[meteorite-list] Brownlees in Rainwater

From: lebofsky at lpl.arizona.edu <lebofsky_at_meteoritecentral.com>
Date: Tue, 20 Nov 2007 07:49:05 -0700 (MST)
Message-ID: <2570.>

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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Received on Tue 20 Nov 2007 09:49:05 AM PST

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