Megatsunami swept over Mars after massive asteroid hit the Red Planet

A view from NASA's Mars Reconnaissance Orbiter of a crater on Mars that formed in 2012.
A view from NASA's Mars Reconnaissance Orbiter of a crater on Mars that formed in 2012. (Image credit: NASA/JPL-Caltech/Univ. of Arizona)

A Martian megatsunami — a giant killer wave that may have reached more than 80 stories tall — 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 of Mars is now cold and dry, a great deal of evidence suggests that an ocean's worth of water covered the Red Planet billions of years ago. Previous research found signs that two meteor strikes might have 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 sq. km).

A 2019 study found what may have been ground zero for the younger megatsunami — Lomonosov Crater, a 75-mile-wide (120 km) hole in the ground in the icy plains of the Martian Arctic. Its large size suggests the cosmic impact that dug the hole itself was big, similar in scale to the one from a 6-mile-wide (10 km) asteroid that struck near what is now the town of Chicxulub in Mexico 66 million years ago, triggering a mass extinction that killed off 75% of Earth's species, including all dinosaurs except birds.

Related: Stunning Mars photos by the Curiosity rover show ancient climate shift

Now the new study finds what may be the origin point of the older megatsunami — 69-mile-wide (111 km) Pohl Crater, which the International Astronomical Union named after science-fiction grandmaster Frederik Pohl in August. 

The scientists focused on the landing site of NASA's Viking 1, the first spacecraft to operate successfully on the Martian surface. Viking 1 touched down in 1976 in Chryse Planitia, a smooth circular plain in the northern equatorial region of Mars. The probe landed near the endpoint of a giant channel, Maja Valles, carved out by an ancient catastrophic flood, the first time scientists identified an extraterrestrial landscape carved by a river.

Unexpectedly, instead of discovering the kind of flood-related features scientists had expected of the site, such as streamlined islands worn smooth by flowing water, they found a boulder-strewn plain. Now the researchers suggest these boulders may be debris from a megatsunami, the giant wave carrying pulverized rock away from the site of the cosmic impact.

"The marine floor would have been tossed up in the air, feeding the wave with sediments and probably aiding the development of a catastrophic debris flow front," study lead author Alexis Rodriguez, a planetary scientist at the Planetary Science Institute in Arizona, told Space.com

The scientists analyzed maps of the Martian surface, created by combining images from previous missions to the planet. This helped them identify Pohl, which is located about 560 miles (900 km) from Viking 1's landing site, within a region of the Martian northern lowlands.

"The northern plains of Mars comprise an enormous basin where about 3.4 billion years ago, an ocean formed and subsequently froze," Rodriguez said. "The ocean is considered 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 ocean's frozen residue and above the channels that discharged the ocean-forming floods." Pohl was the only crater the scientists found that met this criterion, he noted.

The researchers simulated cosmic impacts on this region to see what type of impact might have created Pohl. Their findings suggest that Viking 1's landing site is "part of a megatsunami deposit emplaced about 3.4 billion years ago," Rodriguez said.

Then, the scientists used simulations to understand how a crater with similar dimensions to Pohl might have originated. If an asteroid encountered strong ground resistance, it would have needed to be about 5.6 miles (9 km), with the impact unleashing energy equivalent to 13 million megatons of TNT; if the asteroid met weak ground resistance, it might have been only 1.8 miles (3 km) across, releasing the energy of 500,000 megatons of TNT. (In comparison, the most powerful nuclear bomb ever tested, Russia's Tsar Bomba, had the strength of only 57 megatons of TNT.)

Both simulated impacts generated a megatsunami that reached as far as 930 miles (1,500 km) from the impact site, more than enough to reach Viking 1's landing site. The massive wave might have initially stretched about 1,640 feet (500 meters) high and measured about 820 feet (250 m) tall on land. Those statistics would make the Pohl impact similar to that of Chicxulub: prior work has suggested that 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, the researchers want to further investigate how the ancient Martian ocean might have changed between the two megatsunami to see what potential biological effects that change might have had, Rodriguez said.

"Right after its formation, the crater would have generated submarine hydrothermal systems lasting tens of thousands of years, providing energy and nutrient-rich environments," Rodriguez said in a statement.

The research is described in a paper (opens in new tab) published Thursday (Dec. 1) in the journal Scientific Reports.

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Charles Q. Choi
Contributing Writer

Charles Q. Choi is a contributing writer for Space.com and Live Science. He covers all things human origins and astronomy as well as physics, animals and general science topics. Charles has a Master of Arts degree from the University of Missouri-Columbia, School of Journalism and a Bachelor of Arts degree from the University of South Florida. Charles has visited every continent on Earth, drinking rancid yak butter tea in Lhasa, snorkeling with sea lions in the Galapagos and even climbing an iceberg in Antarctica. Visit him at http://www.sciwriter.us

  • CuriouslyInterested
    Thank you for this article.
    Curious if there's a possibility that the impact could have blasted a significant amount of water into space.
    Reply
  • billslugg
    Yes, an enormous amount of liquid, rocks and dirt would have been blasted into space. The water would have vaporized, probably killing most of whatever microbes might have been there. However, microbes can survive a long time deep inside a rock in outer space. There is no doubt in my mind that transfers of life, if it existed, were fairly common between the rocky planets.
    Reply
  • rod
    The paper cited does says this about life on Mars. "Consequently, the V1L soil salt compositions72 could hold information connected to Mars' Late Hesperian northern ocean. For example, cold brine chemistry modeling work of such salt assemblages suggests that the ocean was likely a Mg–Na–Ca–Fe2+–SO4–Cl–CO3–Br-rich brine75,78. This solution type is unlike Earth's seawater but like some hypersaline continental brines79,80. Their sulfate saturation at ocean temperatures between the mid-260s and low-270s K75,80 could have potentially supported life. For example, on Earth, some hypersaline brines with halotolerant taxa are known81,82."

    Okay, a global Flood on Mars :) and an ocean that *potentially supported life*. This report says a Martian meteorite that was claimed to show life on Mars - failed mission.

    Study nixes Mars life in meteorite found in Antarctica, https://phys.org/news/2022-01-nixes-mars-life-meteorite-antarctica.html
    Reference paper, Organic synthesis associated with serpentinization and carbonation on early Mars, https://www.science.org/doi/10.1126/science.abg7905, 13-Jan-2022. "Abiotic formation of organic molecules Mars rovers have found complex organic molecules in the ancient rocks exposed on the planet’s surface and methane in the modern atmosphere. It is unclear what processes produced these organics, with proposals including both biotic and abiotic sources. Steele et al. analyzed the nanoscale mineralogy of the Mars meteorite ALH 84001 and found evidence of organic synthesis driven by serpentinization and carbonation reactions that occurred during the aqueous alteration of basalt rock by hydrothermal fluids. The results demonstrate that abiotic production of organic molecules operated on Mars 4 billion years ago. —KTS"

    So far, no solid observation(s) showing life on Mars today or in the past. Necessary demonstration in nature is required, just like the heliocentric solar system model had to provide to be accepted over the geocentric model.
    Reply