[meteorite-list] Sterling, help with some calcs please

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Wed, 20 May 2009 18:45:35 -0500
Message-ID: <998A2D9DEC264037B3948CC4228027E0_at_ATARIENGINE2>

EMan, EP, List,

The sea-floor-dredged fragment is of a carbonaceous
chondrite. It's a "fossilized" meteorite, meaning it's
seriously been altered by the terrestrial environment,
with replaced minerals and all the rest. It was found
some years ago. I've seen a photo of it, but can't find
that website today, but it is an encapsulated clast that
can only be identified as carbonaceous by the simple
fact that it's so rich in carbon.

The discovery article is:
"A meteorite from the Cretaceous/Tertiary boundary"
by Frank T. Kyte The Abstract is at:
http://www.nature.com/nature/journal/v396/n6708/abs/396237a0.html
    "Cretaceous/Tertiary boundary sediments are now
widely recognized to contain the record of a large asteroid
or comet impact event, probably at the site of the Chicxulub
crater on the Yucatan peninsula. After nearly two decades
of intensive research, however, much remains unknown
about the specific nature of the projectile and of the impact
event itself. Here we describe a 2.5-mm fossil meteorite
found in sediments retrieved from the Cretaceous/Tertiary
boundary in the North Pacific Ocean that we infer may be
a piece of the projectile responsible for the Chicxulub crater.
Geochemical and petrographic analyses of this meteorite
indicate that it probably came from a typical metal- and
sulphide-rich carbonaceous chondrite rather than the
porous aggregate type of interplanetary dust considered
typical of cometary materials. The fact that meteorite survival
should be enhanced by impacts at low (asteroidal) velocities
also implies that this meteorite had an asteroidal rather
than a cometary origin."

The impact angle at Chicxulub appears to have been low,
20 to 30 degrees above the horizontal. Nice animation at
the bottom of this webpage:
http://www.psi.edu/~betty/chicx3d.html

Then, by a happy coincidence, a year or so ago, an orbital
regression program revealed that the big impactor was likely
a large chunk of the breakup fragments of the parent body
of the Baptistina asteroid family:
http://en.wikipedia.org/wiki/Chicxulub_crater#Astronomical_origin_of_asteroid

The original paper by Bottke can be found here as a pdf:
http://www.boulder.swri.edu/~bottke/Reprints/Bottke_2007_Nature_449_48_Baptistina_KT.pdf

I call it a happy coincidence because the Baptistina Family
are... you guessed it -- carbonaceous chondrites, like the
biggest surviving member, which is 298 Baptistina. The
original or parent body was about 170 kilometers across.
Another fragment of the Baptistina Family is believed to
have made the crater Tycho on the Moon 108 million years
ago. Those guys really got around...

There's a paper that calculates that there should be lots of
Earthite chunks from the Chicxulub impact littering the
Moon and Mars. They call them Chicxulubites!
http://www.igeofcu.unam.mx/divulgacion/geofinternacional/iframes/anteriores/2008/03/poveda.pdf
Add that term to your list of meteorite types... and watch
for them on eBay.

As for the latest Keller piece, I don't bother to read Keller any
more. Here's her own university's press release summarizing it:
http://www.dailyprincetonian.com/2009/05/06/23652/
Her papers are dense and jargonistic, hard for someone who's
not an academic geologist to plow through, but even I found
the "hole" in her original block-buster paper, "proving" a
missing 300,000 years between impact and K-T boundary.
That hole is that 275,000 years of the missing 300,000 years
is missing from her evidence, with no evidence that it's
missing. In other words, there really is no gap, or at most
a possible 25,000 year gap, hard to measure accurately.
That's as good as "right away" for me.

Then I discovered her biggest opponent -- Smit. He's a Dutch/
American sedimentologist. He basically takes her so-called
evidence apart piece-by-piece (and he demonstrates that it
is largely incompentent, although he does not say it in those
words... exactly.) You want to find out what's wrong with
Keller's work? Read this:
http://www.falw.vu/~smit/csdp/debates.htm

Keller's now blaming the Deccan Traps, big flood basalts in
India. Flood basalts coordinate perfectly with big impacts;
the biggest two instances are at the K-T extinction and at
the Permian extinction (the Siberian Traps) Coincidence?
(That, or leprachans...) And it's easy to demonstrate the
mechanism by which impacts CAUSE flood basalts!
http://www.newgeology.us/presentation35.html
And we have an existing perfect example on Mercury, with
antipodean lava flooding opposite a big impact, so even if
Keller's right... She's wrong.

If you Google "keller chicxulub" at Google News, you will
get scads of stuff on the latest silliness.


Sterling K. Webb
--------------------------------------------------------------------------------
----- Original Message -----
From: "Mr EMan" <mstreman53 at yahoo.com>
To: <meteorite-list at meteoritecentral.com>; "E.P. Grondine"
<epgrondine at yahoo.com>
Sent: Wednesday, May 20, 2009 3:01 PM
Subject: Re: [meteorite-list] Sterling, help with some calcs please


>
>>From Mr Buttinsky Eman: I am a wee skeptical regarding meteorite
>>fragments from ancient impacts in general and Chixculub specifically.
>>There is also an H4 fragment recovered in sea floor dredging which was
>>announced as the smoking gun. Unfortunately I continue to get group
>>postings reliably so again I am out on a limb so I haven't read
>>Keller's latest. But I am looking elsewhere for this report.
>
> Elton
>
> --- On Wed, 5/13/09, E.P. Grondine <epgrondine at yahoo.com> wrote:
>>
>> Hi Sterling, all -
>>
>> Given Keller's latest KT announcements, could you give us
>> some rough numbers on infra-red, blast overpressures, winds,
>> and molten rock vapor from the KT impact? Given the
>> kt-fossil meteorite, it seems safe to me to infer a comet
>> impactor.
>>
>> E.P. Grondine
>> Man and Impact in the Americas
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Received on Wed 20 May 2009 07:45:35 PM PDT