Scientists have long suspected that billions of years ago, Mars hosted a large ocean that engulfed the planet's northern lowlands. But one of the major sticking points with this theory is the lack of clear shoreline formations to indicate where ancient Martian seas might have met the coast.
Now, a team led by Alexis Palmero Rodriguez, a planetary scientist based at the Planetary Science Institute in Tucson, Arizona, has proposed an utterly epic answer to this waterfront enigma—ancient Martian tsunamis created by catastrophic meteor impacts.
In a study published Thursday in Scientific Reports, Rodriguez and his colleagues share evidence that two tsunami events may have raged across Mars some 3.4 billion years ago, during the Late Hesperian epoch in Martian history.
By conducting extensive geomorphic and thermal image analysis of Chryse Planitia and Arabia Terra—two regions that are thought to have been adjacent to this bygone shoreline—the team was able to pick out what may be the geological fallout of massive waves that pounded away clear coastal distinctions on the young planet.
These formations include boulders and other rocky detritus that appears to have been deposited at higher elevations as the tsunamis rushed inland. Likewise, the new research identifies gravity-assisted backwash channels etched into Mars, indicating where these floods traveled as they shrank back into the ocean.
What's perhaps most astounding is the team's proposed origin for these flooding events, along with the projected size of the waves. Rodriguez and his colleagues suggest that enormous meteor impacts may be responsible for generating the tsunamis, which would have reached onshore heights of about 50 meters (164 feet), with local variations reaching as high as 120 meters (393 feet).
The first tsunami is estimated to have occurred when Mars was still a relatively warm and wet planet, so it left rocky material in its wake. The second hit a few million years later while Mars was cooling, so it sprinkled ice-rich lobes over the Martian highlands.
Both tsunamis would have significantly blurred the geological features indicating an ancient shoreline. Moreover, while the team only presented evidence backing two of these events, they suspect that there were others given that meteor impacts were much more common in the early solar system.
"We conclude that, on early Mars, tsunamis played a major role in generating and resurfacing coastal terrains," the authors said in the paper.
As a fun aside, Arabia Terra happens to be the region of Mars that astronaut Mark Watney has to traverse in The Martian. It's fun to know that in addition to battling Martian dust storms and erratic surface features, Watney was also standing on the site of ancient Martian tsunamis that demolished the seashore long ago.