The moons of Mars may have formed from a disk of debris kicked up by the impact of a giant meteorite on the planet.
Astronomers have struggled to explain the existence of Phobos (pictured) and Deimos, the small, irregularly shaped moons of the red planet. One view is that they were asteroids captured by Mars. But a team led by Pascal Rosenblatt at the Royal Observatory of Belgium in Brussels tested an alternative idea using computer simulations of how orbiting debris, created by a giant impact, might coalesce.
Relatively large moons form in the inner part of the disk thrown up by such a smash, and migrate outward, causing the outer part of the disk to coalesce into two bodies the sizes of Phobos and Deimos. The inner large moons are eventually dragged inward and fall back to Mars over 5 million years.
Nature Geosci. http://dx.doi.org/10.1038/ngeo2742 (2016)