Cosmogenic isotopic evidence from Chang’e-6 clasts for excavation history and ejecta provenance in the South Pole-Aitken basin

Impact and space weathering play a key role in resurfacing the Moon, yet their effects on the lunar farside remain poorly constrained. Chang’e-6 (CE-6) samples provide a unique opportunity to understand space weathering and material redistributions within the South Pole-Aitken (SPA) Basin. Our combined cosmogenic Sm, Hf, and Cr isotope results indicate an average cosmic-ray exposure (CRE) age of ~500 Ma for the CE-6 soil. Most low-Ti basaltic clasts experienced prolonged exposure similar to the host soil, whereas two were excavated more recently. Three KREEP-bearing clasts falling into two compositional groups show non-overlapping CRE ages, indicative of different excavation histories. Comparison with remote-sensing data suggests the Mg-rich pyroxene annulus and cryptomare as candidate source regions, respectively. These findings suggest that KREEP components are more widely distributed across the lunar farside than previously recognized.