Today, Mars is either very dry, quite dry or totally dry, depending on who you ask. But while the red planet's contemporary wetness remains to be determined, scientists pretty much agree that it once had quite a bit of water on it. These lakes and rivers — massive oceans, even, according to some researchers — were lost when the planet’s atmosphere, protected by a scant magnetic field nowhere near as powerful as the one surrounding Earth, was bombarded with blistering solar wind.
That’s why the planet — which once may have held some kind of life — is now a barren wasteland, at least by all appearances. Given Mars’s current state, it can be hard to wrap one's head around the concept of a Martian world full of surf. Well, good luck wrapping your head around this one: A new study suggests that Mars experienced at least two massive tsunamis during its wet and wild days.
The study, published Thursday in the journal Scientific Reports, points to geologic evidence of two tsunamis — each about 3.4 billion years ago, give or take a few million, just as life was first beginning to emerge on Earth.
They believe they've found the shorelines left behind by these massive events, which may have been triggered by asteroid impacts. Waves may have reached from 100 to 400 feet high, according to lead author Alexis Rodriguez of the Planetary Science Institute. The first event would have covered over 300,000 square miles of the planet, and the second — which likely occurred a few million years later — reached nearly 400,000 square miles.
“So, each had roughly the combined areas of California, Nevada and Oregon," Rodriguez said.
The findings could help solve one marine Martian mystery: Where are the shorelines? If Rodriguez and his colleagues, who used geographical and thermal images to analyze the surface, are correct in their hypothesis, then the shores of these ancient oceans have been hidden under the unusual geographic structures of the tsunamis. They found lobates — piles of rock debris caught up against slopes — that indicate a flow of water up a steep incline with enough force to carry large boulders up to dozens of miles.
“Tsunamis are the most, if not the only, fitting explanation for these observations,” he said. “There are not many processes in nature that can form these features.”
The two tsunamis also tell a tale of a changing climate: In between the two events, the shoreline seemingly shrank back, perhaps because the ocean began to partially freeze. The lobates left behind by the second tsunami actually seem to be waves that froze in place.
“These lobes froze on the land as they reached their maximum extent and the ice never went back to the ocean — which implies the ocean was at least partially frozen at that time,” co-author Alberto Fairén, Cornell visiting scientist in astronomy and principal investigator at the Center of Astrobiology in Madrid, said in a statement. “Our paper provides very solid evidence for the existence of very cold oceans on early Mars. It is difficult to imagine Californian beaches on ancient Mars, but try to picture the Great Lakes on a particularly cold and long winter, and that could be a more accurate image of water forming seas and oceans on ancient Mars.”
If an ancient tsunami really did dump this water into place, the fact that it’s been frozen since the event could make it a prime place to search for microbial life. If any microbes were able to evolve and thrive in the cold, salty oceans of Mars, traces of them might be left trapped in those lobates.
Don’t hold your breath waiting for one of our rovers to go hunting for these promising pockets of tsunami water. NASA and other space agencies follow strict rules about where their space robots can and cannot venture to, and any areas that seem potentially habitable are strictly off-limits. As sterile as NASA tries to make its rovers before they leave home, scientists still worry that some tenacious Earth microbe will invade and invalidate any samples they test on Mars. And if Curiosity rolled into an area still capable of supporting microbes, she could theoretically populate the region with hoards of whatever little buggies had managed to survive on her back. So for now, we can observe the most promising Martian neighborhoods only from above — but Rodriguez hopes that future landers can sample the ancient ice.
Other scientists may disagree with the findings, arguing that the features represent some other ancient phenomenon. To strengthen their case, Fairén, Rodriguez and their colleagues plan on hunting Martian maps to look for more features that might be tied to tsunamis, like lakes formed as tsunamis splashed into impact craters and salt deposits left behind as water receded. Rodriguez and co-author Jianguo Yan of Wuhan University will make an expedition to Tibet, where they believe there are lakes up high in the mountains that show similarities to the supposedly tsunami-induced lakes on Mars.
It might seem like this whole water-on-Mars thing has been totally played out at this point, but there are plenty of questions left to answer. Not all planetary scientists are convinced that Mars ever had an ocean, and the ones who are haven't reached a consensus on how long it lasted. Some studies have suggested that water appeared periodically, filling and disappearing from lakes or even oceans over the course of thousands of years or more, perhaps several times over.
These are questions we have to answer, because liquid water on ancient Mars isn't enough to make scientists all that hopeful for signs of long-extinct life. For Mars to have supported life as we know it, it would have had to retain liquid water long enough for life to evolve. On Earth, that process took close to 1 billion years.