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Enceladus: An Active Cryovolcanic Satellite

Spencer, John R. and Barr, Amy C. and Esposito, Larry W. and Helfenstein, Paul and Ingersoll, Andrew P. and Jaumann, Ralf and McKay, Christopher P. and Nimmo, Francis and Waite, J. Hunter (2009) Enceladus: An Active Cryovolcanic Satellite. In: Saturn from Cassini-Huygens Springer. pp. 683-724. ISBN 978-1-4020-9216-9.

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Abstract

Enceladus is one of the most remarkable satellites in the solar system, as revealed by Cassini's detection of active plumes erupting from warm fractures near its south pole. This discovery makes Enceladus the only icy satellite known to exhibit ongoing internally driven geological activity. The activity is presumably powered by tidal heating maintained by Enceladus' 2:1 mean-motion resonance with Dione, but many questions remain. For instance, it appears difficult or impossible to maintain the currently observed radiated power (probably at least 6 GW) in steady state. It is also not clear how Enceladus first entered its current self-maintaining warm and dissipative state- initial heating from non-tidal sources is probably required. There are also many unanswered questions about Enceladus' interior. The silicate fraction inferred from its density of 1:68gcm−2 is probably differentiated into a core, though we have not direct evidence for differentiation. Above the core there is probably a global or regional liquid water layer, inferred from several models of tidal heating, and an ice shell thick enough to support the ~1 km amplitude topography seen on Enceladus. It is possible that dissipation is largely localized beneath the south polar region. Enceladus' surface geology, ranging from moderately cratered terrain to the virtually crater-free active south polar region, is highly diverse, tectonically complex, and remarkably symmetrical about the rotation axis and the direction to Saturn. South polar activity is concentrated along the four “tiger stripe” fractures, which radiate heat at temperatures up to at least 167K and are the source of multiple plumes ejecting ~200kgs−2 of H2O vapor along with significant N2 (or C2H4), CO2, CH4, NH3, and higher-mass hydrocarbons. The escaping gas maintains Saturn's neutral gas torus, and the plumes also eject a large number of micron-sized H2O ice grains that populate Saturn's E-ring. The mechanism that powers the plumes is not well understood, and whether liquid water is involved is a subject of active debate. Enceladus provides perhaps the most promising potential habitat for life in the outer solar system, and the active plumes allow the unique opportunity for direct sampling of that zone. Enceladus is thus a prime target for Cassini's continued exploration of the Saturn system, and will be a tempting target for future missions.

Document Type:Book Section
Additional Information:DOI: 10.1007/978-1-4020-9217-6_21
Title:Enceladus: An Active Cryovolcanic Satellite
Authors:
AuthorsInstitution or Email of Authors
Spencer, John R.Southwest Research Institute, Boulder, USA
Barr, Amy C.Southwest Research Institute, Boulder, USA
Esposito, Larry W.LASP, University of Colorado, Boulder, USA
Helfenstein, PaulCenter for Radiophysics and Space Research, Cornell University, USA
Ingersoll, Andrew P.Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, USA
Jaumann, RalfUNSPECIFIED
McKay, Christopher P.NASA Ames Research Center, Mountain View, USA
Nimmo, FrancisDept. Earth and Planetary Sciences, University of California Santa Cruz, Santa Cruz, USA
Waite, J. HunterSouthwest Research Institute, San Antonio, USA
Date:2009
Journal or Publication Title:Saturn from Cassini-Huygens
Refereed publication:Yes
In ISI Web of Science:No
Page Range:pp. 683-724
Editors:
EditorsEmail
Dougherty, Michele K.UNSPECIFIED
Esposito, Larry W.UNSPECIFIED
Krimigis, Stamatios M.UNSPECIFIED
Publisher:Springer
ISBN:978-1-4020-9216-9
Status:Published
Keywords:Enceladus, Cassini, active plumes
HGF - Research field:Aeronautics, Space and Transport (old)
HGF - Program:Space (old)
HGF - Program Themes:W EW - Erforschung des Weltraums
DLR - Research area:Space
DLR - Program:W EW - Erforschung des Weltraums
DLR - Research theme (Project):W - Vorhaben CASSINI (old)
Location: Berlin-Adlershof
Institutes and Institutions:Institute of Planetary Research
Deposited By: Susanne Pieth
Deposited On:09 Dec 2009 14:36
Last Modified:09 Dec 2009 14:36

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