Cassini Finds Enceladus is a Powerhouse

MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109 TELEPHONE 818-354-5011
http://www.jpl.nasa.gov

Jia-Rui Cook 818-354-0850
Jet Propulsion Laboratory, Pasadena, Calif.
jccook@jpl.nasa.gov

Joe Fohn 210-522-4630
Southwest Research Institute, San Antonio
jfohn@swri.org

News release: 2011-067 March 7, 2011

Cassini Finds Enceladus is a Powerhouse

PASADENA, Calif. – Heat output from the south polar region of Saturn's moon
Enceladus is much greater than was previously thought possible, according to a new
analysis of data collected by NASA's Cassini spacecraft. The study was published in the
Journal of Geophysical Research on March 4.

Data from Cassini's composite infrared spectrometer of Enceladus' south polar terrain,
which is marked by linear fissures, indicate that the internal heat-generated power is
about 15.8 gigawatts, approximately 2.6 times the power output of all the hot springs in
the Yellowstone region, or comparable to 20 coal-fueled power stations. This is more than
an order of magnitude higher than scientists had predicted, according to Carly Howett,
the lead author of study, who is a postdoctoral researcher at Southwest Research Institute
in Boulder, Colo., and a composite infrared spectrometer science team member.

"The mechanism capable of producing the much higher observed internal power remains a
mystery and challenges the currently proposed models of long-term heat production,"
said Howett.

It has been known since 2005 that Enceladus' south polar terrain is geologically active
and the activity is centered on four roughly parallel linear trenches, 130 kilometers (80
miles) long and about 2 kilometers (1 mile) wide, informally known as the "tiger stripes."
Cassini also found that these fissures eject great plumes of ice particles and water vapor
continually into space. These trenches have elevated temperatures due to heat leaking out
of Enceladus' interior.

A 2007 study predicted the internal heat of Enceladus, if principally generated by tidal
forces arising from the orbital resonance between Enceladus and another moon, Dione,
could be no greater than 1.1 gigawatts averaged over the long term. Heating from natural
radioactivity inside Enceladus would add another 0.3 gigawatts.

The latest analysis, which also involved the composite infrared spectrometer team
members John Spencer at Southwest Research Institute, and John Pearl and Marcia
Segura at NASA's Goddard Space Flight Center in Greenbelt, Md., uses observations
taken in 2008, which cover the entire south polar terrain. They constrained Enceladus'
surface temperatures to determine the region's surprisingly high output.

A possible explanation of the high heat flow observed is that Enceladus' orbital
relationship to Saturn and Dione changes with time, allowing periods of more intensive
tidal heating, separated by more quiescent periods. This means Cassini might be lucky
enough to be seeing Enceladus when it's unusually active.

The new, higher heat flow determination makes it even more likely that liquid water
exists below Enceladus' surface, Howett noted.

Recently, scientists studying ice particles ejected from the plumes discovered that some
of the particles are salt-rich, and are probably frozen droplets from a saltwater ocean in
contact with Enceladus' mineral-rich rocky core. The presence of a subsurface ocean, or
perhaps a south polar sea between the moon's outer ice shell and its rocky interior would
increase the efficiency of the tidal heating by allowing greater tidal distortions of the ice
shell.

"The possibility of liquid water, a tidal energy source and the observation of organic
(carbon-rich) chemicals in the plume of Enceladus make the satellite a site of strong
astrobiological interest," Howett said.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space
Agency and the Italian Space Agency. NASA's Jet Propulsion Laboratory, Pasadena,
Calif., 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 CIRS team is based at NASA's
Goddard Space Flight Center in Greenbelt, Md., where the instrument was built.

More information about the Cassini-Huygens mission is at: http://www.nasa.gov/cassini
and http://saturn.jpl.nasa.gov.

-end-

To remove yourself from this mailing, please go to http://www.kintera.org/TR.asp?a=mrKYI4OAL9IOKcJ&s=jjI0K4NJIfIMK3OPKtE&m=hwK1LmO0JmJ6KrJ

To remove yourself from all mailings from NASA Jet Propulsion Laboratory, please go to http://www.kintera.org/TR.asp?a=pkI4JdPMKcLVImI&s=jjI0K4NJIfIMK3OPKtE&m=hwK1LmO0JmJ6KrJ