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Re: (meteorobs) Amateur micrometeorite hunters pictures



Date: Mon, 17 Dec 2001 20:08:31 +0100
From: "Marco Langbroek" <marco.langbroek@wanadoodot nl>
Subject: Re: (meteorobs) Amateur micrometeorite hunters pictures

- ----- Original Message -----
From: "Jim" <sunwatt@starbanddot net>
Sent: Sunday, December 16, 2001 12:46 AM

> This material was collected where the rain washes off my roof, with a
> small magnet inside a ziplock bag. I have no idea if I found any
> micrometeorites yet.
>
> Maybe someone can have a look and give me their opinion.

>Dear Jim,

>First, let me point out that I am very positive to your experiment. But I am
>affraid that I think that the particles you show are terrestrial soil
>particles. Soil particles often contain magnetite and hence are attracted to
>a magnet. 

Thanks Marco, I think you are right. But never fear, this has been a
learning experience for me, so no shame in being wrong!  <G>

Here is a bit I copied from an email from Mike Zolensky of NASA.

"Even using the magnet is not much help, since the vast majority of
magnetic
material in the atmosphere is from power plants, and dust from those is
everywhere, even at the South Pole.  That is why we collect dust in the
stratosphere, although even up there (20km)the extraterrestrial material
is
only a few percent of all of the dust".

My interest in collecting micrometeorites began on the morning of
November 17th (?) after watching the leonid meteor storm. In which I saw
10 per minute one hour before the predicted maximum. At that time clouds
arrived to spoil the show. I switched on NASA Select TV and watched a
woman speaking about how MM were plentiful, and could be collected after
a rain.

So I did some web searching and found some information that suggested it
might not be so hard to collect mm's. One site suggests the project is
suitable for children 5 to 7 years old with help from a teacher!

http://www.madsci.org/experiments/archive/913517663.As.html
http://www.eecs.umichdot edu/mathscience/funexperiments/agesubject/lessons/jpl/micromet.html


>The morphology and structure of the particles on your photograph
>does not match those for micrometeorites, which generally are spherical or
>subspherical. Admittedly, my own experience is with true spherules (the most
>common type of microscopic meteorite material), but my assesment in this
>case was underlined by a comment I asked from the IDP expert at UNM with
>which I collaborate. I am myself involved in the search for cosmic
>spherules: I've recovered spherules from 400 000 year old sediments from an
>archaeological dig in the Schoeningen quarry, Germany. It took me several
>weeks sifting through the <0.5 mm fraction of sieving residues of a very
>large amount of sediment to find only a handfull of spherules.
>The problem with catching airborn particles at rooftop level is that you
>also catch a lot of man-made pollution (and soilparticles), which sometimes
>travel far by the way, in that way. Some of those mimmic MM's and spherules,
>and sometimes you need a SEM analysis to tell the difference. That is why
>researchers mostly turn to recovering MM's from more pristine environments,
>like polar ice, deep sea sediment cores, or old sealed sediment layers.
>A suggestion for the future: inclusion of a scale bar on the
>photographs would aid assessment. MM's are typically 20-500 microns, with
>most near 200 microns.

I will try and do that. Or at least label the pictures with the
magnification that was used.

>The best thing you can do to start with, is concentrate your search effort
>on perfectly spherical objects in the given size range. That already rules
>out many (but not all) other magnetic particles that are not MM's but which
>you can also trap with your magnetic device.

I have the rainwater that I collected after the Geminid meteor shower,
and will go ahead and pour it through a coffee filter. You never know, I
might get lucky!

Thanks Marco

Jim

>Marco Langbroek
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