WEBVTT 00:00:00.000 --> 00:00:00.840 (dramatic music) 00:00:00.840 --> 00:00:04.563 Saturn is the jewel in the crown of the solar system. 00:00:04.563 --> 00:00:07.430 It's the truly beautiful, majestic planet. 00:00:07.430 --> 00:00:11.063 Saturn just makes us gasp at its beauty. 00:00:12.290 --> 00:00:15.760 The Saturnian system is an absolute wonderland. 00:00:15.760 --> 00:00:19.690 Saturn, second largest of the planets, 00:00:19.690 --> 00:00:24.690 nearly 800 times the volume of Earth, a true gas giant, 00:00:25.790 --> 00:00:30.790 adorned by and adored for its mysterious, captivating rings. 00:00:32.390 --> 00:00:34.700 The study of Saturn's rings has inspired 00:00:34.700 --> 00:00:37.453 great theoretical musings for centuries. 00:00:38.860 --> 00:00:42.420 Almost 300,000 kilometers in diameter, 00:00:42.420 --> 00:00:45.600 the ring system is just 20 meters thick. 00:00:45.600 --> 00:00:48.090 The rings capture the imagination 00:00:48.090 --> 00:00:51.750 to the point you have to understand where they came from 00:00:51.750 --> 00:00:53.400 and what do they mean? 00:00:53.400 --> 00:00:55.530 To try and answer these questions, 00:00:55.530 --> 00:00:58.470 humans designed, built, and launched 00:00:58.470 --> 00:01:01.703 some of the most advanced spacecraft ever conceived. 00:01:02.640 --> 00:01:05.470 It was and is the largest outerplanetary spacecraft 00:01:05.470 --> 00:01:07.330 that's ever been built. 00:01:07.330 --> 00:01:10.143 This is a massive piece of machinery. 00:01:11.120 --> 00:01:14.200 This is the story of the exploration of Saturn, 00:01:14.200 --> 00:01:19.200 its rings and moons, told by those who dared to do it, 00:01:19.320 --> 00:01:21.570 a place that turns out to be much more 00:01:21.570 --> 00:01:24.160 than just a celestial beauty spot. 00:01:24.160 --> 00:01:26.150 The building blocks of life could form 00:01:26.150 --> 00:01:29.420 in the interiors of these icy bodies. 00:01:29.420 --> 00:01:30.680 The kind of conditions we see 00:01:30.680 --> 00:01:33.090 are probably present on tens of billions 00:01:33.090 --> 00:01:35.263 of environments across the Milky Way. 00:01:37.270 --> 00:01:39.310 Saturn could hold the key 00:01:39.310 --> 00:01:43.620 to understanding our true place in the universe. 00:01:43.620 --> 00:01:44.970 It's definitely the most 00:01:44.970 --> 00:01:46.963 interesting place in the solar system. 00:01:51.308 --> 00:01:54.141 (title resonates) 00:01:55.530 --> 00:01:57.530 To the naked eye, the night sky 00:01:57.530 --> 00:02:00.010 is filled with points of light. 00:02:00.010 --> 00:02:04.040 Zoom into almost all of them and they remain just that: 00:02:04.040 --> 00:02:06.303 shining points in a dark universe. 00:02:07.220 --> 00:02:09.630 But one celestial object revealed 00:02:09.630 --> 00:02:13.410 to an Italian polymath that it was special. 00:02:13.410 --> 00:02:15.910 Galileo wasn't the inventor of the telescope, 00:02:15.910 --> 00:02:17.960 but he was one of the first people to use it 00:02:17.960 --> 00:02:20.090 for astronomical observations. 00:02:20.090 --> 00:02:23.943 It was 1610 when Galileo first observed the Saturn system. 00:02:24.930 --> 00:02:27.870 His drawing showed what were described 00:02:27.870 --> 00:02:31.800 as ears or jug handles either side of the planet. 00:02:31.800 --> 00:02:34.620 So Saturn's my face, it appeared that there 00:02:34.620 --> 00:02:36.533 were these weird globes. 00:02:37.640 --> 00:02:39.710 And so he thought well, these might be moons 00:02:39.710 --> 00:02:42.970 but stuck one on each side of the planet Saturn. 00:02:42.970 --> 00:02:45.620 He didn't know Newtonian mechanics, it hadn't been invented. 00:02:45.620 --> 00:02:47.510 He didn't know that moons have to go 00:02:47.510 --> 00:02:49.230 all away around a planet. 00:02:49.230 --> 00:02:51.340 When he went back to look at Saturn 00:02:51.340 --> 00:02:52.590 a couple of years later, 00:02:52.590 --> 00:02:56.045 he noticed that those features had gone. 00:02:56.045 --> 00:02:58.210 (spirited music) 00:02:58.210 --> 00:03:01.290 Galileo even suggested that Saturn had eaten 00:03:01.290 --> 00:03:04.310 his own children as in the ancient Greek myth, 00:03:04.310 --> 00:03:06.663 and that's why the moons had disappeared. 00:03:08.440 --> 00:03:11.000 Galileo lived in Italy, but he was aware 00:03:11.000 --> 00:03:13.000 of other major figures in his time, 00:03:13.000 --> 00:03:16.430 including Constantijn Huygens from the Netherlands, 00:03:16.430 --> 00:03:20.540 and in fact it was Huygens' son, Christiaan Huygens, 00:03:20.540 --> 00:03:22.160 who eventually solved the puzzle 00:03:22.160 --> 00:03:25.143 that was posed by the disappearing handles of Saturn. 00:03:26.530 --> 00:03:30.080 Christiaan Huygens turned his telescope towards Saturn. 00:03:30.080 --> 00:03:32.410 As technology develops, optics developed, 00:03:32.410 --> 00:03:34.160 and he was able to see more. 00:03:34.160 --> 00:03:36.900 And what he saw meant that he was able 00:03:36.900 --> 00:03:39.690 to come up with this radical idea 00:03:39.690 --> 00:03:43.553 that Saturn was surrounded by a ring system, 00:03:45.890 --> 00:03:48.910 and he was able to link back to what Galileo saw 00:03:48.910 --> 00:03:51.630 because if the ring system was tilted 00:03:51.630 --> 00:03:54.490 at an angle to our view from Earth, 00:03:54.490 --> 00:03:58.220 it means that sometimes you'll see the rings tilted 00:03:58.220 --> 00:04:00.220 and you'll see them sort of almost face-on, 00:04:00.220 --> 00:04:01.980 and other times when the planet has moved, 00:04:01.980 --> 00:04:03.360 they'll be edge-on. 00:04:03.360 --> 00:04:07.830 So at particular times, we'd look at the rings edge-on 00:04:07.830 --> 00:04:09.440 and they completely disappear. 00:04:09.440 --> 00:04:11.360 In fact even today when Hubble, 00:04:11.360 --> 00:04:14.850 the best optical telescope we have, looked at Saturn 00:04:14.850 --> 00:04:17.500 across through the ring plane, the rings disappeared. 00:04:20.580 --> 00:04:22.150 But not only that, Christiaan Huygens 00:04:22.150 --> 00:04:25.240 made another amazing discovery: 00:04:25.240 --> 00:04:28.940 that Saturn has a moon and it turns out 00:04:28.940 --> 00:04:32.260 that this moon is a really curious place, 00:04:32.260 --> 00:04:34.090 and is perhaps even more curious 00:04:34.090 --> 00:04:36.140 than the rings of Saturn itself. 00:04:36.140 --> 00:04:40.370 After the discovery by Huygens of Saturn's first moon, 00:04:40.370 --> 00:04:42.950 Giovanni Domenico Cassini discovered 00:04:42.950 --> 00:04:45.500 four more in the next decades, 00:04:45.500 --> 00:04:47.540 and moons continued to be discovered 00:04:47.540 --> 00:04:50.200 over the next few hundred years. 00:04:50.200 --> 00:04:51.190 Mimas. 00:04:51.190 --> 00:04:52.270 Enceladus. 00:04:52.270 --> 00:04:53.820 Hyperion. 00:04:53.820 --> 00:04:56.010 However, from the first there were 00:04:56.010 --> 00:04:59.450 big questions posed by Saturn's rings. 00:04:59.450 --> 00:05:02.470 What were the rings made of? 00:05:02.470 --> 00:05:03.873 How did they arise? 00:05:04.800 --> 00:05:07.663 What's the origin of the rings of Saturn? 00:05:08.610 --> 00:05:12.573 And why does Saturn have rings and not the other planets? 00:05:14.050 --> 00:05:15.630 The only way to answer that question 00:05:15.630 --> 00:05:19.063 is to actually get up close, we need to go to Saturn. 00:05:20.040 --> 00:05:22.820 But getting to planets in the outer solar system 00:05:22.820 --> 00:05:25.650 obviously requires a huge amount of fuel, 00:05:25.650 --> 00:05:27.390 but a large amount of fuel means 00:05:27.390 --> 00:05:29.260 you have an expensive mission 00:05:29.260 --> 00:05:32.580 because you're trying to launch a lot of mass into space 00:05:32.580 --> 00:05:35.170 and you need more fuel to be able to do that. 00:05:35.170 --> 00:05:37.160 So you start to think about, well, 00:05:37.160 --> 00:05:38.830 what are the other ways that you 00:05:38.830 --> 00:05:40.810 can accelerate your spacecraft 00:05:40.810 --> 00:05:42.960 without requiring lots of fuel? 00:05:42.960 --> 00:05:44.190 And one technique that's used 00:05:44.190 --> 00:05:46.810 is what's called a gravitational assist. 00:05:46.810 --> 00:05:49.851 (monitor beeping) 00:05:49.851 --> 00:05:51.270 (inquisitive music) 00:05:51.270 --> 00:05:53.430 As a spacecraft passes a planet 00:05:53.430 --> 00:05:56.200 that is itself moving around the sun, 00:05:56.200 --> 00:05:57.890 it would get dragged along 00:05:57.890 --> 00:06:01.390 and accelerated by the planets during the encounter, 00:06:01.390 --> 00:06:04.400 gaining extra speed like a skateboarder 00:06:04.400 --> 00:06:07.340 briefly holding onto a passing car. 00:06:07.340 --> 00:06:11.410 What's more, a huge opportunity suddenly presented itself. 00:06:11.410 --> 00:06:13.610 It was discovered that the outer planets 00:06:13.610 --> 00:06:15.240 would actually align in a way 00:06:15.240 --> 00:06:18.530 that they hadn't since Thomas Jefferson had been president. 00:06:18.530 --> 00:06:22.160 So we realized that you could fly past Jupiter, 00:06:22.160 --> 00:06:25.060 get a kick, go to Saturn, get a kick, 00:06:25.060 --> 00:06:27.793 go to Uranus, get a kick, go on to Neptune. 00:06:28.950 --> 00:06:32.776 This gravity assist trajectory was called The Grand Tour. 00:06:32.776 --> 00:06:34.120 And if we were gonna go and do this, 00:06:34.120 --> 00:06:36.000 take advantage of this alignment, 00:06:36.000 --> 00:06:39.200 we'd better get going and launch that spacecraft soon. 00:06:39.200 --> 00:06:42.010 NASA quickly responded to the opportunity 00:06:42.010 --> 00:06:44.850 by preparing some pathfinding spacecraft, 00:06:44.850 --> 00:06:46.650 one that would go to Jupiter 00:06:46.650 --> 00:06:48.710 and one that could use a gravity assist 00:06:48.710 --> 00:06:50.733 from Jupiter to go on to Saturn. 00:06:53.528 --> 00:06:55.713 And that was called Pioneer 11. 00:06:59.174 --> 00:07:03.035 (spacecraft beeping) 00:07:03.035 --> 00:07:05.785 (flames roaring) 00:07:07.230 --> 00:07:09.630 The primary purpose of those Pioneers 00:07:09.630 --> 00:07:12.433 was really to pave the way for later spacecraft. 00:07:14.000 --> 00:07:16.521 And that mission was called Voyager. 00:07:16.521 --> 00:07:19.104 (upbeat music) 00:07:23.690 --> 00:07:25.950 And the Voyager mission had two components, 00:07:25.950 --> 00:07:28.500 Voyager 1 and Voyager 2. 00:07:28.500 --> 00:07:30.690 Each of them would get a gravity assist 00:07:30.690 --> 00:07:33.190 from Jupiter to go on to Saturn. 00:07:33.190 --> 00:07:36.370 But that's then where the missions deviated, 00:07:36.370 --> 00:07:40.050 because Voyager 1 was given an extra special task. 00:07:40.050 --> 00:07:43.110 It was to go and visit the moon 00:07:43.110 --> 00:07:47.433 that Christiaan Huygens had discovered in 1655, Titan. 00:07:48.880 --> 00:07:50.570 Titan would become almost 00:07:50.570 --> 00:07:53.893 as important a destination as Saturn itself. 00:07:54.970 --> 00:07:57.770 Titan is a really intriguing moon. 00:07:57.770 --> 00:07:59.210 This is a massive moon, 00:07:59.210 --> 00:08:02.100 probably not worthy of the word moon. 00:08:02.100 --> 00:08:04.310 This is a body which is bigger than Mercury, 00:08:04.310 --> 00:08:06.070 so it's a big moon. 00:08:06.070 --> 00:08:07.780 Its mass is lower than that of Mercury, 00:08:07.780 --> 00:08:10.883 but in terms of size, it's bigger than our smallest planet. 00:08:12.070 --> 00:08:13.890 As we've been looking around the solar system, 00:08:13.890 --> 00:08:16.070 many people have been fixated on Mars 00:08:16.070 --> 00:08:19.750 as the place beyond the Earth most likely to hold life, 00:08:19.750 --> 00:08:21.290 but there's another place in the solar system 00:08:21.290 --> 00:08:22.940 which is probably just as exciting, 00:08:22.940 --> 00:08:26.013 and for some people even more so, and that's Titan. 00:08:28.120 --> 00:08:31.690 The atmosphere of Titan was hinted at a century ago 00:08:31.690 --> 00:08:34.040 and confirmed in the 1940s. 00:08:34.040 --> 00:08:36.690 It's the only satellite in the solar system 00:08:36.690 --> 00:08:38.270 with a dense atmosphere. 00:08:38.270 --> 00:08:39.860 In fact, its atmosphere is actually 00:08:39.860 --> 00:08:42.143 denser than our atmosphere here on Earth. 00:08:43.310 --> 00:08:44.680 Titan is the most interesting moon 00:08:44.680 --> 00:08:47.300 in the solar system, hands-down. 00:08:47.300 --> 00:08:48.720 But getting to Titan 00:08:48.720 --> 00:08:50.950 meant a change of direction, 00:08:50.950 --> 00:08:53.483 curtailing the exploration of the outer plants. 00:08:54.640 --> 00:08:57.950 So Voyager 1 going off to visit Titan 00:08:57.950 --> 00:08:59.700 meant that it was no longer able 00:08:59.700 --> 00:09:02.890 to slingshot on to visit Uranus and Neptune. 00:09:02.890 --> 00:09:05.160 If Voyager 1 had not been able 00:09:05.160 --> 00:09:07.740 to achieve that objective for whatever reason, 00:09:07.740 --> 00:09:11.460 Voyager 2 was going to be diverted to do that job 00:09:11.460 --> 00:09:14.205 at the expense of going on to Uranus and Neptune. 00:09:14.205 --> 00:09:16.630 (upbeat music) 00:09:16.630 --> 00:09:19.637 But that's how they felt about Titan, the importance. 00:09:21.236 --> 00:09:24.080 7-4-6-S-1-9. 00:09:24.080 --> 00:09:24.913 15 seconds. 00:09:24.913 --> 00:09:28.200 When Pioneer 11 eventually arrived at Saturn 00:09:28.200 --> 00:09:30.960 six years after flying by Jupiter, 00:09:30.960 --> 00:09:33.890 it was an immense, exciting moment. 00:09:33.890 --> 00:09:37.560 Five, four, three, two, one. 00:09:39.396 --> 00:09:40.329 We made it! (people cheering) 00:09:40.329 --> 00:09:41.317 Hooray! 00:09:41.317 --> 00:09:44.234 (intriguing music) 00:09:46.400 --> 00:09:50.660 The rings of Saturn were big and beautiful in our pictures 00:09:50.660 --> 00:09:53.743 and we stood in awe at the closeup views. 00:09:55.260 --> 00:09:59.160 My task was to see if we might discover any new rings, 00:09:59.160 --> 00:10:02.220 and amazingly, I watched the first images 00:10:02.220 --> 00:10:04.190 appear on the television screen 00:10:04.190 --> 00:10:07.373 and there was clearly a new ring of Saturn. 00:10:12.350 --> 00:10:14.920 The rings of Saturn had originally 00:10:14.920 --> 00:10:18.550 been named A, B, and C, in order 00:10:18.550 --> 00:10:21.330 from the outermost known ring to the innermost, 00:10:21.330 --> 00:10:24.410 but in the 20th century, we began to discover 00:10:24.410 --> 00:10:27.570 new rings which were then assigned alphabetically 00:10:27.570 --> 00:10:30.590 in the order of discovery, first the D Ring, 00:10:30.590 --> 00:10:35.540 then the E Ring, so the next available letter was F, 00:10:35.540 --> 00:10:38.807 and so I named that ring Ring F of Saturn. 00:10:38.807 --> 00:10:41.307 (tense music) 00:10:44.630 --> 00:10:49.240 Pioneer 11 passed Titan by quite a large distance, 00:10:49.240 --> 00:10:51.023 couple hundred thousand miles away. 00:10:55.680 --> 00:10:57.980 And really all it told us about Titan 00:10:57.980 --> 00:10:59.430 was that it was very, very cold, 00:10:59.430 --> 00:11:02.680 too cold for life as we know it to exist. 00:11:02.680 --> 00:11:04.310 But actually we needed to go back 00:11:04.310 --> 00:11:06.820 and look at this thing in much more detail. 00:11:06.820 --> 00:11:09.520 Fortunately, two more spacecraft 00:11:09.520 --> 00:11:11.690 were already on their way. 00:11:11.690 --> 00:11:15.810 4-7-4-7-4-6-U-S-4-9. 00:11:15.810 --> 00:11:18.760 The Pioneers had told us it was safe, 00:11:18.760 --> 00:11:20.165 it's okay, we can go there. 00:11:20.165 --> 00:11:21.930 (triumphant music) 00:11:21.930 --> 00:11:24.650 So just a year later, Voyager 1, 00:11:24.650 --> 00:11:27.280 equipped with better instruments and better cameras 00:11:27.280 --> 00:11:31.223 was preparing to take a look at Saturn and its rings. 00:11:34.970 --> 00:11:37.890 The encounter was an amazingly thrilling 00:11:37.890 --> 00:11:39.540 and rapid experience, 00:11:39.540 --> 00:11:41.730 all happened within a matter of a few days, 00:11:41.730 --> 00:11:43.860 and even before you could explain 00:11:43.860 --> 00:11:45.620 some of the new phenomena we saw, 00:11:45.620 --> 00:11:49.280 Voyager was off on its way out of the solar system. 00:11:49.280 --> 00:11:51.470 (people cheering) (people applauding) 00:11:51.470 --> 00:11:54.810 Many people referred to that flood of data, 00:11:54.810 --> 00:11:57.310 the camera pictures and other observations, 00:11:57.310 --> 00:12:00.062 as like drinking from a fire hose. 00:12:00.062 --> 00:12:02.846 The estimate is. 00:12:02.846 --> 00:12:05.649 (people chattering) 00:12:05.649 --> 00:12:07.585 (people cheering) (people applauding) 00:12:07.585 --> 00:12:11.090 Do you guys have any questions? 00:12:11.090 --> 00:12:13.470 After the Voyager flybys, we knew there were 00:12:13.470 --> 00:12:15.930 thousands of rings, and it's that moment 00:12:15.930 --> 00:12:18.130 that we stopped naming them with letters. 00:12:18.130 --> 00:12:21.260 It was just impossible, exceeded the alphabet. 00:12:21.260 --> 00:12:24.610 We saw waves propagating through the rings, 00:12:24.610 --> 00:12:27.710 we saw the edges of the rings wiggling. 00:12:27.710 --> 00:12:31.590 A ring could be maintained between two moons, 00:12:31.590 --> 00:12:33.943 one outside the ring and one inside the ring. 00:12:35.430 --> 00:12:38.680 And that's the beauty of this idea of moonlets 00:12:38.680 --> 00:12:40.290 that are sitting within the rings, 00:12:40.290 --> 00:12:42.560 shepherding the gravitational motion 00:12:42.560 --> 00:12:44.043 of the particles within it. 00:12:45.203 --> 00:12:49.220 (intriguing music) (people chattering) 00:12:49.220 --> 00:12:51.060 Maybe it's a scientific prerequisite 00:12:51.060 --> 00:12:52.840 to start with a simple idea, 00:12:52.840 --> 00:12:55.800 but we had imagined the rings were ancient, 00:12:55.800 --> 00:12:59.260 unchanging, and completely uniform, 00:12:59.260 --> 00:13:02.550 and this picture of the rings was completely shattered. 00:13:02.550 --> 00:13:06.100 The rings were changing in time, changing in space, 00:13:06.100 --> 00:13:09.080 they're dynamically changing with waves 00:13:09.080 --> 00:13:13.500 lapping across the rings, so this idea of symmetry, 00:13:13.500 --> 00:13:15.830 of constant persistence of the rings, 00:13:15.830 --> 00:13:18.056 all were immediately questioned. 00:13:18.056 --> 00:13:19.481 (people chattering) 00:13:19.481 --> 00:13:21.220 (inquisitive music) 00:13:21.220 --> 00:13:23.610 But what was the origin of the rings? 00:13:23.610 --> 00:13:25.283 Where did they come from? 00:13:27.180 --> 00:13:29.330 When an object gets closer to the planet 00:13:29.330 --> 00:13:32.280 it gets stretched out, and so a basketball might look 00:13:32.280 --> 00:13:35.470 more like an American football under this stress. 00:13:35.470 --> 00:13:37.800 The question is, can that stress 00:13:37.800 --> 00:13:39.773 be withstood by the object? 00:13:42.200 --> 00:13:45.360 For most competent objects, including humans, 00:13:45.360 --> 00:13:47.490 we can withstand that stress. 00:13:47.490 --> 00:13:51.330 For objects that are piles of rubble or dust 00:13:51.330 --> 00:13:55.000 or are big, say larger than 50 or 100 kilometers, 00:13:55.000 --> 00:13:57.353 they cannot withstand that force. 00:13:59.160 --> 00:14:01.100 If a large moon had once strayed 00:14:01.100 --> 00:14:04.800 too close to Saturn, this destructive force 00:14:04.800 --> 00:14:07.993 would've been enough to tear it into tiny pieces. 00:14:11.010 --> 00:14:12.890 So Saturn once had a moon, 00:14:12.890 --> 00:14:15.400 say an object about the size of Titan, 00:14:15.400 --> 00:14:18.260 if it were dragged in toward the planet by friction, 00:14:18.260 --> 00:14:20.240 first the ice would shatter 00:14:20.240 --> 00:14:22.890 and then later the core, which is made of metal, 00:14:22.890 --> 00:14:25.260 would shatter or might even end up inside the planet, 00:14:25.260 --> 00:14:28.503 and the pieces of ice formed a ring around Saturn. 00:14:29.520 --> 00:14:30.630 And now the mission 00:14:30.630 --> 00:14:32.710 turned to the prize that was worth 00:14:32.710 --> 00:14:35.417 missing out Neptune and Uranus: Titan. 00:14:38.648 --> 00:14:41.900 (tense music) 00:14:41.900 --> 00:14:44.340 The scientific community and the public 00:14:44.340 --> 00:14:47.900 watched with great interest as Voyager 1 00:14:47.900 --> 00:14:49.703 made the first flyby of Titan. 00:14:49.703 --> 00:14:53.623 What Voyager 1 encountered was still this mysterious veil. 00:14:54.650 --> 00:14:58.060 There was an organic haze that encircled the surface 00:14:58.060 --> 00:15:00.393 and you couldn't see the surface as a result. 00:15:01.680 --> 00:15:03.950 That atmosphere is simultaneously 00:15:03.950 --> 00:15:07.270 the bane of my research because it blocks the surface, 00:15:07.270 --> 00:15:10.823 but it's also the reason why Titan is so interesting. 00:15:12.490 --> 00:15:14.730 All of those hazes that mean that you and I 00:15:14.730 --> 00:15:16.360 can't actually see the surface 00:15:16.360 --> 00:15:18.440 with light that our eyes can see, 00:15:18.440 --> 00:15:21.963 make Titan this organic chemistry wonderland. 00:15:26.290 --> 00:15:28.186 One of the other things we figured out was that there was 00:15:28.186 --> 00:15:30.510 methane present in the atmosphere of Titan. 00:15:30.510 --> 00:15:32.290 Now this is important because 00:15:32.290 --> 00:15:34.380 both pressure and temperature measurements 00:15:34.380 --> 00:15:37.180 that Voyager 1 took indicated that 00:15:37.180 --> 00:15:40.860 it gets incredibly close to the triple point of methane. 00:15:40.860 --> 00:15:44.430 This opened the really, really tantalizing possibility 00:15:44.430 --> 00:15:47.193 for lakes and oceans on the surface. 00:15:48.560 --> 00:15:51.690 Some people think if we look in these methane lakes, 00:15:51.690 --> 00:15:54.410 perhaps we'll find a different way of organizing matter, 00:15:54.410 --> 00:15:55.960 a different way of organizing life. 00:15:55.960 --> 00:15:58.360 (monkey calls) 00:15:58.360 --> 00:16:00.660 Titan was still hiding all its mysteries from us, 00:16:00.660 --> 00:16:02.800 so that laid down the gauntlet of the challenge. 00:16:02.800 --> 00:16:05.543 We must now go to the surface of Titan. 00:16:07.510 --> 00:16:09.330 Fortunately, Voyager 1 made 00:16:09.330 --> 00:16:11.210 excellent observations of Titan, 00:16:11.210 --> 00:16:13.930 so thankfully Voyager 2 was allowed 00:16:13.930 --> 00:16:17.513 to go on to the next planet, Uranus, and then to Neptune. 00:16:17.513 --> 00:16:19.870 (triumphant music) 00:16:19.870 --> 00:16:21.580 The Uranian rings had been discovered 00:16:21.580 --> 00:16:24.350 from the ground om 1977, 00:16:24.350 --> 00:16:28.220 Voyager itself discovered the ring of Jupiter in 1979, 00:16:28.220 --> 00:16:31.160 and while we were on our way to the planet Uranus, 00:16:31.160 --> 00:16:33.870 the rings of Neptune were also discovered. 00:16:33.870 --> 00:16:36.870 So by the time the Voyager mission had completed, 00:16:36.870 --> 00:16:40.130 we knew that all of the giant planets had rings, 00:16:40.130 --> 00:16:42.610 just the opposite of what the question had been 00:16:42.610 --> 00:16:46.110 before those missions of why only Saturn has rings, 00:16:46.110 --> 00:16:50.870 but leaving us with deeper questions about Saturn's rings. 00:16:50.870 --> 00:16:52.060 What were they made of? 00:16:52.060 --> 00:16:54.060 How old were they? 00:16:54.060 --> 00:16:57.820 And why are Saturn's rings so particularly different, 00:16:57.820 --> 00:17:00.440 so big and so bright compared to 00:17:00.440 --> 00:17:03.710 the narrower, less massive, darker rings 00:17:03.710 --> 00:17:05.563 of Jupiter, Uranus, and Neptune? 00:17:06.980 --> 00:17:10.980 The rapid flybys that Voyager provided were insufficient 00:17:10.980 --> 00:17:13.970 to answer these questions in more detail, 00:17:13.970 --> 00:17:17.240 but then those failings could be addressed 00:17:17.240 --> 00:17:19.770 by a mission that went into orbit around Saturn 00:17:19.770 --> 00:17:21.601 and stayed for many years. 00:17:21.601 --> 00:17:22.750 (people chattering) 00:17:22.750 --> 00:17:26.497 We already knew that the value of orbiting a system 00:17:26.497 --> 00:17:28.990 and the amount of understanding you can gain 00:17:28.990 --> 00:17:31.100 by being there for a long period of time 00:17:31.100 --> 00:17:33.040 is so amazing that the next step 00:17:33.040 --> 00:17:35.530 was clearly gonna be an orbital mission. 00:17:35.530 --> 00:17:38.510 And if we're going to send another mission to Saturn 00:17:38.510 --> 00:17:41.520 that stays there, it should have a part of it 00:17:41.520 --> 00:17:43.323 that lands on the surface of Titan. 00:17:44.410 --> 00:17:46.830 Planning began in 1982 00:17:46.830 --> 00:17:49.810 for a mission that will be more ambitious and advanced 00:17:49.810 --> 00:17:52.290 than anything that had gone before, 00:17:52.290 --> 00:17:54.763 a mission called Cassini Huygens. 00:18:02.010 --> 00:18:06.430 The spacecraft was about the size of a school bus. 00:18:06.430 --> 00:18:08.270 If you saw it when they were putting it together, 00:18:08.270 --> 00:18:10.520 it was pretty impressive, you just looked up. 00:18:10.520 --> 00:18:11.913 It was a monster. 00:18:13.740 --> 00:18:16.560 It was and is the largest outerplanetary spacecraft 00:18:16.560 --> 00:18:19.050 that's ever been built, and may, 00:18:19.050 --> 00:18:21.398 in my lifetime, ever be built. 00:18:21.398 --> 00:18:22.870 Pressures are excellent. 00:18:22.870 --> 00:18:24.350 T plus 20 seconds. 00:18:24.350 --> 00:18:25.860 The mission was a collaboration 00:18:25.860 --> 00:18:28.050 with the European Space Agency, 00:18:28.050 --> 00:18:31.433 who designed and built a lander called Huygens. 00:18:32.300 --> 00:18:34.900 And this was the vehicle to take us 00:18:34.900 --> 00:18:38.049 down through the clouds, down to the surface of Titan. 00:18:38.049 --> 00:18:41.070 (dramatic music) 00:18:41.070 --> 00:18:42.340 The Huygens probe was actually 00:18:42.340 --> 00:18:44.330 designed to be able to float in liquid 00:18:44.330 --> 00:18:46.330 as well as land on a solid surface 00:18:46.330 --> 00:18:48.720 because we didn't know at the time whether it was going to 00:18:48.720 --> 00:18:51.600 land in a liquid or on a solid surface. 00:18:51.600 --> 00:18:53.080 So we designed the mission to cope 00:18:53.080 --> 00:18:55.323 with as many characteristics as possible. 00:18:56.290 --> 00:18:58.980 No one's ever tried to measure the depths of an ocean 00:18:58.980 --> 00:19:00.010 and how hard a rock is 00:19:00.010 --> 00:19:01.870 depending on which one you're gonna land on. 00:19:01.870 --> 00:19:04.500 We knew from Hubble images that there 00:19:04.500 --> 00:19:06.420 probably wasn't a global ocean, 00:19:06.420 --> 00:19:10.520 but whether there were other liquids was still not known. 00:19:10.520 --> 00:19:12.080 Huygens' team had to prepare for that 00:19:12.080 --> 00:19:15.600 but also a very hard landing, or maybe you can imagine 00:19:15.600 --> 00:19:19.083 a very squish surface full of organic goop. 00:19:19.083 --> 00:19:22.530 (liquid gurgling) 00:19:22.530 --> 00:19:23.810 20 seconds and counting. 00:19:23.810 --> 00:19:25.740 This is Titan Launch Control. 00:19:25.740 --> 00:19:28.630 Without any doubt, the most risky element 00:19:28.630 --> 00:19:32.020 of any space mission is the launch. 00:19:32.020 --> 00:19:33.540 T minus 15 seconds. 00:19:33.540 --> 00:19:36.130 It was a nighttime launch, so you had to get on the bus 00:19:36.130 --> 00:19:38.520 something like two in the morning or something to go out, 00:19:38.520 --> 00:19:40.610 and we did that, and we went out to the launch site, 00:19:40.610 --> 00:19:43.680 and the first opportunity, the launch was scrubbed. 00:19:43.680 --> 00:19:46.750 And so we did the same thing again two days later. 00:19:46.750 --> 00:19:47.983 T minus 10. 00:19:47.983 --> 00:19:49.980 When you've put eight years of your life 00:19:49.980 --> 00:19:52.360 into designing and building and testing something 00:19:52.360 --> 00:19:53.990 which is going to go into space-- 00:19:53.990 --> 00:19:55.320 Nine, eight, seven. 00:19:55.320 --> 00:19:57.660 And then seeing on the top of a rocket 00:19:57.660 --> 00:20:00.960 that's being vibrated on its way to Saturn, 00:20:00.960 --> 00:20:02.300 it is quite a feeling. 00:20:02.300 --> 00:20:03.133 One. 00:20:03.133 --> 00:20:07.950 (explosion booms) (dramatic music) 00:20:07.950 --> 00:20:11.109 When it did go off, it created a huge amount of light, 00:20:11.109 --> 00:20:13.010 (flames crackling) 00:20:13.010 --> 00:20:15.490 and then the rocket went behind the cloud. 00:20:15.490 --> 00:20:17.720 When it went behind that cloud, it was very impressive. 00:20:17.720 --> 00:20:19.490 The whole cloud lit up. 00:20:19.490 --> 00:20:22.478 We all thought oh goodness, has something gone wrong? 00:20:22.478 --> 00:20:24.100 United Station, our fly ring data. 00:20:24.100 --> 00:20:25.630 And then the nose cone came out 00:20:25.630 --> 00:20:30.630 and you were getting all, phew. 00:20:36.847 --> 00:20:39.847 (inquisitive music) 00:20:49.659 --> 00:20:52.026 (people chattering) 00:20:52.026 --> 00:20:53.309 Wait, do I come? 00:20:53.309 --> 00:20:55.374 Go ahead Aswar, come. 00:20:55.374 --> 00:20:56.420 One of the things you have to do 00:20:56.420 --> 00:20:58.080 when you arrive at a big planetary body 00:20:58.080 --> 00:20:59.710 is slam the brakes on pretty quick. 00:20:59.710 --> 00:21:03.230 You need to slow yourself down and get yourself into orbit. 00:21:03.230 --> 00:21:04.750 You typically do this by going 00:21:04.750 --> 00:21:06.380 very close to the planet to slow you down, 00:21:06.380 --> 00:21:09.870 so you get captured by the gravitational pull of Saturn. 00:21:09.870 --> 00:21:13.050 It was an incredibly complex sequence 00:21:13.050 --> 00:21:15.483 that we had basically worked on for two years. 00:21:16.900 --> 00:21:20.590 Even after Pioneer and Voyager, we didn't know enough 00:21:20.590 --> 00:21:23.243 about the possible dangers of the Saturn system. 00:21:24.990 --> 00:21:27.430 And because the Cassini spacecraft was moving 00:21:27.430 --> 00:21:29.750 at about 10 miles per second, 00:21:29.750 --> 00:21:32.360 even hitting a grain of sand or a chunk of ice 00:21:32.360 --> 00:21:34.050 could be deadly to the spacecraft, 00:21:34.050 --> 00:21:37.034 and so we took a number of ways to remove that risk, 00:21:37.034 --> 00:21:38.660 (dramatic music) 00:21:38.660 --> 00:21:40.477 and the best was to turn so that 00:21:40.477 --> 00:21:43.993 the spacecraft antennae was facing forward. 00:21:45.080 --> 00:21:46.700 The high-gain antennae, which is a thing 00:21:46.700 --> 00:21:48.330 which communicates back to Earth, 00:21:48.330 --> 00:21:50.270 was actually protecting it from 00:21:50.270 --> 00:21:53.340 potentially being hit by dust particles, 00:21:53.340 --> 00:21:56.293 so it couldn't be in communication with Earth at that time. 00:21:59.830 --> 00:22:01.790 This was an incredibly nervous 00:22:01.790 --> 00:22:04.713 and dangerous maneuver to do given the unknowns. 00:22:07.230 --> 00:22:08.610 Once Cassini had crossed 00:22:08.610 --> 00:22:10.530 the plane of Saturn's rings, 00:22:10.530 --> 00:22:13.570 the spacecraft had to reorient itself again. 00:22:13.570 --> 00:22:15.550 The thrusters had to be turned 00:22:15.550 --> 00:22:19.010 so that they would point in the direction of motion 00:22:19.010 --> 00:22:21.400 to be able to capture it into orbit. 00:22:21.400 --> 00:22:22.570 During the 90 minutes 00:22:22.570 --> 00:22:24.690 that Cassini's engines were firing, 00:22:24.690 --> 00:22:28.250 the spacecraft was completely shielded from Earth. 00:22:28.250 --> 00:22:30.740 At its closest approach, the spacecraft 00:22:30.740 --> 00:22:34.893 was just 20,000 kilometers from the cloud tops of Saturn. 00:22:36.010 --> 00:22:39.460 All the mission controllers on Earth could do was wait. 00:22:39.460 --> 00:22:43.123 We all held our breath waiting for the signal to return. 00:22:44.630 --> 00:22:47.460 But then we got a signal which was dead-on. 00:22:47.460 --> 00:22:48.340 The doppler has landed. 00:22:48.340 --> 00:22:49.810 And we knew at that moment we had 00:22:49.810 --> 00:22:52.637 successfully gone into orbit, and there was a huge cheer. 00:22:52.637 --> 00:22:57.590 (people cheering) (people applauding) 00:22:57.590 --> 00:22:59.320 It was really a fist pump moment. 00:22:59.320 --> 00:23:01.397 People were jumping up and hugging. 00:23:01.397 --> 00:23:04.910 (people cheering) (people applauding) 00:23:04.910 --> 00:23:06.340 I was watching it in the middle of the night 00:23:06.340 --> 00:23:09.610 via the internet, and I must've went into a huge cheer 00:23:09.610 --> 00:23:11.903 which woke everybody else up in the house. 00:23:14.030 --> 00:23:14.970 When the burn was completed, 00:23:14.970 --> 00:23:18.640 we knew we were in orbit, so we turned away from the Earth 00:23:18.640 --> 00:23:21.070 and photographed the dark side of the rings 00:23:21.070 --> 00:23:22.830 and then after we come back through 00:23:22.830 --> 00:23:23.850 the ring plane crossing again, 00:23:23.850 --> 00:23:26.360 we turn back to the Earth to start play back that data, 00:23:26.360 --> 00:23:28.660 and those images I'll never forget them. 00:23:28.660 --> 00:23:31.750 We've had much prettier images but my gosh, 00:23:31.750 --> 00:23:34.150 to see the ripples and the structure in those rings, 00:23:34.150 --> 00:23:36.966 it was absolutely, like I said, I'll never forget it. 00:23:36.966 --> 00:23:40.452 (triumphant music) 00:23:40.452 --> 00:23:43.580 It's one of those moments you'll take to your grave. 00:23:43.580 --> 00:23:45.340 Cassini Huygens had arrived 00:23:45.340 --> 00:23:49.120 at the Saturnian system, an enormous gas giant 00:23:49.120 --> 00:23:50.055 with 82 moons at present count, 00:23:50.055 --> 00:23:55.055 orbiting on the outside and within 00:23:55.270 --> 00:23:59.870 the hundreds of rings of varying shades and colors. 00:23:59.870 --> 00:24:02.630 We could now truly start to appreciate 00:24:02.630 --> 00:24:06.693 the awesome beauty and complexity of this planetary system. 00:24:07.987 --> 00:24:10.570 (gentle music) 00:24:13.710 --> 00:24:16.150 From a mission engineer's point of view, 00:24:16.150 --> 00:24:18.790 the rings are a hazard. (laughs) 00:24:18.790 --> 00:24:21.370 But once we've discovered that the environment's safe, 00:24:21.370 --> 00:24:23.580 then we can start to open up the stops a little bit 00:24:23.580 --> 00:24:24.733 to allow more activity. 00:24:26.230 --> 00:24:29.360 We knew that we'd have long, consecutive pieces of data 00:24:29.360 --> 00:24:32.380 to test our theories, but we didn't realize 00:24:32.380 --> 00:24:35.840 that because we could orbit Saturn hundreds of time, 00:24:35.840 --> 00:24:39.040 the same aspect could be seen over multiple times 00:24:39.040 --> 00:24:41.070 by all the 12 instruments, 00:24:41.070 --> 00:24:44.380 and that hit us in the head sometimes. 00:24:44.380 --> 00:24:47.690 Oh, this is something unexpected that's happening. 00:24:47.690 --> 00:24:51.260 It's very easy to think of the system as isolated parts, 00:24:51.260 --> 00:24:53.100 especially when you're working with a spacecraft mission 00:24:53.100 --> 00:24:54.180 and you target this feature 00:24:54.180 --> 00:24:55.550 and then you target the satellite. 00:24:55.550 --> 00:24:58.560 Any speculation, any idea we had had from the years 00:24:58.560 --> 00:25:01.463 between Voyager and Cassini, could now be tested. 00:25:02.640 --> 00:25:05.537 And as for the origins of the rings and moons, 00:25:05.537 --> 00:25:08.382 the Cassini team made a further discovery. 00:25:08.382 --> 00:25:11.132 (dramatic music) 00:25:12.260 --> 00:25:14.260 As we have seen quite clearly, 00:25:14.260 --> 00:25:17.220 Saturn's rings are made out of ice, 00:25:17.220 --> 00:25:21.843 which is the fragments of shattered icy moons. 00:25:27.840 --> 00:25:29.840 But the alternate is also true. 00:25:29.840 --> 00:25:32.740 Cassini showed us that the pieces of the ring 00:25:32.740 --> 00:25:34.900 are sticking together to make new moons. 00:25:34.900 --> 00:25:38.570 So the rings are collecting in places to make moons, 00:25:38.570 --> 00:25:41.590 and the moons are being shattered to make new rings. 00:25:41.590 --> 00:25:45.723 So this is sort of a cosmic recycling of material. 00:25:47.290 --> 00:25:49.440 So not only are the rings of Saturn 00:25:49.440 --> 00:25:54.440 most likely made of moons, but they also make new moons. 00:25:54.680 --> 00:25:57.240 One of the best measurements that Cassini made 00:25:57.240 --> 00:25:59.920 was to measure the total mass of the rings. 00:25:59.920 --> 00:26:03.550 This determines how long this recycling process could go on. 00:26:03.550 --> 00:26:06.453 The amount of pollution, the amount of meteoric dust, 00:26:07.360 --> 00:26:09.500 the combination of those two facts 00:26:09.500 --> 00:26:13.870 say that the rings are about 100 million years old. 00:26:13.870 --> 00:26:17.150 This can be extended, perhaps, to a billion years or two, 00:26:17.150 --> 00:26:19.240 but the current one is the rings 00:26:19.240 --> 00:26:22.131 that the dinosaurs would've seen. 00:26:22.131 --> 00:26:24.881 (dinosaur roars) 00:26:37.463 --> 00:26:40.046 (gentle music) 00:26:45.526 --> 00:26:47.320 (intriguing music) 00:26:47.320 --> 00:26:48.890 If we were to look closely, 00:26:48.890 --> 00:26:53.200 many of the ring particles would appear fluffy to your hand. 00:26:53.200 --> 00:26:56.823 They're fairy castle structures sort of like snow. 00:26:59.260 --> 00:27:01.920 You would see a range in particle sizes 00:27:01.920 --> 00:27:06.440 continually colliding, but at a relatively low velocity, 00:27:06.440 --> 00:27:08.970 maybe a millimeter a second, 00:27:08.970 --> 00:27:11.590 which is gentle enough that the surfaces 00:27:11.590 --> 00:27:13.723 might be slightly compressed. 00:27:15.890 --> 00:27:18.350 But occasionally, particles will hit each other 00:27:18.350 --> 00:27:21.770 at a much higher velocity, which will knock off 00:27:21.770 --> 00:27:25.340 a spray of small particles of snow and ice 00:27:25.340 --> 00:27:28.740 which eventually are recaptured by other clumps, 00:27:28.740 --> 00:27:33.470 so the equilibrium, the balance between these two processes, 00:27:33.470 --> 00:27:38.470 leads to a distribution of sizes from dust to mountains, 00:27:38.550 --> 00:27:42.350 and each of the objects being like a pile of rubble 00:27:42.350 --> 00:27:44.783 with a coating of snow on the top. 00:27:48.219 --> 00:27:49.930 (inquisitive music) 00:27:49.930 --> 00:27:51.680 After six months in orbit, 00:27:51.680 --> 00:27:55.030 Cassini was scheduled to deploy the Huygens lander 00:27:55.030 --> 00:27:57.473 on December the 25th, 2004. 00:27:59.210 --> 00:28:01.090 We had Christmas dinner at my home 00:28:01.090 --> 00:28:03.740 and had a lot of the European and American contingent 00:28:03.740 --> 00:28:06.040 because we were all spending Christmas at JPL. 00:28:08.780 --> 00:28:10.480 My whole family was here. 00:28:10.480 --> 00:28:13.470 I made them come to JPL and they watched 00:28:13.470 --> 00:28:15.743 as we released the probe that night. 00:28:18.603 --> 00:28:19.731 (people chattering) 00:28:19.731 --> 00:28:22.620 (people cheering) (people applauding) 00:28:22.620 --> 00:28:23.780 A few days later we turned around 00:28:23.780 --> 00:28:26.553 to take a picture of where the probe was supposed to be. 00:28:27.959 --> 00:28:30.750 It's a little speck and it's not very exciting, 00:28:30.750 --> 00:28:33.310 but it was a genuine confirmation 00:28:33.310 --> 00:28:35.533 it was exactly where we thought it was going to be. 00:28:36.980 --> 00:28:38.330 Because what happens with a probe 00:28:38.330 --> 00:28:39.760 is essentially when you release it, 00:28:39.760 --> 00:28:41.674 you've turned on a little three-week egg timer. 00:28:41.674 --> 00:28:43.390 (dramatic music) (timer ticking) 00:28:43.390 --> 00:28:46.020 Your worst nightmare is silence. 00:28:46.020 --> 00:28:48.847 That's happened too many times to people in space missions 00:28:48.847 --> 00:28:50.773 and it's just a punch in the gut. 00:28:52.510 --> 00:28:54.490 But three weeks later, right on schedule, 00:28:54.490 --> 00:28:55.640 we get the signal back. 00:28:57.570 --> 00:28:58.770 When we arrive at Titan, 00:28:58.770 --> 00:29:01.400 we're traveling at incredible speeds, 00:29:01.400 --> 00:29:05.110 and what you gotta do is go from ballistic, 00:29:05.110 --> 00:29:07.720 incredibly fast speeds at the top of the atmosphere 00:29:07.720 --> 00:29:09.560 to zero speed at the bottom 00:29:09.560 --> 00:29:11.430 of the atmosphere on the surface, 00:29:11.430 --> 00:29:13.310 and this is pretty hard to do. 00:29:13.310 --> 00:29:14.720 There are several elements in order 00:29:14.720 --> 00:29:16.380 to get yourself down to the surface. 00:29:16.380 --> 00:29:18.043 The first is a heat shield. 00:29:19.910 --> 00:29:21.620 Titan has a huge atmosphere, 00:29:21.620 --> 00:29:23.453 and Huygens was just screaming in. 00:29:24.338 --> 00:29:25.342 And if we were to send the probe 00:29:25.342 --> 00:29:28.808 in without protection, it will burn immediately. 00:29:28.808 --> 00:29:30.470 So you have the sacrificial heat shield 00:29:30.470 --> 00:29:33.820 in front of the probe, so the fireball that's created 00:29:33.820 --> 00:29:37.420 as the probe slows down doesn't destroy the lander itself. 00:29:37.420 --> 00:29:38.720 And in the case of Huygens, 00:29:38.720 --> 00:29:41.163 the heat shield was made of many of those tile. 00:29:42.550 --> 00:29:43.560 While the heat shield 00:29:43.560 --> 00:29:45.470 was slowing the probe down, 00:29:45.470 --> 00:29:49.810 Huygens experienced a deceleration of 15G. 00:29:49.810 --> 00:29:53.310 Once it had got to an altitude of 170 kilometers 00:29:53.310 --> 00:29:56.980 and was only traveling at a mere 400 meters per second, 00:29:56.980 --> 00:30:00.233 Huygens deployed the first of its three parachutes. 00:30:01.850 --> 00:30:04.450 The drogue parachute stabilized the probe 00:30:04.450 --> 00:30:06.660 and pulled off the back cover, 00:30:06.660 --> 00:30:09.520 which deployed the main parachute, 00:30:09.520 --> 00:30:13.205 at which point the spent heat shield was discarded. 00:30:13.205 --> 00:30:15.872 (clock ticking) 00:30:16.970 --> 00:30:19.330 But Titan's atmosphere is so thick 00:30:19.330 --> 00:30:21.660 that if we kept that parachute on, 00:30:21.660 --> 00:30:23.900 the batteries would've run out before it got to the surface. 00:30:23.900 --> 00:30:24.920 It was gonna go a little slowly. 00:30:24.920 --> 00:30:26.850 So it actually deployed that parachute 00:30:26.850 --> 00:30:28.320 and then dropped the last chute 00:30:28.320 --> 00:30:31.053 which allowed it to descend at a more reasonable pace. 00:30:32.080 --> 00:30:33.960 You get horizontal winds coming across 00:30:33.960 --> 00:30:35.560 and swinging the probe about, 00:30:35.560 --> 00:30:37.120 so as it descends through the atmosphere 00:30:37.120 --> 00:30:40.703 it's not perfectly still, it's swinging like a pendulum. 00:30:42.040 --> 00:30:46.470 The images from descent show channels on the surface 00:30:46.470 --> 00:30:48.790 and there was no doubt, there were no questions, 00:30:48.790 --> 00:30:51.400 it was obvious what we were seeing. 00:30:51.400 --> 00:30:54.620 And it was just so spectacular to see something 00:30:54.620 --> 00:30:57.190 and know what it was on the surface of Titan 00:30:57.190 --> 00:31:00.161 and for it to be river channels. 00:31:00.161 --> 00:31:03.328 (introspective music) 00:31:14.768 --> 00:31:16.240 It then landed on the surface 00:31:16.240 --> 00:31:18.350 and it started transmitting back to Cassini, 00:31:18.350 --> 00:31:20.350 which was way up overhead. 00:31:20.350 --> 00:31:23.120 The spacecraft, meanwhile, is flying over the top 00:31:23.120 --> 00:31:24.780 and pointing at the point on 00:31:24.780 --> 00:31:27.880 the surface of Titan where the probe is. 00:31:27.880 --> 00:31:30.390 And eventually the spacecraft goes over the horizon. 00:31:30.390 --> 00:31:31.440 The batteries were still going 00:31:31.440 --> 00:31:33.513 even after we lost sight of it. 00:31:34.640 --> 00:31:35.890 The spacecraft turned back 00:31:35.890 --> 00:31:38.070 and started to play the data back. 00:31:38.070 --> 00:31:40.090 Imaging guys turned around an image 00:31:40.090 --> 00:31:41.863 of the surface very, very quickly. 00:31:43.320 --> 00:31:44.330 (keyboard keys clacking) 00:31:44.330 --> 00:31:46.000 And it flickered up on the screen. 00:31:46.000 --> 00:31:47.947 And everybody looks up and goes, 00:31:47.947 --> 00:31:49.110 "What's going on here?" 00:31:49.110 --> 00:31:51.410 It was almost like it was fake. 00:31:51.410 --> 00:31:53.500 To see something like that on a moon 00:31:53.500 --> 00:31:56.620 in the outer solar system, it was just spectacular. 00:31:56.620 --> 00:31:58.230 It still gives me goosebumps to think about 00:31:58.230 --> 00:31:59.940 all of that working so well. 00:31:59.940 --> 00:32:02.270 Seeing something that no human in history 00:32:02.270 --> 00:32:05.920 had ever seen before, it was truly awe-inspiring. 00:32:05.920 --> 00:32:08.143 It was a moment I will never, ever forget. 00:32:09.270 --> 00:32:10.980 It was sitting on this flat lake bed 00:32:10.980 --> 00:32:13.970 and the things that appeared as rocks in the background 00:32:13.970 --> 00:32:17.753 were actually pebbles of ice that had been frozen. 00:32:19.690 --> 00:32:22.110 Titan is an icy satellite. 00:32:22.110 --> 00:32:25.180 Its bedrock is made of water ice. 00:32:25.180 --> 00:32:27.440 But when we look at the surface of Titan 00:32:27.440 --> 00:32:30.900 with the spectrometer, it's actually really hard 00:32:30.900 --> 00:32:34.320 to find any pure water ice spectral signatures, 00:32:34.320 --> 00:32:36.440 and I think that the key there 00:32:36.440 --> 00:32:38.260 is all these atmospheric products 00:32:38.260 --> 00:32:41.090 that are continually falling out across the surface. 00:32:41.090 --> 00:32:42.650 Titan's atmosphere is actually 00:32:42.650 --> 00:32:44.980 mostly nitrogen like Earth's atmosphere, 00:32:44.980 --> 00:32:47.290 but it's cold in the outer solar system, 00:32:47.290 --> 00:32:50.240 and the next most common constituent in the atmosphere 00:32:50.240 --> 00:32:53.220 is methane, and methane in Titan's atmosphere 00:32:53.220 --> 00:32:56.260 plays a role very much like water on Earth. 00:32:56.260 --> 00:32:58.210 So the methane in the atmosphere 00:32:58.210 --> 00:32:59.640 can condense to form clouds, 00:32:59.640 --> 00:33:01.810 it can actually rain out onto the surface, 00:33:01.810 --> 00:33:04.610 it can run across the surface in rivers, 00:33:04.610 --> 00:33:08.180 form lakes and seas, and there may even be 00:33:08.180 --> 00:33:11.570 methane aquifers in the subsurface as well. 00:33:11.570 --> 00:33:14.560 So it really does have a complete hydrological cycle 00:33:14.560 --> 00:33:17.373 where methane plays the role that water does on Earth. 00:33:18.710 --> 00:33:22.970 Carl Sagan and his research partners, Khare and Thompson, 00:33:22.970 --> 00:33:25.190 gave us a really interesting insight 00:33:25.190 --> 00:33:27.750 by doing experiments where they mixed 00:33:27.750 --> 00:33:31.120 nitrogen with methane and then provided 00:33:31.120 --> 00:33:34.697 some free energy source, some light or some particles 00:33:34.697 --> 00:33:35.530 (light booms) 00:33:35.530 --> 00:33:37.540 to break them apart or to ionize them, 00:33:37.540 --> 00:33:40.330 and it led to this incredible organic chemistry 00:33:40.330 --> 00:33:42.640 that was beyond the wildest dreams, 00:33:42.640 --> 00:33:45.440 created this stuff in the laboratory the called tholins. 00:33:46.885 --> 00:33:49.270 The methane dissociates at the top of the atmosphere, 00:33:49.270 --> 00:33:52.090 recombines to form very complex molecules, 00:33:52.090 --> 00:33:55.880 and all of that material falls out onto the surface. 00:33:55.880 --> 00:33:58.120 How long that process has been going on 00:33:58.120 --> 00:34:00.170 is still not well understood, 00:34:00.170 --> 00:34:02.630 but if Titan has had an atmosphere like it has today 00:34:02.630 --> 00:34:05.140 for the entirety of the solar system, 00:34:05.140 --> 00:34:08.920 that's going to produce a volume of sediments 00:34:08.920 --> 00:34:13.830 that means that Titan's crust is not just water ice 00:34:13.830 --> 00:34:15.840 but also has a bunch of organic sediments 00:34:15.840 --> 00:34:17.540 that have been built up over time. 00:34:18.840 --> 00:34:20.950 All of these organic materials have been 00:34:20.950 --> 00:34:24.190 sitting around littering the surface of this moon 00:34:24.190 --> 00:34:26.800 where there's the opportunity, potentially, 00:34:26.800 --> 00:34:29.460 for them to have mixed with liquid water. 00:34:29.460 --> 00:34:32.580 If you react water with these precursor molecules, 00:34:32.580 --> 00:34:34.613 what's been demonstrated is these tholins 00:34:34.613 --> 00:34:37.920 that have been studied in a lab can form amino acids. 00:34:37.920 --> 00:34:40.240 And the universe provides us that mechanism 00:34:40.240 --> 00:34:43.219 when impacts hit the surface of Titan, 00:34:43.219 --> 00:34:45.720 (object whooshes) (impact booms) 00:34:45.720 --> 00:34:48.370 because every impact has enough kinetic energy 00:34:48.370 --> 00:34:50.040 to melt some of the crust. 00:34:50.040 --> 00:34:52.540 The bigger your impacter, the more kinetic energy 00:34:52.540 --> 00:34:54.920 you impart, and so the more melt you can generate. 00:34:54.920 --> 00:34:57.240 And then based on how much melt you generate, 00:34:57.240 --> 00:35:00.860 you have this pool of liquid in the near subsurface 00:35:00.860 --> 00:35:03.330 that's going to cool slowly over time, 00:35:03.330 --> 00:35:06.000 and based on the sizes of impact craters 00:35:06.000 --> 00:35:07.140 that we've seen on Titan, 00:35:07.140 --> 00:35:08.760 this can be anywhere from hundreds 00:35:08.760 --> 00:35:10.423 to tens of thousands of years. 00:35:12.170 --> 00:35:15.220 So we know that Titan has all the ingredients 00:35:15.220 --> 00:35:17.850 necessary for life as we know it, 00:35:17.850 --> 00:35:20.020 and it's been doing these chemistry experiments 00:35:20.020 --> 00:35:22.130 for hundreds of millions of years. 00:35:22.130 --> 00:35:25.120 You also have the opportunity for organic material 00:35:25.120 --> 00:35:27.010 to mix with a different solvent 00:35:27.010 --> 00:35:28.730 in the form of liquid methane, 00:35:28.730 --> 00:35:33.460 and so perhaps there are other prebiotic systems on Titan 00:35:33.460 --> 00:35:35.810 that have progressed that are completely alien 00:35:35.810 --> 00:35:38.523 to the water-based biology we have on Earth. 00:35:39.800 --> 00:35:42.340 It's hard to conceive how a methane-based 00:35:42.340 --> 00:35:46.070 form of life would work, but nature has repeatedly 00:35:46.070 --> 00:35:48.540 surprised us as demonstrated by all the findings 00:35:48.540 --> 00:35:51.490 of the Cassini mission, so I'm not willing to rule out 00:35:51.490 --> 00:35:54.850 the possibility of life in the liquid methane lakes. 00:35:54.850 --> 00:35:58.150 I'm personally skeptical that we would find that. 00:35:58.150 --> 00:36:00.910 There are some difficulties with that. 00:36:00.910 --> 00:36:03.900 So for example long-chained carbon molecules, 00:36:03.900 --> 00:36:06.660 organic molecules, tend not to dissolve very well 00:36:06.660 --> 00:36:09.260 in liquid methane, they'll precipitate out. 00:36:09.260 --> 00:36:12.730 So you could imagine an inverted structure almost 00:36:12.730 --> 00:36:14.390 where because cells are a mixture 00:36:14.390 --> 00:36:17.430 of insoluble and soluble parts, 00:36:17.430 --> 00:36:19.650 it's possible it could work the other way around, 00:36:19.650 --> 00:36:20.890 and I find it much more difficult 00:36:20.890 --> 00:36:23.570 to conceive how that could work. 00:36:23.570 --> 00:36:25.810 Certainly it would be very exotic 00:36:25.810 --> 00:36:28.070 and at present we have no indications 00:36:28.070 --> 00:36:29.900 in any of the current measurements 00:36:29.900 --> 00:36:33.160 from the Cassini or Huygens part of the mission 00:36:33.160 --> 00:36:35.060 that there's anything bizarre 00:36:35.060 --> 00:36:38.630 that we might need to attribute to the activity of life. 00:36:38.630 --> 00:36:40.810 But the only way to find out is to go and look, 00:36:40.810 --> 00:36:44.020 and so you have with Titan this wonderful possibility 00:36:44.020 --> 00:36:45.830 that we might find life as we know it 00:36:45.830 --> 00:36:47.900 or we might find life as we don't know it. 00:36:47.900 --> 00:36:49.720 In any case, just going to look around 00:36:49.720 --> 00:36:51.630 will be a fantastic thing to do, 00:36:51.630 --> 00:36:53.973 so what's not to like, really? 00:36:56.100 --> 00:36:58.200 But as exciting as Titan was, 00:36:59.128 --> 00:37:02.203 there were even more intriguing discoveries to be made. 00:37:03.390 --> 00:37:06.300 When Cassini was approaching Saturn for the first time 00:37:06.300 --> 00:37:09.100 at the end of 2003, our experiment, 00:37:09.100 --> 00:37:11.010 the ultraviolet imagining spectrograph, 00:37:11.010 --> 00:37:12.990 was systematically scanning 00:37:12.990 --> 00:37:15.160 back and forth on the planet Saturn, 00:37:15.160 --> 00:37:17.470 and we were amazed to discover 00:37:17.470 --> 00:37:21.400 that the system was filled with molecules of oxygen, 00:37:21.400 --> 00:37:24.740 and the oxygen was completely unexpected 00:37:24.740 --> 00:37:28.210 and we mapped this out and we noticed 00:37:28.210 --> 00:37:30.260 that the peak in the distribution 00:37:30.260 --> 00:37:34.630 was just a distance four times Saturn's radius 00:37:34.630 --> 00:37:36.130 from the center of the system. 00:37:36.130 --> 00:37:38.390 We knew that the moon Enceladus 00:37:38.390 --> 00:37:40.490 was orbiting just at that distance. 00:37:40.490 --> 00:37:42.650 Enceladus is a tiny moon 00:37:42.650 --> 00:37:45.770 just 500 kilometers in diameter 00:37:45.770 --> 00:37:49.113 with a surface area slightly larger than Texas. 00:37:49.990 --> 00:37:51.840 It coexists with one of Saturn's 00:37:51.840 --> 00:37:53.963 fainter rings, the E Ring. 00:37:54.990 --> 00:37:57.180 The E Ring is just a ring 00:37:57.180 --> 00:37:59.700 of icy grains in the micron range. 00:37:59.700 --> 00:38:01.400 It was tenuous enough ring that we could 00:38:01.400 --> 00:38:03.470 fly through it and examine it. 00:38:03.470 --> 00:38:06.820 We had these tentative ideas that maybe 00:38:06.820 --> 00:38:10.650 there was a connection between the E Ring and Enceladus 00:38:10.650 --> 00:38:12.560 because they were pretty co-located, 00:38:12.560 --> 00:38:15.040 but we didn't really have any understanding 00:38:15.040 --> 00:38:17.270 of how they were playing together. 00:38:17.270 --> 00:38:19.920 Enceladus originally was on the itinerary, 00:38:19.920 --> 00:38:21.620 but only marginally so. 00:38:21.620 --> 00:38:24.170 It was another very interesting Saturn moon, 00:38:24.170 --> 00:38:26.990 small, very shiny, very white, very bright, 00:38:26.990 --> 00:38:29.673 but other than that too small to be interesting. 00:38:29.673 --> 00:38:32.423 (dramatic music) 00:38:37.670 --> 00:38:39.840 And it was in the first close flyby 00:38:39.840 --> 00:38:41.931 that the magnetometer team detected 00:38:41.931 --> 00:38:45.370 something interesting that they didn't expect. 00:38:45.370 --> 00:38:47.800 The magnetic field instrument observed 00:38:47.800 --> 00:38:50.260 that the magnetic field lines didn't quite 00:38:50.260 --> 00:38:51.930 come down to the moon the way they should. 00:38:51.930 --> 00:38:55.610 This significant deflection in the magnetic field 00:38:55.610 --> 00:38:58.440 was extremely unexpected. 00:38:58.440 --> 00:39:00.650 The magnetometer team said 00:39:00.650 --> 00:39:02.330 it looks like it has an atmosphere. 00:39:02.330 --> 00:39:05.100 Well, anybody that knows anything about moons 00:39:05.100 --> 00:39:07.020 says that's too tiny, can't have an atmosphere, 00:39:07.020 --> 00:39:09.550 it's way too small to hold onto anything. 00:39:09.550 --> 00:39:11.250 A moon as small as Enceladus 00:39:11.250 --> 00:39:13.760 has a tiny gravitational field, 00:39:13.760 --> 00:39:16.990 far too week to hold onto an atmosphere. 00:39:16.990 --> 00:39:19.860 What's more, the atmosphere that was there 00:39:19.860 --> 00:39:22.233 didn't seem to be evenly spread out. 00:39:23.197 --> 00:39:24.980 If you flew by the south pole 00:39:24.980 --> 00:39:26.500 it looked like there was an atmosphere, 00:39:26.500 --> 00:39:28.660 but if you flew by at the equator 00:39:28.660 --> 00:39:30.700 you didn't see anything at all. 00:39:30.700 --> 00:39:32.440 But then we went back again and again 00:39:32.440 --> 00:39:33.640 and explored with more instruments 00:39:33.640 --> 00:39:35.100 and then took some images, 00:39:35.100 --> 00:39:36.930 and all of the sudden realized 00:39:36.930 --> 00:39:38.577 that not only it had an atmosphere, 00:39:38.577 --> 00:39:40.270 it was an icy atmosphere, 00:39:40.270 --> 00:39:43.423 but it had these plumes coming out of the southern pole. 00:39:49.220 --> 00:39:52.962 And here's water geysers on a tiny moon. 00:39:52.962 --> 00:39:55.879 (intriguing music) 00:39:57.164 --> 00:39:59.630 And that water that was coming out of 00:39:59.630 --> 00:40:02.370 what we've later found out to be an interior ocean 00:40:02.370 --> 00:40:04.033 was what was forming the E Ring. 00:40:05.290 --> 00:40:07.260 We were able to measure the amount 00:40:07.260 --> 00:40:10.870 of water in those plumes exactly enough 00:40:10.870 --> 00:40:13.760 to explain the ring of oxygen around Saturn 00:40:13.760 --> 00:40:16.160 that we had seen before that approach. 00:40:16.160 --> 00:40:19.480 What an amazing development that the geysers 00:40:19.480 --> 00:40:22.300 on the moon Enceladus are continually erupting 00:40:22.300 --> 00:40:24.970 water molecules broken down by the sun 00:40:24.970 --> 00:40:28.560 to form atoms of oxygen that we could see 00:40:28.560 --> 00:40:32.013 even millions of miles away from the planet Saturn. 00:40:34.010 --> 00:40:36.320 And as we flew through these plumes 00:40:36.320 --> 00:40:39.220 coming out of the south pole, some of that plume material 00:40:39.220 --> 00:40:41.800 was captured by the instrument. 00:40:41.800 --> 00:40:43.050 And we used that to learn more 00:40:43.050 --> 00:40:45.690 about the interior ocean chemistry. 00:40:45.690 --> 00:40:48.020 Not only did it contain water vapor, 00:40:48.020 --> 00:40:52.920 but it had traces of ammonia, methane, H2, CO2, 00:40:52.920 --> 00:40:54.800 and then there was a whole host 00:40:54.800 --> 00:40:57.813 of organic compounds that we could also see. 00:40:58.680 --> 00:41:01.910 The experiment that we did here at Colorado 00:41:01.910 --> 00:41:03.720 is very similar to that. 00:41:03.720 --> 00:41:06.010 We didn't actually fly through the plume 00:41:06.010 --> 00:41:09.200 but we watched a star set through the plume. 00:41:09.200 --> 00:41:11.600 And now we can put all that information together 00:41:11.600 --> 00:41:14.380 to get a picture of the shape of the eruption 00:41:14.380 --> 00:41:15.900 and also the material that's being 00:41:15.900 --> 00:41:18.610 erupted from inside of Enceladus, 00:41:18.610 --> 00:41:21.350 and amazingly enough that material 00:41:21.350 --> 00:41:24.383 has the basic building blocks of life. 00:41:26.090 --> 00:41:28.570 We've been dominated as biologists 00:41:28.570 --> 00:41:31.480 with a fixation on the idea that all life on Earth 00:41:31.480 --> 00:41:33.360 is powered ultimately by the sun. 00:41:33.360 --> 00:41:36.620 Any formation of life going on on Enceladus 00:41:36.620 --> 00:41:38.740 is going to be happening beneath the icy crust 00:41:38.740 --> 00:41:40.460 and the oceans underneath where we see 00:41:40.460 --> 00:41:43.710 the same kind of hydrothermal vent systems 00:41:43.710 --> 00:41:46.350 releasing hydrogen gas into the oceans there, 00:41:46.350 --> 00:41:47.970 which we know for a fact would've 00:41:47.970 --> 00:41:50.070 been present on the early Earth, 00:41:50.070 --> 00:41:52.413 and they don't strictly require the sun. 00:41:53.400 --> 00:41:56.130 We think based on the types of molecules 00:41:56.130 --> 00:41:58.720 and other chemicals we're finding in the plume 00:41:58.720 --> 00:42:01.670 that this process called serpentinization is happening. 00:42:01.670 --> 00:42:04.620 Serpentinization is a geological process. 00:42:04.620 --> 00:42:06.680 It's a fancy way of saying how 00:42:06.680 --> 00:42:09.590 liquid water can react with rocks, 00:42:09.590 --> 00:42:11.340 and serpentinization is thought to be 00:42:11.340 --> 00:42:14.710 really important for supporting microorganisms 00:42:14.710 --> 00:42:17.620 and the base of an ecosystem outside of these 00:42:17.620 --> 00:42:21.270 hydrothermal vents because it makes abundant hydrogen, 00:42:21.270 --> 00:42:23.670 and hydrogen is sort of like rocket fuel 00:42:23.670 --> 00:42:26.380 for a microorganism, it's a great way 00:42:26.380 --> 00:42:30.473 to have a food that can be burned to provide energy. 00:42:31.550 --> 00:42:36.150 To me, Titan is less exciting than Enceladus 00:42:36.150 --> 00:42:39.240 because Enceladus has oceans 00:42:39.240 --> 00:42:43.290 with alkaline fluids from hydrothermal vents going into it, 00:42:43.290 --> 00:42:45.030 and therefore it's exactly analogous 00:42:45.030 --> 00:42:48.423 to how I think life started on Earth. 00:42:51.560 --> 00:42:54.650 This says to me that would be a good place to go, 00:42:54.650 --> 00:42:57.010 measure those plumes, maybe drill down 00:42:57.010 --> 00:42:59.443 and see if there's any form of life there. 00:43:00.700 --> 00:43:02.060 So Enceladus may have 00:43:02.060 --> 00:43:04.220 just the right conditions for life 00:43:04.220 --> 00:43:07.850 to get started far away from the sun, 00:43:07.850 --> 00:43:10.870 and the evidence for its mysterious inner workings 00:43:10.870 --> 00:43:14.183 can be seen in the enormous, diffuse E Ring. 00:43:16.200 --> 00:43:20.390 This is just another case of how the moons make rings, 00:43:20.390 --> 00:43:22.580 so by grinding of their surface, 00:43:22.580 --> 00:43:25.110 which throws dust into orbit around the planet, 00:43:25.110 --> 00:43:29.670 by erupting of geysers, or by shattering them to bits, 00:43:29.670 --> 00:43:33.290 the moons are the parents of the rings that we see, 00:43:33.290 --> 00:43:37.330 but also the children because the rings in some cases 00:43:37.330 --> 00:43:40.453 can collect up to form new moons. 00:43:43.529 --> 00:43:45.630 (whimsical music) 00:43:45.630 --> 00:43:46.660 Cassini would spend 00:43:46.660 --> 00:43:49.740 more than 13 years at the Saturnian system 00:43:49.740 --> 00:43:53.720 and completely 294 orbits of the planet, 00:43:53.720 --> 00:43:56.403 but eventually its fuel would run out. 00:43:58.340 --> 00:44:01.450 Everything has to end, including Cassini. 00:44:01.450 --> 00:44:02.850 (melancholic music) 00:44:02.850 --> 00:44:04.840 We went through this amazing time 00:44:04.840 --> 00:44:05.990 at the end of the mission, 00:44:05.990 --> 00:44:09.420 ending up with orbits which went inside Saturn's rings, 00:44:09.420 --> 00:44:10.900 but we knew at the end, of course, 00:44:10.900 --> 00:44:12.940 that the idea was to actually 00:44:12.940 --> 00:44:16.320 burn the spacecraft up in the atmosphere of Saturn, 00:44:16.320 --> 00:44:18.110 and that's to avoid it hitting these 00:44:18.110 --> 00:44:22.320 astrobiologically feasible places like Enceladus and Titan. 00:44:22.320 --> 00:44:23.630 The last thing we would want to do 00:44:23.630 --> 00:44:26.773 would be contaminate those with something sent from Earth. 00:44:32.800 --> 00:44:34.920 You can go where you've never been before. 00:44:34.920 --> 00:44:36.890 You can get science you will never have 00:44:36.890 --> 00:44:38.440 any other opportunity of getting, 00:44:38.440 --> 00:44:39.990 and you'll keep Enceladus safe. 00:44:41.320 --> 00:44:43.882 No brainer. (laughs) 00:44:43.882 --> 00:44:45.893 But the emotions were all over the map. 00:44:49.520 --> 00:44:52.523 All good things must come to an end, (laughs) right? 00:44:53.428 --> 00:44:55.653 Yes, it's sad in a way, but. 00:44:58.280 --> 00:45:00.620 The spacecraft was oriented so it could 00:45:00.620 --> 00:45:03.450 communicate with the deep space network here on Earth, 00:45:03.450 --> 00:45:06.420 but then the other axis was set 00:45:06.420 --> 00:45:08.830 so that the spacecraft could get the best measurements 00:45:08.830 --> 00:45:13.323 of Saturn's atmosphere as we plunged into it. 00:45:26.530 --> 00:45:31.447 We have loss of signal in X-ray band and CR-band. 00:45:35.127 --> 00:45:39.088 Total loss of signal at 11:55:46 00:45:39.088 --> 00:45:44.088 for the S-band, so that would be the end of the spacecraft. 00:45:44.720 --> 00:45:46.760 I don't think any of us were ready. 00:45:46.760 --> 00:45:49.020 If you ever had pets, and I've gone through 00:45:49.020 --> 00:45:50.960 eight cats and two dogs during 00:45:50.960 --> 00:45:53.000 the 23 years I worked on Cassini, 00:45:53.000 --> 00:45:55.990 and when you know it's time, it's time, 00:45:55.990 --> 00:45:58.730 and it was time to end the spacecraft. 00:45:58.730 --> 00:46:00.330 Now I, don't get me wrong, 00:46:00.330 --> 00:46:02.780 I'm very sentimental about it, but it wasn't a pet, 00:46:02.780 --> 00:46:05.870 it was just an amazing instrument, a robot, 00:46:05.870 --> 00:46:08.920 that did some incredible things at our behest. 00:46:08.920 --> 00:46:10.970 Signal from the spacecraft is gone 00:46:10.970 --> 00:46:14.903 and within the next 45 seconds, so will be the spacecraft. 00:46:16.520 --> 00:46:20.540 I hope you're all as deeply proud 00:46:20.540 --> 00:46:22.710 of this amazing accomplishment. 00:46:22.710 --> 00:46:24.570 Congratulations to you all. 00:46:24.570 --> 00:46:26.400 This has been an incredible mission, 00:46:26.400 --> 00:46:28.320 an incredible spacecraft, 00:46:28.320 --> 00:46:30.573 and you're all an incredible team. 00:46:31.530 --> 00:46:33.480 I'm gonna call this the end of mission. 00:46:34.470 --> 00:46:36.093 Project manager off the net. 00:46:36.927 --> 00:46:39.927 (people applauding) 00:46:45.350 --> 00:46:47.180 Cassini was only made possible 00:46:47.180 --> 00:46:51.360 by the hard work of hundreds of scientists and engineers 00:46:51.360 --> 00:46:53.960 from even before I was born, 00:46:53.960 --> 00:46:57.220 so to be able to be there with them 00:46:57.220 --> 00:47:01.130 for the end of the mission was supremely humbling 00:47:01.130 --> 00:47:04.220 because of the gift that they gave us. 00:47:04.220 --> 00:47:07.259 And I cried like a baby (laughs) the whole time. 00:47:07.259 --> 00:47:09.220 (inquisitive music) 00:47:09.220 --> 00:47:11.820 I've always loved the rings of Saturn. 00:47:11.820 --> 00:47:14.520 The Cassini exploration has allowed us 00:47:14.520 --> 00:47:18.923 to see them really close up, changing before our eyes. 00:47:20.030 --> 00:47:23.490 The idea of oceans beneath the ice 00:47:23.490 --> 00:47:28.090 that might support life is far from the old paradigm. 00:47:28.090 --> 00:47:31.070 It opens up a whole new idea of how life 00:47:31.070 --> 00:47:33.993 might form in solar systems in the cosmos. 00:47:35.200 --> 00:47:36.447 If you were to say to me, 00:47:36.447 --> 00:47:38.380 "Where would I most want to send a rocket?" 00:47:38.380 --> 00:47:40.170 it would be to Enceladus and it would be to look at 00:47:40.170 --> 00:47:43.350 the plumes and alkaline hydrothermal vents under the surface 00:47:43.350 --> 00:47:45.510 because to me, that's the environment 00:47:45.510 --> 00:47:48.570 that's most likely to drive the origin of life. 00:47:48.570 --> 00:47:50.700 Finding life on Enceladus 00:47:50.700 --> 00:47:52.460 or underneath the surface of Titan 00:47:52.460 --> 00:47:55.330 would drastically change our view of the universe 00:47:55.330 --> 00:47:58.670 and our place in it, and it's a future test 00:47:58.670 --> 00:48:01.060 to search out and find out if those ingredients 00:48:01.060 --> 00:48:04.873 have led to the evolution of life on those celestial bodies. 00:48:06.436 --> 00:48:08.580 In the summer of 2019, 00:48:08.580 --> 00:48:11.077 NASA announced that it had approved a mission 00:48:11.077 --> 00:48:15.663 called Dragonfly that would return to the surface of Titan. 00:48:16.670 --> 00:48:19.640 Dragonfly is a mission that's going to Titan 00:48:19.640 --> 00:48:21.963 to study its prebiotic chemistry. 00:48:23.800 --> 00:48:25.880 It's an octocopter. 00:48:25.880 --> 00:48:30.780 By being a mobile lander, Dragonfly is going to allow us 00:48:30.780 --> 00:48:34.053 to truly discover what the surface of Titan is like. 00:48:36.250 --> 00:48:38.440 And it would spend most of its time on the surface 00:48:38.440 --> 00:48:39.760 making scientific measurements, 00:48:39.760 --> 00:48:41.830 but then we'd be able to fly from place to place 00:48:41.830 --> 00:48:43.350 so that we could measure the chemistry 00:48:43.350 --> 00:48:45.893 in different environments. 00:48:46.920 --> 00:48:51.920 Dragonfly's main goal is to taste the surface of Titan 00:48:52.150 --> 00:48:54.410 and tell us what the end product 00:48:54.410 --> 00:48:58.793 of all of this fantastic chemistry that Cassini revealed is. 00:49:00.150 --> 00:49:02.130 And really understand how far 00:49:02.130 --> 00:49:04.880 prebiotic chemistry can progress in an environment we know 00:49:04.880 --> 00:49:06.730 has all the key ingredients for life. 00:49:07.720 --> 00:49:08.960 Dragonfly is scheduled 00:49:08.960 --> 00:49:12.810 to leave Earth for the Saturn system in 2026 00:49:12.810 --> 00:49:16.470 and should arrive at Titan in 2034, 00:49:16.470 --> 00:49:19.700 55 years after Pioneer 11 00:49:19.700 --> 00:49:22.173 gave us our first encounter with Saturn. 00:49:27.248 --> 00:49:30.165 (intriguing music)