Abstract
High resolution photographic spectra of two fireballs have been analyzed. The fireballs were produced by meteoroids of asteroidal origin of the mass of the order of 1 kg. Temperature, size, and mass of the vapor cloud around the meteoroid was derived at selected points along the trajectory. Abundances of 11 elements, including lithium, were determined. The abundances of refractory elements in the vapors of the first meteoroid indicate that only 90–95% of the ablated material was vaporized. The meteoroid was likely a chondritic body. Relative stability of the vapor cloud was disturbed for 0.1 s after a major fragmentation of the meteoroid at the height of 42 km. Size and mass of the cloud decreased after the fragmentation and this enabled more intensive heat transfer from the incoming airflow. Both the vapor temperature and the vaporization temperature of the ablated melt increased. A brief millisecond flare of the fireball was produced under these conditions by a violent vaporization of small amount of material. The composition of the vapors of the second meteoroid can be explained either by an anomalous meteoroid composition with severely depleted Al, Ca, and Mg or by highly incomplete evaporation of the ablated material reaching only about 50%.
Published Version
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