Chemistry of meteor events in Earth’s atmosphere

Abstract:
Equilibrium chemical composition of a mixture of meteoritic vapor and air
during fireball events, i.e. during penetration of large meteoroids into
terrestrial atmosphere, is calculated. Different types of fireballs were
considered, and calculations were performed for wide ranges of
temperatures and pressures. Chemical composition at the quenching point
was estimated by comparison of hydrodynamic and chemical reaction
timescales. For the typical fireball temperatures of 4000 to 5000 K, most
elements are expected to be in the form of atoms and ions. Notable
exceptions are Si and C, which are expected to be mainly in the form of
SiO and CO. Other molecules abundant at these temperatures are N2 and NO.
Metal monoxides are most abundant at 2000 – 2500 K and are formed during
the cooling phase. Conditions for formation of other molecules such as
N2+, CN, C2, OH, and metal oxides are considered. Emission of atoms and
diatomic molecules in meteor trains having temperature of about 2000 –
3000 K is also studied. Examples of observed spectra of meteors and meteor
trains will be shown. Chemical composition of impact-produced clouds
formed during collisions between meteoroids and atmosphereless celestial
bodies is also investigated.