Temperature (left column) and viscosity (right column) profiles at t = 4.55 Gyr for planets with variable bulk-mantle Mg/Si and FeO content as annotated, as a function of pressure (GPa), ranging from the surface (0 GPa) to the core–mantle boundary (138 GPa, 2891 km). In the top row, FeO content is 1 wt%. In the bottom row, Mg/Si = 0.8. Profiles are shown for t = 4.55 Gyr. PT- and SL-cases are shown as solid and dashed lines, respectively. The cases shown in the bottom row with 8 and 20 wt% FeO demonstrate stably stratified mantles.