NASA is about to crash a spacecraft into an asteroid

Dimorphos is a lump of space rock so far away from Earth that we don’t even know what it looks like — and on Monday, we’re going to smash it with a spacecraft. The Double Asteroid Redirection Test (DART) will be traveling at more than 14,000 miles per hour when it hits the asteroid, in what has to be one of the most metal science experiments of all time.

DART is a NASA effort to see if it can change an asteroid’s movement in space. It’s being billed as the world’s first “planetary defense test mission” — a test run to see if we have what it takes to avert a serious asteroid impact on Earth sometime in the future. You know, just in case.

To be extremely clear, neither Dimorphos, or its larger companion Didymos, pose any threat to Earth. In fact, we haven’t identified any asteroids that pose an immediate threat to our planet. These two are just good target practice. Dimorphos and Didymos are a binary asteroid system, with Dimorphos being a ‘moonlet’ of Didymos. As the tiny moonlet orbits the bigger asteroid, it passes between the bigger asteroid and Earth. This means that telescopes both on and off-world can monitor the system and see relatively quickly what a crash does to Dimorphos’ speed and trajectory.

Soon after the impact, telescopes on every continent on the planet will focus on the system to see the aftermath. Off-world, the James Webb Space Telescope, Hubble, and even the asteroid-bound Lucy spacecraft will also train their gaze on the asteroid system, waiting to see what happens when a rock meets a hard spacecraft.

The impact is expected to alter the speed of Dimorphos by a fraction of a percent, researchers say, changing the time it takes to complete its orbit by several minutes. That might not seem like much, but for planetary defense scientists, those minutes are monumental. “This demonstration is extremely important to our future here on the Earth” said Lindley Johnson, NASA’s Planetary Defense Officer, at a press briefing ahead of the mission.

This moment in history is unique, Johnson said; it’s the first time that humans have both knowledge about the threat that asteroids pose, and actually have the tech to do something about it. In the event that we ever do detect a giant rock hurtling towards the planet, having a plan or two in place for how to stop said rock is a good thing — and having a few practice runs under our belt could be even better.

“DART is demonstrating what we call the kinetic impact technique for changing the speed of the asteroid in space and therefore changing its orbit” Johnson said.

There are other options in the planetary defense toolbox, including a ‘gravity tractor,’ a spacecraft that could fly next to an asteroid, gently pulling it to a safer path. There’s also the possibility of firing an ion beam at an asteroid for a long time, pushing it to a different orbit. DART is trying a more direct method first; crashing into it full speed ahead.