The mountains on Saturn's moon Titan defy easy explanation, but readings from the Cassini probe offer a fascinating new possibility: Titan is slowly releasing heat and shriveling up, causing mountains to form on its surface like wrinkles on a raisin.
It's a geological process unlike that of any other icy body, but that's the most likely explanation based on the new data from Cassini. Titan formed about four billion years ago, and ever since it's been very slowly venting heat and radioactive isotopes from inside its core. This causes parts of Titan's subsurface ocean to freeze and buckle, folding parts of the ice shell into each other and reducing the overall diameter of the planet. Since its formation, Titan has lost about four miles in radius and 1% of its volume to this process.
Known as contractional tectonics, it's the exact opposite of what forms mountains on other moons like those of Jupiter. There, extensional tectonics is in play, as forces stretch the ice shell and force up mountains. Scientists suggest the difference might be because of its interior ocean, which is a mix of water and ammonia.
The researchers were tipped off that something unusual was going on with Titan's mountains because most of its ranges are right around the equator with an east-west orientation, suggesting all the mountains shared a common origin. Although contractional tectonics is rare, it's not unheard of - in fact, the Zagros Mountains in Iran were formed by precisely the same process.