Evidence of beaches from ancient Martian ocean detected by Chinese rover

The findings are the latest evidence indicating the existence of this hypothesized ocean, called Deuteronilus, roughly 3.5 to 4 billion years ago.

Ground-penetrating radar data obtained by China's Zhurong rover has revealed buried beneath the Martian surface evidence of what look like sandy beaches from the shoreline of a large ocean that may have existed long ago on the northern plains of Mars.

The findings are the latest evidence indicating the existence of this hypothesized ocean, called Deuteronilus, roughly 3.5 to 4 billion years ago, a time when Mars - now cold and desolate - possessed a thicker atmosphere and warmer climate. An ocean of liquid water on the Martian surface, according to scientists, potentially could have harbored living organisms, much like the primordial seas of early Earth.

The rover, which operated from May 2021 to May 2022, journeyed about 1.2 miles (1.9 km) in an area that exhibits surface features suggestive of an ancient shoreline. Its ground-penetrating radar, which transmitted high-frequency radio waves into the ground that reflected off subsurface features, probed up to 80 meters (260 feet) beneath the surface.

The radar images detected some 33-115 feet (10-35 meters) underground thick layers of material with properties similar to sand, all sloped in the same direction and at an angle similar to that of beaches on Earth just below the water where the sea meets the land. The researchers mapped these structures spanning three quarters of a mile (1.2 km) along the rover's path.

"The Martian surface has changed dramatically over 3.5 billion years, but by using ground-penetrating radar we found direct evidence of coastal deposits that weren't visible from the surface," said Guangzhou University planetary scientist Hai Liu, a member of the science team for China's Tianwen-1 mission that included the rover.

On Earth, beach deposits of this size would have needed millions of years to form, the researchers said, suggesting that on Mars there was a large and long-lived body of water with wave action that distributed sediments carried into it by rivers flowing from nearby highlands.

"The beaches would have been formed by similar processes to those on Earth - waves and tides," said Liu, one of the leaders of the study published on Monday in the journal Proceedings of the National Academy of Sciences. "Such oceans would have profoundly influenced Mars' climate, shaped its landscape and created environments potentially suitable for life to emerge and thrive."