A billion kilometres 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 for speed and violence,
the probe accelerated towards the largest planet in the solar system,
plunged into its fearsome clouds, and was swallowed by its atmosphere
Without its atmosphere, the Earth would not be a home to us
Rain on our faces; wind in our hair; the very air we breathe;
Atmosphere is what turns our planet into our world
To understand the other planets,
we have to understand their atmospheres
The journey of discovery began here on Earth
The first man to explore the limits of the atmosphere was retired
US Air Force colonel Joe Kittinger-at the age of 72, he is still flying
In 1960, he attempted something no one had tried before:
To leave the atmosphere behind
This was the first time anybody had ever been to this high an altitude,
this was the first time man had ever been in an actual space environment,
so I had some concern about what was going to happen
Project Excelsior was an attempt to send a man
up to 100,000 feet in a helium balloon
If successful, Joe Kittinger would be the first human in space
At 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
So any, 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, in the equipment and the team,
but there's always that unknown,
there's always something that you may not have covered
At 50,000ft, Kittinger hit a snag
The glove on his rudimentary space suit sprung a leak
Now what that meant was that the blood would pool in my hand,
and just continuously pool and pool and pool
But I didn't tell my flight surgeon because I didn't want to worry him
and I also felt that if I told him
that he would probably have made me abort the flight
And I, I felt reasonably certainly
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,
and I couldn't see any stars because it was that black
An hour and a half after lift off, Kittinger reached 103,000ft
I was up on a porch, that 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, it was a very profound feeling that I had,
and the realisation 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;
that 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 in that netherworld on the brink 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
I fell face to 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
And I turned over on 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,
of the fabric on the pressure suit
and I... it was a very weird sensation
After four minutes of falling through space,
Kittinger began to re-enter 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
Fifteen minutes before I'd been at the edge of space
and now to me I was in the Garden of Eden
We... we really don't appreciate what a beautiful planet we have
The atmosphere is, 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 sort of 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 an unusual event
From an observatory in St 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
It was a sure sign of an atmosphere
For two hundred years, what lay below the clouds remained a mystery
Was Venus a world like Earth?
The Russians sent a probe to find out
As Venera 4 headed for a splashdown on Venus,
the designers' 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,
and when it was still fifteen miles high, Venera 4 was crushed
The probe didn't splash into an ocean; it never even came close
What kind of hell 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 Xmas, 1971,
Perminov and his team saw the probe's faint signal reporting touch down
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
And er 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 they - first of all they cover the entire planet
and that cloud deck is more than ten miles thick,
so it would 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 diffuse, 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 that 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'd 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 is a constant drizzle of sulphuric acid
And far below, close to the surface,
the probes detected 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 mountain tops were very bright;
as if they were smothered in something reflective
The high mountain peaks all around the planets seem 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 maybe 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
Mountain tops on Earth are covered with frozen water
On Venus, snowcaps are more exotic
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 stranger than was ever imagined
Would our other near neighbour be more similar to Earth?
In 1971, two Russian spacecraft were on their way to Mars
As the probes barrelled in,
Mars was suddenly enveloped in a giant dust storm
After transmitting for just 15 seconds, the craft 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-but there was a horizon,
and beyond it the shadow of a dark sky
Five years later,
another spacecraft headed for touchdown on the surface of Mars
This time it was American- it was called Viking
OK, maybe you can take this opportunity
to summarize where we are to date out
Today we have of coure landed on the surface of Mars
and taken pictures of both before and after landing,
and again since then the present time
where slowly watching the build up of data
that's going be built into colour picture
And what we are going to do is to bring out
first the red to scene out
Here's come to green, wait a second
and then finally the blue
And you see the last is coming down
Now you are going to see the surface of Mars
especially we can configure in colour at present time
As you can see, there're number of difference
Yeah, you're right Oh my gosh
I was all in all to see all the colours
Look at that, that's pretty spectacular
In dust have a redish surface look at that sky
Light blue sky
But there'd been a mistake
Because they expected the sky to be
its familiar colour 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
lts thin atmosphere is tinged with red dust
Mars is a desert world;
from day to night the temperature swings by hundreds of degrees
On Mars, the colours of the heavens are turned on their heads:
Red sky at noon, and blue skies at sunset
So how did Mars and Venus, both rocky planets like the Earth,
get such different atmosphere on our own?
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 neighbouring 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,
pummelled by meteorites and surrounded by a veil of steam
Mars just didn't have enough gravity to hold on to 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 the 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 and water vapour 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 thirty degrees of warming from Earth's greenhouse
which is just enough to keep it in the, the temperature range that it's in
For planetary scientist Andy Ingersoll,
the delicate balance of Earth's climate is fascinating
I would say that we've learned that
there is 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,
the 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
lt'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 will get cold at night
And that's predictable
It's only in between-the Earth is sort of in between
and that's where the weather is unpredictable
There is one other world with weather, and it's written on a colossal scale
The giant planet Jupiter
The whole planet is 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 three hundred year old storms
and I had this picture of these storms calmly spinning
And when Voyager got there and started taking close-up pictures
we realised that 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,
and it really deepened the mystery of why the large storms could have endured
Jupiter's Great Red spot has been around for three centuries,
but its future is by no means certain
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 white ovals that formed about sixty years ago,
and had been keeping their distance from each other
But last year, two of them merged
and so it was a kind of historic event for Jupiter weather men
What forces could be driving the giant storms?
Voyager could only 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 central 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 sixty kilometres per second
And if you want to figure that in miles per hour
That's a big number. One hundred and twenty,
one hundred and forty thousand miles per hour or something like that
In the 1960s,
Al Seiff had designed the heat shields
that saved pioneers like John Glenn and Neil Armstrong from burning up on re-entry
Seiff had a hand in almost every spacecraft NASA ever built
But Jupiter was his biggest challenge
We worked as it turned out,
for nearly twenty 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 four thousand Kelvin and then it starts to vaporise,
and that's exactly what this heat shield did
The heat shield was about eighty per cent vaporised,
about twenty percent 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 Gallileo probe went into a desert of Jupiter and
that if we had have 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 approaching 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 vaporise
and today the Galileo probe is part of the atmosphere of Jupiter
We have actually slightly contaminated this giant planet
Was there another world 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 were captivated
It was the moon Titan
I can think about the 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,
you know, 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 hypothesise and come up with all the theories we want,
but eventually we 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
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 to 95 percent molecular nitrogen,
along with the fact that it's atmosphere is pretty dense,
surface pressure is comparable to that here on the earth,
a little bit more, makes it kind of an analogue with the earth,
which is terribly surprising because no-one expected years ago
you'd find an analogue 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 tantalising 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,
and 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 7 years developing instrumentation
in the space craft itself to,
to go back to Saturn and now we have a 6 year wait for it to get there
Cassini will arrive at Titan in November 2004,
and release a probe that will embark on a journey down
to the shrouded 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 probe will slowly sink into an alien atmosphere,
taking pictures throughout its descent
We don't know in 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 a frigid resemblance to the Earth
Here is a body with a surface and an atmosphere
You could, if properly equipped,
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
Titan has brought back the spirit of the early days of
planetary exploration-there's a new world out there to discover
Our current knowledge of Titan is comparable to our knowledge of Venus
in the 'fifties and 'sixties
In those days when we were trying to study Venus
we kind of imagined Earth-like scenarios
and I suppose we are doing the same for Titan
We're imagining lakes although we imagine they're made of hydro-carbons,
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 going to 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