Saturday Science: Tsunami! On Mars?

Martian coastline, after tsunami?

It looks as though that may very well have happened. Big ones:

Mars, despite its current rusted and parched appearance, was once a world where water flowed freely. Detailed observations of the red planet’s atmosphere and surface have led scientists to speculate that perhaps about 3.8 billion years ago, Mars had enough liquid water to form an ocean occupying almost half of its northern hemisphere.

However, scientists have not been able to find this primordial ocean’s coastline despite there being strong evidence that such large water bodies once existed on the fourth planet from the sun.

A new study has now revived the ancient ocean hypothesis. The study, published in the journal Nature Scientific Reports, suggests the ocean’s shorelines were overrun and buried by two ancient mega tsunamis that occurred approximately 3.4 billion years ago.

It seems the first one, possibly caused by a meteor strike in the Martian ocean, was bad enough. Then the planet cooled down and the oceans froze, to the second one was an ice tsunami.

I don't even want to think about that. But, happily, someone did:

The scientists found evidence for another big meteorite impact, which triggered a second tsunami wave. In the millions of years between the two meteorite impacts and their associated mega-tsunamis, Mars went through frigid climate change, where water turned to ice, Fairén said: "The ocean level receded from its original shoreline to form a secondary shoreline, because the climate had become significantly colder."

The second tsunami formed rounded lobes of ice. "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," he 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."

There's another possibility here that's intriguing: Where did life originate on Earth? The oceans. And brine, as in ocean, doesn't freeze as readily as fresh water.

These icy lobes retained their well-defined boundaries and their flow-related shapes, Fairén said, suggesting the frozen ancient ocean was briny. "Cold, salty waters may offer a refuge for life in extreme environments, as the salts could help keep the water liquid. ... If life existed on Mars, these icy tsunami lobes are very good candidates to search for biosignatures," he said.

That's one thing I love about science -- every answer generates more questions.