Crater Drilling Makes an Impact

By Kevin Ritchart

Earlier this year, a drilling effort off of the coast of Mexico helped to shed light on the extinction of the dinosaurs. Core samples taken from the Chicxulub crater, which was created when a giant asteroid struck the Earth 66 million years ago, are helping scientists to piece together the timeline for both extinction and the return of life to our planet.

Though scientists have drilled the massive crater before, the 2016 expedition is the first offshore effort as well as the first to explore the crater’s peak ring, which is a circular ridge located inside the rim. Scientists are examining core samples taken from the Chicxulub crater’s peak ring to determine if the crater itself was one of the first habitats for microbial life after the asteroid struck the Earth.

Samples taken from farther up in the peak ring have helped to identify the time period when life ceased to exist, and scientists are hopeful that computer modeling will aid them in learning more about the crater’s formation.

Asteroid Aftermath

When the asteroid struck the Earth, the peak ring formed soon after, potentially within minutes. Following impact, granite bedrock from deep below the surface was forced upward — possibly as high as 10 kilometers into the air — before settling in a circular pattern around the crater. Following its formation, the peak ring was covered by a random assortment of rocks called breccia that came to the surface after impact. Then, just hours later, tsunamis filled the crater with sediment.

In April, scientists drilled to a depth of 670 meters and brought up a section of rock that contained pieces of granite and various minerals, which indicated that the drill had reached the peak ring. Researchers are debating the depth at which they crossed from the Cretaceous period, which is the last age of the dinosaurs, and the Paleogene, which began 66 million years ago. The line between these two eras, known as the K-Pg boundary, is typically marked by the discovery of fossilized, small-shelled creatures called foraminifera. The foraminifera were found at a depth of 620 meters, but scientists are currently debating how to refer to the 50-meter section between the foraminifera and the peak ring.

Now that they’ve entered the peak ring, researchers will continue to drill — aiming to go as deep as 1500 meters — as they search for both ancient and modern DNA to further explore and hopefully add to our knowledge about the time following the asteroid’s impact.