The Upper Atmosphere of Venus: A Review

Abstract

The implications of recent data on Venus obtained by Mariner 5, Venera 4 and ground based observations for the aeronomy of Venus is received. The theoretical thermal structure model of McElroy based on a pure CO₂ atmosphere is in good agreement with the temperature deduced from the hydrogen distribution obtained by Mariner 5. No credible mechanism has been devised to recombine CO and O to CO₂ in the upper atmosphere. It is suggested that O₂ is formed but that CO and O₂ recombine to CO₂ in the dense atmosphere far enough above the cloud tops to agree with abundance measurements. Serious difficulties exist for the H₂ model of the upper atmosphere. It is suggested that deuterium can account for the anomalous Lyman α glow observed by Mariner 5 without implying a large D/H planetary ratio. Other problems such as the maintenance of the ionosphere at night and the escape of water are discussed.