Spectroscopy and Acronomy of O2 on Mars

Abstract

High-dispersion photoelectric spectra have been taken of four oxygen A band lines. Synthetic spectra have been calculated, and ratios of the Martian spectra with the synthetic spectra have been taken to enhance any possible Martian lines. The noise level of the spectra is equivalent to about 20 cm-atm of O2. No features this size appear consistently at the expected locations. A simple model including the extra oblateness of the planetary surface and a higher albedo for the polar cap region, results in an effective air factor of 4. This places an upper limit of 5 cm-atm on the abundance of O2 and of 7?10?4 on the mixing ratio. Comparison with recent positive detections by others suggests that the O2 abundance may be variable; and the O3 abundance has been shown to vary by Mariner 9. An aeronomical model incorporating water vapor accounts for the ozone data and qualitatively supports the possibility of variable O2. Large amounts of H2O2 are predicted, and its photolysis provides a copious source of OH to oxidize CO. This sequence appears to account for the low abundances of O2 and CO on Mars, and the corresponding stability of CO2.