planet

Heat-pipe regime

How a world sheds heat when there is too much of it to conduct out: the melt carries it instead. Molten rock rises through narrow conduits, erupts at the surface, cools and radiates to space, and successive layers bury the older ones and drive them downward. There is a satisfying paradox here: because cold surface rock is continually being buried, the lid ends up colder, thicker and stronger — not thinner — despite ferocious melting below. Io is the living example, venting roughly 100 TW this way and erasing every impact crater.