^1,2,3,4Shengdong Chen et al. (>10)
Journal of Geophysical Research: Planets, 131, e2026JE009777
Link to Article [DOI: 10.1029/2026JE009777]
¹State Key Laboratory of Deep Earth Processes and Resources, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, PR China
²Center for Advanced Planetary Science (CAPS), Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, PR China
³Guangdong Provincial Key Laboratory of Mineral Physics and Materials, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, PR China
⁴University of Chinese Academy of Sciences, Beijing, PR China
Published by arrangement with John Wiley & Sons

The Moon’s highly reduced nature contrasts with recent findings of ferric iron (Fe³⁺)-bearing phases, suggesting an active redox cycle on the Moon. While solar wind proton reduction and impact-vaporization oxygen loss from minerals are proposed drivers for lunar reduction, direct nanometer-scale evidence for impact-driven deoxygenation has been lacking. Here we report the discovery of oxygen-deficient magnetite within impact melt glass in Chang’e-6 lunar farside samples from the South Pole-Aitken basin. This subhedral magnetite grain (Length 2.5 μm; width 1.5 μm.) exhibits a non-stoichiometric composition and crystal chemical formula [(Fe²⁺_1.158(7)Mg_0.070(5))_∑1.228(Fe³⁺_1.534(9)Cr³⁺_0.137(14)Al_0.101(8))_∑1.772]_∑3.000(O_3.886□_0.114)_∑4.000, confirming significant oxygen vacancies (□). Magnetite heating experiments (1000°C, in Ar atmosphere) replicated these features, demonstrating thermal deoxygenation generates oxygen vacancies through O₂ evolution and concurrent Fe³⁺ reduction. Our findings provide the first mineral structural evidence that post-shock heating drives deoxygenation in oxygen-bearing minerals, establishing impact-induced oxygen removal as a fundamental mechanism making the localized lunar surface chemically reduced.

^1,2S. N. Mantsevich, ¹Yu. S. Dobrolenskiy, ³O. V. Zakusina, ³T. A. Koroleva, ^3,4V. V. Krupskaya, ⁵N. A. Evdokimova
Journal of Geophysical Research: Planets, 131 e2026JE009946
Link to Article [DOI: 10.1029/2026JE009946]
¹Space Research Institute (IKI RAS), Moscow, Russia
²Physics Department, M.V. Lomonosov Moscow State University, Moscow, Russia
³Institute of Ore Geology, Petrography, Mineralogy and Geochemistry (IGEM RAS), Moscow, Russia
⁴Faculty of Geology, M.V. Lomonosov Moscow State University, Moscow, Russia
⁵Geophysical Institute, University of Alaska, Fairbanks, AK, USA
Published by arrangement with John Wiley & Sons

The acousto-optic tuneable filters can be used as main dispersive or auxiliary elements in compact spectrometers applied for various purposes such as atmospheric gas composition analysis, agriculture, or mineralogical analysis. This paper describes the features that arise when the problem of mineral identification is solved using an acousto-optic spectrometer. Estimates of such spectral device sensitivity are given in terms of the direct minimum detectable percentage ratio between the parent rock and the mineral being identified. It is shown that the minimum detectable value of the mineral percentage content depends significantly on its absorption band characteristics. The presented results can be generalized to reflectance spectra obtained by other types of optical spectrometers with similar characteristics and are of importance for the mineralogical analysis both in studies of the Earth’s surface and other objects in the Solar System.

¹Gowri Giri et al. (>10)
Journal of Geophysical Research: Planets (in Press)
Link to Article [DOI: 10.1029/2026JE009913]
¹Department of Geology, University of Kerala, Thiruvananthapuram, Kerala, India Published by arrangement with John Wiley & Sons Gypsum is a key mineral to reconstruct aqueous processes on Mars. Thus, this study compares gypsum from two contrasting terrestrial environments: the hyperarid Atacama Desert of Chile and the semi-arid Tiruchirappalli Badlands of India, and its comparison with multiple sites on Mars, serving as end-member analogs for Martian gypsum. Using field observations, petrography, X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), and hyperspectral reflectance, we characterized samples from both localities. In Atacama, gypsum occurs as fibrous veinlets within mudstone, with coexisting bassanite and anhydrite. Whereas in Tiruchirappalli, it forms fracture-filling veins with fluid inclusions and iron staining, and is associated with kaolinite-hematite within the Cretaceous mudstones of the Karai Formation. Raman and FTIR confirm the presence of gypsum at both sites, with an additional anhydrite phase in Atacama. These sites exhibit similar hyperspectral absorption features that match those observed by CRISM at Olympia Undae, Columbus Crater, and Mawrth Vallis. When Atacama gypsum formed as a primary evaporite through groundwater evaporation under extreme aridity, Tiruchirappalli gypsum formed diagenetically, precipitating from sulfate-rich fluids into fractures during burial and uplift, with tropical weathering. This spectral equivalence from different pathways shows that orbital spectra alone cannot determine gypsum genesis on Mars without geological context. The framework matches Atacama gypsum to Olympia Undae, Tiruchirappalli to Columbus Crater, and both to Mawrth Vallis. Fluid inclusions and endolithic communities highlight gypsum’s potential to preserve biosignatures. Together, these findings strengthen interpretations of the Martian paleoenvironment and guide gypsum-focused habitability assessments.