Original subtitles

On January, the second, 1959,

with the space age barely a year old,

the Soviet Union launched Lunic, or little moon.

It should have been the first probe to land on the moon.

But within hours of the launch, it became clear

that Lunic was going to miss its target.

As the Soviet scientists watched their tiny probe sail away,

they renamed it Mechta, the dream.

It was headed on a unique journey around the sun

to join the planets of our solar system.

In 1926, when this recording

of Holst's Planet Suite was made,

there were thought to be eight planets.

Then, in 1929, a young man arrived at an observatory

in Flagstaff, Arizona, to start a search for a ninth.

At that time, little was known about the planets.

Closest to the Sun, lies Mercury.

A tiny world of iron and rock, barely visible in the glare.

Then, Venus. Perhaps a second Earth.

Hidden beneath a blanket of cloud.

Then, Earth. And beyond us, Mars, the red planet.

It has seasons, polar caps,

and even the possibility of life.

Far beyond these rocky worlds are the distant giants.

Jupiter, over a thousand times bigger than the Earth.

And Saturn, with its distinctive and dramatic rings.

The two remaining planets are 15 times

the size of the earth, yet they're so distant,

they appear as the faintest of stars.

Uranus, an aqua-marine mystery and finally Neptune.

A world that moves unevenly across the sky.

This irregular movement suggested the presence

of a more distant planet, who's faint gravitational pull

might be toying with Neptune's orbit.

Planet X.

February the 18th, 1930, Clyde Tombaugh sitting

in an office very near to where we're sitting right now,

looking at the photographs

that he had taken of the night sky.

Sitting where this eye at the eyepiece

at that blink comparator back there.

And he had been searching on the plates

that had been centered on a star in the constellation

of Gemeni, the twins, it started that morning.

He had moved very closely, very slowly across

and he would click, click, click, moving, seeing one

image then the other, then the other,

keeping on moving back.

All of these images were negatives

so all of the stars, and anything else,

would be black on a white background.

About four o'clock that afternoon, he crossed the very

center of the plate, he passed the area right

where the guide star was,

the star Delta Geminorum, big, big, bright star.

And moved a little bit more, a little bit more,

and then he saw a very faint, a very faint black dot.

And then he blinked to the other one,

and it appeared on the other plate,

and he saw it appear here, and appear there.

On his plates, taken several days apart,

Tombaugh noticed that a point of light had moved.

He knew instantly, that this was what he was looking for.

It was an historic moment.

He took the walk from the comparitor room,

all the way to the director's office,

and he stopped and he did his tie,

and combed his hair a little bit,

and he said I wanted to appear

a little nonchalant about this.

So then he stepped into the office,

Dr. Slifer, I have found your Planet X.

Planet X was soon named Pluto.

It marks the end of the solar system.

A tiny world of ice, smaller than our moon.

Now known to have it's own satellite, Charron.

Pluto patrols the outer edge of the solar system

in the distant realm of giants.

Worlds of swirling water, like the az-u-an Neptune,

and Uranus, which mysteriously orbits the Sun,

spinning on its back.

Pluto lies way beyond the gargantuan worlds,

the gas planets that have no landscapes.

Saturn with wind reaching thousands of kilometers per hour

and Jupiter, which has an Earth sized storm

that has lasted for centuries.

The closest worlds to the Sun,

are small islands of rock and iron.

Mars, with its faint atmosphere of carbon dioxide

and Venus, smothered in clouds of sulfuric acid.

Then there is Mercury,

boiling in sunlight and freezing at night.

Nine different worlds that appear to have little in common,

except that they orbit a single sun

and are bound together by its gravity.

And then, there's the Earth.

One of the smallest planets in our solar system.

It has a thin atmosphere that clings to a rocky surface.

But the Earth is different, it is special.

It has life.

What process could create such

a variety of different worlds?

Hal Levison is at the forefront of a branch

of astrophysics that is still struggling with the mystery

of how the planets formed.

It's amazing to really consider

that all the planets in the solar system,

the Earth, the rest of the rocky planets,

the cores of the giant planets, Jupiter and Saturn,

and the majority of the outer planets,

Uranus, Neptune, and Pluto formed from material

that is very fine pieces of dust,

much finer than the dust that I'm holding in my hand.

About the consistency, or size,

of particles of dust in cigarette smoke.

I was an astrophysicist interested in a sort of obscure

type of galaxy, when about five years ago I got the bug

of trying to understand how material like this,

can form the planets that we see today.

By the 18th century, astronomers had discovered

that galaxies are filled with drifting clouds of gas,

called nebuli.

Perhaps these clouds were the raw materials of the planets.

Two men, the philosopher Immanuel Kant,

and the mathematician, Simon de Laplace,

looked at how all the planets seemed

to orbit in the same direction.

They suggested the planets were a relic

of a cloud of dust and gas that circled

the Sun during its formation.

In a single process, they concluded,

the solar system was born.

The idea was elegant and quite brilliant,

but it would be centuries before the details

of their theory could be fully worked out.

It would take the arrival of the space age.

September, 1944, London was under siege.

Brutal rockets were raining down from the sky.

Hitler's vengeance weapon threw people into panic.

Nothing had prepared them for a supersonic missile

that took just six minutes to travel

from mainland Europe into the heart of Britain.

The technology behind these missiles was highly advanced.

It had been developed by a brilliant young engineer

called Wernher von Braun.

Von Braun's rocket was called the V2.

Designed to win the war for the Nazis,

eventually it became the foundation

of our journey to the planets.

When Germany fell, American troops

headed straight for the V2 factories.

Before the dust had settled in Europe,

Von Braun and his team of engineers

found themselves working for the United States Army.

In the deserts of New Mexico, the captured rocket parts

were reassembled by U.S. and German engineers.

The modified V2s were soon flying

way beyond the range of conventional cameras.

To record their progress, the engineers fixed

astronomical telescopes to anti-aircraft gun mounts.

The system was designed by Clyde Tombaugh,

discoverer of Pluto, and his films still survive.

Before they left the German rocket factories,

the Americans destroyed as much as they could

to prevent Von Braun's secrets from falling

into the hands of the advancing Red Army.

But when they arrived, the Soviets found just enough

to take back to Moscow.

The man given the task of piecing together the rockets,

was Sergei Pavlovich Korolev

and Boris Chertok was his right hand man.

While their brief was to develop rockets

which could reach America, Korolev's eyes

were fixed firmly on the planets.

But in the early years, it was the Americans who were ahead.

By the end of the decade, they were strapping

film cameras to rockets and sending them

high above the atmosphere.

The cameras had to endure an 18 mile plummet back to Earth.

Miraculously, some survived and astronomers got their first

glimps of the only planet

they couldn't see with their telescopes.

For the first time, scientists could see

the arking horizon of the Earth.

At last, they had a unique glimpse

of the ball of rock and iron that made up our world.

How such a world could have grown from a cloud of dust,

seemed more baffling than ever.

George Wetherill has dedicated his career

to the question of planet formation.

When he started his work, the science

was dominated by one man.

No great scientist ever devoted his life

to understanding this problem, it was sort of a hobby,

something they did on the side

and I think the first person to really devote his life

to this was a Russian scientist named Viktor Safronov,

who started working on these problems

shortly after World War Two and he tried to identify

what all the scientific problems are,

that you need to understand and need to solve

in order to understand the grand problem,

the formation of the solar system.

And to this day, his lists of problems are essentially

the same problems that we're working on today.

Viktor Safronov revisited the 200 year old idea

that the planets formed from a cloud of gas and dust.

He set about trying to break down

this complex process into several simple stages.

The first stage is still not fully understood.

Remember, we're starting off with very fine pieces of dust

and the process of how you get from something like that

to something the size of a boulder,

or even something the size of a mountain

is actually not very well understood.

Party line of the, of what most people think

actually happened was that you had this disc of dust

and the dust sort of settled into the mid-plain

of the proto-planetary nebula, this disc.

And you got what's called a gravitational instability

that formed big clumps of things the size of, maybe,

a hundred meters in diameter.

Safronov's second stage was less complex.

It was called accretion.

This was when the clumps would gather together,

gradually forming the planets in our solar system.

As they grew, a new force became significant, gravity.

A really amazing thing happens though,

that Viktor Safronov discovered,

and that is as these things start to grow,

the bigger something gets, the more it can eat.

So end up with this run away situation

where the bigger guys are getting bigger still,

faster than the little guys are,

and it's sort of a race to eat up all the little guys.

And so you start off with an uncountable number

of objects that are the size of mountains

and you end up with maybe a hundred

in the inner part of the solar system.

Objects about the size of the moon,

or maybe going up to the size of Mars.

Competing worlds hoovered up the surrounding

debris until there was simply no more left.

In the inner solar system, where there are now four planets,

there were once, more than a hundred.

How that army of worlds became just four was still a puzzle,

but Viktor Safronov had a hunch

that the process would leave those planets

splattered with the scars of impact.

Was this what we could see on the moon?

Unknown to the West, Safronov had taken a giant stride

towards a theory of planet formation.

Perhaps somewhere in the solar system there might

be a planet bearing evidence for his theory.

In 1957, the Americans announced

that they were preparing to enter the space age.

They were about to launch

the world's first artificial satellite.

In the Soviet Union, Korolev acted immediately.

For Korolev it was the beginning

of the race with Americas and he wanted

to be first he wanted to be ahead of Americas,

like all of us and I think he want to do this, maybe,

hundred time more than any others.

Then he call my father, he told I want to launch

this first satellite, lets do this

before Americas as soon as we can.

It would be a huge gamble, but finally,

Khrushchev agrees to let him try.

Now Korolev had to convince his engineers

that they could do it.

On October, the fourth, 1957, while the Americans were

still finalizing their plans, Sputnik was launched.

40 years on, Korolev's achievement

is still celebrated in Russia.

That evening, he was very proud.

He realized that it is the great achievement.

And next day, he understood that the reaction

of the outside world is much stronger

than it was in our country and really there feeling was

much stronger than even his feeling,

especially in the United States.

Korolev's rockets had opened the door to space.

We were getting closer to the planets.

Bruce Murray is a veteran of the U.S. space program.

When his career started, the planets

seemed a very long way away.

He still remembers the first time

that he saw Mars through a telescope.

And it just blew me away.

I was so taken with the fact that here was a real object.

It was three dimensional, seemed to be three dimensional,

it was colorful, and glowing and it really drove home to me,

there's another place out there, a real place,

not just something I studied in school somewhere.

As a young man, Bruce Murray was taken under the wing

of physicist, Bob Leighton, who had developed a way

to make time-lapsed films of the planets.

The images were extraordinary because they

could show the planet rotating.

You could time lapse it, you could take one frame,

wait a minute, take another frame and so forth,

and make this time lapse and it brought to everybody,

the image of Mars that the most dedicated astronomers

only infer, 'cause they don't see it that way either.

They have to remember all those frames.

So it was an extraordinary achievement.

And he did it, it was for fun.

Leighton's films brought the planets to life.

For the first time, astronomers could see pictures

of Jupiter moving through space.

The outer planets, the ones that are huge masses of gas,

that, in the case of Jupiter or Saturn,

you could actually see some beautiful structure.

The first thing that strikes one,

as in the inner solar system is diversity,

my Lord, everything is different.

But Mars, the Earth's smaller cousin,

was always the most tantalizing.

Leighton could see mysterious dark patches rotating

with the planet, but what would

a close encounter with the surface reveal?

In 1963 the American probe, Mariner Four set of

to send back the first pictures from another planet.

And also to dust there are...

Bob Leighton was responsible

for bringing back the images. And blue clouds.

And clouds of the terminator and clouds that...

He asked Bruce Murray to join his team.

I was dragged along, sucked along,

however you wanna look at it, into this wonderful experience

of becoming the first experimenters

to look at Mars through a close up camera.

This is control center at JPL.

The space craft is 134 point 217 million miles from Earth

and 50,142 miles from Mars.

After a journey of eight months, Mariner Four

was homing in on its first target.

The first picture will cover an area

of approximately 176 miles square

on the sunlit lip of the planet.

I wish I was as sure as he is.

About 12 minutes from now,

we should be able to determine that the camera's,

T.V. camera's shutter is operating

and that the recorder is running.

The anticipation of not just the scientists,

but the public and the news media, it was incredible,

because Mars was like to have life and in the popular mind

maybe it had Martians as far as they were concerned.

Mariner Four was a fly by.

It would only get one chance at the pictures.

A.S. data reports the scan position

for frame 605 as decimal 323 congratulations.

323, 323 right on the money.

Exactly where they wanted it.

10,000 miles from the surface,

Mariner 4's cameras whirled into life.

These signals came back, if you think of a one element,

one picture element, one sample of light.

The rate at which these came in were from Mars,

was one of these per second.

Hey there we go. There she goes.

That's data.

And so it took three weeks for our

20 pictures to come back.

Give me Bruce Murray's phone number.

Where the devil are the Mars pictures interpretators?

Yeah, data's comin' in boy what are you doing in bed?

There it is. I think we got something.

The planet was not what they had expected.

There was no sign of life here. No vegetation.

Just picture after picture of a dull, flat landscape.

It wasn't until frame 12

that the first features became visible.

What we could see were these huge craters.

300 kilometers, 200 mile craters across on Mars.

Impact craters, and that meant that Mars was preserving

a signature from these earliest times,

three, four billion years ago and so we had

a major conclusion, stunning to everybody,

from these very few pictures we got.

When the news filtered through

to the Soviet Union, one man wasn't

as surprised as his western rivals.

Craters were exactly what Viktor Safronov expected.

Soon Safronov's idea's were being discussed in the west.

Where superior technology allowed George Wetherell

to take the accretion theory further.

I called it the planetismal problem

and it simply says you've got a lot of objects,

small planets moving around the sun in orbits

and what you'd like to understand is

how they accumulate together to form large planets.

Wetherell's computers uncovered

a terrifying period of planet formation.

What you actually find, if you do the problem

with a computer, is that as they grow,

they start to perturb one another,

into orbits which cross the orbit of another planet.

The neat orbits of Safronov's army of planets,

soon became fatally disrupted as they started tugging

each other off course, these different worlds sped

towards each other, colliding with shattering force.

George realized that it was sort

of like a wild frat party.

All sort of hell brakes loose

in the inner part of the solar system.

Things are swung around, half the stuff is either

hits the sun, or gets thrown out to Jupiter,

which can then knock it out of the solar system.

It's a very violent happening party.

If Wetherell is right, than during this period,

the inner solar system must have been

strewn with planetary death.

The four surviving planets would have had to endure

a final stage of intense bombardment.

In 1973, George Wetherell got the chance to test his work.

Mariner 10 was on it's way to Mercury.

78 million kilometers from Earth

and far beyond the scope of even

the most powerful telescopes, the surface

of this planet was a total mystery.

Just a few months before the Mercury mission,

I was at a meeting where, people discussed

what we might find on Mercury in a sort of,

get our minds active for thinking about Mercury

and a very distinguished planetary astronomer,

in answer to a question, proclaimed that Mercury

would have no craters on, or very few craters.

Curious thing is that, the craters

on Mars were also a surprise to most planetary astronomers.

After a journey that took in a fly by of Venus,

By February, Mariner 10 was nearing it's target.

Subsequently, though, however, I had the opportunity

to be invited to JPL and sit in a little room

up above mission control and see the pictures

of Mercury as they came in.

First pictures of Mercury started coming

and at first it was just sort of a fuzzy ball

and you could sort of imagine these small craters,

but after awhile, it got closer and closer.

Pretty soon it started to look just like the moon.

Mercury turned out to be

the most heavily cratered planet in the solar system.

One impact was so great, it left shock waves,

set in stone, on the other side of the planet.

It was proof of the final stage of the accretion theory.

And I was just thrilled by this.

I knew they were there, but actually seeing them,

that I'd been thinking about all these years,

now here they are for me to look at,

made me very excited and I've also excited all these

military men around, they kept saying,

isn't that beautiful, it's just like a '52 drop in 'nam.

Here then, are the inner planets.

The survivors of a life or death struggle.

Mercury, Venus, and Mars.

Each bearing the scars of their creation.

But what of the Earth?

Surely our planet could not have survived unscathed.

Out in Arizona, Hal Levison, reveals evidence

of the violence that once rained down from space.

This hole in the ground was made in a matter of seconds.

Despite being a very awesome sight,

something that tells us that the solar system is still

active and things are still running into each other.

It's a relatively small, insignificant hole in the ground.

Around 50,000 years ago,

a 50 meter fragment of a world blown apart

billions of years earlier, careered into our planet.

Here is evidence on Earth of the final stages of accretion.

But what of the world's that dwarf the inner planets?

How does the accretion theory account for the gassy giants

in the distant regions of our solar system?

We have very different planets.

Types of planets as we get farther from the sun

and that's because as you get farther from the sun,

the temperatures dropped and particularly at about

four times more distant from the sun than the Earth is,

we hit a point where water would condense out

and become a solid.

With water turning to ice,

the amount of material available to form

the outer planets was far greater.

Jupiter and Saturn grew so large, they started sucking

in the primordial gases from the original dust cloud,

swelling them to hundreds of times the mass of the Earth.

This region was populated with many more planets

than exist today, their orbits were also disrupted.

We can find no traces of impacts in their gassy atmospheres,

but evidence can be seen in their rotation.

It's believed that a world the size of the Earth,

collided with Uranus.

As a result, today Uranus still rolls

around the sun, on it's back.

When did these planet building impacts come to an end?

I've found a lot of comets, I've been involved now

in the discovery of 21 of them.

There is nothing like the night we found Shoemaker Levy 9.

We had no idea how important that discovery was going to be.

It made page 23 in the London Times.

That Carolyn and Gene Shoemaker

and I had discovered this comet.

Interest increase several months later

when it was announced that Shoemaker Levy 9

was on a collision course with Jupiter.

This was not page 23 of the London Times,

this was now page one.

This is a very different story.

Shoemaker Levy 9 was gonna show us what it's all about.

In all of civilization, since Galileo

first looked through a telescope in 1609,

and since he first looked at Jupiter in 1610,

this is the first time that we will

ever have seen a comet strike a planet.

July the 16th, 1994.

Impact day and every available telescope

is trained on Jupiter.

Look!

Oh my God! Look at that! Look!

This is how the solar system was built.

Comets hitting planets, comets first hitting each other.

Very slowly and it's kind of an embrace

rather than a collision and then these objects get bigger,

their gravity gets bigger, the collisions get faster

and the speed gets higher and it gets more violent

as the solar system reaches its teenage years it's become

a little bit dysfunctional and finally, when does it end?

Well, what Shoemake Levy 9 taught us

was that it hasn't happened yet.

Right then, in the summer of 1994, around Jupiter,

there's a big yellow police fence that says,

danger, keep out, solar system under construction.

It's still happening. Jupiter grew a little bit

during the week of July 16th 1994.

Water was dumped on Jupiter.

It had more carbon sulfate now than it had then.

It was as if nature had said, OK guys,

I'm gonna show you how it works.

And all you have to do is watch it.

These are the gas giants.

Jupiter and Saturn mark the current limits

of the planet builder's theories.

Far beyond these vast worlds lie the ice giants,

Uranus and Neptune.

But out here the accretion theory runs into trouble.

The formation of Uranus and Neptune are the greatest

mysteries in the formation of the solar system

because everything goes more slowly at greater distances

from the sun so all these processes slow down.

When we try to run the same computer programs

out there that we did in the terrestrial planet zone,

we don't get planets forming.

No matter what we do, we can't form

Uranus and Neptune using those kind of models.

No matter how hard I try, I can't make Uranus and Neptune

go away, they're there and our models can't make them.

So we do indeed have a lot of, a long way to go

before we really figure all this out.

How these worlds formed so quickly is a puzzle.

Scientists don't know enough about early conditions

this far from the sun.

What kinds of worlds went into

the formation of Uranus and Neptune.

In 1992, two astronomers were surveying the space

beyond Neptune and they found a substantial chunk of ice.

Since then, they've found many more.

Called the Kuiper belt, it's now thought

to contain the building blocks

of ice giants that never were.

The Kuiper belt is a region where the small ice mountains

that we were talking about actually started accreting

and building into larger things.

That's really, to me, the region we need to look at.

Because what happened there is

planet formation started there and it was frozen in

in some intermediate state and trying to understand that,

will let us know, in more detail,

how the accretion process started,

but what shut it off is also going to be interesting.

Tell us something about the process as well.

So to me, the future really lies

in the outer part of the solar system.

But there's a planet that lies

at the inner edge of the Kuiper belt.

70 years after it's discovery, the strange tiny world

of Pluto may at last be making sense.

Pluto was discovered in 1930, right.

And it was the odd ball of the solar system.

Most of the planets are in nice circular orbits, not Pluto.

Most of the planets sit in the plain

that represents the accretion disc, not Pluto.

And it was just an odd ball, it was small, and icy,

and it had no similarity to anything else

that we really knew about.

Could this small icy world

be one of the survivors of accretion.

A world that somehow escaped being swallowed up

by the growing Neptune, or being hurled

out of the solar system.

Could Pluto be the missing link

of the formation of the ice giants.

Turns out, Pluto was just the largest known member

of this population, so it went from being this

lonely, remote odd ball, to being essentially,

the grandfather of a population.

And we're talking about, the Kuiper belt,

probably has more objects in it than any

other region in the solar system.

So it's the most populous region in the solar system,

yet we didn't know about 10 years ago.

In the 40 years since Metchtar broke free

from the Earth's gravity,

we've sent probes to all the planets.

We've sampled the corrosive clouds of Venus

and recorded planet wide storms on its surface.

We've viewed dust storms on Mars

and seen canyons that could swallow countries.

We've mapped the icy moons of Jupiter

and plunged into it's atmosphere.

We've skimmed the rings of Saturn.

We've seen active geysers on the most distant

and freezing moon in the solar system.

But just as the first stage of our journey

to the planets draws to a close,

further worlds are opening up.

In 1992, Clyde Tombaugh got what he'd been waiting

for from NASA, permission to visit Pluto.

Clyde was melted, he melted when he got that letter.

He felt that all his life's effort,

all of his life's work, with Pluto,

with his work at White Sands was coming to a head.

He felt that that letter was really a sign

that NASA, through there mission to Pluto,

was finally acknowledging him as the man that he really was.

Clyde Tombaugh died in 1997.

A probe, heading towards Pluto will launch in 2006.

After analyzing the planets composition,

it will head out towards the Kuiper Belt,

piecing together the final clues

of how our solar system was formed.

Whatever the craft finds,

Pluto's importance is now unquestionable.

It will be a manned mission

to Pluto in a very special sense.

It's not going to have a real living person,

but you can bet that's it's gonna have Clyde's spirit

on board on its way to Pluto to see,

what kind of a planet that little guy really is.