Lateral Melt Variations induce Shift in Io’s Peak Tidal Heating

The innermost Galilean moon, Io, exhibits widespread tidally-driven volcanism. Monitoring of its volcanoes has revealed that they are not homogeneously distributed across its surface: volcanic activity is higher at low latitudes and peaks east of the sub- and anti-Jovian points. The observed longitudinal shift in volcanic activity has been presented as evidence of Io having a fluid magma ocean, as dissipation in a radially symmetric solid body cannot explain it. Here, we simulate the feedback between tidal heating and melt production in a solid body and demonstrate that a longitudinal shift in the heating pattern naturally arises from the feedback. Our results provide an alternative explanation for the observed volcanic heat flux without requiring a fluid magma ocean. The feedback between tidal dissipation and interior properties that results in interiors that deviate from radial symmetry is expected to drive the interior evolution of other tidally-active worlds, including icy moons such as Europa and Enceladus and exo-planets/moons with high eccentricity or obliquity.