Was Mars once home to oceans and 'vacation-style' sandy beaches?

Mars may not have always been a barren, lifeless world—it could have once had sunlit shores and rolling ocean waves, just like the Earth.

A new study, based on data from China’s Zhurong rover, gives the “clearest evidence yet” that billions of years ago, large bodies of water stretched across parts of the Red Planet, shaping its terrain in ways eerily similar to Earth’s coastlines. The discovery adds to the growing belief that Mars had a watery past—and possibly the right conditions for life.

Here’s a deeper dive into this fascinating discovery and why it matters.

Discovery of ‘vacation-style’ Martian beaches

Mars may have once had sandy shores and rolling ocean waves, according to a groundbreaking study published in the Proceedings of the National Academy of Sciences (PNAS).

The discovery is based on data from China’s Zhurong Mars rover, which landed in the Utopia Planitia region in 2021. After analysing the rover’s findings, an international team of researchers, including scientists from Penn State, believe they have identified hidden rock layers beneath the Martian surface—strong evidence that a vast ocean once covered the planet’s northern hemisphere.

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“We’re finding places on Mars that used to look like ancient beaches and ancient river deltas,” Benjamin Cardenas, a Penn State assistant professor of geology and study co-author, said in a statement. “We found evidence for wind, waves, no shortage of sand—a proper, vacation-style beach.”

Coastal formations similar to Earth found

The discovery of Mars’ ancient beaches was made possible by Zhurong’s advanced ground-penetrating radar system, which allowed scientists to peer beneath the planet’s surface and map hidden geological structures without excavation.

By using both low- and high-frequency radar, the rover detected buried rock formations, offering a glimpse into Mars’ long-buried past. These underground sedimentary deposits provided crucial clues about how the planet’s landscape was shaped over billions of years, explained Benjamin Cardenas, a co-author of the study.

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When researchers analysed the radar data, they discovered a layered structure strikingly similar to Earth’s beaches. These formations, known as “foreshore deposits,” slope downward towards what was once an ocean, forming as waves and tides carried sediments into the water over time.

“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.

Further analysis ruled out other possible causes, such as river flows, volcanic activity, or wind, leaving oceanic coastlines as the most likely explanation. If confirmed, this strengthens the theory that a vast ocean once covered a significant portion of Mars’ northern hemisphere.

The research team has named this ancient sea ‘Deuteronilus’.

Scientists say this Martian beach appears to have shifted position over time. The data reveals a series of features dipping towards the north – something Cardenas said indicated the beach grew out into the ocean. “In fact, it grew at least 1.3km north into the ocean.”

Why this matters

The discovery of ancient Martian beaches has far-reaching implications for our understanding of the planet’s history—and its potential to have once-supported life. The presence of large bodies of water suggests that Mars was once much warmer and wetter, creating conditions that could have been hospitable to life.

“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 researchers noted.

The next challenge is to further investigate Mars’ lost oceans—how much water was there? When did it disappear? Where did it go? Answering these questions could reshape our understanding of the planet’s climatic evolution.

“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,” Cardenas explained. “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.”

With input from agencies