[meteorite-list] British Study Attempts to Calculate Odds ofBeingHit By a Meteorite

From: Darren Garrison <cynapse_at_meteoritecentral.com>
Date: Mon Jul 31 20:05:56 2006
Message-ID: <n95tc2d78j8jn85sh1pvmbr7urroa2ponh_at_4ax.com>

On Mon, 31 Jul 2006 17:21:49 -0500, you wrote:

> This what I get for doing arithmetic at 3 in the am.
>Off by a factor of two, but so are you. Since you can't
>decide where in the circle of destruction you will be,
>the mean maximum distance would be the radius of the
>circle, or 1358 feet, the circle always being defined as
>having its center at the impact point.
> That's about a quarter mile. Let's see. Up to 6 tons
>TNT force. 100's of tons of ejecta at 100's of mph.
>Ok, you stand on the edge of the circle. I'll take those
>bleacher seats. We'll both have video cameras, and I
>know you'll get the better pictures, but I'll feel safer.
> The question of target ground composition is just
>luck. Unconsciously, I assumed limestone bedrock
>not far down. (There's a quarry right in the dead
>center of my town...) Maybe I'd feel safe it was all
>dirt... And IF we knew the impactor was an iron.
> But it's a one ton stone (all stone; no mesosiderites)
>fragment impacting at hypersonic speed, I don't want
>to be only 1/4 mile away regardless of target. I'll be
>in the bleachers, with my face painted in Team
>Meteorite colors, waving the Meteorite flag,
>video camera (Zoom X10) at the ready.
> But if it's one pound stones falling at 120 mph,
>I'll be running around the strewn field with little red
>tag-flags, GPS, camera, baggies... and a big hard hat.

I was assuming that a one ton meteorite would still be too small to retain
cosmic speeds and this web FAQ agrees with that
http://www.amsmeteors.org/fireball/faqf.html#12 -- if that info is accurate, a
meteorite would need to be 8-10 tons to retain part of its cosmic velocity. And
my assumptions of ground condition, like yours, were based on what is around me.
Here in the foothills of South Carolina I'm sitting on the eroded remnants of
the Appalachians and I have no idea just how deep under me I'd have to dig to
hit any bedrock-- I've read that the clay is hundreds of feet thick towards the
coast-- but I do know that my well is 40 feet deep and goes through clay all the
way down. So for here, with a 1 ton iron falling at 200 to 400 MPH, I'd think
the effect would be a big splat and a shower of dirt. I'd be willing to chance
standing a few hundred feet from that with a camera and an umbrella. When
planes that weigh more than a ton crash at terminal velocity, they don't kill
everything within a 133 acre area. (And, oddly enough, in the mid 1940s a
bomber filled with bombs DID crash right here within a few hundred feet of where
I'm sitting. The pilots parachuted out and took shelter behind the chimney of
my grandmother's house, and the government spent some time aftwards scouring the
area with metal detectors to find every last piece of the plane and payload- but
that's a different story).
Received on Mon 31 Jul 2006 08:06:57 PM PDT