NASA finds fossilized riverbeds on Mars

Although the planet is now cold and barren of water, the discovery of an extensive fossilized system of riverbeds suggests that Mars had once possessed a warm, wet climate, according to new research published in the Geological Society of America publication Geology.

As part of their work, lead author Joel Davis of the University College London Institute of Earth and Planetary Sciences and his colleagues identified a network of more than 17,000 km (10,500 miles) of now-defunct river channels on the northern plain called Arabia Terra. Their find serves as new evidence that the Red Planet contained flowing water roughly four billion years ago.

“Climate models of early Mars predict rain in Arabia Terra, and until now there was little geological evidence on the surface to support this theory,” Davis said in a statement. “This led some to believe that Mars…was a largely frozen planet, covered in ice-sheets and glaciers. We’ve now found evidence of extensive river systems in the area which supports the idea that Mars was warm and wet, providing a more favorable environment for life than a cold, dry planet.”

While scientists first identified channels and valleys on Mars that they believed were caused by erosion from rain and surface runoff, similar to the processes here on Earth, they had been unable to identify such a network at the heavily eroded and densely cratered upland region known as Arabia Terra – that is, until the UCL-led team found them while analyzing high-resolution images captured by NASA’s Mars Reconnaissance Orbiter (MRO).

Fossilized rivers could be targets in the search for life on Mars

Davis and his colleagues examined a portion of the terrain approximately the same size as Brazil in a series of images captured in the highest resolution possible to date: 6 meters per pixel versus the 100 meters per pixel that was previously the benchmark. They identified a handful of valleys as well as several systems of fossilized riverbeds spread throughout Arabia Terra.

These riverbeds were visible as inverted channels similar to those found on Earth and elsewhere on Mars, the study authors explained in a statement. They were made of sand and gravel that had been deposited by a river and left behind when the waters dried up and the surrounding materials eroded. The channels were similar to those found in dry terrestrial environments where the rates of erosion are low, such as the deserts of Oman, Egypt or Utah, they added.

“The networks of inverted channels in Arabia Terra are about 30m high and up to 1-2km wide, so we think they are probably the remains of giant rivers that flowed billions of years ago,” said Davis. “Arabia Terra was essentially one massive flood plain bordering the highlands and lowlands of Mars. We think the rivers were active 3.9-3.7 billion years ago, but gradually dried up before being rapidly buried and protected for billions of years, potentially preserving any ancient biological material that might have been present.”

“These ancient Martian flood plains would be great places to explore to search for evidence of past life. In fact, one of these inverted channels called Aram Dorsum is a candidate landing site for the European Space Agency’s ExoMars Rover mission, which will launch in 2020,” added co-author Dr. Matthew Balme, Senior Lecturer at The Open University. The team now plans to further analyze the channels using higher-resolution data from the MRO’s HiRISE camera.

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Image credit: NASA JPL

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