A recent origin for Saturn's rings from the collisional disruption of an icy moon

TL;DR

This paper proposes that Saturn's rings originated from the collisional disruption of an icy moon, which also led to the formation of Mimas, explaining the rings' high ice content and current configuration.

Contribution

It introduces collisional N-body simulations showing how a disrupted icy moon can produce Saturn's rings and a new moon, Mimas, with a detailed evolutionary scenario.

Findings

Ring material is primarily icy debris from moon disruption.

Mimas likely formed from re-accretion of debris after impact.

The scenario explains the high ice fraction and current orbital positions.

Abstract

The disruption of an icy moon in a collision with an interloping comet a few hundred million years ago is a simple way to create Saturn's rings. A ring parent moon with a mass comparable to Mimas could be trapped in mean motion resonance with Enceladus and Dione in an orbit near the current outer edge of the rings just beyond the Roche zone. I present collisional N-body simulations of cometary impacts that lead to the partial disruption of a differentiated moon with a rocky core and icy mantle. The core can survive largely intact while the debris from the mantle settles into a ring of predominantly ice particles straddling the orbital radius of the parent moon. The nascent ring spreads radially due to collisional viscosity while mass re-accretes onto the remnant rocky core to form a new moon that can be identified as Mimas. The icy debris that migrates into the Roche zone evolves into Saturn's ring system. Torques from tidal interaction with Saturn and resonant interactions with the rings push the recently formed Mimas outward to its current position on the same timescale of a few hundred million years. This scenario accounts for the high ice fraction observed in Saturn's rings and explains why the ring mass is comparable to the mass of Mimas. The prior existence of a ring parent moon in mean motion resonance results in a tidal heating rate for Enceladus in the recent past that is significantly larger than the current rate.