Journal ArticleControls on Iron‐Redox State in Martian Magmas Quantified by Mössbauer Spectroscopy, Colorimetric Wet Chemistry, and XANES SpectroscopyAithala, S P [Department of Earth and Environmental Sciences University of Minnesota Minneapolis MN USA] (ORCID:0000000287575370); Lange, R A [Department of Earth and Environmental Sciences University of Michigan Ann Arbor MI USA] (ORCID:0000000303096178); Hirschmann, M M [Department of Earth and Environmental Sciences University of Minnesota Minneapolis MN USA] (ORCID:0000000312136645)<title>Abstract</title> To elucidate the relationship between oxygen fugacities (<italic>f</italic>O2) recorded in martian basalts and redox processes in the martian interior, superliquidus 100‐kPa furnace experiments on a composition similar to Humphrey (Adirondack basalt) were conducted at variable<italic>f</italic>O2and temperature. Quenched glasses were analyzed by EPMA, Mössbauer spectroscopy, colorimetric wet chemistry, and microbeam X‐ray absorption near edge structure (XANES) spectroscopy. The experiments reveal Mössbauer and wet chemical determinations of silicate glass Fe3+/FeTagreeing within uncertainty, supporting the accuracy of extended‐Voigt‐based fitting of Mössbauer spectra when recoil‐free fraction is considered. Fe3+/FeTratios determined from Mössbauer spectroscopy from Humphrey and previously studied martian‐relevant glass compositions are combined to calibrate models that characterize the relationship between Fe3+/FeT,<italic>f</italic>O2, temperature, and composition in martian silicate liquids. The models demonstrate, similar to previously investigated silicate liquids, that the correlation between and log<italic>f</italic>O2in martian magmas has a slope less than the value (0.25) expected if ferric and ferrous iron oxide mixed ideally. Martian magma Fe3+/FeTratios are more temperature‐sensitive compared to non‐martian compositions, suggesting that temperature variations may contribute to comparatively large<italic>f</italic>O2variations in martian basalt. The models are applied to demonstrate that the Fe3+/FeTincreases required to explain multiple‐log unit changes in<italic>f</italic>O2in shergottite magma would not increase terrestrial magma<italic>f</italic>O2as effectively. To aid in future investigations of martian magma redox, a XANES technique that allows for non‐destructive, microanalytical characterization of Fe3+/FeTin natural martian materials and martian‐relevant experiments is introduced.American Geophysical Union2026-03-0110671827Journal of Geophysical Research: Planets13132169-9097https://doi.org/10.1029/2025JE0091482153786National Science Foundation