About 66 million years ago, a city-size asteroid slammed into what is now the Yucatán Peninsula, ushering in a long period of darkness that snuffed out the nonavian dinosaurs. Researchers have long debated exactly what aspect of this event, known as the Chicxulub impact, caused the rapid change in climate. Was it sulfur particles from vaporized sedimentary rocks? Soot from subsequent global wildfires? Or dust from the very bedrock of the Yucatán?

Now, new research argues that dust was the deadliest aspect of the impact. While soot and sulfur contributed to global darkness and an impact winter that halted photosynthesis for nearly two years, fine dust from the granite pulverized in the impact remained aloft in the atmosphere for up to 15 years. The asteroid impact led to a spiral of extinctions that killed 75% of all species on the planet.