^1,2Emmy B. Hughes,¹Martha Gilmore,³Peter E. Martin,⁴Miriam Eleazer
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2023.115597]
¹Department of Earth and Environmental Sciences, Wesleyan University, 265 Church St., Middletown, CT 06438, United States of America
²School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, United States of America
³Department of Geological Sciences, University of Colorado, Boulder
⁴Department of Astronomy, Wesleyan University, Middletown, CT, United States of America
Copyright Elsevier

While much attention has been given to the identification and characterization of single-phase salts on Mars, relatively little has been applied to mixed evaporative assemblages. Given the likely existence of these assemblages on Mars (e.g., basin deposits) and the lack of data on their spectral signatures, here we present an experimental study of multicomponent S and Cl-bearing Mars-relevant brines. We modeled, synthesized and evaporated brines in the laboratory under both martian and terrestrial (P, T, pCO2) environmental conditions, and characterized the resulting precipitates using Visible–Near Infrared (VNIR), Raman spectroscopy, XRD and SEM-EDS. We compared these results to mineral assemblages calculated using the FREZCHEM thermodynamic model. For mixed brines primarily containing Na+, K+, Mg2+, Ca2+, SO42− and Cl−, epsomite (MgSO4•7H2O) and bischofite (MgCl2•6H2O) overwhelm VNIR and Raman spectra, while anhydrous crystalline salts and Na- and K-sulfates are unidentified. Mg-sulfates are identifiable in the VNIR and Raman even at low or no modeled mass abundance in an evaporative assemblage and are often the only clearly identifiable salt. These results imply that regions of Mg-sulfate identification on Mars may have only minor amounts of Mg-sulfate present, and significant amounts of halides or other sulfates may be undetectable. This may be due to a combination of late-stage Mg-sulfate precipitation and non-linear spectral mixing. Raman is more sensitive than VNIR to the identification of Ca-sulfate salts in these mixed assemblages. We predict that high abundances of mixed chloride and sulfate salts species will be identified as the Curiosity Rover continues to explore the Sulfate Unit of Gale Crater, and note that the Perseverance rover offers the first opportunity to identify such mixed assemblages in Jezero Crater with this combination of techniques.

¹Bruno Reynard,²Christophe Sotin
Earth and Planetary Science Letters 612, 118172 Link to Article [https://doi.org/10.1016/j.epsl.2023.118172]
¹Univ Lyon, ENS Lyon, UCB Lyon 1, Univ St-Etienne, CNRS, Laboratoire de Géologie de Lyon, 69007 Lyon, France
²Laboratoire de Planétologie et Géosciences, Nantes Université, Univ Angers, Le Mans Université, CNRS, UMR 6112, F-44000 Nantes, France
Copyright Elsevier

Density and moment of inertia of icy moons and dwarf planets suggest the presence of a low-density carbonaceous component in their rocky cores. This hypothesis was tested using inner density structure and thermal models. Rocky core densities in dwarf planets and icy moons are found to consist of a mixture of chondritic silicate-sulfide rocks and carbonaceous matter. Carbonaceous matter was originally mixed with ice in a rock-free precursor. In a homogeneous accretion scenario where these components are mixed in solar proportions, ices then differentiated from the carbon-rich refractory core, while hydration of silicates could take place. Thermal models taking into account the presence of carbonaceous matter suggest that originally hydrated silicates are only partially dehydrated in the refractory cores of most moons. Viable scenarios point to a difference in formation or evolution between Ganymede and Titan in spite of their similar size and mass. Fully dehydrated mineralogies, inferred in Europa and possibly the densest dwarf planet Eris, require heterogeneous accretion near the water snow line of the solar or circumplanetary nebula. Progressive gas release from slowly warming carbonaceous matter-rich cores may sustain up to present-day the replenishment of ice-oceanic layers in organics and volatiles. It accounts for the observation of nitrogen, light hydrocarbons and complex organic molecules at the surface, in the atmospheres, or in plumes emanating from moons and dwarf planets. The formation of large carbon-rich bodies in the outer solar system suggests that carbon-rich planets could form at the outskirts of extrasolar systems.

¹Xie, Xiande,²Gu, Xiangping
Acta Geochimica 42, 183 – 194 Link to Article [DOI 10.1007/s11631-023-00594-x]
¹Key Laboratory of Mineralogy and Metallogeny / Guangdong Provincial Key Laboratory of Mineral Physics and Materials, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, 510640, China
²School of Geosciences and Info-Physics, Central South University, Changsha, 410083, China

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¹Tominaga, Takahiro,²Yamaguchi, Naoya,²Sawahata, Hikaru,²Ishii, Fumiyuki
Japanese Journal of Applied Physics 62, SD1019 Link to Article [DOI 10.35848/1347-4065/acaca6]
¹Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa, 920-1192, Japan
²Nanomaterials Research Institute (NanoMaRi), Kanazawa University, Kakuma-machi, Kanazawa, 920-1192, Japan

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¹Nascimento-Dias, Bruno Leonardo,²Alvarenga, Maria Clara Ferreira,³Da Conceição Ben-To, Carolina,¹Zucolotto, Maria Elizabeth
Boletim Paranaense de Geosciencias 80, 212-225 Open Access Link to Article [DOI 10.5380/GEO.V80I2.88719]
¹Universidade Federal do Rio de Janeiro-UFRJ, Museu Nacional. Quinta da Boa Vista -São Cristóvão, RJ, Rio de Janeiro, 20940-040, Brazil
²Universidade Federal do Rio de Janeiro UFRJ, Observatório do Valongo, Ladeira do Pedro Antônio 43 – Centro RJ, Rio de Janeiro, 20080-090, Brazil
³Universidade Federal do Rio de Janeiro UFRJ, Instituto de Geociências, Av. Athos da Silveira Ramos, 274 – Cidade Universitária – Ilha do Fundão RJ, Rio de Janeiro, 21941-916, Brazil

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¹Dai W.,¹ F.,¹Fang L.,¹Siebert J.
Geochemical Research Letters 24, 33-37 Open Access Link to Article [DOI 10.7185/geochemlet.2302]
¹Universite Paris Cité, Institut de Physique du Globe de Paris, CNRS, 1 rue Jussieu, Paris, 75005, France

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¹Galuskin, Evgeny,¹Galuskina, Irina O.,²Kamenetsky, Vadim,³Vapnik, Yevgeny,⁴Kusz, Joachim,¹Zieliński, Grzegorz
Lithosphere (in Press) Open Access Link to Article [DOI 10.2113/2022/8127747]
¹Faculty of Natural Sciences, Institute of Earth Sciences, University of Silesia, Poland
²Institute of Experimental Mineralogy RAS, Chernogolovka, 142432, Russian Federation
³Department of Geological and Environmental Sciences, Ben-Gurion University of the Negev, PO Box 653, Beer-Sheva, 84105, Israel
⁴Faculty of Science and Technology, University of Silesia, ul. 75. Pułku Piechoty 1, Chorzów, 41-500, Poland
⁵Polish Geological Institute-National Research Institute, Rakowiecka 4, Warsaw, 00-975, Poland

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¹Yuan, Jiangyan,¹Huang, Hao,^1,2Chen, Yi,³Yang, Wei,³Tian, Hengci,³Zhang, Di,³Zhang, Huijuan
ACS Earth and Space Chemistry 7, 370 – 378 Link to Article [DOI10.1021/acsearthspacechem.2c00260]
¹State Key Laboratory of Lithospheric Evolution, 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
³Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, 100029, China

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¹Camille R. Butkus,²Alexandra O. Warren,²Edwin S. Kite,^3,4Santiago Torres,^3,4Smadar Naoz,⁵Jennifer B. Glass
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2023.115580]
¹School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA, USA
²Department of the Geophysical Sciences, University of Chicago, Chicago, IL, USA
³Department of Physics & Astronomy, University of California Los Angeles, Los Angeles, CA, USA
⁴Mani L. Bhaumik Institute for Theoretical Physics, Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, CA, USA
⁵School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, USA
Copyright Elsevier

Methane is a promising gaseous biosignature on rocky exoplanets, given a suitable context. Establishing the robustness of methane biosignatures on rocky exoplanets requires assessing potential “false positive” production pathways that could yield large fluxes of methane of abiotic origin. Here we modeled the flux of abiotic methane production from graphite hydrogenation on the surface of Mercury, where a relatively carbon-rich crust and bombardment by solar protons might favor this reaction. We calculated negligible methane flux from this abiotic reaction compared to biological methane flux on Earth. Graphite hydrogenation would only be expected to yield significant methane fluxes on exoplanets with high temperatures and ion fluxes that would preclude habitability for life as we know it. Thus, graphite hydrogenation by stellar wind can likely be ruled out as a potential “false positive” methane biosignature source.

¹Dominik Talla,¹Gerald Giester,¹Manfred Wildner
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2023.115583]
¹Institut für Mineralogie und Kristallographie, Universität Wien, Josef-Holaubek-Platz 2, 1090 Wien, Austria
Copyright Elsevier

The presence and importance of sulfates in our solar system have become common knowledge among the dedicated scientific community, as well as their crucial role in governing the water budget of planets such as Mars. The formation of subsurface oceans and cryovolcanism on icy moons of Jupiter and Saturn owe their existence to melting equilibria influenced by sulfate hydrates in the deeper parts of these celestial bodies. In such a setting, it cannot be ruled out that lower-hydrated sulfates including kieserite, MgSO4·H2O, are also present, given their stability under geologic pressures relevant even down to the lower mantle of the icy satellites. With regard to the composition of the water-soluble fraction in C1 and C2 chondritic meteorites presumed to correspond to that of the rocky cores of the Jovian moons, local kieserite may contain significant amounts of Mn in addition to Ni (and also some Fe). Minor Mn contents are probable even in kieserite occurring on the surface of Mars. Substantial lattice parameter changes and spectral band shifts between kieserite and its isostructural Mn-analogue szmikite, MnSO4·H2O, are well known, nevertheless neither the existence of a potential Mgsingle bondMn solid solution series nor its crystal chemical and spectroscopic behavior has yet been investigated.

This work provides the first evidence for such a continuous solid solution, describes its structural properties, and gives a detailed insight into the position changes of prominent bands in FTIR- and Raman spectra of synthetic samples, as the Mn/Mg ratio increases, with the measurement having been performed both at ambient and low temperatures relevant for Mars and the icy satellites. It reveals that contents of Mn do not cause any significant shift in the H2O stretching vibrational bands, yet influence the position of sulfate-related vibrations much in the same way as the incorporation of other relevant transition metal cations, such as Ni. The contrasting behavior of the ν3 and ν1 stretching vibrations of the H2O molecule in case of Mn- (no shift) and Ni-incorporation (significant shift to lower wavenumber) along with their comparable influence on the position of sulfate bands allow to deduce the chemical composition of kieserite in a ternary Mg–Mn–Ni system based on spectroscopic remote sensing or in situ data from celestial bodies. The assessment of chemical composition from vibrational spectra is facilitated by the observed Vegard-type behavior, where lattice parameters as well as the spectral band positions change along linear trends with increasing substitution of Mg, regardless if by Mn, Fe, or Ni. The observed shift of mainly the H2O stretching vibrations to lower wavenumber values as temperature decreases (in contrast to the bands related to the sulfate group) match thermal behavior observed in other binary solid solutions of sulfate monohydrate phases isostructural with kieserite.