Increased Tidal Dissipation in Rocky Satellites Subjected to Realistic Rheological Responses

We show that a satellite in an eccentric orbit will produce increased tidal dissipation compared to prior models, in certain temperature and frequency domains, when its interior is modeled with realistic rheologies. The magnitude of this dissipation is a function of how the satellite's interior rock responds to tidal stresses. The microphysics of common terrestrial rock samples have been well documented in laboratory settings by the geophysical community, but such data have been somewhat underutilized for Solar System planetary tidal applications. By examining low-to-moderate temperature mantles ( 1400K), we find realistic models, such as the Andrade rheology, produce 4x the dissipative heating compared to the traditional Maxwell model. Further heating is generated from more recent extensions beyond the Andrade rheology that capture an even greater range of grain scale phenomena. This creates a new spectrum of tidal-convective equilibrium points that a cooling or warming planetary object can fall into, thereby driving the system to unique long-term states. This has implications for the thermal-orbital history of tidally active systems, such as the Laplace resonance between Io, Europa, and Ganymede and any similarly resonant exomoon. In particular, enhanced heat production at lower mantle temperatures can significantly improve the ability for Io (and Io-analog exomoons) to recover from low-eccentricity excursions, and return to highly active tidal states, such as the state presently observed on Io. In contrast, during orbital oscillations, less-realistic rheological models often allow mantle temperatures to fall too low for efficient viscoelastic coupling, preventing the durable maintenance of long-term tidal activity.