¹Andrew D. Langendam,¹Andrew G. Tomkins,²Katy A. Evans,³Nicholas C. Wilson,³Colin M. MacRae,⁴Natasha R. Stephen,³Aaron Torpy
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13755]
¹School of Earth, Atmosphere and Environment, Monash University, Melbourne, Victoria, 3800 Australia
²Department of Applied Geology, Curtin University, Perth, Western Australia, 6845 Australia
³Microbeam Laboratory, CSIRO Mineral Resources, Clayton, Victoria, 3169 Australia
⁴Plymouth Electron Microscopy Centre, University of Plymouth, Drake Circus, Plymouth, Devon, PL4 8AA UK
Published by arrangement with John Wiley & Sons

Ureilite meteorites contain regions of localized olivine reduction to Fe metal widely accepted to have formed by redox reactions involving oxidation of graphite, a process known as secondary smelting. However, the possibility that other reductants might be responsible for this process has largely been ignored. Here, 17 ureilite samples are investigated to assess whether, instead of smelting involving only solid reactants, a CHOS gas/fluid could have caused much of the smelting. Features consistent with gas- or supercritical fluid-driven reduction were found to be abundant in all ureilites, such as fracture-focused smelting, plume-like reaction fronts, and addition of sulfur. Many of these are developed away from graphite. In some ureilites, it is clear that the redox process coincided with annealing, and we suggest that this was caused by enhanced diffusion facilitated by a higher density gas or fluid, rather than slow cooling, which requires elevated pressure. The C-CO and CH4-C-H2O buffers were modeled to examine their relative potential to drive reduction. This modeling showed that a CH4-rich fluid is able to produce the observed mineral compositions at elevated pressures. This result, coupled with the observed textures, is used to develop a likely series of reactions. We suggest that at higher pressures, a H2-CH4-H2S-S2-bearing fluid-like phase, and at lower pressures, an equivalent gas, were able to infiltrate grain boundaries and fine fractures. Sulfidation to form troilite may have acted to maintain highly reduced gas/fluid conditions. The presence of hydrocarbons in ureilites supports a role for reduction driven by CHOS gas/fluid.

^1,2Jon M. Friedrich,^2,3,4Michael K. Weisberg,¹Lucille C. Malecek,²C. E. Nehru
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13751]
¹Department of Chemistry, Fordham University, Bronx, New York, 10458 USA
²Department of Earth and Planetary Sciences, American Museum of Natural History, New York, New York, 10024 USA
³Department of Physical Sciences, Kingsborough Community College, Brooklyn, New York, 11235 USA
⁴Graduate Center of the City University of New York, New York, New York, 10016 USA
Publsihed by arrangement with John Wiley & Sons

We use X-ray microtomography (µCT) and digital data extraction techniques for the three-dimensional (3-D) petrographic investigation of the Tucson meteorite. Our results show that the silicate-free metal regions in Tucson exist as discrete objects surrounded by a continuous silicate-containing metal “matrix.” Volumetric measurements of the silicate-free metal regions in Tucson demonstrate that they are akin to the sizes of metallic nodules found in CBa chondrites. Silicate-free metal regions have bladed or prolate shapes. Nonmetallic minerals in Tucson are predominately equant or prolate in shape. Nonmetallic mineral grains and silicate-free metal regions in Tucson share a common orientation and are part of a petrofabric composed of a lineation. Any foliation in Tucson is weakly developed. We interpret the petrofabric as being the result of a single event on the Tucson parent body, during which Tucson experienced shearing forces. Our 3-D petrographic investigation supports the idea that Tucson is an unusual member of the CR chondrite clan.

¹David A. Kring,²Martin J. Whitehouse,^1,3Martin Schmieder
Astrobiology (in Press) Link to Article [https://doi.org/10.1089/ast.2020.2286]
¹Lunar and Planetary Institute, Universities Space Research Association, Houston, Texas, USA
²Department of Geosciences, Swedish Museum of Natural History, Stockholm, Sweden
³HNU–Neu-Ulm University of Applied Sciences, Neu-Ulm, Germany

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^1,2,3Danielle N. Simkus,^2,3José C. Aponte,²Jamie E. Elsila,^2,3Hannah L. McLain,²Eric T. Parker,²Jason P. Dworkin,²Daniel P. Glavin
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13757]
¹NASA Postdoctoral Program at NASA Goddard Space Flight Center, Greenbelt, Maryland, 20771 USA
²Solar System Exploration Division, Code 690, NASA Goddard Space Flight Center, Greenbelt, Maryland, 20771 USA
³Department of Physics, Catholic University of America, Washington, D.C., 20064 USA
Published by arrangement with John Wiley & Sons

Investigating the organic contents of enstatite chondrite meteorites may offer insights into both early inner solar system and early Earth chemistry. Enstatite chondrite meteorites have highly reduced and anhydrous compositions, and their bulk isotopic compositions closely resemble terrestrial values, suggesting that their parent body asteroids accreted within the inner protoplanetary disk and were a primary contributor during Earth’s late accretion (Javoy, 1995; Piani et al., 2020). Here, we present the first report of amino acids in enstatite chondrite meteorite samples. Three EH3 meteorites were analyzed (Dominion Range [DOM] 14021, Larkman Nunatak [LAR] 12001, and Larkman Nunatak 06252). The acid-hydrolyzed water extracts of the meteorites contained low abundances (1.5–215.9 pmol g−1) of n-ω-amino acids (glycine, β-alanine, γ-amino-n-butyric acid [γ-ABA], δ-amino-n-valeric acid [δ-AVA], and ϵ-amino-n-caproic acid [ϵ-ACA]), but amino acids were not present above detection limits in the nonhydrolyzed samples. The low amino acid abundances and the predominance of n-ω-amino acids resemble amino acid distributions previously observed for thermally altered chondrites. These results suggest that the parent body asteroid was not conducive to the synthesis and/or preservation of α-amino acids, or free amino acids in general, and that EH3 chondrite-like material may not have been a primary contributor of diverse or abundant free amino acids to the early Earth.

¹Daniel P.Mason,¹Megan E.Elwood Madden
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2021.114759]
¹School of Geosciences, University of Oklahoma, 100 E Boyd St., Norman, OK, USA
Copyright Elsevier

Raman spectroscopy is an ideal tool to analyze the geochemistry and mineralogy of heterogenous mixtures of solids, liquid, and gases in situ, while maintaining planetary protection protocols. Here we characterize saturated CaCl2, MgCl2, MgSO4, Na2SO4, NaCl, and NaClO4 brines, as well as ultrapure water, and mixed MgSO4-NaCl, MgSO4-NaClO4, Na2SO4-NaCl, Na2SO4-NaClO4, and NaCl-NaClO4 brines from 200 K to 295 K to determine how changes in temperature affect spectral signatures of planetary analogue brines. The resulting reference dataset can be used to interpret spectra from future samples analyzed in situ on planetary bodies. Sulfate and perchlorate brines produced clear, distinct peaks associated with each polyatomic anion. While chloride brines did not produce anion peaks, subtle changes were observed in the OH-stretching region, suggesting changes to the molecular water vibration states due to complexation. Solid-liquid phase transitions were clearly observed in each of the solutions using both 785 nm (red) and 532 nm (green) excitation lasers, particularly in the OH-stretching region between 3000 and 4000 cm−1 with the 532 nm laser. Differences observed in the spectra of frozen sulfate brines suggest that cooling rates may influence the hydration state and/or crystallinity of the solid magnesium and sodium- sulfate salts. These experiments and the resulting spectral library will allow future researchers to use Raman spectroscopy to look for in situ melting, freezing, evaporation, and deliquescence as well as identify the composition of high salinity brines and their frozen products in a range of planetary environments, including permafrost and recurring slope lineae on Mars, potential ice and salt-rich regolith on asteroids such as Ceres, and ice shells and possible seeps or geysers on icy moons and other bodies.

¹Josefine A.M.Nanne,²Francis Nimmo,³Jeffrey N.Cuzzi,¹Thorsten Kleine
Earth and Planetary Science Letters 511, 44-54 Link to Article [https://doi.org/10.1016/j.epsl.2019.01.027]
¹Institut für Planetologie, University of Münster, Wilhelm-Klemm-Straße 10, 48149 Münster, Germany
²Department of Earth and Planetary Sciences, University of California Santa Cruz, Santa Cruz, CA 95064, USA
³Space Science Division, Ames Research Center, Moffett Field, CA 94035, USA
Copyright Elsevier

The isotopic composition of meteorites reveals a fundamental dichotomy between non-carbonaceous (NC) and carbonaceous (CC) meteorites. However, the origin of this dichotomy—whether it results from processes within the solar protoplanetary disk or is an inherited heterogeneity from the solar system’s parental molecular cloud—is not known. To evaluate the origin of the NC–CC dichotomy, we report Ni isotopic data for a comprehensive set of iron meteorites, with a special focus on groups that have not been analyzed before and belong to the CC group. The new Ni isotopic data demonstrate that the NC–CC dichotomy extends to Ni isotopes, and that CC meteorites are characterized by a ubiquitous 58Ni excess over NC meteorites. These data combined with prior observations reveal that, in general, the CC reservoir is characterized by an excess in nuclides produced in neutron-rich stellar environments, such as 50Ti, 54Cr, 58Ni, and r-process Mo isotopes. Because the NC–CC dichotomy exists for refractory (Ti, Mo) and non-refractory (Ni, Cr) elements, and is only evident for nuclides produced in specific, neutron-rich stellar environments, it neither reflects thermal processing of presolar carriers in the disk, nor the heterogeneous distribution of isotopically anomalous Ca–Al-rich inclusions (CAI). Instead, the NC–CC dichotomy reflects the distinct isotopic composition of later infalling material from the solar system’s parental molecular cloud, which affected the inner and outer regions of the disk differently. Simple models of the infall process by themselves can support either infall of increasingly NC-like material onto an initially CC-like disk, or infall of increasingly CC-like material in the absence of disk evolution by spreading. However, provided that CAIs formed close to the Sun, followed by rapid outward transport, their isotopic composition likely reflects that of the earliest infalling material, implying that the composition of the inner disk (i.e., the NC reservoir) is dominated by later infalling material, whereas the outer disk (i.e., the CC reservoir) preserved a compositional signature of the earliest disk. The isotopic difference between the inner and outer disk was likely maintained through the rapid formation of Jupiter, which prevented complete homogenization between material from inside (NC reservoir) and outside (CC reservoir) its orbit.

¹C.M.O’D.Alexander,²M.J.Nilges,¹G.D.Cody,³C.D.K.Herd
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2021.10.007]
¹Earth and Planets Laboratory, Carnegie Institution for Science, 5241 Broad Branch Road NW, Washington, DC 20015, USA
²EPR Laboratory, School of Chemical Sciences, Univ. Illinois at Urbana-Champaign, 505 S. Mathews Avenue, Urbana, IL 61801, USA
³Dept. Earth and Atmospheric Sciences, Univ. Alberta, Edmonton, Alberta T6G 2E3, Canada
Copyright Elsevier

The insoluble organic material (IOM) in primitive chondritic meteorites is very enriched in D (up to δD≈3500 ‰ in bulk). Based largely on a series of electron paramagnetic resonance (EPR) studies of IOM from three meteorites (Orgueil, Murchison and Tagish Lake), it has been suggested that these enrichments are the result of exchange with H2D+ in the solar nebula and that exchange with radicals in the IOM was particularly facile so that they are enormously enriched in D (δD≥95000 ‰). To try to test whether radicals are largely responsible for the D enrichments in IOM, we have used EPR to measure the radical concentrations (spins/g) and g-factors of 18 IOM separates from C1-2 chondrites of varying petrologic type and chemical group that have a much wider range of H isotopic compositions (δD≈600-3500 ‰) than in previous studies. We confirm the previous studies findings that IOM exhibits non-Curie law behavior and that it does not completely saturate even at microwave excitation powers of 200 mW. We also have obtained similar g-factor values. However, our IOM samples typically exhibit a lower and more limited range of spin concentrations, and smaller deviations from Curie law behavior than in previous studies. Nor do we observe correlations between bulk δD and either spins/g or non-Curie law behavior that would be expected if exchange between H2D+ and radicals, as previously proposed, was the cause of the D-enrichments in IOM. Indeed, in general the radical concentrations and the degree of non-Curie law behavior do not seem to correlate with any of the measured IOM properties, with chondrite group or parent body history (e.g., degree of aqueous alteration). The only exceptions are the IOM in four Tagish Lake lithologies whose spin concentrations increase with increasing degree of thermal processing as indicated by decreasing H/C and δD, and increasing aromaticity.

¹Tajana Schneiderman,²Luca Matrà,^3,4Alan P. Jackson,^5,6Grant M. Kennedy,⁷Quentin Kral,^8,9Sebastián Marino,¹⁰Karin I. Öberg,¹¹Kate Y. L. Su,¹⁰David J. Wilner,⁸Mark C. Wyatt
Nature 598, 425-428 Link to Article [https://doi.org/10.1038/s41586-021-03872-x]
¹Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA
²Centre for Astronomy, School of Physics, National University of Ireland Galway, Galway, Ireland
³Centre for Planetary Sciences, University of Toronto at Scarborough, Toronto, Ontario, Canada
⁴School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA
⁵Department of Physics, University of Warwick, Coventry, UK
⁶Centre for Exoplanets and Habitability, University of Warwick, Coventry, UK
⁷LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université Paris Diderot, Sorbonne Paris Cité, Meudon, France
⁸Institute of Astronomy, University of Cambridge, Cambridge, UK
⁹Jesus College, University of Cambridge, Cambridge, UK
¹⁰Center for Astrophysics | Harvard & Smithsonian, Cambridge, MA, USA
¹¹Steward Observatory, University of Arizona, Tucson, AZ, USA

We currently do not have a copyright agreement with this publisher and cannot display the abstract here

¹Deepali Singh,¹Priyadarshini Singh,¹Nidhi Roy,¹Saumitra Mukherjee
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2021.114757]
¹School of Environmental Sciences, Jawaharlal Nehru University, New Delhi 110067, India
Copyright Elsevier

The present study investigated an inter-crater depression, which is hypothesized to have been hydrologically active in the past. Mineralogical analysis of the putative lake was carried out to examine the presence of secondary minerals and decipher its aqueous alteration history. The basin was observed to be predominant in mono- and polyhydrated sulfates and hydrated silica with intermittent exposures of Al phyllosilicates such as montmorillonite and beidellite. Later, mineral profiling of the surrounding terrain was also carried out to infer the origin of these minerals. We recorded signatures of Mg-rich smectite (saponite) and Fe/Ca‑carbonate in crater rims and ejecta here, in addition to the minerals previously identified within the basin. Spectro-morphological examination of the entire region helped in understanding the emplacement of the minerals and construction of the life cycle of the lake. The contrasting environmental conditions required for the formation of these minerals suggest that the basin witnessed multiple hydrological cycles and that it was active for a long period of time. We propose the basin to be an endorheic playa with geologically complex terrain which may hold good biosignature preservation potential for future exploration missions. Finally, our preliminary exploration of the area highlights the importance of inter-crater depressions on Mars and their significance in water budgeting, even if a small percentage of them were hydrologically active.

¹Haijun Cao,^1,2Zongcheng Ling,¹Jian Chen,^1,2,3Xiaohui Fu,⁴Yongliao Zou
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13741]
¹Shandong Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, School of Space Science and Physics, Institute of Space Sciences, Shandong University, Weihai, Shandong, 264209 China
²CAS Center for Excellence in Comparative Planetology, Chinese Academy of Sciences, Hefei, China
³State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Taipa, Macau, China
⁴State Key Laboratory of Space Weather, National Space Science Center, Chinese Academy of Sciences, Beijing, 100190 China
Published by arrangement with John Wiley & Sons

Lunar meteorite Northwest Africa (NWA) 11460 has been classified as a polymict breccia, composed of feldspathic clasts, mafic-rich clasts (gabbroic and troctolitic fragments), granulites, and a wide range of impact melt breccias and dimict breccias. The non-mare clasts have chemical affinities in major element composition to the Apollo ferroan anorthosites (FAN) and magnesian-suite plutonic rocks. In contrast, incompatible trace element (ITE) compositions of the Mg-richer clasts are more consistent with those of FANs rather than magnesian-suite rocks. NWA 11460 has a Mg-rich feldspathic bulk composition (FeO = 4.53 wt%, Al2O3 = 25.87 wt%, and Mg# = 73.8) and relatively ITE-poor (i.e., Th = 0.31 ppm and Sm = 0.65 ppm) characteristics. Feldspathic impact melt materials are approximately similar in composition to the estimated composition for the upper feldspathic lunar crust (as defined by Korotev et al., 2003). The ITE-poor and Mg-rich characteristics different from Apollo 16 feldspathic impact melts indicate that this meteorite has been possibly derived from a region distal to the nearside lunar highlands. Our analysis further suggests that NWA 11460 most likely originated from the farside of the Moon. Compositionally, Mg-rich ITE-poor clasts within NWA 11460 as well as those observed in other feldspathic lunar meteorites (which probably came from many different lunar regions) reveal that Mg-rich rocks with low-ITE components represent an important constituent of lunar crustal rocks. The diversities of highly magnesian non-mare clasts and the low-ITE chemistry provide geochemical clues for the genetic relationship between KREEP components and magnesian plutonic magmatism on the lunar farside.