[meteorite-list] The Hunt For Meteorites Is Focusing On Railway Stations

From: meteorites_at_space.com <meteorites_at_meteoritecentral.com>
Date: Thu Apr 22 09:50:27 2004
Message-ID: <20020414110749.6535.h014.c000.wm_at_mail.space.com.criticalpath.net>

This brings up an interesting question...

I read that the moon if impacted by a large asteroid,
say one that produced a crater 50 to 60 mi in diameter
would several days later shower the earth with ejecta.

Millions of tons of it.

So could it be that there are deposits of moon rocks in
certain areas of the earth where the sediments coincide
with the cratering events on the moon?

Steve Schoner.




On Thu, 24 January 2002, Ron Baalke wrote

>=20
>=20
>=20
>
http://www.guardian.co.uk/science/story/0,3605,638054,00.html
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> Hidden treasures=20
>=20
> The hunt for meteorites is focusing on railway
stations, writes
> Matthew Genge=20
> The Guardian (United Kingdom)
> January 24, 2002
>=20
> If you were in Paddington station on a particular
night, you would have seen
> something very unusual. A man in his late thirties,
smart but casually dressed,
> was behaving quite strangely, seeming more than a
little interested in the
> station's polished floor. Walking slowly across the
atrium, he stared at the
> ground with a look of intense concentration,
occasionally apologising to yet
> another commuter into whose path he had strayed.=20
>=20
> Watch some more and occasionally he would crouch,
with his nose inches from
> the stone. Then he would shake his head, stand up and
pace around some more.
> You'd probably conclude he was just another of the
poor deluded souls that
> amble about the streets of London living in their own
world.=20
>=20
> However, you'd be wrong. You had witnessed history in
the making. The man
> was Dr Birger Schmitz, from the Earth Science Centre
in Gothenburg, and he
> was looking for pieces of rock from space. That
evening was the first meteorite
> hunting expedition in London.=20
>=20
> Among all the places in the world you are likely to
find meteorites, Paddington
> station would seem the least likely. Dr Schmitz,
however, was not looking for
> meteorites lying on the floor but meteorites in the
floor.=20
>=20
> Paddington station is paved with polished blocks of
limestone and in one
> limestone quarry in Sweden, Schmitz and colleages
have found 40 meteorites
> completely encased in the rocks. It is an
occupational hazard to take more than a
> passing interest in limestone floors whether they are
in stations, airports or
> hotels. But you never know when you might get lucky.
Dr Schmitz has already
> found a number in buildings and one that has spent
the past 40 years in a
> limestone slab paving a Swedish driveway.=20
>=20
> Meteorites are difficult to find and, except where
they have been seen to fall,
> cannot be collected in temperate regions such as the
UK. The majority of the
> 21,000 known meteorites are in the Antarctic or in
hot deserts because here
> they survive for long periods of time and can
accumulate. The meteorites with
> the oldest terrestrial residence ages are from the
Antarctic and fell on Earth as
> much as 2.5m years ago.=20
>=20
> In terms of geology and the 4.5bn-year history of the
Earth, this is very recent.
> What makes the meteorites that Schmitz and colleagues
have found in Sweden
> unusual is that they are "fossil meteorites"
contained in limestones 480m years
> old. These are meteorites that fell during a period
of time known as the
> Ordovician, when the Earth's land surface was still a
barren wasteland devoid of
> even plant life.=20
>=20
> These Ordovician fossil meteorites reveal events that
happened in space
> hundreds of millions of kilometres from Earth 480m
years ago. The fossil
> meteorites have been found in a 1.75 metre-thick
layer of limestone deposited
> on the bottom of a shallow sea. Mixed in with and
surrounding the meteorites
> are fossils of straight nautoloids, which are the
shells of strange squid-like
> creatures. One meteorite reputably sits directly on
top of a trilobite fossil and
> could represent the smallest meteoritic extinction
event in history.=20
>=20
> What is particularly puzzling is that so many
meteorites are found in the 6000
> square metres of the quarry. The limestone was
deposited very slowly, at around
> one millimetre per thousand years, so it represents
1.75m years of history. But
> even so, there are a hundred times as many meteorites
embedded in the
> limestone than would be expected from the rate they
fall on Earth today. It
> appears that meteorites may have fallen much more
frequently in the Ordovician
> than now.=20
>=20
> The fossil meteorites are a type of meteorite known
as L ordinary chondrites and
> are still the most common to fall. Trapped argon gas
within these meteorites,
> produced by the decay of radioactive potassium,
provides a clue as to why so
> many meteorites fell in the Ordovician. Argon in L
chondrites was lost 480m
> years ago because of a giant collision that probably
broke the L chondrite
> asteroid to pieces. Could the debris from this
collision have showered the Earth
> with meteorites? Dr Schmitz suggests it did and
points out that more craters
> formed on Earth at this time due to the impact of
larger pieces of the asteroid.=20
>=20
> These giant asteroid collisions have occurred many
times in the history of the
> solar system. There are numerous families of
asteroids in the main asteroid belt
> between Mars and Jupiter, formed by the break-up of a
larger parent asteroid,
> and these could have showered the Earth with
meteorites and larger
> crater-forming objects. Fossil meteorites are,
however, difficult to find in rocks.
> Only where thin slabs are cut for building are they
likely to be recovered. Cosmic
> dust may provide a more reliable way of identifying
these events since enormous
> amounts are produced in asteroid collisions and these
can be recovered from
> rocks deposited in the deep ocean.=20
>=20
> Looking for meteorites in polished limestone slabs
is, however, worthwhile. Next
> time you are waiting for yet another delayed train,
join in the great meteorite
> hunt.=20
>=20
> =B7 Matthew Genge is a meteorite scientist at the
Natural History Museum.
>=20
> ______________________________________________
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>
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=0D
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Received on Sun 14 Apr 2002 02:07:44 PM PDT