¹Christopher D.K. Herd, ¹Sophie Benaroya
Geochimica et Cosmochimica Acta (in Press) (Open Access) Link to Article [https://doi.org/10.1016/j.gca.2025.10.001]
¹Department of Earth and Atmospheric Sciences, 1-26 Earth Sciences Building, University of Alberta, Edmonton, AB T6G 2E3, Canada
Copyright Elsevier

We provide an updated compilation of oxygen fugacity (fO₂) estimates for martian meteorites, with a specific focus on the shergottites. The compilation includes estimates from over 70 distinct lithologies from the martian meteorite suite, calculated from olivine-pyroxene-spinel and Fe-Ti oxide oxybarometers. Olivine-pyroxene-spinel oxybarometry was recalculated from original data sources using an updated model. Results from V- in-olivine and Eu/Gd oxybarometry from the literature are provided for comparison. Oxygen fugacity data are plotted against chondrite-normalized La/Yb ratio to critically examine the correlation between fO₂ and incompatible trace element (ITE) enrichment previously postulated. We find that the correlation holds, when factors including differences in petrogenetic histories, distinctions between shergottite petrologic types, and early vs. late crystallizing assemblages, are taken into consideration. We model the degassing of H, C and S species from primitive martian magmas using the MAGEC model (Sun and Lee, 2022) and successfully reproduce the 2–3 log unit increase recorded within olivine-phyric shergottites between early and late crystallizing assemblages. We find that volatile degassing can account for most of the fO₂ increase in the olivine-phyric shergottites, without requiring extensive auto-oxidation, as long as their fO₂ remains at or below a value equivalent to the fayalite-magnetite-quartz (FMQ) equilibrium throughout their crystallization. With these considerations in mind, we propose a martian mantle redox-ITE trend defined by shergottite sources: a depleted source (La/Yb ∼ 0.1) with fO₂ = FMQ-4 ± 0.7, an intermediate source (La/Yb ∼ 0.5) at fO₂ = FMQ-3 ± 0.75 and an enriched source (Lab/Yb ∼ 1) at fO₂ = FMQ-2 ± 0.75. The depleted/reduced source is likely graphite saturated.

Comparisons with compilations of fO₂ from basaltic eruptives on Earth highlight fundamental differences between the two planets ultimately attributable to differences in degree of mantle convective mixing throughout their histories: terrestrial mantle sources produce basaltic eruptives with a relatively limited range of fO₂, within ±1 log unit of FMQ; any degassing from these magmas results in reduction, not oxidation. The mantle sources of the shergottites – while represented by a similarly limited range of fO₂, ∼FMQ-4 to FMQ-2 – produce basaltic eruptives with a range of low initial (magmatic) fO₂; the more reduced nature of these magmas make them more susceptible to overprinting by degassing of H-C-S species during eruption and emplacement. Whether the mantle sources inferred from the shergottites apply to other martian meteorites (or other martian igneous rocks) remains to be tested; however, post-magma ocean crystallization processes would have acted to oxidize and overprint initial mantle sources defined by the shergottite fO₂-ITE trend.

^1,2Zhiming Chen et al. (>10)
Journal of Geophysical Research (Planets)(in Press) Link to Article [https://doi.org/10.1029/2025JE008976]
¹State Key Laboratory of Deep Earth Processes and Resources, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China
²College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, China
Published by arrangement with John Wiley & Sons

Lunar regolith contains not only materials derived from the local rock unit, but also materials transferred from remote craters, which are crucial for investigating the lithological diversity of the lunar surface. In this study, we conducted detailed petrography and geochemical analyses and measured the cross-sectional area of plagioclase fragments and impact glass particles selected from the Chang’e 6 (CE-6) regolith, the first lunar far-side returned sample. Statistics of plagioclase fragments and impact glass are used to estimate the proportion of the diverse components in the CE-6 regolith. The results reveal 35.7 vol% and 28.2 vol% exotic components in CE-6 plagioclase and impact glass fractions, respectively. As plagioclase, pyroxene and glass particles are the three dominant phases (>95 vol%) in the CE-6 regolith, together with previously reported pyroxene compositions, we estimate that the abundance of the exotic materials is 23.5–33.5 vol%. These exogeneous components include very-low-Ti (VLT) basalt (2%–3%), ferroan anorthosite (5%–9%), Mg-suite (15%–20%), KREEP-related (∼0.1%), and highlands-mare-mixed materials (∼1%). The VLT-basalt component is most likely from the mare basalt unit to the east of the landing site or beneath the local mare layer. Based on the ejecta orientations and model age of impact craters, ferroan anorthite, Mg-suite and KREEP-related materials are likely transferred from Vavilov/Pythagoras (highland anorthosite), Chaffee S/White’ (rich in mafic minerals), and Birkeland (high Th contents) craters, respectively. The abundant non-mare components in the CE-6 regolith contrast to the very scarce exotic materials in the CE-5 lunar regolith, potentially providing valuable insights into the composition of the lunar far-side.

¹Garima Sodha,¹Deepak Dhingra
Journal of Geophysical Research (Planets)(in Press) Link to Article [https://doi.org/10.1029/2024JE008809]
¹Department of Earth Sciences, Indian Institute of Technology Kanpur (IITK), Kanpur, Uttar Pradesh, India
Published by arrangement with John Wiley & Sons

The spatial distribution of Mg-spinel lithology at South Pole-Aitken (SPA) basin is revealed by systematic mineralogical survey along the basin rings. We report Ingenii-Thomson region as a Mg-spinel anomaly, having the largest number of exposures based on newly identified and previously reported occurrences on the Moon. The timing of Mg-spinel formation is constrained by using SPA impact as a key geological time marker. Post-SPA origin of this lithology is favored in this region due to the general lack of pervasive Mg-spinel occurrences along basin rings, being the deepest exposures of the pre-SPA crust. Our detailed mineralogical analyses also highlight several detections of Mg-spinel lithology exhibiting weak 1,000 nm absorption band, emphasizing the need for a detailed analysis of such locations. Collectively, these salient findings have important implications for understanding the compositional diversity of Mg-spinel lithology, refinement of the formation models and determining the role of Mg-spinel lithology in the lunar crustal evolution.

^1,2,3Qing Zhang et al. (>10)
Journal of Geophysical Research (Planets)(in Press) Link to Article [https://doi.org/10.1029/2025JE009196]
¹Key Laboratory of Lunar and Deep Space Exploration, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China
²Institut d’Astrophysique Spatiale, CNRS, Université Paris-Saclay, Orsay, France
³School of Astronomy and Space Science, University of Chinese Academy of Sciences, Beijing, China
Published by arrangement with John Wiley & Sons

The Zhurong rover conducted in situ spectral investigations of southern Utopia Planitia, where the bedrock composition remains relatively unknown due to dust cover. Here we identify some spectrally distinct dark patches sporadically occurring on rocks by combining the Multispectral Camera and Short-Wave Infrared data. These dark patches represent relatively dust-free surfaces and exhibit concave-up blue slopes in the near-infrared not identified in that area from orbital data. This spectral signature is most consistent with silica-enriched leached rinds on basaltic glass. The presence of such weathering rinds could imply leaching in an acidic aqueous environment of igneous rocks previously transported to the landing site as impact ejecta or pyroclastic deposits by explosive volcanism. In situ observations link the dark patches to the northern low-albedo regions, suggesting that the surficial acidic weathering may be more widespread and occurred in the northern lowlands under Amazonian climatic conditions.

¹Huaqing Cao,¹Jing Li,¹Chang Zhang,¹Lige Bai
Journal of Geophysical Research (Planets)(in Press) Link to Article [https://doi.org/10.1029/2024JE008884]
¹State Key Laboratory of Deep Earth Exploration and Imaging, College of GeoExploration Science and Technology, Jilin University, Changchun, China
Published by arrangement with John Wiley & Sons

The Chang’e-4 Lunar Penetrating Radar (LPR) has proven instrumental in uncovering the structure and composition of the Von Kármán crater on the lunar farside. Utilizing high-frequency (HF) LPR data collected during the first 53 lunar days, this study employs Least Squares Migration to achieve high-resolution imaging of shallow subsurface structures. Additionally, the peak frequency shift method is applied to estimate the loss tangent and the TiO2 + FeO content of the shallow regolith. The average loss tangent of the shallow regolith ranges from 4.3 × 10−3 to 5.5 × 10−3, corresponding to an iron-titanium content of 11.2 wt% to 14.7 wt%. Along the Yutu-2 rover’s traverse (300–500 m and 1,000–1,150 m), the regolith exhibits high TiO2 + FeO content, suggesting that these materials may originate from deeper basalt layers. By integrating radar profiles with estimates of TiO2 + FeO content, this study provides a detailed geological interpretation of subsurface layers and unique structures. These findings reconstruct critical geological events in the shallow subsurface at the landing site, offering new insights into the geological evolution of this region.

^1,2Zhan Zhou et al. (>10)
Journal of Geophysical Research (Planets)(in Press) Link to Article [https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2025JE009052]
¹Key Laboratory of Planetary Science and Frontier Technology, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China
²University of Chinese Academy of Sciences, Beijing, China
Published by arrangement with John Wiley & Sons

The Moon has been highly shocked as evidenced by numerous impact craters on its surface. High-pressure minerals are expected to form during these shock events and can be used to unravel the pressure and temperature conditions for the shock events. However, high-pressure minerals are rarely reported in the lunar returned samples, yielding a discrepancy with the prediction. The lunar soils returned by the Chang’e-6 (CE6) mission from the South Pole-Aitken (SPA) basin provide new opportunities to investigate the shock metamorphism of the lunar samples and the shock events on the Moon. Here, we reported the discovery of coesite in a shock-induced melt pocket from a CE6 mare basalt, which could have experienced a shock event with a peak pressure of ∼24 GPa. The coesite exhibits two types of occurrences, a polycrystalline aggregate in the center and a ring along the margin of a silica clast. The coesite could have been formed by solid-state transformation followed by partial conversion to silica glass during decompression. The coesite has a higher survival temperature and a slower back-transformation rate than most other high-pressure minerals, which are favorable for its preservation under high-temperature conditions of lunar soils induced by impacts. These findings provide new insights for the preservation of coesite in natural shock events and indicate that more thermal-resistant high-pressure minerals could have been formed and preserved in lunar samples than previously thought, providing new targets for studying the shock events on the Moon.

¹Jessika L. Valenciano,¹Clive R. Neal,²Scott A. Eckley,³Charles K. Shearer, the ANGSA Science Team
Journal of Geophysical research (Planets)(in Press) Open Access Link to Article [https://doi.org/10.1029/2024JE008580]
¹Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, IN, USA
²Amentum—JETS2, Astromaterials Research and Exploration Science Division, NASA Johnson Space Center, Houston, TX, USA
³Institute of Meteoritics, University of New Mexico, Albuquerque, NM, USA
Published by arrangement with John Wiley & Sons

Double drive tubes 73002 (upper) and 73001 (lower) were collected during Apollo 17 from a landslide deposit at the base of the South Massif in the Taurus-Littrow valley. The drive tubes were opened for the first time as part of the Apollo Next Generation Sample Analysis (ANGSA) project, representing “new” samples from the Moon. Many lithic fragments (>1 mm in size) were extracted from the core during core dissection and preliminary examination (PE), including high-Ti mare basalt clasts. Those >4 mm fragments were three-dimensionally imaged using X-ray computed tomography (XCT). The crystal size distributions of ilmenite were measured in 10 high-Ti mare basalts and within the matrix of an impact melt breccia from drive tube 73002 using thin section “slices” from the 3D XCT scans. Residence times (of the crystals in the melt from which they grew) were estimated using experimental growth rates for each sample with all but 73002,2015 being relatively short (<1 year). Linear (constant) cooling rates were determined, expanding upon data already obtained from other Apollo 17 high-Ti basalts showing that these ANGSA basalt clasts had similar cooling histories to those previously studied. Comparison with ilmenite cooling rate experiments estimated cooling rates of <10°C/h for each clast.

^1,2,3David C. Fernandez-Remolar et al. (>10)
Journal of Geophysical Research (Planets) (in Press) Link to Article [https://doi.org/10.1029/2024JE008837]
¹State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Macau, PR China
²CNSA Macau Center for Space Exploration and Science, Macau, PR China
³University Grenoble Alpes, CEA, CNRS, IBS, Metalloproteins Unit, Grenoble, France
Published by arrangement with John Wiley & Sons

Orbital remote sensing has shown that some regions of the ancient Martian crust contain hundreds of discrete terrains covered by chloride-rich evaporites. In terrestrial evaporitic systems, evaporite sequences typically begin with the deposition of carbonates, followed by sulfates, and finally chlorides, a depositional sequence that has not yet been found on Mars. Instead, sulfate deposits are always separated spatially and temporally from chlorides, suggesting two different depositional regimes. Here, we present a model driven by the Martian chlorine geochemical cycle that allows the formation of chlorides whilst simultaneously inhibiting sulfate and carbonate precipitation. In this model, the chlorides are produced under reducing and acidic conditions. Chloride deposition was driven by hydrothermal alteration of the Martian crust associated with faults, followed by precipitation from ascending saline solutions along the tectonic conduits. These processes occurred under a relatively thick and reducing atmosphere (1–0.1 bar). The crustal circulation of chloride-precipitating fluids may have been driven by tectonic suction and pumping processes. Parental brines from hydrothermal activity sourcing chloride might also have contributed to the sulfates found in Cross and Columbus craters of Terra Sirenum. Our study integrates orbital imaging, topography, and spectroscopy with geochemical modeling and terrestrial analogs. We propose that the Terra Sirenum chloride deposits derive from subsurface brines, with deposition driven using tectonic and hydrothermal processes. Under inferred reducing and anoxic conditions, chloride formed with minimal co-precipitation of sulfates and carbonates. Unlike isolated chloride deposits confined to topographic lows, the Terra Sirenum chlorides are associated with linear features interpreted as faults.

^1,2Joseph Razzell Hollis et al. (>10)
Journal of Geophysical Research (Planets)(in Press) Open Access Link to Article [https://doi.org/10.1029/2024JE008826]
¹Natural History Museum, London, UK
²NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
Published by arrangement with John Wiley & Sons

The NASA Mars 2020 mission Perseverance rover carries a piece of Martian meteorite Sayh al Uhaymir (SaU) 008 as part of the calibration payload for the SHERLOC science instrument. We report SHERLOC observations of the SaU 008 flight piece over the first 1,000 sols of the mission and compare them to measurements done prior to launch, showing consistent detection of the same deep-ultraviolet (DUV) Raman and fluorescence signatures in the same locations. Co-located X-ray fluorescence (XRF) and DUV mapping of a reference SaU 008 piece on Earth confirm that the meteorite is comprised of an igneous mineral matrix consistent with shergottite, rich in olivine, maskelynite, and Fe-Mg pyroxenes detectable by SHERLOC. Terrestrial weathering features consist of fractures and vugs filled with Ca-carbonate. Fluorescence mapping reveals two major signatures: (a) broad-spectrum fluorescence present throughout the igneous matrix but strongest in weathering features, attributed to organic material, and (b) narrow-band 340 nm fluorescence spatially associated with ∼48 ppm cerium in <100 μm Ca-phosphate grains. Raman revealed organic material in both the igneous matrix and terrestrial carbonate in the form of macromolecular carbon (MMC) with defect and graphitic bands at ∼1,380 and ∼1,600 cm−1 respectively. Raman band parameters suggest that MMC associated with terrestrial weathering is less thermally mature, most likely the result of chemical alteration after landing on Earth. This study serves as a demonstration of SHERLOC’s capabilities when supported by co-located XRF data from PIXL and suggests that SHERLOC can detect Ce in phosphate minerals at concentrations as low as 4 ppm.

^1,2,3Yuchun Wu,²Nicolas Mangold,^1,3,4Yang Liu,⁵John Carter,¹Xing Wu,^4,6Lu Pan,⁷Qian Huang,^1,2,3Chaolin Zhang,^1,3Keyi Li,⁶Yongliao Zou
Journal of Geophysical Research (Planets)(in Press) Link to Article [https://doi.org/10.1029/2025JE008951]
¹State Key Laboratory of Solar Activity and Space Weather, National Space Science Center, Chinese Academy of Sciences, Beijing, China
²Laboratoire de Planétologie et Géosciences, Nantes Université, University Angers, Le Mans Université, CNRS, LPG UMR 6112, Nantes, France
³College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, China
⁴National Key Laboratory of Deep Space Exploration, Hefei, China
⁵Institut d’Astrophysique Spatiale, Université Paris-Saclay, CNRS, Orsay, France
⁶School of Earth and Space Sciences, University of Science and Technology of China, Hefei, China
⁷Hubei Subsurface Multi-scale Imaging Key Laboratory, School of Geophysics and Geomatics, China University of Geosciences, Wuhan, China
Published by arrangement with John Wiley & Sons

Tyrrhena Terra, a region located in the cratered highlands between Hellas and Isidis Planitia on Mars, is distinguished by its extensive presence of hydrated minerals. Using 542 hyperspectral images from the Compact Reconnaissance Imaging Spectrometer for Mars, we detected 252 exposures of hydrated minerals. This region is characterized by a widespread distribution of Fe/Mg-smectites/vermiculites and chlorite, with additional detections of Al-phyllosilicates, zeolites, prehnite, hydrated silica, and carbonates. We classified the mineralogical detections in classes of impact crater diameters, locations in craters, and for those
20 km, their relative degradation stages. We found that craters
10 km display a lower mineral diversity than larger ones. In contrast, craters
20 km display a high mineral diversity, especially in central peaks, suggesting a strong influence of hydrothermal processes and deep excavation. Among this diameter range, fresh, young craters exhibit a much higher mineral diversity than degraded, old craters. Fe/Mg-phyllosilicates are dominant in the latter, as well as in sedimentary units of topographically low areas. These results indicate a long-term alteration cycle in the most ancient period, where the initial, diverse hydrated minerals—formed through exhumation and/or hydrothermal circulation within large impacts—were subsequently transformed by surface weathering and/or buried, dissolved, or eroded away by other post-impact processes, then transported and deposited in lowlands by fluvial erosion. Although Tyrrhena Terra is dominated by impact-related hydrated mineral detections, our study shows that the overprint of Noachian age weathering is visible within these detections.