Reports

Alpha Radioactivity of the Lunar Surface at the Landing Sites of Surveyors 5,6, and 7

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Science  27 Mar 1970:
Vol. 167, Issue 3926, pp. 1722-1724
DOI: 10.1126/science.167.3926.1722

Abstract

Evidence has been obtained for a radioactive deposit on the lunar surface at Mare Tranquillitatis with a total intensity of 0.09 ± 0.03 alpha disintegration per second per square centimeter. The presence of polonium-210 in amounts that are close to equilibrium indicates a continuous turnover rate of lunar material at this site of less than 0.1 micrometer per year. The lack of such a deposit at two other lunar sites suggests lower local concentrations of uranium there.