^1,2Laurence A. J. Garvie,³László Trif,⁴Christian G. Hoover
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70000]
¹Buseck Center for Meteorite Studies, Arizona State University, Tempe, Arizona, USA
²School of Earth and Space Exploration, Arizona State University, Tempe, Arizona, USA
³Institute of Materials and Environmental Chemistry, HUN-REN Research Center for Natural Sciences, Budapest, Hungary
⁴School of Sustainable Engineering and the Built Environment, Ira A. Fulton Schools of Engineering, Arizona State University, Tempe, Arizona, USA
Published by arrangement with John Wiley & Sons

Meteorites arriving on Earth possess indigenous organic, isotopic, mineralogic, and magnetic properties that reveal conditions and processes from their formation. However, these properties can rapidly change when exposed to the Earth’s environment. Asteroids, which formed nearly 4.5 billion years ago, inhabit the ultrahigh vacuum of interplanetary space, with a pressure of around 1.3 × 10−11 Pa, equivalent to only a few tens of atoms per cubic centimeter. Fragments of these asteroids, which land on Earth as meteorites, immediately adsorb atmospheric gases into their pore spaces, which can subsequently adsorb into and onto the minerals. In this study, we show that adsorption of atmospheric water can significantly increase the mass of the smectite-rich Tarda (C2-ung) meteorite, with mass gains reaching around 30 wt% at 100% relative humidity (RH) and between 5 and 10 wt% under typical laboratory conditions (up to ~50% RH). In contrast, the serpentine-rich Aguas Zarcas meteorite gains approximately 11 wt% at 100% RH and around 2 wt% at ~50% RH. This water adsorption leads to observable mass fluctuations in clay-rich carbonaceous chondrites (CCs), especially those with high smectite content, which undergo a “breathing-like” process. This process involves the uptake and release of water, influenced by atmospheric humidity. Although this mass change is reversible in the short term, prolonged “breathing” can alter the mineral composition and physical properties of these materials, complicating our understanding of their origins and evolution. For instance, gypsum forms in Tarda after 10 min of exposure to 100% RH at room temperature, while the Aguas Zarcas meteorite forms significant gypsum within 24 h under similar conditions. In addition, mass changes for Tarda are measured with thermal gravimetry in a He atmosphere, by heating the sample at 100°C in a high vacuum, and after curation under an ultradry atmosphere. These experiments show that samples exposed to the atmosphere rapidly adsorb significant water that is not removed by curation under dry N2. Our findings indicate that this “breathing” process can profoundly and rapidly affect the properties of astromaterials, including samples returned from asteroids Ryugu and Bennu. Maintaining these materials in a stable, low-humidity environment can help prevent such changes and preserve their indigenous properties.

¹Coral K. Chen, ²Meng Guo, ¹Jun Korenaga, ³Simone Marchi
Earth and Planetary Science Letters 666, 119493 Link to Article [https://doi.org/10.1016/j.epsl.2025.119493]
¹Department of Earth and Planetary Sciences, Yale University, New Haven, CT 06520, United States of America
²Asian School of the Environment, Nanyang Technological University, 600259, Singapore
³Department of Space Studies, Southwest Research Institute, Boulder, CO 80302, United States of America
Copyright Elsevier

As an important reservoir for incompatible elements, the growth of the continental crust profoundly influenced the composition of the mantle and the atmosphere. The co-evolution of the continental crust, mantle, and atmosphere throughout Earth history can be traced through the transfer of argon and potassium between these three reservoirs. While many argon-constrained crustal growth models have been proposed, none of them consider the effect of late accretion (bombardment by leftover planetesimals in the several hundred million years after the Moon formed) in detail. Our model is the first of its kind to simulate both the volatile delivery and the atmospheric erosion by impacting planetesimals. Whereas the relative fraction of impactor-derived argon in the present-day atmosphere depends on the assumed impactor composition and the starting atmospheric mass, the present-day atmospheric argon originates largely from mantle degassing and crustal processing. For a range of impact parameters, our model results indicate that the early rapid growth of continental crust is required to satisfy the argon budget of the mantle and atmosphere.

¹William M. Lawrence, ¹Geoffrey A. Blake,¹John Eiler
Proceedings of the National Academy of Sciences of the USA (PNAS) 122, e2423345122 Link to Article [https://doi.org/10.1073/pnas.2423345122]
¹Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125

Macromolecular organic solids found in primitive meteorites were the main source of carbon delivered to forming planets in the early Solar System. However, the conditions under which this material formed and its subsequent incorporation into growing planetesimals remains a subject of vigorous debate. Here, we show that C isotope variations among these organics in most carbonaceous chondrites are strongly correlated with mass-independent O isotope anomalies exhibited by their host meteorites. As the latter signature has been argued to track abundances of nebular water generated from photochemical processing of CO gas, the C isotope variability of refractory organic solids may relate to this same process. We propose a framework in which CO photolysis simultaneously produces H2O and generates a pool of C+ ions that serve as precursors for C-rich organic solids, with their C isotope compositions suggesting formation over a relatively narrow and warm range of temperatures in the protoplanetary disk (~200 to 400 K). Two populations of organic precursors with different C isotope compositions became associated with distinct dust reservoirs prior to their delivery to the carbonaceous-chondrite-forming region, which likely resided at lower temperatures (<170 K). This finding places detailed constraints on the location and distribution of chemical reactions that generated both water and organic-rich reservoirs in the early Solar System.

¹Christian Liebske, ^1,3Amir Khan, ^1,2Scott M. McLennan, ¹Paolo A. Sossi
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2025.116666]
¹Institute of Geochemistry and Petrology, ETH Zürich, Switzerland
²Department of Geosciences, Stony Brook University, Stony Brook, NY, USA
³Institute of Geophysics, ETH Zürich, Switzerland
Copyright Elsevier

The terrestrial planets are believed to have accreted from chondritic meteorites of widely varying composition. Yet, making planets from known meteoritic material has proved elusive, be it their nucleosynthetic isotopic anomalies, bulk chemistry or geophysical properties. Because of the inherent non-uniqueness of meteoritic mixing models based on isotopes alone, combining geochemical and geophysical observations is key to identifying the nature of the building blocks of the terrestrial planets. Here, we integrate the recent proliferation of data in the form of geophysical measurements pertaining to Mars’s interior structure from the recent InSight mission including its astronomic-geodetic response, the chemical and isotopic compositions of undifferentiated and differentiated meteorites, and observational constraints on trace element abundances (K/Th ratio) in order to make new inferences on the constitution and provenance of Mars. Using stochastic mixing models of meteoritic material, we find that
0.02% of mixtures, consisting primarily of ordinary- and enstatite chondrites and, to a lesser extent, achondritic material, are able to reproduce the isotopic signature of Mars. Of these, however, none match the geophysical or Mg/Si and K/Th constraints, indicating that Mars is unlikely to have formed from known unmodified meteoritic material. Instead, relatively oxidised building blocks that are intrinsic to the inner solar system and underwent evaporation/condensation processes that lead to volatile-element depletion patterns unlike those in any known meteorite group, would be consistent with the isotopic, geochemical and geophysical properties of Mars.

¹G. Florin, ¹P. Gleißner, ¹H. Becker
Geochimica et Cosmochimica Acta (in Press) Open Access Link to Article [https://doi.org/10.1016/j.gca.2025.06.006]
¹Freie Universität Berlin, Institut für Geologische Wissenschaften, Malteserstr. 74-100, 12249 Berlin, Germany
Copyright Elsevier

In the last decade, several studies have reported enrichments of the heavy isotopes of moderately volatile elements in lunar mare basalts. However, the mechanisms controlling the isotope fractionation are still debated and may differ for elements with variable geochemical behaviour. Here, we present a new comprehensive dataset of mass-dependent copper isotope compositions (δ65Cu) of 30 mare basalts sampled during the Apollo missions. The new δ65Cu data range from +0.14 ‰ to +1.28 ‰ (with the exception of two samples at 0.01 ‰ and –1.42 ‰), significantly heavier than chondrites and the bulk silicate Earth. A comparison with mass fractions of major and trace elements and thermodynamic constraints reveals that Cu isotopic variations within different mare basalt suites are mostly unrelated to fractional crystallisation of silicates or oxides and late-stage magmatic degassing. Instead, we propose that the δ65Cu average of each suite is representative of the composition of its respective mantle source. The observed differences across geographically and temporally distinct mare basalt suites, suggest that this variation relates to large-scale processes that formed isotopically distinct mantle sources. Based on a Cu isotope fractionation model during metal melt saturation in crystal mush zones of the lunar magma ocean, we propose that distinct δ65Cu compositions and Cu abundances of mare basalt mantle sources reflect local metal melt–silicate equilibration and trapping of metal in mantle cumulates during lunar magma ocean solidification. Differences in δ65Cu and mass fractions and ratios of siderophile elements between low- and high-Ti mare basalt sources reflect the evolving compositions of both metal and silicate melt during the late cooling stages of the lunar magma ocean.

^1,2S. Benaroya,^2,3,4J. Gross
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14379]
¹Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta, Canada
²Department of Earth and Planetary Sciences, Rutgers University, Piscataway, New Jersey, USA
³Astromaterials Acquisition and Curation Office, NASA JSC, Houston, Texas, USA
⁴Department of Earth and Planetary Sciences, American Museum of Natural History, New York, New York, USA
Published by arrangement with John Wiley & Sons

Shergottites span a textural, mineralogical, and geochemical range, and finding links between the various petrologic and geochemical groups is of great interest as it provides insight into the conditions of the Martian interior. Here, we compare the texture, mineralogy, mineral chemistry, and geochemistry of REE-enriched intrusive shergottite groups, including poikilitic shergottites, olivine–gabbroic shergottites, and gabbroic shergottites. Due to the similarities of olivine–gabbroic samples to poikilitic and gabbroic shergottites, we suggest that the former may represent an intermediary petrologic type. We suggest a shared magmatic history for these sample groups via a shared stratified magma chamber. Thermodynamic modeling of the proposed shared magmatic history using Magma Chamber Simulator (MCS) and MELTS was able to reproduce the mineralogies and general crystallization histories of samples using a parental melt of bulk silicate mars (BSM) composition and the compositions of olivine–phyric shergottites LAR 06319 and NWA 6234.

¹Yuchen Xu,²Yangting Lin,²Jialong Hao,²Sen Hu,²Wei Yang,¹Yongliao Zou,¹Yang Liu
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14380]
¹State Key Laboratory of Solar Activity and Space Weather, National Space Science Center, Chinese Academy of Sciences, Beijing, China
²Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China
Published by arrangement with John Wiley & Sons

NWA 10493 and NWA 10498, two hot desert finds, are classified as the CO3.0 meteorites based on the Cr2O3 contents in ferroan olivines, representing some of the most primitive chondrites from the CO parent body. The abundances of presolar grains are known to be sensitive to the degree of aqueous alteration and thermal metamorphism. Therefore, an in situ investigation of presolar grains was conducted in the fine-grained matrix of NWA 10493 and NWA 10498 using NanoSIMS C- and O-isotopic image mapping. The matrix-normalized abundance of presolar SiC grains in NWA 10493 is
ppm, which declines to
ppm when the much larger (>1000 nm) grain is excluded. This lower presolar SiC abundance is comparable to the presolar SiC abundance of
ppm calculated in NWA 10498, similar to those from the most aqueously altered CM chondrites based on in situ studies of the fine-grained rims of chondrules. The abundances of O-anomalous grains in both NWA 10493 (54 ± 15 ppm) and NWA 10498 (42 ± 13 ppm) are lower than those reported for the most primitive CO meteorites, indicating slightly higher degrees of thermal alterations. These findings are consistent with the previously observed variations in Cr content within the respective chondrule olivine and point toward classification grades of 3.02–3.05.

¹E. Quirico, ²H. Yabuta, ¹P. Beck, ¹L. Bonal, ^3,5A. Bardyn, ^3,4L.R. Nittler, ³C.M.O’D. Alexander
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2025.05.046]
¹Université Grenoble Alpes, CNRS, Institut de Planétologie et Astrophysique de Grenoble (IPAG), UMR 5274, Grenoble F-38041, France
²Graduate School of Advanced Science and Engineering, Hiroshima University, Hiroshima, Japan
³Earth and Planets Laboratory, Carnegie Institution for Science, 5241 Broad Branch Road, N.W., Washington, DC 20015, USA
⁴School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, USA
⁵Brin Mathematics Research Center, The University of Maryland, 4146 CSIC Bldg. #406, 8169 Paint Branch Drive, College Park, MD 20742-3289, USA
Copyright Elsevier

A significant population of primitive carbonaceous chondrites experienced short-duration heating, which is usually attributed to either impact or solar heating. Shock recovery experiments performed on carbonaceous chondrites have successfully reproduce the typical evolution in the petrographies and mineralogical compositions of natural samples. However, only few studies focused on the chemical and structural transformations of insoluble organic matter (IOM). We report here on shock recovery experiments conducted on two chondrites: Murchison (CM2) and Elephant Moraine EET 90628 (L3.0). Experiments on Murchison show carbonization and oxidation of IOM at all shock intensities (5–50 GPa) and a pronounced structural evolution at 40 GPa associated with complete dehydroxylation of serpentines, as well as formation of olivine and amorphous silicates. The δD value of Murchison IOM (initial δD = 1636 ± 529 ‰) evolves significantly, with the rapid disappearance of isotopic hot spots and a bulk δD of −79 ‰ at 40 GPa. At 40 GPa, the extent of dehydroxylation of serpentines is consistent with stage III heated chondrites, but the structural characteristics of the IOM resembles material from stage II meteorites, i.e. a slight modification of the IOM in a matrix dominated by serpentines.
These experiments only partially reproduce the characteristics of natural samples, and they show that the IOM evolution in short-duration heated C2 chondrites is essentially controlled by the post-shock cooling episode, which lasts from hours to years, compared to < ∼1 µs for the shock peak pressure. The high pressure conditions in the shock do not catalyze the carbonization process and the maturation of IOM. In contrast, the IOM evolution in heated C2 chondrites is better simulated by conventional heating experiments under controlled redox conditions over durations of hours. Shock recovery experiments, however, could be interesting to assess the effect of hypervelocity impacts by small impactors on the surface of airless bodies. Experiments performed on EET 90628 show a structural evolution consistent with natural objects. In particular, the co-evolution of the width and ratio of the peak intensities of the D-band (FWHM-D and ID/IG, respectively) in the Raman spectra of the IOM from the shocked samples is consistent with those measured on type 3 ordinary and carbonaceous chondrites. An interesting finding is that the G-band width and position parameters (FWHM-G and ωG) do not correlate with the shock intensity, just as these parameters do not correlate with the intensity of thermal metamorphism in the case of type 3 chondrites. This lack of correlation is not observed on Earth in the case of coals and kerogens that experienced a progressive thermal history.

¹Daniela Guerrero, ¹Wolf Uwe Reimold, ¹Natalia Hauser, ²Gavin Kenny, ²Martin Whitehouse, ³Philippe Lambert
Geochimica et Cosmochimica (in Press) Link to Article [https://doi.org/10.1016/j.gca.2025.05.049]
¹Postgraduate Program in Geology, Institute of Geosciences, University of Brasília, 70910-900, Brasília, DF, Brazil
²Department of Geosciences, Swedish Museum of Natural History, SE-104 05 Stockholm, Sweden
³CIRIR – Centre International de Recherche et de Restitution sur les Impacts et sur Rochechouart 87600 Rochechouart, France
Copyright Elsevier

The >23 km diameter, ∼207 Ma old Rochechouart impact structure is located in the NW part of the Paleozoic basement of the French Massif Central. Despite significant erosion, this impact structure preserves a heterogeneous suite of impactites, and the transition between the crater floor and the basement. Recent textural and geochronologic studies of U-Pb on zircon from impactites and basement lithologies of this structure have shown a wide variety of shock deformation textures and age distributions. In this study, we present a comprehensive analysis combining detailed textural characterization (CL, BSE, EBSD) and U-Pb geochronological analyses at different spatial resolutions (SIMS and LA-ICP-MS) of zircon from two melt-bearing breccias (suevites) from Chassenon and Videix, and one impact melt rock (IMR) from Babaudus. The analyzed crystals display a variety of shock deformation textures. Identification of FRIGN zircon and grains with high proportions of reidite in the Videix suevite indicates that these types of shock deformation are more widespread than previously reported. In the Chassenon suevite, U-Pb age resetting increases with shock intensity, whereas in the Videix suevite, higher U and/or Th contents also appear to control resetting. In the Babaudus IMR, the similar ages for shocked granular zircons and some unshocked grains suggest that additional factors, beyond shock deformation and zircon composition, influence age resetting. The SIMS analyses yielded more reliable results after common Pb correction. The best estimate of the impact age obtained from this study is 203 ± 4 Ma (2σ, MSWD = 3.4, probability = 0.065) for SIMS analyses of two granular grains from the Babaudus IMR and one granular crystal from the Videix suevite. Zircons with younger (191 ± 4 Ma, post-impact) ages show similar characteristics to those close to the widely accepted age for the impact at 207 Ma, highlighting the challenge of distinguishing between grains and separating ages related to the impact from possible post-impact events (e.g., hydrothermal alteration). Finally, the geochronological results for the Videix and the Chassenon suevites show a clear correlation with provenance results for granitic and gneissic target lithologies, respectively. In contrast, the Babaudus IMR has an age distribution comparable with other impact melt rocks from Montoume and Recoudert but cannot be related to an identified target lithology.

Ali H. EGEH^1,2
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14382]
¹Department of Civil Engineering, Faculty of Engineering, Somali National University (SNU), Mogadishu, Somalia
²Geoscience, Almaas University (AU), Mogadishu, Somalia
Published by arrangement with John Wiley & Sons

The El Ali meteorite, a colossal 15.2 t iron meteorite, was discovered in an area characterized by bushy calcareous evaporates (sedimentary distinctive textures, which align with the description of the meteorite’s find location) near the town of El Ali in West Hiran, Somalia. This paper delves into the fascinating history of this meteorite, tracing its path from obscurity to international prominence and then to the tragedy of losing a local people’s symbol and heritage. For centuries, nomadic local people have used the rusty brown rock as a humble whetstone or honing stone. However, over time it has transformed into a symbol of local heritage and resilience named the “Shiid-birood.” In 2022, a pivotal moment occurred when the meteorite was classified and three previously unknown minerals—elaliite, elkinstantonite, and olsenite—were identified in the meteorite. These findings sparked international media attention to the El Ali meteorite, leading to its official recognition by the Meteoritical Society. Almaas University researchers were the first to interact with the meteorite in Mogadishu, Somalia, and provided initial descriptions, properties, and measurements of the meteorite. Remarkably, the El Ali meteorite ranks as the ninth largest meteorite globally, weighing an impressive 15.2 t. However, secrecy and uncertainty surround its fate. The meteorite has been exported to China, leaving Somalia bereft of its cultural and natural heritage significance. Will it be cut into pieces or preserved intact for exhibitions and future scientific studies? Perhaps, there is still some hope to ensure its return to its rightful place of origin—Somalia.