[meteorite-list] Drilling Project at Chicxulub Crater
From: geoking_at_notkin.net <geoking_at_meteoritecentral.com>
Date: Thu Apr 22 09:37:36 2004
I found this article posted in sci.bio.palenotology, and thought it
would be of interest to some.
Scientists Drill for Clues to Dinosaur Extinction
By Andrew Quinn
SAN FRANCISCO (Reuters) - Scientists have launched a new project to drill
into the gaping crater caused by an ancient asteroid impact, hoping to
determine once and for all what led to the global extinction of the
dinosaurs millions of years ago.
The asteroid impact near the tip of Mexico's Yucatan peninsula about 65
million years ago has long been believed to be a potential cause for the
death of the dinosaurs, which vanished at roughly the same time.
Now scientists are looking at new ways of exploring the vast Chicxulub
crater in hopes of discovering how the impact triggered a massive
environmental catastrophe that extinguished dinosaur life around the
``It's a 100 million year event -- they don't occur that often, thank
God,'' Buck Sharpton of the University of Alaska Fairbanks told a news
briefing on Sunday at a meeting of the American Geophysical Union in San
Sharpton and Luis Marin of Mexican National University are spearheading a
project to drill a 1.2 mile (2 kilometer) hole into the crater to gain a
better understanding of the force of the collision, and its environmental
results. Drilling is slated to start about 50 miles south of Merida,
Mexico, sometime in June. The researchers will be examining rock samples
for indications of how a huge, but relatively isolated, explosion might
have wiped out dinosaur life even half-way around the planet.
The Chicxulub crater is often cited as one of the best preserved records
of an Earthly cosmic disaster.
Discovered only in the 1970s by oil drilling teams, the crater was
relatively unstudied until the 1990s, when scientists linked it to
theories that asteroid impact may have spelled the dinosaurs' doom.
Other scientists hypothesize that a huge upsurge in volcanic activity on
the Earth itself was what killed off the dinosaurs. But the Chicxulub
crater, and fresh information derived from the new drilling project, may
help to back up the theory that an asteroid was to blame.
Impact Like Nothing Recorded In Human History
That impact was like nothing recorded in human history. Millions of years
before humans even existed, a huge meteorite measuring about 6 miles
across and weighing perhaps billions of tons crashed into the planet in a
ball of fire, shrouding the Earth in a dense cloud of dust that blocked
out sunlight and sent temperatures plummeting.
Estimates now put the crater's size at about 125 miles in diameter,
indicating a force of impact equivalent to an earthquake about 10,000
times stronger than the one that leveled San Francisco in 1906 and equal
to the explosive force of hundreds of atomic bombs.
About 60 percent of all recorded species on the earth disappeared around
the time the meteorite struck. On land, nothing larger than a dog
survived, scientists believe.
While researchers agree that vast amounts of dust and debris were sent
shooting into the atmosphere, the actual mechanics of how this may have
caused a global catastrophe have remained obscure.
Sharpton and his team now hope that examination of core samples will give
scientists a better understanding of the chemical make-up of the material
involved -- specifically, by indicating how much sulfur- and carbon-
bearing rock was sent hurtling into the sky.
``This is going to tell us a lot about how these carbonates and sulfates
react to high impact pressures,'' Sharpton said.
Gypsum rock evaporated by the impact might have clogged the atmosphere
with floating sulfur particles, causing a ``nuclear winter'' by blocking
sunlight essential to plant growth, removing the essential first link in
the worldwide food chain.
Sulfur particles falling into the ocean could also have transformed the
world's seas into vast, acidic pools, killing off much of the sea life.
Following this disaster, immense amounts of carbon dioxide released from
vaporized limestone could have contributed to a secondary greenhouse
effect, sending temperatures soaring and killing off much of the remaining
life on the planet.
``You can't initiate an extinction event unless you wipe out all the
critters,'' Sharpton said, noting that the environmental effects of the
impact would have to have been felt worldwide in order to account for the
planetary extinction of so many species.
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Received on Tue 19 Dec 2000 10:21:15 PM PST