Total O pressure in a 55-Cnc e like atmosphere: Shown here are the total O pressure of two different volatile atmosphere compositions – carbon poor (grey) and carbon rich (black) as a function of total volatile pressure (panel a) at a fixed temperature of 2500 K and as a function of temperature at a fixed total volatile pressure of 10 bar (panel b). The total O pressures indicated using the solid lines are calculated using the method outline in this paper, those indicated using the dashed line are calculated using the volatile-free vaporisation method, and the dotted line indicates the total O pressure when no lava ocean vaporisation is assumed. The blue area indicates the estimated surface pressure range of 55-Cnc e and the red area indicates the estimated surface temperature range of 55-Cnc e (Hu et al. 2024).