The terrain of Mars suggests that the red planet once had much
more water on its surface than it does today. Some outflow channels
suggest that massive floods may have rushed across the surface in
the distant past. Some scientists wonder whether Mars may have had
an ocean in its northern hemisphere long ago. While the word is still
out on that, recent spacecraft findings have shown rocks that only
could have formed in the presence of water, as well as evidence of
lakebeds and other interesting features associated with water.