1 00:00:20,080 --> 00:00:16,600 I am Ramon brosser I work here at LC I 2 00:00:22,030 --> 00:00:20,090 study the formation of planets and also 3 00:00:25,090 --> 00:00:22,040 some of their evolution but mostly the 4 00:00:27,100 --> 00:00:25,100 earlier stages because I think that we 5 00:00:29,620 --> 00:00:27,110 can understand a lot of what happened to 6 00:00:31,180 --> 00:00:29,630 the Earth and Mars and Venus and so 7 00:00:33,720 --> 00:00:31,190 forth if we actually understand more 8 00:00:36,380 --> 00:00:33,730 about their information 9 00:00:38,880 --> 00:00:36,390 so today I'm going to walk you 10 00:00:41,430 --> 00:00:38,890 essentially through a little journey 11 00:00:44,220 --> 00:00:41,440 holding your hand as to how the solar 12 00:00:47,880 --> 00:00:44,230 system came to form so very early on 13 00:00:50,760 --> 00:00:47,890 about 4 and 1/2 billion years ago the 14 00:00:53,430 --> 00:00:50,770 Sun formed from a gas of cloud which was 15 00:00:55,940 --> 00:00:53,440 collapsing very slowly I will show you 16 00:01:01,860 --> 00:00:55,950 an animation of that in the next slide 17 00:01:04,770 --> 00:01:01,870 then some of the gas and the solids in 18 00:01:07,469 --> 00:01:04,780 the disk that surrounded the Sun so as 19 00:01:09,420 --> 00:01:07,479 the gas cloud was collapsing you formed 20 00:01:11,160 --> 00:01:09,430 the Sun and it is surrounded by a disc 21 00:01:13,290 --> 00:01:11,170 which is like a spinning pancake 22 00:01:16,530 --> 00:01:13,300 sometimes you know when you go to a 23 00:01:18,540 --> 00:01:16,540 pizza parlor in Italy you see somebody 24 00:01:20,760 --> 00:01:18,550 that holds the pizza on their hand and 25 00:01:22,859 --> 00:01:20,770 they're spinning it like this and you 26 00:01:26,670 --> 00:01:22,869 notice that as he keeps spinning it the 27 00:01:28,469 --> 00:01:26,680 pizza expands right just imagine that 28 00:01:30,210 --> 00:01:28,479 the same thing is happening here with 29 00:01:32,880 --> 00:01:30,220 the Sun so you have the Sun it is 30 00:01:35,520 --> 00:01:32,890 surrounded by a very thin pizza as it 31 00:01:38,550 --> 00:01:35,530 were that is spinning around very slowly 32 00:01:40,260 --> 00:01:38,560 and part of that pizza is expanding 33 00:01:45,059 --> 00:01:40,270 outwards and the inner part is going 34 00:01:49,680 --> 00:01:45,069 closer to the Sun that Pizza around the 35 00:01:51,809 --> 00:01:49,690 Sun is made up of gas and solids some of 36 00:01:54,419 --> 00:01:51,819 these solids will then coagulate to form 37 00:01:56,609 --> 00:01:54,429 the terrestrial planets which will then 38 00:01:59,400 --> 00:01:56,619 happen in this stage and all of this 39 00:02:01,020 --> 00:01:59,410 stuff is being smashed together through 40 00:02:04,020 --> 00:02:01,030 giant impacts such as the one that 41 00:02:08,790 --> 00:02:04,030 formed our Moon and eventually we end up 42 00:02:13,190 --> 00:02:08,800 with a nice set of planets at the end so 43 00:02:15,900 --> 00:02:13,200 here's an animation of a molecular cloud 44 00:02:17,610 --> 00:02:15,910 this is a computer animation this is not 45 00:02:19,470 --> 00:02:17,620 from observation because these things 46 00:02:22,980 --> 00:02:19,480 takes tens of thousands of years and we 47 00:02:26,280 --> 00:02:22,990 only live about 80 years you can see 48 00:02:28,890 --> 00:02:26,290 here that there's this spiral wave here 49 00:02:31,559 --> 00:02:28,900 where you have the gas falling together 50 00:02:34,320 --> 00:02:31,569 and forming the Sun but in because the 51 00:02:37,530 --> 00:02:34,330 gas is rotating it will start to rotate 52 00:02:39,750 --> 00:02:37,540 around the Sun and you get these spiral 53 00:02:42,830 --> 00:02:39,760 like structures that you also see in 54 00:02:45,280 --> 00:02:42,840 spiral galaxies when you look at the sky 55 00:02:48,250 --> 00:02:45,290 now the animation is zoomed 56 00:02:51,280 --> 00:02:48,260 in the central star in our case the Sun 57 00:02:53,500 --> 00:02:51,290 is right here in the beginning and you 58 00:02:55,929 --> 00:02:53,510 see that all of this material is 59 00:02:58,420 --> 00:02:55,939 spiraling spiraling around the Sun and 60 00:03:01,030 --> 00:02:58,430 you get these density waves and so forth 61 00:03:04,390 --> 00:03:01,040 you see clumps of material that are here 62 00:03:06,670 --> 00:03:04,400 and here which ultimately or so we think 63 00:03:10,320 --> 00:03:06,680 will form giant planets such as Jupiter 64 00:03:16,830 --> 00:03:13,770 so we start with the gas with a disc of 65 00:03:19,230 --> 00:03:16,840 gas and solids that surround the very 66 00:03:21,060 --> 00:03:19,240 very early Sun like in the first hundred 67 00:03:24,630 --> 00:03:21,070 thousand to 1 million or two million 68 00:03:27,300 --> 00:03:24,640 years of the solar system we have small 69 00:03:29,340 --> 00:03:27,310 tiny dust grains like the dust that you 70 00:03:31,830 --> 00:03:29,350 get on your shelves and so forth that 71 00:03:34,230 --> 00:03:31,840 you need to wipe off every week that 72 00:03:36,150 --> 00:03:34,240 sort of dust also existed in the solar 73 00:03:40,740 --> 00:03:36,160 system where it's less of a nuisance 74 00:03:43,110 --> 00:03:40,750 than in your home the dust grains then 75 00:03:45,780 --> 00:03:43,120 form together because of gravity you 76 00:03:47,430 --> 00:03:45,790 know gravity attracts right the Sun 77 00:03:49,380 --> 00:03:47,440 holds the planets and so forth together 78 00:03:51,240 --> 00:03:49,390 but gravity is everywhere there's 79 00:03:52,770 --> 00:03:51,250 gravitational attraction between all of 80 00:03:55,410 --> 00:03:52,780 us in this room even though we don't 81 00:03:58,790 --> 00:03:55,420 feel it so the dust grains they form 82 00:04:01,350 --> 00:03:58,800 together and they form pebble sized 83 00:04:03,240 --> 00:04:01,360 objects you know that like like a small 84 00:04:05,360 --> 00:04:03,250 stone that you find on the beach or in 85 00:04:09,060 --> 00:04:05,370 riverbeds or something like that and 86 00:04:11,070 --> 00:04:09,070 these pebbles are drifting into the gas 87 00:04:13,230 --> 00:04:11,080 there they're revolving around the Sun 88 00:04:15,030 --> 00:04:13,240 but there's gas around and you know 89 00:04:17,190 --> 00:04:15,040 sometimes when you're biking and the 90 00:04:17,909 --> 00:04:17,200 wind is in your face it's called a 91 00:04:22,800 --> 00:04:17,919 headwind 92 00:04:26,220 --> 00:04:22,810 the Sun and it slows them down so they 93 00:04:30,270 --> 00:04:26,230 then drift they migrate towards the Sun 94 00:04:32,460 --> 00:04:30,280 the pebbles then stick together to form 95 00:04:34,650 --> 00:04:32,470 larger objects planetesimals essentially 96 00:04:37,590 --> 00:04:34,660 asteroids you know the stuff that we see 97 00:04:39,780 --> 00:04:37,600 around the sky and then these form 98 00:04:42,840 --> 00:04:39,790 together to form small planetary embryos 99 00:04:46,500 --> 00:04:42,850 like moon sized Mar sized mercury sized 100 00:04:48,630 --> 00:04:46,510 planets and eventually then if the gas 101 00:04:50,730 --> 00:04:48,640 is still there and we are lucky we can 102 00:04:54,150 --> 00:04:50,740 get gaseous planets such as Jupiter and 103 00:04:56,070 --> 00:04:54,160 Saturn and if there's no gas in the disk 104 00:04:58,950 --> 00:04:56,080 then we form terrestrial planets like 105 00:05:01,020 --> 00:04:58,960 the earth Mars Venus and so forth which 106 00:05:02,880 --> 00:05:01,030 are mostly rocky with a little bit of 107 00:05:06,360 --> 00:05:02,890 water a little bit of other stuff but 108 00:05:08,880 --> 00:05:06,370 it's mostly rock and metal this is a 109 00:05:10,860 --> 00:05:08,890 very simplified story of how the planets 110 00:05:12,720 --> 00:05:10,870 in the solar system came to be so you 111 00:05:15,510 --> 00:05:12,730 start with very small stuff that grows 112 00:05:17,850 --> 00:05:15,520 progressively larger and you can either 113 00:05:19,350 --> 00:05:17,860 go into gas giant planets or into 114 00:05:21,810 --> 00:05:19,360 terrestrial planets depending on whether 115 00:05:23,460 --> 00:05:21,820 or not there's gas still around and to 116 00:05:24,180 --> 00:05:23,470 give you an idea of the timescale on 117 00:05:27,210 --> 00:05:24,190 which this half 118 00:05:28,890 --> 00:05:27,220 you form moon-sized mars-sized objects 119 00:05:32,490 --> 00:05:28,900 within a hundred thousand years till 120 00:05:34,800 --> 00:05:32,500 about 1 million years and then those 121 00:05:37,080 --> 00:05:34,810 mars-sized objects as I'll show in a 122 00:05:38,850 --> 00:05:37,090 moment will then all smash together to 123 00:05:40,980 --> 00:05:38,860 form planets the size of Earth and Venus 124 00:05:44,070 --> 00:05:40,990 and that takes between ten and a hundred 125 00:05:47,610 --> 00:05:44,080 million years so by about a hundred 126 00:05:49,320 --> 00:05:47,620 million years we're mostly done so these 127 00:05:53,190 --> 00:05:49,330 are the terrestrial planets as we know 128 00:05:56,280 --> 00:05:53,200 them today Venus Earth Mars and so forth 129 00:05:58,020 --> 00:05:56,290 and here's an animation of how the 130 00:05:59,940 --> 00:05:58,030 planets form so you start with a lot of 131 00:06:01,770 --> 00:05:59,950 small stuff that is circling around the 132 00:06:04,470 --> 00:06:01,780 Sun I'm going to speed it up a great 133 00:06:06,030 --> 00:06:04,480 number of times and you can see that I'm 134 00:06:08,430 --> 00:06:06,040 starting to get some waves and I'm 135 00:06:11,190 --> 00:06:08,440 slowly clearing out the region here in 136 00:06:13,710 --> 00:06:11,200 the center where I'm starting to form 137 00:06:17,000 --> 00:06:13,720 planets then in this region stuff 138 00:06:19,620 --> 00:06:17,010 revolves slower so it takes more time to 139 00:06:21,510 --> 00:06:19,630 form planets here you can see that I've 140 00:06:24,420 --> 00:06:21,520 already got a couple of planets here and 141 00:06:28,230 --> 00:06:24,430 then in the outer edges it's takes even 142 00:06:30,510 --> 00:06:28,240 longer so by this time I have enough I 143 00:06:32,610 --> 00:06:30,520 have a little bit of material left so 144 00:06:34,920 --> 00:06:32,620 I'm starting to get these giant impacts 145 00:06:39,000 --> 00:06:34,930 such as what you have for example for 146 00:06:42,900 --> 00:06:39,010 the moon and so forth the giant impacted 147 00:06:45,030 --> 00:06:42,910 form the moon as you can see the number 148 00:06:46,890 --> 00:06:45,040 of ellipses in this animation is 149 00:06:49,830 --> 00:06:46,900 decreasing that is because stuff is 150 00:06:52,530 --> 00:06:49,840 colliding with each other and then forms 151 00:06:54,960 --> 00:06:52,540 larger and larger bodies but also fewer 152 00:06:57,450 --> 00:06:54,970 and fewer of them so I start with a very 153 00:07:00,120 --> 00:06:57,460 large amount of small bodies and then 154 00:07:03,260 --> 00:07:00,130 progressively I get larger bodies of the 155 00:07:06,350 --> 00:07:03,270 size of planets but fewer of them and 156 00:07:08,580 --> 00:07:06,360 towards the very end of the animation I 157 00:07:11,390 --> 00:07:08,590 still have some other stuff flying 158 00:07:14,820 --> 00:07:11,400 around on very strange very highly 159 00:07:17,310 --> 00:07:14,830 elliptical orbits stuff is ejected out 160 00:07:20,340 --> 00:07:17,320 of the solar system some stuff will fall 161 00:07:23,400 --> 00:07:20,350 onto the Sun and ultimately in the top 162 00:07:26,670 --> 00:07:23,410 case I end up with four planets one two 163 00:07:29,190 --> 00:07:26,680 three and another tiny one here and in 164 00:07:31,080 --> 00:07:29,200 this middle case I have also four 165 00:07:33,000 --> 00:07:31,090 planets with this one being on a very 166 00:07:35,640 --> 00:07:33,010 highly eccentric orbit I have a tiny one 167 00:07:37,270 --> 00:07:35,650 there and another two or three here even 168 00:07:39,700 --> 00:07:37,280 though I start with the same 169 00:07:41,200 --> 00:07:39,710 simulation but I just run it on a 170 00:07:42,100 --> 00:07:41,210 different computer I get a different 171 00:07:45,280 --> 00:07:42,110 outcome 172 00:07:48,430 --> 00:07:45,290 so our solar system is unique if I were 173 00:07:50,260 --> 00:07:48,440 to reset the clock back 4.6 billion 174 00:07:52,120 --> 00:07:50,270 years ago and I would run the same 175 00:07:54,850 --> 00:07:52,130 experiment again I would get a different 176 00:07:56,920 --> 00:07:54,860 outcome I will not get four in small 177 00:07:58,570 --> 00:07:56,930 planets in the in in the inner part and 178 00:08:00,970 --> 00:07:58,580 four gas giants at the end I will not 179 00:08:03,430 --> 00:08:00,980 get an earth I will not get a Venus its 180 00:08:05,710 --> 00:08:03,440 unique because every simulation is 181 00:08:09,700 --> 00:08:05,720 different and every system is unique and 182 00:08:11,760 --> 00:08:09,710 different in its own way so if we want 183 00:08:14,260 --> 00:08:11,770 to understand what the earth is made of 184 00:08:16,540 --> 00:08:14,270 right I mean if you take a sample of 185 00:08:18,820 --> 00:08:16,550 rock right how do you know what it's 186 00:08:20,920 --> 00:08:18,830 made of you can analyze it but is it a 187 00:08:24,820 --> 00:08:20,930 good idea of what is very deep inside 188 00:08:26,740 --> 00:08:24,830 the earth I'm not sure that we know but 189 00:08:28,600 --> 00:08:26,750 if I want to unanalyzed what the earth 190 00:08:30,610 --> 00:08:28,610 is made of I have to go very deep in the 191 00:08:32,230 --> 00:08:30,620 earth but I kind of drilled 2,000 192 00:08:37,810 --> 00:08:32,240 kilometers in the earth it's just not 193 00:08:39,909 --> 00:08:37,820 possible we can use a proxy there is 194 00:08:42,550 --> 00:08:39,919 material that is still flying around the 195 00:08:45,400 --> 00:08:42,560 solar system today which is raining on 196 00:08:49,120 --> 00:08:45,410 us every once in a while in meteorites 197 00:08:51,340 --> 00:08:49,130 we have stuff that sometimes falls from 198 00:08:53,740 --> 00:08:51,350 the sky onto the earth in the form of 199 00:08:55,600 --> 00:08:53,750 meteorites and what you can do is you 200 00:08:57,880 --> 00:08:55,610 can classify these meteorites with 201 00:09:00,100 --> 00:08:57,890 something called cosmochemistry where 202 00:09:03,790 --> 00:09:00,110 you analyze their composition you 203 00:09:05,620 --> 00:09:03,800 analyze their structure and self-worth 204 00:09:07,740 --> 00:09:05,630 and then you can classify them into 205 00:09:10,329 --> 00:09:07,750 different groups 206 00:09:12,430 --> 00:09:10,339 these primitive these meteorites are 207 00:09:15,760 --> 00:09:12,440 very old about the age of the solar 208 00:09:18,460 --> 00:09:15,770 system 4.5 4.6 billion years ago and 209 00:09:19,600 --> 00:09:18,470 they're very primitive so they have not 210 00:09:21,670 --> 00:09:19,610 been processed 211 00:09:23,860 --> 00:09:21,680 they basically formed there and they 212 00:09:28,000 --> 00:09:23,870 stayed there flying around the solar 213 00:09:30,730 --> 00:09:28,010 system for the past 4.6 billion years ok 214 00:09:33,550 --> 00:09:30,740 and we want to try to use these 215 00:09:36,970 --> 00:09:33,560 meteorites as an idea to understand what 216 00:09:38,590 --> 00:09:36,980 the earth is made of so the first group 217 00:09:42,400 --> 00:09:38,600 that we know are what is called 218 00:09:44,560 --> 00:09:42,410 enstatite chondrites enstatite chondrite 219 00:09:47,470 --> 00:09:44,570 they're very primitive they're mostly 220 00:09:49,369 --> 00:09:47,480 magnesium silicate so they have 221 00:09:51,169 --> 00:09:49,379 magnesium and silicon and oxygen 222 00:09:53,299 --> 00:09:51,179 in them and that is mostly what they're 223 00:09:56,839 --> 00:09:53,309 made of the Earth's mantle is also made 224 00:10:00,710 --> 00:09:56,849 of a lot of magnesium silicate they are 225 00:10:02,809 --> 00:10:00,720 also very reduced so in other words all 226 00:10:04,429 --> 00:10:02,819 the oxygen is essentially in the 227 00:10:10,779 --> 00:10:04,439 silicate there's no free oxygen 228 00:10:14,289 --> 00:10:10,789 available and they are very very dry in 229 00:10:17,029 --> 00:10:14,299 these meteorites there's almost no water 230 00:10:19,519 --> 00:10:17,039 there's almost no nitrogen there's 231 00:10:24,710 --> 00:10:19,529 almost no carbon and so forth they're 232 00:10:27,919 --> 00:10:24,720 very very dry which means that most 233 00:10:32,839 --> 00:10:27,929 likely these enstatite chondrites formed 234 00:10:35,629 --> 00:10:32,849 very close to the Sun there it is hot so 235 00:10:37,699 --> 00:10:35,639 the volatile material like water which 236 00:10:40,460 --> 00:10:37,709 evaporates at a hundred degrees or so 237 00:10:44,749 --> 00:10:40,470 forth will then be evaporated and you're 238 00:10:49,519 --> 00:10:44,759 only left with very dry rock which is 239 00:10:51,199 --> 00:10:49,529 what these enstatite chondrites are then 240 00:10:52,549 --> 00:10:51,209 we have another group called the 241 00:10:54,649 --> 00:10:52,559 ordinary chondrites 242 00:10:56,809 --> 00:10:54,659 these are called ordinary because they 243 00:11:00,049 --> 00:10:56,819 are the most common meteorite that falls 244 00:11:02,359 --> 00:11:00,059 from the sky the ordinary chondrite are 245 00:11:05,029 --> 00:11:02,369 mostly made of stone so they're not that 246 00:11:07,099 --> 00:11:05,039 hard compressed in magnesium silicate 247 00:11:08,809 --> 00:11:07,109 that you find in the enstatite congratz 248 00:11:11,269 --> 00:11:08,819 but they're more like stone so if you go 249 00:11:13,969 --> 00:11:11,279 to a beach or to a riverbed you pick up 250 00:11:15,710 --> 00:11:13,979 some stones you might get lucky and one 251 00:11:17,299 --> 00:11:15,720 of them is an ordinary chondrite you 252 00:11:19,519 --> 00:11:17,309 just wouldn't know because we don't have 253 00:11:22,189 --> 00:11:19,529 the expertise to be able to distinguish 254 00:11:24,199 --> 00:11:22,199 such rocks they're mostly made of 255 00:11:26,509 --> 00:11:24,209 olivine which is I think isn't is an 256 00:11:28,909 --> 00:11:26,519 iron silicate and so forth and they also 257 00:11:31,669 --> 00:11:28,919 have some metal in it that is oxidized 258 00:11:33,829 --> 00:11:31,679 so they have a higher fraction of oxygen 259 00:11:35,929 --> 00:11:33,839 in them then the enstatite congruous 260 00:11:39,590 --> 00:11:35,939 they have more metal in them as well 261 00:11:41,479 --> 00:11:39,600 and they also have more volatiles these 262 00:11:44,689 --> 00:11:41,489 have a little bit of water in them about 263 00:11:47,569 --> 00:11:44,699 the same amount as the earth house right 264 00:11:52,009 --> 00:11:47,579 so it's about you know one thousandth of 265 00:11:53,389 --> 00:11:52,019 the mass of these objects is water you 266 00:11:55,069 --> 00:11:53,399 just don't know it because it is 267 00:11:56,659 --> 00:11:55,079 embedded in the rock but it's there if 268 00:12:01,489 --> 00:11:56,669 you heat it up you'll find actually that 269 00:12:02,360 --> 00:12:01,499 there's water the third group is called 270 00:12:06,620 --> 00:12:02,370 carbonation 271 00:12:08,540 --> 00:12:06,630 chondrites these are thought to form 272 00:12:11,990 --> 00:12:08,550 very far from the Sun where it's very 273 00:12:14,060 --> 00:12:12,000 cold so they form in an environment 274 00:12:16,940 --> 00:12:14,070 where the temperature is about 50 275 00:12:21,290 --> 00:12:16,950 degrees above absolute zero so it's 276 00:12:23,120 --> 00:12:21,300 about 220 degrees below zero if you were 277 00:12:25,010 --> 00:12:23,130 to be out there in that temperature you 278 00:12:26,900 --> 00:12:25,020 would freeze solid in a few seconds 279 00:12:30,579 --> 00:12:26,910 that's how cold it is it's it's 280 00:12:33,260 --> 00:12:30,589 absolutely devastating for any any life 281 00:12:36,380 --> 00:12:33,270 but they form in there and because they 282 00:12:38,870 --> 00:12:36,390 form so cold they did not lose their 283 00:12:41,120 --> 00:12:38,880 volatiles they keep most of their water 284 00:12:45,620 --> 00:12:41,130 they keep their nitrogen they keep their 285 00:12:47,780 --> 00:12:45,630 carbon hence carbonaceous chondrites and 286 00:12:49,730 --> 00:12:47,790 some of the minerals have been altered 287 00:12:52,490 --> 00:12:49,740 because of water as you know for example 288 00:12:54,079 --> 00:12:52,500 water reacts with everything right you 289 00:12:55,970 --> 00:12:54,089 get milled you and so forth on your 290 00:12:58,550 --> 00:12:55,980 walls because its water reacting with 291 00:13:01,250 --> 00:12:58,560 something if you pour metal and water it 292 00:13:06,710 --> 00:13:01,260 oxidizes in particularly iron water is 293 00:13:09,380 --> 00:13:06,720 reactive water alters the compounds that 294 00:13:11,150 --> 00:13:09,390 exist within the meteorite and we know 295 00:13:12,949 --> 00:13:11,160 that there's water in there because if 296 00:13:15,199 --> 00:13:12,959 you analyze these meteorites you find 297 00:13:17,090 --> 00:13:15,209 water and you find the evidence of water 298 00:13:20,660 --> 00:13:17,100 in the minerals that have been altered 299 00:13:23,930 --> 00:13:20,670 by it so these are the guys that deliver 300 00:13:26,000 --> 00:13:23,940 the water to the Earth's okay these were 301 00:13:27,829 --> 00:13:26,010 the ones that brought us all the rain 302 00:13:31,400 --> 00:13:27,839 that we're getting every day in the 303 00:13:34,280 --> 00:13:31,410 weather right now so let us run a 304 00:13:36,170 --> 00:13:34,290 simulation now of Thresher planet 305 00:13:39,769 --> 00:13:36,180 formation these are the initial 306 00:13:42,019 --> 00:13:39,779 conditions so I have Jupiter here this 307 00:13:42,470 --> 00:13:42,029 is the distance to the Sun on this axis 308 00:13:44,870 --> 00:13:42,480 here 309 00:13:47,720 --> 00:13:44,880 Jupiter is a little about five the earth 310 00:13:49,610 --> 00:13:47,730 is at one right here and this is the 311 00:13:51,800 --> 00:13:49,620 eccentricity of the orbit it measures 312 00:13:53,870 --> 00:13:51,810 how elongated the orbit is so if the 313 00:13:55,400 --> 00:13:53,880 orbit is perfectly circular which I 314 00:13:58,160 --> 00:13:55,410 can't draw but you just have to imagine 315 00:14:00,560 --> 00:13:58,170 it then the eccentricity is zero and if 316 00:14:03,610 --> 00:14:00,570 I have a very elongated ellipse then the 317 00:14:07,280 --> 00:14:03,620 eccentricity is 0.8 or 0.9 or something 318 00:14:10,600 --> 00:14:07,290 okay enstatite chondrites which are the 319 00:14:12,860 --> 00:14:10,610 magnesium silicon rich bone-dry 320 00:14:15,500 --> 00:14:12,870 meteorites form here the ordinary 321 00:14:16,010 --> 00:14:15,510 chondrites which are in between a little 322 00:14:19,100 --> 00:14:16,020 bit of 323 00:14:20,930 --> 00:14:19,110 stone metal form in the middle and the 324 00:14:22,699 --> 00:14:20,940 carbonaceous chondrites which have all 325 00:14:24,590 --> 00:14:22,709 the water and all the carbon and the 326 00:14:27,019 --> 00:14:24,600 nitrogen and so forth in them all the 327 00:14:30,680 --> 00:14:27,029 stuff that life depends on they come 328 00:14:33,440 --> 00:14:30,690 from farther out so Jupiter is going to 329 00:14:35,630 --> 00:14:33,450 perturb all this stuff you see that I'm 330 00:14:38,060 --> 00:14:35,640 starting to form some planets right away 331 00:14:39,800 --> 00:14:38,070 and the growth is from the inside out I 332 00:14:42,650 --> 00:14:39,810 have some planets here but I don't have 333 00:14:44,690 --> 00:14:42,660 planets here yet that is because here it 334 00:14:47,210 --> 00:14:44,700 takes longer for the planets to accrete 335 00:14:49,610 --> 00:14:47,220 than it is here because here I go around 336 00:14:51,680 --> 00:14:49,620 the Sun in about half a year but here it 337 00:14:55,490 --> 00:14:51,690 takes me about three years which is a 338 00:14:58,519 --> 00:14:55,500 factor of six so here I form the planet 339 00:15:00,740 --> 00:14:58,529 six times faster than about here notice 340 00:15:02,840 --> 00:15:00,750 also that the color of these planets is 341 00:15:05,389 --> 00:15:02,850 changing in the beginning they're mostly 342 00:15:08,150 --> 00:15:05,399 red there we go so in the beginning 343 00:15:10,010 --> 00:15:08,160 they're mostly red because they accrete 344 00:15:12,920 --> 00:15:10,020 the stuff from the enstatite congratz 345 00:15:15,079 --> 00:15:12,930 but eventually this stuff the 346 00:15:17,480 --> 00:15:15,089 carbonaceous chondrites and the ordinary 347 00:15:19,250 --> 00:15:17,490 chondrite are being pushed inwards 348 00:15:23,240 --> 00:15:19,260 towards the terrestrial planets by the 349 00:15:25,310 --> 00:15:23,250 action of Jupiter okay so you see this 350 00:15:29,060 --> 00:15:25,320 one is now becoming orange because he is 351 00:15:30,860 --> 00:15:29,070 he is feeding off of material in this 352 00:15:33,590 --> 00:15:30,870 outer disc and these guys are now 353 00:15:36,620 --> 00:15:33,600 becoming green because you know the red 354 00:15:38,030 --> 00:15:36,630 is given some blue material and you end 355 00:15:40,010 --> 00:15:38,040 up then somewhere here in the middle 356 00:15:41,990 --> 00:15:40,020 right I start very dry 357 00:15:43,819 --> 00:15:42,000 I then have some of the blue material 358 00:15:45,620 --> 00:15:43,829 come in and I end up somewhere in the 359 00:15:47,540 --> 00:15:45,630 middle and that is where Earth's water 360 00:15:50,840 --> 00:15:47,550 is coming from I'll play it one more 361 00:15:52,819 --> 00:15:50,850 time so I start here I have local 362 00:15:55,220 --> 00:15:52,829 accretion some of the ordinary chondrite 363 00:15:58,100 --> 00:15:55,230 sand carbonaceous chondrites end up in 364 00:16:00,519 --> 00:15:58,110 the planets in the earth analog which is 365 00:16:03,290 --> 00:16:00,529 sitting roughly in this region here and 366 00:16:05,269 --> 00:16:03,300 because of Jupiter we are actually 367 00:16:07,550 --> 00:16:05,279 getting some of that water so it's only 368 00:16:10,430 --> 00:16:07,560 because of Jupiter if Jupiter was not 369 00:16:12,710 --> 00:16:10,440 there we wouldn't have as much water on 370 00:16:16,819 --> 00:16:12,720 the earths as we do today because there 371 00:16:19,430 --> 00:16:16,829 is no agent that is able to push the 372 00:16:21,440 --> 00:16:19,440 material that is farther away from the 373 00:16:27,230 --> 00:16:21,450 Sun these carbonaceous chondrites onto 374 00:16:29,070 --> 00:16:27,240 the earth okay so ultimately after the 375 00:16:31,950 --> 00:16:29,080 simulation is done 376 00:16:34,500 --> 00:16:31,960 what happens is that I end up mostly 377 00:16:37,410 --> 00:16:34,510 with three planets I know there are four 378 00:16:39,510 --> 00:16:37,420 but in the simulations you get four plus 379 00:16:42,180 --> 00:16:39,520 or minus one so sometimes I get three 380 00:16:46,320 --> 00:16:42,190 sometimes I get four sometimes I get 381 00:16:48,930 --> 00:16:46,330 five sometimes I even get six but on 382 00:16:51,510 --> 00:16:48,940 average we get about four in this case I 383 00:16:53,700 --> 00:16:51,520 get three so I get something that looks 384 00:16:55,260 --> 00:16:53,710 like Venus I get something that looks 385 00:16:56,850 --> 00:16:55,270 like Earth and I get something that 386 00:16:58,740 --> 00:16:56,860 looks a little bit like Mars it's a bit 387 00:16:59,250 --> 00:16:58,750 heavier than Mars but you know that's 388 00:17:01,530 --> 00:16:59,260 fine 389 00:17:03,930 --> 00:17:01,540 in another simulation it would be and I 390 00:17:06,030 --> 00:17:03,940 have some leftover material sitting here 391 00:17:08,660 --> 00:17:06,040 which is essentially not being cleared 392 00:17:12,240 --> 00:17:08,670 out by Jupiter and by the other planets 393 00:17:14,820 --> 00:17:12,250 but what is important is that even 394 00:17:16,829 --> 00:17:14,830 though in this region here very close to 395 00:17:20,340 --> 00:17:16,839 the Sun I started out with the red 396 00:17:22,560 --> 00:17:20,350 material the dry material because of 397 00:17:24,480 --> 00:17:22,570 Jupiter some of the blue material which 398 00:17:26,699 --> 00:17:24,490 was here the carbonaceous chondrites 399 00:17:28,980 --> 00:17:26,709 ended up in the planets and that's why 400 00:17:30,900 --> 00:17:28,990 they have this nice green bluish color 401 00:17:33,960 --> 00:17:30,910 which means that they have accreted some 402 00:17:36,600 --> 00:17:33,970 water and what you can also do is 403 00:17:39,180 --> 00:17:36,610 essentially you can say okay if I now 404 00:17:42,720 --> 00:17:39,190 analyze these planets I can determine 405 00:17:44,760 --> 00:17:42,730 how much material in the planets is from 406 00:17:48,090 --> 00:17:44,770 the enstatite group and the ordinary 407 00:17:50,250 --> 00:17:48,100 group and the carbonaceous group the 408 00:17:53,700 --> 00:17:50,260 last thing I want to discuss is the moon 409 00:17:56,970 --> 00:17:53,710 formation event so the earth has a large 410 00:17:59,400 --> 00:17:56,980 moon the moon is about one-and-a-half 411 00:18:03,270 --> 00:17:59,410 percent of the mass of the Earth is one 412 00:18:05,010 --> 00:18:03,280 over 81 to be precise it's pretty far 413 00:18:08,250 --> 00:18:05,020 from the earth it's about sixty times 414 00:18:11,280 --> 00:18:08,260 the radius of the earth from us so how 415 00:18:12,990 --> 00:18:11,290 did it get there because Mars has two 416 00:18:15,030 --> 00:18:13,000 small satellites but they're very very 417 00:18:16,950 --> 00:18:15,040 small there are only a few kilometers in 418 00:18:18,540 --> 00:18:16,960 size there they're tiny compared to both 419 00:18:21,180 --> 00:18:18,550 the planet and the moon itself but 420 00:18:23,850 --> 00:18:21,190 Earth's moon is very big venus has no 421 00:18:26,220 --> 00:18:23,860 moon either this mercury so how did the 422 00:18:29,630 --> 00:18:26,230 earth get its moon while we think 423 00:18:33,270 --> 00:18:29,640 through a giant impact so what we think 424 00:18:36,690 --> 00:18:33,280 happened was that the earth was sitting 425 00:18:38,940 --> 00:18:36,700 there going around the Sun and an object 426 00:18:41,520 --> 00:18:38,950 the size of Mars roughly the size of 427 00:18:45,740 --> 00:18:41,530 Mars struck the earth 428 00:18:48,660 --> 00:18:45,750 and then because of gravitational 429 00:18:51,870 --> 00:18:48,670 interaction between the material from 430 00:18:54,960 --> 00:18:51,880 the earth and from the impactor that 431 00:18:56,940 --> 00:18:54,970 then formed a disc around the earth here 432 00:18:59,490 --> 00:18:56,950 you have a blob of material which is 433 00:19:01,320 --> 00:18:59,500 spinning around the earth eventually it 434 00:19:03,980 --> 00:19:01,330 has another collision with the earth but 435 00:19:06,870 --> 00:19:03,990 you can see you form this sort of varies 436 00:19:09,660 --> 00:19:06,880 strung-out material that is orbiting the 437 00:19:12,180 --> 00:19:09,670 earth and you have a lot of other stuff 438 00:19:17,100 --> 00:19:12,190 that is just sitting around and spinning 439 00:19:20,100 --> 00:19:17,110 around the earth the idea is this object 440 00:19:22,620 --> 00:19:20,110 it came in it hit the earth and it came 441 00:19:25,380 --> 00:19:22,630 with such force that you basically tore 442 00:19:27,210 --> 00:19:25,390 it apart if you have a rock and you're 443 00:19:29,370 --> 00:19:27,220 trying to tear it apart it's very very 444 00:19:31,560 --> 00:19:29,380 difficult to do that but if you're 445 00:19:33,120 --> 00:19:31,570 somebody like Superman you might be able 446 00:19:37,320 --> 00:19:33,130 to tear it apart if you do it with 447 00:19:40,340 --> 00:19:37,330 enough force okay this thing comes in 448 00:19:43,080 --> 00:19:40,350 incredibly fast you know we're talking 449 00:19:45,870 --> 00:19:43,090 tens of thousands of kilometers per hour 450 00:19:48,990 --> 00:19:45,880 much much faster than any aeroplane is 451 00:19:51,870 --> 00:19:49,000 able to come to go on the earth it hits 452 00:19:53,760 --> 00:19:51,880 the earth at an angle and then it is 453 00:19:56,070 --> 00:19:53,770 kind of torn apart because of the 454 00:19:59,490 --> 00:19:56,080 gravitational forces as you can see here 455 00:20:02,580 --> 00:19:59,500 and you form this blob on both the earth 456 00:20:04,740 --> 00:20:02,590 that increases a lot of material from 457 00:20:07,590 --> 00:20:04,750 there you have material which is then 458 00:20:10,140 --> 00:20:07,600 spinning around the earth and eventually 459 00:20:12,110 --> 00:20:10,150 after a couple of days of that all that 460 00:20:15,920 --> 00:20:12,120 material going around the earth 461 00:20:20,880 --> 00:20:15,930 colliding with itself we form the moon 462 00:20:23,010 --> 00:20:20,890 just one moon and then because of tidal 463 00:20:24,750 --> 00:20:23,020 evolution the moon will be pushed away 464 00:20:26,700 --> 00:20:24,760 from the earth and after four billion 465 00:20:29,580 --> 00:20:26,710 years four and a half billion years that 466 00:20:31,530 --> 00:20:29,590 is where it is today tide tides we're 467 00:20:33,990 --> 00:20:31,540 all familiar with tides if you go to the 468 00:20:36,180 --> 00:20:34,000 beach right you have low and high tide 469 00:20:37,800 --> 00:20:36,190 that's because of the gravitational 470 00:20:39,630 --> 00:20:37,810 attraction of the moon but in of course 471 00:20:42,210 --> 00:20:39,640 when the moon was much closer to the 472 00:20:44,190 --> 00:20:42,220 earth the tides were much stronger so 473 00:20:47,070 --> 00:20:44,200 the tides from the earth push the moon 474 00:20:49,290 --> 00:20:47,080 away that slows down the rotation of the 475 00:20:51,420 --> 00:20:49,300 earth that's why we have a 24-hour day 476 00:20:53,320 --> 00:20:51,430 right now but a few billion years ago it 477 00:20:55,660 --> 00:20:53,330 was like 20 hours or even eight 478 00:20:57,670 --> 00:20:55,670 hours and the moon was closer it's being 479 00:21:01,560 --> 00:20:57,680 pushed away and we end up with the 480 00:21:05,740 --> 00:21:01,570 earth-moon system that we have today so 481 00:21:07,570 --> 00:21:05,750 this is my last slide a summary slide so 482 00:21:11,080 --> 00:21:07,580 earth is composed of a mixture of 483 00:21:13,630 --> 00:21:11,090 meteorite groups right we think that is 484 00:21:15,250 --> 00:21:13,640 what the current analysis of samples 485 00:21:18,400 --> 00:21:15,260 from the earth and meteorite groups 486 00:21:21,640 --> 00:21:18,410 seems to indicate Earth experienced a 487 00:21:23,890 --> 00:21:21,650 very violent and destructive impact 488 00:21:27,790 --> 00:21:23,900 about four and a half billion years ago 489 00:21:29,920 --> 00:21:27,800 which formed the moon also earth 490 00:21:31,660 --> 00:21:29,930 accreted a small amount of water from 491 00:21:32,680 --> 00:21:31,670 carbonaceous chondrites from the outer 492 00:21:36,130 --> 00:21:32,690 solar system 493 00:21:38,620 --> 00:21:36,140 I say a small amount now when I was 494 00:21:40,810 --> 00:21:38,630 living in Taipei before I came here I 495 00:21:43,180 --> 00:21:40,820 never thought that the earth was a dry 496 00:21:46,900 --> 00:21:43,190 planet because it rained almost every 497 00:21:48,910 --> 00:21:46,910 day ok even here in Tokyo this summer 498 00:21:50,860 --> 00:21:48,920 has been incredibly wet I think we've 499 00:21:53,260 --> 00:21:50,870 set a record for the amount of rain and 500 00:21:54,790 --> 00:21:53,270 when my colleagues tell me the earth is 501 00:21:58,000 --> 00:21:54,800 a dry planet I said have you been 502 00:22:00,130 --> 00:21:58,010 outside but it's true because most of 503 00:22:01,840 --> 00:22:00,140 the water is actually on the surface or 504 00:22:05,350 --> 00:22:01,850 at least half of it or something like 505 00:22:08,140 --> 00:22:05,360 that but it's still a very very very 506 00:22:10,060 --> 00:22:08,150 small amount of the total mass of the 507 00:22:14,080 --> 00:22:10,070 earth it just happens to be concentrated 508 00:22:15,910 --> 00:22:14,090 mostly on the surface if you run the 509 00:22:18,040 --> 00:22:15,920 miracle simulations you will find that 510 00:22:20,140 --> 00:22:18,050 the composition of Venus and Mars should 511 00:22:22,360 --> 00:22:20,150 be fairly similar to that of Earth ie 512 00:22:24,070 --> 00:22:22,370 it's made from the same material and you 513 00:22:26,740 --> 00:22:24,080 end up with roughly the same composition 514 00:22:28,390 --> 00:22:26,750 and all planets through forms through 515 00:22:30,730 --> 00:22:28,400 violent collisions as I showed you 516 00:22:32,800 --> 00:22:30,740 halfway through the talk you had all 517 00:22:35,560 --> 00:22:32,810 these these orbits which were spinning 518 00:22:37,690 --> 00:22:35,570 around and eventually stuff was secreted 519 00:22:40,810 --> 00:22:37,700 and you formed larger planets as the 520 00:22:44,010 --> 00:22:40,820 number of bodies decreased so our asura 521 00:22:46,960 --> 00:22:44,020 planets formed violently and rapidly 522 00:22:50,030 --> 00:22:46,970 from a mixture of material that gave us 523 00:22:55,800 --> 00:22:50,040 the earth as we know it today thank you 524 00:23:12,590 --> 00:22:55,810 [Applause] 525 00:23:12,600 --> 00:23:27,280 [Music]