Impact-induced oxidation origin of spherical magnetite in the Chang’e-5 lunar soil

To reveal the formation conditions and evolutionary processes of such minerals, this study conducted detailed microstructural characterization and iron valence-state analyses of spherical magnetite particles identified in Chang’e-5 lunar soil. The results show that the particle is composed of micrometer-scale magnetite grains cemented by Si-O amorphous material lacking volatile elements such as F and Cl.

Combined with its spherical morphology, internal cavity, aggregated grain texture, and Si-O-rich amorphous material between grains, these features suggest that the spherical magnetite most likely formed in an impact-induced, oxygen-bearing silicate vapor/melt environment. Together with recent discoveries of high-valence iron oxides in Chang’e-5 and Chang’e-6 lunar soils, this study further demonstrates that impact-induced oxidation is a key mechanism for the formation of Fe3+-bearing minerals on the lunar surface, providing new constraints on local oxidizing environments and the origin of magnetic anomalies on the Moon.