All language subtitles for How The Universe Works s08e10 Plutos Strangest Secrets.eng

For 13 years, the Cassini spacecraft
explored astounding worlds,

Saturn and its moons.

We discovered things we never imagined.

All of these strange, bizarre
landscapes, geysers erupting out of

We were so stunned by the images.

I mean, people were just going around in
shock.

But Cassini started running out of fuel.

Scientists at NASA had to decide what to
do next. And the answer was actually

pretty spectacular.

Cassini goes where no spacecraft has
gone before.

A death flight revealing the deepest
secrets of Saturn.

Beyond Jupiter lies Saturn, a planet
circled by multiple moons and

rings. It's like a miniature solar
system.

Imagine having a mission with the power,
the instruments, the capability to

explore all aspects of the Saturn
system.

That mission was Cassini.

It would become our eyes and ears in the
Saturnian system for over 13 years.

But by September 2017,

Cassini's almost out of fuel.

Cassini has been orbiting Saturn and
studying that Saturn system for over a

decade. End the mission. We're going to
lose control soon. So rather than let it

just go derelict, we headed into Saturn.

Go out with a bang.

The Kaffini team goes for broke.

They program the probe to head straight
for the planet.

How cool is it to sort of sacrifice
everything you've got to sort of learn

last bit of information and then crash
and burn?

We are in the atmosphere.

As Kaffini was careening toward his
death, It still had instruments that

continued to work, and as each
instrument died, there was still a set

back data and information.

Cassini wasn't designed to plunge
through Saturn's atmosphere.

No one knew how long it would last
before burning up.

I remember sitting in a room with my
colleagues on Cassini and watching that

radio signal, that sharp green peak that
told us Cassini was still linked to the

Earth.

We could monitor the atmosphere as we
flew into it. And right up until the

it was sending back signs.

I was really impressed by how long
Cassini lasted in the Saturn atmosphere.

mean, go NASA engineering.

As Cassini plummeted down at 77 ,000
miles per hour, it was bombarded by gas

molecules in Saturn's atmosphere.

Friction started tearing Cassini apart
as it struggled to maintain contact.

As the antenna turned away, we actually
saw a secondary little peak, and we

thought, okay, Cassini, hang in there,
keep fighting.

And then just that green flat line.

Cassini's heartbeat was gone, and we
knew the mission had ended.

vaporized in the Saturnian atmosphere,
and so it has become a part of Saturn

itself.

Cassini's Death Plunge was just the last
of a series of daring dives.

Prior to ending Cassini's mission by
sending it into Saturn's atmosphere,

engineers and scientists came up with an
idea.

Let's do dives into the region between
the tops of Saturn's clouds and the

innermost area of Saturn's rings.

Beginning in April 2017,

Cassini ventured between Saturn and its
rings 22 times.

Scientists call it the grand finale.

On these dives, Cassini got closer to
Saturn's cloud tops than any spacecraft

ever had before.

Saturn is an enormous ball of hydrogen
and helium, a gas giant.

Fundamentally, it's a really very
different kind of planet than we're used

our everyday life.

Cassini snaps close -ups of the planet's
gaffiest surface.

The pictures reveal.

A turbulent and stormy world.

We think of some storms on Earth as
being particularly violent. If you've

been in a hurricane, that's not a fun
place to be.

But the storms on Saturn, the wind
patterns on Saturn, can make that look

mere breeze in comparison.

On Saturn, one storm stands out.

Its location is marked by a distinct
shape.

One of the really weird things is that
once the bands go around Saturn, they're

all circular until you get to the pole.

And then there's a hexagonal band up
there. No one expected that.

During its lifetime, Cassini took
multiple images of the hexagon.

Whenever we posted an image of the
hexagon, the hits to the website went

the roof.

I think people thought it was so
mysterious.

When I first saw this, I was blown away.

I mean, who could imagine having
something this regular, almost

the atmosphere of a planet? It's really
just phenomenal.

In 2018, Cassini data reveals this
hexagonal storm could be a towering

hundreds of miles in height.

It's this gigantic structure. It's many
thousands of miles across.

And right in the center, right at the
pole, is this sort of permanent vortex,

permanent hurricane.

So it's kind of a creepy eye -like thing
staring back at us.

Each side of the hexagon is as wide as
the Earth.

It seems artificial. How do you get a
hexagon -shaped storm or cloud structure

on Saturn?

Scientists think that Saturn's spin
interacts with the air currents to

this symmetrical shape.

But they don't know why it's lasted for
decades.

That's the puzzle.

How can you get a six -sided jet stream
that's stable for so long?

But while the hexagon's shape is stable,
the color has altered.

Over four years, it has changed from
mostly blue to golden brown.

The transformation is linked to Saturn's
seasons.

The seasons on Saturn are caused by the
same thing on Earth. It's the tilt of

the planet.

And so as Saturn is going around the sun
and its north pole is tipping toward

the sun, you start to get more light up
there.

This sunlight interacts with the
atmosphere, producing suspended

called aerosols.

It actually looks a lot like smog. It
turns things more orange. So over time,

the hexagon went from blue to orange.

The color change happened during one of
Saturn's northern hemisphere summers.

But mysteriously, the very center of the
hexagon remained blue.

Now, this could have been for two
reasons.

Maybe the haze never formed in the eye
because the eye was shielded from the

sun, and the sun is responsible for
creating the brownish haze that we see

Saturn.

Another reason is maybe the actual
vortex is sucking the haze down.

Maybe there's something like the eye of
a hurricane.

There's haze that forms over it, but it
gets sucked down into the eye.

But the storms on Saturn aren't the only
extraordinary thing about the weather.

When Cassini dives through the rings, it
discovers rain.

Rain falling onto the planet from space.

April 2017,

Cassini embarked on its grand finale
following a daring new path.

We decided to time in between the rings
and the planet to go to a place no

spacecraft had ever flown before and
make a unique set of measurements.

It was uncharted territory.

They didn't know exactly what they were
going to find.

There could be stuff there that could
have destroyed the Cassini spacecraft.

Instead, Cassini encountered something
totally unexpected.

Rain.

On Earth, it rains quite a bit.

We're getting that rain from rain
clouds, which are basically just a few

up. On Saturn, it also rains, but it
turns out it's raining onto the top of

upper atmosphere, and that rain is
coming from space.

In 2018, Cassini data revealed the
colossal weight of the downpour.

Icy -grained rain hit Saturn at a rate
of several tons per second.

It's completely unlike anything we've
ever seen.

Suddenly we've discovered rain at
Saturn, but there aren't any rain

Where is it coming from?

The answer is Saturn's ring.

The first thing you think of when you
hear the word Saturn is the ring.

They're the most dramatic and unique
aspect of that planet.

From afar.

Saturn's rings look like just one whole
structure, but when you look up close,

it's actually a bunch of ice crystals
and ice rocks that make Saturn's ring.

The ring material ranges in size, from
duff grain to boulders the size of

houses.

Saturn's rings are well above the
atmosphere of Saturn. They're way out in

space. And under normal circumstances,
those particles of ice making up the

would just orbit Saturn forever.

But things are a little bit weird.

Something is making these orbiting ice
particles fall inward as a kind of

hail.

Material is dripping inwards from the
rings and falling into the clouds of

Saturn. It's like a rain with no rain
cloud.

Like a cosmic rain trickling in and
falling down.

Cassini discovers the rain is a mix of
different kinds of ice particles, but

doesn't reveal why they actually rain
down.

Then the researchers realized the ice
grains were statically charged.

Ultraviolet light from the sun, for
example, can blow off an electron.

And that gives these particles a charge,
just like rubbing a balloon on your

hair makes it stick to a wall because of
the static charge.

Well, if you have particles that are
like that, they can be affected by

magnetism. And Saturn has a very strong
magnetic field.

Earth's magnetic field springs from its
spinning molten iron core.

Although Saturn probably has a rocky
center, it's mostly a giant ball of

hydrogen and helium.

But deep in its interior, scientists
think something much more exotic is

on.

We don't have enough data to know
exactly what's going on in Saturn's

but we do know the broad strokes.

Within Saturn's interior, extreme
pressures and temperatures force

stop acting like a gas, turning it into
spinning liquid metallic hydrogen.

You've got this band of electrons that
can just wander freely through that

fluid. So in that way, liquid hydrogen
under extreme pressure can act like a

metal.

The magnetic field, generated by the
spinning metallic hydrogen outer core,

pulls the ice particles from the rings.

These charged ice particles are then
drawn in by Saturn's field.

They follow the magnetic field lines and
rain down onto the atmosphere of

Saturn.

Cassini had revealed several tons of
material is raining down on Saturn every

second. But how much stuff is actually
in the rings?

Again, Cassini provides the answer.

In the final days of Cassini, we
actually flew in between the planet

the rings.

And the gravity data was able to
separate out how much mass is coming

planet and how much is coming from the
rings.

And the surprise was that the rings are
actually not very massive at all.

Even though they cover an area as big as
the moon's orbit around Earth, Saturn's

rings are 100 ,000 times less massive
than our own small planet.

They're lighter than we thought. There's
not as much material there.

The mass of the rings is a valuable clue
about their age.

A more massive ring can hold itself
together for much longer than a less

ring. So if there's not a lot of stuff
there, it must be younger.

So how long have Saturn's rings been in
place?

And what's keeping them there?

It's something that I don't even think I
could have imagined if I tried.

As Cassini orbited Saturn, It revealed
incredible insights into the planet's

ring.

The photos that came from Cassini of the
rings are unlike anything that I could

ever imagine.

If I was an alien visiting our solar
system, I don't know what would stand

to me more, the blue marble or Saturn
and its amazing rings.

One of the biggest questions about the
rings is how old are they?

Could something like that really have
existed from the beginning of the solar

system, or is it relatively recent?

Cassini provided an answer.

The rings could be as young as only 100
million years old.

A couple of clues, the low mass and the
fact that they're so bright and icy that

it hasn't had time to get polluted from
all the micrometeoroids and darkened.

over a long time like the age of the
solar system.

So the amazing thing is that, you know,
if you were on Earth about the time of

the dinosaurs, there might have been a
Saturn in the sky with no rings.

So if the rings didn't form at the same
time as Saturn, how did they form?

And what's keeping them in place?

To form the rings 100 million years ago,
you need to find an object, maybe a

comet, or a moon gets too close to
Saturn.

Saturn's gravity tears it apart and
forms the ring.

As the object is torn apart, the pieces
spread out around Saturn to form the

rings. They keep colliding, breaking
into smaller and smaller pieces.

Like pebbles on a beach.

subsequent jostling and self -collisions
between each other will take the sharp

edges off of them, creating rounded
particles.

From a distance, Saturn's rings appear
incredibly thin and almost perfectly

flat. But appearances can be deceptive.

One of our last results from Cassini as
it took its final plunge into Saturn was

as he flew past those rings.

We noticed that the rings were actually
not a uniform density.

That's something that nobody had seen.

I mean, you had to get really close to
see that, and it wasn't expected.

I'm a ring scientist, and I just love
seeing that detail and trying to figure

out why do Saturn's rings look the way
they do.

There are very intricate structures,
knife -edged little ringlets, and almost

like the grooves in a record.

Begs the question, of course, where do
those structures come from?

The clue is hidden within the rings.

There's not five rings. There's not 500
rings.

There's thousands of rings. There's
potentially millions of tiny little

with small gaps between them and
sometimes large gaps.

And Cassini saw that there are moons.

embedded inside the rings.

These moons and moonlets seem to be
shaping the rings.

When I think about the rings of Saturn,
I almost hear symphonies playing in my

head. It's all about this wonderful
structure and these harmonies, the

between gravity.

So we use the word resonance.

Saturn's moons stirred the ring
particles with their gravitational pull,

creating waves.

There's a special place where the
resonance exists.

Imagine where the ring particles would
go around twice for each single time the

moon goes around.

It's like pushing someone on a swing. If
you push them at just the right rate,

they go higher and higher.

And these places are where the waves
generated.

So there's this ballet, this dance
between the ring and the moon.

It is one of the most elegant things
I've ever seen.

But the rings aren't just being shaped
into waves by the moon.

They're being held in place by them.

Through gravitational interactions,
these moons might be shaping the rings,

shepherding them, keeping their flock in
a nice, tight orbit around the planet.

In 2017,

Cassini reveals there are more than one
or two moons shepherding the rings.

A whole team of moons holds Saturn's
outermost visible ring, the A -ring, in

place.

One of the really cool things that
Cassini discovered during its death dive

that there are seven moons of Saturn
that are all working together to keep

ring system in configuration.

So it's like the Magnificent Seven
holding this thing together.

Of the seven magnificent moons, the
biggest is Mimas.

It's one -eighth the size of our moon.

The smallest, Pan.

is only 20 miles across.

Acting in combination, these moons hold
all of Saturn's rings in check.

So it's these seven moons working
together, forming the ring system that

today.

Cassini has truly opened our eyes to the
wonder of Saturn's rings.

and many moons.

Saturn has a lot of moons.

I mean, a lot of moons.

And they're all really interesting and
different.

Coming up with an exact number is a
little difficult because it almost

every year as we discover a new one.

The latest count is over 60 moons, each
with a different character.

But one has a split personality and a
very dark size.

May 2017.

Cassini was on its grand finale.

The probe snapped its last photo of a
strange moon two million miles from

Saturn.

Iapetus.

Iapetus was discovered hundreds of years
ago, and right from the start, it was

recognized that one side of it was very
bright and the other side was as dark

as... dark can be.

This dark and light moon confused
Italian astronomer Giovanni Cassini when

first spotted it in 1671.

It's been puzzling scientists ever
since.

So we get there with Cassini, and of
course Hiapetus was a very major target

us because we were interested to know
what was with this.

crazy two -toned moon.

Cassini reveals that the answer lies
even farther out from Saturn in the form

another moon.

There's one pretty big but really dark
moon, Phoebe, that's outside of Iapetus

and is orbiting the opposite direction
around Saturn.

Phoebe orbits Saturn four times farther
out than Iapetus.

As it travels around the planet,
micrometeorite impacts on the moon's

generate a cloud of dark dust.

The dust from Phoebe actually creates a
large ring.

A ring of dark, dusty material that's
drifting inwards towards Saturn, going

opposite direction of Iopetus, which is
the perfect material for Iopetus to

sweep up in its orbit to create one dark
side.

Iapetus has one dark side because it's
tidily locked to Saturn.

One side always faces the planet, while
another side

drives forward through the dust.

It's plowing through a bunch of dust
that's sticking to the front side, kind

like bugs on a windshield.

Cassini discovered this dark dust makes
the leading side warmer than the

trailing bright side by 50 degrees
Fahrenheit.

When you have something that's dark,
like the dust on the leading edge of

Iapetus, that gets warmer. It absorbs
sunlight better. And if it's warmer,

things that can evaporate more easily,
like water, for example, tend to blow

the surface.

The front side gets darker and warmer.

Any visible ice turns to vapor and makes
its way to the colder trailing side,

where it refreezes.

So the white side gets whiter, and the
dark side gets darker.

So you have the self -sustaining dark
side and bright side, and you wind up

this two -faced moon.

Iapetus's two sides are strange.

But Cassini discovers that they're not
the weirdest thing about this moon.

The weirdest thing is that it is a
walnut.

Iapetus has a mountain range that
exactly circles its equator all the way

the moon, a mountain range higher than
the Himalayas.

These mountains are over 12 miles high,
more than twice the altitude of Earth's

highest peak, Mount Everest.

It's crazy. It's this huge, crazy ridge
on this really strange moon.

How do you form a smooth equatorial
mountain ridge around an entire world?

A really interesting idea is that for
some period of time, Just like Saturn

itself has this gigantic ring system,
Iapetus had a ring system as well.

Over time, Iapetus' ring collapsed,
falling into a circle around the moon.

As it fell to the surface, it built up a
mountain range right below where the

ring was orbiting.

So that all that material just built up
and built a mountain range, ringing the

equator all the way around.

Walnut -shaped Iapetus is not the only
strange moon around Saturn.

Cassini discovered a moon hiding many
secrets beneath its icy surface.

Enceladus, a moon that could even harbor
life.

2017, Cassini captured six images of
Enceladus, one of the most

intriguing moons in the solar system.

Enceladus is a relatively small moon of
Saturn that's pretty easy to ignore, but

once you pay attention to it, hosts a
lot of surprises.

We've known something was unusual about
this icy world ever since the Voyager

mission took photographs in 1980.

We thought that Enceladus would be
frozen solid, and yet we knew from

data the surface of Enceladus was bright
white.

And we could see on the surface that
vast tracks of it were smooth, at least

the resolution that we had with Voyager.

And that immediately says that there's
been internal activity, because that's

really on an airless moon. That's the
only process that could erase craters.

Scientists suspected something was
actively resurfacing Enceladus,

filling in its craters to make it smooth
and bright.

Then Cassini sent back pictures of
Enceladus, backlit, and all was

We saw these icy jets shooting out from
Enceladus, and everyone was so amazed

that a moon so tiny and as soon to be a
frozen solid ice cube could be so

active.

Jet of almost luminous material spraying
out of geysers.

When I first saw a picture of a geyser
on Enceladus, I mean, I was floored.

That's amazing. I had no idea that that
was even possible.

The Cassini discovery of geysers on
Enceladus was a game changer.

All of a sudden, here's water jetting
out.

It was, like, too good to be true.

Cassini revealed the geysers are
blasting out liquid water.

Enceladus is not a solid ball of ice.

As we got more data from Cassini, we
found that Enceladus had a wobble that

too large for a body that was frozen
solid all the way through, and that told

that a liquid water ocean circled a
rocky core.

Enceladus has liquid water under its
surface, and it may very well be an

basically covering the inside of that
moon.

But where's the heat coming from?

When planets and moons form.

Their cores are incredibly hot.

But they cool down over time.

The smaller the planet, the faster it
cools.

A tiny world like Enceladus, over a
billion miles from the sun, should have

frozen solid by now.

That's what we expected.

If things were smaller, then they would
be roughly dead and they'd be covered by

craters. But Enceladus shows us that
that's not the case at all.

How could a tiny moon so far from the
sun have enough warmth for liquid water?

One idea is tidal heating.

If you've ever played racquetball, you
know if you play the game the ball heats

up. And this is because as the ball hits
the racquet or the wall, it's getting

squished and then it relaxes.

Saturn's gravity squishes and relaxes
Enceladus as it orbits the planet,

it. like a racquetball.

But this alone wouldn't generate enough
heat to stop Enceladus' water from

freezing. Something else must be going
on in the core.

What if the core of Enceladus is
actually...

kind of gravelly, instead of it just
being solid, it's actually made of rocks

and pebbles and gravel all put together.

Then what happens is, as the tides are
stretching and squeezing it, those rocks

are rubbing together, and that actually
generates even more energy.

2017.

A computer model based on Cassini data
revealed this tidal friction generates

more energy than America's biggest power
station.

Water, heated to 194 degrees Fahrenheit,
rises to the surface.

It sprays through cracks in the moon's
south pole, creating misty plumes.

As we flew seven times through and
tasted and sampled the gas in the

we found salty particles, that the ocean
was salty, very much like the Earth's

ocean. We found hydrocarbons, methane,
carbon dioxide, ammonia.

We found the key ingredients for life
coming out of the jets of Enceladus.

So remarkable.

In 2018, scientists reanalyzed the
Enceladus data and found something

even more remarkable.

Complex organic molecules.

What they found were larger organic
compounds than initially thought there.

first it was just dust and water and
some basic organics. Now they're seeing

more complex stuff coming up from
Enceladus' interior. And that asks the

question, what else is down there?

On Earth, we find life huddled around
hot vents on the seabed.

Could the same be true in the oceans of
Enceladus?

Could these complex organic molecules be
signs of life?

My favorite name for them is goo.

They're gooey things.

And think of life as a collection of
gooey -like molecules. Now, that doesn't

mean that all gooey molecules are
biological, but certainly biology makes

these complex organic molecules.

Deep in Enceladus's oceans, heat from
hydrothermal vents drives chemical

reactions.

Combining simple molecules like methane
and hydrogen into longer, complex

organic molecules.

Complex molecules that could serve as
the precursors to life.

What's amazing is the chemistry of that
ocean.

Everything needed for life is there.

The internal question is, is there life
in the universe? And Enceladus is a

great place to try and answer that
question.

And Cassini revealed secrets of another
moon of Saturn with amazing chemistry.

A giant moon with Earth -like features.

Rivers, lakes, and dunes.

Titan.

September 2017.

Four days before the mission ended,
Cassini flew past one of Saturn's most

spectacular moons,

Titan.

Here's why I like Titan. Not just
because it has a name that means big and

strong, which makes you think of me, but
because it has an extensive atmosphere

that's made primarily of nitrogen just
like Earth.

Titan's always been a mystery.

What is hiding underneath that thick
atmosphere?

Viewed through a telescope, this moon
seemed little more than a hazy orange

ball. Then Cassini launched the Huygens
probe.

It traveled beneath the clouds and sent
back images of Titan's surface.

I almost...

Can't describe how thrilling it was, the
landing of the Huygens probe on the

surface of Titan.

It was like a Jules Verne adventure come
true.

The images that you see as you're coming
through the atmosphere and the world

emerges, and it's this incredible world
that looks so familiar.

Mountains and these streams flowing into
this ocean.

Wow. You might be standing on the shores
of a lake, but this lake doesn't look

like water.

Instead, it's methane.

It's much darker.

It's a frigid, bizarre world with
geologic features that look familiar,

very, very alien setting.

Titan is like a home away from home,
just colder by 350 degrees Fahrenheit.

The Cassini mission revealed that Titan
is really exactly like Earth in terms of

its landscape.

In fact, almost a quarter of the body is
covered in sand dunes, exactly like

what you see behind me.

But Cassini reveals Titan's dunes aren't
what they seem.

The dunes on Titan are made of something
completely different than sand dunes on

the Earth. We know most sand on the
Earth is made of quartz.

But on Titan, sand dunes, it turns out,
are made entirely of organics.

Titan sand is made from tiny particles
of organic gunk called hydrocarbons.

These organic dunes contain the building
blocks of life.

For scientists, this is a tantalizing
hint.

Could Titan harbor life?

Here on Earth, there's life that exists
in so many extreme environments, so it's

not impossible to think that life could
have evolved to use the methane and all

of the other chemical constituents on
Titan.

If life has developed on Titan, it's
going to look really weird. It's going

be really different from life on Earth.

To me, there's going to be this
wonderful moment in history when we

have another example of how life can be.

And if I had to place my bets on it, I
think we're going to find it in the

Saturn system.

But Cassini's discovery of potential
life sentenced the probe to death.

We didn't want to leave it just
indefinitely in orbit because there was

fear that...

You know, should there be any earthly
contamination on the spacecraft, you

want it crashing into Titan or
Enceladus.

Cassini interacted with Titan one last
time.

With a gentle nudge from Titan's
gravity, we call it Titan's goodbye

We ended the mission with a plunge into
Saturn's atmosphere, vaporizing

Cassini. and saying goodbye to our
friend.

I hope you're all deeply proud of this
amazing accomplishment.

I'm going to call this the end of
mission.

Project Manager OpNet.

Although Cassini is gone, its legacy
lives on.

Now we're sifting through all of the
data collected, still finding

putting together the pieces of the
puzzle to understand Saturn, the rings,

the moons.

Cassini is going to go down in history
as one of the most scientifically

productive interplanetary missions that
humanity has ever flown.

I'm immensely proud and... I feel
enormously privileged to have been a

it.

Besides the amazing science Cassini
returned, just the beauty of this

I think, sparked something inside of us.

Whenever I look up at Saturn now, I know
that Cassini is there too.

And so Saturn is even a more special
place.

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