Dynamic Spectra of Small-Mass Meteors

Material deposited by milligram-sized meteors contributes significantly to the total amount of meteoric material in Earth's atmosphere, a value which is not well constrained. Metals from these meteors can coalesce into distinct metal layers, and thus finding the total mass and composition of these meteors would allow for a greater understanding of chemical processes in the ionosphere. An optical EMCCD camera with an attached spectrograph collected 8 clear hours of data over 4 nights in May 2012 from Arecibo, Puerto Rico with high temporal resolution at 22 frames per second. Analysis returned estimates for the mass, velocity, and found the composition of 22 meteors with spectral lines showing various combinations of Na, Mg, Fe, and Ca. Relatively bright meteors that persisted for many frames showed change in the spectra over time implying differential ablation of more volatile elements earlier in the meteor's path. We present clear optical evidence of differential ablation in milligram-sized meteors. These optical observations allow for mass estimates, while prior radar observations that have reported differential ablation are not able to produce accurate mass estimates with the Arecibo radar.