Rhea . ... Rhea is an icy body with a density of 1.33 gm/cm 3 . The low density indicates that it is composed of a rocky core taking up less than one-third of the moon's mass, with the rest composed of water-ice. ... Rhea is heavily cratered with bright whispy markings. ... The second area, in parts of the polar and equatorial regions, has craters under 40 kilometers (25 miles) in diameter. ... Orbital period (days) . ... Credit: Calvin J. Hamilton) . ... Copyright ї 1997 by Calvin J. Hamilton . ...