Pele's hairs and exotic multiply twinned graphite closed-shell microcrystals in meteoritic dust of Chelyabinsk superbolide

TL;DR

This study investigates unique microcrystals and thread-like structures found in meteoritic dust from the Chelyabinsk superbolide, proposing new formation mechanisms and identifying potential carbon nanoclusters involved.

Contribution

It introduces novel meteoritic materials, links their formation to volcanic processes, and proposes a formation mechanism for closed-shell graphite microcrystals based on simulations.

Findings

Discovery of new meteoritic microcrystals and structures

Proposed formation mechanism for closed-shell graphite microcrystals

Identification of C60 fullerene and C18H12 as key precursors

Abstract

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 21st century, which exploded on February 15, 2013 above snowy fields of the Southern Urals, was an exception. Two new types of materials were found during an in-depth study: thread-like structures that were not previously associated with meteorite falls and unique carbon crystals with a size of several micrometers that were not observed before. The nature of formation of thread-like structures is fully similar to the nature of formation of Pele's hair during eruptions of terrestrial volcanos. Multiple twin growth mechanism of 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 closed shell quasi-spherical and hexagonal rod graphite microcrystals.