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Some ancient Martian lakes more recent than previously thought

Artist's depiction of NASA's Mars Reconnaissance Orbiter above the Red Planet. Image Credit: James Vaughan / SpaceFlight Insider

Artist’s depiction of NASA’s Mars Reconnaissance Orbiter above the Red Planet. Image Credit: James Vaughan / SpaceFlight Insider

A new study using data from NASA’s Mars Reconnaissance Orbiter (MRO) and other spacecraft indicate that lakes and streams on Mars formed much later in the planet’s history than previously thought possible. The newly discovered lakes and snow-melt fed streams occurred roughly a billion years after an earlier, well-documented period of wet conditions on Mars. The new findings indicate that conditions on the Martian surface may have been habitable for microbial life during this later period.

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

Wilson and her fellow researchers found evidence of these features in Mars’ Arabia Terra region by analyzing images captured by MRO’s Context Camera and High-Resolution Imaging Science Experiment camera (HiRISE) and data from NASA’s Mars Global Surveyor and the European Space Agency’s Mars Express.

Ancient Martian Lakes in Arabia Terra region on Mars

Left: Valleys much younger than well-known ancient valley networks on Mars are evident near the informally named “Heart Lake” on Mars. Image & Caption Credit: NASA/JPL-Caltech/ASU. Right: This map of an area within the Arabia Terra region on Mars shows where hydrologic modeling predicts locations of depressions that would have been lakes (black), overlaid with a map of the preserved valleys (blue lines – width exaggerated for recognition) that would have been streams. Image & Caption Credit: NASA/JPL-Caltech/Smithsonian

Outflow stream on Mars from relatively recent Martian lakes

Streamlined forms in this Martian valley resulted from the outflow of a lake hundreds of millions of years more recently than an era of Martian lakes previously confirmed. (Click to enlarge) Image & Caption Credit: NASA/JPL-Caltech/MSSS

“One of the lakes in this region was comparable in volume to Lake Tahoe,” Wilson said, referring to a California-Nevada lake that holds about 45 cubic miles (188 cubic kilometers) of water. “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’.”

The chain of lakes and valleys that are part of the Heart Lake valley system extends about 90 miles (about 150 kilometers). The scientists estimate that Heart lake once held approximate 670 cubic miles of water (2,790 cubic kilometers), more than in Lake Ontario of North America’s Great Lakes.

In their report published in the Journal of Geophysical Research: Planets, Wilson and her co-authors map the extent of stream-flow in “fresh shallow valleys” and their associated former lakes. The researchers suggest that the runoff that formed the valleys may have been seasonal.

To determine the time period when fresh shallow valleys in Arabia Terra had formed, researchers began with age estimates for 22 impact craters in the region. They assessed whether the valleys carved into the blankets of surrounding debris ejected from the craters were an indicator of whether the valleys are older or more recent than the craters.

The team concluded that this fairly wet period on Mars occurred sometime between two and three billion years ago, long after it is generally thought that most of Mars’ atmosphere had been lost and most of the remaining water on the planet had frozen. The characteristics of the valleys indicate that the climate was cold.

“The rate at which water flowed through these valleys is consistent with runoff from melting snow,” Wilson said, “These weren’t rushing rivers. They have simple drainage patterns and did not form deep or complex systems like the ancient valley networks from early Mars.”

The researchers found that similar valleys occur elsewhere on Mars between about 35 and 42 degrees latitude, both north and south of the equator. The widespread nature and similar appearance of these valleys suggest that their formation was on a global, rather than on a local scale.

“The rate at which water flowed through these valleys is consistent with runoff from melting snow,” Wilson said, “These weren’t rushing rivers. They have simple drainage patterns and did not form deep or complex systems like the ancient valley networks from early Mars.”

The findings of this study will likely prompt more research to understand how the environment warmed enough to allow a period with flowing water. One possibility is an extreme change in the tilt of the planet, resulting in more direct illumination of polar ice.

 

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Jim Sharkey is a lab assistant, writer and general science enthusiast who grew up in Enid, Oklahoma, the hometown of Skylab and Shuttle astronaut Owen K. Garriott. As a young Star Trek fan he participated in the letter-writing campaign which resulted in the space shuttle prototype being named Enterprise. While his academic studies have ranged from psychology and archaeology to biology, he has never lost his passion for space exploration. Jim began blogging about science, science fiction and futurism in 2004. Jim resides in the San Francisco Bay area and has attended NASA Socials for the Mars Science Laboratory Curiosity rover landing and the NASA LADEE lunar orbiter launch.

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