¹Y.Liu et al. (>10)
Science 377, 1513-1519 Link to Article [DOI: 10.1126/science.abo2756]
¹Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA.
Reprinted with permission of AAAS

The geological units on the floor of Jezero crater, Mars, are part of a wider regional stratigraphy of olivine-rich rocks, which extends well beyond the crater. We investigated the petrology of olivine and carbonate-bearing rocks of the Séítah formation in the floor of Jezero. Using multispectral images and x-ray fluorescence data, acquired by the Perseverance rover, we performed a petrographic analysis of the Bastide and Brac outcrops within this unit. We found that these outcrops are composed of igneous rock, moderately altered by aqueous fluid. The igneous rocks are mainly made of coarse-grained olivine, similar to some martian meteorites. We interpret them as an olivine cumulate, formed by settling and enrichment of olivine through multistage cooling of a thick magma body.

^1,2PAUL FROSSARD,¹CLAUDINE ISRAEL,^3,4AUDREY BOUVIER,¹MAUD BOYET
Science 377, 1527-1532 Link to Article [DOI: 10.1126/science.abq735]
¹Université Clermont Auvergne, CNRS, IRD, OPGC, Laboratoire Magmas et Volcans, F-63000 Clermont-Ferrand, France.
²Institute of Geochemistry and Petrology, ETH Zürich, Zürich, Switzerland.
³Bayerisches Geoinstitut, Universität Bayreuth, 95447 Bayreuth, Germany.
⁴Department of Earth Sciences, University of Western Ontario, London, ON N6A 5B7, Canada.
Reprinted with permission from AAAS

The samarium-146 (146Sm)–neodymium-142 (142Nd) short-lived decay system (half-life of 103 million years) is a powerful tracer of the early mantle-crust evolution of planetary bodies. However, an increased 142Nd/144Nd in modern terrestrial rocks relative to chondrite meteorites has been proposed to be caused by nucleosynthetic anomalies, obscuring early Earth’s differentiation history. We use stepwise dissolution of primitive chondrites to quantify nucleosynthetic contributions on the composition of chondrites. After correction for nucleosynthetic anomalies, Earth and the silicate parts of differentiated planetesimals contain resolved excesses of 142Nd relative to chondrites. We conclude that only collisional erosion of primordial crusts can explain such compositions. This process associated with planetary accretion must have produced substantial loss of incompatible elements, including long-term heat-producing elements such as uranium, thorium, and potassium.

¹K.A.Farley et al. (>10)
Science 377, 6614 Link to Article [DOI: 10.1126/science.abo2]
¹Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA.
Reprinted with permisson from AAAS

The Perseverance rover landed in Jezero crater, Mars, to investigate ancient lake and river deposits. We report observations of the crater floor, below the crater’s sedimentary delta, finding that the floor consists of igneous rocks altered by water. The lowest exposed unit, informally named Séítah, is a coarsely crystalline olivine-rich rock, which accumulated at the base of a magma body. Magnesium-iron carbonates along grain boundaries indicate reactions with carbon dioxide–rich water under water-poor conditions. Overlying Séítah is a unit informally named Máaz, which we interpret as lava flows or the chemical complement to Séítah in a layered igneous body. Voids in these rocks contain sulfates and perchlorates, likely introduced by later near-surface brine evaporation. Core samples of these rocks have been stored aboard Perseverance for potential return to Earth.

¹Michail Samouhos,¹Petros Tsakiridis,²Magued Iskander,¹Maria Taxiarchou,¹Konstantinos Betsis
Planetary and Space Science 212, 105414 Link to Article [https://doi.org/10.1016/j.pss.2021.105414]
¹School of Mining and Metallurgical Engineering, National Technical University of Athens, 9 Heroon Politechniou St, GR15780, Zografou, Athens, Greece
²Civil & Urban Engineering Department, New York University Tandon School of Engineering, 6 Metrotech Ctr, RH419, Brooklyn, NY11201, USA

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¹Jeffrey R.Johnson,²William M.Grundy,³Mark T.Lemmon,⁴W.Liang,⁵James F.BellIII,⁶A.G.Hayes,⁷R.G.Deen
Planetary and Space Science 222, 105563 Link to Article [https://doi.org/10.1016/j.pss.2022.105563]
¹Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA
²Lowell Observatory, Flagstaff, AZ, USA
³Space Science Institute, Boulder, CO, USA
⁴Lunar and Planetary Laboratory, Tucson, AZ, USA
⁵Arizona State University, Tempe, AZ, USA
⁶Cornell University, Ithaca, NY, USA
⁷Jet Propulsion Laboratory, Pasadena, CA, USA

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¹T. Michalik,¹K. Stephan,²E. A. Cloutis,¹K.-D. Matz,³R. Jaumann,⁴A. Raponi,¹K. A. Otto
The Planetary Science Journal 3, 182 Open Access link to Article [DOI https://doi.org/10.3847/PSJ/ac7be0]
¹Institute for Planetary Research, German Aerospace Center, DLR e.V., Rutherfordstr. 2, D-12489 Berlin, Germany; tanja.michalik@dlr.de
²Department of Geography, University of Winnipeg, 515 Portage Avenue, Winnipeg, MB, R3B 2E9, Canada
³Freie Universität Berlin, Malteserstr. 74-100, D-12249 Berlin, Germany
⁴Institute for Space Astrophysics and Planetology (IAPS), National Institute for Astrophysics (INAF), Via Fosso del Cavaliere 100, I-00133 Rome, Italy

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^1,2Tomoya Obase,¹Daisuke Nakashima
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2022.115290]
¹Division of Earth and Planetary Materials Science, Graduate School of Science, Tohoku University, Aoba, Sendai, Miyagi 980-8578, Japan
²Department of Earth and Planetary Sciences, Faculty of Science, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan
Copyright Elsevier

Astronomical observations of solar-like stars and theoretical predictions have proposed a high long-term average solar wind flux in the past, such as more than ~10 times higher than the present-day value at ~3 Ga. Solar-gas-rich meteorites are lithified asteroidal regolith materials that had been exposed to solar wind in the past and some of which may record the ancient solar wind. To test the hypothesis of dense solar wind in the past Solar System, we quantified the past solar wind 36Ar particle fluxes based on the correlations between the solar and cosmogenic noble gas concentrations in individual solar-gas-rich meteorites. As a result, the past solar wind fluxes recorded in six solar-gas-rich meteorites were comparable to the present-day value except for the R chondrite PRE 95410, showing a few times higher solar wind flux. The howardite Kapoeta perhaps records the solar wind flux at some time between ~1 and ~ 2 Ga, suggesting that the solar wind flux in the past at least ~1 Ga had been similar to the present-day value. These results may indicate that the past solar wind flux had been lower than that proposed by the astronomical observations and the theoretical predictions. Otherwise, the six meteorites would have acquired recent solar wind when the solar wind flux had already been down to the present-day level.

¹Matthew A. Pasek, ²Arthur Omran,¹Tian Feng,¹Maheen Gull,¹Carolyn Lang,¹Josh Abbatiello,¹Lyle Garong,¹Ray Johnston,¹Jeffrey Ryan,³Heather Abbott-Lyon
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2022.09.027]
¹School of Geosciences, University of South Florida, 4202 E Fowler Ave NES 204, Tampa, FL 33620, USA
²Department of Chemistry, University of North Florida, Jacksonville, FL 32224, USA
³Department of Chemistry, Kennesaw State University, Kennesaw, GA 30144, USA
Copyright Elsevier

A general assumption about the geochemical behavior of phosphorus (P) is that it exists exclusively in the +5 oxidation as phosphate. However, in extremely reducing environments, other oxidation states of phosphorus such as +3 may also be stable. Such environments—if prevalent globally—may determine planetary habitability, which is in part governed by nutrient availability, including the availability of the element phosphorus. Here we show a route to P liberation from water-rock reactions that are thought to be common throughout the Solar System. We report the speciation of phosphorus in several serpentinite rocks and muds to include the ion phosphite (HPO32- with P3+) and show that reduction of phosphate to phosphite may be predicted from thermodynamic models of serpentinization. Furthermore, the amount of phosphite exceeds the amounts predicted from thermodynamic models in three of nine samples analyzed. As a result, as olivine and other silicates in ultramafic rocks alter to serpentine minerals, phosphorus as the significantly more soluble and reactive phosphite ion should be released under low redox conditions, liberating this key nutrient for life. Thus, this element may be accessible to developing life where water is in direct contact with ultramafic rock, providing a source of this nutrient to potentially habitable worlds.

¹G.Munaretto,¹A.Lucchetti,¹M.Pajola,¹G.Cremonese,^1,2M.Massironi
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2022.115284]
¹INAF, Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio, Italy
²Department of Geosciences, University of Padova, Padova, Italy
Copyright Elsevier

The origin and formation mechanism of Mercury’s hollows, which are bright, often haloed, small, shallow, irregular, rimless and flat floored depressions, represent one of the major open science questions regarding the Hermean surface and the processes shaping it morphology. In this work, we perform a photometric modelling of multiangular and multiband images of Tyagaraja and Canova craters’ hollows to investigate the physical properties of their reflecting material. Thanks to such observations, we demonstrate that we can derive a better topographic correction when compared to the one obtained from the global photometric models of Mercury. Indeed, our parameters, which result from the inversion of the Hapke and Kaasalainen-Shkuratov models, can be useful for both future spectrophotometric analyses of Mercury and laboratory experiments aiming to identify hollows analogue materials. The analysis of our estimated model parameters imply that the Tyagaraja and Canova hollow walls are more backscattering and smoother than the crater floors, in agreement with independent phase ratio analyses. Our results suggest that the hollow forming material is made of roundish particles or particles with a high density of scattering centers, such as holes, vesicles or fractures, consistent with the release of volatiles as part of the hollows’ formation mechanism.

^1,2,3ShiYong Liao,²Birger Schmitz
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2022.115285]
¹Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing, China
²Astrogeobiology Laboratory, Department of Physics, Lund University, Lund, Sweden
³CAS Center for Excellence in Comparative Planetology, Hefei, China
Copyright Elsevier

The breakup of the L-chondrite parent body (LCPB) in the asteroid belt at 466 Ma ago is the largest asteroid breakup documented in Earth’s geological record for the past ca. three billion years. Recovery of abundant macroscopic fossil L chondrites in mid-Ordovician marine sediments as well as reconstructions of the flux of micrometeoritic chrome spinel through the ages have given much new information on the precise timing of the breakup and its effects on Earth. In the present study, we focus on the flux of large micrometeorites to Earth shortly (in the 2 Ma time interval) before the LCPB breakup (pre-LCPB), which may be crucial for understanding the dynamical evolution of the asteroid belt leading up to the breakup. We present chrome-spinel data (32–355 μm grain size) from two mid-Ordovician limestone sections in Sweden (Kinnekulle and Öland, 300 km apart) and one section in western Russia (Lynna River), ca. 1100 km from Kinnekulle. One aim is also to test the level of reproducibility of chrome-spinel flux reconstructions between different sites.

Between 300 and 600 kg of limestone were collected from each section in the stratigraphic interval corresponding to ca. 2 Ma before up to immediately before the LCPB breakup. The relations between H, L and LL meteorites from Kinnekulle (38.7 ± 6.3%, 33.2 ± 6.1% and 28.1 ± 5.8%), Öland (46.0 ± 5.6%, 31.2 ± 3.1% and 24.5 ± 4.8%) and Lynna River (38.2 ± 5.5%, 32.8 ± 5.3% and 29.0 ± 5.1%) sections are indistinguishable from each other within uncertainties, revealing a globally homogeneous influx of H, L and LL meteorites. This gives support for the validity of previous reconstructions for the meteorite flux based on chrome spinel reconstructions for fifteen time windows through the Phanerozoic.

All the pre-LCPB samples from the three regions show a collective dominance of H-chondritic grains (42 ± 3%) over L (31 ± 3%) and LL grains (27 ± 3%), largely similar to the Phanerozoic background flux. Intriguingly, the presence of background concentrations of L-chondritic material also in the pre-LCPB flux demonstrates that the idea of a largely intact LCPB still existing before the final breakup may be far from reality. Apparently, a substantial amount of equilibrated chondritic material from deep levels of an L-chondritic body reached Earth even before the inferred catastrophic disruption at 466 Ma ago. This would concur with a “rubble pile” structure of the L-chondrite parent body and exposure of abundant deep-seated material as a result of earlier disruption and re-accretion events. The LL-chondritic contribution in the pre-LCPB flux is higher than at other Phanerozoic time windows, including the Cambrian. This anomalously enhanced flux thus cannot be ascribed to the Neoproterozoic breakup of the large LL-chondritic Flora asteroid. Previously observed high concentrations of chrome-spinel grains of achondritic origin can be reproduced only in our samples from immediately (< 1 Ma) before the LCPB breakup. We speculate that this, together with the high LL percentage before the breakup, may be explained by dynamic perturbations, possibly in the near-Earth region, leading up to the LCPB event.