Like Earth, Mars experiences climatic variations during the course of a year because of the tilted nature of its orbit (aka. seasonal change). Similarly, these variations in temperature result in interaction between the atmosphere and the polar ice caps. On Earth, seasonal variations in temperature and precipitation cause the polar ice cap in one hemisphere to grow while the ice cap in the other hemisphere shrinks.
Click here for original story, How much carbon dioxide snow falls every winter on Mars?
Source: Phys.org