Geologists to drill into heart of dinosaur-killing impact

This article was written by Alexandra Witze for Nature.com. Neither are affiliated with Asteroid Day. Asteroid Day Expert Christian Koeberl is one of the principal investigators of the ICDP part of the drilling project.

Geophysicists are returning to Earth’s most famous cosmic bullseye. Around 7 April, from a drill-ship off the coast of Yucatán, Mexico, they will start to penetrate the 200-kilometer-wide Chicxulub crater, which formed 66 million years ago when an enormous asteroid smashed into the planet. The aftermath of the impact obliterated most life on Earth, including the dinosaurs.

The expedition is the first to directly probe one of Chicxulub’s most striking features — its ‘peak ring’, a circle of mountains that rise within the crater floor. Scientists have yet to fully explain how peak rings form, even though they are common in big impact craters across the Solar System.

At Chicxulub, researchers will look for evidence to explain how a 14-kilometer-wide asteroid could have punched a hole that pushed rocks from the surface down some 20–30 kilometers. Flowing like liquid, the rocks then rebounded towards the sky — reaching as far as 10 kilometers above the original ground level — and finally splattered down to form a peak ring.

All of this happened in the span of several devastating minutes, says Joanna Morgan, a geophysicist at Imperial College London and the project’s co-chief scientist. “It’s astounding.”

If the 2-month expedition goes as planned, it will bore 1,500 meters into sea-floor rocks. The drill will first pass through carbonate rocks that make up the bottom of the Gulf of Mexico (see map), and eventually reach the fractured ‘impact breccias’ that represent the obliterating impact.

At least a dozen other boreholes and several oil-exploration wells have already penetrated the parts of Chicxulub that lie on land. They include a 1,511-metre-long core drilled near the crater rim in 2001–02 by a large international scientific consortium¹. When combined with seismic surveys², analyses of existing cores reveal a complex picture of nested rings of shattered rock, all created on a very bad day for life on Earth³.

Inner circle

The latest project will be the first to drill offshore at Chicxulub and the first to target its peak ring. “We don’t really know what this material will look like,” says Jaime Urrutia-Fucugauchi, a geophysicist at the National Autonomous University of Mexico in Mexico City. “It could be a real surprise.”

The US$10-million project is funded primarily by the European Consortium for Ocean Research Drilling and involves researchers from Europe, Mexico, the United States and elsewhere. The water at the drill site — about 30 kilometers offshore from the port of Progreso — is too shallow to accommodate conventional ocean-drilling vessels, so the project has hired LB Myrtle, a ‘lift boat’ that will drop three enormous pillars to the sea floor, then jack itself up to form a temporary drilling platform.

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Links to the two funding agencies of the Chicxulub drilling project are http://csdp2.icdp-online.org and http://www.eso.ecord.org/expeditions/364/364.php