This is what I currently have set for Mars:
; === Atmospheric Parameters ===
AtmPressure0 = 0.61e3 ; pressure at zero altitude [Pa]
AtmDensity0 = 0.02 ; density at zero altitude [kg/m^3]
AtmGasConstant = 188.92 ; specific gas constant [J/(K kg)]
AtmGamma = 1.2941...