1 00:00:05,271 --> 00:00:07,773 ROWE: Comets... messengers from 2 00:00:07,874 --> 00:00:09,408 the dawn of the solar system. 3 00:00:11,478 --> 00:00:15,080 For the first time, we sent a spacecraft 4 00:00:15,181 --> 00:00:17,116 to orbit and land on one. 5 00:00:20,887 --> 00:00:23,489 OLUSEYI: To go outside of the inner solar system 6 00:00:23,590 --> 00:00:26,492 and catch a speeding comet 7 00:00:26,593 --> 00:00:30,396 and then send a lander down to land on its surface... 8 00:00:30,497 --> 00:00:32,097 That is nuts. 9 00:00:33,433 --> 00:00:34,933 ROWE: The Rosetta mission answers 10 00:00:35,035 --> 00:00:37,202 our most fundamental questions. 11 00:00:37,303 --> 00:00:40,372 SUTTER: Rosetta is really teaching us 12 00:00:40,473 --> 00:00:43,175 how comets live in real time. 13 00:00:43,276 --> 00:00:44,743 This is a game changer. 14 00:00:44,844 --> 00:00:46,812 ROWE: Rosetta changes our understanding 15 00:00:46,913 --> 00:00:49,448 of the cosmos forever. 16 00:00:49,549 --> 00:00:53,485 The secrets of life itself may be wrapped up on Comet 67P. 17 00:00:53,586 --> 00:00:55,654 ♪♪ 18 00:00:55,755 --> 00:00:57,389 [electricity buzzing] 19 00:01:03,396 --> 00:01:06,665 ♪♪ 20 00:01:06,733 --> 00:01:09,768 ROWE: 530 million miles from the sun, 21 00:01:09,869 --> 00:01:12,571 a tiny lump of ice and rock 22 00:01:12,672 --> 00:01:15,874 starts its journey towards the inner solar system. 23 00:01:18,178 --> 00:01:20,279 THALLER: Scientifically, comets are more precious 24 00:01:20,380 --> 00:01:24,216 than pure gold... They're actual time capsules. 25 00:01:24,317 --> 00:01:26,819 They're preservations of what the chemistry, the environment 26 00:01:26,920 --> 00:01:28,921 was like when our solar system formed, 27 00:01:29,022 --> 00:01:32,858 and they hold clues as to how our chemistry arrived 28 00:01:32,959 --> 00:01:34,359 here on Earth... Comets are some of 29 00:01:34,461 --> 00:01:36,929 the most valuable scientific treasures that exist. 30 00:01:38,498 --> 00:01:42,568 ROWE: Finding a comet we can study is not an easy task. 31 00:01:42,669 --> 00:01:44,229 Finding the right comet for a mission... 32 00:01:44,304 --> 00:01:46,705 It's kind of like you're auditioning them, right? 33 00:01:46,806 --> 00:01:49,775 One comes in, and it's like, oh, the other orbit's okay, 34 00:01:49,876 --> 00:01:51,977 but it's not exactly what we're looking for. 35 00:01:52,078 --> 00:01:53,345 And, oh, this one is too big. 36 00:01:53,446 --> 00:01:55,447 This one's too little. This one's too active. 37 00:01:57,250 --> 00:02:00,619 WALSH: What we really want to see is that comet come from 38 00:02:00,720 --> 00:02:03,455 outer parts of the solar system and get heated up as it 39 00:02:03,556 --> 00:02:04,756 gets close to the sun, 40 00:02:04,858 --> 00:02:07,192 pass around the sun and head back out to the outer part of 41 00:02:07,293 --> 00:02:09,628 the solar system, so you need to get way out in 42 00:02:09,729 --> 00:02:12,231 the solar system and catch a comet on its way in. 43 00:02:13,333 --> 00:02:15,901 ROWE: Comet 67P fits the bill. 44 00:02:17,170 --> 00:02:19,705 The special thing about Comet 67P 45 00:02:19,806 --> 00:02:21,940 is how accessible it is here on Earth. 46 00:02:22,041 --> 00:02:25,244 It actually orbits around the sun once every 6.5 years, 47 00:02:25,345 --> 00:02:27,479 and its orbit doesn't take it all that far out, 48 00:02:27,547 --> 00:02:29,515 only about this far out of the planet Jupiter. 49 00:02:29,616 --> 00:02:31,250 That gives us many chances to actually 50 00:02:31,351 --> 00:02:33,652 reach the comet and successfully rendezvous with it. 51 00:02:35,021 --> 00:02:36,301 [announcer speaking indistinctly] 52 00:02:37,891 --> 00:02:41,226 ROWE: 67P's moment in the spotlight arrived. 53 00:02:41,327 --> 00:02:42,895 [announcer speaking indistinctly] 54 00:02:42,996 --> 00:02:46,398 The European Space Agency launched the groundbreaking 55 00:02:46,499 --> 00:02:47,566 Rosetta probe. 56 00:02:49,269 --> 00:02:51,670 PLAIT: For years, we've studied comets from afar. 57 00:02:51,771 --> 00:02:53,739 We had never seen one up close 58 00:02:53,840 --> 00:02:55,807 with cutting-edge technology to 59 00:02:55,909 --> 00:02:59,077 learn about how comets behave as they orbit the sun. 60 00:03:02,515 --> 00:03:07,519 ROWE: Missions to large, planet-sized objects are hard. 61 00:03:07,620 --> 00:03:11,023 The Hubble space telescope's blurry images revealed 62 00:03:11,124 --> 00:03:14,826 Rosetta's target is just two miles wide, 63 00:03:14,928 --> 00:03:18,130 and not just a small target, a moving one. 64 00:03:19,632 --> 00:03:23,268 Comet 67P races through the solar system 65 00:03:23,369 --> 00:03:25,804 at over 33,000 miles an hour. 66 00:03:27,874 --> 00:03:30,342 The precision involved is pretty incredible. 67 00:03:30,443 --> 00:03:31,877 It's like making that hole-in-one 68 00:03:31,978 --> 00:03:34,379 golf shot from New York to San Francisco. 69 00:03:34,480 --> 00:03:39,418 ROWE: But catching Comet 67P wasn't just a straight shot. 70 00:03:40,486 --> 00:03:43,488 The spacecraft had to actually get the same velocity 71 00:03:43,590 --> 00:03:46,391 as the comet, and with current propulsion systems, 72 00:03:46,492 --> 00:03:49,294 we can't achieve that by flying directly to the comet. 73 00:03:51,864 --> 00:03:54,866 ROWE: Instead, Rosetta performed a slingshot 74 00:03:54,968 --> 00:03:57,469 maneuver that would take 10 years. 75 00:04:01,207 --> 00:04:02,718 SHERIDAN: So what it's doing, it's actually taking 76 00:04:02,742 --> 00:04:04,509 some energy away from the planet, 77 00:04:04,611 --> 00:04:07,279 so it's slowing the planet down a little bit and then 78 00:04:07,380 --> 00:04:09,948 imparting that energy into the probe. 79 00:04:12,518 --> 00:04:15,220 ROWE: Rosetta flew past Jupiter 80 00:04:15,321 --> 00:04:17,823 nearly 100 million miles from the warmth of 81 00:04:17,924 --> 00:04:22,327 the sun and entered the most dangerous part of its journey, 82 00:04:24,030 --> 00:04:25,931 hibernation. 83 00:04:26,032 --> 00:04:28,043 RADEBAUGH: Even though Rosetta had solar panels on it, 84 00:04:28,067 --> 00:04:30,469 it still had to be put to sleep, and the reason for that 85 00:04:30,570 --> 00:04:33,839 is that it had to track 67P a ways away from the sun, 86 00:04:33,940 --> 00:04:36,008 and there just was not enough collection area 87 00:04:36,109 --> 00:04:39,878 and solar power to be able to power the instruments. 88 00:04:39,979 --> 00:04:42,314 SHERIDAN: It's normal to put spacecraft into hibernation, 89 00:04:42,415 --> 00:04:44,983 but the worrying thing at the back of your mind is that it 90 00:04:45,084 --> 00:04:46,818 had never been done for this long before. 91 00:04:46,919 --> 00:04:51,890 ROWE: 31 months of hibernation gave Rosetta's team plenty 92 00:04:51,991 --> 00:04:55,594 of time to worry about what could go wrong. 93 00:04:55,695 --> 00:04:57,896 WALSH: It's dark and cold out there in space. 94 00:04:57,997 --> 00:04:59,464 There's a lot of things going on. 95 00:04:59,565 --> 00:05:01,633 There's a lot of little micro-meteorites out there, 96 00:05:01,734 --> 00:05:04,870 and without the constant communication with 97 00:05:04,971 --> 00:05:06,605 that spacecraft, 98 00:05:06,706 --> 00:05:09,308 just is a little nerve-racking when the day comes 99 00:05:09,409 --> 00:05:11,510 and it's time to flip the switch and turn it back on. 100 00:05:11,611 --> 00:05:16,114 ROWE: January 20th, 2014. 101 00:05:16,215 --> 00:05:19,918 After almost 10 years in space, it was finally time for 102 00:05:20,019 --> 00:05:21,586 Rosetta to wake up, 103 00:05:21,688 --> 00:05:26,925 reactivate its communication system, and phone home. 104 00:05:28,227 --> 00:05:30,595 RADEBAUGH: I mean, the tension was just palpable. 105 00:05:30,697 --> 00:05:32,731 It was just, I mean, how long do we have to wait 106 00:05:32,832 --> 00:05:34,700 before we're gonna get the signal? 107 00:05:34,801 --> 00:05:36,535 SHERIDAN: It's got to work. It has to work. 108 00:05:36,636 --> 00:05:38,970 Oh, gosh, maybe it's just not gonna turn on it all. 109 00:05:39,072 --> 00:05:40,405 Have we lost the spacecraft? 110 00:05:41,808 --> 00:05:43,975 And then the peak appeared on the graph. 111 00:05:45,545 --> 00:05:47,579 [triumphant music] 112 00:05:47,680 --> 00:05:49,881 It's like, yes, we've got contact with the spacecraft. 113 00:05:49,982 --> 00:05:54,419 [triumphant music] 114 00:05:54,520 --> 00:06:02,520 ♪♪ 115 00:06:03,963 --> 00:06:07,232 ROWE: Rosetta began to send back images of its target, 116 00:06:07,333 --> 00:06:10,902 and after months of seeing a small dot in the distance, 117 00:06:11,003 --> 00:06:13,338 the comet slowly came into focus. 118 00:06:15,308 --> 00:06:18,677 THALLER: When I saw this comet, crystal clear, 119 00:06:18,778 --> 00:06:22,514 this mountain floating in space of ice and rock, 120 00:06:22,615 --> 00:06:25,117 my heart just dropped... they are some of the most dramatic, 121 00:06:25,218 --> 00:06:29,654 beautiful images I have ever seen. 122 00:06:29,756 --> 00:06:31,800 PLAIT: Then, as it got closer, and we got to see more 123 00:06:31,824 --> 00:06:33,592 and more details on it, yeah, 124 00:06:33,693 --> 00:06:36,962 that's when things started getting really strange. 125 00:06:38,131 --> 00:06:41,433 WALSH: Quite simply, arrival at 67P, 126 00:06:41,501 --> 00:06:44,069 we expected to see something shaped like a potato, 127 00:06:44,170 --> 00:06:46,405 and we found something shaped like a rubber duck. 128 00:06:47,974 --> 00:06:51,176 ROWE: 67P is no ugly duckling, 129 00:06:51,277 --> 00:06:54,413 but its strange shape created a problem for Rosetta. 130 00:06:56,082 --> 00:06:57,883 Orbiting the comet was going to be 131 00:06:57,984 --> 00:07:00,986 far more difficult than anyone had imagined. 132 00:07:02,255 --> 00:07:04,723 THALLER: A planet has a lot of gravity, 133 00:07:04,824 --> 00:07:07,526 so you can send the spacecraft out there and then just slow it 134 00:07:07,627 --> 00:07:09,094 down a little bit with a rocket burn, 135 00:07:09,195 --> 00:07:10,862 and it will drop into orbit. 136 00:07:10,963 --> 00:07:12,831 In the case of Comet 67P, 137 00:07:12,932 --> 00:07:15,400 you're dealing with a very small little rock. 138 00:07:15,501 --> 00:07:18,003 The spacecraft cannot feel the gravity of that rock, 139 00:07:18,104 --> 00:07:19,824 at least not until it's right up against it. 140 00:07:21,607 --> 00:07:23,318 SHERIDAN: Well, the engineers had to actually plot 141 00:07:23,342 --> 00:07:24,910 triangular orbits. 142 00:07:25,011 --> 00:07:27,746 It was a very complicated set of maneuvers. 143 00:07:29,315 --> 00:07:31,883 ROWE: Once in orbit, Rosetta could start work. 144 00:07:33,219 --> 00:07:34,219 Its first task... 145 00:07:34,253 --> 00:07:37,222 Figure out how 67P formed. 146 00:07:38,324 --> 00:07:41,326 LANZA: So how did this comet get this weird shape? 147 00:07:41,427 --> 00:07:43,295 There's two main ideas. 148 00:07:43,396 --> 00:07:48,467 One is just that it was eroded somehow in the center. 149 00:07:48,568 --> 00:07:51,069 And so it started off as a more spherical thing 150 00:07:51,137 --> 00:07:53,805 and became the shape it is today through some 151 00:07:53,906 --> 00:07:55,474 unknown process. 152 00:07:55,575 --> 00:07:57,075 The other idea is that it started 153 00:07:57,176 --> 00:07:58,710 as two separate objects. 154 00:08:00,079 --> 00:08:02,681 ROWE: Space rocks normally hit each other hard. 155 00:08:05,251 --> 00:08:07,519 They collide with an average impact speed 156 00:08:07,620 --> 00:08:10,422 of more than 11,000 miles an hour. 157 00:08:10,523 --> 00:08:13,692 That's five times faster than a rifle bullet. 158 00:08:14,961 --> 00:08:18,563 Was 67P involved in a pile-up? 159 00:08:18,664 --> 00:08:22,734 A clue came from the distinct layers on the comet's surface. 160 00:08:22,835 --> 00:08:25,670 The layers in Comet 67P 161 00:08:25,771 --> 00:08:27,639 are a little like the layers in an onion. 162 00:08:29,308 --> 00:08:32,677 If you see them aligned, that's a clue that perhaps 163 00:08:32,778 --> 00:08:34,779 the object formed as a single entity 164 00:08:34,881 --> 00:08:37,449 and only eroded later into its present form. 165 00:08:37,550 --> 00:08:40,252 But if you see those layers misaligned like we actually do 166 00:08:40,353 --> 00:08:42,254 in the comet, that's a big clue 167 00:08:42,355 --> 00:08:44,089 that it started out as two separate 168 00:08:44,190 --> 00:08:46,157 objects formed independently, 169 00:08:46,259 --> 00:08:49,761 sticking together to form the comet we see today. 170 00:08:49,862 --> 00:08:52,097 ROWE: The layers prove that 67P was 171 00:08:52,198 --> 00:08:56,001 originally two separate objects that fused together. 172 00:08:56,102 --> 00:08:59,638 The process of potentially putting Comet 67P 173 00:08:59,739 --> 00:09:01,273 together from two different pieces 174 00:09:01,374 --> 00:09:03,608 is important, because it can teach us about what was 175 00:09:03,709 --> 00:09:05,977 happening in the early solar system. 176 00:09:06,078 --> 00:09:07,612 So as far as we can tell, 177 00:09:07,713 --> 00:09:10,415 these two separate bodies must have 178 00:09:10,516 --> 00:09:12,017 been formed in the same area. 179 00:09:12,118 --> 00:09:14,252 They're very similar in composition, 180 00:09:14,353 --> 00:09:16,922 but they are so light and fluffy that they would have 181 00:09:17,023 --> 00:09:19,891 destroyed each other if they had hit fast. 182 00:09:19,992 --> 00:09:21,693 They had a low speed collision 183 00:09:21,794 --> 00:09:24,896 and basically stuck together like two wet snowballs. 184 00:09:26,132 --> 00:09:28,400 ROWE: With one mystery solved, Rosetta began to 185 00:09:28,501 --> 00:09:32,404 investigate the chemical makeup of 67P. 186 00:09:32,505 --> 00:09:34,339 The little comet could answer one 187 00:09:34,440 --> 00:09:36,808 of the biggest questions in planetary science. 188 00:09:36,909 --> 00:09:40,512 From where did our blue planet get its water? 189 00:09:50,623 --> 00:09:54,159 ROWE: The Rosetta Mission, a four billion mile journey 190 00:09:54,260 --> 00:09:58,697 to Comet 67P and a 4.5 billion-year 191 00:09:58,798 --> 00:10:02,400 trip back in time to the birth of the solar system. 192 00:10:03,869 --> 00:10:06,471 This comet is a remnant of 193 00:10:06,572 --> 00:10:09,774 the formation of the solar system itself. 194 00:10:09,875 --> 00:10:14,312 So this is an opportunity to open that time capsule 195 00:10:14,413 --> 00:10:17,849 and get a view into the ancient solar system. 196 00:10:19,318 --> 00:10:22,120 ROWE: Comet 67P could help us answer one 197 00:10:22,221 --> 00:10:25,590 of the most important questions about our planet. 198 00:10:25,691 --> 00:10:27,459 One of the big mysteries that we have 199 00:10:27,560 --> 00:10:29,794 about Earth is where did the water come from? 200 00:10:33,065 --> 00:10:35,133 ROWE: Today, water covers over two-thirds 201 00:10:35,234 --> 00:10:36,334 of the Earth's surface. 202 00:10:38,738 --> 00:10:40,639 But it wasn't always that way. 203 00:10:40,740 --> 00:10:42,974 4.6 billion years ago, 204 00:10:43,075 --> 00:10:45,844 the inner solar system formed from a maelstrom 205 00:10:45,945 --> 00:10:47,078 of rocky debris. 206 00:10:49,148 --> 00:10:51,116 Temperatures were so hot, 207 00:10:51,217 --> 00:10:54,853 any water on the early Earth boiled away. 208 00:10:54,954 --> 00:10:58,823 What the evidence suggests to us is that Earth's water arrived 209 00:10:58,924 --> 00:11:01,059 at Earth after the Earth formed, 210 00:11:01,160 --> 00:11:05,530 and the primary mechanism that we thought were responsible 211 00:11:05,631 --> 00:11:07,565 were our comets. 212 00:11:07,667 --> 00:11:09,444 CHRISTIANSEN: You have to remember that comets are 213 00:11:09,468 --> 00:11:11,836 basically just big balls of ice and dirt. 214 00:11:11,937 --> 00:11:13,905 One of the main goals of the Rosetta mission was 215 00:11:14,006 --> 00:11:15,740 to analyze the water on this comet 216 00:11:15,841 --> 00:11:18,076 and see if it matched the water on Earth. 217 00:11:20,046 --> 00:11:22,213 ROWE: Comets come from two regions at 218 00:11:22,314 --> 00:11:25,216 the outermost reaches of our solar system... 219 00:11:25,317 --> 00:11:27,485 The Oort Cloud 220 00:11:27,586 --> 00:11:29,087 and the Kuiper Belt. 221 00:11:29,188 --> 00:11:32,290 OLUSEYI: The Kuiper Belt is in a plane of our solar system, 222 00:11:32,391 --> 00:11:35,694 and the member that most people are aware of is Pluto, 223 00:11:35,795 --> 00:11:38,596 but beyond that, there is a spherical 224 00:11:38,698 --> 00:11:41,566 distribution of icy bodies, the Oort Cloud. 225 00:11:42,835 --> 00:11:45,904 WALSH: This is a repository of comets that extend for 226 00:11:46,005 --> 00:11:47,472 hundreds of thousands of times 227 00:11:47,573 --> 00:11:49,741 further away from the sun than we find the Earth, 228 00:11:49,842 --> 00:11:53,044 and it's kind of a big, spherical cloud around the sun 229 00:11:53,145 --> 00:11:55,714 that's kind of deep freeze for a bunch of big comets. 230 00:11:55,815 --> 00:11:59,117 ROWE: Billions of icy objects 231 00:11:59,218 --> 00:12:01,286 orbit safely beyond the chaos of 232 00:12:01,387 --> 00:12:03,221 the inner solar system, 233 00:12:03,322 --> 00:12:06,825 locking in primordial water. 234 00:12:06,926 --> 00:12:09,027 WALSH: The life span of a comet is fascinating. 235 00:12:09,128 --> 00:12:12,497 They might do absolutely nothing out there for over 236 00:12:12,598 --> 00:12:15,266 four billion years until the right 237 00:12:15,367 --> 00:12:19,104 tweak of their orbit or tug from a planet changes 238 00:12:19,205 --> 00:12:20,765 everything, and all of a sudden, they're 239 00:12:20,806 --> 00:12:23,875 on a path in towards the sun and that ice that's been in deep 240 00:12:23,976 --> 00:12:26,745 freeze for billions of years starts to heat up. 241 00:12:26,846 --> 00:12:32,484 ROWE: Astronomers believe that Comet 67P's former home turf 242 00:12:32,585 --> 00:12:37,021 was the Kuiper Belt until something sent it 243 00:12:37,123 --> 00:12:39,090 ricocheting inwards. 244 00:12:39,191 --> 00:12:41,826 SHERIDAN: The influence of the gravity of Jupiter, 245 00:12:41,927 --> 00:12:43,661 because Jupiter's such a massive planet, 246 00:12:43,763 --> 00:12:45,997 it actually attracted the comet and pulled it into 247 00:12:46,098 --> 00:12:47,265 the inner solar system. 248 00:12:47,366 --> 00:12:48,933 DURDA: It slowly was perturbed 249 00:12:49,034 --> 00:12:50,635 and migrated into the inner solar system, 250 00:12:50,736 --> 00:12:52,256 where we see it today... It's traveled. 251 00:12:52,304 --> 00:12:54,773 I mean, not just, you know, billions of miles in linear 252 00:12:54,874 --> 00:12:56,040 space, but, I mean, really, 253 00:12:56,108 --> 00:12:57,919 when you think of all the orbits that must have made, 254 00:12:57,943 --> 00:13:01,146 just trillions upon trillions of miles, that's a... 255 00:13:01,247 --> 00:13:03,915 That's quite a journey for such a little object. 256 00:13:04,016 --> 00:13:09,621 ROWE: Now, 67P loops around the sun in a 6.5-year orbit 257 00:13:09,722 --> 00:13:12,190 that travels as far out as Jupiter 258 00:13:12,291 --> 00:13:14,359 and closer in than Mars. 259 00:13:15,728 --> 00:13:18,696 As it gets nearer to the sun, its frozen ice 260 00:13:18,798 --> 00:13:22,233 begins to heat up, leading to a famous effect, 261 00:13:22,334 --> 00:13:24,769 the comet's tail. 262 00:13:24,870 --> 00:13:27,338 Sunlight comes in and heats up the comet's surface, 263 00:13:27,439 --> 00:13:29,351 and it gets transferred to the interior, where there's 264 00:13:29,375 --> 00:13:31,576 a lot of ice, and the ice gets heated up, 265 00:13:31,677 --> 00:13:34,145 and it vaporizes and makes its way to the surface. 266 00:13:34,246 --> 00:13:36,781 And once it's sitting on the surface, the solar wind is 267 00:13:36,882 --> 00:13:37,949 bombarding that comet, 268 00:13:38,050 --> 00:13:40,552 and it drags all of that material out into 269 00:13:40,653 --> 00:13:42,020 a long and beautiful tail. 270 00:13:44,089 --> 00:13:45,924 ROWE: Rosetta flew into the tail to 271 00:13:46,025 --> 00:13:48,893 analyze the water vapor. 272 00:13:48,994 --> 00:13:51,896 Its goal... confirm it's the same type 273 00:13:51,997 --> 00:13:54,866 of water as we have on Earth. 274 00:13:54,967 --> 00:13:56,967 CHRISTIANSEN: Water does come in different flavors, 275 00:13:57,002 --> 00:13:59,070 and I don't mean saltwater or freshwater. 276 00:13:59,171 --> 00:14:02,207 I mean what the water's made of, its molecules. 277 00:14:02,308 --> 00:14:05,043 BYWATERS: We're talking about the actual, actual chemical 278 00:14:05,144 --> 00:14:07,378 makeup on the proton, 279 00:14:07,479 --> 00:14:09,814 neutron, and electron level, 280 00:14:09,915 --> 00:14:13,084 so you might have heard of heavy water before. 281 00:14:13,185 --> 00:14:16,821 And that just means that there is an extra neutron. 282 00:14:16,922 --> 00:14:19,858 WALSH: It's H20, but one of the hydrogens 283 00:14:19,959 --> 00:14:21,893 has an extra neutron, 284 00:14:21,994 --> 00:14:23,528 so we call it deuterium. 285 00:14:23,629 --> 00:14:27,031 And so that water actually weighs more the normal water 286 00:14:27,132 --> 00:14:30,034 because of that extra neutron in the mix. 287 00:14:31,971 --> 00:14:35,640 ROWE: On Earth, there are roughly 160 molecules of 288 00:14:35,741 --> 00:14:39,911 heavy water for every million molecules of normal water. 289 00:14:43,082 --> 00:14:45,116 As Rosetta moved around the comet, 290 00:14:45,217 --> 00:14:49,087 it measured the ratio of hydrogen to deuterium in 291 00:14:49,188 --> 00:14:50,755 the water vapor. 292 00:14:50,856 --> 00:14:54,726 An exact match to Earth's ratio would confirm that comets 293 00:14:54,827 --> 00:14:57,095 were the source of our oceans, 294 00:14:57,196 --> 00:15:01,232 but Rosetta discovered something surprising. 295 00:15:01,333 --> 00:15:05,169 What Rosetta found was that the deuterium to hydrogen ratio 296 00:15:05,271 --> 00:15:08,640 was three times that of the water in Earth's ocean. 297 00:15:08,741 --> 00:15:10,975 That means a comet like 67P 298 00:15:11,076 --> 00:15:13,311 couldn't have been the source of Earth's water. 299 00:15:13,412 --> 00:15:15,446 SHERIDAN: If it was the same as the measurement 300 00:15:15,547 --> 00:15:16,714 of the ocean water, 301 00:15:16,815 --> 00:15:19,055 then we could have said that these comets could have been 302 00:15:19,151 --> 00:15:22,020 a delivery mechanism for the water that we see on Earth. 303 00:15:22,121 --> 00:15:25,690 The fact it was three times higher kind of indicates that 304 00:15:25,791 --> 00:15:27,191 comets, like 67P, 305 00:15:27,293 --> 00:15:30,228 were not the source of the water that we see on Earth today. 306 00:15:34,366 --> 00:15:38,369 ROWE: But although comets like 67P didn't deliver our water, 307 00:15:40,272 --> 00:15:41,973 we can't rule out all comets. 308 00:15:43,275 --> 00:15:45,343 OLUSEYI: We have to keep this in perspective. 309 00:15:45,444 --> 00:15:49,380 67P is but one comet, and what we know about 310 00:15:49,481 --> 00:15:50,548 objects like comets 311 00:15:50,649 --> 00:15:53,584 is that they come in families, and these families 312 00:15:53,686 --> 00:15:55,386 have different compositions. 313 00:15:55,487 --> 00:15:58,022 So it could be that some have Earth-like water, 314 00:15:58,123 --> 00:16:00,191 and those are the ones that brought water to Earth, 315 00:16:00,292 --> 00:16:01,426 and some don't. 316 00:16:03,062 --> 00:16:04,829 BYWATERS: I don't see wrinkles like this 317 00:16:04,930 --> 00:16:06,764 as going back to the drawing board. 318 00:16:06,865 --> 00:16:09,867 Sure, we get more questions sometimes than answers, 319 00:16:09,969 --> 00:16:13,805 but that allows us to probe farther and really expand 320 00:16:13,906 --> 00:16:16,641 our knowledge into how planets formed. 321 00:16:18,110 --> 00:16:20,878 ROWE: The composition of Comet 67P 322 00:16:20,946 --> 00:16:22,647 rewrites our understanding of 323 00:16:22,748 --> 00:16:26,217 the solar system, and the comet 324 00:16:26,318 --> 00:16:28,519 has more secrets to reveal. 325 00:16:28,620 --> 00:16:30,221 THALLER: The reason we went all the way 326 00:16:30,322 --> 00:16:31,856 out to Comet 67P, 327 00:16:31,957 --> 00:16:34,325 and, in fact, the reason we studied comets at all, 328 00:16:34,426 --> 00:16:37,729 is we're looking for clues about the origins of life. 329 00:16:37,830 --> 00:16:41,065 ROWE: As Rosetta examined the icy core of the comet, 330 00:16:41,166 --> 00:16:44,135 it found a treasure trove of molecules. 331 00:16:45,371 --> 00:16:49,607 Could 67P carry the building blocks of life itself? 332 00:17:00,686 --> 00:17:04,622 ROWE: Rosetta's mission to Comet 67P planned to answer 333 00:17:04,723 --> 00:17:07,692 the biggest questions in planetary science, 334 00:17:09,928 --> 00:17:11,996 and none as bigger than figuring out 335 00:17:12,097 --> 00:17:14,799 the origins of life on Earth. 336 00:17:14,900 --> 00:17:17,235 Life on Earth got started not long after 337 00:17:17,336 --> 00:17:21,239 our planet cooled, something like 4.5 billion years ago. 338 00:17:21,340 --> 00:17:23,808 But we don't know the exact process. 339 00:17:23,909 --> 00:17:25,910 Did all that stuff come together here from 340 00:17:26,011 --> 00:17:29,047 molecules on Earth and become more and more complex? 341 00:17:29,148 --> 00:17:31,115 Or was it brought from space? 342 00:17:31,216 --> 00:17:34,519 [explosion blasts] 343 00:17:34,620 --> 00:17:36,087 ROWE: Rosetta began to hunt for 344 00:17:36,188 --> 00:17:40,825 the building blocks of life... Basic organic compounds. 345 00:17:40,926 --> 00:17:43,461 So we always thought that comets probably 346 00:17:43,562 --> 00:17:46,064 carry organic materials, but we really couldn't 347 00:17:46,165 --> 00:17:48,533 confirm that until Rosetta. 348 00:17:48,634 --> 00:17:51,402 RADEBAUGH: It detected aliphatic compounds, 349 00:17:51,503 --> 00:17:54,705 which are organics rich in carbon and hydrogen, and that is 350 00:17:54,807 --> 00:17:56,374 the first time such a substance 351 00:17:56,475 --> 00:17:59,077 has been detected at the surface of a comet. 352 00:17:59,178 --> 00:18:02,246 LANZA: These materials are the raw building blocks 353 00:18:02,347 --> 00:18:04,182 for making things like proteins, 354 00:18:04,283 --> 00:18:05,983 which are required for all life. 355 00:18:06,085 --> 00:18:08,519 This is really important, because this says that 356 00:18:08,620 --> 00:18:11,923 possibly these materials were delivered to Earth by comets. 357 00:18:13,058 --> 00:18:15,660 ROWE: The idea that comets carried the building blocks for 358 00:18:15,761 --> 00:18:18,763 life across the solar system is known as 359 00:18:18,864 --> 00:18:20,665 molecular panspermia. 360 00:18:21,800 --> 00:18:24,635 You can kind of think of comets is being like space 361 00:18:24,736 --> 00:18:26,537 delivery trucks, right? 362 00:18:26,638 --> 00:18:28,206 They're forming out there in deep space. 363 00:18:28,307 --> 00:18:30,575 All this stuff is being formed with them, 364 00:18:30,676 --> 00:18:32,610 and then they bring it to Earth. 365 00:18:32,711 --> 00:18:33,788 Now, you know, you don't want your 366 00:18:33,812 --> 00:18:36,314 delivery truck smashing through your front door, 367 00:18:36,415 --> 00:18:38,916 but in the case of comets, when they impact the Earth, 368 00:18:39,017 --> 00:18:41,886 they can distribute those molecules all over the place. 369 00:18:44,523 --> 00:18:46,791 But in some way, we're kind of skipping a step, right? 370 00:18:46,892 --> 00:18:49,260 I mean, so the comet may be bringing 371 00:18:49,361 --> 00:18:51,395 the ingredients of life to the Earth, 372 00:18:51,497 --> 00:18:53,731 but where'd the comet get those ingredients? 373 00:18:55,134 --> 00:18:57,668 ROWE: The answer may be in deep space, 374 00:18:57,769 --> 00:18:59,637 in the matter and radiation floating 375 00:18:59,738 --> 00:19:02,173 between star systems and a galaxy. 376 00:19:03,242 --> 00:19:05,810 It's called the interstellar medium. 377 00:19:05,911 --> 00:19:08,246 DURDA: The really interesting result 378 00:19:08,347 --> 00:19:11,749 is that the overall composition of Comet 67P 379 00:19:11,850 --> 00:19:13,751 and some of the really interesting ingredients 380 00:19:13,852 --> 00:19:16,087 in that comet are very similar, 381 00:19:16,155 --> 00:19:19,524 identical, in some cases, two materials we find out there 382 00:19:19,625 --> 00:19:20,825 in the interstellar medium, 383 00:19:20,926 --> 00:19:23,661 floating out there in the gas and dust between the stars. 384 00:19:25,531 --> 00:19:28,900 DARTNELL: If this organic chemistry is common on Earth, 385 00:19:29,001 --> 00:19:32,937 it's likely to been common across the entire galaxy. 386 00:19:33,038 --> 00:19:36,440 This chemical kit for making life is universal, 387 00:19:36,575 --> 00:19:39,610 and therefore perhaps life itself is common. 388 00:19:39,711 --> 00:19:43,214 There could be plenty of wet rocks out there in 389 00:19:43,315 --> 00:19:45,683 the night sky teeming with life, 390 00:19:45,784 --> 00:19:48,319 with this universal chemistry kit. 391 00:19:49,821 --> 00:19:51,621 ROWE: But scientists still couldn't figure out 392 00:19:51,657 --> 00:19:53,724 the origin of one vital element. 393 00:19:55,127 --> 00:19:58,329 So phosphorus is one of the atoms that's absolutely 394 00:19:58,430 --> 00:19:59,564 essential for life, 395 00:19:59,665 --> 00:20:02,667 but we don't really know where it comes from. 396 00:20:02,768 --> 00:20:04,502 ROWE: Phosphorus is a vital part of 397 00:20:04,603 --> 00:20:08,472 DNA, cell membranes, and energy production. 398 00:20:08,574 --> 00:20:12,643 But the problem is, it's quite scarce in the universe, 399 00:20:12,744 --> 00:20:15,012 and it's certainly scarce on the surface of the Earth. 400 00:20:15,113 --> 00:20:17,915 Any phosphorus that was around would've been locked up in 401 00:20:18,016 --> 00:20:19,951 the soluble rocks, so that wouldn't have been 402 00:20:20,052 --> 00:20:23,688 available for life to use at that time. 403 00:20:23,789 --> 00:20:27,692 ROWE: If rocks had locked in all the mineralized phosphorus, 404 00:20:27,793 --> 00:20:29,193 where did the phosphorus needed 405 00:20:29,294 --> 00:20:32,663 for biological processes come from? 406 00:20:32,764 --> 00:20:35,700 67P held the key to the mystery. 407 00:20:35,801 --> 00:20:41,339 What we found on the comet is bioavailable forms 408 00:20:41,440 --> 00:20:45,576 of phosphorus, not just mineralized phosphorus. 409 00:20:47,246 --> 00:20:51,582 ROWE: Bioavailable phosphorus is a form that life can use, 410 00:20:51,683 --> 00:20:55,786 but where did Comet 67P get it from? 411 00:20:55,887 --> 00:20:59,223 In January 2020, 412 00:20:59,324 --> 00:21:02,860 astronomers combined data from the Rosetta mission 413 00:21:02,961 --> 00:21:06,297 with ALMA's observations of the star forming region 414 00:21:06,398 --> 00:21:09,967 AFGL 5142. 415 00:21:10,068 --> 00:21:12,937 CHRISTIANSEN: AFGL 5142 is a stellar nursery, 416 00:21:13,038 --> 00:21:15,539 a gas cloud where large and small stars are being born 417 00:21:15,641 --> 00:21:17,942 simultaneously, and it's very close to us, 418 00:21:18,043 --> 00:21:20,878 which means we can study it in great detail. 419 00:21:20,979 --> 00:21:22,513 WALSH: The ALMA Observatory 420 00:21:22,614 --> 00:21:24,882 takes really high-resolution images 421 00:21:24,983 --> 00:21:28,052 of different types of dust and gas in very, 422 00:21:28,153 --> 00:21:31,022 very close to a star that's just formed so you can actually 423 00:21:31,123 --> 00:21:33,557 see the process of formation happening. 424 00:21:33,659 --> 00:21:37,528 ROWE: The largest stars live fast and die young, 425 00:21:37,629 --> 00:21:39,664 exploding in supernovas. 426 00:21:42,834 --> 00:21:44,712 SHERIDAN: So the phosphorous itself, we believe, 427 00:21:44,736 --> 00:21:46,437 is formed in massive stars. 428 00:21:46,538 --> 00:21:49,307 So essentially, it's created a star gets to the end of 429 00:21:49,408 --> 00:21:52,276 its life, and when the star goes supernova, it spews 430 00:21:52,377 --> 00:21:55,546 this phosphorus out into the interstellar medium. 431 00:21:55,647 --> 00:21:58,115 ROWE: When midsized stars burst into life, 432 00:21:58,216 --> 00:22:01,619 they sent shockwaves and radiation through the cloud, 433 00:22:01,720 --> 00:22:04,488 transforming phosphorus into a form 434 00:22:04,589 --> 00:22:08,025 biology can use... Phosphorus monoxide. 435 00:22:09,227 --> 00:22:11,996 The phosphorus monoxide can freeze out and get trapped on 436 00:22:12,097 --> 00:22:15,166 the icy dust grains that remain around the star. 437 00:22:15,267 --> 00:22:17,902 These dust grains can come together to form pebbles, 438 00:22:18,003 --> 00:22:18,903 rocks, and eventually, 439 00:22:19,004 --> 00:22:20,938 comets that become the transporters of 440 00:22:21,039 --> 00:22:22,373 phosphorus monoxide. 441 00:22:22,474 --> 00:22:26,077 ROWE: Scientists traced the cosmic trail of phosphorus 442 00:22:26,178 --> 00:22:28,346 and organics from stars 443 00:22:28,447 --> 00:22:32,016 to comets to planets and even to life. 444 00:22:34,386 --> 00:22:37,421 You could, in theory at least, take the sort of chemistry 445 00:22:37,522 --> 00:22:41,892 find preserved in a comet and use it to construct a cell. 446 00:22:44,162 --> 00:22:46,597 So often, people seem to think of astronomy as 447 00:22:46,698 --> 00:22:48,378 the study of things that are very far away, 448 00:22:48,433 --> 00:22:50,935 that has absolutely no bearing on our day-to-day life. 449 00:22:51,036 --> 00:22:52,837 Nothing is farther from the truth. 450 00:22:52,938 --> 00:22:55,906 We are looking for the origins of ourselves out there, 451 00:22:56,007 --> 00:22:57,708 and we are discovering them. 452 00:22:57,809 --> 00:22:59,176 So a basic question like, 453 00:22:59,277 --> 00:23:02,413 how did phosphorus end up in our DNA when the only place 454 00:23:02,514 --> 00:23:04,949 you seem to find it is around young stars, 455 00:23:05,050 --> 00:23:07,418 clouds thousands of light-years away... 456 00:23:07,519 --> 00:23:10,421 Now we know the mechanism, because we asked the question, 457 00:23:10,522 --> 00:23:13,124 and now we understand ourselves that much better. 458 00:23:15,327 --> 00:23:16,994 ROWE: The next stage of the mission was 459 00:23:17,095 --> 00:23:19,663 to get the lander onto the comet's surface. 460 00:23:19,765 --> 00:23:22,366 But there was a problem. 461 00:23:22,467 --> 00:23:24,902 The craft's landing gear was broken. 462 00:23:25,003 --> 00:23:26,470 [beeping noises] 463 00:23:26,571 --> 00:23:29,106 Would the team have to abort the mission? 464 00:23:39,818 --> 00:23:42,058 ROWE: Rosetta had discovered the building blocks for life 465 00:23:42,154 --> 00:23:43,687 on 67P. 466 00:23:46,858 --> 00:23:50,961 Now the probe faced its toughest challenge so far... 467 00:23:51,062 --> 00:23:54,398 A historic first landing on the surface of a comet. 468 00:23:55,634 --> 00:23:58,068 One of the biggest challenges about setting the Philae lander 469 00:23:58,170 --> 00:23:59,236 down on the surface 470 00:23:59,337 --> 00:24:01,572 is having no idea what the surface is like 471 00:24:01,673 --> 00:24:03,207 when you're designing the lander. 472 00:24:03,308 --> 00:24:06,844 Is it going to be like rock or ice and be very stiff? 473 00:24:06,945 --> 00:24:09,113 Is it gonna be brittle? 474 00:24:09,214 --> 00:24:13,717 ROWE: Philae had harpoons to dig into the soft surfaces 475 00:24:13,819 --> 00:24:18,122 and top thrusters to stop it from bouncing off the comet. 476 00:24:18,223 --> 00:24:20,958 The lander team discovered neither system was 477 00:24:21,059 --> 00:24:22,593 working properly. 478 00:24:22,694 --> 00:24:24,695 With the odds stacked against them, 479 00:24:24,796 --> 00:24:28,132 they decided to go for landing anyway. 480 00:24:31,269 --> 00:24:34,839 Philae made a slow, 12-mile, seven-hour descent. 481 00:24:37,776 --> 00:24:39,710 [whirring noises] 482 00:24:44,483 --> 00:24:45,483 Until finally... 483 00:24:47,486 --> 00:24:48,619 ...touchdown. 484 00:24:49,855 --> 00:24:51,956 [cheering and applause] 485 00:24:52,057 --> 00:24:54,024 So when we got the first signal of touchdown, 486 00:24:54,125 --> 00:24:55,826 we were relieved... The lander was down, 487 00:24:55,927 --> 00:24:56,794 and everything was good to go. 488 00:24:56,895 --> 00:24:58,462 [applause and chatter] 489 00:24:58,563 --> 00:25:01,131 But then we realized things weren't quite going to plan. 490 00:25:02,934 --> 00:25:05,102 ROWE: The data from the lander was intermittent. 491 00:25:06,338 --> 00:25:08,806 The only possible explanation? 492 00:25:08,907 --> 00:25:11,108 It was tumbling end over end. 493 00:25:12,911 --> 00:25:14,512 It could've bounced and bounced right off 494 00:25:14,613 --> 00:25:17,047 the comet and continued all the way into space. 495 00:25:17,148 --> 00:25:18,883 SHERIDAN: We really didn't know. 496 00:25:18,984 --> 00:25:20,417 We just knew we were not on 497 00:25:20,519 --> 00:25:22,620 the ground, and we were rotating and tumbling. 498 00:25:24,022 --> 00:25:27,491 ROWE: Then, 12 minutes later, a ray of hope. 499 00:25:27,592 --> 00:25:29,894 We saw a flash in one of the computers, and we huddled 500 00:25:29,995 --> 00:25:31,061 around it, and we realized 501 00:25:31,196 --> 00:25:32,596 that the lander was actually sending 502 00:25:32,664 --> 00:25:34,732 data back as it was programmed to do. 503 00:25:34,833 --> 00:25:36,233 We were actually doing science on 504 00:25:36,334 --> 00:25:39,136 the comet and getting the results back. 505 00:25:39,237 --> 00:25:41,972 ROWE: The lander stopped tumbling, 506 00:25:42,073 --> 00:25:45,609 Philae's solar panels weren't fully operational, and the tiny 507 00:25:45,710 --> 00:25:48,846 craft's battery had only 60 hours of power left. 508 00:25:48,947 --> 00:25:51,815 It was a race against time. 509 00:25:51,917 --> 00:25:54,385 We had to completely rip up all of our plans 510 00:25:54,486 --> 00:25:55,786 of what we wanted to do, 511 00:25:55,887 --> 00:25:57,821 and then we had to rewrite everything to maximize 512 00:25:57,923 --> 00:25:59,156 the amount of science return 513 00:25:59,257 --> 00:26:01,492 in those 60 hours we had available to us. 514 00:26:03,662 --> 00:26:06,363 ROWE: Philae got to work. 515 00:26:06,464 --> 00:26:08,299 Its first discovery... 516 00:26:08,366 --> 00:26:10,534 The ground was stranger than expected. 517 00:26:12,003 --> 00:26:14,171 One of the things we found about the surface 518 00:26:14,272 --> 00:26:19,710 is the top 40 centimeters were a very fluffy material. 519 00:26:19,811 --> 00:26:22,780 DURDA: It is not dense and rocky... it's pretty fluffy. 520 00:26:22,881 --> 00:26:25,916 You could imagine something on the order of cigar ash. 521 00:26:26,017 --> 00:26:29,520 Imagine the rocks on Comet 67P, 522 00:26:29,621 --> 00:26:32,323 but imagine them being as light and fluffy as cigar ash. 523 00:26:34,292 --> 00:26:36,103 PLAIT: It's so crumbly that if you had in your hands, 524 00:26:36,127 --> 00:26:38,329 you could break it apart with almost no effort at all. 525 00:26:38,430 --> 00:26:42,366 It has a fraction of the strength of Styrofoam 526 00:26:42,467 --> 00:26:44,001 ROWE: Philae's bounced landing 527 00:26:44,102 --> 00:26:46,470 helped investigate the surface. 528 00:26:46,571 --> 00:26:49,440 SHERIDAN: By bouncing, we actually were able to sample 529 00:26:49,541 --> 00:26:51,408 two sites, and interestingly, 530 00:26:51,509 --> 00:26:53,377 both sites were different. 531 00:26:53,478 --> 00:26:56,914 That kind of shows us that the comet is not homogeneous. 532 00:26:57,015 --> 00:26:58,616 It's not all the same material. 533 00:27:00,285 --> 00:27:02,152 ROWE: Philae's instruments revealed 534 00:27:02,253 --> 00:27:07,124 Comet 67P is not just two lobes fused together. 535 00:27:07,225 --> 00:27:09,059 The comet formed from distinct 536 00:27:09,160 --> 00:27:11,562 blocks pulled together by gravity. 537 00:27:12,931 --> 00:27:15,966 Philae's on board camera also fed back vital 538 00:27:16,067 --> 00:27:19,403 clues to the lander's final resting place. 539 00:27:19,504 --> 00:27:21,538 The images taken by the lander were really amazing, 540 00:27:21,640 --> 00:27:24,308 because from those, we were actually able to work out 541 00:27:24,409 --> 00:27:26,210 Philae was on its side. 542 00:27:26,311 --> 00:27:29,146 ROWE: Philae's location was unknown, 543 00:27:29,247 --> 00:27:31,582 far from the planned landing site. 544 00:27:31,683 --> 00:27:34,084 With its battery dead, 545 00:27:34,185 --> 00:27:37,021 it couldn't speak to Rosetta. 546 00:27:37,122 --> 00:27:38,466 SHERIDAN: The problem with not knowing exactly 547 00:27:38,490 --> 00:27:40,991 where on the surface of the comet we were was that some 548 00:27:41,092 --> 00:27:44,094 of the instruments had needed to know that exact location 549 00:27:44,195 --> 00:27:46,664 to actually interpret the data, and without that 550 00:27:46,765 --> 00:27:50,467 information, the results were meaningless. 551 00:27:50,568 --> 00:27:52,670 OLUSEYI: Time is passing, and still 552 00:27:52,771 --> 00:27:55,472 no Philae lander is to be found. 553 00:27:55,573 --> 00:27:57,274 Is there hope? 554 00:27:57,375 --> 00:27:59,376 Is all lost? 555 00:27:59,477 --> 00:28:01,445 HOWETT: When you make or follow a space robot, 556 00:28:01,546 --> 00:28:04,682 you kind of get invested in that success 557 00:28:04,783 --> 00:28:06,684 and the survival of that robot. 558 00:28:06,818 --> 00:28:09,486 You want it to succeed against the harsh reality of space. 559 00:28:09,587 --> 00:28:11,822 You feel like you've... You've lost a pioneer. 560 00:28:11,923 --> 00:28:13,290 You've lost a fellow explorer. 561 00:28:18,530 --> 00:28:20,230 ROWE: As Rosetta scanned the comet, 562 00:28:20,331 --> 00:28:23,534 searching for the lost lander, it faced a new problem. 563 00:28:25,203 --> 00:28:31,041 As this dirty snowball races towards the sun, the radiation 564 00:28:31,142 --> 00:28:32,376 from the sun heats it up, 565 00:28:32,477 --> 00:28:35,913 and so it starts snapping and popping and cracking, 566 00:28:36,014 --> 00:28:38,015 transforming itself. 567 00:28:38,116 --> 00:28:40,017 It's like a firework show. 568 00:28:40,118 --> 00:28:43,087 ROWE: Huge jets blasted material from the surface. 569 00:28:43,188 --> 00:28:45,189 Would the outbursts 570 00:28:45,290 --> 00:28:47,024 launch Philae into space? 571 00:28:55,967 --> 00:28:59,903 ROWE: Rosetta's lander, Philae, was lost somewhere 572 00:29:00,004 --> 00:29:02,439 on the surface of Comet 67P, 573 00:29:02,540 --> 00:29:05,876 its battery dead, and its solar panels useless. 574 00:29:07,746 --> 00:29:10,714 As Rosetta scanned the comet for the missing probe, 575 00:29:10,815 --> 00:29:13,484 it flew less than two miles above the surface, 576 00:29:14,819 --> 00:29:17,521 close enough to cast a shadow. 577 00:29:17,622 --> 00:29:21,125 PLAIT: Seeing the shadow of the spacecraft itself 578 00:29:21,226 --> 00:29:23,026 on the comet 579 00:29:23,128 --> 00:29:25,028 really brought home the fact that 580 00:29:25,130 --> 00:29:27,097 there was a piece of humanity, 581 00:29:27,198 --> 00:29:31,201 one of our machines, right there. 582 00:29:31,302 --> 00:29:33,262 It makes the hair on the back of my neck stand up. 583 00:29:33,304 --> 00:29:34,338 It gives me chills. 584 00:29:37,909 --> 00:29:39,910 ROWE: The low passes allowed Rosetta 585 00:29:40,011 --> 00:29:42,179 to smell the comet's surface. 586 00:29:43,414 --> 00:29:45,682 The ROSINA instruments allowed us to actually measure 587 00:29:45,784 --> 00:29:47,017 the chemicals and the gases 588 00:29:47,118 --> 00:29:50,454 coming off the comet, so we can actually put those together 589 00:29:50,555 --> 00:29:53,190 to make a comet perfume. 590 00:29:53,291 --> 00:29:56,093 So what we've actually done is impregnated those smells of 591 00:29:56,194 --> 00:29:58,028 the comet into a card a bit 592 00:29:58,129 --> 00:29:59,740 like a scratch and sniff card, so you can actually 593 00:29:59,764 --> 00:30:01,031 [sniffing noises] smell. 594 00:30:01,132 --> 00:30:04,067 And that is the smell of the comet. 595 00:30:04,169 --> 00:30:06,770 And it's not very pleasant. 596 00:30:06,871 --> 00:30:09,573 If you can imagine a mixture of something like rotten eggs 597 00:30:09,674 --> 00:30:14,244 and cat urine and, like, bitter almond stuff, 598 00:30:14,345 --> 00:30:16,880 it's like... it's not something I would wanna 599 00:30:16,981 --> 00:30:18,949 have to be able to smell. 600 00:30:19,050 --> 00:30:20,984 To me, it kind of smells like, 601 00:30:21,085 --> 00:30:23,754 um, baby's nappies. 602 00:30:23,855 --> 00:30:27,958 And it's a bit of a pungent, quite an unpleasant smell. 603 00:30:28,092 --> 00:30:31,461 ROWE: Months passed with no sign of Philae. 604 00:30:31,563 --> 00:30:34,097 HOWETT: The comet isn't terribly big. 605 00:30:34,199 --> 00:30:35,342 You know, where could it be hidden? 606 00:30:35,366 --> 00:30:37,267 And if we understood where it was hidden, 607 00:30:37,368 --> 00:30:39,570 we would understand the images that it had returned 608 00:30:39,671 --> 00:30:40,838 so much better. 609 00:30:40,939 --> 00:30:42,579 There was sort of that human part of like, 610 00:30:42,640 --> 00:30:43,874 where is my buddy? 611 00:30:43,975 --> 00:30:46,577 And also that science part of, what was it trying to tell us? 612 00:30:46,678 --> 00:30:50,681 ROWE: Then, an eagle-eyed researcher spotted 613 00:30:50,782 --> 00:30:53,650 something in the corner of an image. 614 00:30:53,751 --> 00:30:55,986 SHERIDAN: The lander itself was a tiny little speck, 615 00:30:56,087 --> 00:30:58,088 and you really have to zoom in to actually see it. 616 00:30:58,189 --> 00:31:01,792 But there was Philae, under a cliff. 617 00:31:01,893 --> 00:31:04,228 OLUSEYI: Seeing the little Philae lander there, 618 00:31:04,329 --> 00:31:07,297 on its side, under a ledge, 619 00:31:07,398 --> 00:31:11,068 in the shadows, was just remarkable. 620 00:31:11,169 --> 00:31:13,370 ROWE: Pinpointing Philae's location on 621 00:31:13,471 --> 00:31:16,874 the smaller lobe solved one final mystery. 622 00:31:16,975 --> 00:31:20,077 It explained data sent back months earlier, 623 00:31:20,178 --> 00:31:24,281 revealing this area of the comet is solid. 624 00:31:26,184 --> 00:31:27,761 HOWETT: There was a real sense of closure, 625 00:31:27,785 --> 00:31:29,263 and there was sort of a Godspeed to it, 626 00:31:29,287 --> 00:31:31,031 you know, like, we know what's happened to you. 627 00:31:31,055 --> 00:31:32,122 Thank you for the science. 628 00:31:32,223 --> 00:31:33,891 And that was its final resting place. 629 00:31:33,992 --> 00:31:37,394 And it was... it was really... It was really wonderful to see. 630 00:31:38,463 --> 00:31:40,163 SHERIDAN: Philae was an amazing success. 631 00:31:40,265 --> 00:31:41,665 Despite all those problems, 632 00:31:41,799 --> 00:31:44,167 we got the lander down... Despite the bounce 633 00:31:44,269 --> 00:31:45,980 and it coming to a rest under the cliff face, 634 00:31:46,004 --> 00:31:50,007 we got actually amazing images on some fantastic measurements 635 00:31:50,074 --> 00:31:52,509 of the gases and the structure of the comet itself, 636 00:31:52,610 --> 00:31:54,912 which we would never have had had we not tried 637 00:31:55,013 --> 00:31:56,093 to put a lander on a comet. 638 00:31:59,450 --> 00:32:01,551 ROWE: Rosetta's mission was not over. 639 00:32:02,687 --> 00:32:06,056 As the comet approached the sun, chaos erupted. 640 00:32:07,825 --> 00:32:11,295 [whooshing noises] 641 00:32:11,396 --> 00:32:14,064 RADEBAUGH: All of a sudden, there were these jets that would 642 00:32:14,165 --> 00:32:17,000 appear and eject a huge amount of material from the interior. 643 00:32:18,269 --> 00:32:20,871 ROWE: When sunlight warms the comet's surface, 644 00:32:20,972 --> 00:32:24,074 ice turns directly into gas. 645 00:32:24,175 --> 00:32:27,744 The uneven surface of the comet funnels the escaping 646 00:32:27,845 --> 00:32:31,281 water vapor into narrow jets of gas and dust. 647 00:32:33,685 --> 00:32:38,488 But Rosetta also spotted huge violent gas outbursts. 648 00:32:40,458 --> 00:32:41,959 [whooshing noises] 649 00:32:42,060 --> 00:32:44,695 We would expect to see jets on comets that 650 00:32:44,796 --> 00:32:46,196 kind of gradually rise and fall 651 00:32:46,297 --> 00:32:47,597 with the solar illumination. 652 00:32:47,699 --> 00:32:49,833 But these outbursts were utterly different. 653 00:32:49,934 --> 00:32:52,536 They would just sharply increase and then stop. 654 00:32:52,637 --> 00:32:56,106 These outbursts weren't timed with the sun. 655 00:32:56,207 --> 00:32:58,308 They came out at random times, 656 00:32:58,409 --> 00:33:01,812 so there must be something else going on. 657 00:33:01,913 --> 00:33:05,515 ROWE: The outbursts exploded in sudden, brief, 658 00:33:05,616 --> 00:33:08,285 high speed events. 659 00:33:08,386 --> 00:33:10,020 Because we only take pictures of 660 00:33:10,121 --> 00:33:12,956 the surface every 5 to 30 minutes, 661 00:33:13,057 --> 00:33:16,860 when we see an outburst in only one image, 662 00:33:16,961 --> 00:33:20,497 we know that the whole event lasted less than that time, 663 00:33:20,598 --> 00:33:22,899 which is very mysterious. 664 00:33:23,001 --> 00:33:26,003 RADEBAUGH: So it was like putting together a puzzle, 665 00:33:26,104 --> 00:33:28,505 and you have 1,000 pieces, and you're putting together, 666 00:33:28,606 --> 00:33:30,407 and you realize, oh, I only actually have 600 667 00:33:30,508 --> 00:33:31,685 of the 1,000 pieces, and I've got to 668 00:33:31,709 --> 00:33:34,044 make sense of this, and it's really frustrating. 669 00:33:34,145 --> 00:33:38,648 ROWE: As the comet swung closer to the sun, Rosetta's 670 00:33:38,750 --> 00:33:43,387 cameras captured 34 outbursts in just three months. 671 00:33:43,488 --> 00:33:45,255 They were all huge. 672 00:33:45,356 --> 00:33:48,158 In the span of only a few minutes, a single jet can 673 00:33:48,259 --> 00:33:51,995 release up to 260 tons of material, 674 00:33:52,096 --> 00:33:55,899 and one jet was spotted releasing 40 pounds of 675 00:33:56,000 --> 00:33:59,636 material every single second. 676 00:33:59,737 --> 00:34:03,206 ROWE: The cause of the outbursts was a complete mystery. 677 00:34:03,307 --> 00:34:07,611 Then, in September 2014, close-up images 678 00:34:07,712 --> 00:34:10,680 revealed a 230-foot-long, 679 00:34:10,782 --> 00:34:15,652 3-foot-wide fracture on the cliff edge named Aswan. 680 00:34:15,753 --> 00:34:18,588 Less than a year later, Rosetta photographed 681 00:34:18,689 --> 00:34:22,726 a large outburst from the same region of the comet. 682 00:34:25,296 --> 00:34:26,530 When the probe investigated 683 00:34:26,631 --> 00:34:30,100 the area, it found a devastated landscape. 684 00:34:30,201 --> 00:34:33,103 The cliff had collapsed in a huge landslide. 685 00:34:34,806 --> 00:34:36,573 SUTTER: This is like a crime scene. 686 00:34:36,674 --> 00:34:39,743 We have the before pictures and the after pictures, 687 00:34:39,844 --> 00:34:43,146 and we have to solve the mystery of how 688 00:34:43,247 --> 00:34:45,382 this happened. 689 00:34:45,483 --> 00:34:48,919 ROWE: What links the outburst and the cliff collapse? 690 00:34:49,020 --> 00:34:51,855 SUTTER: We think there's a domino effect going on here, 691 00:34:51,956 --> 00:34:55,292 where the sun heats up some of the volatiles deep under 692 00:34:55,393 --> 00:34:57,194 the surface, and they sublimate 693 00:34:57,295 --> 00:35:00,330 and turn into a gas, and they find any little crack 694 00:35:00,431 --> 00:35:03,800 or crevice they can to shoot out of the comet. 695 00:35:03,901 --> 00:35:08,505 But that process weakens part of the comet's face. 696 00:35:12,076 --> 00:35:14,578 RADEBAUGH: This is gonna release more material, and, 697 00:35:14,679 --> 00:35:17,914 as it does that, it's going to start forcing gas up through 698 00:35:18,015 --> 00:35:21,118 kind of nozzle-like features, having them act like jets. 699 00:35:21,219 --> 00:35:23,286 And as they do that, then that's gonna cause even 700 00:35:23,387 --> 00:35:24,855 more weakening of the material 701 00:35:24,956 --> 00:35:26,790 and maybe a large-scale collapse, 702 00:35:26,891 --> 00:35:30,193 which could actually cause a giant outburst. 703 00:35:30,294 --> 00:35:33,597 ROWE: We think escaping gas weakens the surface, 704 00:35:33,698 --> 00:35:36,600 which triggers a collapse and a release of gas 705 00:35:36,701 --> 00:35:38,869 in a giant outburst. 706 00:35:38,970 --> 00:35:41,438 Like sticking dynamite charges in the side of 707 00:35:41,539 --> 00:35:43,273 the cliff and then setting them all off. 708 00:35:43,374 --> 00:35:47,110 ♪♪ 709 00:35:47,211 --> 00:35:48,879 [whooshing noises] 710 00:35:52,450 --> 00:35:55,585 ROWE: Comet 67P revealed the hidden geological 711 00:35:55,686 --> 00:35:58,889 activity going on inside these dirty snowballs, 712 00:36:00,224 --> 00:36:03,660 and Rosetta spotted another surprising phenomenon... 713 00:36:05,630 --> 00:36:08,498 ...strange shapes moving across the surface... 714 00:36:09,800 --> 00:36:11,401 ...dunes. 715 00:36:11,502 --> 00:36:15,405 Dunes are driven by wind... Well on an airless comet, 716 00:36:15,506 --> 00:36:16,840 how do you have that happen? 717 00:36:27,685 --> 00:36:30,820 ROWE: Rosetta rewrote the book on how comets form, 718 00:36:30,922 --> 00:36:33,823 how they live, and how to explore them. 719 00:36:35,893 --> 00:36:38,195 When Rosetta flew close to the surface, 720 00:36:38,296 --> 00:36:40,730 it spotted something unexpected... 721 00:36:42,166 --> 00:36:43,767 ...dunes. 722 00:36:43,868 --> 00:36:47,003 DURDA: These are serious dunes, They're about 6 feet high, 723 00:36:47,104 --> 00:36:49,839 and they extend for hundreds of feet in every direction. 724 00:36:49,941 --> 00:36:52,542 So we've got to figure out what this mechanism is that 725 00:36:52,643 --> 00:36:54,188 it's causing this, you know, pretty significant 726 00:36:54,212 --> 00:36:55,879 geologic structure on the... On the comet. 727 00:37:00,051 --> 00:37:02,719 ROWE: Jani Radebaugh is a planetary scientist. 728 00:37:04,589 --> 00:37:07,057 She studies space dunes on Earth. 729 00:37:08,526 --> 00:37:11,895 One of the most fascinating things that Rosetta saw on 67P 730 00:37:11,996 --> 00:37:15,232 was a set of dune-like features on an airless body. 731 00:37:16,767 --> 00:37:17,978 These were found up by the neck 732 00:37:18,002 --> 00:37:20,370 region in a set of soft sediments. 733 00:37:20,471 --> 00:37:22,138 They actually look very similar to 734 00:37:22,240 --> 00:37:24,774 these ripple-like landforms. 735 00:37:24,875 --> 00:37:27,777 They were spaced about 10 yards across, 736 00:37:27,878 --> 00:37:31,748 and there were maybe 10 to 15 of them across the surface. 737 00:37:31,849 --> 00:37:34,951 And we even saw them change over time. 738 00:37:35,052 --> 00:37:36,353 When we first saw these, 739 00:37:36,454 --> 00:37:38,755 no one had any idea what could have formed them. 740 00:37:38,856 --> 00:37:40,557 In fact, people even doubted that they were 741 00:37:40,658 --> 00:37:41,758 dune-like landforms, 742 00:37:41,859 --> 00:37:44,261 because how would they possibly form on a body that 743 00:37:44,362 --> 00:37:47,364 has no atmosphere, let alone any wind? 744 00:37:47,465 --> 00:37:52,335 ROWE: On Earth, land heated unequally creates winds. 745 00:37:52,436 --> 00:37:54,804 RADEBAUGH: The atmosphere on Earth and the really transient 746 00:37:54,905 --> 00:37:55,972 atmosphere on a comet 747 00:37:56,073 --> 00:37:57,774 are very different from each other. 748 00:37:57,875 --> 00:38:00,410 On Earth, it's a stable, thick, dense atmosphere. 749 00:38:00,511 --> 00:38:03,246 It's got constant solar heating that can pick up air 750 00:38:03,347 --> 00:38:05,949 masses and move them across the surface and generate wind. 751 00:38:07,318 --> 00:38:11,121 ROWE: Comet 67P does have an atmosphere, created when 752 00:38:11,222 --> 00:38:14,324 the sun heats the surface, releasing gases. 753 00:38:16,027 --> 00:38:18,061 But this atmosphere has a maximum 754 00:38:18,162 --> 00:38:21,331 pressure 100,000 times lower than Earth's. 755 00:38:23,267 --> 00:38:26,803 Using Rosetta images, researchers in France modeled 756 00:38:26,904 --> 00:38:30,006 the movement of gases on the surface of the comet, 757 00:38:30,107 --> 00:38:32,909 and they think they've found the answer. 758 00:38:33,010 --> 00:38:36,913 Researchers found that there are winds on the comet's surface. 759 00:38:37,014 --> 00:38:38,682 These are brief, and they form 760 00:38:38,783 --> 00:38:41,051 because gases escape on the sunlit side, 761 00:38:41,152 --> 00:38:44,354 and then they rush over to the cold side across the surface, 762 00:38:44,455 --> 00:38:46,423 and this movement of air across the surface is 763 00:38:46,524 --> 00:38:48,992 what picks up the sand and forms the dunes. 764 00:38:50,594 --> 00:38:52,295 ROWE: The grains on the comet are 765 00:38:52,396 --> 00:38:55,465 far bigger than sand grains on Earth. 766 00:38:55,566 --> 00:38:56,766 On the Earth, 767 00:38:56,867 --> 00:38:59,135 the sand dunes are made of grains about this size. 768 00:38:59,236 --> 00:39:03,306 But on the comet, the sand dune grains are this size. 769 00:39:03,407 --> 00:39:05,408 Gravity also plays a really important role 770 00:39:05,509 --> 00:39:07,877 in moving grains around on the comet. 771 00:39:07,978 --> 00:39:10,380 The comet has such a low density that if you were 772 00:39:10,481 --> 00:39:13,083 walking around, you'd be able to fly into orbit very easily, 773 00:39:13,184 --> 00:39:16,252 and so a grain this big but low density would easily be 774 00:39:16,354 --> 00:39:18,154 lofted by the very thin air there. 775 00:39:21,392 --> 00:39:25,195 ROWE: After two years orbiting the sun with Comet 67P, 776 00:39:25,296 --> 00:39:27,731 Rosetta's mission was almost over. 777 00:39:29,166 --> 00:39:31,568 So the plan was to lower the orbiter 778 00:39:31,669 --> 00:39:33,803 down towards the surface in a controlled way. 779 00:39:33,904 --> 00:39:36,272 And this would allow very high-resolution images to be 780 00:39:36,374 --> 00:39:39,142 taken and also to get some gas measurements right 781 00:39:39,243 --> 00:39:40,563 close to the surface of the comet. 782 00:39:43,280 --> 00:39:45,949 ROWE: September 30th, 2016. 783 00:39:46,083 --> 00:39:50,220 Rosetta spent 14 hours slowly free-falling 784 00:39:50,321 --> 00:39:53,890 towards the comet, taking photos on the way down. 785 00:39:58,796 --> 00:40:02,265 SHERIDAN: As Rosetta was lowered, it touched the surface, 786 00:40:02,333 --> 00:40:05,535 and then the link back to Earth was broken, 787 00:40:05,636 --> 00:40:07,270 and the mission was effectively over. 788 00:40:09,140 --> 00:40:10,940 The thing that's kind of wonderful about it is 789 00:40:11,041 --> 00:40:12,442 that there's a little piece of us 790 00:40:12,543 --> 00:40:14,878 on that comet out there right now. 791 00:40:14,979 --> 00:40:16,746 As that comet spins around out 792 00:40:16,847 --> 00:40:19,082 to Jupiter and back every 6.5 years, 793 00:40:19,183 --> 00:40:22,419 it will always have a little bit of humanity on it. 794 00:40:26,023 --> 00:40:29,325 ROWE: There was one final twist to Rosetta's story. 795 00:40:29,427 --> 00:40:31,594 DURDA: We thought we had the last image back 796 00:40:31,695 --> 00:40:34,564 from Rosetta before the planned end of the mission. 797 00:40:34,665 --> 00:40:36,800 But it turns out that actually, 798 00:40:36,901 --> 00:40:39,669 just before touching down, before the come were able to 799 00:40:39,770 --> 00:40:41,137 finish transmitting back to 800 00:40:41,238 --> 00:40:44,207 Earth, an incomplete packet of information was sent back. 801 00:40:45,976 --> 00:40:49,479 ROWE: The computer discarded this incomplete data packet. 802 00:40:49,580 --> 00:40:53,349 Recently, human experts re-examined it. 803 00:40:55,519 --> 00:40:59,856 The result... Rosetta's closest photo of 67P. 804 00:41:01,091 --> 00:41:03,326 And the image is amazing, because when you actually blow 805 00:41:03,427 --> 00:41:05,562 it up and look at it, you can actually feel like 806 00:41:05,663 --> 00:41:07,430 you could reach out and touch the surface. 807 00:41:09,066 --> 00:41:12,235 ROWE: It's a fitting postscript to 808 00:41:12,336 --> 00:41:15,939 the only mission to land on a comet. 809 00:41:18,242 --> 00:41:20,610 DURDA: It's an incredible chance to learn about the geologic 810 00:41:20,711 --> 00:41:22,979 structure at the size scale of 811 00:41:23,080 --> 00:41:25,715 a human being exploring there... It's a way to look at comets 812 00:41:25,816 --> 00:41:27,851 that we've never had before. 813 00:41:29,320 --> 00:41:32,055 ROWE: The Rosetta mission has transformed our understanding 814 00:41:32,156 --> 00:41:33,323 of comets. 815 00:41:33,424 --> 00:41:35,569 WALSH: Between the strange shape and the measurements of 816 00:41:35,593 --> 00:41:37,093 heavy water, we're finding 817 00:41:37,194 --> 00:41:39,039 that there's a big diversity out there of comets, 818 00:41:39,063 --> 00:41:40,897 and that every time we go to visit a new one, 819 00:41:40,998 --> 00:41:43,032 we're probably gonna be surprised all over again. 820 00:41:44,502 --> 00:41:47,704 ROWE: Rosetta may inspire new missions. 821 00:41:47,805 --> 00:41:51,274 THALLER: We may actually be returning to Comet 67P itself. 822 00:41:51,375 --> 00:41:52,775 There's a lot more there to discover 823 00:41:52,877 --> 00:41:55,311 about the origin of our lives, ourselves, 824 00:41:55,412 --> 00:41:56,779 here on Earth. 825 00:41:56,881 --> 00:41:58,548 There's so much more to learn 826 00:41:58,649 --> 00:42:00,783 and so many more mysteries to uncover.