0:00:04 > 0:00:07This is one of the most sophisticated space vehicles
0:00:07 > 0:00:09ever built.
0:00:13 > 0:00:15Curiosity is a billion-dollar rover.
0:00:20 > 0:00:25In six days' time, it will attempt to touch down on Mars.
0:00:25 > 0:00:27Landing a big rover is a tough business.
0:00:27 > 0:00:31It means that everything about the system gets bigger and therefore harder.
0:00:31 > 0:00:34This will be no ordinary landing.
0:00:35 > 0:00:41It will be winched down by a crane hovering in the Martian sky.
0:00:41 > 0:00:46It's so ambitious, it's so audacious, it's so unconventional.
0:00:46 > 0:00:50Horizon has been behind the scenes with NASA's team as they follow
0:00:50 > 0:00:56their rover across 350 million miles of space.
0:00:56 > 0:00:58When Curiosity comes over the horizon,
0:00:58 > 0:01:02this guy is already pointed that direction and as she comes up, then we're talking.
0:01:08 > 0:01:11Curiosity's mission is to discover
0:01:11 > 0:01:13if Mars could ever have supported life.
0:01:15 > 0:01:19But the Red Planet has become known as the Bermuda Triangle of space.
0:01:19 > 0:01:24Two-thirds of missions there have ended in failure.
0:01:26 > 0:01:29In just under a week, the world will learn
0:01:29 > 0:01:34if Curiosity can overcome the odds and touch down on Mars.
0:01:46 > 0:01:50SPEECH OVER RADIOS
0:01:53 > 0:01:57It's 10pm at the Jet Propulsion Laboratory in California.
0:01:57 > 0:02:00OK, copy and we'll make that report to the surface team
0:02:00 > 0:02:02when they come onboard.
0:02:02 > 0:02:05The team behind the Curiosity mission are locked
0:02:05 > 0:02:08in a crucial test at the space flight control centre.
0:02:09 > 0:02:12We're now about five and a half minutes to entry.
0:02:14 > 0:02:18They're practising for a landing they know is the most audacious
0:02:18 > 0:02:21ever attempted on another planet.
0:02:21 > 0:02:23Three minutes to entry.
0:02:23 > 0:02:27They've been rehearsing and testing day and night for months,
0:02:27 > 0:02:33running through each individual step of the mission in painstaking detail.
0:02:33 > 0:02:36Confirming that we have parachute deploy.
0:02:36 > 0:02:42Brian Portock is the flight director for the 350 million-mile journey to Mars.
0:02:43 > 0:02:48Ann Devereaux helped devise a way to stay in touch with the rover.
0:02:50 > 0:02:54Adam Stelzner will mastermind the daredevil landing.
0:02:58 > 0:03:02And leading this test is Chief Engineer, Joel Krajewski.
0:03:05 > 0:03:11The fate of this mission is central to everybody's soul, really.
0:03:11 > 0:03:14Most folks have worked on this for three years, five years, eight years.
0:03:14 > 0:03:17You don't get to do many in a given career.
0:03:17 > 0:03:19You only get to do a few if you're lucky.
0:03:19 > 0:03:22So the stakes for everybody are as high as they can be.
0:03:24 > 0:03:25This is just a rehearsal,
0:03:25 > 0:03:30but on the 6th of August, they'll be doing it for real,
0:03:30 > 0:03:32hoping the Curiosity rover
0:03:32 > 0:03:35will arrive safely at its destination.
0:03:37 > 0:03:41Mars, the Red Planet.
0:03:41 > 0:03:45It's become known as the Bermuda Triangle of space.
0:03:48 > 0:03:51Since the launch of the first rocket there in the 1960s,
0:03:51 > 0:03:56two-thirds of all missions have ended in disaster.
0:03:58 > 0:04:01The mission logs make scary reading.
0:04:01 > 0:04:03"Failed to launch."
0:04:03 > 0:04:04"Missed the planet."
0:04:04 > 0:04:06"Lost radio contact."
0:04:06 > 0:04:08"Lost on arrival."
0:04:11 > 0:04:16The team knows Curiosity might never reach the surface of Mars.
0:04:28 > 0:04:33It's Joel Krajewski's job to make sure this mission is a success.
0:04:33 > 0:04:37His day may begin like many Californians...
0:04:37 > 0:04:40but then he heads to NASA's Jet Propulsion Laboratory.
0:04:49 > 0:04:54Like anyone else, I drive into work every morning
0:04:54 > 0:04:57but every morning as I do so, I pinch myself because
0:04:57 > 0:05:01I get to work on a space mission and that is, that is pretty cool.
0:05:06 > 0:05:08For more than a decade,
0:05:08 > 0:05:12Joel has been engineering rovers to send to the Red Planet.
0:05:14 > 0:05:18Before I got into working on rovers, of course like anybody else
0:05:18 > 0:05:21I thought it was going to be a kind of a tricky business.
0:05:21 > 0:05:24It sounds hard throwing things up into space
0:05:24 > 0:05:26and exploring other planets.
0:05:26 > 0:05:30Once I got into it, I learned that it's even harder than I thought.
0:05:34 > 0:05:39This is the third rover that Joel has worked on.
0:05:39 > 0:05:43But even for a Mars veteran like him, Curiosity has been a huge challenge.
0:05:47 > 0:05:50Curiosity is the most complex vehicle we have sent to Mars.
0:05:50 > 0:05:54Hundreds of people have worked on it for more than eight years
0:05:54 > 0:05:56and we're still working on it.
0:05:56 > 0:06:01Different people understand different aspects of it, but nobody knows it all.
0:06:15 > 0:06:19As the real Curiosity hurtles through space,
0:06:19 > 0:06:23its clone is hidden in a garage at the Jet Propulsion Laboratory.
0:06:34 > 0:06:38It runs on its very own nuclear generator.
0:06:43 > 0:06:47Its components can withstand forces greater than those
0:06:47 > 0:06:50exerted on a supersonic jet.
0:06:55 > 0:06:59And its electronics are designed to work at temperatures far lower
0:06:59 > 0:07:02than the coldest places on Earth.
0:07:06 > 0:07:11It's the most advanced moving vehicle ever sent into space.
0:07:26 > 0:07:30Today, Joel's team are testing the wheels of Curiosity's twin.
0:07:30 > 0:07:36- They're low class. - Is that what we call them?
0:07:36 > 0:07:37That's what we call them.
0:07:37 > 0:07:44It's just one of hundreds of tests the rover has been through in the past nine months.
0:07:44 > 0:07:45That's great.
0:07:46 > 0:07:49The scientists want to land on Mars and explore.
0:07:49 > 0:07:53They want to explore where we land and then also explore
0:07:53 > 0:07:56kilometres away from where we land, and that means we have to drive.
0:07:56 > 0:07:58We'd like to be able to drive over big rocks
0:07:58 > 0:08:00so that we can drive close to a straight line,
0:08:00 > 0:08:06not too much meandering around, and therefore we designed a big rover.
0:08:06 > 0:08:08That makes it tricky.
0:08:08 > 0:08:10The reason Curiosity is so big and expensive
0:08:10 > 0:08:15is because of the science it will be conducting on Mars.
0:08:15 > 0:08:18It will have to drive across difficult terrain
0:08:18 > 0:08:20while carrying a lab full of equipment.
0:08:22 > 0:08:25The scientists would like an infinitely capable vehicle.
0:08:25 > 0:08:29But in the real world, the machine has to fit within a certain volume.
0:08:29 > 0:08:31It has to fit within a certain mass.
0:08:31 > 0:08:34We can only lift so much mass off the Earth
0:08:34 > 0:08:36and have it land safely on Mars.
0:08:39 > 0:08:45The rover is five times as heavy as any vehicle they've ever launched,
0:08:45 > 0:08:48which makes landing it on another planet
0:08:48 > 0:08:51more difficult than anything they've attempted before.
0:08:53 > 0:08:55Landing a big rover is a tough business.
0:08:55 > 0:08:58The landing system is more complex, parachutes are bigger,
0:08:58 > 0:09:01everything gets much bigger and therefore harder.
0:09:05 > 0:09:10# There's a starman waiting in the sky... #
0:09:10 > 0:09:15NASA's engineers have never shied away from tricky landings.
0:09:15 > 0:09:18# There's a starman... #
0:09:18 > 0:09:21During the Apollo missions of the 1970s,
0:09:21 > 0:09:24they weren't satisfied just to put a man on the moon.
0:09:26 > 0:09:31But landing a car on Mars is an entirely different proposition.
0:09:38 > 0:09:43Adam Stelzner has spent years working out how to do it.
0:09:44 > 0:09:48He will take control of the rover as it begins to enter the Martian atmosphere.
0:09:50 > 0:09:54He won't be able to rely upon the systems
0:09:54 > 0:09:58that got the lunar rover down safely onto the surface of the moon.
0:09:59 > 0:10:01Mars is tough.
0:10:01 > 0:10:05The moon, where we've landed lunar modules on the moon before,
0:10:05 > 0:10:07does not have any atmosphere
0:10:07 > 0:10:10and it makes the process of getting down to the surface kind of simple.
0:10:10 > 0:10:15You take a rocket engine, you turn it on and you slow yourself down until you touch down on the surface.
0:10:16 > 0:10:18Unlike the lunar rovers,
0:10:18 > 0:10:23Curiosity will have to battle an unpredictable atmosphere.
0:10:23 > 0:10:26Historically, Mars has been evil.
0:10:26 > 0:10:30You don't know what the weather's going to be like, you don't know
0:10:30 > 0:10:33whether the atmosphere's going to be dense or diffuse.
0:10:33 > 0:10:36Will it be a hot day and not so dense, or a cold and dense day?
0:10:36 > 0:10:41If it's cold and dense, you slow down faster, you end up shorter.
0:10:41 > 0:10:45If it's hot and low density, you end up flying farther.
0:10:45 > 0:10:49The dangers of this unpredictable atmosphere are heightened
0:10:49 > 0:10:54by the speed the spacecraft has to travel at to get to Mars.
0:10:54 > 0:10:58It will arrive at 13,000 miles per hour.
0:10:58 > 0:11:04We have enough energy of motion in the spacecraft that we could
0:11:04 > 0:11:07vaporise the spacecraft in the atmosphere of Mars
0:11:07 > 0:11:10just by slamming into that atmosphere and developing
0:11:10 > 0:11:13so much friction that the vehicle would burn up.
0:11:13 > 0:11:16So it's a challenge.
0:11:18 > 0:11:22The rover will be tucked inside a spacecraft
0:11:22 > 0:11:26when it reaches the dangerous Martian atmosphere.
0:11:26 > 0:11:30Its first line of defence will be the world's biggest heat shield.
0:11:32 > 0:11:34Next, the team have to stop it
0:11:34 > 0:11:38from crashing head-on into the Red Planet.
0:11:39 > 0:11:44So they have designed the biggest supersonic parachute ever made.
0:11:47 > 0:11:52In NASA's giant wind tunnel near San Francisco, they put it to the test.
0:11:52 > 0:11:57'Five, four, three, two, one...'
0:12:01 > 0:12:06The parachute must be deployed at twice the speed of sound.
0:12:06 > 0:12:09Good chute, good chute!
0:12:09 > 0:12:14The tests confirmed the huge canopy should survive the enormous forces
0:12:14 > 0:12:18it will encounter as it's dragged through the Martian atmosphere.
0:12:22 > 0:12:25Finally, Curiosity's engineers
0:12:25 > 0:12:29tested the most risky part of the landing procedure...
0:12:29 > 0:12:31I think we are ready to go.
0:12:31 > 0:12:34..a bizarre hovering crane
0:12:34 > 0:12:39that will have to lower the rover down the final 20 metres to the surface.
0:12:43 > 0:12:46CHEERING
0:12:46 > 0:12:50The sky crane took the engineers years to perfect.
0:12:50 > 0:12:54It has never been used to land anything before.
0:12:54 > 0:12:57But although all of Curiosity's individual landing stages
0:12:57 > 0:13:00passed their tests on Earth before launch,
0:13:00 > 0:13:03they have never been tested all together.
0:13:05 > 0:13:07The Red Planet's evil environment
0:13:07 > 0:13:13will be the first place the whole procedure is ever attempted.
0:13:15 > 0:13:17MUSIC: "Pumped Up Kicks" by Foster The People
0:13:29 > 0:13:35Planning the journey was the first challenge for Joel Krajewski's engineering team.
0:13:35 > 0:13:37Go, go, go, go, go!
0:13:37 > 0:13:40- Nice job! - APPLAUSE
0:13:40 > 0:13:46As Flight Director, Joel's colleague Brian Portock is, in effect, the mission's quarterback.
0:13:46 > 0:13:50CHEERING # Robert's got a quick hand... #
0:13:51 > 0:13:58It's Brian's job to aim and throw the spacecraft across the solar system to a moving receiver...
0:14:00 > 0:14:01..Mars.
0:14:01 > 0:14:03PLAYERS SHOUT
0:14:03 > 0:14:06Everything's in motion in space.
0:14:06 > 0:14:07Run in, run in!
0:14:09 > 0:14:13Mars is moving round the sun and the Earth is also moving round the sun,
0:14:13 > 0:14:16and their motion relative to each other is changing.
0:14:16 > 0:14:18Go, go, go, go!
0:14:18 > 0:14:22Similar to a receiver running out for a pass is in motion...
0:14:22 > 0:14:24Ball!
0:14:24 > 0:14:28..and the quarterback needs to stand back and throw a ball...
0:14:28 > 0:14:30Really good shot!
0:14:30 > 0:14:34..so that the receiver and the ball meet at a point in space
0:14:34 > 0:14:37and a time that's the correct one so that they can catch it.
0:14:39 > 0:14:41Oh, nice!
0:14:41 > 0:14:43CHEERING
0:14:43 > 0:14:47They need to figure out how far the ball needs to travel depending on where the receiver is.
0:14:47 > 0:14:52- Go, go, go!- How fast the receiver's running in that direction.
0:14:52 > 0:14:55Most quarterbacks don't sit down and calculate that on paper.
0:14:55 > 0:14:57Set, go!
0:14:57 > 0:15:00It's all done in their head instinctively, without thinking about it.
0:15:00 > 0:15:04For spacecraft, we do it on paper, or these days, on computers.
0:15:04 > 0:15:06PLAYER SHOUTS
0:15:06 > 0:15:09The other thing a quarterback does is put spin on the ball.
0:15:11 > 0:15:15Spiral so that the ball flies in the correct trajectory.
0:15:16 > 0:15:18So we also are spinning our spacecraft...
0:15:18 > 0:15:21so it maintains its attitude...
0:15:24 > 0:15:28..and so that we can point the solar rays back at the sun and communicate back to the Earth.
0:15:28 > 0:15:31And so, the actual rotation of the ball
0:15:31 > 0:15:34is similar to the rotation of the spacecraft.
0:15:35 > 0:15:37They make it sound simple,
0:15:37 > 0:15:40but firing a spacecraft across the solar system
0:15:40 > 0:15:44involves some really complex ballistic calculations.
0:15:46 > 0:15:50The craft must escape the pull of the Earth's gravity.
0:15:50 > 0:15:55It must contend with solar winds that could blow it off course....
0:15:55 > 0:15:59cosmic radiation which can disrupt radio contact...
0:15:59 > 0:16:03..and the craft is constantly being dragged from its course
0:16:03 > 0:16:06by the gravitational pull of other planets.
0:16:06 > 0:16:13Just a tiny error could result in Curiosity missing Mars altogether.
0:16:13 > 0:16:15To get the distance scales approximately similar,
0:16:15 > 0:16:22the quarterback here is throwing a pass 30 metres, 40 metres away.
0:16:23 > 0:16:28Brian's target of Mars is hundreds of millions of kilometres away.
0:16:29 > 0:16:33It's similar to if this quarterback here were throwing a football
0:16:33 > 0:16:36to a receiver in, say, London, and needing to hit his mark.
0:16:36 > 0:16:38APPLAUSE
0:16:38 > 0:16:42- It'd be the wrong kind of football. LAUGHS:- Yeah!
0:16:46 > 0:16:50In November 2011, at Kennedy Space Centre,
0:16:50 > 0:16:55the rover made its way to the launch pad on an Atlas rocket.
0:16:57 > 0:17:01For the mission team, the launch is the moment of no return.
0:17:03 > 0:17:09While the craft is on the ground, final fixes can always be made.
0:17:09 > 0:17:14But once it's in the air, a fault could mean the end of the mission.
0:17:16 > 0:17:19There's so much energy involved with launching.
0:17:19 > 0:17:22SPACECRAFT BLASTS
0:17:24 > 0:17:27All the little piece parts on the spacecraft
0:17:27 > 0:17:31are designed to survive that vibration and those forces.
0:17:46 > 0:17:47Just the fact that it gets into space
0:17:47 > 0:17:52and we start talking to it for the first time is an incredible achievement.
0:17:52 > 0:17:56- It's spacecraft separation. - APPLAUSE
0:17:56 > 0:17:59It's the first big step on the way to Mars.
0:18:01 > 0:18:09But any damage caused by the launch to Curiosity's components might not be immediately obvious.
0:18:11 > 0:18:13So, for the past eight months,
0:18:13 > 0:18:16the engineers have needed to stay in careful contact,
0:18:16 > 0:18:19to check its course and its vital signs.
0:18:19 > 0:18:22'Re-transmit... Six, three, eight...'
0:18:22 > 0:18:27They need to be sure that they receive every message sent back by the rover...
0:18:27 > 0:18:33and that every instruction they give will be heard loud and clear.
0:18:41 > 0:18:45MUSIC: "Sweet Child O' Mine" by Guns N' Roses
0:18:49 > 0:18:51To communicate with Curiosity,
0:18:51 > 0:18:56the team have to rely on equipment hidden deep in the Mojave desert.
0:19:03 > 0:19:09Ann Devereaux helped engineer the systems that allow the team to stay in touch.
0:19:16 > 0:19:19Now that the spacecraft is nearing the end of its voyage,
0:19:19 > 0:19:23she feels the distance between her and her rover more than ever.
0:19:24 > 0:19:27It's very much akin to having a kid in college.
0:19:29 > 0:19:31We raised her, we taught her everything she knows,
0:19:31 > 0:19:37we gave her all the gear that she needs to investigate her new world, but now she's gone.
0:19:37 > 0:19:41And, you know, we gave her a calling card. We told her to call often,
0:19:41 > 0:19:44but we don't get to talk to her all the time, and, you know,
0:19:44 > 0:19:48we don't know what she does every day until she's in contact with us.
0:19:48 > 0:19:53# Whoa, whoa, whoa Sweet child o' mine. #
0:19:53 > 0:19:59Curiosity can call home using two ultra-high-frequency radios.
0:19:59 > 0:20:02But the distance between Mars and Earth,
0:20:02 > 0:20:04together with the rover's limited power,
0:20:04 > 0:20:07makes it difficult to pick up the signal.
0:20:07 > 0:20:11It's a problem anyone with a car radio knows well.
0:20:11 > 0:20:14RADIO INTERFERENCE WARPS MUSIC
0:20:16 > 0:20:19We're about a hundred miles outside of Los Angeles.
0:20:19 > 0:20:21In the car, I've got the radio going,
0:20:21 > 0:20:24but my favourite radio station is almost gone.
0:20:24 > 0:20:28I'm not that far, certainly compared to Mars,
0:20:28 > 0:20:33and the radio station that I listen to has a 90,000-watt transmitter,
0:20:33 > 0:20:38and so you'd wonder why I can't pick up the station here.
0:20:38 > 0:20:39The problem is my little antenna
0:20:39 > 0:20:43is just not capable of picking up the signal at this distance,
0:20:43 > 0:20:47no matter how powerful it seems the transmitter back at home is.
0:20:47 > 0:20:50MUSIC: "Spread Your Love" by Black Rebel Motorcycle Club
0:20:51 > 0:20:55In space, power is in short supply,
0:20:55 > 0:20:58and Curiosity will need to use almost all of its energy
0:20:58 > 0:21:03to drag its near-ton weight across the surface of Mars.
0:21:05 > 0:21:09That means the rover's transmitters have to get by with just a fraction
0:21:09 > 0:21:15of the 90,000 watts used by a radio station on Earth.
0:21:15 > 0:21:20She only has a ten-watt transmitter, and she's MUCH further away.
0:21:20 > 0:21:24We're about 140 kilometres from Los Angeles -
0:21:24 > 0:21:29Curiosity is going to be 250 million kilometres at Mars.
0:21:29 > 0:21:31We need something bigger for an antenna.
0:21:33 > 0:21:35# Spread you love like a fever
0:21:35 > 0:21:39# Spread your love like a fever
0:21:40 > 0:21:43# Spread your love like a fever
0:21:43 > 0:21:47# Spread your love like a fever. #
0:21:55 > 0:22:00The DSS14 antenna is the biggest dish
0:22:00 > 0:22:03in NASA's Deep Space Communications Network.
0:22:06 > 0:22:12It's their switchboard for every spacecraft in the solar system.
0:22:14 > 0:22:18But all this interplanetary chatter means that Ann can't just pick up
0:22:18 > 0:22:22the phone to Curiosity any time she likes.
0:22:22 > 0:22:26There's a lot of spacecraft out there, and they all want to talk back home, too, right?
0:22:26 > 0:22:28They all want to call home.
0:22:28 > 0:22:33And so, we have to schedule time at one of these antennas, like here at DSS14,
0:22:33 > 0:22:37and tell the people that we need to talk to Curiosity and this is how long we want to talk to her for,
0:22:37 > 0:22:42and they point the antenna so when Curiosity comes over the horizon,
0:22:42 > 0:22:45this guy is already pointed in that direction and as she comes up, then we're talking.
0:22:51 > 0:22:54But a queue for the phone is not the only thing that could kill
0:22:54 > 0:22:58the conversation between the rover and the team back home.
0:23:01 > 0:23:03Once it arrives at Mars,
0:23:03 > 0:23:06the whole mass of the planet will stand in the way.
0:23:08 > 0:23:10Mars itself rotates as the Earth rotates,
0:23:10 > 0:23:14and so sometimes, even if we wanted to talk to Curiosity, we couldn't.
0:23:14 > 0:23:17Because we just have the whole planet between us and Curiosity.
0:23:21 > 0:23:25A Martian day lasts 24 hours and 40 minutes.
0:23:28 > 0:23:29For half of that time,
0:23:29 > 0:23:32the rover will drop behind the red planet's horizon,
0:23:32 > 0:23:35out of view of Earth's antennas.
0:23:40 > 0:23:45When Curiosity arrives, night will be falling on Mars.
0:23:49 > 0:23:53Midway through its perilous landing procedure,
0:23:53 > 0:23:56the team will lose direct contact with the spacecraft.
0:23:58 > 0:24:03But NASA can rely on help from some previous Mars missions.
0:24:04 > 0:24:07We have an ace in the hole. In fact, we have two.
0:24:07 > 0:24:10It's called Mars Reconnaissance Orbiter and Mars Odyssey.
0:24:10 > 0:24:13So, these are two orbiters that we have around Mars already.
0:24:13 > 0:24:17They're sitting there, they're waiting for their sister to come.
0:24:20 > 0:24:23As the Martian night obscures the rover from Earth's view,
0:24:23 > 0:24:27Odyssey will attempt to relay its vital messages
0:24:27 > 0:24:29back to the control room.
0:24:36 > 0:24:40This is just one of hundreds of risky procedures
0:24:40 > 0:24:44that must go right for Curiosity to land safely.
0:24:46 > 0:24:51In designing the most complex landing ever attempted in space,
0:24:51 > 0:24:54the team have had to go out on a limb, staking their reputations
0:24:54 > 0:24:58on a system that has never been used before.
0:24:58 > 0:25:03It's so ambitious. It's so audacious. It's so unconventional.
0:25:03 > 0:25:06It doesn't feel like there's a lot of shelter.
0:25:06 > 0:25:08You can't say, "Oh, I'm doing what they did before
0:25:08 > 0:25:10"and it just didn't work out, I didn't get lucky."
0:25:10 > 0:25:12No, we're not doing what we did before.
0:25:12 > 0:25:17We're doing something completely novel, hanging it way out there.
0:25:17 > 0:25:19Um...
0:25:20 > 0:25:21You feel exposed.
0:25:21 > 0:25:25As chief architect of Curiosity's landing sequence,
0:25:25 > 0:25:28Adam Steltzner has gone through each part of it
0:25:28 > 0:25:30over and over in his head.
0:25:30 > 0:25:35But for now, it only exists in his imagination.
0:25:36 > 0:25:39And in this NASA animation.
0:25:39 > 0:25:43We show up at this near six-kilometre-a-second speed.
0:25:44 > 0:25:48We burn a hole in the sky of Mars for about 100 kilometres long.
0:25:56 > 0:25:59We start out at six kilometres a second,
0:25:59 > 0:26:02and we're still going about a kilometre a second.
0:26:04 > 0:26:08We're not slowing down very much, because there's not enough atmosphere to help us out.
0:26:08 > 0:26:11So eventually we have to pop a parachute.
0:26:15 > 0:26:17That slows us down more. But still not enough.
0:26:18 > 0:26:21It takes us down to about 100 metres a second.
0:26:21 > 0:26:23200 miles an hour, almost.
0:26:23 > 0:26:26You don't want to hit the surface of Mars like that.
0:26:28 > 0:26:31So, about a couple of kilometres from the surface,
0:26:31 > 0:26:34we decide it's time to look for the surface with our radar.
0:26:34 > 0:26:38And once we've seen it, we take this great leap of faith.
0:26:43 > 0:26:45And cut ourselves free,
0:26:45 > 0:26:49light our rockets and start our descent to the surface.
0:27:02 > 0:27:05We slow ourselves all the way down,
0:27:05 > 0:27:07and then, 20 metres above the surface,
0:27:07 > 0:27:11we do this kind of crazy thing...
0:27:11 > 0:27:13called the sky crane manoeuvre.
0:27:13 > 0:27:15Zzz-zzz...
0:27:23 > 0:27:27The average person on the street thinks it's crazy.
0:27:30 > 0:27:34Even the team that's working it, sometimes we think it's crazy.
0:27:34 > 0:27:36The strange part is,
0:27:36 > 0:27:40it's actually the result of reasoned engineering thought.
0:27:47 > 0:27:49Six days from now,
0:27:49 > 0:27:53the team hope Curiosity will execute this unlikely manoeuvre.
0:27:55 > 0:27:57Back on Earth,
0:27:57 > 0:28:01they will be waiting for the message they have all dreamed of...
0:28:04 > 0:28:06..it's safely down.
0:28:21 > 0:28:24The purpose behind all this daredevil engineering
0:28:24 > 0:28:28is to send the biggest payload of scientific equipment
0:28:28 > 0:28:30ever to leave Earth
0:28:30 > 0:28:33to uncover the secrets of Mars.
0:28:34 > 0:28:37It's the latest step in mankind's love affair
0:28:37 > 0:28:41with this curious red light in the night sky.
0:28:44 > 0:28:47Ever since Galileo built his first telescope,
0:28:47 > 0:28:50astronomers professional and amateur alike
0:28:50 > 0:28:54have peered through their lenses at the red planet.
0:29:00 > 0:29:01Oh, yes.
0:29:03 > 0:29:04Do you see it?
0:29:05 > 0:29:07I see it.
0:29:11 > 0:29:14- I see some bright colours. - You see some bright colours?
0:29:19 > 0:29:22- I think it's Mars. - You think it's Mars?
0:29:22 > 0:29:23I think you might be right.
0:29:25 > 0:29:28It's Mars, for goodness' sake - now how could you not be interested?
0:29:34 > 0:29:36It's just beautiful.
0:29:37 > 0:29:41Mars has, you know, intrigued people
0:29:41 > 0:29:43for so many years.
0:29:47 > 0:29:52I think it's that red colour that attracts people,
0:29:52 > 0:29:56and it's just... just the romance of it.
0:29:58 > 0:30:00That's wonderful.
0:30:05 > 0:30:09Curiosity's planetary scientist Ashwin Vasavada
0:30:09 > 0:30:13has shared this fascination since he was a boy.
0:30:14 > 0:30:18Looking at Mars through a telescope, you can see some wonderful things.
0:30:18 > 0:30:22You can see the planet, you can see the polar caps come and go with the seasons.
0:30:22 > 0:30:26I love looking through telescopes, but really, they're almost like
0:30:26 > 0:30:30using a record player for someone who grew up with the internet.
0:30:32 > 0:30:37In 1976, we moved beyond mere telescopes.
0:30:37 > 0:30:41When the Viking space probe beamed back the first-ever images
0:30:41 > 0:30:43from the surface of Mars,
0:30:43 > 0:30:47it inspired a whole generation of space scientists.
0:30:47 > 0:30:52This image is an image taken by the Viking lander in 1976,
0:30:52 > 0:30:55and it kind of is a special image for me,
0:30:55 > 0:30:59because I saw this image in a book I was reading as a young kid.
0:30:59 > 0:31:03And it's the first time I really noticed that planets were other worlds.
0:31:03 > 0:31:05You could stand on a planet, look out and see rocks
0:31:05 > 0:31:08and you could walk off the horizon of the image you're looking at,
0:31:08 > 0:31:12and you wonder what's across that hill.
0:31:12 > 0:31:16It just blew me away, and maybe it's the moment I became a planetary scientist.
0:31:16 > 0:31:21The Viking mission tapped into the public's fascination with Mars.
0:31:22 > 0:31:26It was inspired by one of the most intriguing questions in science.
0:31:26 > 0:31:28Are we alone?
0:31:28 > 0:31:31It's about searching for life in the universe,
0:31:31 > 0:31:34it's about asking this profound question of whether we're alone,
0:31:34 > 0:31:36whether we're all that there is.
0:31:36 > 0:31:40And the only way we can do that, even in this technological age,
0:31:40 > 0:31:43is just by stepping out to our nearest neighbour planet,
0:31:43 > 0:31:47the one next furthest out from the sun, and asking the question there.
0:31:47 > 0:31:51But really, it's going to tell us this profound reality,
0:31:51 > 0:31:54whether we're alone or we're not.
0:32:02 > 0:32:05NASA's Viking mission was hugely ambitious.
0:32:05 > 0:32:09It was their first ever attempt to land robotic probes
0:32:09 > 0:32:12on the surface of Mars.
0:32:12 > 0:32:15And it was going to search for life itself.
0:32:17 > 0:32:20It has an arm, so it can extend out into the area around it
0:32:20 > 0:32:25and pick up sand to bring back to the other laboratories which are on board the lander.
0:32:25 > 0:32:29The Viking landers were equipped with these state-of-the-art biological laboratories
0:32:29 > 0:32:31and they scooped up soil and analysed it.
0:32:31 > 0:32:34They tried to feed any microbes that would be in the soil
0:32:34 > 0:32:37and do very sophisticated experiments to detect life.
0:32:37 > 0:32:40CHEERING
0:32:41 > 0:32:43The delight of landing safely
0:32:43 > 0:32:47and receiving these extraordinary pictures
0:32:47 > 0:32:50was followed by what seemed to be an incredible discovery.
0:32:52 > 0:32:57Initial observations suggested that they had detected microbial life
0:32:57 > 0:32:59in the Martian soil.
0:33:03 > 0:33:05But as the euphoria subsided
0:33:05 > 0:33:10and the scientific data was analysed, a new realisation dawned.
0:33:10 > 0:33:15Viking had in fact failed to find life on Mars.
0:33:18 > 0:33:21And the results were either negative or just ambiguous
0:33:21 > 0:33:24and it made us realise that it's not going to be this easy.
0:33:26 > 0:33:31Since the 1970s, other missions have told us much more about Mars.
0:33:33 > 0:33:37Successful Rovers and orbiters have produced detailed maps
0:33:37 > 0:33:41of the red planet's surface and breakdowns of its atmosphere.
0:33:43 > 0:33:47They have revealed just how hard it would be for life to survive
0:33:47 > 0:33:50in the planet's extreme environment.
0:33:50 > 0:33:54The surface of Mars today is a very harsh place to life.
0:33:54 > 0:33:57There's a lot of things that are hazards to life.
0:33:57 > 0:34:00Now we're interested in knowing whether those same hazards
0:34:00 > 0:34:01were there in the past
0:34:01 > 0:34:05and maybe early Mars as opposed to present Mars was the place to look for life.
0:34:12 > 0:34:15Today, Mars is an inhospitable desert.
0:34:17 > 0:34:21Its thin atmosphere leaves its surface exposed
0:34:21 > 0:34:24to lethal solar and cosmic radiation.
0:34:25 > 0:34:29Average temperatures of minus 55 degrees Celsius
0:34:29 > 0:34:34would make it very hard for life as we know it to survive.
0:34:34 > 0:34:39That's why Curiosity is not expecting to find life here and now.
0:34:39 > 0:34:42Instead, it will try to discover
0:34:42 > 0:34:46if life could have survived there millions of years ago.
0:34:49 > 0:34:52Which means the Rover not only has to travel all the way to Mars,
0:34:52 > 0:34:55it has to travel back in time.
0:35:06 > 0:35:10This desert, 200 miles outside Los Angeles
0:35:10 > 0:35:14has become a second home for the Curiosity team.
0:35:19 > 0:35:23It's an ideal place not just to test the Rover,
0:35:23 > 0:35:26but also to design the mission's science.
0:35:30 > 0:35:34Chief scientist John Grotzinger is in charge of the experiments
0:35:34 > 0:35:37that will enable the Rover to see into the past.
0:35:43 > 0:35:48Not by looking for bones or fossils, but by trying to find
0:35:48 > 0:35:50elements crucial for life.
0:35:51 > 0:35:54Simple things, like liquid water.
0:35:55 > 0:35:58What we're going to do is an acid test.
0:35:58 > 0:36:03Take a few drops, put it on the rock and see if it fizzes.
0:36:03 > 0:36:05And yes, cool, it fizzes.
0:36:05 > 0:36:08And what that tells us is that this work is made out of
0:36:08 > 0:36:10a mineral called carbonate.
0:36:10 > 0:36:15And carbonates on Earth form in lots of water,
0:36:15 > 0:36:18and that tells us that this dry desert that we are in here today,
0:36:18 > 0:36:21600 million years ago, there was an ocean.
0:36:25 > 0:36:29It was liquid water in ancient lakes and seas
0:36:29 > 0:36:31that allowed life to take hold.
0:36:34 > 0:36:39So Curiosity's scientists have carefully chosen a Martian landing site
0:36:39 > 0:36:43similar to this spot in the Mojave Desert.
0:36:45 > 0:36:49Curiosity will hunt for the same evidence of a wetter past
0:36:49 > 0:36:51in the Gale Crater on Mars.
0:36:53 > 0:36:58Here's Gale Crater, with Mount Sharp majestically rising above the plains.
0:37:00 > 0:37:02Mount Sharp is a Martian mountain,
0:37:02 > 0:37:07rising 18,000 feet above the centre of the massive Gale Crater.
0:37:09 > 0:37:15The scientists believe their Rover could find carbonates here, proving
0:37:15 > 0:37:19this Martian crater was also filled with water in its ancient past.
0:37:21 > 0:37:25But that's not the only similarity that Mount Sharp has
0:37:25 > 0:37:28with the mountains here in the Mojave Desert.
0:37:28 > 0:37:33In both places, the team can use the rock itself to travel back in time
0:37:33 > 0:37:37to any moment in the geological past.
0:37:40 > 0:37:45The mountains are formed of layers, built up gradually over millennia.
0:37:45 > 0:37:50Testing each one will reveal what the environment was like there
0:37:50 > 0:37:53at the particular moment in time it was laid down.
0:37:55 > 0:37:58What we see here is a stack of layers that tell us
0:37:58 > 0:38:01about the early environmental history of the Earth,
0:38:01 > 0:38:03representing hundreds of millions of years.
0:38:03 > 0:38:06They read like a book of Earth history and they tell us about
0:38:06 > 0:38:10different chapters in the evolution of early environments and life.
0:38:10 > 0:38:14And the cool thing about going to Mount Sharp at Gale Crater
0:38:14 > 0:38:16is going to be there, we'll have a different book
0:38:16 > 0:38:19about the early environmental history of Mars that will tell us
0:38:19 > 0:38:23something equally interesting, and we don't know what it's going to be yet.
0:38:26 > 0:38:28The team believe the place they've chosen to land is
0:38:28 > 0:38:31the perfect spot to look back in time.
0:38:33 > 0:38:36They want to know if Mars could have supported life
0:38:36 > 0:38:38at any point in its history.
0:38:43 > 0:38:48So that Curiosity can discover all the information the scientists need,
0:38:48 > 0:38:51the engineers have designed it to work just like
0:38:51 > 0:38:55a human exploration team would back here on our own planet.
0:38:55 > 0:39:00What Curiosity can do as we begin to explore Gale,
0:39:00 > 0:39:03is pretty much what a geologist would do on Earth,
0:39:03 > 0:39:06but it's also bringing along a chemistry lab.
0:39:09 > 0:39:13The official name of the mission is Mars Science Laboratory.
0:39:14 > 0:39:16And with good reason.
0:39:18 > 0:39:21We have three different camera systems.
0:39:21 > 0:39:24We have another instrument that involves a laser that gives us
0:39:24 > 0:39:26the ability to zap out and understand
0:39:26 > 0:39:29the composition of the environment around us.
0:39:29 > 0:39:33We've got instruments that can ping things down in the subsurface
0:39:33 > 0:39:35and tell us if there's water down there.
0:39:35 > 0:39:38And then we've got other instruments that can actually tell us
0:39:38 > 0:39:41about the laboratory conditions, like what we would do on Earth.
0:39:43 > 0:39:47It's this chemistry lab, right in the belly of the Rover,
0:39:47 > 0:39:49that makes the mission really special.
0:39:50 > 0:39:54What Curiosity can do, which has never been done before on a Rover mission,
0:39:54 > 0:39:56is to actually drill a hole in the rock,
0:39:56 > 0:40:02take the powder and put it into the chemistry laboratory which is inside the Rover.
0:40:02 > 0:40:05And that I'm really excited about, because it takes us
0:40:05 > 0:40:08to a whole other level with science analysis on Mars.
0:40:17 > 0:40:23This is a clone of an essential piece of Curiosity's mobile chemistry kit.
0:40:23 > 0:40:27It was constructed here at the Goddard Space Laboratory
0:40:27 > 0:40:31by planetary scientist Paul Mahaffy and his team.
0:40:33 > 0:40:35This equipment, known as SAM,
0:40:35 > 0:40:39can reveal the chemicals present in the Martian rock.
0:40:39 > 0:40:42But for it to work,
0:40:42 > 0:40:47SAM needs to be fed the right sort of rock samples, correctly prepared.
0:40:47 > 0:40:52So Curiosity will first have to use all the other tools it has at its disposal.
0:40:54 > 0:40:58The very first tools are the very high resolution cameras
0:40:58 > 0:41:00on the mast of Curiosity.
0:41:04 > 0:41:06And then, when we get even closer to a sample
0:41:06 > 0:41:09that we might see in the distance and then approach,
0:41:09 > 0:41:11we'll start using other tools.
0:41:11 > 0:41:14For example, on the mast is an experiment
0:41:14 > 0:41:15called ChemCam.
0:41:18 > 0:41:21ChemCam will point at a rock and fire a laser.
0:41:25 > 0:41:28And then look at the emissions that come off from that rock,
0:41:28 > 0:41:30and that's really important
0:41:30 > 0:41:34because it can tell the differences between different types of rocks.
0:41:34 > 0:41:38So if we come across a rock that looks substantially different
0:41:38 > 0:41:40from rocks we've looked at before,
0:41:40 > 0:41:42then we might want to approach those samples,
0:41:42 > 0:41:47put out the arm, and start interrogating that rock or that outcrop
0:41:47 > 0:41:50with instruments that are on the arm.
0:41:50 > 0:41:54An element analyser and a very nice microscope,
0:41:54 > 0:41:58and if we examine the outcrop or the rock with those tools
0:41:58 > 0:42:00and decide it's worth even further exploration,
0:42:00 > 0:42:03then what we do is we sample the rock.
0:42:06 > 0:42:11We drill into the rock, we create some powder with the sampling system
0:42:11 > 0:42:15and then we deliver that powder into SAM.
0:42:15 > 0:42:18The chemical analysis of this powdered rock
0:42:18 > 0:42:22is one of the most important tests in the mission.
0:42:23 > 0:42:29That's why the team are still running tests on SAM's twin back here on earth.
0:42:31 > 0:42:35We've put a bit of powdered rock into the oven of SAM,
0:42:35 > 0:42:38and we slowly heat it up from ambient temperature
0:42:38 > 0:42:41to very hot temperature, about 1,000 degrees centigrade.
0:42:41 > 0:42:45And as the sample is heated up, at different temperatures it releases
0:42:45 > 0:42:50different simple gases or complex gases, and that helps us determine
0:42:50 > 0:42:55what the mineralogy, what the mineral composition of the rock is.
0:42:55 > 0:42:59SAM can look for the chemical signatures of water
0:42:59 > 0:43:05and it can also detect organic compounds - the building blocks of life.
0:43:06 > 0:43:10Our very first job on getting to Mars will be to understand
0:43:10 > 0:43:15if there are organic compounds that we can even detect.
0:43:15 > 0:43:18Mars is a very harsh environment.
0:43:18 > 0:43:21Ultraviolet radiation penetrates right down to the surface
0:43:21 > 0:43:24because there is less of an atmosphere than on Earth.
0:43:24 > 0:43:28The same is true for very energetic cosmic radiation
0:43:28 > 0:43:31that pounds in and really has the potential to destroy
0:43:31 > 0:43:35fragile compounds that are very close to the surface.
0:43:35 > 0:43:37So that's a very first-order question -
0:43:37 > 0:43:41are there organic compounds on Mars? Can we detect them with SAM?
0:43:41 > 0:43:44And if there are, then the fun really starts.
0:43:46 > 0:43:50The discovery of organic compounds on Mars
0:43:50 > 0:43:55would cause huge excitement right across the globe.
0:43:56 > 0:44:02Together with liquid water, they are regarded as essentials for life.
0:44:03 > 0:44:06Curiosity's other tests will reveal
0:44:06 > 0:44:08whether the ancient Martian environment
0:44:08 > 0:44:14could have allowed life itself to form from these building blocks.
0:44:27 > 0:44:29Even in the best-case scenario,
0:44:29 > 0:44:34the environment on early Mars would still have been pretty hostile.
0:44:36 > 0:44:41So to understand if extraterrestrial life could have formed,
0:44:41 > 0:44:45astrobiologists like Lewis Dartnell need to find out
0:44:45 > 0:44:49the most extreme conditions in which life could still survive.
0:44:51 > 0:44:56They do it by looking for the limits of life here on Earth.
0:44:57 > 0:45:01Searching out harsh, dangerous environments,
0:45:01 > 0:45:06places where we used to think life could never exist.
0:45:07 > 0:45:09A lot of what we're trying to do
0:45:09 > 0:45:12is understand the limits of terrestrial organisms.
0:45:12 > 0:45:14What's the survival envelope
0:45:14 > 0:45:18of Earth life, so places that are very hot and acidic
0:45:18 > 0:45:21or are very cold and dry, like Antarctica,
0:45:21 > 0:45:24or some very high-pressure, very high temperature places,
0:45:24 > 0:45:27like the black smokers and the hydrothermal vents on the sea floor.
0:45:27 > 0:45:31Because it's by understanding life in these most hostile environments on Earth
0:45:31 > 0:45:35that we understand a lot about the possibility of there being life
0:45:35 > 0:45:37on other worlds, and in similar environments.
0:45:40 > 0:45:46This decaying train line is one of these hostile environments on Earth.
0:45:49 > 0:45:51It's a strange, alien landscape,
0:45:51 > 0:45:57cut through by one of the world's most extraordinary rivers.
0:45:58 > 0:46:00Now, that's...
0:46:02 > 0:46:03That is blood, blood-red.
0:46:07 > 0:46:09That's incredible.
0:46:17 > 0:46:20The Rio Tinto is 100 kilometres long,
0:46:20 > 0:46:25running from the mountains of Andalusia to the Gulf of Cadiz.
0:46:28 > 0:46:32It is been used by NASA to test life-detection equipment
0:46:32 > 0:46:33for Mars missions.
0:46:36 > 0:46:40Rio Tinto is one of those places that you read about time and time again.
0:46:40 > 0:46:44It's commonly used as an example of a Mars-like environment here on Earth.
0:46:44 > 0:46:49I've seen loads of photos in journal papers and books, textbooks,
0:46:49 > 0:46:51but it's only when you come here
0:46:51 > 0:46:54and see with your own eyes that it just jumps out at you.
0:46:54 > 0:46:59That is... That is an alien colour for a river, that is, blood red.
0:46:59 > 0:47:03To understand what Mars might have been like millions of years ago,
0:47:03 > 0:47:10astrobiologist first try to understand these desolate places on earth.
0:47:11 > 0:47:15Actually, the reason that the waters here in Rio Tinto are blood red
0:47:15 > 0:47:17is because the substance is the same.
0:47:17 > 0:47:22The oxidised iron in our blood is the same stuff as in that river
0:47:22 > 0:47:25turning it that grotesque, off colour.
0:47:26 > 0:47:28It's absolutely amazing.
0:47:38 > 0:47:40It had always been thought
0:47:40 > 0:47:44that this strange red colour was a result of pollution,
0:47:44 > 0:47:48that the water had been tainted by iron and other metals
0:47:48 > 0:47:51washed downstream from the mines
0:47:51 > 0:47:54that have existed here since Roman times.
0:47:59 > 0:48:01Well, I can't see anything obviously alive,
0:48:01 > 0:48:05and there's clearly no fish swimming around in here.
0:48:05 > 0:48:08There are no visible signs of life.
0:48:09 > 0:48:13And the Rio Tinto's waters hold another secret,
0:48:13 > 0:48:15which made people think there was no hope
0:48:15 > 0:48:19of even the tiniest life forms ever existing here.
0:48:24 > 0:48:27So, I've got a PH meter here, and I'm going to test the acidity
0:48:27 > 0:48:30of the water in the Rio Tinto at this place here.
0:48:30 > 0:48:35Now, a normal river, a healthy river, would be PH7 - that's neutral.
0:48:35 > 0:48:39And, obviously, the lower the number, the greater the acidity is.
0:48:39 > 0:48:41So I'm going to take a sample...
0:48:41 > 0:48:42here...
0:48:45 > 0:48:49..dunk in the PH probe and we see that it's dropped below 3 already,
0:48:49 > 0:48:542.7 and it's levelling off at about 2.65, so that's acidic.
0:48:54 > 0:48:59That's about 100,000 times more acidic than a normal river.
0:49:01 > 0:49:03And that's almost as acidic as stomach acid.
0:49:03 > 0:49:06That is one acidic river.
0:49:13 > 0:49:16If liquid water ever existed on Mars,
0:49:16 > 0:49:19it might well have been a metallic acid river like this.
0:49:22 > 0:49:25It seems unlikely to think that life
0:49:25 > 0:49:28could have emerged in such a hostile environment,
0:49:28 > 0:49:32but scientists have discovered this blood-red river
0:49:32 > 0:49:36is actually teeming with microscopic bacteria.
0:49:37 > 0:49:41This is a microscope photograph of the river water
0:49:41 > 0:49:45and you can see these thin, hair-like threads
0:49:45 > 0:49:48down the microscope, and these are the microbial filaments themselves,
0:49:48 > 0:49:51these are the cells, these are the life in this water.
0:49:54 > 0:49:57These extraordinary bacteria
0:49:57 > 0:50:01are not just tolerating the strange river conditions -
0:50:01 > 0:50:03they're actually creating them.
0:50:05 > 0:50:10They simply don't behave like life as we know it.
0:50:12 > 0:50:17The community, the ecology of the extremophiles living in this river,
0:50:17 > 0:50:20they don't need to eat complex organic molecules
0:50:20 > 0:50:24like our cells have to, like human cells or animal cells,
0:50:24 > 0:50:27they've got far simpler requirements,
0:50:27 > 0:50:30and all those cells need to munch on are fundamental things
0:50:30 > 0:50:32like iron and sulphur dissolved in the water,
0:50:32 > 0:50:34and they're reacting together
0:50:34 > 0:50:38and use that chemical reaction to power themselves,
0:50:38 > 0:50:42and a by-product - a waste product, if you like - of that living process
0:50:42 > 0:50:47is the sulphuric acid and that's why Rio Tinto is so phenomenally acidic.
0:50:54 > 0:50:56So life can find ways to survive
0:50:56 > 0:51:01even in conditions people thought would mean instant death.
0:51:04 > 0:51:09That raises hope that similar microbes could exist on other planets.
0:51:12 > 0:51:15So scientists are waiting with bated breath
0:51:15 > 0:51:18to see what Curiosity will tell us
0:51:18 > 0:51:21about the conditions on ancient Mars.
0:51:22 > 0:51:25They might not have been all that different
0:51:25 > 0:51:30to some of the places extreme life survives on Earth.
0:51:35 > 0:51:39But before Curiosity can begin its scientific mission,
0:51:40 > 0:51:46..it first has to touch down safely on the Red Planet's surface.
0:51:55 > 0:51:59With landing day now looming close, the responsibility weighs heavily
0:51:59 > 0:52:03on the shoulders of lead engineer Joel Krajewski.
0:52:12 > 0:52:16All engineers are aware, of course, of the risks of a mission like this,
0:52:16 > 0:52:19and the pressure of that, or the stress of that awareness,
0:52:19 > 0:52:22different people handle in different ways.
0:52:23 > 0:52:25I go surfing.
0:52:28 > 0:52:30You spot a good wave...
0:52:31 > 0:52:35..paddle hard, feel the lift behind your feet,
0:52:35 > 0:52:37dig a heel in...
0:52:38 > 0:52:40..and the wave takes you all the way in to shore.
0:52:48 > 0:52:51But no matter how much you've practised...
0:52:53 > 0:52:56..nature can surprise you.
0:52:59 > 0:53:01You can see a good wave...
0:53:02 > 0:53:04..paddle hard for it...
0:53:05 > 0:53:08..and - wham!
0:53:12 > 0:53:13That's a wipe-out.
0:53:17 > 0:53:20I would not want to wipe out in space.
0:53:31 > 0:53:34Back at NASA's Jet Propulsion Laboratory...
0:53:37 > 0:53:40..it's not just Joel who is feeling the pressure.
0:53:42 > 0:53:46Although Curiosity is only weeks from arrival,
0:53:46 > 0:53:49the team is working harder than ever.
0:53:51 > 0:53:54Any loose ends that are going to be messy?
0:53:54 > 0:53:57Like, you know, the eyes not closed, any of that kind of stuff
0:53:57 > 0:54:00- that we're going to have to deal with?- The eyes are all closed.
0:54:00 > 0:54:02With most of the testing now complete,
0:54:02 > 0:54:06it's no longer machine failure that is worrying Joel.
0:54:06 > 0:54:09It's the possibility of human error.
0:54:09 > 0:54:13We have done all of the instrument and engineering check-outs on the vehicle,
0:54:13 > 0:54:17so we know the vehicle survived the launch experience well
0:54:17 > 0:54:18and it's healthy.
0:54:18 > 0:54:21Of course, what's not quite ready is us - we, the team.
0:54:21 > 0:54:24We have to operate this vehicle through the landing event
0:54:24 > 0:54:26and then in the science mission after that,
0:54:26 > 0:54:29and for that, of course, we have to train ourselves.
0:54:31 > 0:54:33RADIO CHATTER
0:54:33 > 0:54:37With 80 days to go until landing,
0:54:37 > 0:54:39the team are carrying out their toughest test.
0:54:42 > 0:54:48A complete rehearsal of the Rover's landing, in real time.
0:54:48 > 0:54:50The spacecraft is now reporting,
0:54:50 > 0:54:54radio has reached entry interface and things are nominal.
0:54:55 > 0:55:01Although it's a simulation, it feels just like the real thing.
0:55:02 > 0:55:05This is the big day, which is to say the big night.
0:55:05 > 0:55:09We've gone through five days of approach,
0:55:09 > 0:55:16but now here, we have only a few hours left until landing
0:55:16 > 0:55:19and so it's kind of... This is for the money!
0:55:19 > 0:55:23As they simulate the Rover's final approach to Mars,
0:55:23 > 0:55:25the atmosphere in the control room is good.
0:55:25 > 0:55:29Even the scientists have arrived to watch the show.
0:55:30 > 0:55:32It's going really well.
0:55:32 > 0:55:37We're just under 30 minutes until we touch down on the surface of Mars.
0:55:37 > 0:55:38Everything's looking good.
0:55:39 > 0:55:42But Joel wants to give the team a real test,
0:55:42 > 0:55:46so this rehearsal won't go perfectly.
0:55:48 > 0:55:52Hidden in the wings, a team of gremlin engineers
0:55:52 > 0:55:56is making it appear as if the spacecraft is encountering problems.
0:55:56 > 0:55:59So we're going to learn, all together now,
0:55:59 > 0:56:03how well the whole team is able to navigate through problems
0:56:03 > 0:56:08and make good choices, precisely in the state of extreme exhaustion.
0:56:10 > 0:56:14You get caught up in it because the screens look the same
0:56:14 > 0:56:16as when we're looking at the real spacecraft,
0:56:16 > 0:56:18the people are sitting in the same positions -
0:56:18 > 0:56:21I'm in the chair I'm going to be in - you're doing the night shift.
0:56:21 > 0:56:23You're kind of tired and kind of on edge
0:56:23 > 0:56:27and so when you see, like, monitors go red and everything,
0:56:27 > 0:56:30for a second... (GASPS) It's very compelling.
0:56:31 > 0:56:34As the simulation of the landing begins,
0:56:34 > 0:56:37it's Adam Stezlner's turn to practise guiding Curiosity
0:56:37 > 0:56:40safely onto the surface of Mars.
0:56:42 > 0:56:45I feel like a fisherman who's caught a whale
0:56:45 > 0:56:48and I just don't know... Can I do this? Am I up for this?
0:56:48 > 0:56:51The huge distance between Earth and Mars
0:56:51 > 0:56:55means that once the team has sent the instruction to land,
0:56:55 > 0:56:58there will be no going back.
0:56:58 > 0:57:01The spacecraft has reached entry interface and things are nominal.
0:57:01 > 0:57:08Any message they send to Curiosity takes 14 minutes to get there,
0:57:08 > 0:57:11so for the final stages the Rover will be on its own.
0:57:13 > 0:57:15For them the landing will be like
0:57:15 > 0:57:18the longest roller coaster ride they've ever taken.
0:57:18 > 0:57:21Stand by for parachute deploy.
0:57:21 > 0:57:23Effectively they make their bet and they say, "OK, go,"
0:57:23 > 0:57:26and it's hands off and the actual landing itself - going through the atmosphere...
0:57:28 > 0:57:31Confirming that we have parachute deploy.
0:57:31 > 0:57:32..jettisoning hardware...
0:57:32 > 0:57:34Heat shield has been jettisoned.
0:57:34 > 0:57:36..firing thrusters...
0:57:36 > 0:57:38Powered flight has begun.
0:57:38 > 0:57:41..that all has to happen autonomously by the vehicle,
0:57:41 > 0:57:43which is actually harder for people, I think.
0:57:48 > 0:57:51It's only a rehearsal, but there is still a tense wait
0:57:51 > 0:57:56as the Rover performs the last of the landing manoeuvres.
0:57:58 > 0:58:02Eventually, Curiosity touches down safely.
0:58:02 > 0:58:04APPLAUSE
0:58:06 > 0:58:07The team did really well
0:58:07 > 0:58:10and they kept their heads under pressure
0:58:10 > 0:58:12and we're still working really well under pressure,
0:58:12 > 0:58:15and so that's all I could ask.
0:58:15 > 0:58:17The rest is in the hands of the fates.
0:58:17 > 0:58:19The team are now preparing
0:58:19 > 0:58:22to go through this procedure one final time.
0:58:22 > 0:58:28In six days, we'll find out if they can do it for real.
0:58:44 > 0:58:47Subtitles by Red Bee Media Ltd