Cosmogenic and Primordial Radionuclides in Lunar Samples by Nondestructive Gamma-Ray Spectrometry

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Abstract
The 7Be, 22Na, 26Al, 44Ti, 46SC, 48V 51Cr, 54Mn, 56Co, 57Co, 57CO, 40K, 238U, and 232Th were measured in lunar fines and portions of three rocks. Major production of cosmogenic radionuclides is due to solar protons, thus their concentrations are far different than those in meteorites. Surface exposures of the rocks and fines are long compared with the 0.74 million year half-life of 26Al. Lunar fines show substantially higher concentrations of low energy reaction products. The ratios of thorium to uranium are extremely constant at 3.8, which indicates very little geochemical differentiation and are in good agreement with a common nucleosynthesis for lunar and earth materials.