Because of its greater distance from the Sun, Mars receives less solar energy than Earth. In addition, the greenhouse effect on its surface is less important. The average annual temperature is -53 ° C (+14 ° C for the Earth). It can vary from approximately -125 ° C up to 23 ° C. The planets low temperatures and wide differences between can be explained by the absence of oceans and the thin atmosphere. On Mars, the vertical variation of temperature is very important. For example, an astronaut could feel a difference of twenty degrees between his head and his feet.
A peculiarity of Mars' atmosphere is the exchange of matter with the polar caps. These caps are made of ice, but covered with a layer of carbon dioxide (CO2) in winter. Their sizes vary a lot seasonally. Their growth (in winter) is due to condensation (transition from gaseous to solid state) of atmospheric CO2, and their decrease (in summer) is due to the sublimation (change from solid to the gas state); the CO2 returns in the atmosphere.