♪ ♪ ♪ ♪ ZACHARY QUINTO: Half a billion miles from the sun... (wind shrieking, loud explosion echoes) ♪ ♪ The giant of the planets... HEIDI BECKER: It's very violent and it's very intimidating.

♪ ♪ QUINTO: Jupiter.

Of all the worlds in the solar system... FRAN BAGENAL: It's the biggest planet.

It sort of pushed a lot of the planets around.

It's the bully of the solar system.

♪ ♪ QUINTO: Jupiter's immense size gives it incredible influence.

(thunder rumbling) Jupiter is the most powerful gravitational object, second to the sun.

QUINTO: And while Jupiter is at a safe distance from Earth today, in the past, it drew much closer.

Four-and-a-half billion years ago, it embarked on a rampage across the solar system, leaving a trail of destruction in its wake.

LYNNAE QUICK: We can think of the asteroid belt as a planetary graveyard.

QUINTO: Jupiter transformed the destiny of the planets, and could even have changed the course of life on Earth.

♪ ♪ (explosion echoes) It is the most influential planet of our cosmic home.

♪ ♪ QUINTO: "The Planets: Jupiter."

Right now, on "NOVA."

♪ ♪ ("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 ♪ ("The Void" ends) ♪ ♪ QUINTO: Beyond the edge of the inner solar system and the desolate wasteland of the asteroid belt... ...is the gas giant Jupiter.

Its serene marbled appearance disguises a planet in turmoil, where violent storms rage through clouds more than a thousand miles deep.

DERRICK H. PITTS: When we look at Jupiter, we find one of the most amazing places we've seen in the solar system.

BECKER: It's very mysterious.

It's covered by clouds that hide what's underneath.

QUINTO: But Jupiter is a planet as influential as it is beautiful.

KONSTANTIN BATYGIN: Jupiter is by far the biggest planet.

Its mass is greater than 300 times that of the Earth.

So it is the most powerful gravitational object, second to the sun.

QUINTO: Four-and-a-half billion years ago, Jupiter's gravity had devastating consequences for the worlds around it.

PITTS: Jupiter had this incredible effect that helped to shape the solar system overall.

♪ ♪ QUINTO: Clearing material from the inner solar system, Jupiter transformed the destiny of the planets-- including our own.

♪ ♪ BATYGIN: You're looking at the crime scene-- the structure of the solar system, what it is today-- and trying to piece together what happened four billion years ago.

♪ ♪ It is an amazingly intriguing problem.

QUINTO: Jupiter is a world with a dark past.

And you don't have to look far to see the evidence.

♪ ♪ In the northern Arizona desert, this is Barringer Crater.

♪ ♪ It was formed 50,000 years ago, when an iron-nickel asteroid 150 feet across hit Earth at 27,000 miles per hour... ♪ ♪ An asteroid that was likely thrown in our direction by Jupiter.

♪ ♪ So what is it that enables Jupiter to influence the Earth from so far away?

♪ ♪ And how did it grow to such dominance?

Only by seeing Jupiter close up could we begin to answer those questions.

♪ ♪ (rocket ignites) ♪ ♪ In 1972, Pioneer 10 becomes the first spacecraft to cross the asteroid belt.

PITTS: Before Pioneer, we really had no idea whether or not a spacecraft would be able to survive all the hazards of a trip like that.

The images brought back to us really blew our minds in terms of what we could see of Jupiter.

To have the incredible detail about the dynamics of the atmosphere really was new and different to us.

MAN: Now the world wants to know, "What have we learned?"

QUINTO: During its brief fly-by, Pioneer observes Jupiter for four days... ♪ ♪ ...proving that missions to the outer solar system are possible.

MISSION CONTROL: We have ignition and we have lift-off of the Titan-Centaur, carrying the first of two Voyager spacecraft to extend man's senses farther into the solar system than ever before.

♪ ♪ QUINTO: The Voyager spacecraft see Jupiter's Earth-sized red spot in unprecedented detail... ♪ ♪ ...discover the planet's rings, and capture the first detailed images of Jupiter's moons.

♪ ♪ BAGENAL: It wasn't until Voyager went up-close and personal, and took amazing pictures of the moons, that we really began to get a sense of just how complex and the variety of the worlds around Jupiter.

♪ ♪ The icy surfaces of Europa, so different, so dynamic.

The volcanos on Io, Ganymede all broken up, and then Callisto was just this big icy surface covered in impact craters.

♪ ♪ QUINTO: We now know the giant planet has more than 79 moons.

Jupiter is a world so large, its immense gravity has assembled a solar system in miniature.

So how did it grow to such incredible size?

MISSION CONTROL: T-minus ten, nine, eight, seven... QUINTO: In 2011, the Juno spacecraft launches from Cape Canaveral.

MISSION CONTROL: Ignition, and lift-off of the Atlas V with Juno, on a trek to Jupiter.

QUINTO: Its mission: to uncover the secrets of Jupiter's formation.

♪ ♪ BAGENAL: When we launched the Juno spacecraft away from the Earth out towards Jupiter, we didn't have enough speed to get away out of the gravity of the sun.

So, we actually had to come back to Earth, get a gravity assist from Earth, and then go out to Jupiter.

♪ ♪ QUINTO: After traveling for five years, on July 4, 2016, the spacecraft finally arrives.

It's an incredible moment for the science team.

BAGENAL: You see all these swirls, you see all sorts of spots coming up.

You see all these vortices.

You see dramatic storm systems interacting.

♪ ♪ It's mind-blowingly beautiful pictures that this little camera has been taking.

♪ ♪ BECKER: JunoCam was able to see the Great Red Spot from up close.

We can see height to the clouds, we can see features that look like storms.

Maybe it's hailing or snowing ammonia.

(chuckles): On Jupiter.

♪ ♪ And the most startling thing that we saw from JunoCam's imagery was that the poles of Jupiter are actually blue.

Juno's objective is to look as close at Jupiter and as deep inside as we possibly can to understand as best as we can, what is it made of?

What is its interior structure like?

Because the answers to those questions help to tell us where and how Jupiter might have formed.

♪ ♪ QUINTO: By analyzing the planet's magnetic and gravitational fields, Juno is able to look deep into Jupiter's interior.

BAGENAL: And what we found is that there is a lot of mass inside.

That mass is the core of the planet around which the hydrogen was pulled in in those early stages of solar system formation.

QUINTO: By discovering the planet's core, Juno is helping us to reconstruct Jupiter's first moments... A story that begins very early in the solar system's history.

♪ ♪ (explosion echoes) Nearly five billion years ago, a distant exploding star sends a shockwave across the galaxy... ♪ ♪ ...causing the cloud of gas and dust that would become our solar system to collapse, forming the sun.

♪ ♪ Farther out, Jupiter's core is already beginning to grow, gathering in vast clouds of gas.

♪ ♪ After 50 million years, the sun's nuclear furnace ignites... ♪ ♪ ...the light of its first dawn revealing Jupiter.

While the terrestrial worlds are little more than rubble, Jupiter is fully formed, allowing it to shape everything that follows.

So when it comes to setting the stage, setting the structure of how the solar system is going to evolve, Jupiter plays the biggest role.

It is the most influential planet of our cosmic home.

♪ ♪ QUINTO: Over the next 100 million years, the four rocky planets of the inner solar system form in their familiar positions: Mercury... Venus... Earth... ...then Mars.

And while this layout is familiar to us, it might be extremely rare.

♪ ♪ BATYGIN: The more we've looked around, the more we've found that the typical solar system is unlike that of our own.

♪ ♪ QUINTO: Our sun is just one of around 300 billion stars in our galaxy.

And almost every one of those stars is likely home to its own system of planets.

LEIGH FLETCHER: When we look out into the rest of our galaxy, we're starting to discover worlds around other stars, we call them exo-planets.

♪ ♪ The planets that we're seeing, they're not all Earth-like objects, they're not all big objects like Jupiter.

The vast majority of them have sizes and masses that are similar to Uranus and Neptune.

♪ ♪ QUINTO: In most other systems, the region of space where our planet orbits is empty.

Instead, close to the star, we see "Super Earths," vast rocky planets between two and ten times more massive than Earth.

But these worlds are thought to have thick, suffocating atmospheres that render them inhospitable to life as we know it.

So what is it that makes our system so different?

Some sequence of events must have happened that made our solar system special.

♪ ♪ QUINTO: As we've explored the planets, we discovered strange anomalies that hint at a catastrophic upheaval that shaped the solar system.

(spacecraft whooshing) Our missions to Venus found that it once had far more water than you'd expect for a planet so close to the sun, just as Earth has today.

The spacecraft we've sent to Mars... (spacecraft humming) ...touched down on a world that is, curiously, just half the size of her sister planets Earth and Venus.

But it was in the region of space closest to Jupiter that our probes discovered the most astonishing evidence.

The asteroid belt actually holds a remarkable amount of information about the solar system's dynamic and dramatic evolution.

QUICK: The asteroid belt sits in between Mars and Jupiter, and it separates the inner solar system from the outer solar system.

People think that the asteroid belt is very densely packed, but the asteroids there are actually very widely separated.

They're spread over this huge volume.

So, if you stand on top of one asteroid, you won't be able to see another one.

It's nothing like what you would imagine in science fiction.

BETHANY EHLMANN: When we send spacecraft outward into the solar system through the asteroid belt, we double-check that there's not going to be a large asteroid in the way, but we really don't need to make any kind of course correction, because the asteroid belt is largely empty space.

♪ ♪ QUINTO: But it hasn't always been like this.

It's thought the asteroid belt once contained enough material to build a planet the size of Mars.

So why is it so empty today?

MISSION CONTROL: Five, four, three, two-- main engine start-- one, zero, and lift-off of the Delta II rocket with Dawn, using ion propulsion to reach the catalysts of our solar system.

♪ ♪ ♪ ♪ Dawn's mission is to investigate the two largest asteroids in the asteroid belt-- Vesta and Ceres.

QUINTO: After a year in orbit around Vesta... ...in March 2015...

...Dawn makes its final approach on Ceres, a body that makes up over a third of the mass of the entire belt.

EHLMANN: It was really exciting because an object that had been sort of grainy and mysterious was suddenly there, revealed before us, ready for exploration.

(hissing, mechanism whirring) ♪ ♪ QUINTO: On approach, the first images Dawn sends back to Earth reveal something unexpected.

EHLMANN: As Ceres came into view, we would see these amazing bright spots on the surface, pockmarking it here and there, nothing like we'd ever seen before.

And the most outstanding ones were found in Occator Crater.

Occator Crater is one of the larger but younger craters on Ceres.

The most intriguing thing, though, is what we see in the center, which is a central pit and then a bright dome of, of this intriguing super-bright material.

QUINTO: Now the mission team's challenge is to identify what the mysterious substance actually is.

EHLMANN: With the instruments on the Dawn mission, we're looking at the chemical fingerprints of the bright materials, and actually, we see that they're salts.

All of this points to the fact that there were once brines, salty waters, that rose near the surface of Ceres to create these deposits.

QUINTO: Dawn goes on to discover over 300 bright spots... ...clues to Ceres' former life.

♪ ♪ EHLMANN: If we were to peel away the dark surface of Ceres, what we'd find underneath is a mixture of rock and ice.

Ceres is not just the largest asteroid; it's a dwarf planet in its, in its own right.

It's spherical and it has differentiated into layers.

We know from Dawn data that there is an ice-rich layer on the outer, comprising the outer crust, tens of kilometers thick.

♪ ♪ QUINTO: But it hasn't always been this way.

EHLMANN: Ceres is frozen today, but early in its history, radioactive elements in its interior would have provided heat that melted the liquid water that's currently ice.

And so we think that, during the early portions of Ceres' history, it had a global ocean.

♪ ♪ QUINTO: In infancy, Ceres was well on its way to becoming a fully-fledged world.

The water that now lies frozen within its interior was once liquid.

Protected beneath a thin layer of ice, ancient Ceres is covered by a deep salt-water ocean.

(asteroids whoosh) But then, something happens to cut its development short.

(asteroids hit) ♪ ♪ As the young Jupiter circles the sun, it clears a path through the gas cloud that envelops the early solar system.

But that process causes it to do something alarming.

♪ ♪ Jupiter begins to spiral inwards... ...plowing straight through the region of space that would become the asteroid belt.

♪ ♪ BATYGIN: When the young Jupiter moves through the primordial asteroid belt, things get scattered around, things get gravitationally deflected, and as a consequence of all of this gravitational interaction, more than 99% of the original mass that was there is basically now gone.

The asteroid belt has been disrupted over time by the movement of the giant planets, and this has acted to throw material from the asteroid belt out of the asteroid belt, into the outer solar system.

BATYGIN: These protoplanetary cores, like Ceres, were never able to graduate to full-fledged planets because there was just not enough material in the orbital neighborhood.

♪ ♪ QUINTO: When Jupiter passed through the primordial asteroid belt, it starved Ceres of material, halting its growth.

And the dwarf planet was condemned to spend eternity as a cold, barren rock.

But Ceres isn't the only world in our solar system whose development was cut short.

Mars would share a similar fate.

♪ ♪ After marauding through what would become the asteroid belt... ...Jupiter enters the region of space where Mars is forming... ♪ ♪ ...continuing its journey spiraling towards the sun.

♪ ♪ As Jupiter bulldozes inwards... ...its immense gravity scatters material in all directions.

♪ ♪ Some is sent careening into the sun... ♪ ♪ ... and some is thrown out into interstellar space.

BATYGIN: It is because of the gravitational clearing of this neighborhood by Jupiter that Mars was unable to grow to more than ten percent of that of the Earth.

This is why Mars is small.

QUINTO: And by clearing material out of the inner solar system, the giant planet may also have prevented the formation of the Super-Earths we see in other systems.

And if it had continued moving inward, our planet, too, might never have formed.

♪ ♪ But then, just as it looks like Jupiter will sweep everything away, the giant planet stops in its tracks.

(thunder rumbling) Because in the far reaches of the outer solar system, another planet is forming... ...the solar system's second gas giant... Saturn.

And its arrival changes everything.

BATYGIN: As Jupiter moved inwards, Saturn moved inwards, and caught up to Jupiter's orbit.

When this happened, the two locked into a special configuration known as a mean motion resonance.

This is where the planets begin to interact gravitationally in a very coherent manner.

And now, locked as a unit, the two reversed their migration course and moved back out.

QUINTO: Saturn caused Jupiter to retreat... ♪ ♪ Leaving behind just enough material from which the inner planets could form... Mercury... Venus... ♪ ♪ ...and our home.

PITTS: Earth is in exactly the right location to provide the environment for life to develop.

So if Jupiter had moved around even more, who knows, maybe life never would have developed in this solar system as we know it.

♪ ♪ QUINTO: And as its voyage across the solar system draws to a close, Jupiter helps to provide our living world with its most precious ingredient.

♪ ♪ Today, two-thirds of our planet's surface is covered by ocean.

(waves crashing) More than 320 million cubic miles of water... each drop teeming with life.

♪ ♪ One of the big questions about the evolution of our solar system is, how did we get water here on this planet?

EDGARD RIVERA-VALENTÍN: We think that the inner planets didn't naturally form with a lot of water.

Water is primarily in the outer solar system.

But if you end up having Jupiter and Saturn moving outwards, then that is able to suddenly deliver more water into the inner solar system.

QUINTO: Locked in a gravitational dance with Saturn, Jupiter moves back through the asteroid belt.

And as it does so, water-rich material is flung inward, where it is incorporated into the growing terrestrial worlds.

EHLMANN: So the movement of the giant planets have actually played an important role, in the delivery of water to the inner solar system.

♪ ♪ BATYGIN: In a sense, it is Jupiter's outwards motion through the asteroid belt that we have to thank for the delivery of water to surface of the Earth.

The Earth would be quite a different planet if not for Jupiter's primordial dance.

♪ ♪ QUINTO: Today, Jupiter has settled into a regular orbit, back beyond the far edge of the asteroid belt... its days of marauding through the solar system at an end.

But its gravity remains a constant threat.

And nowhere is that more apparent than on the closest of Jupiter's large moons.

(distant rumbling) ♪ ♪ Io is the most volcanic world in the solar system.

QUICK: If you were to send a spacecraft to Io and take a picture, you would see hundreds of volcanoes erupting at one time.

(lava churning) BAGENAL: Active volcanoes, lava spewing out-- hot, hot, hot lava.

(distant rumbling, explosions) QUINTO: The biggest lava lake on Io is Loki Patera.

♪ ♪ At more than 120 miles in diameter, it's a million times the area of any lava lake on Earth... its surface constantly churned by waves of molten rock.

♪ ♪ (lava rumbling) But Io is the same size as our moon.

So why isn't it just as cold and dead?

STEVE DESCH: Jupiter is a massive planet.

It's 318 times the mass of the Earth.

And this poor little moon has to orbit near this giant, and meanwhile the other moons are in an orbital resonance with it and they keep tugging it out of a circular orbit.

♪ ♪ When things are in resonances, that means they're meeting each other up at the same point in space constantly so that means that there's a constant tug coming in from all of these moons.

♪ ♪ QUICK: This tugging creates friction.

And this friction becomes heat, very much in the same way as if you were to rub your hands together on a cold day, that friction would create heat.

And this is what we call tidal heating.

DESCH: When you take a moon like Io and you stretch it this way and then let it relax and stretch it this way and let it relax, the friction inside is constantly heating up the rock until you reach the melting point.

♪ ♪ QUINTO: This process raises the temperature in Io's interior to more than 2,000 degrees Fahrenheit... creating its lava lakes... (lava spews, hisses) and powering immense volcanic plumes... that rise up to 200 miles from the moon's surface and out into space.

♪ ♪ Because of Jupiter's great size, the gravitational field that drives Io's volcanism extends far beyond its moons...

Even as far as Earth... ♪ ♪ where there's evidence it's done far more than create the occasional crater.

BRUCE SCHUMACHER: Preserved in the limestone layers along this stretch of river are several thousand dinosaur tracks dating back to the Jurassic period some 150 million years ago.

QUINTO: Etched into the banks of the Purgatoire River are the final traces of a lost world.

SCHUMACHER: Some of these tracks are from a large herbivorous dinosaur, a sauropod, big hind footfalls moving through the area, and right near those are three-toed prints of a meat-eating animal-- something like allosaurus-- and all of those tracks being together tell a story, and the easiest story that one might imagine is that of a predator pursuing prey on this ancient lake shore.

♪ ♪ QUINTO: But today, the dinosaurs are gone.

The course of evolution was dramatically changed, and it's likely Jupiter was responsible.

♪ ♪ BATYGIN: Jupiter has been profoundly implicated in periodic extinctions of life on Earth.

And, indeed, it's quite likely that the asteroid which wiped out the dinosaurs almost 70 million years ago was launched from the asteroid belt by Jupiter's gravitational influence.

(distant rumbling) People often think of the asteroid belt as this unstructured, unchanging population of debris, but as you can see here, there's quite a bit of structure to the asteroid belt.

In green, what we have are the so-called Trojan asteroids.

Objects that occupy the same orbit as Jupiter.

In red, what we have are the Hilda asteroids.

They form this triangular shape because of the resonance that they're in with Jupiter.

The asteroid belt as a whole is kind of dancing to Jupiter's tune.

(muffled rumbling) QUINTO: But it is a delicate balance that can change at any time.

BATYGIN: Because Jupiter exerts such tight control over the long-term changes of asteroid orbits, if an asteroid comes off its well-defined orbital track, so to speak, then Jupiter will just fling it out of the asteroid belt and potentially even send it towards the Earth.

QUINTO: Dislodged from its orbit by Jupiter's gravity, an asteroid six miles across tumbles out of the asteroid belt.

♪ ♪ It is now on a collision course with Earth.

♪ ♪ (loud explosion) ♪ ♪ When it strikes, the impact generates a fireball so hot, anything within a 600-mile radius dies instantly.

♪ ♪ The impact throws some 300 billion tons of sulfur up into the atmosphere.

♪ ♪ And during the "nuclear winter" that follows, 75% of species, plant and animal, are wiped from the face of the Earth, including the largest creatures ever to walk on its surface.

By driving the dinosaurs to extinction, Jupiter cleared the way for us to inherit the planet.

And although it still occasionally flings asteroids our way... Jupiter also protects us.

For objects heading toward Earth from the far reaches of the solar system, the giant planet's immense gravity acts as a shield.

Around 100 years ago, a lump of rock and ice 2.5 miles across is hurtling toward the inner solar system.

But Jupiter stands in its way.

MISSION CONTROL: Five, four, three, two, one.

We have ignition and lift-off of Atlantis and the Galileo spacecraft bound for Jupiter.

♪ ♪ QUINTO: 70 years later, a mission launches that will witness just how effective a shield Jupiter can be.

♪ ♪ On board the space shuttle Atlantis, the Galileo orbiter.

♪ ♪ Three years after Galileo launches, Comet Shoemaker-Levy 9 has been captured by Jupiter's gravity.

And now, locked in the giant planet's deadly embrace, tidal forces begin to tear the comet apart.

♪ ♪ Its journey into the inner solar system cut short, what happens next presents the Galileo scientists with a unique opportunity.

So everyone was observing it and they realized two things.

One is that it had just passed very close to Jupiter and probably had gotten pulled apart by Jupiter's tides, and the other was that it was going to crash into Jupiter two years later.

The discovery that a comet was about to hit Jupiter was a huge surprise and very exciting.

QUINTO: After crossing the inner solar system, Galileo is approaching the spot where it will witness the comet's final moments.

INGERSOLL: We knew Galileo would be able to see the flashes directly.

We knew that the impacts were going to occur on the night side and that Galileo was going to be able to see 'em.

♪ ♪ QUINTO: On July 16, Galileo sees the first fragments of the comet enter Jupiter's southern hemisphere.

INGERSOLL: At 60 kilometers per second, the fragments really heated the atmosphere red hot, almost to the temperatures of the sun.

And the pieces hit the planet one after the other.

♪ ♪ (distant thud) QUINTO: Pieces of Comet Shoemaker-Levy 9 strike Jupiter over the course of six days.

INGERSOLL: They looked like big flashes on Jupiter.

The pictures of the impact were fantastic.

♪ ♪ QUINTO: These powerful pulses of light, captured from 150 million miles away, are the only time we have ever witnessed a comet strike.

(rumbling, comet whooshing) (muffled explosion) The most destructive impact releases energy equivalent to six million megatons of TNT... leaving behind a giant dark cloud 7,500 miles across.

By capturing objects and incinerating them on impact, Jupiter protects us from bodies that might otherwise threaten Earth.

Galileo would go on to study Jupiter for another eight years.

MAN: The spacecraft will orbit Jupiter at least 11 times, making a close flyby of one of the Galilean satellites on each orbit.

♪ ♪ As the probe samples the Jovian atmosphere, scientific results will be relayed to the orbiter.

QUINTO: Galileo records 400 mile per hour winds in Jupiter's clouds.

And measures lightning strikes many times more powerful than those on Earth.

MAN: The spacecraft will sweep within 200 kilometers of the surface of Europa, yielding high resolution images.

Galileo's Europa encounters will give us our first detailed look at this moon's mysteriously fractured surface.

♪ ♪ QUINTO: Galileo's images confirm Europa is an ice moon.

Analysis of its magnetic field reveals Europa's cracked surface floats above an ocean 60 miles deep which contains more water than all the oceans on Earth.

Then, on September 21, 2003, Galileo meets the same fate as the comet that had greeted its arrival.

INGERSOLL: At the end of the mission, the spacecraft was low on fuel and it had suffered a lot of radiation damage and we had to dispose of it.

♪ ♪ BAGENAL: And the best way to do that is to send it into the planet so it burns up.

♪ ♪ You don't want the spacecraft to hit one of the moons, especially a moon like Europa, that may have life.

Because the spacecraft may be carrying life from Earth.

♪ ♪ INGERSOLL: When you have to say goodbye, it's a sad moment.

(clears throat) ♪ ♪ But on the other hand, you can look back and say what a successful life the spacecraft had.

And I think that's the way we all felt.

♪ ♪ QUINTO: Jupiter, the oldest and largest of the planets, is the giant of our solar system.

(rumbling) ♪ ♪ In youth, it went on a rampage.

♪ ♪ For some young planets, that spelled disaster.

But for others, like our own world, it cleared the way for their formation.

♪ ♪ And so Earth-- and all of humanity-- owe Jupiter a great debt.

But the fate of the dinosaurs is a reminder that it's a debt that could be recalled at any time.

DESCH: Solar system evolution is never really done, and the orbits of the planets are just not going to stay stable.

Over million-year time scales, the orbits of the planets are quite predictable.

Over much longer time scales, however, they act in a fundamentally chaotic manner.

QUINTO: Which means the story of Jupiter may have one final twist.

BATYGIN: Among our calculations of long-term evolution of the solar system, we find that about 1% of the time Mercury's orbit can become exceedingly elliptical as a result of gravitational interactions with Jupiter.

(crashing, rumbling) QUINTO: This would have dire consequences for the inner solar system.

Mercury could be thrown into the sun, flung out into interstellar space, or even set on a collision course with Earth.

BATYGIN: In every one of these situations, however, the orbits of the other planets, Earth included, get messed up.

So, the solar system, the inner solar system, becomes an unlivable place if this occurs.

♪ ♪ QUINTO: And so Jupiter, the giant that shaped the birth of our world, might one day bring about its demise.

♪ ♪ ZACHARY QUINTO: A billion miles from the sun... EDGARD RIVERA-VALENTIN: Every time we think we have Saturn pegged, another piece of evidence tells us no, everything we thought was wrong.

QUINTO: The most mysterious and alluring of the planets.

But the discoveries came at a cost.

JULIE WEBSTER: I was supposed to call end of mission.

I couldn't get the words out.

(voice trembling): It's still hard.

QUINTO: "The Planets: Saturn," next time, on "NOVA."

♪ I'm losing sight of our reality ♪ ♪ ♪ ♪ ♪ ♪ ♪ ♪ ♪ ♪ ♪