Our galaxy, far in the future.
A planet shrouded in turbulent, dense clouds.
Buried deep below,
an alien landscape...
Extreme pressures, and a scorched surface
with sky-high temperatures.
But this isn't a distant extraterrestrial world.
It's earth's future, maybe a billion years from now.
We know this because earth has a twin...
Venus.
And Venus has already descended into hell.
Have you ever dreamed about travelling out of this world?
My name is Mike Massimino,
and I turned that fantasy into a reality
when I space-walked to repair the Hubble space telescope.
Great job, Mike.
Now, as we expand our knowledge of our solar system
from Mercury to the cosmic unknowns,
I want to take you on a personal journey to...
"The planets."
Welcome to "the planets."
I'm Mike Massimino.
I got to live out my childhood dream
when I first travelled to space
in 2002.
Looking down at the earth from the Hubble space telescope,
I was blown away by this perfect blue sphere
in the middle of space.
As peaceful and inviting as our planet is,
our neighbor, Venus, is the complete opposite...
No water, scorching temperatures,
and crushing pressure.
And just when you think there's nothing in common
between these two planets,
it turns out they're actually siblings.
Take a look around the solar system...
Eight planets orbiting a central star, the sun.
Among them is earth
and its neighbor, Venus.
Earth, our home, is an oasis for life.
Venus is the stuff of nightmares.
Venus and earth couldn't be more different.
The earth is this beautiful planet,
and there's water everywhere.
It's ice at the poles. It's water in the ocean.
It's in the atmosphere as water vapor.
But then you look at Venus.
It is the worst place imaginable.
It is so hot on the surface, crushing pressures.
It couldn't be any less supportive of life.
To me, the planet Venus
is sort of a classic definition of the word "hell."
If you were to transport to Venus
and experience the environment there,
you'd quickly want to return back to earth.
The conditions on Venus
are among the most inhospitable in the solar system.
It's going to be a competition between whether or not
you're gonna be cooked to death or crushed to death.
Earth and Venus may seem like very different worlds,
but they shouldn't be.
They're roughly the same size, same mass,
and made from the same stuff.
And they started out as twins.
Early Venus and early earth were very similar.
They were twins,
probably nearly identical twins, at their earliest stages.
Given that Venus is so earth-like in so many ways,
it's really odd that it is so different than the earth.
And this makes it one of the biggest mysteries
in the solar system.
Somewhere in their two histories,
the earth and Venus took two very different paths.
The result?
Two totally different worlds.
Their paths were so different, you could hardly believe
that one would have been related to the other.
But now, the opposite thing's going to happen.
We're gonna catch up with our twin.
We're gonna evolve to be a lot more like Venus in the future.
In the future,
the two planets' paths will converge,
and they will become twin-like once again.
There is going to be hell on earth.
The oceans will vaporize. The land will melt.
Our hospitable blue planet will vanish,
replaced by a fiery, molten world.
We are actually on the earth at a time
when there's water and rain,
and it was so easy for life to take hold.
But that's gonna change.
And take a look in at Venus and have a look at our future.
How will this happen?
The roots of our home world's destruction
are buried deep in our twin planet's past.
It's very much true that, in studying the past of Venus,
we are also studying the distant future of earth.
Both planets share a violent birth,
scarred by brutal planet formation,
giant cosmic impacts, and rampant volcanism.
We're trying to reconstruct things
that happened in the ancient, ancient past.
It's almost like forensic planetary geology.
4.6 billion years ago, hundreds of infant planets
begin to form around the new sun.
Among them, the baby Venus and earth.
And as they hurtle around the sun,
collisions are inevitable.
Planet formation is like a demolition derby.
In a derby, the cars are racing around a track,
going around in circles at different speeds.
Well, it's the same thing with planets.
The material is orbiting the sun.
It's going around, and they're all going at different speeds,
at different angels, different trajectories.
And sometimes, boom.
In this derby, planet hits planet.
Two become one...
Violently.
You have these large bodies that are hitting each other
at really high velocity.
It's really a very hot, violent mess.
The amount of energy released
in these impacts is huge.
It completely dwarfs
all of the nuclear weapons on earth combined.
And yet, somehow, on these scales,
you wind up forming gigantic objects that we call planets.
Earth and Venus become voracious planet eaters.
But two spectacular collisions set the twins
on very different paths.
That was the moment Venus and earth went through
this divergence to what has now become
these really dramatically different worlds.
The divergence begins
when a Mars-sized object hits earth.
The impact makes our planet spin faster.
The core spins with it, generating
a powerful magnetic field around the planet.
The field fends off the worst of the sun's radiation.
Around the same time,
Venus takes a head-on hit from another infant planet.
This impact explains something very weird about Venus.
Venus is actually rotating
in the wrong direction.
How could that be?
Well, what if it got hit really hard by some object?
That could do it.
An object so huge,
Venus stops in its tracks and begins to spin backwards.
If you think about how much energy
and what size you need to change a planet's spin,
that is an incredibly large hit.
But the backspin is slow...
243 times slower than earth.
Without a fast spin,
Venus' core can't generate a strong magnetic field.
It has no protection from the deadly stream
of particles blasted from the sun.
Venus does not have a strong magnetic field,
and so it has suffered the full brunt
of this wind blasted out from the sun.
The tale of two planets
now splits radically.
Venus will roast
under a violent, suffocating atmosphere.
Earth will give birth to oceans,
life, and intelligence.
But ultimately, these twins' fates
are the same.
Earth's future is Venus...
Pure hell.
4.6 billion years ago,
two nearly-identical planets formed...
Earth and Venus.
Earth blossomed into a colorful haven
for life to thrive,
while Venus is the definition of hell.
How did they turn out so different?
Images from space probes sent to Venus provide the answer.
Venus is a vision of hell.
And one day, we'll meet our twin's fate.
So, how will our blue planet
become a superheated wasteland?
Only Venus can really tell us.
Something happened to Venus long in its past
to make it a completely different planet
with a completely different personality
than the earth as we know it today.
Two, three, four.
We earthlings sent our first probe
to our sister planet in 1967,
and we've been sending them ever since.
What they found blew scientists' minds...
Rocks that look like granite.
What makes that interesting is that, to make granite,
you need water.
That means that there must have been abundant water
for it to have formed in the first place.
Abundant water on scorched Venus?
Hard to imagine.
But Dr. Lewis Dartnell thinks you can get a glimpse
of a wet Venus here in Iceland.
There's the possibility
that, maybe, in the early solar system,
there were not one, but two planets with oceans...
Two water worlds... Earth and Venus.
And if Venus did once have oceans,
maybe they would've looked a lot like this here,
with a raw, volcanic landscape
descending down into the ocean
with the waves lapping against the coastline,
and maybe a overcast and a misty, hazy atmosphere,
not unlike what we are seeing here today.
But Venus couldn't hold on to its water.
All of that water is gone.
It's just gone. Where did it go?
Something happened, either catastrophically or over time,
to basically dry out this twin of the earth.
The culprit was the young sun.
Since its birth, it's grown stronger.
Our sun, when we look out at it during the day,
seems the same today as it was yesterday.
But that's on a human time scale.
On cosmic time scale,
the sun has been getting hotter and hotter.
Every billion years, the sun gets 10% hotter,
slowly turning up the temperature on Venus.
Not only that,
Venus formed 26 million miles closer to our star.
As it turns out, that distance to the sun was critical.
It's just an unfortunate circumstance
of being in the wrong place at the wrong time.
Earth is far enough away from the sun
to hold on to its water.
But Venus can't take the heat.
The intensity of its sunlight got sort of
just a little bit too much.
It passed this threshold where Venus
couldn't hold its water on the surface anymore.
As temperatures rise,
the oceans start to evaporate.
All of that water in the oceans,
all of those millions of cubic miles of water,
would become water vapor...
Basically steam clouds covering the entire planet,
hiding the surface from the outside.
Water vapor is a greenhouse gas.
The clouds covering Venus trap the sun's heat.
Temperatures on the surface rise.
But the process can't go on forever,
because the clouds of water vapor in the atmosphere
start to disappear,
ripped away by the solar wind.
Over time, if a water molecule was in the upper part
of Venus' atmosphere,
light from the sun could break it apart
into oxygen and hydrogen.
And then, the solar wind could blow that stuff away.
But that is just the beginning.
Without its water vapor to trap heat,
the temperature stops rising temporarily.
Soon, a new force
will send surface temperatures rocketing again.
It will become so hot,
metal snow will fall.
When I think of Venus,
the words "hot," "hazy," and "dead zone"
come to mind...
The exact opposite of our planet.
But scientists believe that one day,
these might be the words to describe earth.
By studying volcanoes, you can start to understand why.
Four billion years ago,
Venus and earth were twins with oceans.
But soon, the two planets' paths diverged.
The growing sun burned off Venus' oceans...
A terrible omen for earth.
On the planet Venus,
we think there could have been oceans, lakes, water, and rain.
But all of that came to an end.
That tells you that the earth's environment has to change, too.
Nothing is forever.
A few billion years ago,
when you looked in our solar system,
you might have seen two earths.
Well, a few billion years from now, in the future,
you might look at our solar system
and see two Venuses.
So we can look to Venus' past and see our fate.
We know that temperatures skyrocketed,
and the scarred surface hints at why.
In Hawaii, planetary geologist Jani Radebaugh
studies the islands' volcanoes.
These volcanoes are a perfect model for early Venus.
What we're seeing out here are lava flows
encroaching on the town of Pahoa,
come all the way down from the Pu'u 'o'o vent
which is about 15 miles away.
Oh, there's hot. You can see that hot stuff.
You can see hot. Quick, quick, quick, quick.
Right there.
It's really beautiful.
Hawaii's volcanic lava fields
look like Venus in miniature.
Both produce the same kind of runny lava,
building flat, shield-like volcanoes.
The big difference is
there are only five active volcanoes on Hawaii.
Venus is covered in them.
One thing that really jumps out all around the planet
is the number and variety of volcanoes.
I mean, Venus could almost be nicknamed "volcano world."
But it's not the erupting lava
that turns up the heat.
It's what comes out with it.
When you think back to the histories of Venus,
I think we must have seen a landscape
very similar to this one,
where you have massive amounts of lava
flowing out of the surface,
dumping huge amounts of gases into the atmosphere,
carbon dioxide, tons of the gas into the atmosphere
every single day.
It would have been amazing to see.
Up close on the surface,
Jani can see the origin of the gases.
If we look behind us, we can see volcanic gases
gushing out of steam vents.
We've got carbon dioxide being delivered to the atmosphere.
It's exactly like what has happened on Venus.
Carbon dioxide has been delivered out of volcanoes
over and over and over again throughout its history,
so that now we have
just a tremendously thick, dense atmosphere.
The net result of all of these volcanic gases
pouring out of volcanoes, major greenhouse gases,
is that they have been absorbing heat
for billions of years of the history of Venus.
The temperature has been gradually creeping up
until, today, the surface of Venus is 900 degrees.
It's like if you go into your kitchen
and set your oven to broil,
wait a couple of minutes and stick your head in it,
and even that's not quite hot enough.
It's a crazy, horrible, hellish spot.
It's hard to imagine such extreme temperatures.
But probes orbiting the planet
revealed just how insanely hot it is.
Scientists studying the images
noticed something strange on the planet's mountains.
It looks like, on the mountains,
that there's apparently snow-like structures.
But this is unlike any snow found on earth.
So, if you look at the white-peaked mountains of Venus,
you would think that it was snow,
but it's actually metals that have rained down
and deposited on the top of those mountains.
Metals like bismuth and lead melt.
Then, they evaporate into the atmosphere.
As they rise, they cool
until they finally fall like snow on the mountaintops.
It's pretty insane... Raining metals.
Where would you ever think about that existing?
On Venus.
In the future,
metallic snow is forecast for earth, too.
And our scorching mountain caps will glitter like Venus.
But Venus tells us that things will get even worse.
The atmosphere will grow heavy enough to crush cars.
Earth and Venus...
In the beginning, they were not so different.
But these two planets have such similar births,
how has earth been able to defend itself
against the gruesome forces that so changed Venus?
The answers are found in our atmosphere.
Earth and Venus were born twins,
but they took different paths.
Earth slowly evolved into a habitable world.
Venus was covered in thick volcanic gases,
trapping the sun's heat.
Temperatures Rose to 900 degrees.
Extreme temperatures
weren't the only problem on Venus' surface.
The thick clouds of gas kept on building up.
A 155-mile-deep layer of carbon dioxide
piles up around the planet.
We don't think about gases as weighing anything,
but they actually do.
Trillions and trillions of tons
of gas press downwards.
There is simply so much air on Venus
that, on the surface, it's pushing down
with a huge amount of force.
Well, atmospheric pressure on Venus is a monster.
Think about it this way.
All right, car.
It's time for you to be crushed, baby.
If you're on Venus, you're gonna have
155 miles of atmosphere above your head.
As a result,
atmospheric pressure is 90 times that on earth.
So, on earth, it's about 14.6 pounds per square inch.
On Venus, we're talking about 1,300 pounds per square inch.
So, if you're driving your car in Venus,
this is what might happen.
This crusher delivers the same force
as the weight of Venus' atmosphere.
This is pretty serious stuff.
And this is why it's so hard on Venus.
You get down to the surface,
you have the crushing atmosphere to deal with.
The extreme pressure and heat
makes Venus nearly impossible to explore.
Only one nation has ever gotten a probe to the planet's surface.
Truly, one of the engineering triumphs of the human race
was the Soviet union's Venera program.
The Russians sent over a dozen probes to the planet Venus.
And only a few of them were able to survive long enough
to even be able to take pictures from the surface.
The probe that sent back these images
was crushed and burnt out in 90 minutes.
Some day in the future,
there are going to be interplanetary tour guides
taking people to every planet in the solar system.
And you can imagine going to Saturn and seeing the rings
and Jupiter and it's panoply of moons.
There are all these great tourist attractions
in the solar system.
At the very bottom of that list is Venus.
That is the last place in the solar system
I would ever want to visit.
The sun's heat and volcanic gases
have transformed Venus into a nightmarish world.
So, why hasn't earth followed the same path?
That's because earth formed farther away from the sun,
staying cool enough to hold on to its oceans.
Oceans do a lot of things for us on earth
because not only, obviously, are we water creatures,
and we depend on the water cycle for our existence
in so many ways,
but people don't realize the oceans also help
to regulate the climate of earth.
Our oceans are full of tiny creatures
that eat carbon dioxide.
Richard Zeebe from the university of Hawaii
is diving on the island's coral reefs.
He's studying how tiny marine organisms
turn carbon dioxide into rock.
What you see here as this white stuff,
this is what we call calcium carbonate.
And on top of this, where you see these brown layers,
this is essentially the living organism.
This is the coral itself.
It takes calcium out of the seawater
and takes carbonate out of the seawater,
combines them, and makes this piece of calcium carbonate.
There's over 70 million billion tons
of carbon locked up in carbonate rocks.
This helps regulate carbon dioxide levels
in the atmosphere, keeping temperatures from rising.
If all the carbon that is being locked up in carbonate rocks
in these corals would be put into the atmosphere as co2,
that would be certainly bad news for us.
Currently, our carbon cycle
helps stabilize our climate.
But in the future, this won't be able to save us.
Forces far greater than the ones at work on earth
will overpower our systems.
Like Venus, our oceans will burn off.
Temperatures will rocket
as our live-giving sun becomes a monster.
By looking at Venus' past,
we can get a glimpse into earth's future.
And it doesn't look bright.
One of our best planetary features
might become our worst enemy.
Venus' hellish landscape
is a glimpse into earth's future.
There will be no more rain.
There will be no more oceans.
This wonderful, life-friendly environment we enjoy now
just won't be here in some hundreds of millions of years.
Right now, we live just the right distance from the sun,
where it's just the right temperature
for water to exist as a liquid.
But that's going to change, just as it did for Venus.
Venus started off, probably, in the habitable zone.
And then the inner limit of the habitable zone crossed
the distance of Venus' orbit.
Well, it's gonna cross the distance of earth's orbit, too.
There is an expiration date to the earth.
And that's due to the sun's evolution.
Ever since its birth, the sun has been getting hotter.
That increased heat devastated Venus.
And, in the future, it will destroy earth.
In 1.1 billion years,
the sun is 10% hotter than today.
The oceans start to evaporate into thick clouds,
which trap more of the sun's heat.
Catastrophically, very rapidly on a geological time scale,
the oceans will put so much water vapor into the atmosphere
that we will get a runaway greenhouse effect.
The clouds forming in the atmosphere
trap more and more heat,
driving temperatures even higher.
Spiraling temperatures cause more evaporation,
so the clouds get thicker.
Which led to more heating, which led to more evaporation.
And you can see where this is going.
It's a vicious cycle. It's a positive feedback.
We have all of this water that will go into the atmosphere,
covering the earth and shrouding it in, basically, steam.
Earth has had oceans for billions of years,
but it could lose them in just 10,000.
All of the water in the earth's oceans
will be in the atmosphere.
We'll have an incredibly dense cloud cover system
where the temperatures on earth
will be approaching 1,000 degrees.
Like Venus in the past,
earth will get hotter and hotter.
But unlike Venus, which topped out at 900 degrees,
temperatures on earth will keep on climbing.
Venus lost its water to space, blasted away by the solar wind.
But earth holds on to its water.
It's protected by our magnetic shield.
But that's no longer a good thing.
That water will stay with us.
The earth could have a thicker, hotter greenhouse atmosphere
than Venus does today, much worse.
This huge volume of water vapor
all pushes down on the surface,
around 4,000 pounds.
That's the weight of the average American car
pressing down on every square inch of earth.
Surface pressure goes through the roof,
reaching 270 times higher than today.
It is ironic to think that the water on earth
will one day help contribute to its demise.
After all, the water has been the source of life on earth.
But, in the far future, it'll become our enemy.
And with no oceans and their microscopic creatures
to absorb the carbon dioxide,
there is nothing to hold back the rising temperatures.
There's no way back for the earth.
In 1.2 billion years,
a probe visiting earth would see an alien world...
A scorched, barren landscape.
The pressure is crushing.
Temperatures reach 1,200 degrees.
Molten metals snow down on the mountaintops.
It's so hot that granite rock melts.
The surface liquefies.
At that point, the earth will become a molten ball
very similar to what it was at the very beginning.
Earth and Venus started as twins.
Venus was destroyed by rampant global warming.
Earth will follow the same path, then overtake it.
It is inevitable that the earth will someday
not only be like Venus, but actually put it to shame.
In 1.3 billion years, earth could hit 3,600 degrees,
four times hotter than Venus.
It will be the hottest and deadliest planet
in our solar system.
For earth and its inhabitants, it's the end of the road.
We couldn't survive the extreme temperatures
or crushing pressure.
Maybe we'll escape to space.
But there's one absolutely crazy way we could stay here...
Move our planet further away from the sun.
I've seen my fair share of crazy ideas at NASA
that end up being the solution
to a big problem.
During my final mission aboard Atlantis,
while a making a repair to the Hubble space telescope,
I stripped a screw and was completely stuck.
Mission control suggested using brute force
and a simple piece of tape.
Likewise, scientists have come up with an unusual solution
to save earth from ending up like Venus.
Earth of the future will become
the most inhospitable planet in the solar system.
Its ocean will boil off, and its surface will melt.
A billion years from now,
earth could be an unimaginably terrible place.
Right now, today, Venus is the evil twin of earth.
But in the distance future,
earth could be the evil twin of Venus.
Earth's surface temperature
will reach 3,600 degrees
with pressure 270 times than today.
At these kind of temperatures,
where rock on the surface of the earth is molten,
it's hard to imagine any place there could be life.
But there is hope.
Astrobiologist Lewis Dartnell thinks
that some forms of life could survive
such terrible conditions.
We're here on top of a volcanic outcrop in Iceland
with this howling Gale whistling past our ears,
the stench of hydrogen sulfide, of sulfurous fumes,
filling our nostrils.
And this is about as close as you get can on earth
to high up in the Venusian atmosphere.
About 30, 35 miles above the surface of the planet Venus,
the air pressure is about the same
as on the earth's surface.
The temperature is pretty similar, as well.
But the cloud droplets are full of concentrated sulfuric acid,
many, many times more concentrated than battery acid.
It's a hostile, horrible environment.
But bizarrely enough,
there's good reasons to think that there may be life,
Venusian life, high up in the clouds
that are kind of high-altitude aerial biosphere.
High above Venus, there are nutrients,
solar energy, and traces of water.
If life can live up there, then perhaps it might survive
high up in the clouds of future earth.
You can easily imagine these micro-organisms evaporating
in water particles and being transported
to the upper atmosphere.
Even though it turned into this toxic greenhouse planet,
life could potentially still survive
in that upper atmosphere.
But what about us?
We couldn't survive the high temperatures
or pressures at the surface.
And a life in the clouds doesn't seem likely.
What's our future?
If there was this life on Venus,
clearly, they weren't advanced enough
to stop the changes in their atmosphere
that led to Venus' current state.
The question is, are we?
Perhaps we will leave our planet
and find a new home.
But there is a more outlandish solution...
Stay on earth and move it farther from the sun.
Moving the earth is at least imaginable because, in fact,
as objects exchange gravitational energy,
they move in or out in the solar system.
It's happened to our planet.
So I could imagine engineering things
where we directed large asteroids and comets
close to the earth, but not to hit it.
The gravity from these large objects
would slowly alter our orbit.
Gravitational energy would be exchanged,
and the earth could slowly move out.
Each gravitational jolt
would only move earth a short distance.
But do it thousands or millions of times,
and we could push the earth away from the sun...
In theory, at least.
Over a billion-year period, it's possible to imagine.
It would require incredible technology
and incredible coordination.
The technology is possible.
Whether humanity as a species could ever coordinate it
is something I'm a little more skeptical about.
It's a crazy option, but if we don't do something,
earth and all of us will die,
and we'll become just like Venus.
Earth and Venus were probably born together
as identical twins, but then their paths diverged.
But now, lifetime is gonna send that cycle all the way back,
and they'll die as identical twins again.
In the grand scheme of things,
they'll just be two charred twins
spinning to oblivion in a backwater of the universe.
On the cosmic scale, life is short.
When you look at how earth evolved and how Venus evolved,
you can see the difference,
even though it's two almost twin planets,
how life and habitability could change over time.
So, habitability isn't always a permanent thing.
On human scales,
the universe seems the same every single day.
But, of course, that's because human life
and human civilization
is but a brief instant in cosmic time.
On cosmic scales, the universe evolves and changes,
and that makes the history of the universe remarkable.
Our tale of two planets converges in the end,
a cautionary tale about forces beyond our control.
Perhaps a billion years of learning from Venus
will save us from the same terrible fate.
Captions by vitac... www.Vitac.Com
captions paid for by discovery communications