Mars' Wet Era Was Longer and Wetter Than We Thought (by About a Billion Years)

Long (and Well) Hydrated

Curiosity about the Red Planet has long been part of our space exploration story, and rightly so. Mars is one planet we know of that probably supported life — a conclusion astronomers arrived at partly because of the confirmed existence of water in Mars' early billion years.

This conclusion is further confirmed by new evidence from NASA's Mars Reconnaissance Orbiter that shows that the now-dry planet had liquid water for longer than we previously thought — about a billion years after Mars' well-documented "wet era."

"We discovered valleys that carried water into lake basins. Several lake basins filled and overflowed, indicating there was a considerable amount of water on the landscape during this time," says Sharon Wilson of the Smithsonian Institution, Washington, and the University of Virginia, Charlottesville.

These bodies of water were not small, either. Comparing NASA's images of Mars' northern Arabia Terra region with those from the European Space Agency's (ESA) Mars Express, Wilson's team was able to identify bodies of water as large as (or even larger than) some of America's Great Lakes. 

Wilson explains, "One of the lakes in this region was comparable in volume to Lake Tahoe. This particular Martian lake was fed by an inlet valley on its southern edge and overflowed along its northern margin, carrying water downstream into a very large, water-filled basin we nicknamed 'Heart Lake.'"

Heart Lake was home to a chain of lakes and valleys about 150 km (90 miles) in total and could've held around 2,790 km3 (670 cubic miles) of water — much more than Lake Ontario.

Life On Mars More Likely?

These newly discovered systems of lakes and streams watered by run-off from melting snow mean that Mars likely had significant amounts of water on it for significantly longer than we previous thought.

In turn, that could mean that the planet had been capable of sustaining microbial life far longer than we initially realized, a discovery that is more than enough to whet astronomers' appetites for further evidence of ancient life in Mars.