A small portion of the 118-megabyte new map of Mars' southern highlands published by the United States Geological Survey.

An incredibly detailed new map of Mars' southern highlands shows how profoundly liquid water sculpted the region long ago, scientists say.

"This map depicts the complicated sequence of geologic processes that have served to modify ancient, rugged highland terrains surrounding the Hellas impact basin and shows evidence for the persistent effects of water and ice in degrading the Martian surface," David Crown, of the Planetary Science Institute (PSI) in Tucson, Arizona, said in a statement.

Crown and his PSI colleague Scott Mest produced the new map, which was published by the United States Geological Survey (USGS). It covers the area on Mars from 27.5 to 42.5 degrees south latitude and 110 to 115 degrees east longitude.

Figure showing the area covered (crosshatched) by the United States Geological Survey's new map of Mars' southern highlands. (Image credit: Scott Mest and David Crown/USGS)

The map sheds particular light on the evolution of two canyon systems in the southern highlands, Waikato Vallis and Reull Vallis. Researchers think both canyons formed when underground water came to the surface, collapsing the ground.

Images from NASA's two Viking orbiters, which began circling the Red Planet in the 1970s, seemed to suggest that Waikato Vallis and Reull Vallis were part of the same ancient canyon system. But the new map — constructed with data collected by NASA's Mars Reconnaissance Orbiter, Mars Odyssey and Mars Global Surveyor spacecraft — reveals that Waikato and Reull were actually separate canyons separated by a plains landscape known as Eridania Planitia.

In fact, water released from Waikato Vallis formed a shallow lake in these plains long ago, scientists said.

While Waikato and Reull are the dominant landforms in the area, the new map also shows many small channels that flowing water carved into the southern highlands, likely about the same time the two big canoyns were forming, researchers said.

"Most highland peaks and the walls of many impact craters show evidence that ice-rich sediments flowed downhill, forming features that resemble rock glaciers on Earth; these features represent the most recent water-related activity in the area, and may be active today," PSI representatives wrote in a description of the new map.

You can download a free copy of the 118-megabyte Mars map from the USGS website here: http://pubs.usgs.gov/sim/3245/

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