^1,2E.Clave et al. (>10)
Journal of Geophysical Research: Planets (in Press) Open Access Link to Article [https://doi.org/10.1029/2025JE009107]
¹Deutsches Zentrum für Luft‐ und Raumfahrt e.V. (DLR), Institute of Space Research, Berlin, Germany
²UniversitéClaude Bernard Lyon 1, ENS de Lyon, CNRS, UJM, LGL‐TPE, UMR 5276, Villeurbanne cedex, France
Published by arrangement with John Wiley & Sons

Over 3.5 years of exploration in Jezero Crater, the Perseverance rover has explored several geological units of diverse origins and natures, performing multi-technique remote analyses of the chemistry and mineralogy of rocks with the SuperCam instrument suite. Three of these units are dominated by mafic to ultramafic rocks: the igneous rocks of Séítah (olivine cumulate on the crater floor), the sedimentary rocks of the Upper Fan (Western delta) and the Margin Unit, of likely igneous origin. Despite their diverse natures, these three different units present similar mineralogical assemblages with: (a) primary igneous minerals (olivine, pyroxene, Cr-rich Ti-Fe oxides), (b) Fe-Mg carbonate, (c) hydrated/hydroxylated silica, and (d) phyllosilicates. The abundance of carbonate is variable, and we estimate it around 3–9 wt.% and up to 6–16 wt.% carbonate mineral in the Upper Fan and Margin Unit, respectively. We propose that most of these carbonates formed through in situ carbonation of mafic/ultramafic material, whether these rocks were emplaced through igneous or sedimentary processes. The distribution of carbonate with elevation in the Upper Fan and Margin Unit suggests a contribution of the lacustrine activity to the carbonate process, possibly enhanced by hydrothermal activity. These in situ observations may be extrapolated to other carbonates-bearing rocks on Mars and would make the amount of carbon potentially stored in Martian ultramafic rocks overall significant. This would suggest that carbonation of ultramafic rocks might have played a key role in pumping CO2 from and therefore in cooling the Martian atmosphere.

^1,2Samantha Hemmelgarn, ²Nicholas Moskovitz, ^3,4Denis Vida
Icarus (in Press) Open Access Link to Article [https://doi.org/10.1016/j.icarus.2026.117128]
¹Department of Astronomy and Planetary Science, Northern Arizona University, 527 S Beaver St, Flagstaff, Flagstaff, AZ, 86011, USA
²Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, AZ, 86001, USA
³Department of Physics and Astronomy, The University of Western Ontario, London, Ontario, Canada
⁴Institute for Earth and Space Exploration, The University of Western Ontario, London, Ontario, Canada
Copyright Elsevier

We use machine learning to develop a framework for classifying meteoroids based on 13 directly observed parameters from the Global Meteor Network. This method adds depth to the  parameter, which uses only three parameters. We employ a semi-qualitative approach using 28,177 meteor events observed in 2023 by the Lowell Observatory Cameras for All-Sky Meteor Surveillance (LO-CAMS) network to evaluate multiple normalization, dimensionality-reduction, and clustering algorithms. We find that a combination of Factor Analysis (FA) and a Gaussian Mixture Model (GMM) results in clusters most consistent with traditional models. Three FA-derived factors corresponding to meteoroid kinematics, activation thresholds, and size/geometry effects describe the underlying structure of meteoroid behavior. The activation factor emerged as the most discriminating factor distinguishing whether a meteor is of asteroidal or cometary origin. Resulting 3, 6, and 11 cluster models reveal progressively finer compositional structure, from broad physical regimes to detailed subdivisions within cometary and asteroidal populations. From these results, we introduce a physically motivated hardness classification scheme: .  is a data-driven extension of  which physically interprets clusters in terms of the densest iron meteoroids down to the softest cometary material. Application to nine well-studied meteor showers and analysis of clusters in orbital space aids in the physical interpretation of  groups. The  model is supported by an analytical FA–GMM formulation that enables application to future datasets. Our results demonstrate that machine learning methods can extract compositional information from modern optical meteor datasets at scale and offers a new framework for interpreting meteoroid populations.

¹Xiaoying Liu et al. (>10)
Journal of Geophysical Research: Planets (in Press) Link to Article [https://doi.org/10.1029/2026JE009653]
¹Key Laboratory of Planetary Science and Frontier Technology, Chinese Academy of Sciences, Beijing, China
Published by arrangement with John Wiley & Sons

Asteroid impact, playing a key role in shaping the Moon, is a consequence of the orbital dynamical evolution of the Solar System. While the impact flux can be deduced from lunar craters, the impactor populations and their temporal variations remain poorly understood. We analyzed Fe-Ni metals in 40 impact clasts from the Chang’e-6 lunar soils and demonstrated that most of them are asteroidal remnants. The majority of these clasts (27 out of 40) originated from local basalt, where the asteroidal materials were accumulated after basaltic eruption at 2.8 billion years ago (Ga). The remaining 13 clasts are exotic feldspathic materials, delivered from the ancient lunar highlands, preserving asteroid remnants from ∼4.3 Ga to the present. By classifying the asteroid impactors based on the Ni, Co, P, Ir, and Au contents of the metals, we identified distinct impactor populations for the two clast types. All carbonaceous chondrite metals are exclusively found in seven of the basaltic impact clasts, providing robust evidence for a late-stage bombardment by carbonaceous asteroids. The significant increase in carbonaceous impactors can be attributed to orbital dynamical events between 4.3 and 2.8 Ga, including giant planet migration, the Yarkovsky effect, or breakup of large carbonaceous asteroids. These findings, together with the exponentially declining impact flux, imply that only a small proportion of carbonaceous asteroids were delivered to the early Earth-Moon system, and provide further constraints on the dynamical evolution of the Solar System.

¹P. J. Gasda et al. (>10)
Journal of Geophysical Resrach: Planets (in Press) Open Access Link to Article [https://doi.org/10.1029/2025JE009153]
¹Los Alamos National Laboratory, Los Alamos, NM, USA
Published by arrangement with John Wiley & Sons

NASA’s Curiosity rover is exploring a 5 km tall sedimentary mound that is hypothesized to record the transition from a warm and wet (phyllosilicate-rich) to a cold and drier (sulfate-rich) Mars. Evidence of magnesium sulfate-bearing rock has shown that Curiosity has crossed through this phyllosilicate-sulfate transition. Recently, Curiosity arrived at the Amapari Marker Band, a darker, indurated unit that can be traced laterally for tens of kilometers in orbiter images. Here, Curiosity found evidence for a very broad lake, and bedforms interpreted as wave-ripple laminated sedimentary rock that likely was deposited in shallow water in the explored location, before becoming a deeper lake. These rocks are enriched in Fe, Mn, and Zn which has major implications for groundwater paleohydrology in Gale crater. Three formation hypotheses are considered: concretion formation during early diagenetic alteration of shallow lake sediments, laterization or leaching of the sediments, and addition of Fe, Mn, and Zn by a mildly acidic and reducing groundwater interacting with a redox and/or pH front in a stratified lake. The preferred interpretation of the metal enrichments within the Amapari Marker band sedimentary rocks is that they formed in a shallow water environment at a redox and/or pH front within the ripple unit, which drove precipitation and concentration of metals. If the enrichments are due to groundwater alteration, these processes could link subsurface and surface environments. Water and the presence of high amounts of redox sensitive elements and other metals are favorable indicators for habitability.

¹A.M. Lee, ^1,2I.B. Smith, ¹J.A. Isen, ¹M.G. Daly
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2026.117127]
¹Centre for Research in Earth and Space Science, York University, Canada
²Planetary Science Institute, USA
Copyright Elsevier

MARSIS detected bright basal reflections at Ultimi Scopuli, near the south pole of Mars, which could imply the presence of liquid water or water saturated sediments. The dielectric permittivity was originally modelled to have a median value of 33 at 4 MHz, which is lower than expected for water in liquid form. Later investigations estimated values as high as 40 or as low as 4, where basal interface roughness is not considered. Besides roughness and water, alternative materials were suggested, such as brines or smectite clays. Two previous studies measured hydrated smectites at cold temperatures and found an apparent permittivity of 39 and 8.4. The larger number could explain the anomalous reflections, but the lower number would not. To review this discrepancy, we conducted experiments using a well-established smectite simulant at various hydration states at 230 K and 4 MHz, used for comparison to previous measurements. Our results show an apparent permittivity between 7 and 12 at 230 K, however, 180 K is considered a more reasonable estimation of basal South Polar Layered Deposits (SPLD) conditions. Our results at 180 K are close to 4, ruling out the presence of smectites as a potential source of the reflections. This study refines the techniques from a past study at York University, especially related to temperature control and gradients, and demonstrates the increasing capabilities of the MARVIN chamber.

¹Robin L. Haller, ¹Martin R. Lee, ²Mark E. Hodson
Geochimica et Cosmochimica Acta (in Press) Open Access Link to Article [https://doi.org/10.1016/j.gca.2026.04.022]
¹School of Geographical and Earth Sciences, University of Glasgow, Glasgow G12 8QQ, UK
²Department of Environment and Geography, University of York, York YO10 5NG, UK
Copyright Elsevier

Mighei-like (CM) meteorites are the most abundant group of hydrated carbonaceous chondrites. They display a wide range of degrees of aqueous alteration, from very mild to near complete, as demonstrated by the relative abundances of phyllosilicates and surviving anhydrous silicates. The reasons for differences in the extent of alteration are debated, and probably reflect variations within the CM parent body/bodies of one or more of water/rock ratio, temperature, and timescale. The least understood is timescale, and so to constrain the duration of aqueous alteration and to investigate precipitation conditions of key CM minerals, we created kinetic models with the software PHREEQC. These models simulated a mineralogically detailed alteration of the CM3 proxy Dominion Range 08006 by an aqueous fluid for different values of water/rock (W/R) ratio (by mass) and temperature over the timespan of 10−5–105 years with incremental time steps. Additional laboratory experiments in which chips of Dominion Range 08006 were reacted with either pure water or a carbonated aqueous solution under reducing conditions were undertaken to validate parts of the models and to evaluate formation conditions of calcite, as the study of calcite in CM chondrites provides invaluable information on aqueous alteration timings and conditions. The models suggest that regardless of their petrologic type, CM chondrites could have been altered from a CM3 over timescales ranging from months to ∼10,000 years depending on temperature. The more highly altered CM1 chondrites that contain magnetite instead of cronstedtite would have needed to react at temperatures of at least 100°C but not necessarily different W/R ratios compared to less altered CM2s. Some of the modelled systems suggest that minimally altered CM chondrites like Asuka 12169 could have been exposed to aqueous solutions at ∼1°C and W/R ratios (by mass) of ∼3 or higher. Significant quantities of calcite only form in laboratory experiments with a carbonated solution, suggesting that at least for early formed calcite, aqueous carbonate was sourced from accreted C-bearing ice instead of indigenous organic carbon. According to the models, a typical CM2 chondrite could have been altered from a CM3 lithology within ∼1,000 years at 50°C and 0.8 W/R ratio (by mass).

¹Sébastien Charnoz,²Jérôme Aléon,¹Marc Chaussidon,³Paolo A. Sossi,⁴Yves Marrocchi,¹Patrick Franco
Nature 652, 925-930 Open Access Link to Article [DOI https://doi.org/10.1038/s41586-026-10257-5]
¹Université Paris Cité, Institut de Physique du Globe de Paris, CNRS, Paris, France
²Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, UMR 7590, Sorbonne Université, Museum National d’Histoire Naturelle, CNRS, Paris, France
³Institute of Geochemistry and Petrology, ETH Zürich, Zürich, Switzerland
⁴Université de Lorraine, CRPG, CNRS, UMR 7358, Nancy, France

We currently do not have a copyright agreement with this publisher and cannot display the abstract here

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.