Mantle’s in-plane obliquity ε_m1 (a) and deviation from the Cassini plane ε_m2 (b) as functions of the core flattening coefficient f_c and viscous relaxation time τ_ν. The white domains correspond to values that fall outside the colour scales. In these regions, the linear approximation is no longer valid and the equations of motions have to be solved treating the core’s in-plane obliquity and angular velocity non-linearly. Black crosses indicate the parameters considered by Peale et al. (2014), shown as red dots in our Figure 1.