The rotation of planets hosting atmospheric tides: from Venus to habitable super-earths

TL;DR

This paper analyzes how atmospheric and solid tides influence the rotational states of Venus-like and super-Earth planets, especially within habitable zones, emphasizing the importance of dissipative mechanisms in planetary spin stability.

Contribution

It provides an analytic expression for the total tidal torque on Venus-like planets, elucidating the transition between solid and thermal tide dominance across different orbital distances.

Findings

Thermal tides dominate far from the star, influencing planetary rotation.

Solid tides are dominant close to the star, affecting spin states.

Habitable zone conditions lead to multiple equilibrium rotation states.

Abstract

The competition between the torques induced by solid and thermal tides drives the rotational dynamics of Venus-like planets and super-Earths orbiting in the habitable zone of low-mass stars. The tidal responses of the atmosphere and telluric core are related to their respective physical properties and strongly depend on the tidal frequency. The resulting torque determines the possible equilibrium states of the planet's spin. We compute here an analytic expression for the total tidal torque exerted on a Venus-like planet. This expression is used to characterize the equilibrium rotation of the body. Close to the star, the solid tide dominates. Far from it, the thermal tide drives the rotational dynamics of the planet. The transition regime corresponds to the habitable zone, where prograde and retrograde equilibrium states appear. We demonstrate the strong impact of the atmospheric properties and of the rheology of the solid part on the rotational dynamics of Venus-like planets, highlighting the key role played by dissipative mechanisms in the stability of equilibrium configurations.