NASA’s Asteroid-Defense Skills Draw Plaudits

BY AYLIN WOODWARD

Here’s one less thing to worry about: Scientists have confirmed that NASA is even better than it thought at protecting us from asteroids.

Despite doomsday movie plots about Earth-ending collisions, a key test of the National Aeronautics and Space Administration’s planetary defense capabilities successfully changed the path of a two-asteroid pair, according to a study published Friday in the journal Science Advances.

In 2022, NASA used a bussized craft to hit a 525-footwide space rock that orbits a larger one. Scientists have been collecting data since to learn more about the impact.

Researchers previously confirmed the hit changed the path of one of the asteroids in the pair. This latest study showed that the orbit of the whole two-asteroid system also changed.

The asteroids share a center of mass, and the speed and trajectory of that point determines the system’s orbit around the sun. The orbit changed by 11.7 microns— about 1/10th the width of a human hair—per second, said Rahil Makadia, a planetary defense scientist at the University of Illinois Urbana-Champaign and study co-author.

That might seem like an incomprehensibly small number, but the change over a year grows to about 2/10ths of a mile.

“You do a very tiny change, but you do it to the asteroid early enough, and that can make the difference between it hypothetically hitting the Earth versus missing it,” said Makadia, who was part of the 2022 NASA mission, nicknamed DART.

The asteroid pair in the test wasn’t actually a threat to the planet. But the research shows that if humanity tried to deflect an asteroid that really was a danger, scientists could confirm whether the effort worked, said Harrison Agrusa, a planetary scientist at the Observatoire de la Côte d’Azur. He wasn’t involved in the new study but was a member of the DART mission.

A key part of the new results, Makadia said, was understanding what prompted the change in the asteroid system’s path. NASA’s 1,300pound DART spacecraft collided with one of the asteroids in the pair at more than 14,000 miles an hour, but the rock still dwarfed the craft.

Debris from the collision provided additional momentum that helped shift the entire system’s orbit, Makadia said.

“You’re doubling the momentum that you bring in with the spacecraft alone,” said study co-author Nancy Chabot, a planetary scientist at the Johns Hopkins University Applied Physics Laboratory. “That’s a really promising result if you need to save the planet.”