[meteorite-list] Czech meteorite fragments 20 years

[Paul Gessler]

Looks like something that was found sitting in a Moroccan sale bin for the 
last 20 years.
They look a lot older than 20 years to me.

Paul G


-----Original Message----- 
From: MEM via Meteorite-list
Sent: Wednesday, October 15, 2014 4:53 PM
To: Meteorite Mailing List
Subject: [meteorite-list] Fw: [Geology2] Meteorite fragments discovered 
20years after bolide event in Czech Republic


<www.sciencedaily.com/releases/2014/10/141014142736.htm>

Meteorite fragments discovered 20 years after bolide event in Czech Republic
Date: October 14, 2014
Source: Astronomy & Astrophysics
Summary: Scientists have discovered meteorite fragments 20 years after the 
corresponding bolide
was seen in the skies of the Czech Republic. This discovery was made 
possible by reanalyzing the trajectory, which moved the impact line by 330 
meters. Interestingly, the meteorites found on the ground are of
different types, pointing to a parent asteroid of heterogeneous composition.



________________________________


First three Benešov meteorites found in April 2011, with metal 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].
Credit: Image courtesy of Astronomy & Astrophysics


Astronomy & Astrophysics is publishing the spectacular discovery of 
meteorite fragments 20 years after the corresponding bolide was seen in the 
skies of the Czech
Republic. This discovery was made possible by reanalyzing the
trajectory, which moved the impact line by 330 meters. Interestingly,
the meteorites found on the ground are of different types, pointing to a 
parent asteroid of heterogeneous composition.
Collisions of meter-sized meteoroids with Earth's atmosphere are
relatively rare, occurring about 40 times a year. They cause very
spectacular events, known as superbolides. One of the best known such
events, the Benešov bolide, occurred on 7 May 1991 at 23h 03m 46s UT
over the Czech Republic. It was recorded during systematic photographic
observations by the European Fireball Network and certainly ended in a
multiple meteorite fall, but no meteorite was found in the weeks and
years after the fall, despite many attempts.
In February 2011, nearly 20 years after the event, P. Spurný and his
colleagues [1] measured the records again and analyzed the data with
improved methods. This led to a new picture of the whole event with a
revised atmospheric trajectory and a new impact location. This allowed
the team to recover the Benešov meteorites, 20 years after the fall,
exactly in the newly predicted area. It is the first time a meteorite is 
found so long after the bolide observation.
The team found four small, highly-weathered meteorites with a total
mass of 12 g. The probability that these four fragments come from
different meteoroids and were found by chance at the same place is
estimated to be 1 in 100,000 or less. Even more interestingly, these
four meteorites are of three different mineralogical types. This means
that the Benešov meteoroid was heterogeneous and contained at least
three different types of material. After the Almahata Sitta fall, this
is the second time that such a heterogeneous composition has been found. It 
raises the possibility that a significant fraction of all asteroids
are heterogeneous and that they were strongly reprocessed by collisions
with other asteroids in the main belt.
________________________________

Story Source:
The above story is based on materials provided by Astronomy & Astrophysics. 
Note: Materials may be edited for content and length.
________________________________

Journal Reference:
    1. Pavel Spurný, Jakub Haloda, Jiří Borovička, Lukáš Shrbený, Patricie 
Halodová. Reanalysis of the Benešov bolide and recovery of polymict breccia 
meteorites – old mystery solved after 20 years. Astronomy & Astrophysics, 
2014; 570: A39 DOI: 10.1051/0004-6361/201424308
________________________________


Astronomy & Astrophysics. "Meteorite fragments discovered 20 years after
bolide event in Czech Republic." ScienceDaily. ScienceDaily, 14 October
2014. <www.sciencedaily.com/releases/2014/10/141014142736.htm>.



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