If Martian life ever existed, this is where we should look.
On the Red Planet’s surface, there are geological features indicative of shorelines that were once present throughout Mars’ Northern Plains. In fact, according to NASA, Mars likely had an ocean covering 19 percent of the planet’s surface.
However, some of these shoreline structures hint to two large meteorites, which hit the planet millions of years apart, triggering a pair of mega-tsunamis. These gigantic waves scarred the Martian landscape, while at the same time, revealed evidence of cold, salty oceans favorable for sustaining life.
"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 University visiting scientist in astronomy and principal investigator at the Center of Astrobiology, Madrid, in a press release.
Fairén, along with lead author Alexis Rodriguez of Cornell’s Planetary Science Institute and 12 other scientists, published their research today (May 19) in Scientific Reports, a publication of the journal Nature.
If one tsunami wasn’t enough, the team also found evidence of another big meteorite impact, which triggered a second tsunami wave. However, in the millions of years between the two impacts, Mars went through a frigid climate change, in which water turned to ice. "The ocean level receded from its original shoreline to form a secondary shoreline, because the climate had become significantly colder," explained Fairén.
This second tsunami resulted in the formation of rounded lobes of ice — a portion of the ice sheet that projects from the main area.
"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."
These icy lobes kept their well-defined boundaries and flow-related shapes, which suggests 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," continued Fairén.
Now that these tsunami-formed features have been identified, what’s next? According to Rodriguez, "As a follow-up investigation we plan to characterize these terrains and assess their potential for future robotic or human in-situ exploration."
The research, "Tsunami Waves Extensively Resurfaced the Shorelines of an Early Martian Ocean," was funded by NASA.
You might also like: Moon Receives Deliveries of Water from Asteroids