The formation of a unique microstructure of minerals on the surface of airless bodies is attributed to space weathering. However, it is difficult to distinguish the contributions of meteorite impacts and solar wind to the modification of lunar soil, resulting in limited research on the space weathering mechanism of airless bodies. The thermochemical reactivity of troilite can be used to distinguish the contributions of impact events and solar wind to the modification of lunar soil and provide evidence for space weathering of lunar soil. We examined the structure of troilite particles in the Chang'e-5 lunar soil and determined whether an impact caused the thermal reaction. Microanalysis showed that troilite underwent substantial mass loss during thermal desulfurization, forming a crystallographically aligned porous structure with iron whiskers, an oxygen-rich layer, and other crystallographic and thermochemical evidence. We used an ab initio deep neural network model and thermodynamic calculations to conduct experiments and determine the anisotropy and crystal growth of troilite. The surface microstructure of troilite was transformed by the thermal reaction in the vacuum on the lunar surface. Similar structures have been found in near-Earth objects (NEOs), indicating that small bodies underwent the same impact-induced thermal events. Thus, thermal reactions in a vacuum are likely ubiquitous in the solar system and critical for space weathering alterations of the soil of airless bodies.

Facing the challenges of in-situ utilization of lunar regolith resources, applying an external electric field to manipulate lunar particles has become a promising method for space particle control, which mainly depends on the particle charging properties in the applied electric field. Using the surficial lunar regolith samples brought back from the Moon by the Chang'e-5 mission (CE5 LS), this work successively studied their charging properties, particle dynamics, and their collision damages to aerospace materials under the action of an external electric field in high-vacuum conditions. The results indicated that the charging process and electrostatic projection of lunar regolith particles under high-vacuum conditions were different from those under atmosphere conditions. The particle diameter range of CE5 LS used in the experiment is 27.7-139.0 lm. For electric field strength of 3-12 kV cm-1, the charge obtained by CE5 LS is 4.8 x 10-15- 4.7 x 10-13 C and the charge-to-mass ratio is 1.2 x 10-5-6.8 x 10-4 C kg-1. The CE5 LS is easier to be negatively charged in an external electric field. Furthermore, significant damages were observed on the target impact surfaces, indicating severe influences of lunar regolith particles on aerospace materials. Our work contributes to a more comprehensive understanding of physical mechanisms controlling the lunar regolith shielding and utilization, and will inspire broad efforts to develop the lunar in-situ engineering solutions. (c) 2024 THE AUTHORS. Published by Elsevier LTD on behalf of Chinese Academy of Engineering and Higher Education Press Limited Company. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).

Leading national space exploration agencies and private enterprises are actively engaged in lunar exploration initiatives to accomplish manned lunar landings and establish permanent lunar bases in the forthcoming years. With limited access to lunar surface materials on Earth, lunar regolith simulants are crucial for lunar exploration research. The Chang'e-5 (CE-5) samples have been characterized by state-of-the-art laboratory equipment, providing a unique opportunity to develop a high-quality lunar regolith simulant. We have prepared a high-fidelity PolyU-1 simulant by pulverizing, desiccating, sieving, and blending natural mineral materials on Earth based on key physical, mineral, and chemical characteristics of CE-5 samples. The results showed that the simulant has a high degree of consistency with the CE-5 samples in terms of the particle morphology, mineral and chemical composition. Direct shear tests were conducted on the simulant, and the measured internal friction angle and cohesion values can serve as references for determining the mechanical properties of CE-5 lunar regolith. The PolyU-1 simulant can contribute to experimental studies involving lunar regolith, including the assessment of interaction between rovers and lunar regolith, as well as the development of in-situ resource utilization (ISRU) technologies. (c) 2024 Published by Elsevier B.V. on behalf of China University of Mining & Technology. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).