HR: 16:45h
AN: P54A-04    [Abstracts]
TI: Tidal Heating Susceptibility in Short Period Terrestrial Exoplanets
AU: * Henning, W G
EM: henning@fas.harvard.edu
AF: Harvard University Department of Earth and Planetary Sciences, 20 Oxford St., Cambridge, MA 02138, United States
AU: O'Connell, R
EM: oconnell@geophysics.harvard.edu
AF: Harvard University Department of Earth and Planetary Sciences, 20 Oxford St., Cambridge, MA 02138, United States
AU: Sasselov, D
EM: dsasselov@cfa.harvard.edu
AF: Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138, United States
AB: We have analyzed the general tidal heating of terrestrial class exoplanets to identify the orbital range where tides dominate planetary heat flux and to analyze possible limiting mechanisms. Calculations show that for Earth- mass planets in short period orbits similar to those of the Hot Jupiters (roughly 1 to 20 days), the potential exists for extreme tidal heating many orders of magnitude beyond what is observed in our solar system, and far in excess of each given planet's radiogenic heating. The long-term eccentricities needed to support such tides may come from indirect secular perturbations or directly from mean-motion resonances with Hot Jupiters. In particular, a 2:1 resonance between a gas giant and terrestrial companion has the potential to create a unique type of supertidal world. We compare the results of various basic methods for estimating tidal heating, including classical frequency independent methods as well as frequency and temperature dependent viscoelastic methods based on Maxwell and Burgers rock rheologies. Equilibrium surface and interior temperatures have been calculated using parameterized convection models for both hypothetical planets and observed exoplanets such as GJ876d, GJ581c and GJ581d. While hotspots are likely, we find that tidal heating will have a negligible impact on the global surface temperatures of these planets unless they exist in unusually low insolation environments such as around red dwarf stars. Results show that equilibrium tidal heat production for Earth-mass planets in the range of Earth's current radiogenic and secular cooling background heat flow (40 TW) results in partial melting at the base of an Earth-like lithosphere. We find the subsequent advection of segregated melt from this layer is insufficient to produce a surface magma ocean below a tidal forcing of 300,000 TW and may thus represent a stable layer configuration. High tidal heat outputs such as this are predicted by models without melting, but may be suppressed by the onset and growth of partial melting and the resulting drop in overall planetary viscosity. The effects of various phenomenology central to these planets such as heliocentric spin-orbit resonances and atmospheric stability are also addressed.
DE: 5418 Heat flow
DE: 5430 Interiors (8147)
DE: 5450 Orbital and rotational dynamics (1221)
DE: 5455 Origin and evolution
DE: 5480 Volcanism (6063, 8148, 8450)
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting