Rare Gas Record in the Largest Apollo 15 Rock

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Science  28 Jan 1972:
Vol. 175, Issue 4020, pp. 421-422
DOI: 10.1126/science.175.4020.421


The spallation krypton data from rock chip 15555,23 indicate a wellshielded location during most of the time during which the rock was exposed to cosmic rays. A krypton-krypton exposure age of 81+17-7 x 106 years is calculated, and the gas retention ages are estimated. No evidence for the presence of products from plutonium-244 or iodine-129 was found.