A tenuous, collisional atmosphere on Callisto

A simulation tool which utilizes parallel processing is developed to describe molecular kinetics in 2D, single-and multi-component atmospheres on Callisto. This expands our previous study the role of collisions 1D Callisto composed radiolytic products (Carberry Mogan et al., 2020) by implementing a temperature gradient from noon midnight across Callisto's surface and introducing sublimated water vapor. We compare single-species, ballistic collisional O2, H2 H2O atmospheres, as well an O2+H2O atmosphere 3-species contain varying amounts. Because vapor pressure extremely sensitive temperatures, density drops several order magnitude with increasing distance subsolar point, flow transitions accordingly. In local temperatures are determined near point transition being O2 When radiolytically produced not negligible O2+H2O+H2 this much lighter molecule, scale height roughly larger than that for heavier species, can cool via collisions. addition, if component dense enough, particles originating day-side precipitating into night-side deposit energy collisions, turn heats relative temperature. Finally, we discuss potential implications presence how simulated densities correlate expected detection thresholds at flyby altitudes proposed JUpiter ICy moons Explorer (JUICE) spacecraft.