A mysterious 'magic island' has appeared out of nowhere in radar images of a hydrocarbon sea on Saturn's giant moon, Titan.
Scientists are struggling to explain the bright 'transient feature' but say it could be the result of waves, bubbles or buoyant solid matter.
The object was spotted by flipping between images of Ligeia Mare, Titan's second-largest sea, captured by the Cassini space probe which has been exploring the Saturnian system since 2004.
Before July 2013 the sea had appeared flat and completely devoid of features, including waves. Then the enigmatic object, dubbed 'magic island' by scientists, suddenly materialised – only to vanish in later images.
Planetary scientist Jason Hofgartner, from Cornell University in New York, said: "This discovery tells us that the liquids in Titan's northern hemisphere are not simply stagnant and unchanging, but rather that changes do occur.
"We don't know precisely what caused this to appear, but we'd like to study it further."
Titan is the only planetary body in the solar system besides Earth known to have large expanses of liquid on its surface.