Massive waves carved features into Mars’ surface that can still be seen today. That’s what a new study focusing on the geologic shape of ancient shorelines along Mars’ northern plains suggests.

We are pretty sure water intermittently flows even today on Mars. Last September, NASA released compelling evidence showing dark, narrow streaks that are believed to be caused by briny liquid water. So Mars isn’t quite as dry as it appears today.

briny water streaks on Mars

These dark streaks are believed to be liquid water. Credit: NASA

Ok, back to the huge waves. How did they form? Scientists from the Planetary Science Institute, Cornell University and elsewhere point the finger at meteorite impacts.

“About 3.4 billion years ago, a big meteorite impact triggered the first tsunami wave. This wave was composed of liquid water. It formed widespread backwash channels to carry the water back to the ocean,” said Alberto Fairén, Cornell visiting scientist in astronomy.

Evidence of another major meteorite impact happened millions of years later. And the red planet was deep into a major climate shift. Frigid temperatures were freezing Mars’ oceans. The next tsunami carried the slushy salt water inland where it froze into 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,” Fairén said. “Our paper provides very strong evidence for the existence of very cold oceans on early Mars.”

Fairén says to picture the Great Lakes in the dead of winter. That’s what these ancient oceans may have looked like.

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These lobes kept their boundaries and flow-related shapes. And because we believe water on Mars was briny, these lobes would make prime targets for searching for biosignatures.

The meteorites and tsunamis

The study shows the waves reached an average height of about 50 meters. But in some local spots, the waves could have reached 120 meters high. To put that into perspective, waves from the 2004 tsunami in the Indian Ocean reached 20 to 30 meters on the island of Sumatra.

As for the meteorites that caused them? The researchers believe the two meteorites created craters stretching 30 kilometers across.

Exploring the frozen lobes

“We have already identified some areas inundated by the tsunamis where the ponded water appears to have emplaced lacustrine sediments, including evaporites,” Alexis Rodriguez, lead author of the study, said. “As a follow-up investigation we plan to characterize these terrains and assess their potential for future robotic or human in-situ exploration.”

Exploring these lobes will be incredibly difficult. And not for reasons you might think. The risk of contaminating any site that may potentially have life is something NASA takes seriously. NASA’s Office of Planetary Protection has strict guidelines for orbiters and landers heading to Mars.

From the Planetary Protection Mars page:

Planetary protection considerations for missions to Mars are thus substantial, and sterilization requirements for spacecraft landing on Mars are strict. Planetary protection requirements for MGS and Mars Odyssey are intended to ensure that the orbiting spacecraft do not inadvertently drop out of orbit and crash onto Mars after their missions are completed. Planetary protection requirements for the Mars Exploration Rovers are intended to ensure that these landers did not transport Earth microbes to the surface of Mars.

Any mission that is approved to explore the most interesting regions of Mars will be under heavy restrictions to ensure we don’t accidentally bring microbes from Earth along for the ride.

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It’s not just Mars that falls under the Planetary Protection umbrella. Restrictions are put in place for any body that may carry water ice. Ceres is one example.

When humans finally make to Mars, one of the biggest challenges (besides getting there) will be not to contaminate the planet.

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