Saturn certainly has some oddball moons and astronomers think they're close to explaining how a weird feature formed on one of them.
Iapetus is nearly 1,000 miles wide and has a 78 day orbit around the ringed gas giant. But one hemisphere of Iapetus is constantly facing Saturn -- in the same way Earth's moon is tidally locked with Earth -- and the little satellite has a very obvious two-tone surface.
PHOTOS: Moons of Saturn
It's Iapetus' weird equatorial ridge of mountains, however, that has had scientists scratching their heads. Now, with the help of 3-D maps composed from Cassini data, researchers think they have the most likely cause of the mountains pinned down.
Typically, mountains on Earth are formed as a side effect of plate tectonics and volcanic activity. Alas, Iapetus appears to have neither and, besides, the 6 mile-high mountains are too steep to be explained away by conventional mountain-forming mechanisms. So how did the mountains get there?
The researchers reckon the material that formed the Iapetian mountains have "exogenic" origin. In other words, they came from space.