A team of researchers from the Pennsylvania State University has recently released a set of topography maps providing new evidence for an ancient northern ocean on Mars. This is the strongest case yet that the red planet once experienced sea-level rise caused by a prolonged warm and wet climate, starkly different from the harsh, frozen landscape of today’s Mars.

“What immediately comes to mind as one the most significant points here is that the existence of an ocean of this size means a higher potential for life,” said study lead author Benjamin Cardenas, an assistant professor of Geosciences at Penn State. “It also tells us about the ancient climate and its evolution. Based on these findings, we know there had to have been a period when it was warm enough and the atmosphere was thick enough to support this much liquid water at one time.”

By using topography data, the researchers were able to show definitive evidence of a 3.5-billion-year-old shoreline with substantial sedimentary accumulation, at least 900 meters thick, and covering hundreds of thousands of square kilometers.