We, Earthlings, can now finally fight back.

Millenia ago, a singular asteroid wiped out the dinosaurs, and for decades, scientists have been exploring the possibility of this happening again. If it does happen, what can we do to prevent it? Is there a solid defense we can conduct against an asteroid? And finally, we now can.

NASA has successfully deflected an asteroid called Dimorphos. Double Asteroid Redirection Test (DART) showed the world that the impact was no accident. Instead, the spacecraft smashed into the asteroid at around 14,000 miles per hour.

With this feat, NASA, for the first time in human history, was able to successfully redirect the orbit of an asteroid.

“This is stuff of science-fiction books and really corny episodes of “StarTrek” from when I was a kid, and now it’s real,” NASA program scientist Tom Statler said.

DART’s bull’s eye was about 9.6 million kilometers from Earth and powered by sophisticated navigational technology. Discovered in 1996, the Didymos asteroid was spinning so fast that scientists believed it had formed a moonlet. Instead, Dimorphos now orbits its parent body at a distance of fewer than 1.2 kilometers.

“This really is about asteroid deflection, not disruption,” said Nancy Chabot, a planetary scientist and mission team leader at Johns Hopkins University’s Applied Physics Laboratory, which is managing the effort.

“This isn’t going to blow up the asteroid. It isn’t going to put it into lots of pieces.”

NASA also confirmed there is zero chance the debris could cause any effects on Earth. DART aims to redirect its orbit. If we’re thinking about a hypothetical asteroid headed towards Earth, this would be enough to change its direction.

“That system is a member of the Apollo asteroids, not the Apollo mission, but a class of asteroids that are ‘Earth-crossing,’ as they call it,'” says Jacqueline McCleary, assistant professor of physics at Northeastern University.

“It’s incredibly sophisticated technologically, but in essence, you are trying to shoot a bullet out of the sky with another bullet,” McCleary says. “In this case you’ve got this satellite hurtling towards this little moonlet Dimorphos, which is like a proof of concept that one can hit an asteroid with enough momentum to cause a change in its orbit.”

In DART’s final moments, it tracked Dimorphos and sent back a series of photographs as it drew closer and closer. During the live-streamlining of the event, DART was only showing a white spot until the last 60 minutes of its journey; it started showing the surface of Dimorphos until it had finally smashed into the asteroid.

“For the first time, humanity has demonstrated the ability to autonomously target and alter the orbit of a celestial object,” Ralph Semmel, director of the Johns Hopkins University Applied Physics Laboratory, said during a news conference after the crash. The laboratory managed the mission for NASA.

“Normally, losing signal from the spacecraft is a very bad thing,” Dr. Semmel said. “But in this case, it was the ideal outcome.”

The DART mission was conceived two decades ago, according to Scientific American. Then, it was a joint project of scientists in the US and Europe, where they were hoping to practice a kinetic asteroid deflection technique. Originally called the AIDA (Asteroid Impact and Deflection Assessment), the original plan was to use NASA’s DART and Europe’s AIM (Asteroid Impact Mission) spacecraft, but Europe pulled out because of the lack of funding.

Double Asteroid Redirection Test
Credit: Matthew Twombly; Source: NASA, Johns Hopkins APL (DART reference)

Then, in 2019, the mission was rebooted as “Hera,” but this new joint project meant a delay in launch. The “Hera” won’t be able to launch until 2024 and will not reach Didymos until 2026. This is why DART was given the go signal. So that NASA could start improving the program with the results of this successful impact.

Deflect an Asteroid
Credit: Matthew Twombly

“This is one of the most important things we’re doing at the moment,” says Detlef Koschny, deputy head of ESA’s Planetary Defense Office. “We’ve been talking about the need to demonstrate that we can deflect an asteroid for many years.”

Watch the triumphant moment of impact of NASA’s DART into Dimorphos.