Horizon (1964–…): Season 41, Episode 6 - Saturn: Lord of the Rings - full transcript
This is the story of the most ambitious
un-manned space project ever launched -
its destination Saturn.
The mission:
to investigate this hauntingly beautiful planet
and its enigmatic rings.
But the climax of the mission
will be Saturn's largest moon, Titan.
The hope is that
by exploring this alien world
we will get closer to answering
that great scientific mystery -
the origin of life.
Tonight, Horizon follows this fantastic voyage
across the solar system
to find out how it all began.
June 30th 2004.
The World's press have gathered for news
of the most critical part of this 3.2 billion dollar mission.
The Cassini spacecraft is scheduled
to go into orbit around its target -
Saturn.
The slightest hitch
during this complex manoeuvre
and the entire mission will be lost.
We are slowing down.
You can image how anxious some of us were...
knowing that it all hinged
on one ninety minute period,
where we would have
to perfectly just slip into orbit.
The Doppler has landed.
This moment was the culmination
of 14 years preparation
and a 7 year trek
across the solar system.
But the real highlight
was when Cassini started to beam back
its images from over a billion miles away.
How're you doing?
Oh it was fantastic. It was just great.
You wait years for this kind of a moment.
Citizens of the Earth -
I would like to present
the majestic rings of Saturn.
This remarkable spacecraft
had travelled over a billion miles
towards the outer reaches
of our Solar system
to a giant swirling ball of gas
over 750 times larger than the Earth,
the mysterious world of Saturn.
Cassini's story can be traced to the launch
of a different mission 27 years ago -
the voyager deep space probes.
When they flew past Saturn
they provided tantalising glimpses
of this distant world.
Saturn's giant rings were seen
closer than ever before
revealing details
that were completely new and unexpected.
Before Voyager got there,
we knew very little about them.
There wasn't a great number
of people even studying the rings.
Voyager got there and found
this bewildering array of structure in the rings,
and people set about trying
to explain it right away.
It had always been assumed
that the rings were as old as Saturn itself.
But the new information
sent back by the probes
pointed to something very different.
We saw processes going on
in the rings that were too fast,
that would have gone to completion
long before the age of the solar system,
the age of the planets
so that Voyager information showed us
the rings must be created much more recently.
Voyager begged the question:
if the rings are not as old as Saturn,
how old are they?
And how did they get there?
And Voyager was to uncover
yet more mysteries.
For the first time detailed images
were taken of Saturn's many moons.
They showed ancient cratered surfaces.
But one stood out,
Saturn's largest moon, Titan.
It was unlike any moon
that had ever been seen -
it had a thick
almost Earth-like atmosphere.
But frustratingly its surface was shrouded
by a layer of orange cloud.
We saw this fuzzy ball,
and the immediate reaction is,
what's below those clouds.
You know, what are these clouds made of,
what is hidden behind that layer?
Titan would remain a mystery.
Voyager had to move on -
out towards Uranus, Neptune
and beyond.
Leaving behind it
more questions than answers
and scientists desperate
to return.
The combination of the spectacular
structure in the rings,
the youthful processes in the rings,
the hazy atmosphere of Titan
just left every scientist
with a great curiosity to explain those things
that we had seen
with the Voyager fly-bys.
Immediately there was a feeling
that we had to return to Saturn
and stay there for a longer time.
So in 1990 work began
on a spectacular new spacecraft.
The result of a unique co-operation
between NASA and European Space Agencies,
the Cassini probe would carry the most complex
array of instruments ever launched into space.
It would be capable of measuring everything
from magnetic fields
to minute particles of cosmic dust,
but at the heart
of this array of instruments
were the eyes of the mission -
the two cameras.
One is a very long focal length,
very high resolution,
but you get a little postage
stamp-like coverage.
And so you want to also carry
a camera with a larger field of view,
shorter focal length that covers
a greater amount of territory,
so you can put your little postage stamp
coverage in context, in geological context.
Cassini was also loaded
with a powerful radar
designed to do what no camera can
and punch through Titan's hazy atmosphere
to reveal the surface below.
But Titan has so intrigued scientists
that they decided to send in
a separate probe for an even closer look.
That probe is called Huygens
after the man
who first discovered Titan.
Rather than viewing from a distance,
we're going for the broke,
Huygens is actually going
to plunge through that atmosphere
and take in situ measurements.
We want to know exactly
what the composition of the atmosphere,
what are the gases
which make up the atmosphere,
and we'd also like
to know about meteorology
or weather in Titan's atmosphere.
This bold plan had
one major draw back -
the resulting craft was massive.
The Cassini spacecraft is
the largest inter-planetary satellite
that NASA has ever
built and launched.
At launch it weighed nearly
fifty eight hundred kilograms
The big problem was how to get this five
and a half tonne leviathan into space.
The most powerful rocket on Earth,
the mighty Titan IV was selected for launch
delivering over 3.9 million pounds of thrust.
But even this would not be enough.
Because this massive space craft
didn't just have to get into space -
it had to travel over a billion miles,
all the way to Saturn.
The only way to travel
this vast distance
would be with a little help
from the planets.
The energy that we needed to get out
in the solar system, out to the planet Saturn
had to be supplemented by, partially provided
by gravitational encounters with the planets.
The important thing is
to gather energy
from the gravity of the planet
you're flying by.
So Cassini was routed
via the Earth's nearest neighbour, Venus.
This planet's gravitational pull
would accelerate Cassini,
increasing its speed by over 8000 mph.
But this still would not be enough.
Cassini would return
for a second boost from Venus.
The Earth would then
accelerate Cassini
flinging it out further -
towards its next rendezvous -
Jupiter.
The probe would clock up
a speed of 50,000 mph
before reaching its final destination -
Saturn.
October 15th 1997:
Cassini was blasted
into the night sky.
All the planets it needed
for its trip to Saturn
were in perfect alignment.
An event that would not re-occur
for over 600 years.
What lay ahead was an epic
7 year journey across the solar system.
When the probe swung back
past the Earth
the radar was checked out.
It scanned a huge swathe
of South America -
and everything was
in working order.
Cassini seemed to be operating flawlessly.
The Europeans also decided to test out
the radio link between Huygens and Cassini.
This was when things started
to go wrong.
Huygens is designed to beam
all its data up to Cassini
as it plunges
through Titan's atmosphere.
The Huygens probe itself
doesn't have enough power,
and it doesn't have
a large enough dish
to transmit its data, the scientific data
that it collects on Titan,
directly back to the Earth.
So what will happen is that it uses
the Cassini space craft as a data relay.
The test was designed to make sure that Cassini
could receive all the data from Huygens.
But when the results came back
they were alarming.
We were expecting to receive
all the simulated data.
Unfortunately we did not receive
very many of those data.
We lost,
well, it's - we lost maybe ninety per cent
of the data, sometime even all of the data, so...
If Cassini could not pick up the precious data
from Huygens as it travelled to Titan
there would be no results, no pictures -
nothing.
The entire mission would be lost.
The Huygens team called a meeting
to break the news.
Imaging specialist Marty Tomasko had spent
over ten years building the camera for Huygens -
he couldn't believe what he was hearing.
They said, 'We've preformed the test
and we didn't get any signal,
but the test accomplished
all of its objectives,'
and some of us were sitting
around the table saying,
'What exactly are you trying
to sell us?' you know...
'You've accomplished the objectives
of conducting the test
but you've actually succeeded in proving
the thing is not going to work.
But the Europeans were hoping
there might be a simple explanation.
Maybe the test is wrong, this is the first thing
you say, 'Oh, the test is wrong,'
we have done something wrong
so everything is good with the hardware,
no problem, it has been tested on ground
so the test must be wrong.
But the test was not wrong.
6 months of painstaking research revealed
a tiny flaw in Cassini's receiver.
It was enough to essentially put
the link between the two out of alignment.
It was as if Huygens was transmitting
on Radio One, on one frequency
and Cassini was receiving on Radio Two,
a slightly different frequency.
So this was potentially disastrous.
Repairing the receiver was impossible.
It was out in space
over 300 million miles away.
There was no way we could repair
so we had to find a new mission scenario
which would...
which would allow us
to live with this problem
but still to recover the - the whole mission.
After months of research
an ingenious plan emerged.
They couldn't retune Cassini's receiver
but they could shift the signal
it was receiving
using a basic principal
known as the Doppler effect.
If they could slow Cassini down,
it would pass through the radio waves
from Huygens at a slower rate.
This means that the radio waves
would hit Cassini at a lower frequency.
This lower frequency signal could then
be picked up by the faulty receiver.
All in all it took us six months
to find a solution,
but it took us two years to design
all the detail of the solution and to test it.
We are now recovering the full Huygens Mission,
we are not going to lose any science,
so it's a very successful recovery.
Scientists were now confident
that Huygens had every chance
of sending back its precious data
when it finally reached Titan.
As a new millennium dawned on Earth,
Cassini had crossed a billion
and a half miles of space
and arrived at Jupiter,
the Giant of the solar system.
Twice a massive as all the other planets combined
its powerful gravitational field
would give Cassini its final boost.
Scientists waited anxiously,
because Cassini's cameras
faced their biggest test yet.
Jupiter's majesty
was revealed as never before -
its swirling clouds and icy moons
were seen with breathtaking clarity.
But Cassini had to move on
across another 500 million miles
of space to its final destination.
For imaging team leader Carolyn Porco,
the Jupiter pictures were a triumph.
But her real goal was always Saturn -
she has devoted her entire career
to studying it
and it is now part of her life.
To know that we can know so much
about our solar system and about our cosmos
for me, makes life meaningful.
It's very much like being in love,
it's very much that kind of a relationship
where you want to know more
and you want to be one with, you know,
the person you're in love with
or the topic that you're studying.
It's... kind of this... It's a connection,
it's really a connection and for me,
it's like being allowed
a glimpse of the miraculous.
By the spring of 2004
Cassini had closed in on Saturn.
But just before contact,
mission planners had calculated a precise
course to send the spacecraft past Phoebe -
Saturn's curious outermost moon.
Almost all Saturn's moons
orbit in the same direction
around its equator,
but not Phoebe.
Satellites, if they form naturally
around the planet are not
expected to be in a plane in...
in any other plane except for
the equatorial plane of the planet
so very early on when people
figured out Phoebe's orbit,
it became clear that it was unlikely
that Phoebe formed as part of the regular
stable of satellites that are around Saturn.
If Phoebe was not formed
along with Saturn
it must have come in
from elsewhere
and been sucked in
by Saturn's gravitational field.
But where had it come from?
Scientists believe
that there are two options.
One is the asteroid belt between Mars
and Jupiter where things are made of rock,
probably not dramatically different
than the rock we have here.
The other is a much more distant
place called the Kuiper Belt -
a mysterious band of rubble left over
from the formation of the outer planets.
These are the most ancient
objects in our solar system.
Those objects are
made primarily of ice,
so they have dramatically
different composition;
everybody knows the difference between a rock
and the stuff you put in your drink to keep it cool
and if you can figure out
a way to tell that difference
from a long way away,
which is what we have
to do with spacecraft
then you can start to get a real
handle on where Phoebe came from.
Until now all that scientists have had
to go on is this picture;
taken by Voyager 23 years ago.
But this time Phoebe was in the cross-hairs
of Cassini's powerful cameras.
Picture after picture returned
with unprecedented detail.
We buzzed Phoebe,
okay, we came within two thousand
kilometres of its surface.
You could, reach out and touch it,
is what it looked like.
So it's very exciting. We saw features
that were, were 30 metres across.
At last Phoebe was giving up
her secrets.
The images revealed an ancient surface
pitted with craters
caused over billions of years.
But to solve the mystery
of where Phoebe had come from
scientists needed to work out
what it was made of.
And that meant turning
to a different piece of equipment.
The technology Cassini used to reveal
Phoebe's origins is aboard this aeroplane.
It was developed to identify different
varieties of rocks at high speed
just by flying over the land.
Previously that was a task
that could only be done slowly -
by geologists painstakingly
collecting samples by hand.
To us and our crude sensors called eyes,
both of these rocks are very similar,
only trained geologists or somebody with lots of
experience can tell you what kind of rocks they are.
However, imagine having
some kind of special goggles
that you could put on your eyes
and that they would make these rocks
not be so drab and white
but stand up with the things
that you would actually like to know.
That even to the layman
they would say,
'This is the rock you want
and this is the rock you don't want.'
The technology that performs
this remarkable feat
is called a mapping spectrometer.
It works by measuring the different
frequencies of light reflected by the rocks below.
Every mineral reflects light
at its own unique set of frequencies.
The spectrometer can spot
these differences
and interprets them as different colours.
The data from the spectrometer is then used
to build up a multi-coloured 3-D map of the area.
The result is a complete picture
of the mineral content of the terrain -
all achieved without anyone
needing to take a sample.
The same equipment has been adapted
for Cassini's trip past Phoebe.
We've taken the concept,
wrapped it in a wrapper that allows
it to operate in space,
put in on a spacecraft
and flown it to Saturn.
Now that is kind of an understatement
because it costs sixty million dollars
and took seven years to build the instrument.
As Cassini approached Phoebe,
the spectrometer got its chance to solve
the riddle of Saturn's wayward moon.
The results were better
than anyone could have hoped.
Actually we were blown away
by data we got on Phoebe.
We found water ice,
we found organic materials,
we found carbon dioxide,
which was a bit of a surprise.
We found poisons, cyanides -
all of those things put together
really painted a very nice
picture in the sense
that it was clear
after we looked at the data
that this object does not come
form the asteroid belt.
Cassini had proved once and for all
that Phoebe had come in from the cold
outer reaches of the solar system.
This was scientists' first glimpse
of these primordial objects
decades before any mission
could ever get there.
But Phoebe was just a taster -
a preview of what was to come.
June 30th 2004:
mission control had piloted
the Cassini spacecraft
across 2.2 billion miles of space
and it was still right on target -
and fast approaching its destination -
Saturn.
What lay ahead was that great enigma -
the riddle of Saturn's rings.
Scientists understand so little about them
they still have even
the most basic questions to answer.
The questions that we scientist
have about Saturn's rings
are the questions that an ordinary
person might be moved to ask
when first seeing them,
you know.
What caused them?
How did they get there?
How long have they been around?
How long are they going to last?
Answering these questions is one
of Cassini's prime objectives.
But to do this,
it first had to get
into orbit around Saturn
and that meant passing
between the rings.
The rings are chaotic and dangerous.
Made up of billions upon billions
of hard rock-like particles.
All the ring particles,
billions and billions of them are
in orbit around the planet Saturn
and they're moving at quite a clip -
something like ten kilometres per second.
Faster than a high-speed bullet.
If you were in Saturn's rings
you would be in a mass of particles
that were bumping into each other
and rolling over each other
If you were a ring particle you would get bombarded
from one side and then from the other,
as one particle bounced
of another one around you.
To carry out its mission
Cassini risked being torn apart.
Even a very small particle
could be the end of Cassini,
if it hits a particle
as small as a grain of rice
that would be enough
because of the high speed
at which it's moving
to end the mission.
At Mission Control tension was building
as the high risk orbit
insertion manoeuvre began.
Saturn orbit insertion was
a bit of a nervous time for us.
There were a lot of things
that had to work right.
The consequences of it not working
would have been pretty serious.
The rings were not the only
danger that Cassini faced.
To get into orbit
it also had to slow down.
That meant firing its main engine -
any malfunction and Cassini
would simply fly past -
lost forever in the void of space.
That engine had not been used very
frequently over a period of seven years,
that makes you nervous.
You know, it's like you have a car,
a brand new car
that you put in the garage,
and every once in a while,
you turn it on,
and then you have an emergency,
and you get in the car, and you
turn it on, it'd better work.
The sequence began
at seven thirty six pm.
First Cassini rotated,
to use its giant antenna
as a shield to protect it
when it passed between the rings.
All eyes were on a signal sent out
by the probe's tiny auxiliary transmitter.
Only if the signal flattened out
at the bottom of the graph
would they know
if Cassini had survived.
A 3.2 billion dollar mission
and 14 years of work
all hinged on this one moment.
The Doppler has landed.
Cassini had arrived.
When the images returned
Saturn was revealed as never before.
I just don't know what to say,
I'm speechless.
Oh absolutely exciting, I mean
this is the culmination 22 years of effort
and just seeing the lord
of the rings in its big glory...
We are amazed about the detail
we are seeing and the sharpness in the rings.
You wait years to have
this kind of a moment.
Despite these remarkable images
the fundamental question of the age
of Saturn's rings remains unanswered.
Some hope that this enduring puzzle
might be solved by taking
a very close look
at what the rings are made of.
The rings are made of ice.
Just like the stuff you've got
in your ice cube trays
and almost a hundred per cent
pure water ice
with some small contaminants.
These contaminants are the key
to finding out the age of the rings,
minute traces of dust that come from meteoroids.
The basic principle is simple -
the older the rings are
the more they will have
been bombarded
and so the dirtier they will be.
The pollution is sort
of a like a clock
because we're pouring material
in on top of the rings
and it's dark, non-icy material
so the level of darkness in the rings
tells us something about their age.
So to discover the level
of pollution in the rings
Cassini's spectrometer took these images.
What they show has surprised scientists.
The spectacular range of structure
in the rings with reds and blue and aquas,
that was something that was
completely unpredictable.
The images show cleaner ice
in shades of blue;
the heavier contamination in red.
The analysis on this is not yet complete
but these new spectrometer images seem
to suggest an intriguing possibility -
that perhaps Saturn's rings were not
all formed at the same time.
It's definitely the case that there's
a gradient in composition across the rings
so that the rings are less icy
on the inside and more icy on the outside.
As we go to the outside the particles
become younger and fresher.
So it appears that the inner rings
shown in red are in fact older,
and that somehow the outer rings
have been made more recently.
To work out exactly how this is happening
will take several years of observations.
But now Cassini is safely in orbit
the scientists will have
all the time they need.
But there is a whole
other aspect to Cassini's voyage -
one that has not yet begun -
It's encounter with Titan -
one of the great mysteries
of our solar system.
It's thick atmosphere
captivates scientists
as it might mean that Titan
in some way resembles the Earth.
Whenever we humans think that we might be approaching
something that is vaguely similar to Earth,
we get very excited about it.
The prospect of something familiar,
but yet so distant, and so strange
is a very exciting combination.
Trying to figure out what
this distant moon will look like
has become an obsession
for planetary scientist Dr Ralph Lorenz.
He has spent the past 15 years
trying to piece together all the scraps
of information available on Titan
to build up a picture
of this mysterious place.
And he believes it is a world
that shares many features with our own.
But on this distant moon
things are also very different.
The landscape may be strangely familiar
much as there is on Earth,
there may be a cycle with the rain
and rivers and streams.
Titan is so cold that methane,
which is a gas on Earth,
can condense into a liquid
and freeze as a solid.
They may have lakes,
but the lakes are made
of lighter fluid.
If Dr Lorenz is right
the methane will also form familiar clouds
but it might turn the sky
a very unfamiliar green.
We might see methane rain
falling from these clouds
but because Titan is smaller
than the Earth it has less gravity
this rain would be unlike
any we have ever seen.
The balance of forces
that holds a raindrop together
is a little bit different on Titan
because the material is different
and so the raindrops could be rather larger
but on Titan with its thick
atmosphere and its low gravity,
these large raindrops would fall maybe
ten times slower than raindrops do on Earth.
The rain falls so slowly,
it just evaporates
before it gets to the ground.
The picture of Titan that emerges
is one of a truly alien world-
a place where huge rain-drops fall
gracefully through a green sky,
a place with lakes and streams
made from lighter fluid.
And stranger still
the entire landscape
is made of water -
frozen hard as rock.
But for the moment this picture
is a very well educated guess
as no one as yet been able to take
a clear picture of Titan's surface,
for this mysterious moon is veiled
by a thick layer of orange cloud.
But Cassini carries two powerful instruments
designed to defeat this layer of haze.
One is Cassini's radar,
scanning over a quarter
of the moon,
it will send back the first
accurate images of Titan's surface.
The second is the European built
Huygens probe.
Huygens will separate from Cassini
and plunge beneath the clouds,
carrying its own unique camera.
Imaging specialist Marty Tomasko
will have no second chances -
the Huygens probe will be
active for just 180 minutes
so it's important that his camera
doesn't miss a thing.
What we were trying to get
is kind of the skydiver's eye view
because if you were outside the probe
and falling down through the atmosphere
we don't want to land near some interesting object
like the Grand Canyon and not know it's there.
So the plan is to spin
the probe as it descends
giving the camera a full 360 degree view.
But Tomasko has also given
the camera 3 lenses
to ensure that it has absolutely
no blind spot.
We have three fields of view,
one that comes out this window
and looks out towards the side,
one that comes out this window
and looks down at intermediate angles
and one that looks almost down
straight towards the ground
and those three images
are taken together
and as the probe rotates we take
a series of twelve of those
over a few seconds or a few minutes
and we plan to put those together
to make panoramic mosaics
of the surface of Titan during our decent.
These panoramic mosaics were created
with the same camera
in a test over the Arizona landscape.
By putting them together
a virtual world can be created.
The hope is that the next time
the camera opens its three eyes
it will be peering down on a new world -
Titan.
But Titan is more than
just a curious alien landscape.
It is a place that perhaps holds the key
to one of the greatest mysteries of the universe -
the origin of life.
For me one of the most important
questions to address
is where did I come from?
This rock is not conscious
and I'd a heck of a lot rather
be me than this rock
but the same stuff
that's in this rock is in me,
it's just organised in a way
to contain enough information
so that that stuff can turn around
and say, what is this?
How did it get here?
And, oh, by the way, how did I get here?
How did you assemble this simple stuff
into something like me
and allow me to ask those questions?
Earth today is teeming with life -
it has taken over the entire planet.
Bizarrely, this makes the Earth a very bad place
to study how life first emerged from the primordial
organic chemicals that first covered it.
It's very difficult to use the Earth
as a laboratory for understanding how life began.
Life eats all of the organic molecules
that are present on the Earth today.
If we go to the laboratory
and try to simulate how life began,
we have limits on time and space;
so a laboratory experiment
might be this big;
a laboratory investigator might work
for two or four or ten years perhaps.
No more than that.
We really need a place where organic evolution
is happening on a planetary scale,
over billions of years,
but is not being ruined
by the presence of life.
So for many years scientists
have been looking for a place
that shares the same primordial chemistry
as the early Earth.
If you look at our solar system,
there are only four bodies
that have atmospheres
and are actually solid bodies themselves:
The Earth, Venus, Mars and Titan.
Venus is just so hot that one can melt
lead on the surface,
there's - there are
no organic molecules.
Mars today is very cold,
very dry, very thin;
not a good place
for organic molecules.
And so we're left with Titan.
Titan has the right ingredients
to create complex organic molecules -
methane and nitrogen.
On the Earth, billions of years ago,
these simple chemicals somehow combined
to form the pre-cursors to life.
Scientists believe
that these same chemical reactions,
the first vital steps
on the road to life,
are occurring today high
in Titan's atmosphere.
The purpose of the experiment
is to simulate the chemistry
that makes complicated molecules
from the simple gases in Titan's atmosphere
and so here we have nitrogen,
which is the primary gas
in Titan's atmosphere,
and we have methane over here.
And these gases are mixed together
and they're run through tubes
and then they end up down here,
which is an electric discharge,
and this simulates the energy
that the sun provides to power the chemistry.
The Sun's rays break up the methane,
which then recombines to form
a set of dark orange chemicals
known as tholins.
These tholins form
the thick orange clouds
that shroud Titan
and hide its surface.
But tholins can make
more than just a haze.
With just one extra ingredient
they form one of the key
components of all living things -
amino acids.
If we were to apply what is the essential
ingredient of all life, liquid water,
then we may well make some amino acid
which is the building blocks of life
and that's the really exciting
thing about tholins.
But the surface of Titan
is at 174 degrees below freezing -
far too cold for liquid water.
However, scientists believe
that Titan's interior may be warmer
and that there could be a layer
of liquid water under the surface.
It is possible that this liquid
could rise upwards through volcanoes.
On the Earth
volcanoes belch rock.
On Titan volcanoes
most likely belch water.
And liquid water has an important
role to play we think
in helping to bring about
the rise of life.
While any water on Titan
would eventually freeze,
it might remain liquid long enough
to allow the formation
of amino acids.
So, with tholins in its atmosphere
and the possibility of water,
Titan might just have
all the ingredients to make the primordial soup
from which life first emerged.
At 2 am on Christmas Day,
three explosive bolts will fire
and the Huygens probe
will be pushed away.
22 days later it will slam
into the upper atmosphere.
A series of parachutes
will then slows its descent.
Only then will the charred
heat shield be ejected.
The chemical analyser will then search
for signs of complex organic chemistry.
At last Huygens' camera will get
the first view of Titan's surface.
Will Huygens discover
streams of liquid methane?
A rock hard surface
of frozen water ice?
Or a soft sludge
of organic chemistry
warmed by a nearby volcano?
Until January 14th 2005,
no one will know.
un-manned space project ever launched -
its destination Saturn.
The mission:
to investigate this hauntingly beautiful planet
and its enigmatic rings.
But the climax of the mission
will be Saturn's largest moon, Titan.
The hope is that
by exploring this alien world
we will get closer to answering
that great scientific mystery -
the origin of life.
Tonight, Horizon follows this fantastic voyage
across the solar system
to find out how it all began.
June 30th 2004.
The World's press have gathered for news
of the most critical part of this 3.2 billion dollar mission.
The Cassini spacecraft is scheduled
to go into orbit around its target -
Saturn.
The slightest hitch
during this complex manoeuvre
and the entire mission will be lost.
We are slowing down.
You can image how anxious some of us were...
knowing that it all hinged
on one ninety minute period,
where we would have
to perfectly just slip into orbit.
The Doppler has landed.
This moment was the culmination
of 14 years preparation
and a 7 year trek
across the solar system.
But the real highlight
was when Cassini started to beam back
its images from over a billion miles away.
How're you doing?
Oh it was fantastic. It was just great.
You wait years for this kind of a moment.
Citizens of the Earth -
I would like to present
the majestic rings of Saturn.
This remarkable spacecraft
had travelled over a billion miles
towards the outer reaches
of our Solar system
to a giant swirling ball of gas
over 750 times larger than the Earth,
the mysterious world of Saturn.
Cassini's story can be traced to the launch
of a different mission 27 years ago -
the voyager deep space probes.
When they flew past Saturn
they provided tantalising glimpses
of this distant world.
Saturn's giant rings were seen
closer than ever before
revealing details
that were completely new and unexpected.
Before Voyager got there,
we knew very little about them.
There wasn't a great number
of people even studying the rings.
Voyager got there and found
this bewildering array of structure in the rings,
and people set about trying
to explain it right away.
It had always been assumed
that the rings were as old as Saturn itself.
But the new information
sent back by the probes
pointed to something very different.
We saw processes going on
in the rings that were too fast,
that would have gone to completion
long before the age of the solar system,
the age of the planets
so that Voyager information showed us
the rings must be created much more recently.
Voyager begged the question:
if the rings are not as old as Saturn,
how old are they?
And how did they get there?
And Voyager was to uncover
yet more mysteries.
For the first time detailed images
were taken of Saturn's many moons.
They showed ancient cratered surfaces.
But one stood out,
Saturn's largest moon, Titan.
It was unlike any moon
that had ever been seen -
it had a thick
almost Earth-like atmosphere.
But frustratingly its surface was shrouded
by a layer of orange cloud.
We saw this fuzzy ball,
and the immediate reaction is,
what's below those clouds.
You know, what are these clouds made of,
what is hidden behind that layer?
Titan would remain a mystery.
Voyager had to move on -
out towards Uranus, Neptune
and beyond.
Leaving behind it
more questions than answers
and scientists desperate
to return.
The combination of the spectacular
structure in the rings,
the youthful processes in the rings,
the hazy atmosphere of Titan
just left every scientist
with a great curiosity to explain those things
that we had seen
with the Voyager fly-bys.
Immediately there was a feeling
that we had to return to Saturn
and stay there for a longer time.
So in 1990 work began
on a spectacular new spacecraft.
The result of a unique co-operation
between NASA and European Space Agencies,
the Cassini probe would carry the most complex
array of instruments ever launched into space.
It would be capable of measuring everything
from magnetic fields
to minute particles of cosmic dust,
but at the heart
of this array of instruments
were the eyes of the mission -
the two cameras.
One is a very long focal length,
very high resolution,
but you get a little postage
stamp-like coverage.
And so you want to also carry
a camera with a larger field of view,
shorter focal length that covers
a greater amount of territory,
so you can put your little postage stamp
coverage in context, in geological context.
Cassini was also loaded
with a powerful radar
designed to do what no camera can
and punch through Titan's hazy atmosphere
to reveal the surface below.
But Titan has so intrigued scientists
that they decided to send in
a separate probe for an even closer look.
That probe is called Huygens
after the man
who first discovered Titan.
Rather than viewing from a distance,
we're going for the broke,
Huygens is actually going
to plunge through that atmosphere
and take in situ measurements.
We want to know exactly
what the composition of the atmosphere,
what are the gases
which make up the atmosphere,
and we'd also like
to know about meteorology
or weather in Titan's atmosphere.
This bold plan had
one major draw back -
the resulting craft was massive.
The Cassini spacecraft is
the largest inter-planetary satellite
that NASA has ever
built and launched.
At launch it weighed nearly
fifty eight hundred kilograms
The big problem was how to get this five
and a half tonne leviathan into space.
The most powerful rocket on Earth,
the mighty Titan IV was selected for launch
delivering over 3.9 million pounds of thrust.
But even this would not be enough.
Because this massive space craft
didn't just have to get into space -
it had to travel over a billion miles,
all the way to Saturn.
The only way to travel
this vast distance
would be with a little help
from the planets.
The energy that we needed to get out
in the solar system, out to the planet Saturn
had to be supplemented by, partially provided
by gravitational encounters with the planets.
The important thing is
to gather energy
from the gravity of the planet
you're flying by.
So Cassini was routed
via the Earth's nearest neighbour, Venus.
This planet's gravitational pull
would accelerate Cassini,
increasing its speed by over 8000 mph.
But this still would not be enough.
Cassini would return
for a second boost from Venus.
The Earth would then
accelerate Cassini
flinging it out further -
towards its next rendezvous -
Jupiter.
The probe would clock up
a speed of 50,000 mph
before reaching its final destination -
Saturn.
October 15th 1997:
Cassini was blasted
into the night sky.
All the planets it needed
for its trip to Saturn
were in perfect alignment.
An event that would not re-occur
for over 600 years.
What lay ahead was an epic
7 year journey across the solar system.
When the probe swung back
past the Earth
the radar was checked out.
It scanned a huge swathe
of South America -
and everything was
in working order.
Cassini seemed to be operating flawlessly.
The Europeans also decided to test out
the radio link between Huygens and Cassini.
This was when things started
to go wrong.
Huygens is designed to beam
all its data up to Cassini
as it plunges
through Titan's atmosphere.
The Huygens probe itself
doesn't have enough power,
and it doesn't have
a large enough dish
to transmit its data, the scientific data
that it collects on Titan,
directly back to the Earth.
So what will happen is that it uses
the Cassini space craft as a data relay.
The test was designed to make sure that Cassini
could receive all the data from Huygens.
But when the results came back
they were alarming.
We were expecting to receive
all the simulated data.
Unfortunately we did not receive
very many of those data.
We lost,
well, it's - we lost maybe ninety per cent
of the data, sometime even all of the data, so...
If Cassini could not pick up the precious data
from Huygens as it travelled to Titan
there would be no results, no pictures -
nothing.
The entire mission would be lost.
The Huygens team called a meeting
to break the news.
Imaging specialist Marty Tomasko had spent
over ten years building the camera for Huygens -
he couldn't believe what he was hearing.
They said, 'We've preformed the test
and we didn't get any signal,
but the test accomplished
all of its objectives,'
and some of us were sitting
around the table saying,
'What exactly are you trying
to sell us?' you know...
'You've accomplished the objectives
of conducting the test
but you've actually succeeded in proving
the thing is not going to work.
But the Europeans were hoping
there might be a simple explanation.
Maybe the test is wrong, this is the first thing
you say, 'Oh, the test is wrong,'
we have done something wrong
so everything is good with the hardware,
no problem, it has been tested on ground
so the test must be wrong.
But the test was not wrong.
6 months of painstaking research revealed
a tiny flaw in Cassini's receiver.
It was enough to essentially put
the link between the two out of alignment.
It was as if Huygens was transmitting
on Radio One, on one frequency
and Cassini was receiving on Radio Two,
a slightly different frequency.
So this was potentially disastrous.
Repairing the receiver was impossible.
It was out in space
over 300 million miles away.
There was no way we could repair
so we had to find a new mission scenario
which would...
which would allow us
to live with this problem
but still to recover the - the whole mission.
After months of research
an ingenious plan emerged.
They couldn't retune Cassini's receiver
but they could shift the signal
it was receiving
using a basic principal
known as the Doppler effect.
If they could slow Cassini down,
it would pass through the radio waves
from Huygens at a slower rate.
This means that the radio waves
would hit Cassini at a lower frequency.
This lower frequency signal could then
be picked up by the faulty receiver.
All in all it took us six months
to find a solution,
but it took us two years to design
all the detail of the solution and to test it.
We are now recovering the full Huygens Mission,
we are not going to lose any science,
so it's a very successful recovery.
Scientists were now confident
that Huygens had every chance
of sending back its precious data
when it finally reached Titan.
As a new millennium dawned on Earth,
Cassini had crossed a billion
and a half miles of space
and arrived at Jupiter,
the Giant of the solar system.
Twice a massive as all the other planets combined
its powerful gravitational field
would give Cassini its final boost.
Scientists waited anxiously,
because Cassini's cameras
faced their biggest test yet.
Jupiter's majesty
was revealed as never before -
its swirling clouds and icy moons
were seen with breathtaking clarity.
But Cassini had to move on
across another 500 million miles
of space to its final destination.
For imaging team leader Carolyn Porco,
the Jupiter pictures were a triumph.
But her real goal was always Saturn -
she has devoted her entire career
to studying it
and it is now part of her life.
To know that we can know so much
about our solar system and about our cosmos
for me, makes life meaningful.
It's very much like being in love,
it's very much that kind of a relationship
where you want to know more
and you want to be one with, you know,
the person you're in love with
or the topic that you're studying.
It's... kind of this... It's a connection,
it's really a connection and for me,
it's like being allowed
a glimpse of the miraculous.
By the spring of 2004
Cassini had closed in on Saturn.
But just before contact,
mission planners had calculated a precise
course to send the spacecraft past Phoebe -
Saturn's curious outermost moon.
Almost all Saturn's moons
orbit in the same direction
around its equator,
but not Phoebe.
Satellites, if they form naturally
around the planet are not
expected to be in a plane in...
in any other plane except for
the equatorial plane of the planet
so very early on when people
figured out Phoebe's orbit,
it became clear that it was unlikely
that Phoebe formed as part of the regular
stable of satellites that are around Saturn.
If Phoebe was not formed
along with Saturn
it must have come in
from elsewhere
and been sucked in
by Saturn's gravitational field.
But where had it come from?
Scientists believe
that there are two options.
One is the asteroid belt between Mars
and Jupiter where things are made of rock,
probably not dramatically different
than the rock we have here.
The other is a much more distant
place called the Kuiper Belt -
a mysterious band of rubble left over
from the formation of the outer planets.
These are the most ancient
objects in our solar system.
Those objects are
made primarily of ice,
so they have dramatically
different composition;
everybody knows the difference between a rock
and the stuff you put in your drink to keep it cool
and if you can figure out
a way to tell that difference
from a long way away,
which is what we have
to do with spacecraft
then you can start to get a real
handle on where Phoebe came from.
Until now all that scientists have had
to go on is this picture;
taken by Voyager 23 years ago.
But this time Phoebe was in the cross-hairs
of Cassini's powerful cameras.
Picture after picture returned
with unprecedented detail.
We buzzed Phoebe,
okay, we came within two thousand
kilometres of its surface.
You could, reach out and touch it,
is what it looked like.
So it's very exciting. We saw features
that were, were 30 metres across.
At last Phoebe was giving up
her secrets.
The images revealed an ancient surface
pitted with craters
caused over billions of years.
But to solve the mystery
of where Phoebe had come from
scientists needed to work out
what it was made of.
And that meant turning
to a different piece of equipment.
The technology Cassini used to reveal
Phoebe's origins is aboard this aeroplane.
It was developed to identify different
varieties of rocks at high speed
just by flying over the land.
Previously that was a task
that could only be done slowly -
by geologists painstakingly
collecting samples by hand.
To us and our crude sensors called eyes,
both of these rocks are very similar,
only trained geologists or somebody with lots of
experience can tell you what kind of rocks they are.
However, imagine having
some kind of special goggles
that you could put on your eyes
and that they would make these rocks
not be so drab and white
but stand up with the things
that you would actually like to know.
That even to the layman
they would say,
'This is the rock you want
and this is the rock you don't want.'
The technology that performs
this remarkable feat
is called a mapping spectrometer.
It works by measuring the different
frequencies of light reflected by the rocks below.
Every mineral reflects light
at its own unique set of frequencies.
The spectrometer can spot
these differences
and interprets them as different colours.
The data from the spectrometer is then used
to build up a multi-coloured 3-D map of the area.
The result is a complete picture
of the mineral content of the terrain -
all achieved without anyone
needing to take a sample.
The same equipment has been adapted
for Cassini's trip past Phoebe.
We've taken the concept,
wrapped it in a wrapper that allows
it to operate in space,
put in on a spacecraft
and flown it to Saturn.
Now that is kind of an understatement
because it costs sixty million dollars
and took seven years to build the instrument.
As Cassini approached Phoebe,
the spectrometer got its chance to solve
the riddle of Saturn's wayward moon.
The results were better
than anyone could have hoped.
Actually we were blown away
by data we got on Phoebe.
We found water ice,
we found organic materials,
we found carbon dioxide,
which was a bit of a surprise.
We found poisons, cyanides -
all of those things put together
really painted a very nice
picture in the sense
that it was clear
after we looked at the data
that this object does not come
form the asteroid belt.
Cassini had proved once and for all
that Phoebe had come in from the cold
outer reaches of the solar system.
This was scientists' first glimpse
of these primordial objects
decades before any mission
could ever get there.
But Phoebe was just a taster -
a preview of what was to come.
June 30th 2004:
mission control had piloted
the Cassini spacecraft
across 2.2 billion miles of space
and it was still right on target -
and fast approaching its destination -
Saturn.
What lay ahead was that great enigma -
the riddle of Saturn's rings.
Scientists understand so little about them
they still have even
the most basic questions to answer.
The questions that we scientist
have about Saturn's rings
are the questions that an ordinary
person might be moved to ask
when first seeing them,
you know.
What caused them?
How did they get there?
How long have they been around?
How long are they going to last?
Answering these questions is one
of Cassini's prime objectives.
But to do this,
it first had to get
into orbit around Saturn
and that meant passing
between the rings.
The rings are chaotic and dangerous.
Made up of billions upon billions
of hard rock-like particles.
All the ring particles,
billions and billions of them are
in orbit around the planet Saturn
and they're moving at quite a clip -
something like ten kilometres per second.
Faster than a high-speed bullet.
If you were in Saturn's rings
you would be in a mass of particles
that were bumping into each other
and rolling over each other
If you were a ring particle you would get bombarded
from one side and then from the other,
as one particle bounced
of another one around you.
To carry out its mission
Cassini risked being torn apart.
Even a very small particle
could be the end of Cassini,
if it hits a particle
as small as a grain of rice
that would be enough
because of the high speed
at which it's moving
to end the mission.
At Mission Control tension was building
as the high risk orbit
insertion manoeuvre began.
Saturn orbit insertion was
a bit of a nervous time for us.
There were a lot of things
that had to work right.
The consequences of it not working
would have been pretty serious.
The rings were not the only
danger that Cassini faced.
To get into orbit
it also had to slow down.
That meant firing its main engine -
any malfunction and Cassini
would simply fly past -
lost forever in the void of space.
That engine had not been used very
frequently over a period of seven years,
that makes you nervous.
You know, it's like you have a car,
a brand new car
that you put in the garage,
and every once in a while,
you turn it on,
and then you have an emergency,
and you get in the car, and you
turn it on, it'd better work.
The sequence began
at seven thirty six pm.
First Cassini rotated,
to use its giant antenna
as a shield to protect it
when it passed between the rings.
All eyes were on a signal sent out
by the probe's tiny auxiliary transmitter.
Only if the signal flattened out
at the bottom of the graph
would they know
if Cassini had survived.
A 3.2 billion dollar mission
and 14 years of work
all hinged on this one moment.
The Doppler has landed.
Cassini had arrived.
When the images returned
Saturn was revealed as never before.
I just don't know what to say,
I'm speechless.
Oh absolutely exciting, I mean
this is the culmination 22 years of effort
and just seeing the lord
of the rings in its big glory...
We are amazed about the detail
we are seeing and the sharpness in the rings.
You wait years to have
this kind of a moment.
Despite these remarkable images
the fundamental question of the age
of Saturn's rings remains unanswered.
Some hope that this enduring puzzle
might be solved by taking
a very close look
at what the rings are made of.
The rings are made of ice.
Just like the stuff you've got
in your ice cube trays
and almost a hundred per cent
pure water ice
with some small contaminants.
These contaminants are the key
to finding out the age of the rings,
minute traces of dust that come from meteoroids.
The basic principle is simple -
the older the rings are
the more they will have
been bombarded
and so the dirtier they will be.
The pollution is sort
of a like a clock
because we're pouring material
in on top of the rings
and it's dark, non-icy material
so the level of darkness in the rings
tells us something about their age.
So to discover the level
of pollution in the rings
Cassini's spectrometer took these images.
What they show has surprised scientists.
The spectacular range of structure
in the rings with reds and blue and aquas,
that was something that was
completely unpredictable.
The images show cleaner ice
in shades of blue;
the heavier contamination in red.
The analysis on this is not yet complete
but these new spectrometer images seem
to suggest an intriguing possibility -
that perhaps Saturn's rings were not
all formed at the same time.
It's definitely the case that there's
a gradient in composition across the rings
so that the rings are less icy
on the inside and more icy on the outside.
As we go to the outside the particles
become younger and fresher.
So it appears that the inner rings
shown in red are in fact older,
and that somehow the outer rings
have been made more recently.
To work out exactly how this is happening
will take several years of observations.
But now Cassini is safely in orbit
the scientists will have
all the time they need.
But there is a whole
other aspect to Cassini's voyage -
one that has not yet begun -
It's encounter with Titan -
one of the great mysteries
of our solar system.
It's thick atmosphere
captivates scientists
as it might mean that Titan
in some way resembles the Earth.
Whenever we humans think that we might be approaching
something that is vaguely similar to Earth,
we get very excited about it.
The prospect of something familiar,
but yet so distant, and so strange
is a very exciting combination.
Trying to figure out what
this distant moon will look like
has become an obsession
for planetary scientist Dr Ralph Lorenz.
He has spent the past 15 years
trying to piece together all the scraps
of information available on Titan
to build up a picture
of this mysterious place.
And he believes it is a world
that shares many features with our own.
But on this distant moon
things are also very different.
The landscape may be strangely familiar
much as there is on Earth,
there may be a cycle with the rain
and rivers and streams.
Titan is so cold that methane,
which is a gas on Earth,
can condense into a liquid
and freeze as a solid.
They may have lakes,
but the lakes are made
of lighter fluid.
If Dr Lorenz is right
the methane will also form familiar clouds
but it might turn the sky
a very unfamiliar green.
We might see methane rain
falling from these clouds
but because Titan is smaller
than the Earth it has less gravity
this rain would be unlike
any we have ever seen.
The balance of forces
that holds a raindrop together
is a little bit different on Titan
because the material is different
and so the raindrops could be rather larger
but on Titan with its thick
atmosphere and its low gravity,
these large raindrops would fall maybe
ten times slower than raindrops do on Earth.
The rain falls so slowly,
it just evaporates
before it gets to the ground.
The picture of Titan that emerges
is one of a truly alien world-
a place where huge rain-drops fall
gracefully through a green sky,
a place with lakes and streams
made from lighter fluid.
And stranger still
the entire landscape
is made of water -
frozen hard as rock.
But for the moment this picture
is a very well educated guess
as no one as yet been able to take
a clear picture of Titan's surface,
for this mysterious moon is veiled
by a thick layer of orange cloud.
But Cassini carries two powerful instruments
designed to defeat this layer of haze.
One is Cassini's radar,
scanning over a quarter
of the moon,
it will send back the first
accurate images of Titan's surface.
The second is the European built
Huygens probe.
Huygens will separate from Cassini
and plunge beneath the clouds,
carrying its own unique camera.
Imaging specialist Marty Tomasko
will have no second chances -
the Huygens probe will be
active for just 180 minutes
so it's important that his camera
doesn't miss a thing.
What we were trying to get
is kind of the skydiver's eye view
because if you were outside the probe
and falling down through the atmosphere
we don't want to land near some interesting object
like the Grand Canyon and not know it's there.
So the plan is to spin
the probe as it descends
giving the camera a full 360 degree view.
But Tomasko has also given
the camera 3 lenses
to ensure that it has absolutely
no blind spot.
We have three fields of view,
one that comes out this window
and looks out towards the side,
one that comes out this window
and looks down at intermediate angles
and one that looks almost down
straight towards the ground
and those three images
are taken together
and as the probe rotates we take
a series of twelve of those
over a few seconds or a few minutes
and we plan to put those together
to make panoramic mosaics
of the surface of Titan during our decent.
These panoramic mosaics were created
with the same camera
in a test over the Arizona landscape.
By putting them together
a virtual world can be created.
The hope is that the next time
the camera opens its three eyes
it will be peering down on a new world -
Titan.
But Titan is more than
just a curious alien landscape.
It is a place that perhaps holds the key
to one of the greatest mysteries of the universe -
the origin of life.
For me one of the most important
questions to address
is where did I come from?
This rock is not conscious
and I'd a heck of a lot rather
be me than this rock
but the same stuff
that's in this rock is in me,
it's just organised in a way
to contain enough information
so that that stuff can turn around
and say, what is this?
How did it get here?
And, oh, by the way, how did I get here?
How did you assemble this simple stuff
into something like me
and allow me to ask those questions?
Earth today is teeming with life -
it has taken over the entire planet.
Bizarrely, this makes the Earth a very bad place
to study how life first emerged from the primordial
organic chemicals that first covered it.
It's very difficult to use the Earth
as a laboratory for understanding how life began.
Life eats all of the organic molecules
that are present on the Earth today.
If we go to the laboratory
and try to simulate how life began,
we have limits on time and space;
so a laboratory experiment
might be this big;
a laboratory investigator might work
for two or four or ten years perhaps.
No more than that.
We really need a place where organic evolution
is happening on a planetary scale,
over billions of years,
but is not being ruined
by the presence of life.
So for many years scientists
have been looking for a place
that shares the same primordial chemistry
as the early Earth.
If you look at our solar system,
there are only four bodies
that have atmospheres
and are actually solid bodies themselves:
The Earth, Venus, Mars and Titan.
Venus is just so hot that one can melt
lead on the surface,
there's - there are
no organic molecules.
Mars today is very cold,
very dry, very thin;
not a good place
for organic molecules.
And so we're left with Titan.
Titan has the right ingredients
to create complex organic molecules -
methane and nitrogen.
On the Earth, billions of years ago,
these simple chemicals somehow combined
to form the pre-cursors to life.
Scientists believe
that these same chemical reactions,
the first vital steps
on the road to life,
are occurring today high
in Titan's atmosphere.
The purpose of the experiment
is to simulate the chemistry
that makes complicated molecules
from the simple gases in Titan's atmosphere
and so here we have nitrogen,
which is the primary gas
in Titan's atmosphere,
and we have methane over here.
And these gases are mixed together
and they're run through tubes
and then they end up down here,
which is an electric discharge,
and this simulates the energy
that the sun provides to power the chemistry.
The Sun's rays break up the methane,
which then recombines to form
a set of dark orange chemicals
known as tholins.
These tholins form
the thick orange clouds
that shroud Titan
and hide its surface.
But tholins can make
more than just a haze.
With just one extra ingredient
they form one of the key
components of all living things -
amino acids.
If we were to apply what is the essential
ingredient of all life, liquid water,
then we may well make some amino acid
which is the building blocks of life
and that's the really exciting
thing about tholins.
But the surface of Titan
is at 174 degrees below freezing -
far too cold for liquid water.
However, scientists believe
that Titan's interior may be warmer
and that there could be a layer
of liquid water under the surface.
It is possible that this liquid
could rise upwards through volcanoes.
On the Earth
volcanoes belch rock.
On Titan volcanoes
most likely belch water.
And liquid water has an important
role to play we think
in helping to bring about
the rise of life.
While any water on Titan
would eventually freeze,
it might remain liquid long enough
to allow the formation
of amino acids.
So, with tholins in its atmosphere
and the possibility of water,
Titan might just have
all the ingredients to make the primordial soup
from which life first emerged.
At 2 am on Christmas Day,
three explosive bolts will fire
and the Huygens probe
will be pushed away.
22 days later it will slam
into the upper atmosphere.
A series of parachutes
will then slows its descent.
Only then will the charred
heat shield be ejected.
The chemical analyser will then search
for signs of complex organic chemistry.
At last Huygens' camera will get
the first view of Titan's surface.
Will Huygens discover
streams of liquid methane?
A rock hard surface
of frozen water ice?
Or a soft sludge
of organic chemistry
warmed by a nearby volcano?
Until January 14th 2005,
no one will know.