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Cassini Encounters Enceladus: Background and the Discovery of a South Polar Hot Spot
J. R. Spencer,1*J. C. Pearl,2M. Segura,2F. M. Flasar,2A. Mamoutkine,2P. Romani,2B. J. Buratti,3A. R. Hendrix,3L. J. Spilker,3R. M. C. Lopes3
The Cassini spacecraft completed three close flybys of Saturn'senigmatic moon Enceladus between February and July 2005. Onthe third and closest flyby, on 14 July 2005, multiple Cassiniinstruments detected evidence for ongoing endogenic activityin a region centered on Enceladus' south pole. The polar regionis the source of a plume of gas and dust, which probably emanatesfrom prominent warm troughs seen on the surface. Cassini's CompositeInfrared Spectrometer (CIRS) detected 3 to 7 gigawatts of thermalemission from the south polar troughs at temperatures up to145 kelvin or higher, making Enceladus only the third knownsolid planetary body—after Earth and Io—that issufficiently geologically active for its internal heat to bedetected by remote sensing. If the plume is generated by thesublimation of water ice and if the sublimation source is visibleto CIRS, then sublimation temperatures of at least 180 kelvinare required.
1 Department of Space Studies, Southwest Research Institute, 1050 Walnut Street, Suite 400, Boulder, CO 80302, USA. 2 NASA Goddard Spaceflight Center, Code 693, Greenbelt, MD 20771, USA. 3 Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA.
* To whom correspondence should be addressed. E-mail: spencer{at}boulder.swri.edu
Cassini observes the active south pole of Enceladus..
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Science
311, 1393-1401
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311, 1419-1422
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Enceladus' water vapor plume..
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Composition and physical properties of Enceladus' surface..
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