New Evidence Suggests Ancient Ocean on Mars May Have Fostered Life

BEIJING, China — Scientists have unveiled new evidence suggesting that Mars may have hosted an ocean with sandy beaches approximately 3.6 billion years ago. Data from China’s Zhurong rover, operational from May 2021 to May 2022, indicated the presence of ancient shorelines where an ocean might have covered about one-third of the planet.

Landing in Utopia Planitia, the rover employed ground-penetrating radar to probe beneath the Martian surface, uncovering rock layers that suggest the existence of ancient beaches and river deltas. This research was published Monday in the journal Proceedings of the National Academy of Sciences.

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

Previous studies hinted at a warmer, wetter Martian climate, and this research adds to the notion that this environment might have persisted for tens of millions of years longer than previously believed, creating conditions conducive to life.

In the 1970s, early missions like NASA’s Mariner 9 and Viking 2 detected features suggesting the existence of an ancient ocean on Mars. These findings raised questions about Utopia Planitia, a region dating back to the Hesperian period, between 3.7 billion and 3 billion years ago, which is known for being relatively dry compared to older regions.

Dr. Aaron Cavosie, a planetary scientist at Curtin University in Australia, noted that past observations indicated that Mars’ climate cooled during the Hesperian period, leading to a drying of its surface. “The Mariner 9 orbiter first imaged giant canyons on Hesperian surfaces, but they are generally viewed as evidence of catastrophic bursts of groundwater rather than evidence for standing water,” Cavosie explained.

The Zhurong rover’s findings are significant because they reveal sediment structures resembling layered beaches on Earth at depths between 10 and 35 meters down. These layers dipped at a 14.5-degree angle and contained particles that matched the size of Earth’s sand grains. “The structures don’t look like sand dunes; they don’t look like an impact crater. They don’t look like lava flows. That’s when we started thinking about oceans,” said coauthor Michael Manga, a professor of Earth and planetary science at the University of California, Berkeley.

Cardenas emphasized that this discovery paints a picture of ancient, habitable environments on Mars that may have been friendly to microbial life. “When we look back at where the earliest life on Earth developed, it was in the interaction between oceans and land,” he said.

Much of Mars’ water is thought to have escaped into space, but researchers suspect that some water became trapped underground or formed minerals. Following the drying of the Martian ocean, volcanic eruptions and dust storms likely buried these ancient shorelines, preserving them from erosion, Cardenas noted.

Yet, some experts advise caution regarding current interpretations of the data. François Forget, a senior research scientist at the French National Centre for Scientific Research, expressed skepticism about whether only ocean shorelines can explain the radar data, suggesting that alternative processes, such as dune formations, might also be responsible.

Conversely, Dr. Joe McNeil, a planetary scientist at London’s Natural History Museum, argues that the findings lend weight to the idea of an ancient northern ocean on Mars. He stated, “If these coastal deposits truly represent deposition of sediments at the edge of an ancient ocean, it suggests a prolonged period of stable liquid water, which has major implications for Mars’ climate history.”