The climate of Mars, like Earth's climate, changes over time. Variations in the tilt of the planet's axis and to its orbit have created warmer climates at times, and ice ages at others. This artist's impression shows how Mars may have looked during a possible ice age between 2.1 million and 400,000 years ago. The polar ice caps may have covered a significant part of the planet.
Image courtesy of NASA/JPL/Brown University.