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On February 15, 2013, over the snow-covered fields of the southern Urals, the Chelyabinsk superbolid, the largest meteor of the 21st century, exploded. This is a unique phenomenon in its scope that has aroused enormous public interest, especially by demonstrating the earth’s lack of defense against this risk. But the story does not end there: the dust left in its path, unique materials synthesized under conditions that cannot be reproduced in the laboratory, have been analyzed. A NASA team discovered unique carbon crystals there, several micrometers in size, never seen before. The team speculates that their formation was due to the meteor breaking up, creating the necessary high temperature and high pressure conditions. This discovery testifies to nature’s unlimited potential to synthesize new materials.
The Chelyabinsk meteor (or boliden), 18 meters in diameter and weighing 11,000 metric tons, passed through the Earth’s atmosphere at a speed of 18.6 kilometers per second. When a space body enters the Earth’s atmosphere, its surface is exposed to high pressures and temperatures. The air flow tears droplets from the celestial body and forms a cloud of meteor dust.
The space rock burned due to friction with the Earth’s thin air and exploded 23.3 kilometers above Chelyabinsk. The blast released more than 30 times the energy of the atomic bomb that destroyed Hiroshima. By comparison, the ground-impacting meteor that triggered mass extinctions, including those of dinosaurs, was about 10 kilometers in diameter and released about 1 billion times the energy of the Hiroshima atomic bomb.
Typically, meteorite dust disappears into the atmosphere without leaving traces, or mixing with the earth’s soil. But this superbolide was an exception. In fact, the explosion deposited hundreds of tons of dust in the stratosphere, enabling a NASA satellite to make unprecedented measurements, including how the material formed a sustained stratospheric dust belt. The results of the Agency’s research team are published in the journal The European Physical Journal Mere.
Crystals never before seen on Earth
By studying this meteor dust, the team wanted to determine if new materials could be synthesized under the unique conditions (temperature and pressure) created by the explosion of the space body as they enter the Earth’s atmosphere. Taskaev, Khovaylo and their team were able to access this dust because it fell on snow-covered ground – the snow preserved it.
First, they observed micrometric-sized carbon microcrystals under an optical microscope. They then examined the same crystals using scanning electron microscopy (SEM) and discovered that they assumed a number of unusual shapes: closed shells, almost spherical and hexagonal rods.
Subsequently, further analysis using Raman spectroscopy and X-ray crystallography showed that the carbon crystals were in fact forms of graphite with a structure never seen before on Earth. The authors believe that these structures were most likely formed by repeatedly adding layers of graphene to closed carbon nuclei. They then explored this process through simulations of molecular dynamics.
Eventually, they found the two “probable suspects” as nuclei for microcrystalline growth: the spherical fuller (or buckminster fuller), C60and the more complex hexacyclooctadecane (-C18 H12-). The authors suggest in a statement that classification of these crystals may help identify past meteorites.
According to their estimates, the concentration of these crystals along the fallow path of the Chelyabinsk superbolide is between 10 and 100 pcs / m². Given the spatial distribution of the gas dust tail over the Earth’s northern hemisphere, such particles must have fallen in large quantities in Russia, European and North American countries, and are found especially in the snow in the mountains of Alaska and Kamchatka.
A defense that is being organized, after a turbulent story
This extraordinary event still caused more than a thousand injuries in the Urals, but the damage would have been much greater if the superbolide had not been fragmented several times before it hit the ground.
In fact, a study, published in 2014 in the journal Nature shows that the meteor under the pressure of the air deformed like a giant tennis ball. Highly compressed, and then fragmented. The acoustic analysis of the videos performed by the researchers reveals 11 fragmentations. Arriving 29 km above the ground, the first meteor was already fragmented into about twenty large rocks weighing about 10 tons each. This process continued through the descent.
In addition, in the contemporary international study, published in the journal Science, the authors estimated that only 4 to 6 tons of the original meteor survived its passage through the atmosphere. About 75% of the meteor has therefore evaporated. Most of what was left was turned to dust. It is especially the explosion wave, which occurred about a minute later, that caused significant damage to the city.
After Chelyabinsk, NASA established a Planetary Defense Coordination Office that collected data from the agency’s near-Earth object observation program. The Center for Near-Earth Object Studies, affiliated with the International Asteroid Warning Network, lists all nearby celestial bodies. The NASA Center is responsible for coordinating a U.S. government response to a threat. Nevertheless, no imminent threat has been detected so far.