AW: [meteorite-list] There are no silly questions? Wait until you haveread that :-)

From: Jörn Koblitz <koblitz_at_meteoritecentral.com>
Date: Wed Oct 20 11:57:38 2004
Message-ID: <E5E6112EA31FA24CB448E091C6883C050EBD09_at_server2000.microfab.de>

Dear Al and Bernhard,

It's true that, beside the 12 distinct chemical groups, we have about 80 ungrouped iron meteorites which - following the existing models of asteroid formation and differentiation ("core formation") - must be derived from 80 different parent bodies (PBs).

As Gero Kurat (Naturhistorisches Museum Wien) has pointed out in a recent paper (see ref below), this is quite strange, as there are only a "hand full" of parent bodies known for stony and stony-iron meteorites. He, therefore, has come up with a very interesting - and I think striking - alternative explanation for the formation of the PBs: that they have never formed by liquid-phase differentiation, but rather by carbonyl decomposition reaction and CVD growth of large monocrystals of FeNi austenite. This process could explain some properties that do not fit into the liquid-phase differentiation model (e.g. primordial noble gas contents). He also argues, that smelting and solidification processes can - even at low cooling rates -
hardly explain the large size of observed FeNi single crystal grains, structure and composition of silicate and intermetallic phases as well as the absence of dendritic structures in the known iron meteorites. To my opinion, Gero Kurat's model can become an sound theory of planetesimal formation in the solar system which expains the large number of ungrouped and chemically exotic iron meteorites.

J?rn / MetBase

Reference:
Gero Kurat (2003) Why iron meteorites cannot be samples of planetesimal smelting. In: Papers presented to the INTERNATIONAL SYMPOSIUM Evolution of Solar System Materials: A New Perspective from Antarctic Meteorites, held at the National Institute of Polar Research, Tokyo, September 3 - 5, 2003. (Abstract #35)

Unfortunately, there is no online link to the abstract, but I can send a scanned image of this abstract to those who are interested.

See also: http://presolar.wustl.edu/ref/LPSC2003_SanJuan.pdf



> -----Urspr?ngliche Nachricht-----
> Von: almitt [mailto:almitt_at_kconline.com]
> Gesendet: Mittwoch, 20. Oktober 2004 03:36
> An: Bernhard Rems
> Cc: Meteorite-list_at_meteoritecentral.com
> Betreff: Re: [meteorite-list] There are no silly questions? Wait until
> you haveread that :-)
>
>
> Hi Bernhard and all,
>
> Bernhard Rems wrote:
>
>
> 4) Iron meteorites originate from the core of a large and destroyed
> planetoid.
>
> Furthermore - there must have been at least two bodies of that size
> (because planetoids do not explode, they have to collide to eject core
> material into the solar system. Is this assumption right or wrong?
>
> AL says:-)
>
> O.K. one other comment from me then I'll give people a brake.
> Most of the
> Iron meteorites come from 12 distinct parent bodies (based on chemical
> classification). We then have an additional 80 some anomalous
> that provide us
> with the remainder of our iron meteorites. Some 86% of all
> iron meteorites
> belong to the 12 main groups.
>
> As McSween says the core of the problem, is iron meteorites
> have pretty plain
> spectra and light coming from them (albedo) is poor. Also
> iron meteorites
> represent a highly differentiated body one that has been
> heated (of course)
> and altered doing a resetting of the isotopes that might help
> us shed light
> on their origin. Silicates we find in iron meteorites
> sometimes help us out a
> bit with this.
>
> --AL Mitterling
>
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Received on Wed 20 Oct 2004 11:44:02 AM PDT