New scientific findings, including a recent study from a Swiss research team at the University of Bern, are reinforcing the long-held hypothesis that Mars once harbored a vast ocean, primarily in its northern hemisphere. This compelling evidence comes from detailed observations of ancient geological structures on the Martian surface, specifically extensive river deltas and channel belts, which bear striking resemblances to those found on Earth where rivers discharge into large, standing bodies of water. Scientists have used high-resolution orbital imagery to identify these features, noting patterns like narrowing channel belts upstream of what would have been ancient coastlines – a phenomenon known as a 'backwater zone' on Earth. The sheer scale and maturity of these deltas suggest sustained water flow and a stable base level, indicating that Martian rivers did not simply empty into transient lakes but into a body of water large enough to be considered an ocean or a very large sea. One study even compared Martian delta features to the unique inverted river delta of the Wedington Sandstone formation on Earth to bolster the argument for an ancient Martian ocean. These discoveries significantly strengthen the argument that early Mars, billions of years ago, was a much wetter and potentially more habitable world than previously imagined. The notion of Mars as a 'blue planet' in its ancient past, capable of sustaining liquid water on its surface for prolonged periods, is increasingly supported by such geological evidence. This research provides crucial insights into the paleoclimate of Mars, challenging models that suggested a perpetually frozen early Mars and opening new avenues for understanding planetary evolution and the potential for extraterrestrial life.