| |
 |
|
|
Science Forum Index » Astro Forum » 65-million-year-old asteroid impact triggered a global...
Page 1 of 1
|
| Author |
Message |
| Andrew Yee... |
 Posted: Mon May 05, 2008 8:55 pm |
|
|
|
Guest
|
Media Relations
Indiana University
Contact:
David Bricker, University Communications
812-856-9035
FOR IMMEDIATE RELEASE: May 5, 2008
65-million-year-old asteroid impact triggered a global hail of carbon
beads
BLOOMINGTON, Ind. -- The asteroid presumed to have wiped out the dinosaurs
struck the Earth with such force that carbon deep in the Earth's crust
liquefied, rocketed skyward, and formed tiny airborne beads that blanketed
the planet, say scientists from the U.S., U.K., Italy, and New Zealand in
this month's Geology.
The beads, known to geologists as carbon cenospheres, cannot be formed
through the combustion of plant matter, contradicting a hypothesis that
the cenospheres are the charred remains of an Earth on fire. If confirmed,
the discovery suggests environmental circumstances accompanying the
65-million-year-old extinction event were slightly less dramatic than
previously thought.
"Carbon embedded in the rocks was vaporized by the impact, eventually
forming new carbon structures in the atmosphere," said Indiana University
Bloomington geologist Simon Brassell, study coauthor and former adviser to
the paper's lead author, Mark Harvey.
The carbon cenospheres were deposited 65 million years ago next to a thin
layer of the element iridium -- an element more likely to be found in
Solar System asteroids than in the Earth's crust. The iridium-laden dust
is believed to be the shattered remains of the 200-km-wide asteroid's
impact. Like the iridium layer, the carbon cenospheres are apparently
common. They've been found in Canada, Spain, Denmark and New Zealand.
But the cenospheres' origin presented a double mystery. The cenospheres
had been known to geologists only as a sign of modern times -- they form
during the intense combustion of coal and crude oil. Equally baffling,
there were no power plants burning coal or crude oil 65 million years ago,
and natural burial processes affecting organic matter from even older ages
-- such as coals from the 300-million-year-old Carboniferous Period -- had
simply not been cooked long or hot enough.
"Carbon cenospheres are a classic indicator of industrial activity,"
Harvey said. "The first appearance of the carbon cenospheres defines the
onset of the industrial revolution."
The scientists concluded the cenospheres could have been created by a new
process, the violent pulverization of the Earth's carbon-rich crust.
Geologists do believe the Earth burned in spots as molten rock and
super-hot ash fell out of the sky and onto flammable plant matter. But the
charcoal-ized products of these fires only appear in some places on Earth,
and are more often found near the asteroid impact site of Chicxulub
Crater, just west of Mexico's Yucatan Peninsula. Some geologists had
thought all carbon particles resulting from the impact was ash from global
scale forest fires, but the present research strongly contradicts that
assumption.
The scientists examined rock samples from eight marine locations in New
Zealand, Italy, Denmark and Spain. They also examined carbon-rich
particles from five non-marine locations in the U.S. and Canada. Following
chemical and microscopic analysis, the researchers concluded the particles
were carbon cenospheres, similar to the ones produced by industrial
combustion.
The scientists also found that the farther the sample site was from the
Chicxulub Crater, the smaller the cenospheres tended to be. That
observation is consistent with the expectation that particles were
produced by the asteroid impact, since once the particles are ejected,
heavier particles should fall back to Earth sooner (and travel shorter
distances) than lighter particles.
Last, the scientists estimated the total mass of carbon cenospheres
ejected by the asteroid collision, assuming a global distribution, to be
perhaps as much as 900 quadrillion kilograms. Whether or not the carbon
cenospheres are truly ubiquitous, however, needs further corroboration.
"There are still clues to unravel about the events occurring around the
time of the impact," Brassell said. "And there are aspects of the Earth's
natural carbon cycle that we didn't previously consider."
Harvey is interested in the unique properties of the cenospheres
themselves. "Perhaps we can generate and study carbon cenospheres to
better understand them," he said. "We also need to look for the
cenospheres in other parts of the world and also around the time of other
extinction events."
Harvey conducted the research while he was a master's student at IU
Bloomington. He is now a geoscientist for Sinclair Knight Merz in New
Zealand. Claire Belcher (University of London) and Alessandro Montanari
(Coldigioco Geological Observatory) also contributed to the study. It was
funded by the Geological Society of America, the Indiana University
Department of Geological Sciences, and the Society for Organic Petrology.
IMAGE CAPTION:
[http://newsinfo.iu.edu/asset/page/normal/4887.html]
Carbon cenospheres are tiny, carbon-rich particles that form when coal and
heavy fuel are heated intensely. Scientists have now learned that
cenospheres can form in the wake of asteroid impacts, too. Photo by: Mark
Harvey |
|
|
| Back to top |
|
| |
|
Page 1 of 1
All times are GMT - 5 Hours
The time now is Tue May 13, 2008 7:18 am
|
|
