¹Bellucci, J.J.,¹Whitehouse, M.J.,^1,2Nemchin, A.A.,¹Snape, J.F.,²Pidgeon, R.T.,²Grange, M.,²Reddy, S.M.,²Timms, N.
Chemical Geology 438, 112-122  Link to Article [DOI: 10.1016/j.chemgeo.2016.05.022]
¹Department of Geosciences, Swedish Museum of Natural History, Stockholm, Sweden
²Department of Applied Geology, Curtin University, Perth, WA, Australia

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¹Fabien Kenig, ¹Luoth Chou, ²Christopher P. McKay, ³W. Andrew Jackson, ^1,4Peter T. Doran, ⁵Alison E. Murray, ⁵Christian H. Fritsen
Journal of Geophysical Research Planets (in Press) Link to Article [DOI: 10.1002/2015JE004964]
¹Department of Earth and Environmental Sciences, University of Illinois at Chicago, Chicago, Illinois, USA
²Space Science Division, NASA Ames Research Center, Moffett Field, California, USA
³Civil and Environmental Engineering Department, Texas Tech University, Lubbock, Texas, USA
⁴Department of Geology and Geophysics, Louisiana State University, Baton Rouge, Louisiana, USA
⁵Division of Earth and Ecosystem Sciences, Desert Research Institute, Reno, Nevada, USA
Published by arrangement with John Wiley & Sons

The cold (-13.4 ˚C), cryoencapsulated, anoxic, interstitial brine of the >27 m-thick ice of Lake Vida (Victoria Valley, Antarctica) contains 49 µg · L^-1 of perchlorate and 11 µg · L^-1 of chlorate. Lake Vida brine (LVBr) may provide an analog for potential oxychlorine-rich subsurface brine on Mars. LVBr volatiles were analyzed by solid-phase microextraction (SPME) gas chromatography-mass spectrometry (GC-MS) with two different SPME fibers. With the exception of volatile organic sulfur compounds, most other volatiles observed were artifacts produced in the GC injector when the thermal decomposition products of oxychlorines reacted with reduced carbon derived from LVBr and the SPME fiber phases. Analysis of MilliQ water with perchlorate (40 µg · L^-1) showed low level of organic artifacts, reflecting carbon limitation. In order to observe sample-derived organic compounds, both in analog samples and on Mars, the molar abundance of reduced carbon in a sample must exceed those of O₂ and Cl₂ produced during decomposition of oxychlorines. This suggests that the abundance of compounds observed by the Sample Analysis at Mars (SAM) instruments in Sheepbed samples (CB-3, CB5, and CB6) may be controlled by an increase in the reduced-carbon/oxychlorine ratio of these samples. To increase chances of in situ detection of Martian organics during pyrolysis-GC-MS, we propose that the derivatization agents stored on SAM may be used as an external source of reduced carbon, increasing artificially the reduced-carbon to perchlorate ratio during pyrolysis, allowing the expression of more abundant and perhaps more diverse Martian organic matter.

¹M. Millan et al. (>10)*
Planetary and Space Science (in Press)   Link to Article [doi:10.1016/j.pss.2016.06.007]
¹LATMOS/IPSL, UVSQ Université Paris-Saclay, UPMC Univ. Paris 06, CNRS, Guyancourt, France, 11 Blvd. d’Alembert, 78280 Guyancourt, France
*Find the extensive, full author and affiliation list on the publishers website

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¹Lydie Bonal, ¹Eric Quirico, ¹Laurène Flandinet, ²Gilles Montagnac
Geochimica et Cosmochimica Acta (in Press) Link to Article [doi:10.1016/j.gca.2016.06.017]
¹Institut de Planétologie et d’Astrophysique de Grenoble – Observatoire des Sciences de l’Univers de Grenoble, Bât. D de Physique, 38041 Grenoble France
²Laboratoire de Géologie de Lyon Terre, Planètes, Environnement – ENS Lyon – Lyon France
Copyright Elsevier

This paper is focused on the characterization of the thermal history of 151 CV, CO and Unequilibrated Ordinary Chondrites (UOCs) from the NASA Antarctic meteorite collection, using an approach based on the structure of the included polyaromatic carbonaceous matter determined by Raman spectroscopy. 114 out of these 151 chondrites provided Raman spectra of carbonaceous matter and allowing to assign a petrologic type, which mostly reflects the peak temperature experienced by the rock on the parent body. A thorough review of literature shows however that it is not possible to deduce a peak temperature because accurate calibration is not available. Twenty three new weakly metamorphosed chondrites have been identified: MIL 07671 (CV3.1); DOM 08006 (CO3.0); DOM 03238, MIL 05024, MIL 05104, MIL 07193 (CO3.1); TIL 82408, LAR 06279 (LL3.05-3.1); EET 90628 (L3.0); GRO 06054, QUE 97008 (L3.05), ALHA 77176, EET 90066, LAR 04380, MET 96515, MIL 05050 (L3.1); ALHA 78133, EET 87735, EET 90909, LEW 87208, PRE 95401 (L3.05-3.1); MCY 05218 (H3.05-3.1) and MET 00506 (H3.1). This study confirms that the width of the D band (FWHMD) and the ratio of the peak intensity of the D and G bands (ID/IG) are the most adapted tracers of the extent of thermal metamorphism in type 3 chondrites. It also unambiguously shows, thanks to the large number of samples, that the width of the G band (FWHMG) does not correlate with the maturity of polyaromatic carbonaceous matter. This parameter is nevertheless very valuable because it shows that Raman spectra of CV chondrites preserve memory of either the metamorphic conditions (possibly oxidation controlled by aqueous alteration) or the nature of the organic precursor. Oxidation memory is our preferred interpretation, however an extensive petrologic characterization of this CV series is required to get firm conclusions. Pre-graphitic carbonaceous matter is reported in seven chondrites and is even the only carbonaceous material detected in the chondrites ALHA 78119 and DAV 92302. This pre-graphitic carbonaceous matter cannot be formed through radiogenic thermal metamorphism without metal catalysis. Shock metamorphism is another possible process for accounting its formation, but it appears less plausible.

^1,2José C. Aponte, ^1,2Hannah L. McLain, ¹Jason P. Dworkin, ¹Jamie E. Elsila
Geochimica et Cosmochimica Acta (in Press) Link to Article [doi:10.1016/j.gca.2016.06.018]
¹Solar System Exploration Division, Code 691, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA
²Department of Chemistry, Catholic University of America, Washington, DC 20064, USA
Copyright Elsevier

Meteoritic water-soluble organic compounds provide a unique record of the processes that occurred during the formation of the solar system and the chemistry preceding the origins of life on Earth. We have investigated the molecular distribution, compound-specific δ13C isotopic ratios and enantiomeric compositions of aliphatic monoamines present in the hot acid-water extracts of the carbonaceous chondrites LAP 02342 (CR2), GRA 95229 (CR2), LON 94101 (CM2), LEW 90500 (CM2), and ALH 83100 (CM1/2). Analyses of the concentration of monoamines in these meteorites revealed: a) the CR2 chondrites studied here contain higher concentrations of monoamines relative to the analyzed CM2 chondrites; b) the concentration of monoamines decreases with increasing carbon number; and c) isopropylamine is the most abundant monoamine in these CR2 chondrites, while methylamine is the most abundant amine species in these CM2 and CM1/2 chondrites. The δ13C values of monoamines in CR2 chondrite do not correlate with the number of carbon atoms; however, in CM2 and CM1/2 chondrites, the 13C enrichment decreases with increasing monoamine carbon number. The δ13C values of methylamine in CR2 chondrites ranged from –1 to +10‰, while in CM2 and CM1/2 chondrites the δ13C values of methylamine ranged from +41 to +59‰. We also observed racemic compositions of sec-butylamine, 3-methyl-2-butylamine, and sec-pentylamine in the studied carbonaceous chondrites. Additionally, we compared the abundance and δ13C isotopic composition of monoamines to those of their structurally related amino acids. We found that monoamines are less abundant than amino acids in CR2 chondrites, with the opposite being true in CM2 and CM1/2 chondrites. We used these collective data to evaluate different primordial synthetic pathways for monoamines in carbonaceous chondrites and to understand the potential common origins these molecules may share with meteoritic amino acids.

¹Olivier Mousis, ²Jean-Marc Simon, ²Jean-Pierre Bellat, ³Frédéric Schmidt, ³Sylvain Bouley, ³Eric Chassefière, ⁴Violaine Sautter, ⁵Yoann Quesnel, ⁶Sylvain Picaud, ⁷Sébastien Lectez
Icarus (in Press) Link to Article [doi:10.1016/j.icarus.2016.05.035]
¹Aix Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, 13388, Marseille, France
²Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303, CNRS-Université de Bourgogne Franche Comté, Dijon, France
³Laboratoire GEOPS (Géosciences Paris Sud), Bat. 509, Université Paris Sud, 91405 Orsay Cedex, France
⁴Muséum d’Histoire Naturelle, Paris, France
⁵Aix-Marseille Université, CNRS, IRD, CEREGE UM34, 13545 Aix-en-Provence, France
⁶Université de Franche-Comté, Institut UTINAM, CNRS/INSU, UMR 6213, Besançon Cedex, France
⁷Leeds University, School of Earth and Environment, Leeds, United Kingdom
Copyright Elsevier

The origin of the martian methane is still poorly understood. A plausible explanation is that methane could have been produced either by hydrothermal alteration of basaltic crust or by serpentinization of ultramafic rocks producing hydrogen and reducing crustal carbon into methane. Once formed, methane storage on Mars is commonly associated with the presence of hidden clathrate reservoirs. Here, we alternatively suggest that chabazite and clinoptilolite, which belong to the family of zeolites, may form a plausible storage reservoir of methane in the martian subsurface. Because of the existence of many volcanic terrains, zeolites are expected to be widespread on Mars and their Global Equivalent Layer may range up to more than ∼ 1 km, according to the most optimistic estimates. If the martian methane present in chabazite and clinoptilolite is directly sourced from an abiotic source in the subsurface, the destabilization of a localized layer of a few millimeters per year may be sufficient to explain the current observations. The sporadic release of methane from these zeolites requires that they also remained isolated from the atmosphere during its evolution. The methane release over the ages could be due to several mechanisms such as impacts, seismic activity or erosion. If the methane outgassing from excavated chabazite and/or clinoptilolite prevails on Mars, then the presence of these zeolites around Gale Crater could explain the variation of methane level observed by Mars Science Laboratory.

¹Steven B. Simon, ^1,2Stephen R. Sutton, ^{1, 3}Lawrence Grossman
Geochimica et Cosmochmica Acta (in Press)  Link to Article [doi:10.1016/j.gca.2016.06.013]
¹Dept. of the Geophysical Sciences, 5734 S. Ellis Ave, The University of Chicago, Chicago, IL 60637
²Center for Advanced Radiation Sources (CARS), 5640 S. Ellis Ave, The University of Chicago, Chicago, IL 60637
³The Enrico Fermi Institute, 5640 S. Ellis Ave, The University of Chicago, Chicago, IL 60637
Copyright Elsevier

One way to better understand processes related to chondrite metamorphism is to evaluate changes in chondrite features as a function of petrologic type. Toward this end the valence and coordination of Ti in olivine and pyroxene in suites of ordinary (H, L, and LL) and enstatite (EH and EL) chondrites of types 3 through 6 have been determined with XANES spectroscopy. Trivalent Ti, typically 10-40% of the Ti in the analytical volumes, was found in ordinary chondrites of all types, despite the stability of oxidized iron in the samples. Average valences and the proportions of Ti that are in tetrahedral coordination generally decrease with increasing grade between types 3.0 and 3.5, increase from 3.5 to 4, and then level off. These trends are consistent with previous studies of chondrite oxidation states using other methods, except here the onset of oxidation is observed at a lower type, ∼3.5, than previously indicated (4). These results are also consistent with previous suggestions that oxidation of higher-grade ordinary chondrite samples involved exposure to aqueous fluids from melting of accreted ice. In the enstatite chondrites, typically 20-90% of the Ti is trivalent Ti, so it is reduced compared to Ti in the ordinary chondrites. Valence decreases slightly from petrologic type 3 to 4 and increases from 4 to 6, but no increases in tetrahedral coordination with petrologic type are observed, indicating a redox environment or process distinct from that of ordinary chondrite metamorphism. The presence of Ti4+ in the E chondrites supports previous suggestions that they formed from oxidized precursors that underwent reduction. Unlike ordinary chondrites, enstatite chondrites are thought to have been derived from a body or bodies that did not accrete ice, which could account for their different valence-coordination-petrologic type relationships. The hypothesis, based on observations of unmetamorphosed chondrules and supported by laboratory experiments, that equilibration of Ti valence is sluggish compared to that of Fe could account for the coexistence of reduced Ti and oxidized Fe seen in chondrites of all petrologic types.

¹Devin L. Schrader, ²Jemma Davidson, ¹Timothy J. McCoy
Geochimica et Cosmochimica Acta (in Press) Link to Article [doi:10.1016/j.gca.2016.06.012]
¹Department of Mineral Sciences, National Museum of Natural History, Smithsonian Institution, 10[th] & Constitution Avenue NW, Washington, D.C. 20560-0119, USA
²Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road NW, Washington, DC 20015-1305, USA
Copyright Elsevier

By investigating the compositional and textural evolution of sulfides within a wide range of relatively pristine, aqueously altered, and thermally metamorphosed chondrites we constrain the equilibration temperatures of sulfide minerals and compare them to the metamorphic history of their host meteorite. Sulfides in Mighei-like carbonaceous chondrites are complex as they equilibrated mostly between 100 and 135°C, but some may have equilibrated at temperatures up to 600°C. This is consistent with some CM chondrite sulfides forming at high temperature during chondrule cooling and others during low-temperature aqueous alteration and/or annealing. Karoonda-like carbonaceous chondrite sulfides equilibrated between 500 and 230°C, which is consistent with formation during cooling and annealing after thermal metamorphism. Sulfides in the LL chondrites equilibrated between 600 and 230°C, and are consistent with formation during chondrule cooling for Semarkona (LL3.00) and during cooling after thermal metamorphism for the equilibrated samples (types 4–6). Sulfides in the Rumuruti-like (R) chondrites equilibrated between 600 and 500°C, and are consistent with formation after thermal metamorphism. The sulfides within the brachinite equilibrated between 600 and 400°C, consistent with formation during cooling after thermal metamorphism.

Contrary to the assertion that pentlandite is solely the product of low-temperature aqueous alteration in many chondrite groups, this study suggests that most sulfides in chondrites are formed at or upon cooling from high-temperature. The evaluation of a single mineral system within samples that retain petrographic context is vital to the interpretation of formation and alteration processes recorded by small extraterrestrial samples, such as those that have been returned by the spacecraft missions Stardust and Hayabusa and will be returned by OSIRIS-REx and Hayabusa2.

¹Richard V. Morris et al. (>10)*
Proceedings for the National Academy of Sciences (in Press) Link to Article [doi: 10.1073/pnas.1607098113]
¹NASA Johnson Space Center, Houston, TX 77058
*Find the extensive, full author and affiliation list on the publishers website

Tridymite, a low-pressure, high-temperature (>870 °C) SiO2 polymorph, was detected in a drill sample of laminated mudstone (Buckskin) at Marias Pass in Gale crater, Mars, by the Chemistry and Mineralogy X-ray diffraction instrument onboard the Mars Science Laboratory rover Curiosity. The tridymitic mudstone has ∼40 wt.% crystalline and ∼60 wt.% X-ray amorphous material and a bulk composition with ∼74 wt.% SiO2 (Alpha Particle X-Ray Spectrometer analysis). Plagioclase (∼17 wt.% of bulk sample), tridymite (∼14 wt.%), sanidine (∼3 wt.%), cation-deficient magnetite (∼3 wt.%), cristobalite (∼2 wt.%), and anhydrite (∼1 wt.%) are the mudstone crystalline minerals. Amorphous material is silica-rich (∼39 wt.% opal-A and/or high-SiO2 glass and opal-CT), volatile-bearing (16 wt.% mixed cation sulfates, phosphates, and chlorides−perchlorates−chlorates), and has minor TiO2 and Fe2O3T oxides (∼5 wt.%). Rietveld refinement yielded a monoclinic structural model for a well-crystalline tridymite, consistent with high formation temperatures. Terrestrial tridymite is commonly associated with silicic volcanism, and detritus from such volcanism in a “Lake Gale” catchment environment can account for Buckskin’s tridymite, cristobalite, feldspar, and any residual high-SiO2 glass. These cogenetic detrital phases are possibly sourced from the Gale crater wall/rim/central peak. Opaline silica could form during diagenesis from high-SiO2 glass, as amorphous precipitated silica, or as a residue of acidic leaching in the sediment source region or at Marias Pass. The amorphous mixed-cation salts and oxides and possibly the crystalline magnetite (otherwise detrital) are primary precipitates and/or their diagenesis products derived from multiple infiltrations of aqueous solutions having variable compositions, temperatures, and acidities. Anhydrite is post lithification fracture/vein fill.

^1,2B. Schmitz, ³Q. -Z. Yin, ³M. E. Sanborn, ¹M. Tassinari, ²C. E. Caplan, ²G. R. Huss
Nature Communications 7,11851      Link to Article [doi:10.1038/ncomms11851]
¹Astrogeobiology Laboratory, Department of Physics, Lund University, 221 00 Lund, Sweden
²Hawai’i Institute of Geophysics and Planetology, University of Hawai’i at Manoa, Honolulu, Hawaii 96822, USA
³Department of Earth and Planetary Sciences, University of California at Davis, Davis, California 95616, USA

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