Beijing/Mars, February 24, 2025 – Ground-penetrating radar data from China’s Zhurong rover has revealed what appear to be sandy beach deposits buried beneath Mars’ surface, lending strong support to the theory that a vast ocean once stretched across the planet’s northern plains.

The findings, published Monday in the journal Proceedings of the National Academy of Sciences, suggest that the hypothesized Deuteronilus Ocean existed roughly 3.5 to 4 billion years ago, during a period when Mars had a thicker atmosphere and a warmer, wetter climate.

During its operational period from May 2021 to May 2022, the rover traversed approximately 1.2 miles (1.9 km) in southern Utopia Planitia—a region that exhibits surface features resembling an ancient shoreline. Using its high-frequency ground-penetrating radar, which probed up to 80 meters (260 feet) below the surface, the rover detected thick layers of material—ranging from 10 to 35 meters deep—that closely mimic the slopes and angles of Earth’s beaches found just below the waterline.

“These coastal deposits were formed by wave and tidal action, much like beaches on Earth,” said Guangzhou University planetary scientist Hai Liu, a member of the Tianwen-1 science team. “By using ground-penetrating radar, we found direct evidence of coastal deposits that weren't visible from the surface.” Liu added that the preservation of these structures beneath layers of dust, meteorite debris, and volcanic material has allowed them to remain intact over billions of years.

Planetary scientist Michael Manga of the University of California, Berkeley, highlighted the significance of these findings: “Shorelines are great locations to look for evidence of past life. It’s thought that the earliest life on Earth began at locations like this, near the interface of air and shallow water.” The study’s authors suggest that the extensive beach deposits indicate a long-lived body of water with active wave action, potentially created by rivers draining from nearby highlands.

Researchers carefully ruled out alternative explanations for the observed formations. “We considered wind-blown dunes, ancient river channels, and even lava flows,” explained Penn State geoscientist Benjamin Cardenas. “However, the patterns we observed best match those of beaches, which simply fit the observations.”

The discovery adds a crucial piece to the puzzle of Mars’ watery past. While satellite images have long hinted at the existence of ancient Martian shorelines, surface features can be distorted or erased by billions of years of erosion. In contrast, these buried deposits provide a more pristine record of the planet’s ancient ocean, offering new insights into Mars’ climatic evolution and its potential to have harbored life.

As scientists continue to explore Mars’ subsurface with advanced techniques, findings like these not only illuminate the planet’s distant past but also refine the search for biosignatures in environments once teeming with liquid water.

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