In 2022, NASA plans to send a probe crashing into an asteroid at more than 13,000 miles per hour to deflect it off its course.
This particular asteroid isn’t a threat to us. But NASA is trying to figure out how it might defend Earth from asteroids more generally — in case a big one really does head our way in the future.
This won’t be the first time a spacecraft was intentionally crashed into a rock in orbit: in 2005, NASA’s Deep Impact probe collided with a comet, in order to throw up debris to help scientists better understand its interior.
But AIDA would be the first time such a collision was conducted solely to help us figure out how to move asteroids around in space. The wealth of data collected by AIM before and after the collision would allow scientists to build improved models of how asteroids respond to such impacts.
This could someday be extremely useful, because if we detected a big asteroid headed for Earth, the simplest way to prevent disaster would be to nudge it slightly it out of our way.
“The amount of momentum you’d need to transfer to an asteroid to change its trajectory slightly — to prevent a future impact — is really quite small,” physicist and former NASA astronaut Ed Lu, who now heads an organization that seeks to protect Earth from asteroids, told me in a recent interview. “It’s a couple of millimeters per second. That means you can run into it with a small spacecraft.”
Even if we do develop the technology to deflect asteroids, that’s still not sufficient. We’d also need to spot a dangerous asteroid far enough in advance to launch a mission. And right now, there’s no certainty we’ll always be able do that.
Scientists have located more than 90 percent of the huge kilometer-wide or larger near-Earth asteroids capable of causing a global catastrophe, and none of them, thankfully, are on track to hit us. But midsize asteroids hit Earth much more regularly (once every few centuries or so) and can cause significant damage, and we’ve still only spotted a small percentage of them. One terrifying example is the Tunguska event: a 30- to 60-meter-wide asteroid that exploded over a remote corner of Siberia in 1908, discharging an amount of energy one thousand times greater than the Hiroshima atomic bomb and knocking down some 80 million trees.