NASA successfully smashes spacecraft into asteroid 7 million miles from Earth

In a historic trial run Monday that could lay the groundwork for saving life on Earth, NASA successfully crashed a spacecraft into a small asteroid, likely altering its orbit.

The Double Asteroid Redirection Test spacecraft, or DART, collided with Dimorphos, a small asteroid measuring 525 feet in diameter that is located roughly 7 million miles from Earth, at 7:14 p.m. ET on Monday. Impact was confirmed when the video signal that had recorded Dimorphos as DART drew near dramatically cut off.

NASA Administrator Bill Nelson called the mission "a successful completion of the first part of the world's first planetary defense test."

"I believe it's going to teach us how, one day, to protect our own planet from an incoming asteroid," Nelson said in a video statement following impact.

The DART craft launched on Nov. 24, 2021, and the mission had an estimated cost of $324.5 million. DART was traveling at 14,000 miles per hour at the time of impact, with the last 4 miles of its journey lasting just one second, NASA said.

Neither Dimorphos nor Didymos, the larger asteroid that it orbits, posed a threat to Earth, either before the impact from DART or afterward. The asteroid was chosen by NASA so as to test the accuracy of rocket guidance systems that might be used in case larger asteroids threaten Earth in the future.

The crash, which NASA broadcast live, is believed to have altered Dimorphos's trajectory. Exactly how much remains to be determined and will depend on whether Dimorphos is found through further investigation to be solid or a gravitationally held-together clump of rocks.

Nancy Chabot, a planetary scientist at the Johns Hopkins University Applied Physics Laboratory and project scientist for the DART mission, explained on NASA's live broadcast how scientists would determine the extent of how the test had changed the trajectory of the asteroid.

"This is a double asteroid system. All we've done here actually is change slightly how Dimorphos goes around Didymos, right? The telescopes on the Earth have studied this for years, so we knew that it [the time it takes Dimorphos to orbit Didymos] used to be 11 hours and 55 minutes, so what is it going to be now? The telescopes are going to measure that period change."

An illustration shows NASA's Double Asteroid Redirection Test spacecraft approaching the Didymos binary asteroid system.
An illustration of NASA's Double Asteroid Redirection Test spacecraft prior to impact at the Didymos binary asteroid system. (NASA/Johns Hopkins/handout via Reuters)

The footage of the head-on collision was captured by a camera embedded on DART, but the impact will also be studied by telescopes on Earth and on satellites.

A computer aboard DART was programmed to self-navigate the spacecraft, which traveled at approximately 3.7 miles per second. As DART neared Dimorphos, the guidance system fired off steering bursts that kept its target on track as it grew steadily bigger in the center of the camera viewfinder.

Though DART was about the size of a golf cart, and the asteroid is as wide as the Washington Monument is tall, its speed should be sufficient to successfully alter the orbit of Dimorphos, NASA said.