1 00:00:09,710 --> 00:00:07,130 [Music] 2 00:00:11,150 --> 00:00:09,720 so thanks again for that introduction as 3 00:00:12,500 --> 00:00:11,160 Laura pointed out my name is sue 4 00:00:14,600 --> 00:00:12,510 Carranza and I'm a skull post doctoral 5 00:00:15,770 --> 00:00:14,610 fellow at MIT and today I'm excited to 6 00:00:17,510 --> 00:00:15,780 tell you a little bit about some of my 7 00:00:19,279 --> 00:00:17,520 thoughts on UV light and the role it 8 00:00:21,170 --> 00:00:19,289 plays on the in the emergence and search 9 00:00:22,370 --> 00:00:21,180 for life in the universe before we get 10 00:00:23,420 --> 00:00:22,380 started I just want to taken one with 11 00:00:24,680 --> 00:00:23,430 acknowledge my colleagues and 12 00:00:26,980 --> 00:00:24,690 collaborators with whom I've done much 13 00:00:30,170 --> 00:00:26,990 of the work that I talk about over here 14 00:00:31,700 --> 00:00:30,180 okay so the session so the meeting 15 00:00:33,350 --> 00:00:31,710 organizers asked me to talk about 16 00:00:35,450 --> 00:00:33,360 prebiotic chemistry and bio signatures 17 00:00:37,340 --> 00:00:35,460 which are two topics which might seem 18 00:00:38,420 --> 00:00:37,350 quite different at face value prebiotic 19 00:00:40,640 --> 00:00:38,430 chemistry is concerned with the question 20 00:00:41,780 --> 00:00:40,650 of the origin of life biosignatures is 21 00:00:43,940 --> 00:00:41,790 concerned with the question of how to 22 00:00:45,470 --> 00:00:43,950 look for it elsewhere but it is it turns 23 00:00:47,690 --> 00:00:45,480 out these questions are related at a 24 00:00:49,640 --> 00:00:47,700 deep and fundamental level provided 25 00:00:51,620 --> 00:00:49,650 chemistry effects by signatures because 26 00:00:53,720 --> 00:00:51,630 theories of abiogenesis can provide 27 00:00:55,580 --> 00:00:53,730 informative priors which we can use to 28 00:00:56,600 --> 00:00:55,590 prioritize scarce telescope time when 29 00:00:58,220 --> 00:00:56,610 are kind of forgot which are the most 30 00:01:00,380 --> 00:00:58,230 interesting planets to scrutinize for 31 00:01:02,479 --> 00:01:00,390 evidence of biosignatures they can also 32 00:01:04,460 --> 00:01:02,489 help us to interpret informative priors 33 00:01:06,830 --> 00:01:04,470 for interpretation of a putative bio 34 00:01:08,179 --> 00:01:06,840 signature if you have a measurement of a 35 00:01:09,200 --> 00:01:08,189 signal and you're trying to describe to 36 00:01:11,149 --> 00:01:09,210 figure out whether to ascribe a 37 00:01:13,100 --> 00:01:11,159 biological or non-biological explanation 38 00:01:14,780 --> 00:01:13,110 the biological explanation is more 39 00:01:16,310 --> 00:01:14,790 convincing if it's in a place where we 40 00:01:18,920 --> 00:01:16,320 think life can emerge in you and a gear 41 00:01:20,620 --> 00:01:18,930 compared to one where it can't but the 42 00:01:22,850 --> 00:01:20,630 link goes the other way as well 43 00:01:24,289 --> 00:01:22,860 biosignatures will will eventually when 44 00:01:26,539 --> 00:01:24,299 we detect them play a critical role in 45 00:01:27,590 --> 00:01:26,549 origin of life specifically the 46 00:01:29,359 --> 00:01:27,600 detection of life on other worlds 47 00:01:31,340 --> 00:01:29,369 provides the strongest lever arm we have 48 00:01:33,050 --> 00:01:31,350 to empirically constrain theories of 49 00:01:34,670 --> 00:01:33,060 abiogenesis which has worked it very 50 00:01:38,390 --> 00:01:34,680 nicely in a kind of basin analysis by 51 00:01:40,310 --> 00:01:38,400 Chen and kipping last year so these two 52 00:01:41,810 --> 00:01:40,320 questions are intimately linked and one 53 00:01:43,940 --> 00:01:41,820 of the kind of mechanistic things that 54 00:01:45,560 --> 00:01:43,950 links both of them is UV radiation and 55 00:01:47,450 --> 00:01:45,570 the rest of this talk I hope to convince 56 00:01:49,250 --> 00:01:47,460 you that UV radiation plays both a 57 00:01:51,410 --> 00:01:49,260 critical controlling role in prebiotic 58 00:01:53,420 --> 00:01:51,420 chemistry potentially as well as for 59 00:01:54,980 --> 00:01:53,430 sure a strong thrilling role in 60 00:01:56,390 --> 00:01:54,990 biosignature gases in particular the 61 00:01:59,810 --> 00:01:56,400 questions about false positives and 62 00:02:01,280 --> 00:01:59,820 build-up ejectable levels I'm gonna talk 63 00:02:02,929 --> 00:02:01,290 about UV light so I just want to orient 64 00:02:04,190 --> 00:02:02,939 you what exactly I mean when I talk 65 00:02:06,050 --> 00:02:04,200 about UV light and I'm gonna use this 66 00:02:08,929 --> 00:02:06,060 excellent plot from Evan Francis paper 67 00:02:10,609 --> 00:02:08,939 to do so when I when I talk about UV I'm 68 00:02:11,630 --> 00:02:10,619 not talking with the XUV yet we're link 69 00:02:13,280 --> 00:02:11,640 shortened about a hundred nanometers 70 00:02:15,229 --> 00:02:13,290 this has really important implications 71 00:02:16,580 --> 00:02:15,239 for processes like atmospheric escape 72 00:02:19,250 --> 00:02:16,590 like we heard about earlier in this 73 00:02:20,990 --> 00:02:19,260 meeting I'm also not gonna be talking 74 00:02:22,280 --> 00:02:21,000 with the visible in the IR what 75 00:02:24,620 --> 00:02:22,290 place critical rules in planetary 76 00:02:25,850 --> 00:02:24,630 climate instead I'll be focusing on this 77 00:02:27,290 --> 00:02:25,860 bit in the middle here which plays 78 00:02:29,270 --> 00:02:27,300 important roles in chemistry 79 00:02:31,760 --> 00:02:29,280 I just want to zoom in there and 80 00:02:33,080 --> 00:02:31,770 emphasize what I and again orient you a 81 00:02:35,930 --> 00:02:33,090 little bit what I mean when I talk about 82 00:02:38,150 --> 00:02:35,940 UV so this is the top of atmosphere of 83 00:02:39,860 --> 00:02:38,160 flux for Earth analog planets orbiting 84 00:02:42,440 --> 00:02:39,870 the Sun here in black versus that the M 85 00:02:45,980 --> 00:02:42,450 dwarf GJ 1214 here in red taken from the 86 00:02:48,620 --> 00:02:45,990 work of Kevin France 2013 this is a 87 00:02:50,690 --> 00:02:48,630 wavelength in nanometers on the x-axis 88 00:02:53,630 --> 00:02:50,700 top of atmosphere flux and photons on 89 00:02:56,240 --> 00:02:53,640 the y-axis and broadly speaking when I 90 00:02:57,440 --> 00:02:56,250 refer to far UV radiation everyone sets 91 00:02:59,570 --> 00:02:57,450 their cut-offs a little bit differently 92 00:03:00,860 --> 00:02:59,580 but when I refer to far UV I'm talking 93 00:03:02,479 --> 00:03:00,870 about wavelength shorter than 200 94 00:03:04,310 --> 00:03:02,489 nanometers this is placed in a 95 00:03:05,720 --> 00:03:04,320 controlling role in atmospheric co2 96 00:03:07,550 --> 00:03:05,730 chemistry in particular the chemistry of 97 00:03:10,130 --> 00:03:07,560 anoxic atmospheres because it's where 98 00:03:11,870 --> 00:03:10,140 co2 and h2o absorb by contrast when I 99 00:03:13,340 --> 00:03:11,880 talk about new UV radiation I'm 100 00:03:15,320 --> 00:03:13,350 referring to wavelengths longer than 101 00:03:16,580 --> 00:03:15,330 about 200 nanometers and those are the 102 00:03:19,070 --> 00:03:16,590 wavelengths that reach the surface for 103 00:03:21,140 --> 00:03:19,080 anoxic worlds and so play controlling 104 00:03:23,600 --> 00:03:21,150 roles and surficial chemistry's you 105 00:03:26,030 --> 00:03:23,610 might be asking why I'm talking about UV 106 00:03:27,680 --> 00:03:26,040 light in the context of chemistry the 107 00:03:29,030 --> 00:03:27,690 big picture is that well pretty much 108 00:03:31,610 --> 00:03:29,040 everything absorbs there so this is a 109 00:03:32,750 --> 00:03:31,620 plot from functions paper in 2014 and we 110 00:03:34,699 --> 00:03:32,760 see that many of the important 111 00:03:36,890 --> 00:03:34,709 biomolecules in the atmosphere absorb in 112 00:03:39,050 --> 00:03:36,900 this band you might say well maybe 113 00:03:41,030 --> 00:03:39,060 that's a little bit biased so I'm not 114 00:03:42,350 --> 00:03:41,040 trying to overwhelm you over here the 115 00:03:44,600 --> 00:03:42,360 big picture here is that these are just 116 00:03:45,890 --> 00:03:44,610 a bunch of molecules that I've 117 00:03:47,660 --> 00:03:45,900 identified as being important for 118 00:03:49,280 --> 00:03:47,670 biochemistry and for atmospheric 119 00:03:50,840 --> 00:03:49,290 chemistry you can ignore almost 120 00:03:52,520 --> 00:03:50,850 everything except the numbers in red 121 00:03:54,110 --> 00:03:52,530 which are the photon wavelengths 122 00:03:56,150 --> 00:03:54,120 corresponding to the energy system of 123 00:03:59,740 --> 00:03:56,160 the bonds of they're associated with and 124 00:04:02,300 --> 00:03:59,750 the big picture takeaway here is that 125 00:04:04,610 --> 00:04:02,310 photons in the UV regime affect all of 126 00:04:06,170 --> 00:04:04,620 these bonds pretty much so that's the 127 00:04:08,360 --> 00:04:06,180 big picture reason that UV is important 128 00:04:09,590 --> 00:04:08,370 and so far have kind of emphasized bond 129 00:04:11,120 --> 00:04:09,600 so I've been kind of emphasizing 130 00:04:13,370 --> 00:04:11,130 catalysis but of course that's not all 131 00:04:14,690 --> 00:04:13,380 that UV does so UV can create the 132 00:04:16,610 --> 00:04:14,700 Telesis and that's a very important 133 00:04:18,289 --> 00:04:16,620 function but it can also an eyes 134 00:04:19,670 --> 00:04:18,299 molecules so knocking off free electrons 135 00:04:21,560 --> 00:04:19,680 and then go on to participate in further 136 00:04:23,900 --> 00:04:21,570 chemistry which I'll touch on later and 137 00:04:25,250 --> 00:04:23,910 it can also perform photo excitation so 138 00:04:27,230 --> 00:04:25,260 it doesn't have to break up a molecule 139 00:04:28,340 --> 00:04:27,240 it can instead boost its electrons into 140 00:04:29,659 --> 00:04:28,350 a high energy state so they can 141 00:04:32,360 --> 00:04:29,669 participate in chemistry that would then 142 00:04:34,350 --> 00:04:32,370 normally be forbidden so that's kind of 143 00:04:35,850 --> 00:04:34,360 the big picture orientation on what UV 144 00:04:38,339 --> 00:04:35,860 and why we care about it when we think 145 00:04:39,839 --> 00:04:38,349 about chemical systems so my talk is 146 00:04:41,129 --> 00:04:39,849 divided into four parts and I've just 147 00:04:42,540 --> 00:04:41,139 kind of gone through the introduction 148 00:04:44,309 --> 00:04:42,550 aisle next to be stepping through the 149 00:04:45,929 --> 00:04:44,319 first part of a core part of my talk 150 00:04:48,209 --> 00:04:45,939 which is how UV light impacts prebiotic 151 00:04:49,529 --> 00:04:48,219 chemistry then I move on to UV light in 152 00:04:51,779 --> 00:04:49,539 the search for biosignatures and then 153 00:04:53,309 --> 00:04:51,789 I'll summarize some conclusions but 154 00:04:55,679 --> 00:04:53,319 first prebiotic chemistry 155 00:04:56,820 --> 00:04:55,689 what is prebiotic chemistry prebiotic 156 00:04:58,649 --> 00:04:56,830 chemistry is a study of trying to 157 00:05:00,779 --> 00:04:58,659 understand how we went from this in 158 00:05:02,399 --> 00:05:00,789 other words the geology a dead planet to 159 00:05:04,080 --> 00:05:02,409 this something that we would recognize 160 00:05:06,149 --> 00:05:04,090 as being a like for example this model 161 00:05:08,459 --> 00:05:06,159 protocell over here as a consequence 162 00:05:10,619 --> 00:05:08,469 prebiotic chemistry has two natural axes 163 00:05:12,659 --> 00:05:10,629 of study one is kind of planetary 164 00:05:14,700 --> 00:05:12,669 science or geochemical it's trying to 165 00:05:15,990 --> 00:05:14,710 understand this what was the milieu what 166 00:05:17,640 --> 00:05:16,000 was the range of environments under 167 00:05:18,930 --> 00:05:17,650 which life emerged here on earth 168 00:05:20,100 --> 00:05:18,940 what were their abundant what were the 169 00:05:22,350 --> 00:05:20,110 chemical conditions what were the 170 00:05:23,730 --> 00:05:22,360 availability of trace of trace compounds 171 00:05:24,899 --> 00:05:23,740 stuff like that 172 00:05:27,480 --> 00:05:24,909 and that's really the concern of 173 00:05:28,800 --> 00:05:27,490 geochemists of planetary scientists and 174 00:05:30,899 --> 00:05:28,810 so on and so forth and it's where I feel 175 00:05:33,420 --> 00:05:30,909 most comfortable for example the second 176 00:05:34,920 --> 00:05:33,430 axis is this what was a transformation 177 00:05:36,450 --> 00:05:34,930 process how do you get from simple 178 00:05:39,600 --> 00:05:36,460 molecules that geology makes available 179 00:05:41,189 --> 00:05:39,610 in bulk to be more complicated to 180 00:05:43,830 --> 00:05:41,199 increasingly complex molecules and 181 00:05:45,809 --> 00:05:43,840 eventually life this so far is most of 182 00:05:47,820 --> 00:05:45,819 the gain domain of synthetic chemists 183 00:05:49,080 --> 00:05:47,830 which I am NOT but I talked them a 184 00:05:52,950 --> 00:05:49,090 little bit so maybe I can tell you a 185 00:05:54,480 --> 00:05:52,960 little bit about that in the context of 186 00:05:55,980 --> 00:05:54,490 origin of life it may confuse you a 187 00:05:58,350 --> 00:05:55,990 little bit that I'm talking about UV 188 00:05:59,730 --> 00:05:58,360 radiation UV radiation in our field is 189 00:06:02,339 --> 00:05:59,740 typically in both as a strong negative 190 00:06:03,809 --> 00:06:02,349 for life after all if we go outside and 191 00:06:06,649 --> 00:06:03,819 we get too much UV we get skin cancer 192 00:06:08,730 --> 00:06:06,659 this is generally considered negative 193 00:06:10,320 --> 00:06:08,740 kind of more directly if you're a 194 00:06:12,329 --> 00:06:10,330 laboratory microbiologist and you want 195 00:06:14,399 --> 00:06:12,339 to sterilize your glassware one tool you 196 00:06:18,209 --> 00:06:14,409 can use to do that is a radiating with 197 00:06:19,619 --> 00:06:18,219 very high energy Shore UV radiation so 198 00:06:21,119 --> 00:06:19,629 in that case how can i how can we 199 00:06:23,850 --> 00:06:21,129 possibly think about UV as potentially 200 00:06:25,619 --> 00:06:23,860 playing a positive role I think one key 201 00:06:27,059 --> 00:06:25,629 point to keep in mind is that you need 202 00:06:28,980 --> 00:06:27,069 to be cautious when we extrapolate from 203 00:06:31,320 --> 00:06:28,990 modern life to past life and gave to the 204 00:06:35,369 --> 00:06:31,330 origin of life the canonical example of 205 00:06:37,079 --> 00:06:35,379 this is probably oxygen and two first 206 00:06:39,059 --> 00:06:37,089 order oxygen is violently violently 207 00:06:40,909 --> 00:06:39,069 toxic I know this might come as a bit of 208 00:06:43,680 --> 00:06:40,919 surprise to all of us here in this room 209 00:06:45,089 --> 00:06:43,690 and because oxygen is integral for both 210 00:06:47,249 --> 00:06:45,099 for not only for us but for pretty much 211 00:06:48,269 --> 00:06:47,259 all complex life here in this planet but 212 00:06:49,859 --> 00:06:48,279 but the reason we 213 00:06:51,509 --> 00:06:49,869 able to tolerate oxygen is because of 214 00:06:53,759 --> 00:06:51,519 extremely complex biochemical machinery 215 00:06:55,019 --> 00:06:53,769 we built um when Oh to interacts with 216 00:06:56,729 --> 00:06:55,029 cells in critically when it's processed 217 00:06:59,219 --> 00:06:56,739 through meta through metabolic light 218 00:07:01,019 --> 00:06:59,229 like pathways it very readily gives rise 219 00:07:03,449 --> 00:07:01,029 to so-called reactive oxygen species 220 00:07:05,339 --> 00:07:03,459 these oxygens reactive oxygen species 221 00:07:07,589 --> 00:07:05,349 love attacking biomolecules and 222 00:07:09,839 --> 00:07:07,599 essentially blowing them up and this is 223 00:07:12,779 --> 00:07:09,849 why many obligate anaerobes are very 224 00:07:14,699 --> 00:07:12,789 very vulnerable to oxygen toxicity we 225 00:07:16,229 --> 00:07:14,709 have actually bought of oh dear this is 226 00:07:17,879 --> 00:07:16,239 a slightly older version they're 227 00:07:19,229 --> 00:07:17,889 supposed to be things like Kerr exudates 228 00:07:23,909 --> 00:07:19,239 and things like that listed here various 229 00:07:25,769 --> 00:07:23,919 enzymes but so we've we have evolved a 230 00:07:27,479 --> 00:07:25,779 suite a very complex pathway sit deeply 231 00:07:29,429 --> 00:07:27,489 to process to come up with that oxygen 232 00:07:30,869 --> 00:07:29,439 and then to be able to then exploit the 233 00:07:34,079 --> 00:07:30,879 free energy gradients that oxygen makes 234 00:07:36,029 --> 00:07:34,089 available to us and in fact it's thought 235 00:07:38,569 --> 00:07:36,039 that at the rise of oxygen led to the 236 00:07:41,549 --> 00:07:38,579 first great mass extinction by many and 237 00:07:43,169 --> 00:07:41,559 even more fundamental and non-intuitive 238 00:07:45,119 --> 00:07:43,179 result comes in the form of liquid water 239 00:07:46,919 --> 00:07:45,129 liquid water is essential for all life 240 00:07:48,539 --> 00:07:46,929 as we know it it fundamentally guides 241 00:07:50,459 --> 00:07:48,549 our search for life in the universe our 242 00:07:52,799 --> 00:07:50,469 astrobiology strategy is to literally 243 00:07:54,479 --> 00:07:52,809 follow the water but so it might 244 00:07:55,619 --> 00:07:54,489 surprise you to learn that h2 is 245 00:07:57,029 --> 00:07:55,629 actually somewhat corrosive to 246 00:07:59,159 --> 00:07:57,039 biomolecules and in particular to 247 00:08:01,589 --> 00:07:59,169 proteins and nucleic acids because it 248 00:08:03,509 --> 00:08:01,599 love doing hydrolysis reactions this has 249 00:08:05,519 --> 00:08:03,519 given rise to what is the so called ah 250 00:08:07,439 --> 00:08:05,529 the so-called water Bihar ducks which 251 00:08:09,509 --> 00:08:07,449 was enunciated in the NRC report on the 252 00:08:11,399 --> 00:08:09,519 limits of life in planetary systems and 253 00:08:13,439 --> 00:08:11,409 another review paper by Steve Benner and 254 00:08:15,479 --> 00:08:13,449 what it essentially boils down to is 255 00:08:17,369 --> 00:08:15,489 this if you take biomolecules for 256 00:08:19,259 --> 00:08:17,379 example this is a schematic of a nucleic 257 00:08:20,759 --> 00:08:19,269 acid and you look at the lifetimes of 258 00:08:22,799 --> 00:08:20,769 each of these each of the bonds that 259 00:08:23,939 --> 00:08:22,809 make it up in liquid water you find that 260 00:08:25,499 --> 00:08:23,949 its standard conditions are all 261 00:08:27,539 --> 00:08:25,509 geologically short they're order a 262 00:08:29,009 --> 00:08:27,549 hundred years or less so theories of the 263 00:08:30,600 --> 00:08:29,019 origin of life that we rely on 264 00:08:32,429 --> 00:08:30,610 drip-feeding in organics and building 265 00:08:33,689 --> 00:08:32,439 them up over mega years that's a little 266 00:08:34,889 --> 00:08:33,699 bit of a problem because they won't just 267 00:08:37,139 --> 00:08:34,899 build up build actually decay on a 268 00:08:38,699 --> 00:08:37,149 relatively short timescale and so this 269 00:08:41,459 --> 00:08:38,709 is called this is a so-called water 270 00:08:42,449 --> 00:08:41,469 paradox it's also why organic chemists 271 00:08:44,219 --> 00:08:42,459 when they perform their synthesis 272 00:08:46,460 --> 00:08:44,229 typically use organic solvents not water 273 00:08:48,389 --> 00:08:46,470 which I recently learned has prompted a 274 00:08:50,879 --> 00:08:48,399 sustainability crisis in organic 275 00:08:52,019 --> 00:08:50,889 chemistry and it's also why even 276 00:08:53,309 --> 00:08:52,029 grizzled organic chemists don't 277 00:08:54,660 --> 00:08:53,319 immediately laugh us out of the room 278 00:08:56,970 --> 00:08:54,670 when we talk about life and organic 279 00:08:58,799 --> 00:08:56,980 solvents untighten because truth be told 280 00:09:00,419 --> 00:08:58,809 many of them were trying to design life 281 00:09:01,060 --> 00:09:00,429 from the ground up they might not use a 282 00:09:03,280 --> 00:09:01,070 liquid 283 00:09:05,650 --> 00:09:03,290 either so the key takeaway from here is 284 00:09:07,480 --> 00:09:05,660 it's not as simple as saying is is this 285 00:09:08,950 --> 00:09:07,490 good for life or bad for life everything 286 00:09:10,510 --> 00:09:08,960 has good aspects and bad aspects you 287 00:09:12,370 --> 00:09:10,520 have to ask does the good outweigh the 288 00:09:13,810 --> 00:09:12,380 bad and ie there's a construct of 289 00:09:16,990 --> 00:09:13,820 chemistry dominant or the destructive 290 00:09:19,060 --> 00:09:17,000 chemistry in this view through this lens 291 00:09:21,730 --> 00:09:19,070 UV starts looking a little bit different 292 00:09:23,230 --> 00:09:21,740 ah it's there there's kind of three 293 00:09:24,790 --> 00:09:23,240 broad families of reasons to think that 294 00:09:26,380 --> 00:09:24,800 UV light is relevant to the origin of 295 00:09:28,150 --> 00:09:26,390 life the first is experimental and 296 00:09:29,980 --> 00:09:28,160 stretches back I think at this point six 297 00:09:31,720 --> 00:09:29,990 decades and it's the fact that in the 298 00:09:33,100 --> 00:09:31,730 laboratory UV life has been shown to a 299 00:09:34,990 --> 00:09:33,110 driver to drive a diverse range of 300 00:09:38,010 --> 00:09:35,000 synthesis it can form each of the major 301 00:09:40,780 --> 00:09:38,020 classes of biomolecules ie sugars 302 00:09:43,900 --> 00:09:40,790 nuclear bases and nucleotides amino 303 00:09:45,430 --> 00:09:43,910 acids lipid the cursors it can also 304 00:09:47,950 --> 00:09:45,440 drive a number of processes including 305 00:09:49,780 --> 00:09:47,960 earth oligomerization and so on and so 306 00:09:51,160 --> 00:09:49,790 forth one of the pathways that I'm most 307 00:09:53,800 --> 00:09:51,170 excited about is that UV light is 308 00:09:55,840 --> 00:09:53,810 integral to the only pathway but the 309 00:09:57,610 --> 00:09:55,850 Selective high-yield synthesis are the 310 00:10:00,880 --> 00:09:57,620 ribonucleotides the main funding mental 311 00:10:02,230 --> 00:10:00,890 components of RNA and UV light is 312 00:10:04,030 --> 00:10:02,240 utterly key to that in ways that I'll 313 00:10:06,370 --> 00:10:04,040 talk about I'll touch on just a little 314 00:10:08,020 --> 00:10:06,380 bit later so that's experimental it 315 00:10:09,880 --> 00:10:08,030 works in the lab there's also a 316 00:10:11,200 --> 00:10:09,890 theoretical argument not only was UV 317 00:10:12,610 --> 00:10:11,210 light the most abundant source of 318 00:10:13,870 --> 00:10:12,620 chemical free energy to the surface of 319 00:10:16,930 --> 00:10:13,880 early Earth by several orders of 320 00:10:19,000 --> 00:10:16,940 magnitude it also turns out that because 321 00:10:20,710 --> 00:10:19,010 that UV light arrives quantized right of 322 00:10:22,630 --> 00:10:20,720 the energy of those molecular bonds it's 323 00:10:24,070 --> 00:10:22,640 capable of directly effecting changes in 324 00:10:26,440 --> 00:10:24,080 the electronic states of molecular 325 00:10:28,090 --> 00:10:26,450 systems in other words it's capable of 326 00:10:29,380 --> 00:10:28,100 affecting irreversible changes in the 327 00:10:31,300 --> 00:10:29,390 entropy of molecules is capable of 328 00:10:32,860 --> 00:10:31,310 kinetically trapping them in ways that 329 00:10:34,320 --> 00:10:32,870 other sources of energy like thermal 330 00:10:36,760 --> 00:10:34,330 energy can't do because there's always a 331 00:10:37,990 --> 00:10:36,770 reversibility problem there and that was 332 00:10:41,140 --> 00:10:38,000 worked out in a very nice paper by 333 00:10:42,730 --> 00:10:41,150 Robert Pascale in 2012 but perhaps the 334 00:10:45,190 --> 00:10:42,740 most compelling piece of evidence is is 335 00:10:46,540 --> 00:10:45,200 historical there's a long body of work 336 00:10:48,100 --> 00:10:46,550 here but I think it reaches the POE 337 00:10:50,740 --> 00:10:48,110 theosis so far and work by Ashley 338 00:10:53,170 --> 00:10:50,750 Beckstead in 2016 what this is a plot 339 00:10:54,580 --> 00:10:53,180 here is of the nucleus of the UV 340 00:10:55,810 --> 00:10:54,590 resistance of different nucleobases so 341 00:10:57,420 --> 00:10:55,820 if you shine light on a nuclear base 342 00:11:01,060 --> 00:10:57,430 will it blow up or not 343 00:11:02,470 --> 00:11:01,070 the blue squares over here the nuclear 344 00:11:04,660 --> 00:11:02,480 bases it like uses the biogenic 345 00:11:06,160 --> 00:11:04,670 nucleobases the red circles are nuclear 346 00:11:07,450 --> 00:11:06,170 bases that life doesn't use there's a 347 00:11:08,830 --> 00:11:07,460 whole bunch more of these red ones way 348 00:11:10,630 --> 00:11:08,840 over here but that later didn't butter 349 00:11:12,820 --> 00:11:10,640 show because you're getting the picture 350 00:11:14,070 --> 00:11:12,830 already this is a log scale over here 351 00:11:15,540 --> 00:11:14,080 the lower you are the more you 352 00:11:17,040 --> 00:11:15,550 resistant you are so something here is 353 00:11:18,750 --> 00:11:17,050 ten times more UV resistant than 354 00:11:20,580 --> 00:11:18,760 something here and we see that the 355 00:11:22,050 --> 00:11:20,590 biogenic nucleobases are united in being 356 00:11:23,970 --> 00:11:22,060 extremely resistant to UV attack they 357 00:11:25,310 --> 00:11:23,980 have extremely efficient non rated photo 358 00:11:28,260 --> 00:11:25,320 excitation happens 359 00:11:29,280 --> 00:11:28,270 photo photo D excitation pathways which 360 00:11:32,880 --> 00:11:29,290 has been evidence that they at least 361 00:11:34,410 --> 00:11:32,890 evolved in high UV environment okay so 362 00:11:35,910 --> 00:11:34,420 UV light might be relevant to the order 363 00:11:37,410 --> 00:11:35,920 of life people have flushed the people 364 00:11:39,780 --> 00:11:37,420 have flushed out a lot in the past 365 00:11:41,160 --> 00:11:39,790 decades but this fundamental idea has 366 00:11:42,180 --> 00:11:41,170 been around for a little while so people 367 00:11:43,500 --> 00:11:42,190 have been thinking about it for a little 368 00:11:45,390 --> 00:11:43,510 while and in particular asking the 369 00:11:47,910 --> 00:11:45,400 question what exactly was the nature of 370 00:11:49,170 --> 00:11:47,920 the UV radiation on early Earth tamiya 371 00:11:50,550 --> 00:11:49,180 knowledge some of the first work on this 372 00:11:52,440 --> 00:11:50,560 was done by charles koch held back at 373 00:11:54,300 --> 00:11:52,450 the turn of the century and the key 374 00:11:56,370 --> 00:11:54,310 result that came out of his work was 375 00:11:57,480 --> 00:11:56,380 that if you just kind of take by do 376 00:11:59,550 --> 00:11:57,490 tional models of the earlier its 377 00:12:00,960 --> 00:11:59,560 atmospheric state and plugged in through 378 00:12:02,220 --> 00:12:00,970 a radiative transfer model you 379 00:12:03,810 --> 00:12:02,230 essentially get nothing at wavelengths 380 00:12:05,460 --> 00:12:03,820 shorter than 200 and that's because of 381 00:12:08,220 --> 00:12:05,470 atmospheric co2 that really robustly 382 00:12:09,600 --> 00:12:08,230 absorbs there you might say well that's 383 00:12:11,250 --> 00:12:09,610 all well and good but that's that's a 384 00:12:12,750 --> 00:12:11,260 final model there's a lot of uncertainty 385 00:12:15,390 --> 00:12:12,760 about the earlier its atmospheric state 386 00:12:17,670 --> 00:12:15,400 how can you be sure that's the case and 387 00:12:19,020 --> 00:12:17,680 the reason we can actually be relatively 388 00:12:21,810 --> 00:12:19,030 certain that's the case boils down to 389 00:12:22,740 --> 00:12:21,820 the existence of atmospheric co2 so we 390 00:12:24,510 --> 00:12:22,750 know that there must have been a certain 391 00:12:26,900 --> 00:12:24,520 minimum amount of co2 in order to solve 392 00:12:29,460 --> 00:12:26,910 the faint young Sun problem the lure and 393 00:12:30,780 --> 00:12:29,470 the minimum amount of co2 that's allowed 394 00:12:31,800 --> 00:12:30,790 when the climate models comes from the 395 00:12:33,540 --> 00:12:31,810 work though of Wordsworth and Pierre 396 00:12:35,280 --> 00:12:33,550 Humber it's if you have a ton of n2 in 397 00:12:37,680 --> 00:12:35,290 the atmosphere you can have as little as 398 00:12:39,900 --> 00:12:37,690 eight hundred micro Birds of co2 and 399 00:12:42,870 --> 00:12:39,910 that's shown here in this what color is 400 00:12:44,370 --> 00:12:42,880 it on this one not great in this purple 401 00:12:46,110 --> 00:12:44,380 line over here so this is showing the UV 402 00:12:47,880 --> 00:12:46,120 surface environment for early Earth 403 00:12:50,070 --> 00:12:47,890 assuming point nine bars of nitrogen 404 00:12:51,960 --> 00:12:50,080 bearing amounts of co2 the black line is 405 00:12:53,550 --> 00:12:51,970 what the young Sun was putting out this 406 00:12:55,890 --> 00:12:53,560 line is eight hundred micro bars of co2 407 00:12:56,670 --> 00:12:55,900 and we see that even with this low co2 408 00:12:58,110 --> 00:12:56,680 inventory 409 00:13:00,300 --> 00:12:58,120 we've already essentially put in place 410 00:13:01,830 --> 00:13:00,310 at 200 nanometer cutoff so even at the 411 00:13:03,870 --> 00:13:01,840 minimum amount of co2 you don't get 412 00:13:05,610 --> 00:13:03,880 anything short of 200 most other 413 00:13:06,690 --> 00:13:05,620 components of the planets of earlier its 414 00:13:10,020 --> 00:13:06,700 atmosphere that we think were there like 415 00:13:12,210 --> 00:13:10,030 h2 n2 ch4 h2o they all those they all 416 00:13:13,530 --> 00:13:12,220 absorb over here there's you can't get 417 00:13:15,720 --> 00:13:13,540 blood from a stone those photons are 418 00:13:17,880 --> 00:13:15,730 already all gone due to co2 as a 419 00:13:19,590 --> 00:13:17,890 consequence you don't know 420 00:13:20,460 --> 00:13:19,600 as a consequence we're not sensitive to 421 00:13:23,070 --> 00:13:20,470 the uncertainty in those parameters 422 00:13:23,970 --> 00:13:23,080 although it is considerable so we don't 423 00:13:26,040 --> 00:13:23,980 care about it in that degree of 424 00:13:27,960 --> 00:13:26,050 uncertainty what about the other extreme 425 00:13:29,460 --> 00:13:27,970 this is the minimum amount of co2 426 00:13:31,050 --> 00:13:29,470 the maximum amount of co2 we could 427 00:13:32,819 --> 00:13:31,060 reasonably have is given by this red 428 00:13:34,379 --> 00:13:32,829 line over here that's if you have 70 429 00:13:35,910 --> 00:13:34,389 bars of co2 in the atmosphere it's what 430 00:13:37,550 --> 00:13:35,920 you get if you volatilize the entire 431 00:13:40,139 --> 00:13:37,560 crustal carbonate inventory of the earth 432 00:13:43,139 --> 00:13:40,149 co2 so it's kind of an extreme upper 433 00:13:44,220 --> 00:13:43,149 limit but it isn't up limit and so you 434 00:13:45,809 --> 00:13:44,230 can think of this as kind of being the 435 00:13:46,920 --> 00:13:45,819 minimum amount of UV and you see that 436 00:13:48,329 --> 00:13:46,930 this curve and this curve aren't 437 00:13:49,949 --> 00:13:48,339 actually that different and that's 438 00:13:51,329 --> 00:13:49,959 because C o2 saturation sets in 439 00:13:53,040 --> 00:13:51,339 relatively early in the absorbing regime 440 00:13:54,809 --> 00:13:53,050 long word of two or four nanometers you 441 00:13:56,460 --> 00:13:54,819 only have scattering and there are 442 00:13:57,540 --> 00:13:56,470 transmission drops of only slowly with 443 00:13:59,610 --> 00:13:57,550 optical depth because it's purely 444 00:14:00,689 --> 00:13:59,620 scattering so as its as a result we have 445 00:14:02,639 --> 00:14:00,699 a pretty good sense of this particular 446 00:14:04,139 --> 00:14:02,649 initial condition which is consistent 447 00:14:06,350 --> 00:14:04,149 with which is consisting with available 448 00:14:08,249 --> 00:14:06,360 geochemical constraints like Smith 449 00:14:09,449 --> 00:14:08,259 interestingly this is also in 450 00:14:11,939 --> 00:14:09,459 concordance with the results of some 451 00:14:13,350 --> 00:14:11,949 experiments my colleague Zoe Todd has 452 00:14:14,970 --> 00:14:13,360 started a program where she takes some 453 00:14:16,230 --> 00:14:14,980 of these UV dependent prebiotic pathways 454 00:14:17,519 --> 00:14:16,240 they're all mentioned they're pretty 455 00:14:19,650 --> 00:14:17,529 much almost all measured in the lab 456 00:14:21,480 --> 00:14:19,660 using a monochromatic source so she 457 00:14:22,740 --> 00:14:21,490 asked the question which sum which many 458 00:14:24,240 --> 00:14:22,750 planetary science think is obvious but 459 00:14:25,350 --> 00:14:24,250 is not obvious in the bio community 460 00:14:26,699 --> 00:14:25,360 which is what is the wavelength 461 00:14:29,040 --> 00:14:26,709 dependence of these pathways could they 462 00:14:30,990 --> 00:14:29,050 work under realistic UV and she finds 463 00:14:32,639 --> 00:14:31,000 that she's only looked at a few of these 464 00:14:35,970 --> 00:14:32,649 pathways so far it turns out lab work is 465 00:14:37,860 --> 00:14:35,980 hard but the few pathway she's looked at 466 00:14:39,389 --> 00:14:37,870 she's found that broadband UV pretty 467 00:14:41,129 --> 00:14:39,399 much every wavelength long word about 468 00:14:43,230 --> 00:14:41,139 200 to 10 nanometers works pretty 469 00:14:44,369 --> 00:14:43,240 effectively all the way up to about 300 470 00:14:45,509 --> 00:14:44,379 at which point it starts dropping off 471 00:14:46,610 --> 00:14:45,519 you're not getting enough juice to get 472 00:14:48,480 --> 00:14:46,620 the thing going 473 00:14:51,299 --> 00:14:48,490 intriguingly and this is much more 474 00:14:52,949 --> 00:14:51,309 tentative so far and the path wishes 475 00:14:54,119 --> 00:14:52,959 looked at shortened the far UV 476 00:14:55,980 --> 00:14:54,129 wavelengths wavelength shorter than 477 00:14:57,900 --> 00:14:55,990 about 2 10 nanometers tend to be 478 00:15:00,449 --> 00:14:57,910 strictly destructive so ah 479 00:15:01,889 --> 00:15:00,459 at these kind of moderate UV what I 480 00:15:03,869 --> 00:15:01,899 called a near UV regime you'll get 481 00:15:05,009 --> 00:15:03,879 constructive chemistry and at the far UV 482 00:15:06,809 --> 00:15:05,019 at least in the two pathways she's 483 00:15:08,670 --> 00:15:06,819 looked at so far she's gotten strict 484 00:15:09,840 --> 00:15:08,680 destruction so that aligns relatively 485 00:15:11,429 --> 00:15:09,850 well with this atmospheric window so 486 00:15:12,840 --> 00:15:11,439 that's nothing serious here because 487 00:15:13,980 --> 00:15:12,850 we've only evaluated if you pass this 488 00:15:16,259 --> 00:15:13,990 but it's something we're continuing to 489 00:15:18,119 --> 00:15:16,269 look into and the story is pretty 490 00:15:22,230 --> 00:15:18,129 similar for early Mars with the caveat 491 00:15:24,509 --> 00:15:22,240 for the for dust ah so you have this UV 492 00:15:25,799 --> 00:15:24,519 what exactly can I do for you it turns 493 00:15:27,509 --> 00:15:25,809 out there's a whole bunch of stuff but I 494 00:15:28,980 --> 00:15:27,519 want to focus on it's on the rule UV 495 00:15:30,420 --> 00:15:28,990 plays in salt and potentially solving 496 00:15:32,790 --> 00:15:30,430 one long-standing problem that's been 497 00:15:35,069 --> 00:15:32,800 around since ever since the planetary 498 00:15:37,379 --> 00:15:35,079 scientists told the told the biochemists 499 00:15:39,329 --> 00:15:37,389 they weren't the prebiotic chemists that 500 00:15:41,369 --> 00:15:39,339 they weren't allowed to have super 501 00:15:43,679 --> 00:15:41,379 methane-rich early earth atmosphere and 502 00:15:45,389 --> 00:15:43,689 it's a question of reductants most of 503 00:15:47,219 --> 00:15:45,399 the carbon that volcanoes cut out comes 504 00:15:49,409 --> 00:15:47,229 in the form of co2 most of the carbon 505 00:15:51,210 --> 00:15:49,419 and biomolecules is reduced how do you 506 00:15:53,099 --> 00:15:51,220 reduce it in the absence of atmospheric 507 00:15:53,669 --> 00:15:53,109 reductants so this has been a puzzle for 508 00:15:56,460 --> 00:15:53,679 a while 509 00:15:57,749 --> 00:15:56,470 ah a few a few years ago it was proposed 510 00:16:00,839 --> 00:15:57,759 that one potential solution to the 511 00:16:02,960 --> 00:16:00,849 puzzle came from UV light and 512 00:16:06,749 --> 00:16:02,970 specifically the idea is if you take 513 00:16:08,399 --> 00:16:06,759 hydrogen sulfide hs- coppers at a 514 00:16:09,929 --> 00:16:08,409 catalytic counterpart and UV light and 515 00:16:12,389 --> 00:16:09,939 shine them together you generate 516 00:16:13,649 --> 00:16:12,399 solvated electrons and solvated 517 00:16:14,399 --> 00:16:13,659 electrons are literally a minus charge 518 00:16:16,829 --> 00:16:14,409 floating around 519 00:16:18,449 --> 00:16:16,839 it is literally reducing power and it's 520 00:16:19,739 --> 00:16:18,459 because it's just a free electron it's 521 00:16:21,779 --> 00:16:19,749 actually quite reactive it can go off 522 00:16:23,039 --> 00:16:21,789 and reduce all sorts of things and so 523 00:16:24,479 --> 00:16:23,049 this was a solution that was put forward 524 00:16:25,859 --> 00:16:24,489 for how do you get reducing power and a 525 00:16:28,409 --> 00:16:25,869 comparatively oxidized earlier 526 00:16:30,389 --> 00:16:28,419 environment there's a couple of problems 527 00:16:32,399 --> 00:16:30,399 with this scenario one is its reliance 528 00:16:33,839 --> 00:16:32,409 on copper as a catalytic partner because 529 00:16:35,429 --> 00:16:33,849 copper is geologically rare and not very 530 00:16:37,109 --> 00:16:35,439 plausible the other is that it's 531 00:16:39,179 --> 00:16:37,119 actually not very efficient 532 00:16:40,889 --> 00:16:39,189 it doesn't in particular it doesn't work 533 00:16:42,389 --> 00:16:40,899 under early Earth UV which is something 534 00:16:43,889 --> 00:16:42,399 that Palmer figured out when he tried to 535 00:16:46,979 --> 00:16:43,899 simulate realistic environments in the 536 00:16:48,389 --> 00:16:46,989 lab however as planetary scientists we 537 00:16:50,429 --> 00:16:48,399 know that sulfide is not the only s 538 00:16:52,559 --> 00:16:50,439 carrier on on earth in fact it's not 539 00:16:54,809 --> 00:16:52,569 even a major one most s comes out of 540 00:16:57,239 --> 00:16:54,819 volcanoes as so2 and in the absence of 541 00:16:59,069 --> 00:16:57,249 oxygen that s will then dissolve into 542 00:17:00,809 --> 00:16:59,079 liquid water it'll district or it'll 543 00:17:01,139 --> 00:17:00,819 sorry not disproportionate dissociate to 544 00:17:04,079 --> 00:17:01,149 form 545 00:17:06,090 --> 00:17:04,089 sulfides the cell fights as a three two 546 00:17:07,740 --> 00:17:06,100 - HS - three - and so on and so forth 547 00:17:09,629 --> 00:17:07,750 and if you just do a very simple model 548 00:17:10,829 --> 00:17:09,639 of that process for shallow ponds you 549 00:17:12,389 --> 00:17:10,839 find that prebiotic ponds should have 550 00:17:15,600 --> 00:17:12,399 been sulphide rich concentrations of 10 551 00:17:16,889 --> 00:17:15,610 micromolar or higher and we told that we 552 00:17:18,899 --> 00:17:16,899 had a discussion with this about her 553 00:17:20,159 --> 00:17:18,909 prebiotic chemistry colleagues I don't 554 00:17:21,299 --> 00:17:20,169 know when those guys sleep because we 555 00:17:22,769 --> 00:17:21,309 had our conversation around 4:00 p.m. 556 00:17:25,019 --> 00:17:22,779 and we had preliminary results next 557 00:17:27,509 --> 00:17:25,029 morning they essentially plugged yeah 558 00:17:29,340 --> 00:17:27,519 they work real hard over there they 559 00:17:30,629 --> 00:17:29,350 plugged it into there about a chemistry 560 00:17:32,310 --> 00:17:30,639 pathways and the net thing that they 561 00:17:34,649 --> 00:17:32,320 found is that not only does sulfide work 562 00:17:37,289 --> 00:17:34,659 it works a lot better it works with it 563 00:17:38,730 --> 00:17:37,299 works under realistic UV radiation so it 564 00:17:40,769 --> 00:17:38,740 provides those others electrons of the 565 00:17:42,810 --> 00:17:40,779 right pace and it works with iron is a 566 00:17:44,639 --> 00:17:42,820 con as a catalytic partner not offer and 567 00:17:46,259 --> 00:17:44,649 that's important because iron is much 568 00:17:47,669 --> 00:17:46,269 more poetically plausible so you get two 569 00:17:49,590 --> 00:17:47,679 improvements for the price of one here 570 00:17:50,850 --> 00:17:49,600 so that's one way in which you can 571 00:17:53,050 --> 00:17:50,860 really help them solve under some of 572 00:17:57,190 --> 00:17:53,060 these long-standing problems 573 00:17:59,920 --> 00:17:57,200 however UV giveth UV taketh away and in 574 00:18:01,330 --> 00:17:59,930 particular because UV is delivering so 575 00:18:03,520 --> 00:18:01,340 much chemical free energy it's doing all 576 00:18:05,200 --> 00:18:03,530 sorts of things one of the things that's 577 00:18:07,540 --> 00:18:05,210 doing is it's controlling the inventory 578 00:18:09,370 --> 00:18:07,550 of UV sensitive molecules of the surface 579 00:18:11,760 --> 00:18:09,380 of the earlier and this is important 580 00:18:14,350 --> 00:18:11,770 where it comes to the nitrogen question 581 00:18:15,700 --> 00:18:14,360 biomolecules incorporate nitrogen we do 582 00:18:18,130 --> 00:18:15,710 have a ton of nitrogen that's floating 583 00:18:19,330 --> 00:18:18,140 all around this as nitrogen gas but as 584 00:18:21,520 --> 00:18:19,340 Colin told us earlier in the meeting 585 00:18:23,830 --> 00:18:21,530 that nitrogen gas on its own isn't very 586 00:18:25,390 --> 00:18:23,840 helpful because it's bound it's it was 587 00:18:27,910 --> 00:18:25,400 nitrogen atoms are printed connected by 588 00:18:29,920 --> 00:18:27,920 the high energy really strong triple 589 00:18:31,420 --> 00:18:29,930 bond it's really hard for even modern 590 00:18:32,890 --> 00:18:31,430 life to break apart that bond light 591 00:18:35,560 --> 00:18:32,900 merging is often the limiting ingredient 592 00:18:36,730 --> 00:18:35,570 in modern biology and it's even harder 593 00:18:39,520 --> 00:18:36,740 to figure out how you could do that 594 00:18:40,990 --> 00:18:39,530 abiotic way one mechanism that's been 595 00:18:43,660 --> 00:18:41,000 proposed for over the last three decades 596 00:18:44,950 --> 00:18:43,670 is all lightning the idea that if you 597 00:18:47,050 --> 00:18:44,960 had lightning in an end to co2 598 00:18:48,460 --> 00:18:47,060 atmosphere that should that should be 599 00:18:50,560 --> 00:18:48,470 able to jazz apart that entry on that 600 00:18:52,510 --> 00:18:50,570 co2 the ends in the O's can then combine 601 00:18:54,040 --> 00:18:52,520 and form NO X which can then rain out 602 00:18:56,110 --> 00:18:54,050 and potentially accumulate in prebiotic 603 00:18:58,180 --> 00:18:56,120 reservoirs this is an idea that's been 604 00:19:00,790 --> 00:18:58,190 simulated with increasing precision over 605 00:19:02,500 --> 00:19:00,800 the past as past few decades culminating 606 00:19:03,730 --> 00:19:02,510 in a recent couple of papers which 607 00:19:05,170 --> 00:19:03,740 predicted the concentration of these 608 00:19:08,440 --> 00:19:05,180 molecules should reach up to 10 609 00:19:10,120 --> 00:19:08,450 millimolar for a reference to the modern 610 00:19:13,060 --> 00:19:10,130 I know X concentration in the bulk ocean 611 00:19:15,040 --> 00:19:13,070 is 50 micromolar so this is so people 612 00:19:16,780 --> 00:19:15,050 were predicting that you get 200 times 613 00:19:18,070 --> 00:19:16,790 as much I know X in big early ocean in 614 00:19:19,900 --> 00:19:18,080 the absence of biological carbon 615 00:19:23,290 --> 00:19:19,910 nitrogen fixation compared to the modern 616 00:19:25,600 --> 00:19:23,300 ocean and this would be correct if the 617 00:19:26,950 --> 00:19:25,610 Sun didn't have any UV emission the 618 00:19:28,590 --> 00:19:26,960 challenge here is that what people 619 00:19:31,090 --> 00:19:28,600 hadn't included before is the fact that 620 00:19:32,980 --> 00:19:31,100 UV light is not--there's robustly known 621 00:19:34,600 --> 00:19:32,990 to photolyze nitrate and nitrite in 622 00:19:36,490 --> 00:19:34,610 natural waters this is observed in situ 623 00:19:37,630 --> 00:19:36,500 and it's also observed in the lab if you 624 00:19:39,250 --> 00:19:37,640 include the effects of this rate 625 00:19:40,570 --> 00:19:39,260 constant you find that the oceans would 626 00:19:41,890 --> 00:19:40,580 never have built up pre medically 627 00:19:44,250 --> 00:19:41,900 relevant by which I'd be more than one 628 00:19:46,300 --> 00:19:44,260 micromolar concentrations of that wax 629 00:19:47,620 --> 00:19:46,310 this is a sink that's about three to 630 00:19:49,240 --> 00:19:47,630 five orders of magnitude stronger than 631 00:19:51,280 --> 00:19:49,250 the earlier sink which was processing at 632 00:19:52,960 --> 00:19:51,290 deep sea hydrothermal vents and this 633 00:19:54,340 --> 00:19:52,970 mechanism would probably keep fixed 634 00:19:57,550 --> 00:19:54,350 nitrogen concentrations low and most 635 00:19:59,260 --> 00:19:57,560 bodies of water you they could get to be 636 00:20:00,880 --> 00:19:59,270 high in a very particular scenario that 637 00:20:03,250 --> 00:20:00,890 is to say specifically in shallow ponds 638 00:20:05,380 --> 00:20:03,260 with large drainage ratios and the idea 639 00:20:06,460 --> 00:20:05,390 there is that if you're delivering your 640 00:20:07,659 --> 00:20:06,470 nitrogen from the atmosphere 641 00:20:09,310 --> 00:20:07,669 it's shallower you dilute the 642 00:20:11,289 --> 00:20:09,320 atmospheric supply over a thinner column 643 00:20:12,879 --> 00:20:11,299 and if you have a large catchment area 644 00:20:14,560 --> 00:20:12,889 you can integrate runoff from a larger 645 00:20:16,509 --> 00:20:14,570 area so maybe you can get more nos that 646 00:20:18,730 --> 00:20:16,519 way and if you have such a favored 647 00:20:20,289 --> 00:20:18,740 lavond then you can access periodically 648 00:20:25,450 --> 00:20:20,299 relevant concentrations of nitrate and 649 00:20:27,639 --> 00:20:25,460 nitrite there's except so this is a 650 00:20:28,779 --> 00:20:27,649 theoretical prediction I was kind of 651 00:20:30,909 --> 00:20:28,789 expecting it to be a theoretical 652 00:20:32,889 --> 00:20:30,919 prediction for a while because night 653 00:20:35,710 --> 00:20:32,899 minerals of nitrate are very very 654 00:20:38,350 --> 00:20:35,720 soluble however nitrogen or organic dung 655 00:20:39,820 --> 00:20:38,360 is not very soluble it turns out that 656 00:20:41,230 --> 00:20:39,830 one of the messengers we have about 657 00:20:43,240 --> 00:20:41,240 ancient nitrogen is in the form of 658 00:20:45,549 --> 00:20:43,250 Kerrigan's and there was a group that 659 00:20:48,340 --> 00:20:45,559 last year published a paper analyzing 660 00:20:51,460 --> 00:20:48,350 Carrigan's from 3.2 billion year old 661 00:20:53,830 --> 00:20:51,470 carriages organic dung from both Oceanic 662 00:20:55,480 --> 00:20:53,840 and lacustrine Lake environments and 663 00:20:57,279 --> 00:20:55,490 they identified a signature in the 664 00:20:58,659 --> 00:20:57,289 nitrogen isotopes in the lakes that was 665 00:20:59,440 --> 00:20:58,669 consistent with nitrogen fixation in 666 00:21:01,210 --> 00:20:59,450 some of the lakes 667 00:21:02,830 --> 00:21:01,220 I'm sorry nitrogen with denitrification 668 00:21:04,149 --> 00:21:02,840 in some of the lakes so it seemed like 669 00:21:06,100 --> 00:21:04,159 microbes are eating nitrate over there 670 00:21:07,419 --> 00:21:06,110 however they did not identify that 671 00:21:09,279 --> 00:21:07,429 feature in all the lakes nor do they 672 00:21:10,990 --> 00:21:09,289 identified in the oceans so the 673 00:21:12,310 --> 00:21:11,000 implication of this is that some lakes 674 00:21:13,930 --> 00:21:12,320 and ponds and early Earth for prebiotic 675 00:21:16,060 --> 00:21:13,940 on prebiotic earth or nitro rich but not 676 00:21:17,740 --> 00:21:16,070 the oceans and not all ponds which is in 677 00:21:19,119 --> 00:21:17,750 broad concealing swith our scenario so 678 00:21:20,440 --> 00:21:19,129 we're kind of excited about the prospect 679 00:21:24,279 --> 00:21:20,450 that maybe we can test these predictions 680 00:21:25,480 --> 00:21:24,289 more rigorously there but still far I've 681 00:21:27,279 --> 00:21:25,490 talked to you only about planetary 682 00:21:29,499 --> 00:21:27,289 science and this is XO claims after all 683 00:21:30,909 --> 00:21:29,509 let's let's go to a different planet ask 684 00:21:36,519 --> 00:21:30,919 for how things change in particular 685 00:21:37,779 --> 00:21:36,529 let's go to M dwarfs the gospel of the M 686 00:21:39,399 --> 00:21:37,789 dwarf has already been presented in this 687 00:21:41,320 --> 00:21:39,409 meeting so I won't go the labor it in 688 00:21:42,700 --> 00:21:41,330 too much depth but just as a quick 689 00:21:44,169 --> 00:21:42,710 reminder for some of our colleagues who 690 00:21:46,930 --> 00:21:44,179 may not be as familiar with it you are 691 00:21:49,539 --> 00:21:46,940 being preached to M dwarfs are a really 692 00:21:51,039 --> 00:21:49,549 interesting class of the class of start 693 00:21:52,299 --> 00:21:51,049 they're the tharok stars that are 694 00:21:53,680 --> 00:21:52,309 smaller dimmer and cooler than our own 695 00:21:55,240 --> 00:21:53,690 Sun they're the most common type of star 696 00:21:56,649 --> 00:21:55,250 in the galaxy studies from Kepler show 697 00:21:58,720 --> 00:21:56,659 that potentially habitable planets are 698 00:21:59,889 --> 00:21:58,730 common around them a statistical finding 699 00:22:01,600 --> 00:21:59,899 which is received experimental 700 00:22:03,129 --> 00:22:01,610 validation with the number of individual 701 00:22:04,629 --> 00:22:03,139 planet discoveries like that or the 702 00:22:06,279 --> 00:22:04,639 Trappist one system which contains 703 00:22:08,590 --> 00:22:06,289 two to three potentially habitable 704 00:22:09,940 --> 00:22:08,600 planets which is quite exciting in 705 00:22:11,200 --> 00:22:09,950 addition they're the only possible 706 00:22:12,610 --> 00:22:11,210 targets for near-term atmospheric 707 00:22:14,230 --> 00:22:12,620 characterization over at least the next 708 00:22:15,549 --> 00:22:14,240 decade or two that's just because M 709 00:22:16,029 --> 00:22:15,559 groups are small so the relative 710 00:22:18,909 --> 00:22:16,039 spectral 711 00:22:20,110 --> 00:22:18,919 amplitude of atmospheric absorption is 712 00:22:22,090 --> 00:22:20,120 much stronger around these 713 00:22:23,650 --> 00:22:22,100 Jex so they're the most common potential 714 00:22:25,240 --> 00:22:23,660 home for life in the universe s rate and 715 00:22:27,490 --> 00:22:25,250 alluded to in the introduction to this 716 00:22:29,380 --> 00:22:27,500 meeting they're the only place we can 717 00:22:30,940 --> 00:22:29,390 look for life beyond Earth and of course 718 00:22:32,440 --> 00:22:30,950 and so this has fueled a robust debate 719 00:22:34,450 --> 00:22:32,450 about whether life can emerge and endear 720 00:22:35,740 --> 00:22:34,460 on these objects this debate has many 721 00:22:37,510 --> 00:22:35,750 axes some of which we've heard about 722 00:22:40,000 --> 00:22:37,520 earlier in this meeting I'm gonna focus 723 00:22:41,200 --> 00:22:40,010 on just one part of this debate which is 724 00:22:42,550 --> 00:22:41,210 the UV environment and then the 725 00:22:46,540 --> 00:22:42,560 implications for the emergence of life 726 00:22:47,830 --> 00:22:46,550 ah 15 minutes actually isn't that long 727 00:22:50,050 --> 00:22:47,840 so I'm gonna skip the build-up and just 728 00:22:52,390 --> 00:22:50,060 go straight to the conclusions which is 729 00:22:54,550 --> 00:22:52,400 that M dwarf planet surfaces are UV poor 730 00:22:55,840 --> 00:22:54,560 so what this is showing this well this 731 00:22:57,580 --> 00:22:55,850 is essentially showing here's a surface 732 00:22:58,930 --> 00:22:57,590 UV radiation environment on M dwarf 733 00:23:00,520 --> 00:22:58,940 planets you have wavelength in 734 00:23:02,770 --> 00:23:00,530 nanometers on the x axis the surface 735 00:23:04,690 --> 00:23:02,780 radiation in photons on the y axis the 736 00:23:06,460 --> 00:23:04,700 black line is what you had access to on 737 00:23:08,020 --> 00:23:06,470 early Earth and the colored lines is 738 00:23:09,460 --> 00:23:08,030 what you'd have access to in an earlier 739 00:23:10,840 --> 00:23:09,470 an analogue planet orbiting these M 740 00:23:13,600 --> 00:23:10,850 dwarfs are filtered through that one bar 741 00:23:14,920 --> 00:23:13,610 one bar and two co2 atmosphere and I 742 00:23:17,170 --> 00:23:14,930 should point out that the data sources 743 00:23:18,460 --> 00:23:17,180 here are primarily from the from the 744 00:23:20,620 --> 00:23:18,470 muscle survey but also from the virtual 745 00:23:22,810 --> 00:23:20,630 planetary leopard Laboratories online 746 00:23:24,880 --> 00:23:22,820 compendium and the key takeaway here is 747 00:23:26,740 --> 00:23:24,890 that ember planet surfaces are UV poor 748 00:23:28,240 --> 00:23:26,750 because a long word of 200 nanometers 749 00:23:30,430 --> 00:23:28,250 which is the only thing that makes it to 750 00:23:32,170 --> 00:23:30,440 the surface the radiation is formed at 751 00:23:33,430 --> 00:23:32,180 the photosphere embers are cool so they 752 00:23:35,530 --> 00:23:33,440 have much less photosphere @qv 753 00:23:36,700 --> 00:23:35,540 so that's all that's going on there we 754 00:23:38,320 --> 00:23:36,710 can quantify this a little bit by 755 00:23:40,300 --> 00:23:38,330 computing the reaction rates for 756 00:23:42,160 --> 00:23:40,310 prebiotic irrelevant processes and we 757 00:23:43,630 --> 00:23:42,170 can say that overall abiotic number of 758 00:23:45,280 --> 00:23:43,640 plants have about two to three orders of 759 00:23:47,230 --> 00:23:45,290 magnitude less by octave you be then 760 00:23:48,820 --> 00:23:47,240 prebiotic earth this has real 761 00:23:50,860 --> 00:23:48,830 implications for potential provided 762 00:23:52,630 --> 00:23:50,870 chemistry and it's not just you wait a 763 00:23:54,250 --> 00:23:52,640 hundred thousand times longer because 764 00:23:55,300 --> 00:23:54,260 you always have thermal back reactions 765 00:23:57,400 --> 00:23:55,310 to your photo chemistry needs to be 766 00:23:58,900 --> 00:23:57,410 building biomolecules faster than your 767 00:24:01,090 --> 00:23:58,910 thermo chemistry destroys them so 768 00:24:02,860 --> 00:24:01,100 there's a threshold amount of UV and if 769 00:24:04,030 --> 00:24:02,870 you don't don't exceed that threshold UV 770 00:24:05,640 --> 00:24:04,040 dependent provided chemistry may not 771 00:24:08,050 --> 00:24:05,650 proceed may not proceed 772 00:24:09,700 --> 00:24:08,060 Paul Rimmer in collaboration with others 773 00:24:10,750 --> 00:24:09,710 including DD ACLU's and John Sutherland 774 00:24:12,520 --> 00:24:10,760 at the University of Cambridge has 775 00:24:14,080 --> 00:24:12,530 started looking at this question he's 776 00:24:15,400 --> 00:24:14,090 looked at it for a couple of pathways in 777 00:24:16,810 --> 00:24:15,410 particular and he's shown that that 778 00:24:18,190 --> 00:24:16,820 driver nucleotide synthesis pathway I 779 00:24:19,390 --> 00:24:18,200 told you about the only one known for 780 00:24:21,370 --> 00:24:19,400 their high yield selective synthesis 781 00:24:23,140 --> 00:24:21,380 can't operate under steady state em door 782 00:24:24,790 --> 00:24:23,150 Q key which has given rise to what 783 00:24:26,980 --> 00:24:24,800 called policy it calls the abiogenesis 784 00:24:28,690 --> 00:24:26,990 own the idea that maybe high mass stars 785 00:24:31,000 --> 00:24:28,700 are much more clayman places for life to 786 00:24:32,320 --> 00:24:31,010 emerge there's one glaring caveat here 787 00:24:33,659 --> 00:24:32,330 that I can tell half of you are sitting 788 00:24:36,239 --> 00:24:33,669 on your hands about and 789 00:24:37,739 --> 00:24:36,249 Flair's Ambrose or flair stars they 790 00:24:39,089 --> 00:24:37,749 flirt who can be they flare often and 791 00:24:40,469 --> 00:24:39,099 when they flare they go from putting out 792 00:24:42,359 --> 00:24:40,479 less UV than the Sun to putting out more 793 00:24:44,219 --> 00:24:42,369 UV to the Sun which raises the question 794 00:24:46,680 --> 00:24:44,229 can intense with transient UV from 795 00:24:48,810 --> 00:24:46,690 flares substitute for high steady-state 796 00:24:50,549 --> 00:24:48,820 UV this question is being addressed on 797 00:24:54,329 --> 00:24:50,559 both booth observational and 798 00:24:57,359 --> 00:24:54,339 experimental II yeah sorry this is a 799 00:25:00,449 --> 00:24:57,369 little bit out of order observational II 800 00:25:02,219 --> 00:25:00,459 uh folks including Max guntur at MIT are 801 00:25:03,930 --> 00:25:02,229 using tests to do flare frequency 802 00:25:04,979 --> 00:25:03,940 distribution studies of M dwarfs trying 803 00:25:06,419 --> 00:25:04,989 to figure out how much they flare and 804 00:25:08,430 --> 00:25:06,429 how much energy that they put out and 805 00:25:10,169 --> 00:25:08,440 their preliminary findings so far is 806 00:25:12,029 --> 00:25:10,179 that maybe ten percent of M dwarfs put 807 00:25:13,949 --> 00:25:12,039 out enough energy may be put out an F 808 00:25:14,940 --> 00:25:13,959 energy to compensate and Paul Rimmer as 809 00:25:16,739 --> 00:25:14,950 I mentioned before is leading 810 00:25:18,359 --> 00:25:16,749 experimental studies to figure out can 811 00:25:20,369 --> 00:25:18,369 the camera can be proposed periodic 812 00:25:22,169 --> 00:25:20,379 chemistry uses intense radiation can it 813 00:25:24,209 --> 00:25:22,179 compensate if the answer to this 814 00:25:26,579 --> 00:25:24,219 question is yes it provides a rare 815 00:25:29,369 --> 00:25:26,589 positive tip for the habitability of 816 00:25:31,409 --> 00:25:29,379 active M so it provides a positive entry 817 00:25:33,209 --> 00:25:31,419 into that ledger if the answer is no I 818 00:25:34,769 --> 00:25:33,219 think that's the most important case of 819 00:25:36,659 --> 00:25:34,779 all because it constitutes a testable 820 00:25:38,489 --> 00:25:36,669 prediction if this pathway is required 821 00:25:40,109 --> 00:25:38,499 for the emergence of life if UV light is 822 00:25:41,339 --> 00:25:40,119 essential for the emergence of life then 823 00:25:42,659 --> 00:25:41,349 you don't find it and then you shouldn't 824 00:25:44,430 --> 00:25:42,669 find like on planets orbiting Emperor's 825 00:25:46,229 --> 00:25:44,440 so if you find biosignatures there any 826 00:25:47,060 --> 00:25:46,239 way you can falsify this theory which is 827 00:25:50,519 --> 00:25:47,070 lovely 828 00:25:51,810 --> 00:25:50,529 so those so that brings the prebiotic 829 00:25:53,729 --> 00:25:51,820 chemistry part of the talk to a close 830 00:25:55,079 --> 00:25:53,739 the key takeaways are we have a pretty 831 00:25:57,149 --> 00:25:55,089 good sense of what early Earth and early 832 00:25:59,459 --> 00:25:57,159 marcia was like it's broadband north of 833 00:26:00,449 --> 00:25:59,469 200 nanometers this can power a lot of 834 00:26:01,769 --> 00:26:00,459 constructive chemistry and in 835 00:26:03,859 --> 00:26:01,779 conjunction with sulfide can solve the 836 00:26:06,029 --> 00:26:03,869 long-standing production problem it 837 00:26:07,319 --> 00:26:06,039 controls other aspects of the surface 838 00:26:08,969 --> 00:26:07,329 environment as well in particular it 839 00:26:10,789 --> 00:26:08,979 controls the abundance of NO x a fixed 840 00:26:12,690 --> 00:26:10,799 nitrogen on the early Earth and 841 00:26:14,579 --> 00:26:12,700 restricts you to ponds if you really 842 00:26:15,719 --> 00:26:14,589 want a lot of that prebiotic amber 843 00:26:17,969 --> 00:26:15,729 plants are a little bit different 844 00:26:20,219 --> 00:26:17,979 because they have a lot less UV this is 845 00:26:21,419 --> 00:26:20,229 potentially quite exciting first we 846 00:26:22,889 --> 00:26:21,429 first have to figure out if flares can 847 00:26:25,019 --> 00:26:22,899 compensate the flare UV can compensate 848 00:26:26,310 --> 00:26:25,029 your steady-state M graph UV if it can't 849 00:26:27,839 --> 00:26:26,320 that's really exciting because you can 850 00:26:29,899 --> 00:26:27,849 potentially use exoplanet observations 851 00:26:32,099 --> 00:26:29,909 to constrain origin of life theories 852 00:26:33,599 --> 00:26:32,109 this seeks me really nicely into the 853 00:26:35,129 --> 00:26:33,609 next part of my talk which is how are we 854 00:26:37,889 --> 00:26:35,139 gonna find life on planets orbiting 855 00:26:40,169 --> 00:26:37,899 other stars UV light and biosignatures 856 00:26:41,519 --> 00:26:40,179 before I jump into this I'm going to 857 00:26:43,349 --> 00:26:41,529 take a moment and pause about the 858 00:26:45,269 --> 00:26:43,359 magnitude of the opportunity exoplanets 859 00:26:47,030 --> 00:26:45,279 offer offer us it's not just that 860 00:26:49,730 --> 00:26:47,040 there's so many potentially habitable x 861 00:26:50,660 --> 00:26:49,740 a potential of potentially hundreds or 862 00:26:52,220 --> 00:26:50,670 thousands that we can hope to 863 00:26:53,330 --> 00:26:52,230 potentially hundreds that we could hope 864 00:26:56,000 --> 00:26:53,340 to observe if we get good enough 865 00:26:58,160 --> 00:26:56,010 telescopes it's that it's the it's this 866 00:26:59,810 --> 00:26:58,170 each and every planet is a prebiotic 867 00:27:01,400 --> 00:26:59,820 chemistry experiment it's a prebiotic 868 00:27:03,350 --> 00:27:01,410 chemistry experiment running at scale 869 00:27:05,330 --> 00:27:03,360 thousands tens of thousands of square 870 00:27:07,580 --> 00:27:05,340 kilometers off wide range of conditions 871 00:27:10,160 --> 00:27:07,590 and cycles operating operating over 872 00:27:11,810 --> 00:27:10,170 geologic time we could we can never do 873 00:27:13,970 --> 00:27:11,820 prebiotic chemistry experiments as well 874 00:27:15,410 --> 00:27:13,980 as planets can and if you can just read 875 00:27:17,480 --> 00:27:15,420 the outcome of those prebiotic chemistry 876 00:27:20,720 --> 00:27:17,490 experiments we can get we can gain 877 00:27:22,910 --> 00:27:20,730 really fundamental insights into the 878 00:27:27,830 --> 00:27:22,920 nature but into what might be laws of 879 00:27:28,700 --> 00:27:27,840 biology exoplanets offer and this has 880 00:27:30,290 --> 00:27:28,710 been the quantum this has been 881 00:27:32,120 --> 00:27:30,300 quantified an abrasion framework by Sant 882 00:27:34,010 --> 00:27:32,130 Edie Andy Sandberg here and by tipping 883 00:27:35,480 --> 00:27:34,020 in Chen and by Lingam and lobe a little 884 00:27:37,100 --> 00:27:35,490 bit and the essential thing that they 885 00:27:38,750 --> 00:27:37,110 point out is that if you detect even one 886 00:27:40,180 --> 00:27:38,760 biosphere beyond Earth you strongly 887 00:27:43,790 --> 00:27:40,190 constrain many theories of abiogenesis 888 00:27:45,290 --> 00:27:43,800 for example one still extent debate is 889 00:27:47,510 --> 00:27:45,300 contingency versus inevitability of 890 00:27:49,820 --> 00:27:47,520 origin of life are there processes out 891 00:27:51,170 --> 00:27:49,830 there that inevitably drive chemical 892 00:27:53,300 --> 00:27:51,180 complexification in the emergence of 893 00:27:54,740 --> 00:27:53,310 life or did a bunch of molecules one day 894 00:27:56,300 --> 00:27:54,750 just to decide the quantum tunnel 895 00:27:57,560 --> 00:27:56,310 together and give us Luca we can't 896 00:27:59,150 --> 00:27:57,570 actually exclude the latter right now 897 00:28:01,190 --> 00:27:59,160 even though we don't like it very much 898 00:28:02,960 --> 00:28:01,200 the detection of even one biosphere 899 00:28:04,100 --> 00:28:02,970 would rule strongly on that beyond Earth 900 00:28:06,020 --> 00:28:04,110 would rule strongly on that and 901 00:28:07,340 --> 00:28:06,030 similarly if we can detect a few then we 902 00:28:08,930 --> 00:28:07,350 can start making broad statements about 903 00:28:12,260 --> 00:28:08,940 what conditions fuel the origin of life 904 00:28:13,520 --> 00:28:12,270 versus disfavor it exoplanets are 905 00:28:14,480 --> 00:28:13,530 particularly outstanding here because 906 00:28:16,040 --> 00:28:14,490 they're an opportunity for an 907 00:28:17,780 --> 00:28:16,050 uncontaminated experiment 908 00:28:18,920 --> 00:28:17,790 I love the solar system bodies I love 909 00:28:20,240 --> 00:28:18,930 each and every one of them they have 910 00:28:21,890 --> 00:28:20,250 fundamental things to teach us in a be 911 00:28:23,540 --> 00:28:21,900 detect life there it'll be an amazing 912 00:28:25,460 --> 00:28:23,550 discovery and it'll tell us a lot about 913 00:28:27,500 --> 00:28:25,470 habitability but it won't necessarily 914 00:28:29,030 --> 00:28:27,510 tell us about the origin of life 915 00:28:30,950 --> 00:28:29,040 particularly if it has it biochemistry 916 00:28:32,660 --> 00:28:30,960 similar to ours and that's because of 917 00:28:34,190 --> 00:28:32,670 the risk of terrestrial contamination we 918 00:28:35,270 --> 00:28:34,200 know the terrestrial bodies swap rocks 919 00:28:37,100 --> 00:28:35,280 back and forth we know this from the 920 00:28:38,240 --> 00:28:37,110 existence of Martian meteorites we know 921 00:28:40,130 --> 00:28:38,250 that the interiors of those meteorites 922 00:28:42,860 --> 00:28:40,140 experience cream and surface climate 923 00:28:44,960 --> 00:28:42,870 conditions not exceeding 40 Celsius and 924 00:28:47,210 --> 00:28:44,970 we know that from n-body simulations for 925 00:28:49,820 --> 00:28:47,220 example by were that all at Penn State 926 00:28:52,250 --> 00:28:49,830 that Earth has transferred on the order 927 00:28:54,140 --> 00:28:52,260 of a mega of a Megaton of matter to the 928 00:28:56,150 --> 00:28:54,150 icy moons alone and much much more of 929 00:28:57,440 --> 00:28:56,160 course to Mars so there's a real risk of 930 00:28:58,670 --> 00:28:57,450 terrestrial contamination if you detect 931 00:29:00,050 --> 00:28:58,680 life there you can't be sure that it 932 00:29:00,950 --> 00:29:00,060 wasn't exchanged back and forth in the 933 00:29:03,350 --> 00:29:00,960 solar system 934 00:29:04,880 --> 00:29:03,360 exoplanets avoid that problem so it 935 00:29:06,830 --> 00:29:04,890 would be super great to to detect life 936 00:29:08,900 --> 00:29:06,840 there so how are we thinking about doing 937 00:29:10,220 --> 00:29:08,910 this the essential paradigm is right now 938 00:29:13,910 --> 00:29:10,230 we are discovering potentially habitable 939 00:29:15,290 --> 00:29:13,920 up to probably rocky worlds today we can 940 00:29:17,540 --> 00:29:15,300 spectrally characterize the atmospheres 941 00:29:19,640 --> 00:29:17,550 of large planets and see what's in them 942 00:29:21,410 --> 00:29:19,650 in future we hope to do the same with 943 00:29:23,480 --> 00:29:21,420 smaller rocky planets and scrutinize 944 00:29:25,910 --> 00:29:23,490 them for evidence of life what do we 945 00:29:27,380 --> 00:29:25,920 mean by evidence of life to think about 946 00:29:29,390 --> 00:29:27,390 this question we can go back to the 947 00:29:31,730 --> 00:29:29,400 granddaddy of them all the only time has 948 00:29:33,770 --> 00:29:31,740 actually been tried which is a very 949 00:29:37,040 --> 00:29:33,780 clever experiment by Carl Sagan and this 950 00:29:38,960 --> 00:29:37,050 collaborators back in 1993 so when when 951 00:29:41,900 --> 00:29:38,970 Galileo was on its way out to Jupiter it 952 00:29:43,310 --> 00:29:41,910 swung by earth on the way so they just 953 00:29:44,570 --> 00:29:43,320 had a very simple idea they stuck out 954 00:29:45,770 --> 00:29:44,580 all its instruments they trained them on 955 00:29:47,210 --> 00:29:45,780 earth and they tried to see if they 956 00:29:49,160 --> 00:29:47,220 could remotely detect evidence of life 957 00:29:50,660 --> 00:29:49,170 on earth it was not as straightforward 958 00:29:53,300 --> 00:29:50,670 as you might imagine as long as these 959 00:29:55,520 --> 00:29:53,310 things like TV signals that is I'm gonna 960 00:29:57,560 --> 00:29:55,530 begin me but the most robust evidence 961 00:29:59,090 --> 00:29:57,570 that they found for life on Earth was 962 00:30:01,130 --> 00:29:59,100 essentially in this auto over here this 963 00:30:03,230 --> 00:30:01,140 is a spectrum of the rational atmosphere 964 00:30:04,670 --> 00:30:03,240 and they have detected a number of 965 00:30:06,710 --> 00:30:04,680 molecules that add relatively high 966 00:30:09,500 --> 00:30:06,720 concentrations so they detected two oh 967 00:30:10,700 --> 00:30:09,510 three which is biogenic but they that's 968 00:30:12,110 --> 00:30:10,710 not a good evidence for life because 969 00:30:13,790 --> 00:30:12,120 there's a robust UV difference false 970 00:30:15,890 --> 00:30:13,800 positive if you UV irradiate an o2 971 00:30:18,170 --> 00:30:15,900 atmosphere you may go three not 972 00:30:20,240 --> 00:30:18,180 convincing they found oh to an end to Oh 973 00:30:21,410 --> 00:30:20,250 which they were more excited about but 974 00:30:22,940 --> 00:30:21,420 again there was significant false 975 00:30:24,560 --> 00:30:22,950 positive risks and they concluded that 976 00:30:25,400 --> 00:30:24,570 they couldn't conclude that life was 977 00:30:27,830 --> 00:30:25,410 there based on that alone 978 00:30:29,600 --> 00:30:27,840 what did eventually convince them was 979 00:30:32,570 --> 00:30:29,610 the existence of seach for in an oxy 980 00:30:34,820 --> 00:30:32,580 gaseous fear ch4 is known to be biogenic 981 00:30:36,020 --> 00:30:34,830 it was Alba I was also present added 982 00:30:37,190 --> 00:30:36,030 abundance about a hundred and forty 983 00:30:38,660 --> 00:30:37,200 eight orders of magnitude out of 984 00:30:39,740 --> 00:30:38,670 thermochemical equilibrium so that was 985 00:30:41,450 --> 00:30:39,750 weird 986 00:30:43,640 --> 00:30:41,460 it had a let it should have had a 987 00:30:44,810 --> 00:30:43,650 lifetime of about ten years which meant 988 00:30:47,900 --> 00:30:44,820 said kinetics should have been able to 989 00:30:49,760 --> 00:30:47,910 restore that equilibrium very quickly so 990 00:30:51,800 --> 00:30:49,770 the so something must be pumping it up 991 00:30:53,030 --> 00:30:51,810 and retain and maintaining it they went 992 00:30:54,440 --> 00:30:53,040 through the list of a byte across the 993 00:30:56,360 --> 00:30:54,450 seas they no II knew about which would 994 00:30:57,830 --> 00:30:56,370 make ch4 concluded that none of them 995 00:30:59,900 --> 00:30:57,840 could maintain the required flux and 996 00:31:01,610 --> 00:30:59,910 concluded that Occam's razor forced to 997 00:31:03,290 --> 00:31:01,620 conclude that there was life there so 998 00:31:04,550 --> 00:31:03,300 this is a kind of analysis that one day 999 00:31:08,389 --> 00:31:04,560 we hope to do with the next planet so 1000 00:31:13,259 --> 00:31:11,159 in terms of oxic atmospheres the biasing 1001 00:31:16,619 --> 00:31:13,269 here that they identified CH 402 and 1002 00:31:17,969 --> 00:31:16,629 ideally h2o remains the most remains 1003 00:31:20,069 --> 00:31:17,979 probably the most robust one we've come 1004 00:31:24,089 --> 00:31:20,079 up with so far the challenge it really 1005 00:31:25,589 --> 00:31:24,099 faces is one of observation the first 1006 00:31:26,969 --> 00:31:25,599 method first you kind of have a 1007 00:31:28,589 --> 00:31:26,979 trade-off between oxygen abundance and 1008 00:31:30,989 --> 00:31:28,599 methane abundance over Earth history as 1009 00:31:32,849 --> 00:31:30,999 Olson at all 2016 and Reinhardt and 1010 00:31:34,169 --> 00:31:32,859 colleagues in 2017 pointed out either 1011 00:31:35,729 --> 00:31:34,179 you have high methane so it's easy to 1012 00:31:37,799 --> 00:31:35,739 detector or high oxygen typically not 1013 00:31:39,209 --> 00:31:37,809 though you also have kind of more 1014 00:31:41,339 --> 00:31:39,219 fundamental observational challenges 1015 00:31:43,829 --> 00:31:41,349 than that for example Oh - absorbs at 1016 00:31:45,419 --> 00:31:43,839 relatively short wavelengths ch4 absorbs 1017 00:31:46,919 --> 00:31:45,429 that are relatively long wavelengths you 1018 00:31:48,599 --> 00:31:46,929 need different different big 1019 00:31:51,029 --> 00:31:48,609 observatories to be able to detect them 1020 00:31:52,649 --> 00:31:51,039 to be able to detect them and it's ch4 1021 00:31:53,999 --> 00:31:52,659 you also run into the problem that ch4 1022 00:31:55,499 --> 00:31:54,009 absorbs like this so does almost every 1023 00:31:56,909 --> 00:31:55,509 other hydrocarbon so you have to figure 1024 00:32:00,119 --> 00:31:56,919 out how can you discriminate those guys 1025 00:32:01,409 --> 00:32:00,129 apart so those are some so these are I'm 1026 00:32:02,579 --> 00:32:01,419 not saying that this is a bad by sector 1027 00:32:04,109 --> 00:32:02,589 them by far the opposite we should 1028 00:32:05,459 --> 00:32:04,119 definitely look for this but these are 1029 00:32:07,549 --> 00:32:05,469 some of the reasons people have kept on 1030 00:32:10,289 --> 00:32:07,559 thinking about this problem a little bit 1031 00:32:13,109 --> 00:32:10,299 so what would an ideal biosignature gas 1032 00:32:14,430 --> 00:32:13,119 be what would i well obviously it would 1033 00:32:16,739 --> 00:32:14,440 be by Jen it could be produced by life 1034 00:32:18,509 --> 00:32:16,749 for example the way oxygen is produced 1035 00:32:19,889 --> 00:32:18,519 by phytoplankton here on earth it would 1036 00:32:21,180 --> 00:32:19,899 be spectrally distinguishable we should 1037 00:32:22,829 --> 00:32:21,190 be able to clearly tell it apart from 1038 00:32:24,749 --> 00:32:22,839 other molecules that might absorb in the 1039 00:32:26,430 --> 00:32:24,759 same region of the spectrum and it 1040 00:32:30,199 --> 00:32:26,440 should have no abiotic pulse positives 1041 00:32:32,999 --> 00:32:31,769 finally we would like it to be 1042 00:32:34,829 --> 00:32:33,009 detectable we need to be able to 1043 00:32:38,729 --> 00:32:34,839 accumulate a detectable concentrations 1044 00:32:40,169 --> 00:32:38,739 on habit of inhabitable planets both the 1045 00:32:41,849 --> 00:32:40,179 UV light comes in to both of these 1046 00:32:44,609 --> 00:32:41,859 questions see these second two questions 1047 00:32:45,569 --> 00:32:44,619 over here that's what I'll do and that's 1048 00:32:47,129 --> 00:32:45,579 the work that I've been doing in that 1049 00:32:50,129 --> 00:32:47,139 that's what a little bit of what I'll 1050 00:32:51,629 --> 00:32:50,139 share with you today I can't talk about 1051 00:32:53,969 --> 00:32:51,639 bio signatures without talking about the 1052 00:32:55,889 --> 00:32:53,979 granddaddy of them all Oh - OH - is a 1053 00:32:57,899 --> 00:32:55,899 excellent bio signature in many ways 1054 00:32:59,819 --> 00:32:57,909 it's biogenic it's detectable it's 1055 00:33:01,889 --> 00:32:59,829 distinguishable it has an excellent 1056 00:33:04,469 --> 00:33:01,899 terrestrial motivation but the big risk 1057 00:33:06,659 --> 00:33:04,479 of it is is that it has a lot of false 1058 00:33:08,789 --> 00:33:06,669 positive possibilities 1059 00:33:10,409 --> 00:33:08,799 driven by both photochemistry and escape 1060 00:33:11,819 --> 00:33:10,419 but a chemistry is a little bit less of 1061 00:33:14,339 --> 00:33:11,829 a concern now thanks to the recent work 1062 00:33:15,959 --> 00:33:14,349 of sunny harmon showing that you showing 1063 00:33:18,389 --> 00:33:15,969 that like me the products of lightning 1064 00:33:19,739 --> 00:33:18,399 suppress this false positive signal but 1065 00:33:20,370 --> 00:33:19,749 the escape different false positives 1066 00:33:22,230 --> 00:33:20,380 remain and the 1067 00:33:24,060 --> 00:33:22,240 fundamental picture that all was down to 1068 00:33:25,590 --> 00:33:24,070 as you can come up with scenarios where 1069 00:33:27,390 --> 00:33:25,600 you have water vapor which is present on 1070 00:33:28,799 --> 00:33:27,400 habitable worlds and you can come up 1071 00:33:30,840 --> 00:33:28,809 with ways that that water we converted 1072 00:33:32,610 --> 00:33:30,850 associate the H can escape the O remains 1073 00:33:34,680 --> 00:33:32,620 and so you filled up at me by to go to 1074 00:33:37,140 --> 00:33:34,690 layer and all these escapes in air is 1075 00:33:38,490 --> 00:33:37,150 basically bow down to that there's ways 1076 00:33:39,720 --> 00:33:38,500 you can discriminate out some of them as 1077 00:33:42,180 --> 00:33:39,730 was shown that Eddie sweeter man in a 1078 00:33:44,310 --> 00:33:42,190 2016 paper and the idea is that for 1079 00:33:46,049 --> 00:33:44,320 example if you're owed to you to Co 1080 00:33:47,630 --> 00:33:46,059 potala co2 catalysis you should have 1081 00:33:50,549 --> 00:33:47,640 lots of co so you can look for that 1082 00:33:52,020 --> 00:33:50,559 alternatively if you're if you have a 1083 00:33:53,610 --> 00:33:52,030 really a lot of o to like a hundred bars 1084 00:33:55,799 --> 00:33:53,620 of it turned by the escape of an ocean 1085 00:33:57,120 --> 00:33:55,809 kind of trophic escape of an ocean that 1086 00:33:58,740 --> 00:33:57,130 should produce OH - OH - die memories 1087 00:34:00,470 --> 00:33:58,750 which you can also look for but there's 1088 00:34:02,909 --> 00:34:00,480 a bit a big regime in the Middle where 1089 00:34:04,649 --> 00:34:02,919 we can't necessarily discriminate out 1090 00:34:05,820 --> 00:34:04,659 all those false positives so that's a 1091 00:34:08,550 --> 00:34:05,830 potential challenge so that's a 1092 00:34:09,960 --> 00:34:08,560 potential challenger though - this is in 1093 00:34:11,639 --> 00:34:09,970 fact a potential challenge with all the 1094 00:34:12,930 --> 00:34:11,649 quote unquote easy simple molecules the 1095 00:34:14,820 --> 00:34:12,940 molecules that it's relatively easy for 1096 00:34:16,169 --> 00:34:14,830 life to me that's because the molecules 1097 00:34:19,050 --> 00:34:16,179 that it's relatively easy for life to 1098 00:34:20,790 --> 00:34:19,060 make are also relatively easy for me for 1099 00:34:22,710 --> 00:34:20,800 like a non life to make a biotic 1100 00:34:25,889 --> 00:34:22,720 processes to make nature can exploit the 1101 00:34:28,260 --> 00:34:25,899 same basic the same basic thermal for 1102 00:34:29,430 --> 00:34:28,270 energy gradients that life can so this 1103 00:34:30,570 --> 00:34:29,440 has motivated people to think a little 1104 00:34:32,399 --> 00:34:30,580 bit about heart to make molecules 1105 00:34:33,510 --> 00:34:32,409 molecules at its root that it's really 1106 00:34:36,270 --> 00:34:33,520 hard to make that you would seem to 1107 00:34:39,570 --> 00:34:36,280 uniquely need life by a biological 1108 00:34:40,680 --> 00:34:39,580 enzymatic machinery can make people have 1109 00:34:42,300 --> 00:34:40,690 mostly thought about of this in the 1110 00:34:43,859 --> 00:34:42,310 context of an ox gamma spheres because 1111 00:34:45,780 --> 00:34:43,869 these hard to make molecules also tend 1112 00:34:48,540 --> 00:34:45,790 to be reactive and the idea is that 1113 00:34:49,859 --> 00:34:48,550 anoxic oxygen is pretty reactive anoxic 1114 00:34:51,720 --> 00:34:49,869 atmospheres are hopefully less reactive 1115 00:34:54,990 --> 00:34:51,730 and even better places for these gases 1116 00:34:56,820 --> 00:34:55,000 to build up this also has a very robust 1117 00:34:58,410 --> 00:34:56,830 geological motivation in the sense that 1118 00:35:00,930 --> 00:34:58,420 for about half of Earth's history it was 1119 00:35:02,550 --> 00:35:00,940 an toxic so if you don't think about 1120 00:35:04,200 --> 00:35:02,560 anoxic atmospheres you will literally 1121 00:35:07,010 --> 00:35:04,210 throw out about half of your potential 1122 00:35:09,570 --> 00:35:07,020 of your potential biospheres 1123 00:35:10,920 --> 00:35:09,580 the first work in this regard to my 1124 00:35:12,990 --> 00:35:10,930 knowledge was done by Sean Domino 1125 00:35:14,700 --> 00:35:13,000 Goldman's group back in 2011 and what 1126 00:35:17,910 --> 00:35:14,710 they did is they looked at the 1127 00:35:20,520 --> 00:35:17,920 organosulfur ch3 organist vm v VMs the 1128 00:35:22,560 --> 00:35:20,530 MVS and so on and so forth as potential 1129 00:35:25,770 --> 00:35:22,570 biosignatures these are the product of 1130 00:35:28,470 --> 00:35:25,780 so fear of sulfur-based of biochemistry 1131 00:35:29,790 --> 00:35:28,480 ah they're essential finding is that 1132 00:35:31,079 --> 00:35:29,800 these are really good biosignatures in 1133 00:35:32,540 --> 00:35:31,089 many ways in particularly they don't 1134 00:35:34,070 --> 00:35:32,550 have false positive risk 1135 00:35:35,540 --> 00:35:34,080 but you need very high fluxes in order 1136 00:35:36,890 --> 00:35:35,550 for them to become built to detectable 1137 00:35:38,990 --> 00:35:36,900 concentrations in the atmosphere and 1138 00:35:41,120 --> 00:35:39,000 that's you be limited and they've and 1139 00:35:43,730 --> 00:35:41,130 they felt that such high fluxes who were 1140 00:35:45,410 --> 00:35:43,740 unrealistic we think that this approach 1141 00:35:50,300 --> 00:35:45,420 overall is a very sensible one 1142 00:35:51,980 --> 00:35:50,310 so at over at MIT William Bane's William 1143 00:35:53,660 --> 00:35:51,990 vanes Janish Krakowski and Sara Seager 1144 00:35:55,580 --> 00:35:53,670 are leading with what we call the all 1145 00:35:56,870 --> 00:35:55,590 small molecules project an effort to 1146 00:35:57,950 --> 00:35:56,880 look at all the things that life makes 1147 00:35:59,810 --> 00:35:57,960 and evaluate them as potential 1148 00:36:01,340 --> 00:35:59,820 biosignatures this is a bit of an 1149 00:36:02,810 --> 00:36:01,350 undertaking given that even after our 1150 00:36:05,810 --> 00:36:02,820 initial course cuts you still have about 1151 00:36:07,040 --> 00:36:05,820 10,000 of them but we're pleased to 1152 00:36:08,420 --> 00:36:07,050 report that the first results in this 1153 00:36:10,250 --> 00:36:08,430 program are hardly starting to roll in 1154 00:36:11,720 --> 00:36:10,260 the first gas I want to tell you a 1155 00:36:13,160 --> 00:36:11,730 little bit about today adding to that 1156 00:36:16,490 --> 00:36:13,170 inventory that's already been built is 1157 00:36:17,750 --> 00:36:16,500 ph3 bossing page three has a number of 1158 00:36:19,640 --> 00:36:17,760 appealing characteristics as a bio 1159 00:36:21,130 --> 00:36:19,650 signature it has strong detectable 1160 00:36:23,450 --> 00:36:21,140 spectral features you can tell in part 1161 00:36:26,540 --> 00:36:23,460 and I should mention this is working led 1162 00:36:28,040 --> 00:36:26,550 by Clark Sousa Silva there has strong 1163 00:36:28,970 --> 00:36:28,050 detectable spectral features you can 1164 00:36:31,100 --> 00:36:28,980 tell it apart from a lot of other 1165 00:36:33,140 --> 00:36:31,110 molecules it has no known geological 1166 00:36:35,300 --> 00:36:33,150 false-positive mechanisms and we looked 1167 00:36:36,980 --> 00:36:35,310 at a lot of them it's a Chili's heel 1168 00:36:38,330 --> 00:36:36,990 after the ads but the organic Sulphurs 1169 00:36:41,690 --> 00:36:38,340 is that it's really efficiently 1170 00:36:43,030 --> 00:36:41,700 photochemically destroyed so and we 1171 00:36:45,050 --> 00:36:43,040 figured that out by doing a lot by 1172 00:36:46,520 --> 00:36:45,060 calculating the conservation of page 1173 00:36:48,770 --> 00:36:46,530 from the atmospheres of various kinds of 1174 00:36:50,450 --> 00:36:48,780 exoplanets as a function of total ph3 1175 00:36:51,920 --> 00:36:50,460 flux to the atmosphere that's what's 1176 00:36:55,040 --> 00:36:51,930 shown in these spaghetti plots over here 1177 00:36:56,420 --> 00:36:55,050 thank you Tom for that name and so let 1178 00:36:57,560 --> 00:36:56,430 me just walk it this is kind of one of 1179 00:36:59,000 --> 00:36:57,570 our core results so let me walk you 1180 00:37:00,620 --> 00:36:59,010 through it a little bit here I'm 1181 00:37:02,300 --> 00:37:00,630 simulating kind of the optimum ejection 1182 00:37:05,000 --> 00:37:02,310 case and h2 dominated atmosphere 1183 00:37:06,230 --> 00:37:05,010 orbiting an M dwarf star so that's the 1184 00:37:09,320 --> 00:37:06,240 kind of easiest thing we can hope to 1185 00:37:11,420 --> 00:37:09,330 detect the x axis here is molar 1186 00:37:14,030 --> 00:37:11,430 concentration the Y exit to access is 1187 00:37:16,130 --> 00:37:14,040 altitude in kilometers the solid lines 1188 00:37:17,930 --> 00:37:16,140 refer to an atmosphere forced by 10 to 1189 00:37:19,700 --> 00:37:17,940 the 10 molecules of pH 3 per square 1190 00:37:23,270 --> 00:37:19,710 centimeter per second and the dashed 1191 00:37:24,740 --> 00:37:23,280 lines by 10 for 10 to the 11 pH 3 ends 1192 00:37:26,860 --> 00:37:24,750 up being detectable at 10 to the 10 in 1193 00:37:29,960 --> 00:37:26,870 emission and 10 to the 11 in 1194 00:37:31,520 --> 00:37:29,970 transmission so how does it so these 1195 00:37:33,350 --> 00:37:31,530 numbers have no context how can you tell 1196 00:37:35,810 --> 00:37:33,360 if this is big or not oh well for 1197 00:37:37,940 --> 00:37:35,820 reference the modern methane flux is 10 1198 00:37:39,740 --> 00:37:37,950 to the 11 so what this means is in order 1199 00:37:41,270 --> 00:37:39,750 for PSA to be detectable it needs to be 1200 00:37:44,180 --> 00:37:41,280 a primary product of the biosphere 1201 00:37:45,980 --> 00:37:44,190 emitted of the same sort of a minute of 1202 00:37:46,880 --> 00:37:45,990 the same rates that methane is so this 1203 00:37:48,980 --> 00:37:46,890 bias tree needs to 1204 00:37:50,809 --> 00:37:48,990 choosing to make pastry at the same rate 1205 00:37:52,460 --> 00:37:50,819 that our biosphere is choosing to make 1206 00:37:53,599 --> 00:37:52,470 methane there are scenarios in which we 1207 00:37:55,910 --> 00:37:53,609 can begin envision this happening 1208 00:37:57,620 --> 00:37:55,920 particularly acidic and acidic a toxic 1209 00:37:59,599 --> 00:37:57,630 and warm environments but this is by no 1210 00:38:01,579 --> 00:37:59,609 means guaranteed so the punchline here 1211 00:38:02,990 --> 00:38:01,589 is if you see pH 3 it's a pretty good 1212 00:38:04,400 --> 00:38:03,000 sign view but life we shouldn't 1213 00:38:08,210 --> 00:38:04,410 necessarily go ahead and put the house 1214 00:38:09,950 --> 00:38:08,220 that you'll find pH 3 the scenario is 1215 00:38:14,390 --> 00:38:09,960 the situation is pretty similar for 1216 00:38:16,640 --> 00:38:14,400 isoprene so isoprene has is a is a 1217 00:38:19,099 --> 00:38:16,650 relatively calm Jaime is a relatively 1218 00:38:20,839 --> 00:38:19,109 big hydrocarbon it has the advantage 1219 00:38:22,339 --> 00:38:20,849 that unlike pastry it is a massive 1220 00:38:24,289 --> 00:38:22,349 product of biochemistry it's emitted of 1221 00:38:26,180 --> 00:38:24,299 the same mass flux that methane is and 1222 00:38:27,859 --> 00:38:26,190 it's emitted by almost every kind of 1223 00:38:29,359 --> 00:38:27,869 lights if it's emitted by microbes its 1224 00:38:31,250 --> 00:38:29,369 emitted by trees it's made up by us 1225 00:38:33,109 --> 00:38:31,260 everything pretty much everything gives 1226 00:38:34,099 --> 00:38:33,119 up by isoprene it's very deeply rooted 1227 00:38:37,039 --> 00:38:34,109 in the chain of the Tree of Life 1228 00:38:38,839 --> 00:38:37,049 it's spectrally detectable with a giant 1229 00:38:40,670 --> 00:38:38,849 glaring caveat that it's easy to confuse 1230 00:38:42,170 --> 00:38:40,680 with ch4 so you need to be careful in 1231 00:38:44,450 --> 00:38:42,180 your observations in a few bands to make 1232 00:38:46,339 --> 00:38:44,460 sure you can distinguish between ch4 an 1233 00:38:48,680 --> 00:38:46,349 ice cream and it has no non false 1234 00:38:50,990 --> 00:38:48,690 positive mechanisms but it's even more 1235 00:38:52,940 --> 00:38:51,000 photo chemically reactive than pH 3 is 1236 00:38:55,069 --> 00:38:52,950 and you'd need on the order of 10 to the 1237 00:38:56,900 --> 00:38:55,079 12 you'd need on the order of 10 to the 1238 00:38:58,730 --> 00:38:56,910 twelfth molecules per square centimeter 1239 00:39:00,140 --> 00:38:58,740 every second detected so you need your 1240 00:39:03,140 --> 00:39:00,150 biosphere to be producing it at about 1241 00:39:05,569 --> 00:39:03,150 about a rate of 20 or 30 times that our 1242 00:39:07,670 --> 00:39:05,579 biosphere produces isoprene today so not 1243 00:39:09,559 --> 00:39:07,680 ruled so not completely implausible but 1244 00:39:10,819 --> 00:39:09,569 also not something it but now some it's 1245 00:39:14,150 --> 00:39:10,829 particularly so it's worth checking for 1246 00:39:15,559 --> 00:39:14,160 but not worth betting the house on the 1247 00:39:16,940 --> 00:39:15,569 key thing that jumps out to us in both 1248 00:39:20,120 --> 00:39:16,950 of these scenarios that M dwarfs are 1249 00:39:21,769 --> 00:39:20,130 really an ideal detection case all of 1250 00:39:23,120 --> 00:39:21,779 these gases are able to build up to much 1251 00:39:24,890 --> 00:39:23,130 higher concentrations and planets 1252 00:39:27,349 --> 00:39:24,900 orbitting M dwarfs because M works our 1253 00:39:28,759 --> 00:39:27,359 low UV environments and the main control 1254 00:39:30,700 --> 00:39:28,769 of the concentrations of all of these 1255 00:39:33,079 --> 00:39:30,710 gases directly or indirectly are UV 1256 00:39:35,599 --> 00:39:33,089 directly UV can directly fertilize these 1257 00:39:37,940 --> 00:39:35,609 molecules but indirectly UV will anyway 1258 00:39:39,740 --> 00:39:37,950 fertilize molecules like co2 and h2o and 1259 00:39:41,210 --> 00:39:39,750 the radicals they generate will then 1260 00:39:43,099 --> 00:39:41,220 wander around a blow of these molecules 1261 00:39:45,019 --> 00:39:43,109 as well in fact for these molecules in 1262 00:39:46,370 --> 00:39:45,029 the scenarios we simulated radical loss 1263 00:39:48,289 --> 00:39:46,380 was the main lost mechanism and 1264 00:39:49,600 --> 00:39:48,299 ultimately that is controlled by the UV 1265 00:39:52,360 --> 00:39:49,610 environment 1266 00:39:54,850 --> 00:39:52,370 that's just that's Illustrated and uh so 1267 00:39:57,070 --> 00:39:54,860 this is a result that that is similar to 1268 00:39:59,350 --> 00:39:57,080 what Segura at all 2005 on procedure 1269 00:40:01,720 --> 00:39:59,360 series Ilan CH sport and this is just an 1270 00:40:05,020 --> 00:40:01,730 illustration of that this here I've 1271 00:40:06,730 --> 00:40:05,030 simulated ps3 build up in to exoplanet 1272 00:40:07,870 --> 00:40:06,740 atmospheres the parameters are identical 1273 00:40:09,640 --> 00:40:07,880 except that one of them orbits a 1274 00:40:11,500 --> 00:40:09,650 sun-like stars and one of them orbits 1275 00:40:12,850 --> 00:40:11,510 Emperor and we see that in the case of 1276 00:40:14,860 --> 00:40:12,860 the Emperor it built it goes much higher 1277 00:40:15,910 --> 00:40:14,870 so better for transmission and it builds 1278 00:40:20,410 --> 00:40:15,920 up to a few orders of magnitude higher 1279 00:40:22,360 --> 00:40:20,420 in concentration so M Dwarfs mmm gross 1280 00:40:25,270 --> 00:40:22,370 remain an ideal a detection case the 1281 00:40:26,770 --> 00:40:25,280 cult of M Perkins continues so to 1282 00:40:29,320 --> 00:40:26,780 summarize the key takeaways from the bio 1283 00:40:31,030 --> 00:40:29,330 signatures part of the talk the gold 1284 00:40:34,030 --> 00:40:31,040 band standard by a signature if you can 1285 00:40:35,320 --> 00:40:34,040 detect it remains o to ch4 in h2o if 1286 00:40:36,820 --> 00:40:35,330 you're not able to detect it and you're 1287 00:40:38,860 --> 00:40:36,830 looking for a single gas by a signature 1288 00:40:41,770 --> 00:40:38,870 for example but this is a to CH for 1289 00:40:43,630 --> 00:40:41,780 trade off the simple molecules like o to 1290 00:40:45,880 --> 00:40:43,640 methane and to and so on and so forth 1291 00:40:47,290 --> 00:40:45,890 are excellent detection prospects but 1292 00:40:48,610 --> 00:40:47,300 they have a substantial false positive 1293 00:40:50,770 --> 00:40:48,620 risk because nature can make those 1294 00:40:52,750 --> 00:40:50,780 molecules relatively easily as well the 1295 00:40:54,730 --> 00:40:52,760 complicated molecules like ch3 1296 00:40:57,160 --> 00:40:54,740 organosulfur is pitched in isoprene a 1297 00:40:59,050 --> 00:40:57,170 little false positive risk but you need 1298 00:41:00,640 --> 00:40:59,060 very high fluxes in order for them to be 1299 00:41:01,900 --> 00:41:00,650 detectable and it's not clearly at 1300 00:41:03,970 --> 00:41:01,910 whether or not that's plausible only 1301 00:41:06,700 --> 00:41:03,980 observations will tell on the end in all 1302 00:41:08,200 --> 00:41:06,710 cases m-dwarf during the aqwal variant 1303 00:41:09,700 --> 00:41:08,210 optimal not just for their small sizes 1304 00:41:11,980 --> 00:41:09,710 but because of their small UV fluxes 1305 00:41:12,850 --> 00:41:11,990 which means that it's easy for these 1306 00:41:16,870 --> 00:41:12,860 gases they build up to high 1307 00:41:18,130 --> 00:41:16,880 concentrations so to bring them bring 1308 00:41:19,780 --> 00:41:18,140 the talk back to the new questions that 1309 00:41:21,220 --> 00:41:19,790 motivated it we wanted to understand a 1310 00:41:22,510 --> 00:41:21,230 little bit about prebiotic chemistry of 1311 00:41:24,430 --> 00:41:22,520 bias occurs in the connection between 1312 00:41:26,110 --> 00:41:24,440 them mediated by UV light these are 1313 00:41:27,760 --> 00:41:26,120 giant fields in Korean which have only 1314 00:41:29,260 --> 00:41:27,770 touched necessarily in a few small parts 1315 00:41:31,090 --> 00:41:29,270 of it so if you have more questions I 1316 00:41:34,120 --> 00:41:31,100 hope you'll ask them well you'll ask 1317 00:41:36,190 --> 00:41:34,130 them to Q&A but to summarize the parts 1318 00:41:37,870 --> 00:41:36,200 of it that I talked about in terms of UV 1319 00:41:39,190 --> 00:41:37,880 light and prebiotic chemistry UV light 1320 00:41:40,330 --> 00:41:39,200 plays a controlling role in the crea 1321 00:41:42,640 --> 00:41:40,340 biotic environment that controls a 1322 00:41:44,110 --> 00:41:42,650 buildup of the environmental reagents 1323 00:41:47,340 --> 00:41:44,120 that could power the emergence of life 1324 00:41:49,600 --> 00:41:47,350 in particular it restricts and ox2 1325 00:41:50,950 --> 00:41:49,610 strictly to shallow ponds so if origin 1326 00:41:52,810 --> 00:41:50,960 of life does require and wax 1327 00:41:55,000 --> 00:41:52,820 it'll have trouble working in erosion 1328 00:41:56,200 --> 00:41:55,010 but it might work in a shallow pond so 1329 00:41:57,310 --> 00:41:56,210 we should think about those in grounds a 1330 00:41:59,380 --> 00:41:57,320 little bit 1331 00:42:01,120 --> 00:41:59,390 if you do have that UV you can also do 1332 00:42:02,500 --> 00:42:01,130 great things for you it can power a wide 1333 00:42:04,390 --> 00:42:02,510 range of synthesis pathways in 1334 00:42:06,630 --> 00:42:04,400 particular if conduction with sulphide 1335 00:42:08,800 --> 00:42:06,640 it can solve the reduction problem and 1336 00:42:10,300 --> 00:42:08,810 Ember ups are a really exciting test 1337 00:42:11,560 --> 00:42:10,310 case in this regard because they're low 1338 00:42:12,670 --> 00:42:11,570 UV environments which means that we 1339 00:42:15,160 --> 00:42:12,680 might be able to use them to test 1340 00:42:16,540 --> 00:42:15,170 theories of abiogenesis in terms of UV 1341 00:42:18,100 --> 00:42:16,550 light and bio signatures you use this 1342 00:42:19,570 --> 00:42:18,110 ability as important here because it's 1343 00:42:21,370 --> 00:42:19,580 the ultimate control on the build-up of 1344 00:42:24,280 --> 00:42:21,380 potential biomolecule signatures in 1345 00:42:26,080 --> 00:42:24,290 planetary atmospheres biosignatures we 1346 00:42:27,670 --> 00:42:26,090 divided to tell it two categories one 1347 00:42:29,320 --> 00:42:27,680 are the simple molecules which tend to 1348 00:42:31,990 --> 00:42:29,330 have high false positive risk but are 1349 00:42:33,910 --> 00:42:32,000 very detectable and the other category 1350 00:42:35,500 --> 00:42:33,920 are the hard to make molecules which 1351 00:42:36,880 --> 00:42:35,510 have a little false positive risk but 1352 00:42:38,230 --> 00:42:36,890 you need very high flux does it affect 1353 00:42:39,100 --> 00:42:38,240 them and it's not clear that biology 1354 00:42:40,830 --> 00:42:39,110 will choose to make that choice 1355 00:42:43,300 --> 00:42:40,840 elsewhere in the universe 1356 00:42:44,260 --> 00:42:43,310 in all scenarios UV controls are built 1357 00:42:46,300 --> 00:42:44,270 up as a consequence 1358 00:42:47,770 --> 00:42:46,310 mber ups means the ideal place to look 1359 00:42:49,690 --> 00:42:47,780 vote for the perspective of constraining 1360 00:42:51,040 --> 00:42:49,700 theories of abiogenesis and also just in 1361 00:42:52,030 --> 00:42:51,050 the perspective of being able to make 1362 00:42:54,910 --> 00:42:52,040 that constraint of the first place 1363 00:42:56,380 --> 00:42:54,920 looking for these IO signatures that's 1364 00:42:57,640 --> 00:42:56,390 about all I've got I'd like to thank my 1365 00:42:59,410 --> 00:42:57,650 colleagues collaborators and especially 1366 00:43:01,060 --> 00:42:59,420 my funding source assignments foundation 1367 00:43:10,259 --> 00:43:01,070 I'll leave my slides up and I'd love to 1368 00:43:14,170 --> 00:43:12,579 thank you for that talk and while the 1369 00:43:15,849 --> 00:43:14,180 mics are going around I wanted to take 1370 00:43:19,299 --> 00:43:15,859 the prior to pass the first question and 1371 00:43:21,309 --> 00:43:19,309 it's about flares so you said that the 1372 00:43:23,799 --> 00:43:21,319 UV controls the build-up of the isoprene 1373 00:43:24,849 --> 00:43:23,809 in the peach 3 but then if the 1374 00:43:27,190 --> 00:43:24,859 steady-state is too low to actually 1375 00:43:28,509 --> 00:43:27,200 destroy them but then the flares would 1376 00:43:30,970 --> 00:43:28,519 have destroyed them because increases 1377 00:43:32,349 --> 00:43:30,980 the UV flux but is the time scale like 1378 00:43:33,970 --> 00:43:32,359 not enough that it can see can you 1379 00:43:35,079 --> 00:43:33,980 building up early that is a great 1380 00:43:36,130 --> 00:43:35,089 question that's something we'd like to 1381 00:43:37,720 --> 00:43:36,140 address in future work what is the 1382 00:43:40,960 --> 00:43:37,730 effect of time written AMA such as 1383 00:43:42,519 --> 00:43:40,970 flares and not just the UV which from 1384 00:43:43,720 --> 00:43:42,529 work by Matt Tilley and I'm taking a 1385 00:43:46,569 --> 00:43:43,730 segura might actually be relatively 1386 00:43:47,799 --> 00:43:46,579 limited but from the particle fluxes so 1387 00:43:49,599 --> 00:43:47,809 that's not something that we understand 1388 00:43:51,039 --> 00:43:49,609 yet my bet is that it would probably not 1389 00:43:52,089 --> 00:43:51,049 do great things for them as biasing 1390 00:43:54,999 --> 00:43:52,099 throughs but we need to think about that 1391 00:44:04,390 --> 00:43:55,009 in a lot more death thank you alright 1392 00:44:07,299 --> 00:44:04,400 question if you can go to see Amelia hi 1393 00:44:10,239 --> 00:44:07,309 I have a question we got a pH 3 SMI your 1394 00:44:13,140 --> 00:44:10,249 signature you were using a hydrogen 1395 00:44:16,269 --> 00:44:13,150 dominated atmospheres regulations but 1396 00:44:19,690 --> 00:44:16,279 you you create a log of pH free without 1397 00:44:21,370 --> 00:44:19,700 any biology involved hydrogen dominated 1398 00:44:22,960 --> 00:44:21,380 atmosphere so how is that the 1399 00:44:24,940 --> 00:44:22,970 biosignature not under habitable 1400 00:44:27,400 --> 00:44:24,950 conditions you don't the formation of pH 1401 00:44:28,630 --> 00:44:27,410 3 in h2 dominated atmospheres is not 1402 00:44:30,190 --> 00:44:28,640 thermodynamically favored at 1403 00:44:32,349 --> 00:44:30,200 temperatures lower than about 800 Kelvin 1404 00:44:34,390 --> 00:44:32,359 in the case of the gas giants where pH 3 1405 00:44:35,589 --> 00:44:34,400 is detected it's thought that it's up 1406 00:44:37,569 --> 00:44:35,599 from deep regions of the atmosphere 1407 00:44:43,620 --> 00:44:37,579 where the conditions are a lot higher 1408 00:44:54,999 --> 00:44:52,690 can we do down here in the front so if I 1409 00:44:57,460 --> 00:44:55,009 understood your points correctly you 1410 00:45:00,519 --> 00:44:57,470 need UV light to power some of those 1411 00:45:01,930 --> 00:45:00,529 prebiotic chemistry and basically as an 1412 00:45:03,880 --> 00:45:01,940 energy source but then I think you're 1413 00:45:05,170 --> 00:45:03,890 also telling us that M drawers are 1414 00:45:07,660 --> 00:45:05,180 particularly good because you don't get 1415 00:45:10,089 --> 00:45:07,670 too much UV so do you foresee there 1416 00:45:12,880 --> 00:45:10,099 being like I don't know maybe not a fine 1417 00:45:15,579 --> 00:45:12,890 tuning problem but a sort of a how 1418 00:45:17,710 --> 00:45:15,589 precise you have to be to be just enough 1419 00:45:19,450 --> 00:45:17,720 as an energy source but not too much UV 1420 00:45:21,789 --> 00:45:19,460 that you're basically killing your 1421 00:45:25,660 --> 00:45:21,799 prospects for 1422 00:45:26,980 --> 00:45:25,670 so I argue that the better way to think 1423 00:45:28,720 --> 00:45:26,990 about this is not let's assume we 1424 00:45:29,980 --> 00:45:28,730 understand how life forms and then try 1425 00:45:32,410 --> 00:45:29,990 to figure out like we can think about 1426 00:45:33,849 --> 00:45:32,420 that a little bit but I think M dwarfs 1427 00:45:35,289 --> 00:45:33,859 are so observationally favorite in so 1428 00:45:36,819 --> 00:45:35,299 many ways they're the ideal test case in 1429 00:45:38,740 --> 00:45:36,829 so many ways we're gonna look for life 1430 00:45:40,359 --> 00:45:38,750 there anyway so you should instead ask 1431 00:45:41,380 --> 00:45:40,369 what can searching for life about M 1432 00:45:43,030 --> 00:45:41,390 gross tell us about theories of 1433 00:45:45,339 --> 00:45:43,040 abiogenesis so we're gonna make the 1434 00:45:46,569 --> 00:45:45,349 measurements anyway I prefer to ask once 1435 00:45:47,380 --> 00:45:46,579 we make those four instruments and we 1436 00:45:48,789 --> 00:45:47,390 find results 1437 00:45:51,789 --> 00:45:48,799 what can the positive negative detection 1438 00:45:54,309 --> 00:45:51,799 tell us a positive detection potentially 1439 00:45:55,569 --> 00:45:54,319 has the opportunity to tell us that UV 1440 00:45:56,710 --> 00:45:55,579 light is not required for the origin of 1441 00:45:58,240 --> 00:45:56,720 life and we need to go back to drawing 1442 00:46:00,609 --> 00:45:58,250 Gordon a lot of this which within of 1443 00:46:04,839 --> 00:46:00,619 itself be quite exciting a negative 1444 00:46:07,210 --> 00:46:04,849 detection well I guess a negative yeah 1445 00:46:08,530 --> 00:46:07,220 well they might be a UV light might have 1446 00:46:09,819 --> 00:46:08,540 helped here but like it wouldn't rule 1447 00:46:11,980 --> 00:46:09,829 out that's true it would at least tell 1448 00:46:13,420 --> 00:46:11,990 you that UV light is not essential by 1449 00:46:14,680 --> 00:46:13,430 contrast and negative detection if you 1450 00:46:16,059 --> 00:46:14,690 keep finding negative defections and you 1451 00:46:17,829 --> 00:46:16,069 do find life elsewhere in the universe 1452 00:46:19,059 --> 00:46:17,839 around higher math stars that would be a 1453 00:46:20,680 --> 00:46:19,069 hint that you'd be life is essential so 1454 00:46:22,049 --> 00:46:20,690 I prefer to think of it in the other way 1455 00:46:24,130 --> 00:46:22,059 around 1456 00:46:25,720 --> 00:46:24,140 do you don't think both of your points 1457 00:46:27,130 --> 00:46:25,730 can be correct then because they seem to 1458 00:46:28,930 --> 00:46:27,140 be then contradicting each other I 1459 00:46:30,460 --> 00:46:28,940 understood you correctly I think that 1460 00:46:31,839 --> 00:46:30,470 this is a big and complicated question 1461 00:46:34,299 --> 00:46:31,849 and we should try to work at it both 1462 00:46:35,799 --> 00:46:34,309 ends if we can and again like the priors 1463 00:46:37,450 --> 00:46:35,809 that I have going into this from what I 1464 00:46:39,910 --> 00:46:37,460 understand at the chemistry aspect of it 1465 00:46:41,770 --> 00:46:39,920 I do favor a little bit the idea that UV 1466 00:46:42,970 --> 00:46:41,780 light is essential so if you ask me to 1467 00:46:45,190 --> 00:46:42,980 put my money on it and that's what 1468 00:46:46,000 --> 00:46:45,200 that's what I would bet on but my 1469 00:46:47,319 --> 00:46:46,010 opinion doesn't matter 1470 00:46:48,490 --> 00:46:47,329 nature's opinion is what matters here 1471 00:46:50,140 --> 00:46:48,500 and what can support it to me about 1472 00:46:51,849 --> 00:46:50,150 exoplanets is that it's an opportunity 1473 00:46:59,770 --> 00:46:51,859 for nature to tell us how she prefers to 1474 00:47:03,069 --> 00:46:59,780 work Colin I've got another question 1475 00:47:05,770 --> 00:47:03,079 about phosphine which is why if we had 1476 00:47:08,319 --> 00:47:05,780 life anything like earth life why would 1477 00:47:12,280 --> 00:47:08,329 it make it at scale because phosphorous 1478 00:47:14,799 --> 00:47:12,290 an essential nutrient and that you with 1479 00:47:17,319 --> 00:47:14,809 the possible exception of using 1480 00:47:19,390 --> 00:47:17,329 methylated compounds to transfer some 1481 00:47:20,829 --> 00:47:19,400 nutrients from the ocean to land where 1482 00:47:23,589 --> 00:47:20,839 they were abundant did the ocean and not 1483 00:47:25,630 --> 00:47:23,599 abundant on land but phosphorous is 1484 00:47:27,940 --> 00:47:25,640 abundant of land and not abundant in the 1485 00:47:31,839 --> 00:47:27,950 ocean so why would we put it into gas 1486 00:47:33,880 --> 00:47:31,849 form to get rid of it I don't know but 1487 00:47:34,660 --> 00:47:33,890 the fundamental answer is life does it 1488 00:47:36,670 --> 00:47:34,670 anyway so 1489 00:47:39,040 --> 00:47:36,680 we should deal with that in particular 1490 00:47:40,840 --> 00:47:39,050 so I think one of the questions you're 1491 00:47:42,790 --> 00:47:40,850 asking is is there by is there detection 1492 00:47:43,420 --> 00:47:42,800 of phosphorous production and the answer 1493 00:47:44,850 --> 00:47:43,430 that question 1494 00:47:47,560 --> 00:47:44,860 broadly speaking seems to be yes 1495 00:47:49,540 --> 00:47:47,570 phosphorus keys being detected over in 1496 00:47:51,580 --> 00:47:49,550 over environments that are anoxic and a 1497 00:47:53,380 --> 00:47:51,590 little bit warm for example it's keeps 1498 00:47:55,540 --> 00:47:53,390 being detected over systems like sewage 1499 00:47:57,670 --> 00:47:55,550 plants it's detected over it's detected 1500 00:47:59,320 --> 00:47:57,680 from the flat land the exhausted various 1501 00:48:01,960 --> 00:47:59,330 animals who's coming out of intestinal 1502 00:48:03,280 --> 00:48:01,970 tracts it's detected and it's also been 1503 00:48:04,840 --> 00:48:03,290 detected in laboratory contexts where 1504 00:48:06,100 --> 00:48:04,850 people have taken these microbes growing 1505 00:48:08,320 --> 00:48:06,110 them on phosphate and it seems to 1506 00:48:09,910 --> 00:48:08,330 convert it most of it to phosphine so it 1507 00:48:11,380 --> 00:48:09,920 seems that life is chosen to do this and 1508 00:48:13,330 --> 00:48:11,390 we should maybe try to figure out why I 1509 00:48:15,970 --> 00:48:13,340 should mention that Jana but Kowski has 1510 00:48:20,080 --> 00:48:15,980 some ideas here in particular under warm 1511 00:48:22,030 --> 00:48:20,090 acidic conditions reduction of I don't 1512 00:48:23,350 --> 00:48:22,040 know the details on this better in his 1513 00:48:25,750 --> 00:48:23,360 paper he argues that reduction of 1514 00:48:26,980 --> 00:48:25,760 phosphate to phosphine can liberate free 1515 00:48:28,360 --> 00:48:26,990 energy so it's potentially an energy 1516 00:48:30,160 --> 00:48:28,370 source if you have phosphate available 1517 00:48:32,110 --> 00:48:30,170 and he also thinks about in the terms of 1518 00:48:33,310 --> 00:48:32,120 a signaling mechanism but I would refer 1519 00:48:37,090 --> 00:48:33,320 to Janish on that one I don't know the 1520 00:48:44,020 --> 00:48:37,100 details of that aspect of it RJ up in 1521 00:48:48,220 --> 00:48:46,510 you mentioned high fluxes of mass 1522 00:48:48,700 --> 00:48:48,230 between planetary bodies in the solar 1523 00:48:52,330 --> 00:48:48,710 system 1524 00:48:54,070 --> 00:48:52,340 and how that that kind of might prevent 1525 00:48:55,510 --> 00:48:54,080 them from giving us much information 1526 00:48:56,710 --> 00:48:55,520 about abiogenesis if we found something 1527 00:48:57,670 --> 00:48:56,720 unlike an icy world or something like 1528 00:48:59,980 --> 00:48:57,680 that cuz I might have come from Earth 1529 00:49:02,880 --> 00:48:59,990 but uh do we have any good idea about 1530 00:49:05,560 --> 00:49:02,890 the flux of mass between stellar systems 1531 00:49:07,810 --> 00:49:05,570 for example like if we found life on a 1532 00:49:09,460 --> 00:49:07,820 planet orbiting an M dwarf how sure 1533 00:49:11,410 --> 00:49:09,470 could we be that it hadn't just pans 1534 00:49:14,140 --> 00:49:11,420 permed from somewhere else that's a 1535 00:49:15,490 --> 00:49:14,150 really great question I actually think 1536 00:49:17,280 --> 00:49:15,500 someone has worked of the numbers on 1537 00:49:19,480 --> 00:49:17,290 this but I don't remember the citation 1538 00:49:20,530 --> 00:49:19,490 so I guess you'll have to take what I 1539 00:49:22,420 --> 00:49:20,540 say with a grain of salt my 1540 00:49:23,890 --> 00:49:22,430 understanding is that it has been 1541 00:49:26,050 --> 00:49:23,900 quantified and it's a very low risk of 1542 00:49:27,400 --> 00:49:26,060 transfer very low rate of transfer but I 1543 00:49:33,940 --> 00:49:27,410 don't remember the reference so I can't 1544 00:49:39,299 --> 00:49:33,950 say that state that for certain yeah I 1545 00:49:47,759 --> 00:49:45,089 and then over the wall to Sara I have a 1546 00:49:49,140 --> 00:49:47,769 quick question and a quick comment I'll 1547 00:49:50,999 --> 00:49:49,150 do the comment first I just wanted to 1548 00:49:52,579 --> 00:49:51,009 emphasize what I presented yesterday 1549 00:49:55,199 --> 00:49:52,589 that we're seeing organosulfur compounds 1550 00:50:00,299 --> 00:49:55,209 in our experiment being a biotic we 1551 00:50:02,669 --> 00:50:00,309 produced the question is if you favor UV 1552 00:50:03,959 --> 00:50:02,679 mechanism to produce nucleobases I was 1553 00:50:05,909 --> 00:50:03,969 intrigued by the fact that you decided 1554 00:50:08,039 --> 00:50:05,919 to completely ignore photons short of 1555 00:50:10,499 --> 00:50:08,049 100 nanometers because if you're going 1556 00:50:12,059 --> 00:50:10,509 to make nucleobases in a nitrogen 1557 00:50:13,439 --> 00:50:12,069 dominated atmosphere you have to break 1558 00:50:15,449 --> 00:50:13,449 the nitrogen somehow and you need 1559 00:50:16,529 --> 00:50:15,459 photons shorter 100 nanometers though I 1560 00:50:18,569 --> 00:50:16,539 missed something 1561 00:50:20,519 --> 00:50:18,579 so there's two really great points here 1562 00:50:21,779 --> 00:50:20,529 one is I think it's a really great point 1563 00:50:23,189 --> 00:50:21,789 about the Organa cell for production 1564 00:50:25,679 --> 00:50:23,199 potentially high up in the atmosphere I 1565 00:50:27,659 --> 00:50:25,689 think it'd be really instructive to gain 1566 00:50:28,679 --> 00:50:27,669 a quantification of the of the amount of 1567 00:50:29,880 --> 00:50:28,689 that we could expect a natural 1568 00:50:31,529 --> 00:50:29,890 environment something as units of 1569 00:50:33,269 --> 00:50:31,539 molecules per square centimeter per 1570 00:50:35,339 --> 00:50:33,279 second that's something we could plug in 1571 00:50:36,509 --> 00:50:35,349 terminal inter models and see if that 1572 00:50:37,890 --> 00:50:36,519 should produce a significant false 1573 00:50:40,109 --> 00:50:37,900 positive feature so that would be really 1574 00:50:41,249 --> 00:50:40,119 cool to have with regards to the second 1575 00:50:42,959 --> 00:50:41,259 base I think that's a really important 1576 00:50:44,880 --> 00:50:42,969 point we're not talking about the 1577 00:50:47,640 --> 00:50:44,890 abiotic synthesis of nucleobases nuclear 1578 00:50:50,009 --> 00:50:47,650 bases are easy you get a nuclear bases 1579 00:50:51,479 --> 00:50:50,019 almost any which way if you just take of 1580 00:50:52,499 --> 00:50:51,489 even moderately reducing mix of 1581 00:50:54,299 --> 00:50:52,509 compounds and even things that are not 1582 00:50:56,309 --> 00:50:54,309 super Mota clear adducing and you just 1583 00:50:57,809 --> 00:50:56,319 blasted for tree energy if you have the 1584 00:50:59,249 --> 00:50:57,819 ingredients available you make nuclear 1585 00:51:01,199 --> 00:50:59,259 bases in high-yield this goes back to 1586 00:51:03,419 --> 00:51:01,209 the classics and C's by arrow back in 1587 00:51:05,549 --> 00:51:03,429 1961 and this has been articulated in 1588 00:51:07,829 --> 00:51:05,559 various ways the key challenge that you 1589 00:51:09,630 --> 00:51:07,839 have is how do you make the nucleotides 1590 00:51:11,489 --> 00:51:09,640 how do you take the people how do you 1591 00:51:13,349 --> 00:51:11,499 can join the nuclear base to the sugar 1592 00:51:14,519 --> 00:51:13,359 to the phosphate group and in particular 1593 00:51:16,409 --> 00:51:14,529 how do you make that intermediate bond 1594 00:51:18,269 --> 00:51:16,419 that high energy and glycosidic c and 1595 00:51:20,399 --> 00:51:18,279 bond that joins the two of them together 1596 00:51:21,899 --> 00:51:20,409 that's what classical synthesis that go 1597 00:51:23,519 --> 00:51:21,909 about that start with the positive with 1598 00:51:25,169 --> 00:51:23,529 the light by making the LEGO pieces and 1599 00:51:26,789 --> 00:51:25,179 putting them together aren't able to do 1600 00:51:28,259 --> 00:51:26,799 so far because that bond is so high 1601 00:51:29,909 --> 00:51:28,269 energy if you inject enough energy into 1602 00:51:32,549 --> 00:51:29,919 the system to make it you break the LEGO 1603 00:51:34,019 --> 00:51:32,559 pieces as well so the the way this 1604 00:51:36,269 --> 00:51:34,029 particular pathway gets around that is 1605 00:51:37,799 --> 00:51:36,279 by cheating a little so the key 1606 00:51:39,569 --> 00:51:37,809 requirement that it has the really key 1607 00:51:41,849 --> 00:51:39,579 requirement in addition to UV is 1608 00:51:43,499 --> 00:51:41,859 availability of HCM and there you have 1609 00:51:44,849 --> 00:51:43,509 the C N bond to begin with so you build 1610 00:51:47,039 --> 00:51:44,859 a door you see you build a molecule 1611 00:51:48,390 --> 00:51:47,049 around it's like you start with it's 1612 00:51:49,649 --> 00:51:48,400 like instead of building a house and 1613 00:51:51,179 --> 00:51:49,659 then the rooms of house and putting it 1614 00:51:52,709 --> 00:51:51,189 together you start with a doorway and 1615 00:51:53,609 --> 00:51:52,719 build the house around that so that's 1616 00:51:58,259 --> 00:51:53,619 the way that they have invokes 1617 00:51:59,579 --> 00:51:58,269 hard to get around that problem I guess 1618 00:52:01,710 --> 00:51:59,589 just a comment that if you want to have 1619 00:52:04,109 --> 00:52:01,720 VN coming from the atmosphere you have 1620 00:52:05,759 --> 00:52:04,119 to break the nitrogen bond yeah you need 1621 00:52:07,170 --> 00:52:05,769 to you need either exogenous delivery or 1622 00:52:08,730 --> 00:52:07,180 you need some kind of mechanism for 1623 00:52:11,130 --> 00:52:08,740 example Attalla source of ch4 high in 1624 00:52:12,809 --> 00:52:11,140 the altitude or scps doing something 1625 00:52:14,279 --> 00:52:12,819 interesting interesting or mechanisms 1626 00:52:15,450 --> 00:52:14,289 like the ones you talked about which is 1627 00:52:17,160 --> 00:52:15,460 one of the reasons would be really great 1628 00:52:25,019 --> 00:52:17,170 to be able to incorporate those into our 1629 00:52:26,400 --> 00:52:25,029 models irrigators universe' why is it 1630 00:52:29,009 --> 00:52:26,410 the question that I thought Sarah was 1631 00:52:31,319 --> 00:52:29,019 going to ask which is what is the effect 1632 00:52:33,089 --> 00:52:31,329 of aerosols or clouds on the UV fluxes 1633 00:52:33,539 --> 00:52:33,099 at the surface that is an excellent 1634 00:52:36,930 --> 00:52:33,549 question 1635 00:52:44,489 --> 00:52:36,940 do I have a slide on this maybe hold on 1636 00:52:46,470 --> 00:52:44,499 how do I escape this where it is sorry I 1637 00:52:48,059 --> 00:52:46,480 have a lot of backup slides okay the 1638 00:52:49,200 --> 00:52:48,069 short term answer is that so we looked 1639 00:52:52,410 --> 00:52:49,210 at this particularly in the context of 1640 00:52:54,509 --> 00:52:52,420 early Mars the short answer is it 1641 00:52:56,339 --> 00:52:54,519 doesn't seem to the key thing that's 1642 00:52:59,309 --> 00:52:56,349 going on here is that long long rid of 1643 00:53:01,319 --> 00:52:59,319 200 nanometres both co2 ice particles 1644 00:53:03,210 --> 00:53:01,329 and h2 ice particles are again in that 1645 00:53:04,589 --> 00:53:03,220 strictly scattering regime which means 1646 00:53:06,420 --> 00:53:04,599 that again optical depth drops off 1647 00:53:08,249 --> 00:53:06,430 relatively slowly with a relatively 1648 00:53:10,259 --> 00:53:08,259 sorry transmission drops up slow with 1649 00:53:12,479 --> 00:53:10,269 the optical depth it goes as 1 over tau 1650 00:53:14,009 --> 00:53:12,489 naught e to the minus tau in order to 1651 00:53:15,809 --> 00:53:14,019 significantly infect the surface of the 1652 00:53:17,249 --> 00:53:15,819 environment you need relatively thick 1653 00:53:19,859 --> 00:53:17,259 cloud decks you need to have context of 1654 00:53:22,019 --> 00:53:19,869 the order of optical depths of 10 to 100 1655 00:53:24,150 --> 00:53:22,029 in order to really suppress it and in 1656 00:53:25,920 --> 00:53:24,160 order and at least from the GCM models 1657 00:53:28,109 --> 00:53:25,930 of for example words were that all 2016 1658 00:53:33,170 --> 00:53:28,119 such thick cloud decks 1659 00:53:40,319 --> 00:53:36,979 and I'm sorry I don't know your name 1660 00:53:43,349 --> 00:53:40,329 well written by leiden observatory you 1661 00:53:46,380 --> 00:53:43,359 mentioned some high production rate for 1662 00:53:48,599 --> 00:53:46,390 some bio signature I was wondering did 1663 00:53:50,609 --> 00:53:48,609 you check about the impact on the 1664 00:53:52,739 --> 00:53:50,619 evolution of the atmosphere because of 1665 00:53:54,720 --> 00:53:52,749 this prediction rate for example in term 1666 00:53:56,430 --> 00:53:54,730 of greenhouse oh-ho 1667 00:53:57,509 --> 00:53:56,440 no we don't that's because impacts are 1668 00:53:59,069 --> 00:53:57,519 harder than we don't know how to do them 1669 00:54:02,609 --> 00:53:59,079 if you do please please please work with 1670 00:54:02,619 --> 00:54:11,490 right up front 1671 00:54:15,099 --> 00:54:13,510 my understanding is that is that 1672 00:54:17,529 --> 00:54:15,109 phosphate is the only really 1673 00:54:21,190 --> 00:54:17,539 biologically available form of 1674 00:54:24,220 --> 00:54:21,200 phosphorus and so on earth that comes 1675 00:54:27,010 --> 00:54:24,230 from a mineral exerting kind of 1676 00:54:29,559 --> 00:54:27,020 mineralogy I think it's new from apatite 1677 00:54:32,470 --> 00:54:29,569 apatite so how common do we expect 1678 00:54:35,079 --> 00:54:32,480 phosphorus to be on planets in terms of 1679 00:54:37,390 --> 00:54:35,089 delivery of phosphorus and how special 1680 00:54:38,829 --> 00:54:37,400 does a those a planets geochemistry have 1681 00:54:41,170 --> 00:54:38,839 to be in order to make a source of 1682 00:54:42,460 --> 00:54:41,180 phosphate do you have there any thoughts 1683 00:54:44,529 --> 00:54:42,470 on that 1684 00:54:46,059 --> 00:54:44,539 so that's a really good question the 1685 00:54:47,620 --> 00:54:46,069 phosphate cycle is something that's 1686 00:54:49,480 --> 00:54:47,630 really complicated and I don't know very 1687 00:54:52,059 --> 00:54:49,490 much about to be honest the phosphorous 1688 00:54:53,620 --> 00:54:52,069 cycle on modern earth so I can't say 1689 00:54:58,059 --> 00:54:53,630 state anything with a very high degree 1690 00:55:01,769 --> 00:54:58,069 of certainty oh yeah let me see if 1691 00:55:05,589 --> 00:55:04,120 don't actually think there is like I 1692 00:55:06,700 --> 00:55:05,599 think you and I both have the same basic 1693 00:55:08,319 --> 00:55:06,710 understanding of it which is that 1694 00:55:11,289 --> 00:55:08,329 phosphorus is important it's often 1695 00:55:13,029 --> 00:55:11,299 limiting is it we did check is there any 1696 00:55:15,099 --> 00:55:13,039 phosphorus on the surface of for example 1697 00:55:16,539 --> 00:55:15,109 earth or in the other rocky planets in 1698 00:55:17,980 --> 00:55:16,549 our solar system to produce these 1699 00:55:19,930 --> 00:55:17,990 detectable signatures and the answer is 1700 00:55:21,279 --> 00:55:19,940 definitely yes we don't even use we 1701 00:55:23,380 --> 00:55:21,289 don't even use a percentage of use much 1702 00:55:25,299 --> 00:55:23,390 much less so the number of phosphorus 1703 00:55:26,500 --> 00:55:25,309 atoms is not a limiting supply but in 1704 00:55:27,640 --> 00:55:26,510 terms of the more to compute I'll do 1705 00:55:29,170 --> 00:55:27,650 chemical cycling anything more 1706 00:55:32,710 --> 00:55:29,180 sophisticated we haven't done that yet 1707 00:55:35,260 --> 00:55:32,720 yeah and a related thing from nuclear 1708 00:55:36,279 --> 00:55:35,270 synthesis talks I've been at it seems 1709 00:55:38,650 --> 00:55:36,289 that although you would expect 1710 00:55:41,470 --> 00:55:38,660 phosphorus to be easily synthesized in 1711 00:55:43,029 --> 00:55:41,480 in high mass stars it's actually hard to 1712 00:55:44,349 --> 00:55:43,039 find where it's being synthesized and 1713 00:55:46,510 --> 00:55:44,359 there are a lot of seems to be open 1714 00:55:58,710 --> 00:55:46,520 questions about nucleosynthesis of 1715 00:56:04,030 --> 00:56:01,690 um I noticed in the like list of names 1716 00:56:06,730 --> 00:56:04,040 you gave her the very start you had John 1717 00:56:08,290 --> 00:56:06,740 Sutherland and I've read so his papers 1718 00:56:09,670 --> 00:56:08,300 were a prebiotic chemistry and I've read 1719 00:56:11,380 --> 00:56:09,680 some papers by this guy Bill Russell 1720 00:56:13,120 --> 00:56:11,390 who's a big proponent of like the 1721 00:56:14,950 --> 00:56:13,130 alkaline hydrothermal vent model and 1722 00:56:16,660 --> 00:56:14,960 they like they always like jab at each 1723 00:56:19,000 --> 00:56:16,670 other they like seem to think that each 1724 00:56:21,520 --> 00:56:19,010 other's ideas are both just on the face 1725 00:56:23,530 --> 00:56:21,530 of it ridiculous and and implausible so 1726 00:56:27,610 --> 00:56:23,540 do you think the alkaline hydrothermal 1727 00:56:29,880 --> 00:56:27,620 vent idea is dumb I know I certainly 1728 00:56:32,230 --> 00:56:29,890 don't think it is so I think that again 1729 00:56:33,820 --> 00:56:32,240 opinions of people tend to be relatively 1730 00:56:35,020 --> 00:56:33,830 useless what's relevant are experiments 1731 00:56:38,500 --> 00:56:35,030 and observations that will ultimately 1732 00:56:40,090 --> 00:56:38,510 constrain these answers I think that the 1733 00:56:43,240 --> 00:56:40,100 vents theory of life has many exciting 1734 00:56:44,710 --> 00:56:43,250 things going for it which is that which 1735 00:56:46,270 --> 00:56:44,720 is among other things it explains in 1736 00:56:48,880 --> 00:56:46,280 many aspects of modern biochemistry for 1737 00:56:51,910 --> 00:56:48,890 example the role of gradients I think 1738 00:56:54,040 --> 00:56:51,920 that what for me though I had the thing 1739 00:56:55,420 --> 00:56:54,050 that really convinces me is showing 1740 00:56:57,070 --> 00:56:55,430 something in a lab and showing that it 1741 00:56:59,260 --> 00:56:57,080 works so one thing that I would really 1742 00:57:00,880 --> 00:56:59,270 love to see from and I know the events 1743 00:57:02,620 --> 00:57:00,890 community is working on this is showing 1744 00:57:03,880 --> 00:57:02,630 simulating some of these scenarios and 1745 00:57:05,890 --> 00:57:03,890 showing how some of these more complex 1746 00:57:07,450 --> 00:57:05,900 biomolecules and systems cycles that 1747 00:57:09,160 --> 00:57:07,460 have been for which the theory isn't 1748 00:57:10,720 --> 00:57:09,170 work that well can be created in the lab 1749 00:57:12,820 --> 00:57:10,730 so that's something that would be really 1750 00:57:14,080 --> 00:57:12,830 cool that we're really cool to see they 1751 00:57:15,670 --> 00:57:14,090 should not be taken by the way as in 1752 00:57:17,260 --> 00:57:15,680 implicit criticism - I haven't done the 1753 00:57:18,760 --> 00:57:17,270 experiments that's because people have 1754 00:57:20,290 --> 00:57:18,770 been thinking about this this synthetic 1755 00:57:21,970 --> 00:57:20,300 kind of chemistry for much longer than 1756 00:57:23,710 --> 00:57:21,980 we're thinking about vent chemistry's so 1757 00:57:26,020 --> 00:57:23,720 they haven't had enough time yet so my 1758 00:57:27,880 --> 00:57:26,030 personal perspective is that we can't 1759 00:57:30,340 --> 00:57:27,890 rule we can't favor or disfavor strongly 1760 00:57:31,630 --> 00:57:30,350 either one yet we need to keep doing 1761 00:57:34,210 --> 00:57:31,640 experiments with the objective of 1762 00:57:36,250 --> 00:57:34,220 linking it fundamentally to in the end 1763 00:57:40,630 --> 00:57:36,260 something we can either measure in the