Traces of an ancient ocean found on Mars

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.

“The big, novel thing that we did in this paper was think about Mars in terms of its stratigraphy and its sedimentary record,” Cardenas explained. “On Earth, we chart the history of waterways by looking at sediment that is deposited over time. We call that stratigraphy, the idea that water transports sediment and you can measure the changes on Earth by understanding the way that sediment piles up. That’s what we’ve done here — but it’s Mars.”

With the help of state-of-the-art software developed by the United States Geological Survey, the experts discovered over 6,500 kilometers of fluvial ridges that are likely eroded river deltas or submarine-channel belts – the remnants of an ancient Martian shoreline. Elements of rock formation – including ridge-system thickness, elevations, locations, and possible sedimentary flow directions – helped the scientists understand the evolution of the region’s paleogeography. 

“The rocks in Aeolis Dorsa [the area that was once an ocean] capture some fascinating information about what the ocean was like,” he said. “It was dynamic. The sea level rose significantly. Rocks were being deposited along its basins at a fast rate. There was a lot of change happening here.”

Since, on Earth, the ancient sedimentary basins contain the stratigraphic records of evolving climate and life, if scientists want to find a record of life on Mars, an ocean as big as that once covering Aeolis Dorsa would be the logical place to start.

“A major goal for the Mars Curiosity rover missions is to look for signs of life. It’s always been looking for water, for traces of habitable life. This is the biggest one yet. It’s a giant body of water, fed by sediments coming from the highlands, presumably carrying nutrients. If there were tides on ancient Mars, they would have been here, gently bringing in and out water. This is exactly the type of place where ancient Martian life could have evolved,” Cardenas concluded.

The study is published in the Journal of Geophysical Research Planets.

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By Andrei Ionescu, Earth.com Staff Writer