When a huge asteroid is barreling toward Earth, it sounds simple: just ram a spacecraft into it to redirect its path. That’s what NASA did with the DART mission in 2022, successfully changing the course of an asteroid named Dimorphos.
But new research from the University of Illinois exposes a worrying twist: if we hit an asteroid in the wrong spot, we might only delay its impact, not prevent it.
Asteroids can pass through certain areas in space called “gravitational keyholes.” These are small zones where a planet’s gravity can pull the asteroid back into a collision course. Imagine a pinball machine where a wayward bump sends the ball hurtling back toward danger.
NASA’s Rahil Makadia notes, “Even if we intentionally push an asteroid away from Earth, we must ensure it doesn’t drift into one of these keyholes afterward. Otherwise, we could face the same impact threat down the road.”
To tackle this, Makadia’s team has designed “probability maps.” These maps highlight the safest impact points on an asteroid. Each area has a different chance of sending the asteroid on a dangerous trajectory after being struck.
Creating these maps requires understanding the asteroid’s features—its shape, surface, and rotation. Ideally, this is done through a space mission that gathers detailed images and data. But if an asteroid is spotted late, scientists can produce basic maps using ground-based telescopes.
They’ve already developed maps for asteroids like Bennu, pinpointing optimal impact zones. These maps factor in potential errors, acknowledging that even the best-laid plans can falter.
While Dimorphos was a safe target for DART, future missions will need meticulous planning. The European Space Agency’s Hera mission is on course to reach the DART impact site in December 2026. This will provide crucial data to enhance our defenses.
So far, we’ve been fortunate—no significant threats have been detected. But as we keep scanning the skies, it’s likely we will eventually find an asteroid on a collision path with Earth. Thanks to ongoing research, we’ll be better prepared to aim accurately when that day comes.
For more details on asteroid impact strategies, check out this article on NASA’s DART mission.
