Evidence of an ancient ocean on Mars has been potentially uncovered by China’s Zhurong rover, scientists report. Data gathered by the now-defunct rover indicates a possible ancient shoreline in Mars’ northern hemisphere. Researchers at Hong Kong Polytechnic University, including lead scientist Bo Wu, believe these findings support long-standing theories of a large Martian ocean that existed billions of years ago. The Zhurong rover, which travelled approximately 2 kilometres within the Utopia Planitia basin, relayed this data through observations from its onboard cameras and ground-penetrating radar.

The study describing the findings was published in the journal Scientific Reports. Through Zhurong’s exploration, researchers identified features possibly related to water activity, including pitted cones, channels, and formations resembling mud volcanoes. Such structures, the scientists suggest, could represent a coastal landscape shaped by the once-existing ocean. Further analysis of the surface deposits indicates that the ocean may have existed around 3.68 billion years ago, potentially containing silt-laden water that left distinct geological layers on the Martian landscape.
Complex History of Water on Mars

The research team posits that Mars’ ancient ocean may have experienced phases of freezing and thawing, contributing to the formation of the observed coastline. Sergey Krasilnikov of Hong Kong Polytechnic University noted that the ocean may have frozen over for about 10,000 to 100,000 years before completely drying up, roughly 260 million years later. Wu acknowledged the difficulty in conclusively determining the shoreline due to erosion over millennia but proposed that asteroid impacts could have preserved certain regions of the coastline.

Future Prospects for Verifying Mars’ Water History

Despite Zhurong’s findings, scientists acknowledge that definitive evidence of Mars’ ancient water history will require analysis of Martian samples on Earth. China’s Tianwen 3 mission, set to launch in 2028, aims to return surface samples by 2031. In comparison, NASA’s Mars Sample Return mission is projected to return samples in the 2030s.