¹Michael C. Bouchard, ¹Bradley L. Jolliff
Icarus (in Press) Open Access Link to Article [https://doi.org/10.1016/j.icarus.2025.116752]
¹Department of Earth and Planetary Sciences, Washington University in St. Louis, Campus Box 1169, 1 Brookings Drive, St. Louis, MO 63130-4899, United States of America
Copyright Elsevier

Perseverance Valley is an erosional feature with the appearance of an eroded gully, located in the western wall of the Noachian aged Endeavour crater in Meridiani Planum, Mars. It is the most lithologically diverse location investigated by the Opportunity rover other than Cape York, where the rover first characterized the pre-, post-, and syn-depositional lithologies of Endeavour crater. We use hierarchical clustering and a similarity index combined with examination of Panoramic camera and Microscopic Imager images to classify these rock suites in Perseverance Valley, and contextualize them with comparison to rocks examined previously along the rim of Endeavour crater. The Perseverance Valley lithologies are classified into four rock suites, a clast-poor impact breccia that forms the “walls” of the valley, a competent basaltic outcrop of rocks that appear “blue” in false color Panoramic camera imagery, an outcrop of pitted rocks that has among the highest silica concentrations investigated by Opportunity, and a loose regolith mixture of martian soil, impact breccia, and local “blue” rocks that makes up the valley floor. Macro and micro textures indicate that the valley is currently being eroded by wind exiting the crater basin from west to east. Units that are offset both within and across Perseverance Valley indicate that the valley location and structure is likely influenced by a system of radial impact faults. Lithologies such as the co-located “blue” (in false color) and silica-rich pitted rocks, and observations of aqueous alteration such as “red” (in false color) zones, show similarities between Perseverance Valley and both Marathon Valley and the Spirit of St. Louis feature. We explore multiple working hypotheses to explain the formation mechanisms of Perseverance Valley, but can now say: the valley is likely structurally controlled including an ~80 m vertical offset by a graben; the valley hosted local aqueous alteration; the floor material of the valley consists of mass-wasted local materials; and the current topographic expression was overprinted by modern aeolian erosion.

¹Shiori Inada, ²Tetsuya Hama, ^1,3Shogo Tachibana
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2025.07.018]
¹Department of Earth and Planetary Science, The University of Tokyo, 7-3-1 Hongo, Tokyo 113-0033, Japan
²Komaba Institute for Science and Department of Basic Science, The University of Tokyo, 3-8-1 Komaba, Tokyo 153-8902, Japan
³UTokyo Organization for Planetary and Space Science, The University of Tokyo, 7-3-1 Hongo, Tokyo 113-0033, Japan
Copyright Elsevier

IIsotopic fractionation resulting from kinetic isotope effects (KIEs) in evaporation is a key to investigating high-temperature evaporation events in the early Solar System. The magnitude of the KIEs is represented by the kinetic isotope fractionation factor , which is predicted as  (: the mass ratio of the isotopic evaporated gas species) to a first approximation based on the Hertz-Knudsen equation. However, the experimentally measured  are often closer to 1 than this prediction to various degrees. In this study, we investigated the reason for this observation based on the transition state theory. To evaluate the classical (high-temperature) limit of , which is given by the isotopic ratio of the imaginary frequencies representing the evaporative motion at the transition state, we constructed a simple model for the vibrational normal mode analysis. In this model, we included the effects of the interaction of the evaporating species with the condensed phase surface, as well as the degrees of freedom of atoms in the condensed phase. The present theory clarified the relationship between the magnitude of the evaporative KIEs and the properties of the potential energy surface: the classical limit of  becomes closer to 1 than  due to the effect of the condensed-phase degrees of freedom when there exists a potential energy barrier, which is related to unstable interaction between the evaporating species and the condensed phase surface. This result is consistent with the previous experimental data and provides general insights into classical KIEs in chemical reactions.

¹S.A. Singerling, ¹F.E. Brenker, ¹B. Tkalcec, ²S.S. Russell, ³T.J. Zega, ⁴T.J. McCoy, ^3,5,6H.C. Connolly Jr., ³D.S. Lauretta
Geochimica et Cosmochimica Acta (in Press) Open Access Link to Article [https://doi.org/10.1016/j.gca.2025.06.028]
¹Schwiete Cosmochemistry Laboratory, Goethe University, Frankfurt, Germany
²Planetary Materials Group, Natural History Museum, London, UK
³Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
⁴Department of Mineral Sciences, National Museum of Natural History, Smithsonian Institution, Washington, DC, USA
⁵Department of Geology, Rowan University, Glassboro, NJ, USA
⁶Department of Earth and Planetary Sciences, American Museum of Natural History, New York, NY, USA
Copyright Elsevier

We describe nanoscale observations obtained via transmission electron microscopy of Na,Ca carbonates in OSIRIS-REx samples of asteroid Bennu. Four Na,Ca carbonate grains were observed (including the one briefly described in McCoy and Russell et al., 2025), ranging in size from 140 nm to 2.36 µm. The stoichiometry of the grains and electron diffraction data best match gaylussite (Na2Ca(CO3)2·5H2O) or pirssonite (Na2Ca(CO3)2·2H2O). The grains rapidly amorphized under the electron beam. We also found that the grains are reactive to the terrestrial atmosphere, with their compositions and textures changing over six months of storage in a standard desiccator. NaCl salts grew on the exteriors of the grains, and the compositions of the carbonates became richer in C, F, Cl, and Ca and poorer in O and Na.
Neither gaylussite nor pirssonite have been observed in planetary materials other than samples from Bennu. On Earth, these phases occur in evaporites or shales from alkali lakes and, less commonly, as veins in alkaline igneous rocks. Thermodynamic modeling has shown that both phases require a low-temperature (<55 °C), Na-rich (>140 g/kg Na2CO3) brine, and their presence in the Bennu samples supports a model of salt formation on the parent body during syndepositional back-reaction of a briny fluid (McCoy and Russell et al., 2025). We argue that these minerals have not been previously observed owing either to their rare formation conditions or their susceptibility to degradation from sample preparation and analysis (e.g., electron/ion beam imaging), terrestrial weathering, and/or storage in a terrestrial environment. This study highlights the importance of collecting and carefully preserving pristine samples from planetary bodies.

¹T. Cuppone,²C. Carli,¹M. Casalini,^1,3A. Stephant,³C. R. Greenwood,^1,2G. Pratesi
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70007]
¹Dipartimento di Scienze della Terra, Università degli Studi di Firenze, Florence, Italy
²Istituto di Astrofisica e Planetologia Spaziali—INAF, Rome, Italy
³School of Physical Sciences, The Open University, Milton Keynes, UK
Published by arrangement with John Wiley & Sons

NWA 13489 is a meteorite that has been classified as a brachinite. Brachinites are olivine-rich primitive achondrites representing residual products after a variable degree of silicate melt extraction on a barely differentiated, noncarbonaceous asteroid. Nevertheless, NWA 13489 displays petrographic and mineralogical characteristics that are anomalous when compared with other meteorites of that group. The petrography and thermometric data of this sample are compatible with a high metamorphic grade origin. NWA 13489 results in intermediate between type 6 and 7 chondrites, with a thermal regime broadly straddling the FeNi-FeS eutectic and the onset of silicate melting, resembling other meteorites defined as primitive achondrites. Evidence from mineral chemistry, bulk trace element geochemistry, and oxygen and chromium isotope systematics shows a “carbonaceous” composition and, therefore, NWA 13489 is not a brachinite. Rather, together with an ungrouped chondrite (the NWA 11961 C3-ungrouped) and other ungrouped achondrites (the paired NWA 10503/10859), NWA 13489 supports the existence of a distinct carbonaceous-like meteorite grouplet.

¹Zahia Djouadi,²Vassilissa Vinogradoff,¹Zelia Dionnet,²Coline Serra,³Douchka Dimitrijevic,⁴Alexandra Malnuit,¹Cateline Lantz,⁵Philippe Claeys,⁵Steven Goderis,²Louis Le Sergeant d’Hendecourt
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70017]
¹CNRS, Institut d’Astrophysique Spatiale, Université Paris-Saclay, Orsay, France
²UMR CNRS 7345, PIIM, Université Aix-Marseille, Marseille, France
³École Centrale de Lyon, Écully, France
⁴Université Paris-Saclay, Orsay, France
⁵Archaeology, Environmental Changes & Geo-Chemistry, Vrije Universiteit Brussel, Brussels, Belgium
Published by arrangement with John Wiley & Sons

Carbonaceous chondrites are meteorites originating from undifferentiated objects of the Solar System, which may retain signatures of primitive matter. Here, we present a comparative study between two CM chondrites Asuka 12236 and Paris, both considered among the most primitive in the carbonaceous chondrite meteorite collection. This work is based on the combination of infrared and Raman micro-spectroscopy, aiming to compare the spectral characteristics of these two peculiar chondrites. We present an average infrared spectrum from the mid to far infrared of Asuka 12236, which has never been reported yet in the literature. Contrary to the average spectrum of Paris, the Asuka 12236 spectrum shows signatures of anhydrous minerals (olivine and or pyroxene) as well as the presence of amorphous phases. These findings are in agreement with the low degree of alteration reported for Asuka 12236. Aromatic primary amines and imines are also detected in Asuka 12236, heterogeneously distributed within the meteorite. In addition, the comparison of the Raman signatures of the two meteorites highlights different carbon structuration and thus thermal histories. Our spectroscopic investigations confirm that Asuka 12236 can be considered more primitive than the Paris carbonaceous chondrite.

¹Svetlana N. Teplyakova,¹Cyril A. Lorenz,¹Marina A. Ivanova
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70013]
¹Vernadsky Institute of Geochemistry and Analytical Chemistry, Moscow, Russia
Published by arrangement with John Wiley & Sons

We investigated the metal nodules, veins, fine-grained particles of ordinary chondrites (OC) Ash Creek (L6), Ghubara (L5), NWA 6096 (L6), Tsarev (L5), Kunya-Urgench (H5), NWA 1588 (H3.8), Tamdakht (H5) and Timochin (H5) using optical microscopy, SEM, and LA-ICP-MS to determine trace element distributions and understand the origin of these metal components. The metal nodules have a fractionated siderophile element composition differing from OC metal, indicating the elements were distributed during melting. Most nodules and veins are depleted in Cu and the highly refractory siderophile elements (HRSE) Re, Os, Ir, Ru, Pt, and Rh. Nodules and veins are enriched in W, Mo, Ni, Co, Au, As, and Sb compared to OC metal. Kunya-Urgench metal shows progressive depletion of refractory siderophile elements, likely due to in situ fractionation of liquid metal injected into the chondrite host. We modeled crystallization of L and H chondrite metal melts, producing results similar to the observed compositions, supporting the hypothesis that the metal components may have originated from unfractionated melted in situ primary metal of chondrites. Variations between modeled and observed W, Fe, and Ga abundances suggest varying redox conditions during melting or metamorphism. Tsarev nodule has a unique HRSE zoning recording its high-temperature thermal history, with modeled cooling to 1300°C in ~1 year, suggesting crystallization in a thermally insulated environment, possibly under a hot layer of impact ejecta. The low-temperature thermal histories (660–200°C) of investigated meteorites’ metal suggest that shock compression and re-heating may have resulted in a subsolidus decomposition/recrystallization of the metal.

¹M. K. McClure et al. (>10)
Nature 643, 649-653 Link to Article [DOI https://doi.org/10.1038/s41586-025-09163-z]
¹Leiden Observatory, Leiden University, Leiden, The Netherlands

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¹Charles E. Woodward,²Dominique Bockélee-Morvan,³David E. Harker,⁴Michael S. P. Kelley,^5,6Nathan X. Roth,⁷Diane H. Wooden,⁸Stefanie N. Milam
The Planetary Science Journal 6, 139 Open Access Link to Article [DOI 10.3847/PSJ/add1d5]
¹Minnesota Institute for Astrophysics, School of Physics and Astronomy, 116 Church Street SE, University of Minnesota, Minneapolis, MN 55455, USA
²Observatoire de Paris, France
³Department of Astronomy and Astrophysics, University of California, San Diego, 9500 Gilman Drive, MC 0424, La Jolla, CA 92093-0424, USA
⁴University of Maryland, Department of Astronomy, 4254 Stadium Drive, College Park, MD 20742-2421, USA
⁵Solar System Exploration Division, Astrochemistry Laboratory Code 691, NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771, USA
⁶Department of Physics, American University, 4400 Massachusetts Avenue NW, Washington, DC 20016, USA
⁷NASA Ames Research Center, SpaceScience Division, MS 245-1, Moffett Field, CA 94035-1000, USA
⁸NASA Goddard Space Flight Center, USA

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¹William F. Bottke,²Alex J. Meyer,³David Vokrouhlický,¹David Nesvorný,⁴Edward B. Bierhaus,⁵Daniella N. DellaGiustina,¹Rachael Hoover,⁶Harold C. Connolly,⁵Dante S. Lauretta
The Planetary Science Journal 6, 150 Open Access Link to Article [DOI 10.3847/PSJ/add46a]
¹Southwest Research Institute, 1050 Walnut St., Suite 300, Boulder, CO 80302, USA
²University of Colorado Boulder, 3775 Discovery Dr., Boulder, CO 80309, USA
³Institute of Astronomy, Charles University, V Holešovičkách 2, CZ-18000, Prague 8, Czech Republic
⁴Lockheed Martin Space, Littleton, CO 80127, USA
⁵Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA
⁶Department of Geology, Rowan University, Glassboro, NJ 08028, USA

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^1,2Fridolin Spitzer,^1,3Timo Hopp,^1,2Christoph Burkhardt,³Nicolas Dauphas,^1,2Thorsten Kleine
Earth and Planetary Science Letters 667, 119530 Open Access Link to Article [https://doi.org/10.1016/j.epsl.2025.119530]
¹Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3 37077, Göttingen, Germany
²Institut für Planetologie, University of Münster, Wilhelm-Klemm-Str. 10 48149, Münster, Germany
³Origins Laboratory, Department of the Geophysical Sciences and Enrico Fermi Institute, The University of Chicago, Chicago 60637, USA
Copyright Elsevier

Differentiated meteorites sample planetesimals formed earlier than the parent bodies of chondritic meteorites. To evaluate whether these two generations of planetesimals formed from the same or distinct materials, we have analyzed the Fe and Ni isotopic compositions for a large set of differentiated meteorites, representing approximately 26 distinct parent bodies. Most of these samples are genetically related to the carbonaceous chondrite (CC)-type reservoir, which is thought to represent some portion of the outer disk. The new data reveal that early and late CC planetesimals cover a similar range of Fe and Ni isotopic compositions, indicating that all these bodies accreted from the same mixture of dust components, either in a long-lived pressure structure of the disk or in different substructures containing the same materials. Many differentiated meteorites have an isotopic composition similar to the late-formed CR chondrites, indicating that the CR chondrite reservoir was established early and remained isolated for essentially the entire disk lifetime. Finally, CI chondrites are the only CC chondrites whose isotopic composition is not represented among differentiated meteorites. Thus, planetesimals with CI chondrite-like isotopic compositions represent a late burst of planetesimal formation and possibly formed by a distinct mechanism and/ or in a different location from the other CC planetesimals.