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ORBONIX · SATURN SYSTEM
RHEA
Saturn's second-largest moon, a heavily
cratered icy world with a bright surface
and an extremely thin atmosphere.
RHEA · NASA / CASSINI
1,528 km
DIAMETER
527,000 km
DISTANCE FROM SATURN
4.52 DAYS
ORBITAL PERIOD
1.24 g/cm³
AVERAGE DENSITY
≈ −174°C
APPROX. SURFACE TEMPERATURE
ICE + ROCK
MAIN COMPOSITION
SATURN'S ICY MOON
Rhea is the second-largest moon of Saturn
and one of the largest icy moons in the
Solar System.
Its surface is dominated by water ice and
is heavily covered with impact craters.
Rhea is tidally locked to Saturn, meaning
the same hemisphere always faces the planet.
NASA's Cassini spacecraft also detected a
very thin exosphere around Rhea containing
oxygen and carbon dioxide.
Unlike Enceladus, Rhea does not show the
same powerful active plumes, but its surface
contains important clues about the history
of the Saturnian system.
HEAVILY CRATERED
Rhea's ancient surface contains
thousands of impact craters.
ICE WORLD
The moon is composed primarily of
water ice mixed with rocky material.
THIN EXOSPHERE
Cassini detected oxygen and carbon
dioxide around Rhea's surface.
DID YOU KNOW?
Rhea is about
1,500 kilometers wide —
roughly the distance from Paris to Rome.
AN ICY, HEAVILY CRATERED MOON
Rhea is Saturn's second-largest moon and has an old, heavily cratered surface dominated by water ice. Bright wispy markings seen in early images were later resolved as tectonic fractures and scarps rather than deposits floating above the surface.
Its relatively quiet exterior provides a contrast with geologically active Enceladus and atmosphere-rich Titan, illustrating the diversity of moons that formed and evolved in the same planetary system.
IMAGE:
NASA / JPL-CALTECH / SPACE SCIENCE INSTITUTE