1 00:00:01,900 --> 00:00:04,066 NARRATOR: Throughout our Solar System, 2 00:00:04,066 --> 00:00:08,000 we find worlds shaped by ice. 3 00:00:09,000 --> 00:00:10,066 SABINE STANLEY: These ice worlds 4 00:00:10,066 --> 00:00:12,300 are so unexpected and surprising. 5 00:00:12,300 --> 00:00:14,766 There is definitely more ice out there 6 00:00:14,766 --> 00:00:17,766 than we really expected or anticipated. 7 00:00:18,933 --> 00:00:22,733 NARRATOR: Today, spacecraft are bringing us closer than ever... 8 00:00:24,266 --> 00:00:26,700 ...to revealing their secrets. 9 00:00:27,800 --> 00:00:29,500 We've got carbon dioxide snow 10 00:00:29,500 --> 00:00:31,933 on Mars. 11 00:00:31,933 --> 00:00:33,100 KELSI SINGER: On Pluto, 12 00:00:33,100 --> 00:00:34,733 we have these nitrogen ice glaciers 13 00:00:34,733 --> 00:00:37,966 that no one would have predicted. 14 00:00:37,966 --> 00:00:39,800 Deep in the planet of Uranus, 15 00:00:39,800 --> 00:00:44,266 you get this extremely dense black hot ice. 16 00:00:44,266 --> 00:00:47,400 MICHAEL WONG: The data has truly transformed 17 00:00:47,400 --> 00:00:50,700 the way that we understand how ice behaves 18 00:00:50,700 --> 00:00:53,966 so far away in the depths of space. 19 00:00:53,966 --> 00:00:57,600 NARRATOR: But many questions remain unanswered. 20 00:00:57,600 --> 00:01:00,266 PETER GAO: How do these icy worlds even form? 21 00:01:00,266 --> 00:01:01,533 How did the ice get there? 22 00:01:01,533 --> 00:01:02,566 Is there life there? 23 00:01:02,566 --> 00:01:04,366 NARRATOR: And of all the worlds 24 00:01:04,366 --> 00:01:06,100 in our Solar System, 25 00:01:06,100 --> 00:01:09,033 ours hits the icy jackpot. 26 00:01:09,033 --> 00:01:11,166 The ice we have here on Earth is special. 27 00:01:11,166 --> 00:01:14,000 And if it didn't have its special properties, 28 00:01:14,000 --> 00:01:15,600 life on Earth would not exist 29 00:01:15,600 --> 00:01:17,333 and you wouldn't be here watching me. 30 00:01:18,333 --> 00:01:21,100 NARRATOR: Why is our cosmic neighborhood 31 00:01:21,100 --> 00:01:24,166 home to so many different and exotic ices? 32 00:01:26,366 --> 00:01:29,966 "Solar System: Icy Worlds." 33 00:01:29,966 --> 00:01:32,766 Right now, on "NOVA." 34 00:01:32,766 --> 00:01:35,133 ♪ ♪ 35 00:02:04,500 --> 00:02:06,833 ♪ ♪ 36 00:02:06,833 --> 00:02:08,800 NARRATOR: Out in the dark expanse 37 00:02:08,800 --> 00:02:11,366 of our Solar System, 38 00:02:11,366 --> 00:02:13,833 far beyond Earth and Mars... 39 00:02:15,466 --> 00:02:18,966 ...we enter the realm of the gas giants. 40 00:02:20,666 --> 00:02:22,966 Where average temperatures of the planets 41 00:02:22,966 --> 00:02:24,633 begin to plummet. 42 00:02:30,900 --> 00:02:33,766 Venture even farther away from Earth, 43 00:02:33,766 --> 00:02:36,400 and we pass the ice giants. 44 00:02:39,200 --> 00:02:42,766 Here, temperatures can drop even lower... 45 00:02:44,833 --> 00:02:49,166 ...down to -370 degrees Fahrenheit. 46 00:02:50,166 --> 00:02:53,833 These worlds are made almost entirely of ice... 47 00:02:55,533 --> 00:02:59,833 ...existing in exotic, seemingly impossible forms. 48 00:03:03,133 --> 00:03:06,066 WONG: Thanks to planetary exploration, 49 00:03:06,066 --> 00:03:08,166 we have witnessed different forms of ice 50 00:03:08,166 --> 00:03:11,466 behaving in ways that we could not have expected. 51 00:03:13,566 --> 00:03:16,666 NARRATOR: Scientists are just beginning to uncover 52 00:03:16,666 --> 00:03:19,733 the icy secrets of our Solar System. 53 00:03:22,433 --> 00:03:25,966 GURNEY: We really don't know much about ice worlds 54 00:03:25,966 --> 00:03:27,166 and planetary scientists 55 00:03:27,166 --> 00:03:28,333 are really discovering 56 00:03:28,333 --> 00:03:29,733 new things every day. 57 00:03:31,066 --> 00:03:33,200 NARRATOR: Discoveries that can shed light on 58 00:03:33,200 --> 00:03:35,833 the strange ways ice behaves 59 00:03:35,833 --> 00:03:38,533 and how dynamic it can be, 60 00:03:38,533 --> 00:03:41,166 not only in our Solar System, 61 00:03:41,166 --> 00:03:44,000 but on other worlds in our galaxy, too. 62 00:03:57,100 --> 00:03:59,900 (ice crackling) 63 00:04:07,666 --> 00:04:09,900 NARRATOR: Over three billion miles from Earth, 64 00:04:09,900 --> 00:04:12,700 the space probe New Horizons 65 00:04:12,700 --> 00:04:15,766 is traveling far beyond the rocky planets. 66 00:04:17,733 --> 00:04:20,333 And after more than nine years, 67 00:04:20,333 --> 00:04:22,566 arrives at its destination. 68 00:04:26,866 --> 00:04:28,466 As it passes Pluto, 69 00:04:29,866 --> 00:04:31,400 ...the probe gives us a glimpse 70 00:04:31,400 --> 00:04:34,533 of a world made of weird ice. 71 00:04:36,133 --> 00:04:37,233 DURFEY: Flyby missions 72 00:04:37,233 --> 00:04:39,100 are do or die. 73 00:04:39,100 --> 00:04:41,100 If you don't get those images, 74 00:04:41,100 --> 00:04:43,600 if you don't get that data, 75 00:04:43,600 --> 00:04:44,966 you've flown by 76 00:04:44,966 --> 00:04:46,300 and you're gone now. 77 00:04:47,700 --> 00:04:50,166 VERBISCER: We only get one shot because traveling at 78 00:04:50,166 --> 00:04:52,100 31,000 miles an hour, 79 00:04:52,100 --> 00:04:54,266 it's not like you can do a U-turn. 80 00:04:56,766 --> 00:05:01,800 NARRATOR: The $780 million high-risk mission pays dividends, 81 00:05:01,800 --> 00:05:04,566 delivering a mother lode of data. 82 00:05:04,566 --> 00:05:06,133 (camera shutter clicking) 83 00:05:07,133 --> 00:05:09,133 New Horizons surprises scientists 84 00:05:09,133 --> 00:05:12,566 with incredible images of Pluto's surface, 85 00:05:12,566 --> 00:05:15,933 revealing features they never expected to see. 86 00:05:17,233 --> 00:05:18,233 GAO: I think when 87 00:05:18,233 --> 00:05:20,600 people first saw images of Pluto, 88 00:05:20,600 --> 00:05:21,866 they were just blown away. 89 00:05:21,866 --> 00:05:25,333 We're seeing incredible diversity in 90 00:05:25,333 --> 00:05:26,633 what the surface looks like. 91 00:05:27,600 --> 00:05:29,333 VERBISCER: I walked into the geology room 92 00:05:29,333 --> 00:05:32,166 and looked at an image on one of the computer screens, 93 00:05:32,166 --> 00:05:35,366 and I wondered why someone was looking at 94 00:05:35,366 --> 00:05:37,366 a picture of Antarctica. 95 00:05:37,366 --> 00:05:39,700 And it dawned on me 96 00:05:39,700 --> 00:05:41,933 (chuckling): gradually, oh, my goodness, 97 00:05:41,933 --> 00:05:44,833 that was not Antarctica, that was actually 98 00:05:44,833 --> 00:05:48,000 a very close picture of Pluto. 99 00:05:48,966 --> 00:05:52,200 WONG: There were tons of mysteries that we needed to unravel. 100 00:05:52,200 --> 00:05:54,133 There were lots of features 101 00:05:54,133 --> 00:05:57,066 that puzzled us. How could that possibly be, 102 00:05:57,066 --> 00:05:59,533 so far away in the Solar System? 103 00:06:05,033 --> 00:06:06,600 NARRATOR: The amount of data collected 104 00:06:06,600 --> 00:06:10,066 allows scientists to map Pluto's surface. 105 00:06:14,433 --> 00:06:16,933 Pluto's most prominent feature 106 00:06:16,933 --> 00:06:21,433 is a great icy plain around 600 miles across. 107 00:06:23,300 --> 00:06:26,133 And, despite the extreme cold, 108 00:06:26,133 --> 00:06:29,833 there are signs of movement in the ice; 109 00:06:29,833 --> 00:06:32,033 lines etched into the surface 110 00:06:32,033 --> 00:06:33,433 as if they are churning. 111 00:06:38,000 --> 00:06:42,233 And then, something even more unexpected. 112 00:06:52,466 --> 00:06:54,300 Glaciers. 113 00:06:56,133 --> 00:06:58,133 Flowing rivers of ice 114 00:06:58,133 --> 00:07:00,500 on a world so cold... 115 00:07:02,066 --> 00:07:04,533 ...it seems nothing should be moving. 116 00:07:08,866 --> 00:07:11,366 Pluto is a wintery puzzle, 117 00:07:11,366 --> 00:07:15,833 with icy landscapes as dramatic as anything seen on Earth. 118 00:07:17,600 --> 00:07:20,366 How is all this dynamism possible 119 00:07:20,366 --> 00:07:23,300 on a world so far from the sun? 120 00:07:28,000 --> 00:07:33,033 ♪ ♪ 121 00:07:37,433 --> 00:07:41,300 Pluto, a place right on the edge of the Solar System, 122 00:07:41,300 --> 00:07:43,366 looks remarkably similar to 123 00:07:43,366 --> 00:07:46,900 some frozen landscapes on Earth, 124 00:07:46,900 --> 00:07:49,433 like this glacier in Alaska. 125 00:07:50,933 --> 00:07:54,033 LEIGHAN FALLEY: Glacier Two for the Root Canal, acknowledge. 126 00:07:55,433 --> 00:07:58,100 (man speaks indistinctly over radio) 127 00:08:00,100 --> 00:08:01,633 FALLEY: Okay, floor above two. 128 00:08:01,633 --> 00:08:03,733 Hang on. 129 00:08:03,733 --> 00:08:05,500 Never a dull moment around here. 130 00:08:06,966 --> 00:08:10,000 Well, isn't this amazing? 131 00:08:10,000 --> 00:08:12,400 Incredible views. Yes. 132 00:08:13,733 --> 00:08:16,066 NARRATOR: This landscape might look frozen solid, 133 00:08:16,066 --> 00:08:18,033 but it is one of the most 134 00:08:18,033 --> 00:08:21,700 geologically active areas on Earth. 135 00:08:21,700 --> 00:08:23,966 SINGER: In the time that you've been flying here, 136 00:08:23,966 --> 00:08:26,633 have you seen a lot of changes in the glacier? 137 00:08:26,633 --> 00:08:28,666 Absolutely. Are you kidding me? 138 00:08:28,666 --> 00:08:31,766 (chuckling): Yes. I've seen immense changes. 139 00:08:32,766 --> 00:08:35,333 SINGER: Some aspects of what we're looking at 140 00:08:35,333 --> 00:08:37,733 that really reminded me of Pluto, 141 00:08:37,733 --> 00:08:39,633 there's the kind of flow lines 142 00:08:39,633 --> 00:08:40,966 in the glacier 143 00:08:40,966 --> 00:08:42,933 indicating the direction of flow. 144 00:08:42,933 --> 00:08:44,566 Oh, Pluto has flow lines? 145 00:08:44,566 --> 00:08:47,266 Yes, they are moving downhill, 146 00:08:47,266 --> 00:08:49,533 similar to these glaciers. 147 00:08:55,166 --> 00:08:56,466 FALLEY: We're coming in for landing. 148 00:08:58,666 --> 00:09:01,033 NARRATOR: Understanding these glacial features 149 00:09:01,033 --> 00:09:03,366 can help scientists understand 150 00:09:03,366 --> 00:09:05,066 how Pluto's glaciers flow. 151 00:09:15,066 --> 00:09:18,633 (plane powering down) 152 00:09:18,633 --> 00:09:20,033 FALLEY: Welcome to the glacier, you guys. 153 00:09:26,066 --> 00:09:28,533 SINGER: Wow. (Falley laughs) 154 00:09:28,533 --> 00:09:30,900 So beautiful. FALLEY: Oh... 155 00:09:30,900 --> 00:09:33,300 FALLEY: One of the greatest ranges on the continent. 156 00:09:36,533 --> 00:09:38,333 (laughs) 157 00:09:38,333 --> 00:09:39,766 Is the glacier under here? 158 00:09:39,766 --> 00:09:41,133 Yes, we're probably 159 00:09:41,133 --> 00:09:44,133 on top of about 700 to 1,500 feet 160 00:09:44,133 --> 00:09:46,300 of glacier ice underneath us. 161 00:09:47,733 --> 00:09:50,366 CARLY HOWETT: If you ever experience visiting or seeing a glacier, 162 00:09:50,366 --> 00:09:52,900 you might think that they're completely stationary. 163 00:09:52,900 --> 00:09:54,366 But actually, if you were to 164 00:09:54,366 --> 00:09:55,366 stand there for long enough, 165 00:09:55,366 --> 00:09:56,900 you would see that they move. 166 00:09:58,066 --> 00:09:59,300 HAKEEM OLUSEYI: Glaciers form on Earth 167 00:09:59,300 --> 00:10:01,633 when snow does not melt 168 00:10:01,633 --> 00:10:03,700 season after season, and it packs down, 169 00:10:03,700 --> 00:10:07,900 and the weight of that snow compresses it into ice. 170 00:10:08,966 --> 00:10:10,400 And as more and more builds up 171 00:10:10,400 --> 00:10:11,933 and it gets heavier and heavier, 172 00:10:11,933 --> 00:10:13,866 it begins to flow. 173 00:10:16,066 --> 00:10:18,666 NARRATOR: These huge glacial ice features in Alaska 174 00:10:18,666 --> 00:10:21,333 have formed in this exact way. 175 00:10:25,366 --> 00:10:27,366 SINGER: This is an incredible landscape. 176 00:10:28,366 --> 00:10:30,866 It really reminds me of what it would be like to 177 00:10:30,866 --> 00:10:33,000 stand on Pluto. 178 00:10:33,000 --> 00:10:34,966 And it's 15 degrees Fahrenheit, 179 00:10:34,966 --> 00:10:37,733 and we're in this totally frozen landscape, 180 00:10:37,733 --> 00:10:40,600 and on Pluto, it's even colder. 181 00:10:40,600 --> 00:10:44,766 It's -390 degrees Fahrenheit. 182 00:10:44,766 --> 00:10:46,933 How can these glaciers be flowing 183 00:10:46,933 --> 00:10:49,800 when it's so cold on the surface of Pluto? 184 00:10:49,800 --> 00:10:51,833 ♪ ♪ 185 00:10:55,066 --> 00:10:58,733 NARRATOR: Water ice is frozen as solid as rock here, 186 00:10:58,733 --> 00:11:02,533 so it doesn't flow in the same way as glaciers on Earth. 187 00:11:06,666 --> 00:11:10,933 And yet, these glaciers look like they are flowing. 188 00:11:17,833 --> 00:11:22,333 We even see two glaciers that appear to flow into each other, 189 00:11:22,333 --> 00:11:26,300 combining to form a mega glacier 190 00:11:26,300 --> 00:11:29,100 that flows onto the ice plains below. 191 00:11:32,400 --> 00:11:35,633 GURNEY: So, at Pluto, we see these glaciers 192 00:11:35,633 --> 00:11:39,000 that are flowing, but it's way too cold 193 00:11:39,000 --> 00:11:41,000 for there to be flowing water, 194 00:11:41,000 --> 00:11:43,133 so what are they actually made of? 195 00:11:43,133 --> 00:11:44,566 So, it might be surprising to hear 196 00:11:44,566 --> 00:11:46,166 that the definition of ice 197 00:11:46,166 --> 00:11:48,666 really depends on who you're talking to. 198 00:11:48,666 --> 00:11:50,533 If you're talking to people 199 00:11:50,533 --> 00:11:52,300 on Earth doing their everyday things, 200 00:11:52,300 --> 00:11:55,300 then ice is just the solid form of water. 201 00:11:55,300 --> 00:11:57,933 But if you're talking to a planetary scientist, 202 00:11:57,933 --> 00:12:01,566 then ice is a way to describe a group of materials. 203 00:12:01,566 --> 00:12:05,100 It's water, but it's also ammonia and methane, 204 00:12:05,100 --> 00:12:06,800 things that are made up of a lot of carbon, 205 00:12:06,800 --> 00:12:09,466 hydrogen, oxygen, nitrogen mixed in. 206 00:12:11,266 --> 00:12:13,200 NARRATOR: On Earth, these are usually found 207 00:12:13,200 --> 00:12:15,366 as a liquid or a gas, 208 00:12:15,366 --> 00:12:16,733 but in the Solar System, 209 00:12:16,733 --> 00:12:20,000 they can be frozen into ices. 210 00:12:20,000 --> 00:12:23,466 OLUSEYI: From afar, we can tell what the composition 211 00:12:23,466 --> 00:12:25,433 of Pluto's surface is. 212 00:12:25,433 --> 00:12:28,333 But once we got there, what we didn't expect 213 00:12:28,333 --> 00:12:31,300 is the configuration of those materials. 214 00:12:31,300 --> 00:12:32,766 ♪ ♪ 215 00:12:34,733 --> 00:12:37,300 NARRATOR: A clue to the composition of the glaciers 216 00:12:37,300 --> 00:12:43,066 is Pluto's surface temperature of -390 degrees Fahrenheit. 217 00:12:43,066 --> 00:12:46,333 That's pretty close to the melting point of nitrogen, 218 00:12:46,333 --> 00:12:49,833 at around -350 degrees Fahrenheit. 219 00:12:51,033 --> 00:12:53,500 Similarly, on Earth, 220 00:12:53,500 --> 00:12:58,166 the melting point of water ice is 32 degrees Fahrenheit, 221 00:12:58,166 --> 00:13:03,900 not far from the average surface temperature of 59 degrees. 222 00:13:03,900 --> 00:13:06,933 HOWETT: For a glacier to move, it has to be made of an ice 223 00:13:06,933 --> 00:13:09,466 that's not too far away from its melting temperature, 224 00:13:09,466 --> 00:13:11,533 'cause at the bottom, what you need is-is 225 00:13:11,533 --> 00:13:13,733 the ice to melt just a little bit 226 00:13:13,733 --> 00:13:15,933 so that the glacier is able to flow, 227 00:13:15,933 --> 00:13:17,900 and on Earth, water does that-- 228 00:13:17,900 --> 00:13:21,133 the water ice isn't that far from its melting temperature-- 229 00:13:21,133 --> 00:13:23,600 but on Pluto, it's so cold, that's not the case 230 00:13:23,600 --> 00:13:26,400 for water ice, but it is the case for nitrogen ice. 231 00:13:26,400 --> 00:13:27,866 Take a breath in. 232 00:13:27,866 --> 00:13:29,200 (inhales) 233 00:13:29,200 --> 00:13:31,200 The air that is in your lungs 234 00:13:31,200 --> 00:13:32,633 includes nitrogen, 235 00:13:32,633 --> 00:13:34,000 and it's a gas for us, 236 00:13:34,000 --> 00:13:35,766 it's the air that we breathe. 237 00:13:35,766 --> 00:13:39,666 On Pluto, it's so cold that that's solid. 238 00:13:39,666 --> 00:13:42,566 (plane engine whirring) 239 00:13:42,566 --> 00:13:44,700 NARRATOR: And it's this solid nitrogen 240 00:13:44,700 --> 00:13:47,833 that creates Pluto's flowing glaciers 241 00:13:47,833 --> 00:13:50,666 that are so similar to Earth's water glaciers. 242 00:13:53,700 --> 00:13:57,033 WONG: The same physical forces are responsible 243 00:13:57,033 --> 00:13:59,966 for carving the landscapes that we see here on Earth 244 00:13:59,966 --> 00:14:02,033 and on Pluto. 245 00:14:02,033 --> 00:14:04,933 It's just using different building blocks. 246 00:14:07,200 --> 00:14:09,200 GAO: I think Pluto has definitely taught us 247 00:14:09,200 --> 00:14:11,733 that the Solar System is a giant laboratory 248 00:14:11,733 --> 00:14:12,933 where different elements can be put together 249 00:14:12,933 --> 00:14:14,266 in all kinds of interesting ways. 250 00:14:14,266 --> 00:14:16,300 ♪ ♪ 251 00:14:21,400 --> 00:14:24,500 NARRATOR: When New Horizons leaves Pluto behind, 252 00:14:24,500 --> 00:14:26,833 it turns back 253 00:14:26,833 --> 00:14:30,366 and takes one last photograph, 254 00:14:30,366 --> 00:14:34,833 revealing Pluto's breathtaking atmosphere, 255 00:14:34,833 --> 00:14:37,766 rich in the nitrogen that condenses on the surface 256 00:14:37,766 --> 00:14:39,300 to create its glaciers. 257 00:14:41,266 --> 00:14:42,766 VERBISCER: What we've seen 258 00:14:42,766 --> 00:14:45,400 in the outer Solar System from the New Horizons spacecraft 259 00:14:45,400 --> 00:14:49,833 at Pluto and beyond has been revolutionary, 260 00:14:49,833 --> 00:14:54,633 showing us diversity in ice that we don't have here on Earth. 261 00:14:57,566 --> 00:15:00,433 NARRATOR: Pluto offers a tantalizing clue 262 00:15:00,433 --> 00:15:02,400 that very distant and cold worlds 263 00:15:02,400 --> 00:15:06,200 may be as active and dynamic as Earth. 264 00:15:08,333 --> 00:15:11,166 ♪ ♪ 265 00:15:11,166 --> 00:15:13,066 Closer to the sun, 266 00:15:13,066 --> 00:15:16,266 as we enter the realm of the ice giants, 267 00:15:16,266 --> 00:15:20,166 ice appears in even more bizarre forms 268 00:15:20,166 --> 00:15:23,633 behaving in unpredictable ways. 269 00:15:25,000 --> 00:15:28,366 It is found not only on the surface 270 00:15:28,366 --> 00:15:31,633 but also deep inside planets. 271 00:15:33,300 --> 00:15:38,166 Neptune, made up of around 80% frozen icy material, 272 00:15:38,166 --> 00:15:42,233 has giant ice storms raging across it. 273 00:15:45,566 --> 00:15:49,066 Another billion miles closer to the sun... 274 00:15:50,100 --> 00:15:52,666 ...is Neptune's icy twin. 275 00:15:55,300 --> 00:15:59,866 ♪ ♪ 276 00:15:59,866 --> 00:16:05,300 Uranus is an enormous planet of icy storms. 277 00:16:05,300 --> 00:16:08,066 GURNEY: When I first saw images of Uranus, 278 00:16:08,066 --> 00:16:10,400 I thought they were absolutely beautiful. 279 00:16:10,400 --> 00:16:14,000 Blue, almost ocean-colored. 280 00:16:15,966 --> 00:16:17,333 NARRATOR: It has a feature 281 00:16:17,333 --> 00:16:20,166 that has puzzled scientists for decades: 282 00:16:20,166 --> 00:16:25,100 its vast, shimmering auroras. 283 00:16:25,100 --> 00:16:27,866 STANLEY: The aurora on Uranus are mysterious 284 00:16:27,866 --> 00:16:29,266 because flashes of light suddenly appear 285 00:16:29,266 --> 00:16:31,000 all over the planetary surface, 286 00:16:31,000 --> 00:16:32,866 and you don't know why they're happening there. 287 00:16:34,833 --> 00:16:37,833 NARRATOR: Their location is puzzling because, on Earth, 288 00:16:37,833 --> 00:16:41,300 auroras are confined to the poles. 289 00:16:41,300 --> 00:16:43,300 STANLEY: Aurora on Earth happen 290 00:16:43,300 --> 00:16:45,833 when high energy particles from the Sun 291 00:16:45,833 --> 00:16:48,066 gets funneled along magnetic field lines 292 00:16:48,066 --> 00:16:50,166 on the Earth towards the polar regions 293 00:16:50,166 --> 00:16:52,566 and there they run into atmospheric particles, 294 00:16:52,566 --> 00:16:54,500 and that causes the atmospheric particles 295 00:16:54,500 --> 00:16:55,700 to shine light. 296 00:16:57,666 --> 00:17:00,300 WONG: Earth's magnetic field is created 297 00:17:00,300 --> 00:17:03,966 by the churning motion of the liquid iron 298 00:17:03,966 --> 00:17:05,200 in Earth's outer core. 299 00:17:05,200 --> 00:17:07,833 Because iron is electrically conducting, 300 00:17:07,833 --> 00:17:12,233 when it moves, it naturally generates a magnetic field. 301 00:17:14,333 --> 00:17:17,133 NARRATOR: Magnetic fields create auroras, 302 00:17:17,133 --> 00:17:20,933 but on Uranus, this poses a mystery. 303 00:17:20,933 --> 00:17:23,133 GURNEY: We know Uranus doesn't have 304 00:17:23,133 --> 00:17:26,166 this flowing metallic core that Earth has, 305 00:17:26,166 --> 00:17:29,433 but it still has, uh, a magnetic field. 306 00:17:29,433 --> 00:17:32,100 So, how is that magnetic field being generated? 307 00:17:33,600 --> 00:17:35,066 NARRATOR: A clue could lie 308 00:17:35,066 --> 00:17:37,433 in Uranus's icy composition. 309 00:17:40,200 --> 00:17:41,700 (thunder rumbles) 310 00:17:43,666 --> 00:17:47,200 GURNEY: If you sent a spacecraft to Uranus, 311 00:17:47,200 --> 00:17:49,666 you would go through the atmosphere 312 00:17:49,666 --> 00:17:52,800 and, uh, you would see, uh, all of this, uh, gas, 313 00:17:52,800 --> 00:17:54,133 uh, because it's a gas giant. 314 00:17:54,133 --> 00:17:56,900 OLUSEYI: It's a turbulent, high-speed wind, 315 00:17:56,900 --> 00:17:59,000 gaseous environment, 316 00:17:59,000 --> 00:18:01,033 and descend inward, 317 00:18:01,033 --> 00:18:03,866 you go from gases to liquids. 318 00:18:05,533 --> 00:18:08,600 GURNEY: It would just get gradually more dense, um, 319 00:18:08,600 --> 00:18:10,000 as the pressure increases. 320 00:18:10,000 --> 00:18:12,433 And then, when you get sufficiently deep enough, 321 00:18:12,433 --> 00:18:17,700 now you enter the ice world in the interior of Uranus. 322 00:18:17,700 --> 00:18:19,900 ♪ ♪ 323 00:18:19,900 --> 00:18:22,666 (thunder crackling) 324 00:18:22,666 --> 00:18:24,166 GAO: The pressures and temperatures 325 00:18:24,166 --> 00:18:26,833 in the interior of Uranus are extreme. 326 00:18:26,833 --> 00:18:29,966 We're looking at pressures three million times that 327 00:18:29,966 --> 00:18:31,533 of the surface pressure of Earth, 328 00:18:31,533 --> 00:18:34,900 and temperatures reaching 9,000 Fahrenheit. 329 00:18:37,033 --> 00:18:39,833 NARRATOR: Surprisingly, even at these extremely high 330 00:18:39,833 --> 00:18:45,400 pressures and temperatures, water can become ice, 331 00:18:45,400 --> 00:18:49,666 but not in the form we're familiar with on Earth. 332 00:18:49,666 --> 00:18:52,166 GURNEY: Deep in the planet of Uranus, 333 00:18:52,166 --> 00:18:54,900 you get this extremely dense, uh, 334 00:18:54,900 --> 00:18:57,900 black, hot ice called "superionic ice." 335 00:19:00,233 --> 00:19:02,600 NARRATOR: At extreme pressures and temperatures 336 00:19:02,600 --> 00:19:04,733 hotter than the sun's surface, 337 00:19:04,733 --> 00:19:09,300 water is crushed into a solid form. 338 00:19:09,300 --> 00:19:10,533 Superionic ice sounds like it comes from 339 00:19:10,533 --> 00:19:12,100 a science fiction novel. 340 00:19:12,100 --> 00:19:14,900 It's really strange, and you just wouldn't expect 341 00:19:14,900 --> 00:19:16,966 that it would exist in real life. 342 00:19:18,500 --> 00:19:20,933 NARRATOR: This strange ice is unlike anything 343 00:19:20,933 --> 00:19:23,700 we find naturally on Earth. 344 00:19:23,700 --> 00:19:24,833 BERDIS: Here on Earth, 345 00:19:24,833 --> 00:19:27,133 we see all different types of ice. 346 00:19:27,133 --> 00:19:29,133 We see sleet, 347 00:19:29,133 --> 00:19:32,700 we see snow, we see ice cubes. 348 00:19:32,700 --> 00:19:35,533 But if we zoom in under a microscope, 349 00:19:35,533 --> 00:19:36,866 we see that they are all 350 00:19:36,866 --> 00:19:39,533 this very similar 351 00:19:39,533 --> 00:19:42,100 hexagon pattern. 352 00:19:42,100 --> 00:19:44,600 This is water ice as we know it on the Earth. 353 00:19:44,600 --> 00:19:46,666 It's called "ice Ih," 354 00:19:46,666 --> 00:19:49,233 and the H stands for this hexagonal shape 355 00:19:49,233 --> 00:19:51,466 that you can see in the structure. 356 00:19:51,466 --> 00:19:53,366 Here, the red balls are the oxygen 357 00:19:53,366 --> 00:19:56,233 and the white is the hydrogen; H2O, 358 00:19:56,233 --> 00:19:58,633 two hydrogens for every oxygen. 359 00:19:58,633 --> 00:19:59,800 STANLEY: There are around 360 00:19:59,800 --> 00:20:01,533 20 different types of water ice 361 00:20:01,533 --> 00:20:03,700 found in the Solar System. 362 00:20:03,700 --> 00:20:08,433 The other types that we don't find here on Earth, uh, can form 363 00:20:08,433 --> 00:20:09,766 when the temperature's really, really high 364 00:20:09,766 --> 00:20:12,433 and the pressure's really high. 365 00:20:12,433 --> 00:20:14,366 NARRATOR: And it's these conditions 366 00:20:14,366 --> 00:20:17,000 deep inside Uranus that, in theory, 367 00:20:17,000 --> 00:20:21,166 could allow this mysterious superionic ice to exist. 368 00:20:23,133 --> 00:20:26,333 GURNEY: Superionic ice is still very new. 369 00:20:26,333 --> 00:20:29,433 It took us a long time to figure out, uh, that it even existed. 370 00:20:30,433 --> 00:20:32,466 NARRATOR: But in 2018, 371 00:20:32,466 --> 00:20:36,533 scientists announced they'd made superionic ice. 372 00:20:36,533 --> 00:20:38,900 MILLOT: We did the experiment, 373 00:20:38,900 --> 00:20:41,500 and then we look at all the evidence, 374 00:20:41,500 --> 00:20:44,900 and we have to say, "Well, it's true." 375 00:20:44,900 --> 00:20:47,733 It's crazy, it's weird, it's strange, 376 00:20:47,733 --> 00:20:49,066 but it's there. 377 00:20:49,066 --> 00:20:51,433 At super-high temperatures and pressures, 378 00:20:51,433 --> 00:20:53,933 ice forms a very different structure. 379 00:20:53,933 --> 00:20:57,233 What you're looking at here are oxygen atoms, shown in red, 380 00:20:57,233 --> 00:20:58,900 now connected with one another, 381 00:20:58,900 --> 00:21:03,700 and the hydrogen atoms, in white, have broken free. 382 00:21:03,700 --> 00:21:06,133 ♪ ♪ 383 00:21:06,133 --> 00:21:07,866 NARRATOR: This unique property 384 00:21:07,866 --> 00:21:11,033 may solve the mystery of Uranus's auroras. 385 00:21:13,333 --> 00:21:15,800 OLUSEYI: Inside of superionic ice, 386 00:21:15,800 --> 00:21:17,666 what's happened is that 387 00:21:17,666 --> 00:21:20,566 the hydrogen atoms have broken free, and now they're free 388 00:21:20,566 --> 00:21:23,200 to flow around within the material, 389 00:21:23,200 --> 00:21:25,800 and they are the conductors of electricity. 390 00:21:27,200 --> 00:21:29,766 WONG: It's like something out of science fiction where 391 00:21:29,766 --> 00:21:32,166 the hydrogen atoms are flowing like water, 392 00:21:32,166 --> 00:21:36,000 conducting electricity, and potentially responsible 393 00:21:36,000 --> 00:21:39,833 for the wacky magnetic fields that we see on Uranus. 394 00:21:41,266 --> 00:21:44,133 NARRATOR: Precisely the kind of magnetic fields 395 00:21:44,133 --> 00:21:47,066 that could help generate Uranus's auroras. 396 00:21:47,066 --> 00:21:50,000 But there's still much to learn. 397 00:21:51,066 --> 00:21:54,133 GURNEY: We don't fully know what's going on inside Uranus. 398 00:21:54,133 --> 00:21:57,333 We're only just beginning looking at these icy worlds. 399 00:21:57,333 --> 00:21:59,933 We're really at the tip of the iceberg. (chuckles) 400 00:22:01,033 --> 00:22:04,700 NARRATOR: And since these ice giants, Uranus and Neptune, 401 00:22:04,700 --> 00:22:06,700 hold vast amounts of water, 402 00:22:06,700 --> 00:22:10,333 this bizarre hot black superionic ice 403 00:22:10,333 --> 00:22:13,566 may turn out to be the most common form of water 404 00:22:13,566 --> 00:22:15,633 in our Solar System. 405 00:22:21,300 --> 00:22:23,533 As we get closer to the Sun, 406 00:22:23,533 --> 00:22:26,433 ice begins to look more familiar. 407 00:22:29,300 --> 00:22:33,033 Almost a billion miles from Uranus 408 00:22:33,033 --> 00:22:34,700 lies Saturn. 409 00:22:35,666 --> 00:22:39,633 Adorned with its famous icy rings. 410 00:22:45,100 --> 00:22:47,666 Saturn's rings are truly the jewel of the Solar System. 411 00:22:47,666 --> 00:22:50,300 The first time anyone sees them through a telescope, 412 00:22:50,300 --> 00:22:52,533 you can't believe your eyes. 413 00:22:52,533 --> 00:22:55,800 NARRATOR: But we never realized the true beauty of them 414 00:22:55,800 --> 00:23:00,166 until NASA's Cassini spacecraft went to visit. 415 00:23:05,466 --> 00:23:08,100 The photographs and data sent back 416 00:23:08,100 --> 00:23:10,700 were spectacular. 417 00:23:13,333 --> 00:23:15,600 OLUSEYI: Saturn's rings 418 00:23:15,600 --> 00:23:19,600 turned out to be made up primarily of water ice 419 00:23:19,600 --> 00:23:23,166 that range in sizes from like 420 00:23:23,166 --> 00:23:26,700 smaller than a millimeter to larger than an automobile. 421 00:23:29,066 --> 00:23:31,766 NARRATOR: Icy mini-moons sweep through the rings. 422 00:23:33,933 --> 00:23:37,333 Creating what look like grooves in a record. 423 00:23:38,800 --> 00:23:40,466 HOWETT: Cassini gave us that view. 424 00:23:40,466 --> 00:23:42,166 They're absolutely astounding. 425 00:23:42,166 --> 00:23:44,966 To see the ripples in them, the gaps in them, 426 00:23:44,966 --> 00:23:47,700 just really, really lovely. 427 00:23:56,866 --> 00:23:59,100 NARRATOR: The rings are joined in their orbits 428 00:23:59,100 --> 00:24:02,100 by over 140 moons. 429 00:24:05,533 --> 00:24:08,066 And Cassini saw something intriguing 430 00:24:08,066 --> 00:24:11,266 on one of the moons farthest from Saturn. 431 00:24:19,233 --> 00:24:22,100 Iapetus is one of the oddest looking moons 432 00:24:22,100 --> 00:24:23,966 in the Solar System. 433 00:24:23,966 --> 00:24:26,333 It resembles a walnut 434 00:24:26,333 --> 00:24:28,900 with a mountain ridge around its middle. 435 00:24:31,100 --> 00:24:35,266 But that's not its strangest feature. 436 00:24:36,966 --> 00:24:38,500 In 2007, 437 00:24:38,500 --> 00:24:42,366 Cassini sent back pictures of Iapetus. 438 00:24:43,633 --> 00:24:46,300 One side icy white, 439 00:24:46,300 --> 00:24:49,633 while the other looks as if it's been painted black. 440 00:24:53,100 --> 00:24:54,466 Iapetus is one of the weirdest looking moons 441 00:24:54,466 --> 00:24:55,500 in the Solar System. 442 00:24:55,500 --> 00:24:58,166 It looks like it has two halves. 443 00:24:58,166 --> 00:25:01,600 One really bright side and one really dark side. 444 00:25:01,600 --> 00:25:02,866 We would expect the moons 445 00:25:02,866 --> 00:25:04,266 in the Saturn system 446 00:25:04,266 --> 00:25:07,333 to have formed with roughly the same brightnesses. 447 00:25:07,333 --> 00:25:09,800 The darkest materials on Iapetus 448 00:25:09,800 --> 00:25:14,233 are 20 times darker than the brightest materials. 449 00:25:14,233 --> 00:25:17,233 How can such a bizarre yin-yang moon exist? 450 00:25:17,233 --> 00:25:20,900 NARRATOR: A clue can be found in the temperature differences 451 00:25:20,900 --> 00:25:23,566 between the white and black halves of the moon. 452 00:25:25,133 --> 00:25:28,000 VERBISCER: The darker side is a warmer region. 453 00:25:28,000 --> 00:25:30,866 The temperatures are hotter on the darker side 454 00:25:30,866 --> 00:25:32,733 than on the bright side. 455 00:25:35,200 --> 00:25:37,500 NARRATOR: The dark side's daytime temperature 456 00:25:37,500 --> 00:25:40,866 can be up to 54 degrees Fahrenheit hotter 457 00:25:40,866 --> 00:25:42,333 than the bright side. 458 00:25:44,633 --> 00:25:45,833 This temperature difference 459 00:25:45,833 --> 00:25:47,700 between the black and white surfaces 460 00:25:47,700 --> 00:25:51,366 creates a peculiar feedback loop. 461 00:25:51,366 --> 00:25:52,900 (helicopter rotor blades whirring) 462 00:25:52,900 --> 00:25:55,033 Which also happens on Earth 463 00:25:55,033 --> 00:25:58,500 where scientists are studying its effects. 464 00:26:06,033 --> 00:26:09,933 WONG: So right behind me, we've got this dark glacial till 465 00:26:09,933 --> 00:26:12,966 right next to bright white snow 466 00:26:12,966 --> 00:26:14,766 created through the erosion 467 00:26:14,766 --> 00:26:16,666 of the majestic mountains around me. 468 00:26:17,966 --> 00:26:21,033 NARRATOR: These dark spots are not solid rock, 469 00:26:21,033 --> 00:26:25,900 but are dust and dirt covering the ice. 470 00:26:25,900 --> 00:26:27,600 And there's a huge, stark contrast 471 00:26:27,600 --> 00:26:30,066 between the brightness of the snow 472 00:26:30,066 --> 00:26:32,766 and the darkness of the glacial till. 473 00:26:33,833 --> 00:26:35,900 NARRATOR: This dark glacial till 474 00:26:35,900 --> 00:26:39,700 has what scientists call a low albedo. 475 00:26:39,700 --> 00:26:42,466 WONG: Which means that it absorbs most of the sunlight 476 00:26:42,466 --> 00:26:44,300 that hits it, heating it up, 477 00:26:44,300 --> 00:26:47,233 and that heat gets transferred to the surrounding snow, 478 00:26:47,233 --> 00:26:50,300 melting it into liquid water, 479 00:26:50,300 --> 00:26:52,233 causing the dark streaks that you see 480 00:26:52,233 --> 00:26:56,133 coming down the side of that cliff. 481 00:26:56,133 --> 00:26:58,900 And a very similar process happens on Iapetus. 482 00:27:01,333 --> 00:27:05,266 NARRATOR: With so little light and heat from the sun, 483 00:27:05,266 --> 00:27:08,866 it's a very slow process. 484 00:27:11,700 --> 00:27:13,366 Over a billion years, 485 00:27:13,366 --> 00:27:17,900 it's estimated the dark regions can lose around 66 feet of ice 486 00:27:17,900 --> 00:27:20,566 compared to the white side. 487 00:27:22,100 --> 00:27:25,000 As this feedback mechanism continues, 488 00:27:25,000 --> 00:27:26,833 it keeps the black side black... 489 00:27:28,033 --> 00:27:30,566 ...and the white side white. 490 00:27:30,566 --> 00:27:32,466 But a mystery remains. 491 00:27:33,833 --> 00:27:37,466 Where did all the dark material come from in the first place? 492 00:27:38,766 --> 00:27:40,066 VERBISCER: Did the dark material 493 00:27:40,066 --> 00:27:41,833 come from inside of Iapetus 494 00:27:41,833 --> 00:27:45,033 or did it come from someplace else? 495 00:27:49,166 --> 00:27:53,300 NARRATOR: The smoking gun was discovered by complete accident. 496 00:27:55,300 --> 00:27:57,933 VERBISCER: So, in 2005, I was observing 497 00:27:57,933 --> 00:28:00,100 another moon of Saturn called Phoebe, 498 00:28:00,100 --> 00:28:04,333 which orbits Saturn much further away than Iapetus does. 499 00:28:05,700 --> 00:28:07,733 SINGER: Phoebe is in an unusual orbit 500 00:28:07,733 --> 00:28:11,000 because it goes backwards with respect to the other moons 501 00:28:11,000 --> 00:28:13,933 in its direction around Saturn. 502 00:28:17,833 --> 00:28:20,700 VERBISCER: If you look at the Cassini images of Phoebe, 503 00:28:20,700 --> 00:28:25,033 you see that it is a pretty heavily cratered surface. 504 00:28:25,033 --> 00:28:28,766 So, it's been hit with things for billions of years, 505 00:28:28,766 --> 00:28:32,033 and material has been excavated 506 00:28:32,033 --> 00:28:34,366 and thrown into the space around Phoebe. 507 00:28:34,366 --> 00:28:37,000 The question is, where did all that material go? 508 00:28:38,533 --> 00:28:40,933 Where are all those dust particles? 509 00:28:40,933 --> 00:28:44,600 So, we got the idea to use the Spitzer Space Telescope 510 00:28:44,600 --> 00:28:47,000 to try and look for dust 511 00:28:47,000 --> 00:28:48,966 in the region around Phoebe. 512 00:28:50,300 --> 00:28:53,866 NARRATOR: The Spitzer Space Telescope used infrared light, 513 00:28:53,866 --> 00:28:55,700 or heat signatures, to detect 514 00:28:55,700 --> 00:28:57,700 what's normally hidden from view. 515 00:28:58,833 --> 00:29:00,166 SINGER: If you were able to see 516 00:29:00,166 --> 00:29:02,800 how the Spitzer telescope sees, 517 00:29:02,800 --> 00:29:05,266 it would be like when you put on night vision goggles, 518 00:29:05,266 --> 00:29:08,800 and all of a sudden, you're able to see in the dark. 519 00:29:14,666 --> 00:29:16,033 VERBISCER: We got our images, 520 00:29:16,033 --> 00:29:18,466 and they were extremely interesting. 521 00:29:19,633 --> 00:29:22,566 NARRATOR: Phoebe rides within a colossal ring 522 00:29:22,566 --> 00:29:25,333 about ten million miles across, 523 00:29:25,333 --> 00:29:27,366 wrapped around Saturn. 524 00:29:28,633 --> 00:29:32,333 VERBISCER: It is the largest ring by far in the Solar System. 525 00:29:32,333 --> 00:29:35,966 This ring is so big that a billion Earths 526 00:29:35,966 --> 00:29:38,166 could fit inside the volume of the ring. 527 00:29:38,166 --> 00:29:40,133 It makes perfect sense that this ring 528 00:29:40,133 --> 00:29:41,566 should be called the Phoebe ring 529 00:29:41,566 --> 00:29:45,766 because it is associated so closely with the moon Phoebe. 530 00:29:47,166 --> 00:29:50,133 NARRATOR: The Phoebe ring moves around Saturn, 531 00:29:50,133 --> 00:29:53,300 in the same direction as its moon Phoebe, 532 00:29:53,300 --> 00:29:56,000 backwards from the other moons and rings. 533 00:30:00,800 --> 00:30:03,966 Each time a passing object or rocky debris 534 00:30:03,966 --> 00:30:07,100 gets too close to Phoebe... 535 00:30:07,100 --> 00:30:08,700 boom. 536 00:30:09,900 --> 00:30:11,966 The resulting impact 537 00:30:11,966 --> 00:30:15,133 throws dark material out into space. 538 00:30:18,366 --> 00:30:20,133 SINGER: Some of this dark material 539 00:30:20,133 --> 00:30:23,700 in this huge ring starts to fall in towards Saturn, 540 00:30:23,700 --> 00:30:25,900 and Iapetus is basically 541 00:30:25,900 --> 00:30:29,033 running through those particles in its orbit. 542 00:30:30,500 --> 00:30:32,900 NARRATOR: How Iapetus orbits Saturn 543 00:30:32,900 --> 00:30:35,433 is key to solving the mystery 544 00:30:35,433 --> 00:30:38,566 of why it has these black and white halves. 545 00:30:41,500 --> 00:30:44,166 (wind howling) 546 00:30:44,166 --> 00:30:47,466 WONG: So Iapetus, like our moon that orbits the Earth, 547 00:30:47,466 --> 00:30:50,733 is tidally locked, which means one side of Iapetus 548 00:30:50,733 --> 00:30:52,333 always faces Saturn, 549 00:30:52,333 --> 00:30:55,100 the other side always faces away from Saturn. 550 00:30:56,166 --> 00:30:59,933 Imagine this snowball is a freshly formed Iapetus, 551 00:30:59,933 --> 00:31:03,966 completely uniform in its brightness on all sides. 552 00:31:03,966 --> 00:31:08,266 Now, as it orbits around Saturn, through the Phoebe ring, 553 00:31:08,266 --> 00:31:11,466 it will pick up dark dust particles 554 00:31:11,466 --> 00:31:13,133 from that ring. 555 00:31:13,133 --> 00:31:16,300 And because it is tidally locked to Saturn, 556 00:31:16,300 --> 00:31:18,033 the same hemisphere 557 00:31:18,033 --> 00:31:20,333 will keep piling on dust 558 00:31:20,333 --> 00:31:22,033 every time it goes around 559 00:31:22,033 --> 00:31:25,033 for millions and millions of years, 560 00:31:25,033 --> 00:31:28,866 continuously darkening this side of Iapetus. 561 00:31:32,633 --> 00:31:33,966 DURFEY: As soon as the front side 562 00:31:33,966 --> 00:31:36,033 of Iapetus became darkened, 563 00:31:36,033 --> 00:31:40,333 the ice underneath started heating up more quickly, 564 00:31:40,333 --> 00:31:43,800 so that would become a gas and migrate around 565 00:31:43,800 --> 00:31:47,500 to the colder, lighter side of Iapetus. 566 00:31:48,900 --> 00:31:52,200 NARRATOR: The ice vaporizes from the darker, warmer side 567 00:31:52,200 --> 00:31:55,433 and refreezes onto the colder, lighter side. 568 00:31:56,800 --> 00:31:58,833 DURFEY: And so, this means over time, 569 00:31:58,833 --> 00:32:01,133 the dark side becomes darker, 570 00:32:01,133 --> 00:32:03,166 the light side becomes lighter. 571 00:32:04,300 --> 00:32:06,433 NARRATOR: It's a slow process, 572 00:32:06,433 --> 00:32:08,833 one dust particle at a time. 573 00:32:10,333 --> 00:32:12,333 But it's the best explanation 574 00:32:12,333 --> 00:32:14,900 of how this peculiar moon 575 00:32:14,900 --> 00:32:18,166 got its self-sustaining, warm, dark face. 576 00:32:19,500 --> 00:32:21,000 OLUSEYI: Iapetus just shows us the potential 577 00:32:21,000 --> 00:32:22,533 of the interconnectedness 578 00:32:22,533 --> 00:32:25,166 between the planetary bodies of our Solar System. 579 00:32:26,200 --> 00:32:29,500 We think they're isolated, but nothing's isolated. 580 00:32:31,100 --> 00:32:33,933 NARRATOR: Iapetus is not the only icy moon affected 581 00:32:33,933 --> 00:32:36,700 by the system it exists within. 582 00:32:37,733 --> 00:32:40,033 Another moon closer to the sun 583 00:32:40,033 --> 00:32:43,266 reveals not only a unique connection with its neighbor, 584 00:32:43,266 --> 00:32:45,533 but also hints 585 00:32:45,533 --> 00:32:47,933 that something potentially profound 586 00:32:47,933 --> 00:32:50,500 could lurk beneath its surface. 587 00:32:54,466 --> 00:32:57,233 NASA LAUNCH ANNOUNCER: T minus five, four, 588 00:32:57,233 --> 00:33:00,666 three, two, one. 589 00:33:00,666 --> 00:33:03,733 Ignition and liftoff 590 00:33:03,733 --> 00:33:07,500 of the Atlas V with Juno on a trek to Jupiter. 591 00:33:09,066 --> 00:33:11,433 NARRATOR: The Juno mission is to investigate the origin 592 00:33:11,433 --> 00:33:14,700 and evolution of the gas giant Jupiter, 593 00:33:14,700 --> 00:33:18,966 the largest planet in our Solar System. 594 00:33:22,566 --> 00:33:24,300 LYNNAE QUICK: The main goal of the Juno spacecraft 595 00:33:24,300 --> 00:33:25,633 is to study Jupiter. 596 00:33:25,633 --> 00:33:27,066 However, 597 00:33:27,066 --> 00:33:28,533 as it orbits Jupiter, 598 00:33:28,533 --> 00:33:30,233 it's taking these wonderful images 599 00:33:30,233 --> 00:33:32,366 of Jupiter's largest moons. 600 00:33:34,900 --> 00:33:36,933 NARRATOR: Ganymede, 601 00:33:36,933 --> 00:33:39,466 the largest moon in the Solar System. 602 00:33:41,000 --> 00:33:43,966 Io, the most volcanically active. 603 00:33:48,166 --> 00:33:51,666 And then, there's the icy moon, Europa, 604 00:33:51,666 --> 00:33:55,300 the odd one out with the smoothest surface. 605 00:33:56,966 --> 00:34:01,300 It's an ancient moon, billions of years old, 606 00:34:01,300 --> 00:34:03,166 and yet, mysteriously, 607 00:34:03,166 --> 00:34:06,066 has a young surface, with few craters. 608 00:34:06,066 --> 00:34:07,466 DURFEY: We can get 609 00:34:07,466 --> 00:34:10,300 an idea of how old a planetary surface is 610 00:34:10,300 --> 00:34:12,400 by counting the number of impact craters. 611 00:34:12,400 --> 00:34:15,333 Europa barely has any impact craters, 612 00:34:15,333 --> 00:34:18,500 which means that its surface must be really young. 613 00:34:19,633 --> 00:34:22,200 NARRATOR: And that's not all that makes Europa different. 614 00:34:25,100 --> 00:34:31,200 It's criss-crossed by a strange network of striking red lines. 615 00:34:31,200 --> 00:34:33,066 GONZALEZ: The surface of Europa 616 00:34:33,066 --> 00:34:37,900 has a lot of interesting cracks and features to it, 617 00:34:37,900 --> 00:34:40,066 and has lots of lines, 618 00:34:40,066 --> 00:34:42,566 which look almost like a network 619 00:34:42,566 --> 00:34:44,866 of blood vessels in an eye. 620 00:34:46,100 --> 00:34:48,133 ♪ ♪ 621 00:34:50,633 --> 00:34:54,433 NARRATOR: These lines are vast ice cracks, 622 00:34:54,433 --> 00:34:58,466 some of which are 15 miles wide, 623 00:34:58,466 --> 00:35:00,800 with a dark red floor. 624 00:35:03,333 --> 00:35:04,900 OLUSEYI: What could be creating 625 00:35:04,900 --> 00:35:08,566 these criss-crossing lines and patterns on Europa's surface? 626 00:35:14,366 --> 00:35:16,600 ♪ ♪ 627 00:35:26,566 --> 00:35:29,266 QUICK: The canyons on Europa are so significant 628 00:35:29,266 --> 00:35:30,600 that NASA's planning a mission 629 00:35:30,600 --> 00:35:32,233 to go to Europa to explore them. 630 00:35:33,266 --> 00:35:35,100 NARRATOR: And in preparation, 631 00:35:35,100 --> 00:35:39,100 scientists are exploring similar environments on Earth, 632 00:35:39,100 --> 00:35:42,066 like these icy terrains in Alaska. 633 00:35:45,500 --> 00:35:47,066 (wind whistling) 634 00:35:54,666 --> 00:35:58,066 SAM HOWELL: I think many of the most important questions 635 00:35:58,066 --> 00:36:01,300 in planetary science can be addressed 636 00:36:01,300 --> 00:36:03,366 by going to worlds like Europa. 637 00:36:05,333 --> 00:36:07,733 NARRATOR: NASA scientist Sam Howell is studying 638 00:36:07,733 --> 00:36:12,700 what may be at the heart of Europa's mysterious appearance. 639 00:36:12,700 --> 00:36:14,300 HOWELL: What I'm most excited about, 640 00:36:14,300 --> 00:36:15,900 coming from a background 641 00:36:15,900 --> 00:36:17,566 in studying plate tectonics here on Earth, 642 00:36:17,566 --> 00:36:19,466 we see systems of rigid, 643 00:36:19,466 --> 00:36:22,000 icy plates moving around similar 644 00:36:22,000 --> 00:36:24,800 to the way Earth's plate tectonics looks on the surface. 645 00:36:24,800 --> 00:36:27,600 But digging in, we expect those processes to be very different. 646 00:36:28,600 --> 00:36:31,366 NARRATOR: Europa's surface features indicate 647 00:36:31,366 --> 00:36:34,300 they are a result of tectonic activity. 648 00:36:35,333 --> 00:36:36,933 BERDIS: This is an up-close image 649 00:36:36,933 --> 00:36:39,166 of Europa's surface, and you can see 650 00:36:39,166 --> 00:36:42,100 this large, dark red band 651 00:36:42,100 --> 00:36:44,100 in the very center of the image. 652 00:36:44,100 --> 00:36:45,600 We know that this feature is created 653 00:36:45,600 --> 00:36:47,300 due to tectonic activity 654 00:36:47,300 --> 00:36:49,633 because it appears that the crust 655 00:36:49,633 --> 00:36:51,633 of Europa has pulled apart, 656 00:36:51,633 --> 00:36:53,233 and you've had material flow up from underneath. 657 00:36:53,233 --> 00:36:55,700 But if we were to take this feature 658 00:36:55,700 --> 00:36:57,733 and extract it from this image, 659 00:36:57,733 --> 00:37:01,566 both sides of the crust would fit back together 660 00:37:01,566 --> 00:37:02,833 like a puzzle piece. 661 00:37:02,833 --> 00:37:06,233 We did not expect to see tectonic activity 662 00:37:06,233 --> 00:37:09,800 on a tiny moon like this, but there it is. 663 00:37:11,633 --> 00:37:13,266 NARRATOR: So far, this kind 664 00:37:13,266 --> 00:37:18,533 of global tectonic activity has only been observed on Earth. 665 00:37:18,533 --> 00:37:20,066 OLUSEYI: Take a look at Earth, 666 00:37:20,066 --> 00:37:22,400 and you'll see that South America looks like 667 00:37:22,400 --> 00:37:25,400 it fits right neatly in there into Africa. 668 00:37:26,433 --> 00:37:29,633 And so, we know that in the Atlantic, 669 00:37:29,633 --> 00:37:31,366 the seafloor is spreading, 670 00:37:31,366 --> 00:37:33,766 and that's what spread those two features apart. 671 00:37:37,233 --> 00:37:41,600 NARRATOR: On Earth, the rocky crust is broken into plates. 672 00:37:41,600 --> 00:37:45,466 They move as softer rock beneath flows very slowly 673 00:37:45,466 --> 00:37:47,933 over geologic time. 674 00:37:47,933 --> 00:37:51,900 QUICK: Europa does not have molten rock like Earth does, 675 00:37:51,900 --> 00:37:55,433 but what we do believe Europa has is a subsurface ocean. 676 00:37:58,466 --> 00:38:00,766 NARRATOR: A vast body of liquid water 677 00:38:00,766 --> 00:38:04,533 that exists underneath its icy surface. 678 00:38:04,533 --> 00:38:06,633 WONG: There is more water 679 00:38:06,633 --> 00:38:08,633 in Europa's subsurface 680 00:38:08,633 --> 00:38:11,533 than all of Earth's oceans, rivers and lakes combined. 681 00:38:14,466 --> 00:38:17,300 NARRATOR: This massive ocean sits beneath a layer 682 00:38:17,300 --> 00:38:22,400 of water ice, which could be up to 15 miles thick in places. 683 00:38:24,733 --> 00:38:27,433 So what force is powerful enough 684 00:38:27,433 --> 00:38:30,766 to crack Europa's extensive icy shell? 685 00:38:32,766 --> 00:38:37,066 BERDIS: As Europa and all of the other large moons orbit Jupiter 686 00:38:37,066 --> 00:38:38,366 and interact with it, 687 00:38:38,366 --> 00:38:40,100 they are all constantly pushing 688 00:38:40,100 --> 00:38:42,633 and pulling and tugging on each other, 689 00:38:42,633 --> 00:38:44,066 and this process is called "tidal heating." 690 00:38:47,000 --> 00:38:49,000 NARRATOR: The tidal heating varies, 691 00:38:49,000 --> 00:38:52,500 depending on how close or far Europa is from Jupiter 692 00:38:52,500 --> 00:38:55,033 and the other moons, 693 00:38:55,033 --> 00:38:57,866 resulting in temperature changes in the ocean. 694 00:38:59,833 --> 00:39:02,533 QUICK: And as the temperature of the ocean changes, 695 00:39:02,533 --> 00:39:06,500 the ice shell thickens and thins and expands and contracts. 696 00:39:06,500 --> 00:39:08,666 (wind whistling) 697 00:39:08,666 --> 00:39:11,133 NARRATOR: The mechanics of which can be seen on Earth. 698 00:39:12,266 --> 00:39:13,733 QUICK: As water freezes, 699 00:39:13,733 --> 00:39:16,633 it takes up more space and expands into ice. 700 00:39:16,633 --> 00:39:19,766 It's very similar to if we were to take a bottle of water 701 00:39:19,766 --> 00:39:21,300 and place it into the freezer. 702 00:39:21,300 --> 00:39:22,833 First, it would expand, 703 00:39:22,833 --> 00:39:24,766 and then we'd notice a large bit of cracking. 704 00:39:24,766 --> 00:39:26,900 This is what is happening on Europa. 705 00:39:29,233 --> 00:39:31,433 NARRATOR: Scaled up to the size of a moon, 706 00:39:31,433 --> 00:39:35,533 these ice expansion cracks create massive canyons 707 00:39:35,533 --> 00:39:37,566 across Europa. 708 00:39:43,666 --> 00:39:46,766 And as these canyons form, 709 00:39:46,766 --> 00:39:50,633 a key ingredient from the ocean below surges up 710 00:39:50,633 --> 00:39:52,266 through the cracks, 711 00:39:52,266 --> 00:39:56,166 giving Europa's markings their distinctive red. 712 00:40:00,766 --> 00:40:03,433 BERDIS: So the red marks that we see on Europa's surface-- 713 00:40:03,433 --> 00:40:05,666 these cracks and lines-- 714 00:40:05,666 --> 00:40:08,233 are salts 715 00:40:08,233 --> 00:40:10,566 that have come up from below the surface. 716 00:40:10,566 --> 00:40:13,433 ♪ ♪ 717 00:40:13,433 --> 00:40:16,233 NARRATOR: Suggesting a tantalizing possibility. 718 00:40:18,133 --> 00:40:21,333 This crisscrossing system of salty canyons means 719 00:40:21,333 --> 00:40:24,133 we might find life in the ocean 720 00:40:24,133 --> 00:40:26,400 underneath Europa's icy shell. 721 00:40:28,700 --> 00:40:31,966 SINGER: Life as we know it needs three basic things: 722 00:40:31,966 --> 00:40:33,533 water, 723 00:40:33,533 --> 00:40:37,400 a source of energy, and also, essential elements. 724 00:40:40,733 --> 00:40:42,633 NARRATOR: Europa has an ocean, 725 00:40:42,633 --> 00:40:45,633 and a source of energy from tidal movements. 726 00:40:47,200 --> 00:40:50,433 But it's missing the final key ingredient: 727 00:40:50,433 --> 00:40:52,933 some essential elements. 728 00:40:53,966 --> 00:40:58,266 However, with a little help from its neighboring moon Io, 729 00:40:58,266 --> 00:41:00,900 these elements can be found on Europa. 730 00:41:02,500 --> 00:41:03,833 SINGER: Io 731 00:41:03,833 --> 00:41:06,133 is an extremely volcanically-active place. 732 00:41:08,900 --> 00:41:10,633 And these volcanoes emit 733 00:41:10,633 --> 00:41:13,066 sulphur and other sulphur products, 734 00:41:13,066 --> 00:41:15,666 and these make it all the way onto Europa. 735 00:41:16,966 --> 00:41:21,766 And sulphur is one of those essential elements that life 736 00:41:21,766 --> 00:41:23,333 on Earth uses. 737 00:41:23,333 --> 00:41:25,833 ♪ ♪ 738 00:41:27,600 --> 00:41:29,733 BERDIS: All of the sulphur that's coming from Io 739 00:41:29,733 --> 00:41:31,600 and landing on Europa's surface 740 00:41:31,600 --> 00:41:35,066 is interacting with the salts and water 741 00:41:35,066 --> 00:41:39,066 that's coming up from underneath Europa's icy crust. 742 00:41:40,366 --> 00:41:43,766 NARRATOR: Chemical reactions between the sulphur from Io 743 00:41:43,766 --> 00:41:47,233 and the salts on Europa create essential molecules 744 00:41:47,233 --> 00:41:49,466 needed for life. 745 00:41:52,700 --> 00:41:54,433 And this allows for this perfect breeding ground 746 00:41:54,433 --> 00:41:57,366 for potential life to form and evolve. 747 00:41:59,000 --> 00:42:02,400 NARRATOR: Europa is such a strong candidate for life 748 00:42:02,400 --> 00:42:06,000 that NASA is already preparing to explore the moon. 749 00:42:08,066 --> 00:42:10,866 The goal is to study Europa's surface 750 00:42:10,866 --> 00:42:12,433 in more detail 751 00:42:12,433 --> 00:42:15,266 so that a future mission can one day land 752 00:42:15,266 --> 00:42:18,600 and explore beneath its icy crust. 753 00:42:20,500 --> 00:42:24,933 And scientists like Sam are already testing ideas 754 00:42:24,933 --> 00:42:27,400 for studying Europa's watery world. 755 00:42:31,233 --> 00:42:34,566 HOWELL: What we're doing is we're deploying a robotic probe 756 00:42:34,566 --> 00:42:36,500 into the ice and under it 757 00:42:36,500 --> 00:42:38,366 to explore what this lake environment is like. 758 00:42:40,300 --> 00:42:42,266 We might have the opportunity 759 00:42:42,266 --> 00:42:44,033 in my own lifetime 760 00:42:44,033 --> 00:42:47,666 to answer a question that's intrinsic to all of us: 761 00:42:47,666 --> 00:42:49,900 are we alone in our universe? 762 00:42:49,900 --> 00:42:52,100 Are we alone in our Solar System? 763 00:42:52,100 --> 00:42:55,166 And one of the most exciting aspects of exploring Europa 764 00:42:55,166 --> 00:42:59,200 is the potential of someday knowing 765 00:42:59,200 --> 00:43:02,600 whether or not there's life in our own Solar System. 766 00:43:04,666 --> 00:43:07,066 NARRATOR: Europa is one of the last ice moons 767 00:43:07,066 --> 00:43:09,666 that can exist this close to the sun. 768 00:43:10,633 --> 00:43:14,166 Worlds existing any closer to the warmth of the sun, 769 00:43:14,166 --> 00:43:17,966 like the rocky worlds of Mars, Earth, and our moon, 770 00:43:17,966 --> 00:43:19,966 have relatively little ice. 771 00:43:21,366 --> 00:43:25,100 Because they lie inside what is known as the ice line. 772 00:43:28,700 --> 00:43:30,800 DURFEY: You can't see the ice line, 773 00:43:30,800 --> 00:43:32,900 but you can see its effects. 774 00:43:32,900 --> 00:43:33,933 When small bodies that are 775 00:43:33,933 --> 00:43:35,666 primarily composed of ice 776 00:43:35,666 --> 00:43:38,233 cross inside of the ice line, 777 00:43:38,233 --> 00:43:40,633 the ice within them begins to vaporize. 778 00:43:42,833 --> 00:43:45,633 NARRATOR: Sometimes, icy rocks are ejected 779 00:43:45,633 --> 00:43:49,200 from the frigid outer regions of the Solar System 780 00:43:49,200 --> 00:43:51,600 and pulled towards the sun. 781 00:43:53,466 --> 00:43:55,933 These are known as comets. 782 00:43:57,933 --> 00:43:59,933 HOWETT: Comets are basically dirty snowballs, 783 00:43:59,933 --> 00:44:02,300 mostly water ice with a little bit of dust, 784 00:44:02,300 --> 00:44:04,366 and as they come into the inner Solar System, 785 00:44:04,366 --> 00:44:05,766 they get heated up by the sun. 786 00:44:07,866 --> 00:44:10,833 NARRATOR: As comets cross this invisible ice line, 787 00:44:10,833 --> 00:44:13,100 their ice starts turning into gas. 788 00:44:14,466 --> 00:44:16,933 HOWETT: And that's what forms these long tails 789 00:44:16,933 --> 00:44:19,033 that we can see when you look at a comet, 790 00:44:19,033 --> 00:44:21,333 and those tails stream away from the sun 791 00:44:21,333 --> 00:44:23,500 as the comet moves in towards it. 792 00:44:27,900 --> 00:44:31,233 NARRATOR: Inside the ice line, ice is rare, 793 00:44:31,233 --> 00:44:34,933 but there are places where it can hang on. 794 00:44:39,833 --> 00:44:43,300 DURFEY: Mars is within the ice line of the Solar System, 795 00:44:43,300 --> 00:44:46,433 but it still has ice in it and on it. 796 00:44:50,933 --> 00:44:53,100 NARRATOR: It's the end of winter, 797 00:44:53,100 --> 00:44:55,700 and it's been dark at Mars's south pole 798 00:44:55,700 --> 00:44:59,466 for over 150 Martian days straight. 799 00:45:01,333 --> 00:45:04,200 Mars holds onto much of its ice at its poles. 800 00:45:06,266 --> 00:45:09,100 The ice sheet here is not like any on Earth. 801 00:45:10,466 --> 00:45:13,366 Because as winter turns to spring, 802 00:45:13,366 --> 00:45:17,300 the surface becomes covered in strange features. 803 00:45:21,233 --> 00:45:24,666 And with the launch of the Mars Reconnaissance Orbiter 804 00:45:24,666 --> 00:45:28,833 in 2005, we began to see them 805 00:45:28,833 --> 00:45:31,533 like never before. 806 00:45:31,533 --> 00:45:33,600 OLUSEYI: The Mars Reconnaissance Orbiter 807 00:45:33,600 --> 00:45:35,433 is a satellite of Mars that takes 808 00:45:35,433 --> 00:45:36,733 photograph after photograph 809 00:45:36,733 --> 00:45:38,033 of Mars's surface, 810 00:45:38,033 --> 00:45:40,066 and so it's able to see these things come and go 811 00:45:40,066 --> 00:45:41,966 and change with the seasons. 812 00:45:45,233 --> 00:45:49,833 NARRATOR: The images show dark fans on the surface 813 00:45:49,833 --> 00:45:53,633 meaning something must have risen into the air above them. 814 00:45:55,333 --> 00:45:56,900 GONZALEZ: We see these features, 815 00:45:56,900 --> 00:45:59,500 and they will go in the direction 816 00:45:59,500 --> 00:46:01,433 depending on the wind pattern of Mars. 817 00:46:01,433 --> 00:46:03,466 So we know that material 818 00:46:03,466 --> 00:46:06,133 is being pushed out from underneath. 819 00:46:07,366 --> 00:46:09,633 NARRATOR: This phenomenon seen on Mars 820 00:46:09,633 --> 00:46:13,500 depends on the type of ice that falls from the Martian skies. 821 00:46:16,833 --> 00:46:19,066 During winter at the South Pole, 822 00:46:19,066 --> 00:46:21,200 more and more snow falls. 823 00:46:23,033 --> 00:46:26,000 But with so little water in Mars's atmosphere, 824 00:46:26,000 --> 00:46:28,933 this isn't the type of snow we have on Earth. 825 00:46:30,033 --> 00:46:33,300 This is carbon dioxide snow. 826 00:46:34,333 --> 00:46:38,033 GAO: Every winter, three to four trillion tons 827 00:46:38,033 --> 00:46:40,400 of carbon dioxide snow falls on Mars. 828 00:46:40,400 --> 00:46:43,633 That's so much snow that the atmospheric pressure 829 00:46:43,633 --> 00:46:47,400 at the surface of Mars decreases by about a third. 830 00:46:47,400 --> 00:46:50,433 NARRATOR: The air is literally freezing to the ground, 831 00:46:50,433 --> 00:46:54,033 forming carbon dioxide ice caps at the poles. 832 00:46:57,000 --> 00:47:00,233 But in spring, as the warmth of the sun reaches 833 00:47:00,233 --> 00:47:04,033 the poles again, something incredible happens. 834 00:47:05,266 --> 00:47:08,033 DURFEY: As the sun comes over the horizon, 835 00:47:08,033 --> 00:47:11,333 the carbon dioxide ice is heated. 836 00:47:17,666 --> 00:47:20,900 This carbon dioxide ice can turn to gas, 837 00:47:20,900 --> 00:47:23,733 and when it does, it forms these geysers 838 00:47:23,733 --> 00:47:27,133 that also bring other material from the subsurface 839 00:47:27,133 --> 00:47:28,466 to the surface. 840 00:47:31,200 --> 00:47:32,933 GONZALEZ: And depending on which way the wind 841 00:47:32,933 --> 00:47:36,500 is blowing, it'll form these nice looking fan features. 842 00:47:37,766 --> 00:47:39,900 NARRATOR: Because of Mars's combination 843 00:47:39,900 --> 00:47:42,233 of atmospheric pressure and temperature... 844 00:47:43,266 --> 00:47:46,300 ...the carbon dioxide turns from ice to gas 845 00:47:46,300 --> 00:47:48,400 without passing through the liquid phase. 846 00:47:50,433 --> 00:47:52,666 WONG: On Mars, its atmosphere 847 00:47:52,666 --> 00:47:55,500 actually falls onto the surface 848 00:47:55,500 --> 00:47:58,766 and then vaporizes back into the atmosphere 849 00:47:58,766 --> 00:48:00,633 on an annual basis. 850 00:48:00,633 --> 00:48:02,266 That's absolutely wild 851 00:48:02,266 --> 00:48:05,033 because it's so different from what's happening here on Earth. 852 00:48:08,266 --> 00:48:10,233 NARRATOR: These conditions on Mars 853 00:48:10,233 --> 00:48:12,533 have enabled carbon dioxide snow 854 00:48:12,533 --> 00:48:15,366 to create unique features on its surface. 855 00:48:18,266 --> 00:48:21,600 But the conditions found on its nearest neighbor, 856 00:48:21,600 --> 00:48:25,833 close enough to see from Mars with the naked eye, 857 00:48:25,833 --> 00:48:29,500 have allowed for something extraordinary to form. 858 00:48:33,700 --> 00:48:35,566 And just like Mars, 859 00:48:35,566 --> 00:48:39,000 Earth, too, has ice caps at its poles. 860 00:48:41,000 --> 00:48:43,433 But the similarities end there. 861 00:48:45,233 --> 00:48:46,900 HOWETT: Earth's ice is really unique 862 00:48:46,900 --> 00:48:49,900 because we operate in a very small temperature range 863 00:48:49,900 --> 00:48:52,200 and a very small pressure range on the surface. 864 00:48:52,200 --> 00:48:55,366 The ice that we experience is a very small subset 865 00:48:55,366 --> 00:48:57,533 of the total ice that's in our universe. 866 00:49:00,400 --> 00:49:02,300 NARRATOR: Earth's temperature and pressure ranges 867 00:49:02,300 --> 00:49:05,800 allow water to exist in all three states: 868 00:49:05,800 --> 00:49:08,733 solid, liquid, and gas. 869 00:49:10,533 --> 00:49:13,866 Earth is the only place known to have floating icebergs 870 00:49:13,866 --> 00:49:17,233 and bodies of water not completely frozen over. 871 00:49:18,500 --> 00:49:21,300 And frozen water under Earth's conditions 872 00:49:21,300 --> 00:49:23,466 has an important property. 873 00:49:25,100 --> 00:49:26,500 We might take this for granted, 874 00:49:26,500 --> 00:49:28,300 but the ice that we have here on Earth 875 00:49:28,300 --> 00:49:31,600 floats because its density 876 00:49:31,600 --> 00:49:34,833 is lower than the water that it is floating in. 877 00:49:34,833 --> 00:49:38,233 And so, the molecules of water ice, 878 00:49:38,233 --> 00:49:41,233 as it freezes, expands out slightly 879 00:49:41,233 --> 00:49:42,933 and moves away from each other 880 00:49:42,933 --> 00:49:45,600 to lower the overall density of the ice, 881 00:49:45,600 --> 00:49:48,633 and this allows it to float on top of the water. 882 00:49:50,200 --> 00:49:53,066 NARRATOR: This property of water ice has enormous consequences 883 00:49:53,066 --> 00:49:55,633 for life on Earth, 884 00:49:55,633 --> 00:49:59,266 the only place life is known to exist to date. 885 00:50:00,433 --> 00:50:03,566 BERDIS: The ice on Earth provides a form of protection 886 00:50:03,566 --> 00:50:05,800 to any life below the surface 887 00:50:05,800 --> 00:50:09,233 that might need protection from anything that could harm it. 888 00:50:11,166 --> 00:50:12,766 NARRATOR: Ice's ability to float 889 00:50:12,766 --> 00:50:15,500 means that, during Earth's colder periods, 890 00:50:15,500 --> 00:50:19,466 bodies of water didn't freeze from the bottom up, 891 00:50:19,466 --> 00:50:21,333 instead remaining a liquid 892 00:50:21,333 --> 00:50:24,800 where life may have held on. 893 00:50:24,800 --> 00:50:27,300 (birds and insects chirping) 894 00:50:27,300 --> 00:50:29,566 For around four billion years, 895 00:50:29,566 --> 00:50:32,400 liquid water on Earth 896 00:50:32,400 --> 00:50:34,333 has allowed an unbroken chain 897 00:50:34,333 --> 00:50:36,366 of life to evolve. 898 00:50:38,866 --> 00:50:41,666 Resulting in oceans. 899 00:50:41,666 --> 00:50:45,500 Home to countless species. 900 00:50:45,500 --> 00:50:48,433 And rivers teeming with life. 901 00:50:49,400 --> 00:50:52,600 All made possible by the unique interplay 902 00:50:52,600 --> 00:50:56,466 between liquid water and floating ice on Earth. 903 00:50:57,666 --> 00:50:59,466 OLUSEYI: The next time you find yourself 904 00:50:59,466 --> 00:51:02,700 making a beverage and you put ice in it, 905 00:51:02,700 --> 00:51:04,866 just take a moment and reflect 906 00:51:04,866 --> 00:51:07,866 on the amazingness of the ice 907 00:51:07,866 --> 00:51:09,600 that made your life possible. 908 00:51:11,066 --> 00:51:13,300 NARRATOR: Across our Solar System, 909 00:51:13,300 --> 00:51:15,600 scientists have found worlds 910 00:51:15,600 --> 00:51:17,533 shaped by ice, 911 00:51:17,533 --> 00:51:20,133 made of a diversity of substances 912 00:51:20,133 --> 00:51:23,100 behaving in unbelievable ways. 913 00:51:25,300 --> 00:51:28,400 DURFEY: There's a massive variety of ice worlds out there. 914 00:51:28,400 --> 00:51:30,833 Each one has something we haven't seen before. 915 00:51:32,266 --> 00:51:34,966 NARRATOR: We are in a golden age of discovery, 916 00:51:34,966 --> 00:51:39,333 but our knowledge of these ice worlds is far from complete. 917 00:51:40,633 --> 00:51:43,266 There is so much left to learn about ice worlds. 918 00:51:43,266 --> 00:51:45,766 Our understanding is only skin deep. 919 00:51:45,766 --> 00:51:48,033 We want to explore these worlds because 920 00:51:48,033 --> 00:51:52,133 it really tells us where we fit into the universe. 921 00:51:52,133 --> 00:51:54,833 Why are we here? How did we first get here? 922 00:51:55,833 --> 00:51:57,933 NARRATOR: We may not have all the answers, 923 00:51:57,933 --> 00:52:01,833 but we now know that ice plays a critical role 924 00:52:01,833 --> 00:52:03,200 in our story. 925 00:52:05,233 --> 00:52:08,100 WONG: Without the kind of ice that we have here on Earth, 926 00:52:08,100 --> 00:52:10,700 we might not even be here to be discussing ice 927 00:52:10,700 --> 00:52:12,866 and all of its wondrous forms. 928 00:52:12,866 --> 00:52:16,900 ♪ ♪ 929 00:52:35,166 --> 00:52:38,033 ♪ ♪ 930 00:52:38,966 --> 00:52:46,500 ♪ ♪ 931 00:52:50,333 --> 00:52:57,866 ♪ ♪ 932 00:53:01,766 --> 00:53:09,300 ♪ ♪ 933 00:53:10,933 --> 00:53:18,466 ♪ ♪ 934 00:53:20,100 --> 00:53:27,633 ♪ ♪