In September 2022, NASA deliberately smashed a spacecraft into a small asteroid called Dimorphos. The goal was simple in theory and huge in consequence: test whether humans could “nudge” a space rock enough to avoid a future impact.
Now, scientists say that single hit did something even more historic than first reported. New measurements show the crash slightly changed how the entire Didymos and Dimorphos system moves around the Sun, marking the first time a human-made object has measurably altered the solar orbit of a natural body.
A tiny time shift with big implications
The headline number sounds almost laughably small. After the DART impact, the binary asteroid system’s roughly 770-day trip around the Sun shortened by about 0.15 seconds, according to the team’s analysis.
Can a fraction of a second really matter in space? NASA’s Thomas Statler put it plainly, saying “even a tiny change can grow to a significant deflection,” given enough time. That is the whole idea behind planetary defense, and it only works if you act early.
The researchers also estimated the system’s orbital speed change at about 1.7 inches per hour. That is slower than the minute hand on a cheap kitchen clock, but over years and decades, tiny drifts can add up.
The binary asteroid that took the hit
Didymos and Dimorphos are locked together by gravity, circling a shared center of mass. In practical terms, that means you cannot push one without subtly affecting the other, like bumping one grocery cart and watching the pair drift together.
Dimorphos, the target, is about 560 feet wide (170 meters). Its larger partner Didymos measures about 2,640 feet across (805 meters), which is close to half a mile.
Before this new solar-orbit result, DART had already proven it could change the way Dimorphos orbits Didymos. Observations showed the moonlet’s roughly 12-hour orbit around Didymos became about 33 minutes shorter after impact.
Debris did the heavy lifting
One of the most important takeaways is that the spacecraft itself was only part of the “push.” When DART slammed into Dimorphos, it blasted a cloud of rock and dust into space, and that escaping material carried momentum away from the asteroid.
Scientists describe this boost using the momentum enhancement factor. In this case, the factor was about two, meaning the debris roughly doubled the effective punch compared with the spacecraft’s impact alone.
That detail is not just academic. If a future hazardous asteroid is more “rubble pile” than solid boulder, the way it sheds material could strongly shape how well a kinetic impact works, and how predictable the result will be.
Volunteer astronomy made the measurement possible
Proving a 0.15-second change in a two-year solar orbit is the kind of challenge that makes scientists sweat. To pin it down, researchers combined radar and ground-based tracking with stellar occultations, which are brief moments when an asteroid passes directly in front of a distant star and the starlight blinks out.
Here is the human part that tends to get overlooked. The team relied on volunteer astronomers around the world who recorded 22 stellar occultations between October 2022 and March 2025, often needing to be in exactly the right location under cooperative weather. Steve Chesley of NASA’s Jet Propulsion Laboratory said the result “would not have been possible” without those observers.
Why this matters for Earth’s living systems
It is easy to file asteroid deflection under “space news” and move on. But the real stakes are ecological, because large impacts can rapidly disrupt climate and food webs, not just flatten a local area.
The Chicxulub impact 66 million years ago is the clearest reminder. Research and climate modeling have shown that an impact can inject soot and other particles into the atmosphere, causing darkness that shuts down photosynthesis and driving severe cooling that stresses ecosystems on land and in the oceans.
At the same time, experts stress that the near-term risk is not panic-level. NASA notes that larger, damaging impacts are rare on human timescales and that there is currently no known asteroid larger than about 460 feet (140 meters) with a significant chance of striking Earth in the next 100 years. Still, “rare” is not “never,” and nature does not do refunds.
Finding threats early is the real make-or-break step
DART showed the nudge concept works, but it also highlighted the catch. To deflect something safely, you need years of warning, because the best strategy is usually a gentle tap far in advance, not a last-second shove.
That is why NASA is building the Near-Earth Object Surveyor mission, a space telescope designed specifically to find and characterize many of the hardest-to-spot near-Earth objects, including dark asteroids and comets that do not reflect much visible light. NASA and JPL say it is expected to launch no earlier than September 2027.
In everyday terms, NEO Surveyor is closer to a smoke detector than a firefighter. It is not the dramatic part, but it is the thing that wakes you up in time to get out.
The study was published in Science Advances.
