Earth, Moon, and Planets 97,
279–293 (2006)
Spectral Investigation of Two Asteroidal Fireballs
Jiri Borovicka
Astronomical Institute, Academy of
Sciences, 251 65 Ondrejov, Czech Republic
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%.
Keywords: Asteroids, composition, meteoroids, meteors,
spectroscopy
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