On the off chance that giant asteroid ends up on a collision course with Earth—and Bruce Willis and Ben Affleck are unavailable—NASA is putting together a backup plan
Step one: Crash a satellite into one and see what happens.
The space agency has entered the preliminary design phase for its Double Asteroid Redirection Test (DART). This represents the first trial of what's called the "kinetic impactor technique" of asteroid deflection. Put another way, NASA hopes that by hurling a refrigerator-sized spacecraft at one of the space rocks at a speed roughly nine times that of a bullet, it can knock the asteroid off course and save the Earth.
The plan is to launch the first DART satellite at a binary asteroid called Didymos ("Twins"); the twin asteroids are scheduled to pass by earth in 2022 and 2024. (Neither pass poses any threat, according to NASA.)
By striking one of the two asteroids, scientists will be able to measure the impact of the collision.
“Since we don’t know that much about their internal structure or composition, we need to perform this experiment on a real asteroid," said Andy Cheng of the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, the DART investigation co-lead.
So why spend millions to create then crash a satellite in this fashion? NASA says it has found 93 asteroids whose orbits bring them close to earth that are big enough to potentially cause "global effects."