New Evidence Suggests Ancient Ocean Once Covered Half of Mars
WASHINGTON, Feb 24 (Reuters) – Ground-penetrating radar data from China’s Zhurong rover has uncovered buried structures on Mars that resemble sandy beaches, providing new evidence for the existence of an ancient ocean. This ocean, known as Deuteronilus, is believed to have covered much of the northern plains approximately 3.5 to 4 billion years ago, during a period when Mars had a thicker atmosphere and a warmer climate.
Scientists suggest that such an ocean could have created conditions suitable for life, similar to early Earth’s primordial seas. The Zhurong rover, which operated between May 2021 and May 2022, traversed about 1.2 miles (1.9 km) in a region with surface features indicative of an ancient shoreline. Using ground-penetrating radar, the rover sent high-frequency radio waves into the ground, detecting subsurface features up to 80 meters (260 feet) deep.
Beneath the surface, researchers identified thick layers of sediment—ranging from 33 to 115 feet (10 to 35 meters)—with properties similar to sand. These layers, sloped at angles consistent with beach formations on Earth, extended over three-quarters of a mile (1.2 km) along the rover’s path.
“The Martian surface has changed significantly over billions of years, but ground-penetrating radar allowed us to detect coastal deposits that aren’t visible from the surface,” said Guangzhou University planetary scientist Hai Liu, a member of China’s Tianwen-1 mission team.
On Earth, such deposits take millions of years to form, implying that Mars once had a long-lived body of water with active wave processes shaping its shores. “The beaches would have formed through similar processes to those on Earth—waves and tides,” Liu explained. “Such an ocean would have significantly influenced Mars’ climate, shaped its landscape, and created environments where life could have emerged.”
Planetary scientist Michael Manga from the University of California, Berkeley, emphasized the significance of shorelines in the search for past life. “It’s believed that life on Earth may have originated near the interface of air and shallow water,” Manga noted.
The study, published in the Proceedings of the National Academy of Sciences, ruled out alternative explanations for the formations. Geoscientist Benjamin Cardenas of Penn State stated that wind-blown dunes, ancient river deposits, and lava flows were considered but did not match the observed patterns. “Beaches simply fit the data best,” he said.
Mars, along with Earth and the rest of the solar system, formed about 4.5 billion years ago. Scientists believe Deuteronilus disappeared roughly a billion years into Martian history when the planet’s climate dramatically changed. Some of its water may have escaped into space, while large amounts could remain trapped underground. A study published last year, based on NASA’s InSight lander seismic data, suggested that a vast reservoir of liquid water might still exist deep within fractured igneous rock.
For decades, satellite images have hinted at possible ancient shorelines on Mars, but surface evidence could have been eroded by wind, meteorite impacts, or volcanic activity. However, the newly discovered structures remained preserved beneath the surface, buried under layers of dust, debris, and sediment over time.
“These are beautifully preserved because they remain entombed in the Martian subsurface,” Cardenas said.