Moons range in shape from highly irregular to spheres.
Their shape reflects their formation history, irregular objects are ill-formed moons or pieces of a larger moon, spherical objects were once molten spheres, probably at the time of their formation. We speculate, from their irregular appearances and low mean densities, that Deimos and Phobos, are captured asteroids. Both Deimos and Phobos are saturated with craters. Deimos has a smoother appearance caused by partial filling of some of its craters. Atlas the second of Saturn's known satellites, orbits near the outer edge of the A-ring Enceladus is one of the innermost moons of Saturn.