NASA smashed an asteroid with a rocket. The debris could hit Mars.

In the future, if nothing is done to stop it, an asteroid not much larger than a football stadium will crash into the planet. Should it hit a city, it will annihilate it much like a non-radioactive nuclear bomb. There are 25,000 asteroids, roughly 460-feet long, like this zipping about in near-Earth space, and about 15,000 of them are yet to be found.

One way to stop them from hitting Earth is to change their trajectory by crashing into them with a small spacecraft. In September 2022, to test this deflection technique, a van-size spacecraft slammed into a 525-foot-long (harmless) near-Earth asteroid named Dimorphos at 14,000 miles per hour—and in doing so, successfully shifted its orbit around a larger space rock named Didymos.

This was DART—NASA’s Double Asteroid Redirection Test mission—humanity’s first ever planetary defense experiment. It was hailed as a huge success, but it produced some surprising after-effects, including a swarm of boulders that were found enveloping Dimorphos several months post-impact. These relatively small boulders posed no threat to Earth, but scientists did wonder where they might eventually end up.

Now, a recently published study—yet to be peer-reviewed—has offered up some answers. By carefully simulating the myriad ways in which these boulders will orbit the Sun over the next 20,000 years, scientists found that there is no possibility of any of them burning up in Earth’s skies.

“But they’re going to cross the orbit of Mars,” says study author Marco Fenucci, a near-Earth object dynamicist at the European Space Agency’s Near-Earth Objects Coordination Centre. And if both Mars and the mini-asteroids meet at that crossing, some of them will puncture through the thin Martian atmosphere. “And they will arrive to the ground and make a crater,” says Fenucci—creating bowl-shaped scars up to 1,000 feet long.