海角大神

When an asteroid collided into Earth some 66 million years ago, wiping out the dinosaurs, it left a crater just off the coast of Mexico鈥檚 Yucatan Peninsula, where it struck. By drilling down into the 鈥減eak ring,鈥� or the innermost ridge of rock tossed up by the impact, scientists say they鈥檝e reached surprising conclusions about how the collision unfolded.

Researchers from more than a dozen countries found that the force of the impact splashed up rock from deep beneath the Earth's crust, bringing it to the surface, results published Friday听in the journal Science.听

鈥淭hese rocks behaved like a fluid for a short period of time, and rocks don鈥檛 tend to do that,鈥� Imperial College London geophysicist Joanna Morgan, who co-led the team,听told The New York Times. 鈥淚t鈥檚 a very dramatic process when you form a large crater.鈥�

The study confirms the team鈥檚 unusual model for how craters form during powerful collisions: Over the course of a few minutes, a mountain of debris higher than Everest piled up, then collapsed again into a chain of smaller peaks, Dr. Morgan told the BBC. The Chicxulub crater, as it鈥檚 known, is the only preserved structure of its kind on Earth, making the team鈥檚 model useful in application to research into craters on the moon, and on other planets. And they also think their findings could help scientists better understand how the asteroid鈥檚 impact unleashed a cataclysmic change in the climate.听

Funded with $10 million from the International Ocean Discovery Program (IODP)听and the International Continental Scientific Drilling Program, the study posed several logistical challenges. About 66 million years鈥� worth of sediment blankets the crater.听Rainforest covers the part that's now dry land, with the other part 鈥撎齣ncluding the center 鈥撎齦ying below the Gulf of Mexico. That means the drilling took place offshore, as听海角大神鈥檚 Ben Thompson wrote back in March, while the team prepared to launch their expedition:听

After drilling through some 60 feet of water and 2,000 feet of earth, the team kept pulling up samples of limestone and brecchia, or fragments of melted rock, before finally hitting paydirt,听according to Sean Gulick, a co-lead author and a marine geophysicist at the University of Texas at Austin.

鈥淚t was limestone, limestone, limestone, breccia. And then suddenly pink granite!鈥� Dr. Gulick told The New York Times. 鈥淚t was exhilarating, it looks like your classic pink granite countertop.鈥�

But the granite also showed signs of intense stress, with deformations and fractures visible to the naked eye.

鈥淭hat was the big find because that says that this peak ring didn鈥檛 come from something shallow at all,鈥� he added. 鈥淚t had to come from deep because it鈥檚 made of deeply buried crustal rocks now at the surface.鈥�