Tim and his colleagues have come to believe that the potential shorelines require at least two highstands of a sea with Martian temperatures above freezing for at least geologically brief periods of time. Stratigraphic sections of layered sediments, giant patterns of cracks, and enormous flood channels all suggest the existence of standing bodies of water. But the idea of oceans stretched most imaginations. This represented a big change in thinking, the kind that makes you automatically very skeptical. MOLA data strongly supports one of Tim's most important shorelines and also indicates an unexpectedly smooth terrain below the shoreline.
Giant channels emptying onto the surface below the shoreline provide further support.
If Tim's idea is correct an ocean may have covered 27 million square kilometers of Mars. Although doubts may remain until astronauts visit the red planet, scientists are paying more attention to the idea of a very wet early Mars. Read all about it in the November 1999 Sky and Telescope.