# How significant is the NASA DART Mission in terms of accomplishing its ulitmate goal? **URL:** \ **Category:** In My Humble Opinion\ **Created:** [September 30, 2022, 2:23pm UTC](https://boards.straightdope.com/t/how-significant-is-the-nasa-dart-mission-in-terms-of-accomplishing-its-ulitmate-goal/972508 "2022-09-30T14:23:01Z")\ **Posts on this page:** 12\ **Page:** 2
**Author:** ![kenobi\_65](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kenobi_65/32/13178_2.png) [@kenobi\_65](https://boards.straightdope.com/u/kenobi_65)\ **Post date:** [October 12, 2022, 1:52pm UTC](https://boards.straightdope.com/t/how-significant-is-the-nasa-dart-mission-in-terms-of-accomplishing-its-ulitmate-goal/972508/21 "2022-10-12T13:52:34Z")
> [@Ludovic](#): > > I don’t think density could be off by an order of magnitude given what they already know about it. And _given_ that it is a self-contained system, the elasticity and point of impact shouldn’t matter. My understanding, and this article seems to agree, that the information about the asteroid (size, shape, composition) was not _precisely_ known, and nor was the exact point of impact (as the ship was autonomously adjusting its flight path as it approached). > **[In a world first, NASA's DART mission is about to smash into an asteroid....](https://theconversation.com/in-a-world-first-nasas-dart-mission-is-about-to-smash-into-an-asteroid-what-will-we-learn-189391)** > > The first ever planetary defence test is about to take place 11 million kilometres from Earth. All we can do is wait and see. ---
**Author:** ![k9bfriender](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/k9bfriender/32/3283_2.png) [@k9bfriender](https://boards.straightdope.com/u/k9bfriender)\ **Post date:** [October 12, 2022, 2:12pm UTC](https://boards.straightdope.com/t/how-significant-is-the-nasa-dart-mission-in-terms-of-accomplishing-its-ulitmate-goal/972508/22 "2022-10-12T14:12:29Z")
> [@Ludovic](#): > > I guess if it was a pile of rubble _and_ it got hit sideways, some of the momentum could have been transferred to the ejecta instead of the main asteroid. That’s exactly the point, some of the energy went into blowing all that material out into space, rather than deflecting the asteroid. A large point of this mission was to tell _how much_ of that energy would be lost. > [@Ludovic](#): > > If it got hit head on I’m not sure what you are defining as “head” and “side” for these purposes. > [@Ludovic](#): > > would _think_, but could be mistaken, that if anything any unexpected ejecta should _add_ to the speed difference rather than subtract because they’d be sent backward That’s not how it would work. It _can’t_ add to the speed difference, as that would violate momentum conservation laws(unless it hits and releases a pocket of gas or something, but I think that’s unlikely enough to be ignored). Best case scenario would be a perfectly rigid collision where all the DART’s momentum is transferred to the asteroid. Any deformation of the asteroid would reduce that transfer, and anything blown off the asteroid would be using energy that is lost to deflection. ---
**Author:** ![solost](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/solost/32/11776_2.png) [@solost](https://boards.straightdope.com/u/solost)\ **Post date:** [October 12, 2022, 2:21pm UTC](https://boards.straightdope.com/t/how-significant-is-the-nasa-dart-mission-in-terms-of-accomplishing-its-ulitmate-goal/972508/23 "2022-10-12T14:21:34Z")
> [@k9bfriender](#): > > That’s exactly the point, some of the energy went into blowing all that material out into space, rather than deflecting the asteroid. A large point of this mission was to tell _how much_ of that energy would be lost. Ohhhh ok 💡 I can see how that would have been likely the largest question mark of the mission. ---
**Author:** ![Ponderoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ponderoid/32/19221_2.png) [@Ponderoid](https://boards.straightdope.com/u/Ponderoid)\ **Post date:** [October 12, 2022, 4:43pm UTC](https://boards.straightdope.com/t/how-significant-is-the-nasa-dart-mission-in-terms-of-accomplishing-its-ulitmate-goal/972508/24 "2022-10-12T16:43:33Z")
I said in another thread that maybe the unexpected extra change was due to this target being a rubble pile. I think their next test target should be a more solid body. ---
**Author:** ![DocCathode](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/doccathode/32/18773_2.png) [@DocCathode](https://boards.straightdope.com/u/DocCathode)\ **Post date:** [October 12, 2022, 5:03pm UTC](https://boards.straightdope.com/t/how-significant-is-the-nasa-dart-mission-in-terms-of-accomplishing-its-ulitmate-goal/972508/25 "2022-10-12T17:03:03Z")
Ultimate goal? You want to know NASA’s ultimate goal? Behold! [http://j.aufbix.org/plif/archive/wc191.gif](http://j.aufbix.org/plif/archive/wc191.gif) ---
**Author:** ![k9bfriender](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/k9bfriender/32/3283_2.png) [@k9bfriender](https://boards.straightdope.com/u/k9bfriender)\ **Post date:** [October 12, 2022, 5:16pm UTC](https://boards.straightdope.com/t/how-significant-is-the-nasa-dart-mission-in-terms-of-accomplishing-its-ulitmate-goal/972508/26 "2022-10-12T17:16:55Z")
> [@Ponderoid](#): > > I think their next test target should be a more solid body. We can’t really tell if things are a solid body or a rubble pile till we get up close, but the bigger a body is, the more likely it is solid. This was a good test, as it was a fairly small asteroid orbiting a larger one. That makes it much easier to tell how much was imparted. ---
**Author:** ![carnivorousplant](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnivorousplant/32/3563_2.png) [@carnivorousplant](https://boards.straightdope.com/u/carnivorousplant)\ **Post date:** [October 12, 2022, 8:16pm UTC](https://boards.straightdope.com/t/how-significant-is-the-nasa-dart-mission-in-terms-of-accomplishing-its-ulitmate-goal/972508/27 "2022-10-12T20:16:55Z")
I would think they would next try to hit a larger asteroid. ---
**Author:** ![k9bfriender](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/k9bfriender/32/3283_2.png) [@k9bfriender](https://boards.straightdope.com/u/k9bfriender)\ **Post date:** [October 12, 2022, 8:35pm UTC](https://boards.straightdope.com/t/how-significant-is-the-nasa-dart-mission-in-terms-of-accomplishing-its-ulitmate-goal/972508/28 "2022-10-12T20:35:07Z")
Sure, but it really does need to be an asteroid in orbit of another asteroid, that’s really the only way we can get any level of accuracy as to how it was affected by the impact. ---
**Author:** ![carnivorousplant](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnivorousplant/32/3563_2.png) [@carnivorousplant](https://boards.straightdope.com/u/carnivorousplant)\ **Post date:** [October 12, 2022, 11:05pm UTC](https://boards.straightdope.com/t/how-significant-is-the-nasa-dart-mission-in-terms-of-accomplishing-its-ulitmate-goal/972508/29 "2022-10-12T23:05:40Z")
I thought they would predict the path, smack it, and predict the path again. How much did the path of t he center of mass of the two change? ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [October 13, 2022, 1:43am UTC](https://boards.straightdope.com/t/how-significant-is-the-nasa-dart-mission-in-terms-of-accomplishing-its-ulitmate-goal/972508/30 "2022-10-13T01:43:55Z")
My understanding is they can’t actually see Dimorphos as a separate body from Didymos, the asteroid it’s in orbit around. The two are too close together to separate by telescopes on Earth. But since they are an eclipsing binary, they can determine the orbital period by measuring the brightness changes as the two orbit each other. So what they’ve found is that the period of the orbit decreased by about 32 minutes after being DARTed. ---
**Author:** ![carnivorousplant](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnivorousplant/32/3563_2.png) [@carnivorousplant](https://boards.straightdope.com/u/carnivorousplant)\ **Post date:** [October 13, 2022, 12:25pm UTC](https://boards.straightdope.com/t/how-significant-is-the-nasa-dart-mission-in-terms-of-accomplishing-its-ulitmate-goal/972508/31 "2022-10-13T12:25:37Z")
> [@dtilque](#): > > The two are too close together to separate by telescopes on Earth. How did they know it is two masses? ---
**Author:** ![eburacum45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eburacum45/32/8690_2.png) [@eburacum45](https://boards.straightdope.com/u/eburacum45)\ **Post date:** [October 13, 2022, 12:55pm UTC](https://boards.straightdope.com/t/how-significant-is-the-nasa-dart-mission-in-terms-of-accomplishing-its-ulitmate-goal/972508/32 "2022-10-13T12:55:52Z")
> [@carnivorousplant](#): > > How did they know it is two masses? Observation of the light curve, confirmed by radar. > **[Dimorphos](https://en.wikipedia.org/wiki/Dimorphos#Observation)** > > Dimorphos (formal designation (65803) Didymos I; provisional designation S/2003 (65803) 1) is a natural satellite or moon of the near-Earth asteroid 65803 Didymos, with which it forms a binary system. The moon was discovered on 20 November 2003 by Petr Pravec in collaboration with other astronomers worldwide. Dimorphos has a diameter of 177 meters (581 ft) across its longest extent and it was the target of the Double Asteroid Redirection Test (DART), a NASA space mission that deliberately colli... > [@](#): > > The satellite Dimorphos was discovered on 20 November 2003, in [photometric](https://en.wikipedia.org/wiki/Photometry_(astronomy)) observations by [Petr Pravec](https://en.wikipedia.org/wiki/Petr_Pravec) and colleagues at the [Ondřejov Observatory](https://en.wikipedia.org/wiki/Ond%C5%99ejov_Observatory) in the Czech Republic. Dimorphos was detected through periodic dips in Didymos’s brightness due to mutual [eclipses](https://en.wikipedia.org/wiki/Eclipse) and [occultations](https://en.wikipedia.org/wiki/Occultation_(astronomy)). With his collaborators, he confirmed from the [Arecibo radar delay-Doppler](https://en.wikipedia.org/wiki/Arecibo_Observatory) images that Didymos is a binary system.[[18]](https://en.wikipedia.org/wiki/Dimorphos#cite_note-22)[[19]](https://en.wikipedia.org/wiki/Dimorphos#cite_note-Naidu2020-23) * * * The DART mission seems to have been unexpectedly successful at changing the orbit of this object; I don’t know why this is, but if the impactor hit dead centre, and penetrated sufficiently well to form a deep, conical crater which then funnelled the ejecta directly backwards, then the tiny asteroid would have briefly become a kind of rocket with nearly all the impacting energy pointing in one direction. Contrast this with an impact that only formed a shallow crater - some of the momentum would have been dissipated sideways and effectively lost. [Previous page](https://boards.straightdope.com/t/how-significant-is-the-nasa-dart-mission-in-terms-of-accomplishing-its-ulitmate-goal/972508.md?page=1)