^1,2,3Laura E. Jenkins, ^1,2Roberta L. Flemming, ^1,2Sam Nicholson, ⁴Mark Burchell, ⁴Kathryn Harriss, ^5,6Anne H. Peslier, ⁵Roy G. Christoffersen, ^7,8Jörg Fritz, ⁹Cornelia Meyer
Journal of Geophysical Research: Planets, 131, e2026JE010049
Open Access Link to Article [DOI: 10.1029/2026JE010049]
¹Department of Earth Sciences, Western University, London, ON, Canada
²Institute for Earth & Space Exploration, Western University, London, ON, Canada
³Now at: Diamond Light Source, Didcot, UK
⁴Centre for Astrophysics and Planetary Science, School of Engineering, Mathematics and Physics, University of Kent, Canterbury, UK
⁵Jacobs, NASA Johnson Space Center (JSC), Houston, TX, USA
⁶Department of Geological Sciences, New Mexico State University, Las Cruces, NM, USA
⁷Saalbau Weltraum Projekt, Heppenheim, Germany
⁸Zentrum für Rieskrater und Impaktforschung Nördlingen (ZERIN), Nördlingen, Germany
⁹Horizontereignis gUG, Berlin, Germany

Published by arrangement with John Wiley & Sons

Shock metamorphism is a ubiquitous process in our solar system. Shock pressure can be related to the lattice strain (ε) of individual minerals within a shocked sample. The lattice strain can be quantified within intact samples by in situ micro-X-ray diffraction (μXRD) using the Williamson-Hall method. The Williamson-Hall lattice strain (W-H ε) method has so far only been calibrated for olivine. This work extends the W-H ε method to high-Ca clinopyroxene. We obtained three sets of experimentally shocked clinopyroxene samples and calculated ε for each sample using μXRD. We created a calibration curve that relates ε to peak shock pressure experienced. Its trend line has the equation P = 222.85ε−8.60 GPa, with an error of ±9 GPa. The calibration curve was applied to the Martian meteorites Nakhla, Zagami, and Allan Hills A77005 (ALHA 77005) to compare these results with the meteorites’ optically determined shock stages. The peak shock pressures returned by the calibration curve are: 15 ± 9 GPa for Nakhla, 35 ± 9 GPa for Zagami, and 68 ± 9 GPa for ALHA 77005. These results agree with the meteorites’ previously determined shock stages. The development of a W-H ε calibration curve for high-Ca clinopyroxene is preliminary; however, it expands this method for evaluating shock metamorphism of shocked clinopyroxene-bearing samples, such as Martian shergottites.

¹M. C. Deahn et al. (>10)
Journal of Geophysical Research: Planets, 131, e2025JE009471
Open Access Link to Article [DOI: 10.1029/2025JE009471]
¹Purdue University, West Lafayette, IN, USA

Published by arrangement with John Wiley & Sons

The Mars 2020 rover is currently traversing the western rim of Jezero, a Middle to Late Noachian‐aged crater formed by an impactor that struck the northwest edge of Isidis Planitia (hereafter referred to as theIsidis basin) on Mars. Previous studies suggest that pre‐Isidis basin and Noachian outcrops are preservedthroughout this region; however, the nature of these exposures in the Jezero crater rim is unclear. It has beenhypothesized that crater‐forming processes should expose these ancient crustal rocks in the Jezero craterrim—presenting a unique opportunity to explore ancient Mars outcrops that are otherwise typically buried byyounger units. Jezero’s rim has undergone extensive erosion and modification since its formation ∼3.9 billionyears ago. To investigate these ancient lithologies, the Mars 2020 Science Team produced a 1:2500 scalegeologic map and interpreted a bedrock map of the ∼14.5 × 3.5 km area around the western Jezero crater rim.We identified, mapped, and defined nine bedrock units on Jezero crater’s rim to make connections to regionalgeologic units and identify deposits or features unique to Jezero crater. We found that the rim likely preserves arecord of pre‐Isidis bedrock, the Isidis and Jezero impacts, and post‐impact geologic processes. We alsoobserved candidate megabreccia, hydrothermal ridges, and regional volcanics that may be targets for futurerover‐based investigations. Our results show that in situ investigation of pre‐Isidis and Noachian‐agedlithologies preserved on the rim will provide insight into the nature of Mars’ early crustal formation andcratering processes.

¹M. M. Morris, ¹J. A. Hurowitz, ¹L. Ehm
Journal of Geophysical Research: Planets, 131, e2026JE010007
Link to Article [DOI: 10.1029/2026JE010007]
¹Department of Geosciences, Stony Brook University, Stony Brook, NY, USA

Published by arrangement with John Wiley & Sons

Fe-Mg carbonates on Mars preserve key evidence of past aqueous chemistry and climate, yet their formation conditions remain poorly constrained. We conducted low-temperature (∼25°C) anoxic precipitation experiments under Mars-like conditions, systematically varying pH, Fe:Mg ratio, Ca²⁺ content, and carbonate saturation state. Results show initial pH and saturation state as primary controls: near-neutral pH favored siderite (FeCO₃) and chukanovite (Fe₂(CO₃)(OH)₂) precipitation, while alkaline conditions promoted the precipitation of hydrated Mg-carbonate and Fe-substituted Mg-hydroxide and layered double hydroxides. Ca²⁺ suppressed amorphous Fe-carbonate precursor precipitation, enhancing the growth of rhombohedral carbonate and enabling partial Ca²⁺ substitution. A limited number of elevated temperature experiments (50°C) did not enhance Mg²⁺ substitution in siderite, but instead resulted in the precipitation of very high-magnesium calcite (MgCa(CO₃)₂) overgrowths. Mg²⁺ incorporation into siderite (at the level of ∼10 mol%) occurred only under low Fe:Mg ratios and high magnesite (MgCO₃) saturation, highlighting kinetic barriers to Mg²⁺ substitution.

¹Emmanuel Jacquet
Meteoritics & Planetary Science (in Press)
Open Access Link to Article [DOI: 10.1111/maps.70247]
¹Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, UMR 7590, Muséum National d’Histoire Naturelle, CNRS, Paris, France

Published by arrangement with John Wiley & Sons

Chondrule sizes are an important discriminant of chondrite groups and chondrule formation theories. Yet most studies report 2-D sizes without attempting the somewhat tedious corrections to 3-D proposed in the past literature. I show here that 3-D size averages can be simply calculated directly from 2-D averages of appropriate powers of sizes (and vice-versa), without having to reconstruct 3-D distributions, although explicit formulas to that end are also provided. This illuminates the comparison between 3-D and 2-D arithmetic size averages, which are confirmed to be little different for the published data sets. Yet I suggest another type of average, the “sphere-weighted average” (i.e., weighted by the chondrule equal-volume sphere area), a measure of the surface/volume ratio of the whole chondrule population, which is more robust against omission of small chondrules. While larger than the arithmetic averages, it is best in line with previous literature estimates based on less exhaustive surveys of chondrules.

¹Chao Li et al. (>10)
Icarus (in Press) Link to Article [DOI: 10.1016/j.icarus.2026.117349]
¹Institute of Natural Resources Survey, China University of Geosciences, Wuhan 430074, China

Copyright Elsevier

The elemental geochemical characteristics analyzed by the Mars Odyssey Gamma-Ray Spectrometer (GRS) have played a key role in understanding Mars geology and geochemical processes. However, GRS data are typical compositional data with a closure effect, which may introduce uncertainty in mapping Martian elemental geochemical provinces. We present a compositional data analysis (CoDA) based on centered log-ratio (clr) and isometric log-ratio (ilr) transformations to address these problems. Based on CoDA, we sequentially applied Exploratory Data Analysis (EDA), Correlation Analysis (CA), Principal Component Analysis (PCA), and Robust Principal Component Analysis (RPCA) to process the 1451 map bins that included Al, K, Fe, Si, Ca, H₂O, Cl, and S. The EDA analysis shows that the internal structure of the data after the clr transformation is closer to a normal distribution. Only clr-based CA analysis indicates consistently negative correlations between each of the key rock-forming elements (Si, Fe, Ca, Al) and each of the volatile elements (H₂O, Cl, S) at the global scale. When considering the closure effect and outliers in the GRS data, we used ilr-based RPCA to obtain the first three robust principal components that better reflect the multivariate geochemical information of the Martian surface. In particular, the geochemical anomalies revealed by RPC1 for the H₂O-S-Cl and Ca-K-Si-Al-Fe are more closely consistent with the distribution characteristics of low thermal inertia–high albedo and high thermal inertia–low albedo, respectively. Exploratory Hierarchical Cluster Analysis (HCA) based on the first three robust principal components revealed that when the number of clusters was set to five, elemental geochemical provinces better reflected the enrichment patterns of elements on the Martian surface. The element abundance statistics and Modified Box-and-Whisker (MBW) analysis for the seven representative sub-provinces across five geochemical provinces reveal more detailed characteristics of element enrichment and depletion. Some sub-provinces have significantly higher S, Cl, H₂O, and Si contents than the global average due to volcanism (e.g., Olympus Mons, Tharsis Montes, and Elysium Mons) and historical groundwater activity regions (e.g., Meridiani Planum); some are consistent with high-density distribution regions of aqueous minerals. Martian element provinces mapped using the CoDA analysis can be combined with other types of data and geological information for further research.

^1,2Zixian Shi, ¹Zhensheng Wang, ¹Renguang Zuo, ^3,4Shijie Li, ²Yiheng Li, ^2,5Razvan Caracas
Earth and Planetary Science Letters, 696, 120392 Link to Article [DOI: 10.1016/j.epsl.2026.120392]
¹State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan, 430074, China
²Université Paris Cité, Institut de Physique du Globe de Paris, CNRS, 1, Rue Jussieu, Paris, 75005, France
³Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China
⁴CAS Center for Excellence in Comparative Planetology, Hefei, China
⁵The Research Institute of the University of Bucharest (ICUB), University of Bucharest, Romania

Copyright Elsevier

The Moon-forming giant impact involved a collision between the proto-Earth and a planetary body named Theia. This resulted in the formation of a protolunar disk, where the Moon formed beyond the Roche limit, and the Earth accreted at the center. As the initial bodies are lost, reconstructing this event presents considerable challenges. Here, we place further constraints on the composition and structure of Theia by integrating improved impact numerical modeling with meteorite data. Our findings indicate that the core mass fraction (CMF) of Theia was below ∼6%, as higher values yield physically untenable mantle compositions and conflict with the Moon’s Fe-poor nature. Chemical composition constraints suggest that Theia’s mantle was composed of differentiated materials similar to aubrites, which may have derived predominantly from the mantle of a disintegrated inner Solar System planet analogous to proto-Mercury. The proto-Earth’s mantle exhibited a composition akin to that of the present-day Earth. Our research mitigates the isotope crisis in the Earth–Moon system and offers a pathway to probe Theia’s mantle mineralogy.

^1,2Sen Hu et al. (>10)
Geochimica et Cosmochimica Acta (in Press)
Open Access Link to Article [DOI: 10.1016/j.gca.2026.10.007]
¹Key Laboratory of Planetary Science and Frontier Technology, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
²University of Chinese Academy of Sciences, Beijing 100190, China

Copyright Elsevier

Chlorine (Cl) serves as a crucial volatile element, providing insight into the magmatic processes and volatile inventory of the Moon. The lunar rocks have notably elevated Cl isotopic compositions; however, no information is available about the Cl and its isotopes on the farside. Here, we report a petrographic, chemical, and Cl isotopic study of apatite in the Chang’e-6 (CE6) mare basalt collected from the South Pole–Aitken (SPA) basin. CE6 mare apatite was measured to have a Cl abundance of 0.04–3.36 wt%. We estimated a Cl abundance of ∼0.6 μg g⁻¹ for the CE6 mantle source, slightly higher than that (0.26–0.32 μg g⁻¹) estimated from Apollo low-titanium mare basalts and lower than that (∼1.3 μg g⁻¹) of Chang’e-5 low-titanium mare basalt. Cl abundances in the mantle source of low-titanium mare basalts exhibit a positive correlation towards the crystallization ages, highlighting a heterogeneous distribution of chlorine in the lunar mantle. The measured chlorine isotopic compositions (δ³⁷Cl, 14.5 ± 2.0‰ to 27.2 ± 2.2‰) are mostly higher than that of nearside mare basalts (0–20‰). CE6 mare apatite shows a positive correlation between Cl abundances and Cl isotopic compositions, comparable with the trend defined by the low-titanium mare apatite collected from the nearside hemisphere. We infer that the high δ³⁷Cl values of CE6 mare apatite were associated with magmatic fractionation of Cl coupled with an elevated chlorine isotopes in the mantle source, favoring the model that the massive formation impact event of SPA would have imprinted the chlorine isotopic compositions in the underlying mantle rocks.

¹Daniel R. Crocker, ²Conel M. O’D. Alexander, ³Mark H. Thiemens, ¹David T. Johnston
Proceedings of the National Academy of Sciences, 123, e2605307123
Link to Article [DOI: 10.1073/pnas.2605307123]
¹Department of Earth and Planetary Science, Harvard University, Cambridge, MA 02138
²Earth and Planets Laboratory, Carnegie Institution for Science, Washington, DC 20015
³Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093

Unraveling the complex formation and alteration history for extraterrestrial organic matter is key to understanding the chemical evolution of the solar system (SS) and potentially even life’s emergence on Earth. In this study, we performed high-precision triple oxygen isotope measurements on insoluble organic matter (IOM) sourced from a diverse suite of carbonaceous chondrites (CCs). Remarkably, the IOM from primitive Type 1 and 2 CCs—including CI, CM, CR, Bells, and Tarda—have oxygen isotope compositions that cluster on or near the CCAM line, which is itself related to the mixing of primitive oxygen isotope reservoirs residing within the early SS. This finding suggests that primitive meteoritic OM acquired oxygen of primitive origin and that those isotopic signatures have been minimally altered by parent body processes, offering critical constraints to assess the synthetic origin of meteoritic OM and evolution of SS oxygen reservoirs.

¹Fanli Lin, ¹Jiansheng Wang, ¹Huaiyuan Wang, ¹Kaijie Dai, ^1,2Kun Ding, ^1,2Zhiping He, ¹Qingli Li
Journal of Geophysical Research: Planets, 131, e2026JE009952
Link to Article [DOI: 10.1029/2026JE009952]
¹Shanghai Key Laboratory of Multidimensional Information Processing, East China Normal University, Shanghai, China
²Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai, China

Published by arrangement with John Wiley & Sons

The Chang’e-5 lunar regolith samples are returned samples of young mare basalt, possessing significant scientific research value. This paper performs nondestructive analysis on one of the Chang’e-5 basalt samples using scanning electron microscopy and micro-Raman spectroscopy. Through the analysis of the mineralogical characteristics, modal abundance, and impact effects of the sample, it is found that the sample is relatively consistent in composition with most Chang’e-5 lunar regolith samples, being low-titanium mare basalt that has undergone a certain degree of impact events. The analysis of quartz and plagioclase indicates that the impact pressure experienced by the young mare basalt is limited to a maximum of 20–25 GPa, with a minimum impact pressure of at least 5.2 GPa. Additionally, both this sample and the Chang’e-5 lunar regolith samples should likely originate from a low-titanium magma source, which may possibly have formed through the partial melting of a mixed magma composed of early refractory cumulates and late ilmenite-bearing cumulates, followed by fractional crystallization in a shallow magma reservoir before being erupted onto the lunar surface, and is compositionally distinct from Apollo and CE-6 basalts as an evolved, low-Ti late-stage basalts. This research can provide mineralogical evidence for understanding the thermal evolution of the Moon, particularly the late-stage volcanic activity and internal thermodynamic changes.

^1,2Shun Wang, ^1,2Yue Teng, ³Yifei Cui, ³Ao Luo, ^1,2Dianqing Li
Journal of Geophysical Research: Planets, 131, e2026JE009810
Link to Article [DOI: 10.1029/2026JE009810]
¹State Key Laboratory of Water Resources Engineering and Management, Wuhan University, Wuhan, China
²School of Water Resources and Hydropower Engineering, Institute of Hydraulic Engineering Risk and Disaster Prevention, Wuhan University, Wuhan, China
³Department of Hydraulic Engineering, Tsinghua University, Beijing, China

Published by arrangement with John Wiley & Sons

Lunar agglutinates, which are glass-rich aggregates formed through space weathering, are a key constituent of lunar regolith and strongly influence its engineering properties. This study develops a high-fidelity agglutinate simulant via high-temperature vacuum sintering, yielding particle morphology and chemical composition similar to those of Chang’e-5 samples. The effects of key sintering parameters, including temperature, binder fraction, structural support agent content, and dwell time, on the microstructure and single-particle compression strength are investigated. Furthermore, a new lunar regolith simulant (WHU-1A) is produced by incorporating different agglutinates, and its mechanical response is assessed through angle-of-repose and small-scale triaxial tests. The results demonstrate that, under controlled density conditions, agglutinate characteristics significantly influence regolith mechanical behavior. Weakly bonded agglutinates induce a limited increase in shear strength, whereas extensively melted agglutinates markedly enhance shear strength but also promote strain softening. This coupled strengthening–softening effect is most pronounced in specimens with high glass content.