^1,3Qi-ao Chen, ¹Wen Yu, ^2,4Hao Yan, ¹Tian Zhang, ¹Hong Tang, ¹Xiongyao Li
Earth and Planetary Science Letters, 692, 120236 (2026) Link to Article [DOI: 10.1016/j.epsl.2026.120236]

¹Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550081, China
²International Center for Isotope Effects Research, State Key Laboratory of Critical Earth Material Cycling and Mineral Deposits, Nanjing University, Nanjing, 210023, China
³College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, 100049, China
⁴Frontiers Science Center for Critical Earth Material Cycling, School of Earth Sciences and Engineering, Nanjing University, Nanjing, 210023, China
Copyright Elsevier

Solar wind implantation is widely recognized as a primary source of hydroxyl (OH) and water on the lunar surface, yet the kinetics and controlling mechanisms of this process remain poorly constrained. Here we present proton implantation experiments on San Carlos olivine conducted at 20, 90, and 130°C to quantify the kinetics and saturation behavior of OH formation. The OH abundance increases with H⁺ fluence following an exponential function and approaches a temperature-dependent saturation level. The fitted saturation concentration decreases with increasing temperature, whereas the apparent rate constant increases, indicating a decoupling between reaction kinetics and OH yield. Post-implantation heating experiments demonstrate negligible OH loss, ruling out thermal instability as the cause of reduced OH abundance at elevated temperatures. Instead, we propose a temperature-dependent branching mechanism in which implanted hydrogen partitions between OH formation and H₂ recombination. Higher temperatures enhance hydrogen mobility, promoting H-H recombination and suppressing OH formation efficiency. The conversion ratio of H⁺ to OH decreases progressively with fluence, providing a unified explanation for the large discrepancies reported in previous studies. These results provide a quantitative framework for solar wind-induced water formation and a mechanistic explanation for the latitude-dependent distribution of OH/H₂O on the Moon.

¹Dante S. Lauretta (>10)
Meteoritics & Planetary Science, 59, 9, 2453–2486 (2024) Open Source Link to Article [10.1111/maps.14227]

¹Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA
Published by arrangement with John Wiley & Sons

On September 24, 2023, NASA’s OSIRIS-REx mission dropped a capsule to Earth containing ~120 g of pristine carbonaceous regolith from Bennu. We describe the delivery and initial allocation of this asteroid sample and introduce its bulk physical, chemical, and mineralogical properties from early analyses. The regolith is very dark overall, with higher-reflectance inclusions and particles interspersed. Particle sizes range from submicron dust to a stone ~3.5 cm long. Millimeter-scale and larger stones typically have hummocky or angular morphologies. Some stones appear mottled by brighter material that occurs as veins and crusts. Hummocky stones have the lowest densities and mottled stones have the highest. Remote sensing of Bennu’s surface detected hydrated phyllosilicates, magnetite, organic compounds, carbonates, and scarce anhydrous silicates, all of which the sample confirms. We also find sulfides, presolar grains, and, less expectedly, Mg,Na-rich phosphates, as well as other trace phases. The sample’s composition and mineralogy indicate substantial aqueous alteration and resemble those of Ryugu and the most chemically primitive, low-petrologic-type carbonaceous chondrites. Nevertheless, we find distinct hydrogen, nitrogen, and oxygen isotopic compositions, and some of the material we analyzed is enriched in fluid-mobile elements. Our findings underscore the value of sample return—especially for low-density material that may not readily survive atmospheric entry—and lay the groundwork for more comprehensive analyses.

¹Liam D. Peterson,²Conel M. O’D. Alexander,²Jianhua Wang,²Emma S. Bullock,^3,4Anthony J. Irving, ⁵Sune G. Nielsen
Meteoritics & Planetary Science 1–15 (in Press) Link to Article [10.1111/maps.70211]

¹Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, USA
²Earth and Planets Laboratory, Carnegie Institution for Science, Washington, DC, USA
³Department of Earth and Space Sciences, University of Washington, Seattle, Washington, USA
⁴Burke Museum of Natural History and Culture, University of Washington, Seattle, Washington, USA
⁵CRPG, CNRS, Université de Lorraine, Vandoeuvre l`es Nancy, France
Published by arrangement with John Wiley & Sons

Recent evidence from primitive achondrites and achondrites suggests that early-formed melted planetesimals are depleted in hydrogen relative to the bulk silicate Earth. Nevertheless, evidence from angrites, the lone oxidized group of achondrites investigated to date, suggests that oxidized planetesimals may be H-rich relative to their reduced counterparts. Additionally, we have limited constraints, derived from a few ungrouped samples, on the H budgets of outer solar system planetesimals that underwent melting. Therefore, in order to provide additional constraints on the H budgets of oxidized and outer solar system planetesimals that experienced melting, we measured the H contents of silicate minerals in brachinite and tafassite group meteorites, respectively. We found that olivine, pyroxene, and plagioclase across both groups are essentially devoid of H (<~2.6 μg/g H2OT; total H as H2O equivalents). Based upon the thermal histories of the tafassite and brachinite parent bodies as well as their petrology and mineralogy, we argue that both bodies were essentially anhydrous prior to their disruption. This result is consistent with prior work on primitive achondrites and achondrites and requires that Earth’s H budget be accounted for by accretion of thermally primitive materials, such as chondrites, comets, and ices or capture of nebular gas.

^1,2Martin Cordiner et al. (>10)
Nature 655, 870–874 Open Access Link to Article [10.1038/s41586-026-10771-6]

¹Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, MD, USA
²Department of Physics, Catholic University of America, Washington DC, USA

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

¹Haoyu Li,¹Ren T. C. Marquez,^1,2Gerrit Budde,³Haolan Tang,⁴Alexander N. Krot,⁵Marina A. Ivanova,⁶Johan Villeneuve,¹ François L. H. Tissot
Proceedings of the National Academy of Sciences 123, 29 Open Access Link to Article [10.1073/pnas.2529765123]

¹The Isotoparium, Division of Geological and Planetary Sciences, Caltech, Pasadena, CA 91125
²Department of Earth, Environmental and Planetary Sciences, Brown University, Providence, RI 02912
³National Key Laboratory of Deep Space Exploration/State Key Laboratory of Lithospheric and Environmental Coevolution, University of Science and Technology of China, Hefei 230026, China
⁴Hawaii Institute of Geophysics and Planetology, University of Hawai’i at Mānoa, Honolulu, HI 96822
⁵Vernadsky Institute of Geochemistry and Analytical Chemistry, Moscow 119991, Russia
⁶Centre de Recherches Pétrographiques et Géochimiques, CNRS, Université de Lorraine, UMR7358, Nancy F-54000, France

The 26Al-26Mg systematics in calcium–aluminum-rich inclusions (CAIs)—the oldest known Solar System solids—has traditionally been used to provide high-resolution temporal constraints on the early Solar System evolution. More recently, the study of variations in the initial Mg isotope composition has emerged as a means to probe for potential compositional heterogeneity in the nascent solar nebula. Here, we report high-precision magnesium isotope data for a collection of 19 CAIs that captures the diversity of refractory inclusions. The data reveal widespread Mg isotope heterogeneity prior to 26Al decay, covering a large range from −0.285 to +0.088‰. Combined with literature data, the distribution of Mg isotope heterogeneity in CAIs forms a continuum and no longer defines distinct populations. Our findings therefore suggest a continuous CAI formation process that captured a rapid temporal change in the composition of infalling material from the parental molecular cloud of the Solar System.

¹M. C. Benner,¹B. S. Prince,¹D. L. Schrader,¹T. J. Zega
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70212]

¹Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA
²Astromaterials Research and Exploration Science (ARES) Division, XI
³Research Office, NASA Johnson Space Center,Houston, Texas, USA3Department of Materials Science & Engineering, University of Arizona, Tucson, Arizona, USA
Published by arrangement with John Wiley & Sons

Here we report on the microstructure and chemistry of sulfide minerals returned from asteroid (162173) Ryugu. We identify a unique sulfide population in particle A0016 composed of violarite (FeNi₂S₄), pyrite (FeS₂), chalcopyrite (CuFeS₂), pyrrhotite (Fe_1-xS), and pentlandite ([Fe,Ni]₉S₈). Violarite, pyrrhotite, and pyrite reveal evidence of formation from a fluid including porosity, phyllosilicate inclusions, and gaps along grain boundaries due to volume change. Violarite grains are polycrystalline with spatially correlated Ni and Co enrichments and contain pyrrhotite lamellae measuring 100s nanometers across. Pyrite assemblages are polycrystalline with spatially anticorrelated Ni and Co enrichments. In comparison, the chalcopyrite grain is a compositionally homogeneous single crystal spatially associated with rutile (TiO₂). The data suggest that particle A0016 experienced multiple generations of fluid flow. The first generation of fluid flow occurred at low temperatures (25 to 100 °C) under alkaline (pH > 8) conditions, leading to the precipitation of pyrrhotite and pentlandite. In comparison, the second generation of fluid flow was acidic (pH < 6.5) and reducing (−0.14 ≤ Eh ≤ −0.36) at elevated temperatures (230 to 300 °C), leading to formation of pyrite, violarite, and chalcopyrite. The elevated temperatures required to produce this sulfide population are consistent with heating from an impact on Ryugu’s parent body.

¹H. T. Manelski et al. (>10)
Journal of Geophysical Research: Planets (in Press) Open Access Link to Article [https://doi.org/10.1029/2026JE009769]
¹Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, IN, USA
Published by arrangement with John Wiley & Sons

To meet the objectives of the many robotic and human missions planned for the Moon in the coming decade, new scientific instruments are currently under development. Laser-induced breakdown spectroscopy (LIBS) is a robust technique for quantifying elemental abundances by focusing a pulsed laser to generate a plasma and collecting its emission spectrum. LIBS is particularly well suited for lunar applications because of its ability to detect key light elements, including hydrogen, an important resource for future human exploration. LIBS mapping is an emerging approach in which dense, regularly spaced grids comprising hundreds of analysis points are acquired, rather than sparse raster measurements. This technique enables the delineation of clasts in brecciated rocks, identification of chemical zoning, and quantification of bulk chemistry over the scanned area. In this work, a comprehensive quantitative LIBS calibration was developed under vacuum using lunar-relevant geologic standards. This calibration was then applied to produce the first LIBS elemental map (6 × 6 mm using 150 micron raster spacing) of a lunar meteorite in lunar atmospheric conditions, with Laâyoune 002 as the target of the study. The derived major-element chemistry is consistent with a feldspathic breccia dominated by Ca-rich plagioclase (anorthite) with minor mafic clasts. The scanned area yields an estimated normative plagioclase abundance of 86%–89%, comparable to other feldspathic lunar meteorites thought to sample nearly pure lunar highlands material. These results demonstrate the utility of LIBS mapping for investigating sub-millimeter-scale chemical heterogeneity in lunar rocks and highlight its potential for future lunar surface missions.

¹Chunjie Cao,¹Duojun Wang,¹Kenan Han,¹Kewei Shen,¹Kexuan Zhang
Journal of Geophysical Research: Planets (in Press) Link to Article [https://doi.org/10.1029/2026JE009722]

¹High Pressure Sciences Experiment Center, College of Earth and Planetary Sciences, University of Chinese Academy ofSciences, Beijing, China
Published by arrangement with John Wiley & Sons

The vesicles of meteorite fusion crusts offer a key window into transient processes during atmospheric entry, yet their formation mechanisms remain poorly constrained. In this study, we investigated the morphology, mineralogical composition, and evolutionary mechanisms of vesicles in the fusion crust and primary lithology of the meteorite NWA 10645 using micro-CT as the primary technique, complemented by SEM–EDS petrography. Vesicle nucleation in the fusion crust was likely driven by volatile supersaturation generated from multiple reservoirs, including apatite, pyroxene, melt inclusions, and mesostasis. After nucleation triggered by apatite devolatilization, isolated vesicles continued to grow and underwent three evolutionary stages: early growth, aggregation, coalescence, and critical rupture. Micro-CT 3D imaging shows that adjacent nucleated vesicles rapidly aggregated within a short time, forming bead-like alignments, then gradually coalesced into larger pores, and evolved into ellipsoidal shapes due to inertial tensile forces generated in the melt during high-velocity atmospheric entry, while near-surface vesicles approached critical rupture. Furthermore, Classical Nucleation Theory (CNT) is applied for the first time to predict a minimum nucleation radius of 23–70 nm, significantly smaller than the vesicle sizes resolved by micro-CT and SEM. This result indicates that vesicle nucleation occurs at a transient nanoscale stage. Diffusion-length estimates further suggest that volatile transport in the melt could support subsequent vesicle growth to experimentally observable micron-scale sizes.

¹J. R. Hill,¹P. R. Christensen
Journal of Geophysical Research: Planets (in Press) Open Access Link to Article [https://doi.org/10.1029/2026JE009775]
¹School of Earth and Space Exploration, Arizona State University, Tempe, Arizona, USA
Published by arrangement with John Wiley & Sons

Martian chloride salt deposits were first identified by Osterloo et al. (2008, https://doi.org/10.1126/science.1150690) and surveyed by Osterloo et al. (2010, https://doi.org/10.1029/2010je003613) primarily using thermal infrared data acquired by the Thermal Emission Imaging System (THEMIS) onboard the 2001 Mars Odyssey spacecraft. Over the subsequent 15 years, the THEMIS instrument has greatly expanded its areal and repeat coverage of the Martian surface. A principal component-based index was also developed to identify chloride salts and quantify the confidence level of their detection. Pairing the expanded data set with this improved analytical technique enabled a more accurate global survey of chloride salts, which identified 1,605 distinct deposits covering 11,974 km2. This includes 777 newly identified deposits, which represents a ∼20% increase in the surface area (∼1,997 km2) of identified chloride salts. The chloride salt deposits are primarily associated with Noachian-aged terrains, with a significant percentage occurring in Early Noachian terrains. A steep drop-off in chloride deposit occurrence was observed at the Noachian-Hesperian boundary. This pushes the period of chloride salt formation and deposition back to the earliest periods of Martian history, when the planet more closely resembled the Earth at the same time.

^1,2Pei Ma,³Hao Zhang
Journal of Geopyhsical Research: Planets (in Press) Link to Article [https://doi.org/10.1029/2026JE009863]
¹Planetary Environmental and Astrobiological Research Laboratory, School of Atmospheric Sciences, Sun Yat‐senUniversity, Zhuhai, China
²Now at Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy ofSciences, Guiyang, China
³School of Earth Sciences and Hubei Key Laboratory of Planetary Geology and Deep SpaceExplorations, China University of Geosciences, Wuhan, China
Published by arrangement with John Wiley & Sons

Lunar-like space weathering causes spectral darkening, reddening, and the attenuation of absorption bands due to metallic iron particles. The commonly cited iron size boundary, particles smaller than 40–50 nm redden spectra, while larger ones only darken, comes mainly from measurements of silica gel powders, and does not reflect the true particle-size effects. Using rigorous Mie theory to calculate absorption efficiencies of metallic iron spheres, we find that particles smaller than 80 nm primarily induce reddening with moderate darkening across the 0.4–2.6 μ⁢m$$ wavelengths, and the Hapke and Lucey‒Riner space weathering models are equivalent in this size range. Particles larger than ∼2 μ⁢m$$ cause darkening with only minor reddening. The upper size limit for reddening is wavelength-dependent; for 0.5–2.6 μ⁢m$$ wavelengths, particles <120 nm always redden the spectrum. Accounting for the polydisperse nature of metallic iron in lunar and laboratory samples, we incorporate the size distribution into the Lucey‒Riner space weathering model and validate it with laboratory data. We also discuss UV bluing, NIR reddening, and spectral brightness induced by metallic iron particles.