iapetus

Iapetus has been called the yin and yang of the Saturn moons because its leading hemisphere has a reflectivity (or albedo) as dark as coal (albedo 0.03-0.05 with a slight reddish tinge) and its trailing hemisphere is much brighter at 0.5-0.6.

Saturn's third largest moon, Iapetus has a mean radius of 457 miles (736 kilometers) and a density only 1.2 times that of liquid water. It has been suggested that Iapetus (like Rhea) is three quarters ice and one quarter rock.