It could reveal clues to how life bounced back after the impact.
About 66 million years ago, a large 9 kilometer (5.6 mile) wide asteroid slammed into Mexico’s Yucatán Peninsula, leading to the extinction of the dinosaurs and most other life on the planet. Scientists have never been able to analyze the buried remains of the asteroid, mainly because the area is controlled by the oil industry. But now, they have their chance.
Scientists will try to drill into the heart of the Chicxulub crater — the buried remnant of the asteroid — in hopes of retrieving rock cores containing clues to how life returned after the impact, and whether the crater itself could have been a home for microbial life.
Not only that, by drilling into a circular ridge inside the 180-kilometer wide crater rim, scientists hope to settle the debate about how peak rings — elevated ring that surrounds impact craters — take shape.
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“Chicxulub is the only preserved structure with an intact peak ring that we can get to,” University of Texas geophysicist Sean Gulick told Science. “All the other ones are either on another planet, or they’ve been eroded.”
At the end of this month (March), a vessel will sail from the Mexican port of Progreso to a point 30 kilometers (18.6 miles) offshore. The boat will then drop three pylons to raise itself above the waves, creating a stable platform.
By April 1, the team plans to start drilling through roughly 500 meters of limestone deposited on the seafloor since the impact. After that, they will start to extract core samples while drilling deeper and deeper.
For two months, the team will work day and night to drill down another kilometer, looking for changes in rock type, cataloging microfossils, and collecting DNA samples. “We’ve got one shot to try and get this down to 1500 meters,” said David Smith, the IODP operations manager at the British Geological Survey in Edinburgh, U.K.
“It seems like a lifetime’s ambition coming true,” said co-lead researcher Joanna Morgan from Imperial College London.
Once they reach the peak ring, the researchers hope to test a leading model for peak ring formation, in which granite from the depths of Earth rebounds after a major impact, forming a central tower that is taller than the crater rim. Within minutes, the tower collapses and collides with material falling in from the rims to form the peak ring.
Confirmation of the model would come from finding rocks “out of order”: deep rocks, probably granite, brought up in the central tower, lying above originally shallower younger rocks. “They’re going to test whether our numerical models are making any sense or not,” says Jay Melosh, a planetary scientist at Purdue University in West Lafayette, Indiana, who helped develop the model.
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The researchers are not only interested in the structure of the peak ring, but also what life it might hold. Remote sensing has suggested that the peak is less dense than expected for granite — a sign that the rocks are porous and fractured, and it is possible that these fractures were filled with hot fluids after the impact.
“Those will be preferred spots for microbes to grow, but it depends whether the fractures have energy and nutrients,” says Charles Cockell, an astrobiologist on the IODP team at the University of Edinburgh. Once the drill comes into contact with these fracture spots in the peak ring, Cockell and his colleagues will take a sample from the core. They will then count and culture any microbes still living in the fractures, and sequence DNA to look for the genes.
The genes may show that the peak ring microbes, descendants of those that lived after the asteroid impact, derive their energy from iron and sulfur deposited by the hot fluids in the fractured rock. And, excitingly, that would mean that the impact crater — the bringer of death — was also a habitat for life.
How ironic!
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