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Re: (meteorobs) Temperatures of newly fallen meteorites

I also enjoyed reading Doug's post.  Thanks, Doug!

At 10:27 AM 3/12/2004, you wrote:
>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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Dr. Tony Phillips, editor
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