1 00:00:01,070 --> 00:00:03,244 Viewers like you make this program possible. 2 00:00:03,244 --> 00:00:05,350 Support your local PBS station. 3 00:00:14,048 --> 00:00:16,154 NARRATOR: Throughout our solar system, 4 00:00:16,154 --> 00:00:20,089 we find worlds shaped by ice. 5 00:00:20,848 --> 00:00:21,883 SABINE STANLEY: These ice worlds 6 00:00:21,883 --> 00:00:24,093 are so unexpected and surprising. 7 00:00:24,093 --> 00:00:26,578 There is definitely more ice out there 8 00:00:26,578 --> 00:00:29,581 than we really expected or anticipated. 9 00:00:30,823 --> 00:00:34,586 NARRATOR: Today, spacecraft are bringing us closer than ever... 10 00:00:36,105 --> 00:00:38,555 ...to revealing their secrets. 11 00:00:39,660 --> 00:00:41,317 We've got carbon dioxide snow 12 00:00:41,317 --> 00:00:43,767 on Mars. 13 00:00:43,767 --> 00:00:44,941 KELSI SINGER: On Pluto, 14 00:00:44,941 --> 00:00:46,563 we have these nitrogen ice glaciers 15 00:00:46,563 --> 00:00:49,808 that no one would have predicted. 16 00:00:49,808 --> 00:00:51,637 Deep in the planet of Uranus, 17 00:00:51,637 --> 00:00:56,090 you get this extremely dense black hot ice. 18 00:00:56,090 --> 00:00:59,197 MICHAEL WONG: The data has truly transformed 19 00:00:59,197 --> 00:01:02,510 the way that we understand how ice behaves 20 00:01:02,510 --> 00:01:05,789 so far away in the depths of space. 21 00:01:05,789 --> 00:01:09,414 NARRATOR: But many questions remain unanswered. 22 00:01:09,414 --> 00:01:12,037 PETER GAO: How do these icy worlds even form? 23 00:01:12,037 --> 00:01:13,349 How did the ice get there? 24 00:01:13,349 --> 00:01:14,384 Is there life there? 25 00:01:14,384 --> 00:01:16,179 NARRATOR: And of all the worlds 26 00:01:16,179 --> 00:01:17,939 in our solar system, 27 00:01:17,939 --> 00:01:20,873 ours hits the icy jackpot. 28 00:01:20,873 --> 00:01:23,013 The ice we have here on Earth is special. 29 00:01:23,013 --> 00:01:25,844 And if it didn't have its special properties, 30 00:01:25,844 --> 00:01:27,397 life on Earth would not exist 31 00:01:27,397 --> 00:01:29,123 and you wouldn't be here watching me. 32 00:01:30,159 --> 00:01:32,920 NARRATOR: Why is our cosmic neighborhood 33 00:01:32,920 --> 00:01:36,026 home to so many different and exotic ices? 34 00:01:38,201 --> 00:01:41,791 "Solar System: Icy Worlds." 35 00:01:41,791 --> 00:01:44,587 Right now, on "NOVA." 36 00:01:44,587 --> 00:01:47,003 ♪ 37 00:02:01,293 --> 00:02:03,571 ♪ 38 00:02:03,571 --> 00:02:05,539 NARRATOR: Out in the dark expanse 39 00:02:05,539 --> 00:02:08,128 of our solar system, 40 00:02:08,128 --> 00:02:10,613 far beyond Earth and Mars... 41 00:02:12,235 --> 00:02:15,825 ...we enter the realm of the gas giants. 42 00:02:17,516 --> 00:02:19,794 Where average temperatures of the planets 43 00:02:19,794 --> 00:02:21,486 begin to plummet. 44 00:02:27,768 --> 00:02:30,598 Venture even farther away from Earth, 45 00:02:30,598 --> 00:02:33,256 and we pass the ice giants. 46 00:02:36,086 --> 00:02:39,607 Here, temperatures can drop even lower... 47 00:02:41,678 --> 00:02:46,027 ...down to - 370 degrees Fahrenheit. 48 00:02:47,063 --> 00:02:50,687 These worlds are made almost entirely of ice... 49 00:02:52,379 --> 00:02:56,693 ...existing in exotic, seemingly impossible forms. 50 00:02:59,938 --> 00:03:02,837 WONG: Thanks to planetary exploration, 51 00:03:02,837 --> 00:03:04,943 we have witnessed different forms of ice 52 00:03:04,943 --> 00:03:08,257 behaving in ways that we could not have expected. 53 00:03:10,362 --> 00:03:13,469 NARRATOR: Scientists are just beginning to uncover 54 00:03:13,469 --> 00:03:16,575 the icy secrets of our solar system. 55 00:03:19,268 --> 00:03:22,788 GURNEY: We really don't know much about ice worlds 56 00:03:22,788 --> 00:03:23,996 and planetary scientists 57 00:03:23,996 --> 00:03:25,170 are really discovering 58 00:03:25,170 --> 00:03:26,585 new things every day. 59 00:03:27,931 --> 00:03:30,037 NARRATOR: Discoveries that can shed light on 60 00:03:30,037 --> 00:03:32,660 the strange ways ice behaves 61 00:03:32,660 --> 00:03:35,353 and how dynamic it can be, 62 00:03:35,353 --> 00:03:38,010 not only in our solar system, 63 00:03:38,010 --> 00:03:40,875 but on other worlds in our galaxy, too. 64 00:03:53,957 --> 00:03:56,753 [ice crackling] 65 00:04:04,451 --> 00:04:06,660 NARRATOR: Over three billion miles from Earth, 66 00:04:06,660 --> 00:04:09,456 the space probe New Horizons 67 00:04:09,456 --> 00:04:12,631 is traveling far beyond the rocky planets. 68 00:04:14,599 --> 00:04:17,187 And after more than nine years, 69 00:04:17,187 --> 00:04:19,431 arrives at its destination. 70 00:04:23,711 --> 00:04:25,299 As it passes Pluto, 71 00:04:26,714 --> 00:04:28,233 ...the probe gives us a glimpse 72 00:04:28,233 --> 00:04:31,374 of a world made of weird ice. 73 00:04:32,996 --> 00:04:34,066 DURFEY: Flyby missions 74 00:04:34,066 --> 00:04:35,930 are do or die. 75 00:04:35,930 --> 00:04:37,932 If you don't get those images, 76 00:04:37,932 --> 00:04:40,418 if you don't get that data, 77 00:04:40,418 --> 00:04:41,798 you've flown by 78 00:04:41,798 --> 00:04:43,179 and you're gone now. 79 00:04:44,560 --> 00:04:47,010 VERBISCER: We only get one shot because traveling at 80 00:04:47,010 --> 00:04:48,943 31,000 miles an hour, 81 00:04:48,943 --> 00:04:51,152 it's not like you can do a U-turn. 82 00:04:53,638 --> 00:04:58,539 NARRATOR: The $780 million high-risk mission pays dividends, 83 00:04:58,539 --> 00:05:01,335 delivering a mother lode of data. 84 00:05:01,335 --> 00:05:02,923 [camera shutter clicking] 85 00:05:03,958 --> 00:05:05,891 New Horizons surprises scientists 86 00:05:05,891 --> 00:05:09,343 with incredible images of Pluto's surface, 87 00:05:09,343 --> 00:05:12,795 revealing features they never expected to see. 88 00:05:14,106 --> 00:05:15,073 GAO: I think when 89 00:05:15,073 --> 00:05:17,420 people first saw images of Pluto, 90 00:05:17,420 --> 00:05:18,697 they were just blown away. 91 00:05:18,697 --> 00:05:22,183 We're seeing incredible diversity in 92 00:05:22,183 --> 00:05:23,495 what the surface looks like. 93 00:05:24,462 --> 00:05:26,187 VERBISCER: I walked into the geology room 94 00:05:26,187 --> 00:05:29,018 and looked at an image on one of the computer screens, 95 00:05:29,018 --> 00:05:32,193 and I wondered why someone was looking at 96 00:05:32,193 --> 00:05:34,195 a picture of Antarctica. 97 00:05:34,195 --> 00:05:36,508 And it dawned on me 98 00:05:36,508 --> 00:05:38,752 [chuckling]: gradually, oh, my goodness, 99 00:05:38,752 --> 00:05:41,651 that was not Antarctica, that was actually 100 00:05:41,651 --> 00:05:44,861 a very close picture of Pluto. 101 00:05:45,862 --> 00:05:49,038 WONG: There were tons of mysteries that we needed to unravel. 102 00:05:49,038 --> 00:05:50,971 There were lots of features 103 00:05:50,971 --> 00:05:53,905 that puzzled us. How could that possibly be, 104 00:05:53,905 --> 00:05:56,390 so far away in the solar system? 105 00:06:01,844 --> 00:06:03,397 NARRATOR: The amount of data collected 106 00:06:03,397 --> 00:06:06,849 allows scientists to map Pluto's surface. 107 00:06:11,232 --> 00:06:13,752 Pluto's most prominent feature 108 00:06:13,752 --> 00:06:18,308 is a great icy plain around 600 miles across. 109 00:06:20,172 --> 00:06:22,968 And, despite the extreme cold, 110 00:06:22,968 --> 00:06:26,662 there are signs of movement in the ice; 111 00:06:26,662 --> 00:06:28,871 lines etched into the surface 112 00:06:28,871 --> 00:06:30,320 as if they are churning. 113 00:06:34,877 --> 00:06:39,122 And then, something even more unexpected. 114 00:06:49,339 --> 00:06:51,169 Glaciers. 115 00:06:52,998 --> 00:06:54,966 Flowing rivers of ice 116 00:06:54,966 --> 00:06:57,313 on a world so cold... 117 00:06:58,866 --> 00:07:01,351 ...it seems nothing should be moving. 118 00:07:05,666 --> 00:07:08,151 Pluto is a wintery puzzle, 119 00:07:08,151 --> 00:07:12,708 with icy landscapes as dramatic as anything seen on Earth. 120 00:07:14,503 --> 00:07:17,195 How is all this dynamism possible 121 00:07:17,195 --> 00:07:20,163 on a world so far from the sun? 122 00:07:24,858 --> 00:07:29,897 ♪ 123 00:07:34,315 --> 00:07:38,147 Pluto, a place right on the edge of the solar system, 124 00:07:38,147 --> 00:07:40,218 looks remarkably similar to 125 00:07:40,218 --> 00:07:43,739 some frozen landscapes on Earth, 126 00:07:43,739 --> 00:07:46,327 like this glacier in Alaska. 127 00:07:47,812 --> 00:07:50,884 LEIGHAN FALLEY: Glacier Two for the Root Canal, acknowledge. 128 00:07:52,299 --> 00:07:54,957 [man speaks indistinctly over radio] 129 00:07:56,890 --> 00:07:58,408 FALLEY: Okay, floor above two. 130 00:07:58,408 --> 00:08:00,514 Hang on. 131 00:08:00,514 --> 00:08:02,309 Never a dull moment around here. 132 00:08:03,759 --> 00:08:06,762 Well, isn't this amazing? 133 00:08:06,762 --> 00:08:09,212 - Incredible views. - Yes. 134 00:08:10,559 --> 00:08:12,906 NARRATOR: This landscape might look frozen solid, 135 00:08:12,906 --> 00:08:14,873 but it is one of the most 136 00:08:14,873 --> 00:08:18,532 geologically active areas on Earth. 137 00:08:18,532 --> 00:08:20,810 SINGER: In the time that you've been flying here, 138 00:08:20,810 --> 00:08:23,503 have you seen a lot of changes in the glacier? 139 00:08:23,503 --> 00:08:25,505 Absolutely. Are you kidding me? 140 00:08:25,505 --> 00:08:28,611 [chuckling]: Yes. I've seen immense changes. 141 00:08:29,647 --> 00:08:32,166 SINGER: Some aspects of what we're looking at 142 00:08:32,166 --> 00:08:34,548 that really reminded me of Pluto, 143 00:08:34,548 --> 00:08:36,481 there's the kind of flow lines 144 00:08:36,481 --> 00:08:37,793 in the glacier 145 00:08:37,793 --> 00:08:39,760 indicating the direction of flow. 146 00:08:39,760 --> 00:08:41,417 Oh, Pluto has flow lines? 147 00:08:41,417 --> 00:08:44,109 Yes, they are moving downhill, 148 00:08:44,109 --> 00:08:46,422 similar to these glaciers. 149 00:08:52,048 --> 00:08:53,360 FALLEY: We're coming in for landing. 150 00:08:55,569 --> 00:08:57,813 NARRATOR: Understanding these glacial features 151 00:08:57,813 --> 00:09:00,125 can help scientists understand 152 00:09:00,125 --> 00:09:01,851 how Pluto's glaciers flow. 153 00:09:11,861 --> 00:09:15,485 [plane powering down] 154 00:09:15,485 --> 00:09:16,901 FALLEY: Welcome to the glacier, you guys. 155 00:09:22,941 --> 00:09:25,392 SINGER: Wow.[Falley laughs] 156 00:09:25,392 --> 00:09:27,739 - So beautiful. - FALLEY:Oh... 157 00:09:27,739 --> 00:09:30,190 FALLEY: One of the greatest ranges on the continent. 158 00:09:33,434 --> 00:09:35,160 [laughs] 159 00:09:35,160 --> 00:09:36,610 Is the glacier under here? 160 00:09:36,610 --> 00:09:37,956 Yes, we're probably 161 00:09:37,956 --> 00:09:40,959 on top of about 700 to 1,500 feet 162 00:09:40,959 --> 00:09:43,168 of glacier ice underneath us. 163 00:09:44,618 --> 00:09:47,207 CARLY HOWETT: If you ever experience visiting or seeing a glacier, 164 00:09:47,207 --> 00:09:49,727 you might think that they're completely stationary. 165 00:09:49,727 --> 00:09:51,211 But actually, if you were to 166 00:09:51,211 --> 00:09:52,212 stand there for long enough, 167 00:09:52,212 --> 00:09:53,765 you would see that they move. 168 00:09:54,939 --> 00:09:56,147 HAKEEM OLUSEYI: Glaciers form on Earth 169 00:09:56,147 --> 00:09:58,494 when snow does not melt 170 00:09:58,494 --> 00:10:00,565 season after season, and it packs down, 171 00:10:00,565 --> 00:10:04,776 and the weight of that snow compresses it into ice. 172 00:10:05,846 --> 00:10:07,261 And as more and more builds up 173 00:10:07,261 --> 00:10:08,746 and it gets heavier and heavier, 174 00:10:08,746 --> 00:10:10,713 it begins to flow. 175 00:10:12,922 --> 00:10:15,511 NARRATOR: These huge glacial ice features in Alaska 176 00:10:15,511 --> 00:10:18,203 have formed in this exact way. 177 00:10:22,242 --> 00:10:24,244 SINGER: This is an incredible landscape. 178 00:10:25,279 --> 00:10:27,696 It really reminds me of what it would be like to 179 00:10:27,696 --> 00:10:29,836 stand on Pluto. 180 00:10:29,836 --> 00:10:31,803 And it's 15 degrees Fahrenheit, 181 00:10:31,803 --> 00:10:34,599 and we're in this totally frozen landscape, 182 00:10:34,599 --> 00:10:37,464 and on Pluto, it's even colder. 183 00:10:37,464 --> 00:10:41,641 It's -390 degrees Fahrenheit. 184 00:10:41,641 --> 00:10:43,746 How can these glaciers be flowing 185 00:10:43,746 --> 00:10:46,646 when it's so cold on the surface of Pluto? 186 00:10:46,646 --> 00:10:48,682 ♪ 187 00:10:51,927 --> 00:10:55,585 NARRATOR: Water ice is frozen as solid as rock here, 188 00:10:55,585 --> 00:10:59,348 so it doesn't flow in the same way as glaciers on Earth. 189 00:11:03,490 --> 00:11:07,736 And yet, these glaciers look like they are flowing. 190 00:11:14,743 --> 00:11:19,161 We even see two glaciers that appear to flow into each other, 191 00:11:19,161 --> 00:11:23,130 combining to form a mega glacier 192 00:11:23,130 --> 00:11:25,961 that flows onto the ice plains below. 193 00:11:29,274 --> 00:11:32,484 GURNEY: So, at Pluto, we see these glaciers 194 00:11:32,484 --> 00:11:35,833 that are flowing, but it's way too cold 195 00:11:35,833 --> 00:11:37,835 for there to be flowing water, 196 00:11:37,835 --> 00:11:39,975 so what are they actually made of? 197 00:11:39,975 --> 00:11:41,424 So, it might be surprising to hear 198 00:11:41,424 --> 00:11:43,012 that the definition of ice 199 00:11:43,012 --> 00:11:45,532 really depends on who you're talking to. 200 00:11:45,532 --> 00:11:47,396 If you're talking to people 201 00:11:47,396 --> 00:11:49,156 on Earth doing their everyday things, 202 00:11:49,156 --> 00:11:52,159 then ice is just the solid form of water. 203 00:11:52,159 --> 00:11:54,748 But if you're talking to a planetary scientist, 204 00:11:54,748 --> 00:11:58,338 then ice is a way to describe a group of materials. 205 00:11:58,338 --> 00:12:01,859 It's water, but it's also ammonia and methane, 206 00:12:01,859 --> 00:12:03,584 things that are made up of a lot of carbon, 207 00:12:03,584 --> 00:12:06,277 hydrogen, oxygen, nitrogen mixed in. 208 00:12:08,072 --> 00:12:09,970 NARRATOR: On Earth, these are usually found 209 00:12:09,970 --> 00:12:12,145 as a liquid or a gas, 210 00:12:12,145 --> 00:12:13,594 but in the solar system, 211 00:12:13,594 --> 00:12:16,839 they can be frozen into ices. 212 00:12:16,839 --> 00:12:20,325 OLUSEYI: From afar, we can tell what the composition 213 00:12:20,325 --> 00:12:22,293 of Pluto's surface is. 214 00:12:22,293 --> 00:12:25,192 But once we got there, what we didn't expect 215 00:12:25,192 --> 00:12:28,126 is the configuration of those materials. 216 00:12:28,126 --> 00:12:29,645 ♪ 217 00:12:31,612 --> 00:12:34,132 NARRATOR: A clue to the composition of the glaciers 218 00:12:34,132 --> 00:12:39,897 is Pluto's surface temperature of -390 degrees Fahrenheit. 219 00:12:39,897 --> 00:12:43,176 That's pretty close to the melting point of nitrogen, 220 00:12:43,176 --> 00:12:46,731 at around - 350 degrees Fahrenheit. 221 00:12:47,905 --> 00:12:50,355 Similarly, on Earth, 222 00:12:50,355 --> 00:12:55,015 the melting point of water ice is 32 degrees Fahrenheit, 223 00:12:55,015 --> 00:13:00,710 not far from the average surface temperature of 59 degrees. 224 00:13:00,710 --> 00:13:03,713 HOWETT: For a glacier to move, it has to be made of an ice 225 00:13:03,713 --> 00:13:06,233 that's not too far away from its melting temperature, 226 00:13:06,233 --> 00:13:08,304 'cause at the bottom, what you need is-is 227 00:13:08,304 --> 00:13:10,513 the ice to melt just a little bit 228 00:13:10,513 --> 00:13:12,792 so that the glacier is able to flow, 229 00:13:12,792 --> 00:13:14,759 and on Earth, water does that-- 230 00:13:14,759 --> 00:13:17,969 the water ice isn't that far from its melting temperature-- 231 00:13:17,969 --> 00:13:20,454 but on Pluto, it's so cold, that's not the case 232 00:13:20,454 --> 00:13:23,250 for water ice, but it is the case for nitrogen ice. 233 00:13:23,250 --> 00:13:24,734 Take a breath in. 234 00:13:24,734 --> 00:13:26,046 [inhales] 235 00:13:26,046 --> 00:13:28,048 The air that is in your lungs 236 00:13:28,048 --> 00:13:29,498 includes nitrogen, 237 00:13:29,498 --> 00:13:30,844 and it's a gas for us, 238 00:13:30,844 --> 00:13:32,639 it's the air that we breathe. 239 00:13:32,639 --> 00:13:36,539 On Pluto, it's so cold that that's solid. 240 00:13:36,539 --> 00:13:39,404 [plane engine whirring] 241 00:13:39,404 --> 00:13:41,544 NARRATOR: And it's this solid nitrogen 242 00:13:41,544 --> 00:13:44,685 that creates Pluto's flowing glaciers 243 00:13:44,685 --> 00:13:47,550 that are so similar to Earth's water glaciers. 244 00:13:50,588 --> 00:13:53,867 WONG: The same physical forces are responsible 245 00:13:53,867 --> 00:13:56,836 for carving the landscapes that we see here on Earth 246 00:13:56,836 --> 00:13:58,838 and on Pluto. 247 00:13:58,838 --> 00:14:01,771 It's just using different building blocks. 248 00:14:04,015 --> 00:14:05,983 GAO: I think Pluto has definitely taught us 249 00:14:05,983 --> 00:14:08,537 that the solar system is a giant laboratory 250 00:14:08,537 --> 00:14:09,745 where different elements can be put together 251 00:14:09,745 --> 00:14:11,057 in all kinds of interesting ways. 252 00:14:11,057 --> 00:14:13,162 ♪ 253 00:14:18,271 --> 00:14:21,343 NARRATOR: When New Horizons leaves Pluto behind, 254 00:14:21,343 --> 00:14:23,690 it turns back 255 00:14:23,690 --> 00:14:27,211 and takes one last photograph, 256 00:14:27,211 --> 00:14:31,698 revealing Pluto's breathtaking atmosphere, 257 00:14:31,698 --> 00:14:34,632 rich in the nitrogen that condenses on the surface 258 00:14:34,632 --> 00:14:36,185 to create its glaciers. 259 00:14:38,153 --> 00:14:39,637 VERBISCER: What we've seen 260 00:14:39,637 --> 00:14:42,260 in the outer solar system from the New Horizons spacecraft 261 00:14:42,260 --> 00:14:46,713 at Pluto and beyond has been revolutionary, 262 00:14:46,713 --> 00:14:51,511 showing us diversity in ice that we don't have here on Earth. 263 00:14:54,445 --> 00:14:57,206 NARRATOR: Pluto offers a tantalizing clue 264 00:14:57,206 --> 00:14:59,174 that very distant and cold worlds 265 00:14:59,174 --> 00:15:03,005 may be as active and dynamic as Earth. 266 00:15:05,145 --> 00:15:07,941 ♪ 267 00:15:07,941 --> 00:15:09,874 Closer to the sun, 268 00:15:09,874 --> 00:15:13,119 as we enter the realm of the ice giants, 269 00:15:13,119 --> 00:15:17,019 ice appears in even more bizarre forms 270 00:15:17,019 --> 00:15:20,540 behaving in unpredictable ways. 271 00:15:21,886 --> 00:15:25,200 It is found not only on the surface 272 00:15:25,200 --> 00:15:28,513 but also deep inside planets. 273 00:15:30,170 --> 00:15:35,003 Neptune, made up of around 80% frozen icy material, 274 00:15:35,003 --> 00:15:39,110 has giant ice storms raging across it. 275 00:15:42,458 --> 00:15:45,945 Another billion miles closer to the sun... 276 00:15:47,015 --> 00:15:49,569 ...is Neptune's icy twin. 277 00:15:52,192 --> 00:15:56,714 ♪ 278 00:15:56,714 --> 00:16:02,064 Uranus is an enormous planet of icy storms. 279 00:16:02,064 --> 00:16:04,860 GURNEY: When I first saw images of Uranus, 280 00:16:04,860 --> 00:16:07,173 I thought they were absolutely beautiful. 281 00:16:07,173 --> 00:16:10,831 Blue, almost ocean-colored. 282 00:16:12,868 --> 00:16:14,180 NARRATOR: It has a feature 283 00:16:14,180 --> 00:16:17,010 that has puzzled scientists for decades: 284 00:16:17,010 --> 00:16:21,981 its vast, shimmering auroras. 285 00:16:21,981 --> 00:16:24,742 STANLEY: The aurora on Uranus are mysterious 286 00:16:24,742 --> 00:16:26,123 because flashes of light suddenly appear 287 00:16:26,123 --> 00:16:27,883 all over the planetary surface, 288 00:16:27,883 --> 00:16:29,781 and you don't know why they're happening there. 289 00:16:31,714 --> 00:16:34,683 NARRATOR: Their location is puzzling because, on Earth, 290 00:16:34,683 --> 00:16:38,135 auroras are confined to the poles. 291 00:16:38,135 --> 00:16:40,137 STANLEY: Aurora on Earth happen 292 00:16:40,137 --> 00:16:42,691 when high energy particles from the Sun 293 00:16:42,691 --> 00:16:44,934 gets funneled along magnetic field lines 294 00:16:44,934 --> 00:16:47,040 on the Earth towards the polar regions 295 00:16:47,040 --> 00:16:49,422 and there they run into atmospheric particles, 296 00:16:49,422 --> 00:16:51,355 and that causes the atmospheric particles 297 00:16:51,355 --> 00:16:52,597 to shine light. 298 00:16:54,565 --> 00:16:57,085 WONG: Earth's magnetic field is created 299 00:16:57,085 --> 00:17:00,778 by the churning motion of the liquid iron 300 00:17:00,778 --> 00:17:02,021 in Earth's outer core. 301 00:17:02,021 --> 00:17:04,644 Because iron is electrically conducting, 302 00:17:04,644 --> 00:17:09,028 when it moves, it naturally generates a magnetic field. 303 00:17:11,133 --> 00:17:13,998 NARRATOR: Magnetic fields create auroras, 304 00:17:13,998 --> 00:17:17,795 but on Uranus, this poses a mystery. 305 00:17:17,795 --> 00:17:20,004 GURNEY: We know Uranus doesn't have 306 00:17:20,004 --> 00:17:23,042 this flowing metallic core that Earth has, 307 00:17:23,042 --> 00:17:26,286 but it still has, uh, a magnetic field. 308 00:17:26,286 --> 00:17:29,013 So, how is that magnetic field being generated? 309 00:17:30,497 --> 00:17:31,947 NARRATOR: A clue could lie 310 00:17:31,947 --> 00:17:34,329 in Uranus's icy composition. 311 00:17:37,125 --> 00:17:38,609 [thunder rumbles] 312 00:17:40,576 --> 00:17:44,063 GURNEY: If you sent a spacecraft to Uranus, 313 00:17:44,063 --> 00:17:46,513 you would go through the atmosphere 314 00:17:46,513 --> 00:17:49,654 and, uh, you would see, uh, all of this, uh, gas, 315 00:17:49,654 --> 00:17:51,000 uh, because it's a gas giant. 316 00:17:51,000 --> 00:17:53,762 OLUSEYI: It's a turbulent, high-speed wind, 317 00:17:53,762 --> 00:17:55,867 gaseous environment, 318 00:17:55,867 --> 00:17:57,835 and descend inward, 319 00:17:57,835 --> 00:18:00,700 you go from gases to liquids. 320 00:18:02,357 --> 00:18:05,394 GURNEY: It would just get gradually more dense, um, 321 00:18:05,394 --> 00:18:06,809 as the pressure increases. 322 00:18:06,809 --> 00:18:09,226 And then, when you get sufficiently deep enough, 323 00:18:09,226 --> 00:18:14,576 now you enter the ice world in the interior of Uranus. 324 00:18:14,576 --> 00:18:16,750 ♪ 325 00:18:16,750 --> 00:18:19,512 [thunder crackling] 326 00:18:19,512 --> 00:18:21,030 GAO: The pressures and temperatures 327 00:18:21,030 --> 00:18:23,688 in the interior of Uranus are extreme. 328 00:18:23,688 --> 00:18:26,829 We're looking at pressures three million times that 329 00:18:26,829 --> 00:18:28,383 of the surface pressure of Earth, 330 00:18:28,383 --> 00:18:31,800 and temperatures reaching 9,000 Fahrenheit. 331 00:18:33,940 --> 00:18:36,701 NARRATOR: Surprisingly, even at these extremely high 332 00:18:36,701 --> 00:18:42,259 pressures and temperatures, water can become ice, 333 00:18:42,259 --> 00:18:46,539 but not in the form we're familiar with on Earth. 334 00:18:46,539 --> 00:18:49,058 GURNEY: Deep in the planet of Uranus, 335 00:18:49,058 --> 00:18:51,751 you get this extremely dense, uh, 336 00:18:51,751 --> 00:18:54,788 black, hot ice called "superionic ice." 337 00:18:57,066 --> 00:18:59,379 NARRATOR: At extreme pressures and temperatures 338 00:18:59,379 --> 00:19:01,519 hotter than the sun's surface, 339 00:19:01,519 --> 00:19:06,110 water is crushed into a solid form. 340 00:19:06,110 --> 00:19:07,318 Superionic ice sounds like it comes from 341 00:19:07,318 --> 00:19:08,906 a science fiction novel. 342 00:19:08,906 --> 00:19:11,702 It's really strange, and you just wouldn't expect 343 00:19:11,702 --> 00:19:13,876 that it would exist in real life. 344 00:19:15,395 --> 00:19:17,811 NARRATOR: This strange ice is unlike anything 345 00:19:17,811 --> 00:19:20,573 we find naturally on Earth. 346 00:19:20,573 --> 00:19:21,712 BERDIS: Here on Earth, 347 00:19:21,712 --> 00:19:24,024 we see all different types of ice. 348 00:19:24,024 --> 00:19:25,992 We see sleet, 349 00:19:25,992 --> 00:19:29,547 we see snow, we see ice cubes. 350 00:19:29,547 --> 00:19:32,378 But if we zoom in under a microscope, 351 00:19:32,378 --> 00:19:33,724 we see that they are all 352 00:19:33,724 --> 00:19:36,382 this very similar 353 00:19:36,382 --> 00:19:38,970 hexagon pattern. 354 00:19:38,970 --> 00:19:41,456 This is water ice as we know it on the Earth. 355 00:19:41,456 --> 00:19:43,527 It's called "ice Ih," 356 00:19:43,527 --> 00:19:46,115 and the H stands for this hexagonal shape 357 00:19:46,115 --> 00:19:48,325 that you can see in the structure. 358 00:19:48,325 --> 00:19:50,223 Here, the red balls are the oxygen 359 00:19:50,223 --> 00:19:53,122 and the white is the hydrogen; H2O, 360 00:19:53,122 --> 00:19:55,504 two hydrogens for every oxygen. 361 00:19:55,504 --> 00:19:56,678 STANLEY: There are around 362 00:19:56,678 --> 00:19:58,404 20 different types of water ice 363 00:19:58,404 --> 00:20:00,544 found in the solar system. 364 00:20:00,544 --> 00:20:05,273 The other types that we don't find here on Earth, uh, can form 365 00:20:05,273 --> 00:20:06,619 when the temperature's really, really high 366 00:20:06,619 --> 00:20:09,277 and the pressure's really high. 367 00:20:09,277 --> 00:20:11,244 NARRATOR: And it's these conditions 368 00:20:11,244 --> 00:20:13,867 deep inside Uranus that, in theory, 369 00:20:13,867 --> 00:20:18,078 could allow this mysterious superionic ice to exist. 370 00:20:20,046 --> 00:20:23,222 GURNEY: Superionic ice is still very new. 371 00:20:23,222 --> 00:20:26,328 It took us a long time to figure out, uh, that it even existed. 372 00:20:27,329 --> 00:20:29,331 NARRATOR: But in 2018, 373 00:20:29,331 --> 00:20:33,404 scientists announced they'd made superionic ice. 374 00:20:33,404 --> 00:20:35,751 MILLOT: We did the experiment, 375 00:20:35,751 --> 00:20:38,340 and then we look at all the evidence, 376 00:20:38,340 --> 00:20:41,757 and we have to say, "Well, it's true." 377 00:20:41,757 --> 00:20:44,588 It's crazy, it's weird, it's strange, 378 00:20:44,588 --> 00:20:45,934 but it's there. 379 00:20:45,934 --> 00:20:48,281 At super-high temperatures and pressures, 380 00:20:48,281 --> 00:20:50,801 ice forms a very different structure. 381 00:20:50,801 --> 00:20:54,114 What you're looking at here are oxygen atoms, shown in red, 382 00:20:54,114 --> 00:20:55,771 now connected with one another, 383 00:20:55,771 --> 00:21:00,500 and the hydrogen atoms, in white, have broken free. 384 00:21:00,500 --> 00:21:02,951 ♪ 385 00:21:02,951 --> 00:21:04,677 NARRATOR: This unique property 386 00:21:04,677 --> 00:21:07,887 may solve the mystery of Uranus's auroras. 387 00:21:10,165 --> 00:21:12,650 OLUSEYI: Inside of superionic ice, 388 00:21:12,650 --> 00:21:14,514 what's happened is that 389 00:21:14,514 --> 00:21:17,414 the hydrogen atoms have broken free, and now they're free 390 00:21:17,414 --> 00:21:20,071 to flow around within the material, 391 00:21:20,071 --> 00:21:22,695 and they are the conductors of electricity. 392 00:21:24,110 --> 00:21:26,630 WONG: It's like something out of science fiction where 393 00:21:26,630 --> 00:21:29,046 the hydrogen atoms are flowing like water, 394 00:21:29,046 --> 00:21:32,877 conducting electricity, and potentially responsible 395 00:21:32,877 --> 00:21:36,743 for the wacky magnetic fields that we see on Uranus. 396 00:21:38,193 --> 00:21:41,023 NARRATOR: Precisely the kind of magnetic fields 397 00:21:41,023 --> 00:21:43,957 that could help generate Uranus's auroras. 398 00:21:43,957 --> 00:21:46,891 But there's still much to learn. 399 00:21:47,996 --> 00:21:50,999 GURNEY: We don't fully know what's going on inside Uranus. 400 00:21:50,999 --> 00:21:54,209 We're only just beginning looking at these icy worlds. 401 00:21:54,209 --> 00:21:56,832 We're really at the tip of the iceberg. [chuckles] 402 00:21:57,902 --> 00:22:01,492 NARRATOR: And since these ice giants, Uranus and Neptune, 403 00:22:01,492 --> 00:22:03,494 hold vast amounts of water, 404 00:22:03,494 --> 00:22:07,153 this bizarre hot black superionic ice 405 00:22:07,153 --> 00:22:10,363 may turn out to be the most common form of water 406 00:22:10,363 --> 00:22:12,538 in our solar system. 407 00:22:18,233 --> 00:22:20,373 As we get closer to the Sun, 408 00:22:20,373 --> 00:22:23,342 ice begins to look more familiar. 409 00:22:26,206 --> 00:22:29,900 Almost a billion miles from Uranus 410 00:22:29,900 --> 00:22:31,591 lies Saturn. 411 00:22:32,558 --> 00:22:36,527 Adorned with its famous icy rings. 412 00:22:42,015 --> 00:22:44,535 Saturn's rings are truly the jewel of the solar system. 413 00:22:44,535 --> 00:22:47,193 The first time anyone sees them through a telescope, 414 00:22:47,193 --> 00:22:49,402 you can't believe your eyes. 415 00:22:49,402 --> 00:22:52,681 NARRATOR: But we never realized the true beauty of them 416 00:22:52,681 --> 00:22:56,996 until NASA's Cassini spacecraft went to visit. 417 00:23:02,311 --> 00:23:04,900 The photographs and data sent back 418 00:23:04,900 --> 00:23:07,524 were spectacular. 419 00:23:10,181 --> 00:23:12,425 OLUSEYI: Saturn's rings 420 00:23:12,425 --> 00:23:16,464 turned out to be made up primarily of water ice 421 00:23:16,464 --> 00:23:20,053 that range in sizes from like 422 00:23:20,053 --> 00:23:23,609 smaller than a millimeter to larger than an automobile. 423 00:23:25,990 --> 00:23:28,648 NARRATOR: Icy mini-moons sweep through the rings. 424 00:23:30,823 --> 00:23:34,240 Creating what look like grooves in a record. 425 00:23:35,690 --> 00:23:37,346 HOWETT: Cassini gave us that view. 426 00:23:37,346 --> 00:23:39,038 They're absolutely astounding. 427 00:23:39,038 --> 00:23:41,834 To see the ripples in them, the gaps in them, 428 00:23:41,834 --> 00:23:44,595 just really, really lovely. 429 00:23:53,777 --> 00:23:55,986 NARRATOR: The rings are joined in their orbits 430 00:23:55,986 --> 00:23:58,954 by over 140 moons. 431 00:24:02,406 --> 00:24:04,857 And Cassini saw something intriguing 432 00:24:04,857 --> 00:24:08,101 on one of the moons farthest from Saturn. 433 00:24:16,144 --> 00:24:18,974 Iapetus is one of the oddest looking moons 434 00:24:18,974 --> 00:24:20,838 in the solar system. 435 00:24:20,838 --> 00:24:23,220 It resembles a walnut 436 00:24:23,220 --> 00:24:25,809 with a mountain ridge around its middle. 437 00:24:28,018 --> 00:24:32,194 But that's not its strangest feature. 438 00:24:33,886 --> 00:24:35,404 In 2007, 439 00:24:35,404 --> 00:24:39,270 Cassini sent back pictures of Iapetus. 440 00:24:40,548 --> 00:24:43,171 One side icy white, 441 00:24:43,171 --> 00:24:46,519 while the other looks as if it's been painted black. 442 00:24:50,005 --> 00:24:51,351 Iapetus is one of the weirdest looking moons 443 00:24:51,351 --> 00:24:52,387 in the solar system. 444 00:24:52,387 --> 00:24:55,045 It looks like it has two halves. 445 00:24:55,045 --> 00:24:58,427 One really bright side and one really dark side. 446 00:24:58,427 --> 00:24:59,670 We would expect the moons 447 00:24:59,670 --> 00:25:01,085 in the Saturn system 448 00:25:01,085 --> 00:25:04,157 to have formed with roughly the same brightnesses. 449 00:25:04,157 --> 00:25:06,608 The darkest materials on Iapetus 450 00:25:06,608 --> 00:25:11,061 are 20 times darker than the brightest materials. 451 00:25:11,061 --> 00:25:14,098 How can such a bizarre yin-yang moon exist? 452 00:25:14,098 --> 00:25:17,757 NARRATOR: A clue can be found in the temperature differences 453 00:25:17,757 --> 00:25:20,484 between the white and black halves of the moon. 454 00:25:22,037 --> 00:25:24,868 VERBISCER: The darker side is a warmer region. 455 00:25:24,868 --> 00:25:27,733 The temperatures are hotter on the darker side 456 00:25:27,733 --> 00:25:29,631 than on the bright side. 457 00:25:32,116 --> 00:25:34,394 NARRATOR: The dark side's daytime temperature 458 00:25:34,394 --> 00:25:37,743 can be up to 54 degrees Fahrenheit hotter 459 00:25:37,743 --> 00:25:39,261 than the bright side. 460 00:25:41,574 --> 00:25:42,713 This temperature difference 461 00:25:42,713 --> 00:25:44,577 between the black and white surfaces 462 00:25:44,577 --> 00:25:48,236 creates a peculiar feedback loop. 463 00:25:48,236 --> 00:25:49,755 [helicopter rotor blades whirring] 464 00:25:49,755 --> 00:25:51,895 Which also happens on Earth 465 00:25:51,895 --> 00:25:55,415 where scientists are studying its effects. 466 00:26:02,871 --> 00:26:06,737 WONG: So right behind me, we've got this dark glacial till 467 00:26:06,737 --> 00:26:09,775 right next to bright white snow 468 00:26:09,775 --> 00:26:11,604 created through the erosion 469 00:26:11,604 --> 00:26:13,572 of the majestic mountains around me. 470 00:26:14,883 --> 00:26:17,921 NARRATOR: These dark spots are not solid rock, 471 00:26:17,921 --> 00:26:22,753 but are dust and dirt covering the ice. 472 00:26:22,753 --> 00:26:24,479 And there's a huge, stark contrast 473 00:26:24,479 --> 00:26:26,930 between the brightness of the snow 474 00:26:26,930 --> 00:26:29,657 and the darkness of the glacial till. 475 00:26:30,727 --> 00:26:32,763 NARRATOR: This dark glacial till 476 00:26:32,763 --> 00:26:36,595 has what scientists call a low albedo. 477 00:26:36,595 --> 00:26:39,356 WONG: Which means that it absorbs most of the sunlight 478 00:26:39,356 --> 00:26:41,185 that hits it, heating it up, 479 00:26:41,185 --> 00:26:44,119 and that heat gets transferred to the surrounding snow, 480 00:26:44,119 --> 00:26:47,191 melting it into liquid water, 481 00:26:47,191 --> 00:26:49,124 causing the dark streaks that you see 482 00:26:49,124 --> 00:26:53,025 coming down the side of that cliff. 483 00:26:53,025 --> 00:26:55,821 And a very similar process happens on Iapetus. 484 00:26:58,168 --> 00:27:02,068 NARRATOR: With so little light and heat from the sun, 485 00:27:02,068 --> 00:27:05,693 it's a very slow process. 486 00:27:08,557 --> 00:27:10,180 Over a billion years, 487 00:27:10,180 --> 00:27:14,771 it's estimated the dark regions can lose around 66 feet of ice 488 00:27:14,771 --> 00:27:17,497 compared to the white side. 489 00:27:19,016 --> 00:27:21,881 As this feedback mechanism continues, 490 00:27:21,881 --> 00:27:23,745 it keeps the black side black... 491 00:27:24,953 --> 00:27:27,473 ...and the white side white. 492 00:27:27,473 --> 00:27:29,371 But a mystery remains. 493 00:27:30,752 --> 00:27:34,376 Where did all the dark material come from in the first place? 494 00:27:35,688 --> 00:27:36,931 VERBISCER: Did the dark material 495 00:27:36,931 --> 00:27:38,691 come from inside of Iapetus 496 00:27:38,691 --> 00:27:41,936 or did it come from someplace else? 497 00:27:46,078 --> 00:27:50,220 NARRATOR: The smoking gun was discovered by complete accident. 498 00:27:52,222 --> 00:27:54,811 VERBISCER: So, in 2005, I was observing 499 00:27:54,811 --> 00:27:56,916 another moon of Saturn called Phoebe, 500 00:27:56,916 --> 00:28:01,196 which orbits Saturn much further away than Iapetus does. 501 00:28:02,577 --> 00:28:04,579 SINGER: Phoebe is in an unusual orbit 502 00:28:04,579 --> 00:28:07,789 because it goes backwards with respect to the other moons 503 00:28:07,789 --> 00:28:10,758 in its direction around Saturn. 504 00:28:14,762 --> 00:28:17,592 VERBISCER: If you look at the Cassini images of Phoebe, 505 00:28:17,592 --> 00:28:21,907 you see that it is a pretty heavily cratered surface. 506 00:28:21,907 --> 00:28:25,669 So, it's been hit with things for billions of years, 507 00:28:25,669 --> 00:28:28,914 and material has been excavated 508 00:28:28,914 --> 00:28:31,261 and thrown into the space around Phoebe. 509 00:28:31,261 --> 00:28:33,919 The question is, where did all that material go? 510 00:28:35,472 --> 00:28:37,819 Where are all those dust particles? 511 00:28:37,819 --> 00:28:41,478 So, we got the idea to use the Spitzer Space Telescope 512 00:28:41,478 --> 00:28:43,860 to try and look for dust 513 00:28:43,860 --> 00:28:45,862 in the region around Phoebe. 514 00:28:47,208 --> 00:28:50,763 NARRATOR: The Spitzer Space Telescope used infrared light, 515 00:28:50,763 --> 00:28:52,592 or heat signatures, to detect 516 00:28:52,592 --> 00:28:54,629 what's normally hidden from view. 517 00:28:55,768 --> 00:28:56,976 SINGER: If you were able to see 518 00:28:56,976 --> 00:28:59,634 how the Spitzer telescope sees, 519 00:28:59,634 --> 00:29:02,085 it would be like when you put on night vision goggles, 520 00:29:02,085 --> 00:29:05,674 and all of a sudden, you're able to see in the dark. 521 00:29:11,542 --> 00:29:12,854 VERBISCER: We got our images, 522 00:29:12,854 --> 00:29:15,374 and they were extremely interesting. 523 00:29:16,547 --> 00:29:19,447 NARRATOR: Phoebe rides within a colossal ring 524 00:29:19,447 --> 00:29:22,208 about ten million miles across, 525 00:29:22,208 --> 00:29:24,279 wrapped around Saturn. 526 00:29:25,591 --> 00:29:29,215 VERBISCER: It is the largest ring by far in the solar system. 527 00:29:29,215 --> 00:29:32,840 This ring is so big that a billion Earths 528 00:29:32,840 --> 00:29:35,049 could fit inside the volume of the ring. 529 00:29:35,049 --> 00:29:37,016 It makes perfect sense that this ring 530 00:29:37,016 --> 00:29:38,466 should be called the Phoebe ring 531 00:29:38,466 --> 00:29:42,711 because it is associated so closely with the moon Phoebe. 532 00:29:44,092 --> 00:29:47,026 NARRATOR: The Phoebe ring moves around Saturn, 533 00:29:47,026 --> 00:29:50,202 in the same direction as its moon Phoebe, 534 00:29:50,202 --> 00:29:52,894 backwards from the other moons and rings. 535 00:29:57,726 --> 00:30:00,833 Each time a passing object or rocky debris 536 00:30:00,833 --> 00:30:03,974 gets too close to Phoebe... 537 00:30:03,974 --> 00:30:05,631 boom. 538 00:30:06,839 --> 00:30:08,841 The resulting impact 539 00:30:08,841 --> 00:30:12,051 throws dark material out into space. 540 00:30:15,296 --> 00:30:17,022 SINGER: Some of this dark material 541 00:30:17,022 --> 00:30:20,611 in this huge ring starts to fall in towards Saturn, 542 00:30:20,611 --> 00:30:22,821 and Iapetus is basically 543 00:30:22,821 --> 00:30:25,927 running through those particles in its orbit. 544 00:30:27,411 --> 00:30:29,793 NARRATOR: How Iapetus orbits Saturn 545 00:30:29,793 --> 00:30:32,313 is key to solving the mystery 546 00:30:32,313 --> 00:30:35,488 of why it has these black and white halves. 547 00:30:38,422 --> 00:30:41,046 [wind howling] 548 00:30:41,046 --> 00:30:44,359 WONG: So Iapetus, like our moon that orbits the Earth, 549 00:30:44,359 --> 00:30:47,638 is tidally locked, which means one side of Iapetus 550 00:30:47,638 --> 00:30:49,226 always faces Saturn, 551 00:30:49,226 --> 00:30:52,022 the other side always faces away from Saturn. 552 00:30:53,127 --> 00:30:56,855 Imagine this snowball is a freshly formed Iapetus, 553 00:30:56,855 --> 00:31:00,789 completely uniform in its brightness on all sides. 554 00:31:00,789 --> 00:31:05,070 Now, as it orbits around Saturn, through the Phoebe ring, 555 00:31:05,070 --> 00:31:08,280 it will pick up dark dust particles 556 00:31:08,280 --> 00:31:09,937 from that ring. 557 00:31:09,937 --> 00:31:13,181 And because it is tidally locked to Saturn, 558 00:31:13,181 --> 00:31:14,907 the same hemisphere 559 00:31:14,907 --> 00:31:17,220 will keep piling on dust 560 00:31:17,220 --> 00:31:18,911 every time it goes around 561 00:31:18,911 --> 00:31:21,914 for millions and millions of years, 562 00:31:21,914 --> 00:31:25,814 continuously darkening this side of Iapetus. 563 00:31:29,577 --> 00:31:30,889 DURFEY: As soon as the front side 564 00:31:30,889 --> 00:31:32,925 of Iapetus became darkened, 565 00:31:32,925 --> 00:31:37,205 the ice underneath started heating up more quickly, 566 00:31:37,205 --> 00:31:40,691 so that would become a gas and migrate around 567 00:31:40,691 --> 00:31:44,419 to the colder, lighter side of Iapetus. 568 00:31:45,869 --> 00:31:49,079 NARRATOR: The ice vaporizes from the darker, warmer side 569 00:31:49,079 --> 00:31:52,358 and refreezes onto the colder, lighter side. 570 00:31:53,739 --> 00:31:55,741 DURFEY: And so, this means over time, 571 00:31:55,741 --> 00:31:57,950 the dark side becomes darker, 572 00:31:57,950 --> 00:32:00,021 the light side becomes lighter. 573 00:32:01,160 --> 00:32:03,266 NARRATOR: It's a slow process, 574 00:32:03,266 --> 00:32:05,716 one dust particle at a time. 575 00:32:07,201 --> 00:32:09,168 But it's the best explanation 576 00:32:09,168 --> 00:32:11,722 of how this peculiar moon 577 00:32:11,722 --> 00:32:15,071 got its self-sustaining, warm, dark face. 578 00:32:16,417 --> 00:32:17,901 OLUSEYI: Iapetus just shows us the potential 579 00:32:17,901 --> 00:32:19,420 of the interconnectedness 580 00:32:19,420 --> 00:32:22,078 between the planetary bodies of our solar system. 581 00:32:23,148 --> 00:32:26,427 We think they're isolated, but nothing's isolated. 582 00:32:28,015 --> 00:32:30,845 NARRATOR: Iapetus is not the only icy moon affected 583 00:32:30,845 --> 00:32:33,641 by the system it exists within. 584 00:32:34,676 --> 00:32:36,955 Another moon closer to the sun 585 00:32:36,955 --> 00:32:40,165 reveals not only a unique connection with its neighbor, 586 00:32:40,165 --> 00:32:42,443 but also hints 587 00:32:42,443 --> 00:32:44,824 that something potentially profound 588 00:32:44,824 --> 00:32:47,413 could lurk beneath its surface. 589 00:32:51,383 --> 00:32:54,110 NASA LAUNCH ANNOUNCER: T minus five, four, 590 00:32:54,110 --> 00:32:57,492 three, two, one. 591 00:32:57,492 --> 00:33:00,564 Ignition and liftoff 592 00:33:00,564 --> 00:33:04,361 of the Atlas V with Juno on a trek to Jupiter. 593 00:33:05,949 --> 00:33:08,262 NARRATOR: The Juno mission is to investigate the origin 594 00:33:08,262 --> 00:33:11,541 and evolution of the gas giant Jupiter, 595 00:33:11,541 --> 00:33:15,924 the largest planet in our solar system. 596 00:33:19,514 --> 00:33:21,171 LYNNAE QUICK: The main goal of the Juno spacecraft 597 00:33:21,171 --> 00:33:22,517 is to study Jupiter. 598 00:33:22,517 --> 00:33:23,967 However, 599 00:33:23,967 --> 00:33:25,417 as it orbits Jupiter, 600 00:33:25,417 --> 00:33:27,108 it's taking these wonderful images 601 00:33:27,108 --> 00:33:29,283 of Jupiter's largest moons. 602 00:33:31,837 --> 00:33:33,839 NARRATOR: Ganymede, 603 00:33:33,839 --> 00:33:36,393 the largest moon in the solar system. 604 00:33:37,946 --> 00:33:40,915 Io, the most volcanically active. 605 00:33:45,092 --> 00:33:48,578 And then, there's the icy moon, Europa, 606 00:33:48,578 --> 00:33:52,237 the odd one out with the smoothest surface. 607 00:33:53,928 --> 00:33:58,105 It's an ancient moon, billions of years old, 608 00:33:58,105 --> 00:34:00,003 and yet, mysteriously, 609 00:34:00,003 --> 00:34:02,902 has a young surface, with few craters. 610 00:34:02,902 --> 00:34:04,283 DURFEY: We can get 611 00:34:04,283 --> 00:34:07,114 an idea of how old a planetary surface is 612 00:34:07,114 --> 00:34:09,219 by counting the number of impact craters. 613 00:34:09,219 --> 00:34:12,153 Europa barely has any impact craters, 614 00:34:12,153 --> 00:34:15,432 which means that its surface must be really young. 615 00:34:16,606 --> 00:34:19,126 NARRATOR: And that's not all that makes Europa different. 616 00:34:22,060 --> 00:34:28,100 It's criss-crossed by a strange network of striking red lines. 617 00:34:28,100 --> 00:34:29,964 GONZALEZ: The surface of Europa 618 00:34:29,964 --> 00:34:34,796 has a lot of interesting cracks and features to it, 619 00:34:34,796 --> 00:34:36,971 and has lots of lines, 620 00:34:36,971 --> 00:34:39,456 which look almost like a network 621 00:34:39,456 --> 00:34:41,803 of blood vessels in an eye. 622 00:34:43,046 --> 00:34:45,083 ♪ 623 00:34:47,568 --> 00:34:51,330 NARRATOR: These lines are vast ice cracks, 624 00:34:51,330 --> 00:34:55,369 some of which are 15 miles wide, 625 00:34:55,369 --> 00:34:57,681 with a dark red floor. 626 00:35:00,201 --> 00:35:01,754 OLUSEYI: What could be creating 627 00:35:01,754 --> 00:35:05,413 these criss-crossing lines and patterns on Europa's surface? 628 00:35:11,212 --> 00:35:13,525 ♪ 629 00:35:23,500 --> 00:35:26,158 QUICK: The canyons on Europa are so significant 630 00:35:26,158 --> 00:35:27,504 that NASA's planning a mission 631 00:35:27,504 --> 00:35:29,161 to go to Europa to explore them. 632 00:35:30,197 --> 00:35:32,026 NARRATOR: And in preparation, 633 00:35:32,026 --> 00:35:36,030 scientists are exploring similar environments on Earth, 634 00:35:36,030 --> 00:35:38,998 like these icy terrains in Alaska. 635 00:35:42,416 --> 00:35:44,003 [wind whistling] 636 00:35:51,597 --> 00:35:54,980 SAM HOWELL: I think many of the most important questions 637 00:35:54,980 --> 00:35:58,156 in planetary science can be addressed 638 00:35:58,156 --> 00:36:00,227 by going to worlds like Europa. 639 00:36:02,229 --> 00:36:04,576 NARRATOR: NASA scientist Sam Howell is studying 640 00:36:04,576 --> 00:36:09,546 what may be at the heart of Europa's mysterious appearance. 641 00:36:09,546 --> 00:36:11,169 HOWELL: What I'm most excited about, 642 00:36:11,169 --> 00:36:12,756 coming from a background 643 00:36:12,756 --> 00:36:14,448 in studying plate tectonics here on Earth, 644 00:36:14,448 --> 00:36:16,346 we see systems of rigid, 645 00:36:16,346 --> 00:36:18,900 icy plates moving around similar 646 00:36:18,900 --> 00:36:21,696 to the way Earth's plate tectonics looks on the surface. 647 00:36:21,696 --> 00:36:24,492 But digging in, we expect those processes to be very different. 648 00:36:25,562 --> 00:36:28,255 NARRATOR: Europa's surface features indicate 649 00:36:28,255 --> 00:36:31,223 they are a result of tectonic activity. 650 00:36:32,259 --> 00:36:33,846 BERDIS: This is an up-close image 651 00:36:33,846 --> 00:36:36,090 of Europa's surface, and you can see 652 00:36:36,090 --> 00:36:39,024 this large, dark red band 653 00:36:39,024 --> 00:36:41,026 in the very center of the image. 654 00:36:41,026 --> 00:36:42,510 We know that this feature is created 655 00:36:42,510 --> 00:36:44,236 due to tectonic activity 656 00:36:44,236 --> 00:36:46,549 because it appears that the crust 657 00:36:46,549 --> 00:36:48,516 of Europa has pulled apart, 658 00:36:48,516 --> 00:36:50,138 and you've had material flow up from underneath. 659 00:36:50,138 --> 00:36:52,589 But if we were to take this feature 660 00:36:52,589 --> 00:36:54,626 and extract it from this image, 661 00:36:54,626 --> 00:36:58,388 both sides of the crust would fit back together 662 00:36:58,388 --> 00:36:59,665 like a puzzle piece. 663 00:36:59,665 --> 00:37:03,082 We did not expect to see tectonic activity 664 00:37:03,082 --> 00:37:06,672 on a tiny moon like this, but there it is. 665 00:37:08,502 --> 00:37:10,124 NARRATOR: So far, this kind 666 00:37:10,124 --> 00:37:15,440 of global tectonic activity has only been observed on Earth. 667 00:37:15,440 --> 00:37:16,993 OLUSEYI: Take a look at Earth, 668 00:37:16,993 --> 00:37:19,306 and you'll see that South America looks like 669 00:37:19,306 --> 00:37:22,309 it fits right neatly in there into Africa. 670 00:37:23,344 --> 00:37:26,520 And so, we know that in the Atlantic, 671 00:37:26,520 --> 00:37:28,280 the seafloor is spreading, 672 00:37:28,280 --> 00:37:30,696 and that's what spread those two features apart. 673 00:37:34,182 --> 00:37:38,497 NARRATOR: On Earth, the rocky crust is broken into plates. 674 00:37:38,497 --> 00:37:42,363 They move as softer rock beneath flows very slowly 675 00:37:42,363 --> 00:37:44,848 over geologic time. 676 00:37:44,848 --> 00:37:48,818 QUICK: Europa does not have molten rock like Earth does, 677 00:37:48,818 --> 00:37:52,373 but what we do believe Europa has is a subsurface ocean. 678 00:37:55,411 --> 00:37:57,620 NARRATOR: A vast body of liquid water 679 00:37:57,620 --> 00:38:01,348 that exists underneath its icy surface. 680 00:38:01,348 --> 00:38:03,453 WONG: There is more water 681 00:38:03,453 --> 00:38:05,455 in Europa's subsurface 682 00:38:05,455 --> 00:38:08,389 than all of Earth's oceans, rivers and lakes combined. 683 00:38:11,358 --> 00:38:14,222 NARRATOR: This massive ocean sits beneath a layer 684 00:38:14,222 --> 00:38:19,331 of water ice, which could be up to 15 miles thick in places. 685 00:38:21,678 --> 00:38:24,336 So what force is powerful enough 686 00:38:24,336 --> 00:38:27,719 to crack Europa's extensive icy shell? 687 00:38:29,721 --> 00:38:33,966 BERDIS: As Europa and all of the other large moons orbit Jupiter 688 00:38:33,966 --> 00:38:35,278 and interact with it, 689 00:38:35,278 --> 00:38:37,004 they are all constantly pushing 690 00:38:37,004 --> 00:38:39,524 and pulling and tugging on each other, 691 00:38:39,524 --> 00:38:41,008 and this process is called "tidal heating." 692 00:38:43,942 --> 00:38:45,909 NARRATOR: The tidal heating varies, 693 00:38:45,909 --> 00:38:49,396 depending on how close or far Europa is from Jupiter 694 00:38:49,396 --> 00:38:51,950 and the other moons, 695 00:38:51,950 --> 00:38:54,815 resulting in temperature changes in the ocean. 696 00:38:56,782 --> 00:38:59,371 QUICK: And as the temperature of the ocean changes, 697 00:38:59,371 --> 00:39:03,375 the ice shell thickens and thins and expands and contracts. 698 00:39:03,375 --> 00:39:05,515 [wind whistling] 699 00:39:05,515 --> 00:39:08,000 NARRATOR: The mechanics of which can be seen on Earth. 700 00:39:09,139 --> 00:39:10,555 QUICK: As water freezes, 701 00:39:10,555 --> 00:39:13,523 it takes up more space and expands into ice. 702 00:39:13,523 --> 00:39:16,664 It's very similar to if we were to take a bottle of water 703 00:39:16,664 --> 00:39:18,217 and place it into the freezer. 704 00:39:18,217 --> 00:39:19,736 First, it would expand, 705 00:39:19,736 --> 00:39:21,669 and then we'd notice a large bit of cracking. 706 00:39:21,669 --> 00:39:23,844 This is what is happening on Europa. 707 00:39:26,191 --> 00:39:28,366 NARRATOR: Scaled up to the size of a moon, 708 00:39:28,366 --> 00:39:32,439 these ice expansion cracks create massive canyons 709 00:39:32,439 --> 00:39:34,510 across Europa. 710 00:39:40,619 --> 00:39:43,657 And as these canyons form, 711 00:39:43,657 --> 00:39:47,523 a key ingredient from the ocean below surges up 712 00:39:47,523 --> 00:39:49,179 through the cracks, 713 00:39:49,179 --> 00:39:53,114 giving Europa's markings their distinctive red. 714 00:39:57,705 --> 00:40:00,363 BERDIS: So the red marks that we see on Europa's surface-- 715 00:40:00,363 --> 00:40:02,572 these cracks and lines-- 716 00:40:02,572 --> 00:40:05,161 are salts 717 00:40:05,161 --> 00:40:07,474 that have come up from below the surface. 718 00:40:07,474 --> 00:40:10,373 ♪ 719 00:40:10,373 --> 00:40:13,203 NARRATOR: Suggesting a tantalizing possibility. 720 00:40:15,102 --> 00:40:18,243 This crisscrossing system of salty canyons means 721 00:40:18,243 --> 00:40:21,039 we might find life in the ocean 722 00:40:21,039 --> 00:40:23,351 underneath Europa's icy shell. 723 00:40:25,630 --> 00:40:28,874 SINGER: Life as we know it needs three basic things: 724 00:40:28,874 --> 00:40:30,462 water, 725 00:40:30,462 --> 00:40:34,362 a source of energy, and also, essential elements. 726 00:40:37,676 --> 00:40:39,540 NARRATOR: Europa has an ocean, 727 00:40:39,540 --> 00:40:42,578 and a source of energy from tidal movements. 728 00:40:44,165 --> 00:40:47,375 But it's missing the final key ingredient: 729 00:40:47,375 --> 00:40:49,895 some essential elements. 730 00:40:50,965 --> 00:40:55,176 However, with a little help from its neighboring moon Io, 731 00:40:55,176 --> 00:40:57,765 these elements can be found on Europa. 732 00:40:59,387 --> 00:41:00,665 SINGER: Io 733 00:41:00,665 --> 00:41:03,012 is an extremely volcanically-active place. 734 00:41:05,773 --> 00:41:07,499 And these volcanoes emit 735 00:41:07,499 --> 00:41:09,915 sulphur and other sulphur products, 736 00:41:09,915 --> 00:41:12,608 and these make it all the way onto Europa. 737 00:41:13,919 --> 00:41:18,683 And sulphur is one of those essential elements that life 738 00:41:18,683 --> 00:41:20,270 on Earth uses. 739 00:41:20,270 --> 00:41:22,790 ♪ 740 00:41:24,551 --> 00:41:26,622 BERDIS: All of the sulphur that's coming from Io 741 00:41:26,622 --> 00:41:28,520 and landing on Europa's surface 742 00:41:28,520 --> 00:41:31,972 is interacting with the salts and water 743 00:41:31,972 --> 00:41:36,010 that's coming up from underneath Europa's icy crust. 744 00:41:37,322 --> 00:41:40,670 NARRATOR: Chemical reactions between the sulphur from Io 745 00:41:40,670 --> 00:41:44,156 and the salts on Europa create essential molecules 746 00:41:44,156 --> 00:41:46,434 needed for life. 747 00:41:49,645 --> 00:41:51,370 And this allows for this perfect breeding ground 748 00:41:51,370 --> 00:41:54,339 for potential life to form and evolve. 749 00:41:55,961 --> 00:41:59,275 NARRATOR: Europa is such a strong candidate for life 750 00:41:59,275 --> 00:42:02,865 that NASA is already preparing to explore the moon. 751 00:42:04,936 --> 00:42:07,697 The goal is to study Europa's surface 752 00:42:07,697 --> 00:42:09,285 in more detail 753 00:42:09,285 --> 00:42:12,115 so that a future mission can one day land 754 00:42:12,115 --> 00:42:15,533 and explore beneath its icy crust. 755 00:42:17,465 --> 00:42:21,849 And scientists like Sam are already testing ideas 756 00:42:21,849 --> 00:42:24,369 for studying Europa's watery world. 757 00:42:28,200 --> 00:42:31,514 HOWELL: What we're doing is we're deploying a robotic probe 758 00:42:31,514 --> 00:42:33,447 into the ice and under it 759 00:42:33,447 --> 00:42:35,345 to explore what this lake environment is like. 760 00:42:37,244 --> 00:42:39,177 We might have the opportunity 761 00:42:39,177 --> 00:42:40,937 in my own lifetime 762 00:42:40,937 --> 00:42:44,596 to answer a question that's intrinsic to all of us: 763 00:42:44,596 --> 00:42:46,805 are we alone in our universe? 764 00:42:46,805 --> 00:42:49,014 Are we alone in our solar system? 765 00:42:49,014 --> 00:42:52,086 And one of the most exciting aspects of exploring Europa 766 00:42:52,086 --> 00:42:56,125 is the potential of someday knowing 767 00:42:56,125 --> 00:42:59,507 whether or not there's life in our own solar system. 768 00:43:01,579 --> 00:43:03,926 NARRATOR: Europa is one of the last ice moons 769 00:43:03,926 --> 00:43:06,584 that can exist this close to the sun. 770 00:43:07,585 --> 00:43:11,002 Worlds existing any closer to the warmth of the sun, 771 00:43:11,002 --> 00:43:14,868 like the rocky worlds of Mars, Earth, and our moon, 772 00:43:14,868 --> 00:43:16,904 have relatively little ice. 773 00:43:18,319 --> 00:43:22,047 Because they lie inside what is known as the ice line. 774 00:43:25,672 --> 00:43:27,708 DURFEY: You can't see the ice line, 775 00:43:27,708 --> 00:43:29,814 but you can see its effects. 776 00:43:29,814 --> 00:43:30,849 When small bodies that are 777 00:43:30,849 --> 00:43:32,610 primarily composed of ice 778 00:43:32,610 --> 00:43:35,164 cross inside of the ice line, 779 00:43:35,164 --> 00:43:37,615 the ice within them begins to vaporize. 780 00:43:39,789 --> 00:43:42,585 NARRATOR: Sometimes, icy rocks are ejected 781 00:43:42,585 --> 00:43:46,106 from the frigid outer regions of the solar system 782 00:43:46,106 --> 00:43:48,556 and pulled towards the sun. 783 00:43:50,420 --> 00:43:52,871 These are known as comets. 784 00:43:54,873 --> 00:43:56,841 HOWETT: Comets are basically dirty snowballs, 785 00:43:56,841 --> 00:43:59,153 mostly water ice with a little bit of dust, 786 00:43:59,153 --> 00:44:01,224 and as they come into the inner solar system, 787 00:44:01,224 --> 00:44:02,640 they get heated up by the sun. 788 00:44:04,745 --> 00:44:07,679 NARRATOR: As comets cross this invisible ice line, 789 00:44:07,679 --> 00:44:09,992 their ice starts turning into gas. 790 00:44:11,372 --> 00:44:13,858 HOWETT: And that's what forms these long tails 791 00:44:13,858 --> 00:44:15,963 that we can see when you look at a comet, 792 00:44:15,963 --> 00:44:18,276 and those tails stream away from the sun 793 00:44:18,276 --> 00:44:20,450 as the comet moves in towards it. 794 00:44:24,834 --> 00:44:28,148 NARRATOR: Inside the ice line, ice is rare, 795 00:44:28,148 --> 00:44:31,876 but there are places where it can hang on. 796 00:44:36,777 --> 00:44:40,229 DURFEY: Mars is within the ice line of the solar system, 797 00:44:40,229 --> 00:44:43,404 but it still has ice in it and on it. 798 00:44:47,892 --> 00:44:50,032 NARRATOR: It's the end of winter, 799 00:44:50,032 --> 00:44:52,655 and it's been dark at Mars's south pole 800 00:44:52,655 --> 00:44:56,417 for over 150 Martian days straight. 801 00:44:58,212 --> 00:45:01,077 Mars holds onto much of its ice at its poles. 802 00:45:03,148 --> 00:45:05,979 The ice sheet here is not like any on Earth. 803 00:45:07,359 --> 00:45:10,224 Because as winter turns to spring, 804 00:45:10,224 --> 00:45:14,263 the surface becomes covered in strange features. 805 00:45:18,198 --> 00:45:21,615 And with the launch of the Mars Reconnaissance Orbiter 806 00:45:21,615 --> 00:45:25,757 in 2005, we began to see them 807 00:45:25,757 --> 00:45:28,484 like never before. 808 00:45:28,484 --> 00:45:30,520 OLUSEYI: The Mars Reconnaissance Orbiter 809 00:45:30,520 --> 00:45:32,350 is a satellite of Mars that takes 810 00:45:32,350 --> 00:45:33,661 photograph after photograph 811 00:45:33,661 --> 00:45:34,939 of Mars's surface, 812 00:45:34,939 --> 00:45:36,975 and so it's able to see these things come and go 813 00:45:36,975 --> 00:45:38,908 and change with the seasons. 814 00:45:42,187 --> 00:45:46,778 NARRATOR: The images show dark fans on the surface 815 00:45:46,778 --> 00:45:50,609 meaning something must have risen into the air above them. 816 00:45:52,301 --> 00:45:53,820 GONZALEZ: We see these features, 817 00:45:53,820 --> 00:45:56,443 and they will go in the direction 818 00:45:56,443 --> 00:45:58,307 depending on the wind patternof Mars. 819 00:45:58,307 --> 00:46:00,343 So we know that material 820 00:46:00,343 --> 00:46:03,036 is being pushed out from underneath. 821 00:46:04,278 --> 00:46:06,487 NARRATOR: This phenomenon seen on Mars 822 00:46:06,487 --> 00:46:10,388 depends on the type of ice that falls from the Martian skies. 823 00:46:13,805 --> 00:46:15,980 During winter at the South Pole, 824 00:46:15,980 --> 00:46:18,154 more and more snow falls. 825 00:46:19,984 --> 00:46:22,918 But with so little water in Mars's atmosphere, 826 00:46:22,918 --> 00:46:25,886 this isn't the type of snow we have on Earth. 827 00:46:26,991 --> 00:46:30,235 This is carbon dioxide snow. 828 00:46:31,340 --> 00:46:34,964 GAO: Every winter, three to four trillion tons 829 00:46:34,964 --> 00:46:37,346 of carbon dioxide snow falls on Mars. 830 00:46:37,346 --> 00:46:40,556 That's so much snow that the atmospheric pressure 831 00:46:40,556 --> 00:46:44,318 at the surface of Mars decreases by about a third. 832 00:46:44,318 --> 00:46:47,356 NARRATOR: The air is literally freezing to the ground, 833 00:46:47,356 --> 00:46:50,980 forming carbon dioxide ice caps at the poles. 834 00:46:53,949 --> 00:46:57,090 But in spring, as the warmth of the sun reaches 835 00:46:57,090 --> 00:47:00,887 the poles again, something incredible happens. 836 00:47:02,164 --> 00:47:04,891 DURFEY: As the sun comes over the horizon, 837 00:47:04,891 --> 00:47:08,239 the carbon dioxide ice is heated. 838 00:47:14,624 --> 00:47:17,835 This carbon dioxide ice can turn to gas, 839 00:47:17,835 --> 00:47:20,665 and when it does, it forms these geysers 840 00:47:20,665 --> 00:47:24,048 that also bring other material from the subsurface 841 00:47:24,048 --> 00:47:25,428 to the surface. 842 00:47:28,155 --> 00:47:29,881 GONZALEZ: And depending on which way the wind 843 00:47:29,881 --> 00:47:33,471 is blowing, it'll form these nice looking fan features. 844 00:47:34,748 --> 00:47:36,854 NARRATOR: Because of Mars's combination 845 00:47:36,854 --> 00:47:39,201 of atmospheric pressure and temperature... 846 00:47:40,236 --> 00:47:43,239 ...the carbon dioxide turns from ice to gas 847 00:47:43,239 --> 00:47:45,379 without passing through the liquid phase. 848 00:47:47,416 --> 00:47:49,590 WONG: On Mars, its atmosphere 849 00:47:49,590 --> 00:47:52,421 actually falls onto the surface 850 00:47:52,421 --> 00:47:55,700 and then vaporizes back into the atmosphere 851 00:47:55,700 --> 00:47:57,495 on an annual basis. 852 00:47:57,495 --> 00:47:59,117 That's absolutely wild 853 00:47:59,117 --> 00:48:01,913 because it's so different from what's happening here on Earth. 854 00:48:05,158 --> 00:48:07,091 NARRATOR: These conditions on Mars 855 00:48:07,091 --> 00:48:09,403 have enabled carbon dioxide snow 856 00:48:09,403 --> 00:48:12,337 to create unique features on its surface. 857 00:48:15,237 --> 00:48:18,550 But the conditions found on its nearest neighbor, 858 00:48:18,550 --> 00:48:22,796 close enough to see from Mars with the naked eye, 859 00:48:22,796 --> 00:48:26,455 have allowed for something extraordinary to form. 860 00:48:30,666 --> 00:48:32,495 And just like Mars, 861 00:48:32,495 --> 00:48:35,947 Earth, too, has ice caps at its poles. 862 00:48:37,984 --> 00:48:40,400 But the similarities end there. 863 00:48:42,195 --> 00:48:43,851 HOWETT: Earth's ice is really unique 864 00:48:43,851 --> 00:48:46,854 because we operate in a very small temperature range 865 00:48:46,854 --> 00:48:49,133 and a very small pressure range on the surface. 866 00:48:49,133 --> 00:48:52,308 The ice that we experience is a very small subset 867 00:48:52,308 --> 00:48:54,517 of the total ice that's in our universe. 868 00:48:57,313 --> 00:48:59,143 NARRATOR: Earth's temperature and pressure ranges 869 00:48:59,143 --> 00:49:02,663 allow water to exist in all three states: 870 00:49:02,663 --> 00:49:05,632 solid, liquid, and gas. 871 00:49:07,427 --> 00:49:10,740 Earth is the only place known to have floating icebergs 872 00:49:10,740 --> 00:49:14,192 and bodies of water not completely frozen over. 873 00:49:15,469 --> 00:49:18,231 And frozen water under Earth's conditions 874 00:49:18,231 --> 00:49:20,440 has an important property. 875 00:49:22,062 --> 00:49:23,443 We might take this for granted, 876 00:49:23,443 --> 00:49:25,238 but the ice that we have here on Earth 877 00:49:25,238 --> 00:49:28,551 floats because its density 878 00:49:28,551 --> 00:49:31,796 is lower than the water that it is floating in. 879 00:49:31,796 --> 00:49:35,144 And so, the molecules of water ice, 880 00:49:35,144 --> 00:49:38,147 as it freezes, expands out slightly 881 00:49:38,147 --> 00:49:39,873 and moves away from each other 882 00:49:39,873 --> 00:49:42,531 to lower the overall density of the ice, 883 00:49:42,531 --> 00:49:45,603 and this allows it to float on top of the water. 884 00:49:47,156 --> 00:49:50,021 NARRATOR: This property of water ice has enormous consequences 885 00:49:50,021 --> 00:49:52,575 for life on Earth, 886 00:49:52,575 --> 00:49:56,200 the only place life is known to exist to date. 887 00:49:57,408 --> 00:50:00,514 BERDIS: The ice on Earth provides a form of protection 888 00:50:00,514 --> 00:50:02,758 to any life below the surface 889 00:50:02,758 --> 00:50:06,210 that might need protection from anything that could harm it. 890 00:50:08,108 --> 00:50:09,696 NARRATOR: Ice's ability to float 891 00:50:09,696 --> 00:50:12,423 means that, during Earth's colder periods, 892 00:50:12,423 --> 00:50:16,392 bodies of water didn't freeze from the bottom up, 893 00:50:16,392 --> 00:50:18,256 instead remaining a liquid 894 00:50:18,256 --> 00:50:21,742 where life may have held on. 895 00:50:21,742 --> 00:50:24,228 [birds and insects chirping] 896 00:50:24,228 --> 00:50:26,506 For around four billion years, 897 00:50:26,506 --> 00:50:29,336 liquid water on Earth 898 00:50:29,336 --> 00:50:31,269 has allowed an unbroken chain 899 00:50:31,269 --> 00:50:33,340 of life to evolve. 900 00:50:35,860 --> 00:50:38,621 Resulting in oceans. 901 00:50:38,621 --> 00:50:42,453 Home to countless species. 902 00:50:42,453 --> 00:50:45,387 And rivers teeming with life. 903 00:50:46,388 --> 00:50:49,529 All made possible by the unique interplay 904 00:50:49,529 --> 00:50:53,429 between liquid water and floating ice on Earth. 905 00:50:54,637 --> 00:50:56,398 OLUSEYI: The next time you find yourself 906 00:50:56,398 --> 00:50:59,573 making a beverage and you put ice in it, 907 00:50:59,573 --> 00:51:01,748 just take a moment and reflect 908 00:51:01,748 --> 00:51:04,751 on the amazingness of the ice 909 00:51:04,751 --> 00:51:06,511 that made your life possible. 910 00:51:07,995 --> 00:51:10,170 NARRATOR: Across our solar system, 911 00:51:10,170 --> 00:51:12,552 scientists have found worlds 912 00:51:12,552 --> 00:51:14,485 shaped by ice, 913 00:51:14,485 --> 00:51:17,108 made of a diversity of substances 914 00:51:17,108 --> 00:51:20,077 behaving in unbelievable ways. 915 00:51:20,077 --> 00:51:22,217 ♪ 916 00:51:22,217 --> 00:51:25,323 DURFEY: There's a massive variety of ice worlds out there. 917 00:51:25,323 --> 00:51:27,808 Each one has something we haven't seen before. 918 00:51:29,224 --> 00:51:31,916 NARRATOR: We are in a golden age of discovery, 919 00:51:31,916 --> 00:51:36,300 but our knowledge of these ice worlds is far from complete. 920 00:51:37,611 --> 00:51:40,200 There is so much left to learn about ice worlds. 921 00:51:40,200 --> 00:51:42,720 Our understanding is only skin deep. 922 00:51:42,720 --> 00:51:44,998 We want to explore these worlds because 923 00:51:44,998 --> 00:51:49,106 it really tells us where we fit into the universe. 924 00:51:49,106 --> 00:51:51,832 Why are we here? How did we first get here? 925 00:51:52,799 --> 00:51:54,870 NARRATOR: We may not have all the answers, 926 00:51:54,870 --> 00:51:58,701 but we now know that ice plays a critical role 927 00:51:58,701 --> 00:52:00,117 in our story. 928 00:52:02,153 --> 00:52:04,983 WONG: Without the kind of ice that we have here on Earth, 929 00:52:04,983 --> 00:52:07,572 we might not even be here to be discussing ice 930 00:52:07,572 --> 00:52:09,747 and all of its wondrous forms. 931 00:52:09,747 --> 00:52:13,781 ♪