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, who 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.
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.
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. “To find these objects, years, decades, even a century before they pose an impact threat to the earth.”