This map depicts a hypothetical Mars with oceans. The view could represent a stage of terraforming (not an early Mars, since the ocean areas do not correspond to such hypotheses). The base map is from the USGS Flagstaff web site, with oceans added based on elevation data from a USGS map at Solar Views and a cloud map modified from one at Visible Earth. Map centered on 180° longitude.
The good ol' red planet may have been blue. New research in Nature suggests that massive oceans once covered a third of its surface. What is the evidence? Ragged, km high features on the planet's surface are actually shorelines. NASA's Mars Global Surveyor sent back topographical data that showed the dips and peaks along the features ranged up to three kilometres from the deepest dip to highest peak. On earth if you drained a basin the shoreline would be flat. What accounts for the complex shoreline of Mars? A major shift of mass, possibly triggered by a volcanic eruption, caused the pole to wander about 50 degrees towards its current location, dramatically warping the topography and shorelines.
I can't help but wonder if life was on Mars was it deep-sea life? If NASA wants to contact me to discuss this more or ship me to Mars just leave a comment at the bottom.
You've probably read these, but the hard scifi author Kim Stanley Robinson has a great trilogy on terraforming Mars.
Can you take a bunch of water with you?
(love your site by the way).
Gubna