[meteorite-list] Info on Sikhote Alin's shrapnel

From: Jason Utas <meteoritekid_at_meteoritecentral.com>
Date: Tue, 17 Nov 2009 03:49:21 -0800
Message-ID: <93aaac890911170349m508d1790te9e42cae85e9f3f8_at_mail.gmail.com>

Fred, Maurizio, Graham,
On the contrary, it is generally accepted the the vast majority of the
jagged shrapnel fragments found were formed when the larger masses
came into direct contact with permafrost and bedrock. Such is said by
Buchwald, Krinov, and..., well, to be frank, I've gone through many,
many kilos of shrapnel as well. While I have seen the rare specimen
that exhibited surface melting, they typically appeared to be smaller
fragments of larger individuals upon which small patches of fusion
crust were preserved (analogous to fragments of stony meteorites with
patches of primary crust on them, from fragmented larger individuals).
Many batches of shrapnel do appear to be somewhat ablated due to the
method by which they have been cleaned (tumbling with ball bearings
tends to wear corners down and gives the false impression of surfaces
having melted). Given the fine scratches and gouges I've seen on the
majority of lightly-cleaned specimens, I'd have to say that, no,
Sikhote shrapnel rarely exhibits any trace of ablation.
Regards,
Jason

On Mon, Nov 16, 2009 at 8:40 PM, <debfred at att.net> wrote:
> ?List, I have searched many Kilos of SA shrapnel without ever finding ONE without some surface melting. From what I have seen shrapnel is ALL air shredding with subsequent atmospheric frictional melting.
> Cheers, Fred Olsen
> -------------- Original message ----------------------
> From: <ensoramanda at ntlworld.com>
>>
> I did not know heat was needed at all to form shrapnel...surely it is just due
> to shearing of fragments from the dramatic collisions of fragments on impact or
> during exposive events on the way down that did not leave enough time for
>> ablation?
>>
>> Graham UK
>>
>> ---- Maurizio Eltri <maurizio.eltri at libero.it> wrote:
>> > Hi all,
>> >
>> > I ask to those who are more experienced
>> > than me,clarification about Sikhote Alin's
>> > splinters formation.
>> > In my opinion there can be two ways to
>> > justify the origin of the fragments found in
>> > the vicinity of the largest craters,
>> > 1) The kinetic energy released at the contact
>> > surfaces of meteorite/ground was enough to
>> > melt the frontlayer of the meteorite with
>> > the subsequent violent expulsion of fragments,
>> > fused or partially fused.
>> > 2) Having the meteorites reached the retardation
>> > point at only 5 km of altitude, they would arrived
>> > at an impact with their hot surfaces, this would
>> > facilitate the expulsion of splinters.
>> > I apologize for my bad English.
>> > Maurizio Eltri
>> >
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Received on Tue 17 Nov 2009 06:49:21 AM PST