1 00:00:00,533 --> 00:00:02,101 (techno-chime melody) 2 00:00:02,101 --> 00:00:05,605 [Announcer] NASA's Jet Propulsion Laboratory presents: 3 00:00:05,605 --> 00:00:06,972 the von Karman Lecture. 4 00:00:06,972 --> 00:00:08,975 A series of talks by scientists 5 00:00:08,975 --> 00:00:11,944 and engineers who are exploring our planet, 6 00:00:11,944 --> 00:00:15,448 our solar system and all that lies beyond. 7 00:00:26,659 --> 00:00:28,260 - Hey, good evening ladies and gentlemen. 8 00:00:28,260 --> 00:00:29,929 How's everyone doing tonight? 9 00:00:29,929 --> 00:00:31,163 (various positive responses from audience) 10 00:00:31,163 --> 00:00:32,264 Excellent. (applause) 11 00:00:32,264 --> 00:00:33,533 That's what we love to hear. 12 00:00:33,533 --> 00:00:35,100 Thanks so much for comin' out tonight. 13 00:00:35,100 --> 00:00:37,536 So, Rosetta has been one of the most difficult 14 00:00:37,536 --> 00:00:39,472 space missions ever attempted. 15 00:00:39,472 --> 00:00:41,841 After 10 years of flight, it caught up with a comet 16 00:00:41,841 --> 00:00:45,110 speeding at 55,000 kilometers per hour 17 00:00:45,110 --> 00:00:47,513 and dropped a lander on its surface. 18 00:00:47,513 --> 00:00:49,148 Then, the mother-craft orbited the comet 19 00:00:49,148 --> 00:00:50,650 for another year and a half, 20 00:00:50,650 --> 00:00:53,353 coming as close as six kilometers to the surface. 21 00:00:53,353 --> 00:00:56,222 In September of 2016, this very mother-ship, 22 00:00:56,222 --> 00:00:59,592 not designed for landing, will touch down onto the comet 23 00:00:59,592 --> 00:01:01,127 to end the mission. 24 00:01:01,127 --> 00:01:03,095 Tonight we have two guests who will not only describe 25 00:01:03,095 --> 00:01:05,865 this upcoming landing but will also talk 26 00:01:05,865 --> 00:01:08,635 about what we learned from Rosetta, about comets 27 00:01:08,635 --> 00:01:11,170 and the formation of our solar system. 28 00:01:11,170 --> 00:01:14,640 Art B. Chmielewski has a very difficult last name, 29 00:01:14,640 --> 00:01:17,877 but thankfully, easy initials: ABC. 30 00:01:17,877 --> 00:01:21,013 ABC got his education at the University of Michigan, 31 00:01:21,013 --> 00:01:24,984 USC, and UCLA, which makes being a college football 32 00:01:24,984 --> 00:01:28,621 and basketball fan, well, challenging. 33 00:01:28,621 --> 00:01:30,957 He has been at JPL for 36 years and participated 34 00:01:30,957 --> 00:01:35,161 in 15 space missions, including Galileo, Ulysses, Cassini, 35 00:01:35,161 --> 00:01:38,297 Deep Space 1, the Mars Telecommunications Orbiter, 36 00:01:38,297 --> 00:01:42,034 Space Technology 6, and Space Technology 8. 37 00:01:42,034 --> 00:01:43,470 Pardon me. 38 00:01:43,470 --> 00:01:45,904 Currently he is the Rosetta US Project Manager, 39 00:01:45,904 --> 00:01:49,274 a job that, as he describes it, requires doing everything 40 00:01:49,274 --> 00:01:52,512 that the scientists are not willing to do. 41 00:01:52,512 --> 00:01:55,081 Dr. Bonnie Buratti is a Senior Research Scientist 42 00:01:55,081 --> 00:01:57,250 at JPL with expertise on the structure 43 00:01:57,250 --> 00:02:00,286 and evolution of icy moons and other small bodies. 44 00:02:00,286 --> 00:02:04,190 She holds degrees from MIT and Cornell in astronomy 45 00:02:04,190 --> 00:02:06,625 and is currently serving on the Science teams 46 00:02:06,625 --> 00:02:09,128 for both the Cassini and New Horizons missions 47 00:02:09,128 --> 00:02:11,130 as well as being the NASA Project Scientist 48 00:02:11,130 --> 00:02:12,665 for the Rosetta Mission. 49 00:02:12,665 --> 00:02:16,169 The author or co-author of over 200 scientific papers, 50 00:02:16,169 --> 00:02:19,004 she was awarded the NASA Exceptional Achievement Medal 51 00:02:19,004 --> 00:02:21,907 and the International Astronomical Union recognized her work 52 00:02:21,907 --> 00:02:24,377 by naming an asteroid after her. 53 00:02:24,377 --> 00:02:26,179 Ladies and gentlemen, first up tonight, 54 00:02:26,179 --> 00:02:27,647 Dr. Bonnie Buratti, 55 00:02:27,647 --> 00:02:29,916 (applause) 56 00:02:35,354 --> 00:02:36,555 - Thank you so much, Marc. 57 00:02:36,555 --> 00:02:37,490 Can everybody hear me? 58 00:02:37,490 --> 00:02:38,490 I guess so. - Yes 59 00:02:38,490 --> 00:02:40,159 and thank you all for coming. 60 00:02:40,159 --> 00:02:44,097 It's just wonderful to see everyone so interested in comets. 61 00:02:44,097 --> 00:02:46,199 I'm gonna start with a little bit of history, 62 00:02:46,199 --> 00:02:49,234 because comets, you know, other than the major planets 63 00:02:49,234 --> 00:02:50,503 that we can see with our naked eye, 64 00:02:50,503 --> 00:02:52,805 they're the things that the ancients have really 65 00:02:52,805 --> 00:02:55,775 wondered about and kind of awed over. 66 00:02:55,775 --> 00:02:57,276 So this is, are we gonna turn the lights down 67 00:02:57,276 --> 00:02:59,278 or keep them up or whatever? 68 00:02:59,278 --> 00:03:00,980 Okay, so this is an image, 69 00:03:00,980 --> 00:03:04,316 this is kind of an iconic image of a comet. 70 00:03:04,316 --> 00:03:08,821 And it shows you what comets are all about: the tail. 71 00:03:08,821 --> 00:03:12,292 Most comets have a nucleus, a rocky center. 72 00:03:12,292 --> 00:03:15,761 In fact, Fred Whipple, who was one of the grandfathers 73 00:03:15,761 --> 00:03:18,797 of modern astronomy, a Harvard professor, 74 00:03:18,797 --> 00:03:20,499 once called them, "Dirty ice balls." 75 00:03:20,499 --> 00:03:22,602 And that is in effect, what they are. 76 00:03:22,602 --> 00:03:25,771 They're lots of frozen, what we call volatiles, 77 00:03:25,771 --> 00:03:28,474 which is a fancy word for gases and dust. 78 00:03:28,474 --> 00:03:31,043 But the thing that we see, that we think of comets, 79 00:03:31,043 --> 00:03:34,113 as being just so beautiful and awesome, are the tail. 80 00:03:34,113 --> 00:03:36,249 And I really like this image here, it's a French image 81 00:03:36,249 --> 00:03:37,517 from 1858. 82 00:03:37,517 --> 00:03:41,420 It's Donati's Comet of 1858 I believe it was. 83 00:03:41,420 --> 00:03:44,623 It shows the two types of tails: the dust tail here 84 00:03:44,623 --> 00:03:46,125 and the ion tail. 85 00:03:46,125 --> 00:03:48,427 This is just dust and this is charged particles, 86 00:03:48,427 --> 00:03:51,029 coming from this very small comet. 87 00:03:51,029 --> 00:03:53,766 They're typically just a mile or so in size 88 00:03:53,766 --> 00:03:56,435 and if you are an astronomy fan, you'll notice 89 00:03:56,435 --> 00:03:57,937 the Big Dipper and Arcturus. 90 00:03:57,937 --> 00:03:59,339 So this picture is accurate. 91 00:03:59,339 --> 00:04:00,673 It's over Paris. 92 00:04:01,841 --> 00:04:03,942 And here's another iconic image, here. 93 00:04:03,942 --> 00:04:07,513 This is of Halley's Comet, during the last appearance 94 00:04:07,513 --> 00:04:08,781 or apparition. 95 00:04:08,781 --> 00:04:11,083 That's a fancy word that astronomers use 96 00:04:11,083 --> 00:04:12,084 to mean an appearance, 97 00:04:12,084 --> 00:04:14,420 This was the one in 1986. 98 00:04:14,420 --> 00:04:16,054 How many people saw it? 99 00:04:16,054 --> 00:04:18,390 It wasn't a very good appearance, apparition. 100 00:04:18,390 --> 00:04:19,592 This is by Bill Liller. 101 00:04:19,592 --> 00:04:22,261 It's a photograph that he took for NASA 102 00:04:22,261 --> 00:04:25,798 and you can see the two tails, the dust tail here 103 00:04:25,798 --> 00:04:27,333 and the ion tail. 104 00:04:27,333 --> 00:04:30,269 And we'll be talking about ions and dust a little bit later. 105 00:04:30,269 --> 00:04:32,004 But one of the things about comets 106 00:04:32,004 --> 00:04:36,642 that has really been pretty consistent in history: 107 00:04:36,642 --> 00:04:38,678 they have been harbingers of doom. 108 00:04:38,678 --> 00:04:41,114 They've been an omen for bad things in the future, 109 00:04:41,114 --> 00:04:42,047 almost always. 110 00:04:42,047 --> 00:04:43,982 This is pretty cross-cultural. 111 00:04:43,982 --> 00:04:46,819 Every civilization you see has that feeling 112 00:04:46,819 --> 00:04:50,123 that comets somehow foretell doom. 113 00:04:50,123 --> 00:04:53,626 So here are two images, just two examples. 114 00:04:53,626 --> 00:04:57,529 Although one is not doom, but this from the Bayeax Tapestry, 115 00:04:57,529 --> 00:05:00,399 which was embroidered in 1066. 116 00:05:00,399 --> 00:05:04,570 That was the year before the fall of the last Norman King, 117 00:05:05,537 --> 00:05:06,539 King Harold. 118 00:05:08,107 --> 00:05:11,243 And you see up there's this little expression in Latin. 119 00:05:11,243 --> 00:05:12,611 And if you did study Latin, you'll notice 120 00:05:12,611 --> 00:05:14,413 there are some grammatical errors in here. 121 00:05:14,413 --> 00:05:17,549 (reads Latin phrase) 122 00:05:17,549 --> 00:05:19,118 It should be (corrects Latin), okay? 123 00:05:19,118 --> 00:05:22,288 But whatever, it means these are, these men, 124 00:05:22,288 --> 00:05:26,058 they are marveling at the star and here we have 125 00:05:26,058 --> 00:05:28,260 an embroidery of a comet, okay? 126 00:05:28,260 --> 00:05:30,329 And it turns out that there was an appearance 127 00:05:30,329 --> 00:05:31,964 of Halley's Comet. 128 00:05:31,964 --> 00:05:35,534 It comes back every, about 75 or 76 years. 129 00:05:35,534 --> 00:05:38,204 There was an appearance in that year in 1066. 130 00:05:38,204 --> 00:05:41,040 And if you see here, there's a fleet of boats 131 00:05:41,040 --> 00:05:43,275 and of the Norman conquest. 132 00:05:43,275 --> 00:05:46,345 And here we, on this side, you see the King, Harold 133 00:05:46,345 --> 00:05:48,714 over there and he's seeing the armies come in 134 00:05:48,714 --> 00:05:50,650 to overthrow the empire. 135 00:05:51,884 --> 00:05:55,188 Now on this side here, this is a fresco 136 00:05:55,188 --> 00:05:56,656 in the church. 137 00:05:56,656 --> 00:05:59,058 There's a little church in Padova, Padua Italy, 138 00:05:59,058 --> 00:06:00,292 which I've acutally been to 'cause 139 00:06:00,292 --> 00:06:01,961 there was a scientific meeting there, once. 140 00:06:01,961 --> 00:06:03,929 This is by Giotto, the Italian artist. 141 00:06:03,929 --> 00:06:06,732 This was made in about 1320. 142 00:06:06,732 --> 00:06:10,503 And here we see, this is a very common devotional theme 143 00:06:10,503 --> 00:06:12,738 called the Adoration of the Magi. 144 00:06:12,738 --> 00:06:15,675 The Zoroastrian priests from Persia 145 00:06:16,876 --> 00:06:19,812 and it shows Halley's Comet here as the star 146 00:06:19,812 --> 00:06:21,180 of Bethlehem. 147 00:06:21,180 --> 00:06:23,916 Now we know that the star of Bethlehem 148 00:06:23,916 --> 00:06:25,751 could not have been Halley's Comet 149 00:06:25,751 --> 00:06:27,820 because the apparition or the appearance 150 00:06:27,820 --> 00:06:31,057 didn't come anywhere near the birth of Jesus. 151 00:06:31,057 --> 00:06:33,792 But, again, here, it is shown as the foretelling 152 00:06:33,792 --> 00:06:38,464 or an apparition or appearance of a prediction 153 00:06:38,464 --> 00:06:40,299 of the birth of Jesus. 154 00:06:41,633 --> 00:06:44,603 So we think that Giotto actually viewed the apparition, 155 00:06:44,603 --> 00:06:48,341 the appearance in 1301 and that's where he got the idea. 156 00:06:48,341 --> 00:06:49,508 Okay, moving along. 157 00:06:49,508 --> 00:06:51,510 Here is a pretty extreme cartoon. 158 00:06:51,510 --> 00:06:54,479 This is also French, of a comet 159 00:06:54,479 --> 00:06:56,882 actually destroying the Earth. 160 00:06:56,882 --> 00:06:58,884 It's pretty vivid. 161 00:06:58,884 --> 00:07:02,854 And I was saying that this idea of comets 162 00:07:02,854 --> 00:07:06,525 just as being destroyers is pretty common in all cultures. 163 00:07:06,525 --> 00:07:10,363 This is Montezuma and this was a 16th-century, 164 00:07:11,864 --> 00:07:14,967 just drawing, a watercolor and it was 165 00:07:14,967 --> 00:07:18,604 So Montezuma was overthrown in 1520. 166 00:07:18,604 --> 00:07:21,373 This was not anytime near one of the appearances 167 00:07:21,373 --> 00:07:24,543 of Halley's Comet but there apparently was another comet 168 00:07:24,543 --> 00:07:27,413 the year he was, you know, assassinated 169 00:07:27,413 --> 00:07:29,448 by the conquistadors. 170 00:07:29,448 --> 00:07:30,583 And Pissaro, I think. 171 00:07:30,583 --> 00:07:31,784 Was it Pissaro? 172 00:07:31,784 --> 00:07:34,052 Wait, you don't, whatever. 173 00:07:34,052 --> 00:07:38,224 So this is seen as an omen of the overthrow of Montezuma. 174 00:07:39,658 --> 00:07:43,161 It's also true the Chinese tracked appearances 175 00:07:43,161 --> 00:07:46,999 of Halley's Comet back to about 400 years BCE. 176 00:07:48,433 --> 00:07:51,470 It turns out that they never realized that it was periodic. 177 00:07:51,470 --> 00:07:53,005 It wasn't really until Halley that we realized 178 00:07:53,005 --> 00:07:54,673 that some of these comets come back. 179 00:07:54,673 --> 00:07:57,409 They get captured by the sun and are periodic. 180 00:07:57,409 --> 00:08:01,947 But, again, when Halley's Comet appeared in 276 BCE, 181 00:08:01,947 --> 00:08:06,118 it was said the next year, the empress dowager passed away. 182 00:08:07,019 --> 00:08:08,454 So again. 183 00:08:08,454 --> 00:08:10,622 But why should we really care about comets? 184 00:08:10,622 --> 00:08:12,758 You know, why do they really matter? 185 00:08:12,758 --> 00:08:14,861 Well, here are three big reasons: 186 00:08:14,861 --> 00:08:18,764 the first one is that they are remnants left over 187 00:08:18,764 --> 00:08:22,401 from the very earliest stages of the solar system. 188 00:08:22,401 --> 00:08:25,671 They are what we call planitesimals, the building-blocks 189 00:08:25,671 --> 00:08:27,939 that came together to form the planets. 190 00:08:27,939 --> 00:08:29,508 And research from Rosetta has shown 191 00:08:29,508 --> 00:08:32,345 they really are leftover remnants. 192 00:08:32,345 --> 00:08:34,346 They supply the Earth with some water. 193 00:08:34,346 --> 00:08:36,749 Probably not all of it but a lot of it, 194 00:08:36,749 --> 00:08:39,251 and organic material. 195 00:08:39,251 --> 00:08:42,955 It's possible that most of the prebiotic material 196 00:08:42,955 --> 00:08:45,023 that led to the origin of life on Earth came 197 00:08:45,023 --> 00:08:47,993 from the outer solar system fed by comets. 198 00:08:47,993 --> 00:08:50,295 These are key to the formation of life. 199 00:08:50,295 --> 00:08:51,497 And the final reason is, 200 00:08:51,497 --> 00:08:54,500 they are really potential destroyers. 201 00:08:54,500 --> 00:08:56,235 So, here's a NASA artist's conception 202 00:08:56,235 --> 00:08:58,570 of what the early solar system looked like. 203 00:08:58,570 --> 00:09:01,040 You can see the sun and the planets forming. 204 00:09:01,040 --> 00:09:04,043 But all these little planetesimals came together 205 00:09:04,043 --> 00:09:05,744 to form the planets. 206 00:09:05,744 --> 00:09:08,680 And as you'll see when we actually look at images 207 00:09:08,680 --> 00:09:12,852 and all the data on the comet that Rosetta explored, 208 00:09:16,755 --> 00:09:18,958 it will actually look like these planetesimals 209 00:09:18,958 --> 00:09:20,225 coming together. 210 00:09:20,225 --> 00:09:23,095 It will look like two planetesimals. 211 00:09:23,095 --> 00:09:26,165 Okay, so where are all these comets, now? 212 00:09:26,165 --> 00:09:29,100 So all that debris that you see here is still around. 213 00:09:29,100 --> 00:09:31,636 But it kinda got shuffled around 214 00:09:31,636 --> 00:09:34,140 and is now in two major areas. 215 00:09:35,307 --> 00:09:37,509 Okay, so first what we have to think big. 216 00:09:37,509 --> 00:09:39,878 A lot of these comets were kinda flung out 217 00:09:39,878 --> 00:09:43,048 of the solar system and all collected in this area 218 00:09:43,048 --> 00:09:44,183 called the oort cloud. 219 00:09:44,183 --> 00:09:45,551 It was named after Jan Oort 220 00:09:45,551 --> 00:09:48,454 who was a Dutch astronomer, actually. 221 00:09:48,454 --> 00:09:49,654 He's since passed away. 222 00:09:49,654 --> 00:09:51,323 But it's really immense, it's huge. 223 00:09:51,323 --> 00:09:52,791 If you look at this, 224 00:09:52,791 --> 00:09:56,828 it's about 100,000 astronomical units, AU, is the distance. 225 00:09:56,828 --> 00:09:58,830 An astronomical unit is the distance 226 00:09:58,830 --> 00:10:00,632 between the Earth and the sun. 227 00:10:00,632 --> 00:10:02,267 It's about 93 million miles. 228 00:10:02,267 --> 00:10:04,003 So this is immense, it's huge. 229 00:10:04,003 --> 00:10:07,205 It's like a large fraction of the distance to the next star. 230 00:10:07,205 --> 00:10:09,575 And the very center there, like a little dot, 231 00:10:09,575 --> 00:10:10,943 is the solar system. 232 00:10:10,943 --> 00:10:13,412 I have it expanded there 500 times. 233 00:10:13,412 --> 00:10:14,813 And this is the Kuiper Belt. 234 00:10:14,813 --> 00:10:17,349 This is this debris, sometimes called the third zone, 235 00:10:17,349 --> 00:10:20,252 debris outside the orbit, this is the orbit of Pluto, here, 236 00:10:20,252 --> 00:10:21,487 and Neptune. 237 00:10:21,487 --> 00:10:23,655 That Pluto is a body that New Horizons 238 00:10:23,655 --> 00:10:26,225 made this first encounter with. 239 00:10:26,225 --> 00:10:27,993 Some of the comets come from there. 240 00:10:27,993 --> 00:10:30,396 Churyumov-Gerasimenko does come, 241 00:10:30,396 --> 00:10:32,797 which we will call 67P from now on 242 00:10:32,797 --> 00:10:35,534 because it is not pronounceable. 243 00:10:35,534 --> 00:10:37,736 (laughter) 244 00:10:37,736 --> 00:10:40,973 Okay, so 67P comes from the Kuiper Belt, 245 00:10:40,973 --> 00:10:44,543 which is where the Jupiter-family comets come from. 246 00:10:44,543 --> 00:10:46,278 But some of the long-period comets 247 00:10:46,278 --> 00:10:49,448 and these comets that come pristine, 248 00:10:49,448 --> 00:10:51,817 from the outer, outside the solar system, 249 00:10:51,817 --> 00:10:52,985 come from the Oort cloud. 250 00:10:52,985 --> 00:10:55,354 Now, don't forget, there's also asteroids, 251 00:10:55,354 --> 00:10:56,755 which are in this little, 252 00:10:56,755 --> 00:10:58,156 the asteroid belt's this little, 253 00:10:58,156 --> 00:11:00,158 but that's also stuff left over 254 00:11:00,158 --> 00:11:02,494 from the origins of the solar system 255 00:11:02,494 --> 00:11:04,330 although it's not quite as pristine as comets. 256 00:11:04,330 --> 00:11:06,098 That's just in that little area there. 257 00:11:06,098 --> 00:11:08,868 So that's kind of the background. 258 00:11:10,035 --> 00:11:11,703 But sometimes these comets are flung, 259 00:11:11,703 --> 00:11:15,574 comets and asteroids are flung into the inner solar system. 260 00:11:15,574 --> 00:11:16,808 And this is an example: 261 00:11:16,808 --> 00:11:19,144 another NASA artist has shown this picture 262 00:11:19,144 --> 00:11:22,047 of an asteroid or a comet hitting the Earth. 263 00:11:22,047 --> 00:11:25,851 And there are some that even believe that the extinction, 264 00:11:25,851 --> 00:11:30,022 the great extinction, when the dinosaurs became extinct, 265 00:11:31,356 --> 00:11:33,492 at the end of the cretacious geologic period, 266 00:11:33,492 --> 00:11:36,128 that it may have actually been a comet that came 267 00:11:36,128 --> 00:11:39,398 and impacted the Earth and blew up all this dust 268 00:11:39,398 --> 00:11:42,468 which caused kind of a global winter. 269 00:11:42,468 --> 00:11:45,270 And eventually, that's the demise of the dinosaurs. 270 00:11:45,270 --> 00:11:48,006 And a lot of other species. 271 00:11:48,006 --> 00:11:52,044 Okay, so, Art is gonna talk about missions, 272 00:11:52,044 --> 00:11:55,147 but before, about the mission itself, 273 00:11:55,147 --> 00:11:58,216 but before he does that, I wanna give like a 30-second 274 00:11:58,216 --> 00:12:02,054 overview of what missions went before Rosetta. 275 00:12:03,455 --> 00:12:05,023 And I also wanna make the point 276 00:12:05,023 --> 00:12:07,692 that the data was not very good. 277 00:12:07,692 --> 00:12:09,795 Okay, I mean like, the best picture. 278 00:12:09,795 --> 00:12:13,598 This is Wild 2, a comet that Stardust looked at. 279 00:12:13,598 --> 00:12:15,901 And that's about the best image we have of a comet. 280 00:12:15,901 --> 00:12:19,004 So this is Halley, which was observed 281 00:12:19,004 --> 00:12:21,607 by the Giotto Spacecraft, named after the artist 282 00:12:21,607 --> 00:12:25,778 who drew that picture of Halley over the manger of Jesus. 283 00:12:26,978 --> 00:12:28,046 That was in 1985. 284 00:12:28,046 --> 00:12:30,215 NASA canceled its own mission. 285 00:12:30,215 --> 00:12:34,586 So there's an actual image close-up of the nucleus, 286 00:12:34,586 --> 00:12:39,091 the rocky center we sometimes call the nucleus, of Halley. 287 00:12:39,091 --> 00:12:41,260 Deep Space 1, which Art and I actually both worked 288 00:12:41,260 --> 00:12:42,128 on that project. 289 00:12:42,128 --> 00:12:43,428 Comet Barrelli. 290 00:12:43,428 --> 00:12:44,529 And here's the scale of miles. 291 00:12:44,529 --> 00:12:46,932 These are all to scale. 292 00:12:46,932 --> 00:12:50,168 Wild 2, Stardust, which also sent back a sample. 293 00:12:50,168 --> 00:12:51,670 And, look at these little pits, here. 294 00:12:51,670 --> 00:12:55,374 Just notice how similar they are to the ones on 67P. 295 00:12:55,374 --> 00:12:58,778 Tempel 1 which was visited by Deep Impact 296 00:13:00,779 --> 00:13:03,214 and later went on to see Hartley. 297 00:13:03,214 --> 00:13:04,749 And the thing about Deep Impact, 298 00:13:04,749 --> 00:13:06,218 this is my last slide before we talk 299 00:13:06,218 --> 00:13:09,288 about the Rosetta mission itself, 300 00:13:09,288 --> 00:13:13,392 actually put a cannon-ball-sized metal projectile 301 00:13:14,827 --> 00:13:18,664 into Tempel 1's surface and this is the explosion 302 00:13:20,031 --> 00:13:21,033 that we saw. 303 00:13:23,468 --> 00:13:27,505 And later on, the Stardust, a kind of a revamped version 304 00:13:27,505 --> 00:13:30,175 of Stardust went by and some scientists claim 305 00:13:30,175 --> 00:13:34,079 they could actually see a crater that the cannon ball made. 306 00:13:34,079 --> 00:13:35,280 But I'm not gonna show that, 307 00:13:35,280 --> 00:13:36,915 'cause personally I couldn't see the crater. 308 00:13:36,915 --> 00:13:40,485 Okay, so Art is gonna talk about the actual mission 309 00:13:40,485 --> 00:13:43,521 and about, later on, landing on the comet. 310 00:13:43,521 --> 00:13:45,224 And then later, I'll come up and talk 311 00:13:45,224 --> 00:13:48,460 about some of the scientific results from the mission. 312 00:13:48,460 --> 00:13:50,663 But Art is on with a model. 313 00:13:59,237 --> 00:14:00,072 - Hi folks. 314 00:14:00,072 --> 00:14:02,341 (applause) 315 00:14:06,211 --> 00:14:09,148 I got my applause, I think I'm done, thank you. 316 00:14:09,148 --> 00:14:11,183 That was, that felt good. 317 00:14:11,183 --> 00:14:12,417 Any other questions? 318 00:14:12,417 --> 00:14:14,886 (laughter) 319 00:14:14,886 --> 00:14:19,090 So let tell you about the Rosetta mission a little bit. 320 00:14:19,090 --> 00:14:23,895 I don't have any charts, but I will use the audience 321 00:14:23,895 --> 00:14:26,431 to demonstrate the mission. 322 00:14:26,431 --> 00:14:29,768 So, first of all how did this comet 323 00:14:29,768 --> 00:14:31,403 to which we traveled form? 324 00:14:31,403 --> 00:14:32,604 Okay? 325 00:14:32,604 --> 00:14:35,007 If we have anybody under 15, come on down 326 00:14:35,007 --> 00:14:37,309 on the stage here, please. 327 00:14:37,309 --> 00:14:38,944 Under 15. 328 00:14:38,944 --> 00:14:41,146 Quick, quick, quick, quick, quick, quick. 329 00:14:41,146 --> 00:14:43,515 Quick, quick quick. 330 00:14:43,515 --> 00:14:45,350 Alright, we have a lot of cometessimals. 331 00:14:45,350 --> 00:14:47,085 (laughter) 332 00:14:47,085 --> 00:14:49,355 Come on up, hop up, up, up. 333 00:14:50,789 --> 00:14:52,958 And if you fall off this stage and injure yourself, 334 00:14:52,958 --> 00:14:53,926 I'll kill you. 335 00:14:53,926 --> 00:14:55,427 (laughter) 336 00:14:55,427 --> 00:14:57,862 Okay, 'cause this hasn't been checked 337 00:14:57,862 --> 00:15:01,099 with safety and security at JPL, so. 338 00:15:01,099 --> 00:15:03,535 Okay, you guys are all little pieces 339 00:15:03,535 --> 00:15:07,640 of dust and gas and we are 4.6 billion years ago. 340 00:15:10,809 --> 00:15:13,912 In the beginnings of the solar system, okay? 341 00:15:13,912 --> 00:15:18,349 So, spread out around the stage, spread out. 342 00:15:18,349 --> 00:15:21,053 And now you just start walking, 343 00:15:21,053 --> 00:15:23,622 wherever you wanna walk, but if you bump into somebody 344 00:15:23,622 --> 00:15:24,856 go straight. 345 00:15:24,856 --> 00:15:27,058 Then you have to grab onto this person, okay? 346 00:15:27,058 --> 00:15:28,727 And then you have to walk with this person. 347 00:15:28,727 --> 00:15:30,362 Just go and if you touch somebody, 348 00:15:30,362 --> 00:15:31,897 you gotta grab onto them. 349 00:15:31,897 --> 00:15:34,199 Yeah, if you touch, you gotta grab on. 350 00:15:34,199 --> 00:15:37,569 And now you have to be close together, close together. 351 00:15:37,569 --> 00:15:39,037 Close together. 352 00:15:39,037 --> 00:15:42,941 If you bump into somebody, grab 'em and keep on walking. 353 00:15:42,941 --> 00:15:45,577 You see, there is a lot of instability in the universe. 354 00:15:45,577 --> 00:15:47,713 And we have our first comet! 355 00:15:47,713 --> 00:15:49,949 (applause) 356 00:15:53,318 --> 00:15:56,054 Okay, thank you cometessimals. 357 00:15:56,054 --> 00:15:57,856 Thank you, big hand for cometessimals. 358 00:15:57,856 --> 00:16:00,125 (applause) 359 00:16:01,559 --> 00:16:03,995 So, this is basically, you can 360 00:16:03,995 --> 00:16:06,565 I know it's hard to leave the stage once you get on it. 361 00:16:06,565 --> 00:16:08,867 (laughter) 362 00:16:08,867 --> 00:16:11,370 A lot of people in Los Angeles area have this problem. 363 00:16:11,370 --> 00:16:13,505 (laughter) 364 00:16:13,505 --> 00:16:17,075 But, so, we're dealing here with a body 365 00:16:17,075 --> 00:16:19,812 that formed very early during the formation 366 00:16:19,812 --> 00:16:21,212 of the solar system. 367 00:16:21,212 --> 00:16:24,249 Formed out of gas, out of dust, 368 00:16:24,249 --> 00:16:28,087 very porous, very, very, 70% of the comet 369 00:16:29,621 --> 00:16:31,056 is actually nothing. 370 00:16:31,056 --> 00:16:35,193 So we have this body that orbits the sun. 371 00:16:35,193 --> 00:16:39,197 And it orbits it on the elliptical orbit, right? 372 00:16:39,197 --> 00:16:42,200 So, let's, I think we need 373 00:16:42,200 --> 00:16:43,936 we need a spacecraft and a comet 374 00:16:43,936 --> 00:16:47,072 to demonstrate the principle so, yes, please. 375 00:16:47,072 --> 00:16:48,039 And what is your name? 376 00:16:48,039 --> 00:16:48,907 Come on up. - Noah. 377 00:16:48,907 --> 00:16:49,975 - What is it? 378 00:16:49,975 --> 00:16:51,977 - Noah - Noah. Dr. Noah. 379 00:16:51,977 --> 00:16:52,944 (laughter) 380 00:16:52,944 --> 00:16:56,081 Yes, Dr. Noah from University-- 381 00:16:56,081 --> 00:16:57,248 - Uh, nothing. 382 00:16:57,248 --> 00:16:59,284 - University of Nothing. (laughter) 383 00:16:59,284 --> 00:17:01,286 It's a very small school 384 00:17:02,888 --> 00:17:06,124 Okay, and can we have another volunteer? 385 00:17:06,124 --> 00:17:08,527 Okay, another volunteer, please. 386 00:17:08,527 --> 00:17:10,395 Under 80 would be good. 387 00:17:10,395 --> 00:17:11,663 (laughter) 388 00:17:11,663 --> 00:17:12,597 Yes, please, come on up, come on up. 389 00:17:12,597 --> 00:17:15,267 Come on up and yeah, come on up. 390 00:17:16,635 --> 00:17:18,637 Kodiak. Kodiak? 391 00:17:18,637 --> 00:17:19,871 - [Kodiak] Yes. 392 00:17:19,871 --> 00:17:22,207 - Okay, and Dr. Noah, Dr. Kodiak. 393 00:17:23,475 --> 00:17:24,309 - Wesley. 394 00:17:24,309 --> 00:17:25,143 - [Art] Doctor-- 395 00:17:25,143 --> 00:17:25,978 - Wesley. 396 00:17:25,978 --> 00:17:27,012 - Doctor Wesley. 397 00:17:27,012 --> 00:17:28,714 (applause) 398 00:17:28,714 --> 00:17:31,215 From University of-- 399 00:17:31,215 --> 00:17:33,652 - Awesome things, I don't know. 400 00:17:33,652 --> 00:17:37,121 - University of Awesome Things, very good. 401 00:17:37,121 --> 00:17:38,824 And you are from University of-- 402 00:17:38,824 --> 00:17:39,758 - [Kodiak] Home. 403 00:17:39,758 --> 00:17:41,159 - Oh, University of Home. 404 00:17:41,159 --> 00:17:43,729 This is the first home-schooled university, okay? 405 00:17:43,729 --> 00:17:44,663 (laughter) 406 00:17:44,663 --> 00:17:46,097 Very good, very good. 407 00:17:46,097 --> 00:17:48,867 Okay, we have to approve the curriculum, still. 408 00:17:48,867 --> 00:17:53,037 Okay, so now, lemme show you what the situation is 409 00:17:53,037 --> 00:17:54,539 with catching up with the comet. 410 00:17:54,539 --> 00:17:57,175 The comet goes around the sun, right? 411 00:17:57,175 --> 00:17:58,877 And when it goes close to the sun, 412 00:17:58,877 --> 00:18:00,646 it puffs up and shoots out all the smoke 413 00:18:00,646 --> 00:18:02,815 and all the dust and jets. 414 00:18:03,848 --> 00:18:05,851 So, we have you, Wesley. 415 00:18:07,052 --> 00:18:08,620 Dr. Wesley will be the sun. 416 00:18:08,620 --> 00:18:09,921 Here, you stand here. 417 00:18:09,921 --> 00:18:11,156 And the reason he's the sun, 418 00:18:11,156 --> 00:18:12,824 because you can tell he's very bright. 419 00:18:12,824 --> 00:18:14,192 (laughter) 420 00:18:14,192 --> 00:18:15,126 Okay. 421 00:18:15,126 --> 00:18:17,195 And then we have a spacecraft 422 00:18:17,195 --> 00:18:19,297 and we're gonna have a comet, right? 423 00:18:19,297 --> 00:18:22,668 So, you are a spacecraft, okay. 424 00:18:22,668 --> 00:18:24,336 And you are a comet. 425 00:18:25,403 --> 00:18:27,239 And, alright, alright. 426 00:18:29,374 --> 00:18:30,775 So now, okay. 427 00:18:30,775 --> 00:18:32,978 You have to land, Noah 428 00:18:32,978 --> 00:18:34,212 Noah? - Yeah. 429 00:18:34,212 --> 00:18:35,113 - You have to land this spacecraft 430 00:18:35,113 --> 00:18:36,815 on this comet, right? 431 00:18:36,815 --> 00:18:38,817 So now, you are a comet. 432 00:18:38,817 --> 00:18:42,154 You go around the sun, right, like this. 433 00:18:43,654 --> 00:18:45,757 You speed up here when you're close to the sun. 434 00:18:45,757 --> 00:18:48,026 Yeah, go, go, very elliptical orbit. 435 00:18:48,026 --> 00:18:49,194 Come on back. 436 00:18:49,194 --> 00:18:50,862 Okay, very good. 437 00:18:50,862 --> 00:18:52,697 And you go on the same orbit. 438 00:18:52,697 --> 00:18:53,965 So what did you notice? 439 00:18:53,965 --> 00:18:56,034 How can you land, you speed up. 440 00:18:56,034 --> 00:18:56,901 (laughter) 441 00:18:56,901 --> 00:18:58,636 Spacecraft, don't cheat. 442 00:18:58,636 --> 00:19:00,872 You don't have huge boosters. 443 00:19:00,872 --> 00:19:02,707 First of all, what did we notice, here? 444 00:19:02,707 --> 00:19:06,378 What do you have to do, Noah, to land on the comet? 445 00:19:06,378 --> 00:19:07,212 - [Noah] I gotta catch up with it. 446 00:19:07,212 --> 00:19:08,680 - You gotta catch up. 447 00:19:08,680 --> 00:19:11,483 And the spacecraft was trying to catch up for ten years. 448 00:19:11,483 --> 00:19:12,984 (laughter) 449 00:19:12,984 --> 00:19:16,855 So, and I wanna have a realistic simulation. 450 00:19:16,855 --> 00:19:17,689 So. 451 00:19:17,689 --> 00:19:19,925 (laughter) 452 00:19:23,028 --> 00:19:24,529 Okay, very well. 453 00:19:24,529 --> 00:19:25,997 Well, catch up, dammit. 454 00:19:25,997 --> 00:19:26,965 (laughter) 455 00:19:26,965 --> 00:19:27,799 (light applause) 456 00:19:27,799 --> 00:19:28,634 Okay, now. 457 00:19:31,269 --> 00:19:33,372 Thank you, Dr. Noah and thank you, Dr. Kodiak, 458 00:19:33,372 --> 00:19:35,573 and thank you, sun. 459 00:19:35,573 --> 00:19:37,709 You are very bright, thank you. 460 00:19:37,709 --> 00:19:39,945 (applause) 461 00:19:43,114 --> 00:19:47,152 So, this was the mission, this was the spacecraft. 462 00:19:47,152 --> 00:19:49,587 It's a, so this was the spacecraft built 463 00:19:49,587 --> 00:19:53,759 by the European Space Agency with instruments from NASA. 464 00:19:55,059 --> 00:19:57,396 NASA had big contribution to this mission. 465 00:19:57,396 --> 00:19:59,998 And huge solar arrays, they're actually the size 466 00:19:59,998 --> 00:20:02,333 of a tennis court. 467 00:20:02,333 --> 00:20:04,035 Because we're flying far away. 468 00:20:04,035 --> 00:20:05,570 And so this spacecraft, 469 00:20:05,570 --> 00:20:08,540 and then there was tiny little lander attached to it, right? 470 00:20:08,540 --> 00:20:11,176 And we had to catch up with the comet 471 00:20:11,176 --> 00:20:13,278 and it did take ten years 472 00:20:14,646 --> 00:20:18,950 because we had to get some boost from Earth 473 00:20:18,950 --> 00:20:20,852 and boost from Mars. 474 00:20:20,852 --> 00:20:23,555 Amazingly difficult thing, because the comet 475 00:20:23,555 --> 00:20:27,726 is actually going at 600,000 miles an hour, right? 476 00:20:29,428 --> 00:20:32,330 So this is more or less like four times 477 00:20:32,330 --> 00:20:35,366 anybody from Texas is here? 478 00:20:35,366 --> 00:20:36,901 Anybody? 479 00:20:36,901 --> 00:20:41,073 Okay, well, it's like four times the speeding bullet, right? 480 00:20:42,307 --> 00:20:44,442 So, you guys don't know what it means, 481 00:20:44,442 --> 00:20:46,444 but yeah, you're not from Texas. 482 00:20:46,444 --> 00:20:48,246 But four times the speed. 483 00:20:48,246 --> 00:20:50,882 So, imagine you have to catch up 484 00:20:50,882 --> 00:20:54,686 with a speeding, four times the speed of a speeding bullet 485 00:20:54,686 --> 00:20:58,957 and hop on, while this thing is spinning on the top of it 486 00:20:58,957 --> 00:21:03,328 and shooting gas and jets and particles, right? 487 00:21:03,328 --> 00:21:05,730 And you absolutely don't know what the surface is. 488 00:21:05,730 --> 00:21:08,900 You don't know if it's, if you're gonna sink in the dust 489 00:21:08,900 --> 00:21:11,903 or you're gonna land on a jet and get blown up. 490 00:21:11,903 --> 00:21:13,037 What's goin' on? 491 00:21:13,037 --> 00:21:14,839 You know, the mission was designed, 492 00:21:14,839 --> 00:21:17,742 this is the amazing thing: this is truly Star Trek. 493 00:21:17,742 --> 00:21:21,880 You go there, you know, and you explore, right? 494 00:21:21,880 --> 00:21:25,751 And so the lander was designed by the Germans, by DLR, 495 00:21:25,751 --> 00:21:29,520 when the comet was just one pixel on a picture, right? 496 00:21:29,520 --> 00:21:32,457 So, you know, how do you design something like this? 497 00:21:32,457 --> 00:21:35,694 And, but we did catch up with the comet 498 00:21:37,396 --> 00:21:40,298 and the only thing is that we were expecting the comet 499 00:21:40,298 --> 00:21:42,534 would be, you know, like one of these pictures, 500 00:21:42,534 --> 00:21:44,302 pretty much regular-shape. 501 00:21:44,302 --> 00:21:46,938 And it turned out that it's a bizarre thing 502 00:21:46,938 --> 00:21:49,840 that looks like this, okay? 503 00:21:49,840 --> 00:21:52,877 And the actual size of this is, 504 00:21:52,877 --> 00:21:56,114 anybody from La Canada, here? 505 00:21:56,114 --> 00:22:00,352 Yeah, it's about maybe a third of size of La Canada. 506 00:22:00,352 --> 00:22:03,321 So, you know, it's actually relatively tiny. 507 00:22:03,321 --> 00:22:05,424 And it's spinning, right? 508 00:22:06,891 --> 00:22:09,795 So, and there are gravity gradients 509 00:22:11,229 --> 00:22:13,999 because, you know, it has this irregular shape. 510 00:22:13,999 --> 00:22:18,569 So, so now, you try to land this tiny lander. 511 00:22:18,569 --> 00:22:20,371 And that did happen in November, 512 00:22:20,371 --> 00:22:21,673 maybe some of you were here. 513 00:22:21,673 --> 00:22:25,209 We talked about it, about a year ago. 514 00:22:25,209 --> 00:22:29,480 The lander did land and because it's such a low gravity, 515 00:22:29,480 --> 00:22:32,917 it, actually we picked a spot, here. 516 00:22:32,917 --> 00:22:34,485 It was supposed to land here 517 00:22:34,485 --> 00:22:36,287 because it was a little flatter. 518 00:22:36,287 --> 00:22:39,324 And there's always this discussion between engineers 519 00:22:39,324 --> 00:22:41,025 and scientists, right? 520 00:22:41,025 --> 00:22:43,061 So Bonnie is here, she's a project scientist, 521 00:22:43,061 --> 00:22:44,395 I'm a project manager. 522 00:22:44,395 --> 00:22:46,431 And the reason we always have these two people 523 00:22:46,431 --> 00:22:51,269 is because we wanna get to the safe middle, okay? 524 00:22:51,269 --> 00:22:52,704 Because if you ask Bonnie, it's like 525 00:22:52,704 --> 00:22:55,272 oh, we wanna land on something exciting. 526 00:22:55,272 --> 00:22:57,475 You know, pam, this is exciting. 527 00:22:57,475 --> 00:22:59,811 This is exciting, okay. 528 00:22:59,811 --> 00:23:01,512 This is boring. 529 00:23:01,512 --> 00:23:02,747 Engineers want boring. 530 00:23:02,747 --> 00:23:04,750 Scientists want exciting, right? 531 00:23:04,750 --> 00:23:08,286 So, we ended up somewhere in the middle, right? 532 00:23:08,286 --> 00:23:11,289 And so the spacecraft did land here. 533 00:23:12,457 --> 00:23:15,193 And it's supposed to fire harpoons 534 00:23:15,193 --> 00:23:17,862 because it was supposed to hold itself down. 535 00:23:17,862 --> 00:23:19,197 Very low gravity. 536 00:23:19,197 --> 00:23:22,100 If I jump, I stay on the ground because gravity. 537 00:23:22,100 --> 00:23:26,271 But, the harpoons didn't fire and the spacecraft bounced 538 00:23:27,706 --> 00:23:30,708 and disappeared from our camera and it went somewhere. 539 00:23:30,708 --> 00:23:34,479 Later, we calculated where it's supposed to be. 540 00:23:34,479 --> 00:23:36,714 We figured it out from basic physics. 541 00:23:36,714 --> 00:23:40,285 And it ended up going across this crater, 542 00:23:40,285 --> 00:23:42,687 which is not a crater and Bonnie will tell you about it. 543 00:23:42,687 --> 00:23:45,590 Bounced over one of the hills, bounced over another hill, 544 00:23:45,590 --> 00:23:48,726 flipped over and got stuck in a hole. 545 00:23:48,726 --> 00:23:50,128 Like a golf ball. 546 00:23:52,163 --> 00:23:54,800 And, but it did transmit for a while. 547 00:23:54,800 --> 00:23:59,070 To the orbiter and the orbiter was going around, 548 00:23:59,070 --> 00:24:01,172 all the time, going around the comet. 549 00:24:01,172 --> 00:24:03,441 And it's still doing this, right now. 550 00:24:03,441 --> 00:24:07,612 And sent some signals, seven out of eight experiments 551 00:24:08,980 --> 00:24:12,750 on the spacecraft worked, so we're very happy. 552 00:24:12,750 --> 00:24:15,453 Some scientists even liked the fact that it moved. 553 00:24:15,453 --> 00:24:19,957 'Cause they got a lot of data from different places. 554 00:24:19,957 --> 00:24:23,194 One experiment, you know, there was a drill 555 00:24:23,194 --> 00:24:27,532 and these guys, when it fell kind of in a strange position, 556 00:24:27,532 --> 00:24:30,201 you know, the drill went, you know instead of, 557 00:24:30,201 --> 00:24:32,170 it was designed to go straight down 558 00:24:32,170 --> 00:24:35,373 and drill into the rigolet, right? 559 00:24:35,373 --> 00:24:39,277 But because the spacecraft was sideways in a hole, 560 00:24:39,277 --> 00:24:42,213 this drill deployed and went something like this, 561 00:24:42,213 --> 00:24:44,415 after 10 years of flight and 10 years 562 00:24:44,415 --> 00:24:46,450 of testing and design of this. 563 00:24:46,450 --> 00:24:48,252 Some of these scientists, you know, 564 00:24:48,252 --> 00:24:52,757 they were doctoral students when they designed the drill. 565 00:24:52,757 --> 00:24:54,925 And the drill did something like this: 566 00:24:54,925 --> 00:24:57,863 Do, do, do, do, do, do, do, do, do. 567 00:25:00,532 --> 00:25:01,766 (laughter) 568 00:25:01,766 --> 00:25:03,100 And just didn't touch the surface 569 00:25:03,100 --> 00:25:04,970 and didn't access the sample. 570 00:25:04,970 --> 00:25:08,706 But that was the first landing and first mission. 571 00:25:08,706 --> 00:25:11,409 That's in the past, that's November 2014. 572 00:25:11,409 --> 00:25:12,877 Later, I'll come back and I'll tell you 573 00:25:12,877 --> 00:25:14,779 about the next landing. 574 00:25:16,180 --> 00:25:19,417 But, first we wanna tell you more what we discovered 575 00:25:19,417 --> 00:25:21,319 the comets, so Bonnie will be back. 576 00:25:21,319 --> 00:25:22,253 Where's Bonnie? 577 00:25:22,253 --> 00:25:23,188 - [Bonnie] I'm over here. 578 00:25:23,188 --> 00:25:24,121 Here you are, okay, good. 579 00:25:24,121 --> 00:25:26,791 - [Bonnie] Handing out prizes. 580 00:25:26,791 --> 00:25:28,059 - [Art] Let's roll the comet back. 581 00:25:28,059 --> 00:25:30,328 (applause) 582 00:25:36,233 --> 00:25:38,302 Even lady scientists go first. 583 00:25:38,302 --> 00:25:41,706 (light audience chatter) 584 00:25:43,174 --> 00:25:44,442 Got that, okay? 585 00:25:50,215 --> 00:25:52,050 - Alright, can everybody hear me? 586 00:25:52,050 --> 00:25:52,884 (affirmative murmurs) 587 00:25:52,884 --> 00:25:54,786 Okay, I think I 588 00:25:54,786 --> 00:25:55,720 Can you hear me now? 589 00:25:55,720 --> 00:25:57,021 - Yes. - Okay. 590 00:25:57,021 --> 00:25:58,523 So, yeah, so you've learned that engineers 591 00:25:58,523 --> 00:26:00,291 are a lot more fun than scientists. 592 00:26:00,291 --> 00:26:01,726 (laughter) 593 00:26:01,726 --> 00:26:02,394 I think that's what you've learned from this. 594 00:26:02,394 --> 00:26:03,628 (light applause) 595 00:26:03,628 --> 00:26:04,828 Okay, so yeah, and for any young people 596 00:26:04,828 --> 00:26:06,398 here in the audience, you know, 597 00:26:06,398 --> 00:26:07,832 engineering is cool. 598 00:26:07,832 --> 00:26:10,034 I think you've learned that. 599 00:26:10,034 --> 00:26:12,704 So, I'm gonna talk about some of the hard science 600 00:26:12,704 --> 00:26:13,938 that we learned. 601 00:26:13,938 --> 00:26:15,440 I'll try to make it as interesting as possible. 602 00:26:15,440 --> 00:26:17,742 But I don't have any props or anything. 603 00:26:17,742 --> 00:26:19,944 I just have a few graphs. 604 00:26:19,944 --> 00:26:22,146 Okay, so here are some of the discoveries 605 00:26:22,146 --> 00:26:23,815 that, you know, we've kind of picked out 606 00:26:23,815 --> 00:26:25,483 to try to emphasize. 607 00:26:26,651 --> 00:26:28,720 The first thing is, as we were saying, 608 00:26:28,720 --> 00:26:31,356 comets are primordial, they existed 609 00:26:31,356 --> 00:26:35,326 from the creation of the solar system 4.6 billion years ago. 610 00:26:35,326 --> 00:26:36,861 They are the building-blocks. 611 00:26:36,861 --> 00:26:40,432 It's the debris left over from the formation of the planets. 612 00:26:40,432 --> 00:26:44,836 And we found out that C-G or 67P as we usually call it, 613 00:26:44,836 --> 00:26:48,139 is composed of two separate planetesimals 614 00:26:48,139 --> 00:26:49,374 and they are pristine. 615 00:26:49,374 --> 00:26:51,876 They haven't been processed very much. 616 00:26:51,876 --> 00:26:53,778 And the activity and water-production 617 00:26:53,778 --> 00:26:55,146 on the comet were huge. 618 00:26:55,146 --> 00:26:56,681 There were just spectacular plumes coming out 619 00:26:56,681 --> 00:26:58,183 and I'll show some. 620 00:26:58,183 --> 00:27:01,052 And we discovered an amino acid, glycine on the comet, 621 00:27:01,052 --> 00:27:02,954 as well as other organics, things that are made 622 00:27:02,954 --> 00:27:06,490 of carbon, hydrogen, oxygen and nitrogen. 623 00:27:06,490 --> 00:27:08,125 And we found layers and these things 624 00:27:08,125 --> 00:27:09,394 that we call dinosaur eggs. 625 00:27:09,394 --> 00:27:10,761 And we think that these dinosaur eggs 626 00:27:10,761 --> 00:27:13,864 are actually the smallest building-blocks. 627 00:27:13,864 --> 00:27:17,035 When you saw the kids kind of running around, 628 00:27:17,035 --> 00:27:19,704 these are the fragments from which comets, 629 00:27:19,704 --> 00:27:22,673 and ultimately the planets, formed. 630 00:27:22,673 --> 00:27:24,642 And we also found some things unexpected 631 00:27:24,642 --> 00:27:25,943 about the composition. 632 00:27:25,943 --> 00:27:27,979 Okay, that's my most boring slide. 633 00:27:27,979 --> 00:27:32,316 So here is, for scale, the size of the comet. 634 00:27:32,316 --> 00:27:33,851 Okay, so this is New York City, 635 00:27:33,851 --> 00:27:36,721 with the East river and the Hudson river on either side. 636 00:27:36,721 --> 00:27:41,192 And this is, it's about as wide, it's longest length, 637 00:27:41,192 --> 00:27:43,494 is about four point some kilometers. 638 00:27:43,494 --> 00:27:44,995 It's about 2 1/2 miles. 639 00:27:44,995 --> 00:27:49,100 So it just fit in the, kind of in the width of Manhattan. 640 00:27:50,234 --> 00:27:52,637 Okay, so it's not very big. 641 00:27:52,637 --> 00:27:55,873 It's a fairly small comet, Halley's about 10 miles 642 00:27:55,873 --> 00:27:57,441 along its longest side. 643 00:27:57,441 --> 00:27:59,310 But the thing that you see about this comet 644 00:27:59,310 --> 00:28:02,246 that is the most amazing and you can see this 645 00:28:02,246 --> 00:28:06,017 here in the model, it has two separate parts. 646 00:28:07,118 --> 00:28:08,953 And these, we're pretty certain, you know, 647 00:28:08,953 --> 00:28:10,688 in science you're never totally certain, 648 00:28:10,688 --> 00:28:13,124 they're separate planetesimals. 649 00:28:13,124 --> 00:28:15,993 They are separate building-blocks of this body. 650 00:28:15,993 --> 00:28:18,096 Now how do we know that? 651 00:28:18,096 --> 00:28:21,032 Well, we've looked at layering in the comet 652 00:28:21,032 --> 00:28:23,167 and the layering seems to be different. 653 00:28:23,167 --> 00:28:25,270 We've also looked at the density. 654 00:28:25,270 --> 00:28:28,106 As Art was saying, it's mainly nothing. 655 00:28:28,106 --> 00:28:29,106 I mean, the density. 656 00:28:29,106 --> 00:28:31,609 So water has a density of one. 657 00:28:31,609 --> 00:28:34,078 The density is about half of that. 658 00:28:34,078 --> 00:28:36,447 So there's a lot of empty spaces in there 659 00:28:36,447 --> 00:28:38,649 and we think that if it were processed 660 00:28:38,649 --> 00:28:42,286 and melted and heated during planet-formation, 661 00:28:42,286 --> 00:28:43,387 it would be more solid. 662 00:28:43,387 --> 00:28:45,089 So it's kind of a fluffy thing. 663 00:28:45,089 --> 00:28:47,725 It just looks like these two pieces, 664 00:28:47,725 --> 00:28:49,894 like the kids out on the stage, 665 00:28:49,894 --> 00:28:51,495 they kind of were wandering around 666 00:28:51,495 --> 00:28:54,132 in the early solar system and just kinda stuck 667 00:28:54,132 --> 00:28:55,399 onto each other. 668 00:28:55,399 --> 00:28:57,234 And some of these things got bigger. 669 00:28:57,234 --> 00:28:58,469 You know, things stuck together 670 00:28:58,469 --> 00:29:00,104 and became the planets and some of them didn't. 671 00:29:00,104 --> 00:29:02,039 They were just left over. 672 00:29:02,039 --> 00:29:03,875 And one of the things you see is there's a lot 673 00:29:03,875 --> 00:29:05,676 of stuff coming out. 674 00:29:05,676 --> 00:29:08,078 We'll talk about these holes here, later. 675 00:29:08,078 --> 00:29:10,147 These are actually the centers of activity 676 00:29:10,147 --> 00:29:14,051 and it seems that all comets have these. 677 00:29:14,051 --> 00:29:18,223 Okay, so we did see a lot of water coming out of the comet. 678 00:29:19,390 --> 00:29:21,392 We didn't actually see ice itself 679 00:29:21,392 --> 00:29:23,461 until later in the mission. 680 00:29:23,461 --> 00:29:26,798 So, altogether, during its active period, 681 00:29:26,798 --> 00:29:29,500 the comet produced enough water to fill 682 00:29:29,500 --> 00:29:32,503 an Olympic swimming pool about every 100 days. 683 00:29:32,503 --> 00:29:34,339 Okay, it was mainly in the form of these jets, 684 00:29:34,339 --> 00:29:37,609 that are hydrogen, the hydroxyl radical 685 00:29:38,809 --> 00:29:40,745 that come from water that's dissociated. 686 00:29:40,745 --> 00:29:44,615 But here's an actual bright spot of fresh ice 687 00:29:44,615 --> 00:29:47,184 which we believe is from a cliff 688 00:29:47,184 --> 00:29:50,287 and the rock, a rock just kind of got split and opened up. 689 00:29:50,287 --> 00:29:52,556 So there's a crust of dark dust 690 00:29:52,556 --> 00:29:54,324 on the outside of this comet, 691 00:29:54,324 --> 00:29:56,460 but inside, there is water-ice 692 00:29:56,460 --> 00:30:00,165 and other volatiles like ammonia and carbon dioxide 693 00:30:00,165 --> 00:30:01,599 and monoxide. 694 00:30:01,599 --> 00:30:05,035 But look at some of these odd little boulders 695 00:30:05,035 --> 00:30:06,236 here in the dust. 696 00:30:06,236 --> 00:30:09,073 You know, where does that come from? 697 00:30:10,274 --> 00:30:12,176 Okay, well, some of it comes from these jets. 698 00:30:12,176 --> 00:30:14,812 This is a jet from August of last year. 699 00:30:14,812 --> 00:30:18,115 And most of the jets we found come out from the neck, okay? 700 00:30:18,115 --> 00:30:20,485 That is actually not a rock, that's just a little crevice 701 00:30:20,485 --> 00:30:23,120 that's sticking out, okay? 702 00:30:23,120 --> 00:30:25,489 But a lot of those boulders, we believe, 703 00:30:25,489 --> 00:30:27,958 that you see on those images, 704 00:30:27,958 --> 00:30:29,861 have actually come out of the vents. 705 00:30:29,861 --> 00:30:32,263 They're little tiny planetesimals 706 00:30:32,263 --> 00:30:34,966 that kind of explode out and collect on the surface 707 00:30:34,966 --> 00:30:36,901 as well as the dust. 708 00:30:36,901 --> 00:30:38,302 Okay, one of the, I wanna talk a little bit 709 00:30:38,302 --> 00:30:41,238 about the chemistry on the comet. 710 00:30:41,238 --> 00:30:43,474 You know, the interesting things about comets 711 00:30:43,474 --> 00:30:46,577 is they are kind of windows into the past. 712 00:30:46,577 --> 00:30:48,112 You know, what was the solar system like 713 00:30:48,112 --> 00:30:51,015 4.6 billion years ago when the planets were formed? 714 00:30:51,015 --> 00:30:53,384 They kind of give the pristine view 715 00:30:53,384 --> 00:30:57,956 of the temperature conditions, the pressure conditions. 716 00:30:57,956 --> 00:30:59,757 Well, this was pretty unexpected. 717 00:30:59,757 --> 00:31:02,527 What are the two major gases in the Earth's atmosphere? 718 00:31:02,527 --> 00:31:04,361 Nitrogen and oxygen. 719 00:31:04,361 --> 00:31:06,263 Okay, molecular nitrogen and oxygen. 720 00:31:06,263 --> 00:31:09,634 Well, guess what, we found both of them on the comet. 721 00:31:09,634 --> 00:31:11,402 Both of these, we didn't expect this. 722 00:31:11,402 --> 00:31:15,406 And these gases are ice and they seem to be embedded 723 00:31:15,406 --> 00:31:16,607 in the comet. 724 00:31:16,607 --> 00:31:18,843 They didn't come in later, they were formed 725 00:31:18,843 --> 00:31:22,646 in the early solar system, telling us that comets formed 726 00:31:22,646 --> 00:31:26,984 in an extremely low temperature environment, 727 00:31:26,984 --> 00:31:29,019 like 30 or less kelvins. 728 00:31:29,019 --> 00:31:31,689 Very, very, you know, 400 degrees below zero. 729 00:31:31,689 --> 00:31:33,057 Colder than you can imagine. 730 00:31:33,057 --> 00:31:35,493 So this is a NASA artist's conception 731 00:31:35,493 --> 00:31:38,495 of what the early solar system looked like. 732 00:31:38,495 --> 00:31:39,764 So, we have planet 733 00:31:39,764 --> 00:31:41,733 this is actually a random solar system. 734 00:31:41,733 --> 00:31:42,966 It could be our own. 735 00:31:42,966 --> 00:31:44,535 Jupiter-like planet, another planet. 736 00:31:44,535 --> 00:31:47,271 There're comets and asteroids falling 737 00:31:47,271 --> 00:31:50,074 into the planets causing craters to form. 738 00:31:50,074 --> 00:31:52,376 There're comets coming from the outer solar system 739 00:31:52,376 --> 00:31:55,445 bringing in these organics, bringing in these 740 00:31:55,445 --> 00:31:59,516 building-blocks of life, bringing in molecules 741 00:31:59,516 --> 00:32:01,419 into the inner solar system where it's too hot 742 00:32:01,419 --> 00:32:03,254 for these things to form. 743 00:32:03,254 --> 00:32:05,188 Most of this was discovered by an instrument 744 00:32:05,188 --> 00:32:07,324 called Rosina on the spacecraft. 745 00:32:07,324 --> 00:32:08,959 There's a little spacecraft there. 746 00:32:08,959 --> 00:32:12,062 Now you might have the question: 747 00:32:12,062 --> 00:32:14,531 well, did the Earth's nitrogen and oxygen 748 00:32:14,531 --> 00:32:16,233 come from comets? 749 00:32:16,233 --> 00:32:18,302 The answer to that, in the atmosphere, I mean: 750 00:32:18,302 --> 00:32:21,839 no, oxygen, we know, came from life. 751 00:32:21,839 --> 00:32:25,743 It was produced by bacteria and other forms of life. 752 00:32:25,743 --> 00:32:28,579 But nitrogen actually came mainly from volcanoes. 753 00:32:28,579 --> 00:32:31,516 We think some of the water-ice, or some of the water 754 00:32:31,516 --> 00:32:35,119 on the Earth may have come from comets, not all of it, 755 00:32:35,119 --> 00:32:36,354 but some of it probably did, 756 00:32:36,354 --> 00:32:38,956 was brought from the outer solar system 757 00:32:38,956 --> 00:32:40,924 into the inner solar system by comets. 758 00:32:40,924 --> 00:32:43,327 That's a question that's still open. 759 00:32:43,327 --> 00:32:45,429 Okay, let's move on here. 760 00:32:45,429 --> 00:32:47,465 Let's look at, look closely at some 761 00:32:47,465 --> 00:32:51,636 of these primordial building-blocks of the solar system. 762 00:32:51,636 --> 00:32:54,005 So if you look in this pit and most of these pits 763 00:32:54,005 --> 00:32:57,475 are areas of previous activity, and if you look, 764 00:32:57,475 --> 00:32:59,743 so we're looking down into the center of the comet. 765 00:32:59,743 --> 00:33:02,346 Look at all these little, this is about 40 meters, here, 766 00:33:02,346 --> 00:33:05,215 so each of these little, they're like boulders, 767 00:33:05,215 --> 00:33:07,585 compacted boulders are about a meter. 768 00:33:07,585 --> 00:33:10,087 We call these dinosaur eggs. 769 00:33:10,087 --> 00:33:12,890 These look like the ultimate building-blocks 770 00:33:12,890 --> 00:33:14,224 of the solar system. 771 00:33:14,224 --> 00:33:16,860 And they seem to form in layers. 772 00:33:16,860 --> 00:33:20,865 And when the comet is active, some of these get blown out, 773 00:33:20,865 --> 00:33:22,766 although some of the bigger ones come from cliffs 774 00:33:22,766 --> 00:33:24,301 and just get broken off. 775 00:33:24,301 --> 00:33:27,471 Because the comet, when it's out far from, you know, out, 776 00:33:27,471 --> 00:33:30,975 it's out now about 3.5 astronomical units, 777 00:33:30,975 --> 00:33:33,010 so it's getting colder and colder. 778 00:33:33,010 --> 00:33:35,679 But when it comes in, to the inner solar system, 779 00:33:35,679 --> 00:33:38,082 it heats up and there's a lot of thermal processing. 780 00:33:38,082 --> 00:33:42,352 So a lot of these cliffs, kind of get fractured, 781 00:33:42,352 --> 00:33:45,889 jets come out of these holes, we have dust from the comet 782 00:33:45,889 --> 00:33:47,792 that falls back onto the surface 783 00:33:47,792 --> 00:33:50,227 and then some boulders get kicked up and fall back on. 784 00:33:50,227 --> 00:33:52,530 It's quite an awesome sight. 785 00:33:53,931 --> 00:33:56,300 Okay, we also discovered a lot of layering on the comet. 786 00:33:56,300 --> 00:33:58,536 This was one of the most significant facts. 787 00:33:58,536 --> 00:34:01,606 And we're not sure how much of that was from the comet 788 00:34:01,606 --> 00:34:03,140 you know, forming like an onion skin. 789 00:34:03,140 --> 00:34:04,442 You know, one skin after the other, 790 00:34:04,442 --> 00:34:06,777 and how much of it is due to some kind 791 00:34:06,777 --> 00:34:08,145 of cracking or processing. 792 00:34:08,145 --> 00:34:10,013 Probably, it's both of it. 793 00:34:10,013 --> 00:34:12,016 Here are some of these boulders. 794 00:34:12,016 --> 00:34:12,950 We see some of the dust. 795 00:34:12,950 --> 00:34:14,852 This is the neck, okay? 796 00:34:14,852 --> 00:34:18,089 So you can see it is clearly two planetesimals 797 00:34:18,089 --> 00:34:18,922 that came together. 798 00:34:18,922 --> 00:34:20,357 They didn't smash. 799 00:34:20,357 --> 00:34:22,693 They came together probably at a fairly low speed. 800 00:34:22,693 --> 00:34:25,429 If they came together really fast, they would, you know, 801 00:34:25,429 --> 00:34:28,799 break apart or melt or process in some way. 802 00:34:28,799 --> 00:34:32,703 So these are two planetesimals, two small bodies. 803 00:34:32,703 --> 00:34:34,272 Okay, here's some more layers. 804 00:34:34,272 --> 00:34:36,774 This image was taken March, March 16th. 805 00:34:36,774 --> 00:34:39,443 The boulders, here are, you know, 806 00:34:39,443 --> 00:34:42,513 possibly areas, we think that some of the fresh ice 807 00:34:42,513 --> 00:34:44,448 is exposed at these cliffs. 808 00:34:44,448 --> 00:34:48,186 There's dust here that escapes from the comet 809 00:34:49,387 --> 00:34:51,222 then comes back on and some of it looks like 810 00:34:51,222 --> 00:34:53,524 that it's even deposited as some, 811 00:34:53,524 --> 00:34:55,793 almost like a wind-blown, like a dune 812 00:34:55,793 --> 00:34:57,295 or something like that. 813 00:34:57,295 --> 00:35:00,297 We do see that, that type of processing on the comet. 814 00:35:00,297 --> 00:35:04,134 Lot of boulders, areas of previous activity. 815 00:35:04,134 --> 00:35:05,469 So, it's quite an awesome sight. 816 00:35:05,469 --> 00:35:09,473 We haven't seen anything like this before, ever. 817 00:35:09,473 --> 00:35:13,811 And there's this phenomenon that geologists called ponding. 818 00:35:13,811 --> 00:35:17,848 And where the dust is thrown up in the jet, 819 00:35:17,848 --> 00:35:19,350 comes back down on the surface 820 00:35:19,350 --> 00:35:22,119 and then gravity kind of pulls it down into a pond. 821 00:35:22,119 --> 00:35:25,722 And you also see layers and thermal processing, 822 00:35:25,722 --> 00:35:28,392 a cliff, some of these boulders. 823 00:35:30,161 --> 00:35:31,428 Some more of it. 824 00:35:31,428 --> 00:35:34,397 In fact this is kind of the ideal example 825 00:35:34,397 --> 00:35:35,766 of a surface that was active. 826 00:35:35,766 --> 00:35:37,802 This is, you know, these are little holes 827 00:35:37,802 --> 00:35:41,138 where previous out-gassings, these jets occurred. 828 00:35:41,138 --> 00:35:43,907 And you see the dust has come back. 829 00:35:43,907 --> 00:35:45,843 It has gone out, fallen back on. 830 00:35:45,843 --> 00:35:49,647 They're boulders, some of them, you know are from the center 831 00:35:49,647 --> 00:35:52,416 of the comet, or from at least the mantle of the comet. 832 00:35:52,416 --> 00:35:55,686 Some of them probably just broke off from this cliff. 833 00:35:55,686 --> 00:35:57,522 You can see some here. 834 00:36:01,558 --> 00:36:04,561 Okay, so I wanted to get to one more idea, 835 00:36:04,561 --> 00:36:06,030 at least one more idea. 836 00:36:06,030 --> 00:36:10,201 And that is that we found organic chemistry on the comet. 837 00:36:11,602 --> 00:36:15,071 What we mean is there are molecules that consist 838 00:36:15,071 --> 00:36:16,907 of the building-blocks of life. 839 00:36:16,907 --> 00:36:20,111 Carbon, hydrogen, oxygen, nitrogen. 840 00:36:20,111 --> 00:36:24,182 These are things that life needs to be sustained. 841 00:36:25,616 --> 00:36:28,385 So, some of these, acetone and formaldehyde, we found, 842 00:36:28,385 --> 00:36:30,254 but I think this was a real clincher: 843 00:36:30,254 --> 00:36:33,890 Rosina discovered glycine, which is an amino acid. 844 00:36:33,890 --> 00:36:35,993 As you probably know, this is one of the, 845 00:36:35,993 --> 00:36:40,030 I think it's 22 molecules, fairly complex molecules 846 00:36:40,030 --> 00:36:41,532 that make up proteins. 847 00:36:41,532 --> 00:36:44,134 Now Stardust, which was, you know, a mission 848 00:36:44,134 --> 00:36:47,638 that went to Wild 2 and captured a sample, 849 00:36:49,039 --> 00:36:51,842 did actually also discover glycine, 850 00:36:51,842 --> 00:36:54,645 but we weren't 100% sure it was from the comet, itself. 851 00:36:54,645 --> 00:36:57,915 It captured a little sample from the tail of the comet, 852 00:36:57,915 --> 00:37:00,751 but we weren't sure that maybe it was from contamination. 853 00:37:00,751 --> 00:37:02,519 But this is actually on the comet. 854 00:37:02,519 --> 00:37:05,456 Here is an amino acid on the comet. 855 00:37:05,456 --> 00:37:08,626 We also see amino acids in meteorites, 856 00:37:10,060 --> 00:37:11,294 which come to the Earth. 857 00:37:11,294 --> 00:37:12,929 Some are from comets, some are from asteroids. 858 00:37:12,929 --> 00:37:14,998 We see it in the interstellar medium. 859 00:37:14,998 --> 00:37:16,867 So it is common in outer space, 860 00:37:16,867 --> 00:37:18,502 but how do they get to the Earth? 861 00:37:18,502 --> 00:37:20,037 Comets are the answer. 862 00:37:20,037 --> 00:37:23,106 Comets, we think delivered some of these amino acids, 863 00:37:23,106 --> 00:37:24,374 these simple building-blocks 864 00:37:24,374 --> 00:37:25,843 that later formed life on the Earth. 865 00:37:25,843 --> 00:37:29,579 We're not exact sure how, but we believe it was too hot 866 00:37:29,579 --> 00:37:31,281 on the Earth, the early Earth, 867 00:37:31,281 --> 00:37:34,318 for these complex molecules to form. 868 00:37:34,318 --> 00:37:37,788 Now you can see also here, there're some of these holes 869 00:37:37,788 --> 00:37:40,124 from previous jets and dust 870 00:37:40,124 --> 00:37:43,594 that kind of fell back onto the comet. 871 00:37:43,594 --> 00:37:47,231 Okay, I wanna show you some of the very late, whoops. 872 00:37:47,231 --> 00:37:48,165 Sorry. 873 00:37:48,165 --> 00:37:49,700 Some of the latest pictures. 874 00:37:49,700 --> 00:37:51,802 In fact, this was one just from less than a week ago. 875 00:37:51,802 --> 00:37:54,038 And it's kind of like an iconic picture, 876 00:37:54,038 --> 00:37:56,006 'cause it shows the comet kind of 877 00:37:56,006 --> 00:38:00,177 in its ebbing active stage, but it shows all the features 878 00:38:02,045 --> 00:38:04,915 that are key to its activity. 879 00:38:04,915 --> 00:38:09,686 These holes, that are not craters, they're actually areas 880 00:38:09,686 --> 00:38:12,223 where previous out-gassing or volatiles, 881 00:38:12,223 --> 00:38:13,757 mainly water-ice occurred. 882 00:38:13,757 --> 00:38:14,992 They're active for a while 883 00:38:14,992 --> 00:38:16,993 and then they kind of become quiescent. 884 00:38:16,993 --> 00:38:18,829 But you also see these cliffs. 885 00:38:18,829 --> 00:38:22,132 You can see that many of them collapsed. 886 00:38:22,132 --> 00:38:26,570 The stresses of thermal heating and processing 887 00:38:26,570 --> 00:38:27,671 caused weakness and they collapsed. 888 00:38:27,671 --> 00:38:29,640 And here you see a little crack 889 00:38:29,640 --> 00:38:31,741 that's almost causing this cliff, 890 00:38:31,741 --> 00:38:33,210 it's about ready to fall over. 891 00:38:33,210 --> 00:38:35,512 And you can see some of the material, the boulders, 892 00:38:35,512 --> 00:38:38,582 the dinosaur eggs are eroding from that cliff. 893 00:38:38,582 --> 00:38:40,317 And here's a cliff we can't quite see into, 894 00:38:40,317 --> 00:38:43,153 but if you look on the edge, there's layering, 895 00:38:43,153 --> 00:38:45,622 a few dinosaur eggs, more layering there, 896 00:38:45,622 --> 00:38:47,725 dust that came back on. 897 00:38:47,725 --> 00:38:51,829 It's really a very active body, quite interesting. 898 00:38:54,264 --> 00:38:56,000 Okay, before we leave, I do 899 00:38:56,000 --> 00:38:57,801 before we get onto the landing, Art is gonna talk 900 00:38:57,801 --> 00:38:59,469 about the landing in a couple minutes. 901 00:38:59,469 --> 00:39:01,105 But there's just one thing I wanna mention. 902 00:39:01,105 --> 00:39:04,040 I just wanna do a little tribute to Claudia Alexander, 903 00:39:04,040 --> 00:39:08,011 who was the project scientist for, was it 20 years? 904 00:39:08,011 --> 00:39:09,580 I mean, she was on before launch. 905 00:39:09,580 --> 00:39:12,349 It was launched in 2005, and she passed away, 906 00:39:12,349 --> 00:39:14,885 way before her time, in 2015. 907 00:39:14,885 --> 00:39:17,488 And I just wanted to, you know, offer a tribute, 908 00:39:17,488 --> 00:39:21,659 and we were able to name a part of the comet after her. 909 00:39:23,593 --> 00:39:25,195 This is Claudia Alexander Gate. 910 00:39:25,195 --> 00:39:28,399 They're these odd features that we saw on the comet, 911 00:39:28,399 --> 00:39:30,100 that we called them gates. 912 00:39:30,100 --> 00:39:31,735 Looked kind of like, that's what they are, 913 00:39:31,735 --> 00:39:33,137 they look like gates. 914 00:39:33,137 --> 00:39:37,040 So this is Claudia Alexander Gate, in her memory. 915 00:39:37,040 --> 00:39:40,810 So with that, I'd like to hand it back to Art, 916 00:39:40,810 --> 00:39:43,881 whose gonna talk about the actual landing. 917 00:39:43,881 --> 00:39:44,715 Thank you. 918 00:39:44,715 --> 00:39:46,984 (applause) 919 00:39:52,623 --> 00:39:55,960 - Okay, once again, do we have any body who is under 15? 920 00:39:55,960 --> 00:39:57,294 Please stand up. 921 00:39:58,461 --> 00:40:01,398 Okay, do we have anybody who is under 30? 922 00:40:01,398 --> 00:40:02,733 Please stand up. 923 00:40:05,903 --> 00:40:08,639 Okay, do we have anybody under 45, 924 00:40:08,639 --> 00:40:12,209 or somebody who'd like to feel that he's under 45? 925 00:40:12,209 --> 00:40:13,544 Please stand up. 926 00:40:16,146 --> 00:40:17,481 Okay, now sit down. 927 00:40:17,481 --> 00:40:18,482 (laughter) 928 00:40:18,482 --> 00:40:19,683 I don't have a job for you, 929 00:40:19,683 --> 00:40:21,452 I just wanted to give you some exercise. 930 00:40:21,452 --> 00:40:22,753 (laughter) 931 00:40:22,753 --> 00:40:23,587 Okay. 932 00:40:24,554 --> 00:40:26,623 Americans don't exercise enough. 933 00:40:26,623 --> 00:40:30,795 Okay, and that would conclude the entertainment portion. 934 00:40:31,995 --> 00:40:35,599 So, Bonnie was talking about dinosaur eggs. 935 00:40:36,967 --> 00:40:38,401 My son is here, Marcus. 936 00:40:38,401 --> 00:40:40,537 Marcus, stand up. 937 00:40:40,537 --> 00:40:41,705 Marcus is 14 now. 938 00:40:41,705 --> 00:40:43,974 (applause) 939 00:40:43,974 --> 00:40:47,744 So, one day I came home and I told Marcus 940 00:40:47,744 --> 00:40:50,513 about these dinosaur eggs and I said, 941 00:40:50,513 --> 00:40:53,884 "Oh, we found dinosaur eggs on the comet." 942 00:40:53,884 --> 00:40:55,052 And that was a few years ago 943 00:40:55,052 --> 00:40:58,589 and Marcus very astutely observed, he said, 944 00:40:59,723 --> 00:41:02,726 "Dad, if comets destroyed dinosaurs, 945 00:41:02,726 --> 00:41:05,229 "how can you have dinosaur eggs on the comet?" 946 00:41:05,229 --> 00:41:07,465 (laughter) 947 00:41:08,631 --> 00:41:12,569 An excellent point, professor Chmielewski. 948 00:41:12,569 --> 00:41:15,806 So, we're coming to the second landing, 949 00:41:17,307 --> 00:41:19,710 completely, completely, we're 950 00:41:21,545 --> 00:41:24,047 This is not a landing that was by any means, 951 00:41:24,047 --> 00:41:26,983 part of the mission or was planned for. 952 00:41:26,983 --> 00:41:29,186 And, but before we get to it, 953 00:41:29,186 --> 00:41:32,356 I just want you to take a slight pause 954 00:41:33,757 --> 00:41:37,627 and think about these pictures that Bonnie showed you. 955 00:41:37,627 --> 00:41:42,365 Because, you know, when you work on a space program 956 00:41:42,365 --> 00:41:45,636 and you first, for example, I work on a mission now. 957 00:41:45,636 --> 00:41:49,206 I started working on a mission, Rosetta is coming down 958 00:41:49,206 --> 00:41:53,810 to its end and I started working on a new mission. 959 00:41:53,810 --> 00:41:56,080 The launch will be in 2024. 960 00:41:58,349 --> 00:42:02,819 Maybe it will be delayed, maybe it will be 2030. 961 00:42:02,819 --> 00:42:06,189 But if it is in 2024, we will get 962 00:42:06,189 --> 00:42:08,425 to its destination in 2034. 963 00:42:09,827 --> 00:42:13,463 And we're gonna orbit this body for three years, 964 00:42:13,463 --> 00:42:17,534 getting data and this presentation like we're giving you, 965 00:42:17,534 --> 00:42:21,105 this right now, will be in 2035, '36, okay? 966 00:42:23,173 --> 00:42:26,576 So this is the kind of planning and effort goes into it. 967 00:42:26,576 --> 00:42:29,479 And then, you know, you launch the spacecraft, 968 00:42:29,479 --> 00:42:31,882 the spacecraft goes there for years. 969 00:42:31,882 --> 00:42:35,185 And one resistor, burns out, you know. 970 00:42:35,185 --> 00:42:37,921 How many times, for no reason, your refrigerator failed? 971 00:42:37,921 --> 00:42:39,456 You know, You open an umbrella 972 00:42:39,456 --> 00:42:42,025 and it goes (makes grinding noise). 973 00:42:42,025 --> 00:42:43,727 And it's like the simplest mechanism. 974 00:42:43,727 --> 00:42:45,862 One thing breaks, you know? 975 00:42:45,862 --> 00:42:49,566 This spacecraft was flying for 10 years 976 00:42:49,566 --> 00:42:53,337 and we even had to put it to sleep for 2 1/2 years, 977 00:42:53,337 --> 00:42:55,839 because we're so far away from the sun 978 00:42:55,839 --> 00:42:59,143 that the solar arrays were just not producing 979 00:42:59,143 --> 00:43:02,813 enough electricity to run the computers 980 00:43:02,813 --> 00:43:04,881 or to run any science instruments. 981 00:43:04,881 --> 00:43:07,617 So, these solar arrays are eight kilowatts 982 00:43:07,617 --> 00:43:10,053 when they are in Earth orbit. 983 00:43:10,053 --> 00:43:14,224 But when you are past Jupiter, they delivered 350 watts. 984 00:43:15,893 --> 00:43:18,261 That's just enough to run couple of heaters 985 00:43:18,261 --> 00:43:21,731 attached to the computer, so the computer doesn't freeze. 986 00:43:21,731 --> 00:43:24,000 And the only thing the computer was doing 987 00:43:24,000 --> 00:43:27,871 is counting down for 2 1/2 years, you know? 988 00:43:27,871 --> 00:43:29,473 Counting down. 989 00:43:29,473 --> 00:43:33,477 Because we were going very far away from the sun, 990 00:43:33,477 --> 00:43:38,382 very cold and then we were waiting for the spacecraft, 991 00:43:38,382 --> 00:43:40,917 which was sleeping, to come closer to the sun 992 00:43:40,917 --> 00:43:44,921 that it will be just enough power to wake up its systems. 993 00:43:44,921 --> 00:43:47,023 And the wake up was, I was here 994 00:43:47,023 --> 00:43:49,259 in the mission control center. 995 00:43:49,259 --> 00:43:52,395 And the wake-up was supposed to be at 10 a.m. 996 00:43:52,395 --> 00:43:55,031 And it was 10:01, it didn't wake up. 997 00:43:55,031 --> 00:43:57,334 10:02, didn't wake up, 10:03. 998 00:43:57,334 --> 00:43:59,570 And usually when something like this happens, 999 00:43:59,570 --> 00:44:01,538 you know, how late is gonna be your computer 1000 00:44:01,538 --> 00:44:02,973 in counting down? 1001 00:44:04,074 --> 00:44:06,710 It woke up 16 minutes late, m'kay? 1002 00:44:08,579 --> 00:44:11,214 And there are some good engineering reasons for this. 1003 00:44:11,214 --> 00:44:12,582 It had to reboot the software 1004 00:44:12,582 --> 00:44:14,151 and it was doing this by itself. 1005 00:44:14,151 --> 00:44:16,453 So it was very impressive that software engineers 1006 00:44:16,453 --> 00:44:17,921 designed it right. 1007 00:44:17,921 --> 00:44:21,191 But we kinda had a problem during the 2 1/2 years 1008 00:44:21,191 --> 00:44:22,259 of its sleep. 1009 00:44:24,094 --> 00:44:27,764 But, you know, and then you get to the comet 1010 00:44:27,764 --> 00:44:31,435 and the comet looks so bizarre, right? 1011 00:44:31,435 --> 00:44:35,606 And then everything works and you get these pictures. 1012 00:44:37,407 --> 00:44:41,378 And some of the scientists, you know, Claudia died, 1013 00:44:41,378 --> 00:44:43,847 without seeing a lot of these pictures. 1014 00:44:43,847 --> 00:44:47,650 There were people, you know, we had some deaths on the team, 1015 00:44:47,650 --> 00:44:50,887 professors who designed the instruments. 1016 00:44:50,887 --> 00:44:52,322 So it's an amazing effort. 1017 00:44:52,322 --> 00:44:56,794 And it's just a testament to people's hearts, 1018 00:44:56,794 --> 00:45:00,797 people's knowledge, people's perseverance, okay. 1019 00:45:00,797 --> 00:45:03,266 So, support your space program. 1020 00:45:03,266 --> 00:45:05,201 (laughter) 1021 00:45:05,201 --> 00:45:09,373 (applause) But it is an incredible thing 1022 00:45:12,776 --> 00:45:14,644 to get these images 1023 00:45:14,644 --> 00:45:18,148 and measurements form a body that is so far away. 1024 00:45:18,148 --> 00:45:20,416 And, by the way, Bonnie was telling you 1025 00:45:20,416 --> 00:45:23,520 about possibly a comet hitting Earth. 1026 00:45:26,156 --> 00:45:29,426 What was it, 65 million years ago? 1027 00:45:29,426 --> 00:45:31,862 You know, there is a chance that we're 1028 00:45:31,862 --> 00:45:34,698 gonna have a comet impact in 3044. 1029 00:45:37,067 --> 00:45:38,802 So don't tell me I didn't warn you. 1030 00:45:38,802 --> 00:45:40,003 (laughing) 1031 00:45:40,003 --> 00:45:40,838 3044. 1032 00:45:42,172 --> 00:45:44,107 And as a matter of fact, if you wanna understand 1033 00:45:44,107 --> 00:45:47,043 comets better, when you come and today is a perfect day. 1034 00:45:47,043 --> 00:45:51,448 Today and tomorrow, because we have Perseid shower, right? 1035 00:45:51,448 --> 00:45:55,419 And what the shower is is basically tiny little particles 1036 00:45:55,419 --> 00:45:56,886 that came out. 1037 00:45:56,886 --> 00:45:59,890 You know, what we see in the sky is a tail of a comet 1038 00:45:59,890 --> 00:46:01,391 and it's humongous, okay? 1039 00:46:01,391 --> 00:46:03,560 This thing is tiny, kilometers, right? 1040 00:46:03,560 --> 00:46:07,897 But the tail is hundreds of thousands of kilometers, right? 1041 00:46:07,897 --> 00:46:09,132 And that's why you can see it. 1042 00:46:09,132 --> 00:46:11,534 These are little tiny pieces of dust 1043 00:46:11,534 --> 00:46:14,538 that when they line up with your eye 1044 00:46:15,705 --> 00:46:18,941 and reflect the sun into your eye, 1045 00:46:18,941 --> 00:46:20,576 you see it as a little mirror. 1046 00:46:20,576 --> 00:46:24,114 And that's how you see these amazing tails. 1047 00:46:24,114 --> 00:46:26,616 Well what do you see today in the sky, 1048 00:46:26,616 --> 00:46:28,485 and as a matter of fact, if you come out, 1049 00:46:28,485 --> 00:46:30,686 there will be a lot of lights so you can't see it. 1050 00:46:30,686 --> 00:46:33,223 But around 11 p.m, I think it is 1051 00:46:33,223 --> 00:46:35,324 you know if you look in the sky, just in this direction 1052 00:46:35,324 --> 00:46:36,826 like you were coming in out of the auditorium, 1053 00:46:36,826 --> 00:46:39,696 you can see the meteor shower. 1054 00:46:39,696 --> 00:46:42,566 And all it is is these tiny little particles 1055 00:46:42,566 --> 00:46:44,600 that came out of the comet, right? 1056 00:46:44,600 --> 00:46:46,536 And Earth is going through it 1057 00:46:46,536 --> 00:46:48,938 and they are reentering atmosphere and burning up. 1058 00:46:48,938 --> 00:46:49,939 And that's what it is. 1059 00:46:49,939 --> 00:46:51,108 These are, you're gonna see, 1060 00:46:51,108 --> 00:46:53,443 be able to see pieces of comet today. 1061 00:46:53,443 --> 00:46:56,947 And the reason they burn up is because they go that fast. 1062 00:46:56,947 --> 00:46:58,748 They go as fast as a comet 1063 00:46:58,748 --> 00:47:02,552 so they reenter like four times the speeding bullet. 1064 00:47:02,552 --> 00:47:04,855 Right, you'll remember that, you can impress your friends. 1065 00:47:04,855 --> 00:47:07,190 Oh, ho, pieces of a comet. 1066 00:47:07,190 --> 00:47:10,760 You know, they go four times as fast as a speeding bullet. 1067 00:47:10,760 --> 00:47:11,994 (laughter) 1068 00:47:11,994 --> 00:47:14,163 Remember that so you can impress your friends. 1069 00:47:14,163 --> 00:47:17,501 Okay, so, this, actually today's lecture 1070 00:47:20,570 --> 00:47:22,672 is a preview of what's gonna happen 1071 00:47:22,672 --> 00:47:25,308 on September the 30th, okay? 1072 00:47:25,308 --> 00:47:28,178 On September the 30th, what's gonna happen, 1073 00:47:28,178 --> 00:47:30,514 I just wanted to remind you that what we did 1074 00:47:30,514 --> 00:47:33,483 is we put down this little lander 1075 00:47:33,483 --> 00:47:36,152 on the surface of a comet, right? 1076 00:47:36,152 --> 00:47:39,789 And now we're far away from the sun. 1077 00:47:39,789 --> 00:47:42,392 Again, we would have to put the spacecraft to sleep 1078 00:47:42,392 --> 00:47:47,264 and we wouldn't know if it's gonna merged 2 1/2 years later. 1079 00:47:47,264 --> 00:47:48,532 We would have no control. 1080 00:47:48,532 --> 00:47:51,634 So instead of waiting for 2 1/2 years 1081 00:47:51,634 --> 00:47:55,705 and managers spending budget, you know, 1082 00:47:55,705 --> 00:47:57,607 we're gonna put it down on a surface 1083 00:47:57,607 --> 00:48:00,576 and just let it go to sleep, but on a comet. 1084 00:48:00,576 --> 00:48:03,513 So, this will be certainly, the end of the mission, 1085 00:48:03,513 --> 00:48:06,650 because we're gonna be coming down to the 1086 00:48:06,650 --> 00:48:09,352 and maybe we should have a little demonstration. 1087 00:48:09,352 --> 00:48:12,622 So Nathan, come on down, come on, come on. 1088 00:48:12,622 --> 00:48:16,293 We need somebody with big muscles this time. 1089 00:48:17,394 --> 00:48:20,097 And, by the way, it's worth it to come 1090 00:48:20,097 --> 00:48:24,034 to these lectures sometimes 'cause I met Nathan. 1091 00:48:24,034 --> 00:48:25,268 Where did we meet, you tell them, 1092 00:48:25,268 --> 00:48:27,036 because, you know, that I have no credibility. 1093 00:48:27,036 --> 00:48:30,339 - We met at open house and at the NASA social event. 1094 00:48:30,339 --> 00:48:32,175 - Yeah, yeah, so we at an open house 1095 00:48:32,175 --> 00:48:35,411 and Nathan was really interested in the comet. 1096 00:48:35,411 --> 00:48:37,280 So we got into conversation. 1097 00:48:37,280 --> 00:48:40,917 And it turns out now he went to school of engineering, 1098 00:48:40,917 --> 00:48:45,488 and I want him to come down and work next summer at JPL. 1099 00:48:45,488 --> 00:48:48,124 Maybe even this Christmas, right? 1100 00:48:48,124 --> 00:48:49,893 - Yeah - So, there, yeah. 1101 00:48:49,893 --> 00:48:51,595 - Thank you for that. 1102 00:48:53,697 --> 00:48:56,966 - Because somebody has to replace me eventually, 1103 00:48:56,966 --> 00:48:58,702 you know, on this job. 1104 00:48:58,702 --> 00:49:01,337 You'll have 'til, you know, 2044. 1105 00:49:01,337 --> 00:49:02,172 - Yes. 1106 00:49:02,172 --> 00:49:03,006 You'll have to have-- 1107 00:49:03,006 --> 00:49:04,174 - I'll be here. 1108 00:49:04,174 --> 00:49:07,277 - Yeah, okay, so, Nathan, gradually this. 1109 00:49:08,344 --> 00:49:09,979 Don't, you'll have to 1110 00:49:09,979 --> 00:49:11,581 We're gonna show you how it's gonna land. 1111 00:49:11,581 --> 00:49:14,483 So you're gonna take this and you're gonna slowly spin it. 1112 00:49:14,483 --> 00:49:17,587 This is more or less how the comet spins, okay? 1113 00:49:17,587 --> 00:49:21,758 It's about 700 million miles away from us, right now. 1114 00:49:25,528 --> 00:49:29,098 And this spacecraft, this is the orbiter, 1115 00:49:29,098 --> 00:49:32,969 not designed for any landing by any means, you know, 1116 00:49:32,969 --> 00:49:34,470 is orbiting it. 1117 00:49:34,470 --> 00:49:39,009 And let's say, well, let's say that this is the sun, right? 1118 00:49:39,009 --> 00:49:41,077 So the spacecraft is orbiting like this 1119 00:49:41,077 --> 00:49:43,980 because it wants to point its solar arrays 1120 00:49:43,980 --> 00:49:45,382 to the sun, right? 1121 00:49:45,382 --> 00:49:48,318 And it has, and the tricky thing here 1122 00:49:48,318 --> 00:49:50,987 keep on working, come on, come on, earn your job. 1123 00:49:50,987 --> 00:49:55,559 Okay, and the antenna has to be pointed to Earth. 1124 00:49:55,559 --> 00:49:59,196 The solar arrays have to be pointed to the sun, right? 1125 00:49:59,196 --> 00:50:01,731 And the instruments at the same time, 1126 00:50:01,731 --> 00:50:02,999 have to be pointed to the comet. 1127 00:50:02,999 --> 00:50:06,169 So you know, it's like it's a contortionist. 1128 00:50:06,169 --> 00:50:07,704 You know, it's like, what is this game 1129 00:50:07,704 --> 00:50:09,271 that you put down your hand and-- 1130 00:50:09,271 --> 00:50:10,106 - [Audience Members] Twister. 1131 00:50:10,106 --> 00:50:11,641 - What is it? Twister? 1132 00:50:11,641 --> 00:50:14,610 Yeah, so the spacecraft is a Twister all the time, right? 1133 00:50:14,610 --> 00:50:17,614 And now, so on the 30th of September, 1134 00:50:17,614 --> 00:50:21,184 we're gonna try to put this huge spacecraft down. 1135 00:50:21,184 --> 00:50:24,087 You can stop now, let's stop the gravity. 1136 00:50:24,087 --> 00:50:25,855 And big hand for Nathan. 1137 00:50:25,855 --> 00:50:26,822 (applause) 1138 00:50:26,822 --> 00:50:29,258 Go ahead and sit down, Nathan. 1139 00:50:29,258 --> 00:50:31,694 So now, this thing is spinning. 1140 00:50:31,694 --> 00:50:33,129 And again there was a discussion 1141 00:50:33,129 --> 00:50:36,266 between different scientists, where you wanna land. 1142 00:50:36,266 --> 00:50:39,069 Some scientists wanted, they thought it would be really cool 1143 00:50:39,069 --> 00:50:41,671 to land somewhere here because we would have, 1144 00:50:41,671 --> 00:50:44,807 coming down, we would have a close-up of the neck region, 1145 00:50:44,807 --> 00:50:48,245 close-up of the head, of the body, right? 1146 00:50:49,679 --> 00:50:53,283 Or minor lobe or major lobe or the head of the duck 1147 00:50:54,917 --> 00:50:57,354 and the butt of the duck, depending, you know, what do you, 1148 00:50:57,354 --> 00:50:59,622 how do you, what terminology you want to use. 1149 00:50:59,622 --> 00:51:02,125 But they wanted to land here. 1150 00:51:02,125 --> 00:51:05,495 Some people wanted to look for Philae. 1151 00:51:05,495 --> 00:51:07,964 You know, for this tiny little lander. 1152 00:51:07,964 --> 00:51:12,869 And there's scientific reasons why we wanna know exactly, 1153 00:51:12,869 --> 00:51:15,905 take a image where the lander is, okay? 1154 00:51:15,905 --> 00:51:18,508 Because if we know exactly where it was, 1155 00:51:18,508 --> 00:51:21,044 we're doing some radio-tomography through the comet, 1156 00:51:21,044 --> 00:51:24,347 we could know exactly what the radio signal 1157 00:51:24,347 --> 00:51:26,048 was piercing through, right? 1158 00:51:26,048 --> 00:51:28,284 So that would improve our data. 1159 00:51:28,284 --> 00:51:29,485 So there was a reason for this 1160 00:51:29,485 --> 00:51:31,054 and some people were voting for this. 1161 00:51:31,054 --> 00:51:33,389 But finally, what won? 1162 00:51:33,389 --> 00:51:34,925 What are we gonna see? 1163 00:51:34,925 --> 00:51:36,660 On the way down? 1164 00:51:36,660 --> 00:51:39,028 The dinosaur eggs, right? 1165 00:51:39,028 --> 00:51:42,398 So finally, the scientists decided 1166 00:51:42,398 --> 00:51:46,570 that we wanna land and fly very close to these pits, 1167 00:51:48,137 --> 00:51:51,007 these silos and be very close, 1168 00:51:51,007 --> 00:51:55,178 point our camera right inside of these dinosaur eggs 1169 00:51:58,414 --> 00:52:01,451 because, you know, these silos go really deep. 1170 00:52:01,451 --> 00:52:03,052 I mean this is just really phenomenal 1171 00:52:03,052 --> 00:52:04,520 from science point-of-view, right? 1172 00:52:04,520 --> 00:52:06,489 You can see inside of the comet 1173 00:52:06,489 --> 00:52:08,023 and see what's in there. 1174 00:52:08,023 --> 00:52:09,492 And this is what we're gonna-- 1175 00:52:09,492 --> 00:52:10,427 (small thud) 1176 00:52:10,427 --> 00:52:12,162 (dismayed audience groans) 1177 00:52:12,162 --> 00:52:14,397 (laughter) 1178 00:52:16,199 --> 00:52:17,633 He knows whose fault it is. 1179 00:52:17,633 --> 00:52:21,004 Okay, so we're gonna look and there are three 1180 00:52:21,004 --> 00:52:23,473 of them lined up in the area here, 1181 00:52:23,473 --> 00:52:25,842 so this is where we're gonna land. 1182 00:52:25,842 --> 00:52:28,478 You can't see it from over there but there is a pit here 1183 00:52:28,478 --> 00:52:29,679 and there's another pit here 1184 00:52:29,679 --> 00:52:31,247 and there are three pits in a row. 1185 00:52:31,247 --> 00:52:33,350 So, this is where we're gonna go 1186 00:52:33,350 --> 00:52:37,753 and try to actually land almost into the pit if we can. 1187 00:52:37,753 --> 00:52:39,355 But we can't have this precision 1188 00:52:39,355 --> 00:52:41,358 because we have to shut down the spacecraft 1189 00:52:41,358 --> 00:52:42,892 when it's that high. 1190 00:52:42,892 --> 00:52:45,862 We have to shut it off, because if we didn't, 1191 00:52:45,862 --> 00:52:47,663 you know there would be instability 1192 00:52:47,663 --> 00:52:49,933 and the spacecraft would shut itself off 1193 00:52:49,933 --> 00:52:52,201 and there would be some uncontrolled situation. 1194 00:52:52,201 --> 00:52:54,337 So we're shutting it down an hour earlier 1195 00:52:54,337 --> 00:52:56,139 and where ever it lands, it lands 1196 00:52:56,139 --> 00:52:58,975 and whatever it shows us, it shows us, okay? 1197 00:52:58,975 --> 00:53:01,043 But probably, you know, it's gonna hit 1198 00:53:01,043 --> 00:53:05,281 with the solar array first, maybe with the antenna. 1199 00:53:05,281 --> 00:53:06,983 It will be spectacular, okay? 1200 00:53:06,983 --> 00:53:08,618 (laughter) 1201 00:53:08,618 --> 00:53:10,120 We engineers, we love it, you know? 1202 00:53:10,120 --> 00:53:12,655 They never, first time they let us do this, you know? 1203 00:53:12,655 --> 00:53:15,024 Demolish the spacecraft at the end, yeah! 1204 00:53:15,024 --> 00:53:17,027 (laughter) 1205 00:53:17,027 --> 00:53:18,127 Yes, scientists. 1206 00:53:18,127 --> 00:53:20,697 (applause) 1207 00:53:20,697 --> 00:53:24,600 And this is what you're gonna see on September the 30th, 1208 00:53:24,600 --> 00:53:27,237 if you like to come back here 1209 00:53:27,237 --> 00:53:31,408 and watch this spectacular death of our spacecraft, 1210 00:53:32,442 --> 00:53:33,909 then please come 1211 00:53:33,909 --> 00:53:38,215 and of course, you know, all the science instruments 1212 00:53:38,215 --> 00:53:41,017 are on one facet, so when we'll be approaching, 1213 00:53:41,017 --> 00:53:42,852 eventually, we're gonna crush it. 1214 00:53:42,852 --> 00:53:46,422 Crush the camera because we're gonna be pointing it down. 1215 00:53:46,422 --> 00:53:49,092 And this will be it for Rosetta. 1216 00:53:50,493 --> 00:53:54,564 So please come back on the 30th of September, eight a.m. 1217 00:53:55,798 --> 00:53:59,435 The actual landing is at 4:10 a.m, 1218 00:53:59,435 --> 00:54:01,671 but you know, it will take, 1219 00:54:01,671 --> 00:54:05,575 just the signal from the comet takes 40 minutes to get here, 1220 00:54:05,575 --> 00:54:08,511 pictures have to be processed, so it will take some time. 1221 00:54:08,511 --> 00:54:13,416 I'll be, and we'll see what's inside of the comet. 1222 00:54:13,416 --> 00:54:15,885 Thank you very much and thank you so much for coming. 1223 00:54:15,885 --> 00:54:18,154 (applause) 1224 00:54:24,560 --> 00:54:27,998 And now I'll be glad to answer easy questions 1225 00:54:27,998 --> 00:54:30,066 and Bonnie will answer very difficult questions. 1226 00:54:30,066 --> 00:54:31,468 (laughter) 1227 00:54:31,468 --> 00:54:33,236 - Also, please go up to the microphone 1228 00:54:33,236 --> 00:54:35,138 if you have a question. 1229 00:54:37,206 --> 00:54:39,675 - Well, I don't know if it's easy or hard, you'll tell me. 1230 00:54:39,675 --> 00:54:41,977 I think a lot of us visualize the comet 1231 00:54:41,977 --> 00:54:44,581 as kind of a very dark exterior 1232 00:54:45,715 --> 00:54:47,817 from all of the water vapor going away. 1233 00:54:47,817 --> 00:54:50,186 And then a kind of powdery interior. 1234 00:54:50,186 --> 00:54:52,622 But we saw layering, but we didn't seen anything 1235 00:54:52,622 --> 00:54:55,558 that bi-modal or anything did we? 1236 00:54:55,558 --> 00:54:58,628 Or is it covered up, or do we think that's right? 1237 00:54:58,628 --> 00:55:00,096 - [Art] Okay. 1238 00:55:00,096 --> 00:55:01,797 - Well, you know we didn't get a very, you know, 1239 00:55:01,797 --> 00:55:04,534 good view of the interior with the camera. 1240 00:55:04,534 --> 00:55:06,803 But there are instruments onboard 1241 00:55:06,803 --> 00:55:10,173 that were able to measure the average density, for example. 1242 00:55:10,173 --> 00:55:11,607 So it's very fluffy. 1243 00:55:11,607 --> 00:55:15,044 You know, there was a morrow, a microwave sounder 1244 00:55:15,044 --> 00:55:19,416 that was able to look down into the upper few centimeters 1245 00:55:19,416 --> 00:55:21,183 of the surface. 1246 00:55:21,183 --> 00:55:23,186 So we did get some knowledge of what it's like 1247 00:55:23,186 --> 00:55:24,386 in the interior. 1248 00:55:24,386 --> 00:55:25,988 It's not what we call differentiated. 1249 00:55:25,988 --> 00:55:29,125 It seems to be pretty fluffy all the way through. 1250 00:55:29,125 --> 00:55:30,760 But you brought up something that's really interesting 1251 00:55:30,760 --> 00:55:32,728 that I didn't mention because it's kind of, 1252 00:55:32,728 --> 00:55:34,230 you know, you can't see everything. 1253 00:55:34,230 --> 00:55:38,601 It's very dark, it reflects only about four to six percent 1254 00:55:38,601 --> 00:55:40,937 of the light that falls on it in the visible. 1255 00:55:40,937 --> 00:55:44,007 And that's about as dark as coal tar. 1256 00:55:45,107 --> 00:55:46,976 It's really very dark. 1257 00:55:46,976 --> 00:55:50,246 - So, lemme just add something. 1258 00:55:50,246 --> 00:55:52,648 This is twice as dark as asphalt, 1259 00:55:52,648 --> 00:55:54,917 that's why it's very difficult to see this nuclei. 1260 00:55:54,917 --> 00:55:56,653 And the reason it is, like Bonnie said, 1261 00:55:56,653 --> 00:56:00,790 is because this dust emanates from the inside, right? 1262 00:56:00,790 --> 00:56:03,092 It's when we get especially to the perihelion, 1263 00:56:03,092 --> 00:56:05,561 close to the sun, everything heats up, 1264 00:56:05,561 --> 00:56:09,299 starts sublimating, goes up and then dust, 1265 00:56:09,299 --> 00:56:12,235 as we cool off and we go away from the sun, 1266 00:56:12,235 --> 00:56:14,337 slowly descends on the surface, right? 1267 00:56:14,337 --> 00:56:18,007 And so the whole thing is covered with very dark 1268 00:56:18,007 --> 00:56:21,677 carbonaceous silicate dust, but it's very 1269 00:56:21,677 --> 00:56:24,814 You know, it's fluffy this, nothing, you know, 1270 00:56:24,814 --> 00:56:27,516 that's why it's very difficult to reflect light. 1271 00:56:27,516 --> 00:56:30,520 Fluffy black carbon powder, alright? 1272 00:56:33,789 --> 00:56:35,624 And that's what makes it so dark. 1273 00:56:35,624 --> 00:56:36,458 - Thank you. 1274 00:56:36,458 --> 00:56:37,593 - [Art] Thank you. 1275 00:56:37,593 --> 00:56:40,529 Oh no, Tommy, no, Tommy, no, no. 1276 00:56:40,529 --> 00:56:41,631 Oh, a question for Bonnie now. 1277 00:56:41,631 --> 00:56:42,898 - [Tommy] A question. 1278 00:56:42,898 --> 00:56:44,033 - This guy has IQ three times mine. 1279 00:56:44,033 --> 00:56:45,535 - Correct, a question for Bonnie. 1280 00:56:45,535 --> 00:56:47,570 What's the process that fills up the silos 1281 00:56:47,570 --> 00:56:49,339 and what sort of time scales is current? 1282 00:56:49,339 --> 00:56:50,873 - It's out-gassing. 1283 00:56:50,873 --> 00:56:53,843 And you know, we're honesty not sure of the time scales. 1284 00:56:53,843 --> 00:56:55,378 We saw changes on the comet. 1285 00:56:55,378 --> 00:56:58,148 We did see increases in the size, 1286 00:56:59,315 --> 00:57:00,950 but most of the ones that you saw, 1287 00:57:00,950 --> 00:57:02,284 that you see on the comet, 1288 00:57:02,284 --> 00:57:06,489 not only on 67P but also on Wild 2 for example, 1289 00:57:06,489 --> 00:57:09,825 are from past appearances, past apparitions. 1290 00:57:09,825 --> 00:57:11,461 But we don't know whether, you know, 1291 00:57:11,461 --> 00:57:15,998 it's only one appearance, one passage towards the sun 1292 00:57:15,998 --> 00:57:18,901 that each vent is caused or it gets, 1293 00:57:18,901 --> 00:57:20,402 it opens up successively. 1294 00:57:20,402 --> 00:57:22,071 We just don't know these things. 1295 00:57:22,071 --> 00:57:24,140 We have seen changes so they do change, 1296 00:57:24,140 --> 00:57:28,211 but we don't if it's million years, thousand years, 1297 00:57:28,211 --> 00:57:29,245 we just don't know. 1298 00:57:29,245 --> 00:57:30,446 - Thanks. 1299 00:57:30,446 --> 00:57:32,915 - But what was fascinating to me, 1300 00:57:32,915 --> 00:57:35,418 about the jets, right, is that some of these jets 1301 00:57:35,418 --> 00:57:36,653 would activate themselves 1302 00:57:36,653 --> 00:57:39,722 and would last only 20 minutes, right? 1303 00:57:39,722 --> 00:57:44,359 And, because the explanation that I heard of this 1304 00:57:44,359 --> 00:57:45,928 was that you can imagine there 1305 00:57:45,928 --> 00:57:49,565 are like this gas bubbles forming underneath 1306 00:57:49,565 --> 00:57:51,834 and so there's this huge gas bubble here, 1307 00:57:51,834 --> 00:57:53,302 underneath the surface. 1308 00:57:53,302 --> 00:57:56,739 And then if something cracks, there is a little opening 1309 00:57:56,739 --> 00:57:59,642 and the gas starts coming out, violently, 1310 00:57:59,642 --> 00:58:03,179 and blows off the top surface like a sewer cover 1311 00:58:03,179 --> 00:58:04,714 into the space. 1312 00:58:04,714 --> 00:58:07,750 And now you have this jet and the jet shoots out 1313 00:58:07,750 --> 00:58:11,587 and leaves this silo underneath and comes out. 1314 00:58:11,587 --> 00:58:14,490 And some of these jets lasted what? 1315 00:58:14,490 --> 00:58:15,324 - [Bonnie] A couple hours. 1316 00:58:15,324 --> 00:58:16,793 - Yeah. - Yeah. 1317 00:58:16,793 --> 00:58:18,261 - But there was one 19 minutes, very, very short. 1318 00:58:18,261 --> 00:58:19,862 - I think the biggest ones were a couple hours. 1319 00:58:19,862 --> 00:58:23,366 - So that's how this surface is processed. 1320 00:58:25,968 --> 00:58:28,704 - So an impossible question for Bonnie: 1321 00:58:28,704 --> 00:58:32,641 Tonight's comet, Swift-Tuttle, whose debris 1322 00:58:32,641 --> 00:58:34,910 we're gonna be entering. 1323 00:58:34,910 --> 00:58:36,678 How well is it characterized? 1324 00:58:36,678 --> 00:58:38,614 Do we know it's all tiny little particles 1325 00:58:38,614 --> 00:58:42,785 or could there be some minor lobe waiting to hit us? 1326 00:58:43,686 --> 00:58:44,521 - I see. 1327 00:58:46,922 --> 00:58:47,856 You know, there are a lot of 1328 00:58:47,856 --> 00:58:49,292 I don't know the answer to that. 1329 00:58:49,292 --> 00:58:51,694 There are a lot of amateurs observing these things 1330 00:58:51,694 --> 00:58:53,763 and I would think that if there were 1331 00:58:53,763 --> 00:58:56,366 Okay, in order to get through the Earth's atmosphere, 1332 00:58:56,366 --> 00:58:59,369 to hit the ground, you have to be 1333 00:58:59,369 --> 00:59:01,637 about maybe half the size of this room. 1334 00:59:01,637 --> 00:59:04,273 And I think if there were anything that big, 1335 00:59:04,273 --> 00:59:07,276 some amateur like, would have observed it 1336 00:59:07,276 --> 00:59:08,744 coming off of the comet. 1337 00:59:08,744 --> 00:59:10,813 So I don't think there's anything that would harm us, 1338 00:59:10,813 --> 00:59:14,049 that's kinda my first, you know, off the top of my head 1339 00:59:14,049 --> 00:59:14,983 what I would say. 1340 00:59:14,983 --> 00:59:16,219 But there could be things like, 1341 00:59:16,219 --> 00:59:17,686 I mean most of these things that we see 1342 00:59:17,686 --> 00:59:19,521 are like fist-sized or even smaller. 1343 00:59:19,521 --> 00:59:21,590 You know, there could be baseball-sized things coming off 1344 00:59:21,590 --> 00:59:23,459 and that's what we see in the atmosphere, 1345 00:59:23,459 --> 00:59:25,027 tonight if you look. 1346 00:59:25,027 --> 00:59:29,565 - And what we see, from Churyumov-Gerasimenko, for example, 1347 00:59:29,565 --> 00:59:32,267 is that most of these particles 1348 00:59:32,267 --> 00:59:35,070 that you see entering tonight are probably 1349 00:59:35,070 --> 00:59:37,640 like the size of a grain of sand and smaller, right? 1350 00:59:37,640 --> 00:59:38,808 - [Bonnie] Yeah, that's true, they're a lot smaller. 1351 00:59:38,808 --> 00:59:40,943 - Because to be removed from the comet 1352 00:59:40,943 --> 00:59:43,112 and not fall back, you know, they would have 1353 00:59:43,112 --> 00:59:46,248 to have very low gravity so they separated themselves, 1354 00:59:46,248 --> 00:59:49,885 went far away that they were not under, you know. 1355 00:59:49,885 --> 00:59:51,721 Gravity is mass of one body 1356 00:59:51,721 --> 00:59:54,823 times the mass of the other body. 1357 00:59:54,823 --> 00:59:57,226 So there would be small sizes 1358 00:59:58,360 --> 01:00:02,097 and that's why these reentries which we see, 1359 01:00:02,097 --> 01:00:05,768 like Bonnie says, they're just tiny particles, sand-sized. 1360 01:00:05,768 --> 01:00:08,971 We saw some boulders fly off Churyumov-Gerasimenko 1361 01:00:08,971 --> 01:00:11,273 and I tell you that this is an exciting thing. 1362 01:00:11,273 --> 01:00:12,475 And I'm sorry to keep you standing, 1363 01:00:12,475 --> 01:00:14,543 but let me just tell you this 'cause this is 1364 01:00:14,543 --> 01:00:16,378 so unintuitional. 1365 01:00:16,378 --> 01:00:19,648 When you're in space and we're used to seeing 1366 01:00:19,648 --> 01:00:22,618 Okay, I see Rhodie here in the first row, 1367 01:00:22,618 --> 01:00:25,287 I see him very well because there's very little air 1368 01:00:25,287 --> 01:00:26,856 and pollution, right? 1369 01:00:26,856 --> 01:00:29,891 And there is also, I know what size is a human being, right? 1370 01:00:29,891 --> 01:00:31,627 So I know he's in the first row, 1371 01:00:31,627 --> 01:00:33,930 he is three meters from me. 1372 01:00:33,930 --> 01:00:37,166 And the gentleman in the yellow shirt, what is your name? 1373 01:00:39,268 --> 01:00:38,000 - Tom. 1374 01:00:39,268 --> 01:00:41,070 And Tom is about 20 meters from me, 1375 01:00:41,070 --> 01:00:45,241 because I don't think he's a tiny, skinny midget, okay. 1376 01:00:46,441 --> 01:00:48,377 I'm thinking he's the same size as Rhodie. 1377 01:00:48,377 --> 01:00:51,447 Now, in space, you don't know if you're looking 1378 01:00:51,447 --> 01:00:55,484 at a grain of sand, right here, or a huge boulder 1379 01:00:55,484 --> 01:00:57,386 there is a kilometer away. 1380 01:00:57,386 --> 01:00:59,689 And as a matter of fact, you know, 1381 01:00:59,689 --> 01:01:01,757 scientists would always try to figure out 1382 01:01:01,757 --> 01:01:03,058 what are we looking at. 1383 01:01:03,058 --> 01:01:04,960 Is it a huge boulder or is it a tiny grain 1384 01:01:04,960 --> 01:01:06,428 in front of the camera? 1385 01:01:06,428 --> 01:01:08,730 And now you have to see with what velocity it moves, 1386 01:01:08,730 --> 01:01:11,600 how quickly it changes its size, you know. 1387 01:01:11,600 --> 01:01:13,536 And on that very basis, they will finally say, 1388 01:01:13,536 --> 01:01:15,037 Oh, this is a boulder. 1389 01:01:15,037 --> 01:01:16,805 And we saw some boulders fly off, 1390 01:01:16,805 --> 01:01:18,440 they're about two, three meters. 1391 01:01:18,440 --> 01:01:20,943 So, to answer gentleman's question, you know, 1392 01:01:20,943 --> 01:01:25,080 if Swift-Tuttle is like Churyumov-Gerasimenko, 1393 01:01:25,080 --> 01:01:27,116 then, you know, we're not gonna see very many 1394 01:01:27,116 --> 01:01:30,520 of these boulders, mostly grains of sand. 1395 01:01:32,487 --> 01:01:36,792 - Okay, my question is about the processes 1396 01:01:36,792 --> 01:01:40,730 that you had in the early formation of the solar system 1397 01:01:40,730 --> 01:01:42,899 versus what we have today. 1398 01:01:44,600 --> 01:01:47,903 I can see how bodies circling around, 1399 01:01:47,903 --> 01:01:49,938 they're colliding, they could sometimes stick 1400 01:01:49,938 --> 01:01:51,807 and form bigger ones and other times they could 1401 01:01:51,807 --> 01:01:54,243 just break them apart and make smaller ones. 1402 01:01:54,243 --> 01:01:57,914 And so, is the asteroid built now in a state 1403 01:01:59,548 --> 01:02:03,852 where it's breaking apart more than it's putting together? 1404 01:02:03,852 --> 01:02:07,356 And if so, what are some of the conditions 1405 01:02:09,191 --> 01:02:12,494 that determine whether you're able to build up 1406 01:02:12,494 --> 01:02:16,332 bigger things or break up into smaller things? 1407 01:02:17,867 --> 01:02:20,502 - Well, I think, you know, a lot of this is hand waving. 1408 01:02:20,502 --> 01:02:22,638 You know, the early part of the solar system, 1409 01:02:22,638 --> 01:02:25,274 but at some point, the bigger stuff is gonna 1410 01:02:25,274 --> 01:02:27,843 just act as a gravity well, you know? 1411 01:02:27,843 --> 01:02:29,478 It's gonna like hog all the stuff. 1412 01:02:29,478 --> 01:02:30,979 As soon as something gets a little big bigger, 1413 01:02:30,979 --> 01:02:32,247 it's gonna have more gravity 1414 01:02:32,247 --> 01:02:33,482 and it's gonna have more pieces. 1415 01:02:33,482 --> 01:02:35,851 But yes, you're right, often they collide. 1416 01:02:35,851 --> 01:02:39,321 Right now, the comet 67P is more 1417 01:02:39,321 --> 01:02:40,689 in a state of erosion. 1418 01:02:40,689 --> 01:02:42,557 I mean, it's not accreting any particles, 1419 01:02:42,557 --> 01:02:44,893 it's blowing them off through the process 1420 01:02:44,893 --> 01:02:48,264 of the venting from the jets, the attrition 1421 01:02:48,264 --> 01:02:52,634 that takes place as it enters the inner solar system. 1422 01:02:52,634 --> 01:02:55,437 So yeah, it's losing mass, now. 1423 01:02:55,437 --> 01:02:57,406 - [Tom] Okay, thank you. 1424 01:02:57,406 --> 01:02:59,008 - And this one, what is interesting 1425 01:02:59,008 --> 01:03:02,878 about Churyumov-Gerasimenko, when we noticed the shape, 1426 01:03:02,878 --> 01:03:05,014 I was teasing scientists, I was telling them, 1427 01:03:05,014 --> 01:03:07,749 "Well, when it comes to perihelion, close to the sun, 1428 01:03:07,749 --> 01:03:09,285 it's gonna split." 1429 01:03:09,285 --> 01:03:11,687 Because we started actually seeing a little crack here, 1430 01:03:11,687 --> 01:03:13,055 right at the neck. 1431 01:03:13,055 --> 01:03:16,024 And I said, "Eh, it probably will split." 1432 01:03:16,024 --> 01:03:18,527 And now you're gonna have Churyumov and Gerasimenko. 1433 01:03:18,527 --> 01:03:20,763 (laughter) 1434 01:03:22,732 --> 01:03:23,566 Yes. 1435 01:03:24,834 --> 01:03:25,768 You can lower your microphone. - When will this-- 1436 01:03:25,768 --> 01:03:27,703 - You can pull it down. 1437 01:03:31,907 --> 01:03:35,477 - When will this comet come around again, 1438 01:03:35,477 --> 01:03:38,247 if it, will it be seen over here? 1439 01:03:39,982 --> 01:03:41,551 And if it is, when? 1440 01:03:44,153 --> 01:03:48,390 - Okay, so the comet has a period of 6 1/2 years. 1441 01:03:48,390 --> 01:03:51,092 So it means every 6 1/2, it comes back, 1442 01:03:51,092 --> 01:03:52,895 but it comes back to the sun. 1443 01:03:52,895 --> 01:03:56,364 That doesn't mean that Earth is very close to it. 1444 01:03:56,364 --> 01:03:58,000 Like for example at the landing, 1445 01:03:58,000 --> 01:04:02,604 the comet will be 3.8 astronomical units from the sun, 1446 01:04:02,604 --> 01:04:05,474 meaning distances between Earth and sun, 1447 01:04:05,474 --> 01:04:09,645 but it will be 4.8 to Earth, so Earth will be further away. 1448 01:04:10,846 --> 01:04:12,581 So, to answer your question, 1449 01:04:12,581 --> 01:04:15,017 it comes back every 6 1/2 years. 1450 01:04:15,017 --> 01:04:19,654 There are comets that, the comet that you'll see today, 1451 01:04:19,654 --> 01:04:24,025 the tail, that one comes back every 133 years. 1452 01:04:24,025 --> 01:04:26,728 So, please, you know, tell me, 1453 01:04:26,728 --> 01:04:28,263 'cause it will be very difficult 1454 01:04:28,263 --> 01:04:32,701 for me to read at that time, when this comet comes back, 1455 01:04:32,701 --> 01:04:35,437 tell if it was really a spectacular shower. 1456 01:04:35,437 --> 01:04:38,740 That will be in, what, about a hundred years or so. 1457 01:04:38,740 --> 01:04:42,411 But this one is 6 1/2 years. 1458 01:04:42,411 --> 01:04:43,579 Good question. 1459 01:04:45,681 --> 01:04:46,782 Yes. 1460 01:04:46,782 --> 01:04:48,017 - Hello. 1461 01:04:48,017 --> 01:04:51,587 So I have a question about the landing. 1462 01:04:51,587 --> 01:04:55,290 You guys say that you guys get a sort of signal, 1463 01:04:55,290 --> 01:04:57,293 when it hits the comet. 1464 01:04:57,293 --> 01:04:58,794 - [Art] Right. 1465 01:04:58,794 --> 01:05:01,764 - And, you guys got pictures, about what the comet looks, 1466 01:05:01,764 --> 01:05:02,931 you know where it lands, you guys don't know 1467 01:05:02,931 --> 01:05:03,966 where it's gonna land. 1468 01:05:03,966 --> 01:05:05,500 - [Art] Right. 1469 01:05:05,500 --> 01:05:08,471 - So, how do you guys know if it's gonna land safely 1470 01:05:08,471 --> 01:05:11,706 and what if it ends up destroying 1471 01:05:11,706 --> 01:05:14,509 and would you guys be guaranteed pictures 1472 01:05:14,509 --> 01:05:16,879 or if it destroys, you guys don't get anything back? 1473 01:05:16,879 --> 01:05:18,948 - Yeah, yeah, yeah, yeah. 1474 01:05:20,349 --> 01:05:23,920 So, you know, we're gonna be getting images 1475 01:05:25,120 --> 01:05:27,690 as we approach the comet, right? 1476 01:05:27,690 --> 01:05:31,226 So, it's actually, let's clarify one thing, 1477 01:05:31,226 --> 01:05:33,763 'cause people are used to: Mars landing. 1478 01:05:33,763 --> 01:05:35,430 And seven minutes, what is it seven minutes of terror. 1479 01:05:35,430 --> 01:05:36,599 - [Bonnie] Minutes of terror. 1480 01:05:36,599 --> 01:05:38,100 - Right, seven minutes? - Right. 1481 01:05:38,100 --> 01:05:40,703 - Well, we have like seven hours of patience, okay? 1482 01:05:40,703 --> 01:05:41,737 (laughter) 1483 01:05:41,737 --> 01:05:42,671 - [Bonnie] I like that. 1484 01:05:42,671 --> 01:05:45,374 - So, it really goes, it goes 1485 01:05:45,374 --> 01:05:48,310 about 50 centimeters per second, so it like, 1486 01:05:48,310 --> 01:05:50,579 you know, it goes like this. 1487 01:05:52,247 --> 01:05:55,050 So, it's very slowly and it's taking images 1488 01:05:55,050 --> 01:05:56,851 as it approaches this, you know? 1489 01:05:56,851 --> 01:05:59,388 So, the interesting thing is, 1490 01:05:59,388 --> 01:06:01,523 you really have to figure this out, 1491 01:06:01,523 --> 01:06:03,459 the gravity, the math, the rotation, 1492 01:06:03,459 --> 01:06:07,096 the geometry, because it's coming with certain speed here, 1493 01:06:07,096 --> 01:06:10,232 and then this thing is spinning, so you aim, 1494 01:06:10,232 --> 01:06:14,836 you know, you aim at, you wanna land here, right? 1495 01:06:14,836 --> 01:06:17,739 But you're actually, maybe, here and you're waiting 1496 01:06:17,739 --> 01:06:19,708 for the comet to rotate. 1497 01:06:19,708 --> 01:06:22,477 So, but it will be images as it descends. 1498 01:06:22,477 --> 01:06:24,880 We don't know if it's gonna even make it 1499 01:06:24,880 --> 01:06:26,915 that close to the surface. 1500 01:06:26,915 --> 01:06:29,017 Because as Bonnie said, you know, 1501 01:06:29,017 --> 01:06:30,285 these are actually two comets, 1502 01:06:30,285 --> 01:06:32,421 they have slightly different density. 1503 01:06:32,421 --> 01:06:34,456 So, there's gravity well, here, okay? 1504 01:06:34,456 --> 01:06:35,991 And we don't understand it very well. 1505 01:06:35,991 --> 01:06:39,828 So, as this thing will be flying, maybe it will dip 1506 01:06:39,828 --> 01:06:41,664 and then hit the head. 1507 01:06:43,432 --> 01:06:47,435 You know, it's very difficult to say what will be happening. 1508 01:06:47,435 --> 01:06:50,572 But it's not sudden descent, it's a slow, 1509 01:06:50,572 --> 01:06:53,175 very slow, ballistic descent. 1510 01:06:53,175 --> 01:06:54,009 - Thank you. 1511 01:06:54,009 --> 01:06:55,511 - [Art] Thank you. 1512 01:06:58,180 --> 01:07:00,216 - Okay, in view of the far distance 1513 01:07:00,216 --> 01:07:03,252 and weak solar radiation, and the orientation problems 1514 01:07:03,252 --> 01:07:06,188 that you had, in this mission or other missions, 1515 01:07:06,188 --> 01:07:09,624 would it be worth concern to use solar, 1516 01:07:09,624 --> 01:07:13,362 I mean thermo-electric thermal generators, 1517 01:07:13,362 --> 01:07:14,797 electric generators? 1518 01:07:14,797 --> 01:07:15,597 - [Bonnie] A solar electric propelled propulsion? 1519 01:07:15,597 --> 01:07:17,132 - Right, right, right. 1520 01:07:17,132 --> 01:07:18,934 General purpose heat source radioisotopic thermoelectric 1521 01:07:18,934 --> 01:07:20,269 generators, as you wanted to say. 1522 01:07:20,269 --> 01:07:21,336 - [Questioner] Thermoelectric generators. 1523 01:07:21,336 --> 01:07:22,872 - Yeah yeah yeah. - Yes. 1524 01:07:22,872 --> 01:07:23,706 - Yeah, RTGs, yeah. 1525 01:07:23,706 --> 01:07:25,173 - [Bonnie] RTGs 1526 01:07:25,173 --> 01:07:28,711 - Yeah, we would, you know, we had RTGs on Cassini. 1527 01:07:29,745 --> 01:07:31,846 We had RTGs on Galileo. 1528 01:07:31,846 --> 01:07:36,084 We would love to have RTGs, but you know, 1529 01:07:36,084 --> 01:07:38,153 it's very difficult to get RTGs these days. 1530 01:07:38,153 --> 01:07:40,689 Like, for example, the mission that I'm working on, 1531 01:07:40,689 --> 01:07:43,859 to Saturn, will have solar arrays, which is a little crazy, 1532 01:07:43,859 --> 01:07:47,129 but you know, because some folks feel 1533 01:07:47,129 --> 01:07:48,030 that RTGs-- 1534 01:07:51,566 --> 01:07:52,801 - [Questioner] Radioactive. 1535 01:07:52,801 --> 01:07:56,472 - Contain the most toxic substance on Earth, 1536 01:07:58,473 --> 01:08:00,308 called Plutonium. 1537 01:08:00,308 --> 01:08:04,446 Named after the god of underground Pluto. 1538 01:08:04,446 --> 01:08:06,681 - [Questioner] Oh, Pluto. 1539 01:08:06,681 --> 01:08:10,652 - And, because of that, you know, we have some 1540 01:08:10,652 --> 01:08:14,056 very difficult to put 'em on a spacecraft 1541 01:08:14,056 --> 01:08:16,491 without protests and lawsuits for many years 1542 01:08:16,491 --> 01:08:17,893 and things like that. 1543 01:08:17,893 --> 01:08:18,694 - It's also a European mission, it's a European mission. 1544 01:08:18,694 --> 01:08:20,128 - [Questioner] Politics. 1545 01:08:20,128 --> 01:08:21,597 - So, they have even worse problems over there. 1546 01:08:21,597 --> 01:08:23,666 - [Questioner] Thank you. 1547 01:08:26,902 --> 01:08:31,006 - Hi, at one point, you showed an image that was, 1548 01:08:33,042 --> 01:08:36,311 it showed a dent on the, on the comet 1549 01:08:36,311 --> 01:08:40,082 and you specified that it was an old hole 1550 01:08:40,082 --> 01:08:43,085 from one of the jets and that it shouldn't be confused 1551 01:08:43,085 --> 01:08:45,187 for, what was it, crater. 1552 01:08:46,522 --> 01:08:47,756 - [Bonnie] Crater, yeah, impact crater. 1553 01:08:47,756 --> 01:08:50,392 - So I wanna know how you knew the difference 1554 01:08:50,392 --> 01:08:53,194 between a crater and a hole from a jet. 1555 01:08:53,194 --> 01:08:56,865 - Okay, when scientists first saw these holes 1556 01:08:56,865 --> 01:08:59,768 on Wild 2, and on other comets, 1557 01:08:59,768 --> 01:09:02,203 the first impression was that they might be craters 1558 01:09:02,203 --> 01:09:05,808 but then, geologists actually count craters 1559 01:09:06,975 --> 01:09:10,012 and measure the diameters of them. 1560 01:09:10,012 --> 01:09:13,248 And from that data, it wasn't typical 1561 01:09:13,248 --> 01:09:16,017 of what impact craters, that is, craters formed 1562 01:09:16,017 --> 01:09:18,453 when another object comes in, hits the object. 1563 01:09:18,453 --> 01:09:21,756 And just the shape of it wasn't right, either. 1564 01:09:21,756 --> 01:09:23,726 It wasn't really the, you know, 1565 01:09:23,726 --> 01:09:25,327 the kind of bowl-shaped thing that you see 1566 01:09:25,327 --> 01:09:27,796 on impact craters like on the moon. 1567 01:09:27,796 --> 01:09:31,166 So, it was, you know, pretty soon after these holes 1568 01:09:31,166 --> 01:09:35,070 were discovered, theorized that they were locations 1569 01:09:35,070 --> 01:09:39,241 where gases that were vents of sublimating gases came out. 1570 01:09:41,142 --> 01:09:42,210 - [Art] An excellent question, thank you for asking. 1571 01:09:42,210 --> 01:09:43,145 - Thank you 1572 01:09:44,446 --> 01:09:45,281 - Yes. 1573 01:09:47,616 --> 01:09:51,787 - When the Rosetta lander lands, will it be still functional 1574 01:09:54,156 --> 01:09:56,892 or will it be, like, obliterated? 1575 01:09:59,295 --> 01:10:00,596 - It will die. 1576 01:10:00,596 --> 01:10:02,898 (laughter) 1577 01:10:02,898 --> 01:10:04,799 (Art sniffles) 1578 01:10:04,799 --> 01:10:07,903 Now, with the, what, it, it will die. 1579 01:10:09,404 --> 01:10:11,974 - [Questioner] Alright then. 1580 01:10:11,974 --> 01:10:15,044 - Okay, so, you know, you can imagine 1581 01:10:17,446 --> 01:10:20,649 this spacecraft with huge solar arrays, 1582 01:10:20,649 --> 01:10:25,053 very difficult to control, so when it does hit the surface, 1583 01:10:25,053 --> 01:10:27,422 it will tumble, it will roll, it will bounce, 1584 01:10:27,422 --> 01:10:30,092 it will come down again, but we will not see it, 1585 01:10:30,092 --> 01:10:31,927 because probably the instruments will be damaged. 1586 01:10:31,927 --> 01:10:35,931 So, but it certainly will not survive the crash. 1587 01:10:38,767 --> 01:10:39,934 Yes? 1588 01:10:39,934 --> 01:10:42,337 - Hi, couple of interrelated questions. 1589 01:10:42,337 --> 01:10:44,406 How close does it get to the sun 1590 01:10:44,406 --> 01:10:46,675 and what, what, did you measure the temperature 1591 01:10:46,675 --> 01:10:49,178 of the surface and why don't we see evidence 1592 01:10:49,178 --> 01:10:51,613 of some kind of melting on the surface if there 1593 01:10:51,613 --> 01:10:55,617 are jets forming underneath the surface? 1594 01:10:55,617 --> 01:10:56,452 - Yeah. 1595 01:10:57,719 --> 01:10:58,953 - We did measure the temperature, 1596 01:10:58,953 --> 01:11:01,656 there were instruments on board to do that. 1597 01:11:01,656 --> 01:11:05,694 And it doesn't have the atmosphere to sustain, 1598 01:11:05,694 --> 01:11:08,263 you know, liquid water, it just sublimates 1599 01:11:08,263 --> 01:11:10,332 into, you know, outer space. 1600 01:11:10,332 --> 01:11:12,968 But we do see quite a bit of thermal processing, 1601 01:11:12,968 --> 01:11:17,338 a lot of the cracking, there's kneeling, there's a crust 1602 01:11:17,338 --> 01:11:21,910 on the top, so we do see a lot of thermal processing of it. 1603 01:11:21,910 --> 01:11:24,513 - So to answer your question about the temperatures. 1604 01:11:24,513 --> 01:11:28,850 So, when we first caught up with the comet 1605 01:11:28,850 --> 01:11:30,552 and we first landed, right? 1606 01:11:30,552 --> 01:11:32,454 The temperature was, cause it changes depending 1607 01:11:32,454 --> 01:11:36,091 on how far you are from the sun, so. 1608 01:11:36,091 --> 01:11:37,860 And this is what's fascinating to me. 1609 01:11:37,860 --> 01:11:42,031 So, it was about 120 kelvin, minus 150 Celsius, right? 1610 01:11:44,132 --> 01:11:45,500 Very cold. 1611 01:11:45,500 --> 01:11:47,369 When you got very close to the sun, 1612 01:11:47,369 --> 01:11:50,572 and it was only one AU, some, the areas 1613 01:11:52,040 --> 01:11:56,712 that were in the sunshine were about room temperature, okay? 1614 01:11:56,712 --> 01:11:58,179 So it was very warm. 1615 01:11:58,179 --> 01:12:01,516 But what was fascinating to me to see on this comet, 1616 01:12:01,516 --> 01:12:05,688 it, you know, like when a sun sets, on Earth, right? 1617 01:12:07,088 --> 01:12:09,525 Well, what time sun sets now? 1618 01:12:11,226 --> 01:12:12,427 Eight o'clock? 1619 01:12:12,427 --> 01:12:14,696 Eight p.m., something like this, seven? 1620 01:12:14,696 --> 01:12:19,634 What was the temperature at 6:30, for example, here? 1621 01:12:19,634 --> 01:12:20,902 Anybody? 1622 01:12:20,902 --> 01:12:21,703 - [Female Audience Member] Maybe 95. 1623 01:12:21,703 --> 01:12:22,871 - What do you think? 1624 01:12:22,871 --> 01:12:23,772 - [Male Audience Member] 80. 1625 01:12:23,772 --> 01:12:24,606 80? 1626 01:12:24,606 --> 01:12:26,074 - [Questioner] 80s 1627 01:12:26,074 --> 01:12:29,077 - Right, 80s, and after the sun set, about an hour, 1628 01:12:29,077 --> 01:12:32,648 at nine o'clock, what was the temperature? 1629 01:12:32,648 --> 01:12:33,848 - 70s, low 70s, high 70s. 1630 01:12:33,848 --> 01:12:35,050 - Yeah, so, you know, we're used to this 1631 01:12:35,050 --> 01:12:35,984 because we have atmosphere. 1632 01:12:35,984 --> 01:12:38,319 On the comet, what we noticed, 1633 01:12:38,319 --> 01:12:39,954 and that was fascinating to me, 1634 01:12:39,954 --> 01:12:42,891 it's like on, off, on, off, you know. 1635 01:12:42,891 --> 01:12:46,562 You're in the sun, you were, you know, 30 C. 1636 01:12:47,996 --> 01:12:51,800 You are in the shade, you go to minus 100, okay? 1637 01:12:53,201 --> 01:12:55,070 So, it's like, you know, if you're on a comet 1638 01:12:55,070 --> 01:12:56,771 and, you know, don't wanna get very cold, 1639 01:12:56,771 --> 01:13:00,875 you would have to be running, you know, with the sun set, 1640 01:13:00,875 --> 01:13:02,945 so you're always past the terminator. 1641 01:13:02,945 --> 01:13:07,649 But, that's really, really something surprising, 1642 01:13:07,649 --> 01:13:11,820 that there's very little thermal inertia on a comet. 1643 01:13:16,824 --> 01:13:20,061 - How well do you know what impact the landing 1644 01:13:20,061 --> 01:13:22,397 is gonna have on the comet in terms 1645 01:13:22,397 --> 01:13:24,566 of when it hits the thing? 1646 01:13:26,969 --> 01:13:28,403 - Very difficult question, so it's you. 1647 01:13:28,403 --> 01:13:31,072 - Yeah (laughter) 1648 01:13:31,072 --> 01:13:33,741 - Well, you know, physics, right? 1649 01:13:33,741 --> 01:13:36,044 Conservation of momentum, right? 1650 01:13:36,044 --> 01:13:39,381 M1 times V1 is equal M2 times V2, right? 1651 01:13:40,615 --> 01:13:43,719 So the mass of the comet, M1 is equal 1652 01:13:45,553 --> 01:13:47,890 to 10 to the 13th kilograms. 1653 01:13:50,325 --> 01:13:54,496 The mass of the spacecraft is 10 to the 3rd, not quite. 1654 01:13:58,633 --> 01:13:59,468 Two, okay? 1655 01:14:00,869 --> 01:14:04,373 The velocity of the comet is 150,000 kilometers 1656 01:14:06,974 --> 01:14:10,178 times velocity of the spacecraft is the same, 1657 01:14:10,178 --> 01:14:13,982 so they nullify each other, so now you have something 1658 01:14:13,982 --> 01:14:17,752 that is 10 to the 13th and 10 to the 2nd. 1659 01:14:17,752 --> 01:14:20,088 So the effect is negligible. 1660 01:14:21,689 --> 01:14:25,293 Will not knock it off its trajectory 1661 01:14:25,293 --> 01:14:27,762 and direct it to Earth. 1662 01:14:27,762 --> 01:14:29,598 - [Questioner] Thanks. 1663 01:14:32,200 --> 01:14:36,071 - How did all the gases get in there in the first, 1664 01:14:36,071 --> 01:14:37,973 well, in the beginning? 1665 01:14:38,874 --> 01:14:40,075 - [Art] Okay. 1666 01:14:40,075 --> 01:14:42,710 - Well, the comets formed in a cold part 1667 01:14:42,710 --> 01:14:44,512 of the cloud of gas and dust 1668 01:14:44,512 --> 01:14:46,781 from which the solar system formed. 1669 01:14:46,781 --> 01:14:50,718 So, out there where it was, it was pretty far out, 1670 01:14:50,718 --> 01:14:53,789 there was just a lot of stuff that you get, 1671 01:14:53,789 --> 01:14:55,223 you know, when it's cold. 1672 01:14:55,223 --> 01:14:56,858 Like if you go to the Earth's poles, for example, 1673 01:14:56,858 --> 01:14:59,861 the North or South poles, isn't there a lot of ice up there? 1674 01:14:59,861 --> 01:15:01,763 Same way in the solar system, if you go out 1675 01:15:01,763 --> 01:15:05,367 to the areas that were cold, you see a lot of ice. 1676 01:15:05,367 --> 01:15:08,536 Not just water-ice, but you see methane, ammonia. 1677 01:15:08,536 --> 01:15:11,172 All those things were frozen and those things all got frozen 1678 01:15:11,172 --> 01:15:13,541 into the comet because it was formed out there 1679 01:15:13,541 --> 01:15:15,477 where it's really cold. 1680 01:15:16,878 --> 01:15:18,947 And then when it comes into the inner solar system, 1681 01:15:18,947 --> 01:15:20,849 it just all sublimates. 1682 01:15:22,817 --> 01:15:25,153 - [Art] We will allow only 80 more questions. 1683 01:15:25,153 --> 01:15:28,089 (laughing) 1684 01:15:28,089 --> 01:15:31,426 - Each spacecraft, you design the instruments 1685 01:15:31,426 --> 01:15:34,896 according to the mission and what you want to accomplish. 1686 01:15:34,896 --> 01:15:37,633 In Voyager or Cassini or Galileo. 1687 01:15:39,334 --> 01:15:43,571 This one is very peculiar and very special. 1688 01:15:43,571 --> 01:15:45,541 How are the instruments designed 1689 01:15:45,541 --> 01:15:49,878 for this particular mission and what did JPL do 1690 01:15:49,878 --> 01:15:52,581 and the European spacecraft, what 1691 01:15:54,015 --> 01:15:57,853 Give me some idea about the instruments and stuff. 1692 01:15:59,421 --> 01:16:00,922 - Wanna talk about a few instruments, Bonnie? 1693 01:16:00,922 --> 01:16:04,192 - Yeah, well, first of all, when you begin a mission, 1694 01:16:04,192 --> 01:16:05,660 you do it for the science. 1695 01:16:05,660 --> 01:16:07,829 I mean, engineering is really fun but you're going there 1696 01:16:07,829 --> 01:16:09,264 to answer questions. 1697 01:16:09,264 --> 01:16:12,400 So you first start out with the questions 1698 01:16:12,400 --> 01:16:14,269 that you wanna answer, okay? 1699 01:16:14,269 --> 01:16:16,905 Well, that's called the science objectives. 1700 01:16:16,905 --> 01:16:18,840 And then to answer those questions, 1701 01:16:18,840 --> 01:16:20,441 you have to have specific instruments, 1702 01:16:20,441 --> 01:16:24,912 so if you want to know the composition of the comet, 1703 01:16:24,912 --> 01:16:26,714 that was a big question, you have to have 1704 01:16:26,714 --> 01:16:28,316 what's known as a spectrometer, 1705 01:16:28,316 --> 01:16:30,218 something that will measure 1706 01:16:30,218 --> 01:16:34,589 how the surface reflects light as a function 1707 01:16:34,589 --> 01:16:35,824 of color or wavelength. 1708 01:16:35,824 --> 01:16:37,558 So we had a spectrometer on board, 1709 01:16:37,558 --> 01:16:40,562 that was a european instrument. 1710 01:16:40,562 --> 01:16:41,964 And we had of course, the camera. 1711 01:16:41,964 --> 01:16:45,133 You basically need a camera, just to understand, 1712 01:16:45,133 --> 01:16:46,635 you know, the shape of the comet. 1713 01:16:46,635 --> 01:16:51,205 We had a microwave sounder, that was a JPL instrument. 1714 01:16:51,205 --> 01:16:54,109 We had an ultraviolet spectrometer, 1715 01:16:56,577 --> 01:16:59,347 to understand the coma or the gases, 1716 01:16:59,347 --> 01:17:01,382 the ions around the comet. 1717 01:17:01,382 --> 01:17:03,418 That was another big objective. 1718 01:17:03,418 --> 01:17:05,987 And then we also had a radar instrument, that was, 1719 01:17:05,987 --> 01:17:08,623 it was really a european team, but JPL used 1720 01:17:08,623 --> 01:17:11,059 the Deep Space Network a lot for that. 1721 01:17:11,059 --> 01:17:14,796 Where we used radio waves, to study the interior 1722 01:17:14,796 --> 01:17:16,031 of the comet. 1723 01:17:16,031 --> 01:17:17,932 So, you go from the science objectives 1724 01:17:17,932 --> 01:17:20,268 to the specific instruments, 1725 01:17:20,268 --> 01:17:22,937 which JPL had a few instruments. 1726 01:17:22,937 --> 01:17:26,842 - 16 instruments on board of this spacecraft. 1727 01:17:26,842 --> 01:17:30,178 You know, normally, you see maybe three, four or five. 1728 01:17:30,178 --> 01:17:33,382 This one had 16 on the orbiter and 10 on the lander. 1729 01:17:33,382 --> 01:17:35,383 26 instruments. 1730 01:17:35,383 --> 01:17:38,152 So, you know, it's very expensive. 1731 01:17:38,152 --> 01:17:40,522 We call it Flagship missions. 1732 01:17:40,522 --> 01:17:43,057 Europeans called Cornerstone missions. 1733 01:17:43,057 --> 01:17:44,726 Very expensive, lot of instruments, 1734 01:17:44,726 --> 01:17:48,262 lot of difficult operations, you know. 1735 01:17:48,262 --> 01:17:50,298 We call it Battlestar Galactica. 1736 01:17:50,298 --> 01:17:52,434 (laughter) 1737 01:17:52,434 --> 01:17:55,904 - Another question about the RTGs. 1738 01:17:55,904 --> 01:18:00,709 Besides that we don't have enough plutonium to actually 1739 01:18:00,709 --> 01:18:05,480 but was the main reason for going with the solar 1740 01:18:05,480 --> 01:18:06,915 rather than RTGs? 1741 01:18:08,316 --> 01:18:12,153 - Well, you know there are a lot of reasons to go 1742 01:18:12,153 --> 01:18:14,021 if you can go solar, you go solar. 1743 01:18:14,021 --> 01:18:17,292 If you think that you can stabilize the spacecraft, 1744 01:18:17,292 --> 01:18:18,226 you go solar. 1745 01:18:18,226 --> 01:18:20,195 It's cheaper, it's safer. 1746 01:18:21,563 --> 01:18:25,567 You know, I worked on nuclear generators 1747 01:18:25,567 --> 01:18:28,903 for Ulysses and Cassini, the RTGs. 1748 01:18:28,903 --> 01:18:31,406 And it didn't effect me at all, you know? 1749 01:18:31,406 --> 01:18:33,274 The radiation has no effect. 1750 01:18:33,274 --> 01:18:35,043 No, okay, sorry about 1751 01:18:39,580 --> 01:18:40,448 Could you please stop recording? 1752 01:18:40,448 --> 01:18:41,849 - You could really act. 1753 01:18:41,849 --> 01:18:44,452 - But, so you know, the process 1754 01:18:44,452 --> 01:18:48,290 of environmental safety approval is very long. 1755 01:18:49,690 --> 01:18:52,260 You know, it costs hundreds of millions of dollars, 1756 01:18:52,260 --> 01:18:56,431 so you do it for cost, you do it for difficulty reasons, 1757 01:18:57,766 --> 01:19:00,034 installations are difficult because you have to, 1758 01:19:00,034 --> 01:19:02,470 you know, if you have radioactive source. 1759 01:19:02,470 --> 01:19:05,773 It's, yeah, you do it for many reasons. 1760 01:19:05,773 --> 01:19:08,576 If you can go solar, you go solar. 1761 01:19:08,576 --> 01:19:11,813 Thank you, and last question, maybe? 1762 01:19:11,813 --> 01:19:13,214 The last question, yes? 1763 01:19:13,214 --> 01:19:14,448 - [Male Stagehand] And questions from the web. 1764 01:19:14,448 --> 01:19:16,150 - [Art] Oh, okay, yeah, maybe in the meantime, 1765 01:19:16,150 --> 01:19:18,987 you can ask your question, please? 1766 01:19:20,121 --> 01:19:23,858 - This project started like 20 years ago, 1767 01:19:23,858 --> 01:19:27,896 and the planning and the making parts, then you know. 1768 01:19:27,896 --> 01:19:32,067 Travel, 10 years, so now we have this information. 1769 01:19:34,268 --> 01:19:36,838 When you planned this project, do you aim 1770 01:19:36,838 --> 01:19:41,009 this special comet, or you happen to be land that comet? 1771 01:19:44,846 --> 01:19:46,414 - Yeah, you were asking if we're planning it 1772 01:19:46,414 --> 01:19:47,949 for this comet? 1773 01:19:47,949 --> 01:19:51,820 - Yeah, how do you choose this one and end up here? 1774 01:19:55,523 --> 01:19:58,325 - Well, we didn't choose this one, 1775 01:19:58,325 --> 01:20:02,563 we chose another one, but the rocket on which 1776 01:20:02,563 --> 01:20:05,466 we were supposed to, the rocket before us, 1777 01:20:05,466 --> 01:20:08,537 we were going to go on a second REN rocket, 1778 01:20:08,537 --> 01:20:10,972 blew up on the launch pad and there were delays. 1779 01:20:10,972 --> 01:20:13,874 So we couldn't go to the comet Virtanen, 1780 01:20:13,874 --> 01:20:15,977 to which originally we wanted to go, 1781 01:20:15,977 --> 01:20:18,212 so we picked this pixel in the sky 1782 01:20:18,212 --> 01:20:20,415 because it was in the right orbit. 1783 01:20:20,415 --> 01:20:23,118 It wasn't going too close to the sun to overheat 1784 01:20:23,118 --> 01:20:24,919 and break up when we land. 1785 01:20:24,919 --> 01:20:27,022 It wasn't going too far, you know. 1786 01:20:27,022 --> 01:20:30,357 the velocity of the comet, to the size, all of these things 1787 01:20:30,357 --> 01:20:32,827 were considered and it was, the main thing was 1788 01:20:32,827 --> 01:20:35,396 that it was in the right place that we could launch 1789 01:20:35,396 --> 01:20:36,831 and catch up with it. 1790 01:20:36,831 --> 01:20:41,102 So it's a lot of flight dynamics calculations go into it. 1791 01:20:41,102 --> 01:20:44,606 Mainly because this is a comet we could catch up with, 1792 01:20:44,606 --> 01:20:46,741 but it wasn't our original choice. 1793 01:20:46,741 --> 01:20:48,376 And it gave us a beautiful surprise 1794 01:20:48,376 --> 01:20:50,645 because its such a bizarre object. 1795 01:20:50,645 --> 01:20:54,582 - So when you launched this spacecraft 1796 01:20:54,582 --> 01:20:56,384 you aimed at this object. 1797 01:20:56,384 --> 01:20:57,318 - [Art] Absolutely, yes. 1798 01:20:57,318 --> 01:20:58,920 - Okay, thank you. 1799 01:20:58,920 --> 01:21:00,321 - We have a couple questions from the web 1800 01:21:00,321 --> 01:21:03,124 that I'm gonna also briefly go over. 1801 01:21:03,124 --> 01:21:05,727 Alexander asks, "Can the weight or density of the comet 1802 01:21:05,727 --> 01:21:08,129 "be compared with any mineral on Earth?" 1803 01:21:08,129 --> 01:21:10,031 I think pumice is the only one I can think of 1804 01:21:10,031 --> 01:21:11,465 that would be, you know, 1805 01:21:11,465 --> 01:21:13,768 that basically would float on water, you know, 1806 01:21:13,768 --> 01:21:15,569 It's hard, not many things on Earth-- 1807 01:21:15,569 --> 01:21:17,539 - But you have to realize that the, 1808 01:21:17,539 --> 01:21:20,809 so this comet is about half the density of water, 1809 01:21:20,809 --> 01:21:23,611 but it's actually, because it's so porous. 1810 01:21:23,611 --> 01:21:27,782 But it's about 80% solids and 20% gases, okay, 1811 01:21:29,784 --> 01:21:31,686 which are frozen. 1812 01:21:31,686 --> 01:21:36,224 And it's reason so light is because lot of pores. 1813 01:21:36,224 --> 01:21:39,594 - And then another person asks, "How do the gases form, 1814 01:21:39,594 --> 01:21:40,862 "inside the comet." 1815 01:21:40,862 --> 01:21:42,430 Well, they're there in the beginning. 1816 01:21:42,430 --> 01:21:44,999 I mean this was, the comet formed in a very cold part 1817 01:21:44,999 --> 01:21:48,670 of the, what we call the protosolar nebula, 1818 01:21:48,670 --> 01:21:51,338 the gas and dust from which the planets formed, 1819 01:21:51,338 --> 01:21:52,673 so it was very cold out there, 1820 01:21:52,673 --> 01:21:54,608 so they were just included in it 1821 01:21:54,608 --> 01:21:57,545 and there's the space between the layers. 1822 01:21:57,545 --> 01:21:59,947 There're little, a lot of little spaces and gases, 1823 01:21:59,947 --> 01:22:01,282 that, you know, as Art mentioned, 1824 01:22:01,282 --> 01:22:04,085 do get pressurized and blow up. 1825 01:22:04,085 --> 01:22:06,321 That's what forms the jets. 1826 01:22:07,489 --> 01:22:09,991 Art, this is one you might wanna take. 1827 01:22:09,991 --> 01:22:13,694 - "Did you take deep space communication delay 1828 01:22:13,694 --> 01:22:17,866 "into account when deciding where to land the spacecraft?" 1829 01:22:21,569 --> 01:22:22,904 Absolutely, yes. 1830 01:22:24,372 --> 01:22:27,441 So, of course, the delays, there are different delays 1831 01:22:27,441 --> 01:22:29,244 and I don't wanna get too technical here, 1832 01:22:29,244 --> 01:22:33,414 but of course there is a delay in the flight time 1833 01:22:33,414 --> 01:22:36,451 of the signal; the signal flies through vacuum 1834 01:22:36,451 --> 01:22:39,353 with the speed of light but because it's so far away, 1835 01:22:39,353 --> 01:22:44,258 you know, light flies with a speed of 300,000 kilometers 1836 01:22:44,258 --> 01:22:46,928 per second, but we are right now 1837 01:22:48,262 --> 01:22:51,766 about 750 million kilometers away, so you know, 1838 01:22:53,301 --> 01:22:57,605 we're, so the signal takes about 39 minutes to get to us. 1839 01:22:57,605 --> 01:23:00,375 So that's one delay and then of course, 1840 01:23:00,375 --> 01:23:04,212 there are the delays because the spacecraft is moving. 1841 01:23:04,212 --> 01:23:06,280 There's the relative motion, right? 1842 01:23:06,280 --> 01:23:10,251 So, there is also for Doppler tracking, right? 1843 01:23:10,251 --> 01:23:12,020 So there's the relative motion of the spacecraft 1844 01:23:12,020 --> 01:23:16,257 moving away from Earth and the antennas on Earth 1845 01:23:16,257 --> 01:23:19,661 are rotating, so there's, you know, it's a nice exercise 1846 01:23:19,661 --> 01:23:21,262 in vector addition. 1847 01:23:24,732 --> 01:23:26,400 - We have everything. 1848 01:23:26,400 --> 01:23:27,334 I wanna thank everybody for coming. 1849 01:23:27,334 --> 01:23:28,602 - Thank you so much for coming. 1850 01:23:28,602 --> 01:23:30,204 - Don't forget to come to the event. 1851 01:23:30,204 --> 01:23:32,573 (applause) 1852 01:23:32,573 --> 01:23:33,408 Thank you. 1853 01:23:34,909 --> 01:23:37,846 - And if you, if you wanna photo-op 1854 01:23:39,313 --> 01:23:41,883 with Churyumov-Gerasimenko please come on, on stage, 1855 01:23:41,883 --> 01:23:46,887 and you can take your picture, your selfie with a comet. 1856 01:23:46,887 --> 01:23:48,089 - [Bonnie] Yeah, that's a good idea.