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Cassini spots Titan ‘mini-Nile’

Largest off-Earth river seen so far

NASA’s Cassini spacecraft has sent back images of what the space agency says is “the first time images have revealed a river system this vast and in such high resolution anywhere other than Earth”.

NASA image mini-Nile

NASA image: Mini-Nile on Titan

The river system on Saturn’s moon Titan has tickled the scientists because of its resemblance to the river Nile: the “mini-Nile” is more than 400 km long and includes a spreading delta where it empties into a sea.

Don’t, however, expect to spot a Titanian Cleopatra dragging lazy fingers behind a slave-paddled boat: the river itself is probably liquid hydrocarbons, NASA says, based on the dark colours in the image and the apparently-smooth surface. Titan’s “water cycle” – except of course that it’s not water – involves ethane and methane rather than H2O.

In its press announcement, NASA suggests that the river’s path also reveals something of the ground underneath.

“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,” said Jani Radebaugh, a Cassini radar team associate at Brigham Young University, Provo, Utah.

“Such faults - fractures in Titan's bedrock -- 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.”

The image shows Titan’s north polar region, with the river flowing into the Ligeia Mare, a sea of a size between the Caspian and the Mediterranean.

While the river's length is tiny compared to the Nile's 6,700 km, the Earthly river's course, like the one on Titan, is partly directed by the faults it encounters on its journey, NASA says. ®

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