Meteoritics & Planetary Science 38, 1005--1021 (2003)

The Moravka meteorite fall:

3. Meteoroid initial size, history, structure and composition

J. Borovicka¹, H.W. Weber², T. Jopek³, P. Jakes⁴, Z. Randa⁵, P.G. Brown⁶, D.O. ReVelle⁷, P. Kalenda⁸, L. Schultz², J. Kucera⁵, J. Haloda⁴, P. Tycova⁴, J. Fryda⁹, and F. Brandstatter¹⁰

¹Astronomical Institute of the Academy of Sciences, 25165 Ondrejov, The Czech Republic
²Max-Plank-Institut für Chemie, Joh. J.-Becher-Weg 27, D-55128 Mainz, Germany
³Astronomical Observatory of A.Mickiewicz University, Sloneczna 36, 60286 Poznan, Poland
⁴Institute of Geochemistry, Mineralogy and Mineral Resources, Faculty of Science, Charles University, Albertov 6, 12843 Prague 2, The Czech Republic
⁵Nuclear Physics Institute, Academy of Sciences, 25068 Rez near Prague, The Czech Republic
⁶Department of Physics and Astronomy, University of Western Ontario, London, Ontario N6A 3K7, Canada
⁷Los Alamos National Laboratory, P.O. Box 1663, MS J557, Los Alamos, New Mexico 87545, USA
⁸CoalExp, Kosmonautu 2, 70030 Ostrava 3, The Czech Republic
⁹Czech Geological Survey, Geologicka 6, 15200 Prague 5, The Czech Republic
¹⁰Department of Mineralogy and Petrography, Museum of Natural History, Burgring 7, A-1010 Vienna, Austria

Abstract. The properties and history of the parent meteoroid of the Morávka H5-6 ordinary chondrites have been studied by a combination of various methods. The pre-atmospheric mass of the meteoroid was computed from fireball radiation, infrasound, seismic signal and the content of noble gases in the meteorites. All methods gave consistent results. The best estimate of the pre-atmospheric mass is (1500 ± 500) kg. The fireball integral bolometric luminous efficiency was 9% and the acoustic efficiency was 0.14%. The meteoroid cosmic ray exposure age was determined to be (6.7 ± 1.0) x 10⁶ years. The meteorite shows a clear deficit of helium, both ³He and ⁴He. This deficit can be explained by solar heating. Numerical backward integration of the meteoroid orbit (determined in a previous paper from video records of the fireball) shows that the perihelion distance was probably lower than 0.5 AU and possibly as low as 0.1 AU five million years ago. The collision which excavated Morávka probably occurred while the parent body was on a near-Earth orbit, as opposed to being confined entirely to the main asteroid belt. An overview of meteorite macroscopic properties, petrology, mineralogy and chemical composition is given. The meteorites show all mineralogical features of H chondrites. The shock level is S2. Minor deviations from other H chondrites in abundances of trace elements La, Ce, Cs, and Rb were found. The ablation crust is enriched with siderophile elements.

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