Samples from the center of Chicxulub crater helped reconstruct the first hours after the asteroid's impact, which marked the end of the long era of the dinosaurs.
The Cretaceous-Paleogene extinction, which more than 65 million years ago destroyed most of life on Earth, is associated with the fall of a massive meteorite. A body about ten kilometers across, flying into the atmosphere at a speed of almost 25 kilometers per second, could create an explosion of such power, which cannot be compared with the entire stock of nuclear weapons. Shockwaves swept across the planet several times, and vast regions were engulfed in flames. Clouds of soot and dust rose into the atmosphere, blocking the sun. Global extinction ended a long period of the Mesozoic and cleared the way for the life of our Cenozoic era.
It is assumed that the center of the impact fell on the current Mexican Yucatan Peninsula, where the vast (mostly underwater) crater Chicxulub has survived. Geologists began collecting ancient samples here a few years ago, and now Sean Gulick and his colleagues at the University of Texas have presented the results of their analysis. Careful work made it possible to identify substances that settled on the surface literally in the very first hours after the disaster. "The First Day of the Cenozoic" is the title of an article published by scientists in the journal Proceedings of the National Academy of Sciences.
Large impact craters are characterized by the formation of a central upland, which arises from the wave motions of rocks. After such a powerful impact, the deposition is especially dense and is better preserved over many years of erosion. These samples were obtained in the Gulf of Mexico, from a depth of about 450 meters, drilling another 1300 meters of the seabed. Having considered them, scientists were able to more accurately reconstruct the first steps of the ancient catastrophe.
In the first day after the impact, the central Chiksulub Upland rose by 130 meters, retaining traces of soot: a giant fire that broke out in the vicinity of the collision site destroyed all living things, and the tsunami raised by it brought coal ash back into the crater. “During the day, the tsunami delivered material from remote areas of the coast, including coal, which was formed from fires caused by the impact, although it fell into the water by itself,” the geologists write.
A slice of one of the cores examined by Sean Gulik's team. Abundant inclusions of soot are visible - all that remains of ancient plants and animals / © International Ocean Discovery Program
Another feature of the samples was the almost complete absence of sulfur-containing deposits: apparently, these minerals completely evaporated as a result of the impact. By filling the atmosphere with sulfur, they could further screen sunlight and cause acid rain. It is the rapid and global climate changes that have occurred after the fall of the asteroid that scientists call the "real killer" of dinosaurs.