Dear Francis,
I was thinking exactly the same angle already posted by Larry, so let me
just comment on your question:
"And at what size level does a meteorite cease to be of interest?"
by offering the opinion:
At the level it ceases to contain any information attributable to
meteoroids, meteorites or their parent bodies. Since this will change with
time and technology, the question may be time and resource dependent.
However, your inquiry about whether any of these particles have been
analyzed (or imo, capable of being analyzed at present), stands.
It would seem to me, that a very good project for schools would be to
organize a collection protocol for educators in the style of the superb
International Monarch Butterfly tagging program (or also like SETI on home
computers), to collect large amounts of this material, set up a factorial
experimental design to test certain hypothesis and bulk sample differences,
by appropriately submitting these for testing.
I would imagine that this is an experiment that neither the ESA nor NASA
have the resources nor mandate to do, yet could lead to profound insight on
the nature of cometary particles on Earth and make a very good contribution
to science by enthusiastic young scientsits to be. Or I darkly suspect,
more likely an application of the scientific method to disprove a popularly
held theory theory regarding most of the materials recovered in this way -
either way, a great exercise for teaching meteorites and science in general
with a problem, methodology, and a participative attitude.
Surely there is some work on this out there, but sample size and scope
restrictions make this an ideal educator's project looking only for someone
like you to organize. Just need a partner in the scientific community
willing to lead in the intrumental analyses and sample preparation.
Best Wishes and Good Health,
Doug
----- Original Message -----
From: <[EMAIL PROTECTED]>
To: "Francis Graham" <[EMAIL PROTECTED]>
Cc: <[email protected]>
Sent: Tuesday, November 20, 2007 8:49 AM
Subject: Re: [meteorite-list] Brownlees in Rainwater
Hello Francis:
I do not pretend to be an expert on this subject, but the simple answer to
at least oneof your questions is that there is no indication that any of
the micrometeorites (and thus what you might get in rainwater) is
planetary or lunar. The ones collected in the upper atmosphere are either
from asteroids or comets. It may be that some very small percentage is
planetary/lunar, but these might be so rare as to be lost in the noise.
Larry Lebofsky
On Tue, November 20, 2007 7:31 am, Francis Graham wrote:
Dear List
I have a question which has been vexing me for some
years. I was introduced to a method of collection of
micrometeorites by Larry Megahan some years ago, which consisted of
collecting rainwater and then wrapping a powerful rare Earth magnet in
Saran (TM)wrap. Placing
the Saran wrap on a glass plate, and examining it under the microscope,
one
could see many ferromagnetic particles. Some were rounded and ablated and
it was a strong guess that these were micrometeorites. I have had some
students try this project and indeed some of the particles are
microspheroids of ablated iron, similar to so called "Brownlee particles"
colected in the stratosphere. But I have reason to be suspicious,
especially if the collection is near a former industrial or mining site.
MY
QUESTION IS, has this method, widely circulated
in presecondary teaching circles, ever been critically evaluated by
electron microprobe analysis, X-Ray fluorescence or some such? And at
what
size level does a meteorite cease to be of interest? It would naively
seem,
that although a very very very tiny percentage of meteorites are lunars
or
Martians, if a way to rapidly identify micrometeorites
can be done, a lot more information on Mars and the Moon could be
obtained,
simply because there are so many micrometeorites. This would include
collection in the stratosphere as Brownlee did, maybe piggybacked on
surveillance aircraft. But one question at a time.
Francis Graham
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