[meteorite-list] Meteorites and sulfurous odors

From: Martin Altmann <altmann_at_meteoritecentral.com>
Date: Sat, 6 Oct 2007 00:53:52 +0200
Message-ID: <003f01c807a2$9b41b450$177f2a59_at_name86d88d87e2>

Hi Mike,

that's the debate, as old as the list itself.
And I have the advantage simply to state: They are cold.

Why I can be so bold?
Because nobody can evidence the opposite.
The dilemma is, that nobody involved in meteoritics will ever attend a
meteorite fall,
so we will always be thrown back to reports of "meteoritical laypeople".

My personal opinion is, that the dark-flight-phase takes minutes in high
altitudes, where the screen in the plane is telling us, that it's a little
bit to drafty to sit outside, the stones then are travelling with still a
good speed.
What could be hot and could keep the temperature? The plasma rather than the
paper-thin fusion crust, we find on the stones.
The irons as better heat-conductors, we have in our collections, display a
recrystallized superficial zone of 1-2mm,
the fusion crusts of stones often show contraction cracks from rapid
cooling.
Somebody mentioned, that the isotopes would be "reset" if temperatures would
exceed 400?..
The fall witnesses in general need a little time to arrive at the stones.
Not to forget, that the sensation of extremely cold and hot is very similar.
Easy to test, if you touch in an artic winter night the mount of your
telescope outside without gloves.
And the expectation of laypeople touching a stone is, that it must be hot,
because they think, the light phenomenon, they observe with ordinary
shooting stars is caused by the glowing of the meteoride itself due to
frictional heat.
I don't know, do you have a homepage about meteorites?
If yes, I'd bet, that 80% of the finds, laypeople are presenting you as
alledged meteorites - without hematites, magetites and those, which they
found in comparing the stone with photos of true meteorites in the web,
will look molten and flow...(eek what is the participle of "to flow" versus
"to fly"?).
Because they expect, that a meteorite must melt during its flight, because
of the heat.

"The hammer will get hot"
But how long the hammer will stay hot?
And if a fast car on the highway misses the bridge arch, will it glow then?

And with those meteorites, which maintain a part of their cosmic velocity,
there I guess, we have a communication problem with the nearby standing
observers....they won't be able anymore to tell us their observations
(and those from a distance will need at least an hour to pluck up
courage...).

(And if one reads the old pamphlets about rainbows, parhelia, halos, comets,
and so on... how hysterical they were reported.. I don't see, why meteorites
should be an excemption)

Well, my thoughts only, I can be wrong...

Would be a nice (and classic) idea, if MetSoc would advertise an award,
for that person, who firstly will measure the temperature of a fresh fallen
meteorite...

(Had anybody put his hands under the Soyuz-capsules, before they torn out
the cosmonauts?)

Best!
Martin



-----Urspr?ngliche Nachricht-----
Von: meteorite-list-bounces at meteoritecentral.com
[mailto:meteorite-list-bounces at meteoritecentral.com] Im Auftrag von Mike
Fowler
Gesendet: Freitag, 5. Oktober 2007 21:15
An: meteorite-list at meteoritecentral.com
Cc: Mike Fowler
Betreff: [meteorite-list] Meteorites and sulfurous odors

> Regarding the reports you mentioned about historic falls, I
> wouldn't take
> the assertions there to seriously. As we all know, meteorites fall
> cold, but
> nevertheless the old reports tells the stone was to hot to tuch, it
> glowed 3
> days, the ground was hot and so on...
>
>
> Best!
> Martin


Hi Martin,

I have to strongly disagree. First of all, who says we all know
meteorites fall cold? I guess you're saying that all the accounts to
the contrary don't count?
What about the piece of Portales Valley that melted into the tarp it
fell on?

Secondly, I'll grant you the possibility that meteorites may "fall"
cold, but after they strike the ground they may not be cold any
longer due to the kinetic energy of motion being instantly converted
the heat. Obviously this applies to heavier stones more than small
ones. A walnut sized meteorite with a correspondingly slow terminal
velocity would likely be cold both falling and after landing. The
larger the stone, the less likely this is to be true. When it comes
to irons, there are two additional factors. One is the higher
terminal velocity for a given weight, due to the higher density. The
second is that upon impact much more of the kinetic energy is
converted to heat, and less is dissipated in crushing, as irons don't
crush like stones might. Think about striking an anvil with a hammer
or a stone.
The hammer will get hot, the stone won't.

I think if you examine the historical accounts you will see that
accounts of cold meteorites almost always refer to small ones and
that accounts of warm or hot ones more often refer to much larger
pieces, or irons.

Although I'm confident of my reasoning, I don't remember reading
anywhere of a similar explanation.

Mike Fowler
Chicago
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Received on Fri 05 Oct 2007 06:53:52 PM PDT