And now the Cassini probe has spotted a 1,500m-high mountain with a deep pit in it, and what looks like a flow of material nearby.
Titan shroudedis a mysterious world. Because it's shrouded in a thick, oily haze, it's extremely hard to identify anything at the moon with confidence. But with temperatures that plunge to minus 180 Celsius at the surface, researchers had suspected it might have ice volcanoes.
Scientists can only speculate what sort of material a cryo-volcano might erupt, but the complex chemistry at Titan suggests it could be a slushy water-ice containing ammonia.
If there are a lot of carbon molecules present, the lava could even look like softened asphalt, candle wax or even polyethylene.
The team which discovered the mountain have dubbed it "The Rose".