[meteorite-list] Fireballs & Known Meteor Showers

[Chris Peterson]

The thing is, we really have a very poor idea what comets are made of. 
Despite a few probes, they remain very mysterious things. Some comets may 
essentially be asteroids with volatiles, some asteroids may be comets that 
no longer have volatiles. The connection between comets and CC-like material 
is pretty tenuous, as well. We don't know if cometary material fails 
(generally, or always) to make it to the ground because it's too fragile, or 
because the meteoroids in a cometary debris trail are simply too small.

The reliable way to say that a fireball is unrelated to a shower is not 
mineralogical, but depends on identifying the source of the parent body- 
either the radiant or the actual orbit. I try to rule out active showers 
with every fireball I investigate. Although I have a fair degree of 
confidence from the beginning whether I'm seeing something of cometary or 
asteroidal origin, it never hurts to support that with evidence. 
Fortunately, there seems to be plenty of instrumented data on the Wisconsin 
event to establish the radiant with fair accuracy. If the radiant matches an 
active shower, we don't know for certain what's going on. But if it doesn't, 
we can conclusively disassociate the fireball from known showers.

Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com


----- Original Message ----- 
From: "Sterling K. Webb" <sterling_k_webb at sbcglobal.net>
To: "Meteorite List" <meteorite-list at meteoritecentral.com>
Cc: <GeoZay at aol.com>
Sent: Friday, April 16, 2010 2:17 PM
Subject: Re: [meteorite-list] Fireballs & Known Meteor Showers


> Carl, List,
>
>> how we know with certainty  that the WI fall is not
>> related to the known shower of the same time period?
>
> The Wisconsin Stone is a probable H5. The source
> of the Lyrid meteor shower is Comet Thatcher (C/1861 G1).
> I doubt that Comet Thatcher is an H5 condrite body.
> It sure don't act like one...
>
> "Certainty" is a tricky term. I've never been to Comet
> Thatcher and drilled into it, so I can't swear you out
> an affidavit that it isn't an H5 body, but the claim that
> it is would be extraordinary.
>
> And extraordinary claims require extraordinary proof,
> as another guy named Carl used to say...
>
>
> Sterling K. Webb