Significantly elevated Ni isotope compositions in the Chang’e-5 drill core reveal continuous micrometeorite-dominated space weathering of the young lunar surface
Siyu Li, Yingnan Zhang, Ziwei Wang, Bing Yang, Liping Qin
Geochimica et Cosmochimica Acta
Available online 6 August 2025
“Space weathering alters the chemical and isotopic compositions of the lunar surface, potentially obscuring insights into the formation and evolution of the Moon and terrestrial planets. The contribution of micrometeorite bombardment to the space weathering process, however, is poorly understood. In this study, the Ni isotopic composition of the Chang’e-5 regolith from different depths of a drilling core was studied to examine both the meteoritic addition and evaporation within the local regolith. The Chang’e-5 lunar drill core samples exhibit significantly elevated Ni abundances and higher δ60Ni values (0.54–1.06 ‰) compared to lunar basalt samples (0.18 ± 0.01 ‰), indicating preferential loss of isotopically light Ni due to impact-induced evaporation of high-Ni-content impactors. Notably, the δ60Ni values decrease significantly with depth, while Ni content remains unchanged, suggesting that continuous micrometeorite bombardment, rather than simple mixing of evaporated impactor material, is responsible for the observed Ni isotopic fractionation. Based on the Ni/Co and the Ni isotopic compositions, we estimate that the primary micrometeorite impactors at the Chang’e-5 site are chondritic, contributing ∼1–2 wt% of the regolith, while ∼10–30 % of the Ni from the impactors was evaporated under near-saturated conditions. This process preferentially enriches the upper regolith in heavier Ni isotopes during more extensive micrometeorite bombardment, supporting continuous space weathering processes in relatively young regolith at the Chang’e-5 landing site. These findings not only highlight the long-term effects of micrometeorite-impact-induced degassing during the space weathering on the lunar surface but also provide new insights into regolith gardening and the progressive surface modification of airless planetary bodies.”
