1 00:00:03,371 --> 00:00:07,406 For 13 years, the cassini spacecraft explored 2 00:00:07,408 --> 00:00:12,845 astounding worlds -- saturn and its moons. 3 00:00:12,847 --> 00:00:16,548 We discovered things we never imagined. 4 00:00:16,550 --> 00:00:19,651 All of these strange, bizarre landscapes -- 5 00:00:19,653 --> 00:00:22,721 geysers erupting out of moons. 6 00:00:22,723 --> 00:00:25,824 We were so stunned by the images. 7 00:00:25,826 --> 00:00:28,827 I mean, people were just going around in shock. 8 00:00:36,303 --> 00:00:40,672 But cassini started running out of fuel. 9 00:00:40,674 --> 00:00:44,543 Scientists at nasa had to decide what to do next, 10 00:00:44,545 --> 00:00:48,280 and the answer was actually pretty spectacular. 11 00:00:48,282 --> 00:00:53,552 Cassini goes where no spacecraft has gone before -- 12 00:00:53,554 --> 00:01:00,726 a death flight revealing the deepest secrets of saturn. 13 00:01:19,613 --> 00:01:23,582 out beyond jupiter lies saturn, 14 00:01:23,584 --> 00:01:27,519 a planet circled by multiple moons and rings. 15 00:01:27,521 --> 00:01:31,757 It's like a miniature solar system. 16 00:01:31,759 --> 00:01:34,560 Imagine having a mission with the power, the instruments, 17 00:01:34,562 --> 00:01:38,964 the capability to explore all aspects of the saturn system. 18 00:01:38,966 --> 00:01:42,167 That mission was cassini. 19 00:01:50,077 --> 00:01:52,311 it would become our eyes and ears 20 00:01:52,313 --> 00:01:56,515 in the saturnian system for over 13 years. 21 00:01:59,386 --> 00:02:05,757 but by September 2017, cassini was almost out of fuel. 22 00:02:05,759 --> 00:02:07,693 Cassini has been orbiting saturn 23 00:02:07,695 --> 00:02:11,330 and studying the saturn system for over a decade. 24 00:02:11,332 --> 00:02:13,799 End the mission -- we're going to lose control soon, 25 00:02:13,801 --> 00:02:16,568 so rather than let it just go derelict, 26 00:02:16,570 --> 00:02:18,637 we headed into saturn. 27 00:02:18,639 --> 00:02:21,373 Go out with a bang. 28 00:02:21,375 --> 00:02:24,676 The cassini team goes for broke. 29 00:02:24,678 --> 00:02:30,082 They program the probe to head straight for the planet. 30 00:02:30,084 --> 00:02:32,451 How cool is it to sort of sacrifice 31 00:02:32,453 --> 00:02:33,952 everything you've got to sort of learn 32 00:02:33,954 --> 00:02:37,556 your last bit of information, and then crash and burn? 33 00:02:37,558 --> 00:02:41,527 Man: We are in the atmosphere. 34 00:02:41,529 --> 00:02:43,862 As cassini was careening toward its death, 35 00:02:43,864 --> 00:02:46,331 it still had instruments that continued to work, 36 00:02:46,333 --> 00:02:48,133 and as each instrument died, 37 00:02:48,135 --> 00:02:52,104 there was still a set sending back data and information. 38 00:02:52,106 --> 00:02:54,273 Cassini wasn't designed to plunge 39 00:02:54,275 --> 00:02:56,375 through saturn's atmosphere. 40 00:02:56,377 --> 00:03:01,046 No one knew how long it would last before burning up. 41 00:03:08,923 --> 00:03:10,656 spilker: I remember sitting in a room 42 00:03:10,658 --> 00:03:12,758 with my colleagues on cassini 43 00:03:12,760 --> 00:03:14,626 and watching that radio signal, 44 00:03:14,628 --> 00:03:18,063 that sharp green peak that told us cassini 45 00:03:18,065 --> 00:03:20,599 was still linked to the earth. 46 00:03:20,601 --> 00:03:23,468 We could monitor the atmosphere as we flew into it, 47 00:03:23,470 --> 00:03:26,805 and right up until the last, it was sending back science. 48 00:03:26,807 --> 00:03:30,042 I was really impressed by how long cassini lasted 49 00:03:30,044 --> 00:03:32,244 in the saturn atmosphere. 50 00:03:32,246 --> 00:03:35,347 I mean, go nasa engineering. 51 00:03:35,349 --> 00:03:37,549 As cassini plummeted down 52 00:03:37,551 --> 00:03:40,819 at 77,000 miles an hour, 53 00:03:40,821 --> 00:03:43,355 it was bombarded by gas molecules 54 00:03:43,357 --> 00:03:45,023 in saturn's atmosphere. 55 00:03:49,430 --> 00:03:52,631 friction started tearing cassini apart 56 00:03:52,633 --> 00:03:55,634 as it struggled to maintain contact. 57 00:04:00,241 --> 00:04:02,474 spilker: As the antenna turned away, 58 00:04:02,476 --> 00:04:04,376 we actually saw a secondary little peak, 59 00:04:04,378 --> 00:04:07,679 and we thought, "okay, cassini. Hang in there. Keep fighting." 60 00:04:07,681 --> 00:04:12,651 and then just that green flatline. 61 00:04:12,653 --> 00:04:16,455 Just heard the signal from the spacecraft is gone, 62 00:04:16,457 --> 00:04:20,392 and in the next 45 seconds, so will be the spacecraft. 63 00:04:20,394 --> 00:04:23,228 Cassini's heartbeat was gone, 64 00:04:23,230 --> 00:04:27,232 and we knew the mission had ended. 65 00:04:27,234 --> 00:04:30,535 It just vaporized in the saturnian atmosphere, 66 00:04:30,537 --> 00:04:34,740 and so it has become a part of saturn itself. 67 00:04:45,586 --> 00:04:47,653 Cassini's death plunge 68 00:04:47,655 --> 00:04:51,890 was the last of a series of daring dives. 69 00:04:51,892 --> 00:04:53,558 Prior to ending cassini's mission 70 00:04:53,560 --> 00:04:55,927 by sending it into saturn's atmosphere, 71 00:04:55,929 --> 00:04:58,497 nasa's engineers and scientists came up with an idea -- 72 00:04:58,499 --> 00:05:01,400 "let's do dives into the region 73 00:05:01,402 --> 00:05:04,002 between the tops of saturn's clouds 74 00:05:04,004 --> 00:05:08,640 and the innermost area of saturn's rings. 75 00:05:08,642 --> 00:05:11,910 Beginning in April of 2017, 76 00:05:11,912 --> 00:05:17,549 cassini ventured between saturn and its rings 22 times. 77 00:05:17,551 --> 00:05:20,652 Scientists called it the grand finale. 78 00:05:22,956 --> 00:05:26,625 On these dives, cassini got closest to saturn's cloud tops 79 00:05:26,627 --> 00:05:29,428 than any spacecraft ever had before. 80 00:05:32,132 --> 00:05:36,635 Saturn is an enormous ball of hydrogen and helium, 81 00:05:36,637 --> 00:05:39,538 a gas giant. 82 00:05:39,540 --> 00:05:42,574 Fundamentally, it's a really very different kind of planet 83 00:05:42,576 --> 00:05:45,410 than we're used to in our everyday lives. 84 00:05:45,412 --> 00:05:50,349 Cassini snaps close-ups of the planet's gaseous surface. 85 00:05:50,351 --> 00:05:54,786 The pictures reveal a turbulent and stormy world. 86 00:05:54,788 --> 00:05:57,756 Durda: We think of some storms on earth as being particularly violent. 87 00:05:57,758 --> 00:05:58,890 If you've ever been in a hurricane, 88 00:05:58,892 --> 00:06:00,759 it's not a fun place to be, 89 00:06:00,761 --> 00:06:03,362 but the storms on saturn, the wind patterns on saturn, 90 00:06:03,364 --> 00:06:07,699 can make that look like a mere breeze in comparison. 91 00:06:07,701 --> 00:06:11,470 On saturn, one storms stands out. 92 00:06:11,472 --> 00:06:15,607 It's location is marked by a distinct shape. 93 00:06:15,609 --> 00:06:17,843 One of the really weird things is that 94 00:06:17,845 --> 00:06:20,078 whereas the bands go around saturn, 95 00:06:20,080 --> 00:06:22,647 they're all circular until you get to the pole, 96 00:06:22,649 --> 00:06:26,118 and then there's a hexagonal band up there. 97 00:06:26,120 --> 00:06:28,820 No one expected that. 98 00:06:28,822 --> 00:06:30,555 During its lifetime, 99 00:06:30,557 --> 00:06:35,060 cassini took multiple images of the hexagon. 100 00:06:35,062 --> 00:06:38,196 Whenever we posted an image of the hexagon, 101 00:06:38,198 --> 00:06:41,133 the hits to the website went through the roof. 102 00:06:41,135 --> 00:06:44,336 I think people thought it was so mysterious. 103 00:06:44,338 --> 00:06:46,438 When I first saw this, I was blown away. 104 00:06:46,440 --> 00:06:49,141 I mean, who could imagine having something this regular, 105 00:06:49,143 --> 00:06:51,743 almost geometric, on the atmosphere of a planet? 106 00:06:51,745 --> 00:06:54,312 It's really just phenomenal. 107 00:06:54,314 --> 00:07:00,285 In 2018, cassini data reveals this hexagonal storm 108 00:07:00,287 --> 00:07:05,190 could be a towering structure hundreds of miles in height. 109 00:07:05,192 --> 00:07:06,825 Plait: It's this gigantic structure. 110 00:07:06,827 --> 00:07:09,094 It's many thousands of miles across, 111 00:07:09,096 --> 00:07:11,096 and right in the center, right at the pole, 112 00:07:11,098 --> 00:07:12,931 is this sort of permanent vortex, 113 00:07:12,933 --> 00:07:14,299 a permanent hurricane. 114 00:07:14,301 --> 00:07:16,701 So, it's kind of a creepy eye-like thing 115 00:07:16,703 --> 00:07:18,603 staring back at us. 116 00:07:18,605 --> 00:07:23,809 Each side of the hexagon is as wide as the earth. 117 00:07:23,811 --> 00:07:25,811 It seems artificial. 118 00:07:25,813 --> 00:07:28,747 How do you get a hexagon-shaped storm 119 00:07:28,749 --> 00:07:31,316 or cloud structure on saturn? 120 00:07:37,024 --> 00:07:40,158 Scientists think that saturn's spin 121 00:07:40,160 --> 00:07:45,564 interacts with air currents to create this symmetrical shape. 122 00:07:45,566 --> 00:07:50,035 But they don't know why it's lasted for decades. 123 00:07:50,037 --> 00:07:51,536 That's the puzzle. 124 00:07:51,538 --> 00:07:53,305 How can you get a six-sided jet stream 125 00:07:53,307 --> 00:07:57,476 that's stable for so long? 126 00:07:57,478 --> 00:08:01,480 But while the hexagon shape is stable, 127 00:08:01,482 --> 00:08:04,549 the color has altered. 128 00:08:04,551 --> 00:08:10,922 Over four years, it changed from mostly blue to golden brown. 129 00:08:10,924 --> 00:08:15,293 The transformation is linked to saturn's seasons. 130 00:08:18,632 --> 00:08:21,933 plait: The seasons on saturn are caused by the same thing on earth. 131 00:08:21,935 --> 00:08:23,902 It's the tilt of the planet, 132 00:08:23,904 --> 00:08:25,904 and so as saturn is going around the sun 133 00:08:25,906 --> 00:08:28,940 and it's north pole is tipping toward the sun, 134 00:08:28,942 --> 00:08:31,443 you start to get more light up there. 135 00:08:31,445 --> 00:08:34,880 This sunlight interacts with the atmosphere, 136 00:08:34,882 --> 00:08:39,451 producing suspended particles called aerosols. 137 00:08:39,453 --> 00:08:41,620 It actually looks a lot like smog. 138 00:08:41,622 --> 00:08:43,321 It turns things more orange, 139 00:08:43,323 --> 00:08:47,826 so over time the hexagon went from blue to orange. 140 00:08:47,828 --> 00:08:49,794 The color change happened 141 00:08:49,796 --> 00:08:53,498 during one of saturn's northern hemisphere summers, 142 00:08:53,500 --> 00:08:56,902 but mysteriously, the very center of the hexagon 143 00:08:56,904 --> 00:08:59,304 remained blue. 144 00:08:59,306 --> 00:09:01,273 Now, this could have been for two reasons. 145 00:09:01,275 --> 00:09:03,141 Maybe the haze never formed in the eye 146 00:09:03,143 --> 00:09:05,310 because the eye was shielded from the sun, 147 00:09:05,312 --> 00:09:08,113 and the sun is responsible for creating the brownish haze 148 00:09:08,115 --> 00:09:10,148 that we see on saturn. 149 00:09:10,150 --> 00:09:13,184 Another reason is maybe the actual vortex 150 00:09:13,186 --> 00:09:14,953 is sucking the haze down. 151 00:09:14,955 --> 00:09:17,122 Maybe there's something like the eye of a hurricane. 152 00:09:17,124 --> 00:09:18,557 There's haze that forms over it, 153 00:09:18,559 --> 00:09:20,525 but it gets sucked down into the eye. 154 00:09:26,833 --> 00:09:28,967 But the storms on saturn 155 00:09:28,969 --> 00:09:33,004 aren't the only extraordinary thing about the weather. 156 00:09:33,006 --> 00:09:38,443 When cassini dives through the rings, it discovers rain, 157 00:09:38,445 --> 00:09:43,515 rain falling onto the planet from space. 158 00:10:00,801 --> 00:10:07,038 April 2017, cassini embarked on its grand finale, 159 00:10:07,040 --> 00:10:10,742 following a daring new path. 160 00:10:10,744 --> 00:10:14,980 We decided to dive in between the rings of the planet, 161 00:10:14,982 --> 00:10:19,084 to go to a place no spacecraft had ever flown before 162 00:10:19,086 --> 00:10:21,453 and make a unique set of measurements. 163 00:10:21,455 --> 00:10:25,557 It was uncharted territory. 164 00:10:25,559 --> 00:10:27,993 Oluseyi: They didn't know exactly what they were going to find. 165 00:10:27,995 --> 00:10:30,061 There could be stuff there that could have destroyed 166 00:10:30,063 --> 00:10:32,897 the cassini spacecraft. 167 00:10:32,899 --> 00:10:35,600 Instead, cassini encountered 168 00:10:35,602 --> 00:10:41,139 something totally unexpected -- rain. 169 00:10:49,349 --> 00:10:51,683 plait: On earth it rains quite a bit. 170 00:10:51,685 --> 00:10:53,351 We're getting that rain from rain clouds 171 00:10:53,353 --> 00:10:55,887 which are basically just a few miles up. 172 00:10:55,889 --> 00:10:59,157 On saturn it also rains, but it turns out it's raining 173 00:10:59,159 --> 00:11:01,926 onto the top of the upper atmosphere, 174 00:11:01,928 --> 00:11:05,897 and that rain is coming from space. 175 00:11:05,899 --> 00:11:10,635 In 2018, cassini data revealed the colossal weight 176 00:11:10,637 --> 00:11:13,805 of the downpour. 177 00:11:13,807 --> 00:11:16,608 Icy-grained rain hits saturn 178 00:11:16,610 --> 00:11:19,077 at a rate of several tons per second. 179 00:11:22,516 --> 00:11:24,649 It's completely unlike anything we've ever seen. 180 00:11:24,651 --> 00:11:26,785 Suddenly we've discovered rain at saturn, 181 00:11:26,787 --> 00:11:28,653 but there aren't any rain clouds. 182 00:11:28,655 --> 00:11:30,422 Where was it coming from? 183 00:11:35,729 --> 00:11:38,863 The answer is saturn's rings. 184 00:11:41,101 --> 00:11:42,834 thaller: The first thing you think of 185 00:11:42,836 --> 00:11:44,536 when you hear the word saturn is the rings. 186 00:11:44,538 --> 00:11:46,504 They're the most dramatic and unique aspect 187 00:11:46,506 --> 00:11:48,173 of that planet. 188 00:11:50,677 --> 00:11:54,879 from afar, saturn's rings look like this one whole structure, 189 00:11:54,881 --> 00:11:58,516 but when you look up close it's actually a bunch of ice crystals 190 00:11:58,518 --> 00:12:02,954 and ice rocks that make saturn's rings. 191 00:12:02,956 --> 00:12:07,225 The size of the ring material ranges from dust grains 192 00:12:07,227 --> 00:12:09,894 to boulders to houses. 193 00:12:16,503 --> 00:12:20,438 saturn's rings are well above the atmosphere of saturn. 194 00:12:20,440 --> 00:12:22,273 They're way out in space. 195 00:12:22,275 --> 00:12:25,110 And under normal circumstances those particles of ice 196 00:12:25,112 --> 00:12:28,546 making up the rings would just orbit saturn forever, 197 00:12:28,548 --> 00:12:30,815 but things are a little bit weird. 198 00:12:33,920 --> 00:12:38,022 Something is making these orbiting ice particles 199 00:12:38,024 --> 00:12:41,726 fall inward as a kind of cosmic hail. 200 00:12:44,397 --> 00:12:47,265 Material is dripping inwards from the rings 201 00:12:47,267 --> 00:12:50,568 and falling into the clouds of saturn. 202 00:12:50,570 --> 00:12:52,737 It's like a rain with no rain cloud. 203 00:12:52,739 --> 00:12:56,307 A cosmic rain trickling in and falling down. 204 00:12:58,411 --> 00:13:00,678 Cassini discovers the rain 205 00:13:00,680 --> 00:13:04,115 is a mix of different kinds of ice particles, 206 00:13:04,117 --> 00:13:08,953 but doesn't reveal why they actually rain down. 207 00:13:08,955 --> 00:13:13,024 Then the researchers realized the ice grains 208 00:13:13,026 --> 00:13:15,627 were statically charged. 209 00:13:15,629 --> 00:13:17,529 Ultraviolet light from the sun, for example, 210 00:13:17,531 --> 00:13:19,230 can blow off an electron, 211 00:13:19,232 --> 00:13:21,833 and that gives these particles a charge, 212 00:13:21,835 --> 00:13:23,768 just like rubbing a balloon on your hair 213 00:13:23,770 --> 00:13:26,437 makes it stick to a wall because of the static charge. 214 00:13:29,075 --> 00:13:32,110 Well, if you have particles that are like that, 215 00:13:32,112 --> 00:13:34,479 they can be affected by magnetism, 216 00:13:34,481 --> 00:13:38,316 and saturn has a very strong magnetic field. 217 00:13:38,318 --> 00:13:40,785 Earth's magnetic field springs 218 00:13:40,787 --> 00:13:44,722 from it's spinning, molten-iron core. 219 00:13:44,724 --> 00:13:48,259 Although saturn probably has a rocky center, 220 00:13:48,261 --> 00:13:52,697 it's mostly a giant ball of hydrogen and helium, 221 00:13:52,699 --> 00:13:55,700 but deep in its interior, scientists think something 222 00:13:55,702 --> 00:13:59,904 much more exotic is going on. 223 00:13:59,906 --> 00:14:01,573 We don't have enough data 224 00:14:01,575 --> 00:14:04,409 to know exactly what's going on in saturn's interior, 225 00:14:04,411 --> 00:14:06,344 but we do know the broad strokes. 226 00:14:06,346 --> 00:14:08,813 Within saturn's interior, 227 00:14:08,815 --> 00:14:12,450 extreme pressures and temperatures force hydrogen 228 00:14:12,452 --> 00:14:14,819 to stop acting like a gas, 229 00:14:14,821 --> 00:14:19,424 turning it into spinning liquid-metallic hydrogen. 230 00:14:19,426 --> 00:14:21,292 You've got this band of electrons 231 00:14:21,294 --> 00:14:23,528 that can just wander freely through that fluid, 232 00:14:23,530 --> 00:14:27,432 so in that way, liquid hydrogen under extreme pressure 233 00:14:27,434 --> 00:14:30,201 can act like a metal. 234 00:14:30,203 --> 00:14:32,971 The magnetic field generated 235 00:14:32,973 --> 00:14:36,241 by the spinning metallic-hydrogen outer core 236 00:14:36,243 --> 00:14:39,777 pulls the ice particles from the rings. 237 00:14:39,779 --> 00:14:41,613 Plait: These charged ice particles 238 00:14:41,615 --> 00:14:44,182 are then drawn in by saturn's field. 239 00:14:44,184 --> 00:14:46,084 They follow the magnetic field lines 240 00:14:46,086 --> 00:14:51,723 and rain down onto the atmosphere of saturn. 241 00:14:51,725 --> 00:14:55,126 Cassini had revealed several tons of material 242 00:14:55,128 --> 00:14:57,862 is raining down on saturn every second, 243 00:14:57,864 --> 00:15:01,065 but how much stuff is actually in the rings? 244 00:15:01,067 --> 00:15:05,470 Again, cassini provides the answer. 245 00:15:05,472 --> 00:15:07,005 Thaller: In the final days of cassini, 246 00:15:07,007 --> 00:15:10,408 we actually flew in between the planet saturn and the rings, 247 00:15:10,410 --> 00:15:13,011 and the gravity data was able to separate out 248 00:15:13,013 --> 00:15:15,013 how much mass is coming from the planet 249 00:15:15,015 --> 00:15:17,215 and how much is coming from the rings, 250 00:15:17,217 --> 00:15:18,449 and the surprise was the rings 251 00:15:18,451 --> 00:15:20,518 are actually not very massive at all. 252 00:15:22,856 --> 00:15:24,989 Even though they cover an area 253 00:15:24,991 --> 00:15:27,792 as big as the moon's orbit around earth, 254 00:15:27,794 --> 00:15:31,396 saturn's rings are 100,000 times less massive 255 00:15:31,398 --> 00:15:34,065 than our own small planet. 256 00:15:36,503 --> 00:15:38,603 They're lighter than we thought. 257 00:15:38,605 --> 00:15:41,639 There's not as much material there. 258 00:15:41,641 --> 00:15:47,679 The mass of the rings is a valuable clue about their age. 259 00:15:47,681 --> 00:15:50,048 A more massive ring can hold itself together 260 00:15:50,050 --> 00:15:52,917 for much longer than a less massive ring, 261 00:15:52,919 --> 00:15:56,387 so if there's not a lot of stuff there, it must be younger. 262 00:15:59,192 --> 00:16:03,227 So, how long have saturn's rings been in place, 263 00:16:03,229 --> 00:16:06,264 and what is keeping them there? 264 00:16:06,266 --> 00:16:08,967 It's something that I don't even think I could have imagined 265 00:16:08,969 --> 00:16:10,635 if I tried. 266 00:16:30,023 --> 00:16:32,457 As cassini orbited saturn, 267 00:16:32,459 --> 00:16:36,427 it revealed incredible insights into the planet's rings. 268 00:16:43,803 --> 00:16:46,504 the photos that came from cassini of the rings 269 00:16:46,506 --> 00:16:50,241 are unlike anything that I could ever imagine. 270 00:16:50,243 --> 00:16:53,478 If I was alien visiting our solar system, 271 00:16:53,480 --> 00:16:55,613 I don't know what would stand out to me more, 272 00:16:55,615 --> 00:17:00,451 the blue marble or saturn and its amazing rings. 273 00:17:00,453 --> 00:17:03,021 One of the biggest questions about the rings 274 00:17:03,023 --> 00:17:04,956 is how old are they. 275 00:17:04,958 --> 00:17:06,724 Could something like that really have existed 276 00:17:06,726 --> 00:17:08,393 from the beginning of the solar system, 277 00:17:08,395 --> 00:17:12,430 or is it relatively recent? 278 00:17:12,432 --> 00:17:16,634 Cassini provided an answer. 279 00:17:16,636 --> 00:17:19,871 The rings could be as young as only 100 million years old. 280 00:17:19,873 --> 00:17:22,507 A couple of clues -- the low mass and the fact 281 00:17:22,509 --> 00:17:23,841 that they're so bright and icy 282 00:17:23,843 --> 00:17:25,977 that it hasn't had time to get polluted 283 00:17:25,979 --> 00:17:28,980 from all the micrometeoroids and darkened 284 00:17:28,982 --> 00:17:32,984 over a long time like the age of the solar system. 285 00:17:32,986 --> 00:17:34,852 Thaller: So, the amazing thing is 286 00:17:34,854 --> 00:17:36,120 that, you know, if you were on earth 287 00:17:36,122 --> 00:17:37,722 about the time of the dinosaurs, 288 00:17:37,724 --> 00:17:40,725 there might have been a saturn in the sky with no rings. 289 00:17:44,631 --> 00:17:47,432 So, if the rings didn't form 290 00:17:47,434 --> 00:17:51,302 at the same time as saturn, how did they form, 291 00:17:51,304 --> 00:17:53,371 and what's keeping them in place? 292 00:18:00,513 --> 00:18:03,047 to form the rings 100 million years ago, 293 00:18:03,049 --> 00:18:04,482 you need to find an object -- 294 00:18:04,484 --> 00:18:07,251 maybe a comet or a moon gets too close to saturn. 295 00:18:07,253 --> 00:18:10,888 Saturn's gravity tears it apart and forms the rings. 296 00:18:13,760 --> 00:18:16,160 As the object is torn apart, 297 00:18:16,162 --> 00:18:21,566 the pieces spread out around saturn to form the rings. 298 00:18:21,568 --> 00:18:27,472 They keep colliding, breaking into smaller and smaller pieces. 299 00:18:27,474 --> 00:18:30,341 Like pebbles on a beach, subsequent jostling 300 00:18:30,343 --> 00:18:32,176 and self collisions between each other 301 00:18:32,178 --> 00:18:33,911 will take the sharp edges off of them 302 00:18:33,913 --> 00:18:35,646 creating rounded particles. 303 00:18:38,718 --> 00:18:41,586 From a distance, saturn's rings appear 304 00:18:41,588 --> 00:18:45,490 incredibly thin and almost perfectly flat, 305 00:18:45,492 --> 00:18:49,427 but appearances can be deceptive. 306 00:18:49,429 --> 00:18:51,596 One of our results from cassini 307 00:18:51,598 --> 00:18:54,065 as it took its final plunge into saturn 308 00:18:54,067 --> 00:18:56,100 was as we flew past those rings, 309 00:18:56,102 --> 00:19:01,138 we noticed that the rings were actually not a uniform density. 310 00:19:01,140 --> 00:19:03,007 That's something that nobody had seen. 311 00:19:03,009 --> 00:19:04,709 I mean, you had to get really close to see that, 312 00:19:04,711 --> 00:19:07,078 and it wasn't expected. 313 00:19:07,080 --> 00:19:09,046 Spilker: I'm a ring scientist, 314 00:19:09,048 --> 00:19:11,415 and I just love seeing that detail 315 00:19:11,417 --> 00:19:12,817 and trying to figure out 316 00:19:12,819 --> 00:19:17,221 why do saturn's rings look the way they do. 317 00:19:17,223 --> 00:19:20,091 There are very intricate structures, 318 00:19:20,093 --> 00:19:21,959 knife-edge little ringlets 319 00:19:21,961 --> 00:19:25,163 and, like, almost like the grooves in a record. 320 00:19:25,165 --> 00:19:26,864 It begs the question, of course, 321 00:19:26,866 --> 00:19:30,668 where do those structures come from. 322 00:19:34,340 --> 00:19:38,376 The clue is hidden within the rings. 323 00:19:38,378 --> 00:19:41,612 There's not five rings. There's not 500 rings. 324 00:19:41,614 --> 00:19:43,281 There's thousands of rings. 325 00:19:43,283 --> 00:19:47,618 There's potentially millions of tiny, little ringlets 326 00:19:47,620 --> 00:19:51,589 with small gaps between them, and sometimes large gaps, 327 00:19:51,591 --> 00:19:57,461 and cassini saw that there are moons embedded inside the rings. 328 00:20:01,768 --> 00:20:06,003 These moons and moonlets seem to be shaping the rings. 329 00:20:09,442 --> 00:20:10,975 When I think about the rings of saturn, 330 00:20:10,977 --> 00:20:13,344 I almost hear symphonies playing in my head. 331 00:20:13,346 --> 00:20:16,514 It's all about this wonderful structure and these harmonies, 332 00:20:16,516 --> 00:20:18,616 the balances between gravity. 333 00:20:18,618 --> 00:20:20,985 So, we use the word "resonance." 334 00:20:23,489 --> 00:20:26,290 Saturn's moons stir the rings particles 335 00:20:26,292 --> 00:20:30,027 with their gravitational pull, creating waves. 336 00:20:33,266 --> 00:20:37,602 There's a special place where the resonance exists. 337 00:20:37,604 --> 00:20:39,937 Imagine where the ring particles are going around twice 338 00:20:39,939 --> 00:20:42,740 for each single time the moon goes around. 339 00:20:42,742 --> 00:20:44,442 It's like pushing someone on a swing. 340 00:20:44,444 --> 00:20:46,310 If you push them at just the right rate 341 00:20:46,312 --> 00:20:48,012 they go higher and higher, 342 00:20:48,014 --> 00:20:52,083 and these places are where the waves generated. 343 00:20:52,085 --> 00:20:53,851 So, there's this ballet, this dance, 344 00:20:53,853 --> 00:20:55,553 between the ring and the moons. 345 00:20:55,555 --> 00:20:58,556 It is one of the most elegant things I've ever seen. 346 00:21:06,332 --> 00:21:08,966 But the rings aren't just being shaped 347 00:21:08,968 --> 00:21:11,335 into waves by the moons. 348 00:21:11,337 --> 00:21:14,538 They're being held in place by them. 349 00:21:14,540 --> 00:21:16,641 Through gravitational interactions, 350 00:21:16,643 --> 00:21:21,145 these moons might be shaping the rings, shepherding them, 351 00:21:21,147 --> 00:21:25,983 keeping their flock in a nice, tight orbit around the planet. 352 00:21:28,588 --> 00:21:32,256 In 2017, cassini reveals 353 00:21:32,258 --> 00:21:34,392 there are more than one or two moons 354 00:21:34,394 --> 00:21:36,727 shepherding the rings. 355 00:21:36,729 --> 00:21:41,499 A whole team of moons holds saturn's outermost visible ring, 356 00:21:41,501 --> 00:21:45,102 the "a" ring, in place. 357 00:21:45,104 --> 00:21:47,238 One of the really cool things that cassini discovered 358 00:21:47,240 --> 00:21:48,673 during its death dive 359 00:21:48,675 --> 00:21:50,608 was that there are seven moons of saturn 360 00:21:50,610 --> 00:21:51,909 that are all working together 361 00:21:51,911 --> 00:21:54,512 to keep that ring system in configuration, 362 00:21:54,514 --> 00:21:56,614 so it's like the magnificent seven 363 00:21:56,616 --> 00:21:58,182 holding this thing together. 364 00:22:02,555 --> 00:22:07,325 Of the seven magnificent moons, the biggest is mimas. 365 00:22:07,327 --> 00:22:09,593 It's one-eighth the size of our moon. 366 00:22:12,332 --> 00:22:16,133 the smallest, pan, is only 20 miles across. 367 00:22:18,271 --> 00:22:19,937 acting in combination, 368 00:22:19,939 --> 00:22:25,176 these moons hold all of saturn's rings in check. 369 00:22:25,178 --> 00:22:28,079 So, it's these seven moons working together 370 00:22:28,081 --> 00:22:30,514 forming the ring system that we see today. 371 00:22:38,825 --> 00:22:42,560 Cassini has truly opened our eyes to the wonder 372 00:22:42,562 --> 00:22:46,397 of saturn's rings and many moons. 373 00:22:46,399 --> 00:22:50,067 Saturn has a lot of moons -- I mean, a lot of moons, 374 00:22:50,069 --> 00:22:53,003 and they're all really interesting and different. 375 00:22:53,005 --> 00:22:54,805 Coming up with the exact number is a little difficult 376 00:22:54,807 --> 00:22:59,043 'cause it almost changes every year as we discover new ones. 377 00:22:59,045 --> 00:23:02,747 The latest count is over 60 moons, 378 00:23:02,749 --> 00:23:05,082 each with a different character, 379 00:23:05,084 --> 00:23:11,255 but one has a split personality and a very dark side. 380 00:23:29,675 --> 00:23:32,309 May 2017. 381 00:23:32,311 --> 00:23:35,279 Cassini was on its grand finale. 382 00:23:38,451 --> 00:23:42,753 the probe snapped its last photo of a strange moon 383 00:23:42,755 --> 00:23:47,792 2 million miles from saturn... 384 00:23:47,794 --> 00:23:49,927 Iapetus. 385 00:23:49,929 --> 00:23:52,363 Iapetus was discovered hundreds of years ago, 386 00:23:52,365 --> 00:23:55,232 and right from the start it was recognized 387 00:23:55,234 --> 00:23:57,334 that one side of it was very bright, 388 00:23:57,336 --> 00:24:02,606 and the other side was as dark as dark can be. 389 00:24:02,608 --> 00:24:04,608 This dark and light moon 390 00:24:04,610 --> 00:24:08,212 confused italian astronomer giovanni cassini 391 00:24:08,214 --> 00:24:13,451 when he first spotted it in 1671. 392 00:24:13,453 --> 00:24:16,987 It's been puzzling scientists ever since. 393 00:24:19,125 --> 00:24:22,226 so, we get there with cassini, and of course iapetus 394 00:24:22,228 --> 00:24:25,196 was a very major target for us 395 00:24:25,198 --> 00:24:26,831 because we were interested to know 396 00:24:26,833 --> 00:24:32,136 what was with this crazy two-toned moon. 397 00:24:34,607 --> 00:24:38,576 Cassini reveals that the answer lies even farther out 398 00:24:38,578 --> 00:24:43,781 from saturn in the form of another moon. 399 00:24:43,783 --> 00:24:46,450 There's one pretty big but really dark moon, 400 00:24:46,452 --> 00:24:49,119 phoebe, that's outside of iapetus 401 00:24:49,121 --> 00:24:52,690 and is orbiting the opposite direction around saturn. 402 00:24:52,692 --> 00:24:58,496 Pheobe orbits saturn four times farther out than iapetus. 403 00:24:58,498 --> 00:25:02,399 As it travels around the planet, micrometeorite impacts 404 00:25:02,401 --> 00:25:07,538 the moon's surface generate a cloud of dark dust. 405 00:25:07,540 --> 00:25:12,209 The dust from phoebe actually creates a large ring. 406 00:25:12,211 --> 00:25:15,346 A ring of dark, dusty material that's drifting inwards 407 00:25:15,348 --> 00:25:18,782 toward saturn going the opposite direction of iapetus, 408 00:25:18,784 --> 00:25:20,651 which is the perfect material for iapetus 409 00:25:20,653 --> 00:25:23,721 to sweep up in its orbit to create one dark side. 410 00:25:29,428 --> 00:25:31,996 Iapetus has one dark side 411 00:25:31,998 --> 00:25:34,598 because it's tidally locked to saturn. 412 00:25:37,136 --> 00:25:41,972 One side always faces the planet 413 00:25:41,974 --> 00:25:47,311 while another side drives forward through the dust. 414 00:25:47,313 --> 00:25:49,713 It's plowing through a bunch of dust 415 00:25:49,715 --> 00:25:51,248 that's sticking to the front side, 416 00:25:51,250 --> 00:25:53,984 kind of like bugs on a windshield. 417 00:25:53,986 --> 00:25:56,620 Cassini discovered this dark dust 418 00:25:56,622 --> 00:25:59,023 makes the leading side warmer 419 00:25:59,025 --> 00:26:03,427 than the trailing bright side by 50 degrees fahrenheit. 420 00:26:03,429 --> 00:26:05,362 When you have something that's dark like the dust 421 00:26:05,364 --> 00:26:08,065 on the leading edge of iapetus, that gets warmer. 422 00:26:08,067 --> 00:26:09,600 It absorbs sunlight better, 423 00:26:09,602 --> 00:26:13,504 and if it's warmer then things that can evaporate more easily, 424 00:26:13,506 --> 00:26:19,777 like water for example, tends to blow off the surface. 425 00:26:19,779 --> 00:26:22,980 The front side gets darker and warmer. 426 00:26:25,551 --> 00:26:27,818 any visible ice turns to vapor 427 00:26:27,820 --> 00:26:30,354 and makes its way to the colder trailing side 428 00:26:30,356 --> 00:26:32,356 where it refreezes. 429 00:26:34,393 --> 00:26:39,730 so, the white side gets whiter and the dark side gets darker. 430 00:26:39,732 --> 00:26:41,966 So, you have this self-sustaining dark side 431 00:26:41,968 --> 00:26:44,768 and bright side, and you wind up with this two-faced moon. 432 00:26:49,008 --> 00:26:54,078 Iapetus' two sides are strange, 433 00:26:54,080 --> 00:26:56,814 but cassini discovers that they're not 434 00:26:56,816 --> 00:27:01,018 the weirdest thing about this moon. 435 00:27:01,020 --> 00:27:04,121 The weirdest thing is that it is a walnut. 436 00:27:09,495 --> 00:27:12,997 iapetus has a mountain range that exactly circles its equator 437 00:27:12,999 --> 00:27:14,698 all the way around the moon, 438 00:27:14,700 --> 00:27:17,334 a mountain range higher than the himalayas. 439 00:27:25,845 --> 00:27:30,247 These mountains are over 12 miles high, 440 00:27:30,249 --> 00:27:33,384 more than twice the altitude of earth's highest peak, 441 00:27:33,386 --> 00:27:37,454 mount everest. 442 00:27:37,456 --> 00:27:40,124 It's crazy. It's this huge crazy ridge 443 00:27:40,126 --> 00:27:42,126 on this really strange moon. 444 00:27:45,064 --> 00:27:48,832 how do you form a smooth equatorial mountain ridge 445 00:27:48,834 --> 00:27:50,668 around an entire world? 446 00:27:50,670 --> 00:27:54,638 A really interesting idea is that for some period of time, 447 00:27:54,640 --> 00:27:57,675 just like saturn itself has this gigantic ring system, 448 00:27:57,677 --> 00:28:00,277 iapetus had a ring system, as well. 449 00:28:02,481 --> 00:28:06,817 Over time, iapetus' ring collapsed, 450 00:28:06,819 --> 00:28:09,453 falling in a circle around the moon. 451 00:28:11,424 --> 00:28:13,057 Walsh: As it fell to the surface, 452 00:28:13,059 --> 00:28:14,425 it built up a mountain range 453 00:28:14,427 --> 00:28:16,627 right below where the ring was orbiting 454 00:28:16,629 --> 00:28:18,128 so that all that material just built up 455 00:28:18,130 --> 00:28:19,697 and built a mountain range 456 00:28:19,699 --> 00:28:21,699 ringing the equator all the way around. 457 00:28:25,638 --> 00:28:27,571 Walnut-shaped iapetus 458 00:28:27,573 --> 00:28:31,375 is not the only strange moon around saturn. 459 00:28:31,377 --> 00:28:33,210 Cassini discovered a moon 460 00:28:33,212 --> 00:28:37,614 hiding many secrets beneath its icy surface -- 461 00:28:37,616 --> 00:28:42,252 enceladus, a moon that could even harbor life. 462 00:29:01,040 --> 00:29:03,874 August 2017, 463 00:29:03,876 --> 00:29:07,811 cassini captured six images of enceladus, 464 00:29:09,882 --> 00:29:14,518 one of the most intriguing moons in the solar system. 465 00:29:14,520 --> 00:29:18,889 Enceladus is a relatively small moon of saturn 466 00:29:18,891 --> 00:29:20,390 that's pretty easy to ignore, 467 00:29:20,392 --> 00:29:25,129 but once you pay attention to it, hosts a lot of surprises. 468 00:29:29,668 --> 00:29:34,271 We've known something was unusual about this icy world 469 00:29:34,273 --> 00:29:39,943 ever since the voyager mission took photographs in 1980. 470 00:29:39,945 --> 00:29:42,746 We thought that enceladus would be frozen solid, 471 00:29:42,748 --> 00:29:46,083 and yet we knew from voyager data the surface 472 00:29:46,085 --> 00:29:48,819 of enceladus was bright white. 473 00:29:48,821 --> 00:29:51,021 Porco: And we could see on the surface 474 00:29:51,023 --> 00:29:54,291 that vast tracks of it were smooth, 475 00:29:54,293 --> 00:29:57,461 at least at the resolution that we had with voyager, 476 00:29:57,463 --> 00:30:01,832 and that immediately says that there's been internal activity 477 00:30:01,834 --> 00:30:04,201 because that's really, on an airless moon, 478 00:30:04,203 --> 00:30:08,405 that's the only process that could erase craters. 479 00:30:08,407 --> 00:30:10,707 Scientists suspected something 480 00:30:10,709 --> 00:30:15,612 was actively resurfacing enceladus, 481 00:30:15,614 --> 00:30:20,751 filling in its craters to make it smooth and bright. 482 00:30:20,753 --> 00:30:25,823 Then cassini sent back pictures of enceladus backlit, 483 00:30:25,825 --> 00:30:28,158 and all was revealed. 484 00:30:28,160 --> 00:30:31,495 We saw these icy jets shooting out from enceladus, 485 00:30:31,497 --> 00:30:35,699 and everyone was so amazed that a moon so tiny 486 00:30:35,701 --> 00:30:41,171 and assumed to be a frozen-solid ice cube could be so active. 487 00:30:46,045 --> 00:30:52,482 Jets of almost luminous material sprang out of geysers. 488 00:30:52,484 --> 00:30:56,119 When I first saw a picture of a geyser on enceladus, 489 00:30:56,121 --> 00:30:58,155 I mean, I was floored. That's amazing. 490 00:30:58,157 --> 00:31:01,391 I had no idea that was even possible. 491 00:31:01,393 --> 00:31:06,763 The cassini discovery of geysers on enceladus was a game changer. 492 00:31:06,765 --> 00:31:09,900 All of the sudden, here's water jetting out. 493 00:31:09,902 --> 00:31:12,703 It was, like, too good to be true. 494 00:31:12,705 --> 00:31:18,342 Cassini revealed the geysers are blasting out liquid water. 495 00:31:18,344 --> 00:31:22,846 Enceladus is not a solid ball of ice. 496 00:31:22,848 --> 00:31:24,748 As we got more data from cassini, 497 00:31:24,750 --> 00:31:27,484 we found that enceladus had a wobble 498 00:31:27,486 --> 00:31:29,086 that was too large for a body 499 00:31:29,088 --> 00:31:31,889 that was frozen solid all the way through, 500 00:31:31,891 --> 00:31:34,491 and that told us that a liquid water ocean 501 00:31:34,493 --> 00:31:36,894 circled a rocky core. 502 00:31:36,896 --> 00:31:39,796 Enceladus has liquid water under its surface, 503 00:31:39,798 --> 00:31:42,132 and it may very well be an ocean 504 00:31:42,134 --> 00:31:45,135 basically covering the inside of that moon, 505 00:31:45,137 --> 00:31:48,705 but where's the heat coming from? 506 00:31:48,707 --> 00:31:51,108 When planets and moons form, 507 00:31:51,110 --> 00:31:54,745 their cores are incredibly hot, 508 00:31:54,747 --> 00:31:57,848 but over time they cool down. 509 00:31:57,850 --> 00:32:02,119 The smaller the planet, the faster it cools. 510 00:32:02,121 --> 00:32:06,823 A tiny world like enceladus over a billion miles from the sun 511 00:32:06,825 --> 00:32:10,594 should have frozen solid by now. 512 00:32:10,596 --> 00:32:12,462 Oluseyi: That's what we expected. 513 00:32:12,464 --> 00:32:14,831 If things are smaller, then they would be roughly dead, 514 00:32:14,833 --> 00:32:16,433 and they'd be covered by craters, 515 00:32:16,435 --> 00:32:21,004 but enceladus shows us that that's not the case at all. 516 00:32:21,006 --> 00:32:24,374 How could a tiny moon so far from the sun 517 00:32:24,376 --> 00:32:26,910 have enough warmth for liquid water? 518 00:32:26,912 --> 00:32:31,315 One idea is tidal heating. 519 00:32:31,317 --> 00:32:32,649 If you've ever played racquetball, 520 00:32:32,651 --> 00:32:34,284 you know as you play the game the ball heats up, 521 00:32:34,286 --> 00:32:37,587 and this is because as the ball hits the racket or the wall, 522 00:32:37,589 --> 00:32:40,257 it's getting squished, and then it relaxes. 523 00:32:43,395 --> 00:32:46,330 saturn's gravity squishes and relaxes 524 00:32:46,332 --> 00:32:48,865 enceladus as it orbits the planet, 525 00:32:48,867 --> 00:32:53,003 heating it like a racquetball, 526 00:32:53,005 --> 00:32:55,906 but this alone wouldn't generate enough heat 527 00:32:55,908 --> 00:32:59,443 to stop enceladus' water from freezing. 528 00:32:59,445 --> 00:33:04,414 Something else must be going on in the core. 529 00:33:04,416 --> 00:33:09,486 Plait: What if the core of enceladus is actually kind of gravelly? 530 00:33:09,488 --> 00:33:12,089 Instead of it just being solid, it's actually made of rocks 531 00:33:12,091 --> 00:33:14,257 and pebbles and gravel all put together. 532 00:33:14,259 --> 00:33:16,760 Then what happens is as the tides are stretching 533 00:33:16,762 --> 00:33:20,263 and squeezing it, those rocks are rubbing together, 534 00:33:20,265 --> 00:33:23,266 and that actually generates even more energy. 535 00:33:26,138 --> 00:33:30,874 2017, a computer model based on cassini data 536 00:33:30,876 --> 00:33:34,745 revealed this tidal friction generates more energy 537 00:33:34,747 --> 00:33:38,949 than america's biggest power station. 538 00:33:38,951 --> 00:33:44,454 Water heated to 194 degrees fahrenheit rises to the surface. 539 00:33:44,456 --> 00:33:46,757 It sprays through cracks in the moon's 540 00:33:46,759 --> 00:33:50,060 south pole creating misty plumes. 541 00:33:53,532 --> 00:33:56,333 As we flew seven times through and tasted and sampled 542 00:33:56,335 --> 00:34:00,003 the gas and the particles, we found salty particles, 543 00:34:00,005 --> 00:34:04,341 that the ocean was salty very much like the earth's ocean. 544 00:34:04,343 --> 00:34:09,012 We found hydocarbons, methane, carbon dioxide, ammonia. 545 00:34:09,014 --> 00:34:12,049 We found the key ingredients for life 546 00:34:12,051 --> 00:34:16,987 coming out of the jets of enceladus -- so remarkable. 547 00:34:19,591 --> 00:34:24,728 In 2018, scientists reanalyze the enceladus data 548 00:34:24,730 --> 00:34:29,766 and found something even more remarkable -- 549 00:34:29,768 --> 00:34:33,737 complex organic molecules. 550 00:34:33,739 --> 00:34:37,607 What they found were larger organic compounds 551 00:34:37,609 --> 00:34:39,076 than initially thought there. 552 00:34:39,078 --> 00:34:42,446 At first, it was just dust and water and some basic organics. 553 00:34:42,448 --> 00:34:44,648 Now they're seeing more complex stuff 554 00:34:44,650 --> 00:34:47,417 coming up from enceladus' interior, 555 00:34:47,419 --> 00:34:51,721 and that asks the question what else is down there. 556 00:34:51,723 --> 00:34:57,127 On earth, we find life huddled around hot vents on the seabed. 557 00:34:57,129 --> 00:35:01,932 Could the same be true in the oceans of enceladus? 558 00:35:01,934 --> 00:35:07,137 Could these complex organic molecules be signs of life? 559 00:35:07,139 --> 00:35:09,506 My favorite name for them is "goo." 560 00:35:09,508 --> 00:35:13,343 they're gooey things, and think of life 561 00:35:13,345 --> 00:35:15,245 as a collection of gooey-like molecules. 562 00:35:15,247 --> 00:35:18,281 Now, that doesn't mean that all gooey molecules are biological, 563 00:35:18,283 --> 00:35:20,383 but certainly biology makes use 564 00:35:20,385 --> 00:35:23,753 of these complex organic molecules. 565 00:35:23,755 --> 00:35:26,623 Deep in enceladus' oceans, 566 00:35:26,625 --> 00:35:32,262 heat from hydrothermal vents drives chemical reactions... 567 00:35:32,264 --> 00:35:36,099 Combining simple molecules like methane and hydrogen 568 00:35:36,101 --> 00:35:41,538 into longer, complex organic molecules, 569 00:35:41,540 --> 00:35:47,744 complex molecules that could serve as the precursors to life. 570 00:35:47,746 --> 00:35:50,814 What's amazing is the chemistry of that ocean. 571 00:35:50,816 --> 00:35:53,116 Everything needed for life is there. 572 00:35:53,118 --> 00:35:55,752 The eternal question is is there life in the universe, 573 00:35:55,754 --> 00:35:59,055 and enceladus is a great place to try and answer that question. 574 00:36:03,962 --> 00:36:06,630 And cassini revealed secrets 575 00:36:06,632 --> 00:36:10,634 of another moon of saturn with amazing chemistry, 576 00:36:10,636 --> 00:36:14,004 a giant moon with earth-like features -- 577 00:36:14,006 --> 00:36:17,707 rivers, lakes, and dunes -- 578 00:36:17,709 --> 00:36:19,709 titan. 579 00:36:36,628 --> 00:36:40,430 September 2017, 580 00:36:40,432 --> 00:36:42,532 four days before the mission ended, 581 00:36:42,534 --> 00:36:45,068 cassini flew past one of saturn's 582 00:36:45,070 --> 00:36:50,106 most spectacular moons, titan. 583 00:36:50,108 --> 00:36:53,243 Here's why I like titan -- not just because it has a name 584 00:36:53,245 --> 00:36:56,112 that means "big" and "strong," which makes you think of me, 585 00:36:56,114 --> 00:36:59,649 but because it has an extensive atmosphere 586 00:36:59,651 --> 00:37:02,886 that's made primarily of nitrogen, just like earth's. 587 00:37:06,491 --> 00:37:09,326 sutter: Titan's always been a mystery. 588 00:37:09,328 --> 00:37:13,563 What is hiding underneath that thick atmosphere? 589 00:37:16,501 --> 00:37:18,468 Viewed through a telescope, 590 00:37:18,470 --> 00:37:22,639 this moon seemed little more than a hazy orange ball. 591 00:37:22,641 --> 00:37:26,343 Then cassini launched the huygens probe. 592 00:37:26,345 --> 00:37:28,612 It traveled beneath the clouds 593 00:37:28,614 --> 00:37:33,416 and sent back images of titan's surface. 594 00:37:33,418 --> 00:37:39,823 I almost can't describe how thrilling it was, 595 00:37:39,825 --> 00:37:42,792 the landing of the huygens probe on the surface of titan. 596 00:37:42,794 --> 00:37:45,462 It was like a jules verne adventure come true. 597 00:37:53,038 --> 00:37:55,038 lanza: The images that you see 598 00:37:55,040 --> 00:37:56,606 as you're coming through the atmosphere 599 00:37:56,608 --> 00:37:58,174 and the world emerges, 600 00:37:58,176 --> 00:38:02,178 and it's this incredible world that looks so familiar. 601 00:38:02,180 --> 00:38:05,749 Mountains and these streams flowing into this ocean. 602 00:38:05,751 --> 00:38:07,250 Wow! 603 00:38:07,252 --> 00:38:10,487 You might be standing on the shores of a lake, 604 00:38:10,489 --> 00:38:12,989 but this lake doesn't look like water. 605 00:38:12,991 --> 00:38:14,324 Instead, it's methane. 606 00:38:14,326 --> 00:38:16,459 It's much darker. 607 00:38:16,461 --> 00:38:18,528 Durda: It's a frigid, bizarre world 608 00:38:18,530 --> 00:38:21,131 with geologic features that look familiar, 609 00:38:21,133 --> 00:38:23,700 but in a very, very alien setting. 610 00:38:23,702 --> 00:38:27,237 Titan is like a home away from home. 611 00:38:27,239 --> 00:38:32,309 It's just colder by about 350 degrees fahrenheit. 612 00:38:32,311 --> 00:38:35,211 The cassini mission revealed that titan is 613 00:38:35,213 --> 00:38:38,148 really exactly like earth in terms of its landscape. 614 00:38:38,150 --> 00:38:40,116 In fact, almost a quarter of the body 615 00:38:40,118 --> 00:38:43,787 is covered in sand dunes exactly like what you see behind me. 616 00:38:48,560 --> 00:38:54,998 But cassini reveals titan's dunes are not what they seem. 617 00:38:55,000 --> 00:38:57,467 The dunes on titan are made of something 618 00:38:57,469 --> 00:38:59,869 completely different than sand dunes on the earth. 619 00:38:59,871 --> 00:39:02,372 You know, most sand on the earth is made of quartz, 620 00:39:02,374 --> 00:39:04,541 but on titan sand dunes, it turns out, 621 00:39:04,543 --> 00:39:06,609 are made entirely of organics. 622 00:39:08,714 --> 00:39:11,748 Titan's sand is made from tiny particles 623 00:39:11,750 --> 00:39:15,385 of organic gunk called hydrocarbons. 624 00:39:20,325 --> 00:39:25,528 these organic dunes contain the building blocks of life. 625 00:39:25,530 --> 00:39:31,401 For scientists, this is a tantalizing hint. 626 00:39:31,403 --> 00:39:34,137 Could titan harbor life? 627 00:39:37,676 --> 00:39:40,110 Here on earth, there's life that exists 628 00:39:40,112 --> 00:39:42,312 in so many extreme environments, 629 00:39:42,314 --> 00:39:45,482 so its not impossible to think that life 630 00:39:45,484 --> 00:39:47,851 could have evolved to use the methane 631 00:39:47,853 --> 00:39:50,820 and all of the other chemical constituents on titan. 632 00:39:50,822 --> 00:39:55,058 If life has developed on titan, it's going to look really weird. 633 00:39:55,060 --> 00:39:58,428 It's going to be really different from life on earth. 634 00:39:58,430 --> 00:40:00,296 To me, there's going to be this wonderful moment 635 00:40:00,298 --> 00:40:02,098 in history when we really do have 636 00:40:02,100 --> 00:40:04,601 another example of how life can be, 637 00:40:04,603 --> 00:40:06,503 and if I had to place my bets on it, 638 00:40:06,505 --> 00:40:10,473 I think we're going to find it in the saturn system. 639 00:40:10,475 --> 00:40:13,777 But cassini's discovery of potential life 640 00:40:13,779 --> 00:40:17,614 sentenced the probe to death. 641 00:40:17,616 --> 00:40:21,017 We didn't want to leave it just indefinitely in orbit 642 00:40:21,019 --> 00:40:24,254 because there's this fear that, you know, 643 00:40:24,256 --> 00:40:27,657 should there be any earthly contamination on the spacecraft, 644 00:40:27,659 --> 00:40:31,094 you don't want it crashing into titan or enceladus. 645 00:40:33,465 --> 00:40:39,102 Cassini interacted with titan one last time. 646 00:40:39,104 --> 00:40:41,971 With a gentle nudge from titan's gravity, 647 00:40:41,973 --> 00:40:45,175 we call it titan's goodbye kiss. 648 00:40:45,177 --> 00:40:50,380 We ended the mission with a plunge into saturn's atmosphere, 649 00:40:50,382 --> 00:40:54,884 vaporizing cassini and saying goodbye to our friend. 650 00:40:59,124 --> 00:41:03,226 I hope you're all as deeply proud 651 00:41:03,228 --> 00:41:06,095 of this amazing accomplishment. 652 00:41:06,097 --> 00:41:08,998 I'm going to call this the end of mission. 653 00:41:09,000 --> 00:41:11,534 Project manager bob mitchell. 654 00:41:11,536 --> 00:41:13,503 [ applause ] 655 00:41:19,311 --> 00:41:24,414 Although cassini is gone, its legacy lives on. 656 00:41:24,416 --> 00:41:26,749 Spilker: Now we're sifting through 657 00:41:26,751 --> 00:41:31,087 all of the data collected, still finding discoveries, 658 00:41:31,089 --> 00:41:34,691 putting together the pieces of the puzzle to understand 659 00:41:34,693 --> 00:41:37,293 saturn, the rings, and the moons. 660 00:41:37,295 --> 00:41:40,363 Cassini is going to go down in history 661 00:41:40,365 --> 00:41:42,765 as one of the most scientifically productive 662 00:41:42,767 --> 00:41:48,137 interplanetary missions that humanity has ever flown. 663 00:41:48,139 --> 00:41:53,643 I'm immensely proud and feel enormously privileged 664 00:41:53,645 --> 00:41:55,278 to have been a part of it. 665 00:42:02,220 --> 00:42:06,656 Besides the amazing science cassini returned, 666 00:42:06,658 --> 00:42:09,325 just the beauty of this planet 667 00:42:09,327 --> 00:42:13,129 I think sparked something inside of us. 668 00:42:13,131 --> 00:42:15,098 Whenever I look up at saturn now, 669 00:42:15,100 --> 00:42:17,734 I know that cassini is there, too, 670 00:42:17,736 --> 00:42:21,704 and so saturn is even a more special place.