Marceau Lecasble, Laurent Remusat, Jean-Christophe Viennet, Boris Laurent, Sylvain Bernard
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2022.08.039]
Muséum National d’Histoire Naturelle, Sorbonne Université, CNRS UMR 7590, IMPMC, Paris, France
Copyright Elsevier

Carbonaceous chondrites contain a diverse suite of more or less soluble compounds, including polycyclic aromatic hydrocarbons (PAHs). These compounds are structured around two or more fused benzene rings, and have shown to be detected in various astrophysical environments. The origin of PAHs in carbonaceous chondrites is debated: they may originate from the interstellar medium (ISM) and thus potentially carry information on accretion processes. Alternatively, they may have formed or transformed during secondary processes on parent bodies and thus carry information about aqueous alteration conditions. Here, we investigate the nature, quantity, and isotopic composition of free PAHs in three recently recovered CM chondrites having experienced substantial and distinct degrees of alteration: the CM2.2 Aguas Zarcas, the CM2.0 Mukundpura and the CM1/2 Kolang. All the CMs investigated contain PAHs, with sizes ranging from 2 (naphthalene) to 5 cycles (benzopyrene). The concentration of PAHs is not correlated to the degree of alteration and larger PAHs are also the most depleted in ¹³C, suggesting an interstellar origin. Yet, the abundance of alkylated PAHs appears correlated to the degree of alteration and all the extracted PAHs are D-depleted, pointing towards hydrogen exchange with water having occurred during aqueous alteration. These combined results suggest that PAHs in CCs likely carry information on both accretion and alteration processes.

David W. Graham, Kevin Konrad¹
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2022.09.016]
College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331 USA
Copyright Elsevier

We report ³He and ⁴He concentrations in 57 sediment samples from the southeast Indian Ocean where ⁶⁰Fe excesses were previously identified in a subset of the same samples (Wallner et al., 2016). The coupled ⁶⁰Fe-³He data allow further evaluation of two competing hypotheses: 1) a nearby supernova (SN) showered Earth with exotic radionuclides such as ⁶⁰Fe during the last 3 million years, or 2) ⁶⁰Fe in terrestrial archives was generated by reactions of galactic cosmic rays (GCRs) on micrometeorite grains that were irradiated for hundreds of millions of years in the interstellar medium, where ³He production by GCRs is larger than the solar wind ³He flux.

^aKeqing Zong et al. (>10)
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2022.06.037]
¹State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Sciences, China University of Geosciences, Wuhan 430074, China
Copyright Elsevier

Lunar soil is a fine mixture of local rocks and exotic components. The bulk-rock chemical composition of the newly returned Chang’E-5 (CE-5) lunar soil was studied to understand its chemical homogeneity, exotic additions, and origin of landing site basalts. Concentrations of 48 major and trace elements, including many low-concentration volatile and siderophile elements, of two batches of the scooped CE-5 soil samples were simultaneously obtained by inductively coupled plasma mass spectrometry (ICP-MS) with minimal sample consumption. Their major and trace elemental compositions (except for Ni) are uniform at milligram levels (2–4 mg), matching measured compositions of basaltic glasses and estimates based on mineral modal abundances of basaltic fragments. This result indicates that the exotic highland and KREEP (K, rare earth elements, and P-rich) materials are very low (<5%) and the bulk chemical composition (except for Ni) of the CE-5 soil can be used to represent the underlying mare basalt. The elevated Ni concentrations reflect the addition of about 1 wt% meteoritic materials, which would not influence the other bulk composition except for some highly siderophile trace elements such as Ir. The CE-5 soil, which is overall the same as the underlying basalt in composition, displays low Mg# (34), high FeO (22.7 wt%), intermediate TiO₂ (5.12 wt%), and high Th (5.14 µg/g) concentrations. The composition is distinct from basalts and soils returned by the Apollo and Luna missions, however, the depletion of volatile or siderophile elements such as K, Rb, Mo, and W in their mantle sources is comparable. The incompatible lithophile trace element concentrations (e.g., Ba, Rb, Th, U, Nb, Ta, Zr, Hf, and REE) of the CE-5 basalts are moderately high and their pattern mimics high-K KREEP. The pattern of these trace elements with K, Th, U, Nb, and Ta anomalies of the CE-5 basalts cannot be explained by the partial melting and crystallization of olivine, pyroxene, and plagioclase. Thus, the mantle source of the CE-5 landing site mare basalt could have contained KREEP components, likely as trapped interstitial melts. To reconcile these observations with the initial unradiogenic Sr and radiogenic Nd isotopic compositions of the CE-5 basalts, clinopyroxene characterized by low Rb/Sr and high Sm/Nd ratios could be one of the main minerals in the KREEP-bearing mantle source. Consequently, we propose that the CE-5 landing site mare basalts very likely originated from partial melting of a shallow and clinopyroxene-rich (relative to olivine and orthopyroxene) upper mantle cumulate with a small fraction (about 1–1.5 %) of KREEP-like materials.

Tiantian Liu^a Kai Wünnemann^a,b GregMichael^a
Earth and Planetary Science Letters (in Press) Link to Article [https://doi.org/10.1016/j.epsl.2022.117817]
^aMuseum für Naturkunde, Leibniz Institute for Evolution and Biodiversity Science, 10115 Berlin, Germany
^bFreie Universität Berlin, Malteserstr., 74-100, 12249 Berlin, Germany
Copyright: Elsevier

The early impact bombardment extensively fractured the lunar crust resulting in the formation of the so-called megaregolith. Previous estimates of megaregolith distribution vary significantly with respect to the vertical extent and the size-frequency distribution of fragments was rarely studied. We built a spatially resolved numerical model to simulate the process of cumulative impact fragmentation, aiming to backtrack the megaregolith evolution history and to constrain its fragment distribution. The results highlight the pivotal role of basin-forming events on the megaregolith formation. Especially the South-Pole Aitken (SPA) impact established the initial megaregolith structure which remained distinct after 0.5 Ga subsequent fragmentation. At 3.8 Ga, the megaregolith displays substantial lateral variation and layering: the highly fractured upper layer of ∼2.5 km is dominated by meter-scale fragments; the disturbed lower layer deeper than tens of kilometers is mainly consisting of kilometer-scale fragments; the transition zone >5 km contains fragments of various size scales.

¹L. M. Thompson,¹J. G. Spray,¹C. O’Connell-Cooper,²J. A. Berger,³A. Yen,⁴R. Gellert,⁴N. Boyd,⁴M. A. McCraig,⁵S. J. VanBommel
Journal of Geophysical Research (Planets) (in Press) Link to Article [https://doi.org/10.1029/2021JE007178]
¹Planetary and Space Science Centre, University of New Brunswick, Fredericton, Canada
²NASA Johnson Space Center, Houston, USA
³Jet Propulsion Laboratory, California Institute of Technology, Pasadena, USA
⁴Department of Physics, University of Guelph, Ontario, Canada
⁵Department of Earth and Planetary Sciences, Washington University in St. Louis, St. Louis, USA
Published by arrangement with John Wiley & Sons

Chemical data acquired by Curiosity’s Alpha Particle X-ray Spectrometer (APXS) during examination of the contact between the upper Mount Sharp group and overlying Stimson formation sandstones at the Greenheugh pediment reveal compositional similarities to rocks encountered earlier in the mission. Mount Sharp group strata encountered below the Basal Siccar Point group unconformity at the base and top of the section, separated by >300 m in elevation, have distinct and related compositions. This indicates enhanced post-depositional fluid flow and alteration focused along this contact. Sandstone targets exposed immediately above the unconformity have basaltic compositions consistent with previously encountered eolian Stimson formation sandstones, except at the contact, where they show the addition of S. Resistant sandstone outcrops above the contact have higher K, Mn and Na and lower Ni concentrations that primarily reflect changes in provenance. They are compositionally related to cap rock float blocks encountered as Curiosity climbed through the Mount Sharp group, and Bradbury group sandstone outcrops. The higher K, pediment sandstones are interpreted to have a similar provenance to some Bradbury group sandstones, further evidence for widespread, alkaline source rock within and/or in the vicinity of Gale crater. The Bradbury and Siccar Point groups may both be younger than the Mount Sharp group. Alternatively, an alkaline source area in and around Gale crater has been eroded by both water and wind at different times (both before and after deposition of the Mount Sharp group), during the evolution of the crater and its infill.

¹Levent Karacasulu,²David Karl,²Aleksander Gurlo,¹Cekdar Vakifahmetoglu
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2022.115270]
¹Department of Materials Science and Engineering, Izmir Institute of Technology, Urla, 35430 Izmir, Turkey
²Technische Universitaet Berlin, Institute of Materials Science and Technology, Chair of Advanced Ceramic Materials, Straße des 17. Juni 135, 10623 Berlin, Germany
Copyright Elsevier

Mars regolith simulant (MGS-1) was densified for the first time via a cold sintering process (CSP) as a novel in-situ resource utilization (ISRU) concept. The technique comprises the utilization of NaOH solution as a liquid media during the densification of simulant powder with <100 μm particle size. In as short as 30 min, with the increase in the NaOH concentration (from 3 M to 10 M) and processing temperature (from 150 °C to 250 °C), the relative densities of the regolith compacts and the mechanical properties were enhanced. The artifacts produced with Mars regolith simulant powder at 250 °C using 10 M NaOH solution yielded a relative density of around 88% and compressive strength reaching ~45 MPa.

^1,2Brandon G. Radoman-Shaw,³Ralph P. Harvey,⁴Gustavo Costa,⁴Nathan S. Jacobson,⁵Amir Avishai,⁴Leah M. Nakley,⁴Daniel Vento
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.13902]
¹Department of Mathematical, Physical, and Engineering Sciences, Texas A&M University – San Antonio, San Antonio, Texas, 78224 USA
²Department of Geography and Environmental Studies, Texas State University, San Marcos, Texas, 78666 USA
³Department of Earth, Environmental, and Planetary Science, Case Western Reserve University, Cleveland, Ohio, 44106 USA
⁴NASA Glenn Research Center, Cleveland, Ohio, 44135 USA
⁵Carl Zeiss SMT-PCS, Pleasanton, California, 94588 USA
Published by arrangement with John Wiley & Sons

Climate models for Venus rely heavily on theoretical modeling and laboratory experimentation due to the extreme surface conditions of the planet and limited in situ surface data. To better explore the relative importance of reactions between the surface and the atmosphere on Venus, we exposed representative volcanic glasses and basaltic minerals to a large-scale simulation of Venus surface conditions with a realistic atmospheric composition. This study consistend of two experiments of 42 and 80 days that replicated both physical conditions and atmosphere composition derived from available in situ near-surface data using the Glenn Extreme Environment Rig (GEER) at the NASA Glenn Research Center. These experiments revealed significant reactivity of common Ca-bearing pyroxenes (diopside and augite) to form anhydrite. Olivine and labradorite showed minimal reactivity. Volcanic glasses, including both natural and synthetic samples, were exceptionally reactive, rapidly forming both anhydrite and thénardite (Na2SO4), as well as transition metal sulfates (i.e., Cu, Cr), halite (NaCl), and sylvite (KCl). Our results document chemical and textural alteration of sample surfaces and provide sufficient evidence for an active sulfur sink on multiple samples, with sulfates as the dominant secondary mineralogy. These experiments suggest likely surface mineralogies and solid phases present on Venus’ surface with significant implications for upcoming missions and provide new data for comparison to high-temperature mineral–gas reactions prevalent on Venus, Earth, and Io.

¹Daiki Yamamoto,²Noriyuki Kawasaki,^3,4Shogo Tachibana,³Michiru Kamibayashi,²Hisayoshi Yurimoto
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2022.09.006]
¹Department of Earth and Planetary Science, Tokyo Institute of Technology, Ookayama, Tokyo 152-8550, Japan
²Department of Natural History Sciences, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan
³Department of Earth and Planetary Science, The University of Tokyo, Hongo, Tokyo 113-0033, Japan
⁴Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, Kanagawa
Copyright: Elsevier

Coarse-grained igneous calcium-aluminum-rich inclusions (CAIs) are suggested to have experienced gas-melt isotope exchange of oxygen during the melting events of their precursors. Therefore, their oxygen isotope variation would preserve information about the high-temperature processes in the earliest Solar System. We experimentally determined oxygen isotope exchange kinetics between CAI analog melt and carbon monoxide (CO) gas at 1420°C and 1460°C under CO gas partial pressures of 0.1, 0.5, and 1 Pa to understand the role of CO gas on the oxygen isotope exchange. We observed oxygen isotope zoning profiles inside the reacted samples that formed through the oxygen isotope exchange reaction at the melt surface and oxygen diffusion in the melt. The zoning profiles were fitted using a three-dimensional spherical diffusion model with time-dependent surface concentration. The oxygen isotope exchange efficiency for colliding CO molecules is estimated to be ∼3.3 × 10–4, which is much smaller than that for H2O (0.28). The oxygen diffusion coefficient obtained in this study is similar to that obtained in the oxygen isotope exchange experiments between the CAI melt and H2O, suggesting that the diffusion species in the melt is O2–, despite the surrounding atmospheres.

A comparison of the isotope exchange reaction kinetics between (1) CAI melt and CO gas, (2) CAI melt and H2O gas, and (3) CO and H2O gases shows that the reaction rate decreases in the order of (3), (2), and (1). The rapid isotope exchange of the reaction (1) indicates that the oxygen isotopic compositions of H2O and CO should have been equilibrated during the melting and crystallization processes of igneous CAIs. Both H2O and CO change the oxygen isotope compositions of molten CAI in the same direction, although reaction (2) controls the isotope exchange timescale between the CAI melt and surrounding gas. Our dataset demonstrates that type B CAIs having melilite with homogeneous oxygen isotope composition should have been heated for 2–3 days at PH2 > 100 Pa above the melilite liquidus (∼1400°C) in the solar protoplanetary disk.

^1,2Lucas Demaret,³Ian B. Hutchinson,³Richard Ingley,³Howell G.M. Edwards,
⁴Nathalie Fagel,⁵Philippe Compere,²Emmanuelle J. Javaux,¹Gauthier Eppe,¹Cédric Malherbe
Astrobiology 22, 9 Link to Article [https://doi.org/10.1089/ast.2021.0128]
¹Mass Spectrometry Laboratory, MolSys Research Unit, University of Liege, Liege, Belgium.
²Early Life Traces & Evolution-Astrobiology, UR Astrobiology, University of Liege, Liege, Belgium.
³Department of Physics and Astronomy, University of Leicester, Leicester, United Kingdom.
⁴Laboratory Argiles, Géochimie et Environnements Sédimentaires, University of Liege, Liege, Belgium.
⁵Laboratory of Functional and Evolutionary Morphology, UR FOCUS, and Centre for Applied Research and
Education in Microscopy (CAREM), University of Liege, Liege, Belgium.

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

^1,2Piotr Rzymski,³Piotr Klimaszyk,⁴Nadiia Kasianchuk,²Paulina Jakubiak,⁵Jędrzej Proch,⁵Przemysław Niedzielski
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2022.115263]
¹Department of Environmental Medicine, Poznan University of Medical Sciences, Poznan, Poland
²Integrated Science Association (ISA), Universal Scientific Education and Research Network (USERN), Poznań, Poland
³Department of Water Protection, Adam Mickiewicz University, 61-642 Poznań, Poland
⁴Faculty of Biology, Adam Mickiewicz University, 61-642 Poznań, Poland
⁵Department of Analytical Chemistry, Faculty of Chemistry, Adam Mickiewicz University, Poznan, Poland
Copyright Elsevier

There is evidence of large subglacial reservoirs of liquid water on Mars, while the debate continues on whether any surface water intermittently flows following the subsurface ice melting in selected locations. The chemical conditions of waters that could be present on Mars were previously subject to modeling studies or experimental research that did not involve perchlorates which are known to be present in Martian regolith. Therefore, the present experimental research aimed to understand the chemistry of water incubated for 21 days with the Martian regolith simulant MGS-1 mixed with different levels of perchlorate (0.25–1.0% corresponding to 1.5–6.0 mM ClO4− ions). The dissolution of chemical compounds from MGS-1 was rapid with electric conductivity (EC) in the 1.8–2.3 mS/cm range after 1 h incubation. Throughout the experiment, fluctuations of pH, EC and oxidation-reduction potential were observed, although generally, the water was rich in ions, highly oxidized and had a circumneutral pH. Dominant elements included S, Mg, Ca, Na, K and Fe. Two patterns of element concentrations were observed: (1) a rapid increase with a peak 3 h after flooding the regolith and then a gradual decrease indicating adsorption and immobilization (Al, Cr, Fe, Si and Ti), and (2) a gradual increase in concentration throughout the experiment (Ca, K, Mg, Na and S). The presence of perchlorate in the simulant did not affect the general patterns of water chemistry parameters, although it appeared to enhance the leaching out of Mg, Na, S (with max concentrations noted in the presence of 1.0% perchlorate), Al, Ca (0.5%) and Cr, Fe, Si and Ti (0.25%). No detectable concentrations of Mn and P were leached from the regolith simulant throughout the experiment. This study provides a pilot experimental overview of the combined physicochemical conditions that modern liquid water on Mars could present with the potential implications for the survival of biological life and use as an in situ resource.