An international research team has discovered evidence supporting the existence of an ocean on ancient Mars.
Researchers from Guangzhou University in China, Pennsylvania State University in the United States, and the University of California, Berkeley, noted on the 24th (local time) that they found traces indicating that an ocean existed in the ancient northern hemisphere of Mars in data obtained by the Mars rover Zhurong. The findings were published in the Proceedings of the National Academy of Sciences (PNAS).
China's Mars rover Zhurong landed in May 2021 in Vastitas Borealis, a broad lowland located in the southern part of Utopia Planitia in the northern hemisphere of Mars, and has been conducting exploration activities for about a year. This area has previously been suggested as a location where sediments were altered by water.
Unlike other rovers, Zhurong is equipped with ground-penetrating radar (GPR) that uses both low-frequency and high-frequency radar to identify underground rock. Thanks to this, Zhurong traveled 1.9 km through areas believed to be ancient coastlines and explored up to 80 meters beneath the surface using GPR.
As a result of the exploration, radar images captured a thick layer of sand-like material existing 10 to 35 meters below the surface. This sediment layer showed a resemblance to Earth's coastal sedimentary layers, sloping at an angle of about 15 degrees towards the direction of the coastline.
Based on this evidence, the research team suggested that a large ocean capable of causing wave action to spread sediments along the sloping coast of Mars existed. They added that considering the rate at which similar coastal sediments form on Earth, ancient Mars likely had a warm and humid environment suitable for life for millions of years.
Michael Menger, a professor at the University of California, Berkeley, and corresponding author of the paper, said, “This sedimentary structure is different from sand dunes or impact craters, and it does not appear to be the result of flowing lava,” adding that the direction and slope of these formations are consistent with sedimentary beach layers formed over a long period by the sea.
References
PNAS (2025), DOI: https://doi.org/10.1073/pnas.2422213122