Comparison of the convective cooling duration of graphite and silicate mantles with a core radius of 1500 km and a mantle thickness of 100−1000 km. The inset panel shows the two models (Hofmeister et al. 2014, and constant thermal conductivity) for thermal conductivity of graphite used to calculate the duration of convective cooling. For models with a graphite mantle, in addition to constant thermal conductivity, two cases of viscosity based on the minimum and maximum values of shear modulus arealso compared.