Saturn's rings...
These cosmic wonders have both dazzled
and baffled astronomers for centuries.
Now new discoveries are set to reveal the true story
of these enigmatic structures.
When you hear the word "Saturn," the first thing you think of
are these beautiful rings, and they've been mysterious
since the very first time humanity observed them.
Where did they come from?
How old are they?
Astonishing new evidence suggests
Saturn's rings are breathtakingly young,
born during the age of dinosaurs.
The solar system's pretty old.
It's 4.5 billion years old.
If the rings have only been around
for tens of millions of years
or a hundred million years, that's weird.
How and why did the rings appear so suddenly?
And could they disappear just as quickly as they formed?
People say nothing lasts forever,
especially if it's a good thing.
Well, Saturn's rings... They may not last forever.
Now scientists battle to understand
how Saturn's rings got to be there...
Start the laser.
...What their destiny is,
and whether there's more to them than meets the eye.
Captions by vitac... www.vitac.com
captions paid for by discovery communications
Saturn's rings... the crown jewels of the solar system,
spanning almost 175,000 miles.
But a closer look reveals that they're extremely delicate...
In most places, only 32 feet thick.
Inside them, ice... Billions of particles,
from superfine frozen dust
to huge chunks the size of icebergs.
Between the rings are strange gaps where moons feast on ice.
This incredible structure seems perfect
and eternal.
But appearances can be deceiving.
Scientists used to think the rings
were as old as Saturn itself.
But when a space probe called Cassini visits Saturn,
it reveals an uncomfortable truth...
Saturn's rings are far too clean.
The rings of Saturn are so bright and beautiful
because they're made of trillions of particles
of pristine ice.
The ice itself is actually not very dirty.
It's very, very reflective.
You almost have this beautiful mirror around Saturn.
And if the rings are old, why are they still so clean?
Nicolas Altobelli is trying to unravel this mystery.
If the rings are clean, could that be
because there isn't much dirt around Saturn?
Nicolas is trying to find out how much dirt falls
onto Saturn's rings.
Dirt in space is known as cosmic dust.
And Nicolas measures cosmic dust with an instrument
that's kept under lock and key
in a hyper-clean lab in the university of Stuttgart.
This is our cosmic dust analyzer instruments.
It's a perfect replica of the cosmic dust analyzer
on the Cassini space probe.
This instrument is made to detect dust particles...
Small grains of matter
which are as tiny as a human hair
up to maybe a few times the size of a grain of sand.
Cassini's cosmic dust analyzer
measures the dust streaming
into the saturnian system over 13 years.
Nicolas analyzes the results,
and what he finds is staggering.
Not only is cosmic dust
definitely falling onto the rings,
it's doing it 10 times faster than anybody thought.
After measuring the true abundance of the dust
far away from Saturn,
we are able to derive a 10-times-higher flux
at the rings than previously expected.
But if so much dust has been pulled into them
over the years,
how are they so bright and clean?
If the rings formed with Saturn 4.5 billion years ago,
they should be much darker.
The inescapable conclusion is that the rings are young,
seriously young.
From our data, the ring are a hundred
or a few hundred millions of years.
It's well possible that the dinosaurs could have
witnessed the formation of the rings.
100 million years is phenomenally young.
Saturn is 4.5 billion years old.
If Nicolas is right, Saturn has only had rings
for a fraction of its life.
We think of the planets as having been around
for 100% of the time of the solar system.
Well, Saturn's rings?
They've only been around for the last 2%
of the solar system's age, so they're very new.
But if the rings are so young,
how did they form?
They're made of billions of tiny particles,
like shrapnel from some violent event.
But what violent event?
And why and when did it happen?
At the university of Arizona,
physicist Erik Asphaug uses computer simulations
to investigate what this event was.
He believes clues can be found in the moons
that surround Saturn today.
The Saturn system is unique
of all the planetary systems.
Go beyond the rings and you get these middle-sized icy moons.
And then suddenly you have the giant moon, Titan.
Saturn has a vast number of moons... 62.
They're all fairly small, except one...
Titan... that's huge.
If you were to put all 61 of Saturn's other moons together,
they'd still be smaller than Titan.
And for theorists like Erik, that seems odd.
How did Saturn get one massive moon
and a whole series of smaller ones?
One of the ideas that I've put forward is that it got
to be that way through a series of collisions.
And what we're looking at now are the byproducts
of a series of collisions that formed Titan,
and it grew collision by collision,
spinning off all these fragments.
And that set up a messy, complex system
that leads to ring formation almost as a cascade of events.
The early solar system was an unstable place,
and very different than it is today.
The planets were in different, changing orbits,
and Saturn had only a handful of moons.
Could those moons have collided and formed huge Titan
and Saturn's other, smaller moons?
So what you're looking at here is one of our simulations,
which has an icy moon and another icy moon.
And so here we go.
And these two satellites will merge,
and it's a real mess because they don't merge right away.
They bounce, and then they bounce
with a little bit less energy, and they keep spinning up.
So when all is said and done, you've formed Titan.
It's an icy, rocky body.
And you end up with a whole forest of new moons of Saturn.
Erik's simulation shows that
the violence of Titan's birth
spawned many other, much smaller moons.
And the behavior of these small moons holds the key
to how Saturn's rings form.
The moons pull on each other.
They cross each other's paths until, billions of years later,
two of them get too close.
They spiral together and collide,
ejecting vast streams of icy material.
Saturn's gravity grabs the shattered moon fragments
and pulls them towards the planet.
Trapped in orbit,
the icy shrapnel spreads into a thick halo.
Over time, colliding particles
flatten the halo into a delicate disc,
eventually forming the rings that we see today.
When we look at Saturn's rings from Earth,
they look fairly static.
They're just the way they are.
Now that we've seen them up close,
we see it's an incredibly dynamic system
evolving all the time.
A series of cataclysmic events
created the rings that we see today.
But what if the formation of the rings isn't the final link
in this chain of violent events?
One of the amazing things is we think
this might be something of a cycle.
Maybe over time the rings will actually congeal
and form moons again.
Maybe Saturn's been doing this for quite a while.
Are Saturn's bright, shining rings destined to die?
Scientists scramble to find answers.
Does an ice-guzzling moon
in the outer edges of the rings hint at their ultimate fate?
Or have the world's most powerful telescopes
already witnessed the beginning of a very different end?
New evidence suggests
that Saturn's rings are astonishingly young.
They could have formed just 100 million years ago,
during the age of the dinosaurs.
This discovery creates a new unsolved mystery...
If the rings are recent additions to our solar system,
might they cease to exist just as abruptly as they began?
One possible answer lurks in the famous dark gaps
that are peppered throughout the rings.
Do these gaps suggest that something is eating the rings
from the inside?
The Cassini probe takes a closer look and captures sight
of one of the weirdest objects astronomers have ever seen...
A tiny, misshapen moon called Pan.
Even among Saturn's bizarre zoo of moons, Pan stands out
because it doesn't look like just a lump of rock
and ice, like most of them do.
It looks like a ravioli.
Hiding in the outer reaches of Saturn's rings,
Pan's weirdness only becomes clear when close up.
Just 17 miles across,
Pan hurtles around Saturn at 37,000 miles per hour.
It crashes into any ice in its path,
adding to its bulging waistline
as it plows through an enormous 200-mile gap in Saturn's rings.
Little Pan isn't the only moon destroying ring particles
as it speeds around Saturn.
Pan isn't alone in its either weird shape
or the fact that it's gobbling up and accreting ring particles.
We know at least one other moon is,
and they look actually very similar.
Both these moons move through the rings
creating large gaps in the ring system.
Data from the Cassini probe
suggests that multiple small moons,
or moonlets, are creating holes in the rings.
Will moonlets eventually gobble up all the ring particles?
Physicist Jurgen Blum investigates this mystery
inside this 490-foot-tall tower in Bremen, Germany.
This tower does something very special...
It gives Jurgen a zero-gravity environment.
And it does it that simply, by letting things fall.
Inside this tower, Jurgen can actually create
his own small slice of Saturn's rings
and see how the icy particles in it behave.
How easily do ring particles turn into ice-gobbling moonlets?
Saturn's rings' particles are in free fall around Saturn,
like the international space station is around the Earth.
This is why we're using the drop tower here.
We are in free fall. We are in zero gravity.
Jurgen builds his own particles to experiment with...
Ice balls the size of small ring particles.
He makes them in the drop tower's freezer.
What we're seeing here is our ice balls.
They are 2 centimeters in diameter,
roughly resembling the smallest pieces
of the main rings of Saturn.
We introduce these ice balls into a container
and bring them to collision under zero gravity.
At Bremen, the team packs experiments like Jurgen's
into standard capsules that perfectly fit the drop shaft.
Inside the capsules,
a high-speed camera records what happens.
We're in the big part of the chamber
which is at the bottom of the drop tower.
The engineers are now closing the capsule,
because in the drop tower,
there will be a vacuum, so air will be out.
But inside the capsule, the air is still in
so that all the instruments operate under normal conditions.
Surprisingly, each of Jurgen's drops
starts at the bottom of the tower, not the top.
The capsule is put into a catapult.
The catapult accelerates the capsule upward,
which gives us zero-gravity flight,
followed by downward zero-gravity time.
Could you fire down the wind pole?
In the control room,
technicians count down to launch.
After launch, the capsules will be in free fall
for nine seconds, enough time for Jurgen
to see if ice particles stick to each other,
turning into moons and destroying the rings.
3, 2, 1...
Without air resistance to get in the way,
the capsule stays in free fall all the way up...
It's dropping.
...And then all the way down the tower,
until it crashes into Styrofoam beads.
Jurgen loads up the data from his last drop tower experiment
with the ice balls. - Here we go.
The experiment tells Jurgen that the speed
at which the ice particles collide is crucial.
When ice particles collide slowly,
they stick and start to form a moonlet.
We think this is the initiation of a moonlet forming process,
so moonlets grow by sticking collisions
and become bigger and bigger.
But if the collision is fast,
the particles don't stick.
They bounce.
So this particle here now bounces, bounces again,
and bounces a third time.
The result is significant
because ring particles move at different speeds.
Those close to Saturn travel far faster
than those further out, and Jurgen believes
that this affects how big a moonlet can grow.
Inside Saturn's rings, chunks of ice collide and clump
together to form an embryonic moonlet.
But as the embryonic moonlet grows,
it stretches further and further across lanes of ice
moving at different speeds.
This means its collisions with icy ring particles
get faster and faster,
stopping its growth but also smashing the moonlet apart.
This process kills the moonlet but returns the stolen ice,
letting the rings live again.
It's almost like they're in the center Lane of a freeway.
On one side, there are slower cars.
On the other side, there are faster cars.
And if you grow too large,
you start impacting the slower ones
and the faster ones at the same time,
and that's going to kind of spin you around
and eventually destroy you.
Thanks to this cutting-edge drop tower,
scientists are convinced
that moonlets are unlikely to kill the rings.
But there are other killers out there.
Could the bringer of life to Earth... sunlight...
Be destroying the rings?
And could jets shooting out from this tiny moon
be building a new set of rings for Saturn?
New research suggests Saturn was born naked.
The bright, shining rings we see today could've appeared
during the time of the dinosaurs,
when Saturn was already over 4 billion years old.
Scientists race to discover whether the rings are on a path
to destruction.
Experiments show that growing moonlets are mostly harmless,
but moonlets aren't the only danger.
We're pretty lucky to live in this very narrow time in history
when we can look to Saturn and see these magnificent rings.
They weren't always there,
and they may not always be there.
2 1/2 miles up
on the summit of Mauna Kea volcano in Hawaii,
planetary scientist James O'Donoghue
uses one of the world's
most advanced ground-based telescopes,
the Keck telescope, to probe Saturn's secrets.
James believes there's a threat to the rings,
and he wants to know how serious it is.
The sunlight is very strong.
Sunlight streams through the solar system
and bounces off Saturn's rings,
giving us an amazing view of them.
But James thinks that sunlight does more than
just let us see the rings.
He thinks that sunlight destroys them.
I've been using this monster for several years to observe Saturn.
We need a huge telescope like this one
so that we can see the fine details,
which we couldn't see with other telescopes.
Keck's enormous mirror helps it image
incredibly dim and distant objects.
This giant 10-meter mirror
is actually composed of 36 individual segments.
These act collectively as one giant mirror.
It's nice to think of the light being uninterrupted from Saturn
all the way through space,
all the way through all of this into the instrument here.
But it's not visible light
that James is interested in.
He's looking for something he can only see in infrared light,
and it will tell him how quickly sunlight is eating up the rings.
Infrared is a longer wavelength of red light,
so just off the visible spectrum.
So that's why we need instrumentation like this
to see it.
James and his team
make a breakthrough observation here.
He spots bright bands of infrared light
encircling Saturn.
James thinks they're evidence of Saturn's rings
being destroyed in front of our eyes.
Sunlight smashes into icy ring particles,
giving them an electric charge.
Saturn's powerful magnetic field
kicks the charged ice particles out of their safe orbits,
letting gravity grab them.
The icy particles spiral along Saturn's magnetic field lines
away from the rings.
They rain down on Saturn's atmosphere,
and where they land, a bright band of infrared light glows.
The harder the spiraling rain falls,
the brighter the bands shine,
revealing just how quickly the rings
are draining into Saturn.
Particles from the ring are raining down
onto the surface of Saturn itself.
Water from the rings is actually following the magnetic field
of Saturn down into the upper clouds.
James studies his latest results
to see how long the rings have left to live.
Here we have an image of Saturn.
This bright line across the middle here
is actually the reflection of sunlight
by the rings themselves.
And away from the rings, you can see the body of the planet.
The line on James' image goes from the top
to the bottom of Saturn and shows James
where the planet has a glowing infrared band.
There is a bright emission coming from the top
and the bottom of Saturn.
The bright spots are the energetic glow
caused by the rings raining down on Saturn.
But do James' latest results reveal a trickle
or a monsoon of water particles?
We were pretty shocked by how much water
was coming into the planet.
In just one day, the rain from Saturn's rings
could fill 17 Olympic-sized swimming pools.
James thinks the rings are fading fast.
There are icy grains of water
streaming along magnetic field lines
from the rings into the planet.
I'd be surprised if the rings lasted any longer
than 100 million years.
Saturn's rings appeared recently,
perhaps only 100 million years ago.
This new discovery suggests they'll be gone just as soon.
So are we lucky to be living at a time
when we can see the rings in their full glory?
People say nothing last forever,
especially if it's a good thing.
Well, Saturn's rings... They may not last forever.
And if there are people around 100 million years from now,
they may not have the rings to look at.
But will Saturn really be naked
when its bright rings rain away?
A weird, wispy ring sits outside the main rings.
Scientists want to know what it is and why it's there.
The bright rings of Saturn that we see today
may be destined to fade,
but what about the weird and wispy ring
that sits outside of them?
What is it and why is it there?
A tiny moon inside of it offers a clue.
There is a big, diffuse ring of water ice around
Saturn called the "E" ring,
and it turns out the moon Enceladus
is right in the middle of it.
All of Saturn's moons are really weird, but Enceladus stands out.
It's like a mirror.
Almost all the sunlight that hits it bounces right off.
Why?
When the Cassini probe sails past Enceladus,
it discovers something astounding.
Enceladus fires out jets of icy particles
at just over 800 miles per hour,
creating plumes that extend hundreds of miles into space.
We actually sent Cassini
out to fly past Enceladus.
And amazingly, as Cassini was flying away from Enceladus
and sunlight was actually backlighting the moon,
we realized that Enceladus was leaking.
Enceladus' plumes of icy particles
are creating the ring it sits in...
The wispy "E" ring.
But how is tiny Enceladus
powering these extraordinary plumes of ice?
Enceladus is a very interesting world
for being such a tiny world.
It's only about a tenth the size of Titan,
about 300 miles across, and yet it has geysers
where water is coming out of the surface
through cracks in the ice from an ocean below.
On Earth, geysers come from underground
stores of water... liquid water.
Could the same process be occurring on tiny,
cold Enceladus?
Planetary scientist Frank Postberg wants to know
if Enceladus' plumes are powered by a hidden liquid-water ocean.
- HV on? - Yes.
Just as the oceans on Earth,
an ocean on Enceladus would be salty.
If the "E" ring was originally part of an ocean on Enceladus,
the salt should still be there,
trapped inside the icy grains of the "E" ring.
So frank is looking for salt.
If we find salts here in the ice grains,
then this is a smoking gun that the plume is really fed
and maintained by a liquid, salty ocean.
As Cassini circles Saturn,
it smashes into "E" ring ice particles, and they explode.
Cassini analyzes the results of this molecular smash-up
and sends the data back to Earth.
But there's a problem...
The readings only tell frank what's in an exploded particle.
It's like finding shards of glass
but trying to work out what wine glass they made.
Okay.
Frank uses trial and error to work it out,
and a carefully made, sophisticated experiment.
He guesses what's inside an "E" ring ice particlE
and then simulates its explosion in his lab.
Now we are preparing a liquid water sample.
Frank and his assistant
prepare batches of water,
each with a different chemical mix.
So now the solution is ready.
Let do the experiment and see what the data looks like.
Frank's apparatus is unique, purpose-designed.
No one else does this experiment.
He puts the sample in.
So the sample we've just prepared flows through this tube
here into this injection system,
which creates this tiny water beam.
And from this side, the laser comes.
And every time it hits the water beam,
this is a similar process as if an ice grain in space
from Enceladus hits the detector on board Cassini.
Okay, start the laser.
Frank's results are a series of peaks on a graph,
and each peak is the signature of a particular chemical.
We know that we hit the water
when right signatures show up here.
Now it's running.
If the results match Cassini's,
Frank will know that the chemical mix
he's put in his experiment matches the chemical mix
of an "E" ring ice particle.
- It's an ice spectrum. - Yeah, it's an ice spectrum.
That's it. Let's record it.
The million-dollar question...
Will Frank's spectrum match the results from Cassini?
Let's just try and compare to the Cassini spectrum,
which I have here on my laptop.
So this is the first peak here, second peak here.
Third peak is, again, the larger guy,
and that one, that one.
After years of trial and error,
Frank has finally found a near-perfect match.
So we have a good match, and it tells us
that the composition of the water
we used resembles the composition
of the subsurface ocean of Enceladus.
And so we know the composition
of the subsurface ocean of Enceladus.
That's great.
Yeah, actually just telling it.
The water frank used for his experiment
contains salt.
So frank now knows the "E" ring ice particles are salty,
and that can only mean one thing.
The "E" ring particles come from a liquid-water ocean
inside Enceladus.
Saturn's moon Enceladus is one of the most
interesting bodies in the solar system.
Geysers of liquid with salt flow up from beneath Enceladus
and burst out of these cracks into space,
And this means that Enceladus
has a liquid-water ocean underneath.
Frank has shown that there is
liquid water inside Enceladus.
The water shoots out of the moon as geysers
and creates a wispy ring around Saturn.
But how long can Enceladus keep powering its geysers
and maintain its ring?
Is this ring, like the others, destined to fade away?
A perplexing reading from Cassini could hold the answer.
This was another smoking gun.
And is Saturn hiding a dark secret...
A giant hidden ring on a scale
that makes the others seem like babies?
Scientists are convinced that Saturn's bright,
shining rings are temporary.
Possibly formed only 100 million years ago,
they're destined to fade just as fast.
Yet, amazingly, one of Saturn's tiny, icy moons, Enceladus,
is shooting geysers of water ice into space,
creating another ring, the "E" ring.
But how long can Enceladus keep powering the "E" ring?
Experiments have shown that Enceladus' geysers are driven
by an underground ocean of liquid water.
But is the ocean, and its stunning geysers, here to stay?
Mission scientist frank Postberg holds a clue
in some strange data from the Cassini space probe.
The data shows that the "E" ring isn't just made of ice.
There's something else in there.
This spectrum is totally different.
This was puzzling.
It was coming from the "E" ring, which we know
is totally dominated by water ice and some salts.
But now we see no water at all in this spectrum.
This spectrum shows that whatever else is
in the "E" ring is almost pure rock,
made of a mineral called silica.
But why are there small grains of pure silica
in amongst the ice of the "E" ring?
We found that this is a very specific thing
which is produced from hot water with rock.
So cold water could not extract any silica from the rock,
but hot water can, only hot water can.
The results reveal something extraordinary.
Beneath Enceladus' icy crust and underneath
its liquid ocean,
Enceladus's core is hot.
The core heats up and shoots out silica-rich water
that mixes into the ocean, stopping it from freezing.
Fissures crack open in the moon's surface,
and jets of ice crystals
traveling around 800 miles per hour
are sucked out by the vacuum of space.
As Enceladus orbits,
Saturn's powerful gravity stretches and squeezes its core,
generating the heat that powers the whole process.
Enceladus, when it orbits Saturn,
is sometimes a little bit closer
and sometimes a little bit farther away.
And that changes the effect of gravity on the moon,
and that stretches it and compresses it
and stretches it and compresses it,
heating up the center of this moon.
Saturn's powerful gravity
keeps the core of tiny Enceladus hot.
And that means that Enceladus could keep on
spilling its icy guts into space for billions of years.
Long after Saturn's main rings have rained away,
the "E" ring will continue to shine.
Turns out, even though it's a small moon,
there's a lot of ice in it.
And when you figure all this out and say,
"well, how much ice is it blowing out?
How much does it have?"
It turns out, yeah, Enceladus
can do this for a long, long time.
But when the main rings are gone,
will the "E" ring be the only ring encircling Saturn?
A weird moon called lapetus
hints there could be something else out there,
something huge.
The main rings of Saturn might be fading away,
but that's hardly the end of the story.
Saturn's moon lapetus offers a clue
that there is more encircling Saturn than meets the eye.
Iapetus was discovered hundreds of years ago...
This tiny, little moon.
And it was quickly determined that it was really strange.
One side of it is very shiny and reflective,
and the other side is actually quite dark.
That's bizarre.
In Boulder, Colorado, planetary scientist
Anne Verbiscer thinks that the reason for this
is in front of our eyes.
We just can't see it.
Anne suspects that Saturn is surrounded
by a ring of jet-black particles that lie outside the main rings
but are invisible to normal telescopes.
As lapetus orbits Saturn,
its leading face plows through this invisible dark ring.
When you're driving, you have a dirty windshield.
Bugs on a windshield is lapetus.
Just like bugs sticking to a windshield,
the dark-ring particles stick to the icy moon,
painting its leading face black.
But how do you prove the existence of a ring
you can't see?
Anne's surprising solution is heat.
So, if you were to look for dark-ring particles
with visible light, they would be pretty hard to detect.
However...
I have a thermal infrared imager here,
and if we look at this cup full of hot water,
you see it's easy to detect against a cold,
black background.
The jet-black mug shows up easily
because it's hotter than its background.
Anne realizes that the invisible ring
should be slightly hotter than the backdrop of space.
So she takes a fresh look at Saturn
with the world's finest infrared telescopes.
The result is astonishing.
When I saw this image, I was extremely relieved
to see that, yes, indeed, the ring is real.
There it is.
In infrared, the dark ring is finally revealed,
and it's a monster.
This ring is enormous.
It is the largest planetary ring in the solar system.
You can see it extends
eh, about out to there,
maybe there, on either side of Saturn here at the center.
The thickness of the ring is equivalent
to 20 Saturns stacked on top of one another.
The giant ring dwarfs the saturnian system,
stretching out 120 times wider than the main rings.
This dark ring solves
the problem of two-faced lapetus,
but how was this enormous ring made in the first place?
From the dark side of lapetus, a trail of black dust leads
8 million miles away from Saturn to a strange,
small moon called Phoebe.
124 miles across,
its surface is dark rock.
As it races through space at almost 4,000 miles per hour,
it leaves a trail of dark debris in its wake,
creating the king of all Saturn's rings.
22 million miles across,
the giant ring made by Phoebe is so enormous
that if it weren't so dark,
it would be the biggest object in our night sky.
It's a little weird to think that Saturn,
one of the most well-observed objects in the solar system,
can hide something from us, especially something that huge.
Long after those beautiful, gaudy rings are gone,
if you have infrared eyes,
Saturn will still be the ringed planet.
Saturn's bright, shining rings dazzle us
with their complexity and beauty.
Possibly formed just 100 million years ago,
when the solar system was already old,
they are destined to fade.
But now we're understanding that the rings we see from Earth
are only part of the story.
Weird and exotic moons are creating new rings
that will encircle Saturn for billions of years to come.
Saturn's rings are here to stay.