Unusual microcrystals discovered in meteorite dust

An investigation using X-ray crystallography and Raman spectroscopy revealed that the carbon crystals were indeed unusually shaped varieties of graphite.

The strange carbon microcrystals were studied by scientists from Chelyabinsk State University.

On February 15, 2013, above Chelyabinsk in the southern Russian Urals, the largest meteorite ever seen in this century entered the Earth’s atmosphere. Unusually, the meteorite’s surface dust survived its impact and is now the subject of extensive research. Some carbon microcrystals in this dust have strange shapes. A group led by Sergey Taskaev and Vladimir Khovaylo from Chelyabinsk State University in Russia recently published a paper on the morphology and simulations of the formation of these crystals in the European Physics Journal Plus.

The surface of a meteor develops meteorite dust as it enters the atmosphere and is subjected to very high temperatures and enormous pressures. The Chelyabinsk meteor was exceptional in its size, the intensity of the burst of air it created when it exploded, the size of the largest pieces that fell to Earth, and the destruction it caused. More importantly, he landed in snowy terrain and the snow helped keep the dust intact.

Taskaev, Khovaylo and their team first observed micrometer-sized carbon microcrystals in this dust under an optical microscope. So they examined the same crystals using scanning electron microscopy (SEM) and found that they took on a variety of unusual shapes: near-spherical closed shells and hexagonal rods. Further analysis using Raman spectroscopy and X-ray crystallography showed that the carbon crystals were actually exotically shaped forms of graphite.

Most likely, these structures will have been formed by repeatedly adding[{” attribute=””>graphene layers to closed carbon nuclei. The researchers explored this process through molecular dynamics simulations of the growth of a number of such structures. They found two ‘likely suspects’ as nuclei for microcrystal growth: the spherical fullerene (or buckminsterfullerene), C60, and the more complex hexacyclooctadecane (-C18H12-). In concluding, Taskaev and Khovaylo suggest that classifying these crystals could help identify past meteorites.

Reference: “Exotic carbon microcrystals in meteoritic dust of the Chelyabinsk superbolide: experimental investigations and theoretical scenarios of their formation” by Sergey Taskaev, Konstantin Skokov, Vladimir Khovaylo, Wolfgang Donner, Tom Faske, Alexander Dudorov, Nick Gorkavyi, Dmitry S. Muratov, Galina Savosteenko, Alexander Dyakonov, Woohyeon Baek, Artem Kuklin, Pavel Avramov and Oliver Gutfleisch, 7 May 2022, The European Physical Journal Plus.
DOI: 10.1140/epjp/s13360-022-02768-7

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