Meteoritics & Planetary Science 38, 1023--1043 (2003)
The Moravka meteorite fall:
4. Meteoroid dynamics and fragmentation in the atmosphere
J. Borovicka1 and P. Kalenda2
1Astronomical Institute
of the Academy of Sciences, 25165 Ondrejov, The Czech Republic
2CoalExp,Kosmonautu 2,70030 Ostrava 3, The Czech Republic
Abstract. Detailed analysis of the fragmentation of the
Morávka meteoroid during the atmospheric entry is presented. The
analysis is based on the measurement of trajectories and decelerations
of fragments seen in a video record and on the locations of energetic
fragmentation events from seismic data obtained at several stations in
the vicinity of the fireball trajectory. About one hundred individual
fragments are seen on video frames. Significant deceleration of the
fireball at the heights of about 45 km revealed that the meteoroid had
already been disrupted here to of order a dozen pieces with masses of
100-200 kg, though the fireball still appeared as a single object. At
heights of 37-29 km, all primary fragments broke-up again under dynamic
pressures up to 5 MPa. The cascade fragmentation then continued even
though smaller pieces breaking off from the larger masses were
increasingly decelerated and the dynamic pressure acting on them
decreased. At each fragmentation a significant part of the mass was
lost in the form of dust or tiny particles. This was the dominant
process of mass loss. The continuous ablation due to melting and
evaporation of meteoroid surface was less efficient with a
corresponding ablation coefficient of only 0.003 s2km-2.
During fragmentation, some pieces achieved lateral velocities up to 300
m/s, about an order of magnitude more than can be explained by
aerodynamic loading. The fragmentation continued even after ablation
ceased, as demonstrated by the incomplete fusion crust covering all
recovered fragments. It is estimated that several hundreds of
meteorites of total mass of about 100 kg landed, mostly in a
mountainous area not suitable for systematic meteorite searches. Six
meteorites of total mass of 1.4 kg were recovered up to the end of May
2003. They positions are consistent with the calculated strewn field.
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