¹Chi Ma,^2,3Alan E. Rubin
American Mineralogist 111, 1186-1191 Link to Article [https://doi.org/10.2138/am-2025-10003]
¹Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125, U.S.A.
²Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, California 90095, U.S.A.
³Maine Mineral & Gem Museum, 99 Main Street, P.O. Box 500, Bethel, Maine 04217, U.S.A.
Copyright: The Mineralogical Society of America

Colomeraite (IMA 2021-061), with an end-member formula NaTi³⁺Si₂O₆, is a new Na pyroxene identified in the Colomera IIE iron meteorite. Colomeraite occurs with albite and K-feldspar in a silicate inclusion. The mean chemical composition of type colomeraite by electron probe microanalysis is (wt%) SiO₂ 54.82, Ti₂O₃ 17.15, TiO₂ 5.58, NaO₂ 12.33, MgO 3.93, FeO 3.59, CaO 1.98, MnO 0.28, Al₂O₃ 0.24, Cr₂O₃ 0.13, K₂O 0.02, total 100.05, giving rise to an empirical formula of (Na_0.88Ca_0.08Mg_0.04)(⁠Mg_0.17Fe_0.11Mn_0.01Al_0.01)Si_2.01O₆, with Ti³⁺ and Ti⁴⁺ partitioned, based on stoichiometry. Colomeraite has the C2/c diopside-type structure with a = 9.70(1) Å, b = 8.88(1) Å, c = 5.30(1) Å, β = 106.8(1)°, V = 437(2) ų, and Z = 4, as revealed by electron backscatter diffraction. The calculated density using the measured composition is 3.36 g/cm³. Colomeraite is a high-pressure and high-temperature Na-Ti³⁺-pyroxene, probably formed from an alkali plagioclase-Ti-rich phase melt via impact mixing of metal and silicates under extremely reducing conditions. The mineral is named after the host meteorite “Colomera.”

^1,2,3Yiping Yang et al. (>10)
American Mineralogist 111, 1036-1045 Link to Article [https://doi.org/10.2138/am-2025-9674]
¹Key Laboratory for Deep Earth Processes and Strategic Mineral Resources, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
²Center for Advanced Planetary Science (CAPS), Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
³Guangdong Provincial Key Laboratory of Mineral Physics and Materials, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
Copyright: The Mineralogical Society of America

Mineral structures record the formation and evolution of the Earth-Moon system. Here we report the discovery of correlated disorder in a silicate mineral kuratite [ideal formula ], which cannot be well documented by classical crystallography, in breccia clasts from near and far sides of the Moon. We employed the advanced three-dimensional electron diffraction (3DED) method in combination with spherical aberration corrected transmission electron microscopy to thoroughly characterize its structural features. The results indicate that the kuratite, coexisting with dendritic pigeonite and ulvöspinel, displays intricate correlated disorder features. These are characterized by alternating arrangements of five correlated site pairs confined within a single disordered layer. The occurrence of a vitrified dendritic pigeonite with similar composition suggests that kuratite formed during the impact-induced melting-cooling processes. This finding shows consistency in impact-driven surface processes between the lunar near and far sides, while demonstrating the utility of advanced nanoscale crystallographic methods for decoding extraterrestrial mineral formation mechanisms.

¹Le Zhang et al. (>10)
Journal of Geophysical Research: Planets (in Press) Link to Article [https://doi.org/10.1029/2026JE009725]
¹State Key Laboratory of Deep Earth Processes and Resources, Guangzhou Institute of Geochemistry, Chinese Academy ofSciences, Guangzhou, China
Published by arrangement with John Wiley & Sons

The Moon’s crust is proposed to be composed of an anorthositic upper crust and a noritic lower crust. While the upper crust was the result of the floatation of plagioclase crystallized at the late-stage of lunar magma ocean (LMO), the petrogenesis of the lower crust is in debate. In this study, we found three high-MgO impact glasses in the Chang’e-6 lunar soil, one being troctolitic (P032) and other two being noritic (P133 and P138). A combination match suggests P133 and P138 likely originated from the Apollo basin’s peak ring, representing lower crust at Apollo basin. The high Mg# and rare earth element signatures of both glasses support a petrogenesis involving the assimilation of KREEP-bearing crust by partial melts derived from early mafic cumulates of the LMO. This study hence indicates that despite the predominant concentration of KREEP material on the lunar nearside, KREEP components are also locally present on the farside.

¹C. Wang,^1,2T. Usui,^3,4M. Melwani Daswani
Journal of Geophysical Research: Planets (in Press) Open Access Link to Article [https://doi.org/10.1029/2025JE009358]
¹Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, Tokyo, Japan,
²Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, Japan,
³The SETIInstitute, Mountain View, CA, USA,
⁴Earth‐Life Science Institute, Institute of Science Tokyo, Tokyo, Japan
Published by arrangement with John Wiley & Sons

Feldspar-rich rocks have increasingly been discovered on the martian surface. They may have been an important part of the ancient martian crust and may be related to Ca/Fe-rich carbonates (one of two types of carbonates on Mars and the other being Mg-rich carbonates), but compared to mafic rocks, their interaction with water on ancient Mars is poorly understood. We conducted 1-D thermochemical modeling to determine how mafic or feldspar-rich rock composition controls the products of aqueous alteration on ancient Mars, with a focus on carbonates, considering the effects of groundwater flow and alteration duration in low-temperature environments. Evaporation of the alteration fluid was also simulated. We found that protolith composition, fluid transport process, and duration of alteration together control the composition, abundance, and distribution of carbonates and other secondary minerals. A causal link may exist between feldspar-rich rocks and some Ca/Fe-carbonates on Mars: Dominantly Mg-rich carbonates form only from mafic protoliths, while Ca/Fe-carbonates can form from either a feldspar-rich protolith generally or from a mafic protolith with a short alteration process. Percolation of atmospheric CO2-equilibrated water also provides a mechanism to suppress surface carbonate formation, dissolve shallow subsurface carbonates, and bury them deeply underground. These idealized scenarios employ simplified assumptions (equilibrium precipitation, laboratory dissolution rates, and specified transport). Absolute timescales are uncertain, so we focus on robust qualitative controls. The simulations demonstrate that crustal heterogeneity can explain the observed dichotomy and that carbonate composition may indicate protolith composition where direct detection is difficult.

^1,2,3,4,5Yuhuan Yuan,^1,2,3,4Ke Wen,^1,2,3,4Yiping Yang,⁶Chaoqun Zhang,^1,2Xiaorong Qin,^1,2,3,4,5Jianxi Zhu,^1,2,3,4,5Hongping He,⁷Joseph W. Stucki
Journal of Geophysical Research: Planets (in Press) Link to Article [https://doi.org/10.1029/2026JE009683]
¹State Key Laboratory of Deep Earth Processes and Resources, Guangzhou Institute of Geochemistry, Chinese Academy ofSciences, Guangzhou, PR China,
²Guangdong Provincial Key Laboratory of Mineral Physics and Materials, GuangzhouInstitute of Geochemistry, Chinese Academy of Sciences, Guangzhou, PR China,
³Center for Advanced Planetary Science,Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, PR China,
⁴Guangdong Research Centerfor Strategic Metals and Green Utilization, Guangzhou, PR China,
⁵University of Chinese Academy of Sciences, Beijing,PR China,
⁶Key Laboratory of Deep Petroleum Intelligent Exploration and Development, Institute of Geology andGeophysics, Chinese Academy of Sciences, Beijing, PR China,
⁷Department of Natural Resources and EnvironmentalSciences, University of Illinois at Urbana–Champaign, Urbana, IL, USA
Published by arrangement with John Wiley & Sons

Nontronite, a Fe3+-rich smectite widely identified on Mars, serves as a key mineral indicator for reconstructing paleo-redox and paleo-aqueous environments. However, uncertainties in interpreting its spectral data hinder a precise understanding of its formation conditions and paleoenvironmental implications. To fill this gap, the present study investigated the controls of nontronite formation and its crystallographic-spectral relationships by synthesizing a series of Fe-Si-Al samples with varying Fe/Si molar ratios under hydrothermal conditions. Results demonstrated that crystalline nontronite forms exclusively within a Fe/Si molar ratio of 0.21–0.48 under the simulated alkaline conditions. Incorporation of Fe3+ into tetrahedral sites as [IV]Fe3+ reduced the tetrahedral-octahedral sheet mismatch, thereby enhancing the crystallinity of nontronite. This crystallographic evolution was systematically observed in Mid Infrared and Visible-Shortwave Infrared spectra: [IV]Fe3+ content negatively correlated with the Si-O vibration wavenumber (near 1,000 cm−1) but positively correlated with the 2Fe3+-OH band position (∼1,430 nm) and depth. Furthermore, band depths at ∼1,430 and ∼2,290 nm are robust proxies for the crystallinity of nontronite in the absence of byproducts. These findings constrain the formation of nontronite on Mars to oxidizing, alkaline subsurface hydrothermal environments during the early Noachian, which represents one of the possible pathways for nontronite formation. These results provide a refined framework for interpreting orbital and in situ spectral data, advancing the understanding of clay mineral formation and environmental evolution on Mars.

¹J. Shawcross,^2,3D. J. Adams,^3,4M. L. Wong,^1,5,6K. J. Smith,^1,7Y. L. Yung
Journal of Geopyhsical Research: Planets (in Press) Open Access Link to Article [https://doi.org/10.1029/2025JE009146]
¹Department of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
²Departmentof Earth and Planetary Sciences, Harvard University, Cambridge, MA, USA
³NHFP Sagan Fellow, NASA HubbleFellowship Program, Space Telescope Science Institute, Baltimore, MD, USA
⁴Earth and Planets Laboratory, CarnegieInstitution for Science, Washington, DC, USA
⁵Department of Water Resources Management, Environmental EngineeringProgram, Central State University, Wilberforce, OH, USA
⁶Department of Planetary Sciences, The University of Arizona,Tucson, AZ, USA, 7NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
Published by arrangement with John Wiley & Sons

Noachian and early Hesperian Mars were likely warm and wet, with an atmosphere abundant in molecular nitrogen. The recent discovery of nitrate deposits in the Yellowknife Bay mudstones at Gale Crater confirm the existence of nitrogen oxides (NO_X) on Noachian Mars. The processes responsible for the production of these nitrates would fractionate nitrogen isotopes: nitrogen oxides will have different isotopic signatures depending on how they were formed—lightning, solar energetic particles (SEPs) and galactic cosmic rays, or photolysis. We used the Caltech–JPL 1D photochemical and transport model KINETICS to simulate nitrogen isotope fractionation in the formation of nitrogen oxide species. At the surface, where deposition occurs, we predict a depletion of δ¹⁵N = −0.845‰ relative to the isotopic composition of atmospheric N₂. Near 200 km altitude, photolysis contributes to positive fractionation. From 300 km to the top of the modeled atmosphere, mass fractionation in the negative direction becomes relevant and produces a depletion of ¹⁵N above 450 km relative to source N₂. Our study predicts a depletion of ¹⁵N in atmospherically derived NO_X relative to the assumed background ratio, which is critical knowledge for constraining the formation history of nitrate on Mars, and whether nitrogen isotopic fractionation could be used as a biosignature.

¹Anuja Sreejayan et al. (>10)
Journal of Geophysical Reseacrh: Planets (in Press) Link to Article [https://doi.org/10.1029/2025JE009544]
¹Department of Geology, University of Kerala, Thiruvananthapuram, Kerala, India
Published by arrangement with John Wiley & Sons

This study reports the first occurrence of melanterite (Fe2+SO4·7H2O), a secondary hydrous sulfate mineral, in Peninsular India and examines its formation through the oxidative weathering of marcasite associated with lignite in Neyveli, Tamil Nadu. The marcasite was exposed to normal atmospheric conditions, and melanterite was formed within 23 days via oxidative weathering. Melanterite occurs as a yellow, prismatic to fibrous, translucent crystal, either as individual fibers or clusters. Though melanterite is mineralogically characterized through different techniques like X-ray diffraction, scanning electron microscopy-energy dispersive X-ray spectroscopy, and electron probe microanalysis (EPMA), the results obtained from EPMA [(Fe0.839 Cu0.000355 Zn0.000466 Ni0.000545) SO4·7H2O] closely match the composition of standard melanterite. Fourier Transform Infrared spectroscopy identified key vibrational peaks for sulfates (450–480 cm−1) and water molecules (1,544–1,650 cm−1), while laser Raman spectroscopy provided evidence for the characteristic vibration of melanterite at 976 cm−1. Hyperspectral analysis also discerned the characteristic Fe2+ peak (0.45–0.9 μm) of melanterite. A spectrum, comparable to that of melanterite, obtained through Compact Reconnaissance Imaging Spectrometer for Mars data from the Ceti Mensa region on Mars, where it is associated with a polysulfate deposit. Since melanterite forms under acidic and oxidizing conditions in low moisture, its occurrence can provide insights into the environmental conditions under which sulfate forms. Thus, this study can provide insights into studying transient wet conditions on Mars.

^1,2Devan M. Nisson et al. (>10)
Journal of Geophysical Research: Planets (in Press) Open Access Link to Article [https://doi.org/10.1029/2025JE009395]
¹Department of Geosciences, Princeton University, Princeton, NJ, USA
²NASA Postdoctoral Program Fellow, NASA Ames Research Center, Moffett Field, CA, USA
Published by arrangement with John Wiley & Sons

Serpentinization produces hydrogen and methane through abiotic water-rock interactions, potentially supporting chemotrophic life in planetary subsurface environments. Serpentine deposits in the Martian Noachian landscapes of Nili Fossae and the Southern Highlands have been considered as potential paleo-habitable zones. However, the geochemical and physical conditions of Martian serpentinization fluids are poorly constrained because of limited data on serpentinite composition and formation environment. Furthermore, the co-occurrence of magnesite and magnesium-enriched serpentines on Mars remains enigmatic. To address such gaps, we investigated antigorite-magnesite paleo-serpentine bodies along the Highland-Vijayan suture of Sri Lanka as Martian analog sites, using thermodynamic batch reaction models to constrain alteration fluids and the production of primary (H2) and secondary (CH4) serpentinization products. Geochemist’s Workbench models combined field X-Ray Fluorescence (XRF) observations with varied protolith compositions (ultramafic or gneissic), precursor fluids (seawater or freshwater), temperatures (100–600°C), volumetric water-to-rock ratios (1–100,000), and CO2 partial pressures (0.01–1 bar). Models successfully reproduced the co-occurrence of antigorite and magnesite observed on Mars, with both minerals forming at 100°C across water-to-rock ratios. Despite their Mg-enriched composition, ultramafic protoliths produced H2 yields (up to 229 mmol/kg at W/R 1 at 100°C), supporting chemotrophic populations up to 107.5 cells/mL. Geochemical models indicate Mg enrichment from ultramafic mineralogy and Fe contribution from regional gneisses. Our thermodynamic equilibrium results show that Mg-rich serpentine systems with sufficient ferrous iron can produce biologically significant H2, establishing Sri Lankan serpentinites as valuable analogs for Noachian Mars habitability.

¹Neil E. Bowles et al. (>10)
Journal of Geophyiscal Research: Planets (in Press) Open Access Link to Article [https://doi.org/10.1029/2025JE009333]
¹Department of Physics, University of Oxford, Oxford, UK
Published by arrangement with John Wiley & Sons

The Lunar Thermal Mapper (LTM) instrument is a UK Space Agency funded infrared radiometer designed and built for the National Aeronautics and Space Administration Lunar Trailblazer mission launched in February 2025. LTM is a pushbroom imaging filter radiometer with 15 channels that cover the wavelength range from 6.25 to 100 μm with a 40–70 m/pixel ground sampling. Lunar Trailblazer’s mission is to understand the form, abundance and distribution of water across the lunar surface. LTM provides an independent measure of temperature to investigate thermal effects on water’s mapped distribution as well as an independent measure of surface mineralogy. The LTM instrument’s 15 infrared channels include four broadband temperature sensing channels (6.25–12.5, 12.5–25, 25–50 and 50–100 μm) plus 11 additional narrow band (∼40 cm−1) filters from ∼7–10 μm to map and discriminate silicate composition. We review the LTM design and calibration campaign at the University of Oxford’s Space Instrumentation facility and show that the instrument has sensitivity from 400 K with a Noise Equivalent Temperature Difference of <0.1 K to <1 K at 110 K for typical integration times (e.g., 30 Hz readout) from a nominal 70–130 km lunar orbit design altitude.

¹Ming Ma et al. (>10)
Journal of Geophysical Research: Planets (in Press) Open Access Link to Article [https://doi.org/10.1029/2026JE009657]
¹School of Surveying and Exploration Engineering, and Key Laboratory of Architectural Cold Climate EnergyManagement, Ministry of Education, Jilin Jianzhu University, Changchun, China
Published by arrangement with John Wiley & Sons

Space weathering substantially distorts the Christiansen feature (CF) observed by LunarReconnaissance Orbiter (LRO) Diviner thermal infrared radiometer, obscuring the intrinsic compositional andthermophysical signals of lunar surface silicate minerals. In this study, we develop a two‐step correctionframework designed to remove space weathering effects from a previously topographically corrected LRODiviner CF map. The method integrates Kaguya 750 nm reflectance, optical maturity (OMAT), FeO, H‐parameter, and npFe0 parameters to model nonlinear space weathering relationships across immature,moderately mature, and mature CF pixels. The corrected CF values exhibited reduced dependence on npFe0abundances, enhanced correlation with bulk FeO abundances, and improved internal consistency withincompositionally homogeneous regions. Comparisons with correction results based on Kaguya OMAT and FeOscale factors indicate that the proposed method more effectively suppresses space weathering inducedvariability while preserving compositionally diagnostic CF signatures. Persistent low CF anomalies in highlandregions suggest additional controls beyond npFe0 accumulation, potentially related to basaltic dustcontamination, subsurface compositional heterogeneity, and silicate amorphization processes. The resulting CFproduct offers a refined thermal infrared perspective on lunar surface composition, indicating clearer basalticdistributions, particularly within the South Pole Aitken basin.