CAPE CANAVERAL, Fla. — NASA’s 2022 DART spacecraft impact on the asteroid Dimorphos altered the pair’s orbit around the sun by a measurable margin, an international research team reported Friday — the first time a human-made object deliberately changed a celestial body’s solar orbit. The findings were published in the journal Science Advances.
The collision trimmed the Dimorphos-Didymos system’s 769-day solar orbit by 0.15 seconds and shrank the asteroids’ approximately 300-million-mile (480-million-kilometer) path around the sun by 2,360 feet (720 meters), researchers said. Neither asteroid was ever a threat to Earth; scientists chose the system precisely because it posed no risk, making it a safe testbed for planetary defense.
The study advances scientists’ understanding of whether kinetic spacecraft impacts could reliably deflect an asteroid threatening Earth — provided the push is delivered years or decades before any potential collision, researchers said.
“This study marks a notable step forward in our ability to prevent future asteroid impacts on Earth,” the international research team wrote in the journal.
Why small changes count
The margin of change is minute against the scale of space — a reduction of just one-tenth of a second and 720 meters in an orbit spanning two years and hundreds of millions of miles. But lead author Rahil Makadia of the University of Illinois Urbana-Champaign said the finding illustrates what matters most about asteroid deflection: timing, not brute force.
“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 test, he added, “the key isn’t delivering a huge shove at the last minute. The key is delivering a tiny shove many years in advance.”
The real-time slowdown measured from the impact was just over 10 micrometers per second.
The debris multiplier
Researchers found that the impact’s effectiveness was amplified by the material it dislodged. The boulders and dust flung off Dimorphos in the crash contributed as much additional push to the asteroid as the spacecraft itself — effectively doubling the total momentum transferred.
A U.S.-Italian team previously estimated that about 35 million pounds (16 million kilograms) of rock and dust were ejected in the collision.
Dimorphos, a rubble-pile asteroid 525 feet (160 meters) in diameter, orbits Didymos, a faster-spinning body 2,560 feet (780 meters) across that carries roughly 200 times more mass than its smaller companion. The pair complete a solar orbit approximately every 769 days.
Steven Chesley, a scientist at NASA’s Jet Propulsion Laboratory who took part in the study, said the result supports planetary defense planning even as a single data point.
“While it is just a single experiment, it is nonetheless an important data point that will be relevant to any future asteroid deflection missions,” Chesley said in an email.
What comes next
The European Space Agency’s Hera spacecraft is expected to reach the Dimorphos-Didymos system in November, where it will spend months conducting close surveys. Two small experimental probes are planned to separate from Hera and attempt to land on the asteroids. Unlike DART, Hera will observe rather than strike.
The DART mission, launched in 2021 as the world’s first planetary defense exercise, initially confirmed in the weeks after the 2022 impact that the strike shortened Dimorphos’s orbit around Didymos. Friday’s study extends that finding to the system’s solar orbit, providing a more complete picture of how the collision reshaped the asteroids’ trajectory. Earth remains safely out of their path for the foreseeable future, scientists said.