Traveling at 14,000 miles per hour, a NASA spacecraft slammed into an asteroid on Monday evening. But the crash was intentional: NASA meant to alter the flying rock’s trajectory in space. The asteroid poses no danger to Earth, but researchers wanted to test whether this approach is feasible in case of a future threat of impact.
The agency's Double Asteroid Redirection Test spacecraft, or DART, hit the asteroid Dimorphos at 7:14 p.m. Eastern time. At the time of the collision, Dimorphos was about 6.8 million miles from Earth.
NASA scientists cheered as images were sent back to the ground from the spacecraft, showing in increments its approach and impact with Dimorphos. Representative Don Beyer from Virginia, who chairs the House Space and Aeronautics Subcommittee, tweeted that the mission was "a historic success... and a very important step forward for planetary defense."
IMPACT SUCCESS! Watch from #DARTMIssion’s DRACO Camera, as the vending machine-sized spacecraft successfully collides with asteroid Dimorphos, which is the size of a football stadium and poses no threat to Earth. pic.twitter.com/7bXipPkjWD— NASA (@NASA) September 26, 2022
The DART spacecraft has been hurtling toward its target since November 24, 2021, when it began its 10-month mission to Dimorphos. The asteroid is about 500 feet in diameter. In comparison, the asteroid that killed the dinosaurs was 6.2 miles wide.
“If a 160-meter asteroid [like Dimorphos] hits a city, it will [be] a bad day for that city, leaving a crater of more than a kilometer, but it won't change the whole planet,” Thomas Zurbuchen, associate administrator at NASA's Science Mission Directorate told Deutsche Welle in 2021.
Dimorphos orbits a half-mile-wide asteroid called Didymos roughly once every 12 hours. Rather than blowing Dimorphos into pieces, the head-on collision was meant to nudge the asteroid’s orbit, making it slightly more bound to Didymos by gravity and increasing its speed by just 1 percent, per CNN's Ashley Strickland. This will likely shorten its orbit time by a few minutes.
“If we are able to see far enough in advance and know that an asteroid might be a problem, pushing it out of the way will be much safer than the big Hollywood idea of blowing it up,” Catriona McDonald, an astrophysicist at Warwick University, tells the Guardian’s Ian Sample.
As DART approached the two objects, it sent images back to Earth at a rate of about one per second. These are the first close-up images of Dimorphos, which in the past has appeared only as a “fuzzy blob in telescopes,” writes the Washington Post’s Joel Achenbach.
A small Italian Space Agency satellite also took images of the impact and its aftermath. Those images will be available in the coming days and weeks. In 2024, the European Space Agency will send a spacecraft to Dimorphos study the asteroid up close.
Scientists weren't exactly sure of Dimorphos's composition—whether it’s a solid rock or a pile of rocks held together by gravity. If the latter, there was a chance the impact could have create an artificial meteor shower, the New York Times’ Jonathan O’Callaghan reported in 2020.
“People assume it’s a solid rock, we have a solid spacecraft, and we’re essentially playing a giant game of billiards in space… and you can basically just solve that out as a simple physics equation,” Cristina Thomas, a planetary scientist at Northern Arizona University who leads the observation team for the DART mission told Science’s Zack Savitsky before the impact. “But there’s so much else that’s happening that makes that not true.”
Scientists say a lot can be learned from the mission, and testing this technology early is crucial in case of future Armageddon or Don’t Look Up scenarios.
“We’ve got to have such technology,” NASA’s planetary defense officer, Lindley Johnson, tells the Post. “It would be prudent upon us to test that all out ahead of time, so we’re not trying to do it for the first time when we really need it to work.”
Editor's note, September 26, 2022: This article was updated to reflect that the DART spacecraft successfully made impact with its asteroid target.