Potassium Isotopic Compositions of Lunar Soils and K Isotope Model Exposure Age ...

Space weathering has long been known to alter the chemical and physical properties of the surfaces of airless bodies such as the Moon. The isotopic compositions of moderately volatile elements in lunar regolith samples could serve as sensitive tracers for assessing the intensity and duration of space weathering. In this study, we develop a new quantitative tool to study space weathering and constrain surface exposure ages based on potassium isotopic compositions of lunar soils. We first report the K isotopic compositions of 13 bulk lunar soils and 20 interval samples from the Apollo 15 deep drill core. We observe significant K isotope fractionation in these lunar soil samples, ranging from 0.00‰ to +11.77‰, compared to the bulk silicate Moon (–0.07 ± 0.09‰). Additionally, a strong correlation between soil maturity and K isotope fractionation is identified for the first time, consistent with other isotope systems of moderately volatile elements such as S, Cu, Zn, Se, and Cd. Subsequently, we conduct numerical ...