Particles, environments, and possible ecologies in the Jovian atmosphere

The eddy diffusion coefficient is estimated as a function of altitude, separately for the Jovian troposphere and mesosphere. The growth-rate and motion of particles is estimated for various substances: the water clouds are probably nucleated by NH/sub 4/Cl and sodium compunds are likely to be absent at and above the levels of the water clouds. Complex organic molecules produced by the L..cap alpha.. photolysis of methane may possibly be the absorbers in the lower mesosphere which account for the low reflectivity of Jupiter in the near-ultraviolet. The optical frequency chromophores are localized at or just below the Jovian tropopause. Candidate chromophore molecules must satisfy the condition that they are produced sufficiently rapidly that convective pyrolysis maintains the observed chromophore optical depth. Organic molecules and polymeric sulfur produced through H/sub 2/S photolysis at lambda>2300 A probably fail this test, even if a slow, deep circulation pattern, driven by latent heat, is present. The condition may be satisfied if complex organic chromophores are produced with high quantum yield by NH/sub 3/ photolysis at lambda<2300 A. However, Jovian photoautotrophs in the upper troposphere satisfy this condition well, even with fast circulation, only biochemical properties of comparable terrestrial organisms are assured. Unless buoyancy canmore » be achieved, a hypothetical organism drifts downward and is pyralyzed. An organism in the form of a thin, gas-filled balloon can grow fast enough to replicate if (i) it can survive at the low mesospheric temperatures, or if (ii) photosynthesis occurs in the troposphere. If hypothetical organisms are capable of slow, powered locomotion and coalescence, they can grow large enough to achieve buoyancy. Ecological niches for sinkers, floaters, and hunters appear to exist in the Jovian atmosphere.« less