Space Weathering–driven Coupled Loss of S and Fe from Troilite on the Moon

Space weathering of sulfides is a key mechanism for the sulfur and iron anomalies on the surfaces of the Moon and other airless bodies. However, the detailed pathway for how space weathering modifies S and Fe contents in iron sulfide remains poorly constrained. In this study, we report a unique space-weathered troilite grain from Chang’E-6 returned samples, which features a porous texture and is associated with iron whiskers. This texture is attributed to the mass loss of troilite into S and Fe ions under solar wind H + irradiation, with Fe ions subsequently deposited to form iron whiskers. Like previous studies on space-weathered iron sulfide, this work found no evidence of amorphization. Our results show that the decomposition rate of troilite on the lunar surface driven by solar wind irradiation is ∼330 nm Myr −1 . This work provides direct mineralogical evidence for the coupled loss of S and Fe in troilite dominated by space weathering. We suggest that the space weathering effect has an important impact on the migration and redistribution of volatile substances (e.g., S) on the surfaces of airless bodies.