List, and Jason,
Such "impact" craters on SA's, especially on shrapnel fragments, have always
raised my curiousity....with no (well, rare) inclusions to explode during
incoming flight as you've mentioned, what accounts for the many 'splash'
type craters on Sikhote Alin?
----- Original Message -----
From: "jason utas" <[email protected]>
To: "Meteorite-list" <[email protected]>;
<[email protected]>
Sent: Sunday, June 10, 2012 6:40 PM
Subject: Re: [meteorite-list] NEW FALL
Hello Graham, All,
Krinov concluded that all of these features we call "craters" are in
fact small pits caused by the vaporization of more volatile inclusions
under the fusion crust of the iron.
In other words, you have a heat-affected zone under the surface of the
iron, and if you get a more volatile inclusion, it can be heated to
the point that it vaporizes/expands, creating a small
explosion...."crater" in the overlying soft/molten metal.
This would explain the vast number of such "craters" seen on Franconia
irons -- since those specimens contain large amounts of disseminated
stony particles and troilite, it makes sense that they would contain a
greater number of inclusions that might create such features (versus a
relatively homogeneous Sikhote-Alin).
The exception to this rule would be craters formed on shrapnel, but
most of those supposed craters I've seen appeared to be exposures of
where round (troilite) inclusions had been. The "raised rims"
appeared to form from the shear/fracture propagating towards the weak
point in the meteorite (the inclusion), creating a surface that gently
sloped upwards to a smooth, round cavity.
I've seen a few exceptions, but not many.
Regards,
Jason
---------- Original Message ----------
From: Graham Ensor <[email protected]>
Date: Sun, Jun 10, 2012 at 6:28 PM
Subject: Re: [meteorite-list] NEW FALL
To: MICHAEL JOHNSON <[email protected]>
Cc: "[email protected]"
<[email protected]>
Wow! where is that from Michael/Mike? Strange that it has so many
small impacts on the oriented ablated leading edge and weird chisel
marks too? Looks like some satellite debris I've seen before but the
stoney and pyroxene inclusions plus the entry speed it would have had
seem to rule that out.
Curious.
Graham
On Mon, Jun 11, 2012 at 1:30 AM, MICHAEL JOHNSON <[email protected]>
wrote:
http://www.rocksfromspace.org/new-fall-2012.html
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