Water Transport from Enceladus to the Rings

Abstract Enceladus continuously ejects approximately 300 kg s −1 of water vapor from its south polar regions, forming an extensive neutral gas torus around Saturn. In this study, we use the direct simulation Monte Carlo method to model the detailed spatial structure of this neutral torus, explicitly incorporating major loss processes, including photolysis, charge exchange, and electron-impact reactions. Our results demonstrate that molecular collisions and chemical reactions significantly enhance the radial and vertical spreading of water-group molecules within the Saturnian system. Specifically, our calculations indicate that 40% of the water-group neutrals emitted by Enceladus’ plumes impact Saturnian rings, with a roughly estimated deposition of 0.03 mm of icy material over one million years. These findings provide insight into the physical and chemical processes that govern Enceladus' neutral torus environment, including implications for the composition of rings and their evolution.