Phobos: Doomed Moon of Mars

Mars, the red planet named for the Roman god of war, has two
tiny moons, Phobos and Deimos, whose names are derived from the Greek for
Fear and Panic. These Martian moons may well be captured asteroids
originating in the main asteroid belt between Mars and Jupiter or perhaps
from even more distant reaches of the Solar System. In this 1978 Viking 1
orbiter image, the largest moon, Phobos, is indeed seen to be a heavily
cratered asteroid-like object. About 17 miles across, Phobos really zips
through the Martian sky. Actually rising above Mars' western horizon and
setting in the east, it completes an orbit in less than 8 hours. But Phobos
is doomed. Phobos orbits so close to Mars, (about 3,600 miles above the surface
compared to 250,000 miles for our Moon) that gravitational tidal forces are
dragging it down.