The origin and evolution of planetary rings

Roche (1847) suggested that Saturn's rings may be the fragments of a disrupted satellite rather than the uncoagulated remnant of a circumplanetary disk from which the regular satellites formed. In order to address this unresolved central issue, attention is given to the dynamical processes of viscous spreading, gas drag, particulate coagulation, and the effect of further matter infall from heliocentric orbit onto the planet/disk, all of which act on a gas/solid disk in Keplerian motion. In view of these considerations, it is suggested that rings were created by the disruption of large satellites which were less sensitive to the destructive processes present during the planet's formation. This hypothesis explains the presence of shepherd satellites, such as large collision fragments, which coexist in the same orbital range as the ring particles.