Phobos and Deimos are potato-shaped, heavily pock-marked rocks that are gravitationally bound to Mars. They are also two of the strangest moons in the Solar System.
For a start, they are tiny compared to their host—Phobos is just 20 kilometers across. They are much less dense than Mars and heavily cratered, suggesting a colorful past. They also have some peculiar features, such as the grooves on the surface of Phobos that stretch for over a kilometer.
