A NASA spacecraft slammed into the surface of a distant asteroid at 7:14 PM ET Monday night, the culmination of the agency’s Dual Asteroid Redirect Test (DART).
An hour before impact, the target asteroid, Dimorphos, was not even visible in images from the spacecraft. In some of the early images sent back to Earth, even Dimorphos’ larger moon Didymus appeared as a speck against a sea of black. The DART spacecraft was traveling at 14,000 miles per hour, and details quickly emerged. Viewers on Earth saw the rough surface of Didymos as the spacecraft traveled autonomously toward Dimorphos. Rocks filled the screen just before it turned bright red, indicating a loss of signal—DART had reached its final destination.
There was consternation in the mission’s operations room when the images appeared. “This asteroid was coming into view for the first time, we really had no idea what to expect. We didn’t really know the shape of the asteroid, but we knew where we were going to hit. said Elena Adams, DART Mission Systems engineer. “So I think we were all kind of holding our breath. I’m surprised none of us passed out for a second.’
Telescopes around the world (and a few in space!) are now turning their attention to the collision site. They will observe how much the impact has changed Dimorphos’ movement. The disaster is part of the first practical planetary defense experiment – an attempt to see if humanity might one day be able to redirect the path of an asteroid headed for our planet.
“We are entering a new era of humanity, an era where we potentially have the ability to defend ourselves against something like a dangerous asteroid collision. What an amazing thing. We’ve never had this opportunity before,” Laurie Glaze, director of NASA’s Planetary Sciences Division, said shortly after the impact.
To be clear, neither Dimorphos nor Didymos pose a threat to Earth. There are no known asteroids that pose a significant and immediate threat to our planet. But NASA is playing a long game. Someday in the future, if an asteroid is spotted on a dangerous path, the agency wants us to have options that would allow us to prevent a catastrophe.
The option that DART is testing is one of the most direct; if we hit something on an asteroid, will that change how that asteroid moves? As Dimorphos’ orbit passes between another asteroid (Didymos) and Earth, researchers will soon have an answer to this question.
Dimorphos is relatively small, so scientists couldn’t actually see the asteroid until just before the collision. But telescopes can see Didymos dim whenever Dimorphos crosses between it and Earth. This allows researchers to know how fast the asteroid is moving. They expect to see Dimorphos’ orbit speed up after the collision, but how well the asteroid’s behavior will match the computer models remains to be seen.
It will likely take several months to fully answer how much the DART mission has changed Dimorphos’ orbit, but some images and data will likely start coming out in the next few days and weeks from sources throughout the solar system.
Before impact, the DART spacecraft launched a smaller satellite, Italy’s LICIACube. This small spacecraft followed DART on its path to doom, taking pictures of the immediate aftermath to be sent back to explorers on Earth. Telescopes on seven continents will also focus on the asteroid system, as will the Lucy spacecraft, the James Webb Space Telescope and the Hubble Space Telescope. Then, in 2024, the European Space Agency will send another spacecraft to study Dimorphos and get a close-up look at the asteroid and the remnants of the spacecraft itself.
But in the meantime, the latest images from the spacecraft offer plenty of tantalizing details for researchers, including Carolyn Ernst, a scientist working on DART’s imaging system, DRACO. At a news conference after the impact, she praised the surprising shapes of the pair of asteroids and the rocks, smooth patches and craters of Didymos that were only visible for a short time.
“These guys, their work is done.” Ernst said, referring to his fellow engineers, “But ours is just getting started,”