Evidence of an Ancient Ocean and Potential Past Life

Evidence of an Ancient Ocean

Ground-penetrating radar data from China's Zhurong rover has revealed evidence of buried sandy beaches beneath the Martian surface. These beaches are believed to be remnants of a large ocean that may have existed on the northern plains of Mars billions of years ago.

The findings add to the growing body of evidence suggesting the existence of this ancient ocean, called Deuteronilus. This ocean is thought to have existed roughly 3.5 to 4 billion years ago, when Mars had a thicker atmosphere and a warmer climate. Scientists believe that this ocean could have potentially harbored living organisms, similar to the primordial seas of early Earth.

The Zhurong rover, which operated from May 2021 to May 2022, traveled about 1.2 miles (1.9 km) in an area that exhibits surface features suggestive of an ancient shoreline. Its ground-penetrating radar detected 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. These structures were mapped 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.

The researchers believe that these beaches were formed by similar processes to those on Earth – waves and tides. Such an ocean would have profoundly influenced Mars' climate, shaped its landscape, and created environments potentially suitable for life to emerge and thrive.

"Shorelines are great locations to look for evidence of past life," said planetary scientist and study co-author Michael Manga of the University of California, Berkeley. "It’s thought that the earliest life on Earth began at locations like this, near the interface of air and shallow water."

The researchers ruled out other possible explanations for the structures Zhurong detected, such as wind-blown dunes or ancient rivers. They concluded that beaches simply fit the observations the best.

The existence of this ancient ocean on Mars raises intriguing questions about the possibility of past life on the Red Planet. While the ocean disappeared approximately a billion years into Martian history, some of the water may have been lost to space while large amounts may remain trapped underground. Further exploration of Mars, including the search for potential biosignatures, is crucial to understanding the planet's history and its potential for harboring life.