[meteorite-list] Moss Meteorite From A Comet?

From: Larry Lebofsky <lebofsky_at_meteoritecentral.com>
Date: Sun Aug 20 08:17:32 2006
Message-ID: <1156076247.44e852d7cda1d_at_hindmost.LPL.Arizona.EDU>

Hi Jeff:

Read the May issue of Mereorite magazine. An article by Swindle and Campins.

Larry

Quoting Jeff Kuyken <info_at_meteorites.com.au>:

> Howdy Bernd, Rick & all,
>
> Just curious because I recently read somewhere (maybe this list actually but
> can't remember) that the CH (or CB?) chondrites may now be the best match to
> a cometary origin. I think this was after Deep Impact. Anyone remember or
> know more?
>
> Cheers,
>
> Jeff
>
> ----- Original Message -----
> From: bernd.pauli_at_paulinet.de
> To: Meteorite-list_at_meteoritecentral.com
> Sent: Sunday, August 20, 2006 6:46 AM
> Subject: [meteorite-list] Moss Meteorite From A Comet?
>
>
> Hello Rick and List,
>
> As you are new on this List, I don't really know who I am talking to, how
> old or how young you are, how much you know about meteorites and comets,
> if you already have any meteorites, whether you have already read any books
> about meteorites, etc., etc. Maybe you would like to introduce yourself to
> us and tell us a little bit about you. Thank you in advance!
>
> Your question is interesting and intriguing. Theoretically, some meteorites
> may have a cometary origin but so far they have not been found or recognized
> yet.
> If there are cometary meteorites in our collections, scientists expect them
> to
> have come from the so-called Kuiper belt beyond 30 AU.
>
> Their silicates should be anhydrous, highly unequilibrated, their chemistry
> would
> resemble that of chondrites but there would be a high amount of C and N. But
> if
> these cometary meteorites were altered through the influence of flowing
> water so
> far out in our Solar System, the most likely candidates here on Earth would
> be
> the CI carbonaceous chondrites.
>
> Some xenolithic inclusions in ordinary chondrite regolith breccias are also
> suspects for a cometary origin.
>
> You will probably have seen a Perseid fireball but no matter what you saw,
> some scientists say that many shower meteors can be as dense as carbonaceous
> chondrites or even as dense as ordinary chondrites.
>
> Especially interesting is the fall of the CI chondrite Revelstoke because it
> could be an example of a weak cometary meteorite. A fireball was observed
> for
> hundreds of kilometers and atmospheric effects were measured nearly 1500 km
> away. The fireball must have been as energetic as the Sikhote-Alin
> meteorite.
> The SA fireball produced several craters and tons of meteoritic irons but
> all
> that was found of the Revelstoke fireball was less than a gram of friable
> black
> rock.
>
> If there are cometary meteorites in our collections,
> here are some of the criteria they should meet:
>
> a) as rare as CI carbonaceous chondrites
> b) dark + weak
> c) highly porous + low density (ca. 2 g/cm3)
> d) nearly solar abundances
> e) high abundance of C, N, and organic compounds
> f) anhydrous silicates
> g) highly unequilibrated silicates
> h) very large abundance of interstellar grains
> i) chondrules and CAIs should be rare or absent
>
> It is so difficult to identify cometary meteorites in case they already
> exist
> in our collections because they could easily be misclassified as
> achondrites.
> There are indeed achondrites like the acapulcoites, lodranites, brachinites,
> winonaites that have chondritic chemical abundances, and there are C-rich
> achondrites, for example the ureilites.
>
> And now back to your question: Is the Moss meteorite from a comet?
>
> Let's *suppose* some cometary meteorites do contain chondrules, then C-rich,
> highly unequilibrated CO, CV, or ordinary chondrites might be good
> candidates
> according to:
>
> CAMPINS H. and SWINDLE T. (1998) Expected characteristics
> of cometary meteorites (MAPS 33-6, 1998, pp. 1201-1211).
>
> In other words, in that case even the Moss meteorite - if it should really
> be classified as a CO.x (preferentially "x" should be 1, 2, or 3) - could
> be of cometary parentage.
>
> Hope this helps ;-)
>
>
> Best regards,
>
> Bernd
>
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Received on Sun 20 Aug 2006 08:17:27 AM PDT