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0:00:03 > 0:00:07- Saturn - the most beautiful planet - in the cosmos.
0:00:10 > 0:00:16- Our understanding of Saturn and - its moons has been revolutionized.
0:00:17 > 0:00:23- In this programme, we reveal the - remarkable story of Saturn's moons.
0:00:25 > 0:00:26- It's forensic.
0:00:26 > 0:00:29- It's like crime scene forensics.
0:00:29 > 0:00:32- We can go there - and take measurements.
0:00:33 > 0:00:36- There are clouds there - and it rains methane.
0:00:36 > 0:00:40- It's cold and there are - methane lakes there.
0:00:43 > 0:00:47- It's even possible that some - of Saturn's moons are home to life.
0:00:49 > 0:00:53- And in the future, - they could even become our new home.
0:01:02 > 0:01:03- Subtitles
0:01:03 > 0:01:05- Subtitles- - Subtitles
0:01:12 > 0:01:14- Saturn is huge.
0:01:19 > 0:01:22- It's more than 700 times - bigger than the earth.
0:01:26 > 0:01:28- But don't let size fool you.
0:01:31 > 0:01:34- Even though Saturn is big - and very heavy...
0:01:34 > 0:01:37- ..it has a lower density than water.
0:01:39 > 0:01:44- So if you could find a bath big - enough and fill it with water...
0:01:44 > 0:01:45- ..Saturn would float.
0:01:46 > 0:01:49- Its density is between - that of air and water.
0:01:51 > 0:01:57- Other planets have rings, but none - so vast and glorious as Saturn's.
0:02:00 > 0:02:04- These rings stretch out into space - for over 66,000 miles.
0:02:10 > 0:02:15- Saturn's rings are made up mostly - of tiny particles of ice and dust.
0:02:16 > 0:02:19- They seem solid - when you look at them...
0:02:21 > 0:02:25- ..but our satellites have gone - straight through them...
0:02:25 > 0:02:28- ..without any damage or bumps.
0:02:32 > 0:02:37- The rings are made of millions - of snowballs, or pieces of ice.
0:02:37 > 0:02:40- They all orbit Saturn together.
0:02:41 > 0:02:43- Some are the size of a house.
0:02:43 > 0:02:46- Millions of smaller ones - are the size of a fist.
0:02:49 > 0:02:52- Racing in and around the rings - are over 60 moons.
0:02:53 > 0:02:58- They all range in size, - from tiny snowballs...
0:02:59 > 0:03:01- ..to large worlds.
0:03:04 > 0:03:07- And all of them - merit study by scientists.
0:03:12 > 0:03:15- We thought planets like Saturn - were too far away...
0:03:16 > 0:03:18- ..for anything to happen on them.
0:03:19 > 0:03:23- We thought there'd be nothing there. - We were so wrong!
0:03:29 > 0:03:33- Saturn's first shocker - was its wild weather.
0:03:38 > 0:03:41- By sending probes like Voyager - to the planet...
0:03:41 > 0:03:45- ..we've discovered that Saturn - has violent storms.
0:03:49 > 0:03:52- These winds - race through Saturn's cloud tops...
0:03:52 > 0:03:56- ..faster than earth's - strongest cyclones.
0:03:58 > 0:04:03- And the lightning bolts are far more - powerful than those on earth.
0:04:06 > 0:04:09- Saturn's ferocious weather - is surprising.
0:04:09 > 0:04:13- On earth, weather is driven - by the heat energy of the sun.
0:04:15 > 0:04:19- The sun warms the land, - generating wind.
0:04:20 > 0:04:25- It causes the seas to evaporate, - creating clouds and rain.
0:04:27 > 0:04:31- Saturn lies too far from the sun - to feel the same warmth...
0:04:32 > 0:04:36- ..so something else must be - creating this violent weather.
0:04:38 > 0:04:39- But what?
0:04:45 > 0:04:51- Our planets have been created - from dust, gas and ice.
0:04:54 > 0:04:59- The same ingredients can still be - found today in places like Iceland.
0:05:03 > 0:05:06- If you want to build - a giant planet like Saturn...
0:05:07 > 0:05:10- ..this pile of raw material - is a great visual analogue.
0:05:10 > 0:05:14- There's a lot of oxygen and hydrogen - in the universe.
0:05:14 > 0:05:16- That makes water, and water ice.
0:05:16 > 0:05:20- The stuff that made the solar system - is this stuff here.
0:05:20 > 0:05:24- Dirty ice, water ice, with a bit - of rocky and metallic minerals...
0:05:24 > 0:05:27- ..left in there - in the cold of space.
0:05:28 > 0:05:33- From a vast cloud of gas, - dust and ice, a star is born.
0:05:40 > 0:05:42- Our star - the sun.
0:05:49 > 0:05:52- The heat of the sun - melts the ice closest to it...
0:05:52 > 0:05:58- ..and blows away the gas, - leaving only rocky debris behind.
0:06:02 > 0:06:05- But further out, - icy material and gas survive.
0:06:07 > 0:06:10- Once you've fired up - that campfire...
0:06:11 > 0:06:14- ..what's left - in the inner solar system...
0:06:14 > 0:06:18- ..is the silicate minerals you - make a planet like the earth from.
0:06:18 > 0:06:20- Away from the sun, - where it's colder...
0:06:20 > 0:06:23- ..you cross the frost line - and what's out there...
0:06:24 > 0:06:27- ..is still cold enough - to maintain the ice behind.
0:06:27 > 0:06:28- There's a lot of it there.
0:06:29 > 0:06:32- At first, you make a solid core - of this material.
0:06:32 > 0:06:34- When you reach a critical mass...
0:06:34 > 0:06:37- ..you have enough gravitational - influence to draw in...
0:06:37 > 0:06:41- ..some of the hydrogen and helium - in the interplanetary cloud.
0:06:43 > 0:06:45- Saturn has begun to form.
0:06:48 > 0:06:49- It draws in gas...
0:06:52 > 0:06:54- ..and it grows bigger and bigger.
0:06:59 > 0:07:03- The planet's gravity - also begins to grow in strength...
0:07:09 > 0:07:11- ..and things get seriously hot.
0:07:15 > 0:07:19- Even today, Saturn's core is hotter - than the surface of the sun.
0:07:24 > 0:07:29- It's this heat, rising up, which - forms Saturn's distinct bands...
0:07:30 > 0:07:32- ..and drives its extreme weather.
0:07:35 > 0:07:37- The planet is rotating very quickly.
0:07:39 > 0:07:41- It rotates once every 10.5 hours...
0:07:42 > 0:07:46- ..and this creates - Saturn's distinctive rings.
0:07:48 > 0:07:51- Air can't move easily - from north to south...
0:07:52 > 0:07:57- ..so it's forced sideways - and it forms the rings we see.
0:07:58 > 0:08:02- At Saturn's north pole, - something remarkable happens.
0:08:05 > 0:08:09- A stream of air that's shaped - like a perfect hexagon.
0:08:16 > 0:08:22- This hexagon on the planet's pole - is created by waves of pressure...
0:08:22 > 0:08:28- ..that go up and down three times - as they travel around the planet.
0:08:30 > 0:08:35- And it's this wave that creates - the hexagonal shape in the clouds.
0:08:40 > 0:08:43- By using cameras - mounted on spacecrafts...
0:08:43 > 0:08:47- ..scientists have revealed - Saturn's wild weather.
0:08:50 > 0:08:54- And these spacecrafts - have also revealed more...
0:08:54 > 0:08:57- ..about the planet's secrets - - the rings.
0:09:00 > 0:09:04- When Galileo first looked at Saturn - through a basic telescope...
0:09:06 > 0:09:09- ..it looked like - the planet had ears.
0:09:13 > 0:09:16- But soon after, - lenses were improved...
0:09:16 > 0:09:22- ..and they discovered the - planet had rings around it.
0:09:25 > 0:09:29- Until recently, we thought it was - the only planet which has rings.
0:09:30 > 0:09:35- It's an astonishing sight to see - Saturn with these rings around it.
0:09:36 > 0:09:37- It's brilliant!
0:09:39 > 0:09:43- I first saw Saturn through a large - telescope in Cardiff.
0:09:43 > 0:09:47- I really wanted my own telescope - and I got one on my 50th birthday!
0:09:48 > 0:09:51- When you see Saturn - through a telescope...
0:09:51 > 0:09:54- ..and you see the rings - around the planet...
0:09:54 > 0:09:59- ..it's surprising that it's so easy - to see something so remarkable.
0:10:00 > 0:10:03- From afar, the rings seem - quiet and serene.
0:10:07 > 0:10:10- But up close - it's a very different picture...
0:10:12 > 0:10:15- ..as a space probe called Cassini - has revealed.
0:10:17 > 0:10:22- Images from Cassini show ice - particles jostling for position...
0:10:23 > 0:10:25- ..whizzing about inside the rings.
0:10:32 > 0:10:34- Some are small - others are huge.
0:10:37 > 0:10:41- We didn't learn about it - until we sent spacecrafts...
0:10:41 > 0:10:45- ..to interesting places - in our solar system.
0:10:47 > 0:10:49- We've seen a revolution...
0:10:49 > 0:10:53- ..in our understanding of Saturn - and its moons.
0:10:53 > 0:10:58- In 2004, Cassini revealed how - amazing these moons actually are.
0:11:02 > 0:11:05- The moons - are all different shapes and sizes.
0:11:06 > 0:11:12- Some are made of rock, others from - gases, or a combination of the two.
0:11:13 > 0:11:16- But each one - has its own unique properties.
0:11:20 > 0:11:23- Sometimes, some of Saturn's - icy moons break up...
0:11:30 > 0:11:33- ..adding new material to the rings.
0:11:37 > 0:11:40- By looking at how the rings - constantly change...
0:11:40 > 0:11:45- ..scientists are able to solve - some of the secrets of the cosmos.
0:11:49 > 0:11:52- All the planets - in our solar system...
0:11:54 > 0:11:58- ..evolved from a disk of dust - and gas 4.5 billion years ago.
0:12:03 > 0:12:08- Saturn's rings give us a glimpse of - how our planet system was formed.
0:12:13 > 0:12:15- The rings around Saturn...
0:12:15 > 0:12:20- ..are similar to conditions in - the early days of our solar system.
0:12:20 > 0:12:25- When the planets were being created, - there was a disc of matter...
0:12:25 > 0:12:28- ..similar to the rings - around Saturn today.
0:12:29 > 0:12:35- Cassini shows structures forming - spontaneously inside the rings.
0:12:37 > 0:12:42- One of the problems with trying to - work out how planets were formed...
0:12:42 > 0:12:46- ..was what caused the dust - to start clumping together.
0:12:46 > 0:12:52- What we see by looking at Saturn's - rings is it happens spontaneously.
0:12:54 > 0:12:58- As they grow, the effect of gravity - becomes more prominent.
0:12:58 > 0:13:00- That's what controls events.
0:13:04 > 0:13:05- Planets form.
0:13:06 > 0:13:10- The more planets form, - the more material is mopped up.
0:13:11 > 0:13:14- As they collect more material, - they clear a path.
0:13:20 > 0:13:24- The telescope sees curious - structures within the rings.
0:13:27 > 0:13:32- The particles collide with each - other and create different patterns.
0:13:39 > 0:13:43- Perhaps similar forces - influenced the earth's formation.
0:13:49 > 0:13:53- Saturn's rings also show us - why planets stop growing.
0:13:55 > 0:13:59- A moon called Pan sits near - the middle of one of Saturn's rings.
0:14:01 > 0:14:04- Pan should be huge - with so much ice around it.
0:14:06 > 0:14:08- But it isn't.
0:14:09 > 0:14:12- Pan is a very odd-looking moon.
0:14:12 > 0:14:15- It's like two saucers back to back.
0:14:16 > 0:14:18- It looks like a flying saucer!
0:14:19 > 0:14:25- Within Saturn's rings, there are - areas where a path has been cleared.
0:14:25 > 0:14:28- Sometimes, this is caused - by a small moon...
0:14:30 > 0:14:35- ..mopping up matter around it - to clear a path for itself.
0:14:39 > 0:14:43- Rather than pull material in, - Pan appears to push it away.
0:14:48 > 0:14:52- This may explain why multiple - planets form around stars...
0:14:53 > 0:14:55- ..instead of single giant planets.
0:14:59 > 0:15:02- Of all Cassini's discoveries...
0:15:02 > 0:15:06- ..the most important - is also the most surprising.
0:15:06 > 0:15:10- A moon that may be home to life.
0:15:13 > 0:15:14- .
0:15:24 > 0:15:24- Subtitles
0:15:24 > 0:15:26- Subtitles- - Subtitles
0:15:36 > 0:15:40- We've been studying our moon - for centuries.
0:15:43 > 0:15:47- Every furrow and every crater - has been carefully studied.
0:15:47 > 0:15:50- We know there is no life - on our moon.
0:15:53 > 0:15:58- But what about other moons - in the Cosmos? Are they dead too?
0:16:01 > 0:16:06- It's fair to say that nobody - expected much from Saturn's moons.
0:16:06 > 0:16:08- They're too far from the sun.
0:16:09 > 0:16:13- They're just snowballs - covered in a thick layer of ice.
0:16:17 > 0:16:21- We can now send spacecrafts - like Cassini to these places.
0:16:22 > 0:16:27- It's remarkable that developments - in optics and microelectronics...
0:16:28 > 0:16:32- ..and the fact we can send probes - to space is unbelievable.
0:16:33 > 0:16:40- At first glance, Saturn's moons bear - striking similarities to our own.
0:16:42 > 0:16:44- Moons like Rhea and Dione.
0:16:46 > 0:16:50- But there's one that reminds us - of the Star Wars film.
0:16:52 > 0:16:58- One tiny moon called Mimas looks - like the Death Star from Star Wars.
0:16:58 > 0:17:00- That huge crater...
0:17:01 > 0:17:05- ..was probably created - by a collision in the distant past.
0:17:05 > 0:17:09- It wasn't enough of an impact - to destroy Mimas...
0:17:09 > 0:17:13- ..but it did leave a massive hole - on its surface.
0:17:14 > 0:17:19- Other moons are more dramatic, like - Iapetus - the moon with two faces.
0:17:21 > 0:17:25- One hemisphere of Iapetus - is extremely white...
0:17:25 > 0:17:29- ..and its brightness - seems to reflect any light.
0:17:30 > 0:17:33- But the other side is dark, - like soot.
0:17:37 > 0:17:40- Every one of Saturn's moons - has a story.
0:17:43 > 0:17:45- Take Enceladus - a small ice moon.
0:17:49 > 0:17:52- Ten years ago, - nobody paid it any attention.
0:17:54 > 0:17:57- But that's all changed - and this is why.
0:18:01 > 0:18:06- Enceladus orbits inside Saturn's - outermost ring the E-ring.
0:18:08 > 0:18:10- This ring puzzled scientists.
0:18:12 > 0:18:16- How could a ring so broad - hold itself together?
0:18:21 > 0:18:24- Enceladus sits right in the middle - of the E-ring.
0:18:25 > 0:18:27- A few scientists...
0:18:29 > 0:18:34- ..suggested that Enceladus was - ejecting water and ice into space.
0:18:34 > 0:18:37- This would explain why the E-ring
0:18:38 > 0:18:40- It turns out they were right.
0:18:46 > 0:18:50- Ten years ago, Cassini captured - an astonishing sight.
0:18:50 > 0:18:54- Hundreds of geysers - shooting water into space.
0:18:59 > 0:19:01- As Enceladus orbits Saturn...
0:19:02 > 0:19:06- ..these geysers create - a shimmering halo around the planet.
0:19:07 > 0:19:08- This is the E-ring.
0:19:16 > 0:19:21- This water also interacts - with Saturn's magnetic field...
0:19:22 > 0:19:25- ..creating auroras - above the planet's poles.
0:19:33 > 0:19:37- How can geysers exist on - a frozen moon so far from the sun?
0:19:43 > 0:19:47- On earth, geysers form - in highly volcanic places.
0:19:49 > 0:19:55- Enceladus, so small and so far from - the sun, should be cold and dead.
0:19:57 > 0:20:01- What heats it is Saturn's gravity.
0:20:03 > 0:20:08- The source of the heat on Enceladus - is the eccentric orbit of that moon.
0:20:09 > 0:20:11- Sometimes it's a little closer - to Saturn.
0:20:12 > 0:20:14- Sometimes it's further away.
0:20:14 > 0:20:17- That heating on Enceladus from that - kneading gravitationally...
0:20:18 > 0:20:21- ..making the moon stretch and pull - is what warms the interior...
0:20:21 > 0:20:25- ..causing the activity on Enceladus - that we see today.
0:20:28 > 0:20:31- Saturn pushes and pulls Enceladus.
0:20:36 > 0:20:38- The moon's core moves...
0:20:41 > 0:20:42- ..and creates heat.
0:20:46 > 0:20:51- The heat melts the ice around it, - creating vast subsurface lakes.
0:20:55 > 0:20:59- This water jets out - through cracks in the surface ice.
0:21:04 > 0:21:08- On earth, where there's liquid water - there's life.
0:21:10 > 0:21:12- Is the same true on Enceladus?
0:21:16 > 0:21:19- There are lakes there, - under the surface.
0:21:19 > 0:21:24- There is water and the temperature - is good, so can it harbour life?
0:21:26 > 0:21:29- We sent Cassini - to fly over these cracks...
0:21:30 > 0:21:32- ..where the water was rushing out.
0:21:35 > 0:21:40- Scientists hoped to find chemicals - like ammonia and salts in the water.
0:21:41 > 0:21:44- They are the building blocks - of life.
0:21:46 > 0:21:48- They weren't disappointed.
0:21:50 > 0:21:53- When Cassini took a closer look - at Enceladus...
0:21:54 > 0:21:58- ..it found everything that is needed - to sustain life.
0:21:58 > 0:22:02- Carbon, nitrogen, hydrogen - and liquid water.
0:22:03 > 0:22:05- This was big news - in the science world.
0:22:10 > 0:22:12- Could life exist on Enceladus?
0:22:16 > 0:22:21- To find out, scientists hope to send - more spacecrafts to collect samples.
0:22:29 > 0:22:31- It's like crime scene forensics.
0:22:32 > 0:22:37- We can go there, take measurements - and find out what all this means.
0:22:41 > 0:22:45- We have discovered so many - amazing things about that moon.
0:22:46 > 0:22:51- I think a detailed reconnaissance - follow-up there would be in order.
0:22:51 > 0:22:54- Not just an orbiter. - I would like to land there.
0:22:54 > 0:22:58- I would like to see - the source of those geysers...
0:22:58 > 0:23:01- ..and understand - how close to the surface...
0:23:01 > 0:23:03- ..is the water - that feeds the geysers?
0:23:07 > 0:23:13- Realizing that Enceladus may harbour - life, scientists want to go there.
0:23:17 > 0:23:21- But there's another moon - vying for their attention.
0:23:22 > 0:23:24- Titan - Saturn's largest moon.
0:23:25 > 0:23:29- Some scientists believe they have - proof that alien life exists here.
0:23:33 > 0:23:37- Beyond Enceladus, - everyone is now looking at Titan...
0:23:37 > 0:23:40- ..as a moon that could sustain life.
0:23:41 > 0:23:45- More than 60 moons - orbit the planet Saturn...
0:23:46 > 0:23:48- ..but one dwarfs them all.
0:23:51 > 0:23:53- Titan is a colossus.
0:23:54 > 0:23:58- A thick orange haze - hides the moon's surface.
0:23:58 > 0:24:03- And when the Cassini mission first - peered beneath the orange mist...
0:24:03 > 0:24:06- ..it revealed a very strange world.
0:24:08 > 0:24:10- Titan is very interesting.
0:24:10 > 0:24:12- It's very cold here.
0:24:12 > 0:24:17- It's about ten times further away - from the sun than earth.
0:24:20 > 0:24:24- Titan has mountains, - lakes and rivers.
0:24:26 > 0:24:32- But instead of water, - the rivers flow with methane.
0:24:36 > 0:24:41- What you have is methane and ethane, - just like the gas we use at home.
0:24:43 > 0:24:47- There are clouds there - and it rains liquid methane.
0:24:48 > 0:24:52- It's incredibly cold here. - You even have lakes of methane.
0:24:53 > 0:24:57- Methane takes the form of a liquid - on Titan's surface.
0:24:57 > 0:25:02- Methane can sustain life, so there's - a lot of scientific interest.
0:25:06 > 0:25:11- And like earth, Titan has a thick, - nitrogen-rich atmosphere.
0:25:15 > 0:25:18- But instead of the oxygen - we breathe...
0:25:18 > 0:25:22- ..Titan's air is spiked - with carbon-rich molecules...
0:25:22 > 0:25:24- ..that stain it a dull orange.
0:25:24 > 0:25:29- Cassini passed through the - top layers of Titan's atmosphere...
0:25:30 > 0:25:33- ..taking measurements - of this orange mist.
0:25:34 > 0:25:38- It's full of molecules similar to - what we call pollution on earth.
0:25:39 > 0:25:44- The orange hue is the effect of - the sun's light on these chemicals.
0:25:44 > 0:25:49- Titan's complex cocktail - of chemicals puzzles scientists.
0:25:50 > 0:25:54- Especially the methane gas.
0:25:56 > 0:26:00- Titan's orange haze - should have lifted - but it hasn't.
0:26:01 > 0:26:04- Something must be replenishing - the orange smog.
0:26:05 > 0:26:06- But what?
0:26:08 > 0:26:12- To answer this, - Cassini released a special probe...
0:26:12 > 0:26:14- ..through Titan's clouds.
0:26:17 > 0:26:22- As the Huygens Lander parachuted - through the clouds, it took photos.
0:26:29 > 0:26:31- The images are incredible.
0:26:31 > 0:26:34- We expected to see - exciting photographs...
0:26:34 > 0:26:40- ..but when they were sent back in - January 2005, they were fantastic.
0:26:42 > 0:26:45- The landscape seemed to have - been shaped by liquid.
0:26:48 > 0:26:50- But that liquid was long gone.
0:26:53 > 0:26:58- Huygens landed in a spot almost - identical to what we're standing on.
0:26:59 > 0:27:04- If we look all around, we can see - this bleak, barren landscape.
0:27:04 > 0:27:07- Pebbles and cobbles - were rounded and smooth.
0:27:07 > 0:27:09- They came through river channels.
0:27:10 > 0:27:13- We see plenty of those - at the Huygens landing site.
0:27:13 > 0:27:15- We also see lots of sand.
0:27:18 > 0:27:21- Huygens landed in a huge desert.
0:27:22 > 0:27:25- It stretches all the way - around Titan's equator...
0:27:26 > 0:27:31- ..with sand-like dunes, sculpted - by the wind like they are on earth.
0:27:35 > 0:27:38- So where were - all the lakes of liquid methane?
0:27:39 > 0:27:41- They had to be at the moon's poles.
0:27:45 > 0:27:46- Cassini went to look.
0:27:49 > 0:27:52- One of the instruments - on Cassini is a radar gun.
0:27:53 > 0:27:56- It shoots radar waves at Titan - which are reflected back.
0:27:58 > 0:28:02- After two years of searching, - Cassini found the lakes.
0:28:02 > 0:28:06- One of the things it found was - near the north pole of Titan...
0:28:06 > 0:28:09- ..were regions - that were not reflecting radar.
0:28:09 > 0:28:11- That sounds a lot like liquid.
0:28:11 > 0:28:15- Liquid absorbs that energy - and doesn't reflect it back.
0:28:16 > 0:28:18- Later observations clinched it.
0:28:20 > 0:28:22- Some regions of Titan - are very smooth...
0:28:23 > 0:28:26- ..and we mapped lake-like - shapes too.
0:28:27 > 0:28:32- It's likely that a liquid created - these lakes on the moon's surface.
0:28:40 > 0:28:43- Lakes like this one in California...
0:28:46 > 0:28:50- ..with a familiar landscape - to ours, on earth.
0:28:52 > 0:28:56- If we were sitting on the margins - of Kraken Mare...
0:28:56 > 0:28:58- ..the largest sea we see on Titan...
0:28:58 > 0:29:02- ..we'd probably see - something similar to this landscape.
0:29:02 > 0:29:05- We'd look out - across a fairly calm surface.
0:29:05 > 0:29:08- We think the winds - are not very strong on Titan...
0:29:09 > 0:29:11- ..so we'd have a calm lake - of methane and ethane.
0:29:12 > 0:29:15- In the distance, - we'd see hills and mountains...
0:29:15 > 0:29:18- ..that formed probably - through tectonic processes...
0:29:18 > 0:29:21- ..in much the same way - that mountains are built on earth.
0:29:22 > 0:29:28- Except on Titan it's so cold that - volcanoes spew water, not lava...
0:29:28 > 0:29:32- ..and the mountains and lake basins - are solid ice.
0:29:35 > 0:29:40- Scientists thought that methane - evaporating from these lakes...
0:29:41 > 0:29:43- ..generated Titan's smog.
0:29:44 > 0:29:49- But that wasn't the case - according to Cassini's measurements.
0:29:50 > 0:29:52- Scientists were stumped.
0:29:55 > 0:29:58- The lakes were somehow - being refilled.
0:30:03 > 0:30:08- Scientist, Jani Radebough believes - these rocky deposits called tufa...
0:30:09 > 0:30:11- ..offer one possible solution.
0:30:15 > 0:30:20- They are formed - when two water types react.
0:30:29 > 0:30:31- This is very exciting.
0:30:32 > 0:30:36- It could be a clue - to the missing methane on Titan.
0:30:36 > 0:30:39- It's rock formed from the chemicals - contained in two fluids.
0:30:40 > 0:30:44- Water emerging at the margin of the - lake interacts with lake water...
0:30:44 > 0:30:46- ..which has a different chemistry.
0:30:47 > 0:30:51- The dissolved chemicals combine with - each other and create this rock.
0:30:55 > 0:30:59- Radar images of Titan's largest lake - reveal rocky structures...
0:31:00 > 0:31:02- ..which look just like tufa.
0:31:04 > 0:31:08- Titan's tufa could be evidence - of a layer of liquid methane...
0:31:09 > 0:31:12- ..that rises in springs - to feed its lakes.
0:31:14 > 0:31:17- Just like they do here, - in California.
0:31:19 > 0:31:23- When those methane springs come in, - they interact with the lakes...
0:31:24 > 0:31:26- ..and rock precipitates out.
0:31:26 > 0:31:30- We see organic rocks - dotting the margins of the lakes...
0:31:30 > 0:31:33- ..and almost certainly - methane bubbles up...
0:31:33 > 0:31:35- ..and emerges - at the margins of the lake.
0:31:39 > 0:31:43- If this is true, the moon's lakes - create all the orange smog.
0:31:44 > 0:31:49- And scientists are a step closer - to solving Titan's mysteries.
0:31:53 > 0:31:54- Titan is exciting.
0:31:57 > 0:32:00- A world that looks familiar to us.
0:32:02 > 0:32:04- And for the first time ever...
0:32:04 > 0:32:08- ..scientists believe - they may have found life here.
0:32:11 > 0:32:11- .
0:32:22 > 0:32:22- Subtitles
0:32:22 > 0:32:24- Subtitles- - Subtitles
0:32:37 > 0:32:39- Saturn.
0:32:40 > 0:32:45- It may look peaceful and serene - but this is an exciting planet.
0:32:53 > 0:32:55- It has massive storms.
0:32:58 > 0:33:00- The rings constantly evolve.
0:33:04 > 0:33:08- But now Saturn's moons - are attracting all the attention.
0:33:09 > 0:33:13- There are mountains, - lakes and rivers here.
0:33:15 > 0:33:19- And now, on Titan, - Saturn's largest moon...
0:33:19 > 0:33:22- ..scientists may have uncovered...
0:33:22 > 0:33:25- ..the first evidence - of extraterrestrial life.
0:33:32 > 0:33:38- Scientists believe that life can - be found in Titan liquid methane.
0:33:41 > 0:33:43- Unlike here on earth...
0:33:43 > 0:33:48- ..Titan is so cold, - creatures would look very different.
0:33:50 > 0:33:53- If life could exist here, - it could still be there today.
0:33:54 > 0:33:56- Not intelligent life.
0:33:56 > 0:33:59- I don't think - they're hiding from us!
0:33:59 > 0:34:02- We're talking about - simple life forms.
0:34:03 > 0:34:05- When we go to another world...
0:34:05 > 0:34:08- ..we look for bacteria - which we assume is small.
0:34:09 > 0:34:12- You could ask the question - why are bacteria so small?
0:34:13 > 0:34:16- I think the answer is - because they live in water.
0:34:21 > 0:34:27- Unlike on earth, it's possible that - bacteria on Titan would be bigger.
0:34:32 > 0:34:35- On Titan, the liquid - is liquid methane, liquid ethane.
0:34:35 > 0:34:37- Very different from water.
0:34:37 > 0:34:40- There's no reason an organism - should be small. It should be huge.
0:34:43 > 0:34:47- Chris McKay believes that Titan's - lakes are home to bacteria...
0:34:47 > 0:34:50- ..the size of sheets of newspaper.
0:34:56 > 0:34:59- If there's life on Titan - living in liquid methane...
0:35:00 > 0:35:03- ..you won't need a microscope - to see it - you'll need a yardstick.
0:35:07 > 0:35:10- The opportunity - to prove that theory came...
0:35:11 > 0:35:15- ..when the Cassini spacecraft - released the Huygens probe...
0:35:16 > 0:35:18- ..through Titan's atmosphere.
0:35:22 > 0:35:27- Simple life forms must eat something - to survive. But what?
0:35:31 > 0:35:36- As Huygens was on its way to Titan, - I'm in a hotel writing a paper...
0:35:36 > 0:35:39- ..saying, hey, - what if there's life on Titan?
0:35:39 > 0:35:41- What would it eat? - How would we detect it?
0:35:42 > 0:35:45- How would this probe flying - through the atmosphere detect it?
0:35:46 > 0:35:50- The day Huygens landed, I submitted - this paper to the journal...
0:35:50 > 0:35:55- ..predicting that if there was life - on Titan it would eat hydrogen.
0:35:55 > 0:35:58- The probe could measure - depletion in hydrogen...
0:35:58 > 0:36:01- ..so let's look for hydrogen.
0:36:03 > 0:36:07- Huygens travels - through Titan's atmosphere...
0:36:07 > 0:36:09- ..sampling the gases as it goes.
0:36:13 > 0:36:17- The upper atmosphere - has plenty of hydrogen.
0:36:17 > 0:36:19- So do the middle layers.
0:36:20 > 0:36:24- But at ground level, there's - a drop-off in hydrogen levels.
0:36:25 > 0:36:28- Something, or perhaps someone, - was using it up.
0:36:30 > 0:36:34- When I heard the report of depletion - of hydrogen, my heart raced.
0:36:35 > 0:36:38- If this is hard data - for the depletion of hydrogen...
0:36:39 > 0:36:43- ..I can't imagine any other way - besides biology to explain that.
0:36:44 > 0:36:49- It's exciting in that it's - consistent with what we predicted...
0:36:49 > 0:36:52- ..but we have to wait - for this to be confirmed...
0:36:52 > 0:36:56- ..by other calculations, - by direct measurements and so on.
0:36:57 > 0:37:03- McKay's theory is very exciting. - It's supported by some evidence.
0:37:04 > 0:37:09- The drop in levels of hydrogen - support his theory to some extent.
0:37:11 > 0:37:15- Could any life survive the harsh - conditions on Titan's surface?
0:37:16 > 0:37:18- We need more evidence.
0:37:22 > 0:37:24- Scientists need more proof.
0:37:26 > 0:37:32- Many want to return to Titan with - more equipment to collect samples.
0:37:35 > 0:37:37- There's much more - to learn about Titan.
0:37:38 > 0:37:43- The findings from Cassini and - Huygens merely scratch the surface.
0:37:43 > 0:37:48- There was talk of sending - a small boat to land on the lakes...
0:37:50 > 0:37:53- ..and take samples of the liquid...
0:37:53 > 0:37:58- ..to see if the lakes and the rain - are similar to what we see on earth.
0:38:02 > 0:38:06- Huygens lasted for just an hour - once it landed on Titan.
0:38:07 > 0:38:11- Compare that to robotic probes - like Spirit and Opportunity...
0:38:12 > 0:38:17- ..which spent years - sending back these images of Mars.
0:38:19 > 0:38:24- Some scientists want to send winged - drones to discover more about Titan.
0:38:30 > 0:38:32- We can do it right now.
0:38:33 > 0:38:37- We have the technology to send - an aeroplane to Titan this minute.
0:38:38 > 0:38:42- Unmanned aerial vehicle technology - has come up in the last decade.
0:38:43 > 0:38:44- We use it all around the world.
0:38:45 > 0:38:49- Because of Titan's thick atmosphere, - it's an easy place to do this.
0:38:49 > 0:38:51- We're ready right now.
0:38:54 > 0:38:58- Are we on the cusp of discovering - whether alien life exists?
0:39:03 > 0:39:07- When I teach first year - biochemistry students...
0:39:07 > 0:39:11- ..I tell them that - before they leave university...
0:39:13 > 0:39:18- ..we may have evidence which - takes us that one step closer...
0:39:19 > 0:39:22- ..and we can say that - alien life exists.
0:39:26 > 0:39:30- Images from spacecraft like Cassini - offer a remarkable glimpse...
0:39:31 > 0:39:32- ..of Enceladus and Titan.
0:39:35 > 0:39:39- Perhaps, one day, - we could travel to these moons...
0:39:39 > 0:39:42- ..and we could even live there.
0:39:47 > 0:39:47- .
0:39:58 > 0:39:58- Subtitles
0:39:58 > 0:40:00- Subtitles- - Subtitles
0:40:13 > 0:40:16- Saturn is a long distance - away from earth.
0:40:19 > 0:40:23- Yet in the future, perhaps humans - will live and work here.
0:40:29 > 0:40:33- That's because it has a special gas - called Helium-3.
0:40:39 > 0:40:43- Helium-3 is a promising candidate - for producing energy.
0:40:43 > 0:40:47- There's an almost endless - energy supply there.
0:40:51 > 0:40:54- The earth's gravity - can't hold on to Helium-3...
0:40:55 > 0:40:59- ..but the large planets like Saturn - and Jupiter have a lot of Helium-3.
0:41:00 > 0:41:05- Enough perhaps to quench our thirst - for fuel for millions of years.
0:41:08 > 0:41:12- Helium-3 may replace oil - as the fuel of the future.
0:41:15 > 0:41:20- Helium-3 produces energy - through the process of fusion.
0:41:25 > 0:41:29- When two atoms are crushed together, - they fuse...
0:41:29 > 0:41:33- ..releasing a burst of pure energy.
0:41:38 > 0:41:43- Best of all, it doesn't release - any harmful radiation waste either.
0:41:46 > 0:41:49- The only trouble with Helium-3...
0:41:49 > 0:41:53- ..is that there's precious little - to be found on earth.
0:41:54 > 0:41:57- One place where you can find - Helium-3 is Saturn.
0:41:58 > 0:42:02- So in centuries to come, - maybe we'll travel to Saturn...
0:42:03 > 0:42:07- ..to harvest Helium-3 - from the planet's atmosphere.
0:42:08 > 0:42:11- It's a very exciting idea.
0:42:16 > 0:42:19- Saturn and Jupiter - have plenty of Helium-3.
0:42:24 > 0:42:28- It'll be difficult - to extract Helium-3 from Jupiter...
0:42:28 > 0:42:31- ..due to the planet's huge gravity.
0:42:34 > 0:42:38- Neptune and Uranus - are too far away to be practical.
0:42:42 > 0:42:43- That leaves Saturn.
0:42:50 > 0:42:53- Some scientists - imagine winged drones...
0:42:54 > 0:42:57- ..flying through - the upper atmosphere of Saturn...
0:42:58 > 0:43:00- ..scooping up the Helium-3.
0:43:02 > 0:43:05- Where should we process - this superfuel?
0:43:05 > 0:43:08- The ideal base would be Titan.
0:43:12 > 0:43:17- In centuries to come, when we travel - to Saturn to harvest Helium-3...
0:43:18 > 0:43:22- ..Titan seems to be the - most obvious place to live and work.
0:43:24 > 0:43:26- Even though it's incredibly cold...
0:43:26 > 0:43:30- ..there's enough - atmospheric pressure...
0:43:30 > 0:43:35- ..to allow domed villages - to be erected.
0:43:39 > 0:43:44- What's interesting about Titan - is that its atmospheric pressure...
0:43:45 > 0:43:47- ..is similar - to what we have on earth.
0:43:54 > 0:43:59- Because Titan's gravity is also - similar to that of earth...
0:43:59 > 0:44:04- ..it's one of the best places in our - solar system to support human life.
0:44:05 > 0:44:10- We could build a processing station - on Titan and harvest the Helium-3.
0:44:16 > 0:44:18- For those people living on Titan...
0:44:19 > 0:44:22- ..everyday life - would be somewhat different.
0:44:24 > 0:44:29- Titan has a very thick atmosphere, - similar to conditions on earth.
0:44:31 > 0:44:35- But the moon is smaller than earth, - so gravity is weaker.
0:44:35 > 0:44:38- If you jumped up - and flapped your arms...
0:44:38 > 0:44:41- ..you could lift yourself - off the surface.
0:44:41 > 0:44:45- Not fly as such, - but you could float a little.
0:44:47 > 0:44:51- If we did use Helium-3 - as the fuel of the future...
0:44:52 > 0:44:56- ..a new generation - of space travel would begin.
0:44:58 > 0:45:03- Travelling to Mars and Jupiter - would take months, not years.
0:45:06 > 0:45:11- Once there's a commercial reason - for going, not just pure science...
0:45:11 > 0:45:13- ..people will invest heavily in it.
0:45:15 > 0:45:18- We're already - on the verge of space tourism...
0:45:19 > 0:45:24- ..with Virgin Galactic hoping - to launch within around five years.
0:45:27 > 0:45:31- At first, only wealthy people - will be able to afford it...
0:45:32 > 0:45:35- ..but that was true of flying - in the 1950s.
0:45:35 > 0:45:39- The only people who could afford - to fly were the rich jet set.
0:45:41 > 0:45:43- I'd like to visit Enceladus.
0:45:44 > 0:45:47- I would travel to its south pole...
0:45:47 > 0:45:52- ..where all that water and ice - is sprayed into space.
0:45:52 > 0:45:54- It must be an amazing sight...
0:45:55 > 0:45:59- ..standing at the edge of - one of those huge ridges of ice...
0:45:59 > 0:46:03- ..and see the gas rise, - then fall as snow all around us.
0:46:04 > 0:46:06- It would be - an amazing place to visit.
0:46:08 > 0:46:13- I'd like to go to Enceladus - to see Saturn's rings close up.
0:46:15 > 0:46:19- Standing so close to them - that the rings fill the sky.
0:46:20 > 0:46:23- That's where I would choose to go.
0:46:27 > 0:46:32- Until fairly recently, - we knew very little about Saturn.
0:46:34 > 0:46:38- But now, some of the planet's - secrets have been revealed.
0:46:39 > 0:46:44- It's an exciting place that may even - harbour life itself.
0:46:46 > 0:46:50- Someday soon, - perhaps we can visit there...
0:46:50 > 0:46:53- ..and see the cosmos - from a new perspective.
0:47:22 > 0:47:24- S4C subtitles by Eirlys A Jones
0:47:24 > 0:47:24- .