This is the strongest evidence so far. It is consistent with a widespread warm, wet climate on the red planet. The shores of an ocean on Mars remain a mute record of the past.
“An ocean of this size means a greater potential for life,” Benjamin Cardenas said in a statement. He is lead author of the study published in Journal of Geophysical Research: Planets.
Stratigraphy as a technique
“There was a period when it was warm enough. And the atmosphere was thick enough to support this amount of liquid water.”
There has long been debate in the scientific community as to whether Mars had an ocean. Now definitive evidence of an approximately 3.5 billion year old coastline has appeared. It has a substantial sedimentary accumulation, at least 900 meters thick. It covered hundreds of thousands of square kilometers.
“On Earth, we trace the history of waterways by looking at the sediments that are deposited over time. We call that stratigraphy. That’s what we’ve done here, but it’s Mars.” The team used software developed by the U.S. Geological Survey. They discovered more than 6,500 kilometers of fluvial ridges.
The area that was once ocean is now known as Aeolis Dorsa. It contains the densest collection of river ridges on the planet. “The rocks there capture fascinating information about what the ocean was like,” they say. “It was dynamic. Sea level rose significantly. Rocks were being deposited along its basins at an accelerated rate. There was a lot of change going on here.”
Life on Mars
“A major goal of the Curiosity rover missions is to look for signs of life,” Cardenas said. “It’s always been looking for water, traces of habitable life. This is the biggest one so far. It’s a giant body of water, fed by sediment from the highlands. This is exactly the kind of place where ancient Martian life could have evolved.”
The shores of an ocean on Mars are a spectacular discovery. Curiosity and NASA’s upcoming missions now know where to target their next searches.