Original subtitles

NARRATOR: Everyone likes a vacation in a warm climate,

but how about a trip to two planets that are as hot as hell?

MAN: If you were walking on the surface of Mercury

you would need one heck of a spacesuit.

NARRATOR: Mysterious Mercury appears lifeless and desolate.

But hidden deep inside is a clue to a different past.

MAN: The smallest planet made out of the densest stuff,

with the most lunar-like landscape at its surface.

And yet generating a magnetic field.

NARRATOR: But it's nearby Venus, goddess of love,

who will really melt your heart

and crush your defenses at the same time.

MAN: So this is a hell.

Real hell!

NARRATOR: Once the twin of Earth,

something went wrong here, terribly wrong.

WOMAN: At some point Venus had an ocean's worth of water

that is now gone.

NARRATOR: What turned Venus from paradise to pressure cooker?

Could this really be our future?

MAN: The ultimate fate of the Earth is to look like Venus looks today.

NARRATOR: And here, on our own doorstep,

there is possibly the greatest survival story of all.

MAN: There is some speculation that Venus might actually still harbor life,

even though it is such a hostile place.

NARRATOR: There has never been a better time

to boldly go where no human has gone before.

To follow in the footsteps of our robot pioneers

and visit the planets of the solar system.

MAN: T minus 40 seconds. Everything looks good for launch.

NARRATOR: Ever wanted to be an astronaut?

Imagine it was you

who was heading to the Hot Zone of the two inner planets.

Where would you go? What would you see?

And how would you survive?

The latest robotic missions

have revealed more about these worlds than ever before.

Armed with this new knowledge,

think of this as your personal travel guide to our near neighbors.

NARRATOR: As the planet closest to the sun,

Mercury is the ultimate summer vacation.

Step out of your spacecraft

and sizzling temperatures are guaranteed...

for a day that lasts three months.

And when the sun finally does set, the nightlife begins--

with a unique cosmic light show.

This is one pockmarked planet worth taking a closer look at.

Like our moon, Mercury is covered in craters.

BRETT DENEVI: You can't look at the moon or Mercury

without seeing impact craters.

NARRATOR: It's a good thing Brett Denevi loves a big impact.

As a member of the imaging team

on the current Messenger Mission to Mercury,

she sees a lot of them.

DENEVI: What's exciting for me is | get to be one of the first people

to see these images of places on the planet that we've never seen before.

NARRATOR: Most people come here to Meteor Crater in Arizona

to see a big hole in the ground.

Brett's desires run deeper.

DENEVI: If you want to study impact craters on Mercury,

this is the best place to come.

| mean, this is the most well preserved impact crater on Earth.

It's the closest you're going to get.

NARRATOR: Wonder what it would be like to take a stroll on Mercury?

You can walk around Meteor Crater in about an hour.

But on Mercury you wouldn't know when to stop.

Craters here stretch as far as the eye can see.

MAN: Apollo 11, this is Houston. Radio check, over.

NARRATOR: Although no human has ever set foot on Mercury,

we have a pretty good idea of what you would see.

MAN: We copy you down, Eagle.

SEAN SOLOMON: If you were walking around on the surface of Mercury,

it would look, outwardly, a lot like the moon.

NARRATOR: When you step onto Mercury,

you step into a world with no real atmosphere;

where the sky is as black as night and ablaze in sunshine.

And where a drive is an off-road trek

through at least a three-billion-year-old battlefield.

DENEVI: Big craters, small craters, craters everywhere.

So that's your first impression looking at it.

NARRATOR: Like the moon,

Mercury took most of its battering early on.

A silent witness to the dawn of time,

it's been undisturbed by a single drop of rain

or breath of wind ever since.

DAVID PAIGE: For the most part the surface of Mercury

has been frozen in time for periods of billions of years.

And you may say, "That's boring," but not necessarily.

It's a good thing because these planets

such as Mercury and the moon

preserve a record of what was going on during this critical early period

of the solar system's formation.

And so we can basically study it there, because it's laying right on the surface.

NARRATOR: Every stone and crater of this pockmarked world

has the potential to gaze back 4.5 billion years.

But counting these craters is just the first challenge

when it comes to revealing a planet like Mercury.

DENEVI: It's always low on the horizon

so it's hard to point a telescope at it from Earth.

It's hard to get into orbit around Mercury

because it's so close to the sun.

NARRATOR: For that reason, Mercury remains

one of the most underexplored planets in our solar system.

Many aspects, like its geological past, are a mystery.

But some things we do know:

this lonely planet has a strange sense of keeping time.

NARRATOR: Once you arrive, you'll have to reset your watch

for a time zone like no other.

DENEVI: It has such an unusual orbit and rotation period,

the days and nights are very strange.

NARRATOR: A Mercurian year is just 88 Earth days long,

thanks to its quick sprint around the sun.

But it rotates so slowly, a single day takes much longer.

DENEVI: The day on Mercury is more like half a year on Earth's terms.

NARRATOR: Although known to us since ancient times,

for thousands of years we had little idea

what the planet really looked like.

NARRATOR: Then, in 1974, NASA's Mariner 10 sends back

the first ever glimpses of its surface.

NEWSREEL NARRATOR: Pictures can be transmitted to tracking stations

and on to the Jet Propulsion Laboratory in California.

MARK ROBINSON: Due to Mercury's slow rotation

and its elliptical orbit around the sun,

when it flew by three times it saw the same half of the planet.

So we've really only seen something like 45% of the planet

at relatively low resolution.

NARRATOR: Hidden in these fuzzy black and white postcards

for over 30 years

are clues that point to one of Mercury's biggest puzzles:

it's been shrinking.

ROBINSON: Mercury doesn't have plate tectonics like the Earth does.

So we know that Mercury's crust is under a lot of compression.

And the only way you can really do that is if the planet shrank.

And so you can think of it as the Incredible Shrinking Planet.

NARRATOR: As Mariner 10 flies past, the mystery deepens.

The spacecraft detects a vast iron core hidden inside.

DENEVI: Mercury's core makes up about 60% of the planet by mass.

It's about twice as big as Earth's.

Why would it have such a huge core for such a small planet?

Some people think there was a huge impact...

that kind of stripped off a lot of the planet.

And now what we're seeing

is just the remnant of a once bigger planet.

NARRATOR: Many questions about Mercury remain unanswered,

questions a new mission will hopefully solve.

MAN: Five, four, three, main engine start,

two, one and zero,

and liftoff of Messenger on NASA's mission to Mercury.

NARRATOR: NASA's Messenger spacecraft

will become the first probe to orbit Mercury.

SOLOMON: Getting a spacecraft into orbit around Mercury

is difficult for two reasons:

the sun and the sun.

The sun as a source of heat and the sun as a source of gravity.

NARRATOR: To sneak past the sun,

Messenger is taking a convoluted route, flying past the Earth once,

Venus twice and Mercury itself three times,

to arrive in fulltime orbit by 2011.

ROBINSON: When you get into orbit you can end up mapping the whole planet

at fairly high resolution.

So we will start having

a mature and fundamental understanding of Mercury,

not only its surface,

but its whole chemistry throughout the whole planet.

From that we can unravel, to some degree, how it formed.

NARRATOR: What other secrets are etched into Mercury's ancient surface?

Already Messenger has sent back some curious clues.

After Messenger's three flybys,

we've now mapped more than 90% of the planet.

Taken from around 124 miles,

these images are the clearest to date of Mercury.

And it's not hard to spot a crater of epic proportions--

the result of yet another titanic collision.

DENEVI: That's the Caloris Basin, this impact basin.

It covers almost three million square kilometers.

It's one of the biggest in the solar system.

NARRATOR: The size of Alaska and California combined,

whatever created Caloris almost destroyed the planet.

ROBINSON: It was something in the order of 100 kilometers in size.

It could have been a huge comet

or it could have been a very large asteroid.

It had a catastrophic effect on the surface.

NARRATOR: Shockwaves rippled around the crust,

buckling it on the opposite side.

And near the center of the crater

is another spectacular geological puzzle--

that has experts scratching their heads.

DENEVI: The Spider is this really strange feature

that's in almost the center of the Caloris Basin.

ROBINSON: Oh, the Spider.

That really annoys me when | hear people call it that

‘cause it doesn't look like a spider.

How many legs does a spider have?

Eight, right?

DENEVI: It looks kind of like a 100-legged spider,

but it has all of these radiating cracks coming out of it.

NARRATOR: Whether The Spider is the result of planetary stretch marks

or some obscure cratering process, no one knows.

ROBINSON: It's a fascinating feature. We don't know how it formed.

It's very tantalizing.

NARRATOR: So, for a planet that appears inactive,

more has been going on deep inside Mercury

than we ever gave it credit for.

There's even more occurring above the surface that can't be seen.

And it involves the relentless force of the sun.

NARRATOR: Like Mercury, the Earth takes a beating

from the sun's violent temper.

Flares, sun storms and other solar hissy fits

can cause electronic mayhem for the satellites

that roam above our heads.

Fortunately, the Earth is protected from this radiation

by a magnetic shield,

a kind of force field generated by our molten iron core.

JAMES SLAVIN: Planetary magnetic fields shield planets,

their surfaces and their atmospheres

from charged particles that are always coming off the sun.

NARRATOR: The auroras that light up our polar skies

are evidence of our protective shield at work.

Without it, life would not exist here.

Visit Mercury and you'll be visiting

the only other planet in the inner solar system

with a magnetic field.

But its very existence defies explanation.

SLAVIN: Now the mystery there is that in order to have a magnetic field,

you need to have an interior to the planet that is at least partially molten.

Mercury, one of the smallest of the planets,

would have been expected to really have frozen all the way through.

And yet we have a relatively strong, very well defined magnetic field

that appears to have a source that's located deep in the planet.

NARRATOR: Whatever mechanism is driving Mercury's magnetic field,

it's too weak to protect it from the full force of the sun.

The solar wind buffets Mercury's thin atmosphere.

And in the process, it puts on a light show.

RONALD VERVACK: The reason you'd want to go to Mercury as a travel destination

would be this night-side view,

because it's going to be highly unique in the solar system.

You have sodium atoms that are streaming off

and giving off this yellow light.

And so you could almost look as like you're standing

in a doughnut of sodium emission.

NARRATOR: With the sunrise three months away,

you'll have plenty of time to sit back and take in the view,

framed in a halo of amber light.

VERVACK: In some sense you can get a very nice light show.

And | know people go to Canada to look at the northern lights all the time.

And so that would be a reason to go to Mercury.

MAN: T minus 40 seconds. Everything looks good for launch.

NARRATOR: Not a night owl?

Then head into the light.

But when you're this close to a stellar rotisserie,

make sure you pack plenty of sunscreen.

If you want a suntan, you can't beat the dusty sands of Mercury.

Stretch out on the ground here

and the sun crackles and fizzes right above you,

appearing almost three times bigger in the sky and seven times as hot.

PAIGE: If you were walking on the surface of Mercury,

you would need one heck of a spacesuit.

Because if you were in the sun it would be extremely hot.

You would see an enormous sun in the sky

that would just burn you to death

if you spent any time in it whatsoever.

NARRATOR: The mercury really climbs on Mercury--

to a toasty 840 degrees Fahrenheit.

That's about twice as hot as your kitchen oven on full heat.

You'll need a bit more than SPF 30 sunscreen here.

To escape the heat, you can always head to the dark side.

But dress warmly.

With virtually no atmosphere to keep the heat in,

the temperature plummets to minus 275 degrees Fahrenheit.

And it's here in the freezer

that Messenger will encounter another puzzle:

Can ice exist on a planet so close to the sun?

PAIGE: It was only when the first radar observations

of the surface of Mercury were obtained back in the '90s

that it was discovered that Mercury in fact had

what appeared to be polar caps in these first radar images.

NARRATOR: Some corners of Mercury's polar craters

are in permanent shadow.

Here, on the most sun-baked planet of all,

water seems to Survive frozen in eternal darkness.

PAIGE: The ice is contained in places where literally the sun never shines.

And so the ice is sequestered in these dark interiors of craters

at the high latitude regions.

NARRATOR: We found the same thing on our moon.

In late 2009, the LCROSS mission

crashed a probe into a deeply shadowed crater,

confirming ice hidden near the lunar south pole.

Where did it come from?

A comet?

PAIGE: It's very interesting because we believe that the water in the Earth,

in its atmosphere, in the oceans and even below the surface

probably came from a similar source.

And so part of the mystery of Mercury

is to try to find out where the water came from

and maybe that might help us find out where the water on Earth came from.

NARRATOR: It may never be possible to send a human to Mercury.

But how about a robot...

In 2011, when Messenger arrives in orbit,

imagine this tough little spacecraft circling a lonely planet,

a very long way from home.

Move away from the sun

and you'd expect things to cool down a little.

Venus: the picture of coolness and calm.

All pale, beguiling and cloaked by clouds.

But the planet of love is shrouded in mystery.

Drop beneath her treacherous veil at your own risk.

Beneath the clouds is the only planet in the solar system

to rotate backwards.

And it does so very slowly.

The sun, if you could see it,

rises in the west and sets in the east.

An entire day here lasts for eight Earth months,

which is longer than the Venusian year.

BAINES: On Venus you can walk around the planet

faster than the planet rotates.

NARRATOR: The sky above is as heavy as it looks--

loaded with CO2.

ELLEN STOFAN: Venus' cloud cover is mostly made of carbon dioxide.

And on the Earth we have the same amount,

but it's tied up in rocks like limestones,

it's tied up in reefs.

On Venus, all that carbon dioxide is in the air.

NARRATOR: It's the differences between these worlds

that are so intriguing.

That's because 4.5 billion years ago,

Venus and Earth started out as planetary twins.

MARK BULLOCK: They were formed right next to each other,

they're very close to each other in the solar system,

they have similar sizes.

DAVID GRINSPOON: Not only that, we now know the planets

were exchanging material early on.

Bits of Earth were falling on Venus, and bits of Venus were falling on Earth.

So if life started on any of these worlds,

it may well have spread among them

through these little chips getting knocked off

from all the impacts that were happening then,

all the big collisions.

ANNOUNCER: You are there...

on the most exciting, nerve-shattering journey in the history of man!

NARRATOR: 50 years ago, it was easy for us to imagine Venus,

closer to the sun and wrapped in clouds,

to be our scorched tropical sister, swarming with life.

GRINSPOON: There was this picture of Venus

as a kind of primitive, steamy Earth,

complete with giant tree ferns and dinosaurs.

MIKHAIL MAROV: Altogether, it seemed to us

that it should be, just possibly, even a populated world.

NARRATOR: In the late 1950s, the Space Race begins.

While America aims for the moon,

Russia sets its sights on meeting the neighbors.

MAROV: Venus and Mars still was in the human dreams

to meet the species which could be very similar to us.

Venus was even easier than Mars to reach.

NARRATOR: But landing on Venus proves surprisingly difficult.

One by one, the Soviet Venera probes

disappear within the thick Venusian atmosphere...

their last transmissions warning

of a world of inconceivably high temperatures and pressure.

Persistence and tough Russian engineering

eventually pay off.

In 1975, the camera on the redesigned Venera 9

finally penetrates the Venusian veil.

But what it sees is nothing like the tropical paradise imagined.

This is the first-ever picture taken from the surface of another planet.

MAROV: And for the first time it was returned

black-and-white panoramas of the Venus surface.

These images were extremely important,

because for the first time we, human beings,

had a chance to see with our naked eyes

completely different other world.

We were very much proud of that.

NARRATOR: Seven years later, Veneras 13 and 14

send back the first color postcards taken under Venusian skies.

MAROV: It means that standing on the surface of Venus

you will meet absolutely incredible situation.

First of all, you will see not the blue skies.

You will see red skies, orange in color.

This is a hell.

Real hell!

NARRATOR: Hell is a good description.

This is what it's like to enter the Venusian underworld;

a volcanic landscape ruled by crushing pressure and searing heat.

No probe survives here for much more than a few hours.

And none have ever returned.

What happened to our twin world?

Was Venus always as barren and hostile as it appears to be?

STOFAN: One of the most intriguing things about Venus

is that we know that at some point in Venus' history,

it had an ocean like the one we have here on Earth.

There have been chemicals measured in the atmosphere

that tell you at some point

Venus had an ocean's worth of water that is now gone.

MAN: Atlantis, Houston.

Everything down here looks real good to us.

NARRATOR: Where did all the water on Venus go?

And what else lies hidden under her veil?

WOMAN: Five, four, three, two, one.

We have ignition and liftoff of Atlantis.

NARRATOR: In 1989, the space shuttle Atlantis

launches the Magellan probe toward Venus.

MAN: Roger, roll, Atlantis.

NARRATOR: After a journey of 15 months,

Magellan uses radar eyes to peer through the clouds from orbit.

Watching from Earth is Ellen Stofan.

STOFAN: When you have that ability to pick up an image

and say, "I'm one of the first three people,

I'm one of the first five people

to ever look at this piece of ground on another planet."

It's such a sense of awe and a sense of discovery.

NARRATOR: Magellan's radar strips away the thick clouds.

For the first time ever, we see all of Venus laid bare.

Welcome to lava land!

STOFAN: There are volcanoes of all sizes,

from a kilometer across to hundreds of kilometers across.

And in that sense it's not all that different

from some areas on the Earth.

But on the other hand,

it's of course this dry world with no vegetation at all.

NARRATOR: It's the sheer number of volcanoes that sets Venus apart.

This is a world that has been tortured by fire.

Over 1,600 giant volcanoes puncture its surface.

It's possible some are still active.

[helicopter]

BULLOCK: If we could just hover like this over Venus

it would probably look a lot like this.

NARRATOR: Mark Bullock enjoys spending time on Venus,

at least the version he finds here on Earth.

BULLOCK: Hawaii has some of the most spectacular shield volcanoes

that are very similar to the volcanoes that we see on Venus.

NARRATOR: The huge, gently sloped volcanoes of Hawaii may be impressive.

On Venus there are at least 150

ranging from this size to ten times larger.

But the observant visitor may notice that Venus is missing something.

STOFAN: The whole impact crater situation on Venus

is really very puzzling.

BULLOCK: With the Magellan images,

we see really a small number of impact craters.

And it's such a small number, it's about a thousand.

Because we know the rate at which impactors come in,

we can actually date the surface

to somewhere between 300 million and 1 billion years old.

NARRATOR: Sometime in the recent geological past,

it seems the entire surface of Venus was remodeled...

and suddenly.

BAINES: The surface geology of Venus is different than the Earth,

basically because a lack of water.

Water is not lubricating that crust, so you don't get plate tectonics.

Instead what seems to happen is that forces inside the planet

are trying to move things around.

But it can't, it's locked.

And then it explodes, very massive, globally explosive episodes

that happen about every half a billion to a billion years.

So you would not want to be on Venus when that happens.

Because once something gives way

the whole planet might just basically explode in a sense

and turn itself over

in a very short amount of time in geological terms.

BULLOCK: Oh, man, look at this!

We can see a river of lava beneath the surface.

Imagine that this lava is on Venus.

Probably something very much like this

occurs either today or in the recent past.

NARRATOR: No one can say for sure

if we'll ever see an eruption like this on Venus.

No one has ever been able to get this close!

BULLOCK: One of the really exciting and high level of scientific interest

is whether Venus is geologically active today.

Because there are reasons to think that the clouds on Venus only exist

because there is ongoing geologic activity.

So this is one of the big secrets of Venus,

it's something that we want to find out.

NARRATOR: In recent years, finding the source

of Venus' thick atmosphere

has become surprisingly relevant for all of us down here on Earth.

BULLOCK: Half a million tons of sulfur dioxide

spewed into the atmosphere every year.

BAINES: The whole Greenhouse Effect was not really recognized

as a Significant effect to influence planetary climates

until we went to Venus

and found that instead of being 90 degrees Fahrenheit

it was 900 degrees Fahrenheit.

And we said, "Whoa, what's wrong with this?

Let's learn about this."

And it taught us about the greenhouse effect.

NARRATOR: The best way to experience Venus

is to hitch an imaginary ride on a Soviet Venera probe.

BULLOCK: Well, it would be a wild ride.

NARRATOR: The clouds start about 40 miles up,

some five times higher than the Earth's.

BAINES: What are those clouds made out of?

They're not made out of water,

they're made out of a completely different substance.

They're made out of sulfuric acid.

Everywhere you go, the atmosphere is going to try to eat you away.

NARRATOR: As you get deeper, things heat up.

The thickening atmosphere allows the sun's heat in, but not out.

It's also getting dense.

So dense, your probe drops like a coin in water.

BULLOCK: As we descended we would gradually,

the surface would gradually appear to us

as if we were approaching the bottom of the ocean.

NARRATOR: Congratulations, you've arrived

on the hottest surface in the solar system!

Here the official temperature is 870 degrees Fahrenheit.

Day or night, equator or pole,

the searing heat never varies more than a few degrees.

And it's why we have so few snapshots from the Venusian surface.

GRINSPOON: So why is it so hard

to bring scientific instruments to the surface of Venus?

What about an ordinary camera?

There's plenty of light there.

Why not just send a camera and take pictures?

I've got my NASA-issued spacesuit here, my special Venus suit.

And let's take this camera and send it to Venus

and see what happens.

BULLOCK: Primarily you don't want to melt.

It's such a hot environment that all the electronics,

all the power, all the communications

have to be very rugged.

GRINSPOON: Oh, that's cool, though!

BULLOCK: Anything mechanical, anything electronic

is just an enormous challenge to have it function on the surface.

NARRATOR: And it's not just the heat that you have to bear.

All that sky above is really heavy,

pressing in at around 90 times the pressure on Earth.

STOFAN: When | was a graduate student

we use to get in conversations about what would get you first,

the temperature or the pressure?

It would be pretty simultaneous, | think.

NARRATOR: To descend to the surface of Venus

is the same as diving over half a mile underwater.

PHIL NUYTTEN: It's an enormous pressure, enormous, crushing pressure.

How do you make things that withstand,

how do things turn and move under those huge outside pressures?

Well, that's what the armor of technology is all about.

The Exosuit, using composite fiber,

strong aluminum alloys and stainless and titanium

and all these things.

It looks like something out of Transformers

or out of a comic book.

That's the same kind of suit that you'd need

on the surface of Venus.

NARRATOR: You'd never guess the dangers on the ground from orbit.

Except maybe for this:

massive double-barreled storms hovering above the poles.

BAINES: These, what we call dipole features, twirling around.

We don't know really what they are.

But the whole feature itself

is only a thousand or two kilometers across,

it's not very big.

But it has like a figure-eight type of look to it.

NARRATOR: Believed to be created by winds that roar around the equator

at speeds up to 230 miles per hour,

these hurricanes can split into three and even four.

And the wild weather doesn't end there.

Because the hottest planet in the solar system even has snow...

but not as we know it.

STOFAN: All of the sudden in the radar images,

all the mountains go white.

Now that's because there's some kind of highly reflective coating.

It wouldn't look white to your eyes

if you could actually land on the surface of Venus.

It might look shiny,

because we actually think it might be some sort of metallic coating,

almost like a pyrite or a fool's gold.

So something sparkly,

which to me is even better than looking at snow.

NARRATOR: These are just some of the puzzles

that the European Space Agency's Venus Express,

now in orbit, is hoping to solve.

As we begin to understand how carbon dioxide controls our climate,

there's never been a better time to learn lessons from our neighbor.

HAKAN SVEDHEM: What we're trying to solve now

with this very, very dense atmosphere, very complex weather patterns,

with the new data from Venus Express

we are really learning by mapping out in three dimensions

how the atmosphere behaves.

NARRATOR: Unprotected by a magnetic shield,

Venus is still being robbed of precious water.

Venus Express has seen how the solar wind

eats away at the atmosphere.

SVEDHEM: We can see that even today

that actually water is still escaping in the form of oxygen and hydrogen.

And that's an indication

that there has been water on Venus in the past.

NARRATOR: Despite all this scientific effort,

we still don't know what triggered Venus' diabolical transformation.

STOFAN: People debate over whether Venus ever had a moon.

If Venus had a satellite at one point,

could that satellite have eventually impacted onto the surface

and caused some catastrophe to happen?

We don't know. It could have been possibly a factor.

NARRATOR: Perhaps such an impact

explains both the strange calendar and climate on Venus.

Was it hit hard enough to flip upside down?

And for its day to be slowed to a crawl?

Was this the moment Venus' climate was thrown into chaos?

GRINSPOON: If | had to guess, or | had to bet,

| would say, "Yeah, Venus did have a life."

And | say that because what we do understand about life on Earth

is that it started early

and doesn't seem to have required any extraordinary conditions.

If there was life of our kind, the organic kind,

on the surface of Venus a long time ago,

then what happened to that life?

Well, one possibility is that it just died out.

But there's another possibility that's a little more exotic,

which is that it may have migrated up into the clouds.

BAINES: There is some speculation that Venus might actually still harbor life

even though it is such a hostile place.

And the reasoning is that,

well, gee, at one time Venus was like the Earth

in the first two billion years or so of its history.

So if life were to grab a hold, maybe life was able to stay ahead

of the environmental disaster that befell Venus

as the water basically left the planet.

NARRATOR: Could life really exist in the clouds of Venus?

The best way to know for sure

is to float into the atmosphere and find out.

BAINES: Right behind us is the Valor balloon

which we intend to fly in the skies of Venus

a couple of years from now.

NARRATOR: Valor will be tackling the acid clouds of Venus

with a little help from frying pan technology.

BAINES: There's been two other balloons,

already launched to Venus in the mid-1980s.

These were the Vega missions.

There were two separate balloons

that the Russians put into the atmosphere.

The one thing they knew to do is put Teflon on that whole balloon,

and the balloons worked perfectly for two days just as designed.

And so we know that Teflon works.

NARRATOR: Battling violent updrafts and acid clouds,

these non-stick pioneers

were swept nearly halfway round the planet.

Kevin expects Valor to go further.

BAINES: We'll circumnavigate the planet, that is fly around the world of Venus,

not just once but up to five times.

And if we do that, if we accomplish that, we will by far have the world's record,

actually it's the universal record,

for flight in the skies of any planet anywhere.

NARRATOR: Underexplored and unbelievably alien,

the hot zone planets are finally being recognized

as prime space travel destinations.

Mercury: a planet that's both freezer and furnace.

DENEVI: As a geologist,

if | could just bring back one rock, one sample.

| mean, that would increase our knowledge of Mercury

by, you know, tenfold or something.

ROBINSON: | would like to go to these polar craters

and figure out what is it.

Even if it's not water, it's something very unusual and very fascinating.

NARRATOR: And Venus, our unfortunate twin sister.

BULLOCK: What we'd like to do is explore the regions

that haven't been explored before.

And so | would pick Alpha Regio here.

That's probably the first place | would go.

BAINES: I'd love to go see

those snow-filled mountain peaks with metallic snow

and see if we can figure out what's going on there.

Maybe some new sports that can be created,

sliding down those metallic snows?

GRINSPOON: And then of course there's the future story

and what's going to happen to Earth in the distant future.

And that's another reason we are really interested in Venus.

Because the ultimate fate of the Earth is to look like Venus looks today.

NARRATOR: Venus and Mercury: two planets of wonder

but trapped in their own alien hells.

Perhaps not obvious destinations

to discover more about our home planet,

but that's the beauty of traveling the solar system;

it's just full of surprises.