1 00:00:01,905 --> 00:00:04,071 NARRATOR: Throughout our Solar System, 2 00:00:04,071 --> 00:00:08,005 we find worlds shaped by ice. 3 00:00:09,005 --> 00:00:10,071 SABINE STANLEY: These ice worlds 4 00:00:10,071 --> 00:00:12,305 are so unexpected and surprising. 5 00:00:12,305 --> 00:00:14,771 There is definitely more ice out there 6 00:00:14,771 --> 00:00:17,771 than we really expected or anticipated. 7 00:00:18,938 --> 00:00:22,738 NARRATOR: Today, spacecraft are bringing us closer than ever... 8 00:00:24,271 --> 00:00:26,705 ...to revealing their secrets. 9 00:00:27,805 --> 00:00:29,505 We've got carbon dioxide snow 10 00:00:29,505 --> 00:00:31,938 on Mars. 11 00:00:31,938 --> 00:00:33,105 KELSI SINGER: On Pluto, 12 00:00:33,105 --> 00:00:34,738 we have these nitrogen ice glaciers 13 00:00:34,738 --> 00:00:37,971 that no one would have predicted. 14 00:00:37,971 --> 00:00:39,805 Deep in the planet of Uranus, 15 00:00:39,805 --> 00:00:44,271 you get this extremely dense black hot ice. 16 00:00:44,271 --> 00:00:47,405 MICHAEL WONG: The data has truly transformed 17 00:00:47,405 --> 00:00:50,705 the way that we understand how ice behaves 18 00:00:50,705 --> 00:00:53,971 so far away in the depths of space. 19 00:00:53,971 --> 00:00:57,605 NARRATOR: But many questions remain unanswered. 20 00:00:57,605 --> 00:01:00,271 PETER GAO: How do these icy worlds even form? 21 00:01:00,271 --> 00:01:01,538 How did the ice get there? 22 00:01:01,538 --> 00:01:02,571 Is there life there? 23 00:01:02,571 --> 00:01:04,371 NARRATOR: And of all the worlds 24 00:01:04,371 --> 00:01:06,105 in our Solar System, 25 00:01:06,105 --> 00:01:09,038 ours hits the icy jackpot. 26 00:01:09,038 --> 00:01:11,171 The ice we have here on Earth is special. 27 00:01:11,171 --> 00:01:14,005 And if it didn't have its special properties, 28 00:01:14,005 --> 00:01:15,605 life on Earth would not exist 29 00:01:15,605 --> 00:01:17,338 and you wouldn't be here watching me. 30 00:01:18,338 --> 00:01:21,105 NARRATOR: Why is our cosmic neighborhood 31 00:01:21,105 --> 00:01:24,171 home to so many different and exotic ices? 32 00:01:26,371 --> 00:01:29,971 "Solar System: Icy Worlds." 33 00:01:29,971 --> 00:01:32,771 Right now, on "NOVA." 34 00:01:32,771 --> 00:01:35,138 ♪ ♪ 35 00:02:04,505 --> 00:02:06,838 ♪ ♪ 36 00:02:06,838 --> 00:02:08,805 NARRATOR: Out in the dark expanse 37 00:02:08,805 --> 00:02:11,371 of our Solar System, 38 00:02:11,371 --> 00:02:13,838 far beyond Earth and Mars... 39 00:02:15,471 --> 00:02:18,971 ...we enter the realm of the gas giants. 40 00:02:20,671 --> 00:02:22,971 Where average temperatures of the planets 41 00:02:22,971 --> 00:02:24,638 begin to plummet. 42 00:02:30,905 --> 00:02:33,771 Venture even farther away from Earth, 43 00:02:33,771 --> 00:02:36,405 and we pass the ice giants. 44 00:02:39,205 --> 00:02:42,771 Here, temperatures can drop even lower... 45 00:02:44,838 --> 00:02:49,171 ...down to -370 degrees Fahrenheit. 46 00:02:50,171 --> 00:02:53,838 These worlds are made almost entirely of ice... 47 00:02:55,538 --> 00:02:59,838 ...existing in exotic, seemingly impossible forms. 48 00:03:03,138 --> 00:03:06,071 WONG: Thanks to planetary exploration, 49 00:03:06,071 --> 00:03:08,171 we have witnessed different forms of ice 50 00:03:08,171 --> 00:03:11,471 behaving in ways that we could not have expected. 51 00:03:13,571 --> 00:03:16,671 NARRATOR: Scientists are just beginning to uncover 52 00:03:16,671 --> 00:03:19,738 the icy secrets of our Solar System. 53 00:03:22,438 --> 00:03:25,971 GURNEY: We really don't know much about ice worlds 54 00:03:25,971 --> 00:03:27,171 and planetary scientists 55 00:03:27,171 --> 00:03:28,338 are really discovering 56 00:03:28,338 --> 00:03:29,738 new things every day. 57 00:03:31,071 --> 00:03:33,205 NARRATOR: Discoveries that can shed light on 58 00:03:33,205 --> 00:03:35,838 the strange ways ice behaves 59 00:03:35,838 --> 00:03:38,538 and how dynamic it can be, 60 00:03:38,538 --> 00:03:41,171 not only in our Solar System, 61 00:03:41,171 --> 00:03:44,005 but on other worlds in our galaxy, too. 62 00:03:57,105 --> 00:03:59,905 (ice crackling) 63 00:04:07,671 --> 00:04:09,905 NARRATOR: Over three billion miles from Earth, 64 00:04:09,905 --> 00:04:12,705 the space probe New Horizons 65 00:04:12,705 --> 00:04:15,771 is traveling far beyond the rocky planets. 66 00:04:17,738 --> 00:04:20,338 And after more than nine years, 67 00:04:20,338 --> 00:04:22,571 arrives at its destination. 68 00:04:26,871 --> 00:04:28,471 As it passes Pluto, 69 00:04:29,871 --> 00:04:31,405 ...the probe gives us a glimpse 70 00:04:31,405 --> 00:04:34,538 of a world made of weird ice. 71 00:04:36,138 --> 00:04:37,238 DURFEY: Flyby missions 72 00:04:37,238 --> 00:04:39,105 are do or die. 73 00:04:39,105 --> 00:04:41,105 If you don't get those images, 74 00:04:41,105 --> 00:04:43,605 if you don't get that data, 75 00:04:43,605 --> 00:04:44,971 you've flown by 76 00:04:44,971 --> 00:04:46,305 and you're gone now. 77 00:04:47,705 --> 00:04:50,171 VERBISCER: We only get one shot because traveling at 78 00:04:50,171 --> 00:04:52,105 31,000 miles an hour, 79 00:04:52,105 --> 00:04:54,271 it's not like you can do a U-turn. 80 00:04:56,771 --> 00:05:01,805 NARRATOR: The $780 million high-risk mission pays dividends, 81 00:05:01,805 --> 00:05:04,571 delivering a mother lode of data. 82 00:05:04,571 --> 00:05:06,138 (camera shutter clicking) 83 00:05:07,138 --> 00:05:09,138 New Horizons surprises scientists 84 00:05:09,138 --> 00:05:12,571 with incredible images of Pluto's surface, 85 00:05:12,571 --> 00:05:15,938 revealing features they never expected to see. 86 00:05:17,238 --> 00:05:18,238 GAO: I think when 87 00:05:18,238 --> 00:05:20,605 people first saw images of Pluto, 88 00:05:20,605 --> 00:05:21,871 they were just blown away. 89 00:05:21,871 --> 00:05:25,338 We're seeing incredible diversity in 90 00:05:25,338 --> 00:05:26,638 what the surface looks like. 91 00:05:27,605 --> 00:05:29,338 VERBISCER: I walked into the geology room 92 00:05:29,338 --> 00:05:32,171 and looked at an image on one of the computer screens, 93 00:05:32,171 --> 00:05:35,371 and I wondered why someone was looking at 94 00:05:35,371 --> 00:05:37,371 a picture of Antarctica. 95 00:05:37,371 --> 00:05:39,705 And it dawned on me 96 00:05:39,705 --> 00:05:41,938 (chuckling): gradually, oh, my goodness, 97 00:05:41,938 --> 00:05:44,838 that was not Antarctica, that was actually 98 00:05:44,838 --> 00:05:48,005 a very close picture of Pluto. 99 00:05:48,971 --> 00:05:52,205 WONG: There were tons of mysteries that we needed to unravel. 100 00:05:52,205 --> 00:05:54,138 There were lots of features 101 00:05:54,138 --> 00:05:57,071 that puzzled us. How could that possibly be, 102 00:05:57,071 --> 00:05:59,538 so far away in the Solar System? 103 00:06:05,038 --> 00:06:06,605 NARRATOR: The amount of data collected 104 00:06:06,605 --> 00:06:10,071 allows scientists to map Pluto's surface. 105 00:06:14,438 --> 00:06:16,938 Pluto's most prominent feature 106 00:06:16,938 --> 00:06:21,438 is a great icy plain around 600 miles across. 107 00:06:23,305 --> 00:06:26,138 And, despite the extreme cold, 108 00:06:26,138 --> 00:06:29,838 there are signs of movement in the ice; 109 00:06:29,838 --> 00:06:32,038 lines etched into the surface 110 00:06:32,038 --> 00:06:33,438 as if they are churning. 111 00:06:38,005 --> 00:06:42,238 And then, something even more unexpected. 112 00:06:52,471 --> 00:06:54,305 Glaciers. 113 00:06:56,138 --> 00:06:58,138 Flowing rivers of ice 114 00:06:58,138 --> 00:07:00,505 on a world so cold... 115 00:07:02,071 --> 00:07:04,538 ...it seems nothing should be moving. 116 00:07:08,871 --> 00:07:11,371 Pluto is a wintery puzzle, 117 00:07:11,371 --> 00:07:15,838 with icy landscapes as dramatic as anything seen on Earth. 118 00:07:17,605 --> 00:07:20,371 How is all this dynamism possible 119 00:07:20,371 --> 00:07:23,305 on a world so far from the sun? 120 00:07:28,005 --> 00:07:33,038 ♪ ♪ 121 00:07:37,438 --> 00:07:41,305 Pluto, a place right on the edge of the Solar System, 122 00:07:41,305 --> 00:07:43,371 looks remarkably similar to 123 00:07:43,371 --> 00:07:46,905 some frozen landscapes on Earth, 124 00:07:46,905 --> 00:07:49,438 like this glacier in Alaska. 125 00:07:50,938 --> 00:07:54,038 LEIGHAN FALLEY: Glacier Two for the Root Canal, acknowledge. 126 00:07:55,438 --> 00:07:58,105 (man speaks indistinctly over radio) 127 00:08:00,105 --> 00:08:01,638 FALLEY: Okay, floor above two. 128 00:08:01,638 --> 00:08:03,738 Hang on. 129 00:08:03,738 --> 00:08:05,505 Never a dull moment around here. 130 00:08:06,971 --> 00:08:10,005 Well, isn't this amazing? 131 00:08:10,005 --> 00:08:12,405 Incredible views. Yes. 132 00:08:13,738 --> 00:08:16,071 NARRATOR: This landscape might look frozen solid, 133 00:08:16,071 --> 00:08:18,038 but it is one of the most 134 00:08:18,038 --> 00:08:21,705 geologically active areas on Earth. 135 00:08:21,705 --> 00:08:23,971 SINGER: In the time that you've been flying here, 136 00:08:23,971 --> 00:08:26,638 have you seen a lot of changes in the glacier? 137 00:08:26,638 --> 00:08:28,671 Absolutely. Are you kidding me? 138 00:08:28,671 --> 00:08:31,771 (chuckling): Yes. I've seen immense changes. 139 00:08:32,771 --> 00:08:35,338 SINGER: Some aspects of what we're looking at 140 00:08:35,338 --> 00:08:37,738 that really reminded me of Pluto, 141 00:08:37,738 --> 00:08:39,638 there's the kind of flow lines 142 00:08:39,638 --> 00:08:40,971 in the glacier 143 00:08:40,971 --> 00:08:42,938 indicating the direction of flow. 144 00:08:42,938 --> 00:08:44,571 Oh, Pluto has flow lines? 145 00:08:44,571 --> 00:08:47,271 Yes, they are moving downhill, 146 00:08:47,271 --> 00:08:49,538 similar to these glaciers. 147 00:08:55,171 --> 00:08:56,471 FALLEY: We're coming in for landing. 148 00:08:58,671 --> 00:09:01,038 NARRATOR: Understanding these glacial features 149 00:09:01,038 --> 00:09:03,371 can help scientists understand 150 00:09:03,371 --> 00:09:05,071 how Pluto's glaciers flow. 151 00:09:15,071 --> 00:09:18,638 (plane powering down) 152 00:09:18,638 --> 00:09:20,038 FALLEY: Welcome to the glacier, you guys. 153 00:09:26,071 --> 00:09:28,538 SINGER: Wow. (Falley laughs) 154 00:09:28,538 --> 00:09:30,905 So beautiful. FALLEY: Oh... 155 00:09:30,905 --> 00:09:33,305 FALLEY: One of the greatest ranges on the continent. 156 00:09:36,538 --> 00:09:38,338 (laughs) 157 00:09:38,338 --> 00:09:39,771 Is the glacier under here? 158 00:09:39,771 --> 00:09:41,138 Yes, we're probably 159 00:09:41,138 --> 00:09:44,138 on top of about 700 to 1,500 feet 160 00:09:44,138 --> 00:09:46,305 of glacier ice underneath us. 161 00:09:47,738 --> 00:09:50,371 CARLY HOWETT: If you ever experience visiting or seeing a glacier, 162 00:09:50,371 --> 00:09:52,905 you might think that they're completely stationary. 163 00:09:52,905 --> 00:09:54,371 But actually, if you were to 164 00:09:54,371 --> 00:09:55,371 stand there for long enough, 165 00:09:55,371 --> 00:09:56,905 you would see that they move. 166 00:09:58,071 --> 00:09:59,305 HAKEEM OLUSEYI: Glaciers form on Earth 167 00:09:59,305 --> 00:10:01,638 when snow does not melt 168 00:10:01,638 --> 00:10:03,705 season after season, and it packs down, 169 00:10:03,705 --> 00:10:07,905 and the weight of that snow compresses it into ice. 170 00:10:08,971 --> 00:10:10,405 And as more and more builds up 171 00:10:10,405 --> 00:10:11,938 and it gets heavier and heavier, 172 00:10:11,938 --> 00:10:13,871 it begins to flow. 173 00:10:16,071 --> 00:10:18,671 NARRATOR: These huge glacial ice features in Alaska 174 00:10:18,671 --> 00:10:21,338 have formed in this exact way. 175 00:10:25,371 --> 00:10:27,371 SINGER: This is an incredible landscape. 176 00:10:28,371 --> 00:10:30,871 It really reminds me of what it would be like to 177 00:10:30,871 --> 00:10:33,005 stand on Pluto. 178 00:10:33,005 --> 00:10:34,971 And it's 15 degrees Fahrenheit, 179 00:10:34,971 --> 00:10:37,738 and we're in this totally frozen landscape, 180 00:10:37,738 --> 00:10:40,605 and on Pluto, it's even colder. 181 00:10:40,605 --> 00:10:44,771 It's -390 degrees Fahrenheit. 182 00:10:44,771 --> 00:10:46,938 How can these glaciers be flowing 183 00:10:46,938 --> 00:10:49,805 when it's so cold on the surface of Pluto? 184 00:10:49,805 --> 00:10:51,838 ♪ ♪ 185 00:10:55,071 --> 00:10:58,738 NARRATOR: Water ice is frozen as solid as rock here, 186 00:10:58,738 --> 00:11:02,538 so it doesn't flow in the same way as glaciers on Earth. 187 00:11:06,671 --> 00:11:10,938 And yet, these glaciers look like they are flowing. 188 00:11:17,838 --> 00:11:22,338 We even see two glaciers that appear to flow into each other, 189 00:11:22,338 --> 00:11:26,305 combining to form a mega glacier 190 00:11:26,305 --> 00:11:29,105 that flows onto the ice plains below. 191 00:11:32,405 --> 00:11:35,638 GURNEY: So, at Pluto, we see these glaciers 192 00:11:35,638 --> 00:11:39,005 that are flowing, but it's way too cold 193 00:11:39,005 --> 00:11:41,005 for there to be flowing water, 194 00:11:41,005 --> 00:11:43,138 so what are they actually made of? 195 00:11:43,138 --> 00:11:44,571 So, it might be surprising to hear 196 00:11:44,571 --> 00:11:46,171 that the definition of ice 197 00:11:46,171 --> 00:11:48,671 really depends on who you're talking to. 198 00:11:48,671 --> 00:11:50,538 If you're talking to people 199 00:11:50,538 --> 00:11:52,305 on Earth doing their everyday things, 200 00:11:52,305 --> 00:11:55,305 then ice is just the solid form of water. 201 00:11:55,305 --> 00:11:57,938 But if you're talking to a planetary scientist, 202 00:11:57,938 --> 00:12:01,571 then ice is a way to describe a group of materials. 203 00:12:01,571 --> 00:12:05,105 It's water, but it's also ammonia and methane, 204 00:12:05,105 --> 00:12:06,805 things that are made up of a lot of carbon, 205 00:12:06,805 --> 00:12:09,471 hydrogen, oxygen, nitrogen mixed in. 206 00:12:11,271 --> 00:12:13,205 NARRATOR: On Earth, these are usually found 207 00:12:13,205 --> 00:12:15,371 as a liquid or a gas, 208 00:12:15,371 --> 00:12:16,738 but in the Solar System, 209 00:12:16,738 --> 00:12:20,005 they can be frozen into ices. 210 00:12:20,005 --> 00:12:23,471 OLUSEYI: From afar, we can tell what the composition 211 00:12:23,471 --> 00:12:25,438 of Pluto's surface is. 212 00:12:25,438 --> 00:12:28,338 But once we got there, what we didn't expect 213 00:12:28,338 --> 00:12:31,305 is the configuration of those materials. 214 00:12:31,305 --> 00:12:32,771 ♪ ♪ 215 00:12:34,738 --> 00:12:37,305 NARRATOR: A clue to the composition of the glaciers 216 00:12:37,305 --> 00:12:43,071 is Pluto's surface temperature of -390 degrees Fahrenheit. 217 00:12:43,071 --> 00:12:46,338 That's pretty close to the melting point of nitrogen, 218 00:12:46,338 --> 00:12:49,838 at around -350 degrees Fahrenheit. 219 00:12:51,038 --> 00:12:53,505 Similarly, on Earth, 220 00:12:53,505 --> 00:12:58,171 the melting point of water ice is 32 degrees Fahrenheit, 221 00:12:58,171 --> 00:13:03,905 not far from the average surface temperature of 59 degrees. 222 00:13:03,905 --> 00:13:06,938 HOWETT: For a glacier to move, it has to be made of an ice 223 00:13:06,938 --> 00:13:09,471 that's not too far away from its melting temperature, 224 00:13:09,471 --> 00:13:11,538 'cause at the bottom, what you need is-is 225 00:13:11,538 --> 00:13:13,738 the ice to melt just a little bit 226 00:13:13,738 --> 00:13:15,938 so that the glacier is able to flow, 227 00:13:15,938 --> 00:13:17,905 and on Earth, water does that-- 228 00:13:17,905 --> 00:13:21,138 the water ice isn't that far from its melting temperature-- 229 00:13:21,138 --> 00:13:23,605 but on Pluto, it's so cold, that's not the case 230 00:13:23,605 --> 00:13:26,405 for water ice, but it is the case for nitrogen ice. 231 00:13:26,405 --> 00:13:27,871 Take a breath in. 232 00:13:27,871 --> 00:13:29,205 (inhales) 233 00:13:29,205 --> 00:13:31,205 The air that is in your lungs 234 00:13:31,205 --> 00:13:32,638 includes nitrogen, 235 00:13:32,638 --> 00:13:34,005 and it's a gas for us, 236 00:13:34,005 --> 00:13:35,771 it's the air that we breathe. 237 00:13:35,771 --> 00:13:39,671 On Pluto, it's so cold that that's solid. 238 00:13:39,671 --> 00:13:42,571 (plane engine whirring) 239 00:13:42,571 --> 00:13:44,705 NARRATOR: And it's this solid nitrogen 240 00:13:44,705 --> 00:13:47,838 that creates Pluto's flowing glaciers 241 00:13:47,838 --> 00:13:50,671 that are so similar to Earth's water glaciers. 242 00:13:53,705 --> 00:13:57,038 WONG: The same physical forces are responsible 243 00:13:57,038 --> 00:13:59,971 for carving the landscapes that we see here on Earth 244 00:13:59,971 --> 00:14:02,038 and on Pluto. 245 00:14:02,038 --> 00:14:04,938 It's just using different building blocks. 246 00:14:07,205 --> 00:14:09,205 GAO: I think Pluto has definitely taught us 247 00:14:09,205 --> 00:14:11,738 that the Solar System is a giant laboratory 248 00:14:11,738 --> 00:14:12,938 where different elements can be put together 249 00:14:12,938 --> 00:14:14,271 in all kinds of interesting ways. 250 00:14:14,271 --> 00:14:16,305 ♪ ♪ 251 00:14:21,405 --> 00:14:24,505 NARRATOR: When New Horizons leaves Pluto behind, 252 00:14:24,505 --> 00:14:26,838 it turns back 253 00:14:26,838 --> 00:14:30,371 and takes one last photograph, 254 00:14:30,371 --> 00:14:34,838 revealing Pluto's breathtaking atmosphere, 255 00:14:34,838 --> 00:14:37,771 rich in the nitrogen that condenses on the surface 256 00:14:37,771 --> 00:14:39,305 to create its glaciers. 257 00:14:41,271 --> 00:14:42,771 VERBISCER: What we've seen 258 00:14:42,771 --> 00:14:45,405 in the outer Solar System from the New Horizons spacecraft 259 00:14:45,405 --> 00:14:49,838 at Pluto and beyond has been revolutionary, 260 00:14:49,838 --> 00:14:54,638 showing us diversity in ice that we don't have here on Earth. 261 00:14:57,571 --> 00:15:00,438 NARRATOR: Pluto offers a tantalizing clue 262 00:15:00,438 --> 00:15:02,405 that very distant and cold worlds 263 00:15:02,405 --> 00:15:06,205 may be as active and dynamic as Earth. 264 00:15:08,338 --> 00:15:11,171 ♪ ♪ 265 00:15:11,171 --> 00:15:13,071 Closer to the sun, 266 00:15:13,071 --> 00:15:16,271 as we enter the realm of the ice giants, 267 00:15:16,271 --> 00:15:20,171 ice appears in even more bizarre forms 268 00:15:20,171 --> 00:15:23,638 behaving in unpredictable ways. 269 00:15:25,005 --> 00:15:28,371 It is found not only on the surface 270 00:15:28,371 --> 00:15:31,638 but also deep inside planets. 271 00:15:33,305 --> 00:15:38,171 Neptune, made up of around 80% frozen icy material, 272 00:15:38,171 --> 00:15:42,238 has giant ice storms raging across it. 273 00:15:45,571 --> 00:15:49,071 Another billion miles closer to the sun... 274 00:15:50,105 --> 00:15:52,671 ...is Neptune's icy twin. 275 00:15:55,305 --> 00:15:59,871 ♪ ♪ 276 00:15:59,871 --> 00:16:05,305 Uranus is an enormous planet of icy storms. 277 00:16:05,305 --> 00:16:08,071 GURNEY: When I first saw images of Uranus, 278 00:16:08,071 --> 00:16:10,405 I thought they were absolutely beautiful. 279 00:16:10,405 --> 00:16:14,005 Blue, almost ocean-colored. 280 00:16:15,971 --> 00:16:17,338 NARRATOR: It has a feature 281 00:16:17,338 --> 00:16:20,171 that has puzzled scientists for decades: 282 00:16:20,171 --> 00:16:25,105 its vast, shimmering auroras. 283 00:16:25,105 --> 00:16:27,871 STANLEY: The aurora on Uranus are mysterious 284 00:16:27,871 --> 00:16:29,271 because flashes of light suddenly appear 285 00:16:29,271 --> 00:16:31,005 all over the planetary surface, 286 00:16:31,005 --> 00:16:32,871 and you don't know why they're happening there. 287 00:16:34,838 --> 00:16:37,838 NARRATOR: Their location is puzzling because, on Earth, 288 00:16:37,838 --> 00:16:41,305 auroras are confined to the poles. 289 00:16:41,305 --> 00:16:43,305 STANLEY: Aurora on Earth happen 290 00:16:43,305 --> 00:16:45,838 when high energy particles from the Sun 291 00:16:45,838 --> 00:16:48,071 gets funneled along magnetic field lines 292 00:16:48,071 --> 00:16:50,171 on the Earth towards the polar regions 293 00:16:50,171 --> 00:16:52,571 and there they run into atmospheric particles, 294 00:16:52,571 --> 00:16:54,505 and that causes the atmospheric particles 295 00:16:54,505 --> 00:16:55,705 to shine light. 296 00:16:57,671 --> 00:17:00,305 WONG: Earth's magnetic field is created 297 00:17:00,305 --> 00:17:03,971 by the churning motion of the liquid iron 298 00:17:03,971 --> 00:17:05,205 in Earth's outer core. 299 00:17:05,205 --> 00:17:07,838 Because iron is electrically conducting, 300 00:17:07,838 --> 00:17:12,238 when it moves, it naturally generates a magnetic field. 301 00:17:14,338 --> 00:17:17,138 NARRATOR: Magnetic fields create auroras, 302 00:17:17,138 --> 00:17:20,938 but on Uranus, this poses a mystery. 303 00:17:20,938 --> 00:17:23,138 GURNEY: We know Uranus doesn't have 304 00:17:23,138 --> 00:17:26,171 this flowing metallic core that Earth has, 305 00:17:26,171 --> 00:17:29,438 but it still has, uh, a magnetic field. 306 00:17:29,438 --> 00:17:32,105 So, how is that magnetic field being generated? 307 00:17:33,605 --> 00:17:35,071 NARRATOR: A clue could lie 308 00:17:35,071 --> 00:17:37,438 in Uranus's icy composition. 309 00:17:40,205 --> 00:17:41,705 (thunder rumbles) 310 00:17:43,671 --> 00:17:47,205 GURNEY: If you sent a spacecraft to Uranus, 311 00:17:47,205 --> 00:17:49,671 you would go through the atmosphere 312 00:17:49,671 --> 00:17:52,805 and, uh, you would see, uh, all of this, uh, gas, 313 00:17:52,805 --> 00:17:54,138 uh, because it's a gas giant. 314 00:17:54,138 --> 00:17:56,905 OLUSEYI: It's a turbulent, high-speed wind, 315 00:17:56,905 --> 00:17:59,005 gaseous environment, 316 00:17:59,005 --> 00:18:01,038 and descend inward, 317 00:18:01,038 --> 00:18:03,871 you go from gases to liquids. 318 00:18:05,538 --> 00:18:08,605 GURNEY: It would just get gradually more dense, um, 319 00:18:08,605 --> 00:18:10,005 as the pressure increases. 320 00:18:10,005 --> 00:18:12,438 And then, when you get sufficiently deep enough, 321 00:18:12,438 --> 00:18:17,705 now you enter the ice world in the interior of Uranus. 322 00:18:17,705 --> 00:18:19,905 ♪ ♪ 323 00:18:19,905 --> 00:18:22,671 (thunder crackling) 324 00:18:22,671 --> 00:18:24,171 GAO: The pressures and temperatures 325 00:18:24,171 --> 00:18:26,838 in the interior of Uranus are extreme. 326 00:18:26,838 --> 00:18:29,971 We're looking at pressures three million times that 327 00:18:29,971 --> 00:18:31,538 of the surface pressure of Earth, 328 00:18:31,538 --> 00:18:34,905 and temperatures reaching 9,000 Fahrenheit. 329 00:18:37,038 --> 00:18:39,838 NARRATOR: Surprisingly, even at these extremely high 330 00:18:39,838 --> 00:18:45,405 pressures and temperatures, water can become ice, 331 00:18:45,405 --> 00:18:49,671 but not in the form we're familiar with on Earth. 332 00:18:49,671 --> 00:18:52,171 GURNEY: Deep in the planet of Uranus, 333 00:18:52,171 --> 00:18:54,905 you get this extremely dense, uh, 334 00:18:54,905 --> 00:18:57,905 black, hot ice called "superionic ice." 335 00:19:00,238 --> 00:19:02,605 NARRATOR: At extreme pressures and temperatures 336 00:19:02,605 --> 00:19:04,738 hotter than the sun's surface, 337 00:19:04,738 --> 00:19:09,305 water is crushed into a solid form. 338 00:19:09,305 --> 00:19:10,538 Superionic ice sounds like it comes from 339 00:19:10,538 --> 00:19:12,105 a science fiction novel. 340 00:19:12,105 --> 00:19:14,905 It's really strange, and you just wouldn't expect 341 00:19:14,905 --> 00:19:16,971 that it would exist in real life. 342 00:19:18,505 --> 00:19:20,938 NARRATOR: This strange ice is unlike anything 343 00:19:20,938 --> 00:19:23,705 we find naturally on Earth. 344 00:19:23,705 --> 00:19:24,838 BERDIS: Here on Earth, 345 00:19:24,838 --> 00:19:27,138 we see all different types of ice. 346 00:19:27,138 --> 00:19:29,138 We see sleet, 347 00:19:29,138 --> 00:19:32,705 we see snow, we see ice cubes. 348 00:19:32,705 --> 00:19:35,538 But if we zoom in under a microscope, 349 00:19:35,538 --> 00:19:36,871 we see that they are all 350 00:19:36,871 --> 00:19:39,538 this very similar 351 00:19:39,538 --> 00:19:42,105 hexagon pattern. 352 00:19:42,105 --> 00:19:44,605 This is water ice as we know it on the Earth. 353 00:19:44,605 --> 00:19:46,671 It's called "ice Ih," 354 00:19:46,671 --> 00:19:49,238 and the H stands for this hexagonal shape 355 00:19:49,238 --> 00:19:51,471 that you can see in the structure. 356 00:19:51,471 --> 00:19:53,371 Here, the red balls are the oxygen 357 00:19:53,371 --> 00:19:56,238 and the white is the hydrogen; H2O, 358 00:19:56,238 --> 00:19:58,638 two hydrogens for every oxygen. 359 00:19:58,638 --> 00:19:59,805 STANLEY: There are around 360 00:19:59,805 --> 00:20:01,538 20 different types of water ice 361 00:20:01,538 --> 00:20:03,705 found in the Solar System. 362 00:20:03,705 --> 00:20:08,438 The other types that we don't find here on Earth, uh, can form 363 00:20:08,438 --> 00:20:09,771 when the temperature's really, really high 364 00:20:09,771 --> 00:20:12,438 and the pressure's really high. 365 00:20:12,438 --> 00:20:14,371 NARRATOR: And it's these conditions 366 00:20:14,371 --> 00:20:17,005 deep inside Uranus that, in theory, 367 00:20:17,005 --> 00:20:21,171 could allow this mysterious superionic ice to exist. 368 00:20:23,138 --> 00:20:26,338 GURNEY: Superionic ice is still very new. 369 00:20:26,338 --> 00:20:29,438 It took us a long time to figure out, uh, that it even existed. 370 00:20:30,438 --> 00:20:32,471 NARRATOR: But in 2018, 371 00:20:32,471 --> 00:20:36,538 scientists announced they'd made superionic ice. 372 00:20:36,538 --> 00:20:38,905 MILLOT: We did the experiment, 373 00:20:38,905 --> 00:20:41,505 and then we look at all the evidence, 374 00:20:41,505 --> 00:20:44,905 and we have to say, "Well, it's true." 375 00:20:44,905 --> 00:20:47,738 It's crazy, it's weird, it's strange, 376 00:20:47,738 --> 00:20:49,071 but it's there. 377 00:20:49,071 --> 00:20:51,438 At super-high temperatures and pressures, 378 00:20:51,438 --> 00:20:53,938 ice forms a very different structure. 379 00:20:53,938 --> 00:20:57,238 What you're looking at here are oxygen atoms, shown in red, 380 00:20:57,238 --> 00:20:58,905 now connected with one another, 381 00:20:58,905 --> 00:21:03,705 and the hydrogen atoms, in white, have broken free. 382 00:21:03,705 --> 00:21:06,138 ♪ ♪ 383 00:21:06,138 --> 00:21:07,871 NARRATOR: This unique property 384 00:21:07,871 --> 00:21:11,038 may solve the mystery of Uranus's auroras. 385 00:21:13,338 --> 00:21:15,805 OLUSEYI: Inside of superionic ice, 386 00:21:15,805 --> 00:21:17,671 what's happened is that 387 00:21:17,671 --> 00:21:20,571 the hydrogen atoms have broken free, and now they're free 388 00:21:20,571 --> 00:21:23,205 to flow around within the material, 389 00:21:23,205 --> 00:21:25,805 and they are the conductors of electricity. 390 00:21:27,205 --> 00:21:29,771 WONG: It's like something out of science fiction where 391 00:21:29,771 --> 00:21:32,171 the hydrogen atoms are flowing like water, 392 00:21:32,171 --> 00:21:36,005 conducting electricity, and potentially responsible 393 00:21:36,005 --> 00:21:39,838 for the wacky magnetic fields that we see on Uranus. 394 00:21:41,271 --> 00:21:44,138 NARRATOR: Precisely the kind of magnetic fields 395 00:21:44,138 --> 00:21:47,071 that could help generate Uranus's auroras. 396 00:21:47,071 --> 00:21:50,005 But there's still much to learn. 397 00:21:51,071 --> 00:21:54,138 GURNEY: We don't fully know what's going on inside Uranus. 398 00:21:54,138 --> 00:21:57,338 We're only just beginning looking at these icy worlds. 399 00:21:57,338 --> 00:21:59,938 We're really at the tip of the iceberg. (chuckles) 400 00:22:01,038 --> 00:22:04,705 NARRATOR: And since these ice giants, Uranus and Neptune, 401 00:22:04,705 --> 00:22:06,705 hold vast amounts of water, 402 00:22:06,705 --> 00:22:10,338 this bizarre hot black superionic ice 403 00:22:10,338 --> 00:22:13,571 may turn out to be the most common form of water 404 00:22:13,571 --> 00:22:15,638 in our Solar System. 405 00:22:21,305 --> 00:22:23,538 As we get closer to the Sun, 406 00:22:23,538 --> 00:22:26,438 ice begins to look more familiar. 407 00:22:29,305 --> 00:22:33,038 Almost a billion miles from Uranus 408 00:22:33,038 --> 00:22:34,705 lies Saturn. 409 00:22:35,671 --> 00:22:39,638 Adorned with its famous icy rings. 410 00:22:45,105 --> 00:22:47,671 Saturn's rings are truly the jewel of the Solar System. 411 00:22:47,671 --> 00:22:50,305 The first time anyone sees them through a telescope, 412 00:22:50,305 --> 00:22:52,538 you can't believe your eyes. 413 00:22:52,538 --> 00:22:55,805 NARRATOR: But we never realized the true beauty of them 414 00:22:55,805 --> 00:23:00,171 until NASA's Cassini spacecraft went to visit. 415 00:23:05,471 --> 00:23:08,105 The photographs and data sent back 416 00:23:08,105 --> 00:23:10,705 were spectacular. 417 00:23:13,338 --> 00:23:15,605 OLUSEYI: Saturn's rings 418 00:23:15,605 --> 00:23:19,605 turned out to be made up primarily of water ice 419 00:23:19,605 --> 00:23:23,171 that range in sizes from like 420 00:23:23,171 --> 00:23:26,705 smaller than a millimeter to larger than an automobile. 421 00:23:29,071 --> 00:23:31,771 NARRATOR: Icy mini-moons sweep through the rings. 422 00:23:33,938 --> 00:23:37,338 Creating what look like grooves in a record. 423 00:23:38,805 --> 00:23:40,471 HOWETT: Cassini gave us that view. 424 00:23:40,471 --> 00:23:42,171 They're absolutely astounding. 425 00:23:42,171 --> 00:23:44,971 To see the ripples in them, the gaps in them, 426 00:23:44,971 --> 00:23:47,705 just really, really lovely. 427 00:23:56,871 --> 00:23:59,105 NARRATOR: The rings are joined in their orbits 428 00:23:59,105 --> 00:24:02,105 by over 140 moons. 429 00:24:05,538 --> 00:24:08,071 And Cassini saw something intriguing 430 00:24:08,071 --> 00:24:11,271 on one of the moons farthest from Saturn. 431 00:24:19,238 --> 00:24:22,105 Iapetus is one of the oddest looking moons 432 00:24:22,105 --> 00:24:23,971 in the Solar System. 433 00:24:23,971 --> 00:24:26,338 It resembles a walnut 434 00:24:26,338 --> 00:24:28,905 with a mountain ridge around its middle. 435 00:24:31,105 --> 00:24:35,271 But that's not its strangest feature. 436 00:24:36,971 --> 00:24:38,505 In 2007, 437 00:24:38,505 --> 00:24:42,371 Cassini sent back pictures of Iapetus. 438 00:24:43,638 --> 00:24:46,305 One side icy white, 439 00:24:46,305 --> 00:24:49,638 while the other looks as if it's been painted black. 440 00:24:53,105 --> 00:24:54,471 Iapetus is one of the weirdest looking moons 441 00:24:54,471 --> 00:24:55,505 in the Solar System. 442 00:24:55,505 --> 00:24:58,171 It looks like it has two halves. 443 00:24:58,171 --> 00:25:01,605 One really bright side and one really dark side. 444 00:25:01,605 --> 00:25:02,871 We would expect the moons 445 00:25:02,871 --> 00:25:04,271 in the Saturn system 446 00:25:04,271 --> 00:25:07,338 to have formed with roughly the same brightnesses. 447 00:25:07,338 --> 00:25:09,805 The darkest materials on Iapetus 448 00:25:09,805 --> 00:25:14,238 are 20 times darker than the brightest materials. 449 00:25:14,238 --> 00:25:17,238 How can such a bizarre yin-yang moon exist? 450 00:25:17,238 --> 00:25:20,905 NARRATOR: A clue can be found in the temperature differences 451 00:25:20,905 --> 00:25:23,571 between the white and black halves of the moon. 452 00:25:25,138 --> 00:25:28,005 VERBISCER: The darker side is a warmer region. 453 00:25:28,005 --> 00:25:30,871 The temperatures are hotter on the darker side 454 00:25:30,871 --> 00:25:32,738 than on the bright side. 455 00:25:35,205 --> 00:25:37,505 NARRATOR: The dark side's daytime temperature 456 00:25:37,505 --> 00:25:40,871 can be up to 54 degrees Fahrenheit hotter 457 00:25:40,871 --> 00:25:42,338 than the bright side. 458 00:25:44,638 --> 00:25:45,838 This temperature difference 459 00:25:45,838 --> 00:25:47,705 between the black and white surfaces 460 00:25:47,705 --> 00:25:51,371 creates a peculiar feedback loop. 461 00:25:51,371 --> 00:25:52,905 (helicopter rotor blades whirring) 462 00:25:52,905 --> 00:25:55,038 Which also happens on Earth 463 00:25:55,038 --> 00:25:58,505 where scientists are studying its effects. 464 00:26:06,038 --> 00:26:09,938 WONG: So right behind me, we've got this dark glacial till 465 00:26:09,938 --> 00:26:12,971 right next to bright white snow 466 00:26:12,971 --> 00:26:14,771 created through the erosion 467 00:26:14,771 --> 00:26:16,671 of the majestic mountains around me. 468 00:26:17,971 --> 00:26:21,038 NARRATOR: These dark spots are not solid rock, 469 00:26:21,038 --> 00:26:25,905 but are dust and dirt covering the ice. 470 00:26:25,905 --> 00:26:27,605 And there's a huge, stark contrast 471 00:26:27,605 --> 00:26:30,071 between the brightness of the snow 472 00:26:30,071 --> 00:26:32,771 and the darkness of the glacial till. 473 00:26:33,838 --> 00:26:35,905 NARRATOR: This dark glacial till 474 00:26:35,905 --> 00:26:39,705 has what scientists call a low albedo. 475 00:26:39,705 --> 00:26:42,471 WONG: Which means that it absorbs most of the sunlight 476 00:26:42,471 --> 00:26:44,305 that hits it, heating it up, 477 00:26:44,305 --> 00:26:47,238 and that heat gets transferred to the surrounding snow, 478 00:26:47,238 --> 00:26:50,305 melting it into liquid water, 479 00:26:50,305 --> 00:26:52,238 causing the dark streaks that you see 480 00:26:52,238 --> 00:26:56,138 coming down the side of that cliff. 481 00:26:56,138 --> 00:26:58,905 And a very similar process happens on Iapetus. 482 00:27:01,338 --> 00:27:05,271 NARRATOR: With so little light and heat from the sun, 483 00:27:05,271 --> 00:27:08,871 it's a very slow process. 484 00:27:11,705 --> 00:27:13,371 Over a billion years, 485 00:27:13,371 --> 00:27:17,905 it's estimated the dark regions can lose around 66 feet of ice 486 00:27:17,905 --> 00:27:20,571 compared to the white side. 487 00:27:22,105 --> 00:27:25,005 As this feedback mechanism continues, 488 00:27:25,005 --> 00:27:26,838 it keeps the black side black... 489 00:27:28,038 --> 00:27:30,571 ...and the white side white. 490 00:27:30,571 --> 00:27:32,471 But a mystery remains. 491 00:27:33,838 --> 00:27:37,471 Where did all the dark material come from in the first place? 492 00:27:38,771 --> 00:27:40,071 VERBISCER: Did the dark material 493 00:27:40,071 --> 00:27:41,838 come from inside of Iapetus 494 00:27:41,838 --> 00:27:45,038 or did it come from someplace else? 495 00:27:49,171 --> 00:27:53,305 NARRATOR: The smoking gun was discovered by complete accident. 496 00:27:55,305 --> 00:27:57,938 VERBISCER: So, in 2005, I was observing 497 00:27:57,938 --> 00:28:00,105 another moon of Saturn called Phoebe, 498 00:28:00,105 --> 00:28:04,338 which orbits Saturn much further away than Iapetus does. 499 00:28:05,705 --> 00:28:07,738 SINGER: Phoebe is in an unusual orbit 500 00:28:07,738 --> 00:28:11,005 because it goes backwards with respect to the other moons 501 00:28:11,005 --> 00:28:13,938 in its direction around Saturn. 502 00:28:17,838 --> 00:28:20,705 VERBISCER: If you look at the Cassini images of Phoebe, 503 00:28:20,705 --> 00:28:25,038 you see that it is a pretty heavily cratered surface. 504 00:28:25,038 --> 00:28:28,771 So, it's been hit with things for billions of years, 505 00:28:28,771 --> 00:28:32,038 and material has been excavated 506 00:28:32,038 --> 00:28:34,371 and thrown into the space around Phoebe. 507 00:28:34,371 --> 00:28:37,005 The question is, where did all that material go? 508 00:28:38,538 --> 00:28:40,938 Where are all those dust particles? 509 00:28:40,938 --> 00:28:44,605 So, we got the idea to use the Spitzer Space Telescope 510 00:28:44,605 --> 00:28:47,005 to try and look for dust 511 00:28:47,005 --> 00:28:48,971 in the region around Phoebe. 512 00:28:50,305 --> 00:28:53,871 NARRATOR: The Spitzer Space Telescope used infrared light, 513 00:28:53,871 --> 00:28:55,705 or heat signatures, to detect 514 00:28:55,705 --> 00:28:57,705 what's normally hidden from view. 515 00:28:58,838 --> 00:29:00,171 SINGER: If you were able to see 516 00:29:00,171 --> 00:29:02,805 how the Spitzer telescope sees, 517 00:29:02,805 --> 00:29:05,271 it would be like when you put on night vision goggles, 518 00:29:05,271 --> 00:29:08,805 and all of a sudden, you're able to see in the dark. 519 00:29:14,671 --> 00:29:16,038 VERBISCER: We got our images, 520 00:29:16,038 --> 00:29:18,471 and they were extremely interesting. 521 00:29:19,638 --> 00:29:22,571 NARRATOR: Phoebe rides within a colossal ring 522 00:29:22,571 --> 00:29:25,338 about ten million miles across, 523 00:29:25,338 --> 00:29:27,371 wrapped around Saturn. 524 00:29:28,638 --> 00:29:32,338 VERBISCER: It is the largest ring by far in the Solar System. 525 00:29:32,338 --> 00:29:35,971 This ring is so big that a billion Earths 526 00:29:35,971 --> 00:29:38,171 could fit inside the volume of the ring. 527 00:29:38,171 --> 00:29:40,138 It makes perfect sense that this ring 528 00:29:40,138 --> 00:29:41,571 should be called the Phoebe ring 529 00:29:41,571 --> 00:29:45,771 because it is associated so closely with the moon Phoebe. 530 00:29:47,171 --> 00:29:50,138 NARRATOR: The Phoebe ring moves around Saturn, 531 00:29:50,138 --> 00:29:53,305 in the same direction as its moon Phoebe, 532 00:29:53,305 --> 00:29:56,005 backwards from the other moons and rings. 533 00:30:00,805 --> 00:30:03,971 Each time a passing object or rocky debris 534 00:30:03,971 --> 00:30:07,105 gets too close to Phoebe... 535 00:30:07,105 --> 00:30:08,705 boom. 536 00:30:09,905 --> 00:30:11,971 The resulting impact 537 00:30:11,971 --> 00:30:15,138 throws dark material out into space. 538 00:30:18,371 --> 00:30:20,138 SINGER: Some of this dark material 539 00:30:20,138 --> 00:30:23,705 in this huge ring starts to fall in towards Saturn, 540 00:30:23,705 --> 00:30:25,905 and Iapetus is basically 541 00:30:25,905 --> 00:30:29,038 running through those particles in its orbit. 542 00:30:30,505 --> 00:30:32,905 NARRATOR: How Iapetus orbits Saturn 543 00:30:32,905 --> 00:30:35,438 is key to solving the mystery 544 00:30:35,438 --> 00:30:38,571 of why it has these black and white halves. 545 00:30:41,505 --> 00:30:44,171 (wind howling) 546 00:30:44,171 --> 00:30:47,471 WONG: So Iapetus, like our moon that orbits the Earth, 547 00:30:47,471 --> 00:30:50,738 is tidally locked, which means one side of Iapetus 548 00:30:50,738 --> 00:30:52,338 always faces Saturn, 549 00:30:52,338 --> 00:30:55,105 the other side always faces away from Saturn. 550 00:30:56,171 --> 00:30:59,938 Imagine this snowball is a freshly formed Iapetus, 551 00:30:59,938 --> 00:31:03,971 completely uniform in its brightness on all sides. 552 00:31:03,971 --> 00:31:08,271 Now, as it orbits around Saturn, through the Phoebe ring, 553 00:31:08,271 --> 00:31:11,471 it will pick up dark dust particles 554 00:31:11,471 --> 00:31:13,138 from that ring. 555 00:31:13,138 --> 00:31:16,305 And because it is tidally locked to Saturn, 556 00:31:16,305 --> 00:31:18,038 the same hemisphere 557 00:31:18,038 --> 00:31:20,338 will keep piling on dust 558 00:31:20,338 --> 00:31:22,038 every time it goes around 559 00:31:22,038 --> 00:31:25,038 for millions and millions of years, 560 00:31:25,038 --> 00:31:28,871 continuously darkening this side of Iapetus. 561 00:31:32,638 --> 00:31:33,971 DURFEY: As soon as the front side 562 00:31:33,971 --> 00:31:36,038 of Iapetus became darkened, 563 00:31:36,038 --> 00:31:40,338 the ice underneath started heating up more quickly, 564 00:31:40,338 --> 00:31:43,805 so that would become a gas and migrate around 565 00:31:43,805 --> 00:31:47,505 to the colder, lighter side of Iapetus. 566 00:31:48,905 --> 00:31:52,205 NARRATOR: The ice vaporizes from the darker, warmer side 567 00:31:52,205 --> 00:31:55,438 and refreezes onto the colder, lighter side. 568 00:31:56,805 --> 00:31:58,838 DURFEY: And so, this means over time, 569 00:31:58,838 --> 00:32:01,138 the dark side becomes darker, 570 00:32:01,138 --> 00:32:03,171 the light side becomes lighter. 571 00:32:04,305 --> 00:32:06,438 NARRATOR: It's a slow process, 572 00:32:06,438 --> 00:32:08,838 one dust particle at a time. 573 00:32:10,338 --> 00:32:12,338 But it's the best explanation 574 00:32:12,338 --> 00:32:14,905 of how this peculiar moon 575 00:32:14,905 --> 00:32:18,171 got its self-sustaining, warm, dark face. 576 00:32:19,505 --> 00:32:21,005 OLUSEYI: Iapetus just shows us the potential 577 00:32:21,005 --> 00:32:22,538 of the interconnectedness 578 00:32:22,538 --> 00:32:25,171 between the planetary bodies of our Solar System. 579 00:32:26,205 --> 00:32:29,505 We think they're isolated, but nothing's isolated. 580 00:32:31,105 --> 00:32:33,938 NARRATOR: Iapetus is not the only icy moon affected 581 00:32:33,938 --> 00:32:36,705 by the system it exists within. 582 00:32:37,738 --> 00:32:40,038 Another moon closer to the sun 583 00:32:40,038 --> 00:32:43,271 reveals not only a unique connection with its neighbor, 584 00:32:43,271 --> 00:32:45,538 but also hints 585 00:32:45,538 --> 00:32:47,938 that something potentially profound 586 00:32:47,938 --> 00:32:50,505 could lurk beneath its surface. 587 00:32:54,471 --> 00:32:57,238 NASA LAUNCH ANNOUNCER: T minus five, four, 588 00:32:57,238 --> 00:33:00,671 three, two, one. 589 00:33:00,671 --> 00:33:03,738 Ignition and liftoff 590 00:33:03,738 --> 00:33:07,505 of the Atlas V with Juno on a trek to Jupiter. 591 00:33:09,071 --> 00:33:11,438 NARRATOR: The Juno mission is to investigate the origin 592 00:33:11,438 --> 00:33:14,705 and evolution of the gas giant Jupiter, 593 00:33:14,705 --> 00:33:18,971 the largest planet in our Solar System. 594 00:33:22,571 --> 00:33:24,305 LYNNAE QUICK: The main goal of the Juno spacecraft 595 00:33:24,305 --> 00:33:25,638 is to study Jupiter. 596 00:33:25,638 --> 00:33:27,071 However, 597 00:33:27,071 --> 00:33:28,538 as it orbits Jupiter, 598 00:33:28,538 --> 00:33:30,238 it's taking these wonderful images 599 00:33:30,238 --> 00:33:32,371 of Jupiter's largest moons. 600 00:33:34,905 --> 00:33:36,938 NARRATOR: Ganymede, 601 00:33:36,938 --> 00:33:39,471 the largest moon in the Solar System. 602 00:33:41,005 --> 00:33:43,971 Io, the most volcanically active. 603 00:33:48,171 --> 00:33:51,671 And then, there's the icy moon, Europa, 604 00:33:51,671 --> 00:33:55,305 the odd one out with the smoothest surface. 605 00:33:56,971 --> 00:34:01,305 It's an ancient moon, billions of years old, 606 00:34:01,305 --> 00:34:03,171 and yet, mysteriously, 607 00:34:03,171 --> 00:34:06,071 has a young surface, with few craters. 608 00:34:06,071 --> 00:34:07,471 DURFEY: We can get 609 00:34:07,471 --> 00:34:10,305 an idea of how old a planetary surface is 610 00:34:10,305 --> 00:34:12,405 by counting the number of impact craters. 611 00:34:12,405 --> 00:34:15,338 Europa barely has any impact craters, 612 00:34:15,338 --> 00:34:18,505 which means that its surface must be really young. 613 00:34:19,638 --> 00:34:22,205 NARRATOR: And that's not all that makes Europa different. 614 00:34:25,105 --> 00:34:31,205 It's criss-crossed by a strange network of striking red lines. 615 00:34:31,205 --> 00:34:33,071 GONZALEZ: The surface of Europa 616 00:34:33,071 --> 00:34:37,905 has a lot of interesting cracks and features to it, 617 00:34:37,905 --> 00:34:40,071 and has lots of lines, 618 00:34:40,071 --> 00:34:42,571 which look almost like a network 619 00:34:42,571 --> 00:34:44,871 of blood vessels in an eye. 620 00:34:46,105 --> 00:34:48,138 ♪ ♪ 621 00:34:50,638 --> 00:34:54,438 NARRATOR: These lines are vast ice cracks, 622 00:34:54,438 --> 00:34:58,471 some of which are 15 miles wide, 623 00:34:58,471 --> 00:35:00,805 with a dark red floor. 624 00:35:03,338 --> 00:35:04,905 OLUSEYI: What could be creating 625 00:35:04,905 --> 00:35:08,571 these criss-crossing lines and patterns on Europa's surface? 626 00:35:14,371 --> 00:35:16,605 ♪ ♪ 627 00:35:26,571 --> 00:35:29,271 QUICK: The canyons on Europa are so significant 628 00:35:29,271 --> 00:35:30,605 that NASA's planning a mission 629 00:35:30,605 --> 00:35:32,238 to go to Europa to explore them. 630 00:35:33,271 --> 00:35:35,105 NARRATOR: And in preparation, 631 00:35:35,105 --> 00:35:39,105 scientists are exploring similar environments on Earth, 632 00:35:39,105 --> 00:35:42,071 like these icy terrains in Alaska. 633 00:35:45,505 --> 00:35:47,071 (wind whistling) 634 00:35:54,671 --> 00:35:58,071 SAM HOWELL: I think many of the most important questions 635 00:35:58,071 --> 00:36:01,305 in planetary science can be addressed 636 00:36:01,305 --> 00:36:03,371 by going to worlds like Europa. 637 00:36:05,338 --> 00:36:07,738 NARRATOR: NASA scientist Sam Howell is studying 638 00:36:07,738 --> 00:36:12,705 what may be at the heart of Europa's mysterious appearance. 639 00:36:12,705 --> 00:36:14,305 HOWELL: What I'm most excited about, 640 00:36:14,305 --> 00:36:15,905 coming from a background 641 00:36:15,905 --> 00:36:17,571 in studying plate tectonics here on Earth, 642 00:36:17,571 --> 00:36:19,471 we see systems of rigid, 643 00:36:19,471 --> 00:36:22,005 icy plates moving around similar 644 00:36:22,005 --> 00:36:24,805 to the way Earth's plate tectonics looks on the surface. 645 00:36:24,805 --> 00:36:27,605 But digging in, we expect those processes to be very different. 646 00:36:28,605 --> 00:36:31,371 NARRATOR: Europa's surface features indicate 647 00:36:31,371 --> 00:36:34,305 they are a result of tectonic activity. 648 00:36:35,338 --> 00:36:36,938 BERDIS: This is an up-close image 649 00:36:36,938 --> 00:36:39,171 of Europa's surface, and you can see 650 00:36:39,171 --> 00:36:42,105 this large, dark red band 651 00:36:42,105 --> 00:36:44,105 in the very center of the image. 652 00:36:44,105 --> 00:36:45,605 We know that this feature is created 653 00:36:45,605 --> 00:36:47,305 due to tectonic activity 654 00:36:47,305 --> 00:36:49,638 because it appears that the crust 655 00:36:49,638 --> 00:36:51,638 of Europa has pulled apart, 656 00:36:51,638 --> 00:36:53,238 and you've had material flow up from underneath. 657 00:36:53,238 --> 00:36:55,705 But if we were to take this feature 658 00:36:55,705 --> 00:36:57,738 and extract it from this image, 659 00:36:57,738 --> 00:37:01,571 both sides of the crust would fit back together 660 00:37:01,571 --> 00:37:02,838 like a puzzle piece. 661 00:37:02,838 --> 00:37:06,238 We did not expect to see tectonic activity 662 00:37:06,238 --> 00:37:09,805 on a tiny moon like this, but there it is. 663 00:37:11,638 --> 00:37:13,271 NARRATOR: So far, this kind 664 00:37:13,271 --> 00:37:18,538 of global tectonic activity has only been observed on Earth. 665 00:37:18,538 --> 00:37:20,071 OLUSEYI: Take a look at Earth, 666 00:37:20,071 --> 00:37:22,405 and you'll see that South America looks like 667 00:37:22,405 --> 00:37:25,405 it fits right neatly in there into Africa. 668 00:37:26,438 --> 00:37:29,638 And so, we know that in the Atlantic, 669 00:37:29,638 --> 00:37:31,371 the seafloor is spreading, 670 00:37:31,371 --> 00:37:33,771 and that's what spread those two features apart. 671 00:37:37,238 --> 00:37:41,605 NARRATOR: On Earth, the rocky crust is broken into plates. 672 00:37:41,605 --> 00:37:45,471 They move as softer rock beneath flows very slowly 673 00:37:45,471 --> 00:37:47,938 over geologic time. 674 00:37:47,938 --> 00:37:51,905 QUICK: Europa does not have molten rock like Earth does, 675 00:37:51,905 --> 00:37:55,438 but what we do believe Europa has is a subsurface ocean. 676 00:37:58,471 --> 00:38:00,771 NARRATOR: A vast body of liquid water 677 00:38:00,771 --> 00:38:04,538 that exists underneath its icy surface. 678 00:38:04,538 --> 00:38:06,638 WONG: There is more water 679 00:38:06,638 --> 00:38:08,638 in Europa's subsurface 680 00:38:08,638 --> 00:38:11,538 than all of Earth's oceans, rivers and lakes combined. 681 00:38:14,471 --> 00:38:17,305 NARRATOR: This massive ocean sits beneath a layer 682 00:38:17,305 --> 00:38:22,405 of water ice, which could be up to 15 miles thick in places. 683 00:38:24,738 --> 00:38:27,438 So what force is powerful enough 684 00:38:27,438 --> 00:38:30,771 to crack Europa's extensive icy shell? 685 00:38:32,771 --> 00:38:37,071 BERDIS: As Europa and all of the other large moons orbit Jupiter 686 00:38:37,071 --> 00:38:38,371 and interact with it, 687 00:38:38,371 --> 00:38:40,105 they are all constantly pushing 688 00:38:40,105 --> 00:38:42,638 and pulling and tugging on each other, 689 00:38:42,638 --> 00:38:44,071 and this process is called "tidal heating." 690 00:38:47,005 --> 00:38:49,005 NARRATOR: The tidal heating varies, 691 00:38:49,005 --> 00:38:52,505 depending on how close or far Europa is from Jupiter 692 00:38:52,505 --> 00:38:55,038 and the other moons, 693 00:38:55,038 --> 00:38:57,871 resulting in temperature changes in the ocean. 694 00:38:59,838 --> 00:39:02,538 QUICK: And as the temperature of the ocean changes, 695 00:39:02,538 --> 00:39:06,505 the ice shell thickens and thins and expands and contracts. 696 00:39:06,505 --> 00:39:08,671 (wind whistling) 697 00:39:08,671 --> 00:39:11,138 NARRATOR: The mechanics of which can be seen on Earth. 698 00:39:12,271 --> 00:39:13,738 QUICK: As water freezes, 699 00:39:13,738 --> 00:39:16,638 it takes up more space and expands into ice. 700 00:39:16,638 --> 00:39:19,771 It's very similar to if we were to take a bottle of water 701 00:39:19,771 --> 00:39:21,305 and place it into the freezer. 702 00:39:21,305 --> 00:39:22,838 First, it would expand, 703 00:39:22,838 --> 00:39:24,771 and then we'd notice a large bit of cracking. 704 00:39:24,771 --> 00:39:26,905 This is what is happening on Europa. 705 00:39:29,238 --> 00:39:31,438 NARRATOR: Scaled up to the size of a moon, 706 00:39:31,438 --> 00:39:35,538 these ice expansion cracks create massive canyons 707 00:39:35,538 --> 00:39:37,571 across Europa. 708 00:39:43,671 --> 00:39:46,771 And as these canyons form, 709 00:39:46,771 --> 00:39:50,638 a key ingredient from the ocean below surges up 710 00:39:50,638 --> 00:39:52,271 through the cracks, 711 00:39:52,271 --> 00:39:56,171 giving Europa's markings their distinctive red. 712 00:40:00,771 --> 00:40:03,438 BERDIS: So the red marks that we see on Europa's surface-- 713 00:40:03,438 --> 00:40:05,671 these cracks and lines-- 714 00:40:05,671 --> 00:40:08,238 are salts 715 00:40:08,238 --> 00:40:10,571 that have come up from below the surface. 716 00:40:10,571 --> 00:40:13,438 ♪ ♪ 717 00:40:13,438 --> 00:40:16,238 NARRATOR: Suggesting a tantalizing possibility. 718 00:40:18,138 --> 00:40:21,338 This crisscrossing system of salty canyons means 719 00:40:21,338 --> 00:40:24,138 we might find life in the ocean 720 00:40:24,138 --> 00:40:26,405 underneath Europa's icy shell. 721 00:40:28,705 --> 00:40:31,971 SINGER: Life as we know it needs three basic things: 722 00:40:31,971 --> 00:40:33,538 water, 723 00:40:33,538 --> 00:40:37,405 a source of energy, and also, essential elements. 724 00:40:40,738 --> 00:40:42,638 NARRATOR: Europa has an ocean, 725 00:40:42,638 --> 00:40:45,638 and a source of energy from tidal movements. 726 00:40:47,205 --> 00:40:50,438 But it's missing the final key ingredient: 727 00:40:50,438 --> 00:40:52,938 some essential elements. 728 00:40:53,971 --> 00:40:58,271 However, with a little help from its neighboring moon Io, 729 00:40:58,271 --> 00:41:00,905 these elements can be found on Europa. 730 00:41:02,505 --> 00:41:03,838 SINGER: Io 731 00:41:03,838 --> 00:41:06,138 is an extremely volcanically-active place. 732 00:41:08,905 --> 00:41:10,638 And these volcanoes emit 733 00:41:10,638 --> 00:41:13,071 sulphur and other sulphur products, 734 00:41:13,071 --> 00:41:15,671 and these make it all the way onto Europa. 735 00:41:16,971 --> 00:41:21,771 And sulphur is one of those essential elements that life 736 00:41:21,771 --> 00:41:23,338 on Earth uses. 737 00:41:23,338 --> 00:41:25,838 ♪ ♪ 738 00:41:27,605 --> 00:41:29,738 BERDIS: All of the sulphur that's coming from Io 739 00:41:29,738 --> 00:41:31,605 and landing on Europa's surface 740 00:41:31,605 --> 00:41:35,071 is interacting with the salts and water 741 00:41:35,071 --> 00:41:39,071 that's coming up from underneath Europa's icy crust. 742 00:41:40,371 --> 00:41:43,771 NARRATOR: Chemical reactions between the sulphur from Io 743 00:41:43,771 --> 00:41:47,238 and the salts on Europa create essential molecules 744 00:41:47,238 --> 00:41:49,471 needed for life. 745 00:41:52,705 --> 00:41:54,438 And this allows for this perfect breeding ground 746 00:41:54,438 --> 00:41:57,371 for potential life to form and evolve. 747 00:41:59,005 --> 00:42:02,405 NARRATOR: Europa is such a strong candidate for life 748 00:42:02,405 --> 00:42:06,005 that NASA is already preparing to explore the moon. 749 00:42:08,071 --> 00:42:10,871 The goal is to study Europa's surface 750 00:42:10,871 --> 00:42:12,438 in more detail 751 00:42:12,438 --> 00:42:15,271 so that a future mission can one day land 752 00:42:15,271 --> 00:42:18,605 and explore beneath its icy crust. 753 00:42:20,505 --> 00:42:24,938 And scientists like Sam are already testing ideas 754 00:42:24,938 --> 00:42:27,405 for studying Europa's watery world. 755 00:42:31,238 --> 00:42:34,571 HOWELL: What we're doing is we're deploying a robotic probe 756 00:42:34,571 --> 00:42:36,505 into the ice and under it 757 00:42:36,505 --> 00:42:38,371 to explore what this lake environment is like. 758 00:42:40,305 --> 00:42:42,271 We might have the opportunity 759 00:42:42,271 --> 00:42:44,038 in my own lifetime 760 00:42:44,038 --> 00:42:47,671 to answer a question that's intrinsic to all of us: 761 00:42:47,671 --> 00:42:49,905 are we alone in our universe? 762 00:42:49,905 --> 00:42:52,105 Are we alone in our Solar System? 763 00:42:52,105 --> 00:42:55,171 And one of the most exciting aspects of exploring Europa 764 00:42:55,171 --> 00:42:59,205 is the potential of someday knowing 765 00:42:59,205 --> 00:43:02,605 whether or not there's life in our own Solar System. 766 00:43:04,671 --> 00:43:07,071 NARRATOR: Europa is one of the last ice moons 767 00:43:07,071 --> 00:43:09,671 that can exist this close to the sun. 768 00:43:10,638 --> 00:43:14,171 Worlds existing any closer to the warmth of the sun, 769 00:43:14,171 --> 00:43:17,971 like the rocky worlds of Mars, Earth, and our moon, 770 00:43:17,971 --> 00:43:19,971 have relatively little ice. 771 00:43:21,371 --> 00:43:25,105 Because they lie inside what is known as the ice line. 772 00:43:28,705 --> 00:43:30,805 DURFEY: You can't see the ice line, 773 00:43:30,805 --> 00:43:32,905 but you can see its effects. 774 00:43:32,905 --> 00:43:33,938 When small bodies that are 775 00:43:33,938 --> 00:43:35,671 primarily composed of ice 776 00:43:35,671 --> 00:43:38,238 cross inside of the ice line, 777 00:43:38,238 --> 00:43:40,638 the ice within them begins to vaporize. 778 00:43:42,838 --> 00:43:45,638 NARRATOR: Sometimes, icy rocks are ejected 779 00:43:45,638 --> 00:43:49,205 from the frigid outer regions of the Solar System 780 00:43:49,205 --> 00:43:51,605 and pulled towards the sun. 781 00:43:53,471 --> 00:43:55,938 These are known as comets. 782 00:43:57,938 --> 00:43:59,938 HOWETT: Comets are basically dirty snowballs, 783 00:43:59,938 --> 00:44:02,305 mostly water ice with a little bit of dust, 784 00:44:02,305 --> 00:44:04,371 and as they come into the inner Solar System, 785 00:44:04,371 --> 00:44:05,771 they get heated up by the sun. 786 00:44:07,871 --> 00:44:10,838 NARRATOR: As comets cross this invisible ice line, 787 00:44:10,838 --> 00:44:13,105 their ice starts turning into gas. 788 00:44:14,471 --> 00:44:16,938 HOWETT: And that's what forms these long tails 789 00:44:16,938 --> 00:44:19,038 that we can see when you look at a comet, 790 00:44:19,038 --> 00:44:21,338 and those tails stream away from the sun 791 00:44:21,338 --> 00:44:23,505 as the comet moves in towards it. 792 00:44:27,905 --> 00:44:31,238 NARRATOR: Inside the ice line, ice is rare, 793 00:44:31,238 --> 00:44:34,938 but there are places where it can hang on. 794 00:44:39,838 --> 00:44:43,305 DURFEY: Mars is within the ice line of the Solar System, 795 00:44:43,305 --> 00:44:46,438 but it still has ice in it and on it. 796 00:44:50,938 --> 00:44:53,105 NARRATOR: It's the end of winter, 797 00:44:53,105 --> 00:44:55,705 and it's been dark at Mars's south pole 798 00:44:55,705 --> 00:44:59,471 for over 150 Martian days straight. 799 00:45:01,338 --> 00:45:04,205 Mars holds onto much of its ice at its poles. 800 00:45:06,271 --> 00:45:09,105 The ice sheet here is not like any on Earth. 801 00:45:10,471 --> 00:45:13,371 Because as winter turns to spring, 802 00:45:13,371 --> 00:45:17,305 the surface becomes covered in strange features. 803 00:45:21,238 --> 00:45:24,671 And with the launch of the Mars Reconnaissance Orbiter 804 00:45:24,671 --> 00:45:28,838 in 2005, we began to see them 805 00:45:28,838 --> 00:45:31,538 like never before. 806 00:45:31,538 --> 00:45:33,605 OLUSEYI: The Mars Reconnaissance Orbiter 807 00:45:33,605 --> 00:45:35,438 is a satellite of Mars that takes 808 00:45:35,438 --> 00:45:36,738 photograph after photograph 809 00:45:36,738 --> 00:45:38,038 of Mars's surface, 810 00:45:38,038 --> 00:45:40,071 and so it's able to see these things come and go 811 00:45:40,071 --> 00:45:41,971 and change with the seasons. 812 00:45:45,238 --> 00:45:49,838 NARRATOR: The images show dark fans on the surface 813 00:45:49,838 --> 00:45:53,638 meaning something must have risen into the air above them. 814 00:45:55,338 --> 00:45:56,905 GONZALEZ: We see these features, 815 00:45:56,905 --> 00:45:59,505 and they will go in the direction 816 00:45:59,505 --> 00:46:01,438 depending on the wind pattern of Mars. 817 00:46:01,438 --> 00:46:03,471 So we know that material 818 00:46:03,471 --> 00:46:06,138 is being pushed out from underneath. 819 00:46:07,371 --> 00:46:09,638 NARRATOR: This phenomenon seen on Mars 820 00:46:09,638 --> 00:46:13,505 depends on the type of ice that falls from the Martian skies. 821 00:46:16,838 --> 00:46:19,071 During winter at the South Pole, 822 00:46:19,071 --> 00:46:21,205 more and more snow falls. 823 00:46:23,038 --> 00:46:26,005 But with so little water in Mars's atmosphere, 824 00:46:26,005 --> 00:46:28,938 this isn't the type of snow we have on Earth. 825 00:46:30,038 --> 00:46:33,305 This is carbon dioxide snow. 826 00:46:34,338 --> 00:46:38,038 GAO: Every winter, three to four trillion tons 827 00:46:38,038 --> 00:46:40,405 of carbon dioxide snow falls on Mars. 828 00:46:40,405 --> 00:46:43,638 That's so much snow that the atmospheric pressure 829 00:46:43,638 --> 00:46:47,405 at the surface of Mars decreases by about a third. 830 00:46:47,405 --> 00:46:50,438 NARRATOR: The air is literally freezing to the ground, 831 00:46:50,438 --> 00:46:54,038 forming carbon dioxide ice caps at the poles. 832 00:46:57,005 --> 00:47:00,238 But in spring, as the warmth of the sun reaches 833 00:47:00,238 --> 00:47:04,038 the poles again, something incredible happens. 834 00:47:05,271 --> 00:47:08,038 DURFEY: As the sun comes over the horizon, 835 00:47:08,038 --> 00:47:11,338 the carbon dioxide ice is heated. 836 00:47:17,671 --> 00:47:20,905 This carbon dioxide ice can turn to gas, 837 00:47:20,905 --> 00:47:23,738 and when it does, it forms these geysers 838 00:47:23,738 --> 00:47:27,138 that also bring other material from the subsurface 839 00:47:27,138 --> 00:47:28,471 to the surface. 840 00:47:31,205 --> 00:47:32,938 GONZALEZ: And depending on which way the wind 841 00:47:32,938 --> 00:47:36,505 is blowing, it'll form these nice looking fan features. 842 00:47:37,771 --> 00:47:39,905 NARRATOR: Because of Mars's combination 843 00:47:39,905 --> 00:47:42,238 of atmospheric pressure and temperature... 844 00:47:43,271 --> 00:47:46,305 ...the carbon dioxide turns from ice to gas 845 00:47:46,305 --> 00:47:48,405 without passing through the liquid phase. 846 00:47:50,438 --> 00:47:52,671 WONG: On Mars, its atmosphere 847 00:47:52,671 --> 00:47:55,505 actually falls onto the surface 848 00:47:55,505 --> 00:47:58,771 and then vaporizes back into the atmosphere 849 00:47:58,771 --> 00:48:00,638 on an annual basis. 850 00:48:00,638 --> 00:48:02,271 That's absolutely wild 851 00:48:02,271 --> 00:48:05,038 because it's so different from what's happening here on Earth. 852 00:48:08,271 --> 00:48:10,238 NARRATOR: These conditions on Mars 853 00:48:10,238 --> 00:48:12,538 have enabled carbon dioxide snow 854 00:48:12,538 --> 00:48:15,371 to create unique features on its surface. 855 00:48:18,271 --> 00:48:21,605 But the conditions found on its nearest neighbor, 856 00:48:21,605 --> 00:48:25,838 close enough to see from Mars with the naked eye, 857 00:48:25,838 --> 00:48:29,505 have allowed for something extraordinary to form. 858 00:48:33,705 --> 00:48:35,571 And just like Mars, 859 00:48:35,571 --> 00:48:39,005 Earth, too, has ice caps at its poles. 860 00:48:41,005 --> 00:48:43,438 But the similarities end there. 861 00:48:45,238 --> 00:48:46,905 HOWETT: Earth's ice is really unique 862 00:48:46,905 --> 00:48:49,905 because we operate in a very small temperature range 863 00:48:49,905 --> 00:48:52,205 and a very small pressure range on the surface. 864 00:48:52,205 --> 00:48:55,371 The ice that we experience is a very small subset 865 00:48:55,371 --> 00:48:57,538 of the total ice that's in our universe. 866 00:49:00,405 --> 00:49:02,305 NARRATOR: Earth's temperature and pressure ranges 867 00:49:02,305 --> 00:49:05,805 allow water to exist in all three states: 868 00:49:05,805 --> 00:49:08,738 solid, liquid, and gas. 869 00:49:10,538 --> 00:49:13,871 Earth is the only place known to have floating icebergs 870 00:49:13,871 --> 00:49:17,238 and bodies of water not completely frozen over. 871 00:49:18,505 --> 00:49:21,305 And frozen water under Earth's conditions 872 00:49:21,305 --> 00:49:23,471 has an important property. 873 00:49:25,105 --> 00:49:26,505 We might take this for granted, 874 00:49:26,505 --> 00:49:28,305 but the ice that we have here on Earth 875 00:49:28,305 --> 00:49:31,605 floats because its density 876 00:49:31,605 --> 00:49:34,838 is lower than the water that it is floating in. 877 00:49:34,838 --> 00:49:38,238 And so, the molecules of water ice, 878 00:49:38,238 --> 00:49:41,238 as it freezes, expands out slightly 879 00:49:41,238 --> 00:49:42,938 and moves away from each other 880 00:49:42,938 --> 00:49:45,605 to lower the overall density of the ice, 881 00:49:45,605 --> 00:49:48,638 and this allows it to float on top of the water. 882 00:49:50,205 --> 00:49:53,071 NARRATOR: This property of water ice has enormous consequences 883 00:49:53,071 --> 00:49:55,638 for life on Earth, 884 00:49:55,638 --> 00:49:59,271 the only place life is known to exist to date. 885 00:50:00,438 --> 00:50:03,571 BERDIS: The ice on Earth provides a form of protection 886 00:50:03,571 --> 00:50:05,805 to any life below the surface 887 00:50:05,805 --> 00:50:09,238 that might need protection from anything that could harm it. 888 00:50:11,171 --> 00:50:12,771 NARRATOR: Ice's ability to float 889 00:50:12,771 --> 00:50:15,505 means that, during Earth's colder periods, 890 00:50:15,505 --> 00:50:19,471 bodies of water didn't freeze from the bottom up, 891 00:50:19,471 --> 00:50:21,338 instead remaining a liquid 892 00:50:21,338 --> 00:50:24,805 where life may have held on. 893 00:50:24,805 --> 00:50:27,305 (birds and insects chirping) 894 00:50:27,305 --> 00:50:29,571 For around four billion years, 895 00:50:29,571 --> 00:50:32,405 liquid water on Earth 896 00:50:32,405 --> 00:50:34,338 has allowed an unbroken chain 897 00:50:34,338 --> 00:50:36,371 of life to evolve. 898 00:50:38,871 --> 00:50:41,671 Resulting in oceans. 899 00:50:41,671 --> 00:50:45,505 Home to countless species. 900 00:50:45,505 --> 00:50:48,438 And rivers teeming with life. 901 00:50:49,405 --> 00:50:52,605 All made possible by the unique interplay 902 00:50:52,605 --> 00:50:56,471 between liquid water and floating ice on Earth. 903 00:50:57,671 --> 00:50:59,471 OLUSEYI: The next time you find yourself 904 00:50:59,471 --> 00:51:02,705 making a beverage and you put ice in it, 905 00:51:02,705 --> 00:51:04,871 just take a moment and reflect 906 00:51:04,871 --> 00:51:07,871 on the amazingness of the ice 907 00:51:07,871 --> 00:51:09,605 that made your life possible. 908 00:51:11,071 --> 00:51:13,305 NARRATOR: Across our Solar System, 909 00:51:13,305 --> 00:51:15,605 scientists have found worlds 910 00:51:15,605 --> 00:51:17,538 shaped by ice, 911 00:51:17,538 --> 00:51:20,138 made of a diversity of substances 912 00:51:20,138 --> 00:51:23,105 behaving in unbelievable ways. 913 00:51:25,305 --> 00:51:28,405 DURFEY: There's a massive variety of ice worlds out there. 914 00:51:28,405 --> 00:51:30,838 Each one has something we haven't seen before. 915 00:51:32,271 --> 00:51:34,971 NARRATOR: We are in a golden age of discovery, 916 00:51:34,971 --> 00:51:39,338 but our knowledge of these ice worlds is far from complete. 917 00:51:40,638 --> 00:51:43,271 There is so much left to learn about ice worlds. 918 00:51:43,271 --> 00:51:45,771 Our understanding is only skin deep. 919 00:51:45,771 --> 00:51:48,038 We want to explore these worlds because 920 00:51:48,038 --> 00:51:52,138 it really tells us where we fit into the universe. 921 00:51:52,138 --> 00:51:54,838 Why are we here? How did we first get here? 922 00:51:55,838 --> 00:51:57,938 NARRATOR: We may not have all the answers, 923 00:51:57,938 --> 00:52:01,838 but we now know that ice plays a critical role 924 00:52:01,838 --> 00:52:03,205 in our story. 925 00:52:05,238 --> 00:52:08,105 WONG: Without the kind of ice that we have here on Earth, 926 00:52:08,105 --> 00:52:10,705 we might not even be here to be discussing ice 927 00:52:10,705 --> 00:52:12,871 and all of its wondrous forms. 928 00:52:12,871 --> 00:52:16,905 ♪ ♪ 929 00:52:35,171 --> 00:52:38,038 ♪ ♪ 930 00:52:38,971 --> 00:52:46,505 ♪ ♪ 931 00:52:50,338 --> 00:52:57,871 ♪ ♪ 932 00:53:01,771 --> 00:53:09,305 ♪ ♪ 933 00:53:10,938 --> 00:53:18,471 ♪ ♪ 934 00:53:20,105 --> 00:53:27,638 ♪ ♪