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First 'cryovolcano' discovered on Titan, ice moon of Saturn

Frosty cone spews molten slush-puppy MAGMA

Boffins believe they have discovered the first "cryovolcano" known to the human race: a mountain on Titan, ice moon of Saturn, which has appeared in much the same way as an Earthly volcano - but which is made of ice and spews freezing slush rather than blazing molten rock.

The feature in question has long been known to astronomers as a bright spot in Titan's Aztlan region, and is named Sotra Facula.

"When we look at our new 3D map of Sotra Facula on Titan, we are struck by its resemblance to volcanoes like Mt Etna in Italy, Laki in Iceland and even some small volcanic cones and flows near my hometown of Flagstaff," says Randolph Kirk, geophysicist at the US Astrogeology Science Center.

"This is the very best evidence, by far, for volcanic topography anywhere documented on an icy satellite," adds Jeffrey Kargel, who worked with Kirk on the 3D ice moon map. "It's possible the mountains are tectonic in origin, but the interpretation of cryovolcano is a much simpler, more consistent explanation."

There has long been a debate in boffinry circles regarding the existence of cryovolcanoes on icy worlds such as Titan. But the scientists probing Sotra Facula - using data from the Cassini probe orbiting Saturn - believe that debate is now over.

"Cryovolcanoes help explain the geological forces sculpting some of these exotic places in our solar system," said Linda Spilker, Cassini project scientist at NASA's Jet Propulsion Laboratory.

Famously, Titan's thick atmosphere is not made up of nitrogen and oxygen like that of Earth: instead it is made of nitrogen and methane with small amounts of ethane and propane mixed in. The hydrocarbon clouds interact with lakes of mixed LNG and LPG barbecue gas in a hydrological cycle - evaporation, rain, runoff - like that of Earth but much colder. The water which is mostly liquid and vapour here acts on Titan more as rock does on our planet.

It now appears that this similarity even extends to the matter of occasionally melting due to subterranean heating and spurting up through surface in molten or semi-molten form to cool and solidify once more as mountains with characteristic deep craters and finger-like flows. At Sotra, according to Cassini's radar, there are two peaks more than 1,000 metres high.

The new ice-volcano discoveries were announced yesterday at a convention in San Francisco. There's more on Sotra Facula from NASA here. ®

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