. . . well, the spacecraft hit the asteroid perfectly—couldn’t have been better. It was lovely to see it in real time, with Dimorphos getting bigger and bigger as DART hurtled towards it at 14,000 mph. It’s the first time our species has tried to alter the motion of an extraterrestrial body.
Well, I’m gobsmacked. Here’s a screenshot I took of Dimorphos about 2 seconds before the spacecraft hit it.
Now we wait. . . . did we alter its orbit?
Thanks for the posting Jerry. Incredible thing to watch live.
Wonderful – science fiction becomes science fact!
But also, science fact applies experimental constraints to SF.
How did Feynamn put it ? : “if it disagrees with experiment, it’s wrong”.
This was an experiment in (1) targetting a body; and (2) the efficiency of momentum transfer into a (probably) “rubble pile” body.
I was just thinking that if they do successfully push the asteroid off course, an entire sub-genre of science fiction will instantly cease to exist.
No, you’ll just be able to drop the word “fiction”. Although we have a long way to go before we get to the point where we can send Bruce Willis up to an asteroid.
Congratulations to everyone at NASA and Johns Hopkins Applied Physics….
et al. 🙂
Well done.
I was really blown away watching the two dots separate, the bigger asteroid take an irregular shape with mountains, shadows, what looked to be a huge crater followed by the little guy taking shape with maybe a sunlit mountain peak at the lower left, followed by that incredible rubble field. And the clarity and resolution in near real time!
I remember the first Nasa surveyor soft landing pictures coming in slowly line by line from the moon in the 1960’s and was blown away by that…now this.
Yes. Huge congrats tothe entire APL/Nasa and international team!
PBS News Hour presented a very comprehensive report about the mission. William Grantham interviewed Miles O’Brien before and just after the event. It’s very impressive how distant and “small” the intended target is and it will be interesting to see and learn about the results of all the number-crunching and data production to follow.
This is a trick question, right? Conservation of momentum. I guess there might be a question about whether the orbit changed in the “right direction”, whatever that is. Or even, if we’re getting really ambitious, the “right amount”.
Conservation of momentum gives one limit. But what we don’t know is how efficiently momentum is transferred from a (fairly solid) body to a (probably) “rubble pile” object.
For “planetary protection” ideas about deflecting potentially hazardous asteroids (“PHA”s), this is really important data.
Conservation of momentum says that “efficiency” will be 100%. None will be lost.
If we know the momentum of both the asteroid and the spacecraft before the impact and there is only one object post impact i.e. the spacecraft remains embedded in the asteroid and there are no separate bits broken off, we’ll know exactly what the momentum of the new object is.
From my reading of the mission, among what is unknown is the exact composition of Dimorphos. If it is more like a rock pile (as it seems to be) the collision should have a bigger effect on its orbit than if it is more solid. They say that’s because a rubbley surface will cause debris to be flung off the surface and those bits are themselves like little rockets imparting the force of their expulsion onto the asteroid. The more rubbley, the more of these little rockets.
Lots to learn. Absolutely facinating
I understand that which is why I qualified my answer with “if there is only one object post impact”.
Conversely I guess, if the momentum appears not to be conserved, we’ll know that the asteroid is more like a rock pile than a solid object.
I posted this on the original post this morning, so I’m copying it here since this is where the action is.
That was so cool!
Jim, do you know how long it will take for NASA to know if the asteroid’s trajectory shifted? Thanks for all the information you’ve given, it made the mission much more interesting and understandable.
Getting astrometric data on Dydimous’s position )and the orbital solution underlying it) will take months to years. But as the position of Dydimous’s position increasingly differs from it’s expected position, that will give a good momentum-transfer measurement.
Outside Hollywood, this is the expected result.
Thanks!
Thanks Mark. Elena adams said in the post impact press conference that maybe a couple of weeks for an answer that they have good confidence in. A number of ground based telescope teams need to infer the change in orbital parameters by measuring a series of brightness changes for the asteroid pair as the smaller asteroid passes in front of the bigger one and disappears behind it. (It is called an eclipsing binary.) They cannot actually resolve the two separate bodies. Because, as we really know now from those incredible photos tonight, both asteroids have irregular shapes with odd shadows, the teams will have to massage the images to the point where expert peers agree on a good answer. So there may be a number tomorrow followed by several numbers before agreement on a best answer. Hope that helps more than it confuses.
Thanks, Jim, you’ve really helped with my comprehension of this amazing feat.
Yeah, that was a really craggy piece of rock with limitless hard shadows. Those last second images were astounding.
Amazing! This is what science and technology (grounded in science) can do!
Totally awesome.
I understand it was roughly equivalent to one of the pyramids being hit by a golf cart, so we’ll see if it had much of an effect. Either way, pretty amazing accomplishment!
The effect of the momentum transfer will be cumulative. The asteroid satellite will progressively be “there not here” which will give the efficiency factor in a few moths.
Conservation of momentum, do your thing!
An amazing feat but also terrifying. I had not thought about our capacity to weaponize our satellites.
I shed a few tears at the human accomplishment whilst simultaneously mourning the fate of the dinosaurs when that one hit. I found it poignant that here is a species capable of preventing the imminent disaster that past life was oblivious to. The contrast is profound.
This may just be confirmation bias, but the close-up images of the asteroid really did make it look like an aggregation of small chunks of rock and grit. I know that’s what an asteroid is, but I didn’t expect the appearance to be so apparent.
It struck me how closely Dimorphos resembles a falafel. 😛
It has become fashionable to ridicule NASA for being old-fashioned and slow and expensive, while companies like SpaceX are already aiming to send a million people to Mars! …but NASA projects keep delivering spectacular results, while SpaceX keeps delivering spectacular “rapid unscheduled disassemblies”, and hasn’t managed to put “Starship” even into low earth orbit. Maybe slow and steady is the right approach to rocket science after all?
Anyway, congrats to everyone involved with this project!
I think that’s just trying to compare two different types of things. It’s not fair to either. NASA isn’t in the business of building rockets and providing launch services and SpaceX is not a government organization tasked with “Drive(ing) advances in science, technology, aeronautics, and space exploration to enhance knowledge, education, innovation, economic vitality, and stewardship of Earth.” NASA hires companies like SpaceX to do the things that they do.
If you want to compare SpaceX to similar entities then you should be comparing them to other rocket building companies like Boeing, ULA, Blue Origin, etc. To date for 2022 SpaceX has launched 43 paying missions to orbit, Boeing 0, ULA 6 and Blue Origin 0. And all of those SpaceX launches were flown by reusable boosters. SpaceX has launched about as much this year as the whole rest of the world combined, and if you take China out of it, with 41 successful launches so far in 2022, the comparison is much more lopsided.
SpaceX is also currently 1 of 3 entities that can launch humans into orbit, along with Russia and China. None of the US legacy rocket building companies can. NASA has now twice purchased batches of future manned launches from SpaceX that were originally intended to be purchased from Boeing, because Boeing has continued to fail to get their spaceship qualified.
SpaceX’s Starship has done much more than blow up. NASA is impressed enough with it that they have awarded SpaceX a contract to provide lunar landing services for their Artemis missions with a version of Starship. If you were interested enough to invest a little time to really look into what SpaceX has been doing with their Starship / Superheavy launch system I think you would be impressed. Yes, they’ve been blowing a lot of stuff up. That’s their method. Judging by the results it works pretty well. If they achieve their intended goal with this new launch system, which is of course not a given because it is extremely ambitious, then it will be a for real game changer. A fully and rapidly reusable launch system, like an airliner, that can launch 100+ tons to orbit, and with refueling can then take that mass anywhere in the solar system you want to go. To give you an idea of the scale, Starship / Superheavy is larger than SLS and the Saturn V, and the take-off thrust of the prototype scheduled to make a 1st orbital launch attempt sometime this year has more than 2 times the thrust of the Saturn V.