Dinosaurs had no warning when the Chicxulub impactor, a six-mile-wide asteroid, crashed into Earth 66 million years ago. If an asteroid of this size were to hit Earth today, a shock wave two million times stronger than a hydrogen bomb would destroy forests and cause a tsunami. A seismic impact equivalent to a magnitude 10 earthquake will destroy cities.

Long after the impact, a cloud of hot dust, ash, and steam will block out the sun and plunge the Earth into frost. But at least we knew he would probably come first. And if NASA has anything to say about it, we might even be able to prevent the apocalypse. NASA’s Planetary Defense Coordination Office investigates, monitors, and assesses the risk associated with potentially hazardous asteroids in our solar system.

“We definitely want to find them all before they find us,” said Lindley Johnson, program manager for the Planetary Defense Coordination Office.

To do this, NASA works with a global coalition of astronomers called the International Asteroid Warning Network (IAWN). So what would they do if an apocalyptic asteroid headed towards Earth?

International warning system

If a hazardous asteroid is heading towards Earth, IAWN has procedures in place to notify the public. First, group members who detected a threat shared their observations on the IAWN network to verify their findings and assess the danger. Once all parties agree that Earth should prepare for an impact, NASA will send an alert.

“I don’t have a red phone or anything on my desk,” Johnson said. “But we have formal procedures for reporting a serious impact.”

If the asteroid had been heading towards the United States, NASA would have notified the White House and the government would have issued an official statement to the public. If it were large enough to pose an international threat, IAWN would notify the UN Office for Outer Space Affairs.

Hunting for asteroids

An asteroid is considered “potentially hazardous” if it is larger than about 460 feet in diameter and crosses Earth’s orbit at a minimum distance of 0.5 AU, which is half the distance between the Earth and the Sun. There are approximately 2,300 known potentially hazardous asteroids, of which approximately 153 are larger than 0.6 miles in diameter. That’s enough to cause a disaster if one were to hit Earth.

To find and track them, NASA and other IAWN partners are searching for new asteroids as well as tracking those already discovered. All their observations are collected in a database at the Minor Planet Center. To date, IAWN has found more than 34,000 near-Earth asteroids. With enough observational data, NASA could confidently predict their orbits at least a century in advance, Johnson said.

The potentially hazardous asteroid Bennu is unlikely to hit Earth within 159 years, causing an explosion equivalent to 24 nuclear bombs. However, according to a study conducted in 2021, the chance of this happening is only 1 in 2,700. If Bennu heads for Earth, NASA has a few tricks up its sleeve to protect our planet.

Protection of the Earth

In most cases, IAWN catches approaching asteroids long before they become an immediate threat to Earth, Johnson said. But NASA would need at least five to ten years’ notice of an approaching asteroid to avert the apocalypse. In 2021, NASA launched its first planetary defense test mission. He crashed an unmanned spacecraft into an asteroid to shift its orbit away from Earth.

The mission was successful, and NASA plans to test more deflection techniques in the future. Emerging “gravitational tractor” technology would send the spacecraft to stay near the asteroid, allowing gravitational interaction to knock the asteroid out of its orbit. NASA is also working on a technique that uses an ion beam to change an asteroid’s path.

But if the threat had emerged less than five years later, NASA would not have had time to reject the asteroid. It may then resort to destruction to minimize and disperse the impact. If he had given NASA only a few months’ notice, there wouldn’t have been much they could have done to save Earth. Fortunately, IAWN’s strategy is to search for asteroids decades, if not centuries, before impact.

“This gives us enough time to try to do something about them while they’re still in space, thus completely avoiding any catastrophe here on Earth,” Johnson said.