Microstructures on Surfaces of Impact Glass Beads in Chang'e‐6 Regolith

Abstract 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.