The air quality this week is bad. Smoke from Canadian wildfires has turned the sky orange in Philadelphia. It covered the Statue of Liberty in Manhattan. In Detroit, which has faced some of the worst conditions in the country, smog has almost clouded the city’s air. The eastern United States isn’t exactly used to smoky days, which can make someone like me, from the wildfire-prone West, brag about how I’ve seen the worst. But those smoky days are nothing compared to those of 66 million years ago. If you want to talk about bad air quality, ask the dinosaurs.
The asteroid that spelled the beginning of their end slammed into Earth at 40,000 miles per hour, blasting a 112-mile-wide crater on Mexico’s Yucatán Peninsula. The explosion was so big that it tore a hole in the atmosphere, bringing “atmosphere to the surface of the Earth,” Kirk Johnson, director of the Smithsonian’s National Museum of Natural History, told me. The impact threw trillions of tons of debris into space, and much of it made its way into the yawning atmosphere and into Earth’s orbit. As the planet continued to orbit, “it got a global cloud of dust and debris that blocked sunlight from hitting the ground,” Johnson said. And it blocked almost all sunlight—plunging the earth into eclipse-level darkness. Some fiery debris fell down from the atmosphere, and within minutes, wildfires were spreading. The massive fire burned “the entire landscape of the planet, not just a few forests in Canada,” Johnson said — and with debris blocking the sun, the fire is “burning in a dark world.”
Given the fires around the world, dinosaurs would be caught in a level of smoke more intense than the kind of wind exposure the United States experienced this week, Brian Toon, a senior research scientist at the University of Colorado Boulder’s Atmospheric and Space Physics Laboratory, told me. Unfortunately—or maybe fortunately for them—many dinosaurs weren’t alive to experience this pitch-black global hell. The asteroid impact event was “a massive, atomic blast thing, like 1 billion Hiroshimas of energy released,” Johnson said. Dinosaurs within about 1,000 miles of the impact site died “just by exploding, basically,” he said — and given the size of the explosion, “if you were a human-sized animal standing anywhere on the planet’s surface, your survival for the first week is very likely.”
Other creatures perished during the ensuing climate upheaval. Within a week, maybe months, the brightest day would look more like a moonlit night, Ken MacLeod, a geology professor at the University of Missouri, told me. The air was not only smoky, he said; it was full of dust and gas. The blackout lasted for about two years, as particles from the asteroid impact remained in the atmosphere and soot from wildfires added to them. The next few decades were “too little light, too hard for photosynthesis to happen,” which starved the herbivores, Brian Huber, a research geologist at the Smithsonian’s National Museum of Natural History, told me.
When would the atmosphere of this dark and alien planet settle into something like the haze that hangs over Detroit today? No one was quite sure: “I would bet years, decades later,” Huber said. Johnson estimated that it would be around a few years after the impact; curators at the American Museum of Natural History in New York City found that 40 percent of sunlight was still blocked two years after the asteroid hit, the museum told me. Although most of the soot and dust particles disappeared within a few years, the sulfate aerosols continued to form a “global, orange-brown smog,” a description of the dinosaur extinction show. According to the museum, it was only four years after the asteroid arrived that full sunlight was seen again. The era in which the dinosaurs perished would be unrecognizable to a modern person. Compared to that, the air pollution Americans are facing right now, Huber said, “is nothing.”
Scientists know all this in part because the tiny amounts of coal and soot—millions and millions of tons of it—that fell to the ground left traces that can still be seen today. The asteroid itself also left a thin layer of debris made of meteorites and ancient parts of what we now call Mexico. You can touch it at Trinidad Lake State Park in southern Colorado, Toon said—evidence from a time in the planet’s history when things looked a lot worse than one might imagine.
So, yes, the smoke this week is bad. Outdoor air quality is poor, and people should take precautions to reduce the amount of air they breathe. And yet, there is something to be thankful for every day. And today, it is that we are not dinosaurs.
