Fig. 4

Change of atmospheric thickness and outgassed partial pressures with planetary mass after 4.5 Gyr of simulated mantle convection. Individual panels compare reduced mantles (IW buffer) with oxidised mantles (QFM buffer), and rows indicate different initial volatile cases (i.e. dry, low, high) from Table 1. The left column of the panel shows the mass-dependence of modelled atmospheric thickness, comparing reduced mantles (black dashed line) with oxidised mantles (green solid line). Shaded areas show the 1\(\sigma\) variation across all simulations therein, while the lines denote the median. In the central and right column we examine the partial pressures of \(\text {H}_{2}\text {O}\) (purple swaths), \(\text {H}_{2}\) (green swaths), \(\text {CO}_{2}\) (orange swaths), and \(\text {CO}\) (red swaths). Shaded areas show the 1\(\sigma\) variation across all simulations therein, considering that for a given volatile and redox scenario, factors causing variation in atmospheric thickness include bulk Mg/Fe/Si ratios, initial mantle temperature profiles and heat sources.