14 December 2010
I always thought volcanoes belched flaming, crackling chunks of rock, oozed hot goopy magma, and buried everything on their slopes.
So when I noticed several presentations on AGU’s schedule about “ice volcanoes,”–such as P22A: Titan: The methane cycle and potential for watery warm spots 1–I was intrigued. Like, inspired to fantasy. I imagined a massive, conical volcano spitting chunks of ice into the atmosphere, looking more or less like an angry holiday snow globe raining icicles onto a bizarre alien landscape. I was eager to glimpse the chilly, eponymous behemoth. I was not disappointed.
The ice volcano (scientifically termed ‘cryovolcano’) on Titan, one of Saturn’s moons, is named Sotra Facula. Randolph Kirk, from the US Geological Survey’s Astrogeology Science Center said the peak is 1500 meters high and 70 kilometers wide. He described it as resembling a shield volcano, like Kilauea.
“That is certainly a shallower slope than we find on Mount Doom,” he said, in reference to the locale in the Lord of the Rings.
Data gathered by the Cassini spacecraft revealed that Sotra Facula is missing a chunk from one of its slopes and is situated next to a deep pockmark in Titan’s surface–one of few indentations on the “rather flat world,” Kirk said. He added, the pit suggests “there’s been some kind of rather violent removal of material below the surface that might be associated with explosive volcanism.”
But scientists don’t know for sure whether the volcano is still active, and what it actually expels.
Jeffrey Kargel, from the University of Arizona, offered two possible suggestions for ‘cryolava’: watery slush, or hydrocarbons. “Think in terms of softened asphalt, candle wax, or polyethylene,” he said.
Hydrocarbon-burping volcanoes aren’t that strange, Kargel continued. They’ve been documented on Earth in the Gulf of Mexico and off the coast of Santa Barbara. And, a cryovolcano producing plumes of water, methane, and carbon dioxide was confirmed to exist on Enceladus, another Saturnian moon. Titan has enough methane in its atmosphere to suggest that Sotra Facula might be a source of the carbon-containing gas. “We do need a source inside Titan to supply methane to the atmosphere,” Kargel said.
A 3D rendering of the Sotra Facula region, courtesy of topographical mapping, revealed that the mountain is not a lonely peak on Titan. Sotra Facula has friends: two nearby peaks, each emerging from a region of sand dunes. These also might be cryovolcanoes, Kirk explained.
“We finally have some proof that Titan is an active world,” Kirk concluded.
–Nadia Drake is a science communication graduate student at UC Santa Cruz.