When Will the Tunguska Meteor Hit Again
Falling star that blasted millions of trees in Siberia only 'grazed' Earth, new research says
A new explanation for a massive blast over a remote Siberian woods in 1908 is even stranger than the mysterious incident itself.
Known as the Tunguska event, the blast flattened more than eighty million trees in seconds, over an area spanning almost 800 square miles (2,000 square kilometers) — just left no crater. A meteor that exploded before hitting the ground was idea by many to exist the culprit. However, a comet or asteroid would likely take left backside rocky fragments after blowing upward, and no "smoking gun" remnants of a cosmic company have ever been found.
Now, a squad of researchers has proposed a solution to this long-standing puzzle: A large atomic number 26 meteor hurtled toward World and came only close enough to generate a tremendous stupor wave. But the meteor then curved away from our planet without breaking upwards, its mass and momentum carrying it onward in its journey through space.
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On the forenoon of June xxx, 1908, the sky above Siberia flared so vivid and hot that a witness continuing dozens of kilometers from the site thought that his shirt had caught fire, said Vladimir Pariev, co-author of the new Tunguska study and a researcher with the P. N. Lebedev Physical Institute of the Russian University of Sciences in Moscow.
Following the bright calorie-free, which lasted for nearly 1 minute, was an explosion that smashed windows and knocked people off their feet in a boondocks more than 35 miles (60 km) away, the BBC reported. "The sky was separate in two, and high to a higher place the forest the whole northern role of the sky appeared covered with fire," another witness said in a testimonial. Energy released past the nail was later estimated by scientists to exist 185 times greater than that of the atomic bomb dropped on Hiroshima in 1945, co-ordinate to NASA.
Initial explanations for the blast included volcanic eruptions and mining accidents, according to NASA, but those claims were not supported past physical show. Other after suggestions were more far-fetched, such as a crashed UFO or a black hole standoff with Earth — a study describing the black hole hypothesis was published in the journal Nature in 1973 (and was soundly debunked in another Nature study published just a few months later).
The most widely accepted scientific explanation is that a rocky asteroid or comet entered Earth'due south atmosphere and so disintegrated with a blindside about 3 to 6 miles (5 to 10 km) above the ground, Pariev told Live Science in an email. Just such an explosion should have strewn the basis with rocky debris, which no one has ever found. Past comparison, a meteor that exploded over Chelyabinsk, Russia, in February 2013 broke into fragments that were discovered within a calendar week, Pariev said.
What if, the researchers questioned, the Tunguska meteor were made of iron rather than rock? Could a massive atomic number 26 meteor "graze" World'southward atmosphere, approaching close enough to generate a powerful shock moving ridge, so yank free of the planet's gravitational pull and escape without fragmenting?
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To test that hypothesis, the scientists calculated meteor paths using computer models. They looked at objects that were as small every bit 164 feet (fifty meters) beyond and as large every bit 656 feet (200 thou) in diameter. Objects were made of rock, ice or fe, and approached in a trajectory that brought them within half dozen to 10 miles (x to fifteen km) of World's surface.
The scientists' calculations showed that space bodies made of rock and ice would completely disintegrate under the enormous pressures generated by their passage through the tropospheric altitudes. "Only asteroids made of iron larger than 100 m [328 anxiety] in diameter tin can survive and not get cracked and fragmented into many separate pieces," they said.
The researchers estimated that the Tunguska meteor likely measured betwixt 328 and 656 feet (100 and 200 one thousand) in diameter, and hurtled through Earth's atmosphere at roughly 45,000 mph (72,000 km/h). During its peppery passage, the meteor would lose some of its mass. Only fe shed past a falling star traveling at such speeds would have escaped every bit gas and plasma, oxidized in the temper and and then dispersed on the ground, becoming nigh indistinguishable from terrestrial iron oxides, according to the written report.
Prior studies take calculated the power of shock waves produced by meteors based on the object inbound Earth's atmosphere at a very steep angle "and either striking the ground or exploding in midair," Pariev said.
In the case of the Tunguska meteor, the iron-rich space object could have entered World's atmosphere at a very shallow angle — well-nigh nine to 12 degrees tangential to the surface. It then would have grazed through the atmosphere, creating a shock wave at an altitude of around 6 to 10 miles (ten to fifteen km) above the ground, capable of flattening trees for hundreds of kilometers and scorching the surface. But because of the meteor's mass and momentum, it didn't break up; information technology then exited the temper and returned to space, the researchers reported.
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Still, some lingering questions about this scenario remain, said Mark Boslough, a enquiry professor at the Academy of New Mexico and physicist with Los Alamos National Laboratory.
Boslough, who was not involved in the study, told Live Science in an email that if an object "skimmed through the temper" and didn't accident up, the resulting stupor wave would exist significantly weaker than an explosion'southward blast wave.
"An object that survived such a transit through the temper could not have descended shut enough to the surface for a sonic boom to do the kind of harm that was observed at Tunguska," Boslough said.
What's more, the pattern of felled trees at the site is radial — emanating from a single point of tremendous energy release, he said. That'southward something you'd expect to encounter subsequently an explosion rather than a sonic smash, "even if it had been stiff enough to blow trees over." Boslough added that bystander accounts at the fourth dimension of the incident "are consistent with an object that was descending toward the surface before it exploded."
While the study authors didn't numerically calculate the impact of a shock wave that a "grazing" fe shooting star of this size could produce, their estimates all the same suggest that such a moving ridge would be powerful plenty to flatten trees and impairment the footing as the Tunguska outcome did, Pariev said in the e-mail.
"Detailed calculations of the stupor waves from a grazing asteroid is the subject of our ongoing research," he added.
The findings were published online in the March issue of the journal Monthly Notices of the Royal Astronomical Club.
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Originally published on Alive Science .
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Source: https://www.livescience.com/tunguska-impact-explained.html
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