ESA’s Mars Express, NASA’s Mars Reconnaissance Orbiter and Mars Global Surveyor have sent back new images and data from the Red Planet that indicate liquid water may have been on the Martian surface roughly a billion years later than previously thought.
Valleys younger than better-known ancient valley networks on Mars are evident on the landscape in the northern Arabia Terra region, particularly in the area mapped here with color-coded topographical information overlaid onto a photo mosaic. The area includes a basin informally named ‘Heart Lake’ at upper left. Data from NASA’s Mars Global Surveyor orbiter are coded here as white and purple for lower elevations, yellow for higher elevation. The elevation information is combined with a mosaic of images from NASA’s Mars Odyssey orbiter, covering an area about 120 miles (about 190 km) wide. The mapped area is centered near 35.91 degrees north latitude, 1 degree east longitude on Mars. Image credit: NASA / JPL-Caltech / ASU.
“We discovered valleys that carried water into lake basins,” said Dr. Sharon Wilson, a researcher at the Smithsonian Institution and the University of Virginia.
“Several lake basins filled and overflowed, indicating there was a considerable amount of water on the landscape during this time.”
Dr. Wilson and her colleagues found evidence of these features in Mars’ northern Arabia Terra region by analyzing images from the Mars Reconnaissance Orbiter and additional data from the Mars Global Surveyor and the Mars Express.
“One of the lakes in this region was comparable in volume to Lake Tahoe,” Dr. Wilson said.
“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 km).
The team calculates Heart Lake held about 670 cubic miles of water (2,790 km3), more than in Lake Ontario of North America’s Great Lakes.
The researchers map the extent of stream-flow in ‘fresh shallow valleys’ and their associated former lakes. They suggest that the runoff that formed the valleys may have been seasonal.
To bracket the time period when the fresh shallow valleys in Arabia Terra formed, they assessed whether or not the valleys carved into the blankets of surrounding debris ejected from 22 impact craters in the area.
They concluded that this fairly wet period on Mars likely occurred between 2 and 3 billion years ago (between the Hesperian and Mid-Amazonian periods), long after it is generally thought that most of the original Martian atmosphere had been lost and most of the remaining water on the planet had frozen.
The characteristics of the valleys support the interpretation that the climate was cold.
“The rate at which water flowed through these valleys is consistent with runoff from melting snow,” said Dr. Wilson, lead author of a paper on the discovery published August 11 in the Journal of Geophysical Research: Planets.
“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.”
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Sharon A. Wilson et al. A Cold-Wet Mid-Latitude Environment on Mars during the Hesperian-Amazonian Transition: Evidence from Northern Arabia Valleys and Paleolakes. Journal of Geophysical Research: Planets, published online August 11, 2016; doi: 10.1002/2016JE005052
This article is based on a press-release issued by NASA.
