1 00:00:02,803 --> 00:00:07,239 Narrator: A dangerous asteroid is heading towards earth. 2 00:00:07,241 --> 00:00:09,975 It's the size of the empire state building, 3 00:00:09,977 --> 00:00:15,714 and it's travelling at 16,000 miles an hour. 4 00:00:15,716 --> 00:00:20,686 It's called apophis, after the egyptian god of chaos. 5 00:00:20,688 --> 00:00:25,657 It will fly close to us in 2029. 6 00:00:25,659 --> 00:00:27,860 It won't hit us...This time, 7 00:00:27,862 --> 00:00:31,430 but when it returns in 2068, 8 00:00:31,432 --> 00:00:34,400 that could be another story. 9 00:00:34,402 --> 00:00:39,171 If it blows up over a city, millions of people will die. 10 00:00:41,208 --> 00:00:43,942 This could be the most devastating single event 11 00:00:43,944 --> 00:00:45,978 in u.S. History. 12 00:00:45,980 --> 00:00:48,280 Narrator: Earth is stuck in the crosshairs 13 00:00:48,282 --> 00:00:50,816 of a potential asteroid strike. 14 00:00:50,818 --> 00:00:55,821 Apophis is one of around 2,000 potentially hazardous asteroids 15 00:00:55,823 --> 00:01:00,292 that present a real and present danger. 16 00:01:00,294 --> 00:01:05,531 Asteroids have hit us before, and they will hit us again. 17 00:01:08,702 --> 00:01:11,537 As far as cosmic dangerous go, 18 00:01:11,539 --> 00:01:13,738 they're number one on the list. 19 00:01:13,740 --> 00:01:15,841 Narrator: This is not a drill. 20 00:01:15,843 --> 00:01:19,078 If we do nothing... 21 00:01:19,080 --> 00:01:21,380 This is our future. 22 00:01:21,382 --> 00:01:28,387 ♪ 23 00:01:28,389 --> 00:01:31,356 -- captions by vitac -- www.Vitac.Com 24 00:01:31,358 --> 00:01:34,393 captions paid for by discovery communications 25 00:01:38,866 --> 00:01:41,800 December 2018. 26 00:01:41,802 --> 00:01:44,636 The u.S. Military detect a huge explosion 27 00:01:44,638 --> 00:01:47,039 in the earth's atmosphere 28 00:01:47,041 --> 00:01:48,674 high over the bering sea 29 00:01:48,676 --> 00:01:52,277 off the coast of alaska. 30 00:01:52,279 --> 00:01:54,980 When an explosion of this magnitude is detected, 31 00:01:54,982 --> 00:01:58,283 everyone's mind goes to the same thing -- nukes. 32 00:01:58,285 --> 00:02:02,521 But when the real answer was found and it was determined 33 00:02:02,523 --> 00:02:04,723 that it didn't even originate from earth, 34 00:02:04,725 --> 00:02:07,059 that was even more shock. 35 00:02:07,061 --> 00:02:09,027 Narrator: The cause of the blast -- 36 00:02:09,029 --> 00:02:11,597 an asteroid. 37 00:02:11,599 --> 00:02:13,699 This asteroid was 30 feet across -- 38 00:02:13,701 --> 00:02:14,500 something like that -- 39 00:02:14,502 --> 00:02:16,702 over a thousand tons, 40 00:02:16,704 --> 00:02:19,805 but it was moving at 20 miles per second, 41 00:02:19,807 --> 00:02:23,408 over 70,000 miles an hour. 42 00:02:23,410 --> 00:02:26,545 Narrator: This asteroid was small, and it exploded 43 00:02:26,547 --> 00:02:28,947 in the atmosphere over the ocean, 44 00:02:28,949 --> 00:02:30,582 so nobody was hurt. 45 00:02:33,988 --> 00:02:35,821 But if it had been bigger 46 00:02:35,823 --> 00:02:38,090 or it had come in over a different place 47 00:02:38,092 --> 00:02:39,591 or it had been moving a lot faster, 48 00:02:39,593 --> 00:02:41,793 this could have been a dangerous object. 49 00:02:41,795 --> 00:02:43,729 But the scariest thing about it 50 00:02:43,731 --> 00:02:46,031 is that we didn't see it coming. 51 00:02:46,033 --> 00:02:51,370 ♪ 52 00:02:51,372 --> 00:02:54,740 narrator: So far, we've been lucky. 53 00:02:54,742 --> 00:02:57,643 But near misses happen all the time. 54 00:03:00,147 --> 00:03:02,414 About once a year, we get something 55 00:03:02,416 --> 00:03:06,318 the equivalent of a nuclear bomb going off in our atmosphere. 56 00:03:06,320 --> 00:03:08,620 And while that sounds horrible, 57 00:03:08,622 --> 00:03:13,659 most of these happen tens of miles up... 58 00:03:13,661 --> 00:03:18,864 Over open ocean, where we go on completely oblivious. 59 00:03:21,435 --> 00:03:26,271 Narrator: We may be oblivious to most of the threats from space, 60 00:03:26,273 --> 00:03:28,440 but they are very real. 61 00:03:28,442 --> 00:03:30,075 We're going to get hit. 62 00:03:30,077 --> 00:03:32,244 Over a certain amount of time, 63 00:03:32,246 --> 00:03:34,613 an asteroid impact is inevitable. 64 00:03:34,615 --> 00:03:38,150 It will happen 100%, absolute certainty. 65 00:03:38,152 --> 00:03:40,219 [ dog barking in distance ] 66 00:03:40,221 --> 00:03:44,890 ♪ 67 00:03:44,892 --> 00:03:47,359 [ rumbling, car alarm blaring ] 68 00:03:47,361 --> 00:03:53,899 ♪ 69 00:03:53,901 --> 00:03:57,402 narrator: Nasa considers the threat from the skies so severe 70 00:03:57,404 --> 00:04:03,108 it has made protection from asteroids a top priority. 71 00:04:03,110 --> 00:04:06,578 These events are not rare. They happen. 72 00:04:06,580 --> 00:04:10,782 And of course it's up to us to make sure that we are detecting 73 00:04:10,784 --> 00:04:14,253 and characterizing, tracking all of the near-earth objects 74 00:04:14,255 --> 00:04:16,722 that potentially could be a threat. 75 00:04:16,724 --> 00:04:19,191 This is not about hollywood. It's not about movies. 76 00:04:19,193 --> 00:04:22,828 This is about ultimately protecting the only planet 77 00:04:22,830 --> 00:04:25,497 we know right now to host life, 78 00:04:25,499 --> 00:04:27,466 and that is the planet earth. 79 00:04:30,237 --> 00:04:32,170 To help plan protecting our home, 80 00:04:32,172 --> 00:04:36,575 we carry out earth defense simulations. 81 00:04:36,577 --> 00:04:37,843 For three days, 82 00:04:37,845 --> 00:04:40,879 200 scientist at the planetary defense conference 83 00:04:40,881 --> 00:04:45,217 battle a simulated asteroid 20 times larger 84 00:04:45,219 --> 00:04:48,353 than the bering sea space rock. 85 00:04:48,355 --> 00:04:52,791 We practice, "alright, what if this hits a major city? 86 00:04:52,793 --> 00:04:55,994 What would we need to do?" 87 00:04:55,996 --> 00:04:58,730 narrator: By running potential impact scenarios, 88 00:04:58,732 --> 00:05:02,934 we can prepare for a real asteroid strike. 89 00:05:02,936 --> 00:05:05,170 This is like a fire drill that you would do at school 90 00:05:05,172 --> 00:05:06,805 or at work, where you practice 91 00:05:06,807 --> 00:05:08,073 and think about, okay, what if? 92 00:05:08,075 --> 00:05:10,108 Where are the exits? How do I get out? 93 00:05:10,110 --> 00:05:12,177 How fast do I get out? 94 00:05:14,281 --> 00:05:16,648 Narrator: The drill starts with the discovery 95 00:05:16,650 --> 00:05:20,452 of a simulated earthbound asteroid. 96 00:05:20,454 --> 00:05:23,055 So, the first information is there's a big asteroid 97 00:05:23,057 --> 00:05:24,523 coming towards the earth. 98 00:05:24,525 --> 00:05:25,824 Then we get a better estimate 99 00:05:25,826 --> 00:05:28,026 of how big it is, how fast it's going, 100 00:05:28,028 --> 00:05:29,795 and where it's going to hit. 101 00:05:29,797 --> 00:05:32,631 Narrator: The asteroid is heading straight for earth 102 00:05:32,633 --> 00:05:36,034 with denver, colorado, in its sights. 103 00:05:38,138 --> 00:05:40,105 The planetary defense scientists 104 00:05:40,107 --> 00:05:44,576 send up a simulated spacecraft to smash into the asteroid 105 00:05:44,578 --> 00:05:46,545 and push it off its path. 106 00:05:46,547 --> 00:05:48,780 But it's a big gamble. 107 00:05:48,782 --> 00:05:50,816 You can push it the wrong way. 108 00:05:50,818 --> 00:05:55,354 You can potentially have unintended consequences. 109 00:05:57,658 --> 00:05:58,757 Narrator: In the simulation, 110 00:05:58,759 --> 00:06:03,395 the spacecraft strikes the asteroid... 111 00:06:03,397 --> 00:06:06,698 Deflecting it away from earth. 112 00:06:06,700 --> 00:06:10,302 But the impact dislodge is a 200-foot chunk, 113 00:06:10,304 --> 00:06:15,207 which is now heading straight towards the eastern seaboard. 114 00:06:15,209 --> 00:06:17,275 So there's this one last piece 115 00:06:17,277 --> 00:06:20,512 that is now going to hit new york. 116 00:06:20,514 --> 00:06:23,382 We know that something that size 117 00:06:23,384 --> 00:06:27,219 is going to have citywide consequences. 118 00:06:27,221 --> 00:06:31,857 That is huge. That's a horrible impact. 119 00:06:31,859 --> 00:06:33,325 Thaller: When you're actually in the conference room 120 00:06:33,327 --> 00:06:34,993 and you understand eventually 121 00:06:34,995 --> 00:06:37,829 that new york city is going to be destroyed... 122 00:06:37,831 --> 00:06:40,532 And you're having strategies about how to evacuate people, 123 00:06:40,534 --> 00:06:43,068 all the timing, when you're doing the simulation 124 00:06:43,070 --> 00:06:44,136 you're in your head. 125 00:06:44,138 --> 00:06:45,303 You're thinking about these things. 126 00:06:45,305 --> 00:06:47,038 You're trying to reason them out, 127 00:06:47,040 --> 00:06:50,342 but can you imagine the feeling in your gut, in your heart, 128 00:06:50,344 --> 00:06:53,011 if this was real? 129 00:06:53,013 --> 00:06:55,180 Narrator: If this were real, the chunk of asteroid 130 00:06:55,182 --> 00:06:57,149 would strike earth's atmosphere 131 00:06:57,151 --> 00:06:59,451 at 43,000 miles an hour. 132 00:07:03,223 --> 00:07:05,824 As the space rock hurtles down, it collides 133 00:07:05,826 --> 00:07:10,695 with molecules in the atmosphere which buffet the falling rock. 134 00:07:10,697 --> 00:07:13,565 It's kind of like doing a belly flop into a pool, right? 135 00:07:13,567 --> 00:07:15,400 You're going from the vacuum of space 136 00:07:15,402 --> 00:07:19,471 into the dense lower atmosphere in mere seconds. 137 00:07:19,473 --> 00:07:21,440 And that's an incredible amount of pressure 138 00:07:21,442 --> 00:07:23,842 to put on the object. 139 00:07:23,844 --> 00:07:26,011 Narrator: The asteroid slams into the air 140 00:07:26,013 --> 00:07:29,881 ahead of it, compressing it violently. 141 00:07:29,883 --> 00:07:34,286 The surface of the asteroid gets hotter and brighter. 142 00:07:34,288 --> 00:07:36,955 Durda: It's actually the air itself that's glowing luminously 143 00:07:36,957 --> 00:07:38,757 from the heating of the shockwave, 144 00:07:38,759 --> 00:07:41,159 the world's most intense sonic boom if you will, 145 00:07:41,161 --> 00:07:44,062 that heats the air to incandescence 146 00:07:44,064 --> 00:07:45,630 as the object passes through. 147 00:07:45,632 --> 00:07:50,001 So that's the source of that brilliant illumination. 148 00:07:50,003 --> 00:07:55,040 Narrator: This bright, burning asteroid is called a bolide. 149 00:07:55,042 --> 00:07:57,709 We witnessed one descending over the russian city 150 00:07:57,711 --> 00:08:00,545 of chelyabinsk in 2013. 151 00:08:00,547 --> 00:08:02,681 All of a sudden, there was a huge fireball 152 00:08:02,683 --> 00:08:03,949 streaking through the sky, 153 00:08:03,951 --> 00:08:06,451 and people had no idea what they were witnessing 154 00:08:06,453 --> 00:08:09,488 because it looked like the sky was on fire. 155 00:08:09,490 --> 00:08:11,423 It was insanity. 156 00:08:11,425 --> 00:08:13,658 Narrator: As the asteroid descends, 157 00:08:13,660 --> 00:08:16,428 the compression of the denser air beneath it 158 00:08:16,430 --> 00:08:21,266 starts to flatten and even disrupt the falling rock. 159 00:08:21,268 --> 00:08:23,001 Oluseyi: There's a high pressure on the front, 160 00:08:23,003 --> 00:08:24,603 there's no pressure on the back 161 00:08:24,605 --> 00:08:26,404 and it's being super heated. 162 00:08:26,406 --> 00:08:30,509 Sutter: And that intense temperature causes the air to glow, 163 00:08:30,511 --> 00:08:32,811 which is how we see this streak of a meteor. 164 00:08:32,813 --> 00:08:35,847 And it also disintegrates the asteroid itself. 165 00:08:35,849 --> 00:08:39,150 It's hard enough to literally melt rock. 166 00:08:39,152 --> 00:08:42,454 This can often lead to them exploding. 167 00:08:42,456 --> 00:08:44,623 Narrator: The combination of heat and pressure invade 168 00:08:44,625 --> 00:08:47,526 the falling asteroid, causing it to blow up. 169 00:08:47,528 --> 00:08:49,995 [ explosion ] 170 00:08:49,997 --> 00:08:52,664 most asteroids don't reach the ground 171 00:08:52,666 --> 00:08:54,366 before they completely disintegrate 172 00:08:54,368 --> 00:08:56,902 in a tremendous release of energy. 173 00:08:56,904 --> 00:08:58,270 Plait: This is what we call an air burst, 174 00:08:58,272 --> 00:09:00,338 and we learned a lot about these 175 00:09:00,340 --> 00:09:05,911 while we were testing nuclear weapons after world war ii. 176 00:09:05,913 --> 00:09:07,345 Some of these bombs were blown up 177 00:09:07,347 --> 00:09:09,147 underground and on the ground, 178 00:09:09,149 --> 00:09:12,050 but they found out when they blew up bombs above the ground, 179 00:09:12,052 --> 00:09:13,518 it actually did more damage. 180 00:09:13,520 --> 00:09:16,454 It was more widespread damage. 181 00:09:16,456 --> 00:09:18,924 Narrator: The explosion of the chelyabinsk asteroid 182 00:09:18,926 --> 00:09:22,928 sent out a powerful shockwave at thousands of miles an hour. 183 00:09:26,500 --> 00:09:30,001 The blast traveled over 100 miles. 184 00:09:30,003 --> 00:09:32,671 It damaged 7,000 buildings 185 00:09:32,673 --> 00:09:35,840 and put 1,500 people in the hospital. 186 00:09:35,842 --> 00:09:38,143 All of the injuries pretty much came from people 187 00:09:38,145 --> 00:09:40,745 who saw, "oh, what's that bright flash in the sky?" 188 00:09:40,747 --> 00:09:44,349 and they came close to a window to look and see what it was, 189 00:09:44,351 --> 00:09:47,419 and then the pressure wave hit and blew glass in their face. 190 00:09:50,223 --> 00:09:54,292 Narrator: The chelyabinsk asteroid was only 65 feet across. 191 00:09:56,530 --> 00:09:58,597 The rock in the defense simulation 192 00:09:58,599 --> 00:10:00,765 is three times more massive, 193 00:10:00,767 --> 00:10:05,870 and it's heading straight for new york city. 194 00:10:05,872 --> 00:10:09,341 Imagine what would happen if an explosion a thousand times 195 00:10:09,343 --> 00:10:13,845 greater than that over hiroshima hit new york. 196 00:10:13,847 --> 00:10:17,582 We're talking about an utter complete destruction of the city 197 00:10:17,584 --> 00:10:21,019 and millions of people. 198 00:10:21,021 --> 00:10:22,253 Narrator: With so little warning, 199 00:10:22,255 --> 00:10:27,158 the only option would be to evacuate new york city. 200 00:10:27,160 --> 00:10:29,194 How do we get everybody out of new york city 201 00:10:29,196 --> 00:10:30,795 within just a few days? 202 00:10:30,797 --> 00:10:32,430 That's where panic sets in. 203 00:10:32,432 --> 00:10:35,433 That's where fear would really become the dominant emotion. 204 00:10:38,005 --> 00:10:39,838 Narrator: Anyone left in new york city 205 00:10:39,840 --> 00:10:42,407 would see the bolide racing in... 206 00:10:45,445 --> 00:10:48,146 ...Followed by a blinding light... 207 00:10:48,148 --> 00:10:52,617 As the asteroid explodes above the city. 208 00:10:52,619 --> 00:10:56,921 The blast would be equivalent to the largest nuclear weapon 209 00:10:56,923 --> 00:10:59,257 ever detonated on earth. 210 00:10:59,259 --> 00:11:01,660 Plait: Buildings would be flattened, melted. 211 00:11:01,662 --> 00:11:04,362 There would be fires for miles around 212 00:11:04,364 --> 00:11:06,698 in the first moments of the explosion. 213 00:11:06,700 --> 00:11:09,534 A million people could be killed instantly 214 00:11:09,536 --> 00:11:11,503 and many more would die later in the rubble, 215 00:11:11,505 --> 00:11:15,540 in the ruins of what would happen there. 216 00:11:15,542 --> 00:11:19,444 Narrator: Everything within nine miles of the blast epicenter 217 00:11:19,446 --> 00:11:21,713 would be completely destroyed. 218 00:11:21,715 --> 00:11:28,853 ♪ 219 00:11:28,855 --> 00:11:33,758 the intense heat and pressure would wreck buildings. 220 00:11:33,760 --> 00:11:37,295 Sutter: It's the worst possible day for new yorkers, 221 00:11:37,297 --> 00:11:39,597 and not just the city itself. 222 00:11:39,599 --> 00:11:42,767 There's something like 15 million people 223 00:11:42,769 --> 00:11:44,936 living in the new york area. 224 00:11:48,675 --> 00:11:53,712 Narrator: The shock wave would race out over 250 square miles. 225 00:11:53,714 --> 00:11:55,680 This would certainly be the worst disaster 226 00:11:55,682 --> 00:11:57,148 that the u.S. Has ever experienced. 227 00:11:57,150 --> 00:12:00,185 We're talking about millions and millions of people 228 00:12:00,187 --> 00:12:02,754 displaced, affected within an instant. 229 00:12:02,756 --> 00:12:09,394 ♪ 230 00:12:09,396 --> 00:12:13,398 narrator: This scenario is just a simulation...For now. 231 00:12:13,400 --> 00:12:18,536 ♪ 232 00:12:18,538 --> 00:12:21,940 the asteroid apophis is heading our way. 233 00:12:24,611 --> 00:12:26,077 If it hits earth, 234 00:12:26,079 --> 00:12:28,413 it might not just kill a city. 235 00:12:28,415 --> 00:12:31,216 It could kill a whole region. 236 00:12:31,218 --> 00:12:32,851 I wouldn't exactly want to be there 237 00:12:32,853 --> 00:12:38,089 when that happens -- want to be very, very far away. 238 00:12:38,091 --> 00:12:43,561 Narrator: Apophis will skim earth in 2029. 239 00:12:43,563 --> 00:12:46,698 But its path could change, 240 00:12:46,700 --> 00:12:49,868 possibly turning a future miss... 241 00:12:49,870 --> 00:12:51,536 Into a direct hit. 242 00:12:51,538 --> 00:12:56,674 ♪ 243 00:13:07,521 --> 00:13:10,221 ♪ 244 00:13:10,223 --> 00:13:13,057 narrator: April 13, 2029, 245 00:13:13,059 --> 00:13:16,060 a speck of light races towards the earth. 246 00:13:16,062 --> 00:13:20,165 It's an 1,100 foot wide asteroid called apophis. 247 00:13:20,167 --> 00:13:24,969 We are about to have an extremely close shave. 248 00:13:26,072 --> 00:13:28,640 It's the closest approach of any asteroid 249 00:13:28,642 --> 00:13:32,477 that didn't actually hit us for a long, long time. 250 00:13:32,479 --> 00:13:36,047 It will be 10 times closer than the moon itself. 251 00:13:36,049 --> 00:13:38,283 It'll be so close that it will be brighter 252 00:13:38,285 --> 00:13:40,485 than some stars. 253 00:13:40,487 --> 00:13:43,421 Narrator: The football-stadium sized apophis 254 00:13:43,423 --> 00:13:46,291 will race over the atlantic. 255 00:13:46,293 --> 00:13:48,059 Plait: If it were sitting on the surface of the earth, 256 00:13:48,061 --> 00:13:50,161 it would weigh about 50 million tons, 257 00:13:50,163 --> 00:13:51,830 something like that, 258 00:13:51,832 --> 00:13:55,200 and that is not the place you want it to be. 259 00:13:55,202 --> 00:14:00,171 You want it to be in space and far away. 260 00:14:00,173 --> 00:14:03,208 Narrator: When we discovered apophis in 2004, 261 00:14:03,210 --> 00:14:06,344 we thought it might be on a collision course with earth 262 00:14:06,346 --> 00:14:08,112 with a potential impact 263 00:14:08,114 --> 00:14:12,750 greater than the largest atomic bomb ever exploded. 264 00:14:12,752 --> 00:14:15,687 Durda: The largest nuclear device, atomic device 265 00:14:15,689 --> 00:14:19,424 ever detonated on our planet was the tsar bomba bomb in russia, 266 00:14:19,426 --> 00:14:22,427 so something like 55 or 56 megatons. 267 00:14:22,429 --> 00:14:26,764 When krakatoa exploded in 1883 268 00:14:26,766 --> 00:14:29,000 that was something like 200 megatons. 269 00:14:29,002 --> 00:14:32,136 Apophis' impact would be 450 megatons. 270 00:14:32,138 --> 00:14:34,439 If something like that were to happen over new york city 271 00:14:34,441 --> 00:14:39,677 or washington d.C., you're going to lose the city. 272 00:14:39,679 --> 00:14:42,714 Narrator: The impact would be at least 10 times greater 273 00:14:42,716 --> 00:14:45,583 than the simulated asteroid strike on new york. 274 00:14:45,585 --> 00:14:52,790 ♪ 275 00:14:52,792 --> 00:14:55,693 sutter: Well, when you put it in those terms, 276 00:14:55,695 --> 00:14:57,762 that's just plain scary. 277 00:14:57,764 --> 00:15:02,000 In a word, an impact from an apophis-sized asteroid 278 00:15:02,002 --> 00:15:07,005 would be bad -- very, very bad. 279 00:15:07,007 --> 00:15:09,374 Narrator: Apophis' orbit will cross earth 280 00:15:09,376 --> 00:15:12,977 every seven years this century. 281 00:15:12,979 --> 00:15:15,179 It won't hit us in 2029, 282 00:15:15,181 --> 00:15:20,351 but this close encounter could change apophis' orbit. 283 00:15:20,353 --> 00:15:25,156 When a small asteroid encounters a bigger body like a planet, 284 00:15:25,158 --> 00:15:28,159 it's like a bunch of roller derby players. 285 00:15:30,363 --> 00:15:31,996 Most of them are clumped together, 286 00:15:31,998 --> 00:15:35,800 but maybe there's one just on their own particular orbit, 287 00:15:35,802 --> 00:15:37,302 and as they circle around, 288 00:15:37,304 --> 00:15:39,270 as they get close to that larger clump, 289 00:15:39,272 --> 00:15:41,005 there'll be some interactions -- 290 00:15:41,007 --> 00:15:42,874 potentially violent interactions -- 291 00:15:42,876 --> 00:15:46,210 that will change the future trajectory 292 00:15:46,212 --> 00:15:49,147 of that lone roller derby skater. 293 00:15:49,149 --> 00:15:50,515 And the next time around, 294 00:15:50,517 --> 00:15:54,852 it might be a wide miss or it might be a head-on impact. 295 00:15:58,959 --> 00:16:01,693 Narrator: It's the same in the solar system. 296 00:16:01,695 --> 00:16:04,295 The combined gravity of the earth and moon 297 00:16:04,297 --> 00:16:09,000 creates what's called a gravitational keyhole, 298 00:16:09,002 --> 00:16:12,003 a gravitational sweet spot, 299 00:16:12,005 --> 00:16:15,873 which could change apophis' orbit. 300 00:16:15,875 --> 00:16:19,310 That will change the potential future trajectory of this rock 301 00:16:19,312 --> 00:16:21,813 and might make it totally harmless 302 00:16:21,815 --> 00:16:23,982 or might increase the chances 303 00:16:23,984 --> 00:16:28,419 of an impact even further in the future. 304 00:16:28,421 --> 00:16:30,822 Narrator: Because of the gravitational keyhole, 305 00:16:30,824 --> 00:16:32,256 there's still a small chance 306 00:16:32,258 --> 00:16:36,661 that apophis will hit earth in 2068. 307 00:16:40,967 --> 00:16:43,901 Plait: That is the important lesson that apophis taught us -- 308 00:16:43,903 --> 00:16:45,470 you can miss the earth, 309 00:16:45,472 --> 00:16:47,572 but if you pass through one of these keyholes, 310 00:16:47,574 --> 00:16:51,642 at some time later, you will hit the earth. 311 00:16:51,644 --> 00:16:56,547 Narrator: We now know apophis will miss the keyhole in 2029, 312 00:16:56,549 --> 00:16:59,951 but there are other keyholes and other close passes. 313 00:16:59,953 --> 00:17:07,392 ♪ 314 00:17:07,394 --> 00:17:11,629 apophis is not a lone threat. 315 00:17:11,631 --> 00:17:16,234 There are an estimated 832,500 asteroids 316 00:17:16,236 --> 00:17:19,003 orbiting the sun. 317 00:17:19,005 --> 00:17:21,839 Most asteroids live their lives 318 00:17:21,841 --> 00:17:25,743 perfectly peacefully past the orbit of mars 319 00:17:25,745 --> 00:17:29,747 or trailing jupiter and don't mind anybody else, 320 00:17:29,749 --> 00:17:33,117 don't cause any troubles, but some asteroids 321 00:17:33,119 --> 00:17:35,653 are on very particular orbits 322 00:17:35,655 --> 00:17:40,258 that cross the orbit of the earth. 323 00:17:40,260 --> 00:17:42,693 Narrator: These asteroids have left the stable orbit 324 00:17:42,695 --> 00:17:44,228 of the asteroid belt 325 00:17:44,230 --> 00:17:48,433 and moved into orbits that get near our own. 326 00:17:48,435 --> 00:17:51,769 These asteroids are called near earth asteroids 327 00:17:51,771 --> 00:17:54,472 or n.E.A.S for short. 328 00:17:54,474 --> 00:17:56,941 Walsh: The near earth asteroid population is interesting 329 00:17:56,943 --> 00:17:58,810 and potentially dangerous because they are the ones 330 00:17:58,812 --> 00:18:00,545 that actually cross the orbit of the earth. 331 00:18:00,547 --> 00:18:03,314 So they're most likely to have, at some point 332 00:18:03,316 --> 00:18:06,017 in the future, an impact with the earth. 333 00:18:07,987 --> 00:18:12,423 Narrator: Most n.E.A.S pose little or no threat to earth. 334 00:18:12,425 --> 00:18:14,492 But we've detected over 2,000, 335 00:18:14,494 --> 00:18:19,363 including the 1,200 foot apophis that do. 336 00:18:19,365 --> 00:18:21,599 These are called p.H.A.S -- 337 00:18:21,601 --> 00:18:25,736 potentially hazardous asteroids. 338 00:18:25,738 --> 00:18:27,872 The difference between a near earth asteroid 339 00:18:27,874 --> 00:18:33,578 and a potentially hazardous asteroid is distance and size. 340 00:18:33,580 --> 00:18:35,079 Anything can get near the earth, 341 00:18:35,081 --> 00:18:37,448 and that could be 20 million miles away, 342 00:18:37,450 --> 00:18:39,884 something like that, and be a near earth asteroid, 343 00:18:39,886 --> 00:18:42,787 but a potentially hazardous one can hit us, 344 00:18:42,789 --> 00:18:45,056 and it's big enough to do damage. 345 00:18:48,995 --> 00:18:51,329 So something that over the next hundred years or so 346 00:18:51,331 --> 00:18:54,765 has a chance of hitting us and doing damage when it does -- 347 00:18:54,767 --> 00:18:57,068 that's a potentially hazardous object. 348 00:18:59,105 --> 00:19:03,274 Narrator: P.H.A.S are asteroids that are 460 feet or larger 349 00:19:03,276 --> 00:19:04,976 that could collide with earth. 350 00:19:07,213 --> 00:19:10,348 Take a 400-foot asteroid -- if it hits, 351 00:19:10,350 --> 00:19:12,316 it would release as much energy 352 00:19:12,318 --> 00:19:15,953 as 3,000 hiroshima nuclear bombs. 353 00:19:22,095 --> 00:19:23,561 Narrator: In July of 2018, 354 00:19:23,563 --> 00:19:25,530 nasa published a map 355 00:19:25,532 --> 00:19:29,300 of all the known n.E.A.S and p.H.A.S. 356 00:19:32,438 --> 00:19:34,605 The animation tracks their discovery 357 00:19:34,607 --> 00:19:38,009 from 1999 through 2018. 358 00:19:40,046 --> 00:19:41,445 Every time I look at this animation, 359 00:19:41,447 --> 00:19:43,481 it does make my heart stop a little bit 360 00:19:43,483 --> 00:19:45,449 because it looks like we're in the middle of a swarm 361 00:19:45,451 --> 00:19:49,353 of angry bees circling all around us. 362 00:19:49,355 --> 00:19:51,656 Narrator: In 1999, we'd identified 363 00:19:51,658 --> 00:19:53,658 under 300 n.E.A.S 364 00:19:53,660 --> 00:19:56,427 scattered through the inner solar system. 365 00:19:56,429 --> 00:20:00,598 10 years later, we'd found 500 more. 366 00:20:00,600 --> 00:20:05,937 By 2018, we'd discovered 18,000 near earth asteroids, 367 00:20:05,939 --> 00:20:10,241 but we estimate there are millions out there. 368 00:20:10,243 --> 00:20:12,977 It seems like we could never find all the asteroids. 369 00:20:12,979 --> 00:20:14,278 They just keep coming. 370 00:20:14,280 --> 00:20:17,248 It's like we're fighting an army of zombies. 371 00:20:17,250 --> 00:20:21,118 Narrator: Zombies that keep hurtling our way, 372 00:20:21,120 --> 00:20:26,891 hitting the earth at up to 64,000 miles an hour. 373 00:20:26,893 --> 00:20:28,526 That is very, very fast. 374 00:20:28,528 --> 00:20:30,695 That is much faster than a rifle bullet. 375 00:20:30,697 --> 00:20:33,497 And that's the key to its destructive power. 376 00:20:36,769 --> 00:20:40,238 Narrator: When a really fast and really large asteroid hits, 377 00:20:40,240 --> 00:20:43,941 the impact is off the charts. 378 00:20:43,943 --> 00:20:46,110 The blast is so intense, 379 00:20:46,112 --> 00:20:49,513 it can melt or even vaporize rock. 380 00:21:01,294 --> 00:21:04,295 ♪ 381 00:21:04,297 --> 00:21:06,497 narrator: January 2019, 382 00:21:06,499 --> 00:21:08,799 a total eclipse of the moon. 383 00:21:08,801 --> 00:21:10,568 Astronomers train their telescopes 384 00:21:10,570 --> 00:21:12,937 on the darkening lunar surface. 385 00:21:14,741 --> 00:21:17,608 They capture a bright flash 386 00:21:17,610 --> 00:21:21,145 that lasts around a quarter of a second. 387 00:21:21,147 --> 00:21:23,281 It was recorded. There were a lot of live webcasts 388 00:21:23,283 --> 00:21:25,616 and things like that going on at the time, 389 00:21:25,618 --> 00:21:27,685 and you can see this flash of light. 390 00:21:27,687 --> 00:21:29,320 What the heck was that? 391 00:21:31,257 --> 00:21:35,459 Narrator: At first, the cause of the flash was a mystery. 392 00:21:35,461 --> 00:21:39,730 It turns out it was actually a meteorite hitting 393 00:21:39,732 --> 00:21:42,300 the surface of the moon, and because it was dark 394 00:21:42,302 --> 00:21:43,668 and because we were all looking at it, 395 00:21:43,670 --> 00:21:46,804 we could actually see it. 396 00:21:46,806 --> 00:21:49,473 Narrator: The moon's dark surface gave us a unique view 397 00:21:49,475 --> 00:21:52,376 of what happens when an asteroid strikes. 398 00:21:52,378 --> 00:21:53,844 What was so exciting about being able 399 00:21:53,846 --> 00:21:57,381 to see this impact on the moon in a dark area 400 00:21:57,383 --> 00:22:00,351 is that we could actually look at the light that it produced 401 00:22:00,353 --> 00:22:01,952 and then back-calculate 402 00:22:01,954 --> 00:22:04,855 exactly what the size of the impactor was. 403 00:22:04,857 --> 00:22:07,391 Narrator: We worked out that the impacting asteroid 404 00:22:07,393 --> 00:22:09,960 was just 20 inches wide. 405 00:22:09,962 --> 00:22:14,265 The crater it blew out was 45 feet across. 406 00:22:14,267 --> 00:22:18,969 How can something so small be so destructive? 407 00:22:18,971 --> 00:22:21,839 The two things that matter the most are how fast it's going 408 00:22:21,841 --> 00:22:23,240 and how massive is the thing. 409 00:22:23,242 --> 00:22:24,842 The more massive, the bigger the boom, 410 00:22:24,844 --> 00:22:26,677 the faster the bigger the boom. 411 00:22:26,679 --> 00:22:29,013 Speed and weight are two very important factors 412 00:22:29,015 --> 00:22:31,782 to assess how much damage an asteroid will do. 413 00:22:31,784 --> 00:22:34,018 Just like a boxer -- if a tiny person like me 414 00:22:34,020 --> 00:22:35,453 were to swing a punch, 415 00:22:35,455 --> 00:22:38,989 it would do a lot less damage than a heavyweight champion. 416 00:22:38,991 --> 00:22:40,157 Bullock: Same thing with asteroids. 417 00:22:40,159 --> 00:22:41,992 The bigger they are, the bigger the punch. 418 00:22:41,994 --> 00:22:43,828 But the same thing is fast, right? 419 00:22:43,830 --> 00:22:46,097 If I hit you really slowly, it's not gonna hurt. 420 00:22:46,099 --> 00:22:48,399 I have to really wind back and pap. 421 00:22:48,401 --> 00:22:51,569 That's what happens with an asteroid. 422 00:22:51,571 --> 00:22:53,270 Narrator: The damage from an asteroid strike 423 00:22:53,272 --> 00:22:55,606 is determined by its kinetic energy. 424 00:22:55,608 --> 00:22:57,942 Kinetic energy depends on two things -- 425 00:22:57,944 --> 00:23:00,044 speed and weight. 426 00:23:02,615 --> 00:23:05,883 Of the two, speed matters most. 427 00:23:08,488 --> 00:23:11,255 If you double the mass, you double the kinetic energy, 428 00:23:11,257 --> 00:23:12,990 but if you double the velocity, 429 00:23:12,992 --> 00:23:15,226 you get four times the kinetic energy. 430 00:23:15,228 --> 00:23:17,895 Three times the speed, nine times the impact energy. 431 00:23:17,897 --> 00:23:19,163 10 times as fast, 432 00:23:19,165 --> 00:23:21,465 it has a hundred times the energy, 433 00:23:21,467 --> 00:23:24,135 so the velocity is what's really critical here. 434 00:23:26,773 --> 00:23:29,340 Narrator: The lunar asteroid weighed only 100 pounds, 435 00:23:29,342 --> 00:23:34,445 but it was traveling at 38,000 miles an hour. 436 00:23:34,447 --> 00:23:38,716 Carrying a huge kinetic energy, which gouged out the crater. 437 00:23:40,753 --> 00:23:45,656 It's the same principle for impacts on earth. 438 00:23:45,658 --> 00:23:49,293 50,000 years ago, a 150-foot asteroid 439 00:23:49,295 --> 00:23:51,595 hit what is now arizona. 440 00:23:53,800 --> 00:23:56,667 The impact blasted out an impressive hole 441 00:23:56,669 --> 00:23:59,136 now called barringer crater. 442 00:23:59,138 --> 00:24:01,906 Durda: It's about 3/4 of a mile across, 443 00:24:01,908 --> 00:24:03,240 over 500 feet deep. 444 00:24:03,242 --> 00:24:04,842 You could put the washington monument 445 00:24:04,844 --> 00:24:06,343 in the bottom of the crater, 446 00:24:06,345 --> 00:24:09,146 and the top of the monument wouldn't quite clear the rim. 447 00:24:09,148 --> 00:24:11,382 It's a pretty impressive hole in the ground. 448 00:24:15,321 --> 00:24:18,489 Narrator: In 2016, impact specialist cathy plesko 449 00:24:18,491 --> 00:24:20,157 visited barringer crater 450 00:24:20,159 --> 00:24:23,360 to see firsthand what mass and speed 451 00:24:23,362 --> 00:24:25,329 do to the surface of the earth. 452 00:24:25,331 --> 00:24:29,667 ♪ 453 00:24:29,669 --> 00:24:35,206 this is awe-inspiring to stand on the rim of a crater like this 454 00:24:35,208 --> 00:24:38,642 understanding just how much energy 455 00:24:38,644 --> 00:24:42,780 it must have taken to excavate this much rock. 456 00:24:46,152 --> 00:24:51,121 The asteroid came in at about 27,000 miles an hour. 457 00:24:53,292 --> 00:24:54,992 It comes slamming into the surface 458 00:24:54,994 --> 00:24:56,494 and just explodes. 459 00:24:56,496 --> 00:24:58,362 Anywhere nearby here 460 00:24:58,364 --> 00:25:00,898 would have seen winds of thousands of miles an hour 461 00:25:00,900 --> 00:25:02,833 as the shockwave came out. 462 00:25:02,835 --> 00:25:08,939 ♪ 463 00:25:08,941 --> 00:25:11,475 narrator: The immense power of an asteroid impact 464 00:25:11,477 --> 00:25:13,377 comes from the kinetic energy 465 00:25:13,379 --> 00:25:17,448 being transferred from the space rock into the surface rock. 466 00:25:19,952 --> 00:25:22,486 It's an extremely violent process, 467 00:25:22,488 --> 00:25:24,555 and it starts with the moment of contact 468 00:25:24,557 --> 00:25:28,759 of the projectile with the surface itself. 469 00:25:28,761 --> 00:25:31,595 Plesko: It pushes into the crust, 470 00:25:31,597 --> 00:25:35,399 and at first, it's just almost punching, like, 471 00:25:35,401 --> 00:25:36,834 sticking your thumb into dough. 472 00:25:36,836 --> 00:25:39,403 It's only about as wide as the object is. 473 00:25:39,405 --> 00:25:41,105 It's going straight down in, 474 00:25:41,107 --> 00:25:45,643 but then it's meeting resistance from the surface of the earth. 475 00:25:45,645 --> 00:25:47,778 And so it squishes, squishes, squishes, 476 00:25:47,780 --> 00:25:51,615 until it runs out of momentum, but then it's very compressed 477 00:25:51,617 --> 00:25:54,184 and all of that energy is in a very small space. 478 00:25:54,186 --> 00:25:56,787 As it releases, it detonates like a bomb. 479 00:25:56,789 --> 00:26:01,792 And that's what makes the impact crater. 480 00:26:01,794 --> 00:26:04,562 Narrator: Simulations of an asteroid strike in the lab 481 00:26:04,564 --> 00:26:07,164 reveal the impact in slow motion. 482 00:26:10,570 --> 00:26:14,138 As the high speed pellet hits the surface, 483 00:26:14,140 --> 00:26:19,410 the sand compresses downwards, then rebounds. 484 00:26:19,412 --> 00:26:21,245 And as that rebound is occurring, 485 00:26:21,247 --> 00:26:23,614 that's when the material is being ejected 486 00:26:23,616 --> 00:26:26,717 out of the crater itself. 487 00:26:26,719 --> 00:26:28,686 You'll see the surface erupting outwards 488 00:26:28,688 --> 00:26:31,889 like the blooming petals of some big rocky flower 489 00:26:31,891 --> 00:26:34,792 as all this debris goes spraying out in every direction. 490 00:26:34,794 --> 00:26:39,830 ♪ 491 00:26:39,832 --> 00:26:42,399 narrator: The 150-foot barringer asteroid 492 00:26:42,401 --> 00:26:46,036 turned the rock to powder. 493 00:26:46,038 --> 00:26:48,172 66 million years ago, 494 00:26:48,174 --> 00:26:50,975 an asteroid around 200 times larger 495 00:26:50,977 --> 00:26:53,310 and moving one and a half times faster 496 00:26:53,312 --> 00:26:55,846 than barringer hit earth. 497 00:26:55,848 --> 00:26:59,083 This asteroid impact -- called k-pg -- 498 00:26:59,085 --> 00:27:00,651 had so much energy, 499 00:27:00,653 --> 00:27:03,520 it turned rock to liquid. 500 00:27:03,522 --> 00:27:05,489 This thing was immense. It's really hard to wrap 501 00:27:05,491 --> 00:27:08,125 your head around just how big it is. 502 00:27:08,127 --> 00:27:11,929 When it hits the back end of it, it is so far back, 503 00:27:11,931 --> 00:27:15,265 that it's where a modern jetliner would fly. 504 00:27:17,703 --> 00:27:19,703 Narrator: The k-pg asteroid hit the ground 505 00:27:19,705 --> 00:27:23,907 with a lethal combination of mass and speed. 506 00:27:23,909 --> 00:27:28,646 A trillion tons traveling at 45,000 miles an hour. 507 00:27:30,583 --> 00:27:32,549 Some rock is completely vaporized. 508 00:27:32,551 --> 00:27:34,251 It just becomes a gas. 509 00:27:34,253 --> 00:27:36,587 You have some rock that is melted. 510 00:27:36,589 --> 00:27:39,823 You have some that's thrown out into space. 511 00:27:41,661 --> 00:27:44,461 This material goes up through that and then falls down 512 00:27:44,463 --> 00:27:46,730 and settles down over a huge area. 513 00:27:46,732 --> 00:27:49,466 That might be dust. It might be pulverized rock. 514 00:27:49,468 --> 00:27:51,669 It might be vaporized metal. 515 00:27:51,671 --> 00:27:55,005 It's all of this hot material raining down everywhere. 516 00:27:57,276 --> 00:28:00,277 Narrator: Some of the rock exploded skywards, 517 00:28:00,279 --> 00:28:03,814 but rock below the surface was slammed by a shockwave 518 00:28:03,816 --> 00:28:06,650 that was completely off the charts. 519 00:28:06,652 --> 00:28:11,255 Rock stopped behaving like rock. 520 00:28:11,257 --> 00:28:14,224 We experience rocks as solid objects, 521 00:28:14,226 --> 00:28:15,726 but if you hit a rock hard enough, 522 00:28:15,728 --> 00:28:17,828 it flows like water. 523 00:28:17,830 --> 00:28:20,664 Narrator: The k-pg asteroid hit so hard, 524 00:28:20,666 --> 00:28:22,566 it pulverized the rock, 525 00:28:22,568 --> 00:28:24,568 turning it into liquid. 526 00:28:24,570 --> 00:28:26,737 Almost like ripples on a pond moving away 527 00:28:26,739 --> 00:28:29,173 from a stone that's been dropped in it. 528 00:28:29,175 --> 00:28:30,574 Durda: It's almost like a splash 529 00:28:30,576 --> 00:28:32,876 in the solid body of the earth itself, 530 00:28:32,878 --> 00:28:35,546 and like water droplets splashing in water, 531 00:28:35,548 --> 00:28:39,016 you'll see that central peak will kind of splash up 532 00:28:39,018 --> 00:28:41,719 and rise to a high altitude and then come back down again. 533 00:28:41,721 --> 00:28:44,521 We think a process very similar to that probably happened 534 00:28:44,523 --> 00:28:47,424 in the rock itself at the center of the crater, 535 00:28:47,426 --> 00:28:49,960 rising up as high as the himalayas 536 00:28:49,962 --> 00:28:53,063 before relaxing back down to their current position again. 537 00:28:53,065 --> 00:28:56,600 Plesko: The material slumps, and so these ripples 538 00:28:56,602 --> 00:28:58,302 are frozen in the rock, 539 00:28:58,304 --> 00:29:01,171 and there are other fragments that go away radially, 540 00:29:01,173 --> 00:29:03,540 almost like the spider web pattern in glass 541 00:29:03,542 --> 00:29:06,977 that you get after it's shot with a bullet. 542 00:29:06,979 --> 00:29:10,581 Narrator: The k-pg impact blew out a crater 543 00:29:10,583 --> 00:29:13,317 111 miles wide. 544 00:29:13,319 --> 00:29:15,786 It is the third largest confirmed 545 00:29:15,788 --> 00:29:18,222 impact structure on earth. 546 00:29:20,493 --> 00:29:23,727 A large and fast asteroid heading our way 547 00:29:23,729 --> 00:29:26,130 is always going to be a problem. 548 00:29:26,132 --> 00:29:28,465 So what do we do? 549 00:29:28,467 --> 00:29:32,035 Wait for oblivion? 550 00:29:32,037 --> 00:29:33,670 Or fight back? 551 00:29:47,887 --> 00:29:49,853 ♪ 552 00:29:49,855 --> 00:29:51,989 narrator: The space in the inner solar system 553 00:29:51,991 --> 00:29:56,193 seems calm, stable, and empty. 554 00:29:56,195 --> 00:29:59,096 It's not. 555 00:29:59,098 --> 00:30:01,398 There are tens of thousands of near earth objects 556 00:30:01,400 --> 00:30:03,033 just whizzing around earth. 557 00:30:03,035 --> 00:30:05,636 Now, space is big. 558 00:30:05,638 --> 00:30:09,940 They're not gonna hit us every time they orbit the sun, 559 00:30:09,942 --> 00:30:12,309 but this does set up the possibility 560 00:30:12,311 --> 00:30:14,545 that, one of these years, 561 00:30:14,547 --> 00:30:17,581 we're gonna end up at the same spot in space 562 00:30:17,583 --> 00:30:20,551 at the same time as that asteroid, 563 00:30:20,553 --> 00:30:22,186 and then it's gonna be an impact. 564 00:30:24,623 --> 00:30:26,256 We're living in a cosmic shooting gallery. 565 00:30:26,258 --> 00:30:28,258 Asteroids strike the earth all the time 566 00:30:28,260 --> 00:30:29,860 through history, 567 00:30:29,862 --> 00:30:31,829 and it's gonna happen again. 568 00:30:31,831 --> 00:30:33,664 Narrator: Scientists are developing strategies 569 00:30:33,666 --> 00:30:37,701 to stop an asteroid from hitting our planet. 570 00:30:37,703 --> 00:30:42,773 Our options -- destroy or deflect the space rock. 571 00:30:42,775 --> 00:30:46,276 But first, we need to detect any dangerous asteroids 572 00:30:46,278 --> 00:30:48,145 heading our way. 573 00:30:48,147 --> 00:30:49,613 Stricker: It's a little bit unnerving to know 574 00:30:49,615 --> 00:30:52,249 that we haven't yet detected all of the asteroids 575 00:30:52,251 --> 00:30:55,085 that exist that could possibly cross our path. 576 00:30:55,087 --> 00:30:57,221 We've discovered a lot of asteroids now, 577 00:30:57,223 --> 00:31:01,091 but we typically discover the big ones. 578 00:31:01,093 --> 00:31:03,894 But for asteroids that are below 100 feet, 579 00:31:03,896 --> 00:31:06,763 there's a lot still out there that we haven't discovered. 580 00:31:06,765 --> 00:31:09,399 And such an asteroid can do some real damage 581 00:31:09,401 --> 00:31:13,470 if it were to explode over a populated area. 582 00:31:13,472 --> 00:31:15,272 Narrator: To prevent such a catastrophe, 583 00:31:15,274 --> 00:31:19,576 we need to find all asteroids whose orbits cross our own. 584 00:31:19,578 --> 00:31:22,813 Detection is crucial in our defense against asteroids. 585 00:31:22,815 --> 00:31:25,883 And the reason is the earlier they're detected, 586 00:31:25,885 --> 00:31:29,853 the easier it is to deflect them away from hitting the earth. 587 00:31:29,855 --> 00:31:32,923 You want to do deflection, the first step is detection. 588 00:31:35,194 --> 00:31:37,728 Narrator: The problem is, asteroids are very hard 589 00:31:37,730 --> 00:31:39,563 to detect. 590 00:31:39,565 --> 00:31:42,165 Finding asteroids and cataloging all their orbits 591 00:31:42,167 --> 00:31:44,167 is really challenging. 592 00:31:44,169 --> 00:31:46,403 They can move quite fast across the sky, 593 00:31:46,405 --> 00:31:48,305 and they might go away 594 00:31:48,307 --> 00:31:53,110 on the other side of the sun for years and years and years. 595 00:31:53,112 --> 00:31:56,613 Narrator: So we can't see them. 596 00:31:56,615 --> 00:31:59,316 And even when they are on this side of the sun, 597 00:31:59,318 --> 00:32:02,085 they're hard to spot. 598 00:32:02,087 --> 00:32:03,921 But the problem is, they're very small 599 00:32:03,923 --> 00:32:05,322 and they're very dark, 600 00:32:05,324 --> 00:32:07,491 and when I say very dark, I mean really dark, 601 00:32:07,493 --> 00:32:08,825 like a lump of coal. 602 00:32:08,827 --> 00:32:11,194 So how do you find a small, dark rock 603 00:32:11,196 --> 00:32:13,830 just wandering around out there in the solar system? 604 00:32:18,671 --> 00:32:22,306 Narrator: The catalina sky survey has the answer. 605 00:32:24,643 --> 00:32:28,345 The huge telescope in the mountains above tucson, arizona, 606 00:32:28,347 --> 00:32:33,116 takes a series of images over a 20-minute period. 607 00:32:33,118 --> 00:32:35,986 It's hunting for anything that moves 608 00:32:35,988 --> 00:32:39,756 because stars don't move, but asteroids do. 609 00:32:42,261 --> 00:32:44,394 Man: If it's a really bright asteroid, 610 00:32:44,396 --> 00:32:46,730 we will see some bright points 611 00:32:46,732 --> 00:32:50,901 of light tracking across the four images. 612 00:32:50,903 --> 00:32:53,670 Ah, here we go. 613 00:32:53,672 --> 00:32:55,605 This is a real object. 614 00:32:55,607 --> 00:32:58,275 You can see it's moving across the sky here 615 00:32:58,277 --> 00:33:00,777 from the lower right to the upper left. 616 00:33:00,779 --> 00:33:04,081 We are very, very excited to have discovered one tonight 617 00:33:04,083 --> 00:33:07,985 because this is an object that's approaching near space, 618 00:33:07,987 --> 00:33:10,887 likely in the neighborhood of earth. 619 00:33:14,560 --> 00:33:16,793 Narrator: Catalina has limitations. 620 00:33:16,795 --> 00:33:19,596 It can only see visible light, 621 00:33:19,598 --> 00:33:25,202 so a particularly dim asteroid could be missed. 622 00:33:25,204 --> 00:33:26,703 Thaller: Asteroids are very cold. 623 00:33:26,705 --> 00:33:28,638 They're usually quite far away from the sun, 624 00:33:28,640 --> 00:33:30,073 but amazingly, the best way 625 00:33:30,075 --> 00:33:32,843 we have to find these is infrared light 626 00:33:32,845 --> 00:33:35,278 because things that are cold by human scales 627 00:33:35,280 --> 00:33:37,914 can still be very warm to an infrared telescope. 628 00:33:37,916 --> 00:33:40,684 So even if asteroids are just a few tens of degrees 629 00:33:40,686 --> 00:33:41,818 above absolute zero, 630 00:33:41,820 --> 00:33:45,522 that's still enough heat to detect them. 631 00:33:45,524 --> 00:33:48,225 Narrator: When the infrared space telescope neowise 632 00:33:48,227 --> 00:33:51,361 turned its gaze onto asteroids, 633 00:33:51,363 --> 00:33:53,864 it had immediate results. 634 00:33:53,866 --> 00:33:55,365 Thaller: Neowise has now detected 635 00:33:55,367 --> 00:34:00,237 close to 160,000 new asteroids and comets in our solar system, 636 00:34:00,239 --> 00:34:02,139 and about 780 of those 637 00:34:02,141 --> 00:34:04,307 are things that are near the earth. 638 00:34:04,309 --> 00:34:07,110 Narrator: 10 of those near objects have been classified 639 00:34:07,112 --> 00:34:12,616 as p.H.A.S -- potentially hazardous asteroids. 640 00:34:12,618 --> 00:34:15,986 Without neowise, we would have missed them. 641 00:34:15,988 --> 00:34:17,487 Using an infrared space telescope 642 00:34:17,489 --> 00:34:22,792 is a way of of better detecting some of the smaller asteroids 643 00:34:22,794 --> 00:34:26,263 and comets in the near earth vicinity. 644 00:34:26,265 --> 00:34:29,066 Narrator: Detection is an important first step, 645 00:34:29,068 --> 00:34:30,333 but it only tells us 646 00:34:30,335 --> 00:34:32,969 that there is another asteroid out there. 647 00:34:32,971 --> 00:34:34,905 Once we've spotted an asteroid, 648 00:34:34,907 --> 00:34:37,774 all we know is that it's a tiny dot of light. 649 00:34:37,776 --> 00:34:40,210 We don't know anything else about it. 650 00:34:40,212 --> 00:34:42,145 So when a new asteroid is discovered, 651 00:34:42,147 --> 00:34:43,413 the most important thing is 652 00:34:43,415 --> 00:34:45,916 to determine its path, to track it, to figure out 653 00:34:45,918 --> 00:34:47,751 exactly how it's orbiting around the sun 654 00:34:47,753 --> 00:34:49,519 and how close it's gonna get to earth. 655 00:34:49,521 --> 00:34:51,254 For that, we have to know where they are now -- 656 00:34:51,256 --> 00:34:54,925 so its current location -- and measure how fast it's going 657 00:34:54,927 --> 00:34:57,060 and which direction it's travelling. 658 00:34:57,062 --> 00:34:59,162 All of these things together are really important 659 00:34:59,164 --> 00:35:00,997 for tracking where it's gonna be next 660 00:35:00,999 --> 00:35:03,166 and whether or not they're gonna hit us. 661 00:35:05,370 --> 00:35:06,636 Narrator: To get this information, 662 00:35:06,638 --> 00:35:09,539 we need something much bigger and more powerful. 663 00:35:11,910 --> 00:35:14,911 The arecibo observatory. 664 00:35:14,913 --> 00:35:16,947 Once catalina or another telescope 665 00:35:16,949 --> 00:35:20,717 detects a near earth asteroid in our cosmic neighborhood, 666 00:35:20,719 --> 00:35:26,056 arecibo's thousand-foot dish swings into action. 667 00:35:26,058 --> 00:35:27,824 They discover these asteroids, 668 00:35:27,826 --> 00:35:30,827 and then once we know where they were, 669 00:35:30,829 --> 00:35:33,530 we can try and point the radio telescope 670 00:35:33,532 --> 00:35:35,365 and see where they are at the moment 671 00:35:35,367 --> 00:35:40,570 and measure their exact location and their trajectory. 672 00:35:40,572 --> 00:35:43,540 Narrator: Arecibo achieves this level of precision 673 00:35:43,542 --> 00:35:46,510 by using radio detection and ranging, 674 00:35:46,512 --> 00:35:49,246 more commonly known as radar. 675 00:35:49,248 --> 00:35:51,948 The planetary radar system at arecibo observatory 676 00:35:51,950 --> 00:35:55,051 is the most powerful radar system in the world. 677 00:35:55,053 --> 00:35:58,054 We focus on potentially hazardous asteroids, 678 00:35:58,056 --> 00:36:03,393 which are those that have a high probability of impacting earth. 679 00:36:03,395 --> 00:36:05,328 Narrator: Arecibo sends out radio signals 680 00:36:05,330 --> 00:36:07,330 toward the newly detected asteroid. 681 00:36:07,332 --> 00:36:09,466 Sutter: It emanates radio signals. 682 00:36:09,468 --> 00:36:14,137 Some of them hit the asteroid just like a radar gun from a cop 683 00:36:14,139 --> 00:36:16,139 might hit the side of your car. 684 00:36:16,141 --> 00:36:17,374 Zambrano-marin: That's pretty similar, 685 00:36:17,376 --> 00:36:19,209 but instead of doing it with a radar gun 686 00:36:19,211 --> 00:36:21,945 on the small scale, we're doing at a really big scale 687 00:36:21,947 --> 00:36:25,115 with one megawatt power hitting objects that are 688 00:36:25,117 --> 00:36:27,350 tens of lunar distances away. 689 00:36:27,352 --> 00:36:30,887 Sutter: And then those radio waves bounce back to earth 690 00:36:30,889 --> 00:36:35,158 and we detect them again, and by comparing the differences 691 00:36:35,160 --> 00:36:38,195 between what we sent and what we received, 692 00:36:38,197 --> 00:36:41,765 we can get a map of the asteroid itself 693 00:36:41,767 --> 00:36:46,603 and we can get where it's moving and how fast it's moving. 694 00:36:46,605 --> 00:36:49,639 Narrator: Speed, size, and location of strike 695 00:36:49,641 --> 00:36:53,710 determine the outcome of an asteroid impact. 696 00:36:53,712 --> 00:36:57,180 But the type of asteroid is another factor. 697 00:36:57,182 --> 00:36:59,950 It can mean the difference between survival 698 00:36:59,952 --> 00:37:02,686 or complete annihilation. 699 00:37:15,601 --> 00:37:19,803 ♪ 700 00:37:19,805 --> 00:37:23,440 narrator: The bering sea asteroid blew up in the atmosphere, 701 00:37:23,442 --> 00:37:27,544 but the barringer crater asteroid hit the ground intact 702 00:37:27,546 --> 00:37:29,179 with its full force. 703 00:37:31,516 --> 00:37:35,018 Why do different asteroids behave differently? 704 00:37:35,020 --> 00:37:38,521 And what will apophis do when it heads our way? 705 00:37:40,692 --> 00:37:44,594 Arecibo's radar may have the answer. 706 00:37:44,596 --> 00:37:47,631 When we bounce radar waves off of these objects, 707 00:37:47,633 --> 00:37:51,034 we can get effectively imagery of the surface 708 00:37:51,036 --> 00:37:52,602 of some of these small objects 709 00:37:52,604 --> 00:37:56,406 that we just cannot do with optical telescopes. 710 00:37:56,408 --> 00:37:59,242 Narrator: This is the radar image of apophis. 711 00:37:59,244 --> 00:38:02,912 It's so far away that all they could image were a few pixels. 712 00:38:05,751 --> 00:38:08,418 So this is our most recent radar image 713 00:38:08,420 --> 00:38:11,421 of asteroid apophis. 714 00:38:11,423 --> 00:38:14,791 And you can see it's only a few pixels, 715 00:38:14,793 --> 00:38:16,893 but it does give us information 716 00:38:16,895 --> 00:38:20,563 on what it actually is. 717 00:38:20,565 --> 00:38:23,133 Narrator: These few pixels are enough to work out 718 00:38:23,135 --> 00:38:26,736 how big apophis is. 719 00:38:26,738 --> 00:38:29,739 Virkki: From this image, we can constrain the size 720 00:38:29,741 --> 00:38:32,042 to be about 1,000 feet, 721 00:38:32,044 --> 00:38:34,678 which is about the same size as the arecibo 722 00:38:34,680 --> 00:38:37,080 radio telescope. 723 00:38:37,082 --> 00:38:40,517 All of that from what were a bunch of pixels. 724 00:38:43,455 --> 00:38:46,222 ♪ 725 00:38:46,224 --> 00:38:48,391 narrator: Knowing the size and mass of an asteroid 726 00:38:48,393 --> 00:38:53,730 is critical to understanding what an asteroid is made of. 727 00:38:53,732 --> 00:38:56,499 If we have the size and the mass, we get the density. 728 00:38:56,501 --> 00:38:58,935 If we have the density, we know what it's made of. 729 00:38:58,937 --> 00:39:02,939 Rock has some density. Metal has a different density. 730 00:39:02,941 --> 00:39:06,009 So we can determine a huge amount about the asteroid 731 00:39:06,011 --> 00:39:08,578 simply by pinging it with radar. 732 00:39:11,550 --> 00:39:13,083 Narrator: Arecibo's data reveals 733 00:39:13,085 --> 00:39:15,518 that not all asteroids are alike. 734 00:39:17,522 --> 00:39:19,556 There's not just one kind of asteroid. 735 00:39:19,558 --> 00:39:21,324 There are actually several kinds, 736 00:39:21,326 --> 00:39:23,226 and this is important to understand 737 00:39:23,228 --> 00:39:25,095 because they behave differently. 738 00:39:25,097 --> 00:39:27,163 They behave differently if they impact us, 739 00:39:27,165 --> 00:39:29,766 and they behave differently if we're trying to prevent them 740 00:39:29,768 --> 00:39:31,101 from impacting us. 741 00:39:31,103 --> 00:39:34,637 We need to know what these asteroids are made of 742 00:39:34,639 --> 00:39:36,005 if they're gonna hit the earth 743 00:39:36,007 --> 00:39:40,310 because that drastically alters the potential effects. 744 00:39:40,312 --> 00:39:43,446 Asteroids come in different shapes, different sizes, 745 00:39:43,448 --> 00:39:46,383 and different compositions, and we think that is 746 00:39:46,385 --> 00:39:49,953 because they are the leftovers of planet formation. 747 00:39:49,955 --> 00:39:52,822 Narrator: To understand how each asteroid formed 748 00:39:52,824 --> 00:39:54,758 and their threat level, we have to go back 749 00:39:54,760 --> 00:40:00,130 4.6 billion years to the start of the solar system. 750 00:40:00,132 --> 00:40:02,132 The reason that there are all these asteroids 751 00:40:02,134 --> 00:40:04,501 floating around in our solar system today 752 00:40:04,503 --> 00:40:07,370 is just because of the early violence of the solar system 753 00:40:07,372 --> 00:40:09,005 as it was forming. 754 00:40:11,810 --> 00:40:13,410 Narrator: At the birth of the solar system, 755 00:40:13,412 --> 00:40:16,446 the sun ignites, 756 00:40:16,448 --> 00:40:19,449 leaving a disk of gas and dust. 757 00:40:22,988 --> 00:40:27,056 Slowly, over time, planets form. 758 00:40:27,058 --> 00:40:29,692 Lots of planets. 759 00:40:29,694 --> 00:40:33,096 Sutter: The early solar system was a messy place. 760 00:40:33,098 --> 00:40:36,466 There were a lot more planets, a lot more forming planets. 761 00:40:36,468 --> 00:40:38,168 They would crash in to each other, 762 00:40:38,170 --> 00:40:40,203 they would merge, they would disintegrate, 763 00:40:40,205 --> 00:40:42,472 they would re-form. 764 00:40:45,210 --> 00:40:48,445 This process of accretion of building planetary worlds 765 00:40:48,447 --> 00:40:51,848 was not just, you know, kind of gentle and happy. 766 00:40:51,850 --> 00:40:54,250 It was violent. 767 00:40:54,252 --> 00:40:57,220 Narrator: It was like a giant cosmic game of pool -- 768 00:40:57,222 --> 00:40:59,889 planet smashing into planet. 769 00:41:03,128 --> 00:41:05,361 The leftovers from this violence 770 00:41:05,363 --> 00:41:09,632 formed a ring of junk between mars and jupiter. 771 00:41:09,634 --> 00:41:12,068 And now we call that junk asteroids. 772 00:41:12,070 --> 00:41:13,837 They're just basically rubble left over 773 00:41:13,839 --> 00:41:16,005 from the formation of the solar system. 774 00:41:20,345 --> 00:41:23,112 Narrator: Rocky leftovers became c-type 775 00:41:23,114 --> 00:41:26,749 or chondrite asteroids. 776 00:41:26,751 --> 00:41:30,353 They're quite dense, so big ones can punch through the atmosphere 777 00:41:30,355 --> 00:41:31,955 and hit the ground. 778 00:41:35,327 --> 00:41:40,296 Radar reveals a rarer type of asteroid. 779 00:41:40,298 --> 00:41:42,899 Some of them really stand out because their density 780 00:41:42,901 --> 00:41:46,970 is so much higher than the rest of the other asteroids. 781 00:41:46,972 --> 00:41:50,540 Narrator: These asteroids are m-type or metal. 782 00:41:53,178 --> 00:41:55,144 Because their mass is great, 783 00:41:55,146 --> 00:41:59,449 they carry more kinetic energy during a strike. 784 00:41:59,451 --> 00:42:03,152 By far, the worst one is this iron meteorite. 785 00:42:03,154 --> 00:42:06,222 This is really heavy, so the difference -- 786 00:42:06,224 --> 00:42:07,690 if you were being hit by this, 787 00:42:07,692 --> 00:42:09,993 it would be the difference between being hit by a rock 788 00:42:09,995 --> 00:42:14,330 and being hit by a metal hammer. 789 00:42:14,332 --> 00:42:16,332 Narrator: We think that both the barringer 790 00:42:16,334 --> 00:42:18,668 and the k-pg dinosaur killer 791 00:42:18,670 --> 00:42:21,104 were caused by metal asteroids. 792 00:42:23,975 --> 00:42:26,643 But there's another more mysterious type 793 00:42:26,645 --> 00:42:28,344 floating through space. 794 00:42:28,346 --> 00:42:34,651 ♪ 795 00:42:34,653 --> 00:42:36,619 December 2018, 796 00:42:36,621 --> 00:42:39,856 nasa's spacecraft osiris-rex approached 797 00:42:39,858 --> 00:42:43,660 the near earth asteroid bennu. 798 00:42:43,662 --> 00:42:46,696 Walsh: Over time, it drifted out of the main asteroid belt, 799 00:42:46,698 --> 00:42:48,865 made its way into the inner solar system, 800 00:42:48,867 --> 00:42:51,000 until it became a near earth asteroid, 801 00:42:51,002 --> 00:42:54,837 accessible for our spacecraft to go and visit. 802 00:42:54,839 --> 00:42:57,574 Narrator: Osiris trained its camera on bennu. 803 00:42:57,576 --> 00:43:04,747 ♪ 804 00:43:04,749 --> 00:43:07,350 one of the biggest surprises on arrival of bennu 805 00:43:07,352 --> 00:43:11,120 was the large number of large boulders on its surface. 806 00:43:11,122 --> 00:43:13,590 Bennu is really littered with huge boulders 807 00:43:13,592 --> 00:43:15,925 and littered with medium-sized boulders 808 00:43:15,927 --> 00:43:18,161 and littered with small boulders. 809 00:43:18,163 --> 00:43:20,830 Narrator: Bennu is not a solid lump of rock. 810 00:43:20,832 --> 00:43:23,533 It's made up of thousands of bits of rock 811 00:43:23,535 --> 00:43:27,136 forming what we call a rubble pile. 812 00:43:27,138 --> 00:43:31,007 These asteroids aren't big, singular, spherical balls 813 00:43:31,009 --> 00:43:32,141 of rock, 814 00:43:32,143 --> 00:43:34,644 but rather they're literally piles of rubble. 815 00:43:34,646 --> 00:43:36,379 They're all sorts of pieces and fragments 816 00:43:36,381 --> 00:43:38,214 from another asteroid that had previously 817 00:43:38,216 --> 00:43:41,217 been disrupted that have all come back together 818 00:43:41,219 --> 00:43:43,987 and formed literally a pile of rocks held together 819 00:43:43,989 --> 00:43:45,555 by their own gravity. 820 00:43:45,557 --> 00:43:48,324 Narrator: We think rubble piles formed from collisions 821 00:43:48,326 --> 00:43:53,563 inside the asteroid belt each impact blasted bits off. 822 00:43:53,565 --> 00:43:56,332 Then, over time, they came back together 823 00:43:56,334 --> 00:43:59,335 to form a loose pile of rocks. 824 00:43:59,337 --> 00:44:01,738 Durda: Imagine taking a big cosmic dump truck 825 00:44:01,740 --> 00:44:03,673 full of gravel and rubble 826 00:44:03,675 --> 00:44:05,541 and dumping it out there in the space 827 00:44:05,543 --> 00:44:08,611 and letting gravity weakly hold it together. 828 00:44:10,782 --> 00:44:13,750 Narrator: When scientists probe deeper into bennu, 829 00:44:13,752 --> 00:44:15,652 they found another surprise. 830 00:44:15,654 --> 00:44:19,656 It's full of holes, like swiss cheese. 831 00:44:19,658 --> 00:44:22,191 If you could slice open one of these asteroids, 832 00:44:22,193 --> 00:44:24,327 you'd see there are a lot of voids. 833 00:44:24,329 --> 00:44:28,231 In fact, 60% of what we're looking at is a void space, 834 00:44:28,233 --> 00:44:30,199 so they're actually really fluffy. 835 00:44:30,201 --> 00:44:31,567 So even though they're made of rocks, 836 00:44:31,569 --> 00:44:35,104 they're sort of the lint of rocks. 837 00:44:35,106 --> 00:44:38,041 Narrator: Bennu helps us understand apophis. 838 00:44:38,043 --> 00:44:43,079 Radar data shows that apophis is also a rubble pile. 839 00:44:43,081 --> 00:44:44,781 If you look at apophis, we really want to know 840 00:44:44,783 --> 00:44:47,083 how its orbit will evolve in the future. 841 00:44:47,085 --> 00:44:49,419 What we learn at bennu about similar-sized 842 00:44:49,421 --> 00:44:51,954 rubble-pile asteroids might help us understand 843 00:44:51,956 --> 00:44:54,991 the future of an asteroid like apophis. 844 00:44:54,993 --> 00:44:57,060 Narrator: So what would happen if the rubble pile 845 00:44:57,062 --> 00:44:59,062 called apophis hits earth? 846 00:44:59,064 --> 00:45:00,963 Durda: You probably don't want that to hit you still, 847 00:45:00,965 --> 00:45:03,166 but it definitely makes it a lot weaker 848 00:45:03,168 --> 00:45:05,435 than something like a solid rock 849 00:45:05,437 --> 00:45:10,206 or even more, a chunk of nickel iron metal. 850 00:45:10,208 --> 00:45:14,043 Narrator: Does its composition make it any less of a threat? 851 00:45:14,045 --> 00:45:17,246 A rubble pile like apophis is especially unnerving 852 00:45:17,248 --> 00:45:19,916 because we don't know, when it interacts with the atmosphere, 853 00:45:19,918 --> 00:45:21,984 if it's gonna stay as one solid piece, 854 00:45:21,986 --> 00:45:24,353 will it break up. 855 00:45:24,355 --> 00:45:27,724 When these rubble piles start interacting with planets, 856 00:45:27,726 --> 00:45:30,293 if they fly near a planet, they can get pulled apart 857 00:45:30,295 --> 00:45:32,128 into all of their little pieces. 858 00:45:32,130 --> 00:45:34,697 Or if they enter the atmosphere of a planet 859 00:45:34,699 --> 00:45:38,301 to impact the surface, they might slowly get pulled apart 860 00:45:38,303 --> 00:45:40,036 as they enter the atmosphere 861 00:45:40,038 --> 00:45:42,505 and end up being an array of little impacts 862 00:45:42,507 --> 00:45:44,407 instead of one big single impact. 863 00:45:46,344 --> 00:45:53,549 ♪ 864 00:45:53,551 --> 00:45:59,322 narrator: But what would happen if these impacts occur at sea? 865 00:45:59,324 --> 00:46:01,290 Will our oceans save us, 866 00:46:01,292 --> 00:46:05,161 or will a giant tsunami wipe us out? 867 00:46:17,375 --> 00:46:19,041 Narrator: 2019, 868 00:46:19,043 --> 00:46:23,613 u.S. Researchers discover deposits of fossils. 869 00:46:23,615 --> 00:46:29,452 They contain both the remains of land and sea creatures. 870 00:46:29,454 --> 00:46:31,854 You see things that are all jumbled together, 871 00:46:31,856 --> 00:46:35,224 so you'll have fossils of sea creatures. 872 00:46:35,226 --> 00:46:39,328 You'll have ocean deposits that are mixed up 873 00:46:39,330 --> 00:46:42,799 with coastal deposits and onshore deposits, 874 00:46:42,801 --> 00:46:45,902 and you see those deposits in places 875 00:46:45,904 --> 00:46:47,270 that are very, very far away 876 00:46:47,272 --> 00:46:49,672 from where you would expect them to be. 877 00:46:49,674 --> 00:46:51,908 And so this material was obviously thrown 878 00:46:51,910 --> 00:46:54,877 very far inland. 879 00:46:54,879 --> 00:46:56,245 Narrator: The jumbled deposits 880 00:46:56,247 --> 00:46:59,649 suggest that the creatures were killed at the same time 881 00:46:59,651 --> 00:47:02,919 in a huge and violent event, 882 00:47:02,921 --> 00:47:04,554 something powerful enough 883 00:47:04,556 --> 00:47:09,692 to sweep ocean-dwelling creatures far inland. 884 00:47:09,694 --> 00:47:11,861 A tsunami. 885 00:47:11,863 --> 00:47:14,030 Tsunamis are usually created 886 00:47:14,032 --> 00:47:17,033 when the ocean floor moves suddenly. 887 00:47:17,035 --> 00:47:19,869 The ground picks up the entire ocean 888 00:47:19,871 --> 00:47:21,771 and shakes it up and down, 889 00:47:21,773 --> 00:47:24,040 and it's sort of like taking a rope and shaking it, 890 00:47:24,042 --> 00:47:26,642 and it moves all across the ocean floor 891 00:47:26,644 --> 00:47:29,145 and ocean surface until it reaches land. 892 00:47:29,147 --> 00:47:33,482 The biggest recent tsunami was caused by the earth's crust 893 00:47:33,484 --> 00:47:35,985 at the bottom of the ocean lifting slightly, 894 00:47:35,987 --> 00:47:39,188 so this means that that entire length of crust 895 00:47:39,190 --> 00:47:42,358 that lifted displaced the water above it, 896 00:47:42,360 --> 00:47:45,361 so the waves, the tsunamis that result, 897 00:47:45,363 --> 00:47:47,496 are really long and wide, 898 00:47:47,498 --> 00:47:49,732 and it can travel across the ocean 899 00:47:49,734 --> 00:47:54,537 at tremendous speeds and up on land. 900 00:47:54,539 --> 00:47:57,139 Narrator: Is this what happened to the fossilized creatures? 901 00:47:57,141 --> 00:48:01,611 Were they killed by a huge tsunami? 902 00:48:01,613 --> 00:48:05,615 Clues come from dating the preserved remains. 903 00:48:05,617 --> 00:48:09,252 They're 66 million years old. 904 00:48:09,254 --> 00:48:11,821 From the same time a six-mile-wide asteroid 905 00:48:11,823 --> 00:48:16,359 crashed into the sea off the yucatán peninsula in mexico. 906 00:48:20,131 --> 00:48:22,331 Are the two events connected? 907 00:48:22,333 --> 00:48:26,869 Do ocean-impacting asteroids trigger tsunamis? 908 00:48:26,871 --> 00:48:28,371 We used to think that a big asteroid 909 00:48:28,373 --> 00:48:31,941 impacting in the ocean would drive a tremendous tsunami, 910 00:48:31,943 --> 00:48:35,745 a huge wall of water out at very rapid speeds, 911 00:48:35,747 --> 00:48:38,848 which would basically scour clean everything. 912 00:48:38,850 --> 00:48:41,817 Narrator: Now new research from 2018 suggests 913 00:48:41,819 --> 00:48:44,353 a very different scenario. 914 00:48:44,355 --> 00:48:47,957 Scientists use super computers to model asteroids 915 00:48:47,959 --> 00:48:51,560 hitting the deep ocean to work out how much of 916 00:48:51,562 --> 00:48:55,865 the asteroid's kinetic energy is converted into a tsunami. 917 00:48:58,770 --> 00:49:02,271 In the simulations, a 1,600-foot asteroid 918 00:49:02,273 --> 00:49:05,408 hits the ocean at 20,000 miles an hour 919 00:49:05,410 --> 00:49:08,978 and dives into the water. 920 00:49:08,980 --> 00:49:12,548 As it goes deeper in, of course it's meeting a lot 921 00:49:12,550 --> 00:49:15,484 of resistance and it slows down and it compresses up. 922 00:49:15,486 --> 00:49:18,921 It compresses and compresses and compresses, and then finally 923 00:49:18,923 --> 00:49:20,589 it runs out of momentum, 924 00:49:20,591 --> 00:49:23,326 and it's at an extremely high pressure. 925 00:49:24,395 --> 00:49:28,931 Narrator: The huge pressure causes the asteroid to vaporize. 926 00:49:28,933 --> 00:49:31,867 Temperatures hotter than the surface of the sun 927 00:49:31,869 --> 00:49:35,938 turn trillions of gallons of water into steam. 928 00:49:36,541 --> 00:49:40,142 The blast creates a huge short lived cavity 929 00:49:40,144 --> 00:49:42,511 in the water's surface 930 00:49:42,513 --> 00:49:44,947 and a splash curtain, a wall of water, 931 00:49:44,949 --> 00:49:47,850 that leaps up several miles. 932 00:49:47,852 --> 00:49:50,786 This curtain then collapses and water falls 933 00:49:50,788 --> 00:49:54,223 back into the cavity, shooting a column of water 934 00:49:54,225 --> 00:49:56,759 five miles up. 935 00:49:56,761 --> 00:49:59,628 Plesko: This very tall column can't support its own weight 936 00:49:59,630 --> 00:50:02,999 and collapses back down. 937 00:50:03,001 --> 00:50:05,534 Narrator: The collapse of so much water triggers 938 00:50:05,536 --> 00:50:08,671 a wave 1,200 feet high. 939 00:50:08,673 --> 00:50:12,074 Could this become a huge tsunami? 940 00:50:16,614 --> 00:50:18,714 If we think about a meteor striking the ocean, 941 00:50:18,716 --> 00:50:21,017 we want to understand how far the waves 942 00:50:21,019 --> 00:50:22,585 might propagate from the site. 943 00:50:22,587 --> 00:50:25,821 We could actually just use a stone and throw it into a pond, 944 00:50:25,823 --> 00:50:27,957 and you might think, "okay, well, it's a big stone, 945 00:50:27,959 --> 00:50:29,325 it's going to make a really big splash, 946 00:50:29,327 --> 00:50:31,794 and that's just going to extend out a long distance." 947 00:50:31,796 --> 00:50:34,964 but it turns out the splash stays the biggest really close 948 00:50:34,966 --> 00:50:36,098 to where it impacts. 949 00:50:36,100 --> 00:50:37,566 And then the ripples die down after that. 950 00:50:37,568 --> 00:50:39,268 So let's try that. 951 00:50:40,571 --> 00:50:43,105 Big splash in the middle. 952 00:50:43,107 --> 00:50:44,573 And we see the ripples going outward, 953 00:50:44,575 --> 00:50:45,941 but they're really pretty small compared 954 00:50:45,943 --> 00:50:48,277 with that initial big splash. 955 00:50:49,680 --> 00:50:53,749 Narrator: It's the same with an ocean impacting asteroid. 956 00:50:53,751 --> 00:50:58,020 The impact creates surface waves that die away quickly 957 00:50:58,022 --> 00:51:01,590 because only a small amount of the asteroid's kinetic energy 958 00:51:01,592 --> 00:51:03,292 gets into the water. 959 00:51:03,294 --> 00:51:05,361 Plait: It's actually pretty tough to make 960 00:51:05,363 --> 00:51:06,629 a tsunami like that. 961 00:51:06,631 --> 00:51:08,931 The energy of the asteroid doesn't couple well 962 00:51:08,933 --> 00:51:11,467 with the water to drive this wave. 963 00:51:11,469 --> 00:51:12,968 Instead, most of the energy 964 00:51:12,970 --> 00:51:15,871 goes into vaporizing the asteroid itself 965 00:51:15,873 --> 00:51:19,075 as well as all of the water around it. 966 00:51:19,077 --> 00:51:21,844 Narrator: Only 1% of the asteroid's kinetic energy 967 00:51:21,846 --> 00:51:24,013 goes into making a wave. 968 00:51:24,015 --> 00:51:28,451 So only low energy waves form, too weak to become 969 00:51:28,453 --> 00:51:32,855 giant tsunamis traveling hundreds of miles. 970 00:51:32,857 --> 00:51:35,558 So what caused the jumbled fossil deposits 971 00:51:35,560 --> 00:51:39,829 found thousands of miles away from the impact site? 972 00:51:39,831 --> 00:51:41,797 Radebaugh: We don't think there could be that much energy 973 00:51:41,799 --> 00:51:45,768 still transmitted that far away from the impact site. 974 00:51:45,770 --> 00:51:48,637 Instead, there has to be a different source of energy 975 00:51:48,639 --> 00:51:50,639 that created different waves 976 00:51:50,641 --> 00:51:53,676 right about the same time as that impact event. 977 00:51:55,480 --> 00:51:58,814 Narrator: Research from 2019 may have the answer. 978 00:51:58,816 --> 00:52:02,685 The kpg asteroid struck on the continental shelf, 979 00:52:02,687 --> 00:52:06,222 the shallow region between land and deep ocean. 980 00:52:06,224 --> 00:52:10,159 The impact triggered a localized tsunami large enough 981 00:52:10,161 --> 00:52:13,095 to kill creatures in the region. 982 00:52:13,097 --> 00:52:16,532 But it also sent a huge shock wave into the bedrock. 983 00:52:18,402 --> 00:52:20,035 There's going to be a shock wave driven 984 00:52:20,037 --> 00:52:21,303 through the ground. 985 00:52:21,305 --> 00:52:23,772 That probably would have killed anything in the area. 986 00:52:23,774 --> 00:52:28,511 If you had a dinosaur that was standing on 987 00:52:28,513 --> 00:52:33,149 the gulf coast of what is now the united states, 988 00:52:33,151 --> 00:52:38,621 that animal would have experienced a seismic pulse, 989 00:52:38,623 --> 00:52:41,390 an earthquake that is stronger than anything 990 00:52:41,392 --> 00:52:43,225 on our current richter scale. 991 00:52:43,227 --> 00:52:46,428 It would have actually driven its legs up into its body cavity 992 00:52:46,430 --> 00:52:47,596 killing it instantly. 993 00:52:47,598 --> 00:52:50,499 There's all manner of mayhem and death 994 00:52:50,501 --> 00:52:51,901 taking place at this time. 995 00:52:51,903 --> 00:52:53,903 There was no escaping this event. 996 00:52:55,573 --> 00:52:59,275 Narrator: The initial shock wave smashed into the ground rock 997 00:52:59,277 --> 00:53:03,045 and traveled through the earth's crust. 998 00:53:03,047 --> 00:53:06,682 The impact would have shaken the crust of the earth, 999 00:53:06,684 --> 00:53:09,618 which also would have triggered earthquakes around the world, 1000 00:53:09,620 --> 00:53:13,622 which themselves may have triggered secondary salamis. 1001 00:53:16,694 --> 00:53:19,929 Narrator: Secondary tsunamis thousands of miles from 1002 00:53:19,931 --> 00:53:24,099 the impact site killed both land and sea creatures. 1003 00:53:24,101 --> 00:53:31,507 The kpg impact went on to wipe out 70% of all life on earth. 1004 00:53:31,509 --> 00:53:37,146 So how did one asteroid strike cause a global kill zone? 1005 00:53:37,148 --> 00:53:39,348 ♪ 1006 00:53:46,023 --> 00:53:55,364 ♪ 1007 00:53:55,366 --> 00:54:00,402 narrator: 66 million years ago, 70% of life on earth died 1008 00:54:00,404 --> 00:54:03,639 after the kpg asteroid strike. 1009 00:54:07,345 --> 00:54:10,980 How could one space rocket hitting the sea cause 1010 00:54:10,982 --> 00:54:13,082 a global catastrophe? 1011 00:54:14,485 --> 00:54:17,253 Lanza: When you have a big rock hitting the ocean, 1012 00:54:17,255 --> 00:54:19,855 the biggest danger is not from the waves 1013 00:54:19,857 --> 00:54:23,559 but actually from the steam that it creates. 1014 00:54:23,561 --> 00:54:27,630 Narrator: The impact vaporized trillions of tons of seawater. 1015 00:54:27,632 --> 00:54:30,566 This steam rose up into the atmosphere 1016 00:54:30,568 --> 00:54:34,236 where it condensed into water vapor. 1017 00:54:34,238 --> 00:54:36,305 Water vapor is a greenhouse gas. 1018 00:54:36,307 --> 00:54:39,408 So that's done going up into the upper atmosphere, 1019 00:54:39,410 --> 00:54:42,177 and it's trapping heat, 1020 00:54:42,179 --> 00:54:44,413 but at different layers it's making clouds. 1021 00:54:44,415 --> 00:54:47,049 It's just throwing everything off kilter. 1022 00:54:47,051 --> 00:54:49,485 Water is a very effective greenhouse gas as you 1023 00:54:49,487 --> 00:54:52,988 will actually affect some very significant climate change 1024 00:54:52,990 --> 00:54:55,591 very quickly as a result of that impact. 1025 00:54:57,495 --> 00:54:59,695 Narrator: Within weeks of the asteroid strike, 1026 00:54:59,697 --> 00:55:03,999 water vapor in the atmosphere caused temperatures to rise. 1027 00:55:05,102 --> 00:55:07,703 But that was only the start. 1028 00:55:08,873 --> 00:55:13,042 The impact also blew out 10 trillion tons of rock, 1029 00:55:13,044 --> 00:55:15,311 ash, and dust. 1030 00:55:16,681 --> 00:55:20,115 This asteroid is so big, six miles wide. 1031 00:55:20,117 --> 00:55:21,784 It's punched a hole in the air. 1032 00:55:21,786 --> 00:55:24,486 There's like a column of low density, a chimney, 1033 00:55:24,488 --> 00:55:27,523 that goes from the ground up to the top of the atmosphere. 1034 00:55:27,525 --> 00:55:29,858 And that means there's very little air resistance 1035 00:55:29,860 --> 00:55:31,427 in that tunnel. 1036 00:55:31,429 --> 00:55:34,196 These rocks can actually blast up into the chimney 1037 00:55:34,198 --> 00:55:36,899 and find it easier to get up out of the atmosphere. 1038 00:55:36,901 --> 00:55:40,369 It sent that material flying up halfway 1039 00:55:40,371 --> 00:55:43,739 to the orbit of the moon, circled around the earth. 1040 00:55:43,741 --> 00:55:47,843 All this ring of material falling back on to the earth. 1041 00:55:47,845 --> 00:55:51,580 And it was like the sky itself was on fire. 1042 00:55:51,582 --> 00:55:53,549 Lanza: So not only do you have rocks falling on you, 1043 00:55:53,551 --> 00:55:56,085 but they're molten, and these rocks 1044 00:55:56,087 --> 00:56:00,556 will start catching plants and anything else on fire. 1045 00:56:00,558 --> 00:56:05,494 ♪ 1046 00:56:05,496 --> 00:56:09,331 narrator: Soot and ash rose into the atmosphere 1047 00:56:09,333 --> 00:56:11,633 blocking out the sun. 1048 00:56:13,604 --> 00:56:16,004 Material was thrown into the atmosphere, 1049 00:56:16,006 --> 00:56:18,507 plunging the planet into a nuclear winter. 1050 00:56:18,509 --> 00:56:24,780 It was complete chaos, and it went dark for two full years. 1051 00:56:24,782 --> 00:56:27,816 Narrator: Without sunlight, temperatures dropped. 1052 00:56:29,587 --> 00:56:34,957 Just months after the impact, the planet cooled by 20 degrees. 1053 00:56:35,726 --> 00:56:38,560 In the immediate area, there's just tremendous destruction. 1054 00:56:38,562 --> 00:56:40,462 Just everything gets destroyed. 1055 00:56:40,464 --> 00:56:43,031 But over the long term, you're talking about ash 1056 00:56:43,033 --> 00:56:46,602 kicked up in the atmosphere, extremely cold weather, 1057 00:56:46,604 --> 00:56:48,871 basically a global ice age. 1058 00:56:50,040 --> 00:56:52,174 Narrator: The freezing temperatures killed off 1059 00:56:52,176 --> 00:56:54,143 most plant life. 1060 00:56:54,145 --> 00:56:56,678 Oluseyi: Imagine how that affected life on earth. 1061 00:56:56,680 --> 00:57:00,682 No plants and the base of the ecosystem collapses. 1062 00:57:04,388 --> 00:57:07,923 Narrator: This dark nuclear winter lasted two years 1063 00:57:07,925 --> 00:57:12,027 and prevented plants from photosynthesizing. 1064 00:57:12,029 --> 00:57:14,630 So if plants can no longer use photosynthesis 1065 00:57:14,632 --> 00:57:16,632 to live, they'll die. 1066 00:57:16,634 --> 00:57:19,368 And then with no plants, then you have no food 1067 00:57:19,370 --> 00:57:21,036 for these larger animals. 1068 00:57:21,038 --> 00:57:23,972 And so anything that eats those animals will also die. 1069 00:57:23,974 --> 00:57:25,207 If you lose your plants, 1070 00:57:25,209 --> 00:57:28,410 you're going to lose your large scale life. 1071 00:57:28,412 --> 00:57:31,547 Narrator: First the plant eating herbivores died off, 1072 00:57:31,549 --> 00:57:35,384 followed by the meat eating carnivores. 1073 00:57:35,386 --> 00:57:39,021 Most of the dinosaurs were just unable to find food 1074 00:57:39,023 --> 00:57:42,024 and to survive through the cold long night. 1075 00:57:43,794 --> 00:57:46,829 Narrator: The global devastation wasn't over yet. 1076 00:57:46,831 --> 00:57:50,199 The rock of the continental shelf where the asteroid hit 1077 00:57:50,201 --> 00:57:52,801 contained carbon and sulfur. 1078 00:57:54,405 --> 00:57:58,006 Lanza: These carbonate rocks were heated and vaporized 1079 00:57:58,008 --> 00:58:00,876 and released carbon dioxide into the atmosphere. 1080 00:58:00,878 --> 00:58:02,978 Yet another greenhouse gas. 1081 00:58:02,980 --> 00:58:05,981 So you're vaporizing a lot of sulfur, 1082 00:58:05,983 --> 00:58:08,817 a lot of salts of different kinds 1083 00:58:08,819 --> 00:58:12,554 that are then lofted up into the upper atmosphere, 1084 00:58:12,556 --> 00:58:15,324 that then plays havoc on the climate. 1085 00:58:19,463 --> 00:58:23,265 Narrator: These greenhouse gases built up in the atmosphere 1086 00:58:23,267 --> 00:58:25,667 forming a warming blanket. 1087 00:58:28,672 --> 00:58:31,740 Triggering the next phase of destruction. 1088 00:58:34,578 --> 00:58:37,279 Global warming on steroids. 1089 00:58:39,583 --> 00:58:44,253 Temperatures rose 10 degrees above normal. 1090 00:58:44,255 --> 00:58:48,357 Then the oceans warmed, as well. 1091 00:58:48,359 --> 00:58:51,894 Oxygen levels dropped, and the seas became toxic 1092 00:58:51,896 --> 00:58:55,297 to simple life forms. 1093 00:58:55,299 --> 00:58:58,300 It actually made it impossible for certain microbes 1094 00:58:58,302 --> 00:59:01,803 to actually live, and they're the basis of the food system. 1095 00:59:01,805 --> 00:59:05,807 So really it changed what could actually live in the ocean 1096 00:59:05,809 --> 00:59:09,444 and how much could live there. 1097 00:59:09,446 --> 00:59:11,680 Narrator: Dead zones appeared in the oceans 1098 00:59:11,682 --> 00:59:14,583 just as they had on land. 1099 00:59:14,585 --> 00:59:20,455 Nearly three quarters of all life on earth died, 1100 00:59:20,457 --> 00:59:23,659 all from one asteroid impact. 1101 00:59:27,765 --> 00:59:29,765 To prevent it from happening again, 1102 00:59:29,767 --> 00:59:33,635 we need to track all potentially dangerous asteroids. 1103 00:59:35,806 --> 00:59:37,105 But that isn't easy 1104 00:59:37,107 --> 00:59:40,676 because these space rocks can change direction. 1105 00:59:54,391 --> 00:59:57,192 ♪ 1106 00:59:57,194 --> 00:59:59,761 narrator: Saricicek, turkey. 1107 00:59:59,763 --> 01:00:02,998 Security cameras record a flash in the sky. 1108 01:00:04,902 --> 01:00:10,138 The flash -- a 3-foot asteroid exploding in the atmosphere. 1109 01:00:10,140 --> 01:00:16,078 ♪ 1110 01:00:16,080 --> 01:00:18,880 lanza: It blew up in the atmosphere and rained down, 1111 01:00:18,882 --> 01:00:20,148 and people saw that. 1112 01:00:20,150 --> 01:00:21,650 It was very noticeable. 1113 01:00:21,652 --> 01:00:24,219 And they went, and they collected those meteorites. 1114 01:00:24,221 --> 01:00:27,990 And then they tried to figure out what they were looking at. 1115 01:00:30,494 --> 01:00:34,129 Narrator: The debris was sent for fragment analysis. 1116 01:00:35,432 --> 01:00:38,300 I have a piece of one here. So first, on the outside, 1117 01:00:38,302 --> 01:00:40,702 you can see it has a really black fusion crust. 1118 01:00:40,704 --> 01:00:42,604 This is from when it fell into the earth's atmosphere, 1119 01:00:42,606 --> 01:00:44,039 so it was melted. 1120 01:00:44,041 --> 01:00:46,375 But when you look on the inside, it reveals 1121 01:00:46,377 --> 01:00:50,612 this beautiful, very light tone, fine grained material. 1122 01:00:50,614 --> 01:00:53,515 And so these meteorites are incredibly distinctive 1123 01:00:53,517 --> 01:00:55,417 and really beautiful. 1124 01:00:55,419 --> 01:00:57,352 Narrator: The meteorites are rocky. 1125 01:00:57,354 --> 01:01:01,657 They're beautiful color comes from a mineral called howardite. 1126 01:01:01,659 --> 01:01:06,528 It's rare, and it doesn't form on earth. 1127 01:01:06,530 --> 01:01:09,931 Howardite meteorites come from the asteroid vesta, 1128 01:01:09,933 --> 01:01:12,701 and we know that because of the dawn mission 1129 01:01:12,703 --> 01:01:14,836 that actually went to vesta and took a look at it 1130 01:01:14,838 --> 01:01:17,906 very carefully, so we know the composition very well. 1131 01:01:17,908 --> 01:01:20,676 And so now suddenly here was a new kind of meteorite 1132 01:01:20,678 --> 01:01:26,114 that's in turkey that matches the vesta family of meteorites 1133 01:01:26,950 --> 01:01:30,118 narrator: But how can we be sure that these bits of space rock 1134 01:01:30,120 --> 01:01:35,724 came from vesta, an asteroid over 100 million miles away. 1135 01:01:35,726 --> 01:01:38,427 It was a fall meteorite, and so what that means 1136 01:01:38,429 --> 01:01:41,296 is that someone saw it, you know, we saw it fall. 1137 01:01:41,298 --> 01:01:43,265 And so we knew its trajectory. 1138 01:01:43,267 --> 01:01:46,034 So we could actually work backwards to say, 1139 01:01:46,036 --> 01:01:48,837 where did that meteorite come from? 1140 01:01:48,839 --> 01:01:50,806 Narrator: Retracing the trajectory of 1141 01:01:50,808 --> 01:01:54,943 the turkish meteorites took the scientists all the way back 1142 01:01:54,945 --> 01:01:57,946 to the 328-mile wide vesta. 1143 01:02:02,086 --> 01:02:04,086 Where they studied vesta's surface, 1144 01:02:04,088 --> 01:02:06,621 they found further evidence. 1145 01:02:06,623 --> 01:02:09,725 On the surface of vesta, there's actually a very large 1146 01:02:09,727 --> 01:02:13,295 and fresh impact crater that is around the same age 1147 01:02:13,297 --> 01:02:14,963 of the turkish meteorite. 1148 01:02:14,965 --> 01:02:17,099 So that really clinched it. 1149 01:02:17,101 --> 01:02:20,802 This thing is definitely from vesta, and we proved it. 1150 01:02:20,804 --> 01:02:25,006 Narrator: So how did bits of vesta end up here on earth? 1151 01:02:25,008 --> 01:02:29,044 22 million years ago, some very large impactor 1152 01:02:29,046 --> 01:02:32,013 struck vesta, made a huge crater, 1153 01:02:32,015 --> 01:02:34,883 and some of the rocks from that crater actually 1154 01:02:34,885 --> 01:02:40,589 escaped from vesta's gravity and were lofted into space. 1155 01:02:40,591 --> 01:02:43,325 Narrator: Some of these rocks from vesta went into orbits 1156 01:02:43,327 --> 01:02:45,894 that intersected with earth. 1157 01:02:46,430 --> 01:02:51,133 22 million years later, one blew up over saricicek. 1158 01:02:54,204 --> 01:02:57,372 This saricicek meteor shows that the asteroid belt 1159 01:02:57,374 --> 01:02:59,174 is an unstable environment. 1160 01:03:01,945 --> 01:03:05,347 Asteroids frequently strike other asteroids. 1161 01:03:08,051 --> 01:03:09,451 Lanza: That's actually happening all the time. 1162 01:03:09,453 --> 01:03:10,986 Things are running into each other 1163 01:03:10,988 --> 01:03:13,121 in our solar system right now. 1164 01:03:13,123 --> 01:03:14,890 And so that makes it really hard for us 1165 01:03:14,892 --> 01:03:18,026 to track all of those objects because we don't actually know 1166 01:03:18,028 --> 01:03:20,228 what happens after they collide with each other. 1167 01:03:20,230 --> 01:03:21,897 Now things are totally different. 1168 01:03:21,899 --> 01:03:24,566 And that changes the whole system. 1169 01:03:24,568 --> 01:03:29,137 Narrator: Each collision makes more asteroids. 1170 01:03:29,139 --> 01:03:30,806 Oluseyi: There's many different possibilities 1171 01:03:30,808 --> 01:03:33,308 of what could happen when asteroids collide. 1172 01:03:33,310 --> 01:03:36,211 Imagine a roller derby situation. 1173 01:03:38,649 --> 01:03:40,682 If you have two groups of players 1174 01:03:40,684 --> 01:03:42,050 that run into each other, 1175 01:03:42,052 --> 01:03:45,253 that could be like two asteroids running into each other. 1176 01:03:45,255 --> 01:03:49,257 And one possible outcome is that one stays intact 1177 01:03:49,259 --> 01:03:51,693 while the other is completely blown apart. 1178 01:03:54,698 --> 01:03:58,099 That sends fragments flying all through the main asteroid belt, 1179 01:03:58,101 --> 01:04:00,068 and then there's a little asteroid fragments 1180 01:04:00,070 --> 01:04:03,138 are on their own independent orbits around the sun. 1181 01:04:04,374 --> 01:04:06,675 A problem with asteroid impacts is that 1182 01:04:06,677 --> 01:04:08,677 we're always making new asteroids. 1183 01:04:08,679 --> 01:04:10,445 There are big asteroids out there, 1184 01:04:10,447 --> 01:04:11,947 and they get hit by other asteroids, 1185 01:04:11,949 --> 01:04:13,415 and then you get shrapnel. 1186 01:04:13,417 --> 01:04:16,117 And now you've got not one big one and one smaller one, 1187 01:04:16,119 --> 01:04:17,853 you've got one big one, one smaller one, 1188 01:04:17,855 --> 01:04:19,621 and millions of little ones. 1189 01:04:19,623 --> 01:04:22,591 Now, most of these aren't very big, but some of them might be 1190 01:04:22,593 --> 01:04:25,160 bigger and could be potentially hazardous. 1191 01:04:26,563 --> 01:04:28,463 Narrator: As the solar system ages, 1192 01:04:28,465 --> 01:04:31,166 the number of asteroids increases. 1193 01:04:31,168 --> 01:04:34,369 Each new space rock travels on a new course 1194 01:04:34,371 --> 01:04:38,006 which could intersect with earth. 1195 01:04:38,008 --> 01:04:40,575 So we're constantly producing new asteroids 1196 01:04:40,577 --> 01:04:42,944 and big collisions in the main asteroid belt. 1197 01:04:42,946 --> 01:04:44,746 And these are producing the small asteroids 1198 01:04:44,748 --> 01:04:49,050 that will eventually drift inward in the solar system. 1199 01:04:49,052 --> 01:04:51,686 Narrator: Tracking this constantly evolving population 1200 01:04:51,688 --> 01:04:55,924 of asteroids gives scientists a huge headache. 1201 01:04:55,926 --> 01:04:58,126 If they break apart, then that gives you 1202 01:04:58,128 --> 01:05:00,629 even more pieces of the asteroid to track. 1203 01:05:00,631 --> 01:05:04,032 It's not a simple thing to track and predict 1204 01:05:04,034 --> 01:05:07,502 the orbits of asteroids and their movements, 1205 01:05:07,504 --> 01:05:11,673 because one tiny little change 1206 01:05:11,675 --> 01:05:17,746 can have huge dramatic impacts for its possible future. 1207 01:05:17,748 --> 01:05:19,714 Bullock: Figuring out exactly where they're going to go 1208 01:05:19,716 --> 01:05:22,050 and keeping track of how they interact with each other, 1209 01:05:22,052 --> 01:05:24,386 this is a huge endeavor. 1210 01:05:24,388 --> 01:05:27,122 Narrator: The sheer volume of asteroids can affect 1211 01:05:27,124 --> 01:05:29,157 the behavior of other asteroids 1212 01:05:29,159 --> 01:05:32,627 as they gravitationally interact. 1213 01:05:32,629 --> 01:05:36,464 Think about your roller derby player skating in circles. 1214 01:05:36,466 --> 01:05:38,266 The path they're going to follow would evolve 1215 01:05:38,268 --> 01:05:41,136 the more people you plop down on the track 1216 01:05:41,138 --> 01:05:42,604 they start interacting with each other, 1217 01:05:42,606 --> 01:05:44,839 and their trajectory will change. 1218 01:05:46,109 --> 01:05:48,410 The more crowded you make the solar system, 1219 01:05:48,412 --> 01:05:50,845 the more things are to change your orbit 1220 01:05:50,847 --> 01:05:53,848 of your individual asteroid. 1221 01:05:55,052 --> 01:05:56,851 It's not like air traffic control, 1222 01:05:56,853 --> 01:05:58,920 where there's a known amount of airplanes 1223 01:05:58,922 --> 01:06:00,755 and they all follow a plan. 1224 01:06:02,225 --> 01:06:04,859 Narrator: This situation is further complicated because 1225 01:06:04,861 --> 01:06:09,898 asteroid orbits can be affected by other more subtle forces. 1226 01:06:10,834 --> 01:06:14,636 One of these is called the yarkovsky or the yorp effect. 1227 01:06:14,638 --> 01:06:17,272 Honestly yorp is more fun to say. 1228 01:06:17,274 --> 01:06:19,941 Narrator: The yorp effect is caused by sunlight 1229 01:06:19,943 --> 01:06:22,110 hitting an asteroid. 1230 01:06:22,112 --> 01:06:24,646 Light is made up of photons that are traveling, 1231 01:06:24,648 --> 01:06:27,115 and these photons actually have momentum. 1232 01:06:27,117 --> 01:06:29,084 So when light shines on something, 1233 01:06:29,086 --> 01:06:31,086 it actually pushes on it. 1234 01:06:33,023 --> 01:06:34,990 Narrator: When sunlight hits an asteroid, 1235 01:06:34,992 --> 01:06:38,259 the photons give it a tiny push... 1236 01:06:39,396 --> 01:06:43,031 ...Enough to change the space rock's trajectory. 1237 01:06:43,033 --> 01:06:48,670 ♪ 1238 01:06:48,672 --> 01:06:51,539 when we know an asteroid is really heading our way, 1239 01:06:51,541 --> 01:06:54,075 it's time to fight back. 1240 01:06:54,077 --> 01:06:56,011 So we've got an asteroid that's headed at us. 1241 01:06:56,013 --> 01:06:57,112 What do we do? 1242 01:06:57,114 --> 01:06:59,147 Two main possibilities -- we deflect it, 1243 01:06:59,149 --> 01:07:01,116 we nudge it a little bit so it misses, 1244 01:07:01,118 --> 01:07:03,418 or we blow it up, we destroy it. 1245 01:07:03,420 --> 01:07:05,487 Which of those do you want to do? 1246 01:07:05,489 --> 01:07:11,059 ♪ 1247 01:07:11,061 --> 01:07:13,628 narrator: It's a tough choice. 1248 01:07:13,630 --> 01:07:18,166 Get it wrong, and we could end up being hit by a swarm 1249 01:07:18,168 --> 01:07:20,802 of radioactive space rocks. 1250 01:07:20,804 --> 01:07:28,009 ♪ 1251 01:07:38,021 --> 01:07:41,756 ♪ 1252 01:07:41,758 --> 01:07:44,559 narrator: An asteroid is heading our way, 1253 01:07:44,561 --> 01:07:47,295 and it may hit us in 2068. 1254 01:07:48,165 --> 01:07:50,732 How do we prevent such a catastrophe 1255 01:07:50,734 --> 01:07:54,569 and stop it from ever getting close? 1256 01:07:54,571 --> 01:07:56,337 Well, you just don't want to take get anywhere near us 1257 01:07:56,339 --> 01:07:57,605 in the first place. 1258 01:07:57,607 --> 01:07:58,706 So what do you do? 1259 01:07:58,708 --> 01:08:01,309 Well, you can destroy them, 1260 01:08:01,311 --> 01:08:04,512 or you can push them out of the way. 1261 01:08:04,514 --> 01:08:06,748 This is something where our science fiction ideas 1262 01:08:06,750 --> 01:08:08,716 have got it almost entirely wrong. 1263 01:08:08,718 --> 01:08:13,354 If you're in a bad movie, a really, really bad movie, 1264 01:08:13,356 --> 01:08:16,024 you can send astronauts to an asteroid, 1265 01:08:16,026 --> 01:08:17,559 put a nuclear bomb in it, 1266 01:08:17,561 --> 01:08:19,427 and blow it up into lots of little bits 1267 01:08:19,429 --> 01:08:21,896 that then burn up harmlessly in our atmosphere. 1268 01:08:21,898 --> 01:08:24,666 Yeah, it doesn't work that way. 1269 01:08:24,668 --> 01:08:26,134 Narrator: Blowing up an asteroid 1270 01:08:26,136 --> 01:08:28,503 would make the problem much worse. 1271 01:08:28,505 --> 01:08:31,906 We are no longer dealing with just one space rock. 1272 01:08:31,908 --> 01:08:34,375 My issue with this is that you may have turned 1273 01:08:34,377 --> 01:08:36,344 one problem into 50. 1274 01:08:36,346 --> 01:08:38,546 Instead of one regular sized asteroid, 1275 01:08:38,548 --> 01:08:40,615 now you have a whole bunch of littler ones, 1276 01:08:40,617 --> 01:08:42,784 and these may still hit the earth and cause damage. 1277 01:08:42,786 --> 01:08:45,520 And you know what? That's not much less fun 1278 01:08:45,522 --> 01:08:47,789 than just having a single big asteroid. 1279 01:08:47,791 --> 01:08:49,424 Now you've just taken all that devastation 1280 01:08:49,426 --> 01:08:52,494 and spread it out for everybody to enjoy. 1281 01:08:52,496 --> 01:08:55,330 Stricker: The problem with using a nuclear device is that 1282 01:08:55,332 --> 01:08:59,200 the products that rain down on earth are now radioactive. 1283 01:08:59,202 --> 01:09:07,709 ♪ 1284 01:09:07,711 --> 01:09:10,845 narrator: If a dangerous asteroid was on its way, 1285 01:09:10,847 --> 01:09:13,581 blowing it up would be a last resort. 1286 01:09:14,751 --> 01:09:17,452 A less risky method is to deflect it off 1287 01:09:17,454 --> 01:09:19,621 its collision course. 1288 01:09:19,623 --> 01:09:21,823 A small nudge early enough 1289 01:09:21,825 --> 01:09:25,493 can change in asteroid's trajectory away from earth. 1290 01:09:26,863 --> 01:09:30,265 You don't have to nudge it very much for it to miss, right? 1291 01:09:30,267 --> 01:09:32,000 So if it's headed straight at it, 1292 01:09:32,002 --> 01:09:33,301 I just touch it slightly, 1293 01:09:33,303 --> 01:09:36,204 by the time it gets to earth, its way off course. 1294 01:09:38,141 --> 01:09:40,742 Narrator: Nasa is investigating ways to change 1295 01:09:40,744 --> 01:09:46,748 an asteroid's path, including using a nuclear burst. 1296 01:09:46,750 --> 01:09:51,886 In a nuclear burst, what we do is we don't actually hit it. 1297 01:09:51,888 --> 01:09:56,257 We come up to it with the device on a spacecraft, 1298 01:09:56,259 --> 01:09:58,993 and then the device would be detonated at a certain height 1299 01:09:58,995 --> 01:10:01,329 above the surface. 1300 01:10:01,331 --> 01:10:03,298 Plait: That heats up the surface of the asteroid, 1301 01:10:03,300 --> 01:10:04,799 which vaporizes. 1302 01:10:04,801 --> 01:10:07,502 You get vaporized rock or metal which blasts off the surface, 1303 01:10:07,504 --> 01:10:09,437 and that's how a rocket works. 1304 01:10:09,439 --> 01:10:11,906 So you blow up a bomb here, and it winds up 1305 01:10:11,908 --> 01:10:15,610 pushing the asteroid in the other direction 1306 01:10:15,612 --> 01:10:18,313 narrator: To prevent any potential nuclear fallout, 1307 01:10:18,315 --> 01:10:21,749 nasa would detonate the bomb a long way from earth 1308 01:10:23,186 --> 01:10:26,754 plesko: Any deflection attempt has to be done years in advance, 1309 01:10:26,756 --> 01:10:28,356 which means it would be done on the other side 1310 01:10:28,358 --> 01:10:30,291 of the solar system from us 1311 01:10:30,293 --> 01:10:33,061 on the opposite side of the object's orbit. 1312 01:10:33,063 --> 01:10:35,697 That means that all of the vapor made during 1313 01:10:35,699 --> 01:10:38,299 the explosion gets blown away by the solar wind. 1314 01:10:39,869 --> 01:10:43,605 Narrator: Nasa is investigating other less explosive methods 1315 01:10:43,607 --> 01:10:45,807 of deflecting an asteroid. 1316 01:10:45,809 --> 01:10:49,777 De-star would blast the asteroid with a laser. 1317 01:10:49,779 --> 01:10:52,747 Oluseyi: We hit it with the laser, material vaporizes 1318 01:10:52,749 --> 01:10:54,882 and flies off the asteroid, 1319 01:10:54,884 --> 01:10:56,784 and because of newton's third law, 1320 01:10:56,786 --> 01:10:58,753 which is that for every action there is an opposite 1321 01:10:58,755 --> 01:11:02,423 an equal reaction, this means that vaporize material 1322 01:11:02,425 --> 01:11:04,926 moving off in one direction moves the asteroid 1323 01:11:04,928 --> 01:11:07,228 in the opposite direction. 1324 01:11:08,665 --> 01:11:10,732 Narrator: Both the laser and the nuclear burst 1325 01:11:10,734 --> 01:11:13,568 are still just ideas on the drawing board. 1326 01:11:16,306 --> 01:11:19,340 But one asteroid deflection mission called 1327 01:11:19,342 --> 01:11:23,544 double asteroid redirection test, or dart for short, 1328 01:11:23,546 --> 01:11:28,049 is already up and running and scheduled for launch in 2021. 1329 01:11:29,619 --> 01:11:31,586 Dart is a kinetic impactor 1330 01:11:31,588 --> 01:11:35,089 and will try to knock an asteroid off course. 1331 01:11:36,593 --> 01:11:38,826 Thaller: At nasa for the longest time, all we've been able to do 1332 01:11:38,828 --> 01:11:41,262 is theorize about how we change their path. 1333 01:11:41,264 --> 01:11:42,363 But now for the first time, 1334 01:11:42,365 --> 01:11:44,866 we're actually gonna practice in. 1335 01:11:44,868 --> 01:11:47,035 Narrator: Leading this groundbreaking mission to bump 1336 01:11:47,037 --> 01:11:51,572 an asteroid off its orbit is dr. Andy chang. 1337 01:11:51,574 --> 01:11:54,876 Chang: Dart is the first planetary defense mission 1338 01:11:54,878 --> 01:11:57,478 that we've ever done, where we take a spacecraft, 1339 01:11:57,480 --> 01:12:01,649 we fly the spacecraft into the asteroid to change 1340 01:12:01,651 --> 01:12:04,585 its course and make it miss the earth. 1341 01:12:04,587 --> 01:12:07,955 Narrator: Dart's target is a 525 foot space rock 1342 01:12:07,957 --> 01:12:12,894 orbiting the large near earth asteroid didymos. 1343 01:12:12,896 --> 01:12:15,129 We pick the near earth asteroid didymos as a target 1344 01:12:15,131 --> 01:12:16,998 for the dart mission because although it's 1345 01:12:17,000 --> 01:12:19,334 a near earth asteroid, it's one that's very safely 1346 01:12:19,336 --> 01:12:20,868 parked away out there in space. 1347 01:12:20,870 --> 01:12:23,104 There's no way we can move didymos or its moon 1348 01:12:23,106 --> 01:12:25,740 in any way big enough to cause a problem for the earth. 1349 01:12:27,677 --> 01:12:29,877 Narrator: The diddy-moon asteroid weighs 1350 01:12:29,879 --> 01:12:33,381 around 10 1/2 billion pounds. 1351 01:12:33,383 --> 01:12:36,551 So how do you knock such a large lump of rock 1352 01:12:36,553 --> 01:12:38,853 off its path? 1353 01:12:50,266 --> 01:12:53,301 ♪ 1354 01:12:53,303 --> 01:12:54,736 narrator: We're sending a spacecraft 1355 01:12:54,738 --> 01:12:58,206 to knock the diddy-moon asteroid off course. 1356 01:12:59,342 --> 01:13:02,944 The asteroid is moving at over 36,000 miles an hour 1357 01:13:02,946 --> 01:13:06,681 and is around seven million miles away. 1358 01:13:06,683 --> 01:13:10,151 So how do you move a 10 and a half billion pound 1359 01:13:10,153 --> 01:13:12,687 space rock? 1360 01:13:12,689 --> 01:13:15,790 You need to hit it really hard to change its orbit, 1361 01:13:15,792 --> 01:13:19,861 so it's going to be coming in at a super high velocity 1362 01:13:19,863 --> 01:13:23,164 in order to impart a bunch of energy momentum to that moon. 1363 01:13:25,001 --> 01:13:26,868 Narrator: Dart will hit the target 1364 01:13:26,870 --> 01:13:29,570 at around 14,000 miles an hour. 1365 01:13:29,572 --> 01:13:33,674 The speed of the dart impact will be more than nine times 1366 01:13:33,676 --> 01:13:37,078 the speed of the rifle bullet from an ak-47. 1367 01:13:39,015 --> 01:13:42,550 Narrator: The impact will give the asteroid a small push. 1368 01:13:42,552 --> 01:13:44,852 To work out how big a push, 1369 01:13:44,854 --> 01:13:49,323 we test impacts with the ames vertical gun. 1370 01:13:49,325 --> 01:13:51,759 Durda: At the nasa ames research center in california, 1371 01:13:51,761 --> 01:13:53,394 there's a very special facility called 1372 01:13:53,396 --> 01:13:55,496 the ames vertical gun range. 1373 01:13:55,498 --> 01:13:57,732 It's a hyper velocity gas gun that allows us 1374 01:13:57,734 --> 01:14:01,869 to shoot little metal bbs at rock targets at speeds 1375 01:14:01,871 --> 01:14:05,940 up to like 13,000, 14,000 miles per hour. 1376 01:14:05,942 --> 01:14:07,875 Narrator: The gun replicates the impact 1377 01:14:07,877 --> 01:14:09,977 the dart mission will make. 1378 01:14:09,979 --> 01:14:12,513 It reveals that an impact will blow off 1379 01:14:12,515 --> 01:14:16,484 a small amount of debris but at extremely high speed, 1380 01:14:16,486 --> 01:14:20,354 enough to give the asteroid an additional kick. 1381 01:14:20,356 --> 01:14:22,957 The impact will blow off pieces of the asteroid, 1382 01:14:22,959 --> 01:14:25,293 so the pieces are thrown off the back. 1383 01:14:25,295 --> 01:14:28,963 And so that that process acts like a little rocket engine. 1384 01:14:28,965 --> 01:14:31,966 That provides an additional momentum change, 1385 01:14:31,968 --> 01:14:34,836 momentum push to the target itself. 1386 01:14:34,838 --> 01:14:37,205 Narrator: The combined push from the kinetic impactor 1387 01:14:37,207 --> 01:14:40,274 and the ejected debris is tiny, 1388 01:14:40,276 --> 01:14:43,444 around 0.0009 of a mile per hour. 1389 01:14:43,446 --> 01:14:46,981 But hopefully it's enough to change the asteroid's orbit. 1390 01:14:46,983 --> 01:14:50,418 If dart works, we could then use a similar mission 1391 01:14:50,420 --> 01:14:53,287 to defend earth when the time comes. 1392 01:14:54,257 --> 01:14:56,757 This isn't some small rock prototype 1393 01:14:56,759 --> 01:14:58,259 that we're doing this test on. 1394 01:14:58,261 --> 01:15:01,496 This is a real dress rehearsal for an asteroid 1395 01:15:01,498 --> 01:15:03,564 that could destroy cities 1396 01:15:03,566 --> 01:15:06,901 or even maybe send the earth in chaos. 1397 01:15:06,903 --> 01:15:10,271 Narrator: The moon of didymos is a solid lump of rock. 1398 01:15:10,273 --> 01:15:13,040 Will a kinetic impactor like dart work 1399 01:15:13,042 --> 01:15:16,143 with a rubble pile asteroid like apophis? 1400 01:15:16,145 --> 01:15:18,145 When you shoot a rubble pile with a projectile, 1401 01:15:18,147 --> 01:15:20,047 it's a little bit more like trying to punch a sandbag. 1402 01:15:20,049 --> 01:15:22,750 You get a lot more a lot more the energy is absorbed 1403 01:15:22,752 --> 01:15:25,620 into just moving the sand around inside the bag 1404 01:15:25,622 --> 01:15:27,755 than ejecting it, and so rubble piles 1405 01:15:27,757 --> 01:15:30,892 might be a little harder to move by this method. 1406 01:15:31,895 --> 01:15:34,896 Narrator: We don't know if we can deflect a rubble pile 1407 01:15:34,898 --> 01:15:36,998 asteroid like apophis. 1408 01:15:37,000 --> 01:15:40,101 They remain a clear and present danger. 1409 01:15:40,970 --> 01:15:43,938 And something we might not survive. 1410 01:15:47,310 --> 01:15:50,845 But there may be a space lifeboat. 1411 01:15:55,718 --> 01:16:00,855 In 2018, scientists reexamined rocks collected by apollo 14 1412 01:16:00,857 --> 01:16:02,990 astronauts from the moon. 1413 01:16:02,992 --> 01:16:09,363 ♪ 1414 01:16:09,365 --> 01:16:14,168 buried in the samples was a rock that shouldn't be there. 1415 01:16:15,471 --> 01:16:18,272 They got something they didn't expect, 1416 01:16:18,274 --> 01:16:20,641 and that was an earth rock. 1417 01:16:20,643 --> 01:16:24,679 They actually picked up a rock from earth on the moon. 1418 01:16:24,681 --> 01:16:26,347 They didn't bring it with them. 1419 01:16:26,349 --> 01:16:29,383 It's very likely that it was something that was lofted up 1420 01:16:29,385 --> 01:16:34,121 when something hit earth, throw up a bunch of rocks. 1421 01:16:34,123 --> 01:16:36,324 Some of those rocks fell on to the moon, 1422 01:16:36,326 --> 01:16:39,327 and that's a meteorite on the moon, 1423 01:16:39,329 --> 01:16:41,562 but it's from earth. 1424 01:16:45,568 --> 01:16:47,435 Narrator: Super computer simulations of 1425 01:16:47,437 --> 01:16:52,206 the kpg asteroid strike revealed how the impact had so much 1426 01:16:52,208 --> 01:16:56,510 energy that it catapulted rocks out of earth's atmosphere 1427 01:16:56,512 --> 01:16:58,412 and into space. 1428 01:16:58,414 --> 01:17:00,581 They were then caught by the moon's gravity 1429 01:17:00,583 --> 01:17:03,718 and pulled down to the lunar surface. 1430 01:17:03,720 --> 01:17:09,557 We now know the material ejected into space from asteroid impacts 1431 01:17:09,559 --> 01:17:12,093 can travel to other planets, as well, 1432 01:17:12,095 --> 01:17:15,796 which would explain the 100 mars meteorites 1433 01:17:15,798 --> 01:17:17,431 we've found here on earth. 1434 01:17:20,069 --> 01:17:22,637 We think that there was probably the exchange of a huge amount 1435 01:17:22,639 --> 01:17:24,705 of material between different bodies, 1436 01:17:24,707 --> 01:17:27,508 earth to the moon and back again and to mars. 1437 01:17:30,647 --> 01:17:33,147 With each impact that occurs in our solar system 1438 01:17:33,149 --> 01:17:36,751 that ejects all types of material that allows material 1439 01:17:36,753 --> 01:17:40,354 to swap from planet to planet, moon to planet, moon to moon. 1440 01:17:40,356 --> 01:17:41,856 And so there's all of this material 1441 01:17:41,858 --> 01:17:44,959 that eventually travels from place to place. 1442 01:17:44,961 --> 01:17:48,062 Narrator: Should another giant asteroid hit our planet, 1443 01:17:48,064 --> 01:17:52,833 this planetary interchange may give life on earth 1444 01:17:52,835 --> 01:17:54,802 a lifeline. 1445 01:17:54,804 --> 01:17:57,471 Lanza: If you think about such an impact today, 1446 01:17:57,473 --> 01:18:00,675 you know, the chances are high that a lot of life would be 1447 01:18:00,677 --> 01:18:05,079 wiped out, much of life, probably all of human life. 1448 01:18:05,081 --> 01:18:08,249 It's certainly possible that a big enough asteroid strike 1449 01:18:08,251 --> 01:18:10,251 could completely sterilize the planet. 1450 01:18:10,253 --> 01:18:13,187 Talking about no life whatsoever. 1451 01:18:13,189 --> 01:18:14,922 Not to put too fine a point on it, 1452 01:18:14,924 --> 01:18:16,991 but if there's a dinosaur killer asteroid out there 1453 01:18:16,993 --> 01:18:19,460 and it hits the earth, the chance of humanity's 1454 01:18:19,462 --> 01:18:23,531 survival of such a thing as a species, mm, not great. 1455 01:18:27,270 --> 01:18:29,503 Narrator: Humans may not survive. 1456 01:18:29,505 --> 01:18:35,109 But some scientists believe that simple life forms could. 1457 01:18:35,111 --> 01:18:39,346 ♪ 1458 01:18:50,193 --> 01:18:55,696 ♪ 1459 01:18:55,698 --> 01:18:58,566 narrator: Asteroids have hit our planet many times 1460 01:18:58,568 --> 01:19:00,134 in the past. 1461 01:19:01,637 --> 01:19:06,540 One giant strike wiped out 70% of all life on earth. 1462 01:19:07,477 --> 01:19:12,113 If another huge asteroid hits us, can life survive? 1463 01:19:12,115 --> 01:19:17,017 ♪ 1464 01:19:17,019 --> 01:19:20,287 sutter: If a giant rock hits the earth and kills almost 1465 01:19:20,289 --> 01:19:25,960 all life on earth, there is a slim line of hope. 1466 01:19:25,962 --> 01:19:29,864 And that's because the dirt, the rocks on earth 1467 01:19:29,866 --> 01:19:35,369 are infused with bacterial life, with microscopic life. 1468 01:19:35,371 --> 01:19:37,905 And in the event of a giant impact, 1469 01:19:37,907 --> 01:19:42,009 some of these bits of rock will be ejected into space 1470 01:19:42,011 --> 01:19:43,477 and might float around. 1471 01:19:43,479 --> 01:19:46,347 After an asteroid impact, whatever ejected 1472 01:19:46,349 --> 01:19:49,216 into the atmosphere could contain microbial life 1473 01:19:49,218 --> 01:19:51,852 that when it falls back down on to the ground 1474 01:19:51,854 --> 01:19:54,488 could re-seed the life on that planet. 1475 01:19:54,490 --> 01:19:59,426 ♪ 1476 01:19:59,428 --> 01:20:02,229 narrator: Some bacteria can survive the harsh conditions 1477 01:20:02,231 --> 01:20:06,934 of space and can cope with an asteroid strike, reentry, 1478 01:20:06,936 --> 01:20:10,037 and landing back on earth's surface. 1479 01:20:10,039 --> 01:20:19,246 ♪ 1480 01:20:19,248 --> 01:20:22,616 I think in terms of life on planet earth, 1481 01:20:22,618 --> 01:20:25,319 I think we've learned that we live on a very resilient planet. 1482 01:20:25,321 --> 01:20:28,222 And I think life in some form, even if it has to crawl 1483 01:20:28,224 --> 01:20:31,091 its way back from bacterial stage, 1484 01:20:31,093 --> 01:20:34,862 I think life on this planet is going to going to eke through. 1485 01:20:36,232 --> 01:20:40,634 Plait: Life is pretty good at figuring out a way of surviving. 1486 01:20:40,636 --> 01:20:43,070 We know that life first formed on the earth 1487 01:20:43,072 --> 01:20:45,239 well over 4 billion years ago 1488 01:20:45,241 --> 01:20:48,275 and has never been wiped out in all of that time. 1489 01:20:48,277 --> 01:20:49,777 There's always been something 1490 01:20:49,779 --> 01:20:52,146 after every major mass extinction. 1491 01:20:52,148 --> 01:20:57,117 So life will continue. It just won't necessarily be us. 1492 01:20:58,120 --> 01:21:00,754 Narrator: An asteroid strike on another world 1493 01:21:00,756 --> 01:21:04,124 may be how life on earth started in the first place. 1494 01:21:04,126 --> 01:21:07,061 Bullock: There's an interesting idea that an asteroid strike 1495 01:21:07,063 --> 01:21:10,164 on another planet could have actually seeded life on earth. 1496 01:21:10,166 --> 01:21:12,233 And the way this works is, you have a life 1497 01:21:12,235 --> 01:21:15,803 that's somehow gotten a foothold on some other planet like mars, 1498 01:21:15,805 --> 01:21:18,038 a big asteroid strike hits that planet 1499 01:21:18,040 --> 01:21:21,208 and knocks a piece of it off, eventually rains down on earth, 1500 01:21:21,210 --> 01:21:25,112 carrying with it life. 1501 01:21:25,114 --> 01:21:30,451 We may owe the existence of life here to asteroid impacts. 1502 01:21:32,855 --> 01:21:35,789 That's speculative, but it's kind of a cool thought. 1503 01:21:38,094 --> 01:21:41,228 Narrator: Life seeding asteroids may have hit us in the past, 1504 01:21:41,230 --> 01:21:44,465 and other asteroids will hit us in the future. 1505 01:21:47,737 --> 01:21:50,004 One of those maybe apophis, 1506 01:21:50,006 --> 01:21:53,107 arriving in less than half a century. 1507 01:21:54,477 --> 01:21:57,678 Maybe we'll deflect it. 1508 01:21:57,680 --> 01:22:02,116 Maybe it'll miss us all on its own. 1509 01:22:02,118 --> 01:22:05,252 Either way, we need to keep tabs on it. 1510 01:22:06,622 --> 01:22:08,789 Thaller: The best thing we can do as a species, and it's funny 1511 01:22:08,791 --> 01:22:10,457 because it almost sounds like I'm advocating 1512 01:22:10,459 --> 01:22:12,293 for more jobs for astronomers. 1513 01:22:12,295 --> 01:22:14,028 We need to keep looking at the sky. 1514 01:22:14,030 --> 01:22:16,196 We need look at the sky longer and deeper, 1515 01:22:16,198 --> 01:22:17,898 with more sensitive instruments 1516 01:22:17,900 --> 01:22:20,567 and get more of a sense of what out there is around us. 1517 01:22:20,569 --> 01:22:24,738 That's what our species needs to do to ultimately survive. 1518 01:22:24,740 --> 01:22:26,507 Because now we have the ability 1519 01:22:26,509 --> 01:22:28,809 to see these things a little bit better, 1520 01:22:28,811 --> 01:22:30,678 we have the ability to protect ourselves better. 1521 01:22:30,680 --> 01:22:32,613 It doesn't have to be a surprise. 1522 01:22:32,615 --> 01:22:35,049 You know, the first time we see a big impact doesn't have to be 1523 01:22:35,051 --> 01:22:37,318 as it's bearing down destroying our planet. 1524 01:22:37,320 --> 01:22:39,853 We can actually see it before it gets to us 1525 01:22:39,855 --> 01:22:42,389 and decide what we want to do about it. 1526 01:22:43,526 --> 01:22:47,828 Narrator: Earth's history is littered with asteroid strikes. 1527 01:22:47,830 --> 01:22:51,598 Some wiped out millions of species. 1528 01:22:51,600 --> 01:22:55,803 Some may have seeded life in the first place. 1529 01:22:55,805 --> 01:22:58,205 What the future holds and our relationship 1530 01:22:58,207 --> 01:23:01,942 with these space rocks, no one knows. 1531 01:23:02,678 --> 01:23:06,447 Even though the chances of something really large hitting 1532 01:23:06,449 --> 01:23:10,384 the earth are pretty small, the consequences are dire. 1533 01:23:10,386 --> 01:23:13,420 It would really destroy our planet or at least life 1534 01:23:13,422 --> 01:23:15,155 as we understand it. 1535 01:23:15,157 --> 01:23:18,425 And so in many ways, asteroids are the greatest 1536 01:23:18,427 --> 01:23:20,060 threat that we face. 1537 01:23:20,062 --> 01:23:24,398 Life is fragile, so of course we live in a larger environment 1538 01:23:24,400 --> 01:23:26,834 where something could come and hit us at any time. 1539 01:23:26,836 --> 01:23:28,402 That's part of being alive. 1540 01:23:28,404 --> 01:23:30,704 There's no guarantee tomorrow will happen. 1541 01:23:30,706 --> 01:23:33,340 But what there is is a high likelihood 1542 01:23:33,342 --> 01:23:35,209 that you'll still be safe tomorrow. 1543 01:23:37,947 --> 01:23:40,748 Bullock: Impacts from space are rare, 1544 01:23:40,750 --> 01:23:43,384 but if they do happen, it's a huge deal. 1545 01:23:43,386 --> 01:23:45,619 And so you've got to put those two things together. 1546 01:23:45,621 --> 01:23:48,489 That means we got to pay attention. 1547 01:23:48,491 --> 01:23:51,191 Durda: Those impacts have happened many times in the past, 1548 01:23:51,193 --> 01:23:54,128 and they're going to continue to happen many times in the future. 1549 01:23:54,130 --> 01:23:57,464 Fortunately it's not probably in our immediate future. 1550 01:23:57,466 --> 01:24:02,002 Impacts are rare, but the earth lives a long time. 1551 01:24:02,004 --> 01:24:04,271 So you're unlikely to get in a car accident, 1552 01:24:04,273 --> 01:24:07,441 but if you drive enough, you're going to get in a car accident. 1553 01:24:10,212 --> 01:24:11,779 Plait: Over a century time scale, 1554 01:24:11,781 --> 01:24:14,048 yes, we should be concerned about these. 1555 01:24:14,050 --> 01:24:17,317 But over the daily, weekly, monthly, even yearly time scale, 1556 01:24:17,319 --> 01:24:19,153 I wouldn't sweat it too much. 1557 01:24:19,155 --> 01:24:21,688 I wouldn't say we should lose sleep over an asteroid 1558 01:24:21,690 --> 01:24:23,257 or comet striking earth, 1559 01:24:23,259 --> 01:24:26,260 but the reality is it will happen again. 1560 01:24:28,864 --> 01:24:31,031 Thaller: So when you think about asteroid strikes, 1561 01:24:31,033 --> 01:24:33,000 remember this wonderful dramatic universe 1562 01:24:33,002 --> 01:24:34,435 you find yourself in. 1563 01:24:34,437 --> 01:24:37,171 We're here because stars died and exploded. 1564 01:24:37,173 --> 01:24:39,173 Life on earth wouldn't be the same 1565 01:24:39,175 --> 01:24:41,208 if we didn't find ourselves in this dramatic 1566 01:24:41,210 --> 01:24:43,510 and even dangerous environment in space. 1567 01:24:43,512 --> 01:24:46,213 But this is who we are. This is nothing new. 1568 01:24:46,215 --> 01:24:49,083 And this will continue for the future of our planet. 1569 01:24:49,085 --> 01:24:55,989 ♪