1 00:00:07,839 --> 00:00:10,880 Hello, and welcome to the Physics World weekly 2 00:00:10,880 --> 00:00:12,980 podcast. I'm Hamish Johnston. 3 00:00:13,724 --> 00:00:15,904 Our guest this week is Rahil 4 00:00:16,364 --> 00:00:16,864 Macadiah 5 00:00:17,324 --> 00:00:19,425 who has just completed a PhD 6 00:00:19,725 --> 00:00:20,704 in aerospace 7 00:00:21,244 --> 00:00:21,744 engineering 8 00:00:22,204 --> 00:00:24,304 at the University of Illinois 9 00:00:24,765 --> 00:00:25,984 Urbana Champaign. 10 00:00:26,809 --> 00:00:29,629 There, he explored how we could deflect 11 00:00:29,929 --> 00:00:31,869 asteroids away from Earth. 12 00:00:32,570 --> 00:00:35,070 We chat about the potential threats 13 00:00:35,450 --> 00:00:37,629 posed by near Earth asteroids 14 00:00:38,090 --> 00:00:40,170 and how they could be sent on their 15 00:00:40,170 --> 00:00:40,670 way. 16 00:00:41,435 --> 00:00:44,255 Macadea also stresses the importance 17 00:00:44,715 --> 00:00:47,854 of getting a deflection right the first time. 18 00:00:48,314 --> 00:00:49,695 Here's that conversation. 19 00:00:57,870 --> 00:01:00,049 Hi, Rahil. Welcome to the podcast. 20 00:01:00,590 --> 00:01:02,670 Hey. Hey, Mish. Thanks for having me. So, 21 00:01:02,670 --> 00:01:05,170 Rahil, before we talk about deflecting 22 00:01:05,709 --> 00:01:06,209 asteroids, 23 00:01:06,724 --> 00:01:09,604 can you give our listeners an idea of 24 00:01:09,604 --> 00:01:10,344 the threat? 25 00:01:10,965 --> 00:01:12,905 What sort of threat is posed 26 00:01:13,284 --> 00:01:15,545 to Earth from asteroids? 27 00:01:16,965 --> 00:01:19,364 Yeah. Sure. I wanna start off by saying 28 00:01:19,364 --> 00:01:21,045 that none of the asteroids that we know 29 00:01:21,045 --> 00:01:24,459 about are currently a significant threat of impacting 30 00:01:24,459 --> 00:01:26,540 the Earth. So for the next hundred years 31 00:01:26,540 --> 00:01:27,200 or so, 32 00:01:27,900 --> 00:01:29,340 none of the objects that we know about 33 00:01:29,340 --> 00:01:31,739 are gonna potentially hit the Earth, come close, 34 00:01:32,060 --> 00:01:33,599 enough to to pose a danger. 35 00:01:33,905 --> 00:01:35,664 So we should all be resting easy. 36 00:01:36,704 --> 00:01:38,545 The the threat really comes from the fact 37 00:01:38,545 --> 00:01:41,024 that we don't know about all of the 38 00:01:41,024 --> 00:01:42,944 asteroids that are out there, so not all 39 00:01:42,944 --> 00:01:44,384 the asteroids in the solar system have been 40 00:01:44,384 --> 00:01:46,864 discovered yet. And if one were to hit 41 00:01:46,864 --> 00:01:47,524 the Earth, 42 00:01:48,030 --> 00:01:50,770 there'd be potentially dire consequences. So 43 00:01:51,230 --> 00:01:52,530 even a smaller object, 44 00:01:52,909 --> 00:01:55,310 say, I don't know, tens of meters in 45 00:01:55,310 --> 00:01:55,810 size 46 00:01:56,829 --> 00:02:00,670 can potentially cause massive infrastructure damage and cause 47 00:02:00,670 --> 00:02:03,025 injuries to to people. Like, there was an 48 00:02:03,025 --> 00:02:03,844 event in 49 00:02:04,305 --> 00:02:05,045 2013 50 00:02:05,105 --> 00:02:05,844 in Chelyabinsk, 51 00:02:06,145 --> 00:02:08,965 Russia, where a meteor exploded over the ground, 52 00:02:09,264 --> 00:02:11,665 and, the the shock wave from that explosion, 53 00:02:11,665 --> 00:02:14,064 you know, shattered windows. And people naturally, when 54 00:02:14,064 --> 00:02:15,824 they see something like a meteor flying through 55 00:02:15,824 --> 00:02:18,010 the sky, they'll flock to the windows. And 56 00:02:18,010 --> 00:02:19,610 as a result of this shock wave, you 57 00:02:19,610 --> 00:02:21,689 know, exploding windows, there are a lot of 58 00:02:21,689 --> 00:02:23,210 cuts and bruises to to a lot of 59 00:02:23,210 --> 00:02:23,710 people. 60 00:02:24,650 --> 00:02:26,730 But if you go, larger up the the 61 00:02:26,730 --> 00:02:28,650 asteroid size scale, so if you have, say, 62 00:02:28,650 --> 00:02:31,129 an asteroid that is hundreds of meters in 63 00:02:31,129 --> 00:02:32,985 size, that one can cause, 64 00:02:33,525 --> 00:02:35,525 potentially massive damage. You know? It can wipe 65 00:02:35,525 --> 00:02:38,585 out cities, potentially do damage on continental scales. 66 00:02:39,205 --> 00:02:40,884 If you go even bigger, which there are 67 00:02:40,884 --> 00:02:43,764 asteroids that are kilometer sized and plus, then 68 00:02:43,764 --> 00:02:45,284 we start getting into the realm of, you 69 00:02:45,284 --> 00:02:47,479 know, the the ones that that, made the 70 00:02:47,479 --> 00:02:50,219 dinosaurs extinct, and there'd be global consequences, 71 00:02:50,840 --> 00:02:52,919 if one that one that size were to 72 00:02:52,919 --> 00:02:54,680 hit the Earth. I see. And the the 73 00:02:54,680 --> 00:02:57,180 Russian asteroid, how how big was that? 74 00:02:58,040 --> 00:02:59,960 I think it was around 25 to 30 75 00:02:59,960 --> 00:03:01,580 meters in diameter. Okay. 76 00:03:02,185 --> 00:03:03,864 So so fairly small, but, 77 00:03:04,664 --> 00:03:06,745 good given that the other asteroids, some of 78 00:03:06,745 --> 00:03:08,924 them are more than kilometers in size. But, 79 00:03:08,985 --> 00:03:10,745 you know, even a a small one can 80 00:03:10,745 --> 00:03:11,884 pack a bunch. And 81 00:03:12,424 --> 00:03:14,669 smaller asteroids routinely go through the atmosphere, 82 00:03:15,229 --> 00:03:16,990 they usually end up not making it to 83 00:03:16,990 --> 00:03:18,590 the ground. So, you know, around five to 84 00:03:18,590 --> 00:03:20,750 10 meters, there were, I think, around four 85 00:03:20,750 --> 00:03:23,489 small impactors just last year in 2024. 86 00:03:24,030 --> 00:03:24,530 But, 87 00:03:25,709 --> 00:03:27,870 those didn't cause any damage. Some of them 88 00:03:27,870 --> 00:03:29,604 make it to the ground in the form 89 00:03:29,604 --> 00:03:31,764 of small meteorites that teams can go out 90 00:03:31,764 --> 00:03:32,425 and recover, 91 00:03:33,365 --> 00:03:34,884 but it's the larger ones that we need 92 00:03:34,884 --> 00:03:37,205 to worry about potentially hitting the earth. I 93 00:03:37,205 --> 00:03:39,205 see. And and so let's say at some 94 00:03:39,205 --> 00:03:40,264 time in the future, 95 00:03:40,805 --> 00:03:41,305 unfortunately, 96 00:03:41,764 --> 00:03:42,425 we detect 97 00:03:43,289 --> 00:03:45,150 a relatively large object 98 00:03:45,610 --> 00:03:47,789 that's bearing down on Earth. 99 00:03:49,050 --> 00:03:50,189 Could we deflect, 100 00:03:50,889 --> 00:03:52,969 such an object? Do we have the the 101 00:03:52,969 --> 00:03:54,509 technology at the moment? 102 00:03:55,610 --> 00:03:57,789 And and and how how would that work? 103 00:03:59,224 --> 00:04:00,905 Yeah. So the answer to that question depends 104 00:04:00,905 --> 00:04:02,425 on a a couple of factors. One of 105 00:04:02,425 --> 00:04:04,605 them is how big the asteroid is. 106 00:04:05,545 --> 00:04:08,425 For for asteroids that are extremely large, some 107 00:04:08,425 --> 00:04:10,840 of the deflection techniques we have, would take 108 00:04:10,840 --> 00:04:12,840 too long or so you need a large 109 00:04:12,840 --> 00:04:14,060 notice period before, 110 00:04:14,840 --> 00:04:16,839 the the potential impact date. But if we're 111 00:04:16,839 --> 00:04:18,279 talking about the realm of, you know, these 112 00:04:18,279 --> 00:04:19,819 hundreds of meter sized objects, 113 00:04:20,439 --> 00:04:23,020 we have what's called the kinetic impact method 114 00:04:23,164 --> 00:04:24,925 where the basic idea is you just take 115 00:04:24,925 --> 00:04:27,024 a spacecraft and smash it into the asteroid, 116 00:04:27,164 --> 00:04:27,664 and 117 00:04:27,964 --> 00:04:29,884 that causes a small deflection because the size 118 00:04:29,884 --> 00:04:31,724 of the spacecraft relative to the size of 119 00:04:31,724 --> 00:04:33,805 the asteroid is pretty small. But if you 120 00:04:33,805 --> 00:04:35,805 give it enough time to accumulate, then the 121 00:04:35,805 --> 00:04:37,724 trajectory of the asteroid is altered enough that 122 00:04:37,724 --> 00:04:40,020 it would miss the Earth. And we successfully 123 00:04:40,080 --> 00:04:42,959 demonstrated this technique with, a mission called DART, 124 00:04:42,959 --> 00:04:44,980 the double asteroid redirection test, 125 00:04:45,439 --> 00:04:47,620 which was an asset mission that launched in 126 00:04:48,000 --> 00:04:48,879 2021. 127 00:04:48,879 --> 00:04:50,399 And in 2022, 128 00:04:50,399 --> 00:04:51,139 it impacted, 129 00:04:51,520 --> 00:04:52,020 Dimorphos, 130 00:04:52,399 --> 00:04:55,185 which was the the smaller moonlet asteroid in 131 00:04:55,185 --> 00:04:57,365 the Didymos binary asteroid system. 132 00:04:58,225 --> 00:05:01,024 And it successfully altered the trajectory of the 133 00:05:01,024 --> 00:05:02,564 secondary around the primary, 134 00:05:03,584 --> 00:05:04,384 and it, 135 00:05:04,785 --> 00:05:06,384 you know, proved that we can do this 136 00:05:06,384 --> 00:05:08,579 kinetic impact method if we ever have the 137 00:05:08,579 --> 00:05:11,159 need to. And Dimorphos was around, 138 00:05:11,779 --> 00:05:15,000 a 150 meters, in diameter, so we've successfully 139 00:05:15,060 --> 00:05:18,019 proven that we can successfully hit asteroids that 140 00:05:18,019 --> 00:05:20,579 are this small. Because the smaller the asteroid 141 00:05:20,579 --> 00:05:22,425 gets, the harder it becomes to target it 142 00:05:22,584 --> 00:05:24,925 because especially if you're coming in very fast 143 00:05:25,144 --> 00:05:26,044 because you have 144 00:05:26,425 --> 00:05:28,345 a small amount of time to to actually 145 00:05:28,345 --> 00:05:30,185 do the targeting when the spacecraft's on its 146 00:05:30,185 --> 00:05:30,685 way. 147 00:05:31,865 --> 00:05:34,345 There are other techniques, that have been studied. 148 00:05:34,745 --> 00:05:37,289 There are there are options that have studied 149 00:05:37,289 --> 00:05:38,750 the use of nuclear devices, 150 00:05:39,129 --> 00:05:40,909 what's called a standoff detonation, 151 00:05:41,529 --> 00:05:43,930 where they would detonate a device at a 152 00:05:43,930 --> 00:05:46,089 certain distance above the the surface of the 153 00:05:46,089 --> 00:05:48,729 asteroid and let the radiation melt away a 154 00:05:48,729 --> 00:05:49,169 layer, 155 00:05:49,610 --> 00:05:51,050 a a top layer of the of the 156 00:05:51,050 --> 00:05:52,110 surface of the asteroid, 157 00:05:52,435 --> 00:05:54,514 and that would impart some momentum as the 158 00:05:54,514 --> 00:05:56,435 the material is getting vaporized and kicked off 159 00:05:56,435 --> 00:05:57,175 the asteroid. 160 00:05:57,954 --> 00:06:00,194 Those are the the sort of two shorter 161 00:06:00,194 --> 00:06:02,914 term deflection methods. There are a couple others 162 00:06:02,914 --> 00:06:05,495 that need a longer time scale between, 163 00:06:05,875 --> 00:06:07,495 discovery and potential impact. 164 00:06:08,199 --> 00:06:10,439 There's what's called the ion beam deflection method 165 00:06:10,439 --> 00:06:11,419 where you can redirect, 166 00:06:11,800 --> 00:06:13,740 an ion beam up up of a spacecraft 167 00:06:13,800 --> 00:06:17,079 towards the asteroid, and that slowly erodes, the 168 00:06:17,079 --> 00:06:19,259 surface of the asteroid to to part momentum 169 00:06:19,319 --> 00:06:20,060 onto it. 170 00:06:21,074 --> 00:06:23,714 And there is the the gravity tractor method 171 00:06:23,714 --> 00:06:25,735 where you basically station keep, 172 00:06:26,035 --> 00:06:27,894 or hover around an asteroid, 173 00:06:28,514 --> 00:06:30,754 with a big enough spacecraft and just the 174 00:06:30,754 --> 00:06:33,735 gravitational interaction between the spacecraft and the asteroid 175 00:06:34,220 --> 00:06:37,040 over decades, maybe even, can cause, 176 00:06:37,660 --> 00:06:39,819 a big enough change to potentially deflect it 177 00:06:39,819 --> 00:06:41,819 away from the Earth. And you you mentioned 178 00:06:41,819 --> 00:06:44,539 that we we we think we're safe for 179 00:06:44,539 --> 00:06:46,894 for about a hundred years or so. Does 180 00:06:46,894 --> 00:06:49,634 that does that mean that, for example, tomorrow, 181 00:06:50,175 --> 00:06:51,235 we could spot, 182 00:06:51,855 --> 00:06:52,754 a large asteroid 183 00:06:53,774 --> 00:06:56,915 that will reach us, let's say, within 184 00:06:57,375 --> 00:06:59,694 a hundred years, or I should say, in 185 00:06:59,694 --> 00:07:01,839 over a hundred years? And so we would 186 00:07:01,839 --> 00:07:02,579 have time 187 00:07:03,039 --> 00:07:03,539 to 188 00:07:03,839 --> 00:07:06,660 really think about how we would deflect it. 189 00:07:08,079 --> 00:07:08,579 And 190 00:07:08,879 --> 00:07:10,899 Yeah. I don't know. Maybe maybe get cracking 191 00:07:11,360 --> 00:07:13,599 in ten years from now when we've when 192 00:07:13,599 --> 00:07:15,060 we've developed some technology 193 00:07:15,595 --> 00:07:18,475 that's suitable for that particular object. Is that 194 00:07:18,634 --> 00:07:19,995 I mean, is that how it would play 195 00:07:19,995 --> 00:07:21,134 out, I suppose? 196 00:07:21,834 --> 00:07:23,514 Yeah. I should say that for the larger 197 00:07:23,514 --> 00:07:26,714 objects, so let's say kilometer size plus, most 198 00:07:26,714 --> 00:07:29,375 of our population models indicate that we've discovered 199 00:07:29,435 --> 00:07:30,839 most, if not all of them, 200 00:07:32,279 --> 00:07:34,439 especially, you know, the 10 kilometer plus size. 201 00:07:34,439 --> 00:07:36,120 Those are the the sort of planet killers 202 00:07:36,120 --> 00:07:37,259 you might think of as. 203 00:07:37,720 --> 00:07:39,800 We we're pretty sure that we've we've discovered 204 00:07:39,800 --> 00:07:41,800 pretty much all of them, because the the 205 00:07:41,800 --> 00:07:43,319 bigger they are, the easier they are to 206 00:07:43,319 --> 00:07:45,639 detect, and telescopes keep getting better and better. 207 00:07:45,639 --> 00:07:48,584 So it would be pretty, difficult to detect 208 00:07:48,584 --> 00:07:49,324 a massive, 209 00:07:49,944 --> 00:07:52,264 asteroid at this point. But, yeah, like you 210 00:07:52,264 --> 00:07:54,425 said, if we're, if we detect one that's 211 00:07:54,425 --> 00:07:56,985 massive enough, it it will likely be that 212 00:07:56,985 --> 00:07:59,064 it's far, far away, the the potential impact 213 00:07:59,064 --> 00:08:01,319 date. So I'll give you a specific example. 214 00:08:01,319 --> 00:08:04,139 There's this asteroid called nineteen fifty d a, 215 00:08:04,680 --> 00:08:06,839 which is larger than a kilometer, we think, 216 00:08:06,839 --> 00:08:10,060 and its potential impact date is the year 217 00:08:10,120 --> 00:08:12,139 2880. 218 00:08:12,895 --> 00:08:15,055 So there are, you know, special cases like 219 00:08:15,055 --> 00:08:16,654 this one where we can predict that, you 220 00:08:16,654 --> 00:08:18,435 know, eight hundred years in advance. 221 00:08:19,055 --> 00:08:20,574 Obviously, we don't need to do anything about 222 00:08:20,574 --> 00:08:22,735 that one anytime soon. But, 223 00:08:23,295 --> 00:08:25,134 a lot of these large asteroids, you know, 224 00:08:25,134 --> 00:08:27,079 we're able predict their trajectories for a pretty 225 00:08:27,079 --> 00:08:28,040 long term and, 226 00:08:28,759 --> 00:08:31,399 conclude whether or not they're a significant impact 227 00:08:31,399 --> 00:08:31,899 hazard. 228 00:08:32,360 --> 00:08:34,440 And I'd just like to talk about some 229 00:08:34,440 --> 00:08:36,139 recent work that you've done. 230 00:08:36,519 --> 00:08:39,100 You've you've looked at the possibility 231 00:08:39,639 --> 00:08:40,620 of an impact, 232 00:08:41,205 --> 00:08:43,625 putting an asteroid into a trajectory 233 00:08:44,165 --> 00:08:46,825 in which it could return to Earth, 234 00:08:47,845 --> 00:08:50,245 which is probably something that we'd like to 235 00:08:50,245 --> 00:08:50,745 avoid 236 00:08:51,205 --> 00:08:52,345 if possible. Yeah. 237 00:08:53,299 --> 00:08:55,299 Can you explain how how this would happen? 238 00:08:55,299 --> 00:08:57,159 Is it is it simply a matter of 239 00:08:57,220 --> 00:08:59,159 of hitting the the asteroid, 240 00:08:59,860 --> 00:09:02,440 you know, with the wrong sort of impulse 241 00:09:02,579 --> 00:09:04,120 or in the wrong direction 242 00:09:04,740 --> 00:09:08,279 and setting it into a alternative orbit that 243 00:09:08,834 --> 00:09:10,534 eventually brings it back to Earth. 244 00:09:12,115 --> 00:09:13,954 Yeah. So it's, you know, the the the 245 00:09:14,115 --> 00:09:15,954 it's the opposite of being in the right 246 00:09:15,954 --> 00:09:17,634 place at the right time. So you're sort 247 00:09:17,634 --> 00:09:20,194 of deflecting the asteroid at the wrong place 248 00:09:20,194 --> 00:09:21,174 at the wrong time, 249 00:09:21,879 --> 00:09:24,120 and what you can do is potentially so 250 00:09:24,120 --> 00:09:26,360 let's say in this hypothetical scenario, there's an 251 00:09:26,360 --> 00:09:28,519 asteroid headed towards the Earth, and we need 252 00:09:28,519 --> 00:09:30,600 to deflect it away. Right? And we send 253 00:09:30,600 --> 00:09:33,000 a deflection mission, let's say, a kinetic impact 254 00:09:33,000 --> 00:09:34,440 there because that's the one we know how 255 00:09:34,440 --> 00:09:34,815 to do. 256 00:09:35,695 --> 00:09:38,654 And we do this deflection, and we, you 257 00:09:38,654 --> 00:09:41,134 know, dismiss the immediate impact threat from the 258 00:09:41,134 --> 00:09:41,634 asteroid. 259 00:09:42,174 --> 00:09:44,014 But lo and behold, because we weren't that 260 00:09:44,014 --> 00:09:46,414 careful, we've put it now in a trajectory 261 00:09:46,414 --> 00:09:48,014 that will return to an to the Earth 262 00:09:48,014 --> 00:09:50,355 on an impacting trajectory forty years later. 263 00:09:51,029 --> 00:09:52,870 So in this scenario, what we've done is 264 00:09:52,870 --> 00:09:55,370 we've triggered what's called a gravitational keyhole. 265 00:09:56,070 --> 00:09:58,570 And these keyholes are basically, you know, predictors 266 00:09:58,789 --> 00:10:00,709 of whether or not an asteroid might hit 267 00:10:00,709 --> 00:10:02,169 the earth in the future. So, 268 00:10:02,629 --> 00:10:05,110 if we blindly deflect an asteroid and push 269 00:10:05,110 --> 00:10:06,330 it through this gravitational 270 00:10:07,085 --> 00:10:09,805 keyhole, it's guaranteed to return to the earth 271 00:10:09,805 --> 00:10:12,305 on an impacting trajectory at a future date. 272 00:10:12,925 --> 00:10:14,925 But the the the nice thing about these 273 00:10:14,925 --> 00:10:17,105 keyholes is that we can compute them beforehand 274 00:10:17,245 --> 00:10:18,285 and map them, 275 00:10:18,925 --> 00:10:20,250 given an asteroid's orbit. 276 00:10:21,129 --> 00:10:23,129 And so if we're careful about it, we 277 00:10:23,129 --> 00:10:25,850 can directly map these keyholes when we're designing 278 00:10:25,850 --> 00:10:28,029 the initial deflection mission in the first place, 279 00:10:28,330 --> 00:10:31,049 such as to avoid any keyholes while deflecting 280 00:10:31,049 --> 00:10:33,389 it clear of the the immediate impact threat. 281 00:10:33,815 --> 00:10:35,995 I see. And and are these these keyholes, 282 00:10:36,054 --> 00:10:38,774 are they are the I mean, do they 283 00:10:38,774 --> 00:10:41,434 tend to be large, or are there lots 284 00:10:41,495 --> 00:10:43,815 of them in the sense that, you know, 285 00:10:43,815 --> 00:10:45,835 if if we didn't think of this, 286 00:10:46,389 --> 00:10:48,309 we you know, what are the odds, I 287 00:10:48,309 --> 00:10:49,909 suppose, if we didn't think of this and 288 00:10:49,909 --> 00:10:53,029 just hit the the, the asteroid as hard 289 00:10:53,029 --> 00:10:55,190 as we could at a certain point in 290 00:10:55,190 --> 00:10:55,690 time? 291 00:10:56,789 --> 00:10:59,085 Would it be very likely that we could 292 00:10:59,165 --> 00:11:01,245 go into one of these keyholes by mistake, 293 00:11:01,245 --> 00:11:03,504 or would we have to be really unlucky? 294 00:11:05,085 --> 00:11:07,345 So that sort of delves into specifics, 295 00:11:08,125 --> 00:11:10,605 because the sizes of the keyholes, they're usually 296 00:11:10,605 --> 00:11:13,059 pretty small. I think the largest ones I've 297 00:11:13,059 --> 00:11:14,980 seen so far are around a kilometer or 298 00:11:14,980 --> 00:11:17,860 a few kilometers in size. And given how 299 00:11:17,860 --> 00:11:20,340 vast space is a kilometer or a few 300 00:11:20,340 --> 00:11:21,799 kilometers is is minuscule, 301 00:11:22,419 --> 00:11:22,899 but, 302 00:11:23,220 --> 00:11:25,299 once again, we start delving into the problem 303 00:11:25,299 --> 00:11:27,615 of, you know, likelihood and consequence. So the 304 00:11:27,615 --> 00:11:30,595 likelihood might be low. And I think 305 00:11:31,215 --> 00:11:31,715 the, 306 00:11:32,095 --> 00:11:34,014 I should mention, yeah, that the largest number 307 00:11:34,014 --> 00:11:36,014 of keyholes I've seen for an asteroid is 308 00:11:36,014 --> 00:11:38,335 is around a couple 100 or so, in 309 00:11:38,335 --> 00:11:39,315 a in a massive 310 00:11:39,690 --> 00:11:41,690 uncertainty region or the the region which you 311 00:11:41,690 --> 00:11:43,790 could find the asteroid at any given day. 312 00:11:45,290 --> 00:11:47,290 But once again, if we were to send 313 00:11:47,290 --> 00:11:48,990 an asteroid through one of these keyholes, 314 00:11:49,370 --> 00:11:50,910 because it's, you know, a 315 00:11:51,545 --> 00:11:53,705 a future predictor of an Earth impact, the 316 00:11:53,705 --> 00:11:56,925 same consequences apply as if that size asteroid 317 00:11:56,985 --> 00:11:59,225 were to hit the Earth. So it's a 318 00:11:59,225 --> 00:12:01,225 it's a trade off between do we wanna 319 00:12:01,225 --> 00:12:04,360 just blindly deflect it, and, obviously, if there 320 00:12:04,360 --> 00:12:07,000 is no way of deflecting an asteroid without 321 00:12:07,000 --> 00:12:07,500 avoiding, 322 00:12:08,839 --> 00:12:10,679 a a keyhole, we need to dismiss the 323 00:12:10,679 --> 00:12:12,919 immediate impact threat. So that's the primary goal. 324 00:12:12,919 --> 00:12:14,679 But if we can be smart about designing 325 00:12:14,679 --> 00:12:16,679 the deflection mission and, you know, kill two 326 00:12:16,679 --> 00:12:19,034 birds with one stone, so to speak, 327 00:12:20,154 --> 00:12:22,875 and dismiss the impact threat, maybe permanently even 328 00:12:22,875 --> 00:12:25,274 from one asteroid. That gives us less to 329 00:12:25,274 --> 00:12:26,654 worry about in the future. 330 00:12:27,274 --> 00:12:31,034 And, I think that the you've found that, 331 00:12:32,074 --> 00:12:32,975 that this 332 00:12:33,670 --> 00:12:36,970 the technique or or or, I suppose, avoiding 333 00:12:37,110 --> 00:12:38,330 gravitational keyholes 334 00:12:39,029 --> 00:12:39,529 involves, 335 00:12:40,149 --> 00:12:42,490 having an understanding of the topography 336 00:12:43,190 --> 00:12:45,429 of the asteroid. So I'm I'm guessing there 337 00:12:45,429 --> 00:12:46,570 that its shape, 338 00:12:46,875 --> 00:12:47,855 etcetera. Why 339 00:12:48,634 --> 00:12:49,934 why is that important? 340 00:12:51,434 --> 00:12:53,674 Yeah. So, yeah, like you mentioned, we need 341 00:12:53,674 --> 00:12:56,875 an understanding of both how the asteroid's local 342 00:12:56,875 --> 00:12:59,134 topography looks like, so what its shape is, 343 00:12:59,319 --> 00:13:01,480 as well as how it's spinning because most 344 00:13:01,480 --> 00:13:02,940 asteroids, are rotating. 345 00:13:03,559 --> 00:13:05,720 So we need to know what orientation of 346 00:13:05,720 --> 00:13:07,639 the asteroid we're gonna be looking at when 347 00:13:07,639 --> 00:13:10,279 we're deflecting it and what the sort of 348 00:13:10,279 --> 00:13:11,179 local topography 349 00:13:11,559 --> 00:13:13,355 it at the is at the point, 350 00:13:13,815 --> 00:13:16,475 on which we're gonna deflect the asteroid because 351 00:13:16,774 --> 00:13:17,835 the local topography 352 00:13:18,215 --> 00:13:19,434 dictates where 353 00:13:19,815 --> 00:13:21,894 would where the ejecta will travel. So if 354 00:13:21,894 --> 00:13:24,294 you deflect an asteroid using a kinetic impact, 355 00:13:24,294 --> 00:13:26,980 what happens is that surface material around the 356 00:13:26,980 --> 00:13:29,460 impact site actually gets kicked up off of 357 00:13:29,460 --> 00:13:30,120 the surface, 358 00:13:30,820 --> 00:13:32,820 and gets released in the opposite direction that 359 00:13:32,820 --> 00:13:34,980 the impactor came from, and that acts as 360 00:13:34,980 --> 00:13:36,120 an additional boost, 361 00:13:36,580 --> 00:13:38,419 on top of the momentum that's imparted by 362 00:13:38,419 --> 00:13:39,080 the spacecraft. 363 00:13:39,855 --> 00:13:42,095 So this additional boost can be significant. It 364 00:13:42,095 --> 00:13:44,014 can be, you know, similar to or larger 365 00:13:44,014 --> 00:13:46,495 than the the the contribution of the spacecraft 366 00:13:46,495 --> 00:13:46,995 itself. 367 00:13:47,615 --> 00:13:49,615 So we wanna be able to accurately model 368 00:13:49,615 --> 00:13:50,355 this deflection, 369 00:13:51,134 --> 00:13:53,695 and that involves accurately modeling the momentum that's 370 00:13:53,695 --> 00:13:55,154 imparted onto the asteroid, 371 00:13:55,480 --> 00:13:57,980 which involves knowing where this ejecta went, 372 00:13:58,679 --> 00:14:00,360 which dictates that we need to know what 373 00:14:00,360 --> 00:14:02,440 the local topography looks like because that's the 374 00:14:02,440 --> 00:14:04,440 local orientation is what dictates the direction of 375 00:14:04,440 --> 00:14:05,179 this ejecta. 376 00:14:06,679 --> 00:14:08,519 But if we have a rough idea, you 377 00:14:08,519 --> 00:14:10,845 know, there are techniques even from the ground 378 00:14:10,845 --> 00:14:11,345 to, 379 00:14:12,125 --> 00:14:14,044 get the sit the shape of an asteroid. 380 00:14:14,044 --> 00:14:15,725 There's, what's called radar, 381 00:14:16,204 --> 00:14:19,004 astrometry. Radar imaging of an asteroid can tell 382 00:14:19,004 --> 00:14:20,544 us what an asteroid looks like. 383 00:14:21,324 --> 00:14:24,064 There's also light curve methods. So you you 384 00:14:24,350 --> 00:14:25,710 sort of measure the amount of light you're 385 00:14:25,710 --> 00:14:27,629 receiving from a given asteroid, and you can 386 00:14:27,629 --> 00:14:30,269 invert that to to get a preliminary shape 387 00:14:30,269 --> 00:14:31,009 of the asteroid. 388 00:14:31,950 --> 00:14:33,470 But the the best way to get an 389 00:14:33,470 --> 00:14:35,629 asteroid shape is obviously go visit it with 390 00:14:35,629 --> 00:14:37,950 a spacecraft beforehand. That'll give you as much 391 00:14:37,950 --> 00:14:41,674 information as as my heart desires and and, 392 00:14:42,215 --> 00:14:43,894 you know, allow us to do this deflection 393 00:14:43,894 --> 00:14:45,035 the best way possible. 394 00:14:45,575 --> 00:14:48,054 And, I mean, I'm just thinking about, you 395 00:14:48,054 --> 00:14:50,475 know, this this idea of hitting 396 00:14:50,855 --> 00:14:53,014 an asteroid. And, you know, you mentioned that 397 00:14:53,014 --> 00:14:55,809 these asteroids, well, they're it's probably going to 398 00:14:55,809 --> 00:14:56,549 be rotating. 399 00:14:57,730 --> 00:15:00,209 It do you I mean, the the problem 400 00:15:00,449 --> 00:15:02,449 I I sort of I suppose a problem 401 00:15:02,449 --> 00:15:04,129 I can think of is that you really 402 00:15:04,129 --> 00:15:04,629 want, 403 00:15:05,970 --> 00:15:08,149 I assume that you want sort of maximum 404 00:15:09,304 --> 00:15:10,524 momentum transfer 405 00:15:11,144 --> 00:15:12,605 from your spacecraft 406 00:15:12,985 --> 00:15:13,725 to the, 407 00:15:14,345 --> 00:15:16,745 to the object. And do you want to 408 00:15:16,745 --> 00:15:20,445 avoid having some of that energy converted into 409 00:15:21,225 --> 00:15:23,945 rotational energy in the sense that you you 410 00:15:23,945 --> 00:15:24,845 whack the 411 00:15:25,750 --> 00:15:28,070 the the the object, and instead of knocking 412 00:15:28,070 --> 00:15:31,110 it off course, you just spin it up 413 00:15:31,110 --> 00:15:32,649 or you reduce its, 414 00:15:33,750 --> 00:15:36,710 spin, and it sort of continues on in 415 00:15:36,710 --> 00:15:39,110 the same direct in its same trajectory. Is 416 00:15:39,110 --> 00:15:40,570 is that a problem as well? 417 00:15:41,485 --> 00:15:43,485 Yeah. That is definitely something to think about 418 00:15:43,485 --> 00:15:45,504 is, yeah, if you hit it off center, 419 00:15:45,725 --> 00:15:48,764 you're imparting a moment onto the asteroid, and 420 00:15:48,764 --> 00:15:50,625 that will change its its spin. 421 00:15:51,644 --> 00:15:52,044 But, 422 00:15:52,524 --> 00:15:54,944 sometimes, you know, the the spin state change 423 00:15:55,160 --> 00:15:58,220 can be overruled by the amount of deflection 424 00:15:58,279 --> 00:15:59,259 an off center, 425 00:16:00,360 --> 00:16:02,519 deflection would give you. So even if you 426 00:16:02,519 --> 00:16:04,360 were hitting it off center, you might get 427 00:16:04,360 --> 00:16:06,120 enough deflection to to put it clear of 428 00:16:06,120 --> 00:16:08,279 the earth. And if, you know, the safe 429 00:16:08,279 --> 00:16:09,899 zone that avoids these keyholes, 430 00:16:11,144 --> 00:16:13,544 is sitting, let's say, 25 meters off of 431 00:16:13,544 --> 00:16:15,544 the center of the asteroid, that's not that 432 00:16:15,544 --> 00:16:17,245 much, that you're losing. 433 00:16:17,784 --> 00:16:19,625 And with this technique, we actually put a 434 00:16:19,625 --> 00:16:21,164 band around the asteroid 435 00:16:21,784 --> 00:16:23,945 such as to avoid missing it. So if 436 00:16:23,945 --> 00:16:26,319 you're too far away from the center, you 437 00:16:26,319 --> 00:16:28,799 know, the the spacecraft can't perfectly target, 438 00:16:29,120 --> 00:16:30,959 the asteroid at the point you've told it 439 00:16:30,959 --> 00:16:33,600 to because there's, you know, algorithmic uncertainties and 440 00:16:33,600 --> 00:16:35,440 and just uncertainties in general in the world 441 00:16:35,440 --> 00:16:36,259 we live in. 442 00:16:36,959 --> 00:16:37,459 And 443 00:16:38,000 --> 00:16:39,600 that would mean that you might miss it, 444 00:16:39,919 --> 00:16:42,324 miss the the aim point, let's say. 445 00:16:43,345 --> 00:16:45,345 And we wanna make sure that in the 446 00:16:45,345 --> 00:16:47,745 first place, we hit the asteroid because that's 447 00:16:47,745 --> 00:16:49,584 the the goal of the deflection. So we 448 00:16:49,584 --> 00:16:51,424 actually put a safety band around the the 449 00:16:51,424 --> 00:16:53,504 perimeter of the asteroid, the visible perimeter of 450 00:16:53,504 --> 00:16:55,600 the asteroid to make sure that we're in 451 00:16:55,600 --> 00:16:58,019 pursuit of doing a better deflection. We're not 452 00:16:58,080 --> 00:17:00,320 missing the deflection altogether because that would, you 453 00:17:00,320 --> 00:17:02,259 know, defeat the entire point of the existence. 454 00:17:02,720 --> 00:17:04,559 And and what's next for you in terms 455 00:17:04,559 --> 00:17:07,140 of your research? You you you've looked at 456 00:17:07,565 --> 00:17:09,105 these gravitational keyholes. 457 00:17:09,404 --> 00:17:11,484 Are you are you gonna do more studies, 458 00:17:11,484 --> 00:17:14,125 I suppose, on different types of asteroids, different 459 00:17:14,125 --> 00:17:14,625 shapes, 460 00:17:15,404 --> 00:17:18,545 different distances from Earth, different orbits, or 461 00:17:19,779 --> 00:17:21,299 are are you go going to be looking 462 00:17:21,299 --> 00:17:24,759 at another aspect of, of asteroid impact? 463 00:17:26,099 --> 00:17:27,140 Yeah. Yeah. I think, 464 00:17:27,539 --> 00:17:29,700 so I do wanna continue looking into this 465 00:17:29,700 --> 00:17:31,000 this better deflection, 466 00:17:31,299 --> 00:17:33,559 you know, a more optimal deflection strategy, 467 00:17:34,099 --> 00:17:36,875 in terms of avoiding keyholes while deflecting asteroids. 468 00:17:37,174 --> 00:17:38,774 One thing I do want to look at 469 00:17:38,774 --> 00:17:40,694 is what happens if we if we use 470 00:17:40,694 --> 00:17:42,214 one of the other techniques I was talking 471 00:17:42,214 --> 00:17:44,534 about earlier to deflect an asteroid because kinetic 472 00:17:44,534 --> 00:17:46,375 impact is the one that we've demonstrated so 473 00:17:46,375 --> 00:17:47,815 far. It's the one we already have in 474 00:17:47,815 --> 00:17:50,279 our arsenal. But, obviously, there are are other 475 00:17:50,279 --> 00:17:51,960 message, the longer term message that I was 476 00:17:51,960 --> 00:17:54,119 talking about, like, I NBM deflection and gravity 477 00:17:54,119 --> 00:17:55,720 tracker have been got getting a lot of 478 00:17:55,720 --> 00:17:58,059 attention in the in the research world after, 479 00:17:58,119 --> 00:17:59,420 you know, the kinetic impact, 480 00:17:59,799 --> 00:18:00,299 success. 481 00:18:00,599 --> 00:18:02,115 So I would like to see how it 482 00:18:02,355 --> 00:18:05,234 how avoiding keyholes while doing these other deflection 483 00:18:05,234 --> 00:18:06,934 techniques, what that looks like. 484 00:18:08,035 --> 00:18:09,795 Another thing that I wanna look into is 485 00:18:09,795 --> 00:18:11,954 potentially better ways of computing these keyholes in 486 00:18:11,954 --> 00:18:13,734 the first place. So it's a very nitpicky 487 00:18:13,875 --> 00:18:16,679 thing. Let's see. You know, improving every part 488 00:18:16,679 --> 00:18:18,380 of this process as much as I can. 489 00:18:19,079 --> 00:18:21,079 But, well, yeah, we'll see where the this 490 00:18:21,079 --> 00:18:24,039 research takes me. Well, that's great. Thanks so 491 00:18:24,039 --> 00:18:26,279 much for coming on the podcast and talking 492 00:18:26,279 --> 00:18:29,259 about that. And and also reassuring our listeners 493 00:18:29,400 --> 00:18:29,900 that, 494 00:18:30,924 --> 00:18:32,765 you know, at the moment, at least, there's 495 00:18:32,765 --> 00:18:35,325 probably not much to worry about in terms 496 00:18:35,325 --> 00:18:39,484 of large asteroid impact. I mean, when when 497 00:18:39,484 --> 00:18:41,484 we say large, I mean, what what are 498 00:18:41,484 --> 00:18:44,125 the what are the sizes of asteroids at 499 00:18:44,125 --> 00:18:46,384 the moment that can sort of sneak through? 500 00:18:46,710 --> 00:18:49,349 Is it the like, that that Russian asteroid, 501 00:18:49,349 --> 00:18:51,909 for example? Did did we see that coming, 502 00:18:51,909 --> 00:18:54,150 or is that just too small for us 503 00:18:54,150 --> 00:18:54,809 to detect? 504 00:18:55,990 --> 00:18:58,809 No. I think that with with Chelyabinsk specifically, 505 00:18:58,950 --> 00:19:00,764 and I I wasn't in the field in 506 00:19:00,764 --> 00:19:01,505 2013, 507 00:19:01,724 --> 00:19:03,565 but, I think what happened with that one 508 00:19:03,565 --> 00:19:05,484 is that it came from the sunward direction. 509 00:19:05,484 --> 00:19:07,164 So none of the telescopes could point in 510 00:19:07,164 --> 00:19:08,845 that direction because, obviously, you can't point the 511 00:19:08,845 --> 00:19:10,144 telescope towards the sun. 512 00:19:10,845 --> 00:19:12,524 And so we're we're sort of looking to 513 00:19:12,524 --> 00:19:14,759 tackle this problem from a couple different avenues. 514 00:19:14,759 --> 00:19:17,000 There's a a new telescope in the Southern 515 00:19:17,000 --> 00:19:19,259 Hemisphere called the Vera Rubin Observatory 516 00:19:19,960 --> 00:19:21,960 that's set to dramatically increase the rate of 517 00:19:21,960 --> 00:19:22,859 asteroid discoveries. 518 00:19:23,559 --> 00:19:26,200 There's also a mission called NEO surveyor, which 519 00:19:26,200 --> 00:19:28,724 will be a space based telescope that NASA's 520 00:19:28,724 --> 00:19:30,484 building right now and hoping to launch in 521 00:19:30,484 --> 00:19:31,464 the next few years, 522 00:19:31,924 --> 00:19:34,404 which will hopefully try to detect these sort 523 00:19:34,404 --> 00:19:36,884 of sunward geometries from the Earth from a 524 00:19:36,884 --> 00:19:38,964 different vantage point in space. So maybe we 525 00:19:38,964 --> 00:19:41,130 can discover these jelly bins like objects. 526 00:19:41,690 --> 00:19:43,369 And in terms of size in general, yeah, 527 00:19:43,369 --> 00:19:45,369 it's this sort of tens of meters to 528 00:19:45,369 --> 00:19:48,089 maybe a 150 meter size range that we 529 00:19:48,089 --> 00:19:49,150 still haven't discovered, 530 00:19:49,609 --> 00:19:51,769 most of them. So that's where the the 531 00:19:51,769 --> 00:19:52,750 next discovery, 532 00:19:53,529 --> 00:19:55,230 effort is is headed. 533 00:19:56,195 --> 00:19:58,195 Well, that's great. Thanks, Rahil. Thanks for coming 534 00:19:58,195 --> 00:20:00,195 on the podcast, and I'll put a link 535 00:20:00,195 --> 00:20:03,315 to, Rahil's paper, in the notes for this 536 00:20:03,315 --> 00:20:05,875 podcast. Best of luck with your research. Thank 537 00:20:05,875 --> 00:20:07,174 you. Thank you so much. 538 00:20:15,160 --> 00:20:17,259 That was the aerospace engineer, 539 00:20:17,799 --> 00:20:18,940 Rahil Macadiah. 540 00:20:19,720 --> 00:20:22,299 Thanks, Rahil, for a fascinating conversation. 541 00:20:23,804 --> 00:20:26,784 Physics World will be at the APS Global 542 00:20:26,924 --> 00:20:30,224 Physics Summit, which will take place in March 543 00:20:30,444 --> 00:20:31,744 in Denver, Colorado 544 00:20:32,284 --> 00:20:33,345 and online. 545 00:20:34,125 --> 00:20:36,944 At the largest physics meeting in the world, 546 00:20:37,330 --> 00:20:39,509 you can join thousands of physicists, 547 00:20:40,049 --> 00:20:42,930 students, and policy leaders for a week of 548 00:20:42,930 --> 00:20:44,549 connection and collaboration. 549 00:20:45,730 --> 00:20:47,509 Explore cutting edge science 550 00:20:47,890 --> 00:20:49,750 shaping our shared future, 551 00:20:50,174 --> 00:20:53,075 and be part of the global physics community 552 00:20:53,615 --> 00:20:55,555 driving innovation forward. 553 00:20:56,335 --> 00:21:00,434 Explore the meeting at summit.aps.org. 554 00:21:00,654 --> 00:21:01,955 And when you're in Denver, 555 00:21:02,335 --> 00:21:04,980 look out for us at IOP Publishing's 556 00:21:05,279 --> 00:21:07,539 booth at the conference exhibition. 557 00:21:08,559 --> 00:21:10,559 I'm afraid that's all the time we have 558 00:21:10,559 --> 00:21:11,779 for this week's podcast. 559 00:21:12,240 --> 00:21:15,375 I'm Hamish Johnston, and our producer is Fred 560 00:21:15,535 --> 00:21:16,035 Isles. 561 00:21:16,575 --> 00:21:20,035 Our theme music is called one three seven, 562 00:21:20,335 --> 00:21:23,134 and it was composed and performed by the 563 00:21:23,134 --> 00:21:23,634 physicist 564 00:21:24,095 --> 00:21:25,075 Philip Moriarty. 565 00:21:25,775 --> 00:21:27,599 We'll be back again next week.