1 00:00:03,200 --> 00:00:06,100 ROWE: Our neighbor, Mars, fascinates us. 2 00:00:06,166 --> 00:00:09,500 It's a planet that is similar to Earth, 3 00:00:10,567 --> 00:00:12,867 but with some big differences. 4 00:00:12,967 --> 00:00:16,567 Mars is rusty, dusty, frigid, and frozen. 5 00:00:16,567 --> 00:00:19,000 It ain't the kind of place you want to raise your kids. 6 00:00:21,166 --> 00:00:23,567 ROWE: Past missions suggest that Mars 7 00:00:23,567 --> 00:00:25,266 was once a very different world. 8 00:00:26,667 --> 00:00:29,100 The Mars we see today has completely changed 9 00:00:29,166 --> 00:00:30,000 from the Mars of a few billion years ago. 10 00:00:30,000 --> 00:00:31,000 from the Mars of a few billion years ago. 11 00:00:32,066 --> 00:00:34,000 RADEBAUGH: If I had a time machine to visit Mars 12 00:00:34,066 --> 00:00:36,166 in the past, I would go in an instant. 13 00:00:37,400 --> 00:00:39,400 ROWE: Without a time machine to explore 14 00:00:39,467 --> 00:00:42,667 ancient Mars, we employ a team of high-tech 15 00:00:42,667 --> 00:00:45,066 robot investigators. 16 00:00:47,200 --> 00:00:48,667 We've got an entire fleet 17 00:00:48,767 --> 00:00:50,767 of robotic spacecraft exploring the planet. 18 00:00:52,100 --> 00:00:56,567 ROWE: Working together, they dig into Mars's past to answer 19 00:00:56,567 --> 00:00:58,467 the ultimate question -- 20 00:00:58,467 --> 00:01:00,000 did Mars once have life? 21 00:01:00,000 --> 00:01:01,000 did Mars once have life? 22 00:01:17,600 --> 00:01:19,300 February 2021. 23 00:01:21,066 --> 00:01:25,300 The newest robot investigator speeds towards Mars, 24 00:01:25,367 --> 00:01:29,066 the most advanced rover NASA has ever sent to 25 00:01:29,066 --> 00:01:30,000 another world. 26 00:01:30,000 --> 00:01:30,367 another world. 27 00:01:30,467 --> 00:01:33,667 This is Perseverance. 28 00:01:33,667 --> 00:01:35,567 The goal of the Perseverance mission is 29 00:01:35,667 --> 00:01:38,867 to look for signs of past life on Mars. 30 00:01:38,967 --> 00:01:40,900 ROWE: First, it must navigate safely 31 00:01:41,000 --> 00:01:42,367 to the surface of the planet. 32 00:01:45,100 --> 00:01:47,367 LANZA: Every landing has its own dangers. 33 00:01:47,367 --> 00:01:49,967 Because the rover must be autonomous, 34 00:01:49,967 --> 00:01:53,166 it has to do everything without our help. 35 00:01:54,400 --> 00:01:57,800 ROWE: Perseverance enters Mars's thin atmosphere at 36 00:01:57,867 --> 00:02:00,000 close to 12,500 miles an hour... 37 00:02:00,000 --> 00:02:00,367 close to 12,500 miles an hour... 38 00:02:05,166 --> 00:02:07,400 and deploys a parachute. 39 00:02:17,667 --> 00:02:19,667 ROWE: The parachute slows Perseverance 40 00:02:19,667 --> 00:02:21,700 to 200 miles per hour. 41 00:02:29,967 --> 00:02:30,000 ROWE: Still too fast to land safely. 42 00:02:30,000 --> 00:02:32,166 ROWE: Still too fast to land safely. 43 00:02:34,467 --> 00:02:36,467 To prevent a violent impact, 44 00:02:36,467 --> 00:02:39,266 the rover must activate the sky crane. 45 00:02:40,667 --> 00:02:43,166 When I first saw the sky crane concept, 46 00:02:43,266 --> 00:02:46,367 I thought, hm, the engineers are kind of losing it. 47 00:02:46,467 --> 00:02:49,467 It seemed to me like a really crazy idea. 48 00:02:54,300 --> 00:02:57,000 ROWE: Perseverance activates its jetpack. 49 00:03:00,667 --> 00:03:04,166 Retro rockets slow the lander's descent to a crawl. 50 00:03:12,100 --> 00:03:15,367 Then, 66 feet above the surface, 51 00:03:15,467 --> 00:03:17,667 the sky crane uses cables to 52 00:03:17,767 --> 00:03:19,900 gently lower the rover to the ground. 53 00:03:37,266 --> 00:03:39,767 ROWE: Step one in the search for Martian life, 54 00:03:39,867 --> 00:03:42,300 find evidence of liquid water. 55 00:03:43,967 --> 00:03:46,900 A good place to start is the 28-mile-wide 56 00:03:47,000 --> 00:03:49,100 Jezero Crater. 57 00:03:49,166 --> 00:03:52,800 Perseverance has landed in a crater called Jezero, and this 58 00:03:52,867 --> 00:03:55,467 looks like a place where there was liquid water in its past. 59 00:03:55,567 --> 00:03:57,266 And the reason we think this is because 60 00:03:57,367 --> 00:04:00,000 there's this beautiful delta deposit right in the middle. 61 00:04:00,000 --> 00:04:00,867 there's this beautiful delta deposit right in the middle. 62 00:04:01,867 --> 00:04:05,266 ROWE: Perseverance turns its high-resolution cameras 63 00:04:05,266 --> 00:04:07,967 onto a cliff side in the crater 64 00:04:10,166 --> 00:04:14,800 and discovers giant five-foot boulders near the top. 65 00:04:14,867 --> 00:04:17,066 A clue to how they got there may 66 00:04:17,066 --> 00:04:19,900 come from the first probes to visit Mars. 67 00:04:21,367 --> 00:04:23,567 One of the very first things we noticed about Mars 68 00:04:23,567 --> 00:04:24,767 when we first sent probes there 69 00:04:24,867 --> 00:04:28,300 with Mariner and Viking was that there were these huge 70 00:04:28,367 --> 00:04:30,000 channels on the surface of Mars. 71 00:04:30,000 --> 00:04:30,200 channels on the surface of Mars. 72 00:04:31,467 --> 00:04:33,867 Looking at these enormous landforms, 73 00:04:33,967 --> 00:04:36,567 we realized that, in some places on Mars, 74 00:04:36,667 --> 00:04:39,467 there may have been enormous floods, 75 00:04:39,567 --> 00:04:41,867 bigger than almost anything we'd ever seen on Earth. 76 00:04:43,367 --> 00:04:47,100 ROWE: Flash floods on Earth cause similar rock formations to 77 00:04:47,166 --> 00:04:51,700 those found in Jezero Crater, suggesting that powerful, 78 00:04:51,767 --> 00:04:55,300 fast-moving torrents carried the giant rocks found by 79 00:04:55,367 --> 00:04:59,000 Perseverance and dumped them at the top of the cliff. 80 00:05:05,000 --> 00:05:08,100 Perseverance is just one member of an elite team 81 00:05:08,166 --> 00:05:10,600 of robots patrolling the ground 82 00:05:10,667 --> 00:05:12,166 and spying from the air. 83 00:05:14,166 --> 00:05:17,467 The Mars Atmospheric and Volatile Evolution 84 00:05:17,467 --> 00:05:21,900 Orbiter, or MAVEN, investigates Mars's atmosphere. 85 00:05:22,000 --> 00:05:25,166 MAVEN smells really good. 86 00:05:25,266 --> 00:05:27,300 It smells the Martian atmosphere. 87 00:05:27,367 --> 00:05:29,367 It tells us what the Martian atmosphere 88 00:05:29,367 --> 00:05:30,000 is made of all across the planet. 89 00:05:30,000 --> 00:05:32,200 is made of all across the planet. 90 00:05:32,266 --> 00:05:35,767 ROWE: Then there's the MARS Reconnaissance Orbiter. 91 00:05:35,867 --> 00:05:38,000 As its name suggests, an orbiting spacecraft 92 00:05:38,066 --> 00:05:40,166 that images surface of MARS. 93 00:05:40,266 --> 00:05:42,667 ROWE: The M.R.O.'s high-resolution cameras 94 00:05:42,667 --> 00:05:46,767 can identify surface features as small as a kitchen table. 95 00:05:49,000 --> 00:05:50,900 And joining the orbital crew, 96 00:05:51,000 --> 00:05:55,166 The European Space Agency's MARS Express. 97 00:05:55,266 --> 00:05:57,200 With its ground-penetrating radar, 98 00:05:57,266 --> 00:06:00,000 it searches for evidence of subsurface water. 99 00:06:00,000 --> 00:06:00,367 it searches for evidence of subsurface water. 100 00:06:03,100 --> 00:06:07,100 And, on the Martian surface, a group of high-tech landers 101 00:06:07,166 --> 00:06:08,700 take a closer look, 102 00:06:08,767 --> 00:06:12,467 including the team's quake specialist, Insight. 103 00:06:12,567 --> 00:06:15,367 This lander probes deep beneath the surface 104 00:06:15,367 --> 00:06:21,200 to discover how Mars's interior shapes the planet over time. 105 00:06:21,266 --> 00:06:24,367 The Insight lander on MARS has a really simple concept. 106 00:06:24,367 --> 00:06:26,767 You land a spacecraft on the surface anywhere 107 00:06:26,767 --> 00:06:29,667 on Mars and then just listen for Mars quakes. 108 00:06:30,867 --> 00:06:34,867 ROWE: And 300 miles south of Insight, veteran rover, 109 00:06:34,967 --> 00:06:38,300 Curiosity is exploring the Gale Crater. 110 00:06:39,367 --> 00:06:43,066 The mission goal for Curiosity is to look for habitability, 111 00:06:43,066 --> 00:06:44,567 and so that's environments 112 00:06:44,567 --> 00:06:46,800 in which life as we currently understand it could exist. 113 00:06:49,867 --> 00:06:53,100 ROWE: Curiosity searches for evidence of calmer, 114 00:06:53,166 --> 00:06:56,300 more permanent water in Mars's past. 115 00:06:57,767 --> 00:07:00,000 Investigating layers of rock at the base of Mount Sharp, 116 00:07:00,000 --> 00:07:01,767 Investigating layers of rock at the base of Mount Sharp, 117 00:07:01,767 --> 00:07:05,467 a three-mile-high mountain in the middle of the crater. 118 00:07:05,467 --> 00:07:08,500 RADEBAUGH: The rock layers start way up at the top of 119 00:07:08,567 --> 00:07:11,100 Mount Sharp, and they move progressively downward, 120 00:07:11,166 --> 00:07:13,400 and basically, we're going backwards in time until we get 121 00:07:13,467 --> 00:07:16,967 to the very bottom, and the very bottom is actually really old. 122 00:07:18,000 --> 00:07:21,166 ROWE: Mount Sharp was built over millions of years, 123 00:07:21,166 --> 00:07:22,767 layer by layer. 124 00:07:24,000 --> 00:07:25,166 The rocks at the base of 125 00:07:25,166 --> 00:07:29,300 the mountain date to 3.5 billion years ago. 126 00:07:29,367 --> 00:07:30,000 These rocks are made up of very fine layers 127 00:07:30,000 --> 00:07:32,467 These rocks are made up of very fine layers 128 00:07:32,567 --> 00:07:36,500 and could only have been formed in calm water. 129 00:07:36,567 --> 00:07:39,700 These sedimentary layers were formed when Gale Crater was 130 00:07:39,767 --> 00:07:41,667 a lake, and sediment settles out, and you get these 131 00:07:41,767 --> 00:07:42,734 beautiful layers. 132 00:07:45,567 --> 00:07:48,600 ROWE: Curiosity explores more of Gale Crater 133 00:07:50,166 --> 00:07:55,166 and discovers rounded pebbles, like those we find on Earth. 134 00:07:55,266 --> 00:07:57,867 When you see a rounded pebble on Earth, 135 00:07:57,867 --> 00:08:00,000 you know that that got rounded in a river channel. 136 00:08:00,000 --> 00:08:00,667 you know that that got rounded in a river channel. 137 00:08:00,667 --> 00:08:02,000 Some of them used to be angular, 138 00:08:02,100 --> 00:08:04,600 but their angles all got knocked off by being rolled 139 00:08:04,667 --> 00:08:06,500 and rounded and moved by water. 140 00:08:08,600 --> 00:08:12,367 So we're very excited when we see rounded pebbles on Mars. 141 00:08:14,100 --> 00:08:16,500 ROWE: The rock layers and rounded pebbles 142 00:08:16,567 --> 00:08:19,500 tell us that over three billion years ago, 143 00:08:19,567 --> 00:08:23,100 Gale Crater was a lake fed by rivers. 144 00:08:24,100 --> 00:08:26,266 LANZA: It was so exciting to understand liquid 145 00:08:26,266 --> 00:08:27,900 water in the context of Gale Crater, 146 00:08:28,000 --> 00:08:30,000 where Curiosity is, and that's just because what we see there 147 00:08:30,000 --> 00:08:31,200 where Curiosity is, and that's just because what we see there 148 00:08:31,266 --> 00:08:32,867 is this long-lasting, 149 00:08:32,967 --> 00:08:35,367 freshwater lake, and that's not like anything else 150 00:08:35,367 --> 00:08:37,600 we've seen on Mars before. 151 00:08:37,667 --> 00:08:39,667 RADEBAUGH: Imagine standing on the edge 152 00:08:39,767 --> 00:08:41,667 and looking out at this big, beautiful 153 00:08:41,767 --> 00:08:45,400 blue lake shining in the distance. 154 00:08:45,467 --> 00:08:47,667 What if there were just a whole array 155 00:08:47,767 --> 00:08:49,900 of craters filled with water off in the distance? 156 00:08:50,000 --> 00:08:51,467 It would be so beautiful. 157 00:08:52,867 --> 00:08:55,600 ROWE: And a good place for life to evolve. 158 00:08:58,967 --> 00:09:00,000 PLAIT: Mars was a nice place. 159 00:09:00,000 --> 00:09:00,667 PLAIT: Mars was a nice place. 160 00:09:00,767 --> 00:09:03,066 It was probably more like Earth is now. 161 00:09:03,066 --> 00:09:06,000 So it wouldn't surprise me if it's supported life. 162 00:09:06,100 --> 00:09:07,667 We're talking microbial life. 163 00:09:07,767 --> 00:09:09,800 We're not talking, you know, Marvin the Martian or anything 164 00:09:09,867 --> 00:09:13,467 like that, but life still is life. 165 00:09:17,100 --> 00:09:20,367 ROWE: Any water Mars once had 166 00:09:20,367 --> 00:09:21,667 is now long gone. 167 00:09:23,400 --> 00:09:27,500 To stay liquid, water needs warmth 168 00:09:27,567 --> 00:09:29,367 and atmospheric pressure. 169 00:09:30,767 --> 00:09:34,000 So, hundreds of miles above the planet, 170 00:09:34,066 --> 00:09:38,567 orbiting members of the team investigate the mystery of 171 00:09:38,667 --> 00:09:41,467 Mars's missing atmosphere. 172 00:09:51,200 --> 00:09:52,400 ROWE: While robot team members, 173 00:09:52,467 --> 00:09:56,767 Curiosity and Perseverance, work the Martian surface, 174 00:09:56,767 --> 00:09:59,867 eight probes orbit the planet, 175 00:10:00,867 --> 00:10:05,266 searching for clues about Mars's ancient wet history. 176 00:10:10,000 --> 00:10:12,266 Leading the pack is MAVEN. 177 00:10:12,266 --> 00:10:12,448 Its mission -- 178 00:10:12,448 --> 00:10:13,700 Its mission -- 179 00:10:13,767 --> 00:10:18,400 to solve the mystery of Mars's lost atmosphere. 180 00:10:18,467 --> 00:10:21,367 Today, the atmosphere of Mars is incredibly thin. 181 00:10:21,467 --> 00:10:23,900 It's only about 1 percent the atmospheric pressure 182 00:10:24,000 --> 00:10:25,700 here on Earth. 183 00:10:25,767 --> 00:10:26,967 ROWE: The weight of gas in 184 00:10:26,967 --> 00:10:30,100 an atmosphere pressing down creates pressure, 185 00:10:31,367 --> 00:10:35,800 and that pressure dictates at what temperature liquids boil. 186 00:10:40,667 --> 00:10:42,448 Here on Earth at sea level, 187 00:10:42,448 --> 00:10:42,467 Here on Earth at sea level, 188 00:10:42,567 --> 00:10:46,000 the boiling point of water is about 212 degrees Fahrenheit, 189 00:10:46,066 --> 00:10:48,767 but up here in the mountains near Denver, 190 00:10:48,867 --> 00:10:50,266 we're at a higher altitude. 191 00:10:50,367 --> 00:10:53,266 We've got a lot less atmosphere pressing down on us, 192 00:10:53,367 --> 00:10:55,467 and so it boils at a lower temperature. 193 00:10:55,567 --> 00:10:56,967 Let's put a thermometer in here. 194 00:11:00,900 --> 00:11:04,367 There's 200 even right there. 195 00:11:04,367 --> 00:11:07,800 That's a lot cooler boiling temperature than at sea level. 196 00:11:07,867 --> 00:11:11,900 Now, if you go to even higher altitudes at 100,000 feet 197 00:11:12,000 --> 00:11:12,448 here on the Earth, the air pressure is about 198 00:11:12,448 --> 00:11:13,867 here on the Earth, the air pressure is about 199 00:11:13,967 --> 00:11:15,567 what it is on the surface of Mars. 200 00:11:15,567 --> 00:11:16,900 On the surface of Mars, 201 00:11:17,000 --> 00:11:19,567 water will boil effectively at ambient temperature. 202 00:11:19,667 --> 00:11:21,166 We wouldn't have to heat it at all. 203 00:11:21,166 --> 00:11:22,667 You just put a glass of water on 204 00:11:22,667 --> 00:11:25,400 the surface of Mars, and it'll boil and disappear away. 205 00:11:27,000 --> 00:11:31,667 ROWE: But the planet's surface tells us that dry Mars 206 00:11:31,667 --> 00:11:33,867 was very different in the past. 207 00:11:33,867 --> 00:11:36,967 THALLER: When you see things like river channels 208 00:11:36,967 --> 00:11:39,266 that probably took millions of years to carve, 209 00:11:39,367 --> 00:11:42,066 that gives you an idea that the atmosphere was once very, 210 00:11:42,066 --> 00:11:42,448 very different. 211 00:11:42,448 --> 00:11:43,300 very different. 212 00:11:43,367 --> 00:11:45,600 It had to be thick to allow 213 00:11:45,667 --> 00:11:47,467 liquid water to exist on the surface. 214 00:11:49,767 --> 00:11:52,066 ROWE: To investigate what happened to that thick 215 00:11:52,066 --> 00:11:53,567 Martian atmosphere, 216 00:11:54,867 --> 00:11:57,967 MAVEN swings into action. 217 00:11:57,967 --> 00:11:59,100 THALLER: One of the main objectives of 218 00:11:59,166 --> 00:12:02,867 the MAVEN mission was to measure argon on Mars. 219 00:12:02,867 --> 00:12:05,600 There are slightly different kinds of argon. 220 00:12:05,667 --> 00:12:06,867 We call these isotopes, 221 00:12:06,967 --> 00:12:08,867 and basically, it means that there's just 222 00:12:08,867 --> 00:12:10,900 an extra neutron in the nucleus. 223 00:12:11,000 --> 00:12:12,448 So there's one type of argon that's just a little bit 224 00:12:12,448 --> 00:12:13,066 So there's one type of argon that's just a little bit 225 00:12:13,066 --> 00:12:16,266 heavier than the other type just by one neutron, 226 00:12:16,367 --> 00:12:17,367 not by much. 227 00:12:19,100 --> 00:12:20,867 ROWE: High up in the atmosphere, 228 00:12:20,867 --> 00:12:25,100 MAVEN tag teams with Curiosity down on the surface. 229 00:12:26,266 --> 00:12:29,800 They measure the amount of light and heavy argon. 230 00:12:31,567 --> 00:12:33,266 THALLER: Now, what's special about argon? 231 00:12:33,367 --> 00:12:35,467 Well, argon is not very reactive, 232 00:12:35,467 --> 00:12:37,100 doesn't really get involved in a lot of chemistry. 233 00:12:37,166 --> 00:12:39,867 It's not really absorbed by rocks, doesn't change much. 234 00:12:39,967 --> 00:12:41,767 Once it's emitted, it kind of hangs around. 235 00:12:42,867 --> 00:12:44,767 And that makes it very valuable, because it means it 236 00:12:44,767 --> 00:12:47,300 stays in pretty much its pristine, pure form 237 00:12:47,367 --> 00:12:48,400 through the history of the planet. 238 00:12:50,567 --> 00:12:52,300 ROWE: When the researchers back on Earth 239 00:12:52,367 --> 00:12:55,767 compare the readings from the two Martian robots, 240 00:12:55,767 --> 00:12:57,867 something doesn't add up. 241 00:12:57,867 --> 00:12:59,467 SUTTER: With Curiosity 242 00:12:59,467 --> 00:13:02,467 on the surface, we see a certain ratio of heavy 243 00:13:02,467 --> 00:13:03,867 to light argon. 244 00:13:03,967 --> 00:13:07,667 And we expect that same ratio to exist up in the atmosphere, 245 00:13:07,767 --> 00:13:11,567 but with MAVEN, we see a different ratio. 246 00:13:11,567 --> 00:13:12,448 We see far less of the light argon 247 00:13:12,448 --> 00:13:14,266 We see far less of the light argon 248 00:13:14,266 --> 00:13:15,800 than we do down on the surface. 249 00:13:15,867 --> 00:13:18,567 So something is messing with that ratio. 250 00:13:20,467 --> 00:13:23,000 The only thing we can think of that can mess with 251 00:13:23,066 --> 00:13:26,867 the ratio of argon is the solar wind from the sun. 252 00:13:32,266 --> 00:13:34,100 ROWE: The sun spits out a constant 253 00:13:34,166 --> 00:13:37,500 stream of particles called the solar wind. 254 00:13:37,567 --> 00:13:40,667 The wind is over a million degrees Fahrenheit 255 00:13:40,767 --> 00:13:42,448 and travels at up to 500 miles a second. 256 00:13:42,448 --> 00:13:43,400 and travels at up to 500 miles a second. 257 00:13:45,266 --> 00:13:47,667 When it reaches Mars, it strips away 258 00:13:47,767 --> 00:13:50,500 gases high up in the atmosphere. 259 00:13:50,567 --> 00:13:52,100 The lighter the argon is, 260 00:13:52,166 --> 00:13:54,467 the higher it gets up into the atmosphere. 261 00:13:54,567 --> 00:13:55,867 That means that that gets blown 262 00:13:55,867 --> 00:13:58,567 away preferentially by the solar wind. 263 00:13:58,667 --> 00:14:00,367 The heavier argon stays a little bit 264 00:14:00,467 --> 00:14:02,700 lower down and a little bit more protected. 265 00:14:02,767 --> 00:14:05,867 So when you look at the ratio in the atmosphere of the light 266 00:14:05,867 --> 00:14:07,400 argon to the heavy argon, 267 00:14:07,467 --> 00:14:10,567 it gives you an idea of how much has been lost over time. 268 00:14:13,100 --> 00:14:15,867 ROWE: MAVEN's data reveals that Mars 269 00:14:15,867 --> 00:14:18,700 has lost 65 percent of the argon 270 00:14:18,767 --> 00:14:22,467 from its atmosphere, and the solar wind continues to 271 00:14:22,567 --> 00:14:23,767 bombard the planet. 272 00:14:24,800 --> 00:14:27,400 The atmosphere of Mars is being stripped away by 273 00:14:27,467 --> 00:14:31,166 solar radiation by a quarter of a pound every second. 274 00:14:32,567 --> 00:14:36,266 ROWE: This rate of atmospheric loss leads to one conclusion. 275 00:14:37,367 --> 00:14:41,300 The solar wind robbed Mars of its once 276 00:14:41,367 --> 00:14:42,448 thick atmosphere, and with it, the planet's water. 277 00:14:42,448 --> 00:14:45,400 thick atmosphere, and with it, the planet's water. 278 00:14:46,667 --> 00:14:48,000 But a question remains. 279 00:14:49,767 --> 00:14:52,266 RADEBAUGH: We know that Mars's atmosphere was much thicker 280 00:14:52,367 --> 00:14:54,867 in the past, really similar to Earth's. 281 00:14:54,967 --> 00:14:57,000 So why is it that Earth's atmosphere 282 00:14:57,100 --> 00:14:58,200 is still mostly there, 283 00:14:58,266 --> 00:15:00,400 whereas Mars's has been stripped away? 284 00:15:02,300 --> 00:15:04,000 ROWE: Earth has a protector, 285 00:15:05,100 --> 00:15:08,166 a magnetic field that shields our atmosphere 286 00:15:08,266 --> 00:15:10,367 from the ravages of the solar wind. 287 00:15:11,800 --> 00:15:12,448 RADEBAUGH: The Earth's magnetic field is generated 288 00:15:12,448 --> 00:15:13,867 RADEBAUGH: The Earth's magnetic field is generated 289 00:15:13,967 --> 00:15:15,100 deep in the core. 290 00:15:15,166 --> 00:15:16,266 There are actually two cores. 291 00:15:16,266 --> 00:15:19,300 There's a solid inner core and a liquid outer core, 292 00:15:19,367 --> 00:15:21,200 and that solid inner core is delivering 293 00:15:21,266 --> 00:15:24,100 heat to the outer core, and as it does this, 294 00:15:24,166 --> 00:15:25,767 it causes convection currents. 295 00:15:26,900 --> 00:15:31,100 The convection currents pull electric charges around 296 00:15:31,166 --> 00:15:35,066 and cause magnetic fields to fold in on themselves. 297 00:15:35,066 --> 00:15:38,367 We call this a dynamo, and this is what's capable 298 00:15:38,467 --> 00:15:40,767 of generating powerful magnetic fields. 299 00:15:43,166 --> 00:15:47,000 ROWE: The magnetic field forms a protective bubble around Earth 300 00:15:47,100 --> 00:15:50,300 that deflects the solar wind away from our planet. 301 00:15:52,166 --> 00:15:56,667 Did Mars once have its own force field? 302 00:15:56,667 --> 00:15:58,700 To find out, 303 00:15:58,767 --> 00:16:02,100 MAVEN hones in on some ancient volcanic rocks 304 00:16:02,166 --> 00:16:03,867 on the Martian surface. 305 00:16:05,667 --> 00:16:08,700 It detects faint magnetic traces. 306 00:16:11,800 --> 00:16:12,448 RADEBAUGH: Martian rocks, typically in the form of lava, 307 00:16:12,448 --> 00:16:14,367 RADEBAUGH: Martian rocks, typically in the form of lava, 308 00:16:14,367 --> 00:16:17,500 become magnetic when the iron particles 309 00:16:17,567 --> 00:16:20,467 in the rocks become aligned with the magnetic field 310 00:16:20,567 --> 00:16:23,300 that's active at the time, and then as the rock cools, 311 00:16:23,367 --> 00:16:25,000 those things get frozen in place. 312 00:16:25,066 --> 00:16:27,500 That sort of freezes a magnetic field into place. 313 00:16:27,567 --> 00:16:31,667 What that tells us, that these volcanic materials 314 00:16:31,667 --> 00:16:32,800 were erupted at a time 315 00:16:32,867 --> 00:16:35,066 where there was a magnetic field present on Mars. 316 00:16:37,200 --> 00:16:41,000 ROWE: Dating the magnetized rocks reveals that Mars had 317 00:16:41,100 --> 00:16:42,448 an active magnetic field for almost a billion years. 318 00:16:42,448 --> 00:16:45,066 an active magnetic field for almost a billion years. 319 00:16:47,266 --> 00:16:50,266 SUTTER: This means that the atmosphere of 320 00:16:50,367 --> 00:16:54,100 Mars was protected for those billion years, 321 00:16:54,166 --> 00:16:56,100 and if the atmosphere was protected, 322 00:16:56,166 --> 00:16:58,000 the liquid water was protected. 323 00:16:58,066 --> 00:17:00,567 And if that liquid water was a home for life, 324 00:17:00,567 --> 00:17:02,667 then that life was protected. 325 00:17:04,867 --> 00:17:08,800 ROWE: But something happened to bring Mars's force field down. 326 00:17:11,367 --> 00:17:12,448 To discover what, our quake specialist, Insight, is ready to 327 00:17:12,448 --> 00:17:16,000 To discover what, our quake specialist, Insight, is ready to 328 00:17:16,100 --> 00:17:19,300 burst open the mystery of the planet's lost 329 00:17:19,367 --> 00:17:20,567 protective shield. 330 00:17:31,367 --> 00:17:34,367 ROWE: Robots are rewriting the history of Mars. 331 00:17:35,767 --> 00:17:38,266 They found that Mars once had 332 00:17:38,266 --> 00:17:41,367 a magnetic field that protected its atmosphere. 333 00:17:43,100 --> 00:17:45,767 Now, another team member, Insight, 334 00:17:45,867 --> 00:17:47,767 probes the planet's interior. 335 00:17:48,900 --> 00:17:51,867 Its mission -- to discover if the secret of 336 00:17:51,867 --> 00:17:53,175 the planet's lost magnetic field lies 337 00:17:53,175 --> 00:17:55,066 the planet's lost magnetic field lies 338 00:17:55,066 --> 00:17:57,800 beneath the Martian surface. 339 00:17:57,867 --> 00:18:00,900 Insight was developed with the world's best seismometer. 340 00:18:01,000 --> 00:18:03,367 This is a really precise, really delicate, 341 00:18:03,467 --> 00:18:05,867 really sensitive instrument, and it just was placed on 342 00:18:05,967 --> 00:18:07,300 the surface and started listening. 343 00:18:09,567 --> 00:18:10,800 ROWE: 2021. 344 00:18:11,867 --> 00:18:16,900 Insight listens for seismic vibrations, called Mars quakes, 345 00:18:17,000 --> 00:18:19,667 as they travel through the planet's interior. 346 00:18:19,767 --> 00:18:22,367 PLAIT: It's detected quite a few Mars quakes, 347 00:18:22,467 --> 00:18:23,175 but these were very small, 348 00:18:23,175 --> 00:18:24,000 but these were very small, 349 00:18:24,066 --> 00:18:26,900 but then it detected two much larger ones. 350 00:18:31,066 --> 00:18:32,200 And these were interesting. 351 00:18:32,266 --> 00:18:34,767 Not only were they more powerful, but they were coming 352 00:18:34,767 --> 00:18:37,266 from the direction of Cerberus Fossae, 353 00:18:37,266 --> 00:18:39,500 which is a very interesting region on Mars. 354 00:18:40,667 --> 00:18:44,367 ROWE: The magnitude 3.1 and 3.3 quakes 355 00:18:44,367 --> 00:18:46,667 came from Cerberus Fossae, 356 00:18:46,667 --> 00:18:51,567 a series of trenches that stretched for 750 miles across 357 00:18:51,567 --> 00:18:53,175 the Martian surface. 358 00:18:53,175 --> 00:18:53,200 the Martian surface. 359 00:18:53,266 --> 00:18:56,800 Some fissures cut through impact craters that 360 00:18:56,867 --> 00:18:58,767 are only a few million years old. 361 00:19:00,300 --> 00:19:03,000 This means Cerberus Fossae 362 00:19:03,100 --> 00:19:04,567 must be younger. 363 00:19:07,567 --> 00:19:10,800 Insight teams up with the Mars Reconnaissance Orbiter, 364 00:19:10,867 --> 00:19:14,000 flying hundreds of miles above. 365 00:19:14,100 --> 00:19:15,967 This eye in the sky 366 00:19:15,967 --> 00:19:18,400 spots an ancient lava flow, 367 00:19:18,467 --> 00:19:21,000 spreading out over a three mile area. 368 00:19:21,066 --> 00:19:23,175 Dating of the flow reveals that it's recent. 369 00:19:23,175 --> 00:19:25,100 Dating of the flow reveals that it's recent. 370 00:19:26,600 --> 00:19:28,767 The Mars Reconnaissance Orbiter spotted, 371 00:19:28,867 --> 00:19:30,667 in the Cerberus Fossae region, 372 00:19:30,767 --> 00:19:35,166 some lavas that appear to be about 50,000 years old. 373 00:19:35,266 --> 00:19:37,500 This is crazy young for Mars. 374 00:19:37,567 --> 00:19:40,500 Mars has been around for billions of years. 375 00:19:40,567 --> 00:19:42,667 50,000 years is nothing. 376 00:19:42,667 --> 00:19:45,066 Humans were around on Earth that long ago. 377 00:19:45,066 --> 00:19:47,000 So this is really recent. 378 00:19:47,100 --> 00:19:50,100 RADEBAUGH: Based on the fact that we had 379 00:19:50,166 --> 00:19:53,175 these two Mars quakes recently, plus the evidence of 380 00:19:53,175 --> 00:19:53,500 these two Mars quakes recently, plus the evidence of 381 00:19:53,567 --> 00:19:56,066 the volcanic eruption just 50,000 years ago, 382 00:19:56,066 --> 00:19:59,567 I mean, now we cannot say that Mars is dead. 383 00:19:59,567 --> 00:20:02,667 We have to say Mars is active. 384 00:20:02,767 --> 00:20:05,700 ROWE: A volcanically active Mars 385 00:20:05,767 --> 00:20:10,400 suggests its interior may still be warm -- if it is, 386 00:20:10,467 --> 00:20:14,367 why did the planet's magnetic field die? 387 00:20:14,367 --> 00:20:17,967 Insight probes deep into the interior of 388 00:20:17,967 --> 00:20:22,567 the Red Planet using vibrations from small Mars quakes. 389 00:20:24,100 --> 00:20:26,967 Insight uses these to kind of construct what the interior of 390 00:20:26,967 --> 00:20:28,266 Mars was like, 391 00:20:28,367 --> 00:20:30,867 because these waves bounce off different layers 392 00:20:30,967 --> 00:20:33,367 inside the interior of Mars in different ways. 393 00:20:34,467 --> 00:20:38,166 ROWE: Insight's seismometer builds a picture of Mars 394 00:20:38,266 --> 00:20:42,367 by completely redrawing the map of the interior of the planet. 395 00:20:44,166 --> 00:20:45,700 RADEBAUGH: It turns out the crust is thinner 396 00:20:45,767 --> 00:20:49,900 than we thought -- it's only 12 to 23 miles thick. 397 00:20:50,000 --> 00:20:53,175 So there's this whole picture of Mars that is unfolding in 398 00:20:53,175 --> 00:20:53,767 So there's this whole picture of Mars that is unfolding in 399 00:20:53,867 --> 00:20:55,767 front of us that is vastly different 400 00:20:55,867 --> 00:20:57,266 than we ever predicted. 401 00:20:58,567 --> 00:21:02,100 ROWE: Insight's new and improved layout of Mars reveals 402 00:21:02,166 --> 00:21:08,467 a 969-mile-deep mantle surrounding a metal-rich core. 403 00:21:10,200 --> 00:21:13,500 New analysis of data from Insight reveals the size of 404 00:21:13,567 --> 00:21:15,600 the core of Mars, and we haven't had this before. 405 00:21:15,667 --> 00:21:16,567 It's so exciting. 406 00:21:16,667 --> 00:21:19,767 It's about 1,100 miles in radius. 407 00:21:19,867 --> 00:21:22,367 This is a little more than half the radius of the body, 408 00:21:22,367 --> 00:21:23,175 which is pretty big, and is much bigger than we expected 409 00:21:23,175 --> 00:21:25,400 which is pretty big, and is much bigger than we expected 410 00:21:25,467 --> 00:21:27,767 for the size of the core of Mars. 411 00:21:28,900 --> 00:21:30,767 ROWE: Mars's larger core 412 00:21:30,867 --> 00:21:33,867 makes up about a quarter of the planet's mass. 413 00:21:33,967 --> 00:21:35,567 And Insight's journey to 414 00:21:35,667 --> 00:21:39,000 the center of Mars reveals another surprise. 415 00:21:40,166 --> 00:21:42,166 LANZA: We have always thought that the core of Mars 416 00:21:42,166 --> 00:21:45,967 was long since solidified and wasn't warm at all. 417 00:21:45,967 --> 00:21:48,600 And Insight is now showing us that actually, 418 00:21:48,667 --> 00:21:51,467 part of the core is probably still molten, 419 00:21:51,467 --> 00:21:52,667 which is shocking. 420 00:21:54,767 --> 00:21:57,600 There's a liquid core at Mars. I mean, this is crazy. 421 00:22:00,467 --> 00:22:02,700 ROWE: Data from past missions may help 422 00:22:02,767 --> 00:22:06,900 explain why Mars's core is still liquid. 423 00:22:07,000 --> 00:22:11,266 Scientists discovered high levels of sulfur in the crust. 424 00:22:12,500 --> 00:22:14,266 Mars seems to have a bit more sulfur, 425 00:22:14,367 --> 00:22:16,266 at least in the surface, than Earth does. 426 00:22:16,266 --> 00:22:18,767 If we extend that composition to the core 427 00:22:18,867 --> 00:22:21,667 and add more sulfur to the iron-nickel core, 428 00:22:21,667 --> 00:22:23,175 that would actually reduce its melting temperature, 429 00:22:23,175 --> 00:22:24,367 that would actually reduce its melting temperature, 430 00:22:24,367 --> 00:22:29,166 making it possible for this core to be molten today. 431 00:22:30,500 --> 00:22:33,367 ROWE: We thought that Mars lost its magnetic field 432 00:22:33,367 --> 00:22:36,667 when the core cooled and solidified. 433 00:22:36,667 --> 00:22:39,367 A molten core changes everything. 434 00:22:40,400 --> 00:22:42,867 Well, how can we explain this lack of a magnetic field 435 00:22:42,867 --> 00:22:45,300 at Mars even though there's a liquid core? 436 00:22:45,367 --> 00:22:47,100 Well, in order to have a magnetic field, 437 00:22:47,166 --> 00:22:50,400 you need the fluid to be moving and rotating and convecting. 438 00:22:51,967 --> 00:22:53,175 ROWE: Over time, as Mars lost heat and cooled down 439 00:22:53,175 --> 00:22:55,567 ROWE: Over time, as Mars lost heat and cooled down 440 00:22:55,567 --> 00:22:59,367 its core stayed molten thanks to the sulfur. 441 00:22:59,467 --> 00:23:02,100 But, with less heat, there was not enough 442 00:23:02,166 --> 00:23:05,800 energy to power the churning convection of liquid metal 443 00:23:05,867 --> 00:23:08,767 that creates an electric current. 444 00:23:08,867 --> 00:23:11,700 The convection in that core would have slowed down 445 00:23:11,767 --> 00:23:14,266 to the point where no magnetic field would be generated. 446 00:23:17,000 --> 00:23:22,000 ROWE: 3.7 billion years ago, Mars's magnetic shield dies. 447 00:23:23,400 --> 00:23:25,767 The solar wind's relentless attack 448 00:23:25,767 --> 00:23:28,867 strips the planet of its atmosphere. 449 00:23:28,867 --> 00:23:31,467 As the atmosphere disappears, 450 00:23:31,567 --> 00:23:35,967 water on the surface gradually boils away. 451 00:23:39,800 --> 00:23:43,166 But did all of the planet's water dissipate? 452 00:23:44,367 --> 00:23:49,166 To find out, our robots once again team up. 453 00:23:58,967 --> 00:24:03,000 ROWE: Since the first probe visited Mars in 1971, 454 00:24:03,100 --> 00:24:06,700 16 missions have investigated the Red Planet from orbit, 455 00:24:08,266 --> 00:24:11,467 while 10 landers have explored the surface. 456 00:24:12,700 --> 00:24:16,767 They've revealed Mars may still be an active planet, 457 00:24:16,867 --> 00:24:20,500 one that once had the right conditions for life. 458 00:24:21,867 --> 00:24:24,266 Mars used to be thought of as this dry, 459 00:24:24,266 --> 00:24:26,567 arid, inhospitable environment. 460 00:24:26,567 --> 00:24:28,867 And thanks to the recent Mars missions, 461 00:24:28,867 --> 00:24:32,200 we know now that they could have sustained life. 462 00:24:33,867 --> 00:24:36,200 ROWE: Could there be any ancient Martian 463 00:24:36,266 --> 00:24:39,567 water left, hidden inside the planet today? 464 00:24:39,667 --> 00:24:44,266 MAVEN investigates by analyzing Mars's atmosphere 465 00:24:44,367 --> 00:24:47,967 for one of water's components -- hydrogen. 466 00:24:47,967 --> 00:24:49,800 The MAVEN mission is looking at 467 00:24:49,867 --> 00:24:51,530 hydrogen that's currently in the Mars atmosphere. 468 00:24:51,530 --> 00:24:52,500 hydrogen that's currently in the Mars atmosphere. 469 00:24:52,567 --> 00:24:55,367 This is a really important thing to study. 470 00:24:57,166 --> 00:25:00,867 ROWE: The gas is produced when the solar wind slams into Mars's 471 00:25:00,967 --> 00:25:03,567 thin atmosphere and smashes apart 472 00:25:03,667 --> 00:25:07,066 molecules of water into hydrogen and oxygen. 473 00:25:08,367 --> 00:25:11,266 Hydrogen molecules come in two forms -- 474 00:25:11,266 --> 00:25:15,400 light, regular hydrogen and the heavier deuterium. 475 00:25:16,667 --> 00:25:18,967 The ratio of the different types 476 00:25:18,967 --> 00:25:21,530 tells us about the history of water on the Red Planet. 477 00:25:21,530 --> 00:25:22,667 tells us about the history of water on the Red Planet. 478 00:25:22,767 --> 00:25:26,967 It turns out that it's much easier to lose the lighter 479 00:25:26,967 --> 00:25:28,500 version, because gravity 480 00:25:28,567 --> 00:25:30,967 just you can't hold on to something that's light as 481 00:25:30,967 --> 00:25:32,300 easily as a heavier thing. 482 00:25:32,367 --> 00:25:34,867 So we expect that, as time goes on, 483 00:25:34,867 --> 00:25:37,200 we'll have less and less light hydrogen 484 00:25:37,266 --> 00:25:38,700 and more and more heavy hydrogen. 485 00:25:39,867 --> 00:25:43,567 DARTNELL: So if we can measure the outflow of hydrogen from 486 00:25:43,667 --> 00:25:46,000 the Martian atmosphere today, 487 00:25:46,066 --> 00:25:49,967 and specifically, whether it's light or heavy hydrogen, 488 00:25:49,967 --> 00:25:51,530 we can start to get some kind of idea about how much water 489 00:25:51,530 --> 00:25:53,967 we can start to get some kind of idea about how much water 490 00:25:53,967 --> 00:25:55,967 has been lost from Mars 491 00:25:55,967 --> 00:25:58,467 and therefore how much might still be there today. 492 00:26:00,266 --> 00:26:03,600 ROWE: 2021 -- scientists at Caltech 493 00:26:03,667 --> 00:26:07,166 analyze data from Mars's rovers and orbiters 494 00:26:07,166 --> 00:26:09,600 to discover the ratio of 495 00:26:09,667 --> 00:26:12,266 deuterium to hydrogen in the atmosphere. 496 00:26:12,266 --> 00:26:16,867 They find less of the heavy hydrogen than expected. 497 00:26:16,867 --> 00:26:20,767 If Mars had lost a lot of its original water 498 00:26:20,867 --> 00:26:21,530 out into outer space, 499 00:26:21,530 --> 00:26:23,400 out into outer space, 500 00:26:23,467 --> 00:26:27,166 we'd expect to find lots of heavy hydrogen 501 00:26:27,266 --> 00:26:30,266 left behind in the atmosphere. 502 00:26:30,367 --> 00:26:33,166 But, in fact, what we found was that the ratio 503 00:26:33,266 --> 00:26:38,400 told us that Mars didn't lose much of its water upwards. 504 00:26:39,467 --> 00:26:42,166 And so maybe the water went downwards. 505 00:26:42,266 --> 00:26:46,367 ROWE: Where is Mars's water hiding? 506 00:26:46,367 --> 00:26:48,567 Some scientists think it could be 507 00:26:48,667 --> 00:26:51,530 stashed away in the Martian rocks. 508 00:26:51,530 --> 00:26:51,767 stashed away in the Martian rocks. 509 00:26:51,767 --> 00:26:54,667 When we look at a rock, we often think this is a really 510 00:26:54,767 --> 00:26:56,867 dry thing, there's no water in there. 511 00:26:56,967 --> 00:26:59,767 But, in fact, there's often a lot of water 512 00:26:59,867 --> 00:27:03,700 in rocks, and it's because it's bound up in minerals. 513 00:27:03,767 --> 00:27:06,266 ROWE: Changes in the crust can drive 514 00:27:06,367 --> 00:27:07,967 these minerals to suck up huge 515 00:27:07,967 --> 00:27:11,700 volumes of water, equivalent to a global layer 516 00:27:11,767 --> 00:27:13,166 over 300 feet deep. 517 00:27:14,166 --> 00:27:17,667 Researchers estimate that as much as 99 percent of 518 00:27:17,667 --> 00:27:21,530 Mars's water could be locked away below the surface. 519 00:27:21,530 --> 00:27:21,867 Mars's water could be locked away below the surface. 520 00:27:23,400 --> 00:27:26,500 And Mars hides water in other ways, too. 521 00:27:26,567 --> 00:27:29,867 Enter the European Space Agency's orbiter, 522 00:27:29,867 --> 00:27:33,000 Mars Express -- probing one mile 523 00:27:33,066 --> 00:27:35,000 beneath the Martian South Pole, 524 00:27:35,100 --> 00:27:39,266 it finds a secret store of water. 525 00:27:39,367 --> 00:27:44,000 Really exciting. We've discovered a system of 526 00:27:44,066 --> 00:27:48,567 lakes beneath the Martian polar ice caps, 527 00:27:48,567 --> 00:27:51,530 lakes of what appears to be liquid water. 528 00:27:51,530 --> 00:27:52,100 lakes of what appears to be liquid water. 529 00:27:53,700 --> 00:27:55,767 THALLER: Now, these lakes are not very deep. 530 00:27:55,767 --> 00:27:57,367 They're probably only a couple of feet deep, 531 00:27:57,367 --> 00:27:59,700 maybe in some places even a couple of inches deep, 532 00:27:59,767 --> 00:28:01,000 but they're quite large. 533 00:28:01,066 --> 00:28:03,567 Some of these are about 20 miles across. 534 00:28:03,567 --> 00:28:05,900 And there's even some suggestion that these are 535 00:28:06,000 --> 00:28:09,367 connected with channels, kind of a system of very shallow 536 00:28:09,467 --> 00:28:11,166 great lakes near the South Pole of Mars. 537 00:28:11,266 --> 00:28:14,767 ROWE: The Martian poles are 538 00:28:14,867 --> 00:28:17,266 the coldest regions on the planet. 539 00:28:17,266 --> 00:28:21,500 Temperatures can reach 200 degrees below zero. 540 00:28:21,567 --> 00:28:24,900 So why is it that underneath this cold ice, 541 00:28:25,000 --> 00:28:26,900 you might even find liquid water? 542 00:28:27,000 --> 00:28:28,667 Well, remember, you're actually going down 543 00:28:28,667 --> 00:28:30,667 closer into the interior 544 00:28:30,667 --> 00:28:33,000 of Mars there, and so that's warm. 545 00:28:33,066 --> 00:28:35,467 It's possible that the geologic activity inside 546 00:28:35,467 --> 00:28:38,400 Mars is warming the ice from the underneath. 547 00:28:39,867 --> 00:28:42,467 ROWE: But heat from the interior of Mars 548 00:28:42,467 --> 00:28:46,367 wouldn't be enough to keep these lakes liquid. 549 00:28:46,467 --> 00:28:49,400 The secret ingredient may be salt. 550 00:28:50,500 --> 00:28:51,530 THALLER: If you've ever spread salt on an icy driveway, 551 00:28:51,530 --> 00:28:53,266 THALLER: If you've ever spread salt on an icy driveway, 552 00:28:53,367 --> 00:28:55,567 you'll notice that where the salt hits the driveway, 553 00:28:55,667 --> 00:28:57,266 the ice begins to melt. 554 00:28:57,266 --> 00:28:59,800 Saltwater actually freezes at 555 00:28:59,867 --> 00:29:02,967 a much lower temperature than water that's fresh. 556 00:29:02,967 --> 00:29:04,400 So if it's salty water, 557 00:29:04,467 --> 00:29:07,567 it could actually stay liquid at lower temperatures. 558 00:29:07,567 --> 00:29:10,867 ROWE: We still aren't 100 percent sure that the lakes 559 00:29:10,967 --> 00:29:12,300 are completely liquid. 560 00:29:12,367 --> 00:29:16,467 Some scientists think they could be lakes of frozen clay. 561 00:29:16,467 --> 00:29:20,600 Until we have a rover that can explore beneath the poles, 562 00:29:20,667 --> 00:29:21,530 we won't know for sure. 563 00:29:21,530 --> 00:29:22,367 we won't know for sure. 564 00:29:24,767 --> 00:29:27,767 The only real way we can tell for sure is to send 565 00:29:27,867 --> 00:29:29,100 some kind of mission that drills 566 00:29:29,166 --> 00:29:33,066 right down through that polar ice and samples 567 00:29:33,066 --> 00:29:34,867 what we find at the bottom. 568 00:29:34,967 --> 00:29:37,500 ROWE: Wherever it may be hiding, 569 00:29:37,567 --> 00:29:40,700 Mars's water is locked away, 570 00:29:40,767 --> 00:29:45,800 but in its past, the planet had impressive lakes and rivers. 571 00:29:45,867 --> 00:29:48,100 Did they ever host life? 572 00:29:48,166 --> 00:29:50,767 To find out, the rovers 573 00:29:50,867 --> 00:29:51,530 take a deep dive into Mars. 574 00:29:51,530 --> 00:29:53,567 take a deep dive into Mars. 575 00:30:07,667 --> 00:30:11,900 Veteran crew member, Curiosity, explores the Gale Crater. 576 00:30:13,000 --> 00:30:15,300 The rover's mission? To find evidence 577 00:30:15,367 --> 00:30:18,500 of whether Mars could have supported life. 578 00:30:20,867 --> 00:30:23,667 Los Alamos National Laboratory. 579 00:30:23,667 --> 00:30:25,967 Principal investigator of Curiosity's 580 00:30:25,967 --> 00:30:26,928 ChemCam, Nina Lanza, works closely with the rover 581 00:30:26,928 --> 00:30:29,667 ChemCam, Nina Lanza, works closely with the rover 582 00:30:29,767 --> 00:30:34,100 patrolling Mars 34 million miles away. 583 00:30:34,166 --> 00:30:37,567 In many ways, Curiosity is like my first child. 584 00:30:37,567 --> 00:30:40,100 We had to take such good care of her while she was still here 585 00:30:40,166 --> 00:30:43,600 on Earth, but like all children, she had to forge her own path. 586 00:30:43,667 --> 00:30:45,767 And so we had to send her on her way 587 00:30:45,767 --> 00:30:48,567 to discover new things on Mars by herself. 588 00:30:53,767 --> 00:30:56,367 ROWE: ChemCam uses a precision laser that 589 00:30:56,367 --> 00:30:56,928 analyzes the chemical composition of Martian rocks. 590 00:30:56,928 --> 00:31:01,166 analyzes the chemical composition of Martian rocks. 591 00:31:01,166 --> 00:31:04,600 LANZA: We have a laser that we focus onto a target 592 00:31:04,667 --> 00:31:09,300 up to 23 feet away, and we vaporize a little material, 593 00:31:09,367 --> 00:31:10,867 and then we look at the light 594 00:31:10,867 --> 00:31:13,066 made by this vaporized material and figure out 595 00:31:13,066 --> 00:31:14,300 what elements are in the rock. 596 00:31:15,467 --> 00:31:18,000 Working with an instrument like ChemCam is really 597 00:31:18,100 --> 00:31:21,100 a childhood dream come true, because I was always hoping 598 00:31:21,166 --> 00:31:23,100 to work on a spaceship, and today, I work on 599 00:31:23,166 --> 00:31:25,166 a spaceship with lasers. 600 00:31:25,166 --> 00:31:26,500 How cool is that? 601 00:31:28,467 --> 00:31:30,367 ROWE: With their long-distance teamwork, Nina 602 00:31:30,467 --> 00:31:34,367 and Curiosity discover rocks with a shiny coating, 603 00:31:34,467 --> 00:31:37,166 laced with manganese. 604 00:31:37,266 --> 00:31:40,000 LANZA: One of the most exciting discoveries from Curiosity in 605 00:31:40,066 --> 00:31:42,867 Gale Crater was the existence of high concentrations 606 00:31:42,967 --> 00:31:46,166 of an element called manganese, and that's because manganese on 607 00:31:46,166 --> 00:31:49,066 Earth is very closely tied to life. 608 00:31:50,800 --> 00:31:54,166 Could the manganese of Mars be linked to life forms? 609 00:31:55,200 --> 00:31:56,928 To investigate, scientists look at similar coatings 610 00:31:56,928 --> 00:31:58,400 To investigate, scientists look at similar coatings 611 00:31:58,467 --> 00:32:02,800 called varnish on desert rocks here on Earth. 612 00:32:02,867 --> 00:32:05,667 So I have an example here of some rock varnish, 613 00:32:05,667 --> 00:32:09,000 and you can see, it's actually incredibly dark. 614 00:32:09,100 --> 00:32:10,567 It has a lot of iron oxide, 615 00:32:10,667 --> 00:32:13,000 manganese oxide, and clay minerals in them. 616 00:32:13,100 --> 00:32:14,467 And the rocks can sometimes have 617 00:32:14,467 --> 00:32:16,667 none of these things in the rock itself. 618 00:32:17,867 --> 00:32:20,800 So the question is, where does this coating come from? 619 00:32:20,867 --> 00:32:23,900 RADEBAUGH: Often, we find microbes associated 620 00:32:24,000 --> 00:32:26,166 with the varnishes and so possibly, 621 00:32:26,166 --> 00:32:26,928 these microbes actually helped fix 622 00:32:26,928 --> 00:32:28,467 these microbes actually helped fix 623 00:32:28,567 --> 00:32:30,300 the manganese onto the surface. 624 00:32:32,066 --> 00:32:35,000 ROWE: The age of these Earth varnishes may provide 625 00:32:35,100 --> 00:32:38,867 a clue to Mars's distant past -- here, 626 00:32:38,967 --> 00:32:42,166 they only appear after a significant event in 627 00:32:42,166 --> 00:32:43,367 our history -- 628 00:32:43,367 --> 00:32:46,567 the creation of the oxygen we breathe. 629 00:32:47,600 --> 00:32:48,867 A couple of billion years ago 630 00:32:48,967 --> 00:32:51,667 on Earth was the great oxygenation event. 631 00:32:53,700 --> 00:32:55,767 Basically, the Earth's atmosphere did not have 632 00:32:55,867 --> 00:32:56,928 a lot of oxygen in it. 633 00:32:56,928 --> 00:32:57,000 a lot of oxygen in it. 634 00:32:57,066 --> 00:32:58,767 It was locked up in minerals and chemicals. 635 00:33:00,066 --> 00:33:03,567 Well, some bacteria discovered how to photosynthesize light, 636 00:33:03,667 --> 00:33:06,467 how to convert energy from light into their metabolism. 637 00:33:06,567 --> 00:33:10,500 And via the chemistry of this, they wound up emitting oxygen. 638 00:33:13,767 --> 00:33:16,767 ROWE: The oxygen was poison to many life forms, 639 00:33:16,867 --> 00:33:19,300 so they died out. 640 00:33:19,367 --> 00:33:21,567 But others thrived, pumping more 641 00:33:21,667 --> 00:33:24,500 and more oxygen into the atmosphere. 642 00:33:24,567 --> 00:33:26,928 Oxygen reacts with the manganese, 643 00:33:26,928 --> 00:33:27,166 Oxygen reacts with the manganese, 644 00:33:27,166 --> 00:33:28,600 binding it to the rocks. 645 00:33:31,367 --> 00:33:33,266 We don't really see these minerals until 646 00:33:33,367 --> 00:33:35,467 after the rise of oxygen in the atmosphere, 647 00:33:35,467 --> 00:33:37,300 so after photosynthesis. 648 00:33:38,767 --> 00:33:43,000 ROWE: For Mars to have these same manganese varnishes, 649 00:33:43,100 --> 00:33:45,500 there must have once been more oxygen 650 00:33:45,567 --> 00:33:47,667 in the planet's atmosphere. 651 00:33:47,667 --> 00:33:49,467 Is it possible that Mars had a lot 652 00:33:49,467 --> 00:33:52,166 of oxygen in its atmosphere in the past, 653 00:33:52,166 --> 00:33:54,467 and there were wee little beasties processing it? 654 00:33:56,500 --> 00:33:56,928 ROWE: And so the search continues, and Curiosity uses 655 00:33:56,928 --> 00:34:00,100 ROWE: And so the search continues, and Curiosity uses 656 00:34:00,166 --> 00:34:01,867 another piece of equipment 657 00:34:01,967 --> 00:34:05,867 to sniff out traces of past Martian life. 658 00:34:05,867 --> 00:34:10,300 One of the key instruments aboard Curiosity is a piece of 659 00:34:10,367 --> 00:34:12,467 lab kit called a gas 660 00:34:12,467 --> 00:34:15,000 chromatography mass spectrometer, 661 00:34:15,100 --> 00:34:19,600 or GC-MS, and all this really is, in essence, is, like, 662 00:34:19,667 --> 00:34:22,667 a very sensitive electronic nose. 663 00:34:25,000 --> 00:34:26,928 Curiosity digs up some Martian soil 664 00:34:26,928 --> 00:34:28,000 Curiosity digs up some Martian soil 665 00:34:28,066 --> 00:34:30,567 and heats it in its portable chem lab. 666 00:34:33,166 --> 00:34:34,867 Like a robotic bloodhound, 667 00:34:34,967 --> 00:34:38,100 it sniffs the vaporized dirt and picks up 668 00:34:38,166 --> 00:34:41,567 the faint smell of a rare molecular compound. 669 00:34:43,567 --> 00:34:47,867 What Curiosity discovered was a compound called thiophene. 670 00:34:47,867 --> 00:34:50,166 This is interesting, because at least on Earth, 671 00:34:50,266 --> 00:34:52,100 thiophene is often found 672 00:34:52,166 --> 00:34:55,567 in fossil material, in coal, 673 00:34:55,667 --> 00:34:56,928 in oil, as well as stromatolites or micro fossils 674 00:34:56,928 --> 00:34:59,767 in oil, as well as stromatolites or micro fossils 675 00:34:59,867 --> 00:35:02,100 of ancient life in the fossil record. 676 00:35:03,700 --> 00:35:06,300 So maybe this thiophene we've now discovered on 677 00:35:06,367 --> 00:35:12,867 Mars is some trace chemical fossil of ancient Martian life. 678 00:35:14,300 --> 00:35:18,567 Or possibly, it was produced by non-biological processes. 679 00:35:23,900 --> 00:35:25,867 DURDA: Curiosity is knocking on the door 680 00:35:25,967 --> 00:35:26,928 of finding the evidence for life on Mars. 681 00:35:26,928 --> 00:35:27,867 of finding the evidence for life on Mars. 682 00:35:29,166 --> 00:35:31,867 We haven't found life, but we've found the interesting 683 00:35:31,967 --> 00:35:34,266 bits that are pieces of the puzzle, 684 00:35:34,367 --> 00:35:36,467 the organic puzzle of life on Mars. 685 00:35:36,467 --> 00:35:39,800 And so it's getting us to that ultimate question, is there 686 00:35:39,867 --> 00:35:41,567 or was there ever life on the planet? 687 00:35:44,000 --> 00:35:45,467 ROWE: To help answer that question, 688 00:35:45,467 --> 00:35:48,300 scientists bring in pinch hitter, Perseverance. 689 00:35:48,367 --> 00:35:49,667 The newest member of the crew 690 00:35:49,767 --> 00:35:53,166 has the latest tech, tools designed based on lessons from 691 00:35:53,166 --> 00:35:54,400 previous missions. 692 00:35:57,100 --> 00:36:00,467 Perseverance is so important, because it leverages all of 693 00:36:00,567 --> 00:36:04,100 the knowledge of the previous rovers, which set the stage for 694 00:36:04,166 --> 00:36:06,567 taking samples on the surface of Mars, 695 00:36:06,667 --> 00:36:09,500 searching for life, and setting up a place for humans to 696 00:36:09,567 --> 00:36:10,667 explore in the future. 697 00:36:13,300 --> 00:36:16,467 ROWE: Perseverance gathers rock and soil samples, 698 00:36:16,567 --> 00:36:20,600 testing some itself and leaving others to be collected 699 00:36:20,667 --> 00:36:23,100 and returned to Earth later. 700 00:36:23,166 --> 00:36:25,367 We are just at the beginning of 701 00:36:25,467 --> 00:36:26,500 the Perseverance mission. 702 00:36:26,567 --> 00:36:26,928 We have so much to learn. 703 00:36:26,928 --> 00:36:29,200 We have so much to learn. 704 00:36:29,266 --> 00:36:32,000 But I think all of us would be so thrilled 705 00:36:32,100 --> 00:36:35,300 if we could actually find definitive signs of past 706 00:36:35,367 --> 00:36:37,000 Martian life -- that would be incredible. 707 00:36:37,100 --> 00:36:39,467 I don't know what form that would take, 708 00:36:39,567 --> 00:36:42,667 but we're going to look for it in every way that we know how. 709 00:36:44,867 --> 00:36:47,200 ROWE: While Perseverance hunts for evidence 710 00:36:47,266 --> 00:36:48,467 of ancient life on Mars, 711 00:36:51,300 --> 00:36:54,400 Curiosity detects hints that life may 712 00:36:54,467 --> 00:36:56,928 exist on the Red Planet now. 713 00:36:56,928 --> 00:36:57,367 exist on the Red Planet now. 714 00:37:10,166 --> 00:37:12,867 ROWE: In Gale Crater, Curiosity detects 715 00:37:12,967 --> 00:37:14,967 a huge surge of methane gas. 716 00:37:16,600 --> 00:37:19,266 DARTNELL: The methane we've detected in the atmosphere of 717 00:37:19,367 --> 00:37:21,967 Mars is potentially very, very exciting. 718 00:37:23,300 --> 00:37:25,467 Most of the methane in our own air, 719 00:37:25,567 --> 00:37:28,000 in Earth's atmosphere, is biogenic. 720 00:37:28,066 --> 00:37:30,467 It was released by living organisms. 721 00:37:31,900 --> 00:37:35,000 Curiosity's result is exciting, because we know 722 00:37:35,100 --> 00:37:37,367 that this can't be ancient methane. 723 00:37:38,667 --> 00:37:41,000 Methane is really interesting, because it has a short 724 00:37:41,100 --> 00:37:42,867 residency time in an atmosphere, 725 00:37:42,867 --> 00:37:45,867 which means it breaks down very quickly. 726 00:37:45,967 --> 00:37:48,767 Whatever is making methane in Gale Crater 727 00:37:48,867 --> 00:37:50,300 is doing it right now. 728 00:37:53,767 --> 00:37:57,266 ROWE: Curiosity has detected methane many times before. 729 00:37:57,367 --> 00:38:00,066 But this is the largest amount so far. 730 00:38:00,066 --> 00:38:00,585 The question is, what created it? 731 00:38:00,585 --> 00:38:03,467 The question is, what created it? 732 00:38:04,867 --> 00:38:07,000 Maybe this Martian methane is 733 00:38:07,100 --> 00:38:11,667 the first trace we found of Martian life, 734 00:38:11,767 --> 00:38:14,367 micro organisms living deep underground. 735 00:38:16,800 --> 00:38:21,467 Or maybe that methane is not biological, but geological. 736 00:38:21,567 --> 00:38:25,300 It's methane that's been given off by volcanic processes in 737 00:38:25,367 --> 00:38:26,567 the past. 738 00:38:26,567 --> 00:38:29,300 The frustration is, we can't quite tell 739 00:38:29,367 --> 00:38:30,585 the difference between the two just yet. 740 00:38:30,585 --> 00:38:31,166 the difference between the two just yet. 741 00:38:31,266 --> 00:38:33,500 All we can do is continue to sniff 742 00:38:33,567 --> 00:38:38,500 the air and document when and where we see it. 743 00:38:40,266 --> 00:38:43,367 ROWE: The picture becomes more intriguing when Curiosity 744 00:38:43,367 --> 00:38:47,200 detects oxygen in greater quantities than expected. 745 00:38:50,467 --> 00:38:53,900 There's a lot more oxygen on Mars than we had suspected, 746 00:38:54,000 --> 00:38:55,200 which is weird in the first place. 747 00:38:55,266 --> 00:39:00,585 And the amount of oxygen is changing seasonally. 748 00:39:00,585 --> 00:39:00,700 And the amount of oxygen is changing seasonally. 749 00:39:02,266 --> 00:39:06,166 There's something in or on Mars 750 00:39:06,166 --> 00:39:09,867 that is adding oxygen to the Martian atmosphere 751 00:39:09,867 --> 00:39:12,400 during the spring and summer and then taking it away during 752 00:39:12,467 --> 00:39:13,500 the fall and winter. 753 00:39:13,567 --> 00:39:16,567 There is something that is actively controlling 754 00:39:16,667 --> 00:39:19,500 the amount of oxygen in the Martian atmosphere. 755 00:39:19,567 --> 00:39:21,000 What is that? 756 00:39:22,300 --> 00:39:26,000 ROWE: Most of Earth's oxygen comes from living organisms 757 00:39:26,100 --> 00:39:30,266 photosynthesizing, and it changes with the seasons. 758 00:39:30,266 --> 00:39:30,585 SUTTER: We have normal, cyclical, seasonal variations in 759 00:39:30,585 --> 00:39:35,000 SUTTER: We have normal, cyclical, seasonal variations in 760 00:39:35,066 --> 00:39:38,767 the amount of oxygen here on Earth because of life. 761 00:39:39,900 --> 00:39:41,600 RADEBAUGH: The most landmass on the Earth 762 00:39:41,667 --> 00:39:44,400 is located in the Northern Hemisphere. 763 00:39:44,467 --> 00:39:46,600 And so that means that during northern summer, 764 00:39:46,667 --> 00:39:48,867 most of the oxygen on Earth is generated. 765 00:39:48,867 --> 00:39:51,567 So there's a peak in oxygen during the northern summer. 766 00:39:52,867 --> 00:39:55,667 ROWE: So where is the oxygen on Mars coming from? 767 00:39:56,867 --> 00:40:00,585 Oxygen is a known result of life of photosynthesis. 768 00:40:00,585 --> 00:40:02,567 Oxygen is a known result of life of photosynthesis. 769 00:40:02,567 --> 00:40:03,867 It's a biosignature. 770 00:40:03,867 --> 00:40:05,700 It's a sign of life. 771 00:40:05,767 --> 00:40:08,166 Is this a sign of life on Mars? 772 00:40:09,867 --> 00:40:12,266 ROWE: The atmospheric changes in oxygen 773 00:40:12,367 --> 00:40:15,300 and methane are a fascinating puzzle 774 00:40:15,367 --> 00:40:19,000 and a tantalizing hint of life. 775 00:40:19,066 --> 00:40:21,567 Life on Mars explaining these changes in 776 00:40:21,567 --> 00:40:24,500 methane and oxygen would be incredibly interesting. 777 00:40:27,967 --> 00:40:30,066 So it's probably wrong. 778 00:40:30,066 --> 00:40:30,585 The answer is probably more boring, and not that chemistry 779 00:40:30,585 --> 00:40:33,200 The answer is probably more boring, and not that chemistry 780 00:40:33,266 --> 00:40:34,467 is boring, but it's -- 781 00:40:34,467 --> 00:40:37,367 it's a little less interesting than life. 782 00:40:37,367 --> 00:40:39,767 We Mars scientists, of course, are always very excited 783 00:40:39,867 --> 00:40:42,800 about seeing signs of maybe extent life on Mars, 784 00:40:42,867 --> 00:40:45,700 but we're going to require really big proof before we feel 785 00:40:45,767 --> 00:40:48,266 truly excited that we've made this discovery. 786 00:40:50,600 --> 00:40:53,400 ROWE: The army of robotic explorers continues 787 00:40:53,467 --> 00:40:55,500 to rewrite the story of Mars, 788 00:40:57,266 --> 00:41:00,467 discovering a once warm, wet world 789 00:41:00,567 --> 00:41:00,585 with the potential for life. 790 00:41:00,585 --> 00:41:02,166 with the potential for life. 791 00:41:05,100 --> 00:41:07,467 Now, a new generation of robots 792 00:41:07,567 --> 00:41:09,767 led by Perseverance will dig 793 00:41:09,767 --> 00:41:13,667 deeper into the Red Planet's troubled past 794 00:41:13,667 --> 00:41:14,900 and its frozen present 795 00:41:16,300 --> 00:41:20,400 and maybe hit the mother lode, life itself. 796 00:41:21,867 --> 00:41:23,367 THALLER: With every new mission to Mars, 797 00:41:23,467 --> 00:41:26,266 I hope that somebody really is going to find evidence 798 00:41:26,266 --> 00:41:28,000 that life either existed there 799 00:41:28,066 --> 00:41:30,300 in the past or maybe even still does now. 800 00:41:31,967 --> 00:41:35,200 And with all of these missions on many places on this planet, 801 00:41:35,266 --> 00:41:38,967 maybe now is the best time to actually answer that question. 802 00:41:38,967 --> 00:41:40,400 Whether or not it's likely 803 00:41:40,467 --> 00:41:42,667 that Perseverance finds life on Mars, 804 00:41:42,667 --> 00:41:45,400 we have set ourselves up for success, and I am 805 00:41:45,467 --> 00:41:49,767 so hopeful that we get to finally answer that question, 806 00:41:49,867 --> 00:41:50,767 the big question. 807 00:41:52,000 --> 00:41:53,066 Are we alone?