NASA's Cassini spacecraft has found deep, steep-sided canyons on Saturn's moon Titan that are flooded with liquid hydrocarbons. The finding represents the first direct evidence of the presence of liquid-filled channels on Titan, as well as the first observation of canyons hundreds of meters deep.

The Cassini observations reveal that the channels -- in particular, a network of them named Vid Flumina -- are narrow canyons, generally less than half a mile (a bit less than a kilometer) wide, with slopes steeper than 40 degrees. The canyons also are quite deep -- those measured are 790 to 1,870 feet (240 to 570 meters) from top to bottom.

The branching channels appear dark in radar images, much like Titan's methane-rich seas. This suggested to scientists that the channels might also be filled with liquid, but a direct detection had not been made until now. Previously it wasn't clear if the dark material was liquid or merely saturated sediment -- which at Titan's frigid temperatures would be made of ice, not rock.

Cassini's radar is often used as an imager, providing a window to peer through the dense haze that surrounds Titan to reveal the surface below. But during this pass, the radar was used as an altimeter, sending pings of radio waves to the moon's surface to measure the height of features there. The researchers combined the altimetry data with previous radar images of the region to make their discovery.

more https://www.nasa.gov/feature/jpl/cassini-finds-flooded-canyons-on-titan