Possible configuration of ancient oceans on Mars:
Topographic portrayal of the surface of Mars
derived from Mars Orbiter Laser Altimeter (MOLA) data.

In the images below, areas of high elevation are white, intermediate elevations are brown, and lower elevations are green. The blue areas represent the region that would have been occupied by an ocean earlier in martian history, according to the hypothesis of Parker and co-workers. Recent data from the Mars Global Surveyor Mission MOLA experiment show that the ancient shoreline proposed by Parker and colleagues (located at the edge of the blue area) lies close to the flat line expected if it were indeed an ancient shoreline. The surface below this line is also smoother at all scales than above, consistent with sedimentation from an ancient ocean smoothing topography below sea level.

In this topographic portrayal of Mars, above, the northern lowlands are occupied by an ocean (blue) whose shoreline is placed at the position of Contact 2, the line that Parker and co-workers interpreted as an ancient shoreline. Thus, this view shows Mars as it might have looked mid-way through its history according to the oceans hypothesis. The Tharsis region, with numerous very large shield volcanoes is seen in the central part of the globe. In the upper right, many channels flow into the northern lowlands at Chryse Planitia.

Credit: NASA Mars Global Surveyor Project; MOLA Team.
Rendering by Peter Neivert, Brown University.

In this topographic portrayal of Mars, above, giant channels emerge from the Tharsis region (left), Valles Marineris (bottom), and the ancient heavily cratered terrain (right), and flow down slope into the northern lowlands in Chryse Planitia (center). The ancient shoreline proposed by Parker and co-workers is at the position where the channels change from heavy scouring of the background terrain into smooth terrain typical of the northern lowlands, suggesting that they once flowed into a standing body of water, or ocean, as portrayed in the blue area here.

Credit: NASA Mars Global Surveyor Project; MOLA Team.
Rendering by Peter Neivert, Brown University.