Mars is a little over one half the size of the Earth. It's temperatures can vary from 22C to -143C depending on your the location. It's atmosphere is 95.3% carbon dioxide, 2.7% nitrogen, 1.6% argon, and traces of oxygen, water vapour and other gases.
If you look on the photo page, you can see that Mars had trenches and canyons that look to be eroded or dragged by glaciers. There is evidence that Mars once had water. There is also strong evidence that an Ice Age occured there millions of years ago. Glaciers dragged the gravel with them on their journey to the south and back, and dug out lakes and craters like on Earth. At some point, the glaciers melted, and evaporated along with water on the surface and was replaced by carbon dioxide glaciers. With no water on the surface, oxygen slowly dissapeared and carbon dioxide took it's place.
Earth, 4 billion years ago, was similar in the way that water was in the atmosphere, but volcanic activity and excrutiating heat made it evaporate after precipitating. Maybe a billion years later, water was able to stabalise (i know i can't spell) in the craters of old volcanos or other craters (Earth was hit every million years or so by asteroids, mainly because of the forming of terrestrial planets, exploding nearby stars, and the early sun's energy explosions).
I believe that in the next century, we will have made monumental achievements in the study of Mars, it's past, and it's future.
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