[meteorite-list] Cometary meteorites

[Jason Utas]

Hello E.P. All,
We do not have examples of anything that even remotely resembles what
actually constitutes cometary material.
What follows is an excerpt from an email that I posted to the list on
August 11th of this year that addresses the same subject.
---
The simple answer is no.  No meteorites have ever been found that
match all criteria for what we believe cometary material should look
like.

http://www.lpi.usra.edu/meetings/LPSC98/pdf/1004.pdf

This is also the sort of topic that has been brought up again and
again on the list.  While I couldn't find any direct references for
some reason, I was able to turn these up:

http://www.mail-archive.com/meteorite-list@meteoritecentral.com/msg84604.html

http://six.pairlist.net/pipermail/meteorite-list/2004-May/000683.html

To condense: a few meteorites, namely the CI's, come close to what we
think cometary material might look like.  But those meteorites weren't/aren't
associated with any known meteor showers, and are likely just
fragments of  D-class asteroids, which may or may not be remnants of
"burned-out" comets (comets that got trapped in the inner solar system
and stripped of most of their volatiles).
But, based on the above paper, even the CI's are probably not actual
"cometary" material, though they fit the bill better than most other
meteorites, for sure.
...
Some more basic reading:
http://www.amsmeteors.org/faqm.html#11

Scroll to section before bottom: "Meteorites from Comets?"

http://www.pibburns.com/catastro/meteors.htm
---

The assertion that CI meteorites are cometary in origin goes against
practically every detail of cometary composition that we have learned
over the past several decades, and the even more general assertion
that cometary meteorites have been found and recognized is thus simply
untrue.

We may or may not have samples of the other asteroid classes; that is
a completely different issue, and if you'd like to start a new thread,
by all means do so.

Regards,
Jason

Jason Utas
University of California, Berkeley 2012
College of Letters and Science
Psychology, Geology


On Tue, Nov 23, 2010 at 4:46 PM, E.P. Grondine <epgrondine at yahoo.com> wrote:
>
> Hi Larry -
>
> And when I started on this list there were no major differentiated parent bodies for other meteorites (following McSween), and now we have what, at least five?
>
> I suppose that if we knew what comets were, then there wouldn't be any need to spend any money finding out what they are. And then there is that tricky problem of the source for C, B, G (and maybe D) asteroids.
>
> E.P.
>
> --- On Tue, 11/23/10, lebofsky at lpl.arizona.edu <lebofsky at lpl.arizona.edu> wrote:
>
> > From: lebofsky at lpl.arizona.edu <lebofsky at lpl.arizona.edu>
> > Subject: Re: [meteorite-list] Cometary meteorites
> > To: "E.P. Grondine" <epgrondine at yahoo.com>
> > Cc: warnerem at astro.umd.edu, meteorite-list at meteoritecentral.com
> > Date: Tuesday, November 23, 2010, 3:48 PM
> > Hi:
> >
> > I have said this to you before that there is about zero
> > evidence that
> > carbonaceous chondrites are from comets. There is only
> > minimal evidence
> > that there are hydrated silicates in comets and at least
> > the CI and CM CCs
> > very much aqueously altered and are consistent with an
> > origin from C, B,
> > and G (and maybe D) asteroids.
> >
> > Larry
> >
> > > Hello Elizabeth, all -
> > >
> > > The general informal consensus within the meteorite
> > community has been
> > > that carbonaceous meteorites are cometary in origin.
> > That being the case,
> > > a few questions:
> > > 1) At what compression/temperature will CO2 dissociate
> > into Carbon and
> > > Oxygen?
> > > 2) Will Epoxi provide fine spectra data for trace
> > elements such as calcium
> > > and aluminum? Platinum Group Elements?
> > >
> > > E.P. Grondine
> > > Man and Impact in the Americas
> > >
> > >
> > >
> > >
> > >
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> > >
> >
> >
> >
>
>
>
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