Scientists are investigating a mystery object that appeared and then vanished again from a giant lake on Titan, the largest moon of Saturn.
They spotted the object in an image taken by Nasa’s Cassini probe last year as it swung around the alien moon, more than a billion kilometres from Earth. Pictures of the same spot captured nothing before or some days later.
Little more than a white blob on a grainy image of Titan’s northern hemisphere, the sighting could be an iceberg that broke free of the shoreline, an effect of rising bubbles, or waves rolling across the normally placid lake’s surface, scientists say.
Astronomers have named the blob the “magic island” until they have a better idea what they are looking at. “We can’t be sure what it is yet because we only have the one image, but it’s not something you would normally see on Titan,” said Jason Hofgartner, a planetary scientist at Cornell University in New York. “It is not something that has been there permanently.”
Titan is one of the most extraordinary places in the solar system. The land is strewn with hydrocarbon dunes that rise above lakes fed by rivers of liquid methane and ethane. The atmosphere is so thick, and the gravity so weak, that a human could strap on wings and flap into the air. That air is laced with lethal hydrogen cyanide.
The largest moon of Saturn – there are more than 60 smaller ones – is the only place beyond Earth known to have stable liquids on its surface and rain falling from its skies. Spacecraft have mapped scores of lakes there. The three biggest are named after mythological beasts, the Kraken, Ligeia and Punga, and are large enough to qualify as seas, or mares.
The US team made their curious discovery while poring over radar images of Ligeia mare, a 150-metre-deep sea that stretches for hundreds of kilometres in Titan’s northern hemisphere. Among the snapshots taken in 2007, 2009 and 2013 was one with the strange white feature, about six miles off the mountainous southern shore.