- Mars once had an ocean, new evidence suggests. The findings support a growing number of other studies with the same conclusion. But this study strongly suggests that an ocean once filled the Valles Marineris, the Grand Canyon of Mars.
- Scientists have found ancient deltas in the Valles Marineris canyon system. They appear to have been created by rivers that flowed into the ocean along the ancient coastline.
- The ocean was at least as big as the Arctic Ocean on Earth and covered about half of Mars, scientists say.
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More Evidence for Ancient Mars
Evidence continues to mount for a long-lost ocean on ancient Mars. Several studies over the past few years have supported this scenario, and now a new study reinforces the idea. An international team of researchers led by the University of Bern, Switzerland, he spoke January 12, 2026 on Newly Recorded Ancient Deltas in the Wide Area Valles Marineris canyon system. These deltas are said to lie along what used to be the coast of the Martian ocean in the northern hemisphere of the planet. Scientists say the ocean was at least as large as Earth’s Arctic Ocean and that it covered about half of Mars.
Scientists found deltas in images taken by various orbits of Mars, including ExoMars Trace Gas Orbiter, Mars Express and Mars Reconnaissance Orbiter. Deltas are located in the southeast Coprates Chasmawhich is part of the huge Valles Marineris canyon system.
New reviewed findings were published in NPJ Space Exploration on January 7, 2026.
University of Bern: Mars was half covered by ocean mediarelations.unibe.ch/media_releas…
— AAS Press Office (@press.aas.org) 2026-01-12T16:58:11.295Z
Ancient river deltas in the Valles Marineris
In the new study, the researchers focused on the Coprates Chasma, located in the southeastern part of the Valles Marineris canyon system. They used high-resolution images from the orbiters to examine geological structures in the area.
Ignatius Argadestya is a Ph.D. student at the Institute of Geological Sciences and the Institute of Physics at the University of Bern. Huh he said:
Unique high-resolution satellite images of Mars have allowed us to study the Martian landscape in great detail through surveying and mapping.
That’s when they found the deltas. Argadestya continued:
While measuring and mapping the Martian images, I was able to recognize mountains and valleys that resemble the mountainous landscape on Earth. However, I was particularly interested in the deltas that I discovered on the edge of one of the mountains.
Deltas, known as deposits on the front of the shoe or delta fansthey were at the lower end of the canyon system. On Earth, they are formed by rivers that empty into standing water. Such deltas have been found elsewhere on Mars, including Crater lakewhere NASA is based Perseverance the rover is currently exploring. As Fritz SchlueneggerProfessor of Exogenous Geology at the Institute of Geological Sciences at the University of Bern explained:
Delta structures develop where rivers damn into the oceans [editor’s note: where rivers flow out from a narrow, confined channel or valley into a wider, open area]as we know from numerous examples on Earth.
An ocean that covered half of Mars
The deltas are further evidence of a vast ocean that once existed in the northern hemisphere of Mars. Schlunegger said:
The structures we were able to identify in the images are clearly the mouth of the river into the ocean.
Previous studies have suggested that an ocean once covered much of the northern hemisphere of Mars. A new study supports this. In fact, he says, the former ocean was at least as large as Earth’s Arctic Ocean and covered about half of Mars. It is hugeespecially when you consider that Mars is only about half the size of Earth. As Schlunegger noted:
We are not the first to postulate the existence and size of the ocean. However, earlier claims were based on less accurate data and partly on indirect arguments. Our sea level reconstruction, on the other hand, is based on clear evidence for such a coastline, as we were able to use high-resolution images.
Life on the blue planet?
So if there was an ocean, was there life? We don’t know that yet, but the presence of ocean, lakes and rivers certainly shows that Mars was indeed much more habitable than it is today. Argadestya said:
We know Mars as a dry, red planet. However, our results show that it was a blue Earth-like planet in the past. This finding also shows that water is precious on the planet and could disappear at some point.
Like paper concludes:
Our research thus provides further documentation of the time period when the availability of liquid water on the surface was highest during the evolution of this planet. We therefore believe that our findings at the environmental level during Late Hesperian to Early Amazonian will have implications for research into evidence of potential life on Mars.
Bottom line: Evidence for an ancient ocean on Mars continues to mount. Valles Marineris canyon deltas along the former coast show that the ocean covered half the planet.
Source: Carp-faced deposits record the highest water level in Mars’ Valles Marineris
Read more:
New evidence of ocean on Mars found in ancient rivers
Vacation-style beaches on Mars? New evidence of a lost ocean
More evidence of an ancient ocean on Mars from a Chinese rover
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