Results of the toy model describing CO₂ mass loss from each terrestrial planet, assuming initial atmospheres of pure CO₂ 5–50% that of Earth’s total estimated CO₂ content of 10²² mol (Sect. 6.1). The vertical orange and purple lines, along with the shaded regions, are the estimated stellar ages with uncertainties (discussed in Sect. 6.2). Whether or not each planet maintains a CO₂ atmosphere with surface pressure of ⪆1 bar depends on the initial CO₂ content, the planetary orbital period, and the stellar age and activity history. The model does not take into account CO₂ outgassing rates – we assume all of the CO₂ outgasses at the start of the model time steps – or magnetic fields, which may be able to shield secondary atmospheres from loss.