 21 from North America, 3 from Oceania, and 1 from unknown. Information about approved <span class="hlt">meteorites</span> can be obtained from the <span class="hlt">Meteoritical</span> Bulletin Database (MBD) available on line at <url href="http://www.lpi.usra.edu/meteor/">http://www.lpi.usra.edu/meteor/.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19860021997','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19860021997"><span>Antarctic <span class="hlt">Meteorite</span> Newsletter, volume 9, no. 2</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gooding, J. L. (Editor)</p> <p>1986-01-01</p> <p>Preliminary description and classifications of <span class="hlt">meteorites</span> that were completed since publication of the February issue are contained. Most <span class="hlt">large</span> (greater than 150 g) specimens (regardless of petrologic type) and all pebble sized (less than 150 g) specimens of special petrologic type are represented by separate descriptions. However, specimens of nonspecial petrologic type are listed only as single line entries. For convenience, new specimens are also recast by petrologic type. Each macroscopic description summarizes features that were visible to the eye at the time the <span class="hlt">meteorite</span> was first examined. Classification is based on microscopic petrography and resonnaissance-level electron-probe microanalysis. The pairing list was updated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1986AnMN....9.....G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1986AnMN....9.....G"><span>Antarctic <span class="hlt">Meteorite</span> Newsletter, volume 9, no. 2</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gooding, J. L.</p> <p>1986-06-01</p> <p>Preliminary description and classifications of <span class="hlt">meteorites</span> that were completed since publication of the February issue are contained. Most <span class="hlt">large</span> (greater than 150 g) specimens (regardless of petrologic type) and all pebble sized (less than 150 g) specimens of special petrologic type are represented by separate descriptions. However, specimens of nonspecial petrologic type are listed only as single line entries. For convenience, new specimens are also recast by petrologic type. Each macroscopic description summarizes features that were visible to the eye at the time the <span class="hlt">meteorite</span> was first examined. Classification is based on microscopic petrography and resonnaissance-level electron-probe microanalysis. The pairing list was updated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19810063258&hterms=flare+gas&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dflare%2Bgas','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19810063258&hterms=flare+gas&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dflare%2Bgas"><span>Solar flare irradiation records in Antarctic <span class="hlt">meteorites</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Goswami, J. N.</p> <p>1981-01-01</p> <p>The observation of tracks from solar flare heavy nuclei in Antarctic <span class="hlt">meteorite</span> samples is reported. In an analysis of nuclear track densities in eight L and H chondrites of low metamorphic grade, it was found that two interior specimens of sample 77216, an L-3 chondrite, contain olivine grains with track densities much higher than the average track densities, indicating precompaction irradiation by solar flares in different shielding conditions. Preliminary data from mass spectroscopic analyses show a <span class="hlt">large</span> excess of noble gases, with a Ne-20/Ne-22 ratio of greater than or equal to 10, indicating the presence of solar-type noble gas. Results of track density measurements in the other Antarctic <span class="hlt">meteorites</span> range from 10,000 to 4,000,000/sq cm, which is within the range observed in non-Antarctic L-group <span class="hlt">meteorites</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920064072&hterms=magnetism&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dmagnetism','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920064072&hterms=magnetism&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dmagnetism"><span>The relict magnetism of <span class="hlt">meteorites</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cisowski, S. M.; Hood, L. L.</p> <p>1991-01-01</p> <p><span class="hlt">Meteorite</span> paleomagnetic studies are reviewed and evaluated. Possible mechanisms for producing early solar system magnetic fields that could have been responsible for the magnetization of some or all <span class="hlt">meteorite</span> classes are explored. A detailed review of paleointensity results derived from the various classes of <span class="hlt">meteorites</span> is given, and the likelihood that the results might related to solar or nebulawide magnetic fields is considered. The implications of <span class="hlt">meteorite</span> magnetism for early solar system evolution are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920064072&hterms=Magnetism&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DMagnetism','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920064072&hterms=Magnetism&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DMagnetism"><span>The relict magnetism of <span class="hlt">meteorites</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cisowski, S. M.; Hood, L. L.</p> <p>1991-01-01</p> <p><span class="hlt">Meteorite</span> paleomagnetic studies are reviewed and evaluated. Possible mechanisms for producing early solar system magnetic fields that could have been responsible for the magnetization of some or all <span class="hlt">meteorite</span> classes are explored. A detailed review of paleointensity results derived from the various classes of <span class="hlt">meteorites</span> is given, and the likelihood that the results might related to solar or nebulawide magnetic fields is considered. The implications of <span class="hlt">meteorite</span> magnetism for early solar system evolution are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040090316&hterms=Radiometric+dating&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DRadiometric%2Bdating','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040090316&hterms=Radiometric+dating&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DRadiometric%2Bdating"><span><span class="hlt">Large</span>-body <span class="hlt">impact</span> and extinction in the Phanerozoic</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Raup, D. M.</p> <p>1992-01-01</p> <p>The kill curve for Phanerozoic marine species is used to investigate <span class="hlt">large</span>-body <span class="hlt">impact</span> as a cause of species extinction. Current estimates of Phanerozoic <span class="hlt">impact</span> rates are combined with the kill curve to produce an <span class="hlt">impact</span>-kill curve, which predicts extinction levels from crater diameter, on the working assumption that <span class="hlt">impacts</span> are responsible for all "pulsed" extinctions. By definition, pulsed extinction includes the approximately 60% of Phanerozoic extinctions that occurred in short-lived events having extinction rates greater than 5%. The resulting <span class="hlt">impact</span>-kill curve is credible, thus justifying more thorough testing of the <span class="hlt">impact</span>-extinction hypothesis. Such testing is possible but requires an exhaustive analysis of radiometric dating of Phanerozoic <span class="hlt">impact</span> events.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18321804','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18321804"><span>Retrospective study assessing efficacy of treatment of <span class="hlt">large</span> colonic <span class="hlt">impactions</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hallowell, G D</p> <p>2008-06-01</p> <p>Cases with a history of colic due to a <span class="hlt">large</span> colonic <span class="hlt">impaction</span> were recruited retrospectively to assess the treatment efficacy and complications of oral and parenteral fluid therapy regimes for correction of primary <span class="hlt">large</span> colon <span class="hlt">impactions</span>. Oral isotonic fluids had been administered at varying intervals following initial treatment with magnesium sulphate and water. There was no significant difference in complication rates between groups. Considering complication rates with <span class="hlt">impaction</span> clearance, hourly administration of oral fluids appears to be the most appropriate treatment regime of those investigated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20010048879&hterms=organic+chemistry&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dorganic%2Bchemistry','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20010048879&hterms=organic+chemistry&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dorganic%2Bchemistry"><span>Organic Chemistry of <span class="hlt">Meteorites</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chang, S.; Morrison, David (Technical Monitor)</p> <p>1994-01-01</p> <p>Studies of the molecular structures and C,N,H-isotopic compositions of organic matter in <span class="hlt">meteorites</span> reveal a complex history beginning in the parent interstellar cloud which spawned the solar system. Incorporation of interstellar dust and gas in the protosolar nebula followed by further thermal and aqueous processing on primordial parent bodies of carbonaceous, <span class="hlt">meteorites</span> have produced an inventory of diverse organic compounds including classes now utilized in biochemistry. This inventory represents one possible set of reactants for chemical models for the origin of living systems on the early Earth. Evidence bearing on the history of <span class="hlt">meteoritic</span> organic matter from astronomical observations and laboratory investigations will be reviewed and future research directions discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20170005325','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20170005325"><span>Kinetic Damage from <span class="hlt">Meteorites</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cooke, W.; Matney, M.; Brown, P.</p> <p>2017-01-01</p> <p>Comparing the natural <span class="hlt">meteorite</span> flux at the Earth's surface to that of space debris, reentering debris is approx. 2 orders of magnitude less of a kinetic hazard at all but the very largest (and therefore rarest) sizes compared to natural impactors. Debris re-entries over several metric tonnes are roughly as frequent as natural impactors, but the survival fraction is expected to be much higher. Kinetic hazards from <span class="hlt">meteorites</span> are very small, with only one recorded (indirect) injury reported. We expect fatalities to be even more rare, on the order of one person killed per several millennia. That several reports exist of small fragments/sand hitting people during <span class="hlt">meteorite</span> falls is consistent with our prediction that this should occur every decade or so.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20170008061','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20170008061"><span>Kinetic Damage from <span class="hlt">Meteorites</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cooke, W.; Brown, P.; Matney, M.</p> <p>2017-01-01</p> <p>Comparing the natural <span class="hlt">meteorite</span> flux at the Earth's surface to that of space debris, re-entering debris is 2 orders of magnitude less of a kinetic hazard at all but the very largest (and therefore rarest) sizes compared to natural impactors. Debris re-entries over several metric tonnes are roughly as frequent as natural impactors, but the survival fraction is expected to be much higher. Kinetic hazards from <span class="hlt">meteorites</span> are very small, with only one recorded (indirect) injury reported. We expect fatalities to be even more rare, on the order of one person killed per several millennia. That several reports exist of small fragments/sand hitting people during <span class="hlt">meteorite</span> falls is consistent with our prediction that this should occur every decade or so.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19860014028','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19860014028"><span>Primordial material in <span class="hlt">meteorites</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kerridge, J. F.</p> <p>1986-01-01</p> <p>Primordial is a term which applied to material that entered the solar system early and became incorporated into a <span class="hlt">meteorite</span> without totally losing its identity. Identification of such material surviving in <span class="hlt">meteorites</span> is so far solely through recognition of anomalous isotopic compositions of generally macroscopic entities contained within those <span class="hlt">meteorites</span>. Isotopic anomalies are, by definition, isotopic compositions which differ from the canonical solar system abundances in ways which cannot be explained in terms of local processes such as mass dependent fractionation, cosmic ray induced spallation or decay of radionuclides. A comprehensive account of isotopic anomalies is impractical here, so it is necessary to be selective. Issues which are potentially addressable through the study of such primordial material are examined. Those issues will be illustrated with specific, but not exhaustive, examples.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20010048879&hterms=Chemistry+organic&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DChemistry%2Borganic','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20010048879&hterms=Chemistry+organic&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DChemistry%2Borganic"><span>Organic Chemistry of <span class="hlt">Meteorites</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chang, S.; Morrison, David (Technical Monitor)</p> <p>1994-01-01</p> <p>Studies of the molecular structures and C,N,H-isotopic compositions of organic matter in <span class="hlt">meteorites</span> reveal a complex history beginning in the parent interstellar cloud which spawned the solar system. Incorporation of interstellar dust and gas in the protosolar nebula followed by further thermal and aqueous processing on primordial parent bodies of carbonaceous, <span class="hlt">meteorites</span> have produced an inventory of diverse organic compounds including classes now utilized in biochemistry. This inventory represents one possible set of reactants for chemical models for the origin of living systems on the early Earth. Evidence bearing on the history of <span class="hlt">meteoritic</span> organic matter from astronomical observations and laboratory investigations will be reviewed and future research directions discussed.</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/2012AGUFM.P44B..03S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.P44B..03S"><span><span class="hlt">Large</span> <span class="hlt">Impact</span> Basin Morphologies on Vesta in Solar System Context</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.; O'Brien, D. P.; Marchi, S.; Sykes, M. V.; Williams, D. A.; Gaskell, R. W.; Jaumann, R.; McCord, T. B.; Russell, C. T.</p> <p>2012-12-01</p> <p>Dawn global imaging and topographic mapping (@ 20-70 m scales) reveals that the 505-km-wide <span class="hlt">impact</span> basin Rheasilvia has a <span class="hlt">large</span> central complex, steep rim scarp and bowl-shaped floor, elements similar to <span class="hlt">large</span> <span class="hlt">impact</span> basins on midsize icy satellites of Saturn. <span class="hlt">Impact</span> melt and debris volumes are generally lower on Vesta and on icy satellites than on lunar basins. These similarities suggest that the Rheasilvia morphology may be a consequence of <span class="hlt">large</span> <span class="hlt">impacts</span> into lower gravity objects. Lower <span class="hlt">impact</span> velocities and planetary curvature may also be important. Low melt volumes are consistent with predictions based on lower <span class="hlt">impact</span> velocities on Vesta. Rheasilvia ejecta deposits extend over 100-150 km from the rim, and generally appear to scale similarly on Vesta and the Moon. Rheasiliva ejecta covers at least all of the southern hemisphere and may be more than 5 km thick near the rim. Oddly, the compositional feature associated with Rheasilvia is offset from its center by more than 100 km. A number of pre-Rheasilvia <span class="hlt">impact</span> basins are mapped, including several <span class="hlt">large</span> structures near the north pole. Most are degraded and original morphologies may be difficult to determine. Rheasilvia partially obliterated the older 400-km-wide 10-km-deep Veneneia basin, the interior of which is highly disrupted. The next largest basin, ~250-km-across is also old and heavily cratered. If it ever possessed a central peak, it has since been obliterated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1987mtpp.book.....M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1987mtpp.book.....M"><span><span class="hlt">Meteorites</span> and their parent planets</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>McSween, Harry Y.</p> <p></p> <p>This book explores the origins of <span class="hlt">meteorites</span> by tracing them back to their parent bodies, which are the sites of various geological processes. Recent discoveries are reviewed which reveal that the chemical and physical properties of <span class="hlt">meteorites</span> contain a record of the processes that formed the solar system. How <span class="hlt">meteorites</span> escape their parent bodies and find their way to earth is explained.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/of/1968/0097/report.pdf','USGSPUBS'); return false;" href="https://pubs.usgs.gov/of/1968/0097/report.pdf"><span>The geologic classification of the <span class="hlt">meteorites</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>Elston, Donald Parker</p> <p>1968-01-01</p> <p> aggregates of grains, and as <span class="hlt">large</span> subround to round, finely granular accretional chondrules. Evidence in Murray indicates that component 3 silicates precipitated abruptly and at low pressures, possibly from a high temperature gas, in an environment that contained dispersed component 1 and 2 materials. All component 3 aggregates in Murray contain component 1 material, most commonly as flakes, and locally as tiny granules and larger spherules, some of which are hollow and some of which were broken prior to their mechanical incorporation in accretionary chondrules. Accretion may have occurred as ices associated with dispersed water-bearing component 1 materials temporarily melted during the precipitation of component 3 silicates, and then abruptly refroze to form an icy cementing material. Group 1 materials may be cometary, and group 2 materials may be asteroidal. Schematic models are proposed. Evidence is reviewed for the lunar origin of the pyroxeneplagioclase achondrites. On the basis of natural remanent magnetism, it is suggested that the very scarce diopside-olivine achondrites may be samples from Mars. A classification of the <span class="hlt">meteorite</span> breccias, including the calcium-poor and calcium-rich mesosiderites, and irons that contain silicate fragments, is proposed. A fragmentation history of the <span class="hlt">meteorites</span> is outlined on the basis of evidence in the polymict breccias, and from gas retention ages in stones and exposure ages in irons. Cometal <span class="hlt">impacts</span> appear to have caused the initial fragmentation, stud possibly the perturbation of orbits, of two inferred asteroidal bodies (enstatite and bronzite), one and possibly both events occurring before 2000 m.y. ago. Several <span class="hlt">impacts</span> apparently occurred on the inferred hypersthene body in the interval 1000 to 2000 m.y. ago. Major breakups of the three bodies apparently occurred as the result of interasteroidal collisions at about 900 m.y. ago, and 600 to 700 m.y. ago. The breakups were followed by a number of fr</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20020041937&hterms=isomer&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Disomer','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20020041937&hterms=isomer&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Disomer"><span>Organics In <span class="hlt">Meteorites</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chang, Sherwood</p> <p>1996-01-01</p> <p>The variety of classes of organic compounds that occur in carbonaceous <span class="hlt">meteorites</span> suggests a rich pre-planetary chemistry with possible connections to interstellar, solar nebular and parent body processes. Structural diversity prevails within all classes examined in detail. Among amino acids for instance, all possible isomers are found up to species containing 4-6 carbon atoms, with abundances decreasing with increasing molecular weight. Such diversity seems limited to those carbonaceous <span class="hlt">meteorites</span> which show evidence of having been exposed to liquid water; <span class="hlt">meteorites</span> lacking such evidence also show much lower abundances and less structural diversity in their organic contents. This apparent dependency on water suggests a role for cometary ices in the chemical evolution of organic compounds on parent bodies. Measurements of the stable isotope compositions of C, H, N and S in classes of compounds and at the individual compound level show strong deviations from average chondritic values. These deviations are difficult to explain by solar system or parent body processes, and precedents for some of these isotopic anomalies exist in interstellar (e.g., high D/H ratios) and circumstellar chemistry. Therefore, presolar origins for much if not all of the <span class="hlt">meteoritic</span> organic compounds (or their precursors) is a distinct possibility. In contrast, evidence of solar nebular origins is either lacking or suspect. Results from molecular and isotopic analyses of <span class="hlt">meteoritic</span> organics, from laboratory simulations and from a model of interstellar grain reactions will be used to flesh out the hypothesis that this material originated with interstellar chemistry, was distributed within the early solar system as cometary ices, and was subsequently altered on <span class="hlt">meteorite</span> parent bodies to yield the observed compounds.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20020041937&hterms=Chemistry+organic&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DChemistry%2Borganic','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20020041937&hterms=Chemistry+organic&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DChemistry%2Borganic"><span>Organics In <span class="hlt">Meteorites</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chang, Sherwood</p> <p>1996-01-01</p> <p>The variety of classes of organic compounds that occur in carbonaceous <span class="hlt">meteorites</span> suggests a rich pre-planetary chemistry with possible connections to interstellar, solar nebular and parent body processes. Structural diversity prevails within all classes examined in detail. Among amino acids for instance, all possible isomers are found up to species containing 4-6 carbon atoms, with abundances decreasing with increasing molecular weight. Such diversity seems limited to those carbonaceous <span class="hlt">meteorites</span> which show evidence of having been exposed to liquid water; <span class="hlt">meteorites</span> lacking such evidence also show much lower abundances and less structural diversity in their organic contents. This apparent dependency on water suggests a role for cometary ices in the chemical evolution of organic compounds on parent bodies. Measurements of the stable isotope compositions of C, H, N and S in classes of compounds and at the individual compound level show strong deviations from average chondritic values. These deviations are difficult to explain by solar system or parent body processes, and precedents for some of these isotopic anomalies exist in interstellar (e.g., high D/H ratios) and circumstellar chemistry. Therefore, presolar origins for much if not all of the <span class="hlt">meteoritic</span> organic compounds (or their precursors) is a distinct possibility. In contrast, evidence of solar nebular origins is either lacking or suspect. Results from molecular and isotopic analyses of <span class="hlt">meteoritic</span> organics, from laboratory simulations and from a model of interstellar grain reactions will be used to flesh out the hypothesis that this material originated with interstellar chemistry, was distributed within the early solar system as cometary ices, and was subsequently altered on <span class="hlt">meteorite</span> parent bodies to yield the observed compounds.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040059886&hterms=ion+Composition+Experiment&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dion%2BComposition%2BExperiment','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040059886&hterms=ion+Composition+Experiment&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dion%2BComposition%2BExperiment"><span>Lunar and Planetary Science XXXV: <span class="hlt">Meteorites</span>: Experiments and Spectroscopy</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>The session "<span class="hlt">Meteorites</span>: Experiments and Spectroscopy" included the following reports:The Suitability of Laser Induced Breakdown Spectroscopy for Determining the Compositions of Extraterrestrial Material; Deconvolving Terrestrial Alteration Mineral Spectral Signatures from <span class="hlt">Meteorite</span> Reflectance Measurements; <span class="hlt">Impacts</span> of Ions and Micrometeorites on Mineral Surfaces: Reflectance and Chemical Changes Found in Ordinary Chondrites; FT-IR Micro-spectroscopy of Fine-grained Planetary Materials: Further Results; Effusion Cell Measurements of the Vapor Pressure of Cobalt at Temperatures up to 2000K: Comparisons with Iron and Nickel; Kinetics of Fe2+-Mg Order-Disorder in P21/c Pigeonite: Implications for Cooling Rates Calculations; Compressional and Shear Wave Velocities in <span class="hlt">Meteorites</span>; Chemical and Mineralogical Size Segregation in the <span class="hlt">Impact</span> Disruption of Anhydrous Stone <span class="hlt">Meteorites</span>; and Shock Pressures of <span class="hlt">Impacts</span> vs. Crystallization Pressures of Shock-induced Melt Veins of the chondrites.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12424385','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12424385"><span>Martian <span class="hlt">meteorite</span> launch: high-speed ejecta from small craters.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Head, James N; Melosh, H Jay; Ivanov, Boris A</p> <p>2002-11-29</p> <p>We performed high-resolution computer simulations of <span class="hlt">impacts</span> into homogeneous and layered martian terrain analogs to try to account for the ages and characteristics of the martian <span class="hlt">meteorite</span> collection found on Earth. We found that craters as small as approximately 3 kilometers can eject approximately 10(7) decimeter-sized fragments from Mars, which is enough to expect those fragments to appear in the terrestrial collection. This minimum crater diameter is at least four times smaller than previous estimates and depends on the physical composition of the target material. Terrain covered by a weak layer such as an <span class="hlt">impact</span>-generated regolith requires larger, therefore rarer, <span class="hlt">impacts</span> to eject <span class="hlt">meteorites</span>. Because older terrain is more likely to be mantled with such material, we estimate that the martian <span class="hlt">meteorites</span> will be biased toward younger ages, which is consistent with the <span class="hlt">meteorite</span> collection.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040059886&hterms=laser+induced+breakdown+spectroscopy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dlaser%2Binduced%2Bbreakdown%2Bspectroscopy','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040059886&hterms=laser+induced+breakdown+spectroscopy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dlaser%2Binduced%2Bbreakdown%2Bspectroscopy"><span>Lunar and Planetary Science XXXV: <span class="hlt">Meteorites</span>: Experiments and Spectroscopy</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>The session "<span class="hlt">Meteorites</span>: Experiments and Spectroscopy" included the following reports:The Suitability of Laser Induced Breakdown Spectroscopy for Determining the Compositions of Extraterrestrial Material; Deconvolving Terrestrial Alteration Mineral Spectral Signatures from <span class="hlt">Meteorite</span> Reflectance Measurements; <span class="hlt">Impacts</span> of Ions and Micrometeorites on Mineral Surfaces: Reflectance and Chemical Changes Found in Ordinary Chondrites; FT-IR Micro-spectroscopy of Fine-grained Planetary Materials: Further Results; Effusion Cell Measurements of the Vapor Pressure of Cobalt at Temperatures up to 2000K: Comparisons with Iron and Nickel; Kinetics of Fe2+-Mg Order-Disorder in P21/c Pigeonite: Implications for Cooling Rates Calculations; Compressional and Shear Wave Velocities in <span class="hlt">Meteorites</span>; Chemical and Mineralogical Size Segregation in the <span class="hlt">Impact</span> Disruption of Anhydrous Stone <span class="hlt">Meteorites</span>; and Shock Pressures of <span class="hlt">Impacts</span> vs. Crystallization Pressures of Shock-induced Melt Veins of the chondrites.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20170006049&hterms=Amino+acids&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DAmino%2Bacids','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20170006049&hterms=Amino+acids&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DAmino%2Bacids"><span><span class="hlt">Meteoritic</span> Amino Acids: Diversity in Compositions Reflects Parent Body Histories</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Elsila, Jamie E.; Aponte, Jose C.; Blackmond, Donna G.; Burton, Aaron S.; Dworkin, Jason P.; Glavin, Daniel P.</p> <p>2016-01-01</p> <p>The analysis of amino acids in <span class="hlt">meteorites</span> dates back over 50 years; however, it is only in recent years that research has expanded beyond investigations of a narrow set of <span class="hlt">meteorite</span> groups (exemplied by the Murchison <span class="hlt">meteorite</span>) into <span class="hlt">meteorites</span> of other types and classes. These new studies have shown a wide diversity in the abundance and distribution of amino acids across carbonaceous chondrite groups, highlighting the role of parent body processes and composition in the creation, preservation, or alteration of amino acids. Although most chiral amino acids are racemic in <span class="hlt">meteorites</span>, the enantiomeric distribution of some amino acids, particularly of the nonprotein amino acid isovaline, has also been shown to vary both within certain <span class="hlt">meteorites</span> and across carbonaceous <span class="hlt">meteorite</span> groups. <span class="hlt">Large</span> -enantiomeric excesses of some extraterrestrial protein amino acids (up to 60) have also been observed in rare cases and point to nonbiological enantiomeric enrichment processes prior to the emergence of life. In this Outlook, we review these recent <span class="hlt">meteoritic</span> analyses, focusing on variations in abundance, structural distributions, and enantiomeric distributions of amino acids and discussing possible explanations for these observations and the potential for future work.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4919777','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4919777"><span><span class="hlt">Meteoritic</span> Amino Acids: Diversity in Compositions Reflects Parent Body Histories</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>2016-01-01</p> <p>The analysis of amino acids in <span class="hlt">meteorites</span> dates back over 50 years; however, it is only in recent years that research has expanded beyond investigations of a narrow set of <span class="hlt">meteorite</span> groups (exemplified by the Murchison <span class="hlt">meteorite</span>) into <span class="hlt">meteorites</span> of other types and classes. These new studies have shown a wide diversity in the abundance and distribution of amino acids across carbonaceous chondrite groups, highlighting the role of parent body processes and composition in the creation, preservation, or alteration of amino acids. Although most chiral amino acids are racemic in <span class="hlt">meteorites</span>, the enantiomeric distribution of some amino acids, particularly of the nonprotein amino acid isovaline, has also been shown to vary both within certain <span class="hlt">meteorites</span> and across carbonaceous <span class="hlt">meteorite</span> groups. <span class="hlt">Large</span> l-enantiomeric excesses of some extraterrestrial protein amino acids (up to ∼60%) have also been observed in rare cases and point to nonbiological enantiomeric enrichment processes prior to the emergence of life. In this Outlook, we review these recent <span class="hlt">meteoritic</span> analyses, focusing on variations in abundance, structural distributions, and enantiomeric distributions of amino acids and discussing possible explanations for these observations and the potential for future work. PMID:27413780</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA07269&hterms=Basketball&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DBasketball','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA07269&hterms=Basketball&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DBasketball"><span>Iron <span class="hlt">Meteorite</span> on Mars</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/> NASA's Mars Exploration Rover Opportunity has found an iron <span class="hlt">meteorite</span> on Mars, the first <span class="hlt">meteorite</span> of any type ever identified on another planet. The pitted, basketball-size object is mostly made of iron and nickel. Readings from spectrometers on the rover determined that composition. Opportunity used its panoramic camera to take the images used in this approximately true-color composite on the rover's 339th martian day, or sol (Jan. 6, 2005). This composite combines images taken through the panoramic camera's 600-nanometer (red), 530-nanometer (green), and 480-nanometer (blue) filters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1993JBAA..103..123H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1993JBAA..103..123H"><span><span class="hlt">Meteorite</span> incidence angles</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hughes, D. W.</p> <p>1993-06-01</p> <p>Think about an asteroid smashing into the surface of the Moon and excavating a crater; or hitting Earth and scattering <span class="hlt">meteorite</span> fragments over a strewn field. Imagine a fragment of cometary dust burning out in the Earth's atmosphere and producing a meteor. These bodies have paths that are inclined at some angle to the vertical. But what is the predominant value of this angle of incidence, i? How does the number of incident bodies vary as a function of angle i? And how do both these affect the prevalence of non- circular lunar craters and the ellipticity of <span class="hlt">meteorite</span> strewn fields?</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19820024358&hterms=schwarz&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dschwarz','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19820024358&hterms=schwarz&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dschwarz"><span>Descriptions of stony <span class="hlt">meteorites</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Score, R.; King, T. V. V.; Schwarz, C. M.; Reid, A. M.; Mason, B.</p> <p>1982-01-01</p> <p>The individual specimens, arranged by class are described. Within the chondrites, the specimens are grouped according to the Van Schmus-Wood classification, and the descriptions follow the order of increasing petrographic type. The original weight of the specimen is given to the nearest gram (nearest 0.1 gram for specimens weighing less than 100 grams). Material on al characterized <span class="hlt">meteorites</span> collected together with descriptions of some <span class="hlt">meteorites</span> is included. Specimens weighing less than 100 grams are listed without descriptions, unless they show distinctive features.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19750006614','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19750006614"><span>Comparison of lunar rocks and <span class="hlt">meteorites</span>: Implications to histories of the moon and parent <span class="hlt">meteorite</span> bodies</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Prinz, M.; Fodor, R. V.; Keil, K.</p> <p>1974-01-01</p> <p>A number of similarities between lunar and <span class="hlt">meteoritic</span> rocks are reported and suggest that the comparison is essential for a clear understanding of <span class="hlt">meteorites</span> as probes of the early history of the solar systems: (1) Monomict and polymict breccias occur in lunar rocks, as well as in achondritic and chondritic <span class="hlt">meteorites</span>, having resulted from complex and repeated <span class="hlt">impact</span> processes. (2) Chondrules are present in lunar, as well as in a few achondritic and most chondritic <span class="hlt">meteorites</span>. It is pointed out that because chondrules may form in several different ways and in different environments, a distinction between the different modes of origin and an estimate of their relative abundance is important if their significance as sources of information on the early history of the solar system is to be clearly understood. (3) Lithic fragments are very useful in attempts to understand the pre- and post-<span class="hlt">impact</span> history of lunar and <span class="hlt">meteoritic</span> breccias. They vary from little modified (relative to the apparent original texture), to partly or completely melted and recrystallized lithic fragments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/938537','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/938537"><span>EVIDENCE FOR COMET STORMS IN <span class="hlt">METEORITE</span> AGES</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Perlmutter, S.; Muller, R.A.</p> <p>1987-10-01</p> <p>Clustering of cosmic-ray exposure ages of H chondritic <span class="hlt">meteorites</span> occurs at 7 {+-} 3 and 30 {+-} 6 Myr ago. There is independent evidence that comet storms have occurred at the same times, based on the fossil record of family and genus extinctions, <span class="hlt">impact</span> craters and glass, and geomagnetic reversals. We suggest that H chondrites were formed by the <span class="hlt">impact</span> of shower comets on asteroids. The duration of the most recent comet shower was {le} 4 Myr, in agreement with storm theory.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20160003883','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20160003883"><span>The Germanium Dichotomy in Martian <span class="hlt">Meteorites</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Humayun, M.; Yang, S.; Righter, K.; Zanda, B.; Hewins, R. H.</p> <p>2016-01-01</p> <p>Germanium is a moderately volatile and siderophile element that follows silicon in its compatibility during partial melting of planetary mantles. Despite its obvious usefulness in planetary geochemistry germanium is not analyzed routinely, with there being only three prior studies reporting germanium abundances in Martian <span class="hlt">meteorites</span>. The broad range (1-3 ppm) observed in Martian igneous rocks is in stark contrast to the narrow range of germanium observed in terrestrial basalts (1.5 plus or minus 0.1 ppm). The germanium data from these studies indicates that nakhlites contain 2-3 ppm germanium, while shergottites contain approximately 1 ppm germanium, a dichotomy with important implications for core formation models. There have been no reliable germanium abundances on chassignites. The ancient <span class="hlt">meteoritic</span> breccia, NWA 7533 (and paired <span class="hlt">meteorites</span>) contains numerous clasts, some pristine and some <span class="hlt">impact</span> melt rocks, that are being studied individually. Because germanium is depleted in the Martian crust relative to chondritic impactors, it has proven useful as an indicator of <span class="hlt">meteoritic</span> contamination of <span class="hlt">impact</span> melt clasts in NWA 7533. The germanium/silicon ratio can be applied to minerals that might not partition nickel and iridium, like feldspars. We report germanium in minerals from the 3 known chassignites, 2 nakhlites and 5 shergottites by LAICP- MS using a method optimized for precise germanium analysis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19810060471&hterms=ice+caps&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dice%2Bcaps','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19810060471&hterms=ice+caps&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dice%2Bcaps"><span>Estimates of total quantity of <span class="hlt">meteorites</span> in the East Antarctic ice cap</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Olsen, E. J.</p> <p>1981-01-01</p> <p>Based on a steady-state model of the East Antarctic ice cap, and current estimates of <span class="hlt">meteorite</span> influx, a model is developed which predicts that the steady-state number of <span class="hlt">meteorites</span> being carried in or on the ice is at least 760,000. This <span class="hlt">large</span> <span class="hlt">meteorite</span> population does not require unusual influx conditions, since the cold, dry climate preserves virtually all <span class="hlt">meteorites</span> that fall with the exception of the fragile, porous carbonaceous chondrites. Application of the model to the Greenland ice cap yields a steady-state population of about 61,000 <span class="hlt">meteorites</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930000972&hterms=sedimentology+stratigraphy&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dsedimentology%2Bstratigraphy','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930000972&hterms=sedimentology+stratigraphy&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dsedimentology%2Bstratigraphy"><span>Does the sedimentology of the Chelmsford formation provide evidence for a <span class="hlt">meteorite</span> <span class="hlt">impact</span> origin of the Sudbury structure?</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Long, D. G. F.</p> <p>1992-01-01</p> <p>The post-'event' fill of the Paleoproterozoic Sudbury Basin consists of at least 600 m of deep-water mudrocks of the Onwatin Formation, overlain by 850 m of lithic-arkosic muddy sandstones in the Chelmsford Formation. While mudstones of the Onwatin reflect deposition in a deep-water, anoxic setting, there is no clear evidence of local breccias, conglomerates, or sand bodies to support the concept that the basin was protected by the steep walls of an <span class="hlt">impact</span> crater. Carbonates in the basal, Vermillion Member are of sedimentary exhalitive origin and were not derived from a shallow marine shelf. Turbidites in the Chelmsford Formation show no evidence of centripetal fill as might be expected from a restricted, circular basin. They appear to have been emplaced by predominantly southwesterly flowing turbidity currents, which showed little to no deflection along the depositional axis of an elongate foreland basin that developed in front of the rising Penokean mountain chain. While the presence of minor sandstone-filled fractures in parts of the Chelmsford Formation suggests the presence of north- or south-directed paleoslopes, no evidence is seen to support the existence of subbasins or a central uplift within the Sudbury Basin. While tilt-corrected paleocurrent orientations are ambiguous, due to postdepositional shortening of strata during cleavage development, strain correction of the observations makes little difference to the net, south-southwest-directed paleoflow.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930000972&hterms=sedimentology&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dsedimentology','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930000972&hterms=sedimentology&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dsedimentology"><span>Does the sedimentology of the Chelmsford formation provide evidence for a <span class="hlt">meteorite</span> <span class="hlt">impact</span> origin of the Sudbury structure?</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Long, D. G. F.</p> <p>1992-01-01</p> <p>The post-'event' fill of the Paleoproterozoic Sudbury Basin consists of at least 600 m of deep-water mudrocks of the Onwatin Formation, overlain by 850 m of lithic-arkosic muddy sandstones in the Chelmsford Formation. While mudstones of the Onwatin reflect deposition in a deep-water, anoxic setting, there is no clear evidence of local breccias, conglomerates, or sand bodies to support the concept that the basin was protected by the steep walls of an <span class="hlt">impact</span> crater. Carbonates in the basal, Vermillion Member are of sedimentary exhalitive origin and were not derived from a shallow marine shelf. Turbidites in the Chelmsford Formation show no evidence of centripetal fill as might be expected from a restricted, circular basin. They appear to have been emplaced by predominantly southwesterly flowing turbidity currents, which showed little to no deflection along the depositional axis of an elongate foreland basin that developed in front of the rising Penokean mountain chain. While the presence of minor sandstone-filled fractures in parts of the Chelmsford Formation suggests the presence of north- or south-directed paleoslopes, no evidence is seen to support the existence of subbasins or a central uplift within the Sudbury Basin. While tilt-corrected paleocurrent orientations are ambiguous, due to postdepositional shortening of strata during cleavage development, strain correction of the observations makes little difference to the net, south-southwest-directed paleoflow.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27078468','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27078468"><span>Vortex-ring-induced <span class="hlt">large</span> bubble entrainment during drop <span class="hlt">impact</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Thoraval, Marie-Jean; Li, Yangfan; Thoroddsen, Sigurdur T</p> <p>2016-03-01</p> <p>For a limited set of <span class="hlt">impact</span> conditions, a drop <span class="hlt">impacting</span> onto a pool can entrap an air bubble as <span class="hlt">large</span> as its own size. The subsequent rise and rupture of this <span class="hlt">large</span> bubble plays an important role in aerosol formation and gas transport at the air-sea interface. The <span class="hlt">large</span> bubble is formed when the <span class="hlt">impact</span> crater closes up near the pool surface and is known to occur only for drops that are prolate at <span class="hlt">impact</span>. Herein we use experiments and numerical simulations to show that a concentrated vortex ring, produced in the neck between the drop and the pool, controls the crater deformations and pinchoff. However, it is not the strongest vortex rings that are responsible for the <span class="hlt">large</span> bubbles, as they interact too strongly with the pool surface and self-destruct. Rather, it is somewhat weaker vortices that can deform the deeper craters, which manage to pinch off the <span class="hlt">large</span> bubbles. These observations also explain why the strongest and most penetrating vortex rings emerging from drop <span class="hlt">impacts</span> are not produced by oblate drops but by more prolate drop shapes, as had been observed in previous experiments.</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/2007AGUFM.P53B1253H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFM.P53B1253H"><span>The survival of <span class="hlt">large</span> organic molecules during hypervelocity <span class="hlt">impacts</span> with water ice: implications for sampling the icy surfaces of moons</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hurst, A.; Bowden, S. A.; Parnell, J.; Burchell, M. J.; Ball, A. J.</p> <p>2007-12-01</p> <p>There are a number of measurements relevant to planetary geology that can only be adequately performed by physically contacting a sample. This necessitates landing on the surface of a moon or planetary body or returning samples to earth. The need to physically contact a sample is particularly important in the case of measurements that could detect medium to low concentrations of <span class="hlt">large</span> organic molecules present in surface materials. <span class="hlt">Large</span> organic molecules, although a trace component of many <span class="hlt">meteoritic</span> materials and rocks on the surface of earth, carry crucial information concerning the processing of <span class="hlt">meteoritic</span> material in the surface and subsurface environments, and can be crucial indicators for the presence of life. Unfortunately landing on the surface of a small planetary body or moon is complicated, particularly if surface topography is only poorly characterised and the atmosphere thin thus requiring a propulsion system for a soft landing. One alternative to a surface landing may be to use an impactor launched from an orbiting spacecraft to launch material from the planets surface and shallow sub-surface into orbit. Ejected material could then be collected by a follow-up spacecraft and analyzed. The mission scenario considered in the Europa-Ice Clipper mission proposal included both sample return and the analysis of captured particles. Employing such a sampling procedure to analyse <span class="hlt">large</span> organic molecules is only viable if <span class="hlt">large</span> organic molecules present in ices survive hypervelocity <span class="hlt">impacts</span> (HVIs). To investigate the survival of <span class="hlt">large</span> organic molecules in HVIs with icy bodies a two stage light air gas gun was used to fire steel projectiles (1-1.5 mm diameter) at samples of water ice containing <span class="hlt">large</span> organic molecules (amino acids, anthracene and beta-carotene a biological pigment) at velocities > 4.8 km/s.UV-VIS spectroscopy of ejected material detected beta-carotene indicating <span class="hlt">large</span> organic molecules can survive hypervelocity <span class="hlt">impacts</span>. These preliminary results</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007SPIE.6694E..08H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007SPIE.6694E..08H"><span>Microfossils of cyanobacteria in carbonaceous <span class="hlt">meteorites</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hoover, Richard B.</p> <p>2007-09-01</p> <p>During the past decade, Environmental and Field Emission Scanning Electron Microscopes have been used at the NASA/Marshall Space Flight Center to investigate freshly fractured interior surfaces of a <span class="hlt">large</span> number of different types of <span class="hlt">meteorites</span>. <span class="hlt">Large</span>, complex, microfossils with clearly recognizable biological affinities have been found embedded in several carbonaceous <span class="hlt">meteorites</span>. Similar forms were notably absent in all stony and nickel-iron <span class="hlt">meteorites</span> investigated. The forms encountered are consistent in size and morphology with morphotypes of known genera of Cyanobacteria and microorganisms that are typically encountered in associated benthic prokaryotic mats. Even though many coccoidal and isodiametric filamentous cyanobacteria have a strong morphological convergence with some other spherical and filamentous bacteria and algae, many genera of heteropolar cyanobacteria have distinctive apical and basal regions and cellular differentiation that makes it possible to unambiguously recognize the forms based entirely upon cellular dimensions, filament size and distinctive morphological characteristics. For almost two centuries, these morphological characteristics have historically provided the basis for the systematics and taxonomy of cyanobacteria. This paper presents ESEM and FESEM images of embedded filaments and thick mats found in-situ in the Murchison CM2 and Orgueil CI1 carbonaceous <span class="hlt">meteorites</span>. Comparative images are also provided for known genera and species of cyanobacteria and other microbial extremophiles. Energy Dispersive X-ray Spectroscopy (EDS) indicates that the <span class="hlt">meteorite</span> filaments typically exhibit dramatic chemical differentiation with distinctive difference between the possible microfossil and the <span class="hlt">meteorite</span> matrix in the immediate proximity. Chemical differentiation is also observed within these microstructures with many of the permineralized filaments enveloped within electron transparent carbonaceous sheaths. Elemental distributions of these</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20070038326','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20070038326"><span>Microfossils of Cyanobacteria in Carbonaceous <span class="hlt">Meteorites</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hoover, Richard B.</p> <p>2007-01-01</p> <p>During the past decade, Environmental and Field Emission Scanning Electron Microscopes have been used at the NASA/Marshall Space Flight Center to investigate freshly fractured interior surfaces of a <span class="hlt">large</span> number of different types of <span class="hlt">meteorites</span>. <span class="hlt">Large</span>, complex, microfossils with clearly recognizable biological affinities have been found embedded in several carbonaceous <span class="hlt">meteorites</span>. Similar forms were notably absent in all stony and nickel-iron <span class="hlt">meteorites</span> investigated. The forms encountered are consistent in size and morphology with morphotypes of known genera of Cyanobacteria and microorganisms that are typically encountered in associated benthic prokaryotic mats. Even though many coccoidal and isodiametric filamentous cyanobacteria have a strong morphological convergence with some other spherical and filamentous bacteria and algae, many genera of heteropolar cyanobacteria have distinctive apical and basal regions and cellular differentiation that makes it possible to unambiguously recognize the forms based entirely upon cellular dimensions, filament size and distinctive morphological characteristics. For almost two centuries, these morphological characteristics have historically provided the basis for the systematics and taxonomy of cyanobacteria. This paper presents ESEM and FESEM images of embedded filaments and thick mats found in-situ in the Murchison CM2 and Orgueil cn carbonaceous <span class="hlt">meteorites</span>. Comparative images are also provided for known genera and species of cyanobacteria and other microbial extremophiles. Energy Dispersive X-ray Spectroscopy (EDS) studies indicate that the <span class="hlt">meteorite</span> filaments typically exhibit dramatic chemical differentiation with distinctive difference between the possible microfossil and the <span class="hlt">meteorite</span> matrix in the immediate proximity. Chemical differentiation is also observed within these microstructures with many of the permineralized filaments enveloped within electron transparent carbonaceous sheaths. Elemental distributions of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120011974','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120011974"><span>Enantiomer Ratios of <span class="hlt">Meteoritic</span> Sugar Derivatives</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cooper, George</p> <p>2012-01-01</p> <p>Carbonaceous <span class="hlt">meteorites</span> contain a diverse suite of soluble organic compounds. Studies of these compounds reveal the Solar System's earliest organic chemistry. Among the classes of organic compounds found in <span class="hlt">meteorites</span> are keto acids (pyruvic acid, etc.), hydroxy tricarboxylic acids (1), amino acids, amides, purines and pyrimidines. The Murchison and Murray <span class="hlt">meteorites</span> are the most studied for soluble and insoluble organic compounds and organic carbon phases. The majority of (indigenous) <span class="hlt">meteoritic</span> compounds are racemic, (i.e., their D/L enantiomer ratios are 50:50). However, some of the more unusual (non-protein) amino acids contain slightly more of one enantiomer (usually the L) than the other. This presentation focuses on the enantiomer analyses of three to six-carbon (3C to 6C) <span class="hlt">meteoritic</span> sugar acids. The molecular and enantiomer analysis of corresponding sugar alcohols will also be discussed. Detailed analytical procedures for sugar-acid enantiomers have been described. Results of several <span class="hlt">meteorite</span> analyses show that glyceric acid is consistently racemic (or nearly so) as expected of non-biological mechanisms of synthesis. Also racemic are 4-C deoxy sugar acids: 2-methyl glyceric acid; 2,4-dihydroxybutyric acid; 2,3-dihydroxybutyric acid (two diastereomers); and 3,4-dihydroxybutyric acid. However, a 4C acid, threonic acid, has never been observed as racemic, i.e., it possesses a <span class="hlt">large</span> D excess. In several samples of Murchison and one of GRA 95229 (possibly the most pristine carbonaceous <span class="hlt">meteorite</span> yet analyzed) threonic acid has nearly the same D enrichment. In Murchison, preliminary isotopic measurements of individual threonic acid enantiomers point towards extraterrestrial sources of the D enrichment. Enantiomer analyses of the 5C mono-sugar acids, ribonic, arabinonic, xylonic, and lyxonic also show <span class="hlt">large</span> D excesses. It is worth noting that all four of these acids (all of the possible straight-chained 5C sugar acids) are present in <span class="hlt">meteorites</span>, including the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014acm..conf..483S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014acm..conf..483S"><span>Origin of igneous <span class="hlt">meteorites</span> and differentiated asteroids</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Scott, E.; Goldstein, J.; Asphaug, E.; Bottke, W.; Moskovitz, N.; Keil, K.</p> <p>2014-07-01</p> <p>Introduction: Igneously formed <span class="hlt">meteorites</span> and asteroids provide major challenges to our understanding of the formation and evolution of the asteroid belt. The numbers and types of differentiated <span class="hlt">meteorites</span> and non-chondritic asteroids appear to be incompatible with an origin by fragmentation of numerous Vesta-like bodies by hypervelocity <span class="hlt">impacts</span> in the asteroid belt over 4 Gyr. We lack asteroids and achondrites from the olivine-rich mantles of the parent bodies of the 12 groups of iron <span class="hlt">meteorites</span> and the ˜70 ungrouped irons, the 2 groups of pallasites and the 4--6 ungrouped pallasites. We lack mantle and core samples from the parent asteroids of the basaltic achondrites that do not come from Vesta, viz., angrites and the ungrouped eucrites like NWA 011 and Ibitira. How could core samples have been extracted from numerous differentiated bodies when Vesta's basaltic crust was preserved? Where is the missing Psyche family of differentiated asteroids including the complementary mantle and crustal asteroids [1]? Why are <span class="hlt">meteorites</span> derived from far more differentiated parent bodies than chondritic parent bodies even though C and S class chondritic asteroids dominate the asteroid belt? New paradigm. Our studies of <span class="hlt">meteorites</span>, <span class="hlt">impact</span> modeling, and dynamical studies suggest a new paradigm in which differentiated asteroids accreted at 1--2 au less than 2 Myr after CAI formation [2]. They were rapidly melted by 26Al and disrupted by hit-and-run <span class="hlt">impacts</span> [3] while still molten or semi-molten when planetary embryos were accreting. Metallic Fe-Ni bodies derived from core material cooled rapidly with little or no silicate insulation less than 4 Myr after CAI formation [4]. Fragments of differentiated planetesimals were subsequently tossed into the asteroid belt. <span class="hlt">Meteorite</span> evidence for early disruption of differentiated asteroids. If iron <span class="hlt">meteorites</span> were samples of Fe-Ni cores of bodies that cooled slowly inside silicate mantles over ˜50--100 Myr, irons from each core would have</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19860022877','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19860022877"><span>Nuclide production in (very) small <span class="hlt">meteorites</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Arnold, J. R.; Nishiizumi, K.</p> <p>1986-01-01</p> <p>One of the most interesting open questions in the study of cosmic-ray effects in <span class="hlt">meteorites</span> is the expected behavior of objects which are very small compared to the mean interaction length of primary galactic cosmic ray (GCR) particles. A reasonable limit might be a pre-atmospheric radius of 5 gram/cm(2), or 1.5 cm for chondrites. These are interesting for at least three reasons: (1) this is a limiting case for <span class="hlt">large</span> objects, and can help us make better models; (2) this size is intermediate between usual <span class="hlt">meteorites</span> and irradiated grams (spherules); and (3) these are the most likely objects to show solar cosmic ray (SCR) effects. Reedy (1984) has recently proposed a model for production by GCR of radioactive and stable nuclides in spherical <span class="hlt">meteorites</span>. Very small objects are expected to deviate from this model in the direction of fewer secondary particles (larger spectral shape parameter), at all depths. The net effect will be significantly lower production of such low-energy products as Mn-53 and Al-26. The SCR production of these and other nuclides will be lower, too, because <span class="hlt">meteorite</span> orbits extend typically out into the asteroid belt, and the mean SCR flux must fall off approximately as r(-2) with distance from the Sun. Kepler's laws insure that for such orbits most of the exposure time is spent near aphelion. None the less the equivalent mean exposure distance, R(exp), is slightly less than the semimajor axis A because of the weighting by R(-2). For the three <span class="hlt">meteorite</span> orbits we have, R(exp) has a narrow range, from about 1.6 to 2.1 a.u. This is probably true for the great majority of <span class="hlt">meteorites</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.1213P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.1213P"><span>Huge waves of <span class="hlt">meteorite</span> origin</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pelinovsky, Efim; Kozelkov, Andrey; Kurkin, Andrey</p> <p>2016-04-01</p> <p>Asteroid and <span class="hlt">meteorite</span> risk is now actively investigated in various aspects. If the <span class="hlt">meteorite</span> falls in the ocean it can generate huge waves with heights exceeded 10 m. For whole history about 10-20 events related with entry of <span class="hlt">meteorite</span> in water are known. The last event occurred on February 15, 2013 when the <span class="hlt">meteorite</span> exploded in sky of Chelyabinsk (Russia) and its big piece entered in the Chebarkul Lake. Very often, huge waves of <span class="hlt">meteorite</span> origin are computed using the conception of equivalent (parametrical) source, whose parameters are determined through <span class="hlt">meteorite</span> characteristics. Recently, direct methods based on numerical simulations of the Reynolds-averaged Navier-Stokes equations (RANS) have been applied to study wave processes generated by the entry of <span class="hlt">meteorite</span>. These approaches and their applications to the historic events are discussed in paper.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19890017427','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19890017427"><span>Antarctic <span class="hlt">Meteorite</span> Location Map Series</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Schutt, John (Editor); Fessler, Brian (Editor); Cassidy, William (Editor)</p> <p>1989-01-01</p> <p>Antarctica has been a prolific source of <span class="hlt">meteorites</span> since <span class="hlt">meteorite</span> concentrations were discovered in 1969. The Antarctic Search For <span class="hlt">Meteorites</span> (ANSMET) project has been active over much of the Trans-Antarctic Mountain Range. The first ANSMET expedition (a joint U.S.-Japanese effort) discovered what turned out to be a significant concentration of <span class="hlt">meteorites</span> at the Allan Hills in Victoria Land. Later reconnaissance in this region resulted in the discovery of <span class="hlt">meteorite</span> concentrations on icefields to the west of the Allan Hills, at Reckling Moraine, and Elephant Moraine. Antarctic <span class="hlt">meteorite</span> location maps (reduced versions) of the Allan Hills main, near western, middle western, and far western icefields and the Elephant Moraine icefield are presented. Other Antarctic <span class="hlt">meteorite</span> location maps for the specimens found by the ANSMET project are being prepared.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015M%26PS...50.1662R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015M%26PS...50.1662R"><span>The <span class="hlt">Meteoritical</span> Bulletin, No. 102</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ruzicka, Alex; Grossman, Jeffrey; Bouvier, Audrey; Herd, Christopher D. K.; Agee, Carl B.</p> <p>2015-09-01</p> <p><span class="hlt">Meteoritical</span> Bulletin 102 contains 3141 <span class="hlt">meteorites</span> including 12 falls (Boumdeid (2003), Boumdeid (2011), Braunschweig, Chelyabinsk, Dongyang, Draveil, Heyetang, Indian Butte, Katol, Ladkee, Ouadangou, Xining), with 2611 ordinary chondrites, 264 HED achondrites, 124 carbonaceous chondrites, 30 ureilites, 20 Martian <span class="hlt">meteorites</span>, 16 primitive achondrites, 16 Rumuruti chondrites, 15 mesosiderites, 12 iron <span class="hlt">meteorites</span>, 10 lunar <span class="hlt">meteorites</span>, 9 enstatite chondrites, 4 enstatite achondrites, 4 Pallasites, 4 ungrouped achondrites, and 2 angrites, and with 1708 from Antarctica, 956 from Africa, 294 from South America, 126 from Asia, 47 from North America, 6 from Europe (including Russia), and 4 from Oceania. Information about approved <span class="hlt">meteorites</span> can be obtained from the <span class="hlt">Meteoritical</span> Bulletin Database (MBD) available on line at <url href="http://www.lpi.usra.edu/meteor/">http://www.lpi.usra.edu/meteor/.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19900018247','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19900018247"><span>Carbon in primitive <span class="hlt">meteorites</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kerridge, John F.</p> <p>1990-01-01</p> <p>No <span class="hlt">meteorites</span> are truly primitive, in the sense of being pristine collections of interstellar grains or solar-nebular condensates. Nonetheless, some chrondritic <span class="hlt">meteorites</span> have been so little altered by secondary processing that they are commonly termed primitive and it is almost a definition of such chondrites that they contain significant quantities of carbon. Most of that carbon is of apparently local, i.e., solar-system, origin but a proportion that ranges from trace, in some cases, to minor, in others, is believed to be exotic, i.e., of circumstellar or interstellar origin, and it is upon such material that researchers focus here. The nature of the <span class="hlt">meteoritic</span> samples and the techniques used to analyse them are briefly discussed and the observational record is surveyed. Clearly, the study of exotic carbon preserved in <span class="hlt">meteorites</span> has been informative about sites of nucleosynthesis, processes of nucleation and growth of grains in stellar outflows, grain survival in the interstellar medium, and many other topics of astrophysical significance. Much more work, particularly of an interdisciplinary nature remains to be done, however.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1995Metic..30Q.540M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1995Metic..30Q.540M"><span>Collisional Records in Iron <span class="hlt">Meteorites</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Marti, K.; Lavielle, B.; Jeannot, J.-P.</p> <p>1995-09-01</p> <p>The asteroid belt is considered to be the ultimate source of iron <span class="hlt">meteorites</span> and it would be of considerable interest to obtain a chronology of break-ups of asteroidal objects. However, as multiple fragmentation of such objects did likely occur, the exposure ages date the break-off of iron masses from shielded locations within the immediate parent object. <span class="hlt">Meteorites</span> which were fragmented in more than one collisional event may have recorded integral effects of cosmic ray interactions in varying geometrical configuration and individual stages may be difficult to unravel; we term such exposure histories "complex". Exposure age histograms based on potassium ages have been discussed by Voshage [1] and he concluded that irons of groups IIIA and IIIB reveal similar histograms and probably were derived from the same parent body. He also noted a cluster for group IVA members ,but no clear evidence for other clusters. We present the collisional evidence based on published noble gas data, coupled to the new production rates which we calculate for central locations, adjusted for off-center locations whenever concentration profiles can be inferred. Unlike potassium ages which show <span class="hlt">large</span> uncertainties for ages < 300 Ma, T38 ages can be obtained for all iron <span class="hlt">meteorites</span>. We note, however,that T38 values of five "old" irons are systematically 15% lower than potassium ages. We confirm the evidence for stochastic events for IIIAB and IVA irons. The statistics are improved because of the larger data base. There are interesting clusters also among ages < 100 Ma, in the range which overlaps the histograms of chondrites. Recent reports [2,3] of H-chondritic inclusions in IIE irons, whose exposure ages are consistent with H-chondrite clusters, point to a genetic link. Group IIAB reveals two clusters with T38 < 100 Ma, and both events appear to involve also IIE irons. Clusterings of two thirds of group IIIE members and of group IID irons appear significant. The youngest IVB ages coincide</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20130010126&hterms=magnetite+alteration+basalt&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dmagnetite%2Balteration%2Bbasalt','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20130010126&hterms=magnetite+alteration+basalt&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dmagnetite%2Balteration%2Bbasalt"><span>Mineralogy of <span class="hlt">Meteorite</span> Groups</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Rubin, Alan E.</p> <p>1997-01-01</p> <p>Approximately 275 mineral species have been identified in <span class="hlt">meteorites</span>, reflecting diverse redox environments, and, in some cases, unusual nebular formation conditions. Anhydrous ordinary, carbonaceous and R chondrites contain major olivine, pyroxene and plagioclase; major opaque phases include metallic Fe-Ni, troilite and chromite. Primitive achondrites are mineralogically similar. The highly reduced enstatite chondrites and achondrites contain major enstatite, plagioclase, free silica and kamacite as well as nitrides, a silicide and Ca-, Mg-, Mn-, Na-, Cr-, K- and Ti-rich sulfides. Aqueously altered carbonaceous chondrites contain major amounts of hydrous phyllosilicates, complex organic compounds, magnetite, various sulfates and sulfides, and carbonates. In addition to kamacite and taenite, iron <span class="hlt">meteorites</span> contain carbides, elemental C, nitrides, phosphates, phosphides, chromite and sulfides. Silicate inclusions in IAB/IIICD and lIE iron <span class="hlt">meteorites</span> consist of mafic silicates, plagioclase and various sulfides, oxides and phosphates. Eucrites, howardites and diogenites have basaltic to orthopyroxenitic compositions and consist of major pyroxene and calcic plagioclase and several accessory oxides. Ureilttes .are made up mainly of calcic, chromian olivine and low-Ca clinopyroxene embedded in a carbonaceous matrix; accessory phases include the C polymorphs graphite, diamond, lonsdaleite and chaoite as well as metallic Fe-Ni, troilite and halides. Angrites are achondrites rich in fassaitic pyroxene (i.e. , AI-Ti diopside); minor olivine with included magnesian kirschsteinite is also present. Martian <span class="hlt">meteorites</span> comprise basalts, Iherzolites, a dunite and an orthopyroxenite. Major phases include various pyroxenes and olivine; minor to accessory phases include various sulfides, magnetite, chromite and Ca-phosphates. Lunar <span class="hlt">meteorites</span> comprise mare basalts with major augite and calcic plagioclase and anorthositic breccias with major calcic plagioclase. Several <span class="hlt">meteoritic</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002cosp...34E2022H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002cosp...34E2022H"><span>The Big Splash: Tsunami from <span class="hlt">Large</span> Asteroid and Comet <span class="hlt">Impacts</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hills, J.; Goda, M.</p> <p></p> <p>Asteroid and comet <span class="hlt">impacts</span> produce a <span class="hlt">large</span> range of damage. Tsunami may produce most of the economic damage in <span class="hlt">large</span> asteroid <span class="hlt">impacts</span>. <span class="hlt">Large</span> asteroid <span class="hlt">impacts</span> produce worldwide darkness lasting several months that may kill more people by mass starvation, especially in developing countries, than would tsunami, but the dust should not severely affect economic infrastructure. The tsunami may even kill more people in developed countries with <span class="hlt">large</span> coastal populations, such as the United States, than the starvation resulting from darkness. We have been determining which regions of Earth are most susceptible to asteroid tsunami by simulating the effect of a <span class="hlt">large</span> asteroid <span class="hlt">impact</span> into mid-ocean. We have modeled the effect of midAtlantic and midPacific <span class="hlt">impacts</span> that produce craters 300 to 150 km in diameter. A KT-size impactor would cause the larger of these craters. We used a computer code that has successfully determined the runup and inundation from historical earthquake-generated tsunami. The code has been progressively improved to eliminate previous problems at the domain boundaries, so it now runs until the tsunami inundation is complete. We find that the larger of these two midAtlantic <span class="hlt">impacts</span> would engulf the entire Florida Peninsula. The smaller one would inundate the eastern third of the peninsula while a tsunami passing through the Gulf of Cuba would inundate the West Coast of Florida. <span class="hlt">Impacts</span> at three different sites in the Pacific show the great vulnerability of Tokyo and its surroundings to asteroid tsunami. Mainland Asia is relatively protected from asteroid tsunami. In Europe, the Iberian Peninsula and the Atlantic Providences of France are highly vulnerable to asteroid tsunami.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20080031650','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20080031650"><span>Previously Unrecognized <span class="hlt">Large</span> Lunar <span class="hlt">Impact</span> Basins Revealed by Topographic Data</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Frey, Herbert V.</p> <p>2008-01-01</p> <p>The discovery of a <span class="hlt">large</span> population of apparently buried <span class="hlt">impact</span> craters on Mars, revealed as Quasi- Circular Depressions (QCDs) in Mars Orbiting Laser Altimeter (MOLA) data [1,2,3] and as Circular Thin Areas (CTAs) [4] in crustal thickness model data [5] leads to the obvious question: are there unrecognized <span class="hlt">impact</span> features on the Moon and other bodies in the solar system? Early analysis of Clementine topography revealed several <span class="hlt">large</span> <span class="hlt">impact</span> basins not previously known [6,7], so the answer certainly is "Yes." How <span class="hlt">large</span> a population of previously undetected <span class="hlt">impact</span> basins, their size frequency distribution, and how much these added craters and basins will change ideas about the early cratering history and Late Heavy Bombardment on the Moon remains to be determined. Lunar Orbiter Laser Altimeter (LOLA) data [8] will be able to address these issues. As a prelude, we searched the state-of-the-art global topographic grid for the Moon, the Unified Lunar Control Net (ULCN) [9] for evidence of <span class="hlt">large</span> <span class="hlt">impact</span> features not previously recognized by photogeologic mapping, as summarized by Wilhelms [lo].</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20100036449','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20100036449"><span>Chiral Biomarkers in <span class="hlt">Meteorites</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hoover, Richard B.</p> <p>2010-01-01</p> <p>The chirality of organic molecules with the asymmetric location of group radicals was discovered in 1848 by Louis Pasteur during his investigations of the rotation of the plane of polarization of light by crystals of sodium ammonium paratartrate. It is well established that the amino acids in proteins are exclusively Levorotary (L-aminos) and the sugars in DNA and RNA are Dextrorotary (D-sugars). This phenomenon of homochirality of biological polymers is a fundamental property of all life known on Earth. Furthermore, abiotic production mechanisms typically yield recemic mixtures (i.e. equal amounts of the two enantiomers). When amino acids were first detected in carbonaceous <span class="hlt">meteorites</span>, it was concluded that they were racemates. This conclusion was taken as evidence that they were extraterrestrial and produced by abiologically. Subsequent studies by numerous researchers have revealed that many of the amino acids in carbonaceous <span class="hlt">meteorites</span> exhibit a significant L-excess. The observed chirality is much greater than that produced by any currently known abiotic processes (e.g. Linearly polarized light from neutron stars; Circularly polarized ultraviolet light from faint stars; optically active quartz powders; inclusion polymerization in clay minerals; Vester-Ulbricht hypothesis of parity violations, etc.). This paper compares the measured chirality detected in the amino acids of carbonaceous <span class="hlt">meteorites</span> with the effect of these diverse abiotic processes. IT is concluded that the levels observed are inconsistent with post-arrival biological contamination or with any of the currently known abiotic production mechanisms. However, they are consistent with ancient biological processes on the <span class="hlt">meteorite</span> parent body. This paper will consider these chiral biomarkers in view of the detection of possible microfossils found in the Orgueil and Murchison carbonaceous <span class="hlt">meteorites</span>. Energy dispersive x-ray spectroscopy (EDS) data obtained on these morphological biomarkers will be</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFMGP33B..03L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFMGP33B..03L"><span>Magnetic Field Anomalies Above <span class="hlt">Large</span> Martian <span class="hlt">Impact</span> Structures</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Langlais, B.; Ostanciaux; Thébault, E.</p> <p>2008-12-01</p> <p>The Mars Global Surveyor NASA mission revealed the complex nature of the lithospheric magnetic field of Mars. Intense anomalies are located above the southern cratered highlands, while the giant <span class="hlt">impact</span> basins (Hellas, Argyre, Utopia) and the northern smoothed lowlands do not show significant anomalies. Here we study the magnetic signal above <span class="hlt">large</span> <span class="hlt">impact</span> craters, with diameters ranging between 100 and 2000 km. Magnetic measurements are carefully screened and selected to avoid non static features. Then the mean magnetic field is evaluated both inside each crater rim and in its immediate vicinity, within one crater radius. The ratio of these two quantities helps to determine which craters modified the magnetic properties of the pre-<span class="hlt">impact</span> lithosphere. In addition, this technique allows the <span class="hlt">impacts</span> located in the strongly magnetized Terra Sirenum and Terra Cimmeria to be studied. Results of this study, as well as comparison of the magnetic measurements to predicted ones for different pre-<span class="hlt">impact</span> magnetization directions will be presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19940030921','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19940030921"><span>Effects due to overlapping <span class="hlt">large</span> <span class="hlt">impact</span> basins on Mars</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Frey, Herbert; Reidy, Anne Marie; Roark, James H.; Stockman, Stephanie</p> <p>1994-01-01</p> <p>Many ancient, highly degraded <span class="hlt">large</span> <span class="hlt">impact</span> basins exist on Mars. In many cases these basins overlap or are overlapped by more easily observed, presumably younger, <span class="hlt">impact</span> basins. While <span class="hlt">impact</span> basin overlap is becoming more recognized, the effects of such overlap have only occassionally been described. Such effects will depend on a variety of factors including the absolute and relative size of the basins, the degree of overlap, the state of the lithosphere and its thermal gradient at the time of <span class="hlt">impact</span>, and the time between <span class="hlt">impacts</span>. There now exists enough evidence for overlapping basins of different sizes that some of these can be discussed. This paper highlights some examples of the obvious effects of basin overlap.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EPSC....8..797G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EPSC....8..797G"><span>The Chelyabinsk Fireball and <span class="hlt">Meteorite</span>.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Galimov, E. M.; Kolotov, V. P.; Nazarov, M. A.; Kostitsyn, Yu. A.; Kubrakova, I. V.; Kononkova, N. N.; Alekseev, I. A.; Koshkarov, L. L.; Badyukov, D. D.; Sevastyanov, V. S.; Pillinger, C. T.; Greenwood, R. C.; Verchovsky, A. B.; Johnson, D.; Tindle, A. G.; Buikin, A.</p> <p>2013-09-01</p> <p>On 15th February 2013 an extraordinarily <span class="hlt">large</span> fireball detonated in the atmosphere over Chelyabinsk, Russia, with a total energy equivalent to 440 kilotons of TNT. It was the most energetic natural atmospheric occurrence since the Tunguska incident in 1908 and caused many injuries and extensive property damage. Geochemical and isotopic data show that the <span class="hlt">meteorite</span> samples recovered after the event are LL5 type ordinary chondrites with a S4 shock history. The many thousands of small fragments comprise either of two distinct lithologies: a hondrule-rich light coloured material (~66%) or a less-abundant (~34%) dark shock-melt rather than mixtures. The break-up of the object, i.e. the explosion, appears to have been dictated by the object's pre-entry two component structure, which probably formed during a major collision in the asteroid belt 290 My ago. The Chelyabinsk event demonstrates that effective asteroid-hazard mitigation requires structural knowledge of threatening body similar to that obtained by the Hayabusa spacecraft at asteroid Itokawa. The observations made for Chelyabinsk suggest that the Tunguska bolide may also have been a structurally weakened object. Studies of the samples are still at an early stage. A full petrological description of the <span class="hlt">meteorite</span> lithologies, geochemical and isotopic analyses, chronological data and fission track information will be available by the time of the conference</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.8372G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.8372G"><span>How Venus surface conditions evolution can be affected by <span class="hlt">large</span> <span class="hlt">impacts</span> at long timescales?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gillmann, Cedric; Golabek, Gregor; Tackley, Paul</p> <p>2016-04-01</p> <p>Using numerical simulations, we investigate how the evolution of Venus' atmosphere and mantle is modified by <span class="hlt">large</span> <span class="hlt">impacts</span>, during Late Veneer and Late Heavy Bombardment. We propose a coupled model of mantle/atmosphere feedback. We also focus on volatile fluxes in and out of the atmosphere: atmospheric escape and degassing. The solid part of the planet is simulated using the StagYY code (Armann and Tackley, 2012) and releases volatiles into the atmosphere through degassing. Physical properties are depth-dependent. The assumed rheology is Newtonian diffusion creep plus plastic yielding. Atmospheric escape modeling involves two different aspects: hydrodynamic escape (0-500 Myr) and non-thermal escape mechanisms (dominant post 4 Ga). Hydrodynamic escape is the massive outflow of volatiles occurring when the solar energy input is strong. Post 4 Ga escape from non-thermal processes is comparatively low. The evolution of surface temperature is calculated from the greenhouse effect dependent on CO2 and water concentrations in the atmosphere, using a one-dimensional gray radiative-convective atmosphere model. It allows us to complete the coupling of the model: feedback of the atmosphere on the mantle is obtained by using surface temperature as a boundary condition for the convection. <span class="hlt">Large</span> <span class="hlt">impacts</span> are capable of contributing to (i) atmospheric escape, (ii) volatile replenishment and (iii) energy transfer to the mantle of the solid planet. We test a wide range of impactor parameters (size, velocity, timing) and different assumptions related to <span class="hlt">impact</span> erosion (Shuvalov, 2010). For energy transfer, 2D distribution of the thermal anomaly created by the <span class="hlt">impact</span> is used, leading to melting and subjected to transport by the mantle convection. Small (0-50 km) <span class="hlt">meteorites</span> have a negligible effect on the global scale: they only affect the <span class="hlt">impact</span> point and do not have lasting consequences on surface conditions. Medium ones (50-150 km) have strong short term influence through volatile</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014MSAIS..26...62D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014MSAIS..26...62D"><span>Search for <span class="hlt">meteorites</span> around Kamil crater and preliminary radiometric measurements</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Di Martino, M.; Taricco, C.; Colombetti, P.; Cora, A.; Mancuso, S.</p> <p></p> <p>About 1600 kg of iron <span class="hlt">meteorite</span> fragments were found in and around the Kamil <span class="hlt">impact</span> crater by an Italian-Egyptian geophysical team in February 2009 and February 2010. Two samples of the Gebel Kamil <span class="hlt">meteorite</span> (one shrapnel and a piece of the only one individual that has been found) were measured at Monte dei Cappuccini Laboratory (INAF) in Torino, using a selective gamma spectrometer and 26Al cosmogenic activity was detected in both fragments.</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/2017M%26PS...52.2017T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017M%26PS...52.2017T"><span>High-pressure minerals in shocked <span class="hlt">meteorites</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tomioka, Naotaka; Miyahara, Masaaki</p> <p>2017-09-01</p> <p>Heavily shocked <span class="hlt">meteorites</span> contain various types of high-pressure polymorphs of major minerals (olivine, pyroxene, feldspar, and quartz) and accessory minerals (chromite and Ca phosphate). These high-pressure minerals are micron to submicron sized and occur within and in the vicinity of shock-induced melt veins and melt pockets in chondrites and lunar, howardite-eucrite-diogenite (HED), and Martian <span class="hlt">meteorites</span>. Their occurrence suggests two types of formation mechanisms (1) solid-state high-pressure transformation of the host-rock minerals into monomineralic polycrystalline aggregates, and (2) crystallization of chondritic or monomineralic melts under high pressure. Based on experimentally determined phase relations, their formation pressures are limited to the pressure range up to 25 GPa. Textural, crystallographic, and chemical characteristics of high-pressure minerals provide clues about the <span class="hlt">impact</span> events of <span class="hlt">meteorite</span> parent bodies, including their size and mutual collision velocities and about the mineralogy of deep planetary interiors. The aim of this article is to review and summarize the findings on natural high-pressure minerals in shocked <span class="hlt">meteorites</span> that have been reported over the past 50 years.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EM%26P..120..101T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EM%26P..120..101T"><span>On a Novel Geometric Analysis of the Bacubirito <span class="hlt">Meteorite</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Terán-Bobadilla, E.; Abundis-Patiño, J. H.; Añorve, C.; Moraila, C. R.; Ortega-Gutiérrez, F.; Aragón-Calvo, M. A.</p> <p>2017-08-01</p> <p>Tridimensional model with <span class="hlt">large</span> level of detail and reliability of the Bacubirito <span class="hlt">meteorite</span> is determined by laser scanner measurements. By means of this model and densities published in the literature, we estimate the mass, main geometrical quantities, and regmaglypts distribution on the <span class="hlt">meteorite</span>. A Monte Carlo method is proposed for uncertainty estimations of the derived geometrical magnitudes. The Bacubirito <span class="hlt">meteorite</span> mass is m = 19.43 ± 0.51 tons with a maximum length of 4.130 ± 0.005 m; Bacubirito is set as the world's fifth largest and the longest reported to date.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19860019351','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19860019351"><span>Trace elements in Antarctic <span class="hlt">meteorites</span>: Weathering and genetic information</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lipschutz, M. E.</p> <p>1986-01-01</p> <p>Antarctic <span class="hlt">meteorite</span> discoveries have created great scientific interest due to the <span class="hlt">large</span> number of specimens recovered (approximately 7000) and because included are representatives of hitherto rare or unknown types. Antarctic <span class="hlt">meteorites</span> are abundant because they have fallen over long periods and were preserved, transported, and concentrated by the ice sheets. The weathering effects on the Antarctic <span class="hlt">meteorites</span> are described. Weathering effects of trace element contents of H5 chondrites were studied in detail. The results are examined. The properties of Antarctic finds and non-Antarctic falls are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015M%26PS...50..305N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015M%26PS...50..305N"><span>Mineralogy, petrology, and distribution of <span class="hlt">meteorites</span> at the Whitecourt crater, Alberta, Canada</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Newman, Jennifer D.; Herd, Christopher D. K.</p> <p>2015-02-01</p> <p>The Whitecourt <span class="hlt">meteorite</span> <span class="hlt">impact</span> crater, Alberta, Canada is a rare example of a well-preserved small <span class="hlt">impact</span> structure, with which thousands of <span class="hlt">meteorite</span> fragments are associated. As such, this crater represents a unique opportunity to investigate the effect of a low-energy <span class="hlt">impact</span> event on an <span class="hlt">impacting</span> iron bolide. Excellent documentation of <span class="hlt">meteorite</span> fragment locations and characteristics has generated a detailed distribution map of both shrapnel and regmaglypted <span class="hlt">meteorite</span> types. The <span class="hlt">meteorites</span>' distribution, and internal and external characteristics support a low-altitude breakup of the impactor which caused atmospherically ablated (regmaglypted) <span class="hlt">meteorites</span> to fall close to the crater and avoid <span class="hlt">impact</span>-related deformation. In contrast, shrapnel fragments sustained deformation at macro- and microscales resulting from the catastrophic disruption of the impactor. The impactor was significantly fragmented along pre-existing planes of weakness, including kamacite lamellae and inclusions, resulting in a bias toward low-mass (<100 g) fragments. <span class="hlt">Meteorite</span> mineralogy was investigated and the accessory minerals were found to be dominated by sulfides and phosphides with rare carlsbergite, consistent with other low-Ni IIIAB iron <span class="hlt">meteorites</span>. Considerations of the total mass of <span class="hlt">meteoritic</span> material recovered at the site relative to the probable fraction of the impactor that was preserved based on modeling suggests that the crater was formed by a higher velocity, lower mass impactor than previously inferred.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19899478','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19899478"><span>[<span class="hlt">Impacts</span> of <span class="hlt">large</span> hydropower station on benthic algal communities].</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Jia, Xing-Huan; Jiang, Wan-Xiang; Li, Feng-Qing; Tang, Tao; Duan, Shu-Gui; Cai, Qing-Hua</p> <p>2009-07-01</p> <p>To investigate the <span class="hlt">impacts</span> of <span class="hlt">large</span> hydropower station in Gufu River on benthic algae, monthly samplings were conducted from September 2004 to June 2007 at the site GF04 which was <span class="hlt">impacted</span> by the hydropower station, with the site GL03 in Gaolan River as reference. During sampling period, no significant differences were observed in the main physicochemical variables between GF04 and GL03, but the hydrodynamics differed significantly. GL03 was basically at a status of slow flow; while GF04, owing to the discharging from the reservoir, was at a riffle status during more than 60% of the sampling period. Such a difference in hydrodynamics induced significant differences in the community similarity of benthic algae and the relative abundance of unattached diatoms, erect diatoms, and stalked diatoms between GF04 and GL03, which could better reflect the <span class="hlt">impacts</span> of irregular draw-off by <span class="hlt">large</span> hydropower station on river eco-system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Sci...354..878M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Sci...354..878M"><span>The formation of peak rings in <span class="hlt">large</span> <span class="hlt">impact</span> craters</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Morgan, Joanna V.; Gulick, Sean P. S.; Bralower, Timothy; Chenot, Elise; Christeson, Gail; Claeys, Philippe; Cockell, Charles; Collins, Gareth S.; Coolen, Marco J. L.; Ferrière, Ludovic; Gebhardt, Catalina; Goto, Kazuhisa; Jones, Heather; Kring, David A.; Le Ber, Erwan; Lofi, Johanna; Long, Xiao; Lowery, Christopher; Mellett, Claire; Ocampo-Torres, Rubén; Osinski, Gordon R.; Perez-Cruz, Ligia; Pickersgill, Annemarie; Poelchau, Michael; Rae, Auriol; Rasmussen, Cornelia; Rebolledo-Vieyra, Mario; Riller, Ulrich; Sato, Honami; Schmitt, Douglas R.; Smit, Jan; Tikoo, Sonia; Tomioka, Naotaka; Urrutia-Fucugauchi, Jaime; Whalen, Michael; Wittmann, Axel; Yamaguchi, Kosei E.; Zylberman, William</p> <p>2016-11-01</p> <p><span class="hlt">Large</span> <span class="hlt">impacts</span> provide a mechanism for resurfacing planets through mixing near-surface rocks with deeper material. Central peaks are formed from the dynamic uplift of rocks during crater formation. As crater size increases, central peaks transition to peak rings. Without samples, debate surrounds the mechanics of peak-ring formation and their depth of origin. Chicxulub is the only known <span class="hlt">impact</span> structure on Earth with an unequivocal peak ring, but it is buried and only accessible through drilling. Expedition 364 sampled the Chicxulub peak ring, which we found was formed from uplifted, fractured, shocked, felsic basement rocks. The peak-ring rocks are cross-cut by dikes and shear zones and have an unusually low density and seismic velocity. <span class="hlt">Large</span> <span class="hlt">impacts</span> therefore generate vertical fluxes and increase porosity in planetary crust.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27856906','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27856906"><span>The formation of peak rings in <span class="hlt">large</span> <span class="hlt">impact</span> craters.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Morgan, Joanna V; Gulick, Sean P S; Bralower, Timothy; Chenot, Elise; Christeson, Gail; Claeys, Philippe; Cockell, Charles; Collins, Gareth S; Coolen, Marco J L; Ferrière, Ludovic; Gebhardt, Catalina; Goto, Kazuhisa; Jones, Heather; Kring, David A; Le Ber, Erwan; Lofi, Johanna; Long, Xiao; Lowery, Christopher; Mellett, Claire; Ocampo-Torres, Rubén; Osinski, Gordon R; Perez-Cruz, Ligia; Pickersgill, Annemarie; Poelchau, Michael; Rae, Auriol; Rasmussen, Cornelia; Rebolledo-Vieyra, Mario; Riller, Ulrich; Sato, Honami; Schmitt, Douglas R; Smit, Jan; Tikoo, Sonia; Tomioka, Naotaka; Urrutia-Fucugauchi, Jaime; Whalen, Michael; Wittmann, Axel; Yamaguchi, Kosei E; Zylberman, William</p> <p>2016-11-18</p> <p><span class="hlt">Large</span> <span class="hlt">impacts</span> provide a mechanism for resurfacing planets through mixing near-surface rocks with deeper material. Central peaks are formed from the dynamic uplift of rocks during crater formation. As crater size increases, central peaks transition to peak rings. Without samples, debate surrounds the mechanics of peak-ring formation and their depth of origin. Chicxulub is the only known <span class="hlt">impact</span> structure on Earth with an unequivocal peak ring, but it is buried and only accessible through drilling. Expedition 364 sampled the Chicxulub peak ring, which we found was formed from uplifted, fractured, shocked, felsic basement rocks. The peak-ring rocks are cross-cut by dikes and shear zones and have an unusually low density and seismic velocity. <span class="hlt">Large</span> <span class="hlt">impacts</span> therefore generate vertical fluxes and increase porosity in planetary crust. Copyright © 2016, American Association for the Advancement of Science.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUSM.V13E..07L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUSM.V13E..07L"><span>Germanium Isotopic Fractionation in Iron <span class="hlt">Meteorites</span> : Comparison with Experimental Data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Luais, B.; Toplis, M.; Tissandier, L.; Roskosz, M.</p> <p>2009-05-01</p> <p> t, values being isotopically lighter than the reference Ge standard after 2 hours (δ74Ge ˜ - 0.5 ‰), reaching a δ 74Ge of ˜ +3‰ after 60 hours. For a series of experiments running for 24 hours, an increase in δ74Ge (from ˜ -0.3 to +10‰) is observed with increasing fO2. The slight enrichment of light isotopes in the metallic phase at very low fO2 and short t could reflect the consequence of Ge diffusion from the silicate to the metal. This small extent of fractionation can be compared with the nearly constant δ74Ge values in magmatic Fe-<span class="hlt">meteorites</span>, indicating that diffusion-induced metal-silicate segregation would produce very small if detectable isotopic fractionation. Therefore, Ge isotopic composition of Fe-<span class="hlt">meteorites</span> would be close to that of their parent bodies. On the other hand, strong enrichment in heavy isotopes at high fO2 and/or long t is indicative of Ge loss by evaporation, and would explain the <span class="hlt">large</span> isotopic fractionation toward heavy δ 74Ge values for the IIE non-magmatic irons, interpreted as <span class="hlt">impact</span>-induced evaporation of Ge. [1] Luais B (2007) EPSL 262 p. 21</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1997JIMO...25..222G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1997JIMO...25..222G"><span>Human Casualties in <span class="hlt">Impact</span> Events</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gritzner, C.</p> <p>1997-10-01</p> <p>It is widespread error to believe that people were never killed by <span class="hlt">meteorites</span>. It was concluded that there no human casualties due to <span class="hlt">meteorite</span> falls because there were no reports about such incidents, but there are reports of these rare events. The statement of no one ever being killed by a <span class="hlt">meteorite</span> may intend that the danger even of asteroid and comet <span class="hlt">impacts</span> onto the Earth is only fiction, but the danger is real. It is a low-probability-high-consequence event for <span class="hlt">large</span> impactors (more than 1 km). Even from <span class="hlt">meteorites</span>, however, people were reported struck to death. This article gives a survey over reports of human casualties from 616 A.D. well to our century.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19980037932','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19980037932"><span>The Thermal and Radiation Exposure History of Lunar <span class="hlt">Meteorites</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Benoit, Paul H.; Sears, Derek W. G.; Symes, Steven J. K.</p> <p>1996-01-01</p> <p>We have measured the natural and induced thermoluminescence (TL) of seven lunar <span class="hlt">meteorites</span> in order to examine their crystallization, irradiation, and recent thermal histories. Lunar <span class="hlt">meteorites</span> have induced TL properties similar to Apollo samples of the same provenance (highland or mare), indicating similar crystallization and metamorphic histories. MacAlplne Hills 88104/5 has experienced the greatest degree of <span class="hlt">impact</span>/regolith processing among the highland-dominated <span class="hlt">meteorites</span>. The basaltic breccia QUE 94281 is dominated by mare component but may also contain a significant highland component. For the mare-dominated <span class="hlt">meteorites</span>, EET 87521 may have a significant highland <span class="hlt">impact</span>-melt component, while Asuka 881757 and Y-793169 have been heavily shocked. The thermal history of Y-793169 included slow cooling, either during <span class="hlt">impact</span> processing or during its initial crystallization. Our natural TL data indicate that most lunar <span class="hlt">meteorites</span> have apparently been irradiated in space a few thousand years, with most less than 15,000 a. Elephant Moraine 87521 has the lowest irradiation exposure time, being less than 1,000 a. Either the natural TL of ALHA81005, Asuka 881757 and Y-82192 was only partially reset by lunar ejection or these <span class="hlt">meteorites</span> were in small perihelia orbits (less than or equal to 0.7 AU).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Icar..264..300M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Icar..264..300M"><span>Consequences of <span class="hlt">large</span> <span class="hlt">impacts</span> on Enceladus' core shape</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Monteux, J.; Collins, G. S.; Tobie, G.; Choblet, G.</p> <p>2016-01-01</p> <p>The intense activity on Enceladus suggests a differentiated interior consisting of a rocky core, an internal ocean and an icy mantle. However, topography and gravity data suggests <span class="hlt">large</span> heterogeneity in the interior, possibly including significant core topography. In the present study, we investigated the consequences of collisions with <span class="hlt">large</span> impactors on the core shape. We performed <span class="hlt">impact</span> simulations using the code iSALE2D considering <span class="hlt">large</span> differentiated impactors with radius ranging between 25 and 100 km and <span class="hlt">impact</span> velocities ranging between 0.24 and 2.4 km/s. Our simulations showed that the main controlling parameters for the post-<span class="hlt">impact</span> shape of Enceladus' rock core are the impactor radius and velocity and to a lesser extent the presence of an internal water ocean and the porosity and strength of the rock core. For low energy <span class="hlt">impacts</span>, the impactors do not pass completely through the icy mantle. Subsequent sinking and spreading of the impactor rock core lead to a positive core topographic anomaly. For moderately energetic <span class="hlt">impacts</span>, the impactors completely penetrate through the icy mantle, inducing a negative core topography surrounded by a positive anomaly of smaller amplitude. The depth and lateral extent of the excavated area is mostly determined by the impactor radius and velocity. For highly energetic <span class="hlt">impacts</span>, the rocky core is strongly deformed, and the full body is likely to be disrupted. Explaining the long-wavelength irregular shape of Enceladus' core by <span class="hlt">impacts</span> would imply multiple low velocity (<2.4 km/s) collisions with deca-kilometric differentiated impactors, which is possible only after the LHB period.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015Icar..245..112R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015Icar..245..112R"><span>Space erosion and cosmic ray exposure ages of stony <span class="hlt">meteorites</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rubincam, David Parry</p> <p>2015-01-01</p> <p>Space erosion from dust <span class="hlt">impacts</span> may set upper limits on the cosmic ray exposure (CRE) ages of stony <span class="hlt">meteorites</span>. A meteoroid orbiting within the asteroid belt is bombarded by both cosmic rays and interplanetary dust particles. Galactic cosmic rays penetrate only the first few meters of the meteoroid; deeper regions are shielded. The dust particle <span class="hlt">impacts</span> create tiny craters on the meteoroid's surface, eroding it away by abrasion at a particular rate. Hence a particular point inside a meteoroid accumulates cosmic ray products only until that point wears away, limiting CRE ages. The results would apply to other regolith-free surfaces in the Solar System as well, so that abrasion may set upper CRE age limits which depend on the dusty environment. Calculations based on N. Divine's dust populations and on micrometeoroid cratering indicate that <span class="hlt">large</span> stony meteoroids in circular ecliptic orbits at 2 AU will record 21Ne CRE ages of ∼176 × 106 y if dust masses are in the range 10-21-10-3 kg. This is in broad agreement with the maximum observed CRE ages of ∼100 × 106 y for stones. High erosion rates in the inner Solar System may limit the CRE ages of Near-Earth Asteroids (NEAs) to ∼120 × 106 y. A characteristic of erosion is that the neon concentrations tend to rise as the surface of the <span class="hlt">meteorite</span> is approached, rather than drop off as for <span class="hlt">meteorites</span> with fixed radii. Pristine samples recovered from space may show the rise. If the abrasion rate for stones were a factor of ∼6 larger than found here, then the ages would drop into the 30 × 106 y range, so that abrasion alone might be able to explain many CRE ages. However, there is no strong evidence for higher abrasion rates, and in any case would probably not be fast enough to explain the youngest ages of 0.1-1 × 106 y. Further, space erosion is much too slow to explain the ∼600 × 106 y ages of iron <span class="hlt">meteorites</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014me13.conf...57J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014me13.conf...57J"><span>Recent documented <span class="hlt">meteorite</span> falls, a review of <span class="hlt">meteorite</span> - asteroid links</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jenniskens, P.</p> <p>2014-07-01</p> <p>Since the previous Meteoroids 2010 meeting, 25 confirmed <span class="hlt">meteorite</span> falls have been reported, and one additional <span class="hlt">meteorite</span> was linked tentatively to an observed fireball. All but two of those are classified as ordinary chondrites. Sutter's Mill is a rare carbonaceous chondrite, while Martian <span class="hlt">meteorite</span> Tissint is a Shergotite. For 18 of these falls the associated fireball was observed, but only four provided a pre-atmospheric orbit derived from video and photographic records. Results were published for Sutter's Mill, Novato, and Chelyabinsk, providing insight into the asteroid belt source regions for CM2, L and LL type chondrites, respectively. Proposed <span class="hlt">meteorite</span>-asteroid links are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19770041329&hterms=projectile&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dprojectile','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19770041329&hterms=projectile&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dprojectile"><span>Rochechouart <span class="hlt">meteorite</span> crater - Identification of projectile</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Janssens, M.-J.; Hertogen, J.; Takahashi, H.; Anders, E.; Lambert, P.</p> <p>1977-01-01</p> <p>Ten samples from the 20-km Rochechouart crater in France have been analyzed for the siderophile elements Ir, Os, Re, Au, Pd, Ni, and Ge by radiochemical neutron activation analysis. The up to 1000-fold enrichment of siderophiles correlates with shock effects, increasing in the following order from least to greatest: basement rocks, glass-free breccias, glassy breccias, <span class="hlt">impact</span> melts. The abundance pattern of the <span class="hlt">meteorite</span> was determined from interelement correlations. Several samples fell off the correlation lines, presumably due to recrystallization and weathering of <span class="hlt">impact</span> glasses during the approximately 165-m.y. age of the crater. The most reliable diagnostic elements were Os, Ir, Ni, and Pd; their abundance ratios suggest that the Rochechouart <span class="hlt">meteorite</span> was a IIA iron.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19770041329&hterms=osmium&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dosmium','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19770041329&hterms=osmium&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dosmium"><span>Rochechouart <span class="hlt">meteorite</span> crater - Identification of projectile</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Janssens, M.-J.; Hertogen, J.; Takahashi, H.; Anders, E.; Lambert, P.</p> <p>1977-01-01</p> <p>Ten samples from the 20-km Rochechouart crater in France have been analyzed for the siderophile elements Ir, Os, Re, Au, Pd, Ni, and Ge by radiochemical neutron activation analysis. The up to 1000-fold enrichment of siderophiles correlates with shock effects, increasing in the following order from least to greatest: basement rocks, glass-free breccias, glassy breccias, <span class="hlt">impact</span> melts. The abundance pattern of the <span class="hlt">meteorite</span> was determined from interelement correlations. Several samples fell off the correlation lines, presumably due to recrystallization and weathering of <span class="hlt">impact</span> glasses during the approximately 165-m.y. age of the crater. The most reliable diagnostic elements were Os, Ir, Ni, and Pd; their abundance ratios suggest that the Rochechouart <span class="hlt">meteorite</span> was a IIA iron.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19720030024&hterms=kr&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dkr','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19720030024&hterms=kr&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dkr"><span>Xe and Kr analyses of silicate inclusions from iron <span class="hlt">meteorites</span>.</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bogard, D. D.; Huneke, J. C.; Burnett, D. S.; Wasserburg, G. J.</p> <p>1971-01-01</p> <p>Measurements have been conducted of the amounts and isotopic composition of Xe and Kr in silicate inclusions of several iron <span class="hlt">meteorites</span>. It is shown that the Xe and Kr contents are comparable to chondritic values. The isotopic compositions show trapped gas of both chondritic and atmospheric composition. <span class="hlt">Large</span> spallation effects occur in some of the <span class="hlt">meteorites</span>; the spallation spectra in some instances differ from those reported for stone <span class="hlt">meteorites</span>. In several <span class="hlt">meteorites</span>, very <span class="hlt">large</span> neutron capture effects on Br and I occur. All samples have pronounced Xe129 excesses which apparently indicate differences in the formation times from chondrites of less than about 100 million years; however, the presence of trapped Xe132 in silicates which were enclosed in molten Fe-Ni and cooled slowly proves that they were not entirely outgassed, so that some of the Xe129 excess may also be trapped.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15666244','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15666244"><span>Organic matter in <span class="hlt">meteorites</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Llorca, Jordi</p> <p>2004-12-01</p> <p>Some primitive <span class="hlt">meteorites</span> are carbon-rich objects containing a variety of organic molecules that constitute a valuable record of organic chemical evolution in the universe prior to the appearance of microorganisms. Families of compounds include hydrocarbons, alcohols, aldehydes, ketones, carboxylic acids, amino acids, amines, amides, heterocycles, phosphonic acids, sulfonic acids, sugar-related compounds and poorly defined high-molecular weight macromolecules. A variety of environments are required in order to explain this organic inventory, including interstellar processes, gas-grain reactions operating in the solar nebula, and hydrothermal alteration of parent bodies. Most likely, substantial amounts of such organic materials were delivered to the Earth via a late accretion, thereby providing organic compounds important for the emergence of life itself, or that served as a feedstock for further chemical evolution. This review discusses the organic content of primitive <span class="hlt">meteorites</span> and their relevance to the build up of biomolecules.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19990098008&hterms=emerging+contaminants&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Demerging%2Bcontaminants','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19990098008&hterms=emerging+contaminants&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Demerging%2Bcontaminants"><span>Evidence for Microfossils in Ancient Rocks and <span class="hlt">Meteorites</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hoover, Richard B.; Rozanov, A. Y.; Zhmur, S. I.; Gorlenko, V. M.</p> <p>1998-01-01</p> <p>The McKay et all. detection of chemical biomarkers and possible microfossils in an ancient <span class="hlt">meteorite</span> from Mars (ALH84001) stimulated research in several areas of importance to the newly emerging field of Astrobiology. Their report resulted in a search for additional evidence of microfossils in ancient terrestrial rocks and <span class="hlt">meteorites</span>. These studies of ancient rocks and <span class="hlt">meteorites</span> were conducted independently (and later collaboratively) in the United States and Russia using the SEM, Environmental Scanning Electron Microscope (ESEM), and Field Emission Scanning Electron Microscope (FESEM). We have encountered in-situ in freshly broken carbonaceous chondrites a <span class="hlt">large</span> number of complex microstructures that appear to be lithified microbial forms. The <span class="hlt">meteoritic</span> microstructures have characteristics similar to the lithified remains of filamentous cyanobacteria and bacterial microfossils we have found in ancient phosphorites, ancient graphites and oil shales. Energy Dispersive Spectroscopy (EDS) and Link microprobe analysis shows the possible microfossils have a distribution of chemical elements characteristic of the <span class="hlt">meteorite</span> rock matrix, although many exhibit a superimposed carbon enhancement. We have concluded that the mineralized bodies encountered embedded in the rock matrix of freshly fractured <span class="hlt">meteoritic</span> surfaces can not be dismissed as recent surface contaminants. Many of the forms found in-situ in the Murchison, Efremovka, and Orgueil carbonaceous <span class="hlt">meteorites</span> are strikingly similar to microfossils of coccoid bacteria, cyanobacteria and fungi such as we have found in the Cambrian phosphorites of Khubsugul, Mongolia and high carbon Phanerozoic and Precambrian rocks of the Siberian and Russian Platforms.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19990098008&hterms=filamentous+fungi&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dfilamentous%2Bfungi','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19990098008&hterms=filamentous+fungi&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dfilamentous%2Bfungi"><span>Evidence for Microfossils in Ancient Rocks and <span class="hlt">Meteorites</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hoover, Richard B.; Rozanov, A. Y.; Zhmur, S. I.; Gorlenko, V. M.</p> <p>1998-01-01</p> <p>The McKay et all. detection of chemical biomarkers and possible microfossils in an ancient <span class="hlt">meteorite</span> from Mars (ALH84001) stimulated research in several areas of importance to the newly emerging field of Astrobiology. Their report resulted in a search for additional evidence of microfossils in ancient terrestrial rocks and <span class="hlt">meteorites</span>. These studies of ancient rocks and <span class="hlt">meteorites</span> were conducted independently (and later collaboratively) in the United States and Russia using the SEM, Environmental Scanning Electron Microscope (ESEM), and Field Emission Scanning Electron Microscope (FESEM). We have encountered in-situ in freshly broken carbonaceous chondrites a <span class="hlt">large</span> number of complex microstructures that appear to be lithified microbial forms. The <span class="hlt">meteoritic</span> microstructures have characteristics similar to the lithified remains of filamentous cyanobacteria and bacterial microfossils we have found in ancient phosphorites, ancient graphites and oil shales. Energy Dispersive Spectroscopy (EDS) and Link microprobe analysis shows the possible microfossils have a distribution of chemical elements characteristic of the <span class="hlt">meteorite</span> rock matrix, although many exhibit a superimposed carbon enhancement. We have concluded that the mineralized bodies encountered embedded in the rock matrix of freshly fractured <span class="hlt">meteoritic</span> surfaces can not be dismissed as recent surface contaminants. Many of the forms found in-situ in the Murchison, Efremovka, and Orgueil carbonaceous <span class="hlt">meteorites</span> are strikingly similar to microfossils of coccoid bacteria, cyanobacteria and fungi such as we have found in the Cambrian phosphorites of Khubsugul, Mongolia and high carbon Phanerozoic and Precambrian rocks of the Siberian and Russian Platforms.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFMGC23A0902M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFMGC23A0902M"><span>Local and Regional <span class="hlt">Impacts</span> of <span class="hlt">Large</span> Scale Wind Energy Deployment</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Michalakes, J.; Hammond, S.; Lundquist, J. K.; Moriarty, P.; Robinson, M.</p> <p>2010-12-01</p> <p>The U.S. is currently on a path to produce 20% of its electricity from wind energy by 2030, almost a 10-fold increase over present levels of electricity generated from wind. Such high-penetration wind energy deployment will entail extracting elevated energy levels from the planetary boundary layer and preliminary studies indicate that this will have significant but uncertain <span class="hlt">impacts</span> on the local and regional environment. State and federal regulators have raised serious concerns regarding potential agricultural <span class="hlt">impacts</span> from <span class="hlt">large</span> farms deployed throughout the Midwest where agriculture is the basis of the local economy. The effects of <span class="hlt">large</span> wind farms have been proposed to be both beneficial (drying crops to reduce occurrences of fungal diseases, avoiding late spring freezes, enhancing pollen viability, reducing dew duration) and detrimental (accelerating moisture loss during drought) with no conclusive investigations thus far. As both wind and solar technologies are deployed at scales required to replace conventional technologies, there must be reasonable certainty that the potential environmental <span class="hlt">impacts</span> at the micro, macro, regional and global scale do not exceed those anticipated from carbon emissions. <span class="hlt">Largely</span> because of computational limits, the role of <span class="hlt">large</span> wind farms in affecting regional-scale weather patterns has only been investigated in coarse simulations and modeling tools do not yet exist which are capable of assessing the downwind affects of <span class="hlt">large</span> wind farms may have on microclimatology. In this presentation, we will outline the vision for and discuss technical and scientific challenges in developing a multi-model high-performance simulation capability covering the range of mesoscale to sub-millimeter scales appropriate for assessing local, regional, and ultimately global environmental <span class="hlt">impacts</span> and quantifying uncertainties of <span class="hlt">large</span> scale wind energy deployment scenarios. Such a system will allow continuous downscaling of atmospheric processes on wind</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://hdl.handle.net/2060/19890012010','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19890012010"><span>Crater size estimates for <span class="hlt">large</span>-body terrestrial <span class="hlt">impact</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Schmidt, Robert M.; Housen, Kevin R.</p> <p>1988-01-01</p> <p>Calculating the effects of <span class="hlt">impacts</span> leading to global catastrophes requires knowledge of the <span class="hlt">impact</span> process at very <span class="hlt">large</span> size scales. This information cannot be obtained directly but must be inferred from subscale physical simulations, numerical simulations, and scaling laws. Schmidt and Holsapple presented scaling laws based upon laboratory-scale <span class="hlt">impact</span> experiments performed on a centrifuge (Schmidt, 1980 and Schmidt and Holsapple, 1980). These experiments were used to develop scaling laws which were among the first to include gravity dependence associated with increasing event size. At that time using the results of experiments in dry sand and in water to provide bounds on crater size, they recognized that more precise bounds on <span class="hlt">large</span>-body <span class="hlt">impact</span> crater formation could be obtained with additional centrifuge experiments conducted in other geological media. In that previous work, simple power-law formulae were developed to relate final crater diameter to impactor size and velocity. In addition, Schmidt (1980) and Holsapple and Schmidt (1982) recognized that the energy scaling exponent is not a universal constant but depends upon the target media. Recently, Holsapple and Schmidt (1987) includes results for non-porous materials and provides a basis for estimating crater formation kinematics and final crater size. A revised set of scaling relationships for all crater parameters of interest are presented. These include results for various target media and include the kinematics of formation. Particular attention is given to possible limits brought about by very <span class="hlt">large</span> impactors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6795618','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6795618"><span><span class="hlt">Large</span>-scale <span class="hlt">impact</span> cratering on the terrestrial planets</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Grieve, R.A.F.</p> <p>1982-01-01</p> <p>The crater densities on the earth and moon form the basis for a standard flux-time curve that can be used in dating unsampled planetary surfaces and constraining the temporal history of endogenic geologic processes. Abundant evidence is seen not only that <span class="hlt">impact</span> cratering was an important surface process in planetary history but also that <span class="hlt">large</span> imapact events produced effects that were crucial in scale. By way of example, it is noted that the formation of multiring basins on the early moon was as important in defining the planetary tectonic framework as plate tectonics is on the earth. Evidence from several planets suggests that the effects of very-<span class="hlt">large</span>-scale <span class="hlt">impacts</span> go beyond the simple formation of an <span class="hlt">impact</span> structure and serve to localize increased endogenic activity over an extended period of geologic time. Even though no longer occurring with the frequency and magnitude of early solar system history, it is noted that <span class="hlt">large</span> scale <span class="hlt">impact</span> events continue to affect the local geology of the planets. 92 references.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20170001717','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20170001717"><span>Hydrogen in Martian <span class="hlt">Meteorites</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Peslier, A. H.; Hervig, R.; Irving, T.</p> <p>2017-01-01</p> <p>Most volatile studies of Mars have targeted its surface via spacecraft and rover data, and have evidenced surficial water in polar caps and the atmosphere, in the presence of river channels, and in the detection of water bearing minerals. The other focus of Martian volatile studies has been on Martian <span class="hlt">meteorites</span> which are all from its crust. Most of these studies are on hydrous phases like apatite, a late-stage phase, i.e. crystallizing near the end of the differentiation sequence of Martian basalts and cumulates. Moreover, calculating the water content of the magma a phosphate crystallized from is not always possible, and yet is an essential step to estimate how much water was present in a parent magma and its source. Water, however, is primarily dissolved in the interiors of differentiated planets as hydrogen in lattice defects of nominally anhydrous minerals (olivine, pyroxene, feldspar) of the crust and mantle. This hydrogen has tremendous influence, even in trace quantities, on a planet's formation, geodynamics, cooling history and the origin of its volcanism and atmosphere as well as its potential for life. Studies of hydrogen in nominally anhydrous phases of Martian <span class="hlt">meteorites</span> are rare. Measuring water contents and hydrogen isotopes in well-characterized nominally anhydrous minerals of Martian <span class="hlt">meteorites</span> is the goal of our study. Our work aims at deciphering what influences the distribution and origin of hydrogen in Martian minerals, such as source, differentiation, degassing and shock.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012pimo.conf..137L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012pimo.conf..137L"><span>Meteor Beliefs Project: <span class="hlt">meteoritic</span> weapons</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kristine Larsen, K.; McBeath, A.</p> <p>2012-01-01</p> <p>A discussion of <span class="hlt">meteoritic</span> iron weapons and weapon-like tools is given, drawing on fictional, mythological, and real-world examples. The evidence suggests that no great significance was attached to such metal purely because of its "heavenly" provenance prior to the early 19th century AD, despite later assumptions, including during the period of increased interest in <span class="hlt">meteorites</span>, cratering events and the early usage of <span class="hlt">meteoritic</span> iron, beginning in the early 20th century.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19780038313&hterms=chihuahua&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dchihuahua','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19780038313&hterms=chihuahua&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dchihuahua"><span>Four new iron <span class="hlt">meteorite</span> finds</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Scott, E. R. D.; Wasson, J. T.; Bild, R. W.</p> <p>1977-01-01</p> <p>Four new iron <span class="hlt">meteorites</span> are described: Buenaventura (IIIB) from Chihuahua, Mexico: mass 114 kg; Denver City (anomalous) from Texas, USA: mass 26.1 kg; Kinsella (IIIB) from Alberta, Canada: mass 3.7 kg; and Tacoma (IA) from Washington, USA: mass 17 g. Denver City is unique - i.e., not related to any other known iron. Tacoma is the smallest iron <span class="hlt">meteorite</span> recorded. The <span class="hlt">meteorites</span> were initially discovered in 1969, 1975, 1946, and between 1925 and 1932, respectively.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016LPICo1926.6003G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016LPICo1926.6003G"><span>Iron <span class="hlt">Meteorites</span> and Upwelling in Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gourlay, B. S.; Behr, E.; Mardon, A.; Behr, E.</p> <p>2016-09-01</p> <p>In Antarctica, a <span class="hlt">meteorite</span> stranding zone, stone <span class="hlt">meteorites</span> are more common than iron. Dr. Evatt's team suggests that the heat conductivity of iron may be opposing the upwelling effects so iron <span class="hlt">meteorites</span> sink under the ice unlike the stone ones.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19750034440&hterms=Oparin&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DOparin','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19750034440&hterms=Oparin&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DOparin"><span>Amino and fatty acids in carbonaceous <span class="hlt">meteorites</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kvenvolden, K. A.</p> <p>1974-01-01</p> <p>Analyses of two carbonaceous <span class="hlt">meteorites</span> have provided much of the latest evidence which seems to support Oparin's theory on the origin of life. The <span class="hlt">meteorites</span> involved are the Murray <span class="hlt">meteorite</span>, which fell in 1950, and the Murchison <span class="hlt">meteorite</span>, which fell in 1969. The amino acids in the two <span class="hlt">meteorites</span> are similar in composition. Eight of the twenty amino acids found belong to amino acids present in proteins. A number of monocarboxylic and dicarboxylic fatty acids were also found in the <span class="hlt">meteorites</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19750034440&hterms=Fatty+Acids&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DFatty%2BAcids','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19750034440&hterms=Fatty+Acids&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DFatty%2BAcids"><span>Amino and fatty acids in carbonaceous <span class="hlt">meteorites</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kvenvolden, K. A.</p> <p>1974-01-01</p> <p>Analyses of two carbonaceous <span class="hlt">meteorites</span> have provided much of the latest evidence which seems to support Oparin's theory on the origin of life. The <span class="hlt">meteorites</span> involved are the Murray <span class="hlt">meteorite</span>, which fell in 1950, and the Murchison <span class="hlt">meteorite</span>, which fell in 1969. The amino acids in the two <span class="hlt">meteorites</span> are similar in composition. Eight of the twenty amino acids found belong to amino acids present in proteins. A number of monocarboxylic and dicarboxylic fatty acids were also found in the <span class="hlt">meteorites</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012icha.book...56L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012icha.book...56L"><span>``Campo del Cielo'' <span class="hlt">Meteorites</span>: Astronomical Heritage and Cultural Colonialism</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>López, Alejandro Martín; Altman, Agustina</p> <p>2012-09-01</p> <p>In the province of Chaco, Argentina, there is a very unique dispersion of metallic <span class="hlt">meteorites</span> called ``Campo del Cielo''. One of the meteoric fragments of this dispersion, the <span class="hlt">meteorite</span> called ``El Chaco'', consisting of 37 tons, is the second heaviest in the world. These <span class="hlt">meteorites</span> are of great importance to the worldview of the Moqoit, aboriginal people that inhabit this region. For the local Creole population the <span class="hlt">meteorites</span> are also relevant, that's why they have being cited in numerous documents and reports since the colonial period. During the first months of 2012, two Argentine artists and the Artistic Director of the German contemporary art exhibition called dOCUMENTA (13) tried to move ``El Chaco'' <span class="hlt">meteorite</span> to Germany in order to exhibit it as an artistic object. Due to the fact that moving the <span class="hlt">meteorite</span> could have a negative <span class="hlt">impact</span> according to the Moqoit cosmology and that they were not able to participate in the decision they begun a manifestation against the movement of El Chaco. The opposition made by aboriginal communities and experts in cultural astronomy was able to stop the transfer. The whole process and its <span class="hlt">impact</span> on the local community have promoted a deep discussion about art, science and cultural colonialism. In this paper we aim to address this debate and its consequences. This will allow us to think about contemporary forms of colonialism that are hidden in many scientific and artistic projects. Furthermore, we aim to debate about the most effective ways of protecting astronomical heritage in the Third World.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1996EM%26P...72..395C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1996EM%26P...72..395C"><span>Video Observations, Atmospheric Path, Orbit and Fragmentation Record of the Fall of the Peekskill <span class="hlt">Meteorite</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ceplecha, Z.; Brown, P.; Hawkes, R. L.; Wertherill, G.; Beech, M.; Mossman, K.</p> <p>1996-02-01</p> <p><span class="hlt">Large</span> Near-Earth-Asteroids have played a role in modifying the character of the surface geology of the Earth over long time scales through <span class="hlt">impacts</span>. Recent modeling of the disruption of <span class="hlt">large</span> meteoroids during atmospheric flight has emphasized the dramatic effects that smaller objects may also have on the Earth's surface. However, comparison of these models with observations has not been possible until now. Peekskill is only the fourth <span class="hlt">meteorite</span> to have been recovered for which detailed and precise data exist on the meteoroid atmospheric trajectory and orbit. Consequently, there are few constraints on the position of <span class="hlt">meteorites</span> in the solar system before <span class="hlt">impact</span> on Earth. In this paper, the preliminary analysis based on 4 from all 15 video recordings of the fireball of October 9, 1992 which resulted in the fall of a 12.4 kg ordinary chondrite (H6 monomict breccia) in Peekskill, New York, will be given. Preliminary computations revealed that the Peekskill fireball was an Earth-grazing event, the third such case with precise data available. The body with an initial mass of the order of 104 kg was in a pre-collision orbit with a = 1.5 AU, an aphelion of slightly over 2 AU and an inclination of 5‡. The no-atmosphere geocentric trajectory would have lead to a perigee of 22 km above the Earth's surface, but the body never reached this point due to tremendous fragmentation and other forms of ablation. The dark flight of the recovered <span class="hlt">meteorite</span> started from a height of 30 km, when the velocity dropped below 3 km/s, and the body continued 50 km more without ablation, until it hit a parked car in Peekskill, New York with a velocity of about 80 m/s. Our observations are the first video records of a bright fireball and the first motion pictures of a fireball with an associated <span class="hlt">meteorite</span> fall.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/11539206','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/11539206"><span>Video observations, atmospheric path, orbit and fragmentation record of the fall of the Peekskill <span class="hlt">meteorite</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ceplecha, Z; Brown, P; Hawkes, R L; Wetherill, G; Beech, M; Mossman, K</p> <p>1996-02-01</p> <p><span class="hlt">Large</span> Near-Earth-Asteroids have played a role in modifying the character of the surface geology of the Earth over long time scales through <span class="hlt">impacts</span>. Recent modeling of the disruption of <span class="hlt">large</span> meteoroids during atmospheric flight has emphasized the dramatic effects that smaller objects may also have on the Earth's surface. However, comparison of these models with observations has not been possible until now. Peekskill is only the fourth <span class="hlt">meteorite</span> to have been recovered for which detailed and precise data exist on the meteoroid atmospheric trajectory and orbit. Consequently, there are few constraints on the position of <span class="hlt">meteorites</span> in the solar system before <span class="hlt">impact</span> on Earth. In this paper, the preliminary analysis based on 4 from all 15 video recordings of the fireball of October 9, 1992 which resulted in the fall of a 12.4 kg ordinary chondrite (H6 monomict breccia) in Peekskill, New York, will be given. Preliminary computations revealed that the Peekskill fireball was an Earth-grazing event, the third such case with precise data available. The body with an initial mass of the order of 10(4) kg was in a pre-collision orbit with a = 1.5 AU, an aphelion of slightly over 2 AU and an inclination of 5 degrees. The no-atmosphere geocentric trajectory would have lead to a perigee of 22 km above the Earth's surface, but the body never reached this point due to tremendous fragmentation and other forms of ablation. The dark flight of the recovered <span class="hlt">meteorite</span> started from a height of 30 km, when the velocity dropped below 3 km/s, and the body continued 50 km more without ablation, until it hit a parked car in Peekskill, New York with a velocity of about 80 m/s. Our observations are the first video records of a bright fireball and the first motion pictures of a fireball with an associated <span class="hlt">meteorite</span> fall.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20100019168&hterms=records&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Drecords','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20100019168&hterms=records&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Drecords"><span>Asteroidal Differentiation - The Record in <span class="hlt">Meteorites</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mittlefehldt, David W.</p> <p>2010-01-01</p> <p> crystallization of a <span class="hlt">largely</span> molten asteroid. For these <span class="hlt">meteorite</span> groups, the rate of heating outpaced the rate at which the melt could be extracted from the interiors, again, assuming 26Al was the energy source. The nature of the heat engine and asteroidal differentiation processes will be discussed as they can be inferred from the petrology and composition of achondrites, irons and stony irons.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20100019168&hterms=Record&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DRecord','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20100019168&hterms=Record&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DRecord"><span>Asteroidal Differentiation - The Record in <span class="hlt">Meteorites</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mittlefehldt, David W.</p> <p>2010-01-01</p> <p> crystallization of a <span class="hlt">largely</span> molten asteroid. For these <span class="hlt">meteorite</span> groups, the rate of heating outpaced the rate at which the melt could be extracted from the interiors, again, assuming 26Al was the energy source. The nature of the heat engine and asteroidal differentiation processes will be discussed as they can be inferred from the petrology and composition of achondrites, irons and stony irons.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19910015684&hterms=hume&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dhume','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19910015684&hterms=hume&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dhume"><span><span class="hlt">Large</span> craters on the meteoroid and space debris <span class="hlt">impact</span> 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>1991-01-01</p> <p>The distribution around the Long Duration Exposure Facility (LDEF) of 532 <span class="hlt">large</span> craters in the Al plates from the Meteoroid and Space Debris <span class="hlt">Impact</span> Experiment (S0001) is discussed along with 74 additional <span class="hlt">large</span> craters in Al plates donated to the Meteoroid and Debris Special Investigation Group by other LDEF experimenters. The craters are 0.5 mm in diameter and larger. Crater shape is discussed. The number of craters and their distribution around the spacecraft are compared with values predicted with models of the meteoroid environment and the manmade orbital debris environment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19910015684&hterms=impact+space+debris&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dimpact%2Bspace%2Bdebris','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19910015684&hterms=impact+space+debris&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dimpact%2Bspace%2Bdebris"><span><span class="hlt">Large</span> craters on the meteoroid and space debris <span class="hlt">impact</span> 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>1991-01-01</p> <p>The distribution around the Long Duration Exposure Facility (LDEF) of 532 <span class="hlt">large</span> craters in the Al plates from the Meteoroid and Space Debris <span class="hlt">Impact</span> Experiment (S0001) is discussed along with 74 additional <span class="hlt">large</span> craters in Al plates donated to the Meteoroid and Debris Special Investigation Group by other LDEF experimenters. The craters are 0.5 mm in diameter and larger. Crater shape is discussed. The number of craters and their distribution around the spacecraft are compared with values predicted with models of the meteoroid environment and the manmade orbital debris environment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20060021587','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20060021587"><span>Ar-Ar Dating of Martian <span class="hlt">Meteorite</span>, Dhofar 378: An Early Shock Event?</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Park, J.; Bogard, D. D.</p> <p>2006-01-01</p> <p>Martian <span class="hlt">meteorite</span>, Dhofar 378 (Dho378) is a basaltic shergottite from Oman, weighing 15 g, and possessing a black fusion crust. Chemical similarities between Dho378 and the Los Angeles 001 shergottite suggests that they might have derived from the same Mars locale. The plagioclase in other shergottites has been converted to maskelenite by shock, but Dho378 apparently experienced even more intense shock heating, estimated at 55-75 GPa. Dho378 feldspar (approximately 43 modal %) melted, partially flowed and vesiculated, and then partially recrystallized. Areas of feldspathic glass are appreciably enriched in K, whereas individual plagioclases show a range in the Or/An ratio of approximately 0.18-0.017. Radiometric dating of martian shergottites indicate variable formation times of 160-475 Myr, whereas cosmic ray exposure (CRE) ages of shergottites indicate most were ejected from Mars within the past few Myr. Most determined Ar-39-Ar-40 ages of shergottites appear older than other radiometric ages because of the presence of <span class="hlt">large</span> amounts of martian atmosphere or interior Ar-40. Among all types of <span class="hlt">meteorites</span> and returned lunar rocks, the <span class="hlt">impact</span> event that initiated the CRE age very rarely reset the Ar-Ar age. This is because a minimum time and temperature is required to facilitate Ar diffusion loss. It is generally assumed that the shock-texture characteristics in martian <span class="hlt">meteorites</span> were produced by the <span class="hlt">impact</span> events that ejected the rocks from Mars, although the time of these shock events (as opposed to CRE ages) are not directly dated. Here we report Ar-39-Ar-40 dating of Dho378 plagioclase. We suggest that the determined age dates the intense shock heating event this <span class="hlt">meteorite</span> experienced, but that it was not the <span class="hlt">impact</span> that initiated the CRE age.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.P51E3989J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.P51E3989J"><span>First Iron <span class="hlt">Meteorites</span> Observed By the Mars Science Laboratory (MSL) Rover Curiosity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Johnson, J. R.; Bell, J. F., III; Gasnault, O.; Le Mouelic, S.; Rapin, W.; Bridges, J.; Wellington, D. F.</p> <p>2014-12-01</p> <p>The MSL rover Curiosity acquired images of two <span class="hlt">large</span> (>1m) boulders that exhibited surface textures and visible/near-infrared spectra (445-1012nm) consistent with iron <span class="hlt">meteorites</span>, similar to those observed by the Mars Exploration Rover (MER) missions. The rocks were first observed on Sol 634 from ~110m distance and subsequently imaged on Sol 637 using Mastcam and the Remote Micro-Imager (RMI) on ChemCam. The rock "Lebanon" was observed from ~43m, and the rock "Littleton" from ~63m, revealing lustrous blue-gray color and small surface pits consistent with regmaglypts. On Sol 640, Lebanon (at ~12m distance), a nearby fragment, and Littleton (~36m) were imaged with Mastcam at 3 times of day. This included multispectral images of Lebanon along with a 6-frame RMI mosaic and a single position on Littleton. After a ~1.5 m drive closer to the rocks, additional Mastcam images were obtained prior to departure. At high resolution the surfaces were smooth with mm-scale, intermittent pockmarks. Collections of sand within regmaglypts suggested previous episodes of at least partial burial and exhumation. Mastcam reflectance spectra were red-sloped, with variations <550nm related to specular reflections, similar to laboratory spectra of iron <span class="hlt">meteorites</span> (and MER spectra of similar rocks). The rocks did not exhibit the cavernous weathering or purple-hued, patchy coatings associated with <span class="hlt">meteorites</span> observed by MER. The lack of such physio-chemical weathering may be consistent with the less acidic environments postulated for Gale Crater rocks. The close proximity of these rocks suggests they were part of the same fall. The lack of an associated <span class="hlt">impact</span> crater suggests the event was either unable to create an <span class="hlt">impact</span> crater (e.g., low angle entry through a thicker atmosphere), or the rocks survived after erosion of associated <span class="hlt">impact</span> structure(s). Iron <span class="hlt">meteorites</span> such as these may therefore provide "witness plates" to processes and environments experienced in this region since their</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008epsc.conf..866F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008epsc.conf..866F"><span>Technological methods in research for icy <span class="hlt">meteorites</span> on cold region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fodor, F.</p> <p>2008-09-01</p> <p>Amongst the less known cosmic origin matters, which are showering our planet Earth are these of icy <span class="hlt">meteorites</span>, which due to their height temperature on <span class="hlt">impact</span> <span class="hlt">largely</span> and completely melt in any zonal temperatures, exception being the two polar zones hence their findings and gathering is only possible these in Antarctica these cosmic sending in bedded in the frozen ice rivers, glaciers are however there and detectable. It is imperative to use an up to date technology for the detection, finding and investigation of these objects as being found preserved in their state of arrivals and embedded in the glaciers. The radioactive isotope content of these so called dirty ice balls and their possible content of organic chemicals could in some way enrich and modify of our concept from the formation of environment of our planet Earth. The same technology could also be used for the mapping of crevices of the two polar regions of the Moon. Our observations obtained from the Hungaria One and Two small planets, shows that there surface beehive as if they were two hinge sizes of ice <span class="hlt">meteorites</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19860022893','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19860022893"><span>The 10Be contents of SNC <span class="hlt">meteorites</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Pal, D. K.; Tuniz, C.; Moniot, R. K.; Savin, W.; Vajda, S.; Kruse,