Obliquity tides do not significantly heat Enceladus
Abstract
The source of the observed heat flow at the south pole of Enceladus remains a mystery. Tidal heating, specifically related to the eccentricity of the orbit has been widely suggested as a possible source. Tyler (2009, 2011) proposed that the tide due to obliquity might drive significant ocean flow, and that the dissipation of the ocean's kinetic energy may be an alternate source for the elevated heat flux. To supply the 15.8±3.1 GW of power observed by the Cassini CIRS instrument (Howett et al. 2011), the obliquity angle would have to be greater than 0.2 degrees for a global ocean. While there is currently no measurement of Enceladus' obliquity, Enceladus is expected to occupy a Cassini state, where the spin pole, orbit normal and an invariable pole remain coplanar while the spin pole and orbit normal precess. If Enceladus currently occupies a Cassini state, it is likely to be Cassini state 1, where the obliquity should be significantly less than the orbital inclination (0.009°), with the exact angle dependent on the interior structure. Unless our assumptions about the interior structure, particularly the degree-2 gravity coefficients, are significantly inaccurate, this result is robust, and consequently obliquity tides are unlikely to contribute significantly towards the heat budget of Enceladus.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.P11B1599C
- Keywords:
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- 5450 PLANETARY SCIENCES: SOLID SURFACE PLANETS / Orbital and rotational dynamics;
- 6280 PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS / Saturnian satellites