Callisto's Ocean Without Full Differentiation: How an Undifferentiated Interior Still Permits a Liquid Layer

Callisto presents an apparent contradiction: its moment of inertia shows it never fully separated into rock and ice, yet magnetic induction data indicate a conducting liquid layer. This study tests whether radiogenic heat in a mixed interior can maintain an ocean under those conditions. Radiogenic powers of 242.1 to 290.5 gigawatts give mean surface fluxes near 3.316 to 3.987 milliwatts per square metre and conductive shell thicknesses of 178.5 to 148.4 kilometres. Antifreeze components lowering the melting point toward 252 kelvin thicken the liquid interval further. No contradiction remains: partial differentiation and a deep, cold ocean are compatible. Computed from stated assumptions, not measured.