[meteorite-list] Fireball Trail Leads To Meteorite Recovery (Neuschwanstein Meteorite)

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:25:36 2004
Message-ID: <200305071806.LAA23034_at_zagami.jpl.nasa.gov>

http://www.abc.net.au/science/news/stories/s849255.htm

Fireball trail leads to ancient space rock
Mark Horstman
ABC Science Online
8 May 2003

A meteor seen streaking across the European sky last year
has been found where it was predicted to land - an
extremely rare achievement that offers insights into the
history of our solar system.

Czech and German scientists describe in today's issue of
Nature how they used photographic evidence to trace the
meteorite's trajectory, predict its likely impact area in the
mountains of Bavaria, and deduce its original orbit around
the Sun.

The scientists are part of the European Fireball Network, an
array of 30 stations with all-sky cameras in Germany,
Austria, and the Czech Republic. For three hours each day
over the last 40 years, the network has monitored more than
a million square kilometres of night sky to record space rocks
entering the Earth's atmosphere as 'shooting stars'.

Despite being seen quite often, it is very rare to actually
catch a falling star. In 43 years, fireball networks in Europe,
Canada and the United States have been able to trace just
four meteorites from their fiery trails to their final resting
place: the famous Pribram meteorite of Czechoslovakia in
1959; Oklahoma in 1970; Canada in 1977; and that was it - until
this one, called the 'Neuschwanstein'.

Late one April night in 2002, many people saw a fireball brighter
than a full moon scorching 91km across the central European sky
for more than five seconds, with a roar heard 100km away that
shook the ground and rattled windows.

Recording by the European Fireball Network shows the luminous
trajectory started at an altitude of 85km as the 300kg meteor
hurtled towards Earth at an angle of nearly 50 degrees and a speed of
21km/sec.

Three months later, a 1.75kg stony meteorite
fragment was found in rugged mountain terrain -
400 metres south of its computed trajectory -
near the well-known German castle of
Neuschwanstein, after which it was named.

Before Neuschwanstein collided with Earth, the
astronomers believe that its aphelion (furthest
point of orbit from the Sun) was in the asteroid
belt, like many fireballs that produce meteorites.

What really surprised them, however, is that
Neuschwanstein's orbit was practically identical
to the 1959 Pribram meteorite's orbit, even
though their ages and compositions are quite
different.

Pribram, along with the 1970 and 1977 finds, are
fairly ordinary space rocks known as H5 chondrites
- primitive and undifferentiated stones with small
spheres of silica (chondrules) from the nebula
that gave birth to our solar system.

By contrast, the Neuschwanstein meteorite is classified
as an EL6 enstatite chondrite, which has less iron oxide,
magnesium, calcium, aluminium, and titanium with its
silicates than the other three, and little or no evidence
of chondrules.

In addition, Neuschwanstein has a cosmic-ray exposure age -
a measure of the time it has been travelling through space
since separating from its parent body - of 48 million years,
compared with 12 million years for Pribram. Both ages are
longer than the typical survival times of meteoric streams.

While it is unlikely that the two came from the same parent
body, statistical evidence suggests they are part of the
same 'Pribram stream'. This stream comprises about a thousand
million meteorite-producing bodies with similar orbits, but
with a greater variety of structures, compositions and ages
than previously believed.

One theory proposed is that spinning 'rubble piles' loosely
bound by gravity could be exposed to tidal forces in close
encounters with planets. This would dislodge surface rocks but
leave them in similar orbits to their parent bodies, which
might explain the diversity of rock chemistries and ages
in meteor streams.
Received on Wed 07 May 2003 02:06:49 PM PDT