[meteorite-list] Regmaglypts

From: Jason Utas <meteoritekid_at_meteoritecentral.com>
Date: Tue, 26 Jan 2010 14:16:13 -0800
Message-ID: <93aaac891001261416p2cbf2ffeg508503956eedc6fa_at_mail.gmail.com>

Phyllis, All,

> Buchwald (1) calls regmaglypts ?a specific hallmark of an iron meteorite,? a term introduced by Berwerth in 1909. ?Also known as ?thumb prints,? Buchwald goes on to state:
>
> ?Regmaglypts are thumb-like pits carved into the surfaces by turbulent supersonic airstreams during the atmospheric flight.?


Buchwald's point of view on the matter are readily accepted as fact,
and there's not really any debate as to whether or not regmaglypts
form in atmospheric flight; they do.

> I beg to differ and offer another interpretation, based on my theory (2) that nickel-irons and stony-irons are cast materials solidified under microgravity conditions. ?This means that surface energy dominates in the liquid state and during solidification until the mass is solid.

Well, "cast" is the wrong word to use unless you're talking about
filling a mold, but I think I understand what you're saying.
The trouble is that you're looking at things in a far too simplistic
manner. The IAB irons are thought to be melt from a larger stony-iron
parent body (namely the one from which Winonaites originate), and a
number of other irons share similar chemical and isotopic silicate
"pairings." This would imply that they actually formed on or in
larger parent bodies, as either impact melt, or at their cores. If
they were entirely melted when these bodies were broken up in the
asteroid belt is open to some debate, but if we do assume that they
were for the purposes of your argument, well....see below.

> Observation of nickel-iron meteorite surface features commonly called regmaglypts indicates that these features can be separated into two different phenomena: flow lines and thumb prints.

Flow lines are merely features in the fusion crust of a meteorite,
which typically consists of a 0.1-1mm thick magnetite/oxide skin on
the surface of the meteorite.
Regmaglypts are sub-crust features that form while the surface of the
meteorite is much more ill-defined. While in incandescent flight, the
border between the actual fusion crust and the Fe-rich incandescent
gas that surrounds the fireball is ambiguous at best, so the sub-crust
iron is essentially ablating directly. We think of meteorites as
possessing a fusion crust because that's how they arrive when they
fall.
The atmospheric reality that is an incandescent fireball is much more complex.

> Flow lines are surface features related to ablation melting during passage through the Earth?s atmosphere.
> Thumb prints have 2 components: (a) angular, linear regions and (b) indentations. ?I propose that each was generated by a different mechanism.
>
> (a) Angular, linear boundaries: Observe a mass of soap bubbles, a system that tries to minimize surface energy. ?Interior bubbles will have polyhedral shapes, producing linear boundaries between bubbles. (3, 4).
>
> (b) Indentations: Metals shrink on cooling.
>
> What do YOU think?!

Simply impossible. Take a look at fresh irons like Boguslavka, Ziz,
Taza, Sikhote Alin. All of these irons have regmaglypts, and yet when
we cut them we see no bubbles.
Now, what you might say is that these irons did have 'veins of
bubbles' and that they fragmented along those veins, but then I would
simply point out that while cutting fragments of these irons, we have
*never* seen a single vug.
In fact, only one iron *ever* was known to contain naturally occuring
"bubbles" [Albion], and they looked nothing like regmaglypts in the
least.

Beyond that, the physics has been done, and we know that substantial
amounts of material (the majority, in most cases) ablates off of the
surfaces of meteorites when they fall to earth. It's simply the only
possible way that they could dissipate the massive amounts of kinetic
energy that they have in space.

Regards,
Jason

> Phyllis Budka
>
> References
> 1. Buchwald, V.N., Handbook of Iron Meteorites, Vol. 1, p. 47, Univ. of California Press, 1975
> 2. See my website at
> http://meteormetals.com/
> 3. Boys, C.V., Soap Bubbles, 1959 Edition by Dover Publications of the original 1911 book.
> 4. Isenberg, Cyril, ?The Science of Soap Films and Soap Bubbles,? 1978, Tieto Ltd
>
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Received on Tue 26 Jan 2010 05:16:13 PM PST