via National Geopgraphic.
New evidence has been analyzed by scientists, building a pretty convincing case that the planet Mars once had oceans located in its northern hemisphere. The new evidence shows that the poles of the planet have shifted, blurring the ancient shorelines as the land warped due to the centrifigal force of the planet's rotation. The researchers believe that the poles have moved as much as 1800 miles form their old position, disturbing the old shorelines of the Arabia and Deuteronilus "seas".
Now if we could just figure out where all the water went. Underground? To the poles? Lost to space? Vacuumed off by Klingons? I want to know, damn it.
A little more on this from Space.com, here.