Was the Red Planet once blue? New evidence points to an ancient ocean on Mars

Mars may have once possessed an ocean at least as large as Earth’s Arctic Ocean, a new study suggests.

Previous research suggested rivers and seas once existed on Mars, raising the question of whether it might have once been capable of supporting life. However, much remains uncertain about how blue the Red Planet once was.

“Together, these instruments act like a geological time machine, helping us reconstruct the planet’s past condition,” study lead author Ignatius Argadestya, a planetary geologist at the University of Bern in Switzerland, told Space.com.

The scientists investigated the southeast part of a 620-mile (1,000-kilometer) canyon known as Coprates Chasma. This gorge makes up part of the Valles Marineris, the largest canyon system on Mars, which stretches more than 2,485 miles (4,000 km) long along the Red Planet’s equator.

Specifically, the researchers focused on geological formations known as scarp-faced deposits at the lower end of Coprates Chasma. These resembled fan deltas on Earth — fan-shaped cones of debris and sand that form where rivers pour into oceans. Although wind-sculpted dunes currently cover these former delta structures on Mars, their original shape is still recognizable.

All the scarp-faced deposits the scientists identified occurred at the same range of elevations — a depth of 11,975 to 12,300 feet (3,650 to 3,750 meters) in the Valles Marineris and the northern lowlands. In addition, they all formed about 3.37 billion years ago.

The researchers suggested these scarp-faced deposits are evidence of an ancient shore. All in all, they estimated Mars once possessed an ocean across its northern hemisphere that was at least as large as the Arctic Ocean on Earth.

“The most important implication is that Mars may have sustained stable surface water on a planetary scale for longer periods than previously thought,” Argadestya said. “Water on Mars may once have formed connected systems across vast distances, rather than existing only in isolated lakes.”

The scientists noted they are not the first to speculate about the existence and size of any ocean on Mars. “What our study contributes is a new line of geological evidence that helps constrain where the shoreline may have been and how high the water once reached,” Argadestya said.

In the future, the scientists plan to investigate the composition of ancient Martian soils. These could help shed light on what kind of erosion Mars experienced from water, Argadestya noted.

The scientists detailed their findings online Jan. 7 in the journal npj Space Exploration.

Charles Q. Choi is a contributing writer for Space.com and Live Science. He covers all things human origins and astronomy as well as physics, animals and general science topics. Charles has a Master of Arts degree from the University of Missouri-Columbia, School of Journalism and a Bachelor of Arts degree from the University of South Florida. Charles has visited every continent on Earth, drinking rancid yak butter tea in Lhasa, snorkeling with sea lions in the Galapagos and even climbing an iceberg in Antarctica. Visit him at http://www.sciwriter.us