Composition and Provenance of the Chang’e-4 Landing Area

This study systematically analyzes the composition and origin of materials in the Chang’e-4 landing area (Von Kármán crater) using 131 in-situ lunar soil spectra from the first 60 lunar days obtained by Visible and Near-infrared Imaging Spectrometer onboard Yutu-2 rover and spectral data from the Moon Mineralogy Mapper (M³). Results show that the 2μm absorption center of the landing area aligns with that of Finsen ejecta, while the 1μm absorption center shifts toward longer wavelength, suggesting an enrichment in olivine or glass of the landing area. The surface materials at the landing area might originate from the distal ejecta of Finsen crater.

Based on the Chang'e-2 Digital Orthophoto Map(DOM) data and the geological characteristics along the traverse area of Yutu-2 rover, we found that the rock types in and around the Von Kármán crater can be classified into three categories. (1)Basalts formed in two different periods. The late-stage basalt is flood lava (approximately 320m thick), originating from Leibniz crater. The old basalts represent the basement rock at the bottom of Kármán crater; (2)Widely distributed weathered deposits. Although their spectra are similar to those of Finsen ejecta, these deposits are located at the distal end of the ejecta rays, exhibit variable thickness, and reveal local fragmented blocks beneath them. This suggests that the deposits likely represent a mixture of ejecta material and local substrate; (3) Highland rocks. The basement rocks that predate the Von Kármán and Von Kármán M craters are represented by a large number of highland rocks, which form the rim plateau around the Von Kármán crater. The distal position and heterogeneous thickness of the Finsen ejecta at the landing area indicate that the Finsen-forming impact event only modified the composition of landing area surface regolith at millimeter- to centimeter-scale depths, without causing significant topographic alteration.