Learning about the impact that changed life on Earth

Learning about the impact that changed life on Earth

The effort to drill into the Chicxulub crater off the coast of Mexico has been declared an outstanding success. A UK/US-led team has spent the past 7 weeks coring into the deep bowl cut out of Earth’s surface 66 million years ago by the asteroid that hastened the end of the dinosaurs. Rocks nearly 1,300 metre below the Gulf seafloor have been pulled up. The samples are expected to reveal new insights on the scale of the impact and its environmental effects.

The operations manager on the project, Dave Smith, said drilling would likely to end soon. “The core recovery, we’re all really chuffed about — the almost 100% core recovery and the quality of the cores we’ve been getting up. It’s been a remarkable success. We’ve got deeper than I thought we might do,” the British Geological Survey man said. The original target was to get down to 1,500 metre, to drill through a feature called the ‘peak ring’. This was created at the centre of the impact hole where the Earth rebounded after being hit by the city-sized space object. In earlier geophysical surveys that were able to sense below the seabed, this ring looked like an arcing chain of mountains.

But even if the 1,500 metre mark was not reached, the team believes it has more than enough material now to answer its key science questions. “It’s been quite magical,” said Imperial College London’s Prof Joanna Morgan, who spoke via a satellite link from the Myrtle drill platform. “Before I came out here, I remember getting quite nervous, quite anxious — what would happen? Would we be successful? But since I’ve been on the Myrtle, I’ve been quite calm because things have been happening, and we’ve been getting lovely cores.”

The rock samples in their metal casings have been stacked in a refrigerated container. They will be transported back to shore and sent first to an American lab for CT scanning, to examine their interior structure.Then they will go to Bremen, Germany, where the 33 individuals on the science team will gather to subject the rocks to a battery of tests.

The space object that slammed into the planet at the end of the Cretaceous Period instantly dug out a hole 100 km wide and 30 km deep. The debris hurled outwards would have darkened the sky and chilled the climate for months on end, driving many creatures to extinction, not just the dinosaurs. But the precise details of how the event progressed can now be refined by examining the drill cores. From the rocks, the research team should be able to tell better how the crater formed, the energy involved in its excavation, and the volume of material that was dispersed.

This will put new limits on the nature of the environmental changes that enveloped the globe. Other intriguing questions will be also be addressed, such as how fast life was able to return to the sterilised impact zone. There is even a suggestion that the hot fluids moving the fractured rocks left by the impact may even have embraced and fostered micro-organisms.

The team now has the data to test this idea. The scientists get a year’s exclusive access to the material, after which others in the research community can take a look. “Ultimately, the cores go to a facility in Texas where anybody can then sample them. Everything is archived. If someone has a new geochemistry measurement, they can go look at the core for a long, long time into the future,” said Prof Morgan.

The science team has members from the US, Mexico, Japan, Australia, Canada, and China, as well as the UK and 5 other European countries. The project was organised through the European Consortium for Ocean Research Drilling (ECORD) and the International Ocean Discovery Program (IODP). Max Alexander, who visited the Myrtle drill boat at the beginning of May, works a lot with the UK Space Agency (UKSA) and arranged for British astronaut Tim Peake, currently on the International Space Station, to take the spectacular photograph of Mexico’s Yucatan Peninsula. Max has also taken images and they were taken for Asteroid Day (30 June) — a campaign that aims to raise awareness of “asteroids, the impact hazard they may pose, and what we can do to protect our planet” from them.

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