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00:00goes out of this world.
00:10This is the story of the most ambitious unmanned space project ever launched.
00:17Its destination, Saturn.
00:20The mission, to investigate this hauntingly beautiful planet and its enigmatic rings.
00:27But the climax of the mission will be Saturn's largest moon, Titan.
00:36The hope is that by exploring this alien world,
00:41we will get closer to answering that great scientific mystery,
00:46the origin of life.
00:50Tonight, Horizon follows this fantastic voyage across the solar system
00:55to find out
00:56how it all began.
00:58Hello, colleague.
01:00Oh, dear God.
01:13June 30th, 2004.
01:18The sun Nouferjima
01:21Three stars, the sun Nouferjima
01:25June the 30th, 2004.
01:28The world's press have gathered for news of the most critical part of this $3.2 billion mission.
01:37The Cassini spacecraft is scheduled to go into orbit around its target, Saturn.
01:47The slightest hitch during this complex manoeuvre and the entire mission will be lost.
01:52We are slowing down.
01:57You can imagine how anxious some of us were, knowing that it all hinged on one 90-minute period where we would have to perfectly just slip into orbit.
02:09The Doppler has flattened out.
02:11This moment was the culmination of 14 years' preparation and a seven-year trek across the solar system.
02:24But the real highlight was when Cassini started to beam back its images from over a billion miles away.
02:32How are you doing?
02:38Oh, it was fantastic. It was just great.
02:41You wait years just to have this kind of a moment.
02:43Citizens of Earth, I would like to present the majestic rings of Saturn.
02:47This remarkable spacecraft had travelled over a billion miles towards the outer reaches of our solar system.
02:59To a giant swirling ball of gas, over 750 times larger than the Earth.
03:15The mysterious world of Saturn.
03:18Cassini's story can be traced to the launch of a different mission, 27 years ago.
03:33The Voyager Deep Space probes.
03:35When they flew past Saturn, they provided tantalizing glimpses of this distant world.
03:45Saturn's giant rings were seen closer than ever before, revealing details that were completely new and unexpected.
03:55Before Voyager got there, we knew very little about them.
03:58There wasn't a great number of people even studying the rings.
04:01Voyager got there and found this bewildering array of structure in the rings.
04:08And people set about trying to explain it right away.
04:13It had always been assumed that the rings were as old as Saturn itself.
04:17But the new information sent back by the probes pointed to something very different.
04:25We saw processes going on in the rings that were too fast.
04:29That would have gone to completion long before the age of the solar system, the age of the planets.
04:35So that Voyager information showed us the rings must be created much more recently.
04:43Voyager begged the question.
04:45If the rings are not as old as Saturn, how old are they?
04:50And how did they get there?
04:54And Voyager was to uncover yet more mysteries.
04:59For the first time, detailed images were taken of Saturn's many moons.
05:11They showed ancient, cratered surfaces.
05:13But one stood out, Saturn's largest moon, Titan.
05:26It was unlike any moon that had ever been seen.
05:29It had a thick, almost Earth-like atmosphere.
05:33But frustratingly, its surface was shrouded by a layer of orange cloud.
05:38We saw this fuzzy ball and the immediate reaction was, what's below those clouds?
05:44You know, what are these clouds made of?
05:46What is hidden behind that layer?
05:50Titan would remain a mystery.
05:53Voyager had to move on, out towards Uranus, Neptune and beyond,
05:59leaving behind it more questions than answers,
06:02and scientists desperate to return.
06:04The combination of the spectacular structure in the rings,
06:11the youthful processes in the rings,
06:14the hazy atmosphere of Titan,
06:17just left every scientist with a great curiosity
06:21to explain those things that we had seen with the Voyager flybys.
06:24Immediately, there was a feeling that we had to return to Saturn
06:27and stay there for a longer time.
06:38So, in 1990, work began on a spectacular new spacecraft.
06:46The result of a unique cooperation between NASA and European space agencies,
06:51the Cassini probe would carry the most complex array of instruments
06:55ever launched into space.
06:58It would be capable of measuring everything from magnetic fields
07:02to minute particles of cosmic dust.
07:07But at the heart of this array of instruments
07:09were the eyes of the mission,
07:12the two cameras.
07:15One is a very long focal length, very high resolution,
07:18but you get little postage stamp-like coverage.
07:22And so you want to also carry a camera
07:24with a larger field of view, shorter focal length,
07:27that covers a greater amount of territory,
07:29so you can put your little postage stamp coverage
07:32in context, in geological context.
07:39Cassini was also loaded with a powerful radar,
07:42designed to do what no camera can,
07:44and punch through Titan's hazy atmosphere
07:47to reveal the surface below.
07:52But Titan has so intrigued scientists
07:54that they decided to send in a separate probe
07:57for an even closer look.
08:01That probe is called Huygens,
08:03after the man who first discovered Titan.
08:08Rather than viewing from a distance,
08:10we're going for broke,
08:11Huygens is actually going to plunge through that atmosphere
08:14and take in-situ measurements.
08:17We want to know exactly
08:18what the composition of the atmosphere,
08:21what are the gases which make up the atmosphere,
08:23and we'd also like to know about meteorology
08:27or weather in Titan's atmosphere.
08:33This bold plan had one major drawback.
08:37The resulting craft was massive.
08:41The Cassini spacecraft is the largest interplanetary satellite
08:48that NASA has ever built and launched.
08:52At launch, it weighed nearly 5,800 kilograms.
08:57The big problem was how to get
08:59this 5.5-ton Leviathan into space.
09:03The most powerful rocket on Earth,
09:12the mighty Titan IV,
09:14was selected for launch,
09:16delivering over 3.9 million pounds of thrust.
09:24But even this would not be enough.
09:26Because this massive spacecraft
09:33didn't just have to get into space.
09:39It had to travel over a billion miles.
09:45All the way to Saturn.
09:47The only way to travel this vast distance
09:51would be with a little help from the planets.
09:56The energy that we needed
09:58to get out in the solar system,
10:00out to the planet Saturn,
10:01had to be supplemented by,
10:03partially provided by,
10:05by gravitational encounters with the planets.
10:07The important thing is to gather energy
10:11from the gravity of the planet you're flying by.
10:17So Cassini was rooted
10:18by the Earth's nearest neighbor, Venus.
10:23This planet's gravitational pull
10:25would accelerate Cassini,
10:28increasing its speed by over 8,000 miles per hour.
10:31But this still would not be enough.
10:37Cassini would return
10:38for a second boost from Venus.
10:42The Earth would then accelerate Cassini,
10:46flinging it out further,
10:47towards its next rendezvous.
10:52Jupiter.
10:53The probe would clock up
10:55a speed of 50,000 miles per hour
10:57before reaching its final destination,
11:00Saturn.
11:01Jupiter.
11:26October the 15th, 1997.
11:29Cassini was blasted
11:30blasted into the night sky.
11:35All the planets it needed for its trip to Saturn were in perfect alignment,
11:41an event that would not reoccur for over 600 years.
11:48What lay ahead was an epic seven-year journey across the solar system.
11:59When the probe swung back past the Earth, the radar was checked out.
12:06It scanned a huge swathe of South America, and everything was in working order.
12:12Cassini seemed to be operating flawlessly.
12:16The Europeans also decided to test out the radio link between Huygens and Cassini.
12:21This was when things started to go wrong.
12:26Huygens is designed to beam all its data up to Cassini as it plunges through Titan's atmosphere.
12:35The Huygens probe itself doesn't have enough power, and it doesn't have a large enough dish,
12:41to transmit its data, the scientific data that it collects on Titan, directly back to the Earth.
12:49So what will happen is that it uses the Cassini spacecraft as a data relay.
12:56The test was designed to make sure that Cassini could receive all the data from Huygens.
13:03But when the results came back, they were alarming.
13:08We were expecting to receive all the simulated data.
13:11Unfortunately, we did not receive very many of those data.
13:15We lost, well, we lost maybe 90% of the data, sometimes even all of the data.
13:24If Cassini could not pick up the precious data from Huygens as it travelled to Titan,
13:33there would be no results, no pictures, nothing.
13:38The entire mission would be lost.
13:42The Huygens team called a meeting to break the news.
13:46Imaging specialist Marty Tomasco had spent over 10 years building the camera for Huygens.
13:52He couldn't believe what he was hearing.
13:55They said, we've performed the test, and we didn't get any signal, but the test accomplished
14:00all of its objectives.
14:03And some of us were sitting around the table saying, what exactly are you trying to sell
14:08us?
14:09You know, you accomplished the objective of conducting the test, but you actually succeeded
14:14in proving the thing is not going to work.
14:18But the Europeans were hoping there might be a simple explanation.
14:22Maybe the test is wrong.
14:23This is the first thing you say, oh, the test is wrong.
14:27We have done something wrong, so everything is good with the hardware, no problem.
14:31It has been tested on ground, so the test must be wrong.
14:38But the test was not wrong.
14:40Six months of painstaking research revealed a tiny flaw in Cassini's receiver.
14:47It was enough to essentially put the link between the two out of alignment.
14:55It was as if Huygens was transmitting on radio one, on one frequency, and Cassini was receiving
15:03on radio two, a slightly different frequency.
15:06So this was potentially disastrous.
15:11Repairing the receiver was impossible.
15:13It was out in space, over 300 million miles away.
15:19There was no way we could repair.
15:21So we had to find a new mission scenario, which would allow us to live with this problem, but
15:29still to recover the whole mission.
15:33After months of research, an ingenious plan emerged.
15:40They couldn't retune Cassini's receiver, but they could shift the signal it was receiving,
15:46using a basic principle known as the Doppler effect.
15:51If they could slow Cassini down, it would pass through the radio waves from Huygens at a slower
15:57rate.
15:59This means that the radio waves would hit Cassini at a lower frequency.
16:05This lower frequency signal could then be picked up by the faulty receiver.
16:13All in all, it took us six months to find a solution, but it took us two years to design
16:20all the detail of the solution and to test it.
16:25We are now recovering the full Huygens mission.
16:28We are not going to lose any science, so it's a very successful recovery.
16:37Scientists were now confident that Huygens had every chance of sending back its precious
16:42data when it finally reached Titan.
16:45As a new millennium dawned on Earth, Cassini had crossed a billion and a half miles of
17:03space and arrived at Jupiter, the giant of the solar system.
17:14Twice as massive as all the other planets combined, its powerful gravitational field would give
17:22Cassini its final boost.
17:27Scientists waited anxiously because Cassini's cameras faced their biggest test yet.
17:34Jupiter's majesty was revealed as never before.
17:49Its swirling clouds and icy moons were seen with breathtaking clarity.
17:55But Cassini had to move on, across another 500 million miles of space, to its final destination.
18:10For imaging team leader Carolyn Porco, the Jupiter pictures were a triumph, but her real goal
18:28was always Saturn.
18:30She has devoted her entire career to studying it, and it is now part of her life.
18:37To know that we can know so much about our solar system and about our cosmos, for me, makes life meaningful.
18:45It's very much like being in love.
18:48It's very much that kind of a relationship where you want to know more, and you want to be one with, you know, the person you're in love with, or the topic that you're studying.
19:00It's kind of this, it's a connection, it's really a connection, and for me, it's like being allowed a glimpse of the miraculous.
19:15By the spring of 2004, Cassini had closed in on Saturn.
19:21Just before contact, mission planners had calculated a precise course to send the spacecraft past Phoebe,
19:30Saturn's curious outermost moon.
19:39Almost all Saturn's moons orbit in the same direction, around its equator, but not Phoebe.
19:49Satellites, if they form naturally, around the planet, are not expected to be in a plane, in any other plane except for the equatorial plane of the planet.
20:00So, very early on, when people figured out Phoebe's orbit, it became clear that it was unlikely that Phoebe formed as part of the regular stable of satellites that are around Saturn.
20:14If Phoebe was not formed along with Saturn, it must have come in from elsewhere,
20:19and been sucked in by Saturn's gravitational field.
20:23But where had it come from?
20:26Scientists believe that there are two options.
20:29One is the asteroid belt between Mars and Jupiter, where things are made of rock,
20:33probably not dramatically different than the rock we have here.
20:39The other is a much more distant place called the Kuiper belt, a mysterious band of rubble left over from the formation of the outer planets.
20:50These are the most ancient objects in our solar system.
21:00Those objects are made primarily of ice.
21:03So they have dramatically different composition.
21:05Everybody knows the difference between a rock and the stuff you put in your drink to keep it cool.
21:10And if you can figure out a way to tell that difference from a long way away, which is what we have to do with spacecraft,
21:18then you can start to get a real handle on where Phoebe came from.
21:22Until now, all that scientists have had to go on is this picture, taken by Voyager 23 years ago.
21:32But this time, Phoebe was in the crosshairs of Cassini's powerful cameras.
21:38Picture after picture returned with unprecedented detail.
21:55We buzzed, Phoebe.
21:57OK, we came within 2,000 kilometers of its surface.
22:00You could reach out and touch it is what it looked like.
22:03So it's very exciting.
22:04We saw features that were 30 meters across.
22:07At last, Phoebe was giving up her secrets.
22:14The images revealed an ancient surface pitted with craters caused over billions of years.
22:21But to solve the mystery of where Phoebe had come from, scientists needed to work out what it was made of.
22:28And that meant turning to a different piece of equipment.
22:37The technology Cassini used to reveal Phoebe's origins is aboard this aeroplane.
22:48It was developed to identify different varieties of rocks at high speed just by flying over the land.
22:54Previously, that was a task that could only be done slowly by geologists painstakingly collecting samples by hand.
23:08To us and our crude sensors called eyes, both of these rocks are very similar.
23:15Uh, only trained geologists or somebody with lots of experience can tell you what kind of rocks they are.
23:20However, imagine having, uh, some kind of special goggles that you could put on your eyes.
23:25And, uh, that they would make these rocks not be so drab and white, but stand out with, uh, things that you would actually like to know.
23:35That even to the laymen, they would say,
23:38this is the rock you want, and this is the rock you don't want.
23:42The technology that performs this remarkable feat is called a mapping spectrometer.
23:47It works by measuring the different frequencies of light reflected by the rocks below.
24:05Every mineral reflects light at its own unique set of frequencies.
24:10The spectrometer can spot these differences and interprets them as different colors.
24:18The data from the spectrometer is then used to build up a multi-colored 3D map of the area.
24:28The result is a complete picture of the mineral content of the terrain,
24:33all achieved without anyone needing to take a sample.
24:41The same equipment has been adapted for Cassini's trip past Phoebe.
24:45We've taken the concept, wrapped it in a wrapper that allows it to operate in space,
24:52put it on a spacecraft and flown it to Saturn.
24:55Now, that is kind of an understatement, uh,
24:58because it cost 60 million dollars and took seven years to build the instrument.
25:02As Cassini approached Phoebe, the spectrometer got its chance to solve the riddle of Saturn's wayward moon.
25:17The results were better than anyone could have hoped.
25:25Actually, we were blown away by the data that we got on Phoebe.
25:29We found water ice, we found organic materials, we found carbon dioxide, which was a bit of a surprise.
25:37We found poisons, cyanides.
25:40All of those things put together really painted a very nice picture in a sense that it was clear
25:46after we looked at the data that this object does not come from the asteroid belt.
25:54Cassini had proved once and for all that Phoebe had come in from the cold outer reaches of the solar system.
26:00This was scientists' first glimpse of these primordial objects, decades before any mission could ever get there.
26:12But Phoebe was just a taster, a preview of what was to come.
26:17June the 30th, 2004.
26:31Mission Control had piloted the Cassini spacecraft across 2.2 billion miles of space,
26:37and it was still right on target.
26:40And fast approaching its destination, Saturn.
26:47What lay ahead was that great enigma, the riddle of Saturn's rings.
26:58Scientists understand so little about them, they still have even the most basic questions to answer.
27:06The questions that we scientists have about Saturn's rings are the questions that
27:12an ordinary person might be moved to ask when first seeing them, you know.
27:17What caused them? How did they get there? How long have they been around? How long are they going to last?
27:24Answering these questions is one of Cassini's prime objectives.
27:28But to do this, it first had to get into orbit around Saturn.
27:32And that meant passing between the rings.
27:41But the rings are chaotic and dangerous, made up of billions upon billions of hard rock-like particles.
27:48All the ring particles, billions and billions of them are in orbit around the planet Saturn,
27:57and they're moving at quite a clip, something like 10 kilometers per second, faster than a high-speed bullet.
28:03If you were in Saturn's rings, you would be in a mass of particles that were bumping into each other and rolling over each other.
28:17If you were a ring particle, you would get bombarded from one side and then from the other,
28:26as one particle bounced off of another all around you.
28:37To carry out its mission, Cassini risked being torn apart.
28:42Even a very small particle could be the end of Cassini. If it hits a particle as small as a grain of rice,
28:51that would be enough, because of the high speed at which it's moving, to end the mission.
29:00At mission control, tension was building as the high-risk orbit insertion maneuver began.
29:06Saturn orbit insertion was a bit of a nervous time for us. There were a lot of things that had to work right.
29:19The consequences of it not working would have been pretty serious.
29:24The rings were not the only danger that Cassini faced. To get into orbit, it also had to slow down.
29:32That meant firing its main engine. Any malfunction, and Cassini would simply fly past.
29:40Lost forever in the void of space.
29:46That engine has not been used very frequently over a period of seven years.
29:50It makes you nervous. You know, it's like you have a car, a brand new car that you put in the garage,
29:55and every once in a while you turn it on. And then you have an emergency, and you get in the car,
29:59and you turn it on, it better work.
30:04The sequence began at 7.36 p.m.
30:10First, Cassini rotated to use its giant antenna as a shield to protect it when it passed between the rings.
30:18All eyes were on a signal sent out by the probe's tiny auxiliary transmitter.
30:38Only if the signal flattened out at the bottom of the graph would they know if Cassini had survived.
30:44A $3.2 billion mission, and 14 years of work, all hinged on this one moment.
30:57The Doppler has flattened out.
31:23Pastors have flattened out!
31:34Cassini had arrived.
31:37When the images returned, Saturn was revealed as never before.
31:42I just don't know what to say.
31:50I'm kind of speechless.
31:52Oh, absolutely exciting.
31:54I mean, this is a culmination of 22 years of effort
31:56and just seeing the Lord of the Rings in its big glory.
32:05We are amazed about the detail that we are seeing
32:07and the sharpness in the rings.
32:09You wait years to have this kind of a moment.
32:12Despite these remarkable images,
32:23the fundamental question of the age of Saturn's rings
32:26remains unanswered.
32:30Some hope that this enduring puzzle
32:32might be solved by taking a very close look
32:35at what the rings are made of.
32:39The rings are made of ice,
32:41just like the stuff you've got in your ice cube trays.
32:44Almost 100% pure water ice with some small contaminants.
32:49These contaminants are the key to finding out the age of the rings,
32:56minute traces of dust that come from meteoroids.
32:59The basic principle is simple.
33:08The older the rings are,
33:10the more they will have been bombarded,
33:12and so the dirtier they will be.
33:14The pollution is sort of like a clock
33:17because we're pouring material in on top of the rings,
33:20and it's dark, non- icy material.
33:22So the level of darkness in the rings
33:26tells us something about their age.
33:32So to discover the level of pollution in the rings,
33:36Cassini's spectrometer took these images.
33:39What they show has surprised scientists.
33:50The spectacular range of structure in the rings
33:53with reds and blue and aquas,
33:55that was something that was completely unpredictable.
34:02The images show cleaner ice in shades of blue,
34:05the heavier contamination in red.
34:07The analysis on this is not yet complete,
34:15but these new spectrometer images
34:17seem to suggest an intriguing possibility,
34:20that perhaps Saturn's rings
34:23were not all formed at the same time.
34:28It's definitely the case
34:30that there's a gradient in composition across the rings
34:33so that the rings are less icy on the inside
34:37and more icy on the outside.
34:39As we go to the outside,
34:41the particles become younger and fresher.
34:45So it appears that the inner rings, shown in red,
34:48are in fact older,
34:50and that somehow the outer rings
34:52have been made more recently.
34:54To work out exactly how this is happening
34:58will take several years of observations.
35:02But now Cassini is safely in orbit.
35:05The scientists will have all the time they need.
35:08But there is a whole other aspect to Cassini's voyage,
35:22one that has not yet begun.
35:25Its encounter with Titan,
35:27one of the great mysteries of our solar system.
35:30Its thick atmosphere captivates scientists,
35:36as it might mean that Titan, in some way,
35:39resembles the Earth.
35:42Whenever we humans think
35:43that we might be approaching something
35:45that is vaguely similar to Earth,
35:46we get very excited about it.
35:49The prospect of something familiar,
35:51but yet so distant and so strange,
35:55is a very exciting combination.
35:58Trying to figure out
36:02what this distant moon will look like
36:04has become an obsession
36:06for planetary scientist Dr. Ralph Laurence.
36:09He has spent the past 15 years
36:11trying to piece together
36:13all the scraps of information available on Titan
36:15to build up a picture of this mysterious place.
36:19And he believes it is a world
36:21that shares many features with our own.
36:24But on this distant moon,
36:29things are also very different.
36:32The landscape may be strangely familiar.
36:35Much as there is on Earth,
36:36there may be a cycle
36:37with rain and rivers and streams.
36:40But Titan is so cold
36:42that methane, which is a gas on Earth,
36:44can condense into a liquid
36:45and freezes a solid.
36:47We may have lakes,
36:49but the lakes are made of lighter fluid.
36:51If Dr. Laurence is right,
36:57the methane will also form familiar clouds,
37:00but it might turn the sky
37:02a very unfamiliar green.
37:07We might see methane rain falling from these clouds,
37:10but because Titan is smaller than the Earth
37:13and has less gravity,
37:14this rain would be unlike any we have ever seen.
37:17The balance of forces
37:20that holds a raindrop together
37:22is a little bit different on Titan
37:24because the material is different,
37:25and so the raindrops could be rather larger.
37:28But on Titan,
37:29with its thick atmosphere
37:30and its low gravity,
37:32these large raindrops would fall
37:34maybe 10 times slower
37:35than raindrops do on Earth.
37:38The rain falls so slowly,
37:40it just evaporates
37:41before it gets to the ground.
37:42The picture of Titan that emerges
37:49is one of a truly alien world,
37:52a place where huge raindrops fall gracefully
37:56through a green sky,
37:58a place with lakes and streams
38:00made from lighter fluid.
38:03And stranger still,
38:05the entire landscape is made of water,
38:09frozen hard as rock.
38:10But for the moment,
38:15this picture is a very well-educated guess,
38:18as no one has yet been able
38:19to take a clear picture of Titan's surface.
38:23For this mysterious moon
38:24is veiled by a thick layer of orange cloud.
38:31But Cassini carries two powerful instruments
38:35designed to defeat this layer of haze.
38:38One is Cassini's radar.
38:42Scanning over a quarter of the moon,
38:44it will send back the first accurate images
38:46of Titan's surface.
38:49The second is the European-built Huygens probe.
38:52Huygens will separate from Cassini
39:05and plunge beneath the clouds,
39:08carrying its own unique camera.
39:13Imaging specialist Marty Tomasco
39:15will have no second chances.
39:18The Huygens probe will be active
39:20for just 180 minutes.
39:22So it's important
39:23that his camera doesn't miss a thing.
39:27What we're trying to get
39:29is kind of the skydiver's eye view,
39:31as if you were outside the probe
39:33and falling down through the atmosphere.
39:34We don't want to land
39:35near some interesting object
39:37like the Grand Canyon
39:38and not know it's there.
39:39So the plan is to spin the probe
39:43as it descends,
39:44giving the camera
39:45a full 360-degree view.
39:49But Tomasco has also given the camera
39:51three lenses
39:51to ensure that it has
39:53absolutely no blind spot.
39:58We have three fields of view.
40:01One that comes out this window
40:02and looks out toward the side,
40:04one that comes out this window
40:06and looks down at intermediate angles,
40:07and one that looks almost down
40:09straight toward the ground.
40:10And those three images
40:11are taken together.
40:12And as the probe rotates,
40:14we take a series of 12 of those
40:15over a few seconds
40:18or a few minutes,
40:19and we plan to put those together
40:20to make panoramic mosaics
40:22of the surface of Titan
40:24during our descent.
40:26These panoramic mosaics
40:28were created with the same camera
40:30in a test over the Arizona landscape.
40:32By putting them together,
40:35a virtual world can be created.
40:39The hope is that the next time
40:41the camera opens its three eyes,
40:44it will be peering down
40:45on a new world,
40:47Titan.
40:56The Titan is more than just
40:58a curious, alien landscape.
41:04It is a place that perhaps
41:06holds the key
41:07to one of the greatest mysteries
41:08of the universe.
41:14The origin of life.
41:17For me,
41:18one of the most important questions
41:19to address
41:21is where did I come from?
41:23This rock
41:24is not conscious,
41:26and I'd a heck of a lot
41:27rather be me
41:28than this rock.
41:29But the same stuff
41:30that's in this rock
41:31is in me.
41:32It's just organized
41:33in a way
41:34to contain enough information
41:35so that that stuff
41:37can turn around
41:38and say,
41:38what is this?
41:40How did it get here?
41:41And oh, by the way,
41:42how did I get here?
41:43How did you assemble
41:44this simple stuff
41:45into something like me
41:47and allow me
41:48to ask those questions?
41:55Earth today
41:56is teeming with life.
41:58It has taken over
41:59the entire planet.
42:01Bizarrely,
42:02this makes the Earth
42:03a very bad place
42:04to study how life
42:05first emerged
42:06from the primordial
42:07organic chemicals
42:09that first covered it.
42:12It's very difficult
42:13to use the Earth
42:15as a laboratory
42:16for understanding
42:17how life began.
42:18Life eats all
42:19of the organic molecules
42:20that are present
42:21on the Earth today.
42:23If we go to the laboratory
42:24and try to simulate
42:26how life began,
42:28we have limits
42:29on time and space.
42:30A laboratory experiment
42:31might be this big.
42:33A laboratory investigator
42:35might work for
42:36two or four
42:37or ten years,
42:38perhaps,
42:39no more than that.
42:40We really need a place
42:41where organic evolution
42:43is happening
42:43on a planetary scale
42:45over billions of years,
42:47but is not being ruined
42:49by the presence of life.
42:52So for many years,
42:54scientists have been
42:55looking for a place
42:56that shares the same
42:57primordial chemistry
42:58as the early Earth.
43:01If you look at
43:02our solar system,
43:03there are only four bodies
43:05that have atmospheres
43:06and are actually
43:07solid bodies themselves.
43:09The Earth,
43:10Venus,
43:10Mars,
43:11and Titan.
43:12Venus is just so hot
43:14that one can melt lead
43:15on the surface.
43:16There are no organic molecules.
43:18Mars today is very cold,
43:20very dry,
43:21very thin,
43:22not a good place
43:23for organic molecules.
43:25And so we're left
43:26with Titan.
43:31Titan has the right
43:32ingredients to create
43:33complex organic molecules,
43:36methane and nitrogen.
43:39On the Earth
43:40billions of years ago,
43:42these simple chemicals
43:43somehow combined
43:44to form the precursors
43:46to life.
43:48Scientists believe
43:49that these same
43:50chemical reactions,
43:52the first vital steps
43:54on the road to life,
43:55are occurring today,
43:57high in Titan's atmosphere.
44:01The purpose of this experiment
44:03is to simulate
44:04the chemistry
44:05that makes complicated molecules
44:08from the simple gases
44:09in Titan's atmosphere.
44:11And so here we have nitrogen,
44:12which is the primary gas
44:14in Titan's atmosphere,
44:16and we have methane
44:16over here,
44:17and these gases
44:18are mixed together
44:19and they're run
44:20through tubes,
44:21and then they end up
44:22down here,
44:23which is an electric discharge.
44:25And this simulates
44:26the energy
44:26that the sun provides
44:28to power the chemistry.
44:32The sun's rays
44:34break up the methane,
44:35which then recombines
44:36to form a set
44:38of dark orange chemicals
44:40known as tholins.
44:43These tholins form
44:44the thick orange clouds
44:46that shroud Titan
44:47and hide its surface.
44:50But tholins can make
44:51more than just a haze.
44:54With just one extra ingredient,
44:56they form one of the key components
44:58of all living things,
45:01amino acids.
45:02If we were to apply
45:07what is the essential ingredient
45:08of all life,
45:09liquid water,
45:11then we may well
45:13make some amino acids,
45:14which are the building blocks
45:15of life,
45:16and that is the really
45:17exciting thing
45:18about tholins.
45:22But the surface of Titan
45:24is 174 degrees
45:27below freezing,
45:28far too cold
45:29for liquid water.
45:32However,
45:33scientists believe
45:34that Titan's interior
45:35may be warmer
45:36and that there could be
45:38a layer of liquid water
45:39under the surface.
45:41It is possible
45:43that this liquid
45:44could rise upwards
45:45through volcanoes.
45:49On the Earth,
45:50volcanoes belch rock.
45:53On Titan,
45:53volcanoes most likely
45:55belch water.
45:56And liquid water
45:58has an important role
45:59to play, we think,
46:01in helping to bring
46:02about the rise
46:04of life.
46:13While any water
46:15on Titan
46:15would eventually freeze,
46:17it might remain
46:18liquid long enough
46:19to allow the formation
46:21of amino acids.
46:22planets.
46:25So, with tholins
46:26in its atmosphere
46:27and the possibility
46:28of water,
46:30Titan might just have
46:31all the ingredients
46:32to make the primordial soup
46:34from which life
46:35first emerged.
46:37at 2am on Christmas Day,
46:53three explosive bolts
46:54will fire
46:54and the Huygens probe
46:56will be pushed away.
46:5722 days later,
47:04it will slam
47:05into the upper atmosphere.
47:19A series of parachutes
47:21will then slow its descent.
47:23only then will the charred
47:27heat shield be ejected.
47:30The chemical analyzer
47:32will then search
47:33for signs
47:33of complex
47:34organic chemistry.
47:39At last,
47:41Huygens' camera
47:42will get the first view
47:44of Titan's surface.
47:46Will Huygens discover
48:03streams of liquid methane?
48:06A rock-hard surface
48:08of frozen water ice?
48:11Or a soft sludge
48:13of organic chemistry
48:14warmed by a new
48:16nearby volcano?
48:19Until January 14, 2005.
48:24No-one will know.
48:37Next week on Horizon,
48:39the hunt for the super-twister.
48:41They are the world's
48:42most deadly tornadoes
48:43and can strike
48:44and can strike
48:44without warning.
48:46But can science
48:47find a way
48:47to predict them?
48:49It could save
48:49hundreds of lives.
48:51because nerede
48:54born in series
48:57DIE
48:58fundo
48:58zoon
48:59in
49:00the
49:01kingdom
49:01Or
49:03in
49:03the
49:04what
49:04Ts
49:05are
49:06not
49:06in
49:06the
49:07year
49:08or
49:08than
49:09beyond
49:09Gold
49:10and
49:10冬
49:11or
49:11potentially
49:12and
49:12you
49:13into
49:14a
49:14time
49:15and
49:16little
49:17e
Recommended
47:00
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