A numerical study of dust distribution in the Enceladus' atmosphere

Enceladus, which is the major source of gas and dust particles in the E-ring of Saturn, became an object of considerable interest after the discovery of its geological activity during the 2005 Cassini flybys. The measurements performed during the flybys have indicated a significant compositional and spatial variation in the gas phase and a presence of dust particles of a micrometer size in the Enceladus' atmosphere. It is believed that the highly nonuniform gas production observed during the flybys is associated with the geological activity and is released by the active geysers located in the south polar region. In addition to being the source of gas detected by the in situ measurments, the geysers produce dust grains seen by the remote sensing instruments. The numerical study presented in this work is performed with a newly developed kinetic model of the Enceladus' atmosphere developed on the basis of the Direct Simulation Monte-Carlo method. A multi vent gas source for the geysers' gas production into the atmosphere has been modeled. In addition to the gas phase, a flow of dust grains is also considered. The dynamics of dust particle flow is determined by its momentum exchange with the surrounding gas environment. The unique element of the model is the self-consistent treatment of a multispecie 3D flow of gas and dust grains with the dust and gas phases being coupled through sublimation/recondensation and momentum exchange. The water number and column density are calculated for conditions that are compared with the available Cassini INMS and UVIS data.