Moon of Saturn · Updated October 2026
Rhea.
Rhea is Saturn's second-largest moon at 1,527 km diameter, an icy body with a heavily cratered surface and a very thin exosphere of oxygen and carbon dioxide. Cassini found it in 2010, the first time a spacecraft had directly sampled an oxygen atmosphere at a world other than Earth.
View Saturn system in 3D →Key facts
Tentative 2008 evidence suggested Rhea might have its own thin ring system, which would have made it the first moon known to have rings. Later imaging found no clear signature.
About Rhea
Rhea's trailing hemisphere is crossed by bright wispy streaks, once thought to be frost and shown by Cassini to be fresh ice exposed on the walls of tectonic fractures. Its low density (1.2 g/cm³) means it is roughly three-quarters water ice.
How to view Rhea in 3D
Rhea orbits Saturn in real time inside the interactive viewer. Open the parent body to see the orbital geometry, or use the object browser to fly directly to the moon and observe its rotation, surface, and orbit.
Open the Saturn system →More about Saturn
Sources & methodology
Numbers cross-referenced with the sources below; updated October 2026.