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. International Conference on Large Meteorite Impacts and Planetary Evolution

    SciTech Connect

    Not Available

    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. Separate abstracts were prepared for papers from this report.

  5. Large meteorite impacts: The K/T model

    NASA Technical Reports Server (NTRS)

    Bohor, B. F.

    1992-01-01

    The Cretaceous/Tertiary (K/T) boundary event represents probably the largest meteorite impact known on Earth. It is the only impact event conclusively linked to a worldwide mass extinction, a reflection of its gigantic scale and global influence. Until recently, the impact crater was not definitively located and only the distal ejecta of this impact was available for study. However, detailed investigations of this ejecta's mineralogy, geochemistry, microstratigraphy, and textures have allowed its modes of ejection and dispersal to be modeled without benefit of a source crater of known size and location.

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

    NASA Technical Reports Server (NTRS)

    Lowe, Donald R.; Byerly, Gary R.

    1988-01-01

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

  7. Antipodal focusing of seismic waves due to large meteorite impacts on Earth

    NASA Astrophysics Data System (ADS)

    Meschede, Matthias A.; Myhrvold, Conor L.; Tromp, Jeroen

    2011-10-01

    We examine focusing of seismic waves at the antipode of large terrestrial meteorite impacts, using the Chicxulub impact as our case study. Numerical simulations are based on a spectral-element method, representing the impact as a Gaussian force in time and space. Simulating the impact as a point source at the surface of a spherically symmetric earth model results in deceptively large peak displacements at the antipode. Earth's ellipticity, lateral heterogeneity and a spatially distributed source limit high-frequency waves from constructively interfering at the antipode, thereby reducing peak displacement by a factor of 4. Nevertheless, for plausible impact parameters, we observe peak antipodal displacements of ˜4 m, dynamic stresses in excess of 15 bar, and strains of 2 × 10-5 . Although these values are significantly lower than prior estimates, mainly based on a point source in a spherically symmetric earth model, wave interference en route to the antipode induces 'channels' of peak stress that are five times greater than in surrounding areas. Underneath the antipode, we observed 'chimneys' of peak stress, strain and velocity, with peak values exceeding 50 bar, 10-5 and 0.1 m s-1, respectively. Our results put quantitative constraints on the feasibility of impact-induced antipodal volcanism and seismicity, as well as mantle plume and hotspot formation.

  8. Impact Crater Particulates: Microscopic Meteoritic Material Surrounding Meteorite Craters

    NASA Astrophysics Data System (ADS)

    Smith, Toby Russell

    1995-01-01

    The influx of extraterrestrial matter onto the Earth is a ongoing process. Every year 40,000 metric tons of extraterrestrial matter is accreted by the Earth (Love 1993). A small fraction of this material arrives at Earth as objects large enough to survive the passage through atmosphere. Some of this material is completely melted as it passes through the atmosphere and arrives at the surface of the Earth as cosmic spherules. Cosmic spherules formed from metallic cosmic material undergoes changes in its elemental abundance as it passes through the atmosphere. The oxidation of the spherules results in the concentration of more refractory elements like Ni and Co into the metallic phase. Cosmic spherules are also formed by the passage of large meteorites through the atmosphere and their resulting impact onto the Earth. I found that the cosmic spherules from a wide variety of sources show a very similar trend in the elemental abundance patterns of their metallic phases. This trend is most obvious in the spherules recovered from the deep -sea and the spherules imbedded in impactite glass recovered from iron meteorite impact crater sites. The metallic spherules recovered from the soil surrounding impact craters do not show the high degree of elemental fractionation found in the deep-sea and impactite spherules. The composition of these spherules indicate that they are a mixture of meteoritic and target material. Metallic spherules are not the only meteoritic material to be found in the soil surrounding meteorite craters. I found that small fragments of the parent meteorite are an ubiquitous component of the soil surrounding the Odessa and Dalgaranga meteorite craters. These fragments occurred as small (most less than 400 mu m in size) heavily weathered fragments of meteoritic metal. The total calculated mass of these fragments is an order of magnitude larger than the mass of ponderable meteorites recovered from the site but 1 to 2 orders of magnitude smaller than the

  9. 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.

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

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

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

  11. 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

  12. 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.

  13. The liming of the Earth after the Chicxulub large meteorite impact at the K/T boundary

    NASA Astrophysics Data System (ADS)

    Agrinier, P.; Michard, G.; Martinez, I.; Scharer, U.; Deutsch, A.

    2005-05-01

    Shock metamorphism induced by large meteorite impacts on Earth decomposes sediments (carbonates: CaCO3, CaMg(CO3)2 and sulfates: CaSO4) into CaO, MgO, CO2 and SO2. For the Chicxulub case at the K/T boundary, up to 2850 Gt of CO2 and up to 550 Gt of SO2 were liberated into the atmosphere (Ivanov et al., 1996; Pierazzo et al., 1998; Gupta et al., 2002). Though numerous works have depicted the resulting environmental consequences of dispersing CO2, SO2, dust into the atmosphere (greenhouse warming, aerosol cooling, acid rains,...), no study has described the fate of the corresponding liberated CaO and MgO (up to 3718 Gt of CaO) in the atmosphere. Considering the high reactivity and the caustic nature of CaO (lime), we argue that spreading lime on the Earth surface increases the pH of natural waters up to 12.5. It would produce harmful environmental effects (carbonate and metal depletion in natural waters, oxydation of organic matter) and symptomatic isotopic 13C- and 18O-depleted, metal-enriched carbonates would form. Neutralization by the natural carbonate acid-base system (H2CO3/HCO3-/CO32-) of waters, by acid rains (H2CO3, H2SO4, HNO3) produced by the impact generated-CO2 and SO2, NOx and atmospheric CO2 pumping control the duration of this high pH effect on lands, while at the surface of the oceans, dilution and mixing with normal pH (? 8) seawater further reduce the duration of this high pH effect. The timescale of this high pH severe effects would be as short as a few months. As a conclusion, due to its high reactivity, lime rapidly neutralizes a significant part of the acidic atmospheric perturbation produced by the impact-liberated CO2, SO2, NOx. Ivanov et al., 1996 ; Geol. Soc. Amer. Spec. Pap., 307, 125-142. Pierazzo et al., 1998; J. Geophys. Res., Planet 103(E12), 28607-28625. Gupta et al., 2002; Earth Planet. Sci. Lett., 201, 1-12

  14. 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

  15. Launch of martian meteorites in oblique impacts

    NASA Astrophysics Data System (ADS)

    Artemieva, Natalia; Ivanov, Boris

    2004-09-01

    A high-velocity oblique impact into the martian surface accelerates solid target material to escape velocity. A fraction of that material eventually falls as meteorites on Earth. For a long time they were called the SNC meteorites (Shergotty, Nakhla, and Chassigny). We study production of potential martian meteorites numerically within the frame of 3D hydrodynamic modeling. The ratio of the volume of escaping solid ejecta to projectile volume depends on the impact angle, impact velocity and the volatile content in the projectile and in the target. The size distribution of ejected fragments appears to be of crucial importance for the atmosphere-ejecta interaction in the case of a relatively small impact (with final crater size <3 km): 10-cm-sized particles are decelerated efficiently, while 30-50% of larger fragments could escape Mars. The results of numerical modeling are compared with shock metamorphic features in martian meteorites, their burial depth, and preatmospheric mass. Although it is impossible to accelerate ejected fragments to escape velocity without substantial compression (above 10 GPa), the maximum temperature increase in dunite (Chassigny) or ortopyroxenite (ALH84001) may be lower than 200 degree. This result is consistent with the observed chaotic magnetization of ALH84001. The probability of microbes' survival may be rather high even for the extreme conditions during the ejection process.

  16. 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

  17. 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

  18. The Effect of Early Impacts on Iron Meteorite Cooling Rates

    NASA Astrophysics Data System (ADS)

    Lyons, R. J.; Ciesla, F. J.; Bowling, T. J.; Davison, T. M.; Collins, G. S.

    2016-08-01

    Sizes and structures of iron meteorite parent bodies have been inferred by comparing metallographic cooling rates to thermal evolution models. We examine the effect that impacts would have on cooling rates of cores of differentiated planetesimals.

  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. PMID:26392614

  1. 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.

  2. Antipodal focusing of seismic waves after larger meteorite impacts

    NASA Astrophysics Data System (ADS)

    Meschede, M.

    2011-12-01

    We examine focusing of seismic waves at the antipode of large terrestrial meteorite impacts, using the Chicxulub impact as our case study. Numerical simulations are based on a spectral-element method, representing the impact as a Gaussian force in time and space. Simulating the impact as a point source at the surface of a spherically symmetric Earth model results in deceptively large peak displacements at the antipode. Earth's ellipticity, lateral heterogeneity and a spatially distributed source limit high-frequency waves from constructively interfering at the antipode, thereby reducing peak displacement by a factor of four. Nevertheless, for plausible impact parameters, we observe peak antipodal displacements of ˜ 4~m, dynamic stresses in excess of 15~bar, and strains of 2 ± 10-5 . While these values are significantly lower than prior estimates, mainly based on a point source in a spherically symmetric Earth model, wave interference en route to the antipode induces ``channels'' of peak stress that are 5~times greater than in surrounding areas. Underneath the antipode we observed ``chimneys'' of peak stress, strain and velocity, with peak values exceeding 50~bar, 10-5 and 0.1~m/s, respectively. Our results put quantitative constraints on the feasibility of impact-induced antipodal volcanism and seismicity, as well as mantle plume and hotspot formation.

  3. Mixing of the lunar regolith. [by meteoritic impact

    NASA Technical Reports Server (NTRS)

    Gault, D. E.; Hoerz, F.; Brownlee, D. E.; Hartung, J. B.

    1974-01-01

    A probabilistic model for mixing and turnover rates for the lunar regolith due to meteoritic impact is presented and evaluated using results from laboratory impact experiments and estimated meteoritic fluxes. The upper millimeter of the lunar surface is shown to be the primary mixing zone in the regolith and an important source for impact melts and vapors. Below this 'mixing layer' the rate of mixing and turnover decreases very rapidly with increasing depth, consistent with well-preserved stratigraphy and resident times deduced from deep drill core tube samples.

  4. The Meteoritic Component in Impact Deposits

    NASA Technical Reports Server (NTRS)

    Kyte, Frank T.

    2002-01-01

    An important part of the history of impacts on Earth, and their influence on the terrestrial environment and biotic evolution, is the provenance of the impacting bolides. This will reflect the history of the large-body object flux in the inner solar system. The physical and chemical properties of projectiles, as well as their orbital evolution, has influenced the dynamics and the relative timing of impact events. Possible impact scenarios include random impacts by individual asteroids or comets, or clusters of impacts due to major collisions in the asteroid or Kuiper belts, or large perturbations of the Oort cloud of comets. Over the last several years, a combination of trace element, isotopic, and petrologic data have yielded significant insights into this impact history. The trace element chemistry of sediments, in particular the concentration of siderophiles (e.g., Ir), is a useful tool to detect impacts and provides supporting evidence for suspected impact deposits. However, siderophiles are not especially useful in distinguishing between types of projectiles. Interelement abundances of PGEs can distinguish a chondritic signature, but since most asteroids, and probably all comets are chondritic, these data do little to distinguish between chondritic source materials. Perhaps the most significant chemical argument used to constrain provenance, is that the total amount of Ir in the global Cretaceous-Tertiary (KT) boundary ejecta layer is considerably less than that expected by a low-velocity, 10 km asteroid impact and is most consistent with the impact of a high-velocity, low-Ir comet. Alternatively, much of the Ir may have been buried in the Chicxulub crater and/or ejected to escape velocity.

  5. 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.

  6. 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. PMID:12804363

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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. PMID:23360995

  12. 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.

  13. 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.

  14. 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. PMID:26369758

  15. 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.

  16. 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. PMID:24934564

  17. 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.

  18. 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.

  19. Pancam Visible/Near-Infrared Spectra of Large Fe-Ni Meteorites at Meridiani Planum, Mars

    NASA Astrophysics Data System (ADS)

    Johnson, J. R.; Herkenhoff, K. E.; Bell, J. F.; Farrand, W. H.; Ashley, J.; Weitz, C.; Squyres, S. W.

    2010-03-01

    The MER Opportunity rover imaged three large Fe-Ni meteorites in 2009. Pancam reflectance spectra of coatings on the rocks are consistent with ferric oxides (e.g., np-hematite), suggestive of chemical weathering on portions of the meteorite surfaces.

  20. Reconstructing the Shock Wave From the Wolfe Creek Meteorite Impact.

    NASA Astrophysics Data System (ADS)

    Heine, C.; O'Neill, C. J.

    2003-12-01

    The Wolfe Creek meteorite crater is an 800m diameter impact structure located in the Tanami Desert near Hall's Creek, Western Australia. The crater formed <300000 years ago, and is the 2nd largest crater from which fragments of the impacting meteorite (a medium octahedrite) have been recovered. We present the results of new ground based geophysical (magnetics and gravity) surveys conducted over the structure in July-August, 2003. The results highlight the simple structure of the crater under the infilling sediments, and track the extent of deformation and the ejecta blanket under the encroaching sanddunes. The variations in the dip of the foliations around the crater rim confirm that the crater approached from East-Northeast, as deduced from the ejecta distribution, and provide constraints on the kinetic energy and angle of the impactor. We also use the distribution of shocked quartz in the target rock (Devonian sandstones) to reconstruct the shock loading conditions of the impact using the Grieve and Robertson (1976) criterion. We also use a Simplified Arbitrary Langrangian-Eulerian hydrocode (SALE 2) to simulate the propagation of shock waves through a material described by a Tillotson equation of state. Using the deformational and PT constraints of the Wolfe-Creek crater, we can estimate the partitioning of kinetic energy as a result of this medium-size impact.

  1. 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.

  2. Outcome of impact disruption of iron meteorites at room temperature

    NASA Astrophysics Data System (ADS)

    Katsura, T.; Nakamura, A.; Takabe, A.; Okamoto, T.; Sangen, K.; Hasegawa, S.; Liu, X.; Mashimo, T.

    2014-07-01

    The iron meteorites and some M-class asteroids are generally understood to originate in the cores of differentiated planetesimals or in the local melt pools of primitive bodies. On these primitive bodies and planetesimals, a wide range of collisional events at different mass scales, temperatures, and impact velocities would have occurred. Iron materials have a brittle-ductile transition at a certain temperature, which depends on metallurgical factors such as grain size and purity, and on conditions such as strain-rate and confining pressure [1]. An evolutional scenario of iron meteorite parent bodies was proposed in which they formed in the terrestrial planet region, after which they were scattered into the main belt by collisions, Yarkovsky thermal forces, and resonances [2]. In this case, they may have experienced collisional evolution in the vicinity of the Earth before they were scattered into the main belt. The size distribution of iron bodies in the main belt may therefore have depended on the disruption threshold of iron bodies at temperature above the brittle-ductile transition. This paper presents the results of impact-disruption experiments of iron meteorite and steel specimens mm-cm in size as projectiles or targets conducted at room temperature using three light-gas guns and one powder gun. Our iron specimens were almost all smaller in size than their counterparts (as targets or projectiles, respectively). The fragment size distribution of iron material was different from that of rocks. In iron fragmentation, a higher percentage of the mass is concentrated in larger fragments, i.e., the mass fraction of fine fragments is much less than that of rocks shown in the Figure (left). This is probably due to the ductile nature of the iron materials at room temperature. Furthermore, the Figure (right) shows that the largest fragment mass fraction f is dependent not only on the energy density but also on the size of the specimens. In order to obtain a generalized

  3. 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.

  4. 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

  5. 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

  6. 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.

  7. Variations in impact effects among IIIE iron meteorites

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

    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.

  8. 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.

  9. 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. PMID:19317624

  10. 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

  11. 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.

  12. 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.

  13. 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.

  14. 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. PMID:25883354

  15. 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.

  16. Distribution of Impact Locations and Velocities of Earth Meteorites on the Moon

    NASA Astrophysics Data System (ADS)

    Armstrong, John C.

    2010-12-01

    Following the analytical work of Armstrong et al. (Icarus 160:183-196, 2002), we detail an expanded N-body calculation of the direct transfer of terrestrial material to the Moon during a giant impact. By simulating 1.4 million particles over a range of launch velocities and ejecta angles, we have derived a map of the impact velocities, impact angles, and probable impact sites on the moon over the last 4 billion years. The maps indicate that the impacts with the highest vertical impact speeds are concentrated on the leading edge, with lower velocity/higher-angle impacts more numerous on the Moon's trailing edge. While this enhanced simulation indicates the estimated globally averaged direct transfer fraction reported in Armstrong et al. (Icarus 160:183-196, 2002) is overestimated by a factor of 3-6, local concentrations can reach or exceed the previously published estimate. The most favorable location for large quantities of low velocity terrestrial material is 50 W, 85 S, with 8.4 times more impacts per square kilometer than the lunar surface average. This translates to 300-500 kg km-2, compared to 200 kg km-2 from the previous estimate. The maps also indicate a significant amount of material impacting elsewhere in the polar regions, especially near the South Pole-Aiken basin, a likely target for sample return in the near future. The magnitudes of the impact speeds cluster near 3 km/s, but there is a bimodal distribution in impact angles, leading to 43% of impacts with very low (<1 km/s) vertical impact speeds. This, combined with the enhanced surface density of meteorites in specific regions, increases the likelihood of weakly shocked terrestrial material being identified and recovered on the Moon.

  17. 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.

  18. 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

  19. 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.

  20. 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).

  1. 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

  2. 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. PMID:21187434

  3. 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.

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

    NASA Technical Reports Server (NTRS)

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

    1986-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

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

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

    NASA Technical Reports Server (NTRS)

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

    1977-01-01

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

  7. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2005-10-01

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

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

    NASA Astrophysics Data System (ADS)

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

    1992-09-01

    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

  10. 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

  11. Chondrule-like particles provide evidence of early Archean meteorite impacts, South Africa and western Australia

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

    The evolution of the Earth and the Earth crust was studied. Two layers, that contain abundant unusual spherical particles which closely resemble chondroules were identified. Chondrules occur on small quantities in lunar soil, however, they are rare in terrestrial settings. Some chondrules in meteorites were formed on the surfaces of planet sized bodies during impact events. Similar chondrule like objects are extremely rare in the younger geologic record and these abundances are unknown in ancient deposits, except in meteorites. It is suggested that a part of the Earth's terminal bombardment history, and conditions favoring chondrule formation existed on the early Earth.

  12. 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.

  13. Ionospheric effects during first 2 hours after the "Chelyabinsk" meteorite impact

    NASA Astrophysics Data System (ADS)

    Berngardt, Oleg; Kurkin, Vladimir; Zherebtsov, Gelii; Grigorieva, Svetlana; Kusonski, Oleg

    In this paper, we analyzed the ionospheric effects within the 100-1500 km ranges from the Chelyabinsk meteorite explosion site from the ISTP SB RAS EKB radar data, and from the IG UB RAS PARUS ionosonde data. Both instruments are located at the Arti Observatory, approximately 200 km north of the supposed explosion location. The ionospheric disturbance caused by the meteorite flyby, explosion, and impact had high dynamics and amplitude. Essential effects, however, were observed at more than 100-200 km from the explosion site, and farther, up to 1500 km. Almost simultaneously with the explosion and for 3 minutes (03:20-03:23 UT), there was a motion away from the radar 400 km southwest of the latter (and approximately 200 km west of the explosion site) at the E-layer height with the characteristic velocities 200 m/s and high spectral width. A short delay of the detected effect at a significant distance from the explosion site also testifies to the hypothesis of a large short-living irregularity formations at the heights of the lower E-layer, with the transversal size of several hundreds of kilometers. The first disturbance in the F-layer was observed 15 minutes after the explosion, and it propagated away from the radar almost radially. The radial disturbances were observed up to about 80-100 minutes. The main disturbances in the F-layer were nearly radial waves with the center close to the explosion site. Analyzing the experimental data allowed us to determine the equivalent ionospheric velocities for individual travel mode. The work was done under financial support of RFBR grant #14-05-00514-a.

  14. On the role of meteoritic impacts in the formation of organic molecules.

    PubMed

    Cerroni, P; Martelli, G

    1984-01-01

    It is suggested that the UV radiation, and shock and plasma phenomena which accompanied the hypervelocity impacts of solid bodies (meteorites and comets) onto the surface of the young Earth may have contributed to the synthesis of prebiotic organic molecules in the primitive atmosphere in a larger amount than was thought previously. The mechanisms responsible for this synthesis are discussed using information obtained from recent experimental and theoretical work on macroscopic hypervelocity impacts.

  15. 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.

  16. 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.

  17. 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

  18. 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.

  19. 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

  20. 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.

  1. Oblique impact - A process for obtaining meteorite samples from other planets

    NASA Technical Reports Server (NTRS)

    Okeefe, John D.; Ahrens, Thomas 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 meteorities 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.

  2. 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.

  3. 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

  4. A major meteorite impact on the Earth 65 million years ago: evidence from the cretaceous-tertiary boundary clay.

    PubMed

    Ganapathy, R

    1980-08-22

    Evidence for a major meteorite impact on the earth 65 million years ago is shown by the presence of meteoritic debris in the "fish clay" from Denmark representing the Cretaceous-Tertiary boundary. Noble metals (iridium, osmium, gold, platinum, rhenium, ruthenium, palladium, nickel, and cobalt), which are sensitive indicators of meteorites and are normally depleted on the terrestrial surface by factors of 10(4) to 10(2) relative to cosmic abundances, are enriched in this boundary clay by factors of 5 to 100 over the expected abundances. With the exception of rhenium, all the enriched noble metals in the clay are present in cosmic proportions, indicating that the impacting celestial body had not undergone gross chemical differentiation. The major extinction of life on the earth at the end of the Cretaceous Period may be related to the meteorite impact.

  5. 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.

    2016-08-01

    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.

  6. 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

  7. Meteorite Impact at the Bedout High, NW Australian Margin, and Seismic Velocities: is There a Connection?

    NASA Astrophysics Data System (ADS)

    Goncharov, A.; Kennard, J.; Becker, L.

    2004-12-01

    The Bedout High in the Roebuck Basin at the NW Australian Margin (NWAM) appears to be a good candidate for a massive impact structure associated with the global Permian/Triassic extinction event. On a regional and crustal scale, the NWAM is one of the best studied offshore areas of Australia: ocean-bottom seismograph (OBS) survey supplemented by deep reflection seismic studies in the region has enabled co-interpretation of conventional deep seismic reflection data and accurate seismic velocity models on several transects, including one across the Bedout High. The purpose of this research is to investigate if there is any manifestation of the meteorite impact on a crustal scale, and also on a finer scale of seismic velocity variation in the basement. The impact of the suggested magnitude may have significantly modified the crustal structure in the region. Depth conversion of reflection seismic data indicates that depth to basement at the top of the Bedout High is approximately 3.9 km, and that the High stands more than 4 km above the surrounding sedimentary basins. The basement and crust in the Roebuck Basin have a number of features that distinguish it from other basins at the NWAM. Rapid crustal thinning outboard of the Bedout High and the presence of a thick layer of magmatic underplating in the lower crust are among these features. The meteorite impact may have been one of the possible causes to have triggered upper mantle melting and generation of a voluminous layer of underplated material. On a finer scale, OBS-derived seismic velocity variation along the basement is speculatively interpreted to be consistent with impact-related effects. However, existing seismic and potential field data do not allow accurate estimates of the extent of the crust affected by the meteorite impact, and effects that it may have had on the subsequent rifting, thermal, sedimentation and hydrocarbon maturation regimes in the area. Further multidisciplinary research is necessary to

  8. 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.

  9. 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

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  11. Early Thermal Evolution of Planetesimals and Its Impact on Processing and Dating of Meteoritic Material

    NASA Astrophysics Data System (ADS)

    Gail, H.-P.; Trieloff, M.; Breuer, D.; Spohn, T.

    Radioisotopic ages for meteorites and their components provide constraints on the evolution of small bodies: timescales of accretion, thermal and aqueous metamorphism, differentiation, cooling, and impact metamorphism. Realizing that the decay heat of short-lived nuclides (e.g., 26Al, 60Fe) was the main heat source driving differentiation and metamorphism, thermal modeling of small bodies is of the utmost importance to set individual meteorite age data into the general context of the thermal evolution of their parent bodies, and to derive general conclusions about the nature of planetary building blocks in the early solar system. As a general result, modeling easily explains that iron meteorites are older than chondrites, as early formed planetesimals experienced a higher concentration of short-lived nuclides and more severe heating. However, core formation processes may also extend to 10 million years (m.y.) after the formation of calcium-aluminum-rich inclusions (CAIs). A general effect of the porous nature of the starting material is that relatively small bodies (less than a few kilometers) will also differentiate if they form within 2 m.y. after CAIs. A particular interesting feature to be explored is the possibility that some chondrites may derive from the outer undifferentiated layers of asteroids that are differentiated in their interiors. This could explain the presence of remnant magnetization in some chondrites due to a planetary magnetic field.

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

    NASA Astrophysics Data System (ADS)

    Rubin, Alan E.

    2016-07-01

    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.

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. 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.

  18. Origin of the sudbury complex by meteoritic impact: neodymium isotopic evidence.

    PubMed

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

    1985-10-25

    Samarium-neodymium isotopic data on whole rocks and minerals of the Sudbury Complex in Canada gave an igneous crystallization age of 1840 +/- 21 x 10(6) 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.

  19. 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.

  20. 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

  1. Laboratory Study of Titan's Surface Chemistry Induced by Meteoritic Impact Processing: Laser-Simulated Hypervelocity Impact on Ices

    NASA Astrophysics Data System (ADS)

    Nna-Mvondo, D.; Khare, B. N.; McKay, C. P.

    2008-12-01

    Titan's dense atmosphere, mostly composed of nitrogen and some methane, allows easy formation of long chains of organic molecules and high-molecular-weight organic solids, known as tholins. Over geologic time, both tholins and condensates of the organic gases accumulate in substantial amounts on the surface as liquid and solid. Titan's surface is then a repository of interesting organic molecules generated in the almost complete absence of water but sitting on top of ice. Until recently, researchers have been very careful in their speculations about what might be happening after these molecules get to the surface of Titan. What kind of organic chemistry occurs on the surface? Titan's thick atmosphere protects the surface and organics from harmful cosmic rays and ultraviolet radiation. It has been suggested that these organics could have been subjected to impact processing on Titan's and participate in the formation of products relevant to life such as amino acids, carboxylic acids, purines and pyrimidines. Subsequent impacts would probably have recycled some of the organic material back into the atmosphere. Furthermore the presence of condensable agents (C2N2, HCN, etc.) along with a natural concentrating mechanism makes polymerization of amino acids or others species likely. Laboratory simulations of meteoritic impact shocks onto Titan's icy surface have not yet been carried out, but preliminary experiments have been performed for planetary icy satellites. In these previous experiments, the possible chemical production induced by micrometeorite impact shocks on ices has been studied using a high-energy pulsed Nd-YAG laser to reproduce the shock phenomena during hypervelocity micrometeorite impacts into the icy material. The results show the production of various organics and inorganics. Here we have decided to extend those experiments to a simulated Titan's environment in order to study the effect of meteoritic impacts on the organic chemistry occurring on Titan

  2. Late Quaternary seismo-stratigraphy of Lake Wanapitei, Sudbury, Ontario, Canada: Arguments for a possible meteorite impact origin

    NASA Astrophysics Data System (ADS)

    Lazorek, Michael; Eyles, Nick; Eyles, Carolyn; Doughty, Mike; L'Heureux, Elizabeth; Milkereit, Berndt

    2006-12-01

    Lake Wanapitei (132.75 km2) fills what has been identified as an Eocene (c. 37 Ma) meteorite impact basin in the Canadian Shield near Sudbury, Ontario, Canada. The area was glaciated many times during the Pleistocene and the basin lies immediately north of the prominent Cartier Moraine built during the last glaciation by the retreating Laurentide Ice Sheet some 11,000 years ago. Study of the deeper geophysics of the basin using magnetic and gravity techniques, and confirmation of its origin, is hampered by lack of data regarding water depths, the form of the bedrock surface and the thickness and character of glacial and postglacial sediment. To this end, more than 300 km of high-resolution single channel seismic chirp and 200 kHz bathymetric data were collected from the basin in the summer of 2002. Water depths reach a maximum of 118 m and acoustic basement is defined by a glacially scoured bedrock surface. The overlying Pleistocene sediment fill exceeds 35 m in thickness and consists of a lowermost late-glacial succession of rhythmically laminated silty clays deposited when the basin was flooded by a deep and regionally extensive ice dammed water body (Glacial Lake Algonquin). Truncation of the upper surface of this succession across large parts of the lake floor records the drainage of Lake Algonquin and the isolation of Wanapitei Lake as a separate water body. Overlying Holocene sediment is up to 10 m thick but is markedly discontinuous and commonly occurs as mounded ‘drifts’ reflecting strong bottom currents and low inputs of modern sediment. The presence of apparently undisturbed Precambrian bedrock below large portions of the lake basin places significant constraints on the dimensions of any meteorite impact structure.

  3. 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. PMID:17741703

  4. 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.

  5. 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.

  6. Shock-Impact Melt Evidence and Possible Aqueous Alteration in Cali (H/L) Meteorite

    NASA Astrophysics Data System (ADS)

    Martínez-Jiménez, M.; Trigo-Rodríguez, J. M.; Brearley, A. J.

    2016-08-01

    We have described a thin section of the Cali meteorite (H/L4) in order to gain additional insights into the nature of the H/L chondrite parent body and a possible relation with the Tieschitz meteorite.

  7. 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

  8. The resonant orbit of the Lost City meteorite

    NASA Technical Reports Server (NTRS)

    Williams, J. G.

    1975-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Kyte, Frank T.

    2002-01-01

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

  10. Health impacts of large dams

    SciTech Connect

    Lerer, L.B.; Scudder, T.

    1999-03-01

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

  11. 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.

  12. 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.

  13. 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.

  14. 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

    2016-01-01

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

  15. 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

  16. Short and Long Term Effects of Meteoritic Impacts on the Evolution of Venus and Its Surface Conditions.

    NASA Astrophysics Data System (ADS)

    Gillmann, C.; Golabek, G.; Tackley, P. J.

    2014-12-01

    The influence of impacts on the history of terrestrial planets from the point of view of both internal dynamics and surface conditions is investigated in this study. We make use of our previous work on Venus' long term evolution through a coupled atmosphere/mantle numerical code. The solid part of the planet is simulated by the StagYY code (Armann and Tackley, 2012) and releases volatiles into the atmosphere through degassing. Coupling with the atmosphere is obtained by using surface temperature as a boundary condition. The evolution of surface temperature is calculated from CO2and water concentrations in the atmosphere with a gray radiative-convective atmospheric model. These concentrations vary due to degassing and escape mechanisms. We take into account hydrodynamic escape, which is dominant during the first hundred million years, and non-thermal processes as observed by the ASPERA instrument and modeled in various works. Impacts can have different effects: they can (i) bring volatiles to the planet, (ii) erode its atmosphere and (iii) modify mantle dynamics due to the large amount of energy they release. A 2D distribution of the thermal anomaly due to the impact is used leading to melting and subjected to transport by the mantle convection. Volatile evolution is still strongly debated. We therefore test a wide range of impactor parameters (size, velocity, timing) and different assumptions related to impact erosion, from large eroding power to more moderate ones (Shuvalov, 2010). Atmospheric erosion appears to have significant effects only for giant impacts and to be mitigated by volatiles brought by the impactor. While small (0-10 km) meteorites have a negligible effect on the global scale, medium ones (50-150 km) are able to bring volatiles to the planet and generate melt, leading to strong short term influence. However, only larger impacts (300+ km) have lasting effects. These can cause volcanic events both immediately after the impact and later on

  17. 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

    2014-01-01

    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

  18. 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

  19. 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

    2014-01-01

    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.

  20. 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.

  1. 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.

  2. 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

  3. The 45th Annual Meteoritical Society Meeting

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

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

  4. 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.

  5. 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

  6. 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

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

    PubMed

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

    2012-07-24

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

  8. Fracture Characterization of Meteorites

    NASA Astrophysics Data System (ADS)

    Bryson, K. L.; Agrawal, P.; Ostrowski, D. R.; Sears, D. W. G.

    2015-07-01

    NASA ARC has been tasked with understanding the behavior of ~100m asteroids entering the atmosphere and quantifying the impact hazard. As part of this task, we report the initial results of a survey of the fracture properties of meteorites.

  9. 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.

  10. 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

  11. Impact melts in the MAC88105 lunar meteorite - Inferences for the lunar magma ocean hypothesis and the diversity of basaltic impact melts

    NASA Technical Reports Server (NTRS)

    Taylor, G. J.

    1991-01-01

    The MAC88105 lunar meteorite, as represented by thin section 78, contains three major types of impact melt breccias. The most abundant type is clast-laden, fine-grained, and rich in Al2O3 (28 wt pct); these clasts constitute most of the meteorite. Their abundance and aluminous nature indicate that the MAC88105 source area was very aluminous. This is consistent with formation of the primordial lunar crust from a global magma ocean. The second type of impact melt is represented by only one clast in 78. It has a basaltic bulk composition similar to many other lunar impact melts, but is significantly richer in P2O5 than most and has a much lower MgO/(MgO + FeO). The third impact-melt type resembles a prominent melt group at Apollo 16, but has lower MgO/(MgO + FeO). These data show that basaltic impact melts are compositionally diverse. Dating samples of the Al-rich impact melts and the new types of basaltic impact melts from this meteorite can test the idea that the Moon suffered a terminal cataclysm 3.9 Ga ago.

  12. 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.

  13. 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. PMID:24037616

  14. 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

  15. 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.

  16. Impact melts in the MAC88105 lunar meteorite: Inferences for the lunar magma ocean hypothesis and the diversity of basaltic impact melts

    SciTech Connect

    Taylor, G.J. )

    1991-11-01

    The MAC88105 lunar meteorite, as represented by thin section 78, contains three major types of impact melt breccias. The most abundant type is clast-laden, fine grained, and rich in Al{sub 2}O{sub 3} (28 wt%); these clasts constitute most of the meteorite. Their abundance and aluminous nature indicate that the MAC88105 source area was very aluminous. This is consistent with formation of the primordial lunar crust from a global magma ocean. The second type of impact melt is represented by only one clast in 78. It has a basaltic bulk composition similar to many other lunar impact melts, but is significantly richer in P{sub 2}O{sub 5} than most and has a much lower MgO/(MgO + FeO). These data show that basaltic impact melts are compositionally diverse. Dating samples of the Al-rich impact melts and the new types of basaltic impact melts from this meteorite can test that idea that the Moon suffered a terminal cataclysm 3.9 Ga ago.

  17. 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

  18. 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.

  19. 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

  20. 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.

  1. 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.

  2. Iron and Stony-iron Meteorites

    NASA Astrophysics Data System (ADS)

    Haack, H.; McCoy, T. J.

    2003-12-01

    (Scott and Wasson, 1975). Within individual groups, the abundance of meteorites in each compositional range is also in good agreement with the expectations based on numerical models ( Scott and Wasson, 1975).For some asteroids, near-catastrophic impacts played an important role in their early geological evolution. Impact events ranging from local melting of the target area to complete disruption of the parent body are recorded in most groups of meteorites (Keil et al., 1994). Major impacts in the early solar system caused remixing of metal and silicate and large-scale redistribution of cold and hot material in the interior of some of the parent bodies. These processes had profound consequences for the geochemical and thermal evolution of the surviving material. Later impacts on the meteorite parent bodies dispersed fragments in the solar system, some of which have fallen on the Earth in the form of meteorites. These fragments provide us with an opportunity to study the geological evolution of a complete suite of rocks from differentiated asteroids in the laboratory.

  3. 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.

  4. 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.

  5. Meteorite impact craters and possibly impact-related structures in Estonia

    NASA Astrophysics Data System (ADS)

    Plado, Jüri

    2012-10-01

    Three structures (Neugrund, Kärdla, and Kaali) of proven impact origin make Estonia the most cratered country in the world by area. In addition, several candidate impact structures exist, waiting for future studies to determine their origin. This article is an overview of these proven and possible impact structures, including some breccia layers. It summarizes the information and descriptions of the morphology; geological characteristics; and mineralogical, chemical, and geophysical data available in the literature. The overview was prepared to make information in many earlier publications in local journals (many of which had been published in Estonian or Russian) accessible to the international community. This review summarizes the facts and observations in a historical fashion, summarizing the current state of knowledge with some additional comments, and providing the references.

  6. 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

  7. Hexagonal diamonds in meteorites: implications.

    PubMed

    Hanneman, R E; Strong, H M; Bundy, F P

    1967-02-24

    A new polymorph of carbon, hexagonal diamond, has been discovered in the Canyon Diablo and Goalpara meteorites. This phase had been synthesized recently under specific high-pressure conditions in the laboratory. Our results: provide strong evidence that diamonds found in these meteorites were produced by intense shock pressures acting on crystalline graphite inclusions present within the meteorite before impact, rather than by disintegration of larger, statically grown diamonds, as some theories propose. PMID:17830485

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. 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.

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

    NASA Astrophysics Data System (ADS)

    Graham, R. A.

    2012-10-01

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

  14. Moderate velocity oblique impact sliding: Production of shocked meteorite textures and palaeomagnetically important metallic spherules in planetary regoliths

    NASA Astrophysics Data System (ADS)

    Potter, David K.; Ahrens, Thomas J.

    2013-04-01

    We detail the production of metallic spherules in laboratory oblique shock impact experiments, and their applicability (1) to textures in a partly shock-melted chondritic meteorite and (2) to the occurrence of palaeomagnetically important fine iron or iron alloy particles in the lunar regolith. Samples recovered from 29-44 GPa, 800 ns, experiments revealed melting and textures reminiscent of metallic spherules in the Yanzhuang H-chondrite, including "dumbbell" forms and other more complex morphologies. Our experiments demonstrate that metallic spherules can be produced via oblique impact sliding at lower velocities (1.85 km s-1) than are generally assumed in previous work associated with bulk-shock melting, and that oblique impact sliding is a viable mechanism for producing spherules in shock-induced veins in moderately shocked meteorites. Significantly, our experiments also produced fine metallic (iron alloy) spherules within the theoretical narrow size range (a few tens of nanometers for slightly ellipsoidal particles) for stable single-domain (SSD) particles, which are the most important palaeomagnetically, since they can record lunar and planetary magnetic fields over geological time periods. The experiments also produced spherules consistent with superparamagnetic (SP) and multidomain (MD) particle sizes. The fine SSD and SP particles on the lunar surface are currently thought to have been formed predominantly by space weathering processes. Our experiments suggest that oblique shock impact sliding may be a further means of producing the SSD and SP iron or iron alloy particles observed in the lunar regolith, and which are likely to occur in the regoliths of Mercury and other planetary bodies.

  15. Iron Meteorite

    NASA Astrophysics Data System (ADS)

    Murdin, P.

    2000-11-01

    A meteorite composed mainly of nickel-iron, with traces of other metals; also referred to simply as an iron, and formerly known as a siderite. Irons account for over 6% of all known meteorite specimens. They are the easiest type to identify, being heavy, magnetic and rust-colored; their metallic sheen tarnishes quickly on the Earth's surface, but otherwise irons show better resistance to weatheri...

  16. 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

  17. 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

  18. 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

  19. 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.

  20. 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.

  1. 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.

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

    NASA Astrophysics Data System (ADS)

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

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  4. 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.

  5. 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.

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

    PubMed Central

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

    2013-01-01

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

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

    PubMed

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

    2013-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

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

  9. 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).

  10. 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.

  11. 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

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  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. 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.

  16. Microfossils in carbonaceous meteorites

    NASA Astrophysics Data System (ADS)

    Hoover, Richard B.

    2009-08-01

    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 bio-contaminants.

  17. The Structure of Arizaro, Salta, Argentina: A New Simple Type Meteorite Impact Site?

    NASA Astrophysics Data System (ADS)

    Acevedo, R. D.; Rocca, M.; Alonso, R.; Rabassa, J.; Ponce, J. F.; Klajnik, K.

    2012-09-01

    A possible new impact crater had been found in Puna, Argentina: the structure of Arizaro (24º 55" 45.30” S, 67º 27" 09.64” W), located at 3,650 m.a.s.l. This structure is probably a new young simple-type impact crater on Tertiary-Quaternary sedimentary deposits.

  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. Crystal-bearing lunar spherules: Impact-melting of the Moon's crust and implications for the origin of meteoritic chondrules

    NASA Astrophysics Data System (ADS)

    Ruzicka, Alex; Snyder, Gregory A.; Taylor, Lawrence A.

    2000-01-01

    Crystal-bearing lunar spherules (CLSs) in lunar breccia (14313, 14315, 14318), soil (68001, 24105), and impact-melt-rock (62295) samples can be classified into two types: feldspathic and olivine-rich. Feldspathic CLSs contain equant, tabular, or acicular plagioclase grains set in glass or a pyroxene-olivine mesostasis; the less common olivine-rich CLSs contain euhedral or skeletal olivine set in glass, or possess a barred-olivine texture. Bulk-chemical and mineral-chemical data strongly suggest that feldspathic CLSs formed by impact-melting of mixtures of ferroan anorthosite and Mg-suite rocks that compose the feldspathic crust of the Moon. It is probable that olivine-rich CLSs also formed by impact-melting, but some appear to have been derived from distinctively magnesian lunar materials, atypical of the Moon's crust. Some CLSs contain reversely-zoned "relict" plagioclase grains that were not entirely melted during CLS formation, thin (?5 ?m thick) rims of troilite or phosphate, and chemical gradients in glassy mesostases attributed to metasomatism in a volatile-rich (Na-K-P-rich) environment. CLSs were rimmed and metasomatized prior to brecciation. Compound CLS objects are also present; these formed by low-velocity collisions in an environment, probably an ejecta plume, that contained numerous melt droplets. Factors other than composition were responsible for producing the crystallinity of the CLSs. We agree with previous workers that relatively slow cooling rates and long ballistic travel times were critical features that enabled these impact-melt droplets to partially or completely crystallize in free-flight. Moreover, incomplete melting of precursor materials formed nucleation sites that aided subsequent crystallization. Clearly, CLSs do not resemble meteoritic chondrules in all ways. The two types of objects had different precursors and did not experience identical rimming processes, and vapor-fractionation appears to have played a less important role in

  20. IMPACT! The Making of a Meteorite - New Visualizations for Museums and Classrooms

    NASA Astrophysics Data System (ADS)

    Stewart, S. T.; Griswold, A.; Sacco, J. C.; Leinhardt, Z. M.

    2006-03-01

    We present a new 7-minute DVD video providing a self-contained explanation of the "lifetime" of a meteor, which is part of a larger E/PO educational package on scientifically accurate visualizations of impact processes.

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

    NASA Astrophysics Data System (ADS)

    Kumar, P. Senthil

    2005-12-01

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

  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. 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

  4. Unique local structures of Ca, Ti, Fe and Zr in natural glasses formed by meteorite impact

    NASA Astrophysics Data System (ADS)

    Yoshiasa, Akira; Tobase, Tsubasa; Okube, Maki; Wang, Ling; Isobe, Hiroshi; Mashimo, Tsutomu; Graduate School of Science; Technology Collaboration; Materials; Structures Laboratory, Tokyo Institute of Technology Collaboration

    2015-06-01

    The local structures of cation in tektite from six strewn fields, impact-related glass, and non-impact-related glass were studied by Ca, Ti, Fe and Zr K-edge X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). Shock compression also causes local structural changes of gest and minor elements as well as transition of host structures. How to be left a record is peculiar by each element. The XAFS measurements were performed at the beam lines BL-NW10A and BL-9C, KEK, Japan. The comparison of XANES spectra and bonding distances between crystalline reference minerals and natural glasses was done. Based on the different valence states of iron, the degrees of oxidation states were estimated. The local structures of Ca, Ti and Zr ions are useful probe for physical conditions and formation process of glasses. Tektites experienced high quenching rates and a reduced atmospheric environment when they were ejected into outer space. Other impact-related glass, which was remained close to the crater, experienced a more complicated environment. The local structural changes of cation in the impact-related glass are rich in a variety. Analysis of local structure is help to compare their formation process and distinguish them.

  5. The Structure at Sierra Ambato, Catamarca, Argentina: A New Meteorite Impact Site?

    NASA Astrophysics Data System (ADS)

    Acevedo, R. D.; Rocca, M.; Alonso, R.; Rabassa, J.; Ponce, J. F.

    2012-09-01

    A new possible impact crater was discovered in Catamarca Province: the structure at Sierra Ambato (28º 03" 23.22” S, 66º 03" 11.06” W), located at Sierras Pampeanas (3,500 m.a.s.l). It has 1.0 km in diameter.

  6. Na-Fe-Phosphate Globules in Impact Metal-Troilite Associations of Chelyabinsk Meteorite

    NASA Astrophysics Data System (ADS)

    Sharygin, V. V.; Karmanov, N. S.; Podgornykh, N. M.

    2016-08-01

    Multi- and monophase phosphate globules have been found in the impact metal-troilite aggregates of the Chelyabinsk chondrite. Their phase composition varies and they contain galileiite, sarcopside, graftonite and Na-Fe-phosphate Na2(Fe,Mn)5(PO4)4.

  7. 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

  8. Cobbles and Meteorites at Meridiani Planum, Mars.

    NASA Astrophysics Data System (ADS)

    Fleischer, Iris; Klingelhöfer, Göstar; Schroeder, Christian; Ashley, James

    The Mars Exploration Rover Opportunity landed on the plains of Meridiani Planum in January 2004 and has since covered a distance of more than 19 kilometers. The Meridiani plains are covered with basaltic sand, with frequent exposures of sulfate rich outcrop rock and a lag de-posit of hematite-rich spherules [1, 2]. Occasionally, Opportunity also encountered loose rocks scattered across the surface. To date, about a dozen of these "cobbles" with dimensions of a few centimeters have been analysed with Opportunity's contact instruments, providing information about elemental chemistry (Alpha Particle X-ray spectrometer, APXS), iron mineralogy and oxidation states (Müssbauer spectrometer, MB) and texture (Microscopic Imager, MI). Based on their chemistry and mineralogy, cobbles can be divided into three distinct groups. The first group comprises light toned fragments of the sulfate-rich bedrock, which are chemically and mineralogically indistinguishable from other outcrop rock. Among the remaining, dark-toned cobbles, two separate groups can be distinguished, referred to as "Barberton group", have high Ni and contain Fe-Ni metal phases and troilite, pointing to a meteoritic origin. They are prob-ably paired and may be mesosiderite fragments [3, 4]. "Arkansas group" cobbles appear to be related to soil and to Meridiani outcrop. They have brecciated textures, possibly pointing to an impact-related origin during which local bedrock and soil may have been mixed [5]. The groups were named after the first specimen of each group encountered by Opportunity. In addition, Opportunity encountered four iron meteorites. The first , "Heat Shield Rock", was encountered in January 2005 and officially recognized as the first iron meteorite on the martian surface with the name "Meridiani Planum" after the location of its find [3, 6, 7]. Three other iron meteorites were encountered between July and October 2009, separated by 10 km from Heat Shield Rock but less than 1 km from each other

  9. Amino acid survival in large cometary impacts

    NASA Astrophysics Data System (ADS)

    Pierazzo, E.; Chyba, C. F.

    1999-11-01

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

  10. Meteorite regolithic breccias

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

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

  11. 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.

  12. Mineralogical Study of Reddish Olivine in Dhofar 307 Lunar Meteorite: Comparison with Brown Olivine in Martian Meteorites

    NASA Astrophysics Data System (ADS)

    Takenouchi, A.; Mikouchi, T.

    2016-08-01

    We compared reddish olivine in Dhofar 307 lunar meteorite to brown olivine in martian meteorites and indicate a possibility of its shock origin. This result suggests that olivine darkening may have widely occurred on the surface of large bodies.

  13. 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.

  14. 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.

  15. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2011-04-01

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

  17. Terrestrial Ages of Antarctic Meteorites- Update 1999

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

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

  18. 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

  19. 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.

  20. Rediscovery of Polish meteorites

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

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

  1. 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.

  2. 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.

  3. 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.

  4. 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 ...

  5. 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.

  6. 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

  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. 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.

  9. 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.

  10. Silicon Isotopic Composition in Large Meteoritic SiC Particles and 22Na Origin of 22Ne.

    PubMed

    Brown, L E; Clayton, D D

    1992-11-01

    Large silicon carbide (SiC) particles extracted from acid-insoluble residues of carbonaceous chondrites are isotopically anomalous in both silicon and carbon and contain isotopically extreme noble gases. These particles are thought to have originated in mass outflows from red giant stars and to have existed in the interstellar medium at the time the solar system formed from an interstellar cloud. Calculations show that the silicon isotope correlations in those large SiC particles can be generated only in the most massive carbon stars. Consequently, the almost pure neon-22 ((22)Ne) in those particles must be interpreted as the condensation of radioactive sodium-22 ((22)Na) in the particles as they flowed away from the stars. The (22)Na is produced through proton capture by (21)Ne at the base of the surface convection zone. Neon-22 does not exist abundantly in helium shells hot enough to burn magnesium, which is necessary to establish the measured silicon isotopic composition.

  11. 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.

  12. 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

  13. Chondrules in apollo 14 samples: implications for the origin of chondritic meteorites.

    PubMed

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

    1972-01-01

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

  14. 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.

  15. 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

  16. 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

    2016-01-01

    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

  17. 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.

  18. 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.

  19. Microfossils in CI and CO Carbonaceous Meteorites

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

  20. An Adulterated Martian Meteorite

    NASA Astrophysics Data System (ADS)

    Taylor, G. J.

    1999-07-01

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

  1. The Kosice meteorite

    NASA Astrophysics Data System (ADS)

    Toth, J.; Svoren, J.

    2012-01-01

    The glare of the bolide on the night of February 28, 2010, illuminated streets and interiors of apartments at some location in eastern Slovakia and northern Hungary. In addition, cannon-like bursts or series of low frequency blasts were heard. Due to bad weather, cloudy skies, and scattered showers, the Central European Fireball Network (operated by Dr. Pavel Spurny of the Czech Academy of Sciences) did not take direct optical records of the bolide and the Slovak Video Meteor Network (operated by the first author) was not operational that night. So, at first sight, it seemed that there were no scientific records of this event. Fortunately, fast photoelectric sensors on seven automated fireball stations in the Czech Republic (6) and Austria (1) detected the illumination of the sky caused by the bolide, which made it possible to determine exact time and duration of the bolide and estimate its brightness. The bolide reached its maximum brightness of at least magnitude -18 in one huge flare. Later on, several surveillance camera data were published showing the moment when the night turned into day for a second, but only two videos from Hungary (Orkeny village, Fazzi Daniella and Vass Gabor; Telki village, contact persons Sarneczky Krisztian, and Kiss Laszlo) actually captured the fireball itself. Thanks to calibration of videos by several members of the Hungarian Astronomical Association (MCSE, http://www.mcse.hu) contributing (in particular, Antal Igaz) and a trajectory analysis by Dr. Jiri Borovicka of the Czech Academy of Sciences gave the hope that significant numbers of meteorite fragments reached the surface. He also calculated the impact area, near the town of Kosice in eastern Slovakia. The data from the Local Seismic Network of Eastern Slovakia (project led by Professor Moczo of Comenius University) confirmed the atmospheric trajectory as well. The expedition consisting of scientists and graduate students of the Astronomical Institute of the Slovak Academy of

  2. Ungrouped iron meteorites in Antarctica - Origin of anomalously high abundance

    NASA Technical Reports Server (NTRS)

    Wasson, John T.

    1990-01-01

    Eighty-five percent of the iron meteorites collected outside Antarctica are assigned to 13 compositionally and structurally defined groups; the remaining 15 percent are ungrouped. Of the 31 iron meteorites recovered from Antarctica, 39 percent are ungrouped. This major difference in the two sets is almost certainly not a stochastic variation, a latitudinal effect, or an effect associated with differences in terrestrial ages. It seems to be related to the median mass of Antarctic irons, which is about 1/100 that of non-Antarctic irons. During impacts on asteroids, smaller fragments tend to be ejected into space at higher velocities than larger fragments, and, on average, small meteoroids have undergone more changes in orbital velocity than large ones. As a result, the set of asteroids that contributes small meteoroids to earth-crossing orbits is larger than the set that contributes large meteoroids. Most small iron meteorites may escape from the asteroid belt as a result of impact-induced changes in velocity that reduce their perihelia to values less than the aphelion of Mars.

  3. Antarctic Meteorite Newsletter

    NASA Technical Reports Server (NTRS)

    Lindstrom, Marilyn

    2000-01-01

    This newsletter contains something for everyone! It lists classifications of about 440 meteorites mostly from the 1997 and 1998 ANSMET (Antarctic Search for Meteorites) seasons. It also gives descriptions of about 45 meteorites 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).

  4. Fluorine in meteorites

    NASA Technical Reports Server (NTRS)

    Allen, R. O., Jr.; Clark, P. J.

    1977-01-01

    Microanalysis using a resonant nuclear reaction was used to measure F concentrations in USGS standard rocks and 21 meteorites. 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 meteoritic 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 meteorites suggest plagioclase as a F containing phase.

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

    USGS Publications Warehouse

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

    2011-01-01

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

  6. Antarctic Meteorite Newsletter, Volume 29, Number 1

    NASA Technical Reports Server (NTRS)

    Satterwhite, Cecilia (Editor); Righter, Kevin (Editor)

    2006-01-01

    This newsletter contains classifications for 597 new meteorites from the 2003 and 2004 ANtarctic Search for METeorites (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 meteorites: 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 impact 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 meteorite 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.

  7. Solution of the α-potential mystery in the γ process and its impact on the Nd/Sm ratio in meteorites.

    PubMed

    Rauscher, Thomas

    2013-08-01

    The 146Sm/144Sm ratio in the early solar system has been constrained by Nd/Sm isotope ratios in meteoritic material. Predictions of 146Sm and 144Sm production in the γ process in massive stars are at odds with these constraints, and this is partly due to deficiencies in the prediction of the reaction rates involved. The production ratio depends almost exclusively on the (γ,n)/(γ,α) branching at 148Gd. A measurement of 144Sm(α,γ)148Gd at low energy had discovered considerable discrepancies between cross-section predictions and the data. Although this reaction cross section mainly depends on the optical α+nucleus potential, no global optical potential has yet been found that can consistently describe the results of this and similar α-induced reactions at the low energies encountered in astrophysical environments. The untypically large deviation in 144Sm(α,γ) and the unusual energy dependence can be explained, however, by low-energy Coulomb excitation, which is competing with compound nucleus formation at very low energies. Considering this additional reaction channel, the cross sections can be described with the usual optical potential variations, compatible with findings for (n, α) reactions in this mass range. Low-energy (α, γ) and (α, n) data on other nuclei can also be consistently explained in this way. Since Coulomb excitation does not affect α emission, the 148Gd(γ,α) rate is much higher than previously assumed. This leads to very small 146Sm/144Sm stellar production ratios, in even more pronounced conflict with the meteorite data. PMID:23971552

  8. Comet and meteorite traditions of Aboriginal Australians

    NASA Astrophysics Data System (ADS)

    Hamacher, Duane W.

    2014-06-01

    This research contributes to the disciplines of cultural astronomy (the academic study of how past and present cultures understand and utilise celestial objects and phenomena) and geomythology (the study of geological events and the formation of geological features described in oral traditions). Of the hundreds of distinct Aboriginal cultures of Australia, many have oral traditions rich in descriptions and explanations of comets, meteors, meteorites, airbursts, impact events, and impact craters. These views generally attribute these phenomena to spirits, death, and bad omens. There are also many traditions that describe the formation of meteorite craters as well as impact events that are not known to Western science.

  9. Antarctic Meteorite Newsletter, Volume 11, Number 2, August 1988

    NASA Technical Reports Server (NTRS)

    1988-01-01

    Presented are classifications and descriptions of a large number of meteorites which include the last samples from the 1984 collection and the first samples from the 1987 collection. There is a particularly good selection of meteorites 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 large mesosiderites. The carbonaceous chondrites include good suites of C2 and C4 meteorites, and 2 highly equilibrated carbonaceous chondrites tentatively identified as C5 and C6 meteorites. Also included are surveys of numerous meteorites for Al-26 and thermoluminescence. These studies provide information on the thermal and radiation histories of the meteorites and can be used as measures of their terrestrial ages.

  10. Harvesting meteorites in the Omani desert: implications for astrobiology

    NASA Astrophysics Data System (ADS)

    Hofmann, Beda A.; Gnos, Edwin; Al-Kathriri, Ali

    2004-03-01

    Meteorites will remain the most accessible, most diverse and most abundant source of extraterrestrial materials for many years to come. New sources of large numbers of meteorites allow the recovery of rare types particularly relevant for astrobiology, including Martian and Lunar samples. Oman has become an important source of meteorites only since 1999. Conditions for search and recovery are particularly favourable in many areas here because of an abundance of flat, light-colored, sand- and vegetation-free surfaces. During search expeditions carried out in the central deserts of Oman in 2001-2003 large numbers of meteorites, including a Martian and a Lunar sample, were recovered. The mass of recovered meteorites is 1334 kg, corresponding to approximately 150 to 200 fall events. We aim to classify all recovered specimens and study pairing and weathering effects. Our expeditions demonstrate the possibility to recover meteorite samples with astrobiological relevance with modest investments of finances and manpower.

  11. The Mazapil meteorite: From paradigm to periphery

    NASA Astrophysics Data System (ADS)

    Beech, Martin

    2002-05-01

    The remarkable fact about the Mazapil meteorite is that it fell on the same night, in 1885, that the Andromedid meteor shower underwent a spectacular outburst. The simultaneity of these two events has driven speculation ever since. From circa 1886 to circa 1950 the circumstances of the Mazapil fall were taken, by a number of researchers, as the paradigm that demonstrated the fact that comets were actually swarms of meteoritic boulders. Beginning circa 1950, however, most researchers began to adopted the stance that the timing of the Mazapil fall was nothing more than pure coincidence. The reason behind this change in interpretation stemmed from, amongst other factors, the fact that none of the prominent annual meteor showers could be clearly shown to deliver meteorites. Also, with the introduction of the icy-conglomerate model for cometary nuclei, by F. Whipple in the early 1950s, it became increasingly clear that only exceptional circumstances would allow for the presence of large meteoritic bodies in cometary streams. Further, by the mid 1960s it had been shown that meteorites could, in fact, be delivered to the Earth from the main belt asteroid region via gravitational resonances. With the removal of the dynamical 'barrier' against the delivery of meteorites from the asteroid region, the idea that the Mazapil meteorite could have been part of the Andromedid stream fell into complete disfavor. This being said, we nonetheless present the results of a study concerning the possible properties of the parent object to the Mazapil meteorite based upon the assumption that it was a member of the Andromedid stream. This study is presented to illustrate the point that while cometary showers do not yield meteorites on the ground, this does not, in fact, substantiate the argument that no meteoritic bodies reside in cometary streams. Indeed, we find no good reason to suppose that an object with the characteristics of the Mazapil meteorite could not have been delivered from

  12. Magnetism in meteorites

    NASA Technical Reports Server (NTRS)

    Herndon, J. M.; Rowe, M. W.

    1974-01-01

    An overview is presented of magnetism in meteorites. A glossary of magnetism terminology followed by discussion of the various techniques used for magnetism studies in meteorites are included. The generalized results from use of these techniques by workers in the field are described. A brief critical analysis is offered.

  13. Vigie-Ciel : a french citizen network to study meteors and meteorites

    NASA Astrophysics Data System (ADS)

    Bouley, S.; Zanda, B.; Colas, F.; Vaubaillon, J.; Marmo, C.; Vernazza, P.; Gattacceca, J.

    2013-12-01

    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 meteorite classes, (ii) collect both fresh and rare meteorite 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 meteorite recovery. We propose to install a network of 100 digital cameras covering the entire French territory to compute impact 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 meteorites. Our project is original in several ways. (i) It is inter-disciplinary, involving experts in meteoritics, 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 large 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 meteorite falls, thus boosting the interest in meteorite and asteroid related science.

  14. Organic compounds in meteorites

    NASA Technical Reports Server (NTRS)

    Anders, E.; Hayatsu, R.; Studier, M. H.

    1973-01-01

    The problem of whether organic compounds originated in meteorites as a primary condensate from a solar gas or whether they were introduced as a secondary product into the meteorite 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 meteorite. 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 meteorites. Organic compounds in meteorites 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.

  15. The Old Woman, California, IIAB iron meteorite

    NASA Astrophysics Data System (ADS)

    Plotkin, Howard; Clarke, Roy S.; McCoy, Timothy J.; Corrigan, Catherine M.

    2012-05-01

    The Old Woman meteorite, 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 meteorite hunters and collectors. The question of the ownership of the 2753 kg group IIAB meteorite, 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 meteorite 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 large 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 meteorite litigation served as an important test case for the ownership and control of meteorites found on federal lands. The Old Woman meteorite 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 meteorite may have transformed via different mechanisms upon subsolidus cooling, making the large slices of Old Woman promising targets for future research.

  16. Weathering and precipitation after meteorite impact of Ni, Cr, Fe, Ca and Mn in K-T boundary clays from Stevns Klint

    NASA Astrophysics Data System (ADS)

    Miyano, Yumiko; Yoshiasa, Akira; Tobase, Tsubasa; Isobe, Hiroshi; Hongu, Hidetomo; Okube, Maki; Nakatsuka, Akihiko; Sugiyama, Kazumasa

    2016-05-01

    Ni, Cr, Fe, Ca and Mn K-edge XANES and EXAFS spectra were measured on K-T boundary clays from Stevns Klint in Denmark. According to XANES spectra and EXAFS analyses, the local structures of Ni, Cr and Fe in K-T boundary clays is similar to Ni(OH)2, Cr2O3 and FeOOH, respectively. It is assumed that the Ni, Cr and Fe elements in impact related glasses is changing into stable hydrate and oxide by the weathering and diagenesis at the surface of the Earth. Ca in K-T boundary clays maintains the diopside-like structure. Local structure of Ca in K-T clays seems to keep information on the condition at meteorite impact. Mn has a local structure like MnCO3 with divalent state. It is assumed that the origin on low abundant of Mn in the Fe-group element in K-T clays was the consumption by life activity and the diffusion to other parts.

  17. Meteoritic event recorded in Antarctic ice

    SciTech Connect

    Harvey, R.P.; Dunbar, N.W.; McIntosh, W.C.; Esser, R.P.; Nishiizumi, Kuni; Taylor, S.; Caffee, M.W.

    1998-07-01

    During systematic sampling of volcanic ash (tephra) layers at a well-known Antarctic meteorite 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 large 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 impact events is not clear.

  18. Lunar Meteorite Queen Alexandra Range 93069 and the Iron Concentration of the Lunar Highlands Surface

    NASA Technical Reports Server (NTRS)

    Korotev, Randy L.; Jolliff, Bradley L.; Rockow, Kaylynn M.

    1996-01-01

    Lunar meteorite 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 meteorites 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 large, impact-melted, partially devitrified clast of magnesian, anorthositic-norite composition. The enrichment in Fe, Sc, and Cr and lower Mg/Fe ratio of lunar meteorites Yamato 791197 and Yamato 82192/3 compared to other feldspathic lunar meteorites 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 meteorites (mean: approx. 5.0%; range: 4.3-6.1 %) and a recent estimate based on data from the Clementine mission (3.6%).

  19. Meteorite Sterlitamak -- A New Crater Forming Fall

    NASA Astrophysics Data System (ADS)

    Petaev, M. I.

    1992-07-01

    The Sterlitamak meteorite 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 impact, 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 large 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 meteorite fragments, from several grams to several hundred grams in weight, were recovered in the crater vicinity. A search for other meteorite 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

  20. Very high-K KREEP-rich clasts in the impact melt breccia of the lunar meteorite SaU 169: New constraints on the last residue of the Lunar Magma Ocean

    NASA Astrophysics Data System (ADS)

    Lin, Y.; Shen, W.; Liu, Y.; Xu, L.; Hofmann, B. A.; Mao, Q.; Tang, G. Q.; Wu, F.; Li, X. H.

    2012-05-01

    In the impact melt breccia (IMB) of Sayh al Uhaymir (SaU) 169, the most KREEP-rich lunar meteorite to date (Gnos et al., 2004), clasts of a new type of lithologies were discovered, consisting of Ca-poor and Ca-rich pyroxenes (60.8 vol.%), Ba-rich K-feldspar (27.9 vol.%), phosphates (5.6 vol.%), Nb-rich ilmenite (4.0 vol.%), zircon (1.2 vol.%) and minor sulfide (0.6 vol.%). These mafic lithic clasts are more enriched in KREEP component (˜1500 × CI) than the host meteorite and are highly enriched in potassium. They are referred to as very high-K (VHK) KREEP lithology, and probably most close to the last residual liquid of the Lunar Magma Ocean without significant dilution by other Mg-rich magmas. The fine-grained matrix of the SaU 169 IMB has very similar mineral chemistry to the VHK KREEP lithology, but contains abundant plagioclase with trace K-feldspar. The matrix shows decoupling of K from the REEP-like component; however, it cannot be simply interpreted by mixing the VHK KREEP lithology with anorthosites, which should have diluted the REEP-like component with the same proportion. SIMS Pb-Pb dating was conducted on zircons in various petrographic settings and with different crystal habits. All analyses show a main age peak at 3921 ± 3 Ma and a smaller one at 4016 ± 6 Ma. The main age peak is identical to the previous Pb-Pb age by Gnos et al. (2006) and U-Pb age by Liu et al. (2009), dating the catastrophic shock event contributed to the formation of SaU 169 IMB. The older ages are consistent with the previous report of an older bulk U-Pb age by Kramers et al. (2007), suggestive of presence of relict crystals in a few large zircon grains. The VHK KREEP clasts predated the fine-grained matrix, but have the same zircon Pb-Pb ages as the latter within the analytical uncertainties. Plagioclase was converted to maskelynite whereas zircon was shocked to diaplectic glass, probably by a second event at ˜2.8 Ga. However, the identical zircon Pb-Pb ages of the

  1. An abiotic origin for hydrocarbons in the Allan Hills 84001 martian meteorite through cooling of magmatic and impact-generated gases

    NASA Technical Reports Server (NTRS)

    Shock, E. L.

    2000-01-01

    Thermodynamic calculations of metastable equilibria were used to evaluate the potential for abiotic synthesis of aliphatic and polycyclic aromatic hydrocarbons (PAHs) in the martian meteorite 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 impact-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 impact 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 impact 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 impact gases could have led to magnetite-catalyzed hydrocarbon synthesis.

  2. Numerous Unpaired Meteorites Exposed on a Deflating Playa Lake at Lucerne Valley, California

    NASA Technical Reports Server (NTRS)

    Rubin, Alan E.; Verish, Robert S.; Moore, Carleton B.; Oriti, Ronald A.

    2000-01-01

    Out of 16 well-characterized 1 to 37 g meteorite specimens recovered from Lucerne Dry Lake (an approximately 3 7 km playa in the southern Mojave Desert of California), there are 9 separate ordinary chondrite finds. The ratio of independent meteorites to total number of specimens (0.6) is among the highest in the world. This is due to lack of initial deep burial of the small meteorites, significant deflation of the lake exposing falls of individual stones (or small numbers of paired meteorites), and the absence of a large meteorite shower in the region. Playas appear to be excellent candidates for high-yield meteorite-collecting areas.

  3. The natural thermoluminescence of meteorites: III. Lunar and basaltic meteorites

    SciTech Connect

    Sears, D.W.G.; Benoit, P.H.; Sears, H.; Batchelor, J.D.; Symes, S. )

    1991-11-01

    Natural thermoluminescence (TL) data have been obtained for the lunar meteorite MacAlpine Hills 88104/5 and for 65 eucrites, howardites, diogenites, and mesosiderites in order to investigate their recent thermal and radiation histories. All these meteorites have low levels of natural TL compared to chondrites, which is primarily because they display anomalous fading (i.e., fading by non-classical mechanisms). However, some have especially low natural TL (<5 krad at 250C in the glow curve) which cannot be attributed to anomalous fading or thermal fading over especially large terrestrial ages, and which must reflect heating within the last 10{sup 5}-10{sup 6} y. The fraction of basaltic meteorites thought to have had small perihelia (about 20%) is comparable to the fraction of chondrites with low natural TL and to the fraction of observed falls and fireballs with small perihelia. This may imply ejection from the asteroid belt via similar mechanisms. Assuming plausible values for cosmic ray dose rate, and that the natural TL of MAC88104/5 was totally drained by ejection form the moon, the parameters for TL decay determined in the present study suggest that the Moon-Earth transit times for MAC88104 and MAC88105, were 2,00 and 1.800 y, respectively, compared with 19,000 and 2,500 y for Y791197 and ALHA81005 were ejected from the moon by the same event should be considered, since diverse rock types are found in close proximity on the lunar surface. The natural TL data confirm most previous published pairings among basaltic meteorites and suggest others.

  4. The mineralogy of meteorites.

    NASA Technical Reports Server (NTRS)

    Mason, B.

    1972-01-01

    Of particular interest among minerals recently discovered in meteorites 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 meteorite, a type III carbonaceous chondrite which fell in 1969; and several alkali-rich silicates found as inclusions in iron meteorites. Knowledge of the compositional range of the common minerals olivine, pyroxene, and plagioclase has also been greatly increased by recent researches.

  5. Radiocarbon datings of Yamato meteorites

    NASA Technical Reports Server (NTRS)

    Kigoshi, K.; Matsuda, E.

    1986-01-01

    The terrestrial ages of five Yamato Meteorites were measured by the content of cosmic-ray-produced carbon-14. Three Yamato Meteorites 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 meteorites being a single meteorite. Also presented is a method adopted in the experimental procedure which includes a check for modern carbon contamination in the meteorites.

  6. A IAB-Complex Iron Meteorite Containing Low-Ca Clinopyroxene: Northwest Africa 468 and its Relationship to Iodranites and Formation by Impact Melting

    NASA Technical Reports Server (NTRS)

    Rubin, Alan E.; Kallemeyn, Gregory W.; Wasson, John T.

    2002-01-01

    Northwest Africa 468 (NWA 468) is a new ungrouped, silicate-rich member of the IAB complex of nonmagmatic iron meteorites. 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 impact 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 impact-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 impact melting of metal-rich carbonaceous-chondrite precursors) but with less separation of metal-rich melts from silicates.

  7. Siderophile elements in brecciated HED meteorites and the nature of projectile materials in HED meteorites

    NASA Astrophysics Data System (ADS)

    Shirai, N.; Okamoto, C.; Yamaguchi, A.; Ebihara, M.

    2016-03-01

    Petrological, mineralogical and geochemical studies were performed on five brecciated HED meteorites (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 meteorites 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 impact 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 meteorites are inconsistent with each other, implying that the impactor components of each HED meteorites are different from each other. The various PGE ratios are consistent with those for metals from chondrites and iron meteorites, and carbonaceous chondrites. This study provides the evidence that IAB and IVA iron meteorites, 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 meteorites during heavy bombardment. The HED meteorites in this study and metals from mesosiderite have different Pd/Ir ratios, probably implying that HED meteorites and mesosiderites formed either at distinct settings on one common parent body or on similar parent bodies.

  8. Minerals of a soil developed in the meteoritic crater of Carancas, Peru, and evidences of phase changes on the impact event

    NASA Astrophysics Data System (ADS)

    Loayza, María L. Cerón; Cabrejos, Jorge A. Bravo

    2013-04-01

    We report studies about the phase transformations in the soil of the Carancas meteoritic 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 impact; 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.

  9. Minerals of a soil developed in the meteoritic crater of Carancas, Peru, and evidences of phase changes on the impact event

    NASA Astrophysics Data System (ADS)

    Loayza, María L. Cerón; Cabrejos, Jorge A. Bravo

    2014-01-01

    We report studies about the phase transformations in the soil of the Carancas meteoritic 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 impact; 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.

  10. Asteroid-Meteorite Links: The Vesta Conundrum(s)

    NASA Technical Reports Server (NTRS)

    Pieters, C. M.; Binzel, R.; Bogard, D.; Hiroi, T.; Mittlefehldt, D. W.; Nyquist, L.; Rivkin, A.; Takeda, H.

    2006-01-01

    Although a direct link between the HED meteorites 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 meteorites requires more than one basaltic parent body, consistent with the abundance of differentiated parent bodies implied by iron meteorites. The timing of the formation of the Vestoids (and presumably the large crater at the south pole of Vesta) is unresolved. Peaks in Ar-Ar dates of eucrites suggest this impact 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.

  11. Chelyabinsk meteorite explains unusual spectral properties of Baptistina Asteroid Family

    NASA Astrophysics Data System (ADS)

    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

    2014-07-01

    melts are rare in meteorites is that high impact 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 impacts: 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 impacts within the main belt are at ∼5 km/s (Bottke, W.F., Nolan, M.C., Greenberg, R., Kolvoord, R.A. [1994]. Collisional lifetimes and impact 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 impact melt unless they are highly porous. However, shock darkening is an equally efficient process that takes place at much lower impact velocities (∼2 km/s) and can cause the observed spectral effects. Spectral effects of shock darkening and impact 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 impact event generated enough impact melt or shock blackening to alter the spectral properties of BAF, but keep the BAF composition largely unchanged. Collisional mixing of shock blackened/impact 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 impact 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).

  12. Mass extinctions caused by large bolide impacts

    SciTech Connect

    Alvarez, L.W.

    1987-07-01

    Evidence indicates that the collision of Earth and a large 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.

  13. Mass extinctions caused by large bolide impacts.

    PubMed

    Alvarez, L W

    1987-07-01

    Evidence indicates that the collisions of Earth and a large piece of Solar System debris 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.

  14. Luminescence dating of the Wabar meteorite craters, Saudi Arabia

    USGS Publications Warehouse

    Prescott, J.R.; Robertson, G.B.; Shoemaker, C.; Shoemaker, E.M.; Wynn, J.

    2004-01-01

    Luminescence dating has been used to find the age of meteorite impact 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 meteorite, 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 impact as young as this has implications for the assessment of hazards from the impact on Earth of small meteorites.

  15. Antimony in iron meteorites

    NASA Technical Reports Server (NTRS)

    Willis, J.

    1981-01-01

    Sb concentrations determined by radiochemical neutron activation analysis in 60 iron meteorites range from 0.2 ng/g to 36 microg/g. The meteorites with the highest Sb concentrations are those of the nonmagmatic groups IAB and IIICD, while meteorites with the lowest Sb concentrations are found in groups IVA and IVB. In all groups Sb is positively correlated with Ni; slopes on log Sb vs log Ni plots decrease with increasing Ni. This decrease may reflect an increasing tendency to avoid schreibersite during the analysis of high-Ni meteorites because Sb partitions strongly into schreibersite. It is found that schreibersite from New Westville is enriched in Cr, Ni, Ge, As, Sb, and Au and depleted in Fe, Co, Ir; the Sb content in schreibersite is 540 times higher than the bulk metal value.

  16. Concentrating Antarctic Meteorites on Blue ice Fields: The Frontier Mountain Meteorite Trap

    NASA Technical Reports Server (NTRS)

    Sandford, Scott A.; DeVincenzi, D. (Technical Monitor)

    2002-01-01

    The collection of meteorites in Antarctica has greatly stimulated advancement in the field of meteoritics by providing the community with significant numbers of rare and unique meteorites types and by yielding large numbers of meteorites that sample older infall epochs (Grady et al., 1998). The majority of Antarctic meteorites 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 meteorites 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 meteorite flux from the Antarctic record (Zolensky, 1998). The terrestrial ages of Antarctic meteorites 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 meteorite 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.

  17. Reconstruction of the Morasko Meteorite Impact: From Atmospheric Entry to Individual Crater Formation - Insight from Numerical Modeling

    NASA Astrophysics Data System (ADS)

    Bronikowska, M.; Artemieva, N. A.; Wünnemann, K.; Szczuciński, W.

    2016-08-01

    Here we present modeling results of the atmospheric break-up of the meteoroid, the distribution of fragments and the formation of craters during the Morasko event. Our goal is to reconstruct the most probable impact scenario.

  18. The Vredefort Pseudotachylytes: A Centennial Reappraisal of S. J. Shand (1916). Shaken, not Stirred by Meteorite Impacting

    NASA Astrophysics Data System (ADS)

    Garde, A. A.; Klausen, M. B.

    2016-08-01

    The famous pseudotachylytes in theVredefort Dome were formed by impact-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.

  19. Meteorite Seymchan structure

    NASA Astrophysics Data System (ADS)

    Hontsova, S. S.; Petrova, E. V.; Muftahetdinova, R. F.; Chulanova, V. N.; Grokhovsky, V. I.

    2016-09-01

    The meteorite Seymchan specimen was studied using optical microscopy and scanning electron microscopy. Olivine grains have roundish shapes, which was formed during matter cooling. Different features of the metal structure such as plessite structure and Neimann bands were observed. The oxide edges were observed in the boundaries between phases. The oxides were formed in the terrestrial conditions. The boundary regions between metal and olivine in the meteorite contain grains of troilite, schreibersite, and chromite.

  20. Mass extinction caused by large bolide impacts

    NASA Technical Reports Server (NTRS)

    Alvarez, Luis W.

    1987-01-01

    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 impact 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.

  1. Chromium isotopic anomalies in the Allende meteorite

    NASA Technical Reports Server (NTRS)

    Papanastassiou, D. A.

    1986-01-01

    Abundances of the chromium isotopes in terrestrial and bulk meteorite samples are identical to 0.01 percent. However, Ca-Al-rich inclusions from the Allende meteorite show endemic isotopic anomalies in chromium which require at least three nucleosynthetic components. Large anomalies at Cr-54 in a special class of inclusions are correlated with large 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.

  2. The preservation of fossil biomarkers during meteorite impact events: Experimental evidence from biomarker-rich projectiles and target rocks

    NASA Astrophysics Data System (ADS)

    Parnell, John; Bowden, Stephen; Lindgren, Paula; Burchell, Mark; Milner, Daniel; Price, Mark; Baldwin, Emily C.; Crawford, Ian A.

    2010-08-01

    A Devonian siltstone from Orkney, Scotland, shows survival of biomarkers in high-velocity impact experiments. The biomarkers were detected in ejecta fragments from experiments involving normal incidence of steel projectiles at 5-6kms-1, and in projectile fragments from impact experiments into sand and water at 2-5kms-1. The associated peak shock pressures were calculated to be in the range of 110-147GPa for impacts of the steel projectiles into the siltstone target, and hydrocode simulations are used to show the variation of peak pressure with depth in the target and throughout the finite volume projectiles. Thermally sensitive biomarker ratios, including ratios of hopanoids and steranes, and the methylphenanthrene ratio, showed an increase in thermal maturity in the ejecta, and especially the projectile, fragments. Measurement of absolute concentrations of selected biomarkers indicates that changes in biomarker ratios reflect synthesis of new material rather than selective destruction. Their presence in ejecta and projectile fragments suggests that fossil biomarkers may survive hypervelocity impacts, and that experiments using biomarker-rich rock have high potential for testing survival of organic matter in a range of impact scenarios.

  3. Combining meteorites and missions to explore Mars.

    PubMed

    McCoy, Timothy J; Corrigan, Catherine M; Herd, Christopher D K

    2011-11-29

    Laboratory studies of meteorites 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 meteorite. Since then, the study of martian meteorites and findings from missions have been linked. Although the meteorite source locations are unknown, impact ejection modeling and spectral mapping of Mars suggest derivation from small craters in terrains of Amazonian to Hesperian age. Whereas most martian meteorites 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 meteorites conflicts with results from recent Mars missions, calling into doubt whether the igneous histor y inferred from the meteorites 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.

  4. Combining meteorites and missions to explore Mars.

    PubMed

    McCoy, Timothy J; Corrigan, Catherine M; Herd, Christopher D K

    2011-11-29

    Laboratory studies of meteorites 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 meteorite. Since then, the study of martian meteorites and findings from missions have been linked. Although the meteorite source locations are unknown, impact ejection modeling and spectral mapping of Mars suggest derivation from small craters in terrains of Amazonian to Hesperian age. Whereas most martian meteorites 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 meteorites conflicts with results from recent Mars missions, calling into doubt whether the igneous histor y inferred from the meteorites 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

  5. Combining meteorites and missions to explore Mars

    PubMed Central

    McCoy, Timothy J.; Corrigan, Catherine M.; Herd, Christopher D. K.

    2011-01-01

    Laboratory studies of meteorites 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 meteorite. Since then, the study of martian meteorites and findings from missions have been linked. Although the meteorite source locations are unknown, impact ejection modeling and spectral mapping of Mars suggest derivation from small craters in terrains of Amazonian to Hesperian age. Whereas most martian meteorites 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 meteorites conflicts with results from recent Mars missions, calling into doubt whether the igneous histor y inferred from the meteorites 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

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

    USGS Publications Warehouse

    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.

    2011-01-01

    Six large iron meteorites have been discovered in the Meridiani Planum region of Mars by the Mars Exploration Rover Opportunity in a nearly 25km-long traverse. Herein, we review and synthesize the available data to propose that the discovery and characteristics of the six meteorites could be explained as the result of their impact into a soft and wet surface, sometime during the Noachian or the Hesperian, subsequently to be exposed at the Martian surface through differential erosion. As recorded by its sediments and chemical deposits, Meridiani has been interpreted to have undergone a watery past, including a shallow sea, a playa, an environment of fluctuating ground water, and/or an icy landscape. Meteorites could have been encased upon impact and/or subsequently buried, and kept underground for a long time, shielded from the atmosphere. The meteorites apparently underwent significant chemical weathering due to aqueous alteration, as indicated by cavernous features that suggest differential acidic corrosion removing less resistant material and softer inclusions. During the Amazonian, the almost complete disappearance of surface water and desiccation of the landscape, followed by induration of the sediments and subsequent differential erosion and degradation of Meridiani sediments, including at least 10-80m of deflation in the last 3-3.5Gy, would have exposed the buried meteorites. We conclude that the iron meteorites support the hypothesis that Mars once had a denser atmosphere and considerable amounts of water and/or water ice at and/or near the surface. ?? The Meteoritical Society, 2011.

  7. The multiple meteorite fall of Neuschwanstein: Circumstances of the event and meteorite search campaigns

    NASA Astrophysics Data System (ADS)

    Oberst, J.; Heinlein, D.; Köhler, U.; Spurný, P.

    2004-10-01

    A large meteorite fall in southern Germany on April 6, 2002 was captured by camera stations of the European Fireball Network (EN), which routinely monitors the night sky over central Europe. From analysis of the images, a prediction on the geographic location of the meteorite strewn field could be made. Following systematic ground searches in difficult high-mountain terrain, three fragments of a rare EL6 enstatite chondrite were recovered during search campaigns in the summers of 2002 and 2003. "Neuschwanstein" is the fourth meteorite fall in history that has been photographed by fireball networks and the fragments of which have been found subsequently. It is the first time since the beginning of the EN operation in the early sixties that the photographic observations have made a meteorite recovery possible.

  8. Meteorite Shower in Park Forest, Illinois

    NASA Astrophysics Data System (ADS)

    Martel, L. M. V.

    2004-08-01

    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 meteorite 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 meteorite 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 meteorite 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 meteorite as an L5 chondrite, one of the most primitive groups of known meteorites. 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 large preatmospheric mass. They estimate the meteoroid was at least 900 kilograms and possibly as large as 7000 kilograms before it broke apart in the atmosphere, of which only about 30 kilograms of fragments have been recovered.

  9. Considerations of large scale impact and the early Earth

    NASA Technical Reports Server (NTRS)

    Grieve, R. A. F.; Parmentier, E. M.

    1985-01-01

    Bodies which have preserved portions of their earliest crust indicate that large scale impact cratering was an important process in early surface and upper crustal evolution. Large impact basins form the basic topographic, tectonic, and stratigraphic framework of the Moon and impact was responsible for the characteristics of the second order gravity field and upper crustal seismic properties. The Earth's crustal evolution during the first 800 my of its history is conjectural. The lack of a very early crust may indicate that thermal and mechanical instabilities resulting from intense mantle convection and/or bombardment inhibited crustal preservation. Whatever the case, the potential effects of large scale impact have to be considered in models of early Earth evolution. Preliminary models of the evolution of a large terrestrial impact basin was derived and discussed in detail.

  10. Organic Molecules in Meteorites

    NASA Astrophysics Data System (ADS)

    Martins, Zita

    2015-08-01

    Carbonaceous meteorites are primitive samples from the asteroid belt, containing 3-5wt% organic carbon. The exogenous delivery of organic matter by carbonaceous meteorites may have contributed to the organic inventory of the early Earth. The majority (>70%) of the meteoritic organic material consist of insoluble organic matter (IOM) [1]. The remaining meteoritic organic material (<30%) consists of a rich organic inventory of soluble organic compounds, including key compounds important in terrestrial biochemistry [2-4]. Different carbonaceous meteorites contain soluble organic molecules with different abundances and distributions, which may reflect the extension of aqueous alteration or thermal metamorphism on the meteorite parent bodies. Extensive aqueous alteration on the meteorite 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 meteorites may also have a contribution from Fischer-Tropsch/Haber-Bosch type gas-grain reactions after the meteorite parent body cooled to lower temperatures [13, 14].The analysis of the abundances and distribution of the organic molecules present in meteorites 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

  11. Large impacts in the Baltic shield with special attention to the Uppland structure

    NASA Technical Reports Server (NTRS)

    Henkel, H.; Lilljequist, R.

    1992-01-01

    Within the Baltic Shield several very large structures have been identified and are suspected to be of meteorite impact origin. Some of these deeply eroded circular features are presented with special attention to the Uppland structure, where several indications point toward an impact 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 large 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. Impact-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

  12. Discovery of Possible Meteoritic Matter on Shatter Cones — 2. Clearwater East Impact Structure, Québec, Canada

    NASA Astrophysics Data System (ADS)

    Buchner, E.; Schmieder, M.

    2016-08-01

    In the frame of the “Shatter Cone Coatings Project,” we investigated shatter cones from the Clearwater East impact structure that contain several Fe-Ni-Co metal and metal oxide particles (kamacite and taenite) and a sulfide particle (troilite?).

  13. What we have learned about Mars from SNC meteorites

    NASA Technical Reports Server (NTRS)

    Mcsween, Harry Y., Jr.

    1994-01-01

    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 meteorites suggest that they, rather than scapolite or hydrous carbonates, are the major crustal sink for CO2. Weathering products in SNC meteorites 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 meteorites, although Xe and Kr isotopes suggest different origins for the atmosphere. Planetary ejection of these rocks has promoted an advance in the understanding of impact physics, which has been accomplished by a model involving spallation during large cratering events. Ejection of all the SNC meteorites (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 impact.

  14. Meteorites: messengers from the early solar system.

    PubMed

    Hofmann, Beda A

    2010-01-01

    Meteorites are fragments from solar system bodies, dominantly asteroids. A small fraction is derived from the Moon and from Mars. These rocks tell a rich history of the early solar system and range from solids little changed since the earliest phases of solid matter condensation in the solar nebula (chondrites) to material representing asteroidal metamorphism and melting, impact processes on the Moon and even aqueous alteration near the surface of Mars. Meteorites are very rare. Currently many meteorites result from searches in Antarctica and the hot deserts of North Africa and Arabia. The present high find rate likely represents a unique short-term event, asking for a careful management of this scarce scientific resource.

  15. Meteorites: messengers from the early solar system.

    PubMed

    Hofmann, Beda A

    2010-01-01

    Meteorites are fragments from solar system bodies, dominantly asteroids. A small fraction is derived from the Moon and from Mars. These rocks tell a rich history of the early solar system and range from solids little changed since the earliest phases of solid matter condensation in the solar nebula (chondrites) to material representing asteroidal metamorphism and melting, impact processes on the Moon and even aqueous alteration near the surface of Mars. Meteorites are very rare. Currently many meteorites result from searches in Antarctica and the hot deserts of North Africa and Arabia. The present high find rate likely represents a unique short-term event, asking for a careful management of this scarce scientific resource. PMID:21138163

  16. The Galim LL/EH Polymict Breccia: Evidence for Impact-Induced Exchange Between Reduced and Oxidized Meteoritic Material

    NASA Technical Reports Server (NTRS)

    Rubin, Alan E.

    1997-01-01

    Galim is a polymict breccia consisting of a heavily shocked (shock stage S6) LL6 chondrite, Galim (a), and an impact-melted EH chondrite, Galim (b). Relict chondrules in Galim (b) served as nucleation sites for euhedral enstatite grains crystallizing from the impact 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 impact-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 impact of another projectile at significantly higher relative velocities.

  17. Meteoritics and cosmology among the Aboriginal cultures of Central Australia

    NASA Astrophysics Data System (ADS)

    Hamacher, Duane W.

    2011-03-01

    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, meteorites, and impact craters. This paper discusses the role of meteoritic 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, meteorites and impact structures suggests the Arrernte and Luritja understood that they are directly related.

  18. A potential hidden layer of meteorites below the ice surface of Antarctica

    PubMed Central

    Evatt, G. W.; Coughlan, M. J.; Joy, K. H.; Smedley, A. R. D.; Connolly, P. J.; Abrahams, I. D.

    2016-01-01

    Antarctica contains some of the most productive regions on Earth for collecting meteorites. These small areas of glacial ice are known as meteorite stranding zones, where upward-flowing ice combines with high ablation rates to concentrate large numbers of englacially transported meteorites onto their surface. However, meteorite collection data shows that iron and stony-iron meteorites 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 meteorites 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 meteorites with a high-enough thermal conductivity (for example, iron meteorites) 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

  19. A potential hidden layer of meteorites below the ice surface of Antarctica.

    PubMed

    Evatt, G W; Coughlan, M J; Joy, K H; Smedley, A R D; Connolly, P J; Abrahams, I D

    2016-01-01

    Antarctica contains some of the most productive regions on Earth for collecting meteorites. These small areas of glacial ice are known as meteorite stranding zones, where upward-flowing ice combines with high ablation rates to concentrate large numbers of englacially transported meteorites onto their surface. However, meteorite collection data shows that iron and stony-iron meteorites 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 meteorites 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 meteorites with a high-enough thermal conductivity (for example, iron meteorites) 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

  20. Thermoluminescence and Antarctic meteorites

    NASA Technical Reports Server (NTRS)

    Sears, D. W. G.; Hasan, F. A.

    1986-01-01

    The level of natural thermoluminescence (TL) in meteorites is the result of competition between build-up, due to exposure to cosmic radiation, and thermal decay. Antarctic meteorites tend to have lower natural TL than non-Antarctic meteorites 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 meteorites. 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 meteorites 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.

  1. Meteorite fusion crust variability.

    NASA Astrophysics Data System (ADS)

    Thaisen, Kevin G.; Taylor, Lawrence A.

    2009-06-01

    Two assumptions commonly employed in meteorite interpretation are that fusion crust compositions represent the bulk-rock chemistry of the interior meteorite and that the vesicles within the fusion crust result from the release of implanted solar wind volatiles. Electron microprobe analyses of thin sections from lunar meteorite Miller Range (MIL) 05035 and eucrite Bates Nunataks (BTN) 00300 were performed to determine if the chemical compositions of the fusion crust varied and/or represented the published bulk rock composition. It was determined that fusion crust compositions are significantly influenced by the incorporation of fragments from the substrate, and by the composition and grain size of those minerals. Because of compositional heterogeneities throughout the meteorite, one cannot assume that fusion crust composition represents the bulk rock composition. If the compositional variability within the fusion crust and mineralogical differences among thin sections goes unnoticed, then the perceived composition and petrogenetic models of formation will be incorrect. The formation of vesicles within these fusion crusts were also compared to current theories attributing vesicles to a solar wind origin. Previous work from the STONE-5 experiment, where terrestrial rocks were exposed on the exterior of a spacecraft heatshield, produced a vesicular fusion crust without prolonged exposure to solar wind suggesting that the high temperatures experienced by a meteorite during passage through the Earth's atmosphere are sufficient to cause boiling of the melt. Therefore, the assumption that all vesicles found within a fusion crust are due to the release of implanted volatiles of solar wind may not be justified.

  2. The Meteoritical Bulletin, No. 101

    NASA Astrophysics Data System (ADS)

    Ruzicka, Alex; Grossman, Jeffrey; Bouvier, Audrey; Herd, Christopher D. K.; Agee, Carl B.

    2015-09-01

    Meteoritical Bulletin 101 contains 2639 meteorites accepted by the Nomenclature Committee in 2012, including 1 fall (Battle Mountain), with 2308 ordinary chondrites, 156 carbonaceous chondrites, 63 HED achondrites, 17 relict meteorites, 16 Rumuruti chondrites, 15 enstatite chondrites, 15 ureilites, 10 iron meteorites, 9 lunar meteorites, 9 primitive achondrites, 8 ungrouped achondrites, 7 mesosiderites, 4 Martian meteorites, 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 meteorites can be obtained from the Meteoritical Bulletin Database (MBD) available on line at http://www.lpi.usra.edu/meteor/.

  3. Antarctic Meteorite Newsletter. Volume 20

    NASA Technical Reports Server (NTRS)

    Lindstrom, Marilyn M.; Satterwhite, Cecilia E.

    1997-01-01

    The availability of 116 new meteorites from the 1994-1996 collections is announced. There are 4 special chondrites, 2 carbonaceous chondrites, and 1 achondrite among the new meteorites. Also included is a redescription of Lodranite GRA95209.

  4. Antarctic Meteorite Newsletter, volume 9, no. 2

    NASA Technical Reports Server (NTRS)

    Gooding, J. L. (Editor)

    1986-01-01

    Preliminary description and classifications of meteorites that were completed since publication of the February issue are contained. Most large (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 meteorite was first examined. Classification is based on microscopic petrography and resonnaissance-level electron-probe microanalysis. The pairing list was updated.

  5. The relict magnetism of meteorites

    NASA Technical Reports Server (NTRS)

    Cisowski, S. M.; Hood, L. L.

    1991-01-01

    Meteorite 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 meteorite classes are explored. A detailed review of paleointensity results derived from the various classes of meteorites is given, and the likelihood that the results might related to solar or nebulawide magnetic fields is considered. The implications of meteorite magnetism for early solar system evolution are discussed.

  6. The r-PROCESS Record in Meteorites

    NASA Astrophysics Data System (ADS)

    Davis, Andrew M.

    2004-09-01

    The r-process record in bulk meteorites and components of primitive meteorites (including refractory inclusions and presolar grains) is reviewed. Small r-process excesses are seen in bulk meteorites and refractory inclusions. Large r-process enhancements have only been observed in presolar diamond. The unique properties and formation conditions of presolar diamond, high purity and high surface-to-volume ratio, may allow it to preserve an r-process signature. It is suggested that the conditions under which r-process matter is ejected from a nascent neutron star dictate that apart from diamonds, strong r-process enhancements are not to be expected in larger presolar grains and other solar system components.

  7. Solar flare irradiation records in Antarctic meteorites

    NASA Technical Reports Server (NTRS)

    Goswami, J. N.

    1981-01-01

    The observation of tracks from solar flare heavy nuclei in Antarctic meteorite 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 large 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 meteorites range from 10,000 to 4,000,000/sq cm, which is within the range observed in non-Antarctic L-group meteorites

  8. Organic Chemistry of Meteorites

    NASA Technical Reports Server (NTRS)

    Chang, S.; Morrison, David (Technical Monitor)

    1994-01-01

    Studies of the molecular structures and C,N,H-isotopic compositions of organic matter in meteorites 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, meteorites 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 meteoritic organic matter from astronomical observations and laboratory investigations will be reviewed and future research directions discussed.

  9. Primordial material in meteorites

    NASA Technical Reports Server (NTRS)

    Kerridge, J. F.

    1986-01-01

    Primordial is a term which applied to material that entered the solar system early and became incorporated into a meteorite without totally losing its identity. Identification of such material surviving in meteorites is so far solely through recognition of anomalous isotopic compositions of generally macroscopic entities contained within those meteorites. Isotopic anomalies are, by definition, isotopic compositions which differ from the canonical solar system abundances in ways which cannot be explained in terms of local processes such as mass dependent fractionation, cosmic ray induced spallation or decay of radionuclides. A comprehensive account of isotopic anomalies is impractical here, so it is necessary to be selective. Issues which are potentially addressable through the study of such primordial material are examined. Those issues will be illustrated with specific, but not exhaustive, examples.

  10. Organics In Meteorites

    NASA Technical Reports Server (NTRS)

    Chang, Sherwood

    1996-01-01

    The variety of classes of organic compounds that occur in carbonaceous meteorites 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 meteorites which show evidence of having been exposed to liquid water; meteorites 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 meteoritic 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 meteoritic 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 meteorite parent bodies to yield the observed compounds.

  11. Meteorites and their parent planets

    NASA Astrophysics Data System (ADS)

    McSween, Harry Y.

    This book explores the origins of meteorites 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 meteorites contain a record of the processes that formed the solar system. How meteorites escape their parent bodies and find their way to earth is explained.

  12. Large-body impact and extinction in the Phanerozoic

    NASA Technical Reports Server (NTRS)

    Raup, D. M.

    1992-01-01

    The kill curve for Phanerozoic marine species is used to investigate large-body impact as a cause of species extinction. Current estimates of Phanerozoic impact rates are combined with the kill curve to produce an impact-kill curve, which predicts extinction levels from crater diameter, on the working assumption that impacts 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 impact-kill curve is credible, thus justifying more thorough testing of the impact-extinction hypothesis. Such testing is possible but requires an exhaustive analysis of radiometric dating of Phanerozoic impact events.

  13. Iron Meteorite on Mars

    NASA Technical Reports Server (NTRS)

    2005-01-01

    NASA's Mars Exploration Rover Opportunity has found an iron meteorite on Mars, the first meteorite 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.

  14. The geologic classification of the meteorites

    USGS Publications Warehouse

    Elston, Donald Parker

    1968-01-01

    aggregates of grains, and as large 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 meteorite breccias, including the calcium-poor and calcium-rich mesosiderites, and irons that contain silicate fragments, is proposed. A fragmentation history of the meteorites is outlined on the basis of evidence in the polymict breccias, and from gas retention ages in stones and exposure ages in irons. Cometal impacts 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 impacts 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

  15. Does the sedimentology of the Chelmsford formation provide evidence for a meteorite impact origin of the Sudbury structure?

    NASA Technical Reports Server (NTRS)

    Long, D. G. F.

    1992-01-01

    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 impact 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.

  16. Large Impact Basin Morphologies on Vesta in Solar System Context

    NASA Astrophysics Data System (ADS)

    Schenk, P.; O'Brien, D. P.; Marchi, S.; Sykes, M. V.; Williams, D. A.; Gaskell, R. W.; Jaumann, R.; McCord, T. B.; Russell, C. T.

    2012-12-01

    Dawn global imaging and topographic mapping (@ 20-70 m scales) reveals that the 505-km-wide impact basin Rheasilvia has a large central complex, steep rim scarp and bowl-shaped floor, elements similar to large impact basins on midsize icy satellites of Saturn. Impact melt and debris volumes are generally lower on Vesta and on icy satellites than on lunar basins. These similarities suggest that the Rheasilvia morphology may be a consequence of large impacts into lower gravity objects. Lower impact velocities and planetary curvature may also be important. Low melt volumes are consistent with predictions based on lower impact velocities on Vesta. Rheasilvia ejecta deposits extend over 100-150 km from the rim, and generally appear to scale similarly on Vesta and the Moon. Rheasiliva ejecta covers at least all of the southern hemisphere and may be more than 5 km thick near the rim. Oddly, the compositional feature associated with Rheasilvia is offset from its center by more than 100 km. A number of pre-Rheasilvia impact basins are mapped, including several large structures near the north pole. Most are degraded and original morphologies may be difficult to determine. Rheasilvia partially obliterated the older 400-km-wide 10-km-deep Veneneia basin, the interior of which is highly disrupted. The next largest basin, ~250-km-across is also old and heavily cratered. If it ever possessed a central peak, it has since been obliterated.

  17. Bulk Compositional Trends in Meteorites: A Guide for Analysis and Interpretation of NEAR XGRS Data from Asteroid 433 Eros

    NASA Technical Reports Server (NTRS)

    Nittler, L. R.; Clark, P. E.; McCoy, T. J.; Murphy, M. E.; Trombka, J. I.

    2000-01-01

    We have compiled a large database of bulk meteorite elemental compositions. We investigate compositional trends in a variety of meteorite classes to aid in interpretation of NEAR XGRS elemental abundance data from the asteroid Eros.

  18. Lunar meteorite LaPaz Icefield 04841: Petrology, texture, and impact-shock effects of a low-Ti mare basalt

    NASA Astrophysics Data System (ADS)

    Hill, E.; Taylor, L. A.; Floss, C.; Liu, Y.

    2009-03-01

    Found during the 2004 U.S. Antarctic Search for Meteorites season, LaPaz Icefield (LAP) 04841 represents an addition to the LaPaz lunar basalts suite and brings the total mass collected to 1.93 kg. The presence of FeNi grains, troilite, and the anorthositic composition of plagioclase are evidence for the lunar origin of this meteorite. Pyroxene and olivine Mn/Fe values plot along the trend set for lunar basalts. Analyses of chromite grains provide a V/(Al + Cr) ratio of 1.33 ± 13, translating to an fO2 one log unit below the IW buffer, in accordance with previous fO2 estimates for lunar basalts. Application of the Zr-cooling speedometer, for ilmenite and ulvöspinel pairs, gives a cooling rate of 5.2 °C/day, matching previous estimates of cooling rates for the LaPaz lunar meteorites and Apollo mare basalts. Mineral modes and chemistries, as well as trace-element patterns, provide compelling evidence for pairing of this meteorite to others in the LaPaz lunar basalt suite.

  19. Meteoritic Amino Acids: Diversity in Compositions Reflects Parent Body Histories

    PubMed Central

    2016-01-01

    The analysis of amino acids in meteorites dates back over 50 years; however, it is only in recent years that research has expanded beyond investigations of a narrow set of meteorite groups (exemplified by the Murchison meteorite) into meteorites 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 meteorites, the enantiomeric distribution of some amino acids, particularly of the nonprotein amino acid isovaline, has also been shown to vary both within certain meteorites and across carbonaceous meteorite groups. Large 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 meteoritic 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

  20. Meteoritic Amino Acids: Diversity in Compositions Reflects Parent Body Histories.

    PubMed

    Elsila, Jamie E; Aponte, José C; Blackmond, Donna G; Burton, Aaron S; Dworkin, Jason P; Glavin, Daniel P

    2016-06-22

    The analysis of amino acids in meteorites dates back over 50 years; however, it is only in recent years that research has expanded beyond investigations of a narrow set of meteorite groups (exemplified by the Murchison meteorite) into meteorites 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 meteorites, the enantiomeric distribution of some amino acids, particularly of the nonprotein amino acid isovaline, has also been shown to vary both within certain meteorites and across carbonaceous meteorite groups. Large 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 meteoritic 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

  1. Meteoritic Amino Acids: Diversity in Compositions Reflects Parent Body Histories.

    PubMed

    Elsila, Jamie E; Aponte, José C; Blackmond, Donna G; Burton, Aaron S; Dworkin, Jason P; Glavin, Daniel P

    2016-06-22

    The analysis of amino acids in meteorites dates back over 50 years; however, it is only in recent years that research has expanded beyond investigations of a narrow set of meteorite groups (exemplified by the Murchison meteorite) into meteorites 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 meteorites, the enantiomeric distribution of some amino acids, particularly of the nonprotein amino acid isovaline, has also been shown to vary both within certain meteorites and across carbonaceous meteorite groups. Large 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 meteoritic 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.

  2. EVIDENCE FOR COMET STORMS IN METEORITE AGES

    SciTech Connect

    Perlmutter, S.; Muller, R.A.

    1987-10-01

    Clustering of cosmic-ray exposure ages of H chondritic meteorites 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, impact craters and glass, and geomagnetic reversals. We suggest that H chondrites were formed by the impact of shower comets on asteroids. The duration of the most recent comet shower was {le} 4 Myr, in agreement with storm theory.

  3. 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.

    1974-01-01

    A number of similarities between lunar and meteoritic rocks are reported and suggest that the comparison is essential for a clear understanding of meteorites 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 meteorites, having resulted from complex and repeated impact processes. (2) Chondrules are present in lunar, as well as in a few achondritic and most chondritic meteorites. 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-impact history of lunar and meteoritic breccias. They vary from little modified (relative to the apparent original texture), to partly or completely melted and recrystallized lithic fragments.

  4. The Germanium Dichotomy in Martian Meteorites

    NASA Technical Reports Server (NTRS)

    Humayun, M.; Yang, S.; Righter, K.; Zanda, B.; Hewins, R. H.

    2016-01-01

    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 meteorites. 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 meteoritic breccia, NWA 7533 (and paired meteorites) contains numerous clasts, some pristine and some impact 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 meteoritic contamination of impact 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.

  5. Microfossils of Cyanobacteria in Carbonaceous Meteorites

    NASA Technical Reports Server (NTRS)

    Hoover, Richard B.

    2007-01-01

    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 large number of different types of meteorites. Large, complex, microfossils with clearly recognizable biological affinities have been found embedded in several carbonaceous meteorites. Similar forms were notably absent in all stony and nickel-iron meteorites 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 meteorites. 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 meteorite filaments typically exhibit dramatic chemical differentiation with distinctive difference between the possible microfossil and the meteorite 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

  6. Enantiomer Ratios of Meteoritic Sugar Derivatives

    NASA Technical Reports Server (NTRS)

    Cooper, George

    2012-01-01

    Carbonaceous meteorites 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 meteorites are keto acids (pyruvic acid, etc.), hydroxy tricarboxylic acids (1), amino acids, amides, purines and pyrimidines. The Murchison and Murray meteorites are the most studied for soluble and insoluble organic compounds and organic carbon phases. The majority of (indigenous) meteoritic 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) meteoritic 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 meteorite 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 large D excess. In several samples of Murchison and one of GRA 95229 (possibly the most pristine carbonaceous meteorite 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 large D excesses. It is worth noting that all four of these acids (all of the possible straight-chained 5C sugar acids) are present in meteorites, including the

  7. Carbon in primitive meteorites

    NASA Technical Reports Server (NTRS)

    Kerridge, John F.

    1990-01-01

    No meteorites are truly primitive, in the sense of being pristine collections of interstellar grains or solar-nebular condensates. Nonetheless, some chrondritic meteorites 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 meteoritic 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 meteorites 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.

  8. Vortex-ring-induced large bubble entrainment during drop impact.

    PubMed

    Thoraval, Marie-Jean; Li, Yangfan; Thoroddsen, Sigurdur T

    2016-03-01

    For a limited set of impact conditions, a drop impacting onto a pool can entrap an air bubble as large as its own size. The subsequent rise and rupture of this large bubble plays an important role in aerosol formation and gas transport at the air-sea interface. The large bubble is formed when the impact crater closes up near the pool surface and is known to occur only for drops that are prolate at impact. 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 large 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 large bubbles. These observations also explain why the strongest and most penetrating vortex rings emerging from drop impacts are not produced by oblate drops but by more prolate drop shapes, as had been observed in previous experiments. PMID:27078468

  9. Vortex-ring-induced large bubble entrainment during drop impact.

    PubMed

    Thoraval, Marie-Jean; Li, Yangfan; Thoroddsen, Sigurdur T

    2016-03-01

    For a limited set of impact conditions, a drop impacting onto a pool can entrap an air bubble as large as its own size. The subsequent rise and rupture of this large bubble plays an important role in aerosol formation and gas transport at the air-sea interface. The large bubble is formed when the impact crater closes up near the pool surface and is known to occur only for drops that are prolate at impact. 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 large 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 large bubbles. These observations also explain why the strongest and most penetrating vortex rings emerging from drop impacts are not produced by oblate drops but by more prolate drop shapes, as had been observed in previous experiments.

  10. Vortex-ring-induced large bubble entrainment during drop impact

    NASA Astrophysics Data System (ADS)

    Thoraval, Marie-Jean; Li, Yangfan; Thoroddsen, Sigurdur T.

    2016-03-01

    For a limited set of impact conditions, a drop impacting onto a pool can entrap an air bubble as large as its own size. The subsequent rise and rupture of this large bubble plays an important role in aerosol formation and gas transport at the air-sea interface. The large bubble is formed when the impact crater closes up near the pool surface and is known to occur only for drops that are prolate at impact. 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 large 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 large bubbles. These observations also explain why the strongest and most penetrating vortex rings emerging from drop impacts are not produced by oblate drops but by more prolate drop shapes, as had been observed in previous experiments.

  11. Origin of igneous meteorites and differentiated asteroids

    NASA Astrophysics Data System (ADS)

    Scott, E.; Goldstein, J.; Asphaug, E.; Bottke, W.; Moskovitz, N.; Keil, K.

    2014-07-01

    Introduction: Igneously formed meteorites and asteroids provide major challenges to our understanding of the formation and evolution of the asteroid belt. The numbers and types of differentiated meteorites and non-chondritic asteroids appear to be incompatible with an origin by fragmentation of numerous Vesta-like bodies by hypervelocity impacts 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 meteorites 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 meteorites 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 meteorites, impact 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 impacts [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. Meteorite evidence for early disruption of differentiated asteroids. If iron meteorites were samples of Fe-Ni cores of bodies that cooled slowly inside silicate mantles over ˜50--100 Myr, irons from each core would have

  12. Mineralogy of Meteorite Groups

    NASA Technical Reports Server (NTRS)

    Rubin, Alan E.

    1997-01-01

    Approximately 275 mineral species have been identified in meteorites, 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 meteorites contain carbides, elemental C, nitrides, phosphates, phosphides, chromite and sulfides. Silicate inclusions in IAB/IIICD and lIE iron meteorites 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 meteorites 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 meteorites comprise mare basalts with major augite and calcic plagioclase and anorthositic breccias with major calcic plagioclase. Several meteoritic

  13. Originof magnetite in martian meteorite ALH84001

    NASA Astrophysics Data System (ADS)

    Scott, E.; Fuller, M.

    2003-04-01

    The magnetization of ALH84001 is predominantly carried by single domain magnetite, which is found in association with carbonate. The magnetite is found in topotactic relationship with the carbonate in regions of iron rich carbonate, whereas in magnesium richer areas periclase is found. The magnetite formed from the carbonate by thermal decomposition of siderite at elevated temperature in a major impact event at about 4.0 Gyr. Chromite is also present in large amounts, but it is predominantly paramagnetic at room temperature with a Neel point close to 100^oK. Carbonate with associated magnetite is also found in the martian meteorite Nakhla. Experiments and theory show that siderite is a major product of percolation and evaporation of brines generated under pressures of more than 0.1bar of carbon dioxide. This is the preferred explanation for the carbonate in nakhla, as well as in ALH84001. Thermal decomposition of siderite may result from deep burial, magmatic heat sources, or as in the case of ALH84001, impact heating.

  14. Antarctic Meteorite Location Map Series

    NASA Technical Reports Server (NTRS)

    Schutt, John (Editor); Fessler, Brian (Editor); Cassidy, William (Editor)

    1989-01-01

    Antarctica has been a prolific source of meteorites since meteorite concentrations were discovered in 1969. The Antarctic Search For Meteorites (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 meteorites at the Allan Hills in Victoria Land. Later reconnaissance in this region resulted in the discovery of meteorite concentrations on icefields to the west of the Allan Hills, at Reckling Moraine, and Elephant Moraine. Antarctic meteorite 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 meteorite location maps for the specimens found by the ANSMET project are being prepared.

  15. The Meteoritical Bulletin, No. 102

    NASA Astrophysics Data System (ADS)

    Ruzicka, Alex; Grossman, Jeffrey; Bouvier, Audrey; Herd, Christopher D. K.; Agee, Carl B.

    2015-09-01

    Meteoritical Bulletin 102 contains 3141 meteorites 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 meteorites, 16 primitive achondrites, 16 Rumuruti chondrites, 15 mesosiderites, 12 iron meteorites, 10 lunar meteorites, 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 meteorites can be obtained from the Meteoritical Bulletin Database (MBD) available on line at http://www.lpi.usra.edu/meteor/.

  16. Huge waves of meteorite origin

    NASA Astrophysics Data System (ADS)

    Pelinovsky, Efim; Kozelkov, Andrey; Kurkin, Andrey

    2016-04-01

    Asteroid and meteorite risk is now actively investigated in various aspects. If the meteorite falls in the ocean it can generate huge waves with heights exceeded 10 m. For whole history about 10-20 events related with entry of meteorite in water are known. The last event occurred on February 15, 2013 when the meteorite exploded in sky of Chelyabinsk (Russia) and its big piece entered in the Chebarkul Lake. Very often, huge waves of meteorite origin are computed using the conception of equivalent (parametrical) source, whose parameters are determined through meteorite characteristics. Recently, direct methods based on numerical simulations of the Reynolds-averaged Navier-Stokes equations (RANS) have been applied to study wave processes generated by the entry of meteorite. These approaches and their applications to the historic events are discussed in paper.

  17. Nuclide production in (very) small meteorites

    NASA Technical Reports Server (NTRS)

    Arnold, J. R.; Nishiizumi, K.

    1986-01-01

    One of the most interesting open questions in the study of cosmic-ray effects in meteorites 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 large objects, and can help us make better models; (2) this size is intermediate between usual meteorites 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 meteorites. 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 meteorite 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 meteorite 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 meteorites.

  18. Comparative zircon U-Pb geochronology of impact melt breccias from Apollo 12 and lunar meteorite SaU 169, and implications for the age of the Imbrium impact

    NASA Astrophysics Data System (ADS)

    Liu, Dunyi; Jolliff, Bradley L.; Zeigler, Ryan A.; Korotev, Randy L.; Wan, Yushan; Xie, Hangqiang; Zhang, Yuhai; Dong, Chunyan; Wang, Wei

    2012-02-01

    The ages of zircons from high-Th impact-melt breccias (IMBs) from meteorite Sayh al Uhaymir (SaU) 169 and from rock fragments in soil samples from Apollo 12 have been determined using the SHRIMP-II ion microprobe. The IMBs are very similar to each other in chemistry, mineralogy and texture, and the zircons from the KREEP-rich (high-Th) crystalline impact melt have similar U and Th contents and identical ages, within uncertainties, of 3920 ± 13 (2σ) Ma (SaU 169) and 3914 ± 7 (2σ) Ma (Apollo 12). The age results support the idea that the high-Th IMBs (Apollo 12 and SaU 169) formed in the same impact event. The similarity of composition and age suggest that SaU 169 and the high-Th IMB fragments of Apollo 12 originated from the same area of the Procellarum KREEP Terrane. We interpret the age of zircon grains in the Apollo 12 high-Th IMB as a precise and direct determination of the age of the Imbrium impact. This age is significantly older than the commonly cited age of 3.85 Ga but is similar to recent determinations from SIMS U-Pb dating of Apollo 14 apatite grains and with anticipated revision of ages by 40Ar-39Ar and 87Rb-86Sr. The present zircon 207Pb-206Pb age is the first direct zircon age determination of the Imbrium impact event from an Apollo sample. Previous measurements of zircon ages of Apollo IMBs have recorded events pre-dating the Imbrium basin-forming event.

  19. Chiral Biomarkers in Meteorites

    NASA Technical Reports Server (NTRS)

    Hoover, Richard B.

    2010-01-01

    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 meteorites, 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 meteorites 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 meteorites 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 meteorite parent body. This paper will consider these chiral biomarkers in view of the detection of possible microfossils found in the Orgueil and Murchison carbonaceous meteorites. Energy dispersive x-ray spectroscopy (EDS) data obtained on these morphological biomarkers will be

  20. The Merna, Nebraska Meteorite Crater

    NASA Astrophysics Data System (ADS)

    Povenmire, H.

    1995-09-01

    This crater-like structure was recognized by geomorphologist, Wakefield Dort in 1992 while examining topographic maps [1]. Using the same tradition as for meteorite discoveries, he named it after the nearest town with a post office, Merna, Nebraska, Zip code, 68856. This researcher has made two extensive field trips to the crater. The f1rst was to examine and confirm its nature and the second to field check the results after a computer simulation of the impacting projectile. This area is characterized by low rolling hills which are under cultivation. This area is unglaciated and the closest recent glacial approach was about 240 km. The prevailing winds are from the northwest and there are many parallel eolian features which have an azimuth of approximately 300 degrees. The predominate erosional factors are snowmelt and the spring rains. Most of the 53 cm annual precipitation occurs from March to May. The soil is predominantly Peoria loess with an estimated depth of approximately 260 m.[2]. This is probably underlaid with limestone bedrock. Well records of the area have not been very helpful in resolving this question. The Merna Crater is an approximately 1.6 km diameter, 23 m deep, well preserved depression with a flat bottom. It is located about 18 km west of and 2.4 km south of Merna, Nebraska. This site is on the U.S.G.S. 7.'5 Callaway N.W., Nebraska 1951 topographic map. The crater covers most of section 9 and the eastern portion of section 8. The coordinates of the crater center are approximately longitude 99 degrees 58' 20"W and latitude 41 degrees 27' 30" N. A significant landmark on section 9 is the Cliff Union Church and Cemetery which is on the eastern rim of the crater. Even though the land has been plowed for more than 150 years, the general topographic features have not been seriously disturbed. It is believed that the crater was caused by an air blast similar to Tunguska but of a much larger magnitude. It is therefore believed that there never was a

  1. Previously Unrecognized Large Lunar Impact Basins Revealed by Topographic Data

    NASA Technical Reports Server (NTRS)

    Frey, Herbert V.

    2008-01-01

    The discovery of a large population of apparently buried impact 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 impact features on the Moon and other bodies in the solar system? Early analysis of Clementine topography revealed several large impact basins not previously known [6,7], so the answer certainly is "Yes." How large a population of previously undetected impact 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 large impact features not previously recognized by photogeologic mapping, as summarized by Wilhelms [lo].

  2. The Chelyabinsk Fireball and Meteorite.

    NASA Astrophysics Data System (ADS)

    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.

    2013-09-01

    On 15th February 2013 an extraordinarily large 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 meteorite 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 meteorite lithologies, geochemical and isotopic analyses, chronological data and fission track information will be available by the time of the conference

  3. Terrestrial microbes in martian and chondritic meteorites

    NASA Astrophysics Data System (ADS)

    Airieau, S.; Piceno, Y.; Andersen, G.

    2007-08-01

    Good extraterrestrial analogs for microbiology are SNC meteorites as Mars analogs, and chondrites as early planet analogs. Chondrites and SNCs are used to trace processes in the early solar system and on Mars. Yet, questions about terrestrial contamination and its effects on the isotopic, chemical and mineral characteristics often arise. A wide biodiversity was found in 21 chondrites of groups CR, CV, CK, CO from ANSMET, CI and CM Falls, and 8 SNCs. Studies documented the alteration of meteorites by weathering and biology [1]-[6], and during aqueous extraction for oxygen isotopic analysis [7], visible biofilms grew in the meteorite solutions in days. To assess biological isotopic and chemical impacts, cultures were incubated 11 months and analyzed by PCR. The sequences for 2 isolates from EET 87770 and Leoville were of a good quality with long sequence reads. In EET 87770, the closest matches were in the genus Microbacterium. Soil and plant isolates were close relatives by sequence comparison. Bacillus, a common soil bacterial genus, grew in a Leoville culture. All SNCs exhibited biological activity measured independently by LAL but only 1 colony was successfully cultured from grains of the SNC Los Angeles. Isotopic analyses of samples with various amounts of microbial contamination could help quantified isotopic impact of microbes on protoplanetary chemistry in these rocks. References: [1] Gounelle, M.& Zolensky M. (2001) LPS XXXII, Abstract #999. [2] Fries, M. et al. (2005) Meteoritical Society Meeting 68, Abstract # 5201. [3] Burckle, L. H. & Delaney, J. S (1999) Meteoritics & Planet. Sci., 32, 475. [4] Whitby, C. et al. (2000) LPS XXXI, Abstract #1732. [5] Tyra M. et al., (2007) Geochim. Cosmochim. Acta, 71, 782 [6] Toporski, J. & Steele A., (2007) Astrobiology, 7, 389 [7]Airieau, S. et al (2005) Geochim. Cosmochim. Acta, 69, 4166.

  4. Hydrocarbon components in carbonaceous meteorites

    NASA Astrophysics Data System (ADS)

    Kissin, Y. V.

    2003-05-01

    Currently, the presence of free n-alkanes and isoprenoid alkanes in carbonaceous meteorites is usually explained either by microbial contamination during the period between the meteorite fall and collection or by contamination from the environment of analytical laboratories and museums. The goal of this research was to repeat analysis of hydrocarbon components in meteorites and to investigate possible meteorite contamination routes discussed in the literature. Experimental analysis of free organic constituents in five carbonaceous meteorites by infrared spectroscopy (IR) and gas chromatographic (GC) methods confirmed the presence of extractable aliphatic components, n-alkanes in the C 15H 32-C 27H 56 range and isoprenoid alkanes (phytane, pristane, and norpristane), in some of these meteorites. The contents of these compounds vary depending on the source. Insoluble organic components of two meteorites (meteorite kerogens) were isolated, and their composition was analyzed by IR and cracking/GC methods. Comparison with the data on several terrestrial contamination sources proposed in the literature shows that the presence of free saturated hydrocarbons in meteorites and the composition of the meteorite kerogen could not be explained either by microbial contamination or by contamination from the laboratory environment. The types of the hydrocarbons in meteorites resemble those typical of ancient terrestrial deposits of organic-rich sediments, except for the absence of lighter hydrocarbons, which apparently slowly evaporated in space, and multi-ring naphthenic compounds of the biologic origin, steranes, terpanes, etc. The prevailing current explanation for the presence of free linear saturated hydrocarbons in carbonaceous meteorites, apart from contamination, is the abiotic route from hydrogen and carbon monoxide. However, the data on the structure of meteorite kerogens require a search for different routes that initially produce complex polymeric structures containing

  5. How Venus surface conditions evolution can be affected by large impacts at long timescales?

    NASA Astrophysics Data System (ADS)

    Gillmann, Cedric; Golabek, Gregor; Tackley, Paul

    2016-04-01

    Using numerical simulations, we investigate how the evolution of Venus' atmosphere and mantle is modified by large impacts, 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. Large impacts 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 impact erosion (Shuvalov, 2010). For energy transfer, 2D distribution of the thermal anomaly created by the impact is used, leading to melting and subjected to transport by the mantle convection. Small (0-50 km) meteorites have a negligible effect on the global scale: they only affect the impact point and do not have lasting consequences on surface conditions. Medium ones (50-150 km) have strong short term influence through volatile

  6. Mineralogy, petrology, and distribution of meteorites at the Whitecourt crater, Alberta, Canada

    NASA Astrophysics Data System (ADS)

    Newman, Jennifer D.; Herd, Christopher D. K.

    2015-02-01

    The Whitecourt meteorite impact crater, Alberta, Canada is a rare example of a well-preserved small impact structure, with which thousands of meteorite fragments are associated. As such, this crater represents a unique opportunity to investigate the effect of a low-energy impact event on an impacting iron bolide. Excellent documentation of meteorite fragment locations and characteristics has generated a detailed distribution map of both shrapnel and regmaglypted meteorite types. The meteorites' distribution, and internal and external characteristics support a low-altitude breakup of the impactor which caused atmospherically ablated (regmaglypted) meteorites to fall close to the crater and avoid impact-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. Meteorite 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 meteorites. Considerations of the total mass of meteoritic 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.

  7. [Impacts of large hydropower station on benthic algal communities].

    PubMed

    Jia, Xing-Huan; Jiang, Wan-Xiang; Li, Feng-Qing; Tang, Tao; Duan, Shu-Gui; Cai, Qing-Hua

    2009-07-01

    To investigate the impacts of large hydropower station in Gufu River on benthic algae, monthly samplings were conducted from September 2004 to June 2007 at the site GF04 which was impacted 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 impacts of irregular draw-off by large hydropower station on river eco-system.

  8. Impact resistant boron/aluminum composites for large fan blades

    NASA Technical Reports Server (NTRS)

    Oller, T. L.; Salemme, C. T.; Bowden, J. H.; Doble, G. S.; Melnyk, P.

    1977-01-01

    Blade-like specimens were subjected to static ballistic impact testing to determine their relative FOD impact resistance levels. It was determined that a plus or minus 15 deg layup exhibited good impact resistance. The design of a large solid boron/aluminum fan blade was conducted based on the FOD test results. The CF6 fan blade was used as a baseline for these design studies. The solid boron/aluminum fan blade design was used to fabricate two blades. This effort enabled the assessment of the scale up of existing blade manufacturing details for the fabrication of a large B/Al fan blade. Existing CF6 fan blade tooling was modified for use in fabricating these blades.

  9. The Thermal and Radiation Exposure History of Lunar Meteorites

    NASA Technical Reports Server (NTRS)

    Benoit, Paul H.; Sears, Derek W. G.; Symes, Steven J. K.

    1996-01-01

    We have measured the natural and induced thermoluminescence (TL) of seven lunar meteorites in order to examine their crystallization, irradiation, and recent thermal histories. Lunar meteorites 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 impact/regolith processing among the highland-dominated meteorites. The basaltic breccia QUE 94281 is dominated by mare component but may also contain a significant highland component. For the mare-dominated meteorites, EET 87521 may have a significant highland impact-melt component, while Asuka 881757 and Y-793169 have been heavily shocked. The thermal history of Y-793169 included slow cooling, either during impact processing or during its initial crystallization. Our natural TL data indicate that most lunar meteorites 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 meteorites were in small perihelia orbits (less than or equal to 0.7 AU).

  10. Recent documented meteorite falls, a review of meteorite - asteroid links

    NASA Astrophysics Data System (ADS)

    Jenniskens, P.

    2014-07-01

    Since the previous Meteoroids 2010 meeting, 25 confirmed meteorite falls have been reported, and one additional meteorite 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 meteorite 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 meteorite-asteroid links are discussed.

  11. Organic chemistry in meteorites

    NASA Astrophysics Data System (ADS)

    Botta, Oliver

    2002-11-01

    Carbonaceous chondrites contain a suite of soluble organic compounds that possess characteristics that help to understand their formation and to trace back the early history of the solar system. Relative amino acid abundances can be used to discriminate between different parent bodies. The Tagish Lake meteorite is a unique sample from a new type of solar system object that will help to further constrain the physical and chemical conditions found on parent bodies. Enantiomeric excesses have been detected in nonbiological amino acids in the Murchison and Murray meteorites that are still difficult to explain in the current scenario for the synthesis of extraterrestrial amino acids. Finally, new classes of compounds, dipeptides and sugar-related molecules, have been detected in CM carbonaceous chondrites.

  12. Rochechouart meteorite crater - Identification of projectile

    NASA Technical Reports Server (NTRS)

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

    1977-01-01

    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, impact melts. The abundance pattern of the meteorite was determined from interelement correlations. Several samples fell off the correlation lines, presumably due to recrystallization and weathering of impact 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 meteorite was a IIA iron.

  13. Space erosion and cosmic ray exposure ages of stony meteorites

    NASA Astrophysics Data System (ADS)

    Rubincam, David Parry

    2015-01-01

    Space erosion from dust impacts may set upper limits on the cosmic ray exposure (CRE) ages of stony meteorites. 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 impacts 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 large 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 meteorite is approached, rather than drop off as for meteorites 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 meteorites.

  14. Analyses from Near (Meteorites) and Far (Spacecraft): Complementary Approaches to Planetary Geochemistry

    NASA Astrophysics Data System (ADS)

    McSween, H. Y.

    2013-12-01

    discovery of hydrogen in low-albedo regions on Vesta is explained by incorporation of carbonaceous chondrite impactor debris, as seen in clasts within howardites. An estimate of Vesta's bulk composition based on HEDs is consistent with the measured bulk density and the calculated mass of the core. The meteorites provide information on igneous and impact chronology and constrain models for Vesta's magmatic differentiation, which can be tested with spacecraft remote sensing observations. Meteorite analyses are limited by lack of geologic context, and spacecraft data are hampered by incomplete geochemical measurements, but taken together they offer great synergy. Mars and Vesta (and, of course, the Moon) illustrate that planets, large and small, can be rigorously deciphered by geochemical analyses, from near and far. [1] McSween, H. Y. et al. (2009) Science, 324, 736-739, [2] McSween, H. Y. and McLennan, S. M. (2013) Treatise in Geochemistry, 2nd ed., in press, [3] Russell C. T., et al. (2012) Science, 336, 684-686, [4] McSween, H. Y. et al. (2012) Space Sci. Rev., 163-174.

  15. Xe and Kr analyses of silicate inclusions from iron meteorites.

    NASA Technical Reports Server (NTRS)

    Bogard, D. D.; Huneke, J. C.; Burnett, D. S.; Wasserburg, G. J.

    1971-01-01

    Measurements have been conducted of the amounts and isotopic composition of Xe and Kr in silicate inclusions of several iron meteorites. It is shown that the Xe and Kr contents are comparable to chondritic values. The isotopic compositions show trapped gas of both chondritic and atmospheric composition. Large spallation effects occur in some of the meteorites; the spallation spectra in some instances differ from those reported for stone meteorites. In several meteorites, very large neutron capture effects on Br and I occur. All samples have pronounced Xe129 excesses which apparently indicate differences in the formation times from chondrites of less than about 100 million years; however, the presence of trapped Xe132 in silicates which were enclosed in molten Fe-Ni and cooled slowly proves that they were not entirely outgassed, so that some of the Xe129 excess may also be trapped.

  16. Meteorites from Cluj-Napoca

    NASA Astrophysics Data System (ADS)

    Radu, Gelu; Pop, Dana

    2003-04-01

    The article represents an interview of the journalist Gelu Radu with the director of the Meteorites Museum from the Geological Faculty of the Cluj-Napoca University (Romania) Dana Pop concerning the History, Collection and Actual state of an unique in Romania Meteorites Museum, founded in 1882 after the fall of the Mociu Meteorit (Cluj County) on 3 february 1882. One discusses about the collection of the Museum and the policy of changes with other similar museums throughout the world.

  17. Local and Regional Impacts of Large Scale Wind Energy Deployment

    NASA Astrophysics Data System (ADS)

    Michalakes, J.; Hammond, S.; Lundquist, J. K.; Moriarty, P.; Robinson, M.

    2010-12-01

    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 impacts on the local and regional environment. State and federal regulators have raised serious concerns regarding potential agricultural impacts from large farms deployed throughout the Midwest where agriculture is the basis of the local economy. The effects of large 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 impacts at the micro, macro, regional and global scale do not exceed those anticipated from carbon emissions. Largely because of computational limits, the role of large 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 large 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 impacts and quantifying uncertainties of large scale wind energy deployment scenarios. Such a system will allow continuous downscaling of atmospheric processes on wind

  18. Iron Meteorites and Upwelling in Antarctica

    NASA Astrophysics Data System (ADS)

    Gourlay, B. S.; Behr, E.; Mardon, A.; Behr, E.

    2016-09-01

    In Antarctica, a meteorite stranding zone, stone meteorites are more common than iron. Dr. Evatt's team suggests that the heat conductivity of iron may be opposing the upwelling effects so iron meteorites sink under the ice unlike the stone ones.

  19. (U-Th)/He Dating of Martian Meteorites: Shock Temperature Conditions Revisited

    NASA Astrophysics Data System (ADS)

    Min, K. K.

    2013-12-01

    Shock impact is one of the most prominent dynamic events to have occurred after the formation of any planetary bodies in our solar system. This near-surface episode caused an instantaneous temperature increase in the impact site and ejected materials, and was followed by a rapid cooling. Constraining shock P-T conditions and post-shock cooling paths of meteorites is crucial to understanding ejection dynamics, evaluating pre-shock features in the meteorites, and testing the possible transfer of viable life to different planets. Tremendous efforts have been devoted to studying the physical conditions of the shock events, and the most established method to constrain shock pressure condition is to compare microscopic textures of meteorites with those of artificially shocked terrestrial rocks. Using the equation of state, the shock pressures can be converted to corresponding 'post-shock temperatures (Tpost-shock),' which represent temperature increases (ΔT) during the shock relative to the pre-shock temperatures. The Tpost-shock can be further converted to Tpeak if the pre-shock temperature for an individual meteorite is known (Tpeak = Tpost-shock - Tpre-shock). An alternative way to estimate the shock T conditions is to use (U-Th)/He system whose sensitivity to temperature is relatively high. This approach can provide the absolute temperature conditions (Tpeak) of the shock event, instead of the T increases (ΔT). This method requires thermal modeling using the following input parameters: (1) pre-atmospheric body radius, (2) depth of a sample from the surface of the parent meteoroid, (3) surface temperature of meteoroid, (4) thermal diffusivity, (5) activation energy and pre-exponential term for He diffusion in merrillite, and (6) diffusion domain size. Most of these input parameters, except the diffusion domain size, are relatively well constrained for Martian meteorites, and uncertainties associated with these parameters have a limited effect on the Tpeak estimates

  20. Amino and fatty acids in carbonaceous meteorites

    NASA Technical Reports Server (NTRS)

    Kvenvolden, K. A.

    1974-01-01

    Analyses of two carbonaceous meteorites have provided much of the latest evidence which seems to support Oparin's theory on the origin of life. The meteorites involved are the Murray meteorite, which fell in 1950, and the Murchison meteorite, which fell in 1969. The amino acids in the two meteorites 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 meteorites.

  1. ``Campo del Cielo'' Meteorites: Astronomical Heritage and Cultural Colonialism

    NASA Astrophysics Data System (ADS)

    López, Alejandro Martín; Altman, Agustina

    2012-09-01

    In the province of Chaco, Argentina, there is a very unique dispersion of metallic meteorites called ``Campo del Cielo''. One of the meteoric fragments of this dispersion, the meteorite called ``El Chaco'', consisting of 37 tons, is the second heaviest in the world. These meteorites are of great importance to the worldview of the Moqoit, aboriginal people that inhabit this region. For the local Creole population the meteorites 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'' meteorite to Germany in order to exhibit it as an artistic object. Due to the fact that moving the meteorite could have a negative impact 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 impact 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.

  2. The 10Be contents of SNC meteorites

    NASA Technical Reports Server (NTRS)

    Pal, D. K.; Tuniz, C.; Moniot, R. K.; Savin, W.; Vajda, S.; Kruse, T.; Herzog, G. F.

    1986-01-01

    Several authors have explored the possibility that the Shergottites, Nakhlites, and Chassigny (SNC) came from Mars. The spallogenic gas contents of the SNC meteorites 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 meteorites. 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 large 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 meteorites 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 meteorites. 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 meteorites.

  3. Meteorite Atmospheric Entry Reproduced in Plasmatron

    NASA Astrophysics Data System (ADS)

    Pittarello, L.; McKibbin, S.; Goderis, S.; Soens, B.; Bariselli, F.; Barros Dias, B. R.; Zavalan, F. L.; Magin, T.; Claeys, Ph.

    2016-08-01

    Plasmatron facility allows experimental conditions that reproduce atmospheric entry of meteorites. Tests on basalt, as meteorite analogue, have been performed. Preliminary results have highlighted melting and evaporation effects.

  4. A Younger Age for the Oldest Martian Meteorite

    NASA Astrophysics Data System (ADS)

    Taylor, G. J.

    2010-05-01

    The Allan Hills (ALH) 84001 Martian meteorite is famous for containing fiercely-disputed evidence for fossil life. Equally important to many cosmochemists, the meteorite 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 large impacts 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 impact 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 large impact basins on Mars.

  5. Ar-Ar Dating of Martian Meteorite, Dhofar 378: An Early Shock Event?

    NASA Technical Reports Server (NTRS)

    Park, J.; Bogard, D. D.

    2006-01-01

    Martian meteorite, 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 large amounts of martian atmosphere or interior Ar-40. Among all types of meteorites and returned lunar rocks, the impact 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 meteorites were produced by the impact 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 meteorite experienced, but that it was not the impact that initiated the CRE age.

  6. Carbon and Oxygen Isotope Measurements of Ordinary Chondrite (OC) Meteorites from Antarctica Indicate Distinct Terrestrial Carbonate Species using a Stepped Acid Extraction Procedure Impacting Mars Carbonate Research

    NASA Astrophysics Data System (ADS)

    Evans, M. E.; Niles, P. B.; Locke, D.

    2015-12-01

    The purpose of this study is to characterize the stable isotope values of terrestrial, secondary carbonate minerals from five OC meteorites collected in Antarctica. These samples were selected for analysis based upon their size and collection proximity to known Martian meteorites. 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 meteorites 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 meteorite, 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

  7. Distribution, Statistics, and Resurfacing of Large Impact Basins on Mercury

    NASA Technical Reports Server (NTRS)

    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.

    2012-01-01

    The distribution and geological history of large impact 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 impact basins on Mercury with that of the Moon to understand similarities and differences in their impact crater and basin populations [1, 2]. A variety of impact 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 large 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.

  8. The impact of large terrestrial carnivores on Pleistocene ecosystems.

    PubMed

    Van Valkenburgh, Blaire; Hayward, Matthew W; Ripple, William J; Meloro, Carlo; Roth, V Louise

    2016-01-26

    Large mammalian terrestrial herbivores, such as elephants, have dramatic effects on the ecosystems they inhabit and at high population densities their environmental impacts 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 largely 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 impact of Pleistocene large 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 impact 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.

  9. The impact of large terrestrial carnivores on Pleistocene ecosystems.

    PubMed

    Van Valkenburgh, Blaire; Hayward, Matthew W; Ripple, William J; Meloro, Carlo; Roth, V Louise

    2016-01-26

    Large mammalian terrestrial herbivores, such as elephants, have dramatic effects on the ecosystems they inhabit and at high population densities their environmental impacts 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 largely 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 impact of Pleistocene large 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 impact 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

  10. The impact of large terrestrial carnivores on Pleistocene ecosystems

    PubMed Central

    Van Valkenburgh, Blaire; Ripple, William J.; Meloro, Carlo; Roth, V. Louise

    2016-01-01

    Large mammalian terrestrial herbivores, such as elephants, have dramatic effects on the ecosystems they inhabit and at high population densities their environmental impacts 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 largely 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 impact of Pleistocene large 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 impact 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

  11. Tree-ring dating of meteorite fall in Sikhote-Alin, Eastern Siberia - Russia

    NASA Astrophysics Data System (ADS)

    Fantucci, R.; Di Martino, Mario; Serra, Romano

    2012-01-01

    This research deals with the fall of the Sikhote-Alin iron meteorite on the morning of 12 February 1947, at about 00:38 h Utrecht, in a remote area in the territory of Primorsky Krai in Eastern Siberia (46°09‧36″N, 134°39‧22″E). The area engulfed by the meteoritic fall was around 48 km2, with an elliptic form and thousands of craters. Around the large craters the trees were torn out by the roots and laid radially to the craters at a distance of 10-20 m; the more distant trees had broken tops. This research investigated through dendrocronology n.6 Scots pine trees (Pinus Sibirica) close to one of the main impact craters. The analysis of growth anomalies has shown a sudden decrease since 1947 for 4-8 years after the meteoritic impact. Tree growth stress, detected in 1947, was analysed in detail through wood microsection that confirmed the winter season (rest vegetative period) of the event. The growth stress is mainly due to the lost crown (needle lost) and it did not seem to be caused due to direct damages on trunk and branches (missing of resin ducts).

  12. Asteroids and meteorites - Parent bodies and delivered samples

    NASA Technical Reports Server (NTRS)

    Greenberg, R.; Chapman, C. R.

    1983-01-01

    Asteroid physical strengths, which critically affect the quantity of ejecta that can be placed in orbits evolving so as to cross that of the earth, vary widely due to initial composition and size, and subsequent geophysical and collisional evolutions. The meteorite yield on earth additionally depends on meteorite strength, which affects longevity in space and survival through the atmosphere. It is presently shown that meteorites may be primarily derived by cratering rather than disruptive fragmentation, and from large, main-belt asteroids rather than from small, earth-approaching bodies. The model presented combines a variety of evidence from various disciplines to yield results that are consistent with meteorite statistics, although no claim is made for the uniqueness of the model and many of its elements remain uncertain.

  13. The role of population in tracking meteorite falls in Africa

    NASA Astrophysics Data System (ADS)

    Khiri, F.; Ibhi, A.; Saint-Gerant, T.; Medjkane, M.; Ouknine, L.

    2016-01-01

    The 158 African meteorite falls recorded during the period 1801 to 2014, account for more than 12.3% of all meteorite 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 large 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 meteorite falls in Africa. In this note, we try by a statistical study, to examine the role of the African population in tracking meteorite falls on this continent.

  14. SNC meteorites and their implications for reservoirs of Martian volatiles

    NASA Technical Reports Server (NTRS)

    Jones, J. H.

    1993-01-01

    The SNC meteorites 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, largely as inferred from the meteoritic 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 meteorites 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 meteorites suspect as indicators of water inventories on Mars.

  15. Exposure and terrestrial ages of four Allan Hills Antarctic meteorites

    NASA Technical Reports Server (NTRS)

    Kirsten, T.; Ries, D.; Fireman, E. L.

    1978-01-01

    Terrestrial ages of meteorites 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 meteorites (No. 5, No. 6, No. 7, and No. 8), whose C-14, Al-26, and Mn-53 radioactivities are known. These meteorites are of particular interest because they belong to a large assemblage of distinct meteorites that lie exposed on a small (110 sq km) area of ice near the Allan Hills.

  16. Construction of an unyielding target for large horizontal impacts.

    SciTech Connect

    Ammerman, Douglas James; Davie, Neil Thomas; Kalan, Robert J.

    2010-10-01

    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 impacts at regulatory speeds of very large objects, such as a full-scale rail cask, or high-speed impacts 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 impact forces of up to 25 million pounds. It is expected that the new target will be capable of withstanding impact 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 impacts 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.

  17. Comets, meteorites and atmospheres.

    PubMed

    Owen, T; Bar-Nun, A

    1996-01-01

    The relatively low value of Xe/Kr in the atmospheres of Earth and Mars seems to rule out meteorites as the major carriers of noble gases to the inner planets. Laboratory experiments on the trapping of gases in ice forming at low temperatures suggest that comets may be a better choice. It is then possible to develop a model for the origin of inner planet atmospheres based on volatiles delivered by comets added to volatiles originally trapped in planetary rocks. The model will be tested by results from the Galileo Entry Probe.

  18. Stardust in meteorites

    PubMed Central

    Davis, Andrew M.

    2011-01-01

    Primitive meteorites, 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

  19. Stardust in meteorites.

    PubMed

    Davis, Andrew M

    2011-11-29

    Primitive meteorites, 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

  20. Comets, meteorites and atmospheres

    NASA Technical Reports Server (NTRS)

    Owen, T.; Bar-Nun, A.

    1996-01-01

    The relatively low value of Xe/Kr in the atmospheres of Earth and Mars seems to rule out meteorites as the major carriers of noble gases to the inner planets. Laboratory experiments on the trapping of gases in ice forming at low temperatures suggest that comets may be a better choice. It is then possible to develop a model for the origin of inner planet atmospheres based on volatiles delivered by comets added to volatiles originally trapped in planetary rocks. The model will be tested by results from the Galileo Entry Probe.

  1. Stardust in meteorites.

    PubMed

    Davis, Andrew M

    2011-11-29

    Primitive meteorites, 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.

  2. Magnetic record in chondrite meteorites

    NASA Technical Reports Server (NTRS)

    Wasilewski, P. J.; Faris, J. L.; Obryan, M. V.

    1993-01-01

    What we know about the magnetic record in chondrite meteorites based on new data and previously published results is summarized. Strips from thin slabs of chondrite meteorites were cut into near cubical subsamples (several mm on edge) numbering approximately 60 to approximately 120 per meteorite. A common orientation was assigned to each subsample from a given meteorite in order to ensure that we could discover the vector makeup of the bulk meteorite. 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.

  3. The extra-large light-gas gun of the Fraunhofer EMI: Applications for impact cratering research

    NASA Astrophysics Data System (ADS)

    Lexow, B.; Wickert, M.; Thoma, K.; SchńFer, F.; Poelchau, M. H.; Kenkmann, T.

    2013-01-01

    The extra-large 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 impact research. In the framework of the MEMIN (Multidisciplinary Experimental and Modeling Impact Research Network) program, the XLLGG is used for mesoscale cratering experiments with projectiles made of steel and of iron meteorites, 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.

  4. Impact craters at falling of large asteroids in Ukraine

    NASA Astrophysics Data System (ADS)

    Vidmachenko, A. P.

    2016-05-01

    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 large 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 large 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 large impact craters. Ukrainian crystalline shield, because of its stability for a long time (more than 1.5 billion years), has the highest density of large 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 impact 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 impact structures. The most detailed was studied the geological structure and the presence of diamonds in Bilylivska astrobleme

  5. Aioun el Atrouss - Evidence for thermal recrystallization of a eurite breccia. [meteoritic mineralogy

    NASA Technical Reports Server (NTRS)

    Duke, M. B.

    1978-01-01

    The Aioun el Atrouss meteorite is a breccia consisting largely 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 meteorite 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 meteorite are presented.

  6. The atmospheric trajectory and heliocentric orbit of the Neuschwanstein meteorite fall on April 6, 2002

    NASA Astrophysics Data System (ADS)

    Spurny, Pavel; Heinlein, Dieter; Oberst, Jürgen

    2002-11-01

    We report the detection of a unique bolide photographed at 5 German, 1 Czech and 1 Austrian station of the European Fireball Network (EN). This slow-moving fireball with initial velocity of 21 km/s reached the maximum absolute brightness of -17.2 magnitude and was photographed down to 16 km. Several meteorite fragments with total mass of about 20 kilograms are expected to have been dropped. One stony meteorite, very probably an ordinary H-chondrite of 1.75 kilograms was recovered in the predicted impact area, which lies completely in rugged high mountain terrain. The bolide's heliocentric orbit is exceptional as it is practically identical to the orbit of the first photographed meteorite fall in history, the Pribram multiple meteorite fall on April 7, 1959. Both orbits are so similar that there is little doubt that both bodies have the same origin. This meteorite case adds much further evidence for the existence of astroidal and meteorite streams.

  7. Large Field Photogrammetry Techniques in Aircraft and Spacecraft Impact Testing

    NASA Technical Reports Server (NTRS)

    Littell, Justin D.

    2010-01-01

    The Landing and Impact 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 impact 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 impact. 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 large fields of views, camera and lens selection, data processing, as well as best practice techniques learned from using the large field of view photogrammetry on a multitude of crash and landing test scenarios unique to the LandIR.

  8. The Chelyabinsk meteorite fall: Geochemistry and Mineralogy

    NASA Astrophysics Data System (ADS)

    Galimov, Eric

    Just after the Chelyabinsk meteorite fall, the Vernadsky Institute and the Committee on Meteorites of the Russian Academy of Sciences have organized an expedition to collect fragments of the meteorite 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 meteorite 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 impact 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 impact 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

  9. Meteoritic Sulfur Isotopic Analysis

    NASA Technical Reports Server (NTRS)

    Thiemens, Mark H.

    1996-01-01

    Funds were requested to continue our program in meteoritic 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 meteorites. 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.

  10. Meteors and meteorites spectra

    NASA Astrophysics Data System (ADS)

    Koukal, J.; Srba, J.; Gorková, S.; Lenža, L.; Ferus, M.; Civiš, S.; Knížek, A.; Kubelík, P.; Kaiserová, T.; Váňa, P.

    2016-01-01

    The main goal of our meteor spectroscopy project is to better understand the physical and chemical properties of meteoroids. Astrometric and spectral observations of real meteors are obtained via spectroscopic CCD video systems. Processed meteor data are inserted to the EDMOND database (European viDeo MeteOr Network Database) together with spectral information. The fully analyzed atmospheric trajectory, orbit and also spectra of a Leonid meteor/meteoroid captured in November 2015 are presented as an example. At the same time, our target is the systematization of spectroscopic emission lines for the comparative analysis of meteor spectra. Meteoroid plasma was simulated in a laboratory by laser ablation of meteorites samples using an (ArF) excimer laser and the LIDB (Laser Induced Dielectric Breakdown) in a low pressure atmosphere and various gases. The induced plasma emissions were simultaneously observed with the Echelle Spectrograph and the same CCD video spectral camera as used for real meteor registration. Measurements and analysis results for few selected meteorite samples are presented and discussed.

  11. Large-Scale Impact Cratering and Early Earth Evolution

    NASA Technical Reports Server (NTRS)

    Grieve, R. A. F.; Cintala, M. J.

    1997-01-01

    The surface of the Moon attests to the importance of large-scale impact 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. Impact melt volumes and "ancient cavity dimensions for specific impacts 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 large impact 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 impact "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 large multiring basins of the Moon being manifested as muted palimpsest-like structures filled with impact melt, it is unlikely they played a role in establishing the freeboard on the early Earth. The composition of the massive impact 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

  12. Magnetic hysteresis properties and 57Fe Mössbauer spectroscopy of iron and stony-iron meteorites: Implications for mineralogy and thermal history

    NASA Astrophysics Data System (ADS)

    Dos Santos, E.; Gattacceca, J.; Rochette, P.; Scorzelli, R. B.; Fillion, G.

    2015-05-01

    Since the solid matter in our solar system began to assemble 4.57 billion years ago, meteorites have recorded a large range of processes, including metamorphism, melting, irradiation and hypervelocity impacts. These processes as well as solar system magnetic fields can be accessed through the investigation of magnetic properties of meteorites. In this work, we present magnetic hysteresis properties, isothermal remanent magnetization acquisition curves and 57Fe Mössbauer spectra for nineteen iron and eleven stony-iron meteorites. These data will be the background for a discussion about the thermal and shock history of these meteorites. 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 meteorites. In particular, strong shock and the associated thermal event that result in disordering of tetrataenite can be easily identified.

  13. Chemical effects of large impacts on the Earth's primitive atmosphere.

    PubMed

    Fegley, B; Prinn, R G; Hartman, H; Watkins, G H

    1986-01-23

    Intense bombardment of the moon and terrestrial planets approximately 3.9-4.0 x 10(9) years ago could have caused the chemical reprocessing of the Earth's primitive atmosphere. In particular, the shock heating and rapid quenching caused by the impact of large bodies into the atmosphere could produce molecules such as HCN and H2CO4 which are important precursors for the abiotic synthesis of complex organic molecules. Here we model the production of HCN and H2CO by thermochemical equilibrium and chemical kinetic calculations of the composition of shocked air parcels for a wide range of temperatures, pressures and initial compositions. For atmospheres with C/O > or = 1, our results suggest that bolide impacts cause HCN volume mixing ratios of approximately 10(-3) to 10(-5) in the impact region and global average ratios of 10(-5) to 10(-12). The corresponding H2CO mixing ratios in the impact region are 10(-7) to 10(-9); no-global mixing can occur, however, as H2CO is rapidly destroyed or rained out of the atmosphere within days to hours. Rainout to the oceans of 3-15% of the HCN produced can provide approximately (3-14) x 10(11) mol HCN per year. This is somewhat larger than other predicted sources of HCN and H2CO on the primitive Earth.

  14. Antarctic Meteorite Newsletter, Volume 28, Number 2

    NASA Technical Reports Server (NTRS)

    Righter, Kevin (Editor); Satterwhite, Cecilia (Editor)

    2005-01-01

    This newsletter contains classifications for 274 new meteorites from the 2003 and 2004 ANtarctic Search for METeorites (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 meteorites, meteorites classified by type, and tentative pairings petrographic descriptions.

  15. Geochemistry and petrography of the MacAlpine Hills lunar meteorites

    SciTech Connect

    Lindstrom, M.M.; McKay, D.S. ); Wentworth, S.J.; Martinez, R.R.; Mittlefehldt, D.W. ); Wang, Mingsheng; Lipschutz, M.E. )

    1991-11-01

    MacAlpine Hills 88104 and 88105 are anorthositic lunar meteorites 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 impact melt clasts. It contains a small amount of highland impact 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 impact melt breccia clasts are very similar to, but distinct from, matrix composition. MAC88104/5 is very similar in composition to the other anorthositic lunar meteorites, but each of the meteorites is distinct. The anorthositic lunar meteorites, especially MAC88104/5 and Y82192/3/86032, are very similar to North Ray Crater feldspathic fragmental breccias in composition and petrography. These fragmental lunar meteorites may have been ancient, deeply buried breccias from the megaregolith. Comparisons of chemical petrographic features and exposure histories suggest that the twelve lunar meteorites were derived from two to nine, but probably four to seven, impact onto the lunar surface. Discrepancies between the proportions of lunar meteorites and results of Apollo missions may be due to unrepresentative sampling. Lunar meteorites provide valuable new information on the nature of the lunar crust.

  16. Wanted: Lunar detectives to unravel the mysteries of the Moon] Crime to be solved: Mass extinctions on the Moon by meteorite impact

    NASA Astrophysics Data System (ADS)

    Neal, Clive R.; Taylor, Lawrence A.

    The criteria and clues for identifying meteorite 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.

  17. Wanted: Lunar detectives to unravel the mysteries of the Moon! Crime to be solved: Mass extinctions on the Moon by meteorite impact!

    NASA Technical Reports Server (NTRS)

    Neal, Clive R.; Taylor, Lawrence A.

    1991-01-01

    The criteria and clues for identifying meteorite 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.

  18. Volatile Mobilization by Large Impacts: Constraining the Initial Conditions of an Impact- generated Martian Greenhouse.

    NASA Astrophysics Data System (ADS)

    Plesko, C. S.; Asphaug, E.; Weaver, R. P.; Wohletz, K. H.; Korycansky, D. G.

    2008-12-01

    There is substantial evidence for the presence of liquid water on the surface of Mars contemporary to the Late Heavy Bombardment. Large asteroid and comet impacts 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 impacts 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 impact 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 large impacts 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).

  19. The meteorite collection at Museo di Storia Naturale, Pisa University, Italy

    NASA Astrophysics Data System (ADS)

    Perchiazzi, Natale; D'Orazio, Massimo; Folco, Luigi

    2004-08-01

    The historical meteorite 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 meteorites, representing about 50 kg of extraterrestrial material. The collection includes 2 carbonaceous chondrites, 12 ordinary chondrites, 1 achondrite, 4 stony-iron meteorites, and 7 iron meteorites, including three remarkable specimens: the main mass of Bagnone (48 kg), the fourth largest mass of Quenggouk (717.5 g), and a large (nearly) complete individual of the Siena showerfall (318.8 g).

  20. Antarctic Meteorite Newsletter. Volume 22

    NASA Technical Reports Server (NTRS)

    Satterwhite, Cecilia (Editor); Lindstrom, Marilyn (Editor)

    1999-01-01

    This Newsletter Contains Classifications of 143 New Meteorites from the 1997 ANSMET Collection. Descriptions are given for 6 meteorites;2 eucrites, and 4 ordinary chondrites. We don't expect much excitement from the rest of the 1997 collection. JSC has examined another 100 meteorites 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.

  1. Ecohydrological modeling for large-scale environmental impact assessment.

    PubMed

    Woznicki, Sean A; Nejadhashemi, A Pouyan; Abouali, Mohammad; Herman, Matthew R; Esfahanian, Elaheh; Hamaamin, Yaseen A; Zhang, Zhen

    2016-02-01

    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 large-scale models are useful for determining broad impacts 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 large-scale stream health models with reach level accuracy similar to regional-scale models thereby allowing for impacts 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. PMID:26595397

  2. Ecohydrological modeling for large-scale environmental impact assessment.

    PubMed

    Woznicki, Sean A; Nejadhashemi, A Pouyan; Abouali, Mohammad; Herman, Matthew R; Esfahanian, Elaheh; Hamaamin, Yaseen A; Zhang, Zhen

    2016-02-01

    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 large-scale models are useful for determining broad impacts 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 large-scale stream health models with reach level accuracy similar to regional-scale models thereby allowing for impacts 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.

  3. The environmental impact of the use of large wind turbines

    NASA Astrophysics Data System (ADS)

    Manning, P. T.

    The existing data base on the environmental impact of large 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 impact 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 large 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.

  4. Organic compounds in meteorites

    NASA Technical Reports Server (NTRS)

    Lawless, J. G.

    1980-01-01

    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 meteorites 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.

  5. Large Meteoroid Impact on the Moon on 17 March 2013

    NASA Technical Reports Server (NTRS)

    Moser, Danielle E.; Suggs, Robert M.; Suggs, Ronnie J.

    2014-01-01

    Since early 2006, NASA's Marshall Space Flight Center has observed over 300 impact 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 impact 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 impact by comparing post-impact images from 28 July 2013 to pre-impact 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 impacts [2]. The meteoroid impactor responsible for this event may have been part of a stream of large 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 impact velocity of 25.6 km/s derived from fireball measurements

  6. Multiple Cosmic Sources for Meteorite Macromolecules?

    PubMed Central

    Watson, Jonathan S.; Meredith, William; Love, Gordon D.; Gilmour, Iain; Snape, Colin E.

    2015-01-01

    Abstract The major organic component in carbonaceous meteorites 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 large 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 meteorites appears to be made up of more than one chapter. Key Words: Abiotic organic synthesis—Carbonaceous chondrite—Cosmochemistry—Meteorites. Astrobiology 15, 779–786. PMID:26418568

  7. Are There High Meteorite Concentrations in the Atacama Desert/Chile?

    NASA Astrophysics Data System (ADS)

    Scherer, P.; Delisle, G.

    1992-07-01

    We have visited numerous regions of the Atacama desert between Copiapo (27 degrees, 15'S) and Calama (22 degrees, 25'S) to assess their potential as a high-yield meteorite concentration surface, easily exploitable by search efforts within a reasonable time frame. According to our observations, this desert is characterized by the following features: a) A high percentage of the desert consists of sloping surfaces on which soil movement occurs, presumably by very infrequent, though heavy rain. b) Vast areas of the desert are covered by a dm-thick sand layer of dark colour. Since the sand is too coarse-grained to be transported by wind it presumably resulted from in-situ weathering of rock debris derived from nearby mountains. We suspect that impacting smaller objects can easily penetrate the sand layer. c) The sand layer is typically dotted by rocks, fist-size or smaller, that are covered by a thick layer of desert paint (reddish-brown to black colour). Most country rocks are of volcanic origin (rhyolite, andesite, basalt) and are typically of grey to black colour. A noticeable colour contrast in particular to potential stony meteorites is almost nonexistent. d) Soil salts with a potential to speed up weathering processes are ubiquitous near the surface. e) The Pampa de Mejillones, 45 km north of Antofagasta, is one of the few light-coloured areas in the Atacama desert. The surface, being of Mio-Pliocene age, consists of an almost continuous layer of light-brown fossil shells (bivalves and gastropodes). Fluvially transported dark rocks from adjacent outcrops rest on top. The latter material is covered again by desert paint. Few meteorite discoveries have been reported from this area (Pampa (a),(b),(c)). f) Numerous old tire tracks, in particular around mines in operation, crisscross most areas of the Atacama. Undetected objects such as large masses of iron bodies are not likely to have remained undiscovered in great numbers any more. We conclude that the potential of

  8. Meteorites on Mars observed with Mars Exploration Rovers

    USGS Publications Warehouse

    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.

    2008-01-01

    Reduced weathering rates due to the lack of liquid water and significantly greater typical surface ages should result in a higher density of meteorites on the surface of Mars compared to Earth. Several meteorites were identified among the rocks investigated during Opportunity's traverse across the sandy Meridiani plains. Heat Shield Rock is a IAB iron meteorite and has been officially recognized as 'Meridiani Planum.' Barberton is olivine-rich and contains metallic Fe in the form of kamacite, suggesting a meteoritic 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 meteorites 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 impact at current atmospheric pressures. Impact 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.

  9. Acritarchs in carbonaceous meteorites and terrestrial rocks

    NASA Astrophysics Data System (ADS)

    Rozanov, Alexei Y.; Hoover, Richard B.

    2013-10-01

    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 large 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 meteorites. 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 meteorites 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 meteorites. 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 meteorites.

  10. Meteorite concentration mechanisms in Antarctica

    NASA Technical Reports Server (NTRS)

    Annexstad, J. O.

    1986-01-01

    The location of most Antarctic meteorite 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.

  11. Interstellar organic matter in meteorites

    NASA Technical Reports Server (NTRS)

    Yang, J.; Epstein, S.

    1983-01-01

    Deuterium-enriched hydrogen is present in organic matter in such meteorites as noncarbonaceous chondrites. The majority of the unequilibrated primitive meteorites contain hydrogen whose D/H ratios are greater than 0.0003, requiring enrichment (relative to cosmic hydrogen) by isotope exchange reactions taking place below 150 K. The D/H values presented are the lower limits for the organic compounds derived from interstellar molecules, since all processes subsequent to their formation, including terrestrial contamination, decrease their D/H ratios. In contrast, the D/H ratios of hydrogen associated with hydrated silicates are relatively uniform for the meteorites analyzed. The C-13/C-12 ratios of organic matter, irrespective of D/H ratio, lie well within those observed for the earth. Present findings suggest that other interstellar material, in addition to organic matter, is preserved and is present in high D/H ratio meteorites.

  12. Large impact on Callisto`s southern hemisphere

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This mosaic of images showing a large 200 kilometer (120 mile) diameter impact 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 impact. Beyond this is a zone of rays which are oriented radially outward and contain material also thrown from the crater. Fewer smaller impact craters are visible in the ejecta blanket surrounding the large 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 large 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.

    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.

    The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC.

    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

  13. The K/T-boundary carbonate breccia succession at the Cantarell Field, Campeche Bay area: a representative example of the influence of the Chicxulub meteorite-impact event on the formation of extraordinary petroleum reservoirs

    NASA Astrophysics Data System (ADS)

    Murillo-Muñeton, G.; Grajales-Nishimura, J. M.; Velasquillo-Martínez, L. G.; García-Hernández, J.

    2013-05-01

    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 impact-metamorphic constituents. At the Cantarell field, this carbonate breccia sedimentary package is a representative example of how the Chuxulub meteorite-impact 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

  14. Trapped noble gases indicate lunar origin for Antarctic meteorite

    NASA Technical Reports Server (NTRS)

    Bogard, D. D.; Johnson, P.

    1983-01-01

    The isotopic abundances of the noble gases (He, Ne, Ar, Kr, Xe) are reported for Antarctic ALHA 81005. It contains solar wind-implanted gases whose absolute and relative concentrations are quite similar to lunar regolith samples but not to other meteorites. ALHA 81005 also contains a large excess Ar-40 component which is identical to the component in lunar fines implanted from the lunar atmosphere. Large concentrations of cosmogenic Ne-21, Kr-82, and Xe-126 in ALHA 81005 indicate a total cosmic ray exposure age of at least 200 million years. The noble gas data alone are strong evidence for a lunar origin of this meteorite.

  15. Unmelted Meteoritic Debris Collected from Eltanin Ejecta in Polarstern Cores from Expedition ANT XII/4

    NASA Technical Reports Server (NTRS)

    Kyte, Frank T.

    2002-01-01

    A total of 1.7g of unmelted meteorite particles have been recovered from FS Polarstern piston cores collected on expedition ANT XII/4 that contain ejecta from the Eltanin impact event. Most of the mass (1.2 g) is a large, 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 large 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 impact by being blown off the back surface of the Eltanin asteroid during its impact into the Bellingshausen Sea.

  16. Extraterrestrial Amino Acids in the Almahata Sitta Meteorite

    NASA Technical Reports Server (NTRS)

    Glavin, Daniel P.; Aubrey, Andrew D.; Callahan, Michael P.; Dworkin, Jason P.; Elsila, Jamie E.; Parker, Eric T.; Bada, Jeffrey L.

    2009-01-01

    Amino acid analysis of a meteorite 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 meteorite 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 meteorite were racemic (D/L approximately 1), indicat ing that these amino acids are indigenous to the meteorite and not te rrestrial contaminants. Several other non-protein amino acids were also identified in the meteorite 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 meteorite Murchison. The extremely love abund ances and unusual distribution of five carbon amino acids in Almahata Sitta compared to Cl, CM, and CR carbonaceous meteorites and may be due to extensive thermal alteration of amino acids on the parent aster oid by partial melting during formation or impact shock heating.

  17. Samarium-neodymium evolution of meteorites

    SciTech Connect

    Prinzhofer, A.; Papanastassiou, D.A.; Wasserburg, G.J. )

    1992-02-01

    The authors have obtained Sm-Nd data on two differentiated meteorites, Ibitira, a eucrite with distinct basaltic texture and with evidence of crystallization; and Morristown, a group 3A mesosiderite; as well as on Acapulco, an unclassified meteorite with chondritic chemical composition and a highly recrystallized texture. They have demonstrated the presence of in situ decay of short-lived {sup 146}Sm in these meteorites with initial abundance of {sup 146}Sm/{sup 144}Sm from 0.009 to 0.007 for the different meteorites. Precisely defined {sup 147}Sm-{sup 143}Nd internal isochrons were obtained yielding ages of 4.60 {+-} 0.03 AE for Acapulco, 4.47 {+-} 0.02 AE for Morristown, and 4.46 {+-} 0.02 AE for Ibitira. The corresponding initial {sup 143}Nd/{sup 144}Nd values obtained were 0.2 {+-} 0.9, 2.1 {+-} 0.7, and 1.6 {+-} 0.8 {var epsilon}u (epsilon units). Detailed consideration of the coupled {sup 147}Sm-{sup 143}Nd and {sup 146}Sm-{sup 142}Nd systematics and of the elevated initial {sup 143}Nd/{sup 144}Nd values indicates the presence of inconsistencies in the data for the two Sm-Nd parent-daughter pairs in spiteof the precise isochrons. The authors present a model which provides an interpretation of the paired Sm-Nd systematics in terms of an impulsive disturbance. The results indicate that three meteorites studied are relatively ancient objects, formed within the first 50 to 100 m.y. of the solar system, by planetary differentiation and impact processes, and were subjected to late metamorphism. The time of late metamorphism is substantially younger than 4.4 AE and possibly as recent as {approximately}3.9 AE. This metamorphism has resulted in partial, very limited reequilibration between plagioclase and phosphate, resulting in the observed shifts in initial {sup 143}Nd/{sup 144}Nd, Sm-Nd model ages, and the {sup 142}Nd/{sup 144}Nd abundances, but preserving the major temporal structures of early original formation and later disturbances.

  18. The Flux of Large Meteoroids Observed with Lunar Impact Monitoring

    NASA Technical Reports Server (NTRS)

    Cooke, W. J.; Suggs, R. M.; Moser, D. E.; Suggs, R. J.

    2014-01-01

    The flux of large 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 large meteoroids in the tens of grams to kilogram mass range. This is accomplished by observing the flash of light produced when a meteoroid impacts 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 impact 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 impact 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].

  19. The fall, recovery and classification of the Park Forest Meteorite

    SciTech Connect

    Simon, Steve B.; Grossman, Larry; Clayton, Robert N.; Mayeda, T. K.; Schwade, J. R.; Sipiera, P. P.; Wacker, John F.; Wadhwa, M.

    2004-04-01

    On the night of March 26, 2003, a large meteorite 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 Meteoritical 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 large as ~7000 kg, of which only ~30 kg have been recovered. This paper describes initial measurements to identify and characterize the Park Forest meteorite, which is classified as an L5 chondrite.

  20. Paleomagnetism of the moon and meteorites

    NASA Astrophysics Data System (ADS)

    Hood, L. L.; Cisowski, S. M.

    1983-04-01

    Paleomagnetic investigations (1979-1982) of the nature of the magnetization process and the magnetizing fields which produced magnetization in lunar and meteoritic materials are surveyed. Natural remanence magnetization (NRM), as well as thermoremanence magnetization (TRM), have been measured in carbonaceous chondrites and and L-chondrites to characterize the formation processes occurring when the magnetization was induced. Chemical remanence magnetism, together with the NRM, has been examined in noncarbonaceous chondrites, and NRM intensity and locations have been probed in achondrites. The magnetism has been concluded to arise either from solar magnetic fields, solar nebula magnetic fields, dynamo magnetic fields in the meteorite parent bodies, or locally generated fields caused by processes such as impacts. Lunar samples with NRM have been dated to origins less than 3.6 b.y., and could have been caused by shocks, such as from impacts less than 3 m.y. ago. Discussions of TRM, dynamo, and possible transient magnetic fields from hypervelocity meteoroid impacts as origins of magnetism on the surface and in a lunar magnetic core are presented.

  1. New material model for simulating large impacts on rocky bodies

    NASA Astrophysics Data System (ADS)

    Tonge, A.; Barnouin, O.; Ramesh, K.

    2014-07-01

    Large impact craters on an asteroid can provide insights into its internal structure. These craters can expose material from the interior of the body at the impact site [e.g., 1]; additionally, the impact sends stress waves throughout the body, which interrogate the asteroid's interior. Through a complex interplay of processes, such impacts 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 impact 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 impact 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 impact 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 impact 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

  2. Seismicity of the St. Lawrence paleorift faults overprinted by a meteorite impact crater: Implications for crustal strength based on new earthquake relocations in the Charlevoix Seismic Zone, Eastern Canada

    NASA Astrophysics Data System (ADS)

    Yu, H.; Harrington, R. M.; Liu, Y.; Lamontagne, M.; Pang, M.

    2015-12-01

    The Charlevoix Seismic Zone (CSZ), located along the St. Lawrence River (SLR) ~100 km downstream from Quebec City, is the most active seismic zone in eastern Canada with five historic earthquakes of M 6-7 and ~ 200 events/year reported by the Canadian National Seismograph Network. Cataloged earthquake epicenters outline two broad linear zones along the SLR with little shallow seismicity in between. Earthquakes form diffuse clusters between major dipping faults rather than concentrating on fault planes. Detailed fault geometry in the CSZ is uncertain and the effect on local seismicity of a meteorite impact structure that overprints the paleorift faults remains ambiguous. Here we relocate 1639 earthquakes occurring in the CSZ between 01/1988 - 10/2010 using the double-difference relocation method HypoDD and waveforms primarily from 7 local permanent stations. We use the layered SLR north shore velocity model from Lamontagne (1999), and travel time differences based on both catalog and cross-correlated P and S-phase picks. Of the 1639 relocated earthquakes, 1236 (75.4%) satisfied selection criteria of horizontal and vertical errors less than 2 km and 1 km respectively. Cross-sections of relocated seismicity show hypocenters along distinct active fault segments. Earthquakes located beneath the north shore of the SLR are likely correlated with the NW Gouffre fault, forming a ~10 km wide seismic zone parallel to the river, with dip angle changing to near vertical at the northern edge of the impact zone. In contrast, seismicity beneath the SLR forms a diffuse cloud within the impact structure, likely representing a highly fractured volume. It further implies that faults could be locally weak and subject to high pore-fluid pressures. Seismicity outside the impact structure defines linear structures aligning with the Charlevoix fault. Relocated events of M > 4 all locate outside the impact structure, indicating they nucleated on the NE-SW-oriented paleorift faults.

  3. Physical Properties of Meteorite Falls in Relation to Planetary Defense

    NASA Astrophysics Data System (ADS)

    Ostrowski, D.; Sears, D. W. G.; Bryson, K.; Agrawal, P.

    2015-07-01

    NASA ARC has set up a new lab to study a suite of physical properties of all types of meteorite falls. This is aide to the Planetary Defense initiative at Ames in determining how to deflect or the impact outcome of potentially hazardous bodies.

  4. The Orgueil meteorite: 150 years of history

    NASA Astrophysics Data System (ADS)

    Gounelle, Matthieu; Zolensky, Michael E.

    2014-10-01

    The goal of this paper is to summarize 150 yr of history of a very special meteorite. The Orgueil meteorite 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 meteorite, 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 meteorites, indeed one of the most studied rocks of any kind. Not only does it contain a large 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

  5. Meteorite fractures and the behavior of meteoroids in the atmosphere

    NASA Astrophysics Data System (ADS)

    Bryson, K.; Ostrowski, D. R.; Sears, D. W. G.

    2015-12-01

    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 meteorite 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 meteorite texture. (2) Coarse irons fractured along kamacite grain boundaries, while (3) fine irons fragmented randomly, c.f. chondrites. (4) Fine irons with large 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 meteorite has the chicken-wire structure of fractures, which explains the very large number of centimeter-sized fragments that showered the Earth. Finally, (6) previous work on Sutter's Mill showed that water-rich meteorites fracture around clasts. To scale the meteorite 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 large object and ns and nl refer to the number of cracks per unit volume of the small and large object. The value for α, the Weibull coefficient, is unclear. Ames meteorite 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.

  6. Panoramic camera systems for meteor tracking and meteorite recovery

    NASA Astrophysics Data System (ADS)

    Brosch, N.; Nemiroff, R.; Shamir, L.

    2006-08-01

    Since 1969, the Antarctic became the most fertile part of the Earth to yield meteorites. The recovered meteorites have been concentrated in specific locations by the actions of wind and snow. It is difficult, therefore to derive their history prior to their arrival onto the Antarctic ice except for an estimate of their space residence. We propose to deploy a system of two or more panoramic cameras in the Antarctic designed to observe meteors and measure their space trajectories. The cameras are patterned after the successful CONCAM systems with the specific difference that each would be equipped with a high-precision light chopper. The CCD images collected by the continuously-operating cameras will yield the angular speed of each detected meteor. Using two or more cameras spaced by a few km or tens of km it will be possible, using triangulation, to derive the space trajectories of these meteors. In case of meteorite-dropping meteors, the trajectory analysis will allow the determination of the approximate ground impact. This would allow recovery of the meteorite(s) in the subsequent Antarctic spring season with the full knowledge of the space history and with a very small chance of weathering.

  7. Noble gases and cosmogenic radionuclides in the Eltanin Pacific meteorite

    SciTech Connect

    Bogard, D D; Garrison, D H; Caffee, M W; Kyte, F; Nishiizumi, K

    2000-01-14

    A 1.5 cm long, 1.2 g specimen of the Eltanin meteorite was found at 10.97 m depth in Polarstern piston core PS2704-1. The early studies indicated that the small fragments of the Eltanin meteorite was debris from a km-sized asteroid which impacted 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 meteorite. 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.

  8. The Martian sources of the SNC meteorites (two, not one), and what can and can't be learned from the SNC meteorites

    NASA Technical Reports Server (NTRS)

    Treiman, A. H.

    1993-01-01

    The SNC meteorites, which almost certainly originate in the Martian crust, have been inferred to come from a single impact 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 meteorites can be located, Mars science will advance considerably. However, many significant questions cannot be answered by the SNC meteorites. These questions await a returned sample.

  9. The relative importance of prebiotic synthesis on the Earth and input from comets and meteorites

    NASA Technical Reports Server (NTRS)

    Miller, S. L.

    1991-01-01

    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 meteorites 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 meteorite 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 large scale input of organic compounds from meteorites and comets is that they must survive passage through the atmosphere and impact. There are some processes that would allow survival such as showers of centimeter to meter sized meteorites and various aerodynamic braking processes for larger objects. Even if a significant amount of the organic material survived impact, 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 meteorites, the amount available from these sources at a given time was only a few percent of that from

  10. Zinc isotope anomalies in Allende meteorite inclusions

    NASA Technical Reports Server (NTRS)

    Loss, R. D.; Lugmair, G. W.

    1990-01-01

    The isotopic compositions of Zn, Cr, Ti, and Ca have been measured in a number of CAIs from the Allende meteorite. The aim was to test astrophysical models which predict large 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.

  11. The natural thermoluminescence of meteorites. III - Lunar and basaltic meteorites

    NASA Technical Reports Server (NTRS)

    Sears, Derek W. G.; Benoit, Paul H.; Sears, Hazel; Batchelor, J. D.; Symes, Steve

    1991-01-01

    Natural thermoluminescence (TL) data were obtained to investigate recent thermal and radiation histories of the lunar meteorite MacAlpine Hills 88104/5 and 65 eucrites, howardites, diogenites, and mesosiderites. All these meteorites have low levels of natural TL compared to chondrites, which is primarily because they display anomalous fading. Some meteorites 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.

  12. Two Very Precisely Instrumentally Documented Meteorite Falls: Zdar nad Sazavou and Stubenberg - Prediction and Reality

    NASA Astrophysics Data System (ADS)

    Spurny, P.; Borovicka, J.; Haloda, J.; Shrbeny, L.; Heinlein, D.

    2016-08-01

    Recently two bright bolides Zdar nad Sazavou (Czechia) and Stubenberg (Germany) were recorded by the cameras of the Czech Fireball Network. Basic data and comparison of the predicted impact areas and real positions of the meteorites will be presented.

  13. Hypoxia impacts large adults first: consequences in a warming world.

    PubMed

    Clark, Melody S; Husmann, Gunnar; Thorne, Michael A S; Burns, Gavin; Truebano, Manuela; Peck, Lloyd S; Abele, Doris; Philipp, Eva E R

    2013-07-01

    Future oceans are predicted to contain less oxygen than at present. This is because oxygen is less soluble in warmer water and predicted stratification will reduce mixing. Hypoxia in marine environments is thus likely to become more widespread in marine environments and understanding species-responses is important to predicting future impacts on biodiversity. This study used a tractable model, the Antarctic clam, Laternula elliptica, which can live for 36 years, and has a well-characterized ecology and physiology to understand responses to hypoxia and how the effect varied with age. Younger animals had a higher condition index, higher adenylate energy charge and transcriptional profiling indicated that they were physically active in their response to hypoxia, whereas older animals were more sedentary, with higher levels of oxidative damage and apoptosis in the gills. These effects could be attributed, in part, to age-related tissue scaling; older animals had proportionally less contractile muscle mass and smaller gills and foot compared with younger animals, with consequential effects on the whole-animal physiological response. The data here emphasize the importance of including age effects, as large mature individuals appear to be less able to resist hypoxic conditions and this is the size range that is the major contributor to future generations. Thus, the increased prevalence of hypoxia in future oceans may have marked effects on benthic organisms' abilities to persist and this is especially so for long-lived species when predicting responses to environmental perturbation.

  14. Evidence from Hydrogen Isotopes in Meteorites for a Subsurface Hydrogen Reservoir on Mars

    NASA Technical Reports Server (NTRS)

    Usui, Tomohiro; Alexander, Conel M. O'D.; Wang, Jianhua; Simon, Justin I.; Jones, John H.

    2015-01-01

    The surface geology and geomorphology of Mars indicates that it was once warm enough to maintain a large 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 impact glasses in three Martian meteorites (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 meteorites crystallized (173-472 Ma) to the time they were ejected by impacts (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) meteorites, 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 large part of the initial water budget of Mars.

  15. Liquid Water on Mars: The Story from Meteorites

    NASA Astrophysics Data System (ADS)

    Taylor, G. J.

    2000-05-01

    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 meteorites, 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 meteorites Baker and colleagues conclude that the rocks from which Martian meteorites derived were intermittently exposed to water or water vapor; they were not exposed for a long time to large 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 meteorite Lafayette. This meteorite 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.

  16. The Orbits of Meteorites from Natural Thermoluminescence. Attachment 5

    NASA Technical Reports Server (NTRS)

    Benoit, P. H.; Sears, D. W. G.

    1997-01-01

    The natural thermoluminescence (TL) of meteorites 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 meteorites are determined largely by thermal history. The primary heat source for most meteorites 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 meteorites can exist in "orbital groups," significant changes in the types and number of meteorites reaching Earth could occur on the less than 10(exp 5)-year time scale.

  17. Re-Os dating of 3AB iron meteorites

    NASA Technical Reports Server (NTRS)

    Esat, Tezer M.; Bennett, Victoria

    1993-01-01

    Recently, Creaser et al., and Volkening and Heumann, have demonstrated the efficient production of large (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 meteorites 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 meteorite 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 meteorite. We have applied NTIMS to Os extracted from the most common group of iron meteorites the IIIAB. These meteorites 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.

  18. The carbon components in SNC meteorites of feldspathic harzburgite composition

    NASA Technical Reports Server (NTRS)

    Wright, I. P.; Douglas, C.; Pillinger, C. T.

    1993-01-01

    Two meteorites collected in Antarctica, ALH A77005 and LEW 88516, have characteristics which link them to the shergottite group of SNC meteorites. 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 meteorites represent samples of a cumulate rock which is itself composed of two different lithologies: in one, large 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 meteorites 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 meteorites, 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.

  19. Molecular asymmetry in extraterrestrial chemistry: Insights from a pristine meteorite.

    PubMed

    Pizzarello, Sandra; Huang, Yongsong; Alexandre, Marcelo R

    2008-03-11

    The nonracemic amino acids of meteorites 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 meteoritic 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 meteorites to terrestrial contaminants and the ubiquitous homochirality of such contamination. We have analyzed the soluble organic composition of a carbonaceous meteorite from Antarctica that was collected and stored under controlled conditions, largely escaped terrestrial contamination and offers an exceptionally pristine sample of prebiotic material. Analyses of the meteorite 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. PMID:18310323

  20. Antarctic Meteorite Classification and Petrographic Database

    NASA Technical Reports Server (NTRS)

    Todd, Nancy S.; Satterwhite, C. E.; Righter, Kevin

    2011-01-01

    The Antarctic Meteorite collection, which is comprised of over 18,700 meteorites, is one of the largest collections of meteorites in the world. These meteorites 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 Meteorite Lab and the Smithsonian Institution and results are published twice a year in the Antarctic Meteorite 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 meteorites is also published on the NASA Curation website [2] and made available through the Meteorite Classification Database allowing scientists to search by a variety of parameters

  1. The Meteoritical Bulletin, no. 85, 2001 September

    USGS Publications Warehouse

    Grossman, J.N.; Zipfel, J.

    2001-01-01

    Meteoritical Bulletin No. 85 lists information for 1376 newly classified meteorites, 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 meteorites (Dar al Gani 876, Northwest Africa 480 and 817, and Sayh al Uhaymir 051 and 094); 6 lunar meteorites (Dhofar 081, 280, and 287, and Northwest Africa 479, 482, and 773); an ungrouped enstatite-rich meteorite (Itqiy); a Bencubbin-like meteorite (Gujba); 9 iron meteorites; and a wide variety of other interesting stony meteorites, including CH, CK, CM, CO, CR, CV, R, enstatite, and unequilibrated ordinary chondrites, primitive achondrites, HED achondrites, and ureilites.

  2. Characterization of multiple lithologies within the lunar feldspathic regolith breccia meteorite Northeast Africa 001

    NASA Astrophysics Data System (ADS)

    Snape, Joshua F.; Joy, Katherine H.; Crawford, Ian A.

    2011-09-01

    Abstract- Lunar meteorite Northeast Africa (NEA) 001 is a feldspathic regolith breccia. This study presents the results of electron microprobe and LA-ICP-MS analyses of a section of NEA 001. We identify a range of lunar lithologies including feldspathic impact melt, ferroan noritic anorthosite and magnesian feldspathic clasts, and several very-low titanium (VLT) basalt clasts. The largest of these basalt clasts has a rare earth element (REE) pattern with light-REE (LREE) depletion and a positive Euanomaly. This clast also exhibits low incompatible trace element (ITE) concentrations (e.g., <0.1 ppm Th, <0.5 ppm Sm), indicating that it has originated from a parent melt that did not assimilate KREEP material. Positive Eu-anomalies and such low-ITE concentrations are uncharacteristic of most basalts returned by the Apollo and Luna missions, and basaltic lunar meteorite samples. We suggest that these features are consistent with the VLT clasts crystallizing from a parent melt which was derived from early mantle cumulates that formed prior to the separation of plagioclase in the lunar magma ocean, as has previously been proposed for some other lunar VLT basalts. Feldspathic impact melts within the sample are found to be more mafic than estimations for the composition of the upper feldspathic lunar crust, suggesting that they may have melted and incorporated material from the lower lunar crust (possibly in large basin-forming events). The generally feldspathic nature of the impact melt clasts, lack of a KREEP component, and the compositions of the basaltic clasts, leads us to suggest that the meteorite has been sourced from the Outer-Feldspathic Highlands Terrane (FHT-O), probably on the lunar farside and within about 1000 km of sources of both Low-Ti and VLT basalts, the latter possibly existing as cryptomaria deposits.

  3. Detailed structural analysis of the rim of a large, complex impact crater: Bosumtwi Crater, Ghana

    NASA Astrophysics Data System (ADS)

    Reimold, Wolf U.; Brandt, Dion; Koeberl, Christian

    1998-06-01

    The 1 Ma Bosumtwi Crater in Ghana is an 11-km-diameter, presumably complex, well-preserved impact structure that is associated with the Ivory Coast tektite strewnfield. Detailed structural geologic studies along a complete traverse through the northwestern rim section indicated four zones characterized by distinct deformation styles from just outside of the crater rim to near the crater floor. Zone 1 is dominated by thick deposits of lithic impact breccia, intercalated in places with products of local mass wasting. Zone 2 contains inward-dipping thrust planes, conjugate radial fractures, isoclinal folding, and overturned stratigraphic sequences. Zone 3 represents a megabreccia zone, in which block size decreases upward and outward toward the rim crest. The innermost zone 4 is dominated by intense thrust faulting of multiple orientations, resulting in complex duplex- and lens-shaped bodies. These deformation styles generally correspond to those previously reported from the rims of simple bowl-shaped meteorite-impact craters and appear to be characteristic of impact structures in general.

  4. Investigation of Orthopyroxene Diversity in Howardite Meteorites

    NASA Technical Reports Server (NTRS)

    Johnson, Kristin N.; Herrin, J. S.; Mittlefehldt, D. W.

    2011-01-01

    The howardite, eucrite and diogenite (HED) family of meteorites 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 impact-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 impact 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 meteorites and the processes by which they were formed an important constraint on understanding Dawn data.

  5. Organic matter in meteorites and comets - Possible origins

    NASA Technical Reports Server (NTRS)

    Anders, Edward

    1991-01-01

    At least six extraterrestrial environments may have contributed organic compounds to meteorites and comets: solar nebula, giant-planet subnebulae, asteroid interiors containing liquid water, carbon star atmospheres, and diffuse or dark interstellar clouds. The record in meteorites 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 large 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.

  6. Endemic Ru Isotopic Anomalies in Iron Meteorites and in Allende

    NASA Technical Reports Server (NTRS)

    Chen, J. H.; Papanastassiou, D. A.; Wasserburg, G. J.

    2003-01-01

    Small variations for Mo isotopes have been observed recently in the Allende meteorite and in iron meteorites, mesosiderites, and pallasites, using ICPMS. Large 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 meteorites.

  7. Large Meteoroid Impact on the Moon 17 March 2013

    NASA Technical Reports Server (NTRS)

    Suggs, Robert M.; Moser, Danielle; Cooke, William J.; Kingery, Aaron; Kring, David A.; Suggs, Ronnie J.

    2013-01-01

    NASA's routine monitoring of lunar impact flashes has recorded nearly 300 impacts 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 impact flash visible for over 1 second, the impact 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 impact crater by Lunar Reconnaissance Orbiter will also be discussed.

  8. Organic Chemistry of Carbonaceous Meteorites

    NASA Technical Reports Server (NTRS)

    Cronin, John R.

    2001-01-01

    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 meteoritic 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 meteorite, Murray meteorite, amino acids, isovaline, chirality, carbon isotopes, PCP.

  9. The Magnetization of Carbonaceous Meteorites

    NASA Technical Reports Server (NTRS)

    Herndon, James Herndon

    1974-01-01

    Alternating field demagnetization experiments have been conducted on representative samples of the carbonaceous meteorites (carbonaceous chondrites and ureilites). The results indicate that many, if not all, of these meteorites possess an intense and stable magnetic moment of extraterrestrial origin. Thermomagnetic analyses have been conducted on samples of all known carbonaceous meteorites. 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.

  10. Squeezing Meteorites to Reveal the Martian Mantle

    NASA Astrophysics Data System (ADS)

    Taylor, G. J.

    2006-12-01

    A piece of a Martian lava flow, Antarctic meteorite Yamato-980459, appears to represent the composition of a magma produced by partial melting of the Martian interior. That's the view of researchers Don Musselwhite, Walter Kiefer, and Allan Treiman (Lunar and Planetary Institute, Houston) and Heather Dalton (Arizona State University). Musselwhite and his colleagues determined that this basaltic Martian meteorite represented a primary melt from the mantle. This was an important discovery because magma produced inside a planet contains significant clues to the composition of the region of the interior in which it formed. The lava flows that decorate the surface of planets tell us about the mantle, the rocky region beneath the crust and above the metallic core. The researchers used apparatus at the Johnson Space Center to determine what minerals are present when samples with the composition of Y-980459 are heated to a range of temperatures and squeezed to a range of pressures like those that planetary scientists expect to exist in the interior of Mars. The results indicate that the magma represented by this special meteorite formed at a depth of about 100 kilometers and a temperature of about 1540 degrees C. From the high temperature and high ratio of magnesium to iron in the magma, Musselwhite and his colleagues infer that the amount of melting to produce the Y-980459 parent magma was high, which suggests that the temperature at the boundary between the metallic core and the rocky mantle was higher than previous estimates. This work gives us clues to the composition and dynamics of the Martian interior--all from a rock chipped off a lava flow on Mars and flung to Earth by an impact.

  11. Formation of Metal and Silicate Globules in Gujba: A New Bencubbin-like Meteorite Fall

    NASA Technical Reports Server (NTRS)

    Rubin, Alan E.; Kallemeyn, Gregory W.; Wasson, John T.; Clayton, Robert N.; Mayeda, Toshiko; Grady, Monica; Verchovsky, Alexander B.; Eugster, Otto; Lorenzetti, Silvio

    2006-01-01

    Gujba is a coarse-grained meteorite fall composed of 41 vol% large kamacite globules, 20 vol% large light-colored silicate globules with cryptocrystalline, barred pyroxene and barred olivine textures, 39 vol% dark-colored, silicate-rich matrix, and rare refractory inclusions. Gujba resembles Bencubbin and Weatherford in texture, oxygen-isotopic composition and in having high bulk delta N-15 values (approximately +685%0). The He-3 cosmic-ray exposure age of Gujba (26 +/- 7 Ma) is essentially identical to that of Bencubbin, suggesting that they were both reduced to meter-size fragments in the same parent-body collision. The Gujba metal globules exhibit metal-troilite quench textures and vary in their abundances of troilite and volatile siderophile elements. We suggest that the metal globules formed as liquid droplets either via condensation in an impact-generated vapor plume or by evaporation of preexisting metal particles in a plume. The lower the abundance of volatile elements in the metal globules, the higher the globule quench temperature. We infer that the large silicate globules also formed from completely molten droplets; their low volatile-element abundances indicate that they also formed at high temperatures, probably by processes analogous to those that formed the metal globules. The coarse-grained Bencubbin-Weatherford-Gujba meteorites may represent a depositional component from the vapor cloud enriched in coarse and dense particles. A second class of Bencubbin-like meteorites (represented by Hammadah a1 Hamra 237 and QUE 94411) may be a finer fraction derived from the same vapor cloud

  12. Local structures of Ca, Ti and Fe in meteorite fusion crusts

    NASA Astrophysics Data System (ADS)

    Tobase, T.; Yoshiasa, A.; Hiratoko, T.; Hongu, H.; Isobe, H.; Nakatsuka, A.; Arima, H.; Sugiyama, K.

    2016-05-01

    The local structures of meteorite fusion crusts were studied by Ca, Ti and Fe K-edge XANES and EXAFS spectroscopy. The surface of meteorites were melted and volatilized with extreme high temperature and large temperature gradient when meteorites were rushed into atmosphere. This study indicated that meteorite 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 meteorite fusion crusts indicates that meteorite fusion crusts are formed into atmospheric oxidation condition. The Ca-O distances in meteorite 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 meteorite fusion crusts and classification of natural glass.

  13. Mineralogy and petrology of two ordinary chondrites and their correlation with other meteorites

    NASA Astrophysics Data System (ADS)

    Owocki, Krzysztof; Pilski, Andrzej

    2009-01-01

    Two ordinary chondrites are compared and classified using transmitted and reflected light microscopy and electron microprobe analyses. Both meteorites were confiscated by the Polish Customs Service at the border with Belarus. The first meteorite (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 large recrystallized feldspars (< 150 μm). The specimen examined experienced weak shock metamorphism (S3) and moderate weathering (although metal in the inner part of the meteorite seems to be unaffected by oxidization). The other meteorite (called in this paper Terespol-2) is a LL6 chondrite which experienced weak shock metamorphism (S3) and is unaffected by weathering. The Terespol-2 meteorite shares its classification with the Dhofar 1401 chondrite but the lack of data prevents further correlation. Both meteorites have been correlated with known findings from the Meteoritical Bulletin 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 meteorites at least came from the same parent body.

  14. Coordinated In Situ Analyses of Organic Nanoglobules in the Sutter's Mill Meteorite

    NASA Technical Reports Server (NTRS)

    Nakamura--Messenger, K.; Messenger, S.; Keller, L. P.; Clemett, S. J.; Nguyen, A. N.; Gibson, E. K.

    2013-01-01

    The Sutter s Mill meteorite 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 meteorite and its rapid recovery provide an opportunity to investigate primordial solar system organic matter in a unique new sample. Organic matter in primitive meteorites 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 meteorites 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 meteorite [6]. In the Tagish Lake meteorite, the principle carriers of large H and N isotopic anomalies are sub-micron hollow organic spherules known as organic nanoglobules [7]. Organic nanoglobules are commonly distributed among primitive meteorites [8, 9] and cometary samples [10]. Here we report in-situ analyses of organic nano-globules in the Sutter's Mill meteorite using UV fluorescence imaging, Fourier-transform infrared spectroscopy (FTIR), scanning transmission electron microscopy (STEM), NanoSIMS, and ultrafast two-step laser mass spectrometry (ultra-L2MS).

  15. Extraterrestrial amino acids in the Almahata Sitta meteorite

    NASA Astrophysics Data System (ADS)

    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.

    2010-10-01

    Amino acid analysis of a meteorite 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 meteorite 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 meteorite were racemic (D/L ˜ 1), indicating that these amino acids are indigenous to the meteorite and not terrestrial contaminants. Several other nonprotein amino acids were also identified in the meteorite 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 impact 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 meteorite clasts and chemically altered by α-decarboxylation.

  16. Iron isotope anomalies. [In carbonaceous meteorites

    SciTech Connect

    Voelkening, J.; Papanastassiou, D.A. )

    1989-12-01

    Precise determinations of the Fe isotope abundances yield identical results for a terrestrial standard and for samples of carbonaceous meteorites. Fe-54/Fe-56 = 0.062669; Fe-57/Fe-56 = 0.023261 + or - 0.000002; and Fe-58/Fe-56 = 0.0031132 + or - 0.0000011 are found. Refractory element-rich inclusions from the Allende carbonaceous meteorite yield hints of deficits in Fe-57/Fe-56 of up to -3.9 + or - 2.6 parts in 10,000 and a hint of excess in Fe-58/Fe-56 of up to 27 + or - 11 parts in 10,000. One special (FUN) inclusion shows a large excess of 2.9 percent, uniquely attributable to Fe-58. This excess correlates with large excesses in the same inclusion in the neutron-rich isotopes Ca-48, Ti-50 and Cr-54. These results strengthen the evidence for an exotic nucleosynthetic component produced by neutron-rich, statistical equilibrium burning, and injected into the interstellar medium. 29 refs.

  17. Martian meteorite Dhofar 019: A new shergottite

    NASA Astrophysics Data System (ADS)

    Taylor, L. A.; Nazarov, M. A.; Shearer, C. K.; McSween, H. Y., Jr.; Cahill, J.; Neal, C. R.; Ivanova, M. A.; Barsukova, L. D.; Lentz, R. C.; Clayton, R. N.; Mayeda, T. K.

    2002-08-01

    Dhofar 019 is a new martian meteorite found in the desert of Oman. In texture, mineralogy, and major and trace element chemistry, this meteorite is classified as a basaltic shergottite. Olivine megacrysts are set within a groundmass composed of finer grained olivine, pyroxene (pigeonite and augite), and maskelynite. Minor phases are chromite-ulvöspinel, ilmenite, silica, K-rich feldspar, merrillite, chlorapatite, and pyrrhotite. Secondary phases of terrestrial origin include calcite, gypsum, celestite, Fe hydroxides, and smectite. Dhofar 019 is most similar to the Elephant Moraine (EETA) 79001 lithology A and Dar al Gani (DaG) 476/489 shergottites. The main features that distinguish Dhofar 019 from other shergottites are lack of orthopyroxene; lower Ni contents of olivine; the heaviest oxygen-isotopic bulk composition; and larger compositional ranges for olivine, maskelynite, and spinel, as well as a wide range for pyroxenes. The large compositional ranges of the minerals are indicative of relatively rapid crystallization. Modeling of olivine chemical zonations yield minimum cooling rates of 0.5-0.8 ?C/h. Spinel chemistry suggests that crystallization took place under one of the most reduced conditions for martian meteorites, at an oxygen fugacity of 3 log units below the quartz-fayalite-magnetite (QFM) buffer. The olivine megacrysts are heterogeneously distributed in the rock. Crystal size distribution analysis suggests that they constitute a population formed under steady-state conditions of nucleation and growth, although a few grains may be cumulates. The parent melt is thought to have been derived from partial melting of a light rare earth element- and platinum group element-depleted mantle source. Shergottites, EETA79001 lithology A, DaG 476/489, and Dhofar 019, although of different ages, comprise a particular type of martian rocks. Such rocks could have formed from chemically similar source(s) and parent melt(s), with their bulk compositions affected by

  18. Geological implications of impacts of large asteroids and comets on the earth

    SciTech Connect

    Silver, L.T.; Schultz, P.H.

    1982-01-01

    The present conference discusses such topics as large object fluxes in near-earth space and the probabilities of terrestrial impacts, the geological record of impacts, dynamics modeling for large body impacts on continents and oceans, physical, chemical, and biological models of large impacts atmospheric effects, dispersed impact 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 impact rates for long- and short-period comets, estimates of crater size for large body impact, a first-order estimate of shock heating and vaporization in oceanic impacts, atmospheric effects in the first few minutes after an impact, a feasibility test for biogeographic extinction, and the planktonic and dinosaur extinctions.

  19. Geological implications of impacts of large asteroids and comets on the earth

    NASA Technical Reports Server (NTRS)

    Silver, L. T. (Editor); Schultz, P. H. (Editor)

    1982-01-01

    The present conference discusses such topics as large object fluxes in near-earth space and the probabilities of terrestrial impacts, the geological record of impacts, dynamics modeling for large body impacts on continents and oceans, physical, chemical, and biological models of large impacts' atmospheric effects, dispersed impact 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 impact rates for long- and short-period comets, estimates of crater size for large body impact, a first-order estimate of shock heating and vaporization in oceanic impacts, atmospheric effects in the first few minutes after an impact, a feasibility test for biogeographic extinction, and the planktonic and dinosaur extinctions.

  20. The Meteoritical Bulletin, No. 88, 2004 July

    USGS Publications Warehouse

    Russell, S.S.; Folco, L.; Grady, M.M.; Zolensky, M.E.; Jones, R.; Righter, K.; Zipfel, J.; Grossman, J.N.

    2004-01-01

    The Meteoritical Bulletin No. 88 lists information for 1610 newly classified meteorites, 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 meteorites, 13 lunar meteorites, and 12 irons including one weighing 3 metric ions (Dronino). ?? Meteoritical Society, 2004.

  1. HYDROGEN CYANIDE IN THE MURCHISON METEORITE

    SciTech Connect

    Pizzarello, Sandra

    2012-08-01

    Carbonaceous chondrites are meteorites 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 meteorite in amounts {<=} 10 ppm. HCN was never searched for in meteorites 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 meteorites 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 meteorites.

  2. Mysterious iodine-overabundance in Antarctic meteorites

    NASA Technical Reports Server (NTRS)

    Dreibus, G.; Waenke, H.; Schultz, L.

    1986-01-01

    Halogen as well as other trace element concentrations in meteorite finds can be influenced by alteration processes on the Earth's surface. The discovery of Antarctic meteorites offered the opportunity to study meteorites which were kept in one of the most sterile environment of the Earth. Halogen determination in Antartic meteorites was compared with non-Antarctic meteorites. 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.

  3. Meteorites and the Antarctic ice sheet

    NASA Technical Reports Server (NTRS)

    Cassidy, W. A.

    1986-01-01

    The majority of the meteorite finds were located in the Allan Hills site. All the expected goals involving the recovery of rare or previously unknown types of meteorites, and even the recovery of lunar ejecta, were realized. The relationship between these remarkable concentrations of meteorites and the Antarctic ice sheet itself were less well documented. Ice flow vector studies were made and concentration models were proposed. Earlier estimates of the abundances of meteorite types were based on the number of falls in the world collections. The accumulated data and the future collected data will allow more reliable estimates of the source region of most meteorites.

  4. Systematic Collection and Analysis of Meteoritic Materials from Meteor Crater, Arizona

    NASA Astrophysics Data System (ADS)

    Kargel, J. S.; Coffin, P.; Kraft, M.; Lewis, J. S.; Moore, C.; Roddy, D.; Shoemaker, E. M.; Wittke, J. H.

    1996-03-01

    We have started a systematic collection and analysis of meteoritic materials from Meteor Crater, Arizona. Since our earlier report (Kargel, J.S., Kraft, M.D., Roddy, D.J., Wittke, J.H., and Lewis, J.S., 1995, Eos, v. 76, p. F337), we have found 47 small fragments of the Canyon Diablo iron meteorite. We also have collected impactite lapilli; oxidized meteorite fragments; and materials we call amalgamated meteoritic/lithic fragments (AMLs), which consist of target rocks fused with and impregnated by oxidized meteoritic iron. The composition of the impactite lapilli is consistent with admixture of about 3 parts Kaibab Formation (siliceous dolomitic limestone) and 1 part oxidized meteorite. In addition, the lapilli contain microscopic spherules of Ni-rich metal (up to 90% Ni), which can only be explained by partial oxidation of Canyon Diablo metal. Our interpretation of the lapilli is that the impact event melted and devolatilized rocks of the Kaibab Formation (siliceous limestone and dolomite), which mixed with molten meteoritic metal. If impact heated metal droplets or vapor condensates attained about 3500 K, then CO2 released from the Kaibab Formation may have thermally decomposed to CO and O2 and caused partial oxidation of the metal.

  5. Ar-Ar ages and thermal histories of enstatite meteorites

    NASA Astrophysics Data System (ADS)

    Bogard, Donald D.; Dixon, Eleanor T.; Garrison, Daniel H.

    2010-05-01

    Compared with ordinary chondrites, there is a relative paucity of chronological and other data to define the early thermal histories of enstatite parent bodies. In this study, we report 39Ar-40Ar dating results for five EL chondrites: Khairpur, Pillistfer, Hvittis, Blithfield, and Forrest; five EH chondrites: Parsa, Saint Marks, Indarch, Bethune, and Reckling Peak 80259; three igneous-textured enstatite meteorites that represent impact melts on enstatite chondrite parent bodies: Zaklodzie, Queen Alexandra Range 97348, and Queen Alexandra Range 97289; and three aubrites, Norton County, Bishopville, and Cumberland Falls Several Ar-Ar age spectra show unusual 39Ar recoil effects, possibly the result of some of the K residing in unusual sulfide minerals, such as djerfisherite and rodderite, and other age spectra show 40Ar diffusion loss. Few additional Ar-Ar ages for enstatite meteorites are available in the literature. When all available Ar-Ar data on enstatite meteorites are considered, preferred ages of nine chondrites and one aubrite show a range of 4.50-4.54Ga, whereas five other meteorites show only lower age limits over 4.35-4.46Ga. Ar-Ar ages of several enstatite chondrites are as old or older as the oldest Ar-Ar ages of ordinary chondrites, which suggests that enstatite chondrites may have derived from somewhat smaller parent bodies, or were metamorphosed to lower temperatures compared to other chondrite types. Many enstatite meteorites are brecciated and/or shocked, and some of the younger Ar-Ar ages may record these impact events. Although impact heating of ordinary chondrites within the last 1Ga is relatively common for ordinary chondrites, only Bethune gives any significant evidence for such a young event.

  6. Martian "microfossils" in lunar meteorites?

    PubMed

    Sears, D W; Kral, T A

    1998-07-01

    One of the five lines of evidence used by McKay et al. (1996) for relic life in the Martian meteorite Allan Hills (ALH) 84001 was the presence of objects thought to be microfossils. These ovoid and elongated forms are similar to structures found in terrestrial rocks and described as "nanobacteria" (Folk, 1993; McBride et al., 1994). Using the same procedures and apparatus as McKay et al. (1996), we have found structures on internal fracture surfaces of lunar meteorites that cannot be distinguished from the objects described on similar surfaces in ALH 84001. The lunar surface is currently a sterile environment and probably always has been. However, the lunar and Martian meteorites share a common terrestrial history, which includes many thousands of years of exposure to Antarctic weathering. Although we do not know the origin of these ovoid and elongated forms, we suggest that their presence on lunar meteorites indicates that the objects described by McKay et al. (1996) are not of Martian biological origin.

  7. Organic Compounds in Carbonaceous Meteorites

    NASA Technical Reports Server (NTRS)

    Cooper, Grorge

    2001-01-01

    Carbonaceous meteorites 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 meteorite is the best-characterized carbonaceous meteorite with respect to organic chemistry. The study of its organic compounds has related principally to aqueous meteorite 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.

  8. Extraterrestrial Organic Compounds in Meteorites

    NASA Technical Reports Server (NTRS)

    Botta, Oliver; Bada, Jeffrey L.; Meyer, Michael (Technical Monitor)

    2003-01-01

    Many organic compounds or their precursors found in meteorites 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 meteorite parent body. The most distinct feature of CI and CM carbonaceous chondrites, two types of stony meteorites, 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 meteorite 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.

  9. Indigenous microfossils in carbonaceous meteorites

    NASA Astrophysics Data System (ADS)

    Hoover, Richard B.; Jerman, Gregory; Rozanov, Alexei Y.; Sipiera, Paul P.

    2004-11-01

    Indigenous embedded microbial filaments, bacterial cells and other microfossils were found in the Orgueil, Ivuna (CI1), Murchison, and Bells (CM2) carbonaceous meteorites. 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 meteorite surfaces. EDAX x-ray spectra shows the microfossils bear signatures of the meteorite matrix and possess elemental ratios indicating they are indigenous and not recent microbial contaminants. Many of the well-preserved biogenic remains in the meteorites 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.

  10. Analysis of the Farmville Meteorite

    NASA Astrophysics Data System (ADS)

    Ferm, Megan

    2011-10-01

    Meteoroids are objects that are constantly bombarded by cosmic rays in outer space. Through spallation reactions between cosmic rays and meteoroid matter, radioactive nuclides, such as 26Al, are produced. 26Al is a positron emitter, meaning that the positron annihilates within a cubic millimeter of the sample. This results in the release of two 511 keV photons, in addition to an 1809 keV gamma ray from the decay to the 26Mg ground state. This study focuses on the detection of 26Al in the Farmville meteorite, which fell in North Carolina in 1934. The meteorite has been centered in our sensitive apparatus, and the conditions for detection require a triple gamma coincidence which greatly reduced background. With the radioisotopes measured within the sample, Monte Carlo transport simulations (using the package Geant4) will be performed to determine the amount of 26Al in the meteorite. With this information, it may be possible to determine the time the meteorite entered Earth's atmosphere (which should be consistent with the reported find time), the time period that the meteoroid was exposed to the cosmic rays, the pre-atmospheric size of the meteoroid and the intensity of cosmic rays in the inner solar system.

  11. Martian "microfossils" in lunar meteorites?

    PubMed

    Sears, D W; Kral, T A

    1998-07-01

    One of the five lines of evidence used by McKay et al. (1996) for relic life in the Martian meteorite Allan Hills (ALH) 84001 was the presence of objects thought to be microfossils. These ovoid and elongated forms are similar to structures found in terrestrial rocks and described as "nanobacteria" (Folk, 1993; McBride et al., 1994). Using the same procedures and apparatus as McKay et al. (1996), we have found structures on internal fracture surfaces of lunar meteorites that cannot be distinguished from the objects described on similar surfaces in ALH 84001. The lunar surface is currently a sterile environment and probably always has been. However, the lunar and Martian meteorites share a common terrestrial history, which includes many thousands of years of exposure to Antarctic weathering. Although we do not know the origin of these ovoid and elongated forms, we suggest that their presence on lunar meteorites indicates that the objects described by McKay et al. (1996) are not of Martian biological origin. PMID:11543077

  12. Martian "microfossils" in lunar meteorites?

    NASA Astrophysics Data System (ADS)

    Sears, Derek W. G.; Kral, Timothy A.

    1998-07-01

    One of the five lines of evidence used by McKay et al. (1996) for relic life in the martian meteorite Allan Hills (ALH) 84001 was the presence of objects thought to be microfossils. These ovoid and elongated forms are similar to structures found in terrestrial rocks and described as "nanobacteria" (Folk, 1993; McBride et al., 1994). Using the same procedures and apparatus as McKay et al. (1996), we have found structures on internal fracture surfaces of lunar meteorites that cannot be distinguished from the objects described on similar surfaces in ALH 84001. The lunar surface is currently a sterile environment, and probably always has been. However, the lunar and martian meteorites share a common terrestrial history, including many thousands of years of exposure to Antarctic weathering. While we do not know the origin of these ovoid and elongated forms, we suggest that their presence on lunar meteorites indicates that the objects described by McKay et al. (1996) are not of martian biological origin.

  13. Lunar sample analysis. [Allende meteorite

    NASA Technical Reports Server (NTRS)

    Housley, R. M.

    1985-01-01

    Recent results on the antarctic meteorite 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.

  14. Cosmogenic radioisotopes in Gebel Kamil meteorite

    NASA Astrophysics Data System (ADS)

    Taricco, C.; Colombetti, P.; Bhandari, N.; Sinha, N.; Di Martino, M.; Vivaldo, G.

    2012-04-01

    Recently a small (45 m in diameter) and very young (< 5,000 years) impact crater was discovered in Egypt (Folco et al., 2010, 2011); it was generated by an iron meteorite named Gebel Kamil (Meteoritical 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.

  15. Antarctic Meteorite Classification and Petrographic Database Enhancements

    NASA Technical Reports Server (NTRS)

    Todd, N. S.; Satterwhite, C. E.; Righter, K.

    2012-01-01

    The Antarctic Meteorite collection, which is comprised of over 18,700 meteorites, is one of the largest collections of meteorites in the world. These meteorites 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 Meteorite Lab and the Smithsonian Institution and results are published twice a year in the Antarctic Meteorite 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 meteorites is also published on the NASA Curation website [2] and made available through the Meteorite 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 meteorite community with faster access to meteorite data concurrent with the publication of the Antarctic Meteorite Newsletter twice a year.

  16. Recent meteorite falls in South Korea

    NASA Astrophysics Data System (ADS)

    Choi, Y.; Kim, M.; Byun, Y.; Yi, H.; Chang, S.; Choi, J.; Sohn, J.; Moon, H.; Park, J.

    2014-07-01

    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 meteorites from the southern part of South Korea followed and, as of today, three meteorites were confirmed and one meteorite, with a mass of about 20 kg, is pending. This discovery of a meteorite in South Korea occurs for the first time in 70 years. The overall trajectory of the fireball matches the area where meteorites were discovered. According to the preliminary analyses, the meteorite is an ordinary chondrite. The origin of the meteorite and its surface properties will be studied.

  17. The Meteoritical Bulletin, No. 100, 2014 June

    NASA Astrophysics Data System (ADS)

    Ruzicka, Alex; Grossman, Jeffrey N.; Garvie, Laurence

    2014-08-01

    Meteoritical Bulletin 100 contains 1943 meteorites 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 meteorites, 15 enstatite chondrites, 11 lunar meteorites, 10 mesosiderites, 10 ungrouped achondrites, 8 pallasites, 8 Martian meteorites, 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 meteorites can be obtained from the Meteoritical Bulletin Database (MBD) available online at http://www.lpi.usra.edu/meteor/

  18. Crustal Stripping by Large Impacts on Asteroid 1 Ceres

    NASA Astrophysics Data System (ADS)

    Bowling, T. J.

    2016-08-01

    The largest craters on Ceres do not have an obvious surface expression on the asteroid. However, the largest expected impacts should leave behind a distinct gravity signature, and may be detected this way.

  19. Economic impact of large public programs: The NASA experience

    NASA Technical Reports Server (NTRS)

    Ginzburg, E.; Kuhn, J. W.; Schnee, J.; Yavitz, B.

    1976-01-01

    The economic impact 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.

  20. Meteorite Falls Observed in U.S. Weather Radar Data in 2015 and 2016 (To Date)

    NASA Technical Reports Server (NTRS)

    Fries, Marc; Fries, Jeffrey; Hankey, Mike; Matson, Robert

    2016-01-01

    To date, over twenty meteorite 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 Meteoritical Society meeting, covering most of 2015 and early 2016. Meteorite Falls: The following events produced evidence of falling meteorites in radar imagery and resulted in meteorites 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 meteorites in data from the KMUX, KVTX, KHNX and KVBX. The Meteoritical Society records the Creston fall as an L6 meteorite 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 meteorite 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 meteorites were recovered. Evidence indicates that this was a relatively large meteorite fall where most of the meteorites are unrecoverable due to terrain. Osceola is an L6 meteorite 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

  1. Mechanical properties of several iron-nickel meteorites

    SciTech Connect

    Mulford, Roberta N; El - Dasher, Bassem

    2011-01-06

    Iron-nickel meteorites 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 large 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 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. 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 meteorites, from the Muonionalusta meteorite (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.

  2. Molybdenum Isotopic Composition of Iron Meteorites, Chondrites and Refractory Inclusions

    NASA Technical Reports Server (NTRS)

    Becker, H.; Walker, R. J.

    2003-01-01

    Recent Mo isotopic studies of meteorites reported evidence for differences in isotopic compositions for whole rocks of some primitive and differentiated meteorites 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 large 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 large 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 meteorites. Here, we present new results for the Mo isotopic composition of iron meteorites, 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.

  3. Multiple Cosmic Sources for Meteorite Macromolecules?

    PubMed

    Sephton, Mark A; Watson, Jonathan S; Meredith, William; Love, Gordon D; Gilmour, Iain; Snape, Colin E

    2015-10-01

    The major organic component in carbonaceous meteorites 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 large 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 meteorites appears to be made up of more than one chapter. PMID:26418568

  4. Multiple Cosmic Sources for Meteorite Macromolecules?

    PubMed

    Sephton, Mark A; Watson, Jonathan S; Meredith, William; Love, Gordon D; Gilmour, Iain; Snape, Colin E

    2015-10-01

    The major organic component in carbonaceous meteorites 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 large 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 meteorites appears to be made up of more than one chapter.

  5. Melt production in large-scale impact events: Calculations of impact-melt volumes and crater scaling

    NASA Technical Reports Server (NTRS)

    Cintala, Mark J.; Grieve, Richard A. F.

    1992-01-01

    Along with an apparent convergence in estimates of impact-melt volumes produced during planetary impact events, intensive efforts at deriving scaling relationships for crater dimensions have also yielded results. It is now possible to examine a variety of phenomena associated with impact-melt production during large cratering events and apply them to planetary problems. This contribution describes a method of combining calculations of impact-melt production with crater scaling to investigate the relationship between the two.

  6. Ar-Ar and I-Xe Ages of Caddo County and Thermal History of IAB Iron Meteorites

    NASA Technical Reports Server (NTRS)

    Bogard, Donald D.; Garrison, Daniel H.; Takeda, Hiroshi

    2005-01-01

    Inclusions in IAB iron meteorites include non-chondritic silicate and those with more primitive chondritic silicate composition. Coarse-grained gabbroic material rich in plagioclase and diopside occurs in the Caddo County IAB iron meteorite and represents a new type of chemically differentiated, extra-terrestrial, andesitic silicate. Other parts of Caddo contain mostly andesitic material. Caddo thus exhibits petrologic characteristics of parent body metamorphism of a chondrite-like parent and inhomogeneous segregation of melts. Proposed IAB formation models include parent body partial melting and fractional crystallization or incomplete differentiation due to internal heat sources, and impact/induced melting and mixing. Benedix et al. prefer a hybrid model whereby the IAB parent body largely melted, then underwent collisional breakup, partial mixing of phases, and reassembly. Most reported 129I- Xe-129 ages of IABs are greater than 4.56 Gyr and a few are greater than or = 4.567 Gyr. These oldest ages exceed the 4.567 Gyr Pb-Pb age of Ca, Al-rich inclusions in primitive meteorites,

  7. Late Bombardment of the Lunar Highlands Recorded in MIL 090034, MIL 090036 and MIL 090070 Lunar Meteorites

    NASA Technical Reports Server (NTRS)

    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

    2013-01-01

    The Kaguya mission detected small but widespread outcrops of nearly pure ferroan anorthosite in and around large impact basins on the Moon. Along with certain lunar rocks, highly feldspathic lunar meteorites 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.

  8. Metal spherules in Wabar, Monturaqui, and Henbury impactites. [iron meteorites

    NASA Technical Reports Server (NTRS)

    Gibbons, R. V.; Horz, F.; Thompson, T. D.; Brownlee, D. E.

    1976-01-01

    The Fe, Ni, and Co contents of 450 spherules with diameters of 3 to 100 microns in impact glasses from three terrestrial meteorite 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 meteorite 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 meteoritic material at the meteorite-target contact was the major fractionation process.

  9. Impact of heuristics in clustering large biological networks.

    PubMed

    Shafin, Md Kishwar; Kabir, Kazi Lutful; Ridwan, Iffatur; Anannya, Tasmiah Tamzid; Karim, Rashid Saadman; Hoque, Mohammad Mozammel; Rahman, M Sohel

    2015-12-01

    Traditional clustering algorithms often exhibit poor performance for large networks. On the contrary, greedy algorithms are found to be relatively efficient while uncovering functional modules from large biological networks. The quality of the clusters produced by these greedy techniques largely 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 large 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. PMID:26386663

  10. The Complicated Geologic Histories of Large Venusian Impact Craters

    NASA Astrophysics Data System (ADS)

    Rumpf, M. E.; Herrick, R.; Gregg, T. K.

    2005-12-01

    One of the more surprising discoveries from the Magellan imaging campaign was that the impact 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 impact craters with radar-dark floors (most of the population) are shallow and probably partially filled with post-impact lavas, and detailed mapping of Mead impact basin (the planet's largest impact structure) has revealed post-impact volcanic embayment. We have recently performed detailed photogeologic mapping, aided by stereo-derived topography, of several 50-100 km diameter impact 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

  11. The meteoritic contribution to the regoliths of Mars, Deimos, and Phobos

    NASA Technical Reports Server (NTRS)

    Flynn, G. J.

    1991-01-01

    The mass influx of meteoritic 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 impacts of objects larger than 1014 grams. Using the measured flux of meteoritic 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 meteoritic material to the surface of Mars annually. This corresponds to the accretion of between 1.8 and 40 cm of meteoritic material per billion years. On the Moon this meteoritic component constitutes 1 to 2 percent of the mare soils. Depending on the indigenous regolith production rate on Mars, the meteoritic material on Mars may be present in sufficient concentration to serve as a resource for the volatile and siderophile elements common in chondritic meteorites 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.

  12. Lunar Meteorites and Implications for Compositional Remote Sensing of the Lunar Surface

    NASA Astrophysics Data System (ADS)

    Korotev, R. L.

    1999-01-01

    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 meteorites 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 meteorites. Yamato 791197 is nominally a feldspathic lunar meteorite (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 large (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 impact 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)

  13. Market impact of a large-scale PV buildings program

    SciTech Connect

    Rannels, J.E.

    1997-12-31

    This paper explores the rapidly changing solar technologies market and the potential impact of a new Federally sponsored Million Solar Roofs Initiative (MSRI) designed to encourage the domestic market for solar building technologies. Photovoltaic (PV) technology has reached a critical point in its development. Over the course of this decade, the PV industry has experienced tremendous growth through greater technology efficiency, the introduction of new solar technology applications (PV shingles, facades, etc.), and lower production costs. In order to achieve its full commercial potential, significant improvements are still needed along with the removal of existing market barriers. DOE`s analysis of the impact of the MSRI indicates that it could significantly reduce the cost of PV technology and improve efficiencies through manufacturing economies of scale, market experience, and industry competition.

  14. Mercury (Hg) in meteorites: Variations in abundance, thermal release profile, mass-dependent and mass-independent isotopic fractionation

    NASA Astrophysics Data System (ADS)

    Meier, Matthias M. M.; Cloquet, Christophe; Marty, Bernard

    2016-06-01

    We have measured the concentration, isotopic composition and thermal release profiles of Mercury (Hg) in a suite of meteorites, including both chondrites and achondrites. We find large variations in Hg concentration between different meteorites (ca. 10 ppb to 14,000 ppb), with the highest concentration orders of magnitude above the expected bulk solar system silicates value. From the presence of several different Hg carrier phases in thermal release profiles (150-650 °C), we argue that these variations are unlikely to be mainly due to terrestrial contamination. The Hg abundance of meteorites shows no correlation with petrographic type, or mass-dependent fractionation of Hg isotopes. Most carbonaceous chondrites show mass-independent enrichments in the odd-numbered isotopes 199Hg and 201Hg. We show that the enrichments are not nucleosynthetic, as we do not find corresponding nucleosynthetic deficits of 196Hg. Instead, they can partially be explained by Hg evaporation and redeposition during heating of asteroids from primordial radionuclides and late-stage impact heating. Non-carbonaceous chondrites, most achondrites and the Earth do not show these enrichments in vapor-phase Hg. All meteorites studied here have however isotopically light Hg (δ202Hg = ∼-7 to -1) relative to the Earth's average crustal values, which could suggest that the Earth has lost a significant fraction of its primordial Hg. However, the late accretion of carbonaceous chondritic material on the order of ∼2%, which has been suggested to account for the water, carbon, nitrogen and noble gas inventories of the Earth, can also contribute most or all of the Earth's current Hg budget. In this case, the isotopically heavy Hg of the Earth's crust would have to be the result of isotopic fractionation between surface and deep-Earth reservoirs.

  15. Cosmogenic radionuclides and mineralogical properties of the Chelyabinsk (LL5) meteorite: What do we learn about the meteoroid?

    NASA Astrophysics Data System (ADS)

    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

    2015-02-01

    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 meteorite, including petrographic and microprobe investigations to unravel intrinsic characteristics of this meteorite. 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 meteorite as an LL5 chondrite. The fragments studied, a few of which are impact 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, 22Na, 26Al, 54Mn, 57Co, 58Co, and 60Co, which indicate that the pre-atmospheric object had a radius >5 m, consistent with other size estimates based on the magnitude of the airburst caused by the atmospheric entry and breakup of the Chelyabinsk meteoroid. Considering the observed 26Al activities of the investigated samples, Monte Carlo simulations, and taking into account the 26Al half-life (0.717 Myr), the cosmic-ray exposure age of the Chelyabinsk meteorite is estimated to be 1.2 ± 0.2 Myr. In contrast to the other radionuclides, 14C showed a very large range only consistent with most samples having been exposed to anthropogenic sources of 14C, which we associate with radioactive contamination of the Chelyabinsk region by past nuclear accidents and waste disposal, which has also been confirmed by elevated levels of anthropogenic 137Cs and

  16. Image of the Mundrabilla Meteorite

    NASA Technical Reports Server (NTRS)

    2001-01-01

    This is a macro photograph of an etched surface of the Mundrabilla meteorite, a small piece of the approximately 3.9 billion-year-old meteorite that was first discovered in Western Australia in 1911. Two more giant chunks, together weighing about 17 tons, were found in 1966. Researchers can learn much from this natural crystal growth experiment since it has spent several hundred million years cooling, and would be impossible to emulate in a lab. This single slice, taken from a 6 ton piece recovered in 1966, measures only 2 square inches. The macro photograph shows a metallic iron-nickel alloy phase of kamcite (38% Ni) and taenite (6% Ni) at bottom right, bottom left, and top left. The darker material is an iron sulfide (FeS or troilite) with a parallel precipitates of duabreelite (iron chromium sulfide (FeCr2S4).

  17. Interstellar Precursors of Meteoritic Organics

    NASA Technical Reports Server (NTRS)

    Charnley, S. B.

    2003-01-01

    The organic inventory initially available to protostellar disks is the first step on the long chemical path to the development of Life. The early earth may have obtained most its volatile material from the arrival of meteorites and comets at its surface. Determining the most likely distribution of meteoritic and cometary organic molecules that could seed primitive planets is a major goal since it sets the initial conditions for, at least part of, the phase of prebiotic chemical evolution. Observations and measurements of the chemical composition of primitive Solar System organics, and of dense molecular clouds, should allow the construction of coherent theoretical picture of the development of organic complexity from interstellar biogenic material to the beginning of prebiotic evolution.

  18. Cosmogenic radionuclides in stone meteorites

    NASA Technical Reports Server (NTRS)

    Cressy, P. J., Jr.

    1976-01-01

    This document presents the techniques and compilation of results of cosmogenic Al-26 measurements at Goddard Space Flight Center on 91 samples of 76 stone meteorites. Short-lived radionuclides, including Na-22, Sc-46, Mn-54, and Co-60, were measured in 13 of these meteorites. About one-third of these data has not previously been published. The results are discussed briefly in terms of (1) depletion of Al-26 and natural potassium due to weathering, (2) possible exposure of several chondrites to an unusually high cosmic-ray flux, (3) comparison of Al-26, Na-22, Sc-46, and Mn5-54 in chondrites with the spallation Ne-22/Ne-21 ratio as a shielding indicator, and (4) comparison of (Al-26)-(Ne-22)/Ne-21 data for achondrite classes with the chondrite trend.

  19. Transient Climate Effects of Large Impacts on Titan

    NASA Technical Reports Server (NTRS)

    Zahnle, Kevin J.; Korycansky, Donald; Nixon, Conor A.

    2013-01-01

    Titan's thick atmosphere and volatile-rich surface cause it to respond to big impacts 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 impact 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 impact (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.

  20. New Insights in Preservation of Meteorites in Hot Deserts: The Oldest Hot Desert Meteorite Collection.

    NASA Astrophysics Data System (ADS)

    Hutzler, A.; Rochette, P.; Bourlès, D.; Gattacceca, J.; Merchel, S.; Jull, A. J. T.; Valenzuela, M.

    2016-08-01

    Terrestrial ages of a subset of a chilean meteorite collection have been determined with cosmogenic nuclides. We show here that provided the environnement is favorable enough, hot desert meteorites can survive over a million year.

  1. Trapped noble gases in meteorites

    NASA Technical Reports Server (NTRS)

    Swindle, Timothy D.

    1988-01-01

    The trapped noble gases in meteorites come in two main varieties, usually referred to as solar and planetary. The solar noble gases are implanted solar-wind or solar-flare materials, and thus their relative elemental abundances provide a good estimate of those of the sun. The planetary noble gases have relative elemental abundances similar to those in the terrestrial atmosphere, but there are also important distinctions. At least one other elemental pattern (subsolar) and several isotopic patterns have also been identified.

  2. No `nanofossils' in martian meteorite

    NASA Astrophysics Data System (ADS)

    Bradley, J. P.; Harvey, R. P.; McSween, H. Y.; Gibson, Everett; Thomas-Keprta, Kathie; Vali, H.

    1997-12-01

    Elongated, segmented forms found on fracture surfaces within the martian meteorite ALH84001 have been proposed to be martian `nanofossils', even though they appear too small to be fossilized bacteria. We have examined similar forms and find that the majority are (non-biological) lamellar growth steps on pyroxene and carbonate crystals. Their segmented surface microstructures are laboratory artefacts resulting from the deposition of conductive heavy-metal coatings.

  3. Chiral Analyses of Organic Compounds in Carbonaceous Meteorites

    NASA Technical Reports Server (NTRS)

    Pizzarello, Sandra

    2004-01-01

    Contents include the following: 1. Characterization of Tagish Lake organic content. The first two grant years were largely devoted to the molecular and isotopic analyses of Tagish Lake organic composition. This carbonaceous meteorite fell in Canada in the winter of the year 2000, and its exceptional atmospheric entry and subsequent recovery (e. g., the sample was recovered and stored by avoiding hand contact and above freezing temperatures) contributed in providing a rare and pristine extraterrestrial material. 2. Chiral analyses of Murchison and Murray soluble organics. One of the most intriguing finding in regard to soluble meteorite organics is the presence within the amino acid suite of some compounds displaying L-enantiomeric excesses. This configuration is exclusive in the amino acids of terrestrial proteins and the finding has raised speculations of a possible role of amino acids from meteorites in the origin of homochirality on the early Earth. The main objective for this NASA funding was the characterization of enantiomeric excesses in meteorites and we have conducted several studies toward establishing their distribution and indignity.

  4. Carbon-14 in lunar soil and in meteorites

    NASA Technical Reports Server (NTRS)

    Fireman, E. L.

    1978-01-01

    C-14 was measured in grain-size fractions of lunar soil 10084 and in samples of the Bruderheim chondrite and of several meteorites recently found in Antarctica (Allan Hills no. 5, 6, and 8). Temperature-release patterns were investigated. It was found that C-14 is released at temperatures below melting from small soil grains (less than 74 microns), but not from meteorites or from large soil grains. Below-melting C-14 contents increase with decreasing grain size in a manner similar to solar-wind-implanted rare-gas isotope contents (Eberhardt et al., 1970), whereas the C-14 released above melting temperatures is independent of grain size, suggesting that below-melting C-14 is solar-wind-implanted and above-melting C-14 is the result of cosmic ray spallations. The activity of C-14 in lunar samples is half that measured in the Bruderheim meteorite, which fell on May 4, 1970. No C-14 activity was observed in the Allan Hills chondrites; the C-14 limits suggest that these meteorites fell more than 25,000 years ago.

  5. Meteorite Associations and Source Regions for Potentially Hazardous Near-Earth Objects

    NASA Astrophysics Data System (ADS)

    Binzel, Richard P.; Vernazza, P.; Thomas, C. A.; DeMeo, F. E.; Bus, S. J.; Rivkin, A. S.; Tokunaga, A. T.

    2008-09-01

    We report results from Vernazza et al. (2008; Nature, August 14 issue) showing that 2/3 of all large near-Earth objects (NEOs), including the potentially hazardous asteroid (PHA) subset, have spectral characteristics consistent with laboratory measurements of LL-chondrite meteorites. Our NEO data (38 S- and Q-types) were obtained through a joint observational program (MIT, Hawaii, IRTF). Comparison meteorite data were obtained from the Brown University RELAB database. Our asteroid-meteorite comparative analysis was performed using quantitative measurements of spectral band centers and band area ratios and using a radiative transfer model for olivine (olv) and orthopyroxene (opx) (Shkuratov 1999; Icarus 137, 235). Most large NEOs (and the PHA subset) show relatively high olv/(olv+opx) ratios in the 70-85% range typical for LL-chondrites. Interestingly, relatively high olivine abundances are found among S-type asteroids in the inner main-belt Flora region (Gaffey 1984; Icarus 60, 38: Chapman 1996; MPS 31, 699) adjacent to the nu6 secular resonance. An LL chondrite association for most large (km-sized) NEOs and PHAs is surprising since LL chondrites are somewhat rare ( 8% of all meteorite falls). One possible explanation is Yarkovsky drift. Large objects (such as km-sized NEOs in our sample) experience relatively little Yarkovsky drift. In contrast, meter-sized objects (which dominate meteorite fall statistics) experience substantial Yarkovsky drift. Limited Yarkovsky drift therefore restricts the delivery of the largest NEOs to the most favorable source region(s), such as the nu6 resonance bordering the Flora region. Substantial Yarkovsky drift of meter-sized objects throughout the main belt allows meteorite fall statistics to sample from numerous main-belt resonances. Thus, meteorite falls sample throughout_the_asteroid_belt (not just the inner belt). Such a size-dependent efficiency therefore enhances the inner main belt as the source for large NEOs and PHAs

  6. Three basaltic earth-approaching asteroids and the source of the basaltic meteorites

    SciTech Connect

    Cruikshank, D.P.; Tholen, D.J.; Bell, J.F.; Hartmann, W.K.; Brown, R.H. Hawaii Univ., Honolulu Planetary Science Institute, Tucson, AZ JPL, Pasadena, CA )

    1991-01-01

    Diameters of 1.2, 1.0, and 3.4 km are respectively derived for the earth-approaching asteroids 1983 RD, 1980 PA, and 1985 DO2, whose spectra are virtually identical to that of the basaltic-surfaced large asteroid, Vesta. While probably not fragments of Vesta, the three asteroids may be fragments of one or more Vesta-like parent bodies; it is suggested that they may be fragments of the source body or bodies of the HED meteorites. While these asteroids regoliths have significant insulating properties, they differ from that of the moon in that lunar-like glasses and agglutinates are largely absent. It is noted that asteroids of this kind may have impacted the earth without leaving the chemical signatures associated with the K-T boundary event. 59 refs.

  7. Cohenite in meteorites: A proposed origin

    USGS Publications Warehouse

    Brett, R.

    1966-01-01

    Cohenite [(Fe, Ni)3C] is found almost exclusively in meteorites containing from 6 to 8 percent nickel (by weight). On the basis of iron-nickel-carbon phase diagrams at 1 atmosphere and of kinetic data, the occurrence of cohenite within this narrow composition range as a low-pressure metastable phase and the nonoccurrence of cohenite in meteorites outside the range 6 to 8 percent nickel can be explained. Cohenite formed in meteorites containing less than 6 to 8 percent nickel decomposed to metal and graphite during cooling; it cannot form in meteorites containing more than about 8 percent. The presence of cohenite in meteorites cannot be used as an indicator of pressure of formation. However, the absence of cohenite in meteorites containing the assemblage, metal plus graphite, requires low pressures during cooling.

  8. The Meteoritical Bulletin, No. 82, 1998 July

    USGS Publications Warehouse

    Grossman, J.N.

    1998-01-01

    Meteoritical Bulletin No. 82 lists information for 974 new meteorites, including 521 finds from Antarctica, 401 finds from the Sahara, 21 finds from the Nullarbor region of Australia, and 7 falls (Ban Rong Du, Burnwell, Fermo, Jalanash, Juancheng, Monahans (1998), and Silao). Many rare types of meteorites are reported: counting pairing groups as one, these include one CR chondrite, two CK chondrites, two CO chondrites, four CV chondrites, one CH chondrite or Bencubbin-like, six C2 (unclassified) chondrites, two EH chondrites, two EL chondrites, three R chondrites, thirty unequilibrated ordinary chondrites, one ungrouped chondrite, three eucrites, six howardites, one diogenite, eleven ureilites, nine iron meteorites, one mesosiderite, two brachinites, one lodranite, one winonaite, and two lunar meteorites (Dar al Gani 400 and EET 96008). All italicized abbreviations refer to addresses tabulated at the end of this document. ?? Meteoritical Society, 1998.

  9. Chlorine Abundances in Martian Meteorites

    NASA Technical Reports Server (NTRS)

    Bogard, D.D.; Garrison, D.H.; Park, J.

    2009-01-01

    Chlorine measurements made in martian surface rocks by robotic spacecraft typically give Chlorine (Cl) abundances of approximately 0.1-0.8%. In contrast, Cl abundances in martian meteorites appear lower, although data is limited, and martian nakhlites were also subjected to Cl contamination by Mars surface brines. Chlorine abundances reported by one lab for whole rock (WR) samples of Shergotty, ALH77005, and EET79001 range 108-14 ppm, whereas Cl in nakhlites range 73-1900 ppm. Measurements of Cl in various martian weathering phases of nakhlites varied 0.04-4.7% and reveal significant concentration of Cl by martian brines Martian meteorites contain much lower Chlorine than those measured in martian surface rocks and give further confirmation that Cl in these surface rocks was introduced by brines and weathering. It has been argued that Cl is twice as effective as water in lowering the melting point and promoting melting at shallower martian depths, and that significant Cl in the shergottite source region would negate any need for significant water. However, this conclusion was based on experiments that utilized Cl concentrations more analogous to martian surface rocks than to shergottite meteorites, and may not be applicable to shergottites.

  10. Cosmogenic records in Antarctic meteorites

    NASA Technical Reports Server (NTRS)

    Goswami, J. N.; Nishiizumi, K.

    1983-01-01

    Aliquot samples of 29 Antarctic L and H chondrites are analyzed for their nuclear track records and Mn-53 activities. The track density in the analyzed samples ranges from 10 to the 4th to approximately 6 x 10 to the 6th per sq cm. A significant finding is the observation of track-rich grains in a set of four L3 chondrites (ALHA 77215, 77216, 77217, and 77252), suspected of belonging to the same fall based on petrographic observations. An additional sample, ALHA 78105, an L6 chondrite, also has track-rich grains. Mn-53 activity is at near saturation level in approximately 65 percent of the analyzed samples, suggesting exposure ages of greater than 10 m.y. in these cases. Very few H chondrites from the 7-m.y. exposure age peak are apparently sampled among the ones investigated in this study. Approximately 6 percent and 4 percent, respectively, of the Antarctic H and L chondrites analyzed thus far for their cosmogenic records have precompaction irradiation features. A combined analysis of Mn-53 and nuclear track data makes it possible to confirm or rule out the proposed pairing of several sets of Antarctic meteorites and to estimate the preatmospheric sizes of some of these meteorites. The results suggest that most of the small Antarctic meteorites (less than 1 kg) have suffered high (greater than 95 percent) ablation mass-loss.

  11. Electrical conductivity of chondritic meteorites

    NASA Technical Reports Server (NTRS)

    Duba, AL; Didwall, E. M.; Burke, G. J.; Sonett, C. P.

    1987-01-01

    The electrical conductivity of samples of the Murchison and Allende carbonaceous chondrites is 4 to 6 orders of magnitude greater than rock forming minerals such as olivine for temperatures up to 700 C. The remarkably high electrical conductivity of these meteorites is attributed to carbon at the grain boundaries. Much of this carbon is produced by pyrolyzation of hydrocarbons at temperatures in excess of 150 C. As the temperature increases, light hydrocarbons are driven off and a carbon-rich residue or char migrates to the grain boundaries enhancing electrical conductivity. Assuming that carbon was present at the grain boundaries in the material which comprised the meteorite parent bodies, the electrical heating of such bodies was calculated as a function of body size and solar distance during a hypothetical T-Tauri phase of the sun. Input conductivity data for the meteorite parent body were the present carbonaceous chondrite values for temperatures up to 840 C and the electrical conductivity values for olivine above 840 C.

  12. Meteoritic material on the moon

    NASA Technical Reports Server (NTRS)

    Morgan, J. W.; Ganapathy, R.; Higuchi, H.; Anders, E.

    1977-01-01

    Three types of meteoritic material are found on the moon: micrometeorites, ancient planetesimal debris from the "early intense bombardment," and debris of recent, craterforming projectiles. Their amounts and compositions have been determined from trace element studies. The micrometeorite component is uniformly distributed over the entire lunar surface, but is seen most clearly in mare soils. It has a primitive, C1-chondrite-like composition, and comprises 1 to 1.5 percent of mature soils. Apparently it represents cometary debris. The ancient component is seen in highland breccias and soils. Six varieties have been recognized, differing in their proportions of refractories (Ir, Re), volatiles (Ge, Sb), and Au. All have a fractionated composition, with volatiles depleted relative to siderophiles. The abundance patterns do not match those of the known meteorite classes. These ancient meteoritic components seem to represent the debris of an extinct population of bodies (planetisimals, moonlets) that produced the mare basins during the first 700 Myr of the moon's history. On the basis of their stratigraphy and geographic distribution, five of the six groups are tentatively assigned to specific mare basins: Imbrium, Serenitatis, Crisium, Nectaris, and Humorum or Nubium.

  13. The circular Uneged Uul structure (East Gobi Basin, Mongolia) - Geomorphic and structural evidence for meteorite impact into an unconsolidated coarse-clastic target?

    NASA Astrophysics Data System (ADS)

    Schmieder, Martin; Seyfried, Hartmut; Gerel, Ochir

    2013-03-01

    geomorphic and structural features resembling those at some eroded complex impact structures on Earth. Morphologically similar central peaks are observed at the Spider and Matt Wilson impact structures in Australia; the central annular ridge reminds of that at Gosses Bluff in Australia; the outer domal ridges might correspond to ring-like features as known from Tin Bider in Algeria. We, therefore, cautiously propose that an impact may have produced the Uneged Uul feature causing structural uplift (˜1000 m) of basement rocks at its center. So far, no convincing evidence for shock metamorphism could be proven by field work and petrographic analyses. However, it is likely that at the time of the deformation event the unconsolidated conglomerates were highly porous and possibly immersed in groundwater buffering the propagation of sudden stress-reducing deformation. Further studies will be in order to unravel the nature of the Uneged Uul structure, which should be considered a promising possible impact structure.

  14. Alteration of Sedimentary Clasts in Martian Meteorite Northwest Africa 7034

    NASA Technical Reports Server (NTRS)

    McCubbin, F. M.; Tartese, R.; Santos, A. R.; Domokos, G.; Muttik, N.; Szabo, T.; Vazquez, J.; Boyce, J. W.; Keller, L. P.; Jerolmack, D. J.; Anand, M.; Moser, D. E.; Delhaye, T.; Shearer, C. K.; Agee, C. B.

    2014-01-01

    The martian meteorite Northwest Africa (NWA) 7034 and pairings represent the first brecciated hand sample available for study from the martian surface [1]. Detailed investigations of NWA 7034 have revealed substantial lithologic diversity among the clasts [2-3], making NWA 7034 a polymict breccia. NWA 7034 consists of igneous clasts, impact-melt clasts, and "sedimentary" clasts represented by prior generations of brecciated material. In the present study we conduct a detailed textural and geochemical analysis of the sedimentary clasts.

  15. Hydrocode Models of Large Impacts into a Noachian Martian Surface: Initial Results

    NASA Astrophysics Data System (ADS)

    Plesko, C. S.; Coker, R. F.; Wohletz, K. H.; Asphaug, E.; Korycansky, D. G.

    2008-03-01

    Segura proposed large impacts 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 impacts capable of causing global effects, and regional effects of smaller impacts.

  16. Operational Impacts of Large Deployments of Offshore Wind (Poster)

    SciTech Connect

    Ibanez, E.; Heaney, M.

    2014-10-01

    The potential operational impact 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.

  17. Electron-impact ionization of helium with large energy transfer

    SciTech Connect

    Bray, I.; Fursa, D. V.; Stelbovics, A. T.

    2006-09-15

    We consider the recently measured case of 730 eV electron-impact ionization of the ground state of helium with 205 and 500 eV coplanar outgoing electrons by Catoire et al. [J. Phys. B 39, 2827 (2006)]. These measurements, which are on a relative scale, show some unexpected structure and variation from the second-order distorted-wave Born approximation R-matrix and Brauner-Briggs-Klar theories. Using the convergent close-coupling method we provide an improved agreement with experiment, but some discrepancies still remain.

  18. Lunar magnetization concentrations (MAGCONS) antipodal to young large impact basins

    NASA Technical Reports Server (NTRS)

    Lin, R. P.; Anderson, K. A.; Hood, L. L.

    1987-01-01

    Electron reflection measurements from Apollo 15 and 16 subsatellites show that patches of strong surface magnetic fields ranging in size from less than about 7 km to greater than 500 km are distributed over the surface of the Moon. With the exception of a few regions, no obvious association to surface geology has been found. Researchers examined the antipodes of 23 winged impact basins for which electron reflection measurements are available. It was concluded that the apparent temporal variations for the basin antipodes may reflect real variations in the lunar magnetic field.

  19. Molecular Isotopic Characterization of the ALH 85013.50 Meteorite: Defining the Extraterrestrial Organic Compounds

    NASA Technical Reports Server (NTRS)

    Fuller, M.; Huang, Y.

    2003-01-01

    The Antarctic Meteorite Program has returned over 16,000 meteorites from the ice sheets of the Antarctic. This more than doubles the number of preexisting meteorite collection and adds important and rare specimens to the assemblage. The CM carbonaceous chondrites are of particular interest because of their high organic component. The Antarctic carbonaceous chondrites provide a large, previously uninvestigated suite of meteorites. Of the 161 CM chondrites listed in the Catalogue of Meteorites 138 of them have been recovered from the Antarctic ice sheets,. However, these meteorites have typically been exposed to Earth s conditions for long periods of time. The extent of terrestrial organic contamination and weathering that has taken place on these carbonaceous chondrites is unknown. In the past, stable isotope analysis was used to identify bulk organics that were extraterrestrial in origin. Although useful, this method could not exclude the possibility of terrestrial contamination contributing to the isotopic measurement. Compound specific isotope analysis of organic meteorite material has provided the opportunity to discern the terrestrial contamination from extraterrestrial organic compounds on the molecular level.

  20. Oxygen isotope relationships in iron meteorites

    NASA Technical Reports Server (NTRS)

    Clayton, R. N.; Mayeda, T. K.; Olsen, E. J.; Prinz, M.

    1983-01-01

    Iron meteorites with oxygen-bearing phases can be classified in terms of their oxygen isotopic abundances. These iron meteorite classes are isotopically similar to various stony meteorite classes, which may indicate a common origin. The group IAB and IIICD irons may be related to the winonaites; group IIE irons may be related to H chondrites; group IVA irons may be related to L or LL chondrites.