DRILLING INTO A DINOSAUR KILLER

Some 66 million years ago, an asteroid — or perhaps a comet — hit Earth. It struck off the coast of what is now the Yucatán Peninsula of Mexico. There, it formed a giant crater. This impact is thought to be at least partly responsible for a mass extinction that included the dinosaurs. The site of this impact has been under investigation for a few decades. Its discovery started in 1980. That’s when a research team found lots of iridium in places worldwide. The metal is rare on Earth, but abundant in asteroids and other space rocks. Yet strangely, plenty of iridium shows up along the boundary between rocks from the Cretaceous and Paleogene periods. It's the first hard evidence for a killer-asteroid impact. Eleven years later, scientists identified the smoking gun — that hidden crater. It circles the coastal Mexican town of Chicxulub Puerto (CHEEK-shuh-loob PWAIR-toh). Yet questions have remained about how the impact might have caused such global destruction. For answers, scientists recently returned to the scene of the crime.