Nickel isotopes in Apollo and Chang’e soils reveal widespread micrometeorite-driven processing of the lunar regolith

Abstract Micrometeorite bombardment is a fundamental surface process on the Moon and other airless bodies, driving elemental evaporation, isotopic fractionation, and material mixing in surface regoliths. Here, we report high-precision stable Ni isotope data for lunar soils returned by the Apollo (11, 12, 14, 15, 16, and 17) and Chang’e (5 and 6) missions, covering geographically and geologically diverse lunar terrains. The analyzed soils show δ 60/58 Ni values of 0.345‰ to 1.280‰ (relative to NIST SRM 986), generally heavier than lunar basalts and the inferred bulk silicate Moon, indicating widespread heavy Ni isotope enrichment during surface processing. Together with published Chang’e-5 drill-core data, these results demonstrate that micrometeorite-driven Ni isotope fractionation is widespread across the lunar surface. Local variability, however, reflects additional controls. The relatively low δ 60/58 Ni values of the immature Apollo 12 soils are consistent with limited cumulative micrometeorite processing, whereas the mature Apollo 16 soils have high Ni concentrations and Ni/Co ratios, indicating additional compositional overprinting by Ni-rich material. Stable Ni isotopes, particularly when combined with regolith maturity and Ni/Co ratios, therefore provide a sensitive tracer of micrometeorite-driven lunar surface processing and its local overprinting.