Mars

Mars is a rocky body about half the size of Earth. As with the other terrestrial planets—Mercury, Venus, and Earth—the surface of Mars has been altered by volcanism, impacts, crustal movement, and atmospheric effects such as dust storms.

Mars has two small moons, Phobos and Deimos, that may be captured asteroids. Potato-shaped, they have too little mass fro gravity to make them spherical. Phobos, the innermost moon, is heavily cratered with deep grooves on its surface.