This is an image of Mars. Click on image for full size version (40K GIF) Image from: NASA

The unusual climate of Mars makes Mars not quite right for life as we know it on Earth. If the climate were warm enough, water would not freeze into the ground but vaporize into the atmosphere. Lots of water vapor in the atmosphere would help keep Mars warm, and prevent water from freezing.

On a cold planet water can be frozen into the ground, like the frozen tundra of the Earth, and therefore trapped. This ground water can only be turned into running water when the climate of Mars undergoes a change.

Over the history of Mars, when the climate changes due to the unusual shape of its orbit, water, which has been stored, frozen, underground, turns to running water and is transferred from regions near the poles to regions near the equator. This phenomena has to do with the unusual global geography of Mars. Scientist think there are two possiblities for how it happens.

Ultimately, as Mars cools off, climate changes are not enough to prevent the water from being permanenty frozen into the ground.