Can We Stop an Asteroid? The Physics Behind NASA’s DART Mission

Slight change to the programming — single-story episodes

0:00Hello internet. This is your captain speaking Lester Nar joined as always by my co-host and our resident PhD Krishna Chowdery. Today we have a wonderful episode. We're going to do a story, a research paper on planetary defense covering one of NASA's most audacious missions, the Dart mission. Uh spoiler alert, it worked. But where it gets interesting is in the how and the why. And we're going to take a quick pause here to talk about a slight change to the programming. For many of you who have been listening to us for quite some time, you know that we do weekly

0:40episodes and the demand has just been insane for us to do more. So, what we're

If an asteroid is coming, I would prefer not to die

0:46going to try out here is actually doing multiple episodes a week, but having our episodes be focused on a single story. So, today we're going to just be focused on the Dart mission with Planetary Defense, but you will see our faces two more times this week with a follow-up story, and we will have the rundown be its own episode type. And I have some ideas about some game show elements to test our resident PhD. As always, we are going to learn about the science from the ground up today because this is from First Principles.

1:35So if there is an asteroid coming to Earth, >> yes, >> I would like to not die. >> Armageddon, Deep Impact. >> Yeah. All of these. I I would I would like that not to happen. Okay. And it turns out the best way to have that happen is actually not to like

DART mission setup — what changed locally

1:53blow it up, but to just gently nudge it out of the way gently because, you know, it's it's a giant asteroid. You got to get a little aggressive because it's a giant asteroid. But at the end of the day, all we have to do is gently nudge it out of the way and maybe it'll avoid Earth. Okay. And the first time that this happened was on September 26th, 2022. This was NASA's double asteroid redirection test. I was watching it live. This was the Dart mission. It collided with a moonlit of a two asteroid system. >> Okay. And I remember watching it live. You could literally see there was a there was a little satellite that acted like a projectile, like a missile, and

2:36it had a camera on it, and it was taking a photo of the moon as it was getting closer and closer and closer. And when it finally hit, the other satellite took photos of it. It hit this moon at 14,000 miles per hour, which is about 6 km/s. And the key result that we got immediately was that the orbit of this moonletit, the name was Dimorphice, orbiting around Ditimus. >> Mhm. >> The orbit of that moon around the main big asteroid had reduced by 33 minutes. >> Okay. So it went from something like 12 hours to 11 1/2 hours. >> So the contact changed the trajectory,

3:18the path that this two moonlit system was traveling on. >> Yeah. But so the contact changed the orbit of the two moonlit system orbit. >> That's what we could confirm. >> Okay. >> What you're saying is what this paper is about. >> I see. >> Okay. Which is >> I I I ran into the moon and now the orbit has changed. >> Yes. But what does that do for how this moon this this two asteroid system goes around Earth? >> Because the the orbit you're talking about is locally. >> Yes. Exactly. And and getting that signal is super easy. 30 minutes less than 12 hours. That's what some like a little bit less than like 5%. >> Right. That's a change that is is doable

3:59like pretty immediately especially cuz we've got the Dart mission in that asteroid system that's like monitoring the two going around, right? So, so, so getting that data is very quick. Happened in 2022. We got that confirmation like within I think like a month. Okay. >> Okay. This is now what 4 years later, 3 and a half years later. >> And now we have a paper that's out in science advances and it confirms that there's a meas measurable change in the

Why this is historically profound for life on Earth

4:27berry center of that two moon system going around the sun. M >> meaning those two asteroids now have a different orbit around the sun itself because of that crash on its moon. >> Does that make sense? >> It makes total sense. And I I want to briefly talk about why the implications of something like this are so historical. >> You know, Earth has been around for 4 billion Yep. >> years. >> Life on Earth has been around for hundreds of millions of years. Yep. >> Some simple life billions of years. >> Yeah. And in the entirety of that time period, the life on Earth has never had control of its own destiny. >> Yeah. >> As it relates to celestial objects and

5:10their impact on the planet. >> So what you're suggesting is that humanity for the first time in the 4 plus billionyear history of Earth >> Yeah. has finally enabled itself to have agency on its cosmic destiny. >> Yeah. >> Based on these objects potentially coming in to impact us. >> Exactly. >> This is a very interesting story for us to understand. >> Yes. Yes. And um I just want to say a quote from the lead author of that paper. He said, "If an asteroid is ever

Near-Earth objects and why Hollywood loves this scenario

5:41on its way to hitting the earth, we can more confidently now say that we have the ability to push them around and away from Earth." Mhm. >> This was by the lead author Rahil Makadia from the University of Illinois Urbana Champagne. And can I just say the news article where this quote comes from, they quote him as a planetary defense researcher. Okay. When I was in grad school on my CV is written graduate student researcher. This guy can write planetary defense researcher on his CV. >> How sick is that? >> That's so awesome, >> right? All right. So, as you said, let's get into the history and why this is so important. The threat comes from these

6:22things called near-earth objects. This is an animation showing all of the near-Earth objects that we've ever seen. The blue circle or the, you know, the blue orbit in the middle, that's the Earth. >> And look at all of these dots. >> Yes. >> All of these dots are threats to us. For those who are listening and not watching the pod currently, there are thousands, hundreds of thousands of these objects in near Earth orbit. It's it's actually a very nauseating amount. >> Yeah. Yeah. It's actually quite like concerning, right? Because if you look like let's just linger on this animation for a second. The the Earth's orbit, there's already a bunch that are sharing

7:03Earth's orbit. Yes. >> Right. Then you see there's a faint line where Mars's orbit is. That's the the red line. And then there's this giant belt almost cloud of orbits. That's the asteroid belt in between Mars and Jupiter right? >> Those are also threats. Not just the ones that are near, >> right, >> in Earth orbit, but like you can imagine like some random gravitational anomaly like Jupiter pushes one of these asteroids out of the way or these two asteroids get a little bit together and then they get nudged into the inner solar system. >> Exactly. It's like in a car accident. if you're changing lanes and you sideswipe the car next to you and then they're now sideswiping the car next to them. >> Yeah. And then there's a 18-wheeler behind like it's it can get bad really

7:44fast. >> Really fast. >> Right. >> Uh similar to the Kesler effect uh when a satellite >> That's right. >> uh crashes in orbit and then it basically creates catast catastrophic failure for everything because there's just these little things flying around and it's going to impact everything. >> Yeah. Exactly. And any momentum transfer can be really bad. Yes. Right. And Hollywood is obviously obsessed with this. We've got, as you were mentioning, Armageddon, Deep Impact. Um, I can't think of many more. Oh, Don't Look Up is a big one. That's the most recent one. That was more about like climate change. >> Yes. >> But it was still like the metaphor was really funny and at the end of the day, the literal movie is about a comet that is coming into Earth and nobody believes the scientists. So, this has actually

Tunguska, Chicxulub, and Chelyabinsk

8:25happened in human recorded history. 1908 was the Tungaska event in Siberia. It was a 50 to 80 m object and it burst 10 m above the surface. So it didn't even make contact with the earth. It exploded because it was heated up by so much. Um and it flattened 30 million trees over hundreds of kilome squared. >> Fortunately, it was in the middle of nowhere in Siberia, right? But imagine if that happened on a population center. >> Yeah. >> It would be way way worse than Hiroshima Nagasaki, right? Yes. Um, in 1980 there was the Alvarez hypothesis which was linking the Cretaceous Paleogene extinction which is the extinction of

9:06the dinosaurs 66 million years ago. Um, it linked that to a cosmic impact. In 1991, the Chickix Club crater was discovered in the Yucatan Peninsula because a bunch of >> oil companies were charting the gravity, the specific gravity around the Yucatan Peninsula looking for oil. Interesting, right? And so, in order to look for oil, what you want to look for is like low density packets >> under the Earth's crust. And one of the best ways to do that is to literally just measure the acceleration due to gravity. The thing that we learn in high school being 9.8 meters/s squared. Well, if you go 9.8 one, you know, all of the

9:48little digits, the little tiny deviations of that acceleration due to gravity. If it's a little less than normal here versus somewhere else, that could mean that there's a low density packet underneath the ground, which is why it's not pulling on whatever object, >> right, >> that you're using to measure that acceleration. So, oil companies were doing that. They actually found a ring of high density. M. Oh, >> and that ring was the size of the Yucatan Peninsula and it was this primordial crater from 66 million years ago. >> I have one clarifying question. When you when you mentioned like low density pocket, >> what you're referring to is like a a lake of oil under the ground. >> Exactly. Okay. Yeah. Yeah. Instead of rock.

10:28>> Instead of rock. Cuz the the oil is less dense than rock. And so what they're looking for is an underground lake of oil. >> Exactly. Yeah. And that underground lake of oil would decrease the effect of gravity in that location. So if you were to measure gravity very very precisely, you'd be able to chart out where the oil is. >> That makes sense. This is also why science is so important to capitalism. Yeah. Because the alpha matters. >> The alpha matters and and like and like the the you know the the closer you get to this precision, >> the more you can unlock, you know. Mhm. >> Um and then finally in 2013 there was the um Chelins Meteor which was a 20 m object over a thousand injuries happened also over

11:09Russia. >> Yes. >> Um this and this was one that was very there was video like you know it was very because we had media and technology devices. It's probably the most prominent >> uh atmospheric large object atmospheric breakup explosion. >> Yeah. >> And you know over a thousand I mean it was a lot. It was >> it was a lot. It was a lot a lot of broken windows and things like that. Um one of the reasons why we have so much footage on that is because Russians >> the Russians love having dash cams. >> Yeah. Yeah. >> Because I don't know. I mean I don't want to say anything. comment in the in the in the thread if you know the reason why that's true. >> Yeah. Yeah. But anyways, Russians love having dash cams and so there's so much

11:51dash cam footage of the meteor just like coming down, right? It's it's pretty incredible. >> I want to just re-emphasize that that 2013 meteor was only 20 m

Why nudging beats blowing the asteroid up

12:03>> Yeah. >> in in I guess diameter. >> Yeah. >> Um it's it's not a super large object. >> No, no, no. >> And the >> like the size of a house. the force and the impact uh and the thousand because the devastation is was pretty severe. Yeah. >> Right. So in any event, >> so our best strategy when it comes to planetary defense is actually to nudge it. We want to give it some momentum and then we want to get out of the way and hopefully that thing gets out of the way, right? Because we've nudged it and it just avoids Earth. It keeps going around the sun but now it's orbit has changed a little bit.

DART’s launch, intercept geometry, and precision hit

12:38In the same analogy of the car accident like before, imagine you're in a James Bond movie and James Bond is in a car in the left lane and the love interest in that movie is handcuffed to the steering wheel in a car in a right lane and they're both going 90 m hour down a road and the the right car is about to hit something. He's like, "Well, let me just bump it >> out of the way cuz that'll change how it's driving out of the way of about to hit this brick wall that's in front of us." Just as like a grounded analogy. >> Yeah. Yeah. Yeah. Is this one of the dream fantasies of yours? Yeah, he had a lot of he had a lot of detail in that one, guys. Um, yeah, but exactly right. We want to just nudge it, get it out of the way. Okay. In 2022,

13:20that was the Dart mission. >> It was the first intentional deflection. It was actually launched out of Vandenberg in 2013, which is right down the street of Southern California. >> Um, it went with the Earth to meet up with this double asteroid system. So this double asteroid system which is Ditimus and um Dorphis. So we can look at an animation of their orbits, right? The green is the double asteroid system. Yes. The teal is Earth. >> Yes. >> And the pink is what we're seeing >> of the our like what what you call it? >> The the dark mission. The dark mission. Right. Okay. Sorry. So let me just recap. The blue is Earth.

14:00>> Yes. The dart mission comes out in pink from Earth. It's following Earth. As you can see, it's just leading it a little bit. >> Yes. >> And the green double asteroid system that we're trying to hit is going to come meet up with us. >> The double asteroid system is actually a near-ear orbit. And there you go. >> Yep. >> That's when the impact happens. You can tell that the impact is happening pretty close to Earth because both are moving together. And then the impact happens here. But Earth is pretty close. That is by design because what we want to do is we want to have all of the observatories on Earth >> looking at this thing to get as much data as possible. The the impact was like 6 million miles >> which >> in the grand scheme of things is not is not that far away.

14:41>> I want to just pull this back up really quick this animation. Um because I think what's so interesting is when you look at where it launches from. Yeah. The launch of Dart happened on the opposite side like it first left Earth right on the opposite side of the sun from where uh the the asteroid was coming in and it did almost a 3/4 orbit. >> Yeah. >> Prior to contact. And I just want to the the the the distance. Look, if I'm trying to throw a paper ball, a a paper towel ball into the trash can from my desk, >> I'm maybe going to hit it six times out of 10.

15:21>> We're trying to send this thing in an orbit >> around the sun. >> Around the sun, >> with the Earth with the Earth, millions of miles >> um and it made direct contact. I just want to really emphasize the level of precision that is required >> to because that's not the point of this this story per se. It's the second piece, >> but that initial part in and of itself is an exceptional piece of just both the engineering, the math, and the operational planning to execute on. >> Yeah. I mean, NASA's just incredible at doing this kind of stuff. Um, and you, as you mentioned, right, like the thing gets released, it makes almost full circle. So, it's almost like if it got

16:01if it got launched in I I wish I knew the exact date that it got launched, right? But if it got launched somewhere, it's going to almost do a full year. >> Yes. >> Around, right before actually getting there. Pretty incredible. Um, so that's

Housekeeping — donate, socials, APS plug

16:17what we want to do, right? We want to have it, we want to have it impact very close and then we want to have all of the observatories watch this impact happen. >> Yes. >> Right. >> Yes. >> Yeah. because we don't have a lot of instruments deeper in space. >> Mhm. >> And so the best way we can capture data is when it's as close to our instruments as possible. >> That's right. Yeah, that's right. And um before we move on >> Yes. Let's do some housekeeping. >> Yes. So housekeeping notes again. We are testing our new format two to three episodes a week. Each episode when it's a research paper or a deep dive is going to be fully focused just on that topic matter. We are also going to do the rundown as its own standalone episode

17:00one so we can have a little bit of fun. Talk about a variety of things, a little grabag. Think about it like uh the weekend update on SNL. And I am determined to make a science game show out of this with Krishna as our recurring contestant, which you can't see from the current angle. He's getting a little bit of indigestion at the thought of that. But if you are intrigued by the concept or you're a longtime listener, as you know, we are a victim like we all are to the billionaire algorithm. So a like, follow, share, subscribe is super valuable for us to help get the show to more people. And if you are really

17:40passionate about what we're doing, it really fills your cup every day, and you want to find a way to support us, we do have our donation portal at ffpod.com/donate. If you want to catch us on socials, so you see us casually as you're scrolling the Tik Toks in between cat dancing videos and whatever the next trending voice over topic is, we are at FFP pod across all of the socials. And I believe that is the conclusion of our show notes this week. >> Yeah. One more thing just from me on a personal end. So for those listening, if anyone is going to APS, the Global

18:21Summit meeting in Denver, that's the American Physical Society Global Summit in Denver this coming week. So the week

Didymos vs Dimorphos and why binary systems matter

18:27of this podcast released on Thursday, I'm giving a talk. So you know, if you're going, just look me up on the schedule and come check out my talk on Thursday. I'm still, you know, doing doing stuff and and talking to people about all the research that I'm doing. And if you want to know about the research that he's doing, which is very interesting, make sure if you're at APS, you go see it and embarrass Krishna by asking for an autograph in front of all the scientists and academics. >> Okay, let's get back to the story, please. >> All right. The target of the Dart mission was the Ditimus Dorphus binary system. Just to show how the two

19:08asteroids compare, the moon, the moonletit that we were trying to target is a bit bigger. It's in between the Statue of Liberty and the Eiffel Tower in terms of how big it is. Ditimus is like Bourj Khalifa type >> in terms of how big it is, like the diameter. >> Um, and what we're trying to kamicazi is the moonlight. Yes. The little the the little small one. Yep. >> Okay. So in during the mission actually the main dart like asteroid or sorry the main dart probe the satellite actually stood behind to watch this unfold and it let out a little like >> uh >> kamicazi satellite drone >> one go.

19:49>> Yeah, exactly. And and so this gu this guy's job was to go and bomb >> Yes. >> Dorphice. Let's say let's say make contact. >> Make contact. Sorry, I I shouldn't. Yeah, in today's world, let's let's rephrase that. We're trying to make contact with Dorphis and the other the the main ship, the mother ship is watching this all in action because it wants to see what is the effect. >> Yes. >> Of that contact on the system. Why binary? It's because we want rapid measurement of deflection, right? >> We want to the orbit is going one way. We want to see if it's slowed down or sped up. Okay? Whatever. And with a with a dual orbit system, it is easier to

20:31ascertain the answer to that than a single object moving. >> Yes. Exactly. And here's why. >> Okay. >> The mutual orbit velocity of Dorphis and Ditimus is about 17 cm/s. >> Okay. >> Okay. Which means that if we were to impact some momentum, 17 cm/s, even for something as large as, you know, a rock, a mountain, let's say, I can reasonably try and discern some change because I'm going at it at 6 km/s. So reasonably, some of my momentum is going to get transferred and then I'm going to be able to see a change. And they were able to see a change. They saw that the mutual orbit period of was altered by 33

21:13m. And this is something that we can rapidly measure. The orbit got smaller. It got shorter by 33 m. And the dart system, which is monitoring this, >> can calculate that, measure it, no problem. M >> make makes total sense. We set up an observer and uh a a probe to make contact. the the initial data point that was going to be captured is is the local orbit going to change from 17 centimeters per second to something else. Because by making contact, going back to our car analogy, if you're in two-lane highway and you're one car and you swerve to the right and make contact with the other car, your momentum in

Momentum enhancement and the beta factor

21:54part will be transferred to that other car. Exactly. Which is why then you have to see the driving scenes with like oh yeah to counteract the transfer of momentum. >> Yeah. And that's why that's why the double the double system matters right because like this is a small enough system where like I can I can make that I can make that change discernable. 33 minutes out of 12 hours >> something I can easily measure. Now >> sense >> when it comes to the big thing. Now let's think about the big thing. There's a there's the big system that's moving around the sun. >> Yes. that thing is moving at 23 kilometers per second. >> Okay. >> Mhm. >> The change that my momentum is going to cause is going to be less than a millimeter per second. >> Mhm.

22:34>> That's way harder to measure. >> Yeah. >> And that is what this paper is doing. >> I see. >> This paper is measuring the big one. >> So, let's get into some of the physics that we were talking about. Right. >> Okay. We've got the kinetic impactor which is this idea of um a sort of satellite drone going in making contact and its momentum getting transferred. Now it's not that simple because it's not a simple momentum conservation undergrad problem. Okay. >> Okay. >> It turns out that when I go and make this contact at high velocity at 6 km/s to this little moon that's going to generate shock waves. So the the asteroid is going to ring a little bit. There's going to be an impact crater and

23:15there's also going to be massive ejector that is flying the opposite direction. So imagine my hand is the moon. I make contact, there's going to be ejector flying this way. It's almost like another little rocket impulse that's going the opposite direction. So what I'm going to get is something called momentum enhancement. >> The amount of momentum that gets transferred is not just how much I went in with, but also how much that it threw out. >> Right? Yes. >> And so there's this beta factor called momentum enhancement factor and that's the ratio of the total momentum that was transferred to the target divided by the total momentum that I had. >> If beta is greater than one, that means

23:56that I've actually impacted more momentum than I originally had because the original object has pushed out a bunch of debris in the opposite direction. Does that make sense? >> Yeah. Yeah. So, so what we're saying is um we have an object, our object's coming in to make contact with something. This actually dovetales with the panspermia story we talked about in our last episode about about impacts and that there's ejecta and the velocity by which you hit something can shoot that stuff very very fast and can potentially spread life. But what is the amount of stuff that gets ejected out >> almost creates this additional push in the direction you were already going in addition to the amount of push that you individually as the object was giving.

24:38>> Yes. And that's that enhancement. >> And that's the enhancement, right? >> And so it's really important for us to calculate what this enhancement is because if, >> god forbid, there's an asteroid coming for us. >> Yes. >> Knowing this value of beta is going to be instrumental for figuring out how fast do I need to nudge it, right? How big of the drone does the satellite need to be in order to make contact? How much momentum am I trying to put in there? because the momentum transfer is not just what I'm putting in initially, but it's this beta factor multiplied by the initial momentum. >> So the the the idea here is is when Morgan Freeman is in the classified room talking and someone says, uh, we have an

25:19Ellie, an extinction level event because this rock is coming and they're saying, "Okay, what options do we have?" NASA would be able to come into the room and say because we had our Dart mission where we were able to get real world data about what the momentum enhancement factor >> is. We know that because this trajectory is X Y or Z, we're going to need to send this amount of payload at this speed because the math is mathing. >> Exactly. And now we have all the parameters to make that math math. >> Right. Right. Okay. >> Okay. With the Dart mission, we got a local version of beta,

26:00>> right? >> Yes. >> But let's do a little lesson in undergrad physics. We're going to talk about systems and what are their components. >> Okay. >> Whenever we do um undergrad physics, we always try to think of what is the system that is isolated from the environment that we're trying to work with. >> For example, the earth, sun, moon system. Yes, there's three bodies,

Local orbit change vs heliocentric deflection

26:22right? when we think about like you know shooting something off Earth or we think about just tides for example actually tides is a bad idea because we need both the sun and the moon but >> if there's stuff that's local to the earth and the moon we don't really need to worry about the sun too much okay >> okay we can have momentum transfer in between the earth and the moon and we'll be fine >> would satellite stuff be an example of that >> yeah satellite stuff would kind of be an example of that because like the sun is kind of far away it's like really big, but it's still like it it doesn't it doesn't like come into the equation or it comes into the equation in in another way. The idea is that like there's

27:03there's granular levels of how we want to describe a physics problem, right? Um, and my point here is when the local measurement was made, when we figured out, oh, the orbit decreased by 30 minutes between the two of them, >> what we what we really did was figure out a local beta. We figured out a local m momentum transfer that happened because of the moon and how much how much escaped the little moon's gravity, right? To create a nudge >> between the moon in relation to the big

27:44Ditimus. Yes. So Dorphus is now speeding up >> in relation >> in relation to Ditimus. >> Right. What we really care about when it comes to planetary defense is the sun binary system. >> What we care about is the heliocentric momentum enhancement factor, not the center of mass frame momentum enhancement factor. Here what we're looking at is >> from Earth. >> Mhm. >> The impact on Denimus. >> Okay. >> Okay. And what you can see is you don't even resolve the binary system. >> It looks like a single dot. >> Yes. But we didn't hit the main dot. >> We hit the moon. And yet there's all

28:24this ejecta that came out. All of that ejecta that came out has escaped the binary system. >> That ejector not only escaped the moon, >> the main ditimis big asteroid couldn't even keep it together. >> Right. So all of that eector escaped the moon. >> Yes. >> And the big asteroid. >> Yes. >> And has gone out into outer space. Yes. which means that there isn't a momentum enhancement factor on the entire system as a whole. It's a really nice like sort of >> little undergrad problem on conservation of energy, right? Which is this idea that like even though I only hit the moon, I'm actually changing the trajectory of the entire moon >> planet or moon asteroid system.

29:07>> I didn't touch the asteroid, but the asteroid's orbit has been changed because I hit its moon. So, so as a maybe a pop culture reference point, let me know if this actually tracks with what you're saying. There's a famous, not a famous, there's a a movie that came out maybe in the last two, three years called Moonfall. >> Okay. >> And the moon >> fell Oh, dude. towards Earth. I know this one. And and so what the point even though the moon had yet to make contact >> with Earth, the simple fact that it moved from its existing orbital position around the Earth to being getting to getting closer totally disrupted a variety of things in Earth because the tides changed and the proximity and it

29:49it's so it's like it's like a local move. It's like local but it it has this larger impact even though it's maybe not the right analogy. >> It's okay. So I want to I want to take that a step further because in that one what you're talking about is local changes again. >> Oh what I'm saying what I'm saying here is like suppose something hit the moon which caused it to fall. Yes. >> Right. >> There would be an energy transfer into the moon. Yes. Right. So looking from Earth's perspective the moon would gain some energy let's say. >> Mhm. >> Now looking from an alien perspective that looks at the earth and moon system as a single system. There would be a change in energy in that entire system. both the earth and the moon would gain some energy. So both that that system as

30:30a whole would change its trajectory around the sun. >> I I >> that's the idea. Is that what is depending on how granular you make your system at the end of the day conservation of energy and conservation of of momentum >> are paramount. Yes. >> So >> if the momentum was transferred to the moon, it'll also be transferred to the earth moon system. Yes. >> Which means that the earth moon system moving around the sun is going to change. That's what's happening here. That's the key that I need that that I need everyone to try to like sort of internalize which is conservation of energy and momentum is true regardless of the size of your system. The the Yeah. Right. At whatever level or layer you're observing the system, >> a change of momentum in one of those

31:12layers >> will will then will uh transcend across all of the either downstream or upstream. I don't know which direction. >> I don't know which direction it is either, but one of those two. Yeah. You you get you get you get exactly what I'm saying, right? And so >> if that ejector is escaping the combined gravity >> of Dimus and Dorphis, >> then it's going to change the trajectory of the entire system.

The core challenge — measuring an 11 micron/sec change

31:36>> I see. >> Which means that I I need to figure out a beta for the entire system, not just what I had figured out before, which is just the little moon, >> right? >> Around this. >> Yes, that makes sense. Because because ultimately from a planetary defense perspective, >> that's what matters. You care about the whole system. >> Yeah. Yeah. Yeah. That's what >> And being able to change the whole system. >> The whole system. >> But in order to do so, you need to understand the component parts component parts necessary to be able to impart that level of change on the whole system. >> Exactly. >> Yeah. And to tell you just how hard that is to do, >> right? >> Um the heliocentric velocity, this is something that I covered a little bit earlier. The system moves at 23 km/s

32:18>> and I'm trying to detect I'm trying to detect a change that is less than 1 millimeter per second. >> This thing is moving at 26 km/s and I need >> 23 20 >> sorry yeah 23 km/s. This thing is moving at 23 km/s. >> Yes. >> And that velocity is going to change by a millimeter per second. actually less >> this to that extent that's several orders of magnitude. A millimeter is a a thousandth of a meter which is a thousandth of a kilometer. So this is >> about 10 millionth. >> Yeah. >> One part in 10 million. >> Yeah. >> Is what I'm trying to sense for an asteroid that is millions of miles away.

32:59>> Uh we like to say this is non-trivial. >> This is this is extremely non-trivial. Right. >> Yeah. >> Like to make that measurement. This is another lesson in again some of our favorite topics on the podcast. Precision measurement, >> right? That's such a key. It's We have a toolbox in science with hammer, screwdriver. Some tools are more useful than others. Yeah. >> Some tools you use all the time, like a hammer. There's a lot of things you can do with a hammer. >> Laser is the thing in physics. You >> see, put a laser in. Yeah. Whatever. But but I I think again measurement it's not measurement is a whole craft in and of itself with a level of density of complexity and expertise necessary to be

33:41able to do so >> in a robust enough way. Yeah. >> Um and this is a measurement challenge. Speaking of measurement challenges, in our uh first nine minutes of our appearance on the Dave Chang uh show, which is on Netflix, check it out, was spent on the double slit experiment, which is a measurement problem. >> Yeah, that is a measurement problem. That that completely caught me off guard cuz like we just got there and he was like, >> "What about the MIT paper?" I'm like, "That was like months ago. What What is going on?" I can't believe he like watched that one like that. That's he's he's an OG fan here >> and he he's also quite quite sharp. I was >> Yeah, dude. He he remembered so much. >> He's quite sharp on you. >> Yeah, that was that was really cool.

34:22>> But the measurement problem is >> measurement problem. And this is where this particular paper comes in. It's measuring this unmeasurable 1 mm/s actually a lot less >> change in a 23 km/s object >> that is millions of miles away. And this was a a paper that came out in Science Advances direct detection of an asteroid's heliocentric deflection. Okay. The target change that they measured was 11 microns per second. >> Jesus. >> Okay. Out of 26 km/s. >> Okay. And what this means to just give you a sense of scale. >> Yes. >> So that asteroid system goes around the earth every 770 days. So that's about 2

35:04years. Mhm. >> And this tiny change in velocity means that the 2 years of orbit has been shortened by 0.15 seconds. >> Oh my goodness. >> Okay. So the sec so a year on that on that asteroid is now shorter than shorter by 0.15 seconds because we crashed into the moon. >> That's incred and so there's there's sort of two things about this which is interesting. one is what an exceptional job we've done to be able to measure such a small scale change >> and and that's what we're going to get into next. >> And then the second piece is now we then have a reference point to be able to say

35:44how much do we need to scale up the because we just sent a small little thing. >> We didn't send a big old cuz also getting payloads into space is expensive and costs money and we don't like to spend too much money now on fundamental science stuff. Um, but now you could go to the the joint chiefs and say we're going to need a 100,000 megat ton X in order to get the level of momentum. But we just have a baseline now. >> Yeah, we have we have the numbers now. Right. >> Right. So in order to in order to make that detection, right? So 11 microns per second. >> Mhm. >> Is the difference between before and after before the explos before the impact and after the impact. Before the impact, it was going at about 26 23 km/s, right? And after the impact, it's

36:27still going at 23 km. >> This is like in the hypersonic velocity like area. >> No, this is not even hypersonic. This is way >> way way. Yeah. Like uh the speed of sound is 343 m/s. So.3 m/s. Okay. >> Okay. This thing has 23. So that's what um 3 >> * 20 60 times about 60 times the speed of sound. Okay. Hypersonic is five. So five and we're happy. >> So we're in UAP land right now. >> Yeah. Yeah. We're we're most likely in UAP land. Here's the idea, right? In order to measure that change of 11 microns per second, what I need to do is have that precision on the before and

37:08after. >> Mhm. >> Before we get into the after. >> Mhm. >> Right. Like if I were to say if I were to measure something like oh the speed of the car like imagine I'm a cop on the on the on the highway and the the guy is going at 70 kilometers/s and then I say oh he decreased his he decreased his um speed by003 km/s. Well I'd need to know what the initial thing was right otherwise like how do you I could just be going like 71. If you said 70, that's only one significant figure. For those students in science, that means it could be 71 or 69 or 68, right? So, we need to know the before and after equally well in order

37:49to make that subtraction. That's a really good point. >> We don't have like the tools in physics where I can like do destructive interference where I don't actually need to know the answer because the answer cancels out. No, we're not doing any fancy. We just need to know what the number is and then do subtraction. >> So, so the point being we need to measure it before this. We need to measure before we do anything. >> Yeah. >> And in that measurement needs to be very very good in >> very very precise down to the micrometer level precise. Yes. >> And the way they did that was so this system Dimus and Dorphus has approached Earth over the past 29 years and we have massive radio telescopes that have bounced microwave signals off this thing. And we can now fit the orbit

38:30>> with uh a simulator like a small body simulator and JPL's comet and asteroid orbit determination program. And from that we can figure out what was the before >> velocity because we have this historical data that has captured pictures over time.

Radar, stellar occultations, and citizen astronomers

38:47>> Yeah. Over 29 years. >> So So you're capturing the movement even though the picture is static. >> Exactly. And it's not just pictures, it's also radar. >> Okay. Right. Because we can beam it and it'll come back. So it'll give us a distance at least from Earth. And then the beam will also get get blues shifted. Yes. Because the guy is either coming away from us or to like if it's if it's moving away then it'll be redshifted. If it's moving towards us the beam that bounces back will be blue shifted. And we can measure that difference in frequency to figure out the velocity. You do this over multiple >> years 29 years and you get a really nice >> right >> um number. And it >> and that's the before. And this is like we basically have a uh it's like a when

39:27you go on a run on an app like whatever Strava or whatever and you get the little trail and it shows like where you've run before. It's like we have that very precise of >> very precisely of the movement of this over time >> over 29 years it's been doing the same thing right over and over again. >> Okay. So now how do we get after cuz it's only been 3 years. We've only got three years not 29 in order to gather this data. So there's two ways to do it. One is through radio astronomy. Astrometry which is the same thing that I was saying earlier. So radio astrometry is simply you >> use radar to bounce a microwave signal there and back. They actually use the Goldstone solar system radar which is part of JPL's deep space network. This

40:08is actually whenever we go to Mammoth. >> Yeah. >> Um you know next time when we go I we should like just pull over and I don't think we can get in cuz it's like security or whatever but >> hey let us in. It's it's still like next time we go I'll I'll point out the radio dishes to you. Um >> so we we use that and from that we can we can get the time delay. So that'll tell us within tens of meters what the position is. We get multiple positions then we can calculate the momenta and also the fact that the signal is redshifted or blue shifted. That Doppler shift is going to give us some idea about velocity. But over 3 years it's not going to give us enough of that error bar going down. It's going to be part of it but we need something else. And this is where something very cool

40:48comes in. It's called stellar occultations. Okay. The idea is the asteroid is going to pass in front of stars in the night sky. No way. >> And it's going to eclipse stars. >> No way. >> And so we can measure whenever it eclipses stars, the star is going to blink. And we know the star doesn't actually blink, >> right? We the star has a constant brightness. So when it like goes down and up and we we know where it's going to be. So we're like, dude, this thing is going to this thing is going to move in front of that star. >> Yeah. like around this time. >> Yeah. >> So, we can have volunteer astronomers. And that's what I found very cool about the story. There were volunteer astronomers that went out. >> Yes. >> And tried to capture these stellar

41:29occultations. We're effectively trying to capture the shadow >> of this asteroid >> passing in front of >> passing in front of a star in the night sky. >> And the star. >> Yeah. The shadow is only about a kilometer wide. >> Oh my god. >> Okay. So you need very precise like timing of like where you need to be in order to capture it and also space. And one thing that I found really cool was there was a guy volunteer again. He observed >> two of these occultations. He drove two days each way in the Australian outback >> to get it >> in order to get this data. >> That's we we that's >> like shout out to this kangaroo jack guy, dude. Like >> the Aussies Aussie Aussie Aussie.

42:09>> Yeah. That's it's pretty awesome. But this is this is so interesting again because sometimes you know there's a lot of uh ast a astrophotographers I guess that that are very popular now on socials and stuff like that and it's a real craft in and of itself. >> Yeah. Yeah. Yeah. This guy had to know where to point like how to get the data exactly where to be because you've got a 1 km radius that you need to you need to get this thing >> and it you can not only do it for the joys of being curious about the universe around us but also be a participant and a contributor um into sort of instit institutional >> yeah research I think he should put planetary defense >> researcher >> researcher on his CV right whatever he's

42:52doing in the Australian outback like that should be that should be part of his CV So with this international network they captured 22 distinct occultations between October 2022 and March 2025. >> Okay. >> And that is where they got all of their data to where they can say 11 micrometers per second is the change in the velocity of this asteroid >> because now we have like another reference point another reference frame by which to like understand because we have the historical data set from the 29 >> and that's the before and we need an after and we need an after. And so basically the the the stars that are behind in between the stars that are behind this passing in between us >> create a a reference point for us to

43:33measure against. >> Yes. >> And that allows us to get the after because we have such a precise understanding of the stars and their positions. >> So it's almost like they're a ruler. The stars become a ruler by which we're measuring >> and it's extremely precise and that's how you get that precision in such a short time. If we just waited for Goldstone radar to keep going, we'd have to wait for it to come back and then like, you know, that's just going to take forever. But if you if we supplement that with this really tight >> astronomical data, right, and then we run the models on it, then we can get the error rate down to where we can really say, yep, >> 11 micrometers per second is how much we took away >> from that asteroid, which means that its year, which is about 2 years, is going

44:14to be shorter by 0.15 seconds. And that's how we get that >> data. >> That's so >> that's how we that's how we conclude that number >> but it's hard work. >> It's really and it's a really creative solution to the time problem because

Beta_H ≈ 2 and what ejecta adds to the system

44:28it's like you have li you know what is it a necessity breeds invention and they're like okay we don't got time >> we don't Yeah. >> What are we going to do? It's >> like well what if >> Yeah. And it worked. >> Very good. >> Very good. And and so now from there we can actually calculate the momentum enhancement along the heliocentric path not just the local path but how much boost did both of them get >> yes >> on their way around the earth the the sun given that >> my you know kamicazi drone satellite had a certain momentum how much momentum boost did they get and the beta that we get is about two a little bit more than two so twice as much momentum was transferred to that system >> than what we put in because of all the ejection that came out the back. So

45:09basically the amount of momentum we put in that same amount was ejected out. >> Mhm. >> Yeah. Yeah. I thought it was pretty cool. >> That's very nice. >> It also confirms like the density of this >> moonlet. Yeah. It's about significantly lower than solid silicate rock which means that it's like highly porous. It's actually not like just like normal rock. It's like a very light rock. >> It's like the rock you are supposed to wash your feet with. What do they call it? Pum like pum. >> Yeah. Yeah. Pummus stone. Exactly. Yeah. Yeah. It's 1630 kg per meter cubed. >> Okay, >> which is so it's still going to um it's still going to sink in water. Water is 1,00 kg per meter cubed. I just want you not that much more dense than water. >> I just want to note we uh just

45:50implemented a latex notation in our script notes. >> Yeah, it's pretty great. >> Uh which sign displays a real formula and I'm looking at this and you just rift that off the cuff so quick. >> Yeah, cuz I can I can actually read it. Also the the beta with the unders like there's a subscript you know beta h along because that's the beta heliospheric along the path. Before I had to like read the latex where it would go slash beta underscore um parenthes squiggly parenthesis h oh my god >> it's now it's in English. >> Yeah now it's in actual English. Very good.

Why this changes planetary defense planning

46:28>> So broader implications. Yes, >> we've got a valid measurement of beta. >> Yes. >> Now, that validates this kinetic impactor. That means that like in the future, we're not blowing things up, >> right? >> Like, if we're going to get twice the momentum enhancement, >> that means like, you know, all we need to really toggle is how big is the payload, >> which we can >> we we can toggle as much as we want, right? We can do multiple hits if we need to. And >> and then um >> like how fast are we moving, how big is the payload, how fast we moving, and then multiple if we need it. Right. >> Right. So, this is now like a strategic advantage for us. It confirms that we can actually do this. >> All the things we've seen in all these asteroid movies, some of which they just tried to send a put a drill. I think Armageddon, they tried to drill and then

47:10blow it up and but then it just created thousands of pieces that still can't Armageddon was incorrect. >> Right. It's less Okay. It's less Hollywood. There's no big nuclear explosions in space, but I just want to live. Right. >> Right. And we just need to nudge it. We just need to hit it. It sideswipe it a little bit. Yeah, exactly. >> Go in the other direction. >> Yeah, it's like a hockey puck, right? Just like, you know, you just move it out of the way. Um, the Near Earth Orbiter Surveyor. So, this thing is NASA's next generation space-based infrared telescope. It's going to launch in 2027 in September, and it's designed to detect dark asteroids that are not visible by groundbased optical telescopes for whatever reason. Sometimes they're coming right at us from the sun. They're like in our orbit,

47:52things like that. So, that's what this surveyor is going to do. that's going to give us more and more, >> you know, just in case some some random crap happens. >> I want to note that the 2013 Russia example that we talked about because some of the questions might be like, "Oh, well, planetary defense, we already know where all this stuff is, so we'll be fine anyway." That 2013 one >> came in it came out of nowhere and no one saw it. >> Yeah. And it was super alarming cuz I was like, I thought you guys had this together, >> right? And and so planetary defense is not We are a single point of failure species. I think I think we have I think NASA says that we've got all of the um all of the like really bad ones like the

48:32dinosaur impact type ones probably under control but still like I like the one the one on Russia right if if that had not exploded out in >> right >> 10 you know whatever the altitude like that could have been really bad that could have taken out a small city. >> Yeah. >> I don't want that either. >> Right. Right. Because the other flip side of this which is just sort of an interesting dynamic in the world we live in today which is uh relevant is I think this is actually the um this is the plot to Paradise the Hulu show. >> Yeah. >> Where it was an external object that was coming in um like a comet or an asteroid

49:14>> and it triggered nuclear war because of its like existential context. So like if something has impact and then there's misin like there's not good information sharing about what the thingy. >> Yeah. I mean we're going to war for a lot less you know and so it just creates you know planetary defense is really important. We we you know we are not well equipped to survive a massive impact. >> No. So we I'd rather not have it. And we now have at least a baseline to be able to provide the defense industry the

ESA’s HERA mission and the next step

49:47answer when they all get around that round table and they have an extinction level event from a celestial or cosmic object headed to Earth. The NASA scientists have the math now. >> Exactly. Yeah. And one last thing that I want to highlight is that this is an international effort. Right. Planetary defense. We're on the same planet. The ESA has her which is arriving at Ditimus and Dorphis. It's actually going to map out the Dart impact crater >> and it's going to directly measure Dorphos's mass via radio tracking and really refine those values of delta V and then beta subsequently and so on and so forth. So it's it's really international effort that we've just

50:29sort of created a a a lab test bed in space right >> of Ddius and Dorphis this binary asteroid system. >> It's very cool. Look, any space story, you know, I'm in on. I I had I owned both Armageddon and Deep Impact on VHS when they both came out in whatever it was, 1997. Um, I still think it's hilarious to think that uh Bruce Willis and Ben Affleck, who were a bunch of guys who worked on an oil rig, were the only people who could save Earth and had to learn how to become astronauts, right? And apparently it was easier to train people who worked in an oil rig to be astronauts than it was to train astronauts how to drill on this thing. >> Ben Affleck did it. And if you the one of the if you're a movie buff, I think

51:09in the the extra scenes, whatever the when we used to have the DVDs with the extra stuff, uh oh, the director like the director's cut where they would voice over while I was playing, >> he was just taking the piss about how ridiculous the plot was to the movie >> the whole time. >> That makes sense. >> Very, very cool story. Dart, our planetary defense story today. Um, and the key piece to this was >> the ability to calculate the heliocentric momentum change. >> It's really it's it's really a precision >> physics and precision astronomy story more than anything else, you know? >> Right. But in the media, we like to say planetary defense. >> Yeah. >> It's what is the how do we make this militarized?

51:49>> Yeah. But I just I just love that like you know for for astronomers like this kind of precision is like unprecedented,

Correction from EP 29 + comment prompt

51:57right? They're like plus or minus 10,000 kilometers, you know, type of guys. >> Right. So, >> right. Right. >> And and so this and just to recap, this was in Science Advances. Um came out uh March 5th, March 6th. Uh University Illinois Orurbana Champagne, which has been a key >> institution we've talked about quite a bit on the pod. also NASA JPL uh John's Hopkins applied physics lab uh and a few European universities uh in collaboration as you were just mentioning from the ESA side. Um really fantastic story. We're going to wrap up on the episode for the day. However, we

52:38have one uh we have two things. One, we need our comment which we did not write out in our script notes. The episode >> Oh, no. Why do you No, we did. It was um Oh, yes. Why do you think the Russians have so many dash cams? >> Oh, yes. Yes. Yes. So, if you're still listening, uh, an hour in because we are now not doing 2 and 1/2 hour episodes. We're doing multiple >> more bite-sized, more digestible episodes that are focus allow us to talk about. So, why do you think they have so many dash cams? And we do want to do one correction from episode 29, which was from the rundown related to the research study about the uh, Neanderl human mating bias. We really appreciate all of the comments from folks on a variety of

53:19platforms on that story. Part of the challenge is with the rundown, it is not a main focus, so we don't necessarily get into the weeds as much. We use some imprecise language in that segment. And the the study itself was really just focused on mating bias. There was a conversation about the difference between consensual and non-consensual

Outro

53:38that was not uh in the purview of the study itself. And so we appreciate that feedback. We will keep that in mind in terms of making sure we are are are much more attuned and accurate as we cover things even if it's in the rundown and not a main story. So we really appreciate that feedback from you guys. I am your host Lester Nar joined as always by my co-host and our resident PhD who is not a planetary defense researcher >> just a measly grad student. >> We'll catch you guys for the next episode this week.