[meteorite-list] nwa869

From: John Divelbiss <j.divelbiss_at_meteoritecentral.com>
Date: Thu Apr 22 10:00:05 2004
Message-ID: <001701c22541$e2a8a400$dc0b5a0c_at_0m824>

Al,

Your point is well taken on the source aspect of this discussion. As with
any type, no matter the name or number assigned to it...there is good chance
they are from the same asteroid. HED's from Vesta, etc.

I just looked at the group I have and quite frankly it is not easy to say
they are different materials. Even under the scope. Yet I see the reports of
L4 or L5 for NWA 869, L6 for 787, now L3.4/4 for 900, and similar
suspicions for 995 (not 905 that I listed in earlier message). Thin sections
of each one may help...but as Dean has stated, his section may have thrown
off the evaluation of his sample relative to its true petrologic type.

All this makes me wonder about the process and "accuracy" of identifying a
particular fall or find. As I understand it, the boundaries between H's and
L's can be somewhat blurred when metal and iron contents are in the
transition percentage levels. All the more bewildering. I'm glad I'm not
assigning these things. How does one know when he or she has got it right?
Personally I'm going like them all for being rocks from space. With that in
mind is seems silly to argue between one fall or # versus another with "mine
is different than yours"... when at first look they do not appear to be any
different.

I will however be cautious of paying too much for so called petrological
type of 3's and 4's when it isn't obvious. I'll stick with "do I like it or
want it or not, relative to the price it is offered at ?".

Thanx again Al for response,

John Divelbiss


----- Original Message -----
From: "almitt" <almitt_at_kconline.com>
To: "John Divelbiss" <j.divelbiss_at_worldnet.att.net>
Cc: "Matteo Chinellato" <mcomemeteorite2000_at_yahoo.it>; "dean bessey"
<deanbessey_at_hotmail.com>; <meteorite-list@meteoritecentral.com>
Sent: Saturday, July 06, 2002 6:07 PM
Subject: Re: [meteorite-list] nwa869


> Hi John and all,
>
> Many of the parent bodies have yet to be identify to the many of the
meteorites we
> have accumulated here on Earth. However there are some suspect parent
bodies which
> have been identified by spectral matches to the asteroids and meteorites.
One such
> match is asteroid Hebe for the H type chondrites. It is obvious from
looking at Hebe's
> surface that it has a variation in spectra as the asteroid rotates
representing the
> different metamorphism (classes) we see from the change in olivine to
pyroxene ratio.
> No doubt the asteroid had a large enough impact at one time to knock it
apart allowing
> the more differentiated classes to show up on the outside, and some of the
outer part
> of the asteroid became buried in the interior as it reassembled into a
rubble pile
> asteroid. It isn't uncommon for H type chondrites to have brecciation of
various
> different classes all in one meteorite. A good example of this is Zag
(H3-6) and
> Noblesville, Indiana an H4 chondrite with H6 clasts. Probably why we get
so many of
> the H type chondrite material now is we are living at a time when the
results of the
> impacts which have been migrating to us over the eons have finally made
their way to
> fall at a constant rate. If we lived in a different time many years from
now or very
> long ago then perhaps and most likely we would sample some other type of
meteorite
> falls. Perhaps it wouldn't be uncommon for some rare type meteorite (to
us) to fall at
> a regular more consistent rate.
>
> How does this tie into NWA 869. As stated earlier we don't know all of the
parent
> bodies yet (a good reason for funding to NASA to build a craft to visit as
many
> asteroids as we can) However there is one asteroid of about 7 km in
diameter that
> resides in the main belt and may be related to the L type chondrites and a
possible
> parent body though a very weak link. Asteroid 3628 Boznemcova exhibits
spectral
> qualities to the L's and LL's. It is obviously too small to be a complete
asteroid and
> has been suggested it is a fragment of a much larger asteroid. Perhaps
this might be
> what is left of the NWA 869 and other L type meteorites and why we sample
a steady
> rate of L type chondrites.
>
> Beside these parent bodies, we are fairly sure of the Vesta and HED type
meteorite
> connections as well as the Martian (SNC), and lunar meteorite to Moon
connections.
> It's what makes reading about and research on meteorites so exciting and
trying to
> figure out all of the complicated puzzles they present to us.
>
> --AL Mitterling
>
>
Received on Sat 06 Jul 2002 07:07:00 PM PDT