Implications for meteoroid chemistry from the height distribution of radar meteors

Abstract

We have gathered substantial evidence from novel radar meteor observations that most meteoroids start to ablate at altitudes considerably in excess of 100 km (at heights up to ∼140 km). This beginning height h b is a strong function of the melting point of the meteoroid. Theoretical modelling indicates that for stony meteoroids observed as faint radio meteors these heights range from h b = 116 km (for entry speeds v ∞ = 70 km s −1) to 90 km (for v ∞ = 15 km s −1). Meteoroids that begin ablating above these heights must have lower temperature melting points. We interpret the observations in terms of a population of the meteoroids largely constituted of heavy organic compounds that are susceptible to gross-fragmentation as they heat and encounter the Earth at speeds greater than ∼30 km s −1.