Radiogenic Against Tidal Heating Across Six Icy Moons: A Uniform Accounting and Its Dividing Line

Six icy moons are placed on a single accounting basis: chondritic radiogenic heating in the rocky fraction against classical tidal dissipation at each moon's present eccentricity. The ratio of tidal to radiogenic power spans from 1.32e-05 for Triton, where tides contribute essentially nothing, to 21.1 for Europa and 55.77 for Enceladus, where tides dominate by large factors. Ganymede's tidal term falls an order of magnitude below its radiogenic term, at a ratio of 0.09988, while Titan's high eccentricity brings it near parity, with a tidal term of 291.1 gigawatts against 332.9 gigawatts radiogenic. The dividing line between radiogenic and tidal worlds falls between Ganymede and Callisto in this accounting. Computed uniformly from stated assumptions, not measured.