They hit the asteroid- Did it work?
The DART mission of Planetary Defense
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Some scientists from the Applied Physics Lab (APL) at Johns Hopkins and NASA walk into a bar. That sounds like an opening line for a joke- stick with me here. The scientists aren’t in the bar for cocktails. They want to play a couple of games- darts and pool. They just hit the bullseye in darts and now they wait to see if the three-ball drops into the corner pocket.
This analogy is my effort to explain the first-ever collision into a celestial body by a human-built spacecraft. It is the work of NASA’s Planetary Defense office (yes there is such a thing). It’s a test to see if hitting an asteroid with a spaceship can change its trajectory. That could be important if a large asteroid is headed right at Earth (ask the dinosaurs).
Last image before DART impact into asteroid. (Credit: NASA/JHAPL)
The mission is called DART- Double Asteroid Redirection Test (It’s actually a “binary asteroid” but that wouldn’t make a good acronym). The 1,300 pound spacecraft was sent on a seven million mile trip to hit the small moon of an asteroid that is no threat to Earth. Monday night, traveling 14,000 MPH, the spacecraft locked onto the smaller asteroid that is less than two football fields wide.
BULLSEYE
The pictures show the rocky surface getting closer and closer, and then the screen goes red. The impact of DART hit the bullseye, landing 17 meters from the actual target. The scientists won the dart game.
The celebration in the APL control room moments after DART's impact. (Credit: NASA/JHU APL)
This was a seven-year project involving 1,000 workers. Lead Mission Systems Engineer Elena Adams said there were nervous moments before impact. “I say both terror and joy at the same time because we saw that we were going to impact… this asteroid. It was coming into the field of view for the first time we really had no idea what to expect,” Adams said at a briefing, adding, “to see it so beautifully concluded today was just an incredible feeling, and also very tiring.”
ADORABLE
Dr. Carolyn Ernst is a research scientist at APL. She gets excited seeing new celestial bodies in space. She was able to see the bigger asteroid Didymous and then concentrate on the target, the smaller Dimorphus. “It really looks just amazing. It looks, just like, adorable. It's this little moon. It's so cute. It looks in a lot of ways like some of the other small asteroids we've seen,” Ernst said.
With a launch back in November, this was an important moment for the scientists. “I have to say I shed a tear… there's a lot of emotion,” said Dr. Julie Bellerose of NASA’s Jet Propulsion Lab.
The final moments of the DART mission and comments from some of the scientists involved. (Credit: NASA/JHU APL)
There were celebrations for winning the dart game. Adams said, “Our first planetary defense test was a success. And I think we can clap to that everyone. Yeah, I think earthlings should sleep better and definitely I will.”
POOL ANGLES
Now to the game of pool. This test will determine if the impact of DART changes the orbit of Dimorphus. All that is needed is a little nudge. If you are playing a game of pool and the cueball is not straight behind the three ball, you need to hit the ball a bit off-center to get it into the corner pocket. That is, in essence, what DART is trying to accomplish.
Last 40 seconds of the DART spacecraft's journey. (Credit: NASA/JHU APL)
Scientists will be watching the orbit of the small asteroid to see if its orbit gets a little longer because DART nudged it. The Hubble and James Webb space telescopes were watching. So were several telescopes on Earth. We won’t know what happened tomorrow. Ernst told reporters, “over the next two months, we're going to see more information from the investigation team on what period change do we actually make,” to the asteroid’s orbit.
It’s been a good visit to the celestial bar so far. The scientists won the dart game and hope the pool game shows they have the potential to defend Earth from asteroids. Bruce Willis, are you watching?
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(Cover image credit: NASA/JHU APL)