The most detailed temperature map to date of the “Tiger Stripe” region on the south pole of Saturn’s moon Enceladus reveals that the area is even warmer than previous measurements indicated. Jets resembling geysers are erupting from cracks in the icy crust of this region, so named because the fissures look like the stripes of a tiger.

The temperature measurements were made by the Cassini spacecraft’s Composite Infrared Spectrometer (CIRS) during the spacecraft’s close flyby of the moon on March 12, 2008. The warmth suggests the possibility that there might be liquid water beneath the ice. Liquid water, together with abundant organic material detected by Cassini as it flew through the jets, would make Enceladus a promising place to search for extraterrestrial life.

“Enceladus has got warmth, water and organic chemicals — some of the essential building blocks needed for life,” said Dennis Matson, Cassini Project Scientist at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “We have quite a recipe for life on our hands, but we have yet to find the final ingredient — liquid water, but Enceladus is only whetting our appetites for more.”

“This latest flyby is the closest we have been to Enceladus while mapping its temperatures,” said CIRS Principal Investigator Michael Flasar of NASA’s Goddard Space Flight Center in Greenbelt, Md. “Seeing them as high as 180 Kelvin (minus 136 Fahrenheit) in the surface cracks near the south pole is amazing, because the temperatures expected on a quiescent Enceladus are only 60 K (minus 352 F).

Some very energetic process below the surface is generating a lot of heat and spewing out the molecules and particles that are seen by the other Cassini instruments when the spacecraft passes over the south polar region. Enceladus continues to surprise and fascinate.” The CIRS team is based at NASA Goddard.

This new view shows that at least three of the south polar fractures are active along almost their full lengths — the fourth one, on the right, was only partially covered by this scan. The infrared radiation was mapped by CIRS at wavelengths between 12 and 16 microns. The infrared data, shown in false color, are superimposed on a grayscale image mosaic of the south pole obtained by Cassini’s cameras on July 14, 2005, during the previous close Enceladus flyby. The warmest parts of the fractures tend to lie on locations of the plume jets identified in earlier images. Numbers on the map indicate latitude and longitude.

“These spectacular new data will really help us understand what powers the geysers. Plus, the surprisingly high temperatures make it more likely that there’s liquid water not far below the surface,” said John Spencer, Cassini scientist on the CIRS team at the Southwest Research Institute, Boulder, Colo.

Cassini flew through the jets during this flyby of the moon, and the spacecraft’s Ion and Neutral Mass Spectrometer saw a much higher density of volatile gases, water vapor, carbon dioxide and carbon monoxide, as well as organic materials, some 20 times denser than expected. Organic materials contain carbon and are necessary for life as we know it. Mission scientists say the organics “taste and smell” like some of those found in a comet. The jets themselves harmlessly peppered Cassini, exerting measurable torque on the spacecraft, and providing an indirect measure of the plume density.

This map was made by scanning the south pole during the period from 16 to 37 minutes after closest approach to Enceladus, at a distance between 14,000 and 32,000 kilometers (about 8,700 and 20,000 miles) as Cassini rapidly receded from its close (50-kilometer or 32-mile) flyby.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL. The Composite Infrared Spectrometer team is based at NASA’s Goddard Space Flight Center, Greenbelt, Md.
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