Moon of Saturn
Iapetus
Iapetus is a moon. It orbits Saturn. It is about 1,469 km across – smaller than our Moon. Iapetus is two-toned: one side is as dark as coal, the other as bright as snow.
Fact file
- Type
- Moon of Saturn
- Diameter
- 1,469 km
- Distance from Saturn
- 3,560,820 km
- Orbital period
- 79.3 days
- Temperature
- -173 °C on average
Iapetus orbits Saturn.
Interesting facts about Iapetus
- Iapetus is two-toned: one side is as dark as coal, the other as bright as snow.
- A mountain ridge up to 20 km high runs round the equator like the seam of a walnut.
- Its discoverer Cassini was puzzled in 1671 that Iapetus could be seen on only one side of Saturn – the dark side was invisible to his telescope.
Frequently asked questions about Iapetus
How big is Iapetus?
Iapetus has a diameter of 1,469 km. That is about 42% of the diameter of our Moon.
How far is Iapetus from Saturn?
Iapetus orbits Saturn at an average distance of 3.6 million km.
How long does Iapetus take to orbit Saturn?
Iapetus orbits Saturn once every 79.3 days.
How cold or warm is it on Iapetus?
On Iapetus the average temperature is −173 °C.
Formation
The dark side comes from dust that Iapetus sweeps up along its orbit. There the ice warms, evaporates and settles on the bright side – so the contrast keeps on growing.
Atmosphere
No atmosphere.
Exploration
In 2007 Cassini flew past at a height of just 1,640 km and returned spectacular images of the equatorial ridge.
Compared with Earth
About 40% the size of our Moon. Its tilted orbit would give you the finest view of Saturn's rings.
Other moons of Saturn
Test your knowledge of Iapetus
Which moon of Saturn is coal-black on one side and snow-white on the other?
Iapetus. Iapetus sweeps up dark dust on its leading side; evaporating ice then makes the effect stronger and stronger.
The full quiz with points and badges is in the 3D model under “Explore”.
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