Adding to the intrigue and the danger is the unpredictability of cometary orbits. The icy objects begin spouting gas as they near the sun and heat up; these gas jets act like little thrusters, making it tough to forecast exactly where a comet is going to go.
Despite all of these factors, however, the focus on asteroids as Earth's primary impact threat is not misplaced, Boslough and Ailor said. The reason is simple: numbers.
"I'm more worried about asteroids than I am comets, because there are so many more asteroids," Boslough said. "The likelihood of an impact from an asteroid is probably 100 times the likelihood of an impact from a comet of the same size."
There are probably trillions of comets out there, but the vast majority of them reside at the extreme outer edge of the solar system, in a shell of icy bodies known as the Oort Cloud. Near-Earth space, meanwhile, is dominated by asteroids. Scientists think millions of NEAs exist, but only about 11,000 have been discovered and tracked so far.