Interplay of endothermic phase transition and electron thermal conductivity results in episodic mantle convection in Super-Earth exoplanets

Details Interplay of endothermic phase transition and electron thermal conductivity results in episodic mantle convection in Super-Earth exoplanets Interplay of endothermic phase transition and electron thermal conductivity results in episodic mantle convection in Super-Earth exoplanets

Dec 2009

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufm.p42b..09v&link_type=abstract

American Geophysical Union, Fall Meeting 2009, abstract #P42B-09

Physics

[5455] Planetary Sciences: Solid Surface Planets / Origin And Evolution, [8120] Tectonophysics / Dynamics Of Lithosphere And Mantle: General, [8147] Tectonophysics / Planetary Interiors

Scientific paper

Pressure and temperature regime in Super-Earth exoplanets withup to ten times the Earth's mass and an earth-like core mass fraction can exceed 1000 GPa and 7000K. Theoretical calculations have shown that such P,T values allow the dissocation of post-perovskite into the oxides to take place, an endothermic phase transition with a highly negative Clapeyron slope (Umemoto et al., Science, 2006). Under the prevailing temperature range (T > 5000 K) in the deep mantle of these planets electronic thermal conductivity also becomes effective with values reaching 70 W/m/K. We have investigated mantle convection models combining the dissociation of post-perovskite and a composite thermal conductivity model including an electronic component. We apply an Arrhenius type rheology with viscosity variation due to temperature of over five orders of magnitude producing conditions for a stagnant lid regime. The convection results exhibit a strong episodicity of the mantle dynamics due to the interaction of the phase transition near the bottom of the mantle with the highly temperature dependent conductivity. We have explored this strongly time dependent behavior of heat and mass transport in the bottom of the mantle by monitoring particle tracers. Detailed analysis of these tracer data confirm that the interaction between the high conductivity and the strongly endothermic phase transition is causing the episodic behavior. Thermal evolution, in particular of a metal core is strongly influenced by this episodic behavior where periods of large heat exchange with the mantle are exchanged with quiescent periods.

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