Grinspoon: I've always been really fascinated by venus
Because it's kind of an alternate earth.
Esposito: Some people consider venus to be a sister planet
To the earth or perhaps a twin.
Grinspoon: But it's a remarkably different twin.
Narrator: Earth's nearest planetary neighbor is an enigma.
Webster: Venus has these incredibly thick clouds
That you can't really see through.
Patel: This is what makes it shine like a beacon in the sky.
Coates: And actually sometimes people think it's a ufo
Because it's so bright in the sky.
Narrator: Humans have looked at venus
And been drawn to it for millennia.
To me it's very haunting, very rich with lessons
And creates this desire to really understand that planet.
Narrator: And understanding venus
Could be key to our very survival.
It's about the same radius as earth.
And perhaps our evolution
Is going to look like venus in the future.
Grinspoon: We can't claim to understand earth
Really if we don't understand venus.
♪♪
-- Captions by vitac -- www.Vitac.Com
Captions paid for by discovery communications
♪♪
Narrator: For centuries, people wondered if this was
What the surface of venus looked like.
Grinspoon: Once we realized that the other planets were, in fact, planets
The natural assumption was that wow, they're probably similar.
Zak: Venus was one of the first objects
Of scientific exploration for russian science.
Lomonosov, who is kind of father of russian science,
Was the first astronomer
Who actually studied the atmosphere of venus.
We figured out the reason why venus is so bright
And apparently featureless
Is because it's completely covered in clouds.
And naturally, we assume these are clouds of water
Like on the earth,
In which case venus would be a great swampy paradise.
Grinspoon: Svante arrhenius, who was a brilliant swedish chemist,
Was one of the first people to actually model
Scientifically what the climate of venus was like,
But he also had ideas about the life on venus
And the vegetation,
And he made observations that he thought confirmed this.
So he actually had a kind of scientific view
But with a lot of imagination filling in the blanks
That promoted this idea of venus as a planet
With a lot of vegetation and a lot of life.
The only way to tell actually whether venus was
A sort of living world with jungles on the surface
Was to actually go there with spacecraft.
Narrator: But before 1975, no human had ever seen an image
From the surface of another planet, let alone venus.
However, a russian mission called venera 9 was on its way.
Zak: On 22 October of 1975, this giant stack of spacecraft,
Of lander and the orbiter,
Approached venus and separated from each other.
Immediately as they started their separate missions,
Which were culminating at the same time
The orbiter approached venus
And started a breaking maneuver with its engines
To slow down the speed just enough
That the gravity field of venus would capture it
And leave it in the highly stretched elliptical orbit
Around the planet.
Narrator: This component of the venera 9 spacecraft had become
The first manmade object to enter orbit around venus.
But the mission was far from over.
And at the same time, the lander started going into
The atmosphere of venus on the side of the planet
Which was not visible from earth,
But thanks to the orbiter,
Which was so high in the sky over venus,
It would later act as a relay station for the lander
To send pictures back to mission control on earth.
The lander was a bowl-shaped capsule covered with
A special ablative surface,
And once it entered the atmosphere of venus
And started breaking,
Layer by layer burning the ablative surface
And at the same time slowing down
Tremendously from its initial entry speed.
Narrator: The searing heat shield decelerated the lander
From 6.6 miles per second
To around 820 feet per second.
Then once it slowed down enough,
There was safe enough to open small opening
At the top of the capsule
And release two small breaking parachutes.
One of those two parachutes was then used to release
The top part of the capsule
And revealed the top of the lander.
Narrator: The speed dropped from 820 feet per second
To 490 feet per second before a third parachute
Was deployed to further slow the descent,
Exposed the antenna and lastly,
To release three final parachutes.
The lander would then spend 20 minutes calmly
Taking measurements of the atmosphere.
But its brutal voyage was not over yet.
Zak: When the probe is around 50 kilometers over the surface,
The commander sent to cut the main lines of the parachute,
Narrator: The little lander was en route to execute
The next steps in humankind's discovery of venus,
A journey we've been on since the mid-20th century.
In 1957, the soviet union stunned the world
With the launch of sputnik.
A year later, the u.S. Launched its first spacecraft.
The space race had begun.
The space race was driven by several major factors.
First of all, it was a military competition of two superpowers,
Which emerged after world war ii,
The united states and the soviet union,
And the second is this ideological competition
Between two systems, socialism in the soviet union
And capitalism as at least soviet union saw it,
And that competition included scientific pursuit.
Grinspoon: Space exploration has a dark side.
We can't deny that we rode to the moon
And to the other planets on, you know, on the wings of war,
That the reason we have these rockets
That can launch payloads into orbit and beyond
Is because they were developed to destroy cities.
Casani: We didn't use the term spacecraft in those days.
We called them payloads because
Everything went on top of a launch vehicle.
The main thing you put on top of the launch vehicle
Was the warhead, which was the payload.
Narrator: Rocket scientists on both sides of the space race concluded
That in order to get to venus, there's a window of time
In which the planets are closest.
This occurs every 19 months.
From the moment the race to venus began in 1961,
Only three opportunities were missed until 1986.
First to launch was the soviet tyazhely sputnik
In February 1961.
It failed to leave low earth orbit.
Venera 1 became the first spacecraft to fly past venus.
But due to a communications failure, no data was received.
The early history of trying to get to venus is full of failure.
There were a lot more failures than successes.
Narrator: Within weeks of the first two attempts
To send a spacecraft to venus,
A discovery from an earth-based radio telescope
Increased the intrigue about our mysterious twin.
Venus was found to have a strange rotation.
The planet seemed to be rotating backwards very slowly.
A day on venus is longer than its year.
You could say, why does venus rotate backwards?
But you can also say, why do all the other planets
Rotate forwards?
I mean, it's a mystery.
Narrator: 18 months after the discovery
Of venus' peculiar rotation,
The next opportunity to get to venus was approaching.
In the second half of summer of 1962,
All these forces finally came together.
Both sides finally had the rockets necessary to launch.
They had the spacecraft,
Which was sophisticated enough to go to venus,
And they had this motivation, money,
And all the political rationale to do this.
So within this short period of time,
From July to the beginning of September,
There were five missions launched --
Two mariner probes
And three russian m.V. Probes, as they were called.
Casani: Mariners 1 and 2 were identical,
And they were both modified ranger spacecraft
Taken off the product line
And converted for a mission to venus
Rather than a ranger mission to the moon.
They were hexagonal in the shape of six boxes
Bolted onto a frame.
There was a high-gain antenna and there was a tower structure
Bolted on top of this hexagonal.
We called her the bus.
Narrator: On July 22, 1962, mariner 1 launched.
But the spacecraft malfunctioned,
And flight control had to manually destroy it.
A month later, the first soviet spacecraft, called 2mv-1 no. 1,
Succeeded in getting into orbit.
But its upper-stage rocket booster failed
And it never left a low earth orbit.
Two days later, mariner 2 blasted off
Successfully from cape canaveral.
Followed by the final two soviet spacecraft
On September 1st and 12th.
Both failed to leave earth's orbit.
Three months later, on December 14, 1962,
Mariner 2 arrived safely at venus.
Mariner 2 became the first spacecraft
To explore another planet in the solar system
And actually return useful scientific data
From the vicinity of another planet.
♪♪
Narrator: In the early '60s,
Mariner 2 became the first successful mission
To return data from venus.
It suggested that the upper atmosphere of venus
Was very hot -- around 940 degrees fahrenheit.
Venus did not appear to be the paradise everyone had hoped for.
There was an editorial in the new york times
When the mariner 2 results were reported,
And it was titled "venus says no."
And it talks about the grand romantic dreams
Of mankind being dashed.
Narrator: Mariner 2 also made another startling discovery
That hinted something was off with earth's twin.
Unlike our planet,
With its north and south magnetic poles,
Venus does not have any significant magnetic field.
Aurnou: It's about the same radius as earth.
It's roughly the same rotation rate.
Maybe it's 100 times slower,
But that's not that different fluid-dynamics-wise.
These are still rapidly rotating bodies.
It's got a big core. We believe. We believe it's molten.
Something's funny that venus has no dynamo.
Esposito: Mariner 2 took measurements of high temperatures on venus,
And there was a dispute about those temperatures
Perhaps being only high in the atmosphere
Or the temperatures really showing unbearably
Hot environment everywhere around the planet.
Zak: So, of course, the immediate challenge was after this,
Both for the soviet union and for the american scientists,
Was to launch more probes, more sophisticated ones,
But design them based on the already available information
And continue this pursuit of what venus is all about.
Narrator: Mariner 2's distant flyby
Had not settled the score for supremacy over venus.
The u.S. And the ussr were about to begin
An even more intense battle for earth's twin.
From now on, once mariner 2 did the job,
It was absolutely paramount for the soviet union to land
On the surface of venus first
And preferably to do imagery and science
On the surface of venus.
Narrator: Over the next 11 years,
There was a frenzy of missions to venus.
♪♪
Venera 9 is plunging into
The increasingly dense atmosphere of venus.
Grinspoon: About 50 kilometers up from the surface of venus,
You pass through a region that is about the surface temperature
And pressure of earth.
So there's a region in the upper atmosphere of venus
That would feel pretty much like it feels in this room.
Zak: I think to any individual who reads the description
Of the landing sequence thinks
That it's really irrational and a really bizarre way
To get equipment to the surface of venus.
But after a little bit closer examination,
We understand that each step of the sequence
Has actually logic behind it.
Narrator: Venus' complex atmosphere
Presented unique challenges to the teams
Trying to plot a landing there.
And in fact, it's counterintuitive,
But part of the problem with a lot of designs
When you're designing an entry probe for venus
Is that you fall too slowly, meaning that it takes too long
And you're going to heat up too much
Before you get to the surface.
And then you keep falling, and the atmosphere
Gets hotter and hotter and more and more dense to the point
Where it's 100 times as dense as the atmosphere on earth,
And that means that you're falling through.
It's not quite a liquid, but it's a gas
That is approaching the properties of a liquid
And that would slow your fall.
[ radio chatter ]
And then when you get to the surface,
It's almost like going through the ocean.
Narrator: Venera 9 was not the first lander
To get to the surface of venus,
But it was the first to send back pictures.
It was a colossal achievement.
Grinspoon: Venera 9 returned the first pictures
From the surface of another planet,
And the fact that that was done first for venus
Before the americans did it with viking in 1976 at mars
Is really remarkable because it's much harder
To land on venus and photograph it than it is on mars.
And that achievement in 1975 by the soviet union,
That was a real triumph of exploration.
Coates: But the ideas of venus
As a verdant, lovely environment,
Possibly with jungles on the surface
And a water-rich environment, were immediately taken away.
♪♪
Grinspoon: Wasn't really until venera 9 operated at the surface
For some time and returned data
That we were sure that we had solid data that told us,
Yes, this is how hot and this is what the pressure and wow,
That's really pretty intense.
After venera 9, we had a sense
Of what some individual places on venus were like.
If you send a probe in one place
And you measure the temperature and pressure on the way down,
It gives you one slice from space to the surface.
But the more we learned about venus,
The more we realized that, like earth,
It's a complex, changing planet
With different things going on in the day side,
And the night side and this latitude and that latitude,
And that to really understand what's going on,
You have to measure multiple places at once.
Narrator: In 1974, nasa approved
A double mission to explore venus,
Both from orbit
And from multiple places around the planet.
This ambitious mission was called pioneer venus.
Esposito: The pioneer venus mission included an orbiter
And four probes -- three small probes
And one large probe -- to look at different parts of the globe
Of venus and to make measurements
As they descended to the surface.
Narrator: The pioneer venus orbiter launched in may 1978,
And the spacecraft carrying the probes followed in August.
The orbiter arrived at venus a few days earlier
And inserted itself into orbit in preparation
To relay data back from the atmospheric probes.
Esposito: The probes were not designed to survive the landing,
But fortunately one did
And continued to send back information
Until the heat of the surface destroyed its electronics.
Narrator: The results from the pioneer venus mission were clear.
No matter where you went on venus,
Its surface was uniformly hot and high pressure.
Esposito: So venus is all bad.
The temperature only varies by a degree
Or two over the whole globe, day to night, pole to equator,
And the thick atmosphere acts like a blanket,
Which keeps the entire surface of venus very hot.
And so there's no place,
No hospitable place on the surface of venus
Where we might imagine humans living.
Narrator: And it's not just the temperature.
The atmospheric pressure on the surface is so high
That it would crush almost every military submarine ever built.
Esposito: So instead of venus being
A sort of tropical paradise, it's hell.
Things have gone terribly bad.
The temperature on the surface is hot enough to melt lead
And the atmosphere is full of poisonous gases
And carbon dioxide.
Grinspoon: It sets up this huge mystery.
Why do you have these twin planets so nearby
And one of them ends up like this?
You know, this paradise for earthly life.
And there's another one right here
Ends up in such a different state.
You know, what happened there and can that happen here?
♪♪
Narrator: To discover why our twin planet's environment
Is so extreme compared to our own,
We must go back to the formation of venus and earth.
♪♪
Coates: The formation of venus and earth was probably pretty similar.
It's made of the same type of stuff.
It seems as though the original rocky stuff that fell together
And made earth probably had a lot of water bound up in it.
And venus, because it seems to have been
Made out of the same stuff,
In the same process at the same time,
Then likely got a similar admixture of water
Just chemically bound up in that rocky material
That made the original planet.
Coates: About 600 million years
After the beginning of the solar system,
There was a very large period of collisions
When the collision rate was very high,
And that's what we call the late heavy bombardment.
So during that time,
There are both comets and asteroids moving around,
Both bringing even more water to the earth and venus.
Narrator: After all the brutality of the initial formation
And the violence of the late heavy bombardment,
Things would have settled down for earth and venus.
Esposito: Venus might have been much more hospitable,
You know, very similar to the earth.
Maybe there were oceans and even life on venus.
♪♪
So why is it that earth today is an oceanic planet
And venus is not, if they both started out similar?
The one obvious difference is that venus
Is significantly closer to the sun.
What happened, we think, was that as the sun heated up,
It triggered something we call the runaway greenhouse.
And the way that works has to do with evaporation.
So if you're evaporating the oceans of a planet,
You're getting more water vapor in the atmosphere.
Well, water vapor itself is a strong greenhouse gas,
Really as strong as co2,
Meaning that it's a gas that absorbs infrared radiation.
It lets the visible through.
It absorbs infrared.
So you get more water vapor.
You're absorbing more infrared.
You have a stronger greenhouse that heats up the surface.
So you can see it's what we call positive feedback
Because the hotter the surface is,
The more water vapor you're getting in the atmosphere.
The more water vapor, the hotter the surface is.
So each part of the cycle reinforces the other.
That's a positive feedback, and that's unstable.
It runs away.
♪♪
So water in the oceans
Evaporated to make a blanket around the planet,
Which made the planet hotter.
But worse than that,
Carbon dioxide was baked out of rocks.
Narrator: The idea that carbon dioxide could create
A powerful greenhouse effect goes all the way back
To the swedish pioneer svante arrhenius.
Svante arrhenius correctly deduced
That there was a lot of carbon dioxide in the atmosphere,
So it was probably hot.
In fact, he was also one of the first people
That considered greenhouse warming on earth, interestingly,
And that partly came out of his work on thinking
About what venus was like.
Narrator: So how did earth escape the same fate as venus
With its runaway greenhouse effect?
The answer begins with rain.
So, on earth, the co2 gets pulled out of the atmosphere
By what we call weathering reactions,
Where water is raining out and makes sort of carbonic acid,
Which, when it runs over rocks, leaches the ions out.
And it ends up in the ocean as carbonate ions
And forms carbonate rocks.
When you see white cliffs of dover or any massive
Deposit of carbonates, you're seeing carbon
That has been pulled out of the atmosphere.
Those carbonate rocks get pooled into the interior
By plate tectonics.
And when you have subduction of oceanic crust
Down deep into the interior
Where they're melted and ultimately
Then the co2 is released under pressure
And becomes dissolved gas,
Which then comes back out those volcanoes,
And that completes the cycle.
But that is facilitated by water and rain
And in these chemical reactions.
If you don't have water,
You sort of break that part of the carbon cycle.
Narrator: But if the process that removes carbon dioxide
From the atmosphere is rain, what happened to venus' water?
The answer is due to a complex interaction
Of the planet's atmosphere and the stream of particles
That constantly come off the sun called the solar wind.
When the water on a planet evaporates
And is in the atmosphere as water vapor
As opposed to condensed on the surface in liquid water,
Then it's much more vulnerable to being lost to space.
And the main way that happens
Is the water gets broken up by ultraviolet light
And what we call photo dissociation,
Which is that these energetic photons of sunlight
Breaks hydrogens off from the oxygen.
And then when you have a free-floating hydrogen,
It's easy for that to escape into space.
In fact, all planets are losing hydrogen
All the time into space.
And when you have a steam atmosphere
And a lot of water photodissociating,
Then you're going to have a stream of hydrogen
Escaping off into space.
And then after a period of time, you're left with less hydrogen
And therefore less water on the planet.
A decade or so ago, people used to think
That the big difference between earth and venus
Was that the earth had a magnetic field.
And then we looked at venus and we said,
"oh, it's lost all its water
Because solar wind strips it away."
We are finding it's more subtle now.
Pretty much all of the planets lose their atmosphere
Right now at about the same rate.
So everything's scrambled.
We're back to the drawing board to really try to understand
How atmospheric escape works and what role,
If any, the magnetic field plays in that process.
Narrator: Whether or not the lack of a magnetic field
Accelerated the loss of venus' water,
The planet became dry and had no water rain
To displace the atmospheric co2.
But where did all this gas come from?
Why is the atmosphere of venus so much thicker than our own?
To find out, scientists would need a closer look.
♪♪
Patel: One of the fantastic things about venus is its cloud layer.
This is what makes it shine like a beacon in the sky.
At the same time, it's one of the most frustrating things
Because it stops us seeing the surface.
So what we need to do is not look with our eyes,
But look with different wavelengths
That can peer through these clouds
And get down to the surface, such as radar wavelengths.
And then we can really see what's going on.
Narrator: After the success of venera 9 and 10 in 1975,
The soviets continued to send a variety of missions to venus.
♪♪
But nasa was determined to try and find out
What more of the surface of venus actually looked like.
And in the early '80s,
They started to develop a mission to do that
Called the venus orbiting imaging radar.
Webster: It had multiple instruments and multiple antennas
And nasa said there's no money,
And so this great thing narrowed down to one instrument,
And we were a spare-parts mission.
We used a voyager spare antenna and a voyager spare bus
And galileo computers.
But the radar itself was a new design.
It had this parabolic antenna so the signal
Would ping off venus
And come back and you have to capture it.
Grinspoon: And you synthesize an image from that
And you do it over and over and over again
And you gradually build up radar images of the surface.
Narrator: The budget version of the mission
Made from old spare parts was renamed magellan.
And on may 4, 1989, it was delivered
To low earth orbit by space shuttle atlantis.
Man: Zero and liftoff.
♪♪
Man #2: There is the orbiter going by the launch tower.
Woman: Throttle down.
Webster: So the designer of magellan was to get into an orbit
And if venus is here,
It would go by really close for an hour, and radar image
And then it would turn back to the earth
And relay back its data for another hour
And then it would correct its wheels and get a star scan
And then turn back and then radar image again.
And we did this 24/7 for a venus day.
♪♪
This is 1989, 1990, 1991.
We're dealing with reel-to-reel tapes
And they're running these tapes back and forth from goldstone.
And then the data from canberra and from madrid
Would actually be flown in in overseas packages.
Narrator: The extreme effort that the scientists and engineers
Made to acquire this data was worth it.
Magellan provided an unprecedented view
Of the venusian surface.
Grinspoon: They mapped near the entire surface of venus,
And that was a huge revelation
Because that was our first global look
At what the geology of venus is really like.
Narrator: The magellan data was indisputable --
Venus is, or was, a world of volcanoes.
♪♪
Grinspoon: It's a world that has been
Resurfaced by volcanism over time.
There are these huge areas of flood basalts
Where this running lava has come out from the interior,
And a lot of venus is covered with that.
But then there are other volcanic features,
These things nicknamed "pancake domes,"
Which are much smaller.
They're about 10 kilometers across
Because they're much more sticky,
Less runny, more viscous magma.
So it's been a volcanically active planet,
Massively, with all different kinds of volcanism
Going through many different phases.
Now, it doesn't mean that it's current.
It could be ancient.
♪♪
Narrator: All of this activity means
That venus has been belching carbon dioxide
Into its atmosphere for billions of years.
And with no rain to absorb the co2,
The atmosphere has become thicker and thicker.
The atmosphere on venus today is almost all co2.
And here on earth, we're concerned about
300 and 400 parts per million co2.
It's a trace gas. It's a minor gas.
If we assume that venus and earth started out similar,
Which I think is likely, although we still want
To gather the data to prove it,
That venus had early oceans more like earth
And had some kind of a tectonic cycle
And probably a carbon cycle with carbonates and volcanoes
Like earth has today, then what happened?
Why is the solid part of the planet, the geology,
Apparently so different from earth's?
And in my view, it probably has to do
With the losing of the water,
That if you lose the water from the surface of the planet,
Then over time you're going to also dry out the crust
And the interior of the planet
Because you are also outgassing water.
You're losing water through that cycle.
And on earth, you're in-gassing water, too,
In the sense that you're pulling water into the interior
All the time through that tectonic cycle.
If you lose that ability to do that
Because you don't have any water on the surface,
You're not going to right away
Dry out the interior of the planet.
But after a billion, two billion years,
You're going to ultimately end up with a dried-out interior
And a dried-out crust.
And that's going to have different material properties.
And, in fact, if you take an earth model
Of plate tectonics and mantle convection
And you dry it out, you change the properties of the rocks
And say, "well, what if these were dry rocks
Instead of hydrated rocks?"
These models will start behaving more like venus.
The rocks get harder. It gets harder to subduct.
Plate tectonics gets sort of choked off,
And it's like the engine runs out of lubrication,
And it gets stuck, and then it starts going in spurts
Rather than running smoothly.
Narrator: Scientists think this could explain another of venus'
Most perplexing mysteries -- its lack of a magnetic field.
Narrator: Venus' dry crust is likely a result
Of losing water from the carbon cycle,
But it could also be responsible
For the lack of what's known as an internal dynamo,
Which is what produces a magnetic field.
Aurnou: I think the easiest explanation
For why venus doesn't have a dynamo
Is probably that heat is trapped within the core.
It appears right now
That there's no plate tectonics on venus.
There's probably convection occurring within the mantle,
But it's not very efficient at getting heat out.
And so that probably traps heat within the core.
If heat can't get out,
Then I can't cool that fluid at the surface.
I can't release those dense blobs into the interior
Falling and convecting.
If it's not convecting
And there's none of that turbulent convection
To stir up a magnetic field,
I think you should then see what you do see.
Narrator: Magellan orbited venus
From August 1990 until October 1994.
The mission mapped 98% of the surface
And greatly increased our understanding
Of the geological processes
That have shaped the planet's history.
Webster: And by that time, it was done.
You know, the computers were resetting,
We were out of fuel,
And then, oh, you got to update because now your timing's off
Because you got slightly out of orbit because of your thrusters.
And it was always an engineering challenge
Because I was just scrambling every day just to keep it going.
But it was a great spacecraft to be your first spacecraft
Because it was a hell of a learning experience for me.
♪♪
Narrator: The last communication with magellan
Was on October 13, 1994,
Before the spacecraft disintegrated
Deep in venus' thick atmosphere.
Well, in the aftermath of magellan,
There was a lot of desire for more venus missions,
And the europeans sort of came to our rescue
With venus express.
It's called venus express
Because it was a mission that was put together very quickly.
And what venus express really is --
I think of it as our first weather satellite
At another planet.
♪♪
Narrator: Venus express gave us much greater insight
Into what was really going on with venus' atmosphere.
♪♪
Grinspoon: So, venus express made these movies
Of the motions of the atmosphere at different depths,
And indeed it's quite dynamic.
The atmosphere of venus does this
What we call four-day super rotation,
Where the atmosphere is whipping around.
Narrator: These high-altitudes zonal winds
Can zip around the equator of venus
At 220 miles per hour.
But above the poles,
The rotational speeds drop almost to zero.
♪♪
The intense heat on the surface of venus
Creates powerful convection currents
That drive a separate, lower-altitude
Circulation of heat from the equator to the poles.
♪♪
With venus express, we saw these vortices near the poles,
In particular of the south pole of venus,
Which had not been seen before.
It was a little bit like water down a bath plug.
So seeing that for the first time was very exciting.
Venus is entirely covered by clouds.
These clouds are made up of droplets of sulfuric acid.
So it's arguably the case that venus has
The worst case of acid rain in the whole solar system.
Narrator: The acid rain on venus
Is created by the vast amounts of sulfur
Released through volcanism
That has dominated the planet's evolution.
♪♪
Acid rain has been a problem on earth, downwind of factories.
And by studying it in an extreme case on another planet,
It helps us understand more
The interaction of acid with water clouds.
Narrator: But scientists believe this extreme
Acid-rain-laden atmosphere is likely hiding a surface
So strange that it defies imagination.
Narrator: The surface of venus is much calmer
Than its turbulent, severe atmosphere would suggest.
♪♪
Here, the wind speeds are very low.
The acid rain has evaporated
Long before it gets this far down.
♪♪
If you could go to the surface of venus,
Not that we can right now,
I think it would be an incredibly strange experience.
Grinspoon: The first thing you would notice is that the quality of light
Would be very different from the quality of light on earth.
That's mostly because the light is being filtered
Through that incredibly thick atmosphere
And also through the globally extensive clouds.
So it would be kind of a red, murky light.
Patel: When you look at things, you're looking through
This massively convective medium where,
Because of the temperature you're looking at
And the swells and stuff,
You see the refraction of light.
♪♪
Grinspoon: You probably would see that sort of shimmery
Kind of effect that you get in desert areas on earth
Just because there is a lot of infrared radiation
Coming up out of the surface, and that is going to be
Affecting the stability of the atmosphere near the surface.
♪♪
[ thunder cracks ]
Patel: You're in this really, really strange environment
Where any movement, and you feel resistance,
And it becomes this viscous, fluid-like thing
That you're having to move through.
♪♪
Narrator: In the future, will there ever be a time
When venus might have cleared its dense atmosphere
And cooled enough for humans to live on its surface?
Some have proposed that venus might once again be hospitable
And potentially after volcanic eruption seas
On the surface of venus.
I don't buy that.
I think the escape rate of the venus atmosphere over time
Is infinitesimally slow
Compared to the magnitude of the atmosphere.
The time it might take for the venus atmosphere
To be cured in that way would probably match the time
That the sun would take to see out the rest of its lifetime,
Swelling into a red giant and engulfing the whole planet.
♪♪
So there's really no future time that I can imagine
Where the atmosphere would be lost enough
So the greenhouse effect would be small enough,
So the surface temperature of venus would be cool enough
That life could exist there.
Narrator: So if venus is never destined to become the paradise
We once imagined through natural processes,
What about through deliberate manipulation?
Can we terraform venus?
Grinspoon: Terraforming is an interesting concept.
It's certainly a valuable thought experiment.
So maybe the way to do it would be
To throw a lot of comets at venus,
Where you would both raise up
The dust from the comet impacts to cool it off,
And then you'd also be sort of sprinkling it back with water.
If you start to have liquid water on the surface,
Then that's going to restart the cycle where you're going to then
Be removing co2 out of the atmosphere by weathering.
It would take a while. It'd be a long-term renovation project.
But there's nothing physically impossible about it.
The problem with terraforming ideas is that,
You know, right now we're in the situation
Where we're rapidly veneraforming earth
That is turning it to be more venus-like.
And so we can't even imagine any of these futures
Unless we get to the point where we're doing a much better job
Of controlling our own actions on earth.
Mccaughrean: What worries me sometimes is this idea
That we can take human beings away
From all of the mess that we've created here.
Sociologically, it seems unlikely
That we're just going to become the perfect citizen
Once we cross the 100-kilometer line and go into space.
But also there's nowhere in the solar system
That's any better to live than the very worst
That we could ever do to the planet earth.
Whatever we do here, it won't be as bad
As living on mars or on venus
Or anywhere else in the solar system.
So at the same time as we're looking outwards and exploring,
We should never forget that this is where we come from
And there is no planet "b."
This place has to be looked after, as well,
As much as we're looking outwards and beyond.
♪♪
Narrator: Perhaps one day, far in the future,
Humankind will not only have the scientific ability
To make venus into a paradise, but the wisdom to realize
That we already have a paradise of our own.
♪♪