¹Elin M. Morton,^1,4Harvey Pickard,²Frank Wombacher,¹Yihang Huang,³Emeliana Palk,¹Rayssa Martins,⁵Sven Kuthning,⁶Maria Schönbächler,¹Mark Rehkämper
The Astrophysical Journal 977, 53 Open Access Link to Article [DOI 10.3847/1538-4357/ad87ed]
¹Department of Earth Science & Engineering, Imperial College London, London SW7 2AZ, UK
²Institut für Geologie und Mineralogie, Universität zu Köln, Zülpicher Str. 49b, 50674 Köln, Germany
³School of Earth Sciences, University of Bristol, Bristol BS8 1RJ, UK
⁴National Environmental Isotope Facility, British Geological Survey, Keyworth, Nottingham, NG12 5GG, UK
⁵Geologischer Dienst NRW—Landesbetrieb, De-Greiff-Straße 195, 47803 Krefeld, Germany
⁶Department of Earth Sciences, ETH Zürich, Clausiusstrasse 25, 8092 Zürich, Switzerland

The origin of volatile depletion in the solar system remains a topic of intense debate. To further inform our understanding of the mechanisms involved, this study characterized the mass-dependent Zn, Cd, and Te isotope compositions and concentrations of a comprehensive suite of carbonaceous chondrites (CCs). In accord with previous studies, Zn and Te display covariations between light isotope enrichments and elemental depletions. Observed here for the first time, Cd shows a similar trend. These correlations are consistent with the interpretation that the primary volatile element budgets of CCs were established by mixing of a volatile-rich CI-like matrix and a volatile-depleted non-matrix endmember (NME) in the solar nebula. All three elements display minor isotopic variations in CI and CM chondrites, as a consequence of aqueous alteration at low temperatures. In contrast, Cd and Te isotope compositions and concentrations are highly variable in CV and CO (Cd) and CK chondrites (Te). This reflects mobilization of the elements during thermal metamorphism at distinct redox conditions. The data of this study show that the NME has Zn, Cd, and Te concentrations that are depleted to an identical level of 0.12 ± 0.03 × CI chondrites, and it is characterized by mass-dependent isotope compositions for all three elements that are fractionated to light isotope values relative to CIs by a similar extent. In conjunction with literature data, this suggests that the concentrations and isotope compositions of NME volatiles record the same depletion processes, and that the NME volatile inventory is likely hosted predominantly in chondrules.

¹Lauren E. McGraw,¹Cristina A. Thomas,²Tim A. Lister,³Becky J. Williams,⁴Andy S. Rivkin,⁵Bryan Holler,⁶Leslie A. Young
The Astrophysical Journal 977, L25 Open Access Link to Article [DOI 10.3847/2041-8213/ad9728]
¹Northern Arizona University, Flagstaff, AZ 86011, USA
²Las Cumbres Observatory, Goleta, CA 93117, USA
³University of Virginia, Charlottesville, VA 22904, USA
⁴JHU/APL, Laurel, MD 20146, USA
⁵Space Telescope Science Institute, Baltimore, MD 21218, USA
⁶Southwest Research Institute, Boulder, CO 80302, USA

Near-Earth object 2024 MK was discovered on 2024 June 16, less than 2 weeks before it made a sub-lunar-distance close approach. This close approach provided an ideal opportunity to determine how planetary encounters affect asteroid surfaces in preparation for the numerous missions to (99942) Apophis during its close approach in 2029. We collected spectroscopic data before and after its close approach to determine if planetary encounters induce spectral changes due to surface refreshing. We used NASA’s Infrared Telescope Facility’s (IRTF) near-infrared spectrometer SpeX prism mode (0.7–2.5 μm) to observe 2024 MK pre and postapproach. We also observed the asteroid before its close approach using Las Cumbres Observatory’s FLOYDS visible spectrometer and after its close approach using IRTF’s SpeX long-wavelength cross-dispersed short grating mode, resulting in full spectral coverage from 0.32 to 4.2 μm. 2024 MK is an S-type asteroid that is compositionally most analogous to an L-ordinary chondrite. Spectral analysis of the 3 μm region indicates no surficial water or hydroxide within the level of noise. Band parameter analysis of the pre and postapproach data shows the planetary encounter did not induce any significant spectral changes, suggesting that surface refreshing did not occur on a measurable scale. Similar studies of other targets at smaller encounter distances are required to determine if the lack of spectral changes on 2024 MK indicates it was not close enough to Earth to affect its surface or if the spectral similarity pre and postapproach instead indicates planetary encounters do not cause surface refreshing.

^1,2M. Galinier1, M. Delbo,^2,1C. Avdellidou,¹L. Galluccio
Astronomy & Astrophysics 683, L3 Open Access Link to Article [DOI https://doi.org/10.1051/0004-6361/202349057]
¹Université Côte d’Azur, CNRS–Lagrange, Observatoire de la Côte d’Azur, CS 34229, 06304 Nice Cedex 4, France
²University of Leicester, School of Physics and Astronomy, University Road, LE1 7RH Leicester, UK

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^1,2J. Bourdelle de Micas,^1,3S. Fornasier,⁴M. Delbo,⁴S. Ferrone,⁵G. van Belle,^6,7P. Ochner,⁴C. Avdellidou
Astronomy & Astrophysics 682, A64 Open Access Link to Article [DOI https://doi.org/10.1051/0004-6361/202347391]
¹LESIA, Observatoire de Paris, Université Paris Cité, Université PSL, CNRS, Sorbonne Université, 5 place Jules Janssen, 92195 Meudon, France
²INAF – Osservatorio Astronomico di Roma, Via Frascati 33, 00078 Monte Porzio Catone, Italy
³Institut Universitaire de France (IUF), 1 rue Descartes, 75231 Paris Cedex 05, France
⁴Université Côte d’Azur, CNRS-Lagrange, Observatoire de la Côte d’Azur, CS 34229, 06304 Nice Cedex 4, France
⁵Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, AZ 86001, USA
⁶INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
⁷Dipartimento di Fisica e Astronomia G. Galilei, Università di Padova, Vicolo dell’ Osservatorio 3, 35122 Padova, Italy

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^1,2M.Birlan et al. (>10)
Astronomy & Astrophysics 689, A334 Open Access Link to Article [DOI https://doi.org/10.1051/0004-6361/202450495]
¹IMCCE, Observatoire de Paris, CNRS UMRO 8028, PSL Research University, 77 av Denfert Rochereau, 75014 Paris Cedex, France
²Astronomical Institute of the Romanian Academy, 5 Cutitul de Argint, 040557, sector 4, Bucharest, Romania

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^1,2Ziyu Wang,¹Honglei Lin,³Binlong Ye,^4,5Yu-Yan Sara Zhao,^1,2Chao Qi,^2,6Jingyan Xu,^1,2Yong Wei
Astronomy & Astrophysics 690, A138 Open Access Link to Article [DOI https://doi.org/10.1051/0004-6361/202450888]
¹Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, PR China
²College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, PR China
³Department of Earth Sciences, University of Hong Kong, Hong Kong 999077, PR China
⁴Research Center for Planetary Science, College of Earth Science, Chengdu University of Technology, Chengdu 610059, PR China
⁵CAS Center for Excellence in Comparative Planetology, Hefei 230026, PR China
⁶State Key Laboratory of Continental Dynamics and Department of Geology, Northwest University, Xi’an 710069, PR China

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¹L.G. Vacher, ¹J. Eschrig, ¹L. Bonal, ²W. Fujiya, ¹L. Flandinet,¹P. Beck
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2024.12.016]
¹Institut de Planétologie et d’Astrophysique de Grenoble, Université Grenoble Alpes, CNRS CNES, 38000 Grenoble, France
²Faculty of Science, Ibaraki University, 2-1-1 Bunkyo, Mito, 310-8512 Ibaraki, Japan
Copyright Elsevier

Non-carbonaceous (NC) meteorites, such as enstatite and ordinary chondrites, are regarded as potential building blocks of terrestrial planets, possibly delivering volatile elements to the inner solar system. However, their parent bodies underwent intense thermal metamorphism during planet formation, raising questions about whether planets accreted volatile-rich or volatile-poor materials. Ordinary chondrites-like materials may have contributed significantly to the formation of Mars, but the impact of thermal metamorphism on their initial volatile content and isotopic composition is unclear. This study reports the bulk-rock hydrogen, carbon, and nitrogen abundances and isotopic compositions (δD, δ13C, δ15N) of unequilibrated ordinary chondrites (UOCs) across petrologic subtypes (PT) 3.00 to 3.9. Upon removing terrestrially contaminated samples, we found that the matrix-normalized hydrogen, carbon, and nitrogen concentrations are inversely correlated with the Raman spectral parameters (FWHMD), a tracer of thermal metamorphism in type 3 chondrites. Only δD shows a correlation with FWHMD, suggesting that δ13C and δ15N were not fractionated despite carbon and nitrogen being outgassed from the interior of the planetesimal. With increasing metamorphism, we proposed that less-metamorphosed UOCs (PT < 3.2) progressively lost deuterium (D) due to the breakdown of D-rich phyllosilicates above 300 °C, as supported by our FTIR analyses. We conducted thermal modeling to better understand how thermal metamorphism influences the delivery of water to terrestrial planets. Our results suggest that UOC-like precursors did not significantly contribute to Mars’ accretion due to the rapid progression of thermal metamorphism within ordinary chondrite planetesimals. However, volatile-rich UOCs may have supplied most of the hydrogen to Mars, implying that Mars’ primitive mantle may have recorded and retained a strong D-rich reservoir in its interior.

¹Dominik C. Hezel,²Kerstin A. Lehnert,³Premkumar Elangovan,²Peng Ji,²Jennifer Mays,⁴Jörn Koblitz
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14293]
¹Goethe-Universität Frankfurt, Institut für Geowissenschaften, Frankfurt am Main, Germany
²Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York, USA
³Astute Digital Solutions Ltd., Guildford, UK
⁴Schulstr. 18A, 27721 Ritterhude, Germany
Published by arrangement with John Wiley & Sons

MetBase has been the world’s largest database for meteorite compositions, but has now passed this torch on to the Astromaterials Data System (Astromat), into which MetBase has recently been merged. This merger had been planned for some time and took almost 1 year to complete. Not only differences in the structure of the databases, in the content and organization of data and metadata, and in the terminology used but also incorporation of new data needed to be resolved to combine the data holdings of MetBase with the Astromat synthesis database. Astromat is NASA’s primary archive for laboratory analyses of astromaterial samples and funded by NASA to provide services for the preservation and open access of data from astromaterials, including meteorites, in alignment with the FAIR principles. After merging MetBase into Astromat’s synthesis database, this now provides the cosmochemical community the largest compilation of cosmochemical analytical data by far: over 2 million analytical data points. Astromat is also part of a bigger ecosystem of geo- and cosmochemcial databases, as its foundation is aligned with other large geochemical databases such as EarthChem and GEOROC. The visualization tools and the teaching tool from MetBase will be further developed and now exist as independent tools. We provide a brief history of the two databases and their journeys, an outlook toward the future, as well as lessons learned from this merger. We recommend that other cosmochemical databases try whenever possible to adopt the Astromat database schema as early as possible, or get in contact for alternative options. We believe MetBase now being a part of Astromat is a match made in heaven and hope Astromat will become a reliable and trusted service within the community.

^1,6,7Hung Kwan Fok,^2,3,4,7Marco Pignatari,^2,7Benoît Côté,^5,1,7Reto Trappitsch
The Astrophysical Journal Letters 977, L24 Open Access Link to Article [DOI 10.3847/2041-8213/ad91ab]
¹Department of Physics, Brandeis University, Abelson-Bass-Yalem 107, Waltham, MA 02453, USA
²Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, HUN-REN, Konkoly Thege M. út 15-17, Budapest 1121, Hungary
³ CSFK, MTA Centre of Excellence, Konkoly Thege Miklós út 15-17, Budapest 1121, Hungary
⁴E. A. milne Centre for Astrophysics, University of Hull, Cottingham Road, Kingston upon Hull, HU6 7RX, UK
⁵Laboratory for Biological Geochemistry, School of Architecture, Civil & Environmental Engineering, École
Polytechnique Fédérale de Lausanne, GR C2 505, Station 2, 1015 Lausanne, Switzerland
⁶Morton K. Blaustein Department of Earth & Planetary Sciences, Johns Hopkins University, Olin Hall, 3300 San Martin Drive, Baltimore, MD 21218, USA
⁷NuGrid Collaboration (https://nugridstars.org)

Presolar grains are stardust particles that condensed in the ejecta or in the outflows of dying stars and can today be extracted from meteorites. They recorded the nucleosynthetic fingerprint of their parent stars and thus serve as valuable probes of these astrophysical sites. The most common types of presolar silicon carbide grains (called mainstream SiC grains) condensed in the outflows of asymptotic giant branch stars. Their measured silicon isotopic abundances are not significantly influenced by nucleosynthesis within the parent star but rather represent the pristine stellar composition. Silicon isotopes can thus be used as a proxy for galactic chemical evolution (GCE). However, the measured correlation of ²⁹Si/²⁸Si versus ³⁰Si/²⁸Si does not agree with any current chemical evolution model. Here, we use a Monte Carlo model to vary nuclear reaction rates within their theoretical or experimental uncertainties and process them through stellar nucleosynthesis and GCE models to study the variation of silicon isotope abundances based on these nuclear reaction rate uncertainties. We find that these uncertainties can indeed be responsible for the discrepancy between measurements and models and that the slope of the silicon isotope correlation line measured in mainstream SiC grains agrees with chemical evolution models within the nuclear reaction rate uncertainties. Our result highlights the importance of future precision reaction rate measurements for resolving the apparent data–model discrepancy.

^1,2,3Akira Tsuchiyama, ⁴Hirotaka Yamaguchi, ⁴Motohiro Ogawa, ⁵Akiko M. Nakamura, ⁶Tatsuhiro Michikami, ⁷Kentaro Uesugi
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2024.116432]
¹Chinese Academy of Sciences (CAS) Key Laboratory of Mineralogy and Metallogeny/Guangdong Provincial Key Laboratory of Mineral Physics and Materials, Guangzhou Institute of Geochemistry, CAS, 511 Kehua Street, Wushan, Tianhe District, Guangzhou 510640, China
²CAS Center for Excellence in Deep Earth Science, 511 Kehua Street, Wushan, Tianhe District, Guangzhou 510640, China
³Research Organization of Science and Technology, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu, Shiga 525-8577, Japan
⁴Division of Earth and Planetary Sciences, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan
⁵Department of Planetology, Graduate School of Science, Kobe University, Rokkodai, Nada-ku, Kobe 657-8501, Japan
⁶Faculty of Engineering, Kindai University, Hiroshima Campus, 1 Takaya Umenobe, Higashi-Hiroshima, Hiroshima 739-2116, Japan
⁷Scattering and Imaging Division, Japan Synchrotron Radiation Research Institute (JASRI/SPring-8), 1-1-1 Kouto, Sayo-Cho, Sayo-Gun, Hyogo 679-5198, Japan
Copyright Elsevier

The shape of regolith particles on airless bodies, such as the Moon and asteroids, reflects the processes that occur on their surfaces. Recent studies have shown that particles on the asteroid Ryugu tend to be angular, whereas some particles on the asteroid Itokawa are rounded, with a larger portions of lunar particles also exhibiting a rounded shape. These differences are thought to result from abrasion, but experimental studies on particle abrasion have been lacking. In this study, we performed experiments simulating the abrasion caused by impact on airless bodies using minerals, rocks, and meteorites related to the Moon and asteroids. Aggregates of particles ranging in size from 1 to 2 mm (6.5 to10 g) were subjected to oscillation in a bead-milling apparatus to assess the amount of abrasion at different oscillation rates, varying from 100 to 3000 rpm for 0.33 to 720 min. The amount of abrasion increased with time and oscillation rate, following a power-law relationship. Once the oscillation rate exceeded a certain threshold, abrasion proceeded rapidly. At rates above 1000 rpm, particles floated and rubbed against each other due to the vertical oscillation of the container, leading to significant abrasion, whereas at rates below 300 rpm, the particles were constrained by Earth’s gravity, resulting in minimal abrasion. This indicates that experiments conducted at ≥1000 rpm effectively simulated the abrasion that occurs on the Moon and asteroids. Scanning electron microscopy was used to observe the particles before and after the experiments, and X-ray microtomography was employed to track the shape changes of individual traceable particles and to measure the three-axial lengths of approximately160 particles. As abrasion progressed, some of the corners and edges of the particles were initially chipped, eventually leading to rounded corners, edges, and surfaces. This process corresponds to “adhesive wear” in tribology, which is caused by tangential relative motion between materials. In carbonaceous chondrite samples, particles tended to split along pre-existing cracks. The particles became smaller, their angularity decreased, and their sphericity increased, while the overall 3D shape of individual particles did not significantly change from their original form; however, the average three-axial ratio became more isotropic. These results indicate that the change in the average three-axial ratio of the Moon and Itokawa regolith particles can be explained by abrasion, as previously proposed. Based on the observed abrasion rates, we discuss the potential for abrasion to be caused by the impact-induced particle motion on the Moon and asteroids, considering models of regolith convection, excavation flow, and maximum acceleration. Although this discussion is rough and only semi-quantitative due to many assumptions, experimental errors, and uncertainties in the models, the results suggest that abrasion can occur on the Moon due to impact-induced particle motion, and that the abrasion observed on Itokawa particles may have occurred not on Itokawa itself, but on its parent body. Ryugu particles, in contrast, are more prone to cracking along pre-existing cracks rather than undergoing significant abrasion, and thus exhibit minimal signs of abrasion.