Vertical structures and compositions of the background atmosphere of Mars over altitude ranges of 80–300 km. (a) Number density profiles of the major neutral constituents, including CO₂, CO, N₂, and O. (b) Electron, ${\text{O}}_2^{+},{\text{CO}}_2^{+}$, and O⁺ density profiles. (c) Background temperature profiles of neutral, ion, and electron and marked by T_n, T_i, and T_e, respectively. (d) Background pressure profiles of neutral, electron, and the major ion species, ${\text{O}}_2^{+}$. The neutral density and temperatures of neutral and plasma were measured as part of the Deep-dip 2 Campaign of MAVEN and adopted from Wu et al. (2020). The plasma densities are calculated under the photochemical equilibrium assumption in the lower-altitude ionosphere.