An expedition eighteen miles off the coast of Mexico is drilling into the seafloor to probe the crater created by the Chicxulub asteroid, the space rock that led to the dinosaur’s demise. Just a few days ago, the team struck granite, getting their first look at rock that had been shaped by the cataclysm 66 million years ago.
Though covered by hundreds of feet of sand and rock, the crater remains the same as it was at the end of the Cretaceous, potentially harboring invaluable insights about the asteroid’s impact.
The Chicxulub asteroid, 8.5 miles across, hurtled into the Earth’s crust and caused solid granite to splash around like water, forming a crater 110 miles wide. The pressure on the Earth’s mantle set off a series of volcanic blasts . Together with the dust from the crater, these volcanoes threw up enough debris to plunge the planet into darkness and cool the climate, touching off a mass extinction .
This expedition hopes to further sort out the chain of events that made Chicxulub such a catastrophe. At a depth of 2,000 feet below the seafloor, the drill reached a structure called the peak ring. The biggest asteroid strikes form two impact rings—an outer ridge in the upper crust and an inner peak ring made of deep crust. Peak rings are formed when the rock shoved deep into the crust rebounds upwards before collapsing and forming a wide ring. The Chicxulub peak ring leapt six miles high before settling into its current form. Reaching this formation and bringing up a sample of its rock was one of the expedition’s main goals.
Here’s Eric Hand, reporting for Science:
“We’re feeling pretty good,” said co–chief scientist Sean Gulick in an interview from the deck of a drilling platform 30 kilometers offshore in the Gulf of Mexico. “I’m not getting much sleep out here, so we’re little delirious.”
Although scientists have drilled into the buried crater before on land, this is the first offshore effort, and also the first to go after the crater’s “peak ring”—a circular ridge inside the crater rim that’s characteristic of the solar system’s largest impact craters. Astronomers see peak rings on the moon, Mars, and Mercury, but they have never been able to sample one on Earth until now.
This expedition will let scientists tackle some long-burning questions. First of all, how did an asteroid that was 8.5 miles wide push the earth’s crust down to twice that depth? Then there’s the biology: how did life recover after this disaster? Did the crater zone itself become a fertile environment for ocean microbes just shortly after the impact? The answers probably lie deeper in the crust. But the core sample from the peak ring is the team’s first major milestone.
Photo credit: JLofi/ECORD_IODP