Erosion
There is very
clear evidence of erosion in many places on Mars including large floods and small river
systems (right). At some time in the past there was clearly water on the surface
There may have been large lakes or even oceans. But it seems that this occurred only
briefly and very long ago; the age of the erosion channels is estimated at about nearly 4
billion years. (Valles Marineris was NOT created by running water. It was formed by
the stretching and cracking of the crust associated with the creation of the Tharsis
bulge.)
Early in its history, Mars was much more like Earth. As with Earth almost all of its carbon dioxide was used up to form carbonate rocks. But lacking the Earth's plate tectonics, Mars is unable to recycle any of this carbon dioxide back into its atmosphere and so cannot sustain a significant greenhouse effect. The surface of Mars is therefore much colder than the Earth would be at that distance from the Sun.