It worked wonders: it shrank Dimorphos' orbit by 33 minutes, making the deflection 25x more effective than the baseline. It did this because, as DART smashed into the asteroid, lots of debris flew back off the asteroid, acting like a rocket jet and giving it more of a push. - ThreadSky

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squigglyvolcano.bsky.social • 28 days ago

It worked wonders: it shrank Dimorphos' orbit by 33 minutes, making the deflection 25x more effective than the baseline. It did this because, as DART smashed into the asteroid, lots of debris flew back off the asteroid, acting like a rocket jet and giving it more of a push.

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squigglyvolcano.bsky.social•28 days ago

One of my favourite parts of the DART mission is that it knocked off so much debris from this asteroid that it created a 30,000km-long comet-like tail that persisted for many months after impact day.

squigglyvolcano.bsky.social•28 days ago

So, DART worked. But it doesn't mean we can use kinetic impactors like it to deflect any asteroid whenever we want, and that's for several reasons.

squigglyvolcano.bsky.social•28 days ago

The first is that asteroids like Dimorphos, and smaller, tend to be rubble piles: not solid single rocks, but boulders weakly bound by their own gravity. Hitting them just right can produce that debris-like thrust effect, but if you hit them too hard, you'll shatter them.

squigglyvolcano.bsky.social•28 days ago

Nobody wants to accidentally "disrupt" an asteroid, because those components can still head for Earth. As I often say, it's like turning a cannonball into a shotgun spray.

squigglyvolcano.bsky.social•28 days ago

This is chaotic, potentially very destructive—and if DART hit Dimorphos a little harder, it would have broken that asteroid too. You have to be very sure that when you hit an Earthbound asteroid, you are deflecting it, not fragmenting it.

squigglyvolcano.bsky.social•28 days ago

The second reason DART isn't a silver bullet is that it did not give Dimorphos as much of a deflection as you think. Yes, the orbit shrank a lot. But you know how much Dimorphos actually moved?

The change in velocity delivered by the impact was 2.7mm/s. https://www.llnl.gov/article/49541/study-looks-velocity-impact-asteroid-dimorphos

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