Ablation, flux, and atmospheric implications of meteors inferred from stratospheric aerosol

Single-particle analyses of stratospheric aerosol show that about half of t he particles contain 0.5 to 1.0 weight percent meteoritic iron by mass, req uiring a total extraterrestrial influx of 8 to 38 gigagrams per year. The s odium/iron ratio in these stratospheric particles is higher and the magnesi um/iron and calcium/iron ratios are Lower than in chondritic meteorites, im plying that the fraction of material that is ablated must lie at the Low en d of previous estimates and that the extraterrestrial component that reside s in the mesosphere and stratosphere is not of chondritic composition.