Chronological sequence of Chang'E-4 landing zone within Von Karman crater

Sequence and timing are critical for understanding the geologic evolution. Here we performed detailed crater size-frequency distribution measurements within the Von Karman crater, where China's Chang'E-4 (CE-4) mission landed, and its surroundings including Alder and Finsen craters, to understand the geologic evolution of the landing zone. The formation time of Von Karmen crater was estimated to be similar to 4(-0.03)(+0.03) Ga, approaching the age of South Pole-Aitken basin. Three major layers under the landing site were dated: The ejecta from Alder crater was considered to be similar to 3.5(-0.2)(+0.01) Ga old, belonging to Imbrian. The floor of Von Karman crater was divided into mare basalt units and Finsen ejecta unit based on spectral differences. Two mare basalt units were estimated to be similar to 3.2(-0.1)(+)(0.0)(7) and 3.3(-0.2)(+0.08) Ga old (Imbrian), respectively, while Finsen crater and its ejecta, where CE-4 landed, were estimated to be similar to 3.1(-0.5)(+0.3) Ga (Eratosthenian). The chronological sequence established above indicates that the CE-4 landing zone has experienced a very complex evolutionary history.