Tidal Heating in a Subsurface Magma Ocean on Io Revisited

Abstract

We investigate the tidal dissipation in Io's hypothetical fluid magma ocean using a new approach based on the solution of the 3D Navier-Stokes equations. Our results indicate that the presence of a shallow magma ocean on top of a solid, partially molten layer leads to an order of magnitude increase in dissipation at low latitudes. Tidal heating in Io's magma ocean does not correlate with the distribution of hot spots, and is maximum for an ocean thickness of about 1 km and a viscosity of less than 104 Pa s. Due to the Coriolis effect, the k2 Love number can depend on the harmonic order. We show that the analysis of k2 may not reveal the presence of a fluid magma ocean if the ocean thickness is less than 2 km. If the fluid layer is thicker than 2 km, k20 approximate to k22/2 approximate to 0.7. Jupiter's moon Io is the most active volcanic body in the Solar System. Although it is generally accepted that Io's volcanic activity is driven by the heat generated by tidal friction, the origin and the distribution of tidal heating within Io's interior remain a subject of debate. Here we investigate the tidal dissipation in Io's hypothetical fluid magma ocean using a new approach based on the solution of general equations describing the motion of viscous fluid. Our results indicate that the presence of a shallow magma ocean on top of a solid, partially molten layer leads to an order of magnitude increase in dissipation at low latitudes. Tidal heating in Io's magma ocean does not correlate with the distribution of hot spots, and is maximum for an ocean thickness of about 1 km and a viscosity of less than 104 Pa s. We also discuss the sensitivity of Io's gravity signature to the presence of a magma ocean and provide estimates of gravitational perturbations induced by tidal deformation. The presence of a shallow magma ocean on top of a partially molten layer leads to a strong increase in tidal dissipation at low latitudes Due to the Coriolis effect, the degree-2 Love numbers for models with a magma ocean can depend on the harmonic order The tidal Love numbers are not sensitive to the presence of a fluid magma ocean if the thickness of the fluid layer is less than 2 km