The Distribution of Radiogenic Elements in Stars with and without Planetary Systems: Implications for Dynamics and Habitability

We present the results of an abundance analysis of U, Th and K in a survey of ~10 sun-like stars for both stars with known planetary systems and without. The presence of these radiogenic isotopes facilitates the long-term dynamic evolution of planetary interiors, including plate tectonics and the cycling of volatile compounds including water and carbon between deep and surface planetary reservoirs. In Earth, radiogenic heating from the mantle is responsible for 18-35% of present-day surface heat flow. Without this heat source Earth would have no plate tectonics or the associated surface-interior exchange of volatile elements crucial to habitability. We therefore examine the abundances of U, Th, and K and analyze the variability of these elements between stars as a proxy for determining the likelihood for variation of radiogenic heating between terrestrial planetary systems. As moderately volatile (K) and refractory elements (U,Th), the relative solar abundance of these species can be taken as an upper bound for total and relative abundances in planets forming within the habitable zone.