Structure of the Martian Upper Atmosphere.

We have computed a number of models of the Martian thermosphere with various constants and boundary values in the hydrostatic and heat-flux equations. The investigation is divided into two main parts. First, we have varied the basic parameters, one or two at a time, to find to what extent an uncertainty in one of these fundamental parameters affects the derived exospheric temperature and other characteristics of the upper atmosphere These models are physically oversimplified but mathematically serve their purpose. Second, with selected specific chemical compositions, we have integrated the equations with allowance for diffusive separation and absorption of sunlight in different spectral regions A rather detailed and general discussion is included of the efficiency with which photon energy is converted into the kinetic energy of heat in the neutral atmosphere. The computed models are thought to be fairly representative of an actual atmosphere with the assumed compositions. It appears that CO vibrational excitation is not so important as a thermostat as was previously suggested, but the rotational levels of CO, and to a smaller extent the fine-structure levels of the ground term of 0, may cause appreciable radiation loss. Direct observation of the Martian corona in the X 1302 resonance radiation of 0 1 should be possible and would allow the main present uncertainties to be removed.