Number density profiles of CO₂ and CO from MCD and MGIT models. Solid and dash-dotted curves represent CO₂ and CO density profiles, respectively. The grey shaded area represents the variation in the NGIMS/MAVEN measured CO₂ density from 6–8 April 2016 for the orbits #2953–2962. The solid black curve in the shaded area represents the averaged value of CO₂ from the NGIMS/MAVEN measurements. The calculated CO/CO₂ volume mixing ratio profiles are plotted with dashed curves with a scale on top of the x-axis.