Science.gov

Sample records for large meteorite impacts

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. 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.

  13. 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

  14. 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

  15. 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.

  16. 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

  17. 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.

  18. 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.

  19. 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

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. 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

  18. 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.

  19. 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.

  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. 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.

  2. 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

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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).

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. 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).

  18. 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

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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

  4. 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.

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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

  11. 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.

  12. 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

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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

  19. 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

  20. 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

  1. 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.

  2. 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

  3. 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

  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. 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.

  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. 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.

  8. 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.

  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 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  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. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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

  13. 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.

  14. 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

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. 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

  1. 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.

  2. 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

  3. 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

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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

  10. 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.

  11. 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.

  12. 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

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. 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.

  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 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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

  10. 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.

  11. 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.

  12. 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

  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. 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

  15. 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.

  16. 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.

  17. 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

  18. 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.

  19. 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

  20. 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.

  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. 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

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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).

  8. 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.

  9. 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.

  10. 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

  11. 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.

  12. 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

  13. 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

  14. 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

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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).

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. 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

  6. 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.

  7. 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.

  8. 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

  9. 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.

  10. 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.

  11. 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.

  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. 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

  14. 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.

  15. 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.

  16. 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).

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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

  3. 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.

  4. 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.

  5. Searching for Meteorites

    NASA Video Gallery

    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 ...

  6. 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.

  7. 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.

  8. 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

  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. 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.

  11. 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

  12. 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.

  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. 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.

  15. 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.

  16. 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.

  17. Electromagnetic depth sounding in the Earth's crust: Survey and modeling of the effects of a meteorite impact on the conductivity structure in Southern Germany

    NASA Astrophysics Data System (ADS)

    Kerch, J.; Bahr, K.

    2010-12-01

    More than 14 million years ago a meteorite hit Bavaria and left a huge hole where the Swabian and the Franconian Jura meet in Southern Germany. The impact clearly changed the earth’s surface but what happened in the depth? How deep did the earth got shaken by the impact? 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 impact. 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 impact 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.

  18. 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('https://ntrs.nasa.gov/search.jsp?R=20040000692&hterms=rainbow&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Drainbow','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040000692&hterms=rainbow&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Drainbow"><span>Microfossils in CI and CO 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.; Rozanov, Alexei Y.; Jerman, Gregory; Costen, James</p> <p>2003-01-01</p> <p>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 <span class="hlt">meteorites</span> have recently been obtained using Field Emission and Environmental Scanning Electron Microscopes These studies indicate the presence of a <span class="hlt">large</span> assemblage of biomarkers and complex lithified and carbonized remains of bodies that we interpret as indigenous microfossils. We discuss the <span class="hlt">meteorites</span>, provide images of many of the biogenic forms found embedded in the freshly fractured <span class="hlt">meteorite</span> surfaces.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19860019352','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19860019352"><span>Terrestrial and exposure histories of 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>Nishiizumi, K.</p> <p>1986-01-01</p> <p>Records of cosmogenic effects were studied in a <span class="hlt">large</span> suite of Antarctic <span class="hlt">meteorites</span>. The cosmogenic nuclide measurements together with cosmic ray track measurements on Antartic <span class="hlt">meteorites</span> 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 <span class="hlt">meteorite</span> 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.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_11 --> <div id="page_12" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="221"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70004674','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70004674"><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, 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.</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 25 km-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 10–80 m of deflation in the last 3–3.5 Gy, 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999psrd.reptE..28T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999psrd.reptE..28T"><span>An Adulterated Martian <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>Taylor, G. J.</p> <p>1999-07-01</p> <p>Martian <span class="hlt">meteorite</span>, 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 <span class="hlt">impact</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013M%26PSA..76.5193F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013M%26PSA..76.5193F"><span>Finding Shatter Cones in <span class="hlt">Meteorites</span> from the Natural History Museum Vienna Collection</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ferrière, L.; Brandstätter, F.; Koeberl, C.</p> <p>2013-09-01</p> <p>New findings of shatter cones in a few <span class="hlt">meteorites</span> from the Natural History Museum Vienna as well as other <span class="hlt">impact</span> metamorphism features are presented. Their occurrence in <span class="hlt">meteorites</span> records hypervelocity collisions in the solar system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930071492&hterms=Percent+Composition&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DPercent%2BComposition','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930071492&hterms=Percent+Composition&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DPercent%2BComposition"><span>Nitrogen isotopic compositions of 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>Prombo, Carol A.; Clayton, Robert N.</p> <p>1993-01-01</p> <p>Iron <span class="hlt">meteorites</span> analyzed in this study have nitrogen concentrations 70 microg/g or less and delta N-15 from -90 to +150 percent. Although the iron <span class="hlt">meteorites</span> have a <span class="hlt">large</span> 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 <span class="hlt">meteorites</span>. The range of greater than 1100 percent observed for delta N-15 in bulk <span class="hlt">meteorites</span> is probably too <span class="hlt">large</span> to be accounted for by physical and chemical mass-dependent fractionation processes in the solar nebula, and thus reflects nebular inhomogeneities of nucleosynthetic origin.</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> <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('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/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://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.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/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/2060/19980019921','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://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/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/2060/19740018174','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('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=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> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_12 --> <div id="page_13" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="241"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=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('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/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('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://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('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/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/2060/20080026035','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('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://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('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://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('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('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('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://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_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <div id="page_14" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="261"> <li> <p><a target="_blank" onclick="trackOutboundLink('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://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('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('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/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://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('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('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('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://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> <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/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> <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.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/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/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://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://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> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_14 --> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://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('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('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=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=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://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://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=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('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('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> <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://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.</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/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://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('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://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('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> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_15 --> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/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/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=PIA07269&hterms=Basketball&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DBasketball','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA07269&hterms=Basketball&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%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://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://www.ncbi.nlm.nih.gov/pubmed/15973403','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15973403"><span>Timescales of shock processes in chondritic and martian <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>Beck, P; Gillet, Ph; El Goresy, A; Mostefaoui, S</p> <p>2005-06-23</p> <p>The accretion of the terrestrial planets from asteroid collisions and the delivery to the Earth of martian and lunar <span class="hlt">meteorites</span> has been modelled extensively. <span class="hlt">Meteorites</span> that have experienced shock waves from such collisions can potentially be used to reveal the accretion process at different stages of evolution within the Solar System. Here we have determined the peak pressure experienced and the duration of <span class="hlt">impact</span> in a chondrite and a martian <span class="hlt">meteorite</span>, and have combined the data with <span class="hlt">impact</span> scaling laws to infer the sizes of the impactors and the associated craters on the <span class="hlt">meteorite</span> parent bodies. The duration of shock events is inferred from trace element distributions between coexisting high-pressure minerals in the shear melt veins of the <span class="hlt">meteorites</span>. The shock duration and the associated sizes of the impactor are found to be much greater in the chondrite (approximately 1 s and 5 km, respectively) than in the martian <span class="hlt">meteorite</span> (approximately 10 ms and 100 m). The latter result compares well with numerical modelling studies of cratering on Mars, and we suggest that martian <span class="hlt">meteorites</span> with similar, recent ejection ages (10(5) to 10(7) years ago) may have originated from the same few square kilometres on Mars.</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('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> <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/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://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/2060/19890012010','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('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/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/2060/19890017427','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('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://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('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> </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://adsabs.harvard.edu/abs/2003AGUFM.V51F0353M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003AGUFM.V51F0353M"><span>Comparing the Hazards From <span class="hlt">Large</span> Volcanic Eruptions and <span class="hlt">Impacting</span> Asteroids</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mason, B. G.; Pyle, D. M.</p> <p>2003-12-01</p> <p>Explosive volcanic eruptions and asteroid <span class="hlt">impacts</span> leave craters that allow direct comparison of the scale and frequency of these severe events. We have compiled data on <span class="hlt">large</span> volcanic eruptions over the past 45 million years, and used this to develop an improved quantitative assessment of the frequency of <span class="hlt">large</span> volcanic eruptions, and to make a comparative assessment of the relative likelihood of the Earth being affected by severe volcanic eruptions, and <span class="hlt">impact</span> events of equal severity. In terms of volcanic activity, the expected frequency of explosive eruptions involving > 1015 kg of rock lies between 1.3 and 22 events per million years. For the events that form terrestrial craters with diameters of order 10 - 25 km, the thermal energy release (during a volcanic eruption) is of the same order of magnitude as the kinetic energy release (from an asteroid <span class="hlt">impact</span>), and ca. 1021 - 1022 J (2 x 105 - 2 x 106 Mt equivalent of TNT). Over the past 5 Ma, volcanic activity dominates the production rate of craters < 45 km diameter. This suggests that over short timescales (< 1 Ma), destructive volcanic eruptions are more frequent than <span class="hlt">impact</span> events of a similar energy. A better comparison of the primary effects of both phenomena may be realised by considering the area destroyed by shock waves (impactors) or hot pyroclastic deposits (volcanoes). Using simple scalings, we show that the primary area destroyed by an impactor is about ten times that for an eruption. Using this area as a measure of severity, we can show that for events with a return period of 100,000 years or less, there are considerably more eruptions of a given severity than there are <span class="hlt">impact</span> events. Impactor events only dominate for return periods of > 200,000 - 500,000 years. We conclude that smaller (< 1012 kg, < 1 km diameter) near-earth orbiters pose a significantly smaller hazard to humans than the regional effects of <span class="hlt">large</span> (1014 - 1015 kg) volcanic eruptions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999ExFl...27...60S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999ExFl...27...60S"><span>Experiments with <span class="hlt">large</span> diameter gravity driven <span class="hlt">impacting</span> liquid jets</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Storr, G. J.; Behnia, M.</p> <p></p> <p>The phenomenon of a liquid jet released under gravity and falling through or <span class="hlt">impacting</span> onto another liquid before colliding with an obstructing solid surface has been studied experimentally under isothermal conditions. Usually the jet diameter was sufficiently <span class="hlt">large</span> to ensure jet coherency until collision. Direct flow visualization was used to study jets released into water pools with no air head space and jets <span class="hlt">impacting</span> onto water pools after falling through an air head space. It is shown that distances predicting the onset of buoyancy and the entrainment of air using derivations from continuous plunging jets, are not applicable for <span class="hlt">impacting</span> jets. The morphology of jet debris after collision with the solid surfaces correlates with the wetting properties of the jet liquid on the surface.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120009917','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120009917"><span>Distribution, Statistics, and Resurfacing of <span class="hlt">Large</span> <span class="hlt">Impact</span> Basins on Mercury</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Fassett, Caleb I.; Head, James W.; Baker, David M. H.; Chapman, Clark R.; Murchie, Scott L.; Neumann, Gregory A.; Oberst, Juergen; Prockter, Louise M.; Smith, David E.; Solomon, Sean C.; Strom, Robert G.; Xiao, Zhiyong; Zuber, Maria T.</p> <p>2012-01-01</p> <p>The distribution and geological history of <span class="hlt">large</span> <span class="hlt">impact</span> basins (diameter D greater than or equal to 300 km) on Mercury is important to understanding the planet's stratigraphy and surface evolution. It is also informative to compare the density of <span class="hlt">impact</span> basins on Mercury with that of the Moon to understand similarities and differences in their <span class="hlt">impact</span> crater and basin populations [1, 2]. A variety of <span class="hlt">impact</span> basins were proposed on the basis of geological mapping with Mariner 10 data [e.g. 3]. This basin population can now be re-assessed and extended to the full planet, using data from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft. Note that small-to- medium-sized peak-ring basins on Mercury are being examined separately [4, 5]; only the three largest peak-ring basins on Mercury overlap with the size range we consider here. In this study, we (1) re-examine the <span class="hlt">large</span> basins suggested on the basis of Mariner 10 data, (2) suggest additional basins from MESSENGER's global coverage of Mercury, (3) assess the size-frequency distribution of mercurian basins on the basis of these global observations and compare it to the Moon, and (4) analyze the implications of these observations for the modification history of basins on Mercury.</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> <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/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/26504224','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26504224"><span>The <span class="hlt">impact</span> of <span class="hlt">large</span> terrestrial carnivores on Pleistocene ecosystems.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Van Valkenburgh, Blaire; Hayward, Matthew W; Ripple, William J; Meloro, Carlo; Roth, V Louise</p> <p>2016-01-26</p> <p><span class="hlt">Large</span> mammalian terrestrial herbivores, such as elephants, have dramatic effects on the ecosystems they inhabit and at high population densities their environmental <span class="hlt">impacts</span> can be devastating. Pleistocene terrestrial ecosystems included a much greater diversity of megaherbivores (e.g., mammoths, mastodons, giant ground sloths) and thus a greater potential for widespread habitat degradation if population sizes were not limited. Nevertheless, based on modern observations, it is generally believed that populations of megaherbivores (>800 kg) are <span class="hlt">largely</span> immune to the effects of predation and this perception has been extended into the Pleistocene. However, as shown here, the species richness of big carnivores was greater in the Pleistocene and many of them were significantly larger than their modern counterparts. Fossil evidence suggests that interspecific competition among carnivores was relatively intense and reveals that some individuals specialized in consuming megaherbivores. To estimate the potential <span class="hlt">impact</span> of Pleistocene <span class="hlt">large</span> carnivores, we use both historic and modern data on predator-prey body mass relationships to predict size ranges of their typical and maximum prey when hunting as individuals and in groups. These prey size ranges are then compared with estimates of juvenile and subadult proboscidean body sizes derived from extant elephant growth data. Young proboscideans at their most vulnerable age fall within the predicted prey size ranges of many of the Pleistocene carnivores. Predation on juveniles can have a greater <span class="hlt">impact</span> on megaherbivores because of their long interbirth intervals, and consequently, we argue that Pleistocene carnivores had the capacity to, and likely did, limit megaherbivore population sizes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4743832','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4743832"><span>The <span class="hlt">impact</span> of <span class="hlt">large</span> terrestrial carnivores on Pleistocene ecosystems</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Van Valkenburgh, Blaire; Ripple, William J.; Meloro, Carlo; Roth, V. Louise</p> <p>2016-01-01</p> <p><span class="hlt">Large</span> mammalian terrestrial herbivores, such as elephants, have dramatic effects on the ecosystems they inhabit and at high population densities their environmental <span class="hlt">impacts</span> can be devastating. Pleistocene terrestrial ecosystems included a much greater diversity of megaherbivores (e.g., mammoths, mastodons, giant ground sloths) and thus a greater potential for widespread habitat degradation if population sizes were not limited. Nevertheless, based on modern observations, it is generally believed that populations of megaherbivores (>800 kg) are <span class="hlt">largely</span> immune to the effects of predation and this perception has been extended into the Pleistocene. However, as shown here, the species richness of big carnivores was greater in the Pleistocene and many of them were significantly larger than their modern counterparts. Fossil evidence suggests that interspecific competition among carnivores was relatively intense and reveals that some individuals specialized in consuming megaherbivores. To estimate the potential <span class="hlt">impact</span> of Pleistocene <span class="hlt">large</span> carnivores, we use both historic and modern data on predator–prey body mass relationships to predict size ranges of their typical and maximum prey when hunting as individuals and in groups. These prey size ranges are then compared with estimates of juvenile and subadult proboscidean body sizes derived from extant elephant growth data. Young proboscideans at their most vulnerable age fall within the predicted prey size ranges of many of the Pleistocene carnivores. Predation on juveniles can have a greater <span class="hlt">impact</span> on megaherbivores because of their long interbirth intervals, and consequently, we argue that Pleistocene carnivores had the capacity to, and likely did, limit megaherbivore population sizes. PMID:26504224</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/1027033','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/1027033"><span>Construction of an unyielding target for <span class="hlt">large</span> horizontal <span class="hlt">impacts</span>.</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ammerman, Douglas James; Davie, Neil Thomas; Kalan, Robert J.</p> <p>2010-10-01</p> <p>Sandia National Laboratories has constructed an unyielding target at the end of its 2000-foot rocket sled track. This target is made up of approximately 5 million pounds of concrete, an embedded steel load spreading structure, and a steel armor plate face that varies from 10 inches thick at the center to 4 inches thick at the left and right edges. The target/track combination will allow horizontal <span class="hlt">impacts</span> at regulatory speeds of very <span class="hlt">large</span> objects, such as a full-scale rail cask, or high-speed <span class="hlt">impacts</span> of smaller packages. The load-spreading mechanism in the target is based upon the proven design that has been in use for over 20 years at Sandia's aerial cable facility. That target, with a weight of 2 million pounds, has successfully withstood <span class="hlt">impact</span> forces of up to 25 million pounds. It is expected that the new target will be capable of withstanding <span class="hlt">impact</span> forces of more than 70 million pounds. During construction various instrumentation was placed in the target so that the response of the target during severe <span class="hlt">impacts</span> can be monitored. This paper will discuss the construction of the target and provide insights on the testing capabilities at the sled track with this new target.</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://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/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('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('http://adsabs.harvard.edu/abs/2016ysc..conf...27V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ysc..conf...27V"><span><span class="hlt">Impact</span> craters at falling of <span class="hlt">large</span> asteroids in Ukraine</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vidmachenko, A. P.</p> <p>2016-05-01</p> <p>Catastrophes of different scale that are associated with the fall of celestial bodies to the Earth - occurred repeatedly in its history. But direct evidence of such catastrophes has been discovered recently. Thus, in the late 1970s studies of terrestrial rocks showed that in layers of the earth's crust that corresponded to the period of 65 million years before the present, marked by the mass extinction of some species of living creatures, and the beginning of the rapid development of others. It was then - a <span class="hlt">large</span> body crashed to Earth in the Gulf of Mexico in Central America. The consequence of this is the Chicxulub crater with a diameter of ~170 km on Yucatan Peninsula. Modern Earth's surface retains many traces of collisions with <span class="hlt">large</span> cosmic bodies. To indicate the craters with a diameter of more than 2 km using the name "astrobleme". Today, it found more than 230. The largest astroblems sizes exceeding 200 km. Ukraine also has some own astroblems. In Ukraine, been found nine <span class="hlt">large</span> <span class="hlt">impact</span> craters. Ukrainian crystalline shield, because of its stability for a long time (more than 1.5 billion years), has the highest density of <span class="hlt">large</span> astroblems on the Earth's surface. The largest of the Ukrainian astroblems is Manevytska. It has a diameter of 45 km. There are also Ilyinetskyi (7 km), Boltysh (25 km), Obolon' (20 km), Ternivka (12-15 km), Bilylivskyi (6 km), Rotmystrivka (3 km) craters. Zelenohayska astrobleme founded near the village Zelenyi Gay in Kirovograd region and consists of two craters: larger with diameter 2.5-3.5 km and smaller - with diameter of 800 m. The presence of graphite, which was the basis for the research of the <span class="hlt">impact</span> diamond in astroblems of this region. As a result, the diamonds have been found in rocks of Ilyinetskyi crater; later it have been found in rocks in the Bilylivska, Obolon' and other <span class="hlt">impact</span> structures. The most detailed was studied the geological structure and the presence of diamonds in Bilylivska astrobleme</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AGUSMSH51B..02K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AGUSMSH51B..02K"><span>Historically <span class="hlt">Large</span> Geomagnetic Storms and Potential Electric Power Grid <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>Kappenman, J. G.</p> <p>2004-05-01</p> <p>While recent work has been done to examine the possible Dst Intensity of historically <span class="hlt">large</span> geomagnetic storms, the <span class="hlt">impacts</span> caused to modern day electric power grids from these storms occurs due to rapid rate-of-change of regional geomagnetic fields which in most cases are driven by <span class="hlt">large</span> ionospheric electrojet current intensifications. These temporally and spatially dynamic disturbance morphologies are not well-characterized by Dst or other broad geomagnetic storm indices. For estimates of storm intensity that correctly scale the threat potential to electric power grids, it is necessary to describe the rate-of-change of geomagnetic field. The rate-of-change of the geomagnetic field (dB/dt usually measured in nT/min) creates at ground level a geoelectric field that causes the flow of geomagnetically-induced currents (GIC) through ground connection points in electric power grids. Therefore in general, the larger the dB/dt, the larger the resulting geo-electric field and GIC in exposed power grid infrastructures and the greater the operational <span class="hlt">impact</span> these induced currents will have on the power grid. Both extensive modeling analysis and recent operational experience suggests that power grids are becoming more vulnerable to geomagnetic storms as they grow in size and complexity. Also, <span class="hlt">large</span> power grid blackouts have occurred at relatively low geomagnetic storm intensities. For example, the regional disturbance intensity that triggered the Hydro Quebec collapse during the March 13, 1989 Superstorm only reached an intensity of 479 nT/min. <span class="hlt">Large</span> numbers of power system <span class="hlt">impacts</span> in the United States were also observed for intensities that ranged from 300 to 600 nT/min during this storm. Yet both recent and historical data indicate that storms with disturbance levels that range from 2000 nT/min to as much ~5000 nT/min may be possible over extensive regions at latitudes of concern for <span class="hlt">large</span> continental power grids across North America and Europe. <span class="hlt">Large</span> GIC have also been</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AGUFM.P42A..05W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AGUFM.P42A..05W"><span>Three Petrologic Classes of <span class="hlt">Impact</span> Melt on <span class="hlt">Large</span> Atmosphereless Bodies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Warren, P. H.; Kallemeyn, G. W.</p> <p>2005-12-01</p> <p><span class="hlt">Impacts</span> have been important in the evolution of the Moon's crust and regolith, and <span class="hlt">impact</span> melt products (breccias, glasses, and "highland basalts") account for a huge fraction of all sampled nonmare materials. As we endeavor to unravel the history of the Moon using these materials, it is important to understand that three fundamentally distinct types of <span class="hlt">impact</span> melt occur. This discussion will focus on the Moon, but the same tripartite classification of <span class="hlt">impact</span> melts should be applicable to Mercury. However, on Earth, Venus and to some extent Mars, atmosphere and even hydrosphere have major complicating influences. The fate of <span class="hlt">impact</span> melt is closely tied to a parameter that Melosh has termed melting/displacement ratio, i.e., volume of <span class="hlt">impact</span> melt over volume of transient crater; hereafter m/d. For any given energy of <span class="hlt">impact</span> in <span class="hlt">large</span>-scale cratering events, d is sensitive to the local gravity, g. As a result, m/d is systematically lower on a planet with modest g, such as the Moon, than it is on Earth. But also, for any given g, m/d increases with the energy (crater size) of the <span class="hlt">impact</span>. As one consequence, it is easy to show that most of the total volume of <span class="hlt">impact</span> melt throughout lunar history, M, was generated by a very small number (probably much less than 10) of the largest <span class="hlt">impacts</span>. In "small" lunar events, with final crater D < ~ 100 km and m/d of order 1-4%, calculations based on Maxwell's z model indicate that roughly half of the <span class="hlt">impact</span> melt is ejected from the transient crater; and the fraction not ejected will be dispersed within the thoroughly disintegrated but relatively cool shallow-subcrater crust. In the largest events (most notably South Pole-Aitken) that contribute most to M, m/d can be as high as 50%. The z models show that only about 1/4 of m is ejected from the transient crater, yet these largest events so dominate M that they still dominate the total inventory of ejected <span class="hlt">impact</span> melt, M*. The ejected <span class="hlt">impact</span> melt winds up cooling rapidly, dispersed in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20100024230','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20100024230"><span><span class="hlt">Large</span> Field Photogrammetry Techniques in Aircraft and Spacecraft <span class="hlt">Impact</span> Testing</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Littell, Justin D.</p> <p>2010-01-01</p> <p>The Landing and <span class="hlt">Impact</span> Research Facility (LandIR) at NASA Langley Research Center is a 240 ft. high A-frame structure which is used for full-scale crash testing of aircraft and rotorcraft vehicles. Because the LandIR provides a unique capability to introduce <span class="hlt">impact</span> velocities in the forward and vertical directions, it is also serving as the facility for landing tests on full-scale and sub-scale Orion spacecraft mass simulators. Recently, a three-dimensional photogrammetry system was acquired to assist with the gathering of vehicle flight data before, throughout and after the <span class="hlt">impact</span>. This data provides the basis for the post-test analysis and data reduction. Experimental setups for pendulum swing tests on vehicles having both forward and vertical velocities can extend to 50 x 50 x 50 foot cubes, while weather, vehicle geometry, and other constraints make each experimental setup unique to each test. This paper will discuss the specific calibration techniques for <span class="hlt">large</span> fields of views, camera and lens selection, data processing, as well as best practice techniques learned from using the <span class="hlt">large</span> field of view photogrammetry on a multitude of crash and landing test scenarios unique to the LandIR.</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('http://adsabs.harvard.edu/abs/2013M%26PS...48....3L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013M%26PS...48....3L"><span>The extra-<span class="hlt">large</span> light-gas gun of the Fraunhofer EMI: Applications for <span class="hlt">impact</span> cratering research</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lexow, B.; Wickert, M.; Thoma, K.; SchńFer, F.; Poelchau, M. H.; Kenkmann, T.</p> <p>2013-01-01</p> <p>The extra-<span class="hlt">large</span> light-gas gun (XLLGG) at the Fraunhofer Ernst-Mach-Institut (EMI, Efringen-Kirchen, Germany) is a two-stage light-gas gun that can accelerate projectile masses of up to 100 g up to velocities of 6 km s-1. The accelerator's set-up allows various combinations of pump and launch tubes for applications in different fields of hypervelocity <span class="hlt">impact</span> research. In the framework of the MEMIN (Multidisciplinary Experimental and Modeling <span class="hlt">Impact</span> Research Network) program, the XLLGG is used for mesoscale cratering experiments with projectiles made of steel and of iron <span class="hlt">meteorites</span>, and targets consisting of sandstone and other rocks. The craters produced with this equipment reach a diameter of up to 40 cm, a size unique in laboratory cratering research. With the implementation of neural networks, the acceleration process is being optimized, currently yielding peak velocities of 7.8 km s-1 for a 100 g projectile. Here, we summarize technical aspects of the XLLGG.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20000031441&hterms=strict+parents&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dstrict%2Bparents','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20000031441&hterms=strict+parents&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dstrict%2Bparents"><span><span class="hlt">Large</span>-Scale <span class="hlt">Impact</span> Cratering and Early Earth Evolution</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Grieve, R. A. F.; Cintala, M. J.</p> <p>1997-01-01</p> <p>The surface of the Moon attests to the importance of <span class="hlt">large</span>-scale <span class="hlt">impact</span> in its early crustal evolution. Previous models of the effects of a massive bombardment on terrestrial crustal evolution have relied on analogies with the Moon, with allowances for the presence of water and a thinner lithosphere. It is now apparent that strict lunar-terrestrial analogies are incorrect because of the "differential scaling" of crater dimensions and melt volumes with event size and planetary gravity. <span class="hlt">Impact</span> melt volumes and "ancient cavity dimensions for specific <span class="hlt">impacts</span> were modeled according to previous procedures. In the terrestrial case, the melt volume (V(sub m)) exceeds that of the transient cavity (V(sub tc)) at diameters > or = 400 km. This condition is reached on the Moon only with transient cavity diameters > or = 3000 km, equivalent to whole Moon melting. The melt volumes in these <span class="hlt">large</span> <span class="hlt">impact</span> events are minimum estimates, since, at these sizes, the higher temperature of the target rocks at depth will increase melt production. Using the modification-scaling relation of Croft, a transient cavity diameter of about 400 km in the terrestrial environment corresponds to an expected final <span class="hlt">impact</span> "basin" diameter of about 900 km. Such a "basin" would be comparable in dimensions to the lunar basin Orientale. This 900-km "basin" on the early Earth, however, would not have had the appearance of Orientale. It would have been essentially a melt pool, and, morphologically, would have had more in common with the palimpsests structures on Callisto and Ganymede. With the terrestrial equivalents to the <span class="hlt">large</span> multiring basins of the Moon being manifested as muted palimpsest-like structures filled with <span class="hlt">impact</span> melt, it is unlikely they played a role in establishing the freeboard on the early Earth. The composition of the massive <span class="hlt">impact</span> melt sheets (> 10 (exp 7) cu km) produced in "basin-forming" events on the early Earth would have most likely ranged from basaltic to more mafic for the</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_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://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('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/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('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://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/2008AGUFM.P53B1454P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFM.P53B1454P"><span>Volatile Mobilization by <span class="hlt">Large</span> <span class="hlt">Impacts</span>: Constraining the Initial Conditions of an <span class="hlt">Impact</span>- generated Martian Greenhouse.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Plesko, C. S.; Asphaug, E.; Weaver, R. P.; Wohletz, K. H.; Korycansky, D. G.</p> <p>2008-12-01</p> <p>There is substantial evidence for the presence of liquid water on the surface of Mars contemporary to the Late Heavy Bombardment. <span class="hlt">Large</span> asteroid and comet <span class="hlt">impacts</span> have been suggested by Carr (Water on Mars, 1996) and Segura et al. (Science, 2002) as possible triggers of warm and wet climate episodes early in Martian history. Here we model <span class="hlt">impacts</span> into complex, stratigraphically realistic models of Noachian Mars as described by Nimmo and Tanaka (Ann. Rev. E. P. Sci. 2005). We do this in order to determine a lower bound on the energy and size scales of <span class="hlt">impact</span> events that could trigger such a climate shift, and thus establish an upper bound on the frequency of such events. The frequency, magnitude, and surface effects of these <span class="hlt">large</span> <span class="hlt">impacts</span> would have had a significant effect on the habitability of Noachian Mars. This effort is supported by LANL/IGPP (CSP, RPW, KHW), by NASA PG&G (EA), and by NASA MFR (CSP, DGK).</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/2010psrd.reptE.147T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010psrd.reptE.147T"><span>A Younger Age for the Oldest Martian <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>Taylor, G. J.</p> <p>2010-05-01</p> <p>The Allan Hills (ALH) 84001 Martian <span class="hlt">meteorite</span> is famous for containing fiercely-disputed evidence for fossil life. Equally important to many cosmochemists, the <span class="hlt">meteorite</span> also contains important information about the construction of the Martian crust by magmas derived from the interior, and the subsequent modification of those igneous rocks by <span class="hlt">large</span> <span class="hlt">impacts</span> and circulating water. A surprising feature of ALH 84001 has been its extremely ancient age, 4.50 billion years, as determined by samarium-neodymium (Sm-Nd) and rubidium-strontium (Rb-Sr) isotopic dating. If correct, the ancient age implies that the magma in which ALH 84001 formed intruded the primordial crust, perhaps forming in a deep ocean of magma that surrounded Mars during its initial differentiation into metallic core, rocky mantle, and primary crust. New age determinations by Thomas Lapen (University of Houston) and colleagues there and at the Johnson Space Center, the Lunar and Planetary Institute, the University of Wisconsin, and the University of Brussels, Belgium, indicate that the rock crystallized in a magma 4.091 billion years ago. They used lutetium-hafnium (Lu-Hf) isotopes in determining the new age. This isotopic system has the advantage of not being affected as readily by <span class="hlt">impact</span> heating and water alteration as are Sm-Nd and Rb-Sr. The new age is consistent with igneous activity throughout Martian history and with a period of heavy bombardment between 4.2 and 4.1 billion years as inferred from the ages of <span class="hlt">large</span> <span class="hlt">impact</span> basins on Mars.</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://adsabs.harvard.edu/abs/2015AGUFM.P33A2126E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.P33A2126E"><span>Carbon and Oxygen Isotope Measurements of Ordinary Chondrite (OC) <span class="hlt">Meteorites</span> from Antarctica Indicate Distinct Terrestrial Carbonate Species using a Stepped Acid Extraction Procedure <span class="hlt">Impacting</span> Mars Carbonate Research</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Evans, M. E.; Niles, P. B.; Locke, D.</p> <p>2015-12-01</p> <p>The purpose of this study is to characterize the stable isotope values of terrestrial, secondary carbonate minerals from five OC <span class="hlt">meteorites</span> collected in Antarctica. These samples were selected for analysis based upon their size and collection proximity to known Martian <span class="hlt">meteorites</span>. They were also selected based on petrologic type (3+) such that they were likely to be carbonate-free before falling to Earth. This study has two main tasks: 1) characterize the isotopic composition of terrestrial, secondary carbonate minerals formed on <span class="hlt">meteorites</span> in Antarctica, and 2) study the mechanisms of carbonate formation in cold and arid environments with Antarctica as an analog for Mars. Two samples from each <span class="hlt">meteorite</span>, each ~0.5g, was crushed and dissolved in pure phosphoric acid for 3 sequential reactions: a) Rx0 for 1 hour at 30°C, b) Rx1 for 18 hours at 30°C, and c) Rx2 for 3 hours at 150°C. CO2 was distilled by freezing with liquid nitrogen from each sample tube, then separated from organics and sulfides with a TRACE GC using a Restek HayeSep Q 80/100 6' 2mm stainless column, and then analyzed on a Thermo MAT 253 IRMS in Dual Inlet mode. This system was built at NASA/JSC over the past 3 years and proof tested with known carbonate standards to develop procedures, assess yield, and quantify expected uncertainties. Two distinct species of carbonates are found based on the stepped extraction technique: 1) Ca-rich carbonate released at low temperatures, and 2) Mg, or Fe-rich carbonate released at high temperatures. Preliminary results indicate that most of the carbonates present in the ordinary chondrites analyzed have δ13C=+5‰, which is consistent with formation from atmospheric CO2 δ13C=-7‰ at -20°C. The oxygen isotopic compositions of the carbonates vary between +4‰ and +34‰ with the Mg-rich and/or Fe-rich carbonates possessing the lowest δ18O values. This suggests that the carbonates formed under a wide range of temperatures. However, the carbonate oxygen</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('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('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, T.; Herzog, G. F.</p> <p>1986-01-01</p> <p>Several authors have explored the possibility that the Shergottites, Nakhlites, and Chassigny (SNC) came from Mars. The spallogenic gas contents of the SNC <span class="hlt">meteorites</span> have been used to: constrain the sizes of the SNC's during the last few million years; to establish groupings independent of the geochemical ones; and to estimate the likelihood of certain entries in the catalog of all conceivable passages from Mars to Earth. The particular shielding dependence of Be-10 makes the isotope a good probe of the irradiation conditions experienced by the SNC <span class="hlt">meteorites</span>. The Be-10 contents of nine members of the group were measured using the technique of accelerator mass spectrometry. The Be-10 contents of Nakhla, Governador Valadares, Chassigny, and probably Lafayette, about 20 dpm/kg, exceed the values expected from irradiation of the surface of a <span class="hlt">large</span> body. The Be-10 data therfore do not support scenario III of Bogard et al., one in which most of the Be-10 in the SNC <span class="hlt">meteorites</span> would have formed on the Martian surface; they resemble rather the Be-10 contents found in many ordinary chondrites subjected to 4 Pi exposures. The uncertainties of the Be-10 contents lead to appreciable errors in the Be-10 ages, t(1) = -1/lambda ln(1 Be-10/Be-10). Nonetheless, the Be-10 ages are consistent with the Ne-21 ages calculated assuming conventional, small-body production rates and short terrestrial ages for the finds. It is believed that this concordance strengthens the case for at least 3 different irradiation ages for the SNC <span class="hlt">meteorites</span>. Given the similar half-thicknesses of the Be-10 and Ne-21 production rates, the ratios of the Be-10 and Ne-21 contents do not appear consistent with common ages for any of the groups. In view of the general agreement between the Be-10 and Ne-21 ages it does not seem useful at this time to construct multiple-stage irradiation histories for the SNC <span class="hlt">meteorites</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014acm..conf..530T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014acm..conf..530T"><span>New material model for simulating <span class="hlt">large</span> <span class="hlt">impacts</span> on rocky bodies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tonge, A.; Barnouin, O.; Ramesh, K.</p> <p>2014-07-01</p> <p><span class="hlt">Large</span> <span class="hlt">impact</span> craters on an asteroid can provide insights into its internal structure. These craters can expose material from the interior of the body at the <span class="hlt">impact</span> site [e.g., 1]; additionally, the <span class="hlt">impact</span> sends stress waves throughout the body, which interrogate the asteroid's interior. Through a complex interplay of processes, such <span class="hlt">impacts</span> can result in a variety of motions, the consequence of which may appear as lineaments that are exposed over all or portions of the asteroid's surface [e.g., 2,3]. While analytic, scaling, and heuristic arguments can provide some insight into general phenomena on asteroids, interpreting the results of a specific <span class="hlt">impact</span> event, or series of events, on a specific asteroid geometry generally necessitates the use of computational approaches that can solve for the stress and displacement history resulting from an <span class="hlt">impact</span> event. These computational approaches require a constitutive model for the material, which relates the deformation history of a small material volume to the average force on the boundary of that material volume. In this work, we present a new material model that is suitable for simulating the failure of rocky materials during <span class="hlt">impact</span> events. This material model is similar to the model discussed in [4]. The new material model incorporates dynamic sub-scale crack interactions through a micro-mechanics-based damage model, thermodynamic effects through the use of a Mie-Gruneisen equation of state, and granular flow of the fully damaged material. The granular flow model includes dilatation resulting from the mutual interaction of small fragments of material (grains) as they are forced to slide and roll over each other and includes a P-α type porosity model to account for compaction of the granular material in a subsequent <span class="hlt">impact</span> event. The micro-mechanics-based damage model provides a direct connection between the flaw (crack) distribution in the material and the rate-dependent strength. By connecting the rate</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1983WiEng...7....1M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1983WiEng...7....1M"><span>The environmental <span class="hlt">impact</span> of the use of <span class="hlt">large</span> wind turbines</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Manning, P. T.</p> <p></p> <p>The existing data base on the environmental <span class="hlt">impact</span> of <span class="hlt">large</span> wind energy conversion systems (WECS) is explored. The maximum blade throw distance has been calculated at 850 m, with a 5% probability of more than 300 m. Good design and inspection procedures reduce the risk. Ice throw can be prevented by aircraft deicing techniques, but detectors are still necessary. TV interference is ameliorated by the use of composite blades and directional antennas, by relocating the nearst transmission or relay station, or by introduction of cable TV. Microwave transmission effects can be avoided by careful siting of WECS in a favorable line of sight whenever within 1 km of a transmitter. Visual <span class="hlt">impact</span> studies have produced few adverse opinions. Noise has not proved an intractable problem, although 30 dB levels have been exceeded 2100 m downwind of the Mod 2 WECS. Further studies are necessary on the effects of heightened ground turbulence produced by <span class="hlt">large</span> WECS. It is expected that few birds will be harmed by slowly rotating blades in the birds' natural domain, a projection confirmed by sporadic studies. Finally, aircraft collisions are regarded as unlikely and actual land use, mostly confined to rural areas, is minimal.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26595397','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26595397"><span>Ecohydrological modeling for <span class="hlt">large</span>-scale environmental <span class="hlt">impact</span> assessment.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Woznicki, Sean A; Nejadhashemi, A Pouyan; Abouali, Mohammad; Herman, Matthew R; Esfahanian, Elaheh; Hamaamin, Yaseen A; Zhang, Zhen</p> <p>2016-02-01</p> <p>Ecohydrological models are frequently used to assess the biological integrity of unsampled streams. These models vary in complexity and scale, and their utility depends on their final application. Tradeoffs are usually made in model scale, where <span class="hlt">large</span>-scale models are useful for determining broad <span class="hlt">impacts</span> of human activities on biological conditions, and regional-scale (e.g. watershed or ecoregion) models provide stakeholders greater detail at the individual stream reach level. Given these tradeoffs, the objective of this study was to develop <span class="hlt">large</span>-scale stream health models with reach level accuracy similar to regional-scale models thereby allowing for <span class="hlt">impacts</span> assessments and improved decision-making capabilities. To accomplish this, four measures of biological integrity (Ephemeroptera, Plecoptera, and Trichoptera taxa (EPT), Family Index of Biotic Integrity (FIBI), Hilsenhoff Biotic Index (HBI), and fish Index of Biotic Integrity (IBI)) were modeled based on four thermal classes (cold, cold-transitional, cool, and warm) of streams that broadly dictate the distribution of aquatic biota in Michigan. The Soil and Water Assessment Tool (SWAT) was used to simulate streamflow and water quality in seven watersheds and the Hydrologic Index Tool was used to calculate 171 ecologically relevant flow regime variables. Unique variables were selected for each thermal class using a Bayesian variable selection method. The variables were then used in development of adaptive neuro-fuzzy inference systems (ANFIS) models of EPT, FIBI, HBI, and IBI. ANFIS model accuracy improved when accounting for stream thermal class rather than developing a global model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.H53A0999S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.H53A0999S"><span>Determining Environmental <span class="hlt">Impacts</span> of <span class="hlt">Large</span> Scale Irrigation in Turkey</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Simpson, K.; Douglas, E. M.; Limbrunner, J. F.; Ozertan, G.</p> <p>2010-12-01</p> <p>In 1989, the Turkish government launched their most comprehensive regional development plan in history entitled the Southeastern Anatolia Project (SAP) which focuses on improving the quality of life and income level within the most underdeveloped region in Turkey. This project aims to integrate sustainable human development through agriculture, industry, transportation, education, health and rural and urban infrastructure building. In May 2008, a new action plan was announced for the region which includes the designation of almost 800,000 hectares of previously unirrigated land to be open for irrigation within the next five years. If not done in a sustainable manner, such a <span class="hlt">large</span>-scale irrigation project could cause severe environmental <span class="hlt">impacts</span>. The first objective of our research is to use computer simulations to reproduce the observed environmental <span class="hlt">impacts</span> of irrigated agriculture in this arid region, primarily by simulating the effects of soil salinization. The second objective of our research is to estimate soil salinization that could result from expanded irrigation and suggest sustainable strategies for the newly irrigated land in Turkey in order to minimize these environmental <span class="hlt">impacts</span>.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_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/2014acm..conf..365M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014acm..conf..365M"><span><span class="hlt">Large</span> meteoroid <span class="hlt">impact</span> on the Moon on 17 March 2013</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Moser, D.; Suggs, R.; Suggs, R. J.</p> <p>2014-07-01</p> <p>Since early 2006, NASA's Marshall Space Flight Center has observed over 300 <span class="hlt">impact</span> flashes on the Moon, produced by meteoroids striking the lunar surface. On 17 March 2013 at 03:50:54.312 UTC, the brightest flash of an 8-year routine observing campaign was observed in two 0.35 m telescopes outfitted with Watec 902H2 Ultimate monochrome CCD cameras recording interleaved 30 fps video. Standard CCD photometric techniques, described in [1], were applied to the video after saturation correction, yielding a peak R magnitude of 3.0 ± 0.4 in a 1/30 second video exposure. This corresponds to a luminous energy of 7.1×10^6 J. GIS tools were used to georeference the lunar <span class="hlt">impact</span> imagery and yielded a crater location at 20.60 ± 0.17° N, 23.92 ± 0.30° W. The camera onboard the Lunar Reconnaissance Orbiter (LRO), a NASA spacecraft mapping the Moon from lunar orbit, discovered the fresh crater associated with this <span class="hlt">impact</span> by comparing post-<span class="hlt">impact</span> images from 28 July 2013 to pre-<span class="hlt">impact</span> images on 12 Feb 2012. The images show fresh, bright ejecta around an 18 m diameter circular crater (15 m inner diameter measured at the level of pre-existing terrain), at 20.7135° N, 24.3302° W. An asymmetrical ray pattern with both high and low reflectance ejecta zones extends 1--2 km beyond the crater, and a series of mostly low reflectance splotches can be seen within 30 km of the crater --- likely due to secondary <span class="hlt">impacts</span> [2]. The meteoroid impactor responsible for this event may have been part of a stream of <span class="hlt">large</span> particles encountered by the Earth/Moon associated with the Virginid Meteor Complex, as evidenced by a cluster of 5 fireballs seen in Earth's atmosphere on the same night by the NASA All Sky Fireball Network and the Southern Ontario Meteor Network. Assuming a velocity-dependent luminous efficiency (ratio of luminous energy to kinetic energy) from [3] and an <span class="hlt">impact</span> velocity of 25.6 km/s derived from fireball measurements, the impactor kinetic energy was 5.4×10^9 J and the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140012497','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140012497"><span><span class="hlt">Large</span> Meteoroid <span class="hlt">Impact</span> on the Moon on 17 March 2013</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Moser, Danielle E.; Suggs, Robert M.; Suggs, Ronnie J.</p> <p>2014-01-01</p> <p>Since early 2006, NASA's Marshall Space Flight Center has observed over 300 <span class="hlt">impact</span> flashes on the Moon, produced by meteoroids striking the lunar surface. On 17 March 2013 at 03:50:54.312 UTC, the brightest flash of an 8-year routine observing campaign was observed in two 0.35 m telescopes outfitted with Watec 902H2 Ultimate monochrome CCD cameras recording interleaved 30 fps video. Standard CCD photometric techniques, described in [1], were applied to the video after saturation correction, yielding a peak R magnitude of 3.0 +/- 0.4 in a 1/30 second video exposure. This corresponds to a luminous energy of 7.1 × 10(exp 6) J. Geographic Information System (GIS) tools were used to georeference the lunar <span class="hlt">impact</span> imagery and yielded a crater location at 20.60 +/- 0.17deg N, 23.92 +/- 0.30deg W. The camera onboard the Lunar Reconnaissance Orbiter (LRO), a NASA spacecraft mapping the Moon from lunar orbit, discovered the fresh crater associated with this <span class="hlt">impact</span> by comparing post-<span class="hlt">impact</span> images from 28 July 2013 to pre-<span class="hlt">impact</span> images on 12 Feb 2012. The images show fresh, bright ejecta around an 18 m diameter circular crater, with a 15 m inner diameter measured from the level of pre-existing terrain, at 20.7135deg N, 24.3302deg W. An asymmetrical ray pattern with both high and low reflectance ejecta zones extends 1-2 km beyond the crater, and a series of mostly low reflectance splotches can be seen within 30 km of the crater - likely due to secondary <span class="hlt">impacts</span> [2]. The meteoroid impactor responsible for this event may have been part of a stream of <span class="hlt">large</span> particles encountered by the Earth/Moon associated with the Virginid Meteor Complex, as evidenced by a cluster of 5 fireballs seen in Earth's atmosphere on the same night by the NASA All Sky Fireball Network [3] and the Southern Ontario Meteor Network [4]. Assuming a velocity-dependent luminous efficiency (ratio of luminous energy to kinetic energy) from [5] and an <span class="hlt">impact</span> velocity of 25.6 km/s derived from fireball measurements</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19940028703','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19940028703"><span>SNC <span class="hlt">meteorites</span> and their implications for reservoirs of Martian volatiles</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Jones, J. H.</p> <p>1993-01-01</p> <p>The SNC <span class="hlt">meteorites</span> and the measurements of the Viking landers provide our only direct information about the abundance and isotopic composition of Martian volatiles. Indirect measurements include spectroscopic determinations of the D/H ratio of the Martian atmosphere. A personal view of volatile element reservoirs on Mars is presented, <span class="hlt">largely</span> as inferred from the <span class="hlt">meteoritic</span> evidence. This view is that the Martian mantle has had several opportunities for dehydration and is most likely dry, although not completely degassed. Consequently, the water contained in SNC <span class="hlt">meteorites</span> was most likely incorporated during ascent through the crust. Thus, it is possible that water can be decoupled from other volatile/incompatible elements, making the SNC <span class="hlt">meteorites</span> suspect as indicators of water inventories on Mars.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19790042425&hterms=Ice+Age&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3DIce%2BAge','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19790042425&hterms=Ice+Age&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3DIce%2BAge"><span>Exposure and terrestrial ages of four Allan Hills 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>Kirsten, T.; Ries, D.; Fireman, E. L.</p> <p>1978-01-01</p> <p>Terrestrial ages of <span class="hlt">meteorites</span> are based on the amount of cosmic-ray-produced radioactivity in the sample and the number of observed falls that have similar cosmic-ray exposure histories. The cosmic-ray exposures are obtained from the stable noble gas isotopes. Noble gas isotopes are measured by high-sensitivity mass spectrometry. In the present study, the noble gas contents were measured in four Allan Hill <span class="hlt">meteorites</span> (No. 5, No. 6, No. 7, and No. 8), whose C-14, Al-26, and Mn-53 radioactivities are known. These <span class="hlt">meteorites</span> are of particular interest because they belong to a <span class="hlt">large</span> assemblage of distinct <span class="hlt">meteorites</span> that lie exposed on a small (110 sq km) area of ice near the Allan Hills.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016pimo.conf..127K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016pimo.conf..127K"><span>The role of population in tracking <span class="hlt">meteorite</span> falls in Africa</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Khiri, F.; Ibhi, A.; Saint-Gerant, T.; Medjkane, M.; Ouknine, L.</p> <p>2016-01-01</p> <p>The 158 African <span class="hlt">meteorite</span> falls recorded during the period 1801 to 2014, account for more than 12.3% of all <span class="hlt">meteorite</span> falls known from the world. Their rate is variable in time and in space. The number of falls continues to grow since 1860. They are concentrated in countries which exhibit <span class="hlt">large</span> population (mainly rural population) with an uniform distribution. Generally, the number of falls follows the increase of the population density (coefficient of correlation r = 0.98). The colonial phenomenon, the education of population in this field, the population lifestyle and the rural exodus, are also factors among others which could explain the variability of the recovery of <span class="hlt">meteorite</span> falls in Africa. In this note, we try by a statistical study, to examine the role of the African population in tracking <span class="hlt">meteorite</span> falls on this continent.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PEPI..242...50D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PEPI..242...50D"><span>Magnetic hysteresis properties and 57Fe Mössbauer spectroscopy of iron and stony-iron <span class="hlt">meteorites</span>: Implications for mineralogy and thermal history</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dos Santos, E.; Gattacceca, J.; Rochette, P.; Scorzelli, R. B.; Fillion, G.</p> <p>2015-05-01</p> <p>Since the solid matter in our solar system began to assemble 4.57 billion years ago, <span class="hlt">meteorites</span> have recorded a <span class="hlt">large</span> range of processes, including metamorphism, melting, irradiation and hypervelocity <span class="hlt">impacts</span>. These processes as well as solar system magnetic fields can be accessed through the investigation of magnetic properties of <span class="hlt">meteorites</span>. In this work, we present magnetic hysteresis properties, isothermal remanent magnetization acquisition curves and 57Fe Mössbauer spectra for nineteen iron and eleven stony-iron <span class="hlt">meteorites</span>. These data will be the background for a discussion about the thermal and shock history of these <span class="hlt">meteorites</span>. Although Mössbauer spectroscopy and hysteresis measurements are not able to provide cooling rates like the conventional metallographic method does, we show that the combination of the ordering degree of taenite phase measured by Mössbauer spectroscopy and hysteresis properties are useful for constraining the thermal and shock history of <span class="hlt">meteorites</span>. In particular, strong shock and the associated thermal event that result in disordering of tetrataenite can be easily identified.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19790042422&hterms=recrystallization&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Drecrystallization','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19790042422&hterms=recrystallization&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Drecrystallization"><span>Aioun el Atrouss - Evidence for thermal recrystallization of a eurite breccia. [<span class="hlt">meteoritic</span> mineralogy</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Duke, M. B.</p> <p>1978-01-01</p> <p>The Aioun el Atrouss <span class="hlt">meteorite</span> is a breccia consisting <span class="hlt">largely</span> of angular fragments of green orthopyroxene and containing scattered clasts of basaltic composition (mostly pigeonite and calcic plagioclase). It appears to be a physical mixture of two <span class="hlt">meteorite</span> types - diogenite (hypersthene achondrite) and eucrite (basaltic achondrite). The results of a mineral analysis are tabulated, and typical pyroxene compositions in orthopyroxene (diogenite), subophitic and granoblastic portions of the <span class="hlt">meteorite</span> are presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20170001522','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20170001522"><span>A Method for Estimating <span class="hlt">Meteorite</span> Fall Mass from Weather Radar Data</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Laird, C.; Fries, M.; Matson, R.</p> <p>2017-01-01</p> <p>Techniques such as weather RADAR, seismometers, and all-sky cameras allow new insights concerning the physics of <span class="hlt">meteorite</span> fall dynamics and fragmentation during "dark flight", the period of time between the end of the meteor's luminous flight and the concluding <span class="hlt">impact</span> on the Earth's surface. Understanding dark flight dynamics enables us to rapidly analyze the characteristics of new <span class="hlt">meteorite</span> falls. This analysis will provide essential information to <span class="hlt">meteorite</span> hunters to optimize recovery, increasing the frequency and total mass of scientifically important freshly-fallen <span class="hlt">meteorites</span> available to the scientific community. We have developed a mathematical method to estimate <span class="hlt">meteorite</span> fall mass using reflectivity data as recorded by National Oceanic and Atmospheric Administration (NOAA) Next Generation RADAR (NEXRAD) stations. This study analyzed eleven official and one unofficial <span class="hlt">meteorite</span> falls in the United States and Canada to achieve this purpose.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1994Metic..29..696D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1994Metic..29..696D"><span>The Chervettaz (L5) <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>Dominik, B.; Bussy, F.; Meisser, N.</p> <p>1994-09-01</p> <p>The Chervettaz <span class="hlt">meteorite</span> was an observed fall on 1901 November 30. Our study confirms the previous classification as an L5 chondrite. Weak deformations indicate stage S3 of shock deformations. We present mineralogical and chemical studies of this undescribed and poorly known Swiss <span class="hlt">meteorite</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA01077&hterms=945&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3D%2526%2523945','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA01077&hterms=945&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3D%2526%2523945"><span><span class="hlt">Large</span> <span class="hlt">impact</span> on Callisto`s southern hemisphere</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1997-01-01</p> <p>This mosaic of images showing a <span class="hlt">large</span> 200 kilometer (120 mile) diameter <span class="hlt">impact</span> crater on Callisto's southern hemisphere was obtained by the solid state imaging (CCD) system on board NASA's Galileo spacecraft during its eighth orbit of Jupiter. This crater is characterized by a bright circular area surrounded by a darker material excavated and ejected by the <span class="hlt">impact</span>. Beyond this is a zone of rays which are oriented radially outward and contain material also thrown from the crater. Fewer smaller <span class="hlt">impact</span> craters are visible in the ejecta blanket surrounding the <span class="hlt">large</span> crater than in the areas more distant from the crater. This lack of craters superposed on the ejecta blanket and on the crater itself, together with the brightness of the central zone, is evidence that the <span class="hlt">large</span> crater is a relatively young feature on Callisto. Scientists use information such as the number of craters in a given area together with the principle of superposition (in which younger landforms are 'on top' of older features) to determine the relative ages of features and terrains.<p/>North is to the top of the mosaic with the sun illuminating the surface from the left. The mosaic, centered at 55 degrees south latitude and 30 degrees west longitude, covers an area approximately 1400 kilometers (850 miles) by 1235 kilometers (740 miles), at a resolution of 867 meters (945 yards) per picture element. The images which make up this mosaic were taken on May 6, 1997, from an altitude of approximately 43,000 kilometers (26,000 miles) above the surface of Callisto.<p/>The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC.<p/>This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov. Background information and educational context for the images can be found at URL http://www.jpl.nasa.gov/galileo/sepo</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012Icar..218..364B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012Icar..218..364B"><span>Photometry of <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>Beck, P.; Pommerol, A.; Thomas, N.; Schmitt, B.; Moynier, F.; Barrat, J.-A.</p> <p>2012-03-01</p> <p>We have measured the bi-directional reflectance phase function on selected <span class="hlt">meteorite</span> samples (1 howardite, 1 eucrite, 1 diogenite, Orgeuil (CI), Tagish Lake (CC), Allende (CV), Lunar <span class="hlt">meteorite</span> (MAC 88105), Forest Vale (H4)) covering part of the geochemical and petrologic diversity expected for asteroid surfaces. Samples were measured as powders, for which we achieved reflectance measurements from phase angles down to 3°, and up to 150°, at five different wavelengths covering the VIS-NIR spectral region. The data were fitted by the photometric model of Hapke (Hapke, B. [1993]. Theory of reflectance and emittance spectroscopy. Cambridge University Press, Cambridge). The physical sense of the retrieved Hapke’s parameters seems unclear but they permit to interpolate the data to any observation geometry. Strong opposition effects were observed for all samples. The absolute intensity of this effect appears moderately variable among our sample suite, and is not correlated with the average sample reflectance. We interpret this observation as Shadow-Hiding Opposition Effect (SHOE). In the case of samples presenting intense absorption bands (the Fe crystal field band at 1 μm of HED and the ordinary chondrite), we observe significant dependence of band depth to phase angle, up to 70°, even for moderate variation of phase angle. In addition, a general trend of spectral reddening with phase angle is observed. This reddening, linear with phase angle, is present in all <span class="hlt">meteorites</span> studied. This behavior is not predicted by classical radiative theories. We propose that small-scale roughness (of the order of or below the wavelength) may induce such a behavior.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22106261','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22106261"><span>Stardust 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>Davis, Andrew M</p> <p>2011-11-29</p> <p>Primitive <span class="hlt">meteorites</span>, interplanetary dust particles, and comets contain dust grains that formed around stars that lived their lives before the solar system formed. These remarkable objects have been intensively studied since their discovery a little over twenty years ago and they provide samples of other stars that can be studied in the laboratory in exquisite detail with modern analytical tools. The properties of stardust grains are used to constrain models of nucleosynthesis in red giant stars and supernovae, the dominant sources of dust grains that are recycled into the interstellar medium by stars.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3228455','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3228455"><span>Stardust in <span class="hlt">meteorites</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Davis, Andrew M.</p> <p>2011-01-01</p> <p>Primitive <span class="hlt">meteorites</span>, interplanetary dust particles, and comets contain dust grains that formed around stars that lived their lives before the solar system formed. These remarkable objects have been intensively studied since their discovery a little over twenty years ago and they provide samples of other stars that can be studied in the laboratory in exquisite detail with modern analytical tools. The properties of stardust grains are used to constrain models of nucleosynthesis in red giant stars and supernovae, the dominant sources of dust grains that are recycled into the interstellar medium by stars. PMID:22106261</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19940016385&hterms=makeup&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dmakeup','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19940016385&hterms=makeup&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dmakeup"><span>Magnetic record in chondrite <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>Wasilewski, P. J.; Faris, J. L.; Obryan, M. V.</p> <p>1993-01-01</p> <p>What we know about the magnetic record in chondrite <span class="hlt">meteorites</span> based on new data and previously published results is summarized. Strips from thin slabs of chondrite <span class="hlt">meteorites</span> were cut into near cubical subsamples (several mm on edge) numbering approximately 60 to approximately 120 per <span class="hlt">meteorite</span>. A common orientation was assigned to each subsample from a given <span class="hlt">meteorite</span> in order to ensure that we could discover the vector makeup of the bulk <span class="hlt">meteorite</span>. The new data set includes: Shaw (L7), Roy (L5/6), Claytonville (L5), Plainview (H5), Etter (H5), Leoville (C3V), and Allende (C3V). In addition to these new results, literature data of sufficient detail, e.g. Bjurbole (L4), ALH769 (L6), Abee (E4), Allende (C3V), and Olivenza (L5), is considered.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20010076403&hterms=economic+scale&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Deconomic%2Bscale','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20010076403&hterms=economic+scale&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Deconomic%2Bscale"><span><span class="hlt">Impact</span> of Parallel Computing on <span class="hlt">Large</span> Scale Aeroelastic Computations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Guruswamy, Guru P.; Kwak, Dochan (Technical Monitor)</p> <p>2000-01-01</p> <p>Aeroelasticity is computationally one of the most intensive fields in aerospace engineering. Though over the last three decades the computational speed of supercomputers have substantially increased, they are still inadequate for <span class="hlt">large</span> scale aeroelastic computations using high fidelity flow and structural equations. In addition to reaching a saturation in computational speed because of changes in economics, computer manufactures are stopping the manufacturing of mainframe type supercomputers. This has led computational aeroelasticians to face the gigantic task of finding alternate approaches for fulfilling their needs. The alternate path to over come speed and availability limitations of mainframe type supercomputers is to use parallel computers. During this decade several different architectures have evolved. In FY92 the US Government started the High Performance Computing and Communication (HPCC) program. As a participant in this program NASA developed several parallel computational tools for aeroelastic applications. This talk describes the <span class="hlt">impact</span> of those application tools on high fidelity based multidisciplinary analysis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014cosp...40E.920G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014cosp...40E.920G"><span>The Chelyabinsk <span class="hlt">meteorite</span> fall: Geochemistry and Mineralogy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Galimov, Eric</p> <p></p> <p>Just after the Chelyabinsk <span class="hlt">meteorite</span> fall, the Vernadsky Institute and the Committee on <span class="hlt">Meteorites</span> of the Russian Academy of Sciences have organized an expedition to collect fragments of the <span class="hlt">meteorite</span> shower. The collected material has been comprehensively studied for textural characteristics, mineral chemistry, major and trace elements, nuclear tracks, and isotopic composition. The texture, mineral chemistry, and major element contents indicate that the Chelyabinsk <span class="hlt">meteorite</span> belongs to the LL5group of ordinary chondrites and was affected by a moderate degree of shock metamorphism (stage S4). The majority (2/3) of the collected stones is composed from a light lithology with a typical chondritic texture. Chondrules ( 63%) are readily delineated and set within a fragmental matrix. The chondrule glass is devitrified. The main phases are olivine and orthopyroxene. Olivine has mosaicism and planar fractures. Rare grains of augite and clinobronzite are present. Small and rare feldspar grains show undulutory extinction, planar deformation features, and are partly isotropic. Troilite (4 vol.%) and FeNi metal (1.3 vol.%) occur as irregularly shaped grains. Accessories are chromite, ilmenite, Cl-apatite, and native Cu. A significant portion (1/3) of the stones consists of a dark <span class="hlt">impact</span> melt breccia containing mineral and chondrule fragments. Feldspar of the lithology is well developed and practically isotropic. No high-pressure phases were found in the <span class="hlt">impact</span> melt. There are black colored thin shock veins in both light and dark lithologies. Olivine Fa 27.9±0.35, N=22; ortopyroxene Fs 22.8±0.79, Wo 1.30±0.26, N=17; feldspar Ab 86; chromite Fe/Fe+Mg=0.90, Cr/Cr+Al=0.85 (at.). Major element composition of the light lithology (wt%): Si=18.3, Ti=0.053, Al=1.12, Cr=0.40, Fe=19.8, Mn=0.26, Ca=1.43, Na=0.74, K=0.11, P=0.10, Ni=1.06, Co=0.046, S=1.7. The dark lithology has almost the same composition but it is distinctly higher in Ag, Pb, Bi. Sm-Nd isotopic characteristics</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040086980&hterms=parent&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dparent','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040086980&hterms=parent&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dparent"><span>Parent-Body Modification of Chondritic <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>Rubin, Alan</p> <p>2003-01-01</p> <p>This proposal focused on the parent-body modification of chondritic materials and substantial progress was made in the last year. A summary of the work accomplished during this period is discussed. The topics include: 1) Chromite-Plagioclase Assemblages in Ordinary Chondrites; 2) The Gujba Bencubbin-like <span class="hlt">meteorite</span> fall; 3) NWA428: A rock that Experienced <span class="hlt">Impact</span>-induced Annealing; 4) Spade: An Annealed H-chondrite <span class="hlt">Impact</span>-melt Breccia; and 5) Post-shock Annealing in Ordinary Chondrites. A list of the papers submitted or published during the period is also presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014LPICo1800.5008M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014LPICo1800.5008M"><span>Petrology and Geochemistry of Lunar <span class="hlt">Meteorite</span> Abar al'Uj 012</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mészáros, M.; Hofmann, B. A.; Korotev, R. L.; Gnos, E.; Greber, N.; Greenwood, R. C.</p> <p>2014-09-01</p> <p>The petrology and geochemistry of Abar al’Uj 012, a feldspathic lunar <span class="hlt">meteorite</span> found in Saudi Arabia is described. The <span class="hlt">meteorite</span> is a vesicular crystalline <span class="hlt">impact</span>-melt breccia, which lacks a fusion crust and has a ferroan anorthosite affinity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5142709','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5142709"><span>Geochemistry and petrography of the MacAlpine Hills lunar <span class="hlt">meteorites</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lindstrom, M.M.; McKay, D.S. ); Wentworth, S.J.; Martinez, R.R.; Mittlefehldt, D.W. ); Wang, Mingsheng; Lipschutz, M.E. )</p> <p>1991-11-01</p> <p>MacAlpine Hills 88104 and 88105 are anorthositic lunar <span class="hlt">meteorites</span> recovered from the same area in Antarctica which are demonstrated to be paired samples of the same fall. Petrographic studies of matrix and clasts show that mAC88104/5 is a polymict breccia dominated by <span class="hlt">impact</span> melt clasts. It contains a small amount of highland <span class="hlt">impact</span> glass and very few regolith glass spherules. It is better classified as a fragmental breccia than a regolith breccia. The bulk composition is ferroan (mg{prime} = 63) and highly aluminous (Al{sub 2}O{sub 3} = 28%). REE and other incompatible element concentrations are very low. Compositions of anorthositic, granulitic, and <span class="hlt">impact</span> melt breccia clasts are very similar to, but distinct from, matrix composition. MAC88104/5 is very similar in composition to the other anorthositic lunar <span class="hlt">meteorites</span>, but each of the <span class="hlt">meteorites</span> is distinct. The anorthositic lunar <span class="hlt">meteorites</span>, especially MAC88104/5 and Y82192/3/86032, are very similar to North Ray Crater feldspathic fragmental breccias in composition and petrography. These fragmental lunar <span class="hlt">meteorites</span> may have been ancient, deeply buried breccias from the megaregolith. Comparisons of chemical petrographic features and exposure histories suggest that the twelve lunar <span class="hlt">meteorites</span> were derived from two to nine, but probably four to seven, <span class="hlt">impact</span> onto the lunar surface. Discrepancies between the proportions of lunar <span class="hlt">meteorites</span> and results of Apollo missions may be due to unrepresentative sampling. Lunar <span class="hlt">meteorites</span> provide valuable new information on the nature of the lunar crust.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19930000983','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19930000983"><span><span class="hlt">Impact</span> cratering record of Fennoscandia</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Pesonen, L. J.; Henkel, H.</p> <p>1992-01-01</p> <p>A compilation of circular topographic, morphological, or geophysical structures in Fennoscandia and adjacent areas reveals 62 craterform structures of which 15 appear to be of extraterrestrial origin due to <span class="hlt">meteorite</span> <span class="hlt">impact</span>. The majority of the structures are probable and possible <span class="hlt">impact</span> craters for which there is not yet sufficient proof for <span class="hlt">impact</span> origin. Four of the proven <span class="hlt">impact</span> craters contain <span class="hlt">large</span> volumes of <span class="hlt">impact</span> melt and many other features of intense shock metamorphism. The age of recognized <span class="hlt">impact</span> craters vary from prehistoric to late Precambrian. We review the Fennoscandian <span class="hlt">impact</span> cratering record giving examples of geophysical signatures of <span class="hlt">impact</span> craters.</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://hdl.handle.net/2060/19910010697','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19910010697"><span>Wanted: Lunar detectives to unravel the mysteries of the Moon! Crime to be solved: Mass extinctions on the Moon by <span class="hlt">meteorite</span> <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>Neal, Clive R.; Taylor, Lawrence A.</p> <p>1991-01-01</p> <p>The criteria and clues for identifying <span class="hlt">meteorite</span> contamination are outlined to aid in the quest for more knowledge regarding the evolution of the Moon and the early Earth. The Warren and Wasson seven criteria for establishing the pristine nature of highland rocks are presented. Other topics covered include iron/nickel metals, monomict nature, and lunar glasses. The major conclusion is that pristinity should not be the primary consideration in the study of lunar rocks. The most important criterion to establish is whether or not the lunar sample contains more than one lunar rock type. Even if a sample is non-pristine, as long as only one lunar rock type is present, petrogenetic interpretation can still be carried out.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1991LPIP...22...53N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1991LPIP...22...53N"><span>Wanted: Lunar detectives to unravel the mysteries of the Moon] Crime to be solved: Mass extinctions on the Moon by <span class="hlt">meteorite</span> <span class="hlt">impact</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Neal, Clive R.; Taylor, Lawrence A.</p> <p></p> <p>The criteria and clues for identifying <span class="hlt">meteorite</span> contamination are outlined to aid in the quest for more knowledge regarding the evolution of the Moon and the early Earth. The Warren and Wasson seven criteria for establishing the pristine nature of highland rocks are presented. Other topics covered include iron/nickel metals, monomict nature, and lunar glasses. The major conclusion is that pristinity should not be the primary consideration in the study of lunar rocks. The most important criterion to establish is whether or not the lunar sample contains more than one lunar rock type. Even if a sample is non-pristine, as long as only one lunar rock type is present, petrogenetic interpretation can still be carried out.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140012496','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140012496"><span>The Flux of <span class="hlt">Large</span> Meteoroids Observed with Lunar <span class="hlt">Impact</span> Monitoring</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cooke, W. J.; Suggs, R. M.; Moser, D. E.; Suggs, R. J.</p> <p>2014-01-01</p> <p>The flux of <span class="hlt">large</span> meteoroids is not well determined due to relatively low number statistics, due mainly to the lack of collecting area available to meteor camera systems (10(2)-10(5) km2). Larger collecting areas are needed to provide reasonable statistics for flux calculations. The Moon, with millions of square kilometers of lunar surface, can be used as a detector for observing the population of <span class="hlt">large</span> meteoroids in the tens of grams to kilogram mass range. This is accomplished by observing the flash of light produced when a meteoroid <span class="hlt">impacts</span> the lunar surface, converting a portion of its kinetic energy to visible light detectable from Earth. A routine monitoring program at NASA's Marshall Space Flight Center has recorded over 300 <span class="hlt">impact</span> flashes since early 2006. The program utilizes multiple 0.35 m (14 inch) Schmidt-Cassegrain telescopes, outfitted with video cameras using the 1/2 inch Sony EXview HAD CCDTM chip, to perform simultaneous observations of the earthshine hemisphere of the Moon when the lunar phase is between 0.1 and 0.5. This optical arrangement permits monitoring of approximately 3.8x10(6) km2 of lunar surface. A selection of 126 flashes recorded in 266.88 hours of photometric skies was analyzed, creating the largest and most homogeneous dataset of lunar <span class="hlt">impact</span> flashes to date. Standard CCD photometric techniques outlined in [1] were applied to the video to determine the luminous energy, kinetic energy, and mass for each impactor, considering a range of luminous efficiencies. The flux to a limiting energy of 2.5x10(-6) kT TNT or 1.05×10(7) J is 1.03×10(-7) km(-2) hr(-1) and the flux to a limiting mass of 30 g is 6.14×10(-10) m(-2) yr(-1). Comparisons made with measurements and models of the meteoroid population indicate that the flux of objects in this size range is slightly lower (but within the error bars) than the power law distribution determined for the near Earth object population by [2].</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950012878&hterms=Evolution+Controversy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DEvolution%2BControversy','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950012878&hterms=Evolution+Controversy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DEvolution%2BControversy"><span>Chondrule-matrix relationships in chondritic <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>Brearley, A. J.</p> <p>1994-01-01</p> <p>The relationship between chondrules and matrix (fine grained material with a grain size less than 5 micrometers) in chondritic <span class="hlt">meteorites</span> has been the subject of considerable controversy and no consensus currently exists. The coexistence of these two components in <span class="hlt">meteorites</span> with bulk compositions that deviate only slightly from CI abundances suggests that cosmochemically their origins are closely linked. Any consideration of the relationship between chondrules and matrix hinges to a <span class="hlt">large</span> degree on the origin of matrix. The entire spectrum of models exists from matrix as a nebular product to derivation entirely from chondrules. Early models of solar nebular evolution viewed chondrites as a two-component mixture of high- and low-temperature condensates. However, this model has been challenged by the recognition that the nebula was probably not uniformly vaporized.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19990005053','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19990005053"><span><span class="hlt">Meteoritic</span> Sulfur Isotopic Analysis</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Thiemens, Mark H.</p> <p>1996-01-01</p> <p>Funds were requested to continue our program in <span class="hlt">meteoritic</span> sulfur isotopic analysis. We have recently detected a potential nucleosynthetic sulfur isotopic anomaly. We will search for potential carriers. The documentation of bulk systematics and the possible relation to nebular chemistry and oxygen isotopes will be explored. Analytical techniques for delta(sup 33), delta(sup 34)S, delta(sup 36)S isotopic analysis were improved. Analysis of sub milligram samples is now possible. A possible relation between sulfur isotopes and oxygen was detected, with similar group systematics noted, particularly in the case of aubrites, ureilites and entstatite chondrites. A possible nucleosynthetic excess S-33 has been noted in bulk ureilites and an oldhamite separate from Norton County. High energy proton (approximately 1 GeV) bombardments of iron foils were done to experimentally determine S-33, S-36 spallogenic yields for quantitation of isotopic measurements in iron <span class="hlt">meteorites</span>. Techniques for measurement of mineral separates were perfected and an analysis program initiated. The systematic behavior of bulk sulfur isotopes will continue to be explored.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19910055023&hterms=Accelerator+mass+spectrometry&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DAccelerator%2Bmass%2Bspectrometry','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19910055023&hterms=Accelerator+mass+spectrometry&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DAccelerator%2Bmass%2Bspectrometry"><span>Determination of the half-life of Ca-41 from measurements of 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>Klein, Jeffrey; Fink, David; Middleton, Roy; Nishiizumi, Kunihiko; Arnold, James</p> <p>1991-01-01</p> <p>Accelerator mass spectrometry is utilized to determine the half-life of Ca-41 from the decrease of its concentration with terrestrial age in five Antarctic <span class="hlt">meteorites</span> and a recent fall. The <span class="hlt">meteorites</span> were selected on the basis of their Cl-36 concentrations, which showed a span of terrestrial ages of about 600 ka, and on the basis of other cosmogenic nuclide concentrations which indicated that the <span class="hlt">meteorites</span> had small preatmospheric sizes, and sufficiently long irradiation times in space that the concentrations of Ca-41 and Cl-36 were in secular equilibrium prior to the <span class="hlt">meteorites</span>' fall to earth. The half-life of Ca-41 is determined at 103 + or - 7 ka. Topics discussed include the effects of undersaturation (short exposure time in space), shielding (the samples are from the interior of a <span class="hlt">large</span> <span class="hlt">meteorite</span>), and weathering on the cosmogenic nuclide concentrations in <span class="hlt">meteorites</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20080030959&hterms=Nunatak&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DNunatak','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20080030959&hterms=Nunatak&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DNunatak"><span>Antarctic <span class="hlt">Meteorite</span> Newsletter, Volume 28, Number 2</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Righter, Kevin (Editor); Satterwhite, Cecilia (Editor)</p> <p>2005-01-01</p> <p>This newsletter contains classifications for 274 new <span class="hlt">meteorites</span> from the 2003 and 2004 ANtarctic Search for <span class="hlt">METeorites</span> (ANSMET) collections. They include samples from the Cumulus Hills, Larkman Nunatak, LaPaz Ice Field, MacAlpine Hills, Dominion Range, Miller Range, Roberts Massif, and Sandford Cliffs. Tables are provided of the newly classified Antarctic <span class="hlt">meteorites</span>, <span class="hlt">meteorites</span> classified by type, and tentative pairings petrographic descriptions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004M%26PSA..39..171P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004M%26PSA..39..171P"><span>The <span class="hlt">meteorite</span> collection at Museo di Storia Naturale, Pisa University, Italy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Perchiazzi, Natale; D'Orazio, Massimo; Folco, Luigi</p> <p>2004-08-01</p> <p>The historical <span class="hlt">meteorite</span> collection of Museo di Storia Naturale, Pisa University, is presented in this catalog. Dating back to at least 1860, the collection currently (as of June 2003) contains 30 specimens of 26 individual <span class="hlt">meteorites</span>, representing about 50 kg of extraterrestrial material. The collection includes 2 carbonaceous chondrites, 12 ordinary chondrites, 1 achondrite, 4 stony-iron <span class="hlt">meteorites</span>, and 7 iron <span class="hlt">meteorites</span>, including three remarkable specimens: the main mass of Bagnone (48 kg), the fourth largest mass of Quenggouk (717.5 g), and a <span class="hlt">large</span> (nearly) complete individual of the Siena showerfall (318.8 g).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFMMR12A..06D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFMMR12A..06D"><span>Where are all the Strongly 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>de Carli, P. S.; Xie, Z.; Sharp, T. G.</p> <p>2008-12-01</p> <p>Recent studies of high pressure minerals in melt veins have shown that the S6 shock stage, designating the most strongly shocked chondriticmeteorites, corresponds to a peak shock pressure of about 25 GPa and an effective shock pressure duration of the order of one second. (Sharp and De Carli 2006) Calculations of the probability distribution of asteroid-asteroid <span class="hlt">impact</span> velocities in the early solar system indicate a broad peak over the range of 2-7 km/s with a mean of 5.29 km/s. (Bottke et al 1994) The peak pressure at the point of <span class="hlt">impact</span> between two bodies of chondritic composition would be about 25 GPa for a 2 km/s <span class="hlt">impact</span>. For a 7 km/s <span class="hlt">impact</span>, the peak pressure would be about 100 GPa. We would therefore expect to find a substantial population of <span class="hlt">meteorites</span> showing evidence of having been shocked to pressures over the range between 25 and 100 GPa. In fact, there are very few chondrites that appear to have been shocked to pressures above 25 GPa. Here we present the results of Autodyn (TM) hydrocode calculations of asteroid-asteroid <span class="hlt">impacts</span> over the velocity range of 2-7 km/s to provide a measure of the range of expected shock effects in <span class="hlt">meteorites</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1988EOSTr..69..616G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1988EOSTr..69..616G"><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>Goodrich, Cyrena Anne</p> <p></p> <p>Harry Y. McSween's latest book, <span class="hlt">Meteorites</span> and Their Parent Planets, is not intended primarily as a textbook or a technical reference for the dedicated researcher in <span class="hlt">meteoritics</span>. Several up-to-date books along these lines already exist (<span class="hlt">Meteorites</span>: A Petrologic-Chemical Synthesis, by R. T. Dodd, Cambridge University Press, London, 1981; <span class="hlt">Meteorites</span>: Their Record of Early Solar System History, by J. T. Wasson, W. H. Freeman, San Francisco, Calif., 1985; <span class="hlt">Meteorites</span> and the Early Solar System, edited by J. F. Kerridge and M. Matthews, University of Arizona Press, Tucson, in press, 1988). Rather, it is intended as an introduction of the field of <span class="hlt">meteoritics</span> and the study of the formation and evolution of the Solar System, and it is aimed at a broad spectrum of scientists and nonscientists.McSween has undertaken a difficult task. Many problems in <span class="hlt">meteoritics</span> require synthesis of information and lines of reasoning from such diverse and highly specialized areas of study as celestial mechanics, astrophysics, cratering dynamics, spectrophotometry, igneous petrology, and isotope geochemistry. Hence these problems are often difficult for the student, or even the advanced researcher, to grasp and are rarely appreciated by the nonscientist. McSween, however, succeeds remarkably well in presenting this complex subject in a way that any curious, intelligent person can understand.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014A%26A...570A..39S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014A%26A...570A..39S"><span>Reanalysis of the Benešov bolide and recovery of polymict breccia <span class="hlt">meteorites</span> - old mystery solved after 20 years</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Spurný, Pavel; Haloda, Jakub; Borovička, Jiří; Shrbený, Lukáš; Halodová, Patricie</p> <p>2014-10-01</p> <p>The main motivation for this work was to explain and solve the old mystery connected with the detailed instrumental observation of the Benešov superbolide on 7 May 1991 over the central part of the Czech Republic. Detailed analyses of this undoubted <span class="hlt">meteorite</span> fall were published in several papers, and this is one of the best documented bolides (at least of the superbolide category) ever observed. However, despite high-quality data, favorable trajectory, relatively <span class="hlt">large</span> terminal mass, and especially great efforts and many attempts, no <span class="hlt">meteorite</span> was found in the weeks and years after the fall. Here we solve and explain this old mystery. In spring 2011, just before the twentieth anniversary of this extraordinary case, we remeasured all available all-sky records and reanalyzed the data. We used slightly different methods and new approaches, which we gradually developed to analyze several recent instrumentally observed <span class="hlt">meteorite</span> falls (Morávka, Neuschwanstein, Jesenice, Bunburra Rockhole, Mason Gully, and Košice). We assembled a new consistent picture of the Benešov event, which resulted in a slightly revised <span class="hlt">impact</span> location and suggested a new strategy that might lead to a recovery of Benešov <span class="hlt">meteorites</span> after 20 years. The reality completely confirmed all our assumptions and surpassed our expectations. We found four small highly weathered fragments irregular in form and completely without fusion crust with a total mass of 11.63 g (1.54 g (H5), 7.72 g (with achondritic clast), 1.99 g, 0.38 g (all LL3.5)). They were recovered exactly in the predicted <span class="hlt">impact</span> area for corresponding masses, namely within 40 m from the highest probability line. Although all fragments are very small and their weathering grade is high (W3 for all pieces), their interior was preserved enough for reliable analysis (except for the smallest one). The <span class="hlt">meteorite</span> is classified as a polymict breccia containing three recognized lithologies with different texture, chemical, and mineralogical</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20000083885','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20000083885"><span>Antarctic <span class="hlt">Meteorite</span> Newsletter. Volume 22</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); Lindstrom, Marilyn (Editor)</p> <p>1999-01-01</p> <p>This Newsletter Contains Classifications of 143 New <span class="hlt">Meteorites</span> from the 1997 ANSMET Collection. Descriptions are given for 6 <span class="hlt">meteorites</span>;2 eucrites, and 4 ordinary chondrites. We don't expect much excitement from the rest of the 1997 collection. JSC has examined another 100 <span class="hlt">meteorites</span> to send to the Smithsonian for classification and they appear to be more of the same LL5 shower. However, past experience tells us that there will be some treasures hidden in the remaining samples. Hope rings eternal, but we can't wait to see the 1998 collection described below.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUSM.T31A..04M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUSM.T31A..04M"><span>The K/T-boundary carbonate breccia succession at the Cantarell Field, Campeche Bay area: a representative example of the influence of the Chicxulub <span class="hlt">meteorite-impact</span> event on the formation of extraordinary petroleum reservoirs</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Murillo-Muñeton, G.; Grajales-Nishimura, J. M.; Velasquillo-Martínez, L. G.; García-Hernández, J.</p> <p>2013-05-01</p> <p>Over the last decade, intense petroleum exploration and exploitation activities have been conducted in the Campeche Bay area. Detailed stratigraphic studies in this region based on seismic, well logs, and core data have allowed the documentation of numerous deep-water carbonate breccia deposits throughout the Cretaceous stratigraphic column. However, the uppermost carbonate breccia succession is very distinctive in terms of its sedimentological properties compared to the underlying and older calcareous breccia layers. The unique characteristics of this deposit include: its unusual thickness, stratigraphic position, distribution, and content of <span class="hlt">impact</span>-metamorphic constituents. At the Cantarell field, this carbonate breccia sedimentary package is a representative example of how the Chuxulub <span class="hlt">meteorite-impact</span> event influenced the formation of a remarkable carbonate reservoir. This deposit was the most important oil-producing stratigraphic horizon for long time in that field. Nevertheless, this reservoir is still important not only in that field but also in other fields in offshore Campeche. The K/T boundary carbonate breccia succession is a typical fining-upward deposit made up, from base to top, of three units. The 50 to 300-m thick, basal Unit 1 consists of a coarse-grained carbonate breccia. Unit 2 is a 10 to 20 m-thick, fine-grained carbonate breccia. The 25 to 30 m-thick, uppermost Unit 3 is a greenish interval of friable sand, silt and clay-sized constituents with abundant ejecta material. In some wells, a 10 to 20 m-thick, non-oil producing fine-grained calcareous breccia occurs interbedded within Unit 3. The K/T boundary carbonate sedimentary package is underlain and overlain by deep-water shaly calcareous facies of Upper Maastrichtian and Lower Paleocene age, respectively. Studies of cronostratigraphic-equivalent outcrop analogs of this K/T boundary carbonate reservoir carried out by the authors in the Sierra de Chiapas (El Guayal, Tabasco and Bochil, Chiapas</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70000457','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70000457"><span><span class="hlt">Meteorites</span> on Mars observed with Mars Exploration Rovers</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Schroder, C.; Rodionov, D.S.; McCoy, T.J.; Jolliff, B.L.; Gellert, Ralf; Nittler, L.R.; Farrand, W. H.; Johnson, J. R.; Ruff, S.W.; Ashley, James W.; Mittlefehldt, D. W.; Herkenhoff, K. E.; Fleischer, I.; Haldemann, A.F.C.; Klingelhofer, G.; Ming, D. W.; Morris, R.V.; de Souza, P.A.; Squyres, S. W.; Weitz, C.; Yen, A. S.; Zipfel, J.; Economou, T.</p> <p>2008-01-01</p> <p>Reduced weathering rates due to the lack of liquid water and significantly greater typical surface ages should result in a higher density of <span class="hlt">meteorites</span> on the surface of Mars compared to Earth. Several <span class="hlt">meteorites</span> were identified among the rocks investigated during Opportunity's traverse across the sandy Meridiani plains. Heat Shield Rock is a IAB iron <span class="hlt">meteorite</span> and has been officially recognized as 'Meridiani Planum.' Barberton is olivine-rich and contains metallic Fe in the form of kamacite, suggesting a <span class="hlt">meteoritic</span> origin. It is chemically most consistent with a mesosiderite silicate clast. Santa Catarina is a brecciated rock with a chemical and mineralogical composition similar to Barberton. Barberton, Santa Catarina, and cobbles adjacent to Santa Catarina may be part of a strewn field. Spirit observed two probable iron <span class="hlt">meteorites</span> from its Winter Haven location in the Columbia Hills in Gusev Crater. Chondrites have not been identified to date, which may be a result of their lower strengths and probability to survive <span class="hlt">impact</span> at current atmospheric pressures. <span class="hlt">Impact</span> craters directly associated with Heat Shield Rock, Barberton, or Santa Catarina have not been observed, but such craters could have been erased by eolian-driven erosion. Copyright 2008 by the American Geophysical Union.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008JGRE..113.6S22S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008JGRE..113.6S22S"><span><span class="hlt">Meteorites</span> on Mars observed with the Mars Exploration Rovers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schröder, C.; Rodionov, D. S.; McCoy, T. J.; Jolliff, B. L.; Gellert, R.; Nittler, L. R.; Farrand, W. H.; Johnson, J. R.; Ruff, S. W.; Ashley, J. W.; Mittlefehldt, D. W.; Herkenhoff, K. E.; Fleischer, I.; Haldemann, A. F. C.; Klingelhöfer, G.; Ming, D. W.; Morris, R. V.; de Souza, P. A.; Squyres, S. W.; Weitz, C.; Yen, A. S.; Zipfel, J.; Economou, T.</p> <p>2008-04-01</p> <p>Reduced weathering rates due to the lack of liquid water and significantly greater typical surface ages should result in a higher density of <span class="hlt">meteorites</span> on the surface of Mars compared to Earth. Several <span class="hlt">meteorites</span> were identified among the rocks investigated during Opportunity's traverse across the sandy Meridiani plains. Heat Shield Rock is a IAB iron <span class="hlt">meteorite</span> and has been officially recognized as ``Meridiani Planum.'' Barberton is olivine-rich and contains metallic Fe in the form of kamacite, suggesting a <span class="hlt">meteoritic</span> origin. It is chemically most consistent with a mesosiderite silicate clast. Santa Catarina is a brecciated rock with a chemical and mineralogical composition similar to Barberton. Barberton, Santa Catarina, and cobbles adjacent to Santa Catarina may be part of a strewn field. Spirit observed two probable iron <span class="hlt">meteorites</span> from its Winter Haven location in the Columbia Hills in Gusev Crater. Chondrites have not been identified to date, which may be a result of their lower strengths and probability to survive <span class="hlt">impact</span> at current atmospheric pressures. <span class="hlt">Impact</span> craters directly associated with Heat Shield Rock, Barberton, or Santa Catarina have not been observed, but such craters could have been erased by eolian-driven erosion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012M%26PS...47.1324W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012M%26PS...47.1324W"><span>40Ar-39Ar age of Northwest Africa 091: More evidence for a link between L chondrites and fossil <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>Weirich, J. R.; Swindle, T. D.; Isachsen, C. E.</p> <p>2012-08-01</p> <p>Most 40Ar-39Ar ages of L chondrites record an event at approximately 500 Ma, indicating a <span class="hlt">large</span> collisional <span class="hlt">impact</span> at that time. However, there is a spread in ages from 400 to 600 Ma in these <span class="hlt">meteorites</span> that is greater than the analytical uncertainty. Identification of, and correction for, trapped Ar in a few L chondrites has given an age of 470 ± 6 Ma. This age coincides with Ordivician fossil <span class="hlt">meteorites</span> that fell to Earth at 467 ± 2 Ma. As these fossil <span class="hlt">meteorites</span> were originally L chondrites, the apparent conclusion is that a <span class="hlt">large</span> <span class="hlt">impact</span> sent a flood of L chondrite material to Earth, while material that remained on the L chondrite parent body was strongly heated and reset. We have reduced 40Ar-39Ar data for Northwest Africa 091 using various techniques that appear in the literature, including identification and subtraction of trapped Ar. These techniques give a range of ages from 455 to 520 Ma, and show the importance of making accurate corrections. By using the most straightforward technique to identify and remove a trapped Ar component (which is neither terrestrial nor primordial), an 40Ar-39Ar age of 475 ± 6 Ma is found for Northwest Africa 091, showing a temporal link to fossil <span class="hlt">meteorites</span>. In addition, high temperature releases of Northwest Africa 091 contain evidence for a second trapped component, and subtraction of this component indicates a possible second collisional <span class="hlt">impact</span> at approximately 800 Ma. This earlier age coincides with 40Ar-39Ar ages of some H and L chondrites, and lunar samples.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4623988','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4623988"><span>Multiple Cosmic Sources for <span class="hlt">Meteorite</span> Macromolecules?</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Watson, Jonathan S.; Meredith, William; Love, Gordon D.; Gilmour, Iain; Snape, Colin E.</p> <p>2015-01-01</p> <p>Abstract The major organic component in carbonaceous <span class="hlt">meteorites</span> is an organic macromolecular material. The Murchison macromolecular material comprises aromatic units connected by aliphatic and heteroatom-containing linkages or occluded within the wider structure. The macromolecular material source environment remains elusive. Traditionally, attempts to determine source have strived to identify a single environment. Here, we apply a highly efficient hydrogenolysis method to liberate units from the macromolecular material and use mass spectrometric techniques to determine their chemical structures and individual stable carbon isotope ratios. We confirm that the macromolecular material comprises a labile fraction with small aromatic units enriched in 13C and a refractory fraction made up of <span class="hlt">large</span> aromatic units depleted in 13C. Our findings suggest that the macromolecular material may be derived from at least two separate environments. Compound-specific carbon isotope trends for aromatic compounds with carbon number may reflect mixing of the two sources. The story of the quantitatively dominant macromolecular material in <span class="hlt">meteorites</span> appears to be made up of more than one chapter. Key Words: Abiotic organic synthesis—Carbonaceous chondrite—Cosmochemistry—<span class="hlt">Meteorites</span>. Astrobiology 15, 779–786. PMID:26418568</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013GeoRL..40.1624H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013GeoRL..40.1624H"><span>Climate <span class="hlt">impacts</span> of a <span class="hlt">large</span>-scale biofuels expansion</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hallgren, Willow; Schlosser, C. Adam; Monier, Erwan; Kicklighter, David; Sokolov, Andrei; Melillo, Jerry</p> <p>2013-04-01</p> <p>A global biofuels program will potentially lead to intense pressures on land supply and cause widespread transformations in land use. These transformations can alter the Earth climate system by increasing greenhouse gas (GHG) emissions from land use changes and by changing the reflective and energy exchange characteristics of land ecosystems. Using an integrated assessment model that links an economic model with climate, terrestrial biogeochemistry, and biogeophysics models, we examined the biogeochemical and biogeophysical effects of possible land use changes from an expanded global second-generation bioenergy program on surface temperatures over the first half of the 21st century. Our integrated assessment model shows that land clearing, especially forest clearing, has two concurrent effects—increased GHG emissions, resulting in surface air warming; and <span class="hlt">large</span> changes in the land's reflective and energy exchange characteristics, resulting in surface air warming in the tropics but cooling in temperate and polar regions. Overall, these biogeochemical and biogeophysical effects will only have a small <span class="hlt">impact</span> on global mean surface temperature. However, the model projects regional patterns of enhanced surface air warming in the Amazon Basin and the eastern part of the Congo Basin. Therefore, global land use strategies that protect tropical forests could dramatically reduce air warming projected in these regions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19800065883&hterms=heterocycles&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dheterocycles','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19800065883&hterms=heterocycles&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dheterocycles"><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>Lawless, J. G.</p> <p>1980-01-01</p> <p>Recent studies of carbonaceous chondrites provide evidence that certain organic compounds are indigenous and the result of an abiotic, chemical synthesis. The results of several investigators have established the presence of amino acids and precursors, mono- and dicarboxylic acids, N-heterocycles, and hydrocarbons as well as other compounds. For example, studies of the Murchison and Murray <span class="hlt">meteorites</span> have revealed the presence of at least 40 amino acids with nearly equal abundances of D and L isomers. The population consists of both protein and nonprotein amino acids including a wide variety of linear, cyclic, and polyfunctional types. Results show a trend of decreasing concentration with increasing carbon number, with the most abundant being glycine (41 n Moles/g). These and other results to be reviewed provide persuasive support for the theory of chemical evolution and provide the only natural evidence for the protobiological subset of molecules from which life on earth may have arisen.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1988GeCoA..52.2311S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1988GeCoA..52.2311S"><span>Boron in chondritic <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>Shaw, D. M.; Higgins, M. D.; Hinton, R. W.; Truscott, M. G.; Middleton, T. A.</p> <p>1988-09-01</p> <p>The B and Li content and distribution in 14 chondrites are investigated experimentally by means of prompt gamma neutron activation on bulk samples, EMPA, and alpha-track imaging of thin polished sections attached to neutron-irradiated cellulose nitrate films. Alpha-track and transmitted-light images are shown, and numerical results are presented in extensive tables. Chondrites of lower equilibration grades are found to contain practically no Li or B in chondrules, inclusions, sulfides, or metal, so that bulk B/Li content represents material from the matrix. Weathering products in Antarctic <span class="hlt">meteorites</span> are shown to be significantly enriched in B and Cl, and the bulk B content in carbonaceous and ordinary chondrites is found to range from 0.2 to 1 ppm (mean 0.55 ppm).</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/2013SPIE.8865E..07R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013SPIE.8865E..07R"><span>Acritarchs in carbonaceous <span class="hlt">meteorites</span> and terrestrial rocks</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rozanov, Alexei Y.; Hoover, Richard B.</p> <p>2013-10-01</p> <p>Acritarchs are a group of organic-walled, acid-resistant microfossils of uncertain or unknown origin. Some are thought to represent the cysts or resting stages of unicellular protists (possibly dinoflagellates), chrysophytes (green algae) or other planktonic eukaryotic algae. Acritarchs are found throughout the geologic column extending back as far at 3.2 Ga. The presence of <span class="hlt">large</span> sphaeromorphs in the Archaean provides evidence that the eukaryotic lineage extends much farther back in time than previously thought possible. Acritarchs are abundant in the Paleoproterozoic shales (1.9-1.6 Ga) of the former Soviet Union and they have been extensively used for the investigation of Proterozoic and Paleozoic biostratigraphy and paleoenvironmental parameters. Scanning Electron Microscope studies have revealed the fossilized remains of organic-walled microfossils of unknown origin and exhibiting characteristics of acritarchs in a variety of carbonaceous <span class="hlt">meteorites</span>. In many cases, these remains are black or brown in color and have Carbon/Oxygen ratios suggesting they have been diagenetically converted into kerogen. It is not feasible that the fossilized remains of organicwalled microfossils such as acritarchs represent biological contaminant that invaded and became embedded in the rock matrix of carbonaceous <span class="hlt">meteorites</span> within the short time periods of their residence on Earth. Consequently, these groups of microfossils are considered to provide an additional line for the existence of indigenous extraterrestrial microbial remains in <span class="hlt">meteorites</span>. This paper presents a brief review of acritarchs in terrestrial rocks and provides images of a number of similar morphotypes of uncertain origin found in freshly fractured samples of carbonaceous <span class="hlt">meteorites</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20030062981&hterms=Ants&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DAnts','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20030062981&hterms=Ants&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DAnts"><span>Unmelted <span class="hlt">Meteoritic</span> Debris Collected from Eltanin Ejecta in Polarstern Cores from Expedition ANT XII/4</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kyte, Frank T.</p> <p>2002-01-01</p> <p>A total of 1.7g of unmelted <span class="hlt">meteorite</span> particles have been recovered from FS Polarstern piston cores collected on expedition ANT XII/4 that contain ejecta from the Eltanin <span class="hlt">impact</span> event. Most of the mass (1.2 g) is a <span class="hlt">large</span>, single specimen that is a polymict breccia, similar in mineralogy and chemistry to howardites or the silicate fraction of mesosiderites. Most of the remaining mass is in several <span class="hlt">large</span> individual pieces (20-75mg each) that are polymict breccias, fragments dominated by pyroxene, and an igneous rock fragment. The latter has highly fractionated REE, similar to those reported in mafic clasts from mesosiderites. Other types of specimens identified include fragments dominated by maskelynite or olivine. These pieces of the projectile probably survived <span class="hlt">impact</span> by being blown off the back surface of the Eltanin asteroid during its <span class="hlt">impact</span> into the Bellingshausen Sea.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140002614','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140002614"><span><span class="hlt">Large</span> Meteoroid <span class="hlt">Impact</span> on the Moon 17 March 2013</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Suggs, Robert M.; Cooke, William; Kingery, Aaron; Kring, David; Moser, Danielle; Suggs, Ronnie J.</p> <p>2013-01-01</p> <p>NASA's routine monitoring of lunar <span class="hlt">impact</span> flashes has recorded nearly 300 <span class="hlt">impacts</span> since 2006. On 17 March 2013 the brightest event to date was observed in two 0.35m telescopes at the Marshall Space Flight Center. With a peak red magnitude brighter than 4.3 and an <span class="hlt">impact</span> flash visible for over 1 second, the <span class="hlt">impact</span> kinetic energy was equivalent to nearly 5 tons of TNT. A possible association with a meteor shower observed in the Earth's atmosphere will be described. Corresponding crater dimensions and observability of the <span class="hlt">impact</span> crater by Lunar Reconnaissance Orbiter will also be discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19860019340','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19860019340"><span><span class="hlt">Meteorite</span> concentration mechanisms in Antarctica</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>1986-01-01</p> <p>The location of most Antarctic <span class="hlt">meteorite</span> finds is on stagnant, highly ablative surfaces known as blue ice. The role of blue ice as transporter, concentrator, and preserver of specimens from the time of fall until find is discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999LPI....30.1929W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999LPI....30.1929W"><span>Bulk Density Measurements of <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>Wilkison, S. L.; Robinson, M. S.</p> <p>1999-03-01</p> <p>We present density measurements of <span class="hlt">meteorites</span> detailing the precision and errors associated with the modified Archimedian method of Consolmagno and Britt. We find that the method is accurate to better than 1%.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20090042810','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20090042810"><span>Extraterrestrial Amino Acids in the Almahata Sitta <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>Glavin, Daniel P.; Aubrey, Andrew D.; Callahan, Michael P.; Dworkin, Jason P.; Elsila, Jamie E.; Parker, Eric T.; Bada, Jeffrey L.</p> <p>2009-01-01</p> <p>Amino acid analysis of a <span class="hlt">meteorite</span> fragment of asteroid 2008 TC(sub 3) called Almahata Sitta was carried out using reverse-phase high-perfo rmance liquid chromatography coupled with UV fluorescence detection a nd time-of-flight mass spectrometry (HPLC-FD/ToF-MS) as part of a sam ple analysis consortium. HPLC analyses of hot-water extracts from the <span class="hlt">meteorite</span> revealed a complex distribution of two- to six-carbon aliph atic amino acids and one- to three carbon amines with abundances rang ing from 0.5 to 149 parts-per-billion (ppb). The enantiomeric ratios of the amino acids alanine, Beta-amino-n-butyric acid (Beta-ABA), 2-amino-2- methylbutanoic acid (isovaline), and 2-aminopentanoic acid (no rvaline) in the <span class="hlt">meteorite</span> were racemic (D/L approximately 1), indicat ing that these amino acids are indigenous to the <span class="hlt">meteorite</span> and not te rrestrial contaminants. Several other non-protein amino acids were also identified in the <span class="hlt">meteorite</span> above background levels including alpha -aminoisobutyric acid (alpha-AIB), 4-amino-2- methybutanoic acid, 4-a mino-3-methylbutanoic acid, and 3-, 4-, and 5-aminopentanoic acid. Th e total abundances of isovaline and AlB in Almahata Sitta are approximately 1000 times lower than the abundances of these amino acids found in the CM carbonaceous <span class="hlt">meteorite</span> Murchison. The extremely love abund ances and unusual distribution of five carbon amino acids in Almahata Sitta compared to Cl, CM, and CR carbonaceous <span class="hlt">meteorites</span> and may be due to extensive thermal alteration of amino acids on the parent aster oid by partial melting during formation or <span class="hlt">impact</span> shock heating.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001SPIE.4540..229M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001SPIE.4540..229M"><span><span class="hlt">Impact</span> of <span class="hlt">large</span> sidelobe discretes in SAR image formation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Maher, John E.; Lynch, E. Douglas; Schneible, Richard; Wicks, Michael C.; Zhang, Yuhong</p> <p>2001-12-01</p> <p>In this paper, the U.S. Air Force's Research Laboratory Space-Time Adaptive Processing (RLSTAP) tool is used to demonstrate the <span class="hlt">impact</span> of <span class="hlt">large</span> sidelobe discretes on modern Synthetic Aperture Radar (SAR) signal and image processing. Sidelobe discretes ay mask or even completely obscure weak target returns of interest in the immediate vicinity of these strong returns. Adaptive processing offers the potential to mitigate the effects of strong sidelobe discretes on image formation. In this paper, we characterize the severity of the problems caused by these discretes. RLSTAP can simulate high-fidelity airborne, spaceborne, or ground based multi-channel radar data in jamming and clutter environments, develop and evaluate new signal and image processing algorithms, and assess the performance of advanced radar systems. RLSTAP is a time domain simulation, updating object positions for every radar pulse and allowing modeling of realistic effects such as returns 'walking' across range bins and Doppler filters. The site-specific clutter model uses terrain elevation and cover data to derive the line-of-site visibility, grazing angle, and clutter type for each range-angle cell. Spatial and temporal clutter statistics are applied to each cell and the signal strength at the receiver is calculated as a function of the backscatter coefficient, range, atmospheric attenuation, antenna gain, and system gains/losses. The scene generation capability in RLSTAP is unique in that it exploits Defense Terrain Elevation Data (DTED) and Land Use Land Cover Data (LULC) to create realistic clutter scenes (data cubes) for any given geographic location. As such, the application of adaptive multi-channel/multi-pulse processing to radar data that is characteristic of the area being imaged is now possible. Furthermore, the selection of waveform parameters, signal and image processing techniques, and associated radar parameters may be improved upon.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/962528','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/962528"><span>The fall, recovery and classification of the Park Forest <span class="hlt">Meteorite</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Simon, Steve B.; Grossman, Larry; Clayton, Robert N.; Mayeda, T. K.; Schwade, J. R.; Sipiera, P. P.; Wacker, John F.; Wadhwa, M.</p> <p>2004-04-01</p> <p>On the night of March 26, 2003, a <span class="hlt">large</span> <span class="hlt">meteorite</span> broke up and fell upon the south suburbs of Chicago. The name Park Forest, for the village that is at the center of the strewnfield, has been approved by the Nomenclature Committee of the <span class="hlt">Meteoritical</span> Society. Satellite data indicate that the bolide traveled from the southwest toward the northeast. The strewnfield has a southwest-northwest trend, however, probably due to the effects of strong weterly winds at high altitudes. Its very low Co-56 and very high Co-60 activities indicate that Park Forest had a preatmospheric mass that was at least ~900 kg and could bave been as <span class="hlt">large</span> as ~7000 kg, of which only ~30 kg have been recovered. This paper describes initial measurements to identify and characterize the Park Forest <span class="hlt">meteorite</span>, which is classified as an L5 chondrite.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20030111472&hterms=fractions&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dfractions','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20030111472&hterms=fractions&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dfractions"><span>Characterization of Martian Soil Fines Fraction in 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>Rao, M. N.; McKay, D. S.</p> <p>2003-01-01</p> <p>Some <span class="hlt">impact</span>-melt glasses in shergottite <span class="hlt">meteorites</span> contain <span class="hlt">large</span> abundances of martian atmospheric noble gases with high (129)Xe/(132)Xe ratios, accompanied by varying (87)Sr/(86)Sr (initial) ratios. These glasses contain Martian Soil Fines (MSF) probably from young volcanic terrains such as Tharsis or Elysium Mons. The composition of the MSF bearing samples is different from the average bulk composition of the host rock. These samples show the following charecteristics: a) simultaeneous enrichment of the felsic component and depletion of the mafic component relative to the host phase and b) significant secondary sulfur/sulfate excesses over the host material. The degree of enrichment and associated depletion varies from one sample to another. Earlier, we found <span class="hlt">large</span> enrichments of felsic (Al, Ca, Na and K) component and depletion of mafic (Fe, Mg, Mn and Ti) component in several <span class="hlt">impact</span> melt glass veins and pods of samples ,77 ,78 , 18, and ,20A in EET79001 accompanied by <span class="hlt">large</span> sulfur/sulfate excesses. Based on these results, we proposed a model where the comminution of basaltic rocks takes place by meteoroid bombardment on the martian surface, leading to the generation of fine-grained soil near the <span class="hlt">impact</span> sites. This fine-grained soil material is subsequently mobilized by saltation and deflation processes on Mars surface due to pervasive aeolian activity. This movement results in mechanical fractionation leading to the felsic enrichment and mafic depletion in the martian dust. We report, here, new data on an <span class="hlt">impact</span>-melt inclusion ,507 (PAPA) from EET79001, Lith B and ,506 (ALPHA) from EET79001, Lith A and compare the results with those obtained on Shergotty <span class="hlt">impact</span> melt glass (DBS).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6409582','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6409582"><span>Geological implications of <span class="hlt">impacts</span> of <span class="hlt">large</span> asteroids and comets on the earth</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Silver, L.T.; Schultz, P.H.</p> <p>1982-01-01</p> <p>The present conference discusses such topics as <span class="hlt">large</span> object fluxes in near-earth space and the probabilities of terrestrial <span class="hlt">impacts</span>, the geological record of <span class="hlt">impacts</span>, dynamics modeling for <span class="hlt">large</span> body <span class="hlt">impacts</span> on continents and oceans, physical, chemical, and biological models of <span class="hlt">large</span> <span class="hlt">impacts</span> atmospheric effects, dispersed <span class="hlt">impact</span> ejecta and their signatures, general considerations concerning mass biological extinctions, the Cretaceous/Tertiary boundary event, geochemical signatures in the stratigraphic record, and other phanerozoic events. Attention is given to terrestrial <span class="hlt">impact</span> rates for long- and short-period comets, estimates of crater size for <span class="hlt">large</span> body <span class="hlt">impact</span>, a first-order estimate of shock heating and vaporization in oceanic <span class="hlt">impacts</span>, atmospheric effects in the first few minutes after an <span class="hlt">impact</span>, a feasibility test for biogeographic extinction, and the planktonic and dinosaur extinctions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19840042864&hterms=dinosaur&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Ddinosaur','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19840042864&hterms=dinosaur&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Ddinosaur"><span>Geological implications of <span class="hlt">impacts</span> of <span class="hlt">large</span> asteroids and comets on the earth</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Silver, L. T. (Editor); Schultz, P. H. (Editor)</p> <p>1982-01-01</p> <p>The present conference discusses such topics as <span class="hlt">large</span> object fluxes in near-earth space and the probabilities of terrestrial <span class="hlt">impacts</span>, the geological record of <span class="hlt">impacts</span>, dynamics modeling for <span class="hlt">large</span> body <span class="hlt">impacts</span> on continents and oceans, physical, chemical, and biological models of <span class="hlt">large</span> <span class="hlt">impacts</span>' atmospheric effects, dispersed <span class="hlt">impact</span> ejecta and their signatures, general considerations concerning mass biological extinctions, the Cretaceous/Tertiary boundary event, geochemical signatures in the stratigraphic record, and other phanerozoic events. Attention is given to terrestrial <span class="hlt">impact</span> rates for long- and short-period comets, estimates of crater size for <span class="hlt">large</span> body <span class="hlt">impact</span>, a first-order estimate of shock heating and vaporization in oceanic <span class="hlt">impacts</span>, atmospheric effects in the first few minutes after an <span class="hlt">impact</span>, a feasibility test for biogeographic extinction, and the planktonic and dinosaur extinctions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19820027475&hterms=Lafayette&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DLafayette','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19820027475&hterms=Lafayette&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DLafayette"><span>Composition and origin of the unusual Oktibbeha County iron <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>Kracher, A.; Willis, J.</p> <p>1981-01-01</p> <p>Oktibbeha County, the most Ni-rich iron <span class="hlt">meteorite</span>, has been analyzed for Ni, Co, Cu, Ga, Ge, As, Sb, Ir, and Au. Cu and Sb are higher than in any other iron, but other trace elements are within the ranges typically found in iron <span class="hlt">meteorites</span>. Extrapolation of trace element trends in group IAB indicates that Oktibbeha County is a member of this group. This sheds light on the origin of groups IAB and IIICD, which are thought to be derived from <span class="hlt">impact</span> melts on parent bodies of chondritic composition. Lafayette (iron), another sample reported in the literature to have a similarly high Ni content, is probably a pseudometeorite.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1710863O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1710863O"><span>Effects of low velocity <span class="hlt">impacts</span> on basaltoids</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Oszkiewicz, Dagmara; Nowak, Monika; Kohout, Tomas; McDermott, Kathryn; Marciniak, Lukasz; Muinonen, Karri; Penttila, Antti</p> <p>2015-04-01</p> <p>According to Antarctic <span class="hlt">Meteorite</span> Collection (ANSMET program) less than 1% of collected <span class="hlt">meteorites</span> belong to the so-called HED (howardite- eucrite-diogenite) <span class="hlt">meteorite</span> group. Those <span class="hlt">meteorites</span> have been identified to originate from asteroid (4) Vesta - the only currently known differentiated and intact asteroid in the Main Asteroid Belt. Few of the known HED <span class="hlt">meteorites</span> cannot be chemically linked to Vesta, the most prominent ones include Ibitira and NWA011. Those <span class="hlt">meteorites</span> among with other evidence suggest that additional differentiated bodies existed in the Solar System at some point during its history. The observational proofs for those bodies are however missing. This mismatch between in-situ <span class="hlt">meteoritic</span> and observational asteroidal evidence is known as the "missing dunite" problem [Burbine et al., 1996]. Several observational, dynamical, chemical and geological hypothesis were put forward to explain the mismatch. For example [Burbine et al., 1996] suggested that the basaltic asteroids were "battered to bits" and are curently beyond our spectroscopic reach. More recently [Weiss et al., 2013] showed that partial differentiation is possible, creating an alternative formation hypothesis for those bodies. Few of the hypothetical explanations of the missing dunite problem (such as modification of V-type spectra by space weathering or <span class="hlt">impact</span> shocking) could be tested experimentally in laboratories. Ideally experimental studies require multiple trials on <span class="hlt">large</span> amounts of various materials. The samples are often permanently altered or even damaged during the experiments. Given the scarcity of HED <span class="hlt">meteorites</span> the best solution would be to perform the studies on analogue materials. In this research we explore the possibility of using the Earth basalts and peridotites as analogues to HED <span class="hlt">meteorites</span>. In particular we analyze the differences and similarities in chemical composition, mineralogy, reflectance spectra and matterial shock induced changes in the selected Earth</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMNH11A1887B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMNH11A1887B"><span><span class="hlt">Meteorite</span> fractures and the behavior of meteoroids in the atmosphere</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bryson, K.; Ostrowski, D. R.; Sears, D. W. G.</p> <p>2015-12-01</p> <p>Arguably the major difficulty faced to model the atmospheric behavior of objects entering the atmosphere is that we know very little about the internal structure of these objects and their methods of fragmentation during fall. In a study of over a thousand <span class="hlt">meteorite</span> fragments (mostly hand-sized, some 40 or 50 cm across) in the collections of the Natural History Museums in Vienna and London, we identified six kinds of fracturing behavior. (1) Chondrites usually showed random fractures with no particular sensitivity to <span class="hlt">meteorite</span> texture. (2) Coarse irons fractured along kamacite grain boundaries, while (3) fine irons fragmented randomly, c.f. chondrites. (4) Fine irons with <span class="hlt">large</span> crystal boundaries (e.g. Arispe) fragmented along the crystal boundaries. (5) A few chondrites, three in the present study, have a distinct and strong network of fractures making a brickwork or chicken-wire structure. The Chelyabinsk <span class="hlt">meteorite</span> has the chicken-wire structure of fractures, which explains the very <span class="hlt">large</span> number of centimeter-sized fragments that showered the Earth. Finally, (6) previous work on Sutter's Mill showed that water-rich <span class="hlt">meteorites</span> fracture around clasts. To scale the <span class="hlt">meteorite</span> fractures to the fragmentation behavior of near-Earth asteroids, it has been suggested that the fracturing behavior follows a statistical prediction made in the 1930s, the Weibull distribution, where fractures are assumed to be randomly distributed through the target and the likelihood of encountering a fracture increases with distance. This results in a relationship: σl = σs(ns/nl)α, where σs and σl refers to stress in the small and <span class="hlt">large</span> object and ns and nl refer to the number of cracks per unit volume of the small and <span class="hlt">large</span> object. The value for α, the Weibull coefficient, is unclear. Ames <span class="hlt">meteorite</span> laboratory is working to measure the density and length of fractures observed in these six types of fracture to determine values for the Weibull coefficient for each type of object.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19920004443','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19920004443"><span>The relative importance of prebiotic synthesis on the Earth and input from comets 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>Miller, S. L.</p> <p>1991-01-01</p> <p>The prebiotic synthesis of hydrogen cyanide and formaldehyde was studied by the action of electric discharges on various model primitive atmospheres containing CH4, CO, and CO2. Photochemical production rates would also have been important and were calculated for HCN and H2CO. A reasonable rate of synthesis of amino acids from these sources is about 10 n moles/(sq cm yr) or 0.10 moles/sq cm in 10(exp 7) yrs. This would give a concentration of 3 x 10(exp -4) M in an ocean of the present size (300 liters/sq cm). The amino acids cannot accumulate over a longer period because the entire ocean passes through the 350 C submarine vents in 10(exp 7) yrs, which decomposes all the organic compounds. A number of workers have calculated the influx of comets and <span class="hlt">meteorites</span> on the primitive earth, both as a destructive process for organic compounds and for any life that was present, as well as a source of organic compounds. Some of the amino acids from the <span class="hlt">meteorite</span> proposed to have hit the earth 65 x 10(exp 6) yrs ago were detected at the Cretaceous/Tertiary boundary sediments. The problem with proposing a <span class="hlt">large</span> scale input of organic compounds from <span class="hlt">meteorites</span> and comets is that they must survive passage through the atmosphere and <span class="hlt">impact</span>. There are some processes that would allow survival such as showers of centimeter to meter sized <span class="hlt">meteorites</span> and various aerodynamic braking processes for larger objects. Even if a significant amount of the organic material survived <span class="hlt">impact</span>, the destructive processes in the hydrothermal vents would remove these compounds on the average in 10(exp 7) yrs or less. If it is assumed that the input rate was sufficient to overcome these destructive processes, then too much carbon and water, especially from comets, would have been added to the surface of the earth. It was concluded that while some organic material was added to the earth from comets and <span class="hlt">meteorites</span>, the amount available from these sources at a given time was only a few percent of that from</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19940028728','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19940028728"><span>The Martian sources of the SNC <span class="hlt">meteorites</span> (two, not one), and what can and can't be learned from the 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>Treiman, A. H.</p> <p>1993-01-01</p> <p>The SNC <span class="hlt">meteorites</span>, which almost certainly originate in the Martian crust, have been inferred to come from a single <span class="hlt">impact</span> crater site, but no known crater fits all criteria. Formation at two separate sites (S from one, NC from the other) is more consistent with the sum of petrologic, geochronologic, and cosmochronologic data. If the source craters for the SNC <span class="hlt">meteorites</span> can be located, Mars science will advance considerably. However, many significant questions cannot be answered by the SNC <span class="hlt">meteorites</span>. These questions await a returned sample.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014LPICo1800.5360B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014LPICo1800.5360B"><span>Using <span class="hlt">Meteorites</span> to Find the Age of the Moon-Forming Event</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bottke, W. F.; Swindle, T. D.; Marchi, S.; Scott, E. R. D.; Vokrouhlicky, D.; Weirich, J. R.</p> <p>2014-09-01</p> <p>Thermal resetting ages of <span class="hlt">meteorites</span> appear to show a maximum at about 100 ± 30 Ma after the formation of CAIs, plausibly related to the <span class="hlt">impact</span> of fragments released by the event that formed the Earth’s Moon.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/756785','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/756785"><span>Noble gases and cosmogenic radionuclides in the Eltanin Pacific <span class="hlt">meteorite</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bogard, D D; Garrison, D H; Caffee, M W; Kyte, F; Nishiizumi, K</p> <p>2000-01-14</p> <p>A 1.5 cm long, 1.2 g specimen of the Eltanin <span class="hlt">meteorite</span> was found at 10.97 m depth in Polarstern piston core PS2704-1. The early studies indicated that the small fragments of the Eltanin <span class="hlt">meteorite</span> was debris from a km-sized asteroid which <span class="hlt">impacted</span> into the deep-ocean basin. In this study, the authors measured {sup 39}Ar-{sup 40}Ar age, noble gases, and cosmogenic radionuclides in splits of specimen as a part of consortium studies of Eltanin <span class="hlt">meteorite</span>. They concluded that the specimen was about 3 m deep from the asteroid surface. The exposure age of the Eltanin asteroid was about 20 Myr.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014M%26PS...49.1769G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014M%26PS...49.1769G"><span>The Orgueil <span class="hlt">meteorite</span>: 150 years of history</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gounelle, Matthieu; Zolensky, Michael E.</p> <p>2014-10-01</p> <p>The goal of this paper is to summarize 150 yr of history of a very special <span class="hlt">meteorite</span>. The Orgueil <span class="hlt">meteorite</span> fell near Montauban in southwestern France on May 14, 1864. The bolide, which was the size of the full Moon, was seen across Western France, and almost immediately made the news in local and Parisian newspapers. Within a few weeks of the fall, a great diversity of analyses were performed under the authority of Gabriel Auguste Daubrée, geology professor at the Paris Museum, and published in the Comptes Rendus de l'Académie des Sciences. The skilled scientists reported the presence of iron sulfides, hydrated silicates, and carbonates in Orgueil. They also characterized ammonium salts which are now gone, and observed sulfates being remobilized at the surface of the stone. They identified the high water and carbon contents, and noted similarities with the Alais <span class="hlt">meteorite</span>, which had fallen in 1806, 300 km away. While Daubrée and his colleagues noted the similarity of the Orgueil organic matter with some terrestrial humus, they were cautious not to make a direct link with living organisms. One century later, Nagy and Claus were less prudent and announced the discovery of "organized" elements in some samples of Orgueil. Their observations were quickly discredited by Edward Anders and others who also discovered that some pollen grains were intentionally placed into the rock back in the 1860s. Orgueil is now one of the most studied <span class="hlt">meteorites</span>, indeed one of the most studied rocks of any kind. Not only does it contain a <span class="hlt">large</span> diversity of carbon-rich compounds, which help address the question of organo-synthesis in the early solar system but its chemical composition is also close to that of the Sun's photosphere and serves as a cosmic reference. Secondary minerals, which make up 99% of the volume of Orgueil, were probably formed during hydrothermal alteration on the parent-body within the first few million years of the solar system; their study is essential to our</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1995Metic..30R.545M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1995Metic..30R.545M"><span>Cratering Dynamics and the Delivery of <span class="hlt">Meteorites</span> to the Earth</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Melosh, H. J.</p> <p>1995-09-01</p> <p>In the past decade it has become clear that <span class="hlt">meteorites</span> falling onto the Earth's surface do not only originate on asteroids or comets, but have also come from the surface of the Moon, Mars, and potentially other major planets or moons in the solar system. One of the most puzzling aspects of a <span class="hlt">large</span>-planet origin for some <span class="hlt">meteorites</span> is the relative lack of shock damage in rocks that must have been ejected at speeds of 2.4 km/sec (moon) to 5.0 km/sec (Mars). Older work equated the ejection velocity to the particle velocity behind a shock wave (or, in more sophisticated analyses, to half the particle velocity because of velocity-doubling at the free surface). The known hugoniot relations for, say, basalt, translate these particle velocities to enormous shock pressures: 44 GPa for lunar ejection and 150 Gpa for Mars, which should have pulverized, melted or even partially vaporized the ejected rocks. Although several of the Martian <span class="hlt">meteorites</span> show moderate degrees of shock (30-40 GPa), some show no detectable signs of shock compression, nor do the lunar <span class="hlt">meteorites</span> show much evidence for shock upon ejection. Ten years ago I proposed that this situation could be resolved if the process of spallation is important in <span class="hlt">impact</span> crater ejection [1]. In this process near-surface rocks are protected from high shock pressures simply by virtue of being near the surface. A free surface is, by definition, a surface of zero pressure, and the encroachment of a shock wave cannot change that fact: The shock pressure may rise rapidly with increasing depth, but a near-surface zone will always be present from which material is ejected at high speeds but with little shock damage. This prediction has now been verified directly by laboratory experiments [2], as well as by the discovery of sub-ballistic ejecta from the Ries crater that is composed of lightly-shocked near-surface rocks that were thrown nearly 200 km from the <span class="hlt">impact</span> site [3]. It also seems that the secondary craters commonly</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://hdl.handle.net/2060/20150019423','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150019423"><span>Evidence from Hydrogen Isotopes in <span class="hlt">Meteorites</span> for a Subsurface Hydrogen Reservoir on Mars</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Usui, Tomohiro; Alexander, Conel M. O'D.; Wang, Jianhua; Simon, Justin I.; Jones, John H.</p> <p>2015-01-01</p> <p>The surface geology and geomorphology of Mars indicates that it was once warm enough to maintain a <span class="hlt">large</span> body of liquid water on its surface, though such a warm environment might have been transient. The transition to the present cold and dry Mars is closely linked to the history of surface water, yet the evolution of surficial water is poorly constrained. We have conducted in situ hydrogen isotope (D/H) analyses of quenched and <span class="hlt">impact</span> glasses in three Martian <span class="hlt">meteorites</span> (Yamato 980459, EETA79001, LAR 06319) by Cameca ims-6f at Digital Terrain Models (DTM) following the methods of [1]. The hydrogen isotope analyses provide evidence for the existence of a distinct but ubiquitous water/ice reservoir (D/H = 2-3 times Earth's ocean water: Standard Mean Ocean Water (SMOW)) that lasted from at least the time when the <span class="hlt">meteorites</span> crystallized (173-472 Ma) to the time they were ejected by <span class="hlt">impacts</span> (0.7-3.3 Ma), but possibly much longer [2]. The origin of this reservoir appears to predate the current Martian atmospheric water (D/H equals approximately 5-6 times SMOW) and is unlikely to be a simple mixture of atmospheric and primordial water retained in the Martian mantle (D/H is approximately equal to SMOW [1]). Given the fact that this intermediate-D/H reservoir (2-3 times SMOW) is observed in a diverse range of Martian materials with different ages (e.g., SNC (Shergottites, Nakhlites, Chassignites) <span class="hlt">meteorites</span>, including shergottites such as ALH 84001; and Curiosity surface data [3]), we conclude that this intermediate-D/H reservoir is likely a global surficial feature that has remained relatively intact over geologic time. We propose that this reservoir represents either hydrated crust and/or ground ice interbedded within sediments. Our results corroborate the hypothesis that a buried cryosphere accounts for a <span class="hlt">large</span> part of the initial water budget of Mars.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19900060763&hterms=Zinc&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DZinc','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19900060763&hterms=Zinc&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DZinc"><span>Zinc isotope anomalies in Allende <span class="hlt">meteorite</span> inclusions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Loss, R. D.; Lugmair, G. W.</p> <p>1990-01-01</p> <p>The isotopic compositions of Zn, Cr, Ti, and Ca have been measured in a number of CAIs from the Allende <span class="hlt">meteorite</span>. The aim was to test astrophysical models which predict <span class="hlt">large</span> excesses of Zn-66 to accompany excesses in the neutron-rich isotopes of Ca, Ti, Cr, and Ni. Some of the CAIs show clearly resolved but small excesses for Zn-66 which are at least an order of magnitude smaller than predicted. This result may simply reflect the volatility and chemical behavior of Zn as compared to the other (more refractory) anomalous elements found in these samples. Alternatively, revision of parameters and assumptions used for the model calculations may be required.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19760016995','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19760016995"><span>Economic <span class="hlt">impact</span> of <span class="hlt">large</span> public programs: The NASA experience</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ginzburg, E.; Kuhn, J. W.; Schnee, J.; Yavitz, B.</p> <p>1976-01-01</p> <p>The economic <span class="hlt">impact</span> of NASA programs on weather forecasting and the computer and semiconductor industries is discussed. Contributions to the advancement of the science of astronomy are also considered.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000psrd.reptE..39T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000psrd.reptE..39T"><span>Liquid Water on Mars: The Story from <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>Taylor, G. J.</p> <p>2000-05-01</p> <p>Two studies shed light on the nature and timing of alteration by water of rocks from Mars. One is an experimental study of the alteration of a rock similar to Martian <span class="hlt">meteorites</span>, conducted by Leslie Baker, Deborah Agenbroad, and Scott Wood (University of Idaho). They exposed crushed pieces of terrestrial lava flows to water at 23 C and 75 C and normal atmospheric pressure, and to hot water at 200 C to 400 C and a pressure 1000 times normal atmospheric to see what minerals would form. On the basis of a detailed comparison between the experimental products and the Martian <span class="hlt">meteorites</span> Baker and colleagues conclude that the rocks from which Martian <span class="hlt">meteorites</span> derived were intermittently exposed to water or water vapor; they were not exposed for a long time to <span class="hlt">large</span> volumes of water. In an independent study, a team led by Tim Swindle (University of Arizona) tried to determine the time of formation of a reddish-brown alteration product in the Martian <span class="hlt">meteorite</span> Lafayette. This <span class="hlt">meteorite</span> appears to have formed from magma 1.3 billion years ago, but the rusty-looking weathering product, a mixture of clay minerals, iron oxide, and iron hydride, formed long after the original rock had crystallized. Although the precise time is not pinned down, their measurements indicate formation during the past 650 million years. Taken together, these studies suggest that water flowed intermittently on the surface of Mars during the past 650 million years.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19940007765&hterms=osmium&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dosmium','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19940007765&hterms=osmium&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dosmium"><span>Re-Os dating of 3AB 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>Esat, Tezer M.; Bennett, Victoria</p> <p>1993-01-01</p> <p>Recently, Creaser et al., and Volkening and Heumann, have demonstrated the efficient production of <span class="hlt">large</span> (approximately 10 exp -11 A) ion beams by negative thermal ionization mass spectrometry (NTIMS) using standard laboratory solutions of Os compounds. Horan et al., have applied NTIMS to a group of 7 IIA iron <span class="hlt">meteorites</span> and obtained a Re-Os closure age of 4596 +/- 152 million years. The initial Os-187/Os-186 ratio was 0.8007 plus or minus 0.0029. In addition they analyzed 3 IIIA <span class="hlt">meteorite</span> samples which indicated an age of 4554 +/- 180 million years and Os initial of 0.8120 +/- 0.0075 which does not overlap with the initial for the IIA irons. We have been independently pursuing a similar program with the direct aim of determining possible variations in the initial (Os-187)/(Os-186) ratio or Re-Os closure age of different classes of iron <span class="hlt">meteorite</span>. We have applied NTIMS to Os extracted from the most common group of iron <span class="hlt">meteorites</span> the IIIAB. These <span class="hlt">meteorites</span> are believed to be of magmatic origin, formed by fractional crystallization of molten cores of asteroidal bodies. The present results point to a significantly lower initial (Os-187)/(Os-186) ratio of 0.7731 plus or minus 0.0050 than previously determined.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007M%26PS...42.1781B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007M%26PS...42.1781B"><span>Petrographic classification of Middle Ordovician fossil <span class="hlt">meteorites</span> from Sweden</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bridges, J. C.; Schmitz, B.; Hutchison, R.; Greenwood, R. C.; Tassinari, M.; Franchi, I. A.</p> <p></p> <p>The maximum diameter of chromite (FeCr2O4) grains within L chondrites reflects the petrographic type of the sample. On the basis of our measurements of nine recent L chondrites, L3 chromite Dmax = 34-50 μm, L4 = 87-150 μm, L5 = 76-158 μm, and L6 = 253-638 μm. This variation reflects the crystallization of the chromite grains during parent body thermal metamorphism. We use this calibration to classify six fossil <span class="hlt">meteorites</span> from the Middle Ordovician in Sweden as type 3 (or 4) to 6. The high flux of L chondrites at 470 Ma contained a range of petrographic types and may have had a higher proportion of lower petrographic type <span class="hlt">meteorites</span> than are found in recent L chondrite falls. The fossil <span class="hlt">meteorites</span> have in places preserved recognizable chondrule textures, including porphyritic olivine, barred olivine, and radiating pyroxene. A <span class="hlt">large</span> relict clast and fusion crust have also been tentatively identified in one fossil <span class="hlt">meteorite</span>. Apart from chromite, all of the original <span class="hlt">meteorite</span> minerals have been replaced by carbonate (and sheet silicate and sulfate) during diagenesis within the limestone host. The preservation of chondrule definition has allowed us to measure the mean diameters of relict chondrules. The range (0.4-0.6 mm) is consistent with measurements made in the same way on recent L chondrites.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18310323','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18310323"><span>Molecular asymmetry in extraterrestrial chemistry: Insights from a pristine <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>Pizzarello, Sandra; Huang, Yongsong; Alexandre, Marcelo R</p> <p>2008-03-11</p> <p>The nonracemic amino acids of <span class="hlt">meteorites</span> provide the only natural example of molecular asymmetry measured so far outside the biosphere. Because extant life depends on chiral homogeneity for the structure and function of biopolymers, the study of these <span class="hlt">meteoritic</span> compounds may offer insights into the establishment of prebiotic attributes in chemical evolution as well as the origin of terrestrial homochirality. However, all efforts to understand the origin, distribution, and scope of these amino acids' enantiomeric excesses (ee) have been frustrated by the ready exposure of <span class="hlt">meteorites</span> to terrestrial contaminants and the ubiquitous homochirality of such contamination. We have analyzed the soluble organic composition of a carbonaceous <span class="hlt">meteorite</span> from Antarctica that was collected and stored under controlled conditions, <span class="hlt">largely</span> escaped terrestrial contamination and offers an exceptionally pristine sample of prebiotic material. Analyses of the <span class="hlt">meteorite</span> diastereomeric amino acids alloisoleucine and isoleucine allowed us to show that their likely precursor molecules, the aldehydes, also carried a sizable molecular asymmetry of up to 14% in the asteroidal parent body. Aldehydes are widespread and abundant interstellar molecules; that they came to be present, survived, and evolved in the solar system carrying ee gives support to the idea that biomolecular traits such as chiral asymmetry could have been seeded in abiotic chemistry ahead of life.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19940016412&hterms=Peridotite&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DPeridotite','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19940016412&hterms=Peridotite&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DPeridotite"><span>The carbon components in SNC <span class="hlt">meteorites</span> of feldspathic harzburgite composition</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wright, I. P.; Douglas, C.; Pillinger, C. T.</p> <p>1993-01-01</p> <p>Two <span class="hlt">meteorites</span> collected in Antarctica, ALH A77005 and LEW 88516, have characteristics which link them to the shergottite group of SNC <span class="hlt">meteorites</span>. Essentially, ALH A77005 and LEW 88516 are feldspathic harzburgites, being comprised of roughly equal quantities of olivine and pyroxene, with an additional few percent of feldspar which has subsequently been converted to maskelynite by shock. The <span class="hlt">meteorites</span> represent samples of a cumulate rock which is itself composed of two different lithologies: in one, <span class="hlt">large</span> pyroxenes poikilitically enclose olivine crystals, while the other consists of interstitial areas made up of pyroxene, olivine, maskelynite, whitlockite, troilite, ilmenite and chlorapatite. It has been proposed that <span class="hlt">meteorites</span> such as ALH A77005 (and LEW 88516) are relict samples of the source peridotite from which the other shergottites formed. As such it should be informative to study in detail the carbon components present within these samples, in order to make comparisons with data from other shergottites. Although not plutonic in origin, and therefore not sampling a truly deep source, analyses of ALH A77005 and LEW 88516 should assist with attempts to define the bulk carbon isotopic composition of Mars. This has been assessed previously through analyses of carbon of presumed magmatic origin in other SNC <span class="hlt">meteorites</span>, but the carbon isotopic compositions obtained seem to be at variance with what might be expected. It is important to constrain the carbon isotopic composition of Mars as well as possible so that models of atmospheric evolution, based on carbon isotopic data, can yield the most reliable results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19980038219','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19980038219"><span>The Orbits of <span class="hlt">Meteorites</span> from Natural Thermoluminescence. Attachment 5</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Benoit, P. H.; Sears, D. W. G.</p> <p>1997-01-01</p> <p>The natural thermoluminescence (TL) of <span class="hlt">meteorites</span> reflects their irradiation and thermal histories. Virtually all ordinary chondrites have been irradiated long enough to reach saturation natural TL levels, and thus natural TL levels in these <span class="hlt">meteorites</span> are determined <span class="hlt">largely</span> by thermal history. The primary heat source for most <span class="hlt">meteorites</span> is the Sun, and thus natural TL levels are determined primarily by the closest approach to the Sun, i.e., perihelion. By converting natural TL levels to perihelia, using an assumed albedo typical of meteoroid bodies, it is found that most ordinary chondrites had perihelia of 0.85 to 1.0 AU prior to reaching Earth. This range is similar to that calculated from meteor and fireball observations. All common classes of ordinary chondrites exhibit similar perihelia distributions; however, H and LL chondrites that fell in the local morning differ in their natural TL distribution from those that fell in the local afternoon or evening. This is consistent with earlier suggestions that time of fall reflects orbital distribution. The data also suggest that the orbits of some of the H chondrites cluster and may have come from a debris 'stream' of meteoroids. If <span class="hlt">meteorites</span> can exist in "orbital groups," significant changes in the types and number of <span class="hlt">meteorites</span> reaching Earth could occur on the less than 10(exp 5)-year time scale.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920032190&hterms=thermoluminescence&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dthermoluminescence','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920032190&hterms=thermoluminescence&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dthermoluminescence"><span>The natural thermoluminescence of <span class="hlt">meteorites</span>. III - Lunar and basaltic <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, Derek W. G.; Benoit, Paul H.; Sears, Hazel; Batchelor, J. D.; Symes, Steve</p> <p>1991-01-01</p> <p>Natural thermoluminescence (TL) data were obtained to investigate recent thermal and radiation histories of the lunar <span class="hlt">meteorite</span> MacAlpine Hills 88104/5 and 65 eucrites, howardites, diogenites, and mesosiderites. All these <span class="hlt">meteorites</span> have low levels of natural TL compared to chondrites, which is primarily because they display anomalous fading. Some <span class="hlt">meteorites</span> have especially low natural TL which must reflect heating within the last 100,000-1,000,000 y. The parameters for TL decay were determined assuming plausible values for cosmic ray dose rate and that the natural TL of MAC88104/5 was totally drained by ejection from the moon. The obtained parameters for TL decay suggest that the moon-earth transit times for MAC88104 and MAC88105 were 2,000 and 1,800 y, respectively, compared with 19,000 and 2,500 y for Y791197 and ALHA81005, respectively.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015M%26PS...50..214C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015M%26PS...50..214C"><span>Constraining the source regions of lunar <span class="hlt">meteorites</span> using orbital geochemical data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Calzada-Diaz, A.; Joy, K. H.; Crawford, I. A.; Nordheim, T. A.</p> <p>2015-02-01</p> <p>Lunar <span class="hlt">meteorites</span> provide important new samples of the Moon remote from regions visited by the Apollo and Luna sample return missions. Petrologic and geochemical analysis of these <span class="hlt">meteorites</span>, combined with orbital remote sensing measurements, have enabled additional discoveries about the composition and age of the lunar surface on a global scale. However, the interpretation of these samples is limited by the fact that we do not know the source region of any individual lunar <span class="hlt">meteorite</span>. Here, we investigate the link between <span class="hlt">meteorite</span> and source region on the Moon using the Lunar Prospector gamma ray spectrometer remote sensing data set for the elements Fe, Ti, and Th. The approach has been validated using Apollo and Luna bulk regolith samples, and we have applied it to 48 <span class="hlt">meteorites</span> excluding paired stones. Our approach is able broadly to differentiate the best compositional matches as potential regions of origin for the various classes of lunar <span class="hlt">meteorites</span>. Basaltic and intermediate Fe regolith breccia <span class="hlt">meteorites</span> are found to have the best constrained potential launch sites, with some <span class="hlt">impact</span> breccias and pristine mare basalts also having reasonably well-defined potential source regions. Launch areas for highland feldspathic <span class="hlt">meteorites</span> are much less well constrained and the addition of another element, such as Mg, will probably be required to identify potential source regions for these.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110005436','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110005436"><span>Investigation of Orthopyroxene Diversity in Howardite <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>Johnson, Kristin N.; Herrin, J. S.; Mittlefehldt, D. W.</p> <p>2011-01-01</p> <p>The howardite, eucrite and diogenite (HED) family of <span class="hlt">meteorites</span> is considered to originate from the asteroid 4-Vesta [1]. Howardites are polymict breccias made mostly of diogenitic and eucritic debris [2], and have recently been divided into two types: regolithic and fragmental [3]. Regolithic howardites have higher noble gas contents due to solar wind exposure, have a greater abundance of <span class="hlt">impact</span>-produced glass, are richer in siderophile elements, e.g. Ni, and may preferentially have a mixing ratio of eucrite to diogenite of approx.2:1 [3]. The hypothesis is that these characteristics are a result of originating from an ancient, well-mixed regolith [3]. Fragmental howardites, by contract, show less evidence of regolithic processing and are suggested to have originated in more recently formed <span class="hlt">impact</span> ejecta [3]. Our work aims to evaluate this hypothesis. We have examined the compositional variations of orthopyroxene (diogenite) clasts within eight howardites. We posited that because regolithic howardites sampled a wider range of the asteroid surface, they would contain orthopyroxene fragments with wider ranges in incompatible element contents than would fragmental howardites that sampled fewer diogenitic source rocks. One purpose of developing an additional method to differentiate regolithic and fragmental howardites is to aid in interpretation of data expected from the Dawn mission to 4-Vesta. The Dawn analyses will be of the regolith layers, making an understanding of regolithic <span class="hlt">meteorites</span> and the processes by which they were formed an important constraint on understanding Dawn data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19910042849&hterms=matter+formation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dmatter%2Bformation','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19910042849&hterms=matter+formation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dmatter%2Bformation"><span>Organic matter in <span class="hlt">meteorites</span> and comets - Possible origins</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Anders, Edward</p> <p>1991-01-01</p> <p>At least six extraterrestrial environments may have contributed organic compounds to <span class="hlt">meteorites</span> and comets: solar nebula, giant-planet subnebulae, asteroid interiors containing liquid water, carbon star atmospheres, and diffuse or dark interstellar clouds. The record in <span class="hlt">meteorites</span> is partly obscured by pervasive reheating that transformed much of the organic matter to kerogen; nonetheless, it seems that all six formation sites contributed. For comets, the <span class="hlt">large</span> abundance of HCHO, HCN, and unsaturated hydrocarbons suggests an interstellar component of 50 percent or more, but the contributions of various interstellar processes, and of a solar-nebula component, are hard to quantify. A research program is outlined that may help reduce these uncertainties.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1991SSRv...56..157A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1991SSRv...56..157A"><span>Organic matter in <span class="hlt">meteorites</span> and comets - Possible origins</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Anders, E.</p> <p>1991-04-01</p> <p>At least six extraterrestrial environments may have contributed organic compounds to <span class="hlt">meteorites</span> and comets: solar nebula, giant-planet subnebulae, asteroid interiors containing liquid water, carbon star atmospheres, and diffuse or dark interstellar clouds. The record in <span class="hlt">meteorites</span> is partly obscured by pervasive reheating that transformed much of the organic matter to kerogen; nonetheless, it seems that all six formation sites contributed. For comets, the <span class="hlt">large</span> abundance of HCHO, HCN, and unsaturated hydrocarbons suggests an interstellar component of 50 percent or more, but the contributions of various interstellar processes, and of a solar-nebula component, are hard to quantify. A research program is outlined that may help reduce these uncertainties.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70023756','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70023756"><span>The <span class="hlt">Meteoritical</span> Bulletin, no. 85, 2001 September</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Grossman, J.N.; Zipfel, J.</p> <p>2001-01-01</p> <p><span class="hlt">Meteoritical</span> Bulletin No. 85 lists information for 1376 newly classified <span class="hlt">meteorites</span>, comprising 658 from Antarctica, 409 from Africa, 265 from Asia (262 of which are from Oman), 31 from North America, 7 from South America, 3 from Australia, and 3 from Europe. Information is provided for 11 falls (Dergaon, Dunbogan, Gujba, Independence, Itqiy, Mora??vka, Oued el Hadjar, Sayama, Sologne, Valera, and Worden). Noteworthy non-Antarctic specimens include 5 martian <span class="hlt">meteorites</span> (Dar al Gani 876, Northwest Africa 480 and 817, and Sayh al Uhaymir 051 and 094); 6 lunar <span class="hlt">meteorites</span> (Dhofar 081, 280, and 287, and Northwest Africa 479, 482, and 773); an ungrouped enstatite-rich <span class="hlt">meteorite</span> (Itqiy); a Bencubbin-like <span class="hlt">meteorite</span> (Gujba); 9 iron <span class="hlt">meteorites</span>; and a wide variety of other interesting stony <span class="hlt">meteorites</span>, including CH, CK, CM, CO, CR, CV, R, enstatite, and unequilibrated ordinary chondrites, primitive achondrites, HED achondrites, and ureilites.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19850018260','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19850018260"><span>Origin and evolution of ordinary chondrite <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>Scott, E. R. D.; Taylor, G. J.; Keil, K.</p> <p>1985-01-01</p> <p>The effects of heating on the chemical composition, minerology, and texture of chondrite <span class="hlt">meteorites</span> are discussed chondrite origin and evolution. Various asteroidal and nebular heating mechanisms are considered to account <span class="hlt">meteorite</span> compositions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19890063360&hterms=Accelerator+mass+spectrometry&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DAccelerator%2Bmass%2Bspectrometry','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19890063360&hterms=Accelerator+mass+spectrometry&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DAccelerator%2Bmass%2Bspectrometry"><span>Update on terrestrial ages of 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>Nishiizumi, K.; Elmore, D.; Kubik, P. W.</p> <p>1989-01-01</p> <p>Cosmic-ray produced Cl-36 (half-life = 3.01 x 10 to the 5th years) has been measured in 90 Antarctic <span class="hlt">meteorites</span> by accelerator mass spectrometry. The terrestrial ages of the <span class="hlt">meteorites</span> were calculated from the results. After excluding possible paired objects, 138 terrestrial ages from 18 different locations are available from C-14, Kr-81, and Cl-36 measurements for application to Antarctic <span class="hlt">meteorite</span> and glaciological studies. The terrestrial ages of Allan Hills <span class="hlt">meteorites</span> vary from 2000 years to 1 million years and are clearly longer than those of Yamato <span class="hlt">meteorites</span> and other Antarctic <span class="hlt">meteorites</span>. The oldest Allan Hills <span class="hlt">meteorites</span> were found close to the eastern edge and in the southeast of the main icefield. Among all Antarctic <span class="hlt">meteorites</span> measured to date, only L and LL chondrites have terrestrial ages older than 370,000 years.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110014367','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110014367"><span>Antarctic <span class="hlt">Meteorite</span> Classification and Petrographic Database</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Todd, Nancy S.; Satterwhite, C. E.; Righter, Kevin</p> <p>2011-01-01</p> <p>The Antarctic <span class="hlt">Meteorite</span> collection, which is comprised of over 18,700 <span class="hlt">meteorites</span>, is one of the largest collections of <span class="hlt">meteorites</span> in the world. These <span class="hlt">meteorites</span> have been collected since the late 1970's as part of a three-agency agreement between NASA, the National Science Foundation, and the Smithsonian Institution [1]. Samples collected each season are analyzed at NASA s <span class="hlt">Meteorite</span> Lab and the Smithsonian Institution and results are published twice a year in the Antarctic <span class="hlt">Meteorite</span> Newsletter, which has been in publication since 1978. Each newsletter lists the samples collected and processed and provides more in-depth details on selected samples of importance to the scientific community. Data about these <span class="hlt">meteorites</span> is also published on the NASA Curation website [2] and made available through the <span class="hlt">Meteorite</span> Classification Database allowing scientists to search by a variety of parameters</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20030110700&hterms=ruthenium&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Druthenium','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20030110700&hterms=ruthenium&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Druthenium"><span>Endemic Ru Isotopic Anomalies in Iron <span class="hlt">Meteorites</span> and in Allende</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chen, J. H.; Papanastassiou, D. A.; Wasserburg, G. J.</p> <p>2003-01-01</p> <p>Small variations for Mo isotopes have been observed recently in the Allende <span class="hlt">meteorite</span> and in iron <span class="hlt">meteorites</span>, mesosiderites, and pallasites, using ICPMS. <span class="hlt">Large</span> effects for Mo have been reported for leaches of Orgueil and in SiC and graphite from Murchison. Variations for Mo in bulk Allende and in Murchison have also been presented by NTIMS. Effects in Ru isotopes can define further the preserved exotic r, s, and p contributions in this mass region, and possible effects in Ru-98 and Ru-99 from Tc-98 (4.2 Ma half-life) and Tc-99 (0.21 Ma half-life). Previous attempts at determination of Ru isotopes yielded no resolved effects. The present work represents a substantial improvement in precision over the earlier work. Chemical and mass spectrometric analytical techniques are presented to determine the Ru isotope compositions in terrestrial standards and in <span class="hlt">meteorites</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1789618','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1789618"><span>Equine Colic Associated with Sand <span class="hlt">Impaction</span> of the <span class="hlt">Large</span> Colon</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Udenberg, T.</p> <p>1979-01-01</p> <p>In most cases the outcome of <span class="hlt">impaction</span> of the colon is favourable and with mild purging and lubrication, the mass can be broken down and the horse returned to normal health. It is important to reevaluate <span class="hlt">impaction</span> cases which neither deteriorate or improve in a 24 hour period and to perform a paracentesis to evaluate the etiology and prognosis. A decision of euthanasia or surgical correction should be made as early as possible. Though initially stable, vital signs will deteriorate rapidly without warning. A critical evaluation of the client's farm management can prevent many <span class="hlt">impaction</span> colics and the service practitioners provide is not complete unless the necessary changes are made. ImagesFigure 1.FIGURE 2.FIGURE 3. PMID:544003</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://hdl.handle.net/2060/19750006596','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19750006596"><span>The Magnetization of 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>Herndon, James Herndon</p> <p>1974-01-01</p> <p>Alternating field demagnetization experiments have been conducted on representative samples of the carbonaceous <span class="hlt">meteorites</span> (carbonaceous chondrites and ureilites). The results indicate that many, if not all, of these <span class="hlt">meteorites</span> possess an intense and stable magnetic moment of extraterrestrial origin. Thermomagnetic analyses have been conducted on samples of all known carbonaceous <span class="hlt">meteorites</span>. In addition to yielding quantitative magnetite estimates, these studies indicate the presence of a thermally unstable component, troilite, which reacts with gaseous oxygen to form magnetite. It is proposed that the magnetite found in some carbonaceous chondrites resulted from the oxidation of troilite during the early history of the solar system. The formation of pyrrhotite is expected as a natural consequence of magnetite formation via this reaction. Consideration is given to the implications of magnetite formation on paleointensity studies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20010102851','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20010102851"><span>Organic Chemistry of 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>Cronin, John R.</p> <p>2001-01-01</p> <p>Chiral and carbon-isotopic analyses of isovaline have been carried out on numerous samples of the Murchison and one sample of the Murray carbonaceous chondrite. The isovaline was found to be heterogeneous with regard to enantiomeric excess (ee) both between samples and within a single Murchison sample. L-Excesses ranging from 0 to 15% were observed. The isovaline delta(sup 13) C was found to be about +18%. No evidence was obtained suggesting terrestrial contamination in the more abundant L-enantiomer. A correlation was observed between isovaline (also alpha - aminoisobutyric acid) concentration and PCP content of five CM chondrites. It is suggested that isovaline, along with other <span class="hlt">meteoritic</span> a-methyl amino acids with ee, are of presolar origin. The possible formation of ee in extraterrestrial amino acids by exposure to circularly polarized light or by magnetochiral photochemistry is discussed. Key words: Murchison <span class="hlt">meteorite</span>, Murray <span class="hlt">meteorite</span>, amino acids, isovaline, chirality, carbon isotopes, PCP.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AGUFM.P33A0233R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AGUFM.P33A0233R"><span>The Complicated Geologic Histories of <span class="hlt">Large</span> Venusian <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>Rumpf, M. E.; Herrick, R.; Gregg, T. K.</p> <p>2005-12-01</p> <p>One of the more surprising discoveries from the Magellan imaging campaign was that the <span class="hlt">impact</span> craters have a spatial distribution closely consistent with a random pattern. First impressions of most craters were that they are also well preserved. These observations led to an initial post-Magellan consensus that the planet is nearly geologically inactive and that activity rapidly ceased a few hundred million years ago. Early mapping efforts were mostly interpreted in terms of a rapid, linear, globally uniform stratigraphic evolution in the nature of volcanism and deformation. A number of challenges to this view have been made as detailed study of the Magellan data has progressed, and several researchers now advocate a more uniformitarian view of the planet. A valuable research tool has been topography derived from Magellan stereo imagery; it provides an order of magnitude improvement in horizontal resolution over the altimetry data (1 km vs. 10 km). Previous studies utilizing the stereo-derived topography have shown that <span class="hlt">impact</span> craters with radar-dark floors (most of the population) are shallow and probably partially filled with post-<span class="hlt">impact</span> lavas, and detailed mapping of Mead <span class="hlt">impact</span> basin (the planet's largest <span class="hlt">impact</span> structure) has revealed post-<span class="hlt">impact</span> volcanic embayment. We have recently performed detailed photogeologic mapping, aided by stereo-derived topography, of several 50-100 km diameter <span class="hlt">impact</span> craters. Most of these craters are not at the top of the stratigraphic column, and in some cases there is a complex, multi-event post-emplacement history. The combined histories of these craters are not consistent with a rapid cessation of geologic activity, and we are still synthesizing the individual histories to evaluate the hypothesis of a linear global stratigraphic evolution. Although the stereo-derived topography greatly aided interpretation, in many cases geologic contacts were ambiguous, individual volcanic flows could not be distinguished, source vents could</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26386663','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26386663"><span><span class="hlt">Impact</span> of heuristics in clustering <span class="hlt">large</span> biological networks.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Shafin, Md Kishwar; Kabir, Kazi Lutful; Ridwan, Iffatur; Anannya, Tasmiah Tamzid; Karim, Rashid Saadman; Hoque, Mohammad Mozammel; Rahman, M Sohel</p> <p>2015-12-01</p> <p>Traditional clustering algorithms often exhibit poor performance for <span class="hlt">large</span> networks. On the contrary, greedy algorithms are found to be relatively efficient while uncovering functional modules from <span class="hlt">large</span> biological networks. The quality of the clusters produced by these greedy techniques <span class="hlt">largely</span> depends on the underlying heuristics employed. Different heuristics based on different attributes and properties perform differently in terms of the quality of the clusters produced. This motivates us to design new heuristics for clustering <span class="hlt">large</span> networks. In this paper, we have proposed two new heuristics and analyzed the performance thereof after incorporating those with three different combinations in a recently celebrated greedy clustering algorithm named SPICi. We have extensively analyzed the effectiveness of these new variants. The results are found to be promising.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JPhCS.712a2095T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JPhCS.712a2095T"><span>Local structures of Ca, Ti and Fe in <span class="hlt">meteorite</span> fusion crusts</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tobase, T.; Yoshiasa, A.; Hiratoko, T.; Hongu, H.; Isobe, H.; Nakatsuka, A.; Arima, H.; Sugiyama, K.</p> <p>2016-05-01</p> <p>The local structures of <span class="hlt">meteorite</span> fusion crusts were studied by Ca, Ti and Fe K-edge XANES and EXAFS spectroscopy. The surface of <span class="hlt">meteorites</span> were melted and volatilized with extreme high temperature and <span class="hlt">large</span> temperature gradient when <span class="hlt">meteorites</span> were rushed into atmosphere. This study indicated that <span class="hlt">meteorite</span> fusion crusts have unique local structures. The local structures of fusion crusts differ from tektites especially in intensity of the shoulder in the rising flank of the edge in Ca XANES spectra. It is consistent with chemical composition change by the volatilization of Si at fusion during atmospheric entry. The high estimated Fe3+/ (Fe2++Fe3+) ratio in <span class="hlt">meteorite</span> fusion crusts indicates that <span class="hlt">meteorite</span> fusion crusts are formed into atmospheric oxidation condition. The Ca-O distances in <span class="hlt">meteorite</span> fusion crusts are 2.612.66 A and are extremely longer than in other natural glasses. The fusion crusts have unique local structure since they experienced extremely high temperature and short quenching time. The XAFS method is effective in distinction of <span class="hlt">meteorite</span> fusion crusts and classification of natural glass.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009Miner..40..107O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009Miner..40..107O"><span>Mineralogy and petrology of two ordinary chondrites and their correlation with other <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>Owocki, Krzysztof; Pilski, Andrzej</p> <p>2009-01-01</p> <p>Two ordinary chondrites are compared and classified using transmitted and reflected light microscopy and electron microprobe analyses. Both <span class="hlt">meteorites</span> were confiscated by the Polish Customs Service at the border with Belarus. The first <span class="hlt">meteorite</span> (called in this paper Terespol-1) is a L/LL6 chondrite, its classification being supported by the equilibrated compositions of olivine and orthopyroxene and the presence of <span class="hlt">large</span> recrystallized feldspars (< 150 μm). The specimen examined experienced weak shock metamorphism (S3) and moderate weathering (although metal in the inner part of the <span class="hlt">meteorite</span> seems to be unaffected by oxidization). The other <span class="hlt">meteorite</span> (called in this paper Terespol-2) is a LL6 chondrite which experienced weak shock metamorphism (S3) and is unaffected by weathering. The Terespol-2 <span class="hlt">meteorite</span> shares its classification with the Dhofar 1401 chondrite but the lack of data prevents further correlation. Both <span class="hlt">meteorites</span> have been correlated with known findings from the <italic><span class="hlt">Meteoritical</span> Bulletin</italic> database and an attempt is made to identify their place of origin (fall event). Results indicate that Terespol-1 is most closely related to the Dhofar 1316 chondrite and we suggest that both <span class="hlt">meteorites</span> at least came from the same parent body.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20130011097','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20130011097"><span>Coordinated In Situ Analyses of Organic Nanoglobules in the Sutter's Mill <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>Nakamura--Messenger, K.; Messenger, S.; Keller, L. P.; Clemett, S. J.; Nguyen, A. N.; Gibson, E. K.</p> <p>2013-01-01</p> <p>The Sutter s Mill <span class="hlt">meteorite</span> is a newly fallen carbonaceous chondrite that was collected and curated quickly after its fall [1]. Preliminary petrographic and isotopic investigations suggest affinities to the CM2 carbonaceous chondrites. The primitive nature of this <span class="hlt">meteorite</span> and its rapid recovery provide an opportunity to investigate primordial solar system organic matter in a unique new sample. Organic matter in primitive <span class="hlt">meteorites</span> and chondritic porous interplanetary dust particles (CP IDPs) is commonly enriched in D/H and N-15/N-14 relative to terrestrial values [2-4]. These anomalies are ascribed to the partial preservation of presolar cold molecular cloud material [2]. Some <span class="hlt">meteorites</span> and IDPs contain gm-size inclusions with extreme H and N isotopic anomalies [3-5], possibly due to preserved primordial organic grains. The abundance and isotopic composition of C in Sutter's Mill were found to be similar to the Tagish Lake <span class="hlt">meteorite</span> [6]. In the Tagish Lake <span class="hlt">meteorite</span>, the principle carriers of <span class="hlt">large</span> H and N isotopic anomalies are sub-micron hollow organic spherules known as organic nanoglobules [7]. Organic nanoglobules are commonly distributed among primitive <span class="hlt">meteorites</span> [8, 9] and cometary samples [10]. Here we report in-situ analyses of organic nano-globules in the Sutter's Mill <span class="hlt">meteorite</span> using UV fluorescence imaging, Fourier-transform infrared spectroscopy (FTIR), scanning transmission electron microscopy (STEM), NanoSIMS, and ultrafast two-step laser mass spectrometry (ultra-L2MS).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010M%26PS...45.1695G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010M%26PS...45.1695G"><span>Extraterrestrial amino acids in the Almahata Sitta <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>Glavin, Daniel P.; Aubrey, Andrew D.; Callahan, Michael P.; Dworkin, Jason P.; Elsila, Jamie E.; Parker, Eric T.; Bada, Jeffrey L.; Jenniskens, Peter; Shaddad, Muawia H.</p> <p>2010-10-01</p> <p>Amino acid analysis of a <span class="hlt">meteorite</span> fragment of asteroid 2008 TC3 called Almahata Sitta was carried out using reverse-phase liquid chromatography coupled with UV fluorescence detection and time-of-flight mass spectrometry (LC-FD/ToF-MS) as part of a sample analysis consortium. LC-FD/ToF-MS analyses of hot-water extracts from the <span class="hlt">meteorite</span> revealed a complex distribution of two- to seven-carbon aliphatic amino acids and one- to three-carbon amines with abundances ranging from 0.5 to 149 parts-per-billion (ppb). The enantiomeric ratios of the amino acids alanine, β-amino-n-butyric acid, 2-amino-2-methylbutanoic acid (isovaline), and 2-aminopentanoic acid (norvaline) in the <span class="hlt">meteorite</span> were racemic (D/L ˜ 1), indicating that these amino acids are indigenous to the <span class="hlt">meteorite</span> and not terrestrial contaminants. Several other nonprotein amino acids were also identified in the <span class="hlt">meteorite</span> above background levels including α-aminoisobutyric acid (α-AIB), 4-amino-2-methylbutanoic acid, 4-amino-3-methylbutanoic acid, and 3-, 4-, and 5-aminopentanoic acid. The total abundances of isovaline and α-AIB in Almahata Sitta are approximately 1000 times lower than the abundances of these amino acids found in the CM carbonaceous chondrite Murchison. The extremely low abundances and unusual distribution of five-carbon amino acids in Almahata Sitta compared to CI, CM, and CR carbonaceous chondrites may reflect extensive thermal alteration of amino acids on the parent asteroid by partial melting during formation or subsequent <span class="hlt">impact</span> shock heating. It is also possible that amino acids were synthesized by catalytic reactions on the parent body after asteroid 2008 TC3 cooled to lower temperatures, or introduced as a contaminant from unrelated <span class="hlt">meteorite</span> clasts and chemically altered by α-decarboxylation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19890040126&hterms=Metamorphic+process&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DMetamorphic%2Bprocess','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19890040126&hterms=Metamorphic+process&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DMetamorphic%2Bprocess"><span>Highly labile elements. [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>Lipschutz, Michael E.; Woolum, Dorothy S.</p> <p>1988-01-01</p> <p>Certain elements of high lability are very responsive to thermal processes, being either highly volatile during primary nebular condensation or highly mobile by postaccretionary metamorphic or shock heating. Data for highly labile elements indicate that different thermal processes were important in the genesis of each of the chondritic groups and a discussion of each is given. Contents of highly labile elements in a given group of contemporary falls differ from those of the same group that fell in Antarctica more than 0.1 Myr ago. This difference is due either to a time-dependent change in <span class="hlt">meteorite</span> sources or, less likely, orbital variation of the <span class="hlt">meteorite</span> flux to Earth.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002EGSGA..27.1022R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002EGSGA..27.1022R"><span>Magnetic Classification of <span class="hlt">Meteorites</span> and Asteroid Probing</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rochette, P.; Sagnotti, L.; Chevrier, V.; Consolmagno, G.; Denise, M.; Folco, L.; Osete, M.; Pesonen, L.</p> <p></p> <p>Magnetic susceptibility (X) provides a versatile rapid and non destructive way to quan- tify the amount of magnetic minerals (FeNi metal, magnetic oxides and sulfides) on <span class="hlt">large</span> volume of material. As petrological studies of <span class="hlt">meteorites</span> suggest that this param- eter should be quite discriminant, we assembled a database of measurements on about 1000 stony <span class="hlt">meteorites</span> from various European collections: Helsinki, Madrid, Paris, Prague, Roma, Siena, Vatican, and other smaller collections. From 1 to >20 pieces and 1 to >100 cc per <span class="hlt">meteorite</span> allow to define a representative mean value, using a <span class="hlt">large</span> coil (8 cm) Kappabridge. For ordinary chondrites, it appears that weathering is responsible for a systematic bias toward low logc for Antarctic (Frontier Mountain) and non Antarctic (mainly from Sahara) finds. Once only falls are considered a quite narrow range of logc is observed for a given class, with no effect of petrological grade except for LL. High grade LLs (heated above 400C) develop the weakly magnetic antitaenite-tetrataenite phases [3] during slow cooling, explaining the difference with low grade taenite-bearing LLs. Outliers from H and L classes are grade 6 material (showing metal segregation) or intermediate types: H/L and L/LL. Once these out- liers 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. The standard deviation for all falls of a given class is only slightly higher than the averaged standard deviation for multiple pieces of the same fall. This supports the hypothesis that all falls from a given ordinary chondrite class (H or L) may come from the same homogeneous par- ent body. 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. On objects without</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA493801','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA493801"><span>Modeling the Economic <span class="hlt">Impacts</span> of <span class="hlt">Large</span> Deployments on Local Communities</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>2008-12-01</p> <p>0.019 0.492 EL PASO* -2.452 -1.021 0.154 RIO BLANCO 0.333 0.247 0.402 ELBERT -2.298 -1.129 0.129 RIO GRANDE 0.823 0.460 0.323 FREMONT* -0.090 0.010...provided an estimate for an area newspaper, on the employment <span class="hlt">impacts</span> of a deployment of troops from Fort Stewart, GA . He found that the deployment of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140010854','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140010854"><span>Transient Climate Effects of <span class="hlt">Large</span> <span class="hlt">Impacts</span> on Titan</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zahnle, Kevin J.; Korycansky, Donald; Nixon, Conor A.</p> <p>2013-01-01</p> <p>Titan's thick atmosphere and volatile-rich surface cause it to respond to big <span class="hlt">impacts</span> in a somewhat Earth-like manner. Here we construct a simple globally-averaged model that tracks the flow of energy through the environment in the weeks, years, and millenia after a big comet strikes Titan. The model Titan is endowed with 1.4 bars of N2 and 0.07 bars of CH4, methane lakes, a water ice crust, and enough methane underground to saturate the regolith to the surface. We find that a nominal Menrva <span class="hlt">impact</span> is big enough to raise the surface temperature by approx. 80 K and to double the amount of methane in the atmosphere. The extra methane drizzles out of the atmosphere over hundreds of years. An upper-limit Menrva is just big enough to raise the surface to water's melting point. The putative Hotei <span class="hlt">impact</span> (a possible 800-1200 km diameter basin, Soderblom et al., 2009) is big enough to raise the surface temperature to 350-400 K. Water rain must fall and global meltwaters might range between 50 m to more than a kilometer deep, depending on the details. Global meltwater oceans do not last more than a few decades or centuries at most, but are interesting to consider given Titan's organic wealth. Significant near-surface clathrate formation is possible as Titan cools but faces major kinetic barriers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008LPI....39.2116P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008LPI....39.2116P"><span>Hydrocode Models of <span class="hlt">Large</span> <span class="hlt">Impacts</span> into a Noachian Martian Surface: Initial Results</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Plesko, C. S.; Coker, R. F.; Wohletz, K. H.; Asphaug, E.; Korycansky, D. G.</p> <p>2008-03-01</p> <p>Segura proposed <span class="hlt">large</span> <span class="hlt">impacts</span> could broil the surface of Noachian Mars. Later, recondensing volatiles would cause ~1 m/day of precipitation for 1-100 years. We model the smallest <span class="hlt">impacts</span> capable of causing global effects, and regional effects of smaller <span class="hlt">impacts</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19860019344','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19860019344"><span>Mysterious iodine-overabundance 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>Dreibus, G.; Waenke, H.; Schultz, L.</p> <p>1986-01-01</p> <p>Halogen as well as other trace element concentrations in <span class="hlt">meteorite</span> finds can be influenced by alteration processes on the Earth's surface. The discovery of Antarctic <span class="hlt">meteorites</span> offered the opportunity to study <span class="hlt">meteorites</span> which were kept in one of the most sterile environment of the Earth. Halogen determination in Antartic <span class="hlt">meteorites</span> was compared with non-Antarctic <span class="hlt">meteorites</span>. No correlation was found between iodine concentration and the weathering index, or terrestrial age. The halogen measurements indicate a contaminating phase rich in iodine and also containing chlorine. Possible sources for this contamination are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70026875','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70026875"><span>The <span class="hlt">Meteoritical</span> Bulletin, No. 88, 2004 July</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Russell, S.S.; Folco, L.; Grady, M.M.; Zolensky, M.E.; Jones, R.; Righter, K.; Zipfel, J.; Grossman, J.N.</p> <p>2004-01-01</p> <p>The <span class="hlt">Meteoritical</span> Bulletin No. 88 lists information for 1610 newly classified <span class="hlt">meteorites</span>, comprising 753 from Antarctica, 302 from Africa, 505 from Asia (495 of which are from Oman), 40 from North America, 5 from South America, 4 from Europe, and 1 of unknown origin. Information is provided for 9 falls (Alby sur Che??ran, Al Zarnkh, Devgaon, Kamioka, Kendrapara, Maromandia, New Orleans, Sivas, and Villalbeto de la Pen??a). Noteworthy specimens include a eucrite fall (Alby sur Che??ran), 6 martian <span class="hlt">meteorites</span>, 13 lunar <span class="hlt">meteorites</span>, and 12 irons including one weighing 3 metric ions (Dronino). ?? <span class="hlt">Meteoritical</span> Society, 2004.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22047644','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22047644"><span>HYDROGEN CYANIDE IN THE MURCHISON <span class="hlt">METEORITE</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Pizzarello, Sandra</p> <p>2012-08-01</p> <p>Carbonaceous chondrites are <span class="hlt">meteorites</span> that may contain abundant organic materials, including soluble compounds as diverse as amino acids and hydrocarbons. We report here the finding of hydrogen cyanide in the Murchison <span class="hlt">meteorite</span> in amounts {<=} 10 ppm. HCN was never searched for in <span class="hlt">meteorites</span> and its detection in sizeable amount is surprising in view of the extensive water phase that is recorded by the petrology of this type of <span class="hlt">meteorites</span> and could have exhausted their HCN content through multiple reactions. The finding adds to the inventory of simple volatile molecules found in both comets and <span class="hlt">meteorites</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AAS...22934608T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AAS...22934608T"><span>The <span class="hlt">Impact</span> of <span class="hlt">Large</span> Scale Environments on Cluster Entropy Profiles</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Trierweiler, Isabella; Su, Yuanyuan</p> <p>2017-01-01</p> <p>We perform a systematic analysis of 21 clusters imaged by the Suzaku satellite to determine the relation between the richness of cluster environments and entropy at <span class="hlt">large</span> radii. Entropy profiles for clusters are expected to follow a power-law, but Suzaku observations show that the entropy profiles of many clusters are significantly flattened beyond 0.3 Rvir. While the entropy at the outskirts of clusters is thought to be highly dependent on the <span class="hlt">large</span> scale cluster environment, the exact nature of the environment/entropy relation is unclear. Using the Sloan Digital Sky Survey and 6dF Galaxy Survey, we study the 20 Mpc <span class="hlt">large</span> scale environment for all clusters in our sample. We find no strong relation between the entropy deviations at the virial radius and the total luminosity of the cluster surroundings, indicating that accretion and mergers have a more complex and indirect influence on the properties of the gas at <span class="hlt">large</span> radii. We see a possible anti-correlation between virial temperature and richness of the cluster environment and find that density excess appears to play a larger role in the entropy flattening than temperature, suggesting that clumps of gas can lower entropy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..14.9907T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..14.9907T"><span>Cosmogenic radioisotopes in Gebel Kamil <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>Taricco, C.; Colombetti, P.; Bhandari, N.; Sinha, N.; Di Martino, M.; Vivaldo, G.</p> <p>2012-04-01</p> <p>Recently a small (45 m in diameter) and very young (< 5,000 years) <span class="hlt">impact</span> crater was discovered in Egypt (Folco et al., 2010, 2011); it was generated by an iron <span class="hlt">meteorite</span> named Gebel Kamil (<span class="hlt">Meteoritical</span> Bulletin No. 98, Weisberg et al. 2010). During systematic searches, many specimens were found in the area surrounding the crater. We present the gamma-activity measurement of a 672 g fragment using a highly selective Ge-NaI spectrometer operating at Monte dei Cappuccini Laboratory (IFSI, INAF) in Torino, Italy. This apparatus allows to reveal the radioisotope activity generated by cosmic rays in the meteoroids as they travel through the interplanetary space before falling on the Earth. From the 26Al activity measurement and its depth production profiles, we infer (i) that the radius of the meteoroid should be about 1 m, constraining to 30-40 ton the range of pre-atmospheric mass previously proposed and (ii) that the fragment should have been located deeply inside the meteoroid, at a depth > 0.7 m. The 44Ti activity is under the detection threshold of the apparatus; using the depth production profiles of this radioisotope and its half-life T1/2 = 59.2 y, we deduce an upper limit to the date of fall.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1158434','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1158434"><span>Operational <span class="hlt">Impacts</span> of <span class="hlt">Large</span> Deployments of Offshore Wind (Poster)</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ibanez, E.; Heaney, M.</p> <p>2014-10-01</p> <p>The potential operational <span class="hlt">impact</span> of deploying 54 GW of offshore wind in the United States was examined. The capacity was not evenly distributed; instead, it was concentrated in regions with better wind quality and close to load centers (Table 1). A statistical analysis of offshore wind power time series was used to assess the effect on the power system. The behavior of offshore wind resembled that of onshore wind, despite the former presenting higher capacity factors, more consistent power output across seasons, and higher variability levels. Thus, methods developed to manage onshore wind variability can be extended and applied to offshore wind.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012PhFl...24e7101Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012PhFl...24e7101Z"><span><span class="hlt">Large</span> bubble entrapment during drop <span class="hlt">impacts</span> on a restricted liquid surface</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zou, Jun; Ji, Chen; Yuan, BaoGang; Ren, YuLiang; Ruan, XiaoDong; Fu, Xin</p> <p>2012-05-01</p> <p>The behavior of millimetric drops <span class="hlt">impacting</span> on a gas-liquid interface restricted by surrounding walls is studied using a high-speed video camera. A novel phenomenon of <span class="hlt">large</span> bubble entrapment is observed in experiments. It is found that the <span class="hlt">large</span> bubble formation is not only dependent on the <span class="hlt">impact</span> velocity of the drop, but also the shape of drop at the moment of contact with the liquid surface and the distance from the <span class="hlt">impact</span> point to surrounding walls.</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/2060/20120003250','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120003250"><span>Antarctic <span class="hlt">Meteorite</span> Classification and Petrographic Database Enhancements</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Todd, N. S.; Satterwhite, C. E.; Righter, K.</p> <p>2012-01-01</p> <p>The Antarctic <span class="hlt">Meteorite</span> collection, which is comprised of over 18,700 <span class="hlt">meteorites</span>, is one of the largest collections of <span class="hlt">meteorites</span> in the world. These <span class="hlt">meteorites</span> have been collected since the late 1970 s as part of a three-agency agreement between NASA, the National Science Foundation, and the Smithsonian Institution [1]. Samples collected each season are analyzed at NASA s <span class="hlt">Meteorite</span> Lab and the Smithsonian Institution and results are published twice a year in the Antarctic <span class="hlt">Meteorite</span> Newsletter, which has been in publication since 1978. Each newsletter lists the samples collected and processed and provides more in-depth details on selected samples of importance to the scientific community. Data about these <span class="hlt">meteorites</span> is also published on the NASA Curation website [2] and made available through the <span class="hlt">Meteorite</span> Classification Database allowing scientists to search by a variety of parameters. This paper describes enhancements that have been made to the database and to the data and photo acquisition process to provide the <span class="hlt">meteorite</span> community with faster access to <span class="hlt">meteorite</span> data concurrent with the publication of the Antarctic <span class="hlt">Meteorite</span> Newsletter twice a year.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1614852','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1614852"><span>The respiratory health <span class="hlt">impact</span> of a <span class="hlt">large</span> urban fire.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Lipsett, M; Waller, K; Shusterman, D; Thollaug, S; Brunner, W</p> <p>1994-01-01</p> <p>OBJECTIVES. In July 1988, a fire destroyed a huge supermarket warehouse in Richmond, Calif, sending smoke into residential neighborhoods for nearly a week. There was no organized public health response. To evaluate the respiratory health <span class="hlt">impact</span> on the general population, a survey of emergency room visits and hospital admissions to the two acute-care hospitals serving the population downwind was conducted. METHODS. Medical records of 489 patients meeting specified diagnostic criteria during the week of the fire and several reference periods were abstracted. Ratios of proportions for respiratory diagnoses (i.e., emergency room visits for a given diagnosis/total emergency room visits) were calculated, comparing the fire week with the reference periods, and 1988 mortality data for the area were reviewed. RESULTS. Ratios of proportions for emergency room visits for asthma and all lower respiratory conditions increased significantly during the fire. Respiratory-related hospitalizations also increased. However, there was no observable increase in respiratory mortality. CONCLUSIONS. This fire was found to have had a moderate <span class="hlt">impact</span> on the respiratory health of local residents. Public health intervention is indicated to prevent respiratory morbidity when extended exposure to structural fire smoke is predictable. PMID:8129061</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014M%26PS...49E...1R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014M%26PS...49E...1R"><span>The <span class="hlt">Meteoritical</span> Bulletin, No. 100, 2014 June</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 N.; Garvie, Laurence</p> <p>2014-08-01</p> <p><span class="hlt">Meteoritical</span> Bulletin 100 contains 1943 <span class="hlt">meteorites</span> including 8 falls (Boumdeid [2011], Huaxi, Košice, Silistra, Sołtmany, Sutter's Mill, Thika, Tissint), with 1575 ordinary chondrites, 139 carbonaceous chondrites, 96 HED achondrites, 25 ureilites, 18 primitive achondrites, 17 iron <span class="hlt">meteorites</span>, 15 enstatite chondrites, 11 lunar <span class="hlt">meteorites</span>, 10 mesosiderites, 10 ungrouped achondrites, 8 pallasites, 8 Martian <span class="hlt">meteorites</span>, 6 Rumuruti chondrites, 3 enstatite achondrites, and 2 angrites, and with 937 from Antarctica, 592 from Africa, 230 from Asia, 95 from South America, 44 from North America, 36 from Oceania, 6 from Europe, and 1 from an unknown location. This will be the last Bulletin published in the current format. Information about approved <span class="hlt">meteorites</span> can be obtained from the <span class="hlt">Meteoritical</span> Bulletin Database (MBD) available online at http://www.lpi.usra.edu/meteor/</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014acm..conf...95C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014acm..conf...95C"><span>Recent <span class="hlt">meteorite</span> falls in South Korea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Choi, Y.; Kim, M.; Byun, Y.; Yi, H.; Chang, S.; Choi, J.; Sohn, J.; Moon, H.; Park, J.</p> <p>2014-07-01</p> <p>In the evening of March 9, 2014, a fireball falling from north to south was observed in South Korea. Multiple explosions were heard and multiple videos recorded in cars from various places, suggesting that the fireball was separated into several pieces. Immediately thereafter, a series of discovery reports about <span class="hlt">meteorites</span> from the southern part of South Korea followed and, as of today, three <span class="hlt">meteorites</span> were confirmed and one <span class="hlt">meteorite</span>, with a mass of about 20 kg, is pending. This discovery of a <span class="hlt">meteorite</span> in South Korea occurs for the first time in 70 years. The overall trajectory of the fireball matches the area where <span class="hlt">meteorites</span> were discovered. According to the preliminary analyses, the <span class="hlt">meteorite</span> is an ordinary chondrite. The origin of the <span class="hlt">meteorite</span> and its surface properties will be studied.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20010097879','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20010097879"><span>Organic Compounds 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>Cooper, Grorge</p> <p>2001-01-01</p> <p>Carbonaceous <span class="hlt">meteorites</span> are relatively enriched in soluble organic compounds. To date, these compounds provide the only record available to study a range of organic chemical processes in the early Solar System chemistry. The Murchison <span class="hlt">meteorite</span> is the best-characterized carbonaceous <span class="hlt">meteorite</span> with respect to organic chemistry. The study of its organic compounds has related principally to aqueous <span class="hlt">meteorite</span> parent body chemistry and compounds of potential importance for the origin of life. Among the classes of organic compounds found in Murchison are amino acids, amides, carboxylic acids, hydroxy acids, sulfonic acids, phosphonic acids, purines and pyrimidines (Table 1). Compounds such as these were quite likely delivered to the early Earth in asteroids and comets. Until now, polyhydroxylated compounds (polyols), including sugars (polyhydroxy aldehydes or ketones), sugar alcohols, sugar acids, etc., had not been identified in Murchison. Ribose and deoxyribose, five-carbon sugars, are central to the role of contemporary nucleic acids, DNA and RNA. Glycerol, a three-carbon sugar alcohol, is a constituent of all known biological membranes. Due to the relative lability of sugars, some researchers have questioned the lifetime of sugars under the presumed conditions on the early Earth and postulated other (more stable) compounds as constituents of the first replicating molecules. The identification of potential sources and/or formation mechanisms of pre-biotic polyols would add to the understanding of what organic compounds were available, and for what length of time, on the ancient Earth.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19850011601','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19850011601"><span>Lunar sample analysis. [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>Housley, R. M.</p> <p>1985-01-01</p> <p>Recent results on the antarctic <span class="hlt">meteorite</span> ALPHA 77003 which contribute to understanding the alteration processes which produced matrix in unequilibrated chondrites are presented. Also included are additional scanning electron microscope results confirming that the matrix in Allende was formed by in situ alteration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004SPIE.5555....1H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004SPIE.5555....1H"><span>Indigenous microfossils 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.; Jerman, Gregory; Rozanov, Alexei Y.; Sipiera, Paul P.</p> <p>2004-11-01</p> <p>Indigenous embedded microbial filaments, bacterial cells and other microfossils were found in the Orgueil, Ivuna (CI1), Murchison, and Bells (CM2) carbonaceous <span class="hlt">meteorites</span>. Biominerals, biofilms, framboids, magnetite platelets, and curious elemental iron ovoids covered with minute fibrils and carbon sheaths were also found. The S-4100 Hitachi Field Emission Scanning Electron Microscope (FESEM) and Energy Dispersive X-ray Analysis (EDAX) were used for in situ investigations of freshly fractured interior <span class="hlt">meteorite</span> surfaces. EDAX x-ray spectra shows the microfossils bear signatures of the <span class="hlt">meteorite</span> matrix and possess elemental ratios indicating they are indigenous and not recent microbial contaminants. Many of the well-preserved biogenic remains in the <span class="hlt">meteorites</span> are encased within carbon-rich, sometimes electron transparent, sheaths. Their size, morphology and ultra microstructure are comparable to microfossils known from the phosphorites of Khubsughul, Mongolia and to some of the living cyanobacteria and other sulfur- and sulfate-reducing bacteria known from the halophilic Microcoleus mats of Sivash Lagoon, Crimea and from Mono Lake in California.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20030066366&hterms=meyer+michael&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dmeyer%2Bmichael','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20030066366&hterms=meyer+michael&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dmeyer%2Bmichael"><span>Extraterrestrial 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>Botta, Oliver; Bada, Jeffrey L.; Meyer, Michael (Technical Monitor)</p> <p>2003-01-01</p> <p>Many organic compounds or their precursors found in <span class="hlt">meteorites</span> originated in the interstellar or circumstellar medium and were later incorporated into planetesimals during the formation of the solar system. There they either survived intact or underwent further processing to synthesize secondary products on the <span class="hlt">meteorite</span> parent body. The most distinct feature of CI and CM carbonaceous chondrites, two types of stony <span class="hlt">meteorites</span>, is their high carbon content (up to 3% of weight), either in the form of carbonates or of organic compounds. The bulk of the organic carbon consists of an insoluble macromolecular material with a complex structure. Also present is a soluble organic fraction, which has been analyzed by several separation and analytical procedures. Low detection limits can be achieved by derivatization of the organic molecules with reagents that allow for analysis by gas chromatography/mass spectroscopy and high performance liquid chromatography. The CM <span class="hlt">meteorite</span> Murchison has been found to contain more than 70 extraterrestrial amino acids and several other classes of compounds including carboxylic acids, hydroxy carboxylic acids, sulphonic and phosphonic acids, aliphatic, aromatic and polar hydrocarbons, fullerenes, heterocycles as well as carbonyl compounds, alcohols, amines and amides. The organic matter was found to be enriched in deuterium, and distinct organic compounds show isotopic enrichments of carbon and nitrogen relative to terrestrial matter.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20160010197','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20160010197"><span><span class="hlt">Meteorite</span> Falls Observed in U.S. Weather Radar Data in 2015 and 2016 (To Date)</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Fries, Marc; Fries, Jeffrey; Hankey, Mike; Matson, Robert</p> <p>2016-01-01</p> <p>To date, over twenty <span class="hlt">meteorite</span> falls have been located in the weather radar imagery of the National Oceanic and Atmospheric Administration (NOAA)'s NEXRAD radar network. We present here the most prominent events recorded since the last <span class="hlt">Meteoritical</span> Society meeting, covering most of 2015 and early 2016. <span class="hlt">Meteorite</span> Falls: The following events produced evidence of falling <span class="hlt">meteorites</span> in radar imagery and resulted in <span class="hlt">meteorites</span> recovered at the fall site. Creston, CA (24 Oct 2015 0531 UTC): This event generated 218 eyewitness reports submitted to the American Meteor Society (AMS) and is recorded as event #2635 for 2015 on the AMS website. Witnesses reported a bright fireball with fragmentation terminating near the city of Creston, CA, north of Los Angeles. Sonic booms and electrophonic noise were reported in the vicinity of the event. Weather radar imagery records signatures consistent with falling <span class="hlt">meteorites</span> in data from the KMUX, KVTX, KHNX and KVBX. The <span class="hlt">Meteoritical</span> Society records the Creston fall as an L6 <span class="hlt">meteorite</span> with a total recovered mass of 688g. Osceola, FL (24 Jan 2016 1527 UTC): This daytime fireball generated 134 eyewitness reports on AMS report number 266 for 2016, with one credible sonic boom report. The fireball traveled roughly NE to SW with a terminus location north of Lake City, FL in sparsely populated, forested countryside. Radar imagery shows distinct and prominent evidence of a significant <span class="hlt">meteorite</span> fall with radar signatures seen in data from the KJAX and KVAX radars. Searchers at the fall site found that recoveries were restricted to road sites by the difficult terrain, and yet several <span class="hlt">meteorites</span> were recovered. Evidence indicates that this was a relatively <span class="hlt">large</span> <span class="hlt">meteorite</span> fall where most of the <span class="hlt">meteorites</span> are unrecoverable due to terrain. Osceola is an L6 <span class="hlt">meteorite</span> with 991 g total mass recovered to date. Mount Blanco, TX (18 Feb 2016 0343 UTC): This event produced only 39 eyewitness reports and is recorded as AMS event #635 for 2016. No</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002EGSGA..27.5504T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002EGSGA..27.5504T"><span><span class="hlt">Impact</span> of <span class="hlt">Large</span>-scale Geological Architectures On Recharge</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Troldborg, L.; Refsgaard, J. C.; Engesgaard, P.; Jensen, K. H.</p> <p></p> <p>Geological and hydrogeological data constitutes the basis for assessment of ground- water flow pattern and recharge zones. The accessibility and applicability of hard ge- ological data is often a major obstacle in deriving plausible conceptual models. Nev- ertheless focus is often on parameter uncertainty caused by the effect of geological heterogeneity due to lack of hard geological data, thus neglecting the possibility of alternative conceptualizations of the <span class="hlt">large</span>-scale geological architecture. For a catchment in the eastern part of Denmark we have constructed different geologi- cal models based on different conceptualization of the major geological trends and fa- cies architecture. The geological models are equally plausible in a conceptually sense and they are all calibrated to well head and river flow measurements. Comparison of differences in recharge zones and subsequently well protection zones emphasize the importance of assessing <span class="hlt">large</span>-scale geological architecture in hydrological modeling on regional scale in a non-deterministic way. Geostatistical modeling carried out in a transitional probability framework shows the possibility of assessing multiple re- alizations of <span class="hlt">large</span>-scale geological architecture from a combination of soft and hard geological information.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20130011272','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20130011272"><span>Late Bombardment of the Lunar Highlands Recorded in MIL 090034, MIL 090036 and MIL 090070 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>Park, J.; Nyquist, L. E.; Shih, C.-Y.; Herzog, G. F.; Yamaguchi, A.; Shirai, N.; Ebihara, M.; Lindsay, F. N.; Delaney, J.; Turrin, B.; Swisher, C., III</p> <p>2013-01-01</p> <p>The Kaguya mission detected small but widespread outcrops of nearly pure ferroan anorthosite in and around <span class="hlt">large</span> <span class="hlt">impact</span> basins on the Moon. Along with certain lunar rocks, highly feldspathic lunar <span class="hlt">meteorites</span> such as MIL 090034 (M34), 090036 (M36), and 090070 (M70) may provide samples of this material. We have measured the Ar-40/Ar-39 release patterns and cosmogenic Ar-38 concentrations of several small (<200 microg) samples separated from M34,36, and 70. From petrographic observations concluded that "some of the clasts and grains experienced generations of modifications," a conclusion that we examine in light of our data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20170002069','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20170002069"><span>Lunar <span class="hlt">Meteorites</span>: A Global Geochemical Dataset</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zeigler, R. A.; Joy, K. H.; Arai, T.; Gross, J.; Korotev, R. L.; McCubbin, F. M.</p> <p>2017-01-01</p> <p>To date, the world's <span class="hlt">meteorite</span> collections contain over 260 lunar <span class="hlt">meteorite</span> stones representing at least 120 different lunar <span class="hlt">meteorites</span>. Additionally, there are 20-30 as yet unnamed stones currently in the process of being classified. Collectively these lunar <span class="hlt">meteorites</span> likely represent 40-50 distinct sampling locations from random locations on the Moon. Although the exact provenance of each individual lunar <span class="hlt">meteorite</span> is unknown, collectively the lunar <span class="hlt">meteorites</span> represent the best global average of the lunar crust. The Apollo sites are all within or near the Procellarum KREEP Terrane (PKT), thus lithologies from the PKT are overrepresented in the Apollo sample suite. Nearly all of the lithologies present in the Apollo sample suite are found within the lunar <span class="hlt">meteorites</span> (high-Ti basalts are a notable exception), and the lunar <span class="hlt">meteorites</span> contain several lithologies not present in the Apollo sample suite (e.g., magnesian anorthosite). This chapter will not be a sample-by-sample summary of each individual lunar <span class="hlt">meteorite</span>. Rather, the chapter will summarize the different types of lunar <span class="hlt">meteorites</span> and their relative abundances, comparing and contrasting the lunar <span class="hlt">meteorite</span> sample suite with the Apollo sample suite. This chapter will act as one of the introductory chapters to the volume, introducing lunar samples in general and setting the stage for more detailed discussions in later more specialized chapters. The chapter will begin with a description of how lunar <span class="hlt">meteorites</span> are ejected from the Moon, how deep samples are being excavated from, what the likely pairing relationships are among the lunar <span class="hlt">meteorite</span> samples, and how the lunar <span class="hlt">meteorites</span> can help to constrain the impactor flux in the inner solar system. There will be a discussion of the biases inherent to the lunar <span class="hlt">meteorite</span> sample suite in terms of underrepresented lithologies or regions of the Moon, and an examination of the contamination and limitations of lunar <span class="hlt">meteorites</span> due to terrestrial weathering. The</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20080030212','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20080030212"><span>Mars Crustal Dichotomy: <span class="hlt">Large</span> Lowland <span class="hlt">Impact</span> Basins may have Formed in Pre-Thinned Crust</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Frey, H. V.</p> <p>2008-01-01</p> <p>Crater retention ages of <span class="hlt">large</span> <span class="hlt">impact</span> basins on Mars suggest most formed in a relatively short time, perhaps in less than 200 million years. <span class="hlt">Large</span> basins in the lowlands have thinner central regions than similar size basins in the highlands. <span class="hlt">Large</span> lowland <span class="hlt">impact</span> basins, which we previously suggested might explain the low topography and thin crust of the northern part of Mars, may have formed in crust already thinned by yet earlier processes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20030110970&hterms=Digestion&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DDigestion','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20030110970&hterms=Digestion&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DDigestion"><span>Molybdenum Isotopic Composition of Iron <span class="hlt">Meteorites</span>, Chondrites and Refractory Inclusions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Becker, H.; Walker, R. J.</p> <p>2003-01-01</p> <p>Recent Mo isotopic studies of <span class="hlt">meteorites</span> reported evidence for differences in isotopic compositions for whole rocks of some primitive and differentiated <span class="hlt">meteorites</span> relative to terrestrial materials. Enrichments of r- and p-process isotopes of up to 3-4 units (e unit = parts in 10(exp 4) over s-process dominated isotopes are the most prominent features. Certain types of presolar grains show <span class="hlt">large</span> enrichments in s-process isotopes, however, it was concluded on grounds of mass balance that incomplete digestion of such grains cannot explain the enrichments of r- and p-process isotopes in whole rocks of primitive chondrites. If the reported variability in r- and p-process isotope enrichments reflects the true isotopic characteristics of the whole rocks, the implications are quite profound. It would suggest the presence of <span class="hlt">large</span> scale Mo isotopic heterogeneity within the solar accretion disk with likely collateral effects for other elements. However, such effects were not found for Ru isotopes, nor for Zr isotopes. Another recent Mo isotopic study by multi collector ICP-MS could not confirm the reported deviations in Allende, Murchison or iron <span class="hlt">meteorites</span>. Here, we present new results for the Mo isotopic composition of iron <span class="hlt">meteorites</span>, chondrites and CAIs obtained by negative thermal ionization mass spectrometry (NTIMS). We discuss analytical aspects and the homogeneity of Mo isotopic compositions in solar system materials.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1045426','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1045426"><span>Mechanical properties of several iron-nickel <span class="hlt">meteorites</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Mulford, Roberta N; El - Dasher, Bassem</p> <p>2011-01-06</p> <p>Iron-nickel <span class="hlt">meteorites</span> exhibit a unique lamellar microstructure, consisting of small regions with steep-iron-nickel composition gradients. The microstructure arises as a result of slow cooling in a planetary core or other <span class="hlt">large</span> mass. The microstructure is further influenced by variable concentrations of other elements such as phosphorous which may have influenced cooling and phase separation. Mechanical properties of these composite structures have been investigated 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 <span class="hlt">large</span> variation in dynamic properties, even within a single sample. Previous studies of the mechanical properties of a typical iron-nickel <span class="hlt">meteorite</span>, 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. This was ascribed to the extreme work-hardening evident in the EBSD measurements. Additional specimens from the Canyon Diablo fall (type IAB, coarse octahedrite) and several fine octahedrite <span class="hlt">meteorites</span>, from the Muonionalusta <span class="hlt">meteorite</span> (IVA) and Gibeon fall (IVA), have been examined to establish a range of error on the previously measured yield, to determine the extent to which deformation upon reentry contributes to yield, and to establish the degree to which the strength varies as a function of microstructure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/9339313','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/9339313"><span>Health <span class="hlt">impacts</span> of <span class="hlt">large</span> releases of radionuclides. The fate and <span class="hlt">impact</span> of radiocontaminants in urban areas.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Roed, J; Andersson, K G; Lange, C</p> <p>1997-01-01</p> <p>The Chernobyl accident made it clear that the contaminants released after a severe nuclear accident may spread over <span class="hlt">large</span> areas, and thereby form a significant external radiation hazard in areas of high population density. Since then, the weathering effects on the deposited radiocontaminants (essentially radiocaesium) have been followed on different types of surface in urban, suburban and industrial areas in order to enable an estimation of the long-term <span class="hlt">impact</span> of such events. Analytical expressions have been derived for the typical behaviour of radiocaesium on the different surfaces, and dose measurements and calculations for different urban environments have pinpointed which surfaces generally contribute most to the dose and consequently are most important to clean. At this point, after nearly a decade, the dose rate from horizontal pavements has decreased by at least a factor of 10, whereas the dose rate from an area of soil or a roof has generally only been halved. The contamination on walls is the most persistent: it has only decreased by 10-20%.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26418568','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26418568"><span>Multiple Cosmic Sources for <span class="hlt">Meteorite</span> Macromolecules?</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sephton, Mark A; Watson, Jonathan S; Meredith, William; Love, Gordon D; Gilmour, Iain; Snape, Colin E</p> <p>2015-10-01</p> <p>The major organic component in carbonaceous <span class="hlt">meteorites</span> is an organic macromolecular material. The Murchison macromolecular material comprises aromatic units connected by aliphatic and heteroatom-containing linkages or occluded within the wider structure. The macromolecular material source environment remains elusive. Traditionally, attempts to determine source have strived to identify a single environment. Here, we apply a highly efficient hydrogenolysis method to liberate units from the macromolecular material and use mass spectrometric techniques to determine their chemical structures and individual stable carbon isotope ratios. We confirm that the macromolecular material comprises a labile fraction with small aromatic units enriched in (13)C and a refractory fraction made up of <span class="hlt">large</span> aromatic units depleted in (13)C. Our findings suggest that the macromolecular material may be derived from at least two separate environments. Compound-specific carbon isotope trends for aromatic compounds with carbon number may reflect mixing of the two sources. The story of the quantitatively dominant macromolecular material in <span class="hlt">meteorites</span> appears to be made up of more than one chapter.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/1761823','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/1761823"><span>Controlling <span class="hlt">large</span> malpractice claims: the unexpected <span class="hlt">impact</span> of damage caps.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Gronfein, W P; Kinney, E D</p> <p>1991-01-01</p> <p>Indiana's comprehensive malpractice reforms, inaugurated in 1975, include a cap on damages, a mandated medical review before trial, and a state insurance fund to pay claims equal to or greater than $100,000. We have found that the amount of compensation going to claimants with such <span class="hlt">large</span> malpractice claims in Indiana is, on average, substantially higher than in Michigan and Ohio. Indiana's mean claim severity between 1977 and 1988 was $404,832, while the means for Michigan and Ohio were $290,022 and $303,220, respectively, with the difference between these three means being highly significant. Although data on claim and claimant characteristics reveal considerable interstate variation, the results of regression analyses show that Indiana claim payment amounts are higher than Michigan or Ohio payments, independent of the effect of factors such as sex, age, severity of injury, allegations of negligence, and year of settlement.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19920014066','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19920014066"><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>1992-01-01</p> <p>Examination of 29.37 sq m of thick aluminum plates from the LDEF, which were exposed to the meteoroid and man-made orbital debris environments for 5.8 years, revealed 606 craters that were 0.5 mm in diameter or larger. Most were nearly hemispherical. There was a <span class="hlt">large</span> variation in the number density of craters around the three axis gravity gradient stabilized spacecraft. A new model of the near-Earth meteoroid environment gives good agreement with the crater fluxes measured on the fourteen faces of the LDEF. The man-made orbital debris model of Kessler, which predicts that 16 pct. of the craters would be caused by man-made debris, is plausible. No chemical analyses of impactor residue that will distinguish between meteoroids and man-made debris is yet available.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19770051852&hterms=gibbon&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dgibbon','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19770051852&hterms=gibbon&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dgibbon"><span>Metal spherules in Wabar, Monturaqui, and Henbury impactites. [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>Gibbons, R. V.; Horz, F.; Thompson, T. D.; Brownlee, D. E.</p> <p>1976-01-01</p> <p>The Fe, Ni, and Co contents of 450 spherules with diameters of 3 to 100 microns in <span class="hlt">impact</span> glasses from three terrestrial <span class="hlt">meteorite</span> craters are determined by electron microprobe analysis. The objects investigated include 250 spherules from Wabar (Saudi Arabia) impactite and 100 each from Monturaqui (Chile) and Henbury (Australia) impactites. The specimens and spherules are described, noting that the Wabar and Henbury craters were produced in sandstone while the Monturaqui crater was formed in siliceous igneous rocks and has an enigmatic sulfide abundance. It is found that the spherules are enriched in Ni and Co relative to the original <span class="hlt">meteorite</span> Fe content and are enriched in Ni relative to Co for Ni contents greater than 50%. The results indicate that, on the average, Henbury spherules are more Ni-enriched than Monturaqui spherules, and Wabar spherules exhibit the least Ni-enrichment. It is suggested that the spherules could have formed without experiencing free flight and that instantaneous dissemination of <span class="hlt">meteoritic</span> material at the <span class="hlt">meteorite</span>-target contact was the major fractionation process.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_24 --> <div id="page_25" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="481"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19940023807','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19940023807"><span>A general theory of <span class="hlt">impacts</span> and mass extinctions, and the consequences of <span class="hlt">large</span>-body <span class="hlt">impact</span> on the Earth</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Rampino, M. R.</p> <p>1994-01-01</p> <p>The theory that <span class="hlt">large</span>-body <span class="hlt">impacts</span> are the primary cause of mass extinctions of life on the Earth now has a sound theoretical and observational foundation. A convergence of evidence suggests that the biosphere may be a sensitive detector of <span class="hlt">large</span> <span class="hlt">impact</span> events, which result in the recorded global mass extinction pulses. The astronomically observed flux of asteroids and comets in the neighborhood of the Earth, and the threshold <span class="hlt">impact</span> size calculated to produce a global environment catastrophe, can be used to predict a time history of <span class="hlt">large</span> <span class="hlt">impact</span> events and related mass extinctions of life that agrees well with the record of approx. 24 extinction events in the last 540 m.y.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999nvm..conf...36K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999nvm..conf...36K"><span>Lunar <span class="hlt">Meteorites</span> and Implications for Compositional Remote Sensing of the Lunar Surface</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Korotev, R. L.</p> <p>1999-01-01</p> <p> together distinct in being fragmental breccias containing subequal parts of feldspathic highland material and VLT mare basalt. Jolliff et al. estimate a mare to highland ratio of 54:46 for QUE 94281 and 62:38 for Y 793274; this difference is well within the range observed for soils collected only centimeters apart (in cores) at interface site like Apollo 15 and 17 [11]. Although the two <span class="hlt">meteorites</span> were found on opposite sides of Antarctica, they are probably launch-paired. The strongest evidence is that the pyroclastic glass spherules that occur in both are of two compositional groups and the two groups are essentially the same in both <span class="hlt">meteorites</span>. Yamato 791197 is nominally a feldspathic lunar <span class="hlt">meteorite</span> (below), but among FLMs, it probably contains the highest abundance of clasts and glasses of mare derivation. As a consequence, its composition is at the high-Fe, low-Mg end of the range for FLMs and is not included in the FLM average of Table 1. Its composition is consistent with about 10% mare-derived material. Similarly, the two small (Y 82) pieces of Y 82192/82193186032 are more mafic than the <span class="hlt">large</span> (Y 86) piece, probably as a result of about 7% mare-derived material. All Apollo missions went to areas in or near the PKT, and, consequently, all Apollo regolith samples are contaminated with Th-rich material from the PKT. At the nominally "typical" highland site, Apollo 16, about 30% of the regolith (<1-mm fines) is Th-rich ejecta from the Imbrium <span class="hlt">impact</span> and about 6% is mare material probably derived from mare basins. Thus Apollo 16 regolith is not typical of the highlands. Among Apollo rocks, the compositions of the FLMs correspond most closely to the feldspathic granulitic breccias of Apollo 16 and 17. (Additional information is contained in original)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19910016756&hterms=you+survive+mars&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dyou%2Bsurvive%2Bmars','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19910016756&hterms=you+survive+mars&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dyou%2Bsurvive%2Bmars"><span>The <span class="hlt">meteoritic</span> contribution to the regoliths of Mars, Deimos, and Phobos</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Flynn, G. J.</p> <p>1991-01-01</p> <p>The mass influx of <span class="hlt">meteoritic</span> material at Earth exhibits two distinct peaks: one centered at 10-5 grams, corresponding to the continuous, planet-wide flux of micrometeorites, and a second corresponding to the rare <span class="hlt">impacts</span> of objects larger than 1014 grams. Using the measured flux of <span class="hlt">meteoritic</span> material at Earth and estimates of the Mars/Earth flux ration, it was calculated that the micrometeorites add between 2,700 and 59,000 tons of <span class="hlt">meteoritic</span> material to the surface of Mars annually. This corresponds to the accretion of between 1.8 and 40 cm of <span class="hlt">meteoritic</span> material per billion years. On the Moon this <span class="hlt">meteoritic</span> component constitutes 1 to 2 percent of the mare soils. Depending on the indigenous regolith production rate on Mars, the <span class="hlt">meteoritic</span> material on Mars may be present in sufficient concentration to serve as a resource for the volatile and siderophile elements common in chondritic <span class="hlt">meteorites</span> but rare in basaltic crustal material. Since a significant fraction of the micrometeorites less than 1200 mm in diameter survive atmospheric entry on Mars without melting, they carry into the regolith the solar wind ions, including H, He, and noble gases, implanted during their space exposure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015M%26PS...50..273P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015M%26PS...50..273P"><span>Cosmogenic radionuclides and mineralogical properties of the Chelyabinsk (LL5) <span class="hlt">meteorite</span>: What do we learn about the meteoroid?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Povinec, Pavel P.; Laubenstein, Matthias; Jull, A. J. Timothy; FerrièRe, Ludovic; BrandstäTter, Franz; Sýkora, Ivan; Masarik, Jozef; BeåO, Juraj; KováčIk, Andrej; Topa, Dan; Koeberl, Christian</p> <p>2015-02-01</p> <p>On February 15, 2013, after the observation of a brilliant fireball and a spectacular airburst over the southern Ural region (Russia), thousands of stones fell and were rapidly recovered, bringing some extremely fresh material for scientific investigations. We undertook a multidisciplinary study of a dozen stones of the Chelyabinsk <span class="hlt">meteorite</span>, including petrographic and microprobe investigations to unravel intrinsic characteristics of this <span class="hlt">meteorite</span>. We also study the short and long-lived cosmogenic radionuclides to characterize the initial meteoroid size and exposure age. Petrographic observations, as well as the mineral compositions obtained by electron microprobe analyses, allow us to confirm the classification of the Chelyabinsk <span class="hlt">meteorite</span> as an LL5 chondrite. The fragments studied, a few of which are <span class="hlt">impact</span> melt rocks, contain abundant shock melt veins and melt pockets. It is likely that the catastrophic explosion and fragmentation of the Chelyabinsk meteoroid into thousands of stones was in part determined by the initial state of the meteoroid. The radionuclide results obtained show a wide range of concentrations of 14C, 22N