CLOUDS OF JUPITER AND NH3-H2O AND NH3-H2S SYSTEMS

The structure and composition of clouds made up of ammonia- and water-bearing condensates are investigated for two principal compositional models for the atmosphere of Jupiter. The thermodynamics of the NH3H2O system are discussed, and it is shown that in every case the clouds are dominated by aqueous NH3 solution, while the topmost cloud layer must always be solid NH3. Water ice and pure liquid ammonia are shown to be very marginal cloud-forming condensates, and liquid ammonia is probably wholly absent from the clouds. Tenuous clouds of solid NH3·H2O and 2NH3·H2O may often be found just beneath the NH3 crystal clouds. A computational method for determining NH3H2O cloud compositions and structures and its applicability to Jupiter and Saturn are discussed. The structure of the NH4SH cloud layer is calculated for a solar-composition model of Jupiter's atmosphere, and a firm upper limit on the abundance of H2S above the solid NH3 cloud layer (XH2S {reversed tilde equals} 10-11) is found. The upper limit on the water vapor mixing ratio (XH2O {reversed tilde equals} 4 × 10-11) is calculated from the vapor pressure equation of 2NH3·H2O. © 1969.