Geochemistry of the Von Kármán crater floor and thickness of the non-mare ejecta over the Chang’e-4 landing area

1Dijun Guo,1,2,3Wenzhe Fa,4Xiaojia Zeng,1Jun Du,4,3Jianzhong Liu
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2021.114327]
1Institute of Remote Sensing and Geographical Information System, School of Earth and Space Sciences, Peking University, Beijing, China
2State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Macau, China
3CAS Center for Excellence in Comparative Planetology, Hefei, China
4Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China
Copyright Elsevier

China’s Chang’e-4 mission has carried out the first ever lunar farside landing exploration on the floor of the Von Kármán crater, a geologically complex region located in the most ancient and deepest South Pole-Aitken (SPA) basin. In order to demonstrate the characteristics of materials in the landing area, we investigated the regional geochemistry and thickness of non-mare ejecta overlaying the mare basalts. Comparative analyses of FeO, TiO2 and Th concentrations suggest that the landing site surface is dominated by non-mare ejecta from nearby craters (e.g., Finsen crater) with part of basaltic materials. The ejecta thickness is estimated based on the excavation depth of dark-haloed and non-dark-haloed craters by using support-vector machine, a supervised machine learning method for classification. The results show that the ejecta thickness in the region of 40 km across the landing site varies from near zero to ~80 m with a mean value of ~41 m. The ejecta at the CE-4 landing site is ~40 m thick, which is comparable to the in situ observations by the Lunar Penetrating Radar onboard the Yutu-2 rover. Our results provide valuable information for interpretation of the on-going returned data and geologic analysis of the Chang’e-4 exploration region.

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