[meteorite-list] Science Team Says Giant Meteorite, Not Volcanoes, Killed Dinosaurs

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu, 4 Mar 2010 14:54:12 -0800 (PST)
Message-ID: <201003042254.o24MsCkJ028128_at_zagami.jpl.nasa.gov>

http://www.psi.edu/press/

SCIENCE TEAM SAYS GIANT METEORITE, NOT VOLCANOES, KILLED DINOSAURS
Ed Stiles
Public Information Office
Planetary Science Institute
520-248-7119
psinews at psi.edu

March 4, 2010 - A team of scientists, including Elisabetta Pierazzo, a
senior scientist at the Tucson-based Planetary Science Institute, has
concluded that a giant meteorite impact is still the best explanation
for the disappearance of dinosaurs and many other species 65.5 million
years ago.

The 41 scientists, from Europe, Mexico, Canada, Japan and the United
States, published their results today in the highly respected scientific
journal Science, concluding that alternative hypotheses are inadequate
in explaining the abrupt mass extinction at the end of the Cretaceous
period.

Scientists refer to this point in the geologic record as the K/Pg
boundary, and attribute it to extreme climate change caused by the
Chicxulub (Chick-shuh-loob) meteorite impact.

Pierazzo, who began modeling the impact as a Ph.D. student, was the
first scientist to develop high-resolution, 3-D simulations of the
Chicxulub event as an oblique impact. This work was done in
collaboration with David Crawford, of Sandia National Laboratory. The
results clearly showed that the effects on Earth's climate were even
more dramatic than had been previously hypothesized. The simulation
showed huge amounts of sulfur oxides were ejected into the upper
atmosphere, drastically altering the Earth's climate.

However, some scientists have disputed the Chicxulub hypothesis,
attributing the climate change and mass extinctions to volcanic activity
in the Deccan Traps, an area on the Indian subcontinent. They theorize
that global cooling and acid rain resulting from this volcanic activity
were the major cause of mass extinctions, not the Chicxulub impact in
Mexico.

"Large amounts of sulfur oxides were injected into the atmosphere during
the Deccan volcanism," Pierazzo said. "But they were distributed in
several pulses that extended over several hundred thousand years before
- and after - the K/Pg boundary. Yet, the major, large biotic changes at
the end of the Cretaceous era appear to have happened abruptly and
exactly at the K/Pg boundary, when Chicxulub hit."

Marine and terrestrial ecosystems showed only minor changes during the
500,000 years leading up to the K/Pg boundary, the researchers conclude
in the Science article. But an abrupt and major decrease in the mass of
living things and species diversity occurs precisely at the boundary.

This data, along with new data derived from ocean drilling samples and
continental sites, as well as reanalysis of previous K/Pg boundary
studies, leads the research team to conclude that the Chicxulub impact
hypothesis has grown stronger than ever.

"Combining all available data from different science disciplines led us
to conclude that a large asteroid impact 65 million years ago in
modern-day Mexico was the major cause of the mass extinctions," says
Peter Schulte, assistant professor at the University of Erlangen in
Germany and lead author of the review paper.

According to analysis of the Chicxulub crater in Yucatan, Mexico and
other data from the geologic record, scientists conclude that the
meteorite was between 10 and 15 kilometers in diameter and hit Earth at
a speed 20 times faster than a rifle bullet. The resulting explosion was
a billion times larger than the Hiroshima atomic bomb and a million
times larger than the biggest nuclear bomb ever tested.
Received on Thu 04 Mar 2010 05:54:12 PM PST