Abstract Analysis of space weathering features in lunar regolith using transmission electron microscopy (TEM) allows researchers to characterize the surface exposure timescale of individual grains from the Moon. TEM analysis of regolith grains from Apollo 17 scoop samples, collected from five different locations in the Taurus‐Littrow Valley (TLV), each with unique surface exposure histories, was conducted. Results show that the extent of space weathering in both mature and immature soil is significant and demonstrate that non‐agglutinitic grains in the samples have almost all experienced exposure to interplanetary space on the lunar surface. Solar energetic particle (SEP) track density derived exposure age distributions, when compared to observations from lunar core samples and regolith development models, suggest evidence of varying degrees of regolith mixing and overturn on the surface of the Moon. Exposure age distributions may be indicative of mixing of mature and immature regolith. Median exposure ages for mature soils saturate between 2.0 and 3.0 Ma while mean values will continue to increase with continued exposure on the lunar surface. The saturation of median exposure ages for individual grains may be attributed to high rates of reworking on the top millimeter of regolith. Recent analysis of LROC reflectance images found that the TLV light mantle could form from reoccurring landslide events. Maximum SEP exposure ages for particles in light mantle soils appear to indicate the relative landslide depositional order. Together, these observations can be used to interpret the mixing and depositional histories of geologic units in the TLV.
McFadden et al. (2026) studied this question.