Surface and CMB heat flux for models with different surface temperature contrasts. The dashed lines are in mW m⁻² (right axis) and the solid lines in W m⁻² (left axis). The shaded regions on either side of the lines represent the minimum and maximum values within a moving average window. If the nightside is not fully molten, the day-side heat flux is roughly three orders of magnitude higher than the nightside heatflux (A). For the case with T_day = 2600 K and T_night = 1800 K, the surface fluxes are of the same order of magnitude (B). For T_day = 3900 K and T_night = 2000 K, the nightside heat flux varies in the range 1–4 W m⁻², whereas the dayside heat flux varies from 0 to −200 W m⁻² (C).