Saturn’s Moon Iapetus has a unique feature which was, until recently, a complete mystery.
Running along its equator is this weird ridge of mountains. The mountains run exactly along the equator, are perfectly straight, and—so far—haven’t shown up like this on any other planet or moon. They’re also the only such mountains anywhere on Iapetus’ surface (reaching as high as 63,000 feet tall). (Giving this strange moon the propensity for ice avalanches!) Pretty weird!
Image Credit: NASA/JPL