Geological characterization of the Chang'e-4 landing area on the lunar farside

On January 3, 2019, China's Chang'e-4 probe, accomplishes the first-ever soft landing on Moon's farside in the Von Karman crater floor mare volcanism plain (177.59 degrees E, 45.46 degrees S) within the South Pole-Aitken (SPA) basin. Its surface in-situ measurements would provide the first ground truth for lunar farside volcanism and SPA materials. We present a detailed geologic context, topographical, morphological, quantitative geochemical and mineralogical characterization of a 20 x 20 km area centered at the Chang'e-4 landing site, using the latest multi-source high-resolution orbital data sets. The landing area is very flat at a baseline of 30 m, with 90% of surface having slope < 5 degrees, and deficient of surface boulder exposures. The landing area mare is superposed by abundant sub-kilometer, block-poor circular impact craters and secondary craters in chains and clusters. Mare basalts at the landing site is dominated by low-titanium basalts, and appear to be less mafic and iron-depleted than all typical kinds of retuned lunar basalt samples and may represent a new kind of mare basalt. The landing site mare is heavily sculptured by a set of linear parallel ridged and furrowed textures formed by ballistic ejecta from the Finsen crater, which are characterized by a more feldspathic composition, while with elevated orthopyroxene abundance, and may represent compositional properties of the primitive SPA basin floor materials. We propose the Finsen ejecta and mare basalt outcrops at the landing area as prioritized targets for Chang'e-4 surface geological and spectroscopic explorations. Follow-on mission data interpretations should consider the mixing effect of local mare basalts and distant feldspathic materials.