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Re: (meteorobs) Temperatures of newly fallen meteorites

Paul and list,

The general literature on meteorites has meteorites as being more frequently cold than warm or hot, although all possibilities occur.  Since ablation is mainly a surface phenomenon you are right that a short atmospheric passage time probably leaves the meteorites core still cold as it ramps up from generally frigid outer space.  But keep in mind that it is really a heat transfer issue where on one hand you can have say a 50 kg ferro-nickel shield shaped oriented piece of metal (I.e. the Cabin Creek fall in the 1880's which was quite hot to touch) getting pretty hot due to its forced frictional interaction (i.e. an iron meteorite with a parent body having differentiated) and the other hand, you might get an oriented elongated nosecone shaped stone cutting though the atmosphere and getting quite frosty upon falling.  Taking into consideration the heat transfer coefficient (iron is higher than stone), orientation/aerodynamics (bullet shaped minimizes frictional heating, shield maximizes and tumbling, the most common still tends to be cold), and weight/size (a faster fall for a larger object take more heat conduction and is somewhat analogous to the question of "what is the right speed to travel in the rain to minimize how wet you get after traveling distance X) you can get a feel for the coldness to touch.  This is undoubtably covered in O. Richard Norton's Cambridge Encyclopedia of 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.  It's my recollection that most meteorites are cold when the hit the ground.  I recall reading somewhere that newly fallen meteorites are often coated with frost if found immediately after falling.  
 
Since the transit time through the atmosphere is so short, there is not enough time for heat to transfer from the surface of the meteor into the interior.  Most of the heat generated by friction is carried away by the ablated material.  Consequently the average temperature of the mass remains low and the meteorite lands cold.
 
I'm suspect there is some hard data in the literature on this subject.  Anyone have a reference?
 
Paul Sharko