Scientists drill for clues to dinosaur extinction

Scientists drill for clues to dinosaur extinction
REUTERS

SAN FRANCISCO, DEC 18: 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 Yucatanpeninsula 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 thevast Chicxulub crater in hopes of discovering how the impact triggered a massive environmental catastrophe that extinguished dinosaur life around the globe.

``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 Francisco.

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 (80 km) 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, thecrater 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 involcanic 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.

That impact was like nothing recorded in human history. Millions of years before humans even existed, a huge meteorite measuring about 6 miles (10 kms) 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 (200 kms) 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 per cent 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 anddebris 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 carbonatesand sulfates react to high impact pressures,'' Sharpton said.

Gypsum rock evaporated by the impact might have clogged theatmosphere 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 dioxidereleased 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.