Scientists have spotted a “mini Nile river” on the surface of Titan, Saturn’s largest moon, flowing over 400 km from its headwaters to a large sea. High resolution images snapped by the international Cassini mission, which is exploring Saturn and its moons, let us glimpse a river system flowing on another planet for the first time.

Titan is a fascinating place, and the only other world we know of with liquid at its surface. Its freezing cold—surface temperatures are about -178 C—but remarkably Earth-like, with a hazy atmosphere, hills, mud flats, even rivers and rain. Instead of water, though, the liquid on Titan is ethane, methane and propane; scientists think this newly photographed river, at the moon’s north pole, is filled with liquid hydrocarbons.

“Titan is the only place we’ve found besides Earth that has a liquid in continuous movement on its surface,” Steve Wall, the radar deputy team lead, based at NASA’s Jet Propulsion Laboratory, said in a release. “This picture gives us a snapshot of a world in motion. Rain falls, and rivers move that rain to lakes and seas, where evaporation starts the cycle all over again. On Earth, the liquid is water; on Titan, it’s methane; but on both it affects most everything that happens.”