When NASA's DART spacecraft slammed into the asteroid Dimorphos in September 2022, the world watched to see if humanity could actually push a space rock off course. The immediate answer was yes — the spacecraft successfully shortened Dimorphos's orbit around its larger companion, Didymos.
But scientists suspected there might be more to the story. And now, a new study published Friday in Science Advances confirms it: the impact didn't just change how Dimorphos orbits Didymos — it altered the entire asteroid duo's path around the sun.
It's the first time in history that humans have deliberately changed a celestial body's orbit around our star.
'This study marks a notable step forward in our ability to prevent future asteroid impacts on Earth,' the international research team wrote.
The changes were small — reductions of just one-tenth of a second and half a mile to a solar lap spanning two years and hundreds of millions of miles. But in planetary defense, small is exactly what you want.
'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,' said lead author Rahil Makadia of the University of Illinois Urbana-Champaign.
'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.'
The researchers also found that all the boulders and debris flung off Dimorphos in the crash provided as much push as the spacecraft itself — a doubling of momentum. Last summer, a separate team estimated that 35 million pounds of rock and dust were ejected.
The good news? Even with the changed course, Earth remains safely out of the asteroids' way for the foreseeable future. That's precisely why this rubble-packed system was chosen for the test.
Scientists expect to learn even more when the European Space Agency's Hera spacecraft reaches the asteroids in November for months of close-up surveying.
For a species that once could only watch helplessly as rocks fell from the sky, this is a quiet but profound milestone. We can now steer the heavens. 🚀
*Sources: Science Advances · Los Angeles Times · NASA*
