Cracks. If the meteor that created the crater had been a bit larger, it might have destroyed Phobos. Instead, many scientists think the impact cracked the moon's interior. The cracks could contain water ice. If so, Phobos could serve as a refueling station for manned Mars-exploration missions. But observations by several spacecraft indicate that there's less water at the surface of Phobos than in almost any other body in the solar system.
