An international team of scientists led by University College London researcher Joel Davis has identified over 10,500 miles (17,000 km) of ancient river channels in a Martian region called Arabia Terra, providing further evidence of water once flowing on Mars.
Map showing distribution of inverted channels (black lines) and valley networks (white lines) in Arabia Terra, Mars. Many of the inverted channels (e.g., southwest region of study area) are not associated with valley networks. Background image is Mars Orbital Laser Altimeter gridded topographic map. Image credit: J.M. Davis et al.
Since the 1970s, planetary researchers have identified valleys and channels on Mars which they think were carved out and eroded by rain and surface runoff, just like on Earth.
Similar structures had not been seen on Arabia Terra until Dr. Davis and co-authors analyzed high resolution imagery from NASA’s Mars Reconnaissance Orbiter.
The team examined images covering an area roughly the size of Brazil at a much higher resolution than was previously possible – 20 feet (6 m) per pixel compared to 330 feet (100 m) per pixel.
While a few valleys were identified, the scientists revealed the existence of many systems of fossilized riverbeds which are visible as inverted channels spread across the Arabia Terra plain.
The inverted channels are similar to those found elsewhere on Mars and Earth. They are made of sand and gravel deposited by a river and when the river becomes dry, the channels are left upstanding as the surrounding material erodes.
On our planet, inverted channels often occur in dry, desert environments like Oman, Egypt, or Utah, where erosion rates are low – in most other environments, the channels are worn away before they can become inverted.
“The networks of inverted channels in Arabia Terra are about 100 feet (30 m) high and up to 0.6-1.2 miles (1-2 km) wide, so we think they are probably the remains of giant rivers that flowed billions of years ago,” Dr. Davis said.
“We think the rivers were active 3.9-3.7 billion years ago (Noachian period), 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,” added co-author Dr. Matthew Balme, of the Open University.
“In fact, one of these inverted channels called Aram Dorsum is a candidate landing site for ESA’s ExoMars Rover mission, which will launch in 2020.”
The team’s findings were published online this month in the journal Geology.
_____
J.M. Davis et al. Extensive Noachian fluvial systems in Arabia Terra: Implications for early Martian climate. Geology, published online August 2, 2016; doi: 10.1130/G38247.1
