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Hot on the Trail of Cold Volcanoes

Cassini Radar images at Hotei Arcus and Western Xanadu, Titan: Evidence for Geologically Recent Cryovolcanic Activity

The Cassini spacecraft is revealing even more intriguing evidence for icy volcanoes on Titan through its radar mapping instrument. Radar images show two locations, the semi-circular Hotei Arcus and another spot in western Xanadu containing lobe-like formations that suggest highly viscous slow-moving volcanic flows. These features are thought to be relatively young because they overlap other geological features that exist in the same location.

Black and white image of the surface of Titan.
The Cassini Radar Mapper imaged Titan on Feb. 22, 2008 (as shown on the left) and April 30, 2006 (as shown on the right).

The radar images above show the outlines of regions "1" and "2" identified by Cassini's Visual and Infrared Mapping Spectrometer (VIMS). VIMS data show these regions to be variable and hypothesized that they result from cryovolcanic activity. The lobate, flow-like features seen in the radar images of region 1 are consistent with this interpretation.

Region 1 is just north of Hotei Arcus and is centered on 28 degrees south latitude by 78 degrees west longitude. The region is about 400 kilometers (249 miles) across. Region 2 is on the western part of Xanadu and is centered on 7 degrees south latitude by 135 degrees west longitude. This region is about 900 kilometers (560 miles) across. In both radar images, north is up, and features as small as 300-500 meters can be resolved.

Scientists who authored the paper "Cassini RADAR Images at Hotei Arcus and Western Xanadu, Titan: Evidence for Geologically Recent Cryovolcanic Activity" conclude that they are cryovolcanic lava flows, although there is a small possibility that they might be sediments instead. They note the strong resemblance of the deposits to lava flow fields on Earth, Venus and other planetary bodies.

Moreover, the formations in Hotei Arcus seem to cover channels that were carved by methane rain, and that means the formations are geologically young, less than a million years old. The formations themselves are likely made of water mixed with ammonia, which acts as an antifreeze, creating slushy ice extruded to the surface through tectonically created cracks in Titan's shell.

Although the radar instrument can't tell whether the cryovolcanoes are active today, Cassini's VIMS instrument indicates ongoing changes in brightness in these regions, which suggests current volcanic activity.

The Cassini Mission has revealed Titan as an ever-evolving world that shares many planetary processes with Earth, Mars and Venus. The two instruments, working in conjunction with each other, continue to lift the veil that surrounds this mysterious moon.


S.D. Wall, R.M. Lopes (JPL) ; E.R. Stofan (Proxemy Research, Bowie, MD); C.A. Wood (Wheeling Jesuit Univ., WV; J.L. Radebaugh (Brigham Young U.); S.M. Horst, U AZ); B.W. Stiles, R.M. Nelson, L.W. Kamp, M.A. Janssen (JPL); R.D. Lorenz (APL); J.I. Lunine (U AZ); T.G. Farr, G. Mitri (JPL) P. Paillou (Observatoire Aquitain des Sciences del'Univers, Floirac, France); F. Paganelli (Proxemy Research); K.L. Mitchell (JPL)

Last Updated: 2 February 2011

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Last Updated: 2 Feb 2011