Mars wasn’t always a dry, desolate world—it may have had sunlit beaches and rolling ocean waves, just like Earth.
A new study, using data from China’s Zhurong rover, has uncovered evidence of ancient coastal deposits beneath the Martian surface, strongly suggesting that a vast ocean once covered part of the planet. This discovery paints a picture of a dynamic, evolving landscape where rivers carved the land, tides moved sediment, and conditions may have been favorable for microbial life.
Mars’ Hidden Beaches Uncovered
Mars may have once had sandy beaches and rolling waves, according to a new study published today (February 24) in the Proceedings of the National Academy of Sciences (PNAS).
An international team of scientists, including researchers from Penn State, analyzed data from China’s Zhurong Mars rover and identified hidden rock layers beneath the planet’s surface. These formations strongly suggest that a vast ocean once covered Mars’ northern region. The findings provide some of the most compelling evidence yet that the planet once had a significant body of water and a more hospitable environment for life, said Benjamin Cardenas, an assistant professor of geology at Penn State and a co-author of the study.
“We’re finding places on Mars that used to look like ancient beaches and ancient river deltas,” Cardenas said. “We found evidence for wind, waves, no shortage of sand — a proper, vacation-style beach.”
Radar Reveals Ancient Coastal Formations
The Zhurong rover landed on Mars in 2021 in a region called Utopia Planitia, where it collected geological data while searching for signs of past water or ice. Unlike previous rovers, it was equipped with ground-penetrating radar, allowing it to scan beneath the planet’s surface. By using both low- and high-frequency radar, the rover could detect buried rock formations and reveal details about Mars’ hidden geological history.
By studying the underground sedimentary deposits, scientists are able to piece together a more complete picture of the red planet’s history, Cardenas explained. When the team reviewed radar data, it revealed a similar layered structure to beaches on Earth: formations called “foreshore deposits” that slope downwards towards oceans and form when sediments are carried by tides and waves into a large body of water.
“This stood out to us immediately because it suggests there were waves, which means there was a dynamic interface of air and water,” Cardenas said. “When we look back at where the earliest life on Earth developed, it was in the interaction between oceans and land, so this is painting a picture of ancient habitable environments, capable of harboring conditions friendly toward microbial life.”
Striking Similarities to Earth’s Coastlines
When the team compared the Martian data with radar images of coastal deposits on Earth, they found striking similarities, Cardenas said. The dip angles observed on Mars fell right within the range of those seen in coastal sedimentary deposits on Earth.
The researchers also ruled out other possible origins for the dipping reflectors, such as ancient river flows, wind or ancient volcanic activity. They suggested that the consistent dipping shape of the formations as well as the thickness of the sediments point to a coastal origin.
Mars Was Once a Dynamic, Evolving World
“We’re seeing that the shoreline of this body of water evolved over time,” Cardenas said. “We tend to think about Mars as just a static snapshot of a planet, but it was evolving. Rivers were flowing, sediment was moving, and land was being built and eroded. This type of sedimentary geology can tell us what the landscape looked like, how they evolved, and, importantly, help us identify where we would want to look for past life.”
The discovery indicates that Mars was once a much wetter place than it is today, further supporting the hypothesis of a past ocean that covered a large portion of the northern pole of the planet, Cardenas explained. The study also provided new information on the evolution of the Martian environment, suggesting that a life-friendly warm and wet period spanned potentially tens of millions of years.
Technology Unlocks a New Era of Mars Exploration
“The capabilities of the Zhurong rover have allowed us to understand the geologic history of the planet in an entirely new way,” said Michael Manga, professor of Earth and planetary science at the University of California, Berkeley, and a corresponding author on the paper. “Its ground-penetrating radar gives us a view of the subsurface of the planet, which allows us to do geology that we could have never done before. All these incredible advancements in technology have made it possible to do basic science that is revealing a trove of new information about Mars.”
Reference: “Ancient ocean coastal deposits imaged on Mars” by Jianhui Li, Hai Liu, Xu Meng, Diwen Duan, Haijing Lu, Jinhai Zhang, Fengshou Zhang, Derek Elsworth, Benjamin T. Cardenas, Michael Manga, Bin Zhou and Guangyou Fang, 24 February 2025, Proceedings of the National Academy of Sciences.
DOI: 10.1073/pnas.2422213122
The other corresponding authors on the paper are Hai Liu of Guangzhou University and Guangyou Fang of the Chinese Academy of Sciences. The other Penn State co-author is Derek Elsworth, the G. Albert Shoemaker Chair and professor of energy and mineral engineering and geosciences. The other authors are Jianhui Li, Xu Meng, Diwen Duan, and Haijing Lu of Guangzhou University; Jinhai Zhang and Bin Zhou of the Chinese Academy of Sciences; and Fengshou Zhang of Tongji University in Shanghai, China.
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3 Comments
Given the moons of mars are so small relative to the planet, why does the article infer that there were tides on Mars?
The sun has an effect on tides equivalent to about 30% of the effect of the moon. This is why the high tides are higher and low tides are lower when the sun and the moon are in alignment, since the two are working together, rather than against each other. The sun is much, much more massive, but very far away. Presumably the tides on Mars were much smaller than on Earth, but the sun would still have caused tides.
Sensation. It’s written for dramatic effect. I hate it but that’s the only way to make most people read it.