Crystals unknown on Earth were hiding in this meteorite


On 15 September 2013, a meteor 18 meters long and weighing about 11,000 tons, it crossed the Russian sky before disintegrating at an altitude of 23 kilometers above the city of Chelyabinsk in the south of the country. The very powerful shock wave caused a lot of damage, causing the windows And windows buildings in the region. The energy released during this explosion was in fact estimated at 30 times the power of the Hiroshima bomb. It is therefore the largest known event of its kind since the fall of the object over Tunguska (Siberia) in 1908, including the explosion inatmosphere it had razed a forest within a radius of 20 kilometers.

In both cases, the disintegration of art meteorite at high altitude it avoided a collision with the earth’s surface that would surely have ended in a much more dramatic catastrophe, reminding humanity that we are continually exposed to this type of risk, currently unpredictable.

A large plume of meteoric dust

The entry into the atmosphere of the so-called Chelyabinsk meteorite, and in particular its explosion, was extensively documented by numerous amateur videos, which allowed scientists to reconstruct the meteorite’s trajectory and define its characteristics.

But to study it more precisely, nothing better than finding fragments. But this is not so obvious. When a meteorite enters Earth’s atmosphere, the warming it experiences usually leaves a small amount of dust behind. The meteorite usually ends up “burning up” almost completely before hitting the ground. It is often very difficult to find this fine dust sprinkled on the landscape of a large area.

However, in the case of the Chelyabinsk meteorite, the relatively large size of the race car produced a large plume of dust that remained suspended in the atmosphere for several days, allowing for easier collection of these tiny particles. In the following months, much larger fragments were also discovered. A piece of about 570 kg he was thus raised from the bottom of Lake Chebarkul. The analysis of these residues showed that it was a ordinary chondritis (rocky meteorite).

Strange and exotic graphite crystals

But it was by analyzing the tiny specks of dust that Russian scientists made a fortuitous and surprising discovery. Under’eye from microscopea new type of crystal was actually observed. Very small in size, few micrometers only, these crystals come in two distinct forms hitherto unknown on Earth: some have an almost spherical shape and others have the shape of a hexagonal rod. X-ray analysis reveals that they are actually crystals of graphiteone of the crystalline forms of carbonthe same that is still commonly used in our pencils.

But these crystals have an additional feature. They contain a carbon nanostructure at the center which could be a buckminsterfullerene, a molecule spherical consisting of 60 atoms carbon and which comes in the form of a soccer ball (hence its nickname footballene). This nanostructure could also be polyhexacyclooctadecane, a molecule made up of carbon and hydrogen.

A specificity of the Chelyabinsk meteorite?

The very exotic architecture of these crystals suggests that they formed under conditions of high temperature and high pressure, which could correspond to the moment of fragmentation of the meteorite in the Earth’s atmosphere. However, the exact mechanism of their formation remains to be elucidated. These results were published in the journal The European Physical Journal Other.

The next step is now to find out whether these crystals are specific to the Chelyabinsk meteorite or not by looking for their traces in the dust samples of other meteorites.

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