On the Distribution and Variation of Radioactive Heat Producing Elements Within Meteorites, the Earth, and Planets

The heat production budget of a planet exerts a first order control on its thermal evolution, tectonics, and likelihood for habitability. However, our knowledge of heat producing element concentrations for silicate-metal bodies in the solar system—including Earth—is limited. Here we review the chronicle of heat producing elements (HPEs) in the solar system, from the interstellar medium, to their incorporation in the protoplanetary disk and accreting planetesimals, to later collisional or atmospheric-erosion modifications. We summarise the state of knowledge of the HPEs in terrestrial planets and meteorites, and current Earth models from emerging constraints, and assess the effect variations may have on the thermal and tectonic history of terrestrial planets.