The NASA Viking missions to Mars included two robot landers which descended to the surface of Mars in 1976. This picture was taken by the Viking Lander 2 of the terrain and sky over a northern mid-latitude dusty plains region on Mars. The reddish dust and rocks which cover most of Mars present a lifeless surface which changes very slowly over time compared to the constantly changing surface of the Earth. The blue-white patches of frost on the dust and rocks indicate the very cold temperatures typical for the surface of Mars, which is half again as far from the Sun as the Earth.

A complex polar ice cap hundreds of kilometers across and perhaps several kilometers in thickness lies close to the day-night border (terminator) of the Mars south pole. Such water ice "residual caps" remain year-round at both poles of Mars. A seasonal ice cap of carbon dioxide ice grows to several meters in thickness all the way down to mid-latitudes on Mars during fall and winter in each hemisphere, and recedes to leave only the polar "residual caps" during the summer of each Mars hemisphere. The connections betweens these polar ice deposits and water vapor, ozone, clouds, and dust in the atmosphere of Mars are a focus of Mars climate studies at the Space Science Institute.