Ice Volcanoes on Titan, as imaged by Cassini. Credit: NASA
Sounding like an attraction on one of The Doctor‘s tours of space and time, the Ice Volcanoes of Titan have recently been discovered in radar images taken by the Cassini orbiter. Titan is a gigantic satellite around Saturn, and is the largest moon in the Solar System. Scientists studying Titan have been puzzled for some time by the presence of Methane in its atmosphere, because solar radiation from the Sun actively breaks it down. They needed some mechanism to replace the Methane, and now they seem to have found it. “When we look at our new 3-D 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,” said Randolph Kirk, who led the 3-D mapping work, and is a Cassini radar team member and geophysicist at the U.S. Geological Survey (USGS) Astrogeology Science Center in Flagstaff, Ariz.
Active volcanoes provide an important link between the interior of a planet (or in this case, moon) and its atmosphere, pumping out billions of tonnes of various gases with each eruption.
Mt Etna erupting, as seen from the International Space Station. Credit: NASA
But Titan’s volcanoes aren’t quite the same as those on Earth: They spew icy slush instead. Titan orbits Saturn, which is extremely far from the warmth of the Sun. It’s so cold that water ice is as hard as rock, and plays the same role.
It has been speculated that tidal forces between Saturn and Titan could flex the moon, warming it’s interior enough to melt some of the ice deep below the surface. And when the interior of a planet is molten and churning, sometimes that molten material bursts its way to the surface and you get volcanoes.
The image to the left shows the radar map that Kirk and his colleagues refer to. The image shows two peaks more than 1,000 meters (3,000 feet) tall and multiple craters as deep as 1,500 meters (5,000 feet). It also shows finger-like flows. All of these are land features that indicate cryovolcanism. The 3-D topography comes from Cassini’s radar instrument. Topography has been vertically exaggerated by a factor of 10. The false color in the initial frames shows different compositions of surface material as detected by Cassini’s visual and infrared mapping spectrometer. In this color scheme, dunes tend to look relatively brown-blue. Blue suggests the presence of some exposed ice. Scientists think the bright areas have an organic coating that hides the ice and is different and lighter than the dunes. The finger-like flows appear bright yellowish-white, like the mountain and caldera. The second set of colors shows elevation, with blue being lowest and yellow and white being the highest. Dunes here appear blue because they tend to occupy low areas. The finger-like flows are harder to see in the elevation data, indicating that they are thin, maybe less than about 100 meters (300 feet) thick.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency (ASI). The Jet Propulsion Laboratory, a division of the California Institute of Technology, Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington. The Cassini orbiter was designed, developed and assembled at JPL. The radar instrument was built by JPL and ASI, working with team members from the U.S. and several European countries. The visual and infrared mapping spectrometer was built by JPL, with a major contribution by ASI. The visual and infrared mapping spectrometer science team is based at the University of Arizona, Tucson.