At this moment, millions of kilometers from Earth, a lonely spacecraft is hurtling toward its doom. One day, its sacrifice may save countless lives.
The first-ever mission of its kind, NASA’s Double Asteroid Redirection Test (DART) is crashing a low-cost “impactor” into an asteroid on Monday. The venture is the first step in developing a planetary defense system able to deflect incoming objects from space.
The DART impactor spacecraft was launched into orbit last November on the back of a SpaceX Falcon 9 rocket. Its target is Dimorphos, a small moonlet that orbits the asteroid Didymos, roughly 11 million kilometers away at the moment and of no current threat to Earth.
After almost a year in transit, the impactor will reach its destination on Sept. 26, at approximately 7:14 pm EST.
NASA will livestream the event starting at 6 pm EST on NASA TV, its website and the agency’s various social media. Photos of the asteroid taken moments before collision will also be available, the agency said.
About the size of a small car and weighing in at 610 kilograms at launch, the DART impactor was designed by the Johns Hopkins Applied Physics Laboratory in collaboration with NASA. It will crash into Dimorphos at a speed of roughly 6.1 kilometers a second, according to Johns Hopkins.
The force of this crash should be enough to slow Dimorphos in its orbit around Didylos, enough for telescopes on Earth to pick up and monitor over the coming days and weeks, said Carolyn Ernst, the mission team’s DRACO instrument specialist, to the Star.
DRACO, short for the Didymos Reconnaissance and Asteroid Camera for Optical navigation, is the only instrument on board the simple spacecraft, according to the team. It serves to both photograph its asteroid target, as well as help autonomously guide the vessel to impact.
“We will be measuring the amount of change we put into (Dimorphos’s) orbital period – how much did we slow it down – so that we can understand what kind of punch did we give to that asteroid,” Ernst said.
This helps scientists estimate how much force is needed to deflect an asteroid – and how feasible the technique is against actual threats in the future, she explained. Observers expect no large asteroids to threaten Earth within the next century, but it’s important to prepare for the possibility, Ernst continued.
Dimorphos was chosen as a target partly for the stability of its orbit: “No matter what we do to this moon, it will not do anything drastic beyond just slow down in its orbit,” Ernst said.
Otherwise, Dimorphos’s relative accessibility and short orbital period of just under 12 hours make the moonlet a prime target for study, she continued.
Looking toward the impact Monday, Ernst said she’s “mostly just excited.”
“I have confidence this is going to work. And for me, I’m most excited to see the asteroids up close, because right now they’re just points of light.”
Trailing the DART impactor is a miniature satellite named LICIACube, shipped up on the same rocket and deployed 15 days before impact. Its mission is to record the collision as well as the resulting plume of asteroid debris, in hopes of identifying Dimorphos’s composition.
A follow-up mission named Hera will launch in 2024 to further probe the aftermath of the crash. Organized by the European Space Commission, the venture aims to create a detailed map of the moonlet’s surface through high-resolution visual, laser and radio science mapping.
According to NASA’s Center for Near Earth Object Studies, there are over 10,000 registered asteroids and comets in Earth’s general neighborhood that measure 140 meters or larger in diameter. Over 850 are more than one kilometer in diameter.
Still, the Center sees no cause for concern yet – it’s extremely unlikely for any of these to hit Earth within the next century, it says.
“What we’re trying to do is we’re just planning,” said Heidi White, an astronomer at U of T’s Dunlap Institute for Astronomy & Astrophysics, who is unaffiliated with the mission.
“If this method is ever needed in the future, we want to make sure that we’ve got it down to a T.”
White ranks NASA’s asteroid deflection idea among the most viable methods of planetary defense that scientists have thought up. Other plausible plans include landing thrusters on incoming space rocks to push them out of their trajectories, as well as simply blowing up the intruders into smaller pieces, White said.
“I feel like this is probably the best place to start,” she continued. “…It’s easier to deflect something than it is to try and explode it.”
Still, there are drawbacks. The main issue, according to Carolyn Ernst, is whether Earth will get enough time to prepare before a collision.
“You need enough time to get the spacecraft built, to get it launched and to hit the asteroid early enough to push it enough to miss,” she said.
“If you said two days from now it’s coming, that’s not enough time”
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