[meteorite-list] Patterns in Sikhote-Alin

From: Lars Pedersen <lbp_at_meteoritecentral.com>
Date: Thu Apr 22 10:17:48 2004
Message-ID: <006601c3c3f3$d52ef700$365ea150_at_star>

Hello David

> So after melting and recooling on Earth do they really
> maintain the pattern
>or is it only present on pieces large enough not to melt?

Yes as Frederic explained, only the surface and a thin layer below is
heated.
The passage thrue the atmosphere takes only a few seconds, so the heating is
intense but short.

If it was heated (as far as I remember above aprox. 700 deg. C. )all the way
true the meteorite, there would be no Widmanstatten patern.

Yes Sikhote-Alinīs do have a very coarce pattern, in fact the patern can be
so wide that a slice looks like it has no patern at all.


Best wishes
Lars Pedersen

----- Original Message -----
From: "meteoriteshow" <meteoriteshow_at_free.fr>
To: "David Hathaway" <dhathaway_at_peak.org>;
<meteorite-list_at_meteoritecentral.com>
Sent: Tuesday, December 16, 2003 12:31 PM
Subject: Re: [meteorite-list] Patterns in Sikhote-Alin


> Dear David,
>
> Melting while crossing the atmosphere is "superficial". Meteorites lose a
> major part of their weight (less for irons than stones) that burns away to
> ashes, but the inside of the meteorite remains at space temperature (i.e.
> abour -270°C). This is the main reason whay they often break into
fragments
> in the atmosphere (because of high stresses due to temperature difference
> btween the inside and the "burning skin"), and actually this is what
> happened to Sikhote Alin, providing numerous fragments. As almost of all
> them show regmaglypts, this means that it happened in the high atmosphere,
> high enough to allow the fragments to keep on burning for a while. But the
> inside did not melt. For smaller fragments, the inside most probably
heated
> up, but not to melting point.
> This is my understanding, and should I be wrong, please do not heasitate
to
> let me know as I'm always open to learning more!
>
> Frederic Beroud
> www.meteoriteshow.com
> IMCA #2491
> ----- Original Message -----
> From: "David Hathaway" <dhathaway_at_peak.org>
> To: <meteorite-list_at_meteoritecentral.com>
> Sent: Tuesday, December 16, 2003 7:28 AM
> Subject: [meteorite-list] Patterns in Sikhote-Alin
>
>
> > I am a little curious about something.....
> >
> > I heard that the sikhote-alin meteorites have a Widmanstatten Pattern
> > although large and difficult to see.
> >
> > I have also heard that the regmaglypts are created when a molten piece
> cools
> > while airborne.. As nearly all the fragments I have seen have
regmaglypts
> I
> > assume all these pieces have been molten.
> >
> > So after melting and recooling on Earth do they really maintain the
> pattern
> > or is it only present on pieces large enough not to melt?
> >
> >
> >
> > ______________________________________________
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> >
>
>
>
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Received on Tue 16 Dec 2003 11:44:10 AM PST