Spinning through space more than 65 million years ago, a six-mile-diameter asteroid collided with Earth, causing Chicxulub Giant Crater and a mass extinction level event. The crater was eventually discovered in the late 1970s and positively identified in the 1990s. Scientists believe it was the asteroid that ended the Cretaceous period and wiped out 75 percent of life on the planet. But what if this wasn’t the only asteroid to hit Earth that day?
Recent discoveries on the Guinea Plateau off the coast of West Africa have identified a second possible impact crater that could help mark the end of the Cretaceous period. Using a seismic reflection data set — a method that sends acoustic waves down a water column to map the sea floor — researchers may have identified another impact maker just over five miles (8.5 km) wide.
Buried under about 980-1,300 feet (300-400 meters) of sediments from the Paleogene period, the dates of the newly discovered Nadir Crater match those of Chicxulub Crater, according to Uisdean Nicholson of Heriot-Watt University.
(Data courtesy of the Republic of Guinea and TGS) (a) Regional map showing the location of Crater Nadir on the Guinea Plateau, off the coast of West Africa. Other important seafloor features are also highlighted, including the Nadir seamount for which the crater is named. (b and c): regional seismic cross-sections across the Guinea Plateau showing the age of sedimentary units across the plateau and the location of the Nadir Crater and Nadir Seamount.
Researchers suggest that the Nadir and Chicxulub craters may have been caused by the same asteroid that broke up in Earth’s atmosphere. If it was indeed caused by an asteroid impact, it is possible that the Nadir Crater came from a second asteroid in an asteroid cluster.
According to Nicholson and colleagues, the analyzed 2D seismic data shows promising signs of an impact crater, such as a raised rim, a central raised area, and highly deformed rock beneath the crater. Other models suggest the asteroid was about 1,300 feet (400 meters) wide and would have smashed into water 2,600 feet (800 meters) away, possibly causing a tsunami and possibly releasing greenhouse gas emissions from black shale deposits.