All language subtitles for The.UnXplained.Mysteries.of.the.Universe.S01E04.1080p.WEB.h264-EDITH_track3_[eng]

WILLIAM SHATNER: Volcanoes scar
the surface of a rocky planet...

...hidden under thick clouds
of acid rain,

while unimaginable heat
makes life impossible.

Welcome to Venus.

For centuries,
we've been fascinated

by our nearest
planetary neighbor,

even dreaming that it might be
an exotic paradise

where humans could live one day.

But in reality,
this glowing yellow orb

is filled with poisonous clouds,

and its temperature
is hot enough to melt lead.

Will Venus remain
a strange, forbidden world?

Or could we turn our neighbor
into another Earth?

Well, that is what
we'll try and find out.

♪ ♪

SHATNER:
When we gaze up at the stars,

we see a vast array
of cosmic wonders,

from majestic constellations
to sweeping comets...

...and much more.

But there is one
particular object

that is perhaps more captivating
and mysterious than the rest.

It's a bright diamond
that shines above the horizon

which we call Venus.

Venus is very bright in the sky.

It's visible in the evening
or in the morning,

depending on the time of year.

And so, people are,
naturally, just very curious

about what that bright thing is
out there,

especially as we started
building accurate models

of the solar system

and realized that it was
the closest planet to us.

PAUL BYRNE:
On paper, Earth and Venus

are really similar.

They're almost
the exact same size,

they're made of
about the same materials,

they're about the same age
and they orbit the same star.

And so, for those reasons
and a host of others,

that's often why we say
that Venus is Earth's twin.

SHATNER:
Is Venus truly
Earth's twin planet?

And if so, what secrets
lie within this luminous world

that hangs in our sky?

O'ROURKE:
Scientists are...

more ignorant about Venus
than we are about

almost any other world
in our solar system.

For example, we know very little
about the interior of Venus.

On Earth, we know
how big our core is

because of seismology,

but we've never measured
Venus quakes.

we haven't put the seismometers
on the surface

that we would need
to make detailed maps

of the interior of Venus.

And so, the planet is just,
all in all, a big mystery.

SHATNER:
The mysteries of Venus

have intrigued mankind
for thousands of years.

Our ancient ancestors
could only speculate

about the true nature
of the planet.

Venus has been
incredibly important

throughout human history.

It is the third-brightest
object in the sky

after the Sun and the Moon.

And that has led humanity
to associate it

with various deities
in different civilizations.

For example, the name "Venus"

was a Latin name that was
given to it by the Romans.

The Romans gave the planet
the name "Venus"

because it's so beautiful
in the sky, and therefore,

they named it after their
goddess of beauty and love.

And so, the brightness of Venus

has given people a great deal
of fascination about it.

SHATNER:
While ancient societies

looked upon Venus
as a divine entity,

during the Enlightenment,

scientists were compelled
to unravel the mysteries

of Earth's so-called twin.

Astronomer Francesco Bianchini

constructs several large
telescopes around the city,

including one directly across
from the Colosseum

that measures an unprecedented
72 feet in length.

Bianchini's goal
is to give humanity

its first up-close look
at Venus.

GRAHAM LAU:
Francesco Bianchini was using

remarkably long telescopes--
refracting telescopes--

with large lenses for their time

to make his observations
of Venus.

He started seeing

these large, dark regions
on the surface of Venus

that he thought
were lakes or oceans of water.

He even created
the first globes of Venus

and mapped out these features.

And for that period of time,

that would make sense,
that there should be

other worlds that,
just like the Earth,

have oceans and lakes
and rivers.

SHATNER:
Bianchini's drawings of Venus
amazed people throughout Europe.

But some scientists
were skeptical of his claim

that Venus had
large bodies of water.

And as it turns out,
his critics were right.

LAU:
We now know that Bianchini
wasn't looking at lakes.

Indeed, he was looking at
the clouds of Venus.

And so, when we look at Venus
with visible light,

we see a world
obscured by clouds.

But even though we now know
that what Bianchini thought

he was seeing of Venus is wrong,

his observations
using these large telescopes

were a huge step
in astronomical observation.

SHATNER:
For centuries, the dense clouds
that shroud Venus

frustrated scientists
who wanted to get

a better look at the planet.

This impenetrable cloud cover
inspired wild theories

about what lies on Venus.

Before the Space Age,
people believed

that Venus
is a sort of swamp world...

...covered in
a planetwide jungle,

where heroes
rode around on dinosaurs

and fought amid
a lot of greenery.

And science fiction writers
were convinced that Venus was

a place where humans
could not only visit

but perhaps thrive
and have great adventures.

SHATNER:
By the middle
of the 20th century,

curiosity about Venus
reached the point

that scientists
realized it was time

for humanity to finally glimpse
the surface of the planet.

From the Baikonur Cosmodrome,

the Soviet Union launches
its Venera 9 spacecraft.

Four months later,
Venera pierces the thick clouds

that have hidden Venus for ages,

and a robotic probe
lands on the planet,

allowing humans to see
the surface of Venus

for the first time in history.

ANNA GÜLCHER:
The pictures taken by Venera 9

in 1975 on the surface of Venus,
they have this yellow gloom

which is kind of an artifact

from the composition
of the atmosphere.

And if you look
at those pictures,

you see these plains
of dark, smooth rocks

that are fractured
and, in places, broken.

It has something alien but also
something very familiar.

JACOB HAQQ-MISRA:
These pictures are breathtaking.

This is a planet that you cannot
see the surface of,

even with a really
powerful telescope.

And so, to see photographs
from Venus, it's just amazing.

And these are still
some of the only pictures

we have that were actually taken
from the surface of Venus.

SHATNER:
The Venera 9 mission

was a breakthrough
in space exploration.

But curiously,
the robotic lander

operated for a mere 53 minutes
before melting down.

What scientists
didn't know at the time--

but would quickly discover--
is that Venus,

for lack of a better word,
is a hellhole.

We now know
the surface conditions on Venus

aren't anything
like they are on Earth.

For example,
the surface temperature

is almost
800 degrees Fahrenheit.

That is the same temperature
your oven is on

in its self-cleaning mode.

The entire planet
has a global layer of clouds

made of sulfuric acid,

and those clouds
drop sulfuric acid rain.

These conditions
are more than enough

to kill you
in several ways simultaneously.

And so, that's why
we often refer to Venus

as Earth's evil twin.

SHATNER:
With such hellish conditions,

it's easy to see

why Venus is now considered
Earth's evil twin.

And yet, some scientists claim
that in the distant past,

Venus was more identical
to Earth.

So, what went wrong?

One of the big questions we have
in planetary science right now

is why did Venus change
to become the world it is today?

What killed it
and could that mechanism

one day affect Earth?

Or perhaps,
why didn't it affect Earth?

Was Venus unlucky,
or has Earth remained lucky?

And the short answer
is we don't know.

SHATNER:
How can we unravel the mystery

of what happened to Venus?

One theory suggests
that a clue lies

in the fact that Venus
is covered with deadly volcanos.

SHATNER:
The shuttle Atlantis launches

from Kennedy Space Center,

carrying the Magellan
space probe.

Magellan's mission
is to orbit Venus,

and take detailed images
of the entire surface.

The photos reveal
an up-close look

at a planet covered
in massive volcanoes.

One of the really
surprising discoveries

of NASA's Magellan radar mission

was about 80% of the surface
is covered in volcanic plains.

We know now that there's
more than 85,000 volcanoes

that are about half a mile
in diameter or bigger.

And so, Venus
is an extremely volcanic world.

SHATNER:
The volcanoes on Venus
are fascinating,

and some experts have wondered:

could they be the reason
why the planet

became Earth's evil,
and inhospitable, twin?

Many people believe that Venus

could have been
a nicer place in the past.

And if Venus formed

in the same way
that Earth formed,

it's possible that
if we hopped in a time machine

and went back in time
one or two billion years,

that Venus had oceans
in the past,

that it was a nice place to live
just like Earth is today.

So, what fascinates me
about Venus is the prospect

that it was a habitable world
like Earth,

but then lost its habitability

in some sort
of planetary catastrophe.

How did Venus
get from a possible

happy, habitable state
in its early history

to this world that we see today?

One hypothesis
that we've put forward

is that it could be
large-scale volcanism.

If you could have
these large volcanic events,

then you have all this magma
kind of flowing out

over millions of years.

These kinds of events
can produce

tremendous amounts of carbon
dioxide into the atmosphere.

Adding more carbon dioxide
makes the planet hotter.

And you end up with
what modern Venus is today.

SHATNER:
Did a cataclysmic
series of volcanic eruptions

turn Venus into
the extremely harsh environment

it is right now?

And if so, is it possible

that a similar catastrophe
could take place

on Earth?

It turns out that Earth
is an extremely volcanic world.

Over the last
500 million years or so,

there have been some gigantic
volcanic eruptions on Earth,

and we know that some
of the largest mass extinctions

recorded in the fossil record

are tied
to those volcanic events.

And so,
you can imagine a scenario

where if you have
enough volcanoes

erupting over
a short enough period of time,

then possibly you start
talking about an Earth

that becomes much more
like Venus than it is today.

Right now, we don't have
enough information to say

whether that's possible or not,

but it sure has got
scientists thinking.

SHATNER:
The possibility
that volcanic eruptions

could make Earth more like Venus
is concerning.

So, how can we learn

whether this doomsday scenario
might happen?

Scientists believe
that clues can be found

by taking a new look
at some old data

about the volcanoes on Venus.

In 1978, NASA launches
the Pioneer Venus Orbiter

to perform observations
of Earth's neighboring planet.

The probe sends
back massive amount of data

about both the atmosphere
and the surface of Venus.

Experts spend
the next several years

poring over this information

including a planetary scientist
named Robert Herrick.

I started my career
as a geoscientist

in the oil industry in Texas

and I got hooked up with a guy
who was working

with Pioneer Venus
gravity and topography data.

That was my entrance
into Venus science.

It was the first time
where the data was released

on this new invention
called the compact disc.

And so we got sent
boxes and boxes of CDs,

and you could load up one image
every 15 seconds or so.

And so, it was really kind
of prohibitively difficult

to do a large-scale scan
of the data,

and so nobody did it.

SHATNER:
In the early 1990s,

Robert stopped analyzing
the information

collected about Venus

and, for decades,
this vast amount of data

was largely forgotten.

Until 2020,
when Robert was inspired

to take a second look
using cutting-edge software.

And this time,
he made a remarkable discovery

about a particular volcano
on Venus.

I had a list of, you know,

the most likely places on Venus

where there was
an active volcano.

And I just sort of started
going through them one by one

and flipping back and forth
between the images

and looking for
something that changed.

Where I hit paydirt
was near the summit

of the very largest volcano
on Venus.

I found a volcanic vent
that had appeared

to change shape
over an eight-month period.

It was pretty exciting.

I'm like,
I think this is important.

It makes it clear that
at least parts of the planet

are currently
volcanically active.

SHATNER:
When Robert published
his results in 2023,

scientists were shocked

because they have long believed

that Venus's
once-deadly volcanoes

went dormant
sometime in the distant past.

But this discovery proved

that there is ongoing
volcanic activity on the planet.

It also showed that we
still have a lot to learn

about the volcanoes
on both Venus and Earth.

It's so peculiar to think that
they used 30-year-old data

and found something
that was never found before.

Why didn't we see it earlier?

So, the 2023 discovery was,
in my eyes, huge.

Since Venus
is volcanically active today,

we can actually get insights
into the volcanoes

we have on the Earth,

and the future of our planet,
in many ways.

It's an important discovery
because both Venus and Earth

are volcanic planets.

Venus is releasing heat

similar to the way Earth
is releasing heat.

And so, we need
to learn the details

about how that occurs.

Studying the volcanoes on Venus
should show us

how we could spare Earth
the same fate as its evil twin.

But the mysteries of our
closest planetary neighbor

go far beyond its fiery surface.

For instance, scientists
are trying to figure out

why Venus
actually spins backwards.

In the archives
of the Saxon State Library

lies an ancient manuscript
known as the Dresden Codex.

Dated to around
the 11th century AD,

the Dresden Codex is the oldest

and best-preserved writing
of the Maya,

a civilization
which ruled Mesoamerica

for more than 3,000 years.

And curiously,
the pages of this text

contain a remarkable connection

to the planet Venus.

The Maya worshipped Venus
and it appears

that they put Venus
as the cornerstone

of their faith
and also their civilization.

And when scientists
looked at the Dresden Codex,

they found what we now call
the Venus Table,

which is able to predict
the position of Venus

to a very high accuracy.

In fact, they kept some
of the most accurate records

in all of human history

before the advent
of modern astronomy.

KANE:
The observations
of Venus by the Mayans

shows that, actually, Venus
has been incredibly important

throughout human history.

And the tracking
of Venus's motion

has been something that people
have paid attention to

for a long time.

SHATNER:
It's astonishing to think
that ancient people

were just as fascinated
by the movement of Venus

as modern astronomers.

But technology has made
tracking the planet much easier

and revealed some curious
aspects of Venus's motion.

In 1962, at NASA's Deep Space
Instrumentation Facility,

located in the Mojave Desert,

experts discovered something
about the rotation of Venus

that no one
had ever noticed before.

It actually spins backwards.

WAY:
Most of the planets in
the solar system are spinning

in the same direction.
But Venus is spinning

in the opposite direction.

It's spinning backwards,

compared to Earth's spin axis.

O'ROURKE: Venus spins
in retrograde.

You can think of that
as Venus spinning backwards,

or you can think of that

as Venus having been
flipped upside down.

But however you think about it,

what it means is that
Venus's spin is a big mystery.

SHATNER:
Is Venus flipped upside down?

It's an extraordinary notion.

And it makes you wonder
what it would be like

to live on a planet
that spins backwards?

For everything Venus
has in common with the Earth,

from its size and its mass,
it has some things

that are really different
from the Earth, also.

If you were on Venus,

or if Earth was doing
what Venus did,

the sun would
actually rise in the west

and set in the east.

So, it would--
it would generally be

a bizarre experience.

SHATNER:
Curiously, Venus's backward spin

isn't the strangest aspect
of its movement.

Because not only
is Venus turning

in the opposite direction,

it also spins so slowly

that it's hardly
rotating at all.

Venus spins incredibly slowly
compared to Earth.

We know that Earth
takes 24 hours

to spin once on its axis.

In comparison, if you were
living on the surface of Venus,

it would take 243 days to

spin once around on Venus.

KANE:
Venus rotates once
every 243 days,

but it takes 225 days
to orbit the sun,

which means it takes
longer to rotate

than it does to orbit the sun.

Its day is longer than its year.

That makes it different to
almost everything else that

we observe within
the solar system.

SHATNER: Scientists are still
trying to learn more about

Venus's unusual spin,

and some have asked
what would happen

if Earth rotated
at such a slow pace?

Experts theorize that
the results would be

nothing short of catastrophic.

VERONICA BRAY:
If the Earth had
a really slow spin,

we would have sections of
the population that would

have to live
entirely in darkness

for a large section of the year.

The rest, on the lit side
of the planet,

would be scorched mercilessly.

McGEE:
Having one side of the planet be

so much hotter than the other
would mean there are

torrential winds that would be
blown from the hot side

and sucked onto the cold side.

You'd have cyclones
and massive storms

at the transition zones.

It would be
a really unfriendly place.

SHATNER:
Could Venus's slow,
backwards spin be one reason

it's such a hostile wasteland?

And if so,
what caused Venus to rotate

so differently from Earth?

According to
planetary scientists,

a clue may lie in the fact that

while Earth
is orbited by a moon,

Venus is not.

BRAY:
We think that the Earth's moon
made Earth habitable.

One way that
the moon has helped us

have a habitable planet

is that it stabilizes
our rotation.

So, there's a lot of
planets in the solar system,

like Venus, that are wobbling
like a spinning top.

And if you have
a large enough wobble,

it can lead to extreme seasons.

And for Earth, the Moon
stabilizes our rotation

and we only wobble a little bit,

giving us relatively
mild seasons,

which helps
the development of life on Earth

and keeps things
habitable for us.

KANE:
The Earth's moon is one of

the distinctive features
of the Earth,

and we're not really sure

why Venus doesn't have a moon.

And it is still something
that we struggle to understand,

how a planet

can have a rotation
that is the opposite to

almost everything else
that we observe,

and is now in a permanent
state of hostile conditions.

A planet that rotates backwards?

It's enough
to make your head spin.

But experts claim what's
even more bizarre about Venus

is its atmosphere,

because the poisonous clouds
that cover it

may actually contain

the seeds of life.

(siren wailing)

SHATNER:
Smoke from more than
a thousand wildfires

sweeps over southern Canada

and the northern United States.

A fiery haze
envelops cities like Chicago

and New York,

rendering the air so toxic

that experts label it
a lethal threat to life.

SUTTER:
At the height of the wildfires,

the pictures taken from
downtown Manhattan

looked like the city
existed on another planet.

But you could be standing in

the middle of
the worst atmosphere

you can possibly
imagine on Earth,

and it's nothing compared to

a normal day on Venus.

CLARA SOUSA-SILVA:
In many ways, Earth is heaven

and Venus is hell.

The surface of Venus
is so, so hot

that it can melt lead.

It is extremely dry
and extremely acidic,

more than any place we've ever
attempted to find life on Earth.

And so Venus has almost
no part of it

that isn't absolutely
hostile to life.

SHATNER:
It's hard to imagine
that humans,

or any other life forms,

could ever survive in the brutal

and inhospitable
environment of Venus.

But, incredibly, that
hasn't stopped scientists

from searching for signs of life

on Earth's evil twin.

SOUSA-SILVA:
On Earth, life has been found

in every conceivable place.

However, if we did
find life on Venus,

a place so different from Earth,
it would mean that life

is not just inevitable,
it is common.

It is everywhere.

And so when we
look for life on Venus,

we look for the unusual,

we look for the strange,

and we don't just
look for the familiar.

SHATNER:
Is Venus home to
strange life forms that,

against all odds, have
somehow managed to survive

in its lethal conditions?

And if so, where on the planet
might they be found?

Well, according to one theory,

it could be
in an unexpected location.

In the scientific
journal Nature,

astronomer Carl Sagan
and biophysicist Harold Morowitz

publish an
intriguing hypothesis.

They propose that if life
does exist on Venus,

it would not be
on the planet's surface,

but rather...

in its clouds.

SOUSA-SILVA:
Venus is a pretty
hostile place to

most life almost everywhere.

However, there are
places in the clouds

that are really like
a summer day

on the surface of the Earth.

You get just enough light
from the sun to get energy,

but still some protection
from the atmosphere.

HAQQ-MISRA:
The cloud decks of
Venus are actually

a fairly Earth-like environment.

And so Carl Sagan
and Harold Morowitz

had an idea that
perhaps microbial life

has found a way to survive

in the atmosphere of Venus

where you've got
these habitable conditions.

Over the last few decades,

we've learned
fascinating information

about so-called extremophiles,

microbial life
that has adapted to

unbelievable conditions
on Earth,

even places where there's
virtually no water,

high into the atmosphere.

Now, whether there's
life on Venus

remains an open question.

But it sure
has got scientists thinking

about what that would mean

for life in the Venus clouds.

SHATNER:
Could there be life
in the clouds of Venus,

as experts theorize?

Planetary scientists not only
believe it is possible,

they also may have actual proof.

And it was found
by looking at Venus

in an entirely different light.

In a groundbreaking paper

published in
the journal Astrobiology,

biochemist Rakesh Mogul
and a team of scientists

made an
astonishing announcement.

They discovered that
although, to the naked eye,

Venus's clouds appear to be
a light-colored, uniform veil,

when the planet is observed
in ultraviolet light...

...it reveals that the clouds

contain mysterious dark patches.

Venus looks very different
in different forms of light.

And in these dark patches

where we see
ultraviolet contrast,

these patches move around
in mesmerizing patterns,

and what we saw is that
their spectral characteristics

are very similar to

microbial algal blooms
that we have here on Earth,

something that is
alive and biological.

So we put that theory out there

that those UV contrasts

look like algal blooms.

So, with Venus,

I'm very much interested
in the potential

for the clouds to be

a habitable zone,
habitable environment.

And that's really exciting.

SHATNER:
The fascinating theory that
life may have found a safe haven

in the clouds of Venus made
headlines around the world,

and it suggests
that Earth's twin planet

may not be as evil
as we commonly think.

Scientists are still arguing

about life existing
in the clouds,

but it's definitely
not impossible.

It's a tantalizing possibility,

and it really illuminates

how little we know about Venus

and the fact that
we can't exclude the idea

that life exists in the clouds.

Finding microscopic life
in the clouds of Venus

would be a monumental discovery.

And what's intriguing is

how NASA plans to
search for that evidence.

They're building a revolutionary
new spacecraft in the form

of a robotic balloon.

SHATNER:
At the dawn of the Space Age,

Venus was a prime target
for planetary exploration.

In 1962, NASA's Mariner 2 probe

made the first successful
flyby of Venus.

And then, in 1970,
the Soviet Union's

Venera 7 spacecraft

made the first successful
landing on the planet.

SHATNER:
Over the next 15 years,
nine more probes landed

on the surface of Venus,

with Vega 2 making
the final touchdown in 1985.

But since that time,

no spacecraft have landed
on Venus,

or even flown
through its atmosphere.

Which begs the question,
why did space agencies shift

their focus away from Venus?

The surface of Venus
is inhospitable

to all our current
spacecraft technologies.

So, when we send things
to Venus,

we know that they can
only survive for a few hours,

because once the circuitry
is as hot as Venus is,

they're cooked, and they die.

And so, the grand
challenge for the future

of Venus exploration is to
build something that survives.

SHATNER:
Will scientists be able
to design a probe

that can withstand
the lethal conditions of Venus?

As it turns out, NASA is working
on this problem right now.

In this remote area,
more than 100 miles away

from the closest major city,

a strange, shimmering
airship rises into the sky.

Known as an aerial
robotic balloon, or aerobot,

the device is
a prototype developed

by NASA's Jet Propulsion
Laboratory.

NASA specifically chose
this barren,

inhospitable location
to test the aerobot

because the climate
conditions closely resemble...

the upper atmosphere of Venus.

BYRNE:
Balloons are the next
technology

for how we explore Venus.

Because the atmosphere
of Venus at an altitude of

around 40 miles
is relatively clement,

where the temperature and
pressure conditions are okay,

a balloon could float for weeks,
months, or even years.

And so, we would be
uniquely positioned to

conduct all kinds of
scientific investigations.

SHATNER:
To help it endure
the harsh environment of Venus,

the aerobot is equipped
with advanced features,

such as a puncture-proof
metallic skin,

and remote-controlled
helium chambers to allow for

precise altitude adjustments.

NASA hopes that these
advancements will enable

the probe to conduct
the most comprehensive

exploration of Venus to date.

I'm really excited about
exploring Venus with a balloon,

because a few years ago,
some astronomers claimed

a detection of phosphine gas
in the clouds of Venus.

That was incredibly exciting
for everyone because

phosphine gas is a biosignature,
it's a sign of life.

Scientists are still arguing
about how much phosphine

is in the atmosphere of Venus,

but if you sent
a balloon to Venus,

you can actually do
geophysical investigations

about the possibility
that life exists in the clouds.

SHATNER:
NASA plans to build a fleet
of aerobots that could be

floating through Venus's
atmosphere within a decade.

However, the best way
to explore our twin planet

would be to send astronauts,
instead of robots.

So, could there be a way

for humans to explore Venus?

The biggest obstacle to humans,
if we want to explore Venus,

is the fact that
the planet is so hot.

This is a very dangerous
environment

for humans to venture.

And so, it be comes
very difficult to think about

how you would do this
in a pragmatic sense.

There have been
science fiction stories,

and even people have
put good faith effort into

building a kind of domain,
like we bring to the bottom

of the oceans,
that are protected from

the sulfuric acid,
and could have

their own sort of
environment.

But all of them are
highly speculative and,

of course, very challenging,
technologically.

SHATNER:
Figuring out how
to keep humans alive on Venus

seems like
an insurmountable problem.

But some experts believe
it's possible,

that science fiction
might soon become...

science fact.

NASA announces a new plan

for an experimental vehicle

that would allow astronauts
to explore the planet Venus.

The proposed device is called

the "High Altitude
Venus Operational Concept,"

otherwise known...

as HAVOC.

HAVOC is essentially
an airship, a blimp,

with a gondola underneath

in which humans,
actual astronauts,

would spend some amount
of time conducting scientific

experiments at about 40
to 45 miles above the surface.

LAU:
Basically, we would live
on these large,

floating platforms;

our own cloud cities on Venus,

allowing humans
to live in the atmosphere,

to do research on Venus
without ever going down.

And then when they're finished,
they could just

take back off again from
these floating platforms.

O'ROURKE:
Something like HAVOC
really illustrates

how people rise
to meet challenges.

The hostile conditions on Venus
are a curse

because it makes it hard
to do things,

but they're also a blessing
in that it forces us

to stretch ourselves
and become creative

and think of new ideas.

SHATNER:
The notion of humans inhabiting
cloud cities above Venus

is fascinating, and hopefully,
it will actually be achieved.

But there's an even
more ambitious proposal

when it comes
to human exploration of Venus.

It involves transforming
the entire planet...

to make it more like Earth.

SHATNER:
In the journal Science,
an intriguing article titled

"The Planet Venus" is published

by astronomer Carl Sagan.

Although Sagan would later
write about the possibility of

life in the clouds of Venus,
in this paper,

he proposes something
far more incredible.

He suggests that it might
be possible to transform Venus

into a planet capable
of sustaining human life.

This concept is referred to
as terraforming.

Terraforming means changing
the environment

to be even more like Earth.

Carl Sagan imagined
that you could change

the surface of Venus

into something which could
have conditions that are similar

to Earth that humans can
survive in.

SUTTER:
Today, humans would be

simultaneously crushed
and melted

if you were to step foot
on Venus.

This is just hell
in planet form.

And so if we want to turn
Venus into a copy of Earth,

we have our work cut out for us.

SHATNER:
The idea of terraforming Venus

into an Earth-like world is
astonishing.

But how could we
possibly achieve

such an extraordinary feat?

Carl Sagan theorized
that one way might be to

seed the clouds of Venus
with algae,

to convert carbon dioxide
into oxygen,

which would potentially trigger
a planet-wide transformation.

O'ROURKE:
Carl Sagan was brilliant,
and he had

almost the right picture
of terraforming Venus.

The only thing he got wrong
is he thought the clouds

were made of ice crystals
and water vapor.

Unfortunately,
we now know that those clouds

are sulfuric acid,
not predominantly water vapor.

And so, we'd have to get
a little more creative

if we wanted to terraform Venus.

But it's definitely
not impossible.

LAU:
When it comes to the concept
of terraforming,

sure, Venus now has
this extremely hot

and dense surface,
this thick atmosphere.

It doesn't seem hospitable.

But as our ability
to geo-engineer

the environment
around us changes,

we have to wonder,
maybe Earth's twin planet

will truly become
our twin planet

as we terraform Venus
and give it a biosphere

just like we have.

Maybe in
the not-too-distant future,

Venus and Earth will look
almost the same.

SHATNER:
Today, terraforming Venus
remains an intriguing concept

that scientists
are still debating.

But in the more
immediate future,

NASA and
the European Space Agency

are planning exciting missions
to study Venus.

The data they collect
will hopefully solve

some of the many mysteries
of Earth's evil twin.

O'ROURKE:
One of the goals of the missions

that NASA and the European Space
Agency are sending to Venus

is to make maps of the surface
at high resolution

of some of the most exciting
types of terrain on Venus.

There's a lot of mountains,
a lot of valleys,

a lot of ridges, that have
only had relatively imprecise

and perhaps inaccurate
measurements thus far.

And so, we could make a variety
of interesting discoveries.

LAU:
Venus really does beg
for further exploration.

Sure, we've had landers
go to Venus in the past,

but there may one day
be a rover concept design

that allows us
to rove on the surface

and get some science
for us to better understand

how to avoid undergoing

the cataclysms
that Venus underwent.

MOGUL:
In science, it's important
to push the boundary,

so studying Venus
is really exciting

because we don't know
a lot about Venus.

There have been a lot of probes
that have been sent

to Venus and they have studied
A, B, and C, and D,

but there's still a lot left
in the alphabet to explore.

In the coming years,
the exciting new missions

to Venus may help answer
some burning questions

about our twin planet.

Could life exist in its clouds?

Or might humans
one day call it home?

It's all cosmically fascinating.

But until we actually journey
to the planet

and see it with our own eyes,

the secrets of Venus
will remain...

unexplained.

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