The paper deals with the numerical simulation of a supersonic viscous flow containing CO₂ molecules near a space body entering the Mars atmosphere. The gas dynamic equations in a shock layer are coupled to the equations of vibrational and chemical kinetics in the mixture CO ₂/CO/O₂/C/O using three theoretical models for CO ₂ vibrational excitation. Threetemperature and two-temperature non-equilibrium approaches as well as the one-temperature thermal equilibrium model have been applied. A comparison of gas flow parameters and heat transfer calculated on the basis of different approximations is presented, and the effect of CO₂ vibrational non-equilibrium is discussed. Transport coefficients in a flow are computed using rigorous kinetic theory algorithms which have been incorporated directly to the numerical schemes. The effect of bulk viscosity in a shock layer is studied.