It is always cold and, at its warmest, temperatures rarely exceed freezing. May. Of particular interest to experts is a frosty patch seen in an unnamed crater. In 1976, the Viking Orbiter saw a region of frost in the same place and scientists suspect that it persists throughout the Martian summer. In the southern hemisphere it is autumn and frost was seen on the rims of some craters, such as Barnard, as early as August. Later, the frost line moved further north, and frost was seen in Lowell crater.
Seasonal variations are greater on Mars than on any other planet with the exception of Pluto.
Mars has a more elliptical orbit than Earth, so its distance from the Sun varies more. At one point during the year, the temperature drops so that carbon dioxide freezes out of the thin Martian atmosphere.