EEPS Seminar: William Moore, Hampton University
Abstract Title: Heat Pipe Planets
A look at the surfaces of the terrestrial planets other than Earth reveals vast plains of extruded lava, of mafic or even ultra-mafic composition, flowing over vast distances at low slopes from sources which are not elevated or even identifiable. On these bodies, tectonic deformation is dominated by compression, and ancient topographic and gravity anomalies have been preserved to the present without significant relaxation. Is there a single explanation for these shared features? The operation of volcanic heat pipes as the dominant heat transport mechanism in the early histories of these bodies may explain these observations and provide a universal model of the way terrestrial bodies transition from a magma-ocean state into subsequent single-plate, stagnant-lid convection or plate tectonic phases. In the heat-pipe cooling mode, magma moves from a high melt-fraction asthenosphere through the lithosphere to erupt and cool at the surface via narrow channels. Despite high surface heat flow, the rapid volcanic resurfacing produces a thick, cold, and strong lithosphere which undergoes contractional strain forced by downward advection of the surface toward smaller radii. In the absence of plate tectonics, heat-pipe cooling is the last significant endogenic resurfacing process experienced by most terrestrial bodies in the solar system, because subsequent stagnant-lid convection produces only weak tectonic deformation. Due to their higher heat content, terrestrial exoplanets appreciably larger than Earth may remain in heat-pipe mode for much of the lifespan of a Sun-like star and would likely be found in this stage of evolution — the stage in which life first arose on Earth.