Can we nudge an asteroid away from a collision course with Earth?

Space · Published 8 October 2026 Swipe more like this →

In short: Earth faces constant bombardment from small asteroids, but larger ones pose a genuine threat. To defend our planet, scientists are testing whether we can physically alter an asteroid's path. Recent experiments suggest that a well-timed impact might be enough to shift a celestial object safely away from our orbit.

The primary challenge in planetary defense is understanding exactly what asteroids are composed of. This knowledge is vital for developing deflection technologies that can successfully set a threatening object on a new collision course. While the European Space Agency's Asteroid Impact Mission (AIM) focuses on studying these compositions, NASA has already demonstrated a practical method of deflection through kinetic impact.

NASA's Double Asteroid Redirection Test (DART) successfully proved this concept by deliberately slamming a spacecraft into the asteroid Dimorphos on September 26, 2022. Dimorphos is a 560-foot (170-meter) moonlet that orbits a larger asteroid, Didymos, which is approximately 2,788 feet (850 meters) across. Because the orbital mechanics of this binary system were already precisely measured, the impact's effects were clearly visible.

The results were more significant than initially expected. The impact, occurring at 4 miles (6.6 kilometers) per second, did more than just move the moonlet; it altered the entire binary system's orbit around the sun. Researchers observed the system's orbital velocity shift by roughly 11.7 microns per second, which equals 1.7 inches per hour. This shift was bolstered by the 'ejecta'—a cloud of debris excavated by the impact that carried away momentum, providing an additional push to Dimorphos.

The mission was a major success. The goal was to reduce Dimorphos's orbital period around Didymos by at least 73 seconds. The orbital period decreased, moving from 11 hours and 55 minutes down to 11 hours and 23 minutes. Even a tiny change in motion over time can be the deciding factor between a hazardous impact and a safe miss for Earth.

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