[meteorite-list] re: Looks too weathered? (The "Neuschwanstein" Meteorite)

From: Marco Langbroek <marco.langbroek_at_meteoritecentral.com>
Date: Thu Apr 22 09:52:08 2004
Message-ID: <004b01c23ed6$f0fe0d20$ddc7ea3e_at_latitude>

Hi list,

Below message was sent by me 2 days ago but didn't get through. So I resend
it, now the list seems to work properly again.

Marco
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Hi all,

There have been a number of people, both on- and off-list, commenting on the
weathering of the Neuschwanstein find.

The most simple and clearcut way in which it can be established whether the
Neuschwanstein is a recent fall or not, is by having the stone measured for
shortlived cosmogenic isotopes. A number of these will disappear from the
stone within only a few weeks or a few months. If they can be measured, then
it is clear that Neuschwanstein is from a recent fall and then quite likely
from the April 6 fireball.

Considering the pairing with Pribram, what remains a problem is the CRE age
for Pribram. I've been writing a short newspiece on the fall for 'Zenit'
(Dutch equivalent of Sky & Telescope) and for that purpose asked Kees Welten
at Berkeley Space Sciences Laboratory for a comment. The only way to solve
the CRE paradox appears to be to assume that Pribram attained part of its
CRE history near the surface of a large parent body before breakup. However,
Kees noted that this possibility seems to be ruled out by a number of the
isotopic aspects measured in Pribram - it really looks like Pribram attained
its CRE history as an object no larger than 2 meters in size, although
certainly more work should be done before the other option can be ruled out
completely.

In answer to what Bob Matson mailed about other falls near this date; the
Dutch Glanerbrug, an LL5 breccia, fell on April 7 1990, and has an orbit
available from a large number of visual observations (which I helped gather
myself back then). This meteorite crossed the node with earth orbit only 10
minutes in time after the point where the Pribram orbit crossed Earth.
Moreover, I have showed in a paper in the September 2001 issue of 'Radiant',
the Journal of our Dutch Meteor Society, that within the standard threshold
boundaries of Drummonds' D' criterion which is a formal way to compare
orbital simularities, the orbits of Pribram (and now also the Arpil 6
fireball) and Glanerbrug are similar enough to comtemplate association. So
we have 3 falls (assuming that Neuschwanstein is related to the April 6
fireball) from April 6-7 whose orbits associate as judged by a formal test
of orbital element comparison: Pribram (H5), Glanerbrug (LL5) and
Neuschwanstein (as yet unclassified).

Marco Langbroek
Received on Thu 08 Aug 2002 08:25:38 AM PDT