Mapping the Nanoscale Distribution and Valence of Fe in Pyroxene from a Chang’e-5 Drilled Lunar Sample

The Chang’e-5 (CE-5) mission retrieved the youngest known lunar mare basalts (∼1–2 Ga) from a previously unsampled region of the Moon, providing critical constraints on late-stage lunar volcanism. By integrating microscopy (scanning electron microscopy, transmission electron microscopy, and high-angle annular dark-field scanning transmission electron microscopy) and spectroscopy analysis (energy-dispersive X-ray spectroscopy and electron energy loss spectroscopy [EELS]), we revealed nanoscale Fe-rich and Fe-poor lamellae in the pyroxene minerals from CE-5 lunar soil samples. The alternating Fe-rich lamellae (30 ± 5 nm) and Fe-poor lamellae (50 ± 8 nm) exhibited an inverse Fe–Ca correlation, with EELS confirming Fe2+/Fe0 dominance (L3-edge at 707 eV) in the Fe-rich lamellae but Fe3+ enrichment (707.5 eV) in the Fe-poor lamellae. These redox contrasts were interpreted as products of (1) magmatic differentiation under low-oxygen-fugacity (f-O2) conditions and (2) postcrystallization alteration from solar-wind proton reduction. These findings advance our understanding of lunar postmagmatic thermal processing and provide insights for the development of lunar resources.