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(meteorobs) Re: Meteoroid Size



In a message dated 98-10-02 16:33:00 EDT, you write:

Lew<< 
 The figures I've always seen in the literature for meteoroid densities were
 (with the exception of the Geminids) always in the sub-gram/cm^3 range also,
 George. One thing I noted was these studies were of brighter shower members.
 Could this unexpectedly high figure for cometary showers be the result of a
 relationship between particle size and density in cometary meteoroid streams?

In other words, are "normal" brighter meteors far more dense than "normal"
 less bright ones for some reason? Thinking about the "dirty snowball" model,
 it seems at least plausible to imagine that any particle large enough to be
 a fireball might actually have been a more dense "rocky" particle embedded
 in the comet nucleus... Jim, did those papers you mention mention or account
 for any sort of sampling bias with respect to size?<<
 
From what I'm reading on page 30, it doesn't indicate a separation of brighter
from dimmer members of a shower in the study. It concludes with the statement
of, "Whipple's dirty snowball model of cometary nuclei may need to be shifted
towards a frozen mudball containing a larger fraction of dust and other
nonvolatile substances than was previously thought."
 
 Lew>>BTW Bob, I understood from Petr that Phaethon (parent body of the
Geminids)
 probably CANNOT have been a comet once, since it is rotating so fast now.
 But then again, if comets really turn out to be very dense, maybe that
 changes the interpretation of Petr's results??<<

Yes, I remember Petr having this in his posting also. This is what got my
attention originally for me to keep it for reference. I'd guess that the
rotation would be so fast that it would fall apart if it was a dirty snowball
composition. But being a mudball would still have the same problems if all the
dense parts were cemented together from the same kind of frozen volatiles
wouldn't it?
 
George Zay
 

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