[meteorite-list] Space Drifters

From: FRANK B CRESSY <fcressy_at_meteoritecentral.com>
Date: Thu Apr 22 09:48:13 2004
Message-ID: <000701c158d6$7208f5c0$5c32ff3f_at_g10fb>

Hello all,

I was wondering how the loss of ablated material on a meteorite would effect
its cosmic ray exposure age. Could the "young" CRE ages obtained for
meteorites be a result of the more "tracked" outer "skin" of a meteoroid
being lost as the body travels through the atmosphere? The article states
that cosmic rays only effect the outer centimeter or so of the meteoroid so
if a significant portion of this outer layer were lost, wouldn't a "young"
cosmic ray age be the result? Also, if a large body broke up in the
atmosphere, wouldn't many of the resulting meteorites, which were originally
in the interior of the body, have a cosmic ray age of zero? I'm sure many of
you out there can clear up my questions.
Thanks,
Frank
P.S. And thank you Ron for always supplying the list with interesting and
thought provoking articles.


> Space exposure ages are determined using cosmic rays. Within a much
> larger asteroid, an eventual meteorite is shielded by an overlying layer
> of rock. After an inter-asteroid collision, the freed meteoroid is
> suddenly exposed to the high-energy elementary particles that permeate
> space.
>
> When these cosmic rays hit the meteoroid, they penetrate a centimetre or
> so. Characteristic tracks are left in the rock, which may be studied
> under a microscope. By counting the numbers of tracks it is possible to
> determine how long it took for the meteorite to travel from its parent
> asteroid to the Earth's surface. Typical values are a few million years.
Received on Fri 19 Oct 2001 03:44:18 PM PDT