A miniature extraterrestrial version of the Nile River has been spotted on the largest moon of Saturn by ESA’s Cassini spacecraft.
ESA researchers deduce that the river is filled with liquid hydrocarbons such as ethane and methane because it appears dark along its entire extent in the high-resolution radar image, indicating a smooth surface.
The river valley stretches more than 400 km from its ‘headwaters’ to a large sea.
“Though there are some short, local meanders, the relative straightness of the river valley suggests it follows the trace of at least one fault, similar to other large rivers running into the southern margin of this same Titan sea,” explained Dr Jani Radebaugh, a Cassini radar team associate at Brigham Young University, the United States.
“Such faults may not imply plate tectonics, like on Earth, but still lead to the opening of basins and perhaps to the formation of the giant seas themselves.”
Titan is the only other world we know of that has stable liquid on its surface. While Earth’s hydrologic cycle relies on water, Titan’s equivalent cycle involves hydrocarbons.
Images from Cassini’s visible-light cameras in late 2010 revealed regions that darkened after recent rainfall.
Cassini’s visual and infrared mapping spectrometer confirmed liquid ethane at a lake in Titan’s southern hemisphere known as Ontario Lacus in 2008.
ESA’s Cassini project scientist Dr Nicolas Altobelli said: “this radar-imaged river by Cassini provides another fantastic snapshot of a world in motion, which was first hinted at from the images of channels and gullies seen by ESA’s Huygens probe as it descended to the moon’s surface in 2005.”