^1,2Ronghua Pang et al. (>10)
Earth and Planetary Science Letters 669, 119572 Link to Article [https://doi.org/10.1016/j.epsl.2025.119572]
¹Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, 550081 Guiyang, China
²University of Chinese Academy of Sciences, 100049 Beijing, China
Copyright Elsevier

The redox processes and the formation of magnetic anomalies on the lunar surface are hot topics in lunar science research. Magnetite is the only confirmed ferromagnetic and high-valence iron oxide mineral in lunar soil samples, making it a key target for studying these processes. A recent study of Chang’e-5 (CE5) lunar samples found that magnetite was widespread in the high-Ti lunar basalt regolith and was formed by impacts on the lunar surface. It remains to be confirmed whether this type of magnetite is broadly distributed, and its magnetic characteristics require further analysis. We conducted a micro-analysis of impact-sputtered troilite in the CE5 and Chang’e-6 (CE6) lunar samples. Submicron magnetite and associated α-Fe were widespread in the impact-sputtered troilite. The oxygen-bearing volatiles generated or released by the impact may be critical in the formation of magnetite. Further analysis of ferromagnetic materials indicates this magnetite type exhibits magnetic vortices that are weaker than those of α-Fe. Impact-derived magnetite and α-Fe may be potential magnetic minerals responsible for the magnetic anomalies on the lunar surface. Our research confirms that impact-induced redox reactions and their products, such as magnetite, are widely distributed in the lunar basalt regolith, which may be one reason for magnetic anomalies on the lunar surface.

^1,2Elizabeth Bailey,²Myriam Telus,³Phoebe J. Lam,⁴Samuel M. Webb
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70001]
¹Department of Astronomy and Astrophysics, University of California Santa Cruz, Santa Cruz, California, USA
²Department of Earth and Planetary Sciences, University of California Santa Cruz, Santa Cruz, California, USA
³Department of Ocean Sciences, University of California Santa Cruz, Santa Cruz, California, USA
⁴Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California, USA
Published by arrangement with John Wiley & Sons

Multiple generations of calcite and dolomite precipitated in CM chondrites during ice melting events that led to episodes of liquid water. Models and laboratory analysis have suggested a long-term transition from oxidizing to reducing conditions during aqueous alteration on the CM parent body. We found that synchrotron X-ray absorption near edge spectroscopy (XANES) can detect relative differences in the oxidation state of trace iron within these carbonates. In CM chondrites, previous work interpreted Mn abundance in calcite as an indicator of relatively early or late formation, and dolomite is understood to form relatively late. In the CM1 chondrite Meteorite Hills 01070, XANES maps reveal that Mn-poor calcite contains more oxidized iron relative to Mn-rich calcite. While these measurements of carbonates support increasing iron reduction with progressive aqueous alteration in MET 01070, comparison among different CM chondrites suggests a complex picture of redox evolution. In addition to carbonates, we performed XANES measurements of the phyllosilicate-rich matrix of Allan Hills 83,100. Pre-edge centroid analysis indicates that this CM1/2 has an oxidation state similar to typical CM2 chondrites. While additional measurements are warranted to confirm the full span of redox trends in CM carbonates, our data do not support a correlation between redox state and petrologic type.