Formation of Phobos and Deimos in an extended circum-Martian accretion disk
Résumé
Recent exploration of Phobos by Mars Express has renewed the interest in the origin of the Martian moons, which remains an open issue. New studies have recently focused on accretion of debris in a circum-Martian disk. Craddock (Icarus, 2011) has proposed a scenario of formation of such a disk (about 10-4 to 10-3 % the mass of Mars) from a giant collision occurred early in Mars' history. Rosenblatt and Charnoz (Icarus, 2012) have shown that moonlets can be formed, with Phobos and Deimos masses, in a compact disk close to the planet. Nevertheless, the orbit of these moonlets rapidly recedes back to Mars and the moonlet system vanishes in much less than 1 Gy.
Citron at al. (Icarus, 2015) have modeled the formation of a disk of debris resulting from a giant collision but with a larger mass (0.1 % of Mars' mass) than in Craddock (2011). They have shown that most of the disk mass is concentrated close to the planet but a small part can extend beyond the synchronous limit (6 Mars' radii).
We study here the accretion of debris in an extended disk, focusing in the edge of this disk where surface density of material is the lowest. However, we take into account the gravitational influence of the more massive bodies formed in the denser part of the disk. Our results highlight the driven mechanisms of accretion in a circum-Martian disk of debris.