¹Lucas R. Smith,^1,2Pierre Haenecour,¹Jessica J. Barnes,¹Kenneth Domanik,²Mason Neuman,^2,3Kun Wang,²Piers Koefoed,¹Elias Bloch,⁴Ryan Ogliore
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70166]
¹Lunar and Planetary Laboratory, The University of Arizona, Tucson, Arizona, USA
²Department of Earth and Planetary Sciences, Washington University in St. Louis, St. Louis, Missouri, USA
³McDonnell Center for the Space Sciences, Department of Physics, Washington University in St. Louis, St. Louis, Missouri,USA4 Department of Physics, University of Central Florida, Orlando, Florida, USA
Published by arrangement with John Wiley & Sons

We performed an in-depth study of the mineralogy, petrology, chemical composition, and presolar grain abundance of the C3.00-ungrouped chondrite Chwichiya 002 using a combination of in situ and bulk analytical methods. Chwichiya 002’s bulk composition is significantly enriched compared to CI chondrites (over 20 × CI for Sr, Ba, U) in rare earth and trace elements like Li, Sr, Ba, U, and Pb, indicating effects of terrestrial weathering. Concentrations of Ti and Al are similar to CI chondrites, but notably depleted relative to other carbonaceous chondrite groupings, suggesting that the parent body of Chwichiya 002 accreted from a source with a near CI composition of refractory elements, and with a low quantity of calcium–aluminum-rich inclusions. A slight reduction in Fe is linked to the predominance of FeO-poor chondrules and olivine, likely a remnant of Chwichiya 002’s formation history. Our findings uncovered phyllosilicates in the matrix and combinations of tochilinite–cronstedtite, confirming that Chwichiya 002 underwent more extensive alteration on its parent body than previously believed. We identified 12 O-anomalous presolar grains (8 Group 1, 4 Group 4) and nine presolar SiC grains, with abundances of 12.1 + 4.6/−3.5 ppm for O-rich grains and 7.8 + 3.6/−2.6 ppm for SiC grains. The relatively low occurrence of O-rich presolar grains is similar to what is seen in CM2 chondrites and samples from asteroid 162173 Ryugu, despite Chwichiya 002 being classified as type 3.00 petrologically. We conclude that Chwichiya 002 formed from a refractory-poor source similar to CM and CO chondrites, primarily consisting of FeO-poor chondrules and olivine, and underwent a moderate level of aqueous alteration on its parent body. Furthermore, the mineralogy, petrology, and compositional data reported in this study, combined with previous data on the O-isotopes of Chwichiya 002, suggest that the sample may better be classified as a CM2.8 or CM 2.9 chondrite.

¹L. Perez,¹M. Roskosz,²F. Danoix,¹L. Kern,¹V. Megevand,¹C. Brillatz,³B. Devouard,³J. Gattacceca,¹M. Gounelle
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70172]
¹IMPMC, Museum National d’Histoire Naturelle, Sorbonne Universite, Paris, France
²Groupe de Physique des Materiaux, CNRS UMR 6634, Universite de Rouen, Saint Etienne du Rouvray, France
³Aix-Marseille Universit´e, CNRS, INRA, IRD, Coll France, CEREGE UM34, Aix en Provence, France
Published by arrangement with John Wiley & Sons

This study provides the first petrographic, crystallographic, and chemical comparison between El Médano 300 (EM 300) and Northwest Africa 8155 (NWA 8155), two particular IAB-ungrouped iron meteorites. Both contain exceptionally large graphite nodules and “flowers”, providing unique insights into carbon behavior in metallic melts and cooling conditions. Despite these similarities, they differ in their petrography, crystallography, and chemical composition. Whereas EM 300 exhibits a homogeneous metallic phase with rounded kamacite grains, originating from at least two taenite crystals, NWA 8155 displays a heterogeneous composition with elongated kamacite crystals, from a unique taenite crystal, along with martensite and residual taenite. Variations in nickel and highly siderophile elements contents point to different degrees of partial melting, indicating in turn formations within two different metallic pools, most probably on separate parent bodies. Troilite textures in EM 300 (spidery), compared to NWA 8155 (bulky), suggest an impact-related origin. Abundant small schreibersite grains in EM 300 indicate faster post-impact cooling. Finally, the absence of silicates in both meteorites suggests efficient metal-silicate segregation or formation within metallic parent bodies. These results provide new insights into the diversity of thermal and collisional histories among IAB-ungrouped iron meteorites, supporting the idea that each one may represent a single parent body and therefore reflecting the diversity of early planetesimal natures and evolutions.

¹Hina Dohi,¹Minako Hashiguchi,¹Koichi Mimura
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70173]
¹Department of Earth and Environmental Sciences, Graduate School of Environmental Studies, Nagoya University, Nagoya, Japan
Published by arrangement with John Wiley & Sons

A substantial fraction of organic carbon in carbonaceous chondrites has long been described as “missing,” reflecting incomplete recovery and limited resolution of operationally defined organic components. Here, we present a quantitative reassessment of the carbon budget in the Murchison meteorite using an integrated extraction–recovery mass-balance approach that constrains the distribution of carbon among operational fractions. Insoluble organic matter accounts for 69% ± 1.4% of total carbon, while acid-hydrolyzable organic matter (AOM) constitutes 15% ± 2.9%, representing a carbon pool comparable to soluble organic matter (SOM, 14% ± 2.7%). Carbonate-derived carbon accounts for 2% ± 2.0% of the total carbon inventory. The total recovered organic carbon reaches 88% ± 1.4% of bulk carbon. Carbon previously regarded as “missing” can be quantitatively reassigned to specific organic fractions, including uncollected AOM (7%) and SOM (2%), substantially reducing the previously unconstrained carbon fraction. Replicate analyses of three independently processed subsamples yield consistent residue-based carbon partitioning, supporting the robustness of the mass-balance framework. These results indicate that much of the missing carbon reflects incomplete recovery in analytical workflows rather than an unidentified reservoir, refining the organic carbon inventory of Murchison and providing a framework for reassessing carbon partitioning in primitive planetary materials.

^1,2,3Yan Fan,^1,4Deze Liu,^1,5Shijie Li,⁶Xiangdong Li,³Shen Liu,¹Dehan Shen,⁷Qing-Zhu Yin
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70175]
¹Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China
²Xi’an Center, China Geological Survey, Xi’an, China
³State Key Laboratory of Continental Dynamics and Department of Geology, Northwest University, Xi’an, China
⁴Department of Earth Sciences, University of Oxford, Oxford, UK
⁵Chinese Academy of Sciences, Center for Excellence in Comparative Planetology, Hefei, China
⁶Environmental Engineering Unit, Department of Civil and Structural Engineering, The Hong Kong Polytechnic University,Kowloon, Hong Kong
⁷Department of Earth and Planetary Sciences, University of California at Davis, Davis, California, USA
Published by arrangement with John Wiley & Sons

This study assesses mercury (Hg) concentrations and their isotopic compositions in Antarctic chondrites, desert chondrites, and drilled samples from the Jilin chondrite (H5). Desert chondrites show mercury concentrations between 2.2 ng g−1 and 156.8 ng g−1, with δ202Hg ranging from −3.69‰ to 1.19‰. Δ199Hg and Δ201Hg vary from −0.23‰ to −0.02‰ and −0.2‰ to 0.02‰, respectively, showing a weak positive correlation among these parameters (slope 0.74 ± 0.24, R2 = 0.46). These Hg concentrations and isotopic composition data of desert chondrites indicate that Hg in desert chondrites has been altered due to terrestrial processes in addition to evaporation loss during its terrestrial residence period. Antarctic chondrites exhibit mercury concentrations from 8.0 ng g−1 to 3940.8 ng g−1, with δ202Hg from −2.51‰ to 1.16‰. Δ199Hg and Δ201Hg range from −0.83‰ to −0.05‰ and −0.71‰ to 0.10‰, with a significant correlation (slope 0.93 ± 0.15, R2 = 0.76), likely influenced by Antarctic snow that has experienced significant photochemical processes during atmospheric mercury depletion events (AMDEs) and has elevated mercury content (such as drifted snow). Jilin meteorite’s δ202Hg, Δ199Hg, and Δ201Hg vary between −3.74‰ to −1.79‰, −0.12‰ to 0.09‰, and −0.12‰ to −0.01‰, respectively. A weak positive correlation between Δ199Hg and Δ201Hg (slope 1.45 ± 0.28, R2 = 0.67) suggests localized Hg evaporation due to shock processes on the parent body; however, Hg isotopic heterogeneity from nebular or parent body processes cannot be excluded. Terrestrial weathering and shock events could alter Hg content and isotopic compositions in chondrites, challenging their use as accurate indicators of Hg’s cosmochemical behavior.

¹A. J. King,¹P. F. Schofield,¹J. Najorka,¹H. C. Bates,¹S. S. Russell,²T. J. McCoy,³T. J. Zega,^3,4,5H. C. Connolly Jr,³D. S. Lauretta
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70169]
¹Planetary Materials Group, Natural History Museum, London, UK
²National Museum of Natural History, Smithsonian Institution, Washington, DC, USA
³Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA
⁴Department of Geology, Rowan University, Glassboro, New Jersey, USA
⁵Department of Earth and Planetary Science, American Museum of Natural History, New York City, New York, USA
Published by arranegment with John Wiley & Sons

Samples returned by NASA’s OSIRIS-REx mission from the carbonaceous asteroid (101955) Bennu hold clues about conditions in the early solar system and the formation of planetary bodies. Initial investigation of Bennu samples found that they are rich in phyllosilicates and other secondary minerals formed during aqueous alteration of a larger parent body. To better understand the phyllosilicate minerals and constrain the extent and settings of alteration, we used X-ray powder diffraction (XRD) to characterize the mineralogy of homogenized aggregate (unsorted) samples and an angular particle from Bennu. We find that these samples consist of abundant (>80 vol%) phyllosilicates and few (≤2 vol%) precursor anhydrous silicates, in excellent agreement with remote observations of the global asteroid surface, and consistent with extensive aqueous alteration of Bennu’s parent body. The XRD patterns and modal mineralogy of the Bennu samples are similar to those of CI carbonaceous chondrites and particles returned from the carbonaceous asteroid (162173) Ryugu by JAXA’s Hayabusa2 mission, offering further support for the close genetic relationship among these materials suggested by other studies. Bennu’s phyllosilicates are dominated by a mixture of trioctahedral Mg-rich clay minerals that formed from alkaline fluids under high water to rock ratios and likely evolved in response to changes in temperature and/or fluid chemistry as alteration progressed. Based on the XRD characteristics of the phyllosilicates, the Bennu samples did not experience a peak temperature at or above ~300°C after aqueous alteration. Finally, we show that the interlayer space of the clay minerals potentially contains up to ~2 wt% water and does not host trapped organic species. The abundance of interlayer water in Bennu samples is notably higher than reported for Ryugu samples (<0.3 wt%), which we speculate is due to differences in either the timing at which the asteroids decoupled from the Main Belt or the sampling depths and/or mechanisms of the respective spacecraft.

¹A. J. Cavosie et al.(>10)
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70163]
¹Space Science and Technology Centre, School of Earth and Planetary Science, Curtin University, Perth, Western Australia, Australia
Publishesd by arrangement with John Wiley & Sons

The framework of the Impact Cratering Committee (ICC) of the Meteoritical Society was approved in 2020, with the first committee members appointed in 2023. The ICC has a mandate to (1) approve, maintain, and update a database of confirmed terrestrial meteorite impact structures, (2) define and regularly update the criteria used for identification of impact structures and their related deposits, and (3) evaluate new candidate sites for inclusion in the ICC database. Prior to certifying a list of confirmed impact structures, the ICC has compiled a list of all impact-diagnostic criteria that are currently considered as representing irrefutable or “gold standard” evidence that can be used independently to confirm whether or not a terrestrial geological structure has an impact origin. The ICC currently recognizes three categories of “gold standard” impact-diagnostic evidence: (1) Shock metamorphic features within rocks or minerals that on Earth have only been reported to occur in impactites, and whose formation conditions (high P–T) have been demonstrated through experiments to only form at conditions created during hypervelocity impacts; (2) meteorites that are spatially and chronologically associated with a site suspected of being an impact structure; and (3) geochemical elemental or isotopic detection of an extraterrestrial signature in melt rocks or breccias associated with a site suspected of being an impact structure. Other mineral and rock features have been reported from impact structures that are important to document, but they do not represent irrefutable or unambiguous evidence of impact. For this reason, we present two lists: The first list describes each impact-diagnostic criterion and provides recommendations for reporting protocols. The second list describes other features commonly reported from impact settings and the rationale for why these are not currently considered by the ICC to represent impact-diagnostic evidence. The ICC will provide a list of confirmed terrestrial impact structures in a subsequent publication and online. Updates to the list based on new discoveries and/or new understanding of impact-diagnostic criteria will be published online by the ICC.

¹Evelyn Füri, ²Fridolin Spitzer, ¹Julie Gamblin, ²Christoph Burkhardt, ¹Béatrice Luais, ¹Julien Boulliung,¹Laurent Zimmermann
Geochimica et Cosmichimica Acta (in Press) Open Access Link to Article [10.1016/j.gca.2026.05.037]
¹Université de Lorraine, CNRS, CRPG, F-54000 Nancy, France
²Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
Copyright Elsevier

Iron meteorites provide key insights into the formation conditions of planetesimals in the early protoplanetary disk. To investigate the sources of nitrogen (N) in non-carbonaceous (NC) and carbonaceous (CC) iron meteorite parent bodies—and to trace the spatiotemporal N isotopic heterogeneity in the inner and outer disk—we present combined N–Ne–Ar isotopic data for 14 irons from the under-studied IIAB-IIG and IID groups, and 14 ungrouped irons of either NC or CC heritage. These measurements, obtained via CO2 laser heating and multi-collection noble gas mass spectrometry, allow us to exclude contributions from solar gases and cosmogenic 15N. New data for two N-rich IIG irons confirm a genetic link with the IIAB group, supporting the view that NC magmatic iron meteorite groups are characterized by low δ15N values (–90 to –80 ‰). These results suggest that NC iron meteorite parent bodies accreted a smaller proportion of 15N-rich (organic) carriers than later-formed chondritic bodies, possibly due to thermal processing at the tar line. Two NC ungrouped magmatic irons have markedly higher δ15N values (–2.0 ‰ and + 9.1 ‰); however, their Ge-depleted compositions raise uncertainty as to whether these signatures reflect primary, parent-body-specific characteristics or result from secondary volatile loss. In contrast, CC magmatic irons, including the IID group and CC ungrouped irons, predominantly record positive δ15N values. Among these, the N isotopic compositions of three CC ungrouped irons—New Baltimore (+104 ‰), Hammond (+112 ‰), and La Caille (+206 ‰)—resemble those of IIC irons and Renazzo-type (CR) carbonaceous chondrites, reinforcing their genetic link to the IIC/CR reservoir, where ammonia ice was likely an important N carrier. This implies that an isotopically CR-like, ammonia‑rich reservoir was established in the outer protoplanetary disk during the earliest stages of its evolution and persisted for several million years. Taken together, these findings indicate that the primary N isotopic composition of differentiated and undifferentiated planetesimals was governed by the local mixture of isotopically distinct N-bearing phases, itself shaped by evolving condensation and evaporation fronts in the early protoplanetary disk

¹Melissa De Andrade Nunes,¹Ricardo I. F. Trindade,¹João Pedro Rodriguez Pinto,²Alvaro P. Crósta,³Gabriel G. Silva,⁴Ludovic Ferrière,¹Camila R. Sales,¹Giovanna M. Tosi
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70155]
¹Institute of Astronomy, Geophysics and Atmospheric Sciences, University of Sao Paulo, Sao Paulo, Brazil
²Institute of Geosciences, University of Campinas, Campinas, Brazil
³Institute of Chemistry, University of Sao Paulo, Sao Paulo, Brazil
⁴Natural History Museum Abu Dhabi, Abu Dhabi, United Arab Emirates
Published by arrangement with John Wiley & Sons

Geraisites are a newly recognized class of tektite from Brazil. They occur as centimeter-sized, elongated to subspherical bodies scattered across surface gravel and shallow subsurface layers within a ~90-km-long strewn field extending between the municipalities of São João do Paraíso and Curral de Dentro, near the border between the states of Minas Gerais and Bahia. This study presents a rock magnetic characterization of geraisites, aimed at understanding their magnetic mineralogy and remanent magnetization. The samples exhibit weak bulk magnetization dominated by a paramagnetic contribution, consistent with typical tektite compositions. In addition, rock magnetic analyses indicate the presence of a ferromagnetic fraction, as evidenced by demagnetization curves and hysteresis behavior. Lowrie–Fuller test and isothermal remanent magnetization decomposition indicate a dominant low-coercivity component consistent with nanoscale magnetite grains in the single-domain to pseudo-single-domain range. In some samples, the remanence behavior suggests overprinting by transient high-field processes, such as lightning-induced remanent magnetization. Furthermore, geraisites show a distinct relationship between magnetic susceptibility and iron content compared to other splash-form tektites, reflecting their relatively enhanced ferromagnetic contribution. Overall, these results provide new insights into the magnetic properties of geraisites and their comparison with other tektite populations.

¹Shivanshu Dwivedi,^1,2Jayanta Kumar Pati,³Wolf Uwe Reimold,¹Anuj Kumar Singh,⁴Gordon Robert John Cooper,¹Dhananjay Mishra,⁵Álvaro Penteado Crósta,¹Kuldeep Prakash
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70162]
¹Department of Earth and Planetary Sciences, Nehru Science Centre, University of Allahabad, Prayagraj, India
²National Center of Experimental Mineralogy and Petrology, University of Allahabad, Prayagraj, India
³Institute of Geosciences, Universidade de Brasılia, Brasılia, Brazil
⁴School of Geosciences, University of the Witwatersrand, Johannesburg, South Africa
⁵Institute of Geosciences, Universidade Estadual de Campinas-UNICAMP, Campinas, Brazil
Published by arrangement with John Wiley & Sons

The Dhala structure in India, one of the oldest and most deeply eroded impact structures known on Earth, exhibits distinct morphological features. Despite decades of investigation, two fundamental attributes of the Dhala structure, its shape (variously described as rectangular, elliptical, to circular) and diameter (2.96 to ~25 km) have remained unresolved. Here, we report extensive new data pertaining to the spatial disposition of different lithounits with pre-, syn- and post-impact fabric data, and the occurrence within target granitoids of overturned fold structures related to the collapse of the central uplift, and provide an updated estimate of the current impact-melt breccia volume of ~2 km3. We propose a firm constraint on the size of the transient crater based on the extent of shock effects within target rocks and drill cores of the crater floor and below. We also provide compelling evidence for the presence of a collapsed structural uplift in the region of the Central Elevated Area (CEA), which is surrounded by a ring of monomict impact breccia exposures. Diagnostic shock deformation features in target granitoid, Giant Quartz Veins (GQVs), and samples from the breccia ring are also reported. Multispectral remote sensing, combined with digital elevation model analysis using sunshading and radial derivative techniques, reveals multiple elliptical to ovoid features around the CEA. These features, along with structural and fabric data, indicate a strong control of pre-impact basement anisotropies on the final crater geometry. We propose a revised diameter of ~10–12 km for the transient cavity and ~25 km for the final structure based on the integrated field and remote sensing data sets. The Dhala structure exhibits a distinctly elliptical morphology, with its major axis oriented in the southwest-northeast direction. The age of the Dhala impact is revised by ~400 Ma, constraining it now to the 1700 to 2100 Ma interval. The revised age constraint is derived from shock-metamorphic features identified within GQVs of approximately 2.1 Ga age, indicating the pre-impact emplacement of these reefs.

¹Gabriele Giuli,^1,2Maria Rita Cicconi,³Angela Trapananti,⁴Sigrid Griet Eeckhout,⁵Giovanni Pratesi,⁶Christian Koeberl
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70156]
¹Scuola di Scienze e Tecnologie, sez. Geologia, Universita di Camerino, Camerino (MC), Italy
²Department of Materials Science and Engineering – Inst. Glass and Ceramics, Friedrich-Alexander-Universität,Erlangen-N€urnberg, Germany
³Scuola di Scienze e Tecnologie, sez. Fisica, Universita di Camerino, Camerino, Italy
⁴European Synchrotron Radiation Facility (ESRF), Grenoble, France
⁵Dip. Scienze della Terra, Universita di Firenze, Florence, Italy
⁵Department of Lithospheric Research, University of Vienna, Vienna, Austria
Published by arrangement with John Wiley & Sons

Two thin sections of Muong Nong-type tektites from the Australasian tektite strewn field have been analyzed by Fe K-edge X-ray absorption near edge spectroscopy (XANES), using a hundreds-of-micrometers–sized beam suitable for spatially resolved analysis of the Fe oxidation state across distinct regions of the samples. Earlier analyses with an unfocused beam were inconclusive regarding different amounts of oxidized iron in the Muong Nong-type tektites, but did indicate different chemical compositions of the lighter and darker colored layers. Experimental XANES spectra are very similar in shape to those of other tektites. However, small and reproducible changes were found in the pre-edge peak involving the centroid energy: the pre-edge peak of the spectra collected within the dark layers are reproducibly 0.2 eV at higher energy than those of the spectra collected within the light matrix. This difference in energy position is four times the estimated energy reproducibility and, therefore, is significant. By comparison with pre-edge peak data of Fe model compounds, we estimate the Fe3+/(Fe2++Fe3+) ratios in the light matrix and dark layers to be 5% and 15% (±5), respectively. The heterogeneous distribution of the Fe oxidation state in Muong Nong-type tektites, as opposed to the homogeneous Fe oxidation state distribution in splash-form tektites, is consistent with previous hypotheses, based on volatile contents, of Muong Nong-type tektites resulting from melts that experienced lower temperatures compared to those of splash-form tektites.