Ancient sandy beaches, moulded by the incessant motion of the waves of a vast ocean that once covered Mars: this extraordinary testimony to the Red Planet's past has been identified about 10 metres deep in the Martian subsurface, thanks to data collected by the Chinese rover Zhurong, active between 2021 and 2022.
The discovery, led by the’University of California at Berkeley and published in the magazine PNAS of the US National Academy of Sciences, provides new evidence to support the hypothesis that Mars, billions of years ago, had a climate warm enough to host a liquid water ocean.
Martian beaches: a possible cradle of life?
The identified beaches could represent a privileged site for searching for traces of ancient life forms. On Earth, in fact, similar environments have been fundamental to the origin of life, making these Martian areas of particular interest to scholars.
The analysis was conducted by the team of Michael Manga, which examined the radar images provided by Zhurong. The rover was equipped with a radar capable of probing up to 80 metres deep, technology similar to that used on Earth to locate underground structures such as pipes or tombs.
Geological evidence of the ancient ocean
Radar images show the presence of sediments arranged in a similar manner to those on land coasts, shaped by the movement of the waves. The particle sizes observed also match those typical of sea sand. On Earth, similar deposits take millions of years to form, suggesting that the Martian ocean has existed for an extended period and that rivers have carried sediment to its shores.
“The structures identified do not resemble dunes, impact craters or lava flows: that is why we think of an ocean.”, explains Manga. “They are laid out parallel to what would have been the old shoreline and present both the right orientation and slope to support this hypothesis.”. This discovery represents a significant step in understanding the geological history of Mars and fuels interest in future missions dedicated to finding traces of life in the Martian subsurface.
