A spacecraft that slammed into a small asteroid two weeks ago redirected the space rock’s orbit around its larger partner in 32 minutes – even better than NASA engineers predicted. The results are great news for humanity’s first test of its planetary defense system.
On September 26, the Double Asteroid Redirection Test (DART) spacecraft disintegrated and created a huge plume of dust when it collided with the asteroid Dimorphos, which is 7 million miles (11 million kilometers) from Earth. DART slammed into Dimorphos at around 14,540 mph (23,400 km/h). The probe’s original goal was to change Dimorphos’ orbit around its largest partner – the 1,280-foot-wide (390-meter) asteroid Didymos – by at least 73 seconds, but the spacecraft has in changed the orbit of Dimorphos by 32 minutes.
That means the 1,210-pound (550-kilogram), $314 million DART spacecraft — a stubby, cube-shaped probe made up of sensors, an antenna, an ion thruster and two 28-foot solar arrays long (8.5 m) – pushed Dimorphos closer to Didymos and shortened the orbital path of the smaller asteroid. The resounding success increases the chances that a method like this could one day be used to push a harmful asteroid off a collision course with Earth.
“This is a watershed moment for planetary defense and a watershed moment for humanity,” NASA Administrator Bill Nelson said at a press conference on Tuesday (October 11). “We showed the world that NASA is serious about defending this planet.”
DART recorded and broadcast its final moments with its on-board Didymos reconnaissance and asteroid camera for optical navigation, which was also responsible for automatically navigating the spacecraft on its collision course.
As DART moved closer and closer to the space rock, its camera feed showed the asteroid’s landscape blossoming from a single pale gray pixel to rugged, steep terrain dotted with sharp, shadowy rocks. DART hit the 525ft-wide (160m) Dimorphos just 56ft (17m) from its exact center – an astronomical “bullseye”.
After the collision, powerful observatories monitored the asteroid from Earth and, in the case of the James Webb Space Telescope (JWST) and the Hubble Space Telescope, from space. By tracking when the combined sunlight reflected from the pair of asteroids dipped, indicating that Dimorphos had passed into Didymos’ larger shadow, the scientists calculated that Dimorphos’ orbital period was shorter by half. -hour than before impact. Follow-up observations from radar instruments also directly measured the same orbit, confirming that it had fallen from 11 hours and 55 minutes to 11 hours and 23 minutes.
“Let’s all take a moment to soak this in,” Lori Glaze, head of NASA’s planetary science division, said at the press conference. “For the first time, mankind has changed the orbit of a planetary body, of a planetary object – the first time.”
Scientists are already getting a better picture of the immediate aftermath of the impact closer to the space rock thanks to the Italian Space Agency’s Light Italian CubeSat for Imaging of Asteroids (LICIACube), a smaller “cubesat” that broke away of DART on September 11. Now orbiting Dimorphos at a distance of 34 miles (55 km), LICIACube began sending photos back to Earth, showing how the asteroid’s trajectory changed and how the collision caused material to explode outward. The LICIACube observations will be supplemented by others from Hubble and JWST over the coming weeks.
All of this will allow scientists to get an idea of the kind of force needed to prevent future asteroids from crashing into our planet with deadly consequences.