¹Elias Wölfer, ¹Christoph Burkhardt, ²Francis Nimmo, ¹Thorsten Kleine
Earth and Planetary Science Letters 663, 119435 Open Access Link to Article [https://doi.org/10.1016/j.epsl.2025.119435]
¹Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
²Department of Earth and Planetary Sciences, University of California Santa Cruz, 1156 High St, Santa Cruz, CA 95064, USA
Copyright Elsevier

The bulk silicate Earth (BSE) is depleted in moderately volatile elements, indicating Earth formed from a mixture of volatile-rich and -poor materials. To better constrain the origin and nature of Earth’s volatile-rich building blocks, we determined the mass-dependent isotope compositions of Ge in carbonaceous (CC) and enstatite chondrites. We find that, similar to other moderately volatile elements, the Ge isotope variations among the chondrites reflect mixing between volatile-rich, isotopically heavy matrix and volatile-poor, isotopically light chondrules. The Ge isotope composition of the BSE is within the chondritic range and can be accounted for as a ∼2:1 mixture of CI and enstatite chondrite-derived Ge. This mixing ratio appears to be distinct from the ∼1:2 ratio inferred for Zn, reflecting the different geochemical behavior of Ge (siderophile) and Zn (lithophile), and suggesting the late-stage addition of volatile-rich CC materials to Earth. On dynamical grounds it has been argued that Earth accreted CC material through a few Moon-sized embryos, in which case the Ge isotope results imply that these objects were volatile-rich, presumably because they were either undifferentiated or accreted volatile-rich objects themselves before being accreted by Earth.

¹Lisa Maria Eckart, ¹Henner Busemann, ¹Daniela Krietsch, ¹Cornelia Mertens, ¹Colin Maden, ²¹Conel M. O’D. Alexander, ^3,4Kevin Righter
Geochimica et Cosmocimica Acta )(in Press) Open Access Link to Article [https://doi.org/10.1016/j.gca.2025.04.021]
¹Institute of Geochemistry and Petrology, ETH Zurich, Clausiusstrasse 25, 8092 Zurich, Switzerland
²Carnegie Institution for Science, 5251 Broad Branch Rd NW, Washington, DC 20015, United States
³NASA Johnson Space Center, 2101 E NASA Pkwy, Houston, TX 77058, United States
⁴Department of Earth and Environmental Sciences, University of Rochester, 227 Hutchison Hall, Rochester, NY 14627, United States
Copyright Elsevier

Carbonaceous chondrites of the Ornans type (COs) include some of the most primitive meteorites known to date, yet most of them show evidence of having experienced mild degrees of thermal alteration in their parent asteroid. Previous studies on aqueously altered CM, CR, and CY chondrites have shown that the noble gases trapped in various components with distinct susceptibility to alteration can be used to assess the extent of parent body processing. In this study, we investigated the noble gas compositions of 51 CO chondrites ranging from petrologic type 3.0 to 3.8, three suspected Mighei-type chondrites (CMs; MIL 090073, DOM 10121, DOM 10299) initially classified as COs, and DOM 10900 with intermediate properties between CMs and COs. The COs show a noble gas mixture typical for carbonaceous chondrites, deriving from primordial carriers such as presolar grains, phase Q, and the carrier of the Ar-rich/V component, which has been observed in anhydrous chondrites, and occasionally air. Additionally, the newly identified W component could be present, which is highly susceptible to water. Combining our results with CO noble gas data from the literature, we show that the 20Netr/132Xecorr ratios correlate best (decrease) with the degree of thermal alteration, likely related to the abundance of presolar diamonds, and may thus serve as tool to subclassify thermally altered chondrites. Based on its 20Netr/132Xecorr ratio, DOM 10847 (paired with DOM 08006) is the most primitive CO, followed by NWA 13464 and Y-74135. The 20Netr/132Xecorr subclassification tool, however, may not be applicable for intergroup comparisons as the stability of the responsible carriers are sensitive to the chemical environment of the parent body. The abundances of heavy noble gases in bulk CO samples are much higher compared to CO etch residues (remaining after demineralization of a bulk meteorite) from the literature, indicating that other carrier(s) than insoluble organic matter must contribute significantly to the heavy noble gas inventory, which is/are susceptible to thermal alteration. DaG 331 was subclassified in this work to be a CO3.1 using the method by Grossmann and Brearley (2005) and the trend line defined by Davidson et al. (2019).
The COs show a wide range in cosmic ray exposure (CRE) ages between 0.17 ± 0.05 Ma (Isna) and 78 Ma (maximum age determined for Dominion Range [DOM] 18286 with an uncertainty of < 10 %), although the majority of CRE ages are > 10 Ma. DOM 18286 has the highest CRE age reported to date for a carbonaceous chondrite. We did not find any age clusters hinting at a major impact event, nor a correlation between CRE ages and the petrologic types. Strikingly, none of the 63 COs analyzed for their noble gases (including literature) contains solar wind, indicating that this group stems from below the regolith surface layer. The COs and CMs show similar matrix-corrected primordial noble gas abundances, suggesting that they accreted their volatiles from a common reservoir.

¹Nathan Asset, ¹Marc Chaussidon, ²Christian Koeberl, ³Johan Villeneuve, ⁴François Robert
Geochimica et Cosmochimica Acta (in Press) Open Access Link to Access [https://doi.org/10.1016/j.gca.2025.05.011]
¹Université Paris-Cité, Institut de Physique du Globe de Paris, CNRS, F-75005 Paris, France
²Department of Lithospheric Research, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria
³Université de Lorraine, CNRS, CRPG, UMR 7358, F-54000 Nancy, France
⁴Institut Origine et Evolution, Muséum National d’Histoire Naturelle, Sorbonne Université, IMPMC-UMR 7590 CNRS, 75005Paris, France
Copyright Elsevier

During the world’s first nuclear explosion, in 1945, glassy melts called “trinitites”, mostly derived from the sands at the surface of the test site, formed and were deposited at or near the hypocenter. The processes of formation of this fallout remain unclear. Here, we show how the oxygen and silicon isotopic compositions of three trinitites allow to refine their formation scenario. The three samples are typical of trinitites, being composed of various crystalline phases (feldspars, quartz, and calcite) and of glassy phases divided into three chemical groups (CaMgFe, alkali, silica) that are mixed in various proportions in the three samples. The three samples show a large range of oxygen and silicon isotopic variations (−10.9 ± 0.6 ‰ <δ30Si < 4.2 ± 0.6 ‰, and 2.3 ± 0.4 < δ18O < 24.2 ± 0.5 ‰). At variance with the Hiroshima fallout deposits, no oxygen mass-independent isotopic fractionation was found in the three trinitites. The chemical and isotopic compositions of the chemical groups reveal that they result from different processes: the silica phases are molten fragments of the site material, while the CaMgFe and alkali phases are produced by the mixing of condensates and molten site material. Models show that the observed silicon isotopic variations resulted from Rayleigh distillation during condensation of the gaseous species injected into the cloud, while the variability in composition of the site materials also played an important role for controlling the oxygen isotopic compositions. From these observations, a general scenario, beginning with the vaporization of the site surface, producing a depression, is proposed. The vaporized material condensed and grew by agglomeration with other condensates and liquid materials. These agglomerates rained on the surface and quenched, forming the trinitites. This scenario is different from the formation of the Hiroshima glasses but shows some similarities to the tektites formation.

¹Elizabeth A. Heiny,¹Edward M. Stolper,¹John M. Eiler
Proceedings of the National Academy of Sciences of the United States of America (PNAS) 122, e2418198122 Link to Article [https://doi.org/10.1073/pnas.2418198122]
¹Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125

The isotope anomalies of noncarbonaceous (NC) and carbonaceous (CC) extraterrestrial materials provide a framework for tracing the distribution and accretion of matter in the early solar system. Here, we extend this framework to sulfur (S)—one of six “life-essential” volatile elements [TC ~ 664 K]—via the mass-independent S-isotope compositions of differentiated meteorites. We observe that on average, NC and CC iron meteorites are characterized by distinct Δ33S (Δ33SNC = 0.013 ± 0.003‰; Δ33SCC = −0.021 ± 0.009‰; 2 SE). The average Δ36S of NC and CC irons are less well resolved (Δ36SNC = −0.006 ± 0.039‰; Δ36SCC = −0.101 ± 0.114‰; 2 SE), but the Δ36S values of the CC irons are concentrated in the lower half of the range of those observed for iron meteorites. A lack of CC achondrite S-isotope analyses prevents direct comparison of the Δ33S and Δ36S of NC and CC achondrites, but the average Δ33S and Δ36S of NC achondrites (Δ33S = 0.02 ± 0.008; Δ36S = −0.019 ± 0.064‰; 2 SE) overlap with those of the NC irons. The average Δ33S values of NC achondrite groups also correlate with nucleosynthetic anomalies of other elements (e.g., Cr) previously used to define isotopic heterogeneity within the NC reservoir. The position of the Earth in Δ33S-Δ36S composition space implies that ~24% of terrestrial S derives from CC materials, while the majority (~76%) was delivered by NC materials.

¹Nathan Asset, ¹Marc Chaussidon, ²Guillaume Lombardi, ³Johan Villeneuve, ⁴Romain Tartèse, ⁵Smail Mostefaoui, ⁵François Robert
Proceedings of the National Academy of Sciences of the United States of America (PNAS) 122, e2426711122 Link to Article [https://doi.org/10.1073/pnas.2426711122]
¹Universite Paris-Cite, Institut de Physique du Globe de Paris, CNRS, Paris F-75005, France
²Laboratoire des Sciences des Procédés et des Matériaux (LSPM—CNRS), Université Sorbonne Paris Nord, Villetaneuse F-93430, France
³Centre de Recherches Pétrographiques et Géochimiques, CNRS, Université de Lorraine, UMR 7358, Vandœuvre-lès-Nancy 54501, France
⁴Department of Earth and Environmental Sciences, The University of Manchester, Manchester M13 9PL, United Kingdom
⁵Institut Origine et Evolution, Muséum National d’Histoire Naturelle, Sorbonne Université, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie – UMR 7590 CNRS, Paris 75005, France

Contrary to all terrestrial rocks, planets and meteorites exhibit oxygen isotope variations decorrelated with the mass difference of their atomic nuclei. It has been proposed that, in the protosolar nebula (PSN), these variations could result from mass independent isotopic fractionation (MIF) either during specific chemical reactions similar to those responsible for the formation of ozone in the Earth’s atmosphere or during ultraviolet (UV)-photolysis of carbon monoxide (CO) gas in the PSN. However, these potential chemical MIF reactions (Chem-MIFs) are not identified in conditions close to the PSN, and there is no experimental demonstration that large MIF signature can be transferred to solids forming in the PSN. Here, we show that MIFs, up to 60‰ depletion in 16O, are produced by high-temperature reactions in a plasma during the condensation of carbonaceous solids from a gas containing two of the most abundant PSN molecular species (H2O and CH4). This effect is attributed to the formation in the plasma of the activated complex H2O2* followed by its stabilization by reactions with CHx• radicals. Although it is premature to assert that this reaction represents the main process resulting in MIF of oxygen isotopes in the solar system, our result demonstrates the potential importance of a Chem-MIF effect in a PSN where plasma zones develop.

^1,2J.S. Gorce, ^2,3E.A. Heiny, ⁴J. Filiberto, ²C. Goodrich
Earth and Planetary Science Letters 662, 119371 Link to Article [https://doi.org/10.1016/j.epsl.2025.119371]
¹Amentum at NASA Johnson Space Center, Houston, TX, 77058, United States
²Lunar and Planetary Institute, USRA, Houston, TX 77058, United States
³Case Western Reserve University, Cleveland, OH 44106, United States
⁴Astromaterials Research and Exploration Sciences, NASA Johnson Space Center, Houston, TX 77058
Copyright Elsevier

There is a growing body of evidence that the range of planetary parent bodies sizes is greater than previously understood as new pressure and temperature (P-T) estimates of amphibolite and eclogite mineral assemblages found in chondrites are determined and subsequently used to estimate parent body sizes. Here we use thermodynamic modelling techniques to estimate that clasts containing eclogite-like minerals found in NWA 801 equilibrated at 13-15 kbars and 720°C under dry metamorphic conditions, and hydrous phases form after peak metamorphism during aqueous alteration at P∼4-6 kbars and T ∼ 200-400°C and a water/rock ratio of ∼0.006 (< 0.5 wt % H2O). Parent body size estimates are similar to previous work (2050-3700 km), but do not require that the eclogitic clasts be sampled from near the center of the parent body to achieve a peak metamorphic pressure of 13-15 kbars. The eclogitic clasts in NWA 801 are part of a growing body of evidence that imply that chondritic parent bodies could have been much larger than what has been suggested in the past (1000s vs 10s-100s km in diameter), and that the diversity of size in chondritic parent bodies is much greater than previously understood.

¹Magdalena H. Huyskens, ^2,3,4Yuri Amelin, ¹Qing-Zhu Yin, ⁵Tsuyoshi Iizuka
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2025.04.030]
¹Department of Earth and Planetary Sciences, University of California, Davis, Davis, CA 95616, USA
²Research School of Earth Sciences, Australian National University, Canberra, ACT 2601, Australia
³Korea Basic Science Institute, Ochang, Cheongwon, Cheongju, Chungbuk 28119, Republic of Korea
⁴State Key Laboratory of Deep Earth Processes and Resources, Guangzhou Institute of Geochemistry CAS, Guangzhou 510640, China
⁵Department of Earth and Planetary Science, The University of Tokyo, Japan
Copyright Elsevier

Ages of angrites, a diverse and rapidly growing group of differentiated meteorites, are important for understanding the history of their parent body, which is proposed to be an archetypal first-generation planetesimal. Angrites also commonly serve as a time reference in the early Solar System chronology. Pb-isotopic ages of angrites can be determined with high precision, and the isotopic composition of uranium thus becomes a major contributor to the age accuracy and its total uncertainty budget. Two main groups of angrites, the rapidly cooled (volcanic and/or impact-generated) and plutonic angrites, were previously found to contain uranium with different 238U/235U ratios. The variations in isotopic compositions between mineral carriers of uranium within individual angrites, which are directly relevant to calculation of accurate Pb-isotopic ages, have not been studied yet. In this study, we determined the 238U/235U for whole rocks, leachate and residue of whole rocks and mineral separates for two rapidly cooled angrites D’Orbigny and Sahara 99,555 and three plutonic angrites NWA 4801, NWA 4590 and Angra dos Reis. For the rapidly cooled angrites, all mineral separates as well as the whole rocks show consistent 238U/235U. Whole rock 238U/235U ratios for the plutonic angrites are distinctly lower than the ratios in the rapidly cooled angrites. In Angra dos Reis and NWA 4590, merrillite has higher 238U/235U than pyroxene, and both minerals have higher 238U/235U ratios than the respective whole rock, suggesting the presence of an unidentified mineral host of uranium with lower 238U/235U. These differences in U isotope composition could be possibly attributed to a combination of mass dependent and mass-independent isotope fractionation driven by the differences of oxidation state, and coordination in the crystals. We recalculated the existing Pb-isotopic dates when possible with the measured 238U/235U for the minerals that were used for the Pb-isotopic dating. The differences in U isotopic composition between cogenetic minerals point to the importance of 238U/235U determination in specific minerals that are used for Pb-isotopic dating for plutonic achondrites, rather than U isotopic data for bulk meteorites

^1,2Elana G. Alevy,³Tasha L. Dunn,⁴Alexander N. Krot,^4,5Paul Cardon-Pilotaz,⁶Juliane Gross
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14358]
¹Department of Geology, Colby College, Waterville, Maine, USA
²Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA
³Department of Geology, Colby College, Waterville, Maine, USA
⁴ Institute of Geophysics and Planetology, School of Ocean and Earth Science Technology, University of Hawai’i at Mānoa, Honolulu, Hawaii, USA
⁵Ecole Normale Supérieure de Lyon, Lyon, France
⁶Astromaterials Acquisition and Curation Office, NASA Johnson Space Center, Houston, Texas, USA
Published by arrangement with John Wiley & Sons

Camel Donga 003 (CD 003) was originally classified as a CK3 chondrite based on its coarse-grained matrix, Ni-rich sulfides, Cr-rich magnetite, and CK-like silicate mineralogy. However, after preliminary backscattered electron imaging and elemental mapping of a 400 mm2 thin section of CD 003, subsequent mineral chemistry analysis confirmed that the sample is a fragmental breccia consisting of three oxidized CV lithologies. In the two largest lithologies, both mineralogically pristine and metasomatically altered refractory inclusions are commonly found in close proximity to one another. This suggests that brecciation and mixing of different lithologies in CD 003 occurred on a submillimeter scale. The least abundant lithology—an 8 × 3 mm clast—is distinguished from the other lithologies by its recrystallized matrix, poorly defined chondrules, and equilibrated olivine (Fa42). The homogeneity of matrix and chondrule olivine indicates that this lithology has been metamorphosed to at least petrologic subtype 3.8 conditions. We can trace the provenance of our sample to the main mass of CD 003, which must contain the CK material described in its original classification. Therefore, the presence of the three oxidized CV lithologies suggests that CD 003 is the first CV/CK3 chondrite breccia.

¹Stu Webb,¹Clive R. Neal,²Bridget Guiza,²James M. D. Day
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14362]
¹Department of Civil & Environmental Engineering & Earth Science, University of Notre Dame, Notre Dame, Indiana, USA
²Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, USA
Published by arrangement with John Wiley & Sons

High-Al Apollo 14 basalt 14053 has been identified as an endogenous partial melt product from the lunar interior based on geochemical analyses, specifically low abundances of highly siderophile elements, but exhibits textural characteristics similar to those of impact melts. Prior studies of this sample have described mineralogical differences between “interior” and “exterior” portions, which have been attributed to exposure at the lunar surface and subsequent metamorphism through subsolidus reheating within or in proximity to an impact-ejecta blanket. It has been demonstrated that quantitative textural analysis is a useful tool for distinguishing between lunar rocks altered by impact processes and those produced by endogenic magmatic processes. Such an approach is used in this study to analyze multiple thin sections cut from interior and exterior portions of 14053. The textural heterogeneity of plagioclase crystals among thin sections revealed in this study suggests that an impact-ejecta blanket likely impinged on the western side of 14053. This thermal metamorphism coarsened the plagioclase grains within that portion of 14053 so intensely that components diffused to form subtle layering and moderate textural heterogeneity that was quantifiable. These results also support previous conclusions that suggest the differences in reduction textures within this sample are due to the limited penetration depth of solar-wind implanted hydrogen prior to reheating. Thermal metamorphism can produce textural changes in lunar samples even if below the solidus temperature, such that the plagioclase texture of an endogenous basalt is sufficiently altered to that resembling an impact melt. These results highlight the significance of quantitative petrographic observations of lunar samples to reveal important petrogenetic information that has to be placed in proper spatial context to be understood.

¹J. Eschrig,¹M. M. M. Meier,^2,3B. A. Hofmann
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14361]
¹Naturmuseum St. Gallen, St. Gallen, Switzerland
²Naturhistorisches Museum Bern, Bern, Switzerland
³Institute of Geological Sciences, University of Bern, Bern, Switzerland
Published by arrangement with John Wiley & Sons

Museums and universities are important for collecting, maintaining, and curating meteorites. To make specimens known and available for research, inventorying and optimal curation are important. However, not all meteorite collections are well curated, especially in smaller institutions. During a 12-month project supported by the Swiss Confederacy under the “SwissCollNet” framework, we viewed, photographed, and inventoried all public and institutional meteorite collections in Switzerland. In total, the 27 collections contain 7616 specimens, derived from 3469 different meteorites. New, switched, and missing specimens were found in many collections. More than half of the collections contained specimens without inventory numbers and unknown or unofficial specimens, several of which could be assigned to a known meteorite fall or find during this project. The identification of switched or unknown samples was done using handheld X-ray fluorescence spectrometry and magnetic susceptibility measurements. In total, 201 specimens were attributed a preliminary classification. We demonstrate the importance of smaller collections, which often hold fragments of rare meteorite types. We underline how large-scale projects like the one presented here allow for unique data, for example, finding specimens missing from one collection in another. By tracking the origin of specimens using historic labels, we show that the history of meteoritics is reflected in the composition of the Swiss collections. During the inventorying process, several prehistoric and modern artifacts made of meteoritic material were found, underlining the potential of analyzing non-geological specimens in museums.