The northern lowlands of early Mars might have had lots of liquid water, but there’s still debate due to a lack of solid proof from underground.
A new study from Penn State researchers shows that Mars may have once had sandy beaches and calm waves. Using data from the Zhurong Mars rover, they found hidden rock layers under Mars’ surface that strongly hint at an ancient northern ocean. This research provides the most substantial evidence yet that Mars once had a significant body of water and was more suitable for life.
Benjamin Cardenas, assistant professor of geology at Penn State, said, “We’re finding places on Mars that used to look like ancient beaches and ancient river deltas. We found evidence for wind, waves, no shortage of sand — a proper, vacation-style beach.”
The Zhurong rover landed on Mars in 2021 at Utopia Planitia and sent back geological data, looking for ancient water or ice. Unlike other rovers, it had radar that could explore underground, using both low and high-frequency signals to identify buried rock formations.
By studying these underground deposits, scientists can better understand Mars’ history. The radar data showed a layered structure similar to Earth’s beaches, called “foreshore deposits,” which slope towards oceans and form from sediments moved by tides and waves.
“This caught our attention because it suggests there were waves, meaning there was a dynamic air-water interface,” Cardenas said. “On Earth, early life developed where oceans and land interacted, so this hints at ancient habitable environments on Mars, suitable for microbial life.”
The team found striking similarities when comparing Mars data with Earth’s coastal deposits. The dip angles on Mars matched those of Earth’s coastal sediments.
They ruled out other origins like rivers, wind, or volcanic activity. The consistent dip shape and sediment thickness suggested a coastal origin.
“We see that Mars’ shoreline evolved,” Cardenas said. “Mars wasn’t just a static planet; it was changing. Rivers flowed, sediment moved, and land was built and eroded. This sedimentary geology helps us understand the landscape and where to look for past life.”
The discovery shows that Mars used to be much wetter, supporting the idea of a past ocean that covered much of its northern pole. The study also reveals that Mars had a warm, wet period lasting potentially tens of millions of years.
“The Zhurong rover’s technology has given us a new way to understand Mars’ geological history,” said Michael Manga, professor at UC Berkeley. “Its radar lets us see underground, enabling geology we couldn’t do before. These technological advancements are uncovering a wealth of new information about Mars.”
Journal Reference:
- Jianhui Li, Hai Liu et al. Ancient ocean coastal deposits imaged on Mars. Proceedings of the National Academy of Sciences (PNAS). DOI: 10.1073/pnas.2422213122
