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Production rates of cosmogenic helium‐3, neon‐21, and neon‐22 in ordinary chondrites and the lunar surface

Abstract— The production of 3He, 21Ne, and 22Ne in meteoroids of various sizes and in the lunar surface was investigated. The LAHET code system, a purely physical model for calculating cosmic‐ray particle fluxes, was used to simulate cosmic‐ray particle interactions with extraterrestrial matter. We discuss the depth and size dependence of the shielding parameter 22Ne/21Ne, which is used for reconstruction of pre‐atmospheric sizes, depth, and exposure histories. The 22Ne/21Ne ratio decreases with increasing depth or pre‐atmospheric size but then increases with depth in very large objects. This increase with depth in the 22Ne/21Ne ratio means that this ratio is a poor indicator of shielding in some large objects. The dependence of 3He/21Ne as function of 22Ne/21Ne was also calculated, and differences between the calculations and the Bern line are discussed.