1 00:00:19,070 --> 00:00:17,060 I want to thank the organizers for the 2 00:00:21,220 --> 00:00:19,080 invitation to present these 3 00:00:23,150 --> 00:00:21,230 interdisciplinary conferences are always 4 00:00:24,650 --> 00:00:23,160 fascinating and I always learn a lot I 5 00:00:26,599 --> 00:00:24,660 didn't realize when I accepted the 6 00:00:28,759 --> 00:00:26,609 invitation just how much of the audience 7 00:00:31,009 --> 00:00:28,769 would actually be biologists as opposed 8 00:00:33,200 --> 00:00:31,019 to earth scientists and I've tried to 9 00:00:34,910 --> 00:00:33,210 make my talk as general as possible but 10 00:00:36,319 --> 00:00:34,920 it's 11 gives these sorts of talks to 11 00:00:39,729 --> 00:00:36,329 these sorts of audiences that one 12 00:00:41,840 --> 00:00:39,739 realizes the assumptions that are 13 00:00:43,970 --> 00:00:41,850 present in one's field that one doesn't 14 00:00:46,040 --> 00:00:43,980 always know that the rest of the world 15 00:00:51,889 --> 00:00:46,050 doesn't know about so hopefully I will 16 00:00:56,150 --> 00:00:51,899 be able to overcome that that barrier so 17 00:00:58,700 --> 00:00:56,160 the point of today's talk or is in part 18 00:01:01,189 --> 00:00:58,710 that our planet has fortunately of 19 00:01:03,979 --> 00:01:01,199 course a sufficient amount of bio 20 00:01:05,960 --> 00:01:03,989 essential elements but it is interesting 21 00:01:07,670 --> 00:01:05,970 and probably not coincidental that the 22 00:01:09,260 --> 00:01:07,680 bio essential elements are also those 23 00:01:11,060 --> 00:01:09,270 elements that are essential for 24 00:01:14,000 --> 00:01:11,070 habitability and in fact really 25 00:01:17,240 --> 00:01:14,010 habitability is probably more germane to 26 00:01:19,609 --> 00:01:17,250 what we're going to be talking about or 27 00:01:21,620 --> 00:01:19,619 what I'm going to be talking about the 28 00:01:23,210 --> 00:01:21,630 most of the talk is actually going to be 29 00:01:24,380 --> 00:01:23,220 about carbon and nitrogen with a little 30 00:01:25,969 --> 00:01:24,390 bit of hydrogen I'm welcome to say 31 00:01:27,920 --> 00:01:25,979 essentially nothing about sulfur and 32 00:01:29,480 --> 00:01:27,930 phosphorus but almost everything that I 33 00:01:32,450 --> 00:01:29,490 say applies to all of these elements 34 00:01:35,090 --> 00:01:32,460 which is to say that the presence of 35 00:01:37,219 --> 00:01:35,100 these elements on the planet is a 36 00:01:39,740 --> 00:01:37,229 product actually not of accretion really 37 00:01:41,390 --> 00:01:39,750 but of a depletion right the amount of 38 00:01:42,920 --> 00:01:41,400 material that was available in the solar 39 00:01:45,080 --> 00:01:42,930 system of all these elements was far 40 00:01:47,179 --> 00:01:45,090 greater than actually we have on the 41 00:01:50,749 --> 00:01:47,189 surface and it's the fact that the 42 00:01:53,300 --> 00:01:50,759 planet managed to save a little bit over 43 00:01:58,700 --> 00:01:53,310 the course of those that depletion that 44 00:02:00,770 --> 00:01:58,710 we have a habitable planet so we this is 45 00:02:02,959 --> 00:02:00,780 of course the blue planet and everybody 46 00:02:04,940 --> 00:02:02,969 looks at it and probably those of you 47 00:02:06,499 --> 00:02:04,950 who live on the surface think that 48 00:02:08,589 --> 00:02:06,509 there's a great deal of water in fact 49 00:02:11,270 --> 00:02:08,599 the earth has very little water 50 00:02:13,430 --> 00:02:11,280 two-thirds of the surface of the of the 51 00:02:13,880 --> 00:02:13,440 planet is covered by water but if you 52 00:02:15,350 --> 00:02:13,890 average 53 00:02:19,190 --> 00:02:15,360 it over the mass of the planet it's 54 00:02:21,650 --> 00:02:19,200 about 300 parts per million the for the 55 00:02:24,199 --> 00:02:21,660 most part this is a very very dry object 56 00:02:26,270 --> 00:02:24,209 but not totally dry if it were totally 57 00:02:27,770 --> 00:02:26,280 dry of course then we would be mercury 58 00:02:28,970 --> 00:02:27,780 or the moon or something like that and 59 00:02:32,780 --> 00:02:28,980 we wouldn't be having these 60 00:02:34,640 --> 00:02:32,790 conversations we wouldn't be here this 61 00:02:38,420 --> 00:02:34,650 the same is true actually even more so 62 00:02:41,300 --> 00:02:38,430 for carbon and nitrogen the supply that 63 00:02:43,550 --> 00:02:41,310 we have is sufficient but it is actually 64 00:02:45,640 --> 00:02:43,560 a very very small fraction of what was 65 00:02:50,240 --> 00:02:45,650 originally available in the solar system 66 00:02:52,250 --> 00:02:50,250 oops so this is a plot of the abundance 67 00:02:53,630 --> 00:02:52,260 of elements in the solar system or the 68 00:02:57,160 --> 00:02:53,640 abundance of the elements in the Sun 69 00:02:59,360 --> 00:02:57,170 it's essentially the same thing and 70 00:03:01,310 --> 00:02:59,370 normalized to the amount of silicon so 71 00:03:03,440 --> 00:03:01,320 10 to the 6th would be an equal amount 72 00:03:05,600 --> 00:03:03,450 of silicon and whatever element that's 73 00:03:08,449 --> 00:03:05,610 plotted here and it's of course a log 74 00:03:10,729 --> 00:03:08,459 scale and nitrogen isn't noted here but 75 00:03:12,170 --> 00:03:10,739 it's there the in fact the availability 76 00:03:15,080 --> 00:03:12,180 of the essential elements hydrogen 77 00:03:16,550 --> 00:03:15,090 carbon nitrogen oxygen in the solar 78 00:03:18,770 --> 00:03:16,560 system is far greater than that of 79 00:03:22,100 --> 00:03:18,780 silicon there's more of that stuff than 80 00:03:23,449 --> 00:03:22,110 there is rock if our planet was made of 81 00:03:27,410 --> 00:03:23,459 that then we would be something like 82 00:03:30,020 --> 00:03:27,420 Jupiter or or or or a star and we 83 00:03:32,990 --> 00:03:30,030 wouldn't have a habitable terrestrial 84 00:03:35,600 --> 00:03:33,000 planet so the initial availability is 85 00:03:36,949 --> 00:03:35,610 not the problem in fact it's going to or 86 00:03:38,780 --> 00:03:36,959 we're going to see that it's going to be 87 00:03:40,789 --> 00:03:38,790 the opposite the process of planet 88 00:03:44,930 --> 00:03:40,799 formation is a process of loss of these 89 00:03:46,610 --> 00:03:44,940 elements and saving just enough now what 90 00:03:48,289 --> 00:03:46,620 the problem of course is is I don't 91 00:03:51,740 --> 00:03:48,299 really know what just enough is and I 92 00:03:53,660 --> 00:03:51,750 maybe some of you do but it's clearly 93 00:03:55,819 --> 00:03:53,670 something similar to what we have within 94 00:03:59,240 --> 00:03:55,829 a couple orders of magnitude right Earth 95 00:04:01,280 --> 00:03:59,250 has just enough but what the band is too 96 00:04:04,660 --> 00:04:01,290 little or less than Earth or greater 97 00:04:07,220 --> 00:04:04,670 than Earth is I think an open question 98 00:04:08,840 --> 00:04:07,230 so here's another way of looking at this 99 00:04:10,130 --> 00:04:08,850 on a mug to use this slide again and 100 00:04:12,620 --> 00:04:10,140 again despite the fact that it's a 101 00:04:14,180 --> 00:04:12,630 little bit fuzzy so this is the 102 00:04:15,860 --> 00:04:14,190 abundance of carbon and this is the 103 00:04:18,199 --> 00:04:15,870 abundance of nitrogen relative to that 104 00:04:21,380 --> 00:04:18,209 of silicon in various solar system 105 00:04:23,570 --> 00:04:21,390 materials starting from the Sun or we 106 00:04:25,310 --> 00:04:23,580 could also look at beyond our solar 107 00:04:27,470 --> 00:04:25,320 system to the interstellar medium and 108 00:04:30,410 --> 00:04:27,480 see great abundances of carbon 109 00:04:32,630 --> 00:04:30,420 also nitrogen icy bodies 110 00:04:35,840 --> 00:04:32,640 undifferentiated bodies also have a 111 00:04:37,610 --> 00:04:35,850 great deal primitive building blocks of 112 00:04:39,830 --> 00:04:37,620 planets as represented by chondritic 113 00:04:41,570 --> 00:04:39,840 meteorites have certain proportions and 114 00:04:44,270 --> 00:04:41,580 then finally we get to earth and you'll 115 00:04:46,250 --> 00:04:44,280 notice that the scale on here is 116 00:04:48,620 --> 00:04:46,260 tremendous so if you want to think about 117 00:04:50,300 --> 00:04:48,630 it this way the earth has something like 118 00:04:52,880 --> 00:04:50,310 10 to the minus four of the original 119 00:04:54,950 --> 00:04:52,890 potential supply of carbon and about 10 120 00:04:57,770 --> 00:04:54,960 to the minus 5 of the original potential 121 00:04:59,990 --> 00:04:57,780 supply of nitrogen so the process of 122 00:05:02,300 --> 00:05:00,000 planet formation or actually first of 123 00:05:05,480 --> 00:05:02,310 all the process of rock formation going 124 00:05:07,340 --> 00:05:05,490 from dust and gas to Rakeem it simple 125 00:05:08,660 --> 00:05:07,350 rocky materials and then going from 126 00:05:11,090 --> 00:05:08,670 those simple rocky materials to 127 00:05:14,090 --> 00:05:11,100 assembling planets is a process of loss 128 00:05:16,580 --> 00:05:14,100 and the key of course is is that the 129 00:05:19,310 --> 00:05:16,590 planet of interest the one that becomes 130 00:05:21,320 --> 00:05:19,320 the habitable planet it is the one that 131 00:05:23,060 --> 00:05:21,330 loses just the right amount doesn't lose 132 00:05:24,860 --> 00:05:23,070 too much because if you can lose four 133 00:05:27,140 --> 00:05:24,870 orders of magnitude why can't you lose 134 00:05:28,430 --> 00:05:27,150 six orders of magnitude or seven orders 135 00:05:32,630 --> 00:05:28,440 of magnitude that's of course what 136 00:05:34,820 --> 00:05:32,640 mercury probably did and so the loss may 137 00:05:38,270 --> 00:05:34,830 must be just the right amount and each 138 00:05:40,670 --> 00:05:38,280 of these processes from going from going 139 00:05:44,210 --> 00:05:40,680 from gas and dust to rocks is a lost 140 00:05:46,730 --> 00:05:44,220 process in the early solar nebula and 141 00:05:48,910 --> 00:05:46,740 then going from rocks to planetary 142 00:05:53,750 --> 00:05:48,920 differentiation is a second stage of 143 00:05:55,040 --> 00:05:53,760 loss so one way to think about it it's 144 00:05:58,130 --> 00:05:55,050 actually a bit of a deceptive way to 145 00:05:59,990 --> 00:05:58,140 think about it is that that the 146 00:06:02,420 --> 00:06:00,000 habitability of our planet depends on 147 00:06:04,580 --> 00:06:02,430 the amount of co2 on our atmosphere and 148 00:06:07,010 --> 00:06:04,590 of course our location relative to the 149 00:06:08,840 --> 00:06:07,020 Sun and we see tremendous variability 150 00:06:13,880 --> 00:06:08,850 just amongst our nearest neighbors 151 00:06:16,160 --> 00:06:13,890 between Venus Earth and Mars and this is 152 00:06:19,340 --> 00:06:16,170 at least apparently on the surface too 153 00:06:20,900 --> 00:06:19,350 much right it it isn't necessarily so 154 00:06:22,490 --> 00:06:20,910 that Venus has too much carbon but 155 00:06:24,950 --> 00:06:22,500 certainly Venus has too much carbon on 156 00:06:27,020 --> 00:06:24,960 its surface to be habitable and Mars has 157 00:06:28,880 --> 00:06:27,030 too little for its place in the solar 158 00:06:30,440 --> 00:06:28,890 system to be habitable at the moment 159 00:06:33,830 --> 00:06:30,450 although that may not have been true 160 00:06:35,600 --> 00:06:33,840 early in in solar system history one 161 00:06:37,700 --> 00:06:35,610 reason that this is deceptive is this is 162 00:06:39,530 --> 00:06:37,710 just a service inventory and in fact 163 00:06:41,270 --> 00:06:39,540 it's not just the surface inventory 164 00:06:42,680 --> 00:06:41,280 that's important it's also the 165 00:06:47,180 --> 00:06:42,690 inventory in the interior of a 166 00:06:49,310 --> 00:06:47,190 terrestrial planet so another way to 167 00:06:51,350 --> 00:06:49,320 look at this this plot or if plot 168 00:06:53,930 --> 00:06:51,360 similar to this was shown yesterday the 169 00:06:56,210 --> 00:06:53,940 so-called habitable zone which depends 170 00:06:58,220 --> 00:06:56,220 of course on the on this stellar 171 00:07:00,950 --> 00:06:58,230 luminosity of the particular star and 172 00:07:03,490 --> 00:07:00,960 the location of the planet relative to 173 00:07:07,550 --> 00:07:03,500 the star and we have Venus Earth and 174 00:07:10,490 --> 00:07:07,560 Mars there this plot of habitability is 175 00:07:12,140 --> 00:07:10,500 is really dependent on some assumptions 176 00:07:15,350 --> 00:07:12,150 about the availability of a greenhouse 177 00:07:18,080 --> 00:07:15,360 gas right it for example this line here 178 00:07:20,900 --> 00:07:18,090 is defined by the maximum saturation of 179 00:07:24,170 --> 00:07:20,910 co2 something like 40 atmospheres of co2 180 00:07:25,970 --> 00:07:24,180 I think if i recall correctly but that 181 00:07:27,440 --> 00:07:25,980 assumes that 40 atmospheres of co2 are 182 00:07:29,390 --> 00:07:27,450 available to the planet which actually 183 00:07:31,610 --> 00:07:29,400 is a fair amount of carbon considering 184 00:07:33,140 --> 00:07:31,620 that we have these hierarchies of loss 185 00:07:35,870 --> 00:07:33,150 that we don't know how far they're going 186 00:07:38,409 --> 00:07:35,880 to go so it isn't just a question of the 187 00:07:40,940 --> 00:07:38,419 solar luminosity in the location within 188 00:07:43,040 --> 00:07:40,950 within the step within the particular 189 00:07:44,900 --> 00:07:43,050 solar system but also the availability 190 00:07:49,040 --> 00:07:44,910 or the retention you can think about it 191 00:07:52,040 --> 00:07:49,050 either way of the of the greenhouse 192 00:07:54,560 --> 00:07:52,050 gases that allow for this band of 193 00:08:03,230 --> 00:07:54,570 habitability which of course is created 194 00:08:07,210 --> 00:08:03,240 by greenhouse gases so starting here and 195 00:08:10,550 --> 00:08:07,220 going to hear I have plotted the Earth's 196 00:08:12,680 --> 00:08:10,560 BSE this is where the earth scientist 197 00:08:15,140 --> 00:08:12,690 has to explain to the biologists this is 198 00:08:16,640 --> 00:08:15,150 simple bulk silicate earth right it's 199 00:08:18,350 --> 00:08:16,650 basically all of the earth except for 200 00:08:20,659 --> 00:08:18,360 its metallic portion and I have a 201 00:08:22,250 --> 00:08:20,669 certain concentration here and if I were 202 00:08:25,190 --> 00:08:22,260 to take that surface inventory that I 203 00:08:27,110 --> 00:08:25,200 showed you before the 400 ppm co2 in the 204 00:08:29,360 --> 00:08:27,120 atmosphere it wouldn't be nearly that or 205 00:08:31,219 --> 00:08:29,370 the one bar or point eight bars of 206 00:08:33,950 --> 00:08:31,229 nitrogen it wouldn't be nearly that most 207 00:08:35,899 --> 00:08:33,960 of this BS e is actually in the interior 208 00:08:39,820 --> 00:08:35,909 most of the volatiles and the earth 209 00:08:44,840 --> 00:08:43,250 so the right amount one thing will 210 00:08:46,579 --> 00:08:44,850 return to this in a moment but the right 211 00:08:49,730 --> 00:08:46,589 amount is not just the surface reservoir 212 00:08:51,230 --> 00:08:49,740 it's the reservoir in the battery if you 213 00:08:53,990 --> 00:08:51,240 will in the interior that replenishes 214 00:08:55,070 --> 00:08:54,000 the surface reservoir and also modulate 215 00:09:01,490 --> 00:08:55,080 the 216 00:09:06,320 --> 00:09:01,500 amount I don't know perhaps some of you 217 00:09:08,360 --> 00:09:06,330 do know it had better be the light 218 00:09:09,770 --> 00:09:08,370 amount earth must plot within the band 219 00:09:13,790 --> 00:09:09,780 of the right amount that's about all I 220 00:09:17,390 --> 00:09:13,800 dunno and of course it surely depends on 221 00:09:22,970 --> 00:09:17,400 things like radial distance and it is a 222 00:09:24,950 --> 00:09:22,980 product not of gain but of loss okay 223 00:09:26,390 --> 00:09:24,960 this plot comes again and again but I 224 00:09:31,550 --> 00:09:26,400 think I've already explained what i need 225 00:09:33,290 --> 00:09:31,560 to do for this particular whoops so yes 226 00:09:34,790 --> 00:09:33,300 alright so the point that I was 227 00:09:35,960 --> 00:09:34,800 beginning to make a moment ago that I'm 228 00:09:38,000 --> 00:09:35,970 going to return to is that this 229 00:09:41,000 --> 00:09:38,010 concentration here is not the 230 00:09:43,250 --> 00:09:41,010 concentration in the atmosphere or even 231 00:09:44,870 --> 00:09:43,260 on the surface but in the entire portion 232 00:09:48,920 --> 00:09:44,880 of the planet apart from that in the 233 00:09:51,890 --> 00:09:48,930 core there we go okay so just as an 234 00:09:53,750 --> 00:09:51,900 example for carbon and there are many 235 00:09:55,730 --> 00:09:53,760 different compilations like this I just 236 00:09:57,800 --> 00:09:55,740 happened to take this one because it's 237 00:09:59,990 --> 00:09:57,810 graphically interesting right the amount 238 00:10:01,880 --> 00:10:00,000 of carbon in the atmosphere is dwarfed 239 00:10:03,770 --> 00:10:01,890 by that which is in the oceans which is 240 00:10:06,740 --> 00:10:03,780 in turn dwarfed by that which is on the 241 00:10:10,340 --> 00:10:06,750 surface rocks such as lime stones and 242 00:10:12,050 --> 00:10:10,350 and so on which is in turn a small 243 00:10:16,400 --> 00:10:12,060 portion compared to that which is in the 244 00:10:19,610 --> 00:10:16,410 interior and what we find is first of 245 00:10:22,010 --> 00:10:19,620 all that um that that is that is this 246 00:10:23,470 --> 00:10:22,020 amount that the planet has and that that 247 00:10:26,840 --> 00:10:23,480 the planet apparently needs to operate 248 00:10:28,810 --> 00:10:26,850 and and and second of all that it's the 249 00:10:30,920 --> 00:10:28,820 exchanges between these which are 250 00:10:32,450 --> 00:10:30,930 intrinsically linked to plate tectonics 251 00:10:36,530 --> 00:10:32,460 which I think mark jelinek is going to 252 00:10:38,930 --> 00:10:36,540 talk about tomorrow that that allow for 253 00:10:40,580 --> 00:10:38,940 not just the beginning of a habitable 254 00:10:43,180 --> 00:10:40,590 planet but the steadiness of that 255 00:10:49,220 --> 00:10:43,190 habitable planet through various 256 00:10:54,720 --> 00:10:49,230 perturbations and in catastrophes so 257 00:10:58,199 --> 00:10:54,730 this whoops a little bit of 258 00:10:59,310 --> 00:10:58,209 slow there we go okay so this is for 259 00:11:01,290 --> 00:10:59,320 carbon I'm not going to show u 260 00:11:03,329 --> 00:11:01,300 equivalent maps for nitrogen and water 261 00:11:04,740 --> 00:11:03,339 but just a summary and actually we can 262 00:11:06,030 --> 00:11:04,750 skip the bottom portion of this plot 263 00:11:08,910 --> 00:11:06,040 just look at the top portion of this 264 00:11:12,240 --> 00:11:08,920 plot in fact for carbon water and 265 00:11:14,819 --> 00:11:12,250 nitrogen the reservoirs in the in the 266 00:11:16,620 --> 00:11:14,829 planet are not entirely on the surface 267 00:11:19,410 --> 00:11:16,630 its carbon that has the greatest amount 268 00:11:22,680 --> 00:11:19,420 of interior reservoir the amount of 269 00:11:24,569 --> 00:11:22,690 carbon in Earth's mantle is greatly 270 00:11:27,019 --> 00:11:24,579 exceeds that on the surface whereas 271 00:11:33,600 --> 00:11:27,029 those for water and nitrogen are 272 00:11:35,810 --> 00:11:33,610 approximately comparable I this is an 273 00:11:38,009 --> 00:11:35,820 example of something that you probably 274 00:11:40,740 --> 00:11:38,019 don't want me to step through in great 275 00:11:42,689 --> 00:11:40,750 detail the reason that i have this is 276 00:11:44,250 --> 00:11:42,699 that you may wonder how it is that we 277 00:11:45,930 --> 00:11:44,260 know what the concentrations of these 278 00:11:47,550 --> 00:11:45,940 elements are in the interior and the 279 00:11:49,170 --> 00:11:47,560 reason that we think we know it is 280 00:11:51,000 --> 00:11:49,180 because we have samples of the interior 281 00:11:53,670 --> 00:11:51,010 that comes from erupted volcanic 282 00:11:57,120 --> 00:11:53,680 products the salts that have preserved 283 00:11:59,639 --> 00:11:57,130 in them undie gas samples of melt that 284 00:12:01,290 --> 00:11:59,649 was made in the interior and we can look 285 00:12:04,439 --> 00:12:01,300 at the concentrations of things like 286 00:12:06,980 --> 00:12:04,449 carbon or water in these melts we can 287 00:12:10,710 --> 00:12:06,990 ratio them to trace elements such as 288 00:12:12,449 --> 00:12:10,720 barium niobium cerium and so on which we 289 00:12:13,949 --> 00:12:12,459 know very well the concentration of 290 00:12:15,629 --> 00:12:13,959 these in the earth because they're very 291 00:12:17,790 --> 00:12:15,639 steady their refractory lyssa file 292 00:12:19,860 --> 00:12:17,800 elements that are very very little 293 00:12:22,309 --> 00:12:19,870 between planetary objects and meteorites 294 00:12:25,620 --> 00:12:22,319 and so forth and from these ratios of 295 00:12:28,860 --> 00:12:25,630 carbon deberia more or water to cerium 296 00:12:31,139 --> 00:12:28,870 we can infer from these undie gas 297 00:12:35,819 --> 00:12:31,149 inclusions what the concentrations are 298 00:12:37,650 --> 00:12:35,829 in the interior and the reason that it's 299 00:12:40,230 --> 00:12:37,660 important or one of the reasons that 300 00:12:43,400 --> 00:12:40,240 it's important is not only are the these 301 00:12:46,019 --> 00:12:43,410 elements important for maintaining the 302 00:12:47,790 --> 00:12:46,029 our climate and and the atmosphere and 303 00:12:52,199 --> 00:12:47,800 so forth but they're also important for 304 00:12:55,500 --> 00:12:52,209 maintaining the dynamics of the interior 305 00:12:59,040 --> 00:12:55,510 so on the left here we have two 306 00:13:00,930 --> 00:12:59,050 different geodynamic models of how the 307 00:13:02,639 --> 00:13:00,940 strength of the lithosphere is affected 308 00:13:04,559 --> 00:13:02,649 either in the case where there's no 309 00:13:06,900 --> 00:13:04,569 water in the interior or in the cases 310 00:13:07,560 --> 00:13:06,910 where there is water in the material 311 00:13:09,690 --> 00:13:07,570 water 312 00:13:11,700 --> 00:13:09,700 greatly weakens rocks that allow strain 313 00:13:13,860 --> 00:13:11,710 localization it allows for the 314 00:13:16,620 --> 00:13:13,870 lithosphere the strong outer layer of 315 00:13:20,730 --> 00:13:16,630 the earth to break and that breakage is 316 00:13:24,150 --> 00:13:20,740 in fact the allowing plate tectonics to 317 00:13:25,680 --> 00:13:24,160 occur so without some amounts of 318 00:13:27,090 --> 00:13:25,690 volatile zin the interior we don't have 319 00:13:30,510 --> 00:13:27,100 plate tectonics and we don't have the 320 00:13:32,810 --> 00:13:30,520 recycling mechanisms that that allow for 321 00:13:35,640 --> 00:13:32,820 the planet to maintain its steady 322 00:13:37,470 --> 00:13:35,650 interior and exterior dynamics actually 323 00:13:39,830 --> 00:13:37,480 these two plots that make the same point 324 00:13:42,210 --> 00:13:39,840 so I don't really relate with them a 325 00:13:43,890 --> 00:13:42,220 really great example of why this is 326 00:13:46,560 --> 00:13:43,900 important is every once in a while of 327 00:13:49,170 --> 00:13:46,570 course the in the history of a planet 328 00:13:52,050 --> 00:13:49,180 there is a tendency for the climate to 329 00:13:53,910 --> 00:13:52,060 go haywire the most extreme examples of 330 00:13:56,760 --> 00:13:53,920 these are the so-called snowball earth 331 00:13:58,920 --> 00:13:56,770 events which happened twice in the 332 00:14:02,580 --> 00:13:58,930 Precambrian or at least twice in the 333 00:14:04,080 --> 00:14:02,590 Precambrian where the where the where 334 00:14:07,110 --> 00:14:04,090 the climate ran away and became 335 00:14:08,880 --> 00:14:07,120 effectively sealed off and the way that 336 00:14:11,520 --> 00:14:08,890 the planet escaped the snowball earth 337 00:14:13,260 --> 00:14:11,530 was the fact that even though weathering 338 00:14:16,140 --> 00:14:13,270 reactions shut down and all sorts of 339 00:14:17,640 --> 00:14:16,150 other reactions shut down so that so 340 00:14:19,200 --> 00:14:17,650 that the plan seemingly became 341 00:14:21,860 --> 00:14:19,210 permanently called the continued 342 00:14:24,780 --> 00:14:21,870 outgassing of co2 from the interior 343 00:14:26,970 --> 00:14:24,790 renewed the greenhouse and and and 344 00:14:29,970 --> 00:14:26,980 brought the earth out of the snowball 345 00:14:32,190 --> 00:14:29,980 event so in effect the interior 346 00:14:35,310 --> 00:14:32,200 volatiles allow for dynamics that 347 00:14:38,340 --> 00:14:35,320 recycle nutrients and so forth and they 348 00:14:41,790 --> 00:14:38,350 also serve as a battery to maintain the 349 00:14:47,670 --> 00:14:41,800 steadiness or the reasonable steadiness 350 00:14:49,290 --> 00:14:47,680 of of the planet's climate so I again I 351 00:14:51,630 --> 00:14:49,300 think Mark jelinek is going to talk more 352 00:14:53,780 --> 00:14:51,640 about this tomorrow so I won't say too 353 00:14:56,910 --> 00:14:53,790 much more but all of these elements 354 00:14:59,160 --> 00:14:56,920 carbon hydrogen nitrogen sulfur 355 00:15:00,990 --> 00:14:59,170 phosphorus are cycling from the interior 356 00:15:03,150 --> 00:15:01,000 to the exterior if the essential 357 00:15:06,270 --> 00:15:03,160 nutrients are being renewed this way the 358 00:15:09,450 --> 00:15:06,280 climate is being held more or less 359 00:15:11,640 --> 00:15:09,460 steady this way and so these volatile 360 00:15:16,830 --> 00:15:11,650 cycles are crucial to the habitability 361 00:15:20,970 --> 00:15:16,840 of the planet okay so how did we get 362 00:15:22,710 --> 00:15:20,980 here we got here starting from here into 363 00:15:24,569 --> 00:15:22,720 sets of processes one would be the 364 00:15:26,100 --> 00:15:24,579 formation of the rocks and then the 365 00:15:30,740 --> 00:15:26,110 other would be the formation from the 366 00:15:35,730 --> 00:15:30,750 rocks of the larger planetary bodies and 367 00:15:37,620 --> 00:15:35,740 so two essential kinds of primitive 368 00:15:39,960 --> 00:15:37,630 meteorites enstatite chondrites and 369 00:15:43,620 --> 00:15:39,970 carbonaceous chondrites illustrated here 370 00:15:48,240 --> 00:15:43,630 and here are our materials that been 371 00:15:50,400 --> 00:15:48,250 assembled from bits of dust and so on 372 00:15:51,689 --> 00:15:50,410 and the answer tight chondrites are 373 00:15:53,280 --> 00:15:51,699 generally thought to be inner solar 374 00:15:55,410 --> 00:15:53,290 system objects they're generally thought 375 00:15:57,600 --> 00:15:55,420 to be quite dry and volatile poor 376 00:16:00,240 --> 00:15:57,610 whereas the carbonaceous chondrites are 377 00:16:01,710 --> 00:16:00,250 thought to be outer not outer but middle 378 00:16:03,210 --> 00:16:01,720 solar system objects the outer solar 379 00:16:06,060 --> 00:16:03,220 system objects would be comments I 380 00:16:08,280 --> 00:16:06,070 suppose and the carbonaceous chondrites 381 00:16:10,319 --> 00:16:08,290 are thought to be rich in volatiles 382 00:16:11,850 --> 00:16:10,329 because they formed outside of the snow 383 00:16:13,860 --> 00:16:11,860 line where there were lots of Isis 384 00:16:15,300 --> 00:16:13,870 available to react with the rocks and 385 00:16:18,000 --> 00:16:15,310 the answer type chondrites are thought 386 00:16:19,439 --> 00:16:18,010 to be volatile depleted but if you look 387 00:16:21,420 --> 00:16:19,449 on this plot you'll see that the 388 00:16:23,610 --> 00:16:21,430 enstatite chondrites have orders of 389 00:16:26,100 --> 00:16:23,620 magnitude more carbon and nitrogen than 390 00:16:28,050 --> 00:16:26,110 that then our planet so it isn't just 391 00:16:30,030 --> 00:16:28,060 the rock formation in the interior of 392 00:16:31,769 --> 00:16:30,040 the solar system that depletes the 393 00:16:35,100 --> 00:16:31,779 system the process of planet formation 394 00:16:37,439 --> 00:16:35,110 is also a depletion process B op beyond 395 00:16:38,970 --> 00:16:37,449 this how is it that the answer type 396 00:16:40,379 --> 00:16:38,980 contracts have so much carbon and 397 00:16:43,650 --> 00:16:40,389 nitrogen when they formed in the inner 398 00:16:46,319 --> 00:16:43,660 solar system good question so here's a 399 00:16:49,139 --> 00:16:46,329 sort of a and I don't think we know the 400 00:16:52,920 --> 00:16:49,149 answer to it actually so here's sort of 401 00:16:54,840 --> 00:16:52,930 a map of broadly speaking in the outer 402 00:16:56,670 --> 00:16:54,850 solar system beyond the frost line where 403 00:16:59,670 --> 00:16:56,680 there are lots of Isis the carbonaceous 404 00:17:03,900 --> 00:16:59,680 chondrites and other icy bodies form and 405 00:17:06,449 --> 00:17:03,910 it is possible for rocks to react with 406 00:17:08,939 --> 00:17:06,459 water and carbon Isis and so forth and 407 00:17:10,439 --> 00:17:08,949 to gain volatiles that can later be 408 00:17:12,240 --> 00:17:10,449 delivered to the interior of the solar 409 00:17:14,549 --> 00:17:12,250 system but also here where it's supposed 410 00:17:17,400 --> 00:17:14,559 to be too hot too hot for Isis to form 411 00:17:20,939 --> 00:17:17,410 the enstatite chondrites gain carbon and 412 00:17:23,970 --> 00:17:20,949 nitrogen there are two answers to this 413 00:17:26,039 --> 00:17:23,980 one well the two partial answers to this 414 00:17:28,409 --> 00:17:26,049 one is is that the carbon and nitrogen 415 00:17:30,240 --> 00:17:28,419 are actually probably not carried in 416 00:17:32,070 --> 00:17:30,250 Isis but they're probably carried in 417 00:17:34,320 --> 00:17:32,080 much more refractory materials 418 00:17:34,860 --> 00:17:34,330 refractory organics that form not by 419 00:17:39,120 --> 00:17:34,870 equilibria 420 00:17:42,750 --> 00:17:39,130 reactions but by by by various kinetic 421 00:17:44,970 --> 00:17:42,760 processes this plot just to focus on 422 00:17:47,490 --> 00:17:44,980 this plot here this is a kinetic model 423 00:17:48,990 --> 00:17:47,500 by Bergen at all a group that i'm 424 00:17:52,440 --> 00:17:49,000 involved with from the University of 425 00:17:54,450 --> 00:17:52,450 Michigan showing the amount of carbon as 426 00:17:56,040 --> 00:17:54,460 a function of radial distance that is 427 00:17:59,130 --> 00:17:56,050 actually contained within refractory 428 00:18:00,450 --> 00:17:59,140 carbon there are probably many such 429 00:18:04,799 --> 00:18:00,460 compounds but mostly in these 430 00:18:08,340 --> 00:18:04,809 calculations these are pahs and so first 431 00:18:09,960 --> 00:18:08,350 of all out here the temperatures of 432 00:18:11,490 --> 00:18:09,970 condensation temperatures of these 433 00:18:14,060 --> 00:18:11,500 refractory organics effectively are 434 00:18:16,590 --> 00:18:14,070 hundreds of degrees greater than that of 435 00:18:18,930 --> 00:18:16,600 water right so first of all they may 436 00:18:21,150 --> 00:18:18,940 form closer into the solar system and 437 00:18:23,730 --> 00:18:21,160 then second of all also radio mixing 438 00:18:25,650 --> 00:18:23,740 between interior and exterior or 439 00:18:27,600 --> 00:18:25,660 exterior and interior portions of the 440 00:18:31,980 --> 00:18:27,610 solar system may bring such materials 441 00:18:38,160 --> 00:18:31,990 into the inner solar system so that gets 442 00:18:40,169 --> 00:18:38,170 us more or less to to hear but also it's 443 00:18:43,350 --> 00:18:40,179 important I or I just mentioned radial 444 00:18:45,299 --> 00:18:43,360 mixing water is probably better studied 445 00:18:50,340 --> 00:18:45,309 than carbon and nitrogen we already know 446 00:18:52,049 --> 00:18:50,350 that if we posit that the early solar 447 00:18:56,700 --> 00:18:52,059 system consisted of essentially dry 448 00:18:58,830 --> 00:18:56,710 object in the interior and icy bodies in 449 00:19:00,960 --> 00:18:58,840 the exterior that just the dynamics of 450 00:19:05,190 --> 00:19:00,970 accretion lead to radial mixing which 451 00:19:07,650 --> 00:19:05,200 bring the fair portion of the icy bodies 452 00:19:09,480 --> 00:19:07,660 into the interior and so if one runs an 453 00:19:12,299 --> 00:19:09,490 accretion model such as this one ends up 454 00:19:14,669 --> 00:19:12,309 with planets that in the interior that 455 00:19:16,620 --> 00:19:14,679 have had delivered great amounts of 456 00:19:18,120 --> 00:19:16,630 water now notice by the way this is a 457 00:19:19,860 --> 00:19:18,130 log scale here you may not be able to 458 00:19:21,840 --> 00:19:19,870 read these numbers 10 to the minus 3 10 459 00:19:24,840 --> 00:19:21,850 to the minus 2 this sort of process 460 00:19:27,750 --> 00:19:24,850 leads to planets that are far more water 461 00:19:31,620 --> 00:19:27,760 rich by at least an order of magnitude 462 00:19:34,260 --> 00:19:31,630 then we actually observe in certainly an 463 00:19:36,360 --> 00:19:34,270 earthen and obviously the other planets 464 00:19:38,580 --> 00:19:36,370 so there isn't any problem bringing the 465 00:19:40,140 --> 00:19:38,590 volatile in there were already what's it 466 00:19:42,060 --> 00:19:40,150 for carbon and nitrogen there wasn't the 467 00:19:43,320 --> 00:19:42,070 problems of all souls being there in the 468 00:19:44,880 --> 00:19:43,330 inner solar system in the first place 469 00:19:48,030 --> 00:19:44,890 because they're in the enstatite Condren 470 00:19:48,810 --> 00:19:48,040 so there is no problem in accreting all 471 00:19:53,659 --> 00:19:48,820 these material 472 00:19:56,820 --> 00:19:53,669 22 growing planets the the depletion is 473 00:19:59,159 --> 00:19:56,830 partial in that oh you know I'm okay for 474 00:20:01,620 --> 00:19:59,169 time still right the the depletion is 475 00:20:03,269 --> 00:20:01,630 partial in the formation of the rocks 476 00:20:05,970 --> 00:20:03,279 but a lot of the depletion actually has 477 00:20:09,120 --> 00:20:05,980 to take place in the stage of planet 478 00:20:13,049 --> 00:20:09,130 formation so that's where we're going to 479 00:20:14,249 --> 00:20:13,059 go from here to here one of the 480 00:20:17,279 --> 00:20:14,259 interesting things that was actually 481 00:20:19,019 --> 00:20:17,289 noted very prominently in a paper in the 482 00:20:21,499 --> 00:20:19,029 geochemical literature by bernard marty 483 00:20:25,919 --> 00:20:21,509 a few years ago is that this process of 484 00:20:28,379 --> 00:20:25,929 planet formation and and and delivery of 485 00:20:31,080 --> 00:20:28,389 volatiles not only delivers volatile in 486 00:20:33,450 --> 00:20:31,090 a depleted state but the depletion is 487 00:20:34,980 --> 00:20:33,460 differential that is to say that the 488 00:20:37,080 --> 00:20:34,990 amount of water that's delivered or 489 00:20:38,850 --> 00:20:37,090 maybe I shouldn't use delivered the 490 00:20:40,259 --> 00:20:38,860 amount of water that's retained the 491 00:20:41,669 --> 00:20:40,269 amount of carbon that's retained in the 492 00:20:43,889 --> 00:20:41,679 amount of nitrogen that's retained in 493 00:20:45,930 --> 00:20:43,899 the planet does not simply look like 494 00:20:47,730 --> 00:20:45,940 taking a carbonaceous chondrite are 495 00:20:50,909 --> 00:20:47,740 taking a building block and reducing 496 00:20:54,629 --> 00:20:50,919 amount it's it's volatile concentration 497 00:20:56,310 --> 00:20:54,639 some elements are depleted more more 498 00:20:59,190 --> 00:20:56,320 severely than others and in particular 499 00:21:01,080 --> 00:20:59,200 nitrogen is very strongly depleted 500 00:21:04,409 --> 00:21:01,090 interestingly it's even more depleted 501 00:21:07,049 --> 00:21:04,419 than a non reactive gases like neon or 502 00:21:10,139 --> 00:21:07,059 argon something that we have yet to 503 00:21:12,779 --> 00:21:10,149 explain whoops this rather complicated 504 00:21:15,570 --> 00:21:12,789 plot is basically the same information 505 00:21:17,340 --> 00:21:15,580 with just a lot more examples in it here 506 00:21:19,710 --> 00:21:17,350 is the bulk silicate earth in terms of 507 00:21:23,240 --> 00:21:19,720 its carbon nitrogen ratio here are all 508 00:21:25,080 --> 00:21:23,250 different kinds of primitive meteorites 509 00:21:26,610 --> 00:21:25,090 carbonaceous chondrites ordinary 510 00:21:29,070 --> 00:21:26,620 chondrite dennis too tight chondrites 511 00:21:30,960 --> 00:21:29,080 and there are a few exceptions but for 512 00:21:32,759 --> 00:21:30,970 the most end although it you'll notice 513 00:21:34,289 --> 00:21:32,769 that some of these exceptions have to do 514 00:21:37,740 --> 00:21:34,299 with who's reporting it rather than what 515 00:21:41,159 --> 00:21:37,750 the objects are because the because of 516 00:21:42,899 --> 00:21:41,169 analytical challenges but almost all of 517 00:21:44,669 --> 00:21:42,909 the primitive objects have low carbon 518 00:21:45,869 --> 00:21:44,679 nitrogen ratio whereas the bulk silicate 519 00:21:47,820 --> 00:21:45,879 or if there's a high carbon nitrogen 520 00:21:50,430 --> 00:21:47,830 ratio so this is telling us something 521 00:21:51,869 --> 00:21:50,440 about the depletion process that is 522 00:21:53,070 --> 00:21:51,879 differential and that's and that 523 00:21:57,450 --> 00:21:53,080 different elements are going to behave 524 00:21:59,340 --> 00:21:57,460 differently so one of the great 525 00:22:01,760 --> 00:21:59,350 catastrophic events of course is blow 526 00:22:04,370 --> 00:22:01,770 off of the atmosphere by impacts 527 00:22:06,260 --> 00:22:04,380 small and large and we know this 528 00:22:08,360 --> 00:22:06,270 occurred the whole process of assembling 529 00:22:11,060 --> 00:22:08,370 a planet to the series of ever larger 530 00:22:15,590 --> 00:22:11,070 energy events perhaps culminating in the 531 00:22:18,220 --> 00:22:15,600 in the moon-forming impact that that was 532 00:22:20,450 --> 00:22:18,230 sufficient to melt the entire Earth and 533 00:22:22,580 --> 00:22:20,460 these impacts of course have the 534 00:22:24,800 --> 00:22:22,590 possibility the likelihood that they 535 00:22:27,020 --> 00:22:24,810 will blow off whatever primitive early 536 00:22:29,210 --> 00:22:27,030 atmosphere the planet has accreted and 537 00:22:31,100 --> 00:22:29,220 there's also the possibility that this 538 00:22:33,650 --> 00:22:31,110 can be differential for example again de 539 00:22:36,980 --> 00:22:33,660 a knob a ten years ago now 12 years ago 540 00:22:38,870 --> 00:22:36,990 pointed out that if there's a impact to 541 00:22:41,810 --> 00:22:38,880 a planet that already has a liquid water 542 00:22:43,460 --> 00:22:41,820 ocean and a co2 nitrogen atmosphere that 543 00:22:45,560 --> 00:22:43,470 that the atmosphere can be lost 544 00:22:48,680 --> 00:22:45,570 differentially to the ocean and that 545 00:22:50,510 --> 00:22:48,690 that may explain why a ratio that I 546 00:22:53,150 --> 00:22:50,520 haven't yet shown you but it's the same 547 00:22:57,530 --> 00:22:53,160 as before that that the carbon is lost 548 00:22:58,970 --> 00:22:57,540 preferentially to the water in in the 549 00:23:04,090 --> 00:22:58,980 bulk silicate ER it's as compared to 550 00:23:07,700 --> 00:23:04,100 it's likely building blocks the other 551 00:23:10,000 --> 00:23:07,710 catastrophic event is core formation so 552 00:23:14,870 --> 00:23:10,010 the atmospheric loss and core formation 553 00:23:17,330 --> 00:23:14,880 we knew 150 years ago in fact as soon as 554 00:23:20,600 --> 00:23:17,340 the advent of of industrial steel that 555 00:23:22,400 --> 00:23:20,610 that that iron metal loves all of the 556 00:23:25,040 --> 00:23:22,410 bio essential elements all of them 557 00:23:28,670 --> 00:23:25,050 carbon nitrogen hydrogen sulfur 558 00:23:31,040 --> 00:23:28,680 phosphorus if it were up to the metal it 559 00:23:32,660 --> 00:23:31,050 would steal all of the material that we 560 00:23:34,460 --> 00:23:32,670 have on the surface that that is bio 561 00:23:37,010 --> 00:23:34,470 essential and also that we need from 562 00:23:39,670 --> 00:23:37,020 habitability so core formation has the 563 00:23:44,690 --> 00:23:39,680 possibility of robbing the surface of 564 00:23:50,600 --> 00:23:44,700 much most all of the bioavailable 565 00:23:54,020 --> 00:23:50,610 element quantifying this is actually for 566 00:23:56,120 --> 00:23:54,030 in geologically plausible conditions is 567 00:23:58,610 --> 00:23:56,130 actually a project that the community 568 00:23:59,990 --> 00:23:58,620 has taken on fairly recently we tend to 569 00:24:01,910 --> 00:24:00,000 think about this in terms of a very 570 00:24:04,040 --> 00:24:01,920 relatively simple parameter called the 571 00:24:05,780 --> 00:24:04,050 partition coefficient the D which is 572 00:24:08,420 --> 00:24:05,790 experimentally the concentration of 573 00:24:10,040 --> 00:24:08,430 carbon that is in the metal alloy as 574 00:24:12,200 --> 00:24:10,050 compared to the silicate that both 575 00:24:15,440 --> 00:24:12,210 ultimately going to form the mantle and 576 00:24:18,500 --> 00:24:15,450 D gas to form the surface reservoirs 577 00:24:21,230 --> 00:24:18,510 and values for carbon tend to be 10 to 578 00:24:23,299 --> 00:24:21,240 the 2 or greater the concentration of 579 00:24:25,370 --> 00:24:23,309 carbon in the metal is a hundred or a 580 00:24:28,360 --> 00:24:25,380 thousand or ten thousand times greater 581 00:24:30,860 --> 00:24:28,370 than that which is in the silicate and 582 00:24:32,360 --> 00:24:30,870 for nitrogen actually it varies as a 583 00:24:34,129 --> 00:24:32,370 function of I haven't told you what this 584 00:24:36,350 --> 00:24:34,139 parameter is on the x-axis but it's 585 00:24:39,230 --> 00:24:36,360 basically the oxidation state of the 586 00:24:41,600 --> 00:24:39,240 system from oxidized to reduced and 587 00:24:43,519 --> 00:24:41,610 nitrogens behavior depends on that but 588 00:24:46,370 --> 00:24:43,529 under most plausible conditions it to 589 00:24:51,710 --> 00:24:46,380 greatly concentrates in the alloy as 590 00:24:54,889 --> 00:24:51,720 compared to the silicate so core 591 00:24:57,620 --> 00:24:54,899 formation is going to take much of the 592 00:24:59,810 --> 00:24:57,630 carbon much of the nitrogen atmospheric 593 00:25:02,990 --> 00:24:59,820 loss is going to is going to 594 00:25:06,560 --> 00:25:03,000 quantitatively remove materials from the 595 00:25:09,019 --> 00:25:06,570 surface when it occurs and we can think 596 00:25:14,269 --> 00:25:09,029 about the formation of early reservoirs 597 00:25:18,680 --> 00:25:14,279 as a magma ocean losing metal to the 598 00:25:21,019 --> 00:25:18,690 interior and losing gas to the to this 599 00:25:22,700 --> 00:25:21,029 to the atmosphere which has the 600 00:25:26,289 --> 00:25:22,710 potential for loss the only thing that 601 00:25:28,460 --> 00:25:26,299 is likely to be retained over time 602 00:25:33,799 --> 00:25:28,470 available to the eventual surface is 603 00:25:35,840 --> 00:25:33,809 that which is in the silicate and so 604 00:25:38,360 --> 00:25:35,850 this is controlled by the solubility of 605 00:25:41,570 --> 00:25:38,370 the materials the solubility of carbon 606 00:25:44,960 --> 00:25:41,580 or or or support carbon monoxide or 607 00:25:47,169 --> 00:25:44,970 nitrogen or or or ammonia and the 608 00:25:50,629 --> 00:25:47,179 partitioning between the silicate and 609 00:25:52,789 --> 00:25:50,639 and the alloy and one can make a map for 610 00:25:56,000 --> 00:25:52,799 the different elements of their relative 611 00:25:59,120 --> 00:25:56,010 propensity to be either in the mantle or 612 00:26:00,980 --> 00:25:59,130 the atmosphere this mantle or the 613 00:26:02,600 --> 00:26:00,990 atmosphere or the mantle or the core 614 00:26:05,060 --> 00:26:02,610 depending on these different parameters 615 00:26:07,610 --> 00:26:05,070 and what one finds is is that for 616 00:26:11,389 --> 00:26:07,620 example carbon loves to be in the core 617 00:26:13,490 --> 00:26:11,399 or the atmosphere it hardly stays in the 618 00:26:15,440 --> 00:26:13,500 silicate as well the other extreme would 619 00:26:18,830 --> 00:26:15,450 be water which has great solubility in 620 00:26:23,269 --> 00:26:18,840 the silicate another way to look at that 621 00:26:24,919 --> 00:26:23,279 is is this way where again the amount 622 00:26:27,350 --> 00:26:24,929 that's retained in the silicate portion 623 00:26:29,120 --> 00:26:27,360 of the earth is minimal for carbon and 624 00:26:32,830 --> 00:26:29,130 maximal for water and inter 625 00:26:34,910 --> 00:26:32,840 for nitrogen this is the differential 626 00:26:38,990 --> 00:26:34,920 retention that I was talking about 627 00:26:40,310 --> 00:26:39,000 before that we see evidence for I will 628 00:26:44,210 --> 00:26:40,320 skip this because the belt is already 629 00:26:47,450 --> 00:26:44,220 wrong however these processes are too 630 00:26:48,920 --> 00:26:47,460 potent I said that there is a loss 631 00:26:52,910 --> 00:26:48,930 process and in fact there is a loss 632 00:26:55,850 --> 00:26:52,920 process and this loss process if one 633 00:26:58,160 --> 00:26:55,860 allows it to occur with either with 634 00:27:00,380 --> 00:26:58,170 atmospheric loss or without atmospheric 635 00:27:02,660 --> 00:27:00,390 loss for even small amounts of metal 636 00:27:04,910 --> 00:27:02,670 transiting into the core one ends up 637 00:27:07,450 --> 00:27:04,920 with ratios of carbon nitrogen carbon 638 00:27:10,640 --> 00:27:07,460 hydrogen and so forth starting from 639 00:27:12,470 --> 00:27:10,650 chondritic materials that are much more 640 00:27:18,140 --> 00:27:12,480 extreme than what we observe in the bulk 641 00:27:20,420 --> 00:27:18,150 silicate earth what's the solution to 642 00:27:22,010 --> 00:27:20,430 this the solution to this is something 643 00:27:24,280 --> 00:27:22,020 that was referred to yesterday and the 644 00:27:27,230 --> 00:27:24,290 discussions is the so-called late veneer 645 00:27:30,280 --> 00:27:27,240 after the catastrophic the largest 646 00:27:32,690 --> 00:27:30,290 catastrophic events of core formation 647 00:27:34,430 --> 00:27:32,700 atmospheric blow-off associated with the 648 00:27:36,860 --> 00:27:34,440 moon-forming impact and so forth of 649 00:27:38,510 --> 00:27:36,870 course accretion continued not nearly as 650 00:27:40,970 --> 00:27:38,520 much accretion but a small amount and 651 00:27:47,740 --> 00:27:40,980 that accretion added chondritic like 652 00:27:52,850 --> 00:27:50,630 we know this occurred accretion models 653 00:27:59,590 --> 00:27:52,860 of course can't possibly stop with the 654 00:28:03,260 --> 00:27:59,600 last final slide climatic of climactic 655 00:28:07,520 --> 00:28:03,270 climatic and climactic are it's tempting 656 00:28:10,880 --> 00:28:07,530 to say 111 means the other climactic 657 00:28:14,630 --> 00:28:10,890 events I and and so depending on when 658 00:28:18,110 --> 00:28:14,640 those last large impacts occurred we 659 00:28:20,570 --> 00:28:18,120 expect something like 10 to the minus 3 660 00:28:22,970 --> 00:28:20,580 10 to the minus 2 even as much as 10 to 661 00:28:25,430 --> 00:28:22,980 the minus one of the mass of the earth 662 00:28:29,680 --> 00:28:25,440 to continue to accrete we know that this 663 00:28:31,970 --> 00:28:29,690 occurred according to the metals the 664 00:28:33,770 --> 00:28:31,980 metals that love to go into the course 665 00:28:34,970 --> 00:28:33,780 in rafal elements like platinum and so 666 00:28:37,190 --> 00:28:34,980 forth those of you who like precious 667 00:28:40,460 --> 00:28:37,200 metal jewelry would wish that our late 668 00:28:42,499 --> 00:28:40,470 veneer would have been greater and so 669 00:28:45,589 --> 00:28:42,509 some amount was added afterwards and 670 00:28:50,829 --> 00:28:45,599 some amount also added other sidra five 671 00:28:56,930 --> 00:28:53,869 however the fact that there is this 672 00:28:59,419 --> 00:28:56,940 differential concentration compared to 673 00:29:02,269 --> 00:28:59,429 late veneer like materials compared to 674 00:29:05,389 --> 00:29:02,279 meteoritic materials shows us that the 675 00:29:07,489 --> 00:29:05,399 sum of the of the bioavailable elements 676 00:29:10,099 --> 00:29:07,499 the sum of the habitable important 677 00:29:12,680 --> 00:29:10,109 elements is some combination between 678 00:29:15,619 --> 00:29:12,690 that material that was processed through 679 00:29:17,930 --> 00:29:15,629 the core forming and atmospheric loss 680 00:29:21,019 --> 00:29:17,940 processes and something added back we 681 00:29:23,539 --> 00:29:21,029 actually need both we need we need early 682 00:29:25,519 --> 00:29:23,549 delivery and processing in the in the in 683 00:29:27,529 --> 00:29:25,529 these catastrophes and then we need 684 00:29:30,439 --> 00:29:27,539 material added afterwards otherwise we 685 00:29:31,399 --> 00:29:30,449 would have to extreme barium first of 686 00:29:33,139 --> 00:29:31,409 all we wouldn't have enough of these 687 00:29:34,699 --> 00:29:33,149 elements and second of all the 688 00:29:40,369 --> 00:29:34,709 fractionation between them would be more 689 00:29:43,299 --> 00:29:40,379 extreme than what we observe okay so the 690 00:29:45,949 --> 00:29:43,309 one that is most extreme in terms of its 691 00:29:48,169 --> 00:29:45,959 magma ocean remnant is hydrogen there's 692 00:29:49,909 --> 00:29:48,179 much more hydrogen than there is the 693 00:29:52,399 --> 00:29:49,919 other elements and it's the one that's 694 00:29:54,859 --> 00:29:52,409 most soluble in the silicate so it's the 695 00:29:58,219 --> 00:29:54,869 one that's retained by the planet these 696 00:30:01,129 --> 00:29:58,229 probably carbon nitrogen sulfur were 697 00:30:03,829 --> 00:30:01,139 probably delivered after in small 698 00:30:06,919 --> 00:30:03,839 amounts after these catastrophic events 699 00:30:08,839 --> 00:30:06,929 whether or not this nitrogen depletion 700 00:30:11,239 --> 00:30:08,849 is owing to the fact that things were 701 00:30:13,489 --> 00:30:11,249 delivered that lost nitrogen in ways 702 00:30:15,680 --> 00:30:13,499 that we don't see in contradict 703 00:30:17,479 --> 00:30:15,690 meteorites is one possibility another 704 00:30:19,909 --> 00:30:17,489 possibility is that there was an 705 00:30:21,319 --> 00:30:19,919 additional process of late loss of a 706 00:30:28,539 --> 00:30:21,329 low-temperature atmosphere which would 707 00:30:33,439 --> 00:30:31,129 it isn't that we gained these elements 708 00:30:40,879 --> 00:30:33,449 it's that we lost them by just the right 709 00:30:43,459 --> 00:30:40,889 amount but the supply to hot inner solar 710 00:30:45,409 --> 00:30:43,469 system planets is is far greater than 711 00:30:47,059 --> 00:30:45,419 what we actually see in other words it 712 00:30:48,769 --> 00:30:47,069 isn't just that we were born in the 713 00:30:50,509 --> 00:30:48,779 inner solar system which was volatile 714 00:30:54,379 --> 00:30:50,519 depleted the process of planet formation 715 00:30:56,190 --> 00:30:54,389 expelled much much of the volatile and 716 00:30:58,200 --> 00:30:56,200 then the fractionation is 717 00:31:00,299 --> 00:30:58,210 is both core formation in atmospheric 718 00:31:02,100 --> 00:31:00,309 loss and the final inventory is a 719 00:31:03,779 --> 00:31:02,110 combination of early delivered elements 720 00:31:05,789 --> 00:31:03,789 in lace veneer and this isn't on the 721 00:31:08,310 --> 00:31:05,799 conclusion but i do want to return to 722 00:31:11,759 --> 00:31:08,320 the point that i made at the outset 723 00:31:13,830 --> 00:31:11,769 which is we would like to know what the 724 00:31:16,519 --> 00:31:13,840 right amount of these elements are in 725 00:31:19,639 --> 00:31:16,529 order to operate a planet that has 726 00:31:22,710 --> 00:31:19,649 steady internal dynamics and also steady 727 00:31:24,240 --> 00:31:22,720 habitable climate and apart from the 728 00:31:25,830 --> 00:31:24,250 fact that Earth is within the window i'm 729 00:31:40,440 --> 00:31:25,840 not sure we know what that window is 730 00:31:42,810 --> 00:31:40,450 thank you questions could you comment on 731 00:31:45,269 --> 00:31:42,820 to what extent should we be looking only 732 00:31:47,250 --> 00:31:45,279 at elements in its atomic form versus 733 00:31:49,470 --> 00:31:47,260 its molecular structures because often 734 00:31:51,690 --> 00:31:49,480 the fractionation seems to be dependent 735 00:31:53,879 --> 00:31:51,700 on the kind of molecules these carbon 736 00:31:57,269 --> 00:31:53,889 nitrogen oxygen sulfur phosphorus form 737 00:32:00,269 --> 00:31:57,279 in minerals how much of a dependence is 738 00:32:03,539 --> 00:32:00,279 it in terms of loss or depletion on a 739 00:32:05,159 --> 00:32:03,549 planet on yeah of course most of the 740 00:32:06,899 --> 00:32:05,169 processes that I'm talking about in 741 00:32:08,490 --> 00:32:06,909 terms of planet formation or very high 742 00:32:09,840 --> 00:32:08,500 temperature processing so all the 743 00:32:12,450 --> 00:32:09,850 molecules that would be thinking about 744 00:32:14,129 --> 00:32:12,460 are quite simple but depending on for 745 00:32:16,830 --> 00:32:14,139 example the oxidation state whether or 746 00:32:20,759 --> 00:32:16,840 not we have n2 or NH 3 whether or not we 747 00:32:22,740 --> 00:32:20,769 have co co 2 or ch4 that's how simple we 748 00:32:25,259 --> 00:32:22,750 are in terms of the kinds of molecules 749 00:32:27,659 --> 00:32:25,269 that may be present the all of these 750 00:32:29,519 --> 00:32:27,669 parameters that are that I'm examining 751 00:32:31,409 --> 00:32:29,529 whether it be partitioning or solubility 752 00:32:33,180 --> 00:32:31,419 depend very strongly on that so that so 753 00:32:34,860 --> 00:32:33,190 that's quite important the only place 754 00:32:37,289 --> 00:32:34,870 where anything more complex may be 755 00:32:40,850 --> 00:32:37,299 involved would be in the other portion 756 00:32:43,889 --> 00:32:40,860 of the process going from dust grains to 757 00:32:45,720 --> 00:32:43,899 say chondritic meteorites are or their 758 00:32:49,769 --> 00:32:45,730 equivalent where the formation of 759 00:32:50,850 --> 00:32:49,779 various refractory organics will have a 760 00:32:53,070 --> 00:32:50,860 lot to do with their preservation 761 00:33:04,120 --> 00:32:53,080 through processes of metamorphism and 762 00:33:10,250 --> 00:33:07,550 yeah you mentioned that the bio 763 00:33:14,060 --> 00:33:10,260 essential elements are 0 files yes and 764 00:33:16,640 --> 00:33:14,070 then you you like comparing bulk silicon 765 00:33:18,170 --> 00:33:16,650 earth but not bulk earth you then came 766 00:33:20,600 --> 00:33:18,180 to some conclusions about the late 767 00:33:23,600 --> 00:33:20,610 veneer but it seems to me that if you 768 00:33:28,550 --> 00:33:23,610 don't instead of using BSE you use BS 769 00:33:30,980 --> 00:33:28,560 bulk earth unpardonable yes if you had 770 00:33:33,320 --> 00:33:30,990 used be e then you could at least to the 771 00:33:34,910 --> 00:33:33,330 extent that we know about the how many 772 00:33:36,320 --> 00:33:34,920 of these essential elements are in the 773 00:33:39,590 --> 00:33:36,330 core i know that's not very well known 774 00:33:41,510 --> 00:33:39,600 but we know a little bit and if we if 775 00:33:43,280 --> 00:33:41,520 you included that in the analysis you 776 00:33:45,200 --> 00:33:43,290 could say something a little bit more 777 00:33:46,790 --> 00:33:45,210 constraining about the late veneer for 778 00:33:48,950 --> 00:33:46,800 example maybe there are so many of these 779 00:33:50,240 --> 00:33:48,960 these elements the bio essential element 780 00:33:51,530 --> 00:33:50,250 in the core that you wouldn't even need 781 00:33:56,060 --> 00:33:51,540 elite veneer to explain some of the 782 00:34:00,470 --> 00:33:56,070 anomalies you see perhaps the guiding 783 00:34:02,270 --> 00:34:00,480 assumption in what I was telling you is 784 00:34:04,280 --> 00:34:02,280 that once things go to the core they 785 00:34:06,620 --> 00:34:04,290 stay there which is to say that they're 786 00:34:08,210 --> 00:34:06,630 not any longer available to be sampled 787 00:34:10,520 --> 00:34:08,220 by the surface or the mantle and so 788 00:34:12,050 --> 00:34:10,530 forth we don't know what those values 789 00:34:13,909 --> 00:34:12,060 are very well so when we look at the 790 00:34:16,370 --> 00:34:13,919 bulk silicate earth what we're looking 791 00:34:18,860 --> 00:34:16,380 at is the mantle the and the surface and 792 00:34:20,659 --> 00:34:18,870 so forth the late veneer sort of by 793 00:34:23,240 --> 00:34:20,669 definition is that material which is 794 00:34:26,960 --> 00:34:23,250 added after the closure or the effective 795 00:34:29,480 --> 00:34:26,970 closure of exchange with the core so I 796 00:34:31,040 --> 00:34:29,490 don't know that knowing the bulk earth 797 00:34:33,200 --> 00:34:31,050 would tell us much about the late veneer 798 00:34:35,480 --> 00:34:33,210 it would tell us a lot about the feeding 799 00:34:37,720 --> 00:34:35,490 zone of the original materials that were 800 00:34:40,280 --> 00:34:37,730 added to the earth enstatite chondrites 801 00:34:45,100 --> 00:34:40,290 carbonaceous chondrites and so on and it 802 00:34:48,470 --> 00:34:47,419 something that I haven't quantified for 803 00:34:50,390 --> 00:34:48,480 you I've just told you that they're both 804 00:34:52,070 --> 00:34:50,400 important is that there's the processes 805 00:34:55,040 --> 00:34:52,080 of core formation and also atmospheric 806 00:34:57,470 --> 00:34:55,050 loss and unless we know those two we 807 00:35:00,230 --> 00:34:57,480 don't necessarily know what the original 808 00:35:02,000 --> 00:35:00,240 supply was because one is still in the 809 00:35:07,310 --> 00:35:02,010 system hard to know the bulk earth and 810 00:35:09,650 --> 00:35:07,320 the other is lost yeah thanks that 811 00:35:11,600 --> 00:35:09,660 really beautiful talk I just maybe 812 00:35:12,740 --> 00:35:11,610 there's a little bit outside of what 813 00:35:16,730 --> 00:35:12,750 you're comfortable with but could you 814 00:35:17,620 --> 00:35:16,740 give us your best estimate of scenarios 815 00:35:19,269 --> 00:35:17,630 for the atmosphere 816 00:35:21,490 --> 00:35:19,279 of the earth between three point eight 817 00:35:23,700 --> 00:35:21,500 and four billion years ago yeah that is 818 00:35:26,740 --> 00:35:23,710 outside of what I was talking about but 819 00:35:31,240 --> 00:35:26,750 but but one thing that something that I 820 00:35:33,160 --> 00:35:31,250 skipped that I think is there we go that 821 00:35:37,299 --> 00:35:33,170 I think is very interesting is it's 822 00:35:39,099 --> 00:35:37,309 generally assumed just ad hoc that that 823 00:35:42,370 --> 00:35:39,109 the early Earth looked on the like the 824 00:35:43,990 --> 00:35:42,380 earliest earth the magma ocean earth 825 00:35:46,569 --> 00:35:44,000 look like the left hand side of this 826 00:35:48,700 --> 00:35:46,579 diagram which I actually think there's 827 00:35:50,620 --> 00:35:48,710 some inconsistency to that which is that 828 00:35:52,390 --> 00:35:50,630 they have a magma ocean and iron metal 829 00:35:54,999 --> 00:35:52,400 and then the atmosphere ought to be co2 830 00:35:58,480 --> 00:35:55,009 and h2o right highly reduced quite 831 00:36:00,370 --> 00:35:58,490 oxidized and it's equally plausible that 832 00:36:01,660 --> 00:36:00,380 the early Earth I don't have nitrogen 833 00:36:03,730 --> 00:36:01,670 here but that the early Earth's 834 00:36:09,730 --> 00:36:03,740 atmosphere the very first atmosphere was 835 00:36:11,589 --> 00:36:09,740 reduced coh to methane and and so on the 836 00:36:14,109 --> 00:36:11,599 density of this atmosphere of course in 837 00:36:15,819 --> 00:36:14,119 the magma ocean stages tens of bars or 838 00:36:18,269 --> 00:36:15,829 hundreds of bars or something like that 839 00:36:20,259 --> 00:36:18,279 Matt cannot have lasted right the 840 00:36:22,210 --> 00:36:20,269 weathering processes and whatever 841 00:36:24,279 --> 00:36:22,220 whatever else must have drawn down most 842 00:36:27,670 --> 00:36:24,289 of the carbon but I would say that the 843 00:36:29,170 --> 00:36:27,680 starting condition would have to be well 844 00:36:30,940 --> 00:36:29,180 no I wouldn't say what have to be could 845 00:36:34,779 --> 00:36:30,950 easily have been something like this and 846 00:36:36,249 --> 00:36:34,789 the transition to what you're talking 847 00:36:37,900 --> 00:36:36,259 about what you think is old but i think 848 00:36:41,859 --> 00:36:37,910 is like hundreds of million years after 849 00:36:43,210 --> 00:36:41,869 this i I think we don't know very much 850 00:36:45,789 --> 00:36:43,220 about and it would it would be 851 00:36:48,370 --> 00:36:45,799 interesting to know one thing that we do 852 00:36:50,620 --> 00:36:48,380 seem to know is that this is that the 853 00:36:52,539 --> 00:36:50,630 rocks on the surface don't reflect this 854 00:36:54,609 --> 00:36:52,549 highly reduced condition going all the 855 00:36:57,220 --> 00:36:54,619 way back to 3.8 to 4 billion years which 856 00:36:59,589 --> 00:36:57,230 is to say that some oxidation process 857 00:37:02,319 --> 00:36:59,599 occurred probably hydrogen loss but 858 00:37:06,069 --> 00:37:02,329 there are other ideas yeah it seems like 859 00:37:08,079 --> 00:37:06,079 I learned a funky it seems like a lot of 860 00:37:10,120 --> 00:37:08,089 the processes should be dependent on the 861 00:37:12,099 --> 00:37:10,130 size of scientism you know obviously 862 00:37:14,319 --> 00:37:12,109 surface area to volume ratio and 863 00:37:15,730 --> 00:37:14,329 atmospheric loss and differentiation so 864 00:37:18,970 --> 00:37:15,740 nuts wondering if you'd taken that into 865 00:37:20,380 --> 00:37:18,980 account in your calculation oh so you're 866 00:37:26,380 --> 00:37:20,390 talking about the planet or the planet 867 00:37:28,569 --> 00:37:26,390 Esmil yeah we do take that into account 868 00:37:30,940 --> 00:37:28,579 in terms of planets but in terms of 869 00:37:31,630 --> 00:37:30,950 differentiation to planetesimals this is 870 00:37:35,350 --> 00:37:31,640 something that we're 871 00:37:36,760 --> 00:37:35,360 beginning to get to at least in in in my 872 00:37:38,440 --> 00:37:36,770 research with collaborators which is 873 00:37:41,920 --> 00:37:38,450 that the material delivered to the 874 00:37:43,510 --> 00:37:41,930 planet is not largely chondritic 875 00:37:45,550 --> 00:37:43,520 meteorites but it's probably largely 876 00:37:47,980 --> 00:37:45,560 planetesimals that had been processed on 877 00:37:50,170 --> 00:37:47,990 small bodies on 100 kilometer or 300 878 00:37:53,140 --> 00:37:50,180 kilometers size bodies and the 879 00:37:55,840 --> 00:37:53,150 metamorphism that occurs on that the the 880 00:37:57,190 --> 00:37:55,850 maturation if you will of the carbon and 881 00:37:58,840 --> 00:37:57,200 nitrogen in the hydrogen and the 882 00:38:01,690 --> 00:37:58,850 diversity of materials that are 883 00:38:03,070 --> 00:38:01,700 delivered no we're not taking that into 884 00:38:10,030 --> 00:38:03,080 account and that might be a very large 885 00:38:13,870 --> 00:38:10,040 part of the story I have a two brave 886 00:38:15,880 --> 00:38:13,880 question first I like the argument in 887 00:38:19,060 --> 00:38:15,890 the process of forming climbing say the 888 00:38:21,880 --> 00:38:19,070 process of losing volatiles so if we 889 00:38:24,910 --> 00:38:21,890 just focus on the tablet of the 890 00:38:28,900 --> 00:38:24,920 volatiles let's talk about later on 891 00:38:31,120 --> 00:38:28,910 linear of supply so in addition to the 892 00:38:34,540 --> 00:38:31,130 highly eccentric higher things like a 893 00:38:38,920 --> 00:38:34,550 distance in yo leo are there any other 894 00:38:41,560 --> 00:38:38,930 sectors are also of importance to the 895 00:38:46,060 --> 00:38:41,570 temptation of volatiles and these 896 00:38:49,540 --> 00:38:46,070 factors can be also quantifiable and my 897 00:38:51,300 --> 00:38:49,550 second question is you as you mentioned 898 00:38:56,200 --> 00:38:51,310 with the economy of the solar system 899 00:38:58,750 --> 00:38:56,210 from rocky body gasps body and eyes 900 00:39:02,770 --> 00:38:58,760 abilities outer world so I'm wondering 901 00:39:04,810 --> 00:39:02,780 if the economy of likeable or universal 902 00:39:07,750 --> 00:39:04,820 for our other planet or system of 903 00:39:09,760 --> 00:39:07,760 certain clinical system Thanks well I 904 00:39:12,010 --> 00:39:09,770 think I know the answer to your second 905 00:39:15,340 --> 00:39:12,020 question I'm not sure I know how to 906 00:39:17,230 --> 00:39:15,350 respond to your first question of course 907 00:39:20,140 --> 00:39:17,240 actually there's a plot that isn't in 908 00:39:21,490 --> 00:39:20,150 here of the composition of stars but I 909 00:39:23,050 --> 00:39:21,500 think many of you are familiar with it 910 00:39:25,540 --> 00:39:23,060 they're more oxygen rich stars and 911 00:39:27,820 --> 00:39:25,550 carbon rich stars and that will have a 912 00:39:31,300 --> 00:39:27,830 considerable effect on the on the 913 00:39:33,450 --> 00:39:31,310 volatile chemistry of the of the dust 914 00:39:36,550 --> 00:39:33,460 and the gas around those stars but 915 00:39:37,990 --> 00:39:36,560 certainly so this is the interstellar 916 00:39:40,210 --> 00:39:38,000 medium here certainly in terms of the 917 00:39:43,330 --> 00:39:40,220 absolute abundance of things like carbon 918 00:39:45,580 --> 00:39:43,340 and nitrogen and obviously hydrogen it 919 00:39:46,990 --> 00:39:45,590 is generally true that any solar 920 00:39:51,190 --> 00:39:47,000 system that is making terrestrial 921 00:39:54,130 --> 00:39:51,200 planets must be shedding those elements 922 00:39:55,810 --> 00:39:54,140 in the process whether they shed them in 923 00:39:58,600 --> 00:39:55,820 the same way that our solar system has I 924 00:40:00,790 --> 00:39:58,610 don't know and I'm not sure I know how 925 00:40:04,120 --> 00:40:00,800 to answer your first question you're 926 00:40:05,530 --> 00:40:04,130 asking whether or not in addition to 927 00:40:07,720 --> 00:40:05,540 heliocentric distance there are other 928 00:40:17,260 --> 00:40:07,730 important variables that affect the lost 929 00:40:19,360 --> 00:40:17,270 processes yeah and and was that question 930 00:40:27,340 --> 00:40:19,370 directed at our solar system or more 931 00:40:29,800 --> 00:40:27,350 generally well there's a certain 932 00:40:31,300 --> 00:40:29,810 stochastic aspect to it right so one 933 00:40:33,520 --> 00:40:31,310 thing that's really important to our 934 00:40:35,530 --> 00:40:33,530 planet apparently is the occurrence of 935 00:40:38,650 --> 00:40:35,540 giant impacts or the frequency of giant 936 00:40:41,650 --> 00:40:38,660 impact and so you know a planet like 937 00:40:45,130 --> 00:40:41,660 Mars which is an embryo which didn't 938 00:40:46,690 --> 00:40:45,140 suffer any truly giant impacts would 939 00:40:49,900 --> 00:40:46,700 certainly have a different loss history 940 00:40:51,490 --> 00:40:49,910 than Earth it has a different history 941 00:40:53,640 --> 00:40:51,500 also because of its heliocentric 942 00:40:55,810 --> 00:40:53,650 distance but the difference between 943 00:40:57,970 --> 00:40:55,820 planets that are effectively embryos 944 00:40:59,350 --> 00:40:57,980 that form very quickly you know Mars is 945 00:41:01,600 --> 00:40:59,360 thought to have formed within the first 946 00:41:03,310 --> 00:41:01,610 couple of million years of the solar 947 00:41:04,770 --> 00:41:03,320 system history as opposed to larger 948 00:41:07,780 --> 00:41:04,780 planets which have this more protracted 949 00:41:09,640 --> 00:41:07,790 impact in accretion history like Earth 950 00:41:14,980 --> 00:41:09,650 and Venus that's that's an important 951 00:41:17,020 --> 00:41:14,990 difference you said in the beginning of 952 00:41:19,840 --> 00:41:17,030 your talk that the tectonics is 953 00:41:23,350 --> 00:41:19,850 essential for the renewal of elements 954 00:41:25,810 --> 00:41:23,360 yes so what do you think about is it 955 00:41:27,850 --> 00:41:25,820 important for the origin of life or the 956 00:41:29,560 --> 00:41:27,860 maintenance of life and what about early 957 00:41:32,140 --> 00:41:29,570 Earth before bit tectonics and what 958 00:41:34,900 --> 00:41:32,150 about math yeah I think I'll let mark 959 00:41:36,370 --> 00:41:34,910 answer that tomorrow I i don't think 960 00:41:38,980 --> 00:41:36,380 that plate tectonics is essential for 961 00:41:40,720 --> 00:41:38,990 the origin of life I don't think it's 962 00:41:42,850 --> 00:41:40,730 necessarily important for the 963 00:41:45,040 --> 00:41:42,860 maintenance of life but I do think it's 964 00:41:46,780 --> 00:41:45,050 important for the maintenance of 965 00:41:51,010 --> 00:41:46,790 habitability and I think the counter 966 00:41:53,220 --> 00:41:51,020 example is Mars if life Mars appears to 967 00:41:57,280 --> 00:41:53,230 have been habitable early in its history 968 00:42:00,479 --> 00:41:57,290 it appears to have what whether or not 969 00:42:03,370 --> 00:42:00,489 it had life I guess I defer to 970 00:42:05,890 --> 00:42:03,380 others about but definitely the 971 00:42:09,209 --> 00:42:05,900 steadiness of our climate and our 972 00:42:12,519 --> 00:42:09,219 habitability is intrinsically limited 973 00:42:14,259 --> 00:42:12,529 intrinsically related to plate tectonics 974 00:42:18,880 --> 00:42:14,269 I would assert but i think that mark is 975 00:42:21,249 --> 00:42:18,890 going to address this tomorrow true all 976 00:42:24,130 --> 00:42:21,259 right thank you great thought a lot to 977 00:42:25,569 --> 00:42:24,140 think about one question is in the near 978 00:42:27,999 --> 00:42:25,579 the end we are talking mentioned there 979 00:42:29,829 --> 00:42:28,009 is a possible late loss of a nitrogen 980 00:42:34,449 --> 00:42:29,839 from low temperature animals here yes 981 00:42:37,449 --> 00:42:34,459 and and I like to hear you to talk more 982 00:42:39,669 --> 00:42:37,459 about that and if that was a case oh 983 00:42:43,599 --> 00:42:39,679 where is that isotopic fractionation 984 00:42:45,370 --> 00:42:43,609 Sigma signature okay so it depends on 985 00:42:47,229 --> 00:42:45,380 the on the light I did I wasn't very 986 00:42:49,269 --> 00:42:47,239 specific about what that late loss was 987 00:42:51,309 --> 00:42:49,279 if the late loss was something like 988 00:42:53,589 --> 00:42:51,319 hydrodynamic escape then there would be 989 00:42:55,059 --> 00:42:53,599 a very strong isotopic signature but it 990 00:42:59,229 --> 00:42:55,069 actually wasn't what I was thinking 991 00:43:03,039 --> 00:42:59,239 about there's a recent paper by slick 992 00:43:04,929 --> 00:43:03,049 ting at all that suggests that not giant 993 00:43:07,929 --> 00:43:04,939 impacts but small impacts are much more 994 00:43:10,150 --> 00:43:07,939 ablative than we previously thought and 995 00:43:14,019 --> 00:43:10,160 and if the loss was by ablation then 996 00:43:15,519 --> 00:43:14,029 first of all we wouldn't expect a that 997 00:43:18,039 --> 00:43:15,529 we wouldn't expect an isotopic 998 00:43:19,299 --> 00:43:18,049 fractionation and second of all then we 999 00:43:20,650 --> 00:43:19,309 need to think about the late veneer 1000 00:43:22,809 --> 00:43:20,660 differently because the whole idea of 1001 00:43:26,079 --> 00:43:22,819 the late veneer is is that small impacts 1002 00:43:27,939 --> 00:43:26,089 add volatile to the planet but if if if 1003 00:43:29,620 --> 00:43:27,949 the ablation is very efficient in some 1004 00:43:31,599 --> 00:43:29,630 of those small impacts in some fraction 1005 00:43:33,880 --> 00:43:31,609 of the small impact then the late veneer 1006 00:43:36,549 --> 00:43:33,890 itself is both in addition and a loss 1007 00:43:38,829 --> 00:43:36,559 process and has the possibility of a 1008 00:43:41,410 --> 00:43:38,839 fractionation not of isotopes but of 1009 00:43:42,849 --> 00:43:41,420 different elements depending on their 1010 00:43:47,650 --> 00:43:42,859 persistence in the atmosphere or 1011 00:43:50,259 --> 00:43:47,660 deposition and solid okay so we need to 1012 00:43:52,100 --> 00:43:50,269 wrap up for lunch we thank the speakers 1013 00:43:55,320 --> 00:43:52,110 this morning once more 1014 00:44:07,720 --> 00:43:55,330 [Applause]