Neighbouring moons, partial melt, and oceans: Tides of rocky and icy outer solar system satellites

There is astonishing diversity in outer solar system satellites. While many of these bodies are of great interest due to their astrobiological potential, they are fascinating celestial bodies in their own right. They feature a vast array of interacting geophysical, geochemcial, and celestial mechanical processes for which straightforward Earth-analogues do not always exist. The thermal evolution of these moons—a primary concern for notions of habitability—is often strongly influenced by tides, the periodic, heat-generating deformation of their ice, water, and rock layers. While significant advancements in tidal modelling have been made in the last 25 years, we still do not understand some of the details behind the basic mechanisms for how tidal deformation in solid and liquid saps energy from the rotational–orbital state of the deformed body. In this lecture, I will review my recent contributions in this field, including discovering the mechanism through which neighbouring moons can accelerate tidal deformation in ocean worlds, and new steps towards a self-consistent geodynamical model of Io’s thermal evolution, before summarising the major gaps that must be resolved if we are to most successfully exploit data returned by Europa Clipper and JUICE.