Lunar farside samples returned by Chang'E-6 Mission : significance for understanding the South Pole-Aitken basin stratigraphic history

Abstract

The Chang'E-6 (CE-6) mission, launched by China on 2024 May 3, marks the first successful retrieval of samples from the farside of the Moon, specifically from the southern mare plain of the Apollo basin within the South Pole-Aitken (SPA) Basin. This study aims to provide a comprehensive geological analysis of the Apollo basin, focusing on the Apollo basin materials that CE-6 may have collected. By examining the regional geology, surface mineralogy, thorium (Th) abundance, and crustal thickness, we seek to understand the implications of these materials for the SPA basin's structure and stratigraphic history. We find that the Apollo basin exhibits significant lateral compositional variations, with Mg-rich noritic materials predominantly in the southwestern portion and more feldspathic materials in the northeast, probably due to the fact that the Apollo basin is situated on different structures of the underlying SPA basin. Those Mg-rich materials, likely representing deep lithologies from local lower crust, are associated with low Th abundance, suggesting a KREEP-poor origin. The inclusion of foreign materials in the CE-6 samples increases the complexity while also enhancing their research potential. In addition to the local mare basalts, Mg-rich noritic materials associated with the Apollo basin and Th-rich materials originating from the SPA basin may also have been collected by CE-6. Laboratory research of these diverse lithologies will contribute to unraveling the characteristics of the farside mantle, the geological history of the giant SPA basin, as well as the cause of the substantial asymmetry between the lunar nearside and farside.