Abstract
Data obtained by the UV spectrophotometer experiments and the radio occultation experiments on Mariners 6 and 7 indicate an atomic oxygen concentration of about 3% in the upper atmosphere, an exospheric temperature of about 350K, and a very low solar EUV heating efficiency for Mars. Laboratory studies do not support mechanisms for rapid recombination of CO and O in the upper atmosphere. Transport appears to control the O concentration. However, there is still a problem of accounting for CO-O2 recombination in the lower atmosphere. A satisfactory self-consistent explanation of all of the Mariner and Venera upper atmosphere data for Mars and Venus still has not been produced. Difficulties with the presently recommended low EUV solar fluxes and high Martian airglow brightness are discussed.
