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.

^1,2AlSalhi M.S.,²Masilamani V.,³Alarifi N.,^1,2Aslam Farooq W.,^1,2Atif M.,¹Ramay S.,¹Saeed Althobaiti H.,⁴Anwar S.,³Elkhedr I.,³Abuamarah B.A.
Journal of King Saud University 33, 101341 Link to Article [DOI
10.1016/j.jksus.2021.101341]
¹Physics and Astronomy Department, College of Science, King Saud University, Riyadh, Saudi Arabia
²Research Chair for Laser Diagnosis of Cancer, King Saud University, Riyadh, Saudi Arabia
³Department of Geology and Geophysics, College of Science King Saud University, Riyadh, Saudi Arabia
⁴Industrial Engineering Department, College of Engineering, King Saud University, P.O. Box 800, Riyadh, 11421, Saudi Arabia

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

^1,2Wouters M.,¹Rahman S.,³Myamoto H.,^1,4Tran N.N.,^1,5Hessel V.
Separation and Purification Technology 260, 118238 Link to Article [DOI
10.1016/j.seppur.2020.118238]
¹School of Chemical Engineering and Advanced Materials, University of Adelaide, Australia
²Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, Netherlands
³Department of Systems Innovation, The University of Tokyo, Japan
⁴Department of Chemical Engineering, Can Tho University, Viet Nam
⁵School of Engineering, University of Warwick, United Kingdom

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¹Kalpana M.S.,¹Babu E.V.S.S.K.,²Mani D.,³Tripathi R.P.,⁴Bhandari N.
Planetary and Space Science 198, 105177 Link to Article [DOI
10.1016/j.pss.2021.105177]
¹National Geophysical Research Institute (Council of Scientific and Industrial Research), Hyderabad, 500007, India
²Centre for Earth, Ocean and Atmospheric Sciences (CEOAS), University of Hyderabad, Gachibowli, Hyderabad, 500046, India
³78, BGKT Extension, Jodhpur, 342005, India
⁴Science and Spirituality Research Institute, Navrangpura, Ahmedabad, 380009, India

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

¹Fredrik Terfelt,^1,2Birger Schmitz
Proceedings of the National Academy of Sciences of teh United States of America 118, e2020977118 Link to Article [https://doi.org/10.1073/pnas.2020977118]
¹Astrogeobiology Laboratory, Department of Physics, Lund University, 221 00 Lund, Sweden;
²Robert A. Pritzker Center for Meteoritics and Polar Studies, Negaunee Integrative Research Center, Field Museum of Natural History, Chicago, IL 60605

The meteoritic material falling on Earth is believed to derive from large break-up or cratering events in the asteroid belt. The flux of extraterrestrial material would then vary in accordance with the timing of such asteroid family-forming events. In order to validate this, we investigated marine sediments representing 15 time-windows in the Phanerozoic for content of micrometeoritic relict chrome-spinel grains (>32 μm). We compare these data with the timing of the 15 largest break-up events involving chrome-spinel–bearing asteroids (S- and V-types). Unexpectedly, our Phanerozoic time windows show a stable flux dominated by ordinary chondrites similar to today’s flux. Only in the mid-Ordovician, in connection with the break-up of the L-chondrite parent body, do we observe an anomalous micrometeorite regime with a two to three orders-of-magnitude increase in the flux of L-chondritic chrome-spinel grains to Earth. This corresponds to a one order-of-magnitude excess in the number of impact craters in the mid-Ordovician following the L-chondrite break-up, the only resolvable peak in Phanerozoic cratering rates indicative of an asteroid shower. We argue that meteorites and small (<1-km-sized) asteroids impacting Earth mainly sample a very small region of orbital space in the asteroid belt. This selectiveness has been remarkably stable over the past 500 Ma.

^1,2Gözen Ertem,³Daniel P.Glavin,⁴Robert P.Volpe,⁵Christopher P.McKay
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2021.114540]
¹SETI Institute, Carl Sagan Center, Mountain View, CA 94043, USA
²Department of Atmospheric and Oceanic Science, University of Maryland, College Park, MD 20742, USA
³NASA Goddard Space Flight Center, Solar System Exploration Division, Greenbelt, MD, USA
⁴Uniformed Services University of the Health Sciences, Bethesda, MD 20814, USA
⁵Space Science Division, NASA Ames Research Center, Moffett Field, CA 94035, USA
Copyright Elsevier

Organic compounds have been delivered to the surface of Mars via meteorites, comets and interplanetary dust particles for billions of years. Determining the effects of high energy radiation and galactic cosmic radiation (GCR) on these organic compounds is critical for understanding the potential for the preservation of organic molecules associated with past or present life, and where to look for possible chemical bio- signatures during future Mars missions. Understanding how these effects are attenuated by the mineral matrix and the depth at which they are buried have been challenging to determine in situ on Mars. There have been very few experimental studies on the survival of organic compounds under radiation from a gamma source under realistic conditions, and their interpretation until now has been difficult due to the lack of data for actual radiation levels on Mars. Using the in-situ data obtained by the MSL/RAD instrument to anchor the dose calculations, here we show that the N-heterocycles purine and uracil, crucial components of biochemical processes in extant living systems, mixed with calcite, anhydrite, and kaolinite as Mars analogue minerals can survive the effects of radiation with a dose corresponding to ~500,000 years on Martian surface. The extent of survival varied not only with the nature of the organic compound, but its depth from the surface. These results provide new experimental data for the degree of protection offered by the regolith, in conjunction with minerals, for organic compounds that may be present on Mars.

¹Tak Kunihiro,¹Tsutomu Ota,¹Masahiro Yamanaka,¹Christian Potiszil,¹Eizo Nakamura
Meteoritics & Planatary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13665]
¹The Pheasant Memorial Laboratory, Institute for Planetary Materials, Okayama University, Yamada 827, Misasa, Tottori, 682-0193 Japan
Published by arrangemment with John Wiley & Sons

Sample return missions represent great opportunities to study terrestrially uncontaminated solar system materials. However, the size of returned samples will be limited, and thus, it is necessary to understand the most appropriate techniques to apply. Accordingly, the sensitivity of laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) and secondary ion mass spectrometry (SIMS) was compared through the analyses of trace elements in reference materials and the Allende CV3 chondrite. While the SIMS method was found to be more sensitive than the laser method toward all elements of interest, the LA-ICPMS appears to be more suitable in terms of precision for certain elements. Using both analytical techniques, we measured chemical composition of an Allende chondrule and its igneous rim. These data were used to understand the nature of the reservoir that interacted with the host chondrule during formation of its igneous rim. We find that the igneous rim is enriched in silica, alkalis, and rare earth elements compared to the host chondrule. We suggest that the igneous rim could be explained by melting of a mixture of the chondrule-like and REE-enriched CAI-like precursors that accreted on the surface of the host chondrule followed by gas-melt interaction with a silica- and alkali-rich gas. Alternatively, these observations could be interpreted as a result of interaction between the chondrule and the melt resulting from partial melting of a pre-existing planetesimal in the early stages of its differentiation.

^1,2,3,4Damaris Montano,^1,5Marta Gasparrini,^2,3Axel Gerdes,⁵Giovanna Della Porta,^2,3Richard Albert
Earth and Planetary Science Letters 568, 117011 Link to Article [https://doi.org/10.1016/j.epsl.2021.117011]
¹IFP Energies nouvelles, 1-4 avenue de Bois-Préau, 92852, Rueil-Malmaison, France
²Institut für Geowissenschaften, Goethe University Frankfurt, Altenhöferallee 1, 60438 Frankfurt am Main, Germany
³Frankfurt Isotope and Element Research Center (FIERCE), Goethe University Frankfurt, Frankfurt am Main, Germany
⁴Sorbonne Université; ED 398 – GRNE, 4, place Jussieu, 75252 Paris, France
⁵Università degli Studi di Milano; Dipartimento di Scienze della Terra “Ardito Desio”, via Mangiagalli 34, 20133 Milan, Italy
Copyright Elsevier

The Nördlinger Ries Crater lacustrine basin (South-West Germany), formed by a meteorite impact in the Miocene (Langhian; ∼14.9 Ma), offers a well-established geological framework to understand the strengths and limitations of U-Pb LA-ICPMS (in situ Laser Ablation-Inductively Coupled Plasma Mass Spectrometry) geochronology as chronostratigraphic tool for lacustrine (and more broadly continental) carbonates. The post-impact deposits include siliciclastic basinal facies at the lake centre and carbonate facies at the lake margins, coevally deposited in a time window of >1.2 and <2 Ma. Depositional and diagenetic carbonate phases (micrites and calcite cements) were investigated from three marginal carbonate facies (Hainsfarth bioherm, Adlersberg bioherm and Wallerstein mound). Petrography combined with C and O stable isotope analyses indicate that most depositional and early diagenetic carbonates preserved pristine geochemical compositions and thus the U-Pb system should reflect the timing of original precipitation. In total, 22 U-Pb ages were obtained on 10 different carbonate phases from five samples. The reproducibility and accuracy of the U-Pb (LA-ICPMS) method were estimated to be down to 1.5% based on repeated analyses of a secondary standard (speleothem calcite ASH-15d) and propagated to the obtained ages. Micrites from the Hainsfarth, Adlersberg and Wallerstein facies yielded ages of 13.90 ± 0.25, 14.14 ± 0.20 and 14.33 ± 0.27 Ma, respectively, which overlap within uncertainties, and are consistent with the weighted average age of 14.30 ± 0.20 Ma obtained from all the preserved depositional and early diagenetic phases. Data indicate that sedimentation started shortly after the impact and persisted for >1.2 and <2 Ma, in agreement with previous constraints from literature, therefore validating the accuracy of the applied method. Later calcite cements were dated at 13.2 ± 1.1 (), 10.2 ± 2.7 and 9.51 ± 0.77 Ma, implying multiple post-depositional fluid events. This study demonstrates the great potential of the U-Pb method for chronostratigraphy in continental systems, where correlations between time-equivalent lateral facies are often out of reach. In Miocene deposits the method yields a time resolution within the 3rd order depositional sequences (0.5–5 Ma).