[meteorite-list] Statistics for falls

From: Sterling K. Webb <kelly_at_meteoritecentral.com>
Date: Thu Jun 17 02:45:09 2004
Message-ID: <40D13E2E.243D35FD_at_bhil.com>

Hi, Tracy, List,

    It all depends on what you mean by "annual meteorite fall rates"?

    Turning to the record and outlining the number of observed, recovered,
analyzed, recorded, named, museumed, and collected space rocks yields a number
at the end of a long, long selection process.

    On the other hand, "annual meteorite fall rate" could mean how many rocks
enter the earth's atmosphere and survive to land on the ground somewhere whether
anybody finds them or not.

    These are two vastly different figures.

    The most widely quoted figure is from Canada's MORP (Meteor Observation and
Recovery Program, I think it stands for. I've been calling it MORP for so long I
forget. They say about 25,000 objects per year yielding 100 gram to 10,000 gram
meteorites on the ground.

    The first person to dare to estimate the figure was Ninninger, of course. He
screwed his courage up enough to suggest 500 such meteorites per year, but
privately wrote that he though it could be ten times bigger (5000 per year).

    If you like digging in the MetList archives, you'll find a fat posting on
Nov. 9, 2000, (and a lot of replies) where I outlined a different method of
estimating the fall rate and came up with a figure of 50,000 to 80,000 per year,
based on how many meteorites hit cars. The method is the same as is used in
nuclear physics to calculate "collisional cross sections." No reason why it
shouldn't work for space rocks too! (Hey! A particle is a particle is a
particle.)

    Oddly enough, with Worden and Park Forest, there have now been more car hits
per decade than even my estimate of a fall rate of 50,000 to 80,000 would have
predicted, corresponding to a rate more like 100,000 to 120,000 per year.
(Credit where credit is due: Rob Matson was the only one who thought my tripling
of the MORP rate was too low and suggested 100,000+ per year.)

    As to whether it's increasing, why, we'd have to agree on what the fall rate
is now, and what it once was and how to measure it and so forth before assessing
whether it was changing... It does seem that things are a little busy right now,
but, is it a blip?

    What's he get if he wins the bet? A lifetime supply of those little pink
umbrellas? The right to pick the channel on the TV over the bar for a month? A
steak dinner? A meteorite magnet to re-direct all the falls over Hawaii to your
house? A meteorite crash helmet to wear on the way to the bar?


Sterling K. Webb
-------------------------------------------------------------------------------
tracy latimer wrote:

> Aloha, all!
> My husband is in the middle of what amounts to a 'bar bet'. He is trying to
> find out annual meteorite fall rates, and whether, in recent years, there
> has been an increase. I have been searching for fall rates online without
> much success; I even attempted to contact the meteorobs newsgroup, but my
> mail to them was bounced back. Does anyone have a link to a resource that
> might have this information?
>
> Duck-n-cover,
> Tracy Latimer
>
> ______________
Received on Thu 17 Jun 2004 02:46:07 AM PDT