Postulates that the major atmospheric constituent is in equilibrium with a frost on the surface. This means that the atmospheric pressure equals the vapor pressure of the frost at equilibrium (which is temperature dependent). The temperature of the frost is determined by radiative equilibrium. During the summer, incident radiation increases the temperature, increasing the vapor pressure, and causes frost to sublime. This increases the atmospheric pressure. In the winter, the poles cool and excess vapor condenses, given up its latent heat. For Mars, with a 6 mbar CO₂ atmosphere, K. For Triton, with a 15 bar N₂ atmosphere, K.