It was a hot Monday in August 2013, just before dawn. A team of scientists stood on the tarmac in Houston. They had the keys to an unusual aircraft: a NASA-owned DC-8 jumbo jet with a laboratory inside it.
They made for a large and diverse group: chemists and geoscientists, meteorologists and climatologists, engineers and pilots. Their primary mission took them over patches of woods across the U.S. Southwest, where they measured the kind of chemicals off-gassed by trees.
But on that particular morning they took the plane slightly north, toward the Sierra Nevadas, where an enormous wildfire—known as the Rim Fire—was chewing through ancient pine forest. And after a couple of hours of flying, once they got to the fire, they drove the plane straight into its enormous plume of smoke—and then they did it again, and again.
This was not the first time they had flown the plane through a smoke cloud. NASA’s DC-8 had made two earlier trips to different wildfires in Oregon and Washington that summer. It measured towers of soot and ash close to the ground and more than 10 miles in the air, from the bottom of the troposphere to the lower reaches of the stratosphere.
“The thing that you’re always surprised by when you fly through the fire is that everything that you can measure, you see enhanced,” said Greg Huey, an atmospheric chemist at Georgia Tech and one of the leaders of the mission. “You just get big signals for everything in one of these fires.”