Turtle: The saturnian system is an absolute wonderland,
bagenal: Saturn just makes us gasp at its beauty.
Narrator: Saturn.
As the second largest of the planets,
it's nearly 800 times the volume of earth.
A true gas giant
known for its mysterious, captivating rings.
Almost 72,000 miles in diameter,
the ring system is barely as thick
as a football field is long.
Waite: The rings capture the imagination
to the point -- you have to understand where they came from,
and what do they mean?
Narrator: To try and answer these questions,
humans designed, built, and launched
some of the most advanced spacecraft ever conceived.
It was and is the largest interplanetary spacecraft
that's ever been built.
This is a massive piece of machinery.
Narrator: This is the story of the exploration of saturn,
its rings, and moons.
Turtle: To see something like that
on a moon in the outer solar system,
it was just spectacular.
It still gives me goosebumps
to think about all of that working so well.
Glein: The building blocks of life
could form in the interiors of these icy bodies.
Titan is the most interesting moon in the solar system,
hands-down.
Narrator: To the naked eye,
the night sky is filled with points of light.
Zoom in on almost any of them, and they remain just that --
Shining points in a dark universe.
But one celestial object revealed itself
to an Italian polymath that it was special.
Esposito: Galileo wasn't the inventor of the telescope,
but he was one of the first people to use it
for astronomical observations.
Patel: It was 1610 when Galileo first observed the saturn system.
Green: His drawings showed what were described
as ears or jug handles either side of the planet.
Esposito: And so, he thought, "well, these might be moons,
but stuck one on each side of the planet saturn."
He didn't know newtonian mechanics hadn't been invented.
He didn't know that moons have to go
all the way around a planet.
Green: When he went back to look at saturn
a couple of years later,
he noticed that those features had gone.
♪♪
Esposito: Galileo even suggested
that saturn had eaten his own children,
as in the ancient Greek myth,
and that's why the moons had disappeared.
♪♪
Galileo lived in Italy,
but he was aware of other major figures in his time,
including constantijn huygens from the Netherlands,
and, in fact, it was huygens' son,
christiaan huygens,
who eventually solved the puzzle that was posed
by the disappearing handles of saturn.
Patel: Christiaan huygens turned his telescope toward saturn.
As technology, it develops, optics are developed,
and he was able to see more.
Green: And what he saw meant that he was able
to come up with this radical idea
that saturn was surrounded by a ring system.
♪♪
And he was able to link back to what Galileo saw,
because if the ring system was tilted at an angle
to our view from earth,
it means that sometimes you'll see the rings tilted
and you see them sort of almost face on,
and another times, when the planet has moved,
they'll be edge-on.
Esposito: In fact, even today, when hubble --
The best optical telescope we have --
Looked at saturn, crossed through the ring plane,
the rings disappeared.
♪♪
But not only that,
christiaan huygens made another amazing discovery --
That saturn has a moon.
And it turns out that this moon is a really curious place
and is perhaps even more curious than the rings of saturn itself.
After the discovery by huygens of saturn's first moon,
Giovanni Domenico Cassini discovered four more
in the next decades,
and moons continued to be discovered
over the next few hundred years.
♪♪
However, from the first, there were big questions
posed by saturn's rings.
♪♪
And why does saturn have rings and not the other planets?
♪♪
Green: The only way to answer that question
is to actually get up close.
We need to go to saturn,
but getting to planets in the outer solar system
obviously requires a huge amount of fuel.
So you start to think about, "well, what are other ways
that you can accelerate your spacecraft
without requiring lots of fuel?"
And one technique that's used
is what's called a gravitational assist.
Esposito: It was discovered that the outer planets
would actually align in a way that they hadn't
since Thomas Jefferson had been president.
Bagenal: So we realized that you could fly past Jupiter,
get a kick.
Go to saturn, get a kick.
Go to uranus, get a kick.
Go on to Neptune.
This gravity assist trajectory was called "the grand tour."
And if we were gonna go and do this --
Take advantage of this alignment --
We'd better get going and launch that spacecraft soon.
Esposito: NASA quickly responded to the opportunity
by preparing some pathfinding spacecraft --
One that would go to Jupiter,
and one that would use of gravity assist from Jupiter
to go on to saturn.
♪♪
And that was called pioneer 11.
♪♪
[ Indistinct chatter ]
When pioneer 11 eventually arrived at saturn
six years after flying by Jupiter,
it was an immense, exciting moment.
We made it! [ Echoing cheering ]
♪♪
Esposito: The rings of saturn were big and beautiful in our pictures,
and we stood in awe at the close-up views.
♪♪
My task was to see if we might discover any new rings,
and, amazingly, I watched the first images
appear on the television screen,
and there was clearly a new ring of saturn.
♪♪
The rings of saturn had originally been named
a, b, and c
in order from the outermost known ring to the innermost,
but in the 20th century, we began to discover new rings,
which were then assigned alphabetically
in the order of discovery.
First the d ring, then the e ring.
So the next available letter was "f,"
and so I named that ring "ring f of saturn."
♪♪
Patel: Pioneer 11 passed titan by quite a large distance --
Couple-hundred-thousand miles away...
♪♪
...and really, all it told us about titan
was that it was very, very cold.
Too cold for life as we know it to exist.
But, actually, we needed to go back
and look at this thing in much more detail.
Narrator: Fortunately, the next generation of spacecraft --
The voyager 1 and 2 -- Were on their way.
[ Indistinct radio chatter ]
Bagenal: The pioneers had told us, "it was safe.
It's okay. We can go there."
♪♪
The primary purpose of those pioneers
was really to pave the way for later spacecraft...
♪♪
And that mission was called voyager.
♪♪
And the voyager mission had two components --
Voyager 1 and voyager 2.
Each of them would get a gravity assist from Jupiter
to go on to saturn.
Green: But that's, then, where the missions deviated,
because voyager 1 was given an extra-special task.
It was to go and visit the moon
that christiaan huygens had discovered in 1655 --
Titan.
Narrator: Titan would become almost as important a destination
as saturn itself.
Patel: This is a massive moon
probably not worthy of the word "moon."
This is a body which is bigger than Mercury,
so it's a big moon.
♪♪
Turtle: The atmosphere of titan was hinted at a century ago
and confirmed in the 1940s.
It's the only satellite in the solar system
with a dense atmosphere.
In fact, its atmosphere is actually denser
than our atmosphere here on earth.
Titan is the most interesting moon in the solar system,
hands-down.
Narrator: But getting to titan meant a change of direction,
shortening the exploration of the outer planets.
Green: So, voyager 1 going off to visit titan
meant that it was no longer able to slingshot on
to visit uranus and Neptune.
If voyager 1 had not been able to achieve that objective
for whatever reason,
voyager 2 was going to be diverted to do that job
at the expense of going on to uranus and Neptune.
♪♪
But that's how they felt about titan -- the importance.
♪♪
Esposito: So, just a year later, voyager 1 --
Equipped with better instruments and better cameras --
Was preparing to take a look at saturn and its rings.
[ Excited chatter ]
[ Indistinct chatter ]
The encounter was amazingly thrilling and rapid experience.
All happened within a matter of a few days,
and even before you could explain
some of the new phenomena we saw,
voyager was off on its way out of the solar system.
[ Cheering ] [ Cheering ] [ Cheering ]
Many people refer to that flood of data --
The camera pictures and other observations --
As like drinking from a fire hose.
They asked somebody else--
♪♪
They asked somebody else--
Narrator: The learnings from the voyager spacecraft
fundamentally changed our understanding
of the saturnian system.
♪♪
Esposito: After the voyager flybys,
we knew there were thousands of rings,
and it's that moment
that we stopped naming them with letters.
It was just impossible. It exceeded the alphabet.
A ring could be maintained between two moons,
one outside the ring and one inside the ring.
♪♪
Waite: And that's the beauty of this idea of moonlets
that are sitting within the rings
shepherding the gravitational motion
of the particles within it.
♪♪
[ Indistinct chatter ]
Esposito: Maybe it's a scientific prerequisite
to start with a simple idea,
but we would imagine the rings were ancient, unchanging,
and completely uniform.
All were immediately questioned.
How long is this -- Oh, I see it.
♪♪
But what was the origin of the rings?
Where did they come from?
When an object gets closer to the planet,
it gets stretched out.
And so, a basketball might look more like a football
under this stress.
The question is, can that stress be withstood by the object?
♪♪
For most competent objects, including humans,
we can withstand that stress.
For objects that are piles of rubble or dust, or are big --
Say larger than 50 or 100 kilometers --
They cannot withstand that force.
♪♪
Narrator: If a large moon had
once strayed too close
to saturn,
this destructive force would have been enough
to tear it into tiny pieces.
♪♪
Esposito: So, if saturn once had a moon --
Say an object about the size of titan --
If it were dragged in toward the planet by friction,
first, the ice would shatter.
And then, later, the core --
Which is made of metal -- Would shatter,
or it might even end up inside the planet.
And the pieces of ice form a ring around saturn.
Narrator: And now, the mission turned
to what scientists deemed worthy
of missing out on Neptune and uranus for...
♪♪
...titan.
♪♪
Esposito: The scientific community and the public
watched with great interest
as voyager 1 made the first flyby of titan.
There was an organic haze that encircled the surface,
and you couldn't see the surface as a result.
MacKenzie: That atmosphere is simultaneously
the bane of my research because it blocks the surface,
but it's also the reason why titan is so interesting.
Patel: One of the other things we figured out
was that there was methane present
in the atmosphere of titan.
This opened the really, really tantalizing possibility
for lakes and oceans on the surface.
Some people think that if we look in these methane leaks,
perhaps we'll find a different way of organizing matter,
a different way of organizing life.
[ Monkey hooting ]
Patel: Titan was still hiding all its mysteries from us,
so that laid down the gauntlet of the challenge --
We must now go to the surface of titan.
♪♪
Esposito: Fortunately, voyager 1 made excellent observations of titan,
so, thankfully, voyager 2 was allowed to go on
to the next planet -- uranus -- And then to Neptune.
♪♪
The uranian rings had been discovered
from the ground in 1977,
voyager itself discovered the ring of Jupiter in 1979,
and while we were on our way to the planet uranus,
the rings of Neptune were also discovered.
So by the time the voyager mission had completed,
we knew that all of the giant planets had rings --
Just the opposite of what the question had been
before those missions -- Of why only saturn has rings --
But leaving us with deeper questions about saturn's rings.
What were they made of? How old were they?
And why are saturn's rings so particularly different?
So big and so bright compared to the narrower,
less massive, darker rings of Jupiter, uranus and Neptune?
♪♪
Those could be addressed by a mission
that went into orbit around saturn
and stayed for many years.
Waite: We already knew that the value of orbiting a system
and the amount of understanding you can gain
by being there for a long period of time is so amazing
that the next step was clearly gonna be an orbital mission.
Esposito: And if we're going to send another mission to saturn
that stays there, it should have a part of it
that lands on the surface of titan.
Narrator: Planning began in 1982
for an exploration that would be more ambitious
and advanced than anything that had gone before --
A mission called Cassini-huygens.
[ Beeping ]
♪♪
Waite: The spacecraft was about the size of a school bus.
You just looked up. It was a monster.
♪♪
Webster: It was and is the largest outerplanetary spacecraft
that's ever been built --
And may, in my lifetime, ever be built.
Man: [ Over radio ] Pressures are excellent.
Woman: [ Over radio ] T-plus 20 seconds.
Narrator: The mission was a collaboration with the European space agency,
who designed and built a lander called huygens.
♪♪
Turtle: The huygens probe was actually designed
to be able to float in liquid
as well as land on a solid surface,
because we didn't know at the time
whether it was going to land in a liquid or on a solid surface.
Witasse: So, we designed a mission
to cope with as many characteristics as possible.
Patel: No one's ever tried to measure the depth of an ocean
and how hard a rock is,
depending on which one you're gonna land on.
MacKenzie: We knew from hubble images
that there probably wasn't a global ocean,
but whether there were other liquids was still not known.
Huygens' team had to prepare for that,
but also a very hard landing.
Or, maybe you can imagine
a very squishy surface full of organic goop.
♪♪
Launch control: [ Over radio ] 20 seconds and counting.
This is titan launch control.
Waite: Without any doubt, the most risky element
of any space mission is the launch.
Launch control: T-minus 15 seconds.
Turtle: It was a nighttime launch, so, you had to get on the bus
something like 2:00 in the morning or something to go out.
And we did that, and we went out to the launch site,
and the first opportunity to launch was scrubbed.
♪♪
Launch control: [ Over radio ] 20 seconds and counting.
This is titan launch control.
Waite: Without any doubt, the most risky element
of any space mission is the launch.
Launch control: T-minus 15 seconds.
Turtle: It was a nighttime launch, so, you had to get on the bus
something like 2:00 in the morning or something to go out.
And the first opportunity to launch was scrubbed.
And so, we did the same thing again two days later.
Launch control: T-minus ten...
When you've put eight years of your life
into designing and building and testing something
which is going to go into space...
Launch control: ...Nine, eight...
Coates: ...And then seeing on the top of a rocket
that's being vibrated and accelerated
on its way to saturn -- It is quite a feeling.
Launch control: One.
♪♪
Coates: When it did go off, it created a huge amount of light.
♪♪
And then, the rocket went behind a cloud.
Waite: When it went behind that cloud, it was very impressive.
The whole cloud, like, lit up.
We all thought, "oh, goodness. Has something gone wrong?"
♪♪
Waite: And then, the nose cone came out
and you hear that, "phew."
[ Engines roaring ]
♪♪
Man: [ Over radio ] Flight, isro comm.
Woman: [ Over radio ] Go ahead, isro comm.
Patel: One of the things you have to do
when you arrive at a big planetary body
is slam the brakes on pretty quick.
You typically do this by going very close to the planet
to slow you down -- So you get captured
by the gravitational pull of saturn.
Webster: It was an incredibly complex sequence
that we had basically worked on for two years.
Esposito: Even after pioneer and voyager, we didn't know enough
about the possible dangers of the saturn system.
And because the Cassini spacecraft was moving
at about 10 miles per second,
even hitting a grain of sand or a chunk of ice
could be deadly to the spacecraft.
And the best was to turn
so the spacecraft antenna was facing forward.
Coates: The high-gain antenna,
which is the thing which communicates back to earth,
was actually protecting it
from potentially being hit by dust particles.
So it couldn't be in communication
with earth at that time.
Narrator: Once Cassini had crossed the plain of saturn's rings,
the spacecraft had to reorient itself again.
The thrusters had to be turned
so that they would point in the direction of motion
to be able to captured it into orbit.
Narrator: During the 90 minutes that Cassini's engines were firing,
the spacecraft was completely shielded from earth.
At its closest approach,
the spacecraft was just 12,427 miles
from the cloud-tops of saturn.
All the mission controllers on earth could do was wait.
We all held our breath waiting for the signal to return.
But then, we got a signal which was dead on...
And we knew at that moment
we had successfully gone into orbit.
[ Cheers and applause ]
♪♪
Oh, it was really a fist-pump moment.
When the burn was completed, we knew her in orbit,
so we turned away from the earth
and photographed the dark side of the rings.
And then, after we come back through the ring-plane
and cross it again, we turn back to the earth,
play back that data.
And those images -- I'll never forget them.
♪♪
Narrator: Cassini-huygens had arrived at the saturnian system,
an enormous gas giant with 82 moons --
That we currently know of -- Orbiting on the outside
and within the hundreds of rings.
♪♪
Maize: From a mission engineer's point of view,
the rings are a hazard. [ Laughs ]
But once we've discovered that the environment's safe,
then we can start to open up the stops a little bit
to allow more activity.
We knew that we'd have long consecutive pieces of data
to test our theories, but we didn't realize that
because we could orbit saturn hundreds of times,
the same aspect could be seen over multiple times
by all the 12 instruments.
Turtle: It's very easy to think of the system as isolated parts,
especially when you're working with a spacecraft mission
and you target this feature,
and then you target this satellite.
Any speculation, any idea we had had
from the years between voyager and Cassini
could now be tested.
Narrator: And as for the origins of the rings and the moons,
the Cassini team made a further discovery.
♪♪
Esposito: As we have seen quite clearly,
saturn's rings are made out of ice,
which is the fragments of shattered icy moons.
♪♪
But the alternate is also true.
Cassini showed us that the pieces of the ring
are sticking together to make new moons.
So the rings are collecting in places to make moons,
and the moons are being shattered to make new rings.
So this is sort of a cosmic recycling of material.
♪♪
Narrator: So, not only are the rings of saturn
most likely made of moons...
But they also make new moons.
Esposito: One of the best measurements that Cassini made
was to measure the total mass of the rings.
This determines how long this recycling process can go on.
The combination of those two facts
say that the rings are about 100 million years old.
This can be extended, perhaps, to a billion years or two,
but the current one is the rings
that the dinosaurs would have seen.
[ Roars ]
♪♪
If we were to look closely, many of the rain particles
would appear fluffy to your hand.
But, occasionally, particles will hit each other
at a much higher velocity,
which will knock off a spray of small particles of snow and ice,
which eventually are recaptured by other clumps.
So the equilibrium --
The balance between these two processes --
Leads to a distribution of sizes from dust to mountains,
and each of the objects being like a pile of rubble
with a coating of snow on the top.
♪♪
Narrator: After six months in orbit,
Cassini was scheduled to deploy the huygens lander
on December the 25th, 2004.
Maize: We had Christmas dinner at my home
and had a lot of the European and American contingent
because we were all spending Christmas at jpl.
♪♪
[ Radio chatter ]
Man: Whoo-hoo!
[ Cheering ] [ Cheering ] [ Cheering ]
Maize: Few days later, we turned around to take a picture
where the probe was supposed to be.
♪♪
Just a little speck.
It's not very exciting, but it was genuine confirmation
it was exactly where we thought it was going to be.
♪♪
Because what happens with the probe is, essentially,
when you release it,
you've turned on a little three-week egg timer.
[ Timer beeping ]
Your worst nightmare is silence.
That's happened too many times to people in space missions,
and it's just a punch in the gut.
♪♪
Narrator: After six months in orbit,
Cassini was scheduled to deploy the huygens' lander to titan
on December the 25th, 2004.
[ Timer beeping ]
Your worst nightmare is silence.
That's happened too many times to people in space missions.
And it's just a punch in the gut.
But three weeks later, right on schedule,
we get the signal back.
Coates: When we arrive at titan,
we're traveling at incredible speeds,
and what you gotta do is go from... [ laughs ]
...ballistic, incredibly fast speeds
at the top of the atmosphere
to zero speed at the bottom of the atmosphere on the surface,
and it is pretty hard to do.
There are several elements in order to get yourself
down to the surface.
The first is a heat shield.
Maize: Titan has a huge atmosphere,
and huygens was just screaming in.
♪♪
So, you have the sacrificial heat shield
in front of the probe,
so the fireball that's created as the probe slows down
doesn't destroy the lander itself.
♪♪
Narrator: While the heat shield was slowing the probe down,
huygens experienced a deceleration of 15 gs.
Once it had gotten to an altitude
of about 110 miles
and had slowed to nearly 1,300 feet per second,
huygens deployed the first of its three parachutes.
♪♪
The pilot parachute stabilized the probe
and pulled off the back cover,
which deployed the main parachute.
At this point, the used-up heat shield was discarded.
♪♪
Maize: But titan's atmosphere is so thick
that if we kept that parachute on,
the batteries would have run out before it got to the surface,
it was going to go so slowly.
So it actually deployed that parachute
and then dropped the last chute,
which allowed it to descend at a more reasonable pace.
Patel: You get horizontal winds coming across
and swinging the probe about.
The images from descent show channels on the surface,
and it was just so spectacular to see something
and know what it was on the surface of titan --
And for it to be river channels.
♪♪
Patel: It then landed on the surface,
and it started transmitting back to Cassini,
which was way up overhead.
Maize: The spacecraft, meanwhile, is flying over the top
and pointing at the point on the surface of titan
where the probe is.
And eventually, the spacecraft goes over the horizon.
The batteries were still going even after we lost sight of it.
The spacecraft turned back and started to play the data back.
The imaging guys turned around an image of the surface
very, very quickly.
[ Keyboard keys clacking ]
And it flickered up on the screen.
And everybody looks up and goes, "what's going on here?"
You know, it was almost like it was fake.
Turtle: To see something like that
on a moon in the outer solar system,
it was just spectacular.
It gives me goosebumps
to think about all of that working so well.
Maize: It was sitting on this flat lake bed,
and the things that appeared as rocks in the background
were actually pebbles of ice that had been frozen.
♪♪
Turtle: Titan is an icy satellite.
Its bedrock is made of water ice.
MacKenzie: But when we look at the surface of titan with the spectrometer,
it's actually really hard to find any
pure water ice spectral signatures,
and I think that the key there is
all these atmospheric products
that are continually falling out across the surface.
Turtle: Titan's atmosphere is actually mostly nitrogen
like earth's atmosphere,
but it's cold in the outer solar system,
and the next most common constituent
in the atmosphere is methane.
And methane in titan's atmosphere
plays a role very much like water on earth.
So the methane in the atmosphere can condense to form clouds.
It can actually rain out onto the surface.
It can run across the surface in rivers,
form lakes and seas.
So it really does have a complete hydrological cycle
where methane plays the role that water does on earth.
Waite: Carl sagan and his research partners, khare and Thompson,
gave us a really interesting insight
by doing experiments where they mixed nitrogen with methane
and then provided some free energy source --
Some light or some particles to break them apart
or to ionize them --
And it led to this incredible organic chemistry
that was beyond the wildest dreams.
Created this stuff in the laboratory they call "tholins."
Turtle: The methane dissociates at the top of the atmosphere,
recombines to form very complex molecules,
and all of that material falls out onto the surface.
How long that process has been going on,
is still not well understood,
but if titan has had an atmosphere like it has today
for the entirety of the solar system,
that's going to produce a volume of sediments
that means that titan's crust is not just water ice,
but also has a bunch of organic sediments
that have been built up over time.
Turtle: All of these organic materials have been sitting around
littering the surface of this moon,
where there's the opportunity, potentially,
for them to have mixed with liquid water.
Waite: If you react water with these precursor molecules,
what's been demonstrated is,
these tholins that have been studied in the lab
can form amino acids.
And the universe provides us that mechanism
when impacts hit the surface of titan...
♪♪
...because every impact has enough kinetic energy
to melt some of the crust.
The bigger your impactor, the more kinetic energy you impart,
and so, the more melt you can generate.
And then, based on how much melt you generate,
you have this pool of liquid in the near subsurface
that's going to cool slowly over time.
And based on the sizes of impact craters
that we've seen on titan, this can be anywhere
from hundreds to tens of thousands of years.
Turtle: And it's been doing these chemistry experiments
for hundreds of millions of years.
So we know that titan has all the ingredients necessary
for life as we know it.
♪♪
Turtle: So we know that titan has all the ingredients necessary
for life as we know it,
and it's been doing these chemistry experiments
for hundreds of millions of years.
You also have the opportunity for organic material to mix
with a different solvent in the form of liquid methane.
And so, perhaps there are other prebiotic systems on titan
that have progressed
that are completely alien to the water-based biology
we have on earth.
Glein: It's hard to conceive
how a methane-based form of life would work,
but nature has repeatedly surprised us,
as demonstrated by all the findings of the Cassini mission.
Certainly, it would be very exotic,
and at present, we have no indications
in any of the current measurements from the Cassini
or huygens' part of the mission that there was anything bizarre
that we might need to attribute to the activity of life.
But the only way to find out is to go and look.
So you have, with titan, this wonderful possibility
that we might find life as we know it,
or we might find life as we don't know it.
♪♪
Narrator: But as exciting as titan was,
there were even more intriguing discoveries to be made.
When Cassini was approaching saturn
for the first time at the end of 2003,
our experiment --
The ultraviolet imaging spectrograph --
Was systematically scanning back and forth
on the planet's center, and we were amazed to discover
that the system was filled with molecules of oxygen,
and the oxygen was completely unexpected.
And we noticed that the peak in the distribution
was just a distance four times saturn's radius
from the center of the system.
We knew that the moon Enceladus was orbiting
just at that distance.
Narrator: Enceladus is a tiny moon --
Just 313 miles in diameter
with a surface area slightly larger than Texas.
It coexists with one of saturn's fainter rings --
The e ring.
The e ring is just a ring of icy grains
in the micron range.
It was tenuous enough ring
that we could fly through it and examine it.
We had these tentative ideas
that maybe there was a connection
between the e ring and Enceladus
because they were pretty co-located,
but we didn't really have any understanding
of how they were playing together.
Enceladus originally was on the itinerary,
but only marginally so.
It was another very interesting saturn moon.
Small, very shiny, very white, very bright,
but other than that, too small to be interesting.
♪♪
Turtle: And it was in the first close flyby
that the magnetometer team detected something interesting
that they didn't expect.
Maize: The magnetic field instrument
observed that the magnetic field lines
didn't quite come down to the moon the way they should.
The magnetometer team said,
"it looks like it has an atmosphere."
Well, anybody that knows anything about moons --
"that's too tiny. It can't have an atmosphere."
It's way too small to hold onto anything.
Narrator: A moon as small as Enceladus has a tiny gravitational field
far too weak to hold on to an atmosphere.
And, bizarrely, the atmosphere that was there
did not seem to be evenly spread out.
Turtle: If you flew by the south pole,
it looked like there was an atmosphere,
but if you flew by at the equator,
you didn't see anything at all.
Maize: But then we went back again and again
and explored with more instruments,
and then took some images, and all of a sudden realize
that it had an atmosphere -- It was icy atmosphere --
But it had these plumes coming out of the southern pole.
♪♪
And here's water geysers, you know, on a tiny moon.
♪♪
And that water that was coming out
of what we later found out to be an interior ocean
was what was forming the e ring.
We were able to measure the amount of water in those plumes
exactly enough to explain the ring of oxygen around saturn
that we had seen before that on approach.
Perryman: And as we flew through these plumes
coming out of the south pole,
some of that plume material was captured by the instrument.
Maize: And we used that to learn more about
the interior ocean chemistry.
Not only did it contain water vapor,
but it had traces of ammonia, methane, h2, co2.
And then, there was a whole host of organic compounds
that we could also see.
Esposito: The experiment that we did here at Colorado,
we watched a star set through the plume,
and now we can put all that information together
to get a picture of the shape of the eruption
and also the material that's being erupted
from inside of Enceladus.
And amazingly enough,
that material has the basic building blocks of life.
♪♪
Lane: We've been dominated as biologists
with a fixation on the idea
that all life on earth is powered, ultimately, by the sun.
Any formation of life going on on Enceladus
is going to be happening beneath the icy crust
in the oceans underneath,
where we see the same kind of hydrothermal vent systems
releasing hydrogen gas into the oceans there,
which we know for a fact
would have been present on the early earth.
And they don't strictly require the sun.
Glein: We think, based on the types of molecules
and other chemicals we're finding in the plume,
that this process called serpentinization is happening.
It's a fancy way of saying
how liquid water can react with rocks.
And serpentinization is thought to be really important
for supporting microorganisms and the base of a ecosystem
outside of these hydrothermal vents
because it makes abundant hydrogen,
and hydrogen is sort of like rocket fuel
for a microorganism.
Esposito: This says to me, "that would be a good place to go.
Measure those plumes.
Maybe drill down
and see if there's any form of life there."
Narrator: So, Enceladus may have just the right conditions
for life to get started...
Far away from the sun,
and the evidence for its mysterious inner workings
can be seen in the enormous, diffuse e ring.
♪♪
Cassini would spend more than 13 years at the saturnian system
and complete 294 orbits of the planet.
But, eventually, its fuel would run out.
Everything has to end, including Cassini.
♪♪
Narrator: Cassini would spend more than 13 years
at the saturnian system,
but, eventually, its fuel would run out.
♪♪
Everything has to end, including Cassini.
Coates: We went through this amazing time at the end of the mission
ending up with orbits which went inside saturn's rings,
but we knew at the end, of course,
that the idea was to actually burn the spacecraft up
in the atmosphere of saturn,
and that's to avoid it hitting these
astrobiologically feasible places
like Enceladus and titan.
The last thing we would want to do
would be contaminate those with something sent from earth.
Perryman: The spacecraft was orientated so it could communicate
with the deep space network here on earth,
but, then, the other axis was set
so that the spacecraft could get
the best measurements of saturn's atmosphere
as we plunged into it.
♪♪
[ Over radio ] We have loss of signal...
[ Indistinct ]
♪♪
Man: [ Over radio ] Call loss of signal at 1-1-5-5-4-6 for the s-band.
So that would be the end of the spacecraft.
♪♪
I don't think any of us were ready.
If you've ever had pets --
You know, and I've gone through eight cats and two dogs
during the 23 years I worked on Cassini,
and when you know it's time, it's time,
and it was timed in the spacecraft.
[ Over radio ] Signal from the spacecraft is gone,
and within the next 45 seconds,
so will be the spacecraft.
I hope you're all as deeply proud
of this amazing accomplishment.
Congratulations to you all.
This has been an incredible mission,
an incredible spacecraft,
and you're at all an incredible team.
I'm gonna call this the end of mission.
Project manager off the net.
[ Applause ]
♪♪
I've always loved the rings of saturn.
The Cassini exploration has allowed us
to see them really close up, changing before our eyes.
The idea of oceans beneath the ice
that might support life
is far from the old paradigm.
It opens up a whole new idea of how life might form
in solar systems in the cosmos.
Narrator: In the summer of 2019, NASA announced
that it had approved a mission called dragonfly
that would return to the surface of titan.
♪♪
Dragonfly is a mission that's going to titan
to study its prebiotic chemistry.
♪♪
It's an octocopter.
MacKenzie: By being a mobile lander,
dragonfly is going to allow us to truly discover
what the surface of titan is like.
And it would spend most of its time on the surface
making scientific measurements.
But then, we'd be able to fly from place to place
so that we could measure the chemistry
in different environments.
Dragonfly's main goal is to taste the surface of titan
and tell us what the end product
of all of this fantastic chemistry
that Cassini revealed is.
Turtle: And really understand how far
prebiotic chemistry can progress in an environment
we know has all the key ingredients for life.
Narrator: Dragonfly is scheduled to leave earth
for the saturnian system around 2027,
and should arrive at titan in 2035 --
Nearly 55 years
after pioneer 11 gave us our first encounter with saturn.
♪♪