WEBVTT 1 00:00:03.439 --> 00:00:07.719 Welcome to Bedtime Astronomy. Explore the wonders of the cosmos 2 00:00:07.759 --> 00:00:12.279 with our soothing Bedtime Astronomie podcast. Each episode offers a 3 00:00:12.359 --> 00:00:16.320 gentle journey through the stars, planets, and beyond, perfect for 4 00:00:16.399 --> 00:00:20.239 unwinding after a long day. Let's travel through the mysteries 5 00:00:20.239 --> 00:00:22.440 of the universe as you drift off into a peaceful 6 00:00:22.480 --> 00:00:23.839 slumber under the night sky. 7 00:00:26.839 --> 00:00:28.679 I want you to close your eyes for a second. Well, 8 00:00:28.719 --> 00:00:30.600 don't do that for your driving, but if you're safe, 9 00:00:30.800 --> 00:00:34.039 close them and I want you to picture the Earth, 10 00:00:34.399 --> 00:00:36.240 not a map, not you know, a globe sitting in 11 00:00:36.240 --> 00:00:39.159 a classroom. I want you to picture that view from space, 12 00:00:40.439 --> 00:00:43.799 the blue marble. What is the one thing that just 13 00:00:44.560 --> 00:00:45.880 dominates that image. 14 00:00:45.960 --> 00:00:46.719 It's the water. 15 00:00:47.119 --> 00:00:49.640 It's the water. It's not the continents, it's not the clouds. 16 00:00:49.679 --> 00:00:52.200 It is that deep, overwhelming blue. 17 00:00:52.359 --> 00:00:55.439 It's the defining feature of our existence. Really, it really is. 18 00:00:55.479 --> 00:00:57.119 I was just ending at the beast last weekend, looking 19 00:00:57.159 --> 00:01:00.359 out at the Pacific, and it just it. It's you. 20 00:01:00.560 --> 00:01:02.640 The sheer volume of it all, seventy one percent of 21 00:01:02.679 --> 00:01:05.640 the surface, right. It drives our weather, it shapes our geology. 22 00:01:05.640 --> 00:01:07.519 I mean, it makes it. Most of your body weight. 23 00:01:07.920 --> 00:01:11.400 We are, for all intents and purposes, water creatures living 24 00:01:11.439 --> 00:01:12.519 on a water planet. 25 00:01:12.640 --> 00:01:15.840 We are Carl Sagan's pale blue dot. And you know, 26 00:01:16.239 --> 00:01:19.359 without that water, we're just another cratered rock spinning in 27 00:01:19.400 --> 00:01:19.760 the dark. 28 00:01:19.799 --> 00:01:25.200 We're Mars exactly. And because it is so fundamental, so 29 00:01:25.359 --> 00:01:28.879 absolutely non negotiable for life as we know it, you 30 00:01:28.920 --> 00:01:32.079 would just hmm, you'd assume that by now, by the 31 00:01:32.159 --> 00:01:34.560 year twenty twenty six, we would have the origin story 32 00:01:34.560 --> 00:01:37.439 of water completely locked down. You'd think we'd have the 33 00:01:37.519 --> 00:01:39.400 receipt for every single drop in the ocean. 34 00:01:39.480 --> 00:01:42.120 It seems like a reasonable assumption. Yeah, it's the most 35 00:01:42.120 --> 00:01:43.719 important substance we have, right. 36 00:01:44.159 --> 00:01:46.439 But here is the thing that absolutely blew my mind 37 00:01:46.480 --> 00:01:49.760 while I was reading this research packet. We don't or rather, 38 00:01:49.840 --> 00:01:52.040 the story we thought we knew, the one I definitely 39 00:01:52.120 --> 00:01:56.200 learned in high school earth science, might be completely wrong. 40 00:01:56.400 --> 00:01:59.799 It's not just wrong, the new data suggests it's well, 41 00:01:59.799 --> 00:02:03.319 it's mathematically impossible. It is a very bold statement, it is, 42 00:02:03.640 --> 00:02:05.640 but that is what the data is telling us. We 43 00:02:05.680 --> 00:02:08.960 are looking at a brand new study published literally yesterday, 44 00:02:09.080 --> 00:02:12.400 January twenty fifth, twenty twenty six, in the Proceedings of 45 00:02:12.439 --> 00:02:15.479 the National Academy of Sciences. It's a study that takes 46 00:02:15.520 --> 00:02:16.719 a look at some very very. 47 00:02:16.599 --> 00:02:18.879 Old rocks, rocks not from Earth. 48 00:02:18.800 --> 00:02:21.680 Not from Earth, No, and it completely upends our entire 49 00:02:21.759 --> 00:02:23.639 understanding of how Earth got its oceans. 50 00:02:23.960 --> 00:02:26.159 And what's so wild is that to figure out where 51 00:02:26.240 --> 00:02:29.240 earth water came from, they didn't look at Earth rocks 52 00:02:29.240 --> 00:02:30.599 at all. They looked at the Moon. 53 00:02:30.719 --> 00:02:32.599 They had to. It's the only clean witness we have. 54 00:02:32.879 --> 00:02:35.879 Okay, we are absolutely going to get into why that is. 55 00:02:36.479 --> 00:02:38.599 We're going to talk about a team led by doctor 56 00:02:38.639 --> 00:02:43.039 Tony Gargano. It's this massive collaboration with the University Space 57 00:02:43.120 --> 00:02:49.159 Research Association, the Lunaran Planetary Institute, NASA, jpl SCRIPTS, the 58 00:02:49.199 --> 00:02:52.280 heavy hitters, basically the heavy hitters of planetary science. Yeah, 59 00:02:52.680 --> 00:02:55.639 and we're going to unpack why they're findings based on 60 00:02:55.680 --> 00:02:58.759 a few handfuls of dust are forcing us to rewrite 61 00:02:58.759 --> 00:02:59.400 the history. 62 00:02:59.199 --> 00:03:02.800 Books and maybe even more importantly, why this rewriting of 63 00:03:02.879 --> 00:03:05.879 history might actually be the key to our future in space. 64 00:03:06.199 --> 00:03:07.479 It's this incredible twist. 65 00:03:07.560 --> 00:03:10.120 It's a total double edged sword. Right, it's bad news 66 00:03:10.159 --> 00:03:12.400 for the old textbooks, but it might be great news 67 00:03:12.400 --> 00:03:15.599 for future astronauts. Absolutely, But Before we get to the future, 68 00:03:16.120 --> 00:03:18.240 we have to deal with the past. We have to 69 00:03:18.319 --> 00:03:20.400 understand the story that we're now tearing. 70 00:03:20.120 --> 00:03:22.080 Down the standard model as it were. 71 00:03:22.520 --> 00:03:25.080 Yeah, so walk me through this, because I remember learning 72 00:03:25.120 --> 00:03:28.319 about the late heavy bombardment. It always sounds like a 73 00:03:28.319 --> 00:03:30.000 heavy metal band to me, but it was actually a 74 00:03:30.039 --> 00:03:34.319 geological era. What was the prevailing theory about why Earth 75 00:03:34.439 --> 00:03:35.000 has water? 76 00:03:35.199 --> 00:03:37.520 Well, to understand the old theory, you have to understand 77 00:03:37.520 --> 00:03:39.759 the environment in which the Earth was born. So you 78 00:03:39.800 --> 00:03:42.439 have to go back in time about four and a 79 00:03:42.479 --> 00:03:46.599 half billion years. The solar system isn't this polite, orderly 80 00:03:46.759 --> 00:03:50.159 clockwork mechanism we see today. It was a construction site. 81 00:03:50.199 --> 00:03:54.400 It was a shooting gallery, chaotic, violent, extremely hot. You 82 00:03:54.439 --> 00:03:57.360 have the proto sun igniting in the center, and surrounding 83 00:03:57.400 --> 00:04:01.199 it is the swirling disk of gas and dust. Now 84 00:04:01.199 --> 00:04:04.159 in that disk, there's a very very important and visible line. 85 00:04:04.159 --> 00:04:06.000 We call it the snow line or the frost line. 86 00:04:06.039 --> 00:04:09.400 Okay, is this like the snow line on a mountain? 87 00:04:09.439 --> 00:04:11.199 You know, you get above a certain altitude and rain 88 00:04:11.280 --> 00:04:12.000 turns to snow. 89 00:04:12.159 --> 00:04:14.560 It's the exact same principle, but it's based on distance 90 00:04:14.599 --> 00:04:17.560 from the Sun, not altitude. Inside that line, close to 91 00:04:17.600 --> 00:04:20.240 the newborn Sun, it is simply too hot for what 92 00:04:20.240 --> 00:04:22.720 we call volatiles to condense into solids. 93 00:04:23.040 --> 00:04:25.600 And volatiles that's just signed to speak for things that 94 00:04:25.600 --> 00:04:27.759 boil easily, right, like water. 95 00:04:27.720 --> 00:04:31.279 Exactly, water, carbon dioxide, methane, ammonia, all the good stuff 96 00:04:31.279 --> 00:04:34.240 for life. If you are inside the snow line, these 97 00:04:34.240 --> 00:04:36.959 things exist only as a gas, and the solar wind, 98 00:04:37.079 --> 00:04:40.800 this incredible torrent of particles from the young Sun, blows 99 00:04:40.800 --> 00:04:41.519 them away. 100 00:04:41.399 --> 00:04:42.399 So they can't stick around. 101 00:04:42.519 --> 00:04:44.639 They can't stick to the little dust grains that are 102 00:04:44.680 --> 00:04:47.439 clumping together to form planets. It's too hot. The stuff 103 00:04:47.519 --> 00:04:51.120 just vaporizes and gets blasted out to the colder outer 104 00:04:51.199 --> 00:04:51.920 Solar system. 105 00:04:52.000 --> 00:04:54.639 And Earth sits squarely inside that line. 106 00:04:54.680 --> 00:04:59.399 We are well inside it. Mercury, Venus, Earth, Mars. We 107 00:04:59.439 --> 00:05:03.279 are the inn rocky planets. So according to the laws 108 00:05:03.279 --> 00:05:06.480 of thermo dynamics, the building blocks of Earth, the planetesimals, 109 00:05:06.720 --> 00:05:09.240 they should have been dry, bone dry, bone dry. Think 110 00:05:09.319 --> 00:05:11.639 of a ceramic pot coming out of kiln. There is 111 00:05:11.680 --> 00:05:14.759 no moisture left in there. It has been baked out completely. 112 00:05:15.000 --> 00:05:18.800 So baby Earth forms. It's a molten magma covered rock. 113 00:05:19.560 --> 00:05:22.560 It's incredibly hot, it is no atmosphere to speak of, 114 00:05:22.720 --> 00:05:25.959 no water. It's basically a healthscape, a dry healthscape. Yes, 115 00:05:26.279 --> 00:05:29.399 but clearly something changed. I mean, I'm looking at the 116 00:05:29.399 --> 00:05:32.319 ocean right now. So the water had to arrive eventually. 117 00:05:32.360 --> 00:05:34.000 It had to come from somewhere. 118 00:05:33.600 --> 00:05:35.920 Correct, And since it couldn't have been there when the 119 00:05:35.920 --> 00:05:39.920 planet formed, the logic, the very sensible logic, dictated it 120 00:05:40.000 --> 00:05:41.160 must have been delivered from. 121 00:05:41.079 --> 00:05:43.040 Outside after things had cooled down a bit. 122 00:05:43.120 --> 00:05:45.519 Exactly. It had to come from past the snow line, 123 00:05:45.839 --> 00:05:48.639 where all that water and ice was still floating around. 124 00:05:48.399 --> 00:05:50.000 Into the cosmic delivery service. 125 00:05:50.240 --> 00:05:54.759 The asteroids and the commets, specifically a class of meteorite 126 00:05:54.800 --> 00:05:59.759 called sea type or carbonaceous chondrites. These are they are 127 00:05:59.839 --> 00:06:04.120 very primitive rocks that formed way out past Mars, out 128 00:06:04.160 --> 00:06:05.959 near Jupiter and beyond in. 129 00:06:05.920 --> 00:06:06.920 The cold, in the cold. 130 00:06:07.000 --> 00:06:10.000 Yes, And because they formed in the cold, they are 131 00:06:10.040 --> 00:06:13.000 loaded with water. It's not liquid water, it's locked inside 132 00:06:13.040 --> 00:06:15.879 their clay minerals. But some of these rocks are up 133 00:06:15.920 --> 00:06:17.560 to twenty percent water by weight. 134 00:06:17.680 --> 00:06:19.600 Wow, twenty percent. It's a very wet rock. 135 00:06:19.920 --> 00:06:23.000 It's a very wet rock. So the theory, the late 136 00:06:23.040 --> 00:06:26.759 heavy bombardment theory, stakes that about four point one to 137 00:06:26.839 --> 00:06:30.160 three point eight billion years ago, the Solar System went 138 00:06:30.199 --> 00:06:35.639 through this massive violent realignment. The giant planets Jupiter and Saturn. 139 00:06:36.040 --> 00:06:37.759 They shifted their orbits, and. 140 00:06:37.720 --> 00:06:40.720 When the gas giants move, everybody else has a really 141 00:06:40.759 --> 00:06:41.240 bad day. 142 00:06:41.360 --> 00:06:46.279 Gravity just goes haywire. They acted like a giant gravitational slingshot. 143 00:06:46.399 --> 00:06:51.000 They destabilized the asteroid belt. They've flung billions of tons 144 00:06:51.040 --> 00:06:54.160 of this rock and ice inward toward the Sun. 145 00:06:54.160 --> 00:06:56.040 And Earth was just standing in the way. 146 00:06:56.160 --> 00:06:59.040 We were in the cosmic crosshairers. The whole inner Solar 147 00:06:59.040 --> 00:07:01.759 System was a shooting out. We got pummeled. And the 148 00:07:01.839 --> 00:07:04.680 idea was that these impacts, millions and millions of them 149 00:07:04.680 --> 00:07:08.480 over hundreds of millions of years, they were the delivery mechanism. 150 00:07:08.519 --> 00:07:09.240 They brought the water. 151 00:07:09.319 --> 00:07:11.680 They brought the water they'd crashed into the young Earth. 152 00:07:11.680 --> 00:07:15.920 They'd vaporize on impact, release their steam into the thin atmosphere, 153 00:07:15.959 --> 00:07:19.360 and eventually, as Earth cooled, that steam would condense. 154 00:07:18.959 --> 00:07:21.319 Into rain, and it would rain for centuries. 155 00:07:20.879 --> 00:07:24.120 Millennia, filling the basins and creating the very first oceans. 156 00:07:24.480 --> 00:07:27.240 You know, it's such an elegant story. It's very clean. 157 00:07:27.319 --> 00:07:30.319 It explains everything. It explains why we have water despite 158 00:07:30.360 --> 00:07:32.959 being a hot planet. It explains the craters we see 159 00:07:33.000 --> 00:07:35.800 all over the Moon in mercury. It fits the timeline. 160 00:07:35.800 --> 00:07:39.360 So why why has it been challenged? Now? Why are 161 00:07:39.399 --> 00:07:42.000 doctor Gargano and his team saying, hold on a minute, 162 00:07:42.040 --> 00:07:42.720 they can't be right. 163 00:07:43.160 --> 00:07:45.399 Well, you know, imagine you have a theory that says 164 00:07:45.480 --> 00:07:48.879 a specific delivery truck dropped off a package at your house. Okay, 165 00:07:49.000 --> 00:07:51.639 you'd expect to find some evidence, right, some tire tracks 166 00:07:51.639 --> 00:07:53.560 in your driveway, maybe a receipt. 167 00:07:53.399 --> 00:07:55.079 Sure, some kind of proof of delivery. 168 00:07:55.240 --> 00:07:58.240 That's what scientists have been looking for, the chemical proof 169 00:07:58.279 --> 00:08:02.160 of delivery. If these see type asteroids brought the water, 170 00:08:02.759 --> 00:08:06.480 the chemical signature of those asteroids should be all over 171 00:08:06.639 --> 00:08:11.000 Earth's crust and mantle. We should see the fingerprints of 172 00:08:11.040 --> 00:08:14.240 that specific type of space rock everywhere we look, and 173 00:08:14.319 --> 00:08:17.639 we don't. We can't find them, or, to be more accurate, 174 00:08:17.959 --> 00:08:19.959 we can't trust what we find here on Earth. 175 00:08:20.319 --> 00:08:22.519 Why not? Is the equipment not good enough to see it? 176 00:08:22.680 --> 00:08:25.279 No, no, the equipment is phenomenal. Now, the problem is 177 00:08:25.279 --> 00:08:29.079 the witness. Earth is a terrible witness to its own history. 178 00:08:29.199 --> 00:08:31.439 Earth has amnesia. 179 00:08:30.759 --> 00:08:33.440 Geological amnesia is the perfect way to put it. Think 180 00:08:33.480 --> 00:08:37.200 about it. Earth is active, it's alive. We have plate tectonics. 181 00:08:37.240 --> 00:08:39.440 The ground you're standing on right now was not there 182 00:08:39.480 --> 00:08:42.799 four billion years ago. It was deep inside the planet. 183 00:08:42.879 --> 00:08:46.039 Right It gets recycled, constantly recycled. It's been subducted down 184 00:08:46.080 --> 00:08:49.360 into the mantle, melted into magma, mixed around like in 185 00:08:49.399 --> 00:08:53.159 a giant blender, and then spewed back out as new 186 00:08:53.240 --> 00:08:54.919 lava at a mid ocean ridge. 187 00:08:55.240 --> 00:08:57.240 And on top of that there's weather. 188 00:08:57.120 --> 00:09:02.879 Oh absolutely, rain, wind, glacier grinding mountains down, rivers, carving canyons. 189 00:09:03.080 --> 00:09:05.759 And then you have biology. You have plants growing over rocks. 190 00:09:05.799 --> 00:09:10.840 You have bacteria literally eating minerals. Earth is constantly, relentlessly 191 00:09:10.879 --> 00:09:12.120 erasing its own scars. 192 00:09:12.360 --> 00:09:15.240 So if a giant water bearing asteroid hit Earth four 193 00:09:15.279 --> 00:09:18.080 billion years ago, the crater is long gone. 194 00:09:18.159 --> 00:09:21.159 The crater is gone, the ejecta blanket is gone. The 195 00:09:21.360 --> 00:09:24.960 chemical evidence has been diluted and smeared and mixed into 196 00:09:24.960 --> 00:09:28.120 the great soup of the Earth's mantle over billions of years. 197 00:09:28.200 --> 00:09:31.360 So asking Earth, where did you get your water, it's 198 00:09:31.440 --> 00:09:33.840 kind of like asking a person who's undergone total plastic 199 00:09:33.879 --> 00:09:36.600 surgery and had their memory erased what they look like 200 00:09:36.639 --> 00:09:37.279 as a baby. 201 00:09:37.440 --> 00:09:41.320 That is a very vivid and slightly disturbing analogy, but yes, 202 00:09:41.919 --> 00:09:45.480 it's fundamentally correct. Earth cannot tell us the truth about 203 00:09:45.519 --> 00:09:48.320 the bombardment because Earth has changed too much. 204 00:09:48.519 --> 00:09:53.080 Which brings us finally to the neighbor, the silent partner 205 00:09:53.120 --> 00:09:55.720 in this whole cosmic dance, the Moon. 206 00:09:56.039 --> 00:09:59.320 The Moon is the perfect control group. It's the key 207 00:09:59.360 --> 00:10:01.960 to the whole miss It formed around the same time 208 00:10:02.000 --> 00:10:05.120 as Earth, in the same neighborhood, from very similar materials, 209 00:10:05.720 --> 00:10:09.799 but it's small. It cooled down fast. It died geologically speaking, 210 00:10:09.960 --> 00:10:13.000 It died geologically very very early on. There are no 211 00:10:13.120 --> 00:10:14.440 plate tectonic. 212 00:10:14.080 --> 00:10:16.200 No volcanoes recycling the crust. 213 00:10:16.000 --> 00:10:18.360 No atmosphere, so there's no wind and no rain to 214 00:10:18.399 --> 00:10:19.159 cause erosion. 215 00:10:19.360 --> 00:10:20.120 It's a museum. 216 00:10:20.320 --> 00:10:22.799 It is a time capsule. The surface of the Moon, 217 00:10:22.879 --> 00:10:25.080 what we call the regolith, is what doctor Gargano in 218 00:10:25.120 --> 00:10:27.840 the study calls a time integrated record. It has just 219 00:10:27.879 --> 00:10:30.919 been sitting there, exposed to the vacuum of space, collecting 220 00:10:31.000 --> 00:10:33.120 dust and debris for billions of years. 221 00:10:33.240 --> 00:10:35.879 So anything that hit Earth during the Late Heavy bombardment 222 00:10:35.919 --> 00:10:37.919 also hit the Moon. Because we're right next to each other. 223 00:10:38.120 --> 00:10:38.879 We're a system. 224 00:10:39.159 --> 00:10:42.559 In cosmic terms, we are holding hens. If Earth got 225 00:10:42.600 --> 00:10:45.840 showered with these waterbloons, the Moon got splashed too. But 226 00:10:45.919 --> 00:10:48.200 unlike Earth, the Moon didn't wipe off the water. It 227 00:10:48.279 --> 00:10:50.639 kept the chemical residue of everything that ever hit it 228 00:10:50.679 --> 00:10:51.679 locked in its surface layer. 229 00:10:51.840 --> 00:10:54.919 Okay, I want to pause on that word you used. Regolith. Yeah, 230 00:10:54.960 --> 00:10:57.480 because when I look at the footage from Paul eleven 231 00:10:57.480 --> 00:11:00.639 a Paul seventeen, I see the astronauts popping around in 232 00:11:00.679 --> 00:11:03.480 this gray stuff. It looks like dirt, looks like fine 233 00:11:03.519 --> 00:11:05.039 gray powder. Is it dirt? 234 00:11:05.440 --> 00:11:07.759 A geologist would have a fit if you called it dirt, 235 00:11:07.799 --> 00:11:11.279 and for good reason. Dirt or soil on Earth is 236 00:11:11.320 --> 00:11:14.840 an incredibly complex thing. It has organic matter, It has 237 00:11:15.120 --> 00:11:17.840 worm casings, decaying leaves, bacteria. 238 00:11:18.080 --> 00:11:19.039 It implies life. 239 00:11:19.120 --> 00:11:23.639 It absolutely implies a living ecosystem. Regolith is purely mechanical. 240 00:11:23.879 --> 00:11:27.120 It is rock that has been pulverized into dust. Imagine 241 00:11:27.120 --> 00:11:29.159 a single rock sitting on the surface of the Moon. 242 00:11:29.320 --> 00:11:32.159 A micrometeorite the size of a grain of sand hits 243 00:11:32.200 --> 00:11:35.919 it at twenty thousand miles per hour. It shatters the rock. 244 00:11:36.320 --> 00:11:39.919 Now over billions of years. That happens trillions upon trillions 245 00:11:39.960 --> 00:11:42.480 of times. So the top layer of the Moon is 246 00:11:42.600 --> 00:11:47.679 just this blanket of loose, jagged, heterogeneous debris. It's dust, 247 00:11:48.159 --> 00:11:50.879 its tiny shards of glass from the heat of impacts, 248 00:11:50.919 --> 00:11:52.240 its rock fragments. 249 00:11:52.480 --> 00:11:55.279 So the team's mission then was to look at this 250 00:11:55.679 --> 00:11:58.759 great powder samples brought back by the Apollo astronauts over 251 00:11:58.799 --> 00:12:02.360 fifty years ago and try to find that chemical receipt 252 00:12:02.399 --> 00:12:03.240 for the asteroids. 253 00:12:03.360 --> 00:12:05.679 Yes, they wanted to see if the tire tracks from 254 00:12:05.679 --> 00:12:07.919 the delivery truck were there in that lunar dust. 255 00:12:08.279 --> 00:12:11.000 But and there is always a butt in science, isn't there. 256 00:12:11.159 --> 00:12:13.120 It wasn't as simple as just putting the dust under 257 00:12:13.159 --> 00:12:15.559 a microscope and seeing a little label that says made 258 00:12:15.559 --> 00:12:16.519 in the asteroid belt. 259 00:12:16.639 --> 00:12:18.200 No, not at all. And this is where the story 260 00:12:18.240 --> 00:12:21.399 gets technically very difficult. This is why it took until 261 00:12:21.399 --> 00:12:24.200 twenty twenty six to get a clear answer, Because the 262 00:12:24.240 --> 00:12:26.600 Moon is a good witness, but it is a messy, 263 00:12:26.960 --> 00:12:27.879 messy witness. 264 00:12:28.080 --> 00:12:30.600 Messy how you just said it doesn't have wind or 265 00:12:30.679 --> 00:12:31.720 rain to mess things up. 266 00:12:31.799 --> 00:12:33.960 It doesn't, but it has impacts. And you have to 267 00:12:33.960 --> 00:12:37.960 remember those meteorites aren't landing softly. They are hitting at 268 00:12:38.000 --> 00:12:42.159 hypersonic speeds. They are exploding. The energy release is massive. 269 00:12:42.159 --> 00:12:44.879 It's like a nuclear bomb. Okay, when a rock hits 270 00:12:44.919 --> 00:12:48.320 the moon, it vaporizes itself, It melts the local moon 271 00:12:48.399 --> 00:12:51.960 rock it hits, it creates a plasma plume. Everything gets 272 00:12:52.000 --> 00:12:54.679 mixed together in this incredibly violent event. 273 00:12:54.879 --> 00:12:58.120 So it's like if I threw a chocolate bar into 274 00:12:58.120 --> 00:13:01.000 a blender full of vanilla ice cre and then just 275 00:13:01.080 --> 00:13:02.840 hit pulse for a fraction of a. 276 00:13:02.759 --> 00:13:04.919 Second, and then you did that a million times of 277 00:13:04.960 --> 00:13:07.960 rebillion years in random spots. The regolith has been reworked, 278 00:13:08.039 --> 00:13:11.799 it's been melted, it's been mixed, vaporized, recondensed. The signal 279 00:13:11.879 --> 00:13:15.519 of the asteroid the impact is blended almost seamlessly into 280 00:13:15.519 --> 00:13:16.799 the signal of the moon itself. 281 00:13:16.879 --> 00:13:19.120 So how on earth do you separate them? How do 282 00:13:19.159 --> 00:13:22.000 you unblend that smoothie? To figure out how much chocolate 283 00:13:22.000 --> 00:13:23.080 bar was originally there? 284 00:13:23.200 --> 00:13:26.639 That is the million dollar question. And for decades scientists 285 00:13:26.759 --> 00:13:29.159 use what we can call the old way. They looked 286 00:13:29.200 --> 00:13:33.279 for specific types of metals. They looked for cideriphiles, cierophile. 287 00:13:33.519 --> 00:13:35.320 I love that word. It sounds like someone who is 288 00:13:35.360 --> 00:13:36.679 just obsessed with hard cider. 289 00:13:36.919 --> 00:13:40.879 I wish no, it means iron loving. These are particular elements, 290 00:13:41.000 --> 00:13:46.600 things like iridium, platinum, gold, osmium, elements that chemically they 291 00:13:46.639 --> 00:13:48.240 bond very strongly with iron. 292 00:13:48.519 --> 00:13:51.480 Okay, And why do we look for those specific elements. 293 00:13:51.759 --> 00:13:54.639 It has to do with how planets form. When the 294 00:13:54.679 --> 00:13:57.919 Earth and the Moon were young and molten, they differentiated, 295 00:13:58.360 --> 00:14:00.919 the heavy stuff sanked, so the heavy iron sank to 296 00:14:01.000 --> 00:14:04.039 the center to form the core. And because these cider 297 00:14:04.080 --> 00:14:07.279 philes love iron, they hitched a ride. They sank down 298 00:14:07.320 --> 00:14:10.000 into the core too. So the crust of the Earth 299 00:14:10.039 --> 00:14:12.759 and the crust of the Moon are naturally very very 300 00:14:12.799 --> 00:14:16.000 poor in these metals. They're all locked away deep inside 301 00:14:16.039 --> 00:14:16.360 the core. 302 00:14:16.480 --> 00:14:19.240 Got it. So the surface is naturally metal pore exactly. 303 00:14:19.759 --> 00:14:22.639 But meteorates, they are primitive. They never went through that 304 00:14:22.720 --> 00:14:27.399 melting and differentiation process. They are chemically a complete jumble, 305 00:14:27.679 --> 00:14:29.960 and they are loaded with iridium and platinum. 306 00:14:30.000 --> 00:14:32.399 So the logic was simple. If you find a rock 307 00:14:32.440 --> 00:14:34.720 on the Moon's surface that has a lot of iridium 308 00:14:34.759 --> 00:14:37.360 in it, that iridium must be alien. It has to 309 00:14:37.399 --> 00:14:38.879 have come from an asteroid impact. 310 00:14:38.919 --> 00:14:42.039 That was the logic. It's a tracer, a chemical fingerprint, 311 00:14:42.080 --> 00:14:44.080 but it turns out it's a flawed fingerprint. 312 00:14:44.559 --> 00:14:47.440 Why didn't it work for this study? What's the flaw? 313 00:14:47.720 --> 00:14:50.120 It's because of that messy factor we just talked about, 314 00:14:50.159 --> 00:14:53.600 the intense heat of the impact. When an impact happens, 315 00:14:53.639 --> 00:14:57.000 you create this big pool of magma, and the physics 316 00:14:57.039 --> 00:15:00.200 gets weird in there. The metal might separate from the 317 00:15:00.279 --> 00:15:03.600 rock the silicate oh, it might sink to the bottom 318 00:15:03.639 --> 00:15:06.960 of the crater melt pool, or if it gets vaporized 319 00:15:06.960 --> 00:15:09.600 into a gas, the heavier metal might condense at a 320 00:15:09.639 --> 00:15:10.720 different temperature than. 321 00:15:10.600 --> 00:15:13.120 The lighter rock, so the signal gets distorted. It's not 322 00:15:13.399 --> 00:15:16.279 a true representation of the original meteorite exactly. 323 00:15:16.279 --> 00:15:19.279 It's a fractionation problem. You might find a rock that 324 00:15:19.360 --> 00:15:21.879 has a really high concentration of iridium, but you don't 325 00:15:21.879 --> 00:15:25.639 know if that represents the average amount of meteorite material delivered, 326 00:15:26.120 --> 00:15:28.519 or if you just got lucky and found a concentrated 327 00:15:28.519 --> 00:15:32.519 little nugget. It's too unreliable for calculating the total volume 328 00:15:32.519 --> 00:15:33.960 of material that arrived. 329 00:15:33.759 --> 00:15:35.840 So using metals is kind of like trying to count 330 00:15:35.840 --> 00:15:38.080 how many people were at a party by looking at 331 00:15:38.080 --> 00:15:40.600 the footprints in the muddy carpet, But the carpet has 332 00:15:40.639 --> 00:15:43.279 been shampooed in vacuum ten times since the party. 333 00:15:43.480 --> 00:15:45.840 That's a pretty decent analogy. Yeah, the deity is noisy. 334 00:15:46.080 --> 00:15:49.679 And so doctor Gargano and his team they realized that 335 00:15:49.759 --> 00:15:53.000 if they wanted a real answer, a mathematical hard limit, 336 00:15:53.639 --> 00:15:56.320 they couldn't rely on the metals. They needed to look 337 00:15:56.320 --> 00:15:58.639 at something much more fundamental. They needed to look at 338 00:15:58.679 --> 00:15:59.519 the rock itself. 339 00:16:00.279 --> 00:16:00.799 Oxygen. 340 00:16:00.919 --> 00:16:04.759 Oxygen. It is the most abundant element in the lunar crust. 341 00:16:04.840 --> 00:16:07.440 It makes up roughly forty five percent of the weight 342 00:16:07.519 --> 00:16:09.879 of any given Moon rock. You can't separate it out. 343 00:16:09.919 --> 00:16:13.559 It is the rock, okay, But oxygen is oxygen? Isn't 344 00:16:13.600 --> 00:16:16.759 it the air I'm breathing right now? How does oxygen 345 00:16:16.799 --> 00:16:18.639 tell you if a rock came from the Moon or 346 00:16:18.639 --> 00:16:19.440 from an asteroid. 347 00:16:19.600 --> 00:16:21.919 This is where we have to talk about isotopes, and 348 00:16:22.000 --> 00:16:24.679 I promise we'll keep this as painless as possible. 349 00:16:24.840 --> 00:16:28.320 You better my high school chemistry is uh, it's very rusty. 350 00:16:28.399 --> 00:16:31.840 Think of oxygen atoms as having different flavors. The standard flavor, 351 00:16:31.879 --> 00:16:34.480 the one you're mostly breathing right now, is oxygen sixteen. 352 00:16:34.639 --> 00:16:37.399 It has eight protons and eight neutrons in its nucleus. 353 00:16:37.480 --> 00:16:40.679 It's the light version. Let's call it vanilla vanilla perfect. 354 00:16:41.039 --> 00:16:44.799 But there are heavier, rarer versions. Oxygen seventeen has one 355 00:16:44.799 --> 00:16:48.360 extra neutron. Oxygen eighteen has two extra neutrons. Let's call 356 00:16:48.360 --> 00:16:49.600 them chocolate and strawberry. 357 00:16:49.799 --> 00:16:53.000 Okay, I'm with you, and I'm getting hungry, But okay, vanilla, 358 00:16:53.559 --> 00:16:54.960 chocolate and strawberry. 359 00:16:55.279 --> 00:16:58.799 Every single object in the Solar System has a specific recipe, 360 00:16:59.080 --> 00:17:02.840 a specific race of these three flavors. Earth has a 361 00:17:03.000 --> 00:17:07.759 very particular blend of vanilla, chocolate and strawberry oxygen. The 362 00:17:07.759 --> 00:17:10.839 Moon has a blend that is almost identical to Earth's, 363 00:17:11.000 --> 00:17:13.960 which is a clue to its origin. But that's another story, right. 364 00:17:14.200 --> 00:17:17.720 But those C type meteorites, the water carriers from the 365 00:17:17.720 --> 00:17:19.079 outer Solar System. 366 00:17:18.920 --> 00:17:22.160 Let me guess they have a totally different recipe. 367 00:17:21.680 --> 00:17:25.440 A totally different recipe. They have a distinct isotopic fingerprint. 368 00:17:25.880 --> 00:17:29.039 They are much richer in the heavy isotopes, the chocolate 369 00:17:29.039 --> 00:17:31.400 and strawberry in a way that really stands out from 370 00:17:31.440 --> 00:17:32.440 Earth and Moon rocks. 371 00:17:32.559 --> 00:17:35.920 So if you physically mix meteorite dust into moon dust, 372 00:17:36.240 --> 00:17:39.359 you change the flavor profile of the resulting rock exactly. 373 00:17:39.359 --> 00:17:41.839 You shift the overall ratio you add more chocolate and 374 00:17:41.880 --> 00:17:44.279 strawberry to the vanilla. But wait, there's a catch, of. 375 00:17:44.200 --> 00:17:46.240 Course there is. Science is never easy. 376 00:17:46.319 --> 00:17:50.200 The heat. Remember how the impact melts and vaporizes the rock. 377 00:17:50.119 --> 00:17:51.480 Yes, the blender effect. 378 00:17:51.720 --> 00:17:55.160 Well, heat also changes the isotope ratio. It's a process 379 00:17:55.160 --> 00:17:58.519 called fractionation. If you boil a pot of water, the 380 00:17:58.599 --> 00:18:02.519 lighter water molecules with the light vanilla oxygen sixteen, they 381 00:18:02.559 --> 00:18:05.359 evaporate a little bit faster. The heavy ones tend to 382 00:18:05.359 --> 00:18:07.319 get left behind, so the water that's left in the 383 00:18:07.319 --> 00:18:08.799 pot gets isotopically heavier. 384 00:18:09.119 --> 00:18:11.480 So the heat changes the flavor profile too. Doesn't that 385 00:18:11.519 --> 00:18:13.960 just ruin the entire experiment. How do you know if 386 00:18:13.960 --> 00:18:16.319 the change in flavor is because you added a meteorite 387 00:18:16.519 --> 00:18:18.720 or just because the rock got cooked in an impact. 388 00:18:19.039 --> 00:18:22.799 This is the absolute genius of the triple oxygen isotope method. 389 00:18:23.039 --> 00:18:24.839 This is the breakthrough, and this is why it's so 390 00:18:24.920 --> 00:18:28.359 much better than the metal method. The changes caused by 391 00:18:28.359 --> 00:18:32.240 heat by this fractionation, they follow a very strict, very 392 00:18:32.279 --> 00:18:36.359 predictable mathematical law. We call it mass dependent fractionation. 393 00:18:36.680 --> 00:18:38.079 Okay, that sounds a little scary. 394 00:18:38.160 --> 00:18:40.160 It just means the change depends on the weight on 395 00:18:40.240 --> 00:18:43.920 the mass. Oxygen eighteen is about twice as heavy relative 396 00:18:43.960 --> 00:18:46.960 to sixteen as seventeen is, so it fractionates twice as much. 397 00:18:47.559 --> 00:18:50.119 If you plot these changes on a graph, all the 398 00:18:50.160 --> 00:18:53.359 heat effects just slide up and down a specific line 399 00:18:53.440 --> 00:18:54.759 with a specific slope. 400 00:18:54.960 --> 00:18:57.240 Okay, so heat moves you up and down along this 401 00:18:57.279 --> 00:18:58.720