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ORBONIX · SATURN SYSTEM
IAPETUS
A remarkable moon of Saturn known for its
dramatic two-tone surface and enormous
equatorial ridge.
IAPETUS · NASA / CASSINI
1,469 km
DIAMETER
3.56 million km
DISTANCE FROM SATURN
79.3 DAYS
ORBITAL PERIOD
1.09 g/cm³
AVERAGE DENSITY
ICE + ROCK
MAIN COMPOSITION
15.5°
ORBITAL INCLINATION
THE TWO-TONE MOON
Iapetus is one of Saturn's most unusual
moons. Its surface has an extreme contrast
between a very dark region and a much
brighter icy region.
The dark material is concentrated on the
leading hemisphere, creating the famous
two-tone appearance of Iapetus.
Iapetus also has a spectacular equatorial
ridge that stretches for hundreds of
kilometers across its surface.
The moon is tidally locked to Saturn,
so the same side always faces the planet.
TWO-TONE SURFACE
One hemisphere is extremely dark while
the other remains bright and icy.
EQUATORIAL RIDGE
A huge ridge follows much of Iapetus'
equator and rises several kilometers
above the surrounding terrain.
DISTANT MOON
Iapetus orbits much farther from Saturn
than Rhea, Titan, Enceladus and Mimas.
DID YOU KNOW?
Iapetus has one of the most dramatic
light-and-dark surfaces
in the Solar System.
WHY IAPETUS HAS TWO FACES
Iapetus has one of the strongest brightness contrasts of any large moon: one hemisphere is much darker than the other. Dark material deposited preferentially on the leading side, combined with thermal effects that move surface ice, helps maintain this striking pattern.
The moon is also notable for a tall equatorial ridge extending across much of its circumference. How that ridge formed is still debated, making Iapetus an unusual laboratory for icy-moon geology.
IMAGE:
NASA / JPL-CALTECH / SPACE SCIENCE INSTITUTE /
CASSINI