(meteorobs) ?Errant Geminid? - Meteorite Destroys Warehouse inAukland, New Zealand?

[Alister]

It is a common myth that meteorites are still hot enough to cause fires. 
Only a *tiny* percentage can. While I don't have peer-reviewed numbers at my 
fingertips, you need to be looking at least at ground arrival size in the 
cubic metre/yard range.

The recent fall on the Alberta-Saskatchewan border (Nov 20-21, 2008) had a 
13-kg (28-lb) piece (smaller than a 10-pin bowling ball) made a hole about 
half its depth, with not the slightest evidence of any singing of the very 
dry grass.

Remember that fireballs stop glowing at altitudes of roughly 50km 
(30-miles), so they have 45km of falling through air that is MINUS 40 F/C or 
colder. (The space shuttle stops glowing at Mach 12, similar altitude, 
160,000 feet).

Ballistically, without atmosphere, d = 1/2 * a * t^2, so 45,000m means 95 
seconds of fall, but one can assume it will be longer because it will be 
slower. Even at 200m/s, the wind chill is almost beyond imagination. Even if 
it started red hot, that's plenty of cooling by the time it hits the ground. 
Remember the Peekskill fall some 10 years ago? Broke through the roof, hit a 
couch, then bruised a person. They said it was warm, nothing more.

It also makes sense when one thinks of the Apollo return capsules - no huge 
cloud of steam when they touched water. None of the returning Soyuz capsules 
cause wildfires. Sure the composition/duration are different from 
meteorites, but they're the same order of magnitude.

You would need to be talking an object that is supersonic fireball all the 
way to ground before it can cause a fire.

The day after the Nov 20 meteorite, there was a report from a farmer whose 
barn had caught fire - we all figured it was an attempt to get insurance 
money - and of course it turned out nowhere near the fall.

Alister Ling
Edmonton, Alberta.


----- Original Message ----- 
From: <Desantisk at aol.com>
To: <meteorobs at meteorobs.org>
Sent: Sunday, December 14, 2008 10:22 AM
Subject: (meteorobs) ?Errant Geminid? - Meteorite Destroys Warehouse 
inAukland, New Zealand?


>
> This link came across the Amateur Astronomers Association of  Pittsburgh
> listserver:
>
> _http://www.nzherald.co.nz/nz/news/article.cfm?c_id=1&objectid=10547987_
> (http://www.nzherald.co.nz/nz/news/article.cfm?c_id=1&objectid=10547987)
>
>
>>From the Monday, December 15, 2008, New Zealand Herald newspaper:
> "Some people were convinced the fire was caused by what may have been a
> meteorite, which was seen from various parts of the upper North Island 
> streaking
> across the sky just after 10 o';clock.?"
>
> Perhaps an errant Geminid?
>
> Kathy DeSantis
> **************Make your life easier with all your friends, email, and
> favorite sites in one place.  Try it now.
> (http://www.aol.com/?optin=new-dp&icid=aolcom40vanity&ncid=emlcntaolcom00000010)
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