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Science

An Ancient Asteroid Impact May Have Caused a Megatsunami on Mars

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The Viking 1 lander arrived on the Martian surface 46 years ago to investigate the planet. It dropped down into what was thought to be an ancient outflow channel. Now, a team of researchers believes they’ve found evidence of an ancient megatsunami that swept across the planet billions of years ago, less than 600 miles from where Viking landed.

In a new paper published today in Scientific Reports, a team identified a 68-mile-wide impact crater in Mars’ northern lowlands that they suspect is leftover from an asteroid strike in the planet’s ancient past.

“The simulation clearly shows that the megatsunami was enormous, with an initial height of approximately 250 meters, and highly turbulent,” said Alexis Rodriguez, a researcher at the Planetary Science Institute and lead author of the paper, in an email to Gizmodo. “Furthermore, our modeling shows some radically different behavior of the megatsunami to what we are accustomed to imagining.”

Rodriguez’s team studied maps of the Martian surface and found the large crater, now named Pohl. Based on Pohl’s position on previously dated rocks, the team believes the crater is about 3.4 billion years old—an extraordinarily long time ago, shortly after the first signs of life we know of appeared on Earth.

According to the research team’s models, the asteroid impact could have been so intense that material from the seafloor may have dislodged and been carried in the water’s debris flows. Based on the size of the crater, the team believes the impacting asteroid could have been 1.86 miles wide or 6 miles wide, depending on the amount of ground resistance the asteroid encountered.

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The impact could have released between 500,000 megatons and 13 million megatons of TNT energy (for comparison, the Tsar Bomba nuclear test was about 57 megatons of TNT energy.)

“A clear next step is to propose a landing site to investigate these deposits in detail to understand the ocean’s evolution and potential habitability,” Rodriguez said. “First, we would need a detailed geologic mapping of the area to reconstruct the stratigraphy. Then, we need to connect the surface modification history to specific processes through numerical modeling and analog studies, including identifying possible mud volcanoes and glacier landforms.”

Both lines of investigation are noble pursuits, but it may be some time before a new Mars lander gets off the ground. NASA is always juggling missions, but its main planetary focus in the future is Venus. The DAVINCI+ and Veritas missions would see two spacecraft arrive at the second planet from the Sun at the turn of the decade.

There are no plans for a future Mars lander, besides the Mars Sample Return mission, which will retrieve the rock core samples currently being extracted by the Perseverance rover on the western edge of the planet’s Jezero Crater.

NASA is canceling and delaying missions as it deals with a budget crunch, so exactly when the agency could turn its attention to the Pohl crater is unclear. With the InSight lander on its last legs, we will soon lose one of our best interrogators of the Martian interior.

More: Stunning New View of Mars Shows Where Ancient Flowing Water Once Carved Its Surface

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Science

Revisiting the “Tsar Bomba” nuclear test

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Enlarge / The mushroom cloud from the Soviet detonation of “Tsar Bomba” on October 30, 1961, was so large that the photographers had a hard time capturing its full dimensions.

The detonation of the first nuclear bombs over Hiroshima and Nagasaki in August 1945 is seared into our collective memory, and the world has been haunted by the prospect of a devastating nuclear apocalypse ever since. Less well-known but equally significant from a nuclear arms race standpoint was the Soviet Union’s successful detonation of hydrogen “superbomb” in the wee hours of October 30, 1961.

Dubbed “Tsar Bomba” (loosely translated, “Emperor of Bombs”), it was the size of a small school bus—it wouldn’t even fit inside a bomber and had to be slung below the belly of the plane. The 60,000-pound (27 metric tons) test bomb’s explosive yield was 50 million tons (50 megatons) of TNT, although the design had a maximum explosive yield of 100 million tons (100 megatons).

The US had conducted the first successful test of a hydrogen bomb (codename: Ivy Mike) in 1954 and had been pondering the development of even more powerful hydrogen superbombs. But the Soviets’ successful test lent greater urgency to the matter. Ultimately, President John F. Kennedy opted for diplomacy, signing the Partial Nuclear Test Ban Treaty on October 7, 1963.

But US nuclear policy—and hence world history—might have turned out very differently, according to Alex Wellerstein, a historian of science at the Stevens Institute of Technology in New Jersey and author of Restricted Data: The History of Nuclear Secrecy in the United States, released earlier this year. He also maintains the NUKEMAP, an interactive tool that enables users to model the impact of various types of nuclear weapons on the geographical location of their choice. 

Wellerstein has analyzed recently declassified documents pertaining to the US response to Tsar Bomba during the Kennedy administration. He described his conclusions in a fascinating article recently published in the Bulletin of the Atomic Scientists, coinciding with the 60th anniversary of the test.

Wellerstein gives a particularly vivid description of the Tsar Bomba detonation in his introduction:

At 11:32 a.m., the bombardier released the weapon. As the bomb fell, an enormous parachute unfurled to slow its descent, giving the pilot time to retreat to a safe distance. A minute or so later, the bomb detonated. A cameraman watching from the island recalled:

A fire-red ball of enormous size rose and grew. It grew larger and larger, and when it reached enormous size, it went up. Behind it, like a funnel, the whole earth seemed to be drawn in. The sight was fantastic, unreal, and the fireball looked like some other planet. It was an unearthly spectacle!

The flash alone lasted more than a minute. The fireball expanded to nearly six miles in diameter—large enough to include the entire urban core of Washington or San Francisco, or all of midtown and downtown Manhattan. Over several minutes it rose and mushroomed into a massive cloud. Within ten minutes, it had reached a height of 42 miles and a diameter of some 60 miles. One civilian witness remarked that it was “as if the Earth was killed.”

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