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W. B. Moore, G. Schubert (Dept. of Earth and Space Sciences and IGPP, UCLA)
Europa's major internal energy sources at the present time are radioactive decay and tidal heating. In a body smaller than the Moon, consisting partly of ice and having a significant iron core, radiogenic heat production is quite small, probably not exceeding a few times 1011 W. Tidal dissipation is capable of much greater heating rates and occurs both in the silicate and icy portions of the body. The maximum temperatures reached within Europa depend on the balance between dissipation and heat transfer. Heating rates greater than 1012 W are required to keep liquid water stable, and even larger rates are required in order to melt silicates, a critical precursor to the development of habitable zones benath the Europan surface. We present detailed quantitative calculations of tidal dissipation in a layered, viscoelastic Europa coupled with parameterized heat transfer in the ice, water, and silicate layers. The heat transfer parameterizations are derived from boundary-layer scalings of convection in temperature- and stress-dependent viscosity fluids with internal heating. The results indicate that, while sufficient heat may exist to keep water liquid under favorable conditions, convective heat transfer in the silicate mantle is at all times efficient enough to prevent silicate melting. This precludes the possiblity of hydrothermal activity akin to the mid-ocean ridge vents of Earth and demonstrates that there is more to finding habitable regions in the solar system than finding liquid water.
The author(s) of this abstract have provided an email address for comments about the abstract: bmoore@artemis.ess.ucla.edu