From: "Ted White" <twhite8 at cox.net>
To: "WSFA members" <WSFAlist at WSFA.org>
Subject: [WSFA] Re: meteorite question
Date: Mon, 14 Jun 2004 11:38:22 -0400
Reply-To: WSFA members <WSFAlist at WSFA.org>

----- Original Message -----
From: <ronkean at juno.com>
To: <WSFAlist at WSFA.org>
Sent: Monday, June 14, 2004 4:32 AM
Subject: [WSFA] Re: meteorite question

>
> On Mon, 14 Jun 2004 00:00:40 -0400 "Ted White" <twhite8 at cox.net> writes:
>
> > I find it astonishing that any meteorite's flaming trip through our
> > atmosphere would leave it *needing* to be dried out in an oven.
> >
>
> At first thought, yes.  But now it occurs to me that a meteorite could
> land in a wet condition if it were raining at the time it fell to earth.
> Perhaps the experts advise drying a freshly fallen meteorite to arrest
> any chemical action which might occur while the meteorite was wet, and to
> avoid having contaminants wick into the interior of the meteorite,
> carried by the water.  Indeed, even if it were not raining on the ground
> at the time, it is conceivable that a meteorite could pick up some
> moisture while passing through the atmosphere, if the meteorite were cool
> enough to not boil it off before reaching the ground.  Perhaps meteors in
> a given range of size and density can cool off while passing through the
> cold air a few miles above sea level.  I have heard of a few instances of
> meteorites striking and penetrating houses, but I don't recall it being
> noted that such meteorites were very hot, or started fires.
>
> The meteorite was 'grapefruit sized', weighing 1.3 kg.  Assuming the
> object was a sphere of 6 cm radius, it would have a density of about
> 1.44, which seems low, for a stony meteorite, and way too low for a
> metallic (iron-nickel) meteorite.  Working it another way, assuming a
> density of 2.5 for a stony meteorite, the radius would be 5 cm, and that
> is just barely consistent with it being 'grapefruit sized'.
>
> Assuming a sphere of 5 cm radius and a density or 2.5, per
>
> http://hyperphysics.phy-astr.gsu.edu/hbase/airfri2.html#c5
>
> the terminal velocity would be about 71 meters per second or 159 miles
> per hour.  It doesn't seem very likely that a 3 pound rock falling at 159
> miles per hour would penetrate a typical plywood roof deck, so perhaps
> meteorites of that size and weight usually hit the earth at considerably
> more than terminal velocity.  In one case I heard of, a meteorite passed
> completely through a house and was recovered in the crawlspace underneath
> the house.

Your calculations are thrown off by reality.  I saw TV footage of both the
holes it made and people holding it.  It wasn't spherical, but was more
"rock-like" in shape.    It wasn't raining when it hit, and I doubt it
picked up any atmospheric moisture.  It was said to have been
"basketball-sized" when it *hit* the atmosphere and obviously lost more
than half its size in the descent.   This implies a *lot* of heat -- enough
to burn off its outer layers.

--Ted White