[meteorite-list] Antarctic meteorite stats

From: tracy latimer <daistiho_at_meteoritecentral.com>
Date: Thu Apr 22 10:16:31 2004
Message-ID: <Sea2-F50HYR5EbYyjlM0000fd60_at_hotmail.com>

Considering that there has been a scientific presence on the Antarctic ice
cap for the past 30+ years, a good place to start might be: How many
witnessed falls are there from Antarctica? Even from remote locations in
the taiga and Yukon, there have been documented falls in that length of
time. And in the last couple of years alone, there have been at least 2
falls I can think of from the Saharan areas.

Tracy Latimer


>From: "Matson, Robert" <ROBERT.D.MATSON_at_saic.com>
>To: 'almitt' <almitt_at_kconline.com>,meteorite-list@meteoritecentral.com
>Subject: [meteorite-list] Antarctic meteorite stats
>Date: Fri, 8 Aug 2003 18:36:18 -0700
>
>Hi All,
>
>On the question of the total mass of all Antarctic meteorites,
>Al commented:
>
> > This is and would be an important consideration. I have noticed
> > that a lot of the Antarctic falls are sometimes very small. Total
> > mass would shed an interesting correlation to non-Antarctic finds.
> > ... Also the Antarctic falls are from hundreds and thousands of
> > years ago. Perhaps as much as 800,000 years ago, so there is a
> > concentration of the falls on the ice sheets which may be
> > distorting the numbers more.
>
>This is part of the reason that despite the huge number of statistical
>samples from Antarctica, it would be very difficult to compute an
>accurate annual meteorite fall rate from them. Among the many
>factors you would have to consider:
>
>1. Movement of the ice sheets over tens of thousands of years.
>Where meteorites are found today is not easily correlated to
>where they actually fell. A square kilometer of a particular patch
>of ice today may correspond to a quite different size and shape
>for that surface in the past. You also have zones of concentration,
>where large effective collection areas have been compressed into
>small strips. Searching 1 km^2 of such a surface may be the
>equivalent of searching 10, 100, or even a 1000 km^2.
>
>2. Variable meteorite fall rate over the last half-million or
>more years. The long lifetime of meteorites in Antarctica means
>that any derived fall rate will represent an average over that
>lifetime. It is likely that the flux today is different from
>what it was several hundred thousand years ago. I doubt that
>scientists have done terrestrial age dating on more than a tiny
>fraction of Antarctic finds, so you have both the uncertainty
>of the average age of all your samples and the temporal
>variability in the flux rate.
>
>3. Pairing uncertainty. Geographical location of the finds doesn't
>help you much if the surface doesn't stay put. ;-) Pairing of rare
>types can at least give you a good estimate of the average number of
>specimens per fall (somewhere in the range of 3-6), so this ratio
>can simply be applied to the common types.
>
>With these factors in mind, has anyone attempted to estimate the annual
>fall rate derived from the number of Antarctic meteorite finds?
>
>Cheers,
>Rob
>
>
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Received on Fri 08 Aug 2003 09:45:06 PM PDT