WEBVTT 1 00:00:03.399 --> 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 --> 00:00:26.679 slumber under the night sky. 7 00:00:26.960 --> 00:00:31.160 Welcome curious minds. Today, we're looking at something pretty radical, 8 00:00:31.440 --> 00:00:34.719 overturning a decade's old idea about Mars. Forget the notion 9 00:00:34.840 --> 00:00:37.640 of just a you know, a fully liquid, maybe dying 10 00:00:37.719 --> 00:00:41.679 heart beneath that dusty red surface. New seismic data this 11 00:00:41.719 --> 00:00:45.399 is from NASA's Insight mission. It reveals Mars holds a 12 00:00:45.439 --> 00:00:49.840 secret a solid core, and it's shockingly similar to Earth's, 13 00:00:49.840 --> 00:00:53.200 which is well, it's a discovery that completely rewrites the history, 14 00:00:53.280 --> 00:00:55.840 the really violent history of the red planet and its 15 00:00:55.840 --> 00:00:56.560 lost oceans. 16 00:00:56.799 --> 00:00:59.280 Yeah. What's truly remarkable here is how our understanding of 17 00:00:59.320 --> 00:01:02.079 Mars just keep evolving. It's constantly pushing the boundaries of 18 00:01:02.079 --> 00:01:04.319 what we thought was possible. You know, it forces us 19 00:01:04.319 --> 00:01:06.719 to reevaluate these long held assumptions we've had. We know, 20 00:01:06.799 --> 00:01:10.920 Mars today is well a cold, dry, seemingly desolate world, 21 00:01:10.959 --> 00:01:14.040 like a frozen desert basically, Yet the evidence that's been 22 00:01:14.079 --> 00:01:17.519 building up it strongly suggests a very different past, one 23 00:01:17.519 --> 00:01:20.359 that held this compelling promise of well abundant liquid water 24 00:01:20.599 --> 00:01:23.439 and perhaps you know, maybe even the potential for life right, 25 00:01:23.640 --> 00:01:26.120 and the key to unlocking this huge mystery, it turns out, 26 00:01:26.159 --> 00:01:29.840 lies hundreds of kilometers down way beneath its now dusty, 27 00:01:30.280 --> 00:01:31.000 arid surface. 28 00:01:31.359 --> 00:01:35.000 Yeah, for years, Mars has felt like this colossal planet 29 00:01:35.040 --> 00:01:38.159 sized cold case, hasn't it? How did it go from 30 00:01:38.280 --> 00:01:43.439 being potentially watery, maybe even vibrant, to the parched desert 31 00:01:43.480 --> 00:01:46.120 it is today. It's a question that's really driven decades 32 00:01:46.120 --> 00:01:50.400 of exploration absolutely and today are let's call them our 33 00:01:50.439 --> 00:01:54.200 forensic team, the scientists working with the Insight Mission. They 34 00:01:54.319 --> 00:01:57.439 finally cracked a really crucial piece of that puzzle. It's 35 00:01:57.519 --> 00:02:02.400 dramatically reshaping our understanding of Mars interior. We're talking incredible 36 00:02:02.439 --> 00:02:05.959 new insights from seismic studies. They literally offer us a 37 00:02:06.040 --> 00:02:10.360 peak into its innermost secrets, like a planetary autopsy report. 38 00:02:10.080 --> 00:02:13.039 Almost, And this raises a really important question for all 39 00:02:13.080 --> 00:02:14.800 of us. I think, what can the very core of 40 00:02:14.840 --> 00:02:18.400 a planet actually tell us about its entire history, it's trajectory, 41 00:02:18.439 --> 00:02:20.680 it's ultimate fate. We'll be looking at how these recent 42 00:02:20.719 --> 00:02:24.719 observations have not just refined, but really significantly deepened our models, 43 00:02:25.080 --> 00:02:28.199 suggesting that Mars might be far more like Earth deep 44 00:02:28.280 --> 00:02:30.719 down than we previously believed. And this is more than 45 00:02:30.759 --> 00:02:34.599 just geology, you know, it's a profound story planetary evolution, 46 00:02:35.360 --> 00:02:39.639 the delicate balance of magnetic fields, and the incredibly specific 47 00:02:39.680 --> 00:02:42.759 conditions that are required for a world to remain hospitable, 48 00:02:43.120 --> 00:02:46.360 to hold on to its life giving potential over well 49 00:02:46.919 --> 00:02:48.000 cosmic time scales. 50 00:02:48.560 --> 00:02:50.960 So our mission today as we dive into this is 51 00:02:51.000 --> 00:02:54.400 really to uncover the secrets of Mars's core, understand why 52 00:02:54.439 --> 00:02:56.879 it's structure and its history matters so much to the 53 00:02:56.919 --> 00:03:00.560 planet's past and maybe its future, and so to see 54 00:03:00.599 --> 00:03:05.159 how science, like a you know, a persistent detective, painstakingly 55 00:03:05.199 --> 00:03:08.639 builds knowledge step by careful steps. So, yeah, prepare to 56 00:03:08.639 --> 00:03:10.840 have your assumptions about the Red planet challenged. 57 00:03:11.280 --> 00:03:14.240 Well. Trace this fascinating journey of scientific discovery right from 58 00:03:14.280 --> 00:03:17.439 the initial hypotheses, which were often based on remote observations, 59 00:03:17.439 --> 00:03:20.039 you know, looking from orbit to the latest and most 60 00:03:20.039 --> 00:03:23.199 precise seismic measurements from insight. And we'll try to connect 61 00:03:23.199 --> 00:03:26.520 these seemingly abstract, kind of complex details to the grand 62 00:03:26.560 --> 00:03:30.680 sweeping narrative of Mars's really dramatic transformation. It really is 63 00:03:30.719 --> 00:03:32.240 a planetary detective story. 64 00:03:32.439 --> 00:03:35.159 Okay, So let's start with the Mars. We think we know, 65 00:03:35.639 --> 00:03:38.039 the one we see today when we look up at 66 00:03:38.080 --> 00:03:41.039 the night sky see that unmistakable red dot, or when 67 00:03:41.039 --> 00:03:43.840 we see those amazing images beamed back by the rovers, 68 00:03:44.879 --> 00:03:48.080 what comes to mind? I mean, it's a vast chili desert, right, 69 00:03:48.120 --> 00:03:49.879 that's the image most of us have precisely. 70 00:03:49.960 --> 00:03:52.639 Yeah, you've captured it perfectly. The Mars we observe today 71 00:03:52.719 --> 00:03:56.520 is characterized by an extremely thin atmosphere, really thin. It's 72 00:03:56.520 --> 00:03:59.479 mostly carbon dioxide, something like ninety five percent. And this 73 00:03:59.560 --> 00:04:03.560 thin on belowe it offers very little protection from solar radiation. 74 00:04:04.000 --> 00:04:06.240 The surface pressure is less than one percent of Earth's 75 00:04:06.280 --> 00:04:07.800 at sea level, just. 76 00:04:07.919 --> 00:04:09.919 Incredibly wow, less than one percent. 77 00:04:10.120 --> 00:04:13.759 Yeah, And temperatures well, they rarely if ever get above freezing, 78 00:04:13.800 --> 00:04:16.879 often plunging way down to minus sixty degrees celsius or 79 00:04:16.879 --> 00:04:19.759 even colder at the poles. And the almost complete lack 80 00:04:19.800 --> 00:04:23.360 of significant stable liquid water on the surface. That's one 81 00:04:23.360 --> 00:04:25.759 of its most defining features right now. It is, by 82 00:04:25.759 --> 00:04:30.720 all accounts, a very harsh place inhospitable, a true frozen desert. 83 00:04:31.000 --> 00:04:33.839 And you think about those pictures, those iconic images from 84 00:04:34.160 --> 00:04:39.759 the rovers, spirit, opportunity, curiosity, perseverance. You see those dusty, 85 00:04:40.279 --> 00:04:45.000 rust colored planes stretching out forever, barren, rocky landscapes, those clear, 86 00:04:45.439 --> 00:04:48.000 often kind of salmon pink skies, sometimes with those swirling 87 00:04:48.079 --> 00:04:50.920 dust devils. It's got this men's geological beauty for sure. 88 00:04:50.920 --> 00:04:53.040 That absolutely not a place you'd picture taking a swim 89 00:04:53.120 --> 00:04:56.399 right or finding a river, seeing oceans. It feels like 90 00:04:56.439 --> 00:04:58.920 a world strip bear of the very things that make 91 00:04:59.079 --> 00:05:03.519 Earth so well alive. But that's not the complete picture, 92 00:05:03.560 --> 00:05:05.959 is it not? By a long shot. That stark reality 93 00:05:05.959 --> 00:05:09.079 of Mars today actually makes the evidence for past water 94 00:05:09.480 --> 00:05:12.720 even more compelling, doesn't it. It really underlines the sheer scale 95 00:05:12.759 --> 00:05:14.720 of the change the planet went through. There's a huge 96 00:05:14.759 --> 00:05:17.680 amount of compelling, really undeniable evidence telling a very different 97 00:05:17.680 --> 00:05:20.800 story about Mars's past, a time when it was a 98 00:05:20.879 --> 00:05:22.040 very different kind of world. 99 00:05:22.360 --> 00:05:26.959 Indeed, Yeah, what's truly remarkable is the overwhelming geological evidence 100 00:05:27.639 --> 00:05:32.519 meticulously gathered over decades by orbiters and rovers like Curiosity 101 00:05:32.600 --> 00:05:38.120 and Perseverance. This evidence suggests that liquid water once flowed freely, abundantly, 102 00:05:38.160 --> 00:05:41.120 even and perhaps for long periods across the Martian surface. 103 00:05:41.319 --> 00:05:44.360 We're talking about conditions that were well, incredibly far more 104 00:05:44.360 --> 00:05:47.279 hospitable than anything we see today, a Mars that would 105 00:05:47.279 --> 00:05:51.920 be honestly unrecognizable to us, maybe resembling a young. 106 00:05:51.720 --> 00:05:54.600 Earth, a young or wow. So what kind of evidence 107 00:05:54.600 --> 00:05:55.920 are we talking about specifically? 108 00:05:56.000 --> 00:05:58.040 Well, comes in many forms, and each one is like 109 00:05:58.079 --> 00:06:02.319 a powerful clue, really undeniable. For instance, we found numerous 110 00:06:02.439 --> 00:06:05.600 dry lake beds. These are expansive basins that clearly once 111 00:06:05.639 --> 00:06:08.920 held standing water, and you see ancient shorelines, delta structures, 112 00:06:09.000 --> 00:06:12.519 sedimentary fans like river deltas exactly. I consider Jeseral Crater 113 00:06:12.680 --> 00:06:15.879 where perseverances right now. The images show these intricate river 114 00:06:15.959 --> 00:06:18.879 deltas very much like say the Mississippi delta here on Earth. 115 00:06:19.079 --> 00:06:21.279 This is where river once flowed into a vast lake, 116 00:06:21.519 --> 00:06:25.319 depositing sediments over potentially millions of years. And within those 117 00:06:25.399 --> 00:06:30.079 ancient sediments, scientists have found specific minerals, things like clays 118 00:06:30.240 --> 00:06:36.279 and sulfates, phyllosilicates like smectite chlorite, or evaporates like gypsum jerriscite. 119 00:06:37.199 --> 00:06:40.199 These are minerals that could only have formed if liquid 120 00:06:40.199 --> 00:06:43.120 water was present for a long time. They're not subtle hints, 121 00:06:43.439 --> 00:06:47.519 they're definitive chemical signatures, like a chemical fingerprint of past 122 00:06:47.600 --> 00:06:50.120 water locked away for billions of years. 123 00:06:50.480 --> 00:06:53.360 Okay, so dry lakes, specific minerals. 124 00:06:53.920 --> 00:06:56.639 What else, Well, beyond that, we see these dramatic valley 125 00:06:56.680 --> 00:06:59.680 networks etched into the landscape. They're not just random cracks, 126 00:07:00.040 --> 00:07:04.199 intricate branching systems, really similar in their shape their morphology 127 00:07:04.519 --> 00:07:07.439 to river systems on Earth. Think of those dendritic patterns 128 00:07:07.439 --> 00:07:10.040 you see in aerial photos of the Amazon Basin, for example, 129 00:07:10.120 --> 00:07:12.959 right like tree branches spreading out precisely. And these aren't 130 00:07:12.959 --> 00:07:16.680 just small channels. They're often kilometers wide, hundreds of meters deep. 131 00:07:16.879 --> 00:07:20.759 They're unmistakable evidence carved by the relentless flow of ancient rivers, 132 00:07:20.839 --> 00:07:23.600 long lived rivers, not just you know, flash floods. And 133 00:07:23.639 --> 00:07:25.600 then there are the sedimentary layers. You can see them 134 00:07:25.600 --> 00:07:29.560 in canyon walls like in valasmarneras or exposed in crater rims. 135 00:07:29.759 --> 00:07:33.000 These finely stratified deposits laid down layer upon layer over 136 00:07:33.079 --> 00:07:36.600 vast time scales. There are textbook examples of deposition and 137 00:07:36.680 --> 00:07:39.480 standing bodies of water to light sediments settle in lakes 138 00:07:39.560 --> 00:07:42.600 or seas here on Earth, it indicates a long sustained 139 00:07:42.600 --> 00:07:45.639 period of water activity. All of this taken together piints 140 00:07:45.680 --> 00:07:48.240 this vivid, irrefutable picture of a world that was once 141 00:07:48.360 --> 00:07:48.959 rich in water. 142 00:07:49.319 --> 00:07:52.519 So yeah, this overwhelming evidence that really begs the question, 143 00:07:52.600 --> 00:07:55.839 doesn't it. How could a planet now so incredibly arid, 144 00:07:55.839 --> 00:07:59.160 so seemingly lifeless, have once supported such an abundance of 145 00:07:59.160 --> 00:08:02.399 liquid water. What allowed for that much thicker atmosphere and 146 00:08:02.439 --> 00:08:05.720 a milder climate, the conditions that were clearly needed for 147 00:08:05.800 --> 00:08:09.319 surface water to exist. It's just such a radical transformation, 148 00:08:09.360 --> 00:08:13.199 a monumental shift. What drove such a huge change? 149 00:08:13.839 --> 00:08:16.879 Okay, To really get a handle on Mars's incredible transformation 150 00:08:17.040 --> 00:08:19.879 from potentially watery to the col dry world we see, 151 00:08:19.920 --> 00:08:23.759 we need to understand something absolutely vital about our own planet. First, Earth, 152 00:08:24.040 --> 00:08:26.800 It's internal engine, it's heart, you could say. So, if 153 00:08:26.800 --> 00:08:28.879 we're trying to figure out Mars's big shift, we really 154 00:08:28.920 --> 00:08:30.600 need to start with Earth, don't we. I mean, why 155 00:08:30.720 --> 00:08:33.679 is our internal engine, so incredibly good at protecting our 156 00:08:33.720 --> 00:08:35.559 atmosphere and keeping life going. 157 00:08:35.679 --> 00:08:37.840 Yeah, well it connect this to the bigger picture, the 158 00:08:37.840 --> 00:08:41.919 whole idea of planetary habitability. A key property of Earth's 159 00:08:42.200 --> 00:08:45.759 remarkable ability to sustain life comes directly from its core. 160 00:08:46.399 --> 00:08:49.200 Our planet has what we call a differentiated core. There's 161 00:08:49.240 --> 00:08:53.080 a solid inner core mostly iron and nickel, and that's 162 00:08:53.080 --> 00:08:57.440 surrounded by a churning, swirling liquid outer core, also mainly 163 00:08:57.480 --> 00:08:59.720 iron and nickel, but mixed with some lighter elements like 164 00:08:59.720 --> 00:09:03.360 soul for an oxygen. It's this dynamic internal structure that's 165 00:09:03.399 --> 00:09:06.399 absolutely critical for generating or its global magnetic field. 166 00:09:06.519 --> 00:09:08.919 Okay, solid inner, liquid outer. 167 00:09:09.840 --> 00:09:14.440 And this specific arrangement is what drives the geodynamo effect. Essentially, 168 00:09:14.480 --> 00:09:18.639 you have convexing currents within that liquid outer layer. Think 169 00:09:18.639 --> 00:09:21.639 of like boiling water, but with molten metal. These currents 170 00:09:21.639 --> 00:09:24.039 are driven by heat escaping from the salt inner core 171 00:09:24.080 --> 00:09:27.240 as it cools and crystallizes, and also by the planet's rotation. 172 00:09:27.639 --> 00:09:30.799 The Coriolis effects stirs things up, and this whole process 173 00:09:30.840 --> 00:09:34.799 generates a powerful expanse of magnetic field. This field stretches 174 00:09:34.879 --> 00:09:38.240 way out into space, forming this invisible protective bubble around 175 00:09:38.279 --> 00:09:40.759 our entire planet. We call it the magnetosphere. It's a 176 00:09:40.799 --> 00:09:42.759 truly amazing self sustaining system. 177 00:09:43.000 --> 00:09:45.240 So it's like an invisible shield. That's a good way 178 00:09:45.279 --> 00:09:48.399 to think about it constantly deflecting all this harmful stuff 179 00:09:48.440 --> 00:09:51.080 from the sun, charged particles exactly. 180 00:09:51.159 --> 00:09:55.000 It deflects harmful charged particles that are constantly blasted out 181 00:09:55.039 --> 00:09:59.080 by the Sun, especially during solar flares and chronal mass ejections. 182 00:09:59.639 --> 00:10:04.080 These solar winds, as they're called, are incredibly energetic streams 183 00:10:04.120 --> 00:10:08.559 of protons and electrons, and without that magnetospheric shield, they 184 00:10:08.600 --> 00:10:12.720 would just relentlessly strip away our atmosphere over geological time. 185 00:10:12.600 --> 00:10:13.519 Like a sand blaster. 186 00:10:13.879 --> 00:10:16.360 Yeah, that's a good analogy. Much like a powerful sand 187 00:10:16.360 --> 00:10:20.360 blaster eroding rock. It's this continuous, silent battle happening way 188 00:10:20.360 --> 00:10:23.879 above our heads. The magnetosphere acts like a bouncer, basically 189 00:10:24.200 --> 00:10:28.360 redirecting these high energy particles around Earth. Without this magnetic protection, 190 00:10:28.720 --> 00:10:31.559 our atmosphere, and along with it, the conditions for life 191 00:10:32.080 --> 00:10:35.000 would slowly but surely vanish. It's also why we get 192 00:10:35.000 --> 00:10:38.039 the auroras, the northern and Southern lights, that some of 193 00:10:38.039 --> 00:10:41.200 those deflected particles interacting with our atmosphere near the poles, 194 00:10:41.440 --> 00:10:43.639 a beautiful side effect of our planet's shield. 195 00:10:43.879 --> 00:10:47.440 Okay, that makes sense. So with that essential understanding of 196 00:10:47.480 --> 00:10:51.240 Earth's shield in mind, what about Mars. Does it have 197 00:10:51.440 --> 00:10:56.080 a similar life preserving magnetic field today? Because I mean, 198 00:10:56.120 --> 00:10:58.879 if it doesn't, that immediately points to a very different situation, 199 00:10:58.960 --> 00:11:02.240 doesn't it maybe one vulnerability of loss currently, No. 200 00:11:02.320 --> 00:11:06.000 It doesn't. Mars utterly lacks a global magnetic field today, 201 00:11:06.039 --> 00:11:09.600 certainly nothing like Earth's. This is a critical difference and 202 00:11:09.639 --> 00:11:12.320 a major reason why Mars is the cold, dry world 203 00:11:12.360 --> 00:11:15.399 we see now. However, and this is a really crucial 204 00:11:15.440 --> 00:11:19.159 piece of the puzzle. The evidence points to a very 205 00:11:19.159 --> 00:11:23.639 different pass from Mars too, from residual magnetization found embedded 206 00:11:23.639 --> 00:11:26.519 in the Martian crust. Essentially, you have rocks on the 207 00:11:26.559 --> 00:11:29.519 surface that still hold a Foffel magnetic signature. This signature 208 00:11:29.559 --> 00:11:31.440 dates back to when they first formed and cooled down 209 00:11:31.480 --> 00:11:33.720 billions of years ago in the presence of an active 210 00:11:33.759 --> 00:11:37.000 magnetic field. Scientists are quite confident that Mars did once 211 00:11:37.039 --> 00:11:38.720 possess such a global field. 212 00:11:38.480 --> 00:11:40.600 So it had a shield too early on, it. 213 00:11:40.639 --> 00:11:45.320 Seems so orbiting spacecraft like Mars Global surveyor actually mapped 214 00:11:45.360 --> 00:11:48.360 these magnetic anomalies in the crust. They confirmed that an 215 00:11:48.360 --> 00:11:51.679 ancient dynamo was active, likely for maybe the first billion 216 00:11:51.759 --> 00:11:54.799 years or so of Mars's history. And this ancient field 217 00:11:54.919 --> 00:11:58.080 was probably generated by a core structure similar to Earth's, 218 00:11:58.120 --> 00:12:01.039 meaning it likely had a soltid inner core and a 219 00:12:01.080 --> 00:12:03.879 liquid outer core capable of driving that dynamo. 220 00:12:04.039 --> 00:12:06.480 Okay, so it had one, but lost it. What are 221 00:12:06.480 --> 00:12:07.879 the implications of that loss? 222 00:12:08.120 --> 00:12:11.879 They're profound, truly profound. It marks a pivotal moment in 223 00:12:11.919 --> 00:12:15.879 Mars's story. Scientists generally hypothesize that the eventual loss of 224 00:12:15.879 --> 00:12:19.120 this magnetic field was a critical turning point, perhaps the 225 00:12:19.159 --> 00:12:23.759 critical turning point. Without that protective shield, the relentless solar 226 00:12:23.759 --> 00:12:28.000 wind would have had direct, unimpeded access to Mars's ancient, much. 227 00:12:27.840 --> 00:12:30.200 Thicker atmosphere, right, no more bouncer. 228 00:12:29.960 --> 00:12:33.480 Exactly, over millions, hundreds of millions of years, this energetic 229 00:12:33.519 --> 00:12:36.759 bombardment would have stripped that atmosphere away, particle by particle 230 00:12:37.120 --> 00:12:40.399 through processes like sputtering where particles get knocked off and 231 00:12:40.519 --> 00:12:43.600 ion pickup, where atmospheric gases get carried away by the 232 00:12:43.600 --> 00:12:46.200 solar wind. Think of it like a constant slow leak 233 00:12:46.240 --> 00:12:49.960 into space. This atmospheric loss, in turn, would have led 234 00:12:50.000 --> 00:12:54.039 directly to the rapid and irreversible loss of surface liquid water. 235 00:12:54.720 --> 00:12:58.440 As the atmospheric pressure dropped, water just couldn't stay liquid 236 00:12:58.440 --> 00:13:01.519 on the surface anymore. It would either freeze or subtlee 237 00:13:01.519 --> 00:13:04.320 may turn directly into gas and escape into space, or 238 00:13:04.360 --> 00:13:08.840 maybe retreat underground. It's this cascading chain of events starting 239 00:13:08.879 --> 00:13:12.159 deep inside the planet with the dying dynamo that ultimately 240 00:13:12.200 --> 00:13:14.360 led to the barren landscape we see today. 241 00:13:14.480 --> 00:13:16.600 Wow, so it all comes back to the core. This 242 00:13:16.720 --> 00:13:20.039 really raises that central question. Then, what exactly happened to 243 00:13:20.039 --> 00:13:23.360 Mars's internal engine? What switched off that planetary dynamo? What 244 00:13:23.440 --> 00:13:27.279 turned Mars from potentially vibrant and watery into the desert? 245 00:13:27.320 --> 00:13:30.480 It is now that's the core mystery, isn't it. And 246 00:13:30.519 --> 00:13:32.799 to answer that, we couldn't just look at the surface anymore. 247 00:13:32.799 --> 00:13:35.639 We had to go deeper, which is precisely why missions 248 00:13:35.679 --> 00:13:37.639 like Insight were conceived right precisely. 249 00:13:37.840 --> 00:13:42.080 Yeah, while missions like NASA's amazing Rover, Spirit, Opportunity, Curiosity, 250 00:13:42.120 --> 00:13:46.360 Perseverance have been fantastic surface geologists, you know, analyzing rocks 251 00:13:46.399 --> 00:13:50.360 and soil and orbiters like esay's exomrs trace gas orbit 252 00:13:50.440 --> 00:13:52.399 or study the water cycle, and NASA has made an 253 00:13:52.440 --> 00:13:55.919 end look specifically at an atmospheric loss. A fundamentally different 254 00:13:56.000 --> 00:13:58.279 kind of mission was needed to probe that core question, 255 00:13:58.519 --> 00:14:01.399 the question about the planets deep into We needed to listen, not. 256 00:14:01.480 --> 00:14:04.799 Just look, and that mission was NASA's Insight Lander. It 257 00:14:04.879 --> 00:14:08.600 touched down quite incredibly back in November twenty eighteen, landed 258 00:14:08.639 --> 00:14:12.399 in a region called Elysium Planitia, chosen because it's relatively 259 00:14:12.440 --> 00:14:15.720 flat geologically quiet, which is ideal for its sensitive instruments. 260 00:14:15.840 --> 00:14:19.200 Its primary goal, really groundbreaking, was to study seismic activity 261 00:14:19.240 --> 00:14:22.080 marsquakes as we call them. The aim was to reveal 262 00:14:22.200 --> 00:14:25.919 for the very first time the planet's internal structure, its crust, 263 00:14:26.159 --> 00:14:30.200 its mantle, and crucially its core. Insight listened patiently to 264 00:14:30.200 --> 00:14:33.080 Mars for four years, making its last contact in December 265 00:14:33.120 --> 00:14:36.279 twenty twenty two. Sadly its solar panels got too dusty 266 00:14:36.320 --> 00:14:38.879 to keep it powered. But it's data that continues to 267 00:14:38.879 --> 00:14:42.159 revolutionize our understanding. It's this treasure trope scientists are still 268 00:14:42.159 --> 00:14:44.799 digging through. Okay, so here's where it gets really interesting. 269 00:14:45.120 --> 00:14:47.440 In twenty twenty one, there was this seminal paper, a 270 00:14:47.480 --> 00:14:49.960 truly landmark study that came out of the Insight mission 271 00:14:50.240 --> 00:14:52.879 led by Simon Staylor and his colleagues. This paper gave 272 00:14:52.960 --> 00:14:55.879 us the very first direct look, the first robust measurement 273 00:14:55.960 --> 00:14:59.039 of Mars core. So, after all that anticipation, all that listening, 274 00:14:59.159 --> 00:15:01.600 what did they actually find? What was the initial verdict 275 00:15:01.600 --> 00:15:03.000 on Mars depth secret. 276 00:15:02.759 --> 00:15:06.200 Well, using that invaluable data from the marsquakes, those faint 277 00:15:06.279 --> 00:15:10.320 rumbles and tremors deep inside the planet, Stealer's team analyzed 278 00:15:10.360 --> 00:15:13.039 how the seismic waves traveled through Mars. Think of it 279 00:15:13.120 --> 00:15:16.519 like shouting into a canyon and timing the echoes. Different 280 00:15:16.519 --> 00:15:20.200 materials inside the planet reflect and transmit seismic waves differently. Okay, 281 00:15:20.240 --> 00:15:23.960 So by precisely timing how these marsquake echoes, specifically the 282 00:15:23.960 --> 00:15:26.720 Pea waves which are compressional waves and s ways the 283 00:15:26.759 --> 00:15:30.240 Shearer waves traveled from the quake's origin through the crust, 284 00:15:30.519 --> 00:15:34.519 the mantle, down into the core, maybe reflecting off internal boundaries, 285 00:15:34.799 --> 00:15:38.159 and then finally traveling back up to inside supersensitive seismometer 286 00:15:38.279 --> 00:15:42.240 called SACE, they could literally map the internal layers like 287 00:15:42.240 --> 00:15:44.440 a planetary sonogram. It was the first time we ever 288 00:15:44.480 --> 00:15:47.440 directly heard Mars's internal structure. Incredible, So what did that 289 00:15:47.480 --> 00:15:49.879 first map show? What did the core look like in 290 00:15:49.879 --> 00:15:53.639 that twenty twenty one study, Right, So, their in depth analysis, 291 00:15:53.960 --> 00:15:56.320 based on about a dozen of the larger marsquakes they 292 00:15:56.320 --> 00:16:00.120 had recorded by then, revealed a few key things. Some 293 00:16:00.159 --> 00:16:02.759 were a bit surprising at the time. They modeled a 294 00:16:02.799 --> 00:16:05.960 core with just a single liquid layer, basically a big 295 00:16:06.080 --> 00:16:09.480 molten ball of metal, and this core was surprisingly large. 296 00:16:09.840 --> 00:16:12.919 They estimated its radius at about eighteen hundred kilometers, which 297 00:16:12.960 --> 00:16:16.440 is roughly half of Mars's total radius, quite big for 298 00:16:16.480 --> 00:16:17.440 a planet Mars. 299 00:16:17.440 --> 00:16:19.320 Off the radius wow Yeah. 300 00:16:19.360 --> 00:16:21.399 And furthermore, it turned out to be less dense than 301 00:16:21.440 --> 00:16:24.480 you'd expect for a purely iron nickel core like Earth's. 302 00:16:24.639 --> 00:16:28.320 Is mostly this density deficit, which they inferred from how 303 00:16:28.360 --> 00:16:31.360 fast the seismic waves traveled through it, strongly suggested it 304 00:16:31.399 --> 00:16:34.120 was rich in lighter elements, things like sulfur or oxygen 305 00:16:34.200 --> 00:16:37.279 carbon maybe hydrogen mixed in with the iron and nickel. 306 00:16:37.679 --> 00:16:40.120 And why is that important for lighter elements. 307 00:16:39.720 --> 00:16:43.039 Well, those lighter elements significantly affect the core's melting temperature 308 00:16:43.080 --> 00:16:45.799 if they lower it. That makes it much more likely 309 00:16:45.840 --> 00:16:48.559 for the core to stay liquid for longer, rather than 310 00:16:48.679 --> 00:16:51.960 solidifying quickly as the planet cools down over billions of years. 311 00:16:52.519 --> 00:16:55.559 So this was a crucial insight. It potentially explained how 312 00:16:55.600 --> 00:16:57.679 Mars might have kept a liquid core and maybe a 313 00:16:57.759 --> 00:17:01.039 dynamo going for some time. And though it's smaller than. 314 00:17:00.960 --> 00:17:04.839 Earth, okay, so large liquid less dens full of lighter elements, 315 00:17:05.119 --> 00:17:08.880 did they say anything about a solid inner core like Earth's. 316 00:17:09.119 --> 00:17:11.640 That's a really crucial detail from Staleler's paper, and it 317 00:17:11.640 --> 00:17:15.279 shows how careful science is. They did not explicitly rule 318 00:17:15.279 --> 00:17:18.599 out the possibility of a solid inner core. The authors 319 00:17:18.599 --> 00:17:22.160 themselves meticulously stated in the paper that the signal strength 320 00:17:22.160 --> 00:17:24.200 from the data they had at that time, and the 321 00:17:24.200 --> 00:17:27.759 specific types of seismic waves they could confidently analyze were 322 00:17:27.799 --> 00:17:31.880 simply not robust enough, not clear enough. They couldn't definitively 323 00:17:31.920 --> 00:17:35.200 identify the faint signals you'd expect from seismic waves crossing 324 00:17:35.240 --> 00:17:38.839 an intercore boundary. So it's an excellent first measurement, truly 325 00:17:38.839 --> 00:17:43.039 a monumental achievement, but they explicitly acknowledged its limitations and 326 00:17:43.160 --> 00:17:45.839 left room for further discoveries. It's at the stage, you know, 327 00:17:46.680 --> 00:17:49.559 waiting for more data or better techniques to perhaps see deeper. 328 00:17:49.799 --> 00:17:52.440 Right, And science is truly a journey, isn't it? Not 329 00:17:52.519 --> 00:17:56.920 just one destination. So while Staler's work was absolutely monumental, 330 00:17:56.960 --> 00:18:00.279 a groundbreaking first look, the story of Mars core or 331 00:18:00.319 --> 00:18:04.000 as you said, didn't stop there. Just recently, new even 332 00:18:04.079 --> 00:18:07.119 more refined results came out. This was from Hwixingbe and 333 00:18:07.240 --> 00:18:10.200 colleagues published in the journal Nature. And this took our 334 00:18:10.240 --> 00:18:12.759 understanding to a whole new level, didn't it. What did 335 00:18:12.799 --> 00:18:16.480 they uncover that was so significant building on that initial 336 00:18:16.519 --> 00:18:18.480 foundation laid by Staler's team. 337 00:18:18.839 --> 00:18:22.000 Yeah, this is a fantastic example of scientific progress in action. 338 00:18:22.079 --> 00:18:24.759 You see one study building directly on the previous one 339 00:18:24.920 --> 00:18:28.400 and also the power of persistent, clever data analysis. This 340 00:18:28.559 --> 00:18:32.359 latest study by Biling colleagues, they leveraged additional insight data 341 00:18:32.759 --> 00:18:35.960 data collected over a longer period after Staler's first analysis, 342 00:18:36.240 --> 00:18:38.319 So that meant a larger catalog of Mars quakes to 343 00:18:38.359 --> 00:18:41.680 work with, including some that were perhaps deeper or more energetic, 344 00:18:41.799 --> 00:18:45.759 sending clearer signals through the core. Okay, more data, more data, yes, 345 00:18:46.440 --> 00:18:50.200 But crucially they also employed some novel and highly sophisticated 346 00:18:50.279 --> 00:18:54.720 data analysis techniques, new ways of processing the signals. By 347 00:18:54.759 --> 00:18:58.319 carefully selecting specific types of seismic events, ones that happened 348 00:18:58.319 --> 00:19:01.440 at just the right distances from d site to maximize 349 00:19:01.480 --> 00:19:04.400 the chance of detecting faint reflections from deep within, and 350 00:19:04.440 --> 00:19:08.359 then expertly extracting an incredibly weak signal from what was 351 00:19:08.400 --> 00:19:12.279 often quite a lot of instrument noise, they managed something remarkable. 352 00:19:12.799 --> 00:19:15.799 It was like seismological detective work, filtering out all the 353 00:19:15.839 --> 00:19:19.079 background chatter to finally hear the planet's deepest whispers clearly. 354 00:19:19.200 --> 00:19:20.960 And what did those whispers tell them? What was the 355 00:19:21.039 --> 00:19:21.680 key finding? 356 00:19:21.799 --> 00:19:25.480 Their key finding was unambiguous. They identified the clear presence 357 00:19:25.519 --> 00:19:28.359 of a solid layer within the liquid Martian core. This 358 00:19:28.519 --> 00:19:31.480 wasn't just a subtle hint. It was the distinct solid 359 00:19:31.599 --> 00:19:34.559 inner core, and they even estimated its radius at approximately 360 00:19:34.759 --> 00:19:36.759 six hundred and ten kilometers. 361 00:19:36.200 --> 00:19:38.240 Six hundred and ten kilometers. How does that compare to 362 00:19:38.279 --> 00:19:39.720 the overall core size. 363 00:19:39.880 --> 00:19:42.799 Well, if the total core radius is around eighteen hundred kilometers, 364 00:19:43.039 --> 00:19:45.680 then six hundred and ten kilometers is a substantial fraction, 365 00:19:46.119 --> 00:19:49.079 about a third of the radius, or roughly fifteen percent 366 00:19:49.200 --> 00:19:53.039 of Mars's total radius is this solid inner core. This 367 00:19:53.079 --> 00:19:55.960 is a profound revision to our understanding. It shifts our 368 00:19:56.000 --> 00:19:59.200 model of Mars's interior from that simple, fully liquid core 369 00:19:59.319 --> 00:20:03.359 picture to a more complex, differentiated one, much more like 370 00:20:03.400 --> 00:20:04.160 Earth's structure. 371 00:20:04.240 --> 00:20:05.920 Okay, wow, so we thought it was just liquid and 372 00:20:05.960 --> 00:20:08.640 now we find this distinct solid part inside. That feels 373 00:20:08.680 --> 00:20:11.319 like a really big shift. What does this solid inner 374 00:20:11.359 --> 00:20:15.200 core actually mean for understanding Mars's history and crucially for 375 00:20:15.240 --> 00:20:17.920 that long loss magnetic field we talked about, Why is 376 00:20:17.960 --> 00:20:21.000 this particular detail solid inside liquid such a big deal? 377 00:20:21.000 --> 00:20:23.720 How does it connect to a planet's life support system? Well, 378 00:20:23.759 --> 00:20:27.079 what's truly profound here is the implication this discovery carries. 379 00:20:27.359 --> 00:20:30.319 It's huge. The very presence of a solid inner core 380 00:20:30.440 --> 00:20:35.440 tells us definitively that crystallization is happening. Solidification is taking 381 00:20:35.480 --> 00:20:39.160 place as the planet cools over geological time. This process 382 00:20:39.319 --> 00:20:42.400 where liquid metal slowly solidifies at the center and in 383 00:20:42.440 --> 00:20:45.759 doing so releases latent heat and lighter elements. This process 384 00:20:45.799 --> 00:20:48.319 is absolutely critical for a planet like Earth to generate 385 00:20:48.400 --> 00:20:51.759 and sustain its magnetic field for billions of years. It's 386 00:20:51.839 --> 00:20:54.119 essentially the engine that drives the planetary dynamo. 387 00:20:54.279 --> 00:20:57.440 Ah. Okay, so the solidifying process itself is the key. 388 00:20:57.599 --> 00:21:00.920 Yeah, exactly. To elaborate a bit on its magnificance, a 389 00:21:01.000 --> 00:21:03.680 core structure with both a solid inner part and a 390 00:21:03.720 --> 00:21:08.039 liquid outer layer is fundamentally much more like Earth's setup 391 00:21:08.759 --> 00:21:12.160 On Earth, It's precisely the temperature differences and the chemical 392 00:21:12.200 --> 00:21:14.920 change is happening at that boundary between the solid inner 393 00:21:14.960 --> 00:21:18.400 core and the swirling liquid outer core, plus the heat 394 00:21:18.440 --> 00:21:21.319 flowing out into the surrounding mantle that drive the vigorous 395 00:21:21.359 --> 00:21:24.559 convection currents in that liquid outer layer. As the core 396 00:21:24.640 --> 00:21:29.079 cools iron crystallizes onto the inner core, this process releases lighter, 397 00:21:29.160 --> 00:21:31.920 more buoyant elements into the liquid outer core, and these 398 00:21:31.960 --> 00:21:35.720 lighter fluids than rise, creating convection like a lava lamp effect, 399 00:21:35.799 --> 00:21:39.279 but with molten metal. These convection currents, this organized movement 400 00:21:39.279 --> 00:21:43.079 of molten electrically conducting metal, coupled with the planet's spin, 401 00:21:43.440 --> 00:21:45.759