Original subtitles

Systems this is prop.

I read you 500, do you read me?

These people are watching their life's work come to an end.

The team is on its way to point.

On another world.

All right. Roger that.

They were all young when they sent her on her way.

These men and women have been traveling vicariously with her for more than two decades.

And now, her work is done, so she must die.

But before she takes the fatal plunge,

they've given her one final, epic challenge.

Gravity has a big bag of tricks,

none lovelier than the ring systems of worlds.

Our own solar system, alone, has four ringed planets.

This one, with the romantic name J-1407B,

is the first we've found circling another sun.

Why haven't we found more ringed planets in our galaxy?

Is it that the rings are so unusual,

or are the methods we use to find exoplanets not very

good at seeing the ring systems that may surround them?

J-1407B's ring system is so vast,

that it eclipsed its star for days.

These rings extend across an astonishing 112 million miles.

They would more than fill the distance between Earth and the sun.

But as enormous as they are, they're shockingly thin.

If the ring system of J-1407B were the size of a dinner plate,

it would have to be 100 times thinner,

as thin as a human hair.

This surprising contrast between the immense territory

of a ring system, and its thinness,

is just as striking in our own solar system.

The outermost ring of Neptune is so dainty,

that it was first thought to be the fragments of a ring.

Not a ring, but a collection of arcs.

That was, until NASA's Voyager 2 spacecraft revealed

that the so-called arcs were clumps,

the thicker parts of a fainter, complete ring.

It's funny that the weirdest planet in the solar system has

attracted the least attention.

Voyager 2 is the only spacecraft that has ever been

sent on a reconnaissance mission to Uranus,

one of the two ice giant planets that circle the sun.

During its 20-year-long summers,

the sun never sets on Uranus.

The winters are equally as long,

20 years of unbroken night.

Unlike its fellow gas planets, Uranus is cold-hearted.

It doesn't generate any internal heat.

Uranus is one crazy world.

The outer edge of Uranus's atmosphere is so hot,

it's hotter than 500 degrees Fahrenheit.

But Uranus also has the coldest clouds in the solar system,

I'm talking nearly 400 degrees below zero.

What kind of ocean is this?

Is it made of ammonia?

Water?

Some scientists think it may be an ocean of liquid diamonds.

Note to space agencies, might be worth another visit.

Then there's that thing about it being sideways.

Uranus revolves around the sun at a roughly 90 degree angle to its own orbital plane.

What could have happened to Uranus that it got knocked on its ass?

Our best guess is that it went something like this.

Uranus was in a terrible accident.

After the second blow, the rotational axis of Uranus tipped 98 degrees.

There's another world in our solar system that we don't

think of as having a ring.

The rings of Jupiter were so dim that no ground-based

telescope ever saw them.

They were discovered when Voyager 1 came flying by.

Our Saturn is graced by the loveliest, largest,

and brightest ring system of any around our sun.

It's the most distant planet that can be seen with the naked eye,

and it made quite an impression on our ancestors.

When I think of the Babylonians of 3,500 years ago looking up

at the planets and stars,

I wonder how unlikely it would have seemed that one of their

species would actually send an emissary to that

distant point of light.

We are in the Deep Space Network room at NASA's Jet Propulsion Laboratory.

In this place, the most ambitious voyages of discovery are directed and monitored.

Why are these people so emotional?

They have committed their professional lives to

a collaboration with this robot.

And now that partnership of decades is about to end

in a most violent way.

The pathway from our Earthbound helplessness to

our presence in Saturn's skies is about to unfold.

What is that shimmering, unsteady thing we're looking at?

That's what Galileo Galilei asked himself in 1610 when he

became the first human to see Saturn as more than

just a point of light.

So, this is the telescope that made the modern

scientific revolution possible.

You know, you really started something.

You looked through that thing and found the cosmos.

That's not to say you didn't make your share of mistakes.

You guessed wrong at what you thought you saw,

believing that Saturn sported two symmetrical moons

on either side of it.

Two years later, when you took a second look,

you were shocked to find that your "moons" had vanished.

This was because both worlds, Earth and Saturn,

were in motion, and the two worlds had changed in position to each other.

You were now looking at Saturn's rings, edge-on.

The Saturn ring system is 175,000 miles across,

but on average only a few hundred feet thick.

They were too thin for your fledgling telescope to see.

But two years after that, you took a third look.

Now, you thought that the planet had arms.

40 years passed, until a Dutch astronomer named

Christiaan Huygens took another look at Saturn with

his own greatly improved telescope.

Huygens was the first to know that worlds could

be circled by rings, and Saturn was one of them.

He also discovered Saturn's largest moon,

which would later be known as Titan.

When it finally came time for us to visit that world,

our spacecraft bore Huygens's name.

In science, there are the Galileos, the Newtons,

the Darwins, the Einsteins.

And then there's another kind of great scientist.

Not the kind that paints a whole new picture of nature,

but, like Christiaan Huygens,

someone who has much to contribute,

filling in a blank or two on that vast canvas.

Such a scientist was Giovanni Domenico Cassini.

He was born early in the 17th century in the town of Perinaldo,

in what is now Italy.

Cassini didn't start out as a scientist.

He began his career as a pseudo-scientist, an astrologer.

Astrology is a collection of ideas based on the notion that

worlds have certain human personality traits,

and that the influence of these distant worlds,

depending on which are rising and falling at the time

of your birth, will determine who you are and

what your fate will be.

It's another form of prejudice,

making unfounded assumptions about who a person

is without bothering to get to know them.

Astronomy and astrology used to be the same thing,

until there was a great awakening to our

actual circumstances in the cosmos.

In 1543, Nicolaus Copernicus,

a Polish cleric demonstrated that,

contrary to popular belief,

we were not the center of the universe...

the Earth and the other planets travelled around the sun.

Demoting the Earth from the center of the universe

was a severe blow to human self-esteem.

More than a century later,

some people still hadn't gotten over it,

and Giovanni Cassini was one of them.

Cassini accepted a terrific job offer,

an appointment by Louis the XIV,

the legendary sun King of France,

Louis believed himself to be an absolute ruler whose dominion was God's will.

But he was also the first monarch in Europe to recognize

the great power of science.

He knew it was vital to national security.

Louis the XIV was inventing the first modern,

governmental, scientific research institute,

The Paris Observatory.

Cassini told the absolute ruler that he would not be

staying long in Paris, a year or two, at most.

But when the King placed his new observatory at Cassini's disposal,

he lost all interest in returning home to Italy ever again.

For the next 125 years,

the Paris Observatory would be led by a Cassini.

Cassini rewarded his patron with a map of the Moon

that remained cutting-edge for a century.

King Louis financed a research expedition to South America

to obtain more accurate measurements of longitude,

intel of enormous value to the captains of his far-flung

fleet and to astronomers.

Cassini took all these data and became the first person

to calculate the scale of the Copernican solar system

that he had once rejected.

With his increasingly powerful telescopes,

he discovered the length of a day on Jupiter

and the bands and spots on that planet's surface.

Cassini discovered Jupiter's Great Red Spot independently

of Robert Hooke in England, and to this day,

they share the credit.

Cassini went on to determine the length of the day on Mars.

He was only off by three minutes.

When he returned to his observations of Jupiter,

he was stumped by the contradictions in them.

The eclipses by Jupiter's moons did not begin when they were supposed to,

they varied from observation to observation.

Could it be that it was due to changes in the distance

of the Earth from Jupiter, as the two worlds moved through the solar system?

If that were true, then light could not travel at

an infinite speed because it was taking longer to reach Earth.

Was the speed of light finite?

This idea was just too crazy for Cassini, too revolutionary.

He rejected it out of hand.

If he had followed the evidence wherever it led,

he would have given us the yardstick for the cosmos that

we still use 350 years later.

But Cassini, ever the conservative,

dismissed the idea as being just too wacky.

Several years later, a Danish astronomer,

Ole Romer, became Cassini's assistant at the Paris Observatory.

Romer made his own observations of the eclipses

of some of Jupiter's moons and found the same discrepancies

in the data that Cassini had dismissed.

But Romer recognized them for what they were,

Pieces of evidence for the finite speed of light.

There was a time, however, when Cassini's faithfulness

to the data was so extreme, that he was willing to risk the

displeasure of King Louis.

The monarch asked Cassini to calculate the exact area of his realm.

No one had ever attempted to make an accurate map,

much less a topographical one that would feature all

the mountains and rivers and valleys of France,

or of any other country for that matter.

Cassini rose to the task, but discovered results that

could not possibly please the King.

Cassini told the King,

"I have some rather disappointing news for you, Your Highness.

We all thought that France was a whole lot bigger than our studies, revealed.

I'm afraid, Your Majesty, your kingdom is much smaller than heretofore thought."

The King surprised everyone with his great good humor,

saying, "Why, Cassini, you've robbed me of more land

than all the armies of my enemies combined."

And then, there is his work on Saturn.

He was the first person to know what the rings of Saturn really were.

He proposed that they were not solid,

but instead composed of countless satellites orbiting

the planet, and he observed that there was

a division between the rings.

Cassini filled in some of the big blanks in our understanding of Saturn,

but how could we possibly ever get there?

Accomplishing that mythic quest was left to one whose

tragic life would have been completely forgotten,

if not for what you are about to see.

Weighing in at more than 12,000 pounds at launch,

NASA's Cassini spacecraft is the size of a bus.

That figure included 70 pounds of plutonium 238 fuel,

enough to last her for more than 20 years.

But that's not what powered her mythic odyssey.

She rode gravity's rainbow all the way to the outer-solar system.

The lineage of the greatest of human achievements stretches

further back than we might assume.

Some of their roots are buried deep inside the tomb of lost hope.

But somehow, dreams rise.

The epic missions of the first golden age of space exploration,

and likely the next,

were made possible by a man whose two names,

one real, one fake, are equally forgotten.

Alexander Shargei's early years are not well-documented,

but it is believed that his mother, a political activist,

was taken from him when he was only five years old.

He took refuge in his father's physics and mathematics textbooks.

But by the time Alexander was 13,

the boy had lost his father, too.

He lived with his grandmother, and despite great hardship,

he managed to be accepted at the most prestigious high school,

and afterwards gained admission to the

best engineering institute in the Ukraine.

But only two months after he arrived there, in 1914,

he was drafted into the Czar's army to fight

in the First World War.

In the hell of war at the front,

Alexander Shargei conceived a scientific strategy

for exploring the Moon, not intended as fiction,

but as blueprint.

But Shargei's hell didn't end with the war.

Now, Shargei was forced to navigate the treacherous

political mine fields of revolutionary Russia.

He was much better at figuring out how to get to the Moon.

Former officers in the Czar's army and those,

such as Shargei, who were forced to join

the counter-revolutionary White Army,

were assumed to be "enemies of the people."

Shargei could find no peace in the Soviet Union,

so in desperation he tried to escape to Poland.

Shargei, weakened by illness, was stopped by guards

and turned back from the border.

These were dangerous times,

and there was no telling what would get you into serious trouble.

No one knows where Shargei spent the next three years.

He simply vanished.

When at last he emerged, Alexander Shargei was no more.

In his desperation to be left alone,

he took the name of a dead man.

He was now Yuri Kondratyuk.

He finally published the book he had been dreaming

about since his time in the trenches.

No publisher was interested,

so he printed it at his own expense.

It was Kondratyuk's letter to a future no one else could see.

He wrote it "To Whoever Will Read This Paper in Order to

Build an Interplanetary Rocket."

In the late 1920s,

Kondratyuk was enlisted to design a grain elevator.

The Soviet Union was going through a metal shortage,

so Kondratyuk's challenge was to build the largest grain

elevator possible without using more than a single nail.

It ended up being so big, they named it "the Mastodon."

Such was the nightmare logic of Stalin's Soviet Union.

You could do the heroic in service to the state,

successfully execute the seemingly impossible order

to build a colossus with but a single nail.

And when it was done,

you could be imprisoned for sabotage.

Who but an enemy of the state would do such a reckless thing

as building a colossal grain elevator with only a single nail.

It made no difference to Kondratyuk's fate that the

grain elevator functioned for another 60 years,

until it burned down.

Kondratyuk was sentenced to three years in a special prison camp,

something new, called a sharashka,

where scientists and engineers slaved away on the nation's most ambitious projects.

Kondratyuk threw himself into a wind power project,

but still he dreamed of exploring the solar system.

Soon after that, he met Sergei Korolev,

who also dreamed of leaving Earth to explore the cosmos.

Korolev would later become the father of the Soviet rocket program.

Korolev wanted to enlist Kondratyuk in his fledgling

rocket program, but Kondratyuk was so terrified

that any change in his status might result in closer scrutiny by

the secret police, he declined.

If the authorities discovered that Kondratyuk was really Shargei,

there was no telling what they would do to him.

When Germany attacked Russia,

Kondratyuk volunteered for armed service at the front,

where he led a communications outfit.

His precise fate is unknown, but he is believed to have

died in battle on a February night in 1942.

Alexander Shargei, aka Yuri Kondratyuk, was only 44.

That was the end of his story,

but not his dream.

In the early days of the Apollo program,

the scientists and engineers struggled to figure out how

a rocket could leave the Earth and land directly on the Moon.

They were stymied.

They couldn't figure it out.

You need a big powerful rocket to reach the Moon.

How could you land such a thing on the surface

of another world without crashing it?

Being able to guarantee that it could take off again and

bring your crew safely home, was even more of a longshot.

This approach, known as "Direct Ascent,"

seemed like a dead-end to a NASA engineer named John Houbolt and his colleagues.

One version of the story goes, two space scientists had kept

the spark of Kondratyuk's dream alive.

They delivered his 40 year-old manuscript to Houbolt.

First of all, to the question of the work,

let it not frighten you...

Speaking about the possibility of flight implementation,

just only remember that there is nothing improbable on the

theoretical side of the flight of a rocket into space...

One, zero.

37 degrees.

It's still looking very good.

You're go.

We got an alarm. Bravo One.

Bravo One. Rocket 1201 alarm.

1201 alarm.

Standby for go, Flight.

Okay, we're go.

We're go. Sync tight. We're go.

Altitude 1600.

Eagle looking great.

Tranquility base here.

The eagle has landed.

The surface appears to be very fine grained

as you get close to it.

It's almost like a powder.

NASA picked up Kondratyuk's vision of a

Lunar Orbiter Rendezvous and took it all the way to the Moon.

But Kondratyuk's horizon extended far beyond.

Kondratyuk envisioned the first reconnaissance of

the solar system by swinging round the planets,

and using the force of their gravity to slingshot

the craft farther out into space.

He dreamt that we would swing from world to world as

our ancestors had done from tree to tree,

bending gravity to human needs on a slightly grander scale.

But what gravity giveth, it can also taketh away.

Why do some worlds have rings, and others don't?

Why no rings for Earth?

Or Mars?

We wouldn't recognize Saturn without them.

He looks naked without his rings,

but how did he get them in the first place?

This is exactly what the French astronomer Édouard Roche asked

himself when he looked at Saturn through his telescope in 1848.

Roche speculated that Saturn's rings were the debris of a moon,

or moons, that had ventured too close,

and were pulled apart by the massive planet.

Roche was able to devise an equation that applies to all worlds.

It tells you how closely a body can come to a planet

before it's pulled apart by the planet's tidal forces of gravity,

and is turned into a ring.

That's the Roche limit.

But until NASA's Cassini spacecraft executed a series

of daredevil maneuvers in the Saturn system,

there was a vigorous scientific debate about

when his rings formed.

Some astronomers suggested they were nearly

as old as the planet itself.

More than 4 billion years ago, when the planet coalesced out

of the disc of gas and dust that surrounded the newborn sun,

a moon, or moons, likely violated Saturn's Roche limit...

Others thought the rings to be fairly recent.

Perhaps, only 100 million years old or so.

And the Cassini spacecraft proved them right.

What is Earth's own Roche limit?

If the Moon were ever to come closer than 12,000 miles,

which, by the way, it's absolutely in no danger of doing.

And it's a good thing, too,

because I like our Moon right where it is.

There's only one other moon in the solar system that moves

me like ours does.

Maybe it's because it's the only one with a thick

atmosphere like Earth's, and the kind of surface features,

lakes and mountains, that remind me of home.

All of this was hidden from view by a dense layer

of orange smog, until the European Space Agency

collaborated with NASA to send a spacecraft to land

on his mysterious surface.

Yes, that would be the one named after you,

Christiaan Huygens, first to see that world through your telescope.

After an interplanetary voyage of seven years,

the Cassini-Huygens spacecraft arrived in the Saturn system,

the fourth of our ships to venture there.

But the first to send a probe to explore the surface of Saturn's moon, Titan

and to reveal a moon of far greater complexity and splendor

than our own rather dull and lifeless Moon.

As Carl Sagan had predicted more than two decades before,

there were seas of methane, and ethane,

and there was water-ice.

When Cassini first arrived in 2004 at Saturn's

northern hemisphere, it was in the depths of winter.

And the Sun didn't come out until five years later,

when Saturn's northern spring began.

Is it just me, or is this whirling hexagon at Saturn's

North Pole every bit as exotic as the fantasies our ancient

ancestors had of these worlds?

The geometrically regular hexagonal shape of this

feature brings to mind the handiwork of intelligence,

terraforming, re-working the surface for some unknown purpose.

But it's actually the result of the sudden change in wind

speeds as vast upwellings of ammonia rise near the poles.

It's the mother of all hurricanes,

a frenzy of thunder and lightning,

containing countless hurricanes within it.

Spring can be a violent, stormy season, on Earth, too.

But it was during Saturn's seven year-long summer that

Cassini was commanded to take her own life.

There's a human conceit that at the moment of death,

we re-live our greatest memories.

You are riffling through the memory bank of a doomed robot,

about to carry out the cruelest command.

The mission planners at NASA's Jet Propulsion Laboratory

call this the "ball of yarn,"

13 years of exploration through the Saturn system.

From the time of her launch in 1997 and throughout her epic voyage,

she has used the gravity assist conceived 100 years before by Yuri Kondratyuk.

But it was her supply of rocket fuel that made it

possible for her Earthbound controllers to steer her into

new trajectories of exploration.

In April of 2017, Cassini was running low on that fuel.

It was time for her most daring maneuvers of all,

before she was to be sent into a final death dive.

These are the mission scientists of Cassini,

some of whom have been working on the project since

the 1990s, when it was no more than a dream.

They know that Cassini must die.

It's too dangerous to let her wander aimlessly.

She might crash into one of the moons in the Saturn system

where life might be hiding.

This would violate NASA's planetary protection

conventions on quarantine in the book of space laws.

If left to chance, Cassini could alter the

possible biological destiny of Titan or Enceladus.

A terrible command must now be given.

Cassini is so far away, it will take the message,

traveling at the speed of light,

more than an hour to reach her.

Every microchip in her has been programmed to resist

the commands she's now receiving.

The inner-turmoil of the loyal robot commanded to defy

her own instincts must be fierce.

The same engineers who ordered her to protect herself

in every situation now force her to plunge to her death.

They must be obeyed.

System lead ace.

We have telemetry AOS at zero one.

One, niner. One two.

She fights off the immense forces by struggling

to right herself one last time.

She fires her thrusters at 100%,

all the while faithfully sending back more data than

her designers ever hoped she would.

Project Manager. Flight Director.

Go ahead.

Okay. We'd call loss of signal at 11:55:4.

She fights the brutal atmospheric resistance until

her fuel tanks are empty,

and there's no more fight left in her.

Project manager on, maybe a trickle of telemetry left, but,

just heard the signal from the spacecraft is gone

and within the next 45 seconds so will be the spacecraft.

Official time of 11:55 universal time.

There are all kinds of stories in the struggle to understand the cosmos.

Sometimes your dreams die with you,

but sometimes the scientists of another age pick them up,

and take them to the Moon, and far beyond.

The name of Yuri Kondratyuk was forgotten,

but there was one who remembered.

When Neil Armstrong returned from his trip to the Moon,

he made a pilgrimage to the childhood home of the man

who made his mythic voyage possible.