The relation between the geophysical activity of the Saturnian satellites and the Cassini Division

The Cassini Division is a 4,500 km wide gap in the rings of Saturn, which inner edge is at the exact 2:1 Inner Lindblad Resonance with Mimas. We here present our latest results regarding the formation and the stability of the Division, in combining N-body simulations of the main satellites of Saturn with hydrodynamical simulations of the rings, with the 1-D code Hydrorings (Charnoz et al. 2011). We show that an inward migration of Mimas over 8,000 to 9,000 km would create the Division in less than 10 Myr, and we get a final mass distribution in the rings that would look like the density distribution derived from optical depth observations assuming a uniform mass extinction coefficient for the ring particles. We also investigated two sources of inward migration of Mimas, i.e. an intense dissipation of Mimas, and an intense dissipation in Enceladus which would have been locked in a mean-motion resonance with Mimas, provoking the inward migration of the two satellites. The scenario involving a past intense dissipation in Mimas keeps the system of Saturn stable, but is inconsistent with the observed age of the surface of Mimas. However, a past intense dissipation in Enceladus is acceptable from a geophysical point of view owing to its present activity, but would have required an eccentricity so high that the system of Saturn would have been destabilized.