Original subtitles

[narrator] Voyager,

the most ambitious space mission in history.

The two Voyager spacecraft are iconic.

Iconic.

Iconic.

They're the first probes to truly explore half the planets in our solar system.

Jupiter, Saturn, Uranus and Neptune.

These went from dots of light in the sky,

to real worlds.

The Voyager missions have ventured far beyond where other probes have explored.

They are the most distant emissary, representatives

of the human species.

They're the first spacecraft to taste interstellar space.

[narrator] Exploring furthe than any humanmade spacecraf has gone before.

[narrator] These are the logs of starships, Voyager 1 and 2.

They have crossed the final frontier

and are now in interstellar space.

Almost a decade ago,

Voyager 1 achieved something that had never been achieved before.

It left our solar system.

When Voyager crossed into interstellar space,

humans became an interstellar species.

[narrator] 14 billion miles from Earth,

their radio signals travelin at the speed of light

still take 21 hours to reach us.

The Voyagers are so far t

that when they look back towards the sun, it's just a pinprick of light.

And they would need an exceptionally powerful telescope

just to see the Earth.

[narrator] Their original four-year mission has been extended to 44,

and counting.

From their current distant vantage point,

they look back on strange new worlds

and bold new science they've discovered.

August 20th, 1977.

[man] We have ignition,

and we have liftoff.

[narrator] The mission begin when Voyager 2 blasts of

Followed two weeks later by its twin, Voyager 1,

which will take a shorter and faster route.

Their destination, Jupiter.

And then, Saturn.

When the time comes that that mission is actually ready to go to the launchpad,

it's a funny mixture of joy

and bittersweet loss.

[woman] They become like your children.

And that launch is like the birth of a baby.

I was standing there, watching it climb up into the sky.

We were cheering, we were so happy.

Voyager was on its way.

[narrator] Though funded to just explore the two gas giants,

mission planners have a muc bigger journey in mind.

To send the Voyager spacec

on a grand tour of the solar system.

To the outermost planets,

Uranus and Neptune,

worlds that have never been explored.

To visit each planet,

the probes must stick to a strict schedule,

with only a quick flyby of each world.

Once reaching Jupiter,

they must use every second to complete close-up studie of the planet

and its largest moons.

One of the biggest challenges with flyby spacecraft is

it may have taken years to get there,

but the actual time that you're close to the planet

is remarkably short.

The Jupiter close-up data

occurred during just three days.

[narrator] February 1979,

Voyager 1 begins beaming pictures back to Earth.

It's an anxious wait.

[Cooper] This is pre interne

And so, when you look at the data coming in,

it's coming in line by line, pixel by pixel.

It was such an exciting time it was hard to know when to sleep.

I brought my sleeping bag into my office

so I wouldn't miss a single exciting picture.

[narrator] Both Voyagers reveal an unbelievably dynamic world.

Scientists were able to take a sequence of images of Jupiter

that they could put together like a flipbook to get a sense of motion.

And it was just astounding.

Now we can see things moving within the atmospher of Jupiter

in a way that we had no sense of before.

[narrator] Together, the spacecraft take over 33,000 images of the gas giant.

These pictures reshape our understanding of Jupiter

Especially its largest moons

Ganymede,

Callisto,

Europa,

and Io.

We saw all sorts of different kinds of landscapes on them

and each one had its own individual type of personality.

Of all the moons around Jupiter, and there are a lot,

Io is the one that shocked everybody.

[Linda] We got back this very unusual picture.

We saw this bright feature on the dark limb of Io.

We wondered, "What could it be?"

At first, they thought that arc might be another moon behind Io.

But the geometry was wrong. There were no moons there.

Well, they figured out that these were volcanic plumes.

And that bright feature on the dark limb

was a volcano erupting on Io.

[narrator] Voyager 1 record ash and lava

blasting 190 miles into spac

Eight times higher than the largest eruptions on Earth.

This is the first time we'd ever seen another volcanically active world

anywhere in the solar system, right?

It really transformed our ideas, our concept of what a moon could be.

[narrator] But astronomers were also baffled.

When scientists first saw these images of Io,

they had to ask the question, "How is this little moon still so hot?"

On Earth, we know, you know, it's a big planet, it's volcanically active

because of plate tectonics, and there's this,

you know, ancient heat system inside the planet.

When you look at a little mo like Io,

you expect, "Ah, it's gonna be dead." RIght?

But instead, it's the most volcanically active body in the solar system.

[narrator] Io's volcanism is powered by tidal heating

[Phil] As it orbits Jupiter

it gets stretched and compressed by the gravity of Jupiter

and the other moons as they all pass by it.

[narrator] The compression and expansion generates heat

melting Io's interior.

A planetary process

never before witnessed.

At Jupiter, the Voyagers discover three new moons

and a ring system invisible from Earth.

Not to be outdone,

the planet itself has a few surprises.

The probes turn to the gas giant's most famous feature,

the Great Red Spot.

[Nina] Jupiter's red spot is a feature

that has existed in its atmosphere since we began looking at Jupiter.

It's incredible.

What it turns out to be is a storm

that has lasted centuries.

[narrator] The Voyagers re a maelstrom of gas

swirling counterclockwise between two bands of high speed winds.

The red spot has been kept in a single place

because it's kind of sandwiched between these two bands of atmosphere.

[Phil] Like a whirlpool or an eddy in two currents

that are moving next to each other.

that may have helped promote its stability over all these centuries.

[narrator] But Voyager's closeup shots show

a far more complex structur than we expected.

[Phil] It turns out, the Great Red Spot is not a single vortex.

It's more complicated than that.

What you might expect from a storm bigger than the Earth.

Voyager actually took close up images of it and sa several smaller vortices

spinning around inside of it

[narrator] These small vortices are ten times large than any hurricane on Earth

But the Voyagers can't detect how they interact with the spot.

It will take a new generatio of space probes

to solve that mystery.

so, after Voyager had flew past,

there were lots of questions that went unanswered.

And Jupiter is a long way from the Earth.

And really, the only way to answer some of them was to go back.

[narrator] 37 years after the Voyager flybys,

the Juno probe arrives at Jupiter.

[Carly] The Juno space probe has a microwave radiometer.

That instrument is able to detect microwave radiatio

coming from very deep inside Jupiter.

And from that we're able to determine things like it's deep composition,

and its deep temperature.

[narrator] Juno finds the Great Red Spot

stretches at least 200 mile below the surface.

And in 2021,

a team combines Juno

with Hubble and ground-based telescopes

to finally discover what powers the gargantuan storm

These small storms that are coming in

are rotating very quickly.

All of that feeds the Great Red Spot and keeps it spinning.

Gives it that spinning energ that it used to survive.

[narrator] The Voyager pro are ready for their next destination, Saturn.

But to get there, they must first fly dangerously close to Jupiter.

[narrator] The next stop on the Voyager probes' grand tour of the solar system

is Saturn.

But the ringed planet is ove 450 million miles away from Jupiter.

To get there,

the Voyagers will need to perform a maneuver

known as a gravitational slingshot,

which will catapult them from one planet to the next

We allowed the large gravity of Jupiter

to actually capture the spacecraft

and start accelerating it towards that massive planet.

But we did it at just the right angle.

So we would move around it, and then continue away from the planet.

Jupiter itself is barreling around the sun

at very fast velocities.

As you pull away from Jupite

you keep some of that velocity with you.

[narrator] If it's successfu

the slingshot will knock yea off the Voyager's journe

If things go wrong, it's game over.

To do a gravitational slingshot,

you need to do three things.

You need to have really good calculations,

excellent planning and perfect timing.

[narrator] Mission controlle achieve all three.

And the maneuver works.

Voyagers 1 and 2 speed up by 225,000 miles an hour

and race towards Saturn.

1980, right on schedule,

Voyager 1 arrives at the ringed planet.

Its sensors probe Saturn's atmosphere

and discover it's mainly hydrogen and helium.

[Phil] Saturn has nearly 100 times the mass of the Earth.

But it has so much more volu

that when you look at its density, it's actually less dense than water.

It's a very old joke in astronomy

that if you put Saturn in a bathtub, it would float.

But it would leave a ring.

[narrator] The most striking discovery emerges from the data

nine years after Voyagers' flybys.

A bizarre cloud formation at the north pole.

[Phil] A giant hexagon over the north pole

with sides 9000 miles long

and it's 18,000 miles across.

Yeah, that's bizarre.

[Carly] We don't often think about very stable geometric shapes

like a hexagon. That feels like it shouldn't happen, right?

You don't get hexagon shaped clouds on the Earth.

[narrator] What could possib create a hexagon

more than twice the size of Earth?

Voyager discovered the hexagon.

But we didn't have enough information to truly understand it.

[narrator] Jump forward 24 years after Voyager,

and another probe arrives at Saturn,

Cassini.

The main difference between the Cassini mission and the Voyager missions,

besides Cassini having more cutting edge equipment on it,

is that it was an orbiter.

It orbited Saturn for 13 years.

The Voyager missions just flew past it.

[narrator] Cassini watches the pole for several years,

capturing thousands of image of the hexagon.

[Phil] The beauty of the Cassini mission is th it showed us what the hexago

looked like years later after Voyager.

Didn't necessarily solve the problem of why this thing exists,

but it gave scientists a lot of ammunition to figure it out.

[narrator] Finally in 2020,

a team solves the mystery.

Many cyclones surround a large jet stream of the planet's north pole.

Where the two weather systems meet,

a hexagon cloud forms.

Something we don't see here on Earth.

[Carly] The trouble with the Earth is it has a lot going on.

We have oceans, we have mountains,

all of that disrupts the atmosphere.

On Saturn, there isn't any of that.

So you're able to have thes very stable airflows

that just wouldn't be possib on the Earth.

[chuckles] Nature's pretty wonderful.

[narrator] Next, the Voyagers turn their gaze to Saturn's rings

Their images are gamechanger

[Heidi] One of my colleague in my undergraduate planetary astronomy class

was a computer whiz.

And he managed to hack into the NASA feed that was going out.

We all piled into his dorm room,

the professors, the students

seeing images coming from the Saturn flyby.

[narrator] We thought that Saturn had just a handful of wide, flat rings.

Voyager's images reveal thousands of separate rings

orbiting the planet.

But there's an even bigger surprise.

An impossible ring.

When the F-ring of Saturn

close up image appeared on the screen,

and instead of being sort o a single ring,

it looked like multiple rings that were braided together.

And my professor, Irwin Shapiro,

famous planetary astronomer professor said,

"That's not possible."

[narrator] Scientists pour over the images

to figure out what's causin the bizarre structure.

Our basic understanding of rings back then,

was that they were collections of little particles

that were all just following the same orbit.

[Dan] You'd expect that syst to have settled out into,

you know, all the traffic on the highway, driving in the same direction,

parallel lanes, all nice and neat.

You don't expect these weird, dynamic interactions that are going on.

[narrator] Then, scientists find two clues

to explain the interactions

And one of the things that was discovered was two satellites

that orbit inside and outside of the F-ring.

Prometheus and Pandora.

It pointed to the idea that the moons and the rings were constantly interacting,

but it didn't really tell us how.

[narrator] Voyagers' discove of the moons doesn't solve the mystery

of the braided F-ring.

But it does tell the Cassini probe,

25 years later, where to loo

Cassini watches the tiny moo

looping and twisting around each other

as they orbit the planet.

When you have two little moons, sort of co-orbiting with the ring,

there's a complex gravitational dance that happens

with the inner moon wanting to speed up particle

the outer moon wanting to slow them down.

And that interesting gravitational dance

is what actually helps confine the ring into

the narrow structure that we actually see.

[Carly] By seeing these moons either side,

there was an idea that they could be shepherding,

they could be holding the ring in place.

[narrator] Saturn's many moo and complicated rings

are like a mini solar system

Now, the two Voyager spacecraft separate

to carry out two individual missions.

Voyager 1 heads off to explo the edge of the solar system

and Voyager 2 flies int the freezing cold

of Saturn's shadow.

For over two hours,

the giant planet blocks all contact with the space probe.

After a tense wait,

Voyager 2 emerges.

But something's wrong with the spacecraft.

[Linda] Picture after pictur of dark sky came back.

And we realized, something had either happened to the cameras,

or something had happened to the scan platform.

[narrator] The scan platform

the vital rotating joint tha points the probe's instrumen

isn't working.

But how can scientists fix a probe

2 billion miles from Earth?

[narrator] August, 1981.

Pioneering space probe, Voyager 2 , is in trouble.

Passing behind Saturn,

one of its key components, the scan platform, jams.

[Linda] The scan platform is kind of like your head and neck.

Imagine the cameras as your eyes.

And if you want to turn to look at something, you'd turn your head.

And your neck has to move.

[narrator] When Voyager 2 passed behind Saturn,

it ploughed through the ring at 29,000 miles an hour.

Maybe a chunk of ice damaged the platform.

Or maybe the maneuver gave the probe whiplash.

We had been so ambitious in looking at the moons and the rings and Saturn,

that we had literally squeezed the lubricant

out of the bearings of the scan platform.

And it got stuck.

[narrator] The broken scan platform could be fata

for the rest of the mission

[Linda] And so, we worried, "Could we fix it?"

We had Uranus and Neptune ahead of us with Voyager 2.

We wanted to be able to fix the scan platform.

[narrator] To fix it,

the engineers employ some space physiotherapy.

We slowly commanded it from Earth and got it to move a little bit at a time,

until finally we could get those beautiful outbound pictures of Saturn

that you see.

[narrator] With Voyager operational again,

NASA agreed to fund the next stage of the missio

[Heidi] I'm eternally gratef that NASA did decide to

complete the grand tour.

It was tremendous relief to know we had a healthy spacecraft,

Voyager 2,

to go on to Uranus and Neptune.

[narrator] 1986,

boosted by a slingshot from Saturn,

Voyager 2 arrives at Uranus

After nine years in space,

the probe is now in uncharted territory.

[Carly] Ahead of Voyager's encounter,

Uranus was really difficult to know much about

We knew what its color was,

but it didn't have any obvious features from the Earth.

It looked sort of like a generic green blob.

[narrator] We did know a couple things.

Uranus has rings

and sits on its side.

[Dan] Unlike most of the other planets,

whose spin axis are oriented more or less perpendicular to their orbital plane,

Uranus is tipped over on its side,

it rolls around the sun like a barrel at times.

There are other times when the sun is shining right dow the equator.

It's very unusual.

[narrator] In a flyby lastin just five and a half hours,

Voyager 2 discovers 11 new moons,

and two more ghostly rings circling Uranus.

But Voyager 2's strangest discovery

is the planet's freakish magnetic field.

Voyager carried a magnetic boom that told us about

the magnetic field of the planet.

And that turned out to be really interesting.

[narrator] The strength and direction of Uranus' magnetic field

turns out to be unlike any other planet.

[Phil] The Earth has a magnetic field

and it's pretty complicated how it behaves.

But you can think of it as if there's a giant bar magnet inside the planet.

There's a north magnetic pol and a south magnetic pole,

and magnetic field lines around them.

[narrator] On Earth, the bar magnet lines up clos to our planet's spin axis.

The Voyager probes foun the same in Saturn and Jupiter.

But Uranus' magnetosphere is different.

The north and south axis of the magnetic field is tilted

by almost 60 degrees,

relative to the spin axis of Uranus.

That's strange.

[Dan] If you imagine transforming the Earth's magnetic field to be like

the Uranus one,

you'd have the magnetic north pole near Miami someplace.

It's way out there in left field.

[narrator] And the magnetic field isn't just tilted.

[Dan] It's off center! The center of the magnetic field,

you think would be at the center of the planet,

it's actually offset by 5000 miles,

which is a lot.

We think it may be generated in the mantle of Uranus,

where there is molten water, not molten iron.

[narrator] Extreme heat and pressure breaks water molecules apart

and rearranges them into a molten crystal structure,

an exotic state called superionic ice.

When we talk about ice,

like, superionic ice inside a giant planet,

we're not talking about ice cubes. [chuckles]

Water has lots of different ways of being.

And some of them are really strange.

[narrator] The half liquid, half solid ice

swirls around in the outer layer of the planet,

moving like liquid metal.

Because the ice conducts electricity,

this produces the offset magnetic field around Uranus

Voyager 2 also uncovered a gigantic magnetic glitch

but it remained hidden in the data

until scientists discovered in 2020.

[Phil] What they found was a blip,

a strengthening of the magnetic field,

and it was about a million miles behind Uranus.

And whatever was causing this was quite large.

[narrator] It's a giant magnetic bubble,

250,000 miles across,

floating in space.

[Phil] This type of magnetic bubble is called a plasmoid,

and it happens when the magnetic field lines ge pinched off

and it can create, sort of a self-contained shell.

This means that the magnetic field around Uranus

is dynamic

and can fracture and interact with the solar win in very interesting ways.

This can also have some of the atmosphere of Uranus in it.

So, it's literally leaking gas into space.

Uranus is belching.

[narrator] It will take another mission to Uranus

to truly understand this strange world.

For now, Voyager 2 is the only spacecraft to ever visit.

And what awaits the probe ne

could be Voyager's greatest discovery yet.

[narrator] 1989, Voyager 2 makes one last flyby.

Neptune is the final stop on the planet hopping tour

of the outer solar system.

It's once in a lifetime opportunity

to study the blue ice giant up close.

[Heidi] We had these hints from our ground-based telescopes

that there was activity in the atmosphere.

But what its nature was,

what was it like?

There absolutely was nothing we had to prepare us

for what we were going to see.

[narrator] Voyager 2 spots four new rings and six more moons.

It detects hydrogen, helium and methane in Neptune's atmosphere.

And it records the fastest winds in the solar system,

pushing white clouds across the planet

at up to 1500 miles an hour

And at their center,

a colossal dark storm.

[Heidi] There was a dark spo

A big, dark spot on the disc of Neptune.

We hadn't seen anything like that from the ground. [laughing]

It was like, "What is that?

Uh, we called it "The Great Dark Spot" because...

that's all we could think of at the time.

[narrator] Five years later

when astronomers looked for the Great Dark Spot wit the Hubble Space telescope,

they get a surprise.

[Heidi] I was gonna look at how it changed with time

and, you know, where it was located, things like that.

And I remember, I got my first images back from Hubble.

No Great Dark Spot.

It was gone.

It simply wasn't there.

[laughs] I'm like, "What happened?"

How is this even possible?

The great Red Spot on Jupiter's lasted for hundreds of years.

This is only five years, and this huge feature

was simply gone.

[narrator] Since Voyager,

we've seen seven different dark spots on Neptune's surface.

None lasting more than a few years.

As to why that is and what's driving that,

um, those are still mysteries that we haven't fully solved.

[narrator] Before leaving the Neptune system,

Voyager 2 turns its gaze to Neptune's largest moon,

Triton.

It was sort of a bit like, Voyager's last hurrah,

sort of one of the last things that it showed us, and it was just phenomenal.

[narrator] Voyager 2's instruments reveal a frozen world.

At 391 degrees below zero,

Triton is one of the coldes objects in the solar system

[Linda] Here was a very intriguing world.

We saw these dark streaks on the surface

and realized that they were actually sticking up above the surface.

What they were seeing was an active cryo volcano

jetting a jet of black material,

something like eight miles up above the surface of Triton.

And then, the atmosphere of Triton was sheering it ou into a large cloud pattern.

That was one of our first indications

of geyser-like activity on a planet other than the Earth.

It was almost pandemonium

trying to figure out how do you generate this kind of activity

on a moon that should be cryogenically frozen solid.

Where is the energy source for this?

[narrator] In 2019,

scientists finally identify

frozen nitrogen and carbon monoxide in the streaks.

We think now what actually is going on there is it's the action of sunlight

shining in some of the darker deposits on the surface of the moon.

Just a little bit of a temperature change

can take the nitrogen and liberate it off the surface.

[narrator] In their grand to of the solar system,

the Voyager probes produ an astounding number of discoveries.

[Dan] Volcanoes on Io, geysers on Triton,

and little weavy features on the Rings of Saturn,

it all turned out to be far, far more interesting and alive

and dynamic than we ever imagined.

[narrator] While Voyager 2 leaves the planets behind,

its twin, Voyager 1, heads to the edge of the solar system.

But not before taking one last snapshot of home.

A family portrait.

[Phil] This idea by Carl Sag to take this family portrai

is just magnificent.

And the scientific need for it may be limited

but the appeal to our sense of beauty,

is staggering.

[narrator] This shot isn't in pursuit of a new discover

It's about finding a new perspective.

[Phil] This family portrait is a series of 60 images

put together into a mosaic.

And in it you can see the sun and six planets,

Venus, Earth, Jupiter, Satur Uranus and Neptune.

As we're sending the images, we noticed along one of these sunbeams,

there was the Earth.

That pale blue dot,

which contains every single person.

We realized just how tiny our planet is.

And how very special.

It's one of the most amazing and beautiful things I've ever seen.

[narrator] February 1990,

the cameras power down for the last time.

But this mission isn't over

The Voyager probes are about to reach the edge of the solar system,

a region no spacecraft has been to before.

[narrator] Far from the sun

at the very edge of the solar system,

lies a vast expanse

where no human-made object has ever entered.

Until the Voyagers.

This is like early explorers leaving sight of land.

They are just surrounded by a vast ocean of night.

They are all alone.

It's sort of like the boat going from the bay, out into the open ocean.

It's a whole different environment.

[narrator] The Voyager pro are about to leave the calm of the solar system

and enter the stormy waters of the galaxy.

They start to exit the heliosphere,

a protective bubble around the whole solar system

and cross into a combat zon

that hosts a cosmic battle between the sun and interstellar space.

Inside the heliosphere,

waves of particles from the sun,

called the solar wind, push outward.

Outside, an ocean of gas and particles

pushes back.

As the solar wind is expanding away from the sun,

it's pushing against this thin stuff between the stars

the interstellar medium.

[Paul] That's the last influence that the sun has

in the bubble surrounding it.

Once you cross that, you are in interstellar space.

[narrator] The heliosphere' frontline protects us

from one of the galaxy's deadliest weapons,

high energy particles called cosmic rays.

Cosmic rays are like tiny bullets

and they travel at close to the speed of light.

[narrator] December 2004,

Voyager 1 detects a sudden drop in the solar wind,

evidence that the space prob is nearing the heart of the battlefield,

a region known as the Termination Shock.

[Paul] The Termination Shoc is the region

where the solar wind starts to meet resistance,

starts to run into something.

And that causes it to slow down.

[narrator] Voyager 1 picks u surges from both opposing forces,

blasts of cosmic rays,

followed by waves of the solar wind.

The instruments onboard Voyager didn't just suddenly change from

sun space to galaxy space.

It actually kind of went back and forth several times

as it was measuring the energies of the particle at that region.

[narrator] This suggests tha the edge of the heliosphere

is not a single battlefront

but rather, a complex regio of skirmishes.

A sea of gigantic, magnetic bubbles

created by the sun's magnetic fields.

The sun's magnetic field rotates with the sun, physically.

But this far out, billions of miles from the sun,

those magnetic field lines get dragged by particles

and there's a lot of different effects on them.

And they can get tangled up and loose.

This creates bubbles,

and some of these bubbles are a hundred million miles across.

[narrator] The magnetic bubb boundary is not watertight.

Some cosmic rays blast through.

[Paul] This heliosphere is much more foamy than we had thought.

There are gaps in our defens

where deadly cosmic rays can find their way through

into the inner solar system

[narrator] The foamy defensi line blocks 90 percent of cosmic rays

but allows 10 percent throug

As Voyager 1 passes throu the battlefield,

it detects fewer and fewer solar particles.

Eventually, there are only cosmic rays

and interstellar space.

In 2012, the probe becomes humankind's first object

to leave the solar system,

followed in 2018 by Voyager.

It's been 50 years since the first satellite

poked their way out of the Earth's atmosphere.

And now, both Voyager spacecraft

have poked their heads out of the sun's atmosphere,

are outside the solar system

and exploring the galaxy.

[narrator] The Voyagers cr the final frontier

and sail the ocean between the stars.

They don't see their first discovery,

they hear it.

In space, no one can hear you scream.

There is no actual soundwaves moving around.

But there are waves of plasma.

Of electrons.

[Phil] So, as Voyager pas through this, we can transla

these changes in the plasma density to soundwaves.

[deep space sounds]

[narrator] This is the soun of interstellar space.

Poetically, I kind of like to think of it as the song the galaxy is singing,

welcoming Voyager to interstellar space.

[Paul] Some of the sounds may even come from distant supernovas.

Think about that, a star dyi

tens of thousands of lightyears away

and here's an echo of it, here.

[narrator] The sounds of deep space tell us more abou our part of the galaxy.

[Paul] As Voyager travel through the interstellar medium,

we can use these sounds to map out its local environment.

And since 2017, we've been mapping how these sounds get higher,

and lower and higher, louder and softer,

and it's telling us that the interstellar medium is not uniform at all.

[narrator] Built to last five years,

Voyager 1 and 2 are now more than 40 years old.

Only one final mission remains,

perhaps the most important mission.

To let the rest of the galax know we're here.

[narrator] The Voyager spacecraft are now outside the solar system.

Our sun is just the brightest star among man

How much longer can the prob keep going?

[Linda] A limiting factor on the mission has turned out to be power.

And every year there are four watts less power

to run each of the Voyager spacecraft.

There are no service stations out there, no way to,

you know, repair things that go wrong.

And it's really remarkable, the fact that they're still out there,

in the cryogenic cold,

you know, operating, they're still working.

They're still alive.

[narrator] In just five year there may be too little powe

to transmit signals to Earth

After a final message home,

the Voyagers will fall silent forever.

This part of the Voyager mission,

flying in interstellar space,

is the long goodbye.

[Dan] They're gonna become our messages in a bottle.

Little bit of humanity,

you know, representing us when we're long gone.

[narrator] The two probes could survive for billions of years.

They could be not only, you know, interstellar voyagers,

they could turn into intergalactic voyagers, ultimately.

[narrator] Maybe the Voyages won't just drift forever.

Maybe they'll be found.

[Michelle] It was kind of a wonderful little jaunt of imagination.

that maybe some alien civilization with incredibly powerful telescopes

might notice that there's a little artificial object

flying through space and be curious about it.

[narrator] Strapped to each Voyager is an aluminum case

On the outer side, is a map of how to find Eart

with directions from different pulsars.

[Michelle] So why use pulsars to direct the aliens to our location?

These are the dead cores of stars after a supernova explosion.

Well, amazingly, pulsars all spin at slightly different rates

So, if you can actually triangulate your location,

based on the rates of different pulsars in the sky,

you can actually have sort of a galactic GPS system.

You can show the aliens where we are with incredible accuracy.

[narrator] Inside each case

a gold plated copper disc.

[Michelle] Looking back on i

it's really kind of this wonderful part of humanity.

We sent aliens out there,

unimaginably, technologically advanced aliens,

we sent them, basically, a vinyl record.

[Paul] Yeah, the golden disc are literally discs.

They actually are records with grooves.

You can play them. You can jam out to them.

It's got a soundtrack of our species.

[Beethoven's 'Fifth Symphony' plays]

[narrator] The records have tracks by Beethoven,

Blind Willie Nelson and Chuck Berry,

the sound of surf, of thunde of birdsong,

and a human heartbeat.

So, will aliens ever find the records and give them a spin?

[Phil] The Golden Record is a lovely idea.

Especially to energize and excite the public about this.

Will it ever be found?

There's a reason we call it space.

[narrator] A tiny, cold spacecraft

is a difficult target to fin

Any species capable of detecting them,

would have a better chance of spotting our planet.

But the Voyagers will long outlive Earth.

[Michelle] It's possible tha they will find it millions,

or even billions of years in the future.

Long after we are gone.

When there really aren't humans anymore.

Or is there even a possibility that when we start traveling to the stars

in the far future, we'll find them.

[narrator] Awaiting discover

or doomed to drift alone,

the Voyager probes have already inspired one civilization,

ours.

Calling these " Voyager "... [kisses] ...it's perfect.

Because that's what they are doing.

They are voyaging out to the outer solar system and beyond

and showing that there is no end to our desire to explore.

[narrator] They've shown us countless wonders of the solar system

and a glimpse of what lies beyond.

[Heidi] We, as a species,

can build ships

that not only sail the oceans of our Earth,

but that can sail outwards,

to the other planets in our system

and reveal new worlds.

[narrator] They are the greatest space mission ever

[Paul] The legacy of Voyagr is our remnant.

It is our memory.

It is a sampling of humanity

that is out there now among the stars.

[narrator] And if they last until the death of the Universe,

as the final stars fade,

and everything goes dark,

they will be humanity's final statement,

"We were here."