Formation of molecules in bright meteors

We calculated equilibrium chemical composition of a mixture of meteoritic vapor and air during fireball events, i.e. during penetration of large meteoroids into terrestrial atmosphere. 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 time scales. For the typical fireball temperatures of 4000-5000 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 N-2 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 N-2(+), CN, C-2 and OH were also considered. The composition of freshly ablated meteoroid material was studied using the MAGMA code. (C) 2010 Elsevier Inc. All rights reserved.