DPS 2001 meeting, November 2001
Session 38. Titan Posters
Displayed, 9:00am Tuesday - 3:00pm Saturday, Highlighted, Friday, November 30, 2001, 9:00-10:30am, French Market Exhibit Hall

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[38.05] Thermal structure and internal constitution of Titan

F. Sohl, H. Hussmann, B. Schwentker, T. Spohn (Institut für Planetologie, Münster), R.D. Lorenz (Lunar and Planetary Laboratory, Tucson)

The mean densities of Ganymede, Callisto, and Titan indicate that their interiors are composed of ice and silicates at nearly equal shares by mass. However, Titan's substantial nitrogen atmosphere suggests that the planetesimals that formed the satellite were enriched in more volatile ices such as NH3 and CH4. The interior of Titan may be differentiated into a rocky core and an icy mantle as a consequence of substantial accretional heating accompanied by partial outgassing and the formation of an early atmosphere. Depending on the amount of volatiles incorporated into the icy mantle, the radiogenic heating rate in the core, and the effectiveness of the heat transfer to the surface, an ammonia-rich liquid water layer may have formed underneath Titan's icy crust and may have survived to the present day. Therefore, we assume the interior of Titan to consist of a rocky core with chondritic heat production underneath a high-pressure ice layer, an isothermal sub-surface ocean, and an outermost ice I shell. The outer ice shell consists of a conductive (stagnant) lid and a convective sub-layer. The temperature and pressure at the base of the ice I layer are estimated from the pressure-dependent ammonia-water melting curve assuming various compositions of the internal ocean. Taking the assumption of thermal equilibrium, we obtain the surface heat flow and the thickness of the stagnant lid and the well-mixed convective sublayer from a parameterized model of convective heat transfer. The convective sublayer typically comprises about 25% of the thickness of the ice I layer and the surface heat flow is of the order of several 1011~W. The ammonia-water ocean extends over a depth range of several 100 km beneath the ice I layer and is underlain by a substantial high-pressure ice shell. Most of Titan's mass is concentrated in the silicate core that encompasses as much as 80% of the satellite's radius. The moment of inertia factor will be measured by the Cassini mission and is predicted to vary between 0.3 and 0.35. Furthermore, radar and optical remote sensing may determine crater morphologies that constrain the outermost ice layer thickness.

The author(s) of this abstract have provided an email address for comments about the abstract: sohl@uni-muenster.de

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