Evidence for a Past Martian Ring from the Orbital Inclination of Deimos

TL;DR

This study proposes that Deimos's high orbital inclination resulted from an ancient massive ring of Mars interacting with a now-absent inner satellite, supporting the cyclic ring-satellite hypothesis and suggesting different surface ages for Phobos and Deimos.

Contribution

It provides numerical evidence that Deimos's inclination can be explained by resonance with a past massive ring, supporting the cyclic ring-satellite hypothesis.

Findings

Deimos's inclination can be generated by resonance with a past massive ring.

The ring-satellite interaction suggests Deimos is about 3.5-4 Gyr old.

Phobos is likely significantly younger than Deimos.

Abstract

We numerically explore the possibility that the large orbital inclination of the martian satellite Deimos originated in an orbital resonance with an ancient inner satellite of Mars more massive than Phobos. We find that Deimos's inclination can be reliably generated by outward evolution of a martian satellite that is about 20 times more massive than Phobos through the 3:1 mean-motion resonance with Deimos at 3.3 Mars radii. This outward migration, in the opposite direction from tidal evolution within the synchronous radius, requires interaction with a past massive ring of Mars. Our results therefore strongly support the cyclic martian ring-satellite hypothesis of Hesselbrock and Minton (2017). Our findings, combined with the model of Hesselbrock and Minton (2017), suggest that the age of the surface of Deimos is about 3.5-4 Gyr, and require Phobos to be significantly younger.