New evidence suggests Mars was once far more Earth-like than previously understood, potentially harboring a vast ocean and river systems billions of years ago. An international team led by the University of Bern has identified geological formations indicative of ancient river deltas using data from Martian orbiters – structures now largely obscured by wind-shaped dunes. The findings, published today in npj space exploration, strengthen the case for past habitability on the Red Planet and offer a more definitive picture of it’s watery past than previous research allowed.
Evidence of Ancient Rivers Discovered on Mars | January 12, 2026
Researchers led by Professor Fritz Schlunegger have uncovered compelling evidence of ancient river systems on Mars, suggesting the planet may have been largely covered by a vast ocean approximately three billion years ago. The discovery offers new insights into the Red Planet’s potential for past habitability and adds to the growing body of evidence pointing to a dramatically different Martian climate in the distant past.
These river deltas were discovered by the researchers on Mars.Photo: Esa/ExoMars – TGO/CaSSIS/Ignatius Argadestya
The international research team, spearheaded by the University of Bern, identified geological structures resembling river deltas using images captured by Martian probes. Their findings are detailed in a study published in the journal «npj space exploration».
“The structures we were able to identify in the images clearly represent the mouth of a river flowing into an ocean,” Professor Schlunegger stated in a University release on Monday.
While these former delta structures are now covered by wind-shaped dunes, researchers say their original form remains distinctly recognizable.
All of the discovered delta structures are located at roughly the same elevation, allowing the team to reconstruct the ancient sea level and coastline. The results indicate the ocean was at least the size of the Arctic Ocean on Earth and stretched across the planet’s northern hemisphere.
Previous studies have also suggested the existence of an ocean on Mars, but the researchers note those conclusions were based on less precise data or indirect evidence. This new reconstruction, they say, is based on more definitive indicators.
The study’s findings confirm that the ocean covered a significant portion of Mars’ northern hemisphere and was at least comparable in size to Earth’s Arctic Ocean. Researchers dated the highest water level on Mars to a period approximately three billion years ago.
Potentially Habitable Conditions
According to the scientists, the discovery reinforces the possibility that Mars once possessed conditions conducive to the development of life.
“We know Mars as a dry, red planet. Our results, however, show that it was once a blue planet,” said study first author Ignatius Argadestya, as quoted by the University. “This also demonstrates how precious water is on a planet and that it can disappear.”
