An Analysis of the Spectrum of Mars

On a high-dispersion spectrogram of Mars taken at Mount Wilson rotational lines of H_2O near λ 8300 and CO_2 near λ 8700 have been detected. Recent laboratory measurements of line strengths by D. Rank have been used to determine the amounts of H_2O and CO_2 in the atmosphere of Mars: 14 ± 7 μ precipitable water and 55 ± 20 m atm CO_2. From the absence of O_2 in the Martian spectra, we set an upper limit of 70 cm atm for the O_2 content. By suitably combining the CO_2 amount with observations by Kuiper and Sinton of the strongly saturated bands in the 2-μ. region, a surface pressure of 25 ± 15 mb has been derived. The implications of the results on the composition of the Martian atmosphere are discussed