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.