Protecting Earth

When a double asteroid swings close to Earth in 2024, it just might get a nasty reception. NASA is studying a mission that would slam a spacecraft into the smaller of the two bodies. Astronomers would then measure how much the impact affected the orbit of the two asteroids around each other — vital information that could help us deflect an asteroid on a collision course with Earth.
An impact by a large asteroid could have devastating effects across a region or even the entire planet. But with enough lead time, it could be possible to nudge an asteroid onto a safe course. One way to provide the nudge might be to ram into the asteroid, changing its speed and direction by a tiny bit.
The new mission, known as DART, would test that technique.
The current concept calls for it to target Didymos, a system of two asteroids that orbit the Sun as a pair, bound by their mutual gravitational pull. The larger body is about half a mile in diameter, while the other is only about 500 feet across.
DART