¹L.Chimiak,²J.Eiler,²A.Sessions,³C.Blumenfeld,⁴M.Klatte,⁵B.M.Stoltz
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2022.01.015]
¹Department of Geological Sciences, University of Colorado—Boulder, Boulder, CO, 80309 USA
²Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, 91125, USA
³Dantari, Inc, Westlake Villiage, CA, 91361, USA
⁴Dottikon Exlusive Synthesis AG, Dottikon, 5605, CH
⁵Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA, 91125, USA
Copyright Elsevier

Strecker synthesis creates α–amino acids from prebiotically plausible substrates (cyanide, ammonia, and aldehydes) and is widely hypothesized to be a key mechanism in the chemistry that led to life on Earth and on other planets. To better constrain the synthetic environments and precursors of abiotic α–amino acids, and to determine unique signatures of abiogenic amino acids, we measured the molecular-averaged and site-specific carbon and nitrogen isotope effects for the Strecker synthesis of alanine. The reaction steps of the Strecker synthesis can be divided into two groups: an initial series of reversible amination and nitrile-addition reactions (‘equilibration’) and a second series of irreversible hydrolysis reactions (‘hydrolysis’). The equilibration of cyanide, acetaldehyde, and ammonia with the intermediate, α–aminopropionitrile (α-APN), has a measured 55.1 ‰ equilibrium nitrogen isotope effect between the 15N–rich amine nitrogen in α-aminopropionitrile and the 15N–poor ammonia and a 20.0 ‰ equilibrium carbon isotope effect between the 13C-poor C–2 site in α–aminopropionitrile and the 13C–rich carbonyl carbon in acetaldehyde. The first irreversible hydrolysis step is inferred to have an up to 10 ‰ normal carbon fractionation (i.e., faster for 12C, slower for 13C) for the whole molecule, but it also has one or more side reactions that deplete the reactive α-APN reservoir by up to 15 ‰. The second hydrolysis step has a 15.4 ‰ normal kinetic isotope effect on the amide (C–1) site of alaninamide, which becomes the carboxyl site of alanine. Other α–amino acids will likely experience similar nitrogen isotope fractionations between ammonia and their amine sites, and similar carbon isotope fractionations between the carbonyl carbon in reactant aldehydes or ketones and the intermediate α–aminonitrile, and between cyanide and the carboxyl site. Therefore, these isotope effects allow us to predict the carbon and nitrogen isotopic contents and intramolecular structures of α-amino acids formed by Strecker synthesis based on their substrates’ isotopic compositions, or to infer the isotopic compositions of substrates from which amino acids formed, for example in the case of the amino-acid-rich carbonaceous chondrites. The site-specific C and N isotopic compositions of amino acids formed by Strecker chemistry contrast with those typical of terrestrial biosynthetic amino acids, so these data also provide a means of discriminating between biogenic and abiogenic α–amino acids.

¹Panerai F.,²Bessire B.,²Haskins J.,¹Foster C.,³Barnard H.,²Stern E.,²Feldman J.
Planetary Science Journal 2, 179 Link to Article [DOI 10.3847/PSJ/ac1749]
¹Center for Hypersonics and Entry System Studies (CHESS), Department of Aerospace Engineering, University of Illinois at Urbana-Champaign, 104 S. Wright Street, Urbana, 61801, IL, United States
²NASA Ames Research Center, Moffett Field, 94035, CA, United States
³Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, 94720, CA, United States

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^1,2Christopher H. House et al. (>10)
Proceeding sof the National Academy of Sciences of the United States of America 119, e2115651119 Link to Article [https://doi.org/10.1073/pnas.2115651119]
¹Department of Geosciences, The Pennsylvania State University, University Park, PA 16802
²Earth and Environmental Systems Institute, The Pennsylvania State University, University Park, PA 16802

Obtaining carbon isotopic information for organic carbon from Martian sediments has long been a goal of planetary science, as it has the potential to elucidate the origin of such carbon and aspects of Martian carbon cycling. Carbon isotopic values (δ13CVPDB) of the methane released during pyrolysis of 24 powder samples at Gale crater, Mars, show a high degree of variation (−137 ± 8‰ to +22 ± 10‰) when measured by the tunable laser spectrometer portion of the Sample Analysis at Mars instrument suite during evolved gas analysis. Included in these data are 10 measured δ13C values less than −70‰ found for six different sampling locations, all potentially associated with a possible paleosurface. There are multiple plausible explanations for the anomalously depleted 13C observed in evolved methane, but no single explanation can be accepted without further research. Three possible explanations are the photolysis of biological methane released from the subsurface, photoreduction of atmospheric CO2, and deposition of cosmic dust during passage through a galactic molecular cloud. All three of these scenarios are unconventional, unlike processes common on Earth.

^1,4,5,6Famiano M.A.,²Boyd R.N.,^3,7Onaka T.,^4,5,8Kajino T.
Physical Review Research 3, 033025 Link to Article [DOI 10.1103/PhysRevResearch.3.033025]
¹Department of Physics, Western Michigan University, Kalamazoo, 49008-5252, MI, United States
²Department of Physics, Department of Astronomy, The Ohio State University, Columbus, 43210, OH, United States
³Department of Physics, Meisei University, 2-1-1 Hodokubo, Hino, 191-8506, Tokyo, Japan
⁴School of Physics, Beihang University (Beijing University of Aeronautics and Astronautics), International Research Center for Big-Bang Cosmology and Element Genesis, Beijing, 100083, China
⁵National Astronomical Observatory of Japan, 2-21-1 Mitaka, Tokyo, 181-8588, Japan
⁶Joint Institute for Nuclear Astrophysics
⁷Department of Astronomy, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
⁸Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan

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^1,2Qin K.,¹Zou X.
Yanshi Xuebao/Acta Petrologica Sinica 37, 2276 – 2286 Link to Article [DOI 10.18654/1000-0569/2021.08.03]
¹Key Laboratory of Mineral Resources, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, 100029, China
²College of Earth and Planetary Sciences, University of Chinese, Academy of Sciences, Beijing, 100049, China

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¹Cao H.,¹Chen J.,¹Fu X.,^1,2Xin Y.,¹Qi X.,¹Shi E.,¹Ling Z.
Journal of Raman Spectroscopy (in Press) Link to Article [DOI 10.1002/jrs.6254]
¹Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, School of Space Science and Physics, Institute of Space Sciences, Shandong University, Weihai, 264209, China
²Key Laboratory of Lunar and Deep Space Exploration, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, 100101, China

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^1,2F.Miozzi,^1,3G.Morard,¹D.Antonangeli,¹M.A.Baron,⁵A.Pakhomova,^1,4A.N.Clark,⁶M.Mezoua,¹G.Fiquet
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2022.01.013]
¹Sorbonne Université, Muséum National d’Histoire Naturelle, UMR CNRS 7590, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, IMPMC, 75005 Paris, France
²Earth and Planets Laboratory, Carnegie Institution for Science, Washington, DC, USA1
³Univ. Grenoble Alpes, Univ. Savoie Mont Blanc, CNRS, IRD, UGE, ISTerre, Grenoble 38000, France1
⁴University of Colorado, Boulder, CO 80309-0399, USA
⁵Deutsches Elektronen-Synchrotron (DESY), Hamburg, Germany
⁶European Synchrotron Radiation Facility (ESRF), Grenoble, France
Copyright Elsevier

Several characteristics of a planet, including its internal dynamics, hinge on the composition and crystallization regime of the core, which, in turn, depends on the phase relations, melting behaviour and thermodynamic properties of constituent materials. The Fe-Si-C ternary system can serve as a proxy for core composition and formation processes under reducing conditions. We conducted laser-heated diamond anvil cell experiments coupled with in situ X-ray diffraction and electron microscopy analysis of the recovered samples, on four different starting compositions in the Fe-Si-C ternary system. Phase relations up to 200 GPa and up to 4000 K were determined. An FeSi phase with a B2 structure and iron carbides with different stoichiometries (i.e. Fe₃C and Fe₇C₃) are the main observed phases, along with pure C (diamond) that has an extended stability field in the subsolidus regime. Carbon is largely soluble in B2-structured FeSi, whereas Si does not partition into the carbides. The melting curve determined for the starting material containing the least amount of light elements is consistent with the one for the Fe-C system. The other starting materials display higher melting temperatures than that of Fe-C, suggesting the existence of at least two different invariant points in the Fe-Si-C system. Applied to planetary interiors, our observations highlight how a small variation in light elements content would deeply affect the solidification style of a core. Bottom-up (Fe-enriched systems) and top-down regimes (C-rich systems), as well as solidification of a crystal mush (Si-enriched systems). These three crystallization regimes influence significantly the possibility of starting and sustaining a dynamo. Our results provide new insights into the differentiation of terrestrial planets in the Solar System and beyond, contributing to the study of planetary diversity.

^1,2Elishevah M.M.E. van Kooten,¹Edith Kubik,¹Julien Siebert,³Benjamin D.Heredia,³Tonny B.Thomsen,¹Frédéric Moynier
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2022.01.008]
¹Université de Paris, Institut de Physique du Globe de Paris, CNRS UMR 7154, 1 rue Jussieu, 75238 Paris, France
²Center for Star and Planet Formation, Globe Institute, University of Copenhagen, Øster Voldgade 5-7, 1350 Copenhagen, Denmark
³Geological Survey of Denmark, GEUS, Øster Voldgade 10, 1350 Copenhagen, Denmark
Copyright Elsevier

FeNi metals represent an important fraction of chondritic components that remains relatively unexplored within most carbonaceous chondrite groups. The compositions of these metals can place constraints on the nature of their precursor materials as well as the physicochemical conditions of chondrule formation. In this study, we have analyzed the major, minor and trace element compositions of metal grains from relatively unaltered carbonaceous chondrites NWA 801 (CR), Leoville (CV3.1), Paris (CM2.9), Maribo (CM2.8) and Bells (CM-an). We observe a predominant and constant sub-solar Co/Ni ratio of CR, CM and CM-an metal grains. In Ni versus Co space, the metal grains fall below modelled curves for equilibrium condensation of metals from a solar gas. From Ni versus Cr plots, we infer that Paris (and possibly Leoville) metal grains could have maintained a primary condensation signature, although for most grains, condensation must have occurred under disequilibrium conditions. CR and isolated CM-an metals mostly fall outside of the predicted condensation fields. Based on metal-silicate partition coefficients of Ni and Co that vary with pressure, we interpret their Co/Ni signatures as having a planetary origin, with presumable extraction by impact jetting. Considering that almost all CM and CR metal grains have the same Co/Ni ratio, we cannot rule out a planetary origin for CM metal grains. We relate the highly siderophile element (HSE) patterns of carbonaceous chondrite metal to mixing and subsequent equilibration of refractory metal nuggets (RMN), FeNi alloys and silicate chondrule precursors. As with the Co/Ni ratios, the HSE patterns of CM, CM-an, CR and CV metal grains are nearly identical, suggesting that the abundance and nature of the metal precursor materials were similar for carbonaceous chondrites. The overall volatility patterns of CV, CM and CR chondrites, suggest that the latter form under more oxidizing conditions than CV chondrites. The volatility patterns of Paris metal grains overlap with CV and CR chondrule metals, implying variable P-T-fO2 conditions during CM chondrule formation. Finally, we comment on the origin of metal grains in various petrological settings. Chondrule rim and isolated metal grains are likely derived and expelled from the equilibrated core metal and were subsequently altered to include and re-equilibrate with materials from the disk. Trace element analyses of the anomalous CM chondrite Bells metal grains show potential relationships with CM chondrite and CH chondrite metal for the chondrule cores and isolated grains, respectively. Small metal grains from CM chondrite Maribo, which are located in the chondrite matrix, potentially have distinct volatility patterns from CR and Paris isolated grains, hinting at a distinct origin for small metal grains and large chondrule-derived metal. Future work on carbonaceous chondrite metal should include an extensive dataset of metal-silicate equilibration calculations on individual chondrules and an investigation of small (micron scale) versus large isolated metal grains.

¹F. Zambon,¹C. Carli,²J. Wright,²D. A. Rothery,¹F. Altieri,^3,4M. Massironi, F. Capaccioni,⁴G. Cremonese
Journal of Geophysical Research, Planets (in Press) Link to Article [https://doi.org/10.1029/2021JE006918]
¹INAF-Istituto di Astrofisica e Planetologia Spaziali, Via del Fosso del Cavaliere, 100 I-00 133 Rome
²The Open University, Walton Hall, Milton Keynes, MK7 6AA UK
³University of Padua, Department of Geoscience, Via Gradenigo 6, I-35 131 Padua Italy
⁴INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio, 5, 35 122 Padua Italy
Published by arrangement with John Wiley & Sons

MESSENGER mission data allowed the entire surface of Mercury to be mapped at various spatial scales, from both geological and compositional stand points. Here, we present a spectral analysis of the H05-Hokusai quadrangle, using data acquired by the Mercury Dual Imaging System-Wide-Angle Camera. We defined a suitable set of parameters, such as reflectance and spectral slopes, to study the spectral variation though the definition of spectral units. The determination of spectral units permits to infer the physical and compositional properties of a surface by processing several parameters simultaneously, instead of the more traditional approach of interpreting each single parameter separately. We identified 11 spectral units within H05, 6 large scale and 5 localized units. The large scale units include the northern smooth plains of Borealis Planitia. South-western H05 is characterized by two widespread spectral units, partially overlapping intercrater plains and intermediate plains. Furthermore, we found very localized spectral units corresponding to the low-reflectance blue material of Rachmaninoff basin and the high-reflectance red material of Nathair Facula. We investigated the link between spectral units and compositional maps obtained by GRS and XRS, to associate compositional information to the spectral units. We found some spectral units are correlated with Mg and Al variations displayed in the elemental maps. This implies that spectral variations associated to these units are mainly linked with composition rather than terrain maturity and/or grain size effects.

¹John O.Edgar,²Katie Gilmour,²Maggie L.White,¹Geoffrey D.Abbott,¹Jon Telling
Earth and Planetary Science Letters 579, 117361 Link to Article [https://doi.org/10.1016/j.epsl.2021.117361]
¹School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK
²School of Engineering, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK
Copyright Elsevier

The surface of Mars is a dynamic, cold environment where aeolian abrasion leads to the fracturing of silicate minerals which can produce oxidants upon exposure to water. Here we report results of a series of laboratory experiments where the abrasion of sand sized (125 – 300 μm) quartz, labradorite, forsterite and opal were conducted under a simulated Martian atmosphere at a range of temperatures common to Mars’ surface (193 to 273 K). Our results suggest that abrasion rates are controlled by temperature; an observation that may have potential for providing insight into Martian paleo-temperatures. On the addition of water, detectable H2O2 was generated in all abraded experiments with crystalline quartz, labradorite and forsterite, but not amorphous opal – supporting previous inferences that mineral crystal structure plays a role in oxidant production. Dissolved Fe concentrations also indicated a strong additional control on net H2O2 production by Fenton reactions. Detectable H2 was similarly measured in abraded experiments with crystalline minerals and not for amorphous opal. Labradorite and forsterite generated minimal H2 and only in more abraded samples, likely due to the reaction of Si• with water. In quartz experiments H2 was only present in samples where a black magnetic trace mineral was also present, and where H2O2 concentrations had been reduced to close to detection. In the quartz samples we infer a mechanism of H2 generation via the previously proposed model of spinel-surface-promoted-electron transfer to water. The presence of H2O2 may exert an additional control on net H2 production rates either directly (via reaction of H2 with OH• and H2O2) or indirectly (by the oxidation of H2 generating sites on mineral surfaces). Overall, our data supports previous inferences that aeolian abrasion can produce additional oxidants within the Martian regolith that can increase the degradation of organic molecules. We further suggest that the apparent control of H2O2 concentrations on net H2 generation in our experiments may help explain some previous apparently contradictory evidence for mineral-water H2 generation at low temperatures.