GEOCHEMICAL MODEL OF VENUS TROPOSPHERE

A geochemical model of the Venus troposphere (0-65 km) based on a theoretical generalization of the available instrumental data and equilibrium calculations in the OHCNS system is proposed. The model is based on the concept of geochemical zoning of the troposphere. The upper zone [above ∼50 ± (2-3) km] is characterized by the predominance of photochemical processes and presumably is comprised of sulfuric acid clouds. The lower zone [below ∼33 ± (2-3) km] is characterized by the predominance of thermochemical processes assumed to be in complete (below) or limited (above) equilibrium. The intermediate zone (from ∼33 to 50 km) represents a zone of mixing of photochemical and thermochemical reaction products. Complexity and nonstability of the microcomponent gaseous and condensate compositions as well as the occurence of redox transformations are considered to be the major features of this zone. The ammonia salts, sulfur, and some complex organic compounds are suggested as probable cloud condensate particles in this zone. The proposed vertical geochemical zoning is modified in relation to diurnal variations. The lower non-sulfuric acid cloud layer practically disappears at noon with the predicted corresponding decrease of mixing ratios of reduced gases (e.g., NH3, CO, H2) within the intermediate zone. The lower cloud layer is restored at night. © 1978.