Geological Characteristics of Von Karman Crater, Northwestern South pole-Aitken Basin: Chang'E-4 Landing Site Region

Von Karman crater (diameter = similar to 186 km), lying in the northwestern South Pole-Aitken (SPA) basin, was formed in the pre-Nectarian. The Von Karman crater floor was subsequently flooded with one or several generations of mare basalts during the Imbrian period. Numerous subsequent impact craters in the surrounding region delivered ejecta to the floor, together forming a rich sample of the SPA basin and farside geologic history. We studied in details the targeted landing region (45.0-46.0 degrees S, 176.4-178.8 degrees E) of the 2018 Chinese lunar mission Chang'E-4, within the Von Kaman crater. The topography of the landing region is generally flat at a baseline of similar to 60 m. Secondary craters and ejecta materials have covered most of the mare unit and can be traced back to at least four source craters (Finsen, Von Karman L, Von Karman L', and Antoniadi) based on preferential spatial orientations and crosscutting relationships. Extensive sinuous ridges and troughs are identified spatially related to ea Jie crater (diameter = similar to 4 km). Reflectance spectral variations due to difference in both composition and physical properties are observed among the ejecta from various-sized craters on the mare unit. The composition trends were used together with crater scaling relationships and estimates of regolith thickness to reconstruct the subsurface stratigraphy. The results reveal a complex geological history of the landing region and set the framework for the in situ measurements of the CE-4 mission, which will provide unique insights into the compositions of farside mare basalt, SPA compositional zone including SPA compositional anomaly and Mg-pyroxene annulus, regolith evolution, and the lunar space environment. Plain Language Summary The South Pole-Aitken (SPA) basin on the farside of the Moon is the largest known impact structure in the solar system. It is the key area to answer several important questions about the Moon, including its internal structure and thermal evolution. We outline the geologic history of an important area (Von Karman crater) within SPA. In 2018,a new Chinese lunar mission Chang'E-4 (CE-4) will be the first to land in the Von Karman crater, within the SPA basin. The scientific instruments of CE-4, mounted on a lander and a rover, will analyze both surface and subsurface of this farside region. Here we present a detailed geological study of the selected landing region of CE-4, based on remote sensing data of the Moon. Our study identified several targets of high scientific interests and proposes testable hypotheses for the CE-4 mission.