Abstract We have computed radiative relaxation times for temperature perturbations in CO 2 with small admixtures of water vapor under conditions which are similar to those occurring in the martian atmosphere. Certain aspects of the influence of radiative transfer on dynamical phenomena in the martian atmosphere are discussed in terms of these radiative relaxation times. It is found that: (i) diurnal changes in the temperature profile will extend to considerably greater heights in the martian atmosphere than is the case on Earth; the diurnal wave will propagate more by radiative transfer than by turbulent diffusion; (ii) a non-negligible diurnal wind system exists on Mars; (iii) non-linear interactions between the motion field and the initial state of radiative equilibrium are much smaller on Mars than on Earth; (iv) radiative de-stabilization of regions with a negative lapse rate may be important in the upper martian atmosphere.