NASA confirms that humanity now has a defense against asteroids.

NASA confirms that humanity now has a defense against asteroids.  

It is possible to divert dangerous celestial bodies away from Earth. Roughly five months after intentionally crashing a rocket into a distant asteroid, NASA has some good news: The mission was a smashing success, and similar methods could prevent Earth from being obliterated by planet-killing space rocks in the future, according to four new studies published in the journal Nature.

In September 2022, NASA’s DART spacecraft successfully collided with the asteroid Dimorphos, a 525-foot-wide (160 meters) “moonlet” that orbits a larger asteroid called Didymos, roughly 7 million miles (11 million kilometers) from Earth. The force of the impact altered Dimorphos’ orbit around Didymos by about 33 minutes, successfully redirecting the smaller space rock’s trajectory, NASA initially reported. (Neither asteroid ever posed a risk to Earth, but the asteroids’ size and shared orbit made them ideal targets for the mission.)

Now, four new studies published March 1 confirm that the mission was even more successful than NASA engineers initially predicted — and that the kinetic impactor technique is indeed a viable method for protecting Earth from potentially deadly asteroids in the future.

“I cheered when DART slammed head on into the asteroid for the world’s first planetary defense technology demonstration, and that was just the start,” Nicola Fox(opens in new tab), associate administrator for the Science Mission Directorate at NASA Headquarters, said in a statement(opens in new tab). “These findings add to our fundamental understanding of asteroids and build a foundation for how humanity can defend Earth from a potentially hazardous asteroid by altering its course.”

NASA launched the Double Asteroid Redirection Test (DART) mission in late November 2021, after five years of planning. The goal was to test a theory of planetary defense called the “kinetic impactor” technique — basically, altering an asteroid’s trajectory by crashing a rocket into it at high speed.

The goal of this wild NASA mission, known as the Double Asteroid Redirection Test (DART), was to inform our approach to defending Earth from any potentially hazardous asteroids in the future, though it’s important to note that there is no known risk of an asteroid impacts for at least a century.

Now, scientists have announced that this DART shortened the period it takes for the moonlet, called Dimorphos, to orbit its asteroid companion, Didymos, by a full 33 minutes, according to a batch of five new studies published on Wednesday in Nature that detail the first comprehensive results from this unprecedented encounter. 

Scientists had predicted that Dimorphos’ period would change by about seven minutes if the spacecraft directly transferred its momentum to the asteroid in a rather ideal scenario, but it was clear soon after the impact that the complicated dynamics of the collision produced a more dramatic change in the trajectory of the asteroid.   

“People may think of the DART mission as a fairly straightforward experiment that is similar to playing billiards in space—one solid spacecraft impacts into one solid asteroid,” said Cristina Thomas, a planetary scientist at Northern Arizona University who led the study about Dimorphos’ orbital shift, in an email to Motherboard. “However, asteroids are far more complex than just a solid rock; in fact most asteroids are what we think of as rubble piles. If you hit a rubble pile with a spacecraft, a lot of material will be ejected and fly away.”