^1,2Liyu Shan, ¹Heng-Ci Tian, ¹Yangting Lin, ¹Wei Yang, ¹Xu Tang, ¹Lixin Gu
Icarus (in Press) Open Access Link to Article [DOI: 10.1016/j.icarus.2026.117330]
¹Key Laboratory of Planetary Science and Frontier Technology, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
²University of Chinese Academy of Sciences, Beijing 100049, China
Copyright Elsevier

Recent studies of the returned Chang’e-5 (5CE) and Chang’e-6 (6CE) lunar soils have revealed differences in space weathering between the nearside and farside of the Moon, yet the relative roles of meteorite impacts and solar wind (SW) irradiation remain debated. Here we report new microstructural observations of eleven 6CE lunar soils, which were previously shown to contain SW-derived water contents within their grain rims. Combined with published data from 6CE and 5CE soils at similar latitudes, our results demonstrate that despite variations among mineral types, the average solar flare track density and mean amorphous layer thickness of 6CE samples are both comparable to those of 5CE samples, implying similar exposure ages at the two landing sites. Moreover, water contents in the grain rims are also comparable between the two sample suites. These similarities in exposure ages, amorphous layer thicknesses, and rim water contents suggest that the contribution of SW to space weathering is remarkably consistent between the two landing sites. In addition, we find that lunar surface water content reaches a time-dependent dynamic equilibrium after ~0.5 Myr, with higher water contents at mid-latitudes than at low latitudes. Meanwhile, long-term micrometeoroid impacts play an important role in modulating the total water content of SW-derived water within the bulk lunar regolith.