A 400km river of methane discovered on Saturn's moon Titan has been dubbed a "miniature extraterrestrial version of the Nile river".
The strange river system is filled with liquid, scientists from the European Space Agency said.
Above: The river of methane
The river appears dark along its entire length in the high-resolution image taken by the Cassini spacecraft.
The Cassini-Huygens mission is joint project by Nasa, ESA and ASI, the Italian space agency.
"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, USA, in a statement.
It is thought the river flows into a giant see made of hydrocarbons including methane and ethane. It is also thought that the alien world has rainfall of liquid ethane.
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