At 7.14pm EDT, Nasa made history by slamming a spacecraft into an asteroid, marking the first time life on Earth has altered the course of a heavenly body.
Nasa’s Double Asteroid Redirection Test spacecraft, or Dart, slammed into the asteroid Dimorphos at 14,400 miles per hour to test whether the impact can alter the asteroid’s orbit. A faint grey smudge in the Dart spacecraft’s camera’s just minutes early, Dimorphos grew to become a huge, greyscale dragon’s egg, studded with boulders, as the spacecraft drew close in the moments before impact.
The space agency hopes that spacecraft like Dart could one day divert asteroids that threaten Earth, providing life on Earth a fighting chance against rare, but potentially deadly asteroid impacts of the type that once wiped out the dinosaurs.
Dart launched in November, 2021, and spent months traveling to its terminal rendezvous with Dimorphos around 6.8 million miles from Earth. The impact itself was an engineering marvel, a golf cart sized spacecraft traveling faster than a bullet, guiding itself toward and then into a small asteroid roughly the size of the Great Pyramid of Giza in the vastness of space.
The engineering team at the control center at the Johns Hopkins Applied Physics Laboratory, in Maryland, which managed Dart’s flight to Dimorphos, erupted in cheers the moment they lost signal with the spacecaft, one of the few circumstances in which mission managers actually want to lose touch with a spacecraft.
“It was not a doughnut!” Johns Hopkins Applied Physics Laboratory Dart impact modeling working group lead Angela Stickle told reporters immediately following the successful impact. Stickle and other engineers had worried early Monday about the possibility that Dimorphos would turn out to be a strange shape that could have allowed Dart to fly through or around the space rock, despite being locked on with its navigation system.
Dimorphos is the moonlet of a larger, companion asteroid, Didymos. The goal of the Dart mission was to both successfully hit Dimorphos, and then measure how much that impact changes the orbit of Dimorphos around Didymos. Nasa scientists estimate its orbit could be altered by about 10 minutes, a change sufficient to divert an asteroid the size of Dimorphos if it were headed toward Earth, so long as the impact occurred a few years before any potential collision with our planet.
Dimorphos did not pose an actual threat to Earth, and will not pose a threat now after the impact, which is why Nasa selected it as a safe laboratory to test the “kinetic impactor” technique of the Dart mission.
“It’s been a successful completion of the first part of the world’s first planetary defense test,” Nasa Administrator Bill Nelson said in a statement following the successful Dart impact. “It’s going to teach us one day how to protect our own planet from an incoming asteroid.”
No known asteroids currently threaten Earth with a major impact of the sort that wiped out the dinosaurs, but Nasa’s Planetary Defense Coordination Office wants to make sure they’re ready whenever that day may come. Dart is just one component of the office’s efforts to identify potentially hazardous asteroids, and develop techniques to divert them.
“We have the technology now to do this,” Nasa’s Planetary Defense Officer Lindley Johnson told reporters at an earlier press event. “To find these objects, years, decades, even a century before they pose an impact threat to the earth.”
While the excitement of the Dart impact is over, the mission itself is far from over.
Scientists will be pouring over the data from telescopes and radar system all over the globe that were monitoring the Dart impact, as well as images from the Hubble and James Webb space telescopes, to better understand how the impact immediately impacted Dimorphos. Those observations will be crucial for determining, over the coming months, how much Dart actually affected the orbit of Dimorphos.
Some of those images will become available over the next few days, Nasa and APL officials said. That includes images from the cameras that had the best seat in the house, the instruments on the Light Italian CubeSat for Imaging of Asteroids, or LiciaCube, of the Italian space agency, which observed Darts impact from a safe distant while following about three minutes behind Dart.