Evidence of two ancient, 400ft-high tsunamis found on Mars

19 May 2016

By analysing geological structures on Mars, researchers have concluded that, in Mars’ ancient, water-laden past, two separate meteorite strikes caused mega-tsunamis to wash over the planet.

It might seem hard for us to imagine now, as we look at the red, seemingly lifeless surface of Mars on satellite imagery, that any amount of water existed there that could create anything close to a wave, let alone a tsunami, but the Martian rocks apparently reveal a different story.

That is, according to a paper published in Nature‘s Scientific Reports by Alberto Fairén and Alexis Rodriguez of the Planetary Science Institute, who analysed what were once the shorelines of oceans along Mars’ northern plains.

Around 400ft high

Once they identified particular deposits of minerals and where they had fallen, they came to the conclusion that, approximately 3.4bn years ago, a huge meteorite struck the Red Planet, triggering an enormous tsunami of liquid water nearly 400ft high.

This surge of water from the cold and salty oceans led to widespread backwash channels, which carried the water back to the ocean.

Yet, as the pair realised, this was not the only cataclysmic event to have happened in the planet’s history.

Further research into the geology of Mars revealed the location of a second meteorite impact that occurred millions of years after the first impact, which again triggered a mega-tsunami.

Old deposits

New deposits

A comparison between the older and younger deposits caused by the two tsunamis. Image via Alexis Rodriguez

Frozen ice tsunami

This tsunami was different, however, as, compared with the first one, this impact occurred during a period of intense flux in the planet’s climate, where much of this liquid water was beginning to turn into ice.

This second tsunami then resulted in the creation of rounded lobes of ice, the pair of researchers said in their paper.

“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,” Fairén said.

“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.”

Tsunami lobes

A 250km long lobe of dark material might be the remnants of a tsunami that hit when Mars’ climate was cold enough to freeze the water into an ice-rich slush that crept across the landscape. Image via Alexis Rodriguez

Possibly harboured life

These icy lobes, like peninsulas from the land mass of ice, likely retained their well-defined boundaries and their flow-related shapes, suggesting this ancient ocean was quite briny.

Based on this, Fairén believes that they would have been excellent habitats for organisms capable of living in extreme environments, otherwise known as extremophiles.

“If life existed on Mars,” he said, “these icy tsunami lobes are very good candidates to search for biosignatures”.

The next step for the pair of Spanish researchers is to do a follow-up investigation and characterise these terrains in greater detail and, Rodriguez said, will help assess their potential for future robotic or human in-situ exploration.

Mars-like surface image via Shutterstock

Colm Gorey was a senior journalist with Silicon Republic