Polar ice spreads and retreats with the changing of the seasons,
carving out layered terrain that helps scientists understand changes
in climate and geology over time. As the ice moves back and forth
across the surface, old layers lying beneath surface layers are exposed,
giving a glimpse into the past geologic history of the planet. The
seasonal warming and cooling of the poles also affects weather and
climate on the planet.
Spying Changes in Mars' South Polar Cap 13 July 2005