¹Chernonozhkin S.M.,²McKibbin S.J.,³Goderis S.,¹Van Malderen S.J.M.,³Claeys P.,¹Vanhaecke F.
Chemical Geology 562, 119996 Link to Article [DOI 10.1016/j.chemgeo.2020.119996]
¹Ghent University, Department of Chemistry, Atomic & Mass Spectrometry – A&MS Research Unit, Campus Sterre, Krijgslaan, 281 – S12, Ghent, 9000, Belgium
²Geowissenschaftliches Zentrum, Abteilung Isotopengeologie, Georg-August-Universität Göttingen, Goldschmidtstraße 1, Göttingen, 37073, Germany
³Vrije Universiteit Brussel, Analytical, Environmental, and Geo-Chemistry, Pleinlaan 2, Brussels, 1050, Belgium

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^1,2Pourkhorsandi H.,^1,3Debaille V.a,Armytage R.M.G.,^1,4van Ginneken M.,²Rochette P.,²Gattacceca J.
Chemical Geology 562, 120056 Link to Article [DOI 10.1016/j.chemgeo.2020.120056]
¹Laboratoire G-Time, Université Libre de Bruxelles, 160/02, 50, Av. F.D. Roosevelt, Brussels, 1050, Belgium
²Aix-Marseille Univ, CNRS, IRD, INRAE, CEREGE, Aix-en-Provence, France
³Jacobs/JETS, NASA Johnson Space Center, 2101 NASA Parkway, Mailcode XI3, Houston, 77058, United States
⁴Royal Belgium Institute of Natural Sciences, rue Vautier 29, Bruxelles, B-1000, Belgium

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¹Garcia-Florentino C.,¹Torre-Fdez I.,¹Ruiz-Galende P.,¹Aramendia J.,¹Castro K.,¹Arana G.,²Maguregui M.,¹Ortiz de Vallejuelo S.F.,¹Madariaga J.M.
Talanta 224, 121863 Link to Article [DOI 10.1016/j.talanta.2020.121863]
¹Department of Analytical Chemistry, Faculty of Science and Technology, University of the Basque Country UPV/EHU, Barrio Sarriena S/n, Leioa, 48940, Spain
²Department of Analytical Chemistry, Faculty of Pharmacy, University of the Basque Country UPV/EHU, P.O. Box 450, Vitoria-Gasteiz, 01080, Spain

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^1,2,3,4Zhang C.,^1,3Miao B.,⁵He H.,^1,3Chen H.,⁵Ranjith P.M.,⁴Xie Q.
Minerals 11, 279 Link to Article [DOI 10.3390/min11030279]
¹Institution of Meteorites and Planetary Materials Research, Guilin University of Technology, Guilin, 541006, China
²Key Laboratory of Lunar and Deep Space Exploration, Chinese Academy of Sciences, Beijing, 100029, China
³Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration, Guilin University of Technology, Guilin, 541006, China
⁴College of Environmental Science and Engineering, Guilin University of Technology, Guilin, 541006, China
⁵Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, 100029, China

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¹Vincenzo Stagno,²Luca Bindi,⁴Sota Takagi,⁴Atsushi Kyono
Progress in Earth and Planetary Science 8, 27 Link to Article [DOI
https://doi.org/10.1186/s40645-021-00421-y%5D
¹Dipartimento di Scienze della Terra, Università La Sapienza, P.zle Aldo Moro 5, I-00185, Rome, Italy
²Dipartimento di Scienze della Terra, Università di Firenze, Via La Pira 4, I-50121, Florence, Italy
³Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Ibaraki, Japan
⁴Division of Earth Evolution Sciences, Graduate School of Life and Environmental Sciences, University of Tsukuba, Ibaraki, Japan

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^1,2Feng Yin,³Thomas G. Sharp,²Ming Chen
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13702]
¹Department of Geology, Hunan University of Science and Technology, Xiangtan, 411201 China
²Guangdong Provincial Key Laboratory of Mineral Physics and Materials, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, 510640 China
³School of Earth and Space Exploration, Arizona State University, Tempe, Arizona, 85287 USA
Published by arrangement with John Wiley & Sons

Coesite embedded in silica glass in suevite from the Xiuyan crater has been studied by scanning and transmission electron microscopy to better understand the mechanisms at formation of coesite. Coesite grains in this study mainly occur as vein-like aggregates (10–40 μm in width) and irregular aggregates (IAs; <40 μm in size). Both aggregate types are composed of subhedral to anhedral coesite crystals with random orientations. Most of the crystals are 100–1000 nm in size, and some display twinning. The shape, twinning, and random orientation of coesite crystals suggest rapid crystallization in amorphous silica that became supercooled. The center of vein-like aggregates crystallized from localized silica melt within diaplectic silica glass, whereas the rim of vein-like aggregates and IAs crystallized from diaplectic silica glass. The size and amount of coesite crystals in the vein-like aggregate vary greatly from the rim to the center of such veins. Microstructures suggest that the crystals nucleated heterogeneously at the outer rim of the vein and nucleated homogeneously within the vein. IAs do not show any changes in size and amount of coesite crystals from the rim to core of such aggregates. Coesite crystals in IAs primarily nucleate heterogeneously in diaplectic silica glass. It can be concluded that vein-like coesite aggregates are mainly formed by crystallization from silica melt, and irregular coesite aggregates should be formed by solid-state transformation of diaplectic silica glass.

¹Bradley T. De Gregorio,²Jessica Opsahl-Ong,³Lysa Chizmadia,¹Todd H. Brintlinger,⁴Andrew J. Westphal,¹Rhonda M. Stroud
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13655]
¹Materials Science and Technology Division, U.S. Naval Research Laboratory, Washington, D.C., 20375 USA
²American Society for Engineering Education, Science & Engineering Apprenticeship Program, Washington, D.C., 20036 USA
³Department of Geology and Physics, Georgia Southwestern State University, Americus, Georgia, 31709 USA
⁴Space Sciences Laboratory, University of California Berkeley, Berkeley, California, 94720 USA
Published by arrangement with John Wiley & Sons

The NASA Stardust Interstellar Dust collection provides our current best sample set for direct laboratory analysis of dust grains from the contemporary interstellar dust stream. While a handful of likely interstellar dust grains were identified within the silica aerogel collection media, interstellar dust also impacted Al foils covering the collector frame. Locating these rare impacts requires labor-intensive collection and examination of tens of thousands of high-resolution SEM images. Here, we implement a Python-based algorithm to dramatically reduce the human time investment needed to locate impact craters. The algorithm employs a circular Hough transform to identify circular features in the foil images, followed by several tests to detect characteristic morphological features of impact craters—a dark center and a bright rim, with inclusion of multi-core processing capabilities to significantly increase processing speed. For most data sets, the code produced a pool of potential crater candidates in 1–5% of the input images, producing a more manageable subset of images for a human expert to review. We used this code to locate 31 impact craters across 12 Stardust interstellar foils, 25 of which were located on three adjacent foils, I1008W,1, I1009N,1, and I1020W,1. Many impacts on these foils formed shallow, oblique craters, with residue compositions consistent with solar cell glass and orientations consistent with debris ejected from the spacecraft solar cells. The code can be integrated into future searches for Stardust interstellar grain impacts and can be implemented as a general utility for dust impact studies on spacecraft materials.

¹Toshiki Koga,²Eric T. Parker,^2,3Hannah L. McLain,^2,3José C. Aponte,²Jamie E. Elsila,²Jason P. Dworkin,²Daniel P. Glavin,¹Hiroshi Naraoka
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13661]
¹Department of Earth and Planetary Sciences, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, 819-0395 Japan
²NASA Goddard Space Flight Center, Greenbelt, Maryland, 20771 USA
³Catholic University of America, Washington, District of Columbia, 20064 USA
Published by arrangement with John Wiley & Sons

The abundances, distributions, and enantiomeric ratios of a family of three- and four-carbon hydroxy amino acids (HAAs) were investigated in extracts of five CM and four CR carbonaceous chondrites by gas chromatography-mass spectrometry analyses. HAAs were detected in both the acid hydrolysates of the hot water extracts and the 6 M HCl extracts of all the CM and CR chondrites analyzed here with total hot water and HCl extractable HAA concentrations ranging from 6.94 to 315 nmol g−1. The HAA analyses performed in this study revealed: (1) the combined (hot water + HCl) extracts of CR2 chondrites contained greater abundances of α-HAAs than that of CM2 chondrites and (2) the combined extracts of CM and CR chondrites contained roughly similar abundances of β- and γ-HAAs. Application of the new GC-MS method developed here resulted in the first successful chromatographic resolution of the enantiomers of an α-dialkyl HAA, d,l-α-methylserine, in carbonaceous chondrite extracts. Meteoritic α-methylserine was found to be mostly racemic within error and did not show l-enantiomeric excesses correlating with the degree of aqueous alteration, a phenomenon observed in meteoritic isovaline, another α-dialkyl amino acid. The HAAs identified in CM and CR chondrite extracts could have been produced during parent body alteration from the Strecker cyanohydrin reaction (for α-HAAs) and an ammonia-involved formose-like reaction (for β-, and γ-HAAs).

¹M.Weyrauch,²J.Zipfel,¹S.Weyer
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2021.06.009]
¹Institut für Mineralogie, Leibniz Universität Hannover, Callinstr. 3, 30167 Hannover, Germany
²Senckenberg Forschungsinstitut und Naturmuseum Frankfurt, 60325 Frankfurt, Germany
Copyright Elsevier

Due to similarities in chemical composition and common Cr, Ti, N and O isotope trends, the metal-rich CR, CH and CB chondrites, often referred to as CR clan chondrites, are thought to be related to each other. This study aims to shed light on this relationship by the investigation of Fe and Ni isotope and trace element compositions of metal grains from CR and CH chondrites, in order to compare the results with previously reported data from CB chondrite metal. In situ trace element and Fe and Ni isotope analyses were conducted by femtosecond-laser ablation-(multicollector-)inductively coupled plasma-mass spectrometry (fs-LA-(MC-)ICP-MS). Furthermore, bulk CB metal and silicate separates were analyzed by solution MC-ICP-MS.

Chemical compositions of metal grains in metal-rich chondrites are depleted in moderately volatile siderophile elements relative to the solar values with the exception of Pd. Such element abundance patterns are consistent with models of incomplete condensation from a gas with solar composition. Both, zoned and unzoned metal grains from CH and CB chondrites display very similar Fe and Ni isotopes compositions, indicating they likely formed within the same event, during non-equilibrium fractional condensation from an impact-induced vapor plume. This scenario is also supported by non-equilibrium Fe isotope signatures between bulk CB metal and silicate. Zoned metal grains likely formed in the fast-cooling outer shell region of the plume and are dominated by kinetic fractionation, resulting in isotopically light cores, while unzoned metal grains condensed under nearly equilibrium conditions, likely in the slow-cooling interior of the plume. Variability in Fe and Ni isotope compositions among different unzoned grains may be explained by 1) a kinetic component during their condensation and/or 2) evaporation and condensation-driven reservoir effects in the plume, which resulted in light and heavy isotope signatures, respectively. Textural differences between CH and CBb are most pronounced in the mean grain size, which may be attributed to grain-size sorting. Such a process could also explain the lack of zoned metals in CBa chondrites, as zoned metal grains in CBb and CH chondrites are by more than a magnitude smaller than the mean metal grain size of CBa chondrites.

In CR chondrites, metal within chondrules likely formed by fractional condensation from a solar type gas followed by subsequent melting leading to equilibration with chondrule silicates. Larger isolated metal grains from the matrix are less processed, and apparently escaped silicate equilibration. Those metal grains are indistinguishable from unzoned grains in CH and CB chondrites in trace elements and Fe and Ni isotopic compositions albeit with a slightly narrower compositional range. Based on these findings we conclude that metal precursors in CR chondrites are strongly related to unzoned metal in CH, and CB chondrites and possibly share a common origin. This metal component would be smallest in CR chondrites, larger in CH and dominant in CB chondrites which is also consistent with age constraints and isotopic anomalies observed in CR clan chondrites.

¹A.Moreras-Marti,^1,2M.Fox-Powell,¹E.Stueeken,^1,3T.Di Rocco,¹T.Galloway,^4,5G.R.Osinski,¹C.R.Cousins,¹A.L.Zerkle
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2021.06.007]
¹School of Earth and Environmental Sciences and Centre for Exoplanet Science, University of St Andrews, Irvine Building, North Street, KY169AL, UK
²Current address: AstrobiologyOU, Open University, Walton Hall, Milton Keynes MK7 6AA, UK
³Current address: Isotope Geology Department, Georg-August-Universitat Gottingen, Wilhelmsplatz 1, 37073 Gottingen, Germany
⁴Department of Earth Sciences, University of Western Ontario, London, Ontario, Canada
⁵Institute for Earth and Space Exploration, University of Western Ontario, London, Ontario, Canada
Copyright Elsevier

In this study, we present quadruple sulfur isotope values (QSI: ³²S,³³S,³⁴S,³⁶S) measured in sediments from two sulfur-rich Mars analogue environments: i) the glacially-fed hydrothermal pools in Iceland (Kerlingarfjöll and Kverkfjöll), and ii) the Lost Hammer hypersaline spring from Axel Heiberg Island, Nunavut, Canada. The localities host different physical and geochemical characteristics, including aqueous geochemistry, volcanic input, temperature, pH and salinity. The δ³⁴S values of sulfur compounds from the Lost Hammer hypersaline spring exhibit large fractionations typical of microbial sulfate reduction (MSR) with or without additional oxidative sulfur cycling and microbial sulfur disproportionation (MSD) (³⁴ε_SO4-CRS from -49.5 to -43.5 ‰), contrary to the small S isotope fractionations reported for the Icelandic hydrothermal sites (³⁴ε_SO4-CRS from –9.9 to -0.7 ‰). Lost Hammer minor S isotope values (Δ³³S and Δ³⁶S), interpreted within the context of a sulfur cycling box model, are consistent with a biogeochemical S cycle including both MSR and MSD. In contrast, the small range in δ³⁴S values within the Iceland hydrothermal pools are consistent with a large volcanic H₂S flux and minimal biological S cycling. The minor S isotope values recorded in the hydrothermal pools, however, indicate further biogeochemical sulfur cycling. Our results demonstrate that contrasting physical and chemical characteristics between sites support different microbial S cycling processes, as recorded in the QSI sedimentary values. The QSI data and the derived models support the strong potential for QSI values to be used as biosignatures in the search for life in Martian S-rich environments. These results also suggests that extreme, metabolic energy-limited environments with low abiotic sulfur fluxes could be more likely to produce unequivocal biological QSI signals than those with more moderate conditions or abundant available energy. This finding carries significant implications for targeting sites on Mars for in situ measurements or future sample return missions.