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Science 10 March 2006:
Vol. 311. no. 5766, pp. 1393 - 1401
DOI: 10.1126/science.1123013
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Research Articles

Cassini Observes the Active South Pole of Enceladus

C. C. Porco,1* P. Helfenstein,2 P. C. Thomas,2 A. P. Ingersoll,3 J. Wisdom,4 R. West,5 G. Neukum,6 T. Denk,6 R. Wagner,7 T. Roatsch,7 S. Kieffer,8 E. Turtle,9 A. McEwen,9 T. V. Johnson,5 J. Rathbun,10 J. Veverka,2 D. Wilson,1 J. Perry,9 J. Spitale,1 A. Brahic,11 J. A. Burns,2 A. D. DelGenio,12 L. Dones,13 C. D. Murray,14 S. Squyres2

Cassini has identified a geologically active province at the south pole of Saturn's moon Enceladus. In images acquired by the Imaging Science Subsystem (ISS), this region is circumscribed by a chain of folded ridges and troughs at ~55°S latitude. The terrain southward of this boundary is distinguished by its albedo and color contrasts, elevated temperatures, extreme geologic youth, and narrow tectonic rifts that exhibit coarse-grained ice and coincide with the hottest temperatures measured in the region. Jets of fine icy particles that supply Saturn's E ring emanate from this province, carried aloft by water vapor probably venting from subsurface reservoirs of liquid water. The shape of Enceladus suggests a possible intense heating epoch in the past by capture into a 1:4 secondary spin/orbit resonance.

1 Cassini Imaging Central Laboratory for Operations, Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301, USA.
2 Department of Astronomy, Cornell University, Ithaca, NY 14853, USA.
3 Division of Geological and Planetary Sciences, California Institute of Technology, 150-21, Pasadena, CA 91125, USA.
4 Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
5 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA.
6 Institut für Geologische Wissenschaften, Freie Universität, 12249 Berlin, Germany.
7 Institute of Planetary Research, German Aerospace Center, Rutherfordstrasse 2, 12489 Berlin, Germany.
8 Department of Geology, University of Illinois, Urbana, IL 61801, USA.
9 Department of Planetary Sciences, University of Arizona, Tucson, AZ 85721, USA.
10 Department of Physics, University of Redlands, 1200 East Colton Avenue, Redlands, CA 92373, USA.
11 Centre d'Etudes de Saclay, Université Paris 7, L'Orme des Merisiers, 91191 Gif-sur-Yvette Cedex, France.
12 Goddard Institute for Space Studies, NASA, 2880 Broadway, New York, NY 10025, USA.
13 Department of Space Studies, Southwest Research Institute, 1050 Walnut Street, Suite 400, Boulder, CO 80302, USA.
14 Astronomy Unit, Queen Mary, University of London, London E1 4NS, UK.

* To whom correspondence should be addressed. E-mail: carolyn{at}ciclops.org

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Science. ISSN 0036-8075 (print), 1095-9203 (online)