1 00:00:05,940 --> 00:00:08,960 >>> GOOD EVENING AND WELCOME. I AM DR. LINDSAY HAYS, A 2 00:00:08,960 --> 00:00:14,340 POSTDOCTURAL FELLOW HERE AT NASA. 3 00:00:14,340 --> 00:00:17,921 TONIGHT'S DISCUSSION IS ABOUT WHAT WE KNOW ABOUT THE EARLY 4 00:00:17,921 --> 00:00:21,350 EARTH AND HOW THAT CAN GUIDE OUR SEARCH FOR HABITABLE PLANETS 5 00:00:21,350 --> 00:00:24,030 ORBITING OTHER STARS. IT WILL BE FOLLOWED BY A 6 00:00:24,030 --> 00:00:27,160 QUESTION AND ANSWER PERIOD WITH THOSE OF YOU IN THE AUDIENCE AS 7 00:00:27,160 --> 00:00:31,830 WELL AS ON SOCIAL MEDIA USING HASHTAG #ASKNASA. 8 00:00:31,830 --> 00:00:41,059 THIS IS FOCUSING ON THE 9 00:00:41,059 --> 00:00:47,909 HABITABILITY OF THE EARLY EARTH. I'M ONE OF THE CO-ORGANIZERS. 10 00:00:47,909 --> 00:00:51,319 I WILL JOIN YOU ALL FOR THE QUESTION AND ANSWER PERIOD BUT I 11 00:00:51,319 --> 00:00:55,390 WOULD LIKE TO INTRODUCE OUR MODERATOR FOR THIS EVENING. 12 00:00:55,390 --> 00:01:01,840 A SENIOR SCIENTIST AT PLANETARY SCIENCE INSTITUTE, DR. DAVID 13 00:01:01,840 --> 00:01:07,430 GRINSPOON. >> THANK YOU, LINDSAY. 14 00:01:07,430 --> 00:01:10,930 THANK YOU ALL FOR COMING OUT THIS AFTERNOON. 15 00:01:10,930 --> 00:01:14,370 A BIG HELLO TO ALL YOU PEOPLE OUT THERE IN NASA TV LAND. 16 00:01:14,370 --> 00:01:18,350 I'M THRILLED TO BE HERE TO PRESENT TO YOU THIS DISCUSSION 17 00:01:18,350 --> 00:01:21,430 OF SOME REALLY EXCITING NEW SCIENCE. 18 00:01:21,430 --> 00:01:25,020 WE LIVE IN A REVOLUTIONARY TIME IN TERMS OF OUR KNOWLEDGE OF THE 19 00:01:25,020 --> 00:01:26,870 UNIVERSE. THIS IS THE TIME OF THE EX OH, 20 00:01:26,870 --> 00:01:31,710 PLANET REVOLUTION. WE KNOW MOST STARS HAVE 21 00:01:31,710 --> 00:01:38,020 PLANETARY SYSTEMS OF THEIR OWN. IT'S A BIG DISCOVERY. 22 00:01:38,020 --> 00:01:41,450 WE'RE ALSO IN A TIME OF RAPID DISCOVERY ABOUT THE HISTORY OF 23 00:01:41,450 --> 00:01:44,710 LIFE ON EARTH AND THE ORIGIN AND EARLY EVOLUTION OF LIFE ON 24 00:01:44,710 --> 00:01:46,810 EARTH. WE'RE HERE THIS AFTERNOON TO TRY 25 00:01:46,810 --> 00:01:50,680 TO BRING ALL THAT TOGETHER. I'VE GOT A PANEL OF EXPERTS HERE 26 00:01:50,680 --> 00:01:54,490 WHO ARE ALL DOING RESEARCH THAT CHIPS AWAY AT THAT PROBLEM OF 27 00:01:54,490 --> 00:01:57,850 LIFE ELSEWHERE AND HOW WE CAN APPLY OUR KNOWLEDGE OF EARTH 28 00:01:57,850 --> 00:02:00,520 HISTORY TO THE QUESTION OF LIFE ELSEWHERE. 29 00:02:00,520 --> 00:02:04,500 LET ME INTRODUCE THE PANELISTS TO YOU. 30 00:02:04,500 --> 00:02:07,810 IF I WERE GOING TO GIVE THEM ALL THE FULL INTRODUCTION THEY WOULD 31 00:02:07,810 --> 00:02:10,140 DESERVE, IT WOULD TAKE THE FULL HOUR. 32 00:02:10,140 --> 00:02:13,420 THEY'RE ALL VERY ACCOMPLISHED PEOPLE AND THE LISTS OF AWARDS 33 00:02:13,420 --> 00:02:20,690 AND DEGREES AND PUBLICATIONS WOULD FILL AN ENCYCLOPEDIA. 34 00:02:20,690 --> 00:02:28,560 BRIEFLY, STARTING ON MY FAR RIGHT, WE HAVE CHRIS HOUSE. 35 00:02:28,560 --> 00:02:30,980 CHRIS IS THE DIRECTOR OF THE PENN STATE ASTRO BIOLOGY 36 00:02:30,980 --> 00:02:34,380 RESEARCH CENTER. HIS RESEARCH FOCUSES ON 37 00:02:34,380 --> 00:02:38,490 MICROBIAL GEO CHEMICAL SIGNATURES OF LIFE. 38 00:02:38,490 --> 00:02:44,620 THAT MEANS HE STUDIES THE TINIEST ORGANISMS AND HOW THEY 39 00:02:44,620 --> 00:02:50,390 AFFECT THE ENVIRONMENT AND APPLIES THAT TO THE QUESTION OF 40 00:02:50,390 --> 00:02:53,840 HOW CAN WE USE THESE CLUES TO UNDERSTAND THE ORIGIN AND EARLY 41 00:02:53,840 --> 00:02:57,940 EVOLUTION OF LIFE HERE AND ELSEWHERE IN THE UNIVERSE. 42 00:02:57,940 --> 00:03:00,890 NEXT TO CHRIS IS DR. PHOEBE COHEN. 43 00:03:00,890 --> 00:03:06,170 SHE'S A PROFESSOR OF GEO SCIENCES AT WILLIAMS COLLEGE. 44 00:03:06,170 --> 00:03:14,060 HER RESEARCH FOCUSES ON LARGER ORGANISMS, THE FOSSIL RECORD, 45 00:03:14,060 --> 00:03:17,600 THE INTERACTIONS BETWEEN EARTH AND LIFE IN DEEP TIME AND IN 46 00:03:17,600 --> 00:03:21,420 PARTICULAR THE ORIGIN OF ANIMALS AND THE ORIGIN OF COMPLEXITY ON 47 00:03:21,420 --> 00:03:28,520 EARTH AND THE QUESTION OF WHERE COMPLEX LIFE MIGHT ARISE IN THE 48 00:03:28,520 --> 00:03:33,650 UNIVERSE. OVER TO MY LEFT, TIM LYONS IS AT 49 00:03:33,650 --> 00:03:37,790 THE DEPARTMENT OF EARTH SCIENCES, UNIVERSITY OF 50 00:03:37,790 --> 00:03:42,760 CALIFORNIA IN RIVERSIDE. TIM STUDIES THE EVOLUTION OF THE 51 00:03:42,760 --> 00:03:46,730 OCEAN OF THE ATMOSPHERE AND OF LIFE AND HOW THESE ARE COUPLED 52 00:03:46,730 --> 00:03:48,650 TOGETHER, HOW THEY AFFECT ONE ANOTHER. 53 00:03:48,650 --> 00:03:52,239 HE LOOKS AT THE CHEMISTRY OF THE MODERN OCEAN AND ASKS HOW CAN 54 00:03:52,239 --> 00:03:55,680 THIS HELP US TO UNDERSTAND ANCIENT OCEANS AND THE 55 00:03:55,680 --> 00:03:59,930 ATMOSPHERE AND THE SEARCH FOR EXTRATERRESTRIAL LIFE. 56 00:03:59,930 --> 00:04:04,610 NEXT WE HAVE DR. DAWN SUMNER. DAWN IS A PROFESSOR OF GEOLOGY 57 00:04:04,610 --> 00:04:06,760 AT THE UNIVERSITY OF CALIFORNIA DAVIS. 58 00:04:06,760 --> 00:04:12,209 SHE STUDIES THE EARLY ENVIRONMENT OF EARTH AND MARS 59 00:04:12,209 --> 00:04:16,310 AND THE EVOLUTION OF BACTERIA ON EARTH AND POTENTIALLY ON MARS 60 00:04:16,310 --> 00:04:19,530 AND OTHER ENVIRONMENTS. THIS RESEARCH HAS TAKEN HER FROM 61 00:04:19,530 --> 00:04:24,840 ANTARCTICA TO THE SURFACE OF MARS WHERE SHE'S ONE OF THE MAIN 62 00:04:24,840 --> 00:04:28,790 SCIENTISTS WORKING ON A LARGE TEAM OF SCIENTISTS RUNNING THE 63 00:04:28,790 --> 00:04:33,440 CURIOSITY RECOVER AND TRYING TO UNDERSTAND WHAT THAT ENVIRONMENT 64 00:04:33,440 --> 00:04:37,530 IS TELLING US ABOUT MARS AND ABOUT LIFE IN THE UNIVERSE. 65 00:04:37,530 --> 00:04:41,460 FINALLY, WE HAVE DR. SHAWN DOMAGAL-GOLDMAN. 66 00:04:41,460 --> 00:04:45,800 SHAWN IS A RESEARCH SPACE SCIENTIST AT GODDARD SPACE 67 00:04:45,800 --> 00:04:49,340 FLIGHT CENTER FOR NASA. HE STUDIES THE INTERACTION OF 68 00:04:49,340 --> 00:04:54,460 LIFE AND PLANETS AND THINKS ABOUT THE SIGNATURES OF LIFE, 69 00:04:54,460 --> 00:04:58,090 THE BIOSIGNATURES, HOW WE WOULD DETECT LIFE ON ANOTHER PLANET 70 00:04:58,090 --> 00:05:01,050 AND USE THAT TO TRACE LIFE'S ORIGINS. 71 00:05:01,050 --> 00:05:07,650 LATELY HE'S BEEN DESIGNING A NEW GENERATION OF TELESCOPES TO FIND 72 00:05:07,650 --> 00:05:15,180 THESE BIOSIGNATURES ON SOME OF THESE PLANETS WE'VE BEEN 73 00:05:15,180 --> 00:05:18,220 DISCOVERING. I'M GOING TO START OFF BY 74 00:05:18,220 --> 00:05:21,870 PITCHING A\h-- I DON'T KNOW IF IT'S A SOFT BALL QUESTION BUT 75 00:05:21,870 --> 00:05:24,710 I'M GOING TO ASK YOU EACH TO RESPOND TO A QUESTION ABOUT 76 00:05:24,710 --> 00:05:29,530 LIFE'S INEVITABILITY. WE TALK AND HEAR A LOT ABOUT 77 00:05:29,530 --> 00:05:34,620 THIS GOLDIE LOCKS ZONE, THE JACKPOT OF SEARCHING FOR LIFE 78 00:05:34,620 --> 00:05:39,090 ELSEWHERE IS DEFINED OF A PLANET THAT WOULD HAVE LIQUID WATER ON 79 00:05:39,090 --> 00:05:46,050 THE SURFACE. IF WE FIND SUCH A PLANET, DOES 80 00:05:46,050 --> 00:05:50,740 THAT MEAN SHOULD IT HAVE LIFE? IS WATER ITSELF A BIOSIGNATURE 81 00:05:50,740 --> 00:05:55,860 OR AS ONE OF MY COLLEAGUES SAID THIS AFTERNOON, HE SAID IF YOU 82 00:05:55,860 --> 00:05:58,960 HAVE A WATER WORLD, HOW DO YOU KEEP IT DEAD? 83 00:05:58,960 --> 00:06:02,720 >> THANKS, DAVID. THAT'S DEFINITELY NOT A SOFT 84 00:06:02,720 --> 00:06:07,080 BALL QUESTION. I'LL START BY SAYING IT'S REALLY 85 00:06:07,080 --> 00:06:12,180 PROFOUND AND WHETHER IT DICTATES WHETHER OR NOT LIFE IS COMMON OR 86 00:06:12,180 --> 00:06:16,690 RARE AND EITHER RESULT WOULD BE TOTALLY PROFOUND FOR OUR PLACE 87 00:06:16,690 --> 00:06:19,210 IN THE COSMOS. CERTAINLY NOT A SOFT BALL. 88 00:06:19,210 --> 00:06:25,630 I ALSO SAY THAT MY OWN PERSONAL OPINION ON THIS HAS CHANGED. 89 00:06:25,630 --> 00:06:31,360 EARLY ON IN MY CAREER I WAS ACTUALLY QUITE OPTIMISTIC THAT 90 00:06:31,360 --> 00:06:37,260 WHENEVER YOU HAVE LIQUID WATER, THEY FORM THE NECESSARY 91 00:06:37,260 --> 00:06:43,440 MATERIALS FOR LIFE AND YOU END UP FORMING LIFE. 92 00:06:43,440 --> 00:06:47,280 BUT LATELY I'VE ACTUALLY STARTED TO REALLY BE OPEN TO THE IDEA 93 00:06:47,280 --> 00:06:52,040 THAT WE NEED TO CONSIDER THE REVERSE POSSIBILITY THAT WHAT WE 94 00:06:52,040 --> 00:06:55,050 HAVE HERE IS QUITE SPECIAL AND UNIQUE WHICH IS ALSO REALLY 95 00:06:55,050 --> 00:07:03,800 PROFOUND AND BASICALLY A LOT OF PEOPLE'S FEELINGS ON THIS IS 96 00:07:03,800 --> 00:07:08,080 DRIVEN BY THE FACT THAT WE SEE LIFE GOES BACK TO THE REALLY 97 00:07:08,080 --> 00:07:12,310 VERY BEGINNINGS OF EARTH, SO THAT IMPLIES A QUICK ORIGIN. 98 00:07:12,310 --> 00:07:16,449 BUT THERE ARE OTHER PIECES OF EVIDENCE WE HAVE OUT THERE THAT 99 00:07:16,449 --> 00:07:20,259 ALSO BEAR IN THE QUESTION. FOR EXAMPLE, WHEN YOU LOOK AT 100 00:07:20,259 --> 00:07:27,560 METEORITES, WE KNOW A LOT OF RUSHING THROUGH THEM AND THERE 101 00:07:27,560 --> 00:07:31,840 WAS ENERGY GRADIENTS AND THEY FORMED A LOT OF ORGANIC MATTER. 102 00:07:31,840 --> 00:07:35,270 SO THAT CAN BE TAKEN AS A VERY OPTIMISTIC VIEW, YOU'RE STARTING 103 00:07:35,270 --> 00:07:39,190 TO GET LIFE GOING, BUT YOU CAN ALSO CONCLUDE THAT THOSE BODIES 104 00:07:39,190 --> 00:07:45,560 AND SOLAR SYSTEMS THEN DIDN'T FORM A BIOSPHERE, THAT THEY 105 00:07:45,560 --> 00:07:52,440 DON'T HAVE CELLS AND METABOLISM. WE HAD WATER RUSHING THROUGH AND 106 00:07:52,440 --> 00:07:56,350 ENERGY WAS THERE, BUT WE ONLY SEEM TO AT LEAST PRESENTLY HAVE 107 00:07:56,350 --> 00:08:00,650 EVIDENCE FOR LIFE HERE, ONE ORIGIN FOR OUR SOLAR SYSTEM. 108 00:08:00,650 --> 00:08:03,120 OF COURSE, THAT COULD CHANGE AS WE STUDY MARS AND THAT'S GOING 109 00:08:03,120 --> 00:08:05,250 TO BE EXCITING TO SEE HOW THAT PLAYS OUT. 110 00:08:05,250 --> 00:08:10,810 >> YOU THINK THE JURY IS OUT? >> THE JURY IS OUT, BUT I'M VERY 111 00:08:10,810 --> 00:08:15,910 OPEN TO THE IDEA THAT WHAT WE HAVE IS VERY SPECIAL HERE. 112 00:08:15,910 --> 00:08:19,139 >> PHOEBE. >> THAT WAS A REALLY GREAT 113 00:08:19,139 --> 00:08:21,980 ANSWER. YOU CAN'T JUST HAVE LIQUID 114 00:08:21,980 --> 00:08:26,740 WATER, YOU HAVE TO HAVE IT FOR AN EXTENDED PERIOD OF TIME. 115 00:08:26,740 --> 00:08:30,389 AS CHRIS ALLUDED TO, YOU ALSO NEED OTHER CONDITIONS IN ORDER 116 00:08:30,389 --> 00:08:34,779 FOR LIFE TO EVOLVE, PROBABLY SOME SORT OF STABILITY OVER SOME 117 00:08:34,779 --> 00:08:37,719 TIME SCALE THAT WE DIDN'T HAVE A HANDLE ON YET WHERE LIQUID WATER 118 00:08:37,719 --> 00:08:41,460 IS EXISTING IN AN ENVIRONMENT THAT IS PERMISSIVE FOR LIFE. 119 00:08:41,460 --> 00:08:44,709 I WOULD SAY THAT YOU NEED WATER PLUS A BUNCH OF OTHER THINGS. 120 00:08:44,709 --> 00:08:47,339 WHAT THOSE THINGS ARE, I DON'T THINK WE HAVE A REALLY GOOD 121 00:08:47,339 --> 00:08:51,510 HANDLE ON RIGHT NOW. >> I WOULD AGREE THAT THE JURY 122 00:08:51,510 --> 00:08:53,680 IS OUT. I THINK IT'S THE RIGHT PLACE TO 123 00:08:53,680 --> 00:08:56,290 START. BUT I'M DRAWN TO THE BACKDROP 124 00:08:56,290 --> 00:08:58,800 BEHIND US. WHEN I WAS A KID AND I STARTED 125 00:08:58,800 --> 00:09:02,070 ALL OF THIS, VISIONS OF THE EARLY EARTH WERE VERY DIFFERENT 126 00:09:02,070 --> 00:09:04,540 THAN THIS. NOW WE SEE WATER AND VOLCANOS 127 00:09:04,540 --> 00:09:08,290 AND THERE ARE DATA THAT WATER MAY HAVE BEEN ON OUR PLANET MORE 128 00:09:08,290 --> 00:09:13,550 THAN 4 BILLION YEARS AGO. THE EVIDENCE FOR LIFE IS QUITE A 129 00:09:13,550 --> 00:09:17,210 BIT YOUNGER THAN THAT, SUGGESTIONS AT 3.7, 3.8 BILLION 130 00:09:17,210 --> 00:09:22,270 OR MORE CONVINCING 3.5. THAT'S A LOT OF TIME BETWEEN 131 00:09:22,270 --> 00:09:25,470 EVIDENCE OF WATER AND LIFE. WE DON'T KNOW WHAT HAPPENED 132 00:09:25,470 --> 00:09:27,690 DURING THAT TIME AND WE DON'T KNOW THAT THAT WOULD BE 133 00:09:27,690 --> 00:09:31,330 INEVITABLE AND PLAY OUT THE SAME WAY EVERY PLACE WE LOOK. 134 00:09:31,330 --> 00:09:37,190 >> YOU'RE ALL SO CAUTIOUS. YOU SOUND LIKE SCIENTISTS. 135 00:09:37,190 --> 00:09:41,770 DAWN? >> I DON'T HAVE A PERSONAL 136 00:09:41,770 --> 00:09:44,850 OPINION. I SHIFT AROUND BACK AND FORTH 137 00:09:44,850 --> 00:09:46,500 ALL THE TIME. BUT ONE OF THE MOST EXCITING 138 00:09:46,500 --> 00:09:51,920 THINGS TO ME IS THAT WE ACTUALLY HAVE TWO ROVERS ON MARS AND 139 00:09:51,920 --> 00:09:55,400 ORBITERS AROUND MARS THAT ARE TELLING US THERE WAS AN 140 00:09:55,400 --> 00:09:59,920 EXTENSIVE HISTORY OF WATER ON EARLY MARS. 141 00:09:59,920 --> 00:10:04,820 WE HAVE INSTRUMENTATION WITH THE CURIOSITY ROVER HAS DEMONSTRATED 142 00:10:04,820 --> 00:10:09,910 THAT WE HAD LIQUID WATER INTERACTIONS BETWEEN THE WATER 143 00:10:09,910 --> 00:10:12,880 AND THE ROCKS WHICH GIVES AN ENERGY GRADIENT AND THE ELEMENTS 144 00:10:12,880 --> 00:10:17,350 THAT ARE NECESSARY FOR LIFE. WE HAVE NOT FOUND EVIDENCE OF 145 00:10:17,350 --> 00:10:20,470 LIFE. WHEN WE LOOK AT EARTH'S FOSSIL 146 00:10:20,470 --> 00:10:24,240 RECORD, IT'S VERY DIFFICULT TO FIND THAT EVIDENCE EVEN THOUGH 147 00:10:24,240 --> 00:10:29,110 WE KNOW LIFE WAS PRESENT. IT'S A WHOLE PROCESS OF 148 00:10:29,110 --> 00:10:34,450 DISCOVERY AND INVESTIGATION, SO AS AN INDIVIDUAL I WANT TO HAVE 149 00:10:34,450 --> 00:10:38,990 AN OPINION, BUT THEN AS I SCIENTIST I AM IN THIS WONDERFUL 150 00:10:38,990 --> 00:10:42,529 PLACE WHERE WE CAN ACTUALLY ASK THOSE QUESTIONS WITH THE 151 00:10:42,529 --> 00:10:46,640 MISSIONS THAT WE HAVE NOW ON MARS AND THE MARS 2020 ROVER 152 00:10:46,640 --> 00:10:51,900 THAT'S BEING PLANNED IS THE NEXT STEP TO DO A LITTLE BIT BETTER 153 00:10:51,900 --> 00:10:57,790 SCIENTIFIC INVESTIGATION. WE HAVE THE CONDITIONS THAT SHOW 154 00:10:57,790 --> 00:11:01,140 LIQUID WATER WAS PRESENT AND MANY OF US THINK FOR A LONG 155 00:11:01,140 --> 00:11:05,529 TIME, AND NOW IS THE QUESTION OF WHETHER OR NOT WE CAN FIND 156 00:11:05,529 --> 00:11:08,679 EVIDENCE OF LIFE IF IT WAS THERE. 157 00:11:08,679 --> 00:11:10,139 >> GREAT. SHAWN? 158 00:11:10,139 --> 00:11:13,790 >> I AGREE WITH DAWN. TO ME I FLIP THAT AROUND FROM 159 00:11:13,790 --> 00:11:17,529 THE QUESTION TO A STATEMENT. EVERY PLANET THAT HAS HAD WATER 160 00:11:17,529 --> 00:11:20,440 HAS HAD LIFE OR EVERY PLANET THAT HAS WATER HAS LIFE, NOT AS 161 00:11:20,440 --> 00:11:22,931 SOMETHING I NECESSARILY BELIEVE BUT AS A HYPOTHESIS THAT WE CAN 162 00:11:22,931 --> 00:11:28,000 TEST WITH THE SPACECRAFT THAT WE DELIVER TO MARS. 163 00:11:28,000 --> 00:11:31,200 WE KNOW IF WATER THROUGHOUT THE SOLAR SYSTEM ON THE MOONS OUT 164 00:11:31,200 --> 00:11:37,680 THERE AND FOR EX0 PLANETS WE'RE FINDING PLANETS IN THE HAPPY 165 00:11:37,680 --> 00:11:46,540 ZONE WHERE THE CONDITIONS COULD ALLOW FOR LIQUID WATER. 166 00:11:46,540 --> 00:11:48,670 THIS IS WHAT'S REALLY GREAT TO ME. 167 00:11:48,670 --> 00:11:52,010 WE COULD HAVE PONDERED THIS AS NATURAL PHILOSOPHERS 500 OR 168 00:11:52,010 --> 00:11:56,060 1,000 YEARS AGO AND EITHER WERE THE FIRST GENERATION OR OUR KIDS 169 00:11:56,060 --> 00:12:03,620 WILL BE THE FIRST GENERATION TO RIGOROUSLY TEST THIS. 170 00:12:03,620 --> 00:12:06,990 THAT'S WHAT KEEPS ME WORKING UP LATE AT NIGHT AND\h-- WELL, MY 171 00:12:06,990 --> 00:12:14,520 BABY WAKES ME UP EARLY IN THE MORNING. 172 00:12:14,520 --> 00:12:17,750 >> IT SEEMS LIKE THE SENSE OF THE JURY IS THAT IF WE FIND A 173 00:12:17,750 --> 00:12:21,680 WATER WORLD, IT'S EXCITING BUT DOESN'T NECESSARILY TELL US FOR 174 00:12:21,680 --> 00:12:26,760 SURE THAT WE'VE FOUND LIFE. BUT AS DAWN SAID, IN A CERTAIN 175 00:12:26,760 --> 00:12:30,930 SENSE ON MARS WE FOUND A WATER WORLD OR WE HAVE GOOD EVIDENCE 176 00:12:30,930 --> 00:12:34,690 THAT IT WAS AT ONE TIME A WATER WORLD AND THEN MARS PERHAPS 177 00:12:34,690 --> 00:12:39,340 BECOMES AN IMPORTANT TEST. IF IT WAS A WATER WORLD AND THIS 178 00:12:39,340 --> 00:12:42,110 IDEA OF INEVITABILITY IS RIGHT WE SHOULD BE ABLE TO FIND THE 179 00:12:42,110 --> 00:12:46,890 LIFE THERE EXCEPT IT'S HARD TO FIND LIFE IN ANCIENT ROCKS. 180 00:12:46,890 --> 00:12:52,079 THAT LEADS TO THE NEXT QUESTION WHICH IS ABOUT SIGNS OF LIFE IN 181 00:12:52,079 --> 00:12:58,360 ANCIENT ROCKS OR ANCIENT TRACERS OF LIFE ON EARTH. 182 00:12:58,360 --> 00:13:01,670 THIS IS A QUESTION FOR ANY OF YOU TO ANSWER AND MAYBE ALL OF 183 00:13:01,670 --> 00:13:05,519 YOU IF YOU WANT TO CHIME IN. WHEN DO YOU THINK IS THE FIRST 184 00:13:05,519 --> 00:13:11,600 REALLY GOOD EVIDENCE AND WHAT IS THAT EVIDENCE AND THE STATE OF 185 00:13:11,600 --> 00:13:16,900 LIFE ON THE PLANET EARTH? ANYBODY WANT TO JUMP IN, OR 186 00:13:16,900 --> 00:13:21,020 SHOULD I? >> I ALLUDED TO THAT. 187 00:13:21,020 --> 00:13:23,360 IT'S AN ONGOING STORY. OF COURSE LIKE ALL OF THESE 188 00:13:23,360 --> 00:13:27,860 THINGS, THERE ARE MANY PEOPLE IN THE COMMUNITY THAT ACCEPT GEO 189 00:13:27,860 --> 00:13:30,760 CHEMICAL EVIDENCE FOR EARLY LIFE AND I HAVE TO MENTION THE I 190 00:13:30,760 --> 00:13:36,050 WORD, ISOTOPES. THEY'RE NOT FOSSILS. 191 00:13:36,050 --> 00:13:38,730 THEY'RE NOT WELL PRESERVE TUESDAY ORGANIC MOLECULES OR 192 00:13:38,730 --> 00:13:42,680 SOMETHING THAT MOST PEOPLE WOULD POINT OUT AND SAY THERE'S LIFE, 193 00:13:42,680 --> 00:13:45,839 BUT THERE ARE SIGNATURES WITHIN THE GEO CHEMISTRY THAT SUGGEST 194 00:13:45,839 --> 00:13:51,339 METABOLIC PROCESSES. THOSE DATE TO 3.7 BILLION YEARS 195 00:13:51,339 --> 00:13:56,720 AGO. BY THE TIME WE GET TO 3.5 196 00:13:56,720 --> 00:14:02,970 MILLION YEARS AGO WE HAVE THINGS CALLED STROMATOLITES AND OTHERS 197 00:14:02,970 --> 00:14:09,220 THAT ARE MICROBIAL MATS. THEY'RE A SEDIMENTARY ORGANIC 198 00:14:09,220 --> 00:14:12,779 MATERIAL THAT'S MEANT TO BE TRAPPED BY ORGANIC FILM AND 199 00:14:12,779 --> 00:14:17,339 THERE ARE MICRO FOSSILS THAT I THINK MOST PEOPLE AT THIS TIME 200 00:14:17,339 --> 00:14:21,010 ACCEPT. SO THE FIRST FOSSIL EVIDENCE IS 201 00:14:21,010 --> 00:14:26,120 ABOUT 3.5 BILLION YEARS AGO. THERE HAS BEEN A RECORD ABOUT 202 00:14:26,120 --> 00:14:35,770 2.7 BILLION YEARS AGO OF ORGANIC MOLECULES THAT SUGGEST OXYGEN. 203 00:14:35,770 --> 00:14:37,690 IN THE PAST YEAR OR SO THAT'S BEEN CHALLENGED BY THE 204 00:14:37,690 --> 00:14:40,980 COLLECTION OF NEW MATERIALS AND MORE SOPHISTICATED LEVEL OF 205 00:14:40,980 --> 00:14:44,860 ANALYSIS. SO I'M COMFORTABLE PUSHING 206 00:14:44,860 --> 00:14:48,390 THINGS BACK TO 3.5 BILLION YEARS AGO, MAYBE FURTHER BACK THAN 207 00:14:48,390 --> 00:14:50,970 THAT. BUT THINGS START TO BECOME 208 00:14:50,970 --> 00:14:53,209 CERTAINLY MORE CONVINCING AS WE GET YOUNGER. 209 00:14:53,209 --> 00:14:55,800 >> I THINK THAT'S SOMETHING REALLY INTERESTING, TOO, IS WHEN 210 00:14:55,800 --> 00:15:00,590 YOU LOOK AT ESPECIALLY THE 3.5 BILLION YEAR OLD ROCKS THAT WE 211 00:15:00,590 --> 00:15:05,519 HAVE, IT'S NOT JUST ONE TYPE OF LIFE. 212 00:15:05,519 --> 00:15:10,019 YOU SEE EVIDENCE FOR A NUMBER OF DIFFERENT TYPES OF METABOLISMS. 213 00:15:10,019 --> 00:15:20,051 WE DON'T KNOW ABOUT OXYGEN PHOTO SYNTHESIS, SULFATE REDUCTION, SO 214 00:15:20,051 --> 00:15:24,540 IT'S IN THE JUST THE FACT THAT LIFE WAS PRESENT AT 3.5 BUT 215 00:15:24,540 --> 00:15:27,459 THERE WERE A LOT OF DIFFERENT TYPES OF LIFE AT THAT POINT, AT 216 00:15:27,459 --> 00:15:31,340 LEAST THAT'S MY OPINION. >> I WOULD SUGGEST THAT A LOT 217 00:15:31,340 --> 00:15:34,050 MIGHT HAVE GONE ON BEFORE THAT. >> RIGHT. 218 00:15:34,050 --> 00:15:39,970 >> YOU HAVE AN ECOLOGY THAT'S ESTABLISHED WITH THE ENVIRONMENT 219 00:15:39,970 --> 00:15:44,529 THAT ORGANISMS ARE GROWING IN. >> THERE'S EARLY SOLID EVIDENCE 220 00:15:44,529 --> 00:15:47,670 OF WHEN LIFE ACTUALLY STARTED. YOU'RE SAYING THAT YOU ARE 221 00:15:47,670 --> 00:15:52,660 SEEING THAT SOLID EVIDENCE THAT HAD SOME LONG HISTORY BEFORE IT. 222 00:15:52,660 --> 00:15:54,699 >> RIGHT. IT'S MUCH EASIER TO FIND GOOD 223 00:15:54,699 --> 00:15:59,290 EVIDENCE FOR LIFE THAT'S FORMING A WHOLE ECOLOGY BECAUSE THEN YOU 224 00:15:59,290 --> 00:16:02,460 START TO ACCUMULATE THE SIGNATURES AND THEY'RE EASIER TO 225 00:16:02,460 --> 00:16:05,690 PRESERVE IN THE ROCK RECORD. IF YOU HAVE ONE OR TWO CELLS 226 00:16:05,690 --> 00:16:09,510 REACTING WITH A MINERAL IN A LITTLE ENVIRONMENT, VERY, VERY 227 00:16:09,510 --> 00:16:12,760 HARD TO SEE. SO THE FIRST GOOD EVIDENCE OF 228 00:16:12,760 --> 00:16:18,540 LIFE IS LIKELY\h-- THERE HAS TO BE QUITE A BIT OF EVOLUTION 229 00:16:18,540 --> 00:16:22,079 BETWEEN THE TIME WHEN YOU FIRST GET LIFE AND YOU HAVE SOMETHING 230 00:16:22,079 --> 00:16:25,490 THAT'S REASONABLE TO PRESERVE IN THE ROCK RECORD. 231 00:16:25,490 --> 00:16:28,269 >> THE DIFFERENCE BETWEEN THE ORIGIN OF LIFE VERSUS THE ORIGIN 232 00:16:28,269 --> 00:16:32,200 OF A BIOSPHERE, I THINK THAT'S SORTS OF WHAT WE'RE TALKING 233 00:16:32,200 --> 00:16:33,790 ABOUT. >> WE HAVE TO DEAL WITH THE FACT 234 00:16:33,790 --> 00:16:37,160 THAT WE HAVE ONLY SO MANY ROCKS OF THAT TIME PERIOD AND MOST 235 00:16:37,160 --> 00:16:45,389 AREN'T VERY WELL PRESERVED. WE'RE ONLY ABLE TO SAMPLE TINY 236 00:16:45,389 --> 00:16:47,589 LITTLE PIECES OF THAT ORIGINAL WORLD. 237 00:16:47,589 --> 00:16:50,910 >> DO YOU THINK IF WE GO TO THE MOON WE CAN FIND OLD EARTH ROCKS 238 00:16:50,910 --> 00:16:53,810 THAT MIGHT GIVE US THAT ANSWER? >> THAT'S INTERESTING. 239 00:16:53,810 --> 00:16:56,440 I'M NOT SURE. >> ONE OF THE REASONS IS TO 240 00:16:56,440 --> 00:16:59,520 EXPLORE MARS IS BECAUSE IT DOESN'T HAVE THE PLATE 241 00:16:59,520 --> 00:17:02,790 TECTONICS. ON EARTH THE ROCKS ARE HEATED UP 242 00:17:02,790 --> 00:17:07,019 AND DESTROYED. MOST OF THE SURFACE OF MARS IS 3 243 00:17:07,019 --> 00:17:11,769 BILLION YEARS OLD AND OLDER. SO IT GIVES US A CHANCE TO LOOK 244 00:17:11,769 --> 00:17:13,829 AT VERY OLD ROCKS IN THE SOLAR SYSTEM. 245 00:17:13,829 --> 00:17:18,189 WE HAVE A WHOLE DIFFERENT SET OF QUESTIONS, BUT MARS HAS A BIG 246 00:17:18,189 --> 00:17:21,569 SUITE OF THESE EARLY ROCKS TO INVESTIGATE. 247 00:17:21,569 --> 00:17:23,809 >> THE SIMPLE ANSWER TO YOUR QUESTION, DAVID, THERE IS 248 00:17:23,809 --> 00:17:25,939 DEFINITELY EARTH MATERIAL ON THE MOON. 249 00:17:25,939 --> 00:17:29,809 GETTING TO IT WOULD BE VERY DIFFICULT BUT IT SHOULD BE 250 00:17:29,809 --> 00:17:33,519 THERE. >> THERE'S THAT SAMPLE\h-- 251 00:17:33,519 --> 00:17:38,109 >> QUITE A LOT. >> THE OTHER REASON WE THINK 252 00:17:38,109 --> 00:17:41,190 ABOUT THIS FROM NASA'S PERSPECTIVE IS THE EARLIER LIFE 253 00:17:41,190 --> 00:17:44,820 EVOLVED THE IMPLICATION IS THE EASIER IT WAS TO EVOLVE IN A 254 00:17:44,820 --> 00:17:46,909 GENERAL SENSE. SO THE LIKELIHOOD WOULD BE THAT 255 00:17:46,909 --> 00:17:51,330 LIFE IS SOMEWHERE ELSE OUT THERE. 256 00:17:51,330 --> 00:17:55,710 WHEN WE'RE LOOKING IN THE EARLIEST PARTS OF EARTH'S ROCK 257 00:17:55,710 --> 00:17:58,679 RECORD FOR SIGNS OF LIFE WE'RE LEARNING LESSONS ABOUT HOW TO 258 00:17:58,679 --> 00:18:03,859 LOOK FOR LIFE PERIOD THAT COULD BE APPLICABLE TO MARS. 259 00:18:03,859 --> 00:18:05,960 >> AS WE LEARN MORE ABOUT THE EARTH, ONE OF THE GREAT 260 00:18:05,960 --> 00:18:19,639 DILEMMAS\h-- SOMETHING LIKE PHOTO SYNTHESIS WAS ALSO DIFFICULT TO 261 00:18:19,639 --> 00:18:23,649 RECONCILE WITH THIS NOTION OF HEAVY BOMBARDMENT OF MATERIALS 262 00:18:23,649 --> 00:18:27,929 JUST BEFORE THAT IN A WORLD THAT WE IMAGINED THAT DIDN'T HAVE 263 00:18:27,929 --> 00:18:29,409 WATER. NOW THAT WE'RE ABLE TO PUSH 264 00:18:29,409 --> 00:18:33,529 WATER BACK AND IN THIS WORKSHOP THAT LINDSAY ALLUDED TO, THAT 265 00:18:33,529 --> 00:18:39,830 IDEA OF HEAVY BOMBARDMENT OF LIFE IS BEING QUESTIONED. 266 00:18:39,830 --> 00:18:47,730 >> AT SOME POINT CERTAINLY THINGS WERE BEING PUMMELLED AT 267 00:18:47,730 --> 00:18:50,760 SUCH A PACE THAT YOU PROBABLY WOULDN'T HAVE WANTED TO HANG OUT 268 00:18:50,760 --> 00:18:52,249 THERE. >> IT'S A QUESTION OF HOW 269 00:18:52,249 --> 00:18:55,389 INTENSE, HOW OFTEN, AND LIFE IS RESILIENT. 270 00:18:55,389 --> 00:18:59,470 SO AGAIN, WE DISCUSSED THE POSSIBILITY OF REFUCHSIA, PLACES 271 00:18:59,470 --> 00:19:02,970 DEEP WITHIN THE EARTH WHERE LIFE CAN POP OUT AND SURVIVE. 272 00:19:02,970 --> 00:19:09,429 AND WE KNOW THAT TODAY, LIFE IS DEEP WITHIN THE SUBSURFACE. 273 00:19:09,429 --> 00:19:15,470 >> SPEAKING OF THE EARLY EARTH AND THINKING ABOUT EXOPLANETS, I 274 00:19:15,470 --> 00:19:19,850 WANT TO ASK A QUESTION ABOUT BIOSIGNATURES. 275 00:19:19,850 --> 00:19:26,460 WHEN WE TALK ABOUT FINDING LIFE, WE THINK ABOUT FINDING OXYGEN OR 276 00:19:26,460 --> 00:19:32,710 METHANE OR OTHER SIGNS OF LIFE. I'M HEARING THAT LIFE HAS A LONG 277 00:19:32,710 --> 00:19:37,559 HISTORY AND HAS CHANGED RADICALLY. 278 00:19:37,559 --> 00:19:43,299 SO THE QUESTION IS IF WE DETECTED A PLANET THAT WAS LIKE 279 00:19:43,299 --> 00:19:48,489 THE EARTH, SAY 3 BILLION YEARS AGO, WOULD WE RECOGNIZE IT AS AN 280 00:19:48,489 --> 00:19:50,899 INHABITED PLANET? WHAT ARE THE BIOSIGNATURES OF 281 00:19:50,899 --> 00:19:54,359 ANCIENT EARTH AND HOW WOULD THEY DIFFER FROM THE BIOSIGNATURES 282 00:19:54,359 --> 00:19:57,409 TODAY? >> CAN I START WITH THE 283 00:19:57,409 --> 00:19:59,669 BIOSIGNATURES OF MODERN EARTH? >> PLEASE. 284 00:19:59,669 --> 00:20:02,779 >> IF YOU LOOKING AT MODERN EARTH THROUGH A TELESCOPE, THE 285 00:20:02,779 --> 00:20:17,389 INDICATOR WOULD BE THE SIMULTANEOUS DISCOVERY OF OXYGEN 286 00:20:17,389 --> 00:20:21,370 AND METHANE. YOU KNOW SOMEONE IS BRINGING THE 287 00:20:21,370 --> 00:20:26,690 METHANE RICH IN OXYGEN. THE MOST LIKELY EXPLANATION IS 288 00:20:26,690 --> 00:20:30,229 IT'S THE LIFE THAT'S BRINGING IT TO THE PARTY. 289 00:20:30,229 --> 00:20:36,780 FOR THE CASE OF ARCHEAN EARTH, IF YOU WENT IN A TIME MACHINE, 290 00:20:36,780 --> 00:20:44,239 YOU WOULD SUFFOCATE BECAUSE THERE WOULD HAVE BEEN NO OXYGEN 291 00:20:44,239 --> 00:20:49,100 TO BREATHE. I WAS ACTUALLY THINKING ABOUT 292 00:20:49,100 --> 00:20:58,080 THIS QUESTION AS A GRADUATE STUDENT AT PENN STATE. 293 00:20:58,080 --> 00:21:02,129 THERE WERE THESE AWFUL, AWFUL SMELLS COMING OUT OF THE LAB 294 00:21:02,129 --> 00:21:04,570 EVERY DAY\h-- >> NOT EVERY DAY. 295 00:21:04,570 --> 00:21:08,979 IT WASN'T HIS STUDENTS AND IT 296 00:21:08,979 --> 00:21:11,450 WASN'T THE PIZZA. IT WAS MICROBES THAT HIS 297 00:21:11,450 --> 00:21:13,869 STUDENTS WERE GROWING IN THE LAB. 298 00:21:13,869 --> 00:21:17,279 I ASKED WHAT'S GOING ON HERE. HE SAID THEY'RE GROWING THESE\h-- 299 00:21:17,279 --> 00:21:19,849 YOU CAN MAYBE GIVE MORE DETAILS ON THE EXPERIMENT BUT THEY'RE 300 00:21:19,849 --> 00:21:23,279 GROWING MICROBES IN THESE OXYGEN-FREE CONDITIONS SIMILAR 301 00:21:23,279 --> 00:21:26,729 TO EARLY EARTH AND THEY'RE MAKING OTHER GASES. 302 00:21:26,729 --> 00:21:30,309 THAT TICKED OFF AN IDEA OF WOULD THESE GASES BE DETECTABLE 303 00:21:30,309 --> 00:21:37,139 REMOTELY. THEY'RE KIND OF SULFUR ATOM WITH 304 00:21:37,139 --> 00:21:40,470 THE REST OF A METHANE MOLECULE ONTO IT. 305 00:21:40,470 --> 00:21:43,580 THEY DON'T LAST IN MODERN ENVIRONMENT BECAUSE THEY GET 306 00:21:43,580 --> 00:21:58,379 OXIDIZED. THERE'S LOTS OF CAVEATS TO THAT 307 00:21:58,379 --> 00:22:00,019 STORY. THAT'S THE SIMPLE VERSION. 308 00:22:00,019 --> 00:22:03,570 I JOKE THAT MAYBE YOU WANT TO SMELL FOR LIFE ON OTHER PLANETS 309 00:22:03,570 --> 00:22:11,190 INSTEAD OF LOOK FOR LIFE WITH A TELESCOPE. 310 00:22:11,190 --> 00:22:12,369 >> YOU SHOULD DEVELOP A SMELL SCOPE. 311 00:22:12,369 --> 00:22:14,249 >> PROFESSOR FARNSWORTH. >> ONE THING ABOUT THAT 312 00:22:14,249 --> 00:22:22,070 PARTICULAR SET OF EXPERIMENTS IS THAT THAT IS NOT WHAT WE WERE 313 00:22:22,070 --> 00:22:26,399 LOOKING FOR. >> IT WASN'T WHAT I WAS LOOKING 314 00:22:26,399 --> 00:22:29,139 FOR EITHER. >> A LOT OF TIMES SCIENTIFIC 315 00:22:29,139 --> 00:22:37,019 DISCOVERIES ARE SERENDIPITOUS. IN THAT CASE CARBON MONOXIDE 316 00:22:37,019 --> 00:22:41,849 INHABITING ONE OF THE ENZYMES OF A CERTAIN ORGANISM AND IT HAD TO 317 00:22:41,849 --> 00:22:43,600 SWITCH IT'S METABOLISM TO SOMETHING THAT WAS TOTALLY 318 00:22:43,600 --> 00:22:47,859 UNKNOWN AT THE TIME. WE DISCOVERED MICROBES CAN GIVE 319 00:22:47,859 --> 00:23:01,940 ENERGY BY MISTAKE AND THAT'S ONE OF THE FUN THINGS IN SCIENCE. 320 00:23:01,940 --> 00:23:05,039 >> I ALSO WOULDN'T GIVE UP ON OXYGEN. 321 00:23:05,039 --> 00:23:10,690 FOR THOSE OF YOU WHO DON'T\h-- THERE ARE BIOLOGICAL WAYS OF 322 00:23:10,690 --> 00:23:16,349 GETTING OXYGEN OR PRODUCING IT TO THE ATMOSPHERE BUT THAT'S NOT 323 00:23:16,349 --> 00:23:20,659 VERY MUCH AND YOU REALLY NEED PHOTO SYNTHESIS TO DO THAT. 324 00:23:20,659 --> 00:23:23,419 ONE OF THE BIG QUESTIONS IN STUDIES OF THE EARLY EARTH IS 325 00:23:23,419 --> 00:23:29,799 WHEN DID THAT START. WE THINK, MOST PEOPLE THAT I 326 00:23:29,799 --> 00:23:32,409 KNOW, THINK THAT THAT STARTED HAPPENING BEFORE IT STARTED 327 00:23:32,409 --> 00:23:35,620 ACCUMULATING IN THE ATMOSPHERE. SO THERE'S NOT ONLY THIS 328 00:23:35,620 --> 00:23:39,149 QUESTION OF WHEN DID THIS BEGIN AND IS IT A VIABLE BIOSIGNATURE 329 00:23:39,149 --> 00:23:44,609 WHICH I THINK IT IS BUT WHAT IS THE INTERACTION OF THE PLANET 330 00:23:44,609 --> 00:23:47,029 THAT ALLOWED TO ACCUMULATE SO IT COULD BE DETECTED FROM 331 00:23:47,029 --> 00:23:51,349 ELSEWHERE. IT REMAINS, I THINK, A PRIMARY 332 00:23:51,349 --> 00:23:55,979 TARGET AS WELL. >> ABSOLUTELY. 333 00:23:55,979 --> 00:23:58,859 >> MOVING A LITTLE BIT FARTHER FORWARD IN THE EVOLUTION OF 334 00:23:58,859 --> 00:24:02,470 EARTH AND POSSIBLY OF OTHER PLANETS, I WANT TO ASK PHOEBE 335 00:24:02,470 --> 00:24:07,880 ABOUT THE BORING BILLION. IN OUR FIELD THERE'S THIS 336 00:24:07,880 --> 00:24:12,289 SLIGHTLY SARCASTIC PHRASE THAT PEOPLE USE, THE BORING BILLION. 337 00:24:12,289 --> 00:24:17,059 REMEMBER, A BILLION YEARS IS A LONG, LONG TIME. 338 00:24:17,059 --> 00:24:21,969 ARGUABLY HUMAN CIVILIZATION IS 10,000 YEARS OLD AND HOMINID IS 339 00:24:21,969 --> 00:24:31,820 MAYBE A MILLION YEARS OLD. WHAT IS THE BORING BILLION AND 340 00:24:31,820 --> 00:24:36,300 WAS IT REALLY BORING? >> THE BORING BILLION IS A TIME 341 00:24:36,300 --> 00:24:39,379 IN EARTH HISTORY AFTER WHAT WE'VE JUST TALKED ABOUT BUT 342 00:24:39,379 --> 00:24:43,470 BEFORE COMPLEX LIFE EVOLVED WHERE IT APPEARS AS IF NOT VERY 343 00:24:43,470 --> 00:24:46,679 MUCH IS HAPPENING. THAT'S FROM THE GEOLOGICAL AND 344 00:24:46,679 --> 00:24:51,129 GEO CHEMICAL RECORDS. HOWEVER, IT'S PROBABLY NOT AS 345 00:24:51,129 --> 00:24:53,599 BORING AS WE THINK IT IS, IN PART BECAUSE THOSE RECORDS 346 00:24:53,599 --> 00:24:55,649 AREN'T VERY FULL. SO A BILLION YEARS, LIKE YOU 347 00:24:55,649 --> 00:24:59,789 SAID, IS A HUGE AMOUNT OF TIME AND WE HAVEN'T SAMPLED THAT TIME 348 00:24:59,789 --> 00:25:04,259 PERIOD SO WE'RE SEEING POCKETS OF THINGS THAT SORT OF LOOK 349 00:25:04,259 --> 00:25:11,679 BORING. I STUDY FOSSILS OF MICRO SCOPIC 350 00:25:11,679 --> 00:25:15,259 ORGANISMS DURING THIS TIME PERIOD AND MOST OF THEM LOOK 351 00:25:15,259 --> 00:25:19,309 LIKE BEACH BALLS. THEY HAVE VERY LITTLE SHAPE, 352 00:25:19,309 --> 00:25:21,799 VERY LITTLE TO DISTINGUISH THEM FROM OTHER LITTLE BEACH BALLS 353 00:25:21,799 --> 00:25:24,539 THAT I FIND IN A ROCK. THAT DOESN'T MEAN THEY'RE NOT 354 00:25:24,539 --> 00:25:29,230 EVOLVING. ORGANISMS ARE ALWAYS EVOLVING, 355 00:25:29,230 --> 00:25:32,080 EVEN IF THEY'RE NOT CHANGING THEIR SHAPE OR FORM. 356 00:25:32,080 --> 00:25:37,489 THIS TIME PERIOD THAT APPEARS IN THE FOSSIL RECORD TO BE BORING 357 00:25:37,489 --> 00:25:41,369 COULD HAVE BEEN A TIME OF MAJOR INNOVATION THAT WE JUST CAN'T 358 00:25:41,369 --> 00:25:45,390 SEE WITH THE TOOLS THAT WE HAVE RIGHT NOW. 359 00:25:45,390 --> 00:25:50,029 >> SO IT MAY JUST SEEM BORING BECAUSE WE DON'T KNOW WHAT WE'RE 360 00:25:50,029 --> 00:25:51,029 TALKING ABOUT. >> RIGHT. 361 00:25:51,029 --> 00:25:53,749 WE DON'T KNOW HOW TO LOOK. I THINK WE HAVE SOME IDEAS ABOUT 362 00:25:53,749 --> 00:25:58,859 HOW TO BUT WE HAVEN'T YET LOOKED IN THE RIGHT PLACES AT THE RIGHT 363 00:25:58,859 --> 00:26:00,919 PROXIES TO GET AT THE INTERESTING BITS. 364 00:26:00,919 --> 00:26:05,789 >> YOU MEAN GENETICALLY IN TERMS OF WHAT IS HAPPENING FROM A DNA 365 00:26:05,789 --> 00:26:06,919 STANDPOINT? >> YEAH. 366 00:26:06,919 --> 00:26:09,850 LIFE IS ALWAYS EVOLVING. WE CAN'T DO BACK AND SEQUENCE 367 00:26:09,850 --> 00:26:22,169 DNA FROM A 2 BILLION YEAR OLD ORGANISM. 368 00:26:22,169 --> 00:26:26,950 SO ALL YOU HAVE LEFT IS THE SHAPE OF THE ORGANISM OR 369 00:26:26,950 --> 00:26:33,639 MOLECULAR FOSSILS WHICH MAY HELP FLUSH OUT THIS BORING TIME 370 00:26:33,639 --> 00:26:36,399 PERIOD. >> TO ME THAT'S ONE OF THE 371 00:26:36,399 --> 00:26:40,129 INTERESTING INTERVALS IN TERMS OF GETTING COMPLEX LIFE AND 372 00:26:40,129 --> 00:26:47,559 WHETHER OR NOT COMPLEX LIFE IS INEVITABLE IN EVOLUTION BECAUSE 373 00:26:47,559 --> 00:26:51,409 COMPLEX LIFE ON EARTH IS MOSTLY SUPPORTED BY OXYGEN AND WE HAD 374 00:26:51,409 --> 00:26:56,729 OXYGEN FOR A LONG PERIOD BEFORE WE GET THAT FOSSIL RECORD. 375 00:26:56,729 --> 00:27:00,419 SO THAT EVEN THOUGH WE DON'T KNOW TOO MUCH FROM IT YET, A LOT 376 00:27:00,419 --> 00:27:03,249 OF TIMES YOU DON'T KNOW MUCH ABOUT SOMETHING THAT'S WHERE 377 00:27:03,249 --> 00:27:05,759 FUTURE DISCOVERIES ARE GOING TO BE. 378 00:27:05,759 --> 00:27:09,109 WE KNOW FROM WHAT WE SEE BEFORE AND AFTER THAT IT'S REALLY, 379 00:27:09,109 --> 00:27:11,830 REALLY IMPORTANT INTERVALS. >> SO IT MAY NOT HAVE BEEN 380 00:27:11,830 --> 00:27:14,879 BORING. I'M GLAD TO HEAR THAT BECAUSE 381 00:27:14,879 --> 00:27:18,849 THAT'S A LONG TIME TO BE BORED. NONETHELESS, IT SEEMS LIKE IT 382 00:27:18,849 --> 00:27:22,460 DID TAKE A LONG TIME FOR COMPLEX LIFE TO APPEAR ON THE EARTH. 383 00:27:22,460 --> 00:27:27,200 JUST AS WE DID DISCUSS THE INEVITABILITY OF LIFE GIVEN THE 384 00:27:27,200 --> 00:27:30,759 RIGHT CONDITIONS AT FIRST, YOU MENTIONED THIS QUESTION OF THE 385 00:27:30,759 --> 00:27:34,849 INEVITABILITY OF COMPLEXITY. WHAT DO YOU GUYS THINK ABOUT 386 00:27:34,849 --> 00:27:36,789 THAT? CAN WE SAY ANYTHING BASED ON THE 387 00:27:36,789 --> 00:27:41,149 TERRESTRIAL RECORD OF WHETHER GIVEN LIFE ON THE PLANET IT 388 00:27:41,149 --> 00:27:46,029 WOULD GET COMPLEX? >> MY FEELING IS THAT BORING IS 389 00:27:46,029 --> 00:27:49,809 AN UNFORTUNATE TERM. THERE WAS A LOT OF INNOVATION AT 390 00:27:49,809 --> 00:27:52,229 THAT TIME. IT SET THE STAGE FOR MORE 391 00:27:52,229 --> 00:27:55,460 COMPLEX LIFE, ANIMALS IN PARTICULAR. 392 00:27:55,460 --> 00:27:58,019 THE GEO CHEMICAL RECORD SUGGESTION THAT THERE WAS A KIND 393 00:27:58,019 --> 00:28:07,109 OF STASIS. IT WAS A TIME OF PERHAPS LOW AND 394 00:28:07,109 --> 00:28:12,289 RELATIVELY STABLE LOW OXYGEN. TO ME THAT'S NOT BORING AT ALL. 395 00:28:12,289 --> 00:28:14,850 IT'S REMARKABLE THAT YOU COULD HAVE A BILLION YEARS OF SUCH 396 00:28:14,850 --> 00:28:16,470 CONDITION. IF YOU THINK ABOUT IT, ONCE YOU 397 00:28:16,470 --> 00:28:19,419 HAVE THIS INNOVATION OF OXYGEN PRODUCTION AND YOU THINK ABOUT 398 00:28:19,419 --> 00:28:26,509 ALL THE REACTIONS, WHY WOULD IT HAVE BEEN SO STABLE. 399 00:28:26,509 --> 00:28:30,300 ONE OF THE FEELINGS THAT IS THAT YOU HAVE THIS LONG PERIOD AND IT 400 00:28:30,300 --> 00:28:41,950 MAY HAVE TAKEN SOMETHING TECH TONIC THAT BROUGHT YOU CLOSER TO 401 00:28:41,950 --> 00:28:44,499 COMPLEXITY AND SPECIFICALLY ANIMALS. 402 00:28:44,499 --> 00:28:48,269 SO IF THERE WERE EXTERNAL DRIVERS OR EVEN INTERNAL DRIVERS 403 00:28:48,269 --> 00:28:51,389 WITHIN THE EARTH LIKE PLATE TECTONICS, MOUNTAIN BUILDING 404 00:28:51,389 --> 00:28:56,919 ACTIVITY, IF THAT'S REQUIRED IT SEEMS LESS AN INEVITABLE TO ME. 405 00:28:56,919 --> 00:29:00,499 >> I CAN IMAGINE A WORLD WHERE LIFE HAPPILY CHUGS ALONG BEING 406 00:29:00,499 --> 00:29:05,059 MICROBIAL FOR BILLIONS OF YEARS. >> NOW THAT WOULD BE BORING. 407 00:29:05,059 --> 00:29:07,820 >> BUT THEY WOULD BE DOING COOL STUFF. 408 00:29:07,820 --> 00:29:12,539 THEY WOULD STILL BE EVOLVING AND CHANGING EVEN IF COMPANY CAN'T 409 00:29:12,539 --> 00:29:19,070 SEE IT WITH OUR EYES. >> I THINK IT WOULD BE A SHAME 410 00:29:19,070 --> 00:29:22,749 TO HAVE A UNIVERSE WHERE THERE WASN'T SOMETHING\h-- FOR 411 00:29:22,749 --> 00:29:28,169 INSTANCE, WE WOULDN'T BE HERE HAVING THIS CONVERSATION. 412 00:29:28,169 --> 00:29:34,009 >> THAT'S TRUE. >> THE BACTERIA CAN DO ENOUGH TO 413 00:29:34,009 --> 00:29:38,529 THE PLANET TO AFFECT THE ATMOSPHERE ENOUGH FOR US TO 414 00:29:38,529 --> 00:29:42,739 DETECT. >> YOU ACTUALLY MENTIONED 415 00:29:42,739 --> 00:29:45,440 SOMETHING A COUPLE MINUTES AGO THAT I WANT TO COME BACK TO. 416 00:29:45,440 --> 00:29:47,960 IT'S STUCK IN MY MIND AND IT BOTHERED ME A LITTLE BIT. 417 00:29:47,960 --> 00:29:52,989 YOU SAID THERE ARE NONBIOLOGICAL WAYS TO MAKE OXYGEN ON THE 418 00:29:52,989 --> 00:29:54,269 EARTH. ALL THIS TALK ABOUT 419 00:29:54,269 --> 00:29:58,830 BIOSIGNATURES AND THE FACT THAT WHEN WE DO LEARN ABOUT EXO 420 00:29:58,830 --> 00:30:01,820 PLANETS IT'S SO HARD TO LEARN ANYTHING, WE'RE GOING TO HAVE 421 00:30:01,820 --> 00:30:06,340 VERY LIMITED CLUES AND WE HAVE THIS CRITERION. 422 00:30:06,340 --> 00:30:08,989 HOW DO WE KNOW WE'RE NOT GOING TO FIND FALSE POSITIVES IF 423 00:30:08,989 --> 00:30:12,509 OXYGEN IS THE KEY TO FINDING LIFE AND THERE ARE WAYS TO MAKE 424 00:30:12,509 --> 00:30:17,629 OXYGEN THAT DON'T NEED LIFE AND ARE THERE OTHER KINDS OF FALSE 425 00:30:17,629 --> 00:30:21,179 POSITIVES AND DO YOU WORRY ABOUT THAT AND HOW DO WE GUARD AGAINST 426 00:30:21,179 --> 00:30:24,289 THAT? >> I CAN TAKE THIS ONE. 427 00:30:24,289 --> 00:30:27,839 WE ACTUALLY JUST HAD A PAPER ACCEPTED. 428 00:30:27,839 --> 00:30:33,269 I TALKED EARLIER ABOUT HOW WOULD WE LOOK FOR LIFE ON A PLANET 429 00:30:33,269 --> 00:30:38,919 THAT DIDN'T HAVE THE SAME BIOSIGNATURES AS MODERN DAY 430 00:30:38,919 --> 00:30:46,019 EARTH. TO ANSWER THAT, I LITERALLY DO 431 00:30:46,019 --> 00:30:49,080 NOT KNOW HOW WE WOULD HAVE STARTED TO ANSWER THAT QUESTION 432 00:30:49,080 --> 00:30:52,930 IF WE DIDN'T HAVE SOME PICTURE LIKE THIS OF WHAT THE EARLY 433 00:30:52,930 --> 00:30:55,210 EARTH LOOKED LIKE. THESE QUESTIONS OF WHY DID 434 00:30:55,210 --> 00:30:58,969 OXYGEN RISE TO BEGIN WITH LED A LOT OF SCIENTISTS INCLUDING SOME 435 00:30:58,969 --> 00:31:02,089 OF THE PEOPLE HERE IN THE ROOM TO DO A LOT OF WORK FIGURING OUT 436 00:31:02,089 --> 00:31:09,349 HOW TO VERY FINELY BALANCE REOX ON A PLANET TO CAUSE A PLANET TO 437 00:31:09,349 --> 00:31:11,509 BE MORE OXIDIZED AND LESS OXIDIZED. 438 00:31:11,509 --> 00:31:16,450 WHEN YOU ADD ALL THOSE UP AND YOU KNOW WHICH PARTS BIOLOGY 439 00:31:16,450 --> 00:31:20,109 CONTRIBUTES TO, YOU CAN TAKE A MODEL WITH ALL THAT STUFF IN AND 440 00:31:20,109 --> 00:31:22,669 PLUNK THE BIOLOGY OUT AND THEN YOU HAVE A MODEL FOR A 441 00:31:22,669 --> 00:31:26,539 NONBIOLOGICAL PLANET. I KNOW, IT'S HARD, RIGHT? 442 00:31:26,539 --> 00:31:28,789 >> RIGHT. SO THE CONVERSE SIDE OF THAT IS 443 00:31:28,789 --> 00:31:32,960 THE MODEL THAT BUILDS ON EARTH AND MOST OF US AGREE THAT WE HAD 444 00:31:32,960 --> 00:31:35,999 ECOSYSTEMS 3.5 BILLION YEARS AGO. 445 00:31:35,999 --> 00:31:39,210 OUR OLDEST ROCKS ARE 4 BILLION YEARS OLD AND IT'S ENTIRELY 446 00:31:39,210 --> 00:31:45,539 POSSIBLE THAT A LARGE PART OF WHAT WE UNDERSTAND IS INFLUENCED 447 00:31:45,539 --> 00:31:49,679 BY\hBIOLOGY. >> OUR MODELS ARE BUILD ON A 448 00:31:49,679 --> 00:31:51,429 WORLD IN WHICH THERE WAS BIOLOGY. 449 00:31:51,429 --> 00:31:55,299 WE ASSUME THAT WE KNOW THE THINGS THAT WERE CONTRIBUTING 450 00:31:55,299 --> 00:32:00,219 WELL ENOUGH TO TAKE THEM BACK OUT OF THE MODELS. 451 00:32:00,219 --> 00:32:04,359 THERE ARE FALSE POSITIVES BUT THE WAY YOU MEASURE OR ACCOUNT 452 00:32:04,359 --> 00:32:06,379 FOR THEM, DISCRIMINATE BETWEEN THE FALSE POSITIVES AND THE TRUE 453 00:32:06,379 --> 00:32:09,409 POSITIVES IS LOOK FOR SOMETHING OTHER THAN OXYGEN. 454 00:32:09,409 --> 00:32:12,319 THIS IS WHERE METHANE BECOMES IMPORTANT. 455 00:32:12,319 --> 00:32:15,139 >> IT COMES DOWN TO THE SCIENTIFIC PROCESS AS WELL. 456 00:32:15,139 --> 00:32:20,729 AS SOON AS YOU FIND SOMETHING THAT YOU THINK MIGHT BE A 457 00:32:20,729 --> 00:32:25,509 BIOSIGNATURE, THERE IS ALWAYS THE QUESTIONS. 458 00:32:25,509 --> 00:32:29,619 WE HAVE A LOT OF ARGUMENTS IN THE COMMUNITY ABOUT WHAT 459 00:32:29,619 --> 00:32:32,480 DIFFERENT THINGS MEAN, BUT THAT'S A VERY PRODUCTIVE WAY. 460 00:32:32,480 --> 00:32:38,790 YOU GO FROM A POSITIVE DETECTION TO MAYBE SOME DAY SOMETHING THAT 461 00:32:38,790 --> 00:32:43,039 MOST PEOPLE AGREE IS A DETECTION OF LIFE ELSEWHERE. 462 00:32:43,039 --> 00:32:47,669 >> THE EARLY EARTH IS UNBIASED. IT'S OUR GREAT NATURAL LAB. 463 00:32:47,669 --> 00:32:52,139 SO WE HAVE ROCKS AND WE HAVE FOSSILS IN MANY CASES AND WE CAN 464 00:32:52,139 --> 00:32:55,820 GO AND LOOK AT THESE AND WE CAN START FROM THE ASSUMPTION THAT 465 00:32:55,820 --> 00:33:00,659 THEY'RE NOT BIOLOGICAL FOSSILS. THE GEO CHEMISTRY IS OFTEN A 466 00:33:00,659 --> 00:33:03,580 CHALLENGE. WE KEEP TESTING THAT AND 467 00:33:03,580 --> 00:33:09,820 CONVINCE OURSELVES AND FROM THAT WE CAN START TO MODEL AN 468 00:33:09,820 --> 00:33:12,049 ATMOSPHERE. THAT'S ALL YEAR GOING TO GET FOR 469 00:33:12,049 --> 00:33:15,799 A LONG TIME FROM AN EXO PLANET. WE CAN THINK ABOUT HOW THAT 470 00:33:15,799 --> 00:33:17,539 CHANGES. >> THIS IS SOMETHING WE'VE ALSO 471 00:33:17,539 --> 00:33:20,950 LEARNED FROM MARS BY LOOKING AT PAST CLAIMS OF EVIDENCE FOR LIFE 472 00:33:20,950 --> 00:33:25,019 ON MARS, WHETHER IT WAS THE VIKING, ONCE THE COMMUNITY 473 00:33:25,019 --> 00:33:28,169 STARTED LOOKING AT IT AND RAISING THE STANDARD OF PROOF 474 00:33:28,169 --> 00:33:31,309 FOR THOSE CLAIMS, WE REALIZED THAT IT'S NOT JUST A SINGLE LINE 475 00:33:31,309 --> 00:33:33,820 OF EVIDENCE. IT'S THE MULTIPLE LINES OF 476 00:33:33,820 --> 00:33:37,299 EVIDENCE THAT YOU REALLY NEED. WE WOULD LIKE TO TAKE THAT TO 477 00:33:37,299 --> 00:33:41,570 EXO PLANET BUT EVERY SINGLE MEASUREMENT I WANT TO ADD TO 478 00:33:41,570 --> 00:33:44,229 THAT TELESCOPE, IT ADDS COST, IT ADDS COMPLEXITY. 479 00:33:44,229 --> 00:33:48,169 >> IT'S A GOOD THING WE HAVE THE EARLY EARTH. 480 00:33:48,169 --> 00:33:55,690 WITHOUT IT WE WOULD BE HOSED AS FAR AS IDEAS ABOUT FROM EXTRA 481 00:33:55,690 --> 00:33:59,599 TERRESTRIAL LIFE. PEOPLE SOMETIMES SAY THAT'S THE 482 00:33:59,599 --> 00:34:02,799 FIELD THAT DOESN'T HAVE DATA OR EVIDENCE. 483 00:34:02,799 --> 00:34:08,681 IN REALITY WE'VE GOT TONS OF DATA AND EVIDENCE AND OUR 484 00:34:08,681 --> 00:34:15,440 GROWING KNOWLEDGE OF PLANETS IN OUR SOLAR SYSTEM AND ELSEWHERE. 485 00:34:15,440 --> 00:34:19,510 HERE'S A QUESTION FOR YOU GUYS. IS THERE A DANGER IN BEING TOO 486 00:34:19,510 --> 00:34:22,580 EARTH CENTERED IN OUR THINKING SINCE WE HAVE THIS ONE BIOSPHERE 487 00:34:22,580 --> 00:34:26,679 AND CLING TO IT TO EXTRAPOLATE ELSEWHERE. 488 00:34:26,679 --> 00:34:33,429 IS IT POSSIBLE THAT WE'RE WRONG THAT LIFE DOESN'T NEED 489 00:34:33,429 --> 00:34:37,549 BIOMOLECULES AND IT DOESN'T EVEN NEED TO BE CARBON BASED AND IF 490 00:34:37,549 --> 00:34:43,190 SO DO WE HAVE A PROSPECT FOR FINDING LIFE AND HOW DO WE EVEN 491 00:34:43,190 --> 00:34:46,070 THINK ABOUT THAT QUESTION? >> FIRST OF ALL, IT'S REALLY 492 00:34:46,070 --> 00:34:51,309 CLEAR FOR EXPLORATION IN OUR OWN SOLAR SYSTEM THAT WE ABSOLUTELY 493 00:34:51,309 --> 00:34:57,990 HAVE TO BE OPEN TO LIFE THAT'S NOT LIKE EARTH. 494 00:34:57,990 --> 00:35:01,230 THAT'S BECAUSE WE CAN LOOK THROUGH THE SOLAR SYSTEM AND WE 495 00:35:01,230 --> 00:35:05,780 CAN CERTAINLY SEE PLACES OF INTEREST THAT ARE WORTH 496 00:35:05,780 --> 00:35:08,700 EXPLORING. CERTAINLY THE ONES MENTIONED, 497 00:35:08,700 --> 00:35:13,390 EUROPA, TITAN, BOTH HAVE PARALLELS TO EARTH AND DIFFERENT 498 00:35:13,390 --> 00:35:21,799 FROM EARTH. THE 499 00:35:21,799 --> 00:35:26,400 SERIES IS OUTGASSING WATER TO THE SOLAR SYSTEM. 500 00:35:26,400 --> 00:35:30,440 AND OF COURSE MARS. SO WE HAVE A NUMBER OF TARGETS 501 00:35:30,440 --> 00:35:36,250 AND ALL OF THOSE ARE GOING TO REQUIRE TO SOME DEGREE THINKING 502 00:35:36,250 --> 00:35:39,790 OUTSIDE THE EARTH CENTRIC BOX. I THINK WE'RE ALL COMFORTABLE 503 00:35:39,790 --> 00:35:43,270 WITH THAT FROM TRYING TO FIGURE OUT HOW A BIOSPHERE COULD 504 00:35:43,270 --> 00:35:46,750 OPERATE, BUT IT'S CHALLENGING WHEN YOU START TO THINK ABOUT 505 00:35:46,750 --> 00:35:50,170 THE BURDEN OF PROOF OF DETECTING LIFE AND TRYING TO AVOID FALSE 506 00:35:50,170 --> 00:35:52,589 POSITIVES. ON EARTH WE HAVE THE BURDEN OF 507 00:35:52,589 --> 00:35:56,029 PROOF OF TRYING TO FIGURE OUT IF LIFE WASN'T THERE BECAUSE LIFE 508 00:35:56,029 --> 00:35:58,690 HAS BEEN SO PERVASIVE FOR BILLIONS OF YEARS AND NOW WE 509 00:35:58,690 --> 00:36:02,339 HAVE THE CHALLENGE OF HAVING TO EXPLORE WHEN THE PRESUMPTION HAS 510 00:36:02,339 --> 00:36:05,910 TO BE NO HYPOTHESIS THAT THIS ISN'T LIFE. 511 00:36:05,910 --> 00:36:08,470 >> ONE OF THE AMAZING THINGS ABOUT THE EXO PLANET REVOLUTION 512 00:36:08,470 --> 00:36:14,170 IS IT HAS PROVIDED US WITH CREATIVE IDEAS. 513 00:36:14,170 --> 00:36:17,260 SO YOU HEAR ABOUT THESE PLANETS AROUND OTHER STARS THAT LOOK 514 00:36:17,260 --> 00:36:20,029 DIFFERENT THAN EARTH. AS A SCIENTIST THAT'S SUPER 515 00:36:20,029 --> 00:36:22,460 EXCITING. YOU CAN SAY, OKAY, NOW I HAVE 516 00:36:22,460 --> 00:36:25,349 SOMETHING TO WORK WITH HERE. WHAT MIGHT LIFE LOOK LIKE ON A 517 00:36:25,349 --> 00:36:30,280 PLANET THE SIZE OF SATURN OR A PLANET THAT'S MUCH, MUCH CLOSER 518 00:36:30,280 --> 00:36:34,150 TO ITS STARS. IN A WAY I THINK THAT'S HELPED 519 00:36:34,150 --> 00:36:37,500 US MOVE AWAY FROM AN EARTH CENTRIC VIEW BY PROVIDING US 520 00:36:37,500 --> 00:36:40,690 WITH OPPORTUNITIES TO EXPLORE OTHER WAYS THAT LIFE COULD 521 00:36:40,690 --> 00:36:45,010 EVOLVE ON PLANETS THAT HAVE NO SIMILARITY OR VERY LITTLE 522 00:36:45,010 --> 00:36:49,349 SIMILARITY TO EARTH. >> IT'S SHOCKED OUR MODELS OF 523 00:36:49,349 --> 00:36:53,559 HOW PLANETS EVOLVE OVER TIME IN A SYSTEM OF PLANETS. 524 00:36:53,559 --> 00:36:58,420 WE HAVEN'T MADE THE BIOLOGICAL AND CHEMICAL MEASUREMENTS YET. 525 00:36:58,420 --> 00:37:04,819 I CAN'T WAIT TO BE SCRATCHING MY HEAD OVER THOSE DATA AND SAY HOW 526 00:37:04,819 --> 00:37:10,690 DID THAT HAPPEN. THAT'S THE MOMENT I'M WAITING 527 00:37:10,690 --> 00:37:12,500 ON. >> IT'S GOING TO BE AN EXCITING 528 00:37:12,500 --> 00:37:16,670 NEXT DECADE OR TWO AS WE START TO LEARN ABOUT THESE EXOPLANETS 529 00:37:16,670 --> 00:37:19,740 AND EXPLORE THE SOLAR SYSTEM FURTHER. 530 00:37:19,740 --> 00:37:26,260 I THINK AT THIS POINT WE WANT TO GET YOUR OPINIONS AND YOUR 531 00:37:26,260 --> 00:37:28,799 QUESTIONS. WE COULD KEEP DISCUSSING AMONGST 532 00:37:28,799 --> 00:37:31,819 OURSELVES FOR A LONG TIME AND CLEARLY GO ON FOR HOURS. 533 00:37:31,819 --> 00:37:35,019 BUT AT THIS POINT I THINK IT WOULD BE GREAT TO SEE IF THERE 534 00:37:35,019 --> 00:37:38,289 ARE ANY QUESTIONS FROM THE AUDIENCE AND ONLINE. 535 00:37:38,289 --> 00:37:41,390 SO I'M GOING TO TURN IT OVER TO LINDSAY NOW WHO WILL RUN THE 536 00:37:41,390 --> 00:37:43,569 QUESTION AND ANSWER PORTION. >> THANKS, DAVID. 537 00:37:43,569 --> 00:37:46,069 I SEE WE HAVE A FEW QUESTIONS HERE IN THE AUDIENCE. 538 00:37:46,069 --> 00:37:49,819 WE'LL GET TO THOSE IN A MOMENT. I'D LIKE TO REMIND THOSE OF YOU 539 00:37:49,819 --> 00:37:54,490 WATCHING AND THOSE FOLLOWING US ON SOCIAL MEDIA TO USE\h@ASKNASA. 540 00:37:54,490 --> 00:37:58,900 WE'LL BE LOOKING FOR QUESTIONS FROM YOU GUYS AS WELL. 541 00:37:58,900 --> 00:38:03,589 >> THAT WAS GREAT. I'M GOING TO OPERATE UNDER THE 542 00:38:03,589 --> 00:38:06,539 OPTIMISTIC PHILOSOPHY THAT WE WILL MAKE THIS DISCOVERY AT 543 00:38:06,539 --> 00:38:09,269 LEAST SOME TIME IN MY LIFETIME HOPEFULLY. 544 00:38:09,269 --> 00:38:13,440 WHEN WE MAKE THIS DISCOVERY AND WE DECIDE THAT THERE'S ENOUGH 545 00:38:13,440 --> 00:38:16,170 EVIDENCE TO PROVE THE BIOSIGNATURES TELL US THERE'S 546 00:38:16,170 --> 00:38:20,560 ENOUGH EVIDENCE TO PROVE LIFE ON AN EXO PLANET. 547 00:38:20,560 --> 00:38:26,450 BESIDES OBVIOUSLY FURTHER SCRUTINY OF THAT DATA AND OF 548 00:38:26,450 --> 00:38:28,910 COURSE I WOULD EXPECT THAT AND HOPE THAT THERE ARE PEOPLE WHO 549 00:38:28,910 --> 00:38:36,529 DISAGREE, BUT WHAT COMES NEXT? >> GREAT QUESTION. 550 00:38:36,529 --> 00:38:40,160 CHANCES ARE THAT DISCOVERY IS NOT GOING TO COME JUST IN A 551 00:38:40,160 --> 00:38:47,480 MOMENT BECAUSE IT'S OFTEN A GRAD WALL PROCESS WHERE YOU DO MORE 552 00:38:47,480 --> 00:38:50,670 OBSERVATION. SO IT MIGHT NOT BE AN AHA BUT AN 553 00:38:50,670 --> 00:38:53,740 EXTENDED LET'S PAY MORE ATTENTION TO THIS ONE AND SORT 554 00:38:53,740 --> 00:38:56,079 OF A GRADUAL DAWNING OF APPRECIATION. 555 00:38:56,079 --> 00:39:01,450 WHAT COMES NEXT IS VERY TRICKY. DO ANY OF YOU HAVE THOUGHTS ON 556 00:39:01,450 --> 00:39:02,910 THAT? WHAT'S THE NEXT STEP? 557 00:39:02,910 --> 00:39:06,010 >> CELEBRATION. >> FIRST WE'RE GOING TO 558 00:39:06,010 --> 00:39:10,950 CELEBRATE, AT LEAST FOR A NIGHT. BUT THEN WE'RE GOING TO HAVE ALL 559 00:39:10,950 --> 00:39:14,130 KINDS OF QUESTIONS ABOUT WHAT HAS HAPPENED TO THAT PLANET OVER 560 00:39:14,130 --> 00:39:16,420 TIME. DOES THAT PLANET HAS SEASONS AND 561 00:39:16,420 --> 00:39:20,250 IF IT HAS SEASONS IS THE LIFE RESPONDING TO THE SEASONAL 562 00:39:20,250 --> 00:39:23,790 CYCLES IN THAT PLANET'S ORBIT. WHAT IS HAPPENING OVER THE 563 00:39:23,790 --> 00:39:25,970 DECADES. IS THAT PLANET EVOLVING OR THE 564 00:39:25,970 --> 00:39:28,530 SPHERE OF THAT PLANET EVOLVING. WHAT IS HAPPENING TO THE CARBON 565 00:39:28,530 --> 00:39:31,579 DIOXIDE SIGNAL. THINGS LIKE THAT ARE WHAT WE 566 00:39:31,579 --> 00:39:38,790 WANT TO LOOK AT. ALL WE'RE GOING TO GET AT FIRST 567 00:39:38,790 --> 00:39:45,360 ARE SPECTRAL SIGNALS. IF WE REALLY WANT TO KNOW MORE 568 00:39:45,360 --> 00:39:48,869 ABOUT THAT PLANET I'VE HEARD IDEAS OF PUTTING A FLEET OF 569 00:39:48,869 --> 00:39:57,430 TELESCOPES THAT CAN GET YOU A MAP OF THE PLANET AND IF THE 570 00:39:57,430 --> 00:39:59,589 FORESTS ARE BIG ENOUGH WHERE THEY CAN HAVE A COLOR SIGNATURE 571 00:39:59,589 --> 00:40:02,680 AND YOU CAN START TO LOOK FOR THAT SORT OF THING, TOO. 572 00:40:02,680 --> 00:40:10,099 >> SOMEONE IS GOING TO WANT TO SEND A FLY-BY EVENTUALLY BUT I'M 573 00:40:10,099 --> 00:40:14,359 NOT THAT PATIENT. >> ANOTHER POINT IS THAT WE KEEP 574 00:40:14,359 --> 00:40:17,500 TALKING ABOUT THAT ONE. REALLY WE'RE TALKING ABOUT A 575 00:40:17,500 --> 00:40:20,319 POPULATION. WE'LL CELEBRATE EVERY SINGLE 576 00:40:20,319 --> 00:40:27,499 TIME THIS HAPPENS, BUT LET'S HOPE IT'S DOZENS OF DISCOVERIES. 577 00:40:27,499 --> 00:40:30,700 >> IT'S MY VIEW THAT ONCE THE EXO PLANET REVOLUTION SINKS IN 578 00:40:30,700 --> 00:40:33,410 AND THE PEOPLE GET ABOUT WHAT WE'RE DISCOVERING THAT THERE 579 00:40:33,410 --> 00:40:36,819 WILL BE PUBLIC SORT TO FUND THE KIND OF INSTRUMENTS THAT SHAWN 580 00:40:36,819 --> 00:40:45,000 IS TRYING TO BUILD TO LEARN MORE ABOUT THESE PLANETS AND THEN I 581 00:40:45,000 --> 00:40:48,510 THINK THERE WILL BE PUBLIC SORT TO BUILD THAT NEXT GENERATION OF 582 00:40:48,510 --> 00:40:52,750 INSTRUMENTS WHERE WE CAN REALLY LEARN MORE ABOUT IT BY SOME 583 00:40:52,750 --> 00:40:56,489 FUTURISTIC OBSERVATIONAL PLATFORMS AND CONCEPTS. 584 00:40:56,489 --> 00:41:01,990 >> I THINK ONE OF THE KEY THINGS IS WHEN YOU MAKE A DISCOVERY, 585 00:41:01,990 --> 00:41:04,510 THE QUESTIONS BLOSSOM OUT FROM THAT. 586 00:41:04,510 --> 00:41:09,039 IT'S HARD TO PREDICT NOW WHAT WOULD BE NEXT, BUT EVERY MAJOR 587 00:41:09,039 --> 00:41:13,750 SCIENTIFIC DISCOVERY HAS LED TO MANY MORE QUESTIONS AND DETAILED 588 00:41:13,750 --> 00:41:21,119 OBSERVATIONS. >> YOU'LL WANT TO PUT A ROVER ON 589 00:41:21,119 --> 00:41:24,630 IT. >> THE ANALOGY IS EFFORTS TO 590 00:41:24,630 --> 00:41:28,799 LOOK AT MICROBIOLOGY IN THE SUBSET OF THE EARTH. 591 00:41:28,799 --> 00:41:32,480 YOU GET AWAY FROM THE SURFACE OF THE EARTH, WE LOOK AT HOW IT 592 00:41:32,480 --> 00:41:39,820 WORKS, WE GOT IT, THERE'S ORGANIC MATTER. 593 00:41:39,820 --> 00:41:42,519 WE HAVE THIS COMFORTABLE UNDERSTANDING OF HOW MICROBES 594 00:41:42,519 --> 00:41:45,819 WORK, AND NOW ALL OF A SUDDEN WE START TO LOOK AT MICROBES THAT 595 00:41:45,819 --> 00:41:51,230 ARE STEMMING DOWN, GOOD EVIDENCE TO A KILOMETER AND ACTUALLY 596 00:41:51,230 --> 00:41:54,500 SEVERAL KILOMETERS WHEN YOU CONSIDER GOLD MINES. 597 00:41:54,500 --> 00:41:58,670 SO WE HAVE A BIOSPHERE THAT'S SEVERAL KILOMETERS INTO THE 598 00:41:58,670 --> 00:42:01,770 EARTH AND THE RULES ARE VERY DIFFERENT IN TERMS OF HOW THE 599 00:42:01,770 --> 00:42:04,640 MICROBES OPERATE, HOW MUCH ENERGY THEY NEED TO ACTUALLY 600 00:42:04,640 --> 00:42:07,559 DUPLICATE. IT'S REALLY WILD. 601 00:42:07,559 --> 00:42:10,700 SO THAT'S A GOOD ANALOGY OF WHEN YOU HAVE A VERY, VERY DIFFERENT 602 00:42:10,700 --> 00:42:17,130 BIOSPHERE, YOU START TO LEARN RULES THAT YOU DIDN'T REALIZE\h-- 603 00:42:17,130 --> 00:42:18,731 YOU LEARN QUESTIONS YOU DIDN'T KNOW YOU HAD. 604 00:42:18,731 --> 00:42:23,770 >> I'VE HEARD IT SAID THIS WEEK THAT THE ANCIENT EARTH IS AN EXO 605 00:42:23,770 --> 00:42:27,079 PLANET. YOU'RE SAYING THE DEEP EARTH IS 606 00:42:27,079 --> 00:42:29,839 AN EXO PLANET IN SOME SENSE. IS THERE ANOTHER QUESTION? 607 00:42:29,839 --> 00:42:34,299 >> IF YOU HAD THIS DREAM TELESCOPE AND YOU COULD TURN IT 608 00:42:34,299 --> 00:42:40,430 AROUND AND POINT IT AT EARTH, HOW FAR BACK COULD YOU GO IN 609 00:42:40,430 --> 00:42:44,060 EARTH'S HISTORY AND SAY WE'VE GOT LIFE THERE AND IF YOU WENT 610 00:42:44,060 --> 00:42:50,980 BACK FARTHER, COULD YOU SAY NOT YET BUT IF WE WAIT A BILLION 611 00:42:50,980 --> 00:42:54,430 YEARS, MAYBE. >> SO COULD WE SEE THE POTENTIAL 612 00:42:54,430 --> 00:43:00,009 FOR LIFE ON A PLANET THAT DOESN'T HAVE LIFE? 613 00:43:00,009 --> 00:43:03,599 >> YES. WHAT KIND OF A SHOT IN THE DARK 614 00:43:03,599 --> 00:43:06,150 ARE WE LOOKING AT HERE. EVEN IF WE WERE LOOKING AT EARTH 615 00:43:06,150 --> 00:43:11,759 WHERE WE KNOW IT'S FULL OF LIFE, HOW FAR BACK IN HISTORY COULD WE 616 00:43:11,759 --> 00:43:15,430 GO ON THIS PLANET AND SEE IT EVEN WITH YOUR DREAM TELESCOPE? 617 00:43:15,430 --> 00:43:26,630 >> I'LL START WITH AN OXYGEN CENTRIC RESPONSE. 618 00:43:26,630 --> 00:43:30,140 IF WE LOOK AT EARTH'S HISTORY, AGAIN THERE ARE MANY PEOPLE THAT 619 00:43:30,140 --> 00:43:32,789 THINK THAT THE PRODUCTION OF OXYGEN MAY HAVE GONE BACK 3 620 00:43:32,789 --> 00:43:36,349 BILLION YEARS AGO. BUT THERE ARE SOME VERY 621 00:43:36,349 --> 00:43:39,119 SOPHISTICATED ANALYTICAL TECHNIQUES THAT WE CAN PULL OUT 622 00:43:39,119 --> 00:43:42,920 OF THE ROCK RECORD THAT SUGGEST THAT IT MAY NOT HAVE ACCUMULATED 623 00:43:42,920 --> 00:43:48,210 IN APPRECIABLE AMOUNTS TO 2.3 BILLION YEARS AGO. 624 00:43:48,210 --> 00:43:51,529 IF YOU JUST WANT TO TAKE THE PERSPECTIVE OF OXYGEN, PERHAPS 625 00:43:51,529 --> 00:43:55,849 YOU COULD GO BACK 2.3 BILLION YEARS AGO AND POINT YOUR 626 00:43:55,849 --> 00:43:58,319 TELESCOPE AND SEE THAT. MAYBE YOU WANT TO SPEAK TO OTHER 627 00:43:58,319 --> 00:44:01,920 GASES. >> OTHER GASES WOULD BE POSSIBLE 628 00:44:01,920 --> 00:44:06,869 BUT THE OTHER THING THAT YOU ALLUDED TO BRIEFLY, IT'S 629 00:44:06,869 --> 00:44:10,049 POSSIBLE THAT FOR THIS BORING BILLION WE TALKED ABOUT, THAT 630 00:44:10,049 --> 00:44:13,049 OXYGEN LEVELS WERE A LITTLE LOWER, METHANE WAS A LITTLE 631 00:44:13,049 --> 00:44:16,269 HIGHER AND IT MAY BE THE COMBINATION OF THOSE TWO IS 632 00:44:16,269 --> 00:44:19,710 EASIER TO DETECT FOR A BILLION OR 2 BILLION YEARS OF EARTH'S 633 00:44:19,710 --> 00:44:23,750 HISTORY THAN THOSE GASES ARE TO DETECT NOW. 634 00:44:23,750 --> 00:44:30,599 THE BIOSPHERE MIGHT HAVE BEEN MORE DETECTABLE IN THE HISTORY 635 00:44:30,599 --> 00:44:34,980 THAN IT IS TODAY. >> IF YOU ACCEPT THAT METHANE IS 636 00:44:34,980 --> 00:44:39,550 A GOOD BIOSIGNATURE, THERE'S A POPULAR NOTION THAT THE EARLY 637 00:44:39,550 --> 00:44:42,730 SUN WAS FAINTER THAN IT IS TODAY. 638 00:44:42,730 --> 00:44:46,430 WE'RE STRESSED WITH THIS IDEA OF HOW YOU MAINTAIN LIQUID WATER ON 639 00:44:46,430 --> 00:44:50,490 THE EARTH'S SURFACE GOING BACK MORE THAN 4 BILLION YEARS. 640 00:44:50,490 --> 00:44:53,150 MOST PEOPLE ACKNOWLEDGE THAT THAT'S PROBABLY SOME COMBINATION 641 00:44:53,150 --> 00:45:00,380 OF GREENHOUSE GASES. SO CARBON DIOXIDE\h-- 642 00:45:00,380 --> 00:45:09,650 >> THE PALE ORANGE DOT. >> A PART OF THAT ANSWER, TOO, 643 00:45:09,650 --> 00:45:14,790 IRRESPECTIVE OF YOUR TECHNOLOGY, IF YOU LOOKED AT THE ANCIENT 644 00:45:14,790 --> 00:45:18,289 EARTH, WHEN WOULD YOU SEE THE BIOSPHERE BEING AS COMPLETELY 645 00:45:18,289 --> 00:45:24,349 DOMINANT AS IT IS TODAY AND REALLY GIVEN HOW DIFFICULT 646 00:45:24,349 --> 00:45:30,460 HORROR HOW RARE ROCKS BECOME THAT ARE THAT OLD, IT'S REALLY 647 00:45:30,460 --> 00:45:35,009 KIND OF AMAZING THAT YOU FIND EVIDENCE FOR LIFE IN ALL OF THE 648 00:45:35,009 --> 00:45:37,560 BEST PRESERVED ROCKS THAT ARE QUITE OLD. 649 00:45:37,560 --> 00:45:41,720 IF WE HAVE THE TECHNOLOGY TO SEE LIFE BECAUSE OF THE METHANE IT 650 00:45:41,720 --> 00:45:49,720 PRODUCES EVEN IN THE ABSENCE OF ANOXIC SPHERE, IT'S A LARGE 651 00:45:49,720 --> 00:45:54,980 PORTION OF THE EARTH'S HISTORY THAT MICROBES MAKE A BIG EFFECT 652 00:45:54,980 --> 00:45:58,740 ON THE PLANET. THE EARLIEST PERIOD MIGHT BE 653 00:45:58,740 --> 00:46:03,569 HARD. >> HOW LONG HAS EARTH BEEN A 654 00:46:03,569 --> 00:46:09,339 PALE BLUE DOT, DID YOU FEEL? >> ABOUT 4.2, 4.3. 655 00:46:09,339 --> 00:46:15,069 >> SOME PEOPLE ARE SAYING THE PRESSURE WASN'T AS HIGH. 656 00:46:15,069 --> 00:46:19,289 I WOULD SAY AT LEAST TWO AND A HALF YEARS, MAYBE UP TO FOUR\h-- 657 00:46:19,289 --> 00:46:24,940 I'M SORRY, BILLION YEARS. WITH MAYBE SOME SPORADIC ORANGE 658 00:46:24,940 --> 00:46:28,990 IN THERE AND SOME SPORADIC WHITE. 659 00:46:28,990 --> 00:46:34,099 >> CARL SEGUIN WAS RIGHT AT LEAST FOR THE LAST COUPLE 660 00:46:34,099 --> 00:46:37,280 BILLION YEARS. >> RIGHT. 661 00:46:37,280 --> 00:46:40,760 >> I THINK WE HAVE ANOTHER QUESTION IN THE AUDIENCE. 662 00:46:40,760 --> 00:46:43,339 >> IT'S CLEAR THAT THE EARTH IS THE GOLD STANDARD FOR 663 00:46:43,339 --> 00:46:45,880 HABITABILITY FOR OBVIOUS REASONS. 664 00:46:45,880 --> 00:46:49,180 IF WE'RE INTERESTED IN THE HABITABILITY OF EXOPLANETS IS 665 00:46:49,180 --> 00:46:57,450 THIS FAIR. KNOWING WHAT YOU KNOW ABOUT THE 666 00:46:57,450 --> 00:47:00,710 CURRENT EARTH AND THE EARLY EARTH, WOULD IT BE DIFFERENT 667 00:47:00,710 --> 00:47:07,880 THAN WE SEE IT IN THE PAST. >> HOW WOULD YOU MAKE A MORE 668 00:47:07,880 --> 00:47:13,849 HABIT PLANET? >> THIS REALLY GETS AT HOW YOU 669 00:47:13,849 --> 00:47:18,160 CAN ACTUALLY, TO ME, ASK THE SCIENTIFIC QUESTIONS. 670 00:47:18,160 --> 00:47:24,950 WE ONLY HAVE ONE EXAMPLE OF LIFE AND FOR THE COMPLEX LIFE WE NEED 671 00:47:24,950 --> 00:47:28,369 HIGH ENERGY SOURCE WHICH IS MOLECULAR OXYGEN. 672 00:47:28,369 --> 00:47:33,269 BUT FOR A LOT OF EARTH'S HISTORY, BEFORE 2.5 BILLION 673 00:47:33,269 --> 00:47:37,859 YEARS OR SO, WE HAD LIFE THAT WAS USING OTHER ENERGY SOURCES, 674 00:47:37,859 --> 00:47:43,470 AND SOME OF IT WAS SUNLIGHT THAT MAY HAVE PRODUCED OXYGEN BUT 675 00:47:43,470 --> 00:47:46,029 THERE ARE OTHER WAYS TO COLLECT THAT. 676 00:47:46,029 --> 00:47:50,269 I THINK IT REALLY DEPENDS ON WHAT TYPE OF BIOSPHERE YOU 677 00:47:50,269 --> 00:47:56,859 CONSIDER BEING MOST SUCCESSFUL. IF YOU NEED LARGE ORGANISMS, WE 678 00:47:56,859 --> 00:48:02,569 NEED A VERY INTENSE ENERGY SOURCE AND THAT FOR PLANTS IS 679 00:48:02,569 --> 00:48:09,630 LIGHT BUT FOR US WE NEED THIS CHEMICAL. 680 00:48:09,630 --> 00:48:14,859 OUR CURRENT EARTH CREATES A REALLY GOOD MODEL WE CAN USE. 681 00:48:14,859 --> 00:48:19,720 WHEN YOU START TALKING ABOUT OTHER THINGS, YOU HAVE TO START 682 00:48:19,720 --> 00:48:23,319 MAKING SO MANY ASSUMPTIONS THAT IT'S REALLY HARD TO SAY ANYTHING 683 00:48:23,319 --> 00:48:26,270 WOULD BE BETTER. >> THAT'S RIGHT. 684 00:48:26,270 --> 00:48:28,160 THE EARTH IS AN EXTRAORDINARY PLACE. 685 00:48:28,160 --> 00:48:31,329 OUR DISTANCE FROM THE SUN OR THE COMBINATION OF GAS IS SOMETHING 686 00:48:31,329 --> 00:48:35,410 THAT WE HAVEN'T MENTIONED IS THE FACT THAT OUR HISTORY WE WERE 687 00:48:35,410 --> 00:48:38,349 DEALT A GOOD HAND IN TERMS OF RADIOACTIVE MATERIALS AND THE 688 00:48:38,349 --> 00:48:41,509 HEAT THAT WAS GENERATED WITHIN THE EARTH WHICH ULTIMATELY LED 689 00:48:41,509 --> 00:48:44,259 TO PLATE TECTONICS, THE MOVEMENT OF PLATES ON THE EARTH'S 690 00:48:44,259 --> 00:48:47,720 SURFACE. THAT'S A CENTRAL THING AND 691 00:48:47,720 --> 00:48:56,990 PERHAPS TIPPING POINT. HARD TO MAINTAIN A PHOSPHOROUS 692 00:48:56,990 --> 00:49:01,970 BALANCE WHICH IS CRITICAL TO LIFE AS WE KNOW IT ON EARTH. 693 00:49:01,970 --> 00:49:04,349 IT'S A WONDERFUL COMBINATION. THE QUESTION IS WHETHER THAT 694 00:49:04,349 --> 00:49:06,869 SAME COMBINATION HAS TO PLAY OUT EVERYWHERE. 695 00:49:06,869 --> 00:49:11,760 >> HERE'S A FOR INSTANCE JUST TO FOCUS ON YOUR QUESTION. 696 00:49:11,760 --> 00:49:14,030 THERE'S A QUESTION THAT CAME UP EARLIER WHY IT TOOK SO LONG FOR 697 00:49:14,030 --> 00:49:25,039 COMPLEX RISE TO TAKE PLACE ON EARTH. 698 00:49:25,039 --> 00:49:28,029 THERE IS THIS IDEA THAT IT TOOK A WHILE FOR OXYGEN TO BUILD UP 699 00:49:28,029 --> 00:49:32,809 AND WE NEEDED TO ENERGETIC SOURCE TO POWER ANIMAL LIFE. 700 00:49:32,809 --> 00:49:36,150 COULD YOU IMAGINE A PLANET SOMEWHAT LIKE EARTH BUT WITH 701 00:49:36,150 --> 00:49:41,049 DIFFERENT CHEMISTRY SO THAT IT DIDN'T TAKE AS LONG FOR OXYGEN 702 00:49:41,049 --> 00:49:43,900 TO BUILD UP SO THAT THERE WASN'T\h-- PEOPLE TALK ABOUT ALL 703 00:49:43,900 --> 00:49:46,710 THIS IRON THAT THE OXYGEN HAD TO REACT TO. 704 00:49:46,710 --> 00:49:49,740 WHAT IF\h-- I DON'T WANT TO USE THE WORD REDUCING, A LESS 705 00:49:49,740 --> 00:49:52,529 REDUCING PLANET. WHAT IF THERE WAS LESS STUFF 706 00:49:52,529 --> 00:49:56,029 THAT THE OXYGEN HAD TO REACT WITH BEFORE IT COULD BUILD UP SO 707 00:49:56,029 --> 00:50:01,830 YOU HAD A PLANET CHEMICALLY PRIMED FOR OXYGEN TO BUILD UP 708 00:50:01,830 --> 00:50:06,089 EARLIER. MIGHT GOTTEN AN EARLIER START TO 709 00:50:06,089 --> 00:50:09,390 COMPLEX LIFE AND BY NOW WE WOULD ALREADY BE INHABITING OTHER 710 00:50:09,390 --> 00:50:14,930 GALAXIES? >> WE'RE VERY GOOD AT FIGURING 711 00:50:14,930 --> 00:50:16,589 OUT WHAT WE MISSED. WE CERTAINLY MISSED PLATE 712 00:50:16,589 --> 00:50:24,339 TECTONICS. IF YOU DID THAT, THERE WOULD BE 713 00:50:24,339 --> 00:50:27,810 A LONGER TERM CONSEQUENCE BECAUSE YOU DO STILL CONTINUE TO 714 00:50:27,810 --> 00:50:30,880 LOSE HYDROGEN AND OXIDIZE OVER LONGER PERIODS OF TIME. 715 00:50:30,880 --> 00:50:34,900 IF YOU MOVE THAT EVENT UP, YOU ACTUALLY ON SOME LEVEL SHORTEN 716 00:50:34,900 --> 00:50:39,310 HABITABILITY SOME DAY IN THE FUTURE, NOT KNOWING EXACTLY WHEN 717 00:50:39,310 --> 00:50:42,289 THAT IS, WHICH BRINGS UP ANOTHER POINT. 718 00:50:42,289 --> 00:50:47,089 IF YOU WANT TO FIND AN OPTIMAL FOR LIFETIME, SMALLER STARS, BUT 719 00:50:47,089 --> 00:50:54,050 NOW WE'RE TALKING ABOUT SCIENCE FICTION AT THIS POINT. 720 00:50:54,050 --> 00:50:57,839 >> THIS TIES IN VERY WELL TO A QUESTION WE HAVE ON SOCIAL MEDIA 721 00:50:57,839 --> 00:51:01,549 WHICH IS IF WE FIND LIFE VERY UNLIKE OUR OWN, HOW WOULD WE BE 722 00:51:01,549 --> 00:51:07,900 ABLE TO TELL? >> THIS GETS AT HOW YOU ACTUALLY 723 00:51:07,900 --> 00:51:13,359 RECOGNIZE SOMETHING AS LIFE AND IT GETS BACK TO THE DEFINITION 724 00:51:13,359 --> 00:51:18,109 OF WHAT LIFE IS. WE USUALLY THINK OF IT AS HAVING 725 00:51:18,109 --> 00:51:26,910 A METABOLISM AND REPRODUCTION. WE COULD EASILY\h-- IT'S 726 00:51:26,910 --> 00:51:29,380 CONCEIVABLE TO ME THAT THERE COULD BE A LIFE THAT'S VERY 727 00:51:29,380 --> 00:51:33,170 DIFFERENT THAN THAT ON EARTH AND WE WOULDN'T RECOGNIZE IT BECAUSE 728 00:51:33,170 --> 00:51:37,700 WE DON'T HAVE THE RIGHT MODELS FOR IDENTIFYING THOSE 729 00:51:37,700 --> 00:51:39,920 CHARACTERISTICS. IN SOME SENSE WE COULD END UP 730 00:51:39,920 --> 00:51:44,619 WITH A FALSE NEGATIVE IF THE LIFE IS SO DIFFERENT IT DOESN'T 731 00:51:44,619 --> 00:51:48,180 ACTUALLY FIT WITH OUR MODEL FOR HOW WE DETECT LIFE. 732 00:51:48,180 --> 00:51:54,319 >> YOU AND SHAWN BOTH MENTIONED THE NOTION OF EQUILIBRIUM AND 733 00:51:54,319 --> 00:52:05,029 DISEQUILIBRIUM. SO WOULD YOU THINK IT WOULD BE 734 00:52:05,029 --> 00:52:08,779 REASONABLE TO SAY THAT ANY KIND OF LIFE WILL AT LEAST BE DOING 735 00:52:08,779 --> 00:52:12,210 SOMETHING CHEMICALLY, EATING SOMETHING, EXCRETING SOMETHING 736 00:52:12,210 --> 00:52:19,010 AND WILL LEAVE SOMETHING IN THE MIX OF GASES OR IS THAT TOO MUCH 737 00:52:19,010 --> 00:52:22,859 OF AN ASSUMPTION? >> BIOTIC PROCESSES CAN GIVE YOU 738 00:52:22,859 --> 00:52:33,420 A SIMILAR EQUILIBRIUM. IT'S ONE OF THOSE CRITICAL 739 00:52:33,420 --> 00:52:38,760 QUESTIONS THAT I THINK AS A SCIENTIST I WANT TO MODEL TO 740 00:52:38,760 --> 00:52:41,869 COMPARE AND TEST THINGS AGAINST, BUT I ALSO WANT TO KEEP IN MIND 741 00:52:41,869 --> 00:52:46,499 THAT MY MODELS ARE LIMITED AND RESTRICTED AND I DON'T KNOW ALL 742 00:52:46,499 --> 00:52:50,710 THESE OTHER THINGS. >> I WOULD FOLLOW THAT WE HAVE 743 00:52:50,710 --> 00:52:54,170 CHEMICAL PRINCIPLES AND WE HOPE THAT THOSE ARE UNIVERSAL 744 00:52:54,170 --> 00:52:58,599 THROUGHOUT THE UNIVERSE. SO THIS SENSE OF DISEQUILIBRIUM, 745 00:52:58,599 --> 00:53:05,069 LIFE IS ABOUT THE FLOW OF ELECTRONS. 746 00:53:05,069 --> 00:53:08,980 SO IF YOU HAVE A SENSE FOR THE CHEMISTRY ON THAT PLANET, YOU 747 00:53:08,980 --> 00:53:11,400 COULD START TO ENVISION REACTIONS THAT COULD LEAD TO 748 00:53:11,400 --> 00:53:14,529 THAT CHEMISTRY THAT COULD BE A SOURCE OF ENERGY. 749 00:53:14,529 --> 00:53:17,400 >> I THINK THAT'S WHY STUDYING THE EARLY EARTH IS SO IMPORTANT 750 00:53:17,400 --> 00:53:22,079 BECAUSE THAT WHAT WE'RE DOING ON OUR PLANET. 751 00:53:22,079 --> 00:53:24,890 WE KNOW LIFE EVOLVED AND WE CAN LOOK AT THE CHEMISTRY ON THE 752 00:53:24,890 --> 00:53:34,119 EARLY EARTH AND SEE HOW IT CHANGED OVER TIME. 753 00:53:34,119 --> 00:53:36,180 >> IF WE WANT TO LOOK FOR THE REALLY WEIRD STUFF, WE SHOULD 754 00:53:36,180 --> 00:53:39,059 START WITH THE WEIRD STUFF THAT WE HAVE DATA ON WHICH ARE THESE 755 00:53:39,059 --> 00:53:42,780 EARLY VERSIONS OF EARTH. BY LOOKING AT THOSE VERSIONS OF 756 00:53:42,780 --> 00:53:46,140 EARTH WE CAN DERIVE THESE PRINCIPLES AND TEST THEM AND 757 00:53:46,140 --> 00:53:49,230 HOPEFULLY COME UP WITH A FUNDAMENTAL THEORY OF BIOGEO 758 00:53:49,230 --> 00:53:53,230 CHEMISTRY. >> OR REQUIRE OBSERVATION OF 759 00:53:53,230 --> 00:53:57,630 THIS OTHER PLANET AND TRY TO UNDERSTAND ITS HISTORY BEFORE WE 760 00:53:57,630 --> 00:54:00,920 CAN DEFINITIVELY SAY IT WAS IN THIS EQUILIBRIUM. 761 00:54:00,920 --> 00:54:12,000 >> I LIKE THAT ANSWER. IT GOES BACK TO SOMETHING THAT 762 00:54:12,000 --> 00:54:15,619 DAWN SAID EARLIER WHERE WE WERE TALKING ABOUT THE EVIDENCE OF 763 00:54:15,619 --> 00:54:19,220 LIFE AT 3.5, THAT THE REASON THAT WE GET ALL COMFORTABLE WITH 764 00:54:19,220 --> 00:54:23,269 IT IS THAT WE SEE SO MANY COMPONENTS OF IT. 765 00:54:23,269 --> 00:54:25,609 THAT COULD BE TRUE OF AN EXO PLANET EVEN IF THE LIFE IS 766 00:54:25,609 --> 00:54:28,549 COMPLETELY DIFFERENT OF LIFE ON EARTH, THAT YOU MIGHT ACTUALLY 767 00:54:28,549 --> 00:54:32,470 SEE EVIDENCE OF AN ECOSYSTEM BEFORE YOU RECOGNIZED ANY LIFE 768 00:54:32,470 --> 00:54:35,420 FORM. >> IF YOU SAW THOSE GASES AND 769 00:54:35,420 --> 00:54:40,300 SAW THEM CHANGING ON SEASONAL TIME SCALES OR CALCULATE THEIR 770 00:54:40,300 --> 00:54:43,440 LIFE TIMES AND THEY'RE NOT DISAPPEARING FAST ENOUGH. 771 00:54:43,440 --> 00:54:48,670 >> WE THINK IT'S SEASONAL VARIATIONS IN CO 2 TODAY. 772 00:54:48,670 --> 00:54:58,920 >> AND A CO-VARIATIONS OF O2. >> THE SIGNS OF LIFE ON EARTH IS 773 00:54:58,920 --> 00:55:01,180 NOT SUBTLE. IF YOU WERE AN ALIEN AND YOU 774 00:55:01,180 --> 00:55:07,269 WERE LOOKING AT MARS YOU WOULD SAY SOME CO2 AND OTHER STUFF AND 775 00:55:07,269 --> 00:55:12,509 THEN YOU WOULD LOOK AT EARTH AND GO WHOA, WE GOT A LIVE ONE HERE 776 00:55:12,509 --> 00:55:19,989 AND IT MAY BE THAT THAT THE CHARACTERISTICS OF LIFE ON OTHER 777 00:55:19,989 --> 00:55:22,420 PLANETS. >> >> I THINK WE HAVE ONE MORE 778 00:55:22,420 --> 00:55:28,329 QUESTION FROM THE AUDIENCE. >> HOW MUCH OF OUR HISTORY HAVE 779 00:55:28,329 --> 00:55:31,589 WE LOST TO PLATE TECTONICS AND HOW WELL HAVE WE PUT THE STORY 780 00:55:31,589 --> 00:55:35,690 BACK TOGETHER AND ALSO HOW LUCKY ARE WE TO HAVE INDIRECT ACCESS 781 00:55:35,690 --> 00:55:48,980 TO THE ROCKS ON MARS? >> WE'VE LOST TOO MUCH TO PLATE 782 00:55:48,980 --> 00:55:51,299 TECTONICS. >> STUDYING OTHER PLANETS FILL 783 00:55:51,299 --> 00:55:54,109 SOME OF THAT GAP. OUR RECORD FOR THE FIRST HALF A 784 00:55:54,109 --> 00:55:57,869 BILLION YEARS IS REALLY SPARSE. WHEN I GOT STARTED THERE WAS 785 00:55:57,869 --> 00:56:01,130 NOTHING. NOW WE HAVE GRAINS AND EVEN 786 00:56:01,130 --> 00:56:04,490 ROCKS THAT GO BEYOND 4 BILLION YEARS. 787 00:56:04,490 --> 00:56:07,510 THE SEA FLOOR IS LOST CONSTANTLY BECAUSE OF PLATE TECTONICS 788 00:56:07,510 --> 00:56:09,380 THROUGH TIME. ONE OF THE CHALLENGES THAT WE'RE 789 00:56:09,380 --> 00:56:11,960 FACED IS WITH TRYING TO RECONSTRUCT AN OCEAN CHEMISTRY 790 00:56:11,960 --> 00:56:15,760 FOR WHICH THERE IS NO SEA FLOOR RECORDED. 791 00:56:15,760 --> 00:56:21,820 WE LOOK AT PLACES LIKE EARLY CONTINENTS AND OR THE MARGIN OF 792 00:56:21,820 --> 00:56:23,730 CONTINENTS THAT ARE STILL PRESERVED. 793 00:56:23,730 --> 00:56:27,569 THERE ARE RISK IN THAT BUT IT'S THE BEST THAT WE HAVE BECAUSE WE 794 00:56:27,569 --> 00:56:31,509 HAVE AN EARTH THAT'S CONSTANTLY RECYCLING. 795 00:56:31,509 --> 00:56:34,310 WE'VE LOST MUCH OF THE RECORD AND THE FURTHER YOU GO BACK, THE 796 00:56:34,310 --> 00:56:37,450 LESS THERE IS. >> HOW LUCKY ARE WE TO BE 797 00:56:37,450 --> 00:56:44,170 EXPLORING MARS? VERY LUCKY. 798 00:56:44,170 --> 00:56:48,789 >> IT'S REALLY GREAT TO BE ABLE TO LOOK AT THESE OLD ROCKS AND 799 00:56:48,789 --> 00:56:54,059 SO WHEN I FIRST GOT INTERESTED IN MARS, A LOT OF IT WAS WE HAVE 800 00:56:54,059 --> 00:56:58,269 A CHANCE TO LOOK AT THE EARLY STAGES OF A PLANET AND EARLY 801 00:56:58,269 --> 00:57:03,890 STAGES OF EARTH, BUT THEN WE ALSO HAVE THE ISSUE THAT IT IS A 802 00:57:03,890 --> 00:57:07,069 DIFFERENT PLANET AND IT CLEARLY HAS A VERY DIFFERENT 803 00:57:07,069 --> 00:57:11,240 EVOLUTIONARY HISTORY. SO YOU'RE IN THIS REALLY 804 00:57:11,240 --> 00:57:14,249 INTERESTING PLACE WHERE WE CAN LOOK AT THE ROCKS THAT THE 805 00:57:14,249 --> 00:57:22,509 CURIOSITY IS SEEING AND WE CAN FIND EVIDENCE THAT RIVERS FLOWED 806 00:57:22,509 --> 00:57:26,059 AND LOOK AT SOME OF THE MINERAL REACTIONS AND UNDERSTAND THE 807 00:57:26,059 --> 00:57:30,410 WATER/ROCK INTERACTIONS BUT WE DON'T KNOW ENOUGH YET TO TIE 808 00:57:30,410 --> 00:57:40,359 THAT BACK TO EARLY EARTH. BUT WITH THE INCREASED DATA AND 809 00:57:40,359 --> 00:57:45,910 THE COMBINATION OF THE CHEMICAL AND IMAGE DATA FROM ORBIT WITH 810 00:57:45,910 --> 00:57:49,109 THE DATA WE'RE GETTING FROM ROVERS ON THE GROUND IS 811 00:57:49,109 --> 00:57:55,039 PROVIDING THIS WHOLE NEW VIEW OF THE COMPLEXITY OF MARS AS A 812 00:57:55,039 --> 00:57:57,789 PLANET. WE WILL BE SEARCHING FOR 813 00:57:57,789 --> 00:58:01,980 EVIDENCE OF LIFE, AND WE WILL BE TRYING TO UNDERSTAND THE 814 00:58:01,980 --> 00:58:04,930 ENVIRONMENT, UNDERSTAND THE GEO CHEMICAL EVOLUTION AND WE DON'T 815 00:58:04,930 --> 00:58:10,749 KNOW WHICH PARTS ARE GOING TO HELP US UNDERSTAND EARTH. 816 00:58:10,749 --> 00:58:14,119 >> ANOTHER QUESTION? >> I JUST WANTED TO SEE IF 817 00:58:14,119 --> 00:58:17,690 ANYBODY HAD ANY LAST FINAL COMMENTS THAT WE WANTED TO MAKE? 818 00:58:17,690 --> 00:58:23,079 THERE WAS SOME INTEREST IN THE DIFFERENT ENVIRONMENTS OFTEN THE 819 00:58:23,079 --> 00:58:26,119 EARLY EARTH THAT MAY BE APPLICABLE TO THE NEW 820 00:58:26,119 --> 00:58:35,709 OBSERVATIONS OF MARINE PLANKTON ON THE ISS? 821 00:58:35,709 --> 00:58:41,700 >> I THINK WHAT YOU TOLD ME TO SAY WAS IT WAS TOOTHPASTE. 822 00:58:41,700 --> 00:58:50,349 DIATOMS AND TOOTHPASTE. >> IN THIS FIELD THERE ARE NEWS 823 00:58:50,349 --> 00:58:53,160 STORIES, SOME OF WHICH TURN OUT TO BE TRUE. 824 00:58:53,160 --> 00:58:58,619 WE READ TODAY THAT THEY FOUND PLANKTON ON THE INTERNATIONAL 825 00:58:58,619 --> 00:59:03,489 SPACE STATION, THE PROPER RESPONSE IS TO SAY OH, REALLY? 826 00:59:03,489 --> 00:59:06,369 SO WE JUST LEARNED ABOUT THIS AND WE'RE SKEPTICAL BUT OF 827 00:59:06,369 --> 00:59:08,650 COURSE WE'RE INTERESTED IN HEARING MORE. 828 00:59:08,650 --> 00:59:14,069 >> THAT'S ABOUT IT. I JUST WANTED TO SAY THANK YOU 829 00:59:14,069 --> 00:59:17,599 GUYS ALL FOR JOINING US TONIGHT. IF YOU WOULD LIKE TO LEARN MORE, 830 00:59:17,599 --> 00:59:22,850 VISIT THE WEBSITE ASTROBIOLOGY.NASA.GOV AND