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Re: (meteorobs) Re: March 9th, 2000, Arkansas fireball
Hi, folks, I've been reading this thread with some interest.
Dave English wrote:
>can have frost on them from the cold entry while others, particularly
>larger iron meteorites, can glow from internal heat that reheated the
>surfaces which may indeed cool off during the free flight. Few here
>agree with me as evidenced by the Feb. '99 discussion.
Dave, what is the mechanism exactly, which you are proposing would heat the
inside of even a pure iron-nickel meteoroid? After all, such objects wouldn't
be substantially heated by the near-Earth environment, I don't think. (Again,
lunar surface temperatures don't exceed 120oC or so - not hot enough to glow,
I don't believe.) And the brief exposure to frictional heating as a particle
entered Earth's atmosphere would SEEM to be too brief to cause much internal
heating: consider that most fireballs, even meteorite dropping ones, aren't
visible for more than a few tens of seconds, are they? And as Ed Majden very
correctly points out, much of that heating is rapidly dissipated by ablation
and vaporization from the surface of the meteoroid...
I'm no metallurgist, but that sounds like a very different circumstance from
the deliberate heating of a block of iron to temper it. So even if there *is*
reliable evidence that ground-burning meteorites have been observed, then the
question really becomes "How COULD this be true?"
Of course, I DEFINITELY agree with the statement that data should never be
thrown out because it doesn't fit accepted theories... However, one of the
key elements in any scientific investigation seems to be knowing what data
can be reliably included - and what data probably cannot.
As an example of this, we frequently hear reports of fireballs which "arced
across the sky", "landed just over the next ridge", "split in two and forked"
and other physically very unlikely descriptions: I understand these are gen-
erally discounted not just by "desk jockies", but by folks who make it their
business (and pleasure) to verify, hunt down, recover and study meteorites.
Clear skies all!
Lew Gramer
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