[meteorite-list] Ablation Zone 5 Layers...AND Crust

From: Pete Shugar <pshugar_at_meteoritecentral.com>
Date: Mon, 23 Nov 2009 23:00:09 -0600
Message-ID: <CAC412699C88486D986D35517B5E5FD5_at_laptop>

Now there's a $27.87 dollar word if I ever heard
one-------------autodidactly
One who is self taught. WOW
----- Original Message -----
From: "MEM" <mstreman53 at yahoo.com>
To: <altmann at meteorite-martin.de>; <meteorite-list at meteoritecentral.com>;
"Greg Stanley" <stanleygregr at hotmail.com>
Sent: Monday, November 23, 2009 12:12 AM
Subject: Re: [meteorite-list] Ablation Zone 5 Layers...AND Crust


>- Greg Stanley wrote:
>> See Fig. 1 on this UCLA web page.
>> http://www.ess.ucla.edu/research/cosmochem/meteorite.asp
>>
>> Not sure if Dr. Wasson has written any papers regarding
>> fusion crusts on irons, but I would think he would endorse
>> anything on the web page.
>
> So Gregg, if your statement is true, Dr.Wasson and/or UCLA endorses the
> formation of "rusty" fusion crust actually formed during decent? ( Fig 1
> or is it the regmaglyts that formed during passage and they are on top of
> the rusty fusion crust?)
>
> The issue is deeper than the semantic arguments, glossary obsolesence and
> lies in the differences of origin, composition, and presence of crust on
> different classes of meteorites. In the old school, a crust is generally
> removable from the underlying substrate and a dipping in molten metal
> alloy pushes the envelope of being a crust, however Buchwald illustrated
> that this was a combination of free metal and oxides. I conceed that
> irons--most all freshly fallen ones anyway , do have a fused surface that
> we can by convention call "crust" but the question remains as to what is
> the crust which is a few microns thick versus coatings and halos etc.
> There is danger of promoting ignorance by making assumptions that
> everything which is called crust is identical.
>
> I am old school and I have the (un)reasonable expectation that where a
> distinction does lie, that the collector can understand why things are the
> way they are and not abuse the descriptions when they try to peddle their
> specimens. Very few understood the distinction of silicate content when
> addressing irons as the presence of silicates,oxides, carbides,phosphides,
> etc largely govern the nature of a particular crust and gives insight into
> what went on during that miliseconds of exposure when the final surface
> was formed.
>
> Why it matters to me is 1) the abuse of the term in describing meteorite
> conditions 2) the science of understanding the differences in crust origin
> and composition and 3) how do we make the distinction amongst flight
> markings and do they differ from "fusion" crust?
>
> I am satisfied that 1)one of the iron specimens cited in this discussion
> apparently do have a silicate content that provided for a glassy fusion
> crust and its origin is intriguing scientifically. 2)That by definition
> alone (fused + coating) the irons do routinely have a "fused
> coating/crust" which differs significantly from our traditional concept of
> "crust" even though it is indistinguishable from the interior to the naked
> eye. (Do folks really "see" the crust or do they see if because it is
> supposed to be there?) At what point in weathering do we "see" that the
> welded crust/layer on an iron has rusted away given it is a few microns
> thick? 90% of the time, the seller will be claiming "crusted" long after
> the crust is gone, IMO.
>
> I've seen little to nothing so far that invalidates describing the
> ablation zone nor crust in layers--Nor did Buchwald, apparently.
>
> Finally, the term "big-head" someone used probably translates to
> "arrogant" Either way it was used in error as I was misunderstood. I did
> not disparage the pioneers in the field or meteoritical study. They
> gained their meteoritical knowledge largely autodidactly when they came
> over. I mentioned their former fields because when an individual crosses
> over into a different field of research, one can not just presume that
> they immediately acquire the entire knowledge base of those who were
> formerly educated in the same field.
>
> Elton
>
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Received on Tue 24 Nov 2009 12:00:09 AM PST