The world had a front-row seat Monday evening as NASA successfully crashed a spacecraft into a distant asteroid to see if it can move the rock, a method that will come in handy should a planet-killing asteroid ever come hurtling toward Earth.

NASA says this particular asteroid is millions of miles away and was not a threat to Earth before the crash, nor will it be a hazard following impact.

Thanks to a camera on board the spaceship, the lead-up to the collision was live-streamed back to Earth. Those logged onto NASA’s YouTube channel saw the Dimorphos asteroid slowly fill the frame in the minutes before impact when the image screen froze — then went to black.

At 30 minutes from impact, Dimorphos was still 7,000 miles away and just a tiny bright speck in the live, but slightly delayed, images streaming back to Earth.

At around 20 minutes from impact, NASA announced on its webcast that the spacecraft had achieved “precision lock” on Dimorphos and would be zeroing in on its target near the center of the asteroid.

At around 5 minutes before impact, Dimorphos was a bigger, brighter spot about 1,110 miles away and its companion asteroid, Didymos, appeared much larger in the foreground.

A few moments later, Didymos dropped out of view and Dimorphos began to fill the screen.

Boulders and shadows became visible on the egg-shaped body as the craft got nearer. The image of Dimorphos began to fill the screen, with the last images seemingly just feet above the asteroids craggy surface.

Moments later, the mission engineers declared a direct hit.

Why did NASA crash a perfectly good spaceship?

Sponsored by NASA’s Planetary Defense Coordination Office and led by the Johns Hopkins University Applied Physics Laboratory, the Double Asteroid Redirection Test, or DART, is a $325 million project designed to crash the 1,260 pound spacecraft traveling at 14,000 mph into Dimorphos, an asteroid that’s 525 feet in diameter and 7 million miles from Earth.

The point of the exercise is to see how significantly the current path of Dimorphos can be altered by the impact in a technique NASA calls “asteroid deflector by kinetic impactor.”

What is Dimorphos and why is it a good test target?

Dimorphos is a moonlet asteroid, orbiting a larger asteroid named Didymos, which is about a half-mile in diameter. Mission officials have stressed that the binary system “is not on a path to collide with Earth and therefore poses no actual threat to the planet” but is the “perfect testing ground” to see if an asteroid’s natural path can be altered via a high-velocity impact.

Thanks to an onboard camera system that streamed one-image-per-second back to Earth, mission engineers, along with the viewing public, had a real-time view, albeit one delayed by the 45 seconds or so that it takes for the video to process and stream back to Earth-based receivers, capturing DART’s approach and collision with Dimorphos.

Was the crash visible by telescopes?

While DART was recording video right up to the moment of its own demise, plenty of other “eyes” were on the collision, including a slew of Earth-bound telescopes as well as a number of spaced-based observers.

NASA says the Hubble and James Webb Space Telescopes were turned toward the Didymos system for the event, as was the Lucy space probe. DART was also carrying a small cube satellite designed and built by the Italian Space Agency that it launched about two weeks ago on its way to the target. The LICIACube had the closest third-party view of the crash from its position at 55 kilometers, around 34 miles, from Dimorphos at the time of impact, according to NASA.

Who was driving when the crash happens?

Launched atop a SpaceX Falcon 9 rocket from California’s Vandenberg Space Force Base in California last November, the DART spacecraft shifted from human controls to a fully autonomous, onboard “smartnav” navigation system about four hours before its meeting with Dimorphos.

Being able to launch a spacecraft that is able to independently find and target a rogue asteroid is a critical element of the DART experiment, according to NASA Program Scientist Tom Statler, speaking last week at a NASA press conference.

“The first test ... (is) our ability to build an autonomously guided spacecraft that will actually achieve the kinetic impact on the asteroid,” Statler said at the press conference. “The second test is the test of how the actual asteroid responds to the kinetic impact.

“Because at the end of the day, the real question is how effectively did we move the asteroid. And, can this technique of kinetic impact be used in the future if we ever needed to?”

When will NASA know if the crash test worked, or not?

Statler said the expectation is that DART’s impact on Dimorphos changed the asteroid’s speed by 1% or so, but it could take weeks or even months to determine the exact level of disruption.

While this may seem like a minor change, the ability to create even a minute change in an asteroid or comet’s trajectory toward Earth, with sufficient lead time, could create the difference between some future near-miss or direct hit.

Are any dangerous asteroids headed for Earth right now?

Right now, no known asteroid larger than 140 meters in size has a significant chance to hit Earth for the next 100 years, but only about 40% of those asteroids have been found as of October 2021, according to NASA.

As the collective knowledge-base and expertise grows to include comprehensive identification and tracking of future potential hazards from space, Statler said the DART mission will help prepare the residents of Earth to take effective action in the event of some distant, pending catastrophe. And it’s an experiment without precedent.

Here’s how to re-watch the crash

If you missed it, or want to watch again, visit NASA’s website to watch a recording of the DART mission asteroid crash.