Thermal evolution of rocky exoplanets covered with graphite

Laboratory and computational studies discussing the mineralogy of fully differentiated carbon-enriched rocky exoplanets have indicated the presence of a graphite outer shell. Our results show that, due to graphite's high thermal conductivity, conduction is the dominant heat transport mechanism in graphite shells of rocky exoplanets. We find that a graphite outer shell behaves like a stagnant lid essentially slowing down planetary cooling due to thermal inertia and thermal resistance of graphite. Clearly, planetary thermal structure and its evolution depend on the mineralogy of different layers in the planet.