It's a physical quest, it's a spiritual quest,
it's a reach out there for what our place is in the universe.
When I joined NASA, I was going to Mars.
I was not just dreaming, I was going to Mars.
Mars has captured our imagination more than any
other planet, and that's for one reason above all -
the hope, the possibility that there may be life on Mars.
This idea is so enticing that we've long wanted to go there.
We've even imagine Martians coming to earth and invading us.
For 40 years, we've been able to address the question
of whether or not there's life on Mars through science,
and the BBC has been there for every revelation.
From the first tantalising images of the surface...
We've just had some amazing photographs sent back
by the American probe to Mars, Mariner 6.
You can see there some of the dark areas, which may be vegetation,
and at the bottom you can see the white polar cap, which has always
been thought to be due to some kind of icy or frosty deposit.
...to the excitements of a successful landing.
The stakes are high when only half of missions make it.
Now it looks after all as if the Beagle may have crash-landed.
When the first evidence of life on Mars filled our screens,
it seemed possible that we were no longer alone in the universe.
It had 10 to 12 segments in it
and appeared to have a head and appeared to have a tail.
Horizon and the BBC have followed the hopes and dreams of astronomers
as they explore the red planet and its mysteries,
and bring us closer than ever to finding life on Mars.
Mars is the planet in our solar system that's most like Earth.
It has days and seasons. It's covered in valleys and volcanoes.
There's even evidence that water once flowed across the surface.
We've seen it up close, in photographs,
and decades of exploration
means we now understand much
about the geology, atmosphere and geography of the Red Planet.
But our fascination with it
really comes down to the one question that remains unanswered.
If Mars is like Earth, then has there ever been life on Mars too?
Finding evidence of life on Mars is a tantalising prospect for us all.
Proof would show that this is not a miracle unique to Earth.
And if it happened twice in our solar system
then the universe must be teeming with life.
The idea of life on Mars is as old as the observatories themselves.
By the late 1800s, telescopes have become powerful enough
for astronomers to map the surface of Mars.
They observed light and dark patches
and thought these could be seas and forests.
Some astronomers, like Percival Lowell, even believed that
they'd seen canals on the surface, built by intelligent life.
That Mars is inhabited by beings of some sort or other
we may consider as certain as it is uncertain what those beings may be.
From childhood, we have been fascinated by what Martian life might look like.
Something is happening to the children of Mars.
Timar, as leader of the Martians you must do something about it.
I know. But what?
Astronomers at NASA also imagined what life on the Red Planet might be like.
But once they applied science their ideas were quite different.
On Mars, deadly ultraviolet radiation from the sun
penetrates to the surface.
Life forms on Mars may have silica shells
to protect them against this radiation.
We know that Mars is very dry.
Life forms on Mars may have developed special
ways of preserving their water content.
There may be a kind of plant, an ice-eater,
with fine, root-like probes,
searching, not for liquid water,
but searching the permafrost, reaching down to get at that ice.
For Horizon, these imaginings were a step too far.
Other scientists had something smaller in mind.
The biologists were more sceptical.
But they'd already begun to design experiments to test the possibility
that micro-organisms may have survived on Mars.
One theory was that they were dormant and that a
cocktail of nutrients would awaken them into life.
Another experiment did imagine that plant-like cells
had adapted to the harsh ultraviolet light on the planet
and might still survive.
But even these ideas about life on Mars were guesswork.
To truly understand what it might be like, we
needed to find out more about the planet itself.
Yet the most sophisticated telescopes couldn't show astronomers
much about the surface or atmosphere.
It was just too far away.
They had to get closer, and that meant going into space.
By 1959, an unmanned spacecraft had successfully reached the moon.
But Mars is over a thousand times further away.
Getting to the Red Planet
would mean pushing current technology to the limit.
It is difficult to overstate the extraordinary
challenge involved in getting to Mars.
The moon is only 380,000 kilometres away, but takes nearly three days
travelling at speeds of up to 40,000 kilometres an hour to reach.
And missions to Mars make these journeys appear pale in comparison.
With 450 million kilometres to cross and round trips of more than a year,
tiny errors in navigation are going to leave you literally lost in space.
And these aren't the only risks. Space is fraught with hazards.
Hard vacuum, solar flares, radiation, searing heat, freezing cold,
all of which can destroy your spacecraft or its delicate electronics.
If anyone was going to be able to solve the problems of getting to Mars,
it would be the trail-blazing team at the jet propulsion laboratory,
who'd been testing and firing rockets since the 1930s.
Caltech's jet propulsion laboratory,
the oldest continuous rocket and missile activity in the Western world.
In this chamber, the spacecraft was subjected to a full spectrum of light
as intense as the sun's in an environment 300 degrees below zero.
Here, a technician in protective clothing measures the light intensity.
Then, in 1964, Mariner 4 was finally ready to launch.
Horizon took a look behind the scenes.
While the first man was orbiting the Earth, a
spacecraft was being assembled to go to Mars.
Named Mariner 4, it carried a television camera
to transmit live pictures back to earth.
In November '64 it was launched.
It was a shot in the dark.
The best maps available to the space scientists
were basically 19th-century, rough and ill-defined.
And yet the journey required incredible precision.
Mariner 4, travelling more than a million miles a day,
would take eight months to reach the planet,
and sweep by only a few thousand miles above the surface.
And on July 14th they made it.
As Mariner 4 swept past Mars, its black and white television camera
snapped 22 close-up pictures of the planet.
These images, the first-ever digital television pictures, were stored
on a tape recorder. Then they had to be radioed back to Earth.
Would you believe that our bitrates in those days were quite low?
I think it was 8.3 bits per second,
a little faster than a pretty good telegrapher can do dots and dashes.
So the eight bits per second came from Mars, from the spacecraft,
to the big antenna out in Goldstone antenna range.
And they were actually teletyped back
and they came in as little strips of zeros and ones. Incredible.
Yuri Van der Wood is keeper of JPL's planetary image archive.
Just outside the office, you will see that here are these little strips.
And you can see the groups of numbers
that indicate the strength of the return signal in light and dark.
As fast as we could staple these little strips on and
we could colour them in, we started to see a picture.
Mariner's first picture shows the lower edge of Mars,
with the planet in the top of the frame and the black of space below.
To the old-timers particularly, it is a thing of tremendous value.
I would almost say I burn candles here at night, you know!
All the frames as we got them had about as much texture,
seemingly, to the eye, as this,
when you just made a Polaroid off the screen.
But since they were digital, they were computer
numbers, we could subtract, and that's what we did.
But when the images were analysed the dream of finding life on Mars seemed remote.
Three centuries of exploration
overturned by a handful of fuzzy pictures.
Mars wasn't at all like the earth.
It seemed dead, like the moon.
The scientists, I think,
were shocked by seeing large, lunar-like craters.
The reason is that the craters on the moon had to have formed
very long ago, the very, very large ones.
And likewise on Mars.
And to find them still preserved there meant that the planet had not
recycled its surface the way the earth does.
There must have been no rainfall, no weathering,
no transport in any way comparable to that of the Earth for billions of years
in order for Mars now, or even parts of it, to resemble the moon.
In 1969, they tried again,
sending two spacecraft with more powerful cameras.
Scientists were hopeful that, although Mars looked like the moon from a distance,
close-up pictures from Mariner 6 might reveal something unexpected.
We've just had some amazing photographs sent
back by the American probe to Mars, Mariner 6.
And just look at that!
Craters on Mars, very similar to those of the moon.
And the largest crater on that picture is about 160 miles across.
And remember, when Mariner took that picture, it was only about as far
from the surface of Mars as we are from Moscow.
And I wonder how those craters got there. What are they?
Are they due to things hitting Mars or are they volcanic?
I believe myself that most of them are likely to be volcanic.
It was Mars' geology that got space scientists really excited.
And there was still a hope that, despite appearances,
conditions on the surface might be suitable for life.
That's beautiful. That's beautiful. Look at those little craters.
This is a narrow-angle camera view and the scale...
on that... is approximately 50 miles across the picture.
But, besides cameras, the spacecraft carried a battery of instruments.
They measured the atmosphere and found it was painfully thin.
A pressure of only seven millibars, 100 times less
than Earth, and containing mainly carbon dioxide.
Temperature readings suggested that the pole
caps were not ice but frozen carbon dioxide.
Mars was even colder and more hostile than we'd thought.
The scientists were disappointed.
They might not have found evidence of life, but seeing
the surface of Mars up close for the first time
was a major achievement for the Mariner team.
While programmes like Horizon reported on the
findings, Mars was largely ignored by the public.
In 1969, they had their eyes firmly set on the moon.
Two, one, zero.
We have commencement. We have lift-off.
We've just heard that all over the world there are
33 countries who have stayed up to take these pictures live.
More than half a billion people tuned in to see Aldrin and Armstrong walk on the moon.
OK, I'm going to move it. Roger, we see Buzz going about his work.
At the time, it was the single most watched live event in history.
The moon landings are an incredible thing to watch even now,
but by the time we set foot on the moon we already knew a lot about it.
To my mind, even more amazing things were being
learned about Mars by the Mariner teams.
But, while Apollo beguiled the public, in the background
scientists were preparing to try something even more ambitious in scale,
actually landing on the surface of Mars.
America may have beaten Russia to put a man on
the moon, but the space race hadn't ended there.
The Soviets already had Mars on their minds.
They were close to launching a spacecraft that would land on the Red Planet.
And in 1971, when the probe Mars 3 successfully reached the surface,
it appeared Russia had won the contest.
But disaster struck.
The lander stopped transmitting information back to earth after just 90 seconds.
Would NASA's attempt fare any better?
One of the Viking team showed off their design,
a machine made in the image of man.
First of all there are two eyes.
And the eyes are even better than those eyes which a human being has.
They can see not only in colour, but also in
stereo and in the infrared part of the spectrum.
It has a sense of touch - the meteorology boom.
It tells it the temperature, whether it's hot or cold,
the relative humidity and how much the wind is blowing.
It has an arm so it can extend out into the area around it
and pick up sand and bring it back to the other laboratories on board the lander.
It has a sense of hearing, in two different ranges of frequency.
Then of course it has this fantastic sense of smell which
is personified by the organic chemistry experiment.
This sense of smell is far more powerful than our olfactory
and can distinguish between the various aromatic compounds which may be in the air.
But by far the most important feature of the lander is its brain.
This particular brain of course is a computer.
It sits down inside the lander, it's roughly the size of a suitcase,
weighs 52lbs and has a vocabulary of 18,000 words.
This brain not only controls the lander
in response to the specific commands that we give it
from the Earth, but it makes decisions on its own.
The lander brain determines its altitude, determines its navigational parameters
and makes logical selections on such things as when to throw away the heat shield,
when to pop the parachute and when to turn on the terminal descent engines.
It is because of these decision-making capabilities
that the lander truly stands out as a piece of automatic intelligence.
And because it has this automatic intelligence
it has really earned its name of "robot".
But don't let this simple explanation fool you.
Building a craft to reach the surface of Mars and operate once there
was an exceptionally difficult technical challenge.
Viking was launched in 1975 and made it into Mars' orbit without any hitches.
As the team gathered for the probe's landing, they
knew the final seven minutes of its ten-month journey
were the hardest part of the mission.
Viking would have to survive a fiery plunge through the planet's thin atmosphere,
slowing from a speed of nearly 21,000 kilometres
per hour to land safely on the service.
23 Gs. 2,600ft. On terminal descent.
1200ft, 140ft per second.
Coming down... straight down.
May I have a screen for touchdown?
...1.5 degrees per second max. 22 Gs.
Touchdown! We have touchdown!
And there's the first piece of information coming in.
Oh... Oh...
Say something.
Yeah, I'm supposed to say something at this point.
I just don't feel like talking!
Well, there are rocks. There are rocks, yes. There's rocks and...
It's just... Oh, it's just incredible to see that the...
Mars, you know, is really there.
Um... instant interpretation is always a little bit hazardous,
nonetheless many of these boulders
do look very similar to ones that we've seen in...
desert terrains here.
Some of these boulders may be vesicular,
that is, basalt rocks possibly,
volcanic rocks that have solidified in a gas-charged environment,
and these gases produce vesicles, or holes.
It just looks like a... perfect set down.
The first picture of the Martian panorama.
As you look at the field of view in general,
I think the most striking impression is one of a lot of rocks.
And this automatically brings to mind
the fact that we had a good deal of luck,
because some of these rocks are about two, three metres across,
and had the spacecraft landed on those rocks
it would have been disabled.
Probably permanently disabled.
Later high-resolution pictures
confirmed the rocks were volcanic but lying on dunes of fine sand.
On the second day, the first pictures in colour.
Mars was indeed the Red Planet.
Or at any rate, blue-red.
But the colours were false.
It was noticed that one of the cables on the space craft wasn't orange enough.
The colour was corrected and Mars turned even redder.
The reason for their mistake?
The sky. Everyone had assumed it would be blue, like on Earth,
but on Mars scattered dust turns the sky pink and makes sunsets purple.
But they weren't just there for the scenery.
It was time to answer the question of whether there was life on Mars.
By the morning of the eighth day the arm had taken its first soil sample.
There was a clear trench on the surface and the
biological laboratories returned their analyses.
Across 200 million miles of space
came the message that was hoped to end three centuries of speculation.
These traces were to be the final arbiters of life on Mars.
They came from a machine on the lander that could make a detailed analysis of the soil.
Technically, it was a gas chromatograph mass
spectrometer, a miracle of miniaturisation.
It could sniff out what molecules were present in the soil.
Its life-detecting task was to search for organic matter in the soil of Mars
by analysing what gases the soil gave off when it was heated,
in a tiny oven the size of a matchbox.
Within a few weeks the instrument on Mars had
produced a complete fingerprint of the soil.
At first, it looked Earth-like.
There was nitrogen, carbon dioxide, argon and traces of oxygen and water.
But on Earth the heavier molecules of living
systems would show further down the chart.
And on Mars the peaks weren't there.
For the biologists it was a bombshell.
Their tests had said life, and yet life without organic matter was unheard of.
So, some questioned the spectrometer's sensitivity.
Others speculated about cannibal micro-organisms
that lived by consuming their own organic debris.
The scientists couldn't explain it.
The Martian soil was active in the instruments
on the lander, but there was no organic matter.
The building blocks for life were there, but life itself wasn't.
Unfortunately, even the tantalising nature of these results
wasn't enough to persuade politicians to support another trip to the Red Planet.
In fact, it was to be 17 years before we would go back to Mars.
And then, in 1992, a new era of Mars exploration began
with the launch of Mars Observer.
We have lift-off!
Lift off of the Type-3 rocket with the Mars Observer
and America's return to the Red Planet.
I believe that before Apollo celebrates the 50th anniversary
of its landing on the moon, the American flag should be planted on Mars.
Observer was the first of five US missions to Mars in the 1990s.
The Red Planet was very much back on the agenda.
And we have lift-off of NASA's Mars Global surveyor,
as America begins its journey back to the Red Planet.
But, despite their high hopes, more than half
of NASA's missions to Mars that decade failed.
Now, it's a mistake many of us have made, but then
most of us aren't in charge of missions into space.
Scientists at NASA couldn't work out why the
Mars Orbiter, worth a small £78 million,
got lost in space, until someone pointed out that
they'd planned everything in feet and inches
rather than metres and centimetres.
Eight days ago, as it approached the Red Planet, contact with the craft was lost.
This was the moment when NASA scientists realised something had gone horribly wrong.
The American space agency NASA is on the verge of
having to admit to another embarrassing failure.
The Mars Polar Lander would be the second
spacecraft that it's lost in just two months.
And there's still no convincing explanation for what might have gone wrong.
The strain is starting to show.
Three days on, and still no sign of their lost lander.
NASA engineers had thought it was just a case
of a misdirected communications antenna.
Now it looks likely that the spacecraft could be seriously damaged.
Thousands of functions are performed during a space mission.
Just one man-made mistake can be catastrophic.
These failures were a timely reminder.
Crossing millions of miles with pinpoint accuracy, and withstanding
the rigours of space to reach Mars, were an extraordinary
challenge for a spacecraft and its operators.
Success was never guaranteed.
Faced with the technical difficulties of
even reaching Mars, the prospect of actually
finding life on the Red Planet was beginning to seem unrealistic.
But then a breakthrough came from an unexpected place.
Here, on Earth, geologists had been investigating Martian meteorites
in the hope they might reveal more about the Red Planet.
And they found something incredible.
For the first time in human history, evidence
has been discovered of life on another planet.
The announcement was made by American scientists late last night.
A spokesman for the US space agency, NASA, called it a startling discovery.
"Life On Mars" by David Bowie
We have a number of forms, which is very tempting
for us to interpret as Martian micro-fossils.
Today, rock 84001 speaks to us
across all those billions of years and millions of miles.
If this discovery is confirmed, it will surely be one of the most
stunning insights into our universe that science has ever uncovered.
The usually sober Horizon got swept up in the story.
It devoted a whole programme to NASA's announcement
that they thought they'd discovered Martian life in a meteorite.
The unlikely location of this discovery was Antarctica.
Each summer, a US expedition heads south to hunt for meteorites.
It's led by Ralph Harvey.
If you wanna go somewhere on Earth where the rocks you find must have
fallen from the sky, you go to a place where
there's a great natural white sheet on the ground.
Antarctica is perfect for that.
Any rock you find at the top of 10,000 ft pile of
ice and snow had to have fallen there from the sky.
When you find a meteorite, it's just really exciting.
You can go for hours and nobody will find a
meteorite, and all of a sudden you run into one.
It's a break, so everybody gets together.
Yeah, another one.
OK...
We ran into the rock.
I remember it was bigger than other rocks we had been collecting.
Because of the brightness of the area, and the colour of the snow
and ice, and the dark glasses, it had a very green tint to me.
And we were all excited for being in this beautiful area and finding this green rock.
It just really stood out in my mind.
I even wrote it down in my journal.
At the end of the season, the find was shipped
back to Houston, to NASA's Johnson Space Centre.
Meteorites are named after local post offices where they fell,
and obviously there's no post offices in Antarctica.
So we named them after the local features.
And ALH stands for Alan Hills.
84 is the year it was collected.
And 01 was the first lab number we pulled out.
Once in the lab, the rock was photographed, described and catalogued,
then put into storage among all the others waiting
to be studied by scientists around the world.
The true nature of this meteorite was nearly lost to science forever.
Unfortunately, 8401 was misclassified as a rock like this.
This is a diogenite.
It's a coarsely crystalline rock from the asteroid belt.
And so 8401 lived its life for 10 years
in a curation facility at the Johnson Space Centre
under the label of diogenite,
until Dave Mittelfeld requested a specimen as part of his study of diogenites.
And then when he looked at 8401, he realised it wasn't a diogenite,
but in fact, was a member of a small group of meteorites,
rather like this one.
This rock is one of a small group that are very special indeed.
They have come to us not from the asteroid belt,
but from our neighbouring planet, from Mars.
Scientists studied this piece of the Red Planet in
microscopic detail, and found something extraordinary.
This is one thousandth of the width of a human
hair, so these are extremely tiny things.
One evening, we were moving around and we came across a region
that appeared to be a little different from what we had normally seen.
And we kept scanning in at higher magnification,
and we saw something that caught our eye.
And we said, "What is that?"
We found this structure.
It had 10 to 12 segments in it. And appeared to have a head and a tail.
And we looked at each other
with a look that kinda said, "This can't be."
And the significance of the structure got to both of us.
I went home and that night, I had difficulty sleeping.
I was saying, "Could we have a micro-fossil here from Mars?"
If it can be established that life has
arisen on Mars quite independently of Earth,
then in my view that would be a discovery more profound
than the work of Copernicus and Darwin and Einstein put together.
It would truly be the most amazing scientific discovery of all time.
NASA scientists believed they'd solved the centuries-old mystery
of whether life had evolved on other planets.
If our evidence continues to pan out, which we think it will,
it will show for the first time that we are not
alone in this giant universe that we live in.
My first trip to NASA was shortly after this discovery.
The place was alive with anticipation.
People were wandering around wearing badges saying, "Mars or Bust".
But the excitement was short lived. Each of the lines of evidence that pointed towards
fossilised Martian life could be explained in other ways.
Scientists found that the organic material
in the meteorite could have been created by non-biological processes.
Or even be the result of contamination from Antarctic ice.
The scientific community was divided.
The only way to know if there had ever been life on Mars was to go back.
Despite the loss of several missions to the Red Planet in the 1990s,
scientists were determined to try and get to Mars once more.
And this time they had the search for life at the very heart of their operation.
The search for life is the search for liquid water.
Life on Earth is basically full of water.
Life forms are basically little bags of water with a few other ingredients added.
But water is the main component.
Water is what makes it work.
On Earth, all life is based on water.
It's the main constituent of every cell.
Because water is basically inert, it's the
perfect medium for different types of molecules
to flow around, meet and react together.
It enables life to form.
Horizon took a look at NASA's attempts to find water on Mars.
When we look at the history of life on Earth, it appears to start very quickly.
Maybe a hundred million years.
That seems like a long time, but for a planet that's short.
So if there was water on Mars for a couple of hundred million years,
then life had a good shot at getting started there.
And soon they found evidence the water had been there for millions of years.
It was all because of one very important picture.
Sent back in December 2000, it was of vast formations of sedimentary rock.
Sediment is basically made of sand.
It can only have been deposited over millions of years
by a huge body of water like a lake or an ocean.
It showed that not only had there been masses of water,
but it had been around long enough for life to form.
The sediments on the surface were now dry and exposed.
If they ever had contained life, it could not possibly have survived.
However, scientists hoped that microbes deeper
down might still be alive, frozen in the ground.
To find the actual organic remains of a Martian
organism, we're gonna need to go to frozen material.
In the ice, life might have been preserved, frozen in a state of suspended animation.
No-one at this stage could know if microbes formed
millions of years ago could have survived on Mars.
But there were indications that it really was possible.
Once again it was Earth that would hold the key to life on Mars.
Antarctica, the closest place on Earth to conditions on Mars.
Until a few years ago, no-one thought life could
survive being deep frozen for millions of years.
But research here has helped change that.
The ground here is permafrost, a mixture of soil and ice frozen together.
A group of Russian scientists teamed up with NASA
to drill down into it in search of micro-organisms.
They drilled so deep, they reached permafrost laid down millions of years ago.
The frozen cores were taken back to their laboratory.
Samples were taken from the centre of the core, then they looked for signs of life.
They discovered that bacteria can survive in the permafrost
for far longer than anyone had thought possible.
They found bacteria that may turn out to have been
at -20 degrees for more than 10 million years.
Probably we have now these bacteria from Antarctic permafrost
between eight and 15 million years old.
Bacteria had been buried alive here in frozen
ground since the beginning of human evolution.
If life can survive in Antarctica for 15 million years,
then something could be waiting to be revived on Mars.
These discoveries put new urgency into the quest to find water on Mars.
There was now a real possibility they might find something alive.
But scientists needed little reminder that getting to Mars would be hazardous.
Professor of Cosmo-Chemistry, William Boynton,
had lost precious equipment on two of the botched missions.
But he decided to try one more time.
This was really my third attempt to get to Mars.
Some of my colleagues said, "Bill, are you crazy?"
"You're doing this a third time?"
"Why are you putting so much time in on this?"
And I just couldn't say no.
I think there was just a calling that I had to go back.
We have a device called a gamma ray spectrometer.
It's designed to determine what elements are
present on Mars that make up the surface.
And probably the most important one of those is hydrogen,
because that's the main constituent element in water.
"We have ignition and lift-off"
"of a Delta Two rocket carrying NASA on an odyssey back to Mars."
On 7th April 2001, NASA launched Odyssey, carrying Boynton's device.
This time, everything went according to plan.
One, two, set.
We are separating the stages.
Second-stage ignition.
Once in Mars' orbit, the instrument was deployed.
The gamma-ray detector could get to work.
The data was radioed back from Odyssey to NASA
to the University of Tucson and finally to Boynton's desk.
As the data came through, a picture started to build.
When I first saw the signal, I was looking through
it and first trying to find the hydrogen signal.
When I saw it, it was so big I couldn't believe it.
I actually had to do some checks to see, could
this be real or somehow did we mess things up?
It could only mean one thing - there is water
ice on Mars today, and there is masses of it.
Boynton and his team had discovered a vast ocean
in the southern hemisphere, a frozen ocean over 5,000 kilometres wide.
What we found is, just in the surface,
if we melted that would be enough to fill Lake Michigan two times over.
There is probably a lot more, because we don't know how deep the ice goes.
That is just in the upper metre.
It could be 10 metres deep, it could be 100 metres deep.
There's a lot of ice there.
The ice they found is trapped in the ground,
a permafrost, just like in Antarctica.
It was a smoking gun.
They'd found the one thing needed for life to evolve.
But the question of whether life was actually there remained unanswered.
In 2003, it was Britain's turn to join the race to find life on the Red Planet.
Beagle 2 was a lander, carrying scientific instruments designed
to search for carbon - something which exists in all living things.
It was also equipped with an ingenious device called a mole,
which could take samples under rocks around the landing site
in the previously inaccessible places
scientists thought life most likely to survive.
After travelling 400 million kilometres, Mars Express, Europe's first Mars rocket,
arrived safely to the planet with Beagle 2 on board.
On Christmas Day 2003, the lander began its hazardous
seven-minute journey through the atmosphere to the surface.
Mission scientists awaited news of Beagle's expected touchdown.
With national pride at stake, Britain took notice.
Good morning. Welcome to Breakfast from BBC News with Bill Turnbull.
No message from Mars - scientists fail to make contact
with the Beagle 2 probe but say all is not yet lost.
That's our main story on Christmas Day, 25th December.
It was a long, tense wait through the night.
Would Britain's first mission to another planet actually make it?
Before dawn, the mastermind of the project, Colin Pillinger, was on the line to NASA,
in the hope that one of its spacecraft had picked up the first signal. It didn't.
I'm afraid it's a bit disappointing, but it's not the end of the world.
Please don't go away from here believing
that we've lost this spacecraft.
Over the next few days, the British public waited to hear from Beagle,
but, sadly, the news didn't improve.
British scientists behind the Beagle 2 mission to Mars
are refusing to give up hope,
despite no signal from the probe for more than 24 hours.
'This morning, the mood among the scientists involved was getting grimmer,
'but no talk yet of giving up.'
On this mission, our faith has been
unshakeable that the mission would go ahead.
We've crossed lots of bridges to get this far.
We'll keep the unshakeable faith until the point comes
when we have to say that it's no longer worth thinking about.
British scientists have again failed to make contact
with the Beagle 2 spacecraft.
It was their fifth attempt to get in touch.
'Another frustrating day.
'Three more attempts to find Beagle overnight, and three more failures.'
And ten days later, they were forced to admit defeat.
It looks after all as if the Beagle may have crash-landed.
Scientists said today that their best chance yet
to make contact with the British spacecraft has failed.
'For Colin Pillinger, the man behind Beagle 2,
'the disappointment was clearly visible.
'But he remained upbeat about its achievements.'
Come on, guys, this isn't gonna be a great British failure.
We have learnt so much that we have to build on this,
and the lesson that we have to learn is to go forward and have another Beagle.
The same name is good enough for us.
It's got us this far. Let's take it on.
The Americans, meanwhile, were hopeful that they'd have more luck with rovers.
Rovers are robotic geologists that travel across the surface of a planet.
Being mobile means that if they see an interesting
feature, they can go an investigate it.
Rovers in all shapes and sizes
are now being created to go to the Red Planet.
Horizon investigated their effectiveness.
'Many could be seen strutting their stuff
'at a conference of rover designers held on a Californian beach.'
There are so few rocks that are small,
that are seen in those two landing sites,
that in fact this rover, it turns out, can go between the big rocks...
'There were rovers from Europe, Russia and Japan.'
It is a big space company...
Amidst all the enthusiasm for robotic
exploration, there was also one voice of caution.
...Primarily the difference between this Marsokhod
and the one that you just saw.
Carol Stoker is working on the robotic exploration
of Mars at NASA's Ames Research Center.
She is an exobiologist, an expert on how to search for life on other worlds.
I think it is going to be extremely difficult to find fossil life on Mars.
It's a very tough problem to find it on Earth.
Any viewer would know from their own experience
that if they just walked out in their back yard - did they find a fossil there?
It's not an easy problem.
To test the effectiveness of robot exploration,
Carol Stoker has been working with a Russian Marsokhod rover
to see if it can discover life on Earth.
'My programme at NASA Ames did a field experiment
'where we took a science team, actually gave
the science team exposure to data from a rover
'that was placed in a very fossil-rich field site.'
And how well did the science team do?
Perhaps they overlooked the odd microscopic fossil?
No, they were missing very obvious things!
They were missing dinosaur tracks the size of dinner plates.
It is an issue of, exactly where do you look?
'You can be six inches to the left of where the fossil is.
'If you are not looking right at it, you won't
see it. That's the problem with a rover -
'it's only going to look where you tell it to look.
'Actually, I think that our best chances of finding evidence of life on Mars'
is to send human crews. There is no question
Human crews will do a better job than all the robotics
technology we can develop in the next 30 years,
even if we spend the entire NASA budget on it.
After 40 years of exploration, evidence that life exists on Mars,
or has ever been present, seems tantalisingly
close but frustratingly just out of reach.
If we are ever to find the answer to this fundamental question,
we are going to have to send people to the surface.
That is going to require tremendous human
endeavour before we have even got off the ground.
When we do send people to Mars,
it will be one of the most challenging trips humanity has ever undertaken,
travelling more than 80 million kilometres across the Solar System.
Robots may have made the trip,
but sending humans will stretch technological expertise to the limit.
And it will stretch humans to the limit too.
Crew members aboard a Mars mission
will have to endure six months of isolation
before they even get to the Red Planet.
Horizon took a look at some of the issues involved.
'A few days into the flight, the lack of
gravity itself will start to affect the crew.
'The journey to Mars will be a biological battle for survival.
'As well as all their experience in space,
'the Russians have a history of ground-based research
'into the long-term damage that space does to the body.
'This volunteer has been in bed for a year.
'Just as would happen in space, with no stress on his body,
'he is suffering bone loss, and his muscles have been wasting away.
'His heart capacity has shrunk.
'Even short bouts of exercise are now exhausting.
'Until Dr Valery Polyakov completed a world-record
14 months' space flight two years ago,
'no-one was sure humans could survive the complete return journey to Mars.
'The aim of this bed-rest research is to develop exercises
'to prevent bodies designed for life on Earth from slowly decaying in space.
'From the Russians' experience on Mir,
'life in space will be dominated by exercise -
'two hours a day, every day, doing a cosmic workout.
'Norm Thagard was the first American astronaut to try out the Russians' regime.
'As a practical matter, you cannot exercise enough
'to maintain the same fitness level that you
would have had had you remained on Earth.'
Not everyone, even on that regimen, can stand up
and walk immediately after returning to Earth.
Mars' gravity is lower than Earth's gravity,
so the amount of physical conditioning you would need would be less,
but you would still need some.
You wouldn't want to go off to Mars with no exercise at all
and then expect to be able to perform useful
work after landing on the surface of the planet.
Then there's the small matter of food.
Anything any astronaut has ever eaten in space began its life on Earth.
But rather than carrying vast stores of pre-packaged food with them,
for the long trip to Mars, the crew might grow their own.
Ground experiments are going on to squeeze every ounce of matter
from the tiny greenhouse they'd have on the rocket.
Plants will grow without gravity, but keeping them alive is complicated.
On their space station Mir, the Russians have
slowly been learning about horticulture in space.
Some plants flown up from Earth do very well,
but starting from seeds is much harder.
Up on Mir now, astronaut Mike Foal is trying to grow rape seedlings.
They're confused. They don't know which way to grow, cos there's no gravity here,
so we've been using strong lights above, because they are attracted to the light.
They will grow up in a month. They'll flower in about two weeks.
I then have to take bee sticks - pieces of bees on sticks -
and I go around the flowers and pollinate them.
They will produce seeds in a month. I will harvest the seeds and keep planting them.
I'm gonna try and plant three generations of seeds,
starting with Earth seeds, going to space seeds.
We have never produced seeds in space that we could plant - never!
We're that far behind on just getting basic life support going in space.
We will need vegetables wherever we're going.
We will need these things, and animals and the rest,
and the micro-organisms that make up an ecological system.
When the Russians first tried rearing Japanese quail chicks on Mir,
the baby birds wouldn't grab hold of anything, so they couldn't feed.
The solution is to fit the birds with harnesses to anchor them down.
It seems they then develop normally.
And the Russians believe quail will make an
excellent compact food source in zero gravity.
But so far, no-one has persuaded them to breed or lay eggs.
And when we reach Mars, there'll be no relief.
The average temperature is minus 50 degrees centigrade,
and it goes down from there to minus 225 degrees at the poles.
The atmosphere is extremely thin and it's almost all
carbon dioxide, and there are frequent dust storms.
We won't be able to live under open skies.
We know that conditions on Mars today are not very good for life.
If you were to go out onto Mars without a spacesuit,
and I don't recommend it, but if you were,
your body fluids would literally start to boil,
because the vapour pressure on Mars is lower than
the boiling point of water at body temperature.
So this would not be a good thing in terms of your ears, eyes, nose and throat.
You would quickly suffocate and essentially drown in your own bodily fluid.
We will have to live inside.
Ground-based experiments that simulate what a life would be like in a Mars colony
are currently being carried out by the European Space Agency.
This year, a crew of six were successfully
sealed inside a habitat in Moscow for 105 days.
Now I am ready to go to bed.
And in 2010, a new mission will run, for 520 days,
the length of a return trip to Mars,
plus a 30-day stopover on the surface.
Despite the challenges we must overcome,
astronomers think it's inevitable that we will go and live on Mars.
It's the only planet out there where one can reasonably expect
that humans could go and establish themselves permanently,
for what ever reason.
People could go and live on Mars.
They can't go and live on Jupiter, but they can go and live on Mars.
I think just because it's available,
almost, we have the capacity to go there already,
that it's inevitable that we will go.
Mars was the first planet we flew by, orbited, landed on and roved upon.
It will be the first planet that humans step foot upon.
When that might happen, is anybody's guess.
As the United States pulls back from its commitments to reach that planet by 2050,
one of the greatest thinkers of our generation
believes the exploration of Mars and the space
beyond should be a priority for humankind.
40 years ago, the best scientific minds believed Mars was similar enough to Earth,
that they would find life there.
Then all their hopes and dreams were dashed.
With each new mission to the Red Planet,
scientists are discovering reasons to keep looking,
all in the hope that, one day, we will finally find proof
that we are not alone in the universe.
Subtitles by Red Bee Media Ltd
E-mail subtitling@bbc.co.uk