[meteorite-list] More Fireball - Meteorite Discussions

From: Robert Verish <bolidechaser_at_meteoritecentral.com>
Date: Thu Apr 22 09:37:38 2004
Message-ID: <20001227190251.69147.qmail_at_web10407.mail.yahoo.com>

Here is another List with 2 other threads about

--- meteorobs-digest
<owner-meteorobs-digest_at_jovian.com> wrote:
> meteorobs-digest Wednesday, December 27 2000
> Volume 03 : Number 533
> Re: (meteorobs) Meteorites and Terminal velocity
> Re: (meteorobs) Meteorites and Terminal velocity
> Re: (meteorobs) Meteorites, Terminal Velocity,
> Temperatures etc.
> (meteorobs) NE Fireball, 12/26/00
> (meteorobs) FM meteor Train heard
> (meteorobs) Dark Flight & recovery temperatures
> (Wayne's comment)
> Date: Tue, 26 Dec 2000 15:35:20 +0100
> From: "Marco Langbroek" <marco.langbroek_at_wanadoo.nl>
> Subject: Re: (meteorobs) Meteorites and Terminal
> velocity
> Hi Dave, George,
> The "glow in the dark" has been reported a number of
> times notably with
> irons. It need not have to do with radiating heat -
> Spratt some years ago
> proposed an incandescent effect through recombining
> ions on the irons
> surface, a form of natural thermoluminiscence.
> Something I would like to offer as a source for some
> warmth with fresh
> falls, is the decay of very short-lived radioactive
> nuclei formed by cosmic
> irradiation while the stone was still in space.
> Perhaps the decay could
> generate some warmth up to a point that it is
> notable by the touch directly
> after the fall. Perhaps this could generate some of
> the reported
> luminiscence. Please note, this is pure conjecture.
> I never thought of that
> before this discussion on meteorobs started - ought
> to ask this to one of my
> professional meteoriticist friends!
> Reheating evidence in meteorites certainly has been
> searched for.
> There's no evidence from meteorites that heating
> effects altered the
> material for more than a few millimeters below the
> surface. In normal irons,
> a profound reheating would destroy the Widmanstatten
> patterning they
> display. In stones, for example chondrules would be
> lost in such a case.
> Strong heating to deep depths into the meteorite
> therefore did not occur.
> I would like to point out also that there is no
> authenticated case of a
> meteorite hot enough to be able to start a fire -
> while many landed into
> matter well combustable, e.g. Spratt gives the
> example of the Forest City
> landing in a haystack.
> - - Marco Langbroek
> ------------------------------
> Date: Tue, 26 Dec 2000 11:10:50 EST
> From: GeoZay_at_aol.com
> Subject: Re: (meteorobs) Meteorites and Terminal
> velocity
> Dave>> Your point about recrystalization from
> reheating has merit but I believe that to form
> smaller crystals the iron meteorite would have to
> completely melt (2795 o F or 1535 o C ) then all of
> the meteorite would have the same very small
> that make up the fusion crust.<<
> I can think of at least one instance where melting
> doesn't have to occur to
> have crystal structure changes in heated iron. The
> process of making cold
> chisels. It's been a long time since I've made one,
> but do recall that you
> heat up the shaped piece of iron to a red hot
> temperature and then dip it
> into cold water. This process results with a changed
> crystal structure and
> very hard metal. No melting was involved.
> GeoZay
> ------------------------------
> Date: Tue, 26 Dec 2000 11:43:06 EST
> From: GeoZay_at_aol.com
> Subject: Re: (meteorobs) Meteorites, Terminal
> Velocity, Temperatures etc.
> Does anybody recall how cold Apollo 13 within the
> crew compartment got when
> they had to shut down power to conserve their
> batteries? i recall hearing
> once that the temperatures were near or at freezing
> of water. The sun didn't
> really help heat them much. I think it would have
> gotten much colder if they
> stayed aloft for a longer period. I also think they
> turned on their heaters
> intermittently so they wouldn't freeze to death? I
> guess the eventual
> interior of a spacecraft without heat could be
> somewhat similar to the
> interior of a meteoroid? Very cold.
> GeoZay

> ------------------------------
> Date: Tue, 26 Dec 2000 14:58:13 -1000
> From: Jim Bedient <bedient_at_amsmeteors.org>
> Subject: (meteorobs) NE Fireball, 12/26/00
> Just got a report of a brilliant green fireball seen
> to the north of Massapequa, Long Island at 6:23 pm
> EST, said to have descended all the way to the
> observer's local horizon. If it's clear up that
> there might be a few witnesses to this one,
> considering the time of day, etc.
> Reports should be submitted via the usual channels.
> Jim Bedient
> www.amsmeteors.org

> ------------------------------


> Date: Wed, 27 Dec 2000 16:16:35 +1100
> From: "Geoff Wolfe" <dxer3_at_hotmail.com>
> Subject: (meteorobs) FM meteor Train heard
> Heard a great train which lasted for 1:10min on the
> 26/12/00 at 19:20 UTC on
> 98.5 Mhz (ABC Classic FM from Maryborough QLD). The
> train also brought in
> reception on TV channel's 0, 1 & 2 (on my
> scanner)from the state of
> Queensland (QLD). Meteor activity has been very low
> of late with rates being
> below 20 - 30 per hour (which is poor for FM -
> Average is around 50 - 60 per hour).
> - - Geoff <Cooma NSW Australia>

Date: Wed, 27 Dec 2000 16:33:11 +0100
From: "Marco Langbroek" <marco.langbroek_at_wanadoo.nl>
Subject:(meteorobs) Dark Flight & recovery
temperatures (Wayne's comment)

Hi Wayne,

It is not as absurd a suggestion as it might seem.
Cosmic irradiation does produce a whole suite of very
short lived cosmogenic nucleides in meteorites with
decay times of a few weeks, a few days, a few hours.
For the latter two categories: these decay in the
hours and days directly after the fall and after that
they are gone and you can't measure them. This is one
why fresh falls should be put into a measuring chamber
at a right equipped institute as quickly as possible.

So far, there have been no instances of meteorites
being measured for cosmogenic nucleide decay quicker
than 50 hours after the fall. We do know what kind of
cosmogenic nucleides exist that have decay times well
over 50 hours - but not those with decay times below
50 hours. And radiogenic decay simply generates
warmth, and can induce luminiscence. Whether it is
visible/feelable, is another question. The radiogenic
activity might be not strong enough for that (it
certainly is not for those cosmogenic nucleide decay
that have been measured so far - you need fairly
sensitive equipment to measure those). So you can
rightfully have doubts about that, but as a suggestion
it is one to entertain for a moment. Physically, its
perfectly viable.

Interestingly, when a meteorite would be warm after
the fall to some extent, this indeed could induce
natural thermoluminiscence as suggested by Spratt, and
this could be shortly visible indeed at night as a
"glow" of the stone easily being mistaken for a
red-hot glow. For those of you who do not know,
thermoluminiscence, as the word says, is induced by
warming crystaline matter, which then releases trapped
ionized particles from flaws in its crystal structure,
particles which upon recombining emit some light. The
technique is used as a dating tool in geology and
archaeology: if you have
flint tools burned in antiquity (as we had in the
Belvedere Archaeological project), which sets the TL
clock at zero effectively after which the trapping
process of new particles starts, and you warm them
stepwise, the flint starts to emit light by
Thermoluminiscence. You can measure it, and if you
also measure the radiation dose of the soil which
contained the flint tools, you can calculate the age
of the flint tools from the amount of TL through
recombining particles emitted. By the way, it is said
natural thermoluminiscence was discovered when Robert
Boyle warmed a diamond in his hand at night and saw it
start to glow (at least, that is how he reported it
a two centuries ago). Therefore, a handwarm meteorite
could glow by Thermoluminiscence I suggest.

- - Marco

- ---
Marco Langbroek private:
Leiden University work:
Faculty of Archaeology
P.O. Box 9515
NL-2300 RA Leiden
The Netherlands

"What seest thou else
  In the dark backward and abysm of time?"

William Shakespeare: The Tempest act I scene 2
- ---

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End of meteorobs-digest V3 #533

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Received on Wed 27 Dec 2000 02:02:51 PM PST

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