^1,2Haojin Hu,^1,3Xiaojia Zeng,⁴Yanxue Wu,¹Yuanyun Wen,^1,5Xiongyao Li,^1,5Jianzhong Liu
Journal of Geophysical Research (Planets)(in Press) Link to Article [https://doi.org/10.1029/2024JE008868]
¹Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China
²University of Chinese Academy of Sciences, Beijing, China
³State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Macau, China
⁴Analysis and Test Center, Guangdong University of Technology, Guangzhou, China
⁵CAS Center for Excellence in Comparative Planetology, Hefei, China
Published by arrangement with John Wiley & Sons

The continuous bombardment of lunar surfaces by asteroids and comets has modified the chemical, mineralogical, and physical properties of the lunar crust. Oxidizing agents from these impactors could alter the redox conditions on the Moon. However, no Fe3+-bearing phase crystallized from impact melt has been reported in the lunar regolith. In this study, a submicron-sized magnetite grain was observed in lunar impact glass from the Chang’e-5 regolith breccia. Our results demonstrate that this magnetite was directly crystallized from the lunar impact melt under oxidizing conditions (IW‒WM buffer). We propose that these impact events could play a role in altering the oxidizing conditions of the lunar crust. Furthermore, impact-melt-crystallized magnetite grains may contribute to some extent to lunar magnetic anomaly signatures, but they are likely a very minor component relative to Fe-Ni alloys.

¹Pan Yan,¹Zhi Cao,¹Zhiyong Xiao,²Yanxue Wu,¹Yunhua Wu,²Mingchao Xiong,²Zilei Chen,³Lifeng Zhong,⁴Dengfeng Li,⁴Qiaofen Liu
Journal of Geophysical Research (Planets)(in Press) Link to Article [https://doi.org/10.1029/2025JE008945]
¹Planetary Environmental and Astrobiological Research Laboratory, School of Atmospheric Sciences, Sun Yat-Sen University, Zhuhai, China
²Analysis and Test Center, Guangdong University of Technology, Guangzhou, China
³Southern Marin Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, China
⁴Guangdong Province Key Laboratory of Marine Resources and Coastal Engineering, School of Marine Sciences, Sun Yat-Sen University, Zhuhai, China
Published by arrangement with John Woiley & Sons

Microstructures are widespread on the surfaces of impact glasses in lunar regolith, recording intricate physical and chemical processes of regolith gardening. The Chang’e-6 mission returned the first regolith sample from the lunar farside, permitting investigation of regolith gardening on the farside and comparison with that on the nearside. Among over 400 glass particles handpicked from 1,500 mg of Chang’e-6 regolith, we investigated 178 impact glass beads, which were recognized based on their morphology, internal structure and geochemistry. The morphology and chemical compositions of microstructures on their surfaces are cataloged and compared with those reported on surfaces of lunar nearside samples, especially Chang’e-5 impact glasses. The various types of microstructures on surfaces of Chang’e-5 impact glasses are also observed on Chang’e-6 impact glasses, although the latter frequently exhibit a greater diversity of morphology and composition. The observations suggest that physical processes of regolith gardening are similar on the nearside and farside, which involve vapor, melt and/or solid phases, and with collision speeds much lower than those of extralunar impactors. On the other hand, there are other morphological types of microstructures on the surfaces of Chang’e-6 impact glass beads that were absent or rare on Chang’e-5 glasses, but they were reported on Apollo and Luna impact glasses. Their origin may be related to the older emplacement ages and/or more abundant exotic components in the protolith of Chang’e-6 regolith than that of Chang’e-5 regolith. During regolith gardening, chemical alterations of protoliths are nonuniform across the Moon, which are related to the contents of exotic components in the regolith.