In context: Our planet can be a beautiful place at times, but, someday, a gargantuan asteroid might just decide to put a premature end to our collective fun. Relative to the size of other astral bodies, it wouldn’t take much space rock to damage the planet — even a 150-meter asteroid is big enough to pose a “significant threat” to Earth. That’s why NASA has been working on DART: the Double Asteroid Redirection Test.
Since bringing an Asteroid’s momentum to a complete stop is unfeasible with our current level of technology, and we’ve yet to construct a sci-fi energy shield around the entire planet, deflection is the next best option in humanity’s arsenal. And deflection is exactly what DART hopes to accomplish.
In essence, DART will use what NASA calls a “kinetic impactor” technique to send a spacecraft into the great void, with the specific intent of achieving a collision with a target asteroid. NASA hopes this will knock potentially-threatening asteroids far enough off course that the Earth is no longer in their trajectory. That’s the long-term goal, anyway. In the short term, NASA needs to make sure their technology works: that’s where its first proper test comes in.