New evidence confirms that Mars once possessed a vast ocean, roughly the size of Earth’s Arctic Ocean, marking the strongest direct indication yet of a wetter, potentially habitable past on the Red Planet. The discovery, based on detailed analysis of images and data from multiple Mars orbiters, reshapes our understanding of Martian geological history.
Evidence From Martian Landscapes
Researchers Ignatius Indi and Fritz Schlunegger from the University of Bern in Switzerland led the study, leveraging high-resolution color imagery from the European Space Agency’s ExoMars Trace Gas Orbiter. This specialized camera, dubbed the Bernese Mars, allowed them to identify subtle differences in surface materials previously invisible in black-and-white scans.
The team focused on Valles Marineris, a colossal canyon system stretching over 4,000 kilometers across the Martian equator. Specifically, they examined Coprates Chasma, a deep region within the canyon formed approximately 3.3 billion years ago. By combining these images with topographic data from NASA’s Mars Reconnaissance Orbiter and Mars Express, scientists reconstructed ancient Martian environments.
Geological Parallels to Earth
The analysis revealed structures strikingly similar to those created on Earth by rivers flowing into oceans or alpine lakes forming at mountain bases. Schlunegger draws a comparison to the Nile Delta: “If you removed the Mediterranean waters… you would see structures very similar to those detected on Mars.” This suggests that Mars once featured comparable fluvial and coastal processes.
The team traced ancient coastlines, estimating the size of the former ocean to be comparable to Earth’s Arctic Ocean—the largest ocean ever to exist on Mars. These findings confirm that long-lasting bodies of surface water were present inside Valles Marineris billions of years ago, potentially connected to a larger northern ocean.
Why This Matters
While previous research has hinted at a past humid Mars—through mineral interactions and evidence of ancient tsunamis—this study provides the most direct, visual confirmation. The persistence of liquid water is critical not just for understanding Mars’s past habitability but also for broader planetary science. The discovery strengthens the case for past life on Mars, but also serves as a reminder that even Earth’s most essential resource is not guaranteed to last forever.
“Oceans on Mars would have acted just like oceans on Earth, and they are vital to the health of the planet,” notes Ezat Heydari, a geochemist at Jackson State University.
The new data reinforces the idea that Mars wasn’t always the arid world we see today, but a planet with a dynamic hydrological cycle that may have supported life for extended periods. This discovery marks a significant step forward in our understanding of planetary evolution and the search for life beyond Earth.
