The significance of lunar glass beads for future resource exploration revealed by Chang'e-5 samples

Glass beads formed from impact melt and vapor are extensively distributed in the lunar regolith samples, containing much information about protolith composition, regolith formation and reworking. However, their understanding is often controversial due to the diversity of their sources and the complexity of later modifications. Recent returned Chang’e-5 regolith provide a unique opportunity to understand microscopic mechanism of regolith reworking and contribution of exotic components because of their shorter gardening history and exposure time. In this study, we present 256 glass beads selected from 1700 mg Chang’e-5 regolith and characterized their representative microstructures. A series of textures such as microcraters, linear scratches and bonded silicate are observed on the surface of impact glass beads, which mainly originate from the low-speed impacts of micrometeorites and their sputtered products to in-situ materials. The major and trace elements data of two sample groups of Chang’e-5 local glass beads with different textures show that homogeneous glass beads are mainly characterized by linear element loss while heterogeneous glass exhibits element redistribution with certain minerals. Based on relatively stable elements, 71 exotic glass beads were identified and divided into seven subtypes, which are associated with impact and transported materials from other regions on the Moon, tens to hundreds of kilometers away from Chang’e-5 landing site. These results indicate that the influence of large-scale impacts might be the major factor for regolith transformation including the addition of exotic materials or alterations in elements. In contrast, the small-scale impacts mainly in-situ transformed the morphology on regolith particles. The production and formation of these glass beads indicate the direction for future exploration of lunar resources