Rhea is the second largest moon of
Saturn. It is particularly heavily cratered. It was discovered in 1672
? by [Giovanni Cassini]
?. Rhea is an icy body with a density of 1.33 gm/cm
3; this low density indicates that it has a rocky core taking up less than one-third of the moon's mass with the rest composed of water-ice. Rhea's features resemble those of
Dione, suggesting similar composition and histories. The temperature on Rhea is -174°C in direct sunlight and between -200°C and -220°C in the shade.
Rhea is heavily cratered and has bright wispy markings on its surface. Its surface can be divided into two geologically different areas based on crater density; the first area contains craters which are larger than 40 kilometers in diameter, whereas the second area, in parts of the polar and equatorial regions, has craters under 40 kilometers in diameter. This suggests that a major resurfacing event occurred some time during its formation.
- Orbital radius: 527,040 km
- diameter: 1530 km
- mass: 2.49*1021 kg
- Surface Area: 7,300,000 km2
- Orbital period: 4.5175 days
- Orbital inclination: 0.35°