Accretional heating of the satellites of Saturn and Uranus

We consider the heating of the larger satellites of Saturn and Uranus (with the exception of Titan) by deposition of impactor kinetic energy during satellite accretion. Satellite growth takes place from cisplanetary and transplanetary planetesimal swarms, proceeding until the planetesimal reservoirs are exhausted. Impact velocities are controlled by the initial orbital eccentricities of the planetesimals, and by gravitational focusing by the planet and the growing satellite. Heat is deposited below the satellite's surface by dissipation of impact‐generated shocks. An effective thermal diffusivity produced by impact mixing provides most of the energy transport within the satellite during accretion. A number of parameters that go into the calculation are poorly constrained. The ones that can have an important influence on the results are the Safronov parameter describing the mean orbital eccentricity of bodies in the cisplanetary impactor swarm, the exponent in the power law size distribution of impacting bodies, and the fraction of the impactor kinetic energy partitioned into subsurface heat. Typical post accretion thermal profiles show temperature maxima several tens of kilometers beneath the surface. The maximum temperature reached is in all cases insufficient to melt H 2 O ice. However, if NH 3 or CH 4 is present within the satellites, accretional heating can produce a zone of relatively warm, mobile, and buoyant material tens of kilometers below the surface. Cooling of the outer regions of the satellite immediately following accretion will produce thermal stresses sufficient to fracture surface materials, perhaps producing conduits that will allow the mobilized material to ascend to the surface. Accretional heating therefore may have been responsible for some of the resurfacing and tectonism that has taken place on many of the Saturnian and Uranian satellites.