This spring, an international team of researchers will drill into the Chicxulub impact crater in central Mexico to probe for traces of a mammoth object that struck the Earth 65 million years ago, possibly killing off the dinosaurs.
Beginning in March, the team will start sinking test holes in the portion of the 125-mile (200-kilometer) wide impact crater that straddles the Yucatan peninsula in Mexico. Later in the summer, the drilling could go as far as two miles (three kilometers) - deeper than any previous expedition has probed into the saucer-like depression.
"The impact was the equivalent of so many nuclear bombs its incomprehensible."
The crater, now buried under more than a half a mile (one kilometer) of limestone deposits, was blasted out by the impact of either a meteorite or comet perhaps 10 miles (16 kilometers) across. Scientists think its size and timing make it the smoking gun that would explain the extinction of the dinosaurs - as well as 70 percent of all species living at the end of the cretaceous period.
"The impact was the equivalent of so many nuclear bombs its incomprehensible," said Virgil "Buck" Sharpton, one of two lead scientists on the project.
Once extracted, the core samples will give scientists a better understanding of how the Earth responded to the impact, both physically and chemically. A second goal will focus on life on Earth at the time, and how long it took it to recover.
Scientists theorize that the object cast an enormous of amount of debris into the atmosphere, creating nuclear winter-type conditions on a global scale and prompting mass extinction.
Indeed, the timing of the Chicxulub crater is thought to coincide with the boundary between the cretaceous and tertiary periods in geologic time.
When looking at the physical boundary in the geologic record, a thin, iridium-rich layer of clay separates the two, according to research first published in the journal Science by Luis Alvarez in 1980. The unusually high levels of iridium point to an extra-terrestrial source, such as an asteroid, for the element.
What is more telling, though, is that the cretaceous layers are often fossil-rich, while the later tertiary layer is relatively fossil-poor, seemingly pointing to a massive extinction event. By studying the core samples, scientists expect to see a blow-by-blow account of how the biosphere bounced back in the eons following the impact.
"We want to see how that evolution occurred," said Sharpton, a professor of geology at the Geophysical Institute of the University of Alaska, Fairbanks
Chicxulub had been known of since the 1950s, thanks to oil wells sunk by Pemex, Mexico's national oil company. However, it was not widely connected to the extinction event until earlier this decade.
Some now think whatever created Chicxulub was the largest object to strike Earth in the last billion years. Other craters found in our solar system that have a similar size and structure include the Mead and Klenova craters on the planet Venus.
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