June 23, 2014
Scientists Scratching Their Heads Over Titan’s Vanishing ‘Magic Island’
Brett Smith for redOrbit.com - Your Universe Online
A mysterious “island” that suddenly appeared and then disappeared on one of Saturn’s moons, as seen in NASA images, has scientists baffled.
According to a paper on the phenomenon published in Nature Geoscience, the transient white patch seen in grainy images of Titan is evidence of dynamic, geological processes on the moon.
"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 study author Jason Hofgartner, a planetary scientist at Cornell University. "We don't know precisely what caused this 'magic island' to appear, but we'd like to study it further."
The study authors speculated that the phenomenon could be a floating iceberg, rising bubbles, or waves rolling across the normally flat surface of the lake.
"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," Hofgartner told The Guardian.
The researchers made their discovery while scouring radar images of Ligeia Mare, a 500-foot-deep sea that stretches for hundreds of miles in Titan's northern half. Among the images captured in 2007, 2009 and 2013 was a single image with the odd white phenomenon, around six miles off the mountainous southern lakeshore.
Determined to be 12 miles long and 6 miles wide, the spot appears in an image from July 10, 2013 but is absent from images of the same area taken prior – as well as on July 26. Hofgartner said the team had eliminated any errors in the radar imaging equipment that may create the white spot.
To discover this feature, the astronomers trusted an old strategy: flipping. After the Cassini probe delivered image data to the Jet Propulsion Laboratory for processing, the team flipped between older Titan images and the newer processed pictures to look for signs of change. This is a long-standing method utilized to spot asteroids, comets and other worlds.
"With flipping, the human eye is pretty good at detecting change," Hofgartner said.
When Cassini flew by Titan last year, it found that Ligeia Mare was flat and smooth. Scientists determined that the liquid methane and ethane lake didn’t have waves or surface ripples larger than one millimeter. That may have changed, as the study authors speculated that bubbles rising to the surface or large waves could have appeared as the spot seen in the July-10 image.
The study authors noted that Titan’s northern hemisphere is entering summer, which arrives in 2017. Warmer weather leads to stronger winds and, potentially, large waves.
"Likely, several different processes – such as wind, rain and tides – might affect the methane and ethane lakes on Titan. We want to see the similarities and differences from geological processes that occur here on Earth," Hofgartner said. "Ultimately, it will help us to understand better our own liquid environments here on the Earth."
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