¹Alison R. Santos, ²Mikhail Yu. Zolotov, ¹Martha S. Gilmore, ³Craig Motil, ³Kyle Phillips, ⁴Valerie Tu
Journal of Geophysical Research: Planets, 131, e2025JE009457
Open Access Link to Article [DOI: 10.1029/2025JE009457]
¹Department of Earth and Environmental Sciences, Wesleyan University, Middletown, CT, USA
²School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA
³NASA Glenn Research Center, Cleveland, OH, USA
⁴Texas State University, Amentum JETSII Contract at NASA Johnson Space Center, Houston, TX, USA

Published by arrangement with John Wiley & Sons

Investigations of the venusian surface suggest chemical alteration (weathering) of rocks in contact with a hot, high-pressure atmosphere. This alteration was anticipated based on mineral stability considerations and has been supported by laboratory experiments conducted under Venus surface conditions. Here, we exposed iron-bearing samples (oxides, sulfides, iron-metal) to a simulated venusian environment (93 bars, 733 K, and a 9-gas mixture) for 60 days at the NASA Glenn Extreme Environments Rig (GEER). Iron metal, pyrrhotite, and troilite were altered to pyrite and magnetite. Some magnetite formed at the expense of hematite. Neither magnetite nor pyrite was altered. Measured concentrations of CO₂, SO₂, and OCS during the run suggest rapid OCS-SO₂ equilibration and drawdown of sulfur-bearing gases through reactions with the vessel and sample materials. The observed alteration assemblages and the gas composition in the vessel suggest experimental gas-phase fugacities (fO₂, fS₂, fSO₂, fOCS, fCO, fCO₂) in the vicinity of the magnetite-pyrite phase boundary and within the uncertainty of the magnetite-hematite boundary. Fugacities (log₁₀fO₂ of −22.5 to −21.5; log₁₀fS₂ of −5.4 to −4.6) and mineralogy in the Fe-O-S system are consistent with observation-based models for the near-surface conditions on Venus. This experiment supports both gas-phase chemical equilibrium and equilibration between gases and minerals in the Fe-O-S system on the surface of Venus, as proposed six decades ago.

¹Sang Woo Kim, ^1,2Kyeong Ja Kim
Journal of Geophysical Research: Planets, 131, e2026JE009892 Link to Article [DOI: 10.1029/2026JE009892]
¹Korea Institute of Geoscience and Mineral Resources (KIGAM), Daejeon, Republic of Korea
²University of Science and Technology (UST), Daejeon, Republic of Korea

Published by arrangement with John Wiley & Sons

The Dynamic Albedo of Neutrons (DAN) instrument on the Curiosity rover has mapped subsurface hydrogen along an extensively analyzed 27-km segment of its traverse in Gale Crater, revealing water-equivalent hydrogen (WEH) of 1–6 wt%. Neutron die-away measurements alone, however, cannot determine whether this hydrogen resides in adsorbed water, hydrated minerals, or ice. Here we use Geant4 Monte Carlo simulations (1⁢08$$ source neutrons per configuration) to quantify what a pulsed neutron generator with time-resolved prompt gamma-ray neutron activation analysis (PGNAA) adds to neutron-only measurements, for eight representative Martian regolith compositions under idealized detection. The model reproduces the established first-order sensitivity of the epithermal die-away constant to WEH (𝜏epi =57$$–77 𝜇$$s for WEH =15$$–1 wt%; power-law 𝑅2 =0.87$$)—an internal benchmark. The central experiment holds WEH fixed at 3 wt% across six compositionally distinct host endmembers: 𝜏epi$$ compresses to 61.4–67.0 µs, whereas simultaneously measured PGNAA ratios (Fe/Cl, apparent Si/Ca, Fe/H) provide complementary elemental constraints: for every host pair, at least one of the three ratios gives ≥7.6⁢𝜎$$ separation under the present idealized uncertainties. In a native-WEH benchmark, 27 of 28 pairs are separated at >5𝜎$$ by 𝜏epi$$ alone, driven largely by the broad assigned WEH range. Fe (Si) capture-to-inelastic ratios decrease monotonically by 36% (44%) for a 20 cm dry overburden, giving model-dependent depth information. These results define the information content of pulse-synchronized neutron–gamma-ray packages and modeling priorities for future Mars, Titan, and lunar volatile payloads.

¹Scott A. Sandford (>10)
Meteoritics & Planetary Science (in Press)
Open Access Link to Article [DOI: 10.1111/maps.70221]
¹NASA Ames Research Center, Moffett Field, California, USA

Published by arrangement with John Wiley & Sons

Regolith samples from the carbonaceous asteroid Bennu were stowed and delivered to Earth in the OSIRIS-REx spacecraft’s Sample Return Capsule (SRC). We applied multiple analytical techniques to study the components of the post-flight SRC, with a focus on assessing the conditions and any contaminants to which the Bennu samples were exposed. Examination of the passive temperature sensors placed inside the SRC, in combination with thermal modeling results, indicate that the samples were not heated above the 75°C limit imposed by OSIRIS-REx mission requirements. The sample canister air filter was found to contain Bennu particulates that had escaped from the sample collector, as well as a range of contaminants likely associated with the original filter component materials. No indications of terrestrial soils were found in the filter. Isotopic analyses of organic compounds and noble gases trapped in the filter show values consistent with terrestrial origins, and there are no indications of trapped asteroidal volatiles. Organic compounds found in the flight filter that were not present in a non-flight control filter include aromatic hydrocarbons, alkylated aromatic hydrocarbons, phenolic-related compounds, aliphatic hydrocarbons, and alcohols. The abundances of these organic compounds typically decrease from outer layers of the filter toward the canister interior, suggesting that they are external contaminants. We conclude that the majority of these organic compounds are chemical byproducts associated with outgassing of the SRC heatshield and backshell following the ablation portion of SRC atmospheric entry. Overall, our findings show that the OSIRIS-REx SRC performed excellently in containerizing the asteroidal samples obtained at Bennu, delivering them safely to the ground at the UTTR, and preventing most, though perhaps not all, external contaminants from reaching them. We discuss lessons learned from the flight and recovery of the OSIRIS-REx SRC that can benefit future sample return missions.

¹Gary R. Huss (>10)
Meteoritics & Planetary Science (in Press) Open Access Link to Article [DOI: 10.1111/maps.70231]
¹Hawai‘i Institute of Geophysics and Planetology, School of Ocean and Earth Science and Technology, University of Hawai‘i at Mānoa, Honolulu, Hawaii, USA

Published by arrangement with John Wiley & Sons

We report on the petrography and oxygen isotopic compositions from in situ analyses of carbonates (Ca-carbonate, dolomite, and Fe-rich magnesite), magnetite, and apatite in particles from asteroid Bennu. Using oxygen isotope thermometry of Ca-carbonate, dolomite, and magnetite, we estimated crystallization temperatures and the oxygen isotopic compositions of the aqueous fluids from which they precipitated. The Ca-carbonate–magnetite pairs formed at lower temperatures (−5 to 20°C) than the dolomite–magnetite pairs (5–89°C); the uncertainties are ±10–16°C. The inferred fluid compositions for Ca-carbonate–magnetite pairs are δ¹⁸O = 0.6‰–9‰ and Δ¹⁷O = 1.8‰–2.7‰, whereas for dolomite–magnetite pairs, they are δ¹⁸O = −2.2‰ to 7.6‰ and Δ¹⁷O = −0.1‰ to 0.9‰. On a three-isotope oxygen diagram (δ¹⁷O vs. δ¹⁸O), 11 out of 13 of our inferred aqueous fluid compositions plot along a single line with a slope of ~0.8, potentially indicating precipitation from a single isotopically evolving fluid. Two dolomite–magnetite pairs appear to be outliers and may have formed from fluids with different oxygen isotopic compositions. The oxygen isotope data presented herein overlap with those reported from samples of asteroid Ryugu, supporting a possible close genetic relationship between these asteroids.

¹Matteo Del Rio, ^2,3Luigi Folco, ^2,3Matteo Masotta, ¹Ana Černok, ^2,3Enrico Mugnaioli
Meteoritics & Planetary Science (in Press)
Open Access Link to Article [DOI: 10.1111/maps.70238]
¹Dipartimento di Matematica, Informatica e Geoscienze, Università di Trieste, Trieste, Italy
²Dipartimento di Scienze della Terra, Università di Pisa, Pisa, Italy
³Center for the Instrument Sharing of the University of Pisa (CISUP), Pisa, Italy

Published by arrangement with John Wiley & Sons

Microkrystites are glassy impact spherules. They contain primary crystallites carrying information on the physical and chemical conditions prevailing during vaporization, melting, and ejection in large impact cratering events. We report on the geochemistry and mineralogy down to nanometer scale of the first microkrystite (ODP1144A,14) from the Australasian tektite/microtektite strewn field. It is a dark-gray, opaque, 160 × 210 μm prolate spheroid, recovered from the microtektite layer in the Ocean Drilling Program Hole 1144A in the South China Sea. The microkrystite shows a micro-glomeroporphyritic texture consisting of clusters of skeletal ferropseudobrookite (Fe²⁺_0.7,Fe³⁺_0.3)_Σ=1(Ti_1.7Fe³⁺_0.3)_Σ=2O₅ crystals (~70 area%) set in a silicate glassy matrix. The latter features nanoscale Fe-Ti liquid-immiscibility textures and Si-rich inclusions composed of quartz, lechatelierite, and shock-produced coesite. Coesite confirms an impact origin of the microkrystite. Major and trace element compositions of the glassy matrix and of the spherules accreted onto the particle surface match those of Australasian microtektites, firmly linking ODP1144A,14 to the Australasian strewn field. Vesicles and partially digested lechatelierite inclusions indicate formation as an impact-melt droplet rather than a vapor condensate. We suggest that the non-silicate part of the ODP1144A,14 microkrystite derived from an immiscible Fe–Ti-rich melt batch (about the size of a droplet) produced by impact melting at T > 1400°C of target Fe-Ti oxides (commonly found in the shocked target ejecta fragments associated with microtektites in the same stratigraphic horizon) that could not fully homogenize with the bulk silicate microtektite precursor melt under the transient disequilibrium conditions that are characteristic of impact melting and fragmentation during high-velocity ejection. We suggest that the involvement of target Fe-Ti oxides during impact melting may have contributed to the Cr-rich, Ni-poor terrestrial mafic component observed in some Australasian tektites and microtektites. This provides further support to earlier assessment of the dual origin, dominantly chondritic and lesser terrestrial, of the mafic component in Australasian tektites and microtektites.

¹S. Effraimidou, ¹I. Baziotis, ¹M. Simopoulou, ²L. Ferrière, ³C. Sanchez-Valle, ³S. Klemme, ³J. Berndt, ⁴P. D. Asimow
Meteoritics & Planetary Science (in Press) Open Access Link to Article [DOI: 10.1111/maps.70228]
¹Department of Natural Resources Management and Agricultural Engineering, Agricultural University of Athens, Athens, Greece
²Natural History Museum Abu Dhabi, Abu Dhabi, United Arab Emirates
³Institut für Mineralogie, Universität Münster, Münster, Germany
⁴Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA

Published by arrangement with John Wiley & Sons

This study investigates the petrography and mineralogy of three L-type ordinary chondrite meteorites: Northwest Africa (NWA) 4137 (L6), Homestead (L5), and Kunashak (L6). We studied the shock-related deformation features in the matrix and the characteristics of the melt veins, including the presence or absence of high-pressure (HP) phases. Our goal is to constrain the shock history of these meteorites, including constraints on peak shock conditions and on post-shock thermal histories. All three studied meteorites are strongly shocked, with textural evidence indicating shock stages up to S4 and development of melt veins. However, NWA 4137 is the only one of these meteorites in which HP phases were observed; we identified wadsleyite, majorite, albitic jadeite, tuite, and xieite within melt veins, indicating peak shock pressure in the range of 11–23 GPa. In contrast, the investigated melt veins in Homestead and Kunashak lack any HP phases despite indicators of comparable shock intensity to that observed in NWA 4137. The absence of HP phases in these two meteorites is attributed to a high post-shock temperature that favored back-transformation into low-P minerals during decompression over preservation of HP phases. These case studies testify to the importance of the full pressure (P)–temperature (T)–time (t) path experienced by meteoritic samples during shock events in determining their ultimate mineralogy.

¹Pengfei Liu (>10)
Proceedings of the National Academy of Sciences (in Press) Link to Article [DOI: 10.1073/pnas.2608395123]
¹Macau Institute of Space Technology and Application, Macau University of Science and Technology, Macau 999078, China
We currently do not have a copyright agreement with this publisher and cannot display the abstract here

On the lunar surface α-Fe and Fe-Ni alloys are widespread and the dominant carriers of the lunar remanent magnetization. Metallic γ-Fe, however, is stable only at high temperatures and has not been documented in lunar samples. Here we report the identification of ambient stable γ-Fe preserved as nanometer-scale particles in Chang’e-6 impact glass fragments from the South Pole-Aitken Basin. Electron holography analyses reveal that these γ-Fe particles have a magnetic vortex domain state. Based on these results, we propose that the formation and preservation of γ-Fe at lunar surface temperature requires incorporation of trace γ-phase-stabilizing elements together with extremely rapid quenching during lunar impact processes. Our findings provide a basis for understanding the lunar core dynamo evolution and impact-induced magnetic recording mechanisms.

¹B. J. K. Wilson, ²G. A. Arcuri, ²T. Casagrande, ²C. M. Andrei, ^2,3B. Langelier, ^2,4,5K. T. Tait, ¹M. G. Daly
Geochimica et Cosmochimica Acta (in Press)
Link to Article [DOI: 10.1016/j.gca.2026.09.024]
¹Centre for Research in Earth and Space Science, Lassonde School of Engineering, York University, Toronto, Ontario, Canada
²Canadian Centre for Electron Microscopy, McMaster University, Hamilton, Ontario, Canada
³Department of Materials Science and Engineering, McMaster University, Hamilton, Ontario, Canada
⁴School of Earth, Environment, and Society, McMaster University, Hamilton, Ontario, Canada
⁵Department of Natural History, Center for Applied Planetary Mineralogy, Royal Ontario Museum, Toronto, Ontario, Canada
Copyright Elsevier

Tarda is a C2-ungrouped carbonaceous chondrite that preserves a record of low-temperature
aqueous alteration on its parent asteroid. While the original fluid has disappeared, constraining its
composition is essential for understanding the chemical environment that influenced both
secondary mineral formation and prebiotic organic chemistry. Magnetite framboids are an
abundant aqueous alteration product in Tarda and likely recorded some of the chemical species
from its mother solution, entrained within the framboidal magnetite grain boundaries. To
investigate this, we conducted a nanoscale study on five magnetite framboids using transmission
electron microscopy, energy dispersive x-ray spectroscopy, and atom probe tomography.
Magnetite framboids in Tarda exhibit a wide range of textures, crystallite sizes, and packing
arrangements, reflecting a progressive sequence of discrete nucleation and growth events likely
occurring in isolated water droplets. Energy dispersive x-ray spectroscopy analysis of four
interacting framboids reveals trace element enrichments of mostly Ti and Si along ~5 nm thick
grain boundaries, with the strongest enrichments observed in the framboids with smaller
crystallites, which likely precipitated at the beginning and end of the local precipitation sequence.
Using atom probe tomography, we captured a ~5 nm thick planar feature enriched in trace
abundances of Na, Mg, Ca, Mn, and Si, likely corresponding to a magnetite boundary. These
findings suggest that magnetite framboids in Tarda formed from a generally alkaline fluid that
contained a diverse suite of cations and evolved as water-rock interaction progressed. While the
fluid composition inferred here resembles alkaline, metal-containing fluids known to promote
organic synthesis on Earth, experimental work is needed to determine how such conditions could
influence complex organic synthesis in asteroid environments

¹Megan D. Mouser, ¹Yingwei Fei
Meteoritics & Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.70230]
¹Amentum, Astromaterials Research and Exploration Science (ARES) Division, NASA Johnson Space Center, Houston, TX, USA

Published by arrangement with John Wiley & Sons

Early terrestrial planetary formation processes included melting of chondritic material, leading to differentiation of small planetary bodies. The differentiation process may have been different for various sized objects in the solar system, where some may have gone through total melting (i.e., magma ocean) to form a core and silicate mantle, while others may have experienced partial melting that modified and differentiated the planetary embryo to varying degrees. Based on evidence of differentiated meteorite specimens and spectroscope evidence of silicate and metal asteroids, differentiated planetary bodies are common in the solar system. This work experimentally explores the partial melting process and how that could lead to core formation on a planetary embryo with internal pressures up to 5 GPa. We identified an efficient mechanism to mobilize metal materials when the silicate matrix reached ≥20% partial melting at pressures >3 GPa that usually disrupt interconnected metallic melt because of the large dihedral angle. The predicted percolative velocity of these metallic blebs would be fast enough to percolate toward the center of a smaller planetary body within a few million years while heat from the decay of short-lived radioisotopes is still prevalent.

¹D. Das et al. (>10)
Meteoritics & Planetary Science (in Press)
Open Access
Link to Article [DOI: 10.1111/maps.70237]
Los Alamos National Laboratory, Los Alamos, New Mexico, USA

Published by arrangement with John Wiley & Sons

Boron and lithium have been observed in Ca-sulfate veins of Gale crater. These elements are highly water mobile and can inform us regarding the aqueous processes that may have taken place in Gale crater. However, the analysis of B in Gale crater is limited to low-Fe rocks and minerals due to spectral interference of Fe with B in ChemCam data. We investigate the distribution of B and Li in various phases (veins, sheet silicate mineral-rich sedimentary rocks, salts, and igneous materials) within samples collected from Death Valley and surrounding locations in Southern California, which we use as a terrestrial analog for Gale crater. In the terrestrial analog samples set that we study, B concentration is found to be predominantly associated with borate minerals while elevated Li concentration is linked with the presence of sheet silicate minerals. Based on these observations, we suggest that B enrichment as evaporites such as borates may have formed during evaporation of borate-enriched fluids in drier atmospheric conditions while Li enrichment may have taken place due to surface adsorption to sheet silicate minerals. Prior literature indicated that different fluid pH conditions and atmospheric humidity levels are necessary for borate enrichment and Li adsorption. The process of adsorption to the surface of sheet silicates is attributed to high pH aqueous conditions while the formation of borate minerals is attributed to a combination of low aqueous pH and high evaporative atmospheric conditions. We infer that the coexistence of borate minerals and Li-containing sheet silicates is indicative of multiple generations of aqueous conditions that likely took place over multiple seasonal cycles. We extend our inference to Gale crater and draw from the similarities between dry-lake deposits of Death Valley to provide a terrestrial-analog backed hypothesis on B and Li enrichment on Mars. We conclude that multiple early and late-stage aqueous events that may have involved the participation of groundwater activity were likely present to account for the observations in Gale crater.