Scientists from Northern Illinois University and Planetary Institute in Houston have generated a more detailed global map of the valley networks on Mars. Their findings suggest the planet once had rainfall and a vast ocean covering most of the northern hemisphere, or about one third of the planet's surface.
Scientists have previously hypothesized that a single ocean existed on ancient Mars, but the matter has been hotly debated.
“All the evidence gathered by analyzing the valley network on the new map points to a particular climate scenario on early Mars,” NIU Geography Professor Wei Luo said. “It would have included rainfall and the existence of an ocean covering most of the northern hemisphere, or about one-third of the planet's surface.”