After 10 months of flying in space, NASA’s Double Asteroid Redirection Test (DART) – the world’s first planetary defense technology demonstration – successfully impacted its asteroid target on Monday, the agency’s first attempt to move an asteroid in space. 

Mission control at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, announced the successful impact at 7:14 p.m. EDT. 

As a part of NASA’s overall planetary defense strategy, DART’s impact with the asteroid Dimorphos demonstrates a viable mitigation technique for protecting the planet from an Earth-bound asteroid or comet, if one were discovered.

“At its core, DART represents an unprecedented success for planetary defense, but it is also a mission of unity with a real benefit for all humanity,” said NASA Administrator Bill Nelson. “As NASA studies the cosmos and our home planet, we’re also working to protect that home, and this international collaboration turned science fiction into science fact, demonstrating one way to protect Earth.”

DART targeted the asteroid moonlet Dimorphos, a small body just 530 feet (160 meters) in diameter. It orbits a larger, 2,560-foot (780-meter) asteroid called Didymos. Neither asteroid poses a threat to Earth. 

The mission’s one-way trip confirmed NASA can successfully navigate a spacecraft to intentionally collide with an asteroid to deflect it, a technique known as kinetic impact. 

The investigation team will now observe Dimorphos using ground-based telescopes to confirm that DART’s impact altered the asteroid’s orbit around Didymos. Researchers expect the impact to shorten Dimorphos’ orbit by about 1%, or roughly 10 minutes; precisely measuring how much the asteroid was deflected is one of the primary purposes of the full-scale test.

“Planetary Defense is a globally unifying effort that affects everyone living on Earth,” said Thomas Zurbuchen, associate administrator for the Science Mission Directorate at NASA Headquarters in Washington. “Now we know we can aim a spacecraft with the precision needed to impact even a small body in space. Just a small change in its speed is all we need to make a significant difference in the path an asteroid travels.”

The spacecraft’s sole instrument, the Didymos Reconnaissance and Asteroid Camera for Optical navigation (DRACO), together with sophisticated guidance, navigation, and control system that works in tandem with Small-body Maneuvering Autonomous Real-Time Navigation (SMART Nav) algorithms, enabled DART to identify and distinguish between the two asteroids, targeting the smaller body.

These systems guided the 1,260-pound (570-kilogram) box-shaped spacecraft through the final 56,000 miles (90,000 kilometers) of space into Dimorphos, intentionally crashing into it at roughly 14,000 miles (22,530 kilometers) per hour to slightly slow the asteroid’s orbital speed. DRACO’s final images, obtained by the spacecraft seconds before impact, revealed the surface of Dimorphos in close-up detail.

Fifteen days before impact, DART’s CubeSat companion Light Italian CubeSat for Imaging of Asteroids (LICIACube), provided by the Italian Space Agency, deployed from the spacecraft to capture images of DART’s impact and the asteroid’s resulting cloud of ejected matter. In tandem with the images returned by DRACO, LICIACube’s images are intended to provide a view of the collision’s effects to help researchers better characterize the effectiveness of kinetic impact in deflecting an asteroid. Because LICIACube doesn’t carry a large antenna, images will be downlinked to Earth one by one in the coming weeks.

“DART’s success provides a significant addition to the essential toolbox we must have to protect Earth from a devastating impact by an asteroid,” said Lindley Johnson, NASA’s Planetary Defense Officer. “This demonstrates we are no longer powerless to prevent this type of natural disaster. Coupled with enhanced capabilities to accelerate finding the remaining hazardous asteroid population by our next Planetary Defense mission, the Near-Earth Object (NEO) Surveyor, a DART successor could provide what we need to save the day.”

With the asteroid pair within 7 million miles (11 million kilometers) of Earth, a global team is using dozens of telescopes stationed around the world and in space to observe the asteroid system. Over the coming weeks, they will characterize the ejecta produced and precisely measure Dimorphos’ orbital change to determine how effectively DART deflected the asteroid. The results will help validate and improve scientific supercomputer models critical to predicting the effectiveness of this technique as a reliable method for asteroid deflection.

“This first-of-its-kind mission required incredible preparation and precision, and the team exceeded expectations on all counts,” said APL Director Ralph Semmel. “Beyond the truly exciting success of the technology demonstration, capabilities based on DART could one day be used to change the course of an asteroid to protect our planet and preserve life on Earth as we know it.”

Roughly four years from now, the European Space Agency’s Hera project will conduct detailed surveys of both Dimorphos and Didymos, with a particular focus on the crater left by DART’s collision and precise measurement of Dimorphos’ mass.

Johns Hopkins APL manages the DART mission for NASA's Planetary Defense Coordination Office as a project of the agency's Planetary Missions Program Office.

NASA’s Double Asteroid Redirection Test (DART) mission is the world’s first full-scale planetary defense test against potential asteroid impacts on Earth. Researchers of the University of Bern and the National Centre of Competence in Research (NCCR) PlanetS now show that instead of leaving behind a relatively small crater, the impact of the DART spacecraft on its target could leave the asteroid near unrecognizable.

66 million years ago, a giant asteroid's impact on the Earth likely caused the extinction of the dinosaurs. Currently, no known asteroid poses an immediate threat. But if one day a large asteroid were to be discovered on a collision course with Earth, it might have to be deflected from its trajectory to prevent catastrophic consequences.

Last November, the DART space probe of the US space agency NASA was launched as a first full-scale experiment of such a maneuver: Its mission is to collide with an asteroid and deflect it from its orbit, to provide valuable information for the development of such a planetary defense system.

In a new study published in The Planetary Science Journal, researchers of the University of Bern and the National Centre of Competence in Research (NCCR) PlanetS have simulated this impact with a new method. Their results indicate that it may deform its target far more severely than previously thought. 

Rubble instead of solid rock

"Contrary to what one might imagine when picturing an asteroid, direct evidence from space missions like the Japanese space agency’s (JAXA) Hayabusa2 probe demonstrates that an asteroid can have a very loose internal structure – similar to a pile of rubble – that is held together by gravitational interactions and small cohesive forces", says study lead-author Sabina Raducan from the Institute of Physics and the National Centre of Competence in Research PlanetS at the University of Bern.

Yet, previous simulations of the DART mission impact mostly assumed a much more solid interior of its asteroid target Dimorphos. "This could drastically change the outcome of the collision of DART and Dimorphos, which is scheduled to take place in the coming September", Raducan points out. Instead of leaving a relatively small crater on the 160-meter-wide asteroid, DART’s impact at a speed of 24’000 km/h could completely deform Dimorphos. The asteroid could also be deflected much more strongly and larger amounts of material could be ejected from the impact than the previous estimates predicted.

A prize-winning new approach

“One of the reasons that this scenario of a loose internal structure has so far not been thoroughly studied is that the necessary methods were not available”, study lead-author Sabina Raducan says. “Such impact conditions cannot be recreated in laboratory experiments and the relatively long and complex process of crater formation following such an impact – a matter of hours in the case of DART – made it impossible to realistically simulate these impact processes up to now”, according to the researcher.  

"With our novel modeling approach, which takes into account the propagation of the shock waves, the compaction, and the subsequent flow of material, we were for the first time able to model the entire cratering process resulting from impacts on small, asteroids like Dimorphos” Raducan reports. For this achievement, she was awarded by ESA and by the mayor of Nice at a workshop on the DART follow-up mission HERA. For this achievement, Raducan was awarded by ESA and by the mayor of Nice at a workshop on the DART follow-up mission HERA.

Widen horizon of expectations

In 2024, the European Space Agency ESA will send a space probe to Dimorphos as part of the space mission HERA. The aim is to visually investigate the aftermath of the DART probe impact. "To get the most out of the HERA mission, we need to have a good understanding of potential outcomes of the DART impact", says study co-author Martin Jutzi from the Institute of Physics and the National Centre of Competence in Research PlanetS. "Our work on the impact simulations adds an important potential scenario that requires us to widen our expectations in this regard. This is not only relevant in the context of planetary defense, but also adds an important piece to the puzzle of our understanding of asteroids in general", Jutzi concludes.