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Sample records for meteorite parent bodies

  1. Meteorites and their parent bodies: Evidence from oxygen isotopes

    NASA Technical Reports Server (NTRS)

    Clayton, R. N.

    1978-01-01

    Isotopic abundance variations among meteorites are used to establish genetic associations between meteorite classes. Oxygen isotope distributions between group II E irons with H-group ordinary chondrites and enstatic meteorites indicate that the parent bodies were formed out of pre-solar material that was not fully mixed at the time condensation occurred within the solar nebula.

  2. 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

  3. 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

  4. 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.

  5. Fractionation and Accretion of Meteorite Parent Bodies

    NASA Technical Reports Server (NTRS)

    Weidenschilling, Stuart J.

    2005-01-01

    Senior Scientist Stuart J. Weidenschilling presents his final administrative report for the research program on which he was the Principal Investigator. The research program resulted in the following publications: 1) Particle-gas dynamics and primary accretion. J. N. Cuzzi and S. J . Weidenschilling. To appear in Meteorites and the Early Solar System 11 (D. Lauretta et a]., Eds.), Univ. Arizona Press. 2005; 2) Timescales of the solar protoplanetary disk. S. Russell, L. Hartmann, J . N. Cuzzi, A. Krot, M. Gounelle and S. J. Weidenschilling. To appear in Meteorites and the Early Solar System II (D. Lauretta et al., Eds.), Univ. Arizona Press, 2005; 3) Nebula evolution of thermally processed solids: Reconciling astrophysical models and chondritic meteorites. J. N. Cuzzi, F. J. Ciesla, M. I. Petaev, A. N. Krot, E. R. D. Scott and S . J. Weidenschilling. To appear in Chondrites and the Protoplanetary Disk (A. Krot et a]., Eds.), ASP Conference Series, 2005; 4) Possible chondrule formation in planetesimal bow shocks: Physical processes in the near vicinity of the planetesimal. L. L. Hood, F. J. Ciesla and S. J. Weidenschilling. To appear in Chondrites and the Protoplanetary Disk (A. Krot et al., Eds.), ASP Conference Series, 2005; 5) From icy grains to comets. In Comets II (M. Festou et al., Eds.), Univ. Arizona Press, pp. 97- 104, 2005; 6) Evaluating planetesimal bow shocks as sites for chondrule formation. F. J . Ciesla, L. L. Hood and S. J. Weidenschilling. Meteoritics & Planetary Science 39, 1809-1 821, 2004; and 7) Radial drift of particles in the solar nebula: Implications for planetesimal formation. Icarus 165, 438-442, 2003.

  6. Chondritic Meteorites: Nebular and Parent-Body Formation Process

    NASA Technical Reports Server (NTRS)

    Rubin, Alan E.

    1997-01-01

    Chondritic meteorites are the products of condensation, agglomeration and accretion of material in the solar nebula; these objects are the best sources of information regarding processes occurring during the early history of the solar system. We obtain large amounts of high-quality chemical and petrographic data and use them to infer chemical fractionation processes that occurred in the solar nebula and on meteorite parent bodies during thermal metamorphism, shock metamorphism and aqueous alteration. We compare diverse groups of chondrites and model their different properties in terms of processes that differed at different nebular locations or on different parent-bodies. In order to expand our set of geochemically important elements (particularly Si, C, P and S) and to distinguish the different oxidation states of Fe, Greg Kallemeyn spent three months (1 Sept. - 30 Nov. 1995) at the Smithsonian Institution to learn Eugene Jarosewich's wet chemical techniques. Key specimens from the recently established CK, CR and R chondrite groups were analyzed.

  7. Metal-rich meteorites from the aubrite parent body

    NASA Technical Reports Server (NTRS)

    Casanova, I.; Mccoy, T. J.; Keil, K.

    1993-01-01

    Three metal-rich meteorites - Mt. Egerton, Horse Creek, and LEW 88055 - were studied and it is suggested that they formed in the aubrite parent body. LEW 85369 and 88631 may also have a common origin, but these rocks have not yet been studied in detail. This body was probably heated to about 1600 C by a very strong heat source. While molten, metal agglomerated into sizeable nodules which never segregated efficiently to form a core, but were trapped in the silicate mantle. Different clasts and lithologies in aubrites solidified and cooled under local equilibrium conditions of oxygen fugacity, and with different thermal histories. Impacts mixed clasts from throughout the parent body, creating the typical aubrite breccias.

  8. Chondritic Meteorites: Nebular and Parent-Body Formation Processes

    NASA Technical Reports Server (NTRS)

    Rubin, Alan E.; Lindstrom, David (Technical Monitor)

    2002-01-01

    It is important to identify features in chondrites that formed as a result of parent-body modification in order to disentangle nebular and asteroidal processes. However, this task is difficult because unmetamorphosed chondritic meteorites are mixtures of diverse components including various types of chondrules, chondrule fragments, refractory and mafic inclusions, metal-sulfide grains and fine-grained matrix material. Shocked chondrites can contain melt pockets, silicate-darkened material, metal veins, silicate melt veins, and impact-melt-rock clasts. This grant paid for several studies that went far in helping to distinguish primitive nebular features from those produced during asteroidal modification processes.

  9. Nature and evolution of the meteorite parent bodies: Evidence from petrology and metallurgy

    NASA Technical Reports Server (NTRS)

    Wood, J. A.

    1978-01-01

    The physical as well as chemical properties of the meteorite parent bodies are reviewed and it is concluded that many differentiated meteorites were likely formed in asteroidal-sized parents. A new model is developed for the formation of pallasites at the interface between an iron core and olivine mantle in differentiated bodies only about 10 km in diameter, which are later incorporated into a second generation of larger (100 km) parent bodies.

  10. Aqueous alteration of meteorite parent bodies: Possible role of unfrozen water and the Antarctic meteorite analogy

    NASA Technical Reports Server (NTRS)

    Gooding, J. L.

    1984-01-01

    Based on oxygen isotrophy the alteration of CM2 chondrites could occur at or near O C (273 K). Such a scenario can be understood if C chondrite parent bodies evolved as rock/ice mixtures that contained unfrozen (mobile or quasi-liquid below 273K) pure water, a well known phenomenon in cold soils on Earth. The importance of unfrozen water diagenesis in C chondrite history can be tested by a combined program of experimental simulations and petrologic study of analogous features developed by weathering of meteorites in or an Antarctic ice.

  11. 39Ar-40Ar Dating of Thermal Events on Meteorite Parent Bodies

    NASA Astrophysics Data System (ADS)

    Bogard, D. D.; Garrison, D. H.

    1999-03-01

    A summary of 39Ar-40Ar ages reveals the impact and thermal history of several meteorite parent bodies, i.e., eucrites, chondrites, mesosiderites, acapulcoites/lodranites, winonaites, enstatites, and IAB and IIE irons.

  12. Meteoritic parent bodies - Nature, number, size and relation to present-day asteroids

    NASA Technical Reports Server (NTRS)

    Lipschutz, Michael E.; Gaffey, Michael J.; Pellas, Paul

    1989-01-01

    The relationship between meteoritic parent bodies and the present-day asteroids is discussed. Results on oxygen isotopic signatures and chemical distinctions among meteorite classes indicate that meteorites derive from a small number of parent bodies relative to the number of asteroids. The spectral properties of the ordinary chondrites and similar inclusions in meteoritic breccias differ from those of the abundant S asteroids (with no process known that can account for these differences); the closest spectral analogs of these chondrites are the rare near-earth Q-type asteroids. These facts lead to the question of why abundant meteorites have rare asteroidal analogs, while the abundant asteroids have rare meteoritic analogs. This question constitutes a prime topic for future studies.

  13. Thermal metamorphism of primitive meteorites. XI - The enstatite meteorites: Origin and evolution of a parent body

    NASA Technical Reports Server (NTRS)

    Biswas, S.; Walsh, T.; Bart, G.; Lipschutz, M. E.

    1980-01-01

    The neutron activation data for Ag, As, Bi, Cd, Co, Cs, Cu, Ga, In, Rb, Se, Te, Tl, and Zn were obtained in samples of Abee heated to 1000-1400 C at low pressures. In addition, these elements were reported in nine enstatite achondrites and in the silicate part of the Mt. Egerton stony-iron. The data show trace element losses above 1000 C by diffusion-controlled processes with apparent activation energies of 8 to 55 kcal/mol; these data together with abundances of aubrites, Mt. Egerton, and E4-6 chondrites, and isotopic results link all enstatite meteorites to a common parent body. The data also indicate that aubrites and the Mt. Egerton material reflect fractional crystallization of a magma produced from enstatite chondrite-like parent material (E6) and the late introduction of chalcophiles and mobile elements transported by an FeS-Fe eutectic from an E4-6 region undergoing open-system metamorphism.

  14. CAIs in CO3 Meteorites: Parent Body or Nebular Alteration?

    NASA Astrophysics Data System (ADS)

    Greenwood, R. C.; Hutchison, R.; Huss, G. R.; Hutcheon, I. D.

    1992-07-01

    It is widely held that alteration of Ca Al-rich inclusions (CAIs) in CV3 and CO3 meteorites occurred in the nebula (Hashimoto 1992). The CO3 chondrites, however, appear to define a metamorphic sequence dominated by parent body, and not nebular, metamorphic effects (Scott and Jones, 1990). To investigate the effects of metamorphism on CAIs we have studied inclusions from 4 CO chondrites: Colony (3.0), Felix (3.2), Lance (3.4), and Warrenton (3.6). In a section of Colony (74 mm^2) 81 CAIs, 30-870 micrometers long, comprise 52 nodular spinel-rich inclusions (fragments of Type-A CAI composed largely of spinel), 12 spinel-pyroxene inclusions, 10 melilite-rich inclusions, 2 hibonite-only inclusions, 2 CaAl4O7-bearing inclusions, and 3 spinel-pyroxene- olivine inclusions. Although a find, CAIs in Colony are relatively fresh, melilite in particular being little altered. In 79% of the spinel-bearing inclusions, spinel has <2wt% FeO, which otherwise ranges to 34.8%. Mg isotopic compositions were determined in 5 selected Colony inclusion; evidence of ^26Mg* from decay of ^26Al was found in 4 CAI. A hibonite-only inclusion has the largest ^26Mg* excess, delta^26Mg 32o/oo. Data show no evidence of isotopic disturbance and define a linear array with slope ^26Mg* /^27Al = (3.4+- 0.6) x 10^-5, like that obtained by Davis and Hinton (1986) in a hibonite-bearing spherule from Ornans. Despite Al/Mg ratios of up to 1500, CaAl4O7 in one inclusion shows no evidence of ^26Mg*; ^26Mg* < 4 x 10^-6. All three melilite-bearing inclusions from Colony C21 (angstrom k(sub)8.3-14.3), C56 (angstrom k(sub)10.5-16) and C62 (angstrom k(sub)15-21) show evidence of radiogenic ^26Mg*. Excess ^26Mg positively correlates with the Al/Mg ratios but the data do not define a unique initial value of ^26Al/^27Al. Data for melilite in C21, in particular, show evidence for disturbance of the Al-Mg system, as is common for Allende CAI (Podosek et al. 1991). Melilites in C56 in contrast show no evidence of

  15. Nature’s Starships. II. Simulating the Synthesis of Amino Acids in Meteorite Parent Bodies

    NASA Astrophysics Data System (ADS)

    Cobb, Alyssa K.; Pudritz, Ralph E.; Pearce, Ben K. D.

    2015-08-01

    Carbonaceous chondrite meteorites are known for having high water and organic material contents, including amino acids. Here we address the origin of amino acids in the warm interiors of their parent bodies (planetesimals) within a few million years of their formation, and we connect this with the astrochemistry of their natal protostellar disks. We compute both the total amino acid abundance pattern and the relative frequencies of amino acids within the CM2 (e.g., Murchison) and CR2 chondrite subclasses based on Strecker reactions within these bodies. We match the relative frequencies to well within an order of magnitude among both CM2 and CR2 meteorites for parent body temperatures <200°C. These temperatures agree with 3D models of young planetesimal interiors. We find theoretical abundances of approximately 7 × 105 parts per billion, which is in agreement with the average observed abundance in CR2 meteorites of (4 ± 7) × 105, but an order of magnitude higher than the average observed abundance in CM2 meteorites of (2 ± 2) × 104. We find that the production of hydroxy acids could be favored over the production of amino acids within certain meteorite parent bodies (e.g., CI1, CM2) but not others (e.g., CR2). This could be due to the relatively lower NH3 abundances within CI1 and CM2 meteorite parent bodies, which leads to less amino acid synthesis. We also find that the water content in planetesimals is likely to be the main cause of variance between carbonaceous chondrites of the same subclass. We propose that amino acid abundances are primarily dependent on the ammonia and water content of planetesimals that are formed in chemically distinct regions within their natal protostellar disks.

  16. Paleo-Magnetic Field Recorded in the Parent Body of the Murchison Meteorite

    NASA Astrophysics Data System (ADS)

    Kletetschka, G.; Páchová, H.

    2014-12-01

    Murchison meteorite is a carbonaceous chondrite containing small amount of chondrules, various inclusions, and matrix with occasional porphyroblasts of olivine and/or pyroxene. We applied magnetic efficiency method (Kletetschka et al 2005, Kohout et al, 2008) in order to get the demagnetization spectra for several randomly oriented fragments of Murchison meteorite. Our method detected not only viscous magnetization removable in low fields, but also very persistent magnetizations in all meterorite fragments. Data suggest that magnetic carriers within the Murchison meteorite were grown in a paleofield of 450 - 850 nT. Meteorite record in other fragments contains an existence of antipodal fields that may be tied to an event of magnetic reversal within the nebular magnetic field or parent asteroid body. Other meteorites show stable record over its entire spectrum, giving magnetic paleofield of 1100 - 1900 nT. Magnetic record in Murchison meteorite comes from magnetite, pyrrhotite and Iron Nickel alloy. Pyrrhotite is suggested to be the main carrier of the paleofield in Murchison. Iron-Nickel alloy generate observable zigzag pattern when magnetically saturated. Kletetschka, G., Kohout, T., Wasilewski, P., and Fuller, M. D., 2005, Recognition of thermal remanent magnetization in rocks and meteorites, The IAGA Scientific Assembly, Volume GAI10: Toulouse, IAGA, p. IAGA2005-A-00945. Kohout, T., Kletetschka, G., Donadini, F., Fuller, M., and Herrero-Bervera, E., 2008, Analysis of the natural remanent magnetization of rocks by measuring the efficiency ratio through alternating field demagnetization spectra: Studia Geophysica Et Geodaetica, v. 52, no. 2, p. 225-235.

  17. Parent Body Influences on Amino Acids in the Tagish Lake Meteorite

    NASA Technical Reports Server (NTRS)

    Glavin, D. P.; Callahan, M. P.; Dworkin, J. P.; Elsila, J. E.; Herd, C. D. K.

    2010-01-01

    The Tagish Lake meteorite is a primitive C2 carbonaceous chondrite with a mineralogy, oxygen isotope, and bulk chemical. However, in contrast to many CI and CM carbonaceous chondrites, the Tagish Lake meteorite was reported to have only trace levels of indigenous amino acids, with evidence for terrestrial L-amino acid contamination from the Tagish Lake meltwater. The lack of indigenous amino acids in Tagish Lake suggested that they were either destroyed during parent body alteration processes and/or the Tagish Lake meteorite originated on a chemically distinct parent body from CI and CM meteorites where formation of amino acids was less favorable. We recently measured the amino acid composition of three different lithologies (11h, 5b, and 11i) of pristine Tagish Lake meteorite fragments that represent a range of progressive aqueous alteration in order 11h < 5b < 11i as inferred from the mineralogy, petrology, bulk isotopes, and insoluble organic matter structure. The distribution and enantiomeric abundances of the one- to six-carbon aliphatic amino acids found in hot-water extracts of the Tagish Lake fragments were determined by ultra performance liquid chromatography fluorescence detection and time of flight mass spectrometry coupled with OPA/NAC derivatization. Stable carbon isotope analyses of the most abundant amino acids in 11h were measured with gas chromatography coupled with quadrupole mass spectrometry and isotope ratio mass spectrometry.

  18. Mineralogy, Petrology, Chronology, and Exposure History of the Chelyabinsk Meteorite and Parent Body

    NASA Technical Reports Server (NTRS)

    Righter, K.; Abell, P.; Agresti, D.; Berger, E. L.; Burton, A. S.; Delaney, J. S.; Fries, M. D.; Gibson, E. K.; Harrington, R.; Herzog, G. F.; Keller, L. P.; Locke, D.; Lindsay, F.; McCoy, T. J.; Morris, R. V.; Nagao, K.; Nakamura-Messenger, K.; Niles, P. B.; Nyquist, L.; Park, J.; Peng, Z. X.; Shih, C. Y.; Simon, J. I.; Swisher, C. C., III; Tappa, M.

    2015-01-01

    The Chelyabinsk meteorite fall on February 15, 2013 attracted much more attention worldwide than do most falls. A consortium led by JSC received 3 masses of Chelyabinsk (Chel-101, -102, -103) that were collected shortly after the fall and handled with care to minimize contamination. Initial studies were reported in 2013; we have studied these samples with a wide range of analytical techniques to better understand the mineralogy, petrology, chronology and exposure history of the Chelyabinsk parent body.

  19. A Petrologic Study of the IAB Iron Meteorites: Constraints on the Formation of the IAB-Winonaite Parent Body

    NASA Technical Reports Server (NTRS)

    Benedix, G. K.; McCoy, T. J.; Keil, K.; Love, S. G.

    1998-01-01

    We have studied IAB iron meteorites and their silicate-bearing inclusions to elucidate the origin of their parent body. We have divided IAB irons into five categories which best describe the inclusions and other properties of the irons.

  20. Electrical conductivity of carbonaceous chondrites and electric heating of meteorite parent bodies

    NASA Technical Reports Server (NTRS)

    Duba, AL

    1987-01-01

    Electromagnetic heating of rock-forming materials most probably was an important process in the early history of the solar system. Electrical conductivity experiments of representative materials such as carbonaceous chondrites are necessary to obtain data for use in electromagnetic heating models. With the assumption that carbon was present at grain boundaries in the material that comprised the meteorite parent bodies, the electrical heating of such bodies was calculated as a function of body size and solar distance using the T-Tauri model of Sonett and Herbert (1977). The results are discussed.

  1. Chronology and petrology of silicates from IIE iron meteorites: evidence of a complex parent body evolution

    NASA Astrophysics Data System (ADS)

    Bogard, Donald D.; Garrison, Daniel H.; McCoy, Timothy J.

    2000-06-01

    IIE iron meteorites contain silicate inclusions the characteristics of which suggest a parent body similar to that of H-chondrites. However, these silicates show a wide range of alteration, ranging from Netschaëvo and Techado, the inclusions of which are little altered, to highly differentiated silicates like those in Kodaikanal, Weekeroo Station, and Colomera, which have lost metal and sulfur and are enriched in feldspar. We find these inclusions to show varying degrees of shock alteration. We made 39Ar- 40Ar age determinations of Watson, Techado, Miles, Colomera, and Sombrerete. Watson has an Ar-Ar age of 3.677 ± 0.007 Gyr, similar to previously reported ages for Kodaikanal and Netschaëvo. We suggest that the various determined radiometric ages of these three meteorites were probably reset by a common impact event. The space exposure ages for these three meteorites are also similar to each other and are considerably younger than exposure ages of other IIEs. 39Ar- 40Ar ages inferred for the other four meteorites analyzed are considerably older than Watson and are: Techado = 4.49 ± 0.01 Gyr, Miles = 4.405 ± 0.012 Gyr, Colomera = 4.470 ± 0.010 Gyr, and Sombrerete = 4.541 ± 0.0012 Gyr. These ages are in fair agreement with previously reported Rb-Sr isochron ages for Colomera and Weekeroo Station. Although several mechanisms to form IIE meteorites have been suggested, it is not obvious that a single mechanism could produce a suite of meteorites with very different degrees of silicate differentiation and with isotopic ages that differ by >0.8 Gyr. We suggest that those IIEs with older isotopic ages are a product of partial melting and differentiation within the parent body, followed by mixing of silicate and metal while both were relatively hot. Netschaëvo and Watson may have formed by this same process or by impact mixing ˜4.5 Gyr ago, but their isotopic ages may have been subsequently reset by shock heating. Kodaikanal apparently is required to have formed

  2. Chronology and Petrology of Silicates From IIE Iron Meteorites: Evidence of a Complex Parent Body Evolution

    NASA Technical Reports Server (NTRS)

    Bogard, Donald D.; Garrison, Daniel H.; McCoy, Timothy J.

    1999-01-01

    IIE iron meteorites contain silicate inclusions whose characteristics suggest a parent body similar to that of H-chondrites. However, these silicates show a wide range of alteration, ranging from Netschadvo and Techado, whose inclusions are little altered. to highly differentiated silicates like-those in Kodaikanal, Weekeroo Station and Colomera, which have lost metal and sulfur and are enriched in feldspar. We find these inclusions to show varying degrees of shock alteration. Because only a limited amount of data on - isotopic ages of HE silicates were available, we made Ar-39 - Ar-40 age determinations of Watson, Techado, miles Colomera, and Sombrerete. Watson has an Ar-Ar age of 3.653 +/- 0.012 Gyr, similar to previously reported ages for Kodaikanal and Netschadvo. We suggest that the various determined radiometric ages of these three meteorites were probably reset by a common impact event. The space exposure ages for these three meteorites are also similar to each other and are considerably younger than exposure ages of other IIEs. Ar-39 - Ar-40 ages inferred for the other four meteorites analyzed are considerably older than Watson and are: Techado =4.49 +/- 0.01 Gyr, Miles =4.412 +/- 0.016 Gyr, Colomera =4.469 +/- 0.012 Gyr, and Sombrerete =4.535 +/- 0.005 Gyr. These ages are in fair agreement with previously reported Rb-Sr isochron ages for Colomera and Weekeroo Station. Although several mechanisms to form HE meteorites previously were suggested, it is not obvious that a single mechanism could produce a suite of meteorites with very different degrees of silicate differentiation and with isotopic ages that differ by >0.8 Gyr. We suggest that those IIEs with older isotopic ages are a product of partial melting and differentiation within the parent body, followed by mixing of silicate and metal while both were relatively hot. Netschadvo and Watson may have formed by this same process or by impact mixing about 4.5 Gyr ago, but their isotopic ages were

  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 asteroid-meteorite connection: Forging a new link to Vesta as the parent body of basaltic achondrite (HED) meteorites

    NASA Technical Reports Server (NTRS)

    Binzel, R. P.

    1993-01-01

    Asteroid 4 Vesta has been at the center of the debate over the identity of the howardite eucrite diogenite (HED) parent body since the early 1970s. Despite its unique (among the 500 largest asteroids) compositional match to HED meteorites, substantial dynamical difficulties in delivering fragments from Vesta to the Earth have precluded any conclusive HED parent body link. These dynamical difficulties arise because Vesta's orbital location is far from known resonances. Consequently, it has been argued as dynamically improbable that meteoroid-sized (1 km) fragments could be excavated from Vesta with sufficient velocities to reach the resonances. Through new astronomical observations, numerous small (4-7 km) asteroids between Vesta and the 3:1 resonance have been discovered to have eucrite and diogenite compositions. Based on similar orbital elements to Vesta, all of these new asteroids are likely large impact fragments excavated from Vesta. Their current orbits imply ejection velocities in excess of 700 m/sec. Smaller (1 km) fragments can therefore be expected to have been ejected with velocities greater than 1 km/sec, sufficient to reach the 3:1 and v6 resonances. Thus it now appears to be dynamically viable for Vesta to be linked as the HED parent body.

  5. Comets as Parent Bodies of CI1 Carbonaceous Meteorites and Possible Habitats of Ice-Microbiota

    NASA Technical Reports Server (NTRS)

    Wickramasinghe, N. Chandra; Wallis, Daryl H.; Rozanov, Alexei Yu.; Hoover, Richard B.

    2011-01-01

    Recent studies of comets and cometary dust have confirmed the presence of biologically relevant organic molecules along with clay minerals and water ice. It is also now well established by deuterium/hydrogen ratios that the CI1 carbonaceous meteorites contain indigenous extraterrestrial water. The evidence of extensive aqueous alteration of the minerals in these meteorites led to the hypothesis that water-bearing asteroids or comets represent the parent bodies of the CI1 (and perhaps CM2) carbonaceous meteorites. These meteorites have also been shown to possess a diverse array of complex organics and chiral and morphological biomarkers. Stable isotope studies by numerous independent investigators have conclusively established that the complex organics found in these meteorites are both indigenous and extraterrestrial in nature. Although the origin of these organics is still unknown, some researchers have suggested that they originated by unknown abiotic mechanisms and may have played a role in the delivery of chiral biomolecules and the origin of life on Early Earth. In this paper we review these results and investigate the thermal history of comets. We show that permanent as well as transient domains of liquid water can be maintained on a comet under a plausible set of assumptions. With each perihelion passage of a comet volatiles are preferentially released, and during millions of such passages the comet could shed crustal debris that may survive transit through the Earth s atmosphere as a carbonaceous meteorite. We review the current state of knowledge of comets and carbonaceous meteorites. We also present the results of recent studies on the long-term viability of terrestrial ice-microbiota encased in ancient glacial ice and permafrost. We suggest that the conditions which have been observed to prevail on many comets do not preclude either survivability (or even the active metabolism and growth) of many types of eukaryotic and prokaryotic microbial

  6. Processing of refractory meteorite inclusions (CAIs) in parent-body atmospheres

    NASA Technical Reports Server (NTRS)

    Podolak, Morris; Bunch, T. E.; Cassen, Pat; Reynolds, Ray T.; Chang, S.

    1990-01-01

    Ca-Al-rich inclusions (CAIs) in refractory meteorites are shown to have been subject to partial melting during a suitably high gas density/small scale height regime arising during gasdynamic deceleration in a temporary atmosphere around an accreting parent body. The presence of dust in such an atmosphere would have increased the pressure gradient with height, lowering the boiloff rate, and permitting dust particles to become trapped in the partially melted material. CAIs may therefore be studied as probes of a primitive atmosphere.

  7. Rapid accretion and differentiation of iron meteorite parent bodies inferred from 182Hf-182W chronometry and thermal modeling

    NASA Astrophysics Data System (ADS)

    Qin, Liping; Dauphas, Nicolas; Wadhwa, Meenakshi; Masarik, Jozef; Janney, Philip E.

    2008-08-01

    New high-precision W isotope measurements are presented for 33 iron meteorites from 8 magmatic groups (IC, IIAB, IID, IIIAB, IIIE, IIIF, I VA and IVB), 2 non-magmatic groups (IAB-IIICD and IIE), and one ungrouped iron (Deep Springs). All magmatic irons have ɛ182W values that are, within errors, equal to, or less radiogenic than, the Solar System initial of - 3.47 ± 0.20. A method was developed to correct the measured ɛ182W values of magmatic iron meteorites for the presence of cosmogenic effects produced during space exposure to galactic cosmic rays. The corrected data provide new constraints on the timing of metal-silicate differentiation in iron meteorite parent bodies, which must have taken place within a few million years (< 2 to 6 My) of condensation of calcium-aluminum-rich inclusions (CAIs). Metal-silicate differentiation ages (from 182Hf-182W systematics) were combined with parent body sizes (from metallographic cooling rates) into a model of planetesimal heating by 26Al-decay, to constrain the accretion timescale of iron meteorite parent bodies. Accretion of iron meteorite parent bodies most likely occurred within 1.5 My of the formation of CAIs. The fast accretion times of iron meteorite parent bodies are consistent with dynamical models indicating that these objects may have originated in the terrestrial planet-forming region, where the accretion rates were high. Our W isotopic data for non-magmatic IAB-IIICD and IIE irons provide new constraints for their formation mechanisms. In particular, they support formation of IAB-IIICD iron meteorites by melting during a single collision event dated at 4-7 My after formation of the Solar System.

  8. Petrogenesis of the Elephant Moraine A79001 meteorite Multiple magma pulses on the shergottite parent body

    NASA Technical Reports Server (NTRS)

    Mcsween, H. Y., Jr.; Jarosewich, E.

    1983-01-01

    The EETA 79001 achondrite consists of two distinct igneous lithologies joined along a planar, non-brecciated contact. Both are basaltic rocks composed primarily of pigeonite, augite, and maskelynite, but one contains zoned megacrysts of olivine, orthopyroxene, and chromite that represent disaggregated xenoliths of harzburzite. Both lithologies probably formed from successive volcanic flows or multiple injections of magma into a small, shallow chamber. Many similarities between the two virtually synchronous magmas suggest that they are related. Possible mechanisms to explain their differences involve varying degrees of assimilation, fractionation from similar parental magmas, or partial melting of a similar source peridotite; of these, assimilation of the observed megacryst assemblage seems most plausible. However, some isotopic contamination may be required in any of these petrogenetic models. The meteorite has suffered extensive shock metamorphism and localized melting during a large impact event that probably excavated and liberated it from its parent body.

  9. 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

  10. 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

  11. Enrichment of the Amino Acid L-Isovaline by Aqueous Alteration on CI and CM Meteorite Parent Bodies

    NASA Technical Reports Server (NTRS)

    Glavin, Daniel P.; Dworkin, Jason P.

    2009-01-01

    The distribution and enantiomeric composition of the 5-carbon (C(sub 5)) amino acids found in Cl-, CM-, and CR-type carbonaceous meteorites were investigated by using liquid chromatography fluorescence detection/TOF-MS coupled with o-phthaldialdehyde/Nacetyl- l-cysteine derivatization. A large L-enantiomeric excess (ee) of the a-methyl amino acid isovaline was found in the CM meteorite Murchison (L(sub ee) = 18.5 +/- 2.6%) and the Cl meteorite Orguell (L(sub ee) = 15.2 +/- 4.0%). The measured value for Murchison is the largest enantiomeric excess in any meteorite reported to date, and the Orgueil measurement of an isovaline excess has not been reported previously for this or any Cl meteorite. The L-isovaline enrichments in these two carbonaceous meteorites cannot be the result of interference from other C(sub 5) amino acid isomers present in the samples, analytical biases, or terrestrial amino acid contamination. We observed no L-isovaline enrichment for the most primitive unaltered Antarctic CR meteorites EET 92042 and QUE 99177. These results are inconsistent with UV circularly polarized light as the primary mechanism for L-isovaline enrichment and indicate that amplification of a small initial isovaline asymmetry in Murchison and Orgueil occurred during an extended aqueous alteration phase on the meteorite parent bodies. The large asymmetry in isovaline and other alpha-dialkyl amino acids found in altered Ct and CM meteorites suggests that amino acids delivered by asteroids, comets, and their fragments would have biased the Earth's prebiotic organic inventory with left-handed molecules before the origin of life.

  12. Preface: Joint Discussion JD5 From Meteors and Meteorites to their Parent Bodies: Current Status and Future Developments

    NASA Astrophysics Data System (ADS)

    Montmerle, Thierry

    2015-03-01

    The Joint Discussion 5 entitled "From Meteors and Meteorites to their Parent Bodies: Current Status and Future Developments" within the IAU GA 2012 was organized with the coordination of the IAU Division III Planetary Systems Sciences and the IAU Commission N. 22 Meteors, Meteorites & Interplanetary Dust, together with the supports by Divisions I Fundamental Astronomy, Division XII Union-Wide Activities, Commission 4 Ephemerides, Commission 6 Astronomical Telegrams, Commission 8 Astrometry, Commission 15 Physical Study of Comets & Minor Planets, and Commission 20 Positions & Motions of Minor Planets, Comets & Satellites.

  13. Combining Hf-W Ages, Cooling Rates, and Thermal Models to Estimate the Accretion Time of Iron Meteorite Parent Bodies

    NASA Astrophysics Data System (ADS)

    Qin, L.; Dauphas, N.; Wadhwa, M.; Masarik, J.; Janney, P. E.

    2007-12-01

    The 182Hf-182W short-lived chronometer has been widely used to date metal-silicate differentiation processes in the early Solar System. However the presence of cosmogenic effects from exposure to GCR can potentially hamper the use of this system for chronology purposes (e.g. [1,2]). These effects must be corrected for in order to calculate metal-silicate differentiation ages. In this study, high-precision W isotope measurements are presented for 32 iron meteorites from 8 magmatic and 2 non-magmatic groups. Exposure ages and pre- atmospheric size estimates are available for most of these samples [3]. Our precision is better than or comparable to the currently most precise literature data and our results agree with previous work [4]. All magmatic irons have ɛ182W equal within error to or more negative than the Solar System initial derived from a CAI isochron [5]. Iron meteorites from the same magmatic groups show variations in ɛ182W. These are most easily explained by exposure to cosmic rays in space. A correction method was developed to estimate pre-exposure ɛ182W for individual iron meteorite groups. Metal-silicate differentiation in most iron meteorite parent bodies must have occurred within 2 Myr of formation of refractory inclusions. For the first time, we combine 182Hf-182W ages with parent body sizes inferred from metallographic cooling rates in a thermal model to constrain the accretion time of iron meteorite parent bodies. The estimated accretion ages are within 1.5 Myr for most magmatic groups, and could be as early as 0.2 Myr after CAI formation. This is consistent with the study of Bottke et al. [6] who argued that iron meteorite parent bodies could represent an early generation of planetesimals formed in the inner region of the Solar System. [1] Masarik J. (1997) EPSL 152, 181-185. [2] Markowski A. et al. (2006) EPSL 250,104-115. [3] Voshage H. (1984) EPSL 71, 181-194. [4] Markowski A. et al. (2006) EPSL 242, 1-15. [5] Kleine T. et al. (2005) GCA 69

  14. Chemical systematics of the Shergotty meteorite and the composition of its parent body (Mars)

    NASA Technical Reports Server (NTRS)

    Laul, J. C.; Smith, M. R.; Waenke, H.; Jagoutz, E.; Dreibus, G.

    1986-01-01

    Sixty elements in two bulk samples of Shergotty meteorite and 30 elements in various mineral separates of Shergotty were identified, using mainly INAA and RNAA techniques. In addition, elements leached out from powdered samples of Shergotty and EETA 79001 meteorites by 0.1 N HCl, as well as the elements of their residues, were analyzed. The results have indicated that Shergotty meteorite is homogeneous in its major element composition, but heterogeneous with respect to large-ion lithophile elements, such as K, Ba, Sr, Zr, Hf, Ta, Th, and rare-earth elements (REEs). It is even more heterogeneous with respect to volatile elements, such as Cd, Te, Tl, and Bi, and the siderophiles Au and Ag. The REE patterns of the Shergotty and EETA 79001 residues are identical, indicating that the parent magmas of both meteorites are compositionally similar. However, their leachate (phosphate) patterns are different, suggesting two components for the Shergotty, one of which is similar to the EETA 79001 leachate.

  15. Products of the Strecker Synthesis as Indicators of Parent Body Conditions of the Murchison Meteorite

    NASA Technical Reports Server (NTRS)

    Lerner, Narcinda R.; Cooper, George W.; Chang, Sherwood (Technical Monitor)

    1996-01-01

    The Strecker synthesis, R2C=O + HCN + NH3 yields R2C(NH2)CN + H2O yields R2C(NH2)CO2H has been proposed as a source of amino acids in meteorites. The detection of carbonlyl compounds, the precursors of the amino acids in the Strecker synthesis, and a-hydroxy acids, important by-products of the Strecker synthesis, in the Murchison meteorite supports this conjecture. However, the following observations raise questions about the Strecker synthesis as the source of a-amino and a-hydroxy acids in Murchison: a) Imino acetic acids are also important by-products of the Strecker synthesis and have not been reported in Murchison. b) a-aminisobutyric acid (AIBA) is one of the most abundant amino acids in Murchison but the Strecker synthesis conducted at room temperature produced only small amounts of AIBA relative to other amino acids. c) If the a-amino and a-hydroxy acids observed in Murchison arose from a common precursor this ought to be reflected in their relative abundances, but the straight chain a-hydroxy acids appeared to be relatively abundant compared with the analogous a-amino acids. In order to address question a) we have examined a non-hydrolyzed aqueous extract of the Murchison meteorite. Imino di acetic acid, Imino propionic acetic acid and Imino butyric acetic acid (both isomers) have been identified in this fraction. The relative abundances of amino acids and imino acetic acids in this fraction are consistent with a Strecker synthesis at low temperature (263 K) as a origin of both the amino acids and the imino acetic acids found on Murchison. To deal with questions b) and c) we have carried out laboratory simulations of the Strecker synthesis. The starting concentrations for carbonlyl compounds used were based on estimates of what these concentrations might have been on the parent body. for the carbonyl compounds this estimate was determined by the amount of carbonyl compound found on Murchison plus the amounts of the corresponding amino acid and hydroxy acid

  16. Mineralogy, petrology, chronology, and exposure history of the Chelyabinsk meteorite and parent body

    NASA Astrophysics Data System (ADS)

    Righter, K.; Abell, P.; Agresti, D.; Berger, E. L.; Burton, A. S.; Delaney, J. S.; Fries, M. D.; Gibson, E. K.; Haba, M. K.; Harrington, R.; Herzog, G. F.; Keller, L. P.; Locke, D.; Lindsay, F. N.; McCoy, T. J.; Morris, R. V.; Nagao, K.; Nakamura-Messenger, K.; Niles, P. B.; Nyquist, L. E.; Park, J.; Peng, Z. X.; Shih, C.-Y.; Simon, J. I.; Swisher, C. C.; Tappa, M. J.; Turrin, B. D.; Zeigler, R. A.

    2015-10-01

    Three masses of the Chelyabinsk meteorite have been studied with a wide range of analytical techniques to understand the mineralogical variation and thermal history of the Chelyabinsk parent body. The samples exhibit little to no postentry oxidation via Mössbauer and Raman spectroscopy indicating their fresh character, but despite the rapid collection and care of handling some low levels of terrestrial contamination did nonetheless result. Detailed studies show three distinct lithologies, indicative of a genomict breccia. A light-colored lithology is LL5 material that has experienced thermal metamorphism and subsequent shock at levels near S4. The second lithology is a shock-darkened LL5 material in which the darkening is caused by melt and metal-troilite veins along grain boundaries. The third lithology is an impact melt breccia that formed at high temperatures (~1600 °C), and it experienced rapid cooling and degassing of S2 gas. Portions of light and dark lithologies from Chel-101, and the impact melt breccias (Chel-102 and Chel-103) were prepared and analyzed for Rb-Sr, Sm-Nd, and Ar-Ar dating. When combined with results from other studies and chronometers, at least eight impact events (e.g., ~4.53 Ga, ~4.45 Ga, ~3.73 Ga, ~2.81 Ga, ~1.46 Ga, ~852 Ma, ~312 Ma, and ~27 Ma) are clearly identified for Chelyabinsk, indicating a complex history of impacts and heating events. Finally, noble gases yield young cosmic ray exposure ages, near 1 Ma. These young ages, together with the absence of measurable cosmogenic derived Sm and Cr, indicate that Chelyabinsk may have been derived from a recent breakup event on an NEO of LL chondrite composition.

  17. 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

  18. Asteroid 6 Hebe: The probable parent body of the H-Type ordinary chondrites and the IIE iron meteorites

    NASA Astrophysics Data System (ADS)

    Gaffey, Michael J.; Gilbert, Sarah L.

    1998-11-01

    The S(IV)-type asteroid 6 Hebe is identified as the probable parent body of the H-type ordinary chondrites and of the IIE iron meteorites. The ordinary chondrites are the most common type of meteorites falling to Earth, but prior to the present study no large mainbelt source bodies have been confirmed. Hebe is located adjacent to both the (6 and 3:1 resonances, and has been previously suggested as a major potential source of the terrestrial meteorite flux. Hebe exhibits subtle rotational spectral variations indicating the presence of some compositional variations across its surface. The silicate portion of the surface assemblage of Hebe is consistent, both in overall average and in its range of variation, with the silicate components in the suite of H-type chondrites. The high albedo of Hebe rules out a lunar-style space weathering process to produce the weakened absorption features and reddish spectral slope in the S-type spectrum of Hebe. Linear unmixing models show that a typical nickel-iron metal spectrum is consistent with the component which modifies an H-chondrite spectrum to produce the S-type spectrum of Hebe. Based on the association between the H chondrites and the IIE iron meteorites, our model suggests that large impacts onto the relatively metal-rich H chondrite target produced melt bodies (sheets or pods) which differentiated to form thin, laterally extensive near-surface layers of NiFe metal. Fragments of the upper silicate portions of these melt bodies are apparently represented by some of the igneous inclusions in H-chondrite breccias. Alternately, masses of metal could have been deposited on the surface of Hebe by the impact of a core or core fragment from a differentiated parent body of H chondrite composition. Subsequent impacts preferentially eroded and depleted the overlying silicate and regolith components exposing and maintaining large masses of metal at the optical surface of Hebe. In this interpretation, the nonmagmatic IIE iron

  19. Variability, absorption features, and parent body searches in "spectrally featureless" meteorite reflectance spectra: Case study - Tagish Lake

    NASA Astrophysics Data System (ADS)

    Izawa, M. R. M.; Craig, M. A.; Applin, D. M.; Sanchez, J. A.; Reddy, V.; Le Corre, L.; Mann, P.; Cloutis, E. A.

    2015-07-01

    Reflectance spectra of many asteroids and other Solar System bodies are commonly reported as "featureless". Here, we show that weak but consistently detectable absorption bands are observable in 200-2500 nm spectra of the Tagish Lake meteorite, a likely compositional and spectral analogue for low-albedo, "spectrally-featureless" asteroids. Tagish Lake presents a rare opportunity to study multiple lithologies within a single meteorite. Reflectance spectra of Tagish Lake display significant variation between different lithologies. The spectral variations are due in part to mineralogical variations between different Tagish Lake lithologies. Ultraviolet reflectance spectra (200-400 nm), few of which have been reported in the literature to date, reveal albedo and spectral ratio variations as a function of mineralogy. Similarly visible-near infrared reflectance spectra reveal variations in albedo, spectral slope, and the presence of weak absorption features that persist across different lithologies and can be attributed to various phases present in Tagish Lake. These observations demonstrate that significant spectral variability may exist between different lithologies of Tagish Lake, which may affect the interpretation of potential source body spectra. It is also important to consider the spectral variability within the meteorite before excluding compositional links between possible parent bodies in the main belt and Tagish Lake. Tagish Lake materials may also be spectral-compositional analogues for materials on the surfaces of other dark asteroids, including some that are targets of upcoming spacecraft missions. Tagish Lake has been proposed as a spectral match for 'ultra-primitive' D or P-type asteroids, and the variability reported here may be reflected in spatially or rotationally-resolved spectra of possible Tagish Lake parent bodies and source objects in the Near-Earth Asteroid population. A search for objects with spectra similar to Tagish Lake has been carried

  20. Deuterium Enrichment of Amino and Hydroxy Acids Found in the Murchison Meteorite: Constraints on Parent Body Conditions

    NASA Technical Reports Server (NTRS)

    Lerner, Narcinda R.; Chang, Sherwood (Technical Monitor)

    1997-01-01

    The alpha-amino and alpha-hydroxy acids found in the Murchison carbonaceous chondrite are deuterium enriched. These compounds are thought to have originated from common deuterium enriched carbonyl precursors, by way of a Strecker synthesis which took place in a solution of HCN, NH3, and carbonyl compounds during the period of aqueous alteration of the meteorite parent body. However, the hydroxy acids found on Murchison are less deuterium enriched than the amino acids. With the objective of determining if the discrepancy in deuterium enrichment between the amino acids and the hydroxy acids found on Murchison is consistent with their formation in a Strecker synthesis, we have measured the deuterium content of alpha-amino and alpha-hydroxy acids produced in solutions of deuterated carbonyl compounds, KCN and NH4Cl, and also in mixtures of such solutions and Allende dust at 263 K and 295 K. Retention of the isotopic signature of the starting carbonyl by both alpha amino acids and alpha hydroxy acids is more dependent upon temperature, concentration and pH than upon the presence of meteorite dust in the solution. The constraints these observations place on Murchison parent body conditions will be discussed.

  1. High-precision sulfur isotope composition of enstatite meteorites and implications of the formation and evolution of their parent bodies

    NASA Astrophysics Data System (ADS)

    Defouilloy, C.; Cartigny, P.; Assayag, N.; Moynier, F.; Barrat, J.-A.

    2016-01-01

    In order to better understand the formation and evolution of their parent bodies, the three isotope ratios of sulfur were analyzed in 33 enstatite meteorites (24 enstatite chondrites and 9 aubrites). The results show that on average all enstatite chondrite groups are enriched in the lightest isotopes compared to other chondrite groups, with means of δ34S of -0.28 ± 0.22‰ for EH3/4, -0.16 ± 0.16‰ for EH5, -0.32 ± 0.15‰ for EL3, -0.67 ± 0.16‰ for EL6 and -0.64 ± 0.00‰ for EL7 (all 1σ). Aubrites show a larger isotope variability in their composition, with a δ34S varying from -1.350‰ to +0.154‰. Contrary to previously published results, our data show a distinct composition for EL6 compared to other enstatite chondrites. This could be related to an impact-induced loss of isotopically heavy oldhamite (δ34S = by 3.62 ± 3.02‰ (1σ)) on the EL parent body. Although the bulk sulfur in both enstatite meteorites and aubrites does not show any significant Δ33S and Δ36S, the oldhamite fraction shows clear evidence of mass independent fractionation on the 36S/32S ratio (in 3 out of 9 analyzes, Δ36S up to +2.2‰), a signal that is not correlated to any 33S/32S anomaly (in 1 out of 9 analyzes, Δ33S down to -0.085‰). Though a nebular or photochemical origin cannot be ruled out, the most plausible mechanism to produce such isolated non-mass dependent 36S/32S anomalies would be a contribution of FeCl2 containing excesses of 36S due to the decay of 36Cl to the leached oldhamite fraction. Even though the sulfur isotopic composition measured in enstatite meteorites is distinct from the Bulk Silicate Earth (BSE), the isotopically lightest samples of EL6, EL7 and aubrites are approaching the isotopic composition of the BSE and enstatite meteorites remain the meteorites with the sulfur isotopic composition the closest to the terrestrial one.

  2. Intrinsic oxygen fugacity measurements on seven chondrites, a pallasite, and a tektite and the redox state of meteorite parent bodies

    USGS Publications Warehouse

    Brett, R.; Sato, M.

    1984-01-01

    Intrinsic oxygen-fugacity (fO2) measurements were made on five ordinary chondrites, a carbonaceous chondrite, an enstatite chondrite, a pallasite, and a tektite. Results are of the form of linear log fO2 - 1 T plots. Except for the enstatite chondrite, measured results agree well with calculated estimates by others. The tektite produced fO2 values well below the range measured for terrestrial and lunar rocks. The lowpressure atmospheric regime that is reported to follow large terrestrial explosions, coupled with a very high temperature, could produce glass with fO2 in the range measured. The meteorite Salta (pallasite) has low fO2 and lies close to Hvittis (E6). Unlike the other samples, results for Salta do not parallel the iron-wu??stite buffer, but are close to the fayalite-quartz-iron buffer in slope. Minor reduction by graphite appears to have taken place during metamorphism of ordinary chondrites. fO2 values of unequilibrated chondrites show large scatter during early heating suggesting that the constituent phases were exposed to a range of fO2 conditions. The samples equilibrated with respect to fO2 in relatively short time on heating. Equilibration with respect to fO2 in ordinary chondrites takes place between grades 3 and 4 of metamorphism. Application of P - T - fO2 relations in the system C-CO-CO2 indicates that the ordinary chondrites were metamorphosed at pressures of 3-20 bars, as it appears that they lay on the graphite surface. A steep positive thermal gradient in a meteorite parent body lying at the graphite surface will produce thin reduced exterior, an oxidized near-surface layer, and an interior that is increasingly reduced with depth; a shallow thermal gradient will produce the reverse. A body heated by accretion on the outside will have a reduced exterior and oxidized interior. Meteorites from the same parent body clearly are not required to have similar redox states. ?? 1984.

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

    NASA Technical Reports Server (NTRS)

    Binzel, Richard P.; Xu, Shui

    1993-01-01

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

  4. Meteoritic, Asteroidal, and Theoretical Constraints on the 500 MA Disruption of the L Chondrite Parent Body

    NASA Astrophysics Data System (ADS)

    Haack, Henning; Farinella, Paolo; Scott, Edward R. D.; Keil, Klaus

    1996-01-01

    The high abundance of heavily shocked and degassedLchondrites with Ar-Ar ages around 500 Myr shows that theLchondrite parent body suffered a major impact 500 Myr ago. We infer from constraints on the thermal evolution of impact heated rocks after the 500-Myr event and the high abundance of shockedLchondrites that the parent body was catastrophically disrupted. The slow cooling rates of some shocked and degassedLchondrites (0.01-1°C year-1) show that they were derived from kilometer-sized impact-heated fragments or rubble piles that were ejected from near the impact point. We suggest that the catastrophic dispersion of the parent body provided some fragments with sufficiently high velocities to put them into resonances and that this initiated the orbital evolution which resulted in the high flux ofLchondrite meteoroids impacting the Earth at present. It appears likely that this was a “slow-track” type of dynamical evolution, with most objects avoiding drastic resonant changes of orbital eccentricity, and undergoing a slow random walk in orbital element space, driven by a sequence of random encounters with Mars and, later on, with the Earth. The ν6secular resonance provides a plausible mechanism to start this evolution, since fragments inserted into it in the main belt frequently have their eccentrici_ties raised to values of about 0.4, sufficient for Mars-crossing but not for Earth-crossing orbits; on the other hand, recent numerical work has shown that the 3:1 mean motion resonance leads almost always to a fast-track evolution, ending up with a solar collision or a hyperbolic ejection within a few Myr.

  5. Composition of solar flare noble gases preserved in meteorite parent body regolith

    NASA Technical Reports Server (NTRS)

    Rao, M. N.; Garrison, D. H.; Bogard, D. D.; Badhwar, G.; Murali, A. V.

    1991-01-01

    Isotopic composition of solar-flare (SF) Ne was determined in acid-etched pyroxene mineral separates from the Kapoeta meteorite, a brecciated meteorite known to contain implanted solar gases. The results yield the SF Ne-20/Ne-22 ratio of 11.6 +/-0.2, confirming previous determinations of this SF ratio in lunar and meteoritic samples. The same SF Ne composition was also obtained by applying an ordinate intercept technique to the same data set. The ordinate intercept technique was then applied to the Ar and He data. The results are SF Ar-36/Ar-38 = 4.9 +/-0.1 and SF He-4/He-3 = 3800 +/-200. These values are significantly different from the solar-wind (SW) Ar and He values. It is estimated that the concentration of the SF component in Kapoeta pyroxenes is about 20 percent that of the SW component, orders of magnitude higher than expected from SW and SF proton flux measurements.

  6. 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

  7. The IVA Parent Body: Evidence from Silicate-Bearing Group IVA Iron Meteorites

    NASA Astrophysics Data System (ADS)

    Ulff-Moller, F.; Kallemeyn, G. W.; Rasmussen, K. L.

    1992-07-01

    The IVA iron meteorites Steinbach (SB), Sao Joao Nepomuceno (SJN), Gibeon and Bishop Canyon are unusual in their contents of silicates. SB is particularly rich in silicates (ca. 50 wt%) and was long classified as a stony iron (Dorfler et al., 1965) but the metal fraction is typical of group IVA iron meteorites (Schaudy et al., 1972). The SB and SJN contain low-Ca pyroxene and tridymite in roughly equal proportions, whereas only tridymite is found in the two other meteorites. Reid et al. (1974) found that coexisting orthopyroxene and clinopyroxenes in SB (En 85) were formed in a narrow two-phase field at 1200 degrees C and preserved by comparatively rapid cooling. We present cooling rate estimates as well as minor element data for the silicates obtained by electron microprobe and trace elements (REE and siderophiles) for the bulk silicate fraction by INAA. The coarse granular texture of the silicates and the presence of finely dispersed sulfide inclusions in the pyroxenes might suggest a cumulate origin, but the high proportion of tridymite combined with MgO-rich pyroxene is unusual if a chondritic magma is assumed. One way of forming excess tridymite is by extreme reduction of a pallasite-type metal/olivine mixture. Our INAA data on SB bulk silicates show a pattern of REE and Sc, Cr, and Mn, which is qualitatively consistent with orthopyroxene that crystallized from a moderately evolved magma with chondritic REE levels. The incompatible elements (including Cr!) in SB pyroxene are correlated and vary up to a factor of 5 (eg., Ti and Al), whereas Ca shows a bimodal variation corresponding roughly to the coexisting orthopyroxene and clinopyroxene. The minor element variations in SB pyroxene thus resemble magmatic zoning. The SJN pyroxene is marginally more MgO-rich (En 86) and shows a similar bimodal Ca distribution although it is possibly one phase. If correct, this suggests slower cooling at a higher temperature than SB. References: Dorfler G., Hecht F. and

  8. Copper stable isotopes as tracers of metal-sulphide segregation and fractional crystallisation processes on iron meteorite parent bodies

    NASA Astrophysics Data System (ADS)

    Williams, Helen M.; Archer, Corey

    2011-06-01

    lowest Δ 65Cu M-FeS values, whereas the converse is observed in the irons with large values D Cu that deviate most from Cu concentration equilibrium. The magnitudes of Cu and Fe isotope fractionation between metal and FeS in the most equilibrated samples are similar: 0.25 and 0.32‰/amu, respectively. As proposed in an earlier study ( Williams et al., 2006) the range in Δ 57Fe M-FeS values can be explained by incomplete Fe isotope equilibrium between metal and sulphide during cooling, where the most rapidly-cooled samples are furthest from isotopic equilibrium and display the smallest Δ 57Fe M-FeS and largest D Cu values. The range in Δ 65Cu M-FeS, however, reflects the combined effects of partial isotopic equilibrium overprinting an initial kinetic signature produced by the diffusion of Cu from metal into exsolving sulphides and the faster diffusion of the lighter isotope. In this scenario, newly-exsolved sulphides initially have low Cu contents (i.e. high D Cu) and extremely light δ 65Cu FeS values; with progressive equilibrium and fractional crystallisation the Cu contents of the sulphides increase as their isotopic composition becomes less extreme and closer to the metal value. The correlation between Δ 65Cu M-FeS and Δ 57Fe M-FeS is therefore a product of the superimposed effects of kinetic fractionation of Cu and incomplete equilibrium between metal and sulphide for both isotope systems during cooling. The correlations between Δ 65Cu M-FeS and Δ 57Fe M-FeS are defined by both magmatic and non-magmatic irons record fractional crystallisation and cooling of metallic melts on their respective parent bodies as sulphur and chalcophile elements become excluded from crystallised solid iron and concentrated in the residual melt. Fractional crystallisation processes at shallow levels have been implicated in the two main classes of models for the origin of the non-magmatic iron meteorites; at (i) shallow levels in impact melt models and (ii) at much deeper levels

  9. Composition of solar flare noble gases preserved in meteorite parent body regolith.

    PubMed

    Rao, M N; Garrison, D H; Bogard, D D; Badhwar, G; Murali, A V

    1991-11-01

    The isotopic composition (long-term average) of solar flare (SF) Ne has been determined by three isotope correlation techniques applied to data measured on chemically etched pyroxene separates prepared from the Kapoeta meteorite, which is known to contain implanted solar gases. The SF 20Ne/22Ne ratio obtained is 11.6 +/- 0.2 and confirms previous determinations of this SF ratio in lunar and meteoritic samples. The same SF Ne composition is also obtained by applying an ordinate intercept technique to the same data set. The ordinate intercept technique was also applied to the Ar and He data, on which the three-isotope correlation technique cannot be applied. The isotopic composition of SF Ar and SF He so obtained are SF 36Ar/38Ar = 4.9 +/- 0.1 and SF 4He/3He = 3800 +/- 200, which are significantly different from the solar wind (SW) Ar and SW He values of approximately 5.35 and approximately 2500, respectively. Correlation between 20Ne/22Ne and 36Ar/38Ar for the same data set also gives a similar SF 36Ar/38Ar ratio of 4.8 +/- 0.2. The determined SF He, Ne and Ar isotopic ratios differ from those in SW by 52%, 17% and 9%, respectively, but the elemental compositions of 4He/36Ar and 20Ne/36Ar do not show obvious differences between SF and SW. The concentration of the SF component in Kapoeta pyroxenes is approximately 20% that of the SW component, which is orders of magnitude higher than expected from SW and SF proton flux measurements. Variations in elemental and isotopic composition of He, Ne and Ar in SF relative to SW are found to correlate well with a (Z/A)2 dependence, indicating a rigidity-dependent particle spectrum in solar flares. PMID:11538179

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

    NASA Astrophysics Data System (ADS)

    van Niekerk, Deon; Keil, Klaus

    2011-10-01

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

  11. The Halite-Bearing Zag and Monahans (1998) Meteorite Breccias: Shock Metamorphism, Thermal Metamorphism and Aqueous Alteration on the H-Chondrite Parent Body

    NASA Technical Reports Server (NTRS)

    Rubin, Alan E.; Zolensky, Michael E.; Bodnar, Robert J.

    2002-01-01

    Zag and Monahans (1998) are H-chondrite regolith breccias comprised mainly of lightcolored metamorphosed clasts, dark clasts that exhibit extensive silicate darkening, and a halite-bearing clastic matrix. These meteorites reflect a complex set of modification processes that occurred on the H-chondrite parent body. The light-colored clasts are thermally metamorphosed H5 and H6 rocks that were fragmented and deposited in the regolith. The dark clasts formed from light-colored clasts during shock events that melted and mobilized a significant fraction of their metallic Fe-Ni and troilite grains. The clastic matrices of these meteorites are rich in solar-wind gases. Parent-body water was required to cause leaching of chondri tic minerals and chondrule glass; the fluids became enriched in Na, K, CI, Br, AI, Ca, Mg and Fe. Evaporation of the fluids caused them to become brines as halides and alkalies became supersaturated; grains of halite (and, in the case of Monahans (1998), halite with sylvite inclusions) precipitated at low temperatures (less than or equal to 100 C) in the porous regolith. In both meteorites fluid inclusions were trapped inside the halite crystals. Primary fluid inclusions were trapped in the growing crystals; secondary inclusions formed subsequently from fluid trapped within healed fractures.

  12. Igneous Evolution of the Core and Mantle in the Parent Body of Group IVA Iron and Stony-Iron Meteorites

    NASA Astrophysics Data System (ADS)

    Scott, E. R. D.; McCoy, T. J.; Haack, H.; Taylor, G. J.

    1992-07-01

    peritectic liquids. Discussion: From the observed size and homogeneity of the Gibeon shower and our fractional crystallization modeling, we can infer that the parental liquid pool was at least many meters in size. Pools this big quickly sink through silicate (unless very reduced), so IVA metal very probably comes from a core. The wide range of metallographic cooling rates that is correlated with Ni concentration in IVA irons must therefore be an artefact. Liquids of pyroxene-silica compositions could be formed in the mantle (Prinz et al., 1984) but trapping them in the core at different stages of core crystallization seems very difficult. We prefer an origin for IVA stony irons by mixing olivine-pyroxene mantle material into the core during core solidification by processes like those that mixed olivine mantle into Fe,Ni cores to make pallasites, followed by addition of silica formed by oxidation of Si from the metal. Pieces of olivine-pyroxene, possibly in the form of a Brenham-like sponge, could be mixed into a crystallizing Fe,Ni core with about 2-4% S at temperatures around 1400 C. Pyroxene might be abundant in the mantle because small body size caused inefficient removal of trapped silicate liquid from an olivine cumulate. Alternatively, temperatures were never high enough to melt the mantle entirely. References: Haack H. and Scott E.R.D. (1992) Geochim. Cosmochim. Acta, submitted. Jones J.H. and Malvin (1990) Metall. Trans., 21B, 697-706. Prinz M., Nehru C.E., Delaney J.S., Fredriksson K., and Palme H. (1984) Meteoritics (abstract) 19, 291-292.

  13. Effect of parent body evolution on equilibrium and kinetic isotope fractionation: a combined Ni and Fe isotope study of iron and stony-iron meteorites

    NASA Astrophysics Data System (ADS)

    Chernonozhkin, Stepan M.; Goderis, Steven; Costas-Rodríguez, Marta; Claeys, Philippe; Vanhaecke, Frank

    2016-08-01

    Various iron and stony-iron meteorites have been characterized for their Ni and Fe isotopic compositions using multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS) after sample digestion and chromatographic separation of the target elements in an attempt to further constrain the planetary differentiation processes that shifted these isotope ratios and to shed light on the formational history and evolution of selected achondrite parent body asteroids. Emphasis was placed on spatially resolved isotopic analysis of iron meteorites, known to be inhomogeneous at the μm to mm scale, and on the isotopic characterization of adjacent metal and silicate phases in main group pallasites (PMG), mesosiderites, and the IIE and IAB complex silicate-bearing iron meteorites. In a 3-isotope plot of 60/58Ni versus62/58Ni, the slope of the best-fitting straight line through the laterally resolved Ni isotope ratio data for iron meteorites reveals kinetically controlled isotope fractionation (βexper = 1.981 ± 0.039, 1 SD), predominantly resulting from sub-solidus diffusion (with the fractionation exponent β connecting the isotope fractionation factors, as α62/58 =α60/58β). The observed relation between δ56/54Fe and Ir concentration in the metal fractions of PMGs and in IIIAB iron meteorites indicates a dependence of the bulk Fe isotopic composition on the fractional crystallization of an asteroidal metal core. No such fractional crystallization trends were found for the corresponding Ni isotope ratios or for other iron meteorite groups, such as the IIABs. In the case of the IIE and IAB silicate-bearing iron meteorites, the Fe and Ni isotopic signatures potentially reflect the influence of impact processes, as the degree of diffusion-controlled Ni isotope fractionation is closer to that of Fe compared to what is observed for magmatic iron meteorite types. Between the metal and olivine counterparts of pallasites, the Fe and Ni isotopic compositions show clearly

  14. The S(IV)-type Asteroids as Ordinary Chondrite Parent Body Candidates: Implications for the Completeness of the Meteorite Sample of Asteroids

    NASA Astrophysics Data System (ADS)

    Gaffey, M. J.

    1995-09-01

    The discrepancy between the abundance of ordinary chondrites (OCs) among the meteorites and the rarity of unambiguously similar assemblages in the asteroid belt has been a major point of discussion within and between the asteroid and meteorite communities. Various resolutions to this apparent paradox have been proposed [e.g., 1-5], including: 1) interpretations of S-type asteroid spectra are incorrect due to space weathering effects; 2) ordinary chondrites derive from a few rare but favorably situated parent bodies; 3) OCs come from a residual population of small unheated mainbelt asteroids; 4) shock effects darken OC parent body surfaces disguising them as C-type asteroids, and 5) OCs come from inner solar system planetesimals ejected to the Oort cloud which have been recently perturbed into Earth-crossing orbits. Although none of these possibilities has yet been rigorously excluded, recent investigations suggest that the resolution of the apparent paradox lies in some combination of the first three options. For option 3, the discovery of a small mainbelt asteroid with an OC-like spectrum indicates OC-assemblages among the smaller mainbelt asteroids [6], although their abundance is still low in the current sample [7]. For option 2, the mineralogical survey indicated that while most S-asteroids could be rigorously excluded on mineralogical criteria, the S(IV) subtype of this class has silicate compositions within the OC range [8]. The S(IV)-objects are concentrated near the 3:1 secular resonance at 2.5 AU providing an efficient escape into Earth-crossing orbits. Unfortunately for a simple resolution of the OC parent body question, S(IV) spectra still exhibit weaker silicate features and redder spectral slopes than OC assemblages. Although significant uncertainties remain, optical alteration of asteroid surfaces interpreted from the Galileo images of Ida and Gaspra may reconcile the mismatch between OC and S(IV) spectra [option 1]. Although only a subset of the S

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

    NASA Astrophysics Data System (ADS)

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

    2001-03-01

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

  16. Catching Constrains on the Parent Body Genesis of Mesosiderites and a Possible Link to HED (Howardite-Eucrite-Diogenite) Meteorites - A New Hope?

    NASA Technical Reports Server (NTRS)

    Baecker, B.; Cohen, Barbara A.

    2016-01-01

    Mesosiderites (MES) are a group of enigmatic stony-iron meteorites exhibiting fragmental matrix breccias and irregular textures; e.g. [1-3]. Mesosiderites contain roughly equal volumes metal (Fe-Ni) and silicates often intimately mixed together (Fig.1). The silicates mostly consist of basaltic, gabbroic, and pyroxenitic components, and appear similar to eucrites and howardites; [4-8]. But unlike HEDs - and other differentiated parent body meteorite groups e.g. ureilites - mesosiderites contain high metal abundances. Several studies have been published to reveal the processes leading to the formation of mesosiderites and attempt to classifiy them [1], [2], [10-15]. Because the silicate inclusions in mesosiderites are often strongly metamorphosed after formation, it is difficult to assess the origin of the silicates and implications for the differentiation process of their parent body [15-17]. Several workers have advanced a formation hypothesis for the mesosiderites where an impact between differentiated bodies occurred prior to 4.47 Ga ago (e.g. [13,18], which could explain the possible incomplete dispersal of the colliding bodies due to their low cosmic ray exposure ages and their special thermal history. However, [13] discuss and favor the model for formation of mesosiderites with the collision of two differentiated bodies, along with disruption events and gravitational re-assembly. The mesosiderites have numerous gabbroid melt clasts with anomalous rare-earth- element (REE) - especially positive Eu - values [19, 20]. HEDs do not show the same. However, the heating mechanisms of both mesosiderites and HED's are puzzling. Mesosiderites are remarkable, they consist of a mix of basalts, which are only found on or near planetary surfaces and undifferentiated metal [1,2]. The probable model is that an asteroid containing a metallic magma impacted onto a second asteroid covered with basalt [18,21]. The mix was then buried under an insulating regolith, and cooled slowly

  17. ON THE EFFECT OF GIANT PLANETS ON THE SCATTERING OF PARENT BODIES OF IRON METEORITE FROM THE TERRESTRIAL PLANET REGION INTO THE ASTEROID BELT: A CONCEPT STUDY

    SciTech Connect

    Haghighipour, Nader; Scott, Edward R. D.

    2012-04-20

    In their model for the origin of the parent bodies of iron meteorites, Bottke et al. proposed differentiated planetesimals, formed in 1-2 AU during the first 1.5 Myr, as the parent bodies, and suggested that these objects and their fragments were scattered into the asteroid belt as a result of interactions with planetary embryos. Although viable, this model does not include the effect of a giant planet that might have existed or been growing in the outer regions. We present the results of a concept study where we have examined the effect of a planetary body in the orbit of Jupiter on the early scattering of planetesimals from the terrestrial region into the asteroid belt. We integrated the orbits of a large battery of planetesimals in a disk of planetary embryos and studied their evolutions for different values of the mass of the planet. Results indicate that when the mass of the planet is smaller than 10 M{sub Circled-Plus }, its effects on the interactions among planetesimals and planetary embryos are negligible. However, when the planet mass is between 10 and 50 M{sub Circled-Plus }, simulations point to a transitional regime with {approx}50 M{sub Circled-Plus} being the value for which the perturbing effect of the planet can no longer be ignored. Simulations also show that further increase of the mass of the planet strongly reduces the efficiency of the scattering of planetesimals from the terrestrial planet region into the asteroid belt. We present the results of our simulations and discuss their possible implications for the time of giant planet formation.

  18. Cathodoluminescence microscopy and spectroscopy of forsterite from Kaba meteorite: An application to the study of hydrothermal alteration of parent body

    NASA Astrophysics Data System (ADS)

    Gucsik, Arnold; Endo, Taro; Nishido, Hirotsugu; Ninagawa, Kiyotaka; Kayama, Masahiro; Bérczi, Szaniszló; Nagy, Szabolcs; Ábrahám, Péter; Kimura, Yuki; Miura, Hitoshi; Gyollai, Ildikó; Simonia, Irakli; Rózsa, Péter; Posta, József; Apai, Dániel; Mihályi, Krisztián; Nagy, Mihály; Ott, Ulrich

    2013-12-01

    Highly forsteritic olivine (Fo: 99.2-99.7) in the Kaba meteorite emits bright cathodoluminescence (CL). CL spectra of red luminescent forsterite grains have two broad emission bands at approximately 630 nm (impurity center of divalent Mn ions) in the red region and above 700 nm (trivalent Cr ions) in the red-IR region. The cores of the grains show CL blue luminescence giving a characteristic broad band emission at 400 nm, also associated with minor red emissions related to Mn and Cr ions. CL color variation of Kaba forsterite is attributed to structural defects. Electron probe microanalyzer (EPMA) analysis shows concentrations of Ca, Al, and Ti in the center of the forsterite grain. The migration of diffusible ions of Mn, Cr, and Fe to the rim of the Kaba meteoritic forsterite was controlled by the hydrothermal alteration at relatively low temperature (estimated at about 250 °C), while Ca and Al ions might still lie in the core. A very unusual phase of FeO (wüstite) was also observed, which may be a terrestrial alteration product of FeNi-metal.

  19. 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

  20. Neodymium, strontium and chromium isotopic studies of the LEW86010 and Angra dos Reis meteorites and the chronology of the angrite parent body

    NASA Technical Reports Server (NTRS)

    Nyquist, L. E.; Bansal, B.; Wiesmann, H.; Shih, C.-Y.

    1994-01-01

    Neodymium, stontium, and chromium isotopic studies of the LEW86010 angrite established its absolute age and the formation interval between its crystallization and condensation of Allende CAIs from the solar nebula. Pyroxene and phosphate were found to contain approximately 8% of its Sm and Nd inventory. A conventional Sm-147-Nd-143 isochron yielded an age of 4.53 +/- 0.04 Ga (2 sigma and Epsilon(sub Nd sup 143)) = 0.45 +/- 1.1. An Sm-146-Nd-142 isochron gives initial Sm-146/Sm-144 = 0.0076 +/- 0.0009 and Epsilon (sub Nd sup 142) = -2.5 +/- 0.4. The Rb-Sr analyses give initial Sr-87/Sr-86 Iota(sub Sr sup 87) = 0.698972 +/- 8 and 0.698970 +/- 18 for LEW and ADOR, respectively, relative to Sr-87/Sr-86 = 0.71025 for NBS987. The difference, Delta Iota(sub Sr Sup 87), between Iota (sub sr sup 87) for the angrites and literature values for Allende CAIs, corresponds to approximately Ma of growth in a solar nebula with a CI chondrite value of Rb-87/Sr-86 = 0.91, or approximately 5 Ma in a nebula with solar photospheric Rb-87/Sr-86 = 1.51. Excess Cr-53 from extinct Mn-53(t(sub 1/2) = 3.7 Ma)in LEW86010 corresponds to initial Mn-53/Mn-55 = 4.4 +/- 1.0 x 10(exp -5) for the inclusions as previously reported by the Paris group (Birck and Allegre, 1988). The Sm-146/Sm-144 value found for LEW86010 corresponds to solar system initial (Sm-146/Sm-144) = 0.0080 +/- 0.0009 for crystallization 8 Ma after Allende, the difference between Pb-Pb ages of angrites and Allende, or 0.0086 +/- 0.0009 for crystallation 18 Ma after Allende, using the Mn-Cr formation interval. The isotopic data are discussed in the context of a model in which an undifferentiated 'chondritic' parent body formed from the solar nebula approximately Ma after Allende CAIs and subsequently underwent differentiation accompanied by loss of volatiles. Parent bodies with Rb/Sr similar to that of CI, CM, or CO chondrites could satisfy the Cr and Sr isotopic systematics. If the angrite parent body had Rb/Sr similar to that of

  1. Enrichment of Non-Terrestrial L-Proteinogenic Amino Acids by Aqueous Alteration on the Tagish Lake Meteorite Parent Body

    NASA Technical Reports Server (NTRS)

    Glavin, Daniel P.; Elsila, Jamie E.; Burton, Aaron S.; Callahan, Michael P.; Dworkin, Jason P.; Herd, Christopher D. K.

    2012-01-01

    The distribution and isotopic and enantiomeric compositions of amino acids found in three distinct fragments of the Tagish Lake C2-type carbonaceous chondrite were investigated via liquid chromatography fluorescence detection time-of-flight mass spectrometry and gas chromatography isotope ratio mass spectrometry. Large L-enantiomeric excesses (L(sub ee) approx. 43 to 59%) of the a-hydrogen aspartic and glutamic amino acids were measured in Tagish Lake, whereas alanine, another alpha-hydrogen protein amino acid, was found to be nearly racemic (D approx. L) using both techniques. Carbon isotope measurements of D- and L-aspartic acid and D- and L-alanine in Tagish Lake fall well outside of the terrestrial range and indicate that the measured aspartic acid enantioenrichment is indigenous to the meteorite. Alternate explanations for the Lexcesses of aspartic acid such as interference from other compounds present in the sample, analytical biases, or terrestrial amino acid contamination were investigated and rejected. These results can be explained by differences in the solid-solution phase behavior of aspartic acid, which can form conglomerate enantiopure solids during crystallization, and alanine, which can only form racemic crystals.

  2. Compositions of group IVB iron meteorites and their parent melt

    NASA Astrophysics Data System (ADS)

    Campbell, Andrew J.; Humayun, Munir

    2005-10-01

    The concentrations of P, V, Cr, Fe, Co, Ni, Cu, Ga, Ge, As, Mo, Ru, Rh, Pd, W, Re, Os, Ir, Pt, and Au in the group IVB iron meteorites Cape of Good Hope, Hoba, Skookum, Santa Clara, Tawallah Valley, Tlacotepec, and Warburton Range have been measured by laser ablation inductively coupled plasma mass spectrometry. The data were fitted to a model of fractional crystallization of the IVB parent body core, from which the composition of the parent melt and metal/melt distribution coefficients for each element in the system were determined, for a chosen value of D(Ni). Relative to Ni and chondritic abundances, the parent melt was enriched in refractory siderophiles, with greatest enrichment of 5× chondritic in the most refractory elements, and was strongly volatile-depleted, down to 0.00014× chondritic in Ge. Comparison to an equilibrium condensation sequence from a gas of solar composition indicates that no single temperature satisfactorily explains the volatility trend in the IVB parent melt; a small (<1%) complement of ultrarefractory components added to metal that is volatile-depleted but otherwise has nearly chondritic abundances (for Fe, Co and Ni) best explains the volatility trend. In addition to this volatility processing, which probably occurred in a nebular setting, there was substantial oxidation of the metal in the IVB parent body, leading to loss of Fe and other moderately siderophile elements such as Cr, Ga, and W, and producing the high Ni contents that are observed in the IVB irons. By assuming that the entire IVB parent body underwent a similar chemical history as its core, the composition of the silicate that is complementary to the IVB parent melt was also estimated, and appears to be similar to that of the angrite parent.

  3. Experimental Studies of Phase Equilibria of Meteorites and Planetary Bodies

    NASA Technical Reports Server (NTRS)

    Stolper, Edward M.

    2005-01-01

    The primary theme of this project was the application of experimental petrology and geochemistry to a variety of problems in meteoritics and planetary geology. The studies were designed to help develop constraints on the histories of primitive meteorites and their components, the environments in which they formed and evolved, and to understand quantitatively the processes involved in the evolution of igneous rocks on the earth and other planetary bodies. We undertook several projects relating to the origin of CAIs and chondrules. Systematics in the thermodynamic properties of CAI-like liquids were investigated and used to elucidate speciation of multi-valent cations and sulfide capacity of silicate melts and to constrain redox conditions and the vapor pressures of volatile species over molten chondrules. We experimentally determined vanadium speciation in meteoritic pyroxenes and in pyroxenes crystallized from CAI-like melts under very reducing conditions. We also found that bulk oxygen isotope compositions of chondrules in the moderately unequilibrated LL chondrites are related to the relative timing of plagioclase crystallization. We completed an experimental study on the vaporization of beta-SiC and SiO2 (glass or cristobalite) in reducing gases and established the conditions under which these presolar grains could have survived in the solar nebula. We expanded our technique for determining the thermodynamic properties of minerals and liquids to iron-bearing systems. We determined activity-composition relationships in Pt-Fe, Pt-Cr and Pt-Fe-Cr alloys. Results were used to determine the thermodynamic properties of chromite-picrochromite spinels including the free energy of formation of end-member FeCr2O4. We also established a new approach for evaluating Pt-Fe saturation experiments. We calculated the T-fO2 relationships in equilibrated ordinary chondrites and thereby constrained the conditions of metamorphism in their parent bodies.

  4. Track record in meteorites

    NASA Astrophysics Data System (ADS)

    Durrani, S. A.

    1981-02-01

    The use of nuclear-track analysis in meteoritic crystals with reference to several areas of research is reviewed. The applications discussed include: fission-track retention ages and cooling rates of meteoritic parent bodies, cosmic-ray studies, determination of pre-atmospheric sizes of meteorites, and search for superheavy elements.

  5. Meteoritic basalts: The nakhlites, their parental magmas, cooling rates, and equivalents on Earth

    NASA Technical Reports Server (NTRS)

    Treiman, Allan H.

    1987-01-01

    Proposed one-bar phase equilibrium experiments, designed to determine the compositions of the nakhlites' parental magmas, are in progress. Proposed field studies on Earth, designed to find occurrences of rocks like the nakhlites, were extraordinarily successful. Other work supported in the past year included: attendance at the 1986 national meeting of the Geological Society of America; attendance at the 18th Lunar and Planetary Science Conference; completion and publication of a study of core formation in the SNC parent body; initiation of a study of the flux of SNC meteorites onto the Earth; and initiation of petrologic study of the Angra dos Reis achondrite.

  6. Sulfide-rich metallic impact melts from chondritic parent bodies

    NASA Astrophysics Data System (ADS)

    Schrader, Devin L.; Lauretta, Dante S.; Connolly, Harold C. _jr., Jr.; Goreva, Yulia S.; Hill, Dolores H.; Domanik, Ken J.; Berger, Eve L.; Yang, Hexiong; Downs, Robert T.

    2010-05-01

    Sacramento Wash 005 (SaW) 005, Meteorite Hills 00428 (MET) 00428, and Mount Howe 88403 (HOW) 88403 are S-rich Fe,Ni-rich metal meteorites with fine metal structures and homogeneous troilite. We compare them with the H-metal meteorite, Lewis Cliff 88432. Phase diagram analyses suggest that SaW 005, MET 00428, and HOW 88403 were liquids at temperatures above 1350°C. Tridymite in HOW 88403 constrains formation to a high-temperature and low-pressure environment. The morphology of their metal-troilite structures may suggest that MET 00428 cooled the slowest, SaW 005 cooled faster, and HOW 88403 cooled the quickest. SaW 005 and MET 00428 contain H-chondrite like silicates, and SaW 005 contains a chondrule-bearing inclusion that is texturally and compositionally similar to H4 chondrites. The compositional and morphological similarities of SaW 005 and MET 00428 suggest that they are likely the result of impact processing on the H-chondrite parent body. SaW 005 and MET 00428 are the first recognized iron- and sulfide-rich meteorites, which formed by impact on the H-chondrite parent body, which are distinct from the IIE-iron meteorite group. The morphological and chemical differences of HOW 88403 suggest that it is not from the H-chondrite body, although it likely formed during an impact on a chondritic parent body.

  7. Compositional Homogeneity of CM Parent Bodies

    NASA Astrophysics Data System (ADS)

    Vernazza, P.; Marsset, M.; Beck, P.; Binzel, R. P.; Birlan, M.; Cloutis, E. A.; DeMeo, F. E.; Dumas, C.; Hiroi, T.

    2016-09-01

    CM chondrites are the most common type of hydrated meteorites, making up ˜1.5% of all falls. Whereas most CM chondrites experienced only low-temperature (˜0°C–120°C) aqueous alteration, the existence of a small fraction of CM chondrites that suffered both hydration and heating complicates our understanding of the early thermal evolution of the CM parent body(ies). Here, we provide new constraints on the collisional and thermal history of CM-like bodies from a comparison between newly acquired spectral measurements of main-belt Ch/Cgh-type asteroids (70 objects) and existing laboratory spectral measurements of CM chondrites. It first appears that the spectral variation observed among CM-like bodies is essentially due to variations in the average regolith grain size. Second, the spectral properties of the vast majority (unheated) of CM chondrites resemble both the surfaces and the interiors of CM-like bodies, implying a “low” temperature (<300°C) thermal evolution of the CM parent body(ies). It follows that an impact origin is the likely explanation for the existence of heated CM chondrites. Finally, similarly to S-type asteroids and (2) Pallas, the surfaces of large (D > 100 km)—supposedly primordial—Ch/Cgh-type main-belt asteroids likely expose the interiors of the primordial CM parent bodies, a possible consequence of impacts by small asteroids (D < 10 km) in the early solar system.

  8. Compositional Homogeneity of CM Parent Bodies

    NASA Astrophysics Data System (ADS)

    Vernazza, P.; Marsset, M.; Beck, P.; Binzel, R. P.; Birlan, M.; Cloutis, E. A.; DeMeo, F. E.; Dumas, C.; Hiroi, T.

    2016-09-01

    CM chondrites are the most common type of hydrated meteorites, making up ∼1.5% of all falls. Whereas most CM chondrites experienced only low-temperature (∼0°C–120°C) aqueous alteration, the existence of a small fraction of CM chondrites that suffered both hydration and heating complicates our understanding of the early thermal evolution of the CM parent body(ies). Here, we provide new constraints on the collisional and thermal history of CM-like bodies from a comparison between newly acquired spectral measurements of main-belt Ch/Cgh-type asteroids (70 objects) and existing laboratory spectral measurements of CM chondrites. It first appears that the spectral variation observed among CM-like bodies is essentially due to variations in the average regolith grain size. Second, the spectral properties of the vast majority (unheated) of CM chondrites resemble both the surfaces and the interiors of CM-like bodies, implying a “low” temperature (<300°C) thermal evolution of the CM parent body(ies). It follows that an impact origin is the likely explanation for the existence of heated CM chondrites. Finally, similarly to S-type asteroids and (2) Pallas, the surfaces of large (D > 100 km)—supposedly primordial—Ch/Cgh-type main-belt asteroids likely expose the interiors of the primordial CM parent bodies, a possible consequence of impacts by small asteroids (D < 10 km) in the early solar system.

  9. The collisional evolution of chondritic parent bodies

    NASA Astrophysics Data System (ADS)

    Blum, Jürgen; Beitz, Eike; Parisi, Mirta Gabriela

    2015-11-01

    Most meteorites are fragments form recent collisions in the asteroid belt. The collision speed between two objects of the asteroid belt is given by the eccentricity and inclination of their respective Keplerian orbits. Typical values are on the order of a few km s-1. In such a hyper-velocity collision, the smaller collision partner (projectile) is destroyed, whereas, depending on the mass ratio of the colliding objects, a crater on the larger body (target) is formed or the target is entirely destroyed, too. The present size distribution of the asteroid belt suggests that an asteroid with 100 km radius is encountered ~1014 times during the lifetime of the Solar System by objects larger than 10 cm in radius, the formed craters cover the surface of the asteroid about 100 times.We will present a numerical study that simulates the statistical bombardment on an asteroidal surface and tracks the resulting morphological changes of the parent body due to the formation of craters, the compaction of the material beneath the craters as well as the formation of a regolith layer. The crater ejecta from recent impacts on a consolidated asteroid are then compared to the known meteorites, particularly concerning the distribution of shock stages.Comparing the compaction of ejected material from the simulated collisions that occurred during the last 20 Myrs, which is the mean cosmic ray exposure age of meteorites, with shock stages of meteorites, we find that meteorites most likely stem from smaller parent bodies that do not have a significant regolith layer. For larger objects that inevitably accrete regolith layers, a prediction of the thickness depending on the largest visible crater can be made. Additionally, we compare the crater distribution of an initially 100 km (radius) large object with a shape model of asteroid (21) Lutetia, assuming it to be initially formed spherical with a radius that is equal to its longest present ellipsoid length, and find a reasonable agreement

  10. 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.

  11. Modelling the differentiation of the acapulcoite-lodranite parent body

    NASA Astrophysics Data System (ADS)

    Neumann, Wladimir Otto; Breuer, Doris; Spohn, Tilman; Henke, Stephan; Gail, Hans-Peter; Schwarz, Winfried; Trieloff, Mario; Hopp, Jens

    2015-08-01

    The acapulcoites and lodranites are rare groups of achondrites that originate from a common parent body. These meteorites are especially interesting because they experienced melting that was, however, not complete. We have performed thermal evolution models of the parent body of the Acapulco and Lodran-like meteorite clan, considering heating by short- and long-lived nuclides, temperature- and porosity-dependent parameters, and compaction of porous material. These models have been compared to the observed maximum metamorphic temperatures and thermo-chronological data available. An optimized set of parameters was determined, which fits to the data for the cooling histories of the meteorites. The optimum fit matches a body with the radius of 270 km that formed 1.66 Ma after CAIs with an initial temperature of 300 K. As the obtained temperatures are higher than the melting temperature of the metal phase, we considered in a second step a more detailed model that further includes melt migration by porous flow using the optimum fit parameters. Segregation of iron is assumed to start at a melt fraction threshold of 5%. The resulting structure has an iron core, a silicate mantle, a partially differentiated layer, an undifferentiated partially melted layer, and an outer unmelted shell. The temperature evolution obtained still fits to the cooling ages, and the burial depths derived range between 4 and 8 km. These layers experienced negligible melt migration, consistent with the observation of partial melting of the meteorites.Our results indicate a larger size and an earlier formation time of the acapulcoite-lodranite parent body, than typical estimates for ordinary chondrites’ parent bodies. This is also consistent with a higher degree of thermal metamorphism observed for the acapulcoite-lodranite parent body. The optimum fit initial temperature of 300 K suggests a formation closer to the Sun than ordinary chondrite parent bodies. The burial depths support excavation by a

  12. Olivine diogenites - The mantle of the eucrite parent body

    NASA Technical Reports Server (NTRS)

    Sack, Richard O.; Azeredo, William J.; Lipschutz, Michael E.

    1991-01-01

    Two olivine-rich Antarctic diogenites (ALH A77256 and ALH 84001) of the howardite-eucrite-diogenite (HED) meteorite association have olivine/pyroxene ratios similar to normative ratios in devolatilized ordinary chondrites. Based on chemical data and petrological analysis, these meteorites represent the residuum of partial melting of the mantle in the eucrite parent body (EPB). Mineral assemblages in these olivine-rich diogenites record a continuum in thermal histories from initial partial melting (1150-1200 C) to subsolidus reequilibration (795 + or - 55 C). The small number of olivine-rich diogenites known hints that only the outer portion of the EPB has been sampled.

  13. Phosphates in pallasite meteorites as probes of mantle processes in small planetary bodies

    NASA Technical Reports Server (NTRS)

    Davis, Andrew M.; Olsen, Edward J.

    1991-01-01

    Trace element analyses of the phosphates minerals in stony-iron pallasite meteorites are used here to investigate the magmatic history of the silicate portions of pallasites. In Eagle Station and seven other pallasites, the phosphates have relatively low concentrations of REEs and are strongly enriched in heavy relative to light REE. These patterns are consistent with formation of phosphate by subsolidus reactions between metal and silicate, in which phosphate inherits the REE pattern of olivine. In Springwater and Santa Rosalia, calcium-rich phosphates have higher concentrations of REE, are enriched in light relative to heavy REE, and have negative europium anomalies. These patterns are consistent with crystallization of phosphate from a europium-depleted chondritic liquid. This is unlikely to have happened near the base of the differentiating parent-body mantle; it suggests that some pallasites may come from regions of their parent bodies much nearer the surface than the core-mantle boundary.

  14. Hydrothermal Convection and Aqueous Alteration in Carbonaceous Chondrite Parent Bodies

    NASA Astrophysics Data System (ADS)

    Palguta, Jennifer; Travis, B. J.; Schubert, G.

    2006-09-01

    Carbonaceous chondrites (CCs) are derived from undifferentiated icy planetesimals and are the most primitive meteorites. The information that we can derive from CCs depends largely on our understanding the effects of water in carbonaceous chondrite parent bodies (CCPBs). The way water influenced the parent bodies’ evolution depends partly on the flow rates and patterns of the water circulation. The first quantitative models for the thermal evolution of CCPBs were based on parameterized hydrothermal convection and homogeneous alteration. Recent work has presented full models of hydrothermal convection in an internally heated, self-gravitating porous sphere. These results illustrate that the convective patterns in CCPBs are not uniform. Some regions of the body experience little to no pore water flow while other regions experience hundreds of pore volumes. It has long been held that CC meteorites of different chemical groups come from distinct parent bodies. Simulations showing heterogeneous patterns of fluid flow in CCPBs have led to the suggestion that parent bodies could be heterogeneously altered and, consequently, one parent body could be a source for multiple groups of CC meteorites. Previously, no numerical convection simulations of CCPBs have included water-rock reactions. We have coupled the computer code MAGHNUM with the reaction package PHREEQC. We use MAGHNUM to simulate the dynamic freezing, thawing and flow of water in a radiogenically-heated, self-gravitating body. The accompanying water-rock interactions are modeled with PHREEQC. Flow and chemistry are coupled through, for example, reaction rates and temperature. This work was supported by a grant from the Institute of Geophysics and Planetary Physics at Los Alamos National Laboratory.

  15. Multiple and fast: The accretion of ordinary chondrite parent bodies

    SciTech Connect

    Vernazza, P.; Barge, P.; Zanda, B.; Hewins, R.; Binzel, R. P.; DeMeo, F. E.; Lockhart, M.; Hiroi, T.; Birlan, M.; Ricci, L.

    2014-08-20

    Although petrologic, chemical, and isotopic studies of ordinary chondrites and meteorites in general have largely helped establish a chronology of the earliest events of planetesimal formation and their evolution, there are several questions that cannot be resolved via laboratory measurements and/or experiments alone. Here, we propose the rationale for several new constraints on the formation and evolution of ordinary chondrite parent bodies (and, by extension, most planetesimals) from newly available spectral measurements and mineralogical analysis of main-belt S-type asteroids (83 objects) and unequilibrated ordinary chondrite meteorites (53 samples). Based on the latter, we suggest that spectral data may be used to distinguish whether an ordinary chondrite was formed near the surface or in the interior of its parent body. If these constraints are correct, the suggested implications include that: (1) large groups of compositionally similar asteroids are a natural outcome of planetesimal formation and, consequently, meteorites within a given class can originate from multiple parent bodies; (2) the surfaces of large (up to ∼200 km) S-type main-belt asteroids mostly expose the interiors of the primordial bodies, a likely consequence of impacts by small asteroids (D < 10 km) in the early solar system; (3) the duration of accretion of the H chondrite parent bodies was likely short (instantaneous or in less than ∼10{sup 5} yr, but certainly not as long as 1 Myr); (4) LL-like bodies formed closer to the Sun than H-like bodies, a possible consequence of the radial mixing and size sorting of chondrules in the protoplanetary disk prior to accretion.

  16. Multiple and Fast: The Accretion of Ordinary Chondrite Parent Bodies

    NASA Astrophysics Data System (ADS)

    Vernazza, P.; Zanda, B.; Binzel, R. P.; Hiroi, T.; DeMeo, F. E.; Birlan, M.; Hewins, R.; Ricci, L.; Barge, P.; Lockhart, M.

    2014-08-01

    Although petrologic, chemical, and isotopic studies of ordinary chondrites and meteorites in general have largely helped establish a chronology of the earliest events of planetesimal formation and their evolution, there are several questions that cannot be resolved via laboratory measurements and/or experiments alone. Here, we propose the rationale for several new constraints on the formation and evolution of ordinary chondrite parent bodies (and, by extension, most planetesimals) from newly available spectral measurements and mineralogical analysis of main-belt S-type asteroids (83 objects) and unequilibrated ordinary chondrite meteorites (53 samples). Based on the latter, we suggest that spectral data may be used to distinguish whether an ordinary chondrite was formed near the surface or in the interior of its parent body. If these constraints are correct, the suggested implications include that: (1) large groups of compositionally similar asteroids are a natural outcome of planetesimal formation and, consequently, meteorites within a given class can originate from multiple parent bodies; (2) the surfaces of large (up to ~200 km) S-type main-belt asteroids mostly expose the interiors of the primordial bodies, a likely consequence of impacts by small asteroids (D < 10 km) in the early solar system; (3) the duration of accretion of the H chondrite parent bodies was likely short (instantaneous or in less than ~105 yr, but certainly not as long as 1 Myr); (4) LL-like bodies formed closer to the Sun than H-like bodies, a possible consequence of the radial mixing and size sorting of chondrules in the protoplanetary disk prior to accretion.

  17. Cosmic-Ray-Exposure Ages of Diogenites and the Collisional History of the HED Parent Body or Bodies

    NASA Technical Reports Server (NTRS)

    Welten, K. C.; Lindner, L.; vanderBorg, K.; Loeken, T.; Scherer, P.; Schultz, L.

    1996-01-01

    Cosmic-ray-exposure ages of meteorites provide information on the collisional history of their parent bodies and the delivery mechanism of meteorites to Earth. The exposure-age distributions of ordinary chondrites show distinct patterns for H, L, and LL types, consistent with their origin on different parent bodies. The exposure-age distributions of howardites, eucrites. and diogenites (HEDS) show a common pattern with major peaks at 22 Ma and 38 Ma This provides additional evidence for a common origin of the HED meteorites, possibly 4 Vesta, although orbital dynamics calculations showed that the delivery of meteorites from Vesta to Earth is difficult. However, the discovery of several kilometer-sized Vesta-like asteroids in the region between Vesta and the 3:1 resonance suggested that these seem more likely parent bodies of the HEDs than Vesta itself. This implies that the exposure-age clusters may represent samples of several parent bodies. Therefore, the near-absence of diogenites with ages <20 Ma might be of interest for the composition of these kilometer-sized fragments of Vesta. Here we present cosmic-ray-exposure ages of 20 diogenites, including 9 new meteorites. In addition, we calculate the probability for each peak to occur by chance, assuming a constant production rate of HED fragments.

  18. The Tishomingo Iron Meteorite and a Possible Genetic Link to Group IVB Iron Meteorites — Evidence from Molybdenum Isotopes

    NASA Astrophysics Data System (ADS)

    Worsham, E. A.; Walker, R. J.; Corrigan, C. M.; McCoy, T. J.

    2012-03-01

    Using Mo isotopes to support or reject a genetic link between the ungrouped iron meteorite Tishomingo and the IVB iron meteorite group is explored. Implications of the possible relationship for the evolution of the IVB parent body are also outlined.

  19. Surface Processes on Small Planetary Bodies: Implications for the Origins of Chondritic Meteorites

    NASA Astrophysics Data System (ADS)

    Akridge, David Glen

    I have conducted both experimental and theoretical work concerning the formation conditions of chondritic meteorites. This work has focused on the size-sorting of chondrules and metal grains, metal abundance in chondrites, gas phase reactions, and the thermal history of meteorite parent bodies containing substantial regoliths. Although many of the major chondritic properties have been assumed to be the result of nebula processes, it is suggested here that the release of volatiles in a parent body regolith would cause gas phase reactions indistinguishable from those occurring in the nebula. The escaping volatiles from either radiogenic 26Al or impact heating could create a dynamic surface dust layer on planetesimals leading to the physical separation of regolith grains of differing size and densities. The thermal history of an H-chondrite parent body (Asteroid 6 Hebe) was numerically modeled using 26Al as the primary heat source. The three layer model consisted of an interior of solid rock overlain by a megaregolith and regolith surfaces coverings. Appropriate porosities, bulk densities, and thermal conductivities were used for each zone. Regolith and megaregolith thicknesses were varied to see which numerical run best matched the metamorphic characteristics of H-chondrites. The results show surprisingly shallow burial depths for most H-chondrites. A moderate 2 km regolith insulates the interior so that H3-6 chondrites can all be formed in the regolith or upper megaregolith. Predicted peak temperatures, cooling rates, and formation time intervals agree well with data obtained from H-chondrites. The release of volatiles (primarily water) during parent body heating events could cause fluidization in the regolith if the upward moving gas flow rate reached a minimum critical velocity. At this minimum velocity particulates are free to move with fluid-like behavior and may segregate based on size and density characteristics. Fluidization experiments at atmospheric and

  20. Evolution of carbonaceous chondrite parent bodies: Insights into cometary nuclei

    NASA Technical Reports Server (NTRS)

    Mcsween, Harry Y., Jr.

    1989-01-01

    It is thought that cometary samples will comprise the most primitive materials that are able to be sampled. Although parent body alteration of such samples would not necessarily detract from scientists' interest in them, the possibility exists that modification processes may have affected cometary nuclei. Inferences about the kinds of modifications that might be encountered can be drawn from data on the evolution of carbonaceous chondrite parent bodies. Observations suggest that, of all the classes of chondrites, these meteorites are most applicable to the study of comets. If the proportion of possible internal heat sources such as Al-26 in cometary materials are similar to those in chondrites, and if the time scale of comet accretion was fast enough to permit incorporation of live radionuclides, comets might have had early thermal histories somewhat like those of carbonaceous chondrite parent bodies.

  1. Thermal history modelling of the H chondrite parent body

    NASA Astrophysics Data System (ADS)

    Henke, S.; Gail, H.-P.; Trieloff, M.; Schwarz, W. H.; Kleine, T.

    2012-09-01

    Context. The cooling histories of individual meteorites can be empirically reconstructed by using ages obtained from different radioisotopic chronometers having distinct closure temperatures. For a given group of meteorites derived from a single parent body such data permit the detailed reconstruction of the cooling history of that body. Particularly suited for this purpose are H chondrites because (i) all of them are thought to derive from a single parent body (possibly asteroid (6) Hebe) and (ii) for several specimens precise radiometric ages over a wide range of closure temperatures are available. Aims: A thermal evolution model for the H chondrite parent body is constructed by using the cooling histories of all H chondrites for which at least three different precise radiometric ages are available. The thermal model thus obtained is then used to constrain some important basic properties of the H chondrite parent body. Methods: Thermal evolution models are calculated using our previously developed code, which incorporates the effects of sintering and uses new thermal conductivity data for porous materials. Several key parameters determining the thermal evolution of the H chondrite parent body are varied together with the unknown original location of the H chondrites within their parent body until an optimal fit between the radiometric age data and the properties of the model is obtained. The fit is performed in an automated way based on an "evolution algorithm" to allow for a simultaneous fit of a large number of data, which depend in a complex way on several parameters. Empirical data for the cooling history of H chondrites are taken from the literature and the thermal model is optimised for eight samples for which radiometric ages are available for at least three different closure temperatures. Results: A set of parameters for the H chondrite parent body is found that yields excellent agreement (within error bounds) between the thermal evolution model and

  2. Magnetic evidence for a partially differentiated carbonaceous chondrite parent body

    PubMed Central

    Carporzen, Laurent; Weiss, Benjamin P.; Elkins-Tanton, Linda T.; Shuster, David L.; Ebel, Denton; Gattacceca, Jérôme

    2011-01-01

    The textures of chondritic meteorites demonstrate that they are not the products of planetary melting processes. This has long been interpreted as evidence that chondrite parent bodies never experienced large-scale melting. As a result, the paleomagnetism of the CV carbonaceous chondrite Allende, most of which was acquired after accretion of the parent body, has been a long-standing mystery. The possibility of a core dynamo like that known for achondrite parent bodies has been discounted because chondrite parent bodies are assumed to be undifferentiated. Resolution of this conundrum requires a determination of the age and timescale over which Allende acquired its magnetization. Here, we report that Allende’s magnetization was acquired over several million years (Ma) during metasomatism on the parent planetesimal in a >  ∼ 20 μT field up to approximately 9—10 Ma after solar system formation. This field was present too recently and directionally stable for too long to have been generated by the protoplanetary disk or young Sun. The field intensity is in the range expected for planetesimal core dynamos, suggesting that CV chondrites are derived from the outer, unmelted layer of a partially differentiated body with a convecting metallic core.

  3. 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.

  4. 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.

  5. Thermal History of the Allende Parent Body

    NASA Astrophysics Data System (ADS)

    Weinbruch, S.; Armstrong, J. T.; Palme, H.

    1992-07-01

    ) data to low temperatures we assume that his experiments were buffered by QFM, resulting in faster diffusion at low temperatures compared to equations reported by Jones and Rubie (1991) and McCoy et al. (1991). At 800 K the observed Fe/Mg concentration profiles cannot be retained for more than 2 x 10^3 years (extrapolated from Buening and Buseck, 1973) to 2 x 10^5 years (extrapolated from Misener, 1974). At temperatures around 700 K and 600 K, respectively the observed concentration profiles could survive several million years. These temperatures may, thus, be regarded as an upper limit for peak metamorphic temperature in the Allende parent body. Extensive Fe/Mg interdiffusion between forsterite and fayalite leading to broad diffusion profiles frequently observed in Allende cannot be the result of parent body metamorphism but must have occurred at high temperatures in the solar nebula. References Buening D.K. and Buseck P.R. (1973) J. Geophys. Res. 78, 6852-6862. Jones R.H. and Rubie D.C. (1991) Earth Planet. Sci. Lett. 106, 73-86. McCoy T.J., Scott E.R.D., Jones R.H., Keil K. and Taylor G.J. (1991) Geochim. Cosmochim. Acta 55, 601-619. Misener D.J. (1974) In Geochemical Transport and Kinetics (ed. A.W. Hofmann), pp. 117-129. Carnegie Inst. Washington 634. Weinbruch S., Palme H., Muller W.F. and El Goresy A. (1990) Meteoritics 25, 115-125.

  6. Modelling the thermal evolution and differentiation of the parent body of acapulcoites and lodranites

    NASA Astrophysics Data System (ADS)

    Neumann, Wladimir; Breuer, Doris; Spohn, Tilman; Henke, Stephan; Gail, Hans-Peter; Schwarz, Winfried; Trieloff, Mario; Hopp, Jens

    2015-04-01

    The acapulcoites and lodranites are rare groups of achondritic meteorites. Several characteristics such as unique oxygen isotope composition and similar cosmic ray exposure ages indicate that these meteorites originate from a common parent body (Weigel et al. 1999). By contrast to both undifferentiated and differentiated meteorites, acapulcoites and lodranites are especially interesting because they experienced melting that was, however, not complete (McCoy et al. 2006). Thus, unravelling their origin contributes directly to the understanding of the initial differentiation stage of planetary objects in the Solar system. The information preserved in the structure and composition of meteorites can be recovered by modelling the evolution of their parent bodies and comparing the results with the laboratory investigations. Model calculations for the thermal evolution of the parent body of the Acapulco and Lodran-like meteorite clan were performed using two numerical models. Both models (from [3] and [4], termed (a) and (b), respectively) solve a 1D heat conduction equation in spherical symmetry considering heating by short- and long-lived radioactive isotopes, temperature- and porosity-dependent parameters, compaction of initially porous material, and melting. The calculations with (a) were compared to the maximum metamorphic temperatures and thermo-chronological data available for acapulcoites and lodranites. Applying a genetic algorithm, an optimised set of parameters of a common parent body was determined, which fits to the data for the cooling histories of these meteorites. The optimum fit corresponds to a body with the radius of 270 km and a formation time of 1.66 Ma after the CAIs. Using the model by (b) that considers differentiation by porous flow and magmatic heat transport, the differentiation of the optimum fit body was calculated. The resulting structure consists of a metallic core, a silicate mantle, a partially differentiated layer, an undifferentiated

  7. The parent magma of the nakhlite meteorites - Clues from melt inclusions

    NASA Technical Reports Server (NTRS)

    Harvey, Ralph P.; Mcsween, Harry Y., Jr.

    1992-01-01

    Several forms of trapped liquid found within nakhlite meteorites have been examined, including interstitial melt and magmatic inclusions within the cores of large olivine grains. Differences in the mineralogy and texture between two types of trapped melt inclusions, and between these inclusions and the mesostasis, indicate that vitrophyric inclusions are most appropriate for estimating the composition of a nakhlite parental magma in equilibrium with early-forming olivine and augite. Parent liquids were calculated from the mineralogy of large inclusions in Nakhla and Governador Valadares, using a system of mass-balance equations solved by linear regression methods. The chosen parental liquids were cosaturated in olivine and augite and had Mg/Fe values consistent with measured augite/liquid Kds. These parental magma compositions are similar to other published compositions for Nakhla, Chassigny, and Shergotty parental melts, and may correspond to a significant magma type on Mars.

  8. Do oblique impacts produce Martian meteorites

    NASA Astrophysics Data System (ADS)

    Nyquist, L. E.

    1983-11-01

    It is pointed out that several achondritic meteorites, classified as shergottites, nakhlites, and chassignites, have a number of unusual characteristics. Following the suggestion of Wood and Ashwal (1981) these meteorites are collectively referred to as SNC meteorites. The major element compositions of the SNC meteorites are, in general, distinct from those of other meteorites and lunar samples, and similar to certain terrestrial rocks. The geochemical and geochronological characteristics of the SNC meteorites strongly imply that their parent body was on the order of lunar size or larger and geologically active. Serious attention must be given to the hypothesis of a Martian origin of the SNC meteorites and to dynamic processes capable of delivering Martian meteorites to earth. In connection with the present investigation, it is suggested that oblique impacts of large meteoroids can produce ejecta which is entrained with the ricocheting projectile and accelerated to velocities in excess of Martian escape velocity.

  9. Meteorite Dunite Breccia MIL 03443: A Probable Crustal Cumulate Closely Related to Diogenites from the HED Parent Asteroid

    NASA Technical Reports Server (NTRS)

    Mittlefehldt, David W.

    2008-01-01

    There are numerous types of differentiated meteorites, but most represent either the crusts or cores of their parent asteroids. Ureilites, olivine-pyroxene-graphite rocks, are exceptions; they are mantle restites [1]. Dunite is expected to be a common mantle lithology in differentiated asteroids. In particular, models of the eucrite parent asteroid contain large volumes of dunite mantle [2-4]. Yet dunites are very rare among meteorites, and none are known associated with the howardite, eucrite, diogenite (HED) suite. Spectroscopic measurements of 4 Vesta, the probable HED parent asteroid, show one region with an olivine signature [5] although the surface is dominated by basaltic and orthopyroxenitic material equated with eucrites and diogenites [6]. One might expect that a small number of dunitic or olivine-rich meteorites might be delivered along with the HED suite. The 46 gram meteoritic dunite MIL 03443 (Fig. 1) was recovered from the Miller Range ice field of Antarctica. This meteorite was tentatively classified as a mesosiderite because large, dunitic clasts are found in this type of meteorite, but it was noted that MIL 03443 could represent a dunite sample of the HED suite [7]. Here I will present a preliminary petrologic study of two thin sections of this meteorite.

  10. Evidence that Polycyclic Aromatic Hydrocarbons in Two Carbonaceous Chondrites Predate Parent-Body Formation

    NASA Technical Reports Server (NTRS)

    Plows, F. L.; Elsila, J. E.; Zare, R. N.; Buseck, P. R.

    2003-01-01

    Organic material in meteorites provides insight into the cosmochemistry of the early solar system. The distribution of polycyclic aromatic hydrocarbons (PAHs) in the Allende and Murchison carbonaceous chondrites was investigated using spatially resolved microprobe laser-desorption laser-ionization mass spectrometry. Sharp chemical gradients of PAHs are associated with specific meteorite features. The ratios of various PAH intensities relative to the smallest PAH, naphthalene, are nearly constant across the sample. These findings suggest a common origin for PAHs dating prior to or contemporary with the formation of the parent body, consistent with proposed interstellar formation mechanisms.

  11. Evidence from Polymict Ureilite Meteorites for a Single "Rubble-Pile" Ureilite Parent Asteroid Gardened by Several Distinct Impactors

    NASA Technical Reports Server (NTRS)

    Downes, Hilary; Mittlefehldt, David W.; Kita, Noriko T.; Valley, John W.

    2008-01-01

    Ureilites are ultramafic achondrite meteorites that have experienced igneous processing whilst retaining heterogeneity in mg# and oxygen isotope ratios. Polymict ureilites represent material derived from the surface of the ureilite parent asteroid(s). Electron microprobe analysis of more than 500 olivine and pyroxene clasts in six polymict ureilites reveals that they cover a statistically identical range of compositions to that shown by all known monomict ureilites. This is considered to be convincing evidence for derivation from a single parent asteroid. Many of the polymict ureilites also contain clasts that have identical compositions to the anomalously high Mn/Mg olivines and pyroxenes from the Hughes 009 monomict ureilite (here termed the Hughes cluster ). Four of the six samples also contain distinctive ferroan lithic clasts that have been derived from oxidized impactors. The presence of several common distinctive lithologies within the polymict ureilites is additional evidence that the ureilites were derived from a single parent asteroid. Olivine in a large lithic clast of augite-bearing ureilitic has an mg# of 97, extending the compositional range of known ureilite material. Our study confirms that ureilitic olivine clasts with mg#s < 85 are much more common than those with mg# > 85, which also show more variable Mn contents, including the melt-inclusion bearing "Hughes cluster" ureilites. We interpret this to indicate that the parent ureilite asteroid was disrupted by a major impact at a time when melt was still present in regions with a bulk mg# > 85, giving rise to the two types of ureilites: common ferroan ones that were already residual after melting and less common magnesian ones that were still partially molten when disruption occurred, some of which are the result of interaction of melts with residual mantle during disruption. A single daughter asteroid re-accreted from the disrupted remnants of the mantle of the proto-ureilite asteroid, giving rise

  12. Paleomagnetism of a primitive achondrite parent body: The acapulcoite-lodranites

    NASA Astrophysics Data System (ADS)

    Schnepf, N. R.; Weiss, B. P.; Andrade Lima, E.; Fu, R. R.; Uehara, M.; Gattacceca, J.; Wang, H.; Suavet, C. R.

    2014-12-01

    Primitive achondrites are a recently recognized meteorite grouping with textures and compositions intermediate between unmelted meteorites (chondrites) and igneous meteorites (achondrites). Their existence demonstrates prima facie that some planetesimals only experienced partial rather than complete melting. We present the first paleomagnetic measurements of acapulcoite-lodranite meteorites to determine the existence and intensity of ancient magnetic fields on their parent body. Our paleomagnetic study tests the hypothesis that their parent body had an advecting metallic core, with the goal of providing one of the first geophysical constraints on its large-scale structure and the extent of interior differentiation. In particular, by analyzing samples whose petrologic textures require an origin on a partially differentiated body, we will be able to critically test a recent proposal that some achondrites and chondrite groups could have originated on a single body (Weiss and Elkins-Tanton 2013). We analyzed samples of the meteorites Acapulco and Lodran. Like other acapulcoites and lodranites, these meteorites are granular rocks containing large (~0.1-0.3 mm) kamacite and taenite grains along with similarly sized silicate crystals. Many silicate grains contain numerous fine (1-10 μm) FeNi metal inclusions. Our compositional measurements and rock magnetic data suggest that tetrataenite is rare or absent. Bulk paleomagnetic measurements were done on four mutually oriented bulk samples of Acapulco and one bulk sample of Lodran. Alternating field (AF) demagnetization revealed that the magnetization of the bulk samples is highly unstable, likely due to the large (~0.1-0.3 mm) interstitial kamacite grains throughout the samples. To overcome this challenge, we are analyzing individual ~0.2 mm mutually oriented silicate grains extracted using a wire saw micromill. Preliminary SQUID microscopy measurements of a Lodran silicate grain suggest magnetization stable to AF levels of

  13. 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.

  14. Amphibole in Martian Meteorites: Composition and Implication for Volatile Content of Parental Magma

    NASA Astrophysics Data System (ADS)

    Williams, K. B.; Sonzogni, Y.; Treiman, A. H.

    2013-12-01

    Titanium-rich amphibole is present in melt inclusions in many martian (SNC) meteorites, suggesting that martian magmas contained water. Amphibole has been reported in melt inclusions within olivine grains in chassignites [1-3], and occurs in melt inclusions within pigeonite grains in most shergottites [4-10]. This study focuses on a comparison of amphibole compositions in two olivine-phyric shergottites: Tissint and Elephant Moraine (EETA) 79001, Lithology A. While amphibole (commonly of kaersutitic composition) is rare in martian meteorites, the mineral is widespread and may be useful in constraining volatile abundances in the martian mantle. Amphibole incorporates hydroxyl into its mineral structure on its O(3) site, which can also contain F-, Cl-, and O2-. Previous chemical analyses of amphiboles in martian meteorites show low halogen abundances, implying high proportions of OH- and/or O2- in the O(3) site [6, 11]. Presence of O2- on O(3) is not considered in this study, even though oxy-kaersutite can be stable at 1 bar pressure [11, 12]. Our chemical data on amphibole in martian meteorites will expand the current compositional database and provide amphibole water content estimates that can then be used to constrain the water content of the parental magma. Amphiboles were identified in polished thin sections of Tissint and EETA79001A by their yellow-orange to light brown pleochroism. Consistent with previous observations of amphibole in shergottites [4-10], the amphiboles are present only in melt inclusions in the cores of pigeonite grains, and never in augite, olivine, or mesostasis. The amphibole grains are subhedral, and range up to 15 μm in diameter. Amphibole formulae were calculated from chemical analyses by normalizing to 23 O, assuming that all iron is ferrous, and assuming that halogens and hydroxyl fully occupy the O(3) site (i.e., F-+Cl-+OH-= 2). Variability in iron oxidation and the possibility of internal amphibole dehydrogenation provide

  15. RAPID TIMESCALES FOR MAGMA OCEAN CRYSTALLIZATION ON THE HOWARDITE-EUCRITE-DIOGENITE PARENT BODY

    SciTech Connect

    Schiller, Martin; Paton, Chad; Bizzarro, Martin; Baker, Joel; Creech, John; Millet, Marc-Alban; Irving, Anthony

    2011-10-10

    Asteroid 4 Vesta has long been postulated as the source for the howardite-eucrite-diogenite (HED) achondrite meteorites. Here we show that Al-free diogenite meteorites record variability in the mass-independent abundance of {sup 26}Mg ({sup 26}Mg*) that is correlated with their mineral chemistry. This suggests that these meteorites captured the Mg-isotopic evolution of a large-scale differentiating magma body with increasing {sup 27}Al/{sup 24}Mg during the lifespan of the short-lived {sup 26}Al nuclide (t {sub 1/2} {approx} 730,000 yr). Thus, diogenites and eucrites represent crystallization products of a large-scale magma ocean associated with the differentiation and magmatic evolution of the HED parent body. The {sup 26}Mg* composition of the most primitive diogenites requires onset of the magma ocean crystallization within 0.6{sup -0.4} {sub +0.5} Myr of solar system formation. Moreover, {sup 26}Mg* variations among diogenites and eucrites imply that near complete solidification of the HED parent body occurred within the following 2-3 Myr. Thermal models predict that such rapid cooling and magma ocean crystallization could only occur on small asteroids (<100 km), implying that 4 Vesta is not the source of the HED meteorites.

  16. Multiple parent bodies of ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Yomogida, K.; Matsui, T.

    1984-01-01

    Thermal histories of chondrite parent bodies are calculated from an initial state with material in a powder-like form, taking into account the effect of consolidation state on thermal conductivity. The very low thermal conductivity of the starting materials makes it possible for a small body with a radius of less than 100 km to be heated by several hundred degrees even if long-lived radioactive elements in chondritic abundances are the only source of heat. The maximum temperature is determined primarily by the temperature at which sintering of the constituent materials occurs. The thermal state of the interior of a chondrite parent body after sintering has begun is nearly isothermal. Near the surface, however, where the material is unconsolidated and the thermal conductivity is much lower, the thermal gradient is quite large. This result contradicts the conventional 'onion-shell' model of chondrite parent bodies. But because the internal temperature is almost constant through the whole body, it supports a 'multiple-parent bodies' model, according to which each petrologic type of chondrite comes from a different parent body.

  17. INAA of CAIs from the Maralinga CK4 chondrite: Effects of parent body thermal metamorphism

    NASA Technical Reports Server (NTRS)

    Lindstrom, D. J.; Keller, L. P.; Martinez, R. R.

    1993-01-01

    Maralinga is an anomalous CK4 carbonaceous chondrite which contains numerous Ca-, Al-rich inclusions (CAI's) unlike the other members of the CK group. These CAI's are characterized by abundant green hercynitic spinel intergrown with plagioclase and high-Ca clinopyroxene, and a total lack of melilite. Instrumental Neutron Activation Analysis (INAA) was used to further characterize the meteorite, with special focus on the CAI's. High sensitivity INAA was done on eight sample disks about 100-150 microns in diameter obtained from a normal 30 micron thin section with a diamond microcoring device. The CAI's are enriched by 60-70X bulk meteorite values in Zn, suggesting that the substantial exchange of Fe for Mg that made the spinel in the CAI's hercynitic also allowed efficient scavenging of Zn from the rest of the meteorite during parent body thermal metamorphism. Less mobile elements appear to have maintained their initial heterogeneity.

  18. New evidence of meteoritic origin of the Tunguska cosmic body

    NASA Astrophysics Data System (ADS)

    Kvasnytsya, Victor; Wirth, Richard; Dobrzhinetskaya, Larissa; Matzel, Jennifer; Jacobsen, Benjamin; Hutcheon, Ian; Tappero, Ryan; Kovalyukh, Mykola

    2013-08-01

    Diamond-lonsdaleite-graphite micro-samples collected from peat after the 1908 catastrophic blast in the Tunguska area were studied with scanning (SEM) and transmission electron (TEM) microscopy, NanoSecondary Ion Mass Spectrometry (NanoSIMS) and Х-ray synchrotron technique. The high-pressure carbon allotropes in the Tunguska samples are being described for the first time and contain inclusions of FeS (troilite), Fe-Ni (taenite), γ-Fe and (FeNi)3P (schreibersite). The samples are nodule-like in shape and consist of 99.5% carbon minerals, e.g. diamond>lonsdaleite>graphite. Micro- and nanoinclusions of troilite (up to 0.5 vol%), taenite, γ-iron and schreibersite fill cracks, cleavages and pores in the carbon matrix. Carbon isotope studies from the two analyses of the Tunguska foil showed δ13C=-16.0±1.9‰ and δ13C=-15.2±2.1‰, suggesting δ13C=-15.6±2‰ as an average characteristic of the carbon reservoir. That value is close to δ13C of some extraterrestrial samples. A negligible concentration of Ir and Os in the carbonaceous matrix promotes some controversial interpretation of the origin of the studied materials. Attributing this fact to the primary inhomogeneity, and considering the micro-structural features such as cracks, deformation of the crystal lattices, etc. coupled with high-pressure carbon allotropes association with metals, sulfides and phosphides, and the high ratio of Fe:Ni=22:1 suggest that the studied samples are meteorite micro-remnants.

  19. 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.

  20. 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

  1. Carbonates and sulfates in CI chondrites - Formation by aqueous activity on the parent body

    NASA Technical Reports Server (NTRS)

    Fredriksson, Kurt; Kerridge, John F.

    1988-01-01

    Compositions and morphologies of dolomites, breunnerites, Ca-carbonates, Ca-sulfates and Mg, Ni, Na-sulfates, and their petrologic interrelations, in four CI chondrites are consistent with their having been formed by aqueous activity on the CI parent body. Radiochronometric data indicate that this activity took place very early in solar-system history. No evidence for original ('primitive') condensates seems to be present. However, alteration apparently took place without change in bulk meteorite composition.

  2. Relative Amino Acid Concentrations as a Signature for Parent Body Processes of Carbonaceous Chondrites

    NASA Technical Reports Server (NTRS)

    Botta, Oliver; Glavin, Daniel P.; Kminek, Gerhard; Bada, Jeffrey L.

    2002-01-01

    Most meteorites are thought to have originated from objects in the asteroid belt. Carbonaceous chondrites, which contain significant amounts of organic carbon including complex organic compounds, have also been suggested to be derived from comets. The current model for the synthesis of organic compounds found in carbonaceous chondrites includes the survival of interstellar organic compounds and the processing of some of these compounds on the meteoritic parent body. The amino acid composition of five CM carbonaceous chondrites, two CIs, one CR, and one CV3 have been measured using hot water extraction-vapor hydrolysis, OPA/NAC derivatization and high-performance liquid chromatography (HPLC). Total amino acid abundances in the bulk meteorites as well as the amino acid concentrations relative to glycine = 1.0 for beta-alanine, alpha-aminoisobutyric acid and D-alanine were determined. Additional data for three Antarctic CM meteorites were obtained from the literature. All CM meteorites analyzed in this study show a complex distribution of amino acids and a high variability in total concentration ranging from approx. 15,300 to approx. 5800 parts per billion (ppb), while the CIs show a total amino acid abundance of approx. 4300 ppb. The relatively (compared to glycine) high AIB content found in all the CMs is a strong indicator that Strecker-cyanohydrin synthesis is the dominant pathway for the formation of amino acids found in these meteorites. The data from the Antarctic CM carbonaceous chondrites are inconsistent with the results from the other CMs, perhaps due to influences from the Antarctic ice that were effective during their residence time. In contrast to CMs, the data from the CI carbonaceous chondrites indicate that the Strecker synthesis was not active on their parent bodies.

  3. Water Transport and the Evolution of CM Parent Bodies

    NASA Technical Reports Server (NTRS)

    Coker, R.; Cohen, B.

    2014-01-01

    Extraterrestrial water-bearing minerals are of great importance both for understanding the formation and evolution of the solar system and for supporting future human activities in space. Asteroids are the primary source of meteorites, many of which show evidence of an early heating episode and varying degrees of aqueous alteration. The origin and characterization of hydrated minerals (minerals containing H2O or OH) among both the main-belt and near-earth asteroids is important for understanding a wide range of solar system formation and evolutionary processes, as well as for planning for human exploration. Current hypotheses postulate asteroids began as mixtures of water ice and anhydrous silicates. A heating event early in solar system history was then responsible for melting the ice and driving aqueous alteration. The link between asteroids and meteorites is forged by reflectance spectra, which show 3-µm bands indicative of bound OH or H2O on the C-class asteroids, which are believed to be the parent bodies of the carbonaceous chondrites in our collections. The conditions at which aqueous alteration occurred in the parent bodies of carbonaceous chondrites are thought to be well-constrained: at 0-25 C for less than 15 Myr after asteroid formation. In previous models, many scenarios exhibit peak temperatures of the rock and co-existing liquid water in more than 75 percent of the asteroid's volume rising to 150 C and higher, due to the exothermic hydration reactions triggering a thermal runaway effect. However, even in a high porosity, water-saturated asteroid very limited liquid water flow is predicted (distances of 100's nm at most). This contradiction has yet to be resolved. Still, it may be possible for water to become liquid even in the near-surface environment, for a long enough time to drive aqueous alteration before vaporizing or freezing then subliming. Thus, we are using physics- and chemistry-based models that include thermal and fluid transport as well

  4. Thermal constraints on the early history of the H-chondrite parent body reconsidered

    NASA Astrophysics Data System (ADS)

    Harrison, Keith P.; Grimm, Robert E.

    2010-09-01

    Reconstructions of the early thermal history of the H-chondrite parent body have focused on two competing hypotheses. The first posits an undisturbed thermal evolution in which the degree of metamorphism increases with depth, yielding an "onion-shell" structure. The second posits an early fragmentation-reassembly event that interrupted this orderly cooling process. Here, we test these hypotheses by collecting a large number of previously published closure age and cooling rate data and comparing them to a suite of numerical models of thermal evolution in an idealized parent body. We find that the onion-shell hypothesis, when applied to a parent body of radius 75-130 km with a thermally insulating regolith, is able to explain 20 of the 21 closure age data and 62 of the 71 cooling rates. Furthermore, six of the eight meteorites for which multiple data (at different temperatures) are available, can be accounted for by onion-shell thermal histories. We therefore conclude that no catastrophic disruption of the H-chondrite parent body occurred during its early thermal history. The relatively small number of data not explained by the onion-shell hypothesis may indicate the formation of impact craters on the parent body which, while large enough to excavate all petrologic types, were small enough to leave the parent body largely intact. Impact events fulfilling these requirements would likely have produced transient crater diameters at least 30% of the parent body diameter.

  5. Future directions in meteorite research

    NASA Technical Reports Server (NTRS)

    Anders, E.; Kerridge, John F.

    1988-01-01

    Information presently available on meteorite composition and history and the areas in meteorite research that should be covered in future in order to shed additional light on the earliest history of the solar system are discussed. Attention is given to the work needed in the classification schemes for chondrites, the question of the identification of parent bodies of the major meteorite and chondrite types, the igneous differentiation of certain asteroids, the effects of irradiation, the solar-system chronology, and issues concerning the early solar system. Other important areas discussed include the elemental composition of chondrites, the magnetic properties of meteorites, the composition and the petrology of chondrules, the properties of primitive material surviving in chondrites, the micrometeorites, the nebula, the presolar material in meteorites, the nucleosynthesis, and the nucleocosmochronology.

  6. Cliftonite in meteorites: A proposed origin

    USGS Publications Warehouse

    Brett, R.; Higgins, G.T.

    1967-01-01

    Cliftonite, a polycrystalline aggregate of graphite with cubic morphology, is known in ten meteorites. Some workers have considered it to be a pseudomorph after diamond, and have used the proposed diamond ancestry as evidence of a meteoritic parent body of at least lunar dimensions. We have synthesized cliftonite in Fe-Ni-C alloys in vacuum, as a product of decomposition of cohenite [(Fe,Ni)3C]. We therefore suggest that a high pressure origin is unnecessary for meteorites which contain cliftonite, and that these meteorites were formed at low pressures. This conclusion is in agreement with other recent evidence.

  7. Carbon isotopes in three SNC meteorites

    NASA Astrophysics Data System (ADS)

    Carr, R. H.; Wright, I. P.; Pillinger, C. T.

    1985-02-01

    The presence of several carbonaceous components in SNC meteorites has been inferred from the analyses of samples of three SNC meteorites, Shergotty, Chassigny, and Elephant Moraine. The identification of the actual species involved, however, has not been possible except for that of the terrestrial materials known to contaminate extraterrestrial samples. Above 700 C, there is evidence of the presence of isotropically heavy and light components in all three meteorites, although there are notable differences in their isotopic compositions. The similarities observed may indicate a common origin for the meteorites, but the possibility that magmatic processes on different parent bodies have produced these features must be more fully explored.

  8. 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.

  9. Do meteorites contain irradiation records from exposure to an enhanced-activity sun?

    NASA Technical Reports Server (NTRS)

    Caffee, M. W.; Hohenberg, C. M.; Nichols, R. H., Jr.; Olinger, C. T.; Wieler, R.; Pedroni, A.; Signer, P.; Swindle, T. D.; Goswami, J. N.

    1991-01-01

    The meteoritic evidence for a T Tauri phase in the sun's evolution is reviewed. Emphasis is given to effects recorded in meteoritic grains before final compaction of the meteorite parent body and the evidence that these precompaction irradiation effects do or do not require an active early sun. Several other effects attributed to such early activity are also reviewed.

  10. 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

  11. Workshop on Parent-Body and Nebular Modification of Chondritic Materials

    NASA Technical Reports Server (NTRS)

    Zolensky, M. E. (Editor); Krot, A. N. (Editor); Scott, E. R. D. (Editor)

    1997-01-01

    Topics considered include: thermal Metamorphosed Antarctic CM and CI Carbonaceous Chondrites in Japanese Collections, and Transformation Processes of Phyllosilicates; use of Oxygen Isotopes to Constrain the Nebular and Asteroidal Modification of Chondritic Materials; effect of Revised Nebular Water Distribution on Enstatite Chondrite Formation; interstellar Hydroxyls in Meteoritic Chondrules: Implications for the Origin of Water in the Inner Solar System; theoretical Models and Experimental Studies of Gas-Grain Chemistry in the Solar Nebula; chemical Alteration of Chondrules on Parent Bodies; thermal Quenching of Silicate Grains in Protostellar Sources; an Experimental Study of Magnetite Formation in the Solar Nebula; the Kaidun Meteorite: Evidence for Pre- and Postaccretionary Aqueous Alteration; a Transmission Electron Microscope Study of the Matrix Mineralogy of the Leoville CV3 (Reduced-Group) Carbonaceous Chondrite: Nebular and Parent-Body Features; rubidium-Strontium Isotopic Systematic of Chondrules from the Antarctic CV Chondrites Yamato 86751 and Yamato 86009: Additional Evidence for Late Parent-Body Modification; oxygen-Fugacity Indicators in Carbonaceous Chondrites: Parent-Body Alteration or High-Temperature Nebular Oxidation; thermodynamic Modeling of Aqueous Alteration in CV Chondrites; asteroidal Modification of C and O Chondrites: Myths and Models; oxygen Fugacity in the Solar Nebular; and the History of Metal and Sulfides in Chondrites.

  12. Enstatite chondrites and enstatite achondrites (aubrites) were not derived from the same parent body

    USGS Publications Warehouse

    Brett, R.; Keil, Klaus

    1986-01-01

    Enstatite achondrites (aubrites) were not derived from known enstatite chondrites by melting and fractionation on one and the same parent body, for these and other reasons: (1) There is no satisfactory mechanism for fractionating metal plus troilite in enstatite chondrites to form these phases in different proportions and with different Ti contents in aubrites. (2) Many enstatite chondrites and aubrites are regolith or fragmental breccias, but clasts of one within the other have not been found. (3) Cosmic ray exposure ages of the two groups are difficult to explain if they are from the same parent body, but are easy to explain if they are from different parent bodies. Siderophile element abundances in metal from the Mt. Egerton meteorite, which consists of enstatite and metallic Fe,Ni, preclude it from being a complementary differentiate of the aubrites. Rather, it appears that Mt. Egerton was formed from the same source material as enstatite chondrites, but the components were mixed in different proportions. ?? 1986.

  13. Composition and evolution of the eucrite parent body - Evidence from rare earth elements. [extraterrestrial basaltic melts

    NASA Technical Reports Server (NTRS)

    Consolmagno, G. J.; Drake, M. J.

    1977-01-01

    Quantitative modeling of the evolution of rare earth element (REE) abundances in the eucrites, which are plagioclase-pigeonite basalt achondrites, indicates that the main group of eucrites (e.g., Juvinas) might have been produced by approximately 10% equilibrium partial melting of a single type of source region with initial REE abundances which were chondritic relative and absolute. Since the age of the eucrites is about equal to that of the solar system, extensive chemical differentiation of the eucrite parent body prior to the formation of eucrites seems unlikely. If homogeneous accretion is assumed, the bulk composition of the eucrite parent body can be estimated; two estimates are provided, representing different hypotheses as to the ratio of metal to olivine in the parent body. Since a large number of differentiated olivine meteorites, which would represent material from the interior of the parent body, have not been detected, the eucrite parent body is thought to be intact. It is suggested that the asteroid 4 Vesta is the eucrite parent body.

  14. 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.

  15. Long-lived magnetism from solidification-driven convection on the pallasite parent body.

    PubMed

    Bryson, James F J; Nichols, Claire I O; Herrero-Albillos, Julia; Kronast, Florian; Kasama, Takeshi; Alimadadi, Hossein; van der Laan, Gerrit; Nimmo, Francis; Harrison, Richard J

    2015-01-22

    Palaeomagnetic measurements of meteorites suggest that, shortly after the birth of the Solar System, the molten metallic cores of many small planetary bodies convected vigorously and were capable of generating magnetic fields. Convection on these bodies is currently thought to have been thermally driven, implying that magnetic activity would have been short-lived. Here we report a time-series palaeomagnetic record derived from nanomagnetic imaging of the Imilac and Esquel pallasite meteorites, a group of meteorites consisting of centimetre-sized metallic and silicate phases. We find a history of long-lived magnetic activity on the pallasite parent body, capturing the decay and eventual shutdown of the magnetic field as core solidification completed. We demonstrate that magnetic activity driven by progressive solidification of an inner core is consistent with our measured magnetic field characteristics and cooling rates. Solidification-driven convection was probably common among small body cores, and, in contrast to thermally driven convection, will have led to a relatively late (hundreds of millions of years after accretion), long-lasting, intense and widespread epoch of magnetic activity among these bodies in the early Solar System. PMID:25612050

  16. About Tagish Lake as a Potential Parent Body for Polar Micrometeorites; Clues from their Hydrogen Isotopic Compositions

    NASA Technical Reports Server (NTRS)

    Engrand, C.; Gounelle, M.; Zolensky, M. E.; Duprat, J.

    2003-01-01

    The origin of the Antarctic micrometeorites (AMMs) is still a matter of debate. Their closest meteoritic counterparts are the C2 chondrites, but the match is not perfect, and the parent body(ies) of the AMMs is(are) still to be identified. Tagish Lake is a new meteorite fall which bears similarity with CI1 and CM2 chondrites, but is distinct from both. Based on the mineralogy of phyllosilicates, Noguchi et al. proposed that the phyllosilicate-rich AMMs and the Tagish Lake meteorites could derive from similar asteroids. The hydrogen isotopic compositions of extra-terrestrial samples can be used to get some insight on their origin. The D/H ratios of AMMs and of Tagish Lake have been measured, but using different analytical techniques. They are therefore not directly comparable. We performed additional hydrogen isotopic analyses of fragments of Tagish Lake using the same experimental setup previously used for the measurement of the hydrogen isotopic composition of AMMs. In this work, we could also analyze separately both lithologies of Tagish Lake (carbonate-poor and -rich). The distributions of delta D values measured in the two lithologies of Tagish Lake are very similar, indicating that fluids with similar hydrogen isotopic compositions altered the meteorite on the parent body for the two lithologies. Yet, the hydrogen isotopic composition of Tagish Lake is different from that of AMMs, suggesting that they do not derive from the same parent body.

  17. Refractory element fractionation in the Allende meteorite: Implications for solar nebula condensation and the chondritic composition of planetary bodies

    NASA Astrophysics Data System (ADS)

    Stracke, Andreas; Palme, Herbert; Gellissen, Marko; Münker, Carsten; Kleine, Thorsten; Birbaum, Karin; Günther, Detlef; Bourdon, Bernard; Zipfel, Jutta

    2012-05-01

    Chondritic meteorites represent primitive undifferentiated solar system material that is compositionally similar to the non-volatile fraction of the Sun. The mineralogy and texture of chondritic meteorites is complex, however, because they are mixtures of several components that formed under different conditions in the solar nebula and were further processed on their parent bodies: chondrules, a volatile rich, fine-grained matrix, including a variety of mineral and lithic clasts, metal, sulfides, and Ca, Al-rich inclusions (CAI). The bulk chemistry of a single aliquot of a chondritic meteorite consequently depends on the size and distribution of its constituents. Here, we investigate the effect of sample heterogeneity on the major and trace element composition of the CV chondrite Allende using a single 30 g slice, which is 22.5 cm2 in dimension and 4 mm thick. Thirty-nine equally sized pieces with an average sample weight of ca. 0.6 g (corresponding to a cube with an edge length of 5 to 6 mm) were powdered and aliquots of 0.12 g and 0.02-0.03 g were analyzed by XRF for major and ICP-MS for trace elements. One sample contained a large CAI, another sample was dominated by a dark inclusion (DI). Excluding these two samples, the concentrations of the major elements Mg, Si and Fe are constant within analytical uncertainty at the millimeter-centimeter scale (S.D. 0.9, 1.3 and 2.6%, respectively). Non-refractory minor and trace elements are similarly constant, including geochemically very different elements such as Mn, Cr, Ni, Co, P, Zn and Pb. This reflects a uniform mixture of the various host phases of these elements during accretion, and excludes elemental redistribution above a millimeter-scale by aqueous alteration and/or thermal metamorphism on the parent body. The refractory elements Al, Ca, Ti etc. are more variable (S.D. 17, 10 and 9%, respectively), which is mainly the result of different proportions of millimeter-size CAI, many of them with strongly

  18. Cubanite: A New Sulfide Phase in CI Meteorites.

    PubMed

    Macdougall, J D; Kerridge, J F

    1977-08-01

    Cubanite (CuFe(2)S(3)), previously unobserved in meteorites, has been discovered in two carbonaceous chondrites, Orgueil and Alais. The association of this mineral with low-copper pyrrhotite suggests that it formed in a low-temperature environment on the meteorite parent body. PMID:17774329

  19. Cubanite - A new sulfide phase in CI meteorites

    NASA Technical Reports Server (NTRS)

    Macdougall, J. D.; Kerridge, J. F.

    1977-01-01

    Cubanite (CuFe2S3) previously unobserved in meteorites, has been discovered in two carbonaceous chondrites, Orgueil and Alais. The association of this mineral with low-copper pyrrhotite suggests that it formed in a low-temperature environment on the meteorite parent body.

  20. Amino acids in the Tagish Lake Meteorite

    NASA Technical Reports Server (NTRS)

    Kminek, G.; Botta, O.; Glavin, D. P.; Bada, J. L.

    2002-01-01

    High-performance liquid chromatography (HPLC) based amino acid analysis of a Tagish Lake meteorite sample recovered 3 months after the meteorite fell to Earth have revealed that the amino acid composition of Tagish Lake is strikingly different from that of the CM and CI carbonaceous chondrites. We found that the Tagish Lake meteorite contains only trace levels of amino acids (total abundance = 880 ppb), which is much lower than the total abundance of amino acids in the CI Orgueil (4100 ppb) and the CM Murchison (16 900 ppb). Because most of the same amino acids found in the Tagish Lake meteorite are also present in the Tagish Lake ice melt water, we conclude that the amino acids detected in the meteorite are terrestrial contamination. We found that the exposure of a sample of Murchison to cold water lead to a substantial reduction over a period of several weeks in the amount of amino acids that are not strongly bound to the meteorite matrix. However, strongly bound amino acids that are extracted by direct HCl hydrolysis are not affected by the leaching process. Thus even if there had been leaching of amino acids from our Tagish Lake meteorite sample during its 3 month residence in Tagish Lake ice and melt water, a Murchison type abundance of endogenous amino acids in the meteorite would have still been readily detectable. The low amino acid content of Tagish Lake indicates that this meteorite originated fiom a different type of parent body than the CM and CI chondrites. The parent body was apparently devoid of the reagents such as aldehyldes/ketones, HCN and ammonia needed for the effective abiotic synthesis of amino acids. Based on reflectance spectral measurements, Tagish Lake has been associated with P- or D-type asteroids. If the Tagish Lake meteorite was indeed derived fiom these types of parent bodies, our understanding of these primitive asteroids needs to be reevaluated with respect to their potential inventory of biologically important organic compounds.

  1. Core formation in the earth and shergottite parent body (SPB) - Chemical evidence from basalts

    NASA Technical Reports Server (NTRS)

    Treiman, A. H.; Drake, M. J.; Janssens, M.-J.; Wolf, R.; Ebihara, M.

    1986-01-01

    Abundances of siderophile and chalcophile elements in the shergottite parental body (SPB) have been compared with those of the earth. To this end, new INAA and RNAA analyses of non-Antarctic meteorites have been performed, and the composition of the shergottite SPB mantle has been inferred from the compositions of the SNC meteorites. The composition of the earth's mantle has been inferred from the compositions of terrestrial basalt. Finally, the effects of volatile depletion, core formation, and mineral/melt fractionation on the abundances of siderophile and chalcophile elements in the SPB and the earth have been taken into consideration. Compared to the earth, the SPB mantle is richer in moderately siderophile elements and more depleted with respect to chalcophile elements. The observed relative abundances of siderophile and chalcophile elements in the SPB and the earth mantles indicate that the SPB underwent accretion and/or differentiation processes which differ from those in the earth.

  2. Extraterrestrial Amino Acids in Orgueil and Ivuna: Tracing the Parent Body of CI Type Carbonaceous Chondrites

    NASA Technical Reports Server (NTRS)

    Meyer, Michael (Technical Monitor); Ehrenfreund, Pascale; Glavin, Daniel P.; Bota, Oliver; Cooper, George; Bada, Jeffrey

    2001-01-01

    Amino acid analyses using HPLC of pristine interior pieces of the CI carbonaceous chondrites Orgueil and Ivuna have found that beta-alanine, glycine, and gamma-amino-n-butyric acid (ABA) are the most abundant amino acids in these two meteorites, with concentrations ranging from approx. 600 to 2,000 parts per billion (ppb). Other alpha-amino acids such as alanine, alpha-ABA, alpha-aminoisobutyric acid (AIB), and isovaline are present only in trace amounts (less than 200 ppb). Carbon isotopic measurements of beta-alanine and glycine and the presence of racemic (D/L 1) alanine and beta-ABA in Orgueil suggest that these amino acids are extraterrestrial in origin. In comparison to the CM carbonaceous chondrites Murchison and Murray, the amino acid composition of the CIs is strikingly distinct, suggesting that these meteorites came from a different type of parent body, possibly an extinct comet, than did the CM carbonaceous chondrites.

  3. The Case against Mercury as the Angrite Parent Body (APB)

    NASA Technical Reports Server (NTRS)

    Hutson, M. L.; Ruzicka, A. M.; Mittlefehldt, D. W.

    2007-01-01

    Angrites are not plausibly from Mercury based on their high FeO contents and ancient ages (e.g., [1]). Rather, the early crystallization ages of angrites argues for a small asteroidal-sized parent body for these meteorites (e.g., [2]). Despite this, recently it has been proposed that Mercury is the APB [3, 4, 5, 6]. Preserved corona and symplectite textures and the presence of 120 triple junctions in NWA 2999 have been cited as requiring a planetary origin [3, 4], with the symplectites in NWA 2999 resulting from rapid decompression during uplift via thrust faults on Mercury [4], and the coronas during subsequent cooling at low pressure. Glasses along grain boundaries and exsolution lamellae possibly indicative of rapid melting and cooling in NWA 4950 are cited as evidence of rapid decompression [6]. To explain the discrepancy between spectral observations of the Mercurian surface and the high FeO contents in angrites, an early (4.5 Ga), collisionally-stripped FeO-rich basaltic surface has been suggested for Mercury [5, 6].

  4. Tafassasset: Evidence of early incipient differentiation on a metal-rich chondritic parent body

    NASA Astrophysics Data System (ADS)

    Breton, Thomas; Quitté, Ghylaine; Toplis, Michael J.; Monnereau, Marc; Birck, Jean-Louis; Göpel, Christa; Charles, Cyril

    2015-09-01

    Tafassasset is a primitive meteorite, the origin of which is still debated. Its possible relationship to either the CR chondrites - considered among the most primitive meteorites - or the brachinites - complex primitive achondrites - makes it an interesting sample for studying the initial stages of planetary accretion and differentiation in the early solar system. Here, we report tungsten (W) isotope data for bulk rock samples as well as for mineral fractions from Tafassasset, along with micro-computed tomography of a piece of the meteorite. Silicates show mass-independent W isotope anomalies, while the metal phase does not. These nucleosynthetic anomalies are interpreted as reflecting the presence of SiC presolar grains in the matrix of the meteorite, carrying s-process184W. After correction of the nucleosynthetic anomalies, a correlation is observed between the 182W/184W isotope compositions and the Hf/W ratios of the different fractions. A 182Hf-182W age of ca. 2.9 Ma after CAIs is inferred from the 182Hf-182W chronometer, slightly older than other estimates based on the 53Mn-53Cr, 26Al-26Mg, and Pb/Pb chronometers, but consistent with the difference in closure temperatures of the different isotopic systems. Numerical modeling of the thermal evolution of Tafassasset indicates accretion of a parent-body less than ∼50 km in diameter, ≤1 Ma after the formation of CAIs, at a time when short-lived radio-nuclides induced metal-silicate separation and partial melting of the silicates with extraction of a basaltic component. According to our new data, Tafassasset may represent an inner part of a CR-like parent body, with a differentiation history similar to, but less severe than, that of brachinites.

  5. Selective sampling during catastrophic disruption: Mapping the location of reaccumulated fragments in the original parent body

    NASA Astrophysics Data System (ADS)

    Michel, Patrick; Jutzi, Martin; Richardson, Derek C.; Goodrich, Cyrena A.; Hartmann, William K.; O`Brien, David P.

    2015-03-01

    In this paper, we simulate numerically the catastrophic disruption of a large asteroid as a result of a collision with a smaller projectile and the subsequent reaccumulation of fragments as a result of their mutual gravitational attractions. We then investigate the original location within the parent body of the small pieces that eventually reaccumulate to form the largest offspring of the disruption as a function of the internal structure of the parent body. We consider four cases that may represent the internal structure of such a body (whose diameter is fixed at 250 km) in various early stages of the Solar System evolution: fully molten, half molten (i.e., a 26 km-deep outer layer of melt containing half of the mass), solid except a thin molten layer (8 km thick) centered at 10 km depth, and fully solid. The solid material has properties of basalt. We then focus on the three largest offspring that have enough reaccumulated pieces to consider. Our results indicate that the particles that eventually reaccumulate to form the largest reaccumulated bodies retain a memory of their original locations in the parent body. Most particles in each reaccumulated body are clustered from the same original region, even if their reaccumulations take place far away. The extent of the original region varies considerably depending on the internal structure of the parent. It seems to shrink with the solidity of the body. The fraction of particles coming from a given depth is computed for the four cases, which can give constraints on the internal structure of parent bodies of some meteorites. As one example, we consider the ureilites, which in some petrogenetic models are inferred to have formed at particular depths within their parent body.

  6. The parent magma of the Nakhla (SNC) meteorite: Reconciliation of composition estimates from magmatic inclusions and element partitioning

    NASA Technical Reports Server (NTRS)

    Treiman, A. H.

    1993-01-01

    The composition of the parent magma of the Nakhla meteorite was difficult to determine, because it is accumulate rock, enriched in olivine and augite relative to a basalt magma. A parent magma composition is estimated from electron microprobe area analyses of magmatic inclusions in olivine. This composition is consistent with an independent estimate based on the same inclusions, and with chemical equilibria with the cores of Nakhla's augites. This composition reconciles most of the previous estimates of Nakhla's magma composition, and obviates the need for complex magmatic processes. Inconsistency between this composition and those calculated previously suggests that magma flowed through and crystallized into Nakhla as it cooled.

  7. Petrology of the Cangas de Onis and nulles regolith breccias Implications for parent body history

    NASA Astrophysics Data System (ADS)

    Williams, C. V.; Rubin, A. E.; Keil, K.; San Miguel, A.

    1985-06-01

    Cangas de Onis and Nulles are H chondrite regolith breccias from northern Spain. Uniform mineral compositions in both Cangas de Onis and Nulles indicate that their matrices consist almost entirely of comminuted equilibrated clasts. If these meteorites are representative samples of the regoliths in which they resided, the regoliths were compositionally homogeneous at the time of breccia consolidation. Zoned taenites within the clastic matrix of Cangas de Onis scatter widely on composition-dimension plots, indicating that these taenites cooled at different rates (about 1 - 1000 K/m.y.) at various depths (1 - 150 km). This suggests that the H chondrite parent body was disrupted and reassembled.

  8. Thermal metamorphism. [of chondrite parent bodies

    NASA Technical Reports Server (NTRS)

    Mcsween, Harry Y., Jr.; Sears, Derek W. G.; Dodd, Robert T.

    1988-01-01

    Most chondrites have experienced thermal metamorphism, resulting in changes in texture, mineralogy and possibly chemical composition. The physical conditions for metamorphism range from approximately 400 to 1000 C at low lithostatic pressure. Metamorphism may have resulted from decay of short-lived radionuclides, electromagnetic induction or accretion of hot materials. Several thermal models for chondrite parent bodies have been proposed. The least metamorphosed type-3 chondrites probably carry the most information about the early solar system, but even these have been affected to some degree by thermal processing.

  9. Terrestrial and exposure histories of Antarctic meteorites

    NASA Technical Reports Server (NTRS)

    Nishiizumi, K.

    1986-01-01

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

  10. Evolution of the Ureilite Parent Body

    NASA Technical Reports Server (NTRS)

    Hudson, P.; Romanek, C.; Paddock, Lindy; Mittlefehldt, D. W.

    2004-01-01

    Ureilites are ultramafic achondrites composed primarily of olivine and pyroxene with intergranular fine-grained metal, sulfides, and silicates. Ureilites contain significant amounts of carbon (up to about 6.5 wt%) as graphite, lonsdaleite, and/or diamond. It has been shown that carbon-silicate redox (i.e. "smelting") reactions are responsible for the negative FeO-MnO (or positive Fe/Mn-Fe/Mg with constant Mn/Mg) trend seen in the mineral and bulk compositions of ureilites and for the positive correlation between modal percent pigeonite and mg#. Carbon redox reactions are strongly exothermic and pressure dependent; so ureilites with the largest mg# are the most reduced, experienced the highest temperatures, and formed at the lowest pressures, i.e. near the surface of the ureilite parent body. Ureilites with the largest mg# have the smallest the delta(sup 18)O and the largest Delta(sup 17)O. To explain this, Singletary and Grove proposed that heterogeneous accretion took place on the ureilite parent body, which lead to a radial distribution of the oxygen isotopes. To further investigate possible relationships, we performed carbon isotope and electron probe measurements on a suite of 27 ureilites in order to see the type of correlation that exists between mg#, oxygen isotopes, and carbon.

  11. Hf-W chronometry of core formation in planetesimals inferred from weakly irradiated iron meteorites

    NASA Astrophysics Data System (ADS)

    Kruijer, Thomas S.; Sprung, Peter; Kleine, Thorsten; Leya, Ingo; Burkhardt, Christoph; Wieler, Rainer

    2012-12-01

    The application of Hf-W chronometry to determine the timescales of core formation in the parent bodies of magmatic iron meteorites is severely hampered by 182W burnout during cosmic ray exposure of the parent meteoroids. Currently, no direct method exists to correct for the effects of 182W burnout, making the Hf-W ages for iron meteorites uncertain. Here we present noble gas and Hf-W isotope systematics of iron meteorite samples whose W isotopic compositions remained essentially unaffected by cosmic ray interactions. Most selected samples have concentrations of cosmogenic noble gases at or near the lowermost level observed in iron meteorites and, for iron meteorite standards, have very low noble gas and radionuclide based cosmic ray exposure ages (<60 Ma). In contrast to previous studies, no corrections of measured W isotope compositions are required for these iron meteorite samples. Their ɛ182W values (parts per 104 deviations from the terrestrial value) are higher than those measured for most other iron meteorites and range from -3.42 to -3.31, slightly elevated compared to the initial 182W/184W of Ca-Al-rich Inclusions (CAI; ɛ182W = -3.51 ± 0.10). The new W isotopic data indicate that core formation in the parent bodies of the IIAB, IIIAB, and IVA iron meteorites occurred ˜1-1.5 Myr after CAI formation (with an uncertainty of ˜1 Myr), consistent with earlier conclusions that the accretion and differentiation of iron meteorite parent bodies predated the accretion of most chondrite parent bodies. One ungrouped iron meteorite (Chinga) exhibits small nucleosynthetic W isotope anomalies, but after correction for these anomalies its ɛ182W value agrees with those of the other samples. Another ungrouped iron (Mbosi), however, has elevated ɛ182W relative to the other investigated irons, indicating metal-silicate separation ˜2-3 Myr later than in the parent bodies of the three major iron meteorite groups studied here.

  12. Comparative Analysis of Micrograins from Asteroid 25143 (Itokawa) and Chelyabinsk Meteorite

    NASA Astrophysics Data System (ADS)

    Voropaev, S.; Kocherov, A.; Gabitov, R.

    2015-07-01

    We compare data concerning dust particles delivered by Hayabusa from the surface of the asteroid Itokawa and rock fragments of the Chelyabinsk meteorite. It is shown that they are LL ordinary chondrites with similar genesis and parent bodies.

  13. A Cometary Origin of the Amino Acids in the Orgueil Meteorite?

    NASA Technical Reports Server (NTRS)

    Botta, O.; Ehrenfreund, P.; Glavin, D. P.; Cooper, G. W.; Kminek, G.; Bada, J. L.

    2000-01-01

    A reexamination of a piece of the Orgueil meteorite revealed that its amino acid composition is strikingly different to two other carbonaceous chondrites, suggesting different parent bodies. A cometary origin for Orgueil would be one possibility.

  14. Cosmic-ray exposure ages of the ordinary chondrites and their significance for parent body stratigraphy

    NASA Technical Reports Server (NTRS)

    Crabb, J.; Schultz, L.

    1981-01-01

    Improved exposure ages are derived for 201 H, 203 L, and 38 LL chondrites in an effort to understand the characteristics of the chondrite parent body. The Ne-21 exposure ages were calculated from literature values taking into account shielding differences, a trapped component and radiogenic He. The exposure age distributions show clear peaks at 4.5 and 20 million years for the H chondrites, while the Ls and LLs appear more as a continuous series of intermediate peaks which may be modeled by at least six peaks between 1 and 35 million years in the case of L chondrites. The observations that every petrological type occurs in each large peak and contain solar wind gases suggest that the parent bodies have been fragmented and reassembled into a megabreccia. The H meteorites are proposed to represent the surface layer of a body with a substantial, active regolith as indicated by the relatively high abundances of solar gases. The L chondrites, on the other hand, are attributed to a parent body that was fragmented by collision about 500 million years ago.

  15. 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.

  16. Sutter's Mill dicarboxylic acids as possible tracers of parent-body alteration processes

    NASA Astrophysics Data System (ADS)

    Pizzarello, Sandra; Garvie, Laurence A. J.

    2014-11-01

    Dicarboxylic acids were searched for in three Sutter's Mill (SM) fragments (SM2 collected prerain, SM12, and SM41) and found to occur almost exclusively as linear species of 3- to 14-carbon long. Between these, concentrations were low, with measured quantities typically less than 10 nmole g-1 of meteorite and a maximum of 6.8 nmole g-1 of meteorite for suberic acid in SM12. The SM acids' molecular distribution is consistent with a nonbiological origin and differs from those of CMs, such as Murchison or Murray, and of some stones of the C2-ungrouped Tagish Lake meteorite, where they are abundant and varied. Powder X-ray diffraction of SM12 and SM41 show them to be dominated by clays/amorphous material, with lesser amounts of Fe-sulfides, magnetite, and calcite. Thermal gravimetric (TG) analysis shows mass losses up to 1000 °C of 11.4% (SM12) and 9.4% (SM41). These losses are low compared with other clay-rich carbonaceous chondrites, such as Murchison (14.5%) and Orgueil (21.1%). The TG data are indicative of partially dehydrated clays, in accordance with published work on SM2, for which mineralogical studies suggest asteroidal heating to around 500 °C. In view of these compositional traits and mineralogical features, it is suggested that the dicarboxylic acids observed in the SM fragments we analyzed likely represent a combination of molecular species original to the meteorite as well as secondary products formed during parent-body alteration processes, such as asteroidal heating.

  17. The great 8 MA event and the structure of the H-chondrite parent body

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    The H-chondrites have been the subject of several recent controversies, including the question of whether Antarctic and non-Antarctic meteorites are or are not the same and whether there or is not evidence for stratigraphic layering in the original parent body. We have identified two distinct groups of H5 chondrites in the Antarctic collection. One group has induced thermoluminescence (TL) peak temperatures less than 190 C and metallographic cooling rates between S to 50 K/Myr, similar to modern falls. It also has a variety of cosmic ray exposure ages, many being greater than 107 years. The other group has TL peak temperatures greater than 190 C, metallographic cooling rates of 100 K/Myr and cosmic ray exposure ages of 8 Ma. The members of this group were generals smaller than those of the greater than 190 C group (including the mode falls) during cosmic ray exposure. Detailed study of the cosmogenic nuclide concentrations of these groups indicates that they are not solely the result of pairing of a few unusual meteorites. It is likely that the greater than 190 C group was an important part of the H-chondrite flux about 1 million years ago, but has since decreased in importance relative to the less than 190 C group. In a previous work, we discussed several possible origins for the greater than 190 C group, including multiple H-chondrite parent bodies, unusual parent body structure, and creation during the 8 Ma event. In this paper, we present new data for H4 chondrites in light of these ideas.

  18. Metallic Fractions of Ordinary Chondrites: Implications to the Structure of Chondritic Parent Bodies

    NASA Astrophysics Data System (ADS)

    Ebihara, M.; Kong, P.

    1995-09-01

    of the equilibrated chondrites must be related with an external heating event rather than the intrinsic activity. The taenite fractions of the unequilibrated L chondrites have been developed into tetrataenite, suggesting that a cooling rate responsible to the development of kamacite and taenite was quite slow. The energy yielding such a slow cooling must have derived from intrinsic source, which heated the parent body to a temperature high enough for the development of kamacite and taenite, but too low to recrystallize silicates. During or after this "metamorphism", an external heating took place on the chondritic parent body, which recrystallized the silicates and modified the structure of kamacite and taenite. This external heating was more violent than the intrinsic one and may have derived from the early activities of the Sun. The highest temperature caused by the external heating was imprinted in the type 6 chondrites which located near the surface of the parent body, being in range of 800 C-950 C [4], and the temperature decreased gradually from the surface to the center of the body. Being different from L chondrites, H chondrites have no apparent difference in taenite components between EOCs and UOCs. If we assume similar thermal histories for both H and L chondrites, H chondritic parent body should be smaller than L's, with even its inner part being influenced to a certain degree during the external heating. References: [1] Kong P. et al. (1995) Proc. NIPR Symp. Antarct. Meteorites, 8, 237-249. [2] Gutlich P. et al. (1978) in Mossbauer Spectroscopy and Transition of Metal Chemistry, Springer-Verlag, Berlin-Heidelberg-New York. [3] Reuter K. B. et al. (1989) Metall. Trans., 20A, 719-725. [4] Dodd R. T. (1981) in Meteorites: A Petrologic-Chemical Synthesis, Cambridge Univ., London.

  19. Magnetite in CI carbonaceous meteorites - Origin by aqueous activity on a planetesimal surface

    NASA Technical Reports Server (NTRS)

    Kerridge, J. F.; Mackay, A. L.; Boynton, W. V.

    1979-01-01

    The composition and morphology of magnetite in CI carbonaceous meteorites appear incompatible with a nebular origin. Mineralization on the meteorite parent body is a more plausible mode of formation. The iodine-xenon age of this material therefore dates an episode of secondary mineralization on a planetesimal rather than the epoch of condensation in the primitive solar nebula.

  20. Catastrophic fragmentation of asteroids: Evidence from meteorites

    NASA Technical Reports Server (NTRS)

    Keil, K.; Haack, H.; Scott, E. R. D.

    1994-01-01

    Meteorites are impact-derived fragments from approximately 85 parent bodies. For seven of these bodies, the meteorites record evidence suggesting that they may have been catastrophically fragmented. We identify three types of catastrophic events: (1) impact and reassemble events greater than 4.4 Gy ago, involving molten or very hot parent bodies (greater than 1200 C); this affected the parent bodies of the ureilites, Shallowater, and the mesosiderites. In each case, the fragments cooled rapidly (approximately 1-1000 C/day) and then reassembled. (2) Later impacts involving cold bodies which, in some cases, reassembled; this occurred on the H and L ordinary chondrite parent bodies. The L parent body probably suffered another catastrophic event about 500 My ago. (3) Recent impacts of cold, multi-kilometer-sized bodies that generated meter-sized meteoroids; this occurred on the parent bodies of the IIIAB irons (650 My ago), the IVA irons (400 My ago), and the H ordinary chondrite (7 My ago).

  1. 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

  2. Heterogeneous distributions of amino acids provide evidence of multiple sources within the Almahata Sitta parent body, asteroid 2008 TC3

    NASA Astrophysics Data System (ADS)

    Burton, Aaron S.; Glavin, Daniel P.; Callahan, Michael P.; Dworkin, Jason P.; Jenniskens, Peter; Shaddad, Muawia H.

    2011-11-01

    Two new fragments of the Almahata Sitta meteorite and a sample of sand from the related strewn field in the Nubian Desert, Sudan, were analyzed for two to six carbon aliphatic primary amino acids by ultrahigh performance liquid chromatography with UV-fluorescence detection and time-of-flight mass spectrometry (LC-FT/ToF-MS). The distribution of amino acids in fragment #25, an H5 ordinary chondrite, and fragment #27, a polymict ureilite, were compared with results from the previously analyzed fragment #4, also a polymict ureilite. All three meteorite fragments contain 180-270 parts-per-billion (ppb) of amino acids, roughly 1000-fold lower than the total amino acid abundance of the Murchison carbonaceous chondrite. All of the Almahata Sitta fragments analyzed have amino acid distributions that differ from the Nubian Desert sand, which primarily contains L-α-amino acids. In addition, the meteorites contain several amino acids that were not detected in the sand, indicating that many of the amino acids are extraterrestrial in origin. Despite their petrological differences, meteorite fragments #25 and #27 contain similar amino acid compositions; however, the distribution of amino acids in fragment #27 was distinct from those in fragment #4, even though both are polymict ureilites from the same parent body. Unlike in CM2 and CR2/3 meteorites, there are low relative abundances of α-amino acids in the Almahata Sitta meteorite fragments, which suggest that Strecker-type chemistry was not a significant amino acid formation mechanism. Given the high temperatures that asteroid 2008 TC3 appears to have experienced and lack of evidence for aqueous alteration on the asteroid, it is possible that the extraterrestrial amino acids detected in Almahata Sitta were formed by Fischer-Tropsch/Haber-Bosch type gas-grain reactions at elevated temperatures.

  3. A petrogenetic model of the relationships among achondritic meteorites

    NASA Technical Reports Server (NTRS)

    Stolper, E.; Hays, J. F.; Mcsween, H. Y., Jr.

    1979-01-01

    Petrological evidence is used to support the hypothesis that although the magma source regions and parent bodies of basaltic achondrite, shergottite, nakhlite, and chassignite meteorites are clearly distinct, they may be simply related. It is proposed that the peridotites which on partial melting generated the parent magmas of the shergottite meteorites differed from those which gave rise to eucritic magmas by being enriched in a component rich in alkalis and other volatiles. Similarly, the source regions of the parent magmas of the nakhlite and chassignite meteorites differed from those on the shergottite parent body by being still richer in this volatile-rich component. These regions could have been related by processes such as mixture of variable amounts of volatile-rich and volatile-poor components in planetary or nebular settings, or alternatively by variable varying degrees of volatile loss from volatile-rich materials.

  4. Imino Acids in the Murchison Meteorite: Evidence of Strecker Reactions

    NASA Technical Reports Server (NTRS)

    Lerner, N. R.; Cooper, G. W.

    2003-01-01

    Both alpha-amino acids and alpha-hydroxy acids occur in aqueous extracts of the Murchison carbonaceous meteorite. The Strecker-cyanohydrin reaction, the reaction of carbonyl compounds, cyanide, and ammonia to produce amino and hydroxy acids, has been proposed as a source of such organic acids in meteorites. Such syntheses are consistent with the suggestion that interstellar precursors of meteoritic organic compounds accreted on the meteorite parent body together with other ices. Subsequent internal heating of the parent body melted these ices and led to the formation of larger compounds in synthetic reactions during aqueous alteration, which probably occurred at temperatures between 273K and 298K. In the laboratory, imino acids are observed as important by-products of the Strecker synthesis.

  5. Annual Occurrence of Meteorite-Dropping Fireballs

    NASA Astrophysics Data System (ADS)

    Konovalova, Natalia; Jopek, Tadeusz J.

    2016-07-01

    The event of Chelyabinsk meteorite has brought about change the earlier opinion about limits of the sizes of potentially dangerous asteroidal fragments that crossed the Earth's orbit and irrupted in the Earth's atmosphere making the brightest fireball. The observations of the fireballs by fireball networks allows to get the more precise data on atmospheric trajectories and coordinates of predicted landing place of the meteorite. For the reason to search the periods of fireball activity is built the annual distribution of the numbers of meteorites with the known fall dates and of the meteorite-dropping fireballs versus the solar longitude. The resulting profile of the annual activity of meteorites and meteorite-dropping fireballs shows several periods of increased activity in the course of the year. The analysis of the atmospheric trajectories and physical properties of sporadic meteorite-dropping fireballs observed in Tajikistan by instrumental methods in the summer‒autumn periods of increased fireballs activity has been made. As a result the structural strength, the bulk density and terminal mass of the studied fireballs that can survive in the Earth atmosphere and became meteorites was obtained. From the photographic IAU MDC_2003 meteor database and published sources based on the orbit proximity as determined by D-criterion of Southworth and Hawkins the fireballs that could be the members of group of meteorite-dropping fireballs, was found. Among the near Earth's objects (NEOs) the searching for parent bodies for meteorite-dropping fireballs was made and the evolution of orbits of these objects in the past on a long interval of time was investigated.

  6. A Parent Magma for the Nakhla Martian Meteorite: Reconciliation of Estimates from 1-Bar Experiments, Magmatic Inclusions in Olivine, and Magmatic Inclusions in Augite

    NASA Technical Reports Server (NTRS)

    Treiman, Allan H.; Goodrich, Cyrena Anne

    2001-01-01

    The composition of the parent magma for the Nakhla (martian) meteorite has been estimated from mineral-melt partitioning and from magmatic inclusions in olivine and in augite. These independent lines of evidence have converged on small range of likely compositions. Additional information is contained in the original extended abstract.

  7. Origin and Evolution of Prebiotic Organic Matter as Inferred from the Tagish Lake Meteorite

    NASA Technical Reports Server (NTRS)

    Herd, Christopher D.; Blinova, Alexandra; Simkus, Danielle N.; Huang, Yongsong; Tarozo, Rafael; Alexander, Conel M.; Gyngard, Frank; Nittler, Larry R.; Cody, George D.; Fogel, Marilyn L.; Kebukawa, Yoko; Kilcoyne, A. L.; Hilts, Robert W.; Slater, Greg F.; Glavin, Daniel P.; Dworkin, Jason P.; Callahan, Michael P.; Elsila, Jamie E.; De Gregorio, Bradley T.; Stroud, Rhonda M.

    2011-01-01

    The complex suite of organic materials in carbonaceous chondrite meteorites probably originally formed in the interstellar medium and/or the solar protoplanetary disk, but was subsequently modified in the meteorites' asteroidal parent bodies. The mechanisms of formation and modification are still very poorly understood. We carried out a systematic study of variations in the mineralogy, petrology, and soluble and insoluble organic matter in distinct fragments of the Tagish Lake meteorite. The variations correlate with indicators of parent body aqueous alteration and at least some molecules of pre-biotic importance formed during the alteration.

  8. Origin and evolution of prebiotic organic matter as inferred from the Tagish Lake meteorite.

    PubMed

    Herd, Christopher D K; Blinova, Alexandra; Simkus, Danielle N; Huang, Yongsong; Tarozo, Rafael; Alexander, Conel M O'D; Gyngard, Frank; Nittler, Larry R; Cody, George D; Fogel, Marilyn L; Kebukawa, Yoko; Kilcoyne, A L David; Hilts, Robert W; Slater, Greg F; Glavin, Daniel P; Dworkin, Jason P; Callahan, Michael P; Elsila, Jamie E; De Gregorio, Bradley T; Stroud, Rhonda M

    2011-06-10

    The complex suite of organic materials in carbonaceous chondrite meteorites probably originally formed in the interstellar medium and/or the solar protoplanetary disk, but was subsequently modified in the meteorites' asteroidal parent bodies. The mechanisms of formation and modification are still very poorly understood. We carried out a systematic study of variations in the mineralogy, petrology, and soluble and insoluble organic matter in distinct fragments of the Tagish Lake meteorite. The variations correlate with indicators of parent body aqueous alteration. At least some molecules of prebiotic importance formed during the alteration. PMID:21659601

  9. Extensive impact melting on the H-chondrite parent asteroid during the cataclysmic bombardment of the early solar system: Evidence from the achondritic meteorite Dar al Gani 896

    NASA Astrophysics Data System (ADS)

    Folco, Luigi; Bland, Philip A.; D'Orazio, Massimo; Franchi, Ian A.; Kelley, Simon P.; Rocchi, Sergio

    2004-05-01

    DaG 896 is an olivine-rich microporphyritic rock of komatiitic composition. Both the olivine composition (Fa 17.5±2.1, [Mn/Mg] = 0.0061) and the bulk oxygen isotopic composition (δ 17O = +2.55, δ 18O = +3.50) indicate that DaG 896 is a sample of the H-chondrite parent body. The bulk chemistry shows an H-chondritic distribution of lithophile elements, whereas chalcophile and siderophile elements are strongly depleted, indicating formation through whole-rock melting (or nearly so) of H-chondrite material, nearly complete loss of the metal plus sulfide component, and crystallization without significant igneous fractionation. Superheated, severely shocked chondritic relics (˜10 vol%), typically in the form of corroded lithic fragments <100 μm in size intimately distributed within the igneous lithology, indicate that melting was triggered by a highly energetic impact, which possibly induced shock pressures of ˜80-100 GPa. The relatively young 3.704 ± 0.035 Ga 40Ar- 39Ar crystallization age is consistent with the impact melting origin, as magmatism in the asteroid belt was active only in the first hundred million years of solar system history. Based on textural data and thermodynamic crystallization modelling, we infer that DaG 896 crystallized from a liquidus temperature of ˜1630°C under relatively slow cooling rates (˜10°C h -1) to ˜1300°C, before quenching. The two-stage cooling history indicates that a reasonable formation environment might be a dike intruding cooler basement below a crater floor. Metal-silicate fractionation may have been accomplished, at least at the centimeter-scale of the studied meteorite sample, through differential acceleration of immiscible liquids of different density during the intense flow regimes associated with the excavation and modification stages of the cratering mechanism. Alternatively, DaG 896 may represent a surface sample of a differentiated melt body at the floor of an impact crater, as gravitational settling

  10. Evidence for a dynamo in the main group pallasite parent body.

    PubMed

    Tarduno, John A; Cottrell, Rory D; Nimmo, Francis; Hopkins, Julianna; Voronov, Julia; Erickson, Austen; Blackman, Eric; Scott, Edward R D; McKinley, Robert

    2012-11-16

    Understanding the origin of pallasites, stony-iron meteorites made mainly of olivine crystals and FeNi metal, has been a vexing problem since their discovery. Here, we show that pallasite olivines host minute magnetic inclusions that have favorable magnetic recording properties. Our paleointensity measurements indicate strong paleomagnetic fields, suggesting dynamo action in the pallasite parent body. We use these data and thermal modeling to suggest that some pallasites formed when liquid FeNi from the core of an impactor was injected as dikes into the shallow mantle of a ~200-kilometer-radius protoplanet. The protoplanet remained intact for at least several tens of millions of years after the olivine-metal mixing event. PMID:23161997

  11. Early Petrogenesis and Late Impact(?) Metamorphism on the GRA 06128/9 Parent Body

    NASA Technical Reports Server (NTRS)

    Nyquist, Laurence E.; Shih, C.-Y.; Reese, Y. D.

    2009-01-01

    Initial studies of GRA06128 and GRA06129 (hereafter GRA 8 and GRA 9) suggested that these alkalic meteorites represent partial melts of a parent body of approximately chondritic composition. A SM-147-Nd-143 isochron age of 4.545 +/- 0.087 Ga was found for GRA 8, but plagioclase (oligoclase) plus whole rock and leachate samples gave an apparent secondary age of approximately 3.5 Ga. The approximately 4.54 Ga age was interpreted to be the crystallization age of GRA 8; the approximately 3.5 Ga as an upper limit to a time of metamorphism. Here we extend Sm-Nd and Rb-Sr analyses to GRA 9.

  12. Porosities of lunar meteorites: Strength, porosity, and petrologic screening during the meteorite delivery process

    NASA Astrophysics Data System (ADS)

    Warren, Paul H.

    2001-05-01

    Porosity has been directly measured for eight lunar meteorite breccias and calculated for two more on the basis of literature density measurements. Lunar meteorite regolith breccias display systematically low porosity in comparison to otherwise analogous Apollo regolith breccias. Among seven meteoritic regolith breccias, porosity ranges from 1 to 11% and averages 7.5+/-(1-σ)3.2%, whereas for 44 analogous Apollo samples (porosities mostly calculated from literature density data) the average is 25+/-(1-σ)7%. The origin of this disparity is enigmatic, but the trend probably reflects mainly a bias in favor of strong, compact breccias among fragments that manage to survive the violent process of launch to lunar escape velocity (2.38 km/s). In addition, compaction during launch may play an important role. The population of lunar meteorites is clearly not a random, unmodified sample of lithic materials near the surface of the parent body.

  13. Thin-sectioning and analysis of fine-grained meteoritic materials

    NASA Technical Reports Server (NTRS)

    Brooks, Donald A. (Editor); Bradley, John P.

    1992-01-01

    The overall theme of the work was the identification of the sources and formation/aggregation mechanisms of the various classes of interplanetary dust particles (IDP's) and to clarify the relationship between IDP's and conventional meteorites. IDP's are believed to be derived from a much broader range of parent bodies than conventional meteorites. Some of these parent bodies (e.g., comets) have escaped that post accretional processing that has affected the parent bodies of meteorites. Therefore, IDP's are likely to preserve a record of early solar system and possibly presolar grain forming reactions. Using analytical electron microscopy (AEM) and more recently micro-infrared (IR) microspectroscopy to examine ultramicrotomed thin sections, we have addressed the questions of IDP formation mechanisms, sources, and their relationship to conventional meteorites. The following sections describe specific findings resulting from these studies.

  14. Elephant Moraine 96029, a very mildly aqueously altered and heated CM carbonaceous chondrite: Implications for the drivers of parent body processing

    NASA Astrophysics Data System (ADS)

    Lee, Martin R.; Lindgren, Paula; King, Ashley J.; Greenwood, Richard C.; Franchi, Ian A.; Sparkes, Robert

    2016-08-01

    Elephant Moraine (EET) 96029 is a CM carbonaceous chondrite regolith breccia with evidence for unusually mild aqueous alteration, a later phase of heating and terrestrial weathering. The presence of phyllosilicates and carbonates within chondrules and the fine-grained matrix indicates that this meteorite was aqueously altered in its parent body. Features showing that water-mediated processing was arrested at a very early stage include a matrix with a low magnesium/iron ratio, chondrules whose mesostasis contains glass and/or quench crystallites, and a gehlenite-bearing calcium- and aluminium-rich inclusion. EET 96029 is also rich in Fe,Ni metal relative to other CM chondrites, and more was present prior to its partial replacement by goethite during Antarctic weathering. In combination, these properties indicate that EET 96029 is one of the least aqueously altered CMs yet described (CM2.7) and so provides new insights into the original composition of its parent body. Following aqueous alteration, and whilst still in the parent body regolith, the meteorite was heated to ∼400-600 °C by impacts or solar radiation. Heating led to the amorphisation and dehydroxylation of serpentine, replacement of tochilinite by magnetite, loss of sulphur from the matrix, and modification to the structure of organic matter that includes organic nanoglobules. Significant differences between samples in oxygen isotope compositions, and water/hydroxyl contents, suggests that the meteorite contains lithologies that have undergone different intensities of heating. EET 96029 may be more representative of the true nature of parent body regoliths than many other CM meteorites, and as such can help interpret results from the forthcoming missions to study and return samples from C-complex asteroids.

  15. Communication with Parents and Body Satisfaction in College Students

    ERIC Educational Resources Information Center

    Taniguchi, Emiko; Aune, R. Kelly

    2013-01-01

    Objective: This study examined how communication with parents is related to college students' body satisfaction. Participants and Methods: Participants ("N" = 134; 58 males and 76 females) completed a survey in March 2011 assessing body satisfaction and perceptions of communication with mothers and fathers. Results: Daughters'…

  16. Siderophile Element Profile Measurements in Iron Meteorites Using Laser Ablation ICP-MS

    NASA Technical Reports Server (NTRS)

    Watson, H. C.; Watson, E. B.; McDonough, W. F.

    2005-01-01

    Understanding the behaviour of siderophile elements during cooling of iron meteorites can lead to insight into the general thermal histories of the meteorites as well as their respective parent bodies. Traditionally trace element analyses in meteorites have been done using techniques that only measure the average concentration in each phase. With these methods, all of the spatial information with respect to the distribution of an element within one phase is lost. Measuring concentration profiles of trace elements in meteorites is now possible, with the advent of high-resolution analytical techniques such as laser ablation, inductively coupled plasma mass spectrometry (LA-ICP-MS) with spatial resolution <20 microns. [e.g. 1,2] and secondary ion mass spectrometry [3]. These profiles can give more insight into both the partitioning and diffusive behavior of siderophile elements in metal systems relevant to iron meteorites, as well as parent body cooling rates.

  17. Aerodynamic Analysis of Tektites and Their Parent Bodies

    NASA Technical Reports Server (NTRS)

    Adams, E. W.; Huffaker, R. M.

    1962-01-01

    Experiment and analysis indicate that the button-type australites were derived from glassy spheres which entered or re-entered the atmosphere as cold solid bodies; in case of average-size specimens, the entry direction was nearly horizontal and the entry speed between 6.5 and 11.2 km/sec. Terrestrial origin of such spheres is impossible because of extremely high deceleration rates at low altitudes. The limited extension of the strewn fields rules out extraterrestrial origin of clusters of such spheres because of stability considerations for clusters in space. However, tektites may have been released as liquid droplets from glassy parent bodies ablating in the atmosphere of the earth. The australites then have skipped together with the parent body in order to re-enter as cold spheres. Terrestrial origin of a parent body would require an extremely violent natural event. Ablation analysis shows that fusion of opaque siliceous stone into glass by aerodynamic heating is impossible.

  18. More evidence for a partially differentiated CV chondrite parent body from paleomagnetic studies of ALH 84028 and ALH 85006

    NASA Astrophysics Data System (ADS)

    Klein, B. Z.; Weiss, B. P.; Carporzen, L.

    2014-12-01

    Recent paleomagnetic studies of the CV carbonaceous chondrites Allende and Kaba and numerical modeling studies have suggested that the CV chondrite parent body may have been partially differentiated, with a molten metallic core, dynamo magnetic field, and an unmelted chondritic lid. To further evaluate this hypothesis, here we present new paleomagnetic analyses of two previously unstudied CV3 chondrites: the unshocked, Allende-type oxidized chondrite ALH 84028 and the weakly shocked, Bali-type oxidized chondrite ALH 85006. We preformed alternating field (AF) and thermal demagnetization experiments, AF-based paleointensity experiments, and rock magnetic experiments on mutually oriented subsamples of each meteorite. Both meteorites pass fusion crust baked contact tests, indicating that their interiors retain a magnetization predating atmospheric entry. In the interior of ALH 84028, we identified a unidirectional medium temperature (blocked to 300°C), high coercivity (blocked to >420 mT) component. In the interior of ALH 85006, we identified MT components blocked up to 400-475°C. The unblocking temperatures and unidirectional nature of the MT components in both meteorites indicates their origin as a partial thermoremanence or thermochemical remanence acquired during metamorphism following accretion of the CV chondrite parent body. Our paleointensity experiments indicate paleofield intensities of 32-73 μT for ALH 84028 and 14-45 μT for ALH 85006 . When combined with similar recent results for Allende and Kaba, there is now consistent evidence for dynamo fields from four CV chondrites with collectively diverse lithologies and shock states. Therefore, the magnetic field on the CV parent body was not a localized event like that expected for a field generated by meteoroid impact plasmas and instead likely had a wide spatial extent. Further, given the younger I-Xe ages for Kaba compared to Allende (9-10 Ma and 2-3 Ma after Stillwater respectively), CV parent body

  19. Ar-39-Ar-40 Evidence for Early Impact Events on the LL Parent Body

    NASA Technical Reports Server (NTRS)

    Dixon, E. T.; Bogard, D. D.; Garrison, D. H.; Rubin, A. E.

    2006-01-01

    We determined Ar-39-Ar-40 ages of eight LL chondrites, and one igneous inclusion from an LL chondrite, with the object of understanding the thermal history of the LL-chondrite parent body. The meteorites in this study have a range of petrographic types from LL3.3 to LL6, and shock stages from S1 to S4. These meteorites reveal a range of K-Ar ages from 23.66 to 24.50 Ga, and peak ages from 23.74 to 24.55 Ga. Significantly, three of the eight chondrites (LL4, 5, 6) have K-Ar ages of -4.27 Ga. One of these (MIL99301) preserves an Ar-39-Ar-40 age of 4.23 +/- 0.03 Ga from low-temperature extractions, and an older age of 4.52 +/- 0.08 Ga from the highest temperature extractions. In addition, an igneous-textured impact melt DOM85505,22 has a peak Ar-39-Ar-40 age of >= 4.27 Ga. We interpret these results as evidence for impact events that occurred at about 4.27 Ga on the LL parent body that produced local impact melts, reset the Ar-39-Ar-40 ages of some meteorites, and exhumed (or interred) others, resulting in a range of cooling ages. The somewhat younger peak age of 3.74 Ga from GR095658 (LL3.3) suggests an additional impact event close to timing of impact-reset ages of some other ordinary chondrites between 3.6-3.8 Ga. The results from MIL99301 suggest that some apparently unshocked (Sl) chondrites may have substantially reset Ar-39-Ar-40 ages. A previous petrographic investigation of MIL99301 suggested that reheating to temperatures less than or equal to type 4 petrographic conditions (600C) caused fractures in olivine to anneal, resulting in a low apparent shock stage of S1 (unshocked). The Ar-39-Ar-40 age spectrum of MIL99301 is consistent with this interpretation. Older ages from high-T extractions may date an earlier impact event at 4.52 +/- 0.08 Ga, whereas younger ages from lower-T extractions date a later impact event at 4.23 Ar-39-Ar-40 0.03 Ga that may have caused annealing of feldspar and olivine

  20. The Effects of Parent Body Processes on Amino Acids in Carbonaceous Chondrites

    NASA Technical Reports Server (NTRS)

    Glavin, Daniel P.; Callahan, Michael P.; Dworkin, Jason P.; Elsila, Jamie E.

    2010-01-01

    To investigate the effect of parent body processes on the abundance, distribution, and enantiomeric composition of amino acids in carbonaceous chondrites, the water extracts from nine different powdered Cl, CM, and CR carbonaceous chondrites were analyzed for amino acids by ultrahigh performance liquid chromatography-fluorescence detection and time-of-flight mass spectrometry (UPLC-FD/ToF-MS). Four aqueously altered type 1 carbonaceous chondrites including Orgueil (C11), Meteorite Hills (MET) 01070 (CM1), Scott Glacier (SCO) 06043 (CM1), and Grosvenor Mountains (GRO) 95577 (CR1) were analyzed using this technique for the first time. Analyses of these meteorites revealed low levels of two- to five-carbon acyclic amino alkanoic acids with concentrations ranging from -1 to 2,700 parts-per-billion (ppb). The type 1 carbonaceous chondrites have a distinct distribution of the five-carbon (C5) amino acids with much higher relative abundances of the gamma- and delta-amino acids compared to the type 2 and type 3 carbonaceous chondrites, which are dominated by a-amino acids. Much higher amino acid abundances were found in the CM2 chondrites Murchison, Lonewolf Nunataks (LON) 94102, and Lewis Cliffs (LEW) 90500, the CR2 Elephant Moraine (EET) 92042, and the CR3 Queen Alexandra Range (QUE) 99177. For example, a-aminoisobutyric acid ((alpha-AIB) and isovaline were approximately 100 to 1000 times more abundant in the type 2 and 3 chondrites compared to the more aqueously altered type 1 chondrites. Most of the chiral amino acids identified in these meteorites were racemic, indicating an extraterrestrial abiotic origin. However, non-racemic isovaline was observed in the aqueously altered carbonaceous chondrites Murchison, Orgueil, SCO 06043, and GRO 95577 with L-isovaline excesses ranging from approximately 11 to 19%, whereas the most pristine, unaltered carbonaceous chondrites analyzed in this study had no detectable L-isovaline excesses. These results are consistent with the

  1. Fireball data analysis: bridging the gap between small solar system bodies and meteorite studies

    NASA Astrophysics Data System (ADS)

    Gritsevich, Maria; Moreno-Ibáñez, Manuel; Kuznetsova, Daria; Bouquet, Alexis; Trigo-Rodríguez, Josep; Peltoniemi, Jouni; Koschny, Detlef

    2015-08-01

    One of the important steps in identification of meteorite-producing fireballs and prediction of impact threat to Earth raised by potentially hazardous asteroids is the understanding and modeling of processes accompanying the object’s entry into the terrestrial atmosphere (Gritsevich et al., 2012). Such knowledge enables characterization, simulation and classification of possible impact consequences with further reommendation for potential meteorite searches. Using dimensionless expressions, which involve the pre-atmospheric meteoroid parameters, we have built physically based parametrisation to describe changes in mass, height, velocity and luminosity of the object along its atmospheric path (Gritsevich and Koschny, 2011; Bouquet et al., 2014). The developed model is suitable to estimate a number of crucial unknown values including shape change coefficient, ablation rate, and surviving meteorite mass. It is also applicable to predict the terminal height of the luminous flight and therefore, duration of the fireball (Moreno-Ibáñez et al., 2015). Besides the model description, we demonstrate its application using the wide range of observational data from meteorite-producing fireballs appearing annually (such as Košice) to larger scale impacts (such as Chelyabinsk, Sikhote-Alin and Tunguska).REFERENCESBouquet A., Baratoux D., Vaubaillon J., Gritsevich M.I., Mimoun D., Mousis O., Bouley S. (2014): Planetary and Space Science, 103, 238-249, http://dx.doi.org/10.1016/j.pss.2014.09.001Gritsevich M., Koschny D. (2011): Icarus, 212(2), 877-884, http://dx.doi.org/10.1016/j.icarus.2011.01.033Gritsevich M.I., Stulov V.P., Turchak L.I. (2012): Cosmic Research, 50(1), 56-64, http://dx.doi.org/10.1134/S0010952512010017Moreno-Ibáñez M., Gritsevich M., Trigo-Rodríguez J.M. (2015): Icarus, 250, 544-552, http://dx.doi.org/10.1016/j.icarus.2014.12.027

  2. Parent body depth-pressure-temperature relationships and the style of the ureilite anatexis

    NASA Astrophysics Data System (ADS)

    Warren, Paul H.

    2012-02-01

    New analyses of mafic silicates from 14 ureilite meteorites further constrain a strong correlation (Singletary and Grove 2003) between olivine-core Fo ratio and the temperature of equilibration (TE) recorded by the composition of pigeonite. This correlation may be compared with relationships implied by various postulated combinations of Fo and pressure P in models for ureilite genesis by a putative process of anatectic (depth-linked, P-controlled) smelting. In such models, any combination of Fo and P together fixes the temperature of smelting. Agreement between the observed correlation and these models is poor. The anatectic smelting model also carries implausible implications for the depth range at which ureilites of a given composition (Fo) form. Actual ureilites (and polymict ureilite clasts: Downes et al. 2008) show a distribution strongly skewed toward the low-Fo end of the compositional range, with approximately 58% in the range Fo76-81. In contrast, the P-controlled smelting model implies that the Fo76-81 region is a small fraction of the volume of the parent body: not more than 3.2%, in a model consistent with the Fo-TE observations; and even ignoring the Fo-TE evidence not more than 11% (percentages cited require optimal assumptions concerning the size of the parent body). This region also must occur deep within the body, where no straightforward model would imply a strong bias in the impact-driven sampling process. The ureilites did not derive preponderantly from one atypical “largest offspring” disruption survivor, because cooling history evidence shows that after the disruption (whose efficiency was increased by gas jetting), all of the known ureilites cooled in bodies that were tiny (mass of order 10-9) in comparison with the precursor body. The Ca/Al ratio of the ureilite starting matter cannot be 2.5 times chondritic, as has been suggested, unless the part of the body from which ureilites come is at most 50% of the whole body. Published variants

  3. 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.

  4. 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.

  5. Time-Resolved Records of Magnetic Activity on the Pallasite Parent Body and Psyche

    NASA Astrophysics Data System (ADS)

    Bryson, J. F. J.; Nichols, C. I. O.; Herrero-Albillos, J.; Kronast, F.; Kasama, T.; Alimadadi, H.; van der Laan, G.; Nimmo, F.; Harrison, R. J.

    2014-12-01

    Although many small bodies apparently generated dynamo fields in the early solar system, the nature and temporal evolution of these fields has remained enigmatic. Time-resolved records of the Earth's planetary field have been essential in understanding the dynamic history of our planet, and equivalent information from asteroids could provide a unique insight into the development of the solar system. Here we present time-resolved records of magnetic activity on the main-group pallasite parent body and (16) Psyche, obtained using newly-developed nanomagnetic imaging techniques. For the pallasite parent body, the inferred field direction remained relatively constant and the intensity was initially stable at ~100 μT before it decreased in two discrete steps down to 0 μT. We interpret this behaviour as due to vigorous dynamo activity driven by compositional convection in the core, ultimately transitioning from a dipolar to multipolar field as the inner core grew from the bottom-up. For Psyche (measured from IVA iron meteorites), the inferred field direction reversed, while the intensity remained stable at >50 μT. Psyche cooled rapidly as an unmantled core, although the resulting thermal convection alone cannot explain these observations. Instead, this behaviour required top-down core solidification, and is attributed either to compositional convection (if the core also solidified from the bottom-up) or convection generated directly by top-down solidification (e.g. Fe-snow). The mechanism governing convection in small body cores is an open question (due partly to uncertainties in the direction of core solidification), and these observations suggest that unconventional (i.e. not thermal) mechanisms acted in the early solar system. These mechanisms are very efficient at generating convection, implying a long-lasting and widespread epoch of dynamo activity among small bodies in the early solar system.

  6. Water and the thermal evolution of carbonaceous chondrite parent bodies

    NASA Technical Reports Server (NTRS)

    Grimm, Robert E.; Mcsween, Harry Y., Jr.

    1989-01-01

    Two hypotheses are proposed for the aqueous alteration of carbonaceous chondrites within their parent bodies, in which respectively the alteration occurs (1) throughout the parent body interior, or (2) in a postaccretional surface regolith; both models assume an initially homogeneous mixture of ice and rock that is heated through the decay of Al-26. Water is seen to exert a powerful influence on chondrite evolution through its role of thermal buffer, permitting substitution of a low temperature aqueous alteration for high temperature recrystallization. It is quantitatively demonstrated that liquid water may be introduced by either hydrothermal circulation, vapor diffusion from below, or venting due to fracture.

  7. Fractional melting and smelting on the ureilite parent body

    NASA Astrophysics Data System (ADS)

    Goodrich, Cyrena Anne; Van Orman, James A.; Wilson, Lionel

    2007-06-01

    We investigate petrologic and physical aspects of melt extraction on the parent asteroid of the ureilite meteorites (UPB). We first develop a petrologic model for simultaneous melting and smelting (reduction of FeO by C) at various depths. For a model starting composition, determined from petrologic constraints to have been CV-like except for elevated Ca/Al (2.5 × CI), we determine (1) degree of melting, (2) the evolution of mg, (3) production of CO + CO 2 gas and (4) the evolution of mineralogy in the residue as a function of temperature and pressure. We then use these relationships to examine implications of fractional vs. batch melt extraction. In the shallowest source regions (˜30 bars), melting and smelting begin simultaneously at ˜1050 °C, so that mg and the abundance of low-Ca pyroxene (initially pigeonite, ultimately pigeonite + orthopyroxene) begin to increase immediately. However, in the deepest source regions (˜100 bars), smelting does not begin until ˜1200 °C, so that mg begins to increase and low-Ca pyroxene (pigeonite) appears only after ˜21% melting. The final residues in these two cases, obtained just after the demise of augite, match the end-members of the ureilite mg range (˜94-76) in pyroxene abundance and type. In all source regions, production of CO + CO 2 by smelting varies over the course of melting. The onset of smelting results in a burst of gas production and very high incremental gas/melt ratios (up to ˜2.5 by mass); after a few % (s)melting, however, these values drastically decline (to <0.05 in the final increments). Physical modelling based on these relationships indicates that melts would begin to migrate upwards after only ˜1-2% melting, and thereafter would migrate continuously (fractionally) and rapidly (reaching the surface in < a year) in a network of veins/dikes. All melts produced during the smelting stage in each source region have gas contents sufficient to cause them to erupt explosively and be lost. However

  8. Near-infrared spectroscopy of 3:1 Kirkwood Gap asteroids II: Probable and plausible parent bodies; primitive and differentiated

    NASA Astrophysics Data System (ADS)

    Fieber-Beyer, Sherry K.; Gaffey, Michael J.

    2014-02-01

    The 3:1 Kirkwood Gap asteroids are a mineralogically diverse set of asteroids located in a region that delivers meteoroids into Earth-crossing orbits. Mineralogical characterizations of asteroids in/near the 3:1 Kirkwood Gap can be used as a tool to “map” conditions and processes in the early Solar System. The chronological studies of the meteorite types provide a “clock” for the relative timing of those events and processes. By identifying the source asteroids of particular meteorite types, the “map” and “clock” can be combined to provide a much more sophisticated understanding of the history and evolution of the late solar nebula and the early Solar System. A mineralogical assessment of twelve 3:1 Kirkwood Gap asteroids has been carried out using near-infrared spectral data obtained from 2010 to 2011 combined with visible spectral data (when available) to cover the spectral interval of 0.4-2.5 μm. Eight of these asteroids have surfaces with basaltic-type silicate assemblages, indicating at least partial melting within their parent bodies. Although HED-like mineralogies are present these objects exhibit subdued features indicating the presence of an additional phase (e.g., NiFe metal) or process (e.g., space weathering). Four of these asteroids appear to be ordinary chondrite assemblages. Three of these are plausibly linked to the probable H-chondrite parent body, (6) Hebe.

  9. Carbonaceous Meteorites Contain a Wide Range of Extraterrestrial Nucleobases

    NASA Technical Reports Server (NTRS)

    Callahan, Michael P.; Smith, Karen E.; Cleaves, H. James, II; Ruzicka, Josef; Stern, Jennifer C.; Glavin, Daniel P.; House, Christopher H.; Dworkin, Jason P.

    2011-01-01

    All terrestrial organisms depend on nucleic acids (RNA and DNA), which use pyrimidine and purine nucleobases to encode genetic information. Carbon-rich meteorites may have been important sources of organic compounds required for the emergence of life on the early Earth; however, the origin and formation of nuc1eobases in meteorites has been debated for over 50 y. So far, the few nuc1eobases reported in meteorites are biologically common and lacked the structural diversity typical of other indigenous meteoritic organics. Here, we investigated the abundance and distribution of nucleobases and nucleobase analogs in formic acid extracts of 12 different meteorites by liquid chromatography-mass spectrometry. The Murchison and Lonewolf Nunataks 94102 meteorites contained a diverse suite of nucleobases, which included three unusual and terrestrially rare nucleobase analogs; purine, 2,6-diminopurine, and 6,8-diaminopurine. In a parallel experiment, we found an identical suite of nucleobases and nucleobase analogs generated in reactions of ammonium cyanide. Additionally, these nucleobase analoge were not detected above our parts-per-billion detection limits in any of the procedural blanks, control samples, a terrestrial soil sample, and an Antarctic ice sample. Our results demonstrate that the purines detected in meteorites are consistent with products of ammonium cyanide chemistry, which provides a plausible mechanism for their synthesis in the asteroid parent bodies, and strongly supports an extraterrestrial origin. The discovery of new nucleobase analogs in meteorites also expands the prebiotic molecular inventory available for constructing the first genetic molecules.

  10. The formation of the Baptistina family by catastrophic disruption: Porous versus non-porous parent body

    NASA Astrophysics Data System (ADS)

    Jutzi, M.; Michel, P.; Benz, W.; Richardson, D. C.

    2009-01-01

    In this paper, we present numerical simulations aimed at reproducing the Baptistina family based on its properties estimated by observations. A previous study by Bottke et al. (2007) indicated that this family is probably at the origin of the K/T impactor, is linked to the CM meteorites and was produced by the disruption of a parent body 170 km in size due to the head-on impact of a projectile 60 km in size at 3 km s-1. This estimate was based on simulations of fragmentation of non-porous materials, while the family was assumed to be of C taxonomic type, which is generally interpreted as being formed from a porous body. Using both a model of fragmentation of non-porous materials, and a model that we developed recently for porous ones, we performed numerical simulations of disruptions aimed at reproducing this family and at analyzing the differences in the outcome between those two models. Our results show that a reasonable match to the estimated size distribution of the real family is produced from the disruption of a porous parent body by the head-on impact of a projectile 54 km in size at 3 km s-1. Thus, our simulations with a model consistent with the assumed dark type of the family requires a smaller projectile than previously estimated, but the difference remains small enough to not affect the proposed scenario of this family history. We then find that the break-up of a porous body leads to different outcomes than the disruption of a non-porous one. The real properties of the Baptistina family still contain large uncertainties, and it remains possible that its formation did not involve the proposed impact conditions. However, the simulations presented here already show some range of outcomes and once the real properties are better constrained, it will be easy to check whether one of them provides a good match.

  11. Workshop on Oxygen in Asteroids and Meteorites

    NASA Technical Reports Server (NTRS)

    2005-01-01

    Contents include the following: Constraints on the detection of solar nebula's oxidation state through asteroid observation. Oxidation/Reduction Processes in Primitive Achondrites. Low-Temperature Chemical Processing on Asteroids. On the Formation Location of Asteroids and Meteorites. The Spectral Properties of Angritic Basalts. Correlation Between Chemical and Oxygen Isotopic Compositions in Chondrites. Effect of In-Situ Aqueous Alteration on Thermal Model Heat Budgets. Oxidation-Reduction in Meteorites: The Case of High-Ni Irons. Ureilite Atmospherics: Coming up for Air on a Parent Body. High Temperature Effects Including Oxygen Fugacity, in Pre-Planetary and Planetary Meteorites and Asteroids. Oxygen Isotopic Variation of Asteroidal Materials. High-Temperature Chemical Processing on Asteroids: An Oxygen Isotope Perspective. Oxygen Isotopes and Origin of Opaque Assemblages from the Ningqiang Carbonaceous Chondrite. Water Distribution in the Asteroid Belt. Comparative Planetary Mineralogy: V Systematics in Planetary Pyroxenes and fo 2 Estimates for Basalts from Vesta.

  12. Rhenium-osmium isotope constraints on the age of iron meteorites

    USGS Publications Warehouse

    Horan, M.F.; Morgan, J.W.; Walker, R.J.; Grossman, J.N.

    1992-01-01

    Rhenium and osmium concentrations and the osmium isotopic compositions of iron meteorites were determined by negative thermal ionization mass spectrometry. Data for the IIA iron meteorites define an isochron with an uncertainty of approximately ??31 million years for meteorites ???4500 million years old. Although an absolute rhenium-osmium closure age for this iron group cannot be as precisely constrained because of uncertainty in the decay constant of 187Re, an age of 4460 million years ago is the minimum permitted by combined uncertainties. These age constraints imply that the parent body of the IIAB magmatic irons melted and subsequently cooled within 100 million years after the formation of the oldest portions of chondrites. Other iron meteorites plot above the IIA isochron, indicating that the planetary bodies represented by these iron groups may have cooled significantly later than the parent body of the IIA irons.

  13. Rhenium-osmium-isotope constraints on the age of iron meteorites

    NASA Technical Reports Server (NTRS)

    Horan, M. F.; Morgan, J. W.; Walker, R. J.; Grossman, J. N.

    1992-01-01

    Rhenium and osmium concentrations and the osmium isotopic compositions of iron meteorites were determined by negative thermal ionization mass spectrometry. Data for the IIA iron meteorites define an isochron with an uncertainty of approximately +/-31 million years for meteorites about 4500 million years old. Although an absolute rhenium-osmium closure age for this iron group cannot be as precisely constrained because of uncertainty in the decay constant of Re-187, an age of 4460 million years ago is the minimum permitted by combined uncertainties. These age constraints imply that the parent body of the IIAB magmatic irons melted and subsequently cooled within 100 million years after the formation of the oldest portions of chondrites. Other iron meteorites plot above the IIA isochron, indicating that the planetary bodies represented by these iron groups may have cooled significantly later than the parent body of the IIA irons.

  14. Forging Asteroid-Meteorite Relationships Through Reflectance Spectroscopy

    NASA Technical Reports Server (NTRS)

    Burbine, T. H.; Binzel, R. P.; Bus, S. J.; Buchanan, P. C.; Hinrichs, J. L.; Meibom, A.; Hiroi, T.; Sunshine, J. M.

    2000-01-01

    Near-infrared spectra were obtained for 196 asteroids as part of SMASSIR. SMASSIR focused on observing asteroids assumed to be one of the following: (1) olivine-rich, (2) objects with "Vesta-like spectra" (the "Vestoids"), and (3) postulated meteorite parent bodies.

  15. 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

    Abstract- The microstructures of six reheated iron meteorites—two IVA irons, Maria Elena (1935), Fuzzy Creek; one IVB iron, Ternera; and three ungrouped irons, Hammond, Babb’s Mill (Blake’s Iron), and Babb’s Mill (Troost’s Iron)—were characterized using scanning and transmission electron microscopy, electron-probe microanalysis, and electron backscatter diffraction techniques to determine their thermal and shock history and that of their parent asteroids. Maria Elena and Hammond were heated below approximately 700-750 °C, so that kamacite was recrystallized and taenite was exsolved in kamacite and was spheroidized in plessite. Both meteorites retained a record of the original Widmanstätten pattern. The other four, which show no trace of their original microstructure, were heated above 600-700 °C and recrystallized to form 10-20 μm wide homogeneous taenite grains. On cooling, kamacite formed on taenite grain boundaries with their close-packed planes aligned. Formation of homogeneous 20 μm wide taenite grains with diverse orientations would have required as long as approximately 800 yr at 600 °C or approximately 1 h at 1300 °C. All six irons contain approximately 5-10 μm wide taenite grains with internal microprecipitates of kamacite and nanometer-scale M-shaped Ni profiles that reach approximately 40% Ni indicating cooling over 100-10,000 yr. Un-decomposed high-Ni martensite (α2) in taenite—the first occurrence in irons—appears to be a characteristic of strongly reheated irons. From our studies and published work, we identified four progressive stages of shock and reheating in IVA irons using these criteria: cloudy taenite, M-shaped Ni profiles in taenite, Neumann twin lamellae, martensite, shock-hatched kamacite, recrystallization, microprecipitates of taenite, and shock-melted troilite. Maria Elena and Fuzzy Creek represent stages 3 and 4, respectively. Although not all reheated irons contain evidence for shock, it was probably the main

  16. Child's Weight Status and Parent's Response to a School-Based Body Mass Index Screening and Parent Notification Program

    ERIC Educational Resources Information Center

    Lee, Jiwoo; Kubik, Martha Y.

    2015-01-01

    This study examined the response of parents of elementary school-aged children to a school-based body mass index (BMI) screening and parent notification program conducted in one Minnesota school district in 2010-2011 and whether parent's response was moderated by child's weight status. Randomly selected parents (N = 122) of second- and…

  17. The Production of Amino Acids in Interstellar Ices: Implications for Meteoritic Organics

    NASA Technical Reports Server (NTRS)

    Sandford, A.; Bernstein, M. P.; Dworkin, J. P.; Cooper, G. W.; Allamandola, L. J.; DeVincenzi, D. (Technical Monitor)

    2002-01-01

    Indigenous amino acids have been detected in a number of meteorites, over 70 in the Murchison meteorite alone. It has been generally accepted that the amino acids in meteorites formed in liquid water on an asteroid or comet parent-body. However, the water in the Murchison meteorite, for example, was depleted of deuterium, making the distribution of deuterium in organic acids in Murchison difficult to explain. Similarly, occasional but consistent meteoritic biases for non-terrestrial L amino acids cannot be reasonably rationalized by liquid water parent-body reactions. We will present the results of a laboratory demonstration showing that the amino acids glycine, alanine, and serine should result from the UV (ultraviolet) photolysis of interstellar ice grains. This suggests that some meteoritic amino acids may be the result of interstellar ice photochemistry, rather than having formed by reactions in liquid water. We will describe some of the potential implications of these findings for the organic materials found in primitive meteorites, in particular how interstellar ice synthesis might more easily accommodate the presence and distribution of deuterium, and the meteoritic bias for L amino acids.

  18. Impact ages of meteorites: A synthesis

    NASA Astrophysics Data System (ADS)

    Bogard, D.

    1995-05-01

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

  19. The 2014 KCG Meteor Outburst: Clues to a Parent Body

    NASA Technical Reports Server (NTRS)

    Moorhead, Althea V.; Brown, Peter G.; Spurny, Pavel; Cooke, William J.

    2015-01-01

    The Kappa Cygnid (KCG) meteor shower exhibited unusually high activity in 2014, producing ten times the typical number of meteors. The shower was detected in both radar and optical systems and meteoroids associated with the outburst spanned at least five decades in mass. In total, the Canadian Meteor Orbit Radar, European Network, and NASA All Sky and Southern Ontario Meteor Network produced thousands of KCG meteor trajectories. Using these data, we have undertaken a new and improved characterization of the dynamics of this little-studied, variable meteor shower. The Cygnids have a di use radiant and a significant spread in orbital characteristics, with multiple resonances appearing to play a role in the shower dynamics. We conducted a new search for parent bodies and found that several known asteroids are orbitally similar to the KCGs. N-body simulations show that the two best parent body candidates readily transfer meteoroids to the Earth in recent centuries, but neither produces an exact match to the KCG radiant, velocity, and solar longitude. We nevertheless identify asteroid 2001 MG1 as a promising parent body candidate.

  20. The 2014 KCG meteor outburst: clues to a parent body

    NASA Astrophysics Data System (ADS)

    Moorhead, Althea V.; Brown, Peter G.; Spurný, Pavel; Cooke, William

    2015-05-01

    The κ Cygnid (KCG) meteor shower exhibited unusually high activity in 2014, producing ten times the typical number of meteors. The shower was detected in both radar and optical systems and meteoroids associated with the outburst spanned at least five decades in mass. In total, the Canadian Meteor Orbit Radar, European Network, and NASA All Sky and Southern Ontario Meteor Network produced thousands of KCG meteor trajectories. Using these data, we have undertaken a new and improved characterization of the dynamics of this little-studied, variable meteor shower. The κ Cygnids have a diffuse radiant and a significant spread in orbital characteristics, with multiple resonances appearing to play a role in the shower dynamics. We conducted a new search for parent bodies and found that several known asteroids are orbitally similar to the KCGs. N-body simulations show that the two best parent body candidates readily transfer meteoroids to the Earth in recent centuries, but neither produces an exact match to the KCG radiant, velocity, and solar longitude. We nevertheless identify asteroid 2001 MG1 as a promising parent body candidate.

  1. Clay minerals in primitive meteorites and interplanetary dust 1

    NASA Technical Reports Server (NTRS)

    Zolensky, M. E.; Keller, L. P.

    1991-01-01

    Many meteorites and interplanetary dust particles (IDPs) with primitive compositions contain significant amounts of phyllosilicate minerals, which are generally interpreted as evidence of protoplanetary aqueous alteration at an early period of the solar system. These meteorites are chondrites (near solar composition) of the carbonaceous and ordinary varieties. The former are subdivided (according to bulk composition and petrology) into CI, CM, CV, CO, CR, and ungrouped classes. IDPs are extraterrestrial particulates, collected in stratosphere, which have chemical compositions indicative of a primitive origin; they are typically distinct from the primitive meteorites. Characterization of phyllosilicates in these materials is a high priority because of the important physico-chemical information they hold. The most common phyllosilicates present in chondritic extraterrestrial materials are serpentine-group minerals, smectites, and micas. We discuss these phyllosilicates and describe the interpretation of their occurrence in meteorites and IDPs and what this indicates about history of their parent bodies, which are probably the hydrous asteroids.

  2. Aqueous Alteration on Ordinary Chondrite Parent Bodies- The Oxygen Isotopic Composition of Water.O

    NASA Astrophysics Data System (ADS)

    Baker, L.; Franchi, I. A.; Wright, I. P.; Pillinger, C. T.

    2003-04-01

    It has become increasingly apparent that aqueous alteration has been a major process on meteorite parent bodies. Understanding the details of such processes can be greatly improved by a knowledge of the isotopic composition of water taking part in aqueous alteration. Studies of the unequilibrated ordinary chondrites (1, 2) have identified the presence of phyllosilicates which necessarily require reaction with water in some form. Using the technique of (3) we have measured the oxygen isotopic composition of water extracted from Semarkona and Bishunpur from room temp to 900^oC. Water release profiles generally define large low temperature peaks that tail off to about 800^oC, with smaller releases superimposed. This is consistent with the main hydrated mineral present being a smectite but with contributions from other hydrated phases. Isotopic compositions at different temperatures allow identification of water originating from distinct reservoirs within the samples, including both terrestrial and extraterrestrial sources. That at low temperatures is dominated by terrestrial water while that released at high temperatures contains a large proportion indigenous to the meteorite. In Semarkona the highest temperature releases originating from O-H structural groups within hydrated minerals possesses a positive Δ17O of ˜+2.4 ppm, in excess of twice that measured in the silicate phases of these meteorites and greater than that measured in any carbonaceous chondrites. These results suggest that during reaction with solid phases water, originally with a Δ17O value equal to or in excess that measured in magnetites ˜+6 ppm (4), must have evolved to lower values after magnetite formation. However, the final water composition, represented by the structural O-H groups, did not achieve isotopic equilibrium with the surrounding phases. Refs: [1] Hutchison R. et al. (1987) GCA 51, 1875-1882. [2] Alexander C. M. O'D. et al. (1989) EPSL 95, 187-207. [3] Baker L. et al. (2002) Anal

  3. Heterogeneous Distributions of Amino Acids Provide Evidence of Multiple Sources Within the Almahata Sitta Parent Body, Asteroid 2008 TC(sub 3)

    NASA Technical Reports Server (NTRS)

    Burton, Aaron S.; Glavin, Daniel P.; Callahan, Michael P.; Dworkin, Jason P.; Jenniskens, Peter; Shaddad, Muawia H.

    2011-01-01

    Two new fragments of the Almahata Sitta meteorite and a sample of sand from the related strewn field in the Nubian Desert, Sudan, were analyzed for two to six carbon aliphatic primary amino acids by ultrahigh performance liquid chromatography with UV-fluorescence detection and time-of-flight mass spectrometry (LC-FT/ToF-MS). The distribution of amino acids in fragment #25, an H5 ordinary chondrite, and fragment #27, a polymict ureilite, were compared with results from the previously analyzed fragment #4, also a polymict ureilite. All three meteorite fragments contain 180-270 parts-per-billion (ppb) of amino acids, roughly 1000-fold lower than the total amino acid abundance of the Murchison carbonaceous chondrite. All of the Almahata Sitta fragments analyzed have amino acid distributions that differ from the Nubian Desert sand, which primarily contains L-alpha-amino acids. In addition, the meteorites contain several amino acids that were not detected in the sand, indicating that many of the amino acids are extraterrestrial in origin. Despite their petrological differences, meteorite fragments #25 and #27 contain similar amino acid compositions; however, the distribution of amino acids in fragment #27 was distinct from those in fragment #4, even though both arc polymict ureilites from the same parent body. Unlike in CM2 and CR2/3 meteorites, there are low relative abundances of alpha-amino acids in the Almahata Sitta meteorite fragments, which suggest that Strecker-type chemistry was not a significant amino acid formation mechanism. Given the high temperatures that asteroid 2008 TC3 appears to have experienced and lack of evidence for aqueous alteration on the asteroid, it is possible that the extraterrestrial amino acids detected in Almahata Sitta were formed by Fischer-Tropsch/Haber-Bosch type gas-grain reactions at elevated temperatures.

  4. About 129Xe ∗ in meteoritic nanodiamonds

    NASA Astrophysics Data System (ADS)

    Fisenko, A. V.; Semjonova, L. F.

    2008-08-01

    The analysis of excess 129Xe in meteoritic nanodiamonds and the kinetics of its release during stepwise pyrolysis allow to suggest that (1) in the solar nebula 129I atoms were adsorbed onto nanodiamond grains and (or) chemisorbed by forming covalent bonds with carbon atoms. Most 129I atoms existed in a surface connected state, but a minor amount of them was in nanopores of the grains. At radioactive decay of 129I the formed 129Xe ( 129Xe ∗) was trapped by diamond grains due to nuclear recoil. (2) During thermal metamorphism or aqueous alteration, the surface-sited 129I atoms were basically lost. On the basis of these assumptions and calculated concentrations of 129Xe ∗ in meteoritic nanodiamonds it is shown that the minimum closing time of the I-Xe system for meteorites of different chemical classes and low petrologic types may be about one million years relative to the minimally thermally metamorphized CO3 meteorite ALHA 77307. With increasing metamorphic grade the closing time of the I-Xe system increases and can range up to several ten millions years. This tendency is in agreement with an onion-shell model of structure and cooling history of meteorite parent bodies where the temperature increases in the direction from surface to center of the asteroids.

  5. Relation of attitude toward body elimination to parenting style and attitude toward the body.

    PubMed

    Corgiat, Claudia A; Templer, Donald I

    2003-04-01

    The purpose was to estimate the relation of attitude toward body elimination in 93 college students (27 men and 66 women), to authoritarian personality features, participants' perception of their mothers' parenting style, and attitudes toward cleanliness, sex, and family nudity. Subjects were administered the Body Elimination Attitude Scale, the Four-item F Scale, the Parental Authority Questionnaire Pertaining to Mothers, and the items "Sex is dirty," "Cleanliness is next to godliness," and "Children should never see other family members nude." Larger scores for disgust toward body elimination were associated with authoritarian personality characteristics, being less likely to describe mother's parenting style as authoritative (open communication) and more likely to describe it as authoritarian and lower scores for tolerance for family nudity. Implications for further research were suggested. PMID:12785652

  6. Chemical fractionations in meteorites. VIII - Iron meteorites and the cosmochemical history of the metal phase

    NASA Technical Reports Server (NTRS)

    Kelly, W. R.; Larimer, J. W.

    1977-01-01

    The chemical composition of the metal phase of iron meteorites is traced through an idealized traditional history from condensation, oxidation, and accretion in the nebula to melting, segregation, and freezing in a parent body, considering the following fifteen elements: Au, Co, Cu, Fe, Ga, Ge, Ir, Mo, Ni, Os, Pd, Pt, Re, Rh, and Ru. Twelve iron meteorite groups resolved by Scott and Wasson (1975) are considered in the framework of cosmochemical historical analysis. The parent bodies of five of these groups seem to have had a traditional history. The others seem to have had more unusual histories. For example, the composition of the metal in group IVB matches that predicted for the metal condensate at 1270 K, implying accretion at high temperatures; and the metal in group IVA has a composition indicative of aggregates undergoing progressive stages of partial melting.

  7. Penecontemporaneous metamorphism, fragmentation, and reassembly of ordinary chondrite parent bodies

    NASA Technical Reports Server (NTRS)

    Grimm, R. E.

    1985-01-01

    The thermal histories of ordinary chondrites and the canonical internal heating or onion shell models, which predict an inverse relation between the petrologic type of chondrites and the metallographic cooling rate, are reviewed. The thermal and accretional requirements of the 'metamorphosed planetesimal' model proposed by Scott and Rajan (1981) are analyzed, and an alternative model consistent with the metallographic cooling rate constraints is suggested in which ordinary chondrite parent bodies are collisionally fragmented and then rapidly reassembled before metamorphic heat has been dissipated.

  8. Characteristics and formation of amino acids and hydroxy acids of the Murchison meteorite

    NASA Technical Reports Server (NTRS)

    Cronin, J. R.; Cooper, G. W.; Pizzarello, S.

    1995-01-01

    Eight characteristics of the unique suite of amino acids and hydroxy acids found in the Murchison meteorite can be recognized on the basis of detailed molecular and isotopic analyses. The marked structural correspondence between the alpha-amino acids and alpha-hydroxy acids and the high deuterium/hydrogen ratio argue persuasively for their formation by aqueous phase Strecker reactions in the meteorite parent body from presolar, i.e., interstellar, aldehydes, ketones, ammonia, and hydrogen cyanide. The characteristics of the meteoritic suite of amino acids and hydroxy acids are briefly enumerated and discussed with regard to their consonance with this interstellar-parent body formation hypothesis. The hypothesis has interesting implications for the organic composition of both the primitive parent body and the presolar nebula.

  9. The 2014 KCG Meteor Outburst: Clues to a Parent Body

    NASA Astrophysics Data System (ADS)

    Moorhead, Althea V.; Brown, Peter G.; Spurný, Pavel; Cooke, William J.; Shrbený, Lukáš

    2015-10-01

    The κ Cygnid (KCG) meteor shower exhibited unusually high activity in 2014, producing ten times the flux of KCG meteors compared to normal years. The shower was detected during the routine operation of several radar and optical systems. Meteoroids associated with the outburst ranged from approximately 10-6-10-5 kg for radar meteors and from 10-3 to 2 kg for optical meteors. The Canadian Meteor Orbit Radar, Czech part of the European Fireball Network, and NASA All Sky and Southern Ontario Meteor Networks produced thousands of KCG meteor trajectories in total. Using these data, we have undertaken a new and improved characterization of the dynamics of this little-studied, variable meteor shower. The KCGs have a diffuse radiant and a significant spread in orbital characteristics. Our analysis of the highest quality KCG trajectories reveals concentrations of stream members near major resonances with Jupiter. We conducted a new search for parent bodies and find that several known asteroids are orbitally similar to the KCGs. Our meteor stream simulations show that the two best parent body candidates readily transfer meteoroids to the Earth in recent centuries, but neither produces a match to the KCG radiant, velocity, and solar longitude. We nevertheless identify asteroid 2001 MG1 as a promising parent body candidate.

  10. Early Energetic Particle Irradiation of the HED Parent Body Regolith

    NASA Technical Reports Server (NTRS)

    Bogard, D. D.; Garrison, D. H.; Rao, M. N.

    1996-01-01

    ratio on the HED parent body was probably < 0.1. The relatively large difference between the derived 21-Ne SCR/GCR ratio in Kapoeta dark feldspar and the estimated production ratio strongly indicates that the early solar irradiation involved a flux -20-50x the recent solar flux. This enhanced proton flux was probably associated with an overall greater solar activity in the first approximately 10(exp 7) to 10(exp 8) years of solar history.

  11. Nature's starships. I. Observed abundances and relative frequencies of amino acids in meteorites

    SciTech Connect

    Cobb, Alyssa K.; Pudritz, Ralph E. E-mail: pudritz@physics.mcmaster.ca

    2014-03-10

    The class of meteorites called carbonaceous chondrites are examples of material from the solar system which have been relatively unchanged from the time of their initial formation. These meteorites have been classified according to the temperatures and physical conditions of their parent planetesimals. We collate available data on amino acid abundance in these meteorites and plot the concentrations of different amino acids for each meteorite within various meteorite subclasses. We plot average concentrations for various amino acids across meteorites separated by subclass and petrologic type. We see a predominance in the abundance and variety of amino acids in CM2 and CR2 meteorites. The range in temperature corresponding to these subclasses indicates high degrees of aqueous alteration, suggesting aqueous synthesis of amino acids. Within the CM2 and CR2 subclasses, we identify trends in relative frequencies of amino acids to investigate how common amino acids are as a function of their chemical complexity. These two trends (total abundance and relative frequencies) can be used to constrain formation parameters of amino acids within planetesimals. Our organization of the data supports an onion shell model for the temperature structure of planetesimals. The least altered meteorites (type 3) and their amino acids originated near cooler surface regions. The most active amino acid synthesis likely took place at intermediate depths (type 2). The most altered materials (type 1) originated furthest toward parent body cores. This region is likely too hot to either favor amino acid synthesis or for amino acids to be retained after synthesis.

  12. Core formation in the shergottite parent body and comparison with the earth

    NASA Technical Reports Server (NTRS)

    Treiman, Allan H.; Jones, John H.; Drake, Michael J.

    1987-01-01

    Abundances of elements in shergottite, nakhlite, and Chassigny meteorites which originated on a single planet, the shergottite parent body (SPB), were examined with the aim of elucidating the chemical conditions of metal separation and core formation in the SPB and of testing present models of planetary core formation. Using partition coefficients and the SPB mantle composition determined in earlier studies, the abundances of Ag, Au, Co, Ga, Mo, Ni, P, Re, S, and W were modeled, with free parameters being oxygen fugacity, proportion of solid metal formed, proportion of metallic liquid formed, and proportion of silicate that is molten. It is shown that the abundances of all elements (except Mo) could be reproduced using models with these four free parameters. In contrast to the SPB, an equivalent model used to predict element abundances in the earth's mantle was shown by Jones and Drake (1986) to be inadequate; there is at present no hypothesis capable of quantitatively reproducing the elemental abundances of the earth's mantle. The contrast suggests that these two terrestrial planets (assuming that the SPB is Mars) may have accreted or differentiated differently.

  13. Plastic deformation of olivine-rich diogenites and implications for mantle processes on the diogenite parent body

    NASA Astrophysics Data System (ADS)

    Tkalcec, Beverley J.; Brenker, Frank E.

    2014-07-01

    Numerous petrologic and geochemical studies so far on the howardite, eucrite, and diogenite (HED) meteorites have produced various crystallization scenarios for their parent body, believed to be the differentiated asteroid 4 Vesta. Structural analyses of diogenites can reveal important insights into postcrystallization deformation on the parent body. Recently published results (Tkalcec et al.) of structural analysis on the olivine-rich diogenite NWA 5480 reveal that it underwent solid-state plastic deformation, although not at the base of a magma chamber. Dynamic mantle downwelling has been proposed as a plausible deformation mechanism (Tkalcec et al.). The purpose of this study is to investigate whether the plastic deformation found in NWA 5480 is an isolated case. We expand the structural analysis on NWA 5480 and extend it to NWA 5784 and MIL 07001,6, two other samples of rare olivine-rich diogenites, using electron-backscattered-diffraction (EBSD) techniques. Our EBSD results show that the diogenites analyzed in this study underwent solid-state plastic deformation, confirming that the observed deformation of NWA 5480 was not an isolated case on the diogenite parent body. The lattice-preferred orientations (LPOs) of olivine in NWA 5784 and NWA 5480 are clearly distinct from that typical for cumulate rocks at the base of magma chambers, indicating a different stress environment and a different deformation mechanism. The LPO of olivine in MIL 07001 is less conclusive. The structural results of this study suggest that plastic deformation occurred on the diogenite parent body at high temperatures (1273 < T ≤ 1573 K) in the solid state, i.e., after crystallization of the diogenites themselves, in a dynamic environment with active stress fields.

  14. Origin and Evolution of Prebiotic Organic Matter As Inferred from the Tagish Lake Meteorite

    NASA Astrophysics Data System (ADS)

    Herd, Christopher D. K.; Blinova, Alexandra; Simkus, Danielle N.; Huang, Yongsong; Tarozo, Rafael; Alexander, Conel M. O.'D.; Gyngard, Frank; Nittler, Larry R.; Cody, George D.; Fogel, Marilyn L.; Kebukawa, Yoko; Kilcoyne, A. L. David; Hilts, Robert W.; Slater, Greg F.; Glavin, Daniel P.; Dworkin, Jason P.; Callahan, Michael P.; Elsila, Jamie E.; De Gregorio, Bradley T.; Stroud, Rhonda M.

    2011-06-01

    The complex suite of organic materials in carbonaceous chondrite meteorites probably originally formed in the interstellar medium and/or the solar protoplanetary disk, but was subsequently modified in the meteorites’ asteroidal parent bodies. The mechanisms of formation and modification are still very poorly understood. We carried out a systematic study of variations in the mineralogy, petrology, and soluble and insoluble organic matter in distinct fragments of the Tagish Lake meteorite. The variations correlate with indicators of parent body aqueous alteration. At least some molecules of prebiotic importance formed during the alteration.

  15. Regolith and Megaregolith Formation of H-Chondrites: Thermal Constraints on the Parent Body

    NASA Astrophysics Data System (ADS)

    Akridge, Glen; Benoit, Paul H.; Sears, Derek W. G.

    1998-03-01

    Spectral reflectivity data and its location near an orbital resonance suggest that Asteroid 6 Hebe may be the source body for H-chondrites, the second largest meteorite group. Recent spacecraft images of asteroids and theoretical modeling indicate that, contrary to previous ideas, asteroids can retain thick regoliths. We model the thermal evolution of a Hebe-sized object coated with a thick insulating regolith and heated by26Al and other long-lived radionuclides. The heat conduction equations for spherically symmetric objects were solved using finite-difference approximations. We assumed a three-layer structure with regolith and megaregolith overlying a rocky core. The three layers differed in bulk density, porosity, and thermal conductivity. Interior peak temperatures were set to match metamorphic temperatures of H6 chondrites. The regolith has a major influence on thermal history, and the results are very different from those for a simple rocky body published by various authors. Regolith insulation produces a uniform interior peak temperature of ∼1250 K and moves the petrographic type boundaries close to the surface of the parent body. Petrologic types 3-6 can be produced within 10 km of the asteroid's surface with only moderate (∼1 km) regolith thicknesses. The calculations indicate that H4-H6 formation would be consistent with the cooling rate estimates and Pb-Pb formation ages if the material originated in the near surface regions. We suggest that many if not all H-chondrites could have been formed in a megaregolith and thick regolith. Their observed properties are consistent with this environment, especially the abundance of regolith breccias and H-chondrites of all petrologic types with implanted solar wind gases.

  16. Ar-39 - Ar-40 Evidence for an Approximately 4.26 Ga Impact Heating Event on the LL Parent Body

    NASA Technical Reports Server (NTRS)

    Dixon, E. T.; Bogard, D. D.; Rubin, A. E.

    2003-01-01

    Miller Range 99301 is a type 6, unbrecciated LL chondrite. MIL 99301 is of interest because some compositional and petrographic features suggest it experienced rather high shock grades, whereas other features suggest it is relatively unshocked. Inconsistent shock indicators could be explained if MIL 99301 was shocked but then partly annealed by heat produced by impacts on the parent body. The hypothesis that MIL 99301 experienced high temperature metamorphism (type 6) followed by a later shock event that heated, but did not melt, the constituent feldspar can be evaluated using (39)Ar-(40)Ar chronology. This is because (39)Ar-(40)Ar ages of shocked ordinary chondrites are generally <4.2 Ga, whereas (39)Ar-(40)Ar ages of unshocked meteorites are generally older, and between 4.52 - 4.38 Ga.

  17. Space Weathering of Ordinary Chondrite Parent Bodies, Its Impact on the Method of Distinguishing H, L, and LL Types and Implications for Itokawa Samples Returned by the Hayabusa Mission

    NASA Technical Reports Server (NTRS)

    Hiroi, T.; Sasaki, S.; Noble, S. K.; Pieters, C. M.

    2011-01-01

    As the most abundance meteorites in our collections, ordinary chondrites potentially have very important implications on the origin and formation of our Solar System. In order to map the distribution of ordinary chondrite-like asteroids through remote sensing, the space weathering effects of ordinary chondrite parent bodies must be addressed through experiments and modeling. Of particular importance is the impact on distinguishing different types (H/L/LL) of ordinary chondrites. In addition, samples of asteroid Itokawa returned by the Hayabusa spacecraft may re veal the mechanism of space weathering on an LLchondrite parent body. Results of space weathering simulations on ordinary chondrites and implications for Itokawa samples are presented here.

  18. Experimental study of segregation in plane front solidification and its relevance to iron meteorite solidification

    NASA Technical Reports Server (NTRS)

    Sellamuthu, R.; Goldstein, J. I.

    1983-01-01

    A directional solidification technique was developed and applied to the problem of fractional crystallization of an iron meteorite parent body. Samples of Fe-Ni alloys close to meteorite compositions and containing S, P, and C were made. The solidified structures contain secondary phases such as sulphides within the proeutectic single crystal austenite (taenite). As a result of these experiments, we propose that the secondary phases observed in iron meteorites were formed during primary solidification of austenite (taenite). The measured composition profiles of Ni, P and C in the alloys were used to explain the elemental distribution within a chemical group of iron meteorites. An analytical procedure was applied to determine the equilibrium distribution coefficients as a function of fraction solidified for Ni and P from the composition profiles. The distribution coefficients of Ni and P agree with previous values. These distribution coefficients are of particular interest in the determination of the elemental distributions in iron meteorites.

  19. Experimental study of segregation in plane front solidification and its relevance to iron meteorite solidification

    NASA Astrophysics Data System (ADS)

    Sellamuthu, R.; Goldstein, J. I.

    1983-11-01

    A directional solidification technique was developed and applied to the problem of fractional crystallization of an iron meteorite parent body. Samples of Fe-Ni alloys close to meteorite compositions and containing S, P, and C were made. The solidified structures contain secondary phases such as sulphides within the pro-eutectic single crystal austenite (taenite). As a result of these experiments, we propose that the secondary phases observed in iron meteorites were formed during primary solidification of austenite (taenite). The measured composition profiles of Ni, P and C in the alloys were used to explain the elemental distribution within a chemical group of iron meteorites. An analytical procedure was applied to determine the equilibrium distribution coefficients as a function of fraction solidified for Ni and P from the composition profiles. The distribution coefficients of Ni and P agree with previous values. These distribution coefficients are of particular interest in the determination of the elemental distributions in iron meteorites.

  20. Chemical compositions of the moon, earth, and eucrite parent body

    NASA Technical Reports Server (NTRS)

    Anders, E.

    1977-01-01

    Model compositions of the moon and earth were calculated on the assumption that these planets had experienced chondrite-like nebular fractionation processes. The model correctly predicts the abundance ratios of certain volatile/refractory element pairs (e.g., Cd/Ba, Ga/La, Sn/Th, and Pb/U), the density of the moon, and the major rock types. The model is also used to reconstruct the composition of the parent eucrite body, which resembles the moon except for a lower content of refractory elements.

  1. A parent body search across several video meteor data bases

    NASA Astrophysics Data System (ADS)

    Šegon, D.; Gural, P.; Andreić, Ž.; Skokić, I.; Korlević, K.; Vida, D.; Novoselnik, F.

    2014-07-01

    A meteor stream search that uses all the known near-Earth objects (NEOs) as parent bodies, with their individual orbital elements as the starting point, has found statistically significant associations when applied to video meteor data bases. By using the combined CMN-SonotaCo data sets containing 133,652 video meteor orbits, 30 comets were associated with meteor showers of which only 23 were previously listed in the IAU MDC data base. Additionally, 43 asteroids with inclinations over 15 degrees may be associated to streams containing ten or more meteor orbits, each possibly representing a new meteor shower. Lastly, by using a modified search that compared the orbital similarity of each meteor to all other video meteors in the data base, 1093 groupings with more than ten meteors were found that may be indicative of several new minor showers. Of those groups, 6 new showers were found to be potentially associated to a parent body. Several dozen additional groups are planned for publication and submittal to the IAU for their consideration as newly discovered streams. Altogether 56,486 (42%) of the meteors in the combined video meteor data base are in one of the meteor stream groupings found, while the rest are likely sporadics. Further analysis is needed to prove that the groupings found are indeed minor showers.

  2. Don Quixote --- a possible parent body of a meteor shower

    NASA Astrophysics Data System (ADS)

    Rudawska, R.; Vaubaillon, J.

    2014-07-01

    This talk addresses the topic of meteoroid stream parent body in relation to meteor showers observed on the Earth. We carry out a further search to investigate the possibility of meteor shower observations caused by particles ejected from (3552) Don Quixote. The (3552) Don Quixote asteroid was discovered in 1983 as an Amor asteroid. The Tisserand parameter for the orbit has a value of 2.315 with respect to Jupiter, which indicates a comet-like orbit. The diameter of the object calculated from the absolute magnitude, is in the range of 12.3--24.5 km. It all makes Don Quixote a good candidate for a short-period comet among known near-Earth objects, which the recently observed cometary activity confirms [1]. We have investigated the orbital evolution of the meteoroid stream originated from Don Quixote. If the object was active in the past, it might be a parent body for a meteor shower observed on the Earth. The model for the generation and evolution of the meteoroid stream in the Solar System is taken from [2]. The asteroid's orbital elements and physical properties are taken from the JPL horizons website. The ejections of meteoroids from the asteroid surface took place when the asteroid was passing its perihelion between 5000 B.C. and 2013 A.D. Next, the orbits of ejected meteoroids were integrated to the year 2050. If a meteoroid is sufficiently close to the Earth, its orbital parameters are saved and compared with known showers.

  3. The evolution of partially differentiated planetesimals Evidence from iron meteorite groups IAB and IIICD

    NASA Technical Reports Server (NTRS)

    Kracher, A.

    1985-01-01

    Some of the properties of IAB and IIICD iron meteorites thought to be derived from partially differentiated planetesimals are summarized, and the physical aspects that may have controlled parent body differentiation and affected the composition of the sulfide melt are outlined. The chemical evolution of the parent body is then discussed, and observations supporting the partial differentiation model are examined. Finally, an attempt is made to reinterpret barometric and chronometric data in light of the partial differentiation model, and tentative conclusions are presented.

  4. The Cooling History and Structure of the Ordinary Chondrite Parent Bodies

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

    Most major meteorite classes exhibit significant ranges of metamorphism. The effects of metamorphism have been extensively characterized, but the heat source(s) and the metamorphic environment are unknown. Proposed beat sources include Al-26, Fe-60, electromagnetic induction, and impact. It is typically assumed that metamorphism occurred in parent bodies of some sort, but it uncertain whether these bodies were highly structured ("onion skins") or were chaotic mixes of material ("rubble piles"). The lack of simple trends of metallographic cooling rates with petrologic type has been considered supportive of both concepts. In this study, we use induced thermoluminescence (TL) as an indicator of thermal history. The TL of ordinary chondrites is produced by sodic feldspar, and the induced TL peak temperature is related to its crystallographic order/disorder. Ordered feldspar has TL peak temperatures of approx. 120 C, and disordered feldspar has TL peak temperatures of approx. 220 C. While ordered feldspar can be easily disordered in the laboratory by heating above 650 C and is easily quenched in the disordered form, producing ordered feldspar requires cooling at geologic cooling rates. We have measured the induced TL properties of 101 equilibrated ordinary chondrites, including 49 H, 29 L, and 23 LL chondrites. For the H chondrites there is an apparent trend of decreasing induced TL peak temperature with increasing petrologic type. H4 chondrites exhibit a tight range of TL peak temperatures, 190 C - 200 C, while H6 chondrites exhibit TL peak temperatures between 180 C and 190 C. H5 chondrites cover the range between H4 and H6, and also extend up to 210 C. Similar results are obtained for LL chondfiles and most L6 chondrites have lower induced TL peak temperatures than L5 chondrites.

  5. Petrology of the Baszkowka L5 chondrite: A record of surface-forming processes on the parent body

    NASA Astrophysics Data System (ADS)

    Przylibski, T. A.; Pilski, A. S.; Zagożdżon, P. P.; Kryza, R.

    2003-06-01

    We review the petrology of Baszkowka, present new microprobe data on mineral constituents, and propose a model for surface properties of the parent body consistent with these data. The low shock index and high porosity of the Baszkowka L5 chondrite mean that considerable primary textural and petrographic detail is preserved, allowing insight into the structure and evolution of the parent body. This meteorite formed in a sedimentary environment resembling that in which pyroclastic rocks are deposited. The origin of the component chondrules, achondritic fragments (mostly olivine and pyroxene aggregates), chondritic-achondritic aggregates, and compound chondrules can be explained by invoking collision of 2 melted or partially melted planetesimals, each covered with a thin crust. This could have happened at an early stage in the evolution of the solar system, between 1 and 2 Myr after its origin. The collision resulted in the formation of a cloud containing products of earlier magmatic crystallization (chondrite and achondrite fragments) from which new chondrules were created. Particle collision in this cloud produced fragmented chondrules, chondritic-achondritic aggregates, and compound chondrules. Within this low-density medium, these particles were accreted on the surface of the larger of the planetesimals involved in the collision. The density of the medium was low enough to prevent grain-size sorting of the components but high enough to prevent the total loss of heat and to enable the welding of fragments on the surface of the body. The rock material was homogenized within the cloud and, in particular, within the zone close to the planetesimal surface. The hot material settled on the surface and became welded as molten or plastic metal, and sulfide components cemented the grains together. The process resembled the formation of welded ignimbrites. Once these processes on the planetesimal surface were completed, no subsequent recrystallization occurred. The high

  6. Laboratory spectroscopy of HED meteorites

    NASA Astrophysics Data System (ADS)

    Farina, M.; Coradini, A.; Carli, C.; Ammannito, E.; Consolmagno, G.; De sanctis, M.; Di Iorio, T.; Turrini, D.

    2011-12-01

    4 Vesta is one of the largest and the most massive asteroid in the Main Asteroid Belt. This asteroid possesses a basaltic surface and apparently formed and differentiated very early in the history of the solar system. There are strong evidences that indicate Vesta as the parent body of Howardites, Diogenites and Eucrites (HEDs). HED meteorites are a subgroup of achondrite meteorites and they are a suite of rocks that formed at high temperature and experienced igneous processing similar to the magmatic rocks found on Earth. The visible and near-infrared (VNIR) reflectance spectra of Vesta's surface show high similarity with the laboratory spectra of HED meteorites. Vesta and HEDs spectra have two crystal field absorption bands close to 0.9 μm and 1.9 μm indicative of the presence of ferrous iron in pyroxenes. The HEDs differ from each other primarily based on variation in pyroxene composition and the pyroxene-plagioclase ratio as well as rocks texture characteristics (e.g., size of crystals). These differences suggest that a combined VNIR spectra studies of Vesta and HED meteorites might reveal the different characteristics of the surface compositions and shed new light on the origin and the thermal history of Vesta. Moreover the link between Vesta and HEDs could provide a test bed to understand the short-lived radionuclide-driven differentiation of planetary bodies. Here we present preliminary result of a study of spectral characteristics of different HED samples, provided to us by the Vatican Observatory. Bidirectional reflectance spectra of slabs of meteorites are performed in the VNIR, between (0.35/2.50) μm, using a Fieldspec spectrometer mounted on a goniometer, in use at the SLAB (Spectroscopy laboratory, INAF, Rome). The spectra are acquired in standard conditions with an incidence angle i=30o and an emission angle e=0o, measuring a spot with a diameter of 5 mm. Different Howardite, Diogenite and Eucrite samples are "mapped" considering several spots on

  7. Magnetic studies on Shergotty and other SNC meteorites

    NASA Astrophysics Data System (ADS)

    Cisowski, S. M.

    1986-06-01

    The results of a study of basic magnetic properties of meteorites within the SNC group, including the four known shergottites and two nakhlites, are presented. An estimate is made of the strength of the magnetic field which produced the remanent magnetization of the Shergotty meteorite, for the purpose of constraining the choices for the parent body of these SNC meteorites. Remanence measurements in several subsamples of Shergotty and Zagami meteorites reveal a large variation in intensity that does not seem to be related to the abundance of remanence carriers. The other meteorites carry only weak remanence, suggesting weak magnetizing fields as the source of their magnetic signal. A paleointensity experiment on a weakly magnetized subsample of Shergotty revealed a low temperature component of magnetization acquired in a field of 2000 gammas, and a high temperature component reflecting a paleofield strength of between 250 and 1000 gammas. The weak field environment that these meteorites seem to reflect is consistent with either a Martian or asteroidal origin, but inconsistent with a terrestrial origin.

  8. Magnetic studies on Shergotty and other SNC meteorites

    NASA Technical Reports Server (NTRS)

    Cisowski, S. M.

    1986-01-01

    The results of a study of basic magnetic properties of meteorites within the SNC group, including the four known shergottites and two nakhlites, are presented. An estimate is made of the strength of the magnetic field which produced the remanent magnetization of the Shergotty meteorite, for the purpose of constraining the choices for the parent body of these SNC meteorites. Remanence measurements in several subsamples of Shergotty and Zagami meteorites reveal a large variation in intensity that does not seem to be related to the abundance of remanence carriers. The other meteorites carry only weak remanence, suggesting weak magnetizing fields as the source of their magnetic signal. A paleointensity experiment on a weakly magnetized subsample of Shergotty revealed a low temperature component of magnetization acquired in a field of 2000 gammas, and a high temperature component reflecting a paleofield strength of between 250 and 1000 gammas. The weak field environment that these meteorites seem to reflect is consistent with either a Martian or asteroidal origin, but inconsistent with a terrestrial origin.

  9. The meteorite Moss - a rare carbonaceous chondrite

    NASA Astrophysics Data System (ADS)

    Bilet, M.; Roaldset, E.

    2014-07-01

    On July 14, 2006, at about 10:20 a.m. local daylight time (UTC+2), a bright fireball travelling SSE-NNV was witnessed from the Baltic Sea to SE Norway. On the east side of the Oslo fiord, around Moss, an explosion and a rumbling sound was heard, and pieces were observed falling. Rapid recovery of meteorite stones gave an opportunity for detailed petrological and geochemical investigations, including analyses of indigenous organic species, and short lived isotopes. The meteorite is a chondritic stone meteorite, with some carbon (0.21-0.25 wt% C). The cosmic-ray exposure (CRE) age is 14 Ma, i.e. when Moss was ejected from its parent body. Gas retention ages are approximately 3.95x10^9 yr (U/Th/He) and 4.43x10^9 yr (K/Ar), respectively. The meteorite has the official name Moss, and is classified as carbonaceous chondrite type CO3.6. It was the first witnessed fall of a CO3 chondrite since Kainsaz in Russia in 1937.

  10. High-pressure experiments on magnesian eucrite compositions - Constraints on magmatic processes in the eucrite parent body

    NASA Technical Reports Server (NTRS)

    Bartels, K. S.; Grove, T. L.

    1991-01-01

    Melting experiments were conducted on synthetic analogs of two magnesian eucrite clasts from howardites, Kapoeta clast rho and Yamato 7308 pigeonite-eucrite clast 1, at 1 atm and 1-kbar pressure at oxygen fugacities in the range of iron-wuestite (IW) to iron-quartz-fayalite (IQF). The compositions of liquids and coexisting minerals (olivine-low-Ca pyroxene-plagioclase spinel) were used to constrain possible melting and crystallization processes in the parent bodies of eucrite basalts. In agreement with previous studies, the experimental results at 1 atm indicate that the olivine-low-Ca pyroxene-plagioclase-spinel-liquid and olivine-low Ca pyroxene-spinel-liquid boundaries are reaction boundaries involving olivine. At 1 kbar, however, the olivine primary-phase volume shrinks, and the reaction relationship involving olivine disappears for both boundaries. The maximum pressure attained in a Vesta-sized eucrite parent body (EPB) is about 1 kbar, and these results provide important constraints on models relating the howardite-eucrite-diogenite (HED) meteorite association through melting and differentiation processes.

  11. Magnetism and mineralogy of Almahata Sitta polymict ureilite (= asteroid 2008 TC3): Implications for the ureilite parent body magnetic field

    NASA Astrophysics Data System (ADS)

    Hoffmann, Viktor H.; Hochleitner, Rupert; Torii, Masayuki; Funaki, Minoru; Mikouchi, Takashi; Kaliwoda, Melanie; Jenniskens, Peter; Shaddad, Muawia H.

    2011-10-01

    The Almahata Sitta meteorite is the first case of recovered extraterrestrial material originating from an asteroid that was detected in near Earth space shortly before entering and exploding in the high atmosphere. The aims of our project within the 2008 TC3 consortium were investigating Almahata Sitta's (AS) magnetic signature, phase composition and mineralogy, focussing on the opaque minerals, and gaining new insights into the magnetism of the ureilite parent body (UPB). We report on the general magnetic properties and behavior of Almahata Sitta and try to place the results in context with the existing data set on ureilites and ureilite parent body models. The magnetic signature of AS is dominated by a set of low-Ni kamacites with large grain sizes. Additional contributions come from micron-sized kamacites, suessite, (Cr) troilite, and daubreelite, mainly found in the olivine grains adjacent to carbon-rich veins. Our results show that the paleomagnetic signal is of extraterrestrial origin as can be seen by comparing with laboratory produced magnetic records (IRM). Four types of kamacite (I-IV) have been recognized in the sample. The elemental composition of the ureilite vein metal Kamacite I (particularly Co) clearly differs from the other kamacites (II-IV), which are considered to be indigenous. Element ratios of kamacite I indicate that it was introduced into the UPB by an impactor, supporting the conclusions of Gabriel and Pack (2009).

  12. Siderophile trace elements in metals and sulfides in enstatite achondrites record planetary differentiation in an enstatite chondritic parent body

    NASA Astrophysics Data System (ADS)

    van Acken, D.; Humayun, M.; Brandon, A. D.; Peslier, A. H.

    2012-04-01

    Siderophile element concentrations were measured by LA-ICP-MS in metals and sulfides from five aubrite meteorites. Siderophile element patterns in aubrites are either similar to those in metal from enstatite chondrites, or can be derived by crystallization from metallic liquids derived by partial melting of E chondrites. Some metal grains in Mt. Egerton, Cumberland Falls, and Aubres show moderate to severe depletion in compatible highly siderophile elements (Re, Os, Ir, Ru) which are consistent with solid metal/liquid metal differentiation of enstatite chondrite-like metal. Metals from chondrite inclusions in Cumberland Falls show more extremely fractionated patterns than those from the aubritic matrix, potentially hinting at fractionation and partial melting processes affecting not only the aubrite parent body, but the chondrite body from which the inclusions were derived as well. Models using experimental partition coefficients show that aubrite metal chemically corresponds to solid metal segregated during differentiation of primary metallic liquids of EH/EL composition that contained both substantial S- and C-contents. This result is consistent with a genetic link between enstatite chondrites and aubrites, but as to whether aubrites were derived from the same body(ies) as enstatite chondrites, or have their origin in multiple, and potentially separated bodies, cannot be answered unequivocally with chemical or isotopic data alone.

  13. Cosmic-ray Exposure Ages of Meteorites

    NASA Astrophysics Data System (ADS)

    Herzog, G. F.

    2003-12-01

    The classic idea of a cosmic-ray exposure (CRE) age for a meteorite is based on a simple but useful picture of meteorite evolution, the one-stage irradiation model. The precursor rock starts out on a parent body, buried under a mantle of material many meters thick that screens out cosmic rays. At a time ti, a collision excavates a precursor rock - a "meteoroid." The newly liberated meteoroid, now fully exposed to cosmic rays, orbits the Sun until a time tf, when it strikes the Earth, where the overlying blanket of air (and possibly of water or ice) again shuts out almost all cosmic rays (cf. Masarik and Reedy, 1995). The quantity tf-ti is called the CRE age, t. To obtain the CRE age of a meteorite, we measure the concentrations in it of one or more cosmogenic nuclides (Table 1), which are nuclides that cosmic rays produce by inducing nuclear reactions. Many shorter-lived radionuclides excluded from Table 1 such as 22Na (t1/2=2.6 yr) and 60Co (t1/2=5.27 yr) can also furnish valuable information, but can be measured only in meteorites that fell within the last few half-lives of those nuclides (see, e.g., Leya et al. (2001) and references therein). Table 1. Cosmogenic nuclides used for calculating exposure ages NuclideHalf-lifea (Myr) Radionuclides 14C0.005730 59Ni0.076 41Ca0.1034 81Kr0.229 36Cl0.301 26Al0.717 10Be1.51 53Mn3.74 129I15.7 Stable nuclides 3He 21Ne 38Ar 83Kr 126Xe a http://www2.bnl.gov/ton. CRE ages have implications for several interrelated questions. From how many different parent bodies do meteorites come? How well do meteorites represent the population of the asteroid belt? How many distinct collisions on each parent body have created the known meteorites of each type? How often do asteroids collide? How big and how energetic were the collisions that produced meteoroids? What factors control the CRE age of a meteorite and how do meteoroid orbits evolve through time? We will touch on these questions below as we examine the data.By 1975, the CRE ages of

  14. School-Based BMI and Body Composition Screening and Parent Notification in California: Methods and Messages

    ERIC Educational Resources Information Center

    Madsen, Kristine A.; Linchey, Jennifer

    2012-01-01

    Background: School-based body mass index (BMI) or body composition screening is increasing, but little is known about the process of parent notification. Since 2001, California has required annual screening of body composition via the FITNESSGRAM, with optional notification. This study sought to identify the prevalence of parental notification…

  15. Spectral variability on primitive asteroids of the Themis and Beagle families: Space weathering effects or parent body heterogeneity?

    NASA Astrophysics Data System (ADS)

    Fornasier, S.; Lantz, C.; Perna, D.; Campins, H.; Barucci, M. A.; Nesvorny, D.

    2016-05-01

    Themis is an old and statistically robust asteroid family populating the outer main belt, and resulting from a catastrophic collision that took place 2.5 ± 1.0 Gyr ago. Within the old Themis family a young sub-family, Beagle, formed less than 10 Myr ago, has been identified. We present the results of a spectroscopic survey in the visible and near infrared range of 22 Themis and 8 Beagle families members. The Themis members investigated exhibit a wide range of spectral behaviors, including asteroids with blue/neutral and moderately red spectra, while the younger Beagle family members look spectrally bluer than the Themis ones and they have a much smaller spectral slope variability. Four Themis members, including (24) Themis, have absorption bands centered at 0.68-0.73 μm indicating the presence of aqueously altered minerals. The best meteorite spectral analogues found for both Themis and Beagle families members are carbonaceous chondrites having experienced different degrees of aqueous alteration, prevalently CM2 but also CV3 and CI, and some of them are chondrite samples being unusual or heated. The presence of aqueous altered materials on the asteroids surfaces and the meteorite matches indicate that the parent body of the Themis family experienced mild thermal metamorphism in the past. We extended the spectral analysis including the data available in the literature on Themis and Beagle families members, and we looked for correlations between spectral behavior and physical parameters using the albedo and size values derived from the WISE data. The analysis of this larger sample confirms the spectral diversity within the Themis family and that Beagle members tend to be bluer and to have an higher albedo. The differences between the two families may be partially explained by space weathering processes, which act on these primitive surfaces in a similar way than on S-type asteroids, i.e. producing reddening and darkening. However we see several Themis members

  16. Mineralogy and chemistry of planets and meteorites

    NASA Technical Reports Server (NTRS)

    1983-01-01

    The data collection and the interpretation with respect to the mineralogy of meteoritic and terrestrial samples are summarized. The key conclusion is that the Moon underwent a series of melting episodes with complex crystal-liquid differentiation. It was not possible to determine whether the Moon melted completely or only partially. The stage is now set for a systematical geochemical and geophysical survey of the Moon. Emphasis was moved to meteorites in order to sort out their interrelationships from the viewpoint of mineral chemistry. Several parent bodies are needed for the achondrites with different chemical properties. Exploration of Mars is required to test ideas based on the possible assignment of shergottites, nakhlites and chassignite to this planet. Early rocks on the Earth have properties consistent with a heavy bombardment and strong volcanic activity prior to 4 billion years ago.

  17. Antarctic meteorites

    NASA Astrophysics Data System (ADS)

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

    1982-04-01

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

  18. Water in SNC meteorites - Evidence for a Martian hydrosphere

    NASA Technical Reports Server (NTRS)

    Karlsson, Haraldur R.; Clayton, Robert N.; Gibson, Everett K., Jr.; Mayeda, Toshiko K.

    1992-01-01

    The Shergotty-Nakhla-Chassigny (SNC) meteorites, purportedly of Martian origin, contain 0.04 to 0.4 percent water by weight. Oxygen isotopic analysis can be used to determine whether this water is extraterrestrial or terrestrial. Such analysis reveals that a portion of the water is extraterrestrial and furthermore was not in oxygen isotopic equilibrium with the host rock. Lack of equilibrium between water and host rock implies that the lithosphere and hydrosphere of the SNC parent body formed two distinct oxygen isotopic reservoirs. If Mars was the parent body, the maintenance of two distinct reservoirs may result from the absence of plate tectonics on the planet.

  19. 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.

  20. Comets, Carbonaceous Meteorites, and the Origin of the Biosphere

    NASA Technical Reports Server (NTRS)

    Hoover, Richard B.

    2007-01-01

    Evidence for indigenous microfossils in carbonaceous meteorites suggests that the paradigm of the endogenous origin of life on Earth should be reconsidered. It is now widely accepted that comets and carbonaceous meteorites played an important role in the delivery of water, organics and life critical biogenic elements to the early Earth and facilitated the origin and evolution of the Earth's Biosphere. However; the detection of embedded microfossils and mats in carbonaceous meteorites implies that comets and meteorites may have played a direct role in the delivery of intact microorganisms and that the Biosphere may extend far into the Cosmos. Recent space observations have found the nuclei of comets to have very low albedos (approx.0.03) and. these jet-black surfaces become very hot (T approx. 400 K) near perihelion. This paper reviews recent observational data-on comets and suggests that liquid water pools could exist in cavities and fissures between the internal ices and rocks and the exterior carbonaceous crust. The presence of light and liquid water near the surface of the nucleus enhances the possibility that comets could harbor prokaryotic extremophiles (e.g., cyanobacteria) capable of growth over a wide range of temperatures. The hypothesis that comets are the parent bodies of the CI1 and the CM2 carbonaceous meteorites is advanced. Electron microscopy images will be presented showing forms interpreted as indigenous-microfossils embedded' in freshly. fractured interior surfaces of the Orgueil (CI1) and Murchison (CM2) meteorites. These forms are consistent in size and morphologies with known morphotypes of all five orders of Cyanobacteriaceae: Energy Dispersive X-ray Spectroscopy (EDS) elemental data shows that the meteoritic forms have anomalous C/O; C/N; and C/S as compared with modern extremophiles and cyanobacteria. These images and spectral data indicate that the clearly biogenic and embedded remains cannot be interpreted as recent biological

  1. Carbonate minerals as high fidelity recorders of the longevity and scale of the aqueous system within CM carbonaceous chondrite parent bodies

    NASA Astrophysics Data System (ADS)

    Lee, M.; Lindgren, P.; Sofe, M. R.

    2011-12-01

    The presence of phyllosilicates and carbonates in the CM carbonaceous chondrites provides clear evidence for water-mediated crystallization very early in the history of the solar system [1]. The relatively coarse crystal size of the carbonates makes them amenable to electron- and ion-beam analysis and so they are potentially powerful tools for unraveling parent body histories. To date most studies have found a single carbonate generation within any one meteorite and together with the limited differences between samples these results are consistent with a brief period of carbonate mineralization within near-static parent body aqueous solutions. Using electron beam imaging and analysis techniques we have characterised the carbonates within a suite of CM meteorites with different degrees of alteration: Murchison, Pollen, Murray, Mighei, LON 94101, Nogoya, Cold Bokkeveld, QUE 93005 and SCO 06043. These meteorites contain five compositionally distinct carbonate minerals, namely aragonite, calcite, magnesian dolomite, calcian dolomite, and breunnerite. Ca-carbonates are dominant in the less altered CMs (e.g. Murchison and Murray) and most grains have crystallized as cements within equant pores in the matrix. Aragonite formed before calcite, and both minerals were subsequently partially or completely replaced by tochilinite and/or Mg-phyllosilicates. The patchy distribution of aragonite and scarcity of carbonate veins indicates low water/rock ratios, and the good preservation of otherwise unstable aragonite suggests that aqueous alteration was short-lived. The more highly altered CMs (e.g. QUE 93005 and SCO 06043) have evidence for four or even more phases of mineralization by Ca-carbonates and Ca-Mg-Fe-Mn-carbonates. These minerals occur within concentrically layered polymineralic grains and fill fractures produced by expansion of chondrules during hydration. Calcite has replaced calcian dolomite, and the Ca-Mg-Fe-Mn-carbonates have themselves been extensively replaced

  2. 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.

  3. Lunar and Planetary Science XXXV: Martian Meteorites: Petrology

    NASA Technical Reports Server (NTRS)

    2004-01-01

    The session "Martian Meteorites: Petrology: included the following reports:Volatile Behavior in Lunar and Terrestrial Basalts During Shock: Implications for Martian Magmas; Problems with a Low-Pressure Tholeiitic Magmatic History for the Chassigny Dunite; Fast Cooling History of the Chassigny Martian Meteorite; Rehomogenized Interstitial and Inclusion Melts in Lherzolitic Shergottite ALH 77005: Petrologic Significance; Compositional Controls on the Formation of Kaersutite Amphibole in Shergottite Meteorites; Chemical Characteristics of an Olivine-Phyric Shergottite, Yamato 980459; Pb-Hf-Sr-Nd Isotopic Systematics and Age of Nakhlite NWA 998; Noble Gases in Two Samples of EETA 79001 (Lith. A); Experimental Constraints on the Iron Content of the Martian Mantle; and Mars as the Parent Body for the CI Carbonaceous Chondrites: New Data.

  4. Formation of the Mont Dieu IIE Non Magmatic Iron Meteorite, and Origin of its Silicate Inclusions

    NASA Astrophysics Data System (ADS)

    van Roosbroek, N.; Goderis, S.; Debaille, V.; Valley, J. W.; Claeys, Ph.

    2012-03-01

    Mont Dieu is an IIE nonmagmatic iron meteorite showing primitive features such as preserved chondrules and glass. SEM and geochemical analyses demonstrate that it most likely originated from an H-chondrite parent body impacted by a Fe-Ni projectile.

  5. Simulation of possible regolith optical alteration effects on carbonaceous chondrite meteorites

    NASA Technical Reports Server (NTRS)

    Clark, Beth E.; Fanale, Fraser P.; Robinson, Mark S.

    1993-01-01

    As the spectral reflectance search continues for links between meteorites and their parent body asteroids, the effects of optical surface alteration processes need to be considered. We present the results of an experimental simulation of the melting and recrystallization that occurs to a carbonaceous chondrite meteorite regolith powder upon heating. As done for the ordinary chondrite meteorites, we show the effects of possible parent-body regolith alteration processes on reflectance spectra of carbonaceous chondrites (CC's). For this study, six CC's of different mineralogical classes were obtained from the Antarctic Meteorite Collection: two CM meteorites, two CO meteorites, one CK, and one CV. Each sample was ground with a ceramic mortar and pestle to powders with maximum grain sizes of 180 and 90 microns. The reflectance spectra of these powders were measured at RELAB (Brown University) from 0.3 to 2.5 microns. Following comminution, the 90 micron grain size was melted in a nitrogen controlled-atmosphere fusion furnace at an approximate temperature of 1700 C. The fused sample was immediately held above a flow of nitrogen at 0 C for quenching. Following melting and recrystallization, the samples were reground to powders, and the reflectance spectra were remeasured. The effects on spectral reflectance for a sample of the CM carbonaceous chondrite called Murchison are shown.

  6. U-Pb Dating of Zircons and Phosphates in Lunar Meteorites, Acapulcoites and Angrites

    NASA Technical Reports Server (NTRS)

    Zhou, Q.; Zeigler, R. A.; Yin, Q. Z.; Korotev, R. L.; Joliff, B. L.; Amelin, Y.; Marti, K.; Wu, F. Y.; Li, X. H.; Li, Q. L.; Lin, Y. T.; Liu, Y.; Tang, G. Q.

    2012-01-01

    Zircon U-Pb geochronology has made a great contribution to the timing of magmatism in the early Solar System [1-3]. Ca phosphates are another group of common accessory minerals in meteorites with great potential for U-Pb geochronology. Compared to zircons, the lower closure temperatures of the U-Pb system for apatite and merrillite (the most common phosphates in achondrites) makes them susceptible to resetting during thermal metamorphism. The different closure temperatures of the U-Pb system for zircon and apatite provide us an opportunity to discover the evolutionary history of meteoritic parent bodies, such as the crystallization ages of magmatism, as well as later impact events and thermal metamorphism. We have developed techniques using the Cameca IMS-1280 ion microprobe to date both zircon and phosphate grains in meteorites. Here we report U-Pb dating results for zircons and phosphates from lunar meteorites Dhofar 1442 and SaU 169. To test and verify the reliability of the newly developed phosphate dating technique, two additional meteorites, Acapulco, obtained from Acapulco consortium, and angrite NWA 4590 were also selected for this study as both have precisely known phosphate U-Pb ages by TIMS [4,5]. Both meteorites are from very fast cooled parent bodies with no sign of resetting [4,5], satisfying a necessity for precise dating.

  7. Analysis of segregation trends observed in iron meteorites using measured distribution coefficients

    NASA Technical Reports Server (NTRS)

    Sellamuthu, R.; Goldstein, J. I.

    1985-01-01

    Fe-Ni alloys of meteoritic composition were solidified by a plane front solidification technique. Distribution coefficients of Ni, P, Ir, Ge, and Cu were determined from the composition data of the plane front solidified alloys. Equations that describe the distribution coefficients (P, Ni, Ir, Ge, and Cu) as a function of S and P content as well as S to P ratio were used to calculate solute partitioning between solid and liquid during the solidification of IIAB, IIIAB, and IVA parent bodies. The calculated P versus Ni, Ir versus Ni, Ge versus Ni, and Cu versus Ni trends are in good agreement with the observed meteorite data for each chemical group. It is concluded that each chemical group formed as a single molten pool in a parent body and that solute partitioning that occurred during solidification is responsible for the observed compositional trends within a single meteorite group.

  8. Analysis of segregation trends observed in iron meteorites using measured distribution coefficients

    NASA Astrophysics Data System (ADS)

    Sellamuthu, R.; Goldstein, J. I.

    1985-02-01

    Fe-Ni alloys of meteoritic composition were solidified by a plane front solidification technique. Distribution coefficients of Ni, P, Ir, Ge, and Cu were determined from the composition data of the plane front solidified alloys. Equations that describe the distribution coefficients (P, Ni, Ir, Ge, and Cu) as a function of S and P content as well as S to P ratio were used to calculate solute partitioning between solid and liquid during the solidification of IIAB, IIIAB, and IVA parent bodies. The calculated P versus Ni, Ir versus Ni, Ge versus Ni, and Cu versus Ni trends are in good agreement with the observed meteorite data for each chemical group. It is concluded that each chemical group formed as a single molten pool in a parent body and that solute partitioning that occurred during solidification is responsible for the observed compositional trends within a single meteorite group.

  9. Part 1: Aspects of lithospheric evolution on Venus. Part 2: Thermal and collisional histories of chondrite parent bodies. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Grimm, Robert E.

    1988-01-01

    The geological evolution of distinctly different kinds of solar system objects is addressed. Venus has been observed over the past decade by orbital radars on both American and Soviet spacecraft. These surface measurements provide clues to the structure and evolution of the lithosphere. The parent bodies of chondritic meteorites, thought to resemble asteroids, represent the other end of the size spectrum of terrestrial objects. Their early thermal and collisional histories may be constrained by the chemical and textural record preserved in meteorite samples. Impact craters on Venus have been observed by the Soviet Venera 15/16 spacecraft. A formalism is presented by which the size-frequency distribution of impact craters may be used to estimate upper bounds on the mean global rates of volcanic resurfacing and lithospheric recycling on that planet over the past several hundred million years. The impact crater density reported from Venera observations, if valid for the entire Venus surface, indicates a mean volcanic flux no greater than 2 cu km/y, corresponding to a maximum average rate of resurfacing of about 4 km/b.y. For the lowest estimated mean crater retention age of the surface of Venus imaged by Venera 15/16, the rate of lithospheric recycling on Venus does not exceed 1.5 sq km/y. Ordinary chondrite meteorites show textural and chemical patterns indicative of varying intensities of thermal metamorphism. The conventional onion-shell model, which envisions highly metamorphosed material in the core and less intensely heated rocks near the surface, predicts an inverse relation between peak temperature and cooking rate, but none has been observed. A metamorphosed-planetesimal model is devised to explain this discrepancy, whereby heating occurs in planetesimals a few kilometers in radius which then accrete to form 100-km-radius parent bodies. Cooling rates are then randomly controlled by burial depth. Thermal and collisional constraints are examined, and the model

  10. Collisional Records in Iron Meteorites

    NASA Astrophysics Data System (ADS)

    Marti, K.; Lavielle, B.; Jeannot, J.-P.

    1995-09-01

    The asteroid belt is considered to be the ultimate source of iron meteorites and it would be of considerable interest to obtain a chronology of break-ups of asteroidal objects. However, as multiple fragmentation of such objects did likely occur, the exposure ages date the break-off of iron masses from shielded locations within the immediate parent object. Meteorites which were fragmented in more than one collisional event may have recorded integral effects of cosmic ray interactions in varying geometrical configuration and individual stages may be difficult to unravel; we term such exposure histories "complex". Exposure age histograms based on potassium ages have been discussed by Voshage [1] and he concluded that irons of groups IIIA and IIIB reveal similar histograms and probably were derived from the same parent body. He also noted a cluster for group IVA members ,but no clear evidence for other clusters. We present the collisional evidence based on published noble gas data, coupled to the new production rates which we calculate for central locations, adjusted for off-center locations whenever concentration profiles can be inferred. Unlike potassium ages which show large uncertainties for ages < 300 Ma, T38 ages can be obtained for all iron meteorites. We note, however,that T38 values of five "old" irons are systematically 15% lower than potassium ages. We confirm the evidence for stochastic events for IIIAB and IVA irons. The statistics are improved because of the larger data base. There are interesting clusters also among ages < 100 Ma, in the range which overlaps the histograms of chondrites. Recent reports [2,3] of H-chondritic inclusions in IIE irons, whose exposure ages are consistent with H-chondrite clusters, point to a genetic link. Group IIAB reveals two clusters with T38 < 100 Ma, and both events appear to involve also IIE irons. Clusterings of two thirds of group IIIE members and of group IID irons appear significant. The youngest IVB ages coincide

  11. Analysis of Chiral Carboxylic Acids in Meteorites

    NASA Technical Reports Server (NTRS)

    Burton, A. S.; Elsila, J. E.; Hein, J. E.; Aponte, J. C.; Parker, E. T.; Glavin, D. P.; Dworkin, J. P.

    2015-01-01

    Homochirality of amino acids in proteins and sugars in DNA and RNA is a critical feature of life on Earth. In the absence of a chiral driving force, however, reactions leading to the synthesis of amino acids and sugars result in racemic mixtures. It is currently unknown whether homochirality was necessary for the origins of life or if it was a product of early life. The observation of enantiomeric excesses of certain amino acids of extraterrestrial origins in meteorites provides evidence to support the hypothesis that there was a mechanism for the preferential synthesis or destruction of a particular amino acid enantiomer [e.g., 1-3]. The cause of the observed chiral excesses is un-clear, although at least in the case of the amino acid isovaline, the degree of aqueous alteration that occurred on the meteorite parent body is correlated to the isovaline L-enantiomeric excess [3, 4]. This suggests that chiral symmetry is broken and/or amplified within the meteorite parent bodies. Besides amino acids, there have been only a few reports of other meteoritic compounds found in enantiomeric excess: sugars and sugar acids [5, 6] and the hydroxy acid lactic acid [7]. Determining whether or not additional types of molecules in meteorites are also present in enantiomeric excesses of extraterrestrial information will provide insights into mechanisms for breaking chiral symmetry. Though the previous measurements (e.g., enantiomeric composition of lactic acid [7], and chiral carboxylic acids [8]) were made by gas chromatography-mass spectrometry, the potential for increased sensitivity of liquid chromatography-mass spectrometry (LC-MS) analyses is important because for many meteorite samples, only small sample masses are available for study. Furthermore, at least in the case of amino acids, many of the largest amino acid enantiomeric excesses were observed in samples that contained lower abundances (tens of ppb) of a given amino acid enantiomer. In the present work, we describe

  12. Effects of parental comments on body dissatisfaction and eating disturbance in young adults: a sociocultural model.

    PubMed

    Rodgers, Rachel F; Paxton, Susan J; Chabrol, Henri

    2009-06-01

    This study examined a sociocultural model of the influence of parental comments on body shape and eating concerns among males and females. Questionnaires were completed by 338 undergraduates. Participants reported levels of perceived parental comments, internalization of media ideals, appearance comparison, body dissatisfaction, drive for thinness and bulimia. Results revealed that, regardless of gender, internalization and appearance comparison only partially mediated the relationship between parental comments and the outcome variables. The final model for females explained a larger proportion of the variability in body shape and eating concerns than in males, with positive and negative parental comments directly related to body dissatisfaction and through it to eating outcomes. In males, only negative comments were directly related to body dissatisfaction. These findings highlight the role of parental influences in sociocultural models of the development of body dissatisfaction and eating concerns, and the gender-specific patterns of sociocultural influence. PMID:19464242

  13. 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.

  14. Parent Reactions to a School-Based Body Mass Index Screening Program

    ERIC Educational Resources Information Center

    Johnson, Suzanne Bennett; Pilkington, Lorri L.; Lamp, Camilla; He, Jianghua; Deeb, Larry C.

    2009-01-01

    Background: This study assessed parent reactions to school-based body mass index (BMI) screening. Methods: After a K-8 BMI screening program, parents were sent a letter detailing their child's BMI results. Approximately 50 parents were randomly selected for interview from each of 4 child weight-classification groups (overweight, at risk of…

  15. Crystal Structure and Chemical Composition of a Presolar Silicate from the Queen Elizabeth Range 99177 Meteorite

    NASA Technical Reports Server (NTRS)

    Nguyen, A. N.; Keller, L. P.; Rahman, Z.; Messenger, S.

    2013-01-01

    Mineral characterization of presolar silicate grains, the most abundant stardust phase, has provided valuable information about the formation conditions in circumstellar environments and in super-nova (SN) outflows. Spectroscopic observations of dust around evolved stars suggest a majority of amor-phous, Mg-rich olivine grains, but crystalline silicates, most of which are pyroxene, have also been observed [1]. The chemical compositions of hundreds of presolar silicates have been determined by Auger spectroscopy and reveal high Fe contents and nonstoichiometric compositions intermediate to olivine and pyroxene [2-6]. The unexpectedly high Fe contents can partly be attributed to secondary alteration on the meteorite parent bodies, as some grains have Fe isotopic anomalies from their parent stellar source [7]. Only about 35 presolar silicates have been studied for their mineral structures and chemical compositions by transmission electron microscopy (TEM). These grains display a wide range of compositions and structures, including crystalline forsterite, crystalline pyroxene, nanocrystalline grains, and a majority of amorphous nonstoichiometric grains. Most of these grains were identified in the primitive Acfer 094 meteorite. Presolar silicates from this meteorite show a wide range of Fe-contents, suggestive of secondary processing on the meteorite parent body. The CR chondrite QUE 99177 has not suffered as much alteration [8] and displays the highest presolar silicate abundance to date among carbonaceous chondrites [3, 6]. However, no mineralogical studies of presolar silicates from this meteorite have been performed. Here we examine the mineralogy of a presolar silicate from QUE 99177.

  16. Tibooburra, a new Australian meteorite find, and other carbonaceous chondrites of high petrologic grade

    NASA Astrophysics Data System (ADS)

    Fitzgerald, M. J.; Jaques, A. L.

    1982-03-01

    Petrological evidence suggests that the Tibooburra meteorite from western New South Wales, like the Allende meteorite, is a CV3 chondrite which has experienced greater metamorphic effects than others of its class. The transitional nature of its bulk composition, which is intermediate between the CO and CV chondrites, is exhibited by several elements and displayed by the multivariate techniques of cluster analysis and principal component analysis. Tibooburra therefore resembles such CV chondrites as Coolidge and Karoonda, which have accreted early in the history of the Vigarano parent body and consequently possess a higher content of high-temperature, Ca-Al-rich inclusions with fewer low-temperature matrix and volatile phases than other CV chondrites. Both the matrix and magnesium silicate phases of these meteorites seem more iron-rich than those in later-accreted meteorites.

  17. Cliftonite: A proposed origin, and its bearing on the origin of diamonds in meteorites

    USGS Publications Warehouse

    Brett, R.; Higgins, G.T.

    1969-01-01

    Cliftonite, a polycrystalline aggregate of graphite with spherulitic structure and cubic morphology, is known in 14 meteorites. Some workers have considered it to be a pseudomorph after diamond, and have used the proposed diamond ancestry as evidence of a meteoritic parent body of at least lunar dimensions. Careful examination of meteoritic samples indicates that cliftonite forms by precipitation within kamacite. We have also demonstrated that graphite with cubic morphology may be synthesized in a Fe-Ni-C alloy annealed in a vacuum. We therefore suggest that a high pressure origin is unnecessary for meteorities which contain cliftonite, and that these meteorities were formed at low pressures. This conclusion is in agreement with other recent evidence. We also suggest that recently discovered cubes and cubo-octahedra of lonsdaleite in the Canyon Diablo meteorite are pseudomorphs after cliftonite, not diamond, as has previously been suggested. ?? 1969.

  18. The isotopic composition of silver and lead in two iron meteorites - Cape York and Grant

    NASA Technical Reports Server (NTRS)

    Chen, J. H.; Wasserburg, G. J.

    1983-01-01

    Anomalies in silver isotope composition in the metal phases of the Cape York (IIIA) and Grant (IIIB) iron meteorites are studied together with the lead isotopic composition of both the metal and sulfide phases of Cape York. Following extensive surface cleaning, the Ag-107/Ag-109 ratio in the metal phases of the meteorites is found to be in excess of the terrestrial ratio, and of that found in the sulfide phases. A definite correlation between the Ag-107/Ag-109 and Pd-108/Ag-109 ratios is observed for these meteorites, indicating the in situ decay of Pd-107 and supporting the widespread presence of Pd in the early universe. Lead, determined after cleaning and with chemical separations using low blank levels, is found to exist in variable proportions in the metal and sulfide phases. The sulfides appear to be dominated by radiogenic modern lead, which may be explained by terrestrial contamination or by late metamorphism in the meteorite parent body.

  19. Aqueous Alteration and Hydrogen Generation on Parent Bodies of Unequilibrated Ordinary Chondrites: Thermodynamic Modeling for the Semarkona Composition

    NASA Technical Reports Server (NTRS)

    Zolotov, M. Y.; Mironenko, M. V.; Shock, E. L.

    2005-01-01

    Ordinary chondrites are the most abundant class of meteorites that could represent rocky parts of solar system bodies. However, even the most primitive unequilibrated ordinary chondrites (UOC) reveal signs of mild alteration that affected the matrix and peripheral zones of chondrules. Major chemical changes include oxidation of kamacite, alteration of glass, removal of alkalis, Al, and Si from chondrules, and formation of phases enriched in halogens, alkalis, and hydrogen. Secondary mineralogical changes include formation of magnetite, ferrous olivine, fayalite, pentlandite, awaruite, smectites, phosphates, carbonates, and carbides. Aqueous alteration is consistent with the oxygen isotope data for magnetite. The presence of secondary magnetite, Ni-rich metal alloys, and ferrous silicates in UOC implies that H2O was the oxidizing agent. However, oxidation by H2O means that H2 is produced in each oxidative pathway. In turn, production of H2, and its redistribution and possible escape should have affected total pressure, as well as the oxidation state of gas, aqueous and mineral phases in the parent body. Here we use equilibrium thermodynamic modeling to explore water-rock reactions in UOC. The chemical composition of gas, aqueous, and mineral phases is considered.

  20. 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

  1. The oxygen isotope evolution of parent body aqueous solutions as recorded by multiple carbonate generations in the Lonewolf Nunataks 94101 CM2 carbonaceous chondrite

    NASA Astrophysics Data System (ADS)

    Lee, M. R.; Sofe, M. R.; Lindgren, P.; Starkey, N. A.; Franchi, I. A.

    2013-11-01

    The CM2 carbonaceous chondrite LON 94101 contains aragonite and two generations of calcite that provide snapshots of the chemical and isotopic evolution of aqueous solutions during parent body alteration. Aragonite was the first carbonate to crystallize. It is rare, heterogeneously distributed within the meteorite matrix, and its mean oxygen isotope values are δ18O 39.9 ± 0.6‰, Δ17O -0.3 ± 1.0‰ (1σ). Calcite precipitated soon afterwards, and following a fall in solution Mg/Ca ratios, to produce small equant grains with a mean oxygen isotope value of δ18O 37.5 ± 0.7‰, Δ17O 1.4 ± 1.1‰ (1σ). These grains were partially or completely replaced by serpentine and tochilinite prior to precipitation of the second generation of calcite, which occluded an open fracture to form a millimetre-sized vein, and replaced anhydrous silicates within chondrules and the matrix. The vein calcite has a mean composition of δ18O 18.4 ± 0.3‰, Δ17O -0.5 ± 0.5‰ (1σ). Petrographic and isotopic results therefore reveal two discrete episodes of mineralisation that produced calcite generations with contrasting δ18O, and mean Δ17O values. The aragonite and equant calcite crystallized over a relatively brief period early in the aqueous alteration history of the parent body, and from static fluids that were evolving chemically in response to mineral dissolution and precipitation. The second calcite generation crystallized from solutions of a lower Δ17O, and a lower δ18O and/or higher temperature. As two generations of calcite whose petrographic characteristics and oxygen isotopic compositions are similar to those in LON 94101 occur in at least one other CM2, multiphase carbonate mineralisation could be the typical outcome of the sequence of chemical reactions during parent body aqueous alteration. It is equally possible however that the second generation of calcite formed in response to an event such as impact fracturing and concomitant fluid mobilisation that affected

  2. Water Transport and the Evolution of CM Parent Bodies

    NASA Technical Reports Server (NTRS)

    Coker, Rob; Cohen, Barbara

    2014-01-01

    Meteorites have amino acids and hydrated minerals which constrain the peak temperature ranges they have experienced. CMs in particular have a narrow range (273-325K). Bulk fluid motion during hydration constrained to small scales (less than mm). Some asteroids are known to have hydrated minerals on their surfaces. It is presumed these two facts may be related. Problem: hydration only occurs (significantly) with liquid water; melting water only occurs early on in nebula (1-10 Myrs ANC); in nebula asteroid surface temperature very cold (approximately 150K). Can indigenous alteration produce CMs and/or surface hydration?

  3. Seeding the Pregenetic Earth: Meteoritic Abundances of Nucleobases and Potential Reaction Pathways

    NASA Astrophysics Data System (ADS)

    Pearce, Ben K. D.; Pudritz, Ralph E.

    2015-07-01

    Carbonaceous chondrites are a class of meteorite known for having high contents of water and organics. In this study, the abundances of the nucleobases, i.e., the building blocks of RNA and DNA, found in carbonaceous chondrites are collated from a variety of published data and compared across various meteorite classes. An extensive review of abiotic chemical reactions producing nucleobases is then performed. These reactions are then reduced to a list of 15 individual reaction pathways that could potentially occur within meteorite parent bodies. The nucleobases guanine, adenine, and uracil are found in carbonaceous chondrites in amounts of 1–500 ppb. It is currently unknown which reaction is responsible for their synthesis within the meteorite parent bodies. One class of carbonaceous meteorite dominates the abundances of both amino acids and nucleobases—the so-called CM2 (e.g., Murchison meteorite). CR2 meteorites (e.g., Graves Nunataks) also dominate the abundances of amino acids, but are the least abundant in nucleobases. The abundances of total nucleobases in these two classes are 330 ± 250 and 16 ± 13 ppb, respectively. Guanine most often has the greatest abundances in carbonaceous chondrites with respect to the other nucleobases, but is 1–2 orders of magnitude less abundant in CM2 meteorites than glycine (the most abundant amino acid). Our survey of the reaction mechanisms for nucleobase formation suggests that Fischer–Tropsch synthesis (i.e., CO, H2, and NH3 gases reacting in the presence of a catalyst such as alumina or silica) is the most likely candidate for conditions that characterize the early states of planetesimals.

  4. Mineralogy and Ar-39 - Ar-40 of an old pristine basalt: Thermal history of the HED parent body

    NASA Technical Reports Server (NTRS)

    Takeda, Hiroshi; Mori, Hiroshi; Bogard, Donald D.

    1994-01-01

    Previous investigations of mineral chemistry and Rb-Sr and Sm-Nd ages indicated that clast,84 from eucrite Yamato 75011 had preserved the pristine nature of its initial crystallization during an early stage of the HED parent body. Microscale mineralogy and Ar-39-Ar-40 ages of this clast, however, revealed local disturbance of microtextures and partially reset ages. This evidence suggests that, in addition to initial crystallization and rapid cooling, the Y75011,84 clast experienced shock deformation, reheating of short duration at higher temperature, and brecciation. These characteristics suggest two or more impact events. Fe-rich olivine filling fractures in pyroxene may have been introduced during the accompanying shock fracturing. The inferred Ar-39-Ar-40 degassing ages for Y75011 matrix and clast, 84 are 3.94 +/- 0.04 Ga and 3.98 +/- 0.03 Ga, respectively. The suggested degassing age for a clast from Y790020, believed to be paired with Y75011, is approximately 4.03 Ga, but could be younger. We consider it likely that all three samples experienced a common degassing event 3.95 +/- 0.05 Ga ago, but we cannot rule out two or more events spaced over a approximately 0.1 Ga interval. Higher temperature extractions of the two clast samples show significantly older apparent ages up to approximately 4.5 Ga and suggest that the time/temperature regime of this event was not sufficient to degas Ar totally. Most likely, the K-Ar ages were reset by thermal metamorphism associated with one or more impact events associated with shock fracturing, formation of Fe-rich olivine veins, and/or meteorite brecciation. The pyroxene annealing that commonly occurs in many eucrites is likely to be a much earlier process than the impact-produced textural changes and reset K-Ar ages observed in these meteorites. The existence of mineralogical and chronological evidence for metamorphism in an otherwise pristine eucrite suggests that the HED parent body experienced an extensive degree of

  5. Mineralogy and Ar-39 - Ar-40 of an old pristine basalt: Thermal history of the HED parent body

    NASA Astrophysics Data System (ADS)

    Takeda, H.; Mori, H.; Bogard, D. D.

    1994-03-01

    Previous investigations of mineral chemistry and Rb-Sr and Sm-Nd ages indicated that clast,84 from eucrite Yamato 75011 had preserved the pristine nature of its initial crystallization during an early stage of the HED parent body. Microscale mineralogy and Ar-39-Ar-40 ages of this clast, however, revealed local disturbance of microtextures and partially reset ages. This evidence suggests that, in addition to initial crystallization and rapid cooling, the Y75011,84 clast experienced shock deformation, reheating of short duration at higher temperature, and brecciation. These characteristics suggest two or more impact events. Fe-rich olivine filling fractures in pyroxene may have been introduced during the accompanying shock fracturing. The inferred Ar-39-Ar-40 degassing ages for Y75011 matrix and clast, 84 are 3.94 +/- 0.04 Ga and 3.98 +/- 0.03 Ga, respectively. The suggested degassing age for a clast from Y790020, believed to be paired with Y75011, is approximately 4.03 Ga, but could be younger. We consider it likely that all three samples experienced a common degassing event 3.95 +/- 0.05 Ga ago, but we cannot rule out two or more events spaced over a approximately 0.1 Ga interval. Higher temperature extractions of the two clast samples show significantly older apparent ages up to approximately 4.5 Ga and suggest that the time/temperature regime of this event was not sufficient to degas Ar totally. Most likely, the K-Ar ages were reset by thermal metamorphism associated with one or more impact events associated with shock fracturing, formation of Fe-rich olivine veins, and/or meteorite brecciation. The pyroxene annealing that commonly occurs in many eucrites is likely to be a much earlier process than the impact-produced textural changes and reset K-Ar ages observed in these meteorites. The existence of mineralogical and chronological evidence for metamorphism in an otherwise pristine eucrite suggests that the HED parent body experienced an extensive degree of

  6. 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.

  7. Origin of iron meteorite groups IAB and IIICD

    NASA Astrophysics Data System (ADS)

    Wasson, J. T.; Willis, J.; Wai, C. M.; Kracher, A.

    1980-08-01

    Several low Ni-iron meteorites previously classified with group IAB are reclassified with group IIICD because of lower Ge, Ga, W, and Ir concentrations and higher As concentrations. The low Ni extreme of IIICD is now 62 mg/g, and that of IAB is 64 mg/g. It is proposed that the meteorites of both groups formed as individual shock melts on a chondritic parent body. The differences in log element-log Ni slopes of the daughter irons demonstrate that there were detailed differences in the composition and size of phases in the parental material (e.g., more Ni in the sulfides or metal of IAB, or more Ge and Ir in the oxides of IIICD).

  8. Geochemistry of Martian Meteorites and the Petrologic Evolution of Mars

    NASA Technical Reports Server (NTRS)

    Mittlefehldt, D. W.

    2002-01-01

    Mafic igneous rocks serve as probes of the interiors of their parent bodies - the compositions of the magmas contain an imprint of the source region composition and mineralogy, the melting and crystallization processes, and mixing and assimilation. Although complicated by their multifarious history, it is possible to constrain the petrologic evolution of an igneous province through compositional study of the rocks. Incompatible trace elements provide one means of doing this. I will use incompatible element ratios of martian meteorites to constrain the early petrologic evolution of Mars. Incompatible elements are strongly partitioned into the melt phase during igneous processes. The degree of incompatibility will differ depending on the mineral phases in equilibrium with the melt. Most martian meteorites contain some cumulus grains, but nevertheless, incompatible element ratios of bulk meteorites will be close to those of their parent magmas. ALH 84001 is an exception, and it will not be discussed. The martian meteorites will be considered in two groups; a 1.3 Ga group composed of the clinopyroxenites and dunite, and a younger group composed of all others.

  9. A Single Lodranite/Acapulcoite Parent Body: Noble Gases in Lodranite QUE 93148 and Acapulcoite ALH 81261

    NASA Astrophysics Data System (ADS)

    Weigel, A.; Eugster, O.; Marti, K.; Michel, R.

    1995-09-01

    We continue our comprehensive studies of the cosmic ray exposure history of lodranites [1] to include new noble gas measurements in the QUE 93148 lodranite and the ALH 81261 acapulcoite. In addition, we model the production rates of cosmogenic nuclides in lodranites and acapulcoites using the HERMES high energy transport code [2], in order to test whether conventional production rates can be extrapolated to this group of small meteoroids which reveal very large values of the shielding parameter 22Ne/21Ne (Table 1). The model calculations are based on the same excitation functions of p- and n-induced reactions as used in recent calculations [3,4]. We extended our studies to acapulcoites, since petrologic, mineralogic, and O-isotopic investigations [5] as well as chemical investigations [6] suggest that lodranites and acapulcoites are residues of varying degree of partial melting, consistent with an origin on a common parent body. Whether a collisional event on the common parent body ejected both types of meteorites can be investigated by an analysis of the transfer times to Earth, specifically their cosmic-ray exposure ages. Because the contents of trapped He, Ne, and Ar in lodranites and acapulcoites are very low we can derive reliable cosmogenic noble gas contents. Using the composition-adjusted production rates for cosmogenic noble gases in achondrites [7], and adopting the shielding-parameter dependence for H-chondrites the exposure ages of [1] are obtained. For lodranites these exposure ages overlap those calculated [8] from 26Al and 10Be measurements. For the acapulcoites our exposure ages agree with those [5] calculated with the Graf-model [9], as well as with the shielding-independent exposure age for Acapulco that is based on the 36Cl-36Ar method[10]. The large spread in the exposure ages can be attributed to the highly variable target element abundances, as multiple measurements on several aliquots show unusually large variations. The fact that the average

  10. SNC meteorites - Clues to Martian petrologic evolution?

    NASA Astrophysics Data System (ADS)

    McSween, H. Y.

    1985-11-01

    Shergottites, nakhlites and the Chassigny meteorites (SNC group) may have originated on Mars. The shergottites are medium-grained basalts, the nakhlites are pyroxenites and the Chassigny is a dunite. The SNC group is petrologically diverse but differs from all other known achondrites in terms of mineral chemistry, the redox state, the oxygen isotopic composition and the radiometric ages. The SNC stones are mafic and ultramafic cumulate rocks with mineralogies that indicate rapid cooling and crystallization from tholeiitic magmas which contained water and experienced a high degree of oxidation. The characteristics suggest formation from a large parent body, i.e., a planet, but not earth. The estimated ages for the rocks match the estimated ages for several mapped Martian volcanoes in the Tharsis region. Additionally, the elemental and isotopic abundances of atmospheric gases embedded in melts in the SNC stones match Viking Lander data for the Martian atmosphere. However, reasons are cited for discounting the possibility that a large meteorite(s) collided with Mars about 180 myr ago and served as the mechanism for ejecting the SNC stones to earth.