China's Zhurong rover uncovers new evidence of ancient ocean on Mars

Data from China's Mars rover Zhurong has provided new evidence that Mars may once have been home to an ancient ocean, shedding light on the planet's history and potential to support life.

Published in the journal Scientific Reports on Thursday, the research combines in situ data from Zhurong and remote sensing observations, revealing features that suggest an ancient nearshore environment in Mars' northern lowlands.

The Zhurong rover, part of China's Tianwen-1 mission, landed on Utopia Planitia, a vast plain in Mars' northern hemisphere, in 2021. The mission aimed to explore Martian geology, and recent analyses suggest that flooding occurred on Utopia Planitia about 3.68 billion years ago. "The ocean surface was likely frozen for a geologically short period," said Bo Wu, a planetary scientist from Hong Kong Polytechnic University.

The study details diverse marine landscape features in southern Utopia, identifying areas like a foreshore highland-lowland transition, a shallow marine zone and a deeper marine environment. These findings reflect a complex evolution of Mars' northern lowlands, with evidence that water reached these areas during the Late Noachian epoch.

Researchers estimate that this ocean disappeared by roughly 3.42 billion years ago as Mars gradually transformed into the cold, dry landscape seen today. Co-author Sergey Krasilnikov noted, "The water was heavily silted, forming the layering structure of the deposits."

While past research has indicated that a Hesperian ocean may have existed in Mars' northern lowlands, this new data provides more refined insights into its scope and nature. According to the study, the region likely underwent several stages: initial flooding, the formation of shallow and deep marine areas in the Early Hesperian epoch, and the eventual loss of subsurface volatiles in the Amazonian epoch.

The discovery of these water-related geological features has profound implications for understanding Mars' habitability. "The presence of an ancient ocean on Mars has been proposed and studied for several decades, yet significant uncertainty remains," Wu said.

According to Wu, these findings not only provide further evidence to support the theory of a Martian ocean but also present a discussion on its probable evolutionary scenario for the first time. The existence of water raises the possibility that Mars once supported microbial life, as water is a key ingredient for life.

When this ocean existed, Mars may have already begun losing its once-thick atmosphere, shifting away from a more Earth-like climate. "In the early history of Mars, when it likely had a warm, dense atmosphere, microbial life would have been more possible," Krasilnikov added.