New research tracking Mars extensive network of valleys and adds to the growing body of evidence suggesting the Red Planet once had an ocean covering a large portion of the northern hemisphere. In a new study, scientists from Northern Illinois University and the Lunar and Planetary Institute in Houston used an innovative computer program to produce a new and more detailed global map of the valley networks.

The findings indicate the networks are more than twice as extensive as had been previously shown in the only other planet-wide map of the valleys forming a belt around the planet between the equator and mid-southern latitudes.

Scientists have previously hypothesized that a single ocean existed on ancient Mars, but the issue 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.".
 
Since the networks were discovered in 1971 by the Mariner 9 spacecraft, scientists have hotly debated whether they were created by erosion from surface water, which would point to a climate with rainfall, or through a process of erosion known as groundwater sapping, which can occur in cold, dry conditions.
 
The large disparity between river-network densities on Mars and Earth had provided a major argument against the idea that runoff erosion formed the valley networks. But the new mapping study reduces the disparity, indicating some regions of Mars had valley network densities more comparable to those found on Earth.
 
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