[meteorite-list] The COMET that killed the dinosaurs

From: Mexicodoug <mexicodoug_at_meteoritecentral.com>
Date: Thu, 21 May 2009 18:34:23 -0400
Message-ID: <8CBA87B6CFFAD05-1260-23EF_at_WEBMAIL-MB12.sysops.aol.com>

Hi Ed,

The case we are discussing is the suspected and curious Nickel and Gold
rich pseudometeorite or meteorite from DSDP Hole 576 recovered by
UCLA's Cosmochemist Frank T. Kyte.

Without giving my personal opinion, here are Kyte's thought on whether
his object and the Chicxulub impactor in general is a COMET:

"Analyses of a small fossil meteorite [sic] as well as the isotopic
composition of Cr in K-T boundary sediments, point to a projectile
similar to carbonaceous chondrite. Physical debris (i.e., Ni-rich
spinels) in the global fallout is restricted to a single layer, and
there is no strong evidence to support any hypothesis other than a
single, geologically instantaneous accretionary event. This
observation, in addition to the apparent lack of an increased flux of
3-He at the K-T boundary are strong arguments against a comet shower at
65 Ma. That the K-T meteorite [sic] is more similar to anhydrous,
porous IDPs is also reason to suspect an asteroidal, rather than a
cometary source for the K-T projectile."

Ref: Catastrophic Events and Mass Extinctions, eds. Christian Koeberl,
Kenneth G. MacLeod: GSA Special Paper 356 Kyte, F.T., (2002) Boulder,
Co., "Traces of the extraterrestrial component in sediments and
inferences for Earth's accretion history", pp. 21-38.

As I said in my original post, "What this "meteorite" fragment proves
is questionable in relation to the [K-T] debate." You would get more
support fro
m Dr. Keller, who as a matter of fact does believe a shower
was likely involved and allows that it could have been cometary and
happened over a longer span of time. Kyte, and old friend of Smit,
believes the opposite. Each of these scientists believes this because
they have woven a scenario on how they think it went down and these are
the deductions from their interpretations of their theories. There is
no absolute answers knowable yet, just a lot of foam trials on the sea.

Best wishes,
Doug




-----Original Message-----
From: E.P. Grondine <epgrondine at hotmail.com>
To: mexicodoug at aim.com; meteorite-list at meteoritecentral.com;
8cba8660c696b38-b6c-795 at webmail-de18.sysops.aol.com;
fpspace at friends-partners.org
Sent: Thu, 21 May 2009 4:49 pm
Subject: The COMET that killed the dinosaurs


Message: 6
Date: Thu, 21 May 2009 16:01:26 -0400
From: Mexicodoug
Subject: Re: [meteorite-list] K-T fossil meteorite picture


Dear Bernd, List,

Thanks for the interesting post on this curious case.

So everyone can enjoy this 0.25cm "fossil" "meteorite" which Kyte
classified as a "CV, CO, or CR carbonaceous chondrite", here is an
original image in color:
http://tinyurl.com/qf8u9w

The "meteorite" is also described as an unclassified hematite and clay
fragment from the core sample DSDP Hole 576 in the western North
Pacific (32? 21.4'N, 164? 16.5'E), 1000 miles WNW of Green Island of
the Hawaiian Islands and 1400 miles ESE of Tokyo
).

The "meteorite" is not yet an official meteorite, relict or not (if it
is certain it is a meteorite - unknown to me why not :-)). Kyte's
office at UCLA has been between his colleagues Wasson and Rubin's and
he was a co-author with them though the publications appear all prior
to the "meteorite", so the answer to why not is probably easy to get.

The extremely high gold concentration in it (which at one point I
believe it was Koeberl said likely disqualified it as a "meteorite")
has not been explained other than by speculation:

http://tinyurl.com/qn3ssc

Kyte has classified the only meteorite from the Pacific Ocean, a 2.4
million year old mesosiderite officially named Eltanin, found 5km below
sea level in other core samples, which he interprets to be part of the
largest meteorite fall dropped, ever recovered on Earth. (TKW 1.2 Kg
mostly in sub centimeter sized weathered fragments).

Here are some very nice thin sections of the alleged relict meteorite
 from another picture in that original Nature Letter for list members'
perusal:
http://tinyurl.com/q4r89e

Source: Letters to Nature, Frank T. Kyte sent this in originally on 2
June 1998:
Kyte, F.T., Nature, "A meteorite from the Cretaceous/Tertiary
boundary", 19 November 1998, V. 396, pp. 237-239.
http://www.nature.com/nature/journal/v396/n6708/full/396237a0.html

 From what I can gather, most scientists have called the K-T boundary
fragment "meteorite" Kyte's interpretatio
n. It should be noted that
Kyte was co-author on several papers with Jan Smit and the two were
close colleagues during the magical period of the early 1980's after
Luis Alvarez did the then eye-opening K-T boundary work wit his son and
collaborators. While the Alvarez' didn't particularly care much for the
search for the crater, one collaborator, Jan Smit believes he was
instrumental in the discovery of the Chicxulub crater and vindication
of Alvarez' Dino extinction theory and fervently defends the work. Smit
doesn't acknowledge challenger Princeton's Gerta Keller's group's
interpretations which would suggest anything different on the grounds
of Occam's Razor, in that a single impact explains everything and any
mess is because there was turbulence afterwards shaking up everything,
something that Keller doesn't buy as an argument stopper. Keller
believes the extinction event is likely more complex, and has applied
her version of chronostratigraphical study in great detail to the
layers, and supports the possibility of multiple impacts and other
terrestrial explanations. The latter two have become rivals and both
(especially Smit) display emotional disdain for the other's work. They
are both good scientists. What this "meteorite" fragment proves is
questionable in relation to the debate. Kyte also classifies a 3.8
billion year old impact on earth as a CV by looking at the chromium
content of ancient sediments.

Best wishes,
Doug






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Received on Thu 21 May 2009 06:34:23 PM PDT