What might a wet Mars have looked like? This artist's concept attempts to fill in the blanks.
This artist's model of shows a theoretical view of Mars — billions of years ago — with liquid water on the surface and a thicker atmosphere.
The globe was created by filling Mars' lower altitudes with water and adding cloud cover. The locations for the ancient ocean are based on current altitudes and do not reflect the actual ancient topography.
More views and download options are available from NASA's Scientific Visualization Service.