If scientists spotted an asteroid coming for Earth and didn’t have a lot of time to react, they would send a bomb out into space to take care of it. But they hope they never have to face that situation.
NASA has described three different methods of dealing with asteroids that threaten our planet, all of which involve changing the objects’ trajectories. According to the space agency, it could launch a large spacecraft and use the vehicle’s gravity to slowly and carefully draw the asteroid away from Earth; crash into the asteroid to change its speed and course, using one or more spacecraft that would serve as “kinetic impactors”; or, in an “Armageddon”-type plan, detonate a device that would blow off the asteroid’s surface material and send it in another direction like firing a rocket would.
“This is a last-resort measure,” Lindley Johnson, the head of NASA’s Planetary Defense Coordination Office, said. “Though quite effective if time is short, it would take a lot of coordination and approval not only within the U.S. government, but also with the international community.”
As Johnson notes, it is all about how much time scientists have. NASA has previously pointed out the issue with using a kinetic impactor: Even if one or more were available immediately upon incoming asteroid detection, they would still need “at least one to two years for smaller asteroids” in lead time, and way more than that if a kinetic impactor needed to be designed and built from scratch or if the asteroid was larger.
This is one reason that astronomers keep their eyes peeled for asteroids — they want to detect them as early as possible. To that end, NASA’s Center for Near-Earth Object Studies is on watch and maintains a database of objects that are passing within Earth’s vicinity, including tracking those that may pose a collision threat to the planet.
“The rate of asteroid discovery has increased considerably,” Johnson said about the last couple of decades. There are almost 8,000 objects currently being tracked, but the solar system is far from completely covered: “We believe there are still over twice that number out there to be found.”