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G. Tobie (LPL, University of Arizona), O. Grasset (LPG, University of Nantes (Fr)), J. I. Lunine (LPL, University of Arizona), A. Mocquet, C. Sotin (LPG, University of Nantes (Fr))
Through coupled thermal and orbital calculations including a full description of tidal dissipation, heat transfer, the H2O-NH3 phase diagram and methane clathrate stability, we propose models for the internal structure and composition of Titan ahead of Cassini-Huygens measurements. The high value of Titan's orbital eccentricity provides a strong constraint on the amount of the tidal energy dissipation on its surface and within its interior since its formation. We show that only models with a few percent of ammonia in the primordial liquid water shell and a significant fraction of methane clathrate within the interior can limit the damping of the eccentricity over the age of the solar system and explain the origin of the atmospheric methane. The present models predict that a liquid ammonia-rich water layer should still be present within Titan under a convective outer layer made of ice I and methane clathrate. Dissociation of methane clathrate near the surface induced by hot thermal upwelling would be able to explain the replenishement of methane in Titan's atmosphere. Forthcoming data from the NASA/ESA Cassini-Huygens mission will allow us to test the present models.
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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.