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.

¹M.R.M.Izawa,^2,3P.L.King,⁴P.Vernazza,^3,5J.A.Berger,³W.A.McCutcheon
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2021.114328]
¹Institute for Planetary Materials, Okayama University – Misasa, 827 Yamada, Misasa, Tottori 682-0122, Japan
²Research School of Earth Sciences, Australian National University Canberra, ACT 2601, Australia
³Inst. Meteoritics, Univ. New Mexico, Albuquerque, NM 87131, USA
⁴Lab. d’Astrophys. de Marseille, Pôle de l’Etoile Site de Château-Gombert 38, Marseille cedex 13, France
⁵NASA Johnson Space Center, 2101 E NASA Pkwy, Houston, TX 77058, United States
Copyright Elsevier

Salt-rich deposits may be more widespread on planetary surfaces than is generally appreciated. Remote observations, laboratory studies of meteorites, and cosmochemical constraints all point towards widespread occurrences of salts (including halides, sulfates, and (bi)carbonates) on asteroids, icy bodies, Mars, and elsewhere. We have investigated the mid-infrared (1.8–25 μm) reflectance spectral properties of mixtures of chondritic (ordinary, enstatite and carbonaceous) meteorites with potassium bromide; a mid-infrared transmissive salt like all halides. Our results demonstrate that halide-chondrite mixtures provide spectral signatures that either reveal the presence of transmissive materials or provide evidence for highly porous regolith. Previously, the nature of the surfaces of the asteroids 624 Hektor and 21 Lutetia was inferred using a limited range of spectra from halide-chondrite mixtures. Here, we provide an extensive dataset of halide-chondrite mixtures to encompass a wider set of possible surface compositions.