The megatsunami hit Mars after a massive asteroid hit the Red Planet
A Martian megatsunami — a giant killer wave that may have reached more than 80 stories high — may have swept through the Red Planet after a cosmic impact similar to the one that likely ended Earth’s age of dinosaurs, a new study finds.
Although the surface of Mars now cold and dry, much evidence suggests that an ocean’s worth of water covered the Red Planet billions of years ago. Previous research found signs that two meteor impacts may have been triggered a pair of megatsunamis (opens in new tab) about 3.4 billion years ago. The older tsunami inundated about 309,000 square miles (800,000 square kilometers), while the more recent one drowned a region of about 386,000 square miles (1 million square kilometers).
A 2019 survey find what might have been ground zero for younger megatsunamis — Lomonosov Crater, a 75-mile (120 km) wide hole in the ground in the icy plains of the Martian Arctic. Its large size suggests that the cosmic impact that dug the hole itself was large, similar in scale to a 6-mile-wide (10 km) an asteroid that struck near the present town of Chicxulub in Mexico 66 million years ago, triggering a mass extinction that killed 75% of Earth’s species, including all dinosaurs except birds.
Now the new study finds what may have been the starting point of the older megatsunami, the 69-mile (111 km) wide Pole Crater, which International Astronomical Union named after the science fiction grandmaster Frederick Paul in August.
Scientists focused on NASA’s landing site Viking 1, the first spacecraft to successfully operate on the surface of Mars. Viking 1 landed in 1976 on Chryse Planitia, a smooth circular plain in the northern equatorial region of Mars. The probe landed near the terminus of a giant channel, the Maja Valles, carved by an ancient catastrophic flood, the first time scientists have identified an alien landscape carved by a river.
Unexpectedly, instead of finding the kind of flood-related features scientists expected from the site, such as simplified islands worn away by flowing water, they found a boulder-strewn plain. Researchers now suggest that these stones may be debris from a megatsunami, the giant wave that carried pulverized rocks away from the site of the cosmic impact.
“The seafloor would have been thrown into the air, feeding the wave with sediment and possibly aiding the development of a catastrophic debris flow front,” study lead author Alexis Rodriguez, a planetary scientist at the Arizona Institute of Planetary Sciences, told Space.com.
Scientists analyzed maps of the Martian surface created by combining images from previous missions to the planet. This helped them identify Paul, who is about 560 miles (900 km) from the Viking 1 landing site, in an area of the northern Martian plain.
“The northern plains of Mars consist of a vast basin where an ocean formed about 3.4 billion years ago and subsequently froze,” Rodriguez said. “The ocean is thought to have formed due to catastrophic floods released from aquifers. So my initial approach to looking for a megatsunami-triggering impact was to look for a crater beneath the frozen remnants of the ocean and above the channels that released the ocean-forming floods.” Pohl was the only crater the scientists found that met that criteria, he noted. .
The researchers simulated cosmic impacts on this region to see what type of impact Pohl might have created. Their findings suggest that the Viking 1 landing site is “part of a megatsunami deposit laid down about 3.4 billion years ago,” Rodriguez said.
The scientists then used simulations to understand how a crater similar in size to Pohl’s could have formed. If an asteroid collided with strong Earth drag, it would have to be about 5.6 miles (9 km) away, with the impact releasing energy equivalent to 13 million megatons of TNT; if the asteroid encountered little ground resistance, it might have been only 1.8 miles (3 km) in diameter, releasing the energy of 500,000 megatons of TNT. (By comparison, the most powerful nuclear bomb ever tested, Russia’s Tsar Bomba, had the power of only 57 megatons of TNT.)
Both simulated impacts generated a megatsunami that reached up to 930 miles (1,500 km) from the impact site, more than enough to reach the landing site of Viking 1. The massive wave may have initially extended about 1,640 feet (500 meters) high and was about 820 feet (250 m) high on land. These statistics would make Pohl’s impact similar to that of Chicxulub: previous work suggests that the impact struck about 650 feet (200 m) below sea level, created a crater about 60 miles (100 km) wide, and triggered a tsunami about 650 feet (200 m) high on land.
In the future, the researchers want to further study how the ancient Martian ocean may have changed between the two megatsunamis to see what potential biological effects that change may have had, Rodriguez said.
“Immediately after its formation, the crater would have generated underwater hydrothermal systems lasting tens of thousands of years, providing an environment rich in energy and nutrients,” Rodriguez said in statement.
The study is described in paper (opens in new tab) published Thursday (Dec. 1) in the journal Scientific Reports.
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