HEAT-PIPE COOLING AS A UNIVERSAL PROCESS OF HOT TERRESTRIAL PLANETS

On all terrestrial bodies other than Earth, endogenic resurfacing has been dominated by volcanic landforms. When volcanism dominates heat transport, a terrestrial body enters a heat-pipe mode, in which hot magma moves through the lithosphere in narrow channels. Even at high heat flow, a heat-pipe planet develops a thick, cold, downward-advecting lithosphere dominated by mafic/ultra-mafic flows and contractional deformation at the surface. Active heat-pipe cooling controls the tectonics of Jupiter’s moon Io, the hottest terrestrial body in the Solar system due to tidal heating. Recent work suggests that the geologic record of early Earth is consistent with first-order predictions of heat-pipe cooling until ~3.2 Ga. Here, we review the geological constraints of the other terrestrial bodies in the Solar system: Mercury, Venus, the Moon, and Mars. We demonstrate that these geologic records are also consistent with early heat-pipe cooling, followed by transitions to single-plate, rigid-lid convective phases. We conclude that heat-pipe cooling is a universal process experienced by all terrestrial bodies of sufficient size. Terrestrial exoplanets appreciably larger than Earth may remain in heat-pipe mode for much of the lifespan of a Sun-like star.