Nova (1974–…): Season 46, Episode 16 - The Planets: Ice Worlds - full transcript

Uranus and Neptune's unexpected rings, supersonic winds and dozens of moons; an up-close view of Pluto before exploring the Kuiper belt

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From the comfort
of our home world,

bathed in the warm light
of our life-giving star...

The 8-4-4 century interface...

we've set out to explore
every one of the planets.

We've pushed further
into the dark of space.

But after decades
of exploration,

just two probes have explored
the most inhospitable

and distant reaches of the
solar system's strangest realm.

This is a region
of the solar system

that we really had
very little information about.

Their instruments waking up
to find astonishing vistas...



unlike anything encountered
before.

It's at that moment you realize

you're looking at something
that's very different.

Places where
all the rules are broken.

This was a really
strange system.

So why is Uranus so tipped
on its side?

Where everything we thought
we knew is being rewritten.

Geysers like this one

even exist on Triton,

where it's 30 times farther
from the sun.

Incredibly,
we have pushed the frontier

all the way to the solar
system's most distant outpost...

Pluto.

A small planet should be
simpler,



and they should run out of
energy in their internal engines

and stop evolving,

like the moon did,
billions of years ago.

Pluto didn't read
any of those textbooks.

"The Planets: Ice Worlds"...

Right now, on "NOVA."

Major funding for "NOVA"
is provided by the following:

("The Void" by Muse playing)

♪ They'll say
no one can see us

♪ That we're estranged
and all alone

♪ They believe
nothing can reach us

♪ And pull us out
of the boundless gloom

♪ They're wrong

♪ They're wrong

♪ They're wrong

Far, far away...

beyond Mars...

Past the storms of Jupiter...

and the rings of Saturn...

Where the distance from the sun
is measured not in millions

but billions of miles...

Lies a region unlike anywhere
else in the solar system.

Out here, the planets are
utterly bizarre...

even unnerving.

Uranus is an oddity even
in a solar system of oddities.

Temperatures approach
absolute zero,

at which everything grinds
to a halt.

Yet, somehow, the worlds here
are still teeming with activity.

Neptune was a great excitement,

all sorts of strange things
going on.

A place where cold doesn't
always mean frozen.

It's at that moment you realize

you're looking at something
that's very different.

And even deeper
into the darkness,

past where the planets end...

a vast expanse scattered
with mysterious bodies awaits.

Our jaws just dropped
to the floor.

If ever there were an object
that turned out to be

far more surprising than
we ever would have imagined,

that's Pluto.

There is no part of the
solar system more puzzling.

This is the realm
of the ice worlds.

60 seconds,
all continuing to go well.

Travelling
to the most distant planets,

Uranus and Neptune, is so hard,

we've only managed it once.

We have ignition,

and we have liftoff.

This first mission

to the farthest part
of the solar system

is only possible thanks
to some help

from the worlds closer
to the sun.

25 seconds into the launch,

all continuing to go well.

Making the most
of a rare planetary alignment.

People realized that there was
an opportunity coming up

in the 1970s

that only comes up
every couple of hundred years,

where the planets in
their orbits kind of line up

in just the right way

so that you can slingshot
from one to the next.

The guidance data
coming back shows

that we're right on the money.

The key idea here is that
you could use the gravity

of each planet to accelerate
the spacecraft,

speed it up,
and shorten the trip time.

If it works, this series
of planetary boosts

will help Voyager cross nearly
900 million additional miles

of space

before reaching
the first of the ice worlds.

This is a region
of the solar system

that we really had
very little information about.

We had excellent cameras
and sensors and so on.

And we used that to go out
into the solar system

and see things
for the first time

we had never seen before.

Almost nine years
into its mission,

Voyager begins its approach to
an entirely unexplored planet

and reveals a world weirder
than we had ever imagined...

A vast ball of gas,

14 times the mass of Earth
and four times its diameter.

Sensors detect an atmosphere
of 83% hydrogen and 15% helium.

But it's the 2.3% methane,

that by absorbing red light
and reflecting blue,

lends Uranus its color.

Just this giant,

pretty much featureless,
blue-green ball

that seemed unreal.

They could see none
of the activity

that you're familiar with
on Jupiter.

And it's at that moment
you realize

you're looking at something
that's very different.

Poor Uranus, it's got rather
boring clouds, truth be told.

So there wasn't a lot to see
with the cameras.

Uranus spins on its axis
once every 17 hours,

which should generate
dramatic storms.

So why is it so featureless?

Voyager detects a clue.

Temperatures here are
the coldest

of any planet
in the solar system.

There's simply not enough heat

to drive the storms seen
on Jupiter and Saturn.

Uranus is an entirely new
class of planet:

an ice giant.

And more surprises are to come.

Uranus has rings.

We knew long ago
from telescopic observations

the rings were there at Uranus,

we didn't know
their configuration

or their shape.

Voyager begins to explore
the ring system

and spots something curious
in the shadows...

Two moons...

Cordelia on the inner edge
of the brightest ring

and Ophelia on the outer edge,
help to organize the system.

Particles within the rings can
be moved inwards or outwards

as these tiny objects
called shepherd moons,

whose gravitational force

can shape and sculpt
the rings themselves

But it's the orientation
of the orbits of these moons

and the rings themselves
that singles out Uranus

as the strangest of worlds.

Uranus looks bizarre.

The rings,
rather than looking like that

when you look
through a telescope,

they're actually orbiting up
and over the top of the planet.

The whole thing is tipped,
like a spinning top.

A bizarre orientation that hints
at an unusual past.

Since the beginning,

everything in the solar system
has been circling

in the same direction.

It begins with the vast cloud
of material

that orbits the young sun.

Over time
the material draws together...

forming each of the planets.

Today they all orbit the sun

and spin on their axes

in the same
counterclockwise direction

as that primordial cloud...

Except for Venus and Uranus,

which spin
in the opposite direction.

But Uranus is even stranger,

because the entire planet is
on its side.

This was a really
strange system.

So why is Uranus so tipped
on its side?

If a roughly Earth-sized object
smashed into Uranus

late in its formation history,

then that would've had
the proper amount of momentum

to basically knock it
on its side.

Not only did the collision tip
the planet over,

but it may also help to explain
another of Uranus's mysteries:

why the planet is so cold.

That impact presumably
relinquished

all of that internal energy
that the planet had

when it first formed

and has left it as a relatively
dead and sluggish world.

We learn so much
during this brief encounter.

But Uranus still holds
many mysteries.

And Voyager's strangest
discoveries are yet to come.

After Uranus,

it must cover another
billion miles of empty space

before it will see
another world.

We can say the numbers,

but can we really wrap our heads
around something that large?

In order to help ourselves
do this,

we can make scale models.

At the center
of the solar system is our sun,

a ball of fire 850,000 miles
in diameter.

But if we scale
the whole system down

by a factor of 600 million,

the sun becomes the size
of this light.

And walking out, you pass
all the rocky inner words

within the first 500 years.

But to get
to the outer solar system

is far harder.

On our scale,
we have to cross the harbor

to reach the next planet,
nearly a mile away.

And we've reached the orbit
of Jupiter,

the largest of the planets
and the first of the gas giants.

Even farther,

at almost twice the distance
from the sun as Jupiter,

we reach Saturn.

Now as we approach Saturn,

the light is getting
noticeably dimmer,

and yet from Earth,
we still see it,

because it's a big,
bright, planet,

and it's surrounded by those
bright, reflected rings

that act as a mirror, sending
so much light back towards us.

Beyond here
the planets are separated

by hundreds of millions of miles
of dark, empty space.

Now, we are three miles
from our model sun.

We're reaching the orbit
of Uranus,

twice again as far from the sun
as Saturn.

Out here at Uranus,

there's only about
.2% of the light

that we get at Earth
from the sun.

Heading out into the dark,

1.7 billion miles from the sun

and we begin to fully understand
the distances Voyager faces

on its journey
to the farthest reaches

of the solar system.

Now finally we've reached
the realm of Neptune,

the outermost
of the giant planets.

Back there
on that little island,

where Earth and
the other planets are basking

in the warmth and the glow
of the nearby sun,

it feels as though
we've come quite a long way.

In 1989, after 12 long years,

Voyager finally crosses
the great expanse of space

between Earth and its
most distant planned objective.

Neptune, an ice giant...

17 times the mass of Earth.

A billion miles farther
from the sun than Uranus,

Neptune is almost chemically
identical.

Yet, bizarrely,
it couldn't be more different.

Neptune in a way
was almost a relief,

because it wasn't featureless,
you know?

It was like, "Oh, good,

a planet with, with clouds
and features again."

Neptune was a great excitement.

It's got swirling clouds,
really strong winds...

At 1,500 miles an hour,
incredibly fast,

the fastest winds that we've got
in the solar system.

One of the things
that Voyager discovered

was an immense, dark vortex
within the atmosphere...

A huge, swirling dark spot.

We say it's a giant storm,

it just... those words don't
fully contain...

we're talking about a storm

the size of the planet Earth
or larger.

And the surprises keep coming.

Even though
it's much farther out,

Voyager discovers
Neptune is warmer than Uranus.

It emits two and a half times

the amount of heat
it receives from the sun.

And the source of the heat
is another oddity

of this strange planet.

In fact, when we look
at this dynamic activity

in these extraordinarily cold
regions,

we really are at a loss

to understand
just what's going on here.

One theory is that the buildup
of pressure

beneath the thick layers
of cloud...

turns the carbon in the methane
into a rain

made of diamonds.

They then melt as they fall
into the interior of the planet,

producing the extra heat.

As the heat makes its way out
into the frozen cold of space,

it churns the entire atmosphere,

whipping up winds
around the globe.

There are no mountain ranges,

no valleys,
no continental boundaries

to get in the way of the
perfect fluid-dynamical flows.

What that means is that when you
start a weather pattern going,

when you start a vortex spinning
or you start a plume rising,

there's very little to get
in the way of it.

So those winds that develop
and go around,

they just keep going around
and around.

There is nothing
to slow them down,

no friction with the surface.

And the extreme cold here makes
the atmosphere less viscous...

allowing the gases
to move faster...

Creating supersonic winds

that outpace anything seen
on Jupiter or Saturn.

Voyager 2 has almost completed
its grand tour.

But the spacecraft's visit
to Neptune

includes an encounter
with another puzzling world.

Roughly the size
of our own moon,

but scarred
by deep cracks and pits,

Triton is covered by a sheen
of icy nitrogen.

We expected it to be
a frozen, silent world.

But one incredible image
that Voyager sends back

contains something
entirely unexpected.

Here, nearly three billion miles
from the sun,

huge geysers erupt nearly
five miles into space.

Geysers like this one
even exist on Triton,

where it's 30 times farther
from the sun,

and it is so cold,
yet you still how...

have this intense geologic
activity going on.

At -391 Fahrenheit,
Voyager found Triton

to be one of the coldest places
in the solar system.

So what could be causing
these eruptions to burst

from the frozen depts?

The surface of Triton is covered

in a thin layer of nitrogen ice,

and it is so cold on Triton,

that nitrogen,
which is a gas on Earth,

is frozen solid to the surface.

But right
where the sun is striking,

it starts to vaporize
a little bit in the subsurface

As weak sunlight passes through
the nitrogen-ice surface,

it heats up a layer
of darker particles

several feet below.

And in some spots
that heat is just enough

to vaporize the frozen nitrogen.

A lot of gas builds up,
and then it bursts through

and creates a geyser that goes
8,000 meters into the sky.

But although the faint light
of the sun

is just strong enough to power
Triton's geysers,

it is likely too weak to explain
the cracks and pits

elsewhere on the surface...

Rugged features
that cover half the moon.

What caused them is thought
to be linked

to Triton's odd path
around Neptune.

Its orbit is really unusual.

It orbits in the opposite
direction that the planet spins.

Now, most moons orbit

in the same direction
that the planet spins,

because we think most moons form
at the same time as the planet

in a disc of material
around the planet.

And since Triton is going
the opposite way,

we think it must have formed
in a different way.

One theory is that billions
of years ago,

Triton wasn't a moon at all.

It formed way beyond Neptune...

A huge, wandering object

that eventually ends up close
enough to Neptune

to be drawn in by its gravity...

And trapped
in its unusual orbit.

So when Triton first goes
into orbit around Neptune,

it's not going to be
a perfectly circular orbit.

We expect it to be
highly eccentric,

where it's getting closer to
and further from Neptune.

And when that happens,

Triton is going to get stretched
and squeezed

by the immense changes
in gravity

as it moves in and out.

And that stretching
and squeezing

is going to put
an intense amount of heat

into Triton.

The ancient molten interior
then explodes up

through the faults
in the moon's crust.

Over time, Triton's orbit
becomes more and more circular.

No longer stretched
and squeezed,

the moon cools,

leaving the rugged surface
we see today.

As it leaves Triton and Neptune
behind,

Voyager's mission is over.

It will never encounter
another planet.

But as it heads out
of our solar system

to the ocean of stars beyond,
it carries with it

an interstellar message
in a bottle,

should it ever encounter
something... or someone... else.

These unique disks contain
photographs of everyday life

as well as voices, the music
of Beethoven and Chuck Berry,

a baby crying, and a heartbeat.

On its lonely journey
into darkness,

Voyager passes through
an unknown region of space...

that in just a few years will be
described

for the first time.

The discovery of the Kuiper Belt

in the 1990s is probably

the single most important
discovery of the space age.

It completely changed
everything.

It was as if we had a map
of the Earth

without the Pacific Ocean on it,

because we didn't know
it was there.

The Kuiper Belt is the most
remote part of the solar system.

Here trillions of frozen lumps
of water, ammonia, and methane

circle the distant sun.

Like, the Kuiper Belt is
what we call

the third zone
of the solar system.

This is what we think is
the most primitive region,

a zone of icy objects
beyond Neptune's orbit.

Incredibly, by the early 2000s

our telescopes become
powerful enough

to just make out these
unbelievably distant objects.

We found Sedna and Eris
and Makemake and Haumea

and Ixion and more.

And we now know of more than
2,000, uh, you know,

Kuiper Belt objects.

This is the solar system's
new frontier.

And in 2006, a new probe
is primed to leave Earth

on a mission to explore it.

Five, four, three, two, one.

We have ignition and liftoff

of NASA's New Horizons
spacecraft...

on a decade-long voyage
to visit the planet Pluto

and then beyond.

It just shoots up so fast,

it's the fastest launch ever
from Earth.

As soon as we were launched

we had to test
all the backup systems

and plan the most sophisticated
flyby of Jupiter

that had ever taken place.

Even with the extra kick
from Jupiter's gravity,

it will still take
ten long years

to reach the Kuiper Belt.

In order to ensure that it was
going to last for the decade,

they built in
a lot of redundancy.

There were sort of two
of everything...

Computers
and the guidance systems.

And they figured out
how to hibernate...

The first spacecraft
that, that hibernated.

But it had really never been
done before,

to put the spacecraft largely
to sleep,

let the spacecraft
just silently coast,

then we could extend the life
of the electronics

No spacecraft mission had ever
really used hibernation

as a day-to-day way to cross
the solar system.

That was scary
because, you know,

you turn it off, and you hope
that it comes back on again.

New Horizon's first target

is the Kuiper Belt's
most famous resident...

The discovery of Pluto

was back in 1930,

and Clyde Tombaugh,

a Kansas farm boy,
was using the telescope

at the Lowell Observatory
in Arizona.

Every clear night

Clyde would go out

and, and take images of the sky
on photographic plates.

And when it was cloudy
or during the day,

he would compare those plates.

When you're looking out
at the sky,

how do you tell something is
a star versus a planet?

Well, planets actually move
relative to the stars

and that's because
they're much closer to us

than the stars.

So what Clyde Tombaugh noticed

that there was this little speck
moving across the stars.

And then Clyde Tombaugh
discovered Pluto.

It is crowned the ninth planet,

a title Pluto enjoys
for 76 years.

But while New Horizons continues
its decade-long voyage,

a debate rages back on Earth...

one that will challenge
Pluto's very status

as a planet.

According to the International
Astronomical Union,

a planet has to be orbiting
the sun.

It needs to be large enough
and massive enough

that its gravity can pull itself
into a spherical shape...

And it has to have cleared
its zone,

meaning that it is sort of
the gravitational bully

of its, of its own realm.

The problem is Pluto's region
of the Kuiper Belt

is packed with hundreds
of icy objects.

Pluto doesn't meet the criteria
for being a planet,

because it hasn't cleared
its orbit.

By that definition,
Pluto clearly belongs

to a, a different, um,
sort of grouping.

Pluto is now classified
as a dwarf planet,

along with
the other larger worlds

of the Kuiper Belt.

But the debate still continues.

I think planetary scientists

really never stopped
calling Pluto a planet.

Pluto is what it is;
it doesn't make any difference

whether we call it a planet,
a full-fledged planet

versus a dwarf planet.

Defining them and labelling
is really a side thing,

it is a periphery
to the important thing,

which is exploration.

We are searching
for frequencies,

stand by.

Standby for telemetry.

After nine years of flight,

NASA attempts to reawaken
New Horizons from hibernation.

The first words he said were,

"Alan, we have lost contact
with the spacecraft."

And all of a sudden,
I get a message

that the spacecraft is
shut down.

I couldn't believe it.

It was, it was heart stopping.

And here we had just days
until the flyby was to begin

to put Humpty Dumpty
back together again.

Nine years
of faultless space travel

would all be a waste

if New Horizons couldn't be
brought back online.

It wasn't easy,
but they pulled it off

with precisely
three-and-a-half hours to spare.

We are in lock with telemetry
with the spacecraft.

Yes!

Give me a hug!

New Horizons gives us
our first close-up glimpses

of the most distant world
ever visited.

A world that, until now,

had only appeared
as a fuzzy blob.

We thought the surface would be
geologically dead,

because Pluto is so small.

When New Horizons came by
and took all of these pictures

it literally broke
everything we thought about it.

Pluto was a shock and
a revelation in so many ways.

It's turned out to be one
of the most fascinating objects

in our entire solar system.

Giant water-ice mountains

as high as the Rocky Mountains
in the United States.

Bladed terrain.

We're seeing ancient parts
of Pluto

but also ridiculously young
parts of Pluto.

We even think we see dunes,

which get blown around
by the very thin atmosphere

A small planet should be
simpler,

and they should run out
of energy

in their internal engines
and stop evolving,

like the moon did
billions of years ago.

Pluto didn't read
any of those textbooks.

One of the most fascinating
features

beamed back by New Horizons

is the region named
after the planet's discoverer:

Tombaugh Regio.

We got our, our first full-frame
view of Pluto

and saw this, this region
that looks like a heart,

this heart-shaped region.

The western lobe of the heart is
called Sputnik Planitia...

a giant plain

of frozen nitrogen, methane,
and carbon monoxide...

That stretches
for over 330,000 square miles.

And at its edge

lies a range of mountains made
of frozen water ice.

They rise nearly four miles into
the dark skies above the plain.

As odd as that is,

there is something even weirder
about the region.

It's the size of the states of
Texas and Oklahoma combined,

and we can't find any craters
on its surface.

There are almost
no impact craters on this,

which means something is
happening on the surface.

Pluto's heart is
young, fresh ice.

So what's creating it?

It's smooth,
but it wasn't completely smooth,

it had this beautiful pattern
of sort of cells or polygons.

Detailed imagery beamed back
by New Horizons

reveals a puzzling network of
hexagon and pentagon shapes...

That crisscross
the frozen nitrogen surface.

It looks like there's material

that's convecting underneath,

like soup on the stove.

You have these things
turning over,

making these shapes on the top.

So we scratched our heads
and wondered

what could be making
this strange behavior.

Our working theory

is that somewhere deep
in Pluto's interior

are radioactive elements that
generate heat as they decay,

warming up a liquid layer
beneath the planet's crust.

We think underneath the exotic
ices on Pluto's surface,

and underneath
the water-ice crust,

which could easily be
a 100 kilometers thick,

that there's actually a layer
of liquid water

that surrounds a rock core.

This sunless ocean of water

that has existed
for billions of years

beneath the surface of Pluto
is being gently warmed

by heat from the interior.

That little bit of heat
that's leaking out,

we think is enough to drive
the convection

and these exotic patterns that
we see on Sputnik Planitia.

And that's because nitrogen is,
it's very soft,

it doesn't take much heat
to make it move.

As the nitrogen
slowly bubbles up,

the area is constantly being
resurfaced,

scouring away
any impact craters.

It's warmer underneath,

and so then the glacial ices are
upwelling in the middle,

and then spread out and
then downwell on the side,

and that's what make those...
makes those polygonal patterns

that we see on the surface.

We had no idea to expect that.

But why all this activity here
and nowhere else?

Perhaps Pluto's heart is
the site of a huge impact...

That long ago punched
a large hole in the surface

almost down
to the vast ocean beneath,

a great hole that slowly filled
with soft nitrogen ice,

and now gently churns
just above a warmer ocean.

So there's a lot more going on
on Pluto

than we had ever imagined.

You don't have to be
a giant planet,

or a terrestrial planet,

to be an amazing place
in the solar system.

It just completely changed
our view

of how small planets operate

and how they can be as,
as complex as big ones.

New Horizons' closest encounter
with Pluto lasts just hours.

Its fleeting visit

reveals the tiny speck

that Clyde Tombaugh saw moving
across the sky

to be a dynamic, vibrant world.

But Tombaugh died nine years
before New Horizons left Earth,

so he never saw Pluto up close.

He had asked if a mission
ever did get launched

that some of his ashes could be
sent on the journey.

And to think that Clyde's ashes,
you know, flew by Pluto,

and, you know,
he was finally visiting

the place that he discovered,
that was pretty cool.

And Pluto holds
a final surprise.

As New Horizons turns
its camera back

for one last look...

It captures an image
of Pluto's atmosphere

glowing in the dark.

There's the blue ring
of its atmosphere

looking hauntingly familiar,
like the Earth's atmosphere.

Not only can we see a number
of layers in the atmosphere,

but we can also see mountains
on the surface of the planet

sticking up
into that atmosphere.

A thin, blue sky

over a hidden ocean of water,

three billion miles from Earth.

That image just epitomized
everything we had done.

That's my favorite picture
from the entire flyby.

And I took to saying

that the solar system had saved
the best for last.

But New Horizons isn't done.

It expands its exploration
of the Kuiper Belt

by continuing on,
towards a new target.

This was an opportunity

for the New Horizons spacecraft

to now look at a different
object out in the Kuiper Belt,

something that might be
much more typical

of what could be found out
in this region.

On January 1, 2019,
it beamed back pictures

of the most distant object
ever visited.

This object may be
the most primitive object

ever encountered
by a spacecraft.

Two icy rocks frozen
in the moment of collision.

By looking at Ultima Thule
today,

we think we're looking back
in time

to the origin
of the solar system.

A window into the processes
that created the solar system

that we call home.

New Horizons gives us a glimpse
of our origins

before it follows Voyager

on an eternal journey out
into the stars.

Just six decades ago,

we left Earth
for the first time.

Since then

we've gone on
to explore the whole expanse

of the solar system.

With each flight,

curiosity has driven us further.

For us to continue doing
something

that is very natural
and intrinsic to all of us,

and that is
answering the big questions

and exploring the unknown.

And as our technology
has evolved,

each encounter has taken us
closer.

I think exploring the planets

is just a,
it's a great adventure

that we can all participate in.

We've landed robotic
explorers...

on Mars...

Venus...

and even a distant moon
of Saturn.

I feel as though

we're absolutely just
at the beginning

of planetary exploration.

These first steps have
only scratched the surface...

But they reveal a solar system
of limitless wonder...

and beauty.

There's still more
for us to discover.

There's still more surprises
out there.

There is a lot
of exploration left for us.

As we continue to push farther

and stay longer

in our quest to piece together

one of the greatest stories
ever told:

The story...

of the planets.

Major funding for "NOVA"
is provided by the following:

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visit ShopPBS
or call 1-800-PLAY-PBS.

This program is also available
on Amazon Prime Video.