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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