In a first of its kind test, NASA crashed a spaceship into an asteroid on Monday to learn how to defend the planet against space rocks.

The experiment should tell us if it's a good idea to hurtle a spaceship into an asteroid. There are no asteroids that pose a threat at the moment. It's only a matter of time before a city is wiped out by an asteroid, according to experts.

NASA's probe traveled about 6.8 million miles before crashing into the asteroid as part of the Double Asteroid Redirection Test. It did not make it through the crash.

The director of NASA's planetary science division said after Monday's collision that the science starts now. We're going to see how effective we were after we impact.

"We're embarking on a new era of humankind, an era in which we possibly have the ability to protect ourselves from something like a dangerous, hazardous asteroid impact," Glaze said.

The asteroid, Dimorphos, is in close proximity to Didymos. NASA chose the asteroids because they are not a threat to the Earth.

The Didymos Reconnaissance and Asteroid Camera for Optical navigation (DRACO) provided a real-time feed of the demise of the craft on Monday. 38 seconds is how long it takes DART's final transmissions to reach Earth.

Initial images from DRACO, which took one image per second to document the impact and aftermath
Initial images from DRACO, which took one image per second to document the impact and aftermath.
NASA

Didymos and its moonlet Dimorphos were shown as a single white dot. The spaceship closed in.

As the DART spacecraft flew closer, Dimorphos emerged as a separate point of light that grew larger and brighter.
As the DART spacecraft flew closer, Dimorphos emerged as a separate point of light that grew larger and brighter.
NASA

Dimorphos became a separate point of light that grew bigger and brighter. The entire screen was filled with the asteroid until it hit the ground.

DRACO took live images as the spacecraft approached the space rock.
DRACO took live images as the spacecraft approached the space rock.
NASA

One of the last frames was beamed from DRACO before the DART was able to eat it. When the live screen went red, the team knew that the spaceship smashed into Dimorphos. The DART mission operations team erupted in applause after the probe's success.

Above, the last image from the DART mission taken by DRACO.
Above, the last image from the DART mission taken by DRACO.
NASA

Scientists think the collision will change the speed of Dimorphos by a fraction of 1%, but they don't think it will be a big deal.

High-resolution photos of the impact will be sent back to Earth by the Italian Space Agency. It could take weeks for scientists on Earth to get that data.

Now that DART has been destroyed, follow-up observations with ground- and space-based telescopes will show how the asteroid system has changed.

Infographic showing the effect of DART's impact on the orbit of Dimorphos.
Infographic showing the effect of DART's impact on the orbit of Dimorphos.
NASA/Johns Hopkins APL

Dimorphos is about 525 feet in diameter and has a mass of around 11 billion pounds.

An illustration shows the scale of Dymorphos and Didymos as compared to recognisable objects on earth like the Eiffel Tower and the Burj Khaliffa.
A scale shows the size of the asteroids compared to recognizable Earth landmarks.
NASA/Johns Hopkins APL

The scientists are hoping that the tiny nudging will change the trajectory of the rock.

After the impact, they will watch for debris that flies off of the asteroid.

An animation looking from behind as NASA's first planetary defense test mission, the Double Asteroid Redirection Test (DART), collides with the asteroid moonlet Dimorphos.
An animation from behind as NASA's first planetary defense test mission, the Double Asteroid Redirection Test, collides with the asteroid moonlet Dimorphos.
NASA/Johns Hopkins APL/Jon Emmerich

The Earth is not prepared for a city-killing asteroid 

It's important to know how to knock an asteroid off its path. Chances are that scientists wouldn't be prepared if the asteroid was headed towards Earth.

In the last three years, NASA has organized seven asteroid impact simulations. A group of international experts were able to stop the asteroid once but only because of a limited warning period.

Insider was told by experts that it would take five to 10 years for NASA to build and launch a mission that could be used to defend against asteroids.

Experts may not spot the rock in time. A lot of asteroids are tracked by NASA. About 40% of city-killer asteroids have been identified so far.

The problem is not theoretical at all. Sometimes large space rocks come too close for comfort and scientists don't spot them until it's too late.

Scientists only had a few days' warning of the asteroid's flyby, which came in 2019. In 2020 an asteroid the size of a car flew within 1,830 miles of Earth. Six hours before it passed Earth, scientists spotted it.