Scientists Uncover Clues to an Ancient Ocean on Mars

After years of hunting for a lost ocean on Mars, a planetary scientist at UC Berkeley and others have finally dug up compelling evidence.

The surface of Mars today is a mostly dry, frigid wasteland. But billions of years ago, the red planet had a thicker atmosphere, warmer climate, and even lakes and rivers. In radar data published from a Chinese rover this week, UC Berkeley’s Michael Manga and his international colleagues suggest Mars also had a giant ocean with sandy beaches.

“This is the first time we’ve really looked underground with this resolution at a place [on Mars] where there would have been oceans,” Manga said. “We identified old beaches beneath the surface of Mars that record the past existence of a huge ocean.”

Zhurong, a Chinese rover, landed in the Martian basin known as Utopia Planitia in 2021 and spent a year exploring. The rover used ground-penetrating radar to probe hundreds of feet below the surface, and a large team from several institutions in China worked with Manga and scientists from Pennsylvania State University to interpret the images the rover brought home.

The imagery reveals abundant layers of buried materials, the scientists said, all angled upward at about 15 degrees to a hypothesized ocean shoreline. That’s nearly the same angle of beach deposits on Earth. The thick deposits also indicate wave action over a long period of time, while the particle size mimics that of sand.

Shorelines have significance for some of Earth’s earliest life. The researchers argued their new study, published on Monday in the journal Proceedings of the National Academy of Sciences, strengthens the case for past life on Mars.

The Mars ocean theory hatched in the 1970s after spacecraft imagery showed an apparent large shoreline and seabed-like indentation. Some scientists discounted the idea since the shore seemed irregular. However, Manga and other scientists came up with several possible explanations, first in 2007 and then in 2017, that supported the ocean hypothesis.

In the new study, the scientists consider other explanations for their data, such as wind-swept dunes or volcanoes. However, they concluded that their findings appeared to be strong signs of an ocean, dubbed Deuteronilus.

Taylor Perron, an MIT professor of Earth, atmospheric and planetary sciences who was not involved with the study, expressed enthusiasm about the fresh results, though he doesn’t consider the question closed.

“This is an exciting additional piece of evidence there might have been an ocean in the northern plains of Mars, which is also consistent with the evidence we see of abundant water in the past there,” Perron said. “But it isn’t quite definitive proof.”

Radar imagery is not as iron-clad as examining the buried rocks directly, as geologists do on Earth, Perron said. To strengthen the conclusion of an ocean, he suggested further radar sampling of other areas on Mars.

“Or, perhaps one day, a geologist on the ground on Mars could take a closer look to see if they are, in fact, sedimentary rocks consistent with an origin in water,” Perron said.