NASA’s DART Mission Alters Orbit of Asteroid System Around Sun in Planetary Defense Milestone
Study confirms 2022 spacecraft impact changed path of Didymos and Dimorphos, marking first time humans have deliberately moved a celestial body around the Sun
CAPE CANAVERAL, Fla.— When NASA’s Double Asteroid Redirection Test (DART) spacecraft intentionally crashed into a small asteroid in 2022, scientists knew they had successfully demonstrated a technique for deflecting potentially hazardous space rocks. Now, new research reveals the impact did more than just alter the asteroid’s orbit around its companion — it changed the entire system’s path around the Sun.
The finding, published Friday in the journal Science Advances, confirms that humanity has for the first time deliberately altered the heliocentric orbit of a celestial body, according to NASA officials .
The DART spacecraft, launched in 2021, struck Dimorphos — a 170-meter-wide (560-foot) moonlet orbiting the larger asteroid Didymos — on Sept. 26, 2022, at approximately 22,530 kilometers per hour (14,000 mph). The mission was designed as the world’s first full-scale planetary defense test .
Previous analysis quickly established that the impact shortened Dimorphos’ 12-hour orbit around Didymos by 33 minutes. But the new study shows the collision ejected so much rocky debris from the binary system that it also affected the pair’s collective 770-day orbit around the Sun .
That orbital period changed by 0.15 seconds, representing a slowdown of approximately 11.7 microns per second in the system’s velocity. While minuscule, the change reduced the asteroids’ 480-million-kilometer (300-million-mile) solar orbit by about 720 meters (2,360 feet) .
“This is a tiny change to the orbit, but given enough time, even a tiny change can grow to a significant deflection,” said Thomas Statler, lead scientist for solar system small bodies at NASA Headquarters in Washington, in a statement. “The team’s amazingly precise measurement again validates kinetic impact as a technique for defending Earth against asteroid hazards and shows how a binary asteroid might be deflected by impacting just one member of the pair” .
Momentum enhancement and debris ejection
The research team, led by Rahil Makadia of the University of Illinois Urbana-Champaign, determined that the impact’s effectiveness was doubled by the material blasted off Dimorphos. Scientists call this the “momentum enhancement factor,” and the study found it was approximately two, meaning the debris loss doubled the push created by the spacecraft alone .
Last summer, a U.S.-Italian team estimated that 35 million pounds (16 million kilograms) of rock and dust were ejected from the asteroid system .
“The change in the binary system’s orbital speed was about 11.7 microns per second, or 1.7 inches per hour,” said Makadia. “Over time, such a small change in an asteroid’s motion can make the difference between a hazardous object hitting or missing our planet” .
The study also provided new insights into the composition of both asteroids. Dimorphos is slightly less dense than previously thought, supporting the theory that it formed from rocky debris shed by a rapidly spinning Didymos — essentially a “rubble pile” asteroid that coalesced from loose material .
How scientists measured the impossible
To detect such a minuscule orbital change, researchers needed extraordinary precision. They employed multiple observation techniques, including radar measurements and a method called stellar occultation — tracking when the asteroids pass directly in front of distant stars, causing the starlight to blink out for fractions of a second .
This technique provides extremely precise measurements of an asteroid’s position, speed and shape. However, it requires observers to be in exactly the right place at the right time, sometimes with multiple stations positioned miles apart along a predicted path .
The team relied on volunteer astronomers around the globe who recorded 22 stellar occultations between October 2022 and March 2025. These citizen scientists traveled to remote locations based on predictions, sometimes driving days into the Australian outback or positioning themselves across narrow observation paths as small as 800 meters wide .
“When combined with years of existing ground-based observations, these stellar occultation observations became key in helping us calculate how DART had changed Didymos’ orbit,” said study co-lead Steve Chesley, a senior research scientist at NASA’s Jet Propulsion Laboratory. “This work is highly weather dependent and often requires travel to remote regions with no guarantee of success. This result would not have been possible without the dedication of dozens of volunteer occultation observers around the world” .
David Herald of the Trans Tasman Occultation Alliance, part of the Royal Astronomical Society of New Zealand, noted that this represents an area of observational astronomy developed by the amateur community over the last 30 years, providing measurements that even the largest professional telescopes cannot achieve .
Planetary defense implications
The experiment was never based on any actual threat to Earth. Didymos and Dimorphos were specifically selected because they posed no danger to our planet before, during or after the DART mission .
But the successful demonstration offers a crucial data point for developing defense strategies against future asteroid threats. The key, researchers emphasize, is early detection and intervention .
“Even though this seems small, a tiny deflection … can add up over decades and make the difference between a potentially hazardous asteroid hitting or missing the Earth in the future,” Makadia said in an email. For any save-the-planet tests, “the key isn’t delivering a huge shove at the last minute. The key is delivering a tiny shove many years in advance” .
Steven Chesley of JPL added: “While it is just a single experiment, it is nonetheless an important data point that will be relevant to any future asteroid deflection missions” .
Expert perspectives
Dr. Preeti Cowan, a research fellow in physics at the University of Auckland, described the finding as even more remarkable than the initial results. “Imagine Earth as the eye of a needle and an incoming asteroid as the thread. The asteroid only needs to be nudged slightly to miss us, and we can both continue safely on our journey. The careful measurements reported here show that such a nudge is not just theoretical — it can be achieved” .
Professor Roberto Armellin of the Auckland Space Institute noted that detecting a velocity change of only a few micrometers per second in the trajectory of the Didymos system “marks the first time humans have measurably altered the heliocentric orbit of a natural celestial body” .
Jay McMahon, an associate professor of aerospace engineering sciences at the University of Colorado Boulder who has worked with the DART team but was not involved in the new study, called the finding “very cool.” “Like any experiment, you can make a prediction about what will happen, but then you have to take the measurements to prove it. And so, this proves it” .
Masatoshi Hirabayashi, an associate professor in aerospace engineering at the Georgia Institute of Technology and another DART scientist not directly involved in the study, noted that knowing the asteroids’ respective mass and densities helps scientists better understand their structure — “a key piece of information of how this binary asteroid formed” .
Upcoming Hera mission
Scientists expect to learn even more later this year when the European Space Agency’s Hera spacecraft arrives at the Didymos system. Launched in 2024, Hera is scheduled to reach the asteroids in November 2026 for follow-up observations .
Unlike DART, Hera will not strike but will conduct months of surveying, including detailed measurements of the impact crater left by the 2022 collision. A pair of small experimental probes will peel away from the main spacecraft and attempt to land on the asteroids .
Makadia expressed optimism about the upcoming data: “Once we get the measurements from Hera, we can then come at these numbers from a completely independent way and confirm them and maybe build on them as well” .
Next steps for planetary defense
NASA is already building on the DART mission’s success with the Near-Earth Object (NEO) Surveyor mission. Managed by NASA’s Jet Propulsion Laboratory, this next-generation space survey telescope is the first designed specifically for planetary defense. The mission will seek out some of the hardest-to-find near-Earth objects, such as dark asteroids and comets that do not reflect much visible light .
The key to effective planetary defense, researchers stress, is detecting potentially hazardous objects far enough in advance to send a kinetic impactor. Even a small deflection applied years before a potential impact could mean the difference between a catastrophic collision and a harmless miss .
“This study marks a notable step forward in our ability to prevent future asteroid impacts on Earth,” the international research team wrote in their Science Advances paper .
The DART spacecraft was designed, built and operated by the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, for NASA’s Planetary Defense Coordination Office, which oversees the agency’s ongoing efforts in planetary defense .
With inputs from
1 NASA: NASA’s DART Mission Changed Orbit of Asteroid Didymos Around Sun
2 NASA Jet Propulsion Laboratory: NASA’s DART Mission Changed Orbit of Asteroid Didymos Around Sun
3 RNZ: NASA’s attempt to kick asteroid off-course was a success
4 Science News: NASA’s DART spacecraft changed an asteroid’s orbit around the sun
6 Scientific American: NASA changed an asteroid’s orbital path around the sun, a first for humankind
8 Scimex: Humans changed the orbit of two asteroids around the Sun
9 1News: Spacecraft changes asteroid’s orbit in a save-the-Earth test
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