Stretching more than 200 miles from its headwaters toward a large and mysterious sea, this river probably looks very familiar. But it is not the Nile. It is an as-yet-unnamed river on Titan, Saturn’s largest moon.
This picture marks the first time scientists have seen a river system that is so vast, and in such high resolution, anywhere other than our own planet. It’s an incredible image–it has Earth-like meanders, oxbows, and general curvature, indicating it follows the trace of a fault line. This doesn’t necessarily mean Titan has plate tectonics like Earth does, but there are enough fractures in its bedrock to help form large basins–and maybe even huge seas. The real Nile, which flows about 4,100 miles, also follows fault lines in some places.
The Titan river is filled with liquid hydrocarbons, which scientists can tell because it appears dark throughout its length. This indicates it has a smooth surface.
Titan is the only other place in our solar system with a hydrologic cycle. Instead of water, it has liquid methane and ethane. It rains methane on Titan, and there are lakes made of ethane–the only other place where liquid exists in a stable form. Many planetary geologists would love to visit this liquidy world, but NASA recently declined to fund a pretty advanced plan to send a boat there and float it in the liquid hydrocarbon sea. That project could still live to see another day, however.
The image is from NASA’s Cassini spacecraft, which has been traveling through the Saturn system for many years now, snapping some of the most incredible imagery in our solar neighborhood. Cassini snapped the image in September. It shows Titan’s north polar region and a river valley flowing into Kraken Mare, a sea that is between the Caspian and Mediterranean in terms of size.