Ridge Formation and De-Spinning of Iapetus via an Impact-Generated Satellite

TL;DR

This paper proposes a new impact-based scenario for forming Iapetus's equatorial ridge and de-spinning it rapidly by creating a debris disk and satellite that interacts with the planet.

Contribution

It introduces a novel impact-driven mechanism involving a debris disk and satellite to explain Iapetus's ridge formation and spin-down, faster than tidal effects alone.

Findings

Impact-generated satellite can de-spin Iapetus faster than Saturn tides.

Satellite eventually stripped by Saturn, ending its influence.

Impact scenario aligns with Iapetus's impact history estimates.

Abstract

We present a scenario for building the equatorial ridge and de-spinning Iapetus through an impact-generated disk and satellite. This impact puts debris into orbit, forming a ring inside the Roche limit and a satellite outside. This satellite rapidly pushes the ring material down to the surface of Iapetus, and then itself tidally evolves outward, thereby helping to de-spin Iapetus. This scenario can de-spin Iapetus an order of magnitude faster than when tides due to Saturn act alone, almost independently of its interior geophysical evolution. Eventually, the satellite is stripped from its orbit by Saturn. The range of satellite and impactor masses required is compatible with the estimated impact history of Iapetus.