NewsNational News


An asteroid recently came close to Earth. Here’s how our planetary defense system works

Space Asteroid Grab
Posted at 3:23 PM, Jan 27, 2023

A truck-sized asteroid zoomed by Earth on January 26. Should we be concerned?

“An object of that size, comes this close to Earth, this is only 2,200 miles above the surface of the Earth, on average once a year,” said Davide Farnocchia, a navigation engineer at NASA’s Jet Propulsion Laboratory.

Asteroids are something NASA has paid close attention to since 1998 when Congress mandated the agency to discover more than 90% of the near-Earth objects, also known as NEOs, larger than 1 kilometer.

“We discovered more than 90% of them. None of them is on an impact trajectory for the next 100 years,” Farnocchia said.

Possible damage depends on the size of the asteroid, and that’s why we have a planetary defense system.

NASA has been funding search programs to observe the night sky in order to discover as many asteroids as possible.

“If there is an asteroid out there, the first thing you have to do is discover it,” he said. “In 25 years, we’ve discovered more than 30,000 NEOs”

“It’s like buying insurance. You invest some effort in trying to discover as many asteroids as possible and assess whether they could come toward the Earth, and if you find one of those that could actually come toward the earth, you take mitigation measures to deal with the problem and avoid any damage,” he said.

These mitigation measures depend on the size of the asteroid. The small ones aren’t a problem.

“Those are not objects that would cause any damage, they would just burn up in the atmosphere,” Farnocchia said.

For medium-sized asteroids, experts may consider moving people out of the way.

“If the object were of the order of tens of meters, you might need to alert people. Like we had the impact in Chelyabinsk in 2013, that was about 30 meters in size,” he said. “There's the meteor crater that’s in Arizona. That's about a crater of about 1 kilometer across.”

For asteroids that could cause damage on a regional or global scale, experts may consider a deflection mission.

“First of all, the object is big so you have good chances of discovering the object ahead of time," Farnocchia said.

“We just had a wonderful example of that with the DART mission,” he said.

Last year, the NASA mission successfully nudged an asteroid, not heading toward Earth, with a spacecraft, changing the trajectory. The impact shortened the asteroid’s orbit by 32 minutes.

With the technology we have today, experts say we will know before an asteroid hits the Earth, and the proper steps will be taken to fix it.