¹Inès Torres Auré, ^2,3John Carter, ¹Cathy Quantin-Nataf, ^2,4Damien Loizeau, ¹Erwin Dehouck, ¹Matthieu Volat
Icarus (in Press) Open Access Link to Article [https://doi.org/10.1016/j.icarus.2026.117113]
¹Laboratoire de Géologie de Lyon : Terre, Planètes, Environnement (LGL-TPE), Université Claude Bernard Lyon 1, CNRS, Villeurbanne, France
²Institut d’Astrophysique Spatiale (IAS), Université Paris Saclay, CNRS, Orsay, France
³Laboratoire d’Astrophysique de Marseille (LAM), Université Aix-Marseille, CNRS, Marseille, France
⁴Qualisat, Bièvres, France
Copyright Elsevier

The Fe/Mg-phyllosilicate-bearing units at Oxia Planum and Mawrth Vallis, two key Noachian sites along the martian dichotomy, exhibit distinct compositions despite their proximity. Using novel spectral criteria developed in this study, we distinguish two clay types: Type-1 (Mg-rich smectites/Fe2+-bearing saponite/vermiculite) and Type-2 (Fe3+-rich nontronite). Hyperspectral (OMEGA/CRISM) and textural (HiRISE/CTX) analyses reveal a regionally extensive basal Type-1 unit continuous across both sites, overlain by a Type-2 unit limited to Mawrth Vallis and southeast of Oxia Planum (above main delta fan elevations). A cratered paleosurface, with a Type-1 spectral signature, marks their boundary, indicating a depositional hiatus. The Type-1 unit’s lateral extent (>600 km) and elevation range (>1300 m) suggest a large-scale aqueous process, while the Type-2 unit’s absence below Oxia Planum’s delta fan implies either post-depositional erosion or environmental controls during deposition at Oxia Planum. Our results constrain early Mars’ climate models, challenging localized deposition/alteration hypotheses and ocean scenarios. These findings reveal that Type-1 clays extend over a much broader area than previously assumed, indicating that the ExoMars Rosalind Franklin rover will not investigate a localized phenomenon but rather a process with significant regional–and potentially global–implications for the geological and climatic history of Mars.

¹Veronika Pazderová, ¹Pavol Matlovič, ^2,3Hadrien Devillepoix
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2026.117107]
¹Faculty of Mathematics, Physics and Informatics, Comenius University, Mlynská Dolina, Bratislava, 842 48, Slovakia
²Space Science and Technology Centre, School of Earth and Planetary Sciences, Curtin University, Kent Street, Perth, 6102, WA, Australia
³International Centre for Radio Astronomy Research, Curtin University, Perth, 6845, WA, Australia
Copyright Elsevier

Meteor spectroscopy is a key method for probing the composition of meteoroids, providing insights into both their overall composition and the relative abundances of individual species. In this study, we present a comparison of meteor spectra recorded simultaneously from multiple observing sites within the Australian segment of the AMOS (All-sky Meteor Orbit System) network. We examine the origins of spectral discrepancies between the respective systems, considering factors such as focusing, spectrum extraction geometry, calibration, and observing geometry. This work represents one of the few detailed examinations of such effects. Our results show that factors such as observing geometry, focusing, calibration procedures, instrument characteristics, and specific data-processing approaches can introduce uncertainties in relative line intensities that are typically unresolved in conventional single-station observations. The four case studies presented in this work demonstrate that the sources of discrepancy in relative line intensities can be identified and potentially accounted for, ensuring that meteoroid composition estimates based on these intensities remain robust.

¹L. J. Riches,^1,2M. D. Suttle,¹I. A. Franchi,¹X. Zhao,^1,2M. M. Grady
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70150]
¹School of Physical Sciences, The Open University, Milton Keynes, UK
²Planetary Materials Group, Natural History Museum, London, UK
Published by arrangement with John Wiley & Sons

Bells is an ungrouped carbonaceous chondrite that has in recent years been proposed as a CR-an. This link to CR chondrites has previously been identified through the analysis of anhydrous silicates, for example, oxygen isotopic compositions of olivine (Marrocchi et al., 2023). In this study, the aqueous alteration extent of Bells has been analyzed through the use of carbonate minerals to see whether Bells’ aqueous history supports a CR origin. The carbonates identified were calcite grains that had O-isotope compositions showing a single generation trend ranging from δ18O = +20.7 to +40.3‰, δ17O = +6.9 to +23.4‰ and Δ17O = −4.1 to +2.4. These are isotopically similar values to carbonates found in other CR-an meteorite Al Rais (δ18O = +28.8 to +34.8‰ Jilly-Rehak et al., 2018). Oxygen isotope compositions plot along a mass-independent slope of 0.75 ± 0.12, which indicates that isotopic evolution is controlled primarily by mixing of fluid and rock reservoirs. Starting temperatures for calcite precipitation are estimated to be ~14°C. These observations here help support a potential reclassification of Bells as a CR-an meteorite.

^1,2M. R. Boyd,¹M. J. Genge
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70142]
¹Department of Earth Science and Engineering, Imperial College London, London, UK
²Grantham Institute—Climate Change and the Environment, Imperial College London, London, UK
Published by arrangement with John Wiley & Sons

Natural microspherules are important tracers of geologic and environmental processes in modern and ancient deposits. However, anthropogenic contamination can dilute natural collections by releasing synthetic microspherules into the environment. We report on a collection of microspherules from Pikes Peak, a granitic batholith mountain in Colorado, USA. Most particles are smooth, glassy spheres and are compositionally homogeneous, while some particles do not indicate formation via a molten or vapor phase and are interpreted as erosional products. The glassy microspherules are compared to spheres found in road paint from London, United Kingdom, and show strong textural and compositional similarities. In particular, Na content is high, which is unexpected in natural spherules. The Pikes Peak spherules are interpreted as microspherules eroded from road markings, illustrating local contamination on the summit. In addition, two microspherules with potential natural origins were found. We propose criteria for distinguishing paint microspherules from their natural counterparts, which is vital when investigating ancient spherule-forming processes as well as the impact of human activity on the environment. Quantifying the mass of microspherules found indicates high erosion rates of road paint, leading to microspherule abundances that could dominate the local microspherule flux.

^1,2L. Folco,^1,2M. Masotta
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70149]
¹Dipartimento di Scienze della Terra, Università di Pisa, Pisa, Italy
²Centro per la Integrazione della Strumentazione dell’Università di Pisa CISUP, Università di Pisa, Pisa, Italy
Published by arrangement with John Wiley & Sons

We report on a petrographic and geochemical study of coated impact melt lapilli and bombs from the ejecta blanket of the Wabar crater field (Saudi Arabia), which formed ~300 years ago by the hypervelocity impact of an iron asteroid against sand dunes. These objects, up to 15 cm across and with aerodynamic shapes, characteristically consist of a thin coat of vesicular Fe-Ni-rich siliceous black glass enveloping a core of pumiceous silica-rich white glass. Both glasses are geochemically indistinguishable from the white or black glass masses found earlier in the ejecta blanket and interpreted as the product of impact melting of the target material and of the mixing of target and impactor impact melts, respectively. The black glass coating studied here contains high concentrations of Fe (8.7 wt%), Ni (4770 μg g−1), and Co (463 μg g−1), indicating high impactor contamination (4–17 wt%) typical of impactor–target interface melts. We propose a qualitative model for the formation of the coated lapilli and bombs within the context of the contact and excavation stages of a crater-forming event, thereby contributing to the understanding of the physical–chemical interactions between impactor and target impact melts during the formation of impact craters in rocky planetary surfaces.

¹Robin L. Haller,¹Martin R. Lee,²Mark E. Hodson
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70145]
¹School of Geographical and Earth Sciences, University of Glasgow, Glasgow, UK
²Department of Environment and Geography, University of York, York, UK
Published by arrangement with John Wiley & Sons

Terrestrial weathering alters the chemical and isotopic composition, and mineralogy, of meteorites; its effects on ordinary chondrites are well-studied, but relatively little is known about the susceptibility of carbonaceous chondrites. We combined laboratory experiments, whereby Chwichiya 002 (C3-ung find), Murchison (CM2 fall) and Kolang (CM1/2 fall) were exposed to artificial rainwater for 30–180 days, with kinetic models to examine the effects of different weathering timespans and environments on mineralogy and petrologic (sub)type. Leachates derived from the Murchison and Kolang experiments were rich in S, Ca, Na, Cl, K, and Mg with less abundant Si and Fe. These results suggest that calcite and pyrrhotite, together with unknown Na-K-Cl bearing minerals, are particularly susceptible to terrestrial alteration. Chwichiya 002 was less reactive than anticipated, possibly due to earlier hot desert weathering. Models predict that primitive chondrites with amorphous material, including Chwichiya 002, oxidize within days when exposed to water, particularly in warm environments (e.g., hot deserts). Terrestrial weathering is expected to rapidly lower the petrologic (sub)type of CM3 chondrites, whereas CM2s react more slowly and their petrologic (sub)type does not change significantly.

^1,2,5Gabriel A. Pinto, ¹Vinciane Debaille, ²Jolantha Eschrig, ³Alexandre Corgne, ⁴Kevin Soto, ⁵Thierry Leduc, ⁵Sophie Decree, ²Steven Goderis
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2026.117102]
¹Laboratoire G-Time & Brussels Laboratory of the Universe (BLU), Université Libre de Bruxelles, 1050 Brussels, Belgium
²Archaeology, Environmental Changes, and Geo-Chemistry, Vrije Universiteit Brussel, 1050 Brussels, Belgium
³Instituto de Ciencias de la Tierra, Universidad Austral de Chile, Valdivia, Chile
⁴Departamento de Ciencias Geológicas, Universidad Católica del Norte, Antofagasta, Chile
⁵Institute of Natural Sciences, Geological Survey of Belgium, 1000 Brussels, Belgium
Copyright Elsevier

Evaporites are frequently reported in carbonaceous chondrites from hot and cold deserts, yet their origin remains debated between formation on the parent body or by post-fall terrestrial alteration. Here, we present a systematic characterization of Ca sulfate and Ca carbonate assemblages in four CO carbonaceous chondrites from different dense collection areas of the Atacama Desert (Los Vientos 123, El Médano 464, Calama 031, Paposo 088). We combine backscattered electron imaging, EDS, X-ray compositional mapping, Raman spectroscopy, and modal point counting to assess the distribution, mineralogy, and formation context of evaporites. Evaporites occur mainly as pore- and vein-filling phases and as replacements of Fe sulfides. Los Vientos 123 and El Médano 464 contain high abundances of Ca sulfates (~2.5 ± 0.35 vol%), Calama 031 is dominated by Ca carbonate veins (1.4 ± 0.26 vol%) with minor Ca sulfate, and Paposo 088 shows only low Ca sulfates contents (0.47 ± 0.15 vol%). These phases are systematically associated with Fe oxyhydroxides, jarosite-like phases, and strongly altered sulfides. The sulfate- and carbonate-rich assemblages in CO chondrites correlate with local soil geochemistry and microclimates. Limestone bedrock and more rain-influenced inland set different evaporite assemblages compared to coastal areas characterized by marine aerosols and salt-rich soils. Raman spectra indicate that the dominant Ca sulfate polymorph is anhydrite, lacking OH-stretching bands, consistent with precipitation from low-water activity, chloride-nitrate-rich brines and limited subsequent hydration. Disordered carbonaceous matter locally sheltered within sulfate-rich areas suggests that secondary evaporites can trap and preserve organic material, even if non-biological. Our results thus support (i) a terrestrial origin for Ca sulfates and Ca carbonates in Atacama CO chondrites; (ii) the stability of anhydrite as an indicator of extremely low water activity; and (iii) process analogues for evaporite formation in Martian settings, where anhydrite regions may be key targets to reconstruct aqueous conditions and assess organic preservation on Mars.

¹Alvaro Penteado Crósta,²Neivaldo Araújo de Castro,³Marcos Alberto Rodrigues Vasconcelos,⁴Airton Natanael Coelho Dias,^5,6Ludovic Ferrière,⁷Wolf Uwe Reimold,⁸Ana Maria Góes,⁹Jackson Alves Martins,²Liliana Sayuri Osako,⁹Raimundo Mariano Gomes Castelo Branco
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70144]
¹Institute of Geosciences, Universidade Estadual de Campinas, Campinas, Brazil
²Geology Department, Federal University of Santa Catarina-UFSC, Florianopolis, Brazil
³Institute of Geosciences, Federal University of Bahia, Salvador, Brazil
⁴Physics, Chemistry and Mathematics Department, Federal University of Sao Carlos, Sorocaba, Brazil
⁵Natural History Museum Abu Dhabi, Abu Dhabi, United Arab Emirates
⁶Department of Lithospheric Research, University of Vienna, Vienna, Austria
⁷Instituto de Geociencias, Universidade de Brasilia, Brasilia, Brazil
⁸Institute of Geosciences, University of Sao Paulo, Sao Paulo, Brazil
⁹Geophysics Laboratory, Centro de Ciencias, Federal University of Ceara, Fortaleza, Brazil
Published by arrangement with John Wiley & Sons

The São Miguel do Tapuio structure (SMT) is a remarkable, nearcircular feature of about 21 km diameter, centered at 5°37.6′ S, 41°23.3′ W in Piauí state, northeastern Brazil. The structure is located within the sedimentary strata of the Paleozoic–Mesozoic Parnaíba Basin and predominantly comprises sandstones of the Devonian Pimenteiras and Cabeças formations. SMT exhibits a rugged morphology, in contrast to the smoother surrounding terrain. An impact origin has been suggested for SMT since the 1980s based on indirect aspects, such as the structure’s morphology with an annular outer rim, inner rings, and an elevated central area. Some of the sandstones found in the inner region were structurally deformed and recrystallized, in contrast to the undeformed equivalent strata outside the structure. A field survey conducted in 2017 yielded a few samples of sandstone and monomict sandstone breccia from near the center of the structure. Here we report the discovery of multiple shocked quartz grains with planar fractures (PFs), feather features (FFs), and planar deformation features (PDFs) in four thin sections of two samples from this central area. Universal stage measurements on all shocked quartz grains (25 grains in total; 16 with PFs, five with PDFs, and four with both PFs and PDFs) confirm that these planar microstructures occur in distinct crystallographic orientations that are indicative of shock pressures up to 20 GPa. Our investigations, thus, have confirmed the impact origin of the SMT. It represents the ninth confirmed impact structure in Brazil and, at 21 km diameter, is the second largest of its kind in South America.

¹S.P. Goudy, ¹M. Telus, ²K. Nagashima, ²G.R. Huss
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2026.04.014]
¹Earth and Planetary Sciences, University of California at Santa Cruz, 1156 High Street, Room A232, Santa Cruz, CA 95064, United States
²Hawaii Institute of Geophysics and Planetology, University of Hawai’i at Mānoa, 1680 East-West Road, POST Building, Office 602, Honolulu, HI 96822, United States
Copyright Elsevier

Here we present petrographic, O isotope, and C isotope data on calcite and petrographic and O isotope data on magnetite in Aguas Zarcas (CM2) and Miller Range (MIL) 13005 (CM1/2) in an effort to test CM aqueous alteration models. Our O and C isotope data for Aguas Zarcas and MIL 13005 are within the ranges reported in previous work for calcite in CMs. Using O isotope data from Δ17O-matched calcite and magnetite grains in our samples, we calculated equilibrium-model formation temperatures for the analyzed calcites in each meteorite. Combining our isotopic and temperature data with literature data, we sort the data into less altered (CM2) and more altered (CM1/2 and CM1) categories, and examine that data for differences between the categories by analyzing the δ18O-δ17O, δ18O-δ13C, and model formation temperature data of the categories. We find potential differing cluster patterns between δ18O and δ13C in calcites between our two CM alteration categories, and find that sparse extant temperature data imply that more altered CMs (types 1 and 1/2) may have undergone alteration at a lower average temperature than CM2s. We also find that the O isotopic compositions between CM1s, CM2s, and CM1/2s do not differ significantly. Through use of a novel mass-balance model, we infer a pre-alteration ice Δ17O within the range of 5.3–13.3‰. We find two generations of calcite formation in MIL 13005 with different proportions of their O being sourced from ices and anhydrous silicates, and one generation of calcites within Aguas Zarcas. We created concentration mixing models through an original machine-learning-based analytical approach, which show that the calcite data can be readily explained using three optimally determined C- and O-bearing sources.

¹Richard J. Anslow,²Maylis Landeau,¹Amy Bonsor,^1,3Jonathan Itcovitz,^1,4Oliver Shorttle
Journal of Geophysical Research: Planets (in Press) Open Access Link to Article [https://doi.org/10.1029/2025JE009328]
¹Institute of Astronomy, University of Cambridge, Cambridge, UK
²Université de Paris, Institut de Physique du Globe deParis, CNRS, Paris, France
³Department of Civil and Environmental Engineering, Imperial College London, London, UK
⁴Department of Earth Sciences, University of Cambridge, Cambridge, UK
Published by arrangement with John Wiley & Sons

The excess abundance of highly siderophile elements (HSEs), as inferred for the terrestrial planets and the Moon, is thought to record a “late veneer” of impacts after the giant impact phase of planet formation. Estimates for total mass accretion during this period typically assume all HSEs delivered remain entrained in the mantle. Here, we present an analytical discussion of the fate of liquid metal diapirs in both a magma pond and a solid mantle, and show that metals from impactors larger than approximately 1 km will sink to Earth’s core, leaving no HSE signature in the mantle. However, by considering a collisional size distribution, we show that to deliver sufficient mass in small impactors to account for Earth’s HSEs, there will be an implausibly large mass delivered by larger bodies, the metallic fraction of which lost to Earth’s core. There is therefore a contradiction between observed concentrations of HSEs, the geodynamics of metal entrainment, and estimates of total mass accretion during the late veneer. To resolve this paradox, and avoid such a mass accretion catastrophe, our results suggest that large impactors must contribute to observed HSE signatures. For these HSEs to be entrained in the mantle, either some mechanism(s) must efficiently disrupt impactor core material into
0.01 mm fragments, or alternatively Earth accreted a significant mass fraction of oxidized (carbonaceous chondrite-like) material during the late veneer. Estimates of total mass accretion accordingly remain unconstrained, given uncertainty in both the efficiency of impactor core fragmentation, and the chemical composition of the late veneer.