A megatsunami swept over 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 raced across 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 mars is now cold and dry, a large body of evidence indicates that an ocean’s worth of water covered the Red Planet billions of years ago. Previous research found signs that two meteor impacts could have caused a couple 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 submerged an area of about 386,000 square miles (1 million square kilometers).
A 2019 study found what it might have been zero for younger megatsunami — Lomonosov Crater, a 75-mile (120 km) wide hole in the ground in the icy plains of the Martian Arctic. Its sheer size suggests that the cosmic impact that excavated the hole itself was large, on a scale similar to that of a 6-mile-wide (10 km) an asteroid that struck near the present-day city of Chicxulub in Mexico 66 million years ago, causing a mass extinction that killed 75% of Earth’s species, including all dinosaurs except birds.
Now a new study reveals what could be the source of an older megatsunami — the 69-mile-wide (111 km) Pohl Crater, which International Astronomical Union named after the science fiction grandmaster Frederik Pohl 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 north equatorial region of Mars. The probe landed near the terminus of a giant channel, the Maya Valles, carved by an ancient catastrophic flood, the first time scientists have identified an alien river-carved landscape.
Unexpectedly, instead of finding the kind of flood-related features scientists expected from the site, such as streamlined islands smoothed by flowing water, they found a plain strewn with boulders. Researchers suggest that these boulders could be debris from a megatsunami, a gigantic wave that carries crushed rock away from the site of a cosmic impact.
“The seafloor would have been uplifted, feeding the wave with sediments and possibly aiding the development of a catastrophic debris flow front,” study lead author Alexis Rodriguez, a planetary scientist at the Arizona Institute for Planetary Sciences, told Space. .com
Scientists analyzed maps of the surface of Mars, created by combining images from previous missions to the planet. This helped them identify Pohl, located about 560 miles (900 km) from the Viking 1 landing site, within the Martian Northern Plains region.
“The northern plains of Mars form a huge basin where an ocean formed about 3.4 billion years ago and then froze,” Rodriguez said. “The ocean is thought to have been created by catastrophic floods that were released from aquifers. So my initial approach to looking for a possible megatsunami 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 scientists found that met this criterion, he pointed out.
The researchers simulated cosmic impacts on this region to see what kind of impact Pohl could have created. Their findings suggest that the Viking 1 landing site is “part of a megatsunami deposit formed about 3.4 billion years ago,” Rodriguez said.
The scientists then used simulations to understand how a crater of similar dimensions to Pohl could have formed. If the asteroid encountered strong ground resistance, it would need to be about 5.6 miles (9 km), with the impact releasing energy equivalent to 13 million megatons of TNT; if the asteroid had 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 a yield of only 57 megatons of TNT.)
Both simulated impacts produced a megatsunami that reached as far as 1,500 km from the impact site, more than enough to reach the landing site of Viking 1. The massive wave may have initially reached about 500 meters in height and measured about 820 feet (250 meters). on land. Those statistics would make the Pohl impact similar to that of Chicxulub: previous work suggested the impact struck about 650 feet (200 m) below sea level, formed a crater about 60 miles (100 km) wide, and triggered a tsunami about 650 feet ( 200 m) high on land.
In the future, researchers want to further investigate how the ancient Martian ocean may have changed between the two megatsunamis to see what potential biological effects that change could have had, Rodriguez said.
“Immediately after formation, the crater would have created submarine hydrothermal systems that would have lasted for tens of thousands of years, providing an environment rich in energy and nutrients,” Rodriguez said in statement.
The research is described in paper (opens in new tab) published Thursday (December 1) in the journal Scientific Reports.
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