The tidal response of super-Earths and large icy worlds

The amount of detected super-Earths increases drastically. Most of the super-Earth candidates orbit at close distances from their central star, and therefore subjected to large tidal forcing. Low mass planets (2 - 10 Earth's mass) with short orbital periods (< 10 - 20 days) seem especially abundant around M-dwarf stars. Owing to strong tidal interaction, these planets are tidally locked, which has many important consequences for their thermal state and putative habitability. Tidal friction in the interior of such planets, both during the primordial despinning and once the planet is locked on an eccentric orbit, should significantly contribute to the internal heat budget. In the present study, we model the interior structure of super-Earths and large icy worlds, we compute their viscoelastic response to tidal forcing, and finally we evaluate the impact of tidal dissipation on the thermal evolution. Preliminary results indicate that for similar mass and orbital configuration, planets containing 50 wt% water ice are 25 to 50 times more dissipative than Earth-like planets, because of the thick and dissipative icy mantle. Even for moderate eccentricities (1%), the total power dissipated in icy planets varies from 100 TW to 300 TW for planet masses ranging from 1 to 10 x Earth's mass, respectively. Such large heat production rates (5 to 15 times larger than the Earth's radiogenic heating) are expected to strongly affect the dynamics of the icy mantle and to favor the presence of liquid water, not only at the surface but also potentially throughout the whole icy mantle, with important consequences for the exobiological potential of icy worlds.