Séminaire de l'INPHYNI: Aurélien Crida

Since their discovery in the XVIIth century, Saturn's rings have fascinated by their beauty and their brightness. After a review of the whole Saturnian system with amazing picture by the Cassini spacecraft, the physics of the rings will be discussed, with a particular focus on the question of their age. A few years ago, the measure of their mass by the Cassini spacecraft led some american colleagues to conclude that they are a recent feature, maybe dating back from the dinosaurs era on Earth! However, this conclusion is based on assumptions that are not necessarily justified, and an other interpretation is possible.

The bombardment by interplanetary dust particles has two main effects: pollution of the 99% water-ice rings, and deceleration of the ice blocks on their orbits. With Gregorio Ricerchi, we have shown that these effects have been dramatically over-estimated by previous studies, reconciling the observations with rings potentially as old as the Solar System. This is important because it allows for all Saturn's regular satellites to be formed from the slow spreading of the rings beyond the Roche radius, explaining their peculiar mass-distance distribution.