Original subtitles

MAN: T minus 40 seconds. Everything looks good for launch.

NARRATOR: Got time for a 24-year vacation?

Then consider a journey

to the most distant planets of our Solar System.

WOMAN: The rest of the solar system beyond the asteroid belt

is really where it's at.

NARRATOR: They are two giant worlds of icy gas.

And one of them has a funny name.

WOMAN: I pronounce the planet's name YOOR-a-nus.

NARRATOR: From orbit, Uranus appears sedate and calm.

But why is the planet on its side?

And Neptune--the second blue planet, and the last world in our solar system.

So far from the sun, you wouldn't expect much to be happening here.

But something is driving its wild winds, the fastest in the solar system.

And what became of its Great Dark Spot?

WOMAN: So this planet just changes its spots.

Leopards don't, but Neptune does.

NARRATOR: Uranus and Neptune: the ice giants.

Strap yourselves in for an incredible voyage

to the most remote and intriguing planets of all.

There has never been a better time

to boldly go where no human has gone before,

to follow in the footsteps of our robot pioneers

and visit the planets of the solar system.

MAN: T minus two minutes and counting.

MAN: Go at throttle up.

NEIL ARMSTRONG: That's one small step for man...

MAN: Oh, man, that's incredible!

NARRATOR: Ever wanted to be an astronaut?

Imagine heading into the ice zone,

the frigid, dark realm beyond the orbit of Saturn.

To travel here means undertaking a voyage of epic proportions.

Think of this as your personal travel guide to the outer solar system.

First stop, Uranus.

At first glance, the seventh planet from the sun

appears as an unmeasurable ball of green-blue fog.

But slip below Uranus' icy veil

and you encounter a world seemingly without end...

because this is a planet made almost entirely of gas:

hydrogen, helium and a splash of methane

that gives the planet its color.

TORRENCE JOHNSON: It's actually very difficult to describe to people

what it feels like in the interior of these gas giant planets

because it's so far from our terrestrial experience.

NARRATOR: The third largest planet has at least 13 rings.

But unlike the broad bands of Saturn, these are thin and dark.

No one's quite sure how they formed,

but they could be the result of collisions

between its small army of at least 27 moons.

But Uranus' most striking feature is its lopsided tilt.

It's the only planet in the solar system to orbit on its side,

resembling a giant bull's-eye.

How did it end up this way?

The answer may surprise you.

HEIDI HAMMEL: I'm fascinated by Neptune and Uranus

because we know so little about these planets.

We've only ever had one spacecraft visit them,

and it was a very brief flyby.

NARRATOR: Astronomer Heidi Hammel is driving to the ice giants--

well, about as close as you can get to them on planet Earth.

HAMMEL: The most exciting thing about Uranus

is that it's completely tilted over on its side.

Its atmosphere changes radically, depending on the season.

And it has a really interesting thin ring system.

So that's the cloud, and these, of course, are the rings.

It's a nice image of Uranus.

NARRATOR: Although separated by 1.6 billion miles,

one of the world's highest telescopes is watching the planet spring into life.

HAMMEL: Uranus has been going through a very special season that we call equinox.

The north polar part that's coming into sunlight

for the first time in two decades

is turning on with all kinds of dynamic cloud activity,

none of which was expected or predicted.

So it's very exciting to get this data

and basically be rewriting textbooks about the Uranus system right now.

We're very happy astronomers.

NARRATOR: For the first time,

this far-flung outpost is being seen in a new light.

And when it comes to image, it's not a moment too soon.

That's because, for most of us, Uranus is the butt of a big cosmic joke.

ANDY INGERSOLL: | pronounce it YOOR-a-nus.

| think people are embarrassed by Your-ANUS.

CAROLYN PORCO: YOOR-a-nus.

Yeah.

HAMMEL: | pronounce the planet's name YOOR-a-nus,

which is very likely closer to the original pronunciation

of the name of the god after whom it was named.

NARRATOR: If you think "Uranus" is a funny name for a planet,

then you may prefer its first name--

"George."

Discovered by William Herschel in 1781,

he christens his new find "Georgium Sidus" after the King of England, George Ill.

But the custom of naming planets from ancient mythology prevails,

and Planet George is no more.

And it's very likely that Uranus would have remained

nothing more than a green-blue blotch at the end of a telescope

if it wasn't for a really bright rocket scientist...

and a little bit of luck.

GARY FLANDRO: A lot of people were saying back in the ‘60s

that it would be impossible for us

ever to explore those distant planets-- too far away.

NARRATOR: As an intern at the Jet Propulsion Laboratory in California,

Gary Flandro is given the task

to investigate a journey to the outer planets.

FLANDRO: So | started drawing pictures of the solar system.

And in that process | noticed that all of the outer planets

turned out to be about the same alignment relative to the Earth in the late '70s.

So | saw that | could almost draw a ruler

between Jupiter, Saturn, Uranus, Neptune.

Pluto was not cooperating, but that seemed not to be a worry.

NARRATOR: This mathematical sleuth work reveals a rare window

where the planets are perfectly aligned for a visit.

EDWARD STONE: There's an opportunity every 176 years

for a single spacecraft to fly by all four giant planets.

That was 1977, and so we created the Voyager mission to start on that journey.

FILM NARRATOR: A complex package of experiments called Voyager

is designed to take the first thorough close-up look at the giant outer planets.

NARRATOR: In an extraordinary feat of engineering,

teams build two spacecraft in just 12 years

and pushed the existing global network of ground stations to new heights.

JOHNSON: The outer solar system is called "outer" for a reason.

It's a long way away.

PORCO: The rest of the solar system beyond the asteroid belt

is really where it's at.

And so that's what Voyager did.

Voyager showed us what was out there.

NARRATOR: On board, there's even a gold record

containing a greeting from Earth,

should the spacecraft encounter any friendly aliens.

CHILD: Hello from the children of planet Earth.

WOMAN: Bonjour, tout le monde.

WOMAN: Kon'nichiwa. O genki desu ka?

MAN: Hola y saludos a todos.

STONE: We knew the Voyagers were going to be the first to reach interstellar space,

so we felt that this was sort of an announcement from Earth

that we were now able to send a message away from our solar system

into orbit around the center of our own galaxy.

NARRATOR: Launched a few weeks apart in 1977,

the twin Voyager spacecraft embark on their epic journeys,

known as "The Grand Tour."

PORCO: It was a first, it was historic.

Just being part of the whole mission, being part of this tremendous enterprise,

the first time in human history we are seeing these bodies up close

was a thrill.

NARRATOR: What would it be like to follow in the footsteps of Voyager,

to experience one of the greatest journeys in space exploration?

63 times larger than the Earth,

here you'd be lucky to celebrate a single birthday.

The planet takes 84 years to make its way around the Sun.

Uranus and sister Neptune are known as the "ice giants"

because of their frigid outer atmospheres,

super-cooled to minus 355 degrees Fahrenheit.

But the biggest, most obvious feature about Uranus is its crazy tilt.

However, it wasn't always this way.

JOHNSON: The traditional explanation was that while Uranus was forming

it may have been hit by a larger chunk of accreting material than normal

and actually knocked it over on its side.

The problem is, when you do the maths on this, it doesn't work.

It's very, very difficult to get a large enough body

traveling fast enough to be very credible at knocking Uranus over on its side.

NARRATOR: Rather than being pounded,

it's now thought that Uranus may have been swept off its feet

by the gravitational tugs of its giant neighbors.

JOHNSON: Uranus' tilt actually results from rather complicated interactions

with Saturn, Neptune and Jupiter, even.

All of these planets do have gravitational effects on one another,

and the effects are more subtle than we used to think.

And it's dynamics,

not a big smack in the face from a large impacting planetesimal.

When Voyager journeys to the outer solar system in the 1970s,

it beams back astounding images of Jupiter, Saturn and many of their moons.

STONE: The wonderful thing about the Voyager mission,

we saw so many things for the first time,

and they were all so different, so diverse and distinctive.

JOHNSON: Being there when the images are coming in

makes you feel like you're on the bridge of the Starship Enterprise.

Because you really feel like you're there, those are just your sensor screens,

and you're getting reports back

from these alien worlds that you're taking a look at.

WOMAN: Who could ever have enough pictures of Saturn's rings?

NARRATOR: So what do Voyager's cameras reveal of Uranus, the lopsided planet?

JOHNSON: Well, Uranus was a real enigma for us.

So we didn't know what to expect.

NARRATOR: In 1986, after a decade of traveling through space,

there are great expectations for the seventh planet from the sun.

BONNIE BURATITI: From the Earth it looked kind of bland.

And quite frankly, from Voyager it looked kind of bland, too.

HAMMEL: The images of Uranus were a little bit disappointing.

STONE: It's a very bland planet with very few clouds.

FLANDRO: Not much going on at Uranus.

NARRATOR: These are the first images of Uranus, taken from Voyager 2.

The planet appears as still as a pond with no cloud detail at all.

And it's silent.

JACK CONNERNEY: We did not hear a whisper from Uranus before the Uranus encounter.

NARRATOR: Unlike Jupiter,

whose magnetic field roars across the radio waves,

at first Uranus doesn't make a peep.

CONNERNEY: Part of that was because the radio source

was on the other side of the planet where the strong magnetic fields are.

And they were beamed away from the spacecraft.

NARRATOR: Voyager discovers that Uranus’ magnetic field is wildly off kilter.

Planetary magnetic fields require the movement of charged particles.

On Earth, this occurs in our molten iron core.

So what's driving Uranus' magnetic field?

There's more going on here than meets the eye.

Just what lies below Uranus' veil of clouds?

To find out means clearing your calendar for the next 24 years

and surviving a flight from hell.

You've escaped the clutch of Earth's gravity,

the first step on your voyage to the outer solar system!

Now, the seatbelt sign is off, but your problems are just beginning.

Zero gravity may look fun, but when it comes to human biology,

we're simply not designed to be in the weightlessness of space.

VOLKER DAMANN: If there is no gravity,

then there is no need for the heart muscle to pump the blood upwards,

so the heart muscle doesn't need to work as hard, so it's de-conditioning.

The same happens with all the muscles.

If you are not working and exercising and working against the drag of gravity,

you're de-conditioning.

NARRATOR: From this control room in Germany,

a medical team scrutinizes the health of the European astronauts

aboard the International Space Station.

DAMANN: The astronauts work out roughly two hours per day.

It's a mandatory physical exercise that we prescribe.

Some people like more to ride the bicycles, others like to use the treadmill.

NARRATOR: Zero gravity for 24 years?

That two-hour daily workout will soon get pretty tedious.

The fact is, no one really knows what effect

two dozen years of weightlessness will have on the human body.

No one has ever been in space that long.

KEVIN FONG: Human missions to the outer planets are going to take years,

maybe more than a decade.

And none of these places support life on their own.

You're going to take everything that you need with you.

You're going to need to take your food, your water, your light, your heat,

your power, your atmosphere, and that's a tricky thing to do.

NARRATOR: And the one item you'll need more than anything is water.

KAREN PICKERING: If you were just to put everything you need in a box

and take it to space with you for a year,

about 90% of the mass you need is water.

NARRATOR: To solve the problem, NASA has been working on its recycling systems.

But it may not suit everyone's taste.

PICKERING: We take waste water streams from a variety of sources.

We take hygiene water from your showers,

washing your hands, brushing your teeth, urine, of course.

And then we can choose several different processes

to bring that waste water clean enough that we can drink it again.

The clean water tastes just like water you'd buy in the grocery store,

though it's distilled, so it doesn't taste as good as the water from your tap

because there's no minerals in it.

But it doesn't taste like waste water, like you know where it came from.

NARRATOR: So with your thirst quenched, you're on your way.

Sit back and relax for the next ten years.

From orbit, Uranus gives little away.

But plunge below its placid-looking clouds

and you encounter a world that's anything but.

HAMMEL: So let's imagine | was riding an atmospheric probe

that's being sent down into the planet Uranus.

NARRATOR: Open your spacecraft window here,

and you'll quickly feel where the ice giants get their name.

In the upper atmosphere, frozen crystals of methane mix with hydrogen and helium.

HAMMEL: We might pass some of these towering anvil clouds

that we know are there.

And as we looked at those we would look for the lightning,

we would listen for the thunder that would accompany them.

NARRATOR: Freefalling here is like descending into a giant green gelato.

But the deeper you go, the thicker and hotter the atmosphere.

Temperatures heat up to thousands of degrees,

heat left over from when the planet formed.

STONE: Eventually the pressure just builds,

and the gas becomes basically a fluid or a liquid.

And there's no real transition,

it's just a continuous increase in pressure and density.

NARRATOR: Keep descending and you'll soon start to boil

in a seemingly bottomless sea,

more than 2,000 times deeper than the Pacific Ocean.

Somewhere down here, a little more than halfway to the planet's center,

Uranus' lopsided magnetic field flutters into life.

CONNERNEY: If you could see down to the surface of the dynamo core,

where the field is generated,

what you might see is parcels of fluid moving about.

And they're generally so conductive

that those parcels of fluid would drag field lines with them.

NARRATOR: Why Uranus' magnetic field is generated here,

and not in the core, no one really knows.

No person or robot has ever been down here.

HAMMEL: If we could get even further we might get to a core, but we're not sure.

Isn't that interesting? We aren't sure if Uranus has a core.

NARRATOR: Down here, one thing is certain:

with a planet-load of water and gas on your back,

and in temperatures of more than 4,200 degrees Fahrenheit,

no life, or robot, will last long.

JOHNSON: There would be no chance of surviving under those conditions.

A probe going into the atmosphere would eventually actually evaporate

and become part of the atmosphere that it was studying.

NARRATOR: Not enthused about the prospect

of being crushed and boiled alive by a giant ball of gas?

Don't worry, there's still plenty more to see and do.

Cruise above the skies of Uranus, and take your pick of 27 moons,

most named after characters from Shakespeare.

HAMMEL: If | were to take a tourist trip to the Uranus system,

| would go to Miranda.

NARRATOR: Only 290 miles across,

moon Miranda is about as wide as the state of New York.

But the geography here is stranger than anything on Earth.

JOHNSON: It's an interesting sort of jigsaw puzzle moon.

It looks like it's been put together by a potter

with not paying too much attention to his materials.

It's got chunks of this and chunks of that,

that sort of look like they are slapped together.

And frankly we still don't really understand Miranda too well.

NARRATOR: When Voyager first spots Miranda,

no one is sure what to make of it.

ROBERT PAPPALARDO: When the images came back of Miranda,

the first ideas were that Miranda was somehow shattered by a huge impact,

broke up and came back together.

NARRATOR: But now scientists think that the moon

may be caught in the middle of a cosmic makeover.

PAPPALARDO: In the early stages of a satellite's history,

the satellite is differentiating.

The rocky bits are falling to the center,

and the icy bits are lower density and moving outward.

And so maybe that's what we're seeing--

Miranda sort of frozen in, in a state of differentiation.

NARRATOR: The result: a part-finished lunar construction zone,

with some pretty impressive sites to visit.

JOHNSON: Miranda's got some spectacular ice cliffs on it

that you could sit on the top of and look down for five or six kilometers.

NARRATOR: Think the Grand Canyon is impressive?

On Miranda, these cliffs are at least three times higher.

PAPPALARDO: If you were to jump from it,

because of the very, very low gravity of Miranda,

it would take minutes to slowly fall down to the surface.

JOHNSON: With this nice blue fuzzy ball of Uranus in the background,

it might be pretty scenic.

NARRATOR: And while you're here,

it's hard to ignore Uranus' other tourist attraction,

its collection of 13 razor-thin rings.

HAMMEL: Uranus' main rings are very tightly confined

with a lot of space in between them, sort of like a series of hula hoops,

increasingly large hula hoops moving away from Uranus.

NARRATOR: How these rings form, no one's completely sure,

but they could be the result of a cosmic demolition derby.

BURATTI: The five major satellites of Uranus

are in pretty regular orbits, and they are stable.

But some of the other objects, especially the outer satellites of Uranus,

scientists have been working on computer models

that show they do frequently collide.

And if they get too close to Uranus, they could break apart.

And of course Uranus does have a very complex family of rings

that we believe is broken-up satellites.

NARRATOR: For the planet that's always been the butt of everyone's joke,

perhaps it's only fair that it has the last laugh.

That's because Uranus' best view is its rear end.

LINDA SPILKER: As we were flying out from Uranus,

we were looking back and looking at the rings

at what we call "high phase angle."

It's equivalent of if you have a dusty windshield

and you drive into the afternoon sun, the dusty particles light up.

So, too, in the Uranus system.

| remember sitting there as that picture came down,

you know, line by line and played out,

and just the joy that, "Oh, my goodness, we didn't know

there was something quite so spectacular to see there at Uranus."

NARRATOR: Take a good last look,

as there's nothing more to see for three more years...

until you arrive at Neptune.

Make sure you have plenty to keep you busy;

being cooped up in a tin can is sure to play tricks on your mind.

FONG: Out in space, separated by such great distances,

you need to start thinking about the psychology

of the space environment.

You're going to be in a close, confined environment

with almost no privacy.

Death is always going to be just a hull's thickness away,

and you have to start thinking about how you can stop your crew's going crazy.

ASTRONAUT: Wooh!

[applause]

NARRATOR: The possibility of going crazy

is something these space travelers know all about.

MAN: Congratulations to the explorers,

to the mission organizers and to the scientists.

NARRATOR: The heroic welcome

is to celebrate their return from a 105-day space mission.

Only thing is, they haven't traveled an inch.

SIMONETTA DI PIPPO: The Mars 500 program

is a simulation project of a mission to Mars.

What we would like to do is to simulate the time delay,

the confinement, the psychological and physiological aspects.

NARRATOR: Sealed away in this Moscow warehouse,

the crew lived every day

as if they were on a long-haul space flight for real.

Watching closely, a team of psychologists and doctors

who monitored every aspect of their mental health.

OLIVER KNICKEL: It was not always easy to stay

in such a confined area for such a long time.

So you always felt kind of limited,

since the space is just limited.

You didn't have the sunlight,

you didn't have the nature.

So this had quite an impact on the crew.

NARRATOR: The psychological effects from this mission of the mind

are still being analyzed.

No one seemed to go crazy on this mission.

But on a voyage to the ice giants, if the isolation doesn't make you insane,

the menu might.

KNICKEL: In order to keep us healthy,

and we hardly had any fresh fruits or vegetables,

we ate this baby food here.

Which might not be the usual food you have in your usual life,

but at least it's kept us healthy,

and | didn't even think it tasted too bad.

NARRATOR: 105 days eating baby food is certainly an achievement.

But who is going to do that for 24 years?

Moving out from Uranus is its ice sister, Neptune,

another mysterious ball of frigid gas.

PORCO: Unlike Uranus, Neptune was immediately beautiful.

Especially when we started to produce color pictures,

because it had this blue-green atmosphere

and these white clouds floating in the atmosphere.

So you couldn't help,

at least | couldn't help but be reminded of the Earth.

NARRATOR: At 30 times the distance of the Earth to the sun,

the star appears not much more than a glimmering point of light.

Out here, the days pass quickly, each 16 Earth hours long.

But you'll need a thick calendar,

with around 90,000 days to a Neptunian year.

That's 165 Earth years to orbit the sun.

Like its neighbor, Neptune is a giant ball of hydrogen and helium,

its color courtesy of a bit of methane.

But it's so blue here that some other chemical mixture is at work.

HAMMEL: In fact, there's something in the clouds of Neptune

that is causing its vivid blue color,

and we don't know what that is yet.

It's one of the mysteries that we're trying to solve

by studying Neptune with our telescopes on the ground and in space.

NARRATOR: And that's not the only mystery:

Something is driving Neptune's wild winds,

the fastest in the solar system.

And why do Neptune's spots vanish almost as quickly as they appear?

JOHNSON: As we were approaching Neptune,

and it was getting larger and larger in the TV screens

in the Voyager project area,

the thing that really got us going very rapidly,

we noticed that Neptune had something that Uranus didn't,

which was a big spot in its atmosphere.

INGERSOLL: Voyager saw several spots,

the biggest one we imaginatively called "The Great Dark Spot."

JOHNSON: It kind of was like watching a blob of ink in swirling water.

NARRATOR: About the size of Earth,

the Great Dark Spot is actually a massive hole,

a window to the darker clouds below.

HAMMEL: So a swirling storm that cleared out a hole in the clouds,

allowing us to see down to deeper layers.

It didn't give the appearance of being stable.

It sort of gave the appearance that at any moment it could fall apart.

And so we weren't all that surprised when within five years it had disappeared.

NARRATOR: In 1994, when NASA turned Hubble, its orbiting telescope,

towards Neptune, its Great Dark Spot had vanished.

HAMMEL: So this planet just changes its spots.

Leopards don't, but Neptune does.

It dramatically changes its spots on timescales of just five years.

That was a surprise that Neptune changes so quickly.

It's a different kind of planet.

NARRATOR: Since then other spots have come and gone.

No one is sure why,

but it could have to do with Neptune's wild equatorial winds.

Take a leap into Neptune's atmosphere,

and you'll be surfing the fastest skies in the solar system.

This wind tunnel in Los Angeles

is barely a ripple of air compared to Neptune's winds.

Because on the last planet in the solar system,

winds roar around the equator at nearly twice the speed of sound.

INGERSOLL: What drives the weather? There's two things.

One is the sun, just kind of like the Earth,

although the sun is pretty weak at Neptune.

And then Neptune has some leftover heat.

And the heat comes out as warm gas.

When the planets formed, all this material came crashing together.

And that crashing together generated heat.

And some of that heat is still there buried down inside Neptune.

And when the heat inside Neptune comes out,

you get updrafts,

and that drives the jet streams

and the whole thing is a big weather machine.

NARRATOR: With no bulky land masses to stop them,

Neptune's jet streams keep going and going.

PORCO: It could be that the winds on Neptune just grew over time.

They kind of developed over time to be very rapid,

even though the energy that started them off was very feeble.

NARRATOR: But what's underneath the sheath of Neptune's ferocious winds?

Does the planet that takes its name from the god of the ocean

live up to its reputation?

Can you really set sail on a Neptunian sea?

HAMMEL: Just about everything about Neptune and its system

relates to water in some way.

NARRATOR: One thing most experts agree on

is that Neptune has plenty of water.

However, exactly what form it takes is less certain.

But it's something almost everyone has an opinion on.

INGERSOLL: There's a lot of water on Neptune,

but it's down deep,

and it's probably too hot to be a liquid right now.

NARRATOR: Down here it's like soaking in a planet-sized steam room.

Gas is squeezed into a liquid.

JOHNSON: Not an ocean, but sort of a strange mixture

of atmosphere heavily laden with denser and denser liquid materials

as the pressure got higher.

HAMMEL: If there were an ocean on Neptune,

it would be very deep inside the planet.

It would not be on the outer part of the planet

where we could put a spacecraft or a boat like this.

NARRATOR: On Earth, the combination of heat and water

is essential for life to exist.

So what are the chances of meeting any locals here?

FRAN BAGENAL: You've got some warmth, you've got hydrocarbons,

you've got water.

You could well have developed some life form.

Somehow | suspect it's not going to be particularly sophisticated.

But who knows?

Maybe there are big stingrays swimming around deep in the ocean.

NARRATOR: Not a fan of the deep?

Don't worry.

Like its icy neighbor,

there's plenty more to see and do without getting your spacesuit wet!

PORCO: Those of us who are interested in rings

got teased mercilessly as we were on approach to Neptune

because it wasn't clear Neptune had rings per se.

They were just impartial arcs is what the mindset was,

that was our idea.

And then finally when we got there we did find Neptune had diffuse rings,

complete rings, but also these rather opaque ring arcs.

NARRATOR: Neptune's rings may not be the prettiest in the Solar System,

but they're still worth a snapshot or two.

HAMMEL: Neptune's rings are clumpy.

There are sections that are very bright and sections that are very thin.

SPILKER: These particles are very dark.

There might be water ice mixed with some organics,

or maybe just organic material.

They only reflect a few percent of the sunlight that they receive,

so very, very dark.

Very different from Saturn's bright, icy rings.

NARRATOR: It's thought these gangly ring arcs

are kept in check by the gravity of tiny satellites,

known as "shepherd moons."

PORCO: This was something in fact | was personally involved in,

in trying to understand how the arcs were there.

And we found that they were being anchored by one of the moons,

the moons that in fact Voyager had found in the ring region.

SPILKER: As a ring scientist I'd be very interested

in collecting some souvenir ring particles.

And so | would probably try and get a space-worthy jet ski equivalent

and then go to explore the rings of Neptune.

NARRATOR: Neptune's ring arcs are one of a kind in the solar system.

But the real showstopper here is Neptune's moon, Triton.

Suspended animation has long been a favorite topic of science fiction.

Like the clients of this cryogenic facility in Arizona,

the space traveler of the future could well become a time traveler.

MARK VOLKER: The purpose is to hold them in a state of suspended animation

until such time as they can be reanimated.

NARRATOR: Inside these canisters are the frozen remains of 88 people,

all hoping for a second shot at life.

The problem with cryogenic suspension is that it's not very user-friendly.

You have to die first.

But for the space traveler of the future, that could all change.

VOLKER: So you could put them in a state of suspended animation,

put them on a spaceship,

and months or years later wake them up at the destination

so they wouldn't have to be alive and conscious

and eating and doing all the other things that you have to do when you're alive.

NARRATOR: Already scientists are working on ways to slow down metabolism.

CHENG CHI LEE: It's about two hours after we have injected the AMP,

and the mice now are in a deep hypothermic state.

NARRATOR: The mice, who don't normally hibernate,

are injected with a nucleotide that inhibits thermoregulation.

A state of hypothermia is then induced by lowering their core temperatures.

After around two hours, the rodents stir.

LEE: So what happens now is the mice is now in an arousal state.

NARRATOR: They're a little sleepy at first, but completely unharmed.

LEE: | hope that within ten years

we can run some of this in a human trial, somewhere down the road.

NARRATOR: Could this really be the future of space travel?

If we're to undertake the incredible journeys to planets like Neptune,

suspended animation may be the only practical solution.

But will a trip out here really be worth the time and fuss?

Well, some planetary scientists think it could be, if only to visit Triton.

PORCO: Well, | remember the night we flew over Triton.

We stayed up all night

because | think the flyby happened early in the morning.

And it was just so unusual.

PAPPALARDO: Oh, boy, Triton is an extremely complex moon

that we understand only in part.

NARRATOR: The largest of Neptune's 13 known moons,

Triton covered in a thin layer of ice...

its surface rippled and textured with features seen nowhere else.

PAPPALARDO: Triton has pits on part its surface

that's called the cantaloupe terrain

because looks a lot like the surface of a cantaloupe.

BURATTI: The other interesting thing about Triton is that it has a violent past.

It was almost certainly captured by Neptune.

The reason we're certain that it was captured

is that it is rotating,

it is going around Neptune in the opposite direction.

NARRATOR: And hiding in these fuzzy pixels

is Triton's biggest party trick of all.

Voyagers' camera captures geysers that shoot high into the air.

PORCO: It was found that there were jets coming off the polar cap of Triton.

And these things were going some 15 kilometers,

or 10 miles, into the air

and then taking a 90-degree turn as they hit a prevailing jet

in this very, very thin atmosphere.

PAPPALARDO: We're not sure if these plumes are powered

from the internal heat engine of Triton,

or are they actually powered by the very weak and far away sun,

which might be causing some local evaporation

to make these plumes.

NARRATOR: These are Triton's ice volcanoes

that purge an inky cocktail onto the gleaming surface.

HAMMEL: When we see black stuff in the outer solar system,

we think organic material.

Organic does not mean life or plants,

organic in our talk means carbon, carbon-bearing.

BURATTI: This is, these are the building blocks of life.

So we think that that dark material may be pre-biotic chemistry going on.

Not life itself, but the precursor to life.

PORCO: So here we find, even our last port of call,

Triton, you know, cold, cold, cold body.

And yet there is this activity going on.

NARRATOR: So you've finally made it to the outer solar system,

following the epic journey of Voyager 2.

After 12 years of traveling, what do you do on a short stop

before turning around and heading back home?

BURATTI: Well, if | were going to the outer solar system, going to Uranus,

| think first of all I'd want to orbit Uranus a couple of times

just to take in those rings.

Because | think that rings

are one of the most beautiful sights in the solar system.

JOHNSON: I'd go picnicking on Triton,

and I'd make sure that | took some really warm clothes with me

and some binoculars

because sitting on Triton

and looking at this beautiful blue Neptune hanging up there

would be quite a trip, actually.

WOMAN: And then I'm sure | would sit waiting for Old Faithful to go off,

however long that was going to take!

HAMMEL: By looking at the other planets in our solar system,

we can learn about planetary systems.

And | think that Uranus and Neptune have stories to tell us

if we can only hear their stories.

NARRATOR: They are the ice giants of the solar system:

two fathomless worlds, impossibly remote and unimaginably hostile.

Uranus: the planet with the funny name, but with hidden beauty.

And Neptune, a seemingly watery world with a spouting moon.

It's unlikely humans will venture out here anytime soon.

Until we do, who knows what other secrets await discovery in the ice?

That's the beauty of traveling the solar system;

it's full of surprises.