Sensitivity of the Fe# anomaly of the overturned silicate layer with respect to the rest of the mantle. (a) Sensitivity of this anomaly versus mantle thickness. Mars and Earth sizes are represented for clarity. Note that the final anomaly is expected to be maximum when the thickness of the mantle is that of the critical Rayleigh number D_Rac and tends to 0 at infinite thickness. (b) Sensitivity of the Fe# anomaly versus the bulk Fe# of the mantle. Earth and Mars compositions are represented for clarity. We extend compositions to lower bulk Fe# than Earth according to R. J. Spaargaren et al. (2023) (dotted line, see text). All other properties remain fixed at Earth-like values except for gravity acceleration, which is scaled linearly to planet size (assumed to be proportional to mantle thickness). The density anomaly secondary axis is valid for both panels (a) and (b).