Moon of Saturn
Rhea
Saturn's second-largest moon, an icy world on a 4.5-day orbit.
Rhea takes 4.5 Earth days to orbit Saturn and keeps the same face toward the planet. It orbits farther out than Dione and Tethys, so Saturn's tides heat it less. Its thin exosphere forms as Saturn's rotating magnetic field sweeps over its icy surface.
How it moves
- Rhea orbits Saturn every 4.518 days at about 527,040 km.
- It is tidally locked to Saturn.
- Its orbit is nearly circular (eccentricity 0.0010).
- Saturn's magnetic field, rotating with the planet, sweeps past Rhea and frees oxygen from its surface.
Facts
- Mean radius
- 763.5 km
- Mass
- 2.310e+21 kg
- Surface gravity
- 0.264 m/s²
- Rotation period
- 108.42 hours
- Orbital period
- 4.518 days
- Average orbital distance
- 527,040 km
- Eccentricity
- 0.001
- Discovered
- December 23, 1672, by Giovanni Domenico Cassini
At Rhea, Cassini directly captured molecules of an oxygen atmosphere at a world other than Earth for the first time.
Sources: nssdc.gsfc.nasa.gov, ssd.jpl.nasa.gov, ssd.jpl.nasa.gov