Exotic carbon microcrystals in meteoritic dust of the Chelyabinsk superbolide: experimental investigations and theoretical scenarios of their formation

When a space body enters Earth’s atmosphere, its surface is exposed to high pressure and temperatures. The airflow tears off small droplets from the meteoroid forming a cloud of meteorite dust. Can new materials be synthesized in these unique conditions (high temperature, pressure, gaseous atmosphere, catalysts)? As a rule, meteoritic dust dissipates in the atmosphere without a trace or is mixed with terrestrial soil. The Chelyabinsk superbolide, the biggest in the twenty-first century, which exploded on February 15, 2013 above snowy fields of the Southern Urals, was an exception. The unique carbon crystals with a size of several micrometers, which were not observed before, were found during an in-depth study of the meteoritic dust. In order to explain the experimental findings, a multiple twin growth mechanism for the formation of closed shell graphite microcrystals was proposed based on DFT and classical/ab initio MD simulations. It was found that among several possible embryo carbon nanoclusters, the C₆₀ fullerene and polyhexacyclooctadecane –C₁₈H₁₂– may be the main suspects, responsible for the formation of the experimentally observed closed shell quasi-spherical and hexagonal rod graphite microcrystals.