[meteorite-list] Chixculub material testing

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:27:49 2004
Message-ID: <200311151829.KAA22157_at_zagami.jpl.nasa.gov>

I just wanted to point out a piece of the impactor was apparently found
when a 65-million year old fossil meteorite was recovered
from the bottom of the Pacific Ocean. I had posted this press release
5 years ago to this list.

Ron Baalke

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University of California-Los Angeles
 
Contact: Stuart Wolpert, stuartw_at_college.ucla.edu, (310) 206-0511
 
Date: November 18, 1998
 
UCLA Geochemist's Fossil Meteorite Provides Strong Evidence that Asteroid
Caused Mass Extinctions 65 Million Years Ago
 
UCLA geochemist Frank T. Kyte has found a fossil meteorite believed to be
from the huge asteroid that crashed to Earth 65 million years ago -- the
probable cause of the extinction of the dinosaurs and many other species
worldwide.
 
In the cover story of the Nov. 19 issue of the journal Nature, Kyte presents
his analysis of the sample and concludes that the cosmic impactor, some six
miles in diameter, that broadsided Mexico's Yucatan peninsula was probably
an asteroid, and not a comet.
 
"The fossil meteorite strongly supports the idea that the impactor was an
asteroid and not a comet," Kyte said. "There is a strong probability that
this is a bullet from a smoking gun."
 
"That was one of the worst days the Earth had in the last billion years, and
it is important to understand what happened."
 
Kyte's analysis of the sample's texture and chemistry confirmed that the
object is a meteorite. He considers it highly likely that the sample is from
the asteroid that struck 65 million years ago, and if so, it is the first
piece of the asteroid that is large enough to study and analyze.
 
What is Kyte's evidence that the meteorite was from an asteroid? First,
comets travel at much higher velocities than asteroids, most likely vaporizing
themselves on collision, Kyte noted. Therefore, the mere fact that a sample
survived the impact is evidence that the object was not a comet, he said.
 
Second, Kyte's analysis suggests that the meteorite came from a typical,
rocky carbonaceous chondrite -- a description of objects in the asteroid
belt -- rather than the porous, fluffy type of interplanetary dust associated
with icy comets.
 
The fossil meteorite was encrusted in mud for 65 million years, buried beneath
more than 50 yards of sediment in the North Pacific Ocean. It no longer has
any of its original minerals, but its texture and shape remain the same, Kyte
said.
 
Kyte located the piece while studying a sediment layer from the Cretaceous/
Tertiary boundary -- whose sediments are widely recognized to contain the
record of a large asteroid or comet impact -- and suspected right away that
he found an important clue to the mystery of what happened 65 million years
ago.
 
"Although the fossil meteorite is only a tenth of an inch in size, it was
1,000 times bigger than anything else in the sediment, "Kyte said. "In this
dark brown sediment, I saw this small white speck."
 
In his National Science Foundation-funded research, Kyte analyzed the piece
using UCLA's electron microprobe and neutron activation laboratories. He
found it to be high in iridium -- an element that is abundant in meteorites.
 
"That's when I knew I had something special -- a small chunk of the asteroid,"
Kyte said.
 
Asteroids, which originate in the asteroid belt between Mars and Jupiter, are
pieces of largely rocky material remaining from early in the evolution of the
solar system. They did not form into planets, probably because of their close
proximity to Jupiter. A typical asteroid travels at about 40,000 miles per
hour, Kyte noted. Comets are from beyond Pluto, and travel about twice as
fast, he said. Comets are believed to be composed of about half rocky
material and half icy material.
 
Some scientists think the destructive meteorite 65 million years ago is an
example of comet showers that bombard the Earth every 25-30 million years,
causing mass extinctions. If the impact was from an asteroid, as Kyte
believes, such theories become harder to defend, he said.
 
The impact 65 million years ago, at the end of what is known as the Cretaceous
period, is believed to have had devastating effects on the world's climate,
and has been implicated in the extinction of the dinosaurs and many other
forms of life. Prior to the crash, a few thousand dinosaur species had
thrived for 160 million years.
 
Questions remain about how the asteroid affected the environment, how long it
took for the extinctions to occur, and the exact size of the massive object.
Received on Sat 15 Nov 2003 01:29:51 PM PST