¹Zhi Cao, ¹Pan Yan, ¹Zhiyong Xiao, ²Yanxue Wu, ³Haiyang Xian, ¹Yunhua Wu, ⁴Lifeng Zhong, ⁵Dengfeng Li, ²Mingchao Xiong, ²Zilei Chen
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.70229]
¹Planetary Environmental and Astrobiological Research Laboratory, School of Atmospheric Sciences, Sun Yat-sen University, Zhuhai, China
²State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Macau, China
³CAS Key Laboratory of Mineralogy and Metallogeny/Guangdong Provincial Key Laboratory of Mineral Physics and Materials, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences (CAS), Guangzhou, China
⁴Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, China
⁵Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering, School of Marine Sciences, Sun Yat-sen University, Zhuhai, China
Published by arrangement with John Wiley & Sons

Microstructures on surfaces of lunar regolith particles record intricate processes during regolith formation and evolution. To acquire the complete morphology and composition of microstructures on surfaces of Chang’e-5 and Chang’e-6 regolith particles, the selected particles were rotated, cleaned using anhydrous ethanol, and loaded into electron microscopes for multiple rounds of analysis. During sample analysis, we noticed a few unusual features on the surfaces of the particles, including ferric-rich iron oxides and NaCl and KCl crystals. These features exhibit overlapping relationships with other microstructures, similar to those formed on the Moon. By comparing the before and after scanning electron microscope (SEM) images, we confirmed that these features resulted from the oxidation of metallic iron particles in the Earth atmosphere and the adhesion of terrestrial contaminants. Our results demonstrate that localized alteration and contamination of lunar regolith samples, although rare, may occur during a limited exposure to the Earth atmosphere, which might hamper interpretations of sample analysis. This work highlights the importance of full-process environmental protection (e.g., inert gas, constant temperature) for pretreatment, transfer and analysis of extraterrestrial samples.