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Re: (meteorobs) Temperatures of newly fallen meteorites

I'm relatively new to the list.
So thank you very much for the post, Doug!!

-Roger Greenwood

On Mar 12, 2004, at 8:14 AM, Peter Brunone wrote:

>
> 	I thought it was very informative, but then again, I'm probably
> on the more uneducated end of the spectrum here (as meteor studies go).
>
> Peter
>
> -----Original Message-----
> From: owner-meteorobs@atmob.org [mailto:owner-meteorobs@atmob.org] On
> Behalf Of joseph_town@attdot net
> Sent: Friday, March 12, 2004 2:32 AM
> To: meteorobs@atmob.org
> Subject: Re: (meteorobs) Temperatures of newly fallen meteorites
>
>
> Doug,
>
> Ease up. I think most of us are aware of all that.
>
> Bill
>
>
> Paul and list,
>
> The general literature on meteorites has meteorites as being more
> frequently= =20 cold than warm or hot, although all possibilities 
> occur.
> Since ablation is=20 mainly a surface phenomenon you are right that a
> short atmospheric passage t= ime=20 probably leaves the meteorites core
> still cold as it ramps up from generally= =20 frigid outer space.  But
> keep in mind that it is really a heat transfer issu= e=20 where on one
> hand you can have say a 50 kg ferro-nickel shield shaped orient= ed=20
> piece of metal (I.e. the Cabin Creek fall in the 1880's which was quite
> hot=20= to=20
> touch) getting pretty hot due to its forced frictional interaction 
> (i.e.
> an=20 iron meteorite with a parent body having differentiated) and the
> other hand,= =20 you might get an oriented elongated nosecone shaped
> stone cutting though the= =20 atmosphere and getting quite frosty upon
> falling.  Taking into consideration=  the=20 heat transfer coefficient
> (iron is higher than stone),=20 orientation/aerodynamics (bullet shaped
> minimizes frictional heating, shield=  maximizes and tumbling,=20 the
> most common still tends to be cold), and weight/size (a faster fall
> for=20= a=20 larger object take more heat conduction and is somewhat
> analogous to the=20 question of "what is the right speed to travel in
> the rain to minimize how w= et you=20 get after traveling distance X)
> you can get a feel for the coldness to touch= . =20 This is undoubtably
> covered in O. Richard Norton's Cambridge Encyclopedia of= =20
> Meteorites, which I don't have handy at the moment.
>
> Saludos
> Doug Dawn
> Mexico
>
>
>
> I think it's unlikely that a meteorite could cause a fire.=A0 It's 
> my=20
> recollection that most meteorites are cold when the hit the ground.=A0 
> I
> rec= all reading=20 somewhere that newly fallen meteorites=A0are
> often=A0coated with frost if fo= und=20 immediately after 
> falling.=A0=A0
> =A0 Since the transit time through the atmosphere is so short, there is
> not=20 enough time for heat to transfer from the surface of the meteor
> into the int= erior.=A0=20 Most of the heat generated by friction is
> carried away by the ablated=20 material.=A0 Consequently the average
> temperature of the mass remains low an= d the=20 meteorite=A0lands 
> cold.
> =A0 I'm suspect there is some hard data in the literature on this
> subject.=A0=20 Anyone have a reference? =A0 Paul Sharko
>
>
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