Astronomers have discovered a bright, mysterious geologic object - that appeared and then vanished again - from Ligeia Mare, the second largest sea on Saturn's moon Titan.
The object was captured by NASA's Cassini mission radar last year as it swung around Titan.
However, pictures of the same spot captured nothing before or some days later.
Scientifically speaking, this spot is considered a "transient feature", but the astronomers have playfully dubbed it "magic island".
This may be the first observation of dynamic, geological processes in Titan's northern hemisphere.
"This discovery tells us that the liquids in Titan's northern hemisphere are not simply stagnant and unchanging, but rather that changes do occur," said Jason Hofgartner from Cornell University in the US.
"We do not know precisely what caused this 'magic island' to appear, but we would like to study it further," Hofgartner added.
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Titan, the largest of Saturn's 62 known moons, is a world of lakes and seas.
To discover this geologic feature, the astronomers relied on an old technique - flipping.
The Cassini spacecraft sent data July 10, 2013, to the Jet Propulsion Laboratory at the California Institute of Technology in the US for image processing.
Within a few days, Hofgartner and his colleagues flipped between older Titan images and the newly processed pictures for any hint of change.
This is a long-standing method used to discover asteroids, comets and other worlds.
"With flipping, the human eye is pretty good at detecting change," Hofgartner added.
Prior to the July 2013 observation, that region of Ligeia Mare had been completely devoid of features, including waves.
The findings appeared in the journal Nature Geoscience.