Original subtitles

A billion kilometers from earth,

a small probe uncoupled from an interplanetary spacecraft

and headed for its target.

It had a date with Jupiter.

In an encounter that would break all records,

the probe accelerated towards

the largest planet in the solar system,

plunged into its thick clouds,

and was swallowed by its atmosphere.

Without its atmosphere, we could not live on Earth.

Rain on our faces.

Wind in our hair.

The very air we breath.

Atmosphere is what makes our planet habitable.

To get an insight into the other planets,

it is vital to understand how their atmospheres work.

The journey of discovery began here on Earth.

The first man to explore the limits of the atmosphere

was U.S. Air Force Colonel Joe Kittinger.

He is still flying at the age of 72.

In 1960 he attempted something no one had tried before.

To leave the Earth's atmosphere behind.

This was the first time anybody'd ever been

to this high of altitude.

This was the first time man had ever been

in an actual space environment.

So I had some concern about what was gonna happen.

Project Excelsior was an attempt to send a man

up to 100,000 feet travelling in a helium balloon.

If successful,

Joe Kittinger would be the first human in space.

63,000 feet, that's where a man,

unprotected, his blood would boil.

Actually boil because of lack of pressure.

So for man, space is 63,000 feet.

Any place above that

you die very quickly without a pressure suit.

The balloon was overhead,

and at the signal they cut the straps

holding the gondola down, and off I lifted.

I had great confidence in myself,

and the equipment, and the team,

but there's always that unknown.

There's always something that you may not have covered.

At 50,000 feet Kittinger hit a snag.

The glove on his rudimentary spacesuit sprung a leak.

Now what that meant was

that the blood would pool in my hand,

and it'd just continually pool and pool and pool.

But I didn't tell my flight sergeant

because I didn't wanna worry him,

and I also felt that if I had told him,

that he would probably've made me abort the flight.

I felt that, reasonably certain, that I could survive

not having a pressure suit glove on my right hand,

so I continued on.

Overhead the sky was black as it could be.

I couldn't see any stars, but it was that black.

An hour and a half after lift off,

Kittinger reached 103,000 feet.

I was up on a porch, I was the highest step in the world,

looking down on our planet.

I could see the clouds below,

and the atmosphere, the haze layer.

It was a very profound feeling that I had.

The realization of really

just how hostile that environment is.

And it's only 20 miles above our earth.

The air outside looks the same, but there's no air there.

It's like being in an environment that's cyanide,

and you take one whiff and you're dead.

Just 20 miles down there was safety, and comfort,

and an environment that man is used to.

Kittinger spent

just 11 minutes on the edge of space,

and then he prepared to return.

So I took that final look around, I said my silent prayer,

I hit the button to start the cameras working,

and I jumped from the gondola.

Yeeehoooo!

I fell faced Earth for a little ways

and I had really no sensation of falling,

because I had no visual reference of anything,

so I thought I was really suspended in space.

I turned over my back about this time and I looked up

and the balloon was racing into the heavens.

I mean at a fantastic rate,

to me it was just flying away.

And what it was, the balloon was standing still

and I was the one that was falling so rapidly.

Kittinger fell to Earth at the speed of sound,

but with no air around him, it was a silent fall.

I had no ripple of the fabric in the pressure suit,

and it was a very weird sensation.

After four minutes of falling through space,

Kittinger began to reenter the protective blue haze

and was hit by the familiar world of cloud, sky, and air.

Joe Kittinger had gone beyond the edge of the sky,

and lived to tell the tale.

15 minutes before I had been at the edge of space,

and now to me I was in the Garden of Eden.

We really don't appreciate what a beautiful planet we have.

The atmosphere is a tiny layer.

It's insignificant in terms of mass,

compared to the mass of the planet,

and yet it is so key to our experience

and our very existence here on this planet.

Dave Grinspoon is an atmospheric scientist.

When I first got excited about the planets,

when I was young,

it was the pictures of the surface of a planet,

it's the most obvious, tangible, thing that grabs you.

But then as I got into studying planets,

I learned about some of the frontiers of knowledge,

some of the real mysteries

that were crucial to understanding exactly

how the solar system got to be the way it is,

how Earth achieved its unique status,

and I found that a lot of the problems

that interested me in that way

had to do with the atmosphere,

with the evolution of the atmosphere.

As far as early astronomers knew,

other planets were just like the moon.

Airless balls of rock.

But in 1761,

a Russian stargazer observed something very strange.

From an observatory in Saint Petersburg,

Mikhail Lomonosov saw the planet Venus

pass across the face of the sun.

He noticed that the edge of the planet

wasn't hard and crisp like the moon.

Venus seemed fuzzy.

As the planet crept past the sun,

he was astonished to see it surrounded by a thick halo,

clear evidence of an atmosphere surrounding Venus.

For 200 years,

what lay below the clouds remained a mystery.

Could Venus be a world like Earth?

The Russians sent a probe to find out.

As Venera 4 headed for a splashdown on Venus,

the designer's main worry

was that their spacecraft might sink

and radio contact would be lost.

In October 1967,

radio dishes across Russia were trained on Venus

eager for news from the world beneath the clouds.

Under a pressure 15 times that on Earth,

15 miles from the surface of Venus,

Venera 4 was crushed.

The probe didn't splash into an ocean,

it never even came close.

What kind of turbulent world lay below the clouds of Venus?

The Russians were determined to land a probe there.

They tested their probes to the limit.

The Soviets set about recreating Venus on Earth.

To mimic the severe atmospheric conditions,

they built the world's biggest pressure cooker.

After four years, they had a craft

they hoped was tough enough to survive

the crushing inferno of Venus.

Venera 7.

Just before Christmas, 1971,

Perminov and his team received the probe's faint signal

reporting touchdown.

They had made it.

The first glimpses we got

of what it really looks like on the surface

were from those Russian Venera pictures

of small pieces of sort of

strange volcanic landscapes on Venus.

Those pictures were mostly of the ground,

but just in the upper corner of the pictures

you could see a little bit of the sky,

this brightly glowing, but featureless,

because it's cloudy, sky.

I always thought that was really neat.

That you were there on the surface of Venus

and you were just catching this little glimpse of what it

looked like to actually look up and see the sky of Venus.

But what had the probe detected

as it fell through that sky?

If you were plummeting down through

the atmosphere of Venus,

first of all you'd have to make it through the clouds,

which are quite extensive.

They are not like clouds on Earth.

First of all, they cover the entire planet,

and that cloud deck is more than ten miles thick,

so it'd take you a long time just to get down

through the clouds.

When you're actually in the clouds themselves, by the way,

they're very diffused, it's more like a fog.

But what would it be like to stand on the surface of Venus?

Now, the first thing that would happen

would be you would scream and nothing else would happen

because you would be instantly consumed

by the hot, high pressure, noxious atmosphere.

But assuming you had a good environmental suit

and you walked out on the surface of Venus,

I think the first thing you would notice

would be the murky red light.

On Venus, in the middle of the day,

it's about as light as on a deeply overcast day on Earth.

So you would never see the sun from the surface of Venus,

but there's sunlight filtering through the clouds.

Venus is a world of unchanging and extreme weather.

In the high clouds there's a constant drizzle

of sulfuric acid.

And far below, close to the surface,

an unending stream of electrical discharges.

Why there is lightning so far below the clouds,

where it's too hot for rain, is a mystery.

This hot, high pressure, corrosive, atmosphere

held one more surprise.

In 1990, an American spacecraft

pierced Venus's clouds with radar.

It saw that some of the highest mountaintops

were very bright.

As if they were covered in something reflective.

The high mountain peaks all around the planet

seemed to be coated with some kind of

metallic or shiny frosting,

something that reflects a lot of radar energy,

and we don't know what it is.

One idea is that it's coated with tellurium,

which is a trace metal on Earth,

but may be common enough on Venus

and seems to have just the right properties

so below a certain temperature,

which would mean above a certain altitude,

it may be frosting all of the peaks of Venus,

the high peaks.

Mountaintops on Earth

are covered with frozen water.

On Venus, the peaks may be covered in metal.

It seems like there's some kind of metallic snow

on the highest peaks of Venus,

which is kind of a strange thing to think about.

Venus turned out to be

far stranger than ever imagined.

But would our other near neighbor be more similar to Earth?

In 1971, two Russian spacecraft were on their way to Mars.

As the probes moved in,

Mars was suddenly enveloped in a giant dust storm.

After transmitting for just 15 seconds,

the probe fell silent.

The flight controllers had no doubt

that the violent dust storm was to blame.

But this was the first picture from the surface of Mars.

Incomplete and fuzzy, it showed a horizon,

and beyond it, the shadow of a dark sky.

Five years later,

another spacecraft headed for touchdown on Mars.

This time the probe was American.

It was called Viking.

Okay, maybe we can take this opportunity

to summarize.

Would you like to summarize where we are today Don?

To date we have of course landed on the surface of Mars,

and taken pictures both immediately after landing

and again since then.

At the present time we're slowly watching the buildup of

data that's going to be built into a color picture.

And the way we're gonna do it is bring up

first the red, which you see now,

here comes the green, it'll be the second,

and then finally the blue.

You see this last one coming down, you're again,

now you're gonna see the surface of Mars

as best we can configure it in color at the present time.

You can see there are a number of different,

yeah if you douse the lights, and oh my Gosh!

I wasn't even seeing all the colors.

Look at that.

That's pretty spectacular.

And it does have a reddish hue.

It does have a reddish hue to it,

and look at that sky.

Light blue sky.

But there'd been a mistake.

Because they expected the sky to be it's familiar color,

the engineers had unwittingly filtered in too much blue.

The next day they showed Mars the way it really is.

This world has a pink sky.

It's thin atmosphere is tinged with red dust.

Mars is a desert world.

From day to night,

the temperature swings by hundreds of degrees Centigrade.

On Mars the colors of the heavens are turned on their heads.

Red sky at noon and blue skies at sunset.

How did Mars, Venus, and the Earth

all end up being so different?

It's a puzzle that atmospheric scientists

are just beginning to solve.

A big part of what I study

is trying to understand the divergence of Earth's atmosphere

from our neighboring terrestrial planet atmospheres

Mars and Venus.

And I say divergence because as far as we can tell,

the three probably started out very similar,

much more similar than they are today.

Four and a half billion years ago,

the planets formed from a giant cloud of dust and ice.

Mars, Venus, and Earth were worlds of seething lava,

pummeled by meteorites and surrounded by a mist of steam.

Mars just didn't have enough gravity probably,

to hold on to all that atmosphere.

But while the Martian air was drifting away,

Earth and Venus remained covered in a thick layer of fog.

After that phase, Earth settled down and formed oceans.

Okay, it rained.

The same thing may have happened on Venus,

Venus probably had oceans when it was young,

but that steam in the atmosphere,

with the enhanced sunlight from being closer to the sun,

led to what we call a runaway greenhouse.

Venus never lost its steamy clouds,

and like a thermal blanket,

they trapped in its heat forever.

The hotter it got, the more steam boiled off the oceans.

The planet became locked in a global greenhouse effect,

and it meant disaster.

And eventually we think Venus's oceans

just kept boiling and boiled away.

Now on Earth we have a little bit of a greenhouse effect,

mostly because of the small amount of CO2

in water vapor in our atmosphere,

and it turns out that's a good thing.

The greenhouse effect gets a bad rap these days

because of global warming,

and we're all worried about having

too much of a greenhouse effect.

But it's interesting that if we didn't have one at all

we wouldn't be able to live here on this planet.

We get about 30 degrees of warming from Earth's greenhouse,

which is just enough to keep it in the temperate range

that it's in.

Planetary scientist Andy Ingersoll

believes that the Earth's climate

has one of the most varied weather patterns.

I would say that we've

learned that there's a fairly narrow habitable zone

around every star.

Mars is too cold, Venus is too hot, Earth is just right,

and the extremes are frightening.

For me, I'm a meteorologist really,

fascinating thing about the Earth

compared to the other planets is that we have

the most unpredictable weather in the whole solar system.

The dominant weather on Venus seems to be

just the circulation of the atmosphere.

It'd be probably pretty boring if you could stand the heat.

Day after day of temperatures hot enough to melt lead.

That's predictable.

On Mars, the dominant weather that you would notice

would be the day night cycle.

Sort of like living in a desert

or semi-desert area on Earth.

It's another sunny day,

and it'll get cold at night.

And that's predictable, and it's only in between that,

the Earth is sort of in between,

and that's where the weather is unpredictable.

There's one other world

with changing weather patterns

and they happen on a dramatic scale.

The giant planet Jupiter.

The whole planet is just atmosphere,

because it's a gas ball.

And there we have examples of storms that last for 300 years

and maybe even longer than that.

I knew that there were 300 year old storms

and I had this picture of these storms

calmly spinning.

When Voyager got there and started taking close up pictures,

we realized that at the smaller scales it was chaos.

Everything was changing,

the little tiny storms were coming and going every few days,

and yet we had these large storms that were very stable.

It really deepened the mystery of why the

large storms could have endured.

One of the biggest storms on Jupiter

is marked by its red spot.

And it's been occurring for around 300 years.

The Great Red Spot is, what,

two or three times the size of the Earth,

but it's only one of a whole class of large storms.

The next largest class is, was,

three wide ovals that formed about 60 years ago

and have been sort of

keeping their distance from each other.

But last year two of them merged,

and so it's a kind of historic event for Jupiter weathermen.

What forces could be driving the giant storms?

The spacecraft Voyager

was only able to look at Jupiter's surface.

To find out more,

a probe would have to dive right into those swirling clouds.

NASA put one of its most experienced engineers

to work on the design.

For Jupiter, the essential problem was

that the planet is so massive, so gigantic,

that in falling into it from a very great distance

as a probe does, as a probe approaches a planet

it essentially just falls into the gravity field.

And the falling into Jupiter

brought you up to speeds of 60 kilometers per second.

If you want to figure that in miles per hour,

that's a big number.

120, 140,000 miles per hour, something like that.

Back in the 1960s,

Al Seiff had designed the heat shields

that saved pioneers like John Glenn and Neil Armstrong

from burning up on reentry.

Seiff had a hand in almost every spacecraft NASA ever built.

The spacecraft is stable.

Galileo is on its way to another world.

But Jupiter was his biggest challenge.

Fly safe.

We worked, as it turned out, for nearly 20 years

in getting that experiment mounted and ready to go

and ready to function and then finally to fly

way out in the solar system to that distance,

and of course it was probably the least certain of success

of any of the missions

because of the challenging entry conditions.

In December 1995 the Galileo probe

began its kamikaze dive into Jupiter.

The heat shield itself was made out of carbon phenolic,

and carbon heats up to about 4,000 Kelvin

and then it starts to vaporize,

and that's exactly what this heat shield did.

The heat shield was about 80% vaporized,

about 20% remaining.

It was white hot, white hot.

Then when the fiery entry was over,

the probe began drifting gently down

into the planet's atmosphere.

It was hoped that Galileo would detect clouds and rainfall,

and uncover the secrets of Jupiter's weather.

But Andy Ingersoll was frustrated.

I was surprised at how little water they found.

Because water is so important to the weather on Earth,

and it presumably was important to the weather on Jupiter.

Although Jupiter is covered with clouds,

Galileo had the bad luck

to fall into a narrow gap between them.

It appears that the Galileo probe

went into a desert of Jupiter.

And that if we'd just gone somewhere else

we would have found the rain.

As it sank ever deeper into the atmosphere,

Galileo detected the winds picking up

and the weather becoming more and more turbulent.

The probe seemed to be getting closer

to the source of the giant storms.

But it could give no more clues.

Three hours after it began its descent,

Galileo ventured too far into Jupiter's boiling interior.

There was no buoyancy to stop it from going down and down

and so these very high temperatures in the interior

ultimately caused the probe to melt and to vaporize,

and today the Galileo probe

is a part of the atmosphere of Jupiter.

We have actually slightly contaminated this giant planet.

Was there another world anywhere

that could compare to the Earth?

For centuries, astronomers had watched

a tiny object circling near the rings of Saturn.

It was bright, like Venus.

It almost seemed to glow.

Could this world have an atmosphere too?

Astronomers could hardly wait to find out.

It was the moon Titan.

I can think about astronomers of yesteryear

like Christiaan Huygens who discovered Titan,

and the astronomers that came after him,

who spent their lives looking through telescopes

trying to eke out any little bit of information they can

about the solar system and about Titan in particular

and feel a tremendous sense of sympathy for them.

Modern day planetary scientists like myself

know that we can hypothesize

and come up with all the theories we want,

but eventually we'll get to where we're going

and we'll be able to see exactly what the truth is.

The first close up pictures

of this enigmatic moon came in 1980 when Voyager flew by it.

I mean it was clear

that it was a satellite with an atmosphere,

which made it very unique,

because so far up until that point

we associated atmospheres with planets.

The composition of Titan's atmosphere,

the fact that it's 90-95% molecular nitrogen,

along with the fact that its atmosphere is pretty dense,

surface pressure is comparable to that here on the Earth,

a little bit more,

makes it kind of an analog with the Earth,

which is terribly surprising

because no one expected years ago

you'd find an analog of the Earth

out at the distance of Saturn.

The surface of Titan

remained hidden from Voyager's cameras.

But since then, the Hubble space telescope

has managed to peer through the thick clouds.

There are tantalizing signs

of what look like continents and oceans.

Some say this mysterious moon has seas of liquid methane.

It is a world planetary scientists

are more eager than ever to explore.

And we, in a matter of,

just a few years once we get to Titan

and once we get to Saturn,

we'll find out a great deal about

what makes this object tick.

Now we have an entire mission

devoted to the study of Saturn,

and Titan is a major target of this mission.

It's the Cassini mission,

which was launched in October of '97,

and I of course was there

and it was the most spectacular thing I'd ever witnessed.

It was also very emotional

because I and my colleagues have spent seven years

developing instrumentation and the spacecraft itself

to go back to Saturn,

and now we have a six year wait for it to get there.

In December 2004,

Cassini will release the European Space Agency probe,

Huygens.

This will embark on a journey through the clouds of Titan

to the surface of this distant moon.

Parachutes will deploy,

the air shell will be jettisoned, and the probe,

which is instrumented with six scientific investigations,

will begin a two and a half hour descent

through the atmosphere.

On the way down it will make measurements of the pressure,

the temperature, the composition of the atmosphere,

and it will continue down until it finally

breaks through what we think to be the lower cloud deck.

The Huygens probe

will slowly sink into Titan's thick atmosphere,

taking pictures throughout its descent.

We don't know what kind of material it might land in.

The surface of Titan is likely to be ice

covered with debris that has rained out of the atmosphere.

There may also be liquid on the surface, seas and lakes.

With pools of methane, oily fog, maybe even rain,

Titan could bear some sort of resemblance to the Earth.

Here is a body with a surface and an atmosphere.

You could, if properly equipped,

you could walk on the surface of Titan.

And you could see the results of wind erosion,

and flowing liquids, and seas, and waves, and winds.

It has almost a feeling of home to it

and I think that's a tremendously powerful feeling for us.

The Huygens probe has brought back

the spirit of the early days of planetary exploration,

taking us to a new world we've never been to before.

Our current knowledge of Titan

is comparable to our knowledge of Venus

in the '50s and '60s.

In those days, when we were trying to study Venus,

we kind of imagined Earth-like scenarios.

And I suppose we're doing the same for Titan.

We're imagining lakes,

although we imagine they're made of hydrocarbons,

but still we sort of feel comfortable with that concept,

and it may turn out that Titan is dry as a bone

just like Venus.

You learn humility.

You study the Earth, and you think you understand it,

and then you say okay, I've got all these principles,

I'm gonna apply them to another planet,

let's go out there.

You're always surprised,

it's always not what you expected,

and that really teaches you how little you know.

And how much there is to know.