Rhea (thing)

Discovered by            Giovanni Domenico Cassini
Date of Discovery        1672
Distance from Saturn     527,040 km
Radius                   764 km
Mass                     2.31 × 10^24 g
Orbital Eccentricity     0.00100
Orbital Inclination      0.35 degree
Orbital Period           4.517500436 days
Rotational Period        Synchronous
Density (gm/cm3)         1.33 

This icy moon is the largest airless satellite orbiting Saturn. Quite similar to Dione, it is rocky and heavily cratered. What is particularly interesting about Rhea is that based on its low density only 1/3 of its mass, at its core, is thought to be rock. The rest is water ice. Also interesting is that the leading face, as it orbits, is more densely cratered than the trailing face. This suggests a period of melting and refreezing at some point in its history.

Sources:
NASA.gov
space.com