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(meteorobs) Re: Hot Meteoroids and Scientific Reasoning

Hello List,

I'd like once again to encourage anyone wanting to discuss meteorites to
bring it over the the meteorite central list.  That said--I liked your
post Mark.  I agree with most of your analysis as to factors affecting
temperatures heat content.  I don't want to challenge the idea that
there are not hot freshly fallen meteorites--  especially in the irons.
An article in this month's meteorite magazine offers some pretty
convincing proof of melting and flow in an iron which may have occurred
in flight.  When the proof is in  we will likely find that heat
retention( apparent temperature upon reaching the ground) in meteorites
is a function of flight duration, static head loads, sheering energies,
and the heat transfer coefficients of the meteorite minerals themselves.
Irons have a high transfer dissipation and stony's don't! Internal heat
sinks are going to consume a lot of the heat before it is radiated.

Observations are remain that there is no reliable evidence that any
freshly fallen meteorite OR space debris has been more than warm to the
touch upon landing.  Reports that the "meteorite" glowed three days in a
hole or better yet 3 days under water, are not in the realm of reliable.
No fire which was  suspected of being started by a meteorite has ever
proven to be started by a meteorite--No meteorites were ever found at
the fire site.  On the other hand, several meteorites -- all chondrites
were found immediately and had condensation ice form. Portales Valley
was warm to the touch-- almost too hot to handle  according to the boys
who pick it up but rapidly became comfortable to hold.  This is far from
fire starting levels.

Fusion crust is the last bit of mineral which was sufficiently melted to
decrystalize/vitrify but was to late to be sucked off into the slip
stream.  It ceased being liquid when the heat being generated dropped
below the melting temperature and this is in the speed range of 6-3 kps.
 The Crust is usually at most .5-4 mm thick and there just isn't much
heat storage capacity in that "wafer wrapping" to warm a cup of tea
little alone start a fire. The post a few days before suggesting that
the crust is still molten and can be slung off the bouncing meteorite
just isn't so.  Not withstanding the physics calculations which preclude
it-If the crust were molten at landing there would be embedded soil and
other impressions in the crust--and those have never been reported.  I
am comfortable with dismissing those reports until they are accompanied
with some evidence.

As to your assertion that science is closed minded on the topic, I must
protest. Science requires proof  and it looks for proof.  Because
science has found that there is no evidence of meteorites causing fires
or combustion of materials-- in spite of claims and rumors,  I think
speaks for science and its objectivity!  I think the aforementioned
Meteorite Magazine article is the first plausible evidence of heat
transfer sufficient to cause combustion but other causes have not been
excluded.  I don't know any research who has signed up to stay forever
with current wisdom if current wisdom can be altered by proof.   

Regard,
Elton Jones


> From: Mark Fox  Wrote:
> Subject: (meteorobs) Hot Meteoroids and Scientific Reasoning
> 
> July 31, 2001
> 
> Greetings Meteor Enthusiasts!
> 
> The recent discussion about whether or not meteorites
> impact earth hot or frosty cold has grasped my
> attention, and inspired me to write this.
> 
> I for one, do not see why meteorites can't be found
> both hot or cold moments after their fiery plunge.  In
> addition to being a meteor enthusiast, I am also an
> amateur meteorite hunter having some good books
> describing the ablation process.  This process, which
> I'm certain many meteorobs readers are already
> familiar with, involves the intense heat that
> liquefies the outer surface of a meteoroid in its
> travel through the upper atmosphere.  As taught, this
> heat, caused by the friction of the air around it,
> happens only briefly, preventing any significant
> amount of heat if at all, from affecting the inside of
> a meteorite.  Once the atmosphere has overcome the
> initial velocity of a space rock (assuming that we are
> talking about a typical sized meteorite with average
> initial velocity) the ablation process ceases and dark
> flight begins where the rock finishes its journey by
> gravity alone.  It is generally accepted that
> somewhere during its final moments in space(sic), the
> molten outside solidifies into what is known as a
> fusion crust before hitting the ground.
> 
> In support of hot meteorites, I must agree that it
> seems possible that some meteorites, preferably the
> iron types, can undergo a kind of "preheating" in
> outer space by the influence of the sun.  After all,
> isn't the sun's radiation how comets grow their
> dazzling tails?  The exact temperature rise it may
> cause in a meteorite can depend upon a great deal of
> factors, including size, composition, distance, the
> orbit, etc. In any event, it boils down to the fact
> that if a meteoroid is hot right before beginning its
> fiery descent, that heat will be largely unaltered if
> some of the rock survives as a meteorite on earth.
> The same reasoning, I think, will hold true for
> whatever the original temperature the meteoroid is at
> right before entering our planet's atmosphere.  Of
> course, this is just one of many ways that could
> explain the possible existence of hot space rocks.
> 
> In regard to scientists' objections to hot meteorites
> on the basis of naive or deceitful witnesses or by how
> the idea collides with their thinking is highly
> deplorable.  Firstly, a scientist should always keep
> an open mind, as it is unscientific to do otherwise.
> Moreover, it should be in the interest of a scientist,
> even if it is only subconscious, to seek the "truth"
> in all things and not a quick "plausible" explanation
> to satisfy his own minute understanding of the
> universe.  Adding to that, it is illogical to dismiss
> the reports of hot space rocks, since as far as I
> know, no scientist has ever been present moments after
> such a celestial impact area to take readings.
> Needless to say, it is also unfair to quickly jump to
> the conclusion that all people are feeble-minded and
> unscrupulous.
> 
> Lastly, it should not be forgotten that the common
> layperson was the essential key in braking the closed
> minds of scientists some two hundred years ago, to
> except that rocks really do fall from the sky, and
> that fireballs can make some strange static-like
> sounds known as electrophonics.  If it weren't for
> them, the science of meteoritics and our appreciation
> of meteor hunting would have been delayed for some
> time and probably not nearly as understood as it is
> now.
> 
> My e-mail is marktfoxvdb@yahoo.com.
> 
> Please forgive me if I have strayed off topic too
> much.
> 
> Best regards,
> 
> Mark Fox
> Newaygo, MI
> Ï
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