Mars bathtub ring discovery points to long lasting ancient ocean

Thursday 16 April 2026 - 09:00

By: Dakir Madiha

Mars bathtub ring discovery points to long lasting ancient ocean

A study published in Nature presents strong new evidence that a vast ocean once covered a significant portion of Mars. Researchers identified a large, flat geological formation resembling continental shelves on Earth, suggesting that liquid water remained stable on the planet for millions of years.

The research was led by Abdallah Zaki from the University of Texas at Austin and Michael Lamb from Caltech. The team detected a broad band of terrain encircling the boundary between Mars’ northern lowlands and southern highlands. This formation resembles a “bathtub ring,” similar to marks left after water recedes, and indicates that an ocean may have once covered about one third of the planet’s surface.

Unlike earlier studies that focused on identifying ancient shorelines, which often appear fragmented and distorted, the researchers targeted continental shelf structures. They used computer simulations to remove Earth’s oceans and identify which features remain most visible. The results showed that continental shelves, not coastlines, provide the clearest long term geological signature of large bodies of water.

Applying this method to Martian topographic data collected by orbiting probes, the team found a consistent flat zone between minus 1,800 and minus 3,800 meters in the northern hemisphere. These formations require extended periods to develop and do not form around smaller bodies of water such as lakes. This suggests that the Martian ocean remained stable over geological timescales rather than appearing briefly.

The findings add to growing evidence that early Mars had a far wetter climate. Previous research has identified river deltas that align with the newly mapped shelf, pointing to a connected hydrological system. This reinforces the idea that Mars once had sustained surface water capable of shaping large scale landscapes.

The discovery has direct implications for the search for past life. Sedimentary deposits along ancient coastlines on Earth often preserve biological records. Similar deposits on Mars could contain traces of past microbial life if it ever existed. Researchers note that further confirmation will require in situ analysis by rovers and more detailed satellite observations.