Saturn's largest moon Titan is a world of rocks, ice and vast hydrocarbon lakes … so why is a patch jutting out into a hydrocarbon lake growing and shrinking?
Radar photos taken by the Cassini-Huygens mission, flying past the moon since 2004, shows the moon's surfact as a dynamic system. Transient features arise and melt back into the surface over the course of years.
The series of photos above show the shape and size of what's dubbed the "magic island" in Ligeia Mare, the moon's second-largest hydrocarbon sea. With an area of around 130,000 square kilometres, Ligeia Mare is half as big again as Lake Superior in North America.
Since Cassini-Huygens has circled the moon, planetary scientists noticed something amiss in region, with one segment appearing to grow, brighten and shrink. The series of 500-kilometre-wide insets of the image above shows the "magic island" and its eight-year evolution.
Other smaller bright spots have blossomed and faded over the course of Cassini's orbits in Ligeia Mare, as well as the largest hydrocarbon sea on Titan, Kraken Mare.
So what's going on?
While scientists called Ligeia Mare's strange spot an "island", the region is actually part of the hydrocarbon lake's surface. The brightening, they think, is due to waves on the lake's surface reflecting radar back, like a mirror tilted on just the right angle.
Other theories are changes in the solids floating on or just below the lake's surface, reflecting or absorbing the radar as its bounced off the moon.
We'll be able to see the next instalment soon: Cassini is due for another flyby in 2017, and will snap more photos as it zooms by.
Related story: Could there be life in Titan's methane sea?
Originally published by Cosmos as What’s behind Titan’s mysterious bright ‘magic island’?
Belinda Smith is a science and technology journalist in Melbourne, Australia.
Read science facts, not fiction...
There’s never been a more important time to explain the facts, cherish evidence-based knowledge and to showcase the latest scientific, technological and engineering breakthroughs. Cosmos is published by The Royal Institution of Australia, a charity dedicated to connecting people with the world of science. Financial contributions, however big or small, help us provide access to trusted science information at a time when the world needs it most. Please support us by making a donation or purchasing a subscription today.