Altitude profiles of CO₂ (left) and O (right) ionization efficiencies for the 240 nominal MAVEN orbits analyzed in this study. The red lines give the respective mean profiles along with standard deviations within the predefined altitude bins. For comparison, the model CO₂ and O ionization efficiencies from Nicholson et al. (2009) are superimposed with the blue lines, appropriate for a median SZA of 55°.