All language subtitles for A.Travelers.Guide.to.the Planets.S01E03.Venus.&.Mercury.2010.1080p.BluRay.DD5.1.x264-c0kE_track3_[eng]

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.