'Magic island' found on Saturn's moon Titan
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.
Prior to 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 away in later images.
Planetary scientist Jason Hofgartner, from Cornell University in New York City, 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 'magic island' 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.
But unlike on Earth, they do not consist of water. Titan's seas, the size of Earth's Great Lakes, are formed by flowing rivers of liquid methane and ethane. Essentially, they are made from lighter fuel.
Beneath Titan's thick, hazy atmosphere, scientists have also discovered icy mountains and dunes made from organic "sand". Titan has weather systems similar to those of watery Earth, with wind and rain carving out strikingly familiar landscapes.
Huygens, a European Space Agency probe deployed from Cassini, landed on Titan in January 2005 - the first spacecraft landing ever accomplished in the outer Solar System.
The craft touched down on a flat, damp, sandy plain covered with ice pebbles.
Details of the "magic island" discovery are published in the journal Nature Geoscience.
Astronomers think the strange feature may arise from changing seasons. The main theories are winds kicking up and forming waves, pictured as a kind of "ghost" island in the radar images, bubbles formed by gases pushing out from the sea floor, and floating or suspended solids.
"Likely, several different processes - such as wind, rain and tides - might affect the methane and ethane lakes on Titan," said Mr Hofgartner. "We want to see the similarities and differences from geological processes that occur here on Earth.
"Ultimately, it will help us to understand better our own liquid environments."