Asteroid Smash

Back in July 2019, a space rock the size of a football field hurtled past Earth at about 54,000 miles per hour. It passed just 45,000 miles from our planet—five times closer than the moon! The space rock, named asteroid 2019 OK, had gone undetected until the day before the near miss, which concerned scientists. If an asteroid that size were to strike Earth, the impact could flatten an area the size of a large city.

Asteroid 2019 OK is one of more than 20,000 known asteroids that pass near Earth as they orbit the sun. Impacts are exceedingly rare, but astronomers around the world keep watch just in case. They scan the skies for space rocks, determine if any pose a threat, and work with engineers to find ways to prevent any collisions. “The sooner a threat is identified, the more options you have to move the object safely out of the way,” says Amy Mainzer, an astronomer at the University of Arizona.

Back in July 2019, a space rock the size of a football field hurtled past Earth. It was traveling about 54,000 miles per hour. It passed just 45,000 miles from our planet. That’s five times closer than the moon!

The space rock was named asteroid 2019 OK. Scientists didn’t detect it until the day before the near miss. That concerned them, because an asteroid that size could cause major damage if it were to strike Earth. The impact could flatten an area the size of a large city.

Asteroid 2019 OK is one of more than 20,000 known asteroids that pass near Earth as they orbit the sun. Impacts are extremely rare, but astronomers around the world keep watch just in case. They scan the skies for space rocks and determine if any pose a threat. They also work with engineers to find ways to prevent any collisions. “The sooner a threat is identified, the more options you have to move the object safely out of the way,” says Amy Mainzer. She’s an astronomer at the University of Arizona.

One possible way to protect Earth from an asteroid strike is to steer potentially hazardous space rocks away from the planet. To test this idea, NASA plans to launch the Double Asteroid Redirection Test (DART) this July. Its mission: Crash a spacecraft into an asteroid 6.8 million miles away to see if that changes the asteroid’s speed and path. Its target: Didymos B, a space rock slightly bigger than 2019 OK.

Didymos B orbits an even larger asteroid, Didymos A. The two asteroids don’t actually pose a threat to Earth. But since Didymos B is part of a pair, it’s an ideal test target for DART. Astronomers will be able to detect whether the impact successfully shifts Didymos B by measuring how its orbit around Didymos A changes.

One possible way to protect Earth from an asteroid strike? Steer potentially dangerous space rocks away from the planet. To test this idea, NASA plans to launch a spacecraft this July. It’s called the Double Asteroid Redirection Test, or DART. Its mission: Crash into an asteroid 6.8 million miles away to see if that changes the asteroid’s speed and path. Its target: Didymos B, a space rock slightly bigger than 2019 OK.

Didymos B orbits an even larger asteroid called Didymos A. The two asteroids don’t actually pose a threat to Earth. But since Didymos B is part of a pair, it’s an ideal test target for DART. Astronomers will measure its orbit around Didymos A before and after the impact. That way they’ll be able to tell whether the spacecraft successfully shifted the asteroid’s path.

DART should reach Didymos B in the fall of 2022. Astronomers are eager to see if it will work. Most agree that the chances of an asteroid colliding with Earth are slim—but because it could happen, it makes sense to plan for it. “The reasonable thing we can do as astronomers is to watch the skies,” says Mainzer.

DART should reach Didymos B in the fall of 2022. Astronomers are eager to see if it will work. Most agree that the chances of an asteroid colliding with Earth are slim. But because it could happen, it makes sense to plan for it. “The reasonable thing we can do as astronomers is to watch the skies,” says Mainzer.