The UnXplained: Mysteries of the Universe

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.

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.

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.

Is Venus truly Earth's twin planet?

And if so, what secrets lie within this luminous world

that hangs in our sky?

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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,