[meteorite-list] Dino Killer size

[mexicodoug at aim.com]

Hi Ted, Darren, Listees,

Thanks to Ted for the link of the first paper (should scientists now 
mind their pdf's or perish rather than call them "papers") to use 
isotope (vs. elemental, i.e. Iridium) presence/ratios to show the 
proposed K/T impactor was a carbonaceous chondrite.  As the authors 
show, it was done by confirming especially high chromium 54-Cr as well 
as a 53-Cr proportion compared with the terrestrial 52-Cr baseline, 
according to the pdf.

Darren, I believe Ed asked if it was a carbonaceous chondrite and that 
is what Ted responded to, not whether it was "wet" or "dry" with water 
and other volatiles, which is another topic entirely.

As to the comment that a dry carbonaceous chondrite is called an 
"asteroid" and a wet one, a "comet", while that sounds nice and 
logical, I think it is a little misleading in common speech (just like 
his comment on dihydrogen monoxide which we all better know as water, 
so perhaps Darren is joking around).  As we know best, the fate of many 
comets is fragmentation (and we've even seen impact), and this is 
nearly complete into little grains as far as we can tell in meteoroid 
streams.  Rubble-Pile is a possibility after "drying" - but has this 
been proven?  Other asteroids are called "dormant comets" under the 
impression that they are mostly inactive at their perihelia, though a 
change could "revive" them.

I am not sure we ought to call something a comet that is half baked and 
has never errupted.  For this reason neither Pluto nor Ceres are 
normally called comets.  Hidalgo, I couldn't begin to guess... But he 
was a great man and also fine Mustang...

Best wishes and Great Health,
Doug


On Sun, 13 Apr 2008 09:32:33 -0700, you wrote:

>According to Cr and Mn isotopic analyses of KTB samples, the impactor 
was a
>carbonaceous chondrite - see report at:
>
>http://www.lpi.usra.edu/meetings/impact2000/pdf/3041.pdf
>

Yes, but it appears that comets are essentially carbonaceous chondrites 
that
formed far enough from the sun to not lose their volitile mineral 
ddihydrogen
monoxide.  So saying that it is a carbonaceous chondrite doesn't 
conclude if it
iwas a wet one (called a "comet") or a dry one (called an "asteroid




-----Original Message-----
From: Darren Garrison <cynapse at charter.net>
To: meteorite-list at meteoritecentral.com
Sent: Sun, 13 Apr 2008 12:51 pm
Subject: Re: [meteorite-list] Dino Killer size



On Sun, 13 Apr 2008 09:32:33 -0700, you wrote:

>According to Cr and Mn isotopic analyses of KTB samples, the impactor 
was a
>carbonaceous chondrite - see report at:
>
>http://www.lpi.usra.edu/meetings/impact2000/pdf/3041.pdf
>

Yes, but it appears that comets are essentially carbonaceous chondrites 
that
formed far enough from the sun to not lose their volitile mineral 
ddihydrogen
monoxide.  So saying that it is a carbonaceous chondrite doesn't 
conclude if it
iwas a wet one (called a "comet") or a dry one (called an "asteroid").
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