Wednesday, June 25, 2014

A Mysterious Shape Just Appeared on the Surface of Titan


Saturn's moon Titan is sort of like a bizarro version of Earth, an extraterrestrial tease that's home to lakes, rivers, rain, and wind. This combination of attributes means the would-be twin is host to a variety of landforms Earthlings might find familiar, including mountains and dunes rippling along the solid surfaces of a relatively smooth (uncratered) sphere. Titan is home to the only thick atmosphere so far observed on a natural satellite, along with the only stable surface bodies of liquid (lakes) observed on any celestial body outside of Earth itself. No matter that Titan's rivers and lakes are actually full of liquid methane and ethane and its surface temperature hovers around −179.2 °C, the moon is a playground for the Earth-bound imagination.

It helps that Titan also seems interested in playing along. Enter "Magic Island," a geologic object that's appeared, relatively suddenly, in recent images collected by NASA's Cassini spacecraft of the moon's second-largest lake Ligeia Mare. The blob, which in the images appears as a bonus blob off the lake's lower coast, is more technically referred to as a "transient object" and comes with a small array of perfectly reasonable explanations: seasonal climate changes kicking up extreme waves, bubbles from undersea gas releases, the thawing of undersea solid material, and-or the presence of suspended solids, like silt or mud, as might be found on a river delta on Earth. 

All of those explanations, however, would seem to be things we might have observed previously. The Magic Island images date from last summer (2013), while the spacecraft has been doing flybys of the moon since 2004. As of just a few days ago, June 18, Cassini has logged over 100 data-gathering passes, though not all of them targeting this particular body of water, of course. Researchers know enough about Titan to at least say their Magic Island is abnormal.

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