^1,2Hamm, M. et al. (>10)
Nature Communications 13, 364 Link to Article [DOI 10.1038/s41467-022-28051-y]
¹Institute of Mathematics, University of Potsdam, Potsdam, Germany
²Institute of Planetary Research, German Aerospace Center (DLR), Berlin, Germany

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¹J.T.Germann,¹S.K.Fieber-Beyer,¹M.J.Gaffey
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2022.114916]
¹Department of Space Studies, University Ave. Stop 9008, University of North Dakota, 58202, USA
Copyright Elsevier

We present the initial results of our visible and near-infrared (VNIR) investigation into the spectral properties of the Tholen G-class asteroids to determine: 1) which spectral properties are common among the G-class, and 2) which surface minerals may be related to the spectral features present. Our study utilized both previously published and newly obtained spectra of five G-class asteroids. Our results indicate that four of these asteroids: (13) Egeria, (19) Fortuna, (84) Klio, and (130) Elektra, exhibit spectral features consistent with hydrated minerals in the VNIR (0.4–2.5-μm). The most notable absorption feature was located at 0.7-μm, which is related to the Fe2+ ➔ Fe3+ charge transfer transition in oxidized Fe-rich phyllosilicates. In addition, several of the asteroids also exhibit subtle absorption features located near 0.95-, 1.4-, 1.9-, and 2.3-μm, which may also be related to hydrated minerals. Only (1) Ceres’ spectrum lacked features related to hydrated minerals in the VNIR. This may indicate that either (1) Ceres contains lower concentrations of hydrated minerals at its surface, or that (1) Ceres has an opaque surface component, which may obscure weak hydrated VNIR features.

^1,2,3,4Yuhei Umeda et al. (>10)
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2022.114901]
¹Graduate School of Engineering, Osaka, Japan
²Institute of Laser Engineering, Osaka University, Osaka, Japan
³Institute for Planetary Materials, Okayama University, Tottori, Japan
⁴Institute for Integrated Radiation and Nuclear Science, Kyoto University, Osaka, Japan
Copyright Elsevier

Carbonate minerals, for example calcite and magnesite, exist on the planetary surfaces of the Earth, Mars, and Venus, and are subjected to hypervelocity collisions. The physical properties of planetary materials at extreme conditions are essential for understanding their dynamic behaviors at hypervelocity collisions and the mantle structure of rocky planets including Super-Earths. Here we report laboratory investigations of laser-shocked calcite at pressures of 200–960 GPa (impact velocities of 12–30 km/s and faster than escape velocity from the Earth) using decay shock techniques. Our measured temperatures above 200 GPa indicated a large difference from the previous theoretical models. The present shock Hugoniot data and temperature measurements, compared with the previous reports, indicate melting without decomposition at pressures of ~110 GPa to ~350 GPa and a bonded liquid up to 960 GPa from the calculated specific heat. Our temperature calculations of calcite at 1 atm adiabatically released from the Hugoniot points suggest that the released products vary depending on the shock pressures and affect the planetary atmosphere by the degassed species. The present results on calcite newly provide an important anchor for considering the theoretical EOS at the extreme conditions, where the model calculations show a significant diversity at present.

¹Karen Valencia,^1,2Aldemar De Moya,^3,4Guillaume Morard,⁵Neil L. Allan,^1,5Carlos Pinilla
American Mineralogist 107, 248–256 Link to Article [http://www.minsocam.org/msa/ammin/toc/2022/Abstracts/AM107P0248.pdf]
¹Departamento de Física y Geociencias, Universidad del Norte, Km 5 Via Puerto Colombia, Barranquilla, Colombia
²Departamento de Ciencias Naturales y Exactas, Universidad de la Costa, Calle 58 No. 55-66, Barranquilla, Colombia
³Sorbonne Université, Institut de Minéralogie, de Physique des Matériaux, et de Cosmochimie (IMPMC), UMR CNRS 7590, IRD,Muséum National d’Histoire Naturelle, Paris, France
⁴Université Grenoble Alpes, CNRS, ISTerre, F-38000 Grenoble
⁵School of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, U.K.
Copyright: The Mineralogical Society of America

Using density functional theory electronic structure calculations, the equation of state, thermody-
namic and elastic properties, and sound wave velocities of Fe3S at pressures up to 250GPa have been
determined. Fe3S is found to be ferromagnetic at ambient conditions but becomes non-magnetic at
pressures above 50 GPa. This magnetic transition changes thec/a ratio leading to more isotropic com-
pressibility, and discontinuities in elastic constants and isotropic sound velocities. Thermal expansion,
heat capacity, and Grüneisen parameters are calculated at high pressures and elevated temperatures
using the quasiharmonic approximation. We estimate Fe-Fe and Fe-S force constants, which vary with
Fe environment, as well as the 56Fe/54Fe equilibrium reduced partition function in Fe3S and compare
these results with recently reported experimental values. Finally, our calculations under the conditions
of the Earth’s inner core allow us to estimate a S content of 2.7wt% S, assuming the only components
of the inner core are Fe and Fe 3S, a linear variation of elastic properties between end-members Fe
and Fe3S, and that Fe3S is kinetically stable. Possible consequences for the core-mantle boundary of
Mars are also discussed.

¹Katarina Kaiser et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13784]
¹IBM Research—Zurich, Rüschlikon, 8003 Switzerland
Published by arrangement with John Wiley & Sons

Using high-resolution atomic force microscopy (AFM) with CO-functionalized tips, we atomically resolved individual molecules from Murchison meteorite samples. We analyzed powdered Murchison meteorite material directly, as well as processed extracts that we prepared to facilitate characterization by AFM. From the untreated Murchison sample, we resolved very few molecules, as the sample contained mostly small molecules that could not be identified by AFM. By contrast, using a procedure based on several trituration and extraction steps with organic solvents, we isolated a fraction enriched in larger organic compounds. The treatment increased the fraction of molecules that could be resolved by AFM, allowing us to identify organic constituents and molecular moieties, such as polycyclic aromatic hydrocarbons and aliphatic chains. The AFM measurements are complemented by high-resolution mass spectrometry analysis of Murchison fractions. We provide a proof of principle that AFM can be used to image and identify individual organic molecules from meteorites and propose a method for extracting and preparing meteorite samples for their investigation by AFM. We discuss the challenges and prospects of this approach to study extraterrestrial samples based on single-molecule identification.

¹Juulia-Gabrielle Moreau,¹Argo Jõeleht,¹Jaan Aruväli,²Mikko J. Heikkilä,³Aleksandra N. Stojic,²Thomas Thomberg,¹Jüri Plado,⁴Satu Hietala
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13782]
¹Department of Geology, Institute of Ecology and Earth Science, University of Tartu, Ravila 14A, Tartu, 50411 Estonia
²Department of Chemistry, University of Helsinki, P.O. Box 55 (A.I. Virtasen aukio 1), FI-00014 Finland
³Institut für Planetologie, Westfälische Wilhelms Universität Münster, Wilhelm-Klemm-Str. 10, Münster, 48149 Germany
⁴Geological Survey of Finland, Neulamäentie 5, Kuopio, FI-70211 Finland
Published by arrangement with John Wiley & Sons

Stoichiometric troilite (FeS) is a common phase in differentiated and undifferentiated meteorites. It is the endmember of the iron sulfide system. Troilite is important for investigating shock metamorphism in meteorites and studying spectral properties and space weathering of planetary bodies. Thus, obtaining coarse-grained meteoritic troilite in quantities is beneficial for these fields. The previous synthesis of troilite was achieved by pyrite or pyrrhotite heating treatments or chemical syntheses. However, most of these works lacked a visual characterization of the step by step process and the final product, the production of large quantities, and they were not readily advertised to planetary scientists or the meteoritical research community. Here, we illustrate a two-step heat treatment of pyrite to synthesize troilite. Pyrite powder was decomposed to pyrrhotite at 1023–1073 K for 4–6 h in Ar; the run product was then retrieved and reheated for 1 h at 1498–1598 K in N2 (gas). The minerals were analyzed with a scanning electron microscope, X-ray diffraction (XRD) at room temperature, and in situ high-temperature XRD. The primary observation of synthesis from pyrrhotite to troilite is the shift of a major diffraction peak from ~43.2°2θ to ~43.8°2θ. Troilite spectra matched an XRD analysis of natural meteoritic troilite. Slight contamination of Fe was observed during cooling to troilite, and alumina crucibles locally reacted with troilite. The habitus and size of troilite crystals allowed us to store it as large grains rather than powder; 27 g of pyrite yielded 17 g of stochiometric troilite.

¹William S.Cassata,²Kevin J.Zahnle,^1,3Kyle M.Samperton,¹Peter C.Stephenson,¹Josh Wimpenny
Earth and Planetary Science Letters 580, 117349 Link to Article [https://doi.org/10.1016/j.epsl.2021.117349]
¹Nuclear and Chemical Sciences Division, Lawrence Livermore National Laboratory, L-235, Livermore, CA 94550, USA
²Space Science Division, NASA Ames Research Center, MS 245-3, Moffett Field, CA 94035, USA
³Trace Nuclear Measurement Technology Group, Savannah River National Laboratory, Aiken, SC 29808, USA
Copyright Elsevier

Trapped, paleoatmospheric xenon (Xe) in the Martian regolith breccia NWA 11220 is mass-dependently fractionated relative to solar Xe by 16.2 ± 2.7‰/amu. These data indicate that fractionation of atmospheric Xe persisted for hundreds of millions of years after planetary formation. Such a protracted duration of atmospheric Xe mass fractionation, which is particularly striking when compared to the non-fractionated state of Martian atmospheric krypton (Kr), cannot be easily reconciled with Xe escape as a neutral atom in a neutral hydrodynamic hydrogen wind. However, Xe escape as an ion coupled to a partially ionized hydrogen or oxygen wind provides a simple solution to problems associated with the neutral escape hypothesis. Ionic Xe escape requires a sufficiently high escape flux of a carrier ion (H+ or O+) and probably requires a structured planetary magnetic field to channel the flow. The end of Xe escape from Mars could be attributed to waning hydrogen sources from volcanic outgassing or from interactions of reduced impactors with surface water and ice. Alternatively, if Xe ions were driven off by O+, the end of Xe escape could be attributed to the decay of solar extreme ultra-violet radiation.

^1,2Damien Daval,³Gaël Choblet,³Christophe Sotin,⁴François Guyot
Journal of Geophysical Research, Planets (in Press) Link to Article [https://doi.org/10.1029/2021JE006995]
¹Université de Strasbourg / CNRS / ENGEES – Institut Terre et Environnement de Strasbourg, UMR, 7063 Strasbourg, France
²Université Grenoble Alpes, Université Savoie Mont Blanc, CNRS, IRD, IFSTTAR, Intitut des Sciences de la Terre, Grenoble, France
³Université de Nantes / CNRS – Laboratoire de Planétologie et Géodynamique, UMR, 6112 Nantes, France
⁴Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Museum National d’Histoire Naturelle, UMR, Sorbonne-Université / CNRS, 7590 Paris, France
Published by arrangement with John Wiley & Sons

The Cassini spacecraft demonstrated that Saturn’s small moon Enceladus may harbor hydrothermal activity. In particular, molecular hydrogen production could result from water-rock interactions in a tidally-heated, water-filled porous rocky core. The lifetime of such reactions is key to assess the habitability potential of Enceladus and to constrain plausible durations of the active stage in a context where the evolution of the moon is debated. Although it has recently been suggested that the serpentinization timescale does not exceed a few hundred million years, this estimation was based on assumptions regarding silicate dissolution kinetics that are prone to overestimate the actual reactivity of primary silicates. Here, we investigated plausible rate-limiting mechanisms governing fluid-rock interactions that could delay the completion of Enceladus’ core serpentinization. In particular, we considered the impact of (i) various secondary mineral assemblages on the Gibbs free energy of Fe-bearing silicate dissolution and associated dissolution rates; (ii) rate-laws alternative to the transition state theory; (iii) diffusion in nanoporous secondary assemblages; (iv) slow water supply. Overall, our results confirm that serpentinization timescales never exceed 500 Myr, and indicate that fluid flow ultimately sets the tempo for serpentinization. Only unreasonable grain sizes in Enceladus’ core (> 1m) or unexpectedly low diffusivity of secondary coatings covering primary silicates would be consistent with serpentinization durations of several billion years. We thus suggest that either the hydrothermal activity has developed recently on Enceladus, or alternative processes (pyrolysis of insoluble organic matter, microbial activity) must be tested to explain the observed H2 flux in Enceladus’ plume.

¹M. A. Torcivia,¹C. R. Neal
Journal of Geophysical Research, Planets (in Press) Link to Article [https://doi.org/10.1029/2020JE006799]
¹University of Notre Dame
Published by arrangement with John Wiley & Sons

The ferroan anorthosite suite (FAS) represents the only direct sampling of the lunar magma ocean (LMO) and potentially contains information on the earliest history of the Moon. Apollo 16 FAS sample 60025 is extremely important for understanding early lunar evolution, but unraveling this information is complicated. For example, 60025 has two distinct Sm-Nd crystallization ages that in themselves encapsulate the complicated history of this sample, along with the cataclastic and heterogeneous textures exhibited. Here we present new in-situ major and trace element plagioclase and pyroxene data gathered from 5 thin sections of 60025 that highlight such complexities. Trace element data are used to derive equilibrium liquids and while many of the minerals analyzed here are consistent with derivation from the LMO, there are also a significant number of plagioclase and pyroxene crystals that crystallized from magmas inconsistent with current models of LMO evolution. Integration of Sm-Nd isotopic data with the elemental data reported here indicated a non-chondritic LMO is possible and we confirm that 60025 is a polymict lunar breccia containing differently sourced material.

¹Reggie L.Hudson,^1,2Yukiko Y.Yarnall
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2022.114899]
¹Astrochemistry Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
²Universities Space Research Association, Greenbelt, MD 20771, USA
Copyright Elsevier

Infrared (IR) spectra of two solid aromatic compounds, benzene (C6H6) and pyridine (C5H5N), have been recorded in their amorphous and crystalline states. Measurements of density and refractive index (λ = 670 nm) are reported for each form of each compound, quantities needed to compute IR intensities and optical constants for use in laboratory experiments and astronomical observations. These are the first such measurements of each compound’s density, refractive index, and spectra at temperatures relevant to the outer solar system and interstellar medium, with all measurements being made in a single laboratory. We have used these results to determine both IR band strengths and optical constants for benzene and pyridine ices in amorphous and crystalline forms. Also, the intensity of benzene’s IR absorbance near 1477 cm−1 is measured in samples containing H2O-ice and compared to the strength of the same band in anhydrous amorphous benzene, the first comparison of this type for this compound. Suggestions are made for applications and future work related to the chemistry of icy bodies in the Solar System and the interstellar medium.