¹Kunihiko Nishiizumi e al. (>10)
Meteoritics & Planetary Science (in Press) Open Access Link to Article [doi: 10.1111/maps.701111]
¹Space Sciences Laboratory, University of California, Berkeley, Berkeley, California, USA
Published by arrangement with John Wiley & Sons

Surface processes on the asteroid Ryugu have been investigated using cosmic-ray-produced radionuclides, 10Be, 26Al, and 36Cl, and stable noble gases, on eight samples returned by the Hayabusa2 spacecraft. The 10Be and 26Al along with 21Ne measurements indicate that the two Chamber A samples A0105 collected during the first touchdown (TD) were exposed to cosmic rays for ~6.8 Myr at a shielding depth of 4–15 g cm−2. Beryllium-10 and 26Al from Chamber C samples from the second TD site, close to the artificial crater, were ejected from shielding depths of 120–160 g cm−2 for C0002, 20–85 g cm−2 for C0106-09, and 120–155 g cm−2 for C0106-10, -11, and -12, respectively. The exposure ages of these four C0106 samples differ, ranging from 1.7–8.8 Myr. These measurements provide unique and clear evidence that Hayabusa2 successfully collected subsurface samples ejected by an artificially produced crater. Chlorine-36 produced by secondary-produced thermal neutrons was observed in the samples, consistent with the high concentration of H and Cl. Helium (He) and Ne of solar wind origin were released at the lowest heating temperature of 200°C during a stepwise pyrolysis.

¹Arka P. Chatterjee, ¹Julien Allaz, ²Christian Huberb, ³Luiz F.G. Morales, ^4,5Amanda Ostwald, ¹Olivier Bachmanna
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2026.02.033]
¹ETH Zürich, Institute of Geochemistry and Petrology, Clausiusstrasse 25, 8092 Zurich, Switzerland
²Brown University, Earth, Environmental and Planetary Sciences, 324 Brook St., Box 1846, Providence, RI 02912, USA
³ETH Zürich, Scientific Centre for Optical and Electron Microscopy (ScopeM), Otto-Stern-Weg 3, 8093 Zurich, Switzerland
⁴Smithsonian National Museum of Natural History, 10th St. & Constitution Ave. NW, Washington, DC 20560, USA
⁵Michigan State University, Department of Earth and Environmental Sciences, 207 Natural Science Bldg, East Lansing, MI 48824, USA
Copyright Elsevier

Martian meteorites, the only available samples of Martian lithologies, provide unique insights into martian magmatism. Olivines in these meteorites contain complex phosphorus (P) zoning, which shed insights into the behaviour of mafic magmas in the martian crust. These olivines crystallized in multiple stages in ascending magmas, and preserved compositional zoning, particularly in P, due to its low diffusivity. Although previous studies have documented P zoning in martian olivines and attributed its formation to rapid crystallization events in magma storage zones within the crust, the processes responsible for the undercooling and fast olivine growth remain unresolved. This study addresses the challenge of interpreting P zoning in martian olivines to better understand the conditions which affected their crystallization histories. Using high-resolution P X-ray maps and microprobe traverses, we show that P zoning in olivine megacrysts from shergottites (martian basalts) and chassignites (martian dunites) consistently records rapid crystallization events at high undercooling due to magma ascent through the martian crust. These zoning patterns, observed in cores, mantles, and rims of olivines from hypabyssal and intrusive samples, highlight different crystallisation conditions during staging, ascent and emplacement of magmas at varying crustal depths. P zoning in olivine-phyric shergottites, viewed in the light of previous thermobarometry results, record initial olivine nucleation in the lower crust, ascent to the mid-crust and final rapid crystallization in the shallow subsurface. Similarly, we inferred multiple cycles of magma ascent and storage in the martian crust from the P zoning in poikilitic and non-poikilitic regions of a poikilitic shergottite. We also provide evidence from P zoning in olivines to differentiate between magma storage relatively deep in the crust and shallow, hypabyssal emplacement. The nature of P zoning during the final stages of olivine crystallization can serve as in-situ evidence of the eruptive behaviour of shallow magma bodies. Further analyses of available meteorites and olivines from future sample return missions will be fundamental to build a holistic model of martian magma plumbing systems and its evolution through time

^1,2Toshimori Sekine, ³Ginga Kitahara, ³Akira Yoshiasa, ⁴Akira Yamaguchi
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2026.02.021]
¹Center for High Pressure Science and Technology Advanced Research, Shanghai 201203, China
²Gradual School of Engineering, University of Osaka, Suita 565-0871, Japan
³Graduate School of Advanced Science, Kumamoto University, Kumamoto 860-8555, Japan
⁴National Institute for Polar Research, Tachikawa 190-8518, Japan
Copyright Elsevier

The fusion crusts of meteorites indicate the quenched high temperature layers, but few studies are known due to the complicated process at the time of formation. We focused on the redox reactions in the outermost of fusion crusts of typical stony meteorites to investigate the dynamic formation process of rapid heating and quenching through interactions with atmosphere. We used X-ray absorption fine structure (XAFS) method to estimate the valence states of three transition elements of Ti, Fe, and Mn. The results showed a range of valence state between 3.7 and 4.0 in Ti and 2.0 and 3.0 in Fe, and about 2.5 in Mn. The close relationship between the valence states between Ti and Fe is not recognized apparently although the valence of Mn is nearly constant. If the redox reaction occurs at extreme high temperature, reduction is expected thermodynamically. Oxidation also is expected at the late stage of formation near the Earth surface when the observed meteorites keep high temperatures. The present results on the valence states of Ti, Fe, and Mn in the outermost fusion crusts of stony meteorites imply Ti effectiveness as a good indicator for redox reaction at extreme high temperatures, as supported in tektites formation.

¹Mason Neuman, ²Catherine A. Macris, ^1,3Astrid Holzheid, ¹Katharina Lodders, ¹Bruce Fegley, ⁴Heng Chen , ¹Kun Wang
Geochimica et Cosmochimica Acta (in Press) Open Access Link to Article [https://doi.org/10.1016/j.gca.2026.02.020]
¹Department of Earth, Environmental, and Planetary Sciences and the McDonnell Center for the Space Sciences, Washington University in St. Louis, St. Louis, MO 63130, USA
²Earth and Environmental Sciences, Indiana University, Indianapolis, IN 46202, USA
³Institute of Geosciences, University of Kiel 24118 Kiel, Germany
⁴Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964, USA
Copyright Elsevier

Moderately volatile element (MVE) depletion and isotopic fractionation are commonly observed in planetary materials. The mechanisms driving these phenomena are subject to intense debate, with some proposing evaporation at various stages of planetary formation as a potential explanation for both elemental depletion and isotopic fractionation. Studying the isotopic fractionation of MVEs can also be useful for investigating the conditions of high-temperature processes in the solar system and on Earth. Evaporation experiments to understand the behavior of isotopic fractionation under variable conditions provide a grounded context for interpreting the geochemical signatures of natural materials. Here we present new experimental data obtained from a novel approach that uses flowing gas to levitate samples and a laser to heat them. This approach offers the advantage of preventing undesired sample-container reactions at elevated temperatures and enabling ultrafast quenching. We analyzed the MVE depletion (e.g., Na, K, Cu, Zn, Ga and Rb) and potassium isotope fractionation associated with heating basalt and loess materials at temperatures up to 2046 °C under multiple oxygen fugacities. Our results show that the oxygen fugacity has a considerable effect on the observed MVE depletion and K isotope fractionation. This effect is likely driven by variations in the ambient gas composition and the specific evaporating species involved. We also found that the starting composition exerts a strong control on the MVE depletion and K isotope fractionation, which we attribute to differences in the relative timescales of K diffusion and evaporation among melt compositions. We additionally computed the evaporation coefficients of K and Zn across various temperature, oxygen fugacities and melt compositions, and systematically explored the relationships between evaporation coefficients and these factors.

¹Kenneth H. Williford et al. (> 10)
Science 391, 6787 Link to Article [DOI: 10.1126/science.adu8264]
¹Blue Marble Space Institute of Science, Seattle, WA, USA.
Reprinted with permission from AAAS

The Perseverance rover landed in Jezero crater on Mars, which once contained a lake of liquid water. We report the rock properties encountered by Perseverance during a 10-kilometer traverse extending over 400 meters in elevation, from beneath Jezero’s western sedimentary fan to the upper crater rim. These rocks consist of coarse-grained olivine, magnesium and iron carbonates, silica, and phyllosilicates, including some of the oldest materials exposed within Jezero. We infer that these rocks formed by olivine accumulation in an igneous system of layered intrusions, followed by exposure to water and carbon dioxide, which caused extensive carbonation of the silicate minerals. Aqueous alteration was more pronounced at lower elevations. Higher-elevation exposures on the crater rim appear similar to olivine-rich rocks distributed over the wider Nili Fossae region.

¹R. J. Hopkins,¹A. D. Rogers,¹L. Ehm
Journal of Geophysical Research: Planets 131, e2025JE009299 Open Access Link to Article [https://doi.org/10.1029/2025JE009299]
¹Stony Brook University, Stony Brook, NY, USA
Published by arrangement with John Wiley & Sons

Throughout Gale crater on Mars, the Curiosity rover has found high abundances (15–73 wt%) of X-ray amorphous materials in the rocks and sediments. The composition of this amorphous fraction is primarily calculated by subtracting crystalline abundances measured by the Chemistry & Mineralogy X-Ray Diffractometer (CheMin) from bulk elemental abundances from the Alpha Particle X-Ray Spectrometer (APXS). If any crystalline phase was underrepresented in the CheMin data, the elemental components of that phase would be overestimated in the amorphous fraction. This study examines the possibility of underrepresented crystalline phases in X-ray diffraction data using mixtures of amorphous ferric sulfate (AFS) and crystalline Ca-sulfate. Two compositionally equivalent mixtures were made with different morphologies: first, a simple mixture of AFS and Ca-sulfate grains and second, Ca-sulfate grains with AFS coatings. Each mixture was characterized with Raman spectroscopy, and two X-ray diffractometers (XRDs): a Bragg-Brentano instrument with CuKα radiation and a Debye-Scherrer instrument with CoKα radiation. Raman peaks from Ca-sulfate dominate both mixtures, but are dampened when AFS coats the Ca-sulfate grains. In XRD data, AFS coatings cause an overestimation of the amorphous percentage, with a difference between the known and refined amorphous abundances of 29–34 wt%, compared to 2–2.8 wt% for the uncoated mixtures. The effects of the coatings were slightly amplified with the Debye-Scherrer XRD, primarily due to the increased scattering and absorption of the CoKα radiation. This has implications for interpreting the XRD data of mixed amorphous-crystalline samples on Mars, as any Fe-rich amorphous coating may cause an overestimation of the amorphous abundance.

^1,2Jitse Alsemgeest,¹Fraukje M. Brouwer,³Luis F. Auqué,¹Kirsten van Zuilen,⁴Natalia Hauser,⁴Wolf Uwe Reimold
Journal of Geophysical Research: Planets 131, e2025JE008966 Open Access Link to Article [https://doi.org/10.1029/2025JE008966]
¹Geology and Geochemistry Cluster, Department of Earth Sciences, VU Amsterdam, Amsterdam, The Netherlands
²Nowat GAIA, Faculty of Geo‐Information Science and Earth Observation, University of Twente, Enschede, The Netherlands
³Department of Geosciences, University of Zaragoza, Zaragoza, Spain
⁴Institute of Geosciences, University of Brasília,CEP, Brasília, Brazil
Published by arrangement with John Wiley & Sons

As hydrous minerals have been observed in impact craters on Mars, impact-generated hydrothermal systems (IGHSs) have been considered as potential habitats for life on that planet. The Vargeão Dome, a 12 km wide impact structure in southern Brazil, was formed in basalts with at least two hydrothermal alteration stages. This structure is a rare terrestrial analog for IGHS evolution on Mars. However, the thermochemical evolution of these stages and their relationship to the impact remain unresolved. Two vein-forming alteration stages were identified by multidisciplinary sample analysis of Vargeão Dome. Fractured and deformed white vein fragments from the first stage occur within red veins from the second. This suggests reactivation of the white vein set during the crater excavation and modification stages. Rare Earth Element and Rb-Sr isotope data indicate different fluid sources for the white and red veins and an evolving fluid system. Thermodynamic modeling indicates a cooling sequence from 100–250 to <25°C for the white vein set, whereas goethite and hematite within the red veins indicate that most IGHS activity occurred at temperatures below 40°C. Considering this and accounting for gravity differences, life-supporting IGHSs on Mars may preferentially form impact structures over 28 km in diameter. Furthermore, impact-reactivation suggests elevated habitat potential in structures with pre-existing fault, fracture, and vein systems. These occur in volcanic areas or terrain older than 3.5 Ga, when Mars was wetter and geologically active. Therefore, the search for evidence of IGHS-supported life should be focused on these kinds of terrains.

¹Cyrena A. Goodrich et al. (>10)
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2026.02.019]
¹Lunar and Planetary Institute, USRA, 3600 Bay Area Blvd, Houston, TX 77058, USA
Copyright Elsevier

Xenoliths of carbonaceous chondrites (CC) in meteoritic breccias can provide samples of primitive solar system materials that are not represented by individual meteorites and thus expand our knowledge of chemical and isotopic reservoirs in the early solar system and early geologic processes on CC parent bodies. The Almahata Sitta (AhS) polymict ureilite contains one such xenolith, referred to here as AhS 202. Hamilton et al. (2020) discovered that, unlike any other known CC, the AhS 202 xenolith contains abundant (∼12–14 vol%) amphibole, a hydrous mineral that characteristically forms in greenschist to amphibolite facies metamorphism and requires a significantly larger parent body than typically inferred (≤100 km diameter) for CC meteorite bodies. Building on that initial work, we report additional analyses of the mineralogy and petrology, and new analyses of the chemical composition, oxygen and chromium isotope compositions, and physical properties of this xenolith that further constrain its petrogenesis and provenance. Our results show that the AhS 202 precursor was chondritic and experienced aqueous alteration similar to many low petrologic type CC meteorites at temperatures of ∼ 30–100 °C and fluid pressures of PH2O < 0.1 kbar, leading to formation of serpentines, magnetite, and chlorite. However, unlike any known CC meteorite, AhS 202 was heated further under water-saturated conditions similar to prograde metamorphism of terrestrial serpentinites, leading to formation of chemically pure diopside, secondary olivine, and tremolite amphibole. Peak metamorphic conditions determined from thermodynamic modeling, constrained by olivine-magnetite oxygen isotope thermometry, were ∼ 380–430 °C and ∼ 0.5–2.25 kbar. Based on our measured density of 2.27 g/cc for AhS 202, these conditions imply parent body sizes of 600–1875 km diameter, confirming the previous estimate (640–1800 km) of Hamilton et al. (2020). The fluid-assisted metamorphic conditions experienced by AhS 202 cannot be represented in current classification systems of meteorite petrologic type, which recognize only anhydrous metamorphism; we discuss an alternative approach to the classification of such materials. Oxygen and chromium isotope compositions show an affinity between AhS 202 and CR chondrites and/or CR-related achondrites, suggesting derivation from a common reservoir. However, petrology, refractory element composition, and extremely low carbon content indicate that it did not form on the same parent body as known CR chondrites or CR-related achondrites. The existence of this sample, in combination with several even higher-pressure clasts observed in CR chondrites (Kimura et al., 2013; Hiyagon et al., 2016), suggests that this reservoir contained multiple large planetesimals.

¹Alexander M. Kling, ¹Michelle S. Thompson
Geochimica et Cosmochimica Acta (in Press) Open Access Link to Article [https://doi.org/10.1016/j.gca.2026.02.016]
¹Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, IN 47907, USA
Copyright Elsevier

Solar wind neon is incorporated into lunar regolith grains and other planetary materials via solar wind implantation. Understanding the abundance of neon relative to other solar wind gases and its trapping and storage within planetary materials can inform on both parent body processing and volatile cycling. Microstructural defects in lunar regolith grains, including vesicles formed by space weathering processes, have previously been identified to store other solar wind-derived volatiles such as hydrogen, water, and helium. Here, we use transmission electron microscopy and electron energy loss spectroscopy to identify the presence of solar wind neon and quantify its abundance in vesicles within a space weathered lunar regolith grain. The direct observation of solar wind neon trapped in vesicles offers a new understanding of the space weathering history of lunar regolith grains and other planetary materials rich in solar wind gases. The storage of solar wind neon in nanoscale vesicles also has implications for its retention, diffusivity, and fractionation which may affect interpretations of the exposure and processing histories of lunar and other planetary materials as derived from noble gas analyses.

¹Anna Zappatini et al. (>10)
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70110]
¹Institute of Geological Sciences, University of Bern, Bern, Switzerland
Published by arrangement with John Wiley & Sons

A fireball camera system installed in 2022 by the Oman Meteorite MonitoringProject (OMMP) as part of the Global Fireball Observatory (GFO) recorded a 3.2 s fireballon March 8, 2022 at 8:15 p.m. UTC. A meteoroid of 4 2 kg entered the atmosphere at14.0 km/s. Its trajectory, with a slope of 68.4°, started at 67.6 km and ended at 30.2 kmwhere the meteoroid traveled at 7.36 km/s. Approximately 50 g survived atmospheric entry.On February 7, 2023, two meteorites of 13.85 g and 8.21 g were recovered at the predictedsite. Gamma spectrometry confirmed their young terrestrial age via short-lived cosmogenicradionuclides 54 Mn and 22 Na. Al-Khadhaf is thus the first camera-observed meteorite fallfrom Oman. Petrography and mineral composition classify it as an ordinary H5–6 S2 W1chondrite. Its pre-impact orbit (a = 1.72 AU, e = 0.45, i = 4.36°) is consistent withasteroid-belt delivery, with both inner-belt and Koronis-family sources remaining plausible.The cosmic ray exposure age of 8.57 1.2 Ma coincides with an exposure-age peak observedamong H chondrites. Al-Khadhaf adds to the record of camera-observed falls, linkingmeteorite compositions to their solar system context via orbit calculations.