0:00:15 > 0:00:16The oceans define the earth.
0:00:20 > 0:00:22They're crucial to life.
0:00:26 > 0:00:29In fact, without the oceans, there would be no life.
0:00:41 > 0:00:44We once thought they were unique to our planet.
0:00:46 > 0:00:47But we were wrong.
0:00:50 > 0:00:54We've recently discovered oceans all over our solar system
0:00:54 > 0:00:56and they're very similar to our own.
0:00:57 > 0:01:03Imagine this at the bottom of Enceladus' Ocean.
0:01:03 > 0:01:07Now scientists are going on an epic journey in search of new life
0:01:07 > 0:01:09in places that never seemed possible.
0:01:10 > 0:01:14Life has got this amazing ability to, you know, just keep surprising us.
0:01:17 > 0:01:20I want to get data back from a probe and be able to say,
0:01:20 > 0:01:23"It's life, Jim, but not as we know it."
0:01:27 > 0:01:31NASA are even planning to dive to the depths of a strange,
0:01:31 > 0:01:34distant ocean, with a remarkable submarine.
0:01:35 > 0:01:38That first picture... Are you kidding?
0:01:38 > 0:01:40That first picture on the surface of a sea, on another planet
0:01:40 > 0:01:43in our solar system changes the world.
0:01:45 > 0:01:49The hunt for oceans in space marks the dawn of a new era
0:01:49 > 0:01:51in the search for alien life.
0:02:13 > 0:02:17Nearly two centuries ago, Charles Darwin set out on a journey
0:02:17 > 0:02:22across the world's oceans to uncover the secrets of life.
0:02:22 > 0:02:25What he came to understand was that the answer to the mystery
0:02:25 > 0:02:29of where we came from lay beneath the hull of his ship, the Beagle.
0:02:31 > 0:02:34As he filled his notebooks with beautiful sketches of the birds
0:02:34 > 0:02:39and animals he came across, he began to formulate an idea that
0:02:39 > 0:02:42life might have actually started in water.
0:02:45 > 0:02:49Darwin's important for the whole story of the evolution of life
0:02:49 > 0:02:52and natural selection, where we all came from,
0:02:52 > 0:02:54how life ultimately started, as well.
0:02:54 > 0:02:56A lot of that goes back to Darwin.
0:02:56 > 0:02:59He had ideas, not very well publicised ideas, not
0:02:59 > 0:03:03in the Origin Of Species, but on how life started in a small, warm pond.
0:03:03 > 0:03:07So Darwin had put his finger on the importance of water
0:03:07 > 0:03:11in the origin and evolution of life very early on.
0:03:11 > 0:03:15Water is so essential that it's dictated where scientists
0:03:15 > 0:03:17look in the search for life in our solar system.
0:03:18 > 0:03:21Life needs water. You look at all life forms on earth.
0:03:21 > 0:03:25The one requirement they all have in common is water.
0:03:25 > 0:03:28An ocean may be a good place to incubate life and,
0:03:28 > 0:03:32not surprisingly, an ocean has got what life needs to survive.
0:03:32 > 0:03:35Everywhere where we look on earth, whether it's frozen
0:03:35 > 0:03:39or boiling hot, wherever we find water, we find life.
0:03:39 > 0:03:41Water is our working fluid.
0:03:41 > 0:03:45You're mostly made up of water, I'm mostly made up of water.
0:03:45 > 0:03:48The search criteria were simple - to find life,
0:03:48 > 0:03:50first find a liquid ocean.
0:03:50 > 0:03:54Only beyond earth, there didn't appear to be any in our solar system.
0:03:56 > 0:03:58There used to be the idea of the Goldilocks Zone,
0:03:58 > 0:04:01where everything was "just right" for water to be in the liquid
0:04:01 > 0:04:05state on the surface of a planet and earth was slap-bang in it.
0:04:05 > 0:04:07Venus was too close to the sun,
0:04:07 > 0:04:10too hot really for liquid water on the surface.
0:04:10 > 0:04:13Mars, thought to be a little bit too far away.
0:04:15 > 0:04:19But is finding liquid water and life on Mars impossible?
0:04:30 > 0:04:32We've been sending evermore complex
0:04:32 > 0:04:35and sophisticated spacecraft to the Red Planet for decades
0:04:35 > 0:04:38and we now know more about it than we ever did.
0:04:40 > 0:04:43Unfortunately, all the scientific evidence gathered so far
0:04:43 > 0:04:48points to Mars being dry, cold and seemingly lifeless.
0:04:49 > 0:04:51But has it always been?
0:04:52 > 0:04:55It's a question that's intrigued scientists
0:04:55 > 0:04:58and astronomers, like Geronimo Villanueva, for years.
0:04:59 > 0:05:03Ironically, the search for evidence of an ancient Martian ocean
0:05:03 > 0:05:07is being conducted from one of the driest places on earth -
0:05:07 > 0:05:09the Atacama Desert in Chile.
0:05:10 > 0:05:13So there is a strong relationship between Mars and Atacama,
0:05:13 > 0:05:15because Mars is a very dry place
0:05:15 > 0:05:17and Atacama is one of the driest places on the planet.
0:05:17 > 0:05:21Actually, the relative humidity measured by Curiosity Rover on Mars
0:05:21 > 0:05:25is practically the same as we are right now, here on this desert.
0:05:25 > 0:05:29Fittingly, it's that lack of water that makes the Atacama
0:05:29 > 0:05:31the perfect place to build one of the biggest
0:05:31 > 0:05:33telescopes in the world,
0:05:33 > 0:05:36because water in the atmosphere here would
0:05:36 > 0:05:41drastically limit the telescope's ability to find water anywhere else.
0:05:41 > 0:05:43Water and many other things like organics are what we're
0:05:43 > 0:05:47looking for, so we come to a place which is devoid of those things,
0:05:47 > 0:05:50like a desert, so we don't get the contamination from those
0:05:50 > 0:05:52things when we observe through the atmosphere.
0:05:52 > 0:05:55So when you come to a place like this,
0:05:55 > 0:05:58you're trying to look through the water in our own atmosphere.
0:05:58 > 0:06:02What's immediately obvious to anyone with even an ordinary telescope,
0:06:02 > 0:06:05is that there IS water on Mars.
0:06:05 > 0:06:08But today, it's frozen solid at the poles.
0:06:09 > 0:06:12Yet the Martian landscape looks strangely as though
0:06:12 > 0:06:16it was carved and shaped by liquid water.
0:06:16 > 0:06:20Planets show all this morphology, geomorphology, driven by water,
0:06:20 > 0:06:22a huge amount of water, so the estimates of how much
0:06:22 > 0:06:25was on the planet vary a lot, because we didn't know.
0:06:25 > 0:06:28I mean, we see all this carving, all these big valleys,
0:06:28 > 0:06:31and so how much water was there is a big question.
0:06:33 > 0:06:36Answering that question was pretty much impossible
0:06:36 > 0:06:41until scientists got lucky in 1984 in another desert.
0:06:41 > 0:06:45This time in the coldest place on earth - Antarctica.
0:06:49 > 0:06:52Here they found a remarkable meteorite.
0:06:53 > 0:06:57Analysis confirmed it was Martian in origin and that they had
0:06:57 > 0:07:01discovered the key that would unlock the mystery of Mars's watery past.
0:07:03 > 0:07:07So once you identify when in the history of our solar system,
0:07:07 > 0:07:11where it came, then you say, "OK, this rock is dated there and it comes from Mars."
0:07:11 > 0:07:14So you have a good reference point in time and in place of that rock.
0:07:16 > 0:07:22Careful analysis revealed that this meteorite was 4.5 billion years old.
0:07:22 > 0:07:26The meteorite also carried crucial chemical information -
0:07:26 > 0:07:30an isotopic signature fixed by the amount of water on Mars
0:07:30 > 0:07:324.5 billion years ago.
0:07:33 > 0:07:37On its own, this signature was worthless, but by measuring
0:07:37 > 0:07:41the amount of water on Mars today, then comparing the signatures
0:07:41 > 0:07:46of recent rocks against the ancient meteorite, all would be revealed.
0:07:46 > 0:07:49And that's where the huge telescope comes in.
0:07:49 > 0:07:53It's so powerful it can detect water molecules on the surface of the planet.
0:07:55 > 0:07:58You can actually see the molecules in every...
0:07:58 > 0:08:00Above a volcano in Mars, above a valley, you can
0:08:00 > 0:08:03actually map those molecules from here.
0:08:03 > 0:08:05It's really astonishing.
0:08:08 > 0:08:13Armed with a precise measurement of the amount of water on Mars today,
0:08:13 > 0:08:16Geronimo was able to make an astonishing calculation.
0:08:17 > 0:08:21We extrapolated back in time and we inferred that there was almost
0:08:21 > 0:08:24seven times more water than there is right now.
0:08:32 > 0:08:35What happened? Mars, topographically speaking, has very low plains
0:08:35 > 0:08:39in the north and a very high altitude place on the south.
0:08:39 > 0:08:43So if you throw water, it will tend to flow into the lower topography,
0:08:43 > 0:08:45which is going to be the northern plains.
0:08:45 > 0:08:47So one of the things we did is,
0:08:47 > 0:08:50OK, so, we had this volume of water and so what do we do with this?
0:08:50 > 0:08:53So one trick was we said, OK, just throw it on the planet
0:08:53 > 0:08:55and let's see where it falls.
0:08:55 > 0:08:58And they just did, like, you know, follow the rivers and everything,
0:08:58 > 0:09:02and it formed an ocean on the northern plains of the planet.
0:09:08 > 0:09:114.5 billion years ago, the Martian ocean
0:09:11 > 0:09:17covered 19% of the planet and was as deep as the Mediterranean.
0:09:17 > 0:09:21In fact, NASA's planetary models reveal a Mars at its warmest,
0:09:21 > 0:09:23complete with an earth-like atmosphere.
0:09:28 > 0:09:32If you were in an alien spacecraft randomly coming to earth,
0:09:32 > 0:09:35the chances are better than even that you're going to land
0:09:35 > 0:09:37up in water, so bring a boat.
0:09:37 > 0:09:40And it's the same on early Mars, and that's a fundamental point,
0:09:40 > 0:09:42that Mars was a water world.
0:09:42 > 0:09:45It would have been better to characterise it as a water world,
0:09:45 > 0:09:47whereas now, of course, it's a desert world.
0:09:47 > 0:09:49But it's that water world that's interesting.
0:09:49 > 0:09:51That's the world that may have had life
0:09:51 > 0:09:54and that's the world we want to investigate.
0:10:04 > 0:10:07It even had waves!
0:10:07 > 0:10:10The reduced gravity on Mars meant that these waves
0:10:10 > 0:10:13would have been twice as tall as those on Earth -
0:10:13 > 0:10:15a surfer's paradise,
0:10:15 > 0:10:18but, according to Nasa scientists,
0:10:18 > 0:10:19most of the time
0:10:19 > 0:10:23you'd have to be pretty tough to catch a Martian wave.
0:10:23 > 0:10:25If we think back to early Mars,
0:10:25 > 0:10:28we would expect it to be an Earth-like environment -
0:10:28 > 0:10:30if it had water
0:10:30 > 0:10:33and a thicker atmosphere, and was warmer.
0:10:33 > 0:10:35The one big difference, I think,
0:10:35 > 0:10:37would be that it would be more like the Arctic Ocean.
0:10:37 > 0:10:39It would be an ice-choked,
0:10:39 > 0:10:41ice-covered ocean.
0:10:41 > 0:10:44So, if you imagine standing on the north shore of Greenland
0:10:44 > 0:10:47looking out at the ice packs moving,
0:10:47 > 0:10:49I think you'd get a good imagination
0:10:49 > 0:10:51of what early Mars might have looked like.
0:10:51 > 0:10:53Would the surfers like it better or less?
0:10:53 > 0:10:56It depends really on the wet suit,
0:10:56 > 0:10:58because it's going to be very cold on early Mars,
0:10:58 > 0:11:04so you've got great waves, but you're inside a wet suit to survive it.
0:11:04 > 0:11:07Not very many people surf in the Arctic Ocean
0:11:07 > 0:11:09and this could be part of the explanation.
0:11:11 > 0:11:13It may have been cold.
0:11:13 > 0:11:16Mars is much further away from the sun than the Earth,
0:11:16 > 0:11:18but four and a half billion years ago,
0:11:18 > 0:11:22life on Mars would have been technically possible.
0:11:22 > 0:11:25This is the time when Mars was the most habitable time.
0:11:25 > 0:11:27When the planet was formed, actually,
0:11:27 > 0:11:29planet Earth and Mars were similar in some aspects.
0:11:29 > 0:11:31It had a thicker atmosphere,
0:11:31 > 0:11:33maybe there was a big ocean there,
0:11:33 > 0:11:35so habitability of the two planets were similar
0:11:35 > 0:11:38and, interestingly, the time that we think this ocean was there
0:11:38 > 0:11:41was a time that life started in our planet.
0:11:41 > 0:11:44So, you know, if the conditions were favourable for life here -
0:11:44 > 0:11:45to start life, you know -
0:11:45 > 0:11:48what could be the conditions on the planet Mars?
0:11:48 > 0:11:52Sadly, however habitable that early ocean was,
0:11:52 > 0:11:54it didn't last.
0:11:54 > 0:11:57Scientists think that the early Martian atmosphere
0:11:57 > 0:12:00was vulnerable to solar radiation and,
0:12:00 > 0:12:03over the course of one and a half billion years,
0:12:03 > 0:12:04it evaporated away
0:12:04 > 0:12:08leaving just 13% frozen at the poles.
0:12:08 > 0:12:10But if Martian life was theoretically possible
0:12:10 > 0:12:13in that ocean millions of years ago,
0:12:13 > 0:12:17is it possible that anything could have survived until now?
0:12:19 > 0:12:22I think the possibility of finding life on Mars now
0:12:22 > 0:12:24traces directly to the possibility
0:12:24 > 0:12:27of finding liquid water on Mars
0:12:27 > 0:12:29that's relatively fresh.
0:12:33 > 0:12:35And finding water has been a large part
0:12:35 > 0:12:38of the Curiosity rover's mission.
0:12:38 > 0:12:42Curiosity has been trundling around Mars since 2012
0:12:42 > 0:12:46and the images it's been sending back have been stunning.
0:12:47 > 0:12:49Sequences, like this blue sunset,
0:12:49 > 0:12:53are starting to change our understanding of the planet,
0:12:53 > 0:12:57but it's the pictures from the Mars reconnaissance orbiter
0:12:57 > 0:12:59of a region called the Newton crater
0:12:59 > 0:13:01that are helping to shed new light
0:13:01 > 0:13:04on the amount of liquid water left on Mars.
0:13:04 > 0:13:06This is a time-lapse sequence
0:13:06 > 0:13:09showing streaks on the crater wall -
0:13:09 > 0:13:12apparently growing and getting darker.
0:13:12 > 0:13:16Scientists think that they might be caused by water.
0:13:16 > 0:13:19These small amounts of water -
0:13:19 > 0:13:22compared to an ocean on Earth or even an ocean on early Mars -
0:13:22 > 0:13:23they're insignificant.
0:13:23 > 0:13:26But as an indicator of Mars still being active
0:13:26 > 0:13:29and still having liquid phases,
0:13:29 > 0:13:32and maybe a hint of bigger and better things elsewhere,
0:13:32 > 0:13:35then I think it's very important.
0:13:35 > 0:13:36What appears to be happening
0:13:36 > 0:13:38is that the moisture in the soil
0:13:38 > 0:13:41is evaporating during the relative warmth of the day
0:13:41 > 0:13:45and condensing back at night when it's colder.
0:13:45 > 0:13:47So, Mars still has a heartbeat.
0:13:47 > 0:13:50It's a faint one if we measure its heartbeat
0:13:50 > 0:13:51in terms of the presence of water.
0:13:51 > 0:13:53At one time, it was huge,
0:13:53 > 0:13:54it was an ocean
0:13:54 > 0:13:57and now there's just a faint glimmer of it.
0:13:57 > 0:14:00The problem is that these small amounts of water
0:14:00 > 0:14:03are exceptionally salty.
0:14:03 > 0:14:05The Curiosity rover has identified,
0:14:05 > 0:14:06in the Martian soil,
0:14:06 > 0:14:09a salt called calcium perchlorate.
0:14:09 > 0:14:12It's this salt that absorbs the Martian dew
0:14:12 > 0:14:15as it condenses onto the cold surface each day.
0:14:18 > 0:14:21The salt also lowers the water's freezing point,
0:14:21 > 0:14:23keeping it a liquid -
0:14:23 > 0:14:25even at sub-zero temperatures.
0:14:27 > 0:14:30But it also makes these faint traces of brine
0:14:30 > 0:14:32so concentrated
0:14:32 > 0:14:35they'd be toxic to conventional life forms.
0:14:35 > 0:14:37So, could they support life on Mars?
0:14:50 > 0:14:54There may be clues in the saltiest parts of the Earth,
0:14:54 > 0:14:57like the Bonneville Salt Flats in Utah.
0:14:57 > 0:14:59It's famous for land-speed records,
0:14:59 > 0:15:02but it's fascinating for astrobiologists
0:15:02 > 0:15:04because the salty surface here
0:15:04 > 0:15:06not only mimics that found on Mars,
0:15:06 > 0:15:09it contains life.
0:15:10 > 0:15:12Even though this looks dead,
0:15:12 > 0:15:16we could probably take some of these crystals right here
0:15:16 > 0:15:18and get bacteria to grow.
0:15:18 > 0:15:20I know it seems ridiculous,
0:15:20 > 0:15:22but, you know, as a microbiologist
0:15:22 > 0:15:24one of the things that
0:15:24 > 0:15:26we've come to appreciate is
0:15:26 > 0:15:30if there's any liquid water present,
0:15:30 > 0:15:32you're typically going to find life.
0:15:32 > 0:15:35So, life has got this amazing ability to, you know,
0:15:35 > 0:15:37just keep surprising us.
0:15:38 > 0:15:42Unfortunately, Mars is way colder
0:15:42 > 0:15:43than the Bonneville Salt Flats.
0:15:43 > 0:15:47The average temperature of minus 50 degrees Celsius
0:15:47 > 0:15:49is a huge challenge for anything living
0:15:49 > 0:15:51on the surface of the red planet...
0:15:54 > 0:15:58..and it's partly to do with the angle of its axis.
0:15:58 > 0:16:01Earth spins on an axis of 23 degrees,
0:16:01 > 0:16:03which should make the planet unstable -
0:16:03 > 0:16:05but it isn't.
0:16:05 > 0:16:08Earth's axis is stabilised by the moon -
0:16:08 > 0:16:09sort of like an outrigger,
0:16:09 > 0:16:12a gravitational outrigger that keeps the Earth stable.
0:16:12 > 0:16:14Mars doesn't have a large moon and so...
0:16:14 > 0:16:16And it's also closer to Jupiter.
0:16:16 > 0:16:19As a result, its axis wobbles significantly.
0:16:19 > 0:16:20Much, much more than Earth's.
0:16:20 > 0:16:24More than double the wobble of Earth's.
0:16:24 > 0:16:26Over 100,000 years,
0:16:26 > 0:16:29Mars' tilt wobbles by as much as ten degrees,
0:16:29 > 0:16:32causing huge climate change.
0:16:32 > 0:16:34Similar but more extreme
0:16:34 > 0:16:36than the Earth's ice ages.
0:16:36 > 0:16:38At the peaks of that cycle,
0:16:38 > 0:16:42the surface of Mars is briefly warm enough to support life -
0:16:42 > 0:16:46but to survive 100,000 years of cold between these peaks
0:16:46 > 0:16:50would demand a strategy of extreme hibernation.
0:16:50 > 0:16:54But for micro-organisms, this strategy of living when it's warm
0:16:54 > 0:16:58and then sleeping when it's freezing cold is a good one.
0:16:58 > 0:17:02Those organisms can be frozen and thawed without any damage at all.
0:17:02 > 0:17:05Every once in a while, when the tilt is right,
0:17:05 > 0:17:08you get a few thousand years of time to have a go at it,
0:17:08 > 0:17:10and then you go back to deep-freeze sleep.
0:17:14 > 0:17:16That all sounds fine in theory,
0:17:16 > 0:17:21but could any living thing possibly hibernate for up to 100,000 years?
0:17:23 > 0:17:25The answer lies in the salt.
0:17:28 > 0:17:32The salt crystals form in cubes and,
0:17:32 > 0:17:34as they form,
0:17:34 > 0:17:37you'll have pockets of liquid
0:17:37 > 0:17:39that become entrapped
0:17:39 > 0:17:42as the solid salt is forming,
0:17:42 > 0:17:45and the micro-organisms that are present become trapped
0:17:45 > 0:17:47in those fluid inclusions,
0:17:47 > 0:17:50those little pockets of fluid.
0:17:50 > 0:17:53How long, then, could a single bacteria survive
0:17:53 > 0:17:56trapped in a salt crystal?
0:17:56 > 0:17:58Melanie took a crystal
0:17:58 > 0:18:00dated at 97,000 years old
0:18:00 > 0:18:03and drilled into its core.
0:18:03 > 0:18:04She extracted the fluid,
0:18:04 > 0:18:07placed it in a nutrient-rich dish
0:18:07 > 0:18:09and walked away.
0:18:09 > 0:18:11When she came back a week later,
0:18:11 > 0:18:13something astonishing had happened.
0:18:17 > 0:18:2097,000-year-old bacteria
0:18:20 > 0:18:22were flourishing in the dish.
0:18:26 > 0:18:29It was pretty amazing, you know,
0:18:29 > 0:18:31to be able to have
0:18:31 > 0:18:33such strong evidence.
0:18:33 > 0:18:35I mean, taking that fluid inclusion up
0:18:35 > 0:18:39and using it to inoculate media, you know,
0:18:39 > 0:18:41and then having something to grow -
0:18:41 > 0:18:43that's pretty...
0:18:43 > 0:18:45Pretty powerful stuff.
0:18:46 > 0:18:48But how could something survive
0:18:48 > 0:18:50for nearly 100,000 years
0:18:50 > 0:18:52trapped in a salt crystal?
0:18:52 > 0:18:56Only the basic metabolisms
0:18:56 > 0:18:58would be still functional,
0:18:58 > 0:19:00so these organisms are probably
0:19:00 > 0:19:04just expending enough energy
0:19:04 > 0:19:07to keep maybe their DNA repaired,
0:19:07 > 0:19:10and that's probably about it.
0:19:19 > 0:19:20So, right here on earth,
0:19:20 > 0:19:23these bacteria have developed a hibernation strategy
0:19:23 > 0:19:28extreme enough to cope with the length of the Martian ice age
0:19:28 > 0:19:29but, even at its warmest,
0:19:29 > 0:19:31Mars is much, much colder
0:19:31 > 0:19:33than the Bonneville Salt Flats.
0:19:33 > 0:19:36Extreme endurance alone wouldn't be enough.
0:19:39 > 0:19:43So, is there any life form capable of hibernating through extreme cold?
0:19:55 > 0:19:59This doesn't look a very likely place to answer that question,
0:19:59 > 0:20:02but biologists Carl Johansson and Byron Adams
0:20:02 > 0:20:05aren't here to drink in the obvious beauty
0:20:05 > 0:20:07of the Bridal Veil Falls in Utah.
0:20:08 > 0:20:10What we want to try and target is that base there,
0:20:10 > 0:20:13where the upper falls are kind of falling down.
0:20:13 > 0:20:15Just right below the main part of the fall,
0:20:15 > 0:20:17you can see all the moss beds that are in there.
0:20:17 > 0:20:19- That's all pretty good stuff. - You get in there.
0:20:19 > 0:20:20That's nice and slick.
0:20:20 > 0:20:21THEY LAUGH
0:20:21 > 0:20:25- All right, let's go.- All right, man.
0:20:28 > 0:20:31They're looking for a creature with an unusual ability -
0:20:31 > 0:20:33one that might prove crucial
0:20:33 > 0:20:34in the search for alien life.
0:20:37 > 0:20:40Unsurprisingly, it loves water,
0:20:40 > 0:20:42and there's plenty of that here.
0:20:42 > 0:20:43Now, this looks good.
0:20:43 > 0:20:46Here's a good way around this way, I think.
0:20:46 > 0:20:48It's a good spot.
0:20:48 > 0:20:50Watch your step, man. It's slippery, bro.
0:20:50 > 0:20:53Yeah, this looks really good here, man.
0:20:53 > 0:20:54Yo, Carl!
0:20:54 > 0:20:56Bag me, bro.
0:20:56 > 0:20:59This creature is so small that it's almost impossible to see
0:20:59 > 0:21:01with the naked eye.
0:21:02 > 0:21:05Being small doesn't mean it's insignificant,
0:21:05 > 0:21:09it just means they have to collect lots of very damp moss
0:21:09 > 0:21:11to make sure they wrangle one.
0:21:12 > 0:21:14Bag 'em and tag 'em.
0:21:16 > 0:21:17It's got her.
0:21:19 > 0:21:21Dude, I'm taking it right here, bro.
0:21:21 > 0:21:23It's, like, raining on me.
0:21:23 > 0:21:25I know it. That's why I wasn't there.
0:21:25 > 0:21:27It's only when they get back to their lab,
0:21:27 > 0:21:29at Brigham Young University,
0:21:29 > 0:21:31that they can see what they've got.
0:21:34 > 0:21:38So, you remember the samples that we just collected up at the waterfall?
0:21:38 > 0:21:40We brought them back to the lab here
0:21:40 > 0:21:41and we put them in some dishes,
0:21:41 > 0:21:44and I'm picking the animals out of those dishes
0:21:44 > 0:21:46and putting them onto a slide,
0:21:46 > 0:21:49and then I'm going to hand this slide to Carl
0:21:49 > 0:21:51so that he can put it under the microscope,
0:21:51 > 0:21:54and then we'll be able to get a better look at them.
0:21:56 > 0:21:59So, when we look at the slide that Byron brought us
0:21:59 > 0:22:01and we start looking through,
0:22:01 > 0:22:05we can see some movement, right here, of an animal.
0:22:05 > 0:22:06This is the tardigrade.
0:22:06 > 0:22:08Tardigrade means this
0:22:08 > 0:22:10Latin name slow-stepper.
0:22:10 > 0:22:11"Tardi" means slow,
0:22:11 > 0:22:13and "grade" refers to foot.
0:22:13 > 0:22:15You can start to see,
0:22:15 > 0:22:17he's got long thin filaments
0:22:17 > 0:22:18coming off his body
0:22:18 > 0:22:20and some actual...
0:22:20 > 0:22:21What almost look like horns
0:22:21 > 0:22:24coming off his head that he uses in feeding.
0:22:24 > 0:22:26Tardigrades are aquatic,
0:22:26 > 0:22:28so you'd expect them to die
0:22:28 > 0:22:30if they weren't in water,
0:22:30 > 0:22:32but they have a very special ability.
0:22:32 > 0:22:34As that sample jar starts to dry out,
0:22:34 > 0:22:36as that specimen starts to dry out,
0:22:36 > 0:22:38what's cool about these guys is
0:22:38 > 0:22:40they can survive that extreme desiccation,
0:22:40 > 0:22:44drying down to like a crispy little booger.
0:22:44 > 0:22:45It's called a tun.
0:22:46 > 0:22:48They roll up into a special...
0:22:48 > 0:22:50A tight ball, essentially -
0:22:50 > 0:22:53they're like a roly-poly bug almost -
0:22:53 > 0:22:56and then go through a series of radical chemical changes
0:22:56 > 0:22:57in the cells in their bodies
0:22:57 > 0:22:59to deal with this loss of water.
0:23:01 > 0:23:04It looks like it's dead,
0:23:04 > 0:23:06but, when they add water,
0:23:06 > 0:23:07it springs back to life.
0:23:16 > 0:23:18It's not really dead, because
0:23:18 > 0:23:19when we add more water to them -
0:23:19 > 0:23:22when environmental conditions are good again -
0:23:22 > 0:23:23they can come right back alive.
0:23:23 > 0:23:26It's very energetically costly for them.
0:23:26 > 0:23:28They can't go back and forth and back and forth,
0:23:28 > 0:23:32but they can survive some really extreme conditions
0:23:32 > 0:23:33and what happens is,
0:23:33 > 0:23:35as their environment starts to dry out,
0:23:35 > 0:23:37in order to survive that,
0:23:37 > 0:23:40they actively pump all the water out of their bodies
0:23:40 > 0:23:41and out of the cells.
0:23:41 > 0:23:44And so the genes that are being expressed
0:23:44 > 0:23:47for normal cellular processes shut down
0:23:47 > 0:23:52and they completely change the way
0:23:52 > 0:23:53they express their DNA.
0:23:53 > 0:23:55They've got one operating system,
0:23:55 > 0:23:59their genes that operate to put them into and maintain them in a tun,
0:23:59 > 0:24:01and then they switch operating systems when they're, you know,
0:24:01 > 0:24:03carrying out life's activities -
0:24:03 > 0:24:05when they're eating and moving around, and mating,
0:24:05 > 0:24:07and all those kinds of things.
0:24:07 > 0:24:10It's almost like two complete life operating systems.
0:24:11 > 0:24:14But drying out and thriving in a temperate lab
0:24:14 > 0:24:16is completely different from surviving
0:24:16 > 0:24:18on the chilly surface of Mars.
0:24:20 > 0:24:21The coldest place on Earth
0:24:21 > 0:24:24that's in any way comparable to the red planet
0:24:24 > 0:24:26is the Antarctic.
0:24:26 > 0:24:28Tardigrades have been found here,
0:24:28 > 0:24:30but can they be reanimated?
0:24:32 > 0:24:35I've got some animals that have been frozen here
0:24:35 > 0:24:37since the last field season in Antarctica,
0:24:37 > 0:24:41so we extracted them from soils in Antarctica,
0:24:41 > 0:24:43shipped them back here frozen solid
0:24:43 > 0:24:46and they've been frozen solid here at
0:24:46 > 0:24:49at least minus 60 since 2012.
0:24:51 > 0:24:54So, this is the sample that we pulled out of that freezer
0:24:54 > 0:24:56and it's thawed out now.
0:24:56 > 0:24:59What I'm going to do now is I'm going to have a look at it.
0:25:01 > 0:25:03So...
0:25:09 > 0:25:11Holy moley!
0:25:15 > 0:25:17It's mind-blowing, dude.
0:25:17 > 0:25:20It's basically the same community that I saw
0:25:20 > 0:25:22when I collected them in Antarctica.
0:25:22 > 0:25:24We put them in a tube,
0:25:24 > 0:25:25froze them,
0:25:25 > 0:25:27shipped them.
0:25:27 > 0:25:29Four or five years later, we want to study them, right?
0:25:29 > 0:25:31Pull them out, we thawed them out
0:25:31 > 0:25:33and now what I'm seeing now
0:25:33 > 0:25:36looks almost exactly like
0:25:36 > 0:25:40what I saw when I was looking at them, like, fresh in Antarctica.
0:25:40 > 0:25:43You know, there's a few of them that didn't survive the trip, right?
0:25:43 > 0:25:45But, for the most part,
0:25:45 > 0:25:47if you were to show me this, like,
0:25:47 > 0:25:49double blind, fresh,
0:25:49 > 0:25:52I would struggle to tell the difference
0:25:52 > 0:25:54between the sample that I got live down there
0:25:54 > 0:25:56versus one that's been in the freezer
0:25:56 > 0:25:58for like four, five...
0:25:58 > 0:26:00Who knows how long, how many years.
0:26:00 > 0:26:03As well as surviving extreme cold,
0:26:03 > 0:26:06tardigrades have another trick up their sleeve.
0:26:06 > 0:26:09In 2007, the European Space Agency
0:26:09 > 0:26:13sent a sample of tardigrades up to the International Space Station
0:26:13 > 0:26:16for an astonishing experiment.
0:26:16 > 0:26:17They took them into space
0:26:17 > 0:26:19put them on a satellite,
0:26:19 > 0:26:21opened up the door, sent them outside,
0:26:21 > 0:26:24exposed them to extreme temperatures -
0:26:24 > 0:26:27vacuum, hot, cold...
0:26:27 > 0:26:29Huge radiation. And then, when they brought them back to Earth,
0:26:29 > 0:26:31they did what you're seeing here.
0:26:31 > 0:26:34They dumped some water on them to see if they actually reanimated.
0:26:34 > 0:26:36- INTERVIEWER:- What happened?- Voila!
0:26:36 > 0:26:39They take the water up, man,
0:26:39 > 0:26:40and they start... Right?
0:26:40 > 0:26:44They swap out the molecules and... Like a machine, man.
0:26:44 > 0:26:47You add the water to it, they take them up,
0:26:47 > 0:26:50the cells start to do their thing again and they come back alive.
0:26:50 > 0:26:52It always blows my...
0:26:52 > 0:26:55Look, I'm an old, fat dude and I've looked at these 100 times,
0:26:55 > 0:26:57thousands of times, millions maybe...
0:26:57 > 0:26:59- You're not that old.- Well...
0:26:59 > 0:27:01..and when I actually look at them under the microscope,
0:27:01 > 0:27:05every single time, I'm like, "Dang, that's cool, man."
0:27:05 > 0:27:10So, the remarkable tardigrade can survive the extremes of space
0:27:10 > 0:27:13AND the killing cold of Antarctica -
0:27:13 > 0:27:15conditions similar to modern-day Mars.
0:27:17 > 0:27:20And, of course, life can also survive
0:27:20 > 0:27:22for tens of thousands of years
0:27:22 > 0:27:24locked away in a salt crystal.
0:27:25 > 0:27:29So, there could possibly be life on Mars.
0:27:29 > 0:27:31It used to have an ocean
0:27:31 > 0:27:33and there might still be traces
0:27:33 > 0:27:34of that ocean left today.
0:27:36 > 0:27:39But what about the rest of our solar system?
0:27:42 > 0:27:44From the early 1960s,
0:27:44 > 0:27:46scientists have been sending probes out
0:27:46 > 0:27:49into the furthest reaches of our solar system -
0:27:49 > 0:27:52looking, in part, for liquid water...
0:27:53 > 0:27:57..but everything appeared largely frozen, dry and lifeless.
0:28:04 > 0:28:08Most of our solar system was colder than anywhere on Earth -
0:28:08 > 0:28:11even the icy wastes of the high Atacama Desert.
0:28:15 > 0:28:17But, in these remote mountains,
0:28:17 > 0:28:20scientists have uncovered tantalising clues
0:28:20 > 0:28:22that could help answer the question,
0:28:22 > 0:28:28"Are Earth's rich and flourishing oceans unique or ubiquitous?"
0:28:30 > 0:28:36And the Voyager probe launched by Nasa in 1977 pointed the way.
0:28:36 > 0:28:41In 1980, it photographed a small moon of Saturn
0:28:41 > 0:28:43called Enceladus.
0:28:43 > 0:28:46It's tiny, about the same size as the UK -
0:28:46 > 0:28:49and, at first, it looked insignificant.
0:28:49 > 0:28:53Enceladus is this bizarre little moon
0:28:53 > 0:28:55that the Voyager spacecraft
0:28:55 > 0:28:58took a few snapshots of.
0:28:58 > 0:29:01The surface could be seen to be cratered in the north -
0:29:01 > 0:29:04a lot of craters on its icy surface.
0:29:04 > 0:29:06Now, to a planetary scientist and astronomer,
0:29:06 > 0:29:08that means old ice.
0:29:09 > 0:29:12But in the south and, in particular,
0:29:12 > 0:29:15down near the south pole,
0:29:15 > 0:29:19what was seen was a fresh ice surface, very few craters.
0:29:21 > 0:29:23If the ice was fresh,
0:29:23 > 0:29:24then where had it come from?
0:29:26 > 0:29:30Scientists had to wait for years before they got an answer,
0:29:30 > 0:29:33and it was provided by the Cassini probe
0:29:33 > 0:29:36which span past Enceladus in 2005.
0:29:37 > 0:29:40And what Cassini saw shocked scientists.
0:29:46 > 0:29:47Plumes of water vapour
0:29:47 > 0:29:49pouring out from the surface
0:29:49 > 0:29:51of the little moon's south pole.
0:29:53 > 0:29:56So, when Cassini returned these images of the plumes,
0:29:56 > 0:29:58the community just went nuts.
0:29:58 > 0:30:01This was astounding to see these jets of water
0:30:01 > 0:30:03erupting out of this bizarre little moon.
0:30:03 > 0:30:06Enceladus is just 500 kilometres in diameter -
0:30:06 > 0:30:09that's about the width of the United Kingdom.
0:30:09 > 0:30:12And to see these jets erupting was phenomenal.
0:30:14 > 0:30:16As Cassini got closer to Enceladus,
0:30:16 > 0:30:19it revealed the plumes were spewing
0:30:19 > 0:30:21not just from one crack,
0:30:21 > 0:30:24but from four huge fractures in the ice.
0:30:27 > 0:30:30Each of them was about 130 kilometres long,
0:30:30 > 0:30:32two kilometres wide
0:30:32 > 0:30:35and about 500 metres deep
0:30:35 > 0:30:38with water vapour pouring out of them.
0:30:38 > 0:30:42That amount of water could only mean one thing.
0:30:42 > 0:30:45Enceladus had to have a liquid ocean
0:30:45 > 0:30:47beneath its frozen surface...
0:30:48 > 0:30:51..but this dark, subterranean ocean
0:30:51 > 0:30:53would be lacking in one thing
0:30:53 > 0:30:55that's crucial for life on Earth.
0:30:55 > 0:30:57Life, as we know it,
0:30:57 > 0:30:59needs not only liquid water,
0:30:59 > 0:31:03it also requires the elemental building blocks for life -
0:31:03 > 0:31:06the carbon, the hydrogen, the oxygen -
0:31:06 > 0:31:10a smattering of the elements across the periodic table.
0:31:10 > 0:31:14And life requires some form of energy.
0:31:24 > 0:31:28On Earth, the energy for life comes primarily from the sun.
0:31:28 > 0:31:33It's captured through the remarkable process of photosynthesis,
0:31:33 > 0:31:37thanks to plant life - like this very primitive aquatic algae.
0:31:37 > 0:31:41This stuff doesn't look like much.
0:31:41 > 0:31:44People try and avoid it when they go into the sea,
0:31:44 > 0:31:46but it's changed the world.
0:31:46 > 0:31:48This is photosynthesis in action.
0:31:49 > 0:31:51The cells that made this up
0:31:51 > 0:31:55arose around about two billion years ago or thereabouts
0:31:55 > 0:31:57and they cracked the trick
0:31:57 > 0:31:58of using the energy of the sun
0:31:58 > 0:32:00to split water and release oxygen,
0:32:00 > 0:32:03and they're still about the major supplier of oxygen on the planet.
0:32:03 > 0:32:07These things produce more oxygen than the rainforests.
0:32:07 > 0:32:08It's remarkable.
0:32:08 > 0:32:10It looks like slime,
0:32:10 > 0:32:11but without this,
0:32:11 > 0:32:13there wouldn't be any animals,
0:32:13 > 0:32:15there wouldn't be any complex life on this planet.
0:32:15 > 0:32:17This makes the world.
0:32:26 > 0:32:29In the darkness of Enceladus' hidden oceans,
0:32:29 > 0:32:33there could be no photosynthesis to capture the sun's energy -
0:32:33 > 0:32:38yet the possibility of finding life there isn't entirely hopeless.
0:32:44 > 0:32:46This is El Tatio.
0:32:54 > 0:32:57It's a massive geyser field.
0:32:57 > 0:33:01It sits 4,300 metres above sea level,
0:33:01 > 0:33:04high in the Atacama Desert,
0:33:04 > 0:33:06and it's a riot of hydrothermal activity.
0:33:11 > 0:33:14And there's something bubbling up here
0:33:14 > 0:33:17that makes the prospect of life on the distant moon of Enceladus
0:33:17 > 0:33:20just a little more feasible.
0:33:20 > 0:33:23But the clue is what we find here on Earth.
0:33:23 > 0:33:26If we look alongside of this geyser,
0:33:26 > 0:33:29we see these geyser pearls.
0:33:30 > 0:33:31This is silica,
0:33:31 > 0:33:33SiO2,
0:33:33 > 0:33:37that has sintered out of this geyser water.
0:33:39 > 0:33:41And the cosmic dust analyser
0:33:41 > 0:33:43on the Cassini spacecraft
0:33:43 > 0:33:47has captured grains like this -
0:33:47 > 0:33:50except much, much smaller.
0:33:50 > 0:33:54And the fact that those grains are found in the plume of Enceladus
0:33:54 > 0:33:58leads us back to the water/rock interaction
0:33:58 > 0:34:00where that silica in the plumes of Enceladus
0:34:00 > 0:34:02could only be there
0:34:02 > 0:34:05if the ocean of Enceladus
0:34:05 > 0:34:09is cycling with an active, rocky,
0:34:09 > 0:34:11potentially hot sea floor.
0:34:12 > 0:34:15Cassini's measurements indicated that,
0:34:15 > 0:34:17deep in the oceans of Enceladus,
0:34:17 > 0:34:20a process very similar to the geysers of El Tatio
0:34:20 > 0:34:22must be underway.
0:34:23 > 0:34:28Imagine this at the bottom of Enceladus' ocean.
0:34:29 > 0:34:33We have reasonably good evidence that the chemistry and,
0:34:33 > 0:34:36in fact, some of the temperature of the water
0:34:36 > 0:34:39that's coming out of these geysers, right now,
0:34:39 > 0:34:43is comparable to the sea floor of Enceladus.
0:34:45 > 0:34:48The bottom of Enceladus' ocean might look like this,
0:34:48 > 0:34:52but it's cut off from the life-giving properties of the sun
0:34:52 > 0:34:54by kilometres of ice.
0:34:54 > 0:34:57So, does that make finding life impossible?
0:35:01 > 0:35:03In the deepest abyss of our own oceans,
0:35:03 > 0:35:06every bit as dark as those on Enceladus,
0:35:06 > 0:35:08life was thought to be impossible
0:35:08 > 0:35:10until a remarkable discovery,
0:35:10 > 0:35:12just a few decades ago,
0:35:12 > 0:35:14changed all that.
0:35:14 > 0:35:17And so, in the late 1970s,
0:35:17 > 0:35:19spring of 1977,
0:35:19 > 0:35:25explorers went down to hydrothermal vents along the East Pacific rise.
0:35:25 > 0:35:28Originally, they thought that
0:35:28 > 0:35:30they might find some hot springs
0:35:30 > 0:35:31at the bottom of the ocean.
0:35:31 > 0:35:35They did not necessarily expect to find
0:35:35 > 0:35:37a tremendous amount of biology -
0:35:37 > 0:35:39but, lo and behold,
0:35:39 > 0:35:41the hydrothermal vents,
0:35:41 > 0:35:43despite being at incredible depths,
0:35:43 > 0:35:44incredible pressures
0:35:44 > 0:35:48and cut off from the energy of our parent star,
0:35:48 > 0:35:51lo and behold, life was thriving.
0:36:00 > 0:36:03And so, it may be that those kinds of eco-systems,
0:36:03 > 0:36:06the kind of geology and chemistry
0:36:06 > 0:36:08that underlies those eco-systems,
0:36:08 > 0:36:11could also power life
0:36:11 > 0:36:13within these ocean moons.
0:36:15 > 0:36:17This huge abundance of life
0:36:17 > 0:36:20was surviving and thriving
0:36:20 > 0:36:24despite being totally cut off from life-giving sunlight.
0:36:24 > 0:36:26Instead of photosynthesis,
0:36:26 > 0:36:30it was powered by an entirely separate chemistry.
0:36:30 > 0:36:34Here, we're bringing together the keystones
0:36:34 > 0:36:37for life as we know it, the keystones for habitability.
0:36:37 > 0:36:39We've got the water,
0:36:39 > 0:36:41we've got the elements
0:36:41 > 0:36:42and we've got a lot of energy.
0:36:47 > 0:36:49Within that winning combination,
0:36:49 > 0:36:54water plays a crucial - if very simple - role.
0:36:54 > 0:36:57If you simply remove the water and have dry surfaces,
0:36:57 > 0:37:00everything would remain stuck in its place on the surface
0:37:00 > 0:37:03and there would be no movement to bring things together to react,
0:37:03 > 0:37:06so I suppose water is the universal lubricant that makes things happen.
0:37:10 > 0:37:12And the evidence for that can be found throughout
0:37:12 > 0:37:15this seemingly inhospitable environment.
0:37:16 > 0:37:20At the most basic level,
0:37:20 > 0:37:23biology is a layer on geology.
0:37:23 > 0:37:27Biology is harnessing some of the stored chemical energy
0:37:27 > 0:37:32that exists in chemically-rich waters interacting with rocks.
0:37:32 > 0:37:34And, right here, we've got a beautiful example
0:37:34 > 0:37:39of exactly that kind of biology being a layer on geology.
0:37:39 > 0:37:41Everything that you see here,
0:37:41 > 0:37:42the red that you see,
0:37:42 > 0:37:44those are microbes
0:37:44 > 0:37:48utilising the rich chemistry of the geyser water.
0:37:50 > 0:37:53The presence of these extreme life forms
0:37:53 > 0:37:56thriving in almost alien chemistries
0:37:56 > 0:37:59raises real hope for scientists -
0:37:59 > 0:38:01not just in the search for life,
0:38:01 > 0:38:05but in answering one of biology's most fundamental questions.
0:38:06 > 0:38:10Is there a second independent origin of life elsewhere
0:38:10 > 0:38:12within our own solar system?
0:38:12 > 0:38:14And if there is,
0:38:14 > 0:38:17then that tells us that life arises
0:38:17 > 0:38:18wherever the conditions are right,
0:38:18 > 0:38:21and we live in a biological universe.
0:38:23 > 0:38:25If we don't find life within these worlds,
0:38:25 > 0:38:27then that may be an indication
0:38:27 > 0:38:29that the origin of life is hard
0:38:29 > 0:38:31and that life is quite rare
0:38:31 > 0:38:34within our solar system and beyond.
0:38:34 > 0:38:37Both outcomes are equally profound.
0:38:40 > 0:38:44Our solar system may be largely cold and inhospitable,
0:38:44 > 0:38:47but, against all expectations,
0:38:47 > 0:38:49we're now discovering it's also wet.
0:38:50 > 0:38:53But just how soggy is it?
0:38:53 > 0:38:57Is the ocean on Enceladus a freakish one-off?
0:38:57 > 0:38:59Would it be the only moon with an ocean?
0:39:01 > 0:39:03Or could there be other bodies out there
0:39:03 > 0:39:06with as much water as the earth?
0:39:09 > 0:39:11High on the list of possibilities
0:39:11 > 0:39:13would have to be Ganymede,
0:39:13 > 0:39:15orbiting around Jupiter.
0:39:15 > 0:39:19This icy moon is the biggest in our whole solar system...
0:39:21 > 0:39:25..but, initially, it didn't look that promising.
0:39:25 > 0:39:26Back in the 1970s,
0:39:26 > 0:39:29when we only had, like, grainy,
0:39:29 > 0:39:31pixely images from the moon,
0:39:31 > 0:39:32we knew it was icy,
0:39:32 > 0:39:34the surface was icy,
0:39:34 > 0:39:36but we had no idea what's inside.
0:39:36 > 0:39:38What is going on? Does it have a magnetic field?
0:39:38 > 0:39:41Does it have other things like we have on Earth?
0:39:41 > 0:39:45So, it was just a ball of ice.
0:39:45 > 0:39:48Nasa sent the Galileo probe
0:39:48 > 0:39:49to take a closer look -
0:39:49 > 0:39:51and, in 1996,
0:39:51 > 0:39:55it found something completely unprecedented -
0:39:55 > 0:39:56a magnetic field.
0:39:57 > 0:40:02And this would ultimately lead to yet another watery discovery.
0:40:02 > 0:40:05The Galileo mission was definitely a breakthrough in a way,
0:40:05 > 0:40:08because it discovered Ganymede's magnetic fields,
0:40:08 > 0:40:11and Ganymede was suddenly not only the largest moon,
0:40:11 > 0:40:15but also the first moon we know of that has its own magnetic field,
0:40:15 > 0:40:17interior magnetic field.
0:40:17 > 0:40:21Intrigued, Nasa focused the huge power of the Hubble Telescope
0:40:21 > 0:40:24on the surface of Ganymede.
0:40:32 > 0:40:34In orbit around Earth,
0:40:34 > 0:40:38this telescope has sent back amazing pictures of the universe
0:40:38 > 0:40:40as well as our solar system.
0:40:46 > 0:40:49And when it was pointed at Ganymede,
0:40:49 > 0:40:52it revealed yet another first -
0:40:52 > 0:40:56the moon had auroras encircling its north and south poles.
0:40:57 > 0:41:00Because Ganymede has a magnetic field,
0:41:00 > 0:41:02it can direct the charged particles
0:41:02 > 0:41:04from Jupiter's magnetosphere
0:41:04 > 0:41:07and they get directed towards the poles of Ganymede -
0:41:07 > 0:41:09and so what that produces is aurora.
0:41:09 > 0:41:12So, just like we have the Northern Lights and Southern Lights of Earth,
0:41:12 > 0:41:15in Ganymede's case, the energetic particles
0:41:15 > 0:41:18are hitting the really tenuous atmosphere which Ganymede has,
0:41:18 > 0:41:22and that actually causes aurora on Ganymede.
0:41:24 > 0:41:26But the auroras on Ganymede
0:41:26 > 0:41:28held another surprise.
0:41:28 > 0:41:30Astronomers had correctly predicted
0:41:30 > 0:41:32they would rock like a seesaw
0:41:32 > 0:41:34as the moon orbited Jupiter,
0:41:34 > 0:41:37tugged by the magnetic pull of that giant planet.
0:41:38 > 0:41:40They'd calculated the rocking
0:41:40 > 0:41:42to reach a full six degrees,
0:41:42 > 0:41:45but the reality was very different.
0:41:47 > 0:41:49What we saw is that it was always rocked by only two degrees -
0:41:49 > 0:41:51so not six -
0:41:51 > 0:41:53but it seems like a small difference,
0:41:53 > 0:41:54but it is significant
0:41:54 > 0:41:56so we see it's only rocking by two degrees,
0:41:56 > 0:41:58and so there must be an effect
0:41:58 > 0:42:00that suppresses this rocking.
0:42:00 > 0:42:03This apparently trivial detail
0:42:03 > 0:42:05led scientists to a thrilling conclusion.
0:42:07 > 0:42:09The only possible explanation
0:42:09 > 0:42:12for this suppressed rocking of the aurora
0:42:12 > 0:42:15is basically magnetic induction in a liquid...
0:42:15 > 0:42:18In a salty, liquid global ocean inside Ganymede.
0:42:20 > 0:42:23They'd discovered an immense ocean
0:42:23 > 0:42:25calculated to be 100 kilometres deep -
0:42:25 > 0:42:28ten times deeper than any ocean on Earth -
0:42:28 > 0:42:31and it encircles the whole moon.
0:42:31 > 0:42:33In Ganymede's ocean,
0:42:33 > 0:42:35there's more water than the whole of the Earth,
0:42:35 > 0:42:39but it lies under 150 kilometres of ice.
0:42:39 > 0:42:42It's still, even for me, really hard to imagine these worlds.
0:42:42 > 0:42:44I mean, I see images of Ganymede
0:42:44 > 0:42:46and four of the moons every day,
0:42:46 > 0:42:49and I have a really good idea of what they look like,
0:42:49 > 0:42:51but it's still most exciting
0:42:51 > 0:42:53when you look through a, like, small telescope
0:42:53 > 0:42:56and see, like, a bright dot next to Jupiter
0:42:56 > 0:42:58and then you know that the moon really exists.
0:42:58 > 0:43:01And knowing now that this bright dot I see in the telescope,
0:43:01 > 0:43:05next to Jupiter, does have an ocean is really exciting.
0:43:05 > 0:43:08Each new ocean discovered gives a boost to the chances
0:43:08 > 0:43:10of finding life in the solar system.
0:43:11 > 0:43:13In 2022,
0:43:13 > 0:43:16the European Space Agency will send a probe
0:43:16 > 0:43:19to peer beneath the icy surface of Ganymede
0:43:19 > 0:43:22in the hope of revealing some of the secrets
0:43:22 > 0:43:25hidden in the icy depths of that huge ocean.
0:43:39 > 0:43:43But is there only one way to cook up life?
0:43:43 > 0:43:46Could you make it from a different set of ingredients?
0:43:46 > 0:43:49Science fiction writers have speculated wildly
0:43:49 > 0:43:51about alternative life forms -
0:43:51 > 0:43:54but, in the cold, hard world of science,
0:43:54 > 0:43:57we only have proof of life as we know it.
0:43:57 > 0:44:00But if an ocean really is critical,
0:44:00 > 0:44:03does it have to be an ocean of water?
0:44:03 > 0:44:06That's a question that drives Nasa's Chris McKay.
0:44:07 > 0:44:09What I'm really interested in finding is
0:44:09 > 0:44:12what I call a second genesis of life.
0:44:12 > 0:44:16Organisms that are clearly not related to any life on Earth.
0:44:16 > 0:44:20All life on Earth is related to itself, forms a single tree.
0:44:20 > 0:44:22You can call that Life One.
0:44:22 > 0:44:24What I'm looking for is Life Two -
0:44:24 > 0:44:26something that's not related.
0:44:26 > 0:44:28It doesn't have to be profoundly different,
0:44:28 > 0:44:29but it has to be different enough
0:44:29 > 0:44:31that we can say with very high confidence
0:44:31 > 0:44:34that they are not related to us.
0:44:34 > 0:44:35We do not have a common ancestor.
0:44:39 > 0:44:42Where such a life form could feasibly emerge
0:44:42 > 0:44:43was anyone's guess -
0:44:43 > 0:44:49until, in 2005, the world's attention turned to Titan,
0:44:49 > 0:44:51the biggest of the moons which orbit around Saturn.
0:44:56 > 0:44:58At that time, all we knew of it
0:44:58 > 0:45:01was that it looked gassy, orange and lifeless.
0:45:01 > 0:45:04We knew that Titan was a fuzz ball from telescopes.
0:45:04 > 0:45:06Before a spacecraft ever went to Titan,
0:45:06 > 0:45:08just looking at Titan with a telescope,
0:45:08 > 0:45:10we could tell that it had a thick atmosphere.
0:45:10 > 0:45:13We didn't know the composition of the atmosphere
0:45:13 > 0:45:16or the temperature of it, but we knew it had a thick atmosphere.
0:45:18 > 0:45:21But then, in 2005,
0:45:21 > 0:45:24the Cassini-Huygens probe span by,
0:45:24 > 0:45:27revealing a surface that was unexpectedly Earth-like.
0:45:30 > 0:45:32It was dotted with huge lakes
0:45:32 > 0:45:34bearing an uncanny geographical similarity
0:45:34 > 0:45:37to the Great Lakes of North America.
0:45:39 > 0:45:41From a physical point of view,
0:45:41 > 0:45:43the presence of liquid
0:45:43 > 0:45:45creates all these other similarities,
0:45:45 > 0:45:49and so we realised that liquid on Earth, liquid on Titan -
0:45:49 > 0:45:52we're going to expect a lot of commonality, and we see it.
0:45:52 > 0:45:55So, visually, when we look at these images of the lakes,
0:45:55 > 0:45:57we see reflections of what we see in aeroplanes
0:45:57 > 0:46:00when we look down as we fly over the Great Lakes.
0:46:00 > 0:46:03There was one crucial difference, though.
0:46:03 > 0:46:04These weren't lakes of water,
0:46:04 > 0:46:07they were lakes of methane -
0:46:07 > 0:46:09and, at minus 180 degrees Celsius,
0:46:09 > 0:46:11they're too cold for any life form
0:46:11 > 0:46:13with an Earth-like chemistry.
0:46:13 > 0:46:16I would contend that we don't understand
0:46:16 > 0:46:19the role of temperature directly in life.
0:46:19 > 0:46:21Now, on Earth, of course,
0:46:21 > 0:46:23we're used to living in a high-temperature liquid
0:46:23 > 0:46:25at high temperature. We're in the fast lane.
0:46:25 > 0:46:28We metabolise very rapidly
0:46:28 > 0:46:30because we're living at high temperature.
0:46:30 > 0:46:32While on Titan,
0:46:32 > 0:46:34the liquid there is cold,
0:46:34 > 0:46:36the temperatures are cold.
0:46:36 > 0:46:38If there's life there, it's obviously in the slow lane.
0:46:38 > 0:46:40It's metabolising very slowly
0:46:40 > 0:46:42but, so what? What's the rush?
0:46:42 > 0:46:44There's not an absolute tempo
0:46:44 > 0:46:46that life must keep to.
0:46:59 > 0:47:01But is that possible?
0:47:01 > 0:47:05Can you have life using methane rather than water?
0:47:05 > 0:47:08With this in mind, scientists at the picturesque and very watery
0:47:08 > 0:47:11Cornell University, in New York,
0:47:11 > 0:47:14are trying to establish whether methane-based life
0:47:14 > 0:47:16is even theoretically possible.
0:47:17 > 0:47:20They took the chemical ingredients that exist on Titan
0:47:20 > 0:47:21and mixed them up.
0:47:25 > 0:47:27Not in a test tube,
0:47:27 > 0:47:28but inside a computer.
0:47:38 > 0:47:42The computer built a three-dimensional membrane -
0:47:42 > 0:47:44the outside wall of a cell.
0:47:46 > 0:47:52Except this alien membrane functions in methane, not water.
0:47:56 > 0:47:59It's not life yet, it's just a house.
0:47:59 > 0:48:02But the very first thing that you have to do is
0:48:02 > 0:48:04you have to have somewhere to shelter,
0:48:04 > 0:48:08and a membrane is a way of keeping the outside to the outside.
0:48:11 > 0:48:12A small step,
0:48:12 > 0:48:15but this was ground-breaking science.
0:48:15 > 0:48:18For the first time, it opened up the possibility
0:48:18 > 0:48:21that there could be a second tree of life.
0:48:21 > 0:48:23We tend to think that life would look like us.
0:48:23 > 0:48:25You just have to look at the Star Trek movies.
0:48:25 > 0:48:27All the aliens kind of look like insects
0:48:27 > 0:48:29and things that we already know,
0:48:29 > 0:48:32but why not be something completely different?
0:48:32 > 0:48:34Something that we can't imagine,
0:48:34 > 0:48:38but something perfectly suited to the conditions that are on Titan?
0:48:44 > 0:48:48But if this extraordinary computer model's right, how would we know?
0:48:50 > 0:48:53At the moment, we can't physically search for life on Titan,
0:48:53 > 0:48:56but that doesn't mean there wouldn't be other telltale signs
0:48:56 > 0:48:59that we can detect.
0:48:59 > 0:49:01If we look at carbon dioxide,
0:49:01 > 0:49:03just out in the field, down the road -
0:49:03 > 0:49:05during winter, it rises
0:49:05 > 0:49:07and during summer, it drops.
0:49:07 > 0:49:11And that's because plants take it up to make leaves.
0:49:11 > 0:49:13They pull in the carbon dioxide, it drops,
0:49:13 > 0:49:15they make leaves.
0:49:15 > 0:49:17In the fall, those leaves fall, decompose,
0:49:17 > 0:49:19the carbon dioxide comes back up.
0:49:19 > 0:49:22So, there's a seasonal phase in carbon dioxide
0:49:22 > 0:49:26that's directly due to biological activity at the surface
0:49:26 > 0:49:31consuming, and then releasing, that carbon dioxide.
0:49:31 > 0:49:33We're pretty sure there's no vegetation on Titan,
0:49:33 > 0:49:35but what could be the equivalent
0:49:35 > 0:49:38of the fluctuations of carbon dioxide
0:49:38 > 0:49:39that would indicate that something
0:49:39 > 0:49:41was alive on the distant moon?
0:49:41 > 0:49:44And the answer, we think, is hydrogen.
0:49:44 > 0:49:47Organisms on Titan would derive their energy
0:49:47 > 0:49:50by reacting hydrogen with various other organic compounds
0:49:50 > 0:49:52and so, if there was life on Titan,
0:49:52 > 0:49:56that life should represent a strong sink -
0:49:56 > 0:49:57a strong loss -
0:49:57 > 0:49:59of hydrogen at the surface.
0:49:59 > 0:50:01And that loss of hydrogen at the surface
0:50:01 > 0:50:04would have an effect on the hydrogen distribution.
0:50:04 > 0:50:08So, we've said that the way to detect life on Titan
0:50:08 > 0:50:10is to look at the distribution of hydrogen.
0:50:10 > 0:50:12If there's no life,
0:50:12 > 0:50:15the distribution will just be flat, uninteresting,
0:50:15 > 0:50:17but if there is life, and the life is growing vigorously,
0:50:17 > 0:50:22it will eat out the lower part of that hydrogen concentration.
0:50:22 > 0:50:25There will be a depletion in hydrogen near the surface.
0:50:29 > 0:50:31In 2005,
0:50:31 > 0:50:35astronomers finally had an opportunity to test this hypothesis
0:50:35 > 0:50:39when the Cassini spacecraft sent down a probe called Huygens
0:50:39 > 0:50:41to land on Titan.
0:50:41 > 0:50:45The pictures the probe sent back were stunning.
0:50:45 > 0:50:48Unfortunately, there were no obvious signs of life...
0:50:49 > 0:50:52..but Huygens was doing more than taking images of Titan -
0:50:52 > 0:50:57it was making detailed measurements of the mysterious atmosphere.
0:50:57 > 0:51:01As it turned out, the most important were the readings it took
0:51:01 > 0:51:04of hydrogen levels as it floated down from space to the surface.
0:51:09 > 0:51:14As the probe landed, scientists noticed something remarkable -
0:51:14 > 0:51:16the hydrogen levels dropped abruptly.
0:51:18 > 0:51:20When I heard about this result,
0:51:20 > 0:51:23for a couple of minutes, I was ecstatic, thinking,
0:51:23 > 0:51:26"Oh, my God, this is just textbook science -
0:51:26 > 0:51:30"prediction, confirmation and a Nobel Prize comes next," right?
0:51:30 > 0:51:33But reality set in soon after
0:51:33 > 0:51:35as I looked at the paper in detail
0:51:35 > 0:51:37and considered how easy it is
0:51:37 > 0:51:40to jump to the answer you want.
0:51:40 > 0:51:43It's really a question of excluding other possibilities.
0:51:49 > 0:51:54On its own, Huygens' sensational measurement was inconclusive.
0:51:54 > 0:51:56What they needed was verification.
0:51:56 > 0:51:59So, Nasa put together a team of their best
0:51:59 > 0:52:00and brightest engineers
0:52:00 > 0:52:03to design a spacecraft capable of exploring
0:52:03 > 0:52:06the unique and technically challenging oceans
0:52:06 > 0:52:07of this liquid world.
0:52:12 > 0:52:15And, after a number of false starts and dead ends,
0:52:15 > 0:52:17they came up with this -
0:52:17 > 0:52:19a submarine.
0:52:20 > 0:52:22I was reading 20,000 Leagues Under The Sea
0:52:22 > 0:52:23and thought, you know,
0:52:23 > 0:52:28"Titan has this wonderful group of seas. What's underneath there?"
0:52:28 > 0:52:29If we don't look there,
0:52:29 > 0:52:31we really haven't seen what's going on in Titan.
0:52:31 > 0:52:35So, we came up with a fairly long submarine.
0:52:35 > 0:52:37As you see from terrestrial submarines,
0:52:37 > 0:52:40they're usually about 10:1 on dimensions,
0:52:40 > 0:52:42length to the diameter,
0:52:42 > 0:52:45and the reason for this is, it really reduces your drag.
0:52:45 > 0:52:47We are obviously a little power-limited.
0:52:47 > 0:52:48We have a lot of communications to do.
0:52:48 > 0:52:51We have four thrusters in the back, here,
0:52:51 > 0:52:54which use electrical energy - so we went with a very long submarine.
0:52:54 > 0:52:57If you can get below the surface of the sea
0:52:57 > 0:52:59and get all the way down to the bottom in certain areas,
0:52:59 > 0:53:02and actually touch the silt that's on the bottom and sample it,
0:53:02 > 0:53:04and learn what that's made of,
0:53:04 > 0:53:07it'll tell you so much about the environment that you're in.
0:53:07 > 0:53:11But if you have a boat that just drives on the surface,
0:53:11 > 0:53:14figuring out how to get a probe all the way down to the bottom,
0:53:14 > 0:53:18get that sample all the way back up to the surface and sample it,
0:53:18 > 0:53:20it really becomes an intractable problem.
0:53:20 > 0:53:22There's so many things that can go wrong doing that.
0:53:22 > 0:53:25And, instead, we said, "If we can encapsulate everything together
0:53:25 > 0:53:27"in a submarine, then we could go right down
0:53:27 > 0:53:30"and do that sampling and come all the way back up to the surface."
0:53:30 > 0:53:33And so the submarine allows us to explore the atmosphere,
0:53:33 > 0:53:35the wind, the waves,
0:53:35 > 0:53:37to sound with a sonar to the bottom,
0:53:37 > 0:53:39to measure the topography,
0:53:39 > 0:53:41to see what the contours of the bottom look like
0:53:41 > 0:53:44and then to go down and actually touch the silt
0:53:44 > 0:53:47that's been settling there for thousands and thousands of years.
0:53:57 > 0:54:00But sailing a large, one-tonne sub
0:54:00 > 0:54:03around Titan's super-cold, methane-rich seas
0:54:03 > 0:54:05isn't without its problems.
0:54:06 > 0:54:09Fortunately, Nasa has the technology
0:54:09 > 0:54:12to replicate conditions on the freezing moon,
0:54:12 > 0:54:13and this is it.
0:54:15 > 0:54:18Inside this huge tank,
0:54:18 > 0:54:21scientists can safely and accurately mix up
0:54:21 > 0:54:24the highly volatile cocktail of chemicals
0:54:24 > 0:54:26that make up the atmosphere of the huge moon.
0:54:28 > 0:54:30As we design and build the craft,
0:54:30 > 0:54:33we can basically use this facility
0:54:33 > 0:54:35to test problems or issues
0:54:35 > 0:54:37that come up for the submarine,
0:54:37 > 0:54:39so we can use this facility
0:54:39 > 0:54:42to basically create the seas of Titan,
0:54:42 > 0:54:45the coldness of Titan, the pressures of Titan.
0:54:45 > 0:54:48They have discovered that one of the biggest problems
0:54:48 > 0:54:50of Titan's methane seas
0:54:50 > 0:54:52is that they're rich in nitrogen,
0:54:52 > 0:54:55and that could make it very difficult to sail the sub around.
0:54:57 > 0:55:00There could be so much nitrogen dissolved in the sea that,
0:55:00 > 0:55:02when the propellers turn on our jets,
0:55:02 > 0:55:04it might just make a lot of bubbles
0:55:04 > 0:55:06and not be able to push against the liquid.
0:55:06 > 0:55:07So we're doing analysis now
0:55:07 > 0:55:10and we hope to do some testing in the near future that shows us
0:55:10 > 0:55:14what happens if you spin a propeller in liquid methane
0:55:14 > 0:55:17and liquid ethane with lots of nitrogen dissolved in it,
0:55:17 > 0:55:20and can you get any thrust out or not?
0:55:20 > 0:55:22This is a really important question to answer.
0:55:22 > 0:55:25There's other ways to propel the submarine if that doesn't work,
0:55:25 > 0:55:27but the design that we came up with
0:55:27 > 0:55:29helps us get to that simple place,
0:55:29 > 0:55:31in terms of space operations.
0:55:39 > 0:55:42The sub will be packed full of scientific instruments
0:55:42 > 0:55:44and bristling with cameras,
0:55:44 > 0:55:47but there's one thing the scientists feel
0:55:47 > 0:55:49will make the mission more than anything else.
0:55:52 > 0:55:54That first picture, are you kidding?
0:55:54 > 0:55:57That first picture from a submarine,
0:55:57 > 0:55:58from anybody's submarine,
0:55:58 > 0:56:02on the surface of a sea on another planet in our solar system,
0:56:02 > 0:56:04changes the world.
0:56:04 > 0:56:06I mean, that's something that none of us have ever seen before.
0:56:06 > 0:56:08That is true discovery.
0:56:08 > 0:56:10That is why we do any of this
0:56:10 > 0:56:11and that would be awesome.
0:56:11 > 0:56:15That first picture alone would make this entire mission worth it.
0:56:15 > 0:56:19No scientist is saying that the cameras of the Titan sub
0:56:19 > 0:56:23will definitely ping back pictures of living organisms,
0:56:23 > 0:56:27but they believe sending a sub to this strange moon
0:56:27 > 0:56:30gives them the best chance of finding a new form of life.
0:56:33 > 0:56:34I grew up when Star Trek
0:56:34 > 0:56:36was just coming out,
0:56:36 > 0:56:37and it was an inspiration to me,
0:56:37 > 0:56:40but the key moment was when I realised
0:56:40 > 0:56:43that the job I wanted was not Kirk's job,
0:56:43 > 0:56:45but Spock's job.
0:56:45 > 0:56:46He's the one with the tricorder.
0:56:46 > 0:56:49He's the one that's detecting life
0:56:49 > 0:56:51and my favourite saying is,
0:56:51 > 0:56:53"It's life, Jim, but not as we know it."
0:56:53 > 0:56:55That's what I want to be able to say.
0:56:55 > 0:56:57I want to get data back from a probe -
0:56:57 > 0:57:00Titan, Mars, Enceladus, wherever -
0:57:00 > 0:57:04and be able to say, "It's life, Jim, but not as we know it."
0:57:08 > 0:57:10Is it possible that we could see stuff
0:57:10 > 0:57:12that hints really strongly at life?
0:57:12 > 0:57:13It's possible. I mean, we might see things
0:57:13 > 0:57:15that look like lichens or algae
0:57:15 > 0:57:17growing on the rocks on the shore.
0:57:17 > 0:57:19We might see massive stuff on the surface,
0:57:19 > 0:57:21but we have no idea.
0:57:21 > 0:57:24We used to think that the rest of our solar system
0:57:24 > 0:57:26was frozen and dead,
0:57:26 > 0:57:29but we now know that there are oceans of water and liquid
0:57:29 > 0:57:32in places we never thought possible.
0:57:32 > 0:57:36In 2015, the New Horizon mission to Pluto
0:57:36 > 0:57:38ticked off the last of the great worlds
0:57:38 > 0:57:41to be explored in the solar system,
0:57:41 > 0:57:43but we're only at the beginning of the quest
0:57:43 > 0:57:46to find the Holy Grail of space science -
0:57:46 > 0:57:47life.
0:57:47 > 0:57:49We're through with the age of discovery.
0:57:49 > 0:57:52We've discovered all the planets, we know what's there.
0:57:52 > 0:57:54We've got a rough map of them all
0:57:54 > 0:57:56and a rough understanding of how they work.
0:57:56 > 0:57:58The next question -
0:57:58 > 0:58:01the question that I think should motivate and guide planetary science
0:58:01 > 0:58:03for the next 20 years - is,
0:58:03 > 0:58:06"Is there any life in these various and diverse oceans?"
0:58:08 > 0:58:10Nearly two centuries ago,
0:58:10 > 0:58:14Charles Darwin set out on a voyage of discovery
0:58:14 > 0:58:15that changed the world.
0:58:15 > 0:58:17Perhaps Nasa's Titan submarine
0:58:17 > 0:58:19will be a modern counterpart
0:58:19 > 0:58:21to Darwin's ship, the Beagle -
0:58:21 > 0:58:24and, in the search for a new form of life,
0:58:24 > 0:58:27will boldly go where no-one has gone before.