Avoiding Armageddon

NASA’s DART makes deep impact, showing we can deflect asteroids away from Earth

Without having to recruit a ragtag bunch of oil drillers led by Bruce Willis to save Earth from certain destruction, NASA seems to have found a way to alter the course of asteroids before they pose a threat like the one in “Armageddon.” The Double Asteroid Redirection Test (DART) kinetic impactor conducted last fall on Dimorphos, a small asteroid with a diameter of about 580 feet, went much better than expected. NASA spent several months analyzing the data, and the Hubble telescope captured images of the impact.

“Smashing head on into the asteroid at 13,000 miles per hour, the DART impactor blasted over 1,000 tons of dust and rock off of the asteroid,” NASA said in a statement.

That might not be worthy of a Michael Bay-directed blockbuster, but it’s still pretty cool.

Major Impact

Dimorphos is in a binary system with the larger asteroid Didymos, which Dimorphos orbits. NASA’s goal in slamming the DART kinetic impactor into Dimorphos was to alter the length of that orbit by 73 seconds. After analysis, scientists determined that Dimorphos now takes 11 hours, 22 minutes to orbit Didymos, meaning DART shortened it by 33 minutes. That’s more than 27 times better than they’d hoped.

“We are so proud of the DART team and the investigation’s latest results,” said Jason Kalirai, Civil Space Mission Area executive at the Johns Hopkins Applied Physics Laboratory. “With the core analysis activities starting after the impact of Dimorphos, the results demonstrate how successful the kinetic impactor technique can be — paving the way for a bright future for planetary defense.”

It marked the first time that humans purposely changed the motion of a celestial object. The findings left the DART team with hope that in the event of an asteroid threatening Earth, we’ll be able to knock it off course before it can enter our atmosphere.

The investigation team at APL found that the impact instantly slowed Dimorphos’ speed along its orbit, indicating that the recoil from blasting parts of the asteroid off made a major change in momentum.

“To serve as a proof-of-concept for the kinetic impactor technique of planetary defense, DART needed to demonstrate that an asteroid could be targeted during a high-speed encounter and that the target’s orbit could be changed. DART has successfully done both,” an investigation team at Northern Arizona University wrote.

Take A Picture

DART was relaying pictures back to Earth for about a month before the collision. Four hours before it slammed into Dimorphos, NASA let the kinetic impactor drive itself via its SMART Nav system. It cruised toward Didymos then spotted and identified Dimorphos an hour and 13 minutes before impact, sending pictures back all the while.

“It was amazing to see it for the first time — no one had ever acquired a resolved image of Dimorphos before,” Carolyn Ernst at the APL told Space.com in an email.

In its final couple of minutes, DART stopped maneuvering so it could send back clear images as it approached the asteroid. It took a picture every second, with the final one that came through taken 1.8 seconds before it crashed into Dimorphos at a 73-degree angle between two boulders.

The 1,340-pound kinetic impactor that cost $330 million was no more, but it accomplished its mission far better than its creators dreamed of.

“DART, as a controlled, planetary-scale impact experiment, provides a detailed characterization of the target, the ejecta morphology, and the entire ejecta evolution process,” investigators from the Planetary Science Institute wrote. “DART will continue to be the model for studies of newly discovered asteroids that show activity caused by natural impacts.”

‘Defender of the Planet’

There are more than 30,000 known asteroids close to Earth, and while we can rather easily keep track of the very big ones, it’s easier for some the size of Dimorphos to slip by undetected. While they aren’t big enough to wipe out humanity, they could still cause major damage if they hit Earth. The findings from DART show that we can intercept an asteroid of Dimorphos’ size without first conducting advance reconnaissance missions, although such missions would be quite valuable. But there might not be time.

“All of us have a responsibility to protect our home planet. After all, it’s the only one we have,” said NASA Administrator Bill Nelson. “This mission shows that NASA is trying to be ready for whatever the universe throws at us. NASA has proven we are serious as a defender of the planet. This is a watershed moment for planetary defense and all of humanity, demonstrating commitment from NASA’s exceptional team and partners from around the world.”

The European Space Agency will send its Hera spacecraft up in October 2024, with it reaching Didymos in 2026 and exploring the binary system in more detail. That mission could provide more insight into the effectiveness of kinetic impactors like DART.

When it comes to studying how to redirect asteroids away from Earth, we don’t want to miss a thing.