Let's slam a spaceship into an asteroid

In 2005, the European Space Agency floated a half-baked “Don Quijote” plan to aim a spacecraft into an asteroid to deflect it. But the plan targeted a very large asteroid that was pretty far away, making it both expensive and unlikely that scientists on the ground could actually measure the asteroid’s deflection.

Instead, Cheng and his colleagues are betting that aiming at a small and close asteroid may be more feasible. Their goal is to crash into the smaller rock in a binary asteroid system called Didymos that is projected to travel past Earth in 2022.

“We are targeting the smaller member of the binary,” Cheng told LiveScience. “That will change the orbit of the system and that can be measured.”

Because the asteroid is relatively modest-sized, about 500 feet (150 meters) wide, the spacecraft would be able to move it noticeably from its regular orbit, allowing the scientists to measure how much the spacecraft shifted the space rocks from their course. Since it will be just 6.5 million miles (10.5 million kilometers) from Earth, scientists can measure the deflection from the ground using telescopes, he added.