Impact-generated magnetite in Chang’e-5 soil as a potential recorder of lunar magnetism

Abstract Magnetite is a principal paleomagnetic recorder on Earth, but lunar magnetism is thought to be dominated by metallic iron and Fe-Ni alloys, with magnetite rare and typically sub-micrometer within troilite. We identify nanometer- to micrometer-scale magnetite in pentlandite-troilite assemblages from a Chang’e-5 regolith breccia. Magnetite occurs at and within pentlandite, locally enclosing pentlandite nanoinclusions, implying a formation pathway distinct from troilite-hosted occurrences. Textures and compositions indicate sequential crystallization from an impact-generated Fe-Ni-S-O melt: rapid pentlandite growth along troilite margins followed by magnetite nucleation at sulfide-silicate interfaces. The lunar low oxygen fugacity stabilizes Fe 2+ -enriched magnetite, unlike terrestrial analogues. High crystallinity and single-domain to single-vortex states indicate strong remanence stability, making these grains reliable recorders of the contemporaneous lunar magnetic fields. These results broaden the inventory of lunar magnetic carriers, demonstrate impact-driven magnetite formation under lunar redox conditions, and motivate use of magnetite to refine the Moon’s magnetic history.