[meteorite-list] NEW FALL

From: jason utas <jasonutas_at_meteoritecentral.com>
Date: Mon, 11 Jun 2012 18:17:25 -0700
Message-ID: <CAK837U0qZ=6J4-ApyannaRTrgXGXyVnyiSQdQn69qrdrfGNr8g_at_mail.gmail.com>

Hello Richard, All,
With proper cleaning techniques, I have seen fine flow lines and
delicate ripples, splashes, and flow-lines on the surfaces of several
irons that had been weathered, but were somewhat restored to their
former glory. Such features are only accompanied by rust when
cleaning is incomplete or when the crust has been removed by
oxidation.

I'm not saying that irons should have all rust removed -- on the
contrary, many irons look better uncleaned, but when considering
Sikhote-Alins, one must look critically at the texture of the surface
one is looking at to determine whether it consists of fusion crust
covered by rust, underlying metal shaped by atmospheric entry, or iron
oxides cemented to the crust or underlying metal.

The 'splash craters' of which you speak always looked like patches of
iron oxides to me. Some looked vaguely 'splashy,' but they were
almost always surrounded by areas of rust and/or bare metal, which
made me think they were the result of improper cleaning.

My observations may be incorrect, but I've yet to see a convincing
"splash crater." Every feature I would call a 'crater' has had an
upraised rim.

Regards,
Jason

On Mon, Jun 11, 2012 at 5:34 PM, Richard Montgomery
<rickmont at earthlink.net> wrote:
> 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" <jasonutas at gmail.com>
> To: "Meteorite-list" <meteorite-list at meteoritecentral.com>;
> <graham.ensor at gmail.com>
> 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 <graham.ensor at gmail.com>
>>> Date: Sun, Jun 10, 2012 at 6:28 PM
>>> Subject: Re: [meteorite-list] NEW FALL
>>> To: MICHAEL JOHNSON <rockmansc at yahoo.com>
>>> Cc: "meteorite-list at meteoritecentral.com"
>>> <meteorite-list at meteoritecentral.com>
>>>
>>>
>>> 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 <rockmansc at yahoo.com>
>>> wrote:
>>>>
>>>> http://www.rocksfromspace.org/new-fall-2012.html
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>
Received on Mon 11 Jun 2012 09:17:25 PM PDT