[meteorite-list] Iridium (+ Osmium ? + Technetium ?) measuring and testing

From: Darren Garrison <cynapse_at_meteoritecentral.com>
Date: Sat, 14 Mar 2009 23:18:33 -0500
Message-ID: <bcuor45dmjn35bd5kigf5cieuhqj0dsdl4_at_4ax.com>

On Sun, 15 Mar 2009 03:25:05 +0100, you wrote:

>A- measuring on the field/ meteorite finding/ first testing:
>I read often that finders/hunters use magnets. What about a metal detector
>measuring Iridium ?
>or is Iridium detection too close to other elements, or too small in content
>to be singled out ?
>and what about Osmium ? or Technetium ?
>
>B- testing
>How is Iridium (or Osmium, or Technetium) analysed and tested ?
>Is there any non-invasive way to test one or more of them, to keep the
>meteorite "as is" ?

I was sitting here trying my best to remember the name of a type of measurement
used to find very small amounts of atoms in materials (as is often the case) it
wasn't coming to me. Fortunately I remembered it being described in a book by
Walter Alverez called T. rex and the Crater of Doom, searched down my copy and
was reminded that it is "neutron activation analysis". Good book on the
detective work behind the discovery of the iridium (and other rare element)
concentrations at the K/T boundary. You should try to get your hands on a copy.
You can preview big chunks of it on Google Books:
http://books.google.com/books?id=kkHhl67ixwEC&printsec=frontcover&dq=rex+and+the+crater+of+doom#PPA66,M1

Use the right-hand search window to search for "neutron activation analysis" in
the book.

http://en.wikipedia.org/wiki/Neutron_activation_analysis

As for technetium, I wouldn't hold my breath about finding much of it. Very
short half life, both in human terms for some isotopes (hours to days) and in
cosmic terms (at most a few million years, a blink of the eye in the age of a
meteorite). The amount (from some googling) produced naturally by uraium decay
and neutron absorbtion in molybdenum seems to be vanishingly small. Doesn't
look to be much to be a mesurable amount to picked up from the solar wind
(though this article is pretty old)
http://www.new.dli.ernet.in/rawdataupload/upload/insa/INSA_1/20005aca_407.pdf

Here's an article touching on the decay products of technetium in meteorites:

http://wwwsoc.nii.ac.jp/jnrs/paper/JN63/jn6325.pdf

and another:

http://www.lpi.usra.edu/meetings/lpsc2004/pdf/1877.pdf
Received on Sun 15 Mar 2009 12:18:33 AM PDT