A Mega-Tsunami on Early Mars

Evidence for a much wetter and livelier planet, three billion years ago.

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A group of researchers led by François Costard from the French National Centre for Scientific Research reports in a recent issue of the Journal of Geophysical Research—Planets on a dramatic tsunami that occurred on Mars billions of years ago, before the planet turned into the dusty desert we see today.

On Earth, tsunamis are usually caused when an earthquake, volcanic eruption, or landslide displaces a huge volume of water, typically in the Pacific Ocean, resulting in huge waves that pile up when they hit a coastline. The crests of these waves can reach ten meters or more in height, as did the one that led to the Fukushima Daiichi nuclear disaster in Japan in 2011.

The tsunami that occurred about three billion years ago on Mars was much more violent. Based on their study of surrounding landforms, Costard’s team identified the site of the tsunami’s origin as Lomonosov crater, which shows signs of having been hit by an asteroid when it was submerged underwater. The crater is nearly 150 kilometers in diameter, so one can only imagine how gigantic the asteroid must have been. The resulting wave must have been several hundred meters high, swallowing the surrounding land areas of the northwestern Arabia Terra region of Mars. It was a catastrophe of extraordinary magnitude.

Deposits inferred to be from tsunamis had already been seen on Mars by Alexis Rodriguez from the Planetary Science Institute in Tucson, Arizona, and colleagues. This new study, however, dates the mega-tsunami to just three billion years ago—a time when scientists had thought oceans no longer existed on Mars, the planet’s magnetic field had collapsed, the atmosphere was disappearing, and the surface had already turned cold and dry.

That storyline may have to be rewritten. If Costard and colleagues are correct, it means that a shallow ocean on Mars existed much more recently than previously thought, and that there was enough water to inundate large areas of land. A few years ago that might have seemed unbelievable. But with the Curiosity rover’s discovery of ancient lake deposits in Gale Crater—suggesting that a large body of water existed there at around the same time as the tsunami—I think the idea of a much wetter Mars, lasting for a longer period of time, will gain a lot of support.

Of course, if oceans and large lakes existed on Mars three billion years ago, it means there could have been habitable environments and possibly life. So if Costard’s research is supported by new studies, a future Mars mission might do well to search for ancient fossils in and around Lomonosov crater.

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