Coursing 400 kilometres towards a dark delta, a river found on Saturn鈥檚 moon Titan is the longest yet seen outside Earth. Bearing a striking resemblance to the Nile, the river hints at ongoing geological activity on the moon.
Titan is considered to be the most Earth-like extraterrestrial body in the solar system. In addition to its thick atmosphere, the moon boasts mountains, lakes and a liquid cycle akin to Earth鈥檚 water cycle.
But at -179 掳C, Titan is too cold for flowing water. Instead, liquid hydrocarbons such as ethane and methane fill its lakes and streams.
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Finding faults
Spotted by NASA鈥檚 Cassini spacecraft, the newfound river follows a relatively straight path into one of Titan鈥檚 large seas, Ligeia Mare. 鈥淲e think it鈥檚 raining in the highlands and flowing down into these river valleys,鈥� says of NASA鈥檚 Jet Propulsion Laboratory in Pasadena, California.
The Nile鈥檚 relatively straight shape is partly controlled by fault lines, which on Earth mark the places where tectonic plates meet. Titan is probably too small to have plates, but the river may also be tracing a fault in the bedrock, says Farr. Pressure could build up on such faults, causing them to shift and form new chasms and lakes, he says.
鈥淯sually when we look at another planet, we鈥檙e cautioned not to bring our Earth experience too much to bear, because we might fool ourselves,鈥� says Farr. 鈥淏ut here we look at a completely alien world and it looks just like the Earth. It鈥檚 hard to believe.鈥�
