NASA’s DART mission proved we are able to change an asteroid’s path by smashing a spacecraft into it, but exactly where we hit a rocky body is important

Margherita Bassi - Daily Correspondent

September 15, 2025 2:21 p.m.

An artistic rendering of NASA’s DART spacecraft approaching Dimorphos. NASA/Johns Hopkins APL/Steve Gribben If researchers one day spot an asteroid on a collision course with Earth, NASA’s Double Asteroid Redirection Test (DART) has already demonstrated that we can change its path by smashing a spaceship into it. But how annoying would it be if the asteroid’s new orbit simply pushed the impact date back by a few years?

In a conference paper published in July by Copernicus Publications, researchers have highlighted that such deflection missions can’t smack into an Earth-threatening asteroid in just any place. That runs the risk of sending the asteroid hurtling through a gravitational keyhole—a region of space where a planet’s gravity can change an asteroid’s orbit, putting it back on track to collide with said planet later.

“This means another deflection mission on possibly much shorter timescales could become necessary. In order to avoid such repetitive doomsday scenarios right off the bat, we should strive to design the initial KI [kinetic impact] deflection mission such that it does not trigger a keyhole,” researchers write in the paper. “In this work, we have developed a method that can aid KI mission decision-makers during the initial design process.”

For those of you worrying what that means for NASA’s DART mission, which smacked into the small asteroid Dimorphos in September 2022, you can rest easy. In this specific case, it didn’t matter where the mission struck, because the asteroid is part of a system that is too massive to be moved into a course that would one day impact our planet. This isn’t true for all hazardous asteroids orbiting the sun, however.

DART Impact

When hit, different regions on an asteroid’s surface have different risks of moving said asteroid through a keyhole. As such, the team used data from the DART mission to create a method that calculates probability maps for these variations.

“Mapping these keyholes onto the asteroids is possible and all it costs before the mission even lifts off is computing power, so we should be doing this to make sure we can pick the best possible targeting point on the surface of the asteroid for any kinetic impact,” Rahil Makadia, a NASA Space Technology researcher at the University of Illinois at Urbana-Champaign, told the Europlanet Science Congress in Finland last week, as reported by New Scientist’s Alex Wilkins.

Ideally, a hazardous asteroid would be detected early enough to allow time for scientists to send a space mission to collect information about the object’s shape, surface landscape, rotation and mass. While this sort of “rendezvous mission is preferred,” Makadia says in a statement, “fortunately, this entire analysis, at least at a preliminary level, is possible using ground-based observations alone,” he explains, meaning not all hope is lost if we don’t have time to send up a mission before impact.

Researchers can thus calculate the asteroid’s different post-impact paths depending on where it is struck, and choose the safest option. “By creating these maps, we can push asteroids away from the Earth such that they do not return on an impacting trajectory in the foreseeable future,” the authors write in the paper.

The non-hazardous asteroid Apophis will serve as a source for gathering more information about the rocky space bodies when it zooms past Earth in 2029, per New Scientist.

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