1 00:00:02,200 --> 00:00:06,367 ROWE: A small black star floats through space. 2 00:00:06,467 --> 00:00:10,800 This is the Sun, billions of years in the future. 3 00:00:10,867 --> 00:00:13,800 It's all that remains of our solar system, 4 00:00:14,967 --> 00:00:18,567 the sole survivor of a dramatic history 5 00:00:18,567 --> 00:00:21,467 of elegant beauty and extreme violence. 6 00:00:23,567 --> 00:00:26,000 Just because things look really nice and serene 7 00:00:26,066 --> 00:00:28,467 now doesn't mean it's always been that way. 8 00:00:30,266 --> 00:00:33,100 There are a lot of planets that could have made it 9 00:00:33,166 --> 00:00:35,867 but didn't, and we just happen to be 10 00:00:35,967 --> 00:00:37,266 one of the lucky ones that did. 11 00:00:38,900 --> 00:00:41,100 ROWE: The players in our solar system's story 12 00:00:41,166 --> 00:00:44,367 are more tangled up than we ever imagined. 13 00:00:44,367 --> 00:00:46,367 The more we look at this stuff, 14 00:00:46,367 --> 00:00:48,967 the more we realize that everything affects everything 15 00:00:48,967 --> 00:00:50,600 else, including us. 16 00:00:50,667 --> 00:00:54,400 ROWE: How did we go from a vibrant family of planets 17 00:00:54,467 --> 00:00:57,100 orbiting the yellow sun to a lone, 18 00:00:57,166 --> 00:00:59,166 dead zombie star? 19 00:01:16,467 --> 00:01:18,100 It's an old familiar story. 20 00:01:20,567 --> 00:01:23,567 A bunch of planets orbit a yellow star 21 00:01:23,567 --> 00:01:26,300 in a quiet suburb of the Milky Way galaxy. 22 00:01:28,567 --> 00:01:30,000 But it's not the whole story. 23 00:01:30,000 --> 00:01:30,266 But it's not the whole story. 24 00:01:31,567 --> 00:01:35,000 Over the past decade, our vision of 25 00:01:35,066 --> 00:01:38,100 our solar system has been completely revamped. 26 00:01:39,266 --> 00:01:41,000 ROWE: Think of the solar system as 27 00:01:41,066 --> 00:01:44,367 an old-fashioned mafia crime family. 28 00:01:44,367 --> 00:01:47,867 The sun is the Don, his quarreling children, 29 00:01:47,967 --> 00:01:49,600 the planets. 30 00:01:49,667 --> 00:01:52,166 Their story, like any good mob movie, 31 00:01:52,166 --> 00:01:54,667 is an epic tale of empire building, 32 00:01:54,667 --> 00:01:58,767 sibling rivalry, greed, and ultra violence. 33 00:02:00,567 --> 00:02:02,667 THALLER: The origin of the solar system was chaotic 34 00:02:02,667 --> 00:02:05,367 and violent -- planets colliding, 35 00:02:05,367 --> 00:02:08,600 planets even changing places. 36 00:02:08,667 --> 00:02:12,166 ROWE: Now, a shift in our understanding reveals 37 00:02:12,166 --> 00:02:17,467 a tale of tangled alliances between family members. 38 00:02:17,567 --> 00:02:19,400 Just think about how much our view 39 00:02:19,467 --> 00:02:21,166 of the solar system has changed. 40 00:02:21,266 --> 00:02:23,967 The planets used to be so far away from each other, 41 00:02:23,967 --> 00:02:25,900 and of course, they had nothing to do with each other. 42 00:02:26,000 --> 00:02:28,767 And now, the history is all about the interaction. 43 00:02:28,767 --> 00:02:30,000 So the idea that everything is just 44 00:02:30,000 --> 00:02:31,567 So the idea that everything is just 45 00:02:31,567 --> 00:02:35,300 its own world and doesn't interact is completely wrong. 46 00:02:35,367 --> 00:02:37,667 We like to think of astronomy as looking up, 47 00:02:37,767 --> 00:02:40,166 looking outward, away from ourselves. 48 00:02:40,266 --> 00:02:42,700 But the more we do that, the more we realize how 49 00:02:42,767 --> 00:02:45,567 connected we are to everything out there. 50 00:02:45,667 --> 00:02:48,667 You probably have some material in your body from 51 00:02:48,667 --> 00:02:50,000 pretty much every world that 52 00:02:50,066 --> 00:02:52,066 ever existed in the solar system. 53 00:02:52,066 --> 00:02:54,567 ROWE: Like any good mobster movie, 54 00:02:54,667 --> 00:02:58,967 our story starts with the humble rise of the Godfather. 55 00:02:58,967 --> 00:03:00,000 in this tale, that's the birth of the Sun. 56 00:03:00,000 --> 00:03:02,000 in this tale, that's the birth of the Sun. 57 00:03:03,367 --> 00:03:06,767 But exactly how that happens is a mystery. 58 00:03:08,166 --> 00:03:10,867 When we're trying to figure out how the solar system began, 59 00:03:10,967 --> 00:03:12,567 you know, we don't have a time machine. 60 00:03:12,567 --> 00:03:17,100 So what can we use to find out about how it formed? 61 00:03:19,166 --> 00:03:22,100 ROWE: The solar system has the answer, 62 00:03:22,166 --> 00:03:25,467 its own time machines -- meteorites. 63 00:03:30,367 --> 00:03:32,367 Meteorites are pieces of the solar system from 64 00:03:32,467 --> 00:03:35,467 the distant past, and they've remained unchanged since then. 65 00:03:35,567 --> 00:03:37,400 So they're like little time capsules. 66 00:03:41,266 --> 00:03:43,266 They're like fossils from before 67 00:03:43,367 --> 00:03:45,000 our solar system even formed. 68 00:03:45,066 --> 00:03:46,266 By studying them, 69 00:03:46,300 --> 00:03:48,767 we can really study what was happening and what was going 70 00:03:48,867 --> 00:03:51,767 on in the very early days of our own solar system. 71 00:03:54,667 --> 00:03:56,567 ROWE: 2020 -- 72 00:03:56,667 --> 00:03:59,767 scientists study ancient material trapped inside 73 00:03:59,767 --> 00:04:00,000 a meteorite found in Murchison, Australia. 74 00:04:00,000 --> 00:04:04,200 a meteorite found in Murchison, Australia. 75 00:04:04,266 --> 00:04:07,967 The Murchison meteorite contains tiny crystals called 76 00:04:07,967 --> 00:04:11,567 presolar grains that predate our sun. 77 00:04:15,100 --> 00:04:18,166 OLUSEYI: And trapped within them is evidence of 78 00:04:18,166 --> 00:04:20,600 the history of the formation of our solar system. 79 00:04:22,100 --> 00:04:23,867 ROWE: The presolar grains are made up of 80 00:04:23,867 --> 00:04:28,600 elements like silicon that form inside giant stars. 81 00:04:33,266 --> 00:04:35,467 When these stars die, they blow out 82 00:04:35,567 --> 00:04:39,166 huge clouds of gas and grains of dust. 83 00:04:39,166 --> 00:04:42,700 The term presolar grain doesn't sound very romantic, 84 00:04:42,767 --> 00:04:45,667 but actually, we might call those stardust, 85 00:04:45,667 --> 00:04:47,266 because these materials are things that were 86 00:04:47,367 --> 00:04:49,667 made in stars that no longer exist. 87 00:04:51,467 --> 00:04:53,767 ROWE: The Murchison meteorite contains grains 88 00:04:53,767 --> 00:04:56,867 from at least 46 different stars. 89 00:04:58,367 --> 00:05:00,000 What the Murchison meteorite tells us is that 90 00:05:00,000 --> 00:05:00,900 What the Murchison meteorite tells us is that 91 00:05:01,000 --> 00:05:03,000 the material that came together 92 00:05:03,100 --> 00:05:06,967 that formed our solar system had its origination in 93 00:05:06,967 --> 00:05:09,066 dozens of different stars. 94 00:05:09,066 --> 00:05:13,600 These stars died and blew out all of these materials. 95 00:05:13,667 --> 00:05:16,900 And then created this huge cloud of gas and dust 96 00:05:17,000 --> 00:05:18,066 called a nebula. 97 00:05:19,100 --> 00:05:21,066 OLUSEYI: The sources of the material in that cloud 98 00:05:21,066 --> 00:05:23,300 could come from one of a number of places. 99 00:05:23,367 --> 00:05:25,700 The material from lots of stars' 100 00:05:25,767 --> 00:05:28,900 atmospheres could be mixed in there. 101 00:05:29,000 --> 00:05:30,000 ROWE: In the mix were the ingredients to build 102 00:05:30,000 --> 00:05:31,600 ROWE: In the mix were the ingredients to build 103 00:05:31,667 --> 00:05:33,400 the solar system, 104 00:05:33,467 --> 00:05:35,367 but we don't know what triggered 105 00:05:35,467 --> 00:05:37,900 the gas and dust to form the Sun. 106 00:05:39,266 --> 00:05:42,000 A 2020 study may have the answer. 107 00:05:44,066 --> 00:05:45,767 BULLOCK: One of the coolest things we've discovered 108 00:05:45,867 --> 00:05:48,567 in the last couple of decades about the Milky Way 109 00:05:48,567 --> 00:05:50,467 is there's a giant stream of stars that's 110 00:05:50,467 --> 00:05:52,900 stretching across virtually the whole sky. 111 00:05:56,266 --> 00:05:58,867 These stars were not born in the galaxy. 112 00:05:58,967 --> 00:06:00,000 They're not from here. 113 00:06:00,000 --> 00:06:00,166 They're not from here. 114 00:06:02,100 --> 00:06:03,500 ROWE: If not from our galaxy, 115 00:06:03,567 --> 00:06:05,667 then from where? 116 00:06:06,700 --> 00:06:10,200 We think these stars actually came from 117 00:06:10,266 --> 00:06:14,166 the Sagittarius Dwarf galaxy, which orbits the Milky Way. 118 00:06:16,166 --> 00:06:18,166 ROWE: Over five billion years ago, 119 00:06:18,266 --> 00:06:21,400 the Sagittarius Dwarf galaxy wanders 120 00:06:21,467 --> 00:06:23,300 too close to the Milky Way. 121 00:06:25,266 --> 00:06:30,000 Our galaxy's powerful gravity drags Sagittarius towards it. 122 00:06:30,000 --> 00:06:30,100 Our galaxy's powerful gravity drags Sagittarius towards it. 123 00:06:30,166 --> 00:06:31,800 The galaxies collide. 124 00:06:33,266 --> 00:06:34,500 As this is happening, 125 00:06:34,567 --> 00:06:37,266 the Milky Way is tearing Sagittarius apart, 126 00:06:37,266 --> 00:06:38,967 ripping stars out of it. 127 00:06:41,166 --> 00:06:46,300 This is truly intergalactic cosmological drama at play. 128 00:06:48,066 --> 00:06:51,166 This collision shakes up the Milky Way. 129 00:06:51,166 --> 00:06:54,100 When a body passes 130 00:06:54,166 --> 00:06:56,367 through the disc of our galaxy, it's 131 00:06:56,467 --> 00:06:58,767 gonna set off ripples, and that's going to compress 132 00:06:58,767 --> 00:07:00,000 the gas clouds, and that's gonna create star formation. 133 00:07:00,000 --> 00:07:02,467 the gas clouds, and that's gonna create star formation. 134 00:07:02,567 --> 00:07:06,166 The Sagittarius Dwarf smashing into the Milky Way 135 00:07:06,166 --> 00:07:09,767 is like dropping a boulder into a pond. 136 00:07:15,700 --> 00:07:18,567 It sets out ripples of density, 137 00:07:18,667 --> 00:07:21,500 and it disturbs everything in the galaxy, 138 00:07:21,567 --> 00:07:23,967 but it doesn't disturb everything equally. 139 00:07:23,967 --> 00:07:26,500 It causes some clumps of dust 140 00:07:26,567 --> 00:07:29,467 and gas to start accumulating together. 141 00:07:33,100 --> 00:07:36,567 ROWE: The disruption in one galactic zip code leads 142 00:07:36,567 --> 00:07:39,700 to new activity in others across the Milky Way. 143 00:07:41,367 --> 00:07:43,867 The ripples trigger gas and dust left over 144 00:07:43,967 --> 00:07:47,567 from the dying stars to split into clumps, 145 00:07:47,667 --> 00:07:50,600 sparking a frenzy of star formation. 146 00:07:51,767 --> 00:07:53,867 LANZA: Look, if you were an observer, 147 00:07:53,967 --> 00:07:57,066 suddenly, out of these little clumps of gas 148 00:07:57,066 --> 00:08:00,000 come bright ignition sparks all at once. 149 00:08:00,000 --> 00:08:00,166 come bright ignition sparks all at once. 150 00:08:04,900 --> 00:08:07,000 If you were to stand there long enough, 151 00:08:07,066 --> 00:08:08,667 watching this stellar nursery, 152 00:08:08,767 --> 00:08:11,000 it might look kind of like a field at night 153 00:08:11,066 --> 00:08:13,100 with fireflies blinking on. 154 00:08:14,600 --> 00:08:17,767 ROWE: Perhaps the Sun formed in this starburst. 155 00:08:18,800 --> 00:08:21,367 OLUSEYI: The passage of the Sagittarius Dwarf 156 00:08:21,467 --> 00:08:23,500 through our galaxy correlates 157 00:08:23,567 --> 00:08:26,467 in time to the formation and birth of our sun. 158 00:08:26,467 --> 00:08:30,000 So maybe our solar system came about as a result of 159 00:08:30,000 --> 00:08:31,367 So maybe our solar system came about as a result of 160 00:08:31,367 --> 00:08:34,567 the Sagittarius Dwarf passing through our galaxy 161 00:08:34,667 --> 00:08:36,300 over five million years ago. 162 00:08:36,367 --> 00:08:39,400 Of course, we don't know for sure if this is what triggered 163 00:08:39,467 --> 00:08:42,467 the formation of our sun, but the timing does fit. 164 00:08:45,567 --> 00:08:48,900 ROWE: 4.6 billion years ago, 165 00:08:49,000 --> 00:08:50,467 part of the cloud seeded with 166 00:08:50,567 --> 00:08:54,700 material from dying stars grows denser, 167 00:08:54,767 --> 00:08:58,100 until it gets so massive, it collapses. 168 00:09:00,100 --> 00:09:03,000 NANCE: As the gas cloud collapses, 169 00:09:03,066 --> 00:09:07,266 it gets hotter and hotter and spins faster and faster, 170 00:09:07,266 --> 00:09:10,400 forming a dense core at its center. 171 00:09:10,467 --> 00:09:16,367 The core is the protostar that will later become our sun. 172 00:09:16,467 --> 00:09:20,767 ROWE: The protostar drags in more and more gas and dust, 173 00:09:20,767 --> 00:09:24,367 creating a region of materials spinning around it 174 00:09:24,467 --> 00:09:26,867 called the protoplanetary disk. 175 00:09:26,967 --> 00:09:30,000 OLUSEYI: As the Sun builds up more mass, 176 00:09:30,000 --> 00:09:31,100 OLUSEYI: As the Sun builds up more mass, 177 00:09:31,166 --> 00:09:33,900 it's getting compressed gravitationally, and so the core 178 00:09:34,000 --> 00:09:35,767 is getting hotter and hotter and hotter. 179 00:09:35,867 --> 00:09:37,367 The densities are increasing. 180 00:09:40,367 --> 00:09:43,567 ROWE: The new Don, the head of our solar mobster family, 181 00:09:43,567 --> 00:09:47,300 immediately reveals a ferocious nature, 182 00:09:47,367 --> 00:09:51,200 blasting out supercharged jets of radiation. 183 00:09:52,266 --> 00:09:57,467 The early sun was not the calm, glowing orb 184 00:09:57,467 --> 00:10:00,000 that we see in our sky today -- it was far more chaotic. 185 00:10:00,000 --> 00:10:00,900 that we see in our sky today -- it was far more chaotic. 186 00:10:03,166 --> 00:10:05,800 It's sort of like in its toddler phase. 187 00:10:05,867 --> 00:10:07,900 It was acting up all the time. 188 00:10:10,066 --> 00:10:13,100 It has all of this energy that pushes material off of 189 00:10:13,166 --> 00:10:15,000 the surface and launches it into 190 00:10:15,066 --> 00:10:16,266 what we call the solar wind. 191 00:10:18,567 --> 00:10:21,200 ROWE: The blizzard of particles races out 192 00:10:21,266 --> 00:10:23,867 at over a million miles an hour. 193 00:10:23,967 --> 00:10:27,000 It smashes into the protoplanetary disk 194 00:10:27,066 --> 00:10:28,767 and blows the gas away. 195 00:10:31,066 --> 00:10:35,100 At the same time, the Sun's core heats up to 18 million 196 00:10:35,166 --> 00:10:37,066 degrees Fahrenheit, 197 00:10:37,066 --> 00:10:41,367 triggering the fusion of hydrogen into helium. 198 00:10:41,367 --> 00:10:43,667 And that releases a tremendous amount of 199 00:10:43,767 --> 00:10:46,400 energy that eventually works its way back to the surface of 200 00:10:46,467 --> 00:10:48,367 the star and comes out as light. 201 00:10:50,100 --> 00:10:53,867 Finally, the Sun becomes the recognizable 202 00:10:53,867 --> 00:10:56,066 sun that we see in our sky today. 203 00:10:58,100 --> 00:11:00,000 ROWE: The sun is now the Godfather, 204 00:11:00,000 --> 00:11:00,867 ROWE: The sun is now the Godfather, 205 00:11:00,867 --> 00:11:03,100 pulling the strings on the solar system. 206 00:11:04,567 --> 00:11:06,767 The young Don's rise to the top 207 00:11:06,867 --> 00:11:09,967 triggers a power struggle with its willful children, 208 00:11:09,967 --> 00:11:11,767 the planets. 209 00:11:11,867 --> 00:11:14,100 It's a brutal fight for survival. 210 00:11:26,500 --> 00:11:29,200 ROWE: 4.6 billion years ago, 211 00:11:30,367 --> 00:11:34,700 our mob family rises in a quiet suburb of the Milky Way. 212 00:11:35,767 --> 00:11:39,767 Its Godfather, the Sun, forms from a collapsed 213 00:11:39,867 --> 00:11:41,100 stellar nebula. 214 00:11:44,867 --> 00:11:48,110 The greedy star scarfs down most of the cloud of gas 215 00:11:48,110 --> 00:11:48,266 The greedy star scarfs down most of the cloud of gas 216 00:11:48,266 --> 00:11:50,200 and dust, but just enough 217 00:11:50,266 --> 00:11:53,166 is left over to build the planets. 218 00:11:53,266 --> 00:11:56,567 We're standing here on a big planet, and we look up in 219 00:11:56,667 --> 00:11:58,967 the sky, and we see other planets going around the Sun, 220 00:11:58,967 --> 00:12:02,266 and it's an obvious and challenging question to ask, 221 00:12:02,266 --> 00:12:03,767 where did these planets come from? 222 00:12:05,700 --> 00:12:09,367 ROWE: How did the leftover gas and dust build the planets? 223 00:12:10,900 --> 00:12:13,767 To solve the mystery, 224 00:12:13,767 --> 00:12:16,100 scientists study other star systems 225 00:12:16,166 --> 00:12:18,110 across the Milky Way. 226 00:12:18,110 --> 00:12:18,300 across the Milky Way. 227 00:12:18,367 --> 00:12:19,867 HOPKINS: We can't go back in time 228 00:12:19,867 --> 00:12:22,066 and watch our own solar system forming. 229 00:12:22,066 --> 00:12:25,567 But we can look at other, new solar systems as they're 230 00:12:25,667 --> 00:12:28,800 forming and use that to understand how our own 231 00:12:28,867 --> 00:12:30,100 might have formed. 232 00:12:34,000 --> 00:12:40,900 ROWE: Star system PDS 70 is one such system. 233 00:12:41,000 --> 00:12:44,900 It's young, just 5.4 million years old. 234 00:12:47,266 --> 00:12:48,110 And nestled inside the protoplanetary disk are 235 00:12:48,110 --> 00:12:50,600 And nestled inside the protoplanetary disk are 236 00:12:50,667 --> 00:12:54,800 two infant planets feeding on gas and dust. 237 00:12:58,000 --> 00:13:00,967 We can see these baby exoplanets pulling in 238 00:13:00,967 --> 00:13:03,567 material and creating these gaps in the disk. 239 00:13:03,667 --> 00:13:05,867 It's an amazing discovery -- it's kind of mind-blowing 240 00:13:05,967 --> 00:13:09,667 that we can see a new solar system being born. 241 00:13:11,600 --> 00:13:14,266 CHRISTIANSEN: These snapshots, these systems like PDS 70, 242 00:13:14,367 --> 00:13:17,967 are so valuable, because they let us test our theories. 243 00:13:17,967 --> 00:13:18,110 We thought planets formed from these discs of dust and gas, 244 00:13:18,110 --> 00:13:21,000 We thought planets formed from these discs of dust and gas, 245 00:13:21,100 --> 00:13:23,500 but we hadn't seen it until now. 246 00:13:23,567 --> 00:13:25,767 ROWE: What we couldn't see was how gas 247 00:13:25,867 --> 00:13:29,200 and dust bind together to grow into planets. 248 00:13:35,567 --> 00:13:37,166 That took an astronaut on 249 00:13:37,166 --> 00:13:40,367 the space station messing around with breakfast. 250 00:13:42,767 --> 00:13:44,200 Ah. 251 00:13:44,266 --> 00:13:45,567 Don Pettit, this one astronaut, 252 00:13:45,567 --> 00:13:47,767 took a bag full of salt and sugar 253 00:13:47,867 --> 00:13:48,110 and coffee grounds and just shook it to see what would 254 00:13:48,110 --> 00:13:50,066 and coffee grounds and just shook it to see what would 255 00:13:50,066 --> 00:13:51,900 happen in 0G. 256 00:13:52,000 --> 00:13:53,600 And to his astonishment, 257 00:13:53,667 --> 00:13:57,467 he saw that they immediately clumped up. 258 00:13:57,467 --> 00:14:01,200 It's effectively electrostatic forces that are causing 259 00:14:01,266 --> 00:14:03,400 those clumps to form -- the salt grains 260 00:14:03,467 --> 00:14:05,867 rub around with each other, and they develop a charge, 261 00:14:05,867 --> 00:14:07,500 an electrical charge. 262 00:14:07,567 --> 00:14:10,367 And so those clumps very naturally form. 263 00:14:12,100 --> 00:14:14,667 ROWE: These clumps were strong. 264 00:14:14,667 --> 00:14:18,110 They didn't fall apart when they hit the sides of the bag. 265 00:14:18,110 --> 00:14:19,367 They didn't fall apart when they hit the sides of the bag. 266 00:14:19,367 --> 00:14:21,567 DURDA: And sitting down on the ground, 267 00:14:21,667 --> 00:14:24,600 down at mission control, was astronaut Stan Love, 268 00:14:24,667 --> 00:14:26,700 going, "Oh, my God, Don, you've solved the first 269 00:14:26,767 --> 00:14:28,567 steps of planetary formation." 270 00:14:30,266 --> 00:14:34,100 A very similar process went on 271 00:14:34,166 --> 00:14:36,266 in the early protoplanetary disk. 272 00:14:36,367 --> 00:14:38,567 Instead of salt, it's mineral grains. 273 00:14:42,567 --> 00:14:46,600 So the dust grains that you start with stick to each other 274 00:14:46,667 --> 00:14:48,110 because of electrostatic forces, 275 00:14:48,110 --> 00:14:48,367 because of electrostatic forces, 276 00:14:48,467 --> 00:14:49,667 basically static cling, 277 00:14:49,767 --> 00:14:51,800 and it's almost exactly identical to how 278 00:14:51,867 --> 00:14:54,100 a dust bunny forms in your room. 279 00:14:54,166 --> 00:14:56,767 SUTTER: These are cosmic dust bunnies that 280 00:14:56,867 --> 00:15:01,367 will some day grow up into giant planets. 281 00:15:01,367 --> 00:15:06,100 ROWE: Astronomers call these cosmic dust bunnies pebbles. 282 00:15:08,000 --> 00:15:11,700 We think clumping dust particles formed trillions 283 00:15:11,767 --> 00:15:15,066 of pebbles each around an inch in diameter. 284 00:15:15,066 --> 00:15:18,110 It's the first step in planet construction. 285 00:15:18,110 --> 00:15:18,667 It's the first step in planet construction. 286 00:15:18,667 --> 00:15:20,967 The next step in forming a planet 287 00:15:20,967 --> 00:15:23,500 involves planetesimals and these are objects that are 288 00:15:23,567 --> 00:15:26,600 roughly half a mile to 100 miles in size. 289 00:15:28,700 --> 00:15:31,567 ROWE: But how pebbles build planetesimals was 290 00:15:31,667 --> 00:15:36,066 a mystery, because pebbles don't play well together. 291 00:15:38,266 --> 00:15:40,166 Grains of protoplanetary material stick 292 00:15:40,166 --> 00:15:42,066 together because of static charge. 293 00:15:42,066 --> 00:15:44,100 The problem is, once they get too big, 294 00:15:44,166 --> 00:15:46,066 that force isn't enough, and they'll just 295 00:15:46,066 --> 00:15:47,567 bounce off each other. 296 00:15:53,667 --> 00:15:57,000 Yet we know that we have to get all the way up to hundreds 297 00:15:57,066 --> 00:15:58,867 of miles across to build our planetesimals. 298 00:15:58,867 --> 00:16:02,567 How do you build a bigger structure when the particles 299 00:16:02,667 --> 00:16:04,166 that you're trying to lump together 300 00:16:04,166 --> 00:16:05,667 are bouncing off of each other? 301 00:16:07,300 --> 00:16:10,467 WALSH: So a new idea came forward about how to make 302 00:16:10,467 --> 00:16:12,667 this big jump from pebble-sized things 303 00:16:12,767 --> 00:16:14,567 all the way up to planetesimals, 304 00:16:14,667 --> 00:16:17,100 and this relies on the interaction of a huge number 305 00:16:17,166 --> 00:16:18,110 of pebbles moving together through the gas 306 00:16:18,110 --> 00:16:19,600 of pebbles moving together through the gas 307 00:16:19,667 --> 00:16:21,567 around the star. 308 00:16:21,567 --> 00:16:25,266 BATYGIN: In the disk of gas and dust that encircles 309 00:16:25,367 --> 00:16:26,500 the young sun, 310 00:16:26,500 --> 00:16:30,800 pebbles will begin to coalesce into these big clouds, 311 00:16:30,867 --> 00:16:35,700 much in the same way that individual fish will form 312 00:16:35,767 --> 00:16:36,900 schools of fish. 313 00:16:37,000 --> 00:16:41,467 ROWE: More and more pebbles join the cloud. 314 00:16:41,467 --> 00:16:44,200 Eventually, you get enough of them 315 00:16:44,266 --> 00:16:46,800 together that they collapse under their own gravity 316 00:16:46,867 --> 00:16:48,110 and make one big planetesimal. 317 00:16:48,110 --> 00:16:48,200 and make one big planetesimal. 318 00:16:59,667 --> 00:17:01,700 ROWE: The planetesimals face a race 319 00:17:01,767 --> 00:17:05,567 against time to grow into planets. 320 00:17:05,567 --> 00:17:07,567 They must grab enough building material 321 00:17:07,667 --> 00:17:11,266 from the protoplanetary disk before their Don, 322 00:17:11,367 --> 00:17:13,867 the Sun, blasts it all away. 323 00:17:26,166 --> 00:17:28,467 ROWE: 4.6 billion years ago, 324 00:17:28,567 --> 00:17:32,166 a fierce battle erupts between the head of the family, 325 00:17:32,166 --> 00:17:35,100 the Sun, and his children, the growing planets. 326 00:17:35,166 --> 00:17:40,367 The Godfather is armed and dangerous and threatening to 327 00:17:40,467 --> 00:17:42,867 destroy the planet's food source 328 00:17:42,967 --> 00:17:45,567 with his weapon of choice, the solar wind. 329 00:17:46,567 --> 00:17:48,270 There's this strong wind of high-energy particles 330 00:17:48,270 --> 00:17:49,367 There's this strong wind of high-energy particles 331 00:17:49,367 --> 00:17:51,000 coming out of the Sun. 332 00:17:51,066 --> 00:17:53,266 That blows away the disk of gas. 333 00:17:54,867 --> 00:17:57,400 ROWE: The planets must fight to grab hold of 334 00:17:57,467 --> 00:18:01,200 the remaining resources before the Sun drives them away. 335 00:18:01,266 --> 00:18:06,700 So it's a race against time -- Jupiter is racing 336 00:18:06,767 --> 00:18:09,200 the Sun to capture as much material as 337 00:18:09,266 --> 00:18:12,200 it can before the Sun blows it all away. 338 00:18:12,266 --> 00:18:15,300 And what we see from studying other solar systems is 339 00:18:15,367 --> 00:18:18,270 that those disks only last for about five million years. 340 00:18:18,270 --> 00:18:19,166 that those disks only last for about five million years. 341 00:18:19,266 --> 00:18:21,300 ROWE: We used to think of the solar system's 342 00:18:21,367 --> 00:18:24,367 protoplanetary disk like an old-school diner 343 00:18:24,467 --> 00:18:27,100 where the mob family came to eat. 344 00:18:27,166 --> 00:18:31,166 The firstborn child, Jupiter, grows by wolfing down 345 00:18:31,166 --> 00:18:34,467 planetesimals, followed by a second course of gas. 346 00:18:35,667 --> 00:18:38,667 HOPKINS: The old model of planet formation is the idea that 347 00:18:38,667 --> 00:18:42,700 these large-ish planetesimals that are miles across 348 00:18:42,767 --> 00:18:44,100 collide and stick to each other, 349 00:18:44,166 --> 00:18:46,467 kind of like modeling clay, until you get a bigger 350 00:18:46,467 --> 00:18:47,700 and bigger object that can 351 00:18:47,767 --> 00:18:48,270 eventually get so massive that it starts to then pull in 352 00:18:48,270 --> 00:18:50,667 eventually get so massive that it starts to then pull in 353 00:18:50,667 --> 00:18:55,400 the more diffuse gas around it to form a gaseous atmosphere. 354 00:18:55,467 --> 00:18:59,400 ROWE: It's a simple idea, but with a big problem -- 355 00:18:59,467 --> 00:19:01,000 time. 356 00:19:01,100 --> 00:19:03,400 By that old model, it would take upwards of 357 00:19:03,467 --> 00:19:06,900 100 million years to accumulate enough planetesimals to do that. 358 00:19:08,000 --> 00:19:10,100 ROWE: Way too long for Jupiter to grow 359 00:19:10,166 --> 00:19:13,000 before the Sun blows all the gas away. 360 00:19:14,767 --> 00:19:16,767 We found a clue to how Jupiter 361 00:19:16,867 --> 00:19:18,270 beat the problem of the disappearing gas 362 00:19:18,270 --> 00:19:19,767 beat the problem of the disappearing gas 363 00:19:19,767 --> 00:19:24,000 in 2017, when the Juno spacecraft investigated 364 00:19:24,100 --> 00:19:25,767 the gas giant's core. 365 00:19:25,867 --> 00:19:28,867 HOPKINS: The traditional theories predict that 366 00:19:28,867 --> 00:19:30,900 Jupiter's core would be kind of like a big ball 367 00:19:31,000 --> 00:19:34,300 of solid iron or rock, surrounded by 368 00:19:34,367 --> 00:19:36,967 a giant gaseous atmosphere. 369 00:19:40,667 --> 00:19:44,867 SUTTER: Juno instead found that Jupiter's core is fuzzy. 370 00:19:44,967 --> 00:19:47,900 There's no boundary between hard rock 371 00:19:48,000 --> 00:19:48,270 and then gaseous atmosphere. 372 00:19:48,270 --> 00:19:49,567 and then gaseous atmosphere. 373 00:19:49,667 --> 00:19:52,467 There's just a gradual transition as you move 374 00:19:52,567 --> 00:19:56,667 outwards from mostly rock and icy to mostly gassy. 375 00:19:58,400 --> 00:20:02,000 ROWE: This fuzzy transition from rock ice core to gas 376 00:20:02,066 --> 00:20:03,367 suggests that young Jupiter 377 00:20:03,367 --> 00:20:06,867 didn't eat a la carte with separate courses of 378 00:20:06,967 --> 00:20:08,600 planetesimals and then gas. 379 00:20:11,300 --> 00:20:16,166 Instead, it devoured the whole buffet in one sitting. 380 00:20:16,166 --> 00:20:18,270 HOPKINS: These fuzzy cores suggest that, 381 00:20:18,270 --> 00:20:18,900 HOPKINS: These fuzzy cores suggest that, 382 00:20:19,000 --> 00:20:21,266 as Jupiter's core was forming, 383 00:20:21,266 --> 00:20:24,667 it was actually incorporating a mixture of gas and ice 384 00:20:24,667 --> 00:20:28,200 and rocks all together in its formation. 385 00:20:28,266 --> 00:20:30,667 ROWE: This was possible because there was still 386 00:20:30,667 --> 00:20:33,900 lots of gas in the protoplanetary disk. 387 00:20:36,367 --> 00:20:37,900 Everything was moving through 388 00:20:38,000 --> 00:20:40,400 this very thick disk of dust and gas. 389 00:20:40,467 --> 00:20:41,867 That means that everything was actually 390 00:20:41,967 --> 00:20:44,300 being slowed down by the drag. 391 00:20:44,367 --> 00:20:46,000 Things were the size of pebbles, 392 00:20:46,100 --> 00:20:47,967 they were feeling the drag, too. 393 00:20:47,967 --> 00:20:48,270 That meant they lost energy and made it easier for Jupiter 394 00:20:48,270 --> 00:20:51,300 That meant they lost energy and made it easier for Jupiter 395 00:20:51,367 --> 00:20:52,767 to pull them in. 396 00:20:54,066 --> 00:20:56,700 ROWE: The young planetesimals grab millions 397 00:20:56,767 --> 00:20:59,600 of pebbles along with lots of gas. 398 00:20:59,667 --> 00:21:03,767 They're drawing in gas as well as these pebbles. 399 00:21:03,867 --> 00:21:06,867 The pebbles basically run out, and they keep drawing 400 00:21:06,967 --> 00:21:08,867 this gas in and get bigger and bigger and bigger. 401 00:21:10,200 --> 00:21:13,700 HOPKINS: This formation model allows you to grow a planet like 402 00:21:13,767 --> 00:21:15,266 Jupiter much more quickly, 403 00:21:15,367 --> 00:21:17,367 because it's gobbling up everything at once at 404 00:21:17,467 --> 00:21:18,270 a very rapid pace, and that allows it to potentially beat 405 00:21:18,270 --> 00:21:20,967 a very rapid pace, and that allows it to potentially beat 406 00:21:20,967 --> 00:21:22,700 the Sun and grow within a few 407 00:21:22,767 --> 00:21:25,967 million years before the Sun blows everything away. 408 00:21:27,900 --> 00:21:29,700 ROWE: Both Jupiter and Saturn 409 00:21:29,767 --> 00:21:33,266 won their race against the Sun and grew large. 410 00:21:34,767 --> 00:21:38,000 But the inner planets were not so lucky. 411 00:21:40,200 --> 00:21:44,767 The Godfather ruthlessly limited the food on their menu. 412 00:21:44,767 --> 00:21:47,300 HOWETT: And so the planets that formed 413 00:21:47,367 --> 00:21:48,270 depend upon what you have to begin with -- if you're making 414 00:21:48,270 --> 00:21:50,467 depend upon what you have to begin with -- if you're making 415 00:21:50,467 --> 00:21:52,667 a cake, and you only have certain ingredients, 416 00:21:52,767 --> 00:21:54,867 you can only make a cake out of those ingredients, 417 00:21:54,967 --> 00:21:56,567 and the planets are the same way. 418 00:21:56,667 --> 00:21:58,166 They could only be made out 419 00:21:58,166 --> 00:22:00,166 of things that are in their vicinity. 420 00:22:00,266 --> 00:22:03,000 In the inner solar system, where it's much warmer, 421 00:22:03,100 --> 00:22:05,667 volatiles like water and ammonia 422 00:22:05,767 --> 00:22:07,967 had evaporated and get blown away. 423 00:22:07,967 --> 00:22:11,700 So the only materials found here for building planets 424 00:22:11,767 --> 00:22:15,000 were rocky, metallic materials. 425 00:22:15,066 --> 00:22:16,767 So the planets that formed in this 426 00:22:16,767 --> 00:22:18,270 inner region are rocky planets with metallic cores. 427 00:22:18,270 --> 00:22:20,667 inner region are rocky planets with metallic cores. 428 00:22:23,200 --> 00:22:25,867 ROWE: The ice giants feasted on materials that 429 00:22:25,967 --> 00:22:29,700 only survive far from the Sun's harmful influence. 430 00:22:31,000 --> 00:22:32,367 HOPKINS: When you get further out, 431 00:22:32,467 --> 00:22:35,767 the distances that Uranus and Neptune are at, ammonia 432 00:22:35,867 --> 00:22:39,266 and methane start to turn into their own frozen ices. 433 00:22:39,266 --> 00:22:40,867 That's why we call them ice giants, because 434 00:22:40,867 --> 00:22:44,367 they're formed primarily out of these solid ices. 435 00:22:44,367 --> 00:22:47,967 ROWE: And there were plenty of these ices to gorge on. 436 00:22:49,767 --> 00:22:51,400 HOWETT: The further you are from the Sun, 437 00:22:51,467 --> 00:22:53,767 the less the effect the solar wind has. 438 00:22:53,867 --> 00:22:55,867 It's a bit like if you're standing next to a fan, where if 439 00:22:55,967 --> 00:22:57,400 you're right next to it, you're really gonna feel it. 440 00:22:57,467 --> 00:22:58,700 You step back a few paces, 441 00:22:58,767 --> 00:23:00,467 it's not as blowy, and so it's 442 00:23:00,567 --> 00:23:02,600 the same thing happening in the outer solar system. 443 00:23:02,667 --> 00:23:04,100 It's not able to strip away 444 00:23:04,166 --> 00:23:06,867 the gasses and the rock quite as much. 445 00:23:06,867 --> 00:23:08,767 ROWE: The ice giants grew to over 446 00:23:08,867 --> 00:23:11,967 14 times the mass of Earth. 447 00:23:11,967 --> 00:23:14,767 The Godfather, the Sun, 448 00:23:14,767 --> 00:23:16,867 ruthlessly controls the family. 449 00:23:16,967 --> 00:23:18,270 But firstborn Jupiter has grown large. 450 00:23:18,270 --> 00:23:20,800 But firstborn Jupiter has grown large. 451 00:23:20,867 --> 00:23:22,900 He craves power 452 00:23:23,000 --> 00:23:26,867 and attempts a hostile takeover of the inner solar system, 453 00:23:26,867 --> 00:23:29,667 triggering mass murder and mayhem. 454 00:23:41,000 --> 00:23:42,967 ROWE: We used to think that all star systems 455 00:23:42,967 --> 00:23:45,000 were similar to our own. 456 00:23:45,066 --> 00:23:49,266 That's because our solar system was the only one we knew. 457 00:23:49,266 --> 00:23:51,867 OLUSEYI: It's hard to get a perspective on 458 00:23:51,867 --> 00:23:53,800 your home if you've not been anywhere else. 459 00:23:53,867 --> 00:23:57,266 We thought it was typical, but now that we've discovered 460 00:23:57,367 --> 00:24:00,266 hundreds of others, it's the weird one. 461 00:24:00,266 --> 00:24:02,266 It may surprise you to learn that we've never found 462 00:24:02,266 --> 00:24:03,445 a solar system around another star 463 00:24:03,445 --> 00:24:04,367 a solar system around another star 464 00:24:04,367 --> 00:24:06,100 that really resembles our own, 465 00:24:06,166 --> 00:24:08,266 with all of these small, rocky planets in the middle of 466 00:24:08,266 --> 00:24:10,567 the solar system and these big gas giants 467 00:24:10,567 --> 00:24:12,367 farther out. 468 00:24:12,467 --> 00:24:17,667 ROWE: We've found star systems with super puff planets, 469 00:24:17,767 --> 00:24:21,467 rocky worlds orbiting tiny red stars, 470 00:24:21,467 --> 00:24:24,667 giant stars with superheated planets 471 00:24:24,767 --> 00:24:26,767 that rain liquid iron, 472 00:24:26,867 --> 00:24:30,000 water worlds, and planets orbiting zombie 473 00:24:30,066 --> 00:24:31,500 white dwarf stars, 474 00:24:31,567 --> 00:24:33,445 but none that look like our home system. 475 00:24:33,445 --> 00:24:34,667 but none that look like our home system. 476 00:24:34,767 --> 00:24:37,500 Every solar system we look at, ours 477 00:24:37,567 --> 00:24:41,000 just look like it's standing off in a corner all by itself. 478 00:24:42,767 --> 00:24:46,467 ROWE: The other systems may be very different from our own, 479 00:24:46,567 --> 00:24:50,467 but they can still show us how the solar system developed. 480 00:24:52,867 --> 00:24:54,900 2021. 481 00:24:55,000 --> 00:24:57,200 Scientists discover six planets orbiting 482 00:24:57,266 --> 00:24:58,967 a small orange star 483 00:24:58,967 --> 00:25:01,567 called TOI-178. 484 00:25:02,567 --> 00:25:03,445 And they range from just a little bit more massive than 485 00:25:03,445 --> 00:25:04,800 And they range from just a little bit more massive than 486 00:25:04,867 --> 00:25:06,767 the Earth, about 1.5 times, 487 00:25:06,867 --> 00:25:09,800 to a bit more than seven times the mass of the Earth. 488 00:25:09,867 --> 00:25:13,000 These are called super-Earths, and it turns out, 489 00:25:13,100 --> 00:25:15,700 these are really abundant out in the universe. 490 00:25:16,767 --> 00:25:20,166 ROWE: Around 40 percent of the star systems we've found 491 00:25:20,266 --> 00:25:24,266 contain at least one super-Earth. 492 00:25:24,266 --> 00:25:27,567 One of the most peculiar aspects about our solar system 493 00:25:27,667 --> 00:25:29,700 is that we don't have any super-Earths. 494 00:25:29,767 --> 00:25:31,600 We see these things everywhere. 495 00:25:31,667 --> 00:25:32,967 Not here. 496 00:25:36,567 --> 00:25:38,467 ROWE: The first clue to solving the mystery of 497 00:25:38,467 --> 00:25:43,266 the missing super-Earths comes from an asteroid called Psyche. 498 00:25:43,266 --> 00:25:45,767 It orbits in the asteroid belt, 499 00:25:45,767 --> 00:25:50,467 a band of rocky objects between Mars and Jupiter. 500 00:25:50,567 --> 00:25:53,967 The asteroid Psyche appears to be a fascinating world 501 00:25:53,967 --> 00:25:57,000 made almost entirely of metal, of iron and nickel. 502 00:25:59,867 --> 00:26:03,445 LANZA: We think it's the core of a now destroyed planet. 503 00:26:03,445 --> 00:26:04,200 LANZA: We think it's the core of a now destroyed planet. 504 00:26:04,266 --> 00:26:07,500 You can think of Psyche as a metallic kernel of 505 00:26:07,567 --> 00:26:11,066 a nut whose shell was smashed off in a huge collision. 506 00:26:16,767 --> 00:26:20,200 ROWE: The asteroid belt is full of similar debris, 507 00:26:20,266 --> 00:26:23,700 like blood splatter at a mafia murder scene. 508 00:26:28,567 --> 00:26:30,700 It points to serious felonies taking 509 00:26:30,767 --> 00:26:33,000 place in the early solar system. 510 00:26:33,066 --> 00:26:33,445 We think that there were once dozens of 511 00:26:33,445 --> 00:26:37,700 We think that there were once dozens of 512 00:26:37,767 --> 00:26:40,900 rocky protoplanets orbiting around the young sun. 513 00:26:43,467 --> 00:26:45,066 Now we only have four. 514 00:26:47,700 --> 00:26:49,967 We find clues to what caused 515 00:26:49,967 --> 00:26:53,667 this planetary homicide in distant star systems. 516 00:26:55,100 --> 00:26:57,867 PLAIT: The first exoplanets that we found orbiting stars 517 00:26:57,867 --> 00:27:00,166 like the Sun are what we call hot Jupiters. 518 00:27:00,166 --> 00:27:02,100 Nobody expected these. 519 00:27:02,166 --> 00:27:03,445 These are planets as big or bigger 520 00:27:03,445 --> 00:27:05,000 These are planets as big or bigger 521 00:27:05,100 --> 00:27:06,567 than Jupiter, but orbiting 522 00:27:06,667 --> 00:27:09,000 super close in to their star. 523 00:27:09,066 --> 00:27:11,467 When the young star is forming, 524 00:27:11,467 --> 00:27:13,400 it blows out all of the material 525 00:27:13,467 --> 00:27:14,367 that's very close to it, 526 00:27:14,367 --> 00:27:16,667 the sheer force of the solar winds, so 527 00:27:16,767 --> 00:27:18,567 there's nothing that could have formed right there. 528 00:27:18,567 --> 00:27:19,600 How the heck did you get 529 00:27:19,667 --> 00:27:23,000 a planet that big, that close to a star? 530 00:27:23,100 --> 00:27:26,200 ROWE: Hot Jupiters forced scientists 531 00:27:26,266 --> 00:27:28,567 to consider a radical idea. 532 00:27:28,667 --> 00:27:31,300 We always assumed that planets were 533 00:27:31,367 --> 00:27:33,367 formed where we see them today. 534 00:27:33,467 --> 00:27:35,767 But these hot Jupiters couldn't have been formed there. 535 00:27:35,767 --> 00:27:39,767 They must have migrated in from further out. 536 00:27:39,867 --> 00:27:41,700 WALSH: That made us look at our solar system 537 00:27:41,767 --> 00:27:43,567 through a different lens. 538 00:27:43,567 --> 00:27:47,867 And all of a sudden, we started seeing signs that, oh, maybe -- 539 00:27:47,867 --> 00:27:49,867 yeah, maybe this happened here. 540 00:27:49,967 --> 00:27:53,367 ROWE: One million years after 541 00:27:53,367 --> 00:27:56,700 the birth of the mafia family-like solar system, 542 00:27:56,767 --> 00:27:59,000 many small rocky planets grow in 543 00:27:59,100 --> 00:28:02,367 the inner part of the protoplanetary disk. 544 00:28:02,367 --> 00:28:03,445 Underboss Jupiter makes a move to take control of 545 00:28:03,445 --> 00:28:06,700 Underboss Jupiter makes a move to take control of 546 00:28:06,767 --> 00:28:08,066 the family. 547 00:28:08,066 --> 00:28:12,567 The giant planet's gravity creates spiraling waves in 548 00:28:12,567 --> 00:28:16,467 the protoplanetary disk, which drag on Jupiter, 549 00:28:16,567 --> 00:28:17,767 slowing it down. 550 00:28:22,767 --> 00:28:25,567 So Jupiter slows down just a little bit in its orbit around 551 00:28:25,567 --> 00:28:27,667 the Sun, and as it slows down, 552 00:28:27,667 --> 00:28:32,000 it falls inwards towards the Sun and migrates closer 553 00:28:32,100 --> 00:28:33,445 and closer. 554 00:28:33,445 --> 00:28:33,467 and closer. 555 00:28:33,567 --> 00:28:35,567 ROWE: Jupiter crashes into 556 00:28:35,667 --> 00:28:39,367 the inner solar system -- in its path, 557 00:28:39,467 --> 00:28:41,300 the infant rocky planets. 558 00:28:43,166 --> 00:28:46,700 You can't take something with 300 times the mass of the Earth 559 00:28:46,767 --> 00:28:48,967 and let it roam around the inner solar system 560 00:28:48,967 --> 00:28:51,567 and hope it's not gonna do anything -- Jupiter is like 561 00:28:51,667 --> 00:28:54,467 a monster truck at a stock car rally race, right? 562 00:28:54,467 --> 00:28:56,367 It's just plowing through everything, 563 00:28:56,367 --> 00:28:57,567 just chaos everywhere. 564 00:29:02,400 --> 00:29:03,445 So here we are, forming our lovely young solar system, 565 00:29:03,445 --> 00:29:04,867 So here we are, forming our lovely young solar system, 566 00:29:04,967 --> 00:29:06,500 and there are all kinds of new planets 567 00:29:06,567 --> 00:29:09,567 forming, and they're settling into nice orderly orbits. 568 00:29:09,567 --> 00:29:11,467 And here comes Jupiter, 569 00:29:11,467 --> 00:29:12,767 the big bully on the block. 570 00:29:14,367 --> 00:29:18,800 ROWE: Enforcer Jupiter pushes its smaller siblings around. 571 00:29:18,867 --> 00:29:22,800 Gravitationally, it starts to destabilize the inner planets, 572 00:29:22,867 --> 00:29:25,867 so nice circular orbits start to go all haywire, 573 00:29:26,867 --> 00:29:28,100 and things begin to actually play 574 00:29:28,166 --> 00:29:30,367 pinball in the early solar system. 575 00:29:31,467 --> 00:29:33,445 ROWE: The growing inner planets fly off in all directions. 576 00:29:33,445 --> 00:29:35,867 ROWE: The growing inner planets fly off in all directions. 577 00:29:35,867 --> 00:29:38,000 Some collide violently. 578 00:29:39,000 --> 00:29:40,300 Many die in the melee. 579 00:29:43,767 --> 00:29:46,600 DURDA: This is like solar system demolition derby 580 00:29:46,667 --> 00:29:48,700 in the early days of the formation of the planets, 581 00:29:48,767 --> 00:29:50,300 where things are smashing into each other 582 00:29:50,367 --> 00:29:53,000 and destroying little planets right and left. 583 00:29:55,867 --> 00:29:58,367 ROWE: This cosmic carnage could explain why 584 00:29:58,467 --> 00:30:00,700 we don't have any super-Earths. 585 00:30:06,300 --> 00:30:09,967 Perhaps our solar system once had large, rocky planets, 586 00:30:11,166 --> 00:30:12,767 but debris from the colliding 587 00:30:12,867 --> 00:30:15,367 inner planets slowed down their orbits, 588 00:30:16,867 --> 00:30:21,500 dragging the young super-Earths into the Sun. 589 00:30:21,567 --> 00:30:24,767 These primordial super-Earths get pushed 590 00:30:24,767 --> 00:30:27,000 onto the Sun and destroyed altogether. 591 00:30:32,600 --> 00:30:33,445 It only takes 100,000 years to destroy 592 00:30:33,445 --> 00:30:36,300 It only takes 100,000 years to destroy 593 00:30:36,367 --> 00:30:38,867 the primordial group of super-Earths that 594 00:30:38,867 --> 00:30:41,100 would have formed in the inner solar system. 595 00:30:41,166 --> 00:30:45,266 ROWE: But not everyone agrees with this version of events. 596 00:30:45,266 --> 00:30:49,266 This is a pretty cool idea, but I'm not convinced by it. 597 00:30:49,367 --> 00:30:52,100 We have a lot of ideas of why we are the way we are today. 598 00:30:52,166 --> 00:30:54,500 What we need is more evidence to be able to separate 599 00:30:54,567 --> 00:30:55,600 these ideas out. 600 00:30:57,166 --> 00:30:59,066 ROWE: An alternative theory suggests that 601 00:30:59,066 --> 00:31:02,567 Jupiter stole everyone else's lunch, 602 00:31:02,667 --> 00:31:03,445 starving the inner solar system of food 603 00:31:03,445 --> 00:31:06,467 starving the inner solar system of food 604 00:31:06,567 --> 00:31:10,200 so the planets couldn't grow into super-Earths. 605 00:31:11,767 --> 00:31:14,266 WALSH: Without Jupiter, Earth and Venus and Mars might 606 00:31:14,266 --> 00:31:16,266 have just kept on growing and growing and growing. 607 00:31:16,266 --> 00:31:17,467 We might have ended up with a bunch 608 00:31:17,567 --> 00:31:19,166 of super-Earths in the inner solar system. 609 00:31:20,567 --> 00:31:23,567 ROWE: Mob underboss Jupiter's unprovoked assault 610 00:31:23,667 --> 00:31:27,166 on his smaller siblings in the inner solar system continued. 611 00:31:28,266 --> 00:31:31,767 The attack caused many casualties and nearly put 612 00:31:31,867 --> 00:31:33,445 our planet in an early grave. 613 00:31:33,445 --> 00:31:34,667 our planet in an early grave. 614 00:31:45,500 --> 00:31:49,266 ROWE: For thousands of years, people have looked up at 615 00:31:49,266 --> 00:31:54,066 the sky and seen the planets orbiting the Sun in harmony. 616 00:31:54,066 --> 00:31:57,367 THALLER: They've seen all of this wonderful order. 617 00:31:57,367 --> 00:31:59,000 And that's what we thought. 618 00:31:59,100 --> 00:32:01,200 Everything formed together, the Sun, 619 00:32:01,266 --> 00:32:04,200 the planets, almost like this beautiful clockwork set up in 620 00:32:04,266 --> 00:32:05,400 the heavens. 621 00:32:05,467 --> 00:32:07,662 Now we know that actually that was far from the truth. 622 00:32:07,662 --> 00:32:08,667 Now we know that actually that was far from the truth. 623 00:32:13,367 --> 00:32:15,467 ROWE: Around two million years after the birth 624 00:32:15,467 --> 00:32:18,667 of the Godfather, the Sun, the underboss, 625 00:32:18,767 --> 00:32:22,200 Jupiter, makes a power grab and crashes 626 00:32:22,266 --> 00:32:23,700 into the inner solar system. 627 00:32:33,266 --> 00:32:35,567 PLAIT: If Jupiter had continued its journey toward the Sun, 628 00:32:35,667 --> 00:32:37,662 it would have ejected a lot of the stuff that was left. 629 00:32:37,662 --> 00:32:38,166 it would have ejected a lot of the stuff that was left. 630 00:32:38,166 --> 00:32:40,166 There would be no inner rocky planets. 631 00:32:40,266 --> 00:32:41,600 It would just be Jupiter. 632 00:32:43,000 --> 00:32:46,667 ROWE: Fortunately, we avoid complete slaughter. 633 00:32:46,767 --> 00:32:50,867 Something stops Jupiter's murderous attack. 634 00:32:50,867 --> 00:32:53,467 Lucky for us, we had an ace in the hole. 635 00:32:53,467 --> 00:32:55,767 We had a friend, and that friend is so 636 00:32:55,767 --> 00:32:59,100 beautiful in the sky today, and we call that friend Saturn. 637 00:33:03,000 --> 00:33:07,000 Saturn is also migrating inward toward the Sun, 638 00:33:07,100 --> 00:33:07,662 but the rate it's moving in depends on the mass of 639 00:33:07,662 --> 00:33:10,367 but the rate it's moving in depends on the mass of 640 00:33:10,367 --> 00:33:12,867 the planet -- Saturn is less massive than Jupiter, 641 00:33:12,867 --> 00:33:14,667 so it's moving in more rapidly. 642 00:33:16,100 --> 00:33:19,867 ROWE: Peace-making consigliere, Saturn, catches up 643 00:33:19,967 --> 00:33:22,700 with Jupiter and brokers a deal. 644 00:33:22,767 --> 00:33:25,266 When they reach each other, they don't collide. 645 00:33:25,367 --> 00:33:28,900 They get stuck in a complicated orbital dance with each other. 646 00:33:29,000 --> 00:33:32,567 ROWE: Their cosmic tango strips out gas from the disc, 647 00:33:32,567 --> 00:33:37,662 clearing a path for Saturn and Jupiter to move back outwards. 648 00:33:37,662 --> 00:33:38,000 clearing a path for Saturn and Jupiter to move back outwards. 649 00:33:38,100 --> 00:33:39,767 So this can actually reverse 650 00:33:39,767 --> 00:33:42,100 their migration, and all of a sudden, we have 651 00:33:42,166 --> 00:33:44,300 the two planets moving outward in the solar system. 652 00:33:44,367 --> 00:33:47,100 So it's like Saturn has a trailer hitch, and it's towing 653 00:33:47,166 --> 00:33:49,266 Jupiter back to the outer solar system, 654 00:33:49,266 --> 00:33:50,266 where we find them today. 655 00:33:53,500 --> 00:33:56,867 PLAIT: Saturn saved the earth, basically. 656 00:33:56,867 --> 00:33:59,367 If it hadn't have been there to pull Jupiter back out from 657 00:33:59,367 --> 00:34:00,567 the inner solar system, 658 00:34:00,600 --> 00:34:02,900 Jupiter would have thrown all the inner planets out. 659 00:34:03,000 --> 00:34:07,266 So no Mercury, no Venus, no Mars, no Earth. 660 00:34:07,266 --> 00:34:07,662 ROWE: Three million years after the birth of the Sun, 661 00:34:07,662 --> 00:34:11,066 ROWE: Three million years after the birth of the Sun, 662 00:34:11,066 --> 00:34:14,200 around 20 baby planets survive Jupiter's 663 00:34:14,266 --> 00:34:16,800 ransacking of the inner solar system, 664 00:34:16,867 --> 00:34:19,367 but the carnage isn't over. 665 00:34:21,867 --> 00:34:24,400 WALSH: The inner solar system's kind of in turmoil. 666 00:34:24,467 --> 00:34:26,967 The gravitational interaction from Jupiter was severe. 667 00:34:28,667 --> 00:34:31,066 Everything is excited, orbits are out of control 668 00:34:31,066 --> 00:34:33,266 and crazy, and things are interacting and having big, 669 00:34:33,367 --> 00:34:34,567 violent collisions. 670 00:34:38,100 --> 00:34:41,166 ROWE: The inner solar system is like a congested highway. 671 00:34:44,000 --> 00:34:47,600 Planets cross lanes, collisions are frequent. 672 00:34:50,600 --> 00:34:52,567 As the bloodshed continues, 673 00:34:52,667 --> 00:34:56,567 the young Earth wanders into the path of a smaller planet. 674 00:34:58,100 --> 00:35:00,066 PLAIT: There's a theory, and it's a pretty good one, 675 00:35:00,066 --> 00:35:02,000 that the Earth, a long time ago, 676 00:35:02,100 --> 00:35:04,767 was hit by another relatively big planet, 677 00:35:04,867 --> 00:35:06,000 and we call that planet Theia. 678 00:35:08,900 --> 00:35:12,767 ROWE: Theia hit Earth at over 25,000 miles an hour. 679 00:35:14,800 --> 00:35:16,700 The impact destroyed Theia 680 00:35:18,100 --> 00:35:19,467 and nearly wiped out Earth. 681 00:35:21,100 --> 00:35:23,800 OLUSEYI: When Earth was struck by Theia, 682 00:35:23,867 --> 00:35:27,367 it was unlike any event before or since. 683 00:35:27,367 --> 00:35:29,367 We think about the event that wiped 684 00:35:29,367 --> 00:35:31,300 out the dinosaurs as a huge collision. 685 00:35:31,367 --> 00:35:34,100 Oh, this one dwarfs that one. 686 00:35:37,667 --> 00:35:40,867 The Earth was completely turned inside out. 687 00:35:40,967 --> 00:35:45,800 The surface was new, it was molten, and it was raining fire, 688 00:35:45,867 --> 00:35:49,867 literally -- lava rock was raining down from the heavens. 689 00:35:53,467 --> 00:35:55,767 ROWE: Earth was badly wounded but survived. 690 00:36:00,066 --> 00:36:03,066 Material from Theia mixed with Earth rock, 691 00:36:03,066 --> 00:36:07,100 building a bigger planet and a new companion. 692 00:36:08,500 --> 00:36:10,000 This collision was so huge, 693 00:36:10,100 --> 00:36:12,266 it blasted off a tremendous amount of material off 694 00:36:12,266 --> 00:36:15,400 the Earth's surface, and this coalesced to form the Moon. 695 00:36:19,867 --> 00:36:22,066 ROWE: That theory may now become fact. 696 00:36:24,266 --> 00:36:26,300 We found two massive chunks of 697 00:36:26,367 --> 00:36:29,166 rock buried deep beneath Earth's surface. 698 00:36:30,367 --> 00:36:33,767 These massive lumps of rock have a different density, 699 00:36:33,767 --> 00:36:35,400 a different composition, 700 00:36:35,467 --> 00:36:37,367 than the rest of the mantle rock around them. 701 00:36:38,667 --> 00:36:41,967 ROWE: A new study in 2021 suggests 702 00:36:41,967 --> 00:36:43,367 they don't come from Earth. 703 00:36:46,066 --> 00:36:47,867 It could be that these dense blobs of 704 00:36:47,867 --> 00:36:50,700 material deep in our mantle are remnants of Theia. 705 00:36:53,367 --> 00:36:54,900 ROWE: Throughout the inner solar system 706 00:36:55,000 --> 00:36:57,467 protoplanet hit protoplanet. 707 00:37:00,600 --> 00:37:04,400 Some high speed crashes ended in catastrophe. 708 00:37:05,900 --> 00:37:07,662 There was drama, a lot of drama. 709 00:37:07,662 --> 00:37:08,400 There was drama, a lot of drama. 710 00:37:08,467 --> 00:37:10,266 It's as much a story of destruction 711 00:37:10,266 --> 00:37:11,600 as it is of creation. 712 00:37:11,667 --> 00:37:14,100 There are a lot of planets that could have made it 713 00:37:14,166 --> 00:37:15,400 but didn't. 714 00:37:15,467 --> 00:37:17,967 And we just happened to be one of the lucky ones that did. 715 00:37:20,300 --> 00:37:24,700 Slower impacts glued the colliding worlds together, 716 00:37:24,767 --> 00:37:27,700 building hybrid planets from the wreckage. 717 00:37:30,767 --> 00:37:34,200 The four terrestrial planets -- Mercury, Venus, 718 00:37:34,266 --> 00:37:37,300 Earth, and Mars -- emerged from the ashes 719 00:37:37,367 --> 00:37:37,662 of the 20 protoplanets and joined the mob family. 720 00:37:37,662 --> 00:37:41,000 of the 20 protoplanets and joined the mob family. 721 00:37:41,066 --> 00:37:43,300 The planets are connected. 722 00:37:43,367 --> 00:37:45,600 You probably have some material in your body 723 00:37:45,667 --> 00:37:47,166 from pretty much every world 724 00:37:47,266 --> 00:37:48,667 that ever existed in the solar system. 725 00:37:48,667 --> 00:37:50,800 Everything mixed around. 726 00:37:50,867 --> 00:37:53,367 That mixing made Earth 727 00:37:53,467 --> 00:37:56,266 larger and better equipped to survive. 728 00:37:57,600 --> 00:37:59,967 The bloodbath also left its mark 729 00:37:59,967 --> 00:38:01,600 on the other surviving planets. 730 00:38:03,300 --> 00:38:04,867 RADEBAUGH: What's strange about Venus is that 731 00:38:04,867 --> 00:38:07,467 it actually spins in the opposite direction. 732 00:38:07,467 --> 00:38:07,662 All the other planets spin sort of with -- 733 00:38:07,662 --> 00:38:09,467 All the other planets spin sort of with -- 734 00:38:09,467 --> 00:38:12,400 with a righthand spin, from the west to the east, 735 00:38:12,467 --> 00:38:15,667 and Venus spins from the east to the west. 736 00:38:15,767 --> 00:38:18,867 LANZA: And also Venus's spin is very slow. 737 00:38:18,867 --> 00:38:22,400 It's 243 times slower than that of Earth's. 738 00:38:22,467 --> 00:38:26,000 You can imagine a big protoplanetary embryo, 739 00:38:26,066 --> 00:38:27,900 almost the size of Venus itself, smashing 740 00:38:28,000 --> 00:38:29,467 almost head-on to Venus, 741 00:38:30,767 --> 00:38:34,600 just in the right angle to stop the rotation, 742 00:38:34,667 --> 00:38:37,662 slow it down, even actually reverse it slightly. 743 00:38:37,662 --> 00:38:37,900 slow it down, even actually reverse it slightly. 744 00:38:38,000 --> 00:38:41,000 And now, it's still spinning like that today. 745 00:38:43,667 --> 00:38:46,900 ROWE: Mercury carries horrific scars from Jupiter's 746 00:38:47,000 --> 00:38:49,567 assault on the inner solar system. 747 00:38:51,066 --> 00:38:53,867 THALLER: Mercury has always seemed to be a bit of 748 00:38:53,967 --> 00:38:55,900 an odd planet, because it really is sort of a cannonball. 749 00:38:56,000 --> 00:38:58,800 It has a giant core compared to the rest of the planet. 750 00:38:58,867 --> 00:39:01,100 So the question is, how do you get 751 00:39:01,166 --> 00:39:03,700 this large core, but very little rock, 752 00:39:03,767 --> 00:39:05,367 very little mantle and crust around it? 753 00:39:06,600 --> 00:39:07,662 ROWE: We think Mercury hit another planet, hard. 754 00:39:07,662 --> 00:39:10,166 ROWE: We think Mercury hit another planet, hard. 755 00:39:11,300 --> 00:39:15,467 DARTNELL: The outer layers of Mercury, its rocky mantle, 756 00:39:15,567 --> 00:39:18,166 was blasted off, leaving behind 757 00:39:18,166 --> 00:39:22,800 just the dense iron cannonball core of this planet, 758 00:39:22,867 --> 00:39:26,567 which ricocheted off and then settled in Mercury's 759 00:39:26,667 --> 00:39:28,800 current orbit, close to the Sun. 760 00:39:33,367 --> 00:39:35,767 ROWE: That leaves one last rocky planet 761 00:39:35,767 --> 00:39:37,662 member of the mafia family -- Mars. 762 00:39:37,662 --> 00:39:39,767 member of the mafia family -- Mars. 763 00:39:42,567 --> 00:39:45,567 It's older and much smaller than its neighbors, 764 00:39:45,667 --> 00:39:46,900 Venus and Earth. 765 00:39:49,467 --> 00:39:52,066 One way to interpret Mars in this scenario is that 766 00:39:52,066 --> 00:39:53,567 Mars was one of those original 767 00:39:53,667 --> 00:39:56,166 20 or 30 planetary embryos, or protoplanets, 768 00:39:56,166 --> 00:39:58,400 and it just survived. 769 00:39:58,467 --> 00:40:00,867 It avoided this big violent end game 770 00:40:00,867 --> 00:40:03,200 of the giant impact stage of planet formation. 771 00:40:04,367 --> 00:40:06,767 ROWE: Mars sat on the sidelines, 772 00:40:06,767 --> 00:40:07,662 far enough away from the action to 773 00:40:07,662 --> 00:40:08,400 far enough away from the action to 774 00:40:08,467 --> 00:40:10,767 be safe from physical harm, 775 00:40:10,867 --> 00:40:15,000 but enforcer Jupiter's violent raid on the inner solar system 776 00:40:15,066 --> 00:40:20,000 still prevented Mars from reaching its full potential. 777 00:40:20,066 --> 00:40:22,700 One big effect of Jupiter's incursion 778 00:40:22,767 --> 00:40:23,700 into the inner solar system is 779 00:40:23,767 --> 00:40:26,000 to blast away a bunch of material, 780 00:40:26,066 --> 00:40:28,266 around where we find Mars today. 781 00:40:28,367 --> 00:40:30,700 THALLER: In some ways, Jupiter kinda ate Mars's lunch. 782 00:40:30,767 --> 00:40:32,667 So Mars just didn't have as much stuff to 783 00:40:32,667 --> 00:40:35,100 work with, and it never became a very big planet. 784 00:40:36,200 --> 00:40:37,662 ROWE: After 60 million years of family feuding, 785 00:40:37,662 --> 00:40:39,667 ROWE: After 60 million years of family feuding, 786 00:40:39,767 --> 00:40:43,500 the battle of the planets is finally over. 787 00:40:43,567 --> 00:40:46,200 OLUSEYI: Out of all the mayhem and chaos of the early 788 00:40:46,266 --> 00:40:49,467 solar system, four terrestrial planets remained. 789 00:40:49,467 --> 00:40:52,100 One of them was Earth. 790 00:40:52,166 --> 00:40:54,467 THALLER: Given everything we've now learned about how violent 791 00:40:54,567 --> 00:40:57,467 it was, we understand just how vulnerable we've been 792 00:40:57,467 --> 00:41:00,166 all the way along -- planets colliding, planets 793 00:41:00,266 --> 00:41:03,567 even changing places -- in some ways now, it's amazing 794 00:41:03,567 --> 00:41:06,000 the Earth even survived. 795 00:41:06,066 --> 00:41:07,662 ROWE: Our planet emerged as one of the winners from underboss 796 00:41:07,662 --> 00:41:09,367 ROWE: Our planet emerged as one of the winners from underboss 797 00:41:09,367 --> 00:41:12,667 Jupiter's homicidal assault on the inner planets. 798 00:41:12,767 --> 00:41:16,767 But Jupiter's return to the outer solar system soon 799 00:41:16,867 --> 00:41:18,467 triggered more mayhem, 800 00:41:18,567 --> 00:41:21,567 mayhem that would threaten Earth with the biggest 801 00:41:21,667 --> 00:41:24,266 bombardment in its history. 802 00:41:38,300 --> 00:41:41,767 ROWE: The mafia family we call the solar system has 803 00:41:41,767 --> 00:41:45,500 survived underboss Jupiter's attack on the inner planets 804 00:41:46,700 --> 00:41:50,500 but faces more disruption from its enforcer 805 00:41:50,567 --> 00:41:52,500 when the giant gas planet heads 806 00:41:52,567 --> 00:41:56,100 out towards where Uranus and Neptune grow, 807 00:41:56,166 --> 00:41:58,853 a journey that may help explain several mysteries about 808 00:41:58,853 --> 00:41:59,166 a journey that may help explain several mysteries about 809 00:41:59,166 --> 00:42:00,300 the solar system, 810 00:42:00,367 --> 00:42:03,467 including the size of the ice giants. 811 00:42:04,667 --> 00:42:06,867 PLAIT: The biggest problem with the outer solar system is 812 00:42:06,967 --> 00:42:08,266 literally bigness. 813 00:42:08,367 --> 00:42:11,867 Uranus and Neptune are too big for where they are. 814 00:42:11,967 --> 00:42:14,367 ROWE: The problem is the availability of 815 00:42:14,367 --> 00:42:16,000 building materials. 816 00:42:16,100 --> 00:42:17,900 This far out from the Sun, 817 00:42:18,000 --> 00:42:21,700 there wasn't enough gas and dust in the protoplanetary disk 818 00:42:21,767 --> 00:42:24,867 to construct such large planets. 819 00:42:24,967 --> 00:42:28,853 One way of solving the riddle of how Uranus and Neptune 820 00:42:28,853 --> 00:42:28,867 One way of solving the riddle of how Uranus and Neptune 821 00:42:28,867 --> 00:42:32,100 are so big is that they didn't form where they are now. 822 00:42:32,166 --> 00:42:33,200 So we think that they formed 823 00:42:33,266 --> 00:42:36,066 further in and then maybe moved out. 824 00:42:37,600 --> 00:42:39,767 ROWE: This is what we think happened. 825 00:42:40,800 --> 00:42:43,767 Five million years after the birth of the Sun, 826 00:42:43,867 --> 00:42:47,767 Jupiter and Saturn reached the same region of space as 827 00:42:47,867 --> 00:42:49,767 Uranus and Neptune. 828 00:42:49,767 --> 00:42:54,600 The four quarreling children call a truce and orbit together. 829 00:42:54,667 --> 00:42:57,600 OLUSEYI: Orbits are on the razor's edge of stability 830 00:42:57,667 --> 00:42:58,853 as it is, and so one thing that helped to stabilize 831 00:42:58,853 --> 00:43:00,667 as it is, and so one thing that helped to stabilize 832 00:43:00,767 --> 00:43:02,667 our solar system in the early days 833 00:43:02,667 --> 00:43:06,500 was that it was in this cloud of gas and dust 834 00:43:06,567 --> 00:43:09,500 that was this protoplanetary disk. 835 00:43:09,567 --> 00:43:12,367 ROWE: Gas in the protoplanetary disk can 836 00:43:12,467 --> 00:43:14,867 slow down planets so they migrate. 837 00:43:14,867 --> 00:43:19,300 But it can also stabilize their orbits. 838 00:43:20,567 --> 00:43:23,400 Like sand on the side of a racing track 839 00:43:23,467 --> 00:43:26,100 that's there to slow down the cars and help them get 840 00:43:26,166 --> 00:43:27,300 back on track, 841 00:43:27,367 --> 00:43:28,853 the gas allows the planets to not veer off too much 842 00:43:28,853 --> 00:43:31,900 the gas allows the planets to not veer off too much 843 00:43:32,000 --> 00:43:35,867 away from their stable compact configuration. 844 00:43:37,200 --> 00:43:40,700 ROWE: The ceasefire between the gas planets is short-lived. 845 00:43:43,800 --> 00:43:48,166 Once the Godfather Sun blows away the last of the gas, 846 00:43:48,166 --> 00:43:52,667 the largest Mafioso children set off on another crime spree. 847 00:43:54,467 --> 00:43:56,400 So when the gas goes away, 848 00:43:56,467 --> 00:43:58,767 you no longer have this dampening effect on the orbits 849 00:43:58,767 --> 00:43:58,853 of the giant planets, and they can start 850 00:43:58,853 --> 00:44:01,667 of the giant planets, and they can start 851 00:44:01,767 --> 00:44:03,066 interacting with each other. 852 00:44:03,066 --> 00:44:06,066 And Jupiter is free to be a bully again, only this time, 853 00:44:06,066 --> 00:44:07,600 he's got a big sidekick -- Saturn. 854 00:44:09,166 --> 00:44:12,400 ROWE: Former peacekeeper, Saturn, joins forces 855 00:44:12,467 --> 00:44:14,600 with Jupiter, and they start 856 00:44:14,667 --> 00:44:16,367 messing with Uranus and Neptune. 857 00:44:18,166 --> 00:44:21,367 So the two largest kids team up together and start pushing 858 00:44:21,467 --> 00:44:23,000 everyone else around. 859 00:44:23,066 --> 00:44:25,600 When you put really big planets that are really massive, 860 00:44:25,667 --> 00:44:26,767 really close to each other, 861 00:44:26,867 --> 00:44:28,567 over time, they start to push on each 862 00:44:28,567 --> 00:44:28,853 other's orbits, and their orbits start to get excited. 863 00:44:28,853 --> 00:44:30,567 other's orbits, and their orbits start to get excited. 864 00:44:30,667 --> 00:44:32,867 The whole thing starts to unravel 865 00:44:32,967 --> 00:44:35,867 and eventually culminates in a violent 866 00:44:35,867 --> 00:44:37,767 and beautiful instability. 867 00:44:41,900 --> 00:44:44,000 ROWE: Gravitational shoves from Jupiter 868 00:44:44,100 --> 00:44:47,100 and Saturn pushed the ice giants outwards. 869 00:44:50,200 --> 00:44:53,467 Uranus still bears the scars from this power move. 870 00:44:58,567 --> 00:44:58,853 For one thing, it's orbiting the Sun on its side. 871 00:44:58,853 --> 00:45:02,000 For one thing, it's orbiting the Sun on its side. 872 00:45:02,100 --> 00:45:03,667 Instead of having its rotation axis 873 00:45:03,667 --> 00:45:04,967 sort of straight up and down, 874 00:45:04,967 --> 00:45:08,467 more or less, it's tipped way over, so its pole is 875 00:45:08,467 --> 00:45:11,266 pointing more or less towards the Sun instead of up and down. 876 00:45:11,367 --> 00:45:12,667 That's really weird. 877 00:45:14,166 --> 00:45:19,000 ROWE: Recent studies suggest a giant impact caused 878 00:45:19,066 --> 00:45:22,300 Uranus's strange orientation. 879 00:45:23,367 --> 00:45:25,066 Over four billion years ago, 880 00:45:25,066 --> 00:45:28,266 a large icy object hits the ice giant 881 00:45:28,367 --> 00:45:28,853 with a glancing blow. 882 00:45:28,853 --> 00:45:29,700 with a glancing blow. 883 00:45:31,667 --> 00:45:34,767 The planet starts to tip over. 884 00:45:34,767 --> 00:45:37,500 Then, the attacker comes around 885 00:45:37,567 --> 00:45:40,166 and smashes into Uranus a second time. 886 00:45:43,800 --> 00:45:48,767 This 1-2 punch knocks the ice giant onto its side. 887 00:45:53,200 --> 00:45:54,367 A clue to the cause of 888 00:45:54,467 --> 00:45:58,166 the collision comes from Neptune's moon, Triton. 889 00:45:59,767 --> 00:46:02,200 RADEBAUGH: What's odd about Triton is that it orbits 890 00:46:02,266 --> 00:46:04,000 the wrong way around Neptune, and that's 891 00:46:04,100 --> 00:46:05,600 the wrong way for the whole solar system, 892 00:46:05,667 --> 00:46:08,100 so everything is going in this direction, Triton is going 893 00:46:08,166 --> 00:46:09,467 the other way. 894 00:46:09,467 --> 00:46:11,400 The other thing is that Triton is made of slightly different 895 00:46:11,467 --> 00:46:14,100 things than it should be at the orbit of Neptune. 896 00:46:14,166 --> 00:46:17,600 Its color, its density, are just a little bit off. 897 00:46:17,667 --> 00:46:20,100 What we think that means is that 898 00:46:20,166 --> 00:46:22,767 it probably didn't form there. 899 00:46:25,867 --> 00:46:28,100 ROWE: We find pointers to Triton's origin 900 00:46:28,166 --> 00:46:28,853 on the dwarf planet Pluto. 901 00:46:28,853 --> 00:46:30,367 on the dwarf planet Pluto. 902 00:46:34,867 --> 00:46:37,100 Pluto sits in the Kuiper belt, 903 00:46:37,166 --> 00:46:42,000 a band of millions of icy objects beyond Neptune. 904 00:46:45,266 --> 00:46:46,967 RADEBAUGH: When we looked at Triton and compared it 905 00:46:46,967 --> 00:46:49,166 with Pluto from telescopes from Earth, 906 00:46:49,166 --> 00:46:52,266 we recognize these two are very similar to each other. 907 00:46:52,367 --> 00:46:54,166 On Triton, there's nitrogen ice, 908 00:46:54,266 --> 00:46:56,767 carbon monoxide ice, there's carbon dioxide ice. 909 00:46:56,767 --> 00:46:58,853 These are the same types of ices that we see on Pluto. 910 00:46:58,853 --> 00:46:59,667 These are the same types of ices that we see on Pluto. 911 00:47:00,800 --> 00:47:04,667 ROWE: This similarity in chemical composition suggests 912 00:47:04,667 --> 00:47:08,266 that Pluto and Triton formed in the same place, 913 00:47:10,100 --> 00:47:12,767 an ancient band of icy objects 914 00:47:12,767 --> 00:47:16,066 called the trans-Neptunian belt. 915 00:47:18,867 --> 00:47:21,967 When the giant planet orbits go berserk, Uranus and Neptune 916 00:47:21,967 --> 00:47:24,767 get tossed into this trans-Neptunian disk. 917 00:47:24,867 --> 00:47:28,853 it's like a big bowling bowl coming in and knocking off 918 00:47:28,853 --> 00:47:29,266 it's like a big bowling bowl coming in and knocking off 919 00:47:29,367 --> 00:47:31,900 bowling pins left and right. 920 00:47:34,767 --> 00:47:36,400 THALLER: Chaos ensues, 921 00:47:36,467 --> 00:47:38,600 and as the two outer planets get pushed through 922 00:47:38,667 --> 00:47:39,867 all of this stuff, 923 00:47:39,867 --> 00:47:42,300 throwing things left, right, and center, all kinds of 924 00:47:42,367 --> 00:47:44,066 collisions are inevitable. 925 00:47:44,066 --> 00:47:47,467 ROWE: One of these collisions knocks Uranus over. 926 00:47:54,166 --> 00:47:57,266 Another small planet heads towards Neptune. 927 00:47:59,500 --> 00:48:04,867 The ice giant grabs it, creating the moon, Triton. 928 00:48:06,100 --> 00:48:08,500 The other trans-Neptunian objects 929 00:48:08,567 --> 00:48:12,266 scatter outwards, forming the Kuiper belt. 930 00:48:15,367 --> 00:48:18,567 Tremors from this planetary bowling match spread far 931 00:48:18,667 --> 00:48:19,667 and wide, 932 00:48:19,667 --> 00:48:22,867 sparking a cataclysmic onslaught of the inner 933 00:48:22,967 --> 00:48:25,700 solar system billions of miles away. 934 00:48:27,467 --> 00:48:28,467 THALLER: The Kuiper belt -- 935 00:48:28,467 --> 00:48:28,853 this very, very distant collection of small, 936 00:48:28,853 --> 00:48:31,100 this very, very distant collection of small, 937 00:48:31,166 --> 00:48:32,867 rocky bodies in the outer solar system -- 938 00:48:32,967 --> 00:48:35,266 you would think that we have no connection to that at all. 939 00:48:35,367 --> 00:48:38,000 But instead, it may be responsible for helping life 940 00:48:38,100 --> 00:48:39,100 get started on Earth. 941 00:48:50,867 --> 00:48:53,066 ROWE: 4.6 billion years ago, 942 00:48:54,066 --> 00:48:58,567 a cloud of gas collapses in a quiet suburb of the Milky Way. 943 00:49:00,066 --> 00:49:03,767 It's the birth of our mobster family solar system. 944 00:49:03,767 --> 00:49:08,266 The Godfather, the Sun, ignites and takes control. 945 00:49:08,266 --> 00:49:12,100 His children, the planets, grow from the disk of gas 946 00:49:12,166 --> 00:49:13,020 and dust left over from the birth of the star. 947 00:49:13,020 --> 00:49:16,066 and dust left over from the birth of the star. 948 00:49:17,500 --> 00:49:21,066 Gas planets form in the cold outer suburbs, 949 00:49:21,066 --> 00:49:24,266 rocky ones in the warm inner real estate. 950 00:49:25,266 --> 00:49:28,000 But the Sun's fearsome nature 951 00:49:28,066 --> 00:49:30,467 threatens the young Earth. 952 00:49:30,567 --> 00:49:34,200 The early Earth, right after its formation, 953 00:49:34,266 --> 00:49:36,367 was not a great place to be alive. 954 00:49:36,367 --> 00:49:37,867 In fact, it would not have been possible 955 00:49:37,967 --> 00:49:39,967 to be alive, because it was so hot. 956 00:49:39,967 --> 00:49:42,767 It had no atmosphere. It had been blown away. 957 00:49:42,767 --> 00:49:43,020 It wasn't even fully solid, and it had no water to speak of. 958 00:49:43,020 --> 00:49:47,400 It wasn't even fully solid, and it had no water to speak of. 959 00:49:48,567 --> 00:49:50,867 The Earth is too close to the Sun to have 960 00:49:50,967 --> 00:49:53,467 formed with the amount of water that we see today. 961 00:49:53,567 --> 00:49:55,800 The protoplanetary disk was just too hot for water 962 00:49:55,867 --> 00:49:56,867 to condense, 963 00:49:58,000 --> 00:50:00,000 and water vapor would have been blown away by 964 00:50:00,100 --> 00:50:02,400 the stellar wind -- for the same reason, 965 00:50:02,467 --> 00:50:06,100 it was also lacking in carbon and volatile organic materials. 966 00:50:07,266 --> 00:50:09,367 DURDA: This raises a big mystery -- where did all that 967 00:50:09,367 --> 00:50:11,066 material ultimately come from 968 00:50:11,066 --> 00:50:13,020 that we now obviously have in abundance on planet Earth? 969 00:50:13,020 --> 00:50:14,600 that we now obviously have in abundance on planet Earth? 970 00:50:18,967 --> 00:50:22,500 ROWE: NASA's Dawn mission to the dwarf planet, Ceres, 971 00:50:22,567 --> 00:50:24,867 provided a clue. 972 00:50:24,867 --> 00:50:28,200 Ceres sits in the asteroid belt, 973 00:50:28,266 --> 00:50:31,967 a band of rocky debris left over from Jupiter's attack on 974 00:50:31,967 --> 00:50:33,066 the inner planets. 975 00:50:34,166 --> 00:50:36,100 The Dawn mission showed us that 976 00:50:36,166 --> 00:50:39,100 Ceres is actually a really wet world. 977 00:50:39,166 --> 00:50:40,967 We thought it was just rock, 978 00:50:40,967 --> 00:50:43,020 but instead, Ceres is rich in water, ammonia, and carbon. 979 00:50:43,020 --> 00:50:46,200 but instead, Ceres is rich in water, ammonia, and carbon. 980 00:50:50,367 --> 00:50:53,100 ROWE: These chemicals are essential for life. 981 00:50:53,166 --> 00:50:57,100 Analysis of other asteroids 982 00:50:57,166 --> 00:51:01,000 found lots of this volatile material. 983 00:51:01,100 --> 00:51:04,600 This is surprising, because this close in, 984 00:51:04,667 --> 00:51:07,300 the Sun should have vaporized them. 985 00:51:09,066 --> 00:51:11,266 They could not have formed in the asteroid belt, because 986 00:51:11,266 --> 00:51:13,020 temperatures were way too high for those materials -- 987 00:51:13,020 --> 00:51:13,767 temperatures were way too high for those materials -- 988 00:51:13,767 --> 00:51:16,100 water, ammonia -- to be able to condense. 989 00:51:16,166 --> 00:51:19,266 They must have formed in the outer solar system and then 990 00:51:19,367 --> 00:51:22,166 been transported to the inner solar system. 991 00:51:24,800 --> 00:51:28,467 ROWE: A 2019 study discovered evidence of a storm of 992 00:51:28,567 --> 00:51:34,567 icy objects raining inwards around 4.48 billion years ago. 993 00:51:34,667 --> 00:51:37,200 At the same time, the giant gas 994 00:51:37,266 --> 00:51:40,400 planets were tearing through the outer solar system. 995 00:51:41,567 --> 00:51:43,020 As Jupiter and Saturn, Uranus and Neptune, 996 00:51:43,020 --> 00:51:44,567 As Jupiter and Saturn, Uranus and Neptune, 997 00:51:44,667 --> 00:51:47,266 are migrating back outwards in the solar system, 998 00:51:47,367 --> 00:51:51,166 they're excavating a whole slew of icy planetesimals, 999 00:51:51,166 --> 00:51:54,200 like a like a snowplow bursting through a snowdrift, 1000 00:51:54,266 --> 00:51:56,400 scattering these things all through the solar system. 1001 00:51:59,667 --> 00:52:01,600 The outer planets hurl millions of 1002 00:52:01,667 --> 00:52:06,300 icy objects in towards their Don, the Sun. 1003 00:52:07,967 --> 00:52:13,000 Some, like Ceres, stop in the asteroid belt. 1004 00:52:15,066 --> 00:52:18,967 Others continue and smash into the inner planets, 1005 00:52:22,100 --> 00:52:23,400 including Earth. 1006 00:52:25,967 --> 00:52:30,600 We are being rained down on by giant asteroids, comets. 1007 00:52:30,667 --> 00:52:33,100 The entire surface of the Earth is molten again. 1008 00:52:33,166 --> 00:52:35,100 I mean, it is a rain of the largest 1009 00:52:35,166 --> 00:52:38,767 objects you can imagine onto the surface of the Earth. 1010 00:52:38,767 --> 00:52:41,100 Everything just would have been completely smashed 1011 00:52:41,166 --> 00:52:42,266 to pieces. 1012 00:52:42,367 --> 00:52:43,020 Imagine something like the dinosaur-killing impact 1013 00:52:43,020 --> 00:52:45,300 Imagine something like the dinosaur-killing impact 1014 00:52:45,367 --> 00:52:46,767 happening once a month. 1015 00:52:48,100 --> 00:52:51,567 ROWE: The onslaught lasts for 30 million years. 1016 00:52:54,567 --> 00:52:56,867 It pulverizes the Earth's surface 1017 00:52:59,266 --> 00:53:02,000 but brings fresh chemicals to replace 1018 00:53:02,100 --> 00:53:04,500 material blasted away by the Sun. 1019 00:53:06,266 --> 00:53:09,066 All of these asteroids and comets raining down on Earth 1020 00:53:09,066 --> 00:53:11,667 of course are causing massive amounts of destruction 1021 00:53:11,767 --> 00:53:12,767 but they're bringing 1022 00:53:12,767 --> 00:53:13,020 the building blocks of life, as well. 1023 00:53:13,020 --> 00:53:14,667 the building blocks of life, as well. 1024 00:53:14,767 --> 00:53:17,667 The carbon-based molecules that make us up, the water that 1025 00:53:17,767 --> 00:53:19,567 every bit of life on Earth needs, 1026 00:53:19,667 --> 00:53:22,166 all of the conditions necessary for life 1027 00:53:22,266 --> 00:53:24,367 were brought by the bombardment. 1028 00:53:24,467 --> 00:53:28,567 If that chaotic bombardment hadn't happened, it's just 1029 00:53:28,667 --> 00:53:31,100 possible that we wouldn't be here today. 1030 00:53:31,166 --> 00:53:34,567 ROWE: Even though some of our mob family now live in 1031 00:53:34,567 --> 00:53:36,500 the outer reaches of the solar system, 1032 00:53:36,567 --> 00:53:38,467 the family ties to the planets 1033 00:53:38,467 --> 00:53:41,600 in the inner regions are still strong. 1034 00:53:41,667 --> 00:53:43,020 HOWETT: The distances between all of 1035 00:53:43,020 --> 00:53:44,000 HOWETT: The distances between all of 1036 00:53:44,100 --> 00:53:46,367 the planets in our solar system are large. 1037 00:53:46,467 --> 00:53:47,867 You get a sense of that 1038 00:53:47,867 --> 00:53:50,000 if you go into the night sky, and Jupiter and Saturn 1039 00:53:50,100 --> 00:53:51,300 are pinpricks of light, 1040 00:53:51,367 --> 00:53:54,500 but really, they're all interconnected in a very 1041 00:53:54,567 --> 00:53:56,400 complex way -- gravity has this 1042 00:53:56,467 --> 00:54:00,867 huge effect and can go over long distances. 1043 00:54:02,100 --> 00:54:04,734 The solar system has this huge, violent past 1044 00:54:04,734 --> 00:54:07,734 as these giants have moved and interacted. 1045 00:54:08,967 --> 00:54:11,567 It's really remarkable how interconnected 1046 00:54:11,567 --> 00:54:13,020 all these planetary bodies really are, 1047 00:54:13,020 --> 00:54:14,166 all these planetary bodies really are, 1048 00:54:14,266 --> 00:54:16,367 even though we think of them as very separate. 1049 00:54:19,467 --> 00:54:21,734 ROWE: This interaction between planets, 1050 00:54:21,734 --> 00:54:23,667 billions of miles apart, 1051 00:54:23,767 --> 00:54:26,300 transformed the inner solar system 1052 00:54:26,367 --> 00:54:28,166 and primed Earth for life. 1053 00:54:29,967 --> 00:54:33,667 But our planet was still uninhabitable. 1054 00:54:36,166 --> 00:54:37,867 RADEBAUGH: The early Earth, right after the bombardment, 1055 00:54:37,967 --> 00:54:40,367 would have been a complete hellscape, 1056 00:54:40,467 --> 00:54:43,020 and it would have been really hot magma everywhere. 1057 00:54:43,020 --> 00:54:43,667 and it would have been really hot magma everywhere. 1058 00:54:43,767 --> 00:54:47,900 Big impact craters with impact melt all across the floors -- 1059 00:54:48,000 --> 00:54:49,734 it would have been unrecognizable. 1060 00:54:50,767 --> 00:54:52,800 Not only was it incredibly hot, 1061 00:54:52,867 --> 00:54:55,900 but it also didn't have an atmosphere, and at that time, 1062 00:54:56,000 --> 00:54:58,567 there was no liquid water on the surface yet. 1063 00:54:58,567 --> 00:55:02,000 Early Earth could not have supported life. 1064 00:55:02,066 --> 00:55:03,867 ROWE: For life to start, 1065 00:55:03,967 --> 00:55:09,100 Earth must cool down and build a new atmosphere. 1066 00:55:09,166 --> 00:55:12,100 The Earth developed its second atmosphere using materials 1067 00:55:12,166 --> 00:55:13,020 delivered by the great bombardment. 1068 00:55:13,020 --> 00:55:14,100 delivered by the great bombardment. 1069 00:55:14,166 --> 00:55:16,367 All of these volatiles, like water 1070 00:55:16,467 --> 00:55:19,600 and carbon organic materials were incorporated 1071 00:55:19,667 --> 00:55:22,066 into the Earth's crust, and then, 1072 00:55:22,066 --> 00:55:23,567 volcanoes were able to outgas 1073 00:55:23,567 --> 00:55:26,967 all of these materials, forming a very thick layer of gas. 1074 00:55:26,967 --> 00:55:30,100 This new atmosphere had a composition that was mostly 1075 00:55:30,166 --> 00:55:33,800 water vapor, carbon dioxide, and nitrogen. 1076 00:55:33,867 --> 00:55:36,367 ROWE: Over the next 30 million years, 1077 00:55:36,367 --> 00:55:40,367 Earth cools -- a solid surface forms. 1078 00:55:42,166 --> 00:55:43,020 DURDA: As the planet is cooling, the water vapor 1079 00:55:43,020 --> 00:55:44,467 DURDA: As the planet is cooling, the water vapor 1080 00:55:44,467 --> 00:55:46,800 in the atmosphere is going to be raining out. 1081 00:55:46,867 --> 00:55:50,100 That's gonna form pools of liquid water 1082 00:55:50,166 --> 00:55:51,266 on the surface of the Earth. 1083 00:55:53,567 --> 00:55:55,100 RADEBAUGH: The earliest evidence for liquid water 1084 00:55:55,166 --> 00:55:57,867 on Earth was 4.3 billion years ago. 1085 00:55:57,967 --> 00:56:00,467 Remember, that's just 200 million years after 1086 00:56:00,467 --> 00:56:02,734 its formation, which is really fast. 1087 00:56:04,266 --> 00:56:07,600 ROWE: Trillions of gallons of water rain down. 1088 00:56:08,767 --> 00:56:12,000 Torrential rains for, I mean, you know, imagine monsoon rains 1089 00:56:12,100 --> 00:56:13,020 for, you know, tens and tens of thousands of years. 1090 00:56:13,020 --> 00:56:15,200 for, you know, tens and tens of thousands of years. 1091 00:56:19,066 --> 00:56:20,667 RADEBAUGH: All this water would have rained 1092 00:56:20,767 --> 00:56:21,767 onto the surface, rained, 1093 00:56:21,767 --> 00:56:25,000 rained, and eventually filled up our oceans. 1094 00:56:27,467 --> 00:56:30,166 ROWE: The oceans pull life-forming chemicals from 1095 00:56:30,266 --> 00:56:35,066 the rocks and the atmosphere, creating the primordial soup. 1096 00:56:36,500 --> 00:56:38,467 Life can begin. 1097 00:56:39,734 --> 00:56:42,266 THALLER: We used to be so disconnected from each other, 1098 00:56:42,266 --> 00:56:43,020 each planet just living entirely separately. 1099 00:56:43,020 --> 00:56:44,567 each planet just living entirely separately. 1100 00:56:44,667 --> 00:56:46,667 Now, we know things mix around. 1101 00:56:46,767 --> 00:56:49,500 Now we know that probably the building blocks of 1102 00:56:49,567 --> 00:56:51,667 life itself and the water in my body 1103 00:56:51,767 --> 00:56:53,600 actually came from the outer solar system. 1104 00:56:53,667 --> 00:56:55,500 I like that. 1105 00:56:56,667 --> 00:56:59,400 ROWE: A series of interconnecting and often 1106 00:56:59,467 --> 00:57:01,467 violent incidents going right back 1107 00:57:01,467 --> 00:57:05,266 to the start of the solar system led to our existence. 1108 00:57:05,367 --> 00:57:09,734 HOWETT: If you look at what the solar system has been through, 1109 00:57:09,734 --> 00:57:13,020 what has to happen for life to happen. 1110 00:57:13,020 --> 00:57:13,100 what has to happen for life to happen. 1111 00:57:13,166 --> 00:57:16,000 When you add all of those things up, we shouldn't exist. 1112 00:57:16,066 --> 00:57:19,100 We just shouldn't be here. The chances are so, so slim. 1113 00:57:19,166 --> 00:57:21,000 And yet here we are. 1114 00:57:22,266 --> 00:57:24,667 PLAIT: The Earth has managed to survive a lot of the nonsense 1115 00:57:24,767 --> 00:57:26,500 the solar system has thrown at it, 1116 00:57:26,567 --> 00:57:29,166 and some of that is probably just luck of the draw. 1117 00:57:29,266 --> 00:57:31,467 So I think even on our worst days, 1118 00:57:31,467 --> 00:57:34,266 we should remember that we're pretty lucky just to be here. 1119 00:57:34,266 --> 00:57:38,367 Earth won the cosmic game of chance, 1120 00:57:39,667 --> 00:57:43,020 but were the other Mafioso children as lucky? 1121 00:57:43,020 --> 00:57:43,100 but were the other Mafioso children as lucky? 1122 00:57:43,166 --> 00:57:44,900 Did Mars and Venus 1123 00:57:45,000 --> 00:57:49,367 also develop environments capable of supporting life? 1124 00:57:59,500 --> 00:58:03,066 ROWE: 200 million years after the birth of the Sun, 1125 00:58:03,066 --> 00:58:05,066 the mafia family prospers. 1126 00:58:07,000 --> 00:58:09,500 The inner planets have the building blocks of 1127 00:58:09,567 --> 00:58:12,266 life thrown in from the outer solar system. 1128 00:58:15,166 --> 00:58:18,100 So, in theory, they could be habitable. 1129 00:58:23,367 --> 00:58:28,600 But when the Russian probe Venera landed on Venus in 1970, 1130 00:58:28,667 --> 00:58:31,300 it found a scorching, hostile world. 1131 00:58:32,967 --> 00:58:35,166 RADEBAUGH: The conditions on Venus are crazy. 1132 00:58:35,266 --> 00:58:38,900 The temperature on the surface is over 800 degrees Fahrenheit, 1133 00:58:39,000 --> 00:58:41,166 so it's hot enough to melt lead. 1134 00:58:41,166 --> 00:58:43,900 The first probes that landed on Venus functioned for 1135 00:58:44,000 --> 00:58:45,367 a little while, and then they were 1136 00:58:45,467 --> 00:58:46,967 crushed like a tin can and melted. 1137 00:58:48,734 --> 00:58:52,767 LANZA: It has a huge, crushing atmospheric pressure, 1138 00:58:52,867 --> 00:58:53,203 which is 90 times that on the Earth's surface, 1139 00:58:53,203 --> 00:58:55,600 which is 90 times that on the Earth's surface, 1140 00:58:55,667 --> 00:58:58,266 and that's entirely carbon dioxide. 1141 00:59:00,900 --> 00:59:03,367 DURDA: And it gets worse still, because gasses in 1142 00:59:03,467 --> 00:59:05,166 the atmosphere have combined 1143 00:59:05,266 --> 00:59:08,367 to make really this concentrated solution of gasses. 1144 00:59:08,367 --> 00:59:10,367 So you've got this noxious, 1145 00:59:10,367 --> 00:59:14,266 acidic, corrosive environment coupled with very, very 1146 00:59:14,367 --> 00:59:16,100 high temperatures. 1147 00:59:16,166 --> 00:59:18,200 Life as we know it could not survive 1148 00:59:18,266 --> 00:59:20,467 on the surface of Venus as it is today. 1149 00:59:25,266 --> 00:59:29,200 ROWE: New climate models suggest that four billion years ago, 1150 00:59:29,266 --> 00:59:34,000 Venus was a very different planet to the one we see today. 1151 00:59:34,100 --> 00:59:38,500 These models suggest that, in the past, Venus had actually 1152 00:59:38,567 --> 00:59:42,000 a cooler surface temperature and had a better composition 1153 00:59:42,066 --> 00:59:43,300 for habitability. 1154 00:59:45,567 --> 00:59:49,000 We think it once had a much thinner atmosphere, much more 1155 00:59:49,066 --> 00:59:51,000 like Earth's atmosphere today. 1156 00:59:51,100 --> 00:59:53,203 It would have had a climate, which was much, much cooler, 1157 00:59:53,203 --> 00:59:55,266 It would have had a climate, which was much, much cooler, 1158 00:59:55,367 --> 00:59:59,266 and therefore, even the possibility of liquid water 1159 00:59:59,266 --> 01:00:02,767 on the surface -- maybe Venus had oceans 1160 01:00:02,834 --> 01:00:05,567 in the way that we find on Earth still today. 1161 01:00:07,367 --> 01:00:09,867 It even makes sense that Venus would be similar to Earth, 1162 01:00:09,867 --> 01:00:11,967 because it formed out of basically 1163 01:00:11,967 --> 01:00:14,900 the same materials, close to the same location from the Sun, 1164 01:00:15,000 --> 01:00:17,567 and ended up being even almost the same size. 1165 01:00:19,200 --> 01:00:22,367 Really, we are twin planets. 1166 01:00:22,367 --> 01:00:23,203 The barrage of icy objects 1167 01:00:23,203 --> 01:00:26,100 The barrage of icy objects 1168 01:00:26,166 --> 01:00:30,100 from the outer solar system that struck Earth also hit Venus. 1169 01:00:31,266 --> 01:00:34,467 LANZA: Just like Earth, Venus got a whole bunch 1170 01:00:34,567 --> 01:00:37,734 of volatiles from bombardments, and those in turn were 1171 01:00:37,734 --> 01:00:41,166 recycled and produced a very nice atmosphere 1172 01:00:41,166 --> 01:00:44,100 and allowed water to exist on the surface as a liquid. 1173 01:00:47,000 --> 01:00:51,200 These early conditions on Venus could have provided 1174 01:00:51,266 --> 01:00:53,166 a habitat, 1175 01:00:53,266 --> 01:00:56,767 the right sort of conditions for life to have got started. 1176 01:00:56,867 --> 01:00:59,066 What about Mars? 1177 01:00:59,066 --> 01:01:01,667 Was it also habitable? 1178 01:01:01,767 --> 01:01:03,834 Looking at it today, all we see 1179 01:01:03,834 --> 01:01:06,467 is a frozen, barren wasteland. 1180 01:01:06,467 --> 01:01:09,400 Part of the reason it's so cold is it's further away 1181 01:01:09,467 --> 01:01:12,066 from the Sun, and it doesn't have a very thick atmosphere. 1182 01:01:12,066 --> 01:01:14,367 So it's very hard for it to retain heat. 1183 01:01:14,467 --> 01:01:17,667 It also has extremely low atmospheric pressure, 1184 01:01:17,767 --> 01:01:20,467 which means that any liquid water on the surface would just 1185 01:01:20,467 --> 01:01:23,203 boil away, and any current water 1186 01:01:23,203 --> 01:01:23,400 boil away, and any current water 1187 01:01:23,467 --> 01:01:26,467 that's on the planet is locked up in ice. 1188 01:01:27,467 --> 01:01:30,767 ROWE: However, recent surveys of Mars reveal 1189 01:01:30,834 --> 01:01:35,834 a very different planet, once capable of supporting life. 1190 01:01:35,834 --> 01:01:37,900 COOPER: As you look across the landscape of Mars, 1191 01:01:38,000 --> 01:01:41,166 you can see these physical features that give us hints 1192 01:01:41,266 --> 01:01:42,767 that water used to exist there, 1193 01:01:42,867 --> 01:01:46,266 like dried lake beds and riverbeds. 1194 01:01:46,367 --> 01:01:49,467 RADEBAUGH: We see abundant evidence of river channels, 1195 01:01:49,567 --> 01:01:52,166 drainages all across the landscape. 1196 01:01:52,266 --> 01:01:53,203 The best way, I think the only way to form these is 1197 01:01:53,203 --> 01:01:55,100 The best way, I think the only way to form these is 1198 01:01:55,166 --> 01:01:56,300 by rainfall. 1199 01:01:56,367 --> 01:01:59,400 There had to have been clouds and rain in Mars's past. 1200 01:01:59,467 --> 01:02:02,767 And there's also sediments and mineral deposits that could 1201 01:02:02,867 --> 01:02:05,867 only form in the presence of liquid water. 1202 01:02:08,066 --> 01:02:11,467 ROWE: We calculate that Mars once had five million 1203 01:02:11,467 --> 01:02:14,367 cubic miles of liquid water on the surface. 1204 01:02:14,367 --> 01:02:17,834 That's enough for an ocean 1205 01:02:17,834 --> 01:02:19,900 bigger than the Earth's Arctic Ocean. 1206 01:02:20,000 --> 01:02:22,567 So we think that Mars had an ocean 1207 01:02:22,567 --> 01:02:23,203 in its northern hemisphere. 1208 01:02:23,203 --> 01:02:24,667 in its northern hemisphere. 1209 01:02:27,066 --> 01:02:29,567 ROWE: To have oceans, 1210 01:02:29,567 --> 01:02:32,467 Mars must have had a thick atmosphere. 1211 01:02:34,367 --> 01:02:36,266 And recently, a space probe 1212 01:02:36,367 --> 01:02:39,834 orbiting the red planet found evidence. 1213 01:02:42,000 --> 01:02:43,667 RADEBAUGH: The MAVEN mission revealed that 1214 01:02:43,734 --> 01:02:46,567 Mars is losing its atmosphere rapidly. 1215 01:02:46,567 --> 01:02:48,266 I mean, this is something like a quarter pound 1216 01:02:48,367 --> 01:02:51,200 a second of atmosphere being stripped away 1217 01:02:51,266 --> 01:02:52,467 by the solar wind. 1218 01:02:52,567 --> 01:02:53,203 We can take those MAVEN loss rates for Mars's atmosphere 1219 01:02:53,203 --> 01:02:55,667 We can take those MAVEN loss rates for Mars's atmosphere 1220 01:02:55,734 --> 01:02:57,000 and extrapolate back in time, 1221 01:02:57,100 --> 01:02:59,967 and we can see that Mars had an atmosphere as thick as 1222 01:02:59,967 --> 01:03:01,967 Earth's in the past. 1223 01:03:01,967 --> 01:03:03,667 With a thicker atmosphere, Mars would 1224 01:03:03,734 --> 01:03:07,166 have been able to retain heat much more effectively 1225 01:03:07,266 --> 01:03:09,166 and would have had increased atmospheric pressure, 1226 01:03:09,266 --> 01:03:11,600 which would have allowed liquid water to persist on 1227 01:03:11,667 --> 01:03:12,567 the surface. 1228 01:03:12,667 --> 01:03:14,367 In the past, Mars would have been just 1229 01:03:14,467 --> 01:03:18,467 a beautiful landscape filled with running rivers and lakes, 1230 01:03:18,467 --> 01:03:21,066 and that water could have potentially sustained 1231 01:03:21,066 --> 01:03:22,367 ancient life. 1232 01:03:25,100 --> 01:03:28,200 All of the observations that we have of Mars to date 1233 01:03:28,266 --> 01:03:31,600 just tell us that it was absolutely a habitable world. 1234 01:03:31,667 --> 01:03:35,867 RADEBAUGH: So now we have an Earth that had kind of 1235 01:03:35,867 --> 01:03:38,166 settled down after the heavy bombardment of Venus 1236 01:03:38,266 --> 01:03:39,900 that might have water on the surface 1237 01:03:40,000 --> 01:03:41,767 and a thinner atmosphere and Mars, with 1238 01:03:41,834 --> 01:03:43,600 a thicker atmosphere and water on the surface, 1239 01:03:43,667 --> 01:03:47,467 water on all three surfaces -- maybe all three were right 1240 01:03:47,467 --> 01:03:48,667 for life. 1241 01:03:48,734 --> 01:03:51,667 It's actually remarkable to think that all three of 1242 01:03:51,734 --> 01:03:53,203 these planets could have been habitable at the same time. 1243 01:03:53,203 --> 01:03:54,900 these planets could have been habitable at the same time. 1244 01:03:56,066 --> 01:03:59,100 ROWE: But this golden age of habitability 1245 01:03:59,166 --> 01:04:00,200 is short-lived. 1246 01:04:02,367 --> 01:04:05,000 Another battle erupts between the planets 1247 01:04:05,066 --> 01:04:08,066 and their Don, the Sun. 1248 01:04:08,066 --> 01:04:12,367 Venus and Mars suffers serious collateral damage. 1249 01:04:24,600 --> 01:04:26,367 ROWE: Four billion years ago, 1250 01:04:26,467 --> 01:04:29,967 the mob family, the solar system, is thriving. 1251 01:04:32,500 --> 01:04:35,300 The children, Earth, Mars and Venus, 1252 01:04:35,367 --> 01:04:38,166 have the conditions to sustain life. 1253 01:04:44,300 --> 01:04:47,100 2020 -- scientists investigate 1254 01:04:47,166 --> 01:04:47,453 how Mars became uninhabitable. 1255 01:04:47,453 --> 01:04:49,567 how Mars became uninhabitable. 1256 01:04:51,767 --> 01:04:55,266 They detect faint magnetic traces coming from 1257 01:04:55,367 --> 01:04:58,834 lava spewed out by ancient volcanic eruptions. 1258 01:05:02,000 --> 01:05:06,967 The magnetic lava on Mars tells us that when that lava 1259 01:05:07,033 --> 01:05:11,967 was molten, there was a strong global magnetic field 1260 01:05:12,033 --> 01:05:13,300 on that planet. 1261 01:05:15,066 --> 01:05:17,453 ROWE: Dating the rocks tells us that Mars's 1262 01:05:17,453 --> 01:05:18,166 ROWE: Dating the rocks tells us that Mars's 1263 01:05:18,166 --> 01:05:23,934 magnetic field was active 4.5 billion years ago. 1264 01:05:24,000 --> 01:05:28,000 Having a magnetic field really helps a planet retain 1265 01:05:28,066 --> 01:05:30,266 its atmosphere, and that's just because a magnetic field 1266 01:05:30,266 --> 01:05:33,500 protects the planet's atmosphere from incoming radiation. 1267 01:05:33,567 --> 01:05:36,266 Solar wind, cosmic rays, you name it. 1268 01:05:43,166 --> 01:05:46,000 ROWE: On Earth, liquid iron churning around 1269 01:05:46,066 --> 01:05:47,453 the hot molten core generates a magnetic field. 1270 01:05:47,453 --> 01:05:49,667 the hot molten core generates a magnetic field. 1271 01:05:51,266 --> 01:05:56,033 The younger Mars would have still had a much 1272 01:05:56,100 --> 01:05:59,767 hotter core, with churning convection currents in 1273 01:05:59,867 --> 01:06:01,133 its interior, 1274 01:06:01,166 --> 01:06:05,600 and these would have generated a global magnetic field in 1275 01:06:05,667 --> 01:06:09,266 exactly the same way the Earth creates its magnetic field. 1276 01:06:09,266 --> 01:06:15,100 ROWE: Mars couldn't maintain its magnetic field, 1277 01:06:15,166 --> 01:06:17,453 because Jupiter's violent assault on the inner 1278 01:06:17,453 --> 01:06:17,734 because Jupiter's violent assault on the inner 1279 01:06:17,734 --> 01:06:20,867 solar system stole the red planet's lunch, 1280 01:06:22,300 --> 01:06:25,467 THALLER: Jupiter migrated in about where Mars is today. 1281 01:06:25,567 --> 01:06:27,767 So that means that most of the material 1282 01:06:27,834 --> 01:06:30,266 was actually swallowed up by the gravity of Jupiter. 1283 01:06:30,266 --> 01:06:33,166 So Mars just got unlucky. 1284 01:06:33,166 --> 01:06:36,667 ROWE: Small planets lose heat faster. 1285 01:06:36,734 --> 01:06:39,367 Tiny Mars cooled down. 1286 01:06:39,467 --> 01:06:42,166 And so as Mars's core cooled, 1287 01:06:42,166 --> 01:06:45,200 the convection in that core would have slowed down, to 1288 01:06:45,266 --> 01:06:47,453 the point where no magnetic field would be generated. 1289 01:06:47,453 --> 01:06:47,834 the point where no magnetic field would be generated. 1290 01:06:47,834 --> 01:06:50,400 Once the magnetic field at Mars is shut off, 1291 01:06:50,467 --> 01:06:53,266 well, that's the end of the protection for the atmosphere. 1292 01:06:55,867 --> 01:06:58,600 ROWE: 3.7 billion years ago, 1293 01:06:58,667 --> 01:07:01,867 the Sun attacks the defenseless Mars. 1294 01:07:01,967 --> 01:07:06,767 The solar wind just bombards it and strips it 1295 01:07:06,834 --> 01:07:09,200 away of the atmosphere very quickly over time. 1296 01:07:10,367 --> 01:07:11,934 ROWE: Without its thermal blanket, 1297 01:07:12,000 --> 01:07:15,767 Mars's surface freezes, and the atmospheric 1298 01:07:15,867 --> 01:07:17,453 pressure plummets. 1299 01:07:17,453 --> 01:07:18,467 pressure plummets. 1300 01:07:18,567 --> 01:07:23,200 As the atmospheric pressure drops, surface water 1301 01:07:23,266 --> 01:07:26,467 gradually evaporates or even boils away. 1302 01:07:32,600 --> 01:07:35,667 ROWE: Venus also suffered a climate catastrophe. 1303 01:07:37,734 --> 01:07:40,000 We find clues on its surface. 1304 01:07:43,500 --> 01:07:46,934 Like all planetary-sized bodies in the solar system, 1305 01:07:47,000 --> 01:07:47,453 Venus has impact craters on it 1306 01:07:47,453 --> 01:07:48,967 Venus has impact craters on it 1307 01:07:49,033 --> 01:07:50,967 from asteroids smacking into it, 1308 01:07:51,033 --> 01:07:54,834 but there aren't that many, which is a little odd. 1309 01:07:54,834 --> 01:07:56,066 ROWE: They're not damaged 1310 01:07:56,066 --> 01:07:58,667 like the craters we see on other worlds. 1311 01:07:58,767 --> 01:08:02,767 LANZA: They look pristine, as if nothing has modified them, 1312 01:08:02,867 --> 01:08:04,367 as if they happened yesterday. 1313 01:08:04,367 --> 01:08:07,266 So that suggests these craters and the surface 1314 01:08:07,266 --> 01:08:09,400 on which they reside are both very young. 1315 01:08:11,000 --> 01:08:13,266 ROWE: There are several theories suggesting that 1316 01:08:13,367 --> 01:08:14,767 volcanic eruptions 1317 01:08:14,867 --> 01:08:17,453 resurfaced the planet around 500 million years ago. 1318 01:08:17,453 --> 01:08:18,100 resurfaced the planet around 500 million years ago. 1319 01:08:20,667 --> 01:08:23,567 One idea is that Venus has a very thick crust, 1320 01:08:23,567 --> 01:08:26,300 and it doesn't move around in plates like Earth's does. 1321 01:08:26,367 --> 01:08:29,367 So it's just a lid over the planet, and eventually, 1322 01:08:29,367 --> 01:08:31,166 the pressure builds up and builds up 1323 01:08:31,266 --> 01:08:33,667 and builds up until it -- boom, lets out all at once. 1324 01:08:39,667 --> 01:08:43,200 RADEBAUGH: A catastrophic event that overturned 1325 01:08:43,266 --> 01:08:46,867 the entire crust of Venus and resurfaced it. 1326 01:08:48,300 --> 01:08:50,066 ROWE: An alternate theory suggests 1327 01:08:50,066 --> 01:08:53,300 the resurfacing happened over millions of years. 1328 01:08:54,567 --> 01:08:57,100 RADEBAUGH: A series of large volcanic eruptions 1329 01:08:57,166 --> 01:08:59,266 that would have completely resurfaced the planet. 1330 01:09:02,767 --> 01:09:05,300 Imagine watching this event on Venus -- I mean, 1331 01:09:05,367 --> 01:09:08,400 the overturn of an entire crust? 1332 01:09:08,467 --> 01:09:10,266 That's just completely awe-inspiring. 1333 01:09:11,867 --> 01:09:15,166 ROWE: Volcanic events release huge amounts of gas. 1334 01:09:18,967 --> 01:09:21,467 Icelandic volcano, Eyjafjallajokull, 1335 01:09:21,567 --> 01:09:26,767 blasts out up to 300,000 tons of carbon dioxide every day. 1336 01:09:29,166 --> 01:09:33,100 Venus's planet-wide volcanism would have been off the charts. 1337 01:09:35,367 --> 01:09:41,734 Such a huge worldwide bout of volcanic activity would release 1338 01:09:41,734 --> 01:09:46,867 huge amounts of carbon dioxide in the Venusian atmosphere. 1339 01:09:46,934 --> 01:09:47,453 ROWE: Scientists think this enormous release of gas 1340 01:09:47,453 --> 01:09:50,667 ROWE: Scientists think this enormous release of gas 1341 01:09:50,734 --> 01:09:54,667 may have triggered the Venusian climate change. 1342 01:09:54,734 --> 01:09:57,166 Carbon dioxide built up in Venus's 1343 01:09:57,166 --> 01:10:01,200 atmosphere, trapping heat from the Sun. 1344 01:10:01,266 --> 01:10:04,100 DARTNELL: As soon as the climate on Venus started to warm up 1345 01:10:04,166 --> 01:10:06,934 a little, there's greater evaporation 1346 01:10:07,000 --> 01:10:10,567 coming off the oceans, and that water vapor 1347 01:10:10,567 --> 01:10:14,033 in the atmosphere is itself a greenhouse gas. 1348 01:10:14,100 --> 01:10:16,266 The climate gets even warmer. 1349 01:10:18,200 --> 01:10:21,767 ROWE: Venus reaches 880 degrees Fahrenheit. 1350 01:10:25,266 --> 01:10:28,834 Any chance for life broils away. 1351 01:10:33,667 --> 01:10:36,834 The Earth also faces a searing hot future 1352 01:10:36,834 --> 01:10:39,200 when the aging Godfather, 1353 01:10:39,266 --> 01:10:44,166 the Sun, bloats up and attacks his family once again, 1354 01:10:44,266 --> 01:10:47,453 transforming into a lethal weapon of mass destruction. 1355 01:10:47,453 --> 01:10:49,266 transforming into a lethal weapon of mass destruction. 1356 01:11:02,066 --> 01:11:05,000 ROWE: For the last four billion years, our mob family, 1357 01:11:05,066 --> 01:11:07,667 the solar system, lived in harmony, 1358 01:11:07,734 --> 01:11:11,133 but nothing lasts forever. 1359 01:11:11,133 --> 01:11:14,133 The godfather, the Sun, 1360 01:11:14,133 --> 01:11:17,367 will grow old, fat, and mean. 1361 01:11:17,367 --> 01:11:21,266 Stars like the Sun only have enough 1362 01:11:21,266 --> 01:11:24,266 hydrogen to fuse for about 10 billion years. 1363 01:11:24,266 --> 01:11:26,619 So that means that in about five billion years, 1364 01:11:26,619 --> 01:11:27,467 So that means that in about five billion years, 1365 01:11:27,567 --> 01:11:31,567 the Sun will actually run out of hydrogen. 1366 01:11:33,767 --> 01:11:37,000 ROWE: With no hydrogen fuel left, fusion stops. 1367 01:11:38,100 --> 01:11:42,400 The core collapses and reignites, fusing helium. 1368 01:11:52,867 --> 01:11:55,934 NANCE: The energy released by all of this fusion causes 1369 01:11:56,000 --> 01:11:56,619 the star to balloon outwards and become a red giant. 1370 01:11:56,619 --> 01:11:59,934 the star to balloon outwards and become a red giant. 1371 01:12:02,367 --> 01:12:05,600 ROWE: The red giant is like a bitter old gangster. 1372 01:12:07,166 --> 01:12:10,667 Bloated and aggressive, it attacks the inner planets. 1373 01:12:14,567 --> 01:12:16,300 Mercury and Venus are gonna be engulfed 1374 01:12:16,367 --> 01:12:18,500 by the Sun as it becomes a red giant. 1375 01:12:19,934 --> 01:12:21,667 It burns up both planets. 1376 01:12:23,000 --> 01:12:25,066 Next in line, Earth. 1377 01:12:26,667 --> 01:12:30,400 Then the universe throws us a lifeline. 1378 01:12:30,467 --> 01:12:35,367 As the Sun expands outward, as it enters its red giant phase, 1379 01:12:35,367 --> 01:12:38,266 it's actually going to be losing mass. 1380 01:12:41,967 --> 01:12:44,066 The red giant blows off gas. 1381 01:12:45,600 --> 01:12:48,834 And as it loses mass, its gravity is weakening. 1382 01:12:48,834 --> 01:12:51,500 OLUSEYI: So this means that the Sun's grip on 1383 01:12:51,567 --> 01:12:54,266 the planets that orbit it is gonna be weakening. 1384 01:12:54,266 --> 01:12:56,619 And so they sort of start moving away from the Sun. 1385 01:12:56,619 --> 01:12:57,567 And so they sort of start moving away from the Sun. 1386 01:12:57,567 --> 01:13:00,166 It's almost like they're running away from the heat. 1387 01:13:00,166 --> 01:13:03,300 If you can't stand the heat, get out of the solar system. 1388 01:13:05,266 --> 01:13:08,767 ROWE: Can Earth and Mars outrun the expanding red giant? 1389 01:13:09,967 --> 01:13:12,367 So it's a race, right? Who is going to get 1390 01:13:12,467 --> 01:13:16,467 far enough from the Sun to escape being engulfed by it? 1391 01:13:18,767 --> 01:13:21,266 MINGARELLI: The eventual fate of the Earth is not clear. 1392 01:13:23,000 --> 01:13:26,100 It's possible that the Earth will be completely swallowed up 1393 01:13:26,166 --> 01:13:26,619 by the Sun's atmosphere, 1394 01:13:26,619 --> 01:13:27,767 by the Sun's atmosphere, 1395 01:13:27,834 --> 01:13:31,367 its new, bloated, red atmosphere. 1396 01:13:36,467 --> 01:13:40,166 Even if the Earth escapes being directly 1397 01:13:40,166 --> 01:13:41,467 engulfed by the Sun, 1398 01:13:41,567 --> 01:13:45,066 it's still not a good day for our planet, because the Sun is 1399 01:13:45,133 --> 01:13:47,500 gonna be really, really close. 1400 01:13:47,567 --> 01:13:50,734 PLAIT: So imagine basically something red-hot, glowing, 1401 01:13:50,734 --> 01:13:52,000 covering the sky. 1402 01:13:52,066 --> 01:13:54,133 The earth will be molten, and in fact, a lot of it 1403 01:13:54,133 --> 01:13:55,567 will vaporize. 1404 01:13:55,667 --> 01:13:56,619 So it's not like you're gonna want to be here anyway. 1405 01:13:56,619 --> 01:13:58,033 So it's not like you're gonna want to be here anyway. 1406 01:13:59,166 --> 01:14:00,667 OLUSEYI: As I look at this scenario, 1407 01:14:00,734 --> 01:14:04,133 what's clear is that life isn't gonna make it on Earth. 1408 01:14:08,967 --> 01:14:12,934 ROWE: Mars had a head start and escapes complete destruction. 1409 01:14:14,066 --> 01:14:16,100 It'll be cooked, I mean, it'll be a molten planet, 1410 01:14:16,166 --> 01:14:17,467 but it'll still be there. 1411 01:14:21,734 --> 01:14:24,266 The aging Don wipes out life in 1412 01:14:24,266 --> 01:14:26,619 the inner solar system but may help it survive elsewhere. 1413 01:14:26,619 --> 01:14:30,767 the inner solar system but may help it survive elsewhere. 1414 01:14:31,867 --> 01:14:34,100 The sun's red giant phase may initially bring 1415 01:14:34,166 --> 01:14:36,567 new opportunities for life in the outer solar system. 1416 01:14:38,467 --> 01:14:42,266 SUTTER: Right now, the outer solar system is locked in ice, 1417 01:14:42,266 --> 01:14:43,567 it's way too cold, 1418 01:14:43,567 --> 01:14:46,734 but when our sun becomes a red giant, it will become much, 1419 01:14:46,734 --> 01:14:47,567 much brighter. 1420 01:14:47,667 --> 01:14:50,467 It will warm up the outer system. 1421 01:14:53,367 --> 01:14:56,619 ROWE: And transform the gas giant's icy moons. 1422 01:14:56,619 --> 01:14:57,600 ROWE: And transform the gas giant's icy moons. 1423 01:14:59,567 --> 01:15:01,767 Europa and Enceladus, that orbit Jupiter 1424 01:15:01,834 --> 01:15:04,934 and Saturn respectively, are currently frozen worlds. 1425 01:15:05,000 --> 01:15:07,367 They have icy crusts and are believed 1426 01:15:07,467 --> 01:15:09,867 to have liquid oceans below those crusts. 1427 01:15:18,467 --> 01:15:21,266 ROWE: Scientists believe that these subsurface oceans 1428 01:15:21,266 --> 01:15:23,734 may harbor life. 1429 01:15:23,734 --> 01:15:26,367 As the temperature increases, 1430 01:15:26,467 --> 01:15:26,619 their frozen exteriors are gonna be thawed, 1431 01:15:26,619 --> 01:15:28,767 their frozen exteriors are gonna be thawed, 1432 01:15:28,867 --> 01:15:30,867 and they'll become entirely ocean worlds. 1433 01:15:35,767 --> 01:15:38,266 CHRISTIANSEN: Any life forms already evolving in their oceans 1434 01:15:38,266 --> 01:15:40,734 will have a whole new world of possibility open to them. 1435 01:15:42,467 --> 01:15:44,033 Or if life isn't there yet, 1436 01:15:44,100 --> 01:15:46,266 then it would certainly have a chance to evolve. 1437 01:15:46,367 --> 01:15:48,667 We may have explosions of life 1438 01:15:48,767 --> 01:15:51,300 on these other outer solar system bodies. 1439 01:15:53,867 --> 01:15:56,619 ROWE: But this burst of new life may be short-lived. 1440 01:15:56,619 --> 01:15:57,133 ROWE: But this burst of new life may be short-lived. 1441 01:15:58,467 --> 01:16:01,066 Even though these ocean worlds may seem like a great 1442 01:16:01,133 --> 01:16:03,967 place to move to after the inner solar system 1443 01:16:04,033 --> 01:16:06,600 is engulfed, I would not start packing yet. 1444 01:16:12,567 --> 01:16:17,600 ROWE: The red giant will grow to over 250 times its current size. 1445 01:16:18,834 --> 01:16:21,200 As the Sun continues to expand, 1446 01:16:21,266 --> 01:16:24,400 these new ocean worlds will start getting hotter 1447 01:16:24,467 --> 01:16:26,619 and hotter, and eventually, all of the water will 1448 01:16:26,619 --> 01:16:26,867 and hotter, and eventually, all of the water will 1449 01:16:26,934 --> 01:16:27,967 evaporate away. 1450 01:16:32,000 --> 01:16:33,967 ROWE: Any new life dies out, 1451 01:16:36,967 --> 01:16:39,400 but bodies in the furthest reaches 1452 01:16:39,467 --> 01:16:42,867 of the solar system fare better. 1453 01:16:42,967 --> 01:16:44,967 PLAIT: The key to surviving the Sun turning 1454 01:16:45,033 --> 01:16:47,100 into a red giant is basically distance. 1455 01:16:47,166 --> 01:16:49,734 So the farther out you are from the Sun now, 1456 01:16:49,734 --> 01:16:51,300 the better off you are then. 1457 01:16:53,867 --> 01:16:56,619 ROWE: The best bet might be the distant dwarf planets, 1458 01:16:56,619 --> 01:16:57,400 ROWE: The best bet might be the distant dwarf planets, 1459 01:16:57,467 --> 01:16:58,867 like Pluto. 1460 01:17:01,266 --> 01:17:03,867 So now we have these objects that might actually 1461 01:17:03,967 --> 01:17:07,033 become the most Earth-like bodies in the solar system. 1462 01:17:07,100 --> 01:17:09,133 These may be our lifeboats. 1463 01:17:13,867 --> 01:17:16,300 PLAIT: I mean, they won't have breathable atmospheres, 1464 01:17:16,367 --> 01:17:18,367 and it's not like they're gonna be great places to live, 1465 01:17:18,467 --> 01:17:21,166 but, you know, the Earth is gonna be basically toast at 1466 01:17:21,266 --> 01:17:23,934 that point, so, you know, what choice do you have? 1467 01:17:24,000 --> 01:17:26,619 ROWE: Humanity may use the warm outer bodies as stepping stones 1468 01:17:26,619 --> 01:17:28,200 ROWE: Humanity may use the warm outer bodies as stepping stones 1469 01:17:28,266 --> 01:17:30,667 to a new home, because when 1470 01:17:30,734 --> 01:17:33,166 the Godfather's sun gets very old, 1471 01:17:33,166 --> 01:17:38,266 he becomes frail and unable to stop other more powerful Dons 1472 01:17:38,367 --> 01:17:41,767 from destroying the solar system forever. 1473 01:17:55,467 --> 01:17:58,567 ROWE: Six billion years in the future. 1474 01:17:59,767 --> 01:18:03,867 The aging Godfather's attack on his children ends. 1475 01:18:06,867 --> 01:18:10,667 The bloated red giant dies, releasing a burst of energy, 1476 01:18:10,767 --> 01:18:12,867 which blasts the outer regions 1477 01:18:12,967 --> 01:18:16,000 of the star, plus the remains of the vaporized 1478 01:18:16,066 --> 01:18:17,796 planets, out into space... 1479 01:18:17,796 --> 01:18:18,033 planets, out into space... 1480 01:18:21,266 --> 01:18:24,367 ...ready to build new stars and new planets. 1481 01:18:25,834 --> 01:18:28,567 What's left are veils of 1482 01:18:28,667 --> 01:18:32,166 beautiful colored gas called a planetary nebula, 1483 01:18:33,233 --> 01:18:35,567 the surviving planets, 1484 01:18:35,567 --> 01:18:40,066 and, at the heart, the remains of the Sun, 1485 01:18:40,133 --> 01:18:45,000 now nothing but a burnt-out core. 1486 01:18:46,300 --> 01:18:47,796 We call those leftover cores from small stars 1487 01:18:47,796 --> 01:18:49,567 We call those leftover cores from small stars 1488 01:18:49,567 --> 01:18:53,567 white dwarf stars, and they're much smaller than the Sun. 1489 01:18:54,767 --> 01:18:57,767 The white dwarf will be about half the Sun's original 1490 01:18:57,834 --> 01:19:02,233 mass and all contained into the size of the Earth. 1491 01:19:02,233 --> 01:19:05,400 ROWE: The dense white dwarf doesn't burn fuel, 1492 01:19:05,467 --> 01:19:07,667 so it can't generate energy. 1493 01:19:09,667 --> 01:19:11,934 The solar system cools. 1494 01:19:13,100 --> 01:19:15,767 We'll start seeing freezing from the outer solar system 1495 01:19:15,834 --> 01:19:17,796 to the inner solar system -- we'll start with Pluto. 1496 01:19:17,796 --> 01:19:18,934 to the inner solar system -- we'll start with Pluto. 1497 01:19:20,266 --> 01:19:22,600 Then Enceladus around Saturn. 1498 01:19:23,767 --> 01:19:26,033 And then Europa around Jupiter, 1499 01:19:26,100 --> 01:19:27,834 and then finally Mars. 1500 01:19:27,834 --> 01:19:32,600 So, you know, they've already had any volatiles sent away. 1501 01:19:32,667 --> 01:19:35,367 Their surfaces are now gonna be metallic and rocky, 1502 01:19:35,367 --> 01:19:39,133 and you're gonna end up with these very frozen, rocky, 1503 01:19:39,133 --> 01:19:41,266 metallic worlds. 1504 01:19:41,266 --> 01:19:44,233 ROWE: The near-dead Godfather 1505 01:19:44,233 --> 01:19:46,867 is now a shadow of his former self. 1506 01:19:47,967 --> 01:19:49,467 And the solar system is at 1507 01:19:49,467 --> 01:19:52,867 the mercy of more powerful mobster stars. 1508 01:19:52,967 --> 01:19:56,400 The white dwarf of the Sun has about half the mass 1509 01:19:56,467 --> 01:19:57,467 of the Sun today, 1510 01:19:57,467 --> 01:19:59,600 which means gravity is half as strong. 1511 01:19:59,667 --> 01:20:02,867 So the planets in their orbits will move further out. 1512 01:20:05,166 --> 01:20:07,400 These outer planets, which survived 1513 01:20:07,467 --> 01:20:09,266 the Sun turning into a red giant, 1514 01:20:09,266 --> 01:20:12,033 their orbits are now much, much larger than they were before, 1515 01:20:12,100 --> 01:20:15,066 up to about a factor of two. 1516 01:20:15,133 --> 01:20:17,796 That's an issue, because there are other stars in the galaxy. 1517 01:20:17,796 --> 01:20:18,400 That's an issue, because there are other stars in the galaxy. 1518 01:20:19,567 --> 01:20:23,100 We're part of the Milky Way Galaxy, and our best estimate 1519 01:20:23,166 --> 01:20:26,867 is that there is something like 100 billion other suns like ours 1520 01:20:26,967 --> 01:20:28,233 orbiting our galaxy. 1521 01:20:29,767 --> 01:20:32,667 PLAIT: Every 20 million years, something like that, 1522 01:20:32,767 --> 01:20:36,066 one of them will pass by close enough to affect the orbits 1523 01:20:36,133 --> 01:20:37,367 of these planets. 1524 01:20:40,367 --> 01:20:44,400 So in this distant future, where our sun is a white dwarf, 1525 01:20:44,467 --> 01:20:47,033 as our orbits are larger and things are moving slower, 1526 01:20:47,100 --> 01:20:47,796 we're way more susceptible to the effects of passing stars. 1527 01:20:47,796 --> 01:20:50,266 we're way more susceptible to the effects of passing stars. 1528 01:20:53,033 --> 01:20:55,500 You can imagine this like ships passing each other in 1529 01:20:55,567 --> 01:20:58,667 the ocean, where there's one whizzes by another, 1530 01:20:58,734 --> 01:21:02,567 it creates waves that knock the other one around. 1531 01:21:02,567 --> 01:21:07,000 BATYGIN: Passing stars will give the planets little nudges, 1532 01:21:07,066 --> 01:21:08,033 little kicks. 1533 01:21:08,100 --> 01:21:13,066 The giant planets will enter a chaotic phase 1534 01:21:13,133 --> 01:21:15,300 where everything except for Jupiter will be 1535 01:21:15,367 --> 01:21:16,934 scattered out of the solar system. 1536 01:21:21,367 --> 01:21:22,600 ROWE: 50 billion years in the future, 1537 01:21:22,667 --> 01:21:27,133 the solar system faces another ruthless gangster 1538 01:21:27,133 --> 01:21:28,767 out on the make. 1539 01:21:28,867 --> 01:21:31,834 Its gravity is gonna yank Jupiter away from the Sun 1540 01:21:31,834 --> 01:21:33,867 and fling it out into interstellar space, 1541 01:21:33,967 --> 01:21:35,600 and Jupiter will become a rogue planet. 1542 01:21:37,667 --> 01:21:41,033 ROWE: All that's left of our once strong mafia family, 1543 01:21:41,100 --> 01:21:44,667 the Sun, eight planets, and countless moons, 1544 01:21:44,734 --> 01:21:47,667 is the small, weak white dwarf. 1545 01:21:47,767 --> 01:21:47,796 Eventually, a white dwarf cools so much that it no longer 1546 01:21:47,796 --> 01:21:51,667 Eventually, a white dwarf cools so much that it no longer 1547 01:21:51,734 --> 01:21:56,166 emits radiation, and it becomes what we call a black dwarf. 1548 01:21:58,367 --> 01:22:01,166 And this is basically just a burnt-out shell 1549 01:22:01,266 --> 01:22:04,767 of a star composed of oxygen and carbon. 1550 01:22:06,300 --> 01:22:08,166 OLUSEYI: It can form a carbon crystal, 1551 01:22:08,266 --> 01:22:10,233 which we happen to call diamonds. 1552 01:22:10,233 --> 01:22:14,567 So think of a black dwarf as a diamond in the sky. 1553 01:22:17,867 --> 01:22:22,500 ROWE: A cosmic gem destined to wander the galaxy for eternity. 1554 01:22:28,367 --> 01:22:31,834 Our solar system formed from chaos but grew 1555 01:22:31,834 --> 01:22:36,100 from collaboration between the planets and the Sun. 1556 01:22:36,166 --> 01:22:37,600 PLAIT: We know the planets affect us. 1557 01:22:37,667 --> 01:22:40,166 We know the Sun affects us -- in a few billion years, 1558 01:22:40,266 --> 01:22:42,066 the Sun is really gonna affect us. 1559 01:22:42,133 --> 01:22:43,934 The more we look at this stuff, 1560 01:22:44,000 --> 01:22:46,500 the more we realize that everything affects everything 1561 01:22:46,567 --> 01:22:47,796 else, including us. 1562 01:22:47,796 --> 01:22:48,300 else, including us. 1563 01:22:49,367 --> 01:22:52,400 HOWETT: Without all of these things interplaying, 1564 01:22:52,467 --> 01:22:54,967 the Earth wouldn't have the stable environment 1565 01:22:55,033 --> 01:22:56,867 that we have today, and life wouldn't be 1566 01:22:56,967 --> 01:22:58,233 able to exist. 1567 01:22:58,266 --> 01:23:00,867 And so the chances are small, but it's worked out well for us. 1568 01:23:03,600 --> 01:23:06,734 WALSH: As we piece together the events that have 1569 01:23:06,734 --> 01:23:08,600 we think shaped our solar system, 1570 01:23:08,667 --> 01:23:11,266 we step back and think about all the moving parts, 1571 01:23:11,367 --> 01:23:14,934 all of the chance encounters, all of the chaos. 1572 01:23:15,000 --> 01:23:17,166 And it's hard not to think that we're really 1573 01:23:17,266 --> 01:23:17,796 lucky to be sitting here on this planet Earth. 1574 01:23:17,796 --> 01:23:19,600 lucky to be sitting here on this planet Earth. 1575 01:23:19,667 --> 01:23:21,934 ROWE: In the future, 1576 01:23:22,000 --> 01:23:24,600 our mafia family will be gone. 1577 01:23:24,667 --> 01:23:27,667 But somewhere out in the Milky Way, 1578 01:23:27,767 --> 01:23:33,066 a new mobster star system may rise from the ashes of our own. 1579 01:23:34,066 --> 01:23:35,367 OLUSEYI: One of the trends that we see in 1580 01:23:35,367 --> 01:23:38,233 our universe is that destruction leads to creation. 1581 01:23:38,233 --> 01:23:42,367 The fact that our star is gonna one day die 1582 01:23:42,367 --> 01:23:44,767 doesn't mean that it's the end of anything. 1583 01:23:44,867 --> 01:23:47,100 It's the beginning of something new. 1584 01:23:47,166 --> 01:23:47,796 So I think in the future, it's only going to get 1585 01:23:47,796 --> 01:23:49,400 So I think in the future, it's only going to get 1586 01:23:49,467 --> 01:23:50,767 more complicated, 1587 01:23:50,834 --> 01:23:53,467 more interesting, and we're gonna find out just how dynamic 1588 01:23:53,467 --> 01:23:55,100 a place the universe really is.