[meteorite-list] Re: Comet: Talking Points, #1

[Marco Langbroek]

Sterling, did you ever see a cosmic dust particle under the microscope, let
alone have you searched for them?

I did. I searched for and found cosmic spherules in sediment samples from an
archaeological excavation. (you see: I like experimentation too. When the 
results of the SEM investigation on one of the particles done by a friend of 
mine who studies cosmic dust as a profession came in, I did not open a beer as I 
don't like beer, but a good bottle of wine)

What we are talking about here is a significant flux of large meteoroids 
entering our atmosphere and creating airbursts (given the lack of impact 
craters), if this theory is correct.

As they disintegrate in the atmosphere they enrich it with dust. Not
just fine dust. Dust in the range of a few micron to up to half a millimeter.
The fine dust capable of blocking sunlight by being airborn for a long time, is
only part of the equation.

And such events leave their detectable mark in lake deposits, dune deposits,
deep sea deposits, ice deposits, peat deposits.

Here is such a case of a detectable dust layer in Antarctic ice (camouflaged by
abundant tephra layers in the same ice deposit, and still then it has been
found). And this one the researchers believe was due to one, only one, big
meteor event over the area:

- Harvey, R. P. et al., 1995: A Meteoritic Event Layer in Antarctic Ice.
Meteoritics 30:5, p. 517

If the skies of AD 540 dayly resounded with thunder from meteoric airbursts, the
enhanced dust influx due to it should be visible. And cosmic origin dust, due to 
not only its isotopic but also its petrological signatures, is recognizable as 
such, nothwithstanding all your blah blah. One of my friends made a career out 
of it.

- Marco


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Dr Marco Langbroek
Dutch Meteor Society (DMS)

e-mail: meteorites at dmsweb.org
private website http://home.wanadoo.nl/marco.langbroek
DMS website http://www.dmsweb.org
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