Discovery of a Benešov meteorites 20 years after a bolide event

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Collisions of meter-sized meteoroids with a Earth’s atmosphere are comparatively rare, occurring about 40 times a year. They means really fantastic events, famous as superbolides. One of a best famous such events, a Benešov bolide, occurred on 7 May 1991 during 23h 03m 46s UT over a Czech Republic. It was available during systematic detailed observations by a European Fireball Network and positively finished in a mixed meteorite fall, though no meteorite was found in a weeks and years after a fall, notwithstanding many attempts.

In Feb 2011, scarcely 20 years after a event, P. Spurný and his colleagues [1] totalled a annals again and analyzed a information with softened methods. This led to a new design of a whole eventuality with a revised windy arena and a new impact location. This authorised a group to redeem a Benešov meteorites, 20 years after a fall, accurately in a newly likely area. It is a initial time a meteorite is found so prolonged after a bolide observation. The group found 4 small, highly-weathered meteorites with a sum mass of 12 g.

Fig. 2. First 3 Benešov meteorites found in Apr 2011, with steel detectors. From left to right: H5 chondrite of 1.56 g, LL3.5 chondrite of 7.72 g with achondrite clast, and LL3.5 chondrite of 1.99 g [2].

Fig. 2. First 3 Benešov meteorites found in Apr 2011, with steel detectors. From left to right: H5 chondrite of 1.56 g, LL3.5 chondrite of 7.72 g with achondrite clast, and LL3.5 chondrite of 1.99 g [2].

The luck that these 4 fragments come from opposite meteoroids and were found by probability during a same place is estimated to be 1 in 100,000 or less. Even some-more interestingly, these 4 meteorites are of 3 opposite mineralogical types. This means that a Benešov meteoroid was extrinsic and contained during slightest 3 opposite forms of material. After a Almahata Sitta fall, this is a second time that such a extrinsic combination has been found. It raises a probability that a poignant fragment of all asteroids are extrinsic and that they were strongly reprocessed by collisions with other asteroids in a categorical belt.[1] The group includes P. Spurný, J. Haloda, J. Borovička, L. Shrbený, and P. Halodová.

[2] The reader can find sum about a meterorite sequence on various, well-documented web sites such as this or this.

Source: Astronomy Astrophysics