For decades, scientists have debated whether Mars once had a large ocean. Images from orbiters have shown valleys, channels and features that look like dried riverbeds. However, clear proof of an ancient ocean has remained difficult to confirm. China’s Zhurong Mars rover has sent back new radar data that adds to this discussion. According to a study in the journal Proceedings of the National Academy of Sciences (PNAS), underground radar scans show structures that look a lot like sandy beach deposits on Earth. These results suggest that Mars may have had a big body of water with waves that shaped the coastlines billions of years ago. This discovery is especially important because it was made using subsurface imaging instead of surface photos. Researchers say these buried formations provide stronger geological proof that liquid water once existed in large amounts on the Red Planet.
Beaches on Mars : Zhurong rover radar data reveal buried shoreline
The findings are based on data from the Zhurong rover, part of China’s Tianwen-1 mission. The rover landed in Utopia Planitia in 2021. This region has long been suspected to have once contained an ocean called the Deuteronilus Ocean.According to the study published in PNAS, the rover used ground-penetrating radar to scan beneath the Martian surface. The radar detected layered sedimentary structures that slope gently upward, similar to coastal deposits formed by wave action on Earth. These formations were found several metres below the surface.Researchers compared the radar patterns to known beach ridges and coastal sediment deposits on Earth. The similarities were strong enough for scientists to suggest that these are ancient shoreline deposits.
Evidence of an ancient Martian ocean in Utopia Planitia
Utopia Planitia is one of the largest impact basins on Mars. For years, planetary scientists have proposed that this northern lowland may have once held a vast ocean during the Late Hesperian period, around 3.5 to 4 billion years ago.According to the researchers, the radar images show repeated dipping reflectors consistent with sediment deposited by wave action. On Earth, similar radar signatures are seen in sandy beaches formed by long-term water activity.The authors of the study say that sand dunes that are pushed by the wind would have different structural patterns. The shape of the Martian deposits shows that they have been in contact with liquid water for a long time, not just for a short time.
How ground-penetrating radar helped detect Mars shoreline structures
Ground-penetrating radar sends radio waves into the ground and records the signals that come back. Different materials reflect radar waves in different ways. This allows scientists to identify layers of rock, ice or sediment.According to the PNAS study, the radar on the Zhurong rover penetrated up to about 80 metres below the surface. The buried layers showed consistent angles and thicknesses that resemble coastal sediment deposits.Because these features are underground, they are less affected by billions of years of surface erosion. This makes the radar proof very useful.
What sandy beaches on Mars mean for the past climate
If Mars had waves strong enough to make sandy beaches, it means that the planet used to have a thicker atmosphere and a warmer climate. To stay stable, liquid water needs to be at a certain temperature and pressure.According to the researchers, the existence of shoreline deposits supports the idea that Mars once had a stable ocean environment rather than brief melting events. A long-lasting ocean would have required a different climate from the cold and dry planet seen today.Scientists note that oceans are also considered favourable environments for life. While this study does not claim to have found life, it strengthens the case that ancient Mars had conditions that may have been habitable.
