Icy-impactor origins of the Martian moons

The origins of the Martian moons, Phobos and Deimos, are still heavily debated. There are currently two leading theories surrounding their origin: giant impact or asteroid capture. Previous studies focused on the giant impact theory showed that circum-Mars debris disks formed post-impact were hot enough to alter any primitive materials the moons are thought to consist of. This study proposes that the use of a water-ice dominated impactor may be able to protect primitive materials through the vaporization of water. Using Smoothed Particle Hydrodynamics (SPH), we simulate giant impacts of Mars and an impactor of varying water-ice to rock compositions. We show that the water content of the impactor was found to decrease disk temperatures, allowing for primitive materials to survive relatively unaltered for impactors initially containing 10% ice or more. • Impact simulations including impactors that have water-ice mantles impacting Mars were performed on the basis of an impact origin of the Martian moons. • Impactors that have water-ice mantles create disks larger than an all-rock impactor. • Adding water-ice to the impactor mantle drastically suppresses the temperature increase in the impact induced disk. • Adding water-ice to the impactor allows water delivery to young Mars, as well as create a disk massive enough to account for the mass of Phobos and Deimos.