Cosmic ray irradiation patterns of Luna 16 and 20 soils: implications to lunar surface dynamic processes

Abstract

Comprehensive fossil track data in mineral grains from several horizons of Luna 16 and 20 cores are presented. The cosmic ray irradiation of Luna 16 soil is distinctly different from Luna 20 soil, the former being more intensely irradiated. Track data for Luna 16/20 samples are compared with those for samples collected from different lunar mare and highland sites. Luna 20 track density distribution patterns are similar to those observed at other lunar sites. However, Luna 16 data are at variance and necessitate a complex irradiation history. Various suggestions made so far for explaining the high irradiation dose of Luna 16 samples appear inadequate. The possibility that the regolith growth at the Luna 16 site is governed by a different mechanism, to some extent controlled by the local topography, is discussed.