A dynamical context for the origin of Phobos and Deimos

TL;DR

This paper proposes a dynamical model where Mars's growth and subsequent scattering explain the low masses of Phobos and Deimos, highlighting the role of planetary embryo interactions and capture processes.

Contribution

It introduces a new scenario involving planetary embryo interactions and scattering to explain the origin and low mass of Martian moons.

Findings

Close planetary encounters can significantly reduce moon system mass.

Scattering events can facilitate capture of small objects as moons.

The model accounts for the collisional history of Phobos and Deimos.

Abstract

We show that a model in which Mars grows near Earth and Venus but is then scattered out of the terrestrial region yields a natural pathway to explain the low masses of the Martian moons Phobos & Deimos. In this scenario, the last giant impact experienced by Mars is followed by an extended period (tens to hundreds of Myr) of close passages by other planetary embryos. These close passages perturb and dynamically heat any system of forming satellites left over by the giant impact and can substantially reduce the mass in the satellite system (sometimes to zero). The close passage of massive perturbing bodies also offers the opportunity to capture small objects by three-body scattering. Both mechanisms lead to low mass moon systems with a substantially collisional history.