Fig. 3: Modelled global averaged carbon isotopic compositions of atmospheric CO2 and CO on early Mars.
From: Synthesis of 13C-depleted organic matter from CO in a reducing early Martian atmosphere
a, δ13CVPDB values of CO2 (blue) and CO (red) as a function of the remaining CO2 after photolysis (f = (CO2) / (CO2 + CO)), assuming the experimental fractionation factor (α1 = 0.871). Dotted lines show the cases for volcanic gas containing 10%, 20% and 30% CO, which has the same δ13CVPDB value as volcanic CO2 (–25 ± 5‰ (ref. 22)). b, The model assuming fractionation factor (α1 = 0.8106) calculated for model Mars atmosphere (Methods). c, Reported carbon isotope ratios used for constraining the model (Methods). The possible ranges of δ13CVPDB values for early atmospheric CO2 and organic matter in Cumberland (CB) drill core are also shown as grey bands in a and b.
