Provenance and evolution of lunar regolith at the Chang’e-6 sampling site

Abstract

China’s Chang’e-6 (CE-6) mission successfully returned the first lunar samples from the South Pole–Aitken basin on the Moon’s farside. Determining the provenance and evolution of the samples will play a crucial role in guiding effective laboratory analyses. Here we conduct a comprehensive search for source impact craters of the CE-6 samples on global, regional and local scales, and systematically model the formation, migration, mixing and maturation of regolith in the landing region driven by continuous bombardment and solar wind irradiation. A catalogue of 1,674 major source craters with ejecta source depths of up to 3 km was established, which cumulatively delivered materials 53.4 ± 15.7 cm thick to the CE-6 landing site. The returned samples are estimated to comprise ~93.3% local basalts, 6.1% South Pole–Aitken basin materials that are likely to contain mantle components and 0.6% highland feldspathic materials from outside the South Pole–Aitken basin. Modelled elemental abundance depth profiles show that the exotic materials are primarily concentrated at depths of 2.5–3 m, with a portion within the sampling depth of 1 m. The estimated exposure time in the top 1 mm is \({2.1}_{-0.9}^{+1.1}\,{\rm{Myr}}\) for the surficial scooped samples and shorter for deeper drilled samples. These findings establish a crucial foundation for CE-6 sample analysis and interpretation, offering key insights into the provenance of exotic materials and the space weathering process on the Moon’s farside.