{ Moons of Saturn }
Discovered by            Giovanni Domenico Cassini
Date of Discovery        1671
Distance from Saturn     3,561,300 km
Radius                   718 km
Mass                     1.6 × 10^24 g
Orbital Eccentricity     0.02828
Orbital Inclination      14.72°
Orbital Period           79.3301825 days
Rotational Period        Synchronous
Density (gm/cm3)         ??? 

Similar to Rhea, Iapetus is an icy moon believed to have a rocky core. One of the striking things about it is its appearance. It seems to have a huge birthmark. While part of the surface is bright, like Rhea, a large area of the leading hemisphere is covered with a reddish dust. It is unknown how the dust got there or what its composition is. Theories abound.

Could it have been swept up from space when meteors struck nearby Phoebe or from some other source? Perhaps, but the dust is not similar in color to Phoebe's surface. But the fact that the coloration is only on the leading face supports this theory. On the other hand, the patterns seem to resemble the volcanic flows of our moon and Mars, in that the dust seems to concentrate at the bottoms of impact craters and other low areas. Perhaps methane or ammonia from within the satellite erupted to the surface at some point in its history.