Geomorphological Data Reinforces Ancient Martian Ocean Hypothesis in Valles Marineris

New research published in January 2026 within the journal npj Space Exploration presents compelling geomorphological data that significantly bolsters the long-standing hypothesis of a massive, ancient ocean covering a substantial portion of Mars' northern hemisphere. This evidence suggests that the Red Planet, billions of years ago, may have harbored conditions comparable to early Earth, raising profound implications for the potential for past extraterrestrial life.

The investigation centered on the Valles Marineris, the Solar System's most extensive canyon network, which traverses the Martian equator. The core of the discovery involves the identification and analysis of scarp-fronted deposits (SFD) situated within the Coprates Chasma region of Valles Marineris. These fan-shaped geological structures are interpreted by the research team as ancient river delta deposits, marking the precise location where fluvial systems discharged into a large, standing body of water. The consistency of these formations is key: they were mapped at a remarkably uniform elevation, estimated to be between -3750 and -3650 meters, which strongly implies a stable paleo-shoreline existed at that altitude.

This rigorous geological mapping was spearheaded by Ignatius Argadestya, a lead researcher and PhD student affiliated with the University of Bern. The collaborative effort also included the Italian National Institute for Astrophysics (INAF), specifically its Padua Astronomical Observatory. To achieve the necessary resolution for this analysis, the team integrated high-resolution imagery from multiple orbital assets, including the European Space Agency's ExoMars Trace Gas Orbiter (utilizing the CaSSIS camera), NASA's Mars Express, and NASA's Mars Reconnaissance Orbiter.

Professor Fritz Schlunegger, a Professor of Exogenous Geology at the University of Bern's Institute of Geological Sciences, emphasized the terrestrial analogy, noting that delta structures universally form where rivers empty into oceans. The reconstructed sea level suggests the ancient Martian ocean was comparable in scale to Earth's present-day Arctic Ocean, an estimate now supported by more precise geological markers. The research places the formation of these deltaic features at approximately three billion years ago, a timeframe critical to understanding the planet's climatic evolution.

The consistency of the shoreline elevation across multiple sites traced westward toward the northern lowlands provides a firmer constraint on the ocean's extent than previous, more indirect arguments. This finding directly advances the search for extraterrestrial habitability by suggesting that Mars maintained stable surface water conditions for extended periods, a prerequisite for the development of life. While earlier evidence pointed to local lakes or ephemeral water flows, the scale and stability implied by this new coastline suggest a much more enduring aqueous environment.

Furthermore, the presence of subsequent features, such as fossilized mud cracks overlaid by wind-sculpted dunes, chronicles the planet's transition from a wet world to its current arid state. This detailed geomorphological reconstruction offers a more tangible framework for future astrobiological investigations. The identified shorelines serve as crucial reference points for prioritizing future landing sites, as deltaic environments are prime locations for preserving chemical and textural biosignatures.