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Sample records for alh84001 martian meteorite

  1. Originof magnetite in martian meteorite ALH84001

    NASA Astrophysics Data System (ADS)

    Scott, E.; Fuller, M.

    2003-04-01

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

  2. Paleomagnetic record of Martian meteorite ALH84001

    NASA Astrophysics Data System (ADS)

    Antretter, Maria; Fuller, Mike; Scott, Edward; Jackson, Mike; Moskowitz, Bruce; Solheid, Peter

    2003-06-01

    The natural remanent magnetization (NRM) of the Martian meteorite ALH84001 is predominantly carried by fine magnetite, which is found in association with carbonate. The magnetite is in epitaxial and topotactic relation with the carbonate and formed from the carbonate in the major impact event at 4.0 Ga. The NRM will therefore record this field. The local preferential crystallographic and shape alignment of the magnetite defines local easy directions of magnetization may account for the observed inhomogeneity of the NRM on a microscopic scale. Normalizing the intensity of the NRM by the saturation isothermal remanence (IRMs) then gives an estimate for the 4.0 Ga Martian field one order smaller than the present geomagnetic field. Such a field is unlikely to be strong enough to generate the high-intensity Martian magnetic anomalies. ALH 84001 in its pristine state as an orthopyroxenite is not a plausible source rock for the Martian anomalies because its magnetite was not formed until the 4.0 Ga event.

  3. Magnetic tests for magnetosome chains in Martian meteorite ALH84001.

    PubMed

    Weiss, Benjamin P; Kim, Soon Sam; Kirschvink, Joseph L; Kopp, Robert E; Sankaran, Mohan; Kobayashi, Atsuko; Komeili, Arash

    2004-06-01

    Transmission electron microscopy studies have been used to argue that magnetite crystals in carbonate from Martian meteorite ALH84001 have a composition and morphology indistinguishable from that of magnetotactic bacteria. It has even been claimed from scanning electron microscopy imaging that some ALH84001 magnetite crystals are aligned in chains. Alignment of magnetosomes in chains is perhaps the most distinctive of the six crystallographic properties thought to be collectively unique to magnetofossils. Here we use three rock magnetic techniques, low-temperature cycling, the Moskowitz test, and ferromagnetic resonance, to sense the bulk composition and crystallography of millions of ALH84001 magnetite crystals. The magnetic data demonstrate that although the magnetite is unusually pure and fine-grained in a manner similar to terrestrial magnetofossils, most or all of the crystals are not arranged in chains. PMID:15155900

  4. Magnetic tests for magnetosome chains in Martian meteorite ALH84001

    PubMed Central

    Weiss, Benjamin P.; Kim, Soon Sam; Kirschvink, Joseph L.; Kopp, Robert E.; Sankaran, Mohan; Kobayashi, Atsuko; Komeili, Arash

    2004-01-01

    Transmission electron microscopy studies have been used to argue that magnetite crystals in carbonate from Martian meteorite ALH84001 have a composition and morphology indistinguishable from that of magnetotactic bacteria. It has even been claimed from scanning electron microscopy imaging that some ALH84001 magnetite crystals are aligned in chains. Alignment of magnetosomes in chains is perhaps the most distinctive of the six crystallographic properties thought to be collectively unique to magnetofossils. Here we use three rock magnetic techniques, low-temperature cycling, the Moskowitz test, and ferromagnetic resonance, to sense the bulk composition and crystallography of millions of ALH84001 magnetite crystals. The magnetic data demonstrate that although the magnetite is unusually pure and fine-grained in a manner similar to terrestrial magnetofossils, most or all of the crystals are not arranged in chains. PMID:15155900

  5. Magnetic tests for magnetosome chains in Martian meteorite ALH84001

    NASA Astrophysics Data System (ADS)

    Weiss, Benjamin P.; Kim, Soon Sam; Kirschvink, Joseph L.; Kopp, Robert E.; Sankaran, Mohan; Kobayashi, Atsuko; Komeili, Arash

    2004-06-01

    Transmission electron microscopy studies have been used to argue that magnetite crystals in carbonate from Martian meteorite ALH84001have a composition and morphology indistinguishable from that of magnetotactic bacteria. It has even been claimed from scanning electron microscopy imaging that some ALH84001magnetite crystals are aligned in chains. Alignment of magnetosomes in chains is perhaps the most distinctive of the six crystallographic properties thought to be collectively unique to magnetofossils. Here we use three rock magnetic techniques, low-temperature cycling, the Moskowitz test, and ferromagnetic resonance, to sense the bulk composition and crystallography of millions of ALH84001magnetite crystals. The magnetic data demonstrate that although the magnetite is unusually pure and fine-grained in a manner similar to terrestrial magnetofossils, most or all of the crystals are not arranged in chains.

  6. Magnetic Tests For Magnetosome Chains In Martian Meteorite ALH84001

    NASA Astrophysics Data System (ADS)

    Weiss, B. P.; Kim, S.; Kirschvink, J. L.; Sankaran, M.; Kobayashi, A.; Komeili, A.

    2003-12-01

    Transmission electron microscopy studies have been used to argue that magnetites in carbonates from Martian meteorite ALH84001 have a composition and morphology indistinguishable from that of magnetotactic bacteria and their magnetofossils (1). It has even been claimed from scanning electron microscopy imaging that some ALH84001 magnetites are aligned in chains (2). If true, this would provide dramatic support for the magnetofossil hypothesis because alignment in chains is perhaps the most distinctive of the six crystallographic properties thought to be collectively unique to magnetosomes. The leading alternative hypothesis is that the ALH84001 magnetites are the inorganic products of shock-heating of the carbonates (3, 4). Here we use three rock magnetic techniques-low-temperature cycling, the Moskowitz test (5), and ferromagnetic resonance (FMR)-to demonstrate that most or all of the magnetites in ALH84001 are unusually pure and fine-grained but are not arranged in magnetosome chains. 1. K. L. Thomas-Keprta et al., Geochim. Cosmochim. Acta 64, 4049-4081 (2000). 2. I. E. Friedmann, J. Wierzchos, C. Ascaso, M. Winklhofer, Proc. Natl. Acad. Sci. USA 98, 2176-2181 (2001). 3. D. C. Golden et al., Am. Mineral. 83, 370-375 (2001). 4. D. J. Barber, E. R. D. Scott, Proc. Natl. Acad. Sci. USA 99, 6556-6561 (2002). 5. B. M. Moskowitz, R. B. Frankel, D. A. Bazylinski, Earth Planet. Sci. Lett. 120, 283-300 (1993).

  7. Kinetic model of carbonate dissolution in Martian meteorite ALH84001

    NASA Astrophysics Data System (ADS)

    Kopp, R. E.; Humayun, M.

    2003-09-01

    The magnetites and sulfides located in the rims of carbonate globules in the Martian meteorite ALH84001 have been claimed as evidence of past life on Mars. Here, we consider the possibility that the rims were formed by dissolution and reprecipitation of the primary carbonate by the action of water. To estimate the rate of these solution-precipitation reactions, a kinetic model of magnesite-siderite carbonate dissolution was applied and used to examine the physicochemical conditions under which these rims might have formed. The results indicate that the formation of the rims could have taken place in < 50 yr of exposure to small amounts of aqueous fluids at ambient temperatures. Plausible conditions pertaining to reactions under a hypothetical ancient Martian atmosphere (1 bar CO 2), the modern Martian atmosphere (8 mbar CO 2), and the present terrestrial atmosphere (0.35 mbar CO 2) were explored to constrain the site of the process. The results indicated that such reactions likely occurred under the latter two conditions. The possibility of Antarctic weathering must be entertained, which, if correct, would imply that the plausibly biogenic minerals (single-domain magnetite of characteristic morphology and sulfide) reported from the rims may be the products of terrestrial microbial activity. This model is discussed in terms of the available isotope data and found to be compatible with the formation of ALH84001 rims. Particularly, anticorrelated variations of radiocarbon with δ 13C indicate that carbonate in ALH84001 was affected by solution-precipitation reactions immediately after its initial fall (˜13,000 yr ago) and then again during its recent exposure prior to collection.

  8. Oxygen isotopic constraints on the genesis of carbonates from Martian meteorite ALH84001

    NASA Astrophysics Data System (ADS)

    Leshin, Laurie A.; McKeegan, Kevin D.; Harvey, Ralph P.

    1997-03-01

    With a crystallization age of 4.5 Ga, ALH84001 is unique among the Martian meteorites. It is also the only Martian meteorite that contains an appreciable amount of carbonate, and significantly, this carbonate occurs without associated secondary hydrated minerals. Moreover, McKay et al. (1996) have suggested that ALH84001 contains evidence of past Martian life in the form of nanofossils, biogenic minerals, and polycyclic aromatic hydrocarbons. The presence of carbonate in ALH84001 is especially significant. The early Martian environment is thought to have been more hospitable to life than todays cold, dry climate. In order to better assess the true delta-O-18 values, as well as the isotopic diversity and complexity of the ALH84001 carbonates, direct measurements of the oxygen and carbon isotopic compositions of individual carbonate phases are needed. Here we report in situ analyses of delta-O-18 values in carbonates from two polished thin sections of ALH84001.

  9. The age of the carbonates in martian meteorite ALH84001.

    PubMed

    Borg, L E; Connelly, J N; Nyquist, L E; Shih, C Y; Wiesmann, H; Reese, Y

    1999-10-01

    The age of secondary carbonate mineralization in the martian meteorite ALH84001 was determined to be 3.90 +/- 0.04 billion years by rubidium-strontium (Rb-Sr) dating and 4.04 +/- 0.10 billion years by lead-lead (Pb-Pb) dating. The Rb-Sr and Pb-Pb isochrons are defined by leachates of a mixture of high-graded carbonate (visually estimated as approximately 5 percent), whitlockite (trace), and orthopyroxene (approximately 95 percent). The carbonate formation age is contemporaneous with a period in martian history when the surface is thought to have had flowing water, but also was undergoing heavy bombardment by meteorites. Therefore, this age does not distinguish between aqueous and impact origins for the carbonates. PMID:10506566

  10. The age of the carbonates in martian meteorite ALH84001

    NASA Technical Reports Server (NTRS)

    Borg, L. E.; Connelly, J. N.; Nyquist, L. E.; Shih, C. Y.; Wiesmann, H.; Reese, Y.

    1999-01-01

    The age of secondary carbonate mineralization in the martian meteorite ALH84001 was determined to be 3.90 +/- 0.04 billion years by rubidium-strontium (Rb-Sr) dating and 4.04 +/- 0.10 billion years by lead-lead (Pb-Pb) dating. The Rb-Sr and Pb-Pb isochrons are defined by leachates of a mixture of high-graded carbonate (visually estimated as approximately 5 percent), whitlockite (trace), and orthopyroxene (approximately 95 percent). The carbonate formation age is contemporaneous with a period in martian history when the surface is thought to have had flowing water, but also was undergoing heavy bombardment by meteorites. Therefore, this age does not distinguish between aqueous and impact origins for the carbonates.

  11. Evidence for the extraterrestrial origin of polycyclic aromatic hydrocarbons in the Martian meteorite ALH84001.

    PubMed

    Clemett, S J; Dulay, M T; Gillette, J S; Chillier, X D; Mahajan, T B; Zare, R N

    1998-01-01

    Possible sources of terrestrial contamination are considered for the observation of polycyclic aromatic hydrocarbons (PAHs) in the Martian meteorite ALH84001. Contamination is concluded to be negligible. PMID:9809015

  12. Origins of magnetite nanocrystals in Martian meteorite ALH84001

    NASA Astrophysics Data System (ADS)

    Thomas-Keprta, K. L.; Clemett, S. J.; McKay, D. S.; Gibson, E. K.; Wentworth, S. J.

    2009-11-01

    The Martian meteorite ALH84001 preserves evidence of interaction with aqueous fluids while on Mars in the form of microscopic carbonate disks. These carbonate disks are believed to have precipitated 3.9 Ga ago at beginning of the Noachian epoch on Mars during which both the oldest extant Martian surfaces were formed, and perhaps the earliest global oceans. Intimately associated within and throughout these carbonate disks are nanocrystal magnetites (Fe 3O 4) with unusual chemical and physical properties, whose origins have become the source of considerable debate. One group of hypotheses argues that these magnetites are the product of partial thermal decomposition of the host carbonate. Alternatively, the origins of magnetite and carbonate may be unrelated; that is, from the perspective of the carbonate the magnetite is allochthonous. For example, the magnetites might have already been present in the aqueous fluids from which the carbonates were believed to have been deposited. We have sought to resolve between these hypotheses through the detailed characterization of the compositional and structural relationships of the carbonate disks and associated magnetites with the orthopyroxene matrix in which they are embedded. Extensive use of focused ion beam milling techniques has been utilized for sample preparation. We then compared our observations with those from experimental thermal decomposition studies of sideritic carbonates under a range of plausible geological heating scenarios. We conclude that the vast majority of the nanocrystal magnetites present in the carbonate disks could not have formed by any of the currently proposed thermal decomposition scenarios. Instead, we find there is considerable evidence in support of an alternative allochthonous origin for the magnetite unrelated to any shock or thermal processing of the carbonates.

  13. Origins of Magnetite Nanocrystals in Martian Meteorite ALH84001

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, Kathie L.; Clemett, Simon J.; Mckay, David S.; Gibson, Everett K.; Wentworth, Susan J.

    2009-01-01

    The Martian meteorite ALH84001 preserves evidence of interaction with aqueous fluids while on Mars in the form of microscopic carbonate disks. These carbonate disks are believed to have precipitated 3.9 Ga ago at beginning of the Noachian epoch on Mars during which both the oldest extant Martian surfaces were formed, and perhaps the earliest global oceans. Intimately associated within and throughout these carbonate disks are nanocrystal magnetites (Fe3O4) with unusual chemical and physical properties, whose origins have become the source of considerable debate. One group of hypotheses argues that these magnetites are the product of partial thermal decomposition of the host carbonate. Alternatively, the origins of mag- netite and carbonate may be unrelated; that is, from the perspective of the carbonate the magnetite is allochthonous. For example, the magnetites might have already been present in the aqueous fluids from which the carbonates were believed to have been deposited. We have sought to resolve between these hypotheses through the detailed characterized of the compo- sitional and structural relationships of the carbonate disks and associated magnetites with the orthopyroxene matrix in which they are embedded. Extensive use of focused ion beam milling techniques has been utilized for sample preparation. We then compared our observations with those from experimental thermal decomposition studies of sideritic carbonates under a range of plausible geological heating scenarios. We conclude that the vast majority of the nanocrystal magnetites present in the car- bonate disks could not have formed by any of the currently proposed thermal decomposition scenarios. Instead, we find there is considerable evidence in support of an alternative allochthonous origin for the magnetite unrelated to any shock or thermal processing of the carbonates.

  14. The temperature of formation of carbonate in Martian meteorite ALH84001: constraints from cation diffusion

    SciTech Connect

    Hutcheon, I D; Kent, A; Phinney, D L; Ryerson, F J

    1999-08-13

    An important test of the hypothesis that Martian meteorite ALH84001 contains fossil remnants of an ancient Martian biota is the thermal history of the carbonate rosettes associated with the proposed biomarkers. If carbonates formed at temperatures over {approximately} 110 C (the limit for terrestrial life), it is unlikely that these minerals are associated with a terrestrial-like biota.

  15. Thermal Decomposition of Siderite-Pyrite Assemblages: Implications for Sulfide Mineralogy in Martian Meteorite ALH84001 Carbonate Globules

    NASA Astrophysics Data System (ADS)

    Golden, D. C.; Ming, D. W.; Lauer, H. V., Jr.; Morris, R. V.

    2004-03-01

    Closed system heating experiments of siderite-pyrite mixtures produce magnetite-pyrrhotite associations similar to those reported for black rims of the carbonate globules in ALH84001 Martian meteorite. These results support an inorganic formation process for magnetite and pyrrhotite in ALH84001.

  16. A search for endogenous amino acids in martian meteorite ALH84001.

    PubMed

    Bada, J L; Glavin, D P; McDonald, G D; Becker, L

    1998-01-16

    Trace amounts of glycine, serine, and alanine were detected in the carbonate component of the martian meteorite ALH84001 by high-performance liquid chromatography. The detected amino acids were not uniformly distributed in the carbonate component and ranged in concentration from 0.1 to 7 parts per million. Although the detected alanine consists primarily of the L enantiomer, low concentrations (<0.1 parts per million) of endogenous D-alanine may be present in the ALH84001 carbonates. The amino acids present in this sample of ALH84001 appear to be terrestrial in origin and similar to those in Allan Hills ice, although the possibility cannot be ruled out that minute amounts of some amino acids such as D-alanine are preserved in the meteorite. PMID:9430583

  17. A search for endogenous amino acids in martian meteorite ALH84001

    NASA Technical Reports Server (NTRS)

    Bada, J. L.; Glavin, D. P.; McDonald, G. D.; Becker, L.

    1998-01-01

    Trace amounts of glycine, serine, and alanine were detected in the carbonate component of the martian meteorite ALH84001 by high-performance liquid chromatography. The detected amino acids were not uniformly distributed in the carbonate component and ranged in concentration from 0.1 to 7 parts per million. Although the detected alanine consists primarily of the L enantiomer, low concentrations (<0.1 parts per million) of endogenous D-alanine may be present in the ALH84001 carbonates. The amino acids present in this sample of ALH84001 appear to be terrestrial in origin and similar to those in Allan Hills ice, although the possibility cannot be ruled out that minute amounts of some amino acids such as D-alanine are preserved in the meteorite.

  18. Nanophase Magnetite and Pyrrhotite in ALH84001 Martian Meteorite: Evidence for an Abiotic Origin

    NASA Technical Reports Server (NTRS)

    Golden, D. C.; Lauer, H. V., Jr. III; Ming, D. W.; Morris, R. V.

    2006-01-01

    The nanophase magnetite crystals in the black rims of pancake-shaped carbonate globules of the Martian meteorite ALH84001 have been studied extensively because of the claim by McKay et al.that they are biogenic in origin. A subpopulation of these magnetite crystals are reported to conform to a unique elongated shape called "truncated hexa-octahedral" or "THO" by Thomas-Keprta et al. They claim these THO magnetite crystals can only be produced by living bacteria thus forming a biomarker in the meteorite. In contrast, thermal decomposition of Fe-rich carbonate has been suggested as an alternate hypothesis for the elongated magnetite formation in ALH84001 carbonates. The experimental and observational evidence for the inorganic formation of nanophase magnetite and pyrrhotite in ALH84001 by decomposition of Fe-rich carbonate in the presence of pyrite are provided.

  19. Modern terrestrial analogues for the carbonate globules in Martian meteorite ALH84001.

    PubMed

    Kazmierczak, Józef; Kempe, Stephan

    2003-04-01

    Modern carbonate globules, located in cracks of submerged volcanic rocks and in calcareous pinnacles in alkaline (sodic) Lake Van, Turkey, appear to be analogues for the approximately 3.9 billion-year-old carbonate globules in Martian meteorite ALH84001. These terrestrial globules have similar diameters and are chemically and mineralogically zoned. Furthermore, they display surface and etching structures similar to those described from ALH84001, which were interpreted as fossilized microbial forms. These terrestrial carbonates formed at low temperatures where Ca-rich groundwaters enter the lake. Chemical, mineralogical, microbiological, and biomolecular methods were used in an attempt to decipher the process responsible for the genesis of these structures. Although the exact mode of formation of Lake Van carbonates remains an enigma, their similarity to the Martian globules indicates that the ALH84001 carbonates may have formed in similar setting on ancient Mars. PMID:12712250

  20. A Petrographic History of Martian Meteorite ALH84001: Two Shocks and an Ancient Age

    NASA Technical Reports Server (NTRS)

    Treiman, Allan H.

    1995-01-01

    ALH84001 is an igneous meteorite, an orthopyroxenite of martian origin. It contains petrographic evidence of two shock metamorphic events, separated by thermal and chemical events. The evidence for two shock events suggests that ALH84001 is ancient and perhaps a sample of the martian highlands. From petrography and mineral chemistry, the history of ALH84001 must include: crystallization from magma, a first shock (impact) metamorphism, thermal metamorphism, low-temperature chemical alteration, and a second shock (impact) metamorphism. Originally, ALH84001 was igneous, an orthopyroxene-chromite cumulate. In the first shock event, the igneous rock was cut by melt-breccia or cataclastic veinlets, now bands of equigranular fine-grained pyroxene and other minerals (crush zones). Intact fragments of the cumulate were fractured and strained (now converted to polygonized zones). The subsequent thermal metamorphism (possibly related to the first shock) annealed the melt-breccia or cataclastic veinlets to their present granoblastic texture and permitted chemical homogenization of all mineral species present. The temperature of metamorphism was at least 875 C, based on mineral thermometers. Next, Mg-Fe-Ca carbonates and pyrite replaced plagioclase in both clasts and granular bands, producing ellipsoidal carbonate globules with sub-micron scale compositional stratigraphy, repeated identically in all globules, The second shock event produced microfault offsets of carbonate stratigraphy and other mineral contacts, radial fractures around chromite and maskelynite, and strain birefringence in pyroxene. Maskelynite could not have been preserved from the first shock event, because it would have crystallized back to plagioclase. The martian source area for ALH84001 must permit this complex, multiple impact history. Very few craters on young igneous surfaces are on or near earlier impact features. It is more likely that ALH84001 was ejected from an old igneous unit (Hesperian or

  1. Evidence for exclusively inorganic formation of magnetite in Martian meteorite ALH84001

    NASA Technical Reports Server (NTRS)

    Golden, D. C.; Ming, D. W.; Morris, R. V.; Brearley, A. J.; Lauer, H. V., Jr.; Treiman, A. H.; Zolensky, M. E.; Schwandt, C. S.; Lofgren, G. E.

    2004-01-01

    Magnetite crystals produced by terrestrial magnetotactic bacterium MV-1 are elongated on a [111] crystallographic axis, in a so-called truncated hexa-Octahedral shape. This morphology has been proposed to constitute a biomarker (i.e., formed only in biogenic processes). A subpopulation of magnetite crystals associated with carbonate globules in Martian meteorite ALH84001 is reported to have this morphology, and the observation has been taken as evidence for biological activity on Mars. In this study, we present evidence for the exclusively inorganic origin of [111]-elongated magnetite crystals in ALH84001. We report three-dimensional(3-D) morphologies for approx.1000 magnetite crystals extracted from: (1) thermal decomposition products of Fe-rich carbonate produced by inorganic hydrothermal precipitation in laboratory experiments; (2) carbonate globules in Martian meteoriteeALH84001; and (3) cells of magnetotactic bacterial strain MV-1. The 3-D morphologies were derived by fitting 3-D shape models to two-dimensional bright-field transmission-electron microscope (TEAM) images obtained at a series of viewing angles. The view down the {110} axes closest to the [111] elongation axis of magnetite crystals ([111]x{110) not equal to 0) provides a 2-D projection that uniquely discriminates among the three [111]-elongated magnetite morphologies found in these samples: [111]-elongated truncated hexaoctahedron ([111]-THO), [111]-elongated cubo-octahedron ([111]-ECO), and [111]-elongated simple octahedron ([111]-ESO). All [111] -elongated morphologies are present in the three types of sample, but in different proportions. In the ALH84001 Martian meteorite and in our inorganic laboratory products, the most common [111]-elongated magnetite crystal morphology is [111]-ECO. In contrast, the most common morphology for magnetotactic bacterial strain MV-1 is [111]-THO. These results show that: (1) the morphology of [111]-elongated magnetite crystals associated with the carbonate

  2. Origin of carbonate-magnetite-sulfide assemblages in Martian meteorite ALH84001.

    PubMed

    Scott, E R

    1999-02-25

    A review of the mineralogical, isotopic, and chemical properties of the carbonates and associated submicrometer iron oxides and sulfides in Martian meteorite ALH84001 provides minimal evidence for microbial activity. Some magnetites resemble those formed by magnetotactic microorganisms but cubic crystals <50 nm in size and elongated grains <25 nm long are too small to be single-domain magnets and are probably abiogenic. Magnetites with shapes that are clearly unique to magnetotactic bacteria appear to be absent in ALH84001. Magnetosomes have not been reported in plutonic rocks and are unlikely to have been transported in fluids through fractures and uniformly deposited where abiogenic magnetite was forming epitaxially on carbonate. Submicrometer sulfides and magnetites probably formed during shock heating. Carbonates have correlated variations in Ca, Mg, and 18O/16O, magnetite-rich rims, and they appear to be embedded in pyroxene and plagiociase glass. Carbonates with these features have not been identified in carbonaceous chondrites and terrestrial rocks, suggesting that the ALH84001 carbonates have a unique origin. Carbonates and hydrated minerals in ALH84001, like secondary phases in other Martian meteorites, have O and H isotopic ratios favoring formation from fluids that exchanged with the Martian atmosphere. I propose that carbonates originally formed in ALH84001 from aqueous fluids and were subsequently shock heated and vaporized. The original carbonates were probably dolomite-magnesite-siderite assemblages that formed in pores at interstitial sites with minor sulfate, chloride, and phyllosilicates. These phases, like many other volatile-rich phases in Martian meteorites, may have formed as evaporate deposits from intermittent floods. PMID:11542931

  3. Morphological Evidence for an Exclusively Inorganic Origin for Magnetite in Martian Meteorite ALH84001

    NASA Technical Reports Server (NTRS)

    Golden, D. C.; Ming, D. W.; Morris, R. V.; Brearley, A. J.; Lauer, H. V., Jr.; Treiman, A.; Zolensky, M. E.; Schwandt, C. S.; Lofgren, G. E.; McKay, G. A.

    2003-01-01

    The origin of magnetite crystals in Martian Meteorite ALH84001 is the focus of a debate about the possibility of past (and present) life on Mars. McKay et al. originally suggested that some of the magnetite crystals associated with carbonate globules in Martian Meteorite ALH84001 are biogenic in ori-gin, because they are single magnetic domain, free of crystalline defects, chemically pure, and coexist with other metastable phases in apparent disequilibrium. Thomas-Keprta et al. reported that a subpopulation of magnetite crystals (approx. 25%) associated with carbonate globules in ALH84001 and magnetite crystals produced by magnetotactic bacterial strain MV-1 have similar morphologies with crystal elongation along the [111] crystallographic axis that they describe as "truncated hexa-octahedral" ([111-THO]) magnetite. Along with several other properties, the [111]-THO morphology has been proposed to constitute a biomarker (i.e., formed only in biogenic processes), so that the presence of [111]-THO magnetite in ALH84001 may be evidence for past life on Mars.

  4. Atomic force microscopy imaging of fragments from the Martian meteorite ALH84001.

    PubMed

    Steele, A; Goddard, D; Beech, I B; Tapper, R C; Stapleton, D; Smith, J R

    1998-01-01

    A combination of scanning electron microscopy (SEM) and environmental scanning electron microscopy (ESEM) techniques, as well as atomic force microscopy (AFM) methods has been used to study fragments of the Martian meteorite ALH84001. Images of the same areas on the meteorite were obtained prior to and following gold/palladium coating by mapping the surface of the fragment using ESEM coupled with energy-dispersive X-ray analysis. Viewing of the fragments demonstrated the presence of structures, previously described as nanofossils by McKay et al. (Search for past life on Mars--possible relic biogenic activity in martian meteorite ALH84001. Science, 1996, pp. 924-930) of NASA who used SEM imaging of gold-coated meteorite samples. Careful imaging of the fragments revealed that the observed structures were not an artefact introduced by the coating procedure. PMID:11541278

  5. Atomic force microscopy imaging of fragments from the Martian meteorite ALH84001.

    PubMed

    Steele, A; Goddard, D; Beech, I B; Tapper, R C; Stapleton, D; Smith, J R

    1998-01-01

    A combination of scanning electron microscopy (SEM) and environmental scanning electron microscopy (ESEM) techniques, as well as atomic force microscopy (AFM) methods has been used to study fragments of the Martian meteorite ALH84001. Images of the same areas on the meteorite were obtained prior to and following gold/palladium coating by mapping the surface of the fragment using ESEM coupled with energy-dispersive X-ray analysis. Viewing of the fragments demonstrated the presence of structures, previously described as nanofossils by McKay et al. (Search for past life on Mars--possible relic biogenic activity in martian meteorite ALH84001. Science, 1996, pp. 924-930) of NASA who used SEM imaging of gold-coated meteorite samples. Careful imaging of the fragments revealed that the observed structures were not an artefact introduced by the coating procedure.

  6. Atomic force microscopy imaging of fragments from the Martian meteorite ALH84001

    NASA Technical Reports Server (NTRS)

    Steele, A.; Goddard, D.; Beech, I. B.; Tapper, R. C.; Stapleton, D.; Smith, J. R.

    1998-01-01

    A combination of scanning electron microscopy (SEM) and environmental scanning electron microscopy (ESEM) techniques, as well as atomic force microscopy (AFM) methods has been used to study fragments of the Martian meteorite ALH84001. Images of the same areas on the meteorite were obtained prior to and following gold/palladium coating by mapping the surface of the fragment using ESEM coupled with energy-dispersive X-ray analysis. Viewing of the fragments demonstrated the presence of structures, previously described as nanofossils by McKay et al. (Search for past life on Mars--possible relic biogenic activity in martian meteorite ALH84001. Science, 1996, pp. 924-930) of NASA who used SEM imaging of gold-coated meteorite samples. Careful imaging of the fragments revealed that the observed structures were not an artefact introduced by the coating procedure.

  7. ALH84001, a cumulate orthopyroxenite member of the Martian meteorite clan

    NASA Technical Reports Server (NTRS)

    Mittlefehldt, David W.

    1994-01-01

    ALH84001, originally classified as a diogenite, is a coarse-grained, cataclastic, orthopyroxenite meteorite related to the martian (SNC) meteorites. The orthopyroxene is relatively uniform in composition, with a mean composition of Wo3.3En69.4Fs27.3. Minor phases are euhedral to subhedral chromite and interstitial maskelynite, An31.1Ab63.2Or5.7, with accessory augite, Wo42.2En45.1Fs12.7, apatite, pyrite and carbonates, Cc11.5Mg58.0Sd29.4Rd1.1. The pyroxenes and chromites in ALH84001 are similar in composition to these phases in EETA79001 lithology a megacrysts but are more homogeneous. Maskelynite is similar in composition to feldspars in the nakhlites and Chassigny. Two generations of carbonates are present, early (pre-shock) strongly zoned carbonates and late (post-shock) carbonates. The high Ca content of both types of carbonates indicates that they were formed at moderately high temperature, possibly approximately 700 C. ALH84001 has a slightly LREE-depleted pattern with La 0.67x and Lu 1.85x CI abundances and with a negative Eu anomaly (Eu/Sm 0.56x CI). The uniform pyroxene composition is unusual for martian meteorites, and suggests that ALH84001 cooled more slowly than did the shergottites, nakhlites of Chassigny. The nearly monomineralic composition, coarse-grain size, homogeneous orthopyroxene and chromite compositions, the interstitial maskelynite and apatite, and the REE pattern suggest that ALH84001 is a cumulate orthopyroxenite containing minor trapped, intercumulus material.

  8. Evaluation of the formation environment of the carbonates in Martian meteorite ALH84001

    NASA Astrophysics Data System (ADS)

    Niles, Paul Breckenridge

    The carbonates in martian meteorite ALH84001 preserve a record of aqueous processes on Mars at 3.9 Ga, and have been suggested to contain signatures of ancient martian life. The conditions of the carbonate formation environment are critical for understanding possible evidence for life on Mars, the history of water on Mars, and the evolution of the martian atmosphere. However, the formation environment of the ALH84001 carbonates continues to be controversial. New isotopic analyses of the ALH84001 carbonates, laboratory experiments, and geochemical modeling performed in this study provide quantitative constraints on the formation environment of the ALH84001 carbonates. Microscale carbon isotope analyses of ALH84001 carbonates reveal variable d 13 C values ranging from +27[per thousand] to +64[per thousand] that are correlated with carbonate chemical compositions. Isotopic analyses of synthetic hydrothermal carbonates with chemical compositions similar to the ALH84001 carbonates do not show similar isotope compositions, correlations, or trends. Combined with earlier oxygen isotope analyses, these data are inconsistent with formation of the carbonates in previously proposed environments, and indicate that the carbonates formed in a short period of time (hours or days) from a low temperature, dynamic aqueous system. A combination of empirical and equilibrium thermodynamic modeling reveals that the precipitating fluids were Mg- and CO 2 -rich, and probably formed through low temperature (<100°C) leaching of rocks with similar compositions to ALH84001. Prior to precipitating the carbonates, the fluids must have had an Mg/Ca ratio greater than ~4 and an Fe/Ca ratio greater than ~1. Three new hypotheses are proposed that involve low temperature (<100°C), dynamic aqueous processes: the carbonates formed (1) in a sublacustrine spring environment during the mixing of two fluids derived from separate chemical and isotopic reservoirs; (2) from high pH fluids that were exposed

  9. Petrological evidence for shock melting of carbonates in the martian meteorite ALH84001.

    PubMed

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

    1997-05-22

    The meteorite ALH84001--a shocked igneous rock of probable martian origin-contains chemically and isotopically heterogeneous carbonate globules, associated with which are organic and inorganic structures that have been interpreted as possible fossil remains of ancient martian biota. A critical assumption underlying this suggestion is that the carbonates formed from low-temperature fluids penetrating the cracks and voids of the host rock. Here we report petrological studies of ALH84001 which investigate the effects of shock on the various mineralogical components of the rock. We find that carbonate, plagioclase and silica were melted and partly redistributed by the same shock event responsible for the intense local crushing of pyroxene in the meteorite. Texture and compositional data show that, during the period of shock decompression, monomineralic melts were injected into pyroxene fractures that were subsequently cooled and resealed within seconds. Our results therefore suggest that the carbonates in ALH84001 could not have formed at low temperatures, but instead crystallized from shock-melted material; this conclusion weakens significantly the arguments that these carbonates could host the fossilized remnants of biogenic activity. PMID:9163421

  10. Hydrothermal origin for carbonate globules in Martian meteorite ALH84001: a terrestrial analogue from Spitsbergen (Norway)

    NASA Astrophysics Data System (ADS)

    Treiman, Allan H.; Amundsen, Hans E. F.; Blake, David F.; Bunch, Ted

    2002-12-01

    Carbonate minerals in the ancient Martian meteorite ALH84001 are the only known solid phases that bear witness to the processing of volatile and biologically critical compounds (CO 2, H 2O) on early Mars. Similar carbonates have been found in xenoliths and their host basalts from Quaternary volcanic centers in northern Spitsbergen (Norway). These carbonates were deposited by hot (i.e., hydrothermal) waters associated with the volcanic activity. By analogy with the Spitsbergen carbonates, the ALH84001 carbonates were probably also deposited by hot water. Hydrothermal activity was probably common and widespread on Early Mars, which featured abundant basaltic rocks, water as ice or liquid, and heat from volcanos and asteroid impacts. On Earth, descendants of the earliest life forms still prefer hydrothermal environments, which are now shown to have been present on early Mars.

  11. Experimental Shock Decomposition of Siderite and the Origin of Magnetite in Martian Meteorite ALH84001

    NASA Technical Reports Server (NTRS)

    Bell, Mary Sue

    2007-01-01

    Shock recovery experiments to determine whether magnetite could be produced by the decomposition of iron-carbonate were initiated. Naturally occurring siderite was first characterized by electron microprobe (EMP), transmission electron microscopy (TEM), Mossbauer spectroscopy, and magnetic susceptibility measurements to be sure that the starting material did not contain detectable magnetite. Samples were shocked in tungsten-alloy holders (W=90%, Ni=6%, Cu=4%) to further insure that any iron phases in the shock products were contributed by the siderite rather than the sample holder. Each sample was shocked to a specific pressure between 30 to 49 GPa. Previously reported results of TEM analyses on 49 GPa experiments indicated the presence of nano-phase spinel-structured iron oxide. Transformation of siderite to magnetite as characterized by TEM was found in the 49 GPa shock experiment. Compositions of most magnetites are greater than 50% Fe sup(+2) in the octahedral site of the inverse spinel structure. Magnetites produced in shock experiments display the same range of single-domain, superparamagnetic sizes (approx. 50 100 nm), compositions (100% magnetite to 80% magnetite-20% magnesioferrite), and morphologies (equant, elongated, euhedral to subhedral) as magnetites synthesized by Golden et al. (2001) or magnetites grown naturally by MV1 magnetotactic bacteria, and as the magnetites in Martian meteorite ALH84001. Fritz et al. (2005) previously concluded that ALH84001 experienced approx. 32 GPa pressure and a resultant thermal pulse of approx. 100 - 110 C. However, ALH84001 contains evidence of local temperature excursions high enough to 1 melt feldspar, pyroxene, and a silica-rich phase. This 49 GPa experiment demonstrates that magnetite can be produced by the shock decomposition of siderite as a result of local heating to greater than 470 C. Therefore, magnetite in the rims of carbonates in Martian meteorite ALH84001 could be a product of shock devolatilization of

  12. Geochemistry of the Martian meteorite ALH84001, revisited

    NASA Astrophysics Data System (ADS)

    Barrat, Jean-Alix; Bollinger, Claire

    2010-04-01

    Major and trace element abundances were determined on powders prepared from four distinct chips from Allan Hills (ALH) 84001 to constrain the bulk rock composition, and to assess the trace element abundances of orthopyroxenes and phosphates. Our new determinations were used to evaluate the composition of the parental melt of this stone. An unrealistic light rare earth element (REE)-enriched parental melt is calculated from the composition of the orthopyroxene and relevant equilibrium partition coefficients. The involvement of a small amount of trapped melt and subsolidus reequilibrations between orthopyroxene and the interstitial phases can account for this discrepancy. A parental melt that displays a trace element pattern (REE, Zr, and Hf) that closely resembles enriched shergottites such as Zagami or Los Angeles is calculated if these effects are taken into account. These results suggest that some shergottitic melts were already erupted on Mars during the Noachian.

  13. Bacterial mineralization patterns in basaltic aquifers: implications for possible life in martian meteorite ALH84001.

    PubMed

    Thomas-Keprta, K L; McKay, D S; Wentworth, S J; Stevens, T O; Taunton, A E; Allen, C C; Coleman, A; Gibson, E K; Romanek, C S

    1998-11-01

    To explore the formation and preservation of biogenic features in igneous rocks, we have examined the organisms in experimental basaltic microcosms using scanning and transmission electron microscopy. Four types of microorganisms were recognized on the basis of size, morphology, and chemical composition. Some of the organisms mineralized rapidly, whereas others show no evidence of mineralization. Many mineralized cells are hollow and do not contain evidence of microstructure. Filaments, either attached or no longer attached to organisms, are common. Unattached filaments are mineralized and are most likely bacterial appendages (e.g., prosthecae). Features similar in size and morphology to unattached, mineralized filaments are recognized in martian meteorite ALH84001.

  14. Bacterial mineralization patterns in basaltic aquifers: implications for possible life in martian meteorite ALH84001

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, K. L.; McKay, D. S.; Wentworth, S. J.; Stevens, T. O.; Taunton, A. E.; Allen, C. C.; Coleman, A.; Gibson, E. K. Jr; Romanek, C. S.

    1998-01-01

    To explore the formation and preservation of biogenic features in igneous rocks, we have examined the organisms in experimental basaltic microcosms using scanning and transmission electron microscopy. Four types of microorganisms were recognized on the basis of size, morphology, and chemical composition. Some of the organisms mineralized rapidly, whereas others show no evidence of mineralization. Many mineralized cells are hollow and do not contain evidence of microstructure. Filaments, either attached or no longer attached to organisms, are common. Unattached filaments are mineralized and are most likely bacterial appendages (e.g., prosthecae). Features similar in size and morphology to unattached, mineralized filaments are recognized in martian meteorite ALH84001.

  15. Bacterial mineralization patterns in basaltic aquifers: implications for possible life in martian meteorite ALH84001.

    PubMed

    Thomas-Keprta, K L; McKay, D S; Wentworth, S J; Stevens, T O; Taunton, A E; Allen, C C; Coleman, A; Gibson, E K; Romanek, C S

    1998-11-01

    To explore the formation and preservation of biogenic features in igneous rocks, we have examined the organisms in experimental basaltic microcosms using scanning and transmission electron microscopy. Four types of microorganisms were recognized on the basis of size, morphology, and chemical composition. Some of the organisms mineralized rapidly, whereas others show no evidence of mineralization. Many mineralized cells are hollow and do not contain evidence of microstructure. Filaments, either attached or no longer attached to organisms, are common. Unattached filaments are mineralized and are most likely bacterial appendages (e.g., prosthecae). Features similar in size and morphology to unattached, mineralized filaments are recognized in martian meteorite ALH84001. PMID:11541429

  16. Biomimetic Properties of Minerals and the Search for Life in the Martian Meteorite ALH84001

    NASA Astrophysics Data System (ADS)

    Martel, Jan; Young, David; Peng, Hsin-Hsin; Wu, Cheng-Yeu; Young, John D.

    2012-05-01

    The existence of extraterrestrial life was heralded by controversial claims made in 1996 that the Martian meteorite ALH84001 harbored relics of ancient microorganisms. We review here the accumulated evidence for and against past extraterrestrial life in this Martian meteorite. The main pro-life arguments—the presence of polycyclic aromatic hydrocarbons, magnetite crystals, carbonate globules, and structures resembling terrestrial life-forms known as nanobacteria—can be deemed ambiguous at best. Although these criteria are compatible with living processes, each one of them can be explained by nonliving chemical processes. By undergoing amorphous-to-crystalline transformations and binding to multiple substrates, including other ions and simple organic compounds, minerals—especially those containing carbonate—have been shown to display biomimetic properties, producing forms that resemble bacteria. This simple and down-to-earth explanation can account fully for the existence of mineral entities resembling putative nano- and microorganisms that have been described not only in the ALH84001 meteorite but also in the human body.

  17. Truncated Hexa-Octahedral Magnetite Crystals in Martian Meteorite ALH84001: Evidence of Biogenic Activity on Early Mars

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, K.; Clemett, S. J.; Schwartz, C.; McIntosh, J. R.; Bazylinski, D. A.; Kirschvink, J.; McKay, D. S.; Gibson, E. K.; Vali, H.; Romanek, C. S.

    2004-01-01

    The landmark paper by McKay et al. [1] cited four lines of evidence associated with the Martian meteorite ALH84001 to support the hypothesis that life existed on Mars approximately 4 Ga ago. Now, more than five years later, attention has focused on the ALH84001 magnetite grains embedded within carbonate globules in the ALH84001 meteorite. We have suggested that up to approx.25% of the ALH84001 magnetite crystals are products of biological activity [e.g., 2]. The remaining magnetites lack sufficient characteristics to constrain their origin. The papers of Thomas Keprta et al. were criticized arguing that the three dimensional structure of ALH84001 magnetite crystals can only be unambiguously determined using electron tomographic techniques. Clemett et al. [3] confirmed that magnetites produced by magnetotactic bacteria strain MV-I display a truncated hexa-octahedral geometry using electron tomography and validated the use of the multi-tilt classical transmission microscopy technique used by [2]. Recently the geometry of the purported martian biogenic magnetites was shown be identical to that for MV-1 magnetites using electron tomography [6].

  18. Magnetite Formation from Thermal Decomposition of Siderite: Implications for Inorganic Magnetite Formation in Martian Meteorite ALH84001

    NASA Technical Reports Server (NTRS)

    Morris, RIchard V.

    2002-01-01

    A biogenic mechanism for formation of a subpopulation magnetite in Martian meteorite ALH84001 has been suggested [McKay et al., 1996; Thomas-Keprta, et al., 2000]. We are developing experimental evidence for an alternating working hypothesis, that the subpopulation was produced inorganically by the thermal decomposition of siderite [Golden et al., 2000].

  19. Constraints on the Thermal History of Martian Meteorites ALH84001 and MIL03346 by Single Crystal XRD, Electron Microprobe and Mössbauer Analyses of Ortho- and Clinopyroxene

    NASA Astrophysics Data System (ADS)

    Domeneghetti, M. C.; Fioretti, A. M.; Cámara, F.; Carraro, A.; McCammon, C.; Tazzoli, V.

    2007-07-01

    Constraints on the thermal history of meteorites can be established by estimating the Fe2+-Mg order degree in their pyroxene using single-crystal XRD. We present here the data obtained on martian meteorites ALH84001 and MIL03346.

  20. Search for past life on Mars: possible relic biogenic activity in martian meteorite ALH84001.

    PubMed

    McKay, D S; Gibson, E K; Thomas-Keprta, K L; Vali, H; Romanek, C S; Clemett, S J; Chillier, X D; Maechling, C R; Zare, R N

    1996-08-16

    Fresh fracture surfaces of the martian meteorite ALH84001 contain abundant polycyclic aromatic hydrocarbons (PAHs). These fresh fracture surfaces also display carbonate globules. Contamination studies suggest that the PAHs are indigenous to the meteorite. High-resolution scanning and transmission electron microscopy study of surface textures and internal structures of selected carbonate globules show that the globules contain fine-grained, secondary phases of single-domain magnetite and Fe-sulfides. The carbonate globules are similar in texture and size to some terrestrial bacterially induced carbonate precipitates. Although inorganic formation is possible, formation of the globules by biogenic processes could explain many of the observed features, including the PAHs. The PAHs, the carbonate globules, and their associated secondary mineral phases and textures could thus be fossil remains of a past martian biota. PMID:8688069

  1. Search for Past Life on Mars: Possible Relict Biogenic Activity in Martian Meteorite ALH84001

    NASA Technical Reports Server (NTRS)

    McKay, David S.; Gibson, Everett K., Jr.; Thomas-Keprta, Kathie L.; Vali, Hojatollah; Romanek, Christopher S.; Clemett, Simon J.; Chillier, Xavier D. F.; Maechling, Claude R.; Zare, Richard N.

    1996-01-01

    Fresh fracture surfaces of the martian meteorite ALH84001 contain abundant polycyclic aromatic hydrocarbons (PAHs). These fresh fracture surfaces also display carbonate globules. Contamination studies suggest the PAHs are indigenous to the meteorite. High resolution scanning and transmission electron microscopy study of surface textures and internal structures of selected carbonate globules show that the globules contain fine-grained, secondary phases of single-domain magnetite and Fe-monosulfides. The carbonate globules are similar in texture and size to some terrestrial bacterially induced carbonate precipitates. Although inorganic formation is possible, formation of the globules by biogenic processes could explain many of the observed features including the PAHs. The PAHs, the carbonate globules, and their associated secondary mineral phases and textures could thus be fossil remains of a past martian biota.

  2. Search for past life on Mars: possible relic biogenic activity in martian meteorite ALH84001.

    PubMed

    McKay, D S; Gibson, E K; Thomas-Keprta, K L; Vali, H; Romanek, C S; Clemett, S J; Chillier, X D; Maechling, C R; Zare, R N

    1996-08-16

    Fresh fracture surfaces of the martian meteorite ALH84001 contain abundant polycyclic aromatic hydrocarbons (PAHs). These fresh fracture surfaces also display carbonate globules. Contamination studies suggest that the PAHs are indigenous to the meteorite. High-resolution scanning and transmission electron microscopy study of surface textures and internal structures of selected carbonate globules show that the globules contain fine-grained, secondary phases of single-domain magnetite and Fe-sulfides. The carbonate globules are similar in texture and size to some terrestrial bacterially induced carbonate precipitates. Although inorganic formation is possible, formation of the globules by biogenic processes could explain many of the observed features, including the PAHs. The PAHs, the carbonate globules, and their associated secondary mineral phases and textures could thus be fossil remains of a past martian biota.

  3. Origin of Magnetite Crystals in Martian Meteorite ALH84001 Carbonate Disks

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, K.L.; Clemett, S.J.; McKay, D.S.; Gibson, E. K.; Wentworth, S. J.

    2010-01-01

    Martian meteorite ALH84001 preserves evidence of interaction with aqueous fluids while on Mars in the form of microscopic carbonate disks which are believed to have precipitated approx.3.9 Ga ago at beginning of the Noachian epoch. Intimately associated within and throughout these carbonate disks are nanocrystal magnetites (Fe3O4) with unusual chemical and physical properties, whose origins have become the source of considerable debate. One group of hypotheses argues that these Fe3O4 are the product of partial thermal decomposition of the host carbonate. Alternatively, the origins of Fe3O4 and carbonate may be unrelated; that is, from the perspective of the carbonate the magnetite is allochthonous. We have sought to resolve between these hypotheses through the detailed characterized of the compositional and structural relationships of the carbonate disks and associated magnetites with the orthopyroxene matrix in which they are embedded [1]. We focus this discussion on the composition of ALH84001 magnetites and then compare these observations with those from our thermal decomposition studies of sideritic carbonates under a range of plausible geological heating scenarios.

  4. Micro-Spectroscopy as a Tool for Detecting Micron-Scale Mineral Variations Across a Rock Surface: An Example Using a Thin Section of Martian Meteorite ALH 84001

    NASA Astrophysics Data System (ADS)

    Dalton, J. B.; Bishop, J. L.

    2003-03-01

    Visible and near-infrared spectra of a portion of martian meteorite ALH84001 were acquired using a high resolution imaging microscope to investigate imaging spectroscopy for mineral detection at small scales.

  5. Magnetite whiskers and platelets in the ALH84001 Martian meteorite: evidence of vapor phase growth.

    PubMed

    Bradley, J P; Harvey, R P; McSween, H Y

    1996-01-01

    Nanometer-sized magnetite crystals associated with carbonates in fracture zones within Martian meteorite ALH84001 have been examined using analytical transmission electron microscopy. Some of the crystals exhibit distinctive morphologies: filamentary rods and ribbon, and platelets. The rods and ribbons are elongated along the crystallographic [100] and [111] directions. Some of the rods contain microstructural defects indicating that they grew by spiral growth about screw dislocations. Platelets are flattened along the [100] and [110] directions. These unique morphologies and microstructures constrain the growth conditions of magnetite. The whiskers and platelets most likely formed in the temperature range 500-800 degrees C by direct condensation from a vapor or precipitation from a supercritical fluid, and their properties are inconsistent with a biogenic origin. PMID:11541129

  6. Magnetite whiskers and platelets in the ALH84001 Martian meteorite: evidence of vapor phase growth.

    PubMed

    Bradley, J P; Harvey, R P; McSween, H Y

    1996-01-01

    Nanometer-sized magnetite crystals associated with carbonates in fracture zones within Martian meteorite ALH84001 have been examined using analytical transmission electron microscopy. Some of the crystals exhibit distinctive morphologies: filamentary rods and ribbon, and platelets. The rods and ribbons are elongated along the crystallographic [100] and [111] directions. Some of the rods contain microstructural defects indicating that they grew by spiral growth about screw dislocations. Platelets are flattened along the [100] and [110] directions. These unique morphologies and microstructures constrain the growth conditions of magnetite. The whiskers and platelets most likely formed in the temperature range 500-800 degrees C by direct condensation from a vapor or precipitation from a supercritical fluid, and their properties are inconsistent with a biogenic origin.

  7. A possible high-temperature origin for the carbonates in the martian meteorite ALH84001.

    PubMed

    Harvey, R P; McSween, H Y

    1996-07-01

    The meteorite Allan Hills (ALH) 84001, commonly accepted to be of martian origin, is unique among known martian meteorites in containing abundant, zoned, pre-terrestrial carbonate minerals. Previous studies of the oxygen isotope compositions of these minerals have suggested that they precipitated from a low-temperature (0-80 degrees C) aqueous fluid in the martian crust--perhaps in a near-surface hydrothermal system. Here we report analyses of the major-element compositions of the carbonates, which provide an independent constraint on the composition and temperature of the fluid from which they formed. We argue that the most likely explanation for the observed compositions, and for the absence of co-existing hydrons minerals, is that the carbonates were formed by reactions between hot (> 650 degrees C), CO2-rich fluids and the ultramatic host rock during an impact event. Impact processes on the martian surface can produce both the hot, CO2-rich fluid (by volatilization of surface carbonates or other CO2 sources) and--by brecciation--the condults through which it flowed. Impact metasomatism is also consistent with the observed oxygen isotope disequillbrium, sequence of mineral formation, and carbonate mineral zoning, reflecting carbonate formation during rapid cooling from high temperatures rather than prolonged exposure to low-temperature fluids. PMID:8657303

  8. A possible high-temperature origin for the carbonates in the martian meteorite ALH84001.

    PubMed

    Harvey, R P; McSween, H Y

    1996-07-01

    The meteorite Allan Hills (ALH) 84001, commonly accepted to be of martian origin, is unique among known martian meteorites in containing abundant, zoned, pre-terrestrial carbonate minerals. Previous studies of the oxygen isotope compositions of these minerals have suggested that they precipitated from a low-temperature (0-80 degrees C) aqueous fluid in the martian crust--perhaps in a near-surface hydrothermal system. Here we report analyses of the major-element compositions of the carbonates, which provide an independent constraint on the composition and temperature of the fluid from which they formed. We argue that the most likely explanation for the observed compositions, and for the absence of co-existing hydrons minerals, is that the carbonates were formed by reactions between hot (> 650 degrees C), CO2-rich fluids and the ultramatic host rock during an impact event. Impact processes on the martian surface can produce both the hot, CO2-rich fluid (by volatilization of surface carbonates or other CO2 sources) and--by brecciation--the condults through which it flowed. Impact metasomatism is also consistent with the observed oxygen isotope disequillbrium, sequence of mineral formation, and carbonate mineral zoning, reflecting carbonate formation during rapid cooling from high temperatures rather than prolonged exposure to low-temperature fluids.

  9. Polycyclic Aromatic Hydrocarbons in the Martian (SNC) Meteorite ALH 84001: Hydrocarbons from Mars, Terrestrial Contaminants, or Both?

    NASA Astrophysics Data System (ADS)

    Thomas, K. L.; Clemett, S. J.; Romanek, C. S.; Macheling, C. R.; Gibson, E. K.; McKay, D. S.; Score, R.; Zare, R. N.

    1995-09-01

    Previous work has shown that pre-terrestrial polycyclic aromatic hydrocarbons (PAHs) exist in interplanetary dust particles (IDPs) and certain meteorites [1-3]. We previously reported the first observation of PAHs in the newest member of the SNC group, Allan Hills 84001 [4] and determined that particular types of organic compounds are indigenous to ALH 84001 because they are associated with certain mineralogical features [4]. We also analyzed two diogenites from Antarctica: one showed no evidence for aromatic hydrocarbons while the other contained PAHs with the same major peaks as those in ALH 84001[4]. PAHs in the diogenite meteorite are not associated with mineral features on the analyzed surface and the most abundant PAHs in the diogenite are lower by a factor of 3 than those in ALH 84001. Furthermore, ALH 84001 contains a number of minor PAHs not found in the diogenite or typical terrestrial soils [4]. In this study we are analyzing a more complete group of Antarctic and non-Antarctic meteorites, including SNCs, to determine: (1) PAHs abundance and diversity in Antarctic meteorites and (2) the contribution of PAHs in SNCs from martian and, possibly, terrestrial sources. ALH 84001 is an unusual orthopyroxenite which contains abundant carbonate spheroids which are ~100-200 micrometers in diameter and range in composition from magnesite to ferroan magnesite [5-7]. These spheroids are not the result of terrestrial contamination: oxygen isotopic compositions indicate that the carbonates probably precipitated from a low-temperature fluid within the martian crust [5] and carbon isotopic abundances are consistent with martian atmospheric CO2 as the carbon source [5]. PAHs may coexist with other low-temperature carbon-bearing phases in a subsurface martian environment. Samples: We are analyzing freshly-fractured meteorite samples, or chips, which have been extracted from the internal regions of the following meteorites: ALH 84001 (crush and uncrush zones), EETA79001

  10. The origin of organic matter in the Martian meteorite ALH84001.

    PubMed

    Becker, L; Popp, B; Rust, T; Bada, J L

    1999-03-30

    Stable carbon isotope measurements of the organic matter associated with the carbonate globules and the bulk matrix material in the ALH84001 Martian meteorite indicate that two distinct sources are present in the sample. The delta 13C values for the organic matter associated with the carbonate globules averaged -26% and is attributed to terrestrial contamination. In contrast, the delta 13C values for the organic matter associated with the bulk matrix material yielded a value of -15%. The only common sources of carbon on the Earth that yield similar delta 13C values, other then some diagenetically altered marine carbonates, are C4 plants. A delta 13C value of -15%, on the other hand, is consistent with a kerogen-like component, the most ubiquitous form of organic matter found in carbonaceous chondrites such as the Murchison meteorite. Examination of the carbonate globules and bulk matrix material using laser desorption mass spectrometry (LDMS) indicates the presence of a high molecular weight organic component which appears to be extraterrestrial in origin, possibly derived from the exogenous delivery, of meteoritic or cometary debris to the surface of Mars. PMID:11542930

  11. The origin of organic matter in the Martian meteorite ALH84001.

    PubMed

    Becker, L; Popp, B; Rust, T; Bada, J L

    1999-01-01

    Stable carbon isotope measurements of the organic matter associated with the carbonate globules and the bulk matrix material in the ALH84001 Martian meteorite indicate that two distinct sources are present in the sample. The delta 13C values for the organic matter associated with the carbonate globules averaged -26% and is attributed to terrestrial contamination. In contrast, the delta 13C values for the organic matter associated with the bulk matrix material yielded a value of -15%. The only common carbon sources on the Earth that yield similar delta 13C values, other then some diagenetically altered marine carbonates, are C4 plants. A delta 13C value of -15%, on the other hand, is consistent with a kerogen-like component, the most ubiquitous form of organic matter found in carbonaceous chondrites such as the Murchison meteorite. Examination of the carbonate globules and bulk matrix material using laser desorption mass spectrometry (LDMS) indicates the presence of a high molecular weight organic component which appears to be extraterrestrial in origin, possibly derived from the exogenous delivery of meteoritic or cometary debris to the surface of Mars. PMID:11543335

  12. Paleomagnetic evidence of a low-temperature origin of carbonate in the Martian meteorite ALH84001.

    PubMed

    Kirschvink, J L; Maine, A T; Vali, H

    1997-03-14

    Indirect evidence for life on Mars has been reported from the study of meteorite ALH84001. The formation temperature of the carbonates is controversial; some estimates suggest 20 degrees to 80 degrees C, whereas others exceed 650 degrees C. Paleomagnetism can be used to distinguish between these possibilities because heating can remagnetize ferrimagnetic minerals. Study of two adjacent pyroxene grains from the crushed zone of ALH84001 shows that each possesses a stable natural remanent magnetization (NRM), implying that Mars had a substantial magnetic field when the grains cooled. However, NRM directions from these particles differ, implying that the meteorite has not been heated significantly since the formation of the internal crushed zone about 4 billion years ago. The carbonate globules postdate this brecciation, and thus formed at low temperatures. PMID:9054354

  13. Paleomagnetic evidence of a low-temperature origin of carbonate in the Martian meteorite ALH84001.

    PubMed

    Kirschvink, J L; Maine, A T; Vali, H

    1997-03-14

    Indirect evidence for life on Mars has been reported from the study of meteorite ALH84001. The formation temperature of the carbonates is controversial; some estimates suggest 20 degrees to 80 degrees C, whereas others exceed 650 degrees C. Paleomagnetism can be used to distinguish between these possibilities because heating can remagnetize ferrimagnetic minerals. Study of two adjacent pyroxene grains from the crushed zone of ALH84001 shows that each possesses a stable natural remanent magnetization (NRM), implying that Mars had a substantial magnetic field when the grains cooled. However, NRM directions from these particles differ, implying that the meteorite has not been heated significantly since the formation of the internal crushed zone about 4 billion years ago. The carbonate globules postdate this brecciation, and thus formed at low temperatures.

  14. Implications of noble gases in a recently recognized Martian meteorite (ALH84001) for the degassing history of Mars

    NASA Technical Reports Server (NTRS)

    Swindle, T. D.

    1994-01-01

    For terrestrial planets, atmospheric compositions are not static, but evolve with time, in part due to degassing of the interior. Unfortunately, the evolution is slow enough that it is usually not observable on human timescales, or even on the timescales of rocks that preserve samples of Earth's ancient atmosphere. Preliminary results on a recently recognized Martian meteorite, ALH84001, indicate that it is a very old rock, and has a relatively high noble gas content suggestive of atmospheric incorporation, but with an isotopic composition slightly inconsistent with currently known Martian reservoirs. Hence, this rock may provide a sample of ancient Martian atmosphere, which can be used to test models of volatile evolution (in particular, degassing) on Mars. ALH84001 is a cumulate orthopyroxenite. Although originally classified as a diogenite, its oxygen isotopes, and several chemical and petrographic features, strong suggest that it is, like the SNC meteorites, Martian. A Sm-Nd crystallization age of 4.5 Ga has been reported. The meteorite is rich in noble gases, compared to most SNC's. In many respects the noble gases are typical of SNC meteorites. However, there are some subtle differences. In particular, the Xe isotopes in SNC meteorites can be explained as a mixture of Martian atmospheric Xe (as represented by glass in EETA 79001), the Xe in the dunite Chassigny (usually assumed to be representative of the Martian interior, and with lower (129)Xe/(132)Xe, (134)Xe/(132)Xe and (136)Xe/(132)Xe ratios), and later additions from known processes like fission, spallation and terrestrial contamination. The isotopic composition of ALH84001 is inconsistent (at greater than 2-3 sigma) with any mixture of those components. Even if no accumulation of fission Xe during the age of the rock is assumed, there is too little (136)Xe and (134)Xe for the amount of (129)Xe measured.

  15. Isotope Geochemistry of Possible Terrestrial Analogue for Martian Meteorite ALH84001

    NASA Technical Reports Server (NTRS)

    Mojzsis, Stephen J.

    2000-01-01

    We have studied the microdomain oxygen and carbon isotopic compositions by SIMS of complex carbonate rosettes from spinel therzolite xenoliths, hosted by nepheline basanite, from the island of Spitsbergen (Norway). The Quaternary volcanic rocks containing the xenoliths erupted into a high Arctic environment and through relatively thick continental crust containing carbonate rocks. We have attempted to constrain the sources of the carbonates in these rocks by combined O-18/O-16 and C-13/C-12 ratio measurements in 25 micron diameter spots of the carbonate and compare them to previous work based primarily on trace-element distributions. The origin of these carbonates can be interpreted in terms of either contamination by carbonate country rock during ascent of the xenoliths in the host basalt, or more probably by hydrothermal processes after emplacement. The isotopic composition of these carbonates from a combined delta.18O(sub SMOW) and delta.13C(sub PDB) standpoint precludes a primary origin of these minerals from the mantle. Here a description is given of the analysis procedure, standardization of the carbonates, major element compositions of the carbonates measured by electron microprobe, and their correlated C and O isotope compositions as measured by ion microprobe. Since these carbonate rosettes may represent a terrestrial analogue to the carbonate "globules" found in the martian meteorite ALH84001 interpretations for the origin of the features found in the Spitsbergen may be of interest in constraining the origin of these carbonate minerals on Mars.

  16. Hydrogeological Interpretation of Candidate Origin Sites for Martian Meteorite ALH84001

    NASA Astrophysics Data System (ADS)

    Gulick, V. C.

    1996-09-01

    Barlow (this meeting) has identified two potential source craters for the martian meteorite ALH84001. The craters are at 11.7(deg) S, 243.3(deg) W (Mare Tyrrhenum site) and 14.0(deg) S, 343.5(deg) W (Sinus Sabaeus site). As noted by Barlow, both craters lie in the heavily cratered terrain (HCT) and are adjacent to fluvial valleys. Here I explore the fluvial history of these areas based upon the surrounding valley morphology. The most prominent valley network at the Sabaeus site is Evros Vallis. This wide, flat-floored valley is approximately 600 km long with an average width of 2.5 km and a depth of 220 m. The eroded volume of the entire Evros network is approximately 6x 10(11) m(3) . This is typical for networks located in the heavily cratered terrain (e.g. Warrego and Parana Valles). Evros is also an isolated valley system. No similar networks are found in the surrounding terrain. Thus it is unlikely that Evros formed as a result of widespread rainfall. A localized water source, such as discharge of a hydrothermal system or localized melting of snowfall, seems more consistent. Previous modeling has demonstrated that only hydrothermal systems associated with high permeability sub-surfaces can discharge sufficient water to form a valley network. The bulk of the discharge from such systems is consequently low temperature, slightly heated water. Precipitation of calcium carbonate by low temperature fluids is consistent with most interpretations of the geochemistry of ALH84001. Available imagery at the Tyrrhenum site is of lesser quality. While eroded units of the HCT are nearby, there are no comparable well developed valley networks at this site. Erosion is instead manifested predominantly as gullies on slopes. This style of erosion suggests that water was not present at this site for the length of time as at the more integrated Sabaeus site. The superposition of fluidized ejecta blankets suggests however that ground water or ground ice was still present at this

  17. Bacterial mineralization patterns in basaltic aquifers: Implications for possible life in Martian meteorite ALH84001

    SciTech Connect

    Thomas-Keprta, K.L.; Wentworth, S.J.; Allen, C.C.; McKay, D.S.; Gibson, E.K. Jr.; Stevens, T.O.; Taunton, A.E.; Coleman, A.; Romanek, C.S.

    1998-11-01

    To explore the formation and preservation of biogenic features in igneous rocks, the authors have examined the organisms in experimental basaltic microcosms using scanning and transmission electron microscopy. Four types of microorganisms were recognized on the basis of size, morphology, and chemical composition. Some of the organisms mineralized rapidly, whereas others show no evidence of mineralization. Many mineralized cells are hollow and do not contain evidence of microstructure. Filaments, either attached or no longer attached to organisms, are common. Unattached filaments are mineralized and are most likely bacterial appendages (e.g., prosthecae). Features similar in size and morphology to unattached, mineralized filaments are recognized in martial meteorite ALH84001.

  18. Ion microprobe measurements of 18O/ 16O ratios of phosphate minerals in the Martian meteorites ALH84001 and Los Angeles

    NASA Astrophysics Data System (ADS)

    Greenwood, James P.; Blake, Ruth E.; Coath, Christopher D.

    2003-06-01

    Oxygen isotope ratios of merrillite and chlorapatite in the Martian meteorites ALH84001 and Los Angeles have been measured by ion microprobe in multicollector mode. δ 18O values of phosphate minerals measured in situ range from ˜3 to 6‰, and are similar to Martian meteorite whole-rock values, as well as the δ 18O of igneous phosphate on Earth. These results suggest that the primary, abiotic, igneous phosphate reservoir on Mars is similar in oxygen isotopic composition to the basaltic phosphate reservoir on Earth. This is an important first step in the characterization of Martian phosphate reservoirs for the use of δ 18O of phosphate minerals as a biomarker for life on Mars. Cumulative textural, major-element, and isotopic evidence presented here suggest a primary, igneous origin for the phosphates in Los Angeles and ALH84001; textural and chemical evidence suggests that phosphates in ALH84001 were subsequently shock-melted in a later event.

  19. Origin of magnetite crystals in Martian meteorite ALH84001 carbonate disks

    NASA Astrophysics Data System (ADS)

    Thomas-Keprta, Kathie; Clemett, Simon; McKay, David; Gibson, Everett; Wentworth, Susan

    The Martian meteorite ALH84001 preserves evidence of interaction with aqueous fluids while on Mars in the form of microscopic carbonate disks. These carbonate disks are believed to have precipitated 3.9 Ga ago at beginning of the Noachian epoch on Mars during which both the oldest extant Martian surfaces were formed, and perhaps the earliest global oceans. In-timately associated within and throughout these carbonate disks are nanocrystal magnetites (Fe3O4) with unusual chemical and physical properties, whose origins have become the source of considerable debate [1,2]. One group of hypotheses argues that these magnetites are the product of partial thermal decomposition of the host carbonate [3,4]. Alternatively, the origins of magnetite and carbonate may be unrelated; that is, from the perspective of the carbonate the magnetite is allochthonous. For example, the magnetites might have already been present in the aqueous fluids from which the carbonates were believed to have been deposited. We have sought to resolve between these hypotheses through the detailed characterization of the compositional and structural relationships of the carbonate disks and associated magnetites with the orthopyroxene matrix in which they are embedded. Extensive use of focused ion beam milling techniques has been utilized for sample preparation. We then compared our ob-servations with those from experimental thermal decomposition studies of sideritic carbonates under a range of plausible geological heating scenarios. We conclude that the vast majority of the nanocrystal magnetites present in the carbonate disks could not have formed by any of the currently proposed thermal decomposition scenarios. Instead, we find there is considerable evidence in support of an alternative allochthonous origin for the magnetite unrelated to any shock or thermal processing of the carbonates [5]. [1] McKay et al. (1996) Science 273, 924-930. [2] Thomas-Keprta et al. (2001) Proc. Natl. Acad. Sci. 98, 2164

  20. Submicron magnetite grains and carbon compounds in Martian meteorite ALH84001: inorganic, abiotic formation by shock and thermal metamorphism.

    PubMed

    Treiman, Allan H

    2003-01-01

    Purported biogenic features of the ALH84001 Martian meteorite (the carbonate globules, their submicron magnetite grains, and organic matter) have reasonable inorganic origins, and a comprehensive hypothesis is offered here. The carbonate globules were deposited from hydrothermal water, without biological mediation. Thereafter, ALH84001 was affected by an impact shock event, which raised its temperature nearly instantaneously to 500-700K, and induced iron-rich carbonate in the globules to decompose to magnetite and other minerals. The rapidity of the temperature increase caused magnetite grains to nucleate in abundance; hence individual crystals were very small. Nucleation and growth of magnetite crystals were fastest along edges and faces of the precursor carbonate grains, forcing the magnetite grains to be platy or elongated, including the "truncated hexa-octahedra" shape. ALH84001 had formed at some depth within Mars where the lithostatic pressure was significantly above that of Mars' surface. Also, because the rock was at depth, the impact heat dissipated slowly. During this interval, magnetite crystals approached chemical equilibria with surrounding minerals and gas. Their composition, nearly pure Fe(3)O(4), reflects those of equilibria; elements that substitute into magnetite are either absent from iron-rich carbonate (e.g., Ti, Al, Cr), or partitioned into other minerals during magnetite formation (Mg, Mn). Many microstructural imperfections in the magnetite grains would have annealed out as the rock cooled. In this post-shock thermal regime, carbon-bearing gas from the decomposition of iron carbonates reacted with water in the rock (or from its surroundings) to produce organic matter via Fischer-Tropschlike reactions. Formation of such organic compounds like polycyclic aromatic hydrocarbons would have been catalyzed by the magnetite (formation of graphite, the thermochemically stable phase, would be kinetically hindered). PMID:14577885

  1. Submicron Magnetite Grains and Carbon Compounds in Martian Meteorite ALH84001: Inorganic, Abiotic Formation by Shock and Thermal Metamorphism

    NASA Astrophysics Data System (ADS)

    Treiman, Allan H.

    2003-06-01

    Purported biogenic features of the ALH84001 Martian meteorite (the carbonate globules, their submicron magnetite grains, and organic matter) have reasonable inorganic origins, and a comprehensive hypothesis is offered here. The carbonate globules were deposited from hydrothermal water, without biological mediation. Thereafter, ALH84001 was affected by an impact shock event, which raised its temperature nearly instantaneously to 500-700K, and induced iron-rich carbonate in the globules to decompose to magnetite and other minerals. The rapidity of the temperature increase caused magnetite grains to nucleate in abundance; hence individual crystals were very small. Nucleation and growth of magnetite crystals were fastest along edges and faces of the precursor carbonate grains, forcing the magnetite grains to be platy or elongated, including the "truncated hexa-octahedra" shape. ALH84001 had formed at some depth within Mars where the lithostatic pressure was significantly above that of Mars' surface. Also, because the rock was at depth, the impact heat dissipated slowly. During this interval, magnetite crystals approached chemical equilibria with surrounding minerals and gas. Their composition, nearly pure Fe3O4, reflects those of equilibria; elements that substitute into magnetite are either absent from iron-rich carbonate (e.g., Ti, Al, Cr), or partitioned into other minerals during magnetite formation (Mg, Mn). Many microstructural imperfections in the magnetite grains would have annealed out as the rock cooled. In this post-shock thermal regime, carbon-bearing gas from the decomposition of iron carbonates reacted with water in the rock (or from its surroundings) to produce organic matter via Fischer-Tropschlike reactions. Formation of such organic compounds like polycyclic aromatic hydrocarbons would have been catalyzed by the magnetite (formation of graphite, the thermochemically stable phase, would be kinetically hindered).

  2. Submicron magnetite grains and carbon compounds in Martian meteorite ALH84001: inorganic, abiotic formation by shock and thermal metamorphism.

    PubMed

    Treiman, Allan H

    2003-01-01

    Purported biogenic features of the ALH84001 Martian meteorite (the carbonate globules, their submicron magnetite grains, and organic matter) have reasonable inorganic origins, and a comprehensive hypothesis is offered here. The carbonate globules were deposited from hydrothermal water, without biological mediation. Thereafter, ALH84001 was affected by an impact shock event, which raised its temperature nearly instantaneously to 500-700K, and induced iron-rich carbonate in the globules to decompose to magnetite and other minerals. The rapidity of the temperature increase caused magnetite grains to nucleate in abundance; hence individual crystals were very small. Nucleation and growth of magnetite crystals were fastest along edges and faces of the precursor carbonate grains, forcing the magnetite grains to be platy or elongated, including the "truncated hexa-octahedra" shape. ALH84001 had formed at some depth within Mars where the lithostatic pressure was significantly above that of Mars' surface. Also, because the rock was at depth, the impact heat dissipated slowly. During this interval, magnetite crystals approached chemical equilibria with surrounding minerals and gas. Their composition, nearly pure Fe(3)O(4), reflects those of equilibria; elements that substitute into magnetite are either absent from iron-rich carbonate (e.g., Ti, Al, Cr), or partitioned into other minerals during magnetite formation (Mg, Mn). Many microstructural imperfections in the magnetite grains would have annealed out as the rock cooled. In this post-shock thermal regime, carbon-bearing gas from the decomposition of iron carbonates reacted with water in the rock (or from its surroundings) to produce organic matter via Fischer-Tropschlike reactions. Formation of such organic compounds like polycyclic aromatic hydrocarbons would have been catalyzed by the magnetite (formation of graphite, the thermochemically stable phase, would be kinetically hindered).

  3. Micro-Spectroscopy as a Tool for Detecting Micron-Scale Mineral Variations Across a Rock Surface: An Example Using a Thin Section of Martian Meteorite ALH 84001

    NASA Technical Reports Server (NTRS)

    Dalton, J. Brad; Bishop, Janice L.

    2003-01-01

    Imaging spectroscopy is a powerful tool for mineral detection across broad spatial regions. A prototype micro-imaging spectrometer at NASA Ames is tested in this study on a scale of tens to hundreds of microns across rock surfaces. Initial measurements were performed in the visible spectral region on a thin section of martian meteorite ALH 84001.

  4. Low-temperature carbonate concretions in the Martian meteorite ALH84001: evidence from stable isotopes and mineralogy.

    PubMed

    Valley, J W; Eiler, J M; Graham, C M; Gibson, E K; Romanek, C S; Stolper, E M

    1997-03-14

    The martian meteorite ALH84001 contains small, disk-shaped concretions of carbonate with concentric chemical and mineralogical zonation. Oxygen isotope compositions of these concretions, measured by ion microprobe, range from delta18O = +9.5 to +20.5 per thousand. Most of the core of one concretion is homogeneous (16.7 +/- 1.2 per thousand) and over 5 per thousand higher in delta18O than a second concretion. Orthopyroxene that hosts the secondary carbonates is isotopically homogeneous (delta18O = 4.6 +/- 1.2 per thousand). Secondary SiO2 has delta18O = 20.4 per thousand. Carbon isotope ratios measured from the core of one concretion average delta13C = 46 +/- 8 per thousand, consistent with formation on Mars. The isotopic variations and mineral compositions offer no evidence for high temperature (>650 degrees C) carbonate precipitation and suggest non-equilibrium processes at low temperatures (< approximately 300 degrees C). PMID:9054355

  5. Low-temperature carbonate concretions in the Martian meteorite ALH84001: evidence from stable isotopes and mineralogy

    NASA Technical Reports Server (NTRS)

    Valley, J. W.; Eiler, J. M.; Graham, C. M.; Gibson, E. K.; Romanek, C. S.; Stolper, E. M.

    1997-01-01

    The martian meteorite ALH84001 contains small, disk-shaped concretions of carbonate with concentric chemical and mineralogical zonation. Oxygen isotope compositions of these concretions, measured by ion microprobe, range from delta18O = +9.5 to +20.5 per thousand. Most of the core of one concretion is homogeneous (16.7 +/- 1.2 per thousand) and over 5 per thousand higher in delta18O than a second concretion. Orthopyroxene that hosts the secondary carbonates is isotopically homogeneous (delta18O = 4.6 +/- 1.2 per thousand). Secondary SiO2 has delta18O = 20.4 per thousand. Carbon isotope ratios measured from the core of one concretion average delta13C = 46 +/- 8 per thousand, consistent with formation on Mars. The isotopic variations and mineral compositions offer no evidence for high temperature (>650 degrees C) carbonate precipitation and suggest non-equilibrium processes at low temperatures (< approximately 300 degrees C).

  6. Carbon- and Sulfur-bearing Minerals in the Martian Meteorite ALH 84001

    NASA Astrophysics Data System (ADS)

    Romanek, C. S.; Thomas, K. L.; Gibson, E. K., Jr.; McKay, D. S.; Socki, R. A.

    1995-09-01

    % Fe), with trace amounts of a cathodoluminescence (CL) activator (bright orange CL requires an activator, Mn or REE, and <2000 ppm Fe [5]). Thin black rims are composed primarily of fine-grained magnetite grains (5 - 50 nm dia.) bound in a Fe-rich carbonate matrix. Sulfur, which is present in some EDS spectra, may be a co-precipitate in the carbonate structure (up to 2 mol% S in carbonate [6]) and a distinct Fe-S-O phase (50 nm dia.), suggesting that sulfur may occurs as an oxidized species (e.g., SO4). Black spheroids are composed of material similar in composition to thin black rims. Finally, vug-filling aggregates are composed almost entirely of Fe-monosulfide, which is documented for the first time in this meteorite. Discussion: Considerable debate exists as to the origin of C- and S-bearing minerals in ALH 84001 [1-4]. When spheroids are dissolved by acid etching, fracture pathways are exposed in the underlying matrix, suggesting that carbonate precipitated along fault traces. Flattened spheroid morphologies support this interpretation as aggregate growth is limited normal to fracture surfaces. The trend of Fe-Ca rich carbonate cores and Fe-S rich rims, and the occurrence of late-stage vug-filling sulfides is consistent with progressive Fe- and S-reduction of subsurface fluids. If the precipitation sequence occurred in an environment containing sulfate, as suggested by the presence of Fe-S-O grains, and Eh (oxidizing potential) was sufficiently high during Fe-reduction, sulfur may have remained in an oxidized state during initial carbonate precipitation [7]. With the progressive reduction of Fe-oxides and precipitation of carbonate Eh would have fallen, initiating the process of sulfate reduction and the precipitation of Fe-monosulfide as a late-stage pore-filling mineral. As such, the complex geochemistry and mineralogy observed in the C- and S-bearing minerals of ALH 84001 can be explained by Eh-pH dependent reactions that occur at relatively low temperatures

  7. Formation of "Chemically Pure" Magnetite from Mg-Fe-Carbonates Implications for the Exclusively Inorganic Origin of Magnetite and Sulfides in Martian Meteorite ALH84001

    NASA Technical Reports Server (NTRS)

    Golden, D. C.; Ming, Douglas W.; Lauer, H. V., Jr.; Morris, R. V.; Trieman, A. H.; McKay, G. A.

    2006-01-01

    Magnetite and sulfides in the black rims of carbonate globules in Martian meteorite ALH84001 have been studied extensively because of the claim by McKay et al. that they are biogenic in origin. However, exclusively inorganic (abiotic) processes are able to account for the occurrence of carbonate-sulfide-magnetite assemblages in the meteorite. We have previously precipitated chemically zoned and sulfide-bearing carbonate globules analogous to those in ALH84001 (at less than or equal to 150 C) from multiple fluxes of variable-composition Ca-Mg-Fe-CO2-S-H2O solutions. Brief heating of precipitated globules to approx. 470 C produced magnetite and pyrrhotite within the globules by thermal decomposition of siderite and pyrite, respectively. We have also shown that morphology of magnetite formed by inorganic thermal decomposition of Fe-rich carbonate is similar to the morphology of so-called biogenic magnetite in the carbonate globules of ALH84001. Magnetite crystals in the rims of carbonate globules in ALH84001 are chemically pure [Note: "Chemically pure" is defined here as magnetite with Mg at levels comparable or lower than Mg detected by [8] in ALH84001 magnetite]. A debate continues on whether or not chemically pure magnetite can form by the thermal decomposition of mixed Mg-Fe-carbonates that have formed under abiotic conditions. Thomas-Keprta et al. argue that it is not possible to form Mg-free magnetite from Mg-Fe-carbonate based on thermodynamic data. We previously suggested that chemically pure magnetite could form by the thermal decomposition of relatively pure siderite in the outer rims of the globules. Mg-Fe-carbonates may also thermally decompose under conditions conducive for formation of chemically pure magnetite. In this paper we show through laboratory experiments that chemically pure magnetite can form by an inorganic process from mixed Mg-Fe-carbonates.

  8. Low-Temperature Thermal History of Martian Meteorite ALH84001 from (U-Th)/He Thermochronometry

    NASA Astrophysics Data System (ADS)

    Min, K.; Reiners, P. W.

    2005-03-01

    Single grain (U-Th)/He ages from ALH84001 are interpreted either by (1) a single intense (maximum temperature of ~430 ºC) shock event at 15 Ma, or (2) stronger shock at sometime between (0.3-0.7) Ga and 15 Ma, followed by a minor shock at 15 Ma.

  9. Ar-Ar chronology of the Martian meteorite ALH84001: evidence for the timing of the early bombardment of Mars.

    PubMed

    Turner, G; Knott, S F; Ash, R D; Gilmour, J D

    1997-09-01

    ALH84001, a cataclastic cumulate orthopyroxenite meteorite from Mars, has been dated by Ar-Ar stepped heating and laser probe methods. Both methods give ages close to 3,900 Ma. The age calculated is dependent on assumptions made about 39Ar recoil effects and on whether significant quantities of 40Ar from the Martian atmosphere are trapped in the meteorite. If, as suggested by xenon and nitrogen isotope studies, Martian atmospheric argon is present, then it must reside predominantly in the K-rich phase maskelynite. Independently determined 129Xe abundances in the maskelynite can be used to place limits on the concentration of the atmospheric 40Ar. These indicate a reduction of around 80 Ma to ages calculated on the assumption that no Martian atmosphere is present. After this correction, the nominal ages obtained are: 3940 +/- 50, 3870 +/- 80, and 3970 +/- 100 Ma. by stepped heating, and 3900 +/- 90 Ma by laser probe (1 sigma statistical errors), giving a weighted mean value of 3,920 Ma. Ambiguities in the interpretation of 39Ar recoil effects and in the contribution of Martian atmospheric 40Ar lead to uncertainties in the Ar-Ar age which are difficult to quantify, but we suggest that the true value lies somewhere between 4,050 and 3,800 Ma. This age probably dates a period of annealing of the meteorite subsequent to the shock event which gave it its cataclastic texture. The experiments provide the first evidence of an event occurring on Mars coincident with the time of the late heavy bombardment of the Moon and may reflect a similar period of bombardment in the Southern Highlands of Mars. Whether the age determined bears any relationship to the time of carbonate deposition in ALH84001 is not known. Such a link depends on whether the temperature associated with the metasomatic activity was sufficient to cause argon loss from the maskelynite and/or whether the metasomatism and metamorphism were linked in time through a common heat source. PMID:11541217

  10. Carbonate Globules from Spitsbergen, Norway: Terrestrial Analogs of the Carbonates in Martian Meteorite ALH84001?

    NASA Technical Reports Server (NTRS)

    De, Subarnarek; Bunch, Ted; Treiman, Allan H.; Amundsen, Hans E. F.; Blake, David F.; DeVincenzi, Donald L. (Technical Monitor)

    2001-01-01

    Pleistocene volcanic centers in NW Spitsbergen, Norway host one of the world's richest occurrences of mantle xenoliths. The xenoliths comprise varieties of spinel lherzolites and pyroxenites. Some of these xenoliths (and their host basalts) contain 10-100 micrometer globules of ankedtic-magnesitic carbonates (AMC). In composition, mineralogy and petrology the AMC globules from Spitsbergen are strikingly similar to the carbonate globules in ALH84001. The AMC globules occur within interstitial quenched glass and as fracture fillings, although we have not seen replacement fabrics analogous to carbonate rosettes replacing glass in ALH84001. Siderite/ankerite forms the core of these concentrically zoned globules while rims are predominantly magnesite. Clay minerals can occasionally be found within and around the globules. Aside from the clay minerals, the principal mineralogical difference between the AMCs and the ALH84001 carbonate rosettes is the presence of concentrated zones of nanophase magnetite in the rosettes, notably absent in the AMCs. However, carbonate globules containing nanophase magnetite have been produced inorganically by hydrothermal precipitation of carbonates and subsequent heating. We heated Spitsbergen AMC at 585 C in a reducing atmosphere to determine whether magnetite could be produced. Optical micrographs of the heated Spitsbergen AMC show dark concentric zones within the AMC. High resolution SEM images of those areas reveal 150-200 nm euhedral crystals that exhibit various morphologies including octahedra and elongated prisms. EDS analyses of areas where the crystals occur contain Fe, O, and minor Si, and P. However, the probe integrates over volumes of material, which also include the surrounding matrix. We have begun TEM observations of both the heated and unheated Spitsbergen AMC to characterize the microstructures of the carbonates, establish the presence/absence of magnetite and determine the relationship of the clay minerals to the

  11. Low-temperature carbonate concretions in the martian meteorite ALH84001: Evidence from stable isotopes and mineralogy

    SciTech Connect

    Valley, J.W.; Eiler, J.M.; Stolper, E.M.

    1997-03-14

    The martian meteorite ALH84001 contains small, disk-shaped concentrations of carbonate with concentric chemical and mineralogical zonation. Oxygen isotope compositions of these concretions, measured by ion microprobe, range from {delta}{sup 18}O = +9.5 to +20.5{per_thousand}. Most of the core of one concretion is homogeneous (16.7 {+-} 1.2{per_thousand}) and over 5{per_thousand} higher in ({delta}{sup 18}O = 4.6 {+-} 1.2{per_thousand}). Secondary SiO{sub 2} has {delta}{sup 18}O = 20.4{per_thousand}. Carbon isotope ratios measured from the core of one concretion average {delta}{sup 13}C = 46 {+-} 8{per_thousand}, consistent with formation on Mars. The isotopic variations and mineral compositions offer no evidence for high temperature (>650{degrees}C) carbonate precipitation and suggest non-equilibrium processes at low temperatures (<{approximately} 300{degrees}C). 44 refs., 3 figs., 1 tab.

  12. A Hypothesis for the Abiotic and Non-Martian Origins of Putative Signs of Ancient Martian Life in ALH84001

    NASA Technical Reports Server (NTRS)

    Treiman, Allan H.

    2001-01-01

    Putative evidence of martian life in ALH84001 can be explained by abiotic and non-martian processes consistent with the meteorite's geological history. Additional information is contained in the original extended abstract.

  13. Stable Isotope Enrichment of Carbonate from the Martian Meteorite ALH84001: Test of a Hypothesis at Wright Valley, Antarctica

    NASA Astrophysics Data System (ADS)

    Socki, R. A.; Gibson, E. K., Jr.; Romanek, C. S.

    1995-09-01

    We report here the stable isotope composition of carbonate measured from a suite of desert soils from the Dry Valleys of Antarctica [1] to determine the 13C enrichments attributed to cryogenic freezing in terrestrial environments. These data are then used to gauge whether cryogenic freezing is a viable aqueous process that can produce extreme 13C enrichments observed in Martian carbonates (e.g., ALH 84001 [2]). Analyses of ALH 84001 have shown that the delta^(13)C of carbonate is the most-positive yet recorded for an SNC meteorite (ca. 42 per mil)[2]. The source of carbon is thought to be Martian atmospheric CO2, which has been recycled through an aqueous medium into the solid phase. The delta^(13)C of the carbonate is consistent with a precipitation temperature below ~300 degrees C [3], assuming the delta^(13)C of Martian CO2 lies somewhere between 26 and 46 per mil [4, 5]. An equilibrium temperature of formation near 0 degrees C is difficult to reconcile if the atmospheric source of carbon is <26 per mil, despite the fact that equilbrium isotope enrichments are large at this temperature (12-14 per mil) [6-8]. Low delta^(13)C for atmospheric CO2 is only compatible with high delta^(13)C for carbonate when non-equilibrium processes are the primary mechanism of isotopic fractionation. An inorganic surficial process known to enrich carbonate by >15 per mil over ambient atmospheric CO2 is cryogenic freezing [9]. Carbonate-bearing soils from Wright Valley, Antarctica were studied as a terrestrial analog to the carbonates in ALH 84001 to characterize isotopic "fingerprints" associated with cryogenic freezing. delta^(13)C and delta^(18)O carbonate values from Prospect Mesa Soil Pit range from +0.89 per mil to -20.46 per mil (PDB) within the "permanently frozen zone" (below 0.4 m), and +4.20 per mil to -11.87 per mil at the surface. The most enriched 13C and 18O tend to occur at the surface where seasonal variations in temperature or precipitation have imposed cyclical

  14. Stable Isotope Enrichment of Carbonate from the Martian Meteorite ALH84001: Test of a Hypothesis at Wright Valley, Antarctica

    NASA Astrophysics Data System (ADS)

    Socki, R. A.; Gibson, E. K., Jr.; Romanek, C. S.

    1995-09-01

    We report here the stable isotope composition of carbonate measured from a suite of desert soils from the Dry Valleys of Antarctica [1] to determine the 13C enrichments attributed to cryogenic freezing in terrestrial environments. These data are then used to gauge whether cryogenic freezing is a viable aqueous process that can produce extreme 13C enrichments observed in Martian carbonates (e.g., ALH 84001 [2]). Analyses of ALH 84001 have shown that the delta^(13)C of carbonate is the most-positive yet recorded for an SNC meteorite (ca. 42 per mil)[2]. The source of carbon is thought to be Martian atmospheric CO2, which has been recycled through an aqueous medium into the solid phase. The delta^(13)C of the carbonate is consistent with a precipitation temperature below ~300 degrees C [3], assuming the delta^(13)C of Martian CO2 lies somewhere between 26 and 46 per mil [4, 5]. An equilibrium temperature of formation near 0 degrees C is difficult to reconcile if the atmospheric source of carbon is <26 per mil, despite the fact that equilbrium isotope enrichments are large at this temperature (12-14 per mil) [6-8]. Low delta^(13)C for atmospheric CO2 is only compatible with high delta^(13)C for carbonate when non-equilibrium processes are the primary mechanism of isotopic fractionation. An inorganic surficial process known to enrich carbonate by >15 per mil over ambient atmospheric CO2 is cryogenic freezing [9]. Carbonate-bearing soils from Wright Valley, Antarctica were studied as a terrestrial analog to the carbonates in ALH 84001 to characterize isotopic "fingerprints" associated with cryogenic freezing. delta^(13)C and delta^(18)O carbonate values from Prospect Mesa Soil Pit range from +0.89 per mil to -20.46 per mil (PDB) within the "permanently frozen zone" (below 0.4 m), and +4.20 per mil to -11.87 per mil at the surface. The most enriched 13C and 18O tend to occur at the surface where seasonal variations in temperature or precipitation have imposed cyclical

  15. Formation of Carbonate Minerals in Martian Meteorite ALH 84001 from Cool Water Near the Surface of Mars

    NASA Astrophysics Data System (ADS)

    Taylor, G. J.

    2011-12-01

    Carbonate minerals in the Allan Hills 84001 meteorite are important because they ought to contain information about the chemistry and temperature of the water they formed in. They are also an important part of testing the idea that the meteorite contains evidence of past life on Mars. Hypotheses for the origin of the carbonates are impressively varied. A key test of the ideas is to determine the temperature at which the carbonates formed. Estimates up to now range from a bit below freezing to 700 oC, too big a range to test anything! To address the problem Itay Halevy, Woodward Fischer, and John Eiler (Caltech) used an approach that involves "clumped" isotope thermometry, which makes comparisons among different isotopic compositions of extracted CO2. This allowed the investigators to use the isotopic abundances of both carbon and oxygen. The results indicate that the carbonates formed at 18 ± 4 oC from a shallow subsurface (upper few meters to tens of meters) pool of water that was gradually evaporating. The wet episode did not last long, leading Halevy and his colleagues to conclude that the environment may have been too transient for life to have emerged here from scratch. On the other hand, if life already existed on the Martian surface this wet near-surface environment would have provided a happy home. An impact blasted the Martian home of ALH 84001, causing a transient heating event, perhaps disturbing the isotopic record...or perhaps not because the event was so short. In any case, the clumped isotope thermometry approach seems to have given a good measurement of the temperature at which the carbonate minerals formed.

  16. Study of a possible magnetite biosignature in Martian meteorite ALH84001: Implications for the biological toxicology of Mars

    NASA Astrophysics Data System (ADS)

    Thomas-Keprta, Kathie Louise

    "Why do we have such a longstanding fascination with Mars? Very simply put, it's about life. The search for life elsewhere in our Solar System has been a major driver for exploring Mars, pretty much since we began seriously looking at that planet."1 The major objective of this work is to describe signs of possible life, that is biosignatures, in rocks from Mars if indeed they are present. Biosignatures are specific identifiable properties that result from living things; they may be implanted in the environment and may persist even if the living thing is no longer present. Over 100 mineral biosignatures have been discussed in the literature; however, only one, magnetite, is addressed by this study. Magnetite is found in many rock types on earth and in meteorites. Previous studies of terrestrial magnetite have used few properties, such as size and chemical composition, to determine one of the modes of origins for magnetite (e.g., biogenic, inorganic). This study has established a rigorous set of six criteria for the identification of intracellularly precipitated biogenic magnetite. These criteria have been applied to a subpopulation of magnetites embedded within carbonates in Martian meteorite ALH84001. These magnetites are found to be chemically and physically indistinguishable from those produced by magnetotactic bacteria strain MV-1, hence, they were likely formed by biogenic processes on ancient Mars. These criteria may be also used to distinguish origins for magnetites from terrestrial samples with complex or unknown histories. The presence of purported past life on early Mars suggests that, if life once began it may still exist today, possibly in oases in the Martian subsurface. Future manned missions should consider potential hazards of an extant biological environment(s) on Mars. 1 Quote attributed to Jack Farmer of Arizona State University in discussing NASA's program of Mars Exploration (see "Deciphering Mars: Follow the Water," Astrobiology Magazine Sept

  17. Siderite globules associated with fossil microbiota from cretaceous cavity and fracture fillings in Southern Belgium: second known terrestrial analog for the carbonate in Martian meteorite ALH84001?

    NASA Astrophysics Data System (ADS)

    Baele, Jean-Marc

    2003-02-01

    Recently discovered siderite globules from Upper Cretaceous cavity and fracture fillings in southern Belgium are described and interpreted with emphasis on the still unsolved problem of the carbonates in meteorite ALH84001, which enclose controversal evidence for ancient Martian life. The most interesting aspects of the carbonates described here are 1) their close association with fossil microbiota, 2) their environment, which is 100% sedimentary, subaerial and not hydrothermal and 3) their morphologies, some of which being similar to those in ALH84001. Although the question of the direct biological influence is not critical in this case, the biogenicity for the minerals will be discussed as a strong possibility and is not only inferred from the simple spatial (and temporal) association of the carbonates and the fossil microbiota. Morphological, textural and chemical data will be presented and interpreted as variations in fluid chemistry related to environmental changes. Although they may appear different from those in Martian meteorite and Spitzbergen xenoliths, the Cretaceous globules originated in subsurface environment which left evident traces of life in the form of fossil microbial/fungal mats. They are thus considered as an opportunity to investigate biosignatures in future research using the wide range of available techniques.

  18. Geochemical evidence for mixing of three components in martian orthopyroxenite ALH 84001. [Abstract only

    NASA Technical Reports Server (NTRS)

    Mittlefehldt, D. W.; Lindstrom, M. M.

    1994-01-01

    ALH 84001, a ferroan martian orthopyroxenite, originally consisted of three petrographically defined components: a cumulus assemblage of orthopyroxene + chromite, a trapped melt assemblage of orthopyroxene(?) + chromite + maskelynite + apatite + augite +/- pyrite, and a metasomatic assemblage of carbonate +/- pyrite. We present the results of Instrumental Neutron Activation Analysis (INAA) study of five bulk samples of ALH 84001, combined with Scanning Ion Mass Spectrometer (SIMS) data on the orthopyroxene, in order to attempt to set limits on the geochemical characteristics of the latter two components, and therefore on the petrogenesis of ALH 84001. The INAA data support the petrographic observations, suggesting that there are at least three components in ALH 84001. We will assume that each of the three geochemically required components can be equated with one of the petrographically observed components. Both trapped melt and metasomatic components in ALH 84001 have higher Na than orthopyroxene based on compositions of maskelynite, apatite, and carbonate. For the metasomatic component, we will assume its Na content is that of carbonate, while for a trapped melt component, we will use a typical Na content inferred for martian meteorite parent melts, approximately 1 wt% Na2O. Under these assumptions, we can set limits on the Light Rare Earth Elements/Heavy Rare Earth Elements (LREE/HREE) ratios of the components, and use this information to compare the petrogenesis of ALH 84001 with other martian meteorites. The above calculations assume that the bulk samples are representative of different portions of ALH 84001. We will also evaluate the possible heterogeneous distribution of mineral phases in the bulk samples as the cause of compositional heterogeneity in our samples.

  19. Reassessment of the "Life on Mars" Hypothesis: Origin of Carbonate-Magnetite Assemblages in Martian Meteorite ALH84001

    NASA Astrophysics Data System (ADS)

    Thomas-Keprta, K. L.; Clemett, S. J.; McKay, D. S.; Gibson, E. K.; Wentworth, S. J.; Fei Corporation

    2007-07-01

    We present here the most detailed and comprehensive TEM analyses of the ALH84001 carbonate disks yet obtained. The results indicate that the disks show a subtle complexity that is incompatible with current "simple purely inorganic processes."

  20. High-temperature Mars-to-Earth transfer of meteorite ALH84001

    NASA Astrophysics Data System (ADS)

    Min, Kyoungwon; Reiners, Peter W.

    2007-08-01

    Martian meteorites provide crucial insights into Martian evolution and interplanetary mass transfer, including the potential for exogenesis. ALH84001 is the oldest Martian meteorite discovered so far, and has been used to derive important conclusions about Martian surface temperatures and very low-temperature Mars-to-Earth transfer. To better constrain the thermal evolution and shock metamorphic history of ALH84001, we applied (U-Th)/He thermochronometry to single grains of phosphate (merrillite) from ALH84001. The (U-Th)/He ages of individual phosphate grains in ALH84001 range from 60 Ma to 1.8 Ga, with a weighted mean of ~830 Ma. This broad age distribution reflects multiple diffusion domains, and requires a relatively high-temperature resetting event younger than ˜ 60 Ma. These new data are combined with the published whole-rock (maskelynite as a main Ar reservoir) 40Ar/ 39Ar age spectra which show 5-8% fractional loss of radiogenic 40Ar since 4.0 Ga. He diffusion in both terrestrial and extraterrestrial apatite has a significantly higher activation energy (138 ˜ 184 kJ/mol) than Ar diffusion in maskelynite (75 kJ/mol), leading to an important "kinetic crossover" in fractional loss contours for these systems. Taken together, the phosphate (U-Th)/He and whole-rock 40Ar/ 39Ar ages require both very low surface temperatures on Mars, and one or more short-lived, high-temperature, shock events after 4.0 Ga. We suggest that the last shock event occurred with ejection of ALH84001 from Mars, and reached a peak temperature of approximately 400 °C. These results undermine the proposed low-temperature ejection hypothesis for ALH84001, but support long-lived extremely cold Martian surface temperatures.

  1. The search for terrestrial nanobacteria as possible analogs for purported Martian nanofossils in the Martian meteorite ALH84001

    NASA Astrophysics Data System (ADS)

    Thomas-Keprta, Kathie L.; Wentworth, Susan J.; McKay, David S.; Stevens, Todd O.; Golden, D. C.; Allen, Carlton C.; Gibson, E. K.

    1997-03-01

    Basalts from the Columbia River (CRB) are studied in order to examine the igneous rock types similar to the main lithology of ALH84001. High resolution SEM and TEM are used to examine Columbia River surfaces for microorganisms in situ and those extracted from the basalt surface. Philips XL 40 field emission gun SEM microscope observations show the presence of small, nanometer-scale coccoid (spheroidal) bacteria on DC-06 and DB-11. It is suggested that these forms may be nanobacteria or appendages of bacteria from CRB samples. Another possibility is that they may be dwarf bacteria.

  2. [Pros and cons for Martian life: scientific debate on ALH84001].

    PubMed

    Yamashita, M

    1997-03-01

    Scientific debate related to possible martian life is summarized in this article. Even there is no firm conclusion yet to convince the existence of life on Mars, intensive studies on the meteorite ALH84001 have invoked many valuable findings. PMID:11540351

  3. Petrography and bulk chemistry of Martian orthopyroxenite ALH84001: implications for the origin of secondary carbonates.

    PubMed

    Gleason, J D; Kring, D A; Hill, D H; Boynton, W V

    1997-08-01

    New petrologic and bulk geochemical data for the SNC-related (Martian) meteorite ALH84001 suggest a relatively simple igneous history overprinted by complex shock and hydrothermal processes. ALH84001 is an igneous orthopyroxene cumulate containing penetrative shock deformation textures and a few percent secondary extraterrestrial carbonates. Rare earth element (REE) patterns for several splits of the meteorite reveal substantial heterogeneity in REE abundances and significant fractionation of the REEs between crushed and uncrushed domains within the meteorite. Complex zoning in carbonates indicates nonequilibrium processes were involved in their formation, suggesting that CO2-rich fluids of variable composition infiltrated the rock while on Mars. We interpret petrographic textures to be consistent with an inorganic origin for the carbonate involving dissolution-replacement reactions between CO2-charged fluids and feldspathic glass in the meteorite. Carbonate formation clearly postdated processes that last redistributed the REE in the meteorite. PMID:11540477

  4. Elongated prismatic magnetite crystals in ALH84001 carbonate globules: potential Martian magnetofossils.

    PubMed

    Thomas-Keprta, K L; Bazylinski, D A; Kirschvink, J L; Clemett, S J; McKay, D S; Wentworth, S J; Vali, H; Gibson, E K; Romanek, C S

    2000-12-01

    Using transmission electron microscopy (TEM), we have analyzed magnetite (Fe3O4) crystals acid-extracted from carbonate globules in Martian meteorite ALH84001. We studied 594 magnetites from ALH84001 and grouped them into three populations on the basis of morphology: 389 were irregularly shaped, 164 were elongated prisms, and 41 were whisker-like. As a possible terrestrial analog for the ALH84001 elongated prisms, we compared these magnetites with those produced by the terrestrial magnetotactic bacteria strain MV-1. By TEM again, we examined 206 magnetites recovered from strain MV-1 cells. Natural (Darwinian) selection in terrestrial magnetotactic bacteria appears to have resulted in the formation of intracellular magnetite crystals having the physical and chemical properties that optimize their magnetic moment. In this study, we describe six properties of magnetite produced by biologically controlled mechanisms (e.g., magnetotactic bacteria), properties that, collectively, are not observed in any known population of inorganic magnetites. These criteria can be used to distinguish one of the modes of origin for magnetites from samples with complex or unknown histories. Of the ALH84001 magnetites that we have examined, the elongated prismatic magnetite particles (similar to 27% of the total) are indistinguishable from the MV-1 magnetites in five of these six characteristics observed for biogenically controlled mineralization of magnetite crystals. PMID:11543573

  5. High-Temperature Mars-to-Earth Transfer of Meteorite ALH84001

    NASA Astrophysics Data System (ADS)

    Min, K.; Reiners, P. W.

    2006-12-01

    Mars is thought to have experienced intense volcanism, impact cratering and fluvial resurfacing during its first ~1.5 Byr, followed by a less-energetic, colder period. Rare meteoritic samples of the Martian crust provide some of the only direct evidence by which to test and develop models of the paleoenvironmental evolution of the planet, its potential habitability by life, and the process of interplanetary mass transport. Thermal histories of Martian meteorites provide crucial evidence bearing not only on long-term, ambient near-surface conditions on Mars, but also on whether meteoroids can be ejected from their large parent bodies without significant heating, a favorable condition for exogenesis (including panspermia) hypotheses. One of the best samples to address these issues is Martian meteorite ALH84001, because it has the oldest crystallization age of ~4.5 Ga, is thought to have resided near the surface since ~4.0 Ga, and has been suggested to have experienced no significant heating during or after its ejection from Mars at 15 Ma. To better constrain the thermal evolution and shock metamorphic history of ALH84001, we applied (U-Th)/He thermochronometry to single grains of merrillite and chlorapatite from ALH84001. The (U-Th)/He ages of individual phosphate grains in ALH84001 range from 60 Ma to 1.8 Ga, with a weighted mean of ~830 Ma. This broad age distribution reflects multiple diffusion domains, and requires a relatively high-temperature resetting event younger than ~60 Ma. These new data are combined with the published whole-rock (maskelynite as a main Ar reservoir) 40Ar/39Ar age spectra which show 5-8 % fractional loss of 40Ar since 4.0 Ga. He diffusion in both terrestrial and extraterrestrial apatite has a significantly higher activation energy (138 ~ 184 kJ/mol) than Ar diffusion in maskelynite (75 kJ/mol), leading to an important "kinetic crossover" in fractional loss contours for these systems. Taken together, the phosphate (U-Th)/He and maskelynite

  6. High Calcium (~80mol%) Late Stage Carbonate in ALH84001

    NASA Astrophysics Data System (ADS)

    Gildea, K. J.; Holland, G.; Lyon, I. C.; Chatzitheodoridis, E.; Burgess, R.

    2006-03-01

    Brief petrological, chemical and textural description of previously undescribed high Ca late stage carbonate in Martian meteorite ALH84001. This carbonate surrounds Mg rich carbonates and rosette fragments.

  7. Petrologic evidence for low-temperature, possibly flood evaporitic origin of carbonates in the ALH84001 meteorite.

    PubMed

    Warren, P H

    1998-07-25

    High-temperature models for origin of the carbonates in Martian meteorite ALH84001 are implausible. The impact metasomatism model, invoking reaction between CO2 rich fluid and the host orthopyroxenite, requires conversion of olivine into orthopyroxene, yet olivine in ALH84001 shows no depletion in carbonate-rich areas; or else conversion of orthopyroxene into silica, which should have yielded a higher silica/carbonate ratio. The impact melt model implies that the fracture-linked carbonates, as products of melt injection, should appear as continuous planar veins, but in many areas they do not. Both vapor deposition and impact melting seem inconsistent with the zoned poikilotopic texture of many large carbonates. The popular hydrothermal model is inconsistent with the virtual absence of secondary hydrated silicates in ALH84001. Prior brecciation should have facilitated alteration. Hydrothermal fluids would be warm, and rate of hydration of mafic silicates obeys an Arrhenius law, at least up to approximately 100 degrees C. Most important, hydrothermal episodes tend to last for many years. Many areas of the ancient Martian crust show evidence for massive flooding. I propose that the carbonates formed as evaporite deposits from floodwaters that percolated through the fractures of ALH84001, but only briefly, as evaporation and groundwater flow caused the water table to quickly recede beneath the level of this rock during the later stages of the flood episode. The setting might have been a layer of megaregolith beneath a surface catchment of pooled floodwater, analogous to a playa lake. Carbonate precipitation would occur in response to evaporative concentration of the water. To explain the scarcity of sulfates in ALH84001, the water table must be assumed to recede quickly relative to the rate of evaporation. During the period when ALH84001 was above the water table, evaporation would have slowed, as the evaporation front passed beneath the surface of the debris layer

  8. Record of fluid-rock interactions on Mars from the meteorite ALH84001.

    PubMed

    Romanek, C S; Grady, M M; Wright, I P; Mittlefehldt, D W; Socki, R A; Pillinger, C T; Gibson, E K

    1994-12-15

    Allan Hills (ALH) 84001 is the most recently recognized member of a suite of meteorites--the SNCs--that almost certainly originated on Mars. Several factors distinguish ALH84001 from the other SNC meteorites. Preliminary studies suggest that it may be older than other martian meteorites. Moreover, it contains abundant, zoned domains of calcium-iron-magnesium carbonate that are indigenous to the sample and thus may hold important clues regarding near-surface processes on Mars and the evolution of the martian atmosphere. We report here analyses of the carbon and oxygen stable-isotope compositions of the carbonates that place constraints on their formation conditions. Our results imply the presence of at least two chemically distinct carbonates--one Ca,Fe-rich, the other Mg-rich--that are enriched in 13C relative to terrestrial carbonates (delta 13C approximately +41/1000), consistent with martian atmospheric CO2 as the carbon source. The oxygen isotope compositions of the carbonates indicate that they precipitated from a low-temperature fluid in the martian crust. Combined with textural and bulk geochemical considerations, the isotope data suggest that carbonate deposition took place in an open-system environment in which the ambient temperature fluctuated. PMID:7990956

  9. The Carbonates in ALH 84001 Record the Evolution of the Martian Atmosphere Through Multiple Formation Events

    NASA Technical Reports Server (NTRS)

    Shaheen, R.; Niles, P. B.; Corrgan, C.

    2012-01-01

    Current Martian conditions restrict the presence of liquid water due to low temperatures (approx 210K), a thin atmosphere (approx 7mb), and intense UV radiation. However, past conditions on Mars may have been different with the possibility that the ancient Martian climate was warm and wet with a dense CO2 atmosphere. The cycling of carbon on Mars through atmospheric CO2 and carbonate minerals is critical for deciphering its climate history. In particular stable isotopes contained in carbonates can provide information of their origin and formation environment as well as possibly hinting at the composition of global reservoirs such as atmospheric CO2. Martian meteorite ALH 84001 contains widely studied carbonate rosettes that have been dated to approx. 3.9 Ga and have been used to interpret climatic conditions present at that time. However, there is mount-ing evidence for multiple episodes of carbonate formation in ALH 84001 with potentially distinct isotopic compositions. This study seeks to tease out these different carbonate assemblages using stepped phosphoric acid dissolution and analysis of carbon and triple oxygen stable isotopes. In addition, we report SIMS analyses of the delta O-18 several petrographically unusual carbonate phases in the meteorite.

  10. Spectral analysis of ALH 84001, a meteorite from Mars

    NASA Astrophysics Data System (ADS)

    Bishop, J.; Pieters, C.; Mustard, J.; Pratt, S.; Hiroi, T.

    1994-07-01

    ALH 84001 has recently been reclassified as a meteorite from Mars (SNC) and contains more than 90% orthopyroxene with minor chromite and accessory phases of augite, maskelynite, and carbonate. This meteorite represents a new class of igneous material from Mars. We have measured reflectance spectra of ALH 84001 as a chip as a powder, dry sieved to less than 125 microns to compare with previous spectral analyses of SNCs and remote observations of Mars. Spectra of the chip and powder in the visible-to-near-infrared region are shown. These spectra are composites of data measured with the RELAB bidirectional spectrometer from 0.3 to 2.55 microns and a Nicolet FTIR for longer wavelengths. As expected, the spectra of the chip have negative slopes and are significantly darker than the spectrum of the particulate sample, which has a positive slope. The strong absorptions near 1 micron and 2 microns are characteristic of low-Ca pyroxene and have band rninima of 0.925 microns and 1.930 microns. The strong absorption near 3 microns is characteristic of water. There is a distinct flattening in the spectrum between 1.0 and 1.5 microns indicating the presence of an additional absorption. This is interpreted to be the result of Fe(2+) in the M1 site of low-Ca pyroxene. Mid-infrared spectra showing the Christiansen feature and the reststrahlen bands are shown for spectra of the powder and of three different locations on the chip. These spectra exhibit several features in this range, some of which are associated with a specific region on the chip. Each of the spectra includes a doublet reststrahlen peak near 1100/cm, and peaks near 880 and 500/cm, which are typical for low-Ca pyroxenes. Weaker features at 940-1000/cm, 600-750/cm, and 530-560/cm are present in spectra from some locations on the chip, but not others, implying compositional and textural variation.

  11. Carbonate formation events in ALH 84001 trace the evolution of the Martian atmosphere

    PubMed Central

    Shaheen, Robina; Niles, Paul B.; Chong, Kenneth; Corrigan, Catherine M.; Thiemens, Mark H.

    2015-01-01

    Carbonate minerals provide critical information for defining atmosphere–hydrosphere interactions. Carbonate minerals in the Martian meteorite ALH 84001 have been dated to ∼3.9 Ga, and both C and O-triple isotopes can be used to decipher the planet’s climate history. Here we report Δ17O, δ18O, and δ13C data of ALH 84001 of at least two varieties of carbonates, using a stepped acid dissolution technique paired with ion microprobe analyses to specifically target carbonates from distinct formation events and constrain the Martian atmosphere–hydrosphere–geosphere interactions and surficial aqueous alterations. These results indicate the presence of a Ca-rich carbonate phase enriched in 18O that formed sometime after the primary aqueous event at 3.9 Ga. The phases showed excess 17O (0.7‰) that captured the atmosphere–regolith chemical reservoir transfer, as well as CO2, O3, and H2O isotopic interactions at the time of formation of each specific carbonate. The carbon isotopes preserved in the Ca-rich carbonate phase indicate that the Noachian atmosphere of Mars was substantially depleted in 13C compared with the modern atmosphere. PMID:25535348

  12. Carbonate formation events in ALH 84001 trace the evolution of the Martian atmosphere.

    PubMed

    Shaheen, Robina; Niles, Paul B; Chong, Kenneth; Corrigan, Catherine M; Thiemens, Mark H

    2015-01-13

    Carbonate minerals provide critical information for defining atmosphere-hydrosphere interactions. Carbonate minerals in the Martian meteorite ALH 84001 have been dated to ∼ 3.9 Ga, and both C and O-triple isotopes can be used to decipher the planet's climate history. Here we report Δ(17)O, δ(18)O, and δ(13)C data of ALH 84001 of at least two varieties of carbonates, using a stepped acid dissolution technique paired with ion microprobe analyses to specifically target carbonates from distinct formation events and constrain the Martian atmosphere-hydrosphere-geosphere interactions and surficial aqueous alterations. These results indicate the presence of a Ca-rich carbonate phase enriched in (18)O that formed sometime after the primary aqueous event at 3.9 Ga. The phases showed excess (17)O (0.7‰) that captured the atmosphere-regolith chemical reservoir transfer, as well as CO2, O3, and H2O isotopic interactions at the time of formation of each specific carbonate. The carbon isotopes preserved in the Ca-rich carbonate phase indicate that the Noachian atmosphere of Mars was substantially depleted in (13)C compared with the modern atmosphere. PMID:25535348

  13. Martian carbonates in ALH 84001: Textural, elemental, and stable isotopic compositional evidence on their formation. [Abstract only

    NASA Technical Reports Server (NTRS)

    Romanek, C. S.; Mittlefehldt, D. W.; Gibson, E. K., Jr.; Socki, R. A.

    1994-01-01

    Martian orthopyroxenite ALH 84001 is unusual compared to other martian meteorites in its abundance of Mg-Fe-Ca carbonites. Becasue textural evidence indicates that these carbonates are undoubtedly of martian origin, we have undertaken stable isotopic studies to elucidate their origin by evaluating whether they represent primordial martian C that was outgassing from the mantle of Mars, or volatile additions to the ALH 84001 protolith that equilibrated with the martian atmosphere. If precipitation occurred in a closed system then the isotopic results are compatible with the observed chemical zonation. A unique temperature of formation can be calculated using the difference in C-13 and O-18 between the Fe and Mg carbonates, assuming that precipitation occurred at a constant temperature. Precipitation of approximately one-half of the CO2 reservoir at 320 C can account for the observed values, with the original CO2 reservoir having a delta C-13 of approximately 45% and delta O-18 of approximately 22%. If carbonate precipitated in equilibrium with a large isotopically homogeneous CO2 reservoir (open system), isotopic differences must be attributed to a change in temperature of at least several hundreds of degrees. This temperature change is compatible with a calculated range of temperatures based on carbonate geothermometry. Clearly, carbonate in ALH 84001 is in delta O-18 disequilibrium with orthopyroxene groundmass. Most likely, the carbonate precipitated from a fluid that equilibrated with the martian atmosphere. The deposits or fluids in equilibrium with these deposits were remobilized in the crust producing the carbonate in ALH 84001. This observation establishes a link for the first time between the atmospheric and lithospheric C and O pools that reside on Mars.

  14. Formation of "Chemically Pure" Magnetite from Mg-Fe-Carbontes: Implications for Exclusively Inorganic Origin of Magnetite and Sulfides in Martian Meteorite ALH84001

    NASA Astrophysics Data System (ADS)

    Golden, D. C.; Ming, D. W.; Lauer, H. V., Jr.; Morris, R. V.; Treiman, A. H.; McKay, G. A.

    2006-03-01

    Pure (Mg-free) magnetite was synthesized by heating Mg-Fe-carbonate at 350°C in the presence of pyrite in an evacuated sealed glass tube. The Mg-free magnetite in the black rims of ALH84001 may have formed by a similar inorganic abiotic process from Mg-Fe-carbonates.

  15. Field Emission Gun Scanning Electron (FEGSEM) and Transmission Electron (TEM) Microscopy of Phyllosilicates in Martian Meteorites ALH84001, Nakhla, and Shergotty

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, Kathie L.; Wentworth, Susan J.; McKay, David S.; Gibson, Everett K.

    2000-01-01

    Here we document the occurrence of phyllosilicates and alteration phases in three martian meteorites, suggest formation conditions required for phyllosilicate formation and speculate on the extent of fluid:rock interactions during the past history of Mars.

  16. Pre-4.0 billion year weathering on Mars constrained by Rb-Sr geochronology on meteorite ALH84001

    NASA Astrophysics Data System (ADS)

    Beard, Brian L.; Ludois, James M.; Lapen, Thomas J.; Johnson, Clark M.

    2013-01-01

    The timing and nature of aqueous alteration of meteorite ALH84001 has important implications for the history of water on early Mars, the evolution of the Martian atmosphere, and the potential for early Mars habitability. Rubidium-Sr isotope analyses of mineral separates from igneous-textured and carbonate-rich aliquots of Martian meteorite ALH84001 constrain the age of alteration and the source of fluids. The carbonate-rich aliquot defines a precise Rb-Sr isochron between maskelynite, orthopyroxene, and chromite of 3952±22 Ma, and this is interpreted to represent a shock resetting event that was broadly coeval with carbonate precipitation. Carbonate, bulk rock, and multi-mineral separates all have high 87Sr/86Sr ratios that can only have been produced by alteration via a fluid derived through interaction with high Rb/Sr phyllosilicates that were produced prior to 3950 Ma. These data confirm that the source of Sr in the fluids was previously altered crustal rock, consistent with fluids that underwent low-temperature water-rock interaction (Eiler et al., 2002; Halvey et al., 2011). These results therefore provide evidence for wet, clay-rich conditions on the surface of Mars prior to ˜4.2 Ga.

  17. Spectral analysis of ALH 84001, a meteorite from Mars. [Abstract only

    NASA Technical Reports Server (NTRS)

    Bishop, J.; Pieters, C.; Mustard, J.; Pratt, S.; Hiroi, T.

    1994-01-01

    ALH 84001 has recently been reclassified as a meteorite from Mars (SNC) and contains more than 90% orthopyroxene with minor chromite and accessory phases of augite, maskelynite, and carbonate. This meteorite represents a new class of igneous material from Mars. We have measured reflectance spectra of ALH 84001 as a chip as a powder, dry sieved to less than 125 microns to compare with previous spectral analyses of SNCs and remote observations of Mars. Spectra of the chip and powder in the visible-to-near-infrared region are shown. These spectra are composites of data measured with the RELAB bidirectional spectrometer from 0.3 to 2.55 microns and a Nicolet FTIR for longer wavelengths. As expected, the spectra of the chip have negative slopes and are significantly darker than the spectrum of the particulate sample, which has a positive slope. The strong absorptions near 1 micron and 2 microns are characteristic of low-Ca pyroxene and have band rninima of 0.925 microns and 1.930 microns. The strong absorption near 3 microns is characteristic of water. There is a distinct flattening in the spectrum between 1.0 and 1.5 microns indicating the presence of an additional absorption. This is interpreted to be the result of Fe(2+) in the M1 site of low-Ca pyroxene. Mid-infrared spectra showing the Christiansen feature and the reststrahlen bands are shown for spectra of the powder and of three different locations on the chip. These spectra exhibit several features in this range, some of which are associated with a specific region on the chip. Each of the spectra includes a doublet reststrahlen peak near 1100/cm, and peaks near 880 and 500/cm, which are typical for low-Ca pyroxenes. Weaker features at 940-1000/cm, 600-750/cm, and 530-560/cm are present in spectra from some locations on the chip, but not others, implying compositional and textural variation.

  18. ALH84001: The Key to Unlocking Secrets About Mars-15 Years and Counting

    NASA Technical Reports Server (NTRS)

    Gibson, Everett K.; McKay, D. S.; Thomas-Keprta, K. L.; Clemett, S. J.

    2011-01-01

    From the December 27, 1984 discovery of ALH84001, and its subsequent identification as a sample of Mars in 1993, mystery and debate has surrounded the meteorite [1]. With the realization that the ALH84001 sample was a orthopyroxenite and one of the oldest SNC meteorites (approx.4.09 Ga) [2] available to study, important and critical information about the Martian hydrosphere and atmosphere along with the early history and evolution of the planet could be obtained by studying the unique carbonate globules (approx.3.9 Ga) in the sample [3]. The initial work showed the carbonate globules were deposited within fractures and cracks in the host-orthopyroxene by low-temperature aqueous fluids [4]. Ideas that the carbonates were formed at temperatures [5] approaching 800 C were ruled out by later experiments [6]. The 1996 announcement by McKay et al. [7] that ALH84001 contained features which could be interpreted as having a biogenic origin generated considerable excitement and criticism. The NASA Administrator Dan Golden said the 1996 ALH84001 announcement saved NASAs Mars planetary exploration program and injected $6 billion dollars over five years into the scientific research and analysis efforts [8]. All of the original four lines of evidence for possible biogenic features within ALH84001 offered by McKay et al. have withstood the test of time. Criticism has been directed at the interpretation of the 1996 analytical data. Research has expanded to other SNC meteorites. Despite the numerous attacks on the ideas, the debate continues after 15 years. The 2009 paper by Thomas-Keprta et al. [9] on the origins of a suite of magnetites within the ALH84001 has offered strong arguments that some of the magnetites can only be formed by biogenic processes and not from thermal decomposition or shock events which happened to the meteorite. NASA s Astrobiology Institute was formed from the foundation laid by the ALH84001 hypothesis of finding life beyond the Earth. The strong

  19. Search for Unique Organic Biomarkers in ALH84001

    NASA Technical Reports Server (NTRS)

    Zare, Richard N.

    1999-01-01

    Four goals were outlined for this project. These were: [1] to reproduce the measurement of polycyclic aromatic hydrocarbons (PAHS) in ALH84001 with both a higher spatial resolution and sensitivity than has been previously reported; [2] to extend such measurements to include other members of the Martian SNC (Shergotties, Nahklites, and Chassigny) meteorite clan, in particular the Antarctic Martian meteorite EETA79001; [3] to address issues of potential organic contamination, because at present very little is known about the effect of terrestrial weathering in the Antarctic environment as it pertains to perturbing an indigenous organic distribution within a meteoritic matrix; and [4] to diversify the range of organic compounds studied to include species that can serve as unique biological markers - "molecular fossils" - derived from once living organisms. In order to achieve this, three specific goals were outlined for the funding period 06/01/97 to 02/28/98. They were: [1] to investigate the effects of terrestrial weathering and organic contamination of meteoritic samples collected from Antarctica; [2] to reproduce and extend upon the measurements of PAHs in ALH84001 with the aim of establishing or refuting the indigeneity of these species; and [3] to extend the analysis of organic compounds in ALH84001 and EETA79001 to address compounds that are considered to be more biologically relevant than PAHS. All three were successfully accomplished, as detailed in the previous performance report. In brief, however, the results achieved were to establish that the PAHs found in ALH84001 were indigenous and not due to contamination, and to determine that a novel and sensitive technique in meteoritic work, capillary zone electrophoresis (CE), could indeed detect amino acids, a potential class of biomarker.

  20. Chains of magnetite crystals in the meteorite ALH84001: evidence of biological origin.

    PubMed

    Friedmann, E I; Wierzchos, J; Ascaso, C; Winklhofer, M

    2001-02-27

    The presence of magnetite crystal chains, considered missing evidence for the biological origin of magnetite in ALH84001 [Thomas-Keprta, K. L., Bazylinski, D. A., Kirschvink, J. L., Clemett, S. J., McKay, D. S., Wentworth, S. J., Vali, H., Gibson, E. K., Jr., & Romanek, C. S. (2000) Geochim. Cosmochim. Acta 64, 4049-4081], is demonstrated by high-power stereo backscattered scanning electron microscopy. Five characteristics of such chains (uniform crystal size and shape within chains, gaps between crystals, orientation of elongated crystals along the chain axis, flexibility of chains, and a halo that is a possible remnant of a membrane around chains), observed or inferred to be present in magnetotactic bacteria but incompatible with a nonbiological origin, are shown to be present. Although it is unlikely that magnetotactic bacteria were ever alive in ALH84001, decomposed remains of such organisms could have been deposited in cracks in the rock while it was still on the surface on Mars. PMID:11226212

  1. Chains of magnetite crystals in the meteorite ALH84001: Evidence of biological origin

    PubMed Central

    Friedmann, E. Imre; Wierzchos, Jacek; Ascaso, Carmen; Winklhofer, Michael

    2001-01-01

    The presence of magnetite crystal chains, considered missing evidence for the biological origin of magnetite in ALH84001 [Thomas-Keprta, K. L., Bazylinski, D. A., Kirschvink, J. L., Clemett, S. J., McKay, D. S., Wentworth, S. J., Vali, H., Gibson, E. K., Jr., & Romanek, C. S. (2000) Geochim. Cosmochim. Acta 64, 4049–4081], is demonstrated by high-power stereo backscattered scanning electron microscopy. Five characteristics of such chains (uniform crystal size and shape within chains, gaps between crystals, orientation of elongated crystals along the chain axis, flexibility of chains, and a halo that is a possible remnant of a membrane around chains), observed or inferred to be present in magnetotactic bacteria but incompatible with a nonbiological origin, are shown to be present. Although it is unlikely that magnetotactic bacteria were ever alive in ALH84001, decomposed remains of such organisms could have been deposited in cracks in the rock while it was still on the surface on Mars. PMID:11226212

  2. Modeling the Chemical Composition of the Fluid that Formed the ALH84001 Carbonates

    NASA Astrophysics Data System (ADS)

    Niles, P. B.; Leshin, L.

    2005-12-01

    The character of aqueous systems on Mars can provide us with important information regarding the history of water and the possibilities for the presence of life on Mars. Evidence of these aqueous systems has been preserved in carbonates found in the martian meteorite ALH84001 whose crystallization age of 4.5 Ga indicates that it has experienced almost all of Mars' history. In addition, the 3.9 Ga age of the carbonates places their formation at a critical time that has been argued to have been `warm and wet' by many studies. The carbonates in the ALH84001 meteorite provide the best opportunity, among all of the martian meteorites, to understand the details of an ancient aqueous system on Mars. Their unique chemical, isotopic and mineralogical composition provides the opportunity to make conclusive statements about the geological conditions in which they formed including the temperature, association with the atmosphere, chemistry of the fluids, and the presence or absence of life. This study uses an empirical model to understand the attributes of the formation fluid based on the unique chemical compositions of the carbonates. This requires the assumption that the ALH84001 carbonate globules formed from a single fluid whose chemical composition changed due to the precipitation of carbonates more calcium rich than the overall fluid composition. The model consists of a simple stepwise stoichiometric calculation of the precipitation of the ALH84001 carbonates from a hypothetical solution. From extensive measurements of the chemical composition of the globules and their abundance in the rock, one can calculate the total amount of magnesium, calcium, and iron removed from the formation fluid as the carbonates precipitated. The unique zoned nature of the ALH84001 carbonates provides a real constraint on the possible fluid compositions consistent with their precipitation. Our results indicate that the fluid that formed the ALH84001 carbonates had an Mg/Ca ratio that was

  3. Leachates formed carbonates in ALH84001 and on early Mars

    NASA Astrophysics Data System (ADS)

    Melwani Daswani, M.; Grady, M. M.; Schwenzer, S. P.; Wright, I. P.

    2013-09-01

    Evidence abounds for liquid water existing on Mars prior to the late heavy bombardment (LHB) ~3.9 Ga ago and physicochemically interacting with rocks to form distinct geomorphological landforms and mineralogical alteration products (e.g. [3, 4, 8, 14]). ALH84001, the oldest (~4.5-4.1 Ga [11, 13]) known martian meteorite, contains secondary carbonate minerals formed on Mars ~3.9-4.0 Ga ago [5], roughly contemporaneous to the LHB. Recent isotopic evidence supports their formation at low temperature (~18 °C [9]) and also by fluids derived from aqueous weathering in the Noachian/Phyllosian, due to the elevated 87Sr/86Sr ratios in the carbonates and bulk rock of ALH84001 [1].

  4. Amino Acids in the Antarctic Martian Meteorite MIL03346

    NASA Technical Reports Server (NTRS)

    Glavin, D. P.; Aubrey, A.; Dworkin, J. P.; Botta, O.; Bada, J. L.

    2005-01-01

    The report by McKay et al. that the Martian meteorite ALH84001 contains evidence for life on Mars remains controversial. Of central importance is whether ALH84001 and other Antarctic Martian meteorites contain endogenous organic compounds. In any investigation of organic compounds possibly derived from Mars it is important to focus on compounds that play an essential role in biochemistry as we know it and that have properties such as chirality which can be used to distinguish between biotic versus abiotic origins. Amino acids are one of the few compounds that fulfill these requirements. Previous analyses of the Antarctic Martian meteorites ALH84001 and EETA79001 have shown that these meteorites contain low levels of terrestrial amino acid contamination derived from Antarctic ice meltwater. Here we report preliminary amino acid investigations of a third Antarctic Martian meteorite MIL03346 which was discovered in Antarctica during the 2003-04 ANSMET season. Additional information is included in the original extended abstract

  5. The Pb isotopic evolution of the Martian mantle constrained by initial Pb in Martian meteorites

    NASA Astrophysics Data System (ADS)

    Bellucci, J. J.; Nemchin, A. A.; Whitehouse, M. J.; Snape, J. F.; Bland, P.; Benedix, G. K.

    2015-12-01

    The Pb isotopic compositions of maskelynite and pyroxene grains were measured in ALH84001 and three enriched shergottites (Zagami, Roberts Massif 04262, and Larkman Nunatuk 12011) by secondary ion mass spectrometry. A maskelynite-pyroxene isochron for ALH84001 defines a crystallization age of 4089 ± 73 Ma (2σ). The initial Pb isotopic composition of each meteorite was measured in multiple maskelynite grains. ALH84001 has the least radiogenic initial Pb isotopic composition of any Martian meteorite measured to date (i.e., 206Pb/204Pb = 10.07 ± 0.17, 2σ). Assuming an age of reservoir formation for ALH84001 and the enriched shergottites of 4513 Ma, a two-stage Pb isotopic model has been constructed. This model links ALH84001 and the enriched shergottites by their similar μ value (238U/204Pb) of 4.1-4.6 from 4.51 Ga to 4.1 Ga and 0.17 Ga, respectively. The model employed here is dependent on a chondritic μ value (~1.2) from 4567 to 4513 Ma, which implies that core segregation had little to no effect on the μ value(s) of the Martian mantle. The proposed Pb isotopic model here can be used to calculate ages that are in agreement with Rb-Sr, Lu-Hf, and Sm-Nd ages previously determined in the meteorites and confirm the young (~170 Ma) ages of the enriched shergottites and ancient, >4 Ga, age of ALH84001.

  6. Sulfide isotopic compositions in shergottites and ALH84001, and possible implications for life on Mars

    SciTech Connect

    Greenwood, J.P.; McSween, H.Y. Jr.; Riciputi, L.R.

    1997-10-01

    The shergottite and ALH84001 meteorites hold keys for understanding geologic and possibly biologic processes on Mars. Recently, it has been proposed that carbonates in ALH84001, and the Fe-sulfides they contain, are products of extraterrestrial biogenic activity. Here we report ion microprobe analyses of sulfides in shergottites and ALH84001. The sulfur isotope ratios of igneous pyrrhotites in shergottites (mean {delta}{sup 34}S{sub CDT}: Shergotty = -0.4{per_thousand}, Zagami = +2.7{per_thousand}, EETA79001A = 1.9{per_thousand}, EETA79001B = -1.7{per_thousand}, LEW88516 = -1.9{per_thousand}, QUE94201 = +0.8{per_thousand}) are similar to those of terrestrial ocean-floor basalts, suggesting that the sulfur isotopic composition of the Martian mantle may be similar to that of the mantle of the Earth. The sulfur isotopic systematics of ALH84001 sulfides are distinct from the shergottites. Measured sulfur isotope ratios of eight pyrite grains ({delta}{sup 34}S{sub CDT} = +2.0 to +7.3{per_thousand}) in crushed zones confirm previously reported analyses of isotopically heavy sulfides and are indistinguishable from an Fe-sulfide zone within a carbonate globule ({delta}{sup 34}S{sub CDT} = +6.0{per_thousand}). Analyses of synthesized, fine-grained mixtures of sulfide, carbonate, and magnetite indicate than the measured sulfur isotope ratio is independent of the presence of carbonate and magnetite in the sputtered volume, confirming the accuracy of the analysis of the fine-grained sulfide in the carbonate globule. Terrestrial biogenic sulfate reduction typically results in light isotopic enrichments. The similarity of {delta}{sup 34}S values of the sulfides in ALH84001 imply that the Fe-sulfide zones within ALH84001 carbonates are probably not the result of bacterial reduction of sulfate. 38 refs., 3 figs., 1 tab.

  7. No `nanofossils' in martian meteorite

    NASA Astrophysics Data System (ADS)

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

    1997-12-01

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

  8. ALH84001: The Key to Unlocking Secrets About Mars-15 Years and Counting

    NASA Technical Reports Server (NTRS)

    Gibson, Everett K.

    2011-01-01

    From the December 27, 1984 discovery of ALH84001, and its subsequent identification as a sample of Mars in 1993, mystery and debate has surrounded the meteorite. With the realization that the ALH84001 sample was a orthopyroxenite and one of the oldest SNC meteorites (4.09 Ga) available to study, important and critical information about the Martian hydrosphere and atmosphere along with the early history and evolution of the planet could be obtained by studying the unique carbonate globules (3.9 Ga) in the sample. The initial work showed the carbonate globules were deposited within fractures and cracks in the host-orthopyroxene by low-temperature aqueous fluids. Ideas that the carbonates were formed at temperatures approaching 800oC were ruled out by later experiments. The 1996 announcement by McKay et al. that ALH84001 contained features which could be interpreted as having a biogenic origin generated considerable excitement and criticism. The NASA Administrator Dan Golden said the 1996 ALH84001 announcement saved NASA s Mars planetary exploration program and injected $6 billion dollars over five years into the scientific research and analysis efforts. All of the original four lines of evidence for possible biogenic features within ALH84001 offered by McKay et al. have withstood the test of time. Criticism has been directed at the interpretation of the 1996 analytical data. Research has expanded to other SNC meteorites. Despite the numerous attacks on the ideas, the debate continues after 15 years. The 2009 paper by Thomas-Keprta et al. on the origins of a suite of magnetites within the ALH84001 has offered strong arguments that some of the magnetites can only be formed by biogenic processes and not from thermal decomposition or shock events which happened to the meteorite. NASA s Astrobiology Institute was formed from the foundation laid by the ALH84001 hypothesis of finding life beyond the Earth. The strong astrobiology outreach programs have expanded because of

  9. Structural and morphological anomalies in magnetosomes: possible biogenic origin for magnetite in ALH84001.

    PubMed

    Taylor, A P; Barry, J C; Webb, R I

    2001-01-01

    We report biogenic magnetite whiskers, with axial ratios of 6 : 1, elongated in the [1 1 1], [1 1 2] and [1 0 0] directions, resembling the magnetite whiskers detected in the Martian meteorite ALH84001 by Bradley et al., and interpreted by those authors as evidence of vapour-phase (abiogenic) growth. Magnetosomal whiskers with extended defects consistent with screw dislocations and magnetosomes resembling flattened twinned platelets, as well as other twinning phenomena and other structural defects, are also reported here. Magnetosomes with teardrop-shaped, cuboidal, irregular and jagged structures similar to those detected in ALH84001 by McKay et al., coprecipitation of magnetite possibly with amorphous calcium carbonate, coprecipitation of magnetite possibly with amorphous silica, the incorporation of titanium in volutin inclusions and disoriented arrays of magnetosomes are also described. These observations demonstrate that the structures of the magnetite particles in ALH84001, their spatial arrangement and coprecipitation with carbonates and proximity to silicates are consistent with being biogenic. Electron-beam-induced flash-melting of magnetosomes produced numerous screw dislocations in the [1 1 1], [1 0 0], and [1 1 0] lattice planes and induced fusion of platelets. From this, the lack of screw dislocations reported in the magnetite particles in ALH84001 (McKay et al., and Bradley et al.) indicates that they have a low-temperature origin. PMID:11136443

  10. LU-HF Age and Isotope Systematics of ALH84001

    NASA Technical Reports Server (NTRS)

    Righter, M.; Lapen, T. J.; Brandon, A. D.; Beard, B. L.; Shafer, J. T.; Peslier, A. H.

    2009-01-01

    Allan Hills (ALH) 84001 is an orthopyroxenite that is unique among the Martian meteorites in having the oldest inferred crystallization age (approx..4.5 to 4.0 Gyr) [e.g., 1-6 and references therein 7]. Its ancient origin makes this stone a critical constraint on early history of Mars, in particular the evolution of different planetary crust and mantle reservoirs. However, because there is significant variability in reported crystallization ages, determination of initial isotope compositions is imprecise making assessment of planetary reservoirs difficult. Here we report a new Lu-Hf mineral isochron age, initial Hf-176/Hf-177 isotope composition, and inferred Martian mantle source compositions for ALH84001 that place constraints on longlived source reservoirs for the enriched shergottite suite of Martian meteorites including Shergotty, Zagami, NWA4468, NWA856, RBT04262, LAR06319, and Los Angeles. Sm-Nd isotope analyses are under way for the same mineral aliquots analyzed for Lu-Hf. The Lu-Hf system was utilized because Lu and Hf are both lithophile and refractory and are not easily redistributed during short-lived thermal pulses associated with shock metamorphism. Moreover, chromite has relatively modest Hf concentrations with very low Lu/Hf ratios [9] yielding tight constraints on initial Hf-176/Hf-177 isotope compositions

  11. [Meteoritics and mineralogy on possible ancient Martian life].

    PubMed

    Tsuchiyama, A

    1996-12-01

    Possible relic biogenic activity in martian meteorite ALH84001 was proposed by McKay et al. (Science, 273, 924-930, 1996). This ancient meteorite of 4.5 billion years old contains abundant carbonates as secondary minerals precipitated from a fluid on the martian surface. They showed the following lines of evidence for the ancient life; (1) unique mineral compositions and biominerals, (2) polycyclic aromatic hydrocarbons (PAHs) in association with the carbonates, and (3) unique structures and morphologies typical of nanobacteria or microfossils. This review is divided into two parts; one is on the martian meteorites in general and ALH84001, which has many features unlike other martian meteorites, and the other is on mineralogical (biomineralogical) and geochemical features of the carbonates and microfossil-like structures. There is little doubt that ALH84001 is from Mars as well as eleven other SNC meteorites. However, the mineralogical and biomineralogical evidence for martian bacteria given by McKay et al. (1996) is controversial, and could be formed by non-biogenic processes. Thus, further study of ALH84001 and other martian meteorites is required. We also need to consider the future Mars mission especially sample return mission.

  12. [Meteoritics and mineralogy on possible ancient Martian life].

    PubMed

    Tsuchiyama, A

    1996-12-01

    Possible relic biogenic activity in martian meteorite ALH84001 was proposed by McKay et al. (Science, 273, 924-930, 1996). This ancient meteorite of 4.5 billion years old contains abundant carbonates as secondary minerals precipitated from a fluid on the martian surface. They showed the following lines of evidence for the ancient life; (1) unique mineral compositions and biominerals, (2) polycyclic aromatic hydrocarbons (PAHs) in association with the carbonates, and (3) unique structures and morphologies typical of nanobacteria or microfossils. This review is divided into two parts; one is on the martian meteorites in general and ALH84001, which has many features unlike other martian meteorites, and the other is on mineralogical (biomineralogical) and geochemical features of the carbonates and microfossil-like structures. There is little doubt that ALH84001 is from Mars as well as eleven other SNC meteorites. However, the mineralogical and biomineralogical evidence for martian bacteria given by McKay et al. (1996) is controversial, and could be formed by non-biogenic processes. Thus, further study of ALH84001 and other martian meteorites is required. We also need to consider the future Mars mission especially sample return mission. PMID:11540347

  13. Workshop on the Issue Martian Meteorites: Where do we Stand and Where are we Going?

    NASA Technical Reports Server (NTRS)

    1998-01-01

    The presentations in this workshop discuss the composition of Martian meteorites. Many of the talks were on a specific meteorite, i.e., Allan Hills 84001 (ALH84001). The discovery earlier of carbonates in ALH84001 lead some researchers to suggest that there was evidence of martian life. Other possible explanations for this phenomena are given. Other papers discuss methods to sterilize martian samples, the existence of water on Mars, the facilities of the Meteorite Processing Laboratory at Johnson Space Center, comparative analyses of geologic processes and the gathering of meteorites.

  14. Variable Carbon Isotopes in ALH84001 Carbonates

    NASA Astrophysics Data System (ADS)

    Niles, P. B.; Leshin, L. A.; Guan, Y.

    2002-12-01

    The Martian meteorite ALH84001 contains a small amount of carbonate that was deposited from aqueous fluids on the Martian surface approximately 3.9 Ga.. McKay et al. (1996) proposed evidence for the existence of life preserved within the carbonate grains. In order to determine the nature of the ancient Martian aqueous system we have combined previously collected oxygen isotopic data with new carbon isotopic measurements performed on the Cameca 6f ion microprobe at Arizona State University. Isotopic measurements were made at high mass resolution with a spot size of 10 microns. The measured carbon isotopic values range from 29.2‰ to 64.5‰ (PDB) with an average uncertainty of +/-1.6‰ (1σ ). These data agree very well with previous acid dissolution and stepped combustion experiments which range from a δ13C of +32‰ to +41‰ . As observed with the oxygen isotopic data, the carbon isotopic composition is correlated with the chemical composition of the carbonates. This allows us to establish that the earliest (Ca-rich) carbonates had the lightest carbon isotopic composition while the latest forming (Mg-rich) carbonates had the heaviest carbon isotopic composition. The large range of carbon isotopic compositions measured in this study cannot be explained by previously proposed models. Temperature change or a Rayleigh distillation process caused by progressive carbonate precipitation are insufficient to create the observed carbon isotopic compositions. Furthermore, processes such as evaporation or photosynthesis will not produce large carbon isotopic variations due to rapid isotopic equilibration with the atmosphere. We propose two possible models for the formation of the ALH84001 carbonates consistent with the isotopic data collected thus far. Carbonates could have formed from an evolving system where the carbon and oxygen isotopic composition of the carbonates reflects a mixing between magmatic hydrothermal fluids and fluids in equilibrium with an isotopically

  15. Martian Meteorite Ages and Implications for Martian Cratering History

    NASA Technical Reports Server (NTRS)

    Nyquist, Laurence E.

    2006-01-01

    New radiometrically determined ages of Martian meteorites add to the growing number with crystallization ages < 1.4 Ga. The observation of mainly geologically young ages for the Martian meteorites, the only exception being the 4.5 Ga ALH84001 [1], is paradoxical when viewed in context of a Martian surface thought to be mostly much older as inferred from the surface density of meteorite craters [2]. There appears to be at least a twofold difference between the observed ages of Martian meteorites and their expected ages as inferred from the ages of Martian surfaces obtained from crater densities.

  16. Mineral Biomarkers in Martian Meteorite Allan Hills 84001?

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, K. L.; Bazylinski, D. A.; Wentworth, S. J.; McKay, D. S.; Golden, D. C.; Gibson, E. K., Jr.; Romanek, C. S.

    1998-01-01

    The occurrence of fine-grained magnetite in the Fe-rich rims surrounding carbonate globules in the martian meteorite ALH84001, originally described in , have been proposed as fossil remains of primitive martian organisms. Here we report observations on size and shape distributions of magnetites from ALH84001 and compare them to biogenic and inorganic magnetite crystals of terrestrial origin. While some magnetite morphology is not unequivocally diagnostic for its biogenicity, such as cubodial forms of magnetite, which are common in inorganically formed magnetites, other morphologies of magnetite (parallel-epiped or elongated prismatic and arrowhead forms) are more likely signatures of biogenic activity. Some ALH 84001 magnetite particles described below have unique morphology and length-to-width ratios that are indistinguishable from a variety of terrestrial biogenic magnetite and distinct from all known inorganic forms of magnetite.

  17. The Origin of Magnetite Crystals in ALH84001 Carbonate Disks

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, K. L.; Clemett, S. J.; Wentworth, S. J.; McKay, D. S.; Gibson, E. K., Jr.

    2012-01-01

    Martian meteorite ALH84001 preserves evidence of interaction with aqueous fluids while on Mars in the form of microscopic carbonate disks believed to have formed approx 3.9 Ga ago at beginning of the Noachian epoch. Intimately associated within and throughout these carbonate disks are nanocrystal magnetites (Fe3O4) with unusual chemical and physical properties, whose origins have become the source of considerable debate. One group of hypotheses argues that these magnetites are the product of partial thermal decomposition of the host carbonate. Alternatively, the origins of magnetite and carbonate may be unrelated; that is, from the perspective of the carbonate the magnetite is allochthonous. We have sought to resolve between these hypotheses through the detailed characterized of the compositional and structural relationships between the carbonate disks, their associated magnetites and the orthopyroxene matrix in which they are embedded. Comparison of these results with experimental thermal decomposition studies of sideritic carbonates conducted under a range of heating scenarios suggests that the magnetite nanocrystals in the ALH84001 carbonate disks are not the products of thermal decomposition.

  18. Covariant C and O Isotope Trends in Some Terrestrial Carbonates and ALH 84001: Possible Linkage Through Similar Formation Processes

    NASA Technical Reports Server (NTRS)

    Volk, Kathryn E.; Niles, Paul B.; Socki, Richard A.

    2011-01-01

    Carbonate minerals found on the surface of Mars and in martian meteorites indicate that liquid water has played a significant role in the planet's history. These findings have raised questions regarding the history of the martian hydrosphere and atmosphere as well as the possibility of life. Sunset Crater, Arizona is a dry environment with relatively high evaporation and brief periods of precipitation. This environment resembles Mars and may make Sunset Crater a good analog to martian carbonates. In this study we sought to identify discrete micro-scale isotopic variation within the carbonate crusts in Sunset Crater to see if they resembled the micro-scale isotope variation found in ALH 84001 carbonates. Sunset Crater carbonate formation may be used as a martian analog and ultimately provide insight into carbonate formation in ALH 84001.

  19. A low temperature transfer of ALH84001 from Mars to Earth.

    PubMed

    Weiss, B P; Kirschvink, J L; Baudenbacher, F J; Vali, H; Peters, N T; Macdonald, F A; Wikswo, J P

    2000-10-27

    The ejection of material from Mars is thought to be caused by large impacts that would heat much of the ejecta to high temperatures. Images of the magnetic field of martian meteorite ALH84001 reveal a spatially heterogeneous pattern of magnetization associated with fractures and rock fragments. Heating the meteorite to 40 degrees C reduces the intensity of some magnetic features, indicating that the interior of the rock has not been above this temperature since before its ejection from the surface of Mars. Because this temperature cannot sterilize most bacteria or eukarya, these data support the hypothesis that meteorites could transfer life between planets in the solar system. PMID:11052940

  20. A low temperature transfer of ALH84001 from Mars to Earth.

    PubMed

    Weiss, B P; Kirschvink, J L; Baudenbacher, F J; Vali, H; Peters, N T; Macdonald, F A; Wikswo, J P

    2000-10-27

    The ejection of material from Mars is thought to be caused by large impacts that would heat much of the ejecta to high temperatures. Images of the magnetic field of martian meteorite ALH84001 reveal a spatially heterogeneous pattern of magnetization associated with fractures and rock fragments. Heating the meteorite to 40 degrees C reduces the intensity of some magnetic features, indicating that the interior of the rock has not been above this temperature since before its ejection from the surface of Mars. Because this temperature cannot sterilize most bacteria or eukarya, these data support the hypothesis that meteorites could transfer life between planets in the solar system.

  1. Determination of the Three-Dimensional Morphology of ALH84001 and Biogenic MV-1 Magnetite: Comparison of Results from Electron Tomography and Classical Transmission Electron Microscopy

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, Kathie L.; Clemett, Simon J.; Schwartz, Cindy; Morphew, Mary; McIntosh, J. Richard; Bazylinski, Dennis A.; Kirschvink, Joseph L.; Wentworth, Susan J.; McKay, David S.; Vali, Hojatollah

    2004-01-01

    Dated at approximately 3.9 billion years of age, carbonate disks, found within fractures of the host rock of Martian meteorite ALH84001, have been interpreted as secondary minerals that formed at low temperature in an aqueous medium. Heterogeneously distributed within these disks are magnetite nanocrystals that are of Martian origin. Approximately one quarter of these magnetites have morphological and chemical similarities to magnetite particles produced by magnetotactic bacteria strain MV-1, which are ubiquitous in aquatic habitats on Earth. Moreover, these types of magnetite particles are not known or expected to be produced by abiotic means either through geological processes or synthetically in the laboratory. The remaining three quarters of the ALH84001 magnetites are likely products of multiple processes including, but not limited to, precipitation from a hydrothermal fluid, thermal decomposition of the carbonate matrix in which they are embedded, and extracellular formation by dissimilatory Fe-reducing bacteria. We have proposed that the origins of magnetites in ALH84001 can be best explained as the products of multiple processes, one of which is biological. Recently the three-dimensional (3-D) external morphology of the purported biogenic fraction of the ALH84001 magnetites has been the subject of considerable debate. We report here the 3-D geometry of biogenic magnetite crystals extracted from MV-1 and of those extracted from ALH84001 carbonate disks using a combination of high resolution classical and tomographic transmission electron microscopy (TEM). We focus on answering the following questions: (1) which technique provides adequate information to deduce the 3-D external crystal morphology?; and, (2) what is the precise 3-D geometry of the ALH84001 and MV-1 magnetites?

  2. Martian Meteorites Record Surface Temperatures on Mars

    NASA Astrophysics Data System (ADS)

    Taylor, G. J.

    2005-07-01

    Using published data for argon (Ar) released when Martian meteorites are heated, David Shuster (California Institute of Technology, now at Berkeley Geochronology Center, Berkeley, CA) and Benjamin Weiss (Massachusetts Institute of Technology) show that the nakhlite group of Martian meteorites and unique Martian meteorite ALH 84001 were probably not heated above about 0 degree C for most of their histories. This indicates that the surface of Mars has been cold for almost four billion years. If a warm, wet environment existed on Mars (inferred from previous studies of surface features and geochemical parameters), it occurred before four billion years ago.

  3. The Microbiological Contamination of Meteorites: A Null Hypothesis

    NASA Technical Reports Server (NTRS)

    Steele, A.; Toporski, J. K. W.; Westall, F. W.; Thomas-Keprta, K.; Gibson, E. K.; Avci, R.; Whitby, C.; McKay, D. S.; Griffin, C.

    2000-01-01

    Using 4 different techniques we have studied 9 meteorites including the Martian meteorites ALH84001 and Nakhla for terrestrial contamination in all 9 we have found evidence of terrestrial microorganisms.

  4. High-Resolution Multiple Sulfur Isotope Studies of Martian Meteorites

    NASA Technical Reports Server (NTRS)

    Mojzsis, S. J.

    2000-01-01

    Sensitive, high resolution measurements of S-32, S-31, and S-34 in individual pyrite grains in martian meteorite ALH84001 by an in situ ion microprobe multi-collection technique reveal mass-independent anomalies in Delta.S-33 (Delta.S-33 = delta.S-33 - 0.516delta.S-34) in addition to the lowest 634S found in an extraterrestrial material. Low delta.S-34 values in two pyrite grains intimately associated with carbonate in ALH84001 can be explained by the sensitivity of sulfur to fractionations in the geologic environment. Anomalies in Delta.S-33 recorded in ALH84001 pyrites probably formed by gas-phase reactions in the early martian atmosphere (>4 Ga). The discovery of clearly resolvable Delta-S33 anomalies in 2 of 12 ALH84001 pyrites analyzed in their petrographic context in thin section, is considered strong evidence for crust-atmosphere exchange and the global cycling of volatile sulfur species on early Mars. These results corroborate previous measurements by Farquhar and co-workers who used a different technique that measures that bulk Delta.S-33 values of martian meteorites. These independent techniques, and their results, suggest that sulfur affected by mass-independent fractionation is common on Mars.

  5. Microdistributions of Rb and Sr in ALH84001 carbonates: Chronological implications for secondary alteration on Mars

    SciTech Connect

    Wadhwa, M.; Sutton, S.R.; Flynn, G.J.

    2005-04-22

    Concentrations of Rb and Sr were analyzed on the micron-scale in various compositional zones of the ALH84001 carbonates. Implications of the measured Rb/Sr ratios for the chronology of these carbonates are discussed. ALH84001 is unique among the Martian meteorites in that it has an ancient crystallization age of {approx}4.5 Ga defined by Sm-Nd isotope systematics. Another aspect that differentiates this Martian meteorite from the others is the presence of Ca-Fe-Mg carbonates (modal abundance {approx}1%) that are thought to have been precipitated during alteration in a near-surface environment. Precise age dating of these carbonates is important since it could provide constraints on the timing of surficial secondary alteration processes on Mars. However, this has been a challenging problem owing to the relatively small abundance of the carbonates in ALH84001 and because these carbonates are difficult to separate from the other minerals in the rock by physical and chemical means. Previous investigations have attempted to separate the carbonates by leaching of carbonate-rich mineral fractions. The single 'bulk carbonate' fraction analyzed by Wadhwa and Lugmair was characterized by a low {sup 87}Rb/{sup 86}Sr ratio of {approx}0.05, the lowest of any mineral in ALH84001, and the corresponding Rb-Sr age estimate ({approx}1.39 Ga) was dependent on the assumption of isotopic equilibrium between the carbonates and plagioclase. As pointed out by Borg et al., such an assumption may not be assured and, therefore, they obtained multiple carbonate-rich leachates with a range of {sup 87}Rb/{sup 86}Sr ratios (0.12-2.62) from which they estimated an age of {approx}3.9 Ga. Although these authors performed painstaking chemical characterization to determine contributions in the leachates from minerals such as phosphates and silicates, it is nevertheless difficult to positively rule out contributions from other as yet unidentified phases. Therefore, the goal of the present

  6. Martian "microfossils" in lunar meteorites?

    PubMed

    Sears, D W; Kral, T A

    1998-07-01

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

  7. Martian "microfossils" in lunar meteorites?

    PubMed

    Sears, D W; Kral, T A

    1998-07-01

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

  8. Martian "microfossils" in lunar meteorites?

    NASA Astrophysics Data System (ADS)

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

    1998-07-01

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

  9. A study of xenon isotopes in a martian meteorite using the RELAX ultrasensitive mass spectrometer

    SciTech Connect

    Whitby, J A; Gilmour, J D; Turner, G

    1997-01-15

    The Refrigerator Enhanced Analyser for Xenon (RELAX), an ultrasensitive resonance ionization time-of-flight mass spectrometer, has been used with a laser microprobe to investigate the isotopic composition of xenon trapped in the martian meteorite ALH84001. The laser microprobe has a spatial resolution of the order of 100{mu}m thus allowing the in situ analysis of individual mineral grains in a polished section when combined with ultrasensitive, low blank sample analysis. We present results showing that the mineral orthopyroxene in ALH84001 contains a trapped xenon component consistent with a martian origin. Additionally, a cosmic ray exposure age of 15Ma for ALH84001 is obtained from spallation derived xenon trapped within an apatite grain.

  10. Ion Microprobe Measurements of Carbon Isotopes in Martian Phosphates: Insights into the Martian Mantle

    NASA Astrophysics Data System (ADS)

    Goreva, J. S.; Leshin, L. A.; Guan, Y.

    2003-03-01

    In-situ measurements of C in the phosphates from meteorites Los Angeles, Zagami, QUE94201 and ALH84001 predict isotopically light martian magmatic C, heavier than previous estimates yet significantly lighter than the terrestrial value.

  11. Truncated hexa-octahedral magnetite crystals in ALH84001: presumptive biosignatures.

    PubMed

    Thomas-Keprta, K L; Clemett, S J; Bazylinski, D A; Kirschvink, J L; McKay, D S; Wentworth, S J; Vali, H; Gibson, E K; McKay, M F; Romanek, C S

    2001-02-27

    McKay et al. [(1996) Science 273, 924-930] suggested that carbonate globules in the meteorite ALH84001 contained the fossil remains of Martian microbes. We have characterized a subpopulation of magnetite (Fe(3)O(4)) crystals present in abundance within the Fe-rich rims of these carbonate globules. We find these Martian magnetites to be both chemically and physically identical to terrestrial, biogenically precipitated, intracellular magnetites produced by magnetotactic bacteria strain MV-1. Specifically, both magnetite populations are single-domain and chemically pure, and exhibit a unique crystal habit we describe as truncated hexa-octahedral. There are no known reports of inorganic processes to explain the observation of truncated hexa-octahedral magnetites in a terrestrial sample. In bacteria strain MV-1 their presence is therefore likely a product of Natural Selection. Unless there is an unknown and unexplained inorganic process on Mars that is conspicuously absent on the Earth and forms truncated hexa-octahedral magnetites, we suggest that these magnetite crystals in the Martian meteorite ALH84001 were likely produced by a biogenic process. As such, these crystals are interpreted as Martian magnetofossils and constitute evidence of the oldest life yet found. PMID:11226210

  12. Truncated hexa-octahedral magnetite crystals in ALH84001: Presumptive biosignatures

    PubMed Central

    Thomas-Keprta, Kathie L.; Clemett, Simon J.; Bazylinski, Dennis A.; Kirschvink, Joseph L.; McKay, David S.; Wentworth, Susan J.; Vali, Hojatollah; Gibson, Everett K.; McKay, Mary Fae; Romanek, Christopher S.

    2001-01-01

    McKay et al. [(1996) Science 273, 924–930] suggested that carbonate globules in the meteorite ALH84001 contained the fossil remains of Martian microbes. We have characterized a subpopulation of magnetite (Fe3O4) crystals present in abundance within the Fe-rich rims of these carbonate globules. We find these Martian magnetites to be both chemically and physically identical to terrestrial, biogenically precipitated, intracellular magnetites produced by magnetotactic bacteria strain MV-1. Specifically, both magnetite populations are single-domain and chemically pure, and exhibit a unique crystal habit we describe as truncated hexa-octahedral. There are no known reports of inorganic processes to explain the observation of truncated hexa-octahedral magnetites in a terrestrial sample. In bacteria strain MV-1 their presence is therefore likely a product of Natural Selection. Unless there is an unknown and unexplained inorganic process on Mars that is conspicuously absent on the Earth and forms truncated hexa-octahedral magnetites, we suggest that these magnetite crystals in the Martian meteorite ALH84001 were likely produced by a biogenic process. As such, these crystals are interpreted as Martian magnetofossils and constitute evidence of the oldest life yet found. PMID:11226210

  13. Truncated hexa-octahedral magnetite crystals in ALH84001: presumptive biosignatures

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, K. L.; Clemett, S. J.; Bazylinski, D. A.; Kirschvink, J. L.; McKay, D. S.; Wentworth, S. J.; Vali, H.; Gibson, E. K. Jr; McKay, M. F.; Romanek, C. S.

    2001-01-01

    McKay et al. [(1996) Science 273, 924-930] suggested that carbonate globules in the meteorite ALH84001 contained the fossil remains of Martian microbes. We have characterized a subpopulation of magnetite (Fe(3)O(4)) crystals present in abundance within the Fe-rich rims of these carbonate globules. We find these Martian magnetites to be both chemically and physically identical to terrestrial, biogenically precipitated, intracellular magnetites produced by magnetotactic bacteria strain MV-1. Specifically, both magnetite populations are single-domain and chemically pure, and exhibit a unique crystal habit we describe as truncated hexa-octahedral. There are no known reports of inorganic processes to explain the observation of truncated hexa-octahedral magnetites in a terrestrial sample. In bacteria strain MV-1 their presence is therefore likely a product of Natural Selection. Unless there is an unknown and unexplained inorganic process on Mars that is conspicuously absent on the Earth and forms truncated hexa-octahedral magnetites, we suggest that these magnetite crystals in the Martian meteorite ALH84001 were likely produced by a biogenic process. As such, these crystals are interpreted as Martian magnetofossils and constitute evidence of the oldest life yet found.

  14. Mineralization of Bacteria in Terrestrial Basaltic Rocks: Comparison With Possible Biogenic Features in Martian Meteorite Allan Hills 84001

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, K. L.; McKay, D. S.; Wentworth, S. J.; Stevens, T. O.; Taunton, A. E.; Allen, C. C.; Gibson, E. K., Jr.; Romanek, C. S.

    1998-01-01

    The identification of biogenic features altered by diagenesis or mineralization is important in determining whether specific features in terrestrial rocks and in meteorites may have a biogenic origin. Unfortunately, few studies have addressed the formation of biogenic features in igneous rocks, which may be important to these phenomena, including the controversy over possible biogenic features in basaltic martian meteorite ALH84001. To explore the presence of biogenic features in igneous rocks, we examined microcosms growing in basaltic small-scale experimental growth chambers or microcosms. Microbial communities were harvested from aquifers of the Columbia River Basalt (CRB) group and grown in a microcosm containing unweathered basalt chips and groundwater (technique described in. These microcosms simulated natural growth conditions in the deep subsurface of the CRB, which should be a good terrestrial analog for any putative martian subsurface ecosystem that may have once included ALH84001. Here we present new size measurements and photomicrographs comparing the putative martian fossils to biogenic material in the CRB microcosms. The range of size and shapes of the biogenic features on the CRB microcosm chips overlaps with and is similar to those on ALH84001 chips. Although this present work does not provide evidence for the biogenicity of ALH84001 features, we believe that, based on criteria of size, shape, and general morphology, a biogenic interpretation for the ALH84001 features remains plausible.

  15. A mild, near-surface aqueous environment on Noachian Mars preserved in ALH84001

    NASA Astrophysics Data System (ADS)

    Halevy, I.; Fischer, W. W.; Eiler, J. M.

    2011-12-01

    Despite widespread evidence for liquid water at the surface of Mars during parts of the Noachian epoch, the temperature of early aqueous environments has been impossible to establish, raising questions of whether Mars' surface was ever warmer than today. This has hindered insight into aqueous alteration processes, which, on the basis of orbital spectroscopy, appear to have been prevalent on Noachian Mars. It is important to understand such processes, as they link the observed secondary mineral assemblages to interactions between primary igneous silicates and the surface environment (atmosphere-hydrosphere). We have addressed this problem by determining the precipitation temperatures of secondary carbonate minerals preserved in the oldest known sample of Mars' crust-the meteorite Allan Hills 84001 (ALH84001). Using carbonate 'clumped' isotope thermometry we have found that the carbonates in ALH84001, which are 3.9-4.0 billion years old, formed at a temperature of ~18±4°C. With temperature known, we used the carbon and oxygen isotopic composition of the carbonates, as constrained by both our measurements and previous acid digestion and ion microprobe studies, to develop a model for their formation process and environment. The observed isotopic variation is best explained by carbonate precipitation out of a gradually evaporating, shallow subsurface aqueous solution (e.g. a regolith aquifer) at near-constant temperatures. Furthermore, on the basis of the isotopic composition of the earliest precipitated carbonates in ALH84001, the volatiles from which they formed (H2O and CO2) came not from depth, but from the early Martian surface. The occurrence of carbonates in other SNC meteorites and as a minor component of Martian dust implies that environments analogous to the one we studied may have been important in generating some of the observed secondary mineral assemblages by interaction between Mars' igneous crust and its atmosphere-hydrosphere.

  16. Reduced Martian Carbon: Evidence from Martian Meteorites

    NASA Technical Reports Server (NTRS)

    Gibson, Everett K.; McKay, David S.; Thomas-Keprta, Kathie L.; Clemett, SImon J.; Pillinger, COlin T.; Wright, Ian P.; Verchovsky, A. P.

    2010-01-01

    Identification of indigenous reduced carbon species on Mars has been a challenge since the first hypotheses about life on Mars were proposed. Ranging from the early astronomical measurements to analyses of samples from the Martian surface in the form of Martian meteorites. The first direct attempt to analyze the carbon species on the surface was in 1976 with the Viking GC-MS in-situ experiment which gave inconclusive results at two sites on Mars [1]. With the recognition in 1983 that samples of the Martian surface were already present on Earth in the form of Martian meteorites by Bogard and Johnson [2] new opportunities became available for direct study of Mars's samples in te rlraesbtrioalratories. Carbon isotopic compositional information suggested a reduced carbon component was present in the Martian meteorites [3-5]. Polycyclic aromatic hydrocarbons associated with carbonate globules in ALH84001 were later identified [6,7]. Jull et al [8] noted that an insoluble component was present within Nakhla and more than 75% of its C lacked any 14C, which is modern-day carbon contaminant. This carbon fraction was believed to be either indigenous (i..e. Martian) or ancient meteoritic carbon phase. Within the fractures of Nakhla and ALH84001, Fisk et al [9,10] identified reduced carbon-enriched areas. Gibson et al. [11] using a combination of NanoSIMS, Focused Electron microscopy, Laser Raman Spectroscopy and Stepped-Combustion Static Mass Spectrometry analyses the presence of possible indigenous reduced carbon components within the 1.3 Ga old Nakhla.

  17. Bulk and stable isotopic compositions of carbonate minerals in Martian meteorite Allan Hills 84001: no proof of high formation temperature.

    PubMed

    Treiman, A H; Romanek, C S

    1998-07-01

    Understanding the origin of carbonate minerals in the Martian meteorite Allan Hills (ALH) 84001 is crucial to evaluating the hypothesis that they contain traces of ancient Martian life. Using arguments based on chemical equilibria among carbonates and fluids, an origin at >650 degrees C (inimical to life) has been proposed. However, the bulk and stable isotopic compositions of the carbonate minerals are open to multiple interpretations and so lend no particular support to a high-temperature origin. Other methods (possibly less direct) will have to be used to determine the formation temperature of the carbonates in ALH84001. PMID:11543073

  18. Bulk and Stable Isotopic Compositions of Carbonate Minerals in Martian Meteorite Allan Hills 84001: No Proof of High Formation Temperature

    NASA Technical Reports Server (NTRS)

    Treiman, Allan H.; Romanek, Christopher S.

    1998-01-01

    Understanding the origin of carbonate minerals in the Martian meteorite Allan Hills (ALH) 84001 is crucial to evaluating the hypothesis that they contain traces of ancient Martian life. Using arguments based on chemical equilibria among carbonates and fluids, an origin at greater than 650 C (inimical to life) has been proposed. However, the bulk and stable isotopic compositions of the carbonate minerals are open to multiple interpretations and so lend no particular support to a high-temperature origin. Other methods (possibly less direct) will have to be used to determine the formation temperature of the carbonates in ALH 84001.

  19. Did an Impact Make the Mysterious Microscopic Magnetite Crystals in ALH 84001?

    NASA Astrophysics Data System (ADS)

    Taylor, G. J.

    2007-10-01

    Fervent debate swirls around microscopic crystals of magnetite (Fe3O4) in Martian meteorite ALH 84001. Some investigators suggest that the crystals are evidence of past life on Mars, citing magnetite crystals of similar chemical compositions and sizes made by magnetotactic bacteria on Earth. Others cite assorted experiments and observations to argue that the important little crystals formed entirely by non-biological processes, hence say nothing about life on Mars. One of those processes is the decomposition of iron carbonate (the mineral siderite), which occurs in ALH 84001. Researchers argue that heating this mineral causes it to decompose into magnetite and CO2 gas. Experiments showing this were done by heating siderite and observing that it decomposed and formed magnetite, but nobody had shock-heated siderite to see if magnetite crystals formed. (Shock is a rapid, strong rise and fall in pressure. It happens under many circumstances, including meteorite impacts.) The lack of shock experiments has been solved by Mary Sue Bell (University of Houston and Jacobs Engineering). She experimentally shocked samples of siderite at the Experimental Impact Laboratory at the Johnson Space Center. She shows that magnetite crystals of the right size and composition formed when samples were shocked to 49 GPa (about 500,000 times the pressure at the Earth's surface). This is more evidence for a non-biological origin for the magnetite crystals in ALH 84001 and is consistent with what we know about the impact history of the rock. There seems to be growing evidence against a biological origin, but don't expect these results to completely settle the debate!

  20. Microscale carbon isotope variability in ALH84001 carbonates and a discussion of possible formation environments

    NASA Astrophysics Data System (ADS)

    Niles, P. B.; Leshin, L. A.; Guan, Y.

    2005-06-01

    The carbonates in martian meteorite ALH84001 preserve a record of aqueous processes on Mars at 3.9 Ga, and have been suggested to contain signatures of ancient martian life. The conditions of the carbonate formation environment are critical for understanding possible evidence for life on Mars, the history of water on Mars, and the evolution of the martian atmosphere. Despite numerous studies of petrographic relationships, microscale oxygen isotope compositions, microscale chemical compositions, and other minerals associated with the carbonates, formation models remain relatively unconstrained. Microscale carbon isotope analyses of ALH84001 carbonates reveal variable δ 13C values ranging from +27 to +64 ‰. The isotopic compositions are correlated with chemical composition and extent of crystallization such that the Mg-poor, early-formed carbonates are relatively 13C depleted and the Mg-rich, later forming carbonates, are 13C enriched. These data are inconsistent with many of the previously proposed environments for carbonate formation, and a new set of hypotheses are proposed. Specifically, two new models that account for the data involve low temperature (<100°C) aqueous processes: (1) the carbonates formed during mixing of two fluids derived from separate chemical and isotopic reservoirs; or (2) the carbonates formed from high pH fluids that are exposed to a CO 2-rich atmosphere and precipitate carbonate, similar to high pH springs on Earth.

  1. Martian surface paleotemperatures from thermochronology of meteorites.

    PubMed

    Shuster, David L; Weiss, Benjamin P

    2005-07-22

    The temporal evolution of past martian surface temperatures is poorly known. We used thermochronology and published noble gas and petrographic data to constrain the temperature histories of the nakhlites and martian meteorite ALH84001. We found that the nakhlites have not been heated to more than 350 degrees C since they formed. Our calculations also suggest that for most of the past 4 billion years, ambient near-surface temperatures on Mars are unlikely to have been much higher than the present cold (<0 degrees C) state. PMID:16040703

  2. Martian Surface Paleotemperatures from Thermochronology of Meteorites

    NASA Astrophysics Data System (ADS)

    Shuster, David L.; Weiss, Benjamin P.

    2005-07-01

    The temporal evolution of past martian surface temperatures is poorly known. We used thermochronology and published noble gas and petrographic data to constrain the temperature histories of the nakhlites and martian meteorite ALH84001. We found that the nakhlites have not been heated to more than 350°C since they formed. Our calculations also suggest that for most of the past 4 billion years, ambient near-surface temperatures on Mars are unlikely to have been much higher than the present cold (<0°C) state.

  3. Magnetism and the putative early Martian life

    NASA Astrophysics Data System (ADS)

    Rochette, P.

    2001-08-01

    A short critical review is provided on three questions linking magnetism and the putative early Mars life. Was there a large internal Martian magnetic field, during which period, and is it a requisite for life? What is the origin of the paleomagnetic signal of Martian meteorites, including ALH84001? What is the present credibility of the case for fossil bacterial magnetite grains in ALH84001?

  4. Launch of martian meteorites in oblique impacts

    NASA Astrophysics Data System (ADS)

    Artemieva, Natalia; Ivanov, Boris

    2004-09-01

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

  5. Isotopic evidence for a terrestrial source of organic compounds found in martian meteorites Allan Hills 84001 and Elephant Moraine 79001.

    PubMed

    Jull, A J; Courtney, C; Jeffrey, D A; Beck, J W

    1998-01-16

    Stepped-heating experiments on martian meteorites Allan Hills 84001 (ALH84001) and Elephant Moraine 79001 (EETA79001) revealed low-temperature (200 to 430 degrees Celsius) fractions with a carbon isotopic composition delta13C between -22 and -33 per mil and a carbon-14 content that is 40 to 60 percent of that of modern terrestrial carbon, consistent with a terrestrial origin for most of the organic material. Intermediate-temperature (400 to 600 degrees Celsius) carbonate-rich fractions of ALH84001 have delta13C of +32 to +40 per mil with a low carbon-14 content, consistent with an extraterrestrial origin, whereas some of the carbonate fraction of EETA79001 is terrestrial. In addition, ALH84001 contains a small preterrestrial carbon component of unknown origin that combusts at intermediate temperatures. This component is likely a residual acid-insoluble carbonate or a more refractory organic phase. PMID:9430584

  6. New Insights into the Origin of Magnetite Crystals in ALH84001 Carbonate Disks

    NASA Technical Reports Server (NTRS)

    Thomas-Keptra, Katie L.; Clemett, S. J.; Wentworth S. J.; Mckay, D. S.; Gibson, E. K., Jr.

    2010-01-01

    Martian meteorite ALH84001 preserves evidence of interaction with aqueous fluids while on Mars in the form of microscopic carbonate disks believed to have formed approx.3.9 Ga ago at beginning of the Noachian epoch. Intimately associated within and throughout these carbonate disks are nanocrystal magnetites (Fe3O4) with unusual chemical and physical properties, whose ori gins have become the source of considerable debate. One group of hypotheses argues that these magnetites are the product of partial thermal decomposition of the host carbonate. Alternatively, the origins of magnetite and carbonate may be unrelated: that is, from the perspective of the carbonate the magnetite is allochthonous. We have sought to resolve between these hypotheses through the detailed characterized of the compositional and structural relationships between the carbonate disks, their associated magnetites and the orthopyroxene matrix in which they are embedded [1]. Comparison of these results with experimental thermal decomposition studies of sideritic carbonates conducted under a range of heating scenarios suggests that the magnetite nanocrystals in the ALH84001 carbonate disks are not the products of thermal decomposition.

  7. New insights into the origin of magnetite crystals in ALH84001 carbonate disks

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, K. L.; Clemett, S. J.; Wentworth, S. J.; McKay, D. S.; Gibson, E. K.

    2009-01-01

    Martian meteorite ALH84001 preserves evidence of interaction with aqueous fluids while on Mars in the form of microscopic carbonate disks which are believed to have precipitated approximately 3.9 Ga ago at beginning of the Noachian epoch. Intimately associated within and throughout these carbonate disks are nanocrystal magnetites (Fe3O4) with unusual chemical and physical properties, whose origins have become the source of considerable debate. One group of hypotheses argues that these Fe3O4 are the product of partial thermal decomposition of the host carbonate. Alternatively, the origins of Fe3O4 and carbonate may be unrelated; that is, from the perspective of the carbonate the magnetite is allochthonous. We have sought to resolve between these hypotheses through the detailed characterized of the compositional and structural relationships of the carbonate disks and associated magnetites with the orthopyroxene matrix in which they are embedded. We focus this discussion on the composition of ALH84001 magnetites and then compare these observations with those from experimental thermal decomposition studies of sideritic carbonates under a range of plausible geological heating scenarios.

  8. Polycyclic aromatic hydrocarbons (PAHs) in Antarctic Martian meteorites, carbonaceous chondrites, and polar ice.

    PubMed

    Becker, L; Glavin, D P; Bada, J L

    1997-01-01

    Recent analyses of the carbonate globules present in the Martian meteorite ALH84001 have detected polycyclic aromatic hydrocarbons (PAHs) at the ppm level (McKay et al., 1996). The distribution of PAHs observed in ALH84001 was interpreted as being inconsistent with a terrestrial origin and were claimed to be indigenous to the meteorite, perhaps derived from an ancient martian biota. We have examined PAHs in the Antarctic shergottite EETA79001, which is also considered to be from Mars, as well as several Antarctic carbonaceous chondrites. We have found that many of the same PAHs detected in the ALH84001 carbonate globules are present in Antarctic carbonaceous chondrites and in both the matrix and carbonate (druse) component of EETA79001. We also investigated PAHs in polar ice and found that carbonate is an effective scavenger of PAHs in ice meltwater. Moreover, the distribution of PAHs in the carbonate extract of Antarctic Allan Hills ice is remarkably similar to that found in both EETA79001 and ALH84001. The reported presence of L-amino acids of apparent terrestrial origin in the EETA79001 druse material (McDonald and Bada, 1995) suggests that this meteorite is contaminated with terrestrial organics probably derived from Antarctic ice meltwater that had percolated through the meteorite. Our data suggests that the PAHs observed in both ALH84001 and EETA79001 are derived from either the exogenous delivery of organics to Mars or extraterrestrial and terrestrial PAHs present in the ice meltwater or, more likely, from a mixture of these sources. It would appear that PAHs are not useful biomarkers in the search for extinct or extant life on Mars. PMID:11541466

  9. Polycyclic aromatic hydrocarbons (PAHs) in Antarctic Martian meteorites, carbonaceous chondrites, and polar ice.

    PubMed

    Becker, L; Glavin, D P; Bada, J L

    1997-01-01

    Recent analyses of the carbonate globules present in the Martian meteorite ALH84001 have detected polycyclic aromatic hydrocarbons (PAHs) at the ppm level (McKay et al., 1996). The distribution of PAHs observed in ALH84001 was interpreted as being inconsistent with a terrestrial origin and were claimed to be indigenous to the meteorite, perhaps derived from an ancient martian biota. We have examined PAHs in the Antarctic shergottite EETA79001, which is also considered to be from Mars, as well as several Antarctic carbonaceous chondrites. We have found that many of the same PAHs detected in the ALH84001 carbonate globules are present in Antarctic carbonaceous chondrites and in both the matrix and carbonate (druse) component of EETA79001. We also investigated PAHs in polar ice and found that carbonate is an effective scavenger of PAHs in ice meltwater. Moreover, the distribution of PAHs in the carbonate extract of Antarctic Allan Hills ice is remarkably similar to that found in both EETA79001 and ALH84001. The reported presence of L-amino acids of apparent terrestrial origin in the EETA79001 druse material (McDonald and Bada, 1995) suggests that this meteorite is contaminated with terrestrial organics probably derived from Antarctic ice meltwater that had percolated through the meteorite. Our data suggests that the PAHs observed in both ALH84001 and EETA79001 are derived from either the exogenous delivery of organics to Mars or extraterrestrial and terrestrial PAHs present in the ice meltwater or, more likely, from a mixture of these sources. It would appear that PAHs are not useful biomarkers in the search for extinct or extant life on Mars.

  10. Polycyclic aromatic hydrocarbons (PAHs) in Antarctic Martian meteorites, carbonaceous chondrites, and polar ice

    SciTech Connect

    Becker, L. |; Glavin, D.P.; Bada, J.L.

    1997-01-01

    Recent analyses of the carbonate globules present in the Martian meteorite ALH84001 have detected polycyclic aromatic hydrocarbons (PAHs) at the ppm level. The distribution of PAHs observed in ALH84001 was interpreted as being inconsistent with a terrestrial origin and were claimed to be indigenous to the meteorite, perhaps derived from an ancient martian biota. We have examined PAHs in the Antarctic shergottite EETA79001, which is also considered to be from Mars, as well as several Antarctic carbonaceous chondrites. We have found that many of the same PAHs detected in the ALH84001 carbonate globules are present in Antarctic carbonaceous chondrites and in both the matrix and carbonate (druse) component of EETA79001. We also investigated PAHs in polar ice and found that carbonate is an effective scavenger of PAHs in ice meltwater. Moreover, the distribution of PAHs in the carbonate extract of Antarctic Allan Hills ice is remarkably similar to that found in both EETA79001 and ALH84001. The reported presence of L-amino acids of apparent terrestrial origin in the EETA79001 druse material suggests that this meteorite is contaminated with terrestrial organics probably derived from Antarctic ice meltwater that had percolated through the meteorite. Our data suggests that the PAHs observed in both ALH84001 and EETA79001 are derived from either the exogenous delivery of organics to Mars or extraterrestrial and terrestrial PAHs present in the ice meltwater or, more likely, from a mixture of these sources. It would appear that PAHs are not useful biomarkers in the search for extinct or extant life on Mars. 33 refs., 3 figs., 1 tab.

  11. A Younger Age for ALH84001 and Its Geochemical Link to Shergottite Sources in Mars

    NASA Astrophysics Data System (ADS)

    Lapen, T. J.; Righter, M.; Brandon, A. D.; Debaille, V.; Beard, B. L.; Shafer, J. T.; Peslier, A. H.

    2010-04-01

    Martian meteorite ALH84001 (ALH) is the oldest known igneous rock from Mars and has been used to constrain its early history. Lutetium-hafnium (Lu-Hf) isotope data for ALH indicate an igneous age of 4.091 ± 0.030 billion years, nearly coeval with an interval of heavy bombardment and cessation of the martian core dynamo and magnetic field. The calculated Lu/Hf and Sm/Nd (samarium/neodymium) ratios of the ALH parental magma source indicate that it must have undergone extensive igneous processing associated with the crystallization of a deep magma ocean. This same mantle source region also produced the shergottite magmas (dated 150 to 570 million years ago), possibly indicating uniform igneous processes in Mars for nearly 4 billion years.

  12. A younger age for ALH84001 and its geochemical link to shergottite sources in Mars.

    PubMed

    Lapen, T J; Righter, M; Brandon, A D; Debaille, V; Beard, B L; Shafer, J T; Peslier, A H

    2010-04-16

    Martian meteorite ALH84001 (ALH) is the oldest known igneous rock from Mars and has been used to constrain its early history. Lutetium-hafnium (Lu-Hf) isotope data for ALH indicate an igneous age of 4.091 +/- 0.030 billion years, nearly coeval with an interval of heavy bombardment and cessation of the martian core dynamo and magnetic field. The calculated Lu/Hf and Sm/Nd (samarium/neodymium) ratios of the ALH parental magma source indicate that it must have undergone extensive igneous processing associated with the crystallization of a deep magma ocean. This same mantle source region also produced the shergottite magmas (dated 150 to 570 million years ago), possibly indicating uniform igneous processes in Mars for nearly 4 billion years. PMID:20395507

  13. A younger age for ALH84001 and its geochemical link to shergottite sources in Mars.

    PubMed

    Lapen, T J; Righter, M; Brandon, A D; Debaille, V; Beard, B L; Shafer, J T; Peslier, A H

    2010-04-16

    Martian meteorite ALH84001 (ALH) is the oldest known igneous rock from Mars and has been used to constrain its early history. Lutetium-hafnium (Lu-Hf) isotope data for ALH indicate an igneous age of 4.091 +/- 0.030 billion years, nearly coeval with an interval of heavy bombardment and cessation of the martian core dynamo and magnetic field. The calculated Lu/Hf and Sm/Nd (samarium/neodymium) ratios of the ALH parental magma source indicate that it must have undergone extensive igneous processing associated with the crystallization of a deep magma ocean. This same mantle source region also produced the shergottite magmas (dated 150 to 570 million years ago), possibly indicating uniform igneous processes in Mars for nearly 4 billion years.

  14. Nature of Reduced Carbon in Martian Meteorites

    NASA Technical Reports Server (NTRS)

    Gibson, Everett K., Jr.; McKay, D. S.; Thomas-Keprta, K. L.; Clemett, S. J.; White, L. M.

    2012-01-01

    Martian meteorites provide important information on the nature of reduced carbon components present on Mars throughout its history. The first in situ analyses for carbon on the surface of Mars by the Viking landers yielded disappointing results. With the recognition of Martian meteorites on Earth, investigations have shown carbon-bearing phases exist on Mars. Studies have yielded presence of reduced carbon, carbonates and inferred graphitic carbon phases. Samples ranging in age from the first approximately 4 Ga of Mars history [e.g. ALH84001] to nakhlites with a crystallization age of 1.3 Ga [e.g. Nakhla] with aqueous alteration processes occurring 0.5-0.7 Ga after crystallizaton. Shergottites demonstrate formation ages around 165-500 Ma with younger aqueous alterations events. Only a limited number of the Martian meteorites do not show evidence of significance terrestrial alterations. Selected areas within ALH84001, Nakhla, Yamato 000593 and possibly Tissint are suitable for study of their indigenous reduced carbon bearing phases. Nakhla possesses discrete, well-defined carbonaceous phases present within iddingsite alteration zones. Based upon both isotopic measurements and analysis of Nakhla's organic phases the presence of pre-terrestrial organics is now recognized. The reduced carbon-bearing phases appear to have been deposited during preterrestrial aqueous alteration events that produced clays. In addition, the microcrystalline layers of Nakhla's iddingsite have discrete units of salt crystals suggestive of evaporation processes. While we can only speculate on the origin of these unique carbonaceous structures, we note that the significance of such observations is that it may allow us to understand the role of Martian carbon as seen in the Martian meteorites with obvious implications for astrobiology and the pre-biotic evolution of Mars. In any case, our observations strongly suggest that reduced organic carbon exists as micrometer- size, discrete structures

  15. The Hydrological Cycle on Mars as Inferred from the Multi O-isotopic Composition of Carbonates in ALH84001

    NASA Astrophysics Data System (ADS)

    Shaheen, R.; Niles, P. B.; Chong, K.; Thiemens, M. H.

    2011-12-01

    Carbonate minerals provide valuable record of the atmosphere in which they are formed. This work utilizes C and O triple isotopic compositions of the carbonate minerals found in ALH84001 to explore the interaction between atmosphere-hydrosphere and lithosphere. The origin of carbonates found in the Martian meteorite ALH84001 (<1%) is heavily debated with low temperature aqueous precipitation, biogenic production, evaporative processes, high temperature reactions, and impact induced melting and reprecipitation are all candidate processes. These carbonates are heterogeneous chemically (Mg, Ca and Fe-Mn rich) and isotopically (δ13CPDB = +27 to 46 %; δ18OVSMOW = +9.5 to 20.6%) on micrometer scales. Our stepped phosphoric acid dissolution experiments released CO2 from multiple phases of Martian carbonate in the rock (12h acid digestion at 25o C for Ca rich phase and 3h acid digestion at 150oC for Mg rich phase). Both Ca and Mg rich phases showed 0.7% excess 17O (Δ17O = δ17O - 0.52δ18O) in contrast to terrestrial carbonate minerals formed by surficial weathering of the meteorite with no oxygen isotopic anomaly Δ17O ≈ 0 (one hour acid digestion at 25o C). The newly identified Ca-rich carbonate phase is 18O enriched (δ18O = +25%) in contrast to all of the other Ca-rich carbonates previously described. It also contains excess 17O (Δ17O = 0.7%) indicating incorporation of oxygen from an atmospheric source of Martian origin. These oxygen isotope characteristics differentiate this phase from the more commonly described carbonate globules or rosettes and suggest formation from separate aqueous event. This is confirmed by the carbon isotope composition of this new carbonate phase (δ13C= +20%) which differs from the other Martian carbonates in the meteorite and from terrestrial sources. This difference may be an evidence of the long term evolution of carbon isotopes in the atmosphere of Mars. The discovery of highly enriched (O isotopes) Ca-rich phase of Martian

  16. FTIR Analysis of Water in Pyroxene and Plagioclase in ALH 84001 and Nakhlites

    NASA Technical Reports Server (NTRS)

    Peslier, A. H.; Cintala, M. J.; Montes, R.; Cardenas, F.

    2016-01-01

    Determining the volatile budget of the interior of Mars is crucial for our understanding of that planet's formation, geodynamics, cooling history and the origin of its volcanism and atmosphere as well as its potential for life. Surficial water is evident from spacecraft and rover data in polar caps and the atmosphere, in the presence of river channels, and in the detection of water-bearing minerals. Meteorites, however, are our best candidates for estimating the amount of water present at depth, even if all are crustal samples. The last 10 years have seen a blooming of studies measuring water and halogens in Martian meteorites. The bulk of these studies target phosphate, a typically late-stage phase in the igneous Martian meteorites that potentially would concentrate incompatible element hydrogen (H quantified traditionally as "water", i.e., H2O concentrations in weight) near the end of the crystallization sequence. However, determining the amount of water, F, and Cl in the magma from which a phosphate crystallized from is not straightforward and in most instances not possible. On the other hand, phosphates have turned out to be very useful in identifying hydrothermal processes that could have added water while or after the magma flowed and crystallized. Another caveat of analyzing Martian meteorite phases for water is that shocked phases such as maskelynite and impact melts appear to have incorporated water from the Martian atmosphere, as evidenced by high H isotope ((delta)D) signatures, and therefore their water concentrations cannot be interpreted in terms of deep planetary processes. The best candidates for estimating the water content of the Martian interior have been melt inclusions (glass or amphibole-bearing) which the enclosing mineral (usually olivine) would have prevented from exchanging volatiles with the surroundings after crystallization. Even some of these, however, have high (delta)D, meaning they were affected by H exchange via impact events or

  17. Statistical Analyses Comparing Prismatic Magnetite Crystals in ALH84001 Carbonate Globules with those from the Terrestrial Magnetotactic Bacteria Strain MV-1

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, Kathie L.; Clemett, Simon J.; Bazylinski, Dennis A.; Kirschvink, Joseph L.; McKay, David S.; Wentworth, Susan J.; Vali, H.; Gibson, Everett K.

    2000-01-01

    Here we use rigorous mathematical modeling to compare ALH84001 prismatic magnetites with those produced by terrestrial magnetotactic bacteria, MV-1. We find that this subset of the Martian magnetites appears to be statistically indistinguishable from those of MV-1.

  18. Sulfur isotopic systematics in alteration assemblages in martian meteorite Allan Hills 84001

    SciTech Connect

    Shearer, C.K.; Layne, G.D.; Papike, J.J.; Spilde, M.N.

    1996-08-01

    ALH84001 is a coarse-grained, clastic orthopyroxenite meteorite related to the SNC meteorite group (shergottites, nakhlites, Chassigny). Superimposed upon the orthopyroxene-dominant igneous mineral assemblage is a hydrothermal signature. This hydrothermal overprint consists of carbonate assemblages occurring in spheroidal aggregates and fine-grained carbonate-sulfide vug-filling. The sulfide in this assemblage has been identified as pyrite, an unusual sulfide in meteorites. Previously, Burgess et al. (1989) reported a bulk {delta} {sup 34}S for a SNC group meteorite (Shergotty) of -0.5 {+-} 1.5%. Here, we report the first martian {delta} {sup 34}S values from individual sulfide grains. Using newly developed ion microprobe techniques, we were able to determine {delta} {sup 34}S of the pyrite in ALH84001 with a 1 {alpha} precision of better than {+-}0.5%. The {delta} {sup 34}S values for the pyrite range from +4.8 to +7.8%. Within the stated uncertainties, the pyrite from ALH84001 exhibits a real variability in {delta} {sup 34}S in this alteration assemblage. In addition, these sulfides are demonstrably enriched in {sup 34}S relative to Canon Diablo troilite and sulfides from most other meteorites. This signature implies that the planetary body represented by ALH 84001 experienced processes capable of fractionating sulphur isotopes and that hydrothermal conditions changed during pyrite precipitation (T, pH, fluid composition, etc.). These new data are not consistent with the pyrite recording either biogenic activity or atmospheric fractionation of sulphur through nonthermal escape mechanisms or oxidation processes. This study also demonstrates the usefulness of ion microprobe measurements of sulphur isotopes in constraining conditions on other planetary bodies.

  19. Sulfur isotopic systematics in alteration assemblages in martian meteorite Allan Hills 84001

    NASA Astrophysics Data System (ADS)

    Shearer, C. K.; Layne, G. D.; Papike, J. J.; Spilde, M. N.

    1996-08-01

    ALH84001 is a coarse-grained, clastic orthopyroxenite meteorite related to the SNC meteorite group ( shergottites, nakhlites, Chassigny). Superimposed upon the orthopyroxene-dominant igneous mineral assemblage is a hydrothermal signature. This hydrothermal overprint consists of carbonate assemblages occurring in spheroidal aggregates and fine-grained carbonate-sulfide vug-filling. The sulfide in this assemblage has been identified as pyrite, an unusual sulfide in meteorites. Previously, Burgess et al. (1989) reported a bulk δ 34S for a SNC group meteorite (Shergotty) of -0.5 ± 1.5‰. Here, we report the first martian δ 34S values from individual sulfide grains. Using newly developed ion microprobe techniques, we were able to determine δ 34S of the pyrite in ALH84001 with a 1 a precision of better than ±0.5‰. The δ 34S values for the pyrite range from +4.8 to +7.8‰. Within the stated uncertainties, the pyrite from ALH84001 exhibits a real variability in δ 34S in this alteration assemblage. In addition, these sulfides are demonstrably enriched in 34S relative to Canon Diablo troilite and sulfides from most other meteorites. This signature implies that the planetary body represented by ALH84001 experienced processes capable of fractionating sulphur isotopes and that hydrothermal conditions changed during pyrite precipitation (T, pH, fluid composition, etc.). The fractionated signature of the sulphur in the pyrite is most likely attributed to either conditions of pyrite precipitation (low temperature, reduced (low fo 2) and moderately alkaline (pH > 8) environment) or enrichment of fluids in 34S by surface processes (weathering or impact processes) prior to precipitation. These new data are not consistent with the pyrite recording either biogenic activity or atmospheric fractionation of sulphur through nonthermal escape mechanisms or oxidation processes. This study also demonstrates the usefulness of ion microprobe measurements of sulphur isotopes in

  20. A Younger Age for the Oldest Martian Meteorite

    NASA Astrophysics Data System (ADS)

    Taylor, G. J.

    2010-05-01

    The Allan Hills (ALH) 84001 Martian meteorite is famous for containing fiercely-disputed evidence for fossil life. Equally important to many cosmochemists, the meteorite also contains important information about the construction of the Martian crust by magmas derived from the interior, and the subsequent modification of those igneous rocks by large impacts and circulating water. A surprising feature of ALH 84001 has been its extremely ancient age, 4.50 billion years, as determined by samarium-neodymium (Sm-Nd) and rubidium-strontium (Rb-Sr) isotopic dating. If correct, the ancient age implies that the magma in which ALH 84001 formed intruded the primordial crust, perhaps forming in a deep ocean of magma that surrounded Mars during its initial differentiation into metallic core, rocky mantle, and primary crust. New age determinations by Thomas Lapen (University of Houston) and colleagues there and at the Johnson Space Center, the Lunar and Planetary Institute, the University of Wisconsin, and the University of Brussels, Belgium, indicate that the rock crystallized in a magma 4.091 billion years ago. They used lutetium-hafnium (Lu-Hf) isotopes in determining the new age. This isotopic system has the advantage of not being affected as readily by impact heating and water alteration as are Sm-Nd and Rb-Sr. The new age is consistent with igneous activity throughout Martian history and with a period of heavy bombardment between 4.2 and 4.1 billion years as inferred from the ages of large impact basins on Mars.

  1. X-ray microprobe measurements of the chemical compositions of ALH84001 carbonate globules

    SciTech Connect

    Flynn, G.J.; Sutton, S.R.; Keller, L.P.

    2004-01-28

    We measured minor element contents of carbonate from ALH84001 and report trends in tbe Ca, V, Mn and Sr in carbonate and the associated magnetite bands. McKay et al. suggested that carbonate globules in the ALH84001 meteorite from Mars contained evidence consistent with the development of bacterial life early in the history of Mars. This result provoked an extensive study of the ALH84001 meteorite. More recently Thomas-Keprta et al. have published a study showing that the magnetite associated with carbonate rims are of the size and shape produced by terrestrial bacteria. This paper has revived interest in ALH84001. The typical ALH84001 carbonate globule consists of four regions: a core of Fe-rich carbonate, a thin magnetite-rich band, a rim of Mn-rich carbonate, and another thin magnetite-rich band. Trace element analysis of each of these phases may allow us to address several important questions about these carbonates: (1) The origin of the magnetite-rich bands in the ALH84001 carbonate globules. If the magnetites are derived from the underlying carbonate through thermal decomposition (as proposed by Golden et al.), then we expect to see 'inherited' trace elements in these magnetite bands. (2) The origin of the rim carbonate, by determining whether the carbonate in the core has the same trace elements as the rim carbonates. (3) The age of the rim carbonate. Borg et al. dated the formation of the rim carbonate using the Rb/Sr chronometer. Borg et al. performed their measurements on an aliquot of what they called a high-Rb, low-Sr carbonate separate from the rim. We previously measured the trace element contents of chips from core and rim carbonates from an ALH84001 carbonate globule using an X-Ray Microprobe on Beamline X26A at the National Synchrotron Light Source. These measurements showed the rim carbonate had a very low Rb content, with Sr>>Rb, inconsistent with the {approx}5 ppm Rb reported by Borg et al. in the sample they dated by the Rb/Sr chronometer. The

  2. Thermal Decomposition of an Impure (Roxbury) Siderite: Relevance to the Presence of Chemically Pure Magnetite Crystals in ALH84001 Carbonate Disks

    NASA Technical Reports Server (NTRS)

    McKay, D.S.; Gibson, E.K.; Thomas-Keprta, K.L.; Clemett, S.J.; Wentworth, S.J.

    2009-01-01

    The question of the origin of nanophase magnetite in Martian meteorite ALH84001 has been widely debated for nearly a decade. Golden et al. have reported producing nearly chemically pure magnetite from thermal decomposition of chemically impure siderite [(Fe, Mg, Mn)CO3]. This claim is significant for three reasons: first, it has been argued that chemically pure magnetite present in the carbonate disks in Martian meteorite ALH84001 could have formed by the thermal decomposition of the impure carbonate matrix in which they are embedded; second, the chemical purity of magnetite has been previously used to identify biogenic magnetite; and, third, previous studies of thermal decomposition of impure (Mg,Ca,Mn)-siderites, which have been investigated under a wide variety of conditions by numerous researchers, invariably yields a mixed metal oxide phase as the product and not chemically pure magnetite. The explanation for this observation is that these siderites all possess the same crystallographic structure (Calcite; R3c) so solid solutions between these carbonates are readily formed and can be viewed on an atomic scale as two chemically different but structurally similar lattices.

  3. Evidence for life in a martian meteorite?

    PubMed

    McSween, H Y

    1997-07-01

    The controversial hypothesis that the ALH84001 meteorite contains relics of ancient martian life has spurred new findings, but the question has not yet been resolved. Organic matter probably results, at least in part, from terrestrial contamination by Antarctic ice meltwater. The origin of nanophase magnetites and sulfides, suggested, on the basis of their sizes and morphologies, to be biogenic remains contested, as does the formation temperature of the carbonates that contain all of the cited evidence for life. The reported nonfossils may be magnetite whiskers and platelets, probably grown from a vapor. New observations, such as the possible presence of biofilms and shock metamorphic effects in the carbonates, have not yet been evaluated. Regardless of the ultimate conclusion, this controversy continues to help define strategies and sharpen tools that will be required for a Mars exploration program focused on the search for life. PMID:11541665

  4. Isotopic Composition of Trapped and Cosmogenic Noble Gases in Several Martian Meteorites

    NASA Technical Reports Server (NTRS)

    Garrison, Daniel H.; Bogard, Donald D.

    1997-01-01

    Isotopic abundances of the noble gases were measured in the following Martian meteorites: two shock glass inclusions from EET79001, shock vein glass from Shergotty and Y793605, and whole rock samples of ALH84001 and QUE94201. These glass samples, when combined with literature data on a separate single glass inclusion from EET79001 and a glass vein from Zagami, permit examination of the isotopic composition of Ne, Ar, Kr, and Xe trapped from the Martian atmosphere in greater detail. The isotopic composition of Martian Ne, if actually present in these glasses, remains poorly defined. The Ar-40/Ar-36 ratio of Martian atmospheric Ar may be much less than the ratio measured by Viking and possibly as low as approx. 1900. The atmospheric Ar-36/Ar-38 ratio is less than or equal to 4.0. Martian atmospheric Kr appears to be enriched in lighter isotopes by approx. 0.4%/amu compared to both solar wind Kr and to the Martian composition previously reported. The Martian atmospheric Ar-36/Xe-132 and Kr-84/Xe-132 Xe elemental ratios are higher than those reported by Viking by factors of approx. 3.3 and approx. 2.5, respectively. Cosmogenic gases indicate space exposure ages of 13.9 +/- 1 Myr for ALH84001 and 2.7 +/- 0.6 Myr for QUE94201. Small amounts of Ne-21 produced by energetic solar protons may be present in QUE94201, but are not present in ALH84001 or Y793605. The space exposure age for Y793605 is 4.9 +/- 0.6 Myr and appears to be distinctly older than the ages for basaltic shergottites.

  5. Organic Carbon Exists in Mars Meteorites: Where is it on the Martian Surface?

    NASA Technical Reports Server (NTRS)

    McKay, D. S.; Clemett, S. J.; Gibson, E. K., Jr.; Thomas-Keprta, K. L.; Wentworth, S. J.

    2010-01-01

    The search for organic carbon on Mars has been a major challenge. The first attempt was the Viking GC-MS in situ experiment which gave inconclusive results at two sites oil. After the discovery that the SNC meteorites were from Mars, reported C isotopic compositional information which suggested a reduced C component present in the Martian meteorites reported the presence of reduced C components (i.e., polycyclic aromatic hydrocarbons) associated with the carbonate globules in ALH84001. Jull et al. noted in Nakhla there was acid insoluble C component present with more than 75% of its C lacking any C-14, which is modern-day terrestrial carbon. This C fraction was believed to be either indigenous martian or ancient meteoritic carbon. Fisk et al. have shown textural evidence along with C-enriched areas within fractures in Nakhla and ALH84001. Westall et al. have shown the presence of a large irregular fragment of organic material completely embedded within a chip of ALH84001. Interior samples from the Naklnla SNC made available by the British Museum of Natural History, were analyzed. Petrographic examination of Nakhla showed evidence of fractures (approx.0.5 microns wide) filled with dark brown to black dendritic material with characteristics similar to those observed by. Iddingsite is also present along fractures in olivine. Fracture filling and dendritic material was examined by SEM-EDX, TEM-EDX, Focused Electron Beam microscopy, Laser Raman Spectroscopy, Nano-SIMS Ion Micro-probe, and Stepped-Combustion Static Mass Spectrometry. Observations from the first three techniques are discussed.

  6. Covariant C and O Isotope Trends in Arctic Carbonate Crusts and ALH 84001: Potential Biomarker or Indicator of Cryogenic Formation Environment?

    NASA Technical Reports Server (NTRS)

    Socki, Richard A.; Niles, Paul B.; Blake, Weston; Leveille, Richard

    2009-01-01

    This work seeks to use the chemical, isotopic, and mineralogical characteristics of secondary carbonate minerals produced during brief aqueous events to identify the conditions of the aqueous environment in which they formed. Liquid water near the surface of Mars is subject to either rapid freezing and/or evaporation. These processes are also active on Earth, and produce secondary minerals that have complex chemical, mineralogical, and isotopic textures and compositions that can include covariant relationships between Delta C-13 (sub VPDB) and delta O-18 (sub VSMOW). The extremely well studied four billion year old carbonates preserved in martian meteorite ALH 84001 also show covariant delta C-13 and delta O-18 compositions, but these variations are manifested on a micro-scale in a single thin section while the variation observed so far in terrestrial carbonates is seen between different hand samples.

  7. Investigations into an unknown organism on the martian meteorite Allan Hills 84001

    NASA Technical Reports Server (NTRS)

    Steele, A.; Goddard, D. T.; Stapleton, D.; Toporski, J. K.; Peters, V.; Bassinger, V.; Sharples, G.; Wynn-Williams, D. D.; McKay, D. S.

    2000-01-01

    Examination of fracture surfaces near the fusion crust of the martian meteorite Allan Hills (ALH) 84001 have been conducted using scanning electron microscopy (SEM) and atomic force microscopy (AFM) and has revealed structures strongly resembling mycelium. These structures were compared with similar structures found in Antarctic cryptoendolithic communities. On morphology alone, we conclude that these features are not only terrestrial in origin but probably belong to a member of the Actinomycetales, which we consider was introduced during the Antarctic residency of this meteorite. If true, this is the first documented account of terrestrial microbial activity within a meteorite from the Antarctic blue ice fields. These structures, however, do not bear any resemblance to those postulated to be martian biota, although they are a probable source of the organic contaminants previously reported in this meteorite.

  8. Scanning Electron Microscopy Investigation of a Sample Depth Profile Through the Martian Meteorite Nakhla

    NASA Technical Reports Server (NTRS)

    Toporski, Jan; Steele, Andrew; Westall, Frances; McKay, David S.

    2000-01-01

    The ongoing scientific debate as to whether or not the Martian meteorite ALH84001 contained evidence of possible biogenic activities showed the need to establish consistent methods to ascertain the origin of such evidence. To distinguish between terrestrial organic material/microbial contaminants and possible indigenous microbiota within meteorites is therefore crucial. With this in mind a depth profile consisting of four samples from a new sample allocation of Martian meteorite Nakhla was investigated using scanning electron microscopy (SEM) and energy dispersive X-ray analysis. SEM imaging of freshly broken fractured chips revealed structures strongly recent terrestrial microorganisms, in some cases showing evidence of active growth. This conclusion was supported by EDX analysis, which showed the presence of carbon associated with these structures, we concluded that these structures represent recent terrestrial contaminants rather than structures indigenous to the meteorite. Page

  9. Focused Ion Beam Microscopy of ALH84001 Carbonate Disks

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, Kathie L.; Clemett, Simon J.; Bazylinski, Dennis A.; Kirschvink, Joseph L.; McKay, David S.; Vali, Hojatollah; Gibson, Everett K., Jr.; Romanek, Christopher S.

    2005-01-01

    Our aim is to understand the mechanism(s) of formation of carbonate assemblages in ALH84001. A prerequisite is that a detailed characterization of the chemical and physical properties of the carbonate be established. We present here analyses by transmission electron microscopy (TEM) of carbonate thin sections produced by both focused ion beam (FIB) sectioning and ultramicrotomy. Our results suggest that the formation of ALH84001 carbonate assemblages were produced by considerably more complex process(es) than simple aqueous precipitation followed by partial thermal decomposition as proposed by other investigators [e.g., 1-3].

  10. Magnetite and Carbonate Textures in ALH84001: Experimental Insights

    NASA Technical Reports Server (NTRS)

    Koziol, Andrea M.

    2001-01-01

    Synthetic siderite and synthetic siderite-magnesite carbonates were equilibrated with hematite, magnetite, and CO2 at elevated pressure and temperature. Comparisons are made to textures seen in the carbonate globules in ALH84001. Additional information is contained in the original extended abstract.

  11. 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.

  12. Possible Meteorites in the Martian Hills

    NASA Technical Reports Server (NTRS)

    2006-01-01

    From its winter outpost at 'Low Ridge' inside Gusev Crater, NASA's Mars Exploration Rover Spirit took this spectacular, color mosaic of hilly, sandy terrain and two potential iron meteorites. The two light-colored, smooth rocks about two-thirds of the way up from the bottom of the frame have been labeled 'Zhong Shan' and 'Allan Hills.'

    The two rocks' informal names are in keeping with the rover science team's campaign to nickname rocks and soils in the area after locations in Antarctica. Zhong Shang is an Antarctic base that the People's Republic of China opened on Feb. 26, 1989, at the Larsemann Hills in Prydz Bay in East Antarctica. Allan Hills is a location where researchers have found many Martian meteorites, including the controversial ALH84001, which achieved fame in 1996 when NASA scientists suggested that it might contain evidence for fossilized extraterrestrial life. Zhong Shan was the given name of Dr. Sun Yat-sen (1866-1925), known as the 'Father of Modern China.' Born to a peasant family in Guangdong, Sun moved to live with his brother in Honolulu at age 13 and later became a medical doctor. He led a series of uprisings against the Qing dynasty that began in 1894 and eventually succeeded in 1911. Sun served as the first provisional president when the Republic of China was founded in 1912.

    The Zhong Shan and Allan Hills rocks, at the left and right, respectively, have unusual morphologies and miniature thermal emission spectrometer signatures that resemble those of a rock known as 'Heat Shield' at the Meridiani site explored by Spirit's twin, Opportunity. Opportunity's analyses revealed Heat Shield to be an iron meteorite.

    Spirit acquired this approximately true-color image on the rover's 872nd Martian day, or sol (June 16, 2006), using exposures taken through three of the panoramic camera's filters, centered on wavelengths of 600 nanometers, 530 nanometers, and 480 nanometers.

  13. A nitrogen and argon stable isotope study of Allan Hills 84001: implications for the evolution of the Martian atmosphere.

    PubMed

    Grady, M M; Wright, I P; Pillinger, C T

    1998-07-01

    The abundances and isotopic compositions of N and Ar have been measured by stepped combustion of the Allan Hills 84001 (ALH 84001) Martian orthopyroxenite. Material described as shocked is N-poor ([N] approximately 0.34 ppm; delta 15N approximately +23%); although during stepped combustion, 15N-enriched N (delta 15N approximately +143%) is released in a narrow temperature interval between 700 degrees C and 800 degrees C (along with 13C-enriched C (delta 13C approximately +19%) and 40Ar). Cosmogenic species are found to be negligible at this temperature; thus, the isotopically heavy component is identified, in part, as Martian atmospheric gas trapped relatively recently in the history of ALH84001. The N and Ar data show that ALH84001 contains species from the Martian lithosphere, a component interpreted as ancient trapped atmosphere (in addition to the modern atmospheric species), and excess 40Ar from K decay. Deconvolution of radiogenic 40Ar from other Ar components, on the basis of end-member 36Ar/14N and 40Ar/36Ar ratios, has enabled calculation of a K-Ar age for ALH 84001 as 3.5-4.6 Ga, depending on assumed K abundance. If the component believed to be Martian palaeoatmosphere was introduced to ALH 84001 at the time the K-Ar age was set, then the composition of the atmosphere at this time is constrained to: delta 15N > or = +200%, 40Ar/36Ar < or = 3000 and 36Ar/14N > or = 17 x 10(-5). In terms of the petrogenetic history of the meteorite, ALH 84001 crystallised soon after differentiation of the planet, may have been shocked and thermally metamorphosed in an early period of bombardment, and then subjected to a second event. This later process did not reset the K-Ar system but perhaps was responsible for introducing (recent) atmospheric gases into ALH 84001; and it might mark the time at which ALH 84001 suffered fluid alteration resulting in the formation of the plagioclase and carbonate mineral assemblages. PMID:11543078

  14. The provenance and formation of reduced carbon phases on Mars from the study of Martian meteorites.

    NASA Astrophysics Data System (ADS)

    Steele, A.; McCubbin, F. M.; Fries, M.

    2015-12-01

    Organic carbon compounds are essential building blocks of terrestrial life, so the occurrence and origin (biotic or abiotic) of organic compounds on Mars is of great significance. Indeed, the question of Martian organic matter is among the highest priority targets for robotic spacecraft missions in the next decade includ- ing the Mars Science Laboratory and Mars 2020. Sev- eral Martian meteorites contain organic carbon (i.e., macromolecular reduced carbon-rich material, not nec- essarily related to biota), but there is little agreement on its origins. Initial hypotheses for the origin of this organic carbon included: terrestrial contamination; chondritic meteoritic input; thermal decomposition of Martian carbonate minerals; direct precipitation from cooling aqueous fluids; and the remains of ancient Martian biota. We report on results from the analysis of 14 martian meteorites and show the distribution of organic phases throughout the samples analyzed. We will present formation scearios for each of the types of organic matter discovered. These studies when combined show 4 possible pools of reduced carbon on Mars. 1) impact generated graphite in the Tissint meteorite, 2) secondary hydrothermal generated graphite in ALH 84001, 3) primary igneous reduced carbon in 12 Martian meteorites associated with spinel inclusions in olivine and pyroxene 4) and potentially primary hydrothermally formed organic carbon / nitrogen containing organic species in the maskelynite phases of the Tissint meteorite. These studies show that Mars has produced reduced carbon / organic carbon via several mechanisms and reveal that the building blocks of life, if not life itself, are present on Mars.

  15. A Single Grain U-Pb and Pb-Pb Dating and D/H Ratios of the Phosphate Mineral in ALH84001

    NASA Astrophysics Data System (ADS)

    Koike, M.; Ota, Y.; Takahata, N.; Sano, Y.; Sugiura, N.

    2012-12-01

    There are many studies that determine U-Pb and Pb-Pb ages of phosphates in Martian meteorites. Phosphate minerals such as an apatite (Ca5(PO4)3[OH, F, Cl]) and a whitlockite (Ca9 [Mg, Fe2+] (PO4)6 PO3OH) contain water in the form of OH, which provides us hydrogen isotopic information. The goal of this study is to obtain a crystallization age and hydrogen isotopic distributions of each grain and to relate them to the surface evolution of Mars. ALH84001 is known to be about 4 billion years old [1]. Its carbonates and maskelynite showed high D/H ratios with large deviations, which indicates large fractionation at early Mars surface [2]. Due to small grain sizes and limited spatial resolutions of measurements, previous studies used several grains for one age or one series of isotopic distributions. Here we determined single grain ages and D/H ratios using NanoSIMS with a high spatial resolution. A thin section of ALH84001 was polished and carbon-coated. The section was then observed by SEM-EDS to locate phosphate minerals. A large phosphate grain (>100μm) was found and analyzed by NanoSIMS. A ~10nA O- primary ion beam (with spot diameter of ~20μm) was used for U-Pb and Pb-Pb measurements and a ~1nA (spot diameter of <10μm) was for D/H ratio measurements. An apatite from a Prairie Lake circular complex, PRAP, with a known age (1156 Ma; [3]) was used as a standard for U-Pb. The D/H ratio and the water content of an apatite from Morocco were measured by conventional methods to use as a D/H standard. 238U-206Pb isochron, 207Pb-206Pb isochron, and total U-Pb isochron age, a regression line in 3-D space (238U/206Pb-207Pb/206Pb-204Pb/206Pb) showed a consistent age ~4 Ga. The ages obtained in this study were also consistent with previous U-Pb dating within experimental errors. D/H ratios in the same grain showed high values and a considerable deviation, which seems to be due to mixing of terrestrial water. References: [1] Terada K. et al. 2003 Meteoritics & Planet. Sci. 38

  16. What Were the Major Factors That Controlled Mineralogical Similarities and Differences of Basaltic, Lherzolitic and Clinopyroxentic Martian Meteorites Within Each Group

    NASA Technical Reports Server (NTRS)

    Mikouchi, T.; Miyamoto, M.; McKay, G. A.

    1998-01-01

    Twelve martian meteorites that have been re- covered so far are classified into five groups (basalt, lherzolite, clinopyroxenite, dunite, and orthopyroxenite) mainly from petrology and chemistry. Among them, the dunite and orthopyroxenite groups consist of only one meteorite each (dunite: Chassigny, orthopyroxenite: ALH 84001). The basalt group is the largest group and consists of four meteorites (Shergotty, Zagani, EETA 79001, and QUE 94201). The lherzolitic and clinopyroxenitic groups include three meteorites each (Lherzolite: ALH 77005, LEW 88516, and Y793605, clinopyroxenite: Nakhla, Governador Valadares, and Lafayette). These meteorites within each group are generally similar to the others, but none of them is paired with the others. In this abstract, we discuss the major factors that controlled mineralogical similarities and differences of basaltic, lherzolitic, and clinopyroxenitic meteorites within each group. This may help in understanding their petrogenesis and original locations on Mars in general.

  17. Carbonates in Martian Meteorites - A Reappraisal

    NASA Astrophysics Data System (ADS)

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

    1995-09-01

    The occurrence of carbonates in martian meteorites was first established after acid dissolution and stepped combustion analyses of whole-rock Nakhla [1]. The release of CO2 after a 24 hr. reaction with 100% H3PO4 at 25 degrees C was taken to imply that the carbonate mineral present was calcite, a proposal subsequently confirmed by petrographic examination [2]. The isotopic composition of the carbon comprising the calcite was enriched in 13C (isotopically heavy) with delta^(l3)C ~ +12 per mil. An extended period of acid attack, also at 25 degrees C, released small quantities of even more 13C-enriched CO2 (delta^(13)C ~ +49 per mil), but the isotopic data were considered uncertain, and thus little significance was attached to the result, beyond the suggestion that some carbonate was perhaps dolomite or iron-bearing. Now, however, following the analysis of Fe-Mg-rich carbonates in ALH 84001 [3-5], it is apparent that previously-reported data might underestimate the abundance and delta^(13)C of carbonates in SNCs [6], and that a much higher proportion might occur as siderite or dolomite end-members. Iron- and magnesium-rich carbonates are only partially attacked at 25 degrees C, even after extended exposure to H3PO4 [7]. Given that the delta^(13)C of carbonates in SNCs has been used to deduce both environmental conditions on Mars [4, 6], and the evolution of the martian atmosphere [8], it is desirable that correct delta^(l3)c values are known. We have undertaken a reappraisal of the chemical and isotopic composition of carbonates in martian meteorites, by a programme of high resolution stepped combustion analyses and high temperature (75 degrees C) acid dissolution . Carbonates in most martian meteorites are extremely fine-grained. and therefore not easv to identify by traditional optical microscopic methods; it is not possible to determine readily the mineralogical composition of the grains. Comparison of combustion data from SNCs with that from pure materials allows

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

    NASA Technical Reports Server (NTRS)

    Shock, E. L.

    2000-01-01

    Thermodynamic calculations of metastable equilibria were used to evaluate the potential for abiotic synthesis of aliphatic and polycyclic aromatic hydrocarbons (PAHs) in the martian meteorite Allan Hills (ALH) 84001. The calculations show that PAHs and normal alkanes could form metastably from CO, CO2, and H2 below approximately 250-300 degrees C during rapid cooling of trapped magmatic or impact-generated gases. Depending on temperature, bulk composition, and oxidation-reduction conditions, PAHs and normal alkanes can form simultaneously or separately. Moreover, PAHs can form at lower H/C ratios, higher CO/CO2 ratios, and higher temperatures than normal alkanes. Dry conditions with H/C ratios less than approximately 0.01-0.001 together with high CO/CO2 ratios also favor the formation of unalkylated PAHs. The observed abundance of PAHs, their low alkylation, and a variable but high aromatic to aliphatic ratio in ALH 84001 all correspond to low H/C and high CO/CO2 ratios in magmatic and impact gases and can be used to deduce spatial variations of these ratios. Some hydrocarbons could have been formed from trapped magmatic gases, especially if the cooling was fast enough to prevent reequilibration. We propose that subsequent impact heating(s) in ALH 84001 could have led to dissociation of ferrous carbonates to yield fine-grain magnetite, formation of a CO-rich local gas phase, reduction of water vapor to H2, reequilibration of the trapped magmatic gases, aromatization of hydrocarbons formed previously, and overprinting of the synthesis from magmatic gases, if any. Rapid cooling and high-temperature quenching of CO-, H2-rich impact gases could have led to magnetite-catalyzed hydrocarbon synthesis.

  19. Paleointensity of the Martian field from SQUID Microscopy

    NASA Astrophysics Data System (ADS)

    Weiss, B. P.; Fong, L. E.; Lima, E. A.; Baudenbacher, F. J.; Vali, H.

    2005-12-01

    Crustal magnetic anomalies in the southern Martian hemisphere have intensities an order of magnitude larger than typical crustal anomalies on Earth. Two possible explanations for this difference are that compared to the present-day Earth, Mars has either (i) larger amounts of crustal ferromagnetic minerals or (ii) the crust was magnetized by a larger paleofield. ALH84001, the only pre-Amazonian Martian meteorite, possesses a stable magnetization dating to 4 Ga or earlier. Previous paleomagnetic studies with SQUID moment magnetometers on bulk ALH84001 grains have estimated that the paleointensity of the field which magnetized the meteorite was between 0.1-1 times that of the Earth's present field. However, these estimates may be lower limits on the true paleointensity because the orientation of the magnetization in ALH84001 is spatially heterogeneous on the submillimeter scale. This complication could have profound implications for hypothesis (ii) above. Here we first demonstrate that superconducting quantum interference device (SQUID) microscopy can recover the same magnetization intensity and direction of a well characterized modern-day terrestrial basalt as that measured with a 2G Enterprises SQUID moment magnetometer. A SQUID microscope paleointensity analysis of this basalt gives the expected present day field intensity of a few tens of microtesla. We further show that our new high resolution SQUID microscopy study of ALH84001, which has mapped its heterogeneous magnetization with the highest resolution yet (0.1 mm), favors the upper range of previous paleointensity estimates for the 4 Ga Martian paleofield (e.g., within a factor of several of that of the present-day Earth). However, this field, were it dynamo in origin, is still too weak to easily explain the intensity of the Martian magnetic anomalies.

  20. New Meteorite Type NWA 8159 Augite Basalt: Specimen from a Previously Unsampled Location on Mars?

    NASA Technical Reports Server (NTRS)

    Agee, C. B.; Muttik, N.; Ziegler, K.; Walton, E. L.; Herd, C. D. K.; McCubbin, F. M.; Santos, A. R.; Simon, J. I.; Peters, T. J.; Tappa, M. J.; Sanborn, M. E.; Yin, Q.-Z.

    2014-01-01

    Up until recently the orthopyroxenite ALH 84001, a singleton martian meteorite type, was the only sample that did not fit within the common SNC types. However with the discovery of the unique basaltic breccia NWA 7034 pairing group [1] the diversity of martian meteorites beyond SNC types was expanded, and now with Northwest Africa (NWA) 8159, and its possible pairing NWA 7635 [2], the diversiy is expanded further with a third unique non-SNC meteorite type. The existence of meteorite types beyond the narrow range seen in SNCs is what might be expected from a random cratering sampling of a geologically long-lived and complex planet such as Mars.

  1. Searching for traces of life associated with carbonates in martian meteorites

    NASA Astrophysics Data System (ADS)

    Lepot, K.; Kearsley, A. T.; Chater, R. J.; McPhail, D. J.

    Martian meteorites provide an obvious starting point for the search for evidence of life on Mars. Peculiar structures shown by electron microscopy of fragments from the Antarctic meteorite ALH84001 have been reported to demonstrate shapes and a size distribution similar to those of cultured terrestrial nanobacteria. However, the association of these putative fossil forms with bacteria is only morphological, and no traces of undisputed biological organic matter have yet been demonstrated in close association with these structures. Similar, and larger, apparent microbial fossils have been found within samples of the Martian basaltic shergottite meteorite Los Angeles 001 (LA 001). Here they are associated with calcium carbonate deposition, known from isotopic studies to be terrestrial in origin, and also with silica-bearing globular encrustations, reminiscent of biofilm. This association is typical of bacterially-mediated mineral precipitation, which may occur directly on bacterial cells or on their surroundings. We have used analytical electron microscopy to locate and document possible bacterial shapes in LA 001, prior to Focussed Ion Beam cross-sectioning and Secondary Ion Mass Spectrometry of the internal sections revealed. We intend to compare the morphology and composition of internal structures to those of bacteria preserved in terrestrial carbonate stromatolites, siliceous sinters and abiotic precipitates, in order to determine whether major element compositional variation, isotopic and trace element partitioning can be used to reliably fingerprint bacterial activity as responsible for the meteoritic structures.

  2. Carbonates in the Martian meteorite Allan Hills 84001 formed at 18 ± 4 °C in a near-surface aqueous environment

    PubMed Central

    Halevy, Itay; Fischer, Woodward W.; Eiler, John M.

    2011-01-01

    Despite evidence for liquid water at the surface of Mars during the Noachian epoch, the temperature of early aqueous environments has been impossible to establish, raising questions of whether the surface of Mars was ever warmer than today. We address this problem by determining the precipitation temperature of secondary carbonate minerals preserved in the oldest known sample of Mars’ crust—the approximately 4.1 billion-year-old meteorite Allan Hills 84001 (ALH84001). The formation environment of these carbonates, which are constrained to be slightly younger than the crystallization age of the rock (i.e., 3.9 to 4.0 billion years), has been poorly understood, hindering insight into the hydrologic and carbon cycles of earliest Mars. Using “clumped” isotope thermometry we find that the carbonates in ALH84001 precipitated at a temperature of approximately 18 °C, with water and carbon dioxide derived from the ancient Martian atmosphere. Furthermore, covarying carbonate carbon and oxygen isotope ratios are constrained to have formed at constant, low temperatures, pointing to deposition from a gradually evaporating, subsurface water body—likely a shallow aquifer (meters to tens of meters below the surface). Despite the mild temperatures, the apparently ephemeral nature of water in this environment leaves open the question of its habitability. PMID:21969543

  3. Carbonates in the Martian meteorite Allan Hills 84001 formed at 18 +/- 4 degrees C in a near-surface aqueous environment.

    PubMed

    Halevy, Itay; Fischer, Woodward W; Eiler, John M

    2011-10-11

    Despite evidence for liquid water at the surface of Mars during the Noachian epoch, the temperature of early aqueous environments has been impossible to establish, raising questions of whether the surface of Mars was ever warmer than today. We address this problem by determining the precipitation temperature of secondary carbonate minerals preserved in the oldest known sample of Mars' crust--the approximately 4.1 billion-year-old meteorite Allan Hills 84001 (ALH84001). The formation environment of these carbonates, which are constrained to be slightly younger than the crystallization age of the rock (i.e., 3.9 to 4.0 billion years), has been poorly understood, hindering insight into the hydrologic and carbon cycles of earliest Mars. Using "clumped" isotope thermometry we find that the carbonates in ALH84001 precipitated at a temperature of approximately 18 °C, with water and carbon dioxide derived from the ancient Martian atmosphere. Furthermore, covarying carbonate carbon and oxygen isotope ratios are constrained to have formed at constant, low temperatures, pointing to deposition from a gradually evaporating, subsurface water body--likely a shallow aquifer (meters to tens of meters below the surface). Despite the mild temperatures, the apparently ephemeral nature of water in this environment leaves open the question of its habitability. PMID:21969543

  4. Carbonates in the Martian meteorite Allan Hills 84001 formed at 18 +/- 4 degrees C in a near-surface aqueous environment.

    PubMed

    Halevy, Itay; Fischer, Woodward W; Eiler, John M

    2011-10-11

    Despite evidence for liquid water at the surface of Mars during the Noachian epoch, the temperature of early aqueous environments has been impossible to establish, raising questions of whether the surface of Mars was ever warmer than today. We address this problem by determining the precipitation temperature of secondary carbonate minerals preserved in the oldest known sample of Mars' crust--the approximately 4.1 billion-year-old meteorite Allan Hills 84001 (ALH84001). The formation environment of these carbonates, which are constrained to be slightly younger than the crystallization age of the rock (i.e., 3.9 to 4.0 billion years), has been poorly understood, hindering insight into the hydrologic and carbon cycles of earliest Mars. Using "clumped" isotope thermometry we find that the carbonates in ALH84001 precipitated at a temperature of approximately 18 °C, with water and carbon dioxide derived from the ancient Martian atmosphere. Furthermore, covarying carbonate carbon and oxygen isotope ratios are constrained to have formed at constant, low temperatures, pointing to deposition from a gradually evaporating, subsurface water body--likely a shallow aquifer (meters to tens of meters below the surface). Despite the mild temperatures, the apparently ephemeral nature of water in this environment leaves open the question of its habitability.

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

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

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

  6. Olivine and Carbonate Globules in ALH84001: A Terrestrial Analog, and Implications for Water on Mars

    NASA Technical Reports Server (NTRS)

    Treiman, A. H.

    2005-01-01

    Carbonate globules in ALH84001 are associated with small olivine grains an unexpected finding because the olivines equilibrated at high T while the carbonate is chemically zoned and unequilibrated. A possible explanation comes from a terrestrial analog on Spitsbergen (Norway), where some carbonate globules grew in cavities left by aqueous dissolution of olivine. For ALH84001, the same process may have acted, with larger olivines dissolved out and smaller ones shielded inside orthopyroxene. Carbonate would have been deposited in holes where the olivine had been. Later shocks crushed remaining void space, and mobilized feldspathic glass around the carbonates.

  7. Comparing Meteorite and Spacecraft Noble Gas Measurements to Trace Processes in the Martian Crust and Atmosphere

    NASA Astrophysics Data System (ADS)

    Swindle, T. D.

    2014-12-01

    Our knowledge of the noble gas abundances and isotopic compositions in the Martian crust and atmosphere come from two sources, measurements of meteorites from Mars and in situ measurements by spacecraft. Measurements by the Viking landers had large uncertainties, but were precise enough to tie the meteorites to Mars. Hence most of the questions we have are currently defined by meteorite measurements. Curiosity's SAM has confirmed that the Ar isotopic composition of the atmosphere is highly fractionated, presumably representing atmospheric loss that can now be modeled with more confidence. What turns out to be a more difficult trait to explain is the fact that the ratio of Kr/Xe in nakhlites, chassignites and ALH84001 is distinct from the atmospheric ratio, as defined by measurements from shergottites. This discrepancy has been suggested to be a result of atmosphere/groundwater/rock interaction, polar clathrate formation, or perhaps local temperature conditions. More detailed atmospheric measurements, along with targeted simulation experiments, will be needed to make full use of this anomaly.

  8. The Shergottite Age Paradox and the Relative Probabilities of Ejecting Martian Meteorites of Differing Ages

    NASA Technical Reports Server (NTRS)

    Borg, L. E.; Shih, C.-Y.; Nyquist, L. E.

    1998-01-01

    The apparent paradox that the majority of impacts yielding Martian meteorites appear to have taken place on only a few percent of the Martian surface can be resolved if all the shergottites were ejected in a single event rather than in multiple events as expected from variations in their cosmic ray exposure and crystallization ages. If the shergottite-ejection event is assigned to one of three craters in the vicinity of Olympus Mons that were previously identified as candidate source craters for the SNC (Shergottites, Nakhlites, Chassigny) meteorites, and the nakhlite event to another candidate crater in the vicinity of Ceraunius Tholus, the implied ages of the surrounding terranes agree well with crater density ages. EN,en for high cratering rates (minimum ages), the likely origin of the shergottites is in the Tharsis region, and the paradox of too many meteorites from too little terrane remains for multiple shergottite-ejection events. However, for high cratering rates it is possible to consider sources for the nakhlltes which are away from the Tharsis region. The meteorite-yielding impacts may have been widely dispersed with sources of the young SNC meteorites in the northern plains, and the source of the ancient orthopyroxenite, ALH84001, in the ancient southern uplands. Oblique-impact craters can be identified with the sources of the nakhlites and the orthopyroxenite,, respectively, in the nominal cratering rate model, and with the shergottites and orthopyroxenite, respectively, in the high cratering rate model. Thus, oblique impacts deserve renewed attention as an ejection mechanism for Martian meteorites.

  9. The role of vaterite and aragonite in the formation of pseudo-biogenic carbonate structures: implications for Martian exobiology.

    PubMed

    Vecht, A; Ireland, T G

    2000-08-01

    A simple synthesis of various forms of calcium carbonate with spherical and 'floral' morphologies is reported. Vaterite formation occurs at approximately 25 degrees C, aragonite at approximately 70 degrees C and calcite at about approximately 80 degrees C. These are produced when CO2 is reacted with an aqueous solution of calcium chloride in the presence of ammonia. These conditions may have existed at the surface of Mars in the past, leading us to conclude that such mineral formations may be common there. Although the initial phases are modified over time with changing temperature and pressure conditions, they still influence the final morphology of the carbonates observed. A comparison of these structures with those found in the Martian meteorite ALH84001 suggests, but does not confirm, a non-biogenic origin for the ALH84001 carbonates. PMID:11543352

  10. The role of vaterite and aragonite in the formation of pseudo-biogenic carbonate structures: implications for Martian exobiology.

    PubMed

    Vecht, A; Ireland, T G

    2000-08-01

    A simple synthesis of various forms of calcium carbonate with spherical and 'floral' morphologies is reported. Vaterite formation occurs at approximately 25 degrees C, aragonite at approximately 70 degrees C and calcite at about approximately 80 degrees C. These are produced when CO2 is reacted with an aqueous solution of calcium chloride in the presence of ammonia. These conditions may have existed at the surface of Mars in the past, leading us to conclude that such mineral formations may be common there. Although the initial phases are modified over time with changing temperature and pressure conditions, they still influence the final morphology of the carbonates observed. A comparison of these structures with those found in the Martian meteorite ALH84001 suggests, but does not confirm, a non-biogenic origin for the ALH84001 carbonates.

  11. Olivine in Martian Meteorite Allan Hills 84001: Evidence for a High-Temperature Origin and Implications for Signs of Life

    NASA Technical Reports Server (NTRS)

    Shearer, C. K.; Leshin, L. A.; Adcock, C. T.

    1999-01-01

    Olivine from Martian meteorite Allan Hills (ALH) 84001 occurs as clusters within orthopyroxene adjacent to fractures containing disrupted carbonate globules and feldspathic shock glass. The inclusions are irregular in shape and range in size from approx. 40 microns to submicrometer. Some of the inclusions are elongate and boudinage-like. The olivine grains are in sharp contact with the enclosing orthopyroxene and often contain small inclusions of chromite The olivine exhibits a very limited range of composition from Fo(sub 65) to Fo(sub 66) (n = 25). The delta(sup 18)O values of the olivine and orthopyroxene analyzed by ion microprobe range from +4.3 to +5.3% and are indistinguishable from each other within analytical uncertainty. The mineral chemistries, O-isotopic data, and textural relationships indicate that the olivine inclusions were produced at a temperature greater than 800 C. It is unlikely that the olivines formed during the same event that gave rise to the carbonates in ALH 84001, which have more elevated and variable delta(sup 18)O values, and were probably formed from fluids that were not in isotopic equilibrium with the orthopyroxene or olivine The reactions most likely instrumental in the formation of olivine could be either the dehydration of hydrous silicates that formed during carbonate precipitation or the reduction of orthopyroxene and spinel If the olivine was formed by either reaction during a postcarbonate beating event, the implications are profound with regards to the interpretations of McKay et al. Due to the low diffusion rates in carbonates, this rapid, high-temperature event would have resulted in the preservation of the fine-scale carbonate zoning' while partially devolatilizing select carbonate compositions on a submicrometer scale. This may have resulted in the formation of the minute magnetite grains that McKay et al attributed to biogenic activity.

  12. Martian paleomagnetism with the SQUID microscope

    NASA Astrophysics Data System (ADS)

    Weiss, Benjamin Paul

    Rocks should preserve natural remanent magnetizations with stable directional and intensity information at levels ˜1000 times below that of the noise level on today's best moment magnetometers. The superconducting quantum interference device (SQUID) Microscope is a new, high-resolution magnetometer that can now detect such weak signals. It maps the magnetic fields above samples with a spatial resolution of <100 mum and a moment sensitivity of <10 -15 Am2. It therefore provides data with a resolution directly comparable with that of other common petrographic techniques. This thesis describes applications of SQUID microscopy to a variety of problems in the planetary sciences. A SQUID microscope paleomagnetic conglomerate test demonstrates that ALH84001 has been cooler than ˜40°C since before its ejection from the surface of Mars at 15 Ma. Because this temperature cannot sterilize most bacteria or eukarya, these data support the hypothesis that meteorites could transfer life between planets in the solar system. These and other data on panspermia demand a re-evaluation of the long-held assumption that terrestrial life evolved in isolation on Earth. Subsequent magnetic and textural studies of the meteorite show that 4 Ga ALH84001 carbonates containing magnetite and pyrrhotite carry a stable natural remanent magnetization. 40Ar/39Ar thermochronology demonstrates that this magnetization originated at 3.9--4.1 Ga on Mars. This magnetization is the oldest known for a planetary rock, and its strong intensity suggests that Mars had generated a geodynamo at or before 4 Ga. The intensity of the field that magnetized ALH84001 was roughly within an order of magnitude of that at the surface of the present-day Earth, sufficient for magnetotaxis by the bacteria whose magnetofossils have been reported in ALH84001 and possibly for the production of the strong crustal anomalies. 40Ar/39Ar thermochronology calculations also provide an explanation for why ALH84001 contains a sample of

  13. Possible Meteorites in the Martian Hills (False Color)

    NASA Technical Reports Server (NTRS)

    2006-01-01

    From its winter outpost at 'Low Ridge' inside Gusev Crater, NASA's Mars Exploration Rover Spirit took this spectacular, color mosaic of hilly, sandy terrain and two potential iron meteorites. The two light-colored, smooth rocks about two-thirds of the way up from the bottom of the frame have been labeled 'Zhong Shan' and 'Allan Hills.'

    The two rocks' informal names are in keeping with the rover science team's campaign to nickname rocks and soils in the area after locations in Antarctica. Zhong Shang is an Antarctic base that the People's Republic of China opened on Feb. 26, 1989, at the Larsemann Hills in Prydz Bay in East Antarctica. Allan Hills is a location where researchers have found many Martian meteorites, including the controversial ALH84001, which achieved fame in 1996 when NASA scientists suggested that it might contain evidence for fossilized extraterrestrial life. Zhong Shan was the given name of Dr. Sun Yat-sen (1866-1925), known as the 'Father of Modern China.' Born to a peasant family in Guangdong, Sun moved to live with his brother in Honolulu at age 13 and later became a medical doctor. He led a series of uprisings against the Qing dynasty that began in 1894 and eventually succeeded in 1911. Sun served as the first provisional president when the Republic of China was founded in 1912.

    The Zhong Shan and Allan Hills rocks, at the left and right, respectively, have unusual morphologies and miniature thermal emission spectrometer signatures that resemble those of a rock known as 'Heat Shield' at the Meridiani site explored by Spirit's twin, Opportunity. Opportunity's analyses revealed Heat Shield to be an iron meteorite.

    Spirit acquired this false-color image on the rover's 872nd Martian day, or sol (June 16, 2006), using exposures taken through three of the panoramic camera's filters, centered on wavelengths of 750 nanometers, 530 nanometers, and 430 nanometers. The image is presented in false color to emphasize differences among

  14. Coordinated In Situ Nanosims Analyses of H-C-O Isotopes in ALH 84001 Carbonates

    NASA Technical Reports Server (NTRS)

    Usui, T.; Alexander, C. M. O'D.; Wang, J.; Simon, J. I.; Jones, J. H.

    2016-01-01

    The surface geology and geomorphology of Mars indicate that it was once warm enough to maintain a large body of liquid water on its surface, though such a warm environment might have been transient. This study reports the hydrogen, carbon, and oxygen isotope compositions of the ancient atmosphere/hydrosphere of Mars based on in situ ion microprobe analyses of approximately 4 Ga-old carbonates in Allan Hills (ALH) 84001. The ALH 84001 carbonates are the most promising targets because they are thought to have formed from fluid that was closely associated with the Noachian atmosphere. While there are a number of carbon and oxygen isotope studies of the ALH 84001 carbonates, in situ hydrogen isotope analyses of these carbonates are limited and were reported more than a decade ago. Well-documented coordinated in situ analyses of carbon, oxygen and hydrogen isotopes provide an internally consistent dataset that can be used to constrain the nature of the Noachian atmosphere/hydrosphere and may eventually shed light on the hypothesis of ancient watery Mars.

  15. Analyses at High Spatial Resolution of Organic Molecules in Extraterrestrial Samples: Two-Step Laser Mass Spectrometry: Search for Polycyclic Aromatic Hydrocarbons in Antarctic Meteorite and Micrometeorite Samples

    NASA Technical Reports Server (NTRS)

    Zare, Richard N.

    1998-01-01

    Perhaps the best way to summarize the past three-year grant period is to cite the publications and present a brief synopsis of each: 1. "Indigenous Polycyclic Aromatic Hydrocarbon Molecules in Circumstellar Graphite Grains." Bulk C-12/C-13 isotope ratios observed in some graphite grains extracted from primitive meteorites point strongly to a circumstellar origin. By applying our technique of microprobe two-step laser desorption laser ionization mass spectrometry ((mu)L(sup 2)MS) to individual circumstellar graphite grains we have measured the C-12/C-13 isotope ratio of various polycyclic aromatic hydrocarbons (PAHS) found in these grains. 2. "Deuterium Enrichments in Cluster IDPS," Large enrichments in the D/H isotope ratios in IDPs likely arise from the preservation of presolar molecules. 3. "Evidence for thermalization of surface-disorder molecules at heating rates of 10(exp 8) K/s". A careful study of the ((mu)L(sup 2)MS) of aniline-d(sub 7) from a single-crystal surface (0001) of sapphire (al2O3) shows that all measured properties are consistent with a thermal mechanism for desorption. 4. "Search for past life on Mars; possible relic biogenic activity in Martian meteorite ALH 84001. The authors examined the Martian meteorite ALH 84001 and found several lines of evidence compatible with existence of past primitive (single-cell) life on early Mars. 5. "Microprobe two-step laser mass spectrometry as an analytical tool for meteorite samples". THis paper presents a comprehensive review of (mu)L(sup 2)MS and how this technique can be applied to meteoritic samples. 6. "Indigenous polycyclic aromatic hydrocarbons in circumstellar graphite grains from primitive meteorites". The C-12/C-13 isotope ratios were measured for PAHs in a total of 89 spherical graphite grains. 7. "Observation of indigenous polycyclic aromatic hydrocarbons in "Giant" carbonaceous antarctic micrometeorites." The (mu)L(sup 2)MS method was used to establish the nature and distribution of PAHs in

  16. An Adulterated Martian Meteorite

    NASA Astrophysics Data System (ADS)

    Taylor, G. J.

    1999-07-01

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

  17. Peering Through a Martian Veil: ALHA84001 Sm-Nd Age Revisited

    NASA Technical Reports Server (NTRS)

    Nyquist, Laurence E.; Shih, Chi-Yu

    2013-01-01

    The ancient Martian orthopyroxenite ALH84001experienced a complex history of impact and aqueous alteration events. Here we summarize Sm-147-Nd-143 and Sm-146-Nd-142 analyses performed at JSC. Further, using REE data, we model the REE abundance pattern of the basaltic magma parental to ALH84001 cumulus orthopyroxene. We find the Sm-146-Nd-142 isotopic data to be consistent with isotopic evolution in material having the modeled Sm/Nd ratio from a time very close to the planet's formation to igneous crystallization of ALH84001 as inferred from the Sm-Nd studies.

  18. Chlorine Abundances in Martian Meteorites

    NASA Technical Reports Server (NTRS)

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

    2009-01-01

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

  19. Organic Carbon Exists in Mars Meteorites: where is it on the Martian Surface?

    NASA Astrophysics Data System (ADS)

    McKay, David; Clemett, Simon; Gibson, Everett; Thomas-Keprta, Kathie; Wentworth, Susan

    The search for organic carbon on Mars has been a major challenge. The first attempt was the Viking GC-MS in situ experiment which gave inconclusive results at two sites on Mars [1]. After the discovery that the SNC meteorites were from Mars [2], [3-5] reported C isotopic compositional information which suggested a reduced C component present in the Martian meteorites. [6 7] reported the presence of reduced C components (i.e., polycyclic aromatic hydrocarbons) associated with the carbonate globules in ALH84001. Jull et al. [8] noted in Nakhla there was an acid insoluble C component present with more than 75% of its C lacking any 14 C, which is modern-day terrestrial carbon. This C fraction was believed to be either indigenous martian or ancient meteoritic carbon. Fisk et al. [9, 10] have shown textural evidence along with C-enriched areas within fractures in Nakhla and ALH84001. Westall et al. [11] have shown the presence of a large irregular fragment of organic material completely embedded within a chip of ALH84001. Interior samples from the Nakhla SNC made available by the British Museum of Natural His-tory, were analyzed. Petrographic examination [12] of Nakhla showed evidence of fractures ( 0.5 m wide) filled with dark brown to black dendritic material with characteristics similar to those observed by [10]. Iddingsite is also present along fractures in olivine. Fracture filling and dendritic material was examined by SEM-EDX, TEM-EDX, Focused Electron Beam mi-croscopy, Laser Raman Spectroscopy, Nano-SIMS Ion Micro-probe, and Stepped-Combustion Static Mass Spectrometry. Observations from the first three techniques are discussed in [12 and 13]. Nano-SIMS Ion Microprobe studies of the C-bearing fractures, containing the optically dark dendritic material, show direct correlation between C- and CN- abundances. Ion abun-dances for epoxy are distinct from those of the dendritic material[12] . Laser Raman Spectrometry was utilized to examine the optically dark dendritic

  20. Carbonates in ALH 84001: Part of the Story of Water on Mars

    NASA Astrophysics Data System (ADS)

    Corrigan, C. M.

    2004-07-01

    Carbonate-rich regions in ALH 84001 are complicated. There are familiar forms of carbonate as well as fascinating textural forms previously unreported including carbonate rosettes, planiform "slab" carbonates, distinct "post-slab" magnesium carbonates (magnesite), and carbonates interstitial to feldspathic glass and orthopyroxene. Slab carbonates reveal portions of the carbonate growth sequence not seen in the rosettes and suggest that initial nucleating compositions were rich in calcium. They formed in two major stages. The first stage involved growth of the rosettes and slab carbonates. This step was controlled by the rate of crystal nucleation, how fast the ingredients were delivered to the growing crystals, and how much fluid was available. Cosmochemists call this type of growth "kinetically controlled." Next, an alteration event formed the magnesite-siderite (iron carbonate) layers on the exterior surfaces of the carbonate. Post-slab magnesite, intimately associated with silica glass, is compositionally similar to the magnesite in these secondary exterior layers, but represents a later generation of carbonate growth. Formation of feldspathic glasses had little or no thermal effect on carbonates, as indicated by the lack of thermal decomposition or any compositional changes associated with glass/carbonate contacts. The carbonates tell an important story about water in the ancient crust of Mars. The presence of numerous, distinct generations of carbonate formation and relatively clear fracture chronology within carbonate further suggest that interactions between ALH 84001 and the crustal fluids of Mars were discontinuous and occurred only a few times over its 4.5 Ga history. The reactivation and remobilization of fluids (causing events such as formation of magnesite-siderite-magnesite layers and precipitation of post-slab magnesite) and the fracturing within the rock were almost certainly driven by impacts. The evidence for punctuated, impact-driven interaction

  1. (U-Th)/He Dating of Merrillites and Chlorapatites From Martian Meteorite Los Angeles

    NASA Astrophysics Data System (ADS)

    Min, K. K.; Reiners, P. W.; Nicolescu, S.; Greenwood, J. P.

    2003-12-01

    radius of the original body ejected from Mars was probably larger than ˜100 cm. The few old and variable ages observed may be due to exceptionally large (>600 micrometers) phosphate grains found in the LA, or incomplete He degassing during the shock metamorphism caused by heterogeneous heating as revealed in the other Martian meteorites. This study shows that phosphate (U-Th)/He thermochronometry can be used to understand the timing and dynamics of collision-related shock metamorphic processes in other meteorites, such as ALH84001.

  2. Three-Dimensional Morphological Analysis of ALH84001 Magnetite Using Electron Tomography

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, Kathie L.; Clemett, Simon J.; Shimmin, Joel; Morphew, Mary; McIntosh, J. Richard; Bazylinski, Dennis A.; Kirschvink, Joseph L.; Wentworth, Susan J.; McKay, David S.; Vali, Hojatollah

    2003-01-01

    We report here the crystal morphologies of MV-1 and ALH84001 magnetites as calculated by back-projection using electron tomography. In the present study, we used a 300 keV TEM with a field emission gun (Tecnai F-30 from FEI Inc.), equipped with a 2048 x 2048 pixel CCD camera from Gatan Inc. to image magnetite crystals over tilt ranges of approx. +/- 72 deg in 2 deg tilt intervals. The images were aligned for back-projection, either manually, or through the use of fiducial 5 nm Au spheres affixed to the specimen prior to microscopy. Three-dimensional (3-D) reconstructions were computed using weighted back-projection of the tilted views. The tomograms were viewed and analyzed as a series of slices 1.0 nm thick, taken parallel to the specimen-supporting grid, using the IMOD software package. The shape of each magnetite crystal was determined by defining the external contour of a given magnetite in each slice and assembling a stack of these contours in 3-D. To aid in visualization, the stacked contour array was reduced to an optimal mesh by Delaunay triangulation. The surface normal to each of the triangles in the mesh was calculated and the triangle faces colored according to the orientation of that surface normal relative to the principal crystallographic axis of magnetite. Green surfaces correspond to {111} orientations, blue surfaces to {100} orientations, and red surfaces to {110} orientations. Triangles whose surface normal did not correspond to one of the principal axes were colored gray. Within the experimental and numerical uncertainties of the deconvolution, the tomographic reconstruction of both MV-1 and ALH84001 magnetites are equivalent and correspond to a truncated hexa-octahedral morphology.

  3. Organic Carbon Exists in Mars Meteorites: where is it on the Martian Surface?

    NASA Astrophysics Data System (ADS)

    McKay, David; Clemett, Simon; Gibson, Everett; Thomas-Keprta, Kathie; Wentworth, Susan

    The search for organic carbon on Mars has been a major challenge. The first attempt was the Viking GC-MS in situ experiment which gave inconclusive results at two sites on Mars [1]. After the discovery that the SNC meteorites were from Mars [2], [3-5] reported C isotopic compositional information which suggested a reduced C component present in the Martian meteorites. [6 7] reported the presence of reduced C components (i.e., polycyclic aromatic hydrocarbons) associated with the carbonate globules in ALH84001. Jull et al. [8] noted in Nakhla there was an acid insoluble C component present with more than 75% of its C lacking any 14 C, which is modern-day terrestrial carbon. This C fraction was believed to be either indigenous martian or ancient meteoritic carbon. Fisk et al. [9, 10] have shown textural evidence along with C-enriched areas within fractures in Nakhla and ALH84001. Westall et al. [11] have shown the presence of a large irregular fragment of organic material completely embedded within a chip of ALH84001. Interior samples from the Nakhla SNC made available by the British Museum of Natural His-tory, were analyzed. Petrographic examination [12] of Nakhla showed evidence of fractures ( 0.5 m wide) filled with dark brown to black dendritic material with characteristics similar to those observed by [10]. Iddingsite is also present along fractures in olivine. Fracture filling and dendritic material was examined by SEM-EDX, TEM-EDX, Focused Electron Beam mi-croscopy, Laser Raman Spectroscopy, Nano-SIMS Ion Micro-probe, and Stepped-Combustion Static Mass Spectrometry. Observations from the first three techniques are discussed in [12 and 13]. Nano-SIMS Ion Microprobe studies of the C-bearing fractures, containing the optically dark dendritic material, show direct correlation between C- and CN- abundances. Ion abun-dances for epoxy are distinct from those of the dendritic material[12] . Laser Raman Spectrometry was utilized to examine the optically dark dendritic

  4. Formation of meteorite hydrocarbons from thermal decomposition of siderite (FeCO 3)

    NASA Astrophysics Data System (ADS)

    McCollom, Thomas M.

    2003-01-01

    Thermal decomposition of siderite has been proposed as a source of magnetite in martian meteorites. Laboratory experiments were conducted to evaluate the possibility that this process might also result in abiotic synthesis of organic compounds. Siderite decomposition in the presence of water vapor at 300°C generated a variety of organic products dominated by alkylated and hydroxylated aromatic compounds. The results suggest that formation of magnetite by thermal decomposition of siderite on the precursor rock of the martian meteorite ALH84001 would have been accompanied by formation of organic compounds and may represent a source of extraterrestrial organic matter in the meteorite and on Mars. The results also suggest that thermal decomposition of siderite during metamorphism could account for some of the reduced carbon observed in metasedimentary rocks from the early Earth.

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

    NASA Astrophysics Data System (ADS)

    Min, K. K.

    2013-12-01

    . The diffusion domain size of phosphates in Martian meteorites is highly variable, therefore careful examination using Scanning Electron Microscopy and low-T stepped heating experiments is required to determine the distribution of diffusion domain radii. The Tpeak estimates for four Martian meteorites (Zagami, ALHA77005, Los Angeles, and ALH84001) show a general trend of positive correlation with Tpost-shock determined by the traditional method. For the most intensively shocked meteorite of ALHA77005, the two independent methods yield consistent Tpeak estimates. However, for the remaining three meteorites, which experienced less intensive shock, there is a systematic bias: the direct Tpeak estimates (He diffusion modeling) are higher than the Tpeak converted from Tpost-shock (traditional method). The discrepancy can be related to (1) highly uncertain Tpre-shock for each Martian meteorite, (2) large variation of Tpost-shock estimated from different research groups, and (3) He loss during thermal events in addition to the ejection-related shock. Helium diffusion modeling for other shergottites, which experienced less intensive shock (e.g., Shergotty, QUE94201), will further clarify the systematic bias between the two methods.

  6. Martian Alteration in Unique Meteorite NWA 8159?

    NASA Astrophysics Data System (ADS)

    Hallis, L. J.; Simpson, S.; Mark, D.; Lee, M. R.

    2016-08-01

    This study aims to determine if the olivine alteration in martian meteorite NWA 8159 has a martian origin. If so, the unique nature of this meteorite presents evidence for aqueous processes at a new time and location on the martian surface.

  7. Radiometric Ages of Martian Meteorites compared to Martian Surfaces Ages

    NASA Technical Reports Server (NTRS)

    Nyquist, L. E.; Shih, C.-Y.

    1999-01-01

    The surprisingly young Rb-Sr age of the Shergotty meteorite contributed to early suggestions that it might be of martian origin. their redox state and oxygen isotopic compositions linked the shergottites to the clino-pyroxenite nakhlites and the dunite Chassigny, causing them to be grouped as SNC meteorites. These characteristics, but especially the similarity of the elemental and isotopic compositions of gases trapped in shergottites to those of the martian atmosphere, have caused the martian origin of the SNC and related meteorites to be widely accepted. Although the young ages were one of the early hints of a martian origin for the SNC meteorites, their interpretation has remained somewhat ambiguous. We will review the radiometric ages of the martian meteorites and attempt to place them into the context of martian surface ages.

  8. Silicate mineralogy of martian meteorites

    NASA Astrophysics Data System (ADS)

    Papike, J. J.; Karner, J. M.; Shearer, C. K.; Burger, P. V.

    2009-12-01

    Basalts and basaltic cumulates from Mars (delivered to Earth as meteorites) carry a record of the history of that planet - from accretion to initial differentiation and subsequent volcanism, up to recent times. We provide new microprobe data for plagioclase, olivine, and pyroxene from 19 of the martian meteorites that are representative of the six types of martian rocks. We also provide a comprehensive WDS map dataset for each sample studied, collected at a common magnification for easy comparison of composition and texture. The silicate data shows that plagioclase from each of the rock types shares similar trends in Ca-Na-K, and that K 2O/Na 2O wt% of plagioclase multiplied by the Al content of the bulk rock can be used to determine whether a rock is "enriched" or "depleted" in nature. Olivine data show that meteorite Y 980459 is a primitive melt from the martian mantle as its olivine crystals are in equilibrium with its bulk rock composition; all other olivine-bearing Shergottites have been affected by fractional crystallization. Pyroxene quadrilateral compositions can be used to isolate the type of melt from which the grains crystallized, and minor element concentrations in pyroxene can lend insight into parent melt compositions. In a comparative planetary mineralogy context, plagioclase from Mars is richer in Na than terrestrial and lunar plagioclase. The two most important factors contributing to this are the low activity of Al in martian melts and the resulting delayed nucleation of plagioclase in the crystallizing rock. Olivine from martian rocks shows distinct trends in Ni-Co and Cr systematics compared with olivine from Earth and Moon. The trends are due to several factors including oxygen fugacity, melt compositions and melt structures, properties which show variability among the planets. Finally, Fe-Mn ratios in both olivine and pyroxene can be used as a fingerprint of planetary parentage, where minerals show distinct planetary trends that may have been

  9. Isotope ratios of H, C, and O in CO2 and H2O of the martian atmosphere.

    PubMed

    Webster, Chris R; Mahaffy, Paul R; Flesch, Gregory J; Niles, Paul B; Jones, John H; Leshin, Laurie A; Atreya, Sushil K; Stern, Jennifer C; Christensen, Lance E; Owen, Tobias; Franz, Heather; Pepin, Robert O; Steele, Andrew; Achilles, Cherie; Agard, Christophe; Alves Verdasca, José Alexandre; Anderson, Robert; Anderson, Ryan; Archer, Doug; Armiens-Aparicio, Carlos; Arvidson, Ray; Atlaskin, Evgeny; Aubrey, Andrew; Baker, Burt; Baker, Michael; Balic-Zunic, Tonci; Baratoux, David; Baroukh, Julien; Barraclough, Bruce; Bean, Keri; Beegle, Luther; Behar, Alberto; Bell, James; Bender, Steve; Benna, Mehdi; Bentz, Jennifer; Berger, Gilles; Berger, Jeff; Berman, Daniel; Bish, David; Blake, David F; Blanco Avalos, Juan J; Blaney, Diana; Blank, Jen; Blau, Hannah; Bleacher, Lora; Boehm, Eckart; Botta, Oliver; Böttcher, Stephan; Boucher, Thomas; Bower, Hannah; Boyd, Nick; Boynton, Bill; Breves, Elly; Bridges, John; Bridges, Nathan; Brinckerhoff, William; Brinza, David; Bristow, Thomas; Brunet, Claude; Brunner, Anna; Brunner, Will; Buch, Arnaud; Bullock, Mark; Burmeister, Sönke; Cabane, Michel; Calef, Fred; Cameron, James; Campbell, John; Cantor, Bruce; Caplinger, Michael; Caride Rodríguez, Javier; Carmosino, Marco; Carrasco Blázquez, Isaías; Charpentier, Antoine; Chipera, Steve; Choi, David; Clark, Benton; Clegg, Sam; Cleghorn, Timothy; Cloutis, Ed; Cody, George; Coll, Patrice; Conrad, Pamela; Coscia, David; Cousin, Agnès; Cremers, David; Crisp, Joy; Cros, Alain; Cucinotta, Frank; d'Uston, Claude; Davis, Scott; Day, Mackenzie; de la Torre Juarez, Manuel; DeFlores, Lauren; DeLapp, Dorothea; DeMarines, Julia; DesMarais, David; Dietrich, William; Dingler, Robert; Donny, Christophe; Downs, Bob; Drake, Darrell; Dromart, Gilles; Dupont, Audrey; Duston, Brian; Dworkin, Jason; Dyar, M Darby; Edgar, Lauren; Edgett, Kenneth; Edwards, Christopher; Edwards, Laurence; Ehlmann, Bethany; Ehresmann, Bent; Eigenbrode, Jen; Elliott, Beverley; Elliott, Harvey; Ewing, Ryan; Fabre, Cécile; Fairén, Alberto; Farley, Ken; Farmer, Jack; Fassett, Caleb; Favot, Laurent; Fay, Donald; Fedosov, Fedor; Feldman, Jason; Feldman, Sabrina; Fisk, Marty; Fitzgibbon, Mike; Floyd, Melissa; Flückiger, Lorenzo; Forni, Olivier; Fraeman, Abby; Francis, Raymond; François, Pascaline; Freissinet, Caroline; French, Katherine Louise; Frydenvang, Jens; Gaboriaud, Alain; Gailhanou, Marc; Garvin, James; Gasnault, Olivier; Geffroy, Claude; Gellert, Ralf; Genzer, Maria; Glavin, Daniel; Godber, Austin; Goesmann, Fred; Goetz, Walter; Golovin, Dmitry; Gómez Gómez, Felipe; Gómez-Elvira, Javier; Gondet, Brigitte; Gordon, Suzanne; Gorevan, Stephen; Grant, John; Griffes, Jennifer; Grinspoon, David; Grotzinger, John; Guillemot, Philippe; Guo, Jingnan; Gupta, Sanjeev; Guzewich, Scott; Haberle, Robert; Halleaux, Douglas; Hallet, Bernard; Hamilton, Vicky; Hardgrove, Craig; Harker, David; Harpold, Daniel; Harri, Ari-Matti; Harshman, Karl; Hassler, Donald; Haukka, Harri; Hayes, Alex; Herkenhoff, Ken; Herrera, Paul; Hettrich, Sebastian; Heydari, Ezat; Hipkin, Victoria; Hoehler, Tori; Hollingsworth, Jeff; Hudgins, Judy; Huntress, Wesley; Hurowitz, Joel; Hviid, Stubbe; Iagnemma, Karl; Indyk, Steve; Israël, Guy; Jackson, Ryan; Jacob, Samantha; Jakosky, Bruce; Jensen, Elsa; Jensen, Jaqueline Kløvgaard; Johnson, Jeffrey; Johnson, Micah; Johnstone, Steve; Jones, Andrea; Joseph, Jonathan; Jun, Insoo; Kah, Linda; Kahanpää, Henrik; Kahre, Melinda; Karpushkina, Natalya; Kasprzak, Wayne; Kauhanen, Janne; Keely, Leslie; Kemppinen, Osku; Keymeulen, Didier; Kim, Myung-Hee; Kinch, Kjartan; King, Penny; Kirkland, Laurel; Kocurek, Gary; Koefoed, Asmus; Köhler, Jan; Kortmann, Onno; Kozyrev, Alexander; Krezoski, Jill; Krysak, Daniel; Kuzmin, Ruslan; Lacour, Jean Luc; Lafaille, Vivian; Langevin, Yves; Lanza, Nina; Lasue, Jeremie; Le Mouélic, Stéphane; Lee, Ella Mae; Lee, Qiu-Mei; Lees, David; Lefavor, Matthew; Lemmon, Mark; Lepinette Malvitte, Alain; Léveillé, Richard; Lewin-Carpintier, Éric; Lewis, Kevin; Li, Shuai; Lipkaman, Leslie; Little, Cynthia; Litvak, Maxim; Lorigny, Eric; Lugmair, Guenter; Lundberg, Angela; Lyness, Eric; Madsen, Morten; Maki, Justin; Malakhov, Alexey; Malespin, Charles; Malin, Michael; Mangold, Nicolas; Manhes, Gérard; Manning, Heidi; Marchand, Geneviève; Marín Jiménez, Mercedes; Martín García, César; Martin, Dave; Martin, Mildred; Martínez-Frías, Jesús; Martín-Soler, Javier; Martín-Torres, F Javier; Mauchien, Patrick; Maurice, Sylvestre; McAdam, Amy; McCartney, Elaina; McConnochie, Timothy; McCullough, Emily; McEwan, Ian; McKay, Christopher; McLennan, Scott; McNair, Sean; Melikechi, Noureddine; Meslin, Pierre-Yves; Meyer, Michael; Mezzacappa, Alissa; Miller, Hayden; Miller, Kristen; Milliken, Ralph; Ming, Douglas; Minitti, Michelle; Mischna, Michael; Mitrofanov, Igor; Moersch, Jeff; Mokrousov, Maxim; Molina Jurado, Antonio; Moores, John; Mora-Sotomayor, Luis; Morookian, John Michael; Morris, Richard; Morrison, Shaunna; Mueller-Mellin, Reinhold; Muller, Jan-Peter; Muñoz Caro, Guillermo; Nachon, Marion; Navarro López, Sara; Navarro-González, Rafael; Nealson, Kenneth; Nefian, Ara; Nelson, Tony; Newcombe, Megan; Newman, Claire; Newsom, Horton; Nikiforov, Sergey; Nixon, Brian; Noe Dobrea, Eldar; Nolan, Thomas; Oehler, Dorothy; Ollila, Ann; Olson, Timothy; de Pablo Hernández, Miguel Ángel; Paillet, Alexis; Pallier, Etienne; Palucis, Marisa; Parker, Timothy; Parot, Yann; Patel, Kiran; Paton, Mark; Paulsen, Gale; Pavlov, Alex; Pavri, Betina; Peinado-González, Verónica; Peret, Laurent; Perez, Rene; Perrett, Glynis; Peterson, Joe; Pilorget, Cedric; Pinet, Patrick; Pla-García, Jorge; Plante, Ianik; Poitrasson, Franck; Polkko, Jouni; Popa, Radu; Posiolova, Liliya; Posner, Arik; Pradler, Irina; Prats, Benito; Prokhorov, Vasily; Purdy, Sharon Wilson; Raaen, Eric; Radziemski, Leon; Rafkin, Scot; Ramos, Miguel; Rampe, Elizabeth; Raulin, François; Ravine, Michael; Reitz, Günther; Rennó, Nilton; Rice, Melissa; Richardson, Mark; Robert, François; Robertson, Kevin; Rodriguez Manfredi, José Antonio; Romeral-Planelló, Julio J; Rowland, Scott; Rubin, David; Saccoccio, Muriel; Salamon, Andrew; Sandoval, Jennifer; Sanin, Anton; Sans Fuentes, Sara Alejandra; Saper, Lee; Sarrazin, Philippe; Sautter, Violaine; Savijärvi, Hannu; Schieber, Juergen; Schmidt, Mariek; Schmidt, Walter; Scholes, Daniel; Schoppers, Marcel; Schröder, Susanne; Schwenzer, Susanne; Sebastian Martinez, Eduardo; Sengstacken, Aaron; Shterts, Ruslan; Siebach, Kirsten; Siili, Tero; Simmonds, Jeff; Sirven, Jean-Baptiste; Slavney, Susie; Sletten, Ronald; Smith, Michael; Sobrón Sánchez, Pablo; Spanovich, Nicole; Spray, John; Squyres, Steven; Stack, Katie; Stalport, Fabien; Stein, Thomas; Stewart, Noel; Stipp, Susan Louise Svane; Stoiber, Kevin; Stolper, Ed; Sucharski, Bob; Sullivan, Rob; Summons, Roger; Sumner, Dawn; Sun, Vivian; Supulver, Kimberley; Sutter, Brad; Szopa, Cyril; Tan, Florence; Tate, Christopher; Teinturier, Samuel; ten Kate, Inge; Thomas, Peter; Thompson, Lucy; Tokar, Robert; Toplis, Mike; Torres Redondo, Josefina; Trainer, Melissa; Treiman, Allan; Tretyakov, Vladislav; Urqui-O'Callaghan, Roser; Van Beek, Jason; Van Beek, Tessa; VanBommel, Scott; Vaniman, David; Varenikov, Alexey; Vasavada, Ashwin; Vasconcelos, Paulo; Vicenzi, Edward; Vostrukhin, Andrey; Voytek, Mary; Wadhwa, Meenakshi; Ward, Jennifer; Weigle, Eddie; Wellington, Danika; Westall, Frances; Wiens, Roger Craig; Wilhelm, Mary Beth; Williams, Amy; Williams, Joshua; Williams, Rebecca; Williams, Richard B; Wilson, Mike; Wimmer-Schweingruber, Robert; Wolff, Mike; Wong, Mike; Wray, James; Wu, Megan; Yana, Charles; Yen, Albert; Yingst, Aileen; Zeitlin, Cary; Zimdar, Robert; Zorzano Mier, María-Paz

    2013-07-19

    Stable isotope ratios of H, C, and O are powerful indicators of a wide variety of planetary geophysical processes, and for Mars they reveal the record of loss of its atmosphere and subsequent interactions with its surface such as carbonate formation. We report in situ measurements of the isotopic ratios of D/H and (18)O/(16)O in water and (13)C/(12)C, (18)O/(16)O, (17)O/(16)O, and (13)C(18)O/(12)C(16)O in carbon dioxide, made in the martian atmosphere at Gale Crater from the Curiosity rover using the Sample Analysis at Mars (SAM)'s tunable laser spectrometer (TLS). Comparison between our measurements in the modern atmosphere and those of martian meteorites such as ALH 84001 implies that the martian reservoirs of CO2 and H2O were largely established ~4 billion years ago, but that atmospheric loss or surface interaction may be still ongoing. PMID:23869013

  10. Isotope ratios of H, C, and O in CO2 and H2O of the martian atmosphere.

    PubMed

    Webster, Chris R; Mahaffy, Paul R; Flesch, Gregory J; Niles, Paul B; Jones, John H; Leshin, Laurie A; Atreya, Sushil K; Stern, Jennifer C; Christensen, Lance E; Owen, Tobias; Franz, Heather; Pepin, Robert O; Steele, Andrew; Achilles, Cherie; Agard, Christophe; Alves Verdasca, José Alexandre; Anderson, Robert; Anderson, Ryan; Archer, Doug; Armiens-Aparicio, Carlos; Arvidson, Ray; Atlaskin, Evgeny; Aubrey, Andrew; Baker, Burt; Baker, Michael; Balic-Zunic, Tonci; Baratoux, David; Baroukh, Julien; Barraclough, Bruce; Bean, Keri; Beegle, Luther; Behar, Alberto; Bell, James; Bender, Steve; Benna, Mehdi; Bentz, Jennifer; Berger, Gilles; Berger, Jeff; Berman, Daniel; Bish, David; Blake, David F; Blanco Avalos, Juan J; Blaney, Diana; Blank, Jen; Blau, Hannah; Bleacher, Lora; Boehm, Eckart; Botta, Oliver; Böttcher, Stephan; Boucher, Thomas; Bower, Hannah; Boyd, Nick; Boynton, Bill; Breves, Elly; Bridges, John; Bridges, Nathan; Brinckerhoff, William; Brinza, David; Bristow, Thomas; Brunet, Claude; Brunner, Anna; Brunner, Will; Buch, Arnaud; Bullock, Mark; Burmeister, Sönke; Cabane, Michel; Calef, Fred; Cameron, James; Campbell, John; Cantor, Bruce; Caplinger, Michael; Caride Rodríguez, Javier; Carmosino, Marco; Carrasco Blázquez, Isaías; Charpentier, Antoine; Chipera, Steve; Choi, David; Clark, Benton; Clegg, Sam; Cleghorn, Timothy; Cloutis, Ed; Cody, George; Coll, Patrice; Conrad, Pamela; Coscia, David; Cousin, Agnès; Cremers, David; Crisp, Joy; Cros, Alain; Cucinotta, Frank; d'Uston, Claude; Davis, Scott; Day, Mackenzie; de la Torre Juarez, Manuel; DeFlores, Lauren; DeLapp, Dorothea; DeMarines, Julia; DesMarais, David; Dietrich, William; Dingler, Robert; Donny, Christophe; Downs, Bob; Drake, Darrell; Dromart, Gilles; Dupont, Audrey; Duston, Brian; Dworkin, Jason; Dyar, M Darby; Edgar, Lauren; Edgett, Kenneth; Edwards, Christopher; Edwards, Laurence; Ehlmann, Bethany; Ehresmann, Bent; Eigenbrode, Jen; Elliott, Beverley; Elliott, Harvey; Ewing, Ryan; Fabre, Cécile; Fairén, Alberto; Farley, Ken; Farmer, Jack; Fassett, Caleb; Favot, Laurent; Fay, Donald; Fedosov, Fedor; Feldman, Jason; Feldman, Sabrina; Fisk, Marty; Fitzgibbon, Mike; Floyd, Melissa; Flückiger, Lorenzo; Forni, Olivier; Fraeman, Abby; Francis, Raymond; François, Pascaline; Freissinet, Caroline; French, Katherine Louise; Frydenvang, Jens; Gaboriaud, Alain; Gailhanou, Marc; Garvin, James; Gasnault, Olivier; Geffroy, Claude; Gellert, Ralf; Genzer, Maria; Glavin, Daniel; Godber, Austin; Goesmann, Fred; Goetz, Walter; Golovin, Dmitry; Gómez Gómez, Felipe; Gómez-Elvira, Javier; Gondet, Brigitte; Gordon, Suzanne; Gorevan, Stephen; Grant, John; Griffes, Jennifer; Grinspoon, David; Grotzinger, John; Guillemot, Philippe; Guo, Jingnan; Gupta, Sanjeev; Guzewich, Scott; Haberle, Robert; Halleaux, Douglas; Hallet, Bernard; Hamilton, Vicky; Hardgrove, Craig; Harker, David; Harpold, Daniel; Harri, Ari-Matti; Harshman, Karl; Hassler, Donald; Haukka, Harri; Hayes, Alex; Herkenhoff, Ken; Herrera, Paul; Hettrich, Sebastian; Heydari, Ezat; Hipkin, Victoria; Hoehler, Tori; Hollingsworth, Jeff; Hudgins, Judy; Huntress, Wesley; Hurowitz, Joel; Hviid, Stubbe; Iagnemma, Karl; Indyk, Steve; Israël, Guy; Jackson, Ryan; Jacob, Samantha; Jakosky, Bruce; Jensen, Elsa; Jensen, Jaqueline Kløvgaard; Johnson, Jeffrey; Johnson, Micah; Johnstone, Steve; Jones, Andrea; Joseph, Jonathan; Jun, Insoo; Kah, Linda; Kahanpää, Henrik; Kahre, Melinda; Karpushkina, Natalya; Kasprzak, Wayne; Kauhanen, Janne; Keely, Leslie; Kemppinen, Osku; Keymeulen, Didier; Kim, Myung-Hee; Kinch, Kjartan; King, Penny; Kirkland, Laurel; Kocurek, Gary; Koefoed, Asmus; Köhler, Jan; Kortmann, Onno; Kozyrev, Alexander; Krezoski, Jill; Krysak, Daniel; Kuzmin, Ruslan; Lacour, Jean Luc; Lafaille, Vivian; Langevin, Yves; Lanza, Nina; Lasue, Jeremie; Le Mouélic, Stéphane; Lee, Ella Mae; Lee, Qiu-Mei; Lees, David; Lefavor, Matthew; Lemmon, Mark; Lepinette Malvitte, Alain; Léveillé, Richard; Lewin-Carpintier, Éric; Lewis, Kevin; Li, Shuai; Lipkaman, Leslie; Little, Cynthia; Litvak, Maxim; Lorigny, Eric; Lugmair, Guenter; Lundberg, Angela; Lyness, Eric; Madsen, Morten; Maki, Justin; Malakhov, Alexey; Malespin, Charles; Malin, Michael; Mangold, Nicolas; Manhes, Gérard; Manning, Heidi; Marchand, Geneviève; Marín Jiménez, Mercedes; Martín García, César; Martin, Dave; Martin, Mildred; Martínez-Frías, Jesús; Martín-Soler, Javier; Martín-Torres, F Javier; Mauchien, Patrick; Maurice, Sylvestre; McAdam, Amy; McCartney, Elaina; McConnochie, Timothy; McCullough, Emily; McEwan, Ian; McKay, Christopher; McLennan, Scott; McNair, Sean; Melikechi, Noureddine; Meslin, Pierre-Yves; Meyer, Michael; Mezzacappa, Alissa; Miller, Hayden; Miller, Kristen; Milliken, Ralph; Ming, Douglas; Minitti, Michelle; Mischna, Michael; Mitrofanov, Igor; Moersch, Jeff; Mokrousov, Maxim; Molina Jurado, Antonio; Moores, John; Mora-Sotomayor, Luis; Morookian, John Michael; Morris, Richard; Morrison, Shaunna; Mueller-Mellin, Reinhold; Muller, Jan-Peter; Muñoz Caro, Guillermo; Nachon, Marion; Navarro López, Sara; Navarro-González, Rafael; Nealson, Kenneth; Nefian, Ara; Nelson, Tony; Newcombe, Megan; Newman, Claire; Newsom, Horton; Nikiforov, Sergey; Nixon, Brian; Noe Dobrea, Eldar; Nolan, Thomas; Oehler, Dorothy; Ollila, Ann; Olson, Timothy; de Pablo Hernández, Miguel Ángel; Paillet, Alexis; Pallier, Etienne; Palucis, Marisa; Parker, Timothy; Parot, Yann; Patel, Kiran; Paton, Mark; Paulsen, Gale; Pavlov, Alex; Pavri, Betina; Peinado-González, Verónica; Peret, Laurent; Perez, Rene; Perrett, Glynis; Peterson, Joe; Pilorget, Cedric; Pinet, Patrick; Pla-García, Jorge; Plante, Ianik; Poitrasson, Franck; Polkko, Jouni; Popa, Radu; Posiolova, Liliya; Posner, Arik; Pradler, Irina; Prats, Benito; Prokhorov, Vasily; Purdy, Sharon Wilson; Raaen, Eric; Radziemski, Leon; Rafkin, Scot; Ramos, Miguel; Rampe, Elizabeth; Raulin, François; Ravine, Michael; Reitz, Günther; Rennó, Nilton; Rice, Melissa; Richardson, Mark; Robert, François; Robertson, Kevin; Rodriguez Manfredi, José Antonio; Romeral-Planelló, Julio J; Rowland, Scott; Rubin, David; Saccoccio, Muriel; Salamon, Andrew; Sandoval, Jennifer; Sanin, Anton; Sans Fuentes, Sara Alejandra; Saper, Lee; Sarrazin, Philippe; Sautter, Violaine; Savijärvi, Hannu; Schieber, Juergen; Schmidt, Mariek; Schmidt, Walter; Scholes, Daniel; Schoppers, Marcel; Schröder, Susanne; Schwenzer, Susanne; Sebastian Martinez, Eduardo; Sengstacken, Aaron; Shterts, Ruslan; Siebach, Kirsten; Siili, Tero; Simmonds, Jeff; Sirven, Jean-Baptiste; Slavney, Susie; Sletten, Ronald; Smith, Michael; Sobrón Sánchez, Pablo; Spanovich, Nicole; Spray, John; Squyres, Steven; Stack, Katie; Stalport, Fabien; Stein, Thomas; Stewart, Noel; Stipp, Susan Louise Svane; Stoiber, Kevin; Stolper, Ed; Sucharski, Bob; Sullivan, Rob; Summons, Roger; Sumner, Dawn; Sun, Vivian; Supulver, Kimberley; Sutter, Brad; Szopa, Cyril; Tan, Florence; Tate, Christopher; Teinturier, Samuel; ten Kate, Inge; Thomas, Peter; Thompson, Lucy; Tokar, Robert; Toplis, Mike; Torres Redondo, Josefina; Trainer, Melissa; Treiman, Allan; Tretyakov, Vladislav; Urqui-O'Callaghan, Roser; Van Beek, Jason; Van Beek, Tessa; VanBommel, Scott; Vaniman, David; Varenikov, Alexey; Vasavada, Ashwin; Vasconcelos, Paulo; Vicenzi, Edward; Vostrukhin, Andrey; Voytek, Mary; Wadhwa, Meenakshi; Ward, Jennifer; Weigle, Eddie; Wellington, Danika; Westall, Frances; Wiens, Roger Craig; Wilhelm, Mary Beth; Williams, Amy; Williams, Joshua; Williams, Rebecca; Williams, Richard B; Wilson, Mike; Wimmer-Schweingruber, Robert; Wolff, Mike; Wong, Mike; Wray, James; Wu, Megan; Yana, Charles; Yen, Albert; Yingst, Aileen; Zeitlin, Cary; Zimdar, Robert; Zorzano Mier, María-Paz

    2013-07-19

    Stable isotope ratios of H, C, and O are powerful indicators of a wide variety of planetary geophysical processes, and for Mars they reveal the record of loss of its atmosphere and subsequent interactions with its surface such as carbonate formation. We report in situ measurements of the isotopic ratios of D/H and (18)O/(16)O in water and (13)C/(12)C, (18)O/(16)O, (17)O/(16)O, and (13)C(18)O/(12)C(16)O in carbon dioxide, made in the martian atmosphere at Gale Crater from the Curiosity rover using the Sample Analysis at Mars (SAM)'s tunable laser spectrometer (TLS). Comparison between our measurements in the modern atmosphere and those of martian meteorites such as ALH 84001 implies that the martian reservoirs of CO2 and H2O were largely established ~4 billion years ago, but that atmospheric loss or surface interaction may be still ongoing.

  11. Discovery of Biological Structures in the Tissint Mars Meteorite

    NASA Astrophysics Data System (ADS)

    Wallis, J.; Wickramasinghe, N. C.; Wallis, Daryl; Miyake, Nori; Wallis, Max; Di Gregorio, Barry; Mufti, Shirwan Al

    2012-03-01

    Preliminary SEM/EDAX studies of the Tissint meteorite shows projections of interior spherical globules rich in C and O. Such concentrations of carbonaceous material in a matrix of mineral grains poses a mystery if biological processes are excluded. They are consistent with remnants of biological structures, thus supporting earlier similar claims for the Mars meteorite ALH84001..

  12. What we have learned about Mars from SNC meteorites

    NASA Technical Reports Server (NTRS)

    Mcsween, Harry Y., Jr.

    1994-01-01

    The SNC meteorites are thought to be igneous martian rocks, based on their young crystallization ages and a close match between the composition of gases implanted in them during shock and the atmosphere of Mars. A related meteorite, ALH84001, may be older and thus may represent ancient martian crust. These petrologically diverse basalts and ultramafic rocks are mostly cumulates, but their parent magmas share geochemical and radiogenic isotopic characteristics that suggest they may have formed by remelting the same mantle source region at different times. Information and inferences about martian geology drawn from these samples include the following: Planetary differentiation occured early at approximately 4.5 GA, probably concurrently with accretion. The martian mantle contains different abundances of moderately volatile and siderophile elements and is more Fe-rich than that of the Earth, which has implications for its mineralogy, density, and origin. The estimated core composition has a S abundance near the threshold value for inner core solidification. The former presence of a core dynamo may be suggested by remanent magnetization in Shergottite-Nakhlite-Chassignite (SNC) meteorites, although these rocks may have been magnetized during shock. The mineralogy of martian surface units, inferred from reflectance spectra, matches that of basaltic shergottites, but SNC lithologies thought to have crystallized in the subsurface are not presently recognized. The rheological properties of martian magmas are more accurately derived form these metorites than from observations of martian flow morphology, although the sampled range of magma compositions islimited. Estimates of planetary water abundance and the amount of outgassed water based on these meteorites are contridictory but overlap estimates based on geological observations and atmospheric measurements. Stable isotope measurements indicate that the martian hydrosphere experienced only limited exchange with the

  13. Chains of Magnetite Crystals in the Meteorite ALH84001: Evidence of Biological Origin

    NASA Technical Reports Server (NTRS)

    Friedmann, E. I.; Wierzchos, J.; Ascaso, C.; Winklhofer, M.

    2001-01-01

    The presence of magnetite crystal chains, missing evidence for their biological origin, as well as five morphological characteristics incompatible with a nonbiological origin are demonstrated by high-power stereo backscattered scanning electron microscopy. Additional information is contained in the original extended abstract.

  14. Evolution of the martian mantle as recorded by igneous rocks

    NASA Astrophysics Data System (ADS)

    Balta, J. B.; McSween, H. Y.

    2013-12-01

    Martian igneous rocks provide our best window into the current state of the martian mantle and its evolution after accretion and differentiation. Currently, those rocks have been examined in situ by rovers, characterized in general from orbiting spacecraft, and analyzed in terrestrial laboratories when found as meteorites. However, these data have the potential to bias our understanding of martian magmatism, as most of the available meteorites and rover-analyzed rocks come from the Amazonian (<2 Ga) and Hesperian (~3.65 Ga) periods respectively, while igneous rocks from the Noachian (>3.8 Ga) have only been examined by orbiters and as the unique meteorite ALH 84001. After initial differentiation, the main planetary-scale changes in the structure of Mars which impact igneous compositions are cooling of the planet and thickening of the crust with time. As the shergottite meteorites give ages <500 Ma1, they might be expected to represent thick-crust, recent volcanism. Using spacecraft measurements of volcanic compositions and whole rock compositions of meteorites, we demonstrate that the shergottite meteorites do not match the composition of the igneous rocks composing the young volcanoes on Mars, particularly in their silica content, and no crystallization or crustal contamination trend reproduces the volcanoes from a shergottite-like parent magma. However, we show that the shergottite magmas do resemble older martian rocks in composition and mineralogy. The Noachian-aged meteorite ALH 84001 has similar radiogenic-element signatures to the shergottites and may derive from a similar mantle source despite the age difference2. Thus, shergottite-like magmas may represent melting of mantle sources that were much more abundant early in martian history. We propose that the shergottites represent the melting products of an originally-hydrous martian mantle, containing at least several hundred ppm H2O. Dissolved water can increase the silica content of magmas and thus

  15. Life on Mars: Evidence from Martian Meteorites

    NASA Technical Reports Server (NTRS)

    McKay, David S.; Thomas-Keptra, Katie L.; Clemett, Simon J.; Gibson, Everett K., Jr.; Spencer, Lauren; Wentworth, Susan J.

    2009-01-01

    New data on martian meteorite 84001 as well as new experimental studies show that thermal or shock decomposition of carbonate, the leading alternative non-biologic explanation for the unusual nanophase magnetite found in this meteorite, cannot explain the chemistry of the actual martian magnetites. This leaves the biogenic explanation as the only remaining viable hypothesis for the origin of these unique magnetites. Additional data from two other martian meteorites show a suite of biomorphs which are nearly identical between meteorites recovered from two widely different terrestrial environments (Egyptian Nile bottomlands and Antarctic ice sheets). This similarity argues against terrestrial processes as the cause of these biomorphs and supports an origin on Mars for these features.

  16. Formations of Bacteria-like Textures by dynamic reactions in Meteorite and Syntheses

    NASA Astrophysics Data System (ADS)

    Miura, Y.

    2009-05-01

    1. Introduction Spherule texture can be formed in dynamic reaction during meteoritic impact in air. However, there are no reports on nano-bacteria-like (i.e. spherule-chained) textures with iron (and Nickel) oxides (with chlorine) in composition and micro-texture with 100nm order [1] in meteorite and synthetic experiment. The purpose of the present study is to elucidate spherule-chained texture with micro-texture of 100nm in order found in the Kuga iron meteorite, Iwakuni, Yamaguchi, Japan, and its first artificial synthesis in laboratory. 2. Two textures in the Kuga meteorite: The Kuga iron meteorite found in Kuga, Iwakuni, Yamaguchi, Japan reveals spherule-chained texture with Fe, Ni-rich composition with 10μm in size, where each spherule contained "long micro-texture in 100nm in size"[1,2]. The complex texture of flow and chained shapes can be found only in the fusion crust of the meteorite formed by quenched and random processes with vapor-melting process in air of the Earth. The FE-ASEM with EDX analyses by an in-situ observation indicate that the matrix of the spherule-chained texture with Fe, Ni, O-rich (with minor Cl) composition is carbon-rich composition formed by impact reactions in air. 3. Comparison with Martian meteorite Remnant of life in ocean can be found by mineralized fossil, which can be found in the Martian meteorite ALH84001 as bacteria-like chained texture of magnetite in composition (in 100nm order) around carbonate spherules [3]. Similarity of bacteria-like texture of the ALH84001 compared with the Kuga meteorites in this study are composition of Fe-rich, C-bearing, and chained texture of small size replaced by Fe and O-rich composition in air. Major difference of these textures is no carbonates minerals in the Kuga meteorite at dynamic reaction in air [1, 2, 3]. 4. First synthesis of bacteria- like akaganeite: A bacteria-like texture with Fe oxides (with minor chlorine as akaganeite-like compositions) is synthesized by chlorine and water

  17. Phosphates and Carbon in Martian Meteorites

    NASA Technical Reports Server (NTRS)

    Mojzsis, Stephen J.

    2000-01-01

    This paper proposes tests for exobiological examination of samples prior to obtaining martian rocks of known provenance via future sample-return missions. If we assume that all of the secondary minerals in martian meteorite ET79001 were indeed cogenetic and originate from Mars, we list conclusions that can be drawn that are of exobiological interest. This work serves as a preamble for the subsequent work listed below.

  18. Microfossils, biominerals, and chemical biomarkers in meteorites

    NASA Astrophysics Data System (ADS)

    Hoover, Richard B.; Rozanov, Alexei Y.

    2003-01-01

    The discovery of biominerals, chemical biomarkers and evidence of microfossils in the Mars meteorite (ALH84001) stimulated research into biomarkers, microbial extremophiles and provided impetus to the newly emerging fields of Astrobiology and Bacterial Paleontology. The debate following the ALH84001 results has highlighted the importance of developing methodologies for recognition of mineral and elemental bioindicators, chemical biomarkers and microfossils in terrestrial rocks and meteorites prior to sample return missions to comets, asteroids, and Mars. Comparative studies of living and fossil micro-organisms and biomarkers are vital to developing expertise needed to recognize indigenous biosignatures and recent contaminants. This paper reviews elemental and mineral bioindicators, chemical biomarkers and keropgen in terrestrial rocks and meteorites. Electron Microscopy images of hyperthermophilic nanobacteria, sulfur and sulfate reducing bacteria, and mineralized microfossils and kerogen found in-situ in carbonaceous meteorite rock matrix are presented.

  19. Lunar and Planetary Science XXXV: Martian Meteorites: Chemical Weathering

    NASA Technical Reports Server (NTRS)

    2004-01-01

    The session "Martian Meteorites: Chemical Weathering" included the following reports:Chemical Weathering Records of Martian Soils Preserved in the Martian Meteorite EET79001; Synchrotron X-Ray Diffraction Analysis of Meteorites in Thin Section: Preliminary Results; A Survey of Olivine Alteration Products Using Raman Spectroscopy; and Rb-Sr and Sm-Nd Isotope Systematics of Shergottite NWA 856: Crystallization Age and Implications for Alteration of Hot Desert SNC Meteorites.

  20. The Germanium Dichotomy in Martian Meteorites

    NASA Technical Reports Server (NTRS)

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

    2016-01-01

    Germanium is a moderately volatile and siderophile element that follows silicon in its compatibility during partial melting of planetary mantles. Despite its obvious usefulness in planetary geochemistry germanium is not analyzed routinely, with there being only three prior studies reporting germanium abundances in Martian meteorites. The broad range (1-3 ppm) observed in Martian igneous rocks is in stark contrast to the narrow range of germanium observed in terrestrial basalts (1.5 plus or minus 0.1 ppm). The germanium data from these studies indicates that nakhlites contain 2-3 ppm germanium, while shergottites contain approximately 1 ppm germanium, a dichotomy with important implications for core formation models. There have been no reliable germanium abundances on chassignites. The ancient meteoritic breccia, NWA 7533 (and paired meteorites) contains numerous clasts, some pristine and some impact melt rocks, that are being studied individually. Because germanium is depleted in the Martian crust relative to chondritic impactors, it has proven useful as an indicator of meteoritic contamination of impact melt clasts in NWA 7533. The germanium/silicon ratio can be applied to minerals that might not partition nickel and iridium, like feldspars. We report germanium in minerals from the 3 known chassignites, 2 nakhlites and 5 shergottites by LAICP- MS using a method optimized for precise germanium analysis.

  1. Amino acids in the Martian meteorite Nakhla

    PubMed Central

    Glavin, Daniel P.; Bada, Jeffrey L.; Brinton, Karen L. F.; McDonald, Gene D.

    1999-01-01

    A suite of protein and nonprotein amino acids were detected with high-performance liquid chromatography in the water- and acid-soluble components of an interior fragment of the Martian meteorite Nakhla, which fell in Egypt in 1911. Aspartic and glutamic acids, glycine, alanine, β-alanine, and γ-amino-n-butyric acid (γ-ABA) were the most abundant amino acids detected and were found primarily in the 6 M HCl-hydrolyzed, hot water extract. The concentrations ranged from 20 to 330 parts per billion of bulk meteorite. The amino acid distribution in Nakhla, including the d/l ratios (values range from <0.1 to 0.5), is similar to what is found in bacterially degraded organic matter. The amino acids in Nakhla appear to be derived from terrestrial organic matter that infiltrated the meteorite soon after its fall to Earth, although it is possible that some of the amino acids are endogenous to the meteorite. The rapid amino acid contamination of Martian meteorites after direct exposure to the terrestrial environment has important implications for Mars sample-return missions and the curation of the samples from the time of their delivery to Earth. PMID:10430856

  2. Amino acids in the Martian meteorite Nakhla

    NASA Technical Reports Server (NTRS)

    Glavin, D. P.; Bada, J. L.; Brinton, K. L.; McDonald, G. D.

    1999-01-01

    A suite of protein and nonprotein amino acids were detected with high-performance liquid chromatography in the water- and acid-soluble components of an interior fragment of the Martian meteorite Nakhla, which fell in Egypt in 1911. Aspartic and glutamic acids, glycine, alanine, beta-alanine, and gamma-amino-n-butyric acid (gamma-ABA) were the most abundant amino acids detected and were found primarily in the 6 M HCl-hydrolyzed, hot water extract. The concentrations ranged from 20 to 330 parts per billion of bulk meteorite. The amino acid distribution in Nakhla, including the D/L ratios (values range from <0.1 to 0.5), is similar to what is found in bacterially degraded organic matter. The amino acids in Nakhla appear to be derived from terrestrial organic matter that infiltrated the meteorite soon after its fall to Earth, although it is possible that some of the amino acids are endogenous to the meteorite. The rapid amino acid contamination of Martian meteorites after direct exposure to the terrestrial environment has important implications for Mars sample-return missions and the curation of the samples from the time of their delivery to Earth.

  3. Evidence for Ancient Martian Life

    NASA Technical Reports Server (NTRS)

    Gibson, Everett K., Jr.

    1999-01-01

    Three SNC meteorites ranging in age from 4.5 Ga. to 1.3 Ga. to 165 m.y. contain features suggestive, of past biogenic activity on Mars. Because we do not know what past martian life looks like or its physical or chemical properties, the only tools or criteria which the scientific community have to evaluate evidence of past life is to use evidence for early life on earth. There are features within ALH8400 I's carbonate globules and the pre-terrestrial aqueous alteration phases of Nakhla and Shergotty which have been interpreted as possible evidence for past life on early Mars. Eight criteria have been established for the recognition of past life within terrestrial geologic samples. They are: (a) geologic context; (b) sample's age and stratigraphic location (c) cellular morphology; (d) colonies; (e) biominerals; (f) stable isotope patterns unique to biology; (g) organic biomarkers; (h) indigenous features to the sample. For general acceptance of past life, essentially most or all of these criteria must be met. Studies have shown conclusively that the reduced carbon components in ALH84001 and Nakhla are indigenous to the meteorites and are not terrestrial contaminants Based on carbon isotopic compositions and mineralogical morphologies, there is no question or disagreement that the carbonate globules or embedded magnetites in ALH84001 and the pre-terrestrial aqueous alteration products in Nakhla and Shergotty were formed on Mars. Possible microfossil structures and some reduced carbon components in the carbonates and pre-terrestrial aqueous alteration products are, therefore, almost certainly indigenous, but other possible evidence for life (e.g. amino acids) may be a result of terrestrial contamination Our hypothesis of possible early life on Mars was presented in August 1996. Today, we believe it stands stronger than when originally presented. To date, no fatal strikes have been made to any of our original four lines of evidence. While details of the hypothesis are

  4. SNC Meteorites and Martian Reservoirs

    NASA Technical Reports Server (NTRS)

    Jones, J. H.

    2002-01-01

    The martian mantle is apparently heterogeneous, which opens the possibility that it is layered, with each layer convectively isolated. If this is correct, melt generation should occur either at thermal boundary layers or in plumes generated at those boundaries. Mantle layering may be a good means of slowing the planet's cooling rate, allowing young volcanism. Layering may also provide a means for keeping the crust and upper mantle cool, allowing the preservation of ancient variations in crustal thickness.

  5. Evidence for methane in Martian meteorites

    PubMed Central

    Blamey, Nigel J. F.; Parnell, John; McMahon, Sean; Mark, Darren F.; Tomkinson, Tim; Lee, Martin; Shivak, Jared; Izawa, Matthew R. M.; Banerjee, Neil R.; Flemming, Roberta L.

    2015-01-01

    The putative occurrence of methane in the Martian atmosphere has had a major influence on the exploration of Mars, especially by the implication of active biology. The occurrence has not been borne out by measurements of atmosphere by the MSL rover Curiosity but, as on Earth, methane on Mars is most likely in the subsurface of the crust. Serpentinization of olivine-bearing rocks, to yield hydrogen that may further react with carbon-bearing species, has been widely invoked as a source of methane on Mars, but this possibility has not hitherto been tested. Here we show that some Martian meteorites, representing basic igneous rocks, liberate a methane-rich volatile component on crushing. The occurrence of methane in Martian rock samples adds strong weight to models whereby any life on Mars is/was likely to be resident in a subsurface habitat, where methane could be a source of energy and carbon for microbial activity. PMID:26079798

  6. Evidence for methane in Martian meteorites

    NASA Astrophysics Data System (ADS)

    Blamey, Nigel J. F.; Parnell, John; McMahon, Sean; Mark, Darren F.; Tomkinson, Tim; Lee, Martin; Shivak, Jared; Izawa, Matthew R. M.; Banerjee, Neil R.; Flemming, Roberta L.

    2015-06-01

    The putative occurrence of methane in the Martian atmosphere has had a major influence on the exploration of Mars, especially by the implication of active biology. The occurrence has not been borne out by measurements of atmosphere by the MSL rover Curiosity but, as on Earth, methane on Mars is most likely in the subsurface of the crust. Serpentinization of olivine-bearing rocks, to yield hydrogen that may further react with carbon-bearing species, has been widely invoked as a source of methane on Mars, but this possibility has not hitherto been tested. Here we show that some Martian meteorites, representing basic igneous rocks, liberate a methane-rich volatile component on crushing. The occurrence of methane in Martian rock samples adds strong weight to models whereby any life on Mars is/was likely to be resident in a subsurface habitat, where methane could be a source of energy and carbon for microbial activity.

  7. Evidence for methane in Martian meteorites.

    PubMed

    Blamey, Nigel J F; Parnell, John; McMahon, Sean; Mark, Darren F; Tomkinson, Tim; Lee, Martin; Shivak, Jared; Izawa, Matthew R M; Banerjee, Neil R; Flemming, Roberta L

    2015-01-01

    The putative occurrence of methane in the Martian atmosphere has had a major influence on the exploration of Mars, especially by the implication of active biology. The occurrence has not been borne out by measurements of atmosphere by the MSL rover Curiosity but, as on Earth, methane on Mars is most likely in the subsurface of the crust. Serpentinization of olivine-bearing rocks, to yield hydrogen that may further react with carbon-bearing species, has been widely invoked as a source of methane on Mars, but this possibility has not hitherto been tested. Here we show that some Martian meteorites, representing basic igneous rocks, liberate a methane-rich volatile component on crushing. The occurrence of methane in Martian rock samples adds strong weight to models whereby any life on Mars is/was likely to be resident in a subsurface habitat, where methane could be a source of energy and carbon for microbial activity. PMID:26079798

  8. Evidence for methane in Martian meteorites.

    PubMed

    Blamey, Nigel J F; Parnell, John; McMahon, Sean; Mark, Darren F; Tomkinson, Tim; Lee, Martin; Shivak, Jared; Izawa, Matthew R M; Banerjee, Neil R; Flemming, Roberta L

    2015-06-16

    The putative occurrence of methane in the Martian atmosphere has had a major influence on the exploration of Mars, especially by the implication of active biology. The occurrence has not been borne out by measurements of atmosphere by the MSL rover Curiosity but, as on Earth, methane on Mars is most likely in the subsurface of the crust. Serpentinization of olivine-bearing rocks, to yield hydrogen that may further react with carbon-bearing species, has been widely invoked as a source of methane on Mars, but this possibility has not hitherto been tested. Here we show that some Martian meteorites, representing basic igneous rocks, liberate a methane-rich volatile component on crushing. The occurrence of methane in Martian rock samples adds strong weight to models whereby any life on Mars is/was likely to be resident in a subsurface habitat, where methane could be a source of energy and carbon for microbial activity.

  9. A search for nitrates in Martian meteorites

    NASA Astrophysics Data System (ADS)

    Grady, Monica M.; Wright, I. P.; Pillinger, C. T.

    1995-03-01

    Martian atmospheric nitrogen is highly enriched in N-15; nitrates formed by interaction of the atmosphere with the Martian regolith should therefore also be characterized by an elevated delta N-15 value. A search has been made for nitrates in two Martian meteorites, in order to determine the extent of possible regolith-atmosphere interaction. Shock-produced glass from the Elephant Moraine (EET) A79001 shergottite (E1,149) and a water-soluble extract from Nakhla were analyzed by Fourier transform infrared (FTIR) spectroscopy and stepped combustion-stable isotope mass spectrometry. FTIR of both meteorites had features at 1375/cm and 1630/cm, consistent with nitrates. On account of their low thermal stability, nitrates break down at temperatures below 600 C; in this temperature range, E1,149 yeilded approximately 1250 ppb nitrogen with delta N-15 -8 +/- 5%. If this nitrogen is from a nitrate, then it cannot be distinquished from terrestial salts by its isotopic composition. The water-soluble extract from Nakhla also released nitrogen at low temperatures, approximately 17 ppb with delta N-15 approximately -11 +/- 4%. Since Nakhla is an observed 'fall', this is unlikely to be a terrestial weathering product. Nitrates apparently occur in E1,149 and Nakhla, but in very low abundance, and their origin is unclear. The isotopic composition of the salts, which is within the range of that proposed for Martian magmatic volatiles, is far removed from that of nitrogen in the present-day Martian atmosphere. If the nitrates are Martian in origin, they did not form in recent times from reactions involving atmospheric gases. Rather, the nitrates could be the result of an earlier episode of atmospheric interaction with the regolith, or with implantation of magmatic volatiles introduced during degassing.

  10. A review of meteorite evidence for the timing of magmatism and of surface or near-surface liquid water on Mars

    NASA Astrophysics Data System (ADS)

    Borg, Lars; Drake, Michael J.

    2005-09-01

    There is widespread photogeological evidence for ubiquitous water flowing on the surface of Mars. However, the age of surface and near-surface water cannot be deduced with high precision from photogeology. While there is clear evidence for old and young fluvial features in the photogeologic record, the uncertainty in the absolute calibration of the Martian crater flux results in uncertainties of +/-1.5 Gyr in the middle period of Martian geologic history. Aqueous alteration of primary igneous minerals produces secondary minerals in Martian meteorites. Here we use the ages of secondary alteration minerals in Martian meteorites to obtain absolute ages when liquid water was at or near the surface of Mars. Aqueous alteration events in Martian meteorites occurred at 3929 +/- 37 Ma (carbonates in ALH84001), 633 +/- 23 Ma (iddingsite in nakhlites), and 0-170 Ma (salts in shergottites). Furthermore, these events appear to be of short duration, suggesting episodic rather than continuous aqueous alteration of the meteorites. The Martian meteorites appear to be contaminated by Martian surface Pb characterized by a 207Pb/206Pb ratio near 1. Lead of this composition could be produced by water-based alteration on the Martian surface. The high 129Xe/132Xe ratio in the Martian atmosphere compared to Martian meteorites indicates fractionation of I from Xe within ~100 Myr after nucleosynthesis of 129I. Such fractionation is difficult to achieve through magmatic processes. However, water very efficiently fractionates I from Xe, raising the intriguing possibility that Mars had a liquid water ocean within its first 100 Myr.1.

  11. Squeezing Meteorites to Reveal the Martian Mantle

    NASA Astrophysics Data System (ADS)

    Taylor, G. J.

    2006-12-01

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

  12. Martian meteorite Dhofar 019: A new shergottite

    NASA Astrophysics Data System (ADS)

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

    2002-08-01

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

  13. Bacteria in the Tatahouine meteorite: nanometric-scale life in rocks.

    PubMed

    Gillet, P h; Barrat, J A; Heulin, T h; Achouak, W; Lesourd, M; Guyot, F; Benzerara, K

    2000-02-15

    We present a study of the textural signature of terrestrial weathering and related biological activity in the Tatahouine meteorite. Scanning and transmission electron microscopy images obtained on the weathered samples of the Tatahouine meteorite and surrounding soil show two types of bacteria-like forms lying on mineral surfaces: (1) rod-shaped forms (RSF) about 70-80 nm wide and ranging from 100 nm to 600 nm in length; (2) ovoid forms (OVF) with diameters between 70 and 300 nm. They look like single cells surrounded by a cell wall. Only Na, K, C, O and N with traces of P and S are observed in the bulk of these objects. The chemical analyses and electron diffraction patterns confirm that the RSF and OVF cannot be magnetite or other iron oxides, iron hydroxides, silicates or carbonates. The sizes of the RSF and OVF are below those commonly observed for bacteria but are very similar to some bacteria-like forms described in the Martian meteorite ALH84001. All the previous observations strongly suggest that they are bacteria or their remnants. This conclusion is further supported by microbiological experiments in which pleomorphic bacteria with morphology similar to the OVF and RSF objects are obtained from biological culture of the soil surrounding the meteorite pieces. The present results show that bacteriomorphs of diameter less than 100 nm may in fact represent real bacteria or their remnants. PMID:11543579

  14. Volatile trace elements in and cluster analysis of Martian meteorites

    NASA Astrophysics Data System (ADS)

    Wang, Ming-Sheng; Mokos, Jennifer A.; Lipschutz, Michael E.

    1998-07-01

    We report data for 15 mainly volatile trace elements (Ag, Au, Bi, Cd, Co, Cs, Ga, In, Rb, Sb, Se, Te, Tl, U, Zn) by radiochemical neutron activation analysis (RNAA) in whole-rock samples of 5 martian meteorites which, with 7 others studied earlier, completes the 12-member martian meteorite suite. Nearly all of these elements exhibit highly variable compositional continua and are richer in the martian suite compared with other basaltic meteorites. From cluster analysis, we find that the clustering of subtypes based on these elements is virtually identical to that based on contents of major refractory elements and mineralogic/petrographic characteristics, implying that each source region on Mars was closed to volatile transport. Martian meteorite data can be used to infer volatile element contents in that planet.

  15. Weathering and Secondary Minerals in the Martian Meteorite Shergotty

    NASA Technical Reports Server (NTRS)

    Wentworth, Susan J.; Thomas-Keprta, Kathie L.; McKay, David S.

    2000-01-01

    The Shergotty martian meteorite contains weathering features and secondary minerals much like those in Nakhla, including secondary silicates, NaCl, and Ca-sulfate. It is likely that the weathering occurred on Mars.

  16. My favorite Martians: NASA uncovers evidence of ancient life on Mars.

    PubMed

    Dasch, P; Kross, J

    1996-01-01

    The possibility of life on Mars is explored through the recently found meteorite ALH84001. Thought to have left Mars 16 million years ago, the meteorite was found on an Antarctic ice shelf in 1984. Carbonate globules were found containing microfossils and unusual mineral compounds. NASA researchers believe they have found single-celled fossils resembling nanobacteria fossils found on Earth, but caution that much more research is required.

  17. My favorite Martians: NASA uncovers evidence of ancient life on Mars.

    PubMed

    Dasch, P; Kross, J

    1996-01-01

    The possibility of life on Mars is explored through the recently found meteorite ALH84001. Thought to have left Mars 16 million years ago, the meteorite was found on an Antarctic ice shelf in 1984. Carbonate globules were found containing microfossils and unusual mineral compounds. NASA researchers believe they have found single-celled fossils resembling nanobacteria fossils found on Earth, but caution that much more research is required. PMID:11539593

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

    NASA Technical Reports Server (NTRS)

    Jones, J. H.

    1993-01-01

    The SNC meteorites and the measurements of the Viking landers provide our only direct information about the abundance and isotopic composition of Martian volatiles. Indirect measurements include spectroscopic determinations of the D/H ratio of the Martian atmosphere. A personal view of volatile element reservoirs on Mars is presented, largely as inferred from the meteoritic evidence. This view is that the Martian mantle has had several opportunities for dehydration and is most likely dry, although not completely degassed. Consequently, the water contained in SNC meteorites was most likely incorporated during ascent through the crust. Thus, it is possible that water can be decoupled from other volatile/incompatible elements, making the SNC meteorites suspect as indicators of water inventories on Mars.

  19. 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.

  20. Terrestrial microbes in martian and chondritic meteorites

    NASA Astrophysics Data System (ADS)

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

    2007-08-01

    Introduction: The best extraterrestrial analogs for microbiology are meteorites. The chemistry and mineralogy of Asteroid Belt and martian (SNC) meteorites are used as tracers of processes that took place in the early solar system. Meteoritic falls, in particular those of carbonaceous chondrites, are regarded as pristine samples of planetesimal evolution as these rocks are primitive and mostly unprocessed since the formation of the solar system 4.56 billion years ago. Yet, questions about terrestrial contamination and its effects on the meteoritic isotopic, chemical and mineral characteristics often arise. Meteorites are hosts to biological activity as soon as they are in contact with the terrestrial biosphere, like all rocks. A wide biodiversity was found in 21 chondrites and 8 martian stones, and was investigated with cell culture, microscopy techniques, PCR, and LAL photoluminetry. Some preliminary results are presented here. The sample suite included carbonaceous chondrites of types CR, CV, CK, CO, CI, and CM, from ANSMET and Falls. Past studies documented the alteration of meteorites by weathering and biological activity [1]-[4]. Unpublished observations during aqueous extraction for oxygen isotopic analysis [5], noted the formation of biofilms in water in a matter of days. In order to address the potential modification of meteoritic isotopic and chemical signatures, the culture of microbial contaminating species was initiated in 2005, and after a prolonged incubation, some of the species obtained from cell culture were analyzed in 2006. The results are preliminary, and a systematic catalog of microbial contaminants is developing very slowly due to lack of funding. Methods: The primary method was cell culture and PCR. Chondrites. Chondritic meteorite fragments were obtained by breaking stones of approximately one gram in sterile mortars. The core of the rocks, presumably less contaminated than the surface, was used for the present microbial study, and the

  1. Ancient Crustal Diversity Preserved within Martian Meteorite NWA 7034

    NASA Astrophysics Data System (ADS)

    Santos, A. R.; Agee, C. B.; McCubbin, F. M.; Shearer, C. K.; Burger, P. V.

    2014-12-01

    The martian meteorite Northwest Africa (NWA) 7034 is a breccia containing a variety of igneous clasts and igneous derived mineral fragments suspended in a matrix of fine grained material. Igneous clasts were examined using electron probe microanalysis (major and minor element compositions), BSE images (modal mineralogy), and secondary ion mass spectrometry (REEs). The clasts contain minerals of similar composition to martian meteorites and surface rocks, although mineral abundances differ between these clasts and other martian rocks. The clasts vary in rock type and include basalt, andesite, trachyandesite, and an exotic phosphate and FeTi-oxide rich lithology that is more Fe-rich than Wishstone-class rocks analyzed by MER. Many of the basaltic clast compositions match those of Gusev Crater rocks, as well as the average composition of the martian crust determined from orbital data, providing a strong link between this meteorite and the martian crust. Furthermore, studies have shown the majority of igneous materials in this meteorite to be ~4.4 Ga (Yin et al., 2014; Nyquist et al., 2013, Tartèse et al., 2014); this suggests these clasts represent some of the earliest formed martian crust. The range in rock types contained within this meteorite suggest early Mars was capable of producing crust that was diverse in composition, chemically enriched, and oxidized (ΔFMQ +0.7 to +4), at least in local regions. The reason for the difference in chemistry between these ancient crustal rocks and the younger SNC meteorites remains to be determined, but the lithologic diversity recorded by NWA 7034 provides evidence for a petrologically diverse martian surface both spatially and temporally.

  2. Petrology of Martian meteorite Northwest Africa 998

    NASA Astrophysics Data System (ADS)

    Treiman, Allan H.; Irving, Anthony J.

    2008-05-01

    Nakhlite Northwest Africa (NWA) 998 is an augite-rich cumulate igneous rock with mineral compositions and oxygen isotopic composition consistent with an origin on Mars. This 456-gram, partially fusion-crusted meteorite consists of (by volume) ˜75% augite (core composition Wo39En39Fs22), ˜9% olivine (Fo35), ˜7% plagioclase (Ab61An35) as anhedra among augite and olivine, ˜3.5% low-calcium pyroxenes (pigeonite and orthopyroxene) replacing or forming overgrowths on olivine and augite, ˜1% titanomagnetite, and other phases including potassium feldspar, apatite, pyrrhotite, chalcopyrite, ilmenite, and fine-grained mesostasis material. Minor secondary alteration materials include "iddingsite" associated with olivine (probably Martian), calcite crack fillings, and iron oxide/hydroxide staining (both probably terrestrial). Shock effects are limited to minor cataclasis and twinning in augite. In comparison to other nakhlites, NWA 998 contains more low-calcium pyroxenes and its plagioclase crystals are blockier. The large size of the intercumulus feldspars and the chemical homogeneity of the olivine imply relatively slow cooling and chemical equilibration in the late- and post-igneous history of this specimen, and mineral thermometers give subsolidus temperatures near 730 °C. Oxidation state was near that of the QFM buffer, from about QFM-2 in earliest crystallization to near QFM in late crystallization, and to about QFM + 1.5 in some magmatic inclusions. The replacement or overgrowth of olivine by pigeonite and orthopyroxene (with or without titanomagnetite), and the marginal replacement of augite by pigeonite, are interpreted to result from late-stage reactions with residual melts (consistent with experimental phase equilibrium relationships). Apatite is concentrated in planar zones separating apatite-free domains, which suggests that residual magma (rich in P and REE) was concentrated in planar (fracture?) zones and possibly migrated through them. Loss of late magma

  3. A Pb isotopic resolution to the Martian meteorite age paradox

    NASA Astrophysics Data System (ADS)

    Bellucci, J. J.; Nemchin, A. A.; Whitehouse, M. J.; Snape, J. F.; Kielman, R. B.; Bland, P. A.; Benedix, G. K.

    2016-01-01

    Determining the chronology and quantifying various geochemical reservoirs on planetary bodies is fundamental to understanding planetary accretion, differentiation, and global mass transfer. The Pb isotope compositions of individual minerals in the Martian meteorite Chassigny have been measured by Secondary Ion Mass Spectrometry (SIMS). These measurements indicate that Chassigny has mixed with a Martian reservoir that evolved with a long-term 238U/204Pb (μ) value ˜ two times higher than those inferred from studies of all other Martian meteorites except 4.428 Ga clasts in NWA7533. Any significant mixing between this and an unradiogenic reservoir produces ambiguous trends in Pb isotope variation diagrams. The trend defined by our new Chassigny data can be used to calculate a crystallization age for Chassigny of 4.526 ± 0.027 Ga (2σ) that is clearly in error as it conflicts with all other isotope systems, which yield a widely accepted age of 1.39 Ga. Similar, trends have also been observed in the Shergottites and have been used to calculate a >4 Ga age or, alternatively, attributed to terrestrial contamination. Our new Chassigny data, however, argue that the radiogenic component is Martian, mixing occurred on the surface of Mars, and is therefore likely present in virtually every Martian meteorite. The presence of this radiogenic reservoir on Mars resolves the paradox between Pb isotope data and all other radiogenic isotope systems in Martian meteorites. Importantly, Chassigny and the Shergottites are likely derived from the northern hemisphere of Mars, while NWA 7533 originated from the Southern hemisphere, implying that the U-rich reservoir, which most likely represents some form of crust, must be widespread. The significant age difference between SNC meteorites and NWA 7533 is also consistent with an absence of tectonic recycling throughout Martian history.

  4. 'Bounce' and Martian Meteorite of the Same Mold

    NASA Technical Reports Server (NTRS)

    2004-01-01

    These two sets of bar graphs compare the elemental compositions of six martian rocks: 'Bounce,' located at Meridiani Planum; EETA79001-B, a martian meteorite found in Antarctica in 1979; a rock found at the Mars Pathfinder landing site; Shergotty, a martian meteorite that landed in India in 1865; 'Adirondack,' located at Gusev Crater; and 'Humphrey,' also located at Gusev Crater. The graph on the left compares magnesium/iron ratios in the rocks, and the graph on the right compares aluminum/calcium ratios. The results illustrate the diversity of rocks on Mars and indicate that Bounce probably shares origins with the martian meterorite EETA79001-B. The Bounce data was taken on sol 68 by the alpha particle X-ray spectrometer on Mars Exploration Rover Opportunity.

  5. Volatile and other trace elements in Martian meteorites

    NASA Astrophysics Data System (ADS)

    Wang, Ming-Sheng; Mokos, Jennifer; Lipschutz, Michael E.

    1997-03-01

    We summarize RNAA data for 15 trace elements - U, Au, Co, Sb, Ga, Rb, Ag, Se, Cs, Te, Zn, Cd, Bi, Tl and In (in order of putative volatility during nebular condensation and accretion) - in 11 of the 12 known Martian meteorites. We have not yet measured Yamato 793605. Some shergottite data (Shergotty, Zagami, ALH A77005, EET A79001, LEW 88516) were published previously. Data for the six other Martian meteorites are new: the nakhlites and Chassigny samples studied were previously analyzed at NASA/JSC using INAA.

  6. LU-HF Age of Martian Meteorite Larkman Nunatek 06319

    NASA Technical Reports Server (NTRS)

    Shafer, J. T.; Brandon, A. D.; Lapen, T. J.; Righter, M.; Beard, B.; Peslier, A. H.

    2009-01-01

    Lu-Hf isotopic data were collected on mineral separates and bulk rock powders of LAR 06319, yielding an age of 197+/- 29 Ma. Sm-Nd isotopic data and in-situ LA-ICP-MS data from a thin section of LAR 06319 are currently being collected and will be presented at the 2009 LPSC. These new data for LAR 06319 extend the existing data set for the enriched shergottite group. Martian meteorites represent the only opportunity for ground truth investigation of the geochemistry of Mars [1]. At present, approximately 80 meteorites have been classified as Martian based on young ages and distinctive isotopic signatures [2]. LAR 06319 is a newly discovered (as part of the 2006 ANSMET field season) martian meteorite that represents an important opportunity to further our understanding of the geochemical and petrological constraints on the origin of Martian magmas. Martian meteorites are traditionally categorized into the shergottite, nakhlite, and chassignite groups. The shergottites are further classified into three distinct isotopic groups designated depleted, intermediate, and enriched [3,4] based on the isotope systematics and compositions of their source(s).

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

    NASA Technical Reports Server (NTRS)

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

    2014-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2015-01-01

    The surface geology and geomorphology of Mars indicates that it was once warm enough to maintain a large body of liquid water on its surface, though such a warm environment might have been transient. The transition to the present cold and dry Mars is closely linked to the history of surface water, yet the evolution of surficial water is poorly constrained. We have conducted in situ hydrogen isotope (D/H) analyses of quenched and impact glasses in three Martian meteorites (Yamato 980459, EETA79001, LAR 06319) by Cameca ims-6f at Digital Terrain Models (DTM) following the methods of [1]. The hydrogen isotope analyses provide evidence for the existence of a distinct but ubiquitous water/ice reservoir (D/H = 2-3 times Earth's ocean water: Standard Mean Ocean Water (SMOW)) that lasted from at least the time when the meteorites crystallized (173-472 Ma) to the time they were ejected by impacts (0.7-3.3 Ma), but possibly much longer [2]. The origin of this reservoir appears to predate the current Martian atmospheric water (D/H equals approximately 5-6 times SMOW) and is unlikely to be a simple mixture of atmospheric and primordial water retained in the Martian mantle (D/H is approximately equal to SMOW [1]). Given the fact that this intermediate-D/H reservoir (2-3 times SMOW) is observed in a diverse range of Martian materials with different ages (e.g., SNC (Shergottites, Nakhlites, Chassignites) meteorites, including shergottites such as ALH 84001; and Curiosity surface data [3]), we conclude that this intermediate-D/H reservoir is likely a global surficial feature that has remained relatively intact over geologic time. We propose that this reservoir represents either hydrated crust and/or ground ice interbedded within sediments. Our results corroborate the hypothesis that a buried cryosphere accounts for a large part of the initial water budget of Mars.

  9. Pyroxenes in Martian meteorites as petrogenetic indicators

    NASA Technical Reports Server (NTRS)

    McKay, Gordon; Le, L.; Mikouchi, T.; Makishima, J.; Schwandt, C.

    2006-01-01

    Pyroxenes in Martian meteorites are important recorders of petrogenetic processes. Understanding the details of pyroxene major and minor element compositional variations can provide important insights into those processes. A combination of careful petrographic analysis of natural samples and experimental crystallization studies can lead to better understanding of the processes that gave rise to these samples on Mars. In addition, experimentally determined major, minor and trace element partition coefficients are important for using natural pyroxenes to estimate the compositions of the melts from which they crystallized and the oxidation conditions that prevailed during crystallization. We will report on minor element (Al, Ti, Cr) zoning in nakhlite pyroxenes and in synthetic pyroxenes that we have grown for the purposes of determining pyroxene/melt partition coefficients for Sr and REE. The natural pyroxenes have patchy Al zoning that, by analogy with our experimental pyroxenes, we interpret as sector zoning. The irregular patchy nature of the zoning is probably the result of the vagaries of growth kinetics and local environment during crystal growth. More slowly cooled nakhlites have the most distinct bimodal zoning, with one mode having Al2O3 around 0.5-0.6 wt%, and the other around 0.9 %. Average Al content increases with increasing cooling rate. This feature is puzzling, since the cumulus pyroxenes were almost certainly present at the time of eruption. Al and Ti are strongly correlated, but Cr is completely decoupled from those elements. The synthetic pyroxenes are distinctly sector zoned in Al and Ti, and the sector-to-sector variation in Al within a single crystal has important effects on trace element partition coefficients. Trivalent REE are strongly correlated with Al, while divalent elements (Sr, Eu+2) show a significantly weaker correlation. For example, as the Al2O3 content varies from 0.3 to 0.6 wt % from one sector to another, D(Gd) increases by

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

    NASA Astrophysics Data System (ADS)

    Takenouchi, A.; Mikouchi, T.

    2016-08-01

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

  11. Isotopic Evidence for a Martian Regolith Component in Martian Meteorites

    NASA Technical Reports Server (NTRS)

    Rao, M. N.; Nyquist, L. E.; Bogard, D. D.; Garrison, D. H.; Sutton, S.

    2009-01-01

    Noble gas measurements in gas-rich impact-melt (GRIM) glasses in EET79001 shergottite showed that their elemental and isotopic composition is similar to that of the Martian atmosphere [1-3]. The GRIM glasses contain large amounts of Martian atmospheric gases. Those measurements further suggested that the Kr isotopic composition of Martian atmosphere is approximately similar to that of solar Kr. The (80)Kr(sub n) - (80)Kr(sub M) mixing ratio in the Martian atmosphere reported here is approximately 3%. These neutron-capture reactions presumably occurred in the glass-precursor regolith materials containing Sm- and Br- bearing mineral phases near the EET79001/ Shergotty sites on Mars. The irradiated materials were mobilized into host rock voids either during shock-melting or possibly by earlier aeolian / fluvial activity.

  12. Search for organic molecules at the Mars surface: The “Martian Organic Material Irradiation and Evolution” (MOMIE) project

    NASA Astrophysics Data System (ADS)

    Stalport, F.; Coll, P.; Szopa, C.; Raulin, F.

    2008-12-01

    The life on Mars remains an open question because of the lack of proof of its past emergence and its current presence. The only indices of a potential Martian life were provided by the Viking Landers, and the study of the Martian meteorite ALH84001 discovered in the Antarctic. In the two case, the results of experiments could be explained either by the presence of life forms or by abiotic processes. The recent data of Mars Express orbiter and Mars Exploration Rovers show different proofs of a past environment favourable for life. Among the targets we seek, the organic molecules are primordial because they are necessary to the origin of life. A key question is to know if they are present, in which concentration and under which form. Within the framework of a search for organic, we are developing an experimental setup simulating as close as possible the environmental conditions of Mars surface in order to determine how organic species evolve. We present here the first step of the development of this experiment which focuses on the study of the impact of the solar UV radiations reaching the Mars surface on glycine. First results show that glycine does not resist if directly exposed to UV radiations.

  13. The source crater of martian shergottite meteorites.

    PubMed

    Werner, Stephanie C; Ody, Anouck; Poulet, François

    2014-03-21

    Absolute ages for planetary surfaces are often inferred by crater densities and only indirectly constrained by the ages of meteorites. We show that the <5 million-year-old and 55-km-wide Mojave Crater on Mars is the ejection source for the meteorites classified as shergottites. Shergottites and this crater are linked by their coinciding meteorite ejection ages and the crater formation age and by mineralogical constraints. Because Mojave formed on 4.3 billion-year-old terrain, the original crystallization ages of shergottites are old, as inferred by Pb-Pb isotope ratios, and the much-quoted shergottite ages of <600 million years are due to resetting. Thus, the cratering-based age determination method for Mars is now calibrated in situ, and it shifts the absolute age of the oldest terrains on Mars backward by 200 million years.

  14. The source crater of martian shergottite meteorites.

    PubMed

    Werner, Stephanie C; Ody, Anouck; Poulet, François

    2014-03-21

    Absolute ages for planetary surfaces are often inferred by crater densities and only indirectly constrained by the ages of meteorites. We show that the <5 million-year-old and 55-km-wide Mojave Crater on Mars is the ejection source for the meteorites classified as shergottites. Shergottites and this crater are linked by their coinciding meteorite ejection ages and the crater formation age and by mineralogical constraints. Because Mojave formed on 4.3 billion-year-old terrain, the original crystallization ages of shergottites are old, as inferred by Pb-Pb isotope ratios, and the much-quoted shergottite ages of <600 million years are due to resetting. Thus, the cratering-based age determination method for Mars is now calibrated in situ, and it shifts the absolute age of the oldest terrains on Mars backward by 200 million years. PMID:24603150

  15. Exposure and Terrestrial Histories of New Lunar and Martian Meteorites

    NASA Technical Reports Server (NTRS)

    Nishiizumi, K.; Hillegonds, D. J.; McHargue, L. R.; Jull, A. J. T.

    2004-01-01

    Cosmogenic nuclide studies of lunar and Martian meteorites have contributed significantly to our understanding of these objects. By measuring a combination of cosmogenic stable- and radionuclides, we can determine a number of important properties of those meteorites. Most lunar meteorites have complex cosmic ray exposure histories, having been exposed both at some depth on the lunar surface (2 irradiation) before their ejection and as small bodies in space (4 irradiation) during transport from the Moon to the Earth. On the other hand, we have not observed evidence of complex exposure history for any Martian meteorites, so far. These exposures were then followed by residence on Earth s surface, a time commonly referred to as the terrestrial age. In addition to their complement of galactic cosmic ray (GCR) produced nuclides some lunar and Martian meteorites contain nuclides produced by solar cosmic rays (SCR). Unraveling the complex history of these objects requires the measurement of at least four cosmogenic nuclides. The specific goals of these measurements are to constrain or set limits on the following shielding or exposure parameters: (1) the depth of the sample at the time of ejection from the Moon or Mars; (2) the transit time (4 exposure age) from ejection off the lunar or Martian surface to the time of capture by the Earth and (3) the terrestrial residence time. The sum of the transit time and residence time yield an ejection age. The ejection age, in conjunction with the sample depth on the Moon or Mars, can then be used to model impact and ejection mechanisms.

  16. Martian Meteorites and Spacecraft Data: Synergy or Mismatch?

    NASA Astrophysics Data System (ADS)

    McSween, H. Y., Jr.

    2014-12-01

    Martian basaltic meteorites sample more sites than rovers have but, with only a few exceptions, they consist young (Amazonian) igneous rocks. Mars rovers mostly have sampled old (Late Hesperian) sedimentary rocks, although Gusev rocks analyzed by Spirit constitute the best-characterized igneous province on Mars. Because we have only one sedimentary meteorite - NWA 7034, a regolith breccia composed of igneous clasts - we will focus on comparing igneous rocks. Basaltic rocks analyzed so far on the planet's surface are more alkaline than the meteorites. Limited trace element ratios from rover APXS also indicate differences in composition from meteorites. Orbital geochemical and mineralogical data are generally consistent with a basaltic surface, showing localized exposures of sedimentary rocks. Compositional differences may arise from melting and fractionation at different depths, under different redox states, or with different water contents. The various data sets do show some linkages, however. Major mineral compositions are similar (and different from Earth), and rocks tend to be oxidized. Although no hydrous igneous minerals occur (except apatite), many parent magmas contained water that was mostly lost on ascent. It is surprising, then, that calc-alkaline rocks have not been found. Highly fractionated rocks are uncommon, but tephrites and mugearites occur in Gusev, Gale, and NWA 7034. Feldspathic rocks discovered by remote sensing and encountered at Gale are not yet understood. The geochemically distinct magmas represented by different classes of martian meteorites and surface rocks demonstrate that the mantle sources for magmas are heterogeneous. These differences are primary, likely inherited from a magma ocean, since there is no crustal recycling. With only one source of data (either meteoritic or spacecraft), we would have a greatly simplified and incorrect view of martian petrogenesis.

  17. Terrestrial microbes in martian and chondritic meteorites

    NASA Astrophysics Data System (ADS)

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

    2007-08-01

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

  18. Water in Pyroxene and Olivine from Martian Meteorites

    NASA Technical Reports Server (NTRS)

    Peslier, A. H.

    2012-01-01

    Water in the interior of terrestrial planets can be dissolved in fluids or melts and hydrous phases, but can also be locked as protons attached to structural oxygen in lattice defects in nominally anhydrous minerals (NAM) like olivine, pyroxene, or feldspar [1-3]. Although these minerals contain only tens to hundreds of ppm H2O, this water can amount to at least one ocean in mass when added at planetary scales because of the modal dominance of NAM in the mantle and crust [4]. Moreover these trace amounts of water can have drastic effects on melting temperature, rheology, electrical and heat conductivity, and seismic wave attenuation [5]. There is presently a debate on how much water is present in the martian mantle. Secondary ionization mass spectrometry (SIMS) studies of NAM [6], amphiboles and glass in melt inclusions [7-10], and apatites [11, 12] from Martian meteorites report finding as much water as in the same phases from Earth's igneous rocks. Most martian hydrous minerals, however, generally have the relevant sites filled with Cl and F instead of H [13, 14], and experiments using Cl [15] in parent melts can reproduce Martian basalt compositions as well as those with water [16]. We are in the process of analyzing Martian meteorite minerals by Fourier transform infrared spectrometry (FTIR) in order to constrain the role of water in this planet s formation and magmatic evolution

  19. Formation and Evolution of Mars Inferred from Martian Meteorites

    NASA Astrophysics Data System (ADS)

    Borg, L. E.; Symes, S.

    2011-12-01

    The return of samples from Mars has been a long standing NASA objective that, if achieved, would dramatically change our view of the formation and evolution of the terrestrial planets, as well as the physical and chemical conditions in the solar system at the time when life formed on Earth. Significant insight into Mars has been gleaned from the >50 martian meteorites that have landed on Earth. These meteorites fall into 3 categories: First, 165 to 570 Ma basalts and basaltic cumulates, second 1.3 Ga clinopyroxenites and dunites, and third a >4 Ga orthopyroxenite. The basaltic meteorites form a continuum between those with geochemical and isotopic characteristics indicating derivation from depleted and enriched sources. This is most easily explained as mixing between a depleted mantle reservoir and a poorly constrained enriched reservoir in the mantle or crust. Like some basalts. the clinopyroxenites/dunites are slightly enriched in incompatible elements relative to chondrites, but cannot be related to the basaltic meteorites by any simple process. This is most clearly supported by their vastly different short-lived isotopic compositions (e.g. 182W and 142Nd) compared to the basalts. Although all samples have undergone some low temperature alteration on Mars, the orthopyroxenite has undergone significantly more. These observations led to several fundamental conclusions: (1) the young ages indicate the planet is geologically active at present, (2) non-chondritic 182W and 142Nd suggest core formation and silicate differentiation occurred <5 Ma and <25Ma after CAIs, respectively, (3) preservation of isotopic anomalies in short-lived isotopic systems requires geochemical reservoirs on Mars to remain isolated for much of Mars history, (4) basalt geochemical relationships indicate these reservoirs mixed recently during basalt genesis and that these samples are closely related, and (5) water based alteration present in the meteorites occurred throughout martian history

  20. Synchrotron Characterization of Hydrogen and Ferric Iron in Martian Meteorites

    NASA Technical Reports Server (NTRS)

    Dyar, Melinda D.

    2003-01-01

    The hydrogen budget of the Martian interior is distributed among several phases: melts, hydrous minerals, and nominally anhydrous minerals like olivine, pyroxene, and garnet. All these phases are vulnerable to loss of hydrogen during shock, excavation and transport via the mechanism of dehydrogenation, in which the charge on the H protons is left behind as polarons on Fe atoms. Thus, both H and F(3x) must be analyzed in order to reconstruct hydrogen and oxygen fugacities on Mars. To date, SIMS data have elucidated D/H and H contents of hydrous phases in SNC meteorites, but anhydrous martian minerals have not been systematically examined for trace hydrogen. Ferric iron has been quantified using XANES in many marital phases, but integrated studies of both Fe(3x) and H on the same spots are really needed to address the H budget. Here, we measure and profile H and Fe(3x) abundances in and across individual grains of glass and silicates in Martian meteorites. We use the new technology of synchrotron microFI'lR spectroscopy to measure the hydrogen contents of hydrous and nominally anhydrous minerals in martian meteorites on 30-100 microns thick, doubly polished thin sections on spots down to 3 x 3 microns. Synchrotron microXANES was used to analyze Fe(3x) on the same scale, and complementary SIMS D/H data will be collected where possible, though at a slightly larger scale. Development of this combination of techniques is critical because future sample return missions will generate only microscopic samples for study. Results have been used to quantitatively assess the distribution of hydrogen and ferric iron among phases in the martian interior, which will better constrain the geodynamic processes of the interior, as well as the overall hydrogen and water budgets on Mars.

  1. Martian meteorites and Martian magnetic anomalies: a new perspective from NWA 7034 (Invited)

    NASA Astrophysics Data System (ADS)

    Gattacceca, J.; Rochette, P.; Scozelli, R. B.; Munayco, P.; Agee, C. B.; Quesnel, Y.; Cournede, C.; Geissman, J. W.

    2013-12-01

    The magnetic anomalies observed above the Martian Noachian crust [1] require strong crustal remanent magnetization in the 15-60 A/m range over a thickness of 20-50 km [2,3]. The Martian rocks available for study in the form of meteorites do contain magnetic minerals (magnetite and/or pyrrhotite) but in too small amount to account for such strong remanent magnetizations [4]. Even though this contradiction was easily explained by the fact that Martian meteorites (mostly nakhlites and shergottites) are not representative of the Noachian Martian crust, we were left with no satisfactory candidate lithology to account for the Martian magnetic anomalies. The discovery in the Sahara of a new type of Martian meteorite (NWA 7034 [5] and subsequent paired stones which are hydrothermalized volcanic breccia) shed a new light on this question as it contains a much larger amount of ferromagnetic minerals than any other Martian meteorite. We present here a study of the magnetic properties of NWA 7034, together with a review of the magnetic properties of thirty other Martian meteorites. Magnetic measurements (including high and low temperature behavior and Mössbauer spectroscopy) show that NWA 7034 contains about 15 wt.% of magnetite with various degrees of substitution and maghemitization up to pure maghemite, in the pseudo-single domain size range. Pyrrhotite, a common mineral in other Martian meteorites is not detected. Although it is superparamagnetic and cannot carry remanent magnetization, nanophase goethite is present in significant amounts confirming that NWA 7034 is the most oxidized Martian meteorite studied so far, as already indicated by the presence of maghemite (this study) and pyrite [5]. These magnetic properties show that a kilometric layer of a lithology similar to NWA 7034 magnetized in a dynamo field would be enough to account for the strongest Martian magnetic anomalies. Although the petrogenesis of NWA 7034 is still debated, as the brecciation could be either

  2. Sublimation: A Mechanism for the Enrichment of Organics in Antarctic Ice

    NASA Technical Reports Server (NTRS)

    Becker, Luann; McDonald, Gene D.; Glavin, Daniel P.; Bada, Jeffrey L.; Bunch, Theodore E.; Chang, Sherwood (Technical Monitor)

    1997-01-01

    Recent analyses of the carbonate globules present in the Martian meteorite ALH84001 have detected polycyclic aromatic hydrocarbons (PAHs) at the ppm level. The distribution of PAHs observed in ALH84001 was interpreted as being inconsistent with a terrestrial origin and were claimed to be indigenous to the meteorite, perhaps derived from an ancient Martian biota. However, Becker et al., have examined PAHs in the Martian meteorite EETA79001, in several Antarctic carbonaceous chondrites and Antarctic Allan Hills Ice and detected many of the same PAHs found in ALH84001. The reported presence of L-amino acids of apparent terrestrial origin in the EETA79001 druse material, suggests that this meteorite is contaminated with terrestrial/extraterrestrial organics probably derived from Antarctic ice meltwater that had percolated through the meteorite. The detection of PAHs and L-amino acids in these Martian meteorites suggests that despite storage in the Antarctic ice, selective changes of certain chemical and mineralogical phases has occurred.

  3. Geochemistry and setting of Martian weathering: The Lafayette meteorite

    NASA Technical Reports Server (NTRS)

    Treiman, A. H.; Barrett, R. A.; Gooding, J. L.

    1992-01-01

    Lafayette, one of the SNC (martian) meteorites, contains preterrestrial alteration materials rich in smectite and ferric oxides. The compositions and textures of the veinlets suggest that they were formed in episodic alteration events by waters that contained a relatively small load of dissolved salts. The Lafayette achondrite, one of the nakhlites of probable martian origin, is an igneous rock consisting mostly of augite and olivine, with interstitial feldspar, sulfides (pyrite), high-Si glass, and other phases. Like Nakhla itself, Lafayette contains veinlets of hydrous alteration materials. We studied thin sections of sample ME2116 (Field Museum, Chicago), using scanning and transmission electron microscopy (SEM and TEM) with energy dispersive X-ray spectrometry (EDS).

  4. Water in SNC meteorites: evidence for a martian hydrosphere.

    PubMed

    Karlsson, H R; Clayton, R N; Gibson, E K; Mayeda, T K

    1992-03-13

    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.

  5. Peology and Geochemistry of New Paired Martian Meteorites 12095 and LAR 12240

    NASA Technical Reports Server (NTRS)

    Funk, R. C.; Brandon, A. D.; Peslier, A.

    2015-01-01

    The meteorites LAR 12095 and LAR 12240 are believed to be paired Martian meteorites and were discovered during the Antarctic Search for Meteorites (ANSMET) 2012-2013 Season at Larkman Nunatak. The purpose of this study is to characterize these olivine-phyric shergottites by analyzing all mineral phases for major, minor and trace elements and examining their textural relationships. The goal is to constrain their crystallization history and place these shergottites among other Martian meteorites in order to better understand Martian geological history.

  6. Organic Carbon Features Identified in the Nakhla Martian Meteorite

    NASA Technical Reports Server (NTRS)

    Mckay, D. S.; Thomas-Keprta, K. L.; Clemett, S. J.; Gibson, E. K., Jr.; Le, L.; Rahman, Z.; Wentworth, S. J.

    2011-01-01

    We report, for the first time, the identification of specific carbonaceous phases, present within iddingsite alteration zones of the Nakhla meteorite that possess discrete, well defined, structurally coherent morphologies. These structures bear superficial similarity to the carbonaceous nanoglobules [1] found in primitive chondrites interplanetary dust particles, although they are an order-of-magnitude larger in size. Introduction: It has been known for many years that some members of the Martian meteorite clan contain organic matter [e.g., 2-4]. Based on both isotopic measurements [5] and circumstantial observations [4] (e.g., the similarity organic signatures present in both Antarctic finds and non-Antarctic falls) a credible argument has been made for a preterrestrial origin for the majority of these organics. The Nakhla meteorite is of particular interest in that it has been shown to contain both an acid-labile organic fraction as well as an acid-insoluble high molecular weight organic component [4]. Pyrolysis-gas chromatography-mass spectrometry of the latter component indicates it to be composed of aromatic and alkyl-aromatic functionalities bound into a macromolecule phase through ether linkages [4]. However, the spatial, textural and mineralogical associations of this carbonaceous macromolecular material have remained elusive [6].

  7. Cryogenic Origin for Mars Analog Carbonates in the Bockfjord Volcanic Complex Svalbard (Norway)

    NASA Technical Reports Server (NTRS)

    Amundsen, H. E. F.; Benning, L.; Blake, D. F.; Fogel, M.; Ming, D.; Skidmore, M.; Steele, A.

    2011-01-01

    The Sverrefjell and Sigurdfjell eruptive centers in the Bockfjord Volcanic Complex (BVC) on Svalbard (Norway) formed by subglacial eruptions ca. 1 Ma ago. These eruptive centers carry ubiquitous magnesian carbonate deposits including dolomitemagnesite globules similar to those in the Martian meteorite ALH84001. Carbonates in mantle xenoliths are dominated by ALH84001 type carbonate globules that formed during quenching of CO2-rich mantle fluids. Lava hosted carbonates include ALH84001 type carbonate globules occurring throughout lava vesicles and microfractures and massive carbonate deposits associated with vertical volcanic vents. Massive carbonates include < or equal 5 cm thick magnesite deposits protruding downwards into clear blue ice within volcanic vents and carbonate cemented lava breccias associated with volcanic vents. Carbonate cements comprise layered deposits of calcite, dolomite, huntite, magnesite and aragonite associated with ALH84001 type carbonate globules lining lava vesicles. Combined Mossbauer, XRD and VNIR data show that breccia carbonate cements at Sverrefjell are analog to Comanche carbonates at Gusev crater.

  8. Characterization of Spitsbergen Disks by Transmission Electron Microscopy and Raman Spectroscopy

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, K. L.; Clemett, S. J.; Le, L.; Ross, K.; McKay, David S.; Gibson, E. K., Jr.

    2010-01-01

    'Carbonate disks' found in the fractures and pores spaces of peridotite xenoliths and basalts from the island of Spitsbergen in the Norwegian Svalbard archipelago have been suggested to be "The best (and best documented) terrestrial analogs for the [Martian meteorite] ALH84001 carbonate globules ..." Previous studies have indicated that Spitsbergen carbonates show broadly comparable internal layering and mineral compositions to ALH84001 carbonate-magnetite disks. We report here for the first time, the detailed mineral characterization of Spitsbergen carbonates and their spatial relationship to the host mineral assemblages in the xenolith, using high resolution TEM (as used previously for ALH84001 carbonate disks). These studies were conducted in concert with complementary Raman and SEM analysis of the same samples. Our results indicate that there are significant chemical and physical differences between the disks in Spitsbergen and the carbonates present in ALH84001.

  9. Identification of Iron-Bearing Phases on the Martian Surface and in Martian Meteorites and Analogue Samples by Moessbauer Spectroscopy

    NASA Technical Reports Server (NTRS)

    Klingelhoefer, G.; Agresti, D. G.; Schroeder, C.; Rodionov, D.; Yen, A.; Ming, Doug; Morris, Richard V.

    2007-01-01

    The Moessbauer spectrometers on the Mars Exploration Rovers (MER) Spirit (Gusev Crater) and Opportunity (Meridiani Planum) have each analyzed more than 100 targets during their ongoing missions (>1050 sols). Here we summarize the Fe-bearing phases identified to date and compare the results to Moessbauer analyses of martian meteorites and lunar samples. We use lunar samples as martian analogues because some, particularly the low-Ti Apollo 15 mare basalts, have bulk chemical compositions that are comparable to basaltic martian meteorites [1,2]. The lunar samples also provide a way to study pigeonite-rich samples. Pigeonite is a pyroxene that is not common in terrestrial basalts, but does often occur on the Moon and is present in basaltic martian meteorites

  10. Martian carbon dioxide: Clues from isotopes in SNC meteorites

    NASA Technical Reports Server (NTRS)

    Karlsson, H. R.; Clayton, R. N.; Mayeda, T. K.; Jull, A. J. T.; Gibson, E. K., Jr.

    1993-01-01

    Attempts to unravel the origin and evolution of the atmosphere and hydrosphere on Mars from isotopic data have been hampered by the impreciseness of the measurements made by the Viking Lander and by Earth-based telescopes. The SNC meteorites which are possibly pieces of the Martian surface offer a unique opportunity to obtain more precise estimates of the planet's volatile inventory and isotopic composition. Recently, we reported results on oxygen isotopes of water extracted by pyrolysis from samples of Shergotty, Zagami, Nakhla, Chassigny, Lafayette, and EETA-79001. Now we describe complementary results on the stable isotopic composition of carbon dioxide extracted simultaneously from those same samples. We will also report on C-14 abundances obtained by accelerator mass spectrometry (AMS) for some of these CO2 samples.

  11. Petrology and Geochemistry of New Paired Martian Meteorites Larkman Nunatak 12240 and Larkman Nunatak 12095

    NASA Astrophysics Data System (ADS)

    Funk, R. C.; Peslier, A. H.; Brandon, A. D.; Humayun, M.

    2016-08-01

    Two of the latest Martian meteorites found in Antarctica, paired olivine-phyric shergottites LAR 12240 and LAR 12095, are described in order to decipher their petrological context, and place constraints on the geological history of Mars.

  12. Report of the Workshop on Unmixing the SNCs: Chemical, Isotopic, and Petrologic Components of Martian Meteorites

    NASA Technical Reports Server (NTRS)

    Treiman, Allan H. (Editor); Herd, Christopher D. K. (Editor)

    2002-01-01

    Geochemical and petrologic studies of the Martian meteorites (nicknamed the SNCs) have proliferated in the past few years, from a wealth of new samples and the perfection of new analytical methods. An intriguing result from these studies is that the chemical and isotopic compositions of the Martian meteorites, all basalts or derived from basaltic magma, can be modeled as mixtures of a limited number of components. These mixing components were the focus of the workshop.

  13. Tissint martian meteorite: a fresh look at the interior, surface, and atmosphere of Mars.

    PubMed

    Aoudjehane, H Chennaoui; Avice, G; Barrat, J-A; Boudouma, O; Chen, G; Duke, M J M; Franchi, I A; Gattacceca, J; Grady, M M; Greenwood, R C; Herd, C D K; Hewins, R; Jambon, A; Marty, B; Rochette, P; Smith, C L; Sautter, V; Verchovsky, A; Weber, P; Zanda, B

    2012-11-01

    Tissint (Morocco) is the fifth martian meteorite collected after it was witnessed falling to Earth. Our integrated mineralogical, petrological, and geochemical study shows that it is a depleted picritic shergottite similar to EETA79001A. Highly magnesian olivine and abundant glass containing martian atmosphere are present in Tissint. Refractory trace element, sulfur, and fluorine data for the matrix and glass veins in the meteorite indicate the presence of a martian surface component. Thus, the influence of in situ martian weathering can be unambiguously distinguished from terrestrial contamination in this meteorite. Martian weathering features in Tissint are compatible with the results of spacecraft observations of Mars. Tissint has a cosmic-ray exposure age of 0.7 ± 0.3 million years, consistent with those of many other shergottites, notably EETA79001, suggesting that they were ejected from Mars during the same event.

  14. Tissint martian meteorite: a fresh look at the interior, surface, and atmosphere of Mars.

    PubMed

    Aoudjehane, H Chennaoui; Avice, G; Barrat, J-A; Boudouma, O; Chen, G; Duke, M J M; Franchi, I A; Gattacceca, J; Grady, M M; Greenwood, R C; Herd, C D K; Hewins, R; Jambon, A; Marty, B; Rochette, P; Smith, C L; Sautter, V; Verchovsky, A; Weber, P; Zanda, B

    2012-11-01

    Tissint (Morocco) is the fifth martian meteorite collected after it was witnessed falling to Earth. Our integrated mineralogical, petrological, and geochemical study shows that it is a depleted picritic shergottite similar to EETA79001A. Highly magnesian olivine and abundant glass containing martian atmosphere are present in Tissint. Refractory trace element, sulfur, and fluorine data for the matrix and glass veins in the meteorite indicate the presence of a martian surface component. Thus, the influence of in situ martian weathering can be unambiguously distinguished from terrestrial contamination in this meteorite. Martian weathering features in Tissint are compatible with the results of spacecraft observations of Mars. Tissint has a cosmic-ray exposure age of 0.7 ± 0.3 million years, consistent with those of many other shergottites, notably EETA79001, suggesting that they were ejected from Mars during the same event. PMID:23065902

  15. Evidence for Past Life on Early Mars: How the Evidence Stands

    NASA Astrophysics Data System (ADS)

    Gibson, Everett K.; Thomas-Keprta, Kathie L.; Clemett, Simon J.; McKay, David S.; Romanek, Christopher; Wentworth, Susan J.

    2004-06-01

    Martian Meteorite ALH84001 contains four unusual features which have been interpreted as possible signatures of relic biogenic activity. After six years of intense study by the world's scientific community, the current status of the biogenic hypothesis is reviewed and shown to still be valid. Furthermore additional features have been observed in two younger Martian meteorites. The strongest argument for possible evidence of biogenic activity within the ALH84001 meteorite is the presence of truncated hexa-octahedral magnetite crystals which are only known on Earth to be the products of biology.

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

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

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

  17. Evidence From Hydrogen Isotopes in Meteorites for a Martian Permafrost

    NASA Technical Reports Server (NTRS)

    Usui, T.; Alexander, C. M. O'D.; Wang, J.; Simon, J. I.; Jones, J. H.

    2014-01-01

    Fluvial landforms on Mars suggest that it was once warm enough to maintain persistent liquid water on its surface. The transition to the present cold and dry Mars is closely linked to the history of surface water, yet the evolution of surficial water is poorly constrained. We have investigated the evolution of surface water/ ice and its interaction with the atmosphere by measurements of hydrogen isotope ratios (D/H: deuterium/ hydrogen) of martian meteorites. Hydrogen is a major component of water (H2O) and its isotopes fractionate significantly during hydrological cycling between the atmosphere, surface waters, ground ice, and polar cap ice. Based on in situ ion microprobe analyses of three geochemically different shergottites, we reported that there is a water/ice reservoir with an intermediate D/H ratio (delta D = 1,000?2500 %) on Mars. Here we present the possibility that this water/ice reservoir represents a ground-ice/permafrost that has existed relatively intact over geologic time.

  18. The challenge of remote exploration for extraterrestrial fossil life

    NASA Astrophysics Data System (ADS)

    Benoit, Paul H.; Taunton, Anne E.

    1997-07-01

    The discovery of possible fossils of nanobacteria in a meteorite from Mars is both an exciting development and a considerably challenge for future work. The meteorite bearing the possible fossils, ALH84001, has been on Earth for over ten thousand years, and thus the possibility that the `fossils' are terrestrial contamination must be considered. We suggest that the only way to fully resolve the issue of possible martian life is to study directly- sampled pieces of Mars, either using in situ instrumentation or via sample return. The small size of the possible fossils, and their relatively low abundance in bulk rock samples make in situ analysis difficult and indirect. We suggest that addressing the issue of ancient life on Mars will require sample return, probably assisted by in situ screening by landers/rovers. Our study of ALH84001 confirms the observation of McKay et al. of the existence of `fossils' in ALH84001, and we find that they are highly abundant on all the carbonate nodules we examined. Examination of lunar meteorites and two other martian meteorites, with terrestrial and laboratory histories very similar to that of ALH84001, shows that nano-`fossils' are absent, suggesting that the features in ALH84001 are probably not terrestrial contamination.

  19. Extinct Life on Mars: Looking for Traces of Viruses Instead of Bacteria

    NASA Astrophysics Data System (ADS)

    Ksanfomality, Leonid

    The finds in the ALH 84001 meteorite were reported as a sign of traces and fossils of ancient Martian primitive life. Despite many experiments, the issue has not been settled. A study of geochemical data suggests that simple inorganic processes sometimes offer a more plausible explanation of the suspicious structures found in the ALH 84001 meteorite that had been discussed by many authors. A photo of certain micro structures got in the paper of N. Yushkin (Fig. 1) proves the point. (Figure: The inorganic structures in granites.) It is known that viruses possess an ability to survive under very severe external conditions. The Martian biogenic activity (if any) could leave its virus' sign. Thus it could make a sense to look for viruses or even DNA traces both in the body of the ALH 84001 meteorite and on Mars in future space missions instead of traces of the extinct bacteria.

  20. A Short, Critical Evaluation of Proposed Signs of Ancient Martian

    NASA Astrophysics Data System (ADS)

    Treiman, Allan

    Unambiguous identification of fossil traces of life (terrestrial or extraterrestrial) can be difficult or impossible. For instance, many shapes in the 0.1 - 10 micron size range can form biologically or abiotically. Published images of such shapes in ALH84001 have been Rorschach tests of our preconceptions: biologists tend to see biological influences; inorganic chemists or petrolgists see abiotic processes. Similarly, many complex carbon compounds can also form from biologic or abiotic precursors; some see degraded biological matter, other see organic syntheses. In this light, W. Schopf's checklist of characteristics for microfossils has not provided an answer to whether there are traces of ancient martian life in ALH84001; members of D. McKay's research group claim to have satisfied all these criteria, yet few biologists or meteoriticists have been convinced. The job of the exobiologist has been complicated greatly by recent recognition of life in nearly all low-T environments on Earth. If all our terrestrial systems are influenced by biology, how can we recognize a sterile system?

  1. The chlorine isotopic composition of Martian meteorites 1: Chlorine isotope composition of Martian mantle and crustal reservoirs and their interactions

    NASA Astrophysics Data System (ADS)

    Williams, J. T.; Shearer, C. K.; Sharp, Z. D.; Burger, P. V.; McCubbin, F. M.; Santos, A. R.; Agee, C. B.; McKeegan, K. D.

    2016-05-01

    The Martian meteorites record a wide diversity of environments, processes, and ages. Much work has been done to decipher potential mantle sources for Martian magmas and their interactions with crustal and surface environments. Chlorine isotopes provide a unique opportunity to assess interactions between Martian mantle-derived magmas and the crust. We have measured the Cl-isotopic composition of 17 samples that span the range of known ages, Martian environments, and mantle reservoirs. The 37Cl of the Martian mantle, as represented by the olivine-phyric shergottites, NWA 2737 (chassignite), and Shergotty (basaltic shergottite), has a low value of approximately -3.8‰. This value is lower than that of all other planetary bodies measured thus far. The Martian crust, as represented by regolith breccia NWA 7034, is variably enriched in the heavy isotope of Cl. This enrichment is reflective of preferential loss of 35Cl to space. Most basaltic shergottites (less Shergotty), nakhlites, Chassigny, and Allan Hills 84001 lie on a continuum between the Martian mantle and crust. This intermediate range is explained by mechanical mixing through impact, fluid interaction, and assimilation-fractional crystallization.

  2. Fractionated (Martian) Noble Gases — EFA, Experiments and Meteorites

    NASA Astrophysics Data System (ADS)

    Schwenzer, S. P.; Barnes, G.; Bridges, J. C.; Bullock, M. A.; Chavez, C. L.; Filiberto, J.; Herrmann, S.; Hicks, L. J.; Kelley, S. P.; Miller, M. A.; Moore, J. M.; Ott, U.; Smith, H. D.; Steer, E. D.; Swindle, T. D.; Treiman, A. H.

    2016-08-01

    Noble gases are tracers for physical processes, including adsorption, dissolution and secondary mineral formation. We examine the Martian fractionated atmosphere through literature, terrestrial analogs and experiments.

  3. Unmixing the SNCs: Chemical, Isotopic, and Petrologic Components of the Martian Meteorites

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This volume contains abstracts that have been accepted for presentation at the conference on Unmixing the SNCs: Chemical, Isotopic, and Petrologic Components of Martian Meteorites, September 11-12, 2002, in Houston, Texas. Administration and publications support for this meeting were provided by the staff of the Publications and Program Services Department at the Lunar and Planetary Institute.

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

    PubMed

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

    2013-01-01

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

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

    PubMed

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

    2013-01-01

    High-pressure minerals in meteorites provide clues for the impact processes that excavated, launched and delivered these samples to Earth. Most Martian meteorites are suggested to have been excavated from 3 to 7 km diameter impact craters. Here we show that the Tissint meteorite, a 2011 meteorite fall, contains virtually all the high-pressure phases (seven minerals and two mineral glasses) that have been reported in isolated occurrences in other Martian meteorites. Particularly, one ringwoodite (75 × 140 μm(2)) represents the largest grain observed in all Martian samples. Collectively, the ubiquitous high-pressure minerals of unusually large sizes in Tissint indicate that shock metamorphism was widely dispersed in this sample (~25 GPa and ~2,000 °C). Using the size and growth kinetics of the ringwoodite grains, we infer an initial impact crater with ~90 km diameter, with a factor of 2 uncertainty. These energetic conditions imply alteration of any possible low-T minerals in Tissint. PMID:23360995

  6. Contribution of Organic Material to the Stable Isotope Composition of Some Terrestrial Carbonates as Analogs for Martian Processes

    NASA Technical Reports Server (NTRS)

    Socki, Richard A.; Gibson, Everett K., Jr.; Bissada, K. K.

    2005-01-01

    Understanding the isotopic geochemistry of terrestrial carbonate formation is essential to understanding the evolution of the Martian atmosphere, hydrosphere, and potential biosphere. Carbonate minerals, in particular, are important secondary minerals for interpreting past aqueous environments, as illustrated by the carbonates present in ALH84001 [1]. Models for the history of Mars suggest that the planet was warmer, wetter, and possessed a greater atmospheric pressure within the first billion years as compared to present conditions [2],[3],[4], and likely had an active hydrologic cycle. Morse and Marion [5] point out that associated with this hydrologic cycle would be the active chemical weathering of silicate minerals and thus consumption of atmospheric CO2 and deposition of carbonate and silica. It is during this warmer and wetter period of Martian history that surface and/or near-surface conditions would be most favorable for harboring possible microbiological life. Carbonates within ALH84001 offer evidence that fluids were present at 3.9 Gy on Mars [6]. A more through understanding of the effects of aqueous weathering and the potential contribution of organic compounds on the isotopic composition of Martian carbonate minerals can be gained by studying some terrestrial occurrences of carbonate rocks.

  7. Insights into the Martian Regolith from Martian Meteorite Northwest Africa 7034

    NASA Technical Reports Server (NTRS)

    McCubbin, Francis M.; Boyce, Jeremy W.; Szabo, Timea; Santos, Alison R.; Domokos, Gabor; Vazquez, Jorge; Moser, Desmond E.; Jerolmack, Douglas J.; Keller, Lindsay P.; Tartese, Romain

    2015-01-01

    Everything we know about sedimentary processes on Mars is gleaned from remote sensing observations. Here we report insights from meteorite Northwest Africa (NWA) 7034, which is a water-rich martian regolith breccia that hosts both igneous and sedimentary clasts. The sedimentary clasts in NWA 7034 are poorly-sorted clastic siltstones that we refer to as protobreccia clasts. These protobreccia clasts record aqueous alteration process that occurred prior to breccia formation. The aqueous alteration appears to have occurred at relatively low Eh, high pH conditions based on the co-precipitation of pyrite and magnetite, and the concomitant loss of SiO2 from the system. To determine the origin of the NWA 7034 breccia, we examined the textures and grain-shape characteristics of NWA 7034 clasts. The shapes of the clasts are consistent with rock fragmentation in the absence of transport. Coupled with the clast size distribution, we interpret the protolith of NWA 7034 to have been deposited by atmospheric rainout resulting from pyroclastic eruptions and/or asteroid impacts. Cross-cutting and inclusion relationships and U-Pb data from zircon, baddelleyite, and apatite indicate NWA 7034 lithification occurred at 1.4-1.5 Ga, during a short-lived hydrothermal event at 600-700 C that was texturally imprinted upon the submicron groundmass. The hydrothermal event caused Pb-loss from apatite and U-rich metamict zircons, and it caused partial transformation of pyrite to submicron mixtures of magnetite and maghemite, indicating the fluid had higher Eh than the fluid that caused pyrite-magnetite precipitation in the protobreccia clasts. NWA 7034 also hosts ancient 4.4 Ga crustal materials in the form of baddelleyites and zircons, providing up to a 2.9 Ga record of martian geologic history. This work demonstrates the incredible value of sedimentary basins as scientific targets for Mars sample return missions, but it also highlights the importance of targeting samples that have not been

  8. SNC Meteorites, Organic Matter and a New Look at Viking

    NASA Technical Reports Server (NTRS)

    Warmflash, David M.; Clemett, Simon J.; McKay, David S.

    2001-01-01

    Recently, evidence has begun to grow supporting the possibility that the Viking GC-MS would not have detected certain carboxylate salts that could have been present as metastable oxidation products of high molecular weight organic species. Additionally, despite the instrument's high sensitivity, the possibility had remained that very low levels of organic matter, below the instrument's detection limit, could have been present. In fact, a recent study indicates that the degradation products of several million microorganisms per gram of soil on Mars would not have been detected by the Viking GC-MS. Since the strength of the GC-MS findings was considered enough to dismiss the biology packet, particularly the LR results, any subsequent evidence suggesting that organic molecules may in fact be present on the Martian surface necessitates a re-evaluation of the Viking LR data. In addition to an advanced mass spectrometer to look for isotopic signatures of biogenic processes, future lander missions will include the ability to detect methane produced by methanogenic bacteria, as well as techniques based on biotechnology. Meanwhile, the identification of Mars samples already present on Earth in the form of the SNC meteorites has provided us with the ability to study samples of the Martian upper crust a decade or more in advance of any planned sample return missions. While contamination issues are of serious concern, the presence of indigenous organic matter in the form of polycyclic aromatic hydrocarbons has been detected in the Martian meteorites ALH84001 and Nakhla, while there is circumstantial evidence for carbonaceous material in Chassigny. The radiochronological ages of these meteorites are 4.5 Ga, 1.3 Ga, and 165 Ma respectively representing a span of time in Earth history from the earliest single-celled organisms to the present day. Given this perspective on organic material, a biological interpretation to the Viking LR results can no longer be ruled out. In the LR

  9. New Martian Meteorite Is One of the Most Oxidized Found to Date

    NASA Technical Reports Server (NTRS)

    Hui, Hejiu; Peslier, Anne; Lapen, Thomas J.; Shafer, John T.; Brandon, Alan D.; Irving, Anthony J.

    2014-01-01

    As of 2013, about 60 meteorites from the planet Mars have been found and are being studied. Each time a new Martian meteorite is found, a wealth of new information comes forward about the red planet. The most abundant type of Martian meteorite is a shergottite; its lithologies are broadly similar to those of Earth basalts and gabbros; i.e., crustal igneous rocks. The entire suite of shergottites is characterized by a range of trace element, isotopic ratio, and oxygen fugacity values that mainly reflect compositional variations of the Martian mantle from which these magmas came. A newly found shergottite, NWA 5298, was the focus of a study performed by scientists within the Astromaterials Research and Exploration Science (ARES) Directorate at the Johnson Space Center (JSC) in 2012. This sample was found in Morocco in 2008. Major element analyses were performed in the electron microprobe (EMP) laboratory of ARES at JSC, while the trace elements were measured at the University of Houston by laser inductively coupled plasma mass spectrometry (ICPMS). A detailed analysis of this stone revealed that this meteorite is a crystallized magma that comes from the enriched end of the shergottite spectrum; i.e., trace element enriched and oxidized. Its oxidation comes in part from its mantle source and from oxidation during the magma ascent. It represents a pristine magma that did not mix with any other magma or see crystal accumulation or crustal contamination on its way up to the Martian surface. NWA 5298 is therefore a direct, albeit evolved, melt from the Martian mantle and, for its lithology (basaltic shergottite), it represents the oxidized end of the shergottite suite. It is thus a unique sample that has provided an end-member composition for Martian magmas.

  10. The Nakhla Martian Meteorite is a Cumulate Igenous Rock. Comment on "Glass-Bearing Inclusions in Nakhla (SNC Meteorite) Augite: Heterogeneously Trapped Phases"

    NASA Technical Reports Server (NTRS)

    Treiman, A. H.

    2003-01-01

    All the properties of the Nakhla Martian meteorite suggest that it is a cumulate igneous rock, formed from a basaltic parental magma. Anomalous magmatic inclusions in Nakhla s augite grains can be explained by disequilibrium processes during crystal growth, and have little significance in the geological history of the meteorite.

  11. Martian Pyroxenes in the Shergottite Meteorites; Zagami, SAU005, DAG476 and EETA79001

    NASA Astrophysics Data System (ADS)

    Stephen, N.; Benedix, G. K.; Bland, P.; Hamilton, V. E.

    2010-12-01

    The geology and surface mineralogy of Mars is characterised using remote sensing techniques such as thermal emission spectroscopy (TES) from instruments on a number of spacecraft currently orbiting Mars or gathered from roving missions on the Martian surface. However, the study of Martian meteorites is also important in efforts to further understand the geological history of Mars or to interpret mission data as they are believed to be the only available samples that give us direct clues as to Martian igneous processes [1]. We have recently demonstrated that the spectra of Martian-specific minerals can be determined using micro-spectroscopy [2] and that these spectra can be reliably obtained from thin sections of Martian meteorites [3]. Accurate modal mineralogy of these meteorites is also important [4]. In this study we are using a variety of techniques to build upon previous studies of these particular samples in order to fully characterise the nature of the 2 common pyroxenes found in Martian Shergottites; pigeonite and augite [5], [6]. Previous studies have shown that the Shergottite meteorites are dominated by pyroxene (pigeonite and augite in varying quantities) [4], [5], commonly but not always olivine, plagioclase or maskelynite/glass and also hydrous minerals, which separate the Martian meteorites from other achondrites [7]. Our microprobe study of meteorites Zagami, EETA79001, SAU005 and DAG476 in thin-section at the Natural History Museum, London shows a chemical variability within both the pigeonite and augite composition across individual grains in all thin sections; variation within either Mg or Ca concentration varies from core to rim within the grains. This variation can also be seen in modal mineralogy maps using SEM-derived element maps and the Photoshop® technique previously described [4], and in new micro-spectroscopy data, particularly within the Zagami meteorite. New mineral spectra have been gathered from the Shergottite thin-sections by

  12. New approaches to the study of Antarctic lithobiontic microorganisms and their inorganic traces, and their application in the detection of life in Martian rocks.

    PubMed

    Ascaso, C; Wierzchos, J

    2002-12-01

    Microbial life in the harsh conditions of Antarctica's cold desert may be considered an analogue of potential life on early Mars. In order to explore the development and survival of this epilithic and endolithic form of microbial life, our most sophisticated, state-of-the-art visualization technologies have to be used to their full potential. The study of any ecosystem requires a knowledge of its components and the processes that take place within it. If we are to understand the structure and function of each component of the microecosystems that inhabit lithic substrates, we need to be able to quantify and identify the microorganisms present in each lithobiontic ecological niche and to accurately characterize the mineralogical features of these hidden microhabitats. Once we have established the techniques that will allow us to observe and identify these microorganisms and mineral substrates in situ, and have confirmed the presence of water, the following questions can be addressed: How are the microorganisms organized in the fissures or cavities? Which microorganisms are present and how many are there? Additional questions that logically follow include: What are the existing water relationships in the microhabitat and what effects do the microorganisms have on the mineral composition? Mechanical and chemical changes in minerals and mineralization of microbial cells can give rise to physical and/or chemical traces (biomarkers) and to microbial fossil formation. In this report, we describe the detection of chains of magnetite within the Martian meteorite ALH84001, as an example of the potential use of SEM-BSE in the search for plausible traces of life on early Mars. PMID:12497188

  13. New approaches to the study of Antarctic lithobiontic microorganisms and their inorganic traces, and their application in the detection of life in Martian rocks.

    PubMed

    Ascaso, C; Wierzchos, J

    2002-12-01

    Microbial life in the harsh conditions of Antarctica's cold desert may be considered an analogue of potential life on early Mars. In order to explore the development and survival of this epilithic and endolithic form of microbial life, our most sophisticated, state-of-the-art visualization technologies have to be used to their full potential. The study of any ecosystem requires a knowledge of its components and the processes that take place within it. If we are to understand the structure and function of each component of the microecosystems that inhabit lithic substrates, we need to be able to quantify and identify the microorganisms present in each lithobiontic ecological niche and to accurately characterize the mineralogical features of these hidden microhabitats. Once we have established the techniques that will allow us to observe and identify these microorganisms and mineral substrates in situ, and have confirmed the presence of water, the following questions can be addressed: How are the microorganisms organized in the fissures or cavities? Which microorganisms are present and how many are there? Additional questions that logically follow include: What are the existing water relationships in the microhabitat and what effects do the microorganisms have on the mineral composition? Mechanical and chemical changes in minerals and mineralization of microbial cells can give rise to physical and/or chemical traces (biomarkers) and to microbial fossil formation. In this report, we describe the detection of chains of magnetite within the Martian meteorite ALH84001, as an example of the potential use of SEM-BSE in the search for plausible traces of life on early Mars.

  14. An assessment of the meteoritic contribution to the Martian soil

    SciTech Connect

    Flynn, G.J. ); McKay, D.S. )

    1990-08-30

    The addition of meteoritic material to the Mars soils should perturb their chemical compositions, as has been detected for soils on the Moon and sediments on Earth. Using the measured mass influx at Earth and estimates of the Mars/Earth flux ratio, the authors estimate the continuous, planet-wide meteoritic mass influx on Mars to be between 2,700 and 59,000 t/yr. If distributed uniformly into a soil with a mean planetary production rate of 1 m/b.y., consistent with radar estimates of the soil depth overlaying a bouldered terrain in the Tharsis region, their estimated mass influx would produce a meteoritic concentration in the Mars soil ranging from 2 to 29% by mass. Analysis of the Viking X ray fluorescence data indicates that the Mars soil composition is inconsistent with typical basaltic rock fragments but can be fit by a mixture of 60% basaltic rock fragments and 40% meteoritic material. The meteoritic influx they calculate is sufficient to provide most or all of the material required by the Clark and Baird model. Particles in the mass range from 10{sup {minus}7} to 10{sup {minus}3} g, about 60-1,200 {mu}m in diameter, contribute 80% of the total mass flux of meteoritic material in the 10{sup {minus}13} to 10{sup 6} g mass range at Earth. On Earth atmospheric entry all but the smallest particles (generally {le} 50 {mu}m in diameter) in the 10{sup {minus}7} to 10{sup {minus}3} g mass range are heated sufficiently to melt or vaporize. Mars, because of its lower escape velocity and larger atmospheric scale height, is a much more favorable site for unmelted survival of micrometeorites on atmospheric deceleration. They calculate that a significant fraction of particles throughout the 60-1,200 {mu}m diameter range will survive Mars atmospheric entry unmelted.

  15. Ultraviolet-radiation-induced methane emissions from meteorites and the Martian atmosphere.

    PubMed

    Keppler, Frank; Vigano, Ivan; McLeod, Andy; Ott, Ulrich; Früchtl, Marion; Röckmann, Thomas

    2012-06-01

    Almost a decade after methane was first reported in the atmosphere of Mars there is an intensive discussion about both the reliability of the observations--particularly the suggested seasonal and latitudinal variations--and the sources of methane on Mars. Given that the lifetime of methane in the Martian atmosphere is limited, a process on or below the planet's surface would need to be continuously producing methane. A biological source would provide support for the potential existence of life on Mars, whereas a chemical origin would imply that there are unexpected geological processes. Methane release from carbonaceous meteorites associated with ablation during atmospheric entry is considered negligible. Here we show that methane is produced in much larger quantities from the Murchison meteorite (a type CM2 carbonaceous chondrite) when exposed to ultraviolet radiation under conditions similar to those expected at the Martian surface. Meteorites containing several per cent of intact organic matter reach the Martian surface at high rates, and our experiments suggest that a significant fraction of the organic matter accessible to ultraviolet radiation is converted to methane. Ultraviolet-radiation-induced methane formation from meteorites could explain a substantial fraction of the most recently estimated atmospheric methane mixing ratios. Stable hydrogen isotope analysis unambiguously confirms that the methane released from Murchison is of extraterrestrial origin. The stable carbon isotope composition, in contrast, is similar to that of terrestrial microbial origin; hence, measurements of this signature in future Mars missions may not enable an unambiguous identification of biogenic methane.

  16. Ultraviolet-radiation-induced methane emissions from meteorites and the Martian atmosphere.

    PubMed

    Keppler, Frank; Vigano, Ivan; McLeod, Andy; Ott, Ulrich; Früchtl, Marion; Röckmann, Thomas

    2012-06-01

    Almost a decade after methane was first reported in the atmosphere of Mars there is an intensive discussion about both the reliability of the observations--particularly the suggested seasonal and latitudinal variations--and the sources of methane on Mars. Given that the lifetime of methane in the Martian atmosphere is limited, a process on or below the planet's surface would need to be continuously producing methane. A biological source would provide support for the potential existence of life on Mars, whereas a chemical origin would imply that there are unexpected geological processes. Methane release from carbonaceous meteorites associated with ablation during atmospheric entry is considered negligible. Here we show that methane is produced in much larger quantities from the Murchison meteorite (a type CM2 carbonaceous chondrite) when exposed to ultraviolet radiation under conditions similar to those expected at the Martian surface. Meteorites containing several per cent of intact organic matter reach the Martian surface at high rates, and our experiments suggest that a significant fraction of the organic matter accessible to ultraviolet radiation is converted to methane. Ultraviolet-radiation-induced methane formation from meteorites could explain a substantial fraction of the most recently estimated atmospheric methane mixing ratios. Stable hydrogen isotope analysis unambiguously confirms that the methane released from Murchison is of extraterrestrial origin. The stable carbon isotope composition, in contrast, is similar to that of terrestrial microbial origin; hence, measurements of this signature in future Mars missions may not enable an unambiguous identification of biogenic methane. PMID:22678286

  17. Comparison of Martian Meteorites and Martian Regolith as Shield Materials for Galactic Cosmic Rays

    NASA Technical Reports Server (NTRS)

    Kim, Myung-Hee Y.; Thibeault, Sheila A.; Simonsen, Lisa C.; Wilson, John W.

    1998-01-01

    Theoretical calculations of radiation attenuation due to energetic galactic cosmic rays behind Martian rock and Martian regolith material have been made to compare their utilization as shields for advanced manned missions to Mars because the detailed chemical signature of Mars is distinctly different from Earth. The modified radiation fields behind the Martian rocks and the soil model were generated by solving the Boltzmann equation using a HZETRN system with the 1977 Solar Minimum environmental model. For the comparison of the attenuation characteristics, dose and dose equivalent are calculated for the five different subgroups of Martian rocks and the Martian regolith. The results indicate that changes in composition of subgroups of Martian rocks have negligible effects on the overall shielding properties because of the similarity of their constituents. The differences for dose and dose equivalent of these materials relative to those of Martian regolith are within 0.5 and 1 percent, respectively. Therefore, the analysis of Martian habitat construction options using in situ materials according to the Martian regolith model composition is reasonably accurate. Adding an epoxy to Martian regolith, which changes the major constituents of the material, enhances shielding properties because of the added hydrogenous constituents.

  18. In Situ Mars Compositions Determined by Alpha Particle X-Ray Spectrometry (APXS): Overview and Comparison with Martian Meteorite Dataset

    NASA Astrophysics Data System (ADS)

    Thompson, L. M.; Gellert, R.; Spray, J. G.; Schmidt, M. E.; Izawa, M.; MSL APXS Team

    2016-08-01

    APXS instruments have flown on every rover mission to Mars. This work provides an overview of the diverse in situ chemistry encountered, with emphasis on MSL Curiosity mission results, and compares this with the martian meteorite data set.

  19. The Noble Gas Concentration of the Martian Meteorites GRV 99027 and NWA 7906/NWA 7907 (Paired with NWA 7034)

    NASA Astrophysics Data System (ADS)

    Stephenson, P. C.; Leya, I.

    2016-08-01

    We report the noble gas inventory and cosmic ray exposure (CRE) ages for three martian meteorites: Grove Mountains 99027 (a shergottite), Northwest Africa 7906, and Northwest Africa 7907 (both basaltic breccias paired with NWA 7034).

  20. Analysis of Arctic Carbonates Profiles by Raman Spectroscopy using Exomars Raman Laser Spectrometer

    NASA Astrophysics Data System (ADS)

    Sansano, A.; López, G.; Medina, J.; Rull, F.

    2011-10-01

    This work details the analysis performed by Raman spectroscopy on carbonate samples from the Svalbard Islands (Norway) in the Arctic. This place is considered a potential Martian analog because the carbonate formation show close similarities with the formation in ALH84001 meteorite. The results obtained illustrate the performances of the Raman instrument included in the Exomars (ESA) mission.

  1. Magnetite biomineralization and ancient life on Mars.

    PubMed

    Frankel, R B; Buseck, P R

    2000-04-01

    Certain chemical and mineral features of the Martian meteorite ALH84001 were reported in 1996 to be probable evidence of ancient life on Mars. In spite of new observations and interpretations, the question of ancient life on Mars remains unresolved. Putative biogenic, nanometer magnetite has now become a leading focus in the debate. PMID:10742183

  2. Magnetite biomineralization and ancient life on Mars.

    PubMed

    Frankel, R B; Buseck, P R

    2000-04-01

    Certain chemical and mineral features of the Martian meteorite ALH84001 were reported in 1996 to be probable evidence of ancient life on Mars. In spite of new observations and interpretations, the question of ancient life on Mars remains unresolved. Putative biogenic, nanometer magnetite has now become a leading focus in the debate.

  3. The provenance, formation, and implications of reduced carbon phases in Martian meteorites

    NASA Astrophysics Data System (ADS)

    Steele, Andrew; McCubbin, Francis M.; Fries, Marc D.

    2016-08-01

    This review is intended to summarize the current observations of reduced carbon in Martian meteorites, differentiating between terrestrial contamination and carbon that is indigenous to Mars. Indeed, the identification of Martian organic matter is among the highest priority targets for robotic spacecraft missions in the next decade, including the Mars Science Laboratory and Mars 2020. Organic carbon compounds are essential building blocks of terrestrial life, so the occurrence and origin (biotic or abiotic) of organic compounds on Mars is of great significance; however, not all forms of reduced carbon are conducive to biological systems. This paper discusses the significance of reduced organic carbon (including methane) in Martian geological and astrobiological systems. Specifically, it summarizes current thinking on the nature, sources, and sinks of Martian organic carbon, a key component to Martian habitability. Based on this compilation, reduced organic carbon on Mars, including detections of methane in the Martian atmosphere, is best described through a combination of abiotic organic synthesis on Mars and infall of extraterrestrial carbonaceous material. Although conclusive signs of Martian life have yet to be revealed, we have developed a strategy for life detection on Mars that can be utilized in future life-detection studies.

  4. MN Carbonates in the Martian Meteorite Nakhla: Possible Evidence of Brine Evaporation

    NASA Technical Reports Server (NTRS)

    Bailey, J. V.; McKay, D. S.; Wentworth, S. J.

    2003-01-01

    The importance of secondary phases in martian meteorites lies in their potential to provide clues about the martian environments responsible for their formation. During this study, we analyzed a number of carbonate-bearing fracture surfaces from the Nakhla meteorite. Here we describe the physical and chemical properties of several manganese-calcium-rich siderites. Additionally, we describe a potential model for the formation and alteration of these carbonates, and we suggest constraints on the conditions responsible for their precipitation. Nakhla is an olivine-bearing clinopyroxenite with minor amounts of feldspar, FeS, and Fe oxides. Secondary mineral assemblages include vein filling clay with embedded iron oxides, a calcium sulfate, amorphous silica, chlorapatite, halite and carbonates. Bridges and Grady suggested that the carbonates in Nakhla formed from brine evaporation. Isotope studies of the Mn rich siderite are also consistent with formation from hydrothermal fluids with an upper T constraint of 170 C.

  5. 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

  6. Habitability Conditions Constrained by Martian Meteorites: Implications for Microbial Colonization and Mars Sample Return

    NASA Astrophysics Data System (ADS)

    Shivak, J. N.; Banerjee, N.; Flemming, R. L.

    2013-12-01

    We report the results of a comparative study of the crustal environmental conditions recorded by several Martian meteorites (Nakhla, Los Angeles, and Zagami). Though no samples have yet been returned from Mars, numerous meteorites are known and these provide the only samples of the Martian crust currently available for study. Terrestrial basalts and other mafic igneous rocks are analogous in many ways to much of the Martian crust, as evidenced by the composition of known Martian meteorites and measurements from planetary missions [1]. Microorganisms are known to thrive in the terrestrial geosphere and make use of many different substrates within rock in the subsurface of the Earth [2]. The action of aqueous solutions in the Martian crust has been well established through the study of alteration mineral assemblages present in many Martian meteorites, such as the nakhlites [3]. Aqueous activity in terrestrial chemolithoautotrophic habitats provides numerous energy and nutrient sources for microbes [4], suggesting the potential for habitable endolithic environments in Martian rocks. Fayalite in Nakhla has experienced extensive aqueous alteration to reddish-brown 'iddingsite' material within a pervasive fracture system. Textural imaging shows the replacement of primary olivine with various alteration phases and infiltration of this alteration front into host grains. Geochemical analysis of the alteration material shows the addition of iron and silica and removal of magnesium during alteration. Novel In situ Micro-XRD and Raman Spectroscopy of this material reveals a new assemblage consisting of iron oxides, smectite clays, carbonates, and a minor serpentine component. The alteration mineral assemblage here differs from several that have been previously reported [4] [5], allowing for a reevaluation of the environmental conditions during fluid action. Los Angeles and Zagami show no evidence of aqueous activity, though their primary basaltic mineralogies show many

  7. Origin and age of the earliest Martian crust from meteorite NWA 7533.

    PubMed

    Humayun, M; Nemchin, A; Zanda, B; Hewins, R H; Grange, M; Kennedy, A; Lorand, J-P; Göpel, C; Fieni, C; Pont, S; Deldicque, D

    2013-11-28

    The ancient cratered terrain of the southern highlands of Mars is thought to hold clues to the planet's early differentiation, but until now no meteoritic regolith breccias have been recovered from Mars. Here we show that the meteorite Northwest Africa (NWA) 7533 (paired with meteorite NWA 7034) is a polymict breccia consisting of a fine-grained interclast matrix containing clasts of igneous-textured rocks and fine-grained clast-laden impact melt rocks. High abundances of meteoritic siderophiles (for example nickel and iridium) found throughout the rock reach a level in the fine-grained portions equivalent to 5 per cent CI chondritic input, which is comparable to the highest levels found in lunar breccias. Furthermore, analyses of three leucocratic monzonite clasts show a correlation between nickel, iridium and magnesium consistent with differentiation from impact melts. Compositionally, all the fine-grained material is alkalic basalt, chemically identical (except for sulphur, chlorine and zinc) to soils from Gusev crater. Thus, we propose that NWA 7533 is a Martian regolith breccia. It contains zircons for which we measured an age of 4,428 ± 25 million years, which were later disturbed 1,712 ± 85 million years ago. This evidence for early crustal differentiation implies that the Martian crust, and its volatile inventory, formed in about the first 100 million years of Martian history, coeval with earliest crust formation on the Moon and the Earth. In addition, incompatible element abundances in clast-laden impact melt rocks and interclast matrix provide a geochemical estimate of the average thickness of the Martian crust (50 kilometres) comparable to that estimated geophysically. PMID:24256724

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

    NASA Technical Reports Server (NTRS)

    Park, J.; Bogard, D. D.

    2006-01-01

    Martian meteorite, Dhofar 378 (Dho378) is a basaltic shergottite from Oman, weighing 15 g, and possessing a black fusion crust. Chemical similarities between Dho378 and the Los Angeles 001 shergottite suggests that they might have derived from the same Mars locale. The plagioclase in other shergottites has been converted to maskelenite by shock, but Dho378 apparently experienced even more intense shock heating, estimated at 55-75 GPa. Dho378 feldspar (approximately 43 modal %) melted, partially flowed and vesiculated, and then partially recrystallized. Areas of feldspathic glass are appreciably enriched in K, whereas individual plagioclases show a range in the Or/An ratio of approximately 0.18-0.017. Radiometric dating of martian shergottites indicate variable formation times of 160-475 Myr, whereas cosmic ray exposure (CRE) ages of shergottites indicate most were ejected from Mars within the past few Myr. Most determined Ar-39-Ar-40 ages of shergottites appear older than other radiometric ages because of the presence of large amounts of martian atmosphere or interior Ar-40. Among all types of meteorites and returned lunar rocks, the impact event that initiated the CRE age very rarely reset the Ar-Ar age. This is because a minimum time and temperature is required to facilitate Ar diffusion loss. It is generally assumed that the shock-texture characteristics in martian meteorites were produced by the impact events that ejected the rocks from Mars, although the time of these shock events (as opposed to CRE ages) are not directly dated. Here we report Ar-39-Ar-40 dating of Dho378 plagioclase. We suggest that the determined age dates the intense shock heating event this meteorite experienced, but that it was not the impact that initiated the CRE age.

  9. Origin and age of the earliest Martian crust from meteorite NWA 7533.

    PubMed

    Humayun, M; Nemchin, A; Zanda, B; Hewins, R H; Grange, M; Kennedy, A; Lorand, J-P; Göpel, C; Fieni, C; Pont, S; Deldicque, D

    2013-11-28

    The ancient cratered terrain of the southern highlands of Mars is thought to hold clues to the planet's early differentiation, but until now no meteoritic regolith breccias have been recovered from Mars. Here we show that the meteorite Northwest Africa (NWA) 7533 (paired with meteorite NWA 7034) is a polymict breccia consisting of a fine-grained interclast matrix containing clasts of igneous-textured rocks and fine-grained clast-laden impact melt rocks. High abundances of meteoritic siderophiles (for example nickel and iridium) found throughout the rock reach a level in the fine-grained portions equivalent to 5 per cent CI chondritic input, which is comparable to the highest levels found in lunar breccias. Furthermore, analyses of three leucocratic monzonite clasts show a correlation between nickel, iridium and magnesium consistent with differentiation from impact melts. Compositionally, all the fine-grained material is alkalic basalt, chemically identical (except for sulphur, chlorine and zinc) to soils from Gusev crater. Thus, we propose that NWA 7533 is a Martian regolith breccia. It contains zircons for which we measured an age of 4,428 ± 25 million years, which were later disturbed 1,712 ± 85 million years ago. This evidence for early crustal differentiation implies that the Martian crust, and its volatile inventory, formed in about the first 100 million years of Martian history, coeval with earliest crust formation on the Moon and the Earth. In addition, incompatible element abundances in clast-laden impact melt rocks and interclast matrix provide a geochemical estimate of the average thickness of the Martian crust (50 kilometres) comparable to that estimated geophysically.

  10. Distinctive Carbonates in Five Martian Meteorites: Search for Water on Mars

    NASA Technical Reports Server (NTRS)

    Wentworth, Susan J.; Bailey, Jake; McKay, David S.; Thomas-Keprta, Kathie L.; Velbel, Michael

    2003-01-01

    Recently published results from Mars orbital data strongly support both the idea that large bodies of water were present at the surface in the past and the possibility that significant amounts of water ice are currently present in the regolith just below the planet's surface. These new findings increase the significance of the evidence in martian meteorites that some low-temperature aqueous alteration and secondary mineral deposition occurred on Mars.

  11. Petrology and Geochemistry of New Paired Martian Meteorites Larkman Nunatak 12240 and Larkman Nunatak 12095

    NASA Technical Reports Server (NTRS)

    Funk, R. C.; Peslier, A. H.; Brandon, A. D.; Humayun, M.

    2016-01-01

    Two of the latest Martian meteorites found in Antarctica, paired olivine-phyric shergottites LAR 12240 and LAR 12095, are described in order to decipher their petrological context, and place constraints on the geological history of Mars. This project identifies all phases found in LAR 12240 and 12095 and analyzes them for major and trace elements. The textural relationships among these phases are examined in order to develop a crystallization history of the magma(s) that formed these basalts.

  12. PYTi-NiCr Signatures in the Columbia Hills are Present in Certain Martian Meteorites

    NASA Technical Reports Server (NTRS)

    Clark, B. C.; Gellert, R.; Ming, D. W.; Morris, R. V.; Mittlefehldt, D. W.; Squyres, S. W.

    2006-01-01

    Uniquely high levels of phosphorus and titanium were observed in several samples [1-3] by the APXS x-ray fluorescence measurements as the MER Spirit rover climbed Husband Hill (Columbia Hills, Gusev crater, Mars). A careful study of many such samples and their geochemical variability has revealed additional elements in this pattern, and that the derived multi-element signature is also unambiguously manifested in several martian meteorites.

  13. Putative indigenous carbon-bearing alteration features in martian meteorite Yamato 000593.

    PubMed

    White, Lauren M; Gibson, Everett K; Thomas-Keprta, Kathie L; Clemett, Simon J; McKay, David S

    2014-02-01

    We report the first observation of indigenous carbonaceous matter in the martian meteorite Yamato 000593. The carbonaceous phases are heterogeneously distributed within secondary iddingsite alteration veins and present in a range of morphologies including areas composed of carbon-rich spheroidal assemblages encased in multiple layers of iddingsite. We also observed microtubular features emanating from iddingsite veins penetrating into the host olivine comparable in shape to those interpreted to have formed by bioerosion in terrestrial basalts. PMID:24552234

  14. Putative indigenous carbon-bearing alteration features in martian meteorite Yamato 000593.

    PubMed

    White, Lauren M; Gibson, Everett K; Thomas-Keprta, Kathie L; Clemett, Simon J; McKay, David S

    2014-02-01

    We report the first observation of indigenous carbonaceous matter in the martian meteorite Yamato 000593. The carbonaceous phases are heterogeneously distributed within secondary iddingsite alteration veins and present in a range of morphologies including areas composed of carbon-rich spheroidal assemblages encased in multiple layers of iddingsite. We also observed microtubular features emanating from iddingsite veins penetrating into the host olivine comparable in shape to those interpreted to have formed by bioerosion in terrestrial basalts.

  15. Magnetotactic bacteria on Earth and on Mars.

    PubMed

    McKay, Christopher P; Friedmann, E Imre; Frankel, Richard B; Bazylinski, Dennis A

    2003-01-01

    Continued interest in the possibility of evidence for life in the ALH84001 Martian meteorite has focused on the magnetite crystals. This review is structured around three related questions: is the magnetite in ALH84001 of biological or non-biological origin, or a mixture of both? does magnetite on Earth provide insight to the plausibility of biogenic magnetite on Mars? could magnetotaxis have developed on Mars? There are credible arguments for both the biological and non-biological origin of the magnetite in ALH84001, and we suggest that more studies of ALH84001, extensive laboratory simulations of non-biological magnetite formation, as well as further studies of magnetotactic bacteria on Earth will be required to further address this question. Magnetite grains produced by bacteria could provide one of the few inorganic traces of past bacterial life on Mars that could be recovered from surface soils and sediments. If there was biogenic magnetite on Mars in sufficient abundance to leave fossil remains in the volcanic rocks of ALH84001, then it is likely that better-preserved magnetite will be found in sedimentary deposits on Mars. Deposits in ancient lakebeds could contain well-preserved chains of magnetite clearly indicating a biogenic origin.

  16. Magnetotactic bacteria on Earth and on Mars.

    PubMed

    McKay, Christopher P; Friedmann, E Imre; Frankel, Richard B; Bazylinski, Dennis A

    2003-01-01

    Continued interest in the possibility of evidence for life in the ALH84001 Martian meteorite has focused on the magnetite crystals. This review is structured around three related questions: is the magnetite in ALH84001 of biological or non-biological origin, or a mixture of both? does magnetite on Earth provide insight to the plausibility of biogenic magnetite on Mars? could magnetotaxis have developed on Mars? There are credible arguments for both the biological and non-biological origin of the magnetite in ALH84001, and we suggest that more studies of ALH84001, extensive laboratory simulations of non-biological magnetite formation, as well as further studies of magnetotactic bacteria on Earth will be required to further address this question. Magnetite grains produced by bacteria could provide one of the few inorganic traces of past bacterial life on Mars that could be recovered from surface soils and sediments. If there was biogenic magnetite on Mars in sufficient abundance to leave fossil remains in the volcanic rocks of ALH84001, then it is likely that better-preserved magnetite will be found in sedimentary deposits on Mars. Deposits in ancient lakebeds could contain well-preserved chains of magnetite clearly indicating a biogenic origin. PMID:14577877

  17. Magnetotactic bacteria on Earth and on Mars

    NASA Technical Reports Server (NTRS)

    McKay, Christopher P.; Friedmann, E. Imre; Frankel, Richard B.; Bazylinski, Dennis A.

    2003-01-01

    Continued interest in the possibility of evidence for life in the ALH84001 Martian meteorite has focused on the magnetite crystals. This review is structured around three related questions: is the magnetite in ALH84001 of biological or non-biological origin, or a mixture of both? does magnetite on Earth provide insight to the plausibility of biogenic magnetite on Mars? could magnetotaxis have developed on Mars? There are credible arguments for both the biological and non-biological origin of the magnetite in ALH84001, and we suggest that more studies of ALH84001, extensive laboratory simulations of non-biological magnetite formation, as well as further studies of magnetotactic bacteria on Earth will be required to further address this question. Magnetite grains produced by bacteria could provide one of the few inorganic traces of past bacterial life on Mars that could be recovered from surface soils and sediments. If there was biogenic magnetite on Mars in sufficient abundance to leave fossil remains in the volcanic rocks of ALH84001, then it is likely that better-preserved magnetite will be found in sedimentary deposits on Mars. Deposits in ancient lakebeds could contain well-preserved chains of magnetite clearly indicating a biogenic origin.

  18. Magnetotactic Bacteria on Earth and on Mars

    NASA Astrophysics Data System (ADS)

    McKay, Christopher P.; Friedmann, E. Imre; Frankel, Richard B.; Bazylinski, Dennis A.

    2003-06-01

    Continued interest in the possibility of evidence for life in the ALH84001 Martian meteorite has focused on the magnetite crystals. This review is structured around three related questions: Is the magnetite in ALH84001 of biological or non-biological origin, or a mixture of both? Does magnetite on Earth provide insight to the plausibility of biogenic magnetite on Mars? Could magnetotaxis have developed on Mars? There are credible arguments for both the biological and non-biological origin of the magnetite in ALH84001, and we suggest that more studies of ALH84001, extensive laboratory simulations of non-biological magnetite formation, as well as further studies of magnetotactic bacteria on Earth will be required to further address this question. Magnetite grains produced by bacteria could provide one of the few inorganic traces of past bacterial life on Mars that could be recovered from surface soils and sediments. If there was biogenic magnetite on Mars in sufficient abundance to leave fossil remains in the volcanic rocks of ALH84001, then it is likely that better-preserved magnetite will be found in sedimentary deposits on Mars. Deposits in ancient lakebeds could contain well-preserved chains of magnetite clearly indicating a biogenic origin.

  19. Chalcophile Elements in Martian Meteorites Indicate a Low Sulfur Content in the Martian Interior

    NASA Astrophysics Data System (ADS)

    Wang, Z.; Becker, H.

    2016-08-01

    Fractionation of chalcophile elements shows that the parent magmas of SNC meteorites formed and evolved at sulfide undersaturated conditions. The Mars has low sulfur contents in the mantle and the core.

  20. Life from Mars? The story and its implications.

    NASA Astrophysics Data System (ADS)

    Score, R.; Mittlefehldt, D. W.; Jakosky, B.; Yarus, M.

    1997-02-01

    After the announcement on 7 August 1996 by NASA officials that traces of fossil microbes have been detected in meteorite ALH84001, a symposium was held on 29 August 1996, at Boulder, Colorado, where scholars from a range of disciplines discussed the evidence for life on Mars and its implications. This special issue presents articles based on several of the talks given at that symposium. These papers include: 1. The thrill of the search - finding ALH84001 (R. Score). 2. Uncovering Martians hidden among us - the source of ALH84001 (D. W. Mittlefehldt). 3. Laying out the evidence - the case for life on Mars (B. Jakosky). 4. Is the case persuasive? A skeptical view (M. Yarus).

  1. Trace Element Geochemistry of Martian Iddingsite in the Lafayette Meteorite

    NASA Technical Reports Server (NTRS)

    Treiman, Allan H.; Lindstrom, David J.

    1997-01-01

    The Lafayette meteorite contains abundant iddingsite, a fine-grained intergrowth of smectite clay, ferrihydrite, and ionic salt minerals. Both the meteorite and iddingsite formed on Mars. Samples of iddingsite, olivine, and augite pyroxene were extracted from Lafayette and analyzed for trace elements by instrumental neutron activation. Our results are comparable to independent analyses by electron and ion microbeam methods. Abundances of most elements in the iddingsite do not covary significantly. The iddingsite is extremely rich in Hg, which is probably terrestrial contamination. For the elements Si, Al, Fe, Mn, Ni, Co, and Zn, the composition of the iddingsite is close to a mixture of approximately 50% Lafayette olivine + approximately 40% Lafayette siliceous glass + approximately 1O% water. Concordant behavior among these elements is not compatible with element fractionations between smectite and water, but the hydrous nature and petrographic setting of the iddingsite clearly suggest an aqueous origin. These inferences are both consistent, however, with deposition of the iddingsite originally as a silicate gel, which then crystallized (neoformed) nearly isochemically. The iddingsite contains significantly more magnesium than implied by the model, which may suggest that the altering solutions were rich in Mg(2+).

  2. New Bulk Sulfur Measurements of Martian Meteorites - Implications for Sulfur Cycle on Mars

    NASA Astrophysics Data System (ADS)

    Ding, S.; Dasgupta, R.; Lee, C.; Wadhwa, M.

    2013-12-01

    Magmatic degassing was likely critical in giving rise to a thick atmosphere of ancient Mars and SO2 and H2S could have been key greenhouse gases. How much S was released depends on (1) the S content of the mantle-derived magma and (2) the magmatic sulfur budget of the basaltic crust. While the former is estimated by S content of basaltic melts at sulfide saturation (SCSS) [1,2], assuming mantle-derived magma is sulfide saturated, it is unclear how much S gets trapped during crystallization of basalts in the crust versus how much is released to the atmosphere. S content of the martian crust can be estimated from martian meteorites, yet bulk S concentration data of martian meteorites is limited [3]. Further, most martian meteorites contain cumulus minerals and some have experienced secondary alteration (weathering/ impact effects), which could either deplete or enrich S in these samples. To better constrain the degassing of S from the martian interior, we measured bulk S contents of 7 martian meteorites via high mass-resolution solution ICP-MS [4]. Basaltic shergottites Los Angeles, Zagami and NWA 856 have S contents of 2865×224, 1954×91 and 1584×10 ppm, respectively while clinopyroxenites Nakhla and NWA 998 give values of 690×60 and 253×42 ppm S. Olivine-phyric shergottites NWA 1068 and Tissint have intermediate S contents of 1280×48 and 2120×68 ppm. The meteorites have lower S contents than the predicted SCSS of ~3500-4500 ppm [2] along liquid line of descent for a liquid similar to Yamato 980459 at 1 GPa, estimated using alphaMELTS. Taking into account the possible proportion of inter-cumulus liquid (f= 6-70 wt.%) in the analyzed meteorites estimated by previous studies, the degassed S could be as low as ~300-1900 ppm (estimated by the difference between the SCSS×f and the S in the meteorites). However, nakhlite Nakhla and basaltic shergottites NWA 856 and Zagami show higher S than the calculated SCSS×f. In these two meteorites, sulfides occur as

  3. Natural bridgmanite-periclase aggregates in Martian meteorites

    NASA Astrophysics Data System (ADS)

    Tschauner, O. D.; Ma, C.; Prescher, C.; Prakapenka, V.

    2014-12-01

    We use a combination of in-house- and synchrotron-based micro-mapping techniques to identify and characterize natural parageneseis of bridgmanite (MgSiO3 in the perovskite structure, IMA 2014-017) and periclase in shocked meteorites. The goal is to evaluate if shock-generated bridgmanite-melt, bridgmanite-periclase intergrowths provide information on element partitioning and rock-deformation that complement experimental studies. As in case of any natural rock recovered from high P-T conditions, chemical and physical changes during release require careful assessment. Major- and minor element concentrations are measured quantitatively with EPMA. Phase identification,-distribution, as well as internal structural parameters are evaluated based on micro-diffraction mappings. Laue diffraction peak profile analysis permits examination of dislocations active during deformation of bridgmanite-periclase aggregates.

  4. Chemical Weathering Records of Martian Soils Preserved in the Martian Meteorite EET79001

    NASA Technical Reports Server (NTRS)

    Rao, M. N.; Wentworth, S. J.; McKay, D. S.

    2004-01-01

    Impact-melt glasses, rich in Martian atmospheric gases, contain Martian soil fines (MSF) mixed with other coarse-grained regolith fractions which are produced during impact bombardment on Mars surface. An important characteristic of the MSF fraction is the simultaneous enrichment of felsic component accompanied by the depletion of mafic component relative to the host phase in these glasses. In addition, these glasses yield large sulfur abundances due to the occurrence of secondary mineral phases such as sulfates produced during acid-sulfate weathering of the regolith material near the Martian surface. Sulfurous gases released into atmosphere by volcanoes on Mars are oxidized to H2SO4 which deposit back on the surface of Mars as aerosol particles. Depending on the water availability, sulfuric acids dissolve into solutions which aggressively decompose the Fe-Mg silicates in the Martian regolith. During chemical weathering, structural elements such as Fe, Mg and Ca (among others) are released into the transgressing solutions. These solutions leach away the soluble components of Mg, Ca and Na, leaving behind insoluble iron as Fe3(+) hydroxysulfate mixed with poorly crystalline hydroxide- precipitates under oxidizing conditions. In this study, we focus on the elemental distribution of FeO and SO3 in the glass veins of EET79001, 507 sample, determined by Electron Microprobe and FE SEM measurements at JSC. This glass sample is an aliquot of a bigger glass inclusion ,104 analysed by where large concentrations of Martian atmospheric noble gases are found.

  5. Studies of Magmatic Inclusions in the Basaltic Martian Meteorites Shergotty, Zagami, EETA 79001 and QUE 94201

    NASA Technical Reports Server (NTRS)

    Harvey, Ralph P.; McKay, Gordon A.

    1997-01-01

    Currently there are 12 meteorites thought by planetary scientists to be martian samples, delivered to the Earth after violent impacts on that planet's surface. Of these 12 specimens, 4 are basaltic: Shergotty, Zagami, EETA 79001 and QUE 94201. Basalts are particularly important rocks to planetary geologists- they are the most common rocks found on the surfaces of the terrestrial planets, representing volcanic activity of their parent worlds. In addition, because they are generated by partial melting of the mantle and/or lower crust, they can serve as guide posts to the composition and internal processes of a planet. Consequently these four meteorites can serve as 'ground-truth' representatives of the predominant volcanic surface rocks of Mars, and offer researchers a glimpse of the magmatic history of that planet. Unfortunately, unraveling the parentage of a basaltic rock is not always straightforward. While many basalts are simple, unaltered partial melts of the mantle, others have undergone secondary processes which change the original parental chemistry, such as assimilation of other crustal rocks, mixing with other magmas, accumulation, re-equilibration between mineral species after crystallization, loss of late-stage magmatic fluids and alteration by metamorphic or metasomatic processes. Fortunately, magmatic inclusions can trap the evolving magmatic liquid, isolating it from many of these secondary processes and offering a direct look at the magma during different stages of development. These inclusions form when major or minor phases grow skeletally, surrounding small amounts of the parental magma within pockets in the growing crystal. The inclusion as a whole (usually consisting of glass with enclosed crystals) continues to represent the composition of the parental magma at the time the melt pocket closed, even when the rock as a whole evolves under changing conditions. The four basaltic martian meteorites contain several distinct generations of melt

  6. SNC meteorites - Clues to Martian petrologic evolution?. [Shergottites, Nakhlites and Chassigny

    NASA Technical Reports Server (NTRS)

    Mcsween, H. Y., Jr.

    1985-01-01

    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.

  7. Estimating different eruptive style volcanic areas of Mars from NASA Martian Meteorites Compendium data

    NASA Astrophysics Data System (ADS)

    Mari, Nicola; Verrino, Miriam

    2016-04-01

    The geomorphological characteristics of the Martian surface suggest that both effusive and explosive eruptive behaviour occurred. We investigated whether data about magma viscosity could be extrapolated from Mars SNCs (Shergotty, Nakhla, and Chassigny classes) meteorites, by using available geochemical and petrographic data from the NASA Martian Meteorites Compendium. Viscosity was used to characterize how eruptive style could change in different volcanic regions of planet Mars. Data about composition and crystallinity of 41 SNCs meteorites were used and classified, avoiding meteorites with poor/incomplete database. We assumed Mars as a one-plate planet, fO2 = QFM, and H2O wt% = 0 for each sample. Collected data from the Mars Global Surveyor Thermal Emission Spectrometer (MGS TES) identified the source regions for almost all the studied SNCs meteorites. As input for thermodynamic simulations we first needed to find the depth and pressure of the magmatic source for each meteorite sample through available Thermal Emission Imaging System (THEMIS). Data about average surface temperatures was used to establish whether a magmatic source is shallow or deep. Successively, we found the magma source depth (and pressure) by using the relationship with the heights of the volcanic edifice. The subsolidus equilibration temperatures found through petrologic softwares were used to calculate viscosity. Results indicate a crystallization temperature in a range from 1,120°C to 843°C, follow by a variation in viscosity from 101,43 to 105,97 Pa s. Viscosity seems to be higher in Tharsis, Elysium, Amazonis, and Syrtis Major regions than the remnant areas. According to past experimental studies about magma viscosity, we classified the eruptive style into effusive (101-103,5 Pa s), intermediate (103,5-104,5 Pa s), and explosive (104,5-106 Pa s). The Hellas Basin, Argyre Basin, Ganges Chasma, Eos Chasma, and Nili Fossae regions show an eruptive behaviour between effusive and intermediate

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

    NASA Technical Reports Server (NTRS)

    Treiman, A. H.

    1993-01-01

    The SNC meteorites, which almost certainly originate in the Martian crust, have been inferred to come from a single impact crater site, but no known crater fits all criteria. Formation at two separate sites (S from one, NC from the other) is more consistent with the sum of petrologic, geochronologic, and cosmochronologic data. If the source craters for the SNC meteorites can be located, Mars science will advance considerably. However, many significant questions cannot be answered by the SNC meteorites. These questions await a returned sample.

  9. Possible Evidence for Life in ALH84001

    NASA Technical Reports Server (NTRS)

    McKay, David; Gibson, Everett; Thomas-Keprta, Kathie

    1999-01-01

    Since our original paper in Science in August 1996, considerable new data has appeared from laboratories throughout the world, and our own team has had a chance to examine the sample in greater detail. The following summary touches on our original data and interpretation, and points out new data from us and from other groups, and the resulting changes and refinements in interpretations which we have made during the past three years. Additional information is contained in the original extended abstract.

  10. Possible Evidence for Life in ALH84001

    NASA Technical Reports Server (NTRS)

    McKay, David; Gibson, Everett K., Jr.; Thomas-Keprta, Kathie

    1999-01-01

    Since our original paper Science in August 1996, considerable new data has appeared from laboratories throughout the world, and our own team has had a chance to examine the sample in greater detail. The following summary touches on our original data and interpretation, and points out new data from us and from other groups, and the resulting changes and refinements in interpretations which we have made during the past three years.

  11. Solving the Martian meteorite age conundrum using micro-baddeleyite and launch-generated zircon.

    PubMed

    Moser, D E; Chamberlain, K R; Tait, K T; Schmitt, A K; Darling, J R; Barker, I R; Hyde, B C

    2013-07-25

    Invaluable records of planetary dynamics and evolution can be recovered from the geochemical systematics of single meteorites. However, the interpreted ages of the ejected igneous crust of Mars differ by up to four billion years, a conundrum due in part to the difficulty of using geochemistry alone to distinguish between the ages of formation and the ages of the impact events that launched debris towards Earth. Here we solve the conundrum by combining in situ electron-beam nanostructural analyses and U-Pb (uranium-lead) isotopic measurements of the resistant micromineral baddeleyite (ZrO2) and host igneous minerals in the highly shock-metamorphosed shergottite Northwest Africa 5298 (ref. 8), which is a basaltic Martian meteorite. We establish that the micro-baddeleyite grains pre-date the launch event because they are shocked, cogenetic with host igneous minerals, and preserve primary igneous growth zoning. The grains least affected by shock disturbance, and which are rich in radiogenic Pb, date the basalt crystallization near the Martian surface to 187 ± 33 million years before present. Primitive, non-radiogenic Pb isotope compositions of the host minerals, common to most shergottites, do not help us to date the meteorite, instead indicating a magma source region that was fractionated more than four billion years ago to form a persistent reservoir so far unique to Mars. Local impact melting during ejection from Mars less than 22 ± 2 million years ago caused the growth of unshocked, launch-generated zircon and the partial disturbance of baddeleyite dates. We can thus confirm the presence of ancient, non-convecting mantle beneath young volcanic Mars, place an upper bound on the interplanetary travel time of the ejected Martian crust, and validate a new approach to the geochronology of the inner Solar System.

  12. Solving the Martian meteorite age conundrum using micro-baddeleyite and launch-generated zircon.

    PubMed

    Moser, D E; Chamberlain, K R; Tait, K T; Schmitt, A K; Darling, J R; Barker, I R; Hyde, B C

    2013-07-25

    Invaluable records of planetary dynamics and evolution can be recovered from the geochemical systematics of single meteorites. However, the interpreted ages of the ejected igneous crust of Mars differ by up to four billion years, a conundrum due in part to the difficulty of using geochemistry alone to distinguish between the ages of formation and the ages of the impact events that launched debris towards Earth. Here we solve the conundrum by combining in situ electron-beam nanostructural analyses and U-Pb (uranium-lead) isotopic measurements of the resistant micromineral baddeleyite (ZrO2) and host igneous minerals in the highly shock-metamorphosed shergottite Northwest Africa 5298 (ref. 8), which is a basaltic Martian meteorite. We establish that the micro-baddeleyite grains pre-date the launch event because they are shocked, cogenetic with host igneous minerals, and preserve primary igneous growth zoning. The grains least affected by shock disturbance, and which are rich in radiogenic Pb, date the basalt crystallization near the Martian surface to 187 ± 33 million years before present. Primitive, non-radiogenic Pb isotope compositions of the host minerals, common to most shergottites, do not help us to date the meteorite, instead indicating a magma source region that was fractionated more than four billion years ago to form a persistent reservoir so far unique to Mars. Local impact melting during ejection from Mars less than 22 ± 2 million years ago caused the growth of unshocked, launch-generated zircon and the partial disturbance of baddeleyite dates. We can thus confirm the presence of ancient, non-convecting mantle beneath young volcanic Mars, place an upper bound on the interplanetary travel time of the ejected Martian crust, and validate a new approach to the geochronology of the inner Solar System. PMID:23887429

  13. Martian meteorite Tissint records unique petrogenesis among the depleted shergottites

    NASA Astrophysics Data System (ADS)

    Basu Sarbadhikari, A.; Babu, E. V. S. S. K.; Vijaya Kumar, T.; Chennaoui Aoudjehane, H.

    2016-07-01

    Tissint, a new unaltered piece of Martian volcanic materials, is the most silica-poor and Mg-Fe-rich igneous rock among the "depleted" olivine-phyric shergottites. Fe-Mg zoning of olivine suggests equilibrium growth (<0.1 °C h-1) in the range of Fo80-56 and olivine overgrowth (Fo55-18) through a process of rapid disequilibrium (~1.0-5.0 °C h-1). The spatially extended (up to 600 μm) flat-top Fe-Mg profiles of olivine indicates that the early-stage cooling rate of Tissint was slower than the other shergottites. The chemically metastable outer rim of olivine (

  14. Martian meteorite Tissint records unique petrogenesis among the depleted shergottites

    NASA Astrophysics Data System (ADS)

    Basu Sarbadhikari, A.; Babu, E. V. S. S. K.; Vijaya Kumar, T.; Chennaoui Aoudjehane, H.

    2016-09-01

    Tissint, a new unaltered piece of Martian volcanic materials, is the most silica-poor and Mg-Fe-rich igneous rock among the "depleted" olivine-phyric shergottites. Fe-Mg zoning of olivine suggests equilibrium growth (<0.1 °C h-1) in the range of Fo80-56 and olivine overgrowth (Fo55-18) through a process of rapid disequilibrium (~1.0-5.0 °C h-1). The spatially extended (up to 600 μm) flat-top Fe-Mg profiles of olivine indicates that the early-stage cooling rate of Tissint was slower than the other shergottites. The chemically metastable outer rim of olivine (

  15. Effect of Shock on the Magnetic Properties of Pyrrhotite, the Martian Crust, and Meteorites

    NASA Technical Reports Server (NTRS)

    Louzad, Karin L.; Stewart, Sarah T.; Weiss, Benjamin P.

    2007-01-01

    We performed planar shock recovery experiments on natural pyrrhotite at pressures up to 6.9 GPa. We find that high-field isothermal remanent magnetization in pyrrhotite is demagnetized up to 90% by shock due to preferential removal of low coercivity components of magnetization. Contrary to static experiments, we do not observe complete demagnetization. Post shock permanent changes in magnetic properties include increasing saturation isothermal remanent magnetization, bulk coercivity and lowtemperature memory, and changes in squareness of hysteresis. These changes are consistent with an increase in the volume fraction of single domain grains. The lack of magnetic anomalies over large Martian impact basins is not expected to be solely due to shock demagnetization of the crust. We find that pyrrhotite-bearing rocks and meteorites can retain records of Martian magnetic fields even if shocked to pressures approaching 7 GPa. However, some paleointensity techniques may underestimate this field.

  16. Putative Indigenous Carbon-Bearing Alteration Features in Martian Meteorite Yamato 000593

    PubMed Central

    Gibson, Everett K.; Thomas-Keprta, Kathie L.; Clemett, Simon J.; McKay, David S.

    2014-01-01

    Abstract We report the first observation of indigenous carbonaceous matter in the martian meteorite Yamato 000593. The carbonaceous phases are heterogeneously distributed within secondary iddingsite alteration veins and present in a range of morphologies including areas composed of carbon-rich spheroidal assemblages encased in multiple layers of iddingsite. We also observed microtubular features emanating from iddingsite veins penetrating into the host olivine comparable in shape to those interpreted to have formed by bioerosion in terrestrial basalts. Key Words: Meteorite—Yamato 000593—Mars—Carbon. Astrobiology 14, 170–181. PMID:24552234

  17. Exsolution and shock microstructures of igneous pyroxene clasts in the Northwest Africa 7533 Martian meteorite

    NASA Astrophysics Data System (ADS)

    Leroux, Hugues; Jacob, Damien; Marinova, Maya; Hewins, Roger H.; Zanda, Brigitte; Pont, Sylvain; Lorand, Jean-Pierre; Humayun, Munir

    2016-05-01

    Northwest Africa (NWA) 7533 is a Martian regolith breccia. This meteorite (and its pairings) offers a good opportunity to study (near-) surface processes that occurred on early Mars. Here, we have conducted a transmission electron microscope study of medium- and coarse-grained (a few tens to hundreds of micrometers) Ca-rich pyroxene clasts in order to define their thermal and shock histories. The pyroxene grains have a high-temperature (magmatic) origin as revealed by the well-developed pigeonite-augite exsolution microstructure. Exsolution lamella characteristics (composition, thickness, and spacing) indicate a moderately slow cooling. Some of the pyroxene clasts display evidence for local decomposition into magnetite and silica at the submicron scale. This phase decomposition may have occurred at high temperature and occurred at high oxygen fugacity at least 2-3 log units above the QFM buffer, after the formation of the exsolution lamellae. This corresponds to oxidizing conditions well above typical Martian magmatic conditions. These oxidizing conditions seem to have prevailed early and throughout most of the history of NWA 7533. The shock microstructure consists of (100) mechanical twins which have accommodated plastic deformation. Other pyroxene shock indicators are absent. Compared with SNC meteorites that all suffered significant shock metamorphism, NWA 7533 appears only mildly shocked. The twin microstructure is similar from one clast to another, suggesting that the impact which generated the (100) twins involved the compacted breccia and that the pyroxene clasts were unshocked when they were incorporated into the NWA 7533 breccia.

  18. Martian Surface Composition From Multiple Datasets, Part II: Chemical Analysis of Global Mineral Distributions from MGS-TES

    NASA Astrophysics Data System (ADS)

    Hamilton, V. E.; Rogers, D.

    2010-12-01

    Koeppen and Hamilton [2008, JGR-Planets] produced global mineral maps of Mars from Thermal Emission Spectrometer (TES) data using a library of mineral and amorphous phase spectra and a linear least squares fitting algorithm. Here we will use known or estimated bulk chemistries of the phases in the Koeppen and Hamilton [2008] spectral library, along with each phase's modeled abundance in the TES data from that work, to calculate effective bulk chemistry for Martian dark regions at a spatial resolution of ~3x6 km. By doing this, we are able to analyze global bulk chemical variation as well as enable direct comparisons between TES data and chemical/elemental abundance maps (e.g., wt.% SiO2) produced using data collected by the Gamma Ray Spectrometer. A second chemical analysis also makes use of the Koeppen and Hamilton [2008] global mineral maps and focuses on the spatial variations in solid solution chemistry among feldspars, pyroxenes, high silica phases (e.g., silica, phyllosilicates, zeolites), and sulfates. Koeppen and Hamilton [2008] demonstrated that there is a range of Mg-Fe olivine compositions on Mars and that there are distinct geographic distributions of those phases, pointing to spatial variations in geologic processes. We use the same methodology to search for correlations between geography (e.g., geologic unit, latitude), elevation, and chemical (solid solution) composition. Preliminary analyses of pyroxene chemical variation reveal that globally, low-Ca pyroxenes are dominated by the clinopyroxene pigeonite and that among orthopyroxenes, Mg-rich phases (enstatite) are virtually never identified and phases with greater proportions of Fe (bronzite and hypersthene) are identified in distinct geographic and/or geologic terrains. Only the distribution of hypersthene (the composition of pyroxene in the Martian meteorite ALH 84001) correlates with the OMEGA-mapped distribution of low-Ca pyroxene suggesting that OMEGA-based maps of high-Ca pyroxene may include

  19. Attempts to comprehend Martian surface processes through interpretation of the oxygen isotopic compositions of carbonates in SNC meteorites

    NASA Technical Reports Server (NTRS)

    Wright, I. P.; Pillinger, C. T.; Grady, Monica M.

    1992-01-01

    The SNC meteorites are known to contain trace quantities of a variety of secondary minerals such as carbonates, sulfates, and aluminosilicates. Since these constituents are thought to be mostly preterrestrial in origin, their study has the potential to provide rigorous constraints on the nature of martian weathering processes. However, this line of investigation is potentially complicated by the presence within the meteorite samples of any additional weathering products produced by terrestrial processes. Examination of such terrestrial components is important since weathering processes that affect meteorite samples following their fall to Earth might have some bearing on the nature of analogous processes at the surface of Mars. It is obviously necessary to try and distinguish which secondary components in SNC meteorites are terrestrial in origin from those that are preterrestrial. Herein consideration is made of the stable isotopic compositions of weathering products in two SNC meteorites: EET A79001 (a sample collected from Antarctica) and Nakhla (a fall from Egypt, 1911).

  20. A model composition for Mars derived from the oxygen isotopic ratios of martian/SNC meteorites

    NASA Astrophysics Data System (ADS)

    Delaney, J. S.

    1994-07-01

    Oxygen is the most abundant element in most meteorites, yet the ratios of its isotopes are seldom used to constrain the compositional history of achondrites. The two major achondrite groups have O isotope signatures that differ from any plausible chondritic precursors and lie between the ordinary and carbonaceous chondrite domains. If the assumption is made that the present global sampling of chondritic meteorites reflects the variability of O reservoirs at the time of planetessimal/planet aggregation in the early nebula, then the O in these groups must reflect mixing between known chondritic reservoirs. This approach, in combination with constraints based on Fe-Mn-Mg systematics, has been used previously to model the composition of the basaltic achondrite parent body (BAP) and provides a model precursor composition that is generally consistent with previous eucrite parent body (EPB) estimates. The same approach is applied to Mars exploiting the assumption that the SNC and related meteorites sample the martian lithosphere. Model planet and planetesimal compositions can be derived by mixing of known chondritic components using O isotope ratios as the fundamental compositional constraint. The major- and minor-element composition for Mars derived here and that derived previously for the basaltic achondrite parent body are, in many respects, compatible with model compositions generated using completely independent constraints. The role of volatile elements and alkalis in particular remains a major difficulty in applying such models.

  1. Mars as the parent body of the CI carbonaceous chondrites and implications for Mars biological and climatic history

    NASA Astrophysics Data System (ADS)

    Brandenburg, John E.

    1997-07-01

    The hypothesis that CI meteorites have an origin on Mars is presented along with supporting data and implications. A Martian origin for the CI will support Martian biogenesis and effect assessments of Martian histories, suggesting Mars and Earth evolved in parallel in both biologic and geologic realms for a long period. The CI containing a Martian pattern of oxygen isotopes and mineralogy indicative of deposition by liquid water. The CI contain no evidence of hypervelocity impact, but contain space-exposed olivine grains and are thus regolith material, indicating their formation under a planetary atmosphere. They contain organic matter similar to that found in Martian meteorites, ALH84001 and EETA79001. A scenario of formation of CI meteorites as being water altered late planetary accretion material is proposed. The 4.5 Gyr age of the CI, matching ALH84001, and their high concentration of organic matter, including possible fossil bacteria, strongly supports the hypothesis of early Martian biogenesis. With CI plus ALH84001 being old, and the SNCs being young, the Martian crustal age dichotomy is now well reflected in Martian meteorite ages. This suggests Mars has a strongly bimodal pattern of crustal ages, either very old or very young with liquid water moving on the planets surface until late in the planets history.

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

  3. X-ray Microtomography of Martian Meteorites and Implications for Mars Sample Return

    NASA Astrophysics Data System (ADS)

    Smith, Caroline; Ahmed, Farah; Sykes, Daniel; Schroeven-Deceuninck, Hilde

    2013-04-01

    Martian meteorites are some of the rarest and most scientifically interesting meteorite samples available for study, providing unique insights into the formation and geological evolution of Mars. With such rare and valuable material it is imperative to ensure that the most suitable samples are selected for each scientific study, particularly when material may be compromised or even completely destroyed during those analyses. X-ray micro CT-scanning is completely non-destructive and requires no sample preparation. The technique provides detailed insights into the mineralogical and textural characteristics of geological materials that would otherwise be determined using optical and/or electron microscopy with the necessary destructive and invasive sample preparation of a polished section or block. We have been carrying out a systematic study of Martian meteorites in the Natural History Museum Collection as part of a detailed curatorial and research program. Our results indicate that the level of detail that can be obtained using micro-CT rivals that using traditional electron microscopy, with the added advantage that three dimensional data is generated. For all samples it is possible to determine and delineate between different mineral phases including olivine, pyroxene, feldspar glass and opaque phases. Cracks and voids are also easily detected; an important result for samples which potentially contain trapped pockets of Martian atmosphere such as Tissint. Depending on sample size, different phases are resolvable down to a scale of ~5 micrometres. The complete lack of sample preparation required and the non-destructive nature of X-ray microtomography means that it could prove an extremely powerful tool during initial investigations of samples returned from Mars for Planetary Protection and preliminary mineralogical and textural characterisation. Indeed, if a sample container could be designed with an X-ray transparent 'window', it should be possible to determine

  4. Petrogenesis of Igneous-Textured Clasts in Martian Meteorite Northwest Africa 7034

    NASA Technical Reports Server (NTRS)

    Santos, A. R.; Agee, C. B.; Humayun, M.; McCubbin, F. M.; Shearer, C. K.

    2016-01-01

    The martian meteorite Northwest Africa 7034 (and pairings) is a breccia that samples a variety of materials from the martian crust. Several previous studies have identified multiple types of igneous-textured clasts within the breccia [1-3], and these clasts have the potential to provide insight into the igneous evolution of Mars. One challenge presented by studying these small rock fragments is the lack of field context for this breccia (i.e., where on Mars it formed), so we do not know how many sources these small rock fragments are derived from or the exact formation his-tory of these sources (i.e., are the sources mantle de-rived melt or melts contaminated by a meteorite impactor on Mars). Our goal in this study is to examine specific igneous-textured clast groups to determine if they are petrogenetically related (i.e., from the same igneous source) and determine more information about their formation history, then use them to derive new insights about the igneous history of Mars. We will focus on the basalt clasts, FTP clasts (named due to their high concentration of iron, titanium, and phosphorous), and mineral fragments described by [1] (Fig. 1). We will examine these materials for evidence of impactor contamination (as proposed for some materials by [2]) or mantle melt derivation. We will also test the petrogenetic models proposed in [1], which are igneous processes that could have occurred regardless of where the melt parental to the clasts was formed. These models include 1) derivation of the FTP clasts from a basalt clast melt through silicate liquid immiscibility (SLI), 2) derivation of the FTP clasts from a basalt clast melt through fractional crystallization, and 3) a lack of petrogenetic relationship between these clast groups. The relationship between the clast groups and the mineral fragments will also be explored.

  5. The age of the martian meteorite Northwest Africa 1195 and the differentiation history of the shergottites

    SciTech Connect

    Symes, S; Borg, L; Shearer, C; Irving, A

    2007-04-05

    Samarium-neodymium isotopic analyses of unleached and acid-leached mineral fractions from the recently identified olivine-bearing shergottite Northwest Africa 1195 yield a crystallization age of 348 {+-} 19 Ma and an {var_epsilon}{sub Nd}{sup 143} value of +40.1 {+-} 1.3. Maskelynite fractions do not lie on the Sm-Nd isochron and appear to contain a martian surface component with low {sup 147}Sm/{sup 144}Nd and {sup 143}Nd/{sup 144}Nd ratios that was added during shock. The Rb-Sr system is disturbed and does not yield an isochron. Terrestrial Sr appears to have affected all of the mineral fractions, although a maximum initial {sup 87}Sr/{sup 86}Sr ratio of 0.701614 {+-} 16 is estimated by passing a 348 Ma reference isochron through the maskelynite fraction that is least affected by contamination. The high initial {var_epsilon}{sub Nd}{sup 143} value and the low initial {sup 87}Sr/{sup 86}Sr ratio, combined with the geologically young crystallization age, indicate that Northwest Africa 1195 is derived from a source region characterized by a long-term incompatible element depletion. The age and initial Sr and Nd isotopic compositions of Northwest Africa 1195 are very similar to those of Queen Alexandra Range 94201, indicating these samples were derived from source regions with nearly identical Sr-Nd isotopic systematics. These similarities suggest that these two meteorites share a close petrogenetic relationship and might have been erupted from a common volcano. The meteorites Yamato 980459, Dar al Gani 476, Sayh al Uhaymir 005/008, and Dhofar 019 also have relatively old ages between 474-575 Ma and trace element and/or isotopic systematics that are indicative of derivation from incompatible-element-depleted sources. This suggests that the oldest group of meteorites is more closely related to one another than they are to the younger meteorites that are derived from less incompatible-element-depleted sources. Closed-system fractional crystallization of this suite of

  6. Formation of a Martian Pyroxenite: A Comparative Study of the Nakhlite Meteorites and Theo's Flow

    NASA Technical Reports Server (NTRS)

    Friedman, R. C.; Taylor, G. J.; Treiman, A. H.

    1999-01-01

    The unusual composition of the nakhlites, a group of pyroxenitic martian meteorites with young ages, presents an opportunity to learn about nonbasaltic magmatic activity on another planet. However, the limited number of these meteorites makes unraveling their history difficult. A promising terrestrial analog for the formation of the nakhlites is Theo's Flow in Ontario, Canada. This atypical, 120 m-thick flow differentiated in place, forming distinct layered lithologies of peridotite, pyroxenite, and gabbro. Theo's pyroxenite and the nakhlites share strikingly similar petrographies, with concentrated euhedral to subhedral augite grains set in a plagioclase-rich matrix. These two suites of rocks also share specific petrologic features, mineral and whole-rock compositional features, and size and spatial distributions of cumulus grains. The numerous similarities suggest that the nakhlites formed by a similar mechanism in a surface lava flow or shallow intrusion. Their formation could have involved settling of crystals in a phenocryst-laden flow or in situ nucleation and growth of pyroxenes in an ultramafic lava flow. The latter case is more likely and requires steady-state nucleation and growth of clusters of pyroxene grains (and olivine in the nakhlites), circulating in a strongly convecting melt pool, followed by settling and continued growth in a thickening cumulate pile. Trapped pockets of intercumulus liquid in the pile gradually evolved, finally growing Fe-enriched rims on cumulus grains. With sufficient evolution, the melt reached plagioclase supersaturation, causing rapid growth of plagioclase sprays and late-stage mesostasis growth.

  7. Geochronology of the Martian meteorite Zagami revealed by U-Pb ion probe dating of accessory minerals

    NASA Astrophysics Data System (ADS)

    Zhou, Qin; Herd, Christopher D. K.; Yin, Qing-Zhu; Li, Xian-Hua; Wu, Fu-Yuan; Li, Qiu-Li; Liu, Yu; Tang, Guo-Qiang; McCoy, Timothy J.

    2013-07-01

    The precise chronology of geological events on Mars is hampered by the lack of absolute ages for the Martian timescale, and the significant uncertainties that result from the extrapolation of the lunar timescale to Mars (Hartmann and Neukum, 2001). Martian meteorites represent the only samples of Mars currently available. Attempts to identify source craters for the meteorites have thus far proven inconclusive (Hamilton et al., 2003; Lang et al., 2009; Mouginis-Mark and Boyce, 2012>), precluding their use in constraining the absolute Martian timescale. The majority of the known Martian meteorites are basalts ("shergottites"); all dated shergottites have mineral separate (Rb-Sr or Sm-Nd) ages of <600 Ma (Borg et al., 2005). Here we report a 238U/206Pb age of 182.7±6.9 Ma by ion microprobe analysis of baddeleyite (ZrO2) grains in the Zagami shergottite. There is no correlation between discordancy and baddeleyite grain location relative to shock metamorphism. Mineral petrography demonstrates that baddeleyite is the result of late-stage igneous crystallization, and Raman spectroscopy shows that baddeleyite has not been transformed by shock into preservable high-pressure polymorphs. Supported by an age of 153±81 Ma for phosphate grains, obtained using the same method, we conclude that Zagami crystallized at ~180 Ma, in agreement with previous results from mineral separate geochronology. Therefore, the shergottites represent igneous rocks preferentially ejected from young terrains on Mars in a small number of ejection events.

  8. Cation diffusion in calcite: determining closure temperatures and the thermal history for the Allan Hills 84001 meteorite.

    PubMed

    Fisler, D K; Cygan, R T

    1998-07-01

    The presence of zoned Fe, Mg, Ca, and Mn in the carbonate phases associated with the cracks and inclusions of the Allan Hills (ALH) 84001 meteorite provides evidence for constraining the thermal history of the meteorite. Using self- and tracer-diffusion coefficients obtained from laboratory experiments on natural calcite, cooling rates are calculated for various temperatures and diffusion distances to assist in the evaluation of the compositional zoning associated with the carbonate phases in ALH 84001. The closure temperature model provides the average temperature below which compositional zoning will be preserved for a given cooling rate, that is, the temperature at which diffusion will be ineffective in homogenizing the phase. The validity of various theories for the formation of the carbonate globules may be examined, therefore, in view of the diffusion-limited kinetic constraints. Experiments using a thin film-mineral diffusion couple and ion microprobe for depth profiling analysis were performed for the temperature range of 550-800 degrees C to determine self- and tracer-diffusion coefficients for Ca and Mg and in calcite. The resulting activation energies for Ca (Ea(Ca) = 271 +/- 80 kJ/mol) and for Mg (Ea(Mg) = 284 +/- 74 kJ/mol) were used then to calculate a series of cooling rate, grain size, and closure temperature curves. The data indicate, for example, that by the diffusion of Mg in calcite, a 10 micrometers compositional zone would be completely homogenized at a temperature of 300 degrees C for cooling rates <100 K/Ma. These data provide no constraint on formation models that propose a low-temperature fluid precipitation mechanism; however, they indicate that the carbonate globules were not exposed to a high-temperature environment for long time scales following formation. PMID:11543076

  9. Cation diffusion in calcite: determining closure temperatures and the thermal history for the Allan Hills 84001 meteorite.

    PubMed

    Fisler, D K; Cygan, R T

    1998-07-01

    The presence of zoned Fe, Mg, Ca, and Mn in the carbonate phases associated with the cracks and inclusions of the Allan Hills (ALH) 84001 meteorite provides evidence for constraining the thermal history of the meteorite. Using self- and tracer-diffusion coefficients obtained from laboratory experiments on natural calcite, cooling rates are calculated for various temperatures and diffusion distances to assist in the evaluation of the compositional zoning associated with the carbonate phases in ALH 84001. The closure temperature model provides the average temperature below which compositional zoning will be preserved for a given cooling rate, that is, the temperature at which diffusion will be ineffective in homogenizing the phase. The validity of various theories for the formation of the carbonate globules may be examined, therefore, in view of the diffusion-limited kinetic constraints. Experiments using a thin film-mineral diffusion couple and ion microprobe for depth profiling analysis were performed for the temperature range of 550-800 degrees C to determine self- and tracer-diffusion coefficients for Ca and Mg and in calcite. The resulting activation energies for Ca (Ea(Ca) = 271 +/- 80 kJ/mol) and for Mg (Ea(Mg) = 284 +/- 74 kJ/mol) were used then to calculate a series of cooling rate, grain size, and closure temperature curves. The data indicate, for example, that by the diffusion of Mg in calcite, a 10 micrometers compositional zone would be completely homogenized at a temperature of 300 degrees C for cooling rates <100 K/Ma. These data provide no constraint on formation models that propose a low-temperature fluid precipitation mechanism; however, they indicate that the carbonate globules were not exposed to a high-temperature environment for long time scales following formation.

  10. Life on Mars, Where do we stand after seven years of investigations.

    NASA Astrophysics Data System (ADS)

    Gibson, E.

    2003-04-01

    The question "Is there life on Mars?" is one of the most challenging questions for the scientific community to answer. Until documented samples are returned to Earth from Mars by space probes, the only samples available for study are twenty-six undocumented, randomly selected Martian samples delivered to Earth. Martian meteorites offer a unique opportunity to study near-surface samples from Mars. Martian meteorites of widely differing ages (ALH84001 - crystallization age of 4.5 Gy. with 3.9 Gy. old carbonates; Nakhla D crystallization age of 1.3 Gy. and clays of possibly 600-700 Ma. years age; and Shergotty D 165 Ma. crystallization age) contain evidence of water produced alteration products (hydrates, clays, sulfates, carbonates, halites, etc.). ALH84001 and Nakhla has been shown to contain indigenous reduced carbon compounds with isotopic compositions which are not products of terrestrial contaminants. Unique magnetite biomarkers are found within the ALH84001 low-temperature carbonate globules and display six unique properties of magnetites produced by the reference MV-1 magnetosome bacteria. Recently, the three-dimensional morphologies of the magnetites from both MV-1 magnetosome bacteria and the "biogenic" population of magnetites within the carbonates of ALH84001 have been show to be crystallographically equivalent. The determination that the properties of both MV-1 and ALH84001 magnetites are essentially identical provides further support for our interpretation that these Martian magnetites were produced by similar biogenic processes on Mars. To date, all of the models presented utilizing thermal decomposition of iron-rich carbonates to produce magnetites within ALH84001's carbonates fail to produce the unique properties of the biogenic magnetites. In addition, morphological structures are present within the three Martian meteorites which are identical to fossilized bacteria. Despite more than seven years of extensive research by the scientific community, the

  11. The age of the martian meteorite Northwest Africa 1195 and the differentiation history of the shergottites

    NASA Astrophysics Data System (ADS)

    Symes, Steven J. K.; Borg, Lars E.; Shearer, Charles K.; Irving, Anthony J.

    2008-03-01

    Samarium-neodymium isotopic analyses of unleached and acid-leached mineral fractions from the recently identified olivine-bearing shergottite Northwest Africa 1195 yield a crystallization age of 347 ± 13 Ma and an ɛNd143 value of +40.1 ± 0.9. Maskelynite fractions do not lie on the Sm-Nd isochron and appear to contain a martian surface component with low 147Sm/ 144Nd and 143Nd/ 144Nd ratios that was added during shock. The Rb-Sr system is disturbed and does not yield an isochron. Terrestrial Sr appears to have affected all of the mineral fractions, although a maximum initial 87Sr/ 86Sr ratio of 0.7016 is estimated by passing a 347 Ma reference line through the maskelynite fraction that is least affected by contamination. The high initial ɛNd143 value and the low initial 87Sr/ 86Sr ratio, combined with the geologically young crystallization age, indicate that Northwest Africa 1195 is derived from a source region characterized by a long-term incompatible-element depletion. The age and initial Sr and Nd isotopic compositions of Northwest Africa 1195 are very similar to those of Queen Alexandra Range 94201, indicating these samples were derived from source regions with similar Sr-Nd isotopic systematics. These similarities suggest that these two meteorites share a close petrogenetic relationship and might have been erupted from a common volcano. The meteorites Yamato 980459, Dar al Gani 476, Sayh al Uhaymir 005/008, and Dhofar 019 also have relatively old ages between 474 and 575 Ma and trace element and/or isotopic systematics that are indicative of derivation from incompatible-element-depleted sources. This suggests that the oldest group of meteorites is more closely related to one another than they are to the younger meteorites that are derived from less incompatible-element-depleted sources. Closed-system fractional crystallization of this suite of meteorites is modeled with the MELTS algorithm using the bulk composition of Yamato 980459 as a parent. These

  12. A Search for Amino Acids and Nucleobases in the Martian Meteorite Roberts Massif 04262 Using Liquid Chromatography-Mass Spectrometry

    NASA Technical Reports Server (NTRS)

    Callahan, Michael P.; Burton, Aaron S.; Elsila, Jamie E.; Baker, Eleni M.; Smith, Karen E.; Glavin, Daniel P.; Dworkin, Jason P.

    2013-01-01

    The investigation into whether Mars contains signatures of past or present life is of great interest to science and society. Amino acids and nucleobases are compounds that are essential for all known life on Earth and are excellent target molecules in the search for potential Martian biomarkers or prebiotic chemistry. Martian meteorites represent the only samples from Mars that can be studied directly in the laboratory on Earth. Here, we analyzed the amino acid and nucleobase content of the shergottite Roberts Massif (RBT) 04262 using liquid chromatography-mass spectrometry. We did not detect any nucleobases above our detection limit in formic acid extracts; however, we did measure a suite of protein and nonprotein amino acids in hot-water extracts with high relative abundances of beta-alanine and gamma-amino-eta-butyric acid. The presence of only low (to absent) levels of several proteinogenic amino acids and a lack of nucleobases suggest that this meteorite fragment is fairly uncontaminated with respect to these common biological compounds. The distribution of straight-chained amine-terminal eta-omega-amino acids in RBT 04262 resembled those previously measured in thermally altered carbonaceous meteorites. A carbon isotope ratio of -24(0/00) +/- 6(0/00) for beta-alanine in RBT 04262 is in the range of reduced organic carbon previously measured in Martian meteorites (Steele et al. 2012). The presence of eta-omega-amino acids may be due to a high temperature Fischer-Tropschtype synthesis during igneous processing on Mars or impact ejection of the meteorites from Mars, but more experimental data are needed to support these hypotheses.

  13. A search for amino acids and nucleobases in the Martian meteorite Roberts Massif 04262 using liquid chromatography-mass spectrometry

    NASA Astrophysics Data System (ADS)

    Callahan, Michael P.; Burton, Aaron S.; Elsila, Jamie E.; Baker, Eleni M.; Smith, Karen E.; Glavin, Daniel P.; Dworkin, Jason P.

    2013-05-01

    The investigation into whether Mars contains signatures of past or present life is of great interest to science and society. Amino acids and nucleobases are compounds that are essential for all known life on Earth and are excellent target molecules in the search for potential Martian biomarkers or prebiotic chemistry. Martian meteorites represent the only samples from Mars that can be studied directly in the laboratory on Earth. Here, we analyzed the amino acid and nucleobase content of the shergottite Roberts Massif (RBT) 04262 using liquid chromatography-mass spectrometry. We did not detect any nucleobases above our detection limit in formic acid extracts; however, we did measure a suite of protein and nonprotein amino acids in hot-water extracts with high relative abundances of β-alanine and γ-amino-n-butyric acid. The presence of only low (to absent) levels of several proteinogenic amino acids and a lack of nucleobases suggest that this meteorite fragment is fairly uncontaminated with respect to these common biological compounds. The distribution of straight-chained amine-terminal n-ω-amino acids in RBT 04262 resembled those previously measured in thermally altered carbonaceous meteorites (Burton et al. 2012; Chan et al. 2012). A carbon isotope ratio of -24‰ ± 6‰ for β-alanine in RBT 04262 is in the range of reduced organic carbon previously measured in Martian meteorites (Steele et al. 2012). The presence of n-ω-amino acids may be due to a high temperature Fischer-Tropsch-type synthesis during igneous processing on Mars or impact ejection of the meteorites from Mars, but more experimental data are needed to support these hypotheses.

  14. Shock-Induced Phase Transitions in the Martian Meteorite Tissint: Mechanisms and Constraints on Shock Pressure

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    Martian meteorites are important samples for understanding the origin and age of the Martian crust. All of these samples have been shocked to some degree during their ejection from Mars or earlier. Tissint, a picritic shergottite, has many high-pressure phases that have been used to constrain shock conditions and suggest a deep crustal origin [1] and to argue for multiple impact events [2]. Here we investigate the products and mechanisms of various olivine transformation reactions. Olivine in and adjacent to shock-melt veins and pockets is transformed into high-pressure minerals. In the hottest parts of the sample, olivine dissociated into 50-nm crystals of magnesiowüstite intergrown with either a pyroxene-composition glass or with low-Ca clinopyroxene. In both cases, the olivine is inferred to have transformed to silicate perovskite + magnesiowüstite during shock with subsequent breakdown of the perovskite after pressure release. Olivine along the margins of shock veins transformed into ringwoodite. Polycrystalline ringwoodite formed at the olivine-melt interface wheras coherent ringwoodite lamellae formed farther from the melt. These ringwoodite lamellae have the same topotaxial relationship to olivine as seen in static high-pressure experiments [3] and shocked meteorites [4]: (100)Ol || {111}Rw and [011]Ol || <110>Rw. The various olivine reactions can be explained by a single shock to above 24 GPa where only the highest temperatures allowed the dissociation of olivine to silicate-perovskite plus magnesiowüstite. The silicate perovskite in the melt pocket transformed to pyroxene because the melt pocket remained very hot after pressure release. At lower temperatures, the kinetically easier polymorphic transformation of olivine to metastable ringwoodite occurred. At the lowest temperatures, this reaction was facilitated by nucleation of ringwoodite lamellae on stacking faults in olivine. The variation in assemblages that we see are consistent with a single shock

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

    NASA Technical Reports Server (NTRS)

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

    1998-01-01

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

  16. Ar-40/Ar-39 Studies of Martian Meteorite RBT 04262 and Terrestrial Standards

    NASA Technical Reports Server (NTRS)

    Park, J.; Herzog, G. F.; Turrin, B.; Lindsay, F. N.; Delaney, J. S.; Swisher, C. C., III; Nagao, K.; Nyquist, L. E.

    2014-01-01

    Park et al. recently presented an Ar-40/Ar-39 dating study of maskelynite separated from the Martian meteorite RBT 04262. Here we report an additional study of Ar-40/Ar-39 patterns for smaller samples, each consisting of only a few maskelynite grains. Considered as a material for Ar-40/Ar-39 dating, the shock-produced glass maskelynite has both an important strength (relatively high K concentration compared to other mineral phases) and some potentially problematic weaknesses. At Rutgers, we have been analyzing small grains consisting of a single phase to explore local effects that might be averaged and remain hidden in larger samples. Thus, to assess the homogeneity of the RBT maskelynite and for comparison with the results of, we analyzed six approx. 30 microgram samples of the same maskelynite separate they studied. Furthermore, because most Ar-40/Ar-39 are calculated relative to the age of a standard, we present new Ar-40/Ar-39 age data for six standards. Among the most widely used standards are sanidine from Fish Canyon (FCs) and various hornblendes (hb3gr, MMhb-1, NL- 25), which are taken as primary standards because their ages have been determined by independent, direct measurements of K and A-40.

  17. Constraints on the Martian cratering rate imposed by the SNC meteorites and Vallis Marineris layered deposits

    NASA Astrophysics Data System (ADS)

    Brandenburg, J. E.

    Following two independent lines of evidence -- estimates of the age and formation time of a portion of the Martian geologic column exposed in the layered deposits and the crystallization and ejection ages of the SNC meteorites -- it appears that the Martian cratering rate must be double the lunar rate or even higher. This means models such as NHII or NHIII (Neukum and Hiller models II and III), which estimate the Martian cratering rate as being several times lunar are probably far closer to reality on Mars than lunar rates. The effect of such a shift is profound: Mars is transformed from a rather Moon-like place into a planet with vigorous dynamics, multiple large impacts, erosion, floods, and volcanism throughout its history. A strong shift upward in cratering rates on Mars apparently solves some glaring problems; however, it creates others. The period of time during which Earth-like atmospheric conditions existed, the liquid water era on Mars, persists in NHIII up to only 0.5 b.y. ago. Scenarios of extended Earth-like conditions on Mars have been discounted in the past because they would have removed many of the craters from the early bombardment era found in the south. It does appear that some process of crater removal was quite vigorous in the north during Mars' past. Evidence exists that the northern plains may have been the home of long-lived seas or perhaps even a paleo-ocean, so models exist for highly localized destruction of craters in the north. However, the question of how the ancient crater population could be preserved in the south under a long liquid-water era found in any high-cratering-rate models is a serious question that must be addressed. It does appear to be a higher-order problem because it involves low-energy dynamics acting in localized areas, i.e., erosion of craters in the south of Mars, whereas the two problems with the low-cratering-rate models involve high-energy events acting over large areas: the formation of the Vallis Marineris

  18. A new Martian meteorite from Morocco: the nakhlite North West Africa 817

    NASA Astrophysics Data System (ADS)

    Sautter, V.; Barrat, J. A.; Jambon, A.; Lorand, J. P.; Gillet, Ph.; Javoy, M.; Joron, J. L.; Lesourd, M.

    2002-02-01

    North West Africa (NWA 817) is a single stone of 104 g found in the Sahara (Morocco) by meteorite hunters in November 2000. The meteorite is an unbrecciated, medium-grained olivine-bearing clinopyroxenite with a cumulate texture. It consists of zoned euhedral subcalcic augite (Wo 42En 38-22Fs 20-36), olivine spanning a wide range of compositions (from Fa 56 in the core to Fa 86) with rare magmatic inclusions and an intercumulus mesostasis made of Fe-bearing albitic plagioclase, Si-rich glass, Ti-magnetite with unusual skeletal growth morphologies containing ilmenite exsolutions, acicular pyroxene, olivine and cristobalite. Trace minerals are sulfide droplets and Cl-apatite. Mineral modes (in vol%) are augite 69%, olivine 10%, mesostasis 20% and Fe-Ti oxides 1%. Pervasive alteration produced a reddish clay mineral (hydrous ferrous silicate) in both olivine crystals and the mesostasis. The major element composition of NWA 817 is very similar to that of the other nakhlites: high FeO, MgO and CaO concentrations reflect the abundance of cumulus augite and olivine. Key element ratios such as FeO/MnO (=37), Na/Al (=0.40), K/La (=449), Ga/Al (=3.9×10 -4) and oxygen isotopic composition (Δ 17O=+0.37‰) are clear evidence for a Martian origin. The incompatible trace element pattern as in Nakhla displays a strong light rare earth element enrichment relative to chondrite (La n/Yb n=4.89). However, when compared to the other nakhlites, NWA 817 has specific features: (1) a higher modal proportion of mesostasis; (2) quench textures of Ti-magnetite and Fe-rich clinopyroxene; (3) more Mg-rich olivine core compositions whereas the augite core composition is identical for all nakhlites; (4) a stronger Fe enrichment toward crystal rims of these cumulus minerals. The intercumulus minerals (Ti-magnetite with skeletal growth morphology, acicular chains of clinopyroxene and Fe 3+-rich feldspar) indicate rapid crystallization in response to a high degree of undercooling at the end of

  19. The Northwest Africa (NWA) 5790 meteorite: A mesostasis-rich nakhlite with little or no Martian aqueous alteration

    NASA Astrophysics Data System (ADS)

    Tomkinson, Tim; Lee, Martin R.; Mark, Darren F.; Dobson, Katherine J.; Franchi, Ian A.

    2015-02-01

    Northwest Africa (NWA) 5790 is the most recently discovered member of the nakhlite group. Its mineralogy differs from the other nakhlites with a high abundance mesostasis (38.1 ± 3.6 vol%) and scarcity of olivine (4.0 ± 2.2 vol%). Furthermore, zoning of augite phenocrysts, and other petrographic and chemical characteristics suggest that NWA 5790 samples the chilled margin of its parent lava flow/sill. NWA 5790 contains calcite and rare clay minerals that are evidence for its exposure to liquid water. The calcite forms a cement to coatings of dust on the outer surface of the find and extends into the interior of the meteorite within veins. The presence of microbial remains within the coating confirms that the dust and its carbonate cement are terrestrial in origin, consistent with the carbon and oxygen isotope composition of the calcite. The clay minerals are finely crystalline and comprise ~0.003 vol% of the meteorite. δD values of the clay minerals range from -212 ± 109‰ to -96 ± 132‰, and cannot be used to distinguish between a terrestrial or Martian origin. As petrographic results are also not definitive, we conclude that secondary minerals produced by Martian groundwaters are at best very rare within NWA 5790. The meteorite has therefore sampled a region of the lava flow/sill with little or no exposure to the aqueous solutions that altered other nakhlites. This isolation could relate to the scarcity of olivine in NWA 5790 because dissolution of olivine in other nakhlites by Martian groundwaters enhanced their porosity and permeability, and provided solutes for secondary minerals.

  20. Gypsum, jarosite, and hydrous iron-phosphate in Martian meteorite Roberts Massif 04262: Implications for sulfate geochemistry on Mars.

    NASA Astrophysics Data System (ADS)

    Greenwood, J. P.

    2008-12-01

    Gypsum has been identified on Mars by MEX OMEGA [1] and jarosite identified via MER-B lander [2] and both minerals are examples of the importance of calcium and iron sulfates in Martian weathering processes. The weathering of Martian basalt to form Ca and iron sulfates should be an important process on Mars. Martian jarosite has been identified in MIL 03346 [3] and Ca-sulfate has been identified in EETA 79001 [4], but both phases have yet to be identified in the same Martian sample. In Roberts Massif 04262, an olivine-phyric shergottite, iron-sulfide and calcium-phosphate minerals are undergoing reaction (dissolution and reprecipitation?) to form gypsum, jarosite, and an iron-phosphate phase, presumably during the meteorite's residence in Antarctica. If true, then an acidic and oxidizing fluid was present in this meteorite, due to the formation of jarosite which requires fluid of this type to form [5]. The weathering of iron-sulfides on Earth to form acidic and oxidizing fluids is common, thus this can be reconciled with the formation of an acidic fluid in a basic rock. Presumably, under more extensive weathering of silicate minerals in Martian basalt, the pH would be raised to values where jarosite would not be stable. While the weathering of RBT 04262 is likely occurring in Antarctica, a similar susceptibility of the apatite and pyrrhotite to incipient weathering on Mars may be expected. Oxidizing crustal fluids on Mars may attack iron- sulfides first in Martian basalts. The weathering of iron-sulfides leads to increasing acidity of fluids, which would enhance the dissolution of the calcium-phosphate minerals [6]. The formation of jarosite, gypsum, and iron-phosphate minerals during the early stages of weathering of Martian basalts may be an important process on Mars globally. [1] Gendrin, A. et al. (2005) Science, 307, 1587-1591. [2] Klingelhöfer et al. (2004) Science, 306, 1740- 1745. [3] Vicenzi E. P. et al. (2007) LPSC XXXVIII, Abstract 2335. [4] Gooding J

  1. Smectite Formation in Gale Crater, Mars and in the Nakhlite Martian Meteorites

    NASA Astrophysics Data System (ADS)

    Bridges, J.; Schwenzer, S. P.; Leveille, R. J.; Westall, F.; Wiens, R. C.; Mangold, N.; Bristow, T.; Edwards, P.

    2014-12-01

    Recent, detailed analyses of the nakhlite martian meteorites have enabled characterization of a ferric saponite and ferric serpentine (Hicks et al. 2014 10.1016/j.gca.2014.04.010). This nakhlite assemblage is part of a rapidly cooled, hydrothermal assemblage, cooled from ~150 oC, with the clay forming at ~50 oC (Bridges and Schwenzer 2012 10.1016/j.epsl.2012.09.044). Although there are differences between the overall secondary assemblage in the nakhlites and that identified in the Yellowknife Bay mudstones by CheMin (Vaniman et al. 2014 10.1126/science1243480), the trioctahedral iron-rich saponite is probably the closest analogue known to the smectite found in Gale Crater. MSL analysed mudstones at the Yellowknife Bay, deposited in a fluvio-lacustrine setting followed by diagenesis ~50 oC (Grotzinger et al. 2014 10.1126/science.1242777). The mineralogical information provides allows us to constrain mineral reactions, W/R, pH, and redox associated using thermochemical modelling, and comparisons to the nakhlites. We use a 2 stage fluid model, with an initial Deccan-type brine composition (Minissale et al. 2000 10.1016/S0012-821X(00)00200-4) which reacts with the known rock compositions - using ChemCam and APXS data to produce a pore fluid. CHIM-XPT was used for the modelling. Initial reaction of the early brine with olivine in the mudstone produces relatively Mg-rich phyllosilicate. This early diagenesis may correspond to the formation of Mg-Fe rich ridges (Leveille et al. 10.1002/2014JE004620). Subsequent reaction of the resultant fluid separated at a W/R of 100, produced a fluid that we then reacted with a range of different mineral and amorphous mixtures, T, W/R conditions. A mixture of 70% amorphous, 20% olivine, 10% host rock produced a clay-Fe oxide dominated assemblage, similar to that in Sheepbed. The clay has a similar composition to ferric saponite and gel in the nakhlites (Bridges et al. JGR, subm.).

  2. A model composition for Mars derived from the oxygen isotopic ratios of martian/SNC meteorites. [Abstract only

    NASA Technical Reports Server (NTRS)

    Delaney, J. S.

    1994-01-01

    Oxygen is the most abundant element in most meteorites, yet the ratios of its isotopes are seldom used to constrain the compositional history of achondrites. The two major achondrite groups have O isotope signatures that differ from any plausible chondritic precursors and lie between the ordinary and carbonaceous chondrite domains. If the assumption is made that the present global sampling of chondritic meteorites reflects the variability of O reservoirs at the time of planetessimal/planet aggregation in the early nebula, then the O in these groups must reflect mixing between known chondritic reservoirs. This approach, in combination with constraints based on Fe-Mn-Mg systematics, has been used previously to model the composition of the basaltic achondrite parent body (BAP) and provides a model precursor composition that is generally consistent with previous eucrite parent body (EPB) estimates. The same approach is applied to Mars exploiting the assumption that the SNC and related meteorites sample the martian lithosphere. Model planet and planetesimal compositions can be derived by mixing of known chondritic components using O isotope ratios as the fundamental compositional constraint. The major- and minor-element composition for Mars derived here and that derived previously for the basaltic achondrite parent body are, in many respects, compatible with model compositions generated using completely independent constraints. The role of volatile elements and alkalis in particular remains a major difficulty in applying such models.

  3. Evidence of martian perchlorate, chlorate, and nitrate in Mars meteorite EETA79001: Implications for oxidants and organics

    NASA Astrophysics Data System (ADS)

    Kounaves, Samuel P.; Carrier, Brandi L.; O'Neil, Glen D.; Stroble, Shannon T.; Claire, Mark W.

    2014-02-01

    The results from the Viking mission in the mid 1970s provided evidence that the martian surface contained oxidants responsible for destroying organic compounds. In 2008 the Phoenix Wet Chemistry Lab (WCL) found perchlorate (ClO4-) in three soil samples at concentrations from 0.5 to 0.7 wt%. The detection of chloromethane (CH3Cl) and dichloromethane (CH2Cl2) by the Viking pyrolysis gas chromatograph-mass spectrometer (GC-MS) may have been a result of ClO4- at that site oxidizing either terrestrial organic contaminates or, if present, indigenous organics. Recently, the Sample Analysis at Mars (SAM) instrument on the Mars Science Laboratory (MSL) Curiosity directly measured the presence of CH3Cl, CH2Cl2 and, along with measurements of HCl and oxygen, indirectly indicate the presence of ClO4-. However, except for Phoenix, no other direct measurement of the ClO4- anion in martian soil or rock has been made. We report here ion chromatographic (IC) and isotopic analyses of a unique sawdust portion of the martian meteorite EETA79001 that show the presence by mass of 0.6 ± 0.1 ppm ClO4-, 1.4 ± 0.1 ppm ClO3-, and 16 ± 0.2 ppm NO3- at a quantity and location within the meteorite that is difficult to reconcile with terrestrial contamination. The sawdust sample consists of basaltic material with a minor salt-rich inclusion in a mass ratio of ∼300:1, thus the salts may be 300 times more concentrated within the inclusion than the whole sample. The molar ratios of NO3-:ClO4- and Cl:ClO4-, are very different for EETA79001 at ∼40:1 and 15:1, respectively, than the Antarctic soils and ice near where the meteorite was recovered at ∼10,000:1 and 5000:1, respectively. In addition, the isotope ratios for EETA79001 with δ15N = -10.48 ± 0.32‰ and δ18O = +51.61 ± 0.74‰ are significantly different from that of the nearby Miller Range blue ice with δ15N = +102.80 ± 0.14‰ and δ18O = +43.11 ± 0.64‰. This difference is notable, because if the meteorite had been

  4. The chlorine isotope composition of Martian meteorites 2. Implications for the early solar system and the formation of Mars

    NASA Astrophysics Data System (ADS)

    Sharp, Zachary; Williams, Jeffrey; Shearer, Charles; Agee, Carl; McKeegan, Kevin

    2016-01-01

    We determined the chlorine isotope composition of 16 Martian meteorites using gas source mass spectrometry on bulk samples and in situ secondary ion microprobe analysis on apatite grains. Measured δ37Cl values range from -3.8 to +8.6‰. The olivine-phyric shergottites are the isotopically lightest samples, with δ37Cl mostly ranging from -4 to -2‰. Samples with evidence for a crustal component have positive δ37Cl values, with an extreme value of 8.6‰. Most of the basaltic shergottites have intermediate δ37Cl values of -1 to 0‰, except for Shergotty, which is similar to the olivine-phyric shergottites. We interpret these data as due to mixing of a two-component system. The first component is the mantle value of -4 to -3‰. This most likely represents the original bulk Martian Cl isotope value. The other endmember is a 37Cl-enriched crustal component. We speculate that preferential loss of 35Cl to space has resulted in a high δ37Cl value for the Martian surface, similar to what is seen in other volatile systems. The basaltic shergottites are a mixture of the other two endmembers. The low δ37Cl value of primitive Mars is different from Earth and most chondrites, both of which are close to 0‰. We are not aware of any parent-body process that could lower the δ37Cl value of the Martian mantle to -4 to -3‰. Instead, we propose that this low δ37Cl value represents the primordial bulk composition of Mars inherited during accretion. The higher δ37Cl values seen in many chondrites are explained by later incorporation of 37Cl-enriched HCl-hydrate.

  5. Water-extractable and exchangeable phosphate in Martian and carbonaceous chondrite meteorites and in planetary soil analogs

    NASA Astrophysics Data System (ADS)

    Mautner, Michael N.; Sinaj, Sokrat

    2002-09-01

    solutions with high phosphate concentrations can form in the pores of planetary lava ash and basalts and in carbonaceous asteroids and meteorites. These solutions can help prebiotic synthesis and early microbial nutrition. The Martian and carbonaceous chondrite materials contain sufficient phosphate for space-based agriculture.

  6. 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

  7. Reassessing the cooling rate and geologic setting of Martian meteorites MIL 03346 and NWA 817

    NASA Astrophysics Data System (ADS)

    Richter, Frank; Chaussidon, Marc; Mendybaev, Ruslan; Kite, Edwin

    2016-06-01

    Lithium concentration and isotopic fractionation profiles across augite grains from two Martian meteorites - MIL 03346 and NWA 817 - were used to determine their thermal history and implications for their geologic setting. The iron-magnesium zoning and associated magnesium isotopic fractionation of olivine grains from NWA 817 were also measured and provide a separate estimate of the cooling rate. The observed correlation of concentration with isotopic fractionation provides the essential evidence that the zoning of these grains was in fact due to diffusion and thus can be used as a measure of their cooling rate. The diffusion rate of lithium in augite depends on the oxygen fugacity, which has to be taken into account when determining a cooling rate based on the lithium zoning. The Fe-Mg exchange in olivine is much less sensitive to oxygen fugacity, but it is significantly anisotropic and for this reason we determined the direction relative to crystallographic axes of the line along which the Fe-Mg zoning was measured. We found that the cooling rate of NWA 817 determined from the lithium zoning in augite grains and that based on the Fe-Mg zoning of olivines are in good agreement at an oxygen fugacity close to that of quartz-fayalite-magnetite oxygen buffer. The cooling rate of MIL 03346 was found to be resolvably faster than that of NWA 817 - of the order of 1 °C/h for the former and of the order of 0.2 °C/h for the latter. An important observation regarding the history of MIL 03346 and NWA 817 is that the lithium and Fe-Mg zoning are only observed where the augite or olivine is in contact with the mesostasis, which implies that they were already about 80% crystallized at the time diffusion began. The augite and olivine core compositions while very homogeneous are not in equilibrium with each other, which we interpret to imply that prior to the rapid cooling there must have been a protracted period of the order of years above the solidus, during which the much

  8. Meteorites on Mars as Planetary Research Tools with Special Considerations for Martian Weathering Processes

    NASA Astrophysics Data System (ADS)

    Ashley, James Warren

    2011-09-01

    The occurrence of exogenic, meteoritic materials on the surface of any world presents opportunities to explore a variety of significant problems in the planetary sciences. In the case of Mars, meteorites found on its surface may help to (1) constrain atmospheric conditions during their time of arrival; (2) provide insights into possible variabilities in meteoroid type sampling between Mars and Earth space environments; (3) aid in our understanding of soil, dust, and sedimentary rock chemistry; (4) assist with the calibration of crater-age dating techniques; and (5) provide witness samples for chemical and mechanical weathering processes. The presence of reduced metallic iron in approximately 88 percent of meteorite falls renders the majority of meteorites particularly sensitive to oxidation by H2O interaction. This makes them excellent markers for H2O occurrence. Several large meteorites have been discovered at Gusev Crater and Meridiani Planum by the Mars Exploration Rovers (MERs). Significant morphologic characteristics interpretable as weathering features in the Meridiani suite of iron meteorites include a (1) large pit lined with delicate iron protrusions suggestive of inclusion removal by corrosive interaction; (2) differentially eroded kamacite and taenite lamellae on three of the meteorites, providing relative timing through cross-cutting relationships with deposition of (3) an iron oxide-rich dark coating; and (4) regmaglypted surfaces testifying to regions of minimal surface modification; with other regions in the same meteorites exhibiting (5) large-scale, cavernous weathering. Iron meteorites found by Mini-TES at both Meridiani Planum and Gusev Crater have prompted laboratory experiments designed to explore elements of reflectivity, dust cover, and potential oxide coatings on their surfaces in the thermal infrared using analog samples. Results show that dust thickness on an iron substrate need be only one tenth as great as that on a silicate rock to

  9. Isotope Variations in Terrestrial Carbonates and Thermal Springs as Biomarkers: Analogs for Martian Processes

    NASA Technical Reports Server (NTRS)

    Socki, Richard A.; Gibson, Everett K., Jr.; Bissada, K. K.

    2006-01-01

    Stable isotope measurements of carbonate minerals contained within ALH84001 [1] suggest that fluids were present at 3.9 Gy on Mars [2, 3, 4, 5]. Both oxygen and carbon isotopes provide independent means of deciphering paleoenvironmental conditions at the time of carbonate mineral precipitation. In terrestrial carbonate rocks oxygen isotopes not only indicate the paleotemperature of the precipitating fluid, but also provide clues to environmental conditions that affected the fluid chemistry. Carbon isotopes, on the other hand, can indicate the presence or absence of organic compounds during precipitation (i.e. biogenically vs. thermogenically-generated methane), thus serving as a potential biomarker. We have undertaken a study of micro scale stable isotope variations measured in some terrestrial carbonates and the influence of organic compounds associated with the formation of these carbonates. Preliminary results indicate that isotope variations occur within narrow and discrete intervals, providing clues to paleoenvironmental conditions that include both biological and non-biological activity. These results carry implications for deciphering Martian isotope data and therefore potential biological prospecting on the planet Mars. Recently, Fourier Transform Spectrometer observations have detected methane occurring in the Martian atmosphere [6] that could be attributed to a possible biogenic source. Indeed, Mars Express has detected the presence of methane in the Martian atmosphere [7], with evidence indicating that methane abundances are greatest above those basins with high water concentrations.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  11. The history of Allan Hills 84001 revised: multiple shock events.

    PubMed

    Treiman, A H

    1998-07-01

    The geologic history of Martian meteorite Allan Hills (ALH) 84001 is more complex than previously recognized, with evidence for four or five crater-forming impacts onto Mars. This history of repeated deformation and shock metamorphism appears to weaken some arguments that have been offered for and against the hypothesis of ancient Martian life in ALH 84001. Allan Hills 84001 formed originally from basaltic magma. Its first impact event (I1) is inferred from the deformation (D1) that produced the granular-textured bands ("crush zones") that transect the original igneous fabric. Deformation D1 is characterized by intense shear and may represent excavation or rebound flow of rock beneath a large impact crater. An intense thermal metamorphism followed D1 and may be related to it. The next impact (I2) produced fractures, (Fr2) in which carbonate "pancakes" were deposited and produced feldspathic glass from some of the igneous feldspars and silica. After I2, carbonate pancakes and globules were deposited in Fr2 fractures and replaced feldspathic glass and possibly crystalline silicates. Next, feldspars, feldspathic glass, and possibly some carbonates were mobilized and melted in the third impact (I3). Microfaulting, intense fracturing, and shear are also associated with I3. In the fourth impact (I4), the rock was fractured and deformed without significant heating, which permitted remnant magnetization directions to vary across fracture surfaces. Finally, ALH 84001 was ejected from Mars in event I5, which could be identical to I4. This history of multiple impacts is consistent with the photogeology of the Martian highlands and may help resolve some apparent contradictions among recent results on ALH 84001. For example, the submicron rounded magnetite grains in the carbonate globules could be contemporaneous with carbonate deposition, whereas the elongate magnetite grains, epitaxial on carbonates, could be ascribed to vapor-phase deposition during I3. PMID:11543074

  12. Using vanadium in spinel as a sensor of oxygen fugacity in meteorites: Applications to Mars, Vesta, and other asteroids.

    SciTech Connect

    Righter, K.; Sutton, S.; Danielson, L.; Pando, K.; Le, L.; Newville, M.

    2009-03-23

    Some meteorites do not contain mineral assemblages required to apply traditional oxy-barometers. Here we introduce a technique using vanadium X-ray absorption features in spinels to characterize the oxygen fugacity of meteoritic dunites, pyroxenites, and chondrites. Igneous and metamorphic rocks commonly contain a mineral assemblage that allows oxygen fugacity to be calculated or constrained such as FeTi oxides, olivine-opx-spinel, or some other oxybarometer. Some rocks, however, contain a limited mineral assemblage and do not provide constraints on fO{sub 2} using mineral equilibria. Good examples of the latter are orthopyroxenites or dunites, such as diogenites, ALH 84001, chassignites, or brachinites. In fact it is no surprise that the fO{sub 2} of many of these samples is not well known, other than being 'reduced' and below the metal saturation value. In order to bridge this gap in our understanding, we have initiated a study of V in chromites in natural meteorite samples. Because the V pre-edge peak intensity and energy in chromites varies with fO{sub 2}, and this has been calibrated over a large fO{sub 2} range, we can apply this relation to rocks for which we otherwise have no fO{sub 2} constraints.

  13. Shock Recovery and Heating Experiments on Baddeleyite: Implications for U-Pb Isotopic Systematics of Martian Meteorites

    NASA Astrophysics Data System (ADS)

    Misawa, K.; Niihara, T.; Kaiden, H.; Sekine, T.; Mikouchi, T.

    2009-12-01

    Introduction: Radiometric ages of Martian meteorites, shergottites are generally young (i.e., ~165-475 Ma), and are in the late Amazonian chronostratigraphic unit [1]. Bouvier et al. [2-4] reported ~4.1-4.3 Ga old Pb-Pb ages for shergottites, and suggested that young Rb-Sr, Sm-Nd, and Lu-Hf ages so far obtained were affected by alteration of phosphates, interaction with Martian subsurface fluids, or intense shock metamorphism. Baddeleyite (ZrO2) with apparently primary igneous morphology is an important phase in shergottites for U-Pb age determination. In order to investigate shock effects on U-Pb isotopic systematics of baddeleyite, we undertook shock recovery and heating experiments on baddeleyite. Experimental: We used coarse-grained baddeleyite from Phalaborwa for a starting material. The baddeleyite was mixed with a coarse-grained terrestrial basalt with a weight ratio of 1:2. Shock-recovery experiments were performed using a propellant gun at NIMS [5]. The run products were placed in a vertical gas-mixing furnace and heated for 1-3 h at 1000-1300oC under log fO2 of IW+2.5 at 105 Pa. Textures were observed by a scanning electron microprobe and Raman spectra of shocked baddeleyite were obtained. In situ U-Th-Pb isotopic analysis was carried out with the SHRIMP II at NIPR [6]. Results and Discussion: We observed Raman peak shifts of 2-4 cm-1 in the 34-57 GPa samples. Lead loss from baddeleyite was not observed for the experimentally shocked samples. In addition, the U-Pb and Pb-Pb ages of shocked and heated baddeleyites are indistinguishable from those of unshocked baddeleyite within errors except minor lead loss from the baddeleyite shocked at 57 GPa and heated for 1 h at 1300oC. Although duration of peak shock-pressure and grain size of baddeleyite are different from the nature of basaltic shergottites, our experimental results suggest that it is hard to completely reset U-Pb isotopic systematics of baddeleyite in Martian meteorite by shock events below ~60

  14. Water-extractable and exchangeable phosphate in martian and carbonaceus meteorites and planetary soil analogues

    NASA Astrophysics Data System (ADS)

    Sinaj, S.; Mautner, M.

    2003-04-01

    Aqueous extraction contributes to the formation and weathering of planetary materials, and renders electrolytes available for biology. In this context, water-extractable phosphate is measured in the Mars meteorites Nakhla, Dar al Gani 476 (DaG 476), Elephant Morraine 79001 (EETA 79001) and terrestrial analogues, and in the Murchison CM2 and Allende CV3 carbonaceous chondrites. The Mars meteorites contain high levels of readily extractable phosphate in H_2O/N_2, up to 15 mg kg-1 in Nakhla and DaG 476 and 38 mg kg-1 in EETA79001, while the terrestrial analogues and the carbonaceous chondrites contain lower levels, 0.5 - 6 mg kg-1. Correspondingly, high phosphate concentrations of 4 to >28mg L-1 are obtained in extracts of the Mars meteorites, exceeding the concentrations of 0.4 - 2.0 mg L-1 in the extracts of the terrestrial analogues. Planetary conditions under N_2 and CO_2 atmospheres, at solid/water ratios of 0.01 to 1.0 kg L-1, extraction times of 1 to 21 days and temperatures of 20 - 121 ^oC affect the amounts of extractable phosphate by factors of 2 - 5 in most materials. Phosphate fixing capacity and long-term extractable phosphate are assessed by the isotopic exchange kinetics (IEK) method, which quantifies the amount of P isotopically exchangeable within 1 minute (E1min), between 1 min and 3 months (E1min-3m) and the amount of P that can not be exchanged within 3 months (E>3m). The IEK results show that the DaG 476 Mars meteorite and terrestrial analogues have low, while the carbonaceous chondrites have high, P fixing capacities. Aqueous weathering under early planetary CO_2 atmospheres has large effects on the available phosphate. For example, the fraction of total P that is exchangeable in 3 months increases from 1.6 to 11% in the DaG 476 Mars meteorite, from 13.0 to 51.6% in Allende and from 43.9 to 90.4% in Murchison. Solutions with high phosphate concentrations can form in pores of planetary lava ash and basalts, and in carbonaceous asteroids and

  15. Signatures in Martian Volatiles and the Magma Sources of NC Meteorites

    NASA Technical Reports Server (NTRS)

    Marti, K.; Mathew, K. J.

    2004-01-01

    We report nitrogen and xenon isotopic signatures in Yamato nakhlites and use the data to assess properties of the magma source of NC meteorites in planet Mars. The Chassigny meteorite was investigated by Floran et al, who classified it as a cumulate dunite with hydrous amphibole-bearing melt inclusions with no preferred orientation of the olivines. Their inferred composition of the parent magma, which was based on electron microprobe analyses, has been questioned. The trace and minor elements in minerals were analyzed in nakhlites and in Chassigny and the authors conclude that nakhlites may represent samples from different horizons of the same lithologic unit, but that Chassigny was not co-magmatic with the nakhlites.

  16. Rare-earth-element minerals in martian breccia meteorites NWA 7034 and 7533: Implications for fluid-rock interaction in the martian crust

    NASA Astrophysics Data System (ADS)

    Liu, Yang; Ma, Chi; Beckett, John R.; Chen, Yang; Guan, Yunbin

    2016-10-01

    Paired martian breccia meteorites, Northwest Africa (NWA) 7034 and 7533, are the first martian rocks found to contain rare-earth-element (REE) phosphates and silicates. The most common occurrence is as clusters of anhedral monazite-(Ce) inclusions in apatite. Occasionally, zoned, irregular merrillite inclusions are also present in apatite. Monazite-bearing apatite is sometimes associated with alkali-feldspar and Fe-oxide. Apatite near merrillite and monazite generally contains more F and OH (F-rich region) than the main chlorapatite host and forms irregular boundaries with the main host. Locally, the composition of F-rich regions can reach pure fluorapatite. The chlorapatite hosts are similar in composition to isolated apatite without monazite inclusions, and to euhedral apatite in lithic clasts. The U-Th-total Pb ages of monazite in three apatite are 1.0 ± 0.4Ga (2σ), 1.1 ± 0.5Ga (2σ), and 2.8 ± 0.7Ga (2σ), confirming a martian origin. The texture and composition of monazite inclusions are mostly consistent with their formation by the dissolution of apatite and/or merrillite by fluid at elevated temperatures (>100 °C). In NWA 7034, we observed a monazite-chevkinite-perrierite-bearing benmoreite or trachyandesite clast. Anhedral monazite and chevkinite-perrierite grains occur in a matrix of sub-micrometer REE-phases and silicates inside the clast. Monazite-(Ce) and -(Nd) and chevkinite-perrierite-(Ce) and -(Nd) display unusual La and Ce depletion relative to Sm and Nd. In addition, one xenotime-(Y)-bearing pyrite-ilmenite-zircon clast with small amounts of feldspar and augite occurs in NWA 7034. One xenotime crystal was observed at the edge of an altered zircon grain, and a cluster of xenotime crystals resides in a mixture of alteration materials. Pyrite, ilmenite, and zircon in this clast are all highly altered, zircon being the most likely source of Y and HREE now present in xenotime. The association of xenotime with zircon, low U and Th contents, and the

  17. Carbonates, surfates, phosphates, nitrates, and organic materials: Their association in a Martian meteorite

    NASA Technical Reports Server (NTRS)

    Wright, I. P.; Grady, M. M.; Pillinger, C. T.

    1993-01-01

    The debate concerning the evolution of CO2 on Mars continues. It would appear that in order to explain the valley networks and other relict fluvial landforms it is necessary to accept that liquid water was once present at the surface of Mars. This in turn requires, at some point in the planet's history, a higher surface temperature than exists today, proposition explained traditionally by an early dense CO2, atmosphere. However, there are a number of problems with this notion: for instance, CO2 alone is not an efficient greenhouse gas because of its tendency to form clouds. Moreover, if there was an early dense CO2 atmosphere, it is necessary to explain where the elemental constituents now reside. There are two possibilities for the latter, namely loss to outer space of atmospheric CO2 or the formation of vast carbonate deposits. While some models of atmospheric loss predict that up to 0.4 bar of CO2 could be removed from the Martian surface, this is still not enough to account for the original atmospheric inventory, usually considered to have been in the range of 1-5 bar. Thus, most models of the evolution of the Martian surface require removal of CO2 from the atmosphere and into carbonate deposits. However, as yet, the evidence for the existence of carbonates on Mars is fairly scant. This is an issue that would have been resolved by results obtained from Mars Observer.

  18. Carbonates, surfates, phosphates, nitrates, and organic materials: Their association in a Martian meteorite

    NASA Astrophysics Data System (ADS)

    Wright, I. P.; Grady, M. M.; Pillinger, C. T.

    The debate concerning the evolution of CO2 on Mars continues. It would appear that in order to explain the valley networks and other relict fluvial landforms it is necessary to accept that liquid water was once present at the surface of Mars. This in turn requires, at some point in the planet's history, a higher surface temperature than exists today, proposition explained traditionally by an early dense CO2, atmosphere. However, there are a number of problems with this notion: for instance, CO2 alone is not an efficient greenhouse gas because of its tendency to form clouds. Moreover, if there was an early dense CO2 atmosphere, it is necessary to explain where the elemental constituents now reside. There are two possibilities for the latter, namely loss to outer space of atmospheric CO2 or the formation of vast carbonate deposits. While some models of atmospheric loss predict that up to 0.4 bar of CO2 could be removed from the Martian surface, this is still not enough to account for the original atmospheric inventory, usually considered to have been in the range of 1-5 bar. Thus, most models of the evolution of the Martian surface require removal of CO2 from the atmosphere and into carbonate deposits. However, as yet, the evidence for the existence of carbonates on Mars is fairly scant. This is an issue that would have been resolved by results obtained from Mars Observer.

  19. Shock-implanted noble gases - An experimental study with implications for the origin of Martian gases in shergottite meteorites

    NASA Technical Reports Server (NTRS)

    Bogard, Donald D.; Horz, Friedrich; Johnson, Pratt H.

    1986-01-01

    The shock-implantation of gases is studied by artificially shocking whole rock and power samples of terrestrial basalt to pressures of 2-40 GPa. Ar, Kr, Xe, and Ne were implanted into the silicate. It is observed that the amount of implanted gas is linearly proportional to its partial pressure over a pressure range of 0.0001 to 0.1 atmosphere. The fractionation effect in the implanted gas and the gas diffusion properties are examined. The amounts of gas that would have been implanted with 100 percent efficiency are calculated from the measured porosities of the power samples and are compared to observed abundances. It is determined that the implantation efficiencies are approximately 0.5 percent at 2 GPa, 7 percent at 5 GPa, and greater than 50 percent at both 20 and 35 GPa. The experimental data correlate with the shock implantation of Martian gases without mass fractionation into the shock-melted phase of meteorite EETA 79001.

  20. Weathering of Martian Evaporites

    NASA Technical Reports Server (NTRS)

    Wentworth, S. J.; Velbel, M. A.; Thomas-Keprta, K. L.; Longazo, T. G.; McKay, D. S.

    2001-01-01

    Evaporites in martian meteorites contain weathering or alteration features that may provide clues about the martian near-surface environment over time. Additional information is contained in the original extended abstract.

  1. Sm-Nd and Rb-Sr Isotopic Systematics of a Heavily Shocked Martian Meteorite Tissint and Petrogenesis of Depleted Shergottites

    NASA Technical Reports Server (NTRS)

    Shih, C.-Y.; Nyquist, L. E.; Park, J.; Agee, Carl B.

    2014-01-01

    Tissint is a very fresh Martian meteorite that fell near the town of Tissint in Morocco on July 18, 2011. It contains abundant olivine megacrysts (23%) in a fine-grained matrix of pyroxene (55%), maskelynitized plagioclase (15%), opaques (4%) and melt pockets (3%) and is petrographically similar to lithologies A and C of picritic shergottite EETA 79001 [1,2]. The presence of 2 types of shock-induced glasses and all 7 high-pressure mineral phases that were ever found in melt pockets of Martian meteorites suggests it underwent an intensive shock metamorphism of 25 GPa and 2000 C localized in melt pockets [2]. Mineral textures suggest that olivines, pyroxenes and plagioclases probably did not experience such hightemperature. Earlier determinations of its age yielded 596+/-23 Ma [3] and 616+/-67 Ma [4], respectively, for the Sm-Nd system and 583+/-86 Ma for the Lu-Hf system [4], in agreement with the 575+/-18 Ma age of the oldest olivine-phyric depleted shergottite Dho 019 [5]. However, the exposure ages of Tissint (1 Ma [1, 6, 7]) and Dho 019 (20 Ma [8]) are very different requiring two separate ejection events. These previously determined Sm-Nd and Lu-Hf ages are older than the Ar-Ar maskelynite plateau age of 524+/-15 Ma [9], reversing the pattern usually observed for Martian meteorites. In order to clarify these age issues and place models for Tissint's petrogenesis on a firm basis, we present new Rb-Sr and Sm- Nd isotopic results for Tissint, and discuss (a) the shock effects on them and the Ar-Ar chronometer, (b) correlation of the determined ages with those of other depleted shergottites, and (c) the petrogenesis of depleted shergottites. Since the meteorite is a recent fall, terrestrial contamination is expected to be minimal, but, the strong shock metamorphism might be expected to compromise the equilibrium of the isotopic systems.

  2. Evidence for Differential Comminution/Aeolian Sorting and Chemical Weathering of Martian Soils Preserved in Mars Meteorite EET79001

    NASA Technical Reports Server (NTRS)

    Rao, M. N.; McKay, David S.

    2004-01-01

    Impact-melt glasses containing Martian atmospheric gases in Mars meteorite EET79001 are formed from Martian soil fines that had undergone meteoroid-comminution and aeolian sorting accompanied by chemical weathering near Mars surface. Using SiO2 and SO3 as proxy for silicates and salts respectively in Mars soils, we find that SiO2 and SO3 correlate negatively with FeO and MgO and positively with Al2O3 and CaO in these glasses, indicating that the mafic and felsic components are depleted and enriched relative to the bulk host (Lith A/B) respectively as in the case of Moon soils. Though the overall pattern of mineral fractionation is similar between the soil fines on Mars and Moon, the magnitudes of the enrichments/depletions differ between these sample-suites because of pervasive aeolian activity on Mars. In addition to this mechanical processing, the Martian soil fines, prior to impact-melting, have undergone acid-sulfate dissolution under oxidizing/reducing conditions. The S03 content in EET79001,507 (Lith B) glass is approx.18% compared to < 2% in EET79001, 506 (Lith A). SiO2 and SO3 negatively correlate with each other in ,507 glasses similar to Pathfinder soils. The positive correlation found between FeO and SO3 in ,507 glasses as well as Pathfinder rocks and soils is consistent with the deposition of ferric-hydroxysulfate on regolith grains in an oxidizing environment. As in the case of Pathfinder soils, the Al 2O3 vs SiO2 positive correlation and FeO VS S102 negative correlation observed in ,507 glasses indicate that SiO2 from the regolith is mobilized as soluble silicic acid at low pH. The large off-set in the end-member FeO abundance ( SO3=0) between Pathfinder soil-free rock and sulfur-free rock in ,507 glass precursors suggests that the soils comprising the ,507 glasses contain much larger proportion of fine-grained Martian soil fraction that registers strong mafic depletion relative to Lith B. This inference is strongly supported by the Al2O3 - SO3

  3. Carbonate Cements from the Sverrefjell and Sigurdfjell Volcanoes, Svalbard Norway: Analogs for Martian Carbonates

    NASA Technical Reports Server (NTRS)

    Blake, D. F.; Treiman, A. H.; Morris, R.; Bish, D.; Amundsen, H.E.F.; Steele, A.

    2011-01-01

    The Sverrefjell and Sigurdfjell volcanic complexes erupted at 1Ma on Svalbard, Norway. Sverrefjell is a cone of cinders, pillow lavas and dikes; Sigurdfjell is elongate in outcrop and may represent a fissure eruption [1]. The lavas of both volcanos were volatile rich. The volcanos erupted under ice and were subsequently dissected by glaciation (glacial eratics are present on most of Sverrefjell, even on its summit). Eruption beneath an ice sheet is inferred, based on the presence of pillow lavas from near sea level to 1000 m above sea level. Sverrefjell contains the largest fraction of ultramafic xenoliths of any volcanic complex in the world, in places accounting for as much as 50% of the volume of the outcrop. The Sverrefjell and Sigurdfell volcanos contain carbonate cements of several varieties: (1) Amundsen [2] reported Mg-Fe-rich carbonate in sub-mm globules in basalts and ultramafic xenoliths from the volcanos. These globules are the best terrestrial analogs to the carbonate globules in the Mars meteorite ALH84001 [3]. (2) Thick (1-3 cm) coatings of carbonate cement drape the walls of vertical volcanic pipes or conduits on the flanks and near the present summit of Sverrefjell. Similar occurrences are found on Sigurdfjell. (3) Breccia-filled pipes or vents occur on Sverrefjell and Siggurdfjell in which the breccia fragments are cemented by carbonate. The fragments themselves commonly contain carbonate globules similar to those found in the basalts and ultramafic xenoliths.

  4. Stable Chlorine Isotopes and Elemental Chlorine by Thermal Ionization Mass Spectrometry and Ion Chromatography; Martian Meteorites, Carbonaceous Chondrites and Standard Rocks

    NASA Technical Reports Server (NTRS)

    Nakamura, N.; Nyquist, L. E.; Reese, Y.; Shih, C.-Y.; Fujitani, T.; Okano, O.

    2011-01-01

    Recently significantly large mass fractionation of stable chlorine isotopes has been reported for terrestrial and lunar samples [1,2]. In addition, in view of possible early solar system processes [3] and also potential perchlorate-related fluid/microbial activities on the Martian surface [4,5], a large chlorine isotopic fractionation might be expected for some types of planetary materials. Due to analytical difficulties of isotopic and elemental analyses, however, current chlorine analyses for planetary materials are controversial among different laboratories, particularly between IRMS (gas source mass spectrometry) and TIMS (Thermal Ionization Mass Spectrometry) groups [i.e. 1,6,7] for isotopic analyses, as well as between those doing pyrohydrolysis and other groups [i.e. 6,8]. Additional careful investigations of Cl isotope and elemental abundances are required to confirm real chlorine isotope and elemental variations for planetary materials. We have developed a TIMS technique combined with HF-leaching/ion chromatography at NASA JSC that is applicable to analysis of small amounts of meteoritic and planetary materials. We present here results for several standard rocks and meteorites, including Martian meteorites.

  5. Formation of iddingsite veins in the martian crust by centripetal replacement of olivine: Evidence from the nakhlite meteorite Lafayette

    NASA Astrophysics Data System (ADS)

    Lee, M. R.; Tomkinson, T.; Hallis, L. J.; Mark, D. F.

    2015-04-01

    The Lafayette meteorite is an olivine clinopyroxenite that crystallized on Mars ∼1300 million years ago within a lava flow or shallow sill. Liquid water entered this igneous rock ∼700 million years later to produce a suite of secondary minerals, collectively called 'iddingsite', that occur as veins within grains of augite and olivine. The deuterium/hydrogen ratio of water within these secondary minerals shows that the aqueous solutions were sourced from one or more near-surface reservoirs. Several petrographically distinct types of veins can be recognised by differences in their width, shape, and crystallographic orientation. Augite and olivine both contain veins of a very fine grained hydrous Fe- and Mg-rich silicate that are ∼1-2 μm in width and lack any preferred crystallographic orientation. These narrow veins formed by cementation of pore spaces that had been opened by fracturing and probably in response to shock. The subset of olivine-hosted veins whose axes lie parallel to (0 0 1) have serrated walls, and formed by widening of the narrow veins by interface coupled dissolution-precipitation. Widening started by replacement of the walls of the narrow precursor veins by Fe-Mg silicate, and a crystallographic control on the trajectory of the dissolution-precipitation front created micrometre-scale {1 1 1} serrations. The walls of many of the finely serrated veins were subsequently replaced by siderite, and the solutions responsible for carbonation of olivine also partially recrystallized the Fe-Mg silicate. Smectite was the last mineral to form and grew by replacement of siderite. This mineralization sequence shows that Lafayette was exposed to two discrete pulses of aqueous solutions, the first of which formed the Fe-Mg silicate, and the second mediated replacement of vein walls by siderite and smectite. The similarity in size, shape and crystallographic orientation of iddingsite veins in the Lafayette meteorite and in terrestrial basalts demonstrates a

  6. Petrography and composition of Martian regolith breccia meteorite Northwest Africa 7475

    NASA Astrophysics Data System (ADS)

    Wittmann, Axel; Korotev, Randy L.; Jolliff, Bradley L.; Irving, Anthony J.; Moser, Desmond E.; Barker, Ivan; Rumble, Douglas

    2015-02-01

    The Northwest Africa (NWA) 7475 meteorite is one of the several stones of paired regolith breccias from Mars based on petrography, oxygen isotope, mineral compositions, and bulk rock compositions. Its inventory of lithic clasts is dominated by vitrophyre impact melts that were emplaced while they were still molten. Other clast types include crystallized impact melt rocks, evolved plutonic rocks, possible basalts, contact metamorphosed rocks, and siltstones. Impact spherules and vitrophyre shards record airborne transport, and accreted dust rims were sintered on most clasts, presumably during residence in an ejecta plume. The clast assemblage records at least three impact events, one that formed an impact melt sheet on Mars ≤4.4 Ga ago, a second that assembled NWA 7475 from impactites associated with the impact melt sheet at 1.7-1.4 Ga, and a third that launched NWA 7475 from Mars ~5 Ma ago. Mildly shocked pyroxene and plagioclase constrain shock metamorphic conditions during launch to >5 and <15 GPa. The mild postshock-heating that resulted from these shock pressures would have been insufficient to sterilize this water-bearing lithology during launch. Magnetite, maghemite, and pyrite are likely products of secondary alteration on Mars. Textural relationships suggest that calcium-carbonate and goethite are probably of terrestrial origin, yet trace element chemistry indicates relatively low terrestrial alteration. Comparison of Mars Odyssey gamma-ray spectrometer data with the Fe and Th abundances of NWA 7475 points to a provenance in the ancient southern highlands of Mars. Gratteri crater, with an age of ~5 Ma and an apparent diameter of 6.9 km, marks one possible launch site of NWA 7475.

  7. Amino acid distribution in meteorites: diagenesis, extraction methods, and standard metrics in the search for extraterrestrial biosignatures.

    PubMed

    McDonald, Gene D; Storrie-Lombardi, Michael C

    2006-02-01

    The relative abundance of the protein amino acids has been previously investigated as a potential marker for biogenicity in meteoritic samples. However, these investigations were executed without a quantitative metric to evaluate distribution variations, and they did not account for the possibility of interdisciplinary systematic error arising from inter-laboratory differences in extraction and detection techniques. Principal component analysis (PCA), hierarchical cluster analysis (HCA), and stochastic probabilistic artificial neural networks (ANNs) were used to compare the distributions for nine protein amino acids previously reported for the Murchison carbonaceous chondrite, Mars meteorites (ALH84001, Nakhla, and EETA79001), prebiotic synthesis experiments, and terrestrial biota and sediments. These techniques allowed us (1) to identify a shift in terrestrial amino acid distributions secondary to diagenesis; (2) to detect differences in terrestrial distributions that may be systematic differences between extraction and analysis techniques in biological and geological laboratories; and (3) to determine that distributions in meteoritic samples appear more similar to prebiotic chemistry samples than they do to the terrestrial unaltered or diagenetic samples. Both diagenesis and putative interdisciplinary differences in analysis complicate interpretation of meteoritic amino acid distributions. We propose that the analysis of future samples from such diverse sources as meteoritic influx, sample return missions, and in situ exploration of Mars would be less ambiguous with adoption of standardized assay techniques, systematic inclusion of assay standards, and the use of a quantitative, probabilistic metric. We present here one such metric determined by sequential feature extraction and normalization (PCA), information-driven automated exploration of classification possibilities (HCA), and prediction of classification accuracy (ANNs). PMID:16551224

  8. Amino Acid Distribution in Meteorites: Diagenesis, Extraction Methods, and Standard Metrics in the Search for Extraterrestrial Biosignatures

    NASA Astrophysics Data System (ADS)

    McDonald, Gene D.; Storrie-Lombardi, Michael C.

    2006-03-01

    The relative abundance of the protein amino acids has been previously investigated as a potential marker for biogenicity in meteoritic samples. However, these investigations were executed without a quantitative metric to evaluate distribution variations, and they did not account for the possibility of interdisciplinary systematic error arising from inter-laboratory differences in extraction and detection techniques. Principal component analysis (PCA), hierarchical cluster analysis (HCA), and stochastic probabilistic artificial neural networks (ANNs) were used to compare the distributions for nine protein amino acids previously reported for the Murchison carbonaceous chondrite, Mars meteorites (ALH84001, Nakhla, and EETA79001), prebiotic synthesis experiments, and terrestrial biota and sediments. These techniques allowed us (1) to identify a shift in terrestrial amino acid distributions secondary to diagenesis; (2) to detect differences in terrestrial distributions that may be systematic differences between extraction and analysis techniques in biological and geological laboratories; and (3) to determine that distributions in meteoritic samples appear more similar to prebiotic chemistry samples than they do to the terrestrial unaltered or diagenetic samples. Both diagenesis and putative interdisciplinary differences in analysis complicate interpretation of meteoritic amino acid distributions. We propose that the analysis of future samples from such diverse sources as meteoritic influx, sample return missions, and in situ exploration of Mars would be less ambiguous with adoption of standardized assay techniques, systematic inclusion of assay standards, and the use of a quantitative, probabilistic metric. We present here one such metric determined by sequential feature extraction and normalization (PCA), information-driven automated exploration of classification possibilities (HCA), and prediction of classification accuracy (ANNs).

  9. Using Vanadium in Spinel as a Sensor of Oxygen Fugacity in Meteorites: Applications to Mars, Vesta, and Other Asteroids

    NASA Technical Reports Server (NTRS)

    Righter, K.; Sutton, S.; Danielson, L.; Le, L.; Newville, M.; Pando, K.

    2009-01-01

    Igneous and metamorphic rocks commonly contain a mineral assemblage that allows oxygen fugacity to be calculated or constrained such as FeTi oxides, olivine-opx-spinel, or some other oxybarometer [1]. Some rocks, however, contain a limited mineral assemblage and do not provide constraints on fO2 using mineral equilibria. Good examples of the latter are orthopyroxenites or dunites, such as diogenites, ALH 84001, chassignites, or brachinites. In fact it is no surprise that the fO2 of many of these samples is not well known, other than being "reduced" and below the metal saturation value. In order to bridge this gap in our understanding, we have initiated a study of V in chromites in natural meteorite samples. Because the V pre-edge peak intensity and energy in chromites varies with fO2 (Fig. 1) [2], and this has been calibrated over a large fO 2 range, we can apply this relation to rocks for which we otherwise have no fO2 constraints.

  10. Reaction sequence of iron sulfide minerals in bacteria and their use as biomarkers.

    PubMed

    Pósfai, M; Buseck, P R; Bazylinski, D A; Frankel, R B

    1998-05-01

    Some bacteria form intracellular nanometer-scale crystals of greigite (Fe3S4) that cause the bacteria to be oriented in magnetic fields. Transmission electron microscope observations showed that ferrimagnetic greigite in these bacteria forms from nonmagnetic mackinawite (tetragonal FeS) and possibly from cubic FeS. These precursors apparently transform into greigite by rearrangement of iron atoms over a period of days to weeks. Neither pyrrhotite nor pyrite was found. These results have implications for the interpretation of the presence of pyrrhotite and greigite in the martian meteorite ALH84001. PMID:9572727

  11. Modeling Chemical and Isotopic Variations in Lab Formed Hydrothermal Carbonates

    NASA Technical Reports Server (NTRS)

    Niles, P. B.; Leshin, L. A.; Golden, D. C.; Socki, R. A.; Guan, Y.; Ming, D. W.

    2005-01-01

    Chemical and mineralogical data (e.g. [1]) from Mars suggest that the history of liquid water on the planet was more sporadic in nature than long-lived. The non-equilibrium chemical and isotopic compositions of the carbonates preserved in the martian meteorite ALH84001 are direct evidence of ancient secondary minerals that have not undergone significant diagenesis or stabilization processes typical of long-lived aqueous systems on Earth. Thus secondary minerals and sediments on Mars may primarily record the characteristics of the aqueous environment in which they formed without being significantly overprinted by subsequent diagenetic processes during burial.

  12. Mars as the Parent Body for the CI Carbonaceous Chondrites: Confirmation of Early Mars Biology

    NASA Astrophysics Data System (ADS)

    Brandenburg, J. E.

    2003-07-01

    Mounting evidence suggests that CI Carbonaceaous Chondrites belong in the Mars meteorite family. They thus represent samples, like ALH84001, of the Noachian surface environment, and are rich in organic matter, suggesting a living environment.

  13. Carbonate and Magnetite Parageneses as Monitors of Carbon Dioxide and Oxygen Fugacity

    NASA Technical Reports Server (NTRS)

    Koziol, Andrea M.

    2000-01-01

    The stable coexistence of siderite with other key minerals, such as graphite or magnetite, is only possible under certain restrictive conditions of CO2 and O2 fugacity. Carbonate parageneses in Mars meteorite ALH 84001 are analyzed.

  14. Comparison of Laser Induced Breakdown Spectroscopy (LIBS) on Martian Meteorite NWA 7034 to ChemCam Observations at Gale Crater, Mars

    NASA Astrophysics Data System (ADS)

    Gordon, S.; Newsom, H. E.; Agee, C. B.; Santos, A. R.; Clegg, S. M.; Wiens, R. C.; Lasue, J.; Sautter, V.

    2014-12-01

    The ChemCam instrument on board the Mars Science Laboratory (MSL) Curiosity rover uses laser-induced breakdown spectroscopy (LIBS) to analyze rock and soil targets on Mars from up to 7 m away. The Nd:KGW laser can shoot up to 1000 shots at one location and profile up to 1 mm depth into a rock. Identical LIBS instrumentation is located at Los Alamos National Laboratory and was used to analyze martian meteorite NWA 7034, a non-SNC basaltic breccia whose bulk composition matches the martian surface. Initial LIBS analysis of NWA 7034 included observations on two basaltic clasts in the meteorite. Electron microprobe analysis (EPMA) was performed on the two clasts for comparison with elemental compositions measured using LIBS. The two instruments give similar compositions of major oxides within the error of both techniques. EPMA analysis was also completed on three light-toned clasts and a dark-toned clast in the meteorite. The light-toned clasts have Al/Si vs. (Fe+Mg)/Si compositions ranging from felsic to mafic, and the dark-toned clast shows a mafic composition. A Sammon's map was created to compare LIBS data for NWA 7034 and ChemCam targets Stark, Crestaurum, Link, Portage, Jake_M, Mara, Thor_Lake, Coronation, Pearson, and Prebble. This nonlinear statistical mapping technique is used for clustering assessment of LIBS data in two dimensions. The map shows NWA 7034 clustering in its own location, and the closest similar ChemCam rock targets are La_Reine and Ashuamipi, which are both coarse grained targets that have a mafic component consistent with augite. The most similar ChemCam soil targets are the Crestaurum and Portage. Creation of maps with a greater number of targets will show more of the similarities between NWA 7034 and ChemCam target rocks and soils. Further analysis will compare NWA 7034 LIBS data, data from the paired meteorite NWA 7533, and a variety of ChemCam targets that are similar in morphology and texture.

  15. Wet inside and out? Constraints on water in the Martian mantle and on outgassed water, based on melt inclusions in SNC meteorites

    NASA Technical Reports Server (NTRS)

    Mcsween, H. Y., Jr.; Harvey, R. P.

    1993-01-01

    Constraints on the volatile inventory and outgassing history of Mars are critical to understanding the origin of ancient valley systems and paleoclimates. Planetary accretion models for Mars allow either a volatile-rich or volatile-poor mantle, depending on whether the accreted materials were fully oxidized or whether accretion was homogeneous so that water was lost through reaction with metallic iron. The amount of water that has been outgassed from the interior is likewise a contentious subject, and estimates of globally distributed water based on various geochemical and geological measurements vary from a few meters to more than a thousand meters. New data on SNC meteorites, which are thought to be Martian igneous rocks, provide constraints on both mantle and outgassed water.

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

    NASA Technical Reports Server (NTRS)

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

    2013-01-01

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

  17. Dating the Martian meteorite Zagami by the 87Rb-87Sr isochron method with a prototype in situ resonance ionization mass spectrometer

    PubMed Central

    Scott Anderson, F; Levine, Jonathan; Whitaker, Tom J

    2015-01-01

    RATIONALE The geologic history of the Solar System builds on an extensive record of impact flux models, crater counts, and ∼270 kg of lunar samples analyzed in terrestrial laboratories. However, estimates of impactor flux may be biased by the fact that most of the dated Apollo samples were only tenuously connected to an assumed geologic context. Moreover, uncertainties in the modeled cratering rates are significant enough to lead to estimated errors for dates on Mars and the Moon of ∼1 Ga. Given the great cost of sample return missions, combined with the need to sample multiple terrains on multiple planets, we have developed a prototype instrument that can be used for in situ dating to better constrain the age of planetary samples. METHODS We demonstrate the first use of laser ablation resonance ionization mass spectrometry for 87Rb-87Sr isochron dating of geological specimens. The demands of accuracy and precision have required us to meet challenges including regulation of the ambient temperature, measurement of appropriate backgrounds, sufficient ablation laser intensity, avoidance of the defocusing effect of the plasma created by ablation pulses, and shielding of our detector from atoms and ions of other elements. RESULTS To test whether we could meaningfully date planetary materials, we have analyzed a piece of the Martian meteorite Zagami. In each of four separate measurements we obtained 87Rb-87Sr isochron ages for Zagami consistent with its published age, and, in both of two measurements that reached completion, we obtained better than 200 Ma precision. Combining all our data into a single isochron with 581 spot analyses gives an 87Rb-87Sr age for this specimen of 360 ±90 Ma. CONCLUSIONS Our analyses of the Zagami meteorite represent the first successful application of resonance ionization mass spectrometry to isochron geochronology. Furthermore, the technique is miniaturizable for spaceflight and in situ dating on other planetary bodies. © 2014 The

  18. Yamato 980459: Crystallization of Martian Magnesian Magma

    NASA Technical Reports Server (NTRS)

    Koizumi, E.; Mikouchi, T.; McKay, G.; Monkawa, A.; Chokai, J.; Miyamoto, M.

    2004-01-01

    Recently, several basaltic shergottites have been found that include magnesian olivines as a major minerals. These have been called olivinephyric shergottites. Yamato 980459, which is a new martian meteorite recovered from the Antarctica by the Japanese Antarctic expedition, is one of them. This meteorite is different from other olivine-phyric shergottites in several key features and will give us important clues to understand crystallization of martian meteorites and the evolution of Martian magma.

  19. Natural dissociation of olivine to (Mg,Fe)SiO3 perovskite and magnesiowüstite in a shocked Martian meteorite

    PubMed Central

    Miyahara, Masaaki; Ohtani, Eiji; Ozawa, Shin; Kimura, Makoto; El Goresy, Ahmed; Sakai, Takeshi; Nagase, Toshiro; Hiraga, Kenji; Hirao, Naohisa; Ohishi, Yasuo

    2011-01-01

    We report evidence for the natural dissociation of olivine in a shergottite at high-pressure and high-temperature conditions induced by a dynamic event on Mars. Olivine (Fa34-41) adjacent to or entrained in the shock melt vein and melt pockets of Martian meteorite olivine-phyric shergottite Dar al Gani 735 dissociated into (Mg,Fe)SiO3 perovskite (Pv)+magnesiowüstite (Mw), whereby perovskite partially vitrified during decompression. Transmission electron microscopy observations reveal that microtexture of olivine dissociation products evolves from lamellar to equigranular with increasing temperature at the same pressure condition. This is in accord with the observations of synthetic samples recovered from high-pressure and high-temperature experiments. Equigranular (Mg,Fe)SiO3 Pv and Mw have 50–100 nm in diameter, and lamellar (Mg,Fe)SiO3 Pv and Mw have approximately 20 and approximately 10 nm in thickness, respectively. Partitioning coefficient, KPv/Mw = [FeO/MgO]/[FeO/MgO]Mw, between (Mg,Fe)SiO3 Pv and Mw in equigranular and lamellar textures are approximately 0.15 and approximately 0.78, respectively. The dissociation of olivine implies that the pressure and temperature conditions recorded in the shock melt vein and melt pockets during the dynamic event were approximately 25 GPa but 700 °C at least. PMID:21444781

  20. U-Pb isotopic systematics of shock-loaded and annealed baddeleyite: Implications for crystallization ages of Martian meteorite shergottites

    NASA Astrophysics Data System (ADS)

    Niihara, Takafumi; Kaiden, Hiroshi; Misawa, Keiji; Sekine, Toshimori; Mikouchi, Takashi

    2012-08-01

    Shock-recovery and annealing experiments on basalt-baddeleyite mixtures were undertaken to evaluate shock effects on U-Pb isotopic systematics of baddeleyite. Shock pressures up to 57 GPa caused fracturing of constituent phases, mosaicism of olivine, maskelynitization of plagioclase, and melting, but the phase transition from monoclinic baddeleyite structure to high-pressure/temperature polymorphs of ZrO2 was not confirmed. The U-Pb isotopic systems of the shock-loaded baddeleyite did not show a large-scale isotopic disturbance. The samples shock-recovered from 47 GPa were then employed for annealing experiments at 1000 or 1300 °C, indicating that the basalt-baddeleyite mixture was almost totally melted except olivine and baddeleyite. Fine-grained euhedral zircon crystallized from the melt was observed around the relict baddeleyite in the sample annealed at 1300 °C for 1 h. The U-Pb isotopic systems of baddeleyite showed isotopic disturbances: many data points for the samples annealed at 1000 °C plotted above the concordia. Both radiogenic lead loss/uranium gain and radiogenic lead gain/uranium loss were observed in the baddeleyite annealed at 1300 °C. Complete radiogenic lead loss due to shock metamorphism and subsequent annealing was not observed in the shock-loaded/annealed baddeleyites studied here. These results confirm that the U-Pb isotopic systematics of baddeleyite are durable for shock metamorphism. Since shergottites still preserve Fe-Mg and/or Ca zonings in major constituent phases (i.e. pyroxene and olivine), the shock effects observed in Martian baddeleyites seem to be less intense compared to that under the present experimental conditions. An implication is that the U-Pb systems of baddeleyite in shergottites will provide crystallization ages of Martian magmatic rocks.

  1. Microbial Contamination of Allende and Murchison Carbonaceous Chondrites; Developing a Protocol for Life Detection in Extraterrestrial Materials Using Biotechnology

    NASA Technical Reports Server (NTRS)

    Steele, A.; Whitby, C.; Griffin, C.; Toporski, J. K. W.; Westall, F.; Saunders, J. R.; McKay, D. S.

    2001-01-01

    The arguments used to refute the McKay et al., (1996) hypothesis of possible Martian life in ALH84001 failed to use contamination of the meteorite as a source. This has worrying implications for our ability to detect terrestrial microbiota in meteorites and therefore any potential extraterrestrial biosignatures in both meteorites and possible returned samples. We report on imaging and microbial culturing of both Allende and Murchison carbonaceous chondrites and on the use of molecular biology techniques on a sample of Allende. Contaminating fungi and bacteria were observed (in the case of Murchison) and cultured from both meteorites. DNA was successfully extracted and subsequent PCR showed the presence of both bacterial and fungal DNA although no Archaea were detected. These results show that it is possible to use molecular biological techniques on very small quantities (300 mg) of extraterrestrial material.

  2. The Possibility of Past Life on Mars

    NASA Astrophysics Data System (ADS)

    Gibson, E. K.; McKay, D. S.; Thomas-Keprta, K.; Vali, H.; Romanek, C. S.; Clemett, S.; Chiller, X.; Maechling, C.; Zare, R. N.

    1996-09-01

    An igneous Mars meteorite, ALH84001, of unknown geologic context, was penetrated by fluids along fractures and pore spaces, which then became the sites of secondary mineral formation. Freshly broken fracture surfaces display carbonate globules with associated abundant polycyclic aromatic hydrocarbons (PAHs). Studies by others have shown that the igneous material crystalized 4.5 Ga, and that the carbonate globules formed 3.6 Ga. ALH84001 was removed from the martian surface 16 My ago by an impact and arrived on Antarctica 13,000 years ago. It appears to be essentially free of terrestrial weathering. The PAHs are present at concentrations ~ 10(3) to 10(5) times higher than are found in the surrounding terrestrial ice, and contamination studies indicate that the observed organic material is indigenous to the meteorite. The carbonate globules are rimmed by fine-grained, secondary phases of single-domain magnetite and iron sulfides, that could have resulted from oxidation and reduction reactions known to be important in terrestrial microbial systems. SEM and TEM images of the carbonate globules show features resembling terrestrial microorganisms, terrestrial biogenic carbonate structures, or microfossils. Although there are alternative explanations for each of the above phenomena taken individually, when they are considered collectively, particularly in view of their spatial association, we conclude that they may be evidence for primitive life on early Mars.

  3. Alteration of Rock Fragments from Columbia River Basalt Microcosms

    NASA Technical Reports Server (NTRS)

    Wentworth, Susan J.; Thomas-Keprta, Kathie L.; Velbel, Michael A.; McKay, David S.; Stevens, Todd O.

    1999-01-01

    During an earlier study, microorganisms were grown microcosms consisting of sterilized chips of Columbia River Basalt (CRB) and natural CRB ground water with its natural microflora; environmental conditions simulated a deep subsurface, anaerobic, dark environment. Subsequent scanning and transmission electron microscope (SEM and TEM) studies revealed the presence of several types of bacteria and biofilm, some of which were mineralized. Some of these biological features are very similar to possible biogenic features found in two meteorites from Mars, ALH84001 (found in Antarctica) and Nakhla (observed to fall in Egypt). Both ALH84001 and Nakhla contain traces of low-temperature aqueous alteration of silicates, oxides, and sulfides. The goals of this study are to use high-resolution field-emission SEM (FE-SEM) to examine the CRB samples for evidence of alteration features similar to those in the martian meteorites, to determine the extent of alteration during the CRB microcosm experiments, and to determine whether effects of biological activity can be distinguished from inorganic effects.

  4. Search for past/present life on Mars, studies of organics biomarkers: the MOMIE project

    NASA Astrophysics Data System (ADS)

    Stalport, S.; Coll, C.; Szopa, S.; Raulin, R.

    The life on Mars remains an open question because lack of obvious proof of its past apparition and its current presence We still dispose insufficient data because only the Viking landers in the Seventies and meteorite ALH84001 discovered in the Antarctic were likely to prove a Martian biological activity existence In these two cases the answers were puzzling the results of the experiments of the Viking landers could as well to be explained by the presence of life forms that by abiotic processes in addition no organic molecules was detected Many biomarkers potentially Martians were present on ALH84001 but they had also an abiotic explanation moreover nothing did not exclude a contamination by terrestrial organisms However recent data of Mars Express orbiter and the twin rovers Spirit and Opportunity seem show different proofs of a past environment with liquid water and mild temperatures favorable for life Among the biomarkers we seek the organic molecules are primordial because they are necessary to the origin of life as we know it However these molecules except methane recently discovered have never been detected on Mars by the in situ analyzes of the Viking landers A key question is to know if organic molecules are indeed present in which concentration and under which form Indeed even if endogenous organic molecules were never synthesized those brought by exogenous sources like interplanetary dust should be present in detectable amount Moreover the track of the endogenous organic molecules should not be dropped out because these molecules are able to

  5. A new approach to cosmogenic corrections in 40Ar/39Ar chronometry: Implications for the ages of Martian meteorites

    NASA Astrophysics Data System (ADS)

    Cassata, W. S.; Borg, L. E.

    2016-08-01

    Anomalously old 40Ar/39Ar ages are commonly obtained from Shergottites and are generally attributed to uncertainties regarding the isotopic composition of the trapped component and/or the presence of excess 40Ar. Old ages can also be obtained if inaccurate corrections for cosmogenic 36Ar are applied. Current methods for making the cosmogenic correction require simplifying assumptions regarding the spatial homogeneity of target elements for cosmogenic production and the distribution of cosmogenic nuclides relative to trapped and reactor-derived Ar isotopes. To mitigate uncertainties arising from these assumptions, a new cosmogenic correction approach utilizing the exposure age determined on an un-irradiated aliquot and step-wise production rate estimates that account for spatial variations in Ca and K is described. Data obtained from NWA 4468 and an unofficial pairing of NWA 2975, which yield anomalously old ages when corrected for cosmogenic 36Ar using conventional techniques, are used to illustrate the efficacy of this new approach. For these samples, anomalous age determinations are rectified solely by the improved cosmogenic correction technique described herein. Ages of 188 ± 17 and 184 ± 17 Ma are obtained for NWA 4468 and NWA 2975, respectively, both of which are indistinguishable from ages obtained by other radioisotopic systems. For other Shergottites that have multiple trapped components, have experienced diffusive loss of Ar, or contain excess Ar, more accurate cosmogenic corrections may aid in the interpretation of anomalous ages. The trapped 40Ar/36Ar ratios inferred from inverse isochron diagrams obtained from NWA 4468 and NWA 2975 are significantly lower than the Martian atmospheric value, and may represent upper mantle or crustal components.

  6. Craters of the Moon National Monument as a Terrestrial Mars Analog: Examination of Mars Analog Phosphate Minerals, Phosphate Mineral Shock-Recovery Experiments, and Phosphate Minerals in Martian Meteorites

    NASA Astrophysics Data System (ADS)

    Adcock, C. T.; Hausrath, E.; Tschauner, O. D.; Udry, A.

    2015-12-01

    Martian analogs, meteorites, and data from unmanned missions have greatly advanced our understanding of martian surface and near-surface processes. In particular, terrestrial analogs allow us to investigate Mars-relevant geomorphic, geochemical, petrogenetic, and hydrologic processes, as well as potential habitability. Craters of the Moon National Monument (COTM), located on the Snake River Plain of Idaho in the United States, represents a valuable phosphate-rich Mars analog, allowing us to examine phosphate minerals, important as volatile indicators and potential nutrient providers, under Mars-relevant conditions. COTM is in an arid to semi-arid environment with sub-freezing lows much of the year. Though wetter than present day Mars (24 - 38 cm MAP) [1], COTM may be analogous to a warmer and wetter past Mars. The area is also the locale of numerous lava flows, a number of which have been dated (2,000 to >18,000 y.b.p.) [2]. The flows have experienced weathering over time and thus represent a chronosequence with application to weathering on Mars. The flows have unusual chemistries, including high average phosphate contents (P2O5 1.75 wt% n=23 flows) [2], close to those in rocks analyzed at Gusev Crater, Mars (P2O5 1.79 wt% n=18 rocks) [3]. The Mars-like high phosphorus contents indicate a potential petrogenetic link and are also of astrobiological interest. Further, current samples of Mars phosphate minerals are limited to meteorites which have been heavily shocked - COTM represents a potential pre-shock and geochemical analog to Mars. We investigated weathering on COTM basalts and shock effects on Mars-relevant phosphate minerals. We used scanning electron microscopy, backscattered electron imagery, and X-Ray analysis/mapping to investigate COTM thin sections. Synchrotron diffraction was used to investigate martian meteorites and laboratory shocked Mars/COTM-relevant minerals for comparison. Results of our investigations indicate porosity development correlates

  7. Magnetite morphology and life on Mars.

    PubMed

    Buseck, P R; Dunin-Borkowski, R E; Devouard, B; Frankel, R B; McCartney, M R; Midgley, P A; Pósfai, M; Weyland, M

    2001-11-20

    Nanocrystals of magnetite (Fe(3)O(4)) in a meteorite from Mars provide the strongest, albeit controversial, evidence for the former presence of extraterrestrial life. The morphological and size resemblance of the crystals from meteorite ALH84001 to crystals formed by certain terrestrial bacteria has been used in support of the biological origin of the extraterrestrial minerals. By using tomographic and holographic methods in a transmission electron microscope, we show that the three-dimensional shapes of such nanocrystals can be defined, that the detailed morphologies of individual crystals from three bacterial strains differ, and that none uniquely match those reported from the Martian meteorite. In contrast to previous accounts, we argue that the existing crystallographic and morphological evidence is inadequate to support the inference of former life on Mars. PMID:11717421

  8. Magnetite morphology and life on Mars

    PubMed Central

    Buseck, Peter R.; Dunin-Borkowski, Rafal E.; Devouard, Bertrand; Frankel, Richard B.; McCartney, Martha R.; Midgley, Paul A.; Pósfai, Mihály; Weyland, Matthew

    2001-01-01

    Nanocrystals of magnetite (Fe3O4) in a meteorite from Mars provide the strongest, albeit controversial, evidence for the former presence of extraterrestrial life. The morphological and size resemblance of the crystals from meteorite ALH84001 to crystals formed by certain terrestrial bacteria has been used in support of the biological origin of the extraterrestrial minerals. By using tomographic and holographic methods in a transmission electron microscope, we show that the three-dimensional shapes of such nanocrystals can be defined, that the detailed morphologies of individual crystals from three bacterial strains differ, and that none uniquely match those reported from the Martian meteorite. In contrast to previous accounts, we argue that the existing crystallographic and morphological evidence is inadequate to support the inference of former life on Mars. PMID:11717421

  9. Observation and Analysis of In Situ Carbonaceous Matter in Naklha. Part 2

    NASA Technical Reports Server (NTRS)

    Gibson, E. K., Jr.; Clemett, S. J.; Thomas-Kerpta, K. L.; McKay, D. S.; Wentworth, S. J.; Robert, F.; Verchovsky, A. B.; Wright, I. P.; Pillinger, C. T.; Rice, T.; VanLeer, B.

    2006-01-01

    The search for indigenous carbon components on Mars has been a challenge. The first attempt was the Viking GC-MS in situ experiment which gave inconclusive results at two sites on Mars [1]. After the discovery that the SNC meteorites were from Mars [2], [3-5] reported C isotopic compositional information which suggested a reduced C component present in the martian meteorites. [6 & 7] reported the presence of reduced C components (i.e., polycyclic aromatic hydrocarbons) associated with the carbonate globules in ALH84001. Jull et al. [8] noted in Nakhla there was an acid insoluble C component present with more than 75% of its C lacking any C-14, which is modern-day carbon. This C fraction was believed to be either indigenous martian or ancient meteoritic carbon. Fisk et al. [9, 10] have shown textural evidence along with C-enriched areas within fractures in Nakhla and ALH84001. To further understand the nature of possible indigenous reduced C components, we have carried out a variety of measurements on martian meteorites. For this presentation we will discuss only the Nakhla results. Interior samples from the Nakhla SNC meteorite, recently made available by the British Museum of Natural History, were analyzed. Petrographic examination [11, McKay et al., this volume] of Nakhla showed evidence of fractures (approx.0.5 micron wide) filled with dark brown to black dendritic material [Fig. 1] with characteristics similar to those observed by [10]. Iddingsite is also present along fractures in olivine. Fracture filling and dendritic material was examined by SEM-EDX, TEM-EDX, Focused Electron Beam microscopy, Laser Raman Spectroscopy, Nano-SIMS Ion Micro-probe, and Stepped-Combustion Static Mass Spectrometry.

  10. The Meteoritical Bulletin, No. 101

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

    Meteoritical Bulletin 101 contains 2639 meteorites accepted by the Nomenclature Committee in 2012, including 1 fall (Battle Mountain), with 2308 ordinary chondrites, 156 carbonaceous chondrites, 63 HED achondrites, 17 relict meteorites, 16 Rumuruti chondrites, 15 enstatite chondrites, 15 ureilites, 10 iron meteorites, 9 lunar meteorites, 9 primitive achondrites, 8 ungrouped achondrites, 7 mesosiderites, 4 Martian meteorites, and 2 Pallasites, and with 1812 from Antarctica, 437 from Asia, 301 from Africa, 43 from South America, 21 from Europe (including Russia), 21 from North America, 3 from Oceania, and 1 from unknown. Information about approved meteorites can be obtained from the Meteoritical Bulletin Database (MBD) available on line at http://www.lpi.usra.edu/meteor/.

  11. Signatures in magnetites formed by (Ca,Mg,Fe)CO3 thermal decomposition: Terrestrial and extraterrestrial implications

    NASA Astrophysics Data System (ADS)

    Jimenez-Lopez, Concepcion; Rodriguez-Navarro, Carlos; Rodriguez-Navarro, Alejandro; Perez-Gonzalez, Teresa; Bazylinski, Dennis A.; Lauer, Howard V.; Romanek, Christopher S.

    2012-06-01

    It has never been demonstrated whether magnetite synthesized through the heat-dependent decomposition of carbonate precursors retains the chemical and structural features of the carbonates. In this study, synthetic (Ca,Mg,Fe)CO3 was thermally decomposed by heating from 25 to 700 °C under 1 atm CO2, and by in situ exposure under vacuum to the electron beam of a transmission electron microscope. In both cases, the decomposition of the carbonate was topotactic and resulted in porous pseudomorphs composed of oriented aggregates of magnetite nanocrystals. Both calcium and magnesium were incorporated into nanophase magnetite, forming (Ca,Mg)-magnetites and (Ca,Mg)-ferrites when these elements were present in the parent material, thus preserving the chemical signature of the precursor. These results show that magnetites synthesized in this way acquire a chemical and structural inheritance from their carbonate precursor that indicates how they were produced. These results are not only important in the determination of the origin of chemically-impure, oriented nanophase magnetite crystals in general, but they also provide important insights into the origin of the large, euhedral, chemically-pure, [111]-elongated magnetites found within Ca-, Mg- and Fe-rich carbonates of the Martian meteorite ALH84001. Based on our experimental results, the chemically-pure magnetites within ALH84001 cannot be genetically related to the Ca-, Mg- and Fe-rich carbonate matrix within which they are embedded, and an alternative explanation for their occurrence is warranted.

  12. Aqueous Chemical Modeling of Sedimentation on Early Mars with Application to Surface-Atmosphere Evolution

    NASA Technical Reports Server (NTRS)

    Catling, David C.

    2004-01-01

    This project was to investigate models for aqueous sedimentation on early Mars from fluid evaporation. Results focused on three specific areas: (1) First, a fluid evaporation model incorporating iron minerals was developed to compute the evaporation of a likely solution on early Mars derived from the weathering of mafic rock. (2) Second, the fluid evaporation model was applied to salts within Martian meteorites, specifically salts in the nakhlites and ALH84001. Evaporation models were found to be consistent with the mineralogy of salt assemblages-anhydrite, gypsum, Fe-Mg-Ca carbonates, halite, clays-- and the concentric chemical fractionation of Ca-to Mg-rich carbonate rosettes in ALH84001. We made progress in further developing our models of fluid concentration by contributing to updating the FREZCHEM model. (3) Third, theoretical investigation was done to determine the thermodynamics and kinetics involved in the formation of gray, crystalline hematite. This mineral, of probable ancient aqueous origin, has been observed in several areas on the surface of Mars by the Thermal Emission Spectrometer on Mars Global Surveyor. The "Opportunity" Mars Exploration Rover has also detected gray hematite at its landing site in Meridiani Planum. We investigated how gray hematite can be formed via atmospheric oxidation, aqueous precipitation and subsequent diagenesis, or hydrothermal processes. We also studied the geomorphology of the Aram Chaos hematite region using Mars Orbiter Camera (MOC) images.

  13. Hydrogen isotope evidence for loss of water from Mars through time

    NASA Astrophysics Data System (ADS)

    Greenwood, James P.; Itoh, Shoichi; Sakamoto, Naoya; Vicenzi, Edward P.; Yurimoto, Hisayoshi

    2008-03-01

    The high D/H of the Martian atmosphere (~5-6 × terrestrial) is considered strong evidence for the loss of Martian water to space. The timing and magnitude of the loss of water from Mars can be constrained by measurements of D/H in Martian meteorites. Previous studies of Martian meteorites have shown a large range in D/H, from terrestrial values to as high as the current Martian atmosphere. Here we show that the ancient (~4 Ga) Mars meteorite ALH84001 has a D/H 4 × terrestrial and that the young (~0.17 Ga) Shergotty meteorite has a D/H 5.6 × terrestrial. We also find that the young Los Angeles shergottite has zoning in D/H that can be correlated to igneous growth zoning, strongly suggesting assimilation of D-enriched water during igneous crystallization near the Martian surface. In contrast to previous studies, we find higher and less variable D/H ratios in these three meteorites. Our results suggest a two-stage evolution for Martian water-a significant early loss of water to space (prior to 3.9 Ga) followed by only modest loss to space in the last 4 billion years. The current Martian atmospheric D/H has remained essentially unchanged for the last 165 Ma.

  14. Volatiles (nitrogen, noble gases) in recently discovered SNC meteorites, extinct radioactivities and evolution

    NASA Astrophysics Data System (ADS)

    Mathew, K. J.; Marty, B.; Marti, K.; Zimmermann, L.

    2003-09-01

    We report noble gas and nitrogen analyses of newly discovered SNC meteorites, one nakhlite (NWA817) and four shergottites (NWA480, NWA856, NWA1068, and SaU 005). The K-Ar age (1.3 Ga) as well as the cosmic-ray exposure (CRE) age (10.0±1.3 Ma) of nakhlite NWA817 agree with data of Nakhla. The CRE ages of NWA480, NWA856, and NWA1068 (2.35±0.20, 2.60±0.21 and 2.01±0.65 Ma, respectively) are consistent, within uncertainties, with other basaltic shergottites, but the CRE age of SaU 005 (1.25±0.07 Ma) is distinct and indicates a different ejection event. Bulk K-Ar ages of all shergottites exceed the reported radiometric ages and reveal the presence of inherited radiogenic 40Ar in basaltic lavas. The isotopic composition of nitrogen trapped in these SNC meteorites is not homogeneous, since δ 15N values of either +15 to 20‰ or +45‰, indicate different nitrogen reservoirs. All shergottites contain fission xenon from 238U, and fission Xe of extinct ( T1/2=82 Ma) 244Pu, previously identified in ALH84001, in Chassigny and in Nakhla is also present in at least one shergottite (NWA856). The shergottites contain less fissiogenic Xe than other SNC, suggesting that either their source was more degassed or that the magma source region closed at a later time. In nakhlites, fission xenon from 244Pu correlates with uranium, a geochemical proxy of plutonium. Thus it is possible that fissiogenic Xe was not inherited during magma differentiation, but rather was produced in situ and retained in refractory mineral assemblages. In this interpretation, the magma evolution that settled the mineralogy and geochemistry of nakhlites took place at a time when 244Pu was alive and pre-dated the (late) events recorded in their radiometric ages. Alternatively, fissiogenic xenon was trapped from a mantle source during closed system evolution of the parent magmas, in which case such evolution might have taken place at considerable depth (pressure) in order to inhibit magma degassing during the

  15. The Meteoritical Bulletin, No. 102

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

    Meteoritical Bulletin 102 contains 3141 meteorites including 12 falls (Boumdeid (2003), Boumdeid (2011), Braunschweig, Chelyabinsk, Dongyang, Draveil, Heyetang, Indian Butte, Katol, Ladkee, Ouadangou, Xining), with 2611 ordinary chondrites, 264 HED achondrites, 124 carbonaceous chondrites, 30 ureilites, 20 Martian meteorites, 16 primitive achondrites, 16 Rumuruti chondrites, 15 mesosiderites, 12 iron meteorites, 10 lunar meteorites, 9 enstatite chondrites, 4 enstatite achondrites, 4 Pallasites, 4 ungrouped achondrites, and 2 angrites, and with 1708 from Antarctica, 956 from Africa, 294 from South America, 126 from Asia, 47 from North America, 6 from Europe (including Russia), and 4 from Oceania. Information about approved meteorites can be obtained from the Meteoritical Bulletin Database (MBD) available on line at http://www.lpi.usra.edu/meteor/.

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

    NASA Astrophysics Data System (ADS)

    Jenniskens, P.

    2014-07-01

    Since the previous Meteoroids 2010 meeting, 25 confirmed meteorite falls have been reported, and one additional meteorite was linked tentatively to an observed fireball. All but two of those are classified as ordinary chondrites. Sutter's Mill is a rare carbonaceous chondrite, while Martian meteorite Tissint is a Shergotite. For 18 of these falls the associated fireball was observed, but only four provided a pre-atmospheric orbit derived from video and photographic records. Results were published for Sutter's Mill, Novato, and Chelyabinsk, providing insight into the asteroid belt source regions for CM2, L and LL type chondrites, respectively. Proposed meteorite-asteroid links are discussed.

  17. SNC Meteorites and Martian Reservoirs

    NASA Technical Reports Server (NTRS)

    Jones, J. H.

    2002-01-01

    Jones first suggested that the inverse covariation of initial epsilon (Nd-143) and Sr-87/Sr-86 of the shergottites could be explained by interaction between mantle-derived magmas with another isotopic reservoir(s) (i.e., assimilation or contamination). In that model, magmas were generated in a source region that was isotopically similar to the Nakhla source and the second reservoir(s) was presumed to be crust. The text also permitted the second reservoir to be another type of mantle, but I can confirm that a second mantle reservoir was never seriously considered by that author. Other features of this model were that (i) it occurred at a particular time, 180 m.y. ago, and (ii) the interacting reservoirs had been separated at approximately 4.5 b.y. In a later paper Jones explored this mixing model more quantitatively and concluded that magmas from a Nakhla-like source region at 180 m.y. would fall on or near an isotopic Nd-Sr-Pb hyperplane defined by the shergottites. This criterion was a necessary prerequisite for the parent magma(s) of the shergottites to have initially been Nakhla-like isotopically. At this juncture, it is perhaps worthwhile to note that this mixing model was not presented to explain geochemical variations but as a justification for a 180 m.y. crystallization age for the shergottites and a 1.3 b.y. crystallization age for the nakhlites. In the mid-1980's crystallization ages estimated for Nakhla ranged from approximately 1.3 b.y to 4.5 b.y. Similarly, preferred crystallization ages for the shergottites ranged from 360 m.y., to 1.3 b.y., to 4.5 b.y. In all these models, the 180 m.y. event seen in the shergottites was deemed to be metamorphic. The fit between the Nakhla-like source region and the shergottite hyperplane was a validation both of the 1.3 b.y. igneous age of Nakhla and the 180 m.y. igneous age of the shergottites.

  18. Negative δ 18O values in Allan Hills 84001 carbonate: Possible evidence for water precipitation on mars

    NASA Astrophysics Data System (ADS)

    Holland, G.; Saxton, J. M.; Lyon, I. C.; Turner, G.

    2005-03-01

    The Martian meteorite ALH84001 contains ˜1% by weight of carbonate formed by secondary processes on the Martian surface or in the shallow subsurface. The major form of this carbonate is chemically and isotopically zoned rosettes which have been well documented elsewhere. This study concentrates upon carbonate regions ˜200 μm across which possess previously unobserved magnesium rich inner cores, interpreted here as rosette fragments, surrounded by a later stage cement containing rare Ca-rich carbonates (up to Ca 81Mg 07Fe 04Mn 07) intimately associated with feldspar. High spatial resolution ion probe analyses of Ca-rich carbonate surrounding rosette fragments have δ 18O V-SMOW values as low as -10 ‰. These values are not compatible with deposition from a global Martian atmosphere invoked to explain ALH84001 rosettes. The range of δ 18O values are also incompatible with a fluid that has equilibrated with the Martian crust at high temperature or from remobilisation of carbonate of rosette isotopic composition. At Martian atmospheric temperatures, the small CO 2(gas)-CO 2(ice) fractionation makes meteoric CO 2 an unlikely source for -10 ‰ carbonates. In contrast, closed system Rayleigh fractionation of H 2O can generate δ 18O H2O -30 ‰, as observed at high latitudes on Earth. We suggest that atmospheric transport and precipitation of H 2O in a similar fashion to that on Earth provides a source of suitably 18O depleted water for generation of carbonate with δ 18O V-SMOW = -10 ‰.

  19. Iron Meteorite on Mars

    NASA Technical Reports Server (NTRS)

    2005-01-01

    NASA's Mars Exploration Rover Opportunity has found an iron meteorite on Mars, the first meteorite of any type ever identified on another planet. The pitted, basketball-size object is mostly made of iron and nickel. Readings from spectrometers on the rover determined that composition. Opportunity used its panoramic camera to take the images used in this approximately true-color composite on the rover's 339th martian day, or sol (Jan. 6, 2005). This composite combines images taken through the panoramic camera's 600-nanometer (red), 530-nanometer (green), and 480-nanometer (blue) filters.

  20. Lunar and Planetary Science XXXV: Astrobiology

    NASA Technical Reports Server (NTRS)

    2004-01-01

    The presentations in this session are: 1. A Prototype Life Detection Chip 2. The Geology of Atlantis Basin, Mars, and Its Astrobiological Interest 3. Collecting Bacteria Together with Aerosols in the Martian Atmosphere by the FOELDIX Experimental Instrument Developed with a Nutrient Detector Pattern: Model Measurements of Effectivity 4. 2D and 3D X-ray Imaging of Microorganisms in Meteorites Using Complexity Analysis to Distinguish Field Images of Stromatoloids from Surrounding Rock Matrix in 3.45 Ga Strelley Pool Chert, Western Australia 4. Characterization of Two Isolates from Andean Lakes in Bolivia Short Time Scale Evolution of Microbiolites in Rapidly Receding Altiplanic Lakes: Learning How to Recognize Changing Signatures of Life 5. The Effect of Salts on Electrospray Ionization of Amino Acids in the Negative Mode 6. Determination of Aromatic Ring Number Using Multi-Channel Deep UV Native Fluorescence 7. Microbial D/H Fractionation in Extraterrestrial Materials: Application to Micrometeorites and Mars 8. Carbon Isotope Characteristics of Spring-fed Iron-precipitating Microbial Mats 9. Amino Acid Survival Under Ambient Martian Surface UV Lighting Extraction of Organic Molecules from Terrestrial Material: Quantitative Yields from Heat and Water Extractions 10. Laboratory Detection and Analysis of Organic Compounds in Rocks Using HPLC and XRD Methods 11. Thermal Decomposition of Siderite-Pyrite Assemblages: Implications for Sulfide Mineralogy in Martian Meteorite ALH84001 Carbonate Globules 12. Determination of the Three-Dimensional Morphology of ALH84001 and Biogenic MV-1 Magnetite: Comparison of Results from Electron Tomography and Classical Transmission Electron Microscopy 13. On the Possibility of a Crypto-Biotic Crust on Mars Based on Northern and Southern Ringed Polar Dune Spots 14. Comparative Planetology of the Terrestrial Inner Planets: Implications for Astrobiology 15. A Possible Europa Exobiology 16. A Possible Biogeochemical Model for Titan

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

    USGS Publications Warehouse

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

    2004-01-01

    The Meteoritical Bulletin No. 88 lists information for 1610 newly classified meteorites, comprising 753 from Antarctica, 302 from Africa, 505 from Asia (495 of which are from Oman), 40 from North America, 5 from South America, 4 from Europe, and 1 of unknown origin. Information is provided for 9 falls (Alby sur Che??ran, Al Zarnkh, Devgaon, Kamioka, Kendrapara, Maromandia, New Orleans, Sivas, and Villalbeto de la Pen??a). Noteworthy specimens include a eucrite fall (Alby sur Che??ran), 6 martian meteorites, 13 lunar meteorites, and 12 irons including one weighing 3 metric ions (Dronino). ?? Meteoritical Society, 2004.

  2. Martian Igneous Geochemistry: The Nature of the Martian Mantle

    NASA Technical Reports Server (NTRS)

    Mittlefehldt, D. W.; Elkins-Tanton, L. T.; Peng, Z. X.; Herrin, J. S.

    2012-01-01

    Mafic igneous rocks probe the interiors of their parent objects, reflecting the compositions and mineralogies of their source regions, and the magmatic processes that engendered them. Incompatible trace element contents of mafic igneous rocks are widely used to constrain the petrologic evolution of planets. We focus on incompatible element ratios of martian meteorites to constrain the petrologic evolution of Mars in the context of magma ocean/cumulate overturn models [1]. Most martian meteorites contain some cumulus grains, but regardless, their incompatible element ratios are close to those of their parent magmas. Martian meteorites form two main petrologic/ age groupings; a 1.3 Ga group composed of clinopyroxenites (nakhlites) and dunites (chassignites), and a <1 Ga group composed of basalts and lherzolites (shergottites).

  3. Nannobacteria as a by-product of enzyme-driven tissue decay

    NASA Astrophysics Data System (ADS)

    Schieber, Jürgen; Arnott, Howard J.

    2003-08-01

    Spheroidal features, 50 to 200 nm in size and found in sedimentary rocks, have been described as nannobacteria. The idea that they are minute fossilized life forms—and especially the discovery of such features in Martian meteorite ALH84001—sparked a lively debate with regard to identification of ancient microbial life. Because biologists consider 200 300 nm to be the lower viable size limit for microorganisms, an alternative explanation is needed for features that have been described as nannobacteria by geologists. We report here on tissue-decay experiments that produced abundant proteinaceous spheroids in the size range of nannobacteria (described as nannoballs in the remainder of this paper). Experimental conditions were comparable to those found in Earth's surface sediments, and diagenetic mineralization of these spheroids may be a common process for preservation of nannoballs that are observed in the rock record.

  4. A Seventh Criterion for the Identification of Bacterial Magnetofossils

    NASA Astrophysics Data System (ADS)

    Kirschvink, J. L.

    2001-05-01

    The controversy surrounding the presence of ancient bacterial life on Mars is at present focused on the existence of bacterial magnetofossils in the ALH84001 meteorite. Thomas-Keprta et al. (GCA 64:4049-4081, 2000) and Friedmann et al. (PNAS 98:2176-2181, 2001) have used six fingerprints of natural selection on the morphology and organization of bacterial magnetites as a guide for evaluating a biological origin of the fine-grained magnetite in the rims of the ALH84001 carbonate blebs. These six factors include unusual crystal morphology, elongation along the magnetically-easy \\{111\\} axis, high chemical purity, defect-free crystal lattice, a narrow size and shape distribution corresponding to the single-domain stability field, and the alignment of similarly-sized and shaped particles in linear chains. All six of these features can be viewed as maximizing in the net magnetic moment and magnetic stability of the bacterial cells, increasing the biological efficiency of magnetotaxis. All six of these are present in a well-defined sub-population of the Martian magnetites, whereas the closest inorganic analog found to date meets at most 3. Thomas-Keprta et al. (PNAS 98: 2164-2169, 2001) report yet another distinctive feature common to both Martian magnetites and bacterial strain MV-1, which is a hexa-octahedral morphology truncated at the long ends by a series of [100] and [111] faces. The net effect of these truncations is to remove all right-angle edges from the ends of these elongate magnetosomes, rounding them out. This general feature is in fact very common among the magnetosomes present in populations of living magnetotactic bacteria, and leads to the question of why this type of rounding would be supported by natural selection. I suspect that the answer might lie in the detailed magnetization pattern of elongate magnetic particiles. Recent numerical calculations of the magnetization patterns of rectangular magnetite crystals reveals the tendency for them to

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

    USGS Publications Warehouse

    Grossman, J.N.; Zipfel, J.

    2001-01-01

    Meteoritical Bulletin No. 85 lists information for 1376 newly classified meteorites, comprising 658 from Antarctica, 409 from Africa, 265 from Asia (262 of which are from Oman), 31 from North America, 7 from South America, 3 from Australia, and 3 from Europe. Information is provided for 11 falls (Dergaon, Dunbogan, Gujba, Independence, Itqiy, Mora??vka, Oued el Hadjar, Sayama, Sologne, Valera, and Worden). Noteworthy non-Antarctic specimens include 5 martian meteorites (Dar al Gani 876, Northwest Africa 480 and 817, and Sayh al Uhaymir 051 and 094); 6 lunar meteorites (Dhofar 081, 280, and 287, and Northwest Africa 479, 482, and 773); an ungrouped enstatite-rich meteorite (Itqiy); a Bencubbin-like meteorite (Gujba); 9 iron meteorites; and a wide variety of other interesting stony meteorites, including CH, CK, CM, CO, CR, CV, R, enstatite, and unequilibrated ordinary chondrites, primitive achondrites, HED achondrites, and ureilites.

  6. Meteorites, Microfossils and Exobiology

    NASA Technical Reports Server (NTRS)

    Hoover, Richard B.

    1997-01-01

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

  7. A Search for Titanium Stable Isotopic Variations in Meteorites and the Earth

    NASA Astrophysics Data System (ADS)

    Deng, Z. B.; Moynier, F.; van Zuilen, K.; Pringle, E. A.; Chaussidon, M.

    2016-08-01

    We measure Ti stable isotopic composition of reference materials and 27 meteorite samples. All the chondrite groups are undistinguishable from terrestrial igneous rocks, martian meteorites and angrites in Ti stable isotopic composition.

  8. On the detection of bacterial biomarkers and the implications for astrobiology

    NASA Astrophysics Data System (ADS)

    Toporski, J.; Steele, A.; Westall, F.; Avci, R.; McKay, D.

    Unequivocal detection of bacterial biomarkers is an important challenge in our venture to determine strategies how to best recognize signatures of life rocks, one of the stated main goals of the NASA Astrobiolgy Road Map, the need to be able to recognize the signature of life in rocks from Earth's fossil record as well as in extraterrestrial materials. As has become apparent in the current debate over the true nature of the earliest evidence of life on Earth (Schopf et al. (2002) Nature, 416, 72-76; Brasier et al. (2002) Nature, 416, 76-81), we still have difficulties to unambiguously identify this possible evidence. In the astrobiology community, this issue has appreciated intense discussion for over five years, regarding the possible evidence of past biogenic activities in Martian meteorite ALH84001 (e.g. McKay et al. (1996) Science, 273, 924-930; Treiman (2001) 32nd LPSC, Abstr. #1304), with yet no conclusive answer on hand. To complicate matters, the issue of distinguishing between evidence of past life and evidence of viable life in extraterrestrial materials became apparent through the discovery of recent microbial contaminants in ALH84001 (Steele et al. (2000) MAPS, 35, 237-241), although this meteorite was considered to contain no evidence of life by others. As a valuable offspring of these discussions on benchmark research it emerged that it is inevitable to tackle this challenge by multi-disciplinary and thus multi-technical means. We will present a number of multi-disciplinary and multi-technical approaches we successfully applied in our studies on fossil bacterial biofilms and the search for evidence of life in meteorites, including techniques such as Time of Flight - Secondary Ion Mass Spectroscopy (ToF-SIMS) in combination with electron microscopy and X-ray analytical tools, as well as the application of biotechnology.

  9. Noble gases in 18 Martian meteorites and angrite Northwest Africa 7812—Exposure ages, trapped gases, and a re-evaluation of the evidence for solar cosmic ray-produced neon in shergottites and other achondrites

    NASA Astrophysics Data System (ADS)

    Wieler, R.; Huber, L.; Busemann, H.; Seiler, S.; Leya, I.; Maden, C.; Masarik, J.; Meier, M. M. M.; Nagao, K.; Trappitsch, R.; Irving, A. J.

    2016-02-01

    We present noble gas data for 16 shergottites, 2 nakhlites (NWA 5790, NWA 10153), and 1 angrite (NWA 7812). Noble gas exposure ages of the shergottites fall in the 1-6 Ma range found in previous studies. Three depleted olivine-phyric shergottites (Tissint, NWA 6162, NWA 7635) have exposure ages of ~1 Ma, in agreement with published data for similar specimens. The exposure age of NWA 10153 (~12.2 Ma) falls in the range of 9-13 Ma reported for other nakhlites. Our preferred age of ~7.3 Ma for NWA 5790 is lower than this range, and it is possible that NWA 5790 represents a distinct ejection event. A Tissint glass sample contains Xe from the Martian atmosphere. Several samples show a remarkably low (21Ne/22Ne)cos ratio < 0.80, as previously observed in a many shergottites and in various other rare achondrites. This was explained by solar cosmic ray-produced Ne (SCR Ne) in addition to the commonly found galactic cosmic ray-produced Ne, implying very low preatmospheric shielding and ablation loss. We revisit this by comparing measured (21Ne/22Ne)cos ratios with predictions by cosmogenic nuclide production models. Indeed, several shergottites, acalpulcoites/lodranites, angrites (including NWA 7812), and the Brachina-like meteorite LEW 88763 likely contain SCR Ne, as previously postulated for many of them. The SCR contribution may influence the calculation of exposure ages. One likely reason that SCR nuclides are predominantly detected in meteorites from rare classes is because they usually are analyzed for cosmogenic nuclides even if they had a very small (preatmospheric) mass and hence low ablation loss.

  10. Detection of Bacterial Magnetofossils with Ferromagnetic Resonance and Rock Magnetic Techniques

    NASA Astrophysics Data System (ADS)

    Kirschvink, J. L.; Kim, S.; Weiss, B.

    2001-12-01

    Intracellular biomineralization of magnetite is a biochemical process used by members of the Bacteria, Protist, and Animal kingdoms, and the fossil remains of this process on Earth (termed magnetofossils) have been documented in sediments as old as the ~2 Byr Gunflint Chert. Magnetofossils 4 Byr old have also been reported from carbonates in the Martian meteorite ALH84001; if this interpretation is correct, they represent the oldest evidence for life yet found. Past techniques for identification of bacterial magnetofossils have relied on the use of particle extraction and high-resolution electron microscopy (HRTEM). Because these techniques are time-consuming and fairly complex, they are not appropriate for screening large volumes of sediments on Earth and could not be used remotely on a Martian lander. For this reason, we have been testing a variety of ferromagnetic resonance and low-temperature rock magnetic techniques to determine if they are capable of identifying correctly rock samples known to contain abundant magnetofossils. An instrument capable of making such a determination, if deployed on the Martian surface, could be extraordinarily valuable for selecting samples for return to Earth. Several features of the ferromagnetic resonance (FMR) spectra have signatures only displayed by pure samples of magnetite from the magnetotactic bacteria, and from samples known to contain abundant magnetofossils. These unique features apparently arise from the elongated shape and narrow size distribution of the single-domain magnetite produced by these bacteria. Preliminary results from ALH84001 carbonates also have these features. We are also currently obtaining FMR spectra and low-temperature rock magnetic data on samples of Archean and Early Proterozoic sediments from Australia to search for older evidence of intracellular magnetite biomineralization on Earth.

  11. Lunar and Planetary Science XXXV: Meteorites to and from the Moon and Mars: My Planet or Yours?

    NASA Technical Reports Server (NTRS)

    2004-01-01

    The titles in this section include: 1) Meteorites from Mars - Constraints from Numerical Modeling; 2) Iron Oxidation Products in Martian Ordinary Chondrite Finds as Possible Indicators of Liquid Water Exposure at Mars Exploration Rover Landings Sites; 3) Meteorites on Mars; 4) Sulfide Stability of Planetary Basalts; 5) Exposure and Terrestrial Histories of New Lunar and Martian Meteorites.

  12. Non-chemically Pure Magnetites Produced from Thermal Decomposition of Ankerites

    NASA Astrophysics Data System (ADS)

    Jiménez López, C.; Romanek, C.; Rodríguez-Navarro, A.; Pérez-González, T.; Rodríguez Navarro, C.

    2008-12-01

    It has been claimed that chemically pure magnetites (Fe3O4) can be obtained from thermal decomposition of (Fe, Mg, Ca)CO3 (Golden et al., 2004). Such an observation is critical, since it opens the possibility of an inorganic way of formation of the magnetites found on Martian meteorite ALH84001. Such a chemical purity is one of the parameters used, so far, to recognize bacterial origin of natural magnetites (Thomas-Keptra et al., 2001), since it has been demonstrated that biologically-controlled magnetites are chemically pure (Bazylinski and Frankel, 2004) . However, while Golden et al. (2004) obtained pure magnetite from an almost pure precursor, the ankerite cores in ALH84001 in which magnetites are embedded are far from being chemically pure, since they contain considerable amounts of Ca and Mg (Kopp and Humayun, 2003). In this study we have performed several experiments to analyze the chemical purity of magnetites produced by thermal decomposition of four ankerite samples sinthetized in the laboratory, and containing different amounts of Ca, Fe and Mg. Such a thermal decomposition was achieved by two procedures: (1) by heating the samples at 470°C under CO2 pressure and (2) by decomposing the ankerite "in situ" under the TEM (Transmission electron Microscopy) electron beam. Magnetite produced by the first procedure was analyzed by XRD to determine whether or not the resulting solid was a mixture of oxides or rather a solid solution of (Ca, Fe and Mg)oxide. Magnetites formed by the two methods were studied by High Resolution TEM. The chemical composition of about 20 crystals of each experiment was analyzed by EDAX. Under our experimental conditions, ankerites decomposed in magnetite crystals of about 5 nanometers in size. Magentite crystals arranged to keep the morphology of the precursor. Our results confirm that any of these magnetites is chemically pure, but rather, each one of them is a solid solution of Ca and Mg. Therefore, chemically pure magnetites

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

    Meteoritical Bulletin 100 contains 1943 meteorites including 8 falls (Boumdeid [2011], Huaxi, Košice, Silistra, Sołtmany, Sutter's Mill, Thika, Tissint), with 1575 ordinary chondrites, 139 carbonaceous chondrites, 96 HED achondrites, 25 ureilites, 18 primitive achondrites, 17 iron meteorites, 15 enstatite chondrites, 11 lunar meteorites, 10 mesosiderites, 10 ungrouped achondrites, 8 pallasites, 8 Martian meteorites, 6 Rumuruti chondrites, 3 enstatite achondrites, and 2 angrites, and with 937 from Antarctica, 592 from Africa, 230 from Asia, 95 from South America, 44 from North America, 36 from Oceania, 6 from Europe, and 1 from an unknown location. This will be the last Bulletin published in the current format. Information about approved meteorites can be obtained from the Meteoritical Bulletin Database (MBD) available online at http://www.lpi.usra.edu/meteor/

  14. The Geologic History of Mars: An Astrobiology Perspective

    NASA Technical Reports Server (NTRS)

    Gibson, Everett K.; Westall, Frances; McKay, David S.; Thomas-Keprta, Kathie; Socki, Richard A.

    2000-01-01

    Fourteen SNC meteorites contain information which must be incorporated with recent spaceflight data for developing Mars' geologic history. SNCs have crystallization ages of 4500 to 160 m.y. Tle oldest meteorite ALH84001 contains information on the Noachian period of Mars' history. There are no meteorites from the Hesperian period and the remaining 13 meteorites fall into two age groups within the Amazonian: The nakhlites around 1300 m.y. and the shergottites between 800-160 m.y. Oxygen isotopic analysis of Martian samples shows two distinct O2 reservoirs throughout Martian history indicating late additions of volatiles and a lack of plate tectonics prior to 3.9 Gy. Evidence for percolation of aqueous brines through impact-produced fractures in the rocky surface is contained in the 3.9 Gy-old ALH84001 carbonate deposits. These carbonates precipitated at approx. 100 C. At this time life had already evolved on Earth. Early Mars could have hosted life similar to the bacteria that inhabited early Earth. Potential microorganisms could have been transported into fractures by carbonate-bearing waters and their remains could have become incorporated into the precipitated carbonate. Since Mars had a weak magnetic field at this time, it can be hypothesized that some of the Martian microorganisms may have been similar to terrestrial magnetotactic bacteria. Over geologic time episodic cratering, and tectonic events have occurred on Mars along with the periodic release of subsurface waters which may have produced clays within SNC meteorites. The geochemical data contained within SNC meteorites complements previous observational data and the recent Mars Global Surveyor data to provide a geological and environmental history which spans almost the entire lifespan on Mars. One of the outstanding features of this model is the possible creation of an early (about 4 Gy) volatile reservoir distinct from the outgassed Mars volatiles, and the persistence of this reservoir throughout most

  15. Magnetite in Martian Meteorite Mil 03346 and Gusev Adirondack Class Basalt: Mossbauer Evidence for Variability in the Oxidation State of Adirondack Lavas

    NASA Technical Reports Server (NTRS)

    Morris, R. V.; McKay, G. A.; Ming, D. W.; Klingelhoefer, G.; Schroeder, C.; Rodionov, D.; Yen, A.

    2006-01-01

    The Moessbauer spectrometers on the Mars Exploration Rovers Spirit (Gusev crater) and Opportunity (Meridiani Planum) have returned information on the oxidation state of iron, the mineralogical composition of Fe-bearing phases, and the distribution of Fe among oxidation states and phases [1,2,3]. To date, approx.100 and approx.85 surface targets have been analyzed by the Spirit and Opportunity spectrometers, respectively. Twelve component subspectra (8 doublets and 4 sextets) have been identified and most have been assigned to mineralogical compositions [4]. Two sextet subspectra result from the opaque and strongly magnetic mineral magnetite (Fe3O4 for the stoichiometric composition), one each for the crystallographic sites occupied by tetrahedrally-coordinated Fe3+ and by octahedrally-coordinated Fe3+ and Fe2+. At Gusev crater, the percentage of total Fe associated with magnetite for rocks ranges from 0 to approx. 35% (Fig. 1) [3]. The range for soils (approx.5 to approx.12% of total Fe from Mt, with one exception) is narrower. The ubiquitous presence of Mt in soil firmly establishes the phase as the strongly magnetic component in martian soil [4,5].

  16. Magnetite in Martian Meteorite Mil 03346 and Gusev Adirondack Class Basalt: Moessbauer Evidence for Variability in the Oxidation State of Adirondack Lavas

    NASA Technical Reports Server (NTRS)

    Morris, R. V.; McKay, G. A.; Ming, D. W.; Klingelhoefer, G.; Schroeder, C.; Rodionov, D.; Yen, A.

    2006-01-01

    The Moessbauer spectrometers on the Mars Exploration Rovers Spirit (Gusev crater) and Opportunity (Meridiani Planum) have returned information on the oxidation state of iron, the mineralogical composition of Fe-bearing phases, and the distribution of Fe among oxidation states and phases [1,2,3]. To date, 100 and 85 surface targets have been analyzed by the Spirit and Opportunity spectrometers, respectively. Twelve component subspectra (8 doublets and 4 sextets) have been identified and most have been assigned to mineralogical compositions [4]. Two sextet subspectra result from the opaque and strongly magnetic mineral magnetite (Fe3O4 for the stoichiometric composition), one each for the crystallographic sites occupied by tetrahedrally-coordinated Fe3+ and by octahedrally-coordinated Fe3+ and Fe2+. At Gusev crater, the percentage of total Fe associated with magnetite for rocks ranges from 0 to 35% (Fig. 1) [3]. The range for soils (5 to 12% of total Fe from Mt, with one exception) is narrower. The ubiquitous presence of Mt in soil firmly establishes the phase as the strongly magnetic component in martian soil

  17. Tissintite, (Ca, Na, □)AlSi2O6, a highly-defective, shock-induced, high-pressure clinopyroxene in the Tissint martian meteorite

    NASA Astrophysics Data System (ADS)

    Ma, Chi; Tschauner, Oliver; Beckett, John R.; Liu, Yang; Rossman, George R.; Zhuravlev, Kirill; Prakapenka, Vitali; Dera, Przemyslaw; Taylor, Lawrence A.

    2015-07-01

    Tissintite is a new vacancy-rich, high-pressure clinopyroxene, with a composition essentially equivalent to plagioclase. It was discovered in maskelynite (shocked plagioclase) and is commonly observed included within, or in contact with, shock-melt pockets in the Tissint meteorite, a depleted olivine-phyric shergottite fall from Mars. The simple composition of tissintite (An58-69) and its precursor plagioclase (An59-69) together with the limited occurrence, both spatially (only in maskelynite less than ˜25 μm of a shock melt pocket) and in terms of bulk composition, make tissintite a "goldilocks" phase. It formed during a shock event severe enough to allow nucleation and growth of vacancy-rich clinopyroxene from a melt of not too calcic and not too sodic plagioclase composition that was neither too hot nor too cold. With experimental calibration, these limitations on occurrence can be used to place strong constraints on the thermal history of a shock event. The kinetics for nucleation and growth of tissintite are probably slower for more-sodic plagioclase precursors, so tissintite is most likely to occur in depleted olivine-phyric shergottites like Tissint and other highly shocked meteorites and lunar and terrestrial rocks that consistently contained calcic plagioclase precursors in the appropriate compositional range for a shock of given intensity. Tissintite, (Ca0.45Na0.31□0.24) (Al0.97Fe0.03Mg0.01) (Si1.80Al0.20)O6, is a C 2 / c clinopyroxene, containing 42-60 mol% of the Ca-Eskola component, by far the highest known. The cell parameters are a = 9.21 (17) Å, b = 9.09 (4) Å, c = 5.20 (2) Å, β = 109.6 (9)°, V = 410 (8) Å3, Z = 4. The density is 3.32 g/cm3 and we estimate a cell volume for the Ca-Eskola end-member pyroxene of 411 ± 13 Å3, which is consistent with a previous estimate and, therefore, supports the importance of this component in clinopyroxenes from ultra-high pressure metamorphic rocks from the Earth's upper mantle. At least in C 2 / c

  18. A comparison of the iddingsite alteration products in two terrestrial basalts and the Allan Hills 77005 martian meteorite using Raman spectroscopy and electron microprobe analyses

    NASA Astrophysics Data System (ADS)

    Kuebler, Karla E.

    2013-04-01

    We document the secondary mineral assemblages in two occurrences of terrestrial iddingsite, Lunar Crater, Nevada (LC) and Mauna Kea, Hawaii (MK), and compare these with the iddingsite in Allan Hills (ALHA) 77005. Short Raman spectroscopic traverses across olivine alteration fronts provide information about changes in mineralogy with alteration. Data from the Raman traverses are combined with electron microprobe (EMP) traverses at the same locations which provide information regarding element mobility and confirm mineral identifications made by Raman spectroscopy. This information is used with petrographic observations to argue for the martian origin of the iddingsite and jarosite, infer the sequence of alteration, and deliberate on the conditions and settings of alteration. Raman spectra indicate the presence of different iron oxides/oxyhydroxides in each sample (goethite in LC, maghemite in MK, and akaganéite in ALHA), and the terrestrial samples show different element mobility trends (loss of MgO and SiO2, retention of FeO) than ALHA (loss of MgO and FeO, influx of SiO2), whose trends reflect the deposition of jarosite. Altered olivine occur throughout the LC samples but only in the exteriors of the MK samples. The LC and MK alteration products formed by surface alteration, but ALHA 77005 is a lherzolite, and the olivine hosting the iddingsite are enclosed by orthopyroxene (appear to be restricted to the light lithology), suggesting that it formed at depth during magma consolidation. The ALHA iddingsite is an example of "deuteric alteration" (reaction with fluids that separated from the magma as crystallization progressed towards completion).

  19. Meteoritic basalts. Final report, 1986-1989

    SciTech Connect

    Treiman, A.H.

    1989-10-01

    The objectives were to: explain the abundances of siderophile elements in the SNC meteorite suite, of putative Martian origin; discover the magmatic origins and possibly magma compositions behind the Nakhla meteorite, one of the SNC meteorites; and a re-evaluation of the petrology of Angra dos Reis, a unique meteorite linked to the earliest planetary bodies of the solar nebula. A re-evaluation of its petrography showed that the accepted scenario for its origin, as a cumulate igneous rock, was not consistent with the meteorite's textures (Treiman). More likely is that the meteorite represents a prophyritic igneous rock, originally with magma dominant. Studies of the Nakhla meteorite, of possible Martian origin, although difficult, were successful. It became necessary to reject the basic categorization of Nakhla: that is was a cumulate igneous rock. Detailed studies of the chemical zoning of Nakhlas' minerals, coupled with the failure of experimental studies to yield expected results, forced the conclusion that Nakhla is not a cumulate rock in the usual sense: a rock composed of igneous crystals and intercrystal magma. Study of the siderophile element abundances in the SNC meteorite groups involved trying to find reasonable core formation processes and parameters that would reproduce the observed abundances. Modelling was successful, and delimited a range of models which overlap with those reasonable from geophysical constraints.

  20. Prospects for Chronological Studies of Martian Rocks and Soils

    NASA Technical Reports Server (NTRS)

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

    2008-01-01

    Chronological information about Martian processes comes from two sources: Crater-frequency studies and laboratory studies of Martian meteorites. Each has limitations that could be overcome by studies of returned Martian rocks and soils. Chronology of Martian volcanism: The currently accepted chronology of Martian volcanic surfaces relies on crater counts for different Martian stratigraphic units [1]. However, there is a large inherent uncertainty for intermediate ages near 2 Ga ago. The effect of differing preferences for Martian cratering chronologies [1] is shown in Fig. 1. Stoeffler and Ryder [2] summarized lunar chronology, upon which Martian cratering chronology is based. Fig. 2 shows a curve fit to their data, and compares to it a corresponding lunar curve from [3]. The radiometric ages of some lunar and Martian meteorites as well as the crater-count delimiters for Martian epochs [4] also are shown for comparison to the craterfrequency curves. Scaling the Stoeffler-Ryder curve by a Mars/Moon factor of 1.55 [5] places Martian shergottite ages into the Early Amazonian to late Hesperian epochs, whereas using the lunar curve of [3] and a Mars/Moon factor 1 consigns the shergottites to the Middle-to-Late Amazonian, a less probable result. The problem is worsened if a continually decreasing cratering rate since 3 Ga ago is accepted [6]. We prefer the adjusted St ffler-Ryder curve because it gives better agreement with the meteorite ages (Fig.

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

    NASA Astrophysics Data System (ADS)

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

    2004-03-01

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

  2. Meteorites and the Evolution of Our Solar System

    NASA Technical Reports Server (NTRS)

    Nava, David F.

    1999-01-01

    The study of meteorites has long been of intense interest ever since these objects were discovered to be of extraterrestrial origin. Meteorite research contributes to unraveling the mysteries in understanding the formation and evolution processes of our solar system. Meteorites, of which there are a variety of widely diverse types of chemical and mineralogical compositions, are the most ancient of solar system objects that can be studied in the laboratory. They preserve a unique historical record of the astronomical and astrophysical events of our solar system. This record is being discerned by a host of ever evolving analytical laboratory methods. Recent discoveries of what are believed to be Martian meteorites, lunar meteorites, a meteorite containing indigenous water, and the recovery from the Cretaceous layer of a small meteorite fragment thought to be from the dinosaur-killing asteroid have fueled additional excitement for studying meteorites.

  3. Timeline of Martian Volcanism

    NASA Astrophysics Data System (ADS)

    Martel, L. M. V.

    2011-05-01

    A recent study of Martian volcanism presents a timeline of the last major eruptions from 20 large volcanoes, based on the relative ages of caldera surfaces determined by crater counting. Stuart Robbins, Gaetano Di Achille, and Brian Hynek (University of Colorado) counted craters on high-resolution images from the the Context Camera (CTX) on Mars Reconnaissance Orbiter to date individual calderas, or terraces within calderas, on the 20 major Martian volcanoes. Based on their timeline and mapping, rates and durations of eruptions and transitions from explosive to effusive activity varied from volcano to volcano. The work confirms previous findings by others that volcanism was continuous throughout Martian geologic history until about one to two hundred million years ago, the final volcanic events were not synchronous across the planet, and the latest large-scale caldera activity ended about 150 million years ago in the Tharsis province. This timing correlates well with the crystallization ages (~165-170 million years) determined for the youngest basaltic Martian meteorites.

  4. Mineralogy of Meteorite Groups

    NASA Technical Reports Server (NTRS)

    Rubin, Alan E.

    1997-01-01

    Approximately 275 mineral species have been identified in meteorites, reflecting diverse redox environments, and, in some cases, unusual nebular formation conditions. Anhydrous ordinary, carbonaceous and R chondrites contain major olivine, pyroxene and plagioclase; major opaque phases include metallic Fe-Ni, troilite and chromite. Primitive achondrites are mineralogically similar. The highly reduced enstatite chondrites and achondrites contain major enstatite, plagioclase, free silica and kamacite as well as nitrides, a silicide and Ca-, Mg-, Mn-, Na-, Cr-, K- and Ti-rich sulfides. Aqueously altered carbonaceous chondrites contain major amounts of hydrous phyllosilicates, complex organic compounds, magnetite, various sulfates and sulfides, and carbonates. In addition to kamacite and taenite, iron meteorites contain carbides, elemental C, nitrides, phosphates, phosphides, chromite and sulfides. Silicate inclusions in IAB/IIICD and lIE iron meteorites consist of mafic silicates, plagioclase and various sulfides, oxides and phosphates. Eucrites, howardites and diogenites have basaltic to orthopyroxenitic compositions and consist of major pyroxene and calcic plagioclase and several accessory oxides. Ureilttes .are made up mainly of calcic, chromian olivine and low-Ca clinopyroxene embedded in a carbonaceous matrix; accessory phases include the C polymorphs graphite, diamond, lonsdaleite and chaoite as well as metallic Fe-Ni, troilite and halides. Angrites are achondrites rich in fassaitic pyroxene (i.e. , AI-Ti diopside); minor olivine with included magnesian kirschsteinite is also present. Martian meteorites comprise basalts, Iherzolites, a dunite and an orthopyroxenite. Major phases include various pyroxenes and olivine; minor to accessory phases include various sulfides, magnetite, chromite and Ca-phosphates. Lunar meteorites comprise mare basalts with major augite and calcic plagioclase and anorthositic breccias with major calcic plagioclase. Several meteoritic

  5. Combining meteorites and missions to explore Mars.

    PubMed

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

    2011-11-29

    Laboratory studies of meteorites and robotic exploration of Mars reveal scant atmosphere, no evidence of plate tectonics, past evidence for abundant water, and a protracted igneous evolution. Despite indirect hints, direct evidence of a martian origin came with the discovery of trapped atmospheric gases in one meteorite. Since then, the study of martian meteorites and findings from missions have been linked. Although the meteorite source locations are unknown, impact ejection modeling and spectral mapping of Mars suggest derivation from small craters in terrains of Amazonian to Hesperian age. Whereas most martian meteorites are young (< 1.3 Ga), the spread of whole rock isotopic compositions results from crystallization of a magma ocean > 4.5 Ga and formation of enriched and depleted reservoirs. However, the history inferred from martian meteorites conflicts with results from recent Mars missions, calling into doubt whether the igneous histor y inferred from the meteorites is applicable to Mars as a whole. Allan Hills 84001 dates to 4.09 Ga and contains fluid-deposited carbonates. Accompanying debate about the mechanism and temperature of origin of the carbonates came several features suggestive of past microbial life in the carbonates. Although highly disputed, the suggestion spurred interest in habitable extreme environments on Earth and throughout the Solar System. A flotilla of subsequent spacecraft has redefined Mars from a volcanic planet to a hydrologically active planet that may have harbored life. Understanding the history and habitability of Mars depends on understanding the coupling of the atmosphere, surface, and subsurface. Sample return that brings back direct evidence from these diverse reservoirs is essential.

  6. Combining meteorites and missions to explore Mars.

    PubMed

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

    2011-11-29

    Laboratory studies of meteorites and robotic exploration of Mars reveal scant atmosphere, no evidence of plate tectonics, past evidence for abundant water, and a protracted igneous evolution. Despite indirect hints, direct evidence of a martian origin came with the discovery of trapped atmospheric gases in one meteorite. Since then, the study of martian meteorites and findings from missions have been linked. Although the meteorite source locations are unknown, impact ejection modeling and spectral mapping of Mars suggest derivation from small craters in terrains of Amazonian to Hesperian age. Whereas most martian meteorites are young (< 1.3 Ga), the spread of whole rock isotopic compositions results from crystallization of a magma ocean > 4.5 Ga and formation of enriched and depleted reservoirs. However, the history inferred from martian meteorites conflicts with results from recent Mars missions, calling into doubt whether the igneous histor y inferred from the meteorites is applicable to Mars as a whole. Allan Hills 84001 dates to 4.09 Ga and contains fluid-deposited carbonates. Accompanying debate about the mechanism and temperature of origin of the carbonates came several features suggestive of past microbial life in the carbonates. Although highly disputed, the suggestion spurred interest in habitable extreme environments on Earth and throughout the Solar System. A flotilla of subsequent spacecraft has redefined Mars from a volcanic planet to a hydrologically active planet that may have harbored life. Understanding the history and habitability of Mars depends on understanding the coupling of the atmosphere, surface, and subsurface. Sample return that brings back direct evidence from these diverse reservoirs is essential. PMID:21969535

  7. Combining meteorites and missions to explore Mars

    PubMed Central

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

    2011-01-01

    Laboratory studies of meteorites and robotic exploration of Mars reveal scant atmosphere, no evidence of plate tectonics, past evidence for abundant water, and a protracted igneous evolution. Despite indirect hints, direct evidence of a martian origin came with the discovery of trapped atmospheric gases in one meteorite. Since then, the study of martian meteorites and findings from missions have been linked. Although the meteorite source locations are unknown, impact ejection modeling and spectral mapping of Mars suggest derivation from small craters in terrains of Amazonian to Hesperian age. Whereas most martian meteorites are young (< 1.3 Ga), the spread of whole rock isotopic compositions results from crystallization of a magma ocean > 4.5 Ga and formation of enriched and depleted reservoirs. However, the history inferred from martian meteorites conflicts with results from recent Mars missions, calling into doubt whether the igneous histor y inferred from the meteorites is applicable to Mars as a whole. Allan Hills 84001 dates to 4.09 Ga and contains fluid-deposited carbonates. Accompanying debate about the mechanism and temperature of origin of the carbonates came several features suggestive of past microbial life in the carbonates. Although highly disputed, the suggestion spurred interest in habitable extreme environments on Earth and throughout the Solar System. A flotilla of subsequent spacecraft has redefined Mars from a volcanic planet to a hydrologically active planet that may have harbored life. Understanding the history and habitability of Mars depends on understanding the coupling of the atmosphere, surface, and subsurface. Sample return that brings back direct evidence from these diverse reservoirs is essential. PMID:21969535

  8. Analysis of Siderite Thermal Decomposition by Differential Scanning Calorimetry

    NASA Technical Reports Server (NTRS)

    Bell, M. S.; Lin, I.-C.; McKay, D. S.

    2000-01-01

    Characterization of carbonate devolitilization has important implications for atmospheric interactions and climatic effects related to large meteorite impacts in platform sediments. On a smaller scale, meteorites contain carbonates which have witnessed shock metamorphic events and may record pressure/temperature histories of impact(s). ALH84001 meteorite contains zoned Ca-Mg-Fe-carbonates which formed on Mars. Magnetite crystals are found in the rims and cores of these carbonates and some are associated with void spaces leading to the suggestion by Brearley et al. that the crystals were produced by thermal decomposition of the carbonate at high temperature, possibly by incipient shock melting or devolitilization. Golden et al. recently synthesized spherical Mg-Fe-Ca-carbonates from solution under mild hydrothermal conditions that have similar carbonate compositional zoning to those of ALH84001. They have shown experimental evidence that the carbonate-sulfide-magnetite assemblage in ALH84001 can result from a multistep inorganic process involving heating possibly due to shock events. Experimental shock studies on calcium carbonate prove its stability to approx. 60 GPa, well in excess of the approx. 45 GPa peak pressures indicated by other shock features in ALH84001. In addition, Raman spectroscopy of carbonate globules in ALH84001 indicates no presence of CaO and MgO. Such oxide phases should be found associated with the magnetites in voids if these magnetites are high temperature shock products, the voids resulting from devolitilization of CO2 from calcium or magnesium carbonate. However, if the starting material was siderite (FeCO3), thermal breakdown of the ALH84001 carbonate at 470 C would produce iron oxide + CO2. As no documentation of shock effects in siderite exists, we have begun shock experiments to determine whether or not magnetite is produced by the decomposition of siderite within the < 45GPa pressure window and by the resultant thermal pulse to approx

  9. On the weathering of Martian igneous rocks

    NASA Technical Reports Server (NTRS)

    Dreibus, G.; Waenke, H.

    1992-01-01

    Besides the young crystallization age, one of the first arguments for the martian origin of shergottite, nakhlite, and chassignite (SNC) meteorites came from the chemical similarity of the meteorite Shergotty and the martian soil as measured by Viking XRF analyses. In the meantime, the discovery of trapped rare gas and nitrogen components with element and isotope ratios closely matching the highly characteristic ratios of the Mars atmosphere in the shock glasses of shergottite EETA79001 was further striking evidence that the SNC's are martian surface rocks. The martian soil composition as derived from the Viking mission, with its extremely high S and Cl concentrations, was interpreted as weathering products of mafic igneous rocks. The low SiO2 content and the low abundance of K and other trace elements in the martian soils point to a mafic crust with a considerably smaller degree of fractionation compared to the terrestrial crust. However, the chemical evolution of the martian regolith and soil in respect to surface reaction with the planetary atmosphere or hydrosphere is poorly understood. A critical point in this respect is that the geochemical evidence as derived from the SNC meteorites suggests that Mars is a very dry planet that should have lost almost all its initially large water inventory during its accretion.

  10. A reduced organic carbon component in martian basalts.

    PubMed

    Steele, A; McCubbin, F M; Fries, M; Kater, L; Boctor, N Z; Fogel, M L; Conrad, P G; Glamoclija, M; Spencer, M; Morrow, A L; Hammond, M R; Zare, R N; Vicenzi, E P; Siljeström, S; Bowden, R; Herd, C D K; Mysen, B O; Shirey, S B; Amundsen, H E F; Treiman, A H; Bullock, E S; Jull, A J T

    2012-07-13

    The source and nature of carbon on Mars have been a subject of intense speculation. We report the results of confocal Raman imaging spectroscopy on 11 martian meteorites, spanning about 4.2 billion years of martian history. Ten of the meteorites contain abiotic macromolecular carbon (MMC) phases detected in association with small oxide grains included within high-temperature minerals. Polycyclic aromatic hydrocarbons were detected along with MMC phases in Dar al Gani 476. The association of organic carbon within magmatic minerals indicates that martian magmas favored precipitation of reduced carbon species during crystallization. The ubiquitous distribution of abiotic organic carbon in martian igneous rocks is important for understanding the martian carbon cycle and has implications for future missions to detect possible past martian life. PMID:22628557

  11. A reduced organic carbon component in martian basalts.

    PubMed

    Steele, A; McCubbin, F M; Fries, M; Kater, L; Boctor, N Z; Fogel, M L; Conrad, P G; Glamoclija, M; Spencer, M; Morrow, A L; Hammond, M R; Zare, R N; Vicenzi, E P; Siljeström, S; Bowden, R; Herd, C D K; Mysen, B O; Shirey, S B; Amundsen, H E F; Treiman, A H; Bullock, E S; Jull, A J T

    2012-07-13

    The source and nature of carbon on Mars have been a subject of intense speculation. We report the results of confocal Raman imaging spectroscopy on 11 martian meteorites, spanning about 4.2 billion years of martian history. Ten of the meteorites contain abiotic macromolecular carbon (MMC) phases detected in association with small oxide grains included within high-temperature minerals. Polycyclic aromatic hydrocarbons were detected along with MMC phases in Dar al Gani 476. The association of organic carbon within magmatic minerals indicates that martian magmas favored precipitation of reduced carbon species during crystallization. The ubiquitous distribution of abiotic organic carbon in martian igneous rocks is important for understanding the martian carbon cycle and has implications for future missions to detect possible past martian life.

  12. The Martian Surface

    NASA Astrophysics Data System (ADS)

    Bell, Jim

    2008-06-01

    Dedication; Acknowledgements; Foreword; Part I. Introduction and Historical Perspective: 1. Exploration of the Martian surface: 1992-2007; 2. Historical context: the pre-MGS view of Mars' surface composition; Part II. Elemental Composition: Orbital and In Situ Surface Measurements: Part II. A. Results and Interpretations from New In Situ APXS Measurements: 3. Martian surface chemistry: APXS results from the Pathfinder landing site; 4. Mars exploration rovers - chemical composition by the APXS; Part II. B. Results and Interpretations from New Orbital Elemental Measurements: 5. Elemental abundances determined via the Mars Odyssey GRS; 6. Volatiles on Mars: scientific results from the Mars Odyssey Neutron Spectrometer; Part III. Mineralogy and Remote Sensing of Rocks, Soil, Dust, and Ices: Part III. A. Visible to Near-IR Telescopic and Orbital Measurements: 7. Mineralogy of the Martian surface from Mars Express OMEGA Observations; 8. Visible to near-IR multispectral orbital observations; Part III. B. Mid-IR and Magnetic Orbital Measurements: 9. Global mineralogy mapped from the Mars Global Surveyor Thermal Emission Spectrometer; 10. The compositional diversity and physical properties mapped from the Mars Odyssey Thermal Emission Imaging System; 11. Mars' crustal magnetization: a window into the past; Part III. C. Observations from Surface Landers/Rovers: 12. Multispectral imaging from Mars Pathfinder; 13. Mars Exploration Rover Pancam multispectral imaging of rocks, soil, and dust at Gusev Crater and Meridiani Planum ; 14. The mineralogy of Gusev Crater and Meridiani Planum derived from the Miniature Thermal Emission Spectrometers on the Spirit and Opportunity Rovers; 15. Iron mineralogy and aqueous alteration on Mars from the MER Mössbauer Spectrometers; 16. Magnetic properties results from surface landers and rovers; Part III. D: 17. Martian meteorites as crustal samples; Part IV. Physical Properties of Surface Materials: 18. The thermal inertia of the surface of

  13. Iron Meteorite

    NASA Astrophysics Data System (ADS)

    Murdin, P.

    2000-11-01

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

  14. Identification of new meteorite, Mihonoseki (L), from broken fragments in Japan

    NASA Technical Reports Server (NTRS)

    Miura, Y.; Noma, Y.

    1993-01-01

    New meteorite of Mihonoseki fallen in Shimane-ken was identified by fine broken pieces by using an energy-dispersive scanning electron microprobe analyzer. It shows fusion-crust (i.e. Fe-Si melt), meteoritic minerals (kamacite, taenite, troilite, amorphous plagioclase etc.) and chrondrule with clear glassy rim. Mineralogical, and petrological data of several fine grains suggest that broken fragments of Mihonoseki are L3/4 chondritic meteorite which is the first identification in a Japanese fallen meteorite. The prompt identification method of meteorite-fragments will be applied to the next lunar, Martian and asteroid explorations, as well as meteorite falls on the terrestrial surface.

  15. Fractionated martian atmosphere in the nakhlites?

    NASA Technical Reports Server (NTRS)

    Drake, Michael J.; Swindle, Timothy D.; Owen, Tobias; Musselwhite, Donald S.

    1994-01-01

    Considerable evidence points to a martian origin of the shergottite-nakhlite-chassignite (SNC) meteorites. Noble gas isotopic compositions have been measured in most SNC meteorites. The Xe-129/Xe-132 vs. Kr-84/Xe-132 ratios in Chassigny, most shergottites, and lithology C of EETA 79001 define a linear array. This array is thought to be a mixing line between martian mantle and martian atmosphere. One of the SNC meteorites, Nakhla, contains a leachable component that has an elevated Xe-129/Xe-132 ratio relative to its Kr-84/Xe-132 ratio when compared to this approximately linear array. The leachable component probably consists in part of iddingsite, an alteration product produced by interaction of olivine with aqueous fluid at temperatures lower than 150 C. The elevated Xe isotopic ratio may represent a distinct reservoir in the martian crust or mantle. More plausibly, it is elementally fractionated martian atmosphere. Formation of sediments fractionates the noble gases in the correct direction. The range of sediment/atmosphere fractionation factors is consistent with the elevated Xe-129/Xe-132 component in Nakhla being contained in iddingsite, a low temperature weathering product. The crystallization age of Nakhla is 1.3 Ga. Its low-shock state suggests that it was ejected from near the surface of Mars. As liquid water is required for the formation of iddingsite, these observations provide further evidence for the near surface existence of aqueous fluids on Mars more recently than 1.3 Ga.

  16. Geochemistry of Carbonates on Mars: Implications for Climate History and Nature of Aqueous Environments

    NASA Astrophysics Data System (ADS)

    Niles, Paul B.; Catling, David C.; Berger, Gilles; Chassefière, Eric; Ehlmann, Bethany L.; Michalski, Joseph R.; Morris, Richard; Ruff, Steven W.; Sutter, Brad

    2013-01-01

    Ongoing research on martian meteorites and a new set of observations of carbonate minerals provided by an unprecedented series of robotic missions to Mars in the past 15 years help define new constraints on the history of martian climate with important crosscutting themes including: the CO2 budget of Mars, the role of Mg-, Fe-rich fluids on Mars, and the interplay between carbonate formation and acidity. Carbonate minerals have now been identified in a wide range of localities on Mars as well as in several martian meteorites. The martian meteorites contain carbonates in low abundances (<1 vol.%) and with a wide range of chemistries. Carbonates have also been identified by remote sensing instruments on orbiting spacecraft in several surface locations as well as in low concentrations (2-5 wt.%) in the martian dust. The Spirit rover also identified an outcrop with 16 to 34 wt.% carbonate material in the Columbia Hills of Gusev Crater that strongly resembled the composition of carbonate found in martian meteorite ALH 84001. Finally, the Phoenix lander identified concentrations of 3-6 wt.% carbonate in the soils of the northern plains. The carbonates discovered to date do not clearly indicate the past presence of a dense Noachian atmosphere, but instead suggest localized hydrothermal aqueous environments with limited water availability that existed primarily in the early to mid-Noachian followed by low levels of carbonate formation from thin films of transient water from the late Noachian to the present. The prevalence of carbonate along with evidence for active carbonate precipitation suggests that a global acidic chemistry is unlikely and a more complex relationship between acidity and carbonate formation is present.

  17. The Meteoritical Bulletin, No. 87, 2003 July

    USGS Publications Warehouse

    Russell, S.S.; Zipfel, J.; Folco, L.; Jones, R.; Grady, M.M.; McCoy, T.; Grossman, J.N.

    2003-01-01

    Meteoritical Bulletin No. 87 lists information for 1898 newly classified meteorites, comprising 1048 from Antarctica, 462 from Africa, 356 from Asia (355 of which are from Oman), 18 from North America, 5 from South America, 5 from Europe, and 3 from Australia. Information is provided for 10 falls (Beni M'hira, Elbert, Gasseltepaoua, Hiroshima, Kilabo, Neuschwanstein, Park Forest, Pe??, Pe??te??lkole??, and Thuathe). Two of these-Kilabo and Thuathe-fell on the same day. Orbital characteristics could be calculated for Neuschwanstein. Noteworthy specimens include 8 Martian meteorites (5 from Sahara, 2 from Oman and 1 from Antarctica), 13 lunar meteorites (all except one from Oman), 3 irons, 3 pallasites, and many carbonaceous chondrites and achondrites.

  18. Meteorite craters

    NASA Technical Reports Server (NTRS)

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

    1986-01-01

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

  19. Martian ages

    NASA Technical Reports Server (NTRS)

    Neukum, G.; Hiller, K.

    1981-01-01

    Four discussions are conducted: (1) the methodology of relative age determination by impact crater statistics, (2) a comparison of proposed Martian impact chronologies for the determination of absolute ages from crater frequencies, (3) a report on work dating Martian volcanoes and erosional features by impact crater statistics, and (4) an attempt to understand the main features of Martian history through a synthesis of crater frequency data. Two cratering chronology models are presented and used for inference of absolute ages from crater frequency data, and it is shown that the interpretation of all data available and tractable by the methodology presented leads to a global Martian geological history that is characterized by two epochs of activity. It is concluded that Mars is an ancient planet with respect to its surface features.

  20. Martian ages

    NASA Astrophysics Data System (ADS)

    Neukum, G.; Hiller, K.

    1981-04-01

    Four discussions are conducted: (1) the methodology of relative age determination by impact crater statistics, (2) a comparison of proposed Martian impact chronologies for the determination of absolute ages from crater frequencies, (3) a report on work dating Martian volcanoes and erosional features by impact crater statistics, and (4) an attempt to understand the main features of Martian history through a synthesis of crater frequency data. Two cratering chronology models are presented and used for inference of absolute ages from crater frequency data, and it is shown that the interpretation of all data available and tractable by the methodology presented leads to a global Martian geological history that is characterized by two epochs of activity. It is concluded that Mars is an ancient planet with respect to its surface features.

  1. Detection of oxygen isotopic anomaly in terrestrial atmospheric carbonates and its implications to Mars

    PubMed Central

    Shaheen, R.; Abramian, A.; Horn, J.; Dominguez, G.; Sullivan, R.; Thiemens, Mark H.

    2010-01-01

    The debate of life on Mars centers around the source of the globular, micrometer-sized mineral carbonates in the ALH84001 meteorite; consequently, the identification of Martian processes that form carbonates is critical. This paper reports a previously undescribed carbonate formation process that occurs on Earth and, likely, on Mars. We identified micrometer-sized carbonates in terrestrial aerosols that possess excess 17O (0.4–3.9‰). The unique O-isotopic composition mechanistically describes the atmospheric heterogeneous chemical reaction on aerosol surfaces. Concomitant laboratory experiments define the transfer of ozone isotopic anomaly to carbonates via hydrogen peroxide formation when O3 reacts with surface adsorbed water. This previously unidentified chemical reaction scenario provides an explanation for production of the isotopically anomalous carbonates found in the SNC (shergottites, nakhlaites, chassignites) Martian meteorites and terrestrial atmospheric carbonates. The anomalous hydrogen peroxide formed on the aerosol surfaces may transfer its O-isotopic signature to the water reservoir, thus producing mass independently fractionated secondary mineral evaporites. The formation of peroxide via heterogeneous chemistry on aerosol surfaces also reveals a previously undescribed oxidative process of utility in understanding ozone and oxygen chemistry, both on Mars and Earth. PMID:21059939

  2. Detection of oxygen isotopic anomaly in terrestrial atmospheric carbonates and its implications to Mars.

    PubMed

    Shaheen, R; Abramian, A; Horn, J; Dominguez, G; Sullivan, R; Thiemens, Mark H

    2010-11-23

    The debate of life on Mars centers around the source of the globular, micrometer-sized mineral carbonates in the ALH84001 meteorite; consequently, the identification of Martian processes that form carbonates is critical. This paper reports a previously undescribed carbonate formation process that occurs on Earth and, likely, on Mars. We identified micrometer-sized carbonates in terrestrial aerosols that possess excess (17)O (0.4-3.9‰). The unique O-isotopic composition mechanistically describes the atmospheric heterogeneous chemical reaction on aerosol surfaces. Concomitant laboratory experiments define the transfer of ozone isotopic anomaly to carbonates via hydrogen peroxide formation when O(3) reacts with surface adsorbed water. This previously unidentified chemical reaction scenario provides an explanation for production of the isotopically anomalous carbonates found in the SNC (shergottites, nakhlaites, chassignites) Martian meteorites and terrestrial atmospheric carbonates. The anomalous hydrogen peroxide formed on the aerosol surfaces may transfer its O-isotopic signature to the water reservoir, thus producing mass independently fractionated secondary mineral evaporites. The formation of peroxide via heterogeneous chemistry on aerosol surfaces also reveals a previously undescribed oxidative process of utility in understanding ozone and oxygen chemistry, both on Mars and Earth. PMID:21059939

  3. Detection of oxygen isotopic anomaly in terrestrial atmospheric carbonates and its implications to Mars.

    PubMed

    Shaheen, R; Abramian, A; Horn, J; Dominguez, G; Sullivan, R; Thiemens, Mark H

    2010-11-23

    The debate of life on Mars centers around the source of the globular, micrometer-sized mineral carbonates in the ALH84001 meteorite; consequently, the identification of Martian processes that form carbonates is critical. This paper reports a previously undescribed carbonate formation process that occurs on Earth and, likely, on Mars. We identified micrometer-sized carbonates in terrestrial aerosols that possess excess (17)O (0.4-3.9‰). The unique O-isotopic composition mechanistically describes the atmospheric heterogeneous chemical reaction on aerosol surfaces. Concomitant laboratory experiments define the transfer of ozone isotopic anomaly to carbonates via hydrogen peroxide formation when O(3) reacts with surface adsorbed water. This previously unidentified chemical reaction scenario provides an explanation for production of the isotopically anomalous carbonates found in the SNC (shergottites, nakhlaites, chassignites) Martian meteorites and terrestrial atmospheric carbonates. The anomalous hydrogen peroxide formed on the aerosol surfaces may transfer its O-isotopic signature to the water reservoir, thus producing mass independently fractionated secondary mineral evaporites. The formation of peroxide via heterogeneous chemistry on aerosol surfaces also reveals a previously undescribed oxidative process of utility in understanding ozone and oxygen chemistry, both on Mars and Earth.

  4. An alternative hypothesis for high-T 40Ar/39Ar age spectrum discordance in polyphase extraterrestrial materials

    NASA Astrophysics Data System (ADS)

    Cassata, W. S.; Shuster, D. L.; Renne, P. R.; Weiss, B. P.

    2009-12-01

    A common feature observed in 40Ar/39Ar age spectra of extraterrestrial (ET) rocks is a conspicuous decrease in the ages of high temperature extractions relative to lower temperature steps and a correlated increase in Ca/K, often succeeded by a monotonic increase in ages. This feature is routinely attributed to recoil-implanted 39Ar from a potassium (K)-rich donor phase into a K-poor receptor phase (e.g., 1,2). While 39Ar recoil redistribution is undoubtedly manifested in many terrestrial and ET 40Ar/39Ar whole-rock age spectra, it cannot easily explain the magnitude of high release temperature 40Ar*/39ArK anomalies observed in Martian meteorites ALH 84001 and Nakhla, as well as other course-grained meteorites and lunar rocks. Depending on the aliquot and sample, 50 - 100% of the pyroxene release spectra in ALH 84001 and Nakhla appear strongly perturbed to lower ages. As the mean recoil distance of 39Ar ~0.1 µm, the recoil hypothesis demands that a high-K phase be ubiquitously distributed amongst sub-micron to micron sized pyroxene crystals to account for the observed pyroxene age spectra. However, in both Nakhla and ALH 84001, pyroxene is often completely isolated from high-K phases and individual grains commonly exceed 100 µm in diameter. 40Ar/39Ar analyses of pyroxene-bearing terrestrial basalts, wherein fine-grained pyroxene and plagioclase are intimately adjoined, show that recoil-implanted 39Ar into pyroxene produces much less precipitous anomalies in 40Ar*/39ArK, as predicted by the recoil lengthscale. An alternative hypothesis is that whole-rock age spectra of ET samples with anomalously low ages at high temperatures may reflect diffusive 40Ar distributions within considerably degassed pyroxene grains. Owing to apparent differences in activation energies between glass and/or plagioclase and pyroxene, 40Ar may diffuse more rapidly from pyroxene under certain high-temperature conditions (i.e., above the temperature at which the extrapolated Ar Arrhenius

  5. Solar proton produced neon in shergottite meteorites

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

    Cosmogenic radionuclides produced by near-surface, nuclear interactions of energetic solar protons (approx. 10-100 MeV) were reported in several lunar rocks and a very small meteorites. We recently documented the existence and isotopic compositions of solar-produced (SCR) Ne in two lunar rocks. Here we present the first documented evidence for SCR Ne in a meteorite, ALH77005, which was reported to contain SCR radionuclides. Examination of literature data for other shergottites suggests that they may also contain a SCR Ne component. The existence of SCR Ne in shergottites may be related to a Martian origin.

  6. Mars Atmospheric Composition, Isotope Ratios and Seasonal Variations: Overview and Updates of the SAM Measurements at Gale Crater

    NASA Technical Reports Server (NTRS)

    Niles, Paul

    2014-01-01

    We will summarize the in situ measurements of atmospheric composition and the isotopic ratios of D/H in water, C-13/C-12, O-18/O-16, O-17 / O-16, and C-13 O-18 / C-12 O-16 in carbon dioxide, and Ar-38 / Ar-36, Kr-x / Kr-84, and N-15 / N-14 made in the martian atmosphere at Gale Crater from the Curiosity Rover using the Sample Analysis at Mars (SAM)'s Quadrupole Mass Spectrometer (QMS) and Tunable Laser Spectrometer (TLS). With data over 700 sols since the Curiosity landing, we will discuss evidence and implications for changes on seasonal and other timescales. We will also present results for continued methane and methane enrichment experiments over this time period. Comparison between our measurements in the modern atmosphere and those of martian meteorites like ALH 84001 implies that the martian reservoirs of CO2 and H2O were largely established approximately 4 billion years ago, but that atmospheric loss or surface interaction may be still ongoing.

  7. Liquid Water on Mars: The Story from Meteorites

    NASA Astrophysics Data System (ADS)

    Taylor, G. J.

    2000-05-01

    Two studies shed light on the nature and timing of alteration by water of rocks from Mars. One is an experimental study of the alteration of a rock similar to Martian meteorites, conducted by Leslie Baker, Deborah Agenbroad, and Scott Wood (University of Idaho). They exposed crushed pieces of terrestrial lava flows to water at 23 C and 75 C and normal atmospheric pressure, and to hot water at 200 C to 400 C and a pressure 1000 times normal atmospheric to see what minerals would form. On the basis of a detailed comparison between the experimental products and the Martian meteorites Baker and colleagues conclude that the rocks from which Martian meteorites derived were intermittently exposed to water or water vapor; they were not exposed for a long time to large volumes of water. In an independent study, a team led by Tim Swindle (University of Arizona) tried to determine the time of formation of a reddish-brown alteration product in the Martian meteorite Lafayette. This meteorite appears to have formed from magma 1.3 billion years ago, but the rusty-looking weathering product, a mixture of clay minerals, iron oxide, and iron hydride, formed long after the original rock had crystallized. Although the precise time is not pinned down, their measurements indicate formation during the past 650 million years. Taken together, these studies suggest that water flowed intermittently on the surface of Mars during the past 650 million years.

  8. Chalcophile Siderophile Trace Element Systematics of Hydrothermal Pyrite from Martian Regolith Breccia NWA 7533

    NASA Astrophysics Data System (ADS)

    Lorand, J.-P.; Hewins, R. H.; Humayun, M.; Remusat, L.; Zanda, B.; La, C.; Pont, S.

    2016-08-01

    Martian impact breccia NWA 7533 contains hydrothermal pyrite. Laser ablation ICPMS analyses show that its chalcophile siderophile element content was inherited from both early meteorite bombardment and later hydrothermal inputs from H2S fluids.

  9. Martian Noble Gases in Recently Found Shergottites, Nakhlites, and Breccia Northwest Africa 8114

    NASA Astrophysics Data System (ADS)

    Busemann, H.; Seiler, S.; Wieler, R.; Kuga, M.; Maden, C.; Irving, A. J.; Clay, P. L.; Joy, K. H.

    2015-07-01

    New noble gas data for several recently found martian meteorites will be presented to determine cosmic-ray exposure ages and source pairing. The presence of trapped (atmospheric) components and discrepancies to earlier data sets will be discussed.

  10. 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.

  11. Indigenous Carbonaceous Matter in the Nakhla Mars Meteorite

    NASA Technical Reports Server (NTRS)

    Clemett, S. J.; Thomas-Keprta, K. L.; Rahman, Z.; Le, L.; Wentworth, S. J.; Gibson, E. K.; McKay, D. S.

    2016-01-01

    Detailed microanalysis of the Martian meteorite<