THE APOLLO 17 ULTRAVIOLET SPECTROMETER - LUNAR ATMOSPHERE MEASUREMENTS REVISITED

Ultraviolet resonance fluorescence of solar radiation provides the most sensitive means of detecting the expected major constituents of the tenuous daytime lunar atmosphere. Such an experiment was carried out with the Apollo 17 Ultraviolet Spectrometer in December 1972 [Fastie et al, 1973b] and produced only upper limits to the number density of H, H2, O, C, N, CO and two noble gases near the surface of the moon. The complete data set of 47 terminator crossing observations, which were not utilized in the earlier analysis, has been re-examined and more stringent upper limits to the column emission rates for several species have been derived. These results, together with most recent values for the atomic and molecular fluorescence efficiencies, lead to more definitive limits on the content of the lunar atmosphere. The revised upper limit on atomic oxygen density allows for the possibility of comparable O/Na ratios in the atmosphere of both the Moon and Mercury.