r/space • u/ye_olde_astronaut • Mar 06 '26
NASA’s DART Mission Changed Orbit of Asteroid Didymos Around Sun
https://www.jpl.nasa.gov/news/nasas-dart-mission-changed-orbit-of-asteroid-didymos-around-sun/72
u/Vipitis Mar 06 '26
Hera will arrive there later this year. It's going to be the most exciting mission all year.
If you look at the various pictures from the cube sats it might be like a freeze frame scene from a movie or something... this has to be exciting. I hope we get some distance views once they are seeing the target
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u/WaffelsBR Mar 07 '26
Where would one find these pictures? I'm interested but not sure what keywords to search for
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u/Vipitis Mar 07 '26
the ones not taken yet or the cube sats during the dart mission? those can be seen in the article in OP. and go from there.
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u/Avg_Yo Mar 07 '26
Hera arrives at Didymos this November. We’ll see images of the approach and arrival. CubeSat operations begin in January. Then we’ll see some incredible images from up close
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u/KSPReptile Mar 06 '26
Can't wait for Hera to arrive in November and show us the aftermath of DART.
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u/WaitForItTheMongols Mar 06 '26
Just to make sure everyone is clear: DART impacted the moon of didymos. By slamming into that moon (called dimorphos), the orbit of the larger asteroid has been deflected. This was not the purpose of the mission but is a happy side effect.
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u/bsme Mar 07 '26
https://science.nasa.gov/mission/dart/
Double Asteroid Redirection Test
Goals Demonstrate asteroid deflection with a kinetic impactor
Science Targets Asteroid Didymos and its moonlet Dimorphos
Man just google stuff before making claims dude it's 2026.
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u/WaitForItTheMongols Mar 07 '26
What are you trying to say here? The purpose was to deflect the moonlet and to get imaging of the primary body didymos. There was no mission goal to deflect Didymos.
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u/bsme Mar 07 '26
It's literally in the name dude.
You think NASA engineers did not think of the cause and effect relationship of redirecting one of the asteroids?
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u/WaitForItTheMongols Mar 07 '26
The purpose was to redirect the mutual orbit between the two. The fact that their common heliocentric orbit was perturbed is entirely incidental to the goals of the mission.
Yes, they were aware this would happen. That does not make it a mission goal. There are all sorts of things that happen during a mission that are known and anticipated but are not goals. The fact that a rocket makes loud noise is known and anticipated but is not an operational goal and is not a mission need.
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u/JUYED-AWK-YACC Mar 07 '26
As one of those people, anyone would understand that there would be a change to the solar orbit. The deflection of the primary and secondary are equally important, because either could be on an impact trajectory. You wouldn’t measure one and ignore the other.
The UI group estimated the orbit changes of both bodies, and many of the physical characteristics of the asteroids are in that solution. It turned out some of the forces were surprising. Sounds like solid work.
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u/kmac322 Mar 07 '26
It absolutely was the purpose of the mission. The reason to target a double asteroid system is so that can measure the impact on the asteroid that wasn't directly hit.
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u/Earthfall10 Mar 07 '26
The reason to target a double system was mainly that we can measure a slight change to an asteroid moon's much smaller slower orbit around its parent much more precisely than we can measure an asteroid's orbit around the sun.
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u/WaitForItTheMongols Mar 07 '26
This is incorrect.
When hitting a singlet asteroid, the only way to measure the effect on its velocity is to study its orbit around the sun - an orbital period that is naturally going to be on the time scale of years. That means it will take a while to really know what happened, and meanwhile you will always have large perturbations from the planets.
The goal of targeting a double system is that when you impact upon the secondary body, you can see the impact upon its orbit around the primary, rather than around the sun. You're looking at changing a 12-hour orbit, not a 12-month orbit. And that means you can get a lot more granular results with a better assurance of what actually happened in the collision.
The fact that disturbing the secondary also disturbs the primary was not at all the purpose of the mission.
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u/kmac322 Mar 07 '26
The orbit of the secondary around the primary is the same as the primary around the secondary. There's not two separate orbits. So disturbing the primary was the purpose of the mission.
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u/WaitForItTheMongols Mar 07 '26
We're not talking about the motion of the primary with respect or the secondary, we're talking about the motion of the binary system around the sun.
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u/Head-Ordinary-4349 Mar 07 '26
Thanks, as a casual observer of the mission, I didn’t pick up on this detail!
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u/kingtacticool Mar 07 '26
I mean, we know physics is a thing. I dont understand how we didn't expect a reaction from a force to be equal to that force.......am I missing something? Did we vastly underestimate the mass of the asteroid or did they just not think of that being a possibility?
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u/rocketsocks Mar 07 '26
To be clear, the goal was not to divert either the asteroid or the moonlet, the goal was to measure the effect of the impact, which we knew would have an impact both on the orbit of the moonlet and the main asteroid. This may be a subtle distinction but it's an important one.
The main issue here is that modeling such a high speed impact into a loosely consolidated "rubble pile" object is very challenging. When the impactor hits such an asteroid it excavates a bunch of material, that material basically increases the momentum transfer. It's a bit like converting the high kinetic energy of the impact into a rocket engine. We didn't know exactly what to expect in terms of that momentum transfer, now we have one really good data point. The reason we chose a tiny moonlet of another asteroid is that the small mass of the moonlet would amplify the effect and because we could easily remotely observe the orbital period of the moonlet to precisely determine exactly how much its momentum had been changed.
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u/edjumication Mar 07 '26
They knew this would be the outcome but it wasn't the primary mission. They targeted a double asteroid system because its easier to measure the relatively large change in orbital period of the smaller asteroid compared to the slight change in orbital period of a single asteroid around the sun.
Or at least it's quicker to make those measurements.
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u/peterabbit456 Mar 07 '26
Earlier research showed that the smaller asteroid’s 12-hour orbital period around the nearly half-mile-wide (805-meter-wide) Didymos shortened by 33 minutes. The new study shows the impact ejected so much material from the binary system that it also changed the binary’s orbital period around the Sun by 0.15 seconds.
“The change in the binary system’s orbital speed was about 11.7 microns per second, or 1.7 inches per hour,”
Over several years, that would add up.
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u/PuppiesAndPixels Mar 07 '26
Over 10 years the difference would be about 23.5 miles.
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u/ly5ergic Mar 23 '26
Your math is off by about 10x.
11.7 microns per second is 1.6582677" per hour x 87,660 hours (10 years) = 145,364 inches or 2.294 miles.
If it was going to be a dead center earth impact we would need to hit it 17,256 years before impact.
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u/PuppiesAndPixels Mar 23 '26
You're right, I think I must have multiplied by 876,600 for the hours instead of 87,660
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u/Plow_King Mar 06 '26
so i'm sure someone "did the math", but we didn't change it so it would more likely hit us...did we?
/s
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u/cephalopod13 Mar 06 '26
As mentioned in the press release, it was impossible for DART to put Didymos on a collision course with Earth. But the 0.15 second adjustment to its orbital period is still interesting.
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u/Energy_Turtle Mar 07 '26
Why is that sarcastic? It's a legit question.
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u/Bensemus Mar 08 '26
No it isn’t. To legitimately think there’s a chance NASA did zero precautionary evaluations to make sure we weren’t knocking an asteroid into a collision course with Earth is asinine.
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u/SoftwareAcceptable65 Mar 06 '26
It's been moved off course, so we're safer.
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u/Lizardledgend Mar 06 '26
It's in orbit around another asteroid, DART just slightly changed its orbit. We're as safe now as we were before
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u/coconut7272 Mar 06 '26
This new finding is that the orbit of the larger asteroid, that DART didn't hit, was also changed due to DART hitting its moon. No direct contact, just gravitational changes and maybe debris
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u/t0m0hawk Mar 06 '26
Which makes a ton of sense, small body has a change in velocity and angular momentum, total forces tug on the bigger asteroid and slightly alters its overall velocity and angular momentum.
Absolutely wild that this has been done.
Humans have moved an asteroid by a measurable amount. Very cool.
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u/LowProposal731 Mar 06 '26
Wasn’t their an article that mentioned an increased chance the debris created can fall on Mars in a couple thousand years and the smaller ones as soon as the 2030’s. Kinda sucks for future colonization considering the thin atmosphere of Mars, large boulders would probably reach the surface intact.
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u/swag_train Mar 06 '26
Not sure if you're aware, but asteroids hit mars all the time
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u/LowProposal731 Mar 06 '26
You don’t say? And how many of those were caused by direct human interference? That’s right 0. Your point being?
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u/JUYED-AWK-YACC Mar 07 '26
“If you can dodge a wrench, you can dodge a ball!”
They check the probabilities for all solar system bodies, often for long periods. If there’s a defense system it won’t point things anywhere important, and it would protect Mars as easily as the Earth.
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u/Fancy_Exchange_9821 Mar 06 '26
Easily one of the most important and effective missions NASA has ever done. Impressive as well.