Lunar regolith and substructure at Chang'E-4 landing site in South Pole-Aitken basin

The South Pole-Aitken (SPA) basin is the oldest and largest impact structure on the Moon, and it gives particular insight on the lunar interior composition(1-3). However, the surface of the SPA basin has been substantially modified by consequent impacts and basalt flooding. The exploration of the surficial material and the substructure of the SPA basin is one of the main scientific goals of the Chinese spacecraft Chang'E-4 that landed in the Von Karman crater inside the SPA basin(4,5). Here we report the lunar penetrating radar profiles along the track of the lunar rover Yutu-2, which show a three-unit substructure at the landing site. The top unit consists of the similar to 12-m-thick lunar regolith and similar to 120 m multilayered ejecta that were delivered from several adjacent craters. The middle unit is the mare basalts filling the Von Karman crater. The lowest unit is another ejecta layer with a thickness of >= 200 m, likely from the Leibnitz crater. These discoveries fully support the local stratigraphy and geological explanation presented previously(6). Our results reveal that the surface materials at the Chang'E-4 landing site are unambiguously dominated by the ejecta from the Finsen crater with a minor contribution from other neighbouring craters. The regolith measured by Yutu-2 is representative of the initial lunar deep interior materials, rather than the later erupted basalts.

Automated summary

The lunar penetrating radar profiles taken by the lunar rover Yutu-2 revealed a three-unit substructure at the landing site in the South Pole-Aitken (SPA) basin, supporting the local stratigraphy and geological explanation. The surface materials at the Chang'E-4 landing site are dominated by ejecta from the Finsen crater, indicating that they represent the initial lunar deep interior materials rather than later erupted basalts.