A recent impact origin of Saturn's rings and mid-sized moons

TL;DR

This study uses high-resolution simulations to explore how collisions between icy moons could have generated Saturn's young rings and affected its moons' evolution, suggesting impacts as a key ring formation mechanism.

Contribution

It demonstrates that moon collisions can produce debris and ejecta capable of forming or rejuvenating Saturn's rings, a novel impact-based origin scenario.

Findings

Impacts can place pure-ice ejecta into Saturn's Roche limit.

Fragments of rock and ice can be scattered onto orbits intersecting moons.

Impact debris could lead to moon disruption and ring formation.

Abstract

We simulate the collision of precursor icy moons analogous to Dione and Rhea as a possible origin for Saturn's remarkably young rings. Such an event could have been triggered a few hundred million years ago by resonant instabilities in a previous satellite system. Using high-resolution smoothed particle hydrodynamics simulations, we find that this kind of impact can produce a wide distribution of massive objects and scatter material throughout the system. This includes the direct placement of pure-ice ejecta onto orbits that enter Saturn's Roche limit, which could form or rejuvenate rings. In addition, fragments and debris of rock and ice totalling more than the mass of Enceladus can be placed onto highly eccentric orbits that would intersect with any precursor moons orbiting in the vicinity of Mimas, Enceladus, or Tethys. This could prompt further disruption and facilitate a collisional cascade to distribute more debris for potential ring formation, the re-formation of the present-day moons, and evolution into an eventual cratering population of planeto-centric impactors.