All language subtitles for 720p.BluRay.DTS.x264-PublicHD-English

(NARRATOR READING)

NARRATOR: From the beginning of mankind,
people have looked up to the stars,

wondering what marvels could
be found out there.

As science and technology developed,
we finally got some answers.

We learned about our neighbouring planets
that spin around the sun, just like the Earth.

We found cosmic nebulae
of incredible beauty,

stars exploding into supernovas
and even black holes.

Is mankind ready for its biggest discovery?

With our instruments,
satellites and spacecraft

becoming more and more advanced,

we are finding more and more distant planets.

Is there another Earth
in the vast depths of space?

And could there be alien life?

The answers are out there,

in our universe.

Earth. Our beautiful blue planet. Our home.

Seven billion people live here.

By the sea,

on land,

in the mountains

and in vast cities.

We have evolved from cavemen
to the information society.

Science is exploring all aspects of nature,

be it on our planet or beyond it.

Huge archives of data have been created,

providing answers to many questions.

We have come a long way

from the beginning of the space age,
when the first satellites were launched,

and man set foot on the moon.

Our probes have visited all the planets
of our solar system

and delivered a lot of data.

We now have a good understanding of how
our home system in this universe works.

There are eight major planets.

Mercury, which is closest to the sun,
and very barren.

Venus, with her thick atmosphere
and furious volcanoes.

Earth, the only known planet to host life.

And Mars, the Red Planet, a neighbour
that has had a lot of human-made visitors.

Farther out is Jupiter, a giant made of gas,
with over 60 moons.

Saturn, with its mighty ring system.

And, finally, Uranus and Neptune,
the "ice giants".

Beyond them lie huge asteroid fields

and some dwarf planets, like Pluto and Eris.

All these heavenly bodies revolve
around the sun.

It's the centre of our solar system
and also its superpower.

Without the sun,
life on Earth wouldn't be possible at all.

Basically, the sun is a gigantic energy
reactor that produces radiation and light.

In order to be able to look at the sun
with our human eyes,

we need to decrease its luminosity
by 98% first.

We are now looking at the pulsating surface.

The temperature here is
over 3 million degrees Fahrenheit.

The darker areas are the sunspots.
They are plasma craters the size of the Earth,

where temperatures are lower.

The brightest areas, on the other hand,
are solar flares.

The plasma there reaches temperatures
of up to 10 million degrees.

These flares can cause ripples that look
just like ripples on a pond from here,

when in fact the waves are 2 miles high,

and move at hundreds
of thousands of miles per hour.

But the highest temperatures are
found in the very core of the sun,

going up to almost 30 million degrees,

because in here
hydrogen is constantly fused into helium.

Through this process of nuclear fusion,
the sun releases energy

equalling millions of atomic bombs
every second.

A great deal of this energy is
released in the form of photons.

These photons dart around the core
at light speed,

but they collide with matter so often,

that it takes them thousands of years
to finally escape into open space.

From there,
they only need about eight minutes

to cover the 100 million miles to Earth

and arrive here as what we know as sunlight.

But the sun doesn't only supply light.

It's responsible for 99% of the Earth's
energy intake.

In the entire history of mankind,
we have produced less energy

than the sun blows out in a second.

This begs the question,
how is such a powerful object created?

The answer is, it is born from a cloud
of cosmic dust and gas.

These vast accumulations of matter can
be found all over the universe.

They are called nebulae.

These nebulae come
in many shapes and sizes,

and many of them are of stunning beauty.

For example, there is the Horsehead Nebula,
looking like a stallion

rising out of a pink mist.

And the Witch Head Nebula,
furiously staring into space

with eyes made of gigantic stars.

Or the Flame Nebula that resembles
an inferno towering for millions of miles.

We are now looking at the Carina Nebula.

Here, the gigantic star, Eta Carinae,

is the father of numerous baby stars.

Eta Carinae has a mass
100 times greater than our sun.

The star dust this nebula is made of
consists of crystals,

amorphous substances and molecular chains.

This matter is blown apart
by the radiating emissions of Eta Carinae.

The particles are
pushed away at different speeds,

depending on their density. The results are
chaotic shapes of fascinating beauty.

Many different patterns emerge,
with finger-like tubes being quite common.

Here is a famous example that has
been named the "Pillars of Creation".

Quite fittingly, because in each
of these fingertips, new stars are born.

The matter here is very dense,
compressed by solar radiation and gravity.

Eventually, the pressure gets so high,
it triggers an atomic explosion.

The new star has ignited.

Instantly, a massive eruption
of solar radiation occurs,

which develops into a shockwave.

In the Eagle Nebula, we can see
such a shockwave in the bright contour

at the top of the formation. This shockwave
acts like a battering ram that compresses

and ignites matter,
continuing the process of star birth.

In some cases,
the collected mass isn't big enough,

and the young sun fails to
keep a nuclear reaction running.

The result is a brown dwarf,

an astral body
in between a sun and a huge planet.

But if the ignition succeeds,
another chain reaction is triggered,

one that may ultimately lead
to the creation of life.

The gravity of the newborn sun sets
the matter around it in motion.

Nearby portions of the nebula are pulled in,
and begin to spiral around the sun.

A protoplanetary disc is formed.

As the matter whirls about,
a process of accretion begins.

This is an effect of zero gravity that
causes particles to cling together.

That way,
bigger masses of material start to form.

As these become larger,
they grow into asteroids.

Directed by the sun's gravitational attraction,
the asteroids move around at high speed.

They crash into each other repeatedly,

resulting in the formation
of even bigger masses of rock.

Eventually, some of them grow large enough
to have a significant gravitational pull,

and, therefore,
pick up more and more material.

Over time,
this process leads them to become planets.

Some of these planets even develop
an atmosphere by collecting particles of gas

?oating through the surrounding space.

And our Earth was made the same way.

After a core had formed from materials
of our sun's protoplanetary disc,

the young Earth was constantly bombarded
by asteroids and other celestial bodies.

Back then, Earth was much closer to the sun,
and was very, very hot.

Its surface was made of one big ocean of lava.

There was no solid crust, no land,
not even water,

just heat, lava and fire.

Comets kept crashing
into that brooding surface,

raising the temperature with every hit.

Eventually, the young planet suffered
a massive collision with something huge,

another planet in the making.

The impact was so severe,
it ripped off a part of the Earth's mantle.

The debris then formed a ring around Earth.
Again through the process of accretion,

this rubble formed the moon
over the course of millions of years.

Earth, on the other hand, was thrown into
a furious rotation by that horrendous impact.

It was spinning so fast,
a day lasted only six hours.

After hundreds of millions of years,
it gradually slowed down again.

Also, the contents of the sun's
protoplanetaly disc were finally used up,

having formed the other planets and moons.

Accordingly,
the astral bombardment decreased,

so the surface could cool off.

This led to the formation
of a solid crust of stone.

Still, there were frequent volcanic eruptions.

They spat out lava and gases,
and the Earth went through many changes.

Huge meteors of ice had
brought water from the depths of space,

which now filled the first oceans.
Over time, an atmosphere was formed.

Vaporised water condensed, and returned
to the surface in the form of rain.

A hydrological cycle was set in motion
and over subsequent millions of years,

evaporation and rainfall eroded
the rocky surface of Earth.

The Earth's first supercontinent broke apart
several times, and slowly,

land masses took the shapes
of the continents we know today.

So there it was, Earth as we know it today.

Along with its silent companion, the moon.

Being the closest astral body to Earth,

the moon has fuelled the imagination
of mankind for millennia.

The idea of aliens on the moon
has been communicated

through paintings, songs and literature.
Even some of the first silent movies

depicted life on the moon. But by the time
man first landed on the moon in 1969,

it was rightly anticipated that the astronauts
would not encounter any moonsfolk.

Still, the moon remains truly fascinating.

Earth's companion is the fifth largest moon
in our solar system.

It needs four weeks to
orbit once around Earth,

a fact that is mirrored
in our everyday language.

The word "month" is a derivative of "moon".

Through its gravitational pull,
the moon is responsible for the ebb and flow

of tides in our earthly oceans.

It even in?uences the navigation and
spawning behaviour of some species of fish

and insects down here.

As far as looks are concerned,
the moon remains a bit dull,

because it is completely covered in grey dust.

The dust layer is produced by meteor strikes.

Due to the lack of an atmosphere,
they crash onto the surface of the moon

without any damping,
and are pulverised in the process.

The "moon dust" produced this way
actually resembles sand.

Or, scientifically speaking, regolith.

Despite the lack of water up here,
we still group the moon's surface

into areas of "lands" and "seas".

This is due to the antiquated belief that the
dark areas on the moon contained water.

We now know that those "seas" are
in fact basins of solidified lava.

In the moon's early days,
its core was still molten.

Heavy asteroid hits broke through the crust,

and the impact craters became filled with lava.

Interestingly enough, the moon is
still geologically active today.

In fact, moon-quakes occur
up to 10 times a day.

Most of these are moderate, but some
reach up to Level 5 on the Richter scale.

Fortunately, the rocks up here
don't seem to mind.

Even if the moon's landscape
is lacking variation,

we still have a great view from here.

Our blue mother planet rises majestically
and you also get a perfect view of the stars,

without an atmosphere
or light pollution hindering the outlook,

like it does from Earth.

For the same reason, scientists launched
gigantic telescopes into Earth's orbit.

They make a great addition
to deep-space exploration,

providing answers on the creation
of the universe itself

Also, they capture stunning images
of stellar nebulae.

A great example is this shot
of the America Nebula

that shows the formation's resemblance
to the North American continent.

The cameras can also register light
that is invisible to human eyes.

In infrared view, for example,
this nebula looks entirely different,

but no less fascinating.

A totally different visual
experience is provided

by the Rho Ophiuchi cloud complex,

which is the star factory closest to Earth.

The 300 suns we find here have
an average age of 300,000 years.

That really makes them babies,
from a star's point of view.

After all, the oldest discovered stars have
been around for over 12 billion years.

The Pleiades, also known as the "Seven
Sisters", are also readily visible from Earth.

That makes them the subject
of many old scriptures and legends.

These suns were created when dinosaurs
were still roaming the Earth,

about 100 million years ago.

Some experts believe
that our sun also was born

in a dense star-forming region
like the Pleiades,

and moved to its current position
over the course of millions of years.

All this information can be deduced
from today's opportunities to examine

the incredible clockwork that is space.

Early astronomers didn't have that luxury.

In the very beginning,
they had to use their naked eye

to make out the different stellar objects.

One of the brightest in the night sky
was Jupiter,

so the Romans named it after their main god.

As telescopes were invented and improved,

vision got clearer and clearer.

Today, especially thanks to human
space probes like Voyager,

we have a very good understanding
of this largest planet in our solar system.

The Babylonians called Jupiter
the "King's Star",

and, indeed, it reigns over its own little realm.

With its 63 moons, some even planet-sized,

it can almost be described
as its own solar system.

When we take a close look at the planet,
the first thing we notice are

the colourful cloud formations.
Jupiter is a gas giant,

meaning that it's almost exclusively
made of gas.

In 1995, the spacecraft Galileo launched
a probe into these clouds.

On the way down, it recorded violent wind
speeds, and a massively growing pressure.

After diving only 100 miles, the pressure
got high enough to crush the probe.

Further down,
there isn't much else to see anyway.

As the pressure gets higher and higher,

the atmospheric gasses are
liquefied without a visible transition.

This means that Jupiter doesn't even have
any defined surface we could land on.

A very distinctive external feature of
Jupiter's atmosphere is the "Big Red Spot",

a gigantic whirlwind with a fixed position.

Its diameter is three times that of Earth,
and it doesn't seem to run out of steam

After all, its existence was
already recorded in 1664.

All four of the outer planets Jupiter, Saturn,
Uranus and Neptune are gas giants,

so they share a lot of similarities,
like a lack of a surface.

Saturn looks very special, though.
It is accompanied by a massive ring system.

Saturn is the sixth planet of our solar system.

Even though it's almost 1 billion miles away,

it's visible to the naked eye in our night sky.

This is because of its huge size,

over 700 Earth-sized planets
could fit inside it.

Saturn's distinctive ring system
is also gigantic.

Using even the simplest of telescopes,
it can be seen from Earth.

But what are these rings made of?

Once we get closer, we can differentiate
between thousands of sharply-defined rings.

As it turns out, they are not as solid
as they first appear.

In fact, they are made up of asteroids
that circle around the planet.

It's a diverse range of compounds
of different sizes,

from specks of dust up to 10 metres wide.

Some of the smaller moons of Saturn are
ploughing right through these rings.

These moons are called "shepherd" moons,
because their orbits ensure that the rings

are kept nicely in shape,
a shape they have had for millions of years.

Even though Saturn's ring system
really stands out,

the other three gas giants
in our solar system have rings as well.

Those of Jupiter, Uranus and Neptune are
not as visible, though.

They are mostly made up of very
small particles, like cigarette smoke

mixed with some grains of sand.

While Saturn and Jupiter can't
be easily confused,

Uranus and Neptune appear very much alike.

They are the most distant from the sun,

so they don't get too much warmth
and energy.

That's why they are in a subclass
of the ice giants.

And Uranus is the icier one of the two,
even though it is not as far away as Neptune.

But it lacks any form of internal heat source,

which really is an exception
in our solar system.

Scientists assume this has something to do

with a massive collision
Uranus must have had in the past.

Proof of this is the fact that
the axis of Uranus is severely tilted.

Seen from Earth,
we look at it almost from above.

Neptune, on the other hand,
has an internal energy source

and, therefore,
displays a lot more weather effects.

In the upper layers of the atmosphere,
we see gigantic clouds,

several thousand miles long.

They form in stripes, because of the
high rotation speed of the planet.

At the poles, we have auroras,
northern lights that look much more

complex than those we have on Earth.

This phenomenon occurs
when charged particles

of the solar winds enter the atmosphere.

Jupiter's auroras are even bigger, though.

No surprise, as the planet is
almost too big to be true.

If it had gathered some more mass
during its creation,

it could have ignited to
become a sun all of its own.

In that case,
our solar system would have two suns today.

And while this may sound unusual,
our universe has many systems

with more than one central star.

In the Orion Nebula, we even find
four suns very close to one another.

Also, they are among the biggest suns
in the entire cosmos,

hundreds of times bigger than ours.

Their incredible power has
spawned the creation of thousands

of young stars in their vicinity.

Many of these newborn suns are
surrounded by protoplanetary discs,

where matter is shaped up into asteroids,
moons and planets.

Maybe one of those planets will be home
to intelligent life one day.

Our vast powerful universe certainly offers
limitless possibilities.

New worlds are created
on a literally astronomical scale.

Nebulae like Orion cover distances
of hundreds of light years,

producing thousands of new suns.

But everything that has a beginning,
also has an end.

There is not just birth and creation
on mind-bending scales,

but also chaos and destruction
in the same magnitude.

Even incredibly powerful objects
like a sun have to die one day.

But when they go,
they leave behind sites of new conception,

and incredible sights.

The constellation of Taurus is home to one
of the most studied objects in visible space,

the Crab Nebula.

Its torn and furrowed structures
make this nebula look like

a star's explosion frozen in time.

Ancient Chinese astronomers were able to
witness the actual event in 1054 A.D.

The explosion was described as so bright,

it could be seen during daytime here on Earth.

In the 1,000 years that have passed since,
the remaining core of the crab-sun

has turned into an extremely dense
neutron star.

An even more eerie sight is
provided by the Helix Nebula.

Here, the result of a supernova
resembles a gigantic eye.

This similarity becomes most obvious
when viewed in the infrared spectrum.

This disturbing appearance is
more than fitting

for the fatal events that took place there.

When the sun exploded, all planets and
moons of that solar system were either

torn apart by gravitational forces
or vaporised by the expanding sun

But at least some comets survived and still
make their way through this galactic rubble-

Even if we know a lot
about these faraway systems,

it's questionable if mankind
will ever reach them.

Considering that even if we could
travel at light speed,

it would take several thousand years
to get there.

For now, it makes sense to concentrate
on the astral objects in our own vicinity.

And scientists have been very busy here.

The first planet that had
a human-built visitor was Venus

The probe Mariner 2 flew by
in December, 1962.

Venus is the second brightest object
in the night sky, after the moon.

Sometimes we can even see it during daytime.

The reason for this is Venus' dense
light-reflecting atmosphere,

combined with its close proximity to Earth.

And, in addition to being our nearest
neighbour, Venus is even called

the "sister planet" of Earth.

This is because the two of them share

approximately the same size,
density and mass.

Likewise, the gravitational force
on Venus is close to 90% of ours.

But, in spite of these resemblances, there are
major differences that spoil any potential

for Venus to serve as a holiday destination

The number one barrier is Venus' atmosphere.

Comprising almost exclusively
of carbon dioxide, it is toxic for us.

Even worse is the heat.

The temperature on Venus can
reach over 800 degrees Fahrenheit,

making it the hottest place
in our solar system.

Then there is an incredibly high
surface pressure.

The first Russian probes
to arrive here in the 1960s

were literally crushed
by atmospheric pressure.

With the right technology, though, it would
still be possible to land a rover on Venus.

Looking around down here can give you
an idea of what hell might be like.

Sulphuric clouds,
acid rain and active volcanoes

are all on the list of local attractions.

In addition, the heavy clouds are rocked
by lightning and thunderclaps.

The surface is adorned with huge volcanoes.

Among them is Maat Mons,
a giant 5 miles high,

towering over the other Venusian volcanoes.

In total, there are over 50,000 of them.

Another distinctive feature of Venus
are its lava channels of incredible size.

One of them even out-competes the Nile,
Earth's longest river.

It's called Hildr Fossa,
and measures 4,200 miles long.

Even though Venus is our nearest neighbour,

the best-explored extraterrestrial planet
is Mars.

This makes sense, as it would be much
better suited for actual human visitors.

Scientists are currently expecting
a manned mission to the Red Planet

in the '30s or '40s of this century.

So what do we know so far?

Mars is a rocky body, just like Earth.

But it's only half the diameter of Earth,

which makes it the second smallest planet
of our solar system.

Its red colour comes from high amounts
of iron oxide, also known as rust,

that is spread throughout the planet
and its atmosphere.

The air here consists of carbon dioxide
and is very thin,

so Mars cannot store
much of the sun's warmth.

Near the equator, temperatures are around
32 degrees Fahrenheit during the daytime.

At night, it plummets to minus 121.

To explore these conditions in detail,

mankind has sent a number of rovers up here.

And aside from environmental data,

they have also captured
some really nice views.

In summer,
the pole caps made of ice melt down,

which allows for
distinctive cirrus clouds to form.

We can actually see these in the sky here.

In spring, storms are common, which
whip up large quantities of Martian dust.

With wind speeds up to 300 miles an hour,
400 kilometres an hour,

a lot of the surface is cast under a dusty veil.

Sometimes, even small cyclones
called "dust devils " come up.

The landscapes on Mars
offer quite a bit of variation.

In the cooler north, we find the low plains,
which are broad dust-covered ?atlands.

The southern hemisphere has
geologically older formations

and more craters.

The biggest Mars crater
is called Hellas Planitia.

Its basin has a diameter of 1,300 miles,
2,000 kilometres,

and its bottom marks
the lowest point on the entire planet.

Running in parallel to the equator
are the Valles Marineris.

These "Mariner Valleys " are the largest
network of canyons in our solar system.

They stretch out for over 2, 500 miles,

and are up to 440 miles wide.

In the western part they develop
into a maze-like system of valleys

called Noctis Labyrinthus,

the "Labyrinth of the Night".

Speaking of vast proportions,

Mars holds at least two more records.

One being the volcano with the widest base
area, a giant named Alba Patera.

In relation to its 1,000-miles diameter,

its height of 4 miles isn't too impressive,

but Mars also has the Olympus Mons,

reaching 16 miles high,

and the highest elevation
in our whole solar system.

Apart from Earth,

Mars is by far the planet most thoroughly
explored and researched by mankind.

We know that Mars must have had a much
denser atmosphere millions of years ago,

and probably had liquid water on its surface.

Back then, it offered much better conditions
for the creation of life.

That changed when its atmosphere
was thinned out by solar winds.

Still, in the ice of its polar caps,

there could be primitive life
in the form of bacteria or microbes.

After all, such life has been found
in the perpetual ice of our own poles.

And while the chances for life on Mars
might have been better in the past,

they could be far worse,
like those on Mercury for example.

Things are downright hostile there.

Mercury is the last "Earth-like" planet
in our solar system.

Actually, apart from having
a rocky body like Earth,

it has not many other earthly properties.

Visually, this planet resembles the moon.

This corresponds well with Mercury being

the smallest regular planet
in our solar system.

And just like the moon,
Mercury has no atmosphere at all,

which is evident
from the crater-littered surface.

From up here, these craters may
look like innocent footprints in sand,

but once we get closer,
they reveal their true size. They are gigantic.

The largest one is known as the Calorie Basin.

It has a diameter of over 1,000 miles.

This means it must have been caused
by the impact of an astral body

more than 60 miles wide.

Mercury is the planet closest to the sun.

Because of this proximity,

its sun-facing half is heated
to extreme temperatures

reaching 750 degrees Fahrenheit.

On the dark night side, on the other hand,

temperatures go as low as minus 275 degrees.

These conditions make Mercury

the planet with the widest range
of temperature variation.

The day-cycles are similarly extreme.

Due to Mercury's eccentric spin
around the sun,

a night on Mercury lasts for 176 Earth days.

On Mercury, we are almost at the centre
of our solar system.

While a lot of data has been gathered
on the planets and the sun here,

the outer reaches of our domain
still hold a number of secrets.

Beyond Neptune lies the Kuiper Belt,
a vast field of asteroids.

It is home to over 70, 000 objects
of more than 60 miles in size.

These objects are left over from the creation
of our solar system,

material that wasn't included
in the formation of our planets.

Some of these objects gained
more respectable mass.

Best known among them is Pluto.
Identified in the year 1930,

it was the first discovered dwarf planet.

And in 1978,
its companion Charon was found.

The two of them rotate around each other,

as if they were doing a little waltz
through space.

Near the beginning of the second millennium,

more and more dwarf planets
were discovered.

The biggest one among them is Eris.

It's about a fifth the size of our moon

and its bright surface
is made of frozen methane.

Just like their full-grown counterparts,

all dwarf planets have been
named after earthly deities.

Makemake is a Polynesian god,

Sedna, the Inuit goddess of the sea,

and Haumea,
the Hawaiian goddess of child birth.

Still, all of these are
hardly more than asteroids,

drifting through cold, dark space.

The real wonders are outside the boundaries
of our solar system.

After all, our sun is only one star

of an estimated 400 billion in our galaxy,
the Milky Way.

And recent calculations have
come to the conclusion

that over half these suns could
have one or more Earth-sized planets.

So let's have a closer look at the structure
of our home galaxy.

From Earth, you can see parts
of the Milky Way with your naked eye.

It's made from the light
of millions of faraway stars,

arranged in a disc-like structure.

Since we are looking at it from the inside,

it appears to be a band of milky fog
across the sky.

Seen from outside, two mighty spiral arms
define the appearance of our galaxy.

These arms are occupied
by particularly bright stars.

The dark areas in between are by no means
empty, but the suns there are less powerful.

Our own solar system lies far outside
the centre of our galaxy,

within the Orion-Cygnus Arm.

Altogether, the Milky Way has a diameter
of about 100,000 light years.

So even if we could travel as fast as light,
almost 700 million miles an hour,

it would take over 100,000 years
to get from one end to the other.

This begs the question how a formation
of this size can be held together at all.

The spiral shapes and bright centres
of most galaxies

give a hint toward the explanation.

All these individual solar systems
revolve around a central point of gravity.

But what force in the universe could
have such an immense gravity?

The answer would have shocked
astronomers just 50 years ago.

It is a black hole.

They were thought to be science fiction,
but these behemoths really do exist.

Basically, they are stars that have imploded
from the pressure of their own gravity.

This caused a chain reaction,

that draws more and more matter
to the centre of the black hole.

In effect, it becomes denser and denser.

Accordingly,
the mass and gravity keep increasing,

so the black hole grows
more and more powerful.

The stars in the bright centre of most galaxies

are flung around the black hole like yo-yos,

travelling at speeds
of millions of miles an hour.

Black holes seem gruesome in one way,

because they relentlessly obliterate
anything that comes their way.

But most of the suns, planets and moons
are a safe distance away,

so they are not in any danger
of being sucked in.

Instead, the black holes are
the central focus for all of them,

determining the shape and size
of the different galaxies.

A formation like this wouldn't exist
without a black hole,

and we would miss out on some of the
most exciting examples of natural beauty.

Like the Messier 74 galaxy, for example.

It's a classical spiral-shaped galaxy,
not unlike our own.

However, the arms of M74 are
decorated with bright, pink areas.

Those are clouds of gases, lit up
by the ultraviolet light from young stars.

Much more asymmetrical is
the appearance of Messier 66,

the biggest galaxy of the Leo Triplets.

Its displaced looks are
due to the gravitational forces

of its two nearby siblings.

Galaxies are drifting through space,
which allows for exceptional compositions.

For example,
this pair of galaxies known as Arp 273.

Scientists assume that the smaller galaxy
has fully passed through the bigger one,

and as a result,
created a form that reminds us of a rose.

In a couple billion years, our own galaxy
may collide with our neighbour, Andromeda.

Something similar has happened
with the Antennae galaxies.

These two galaxies merged
when they crashed into each other,

and the resulting forces have
spawned billions of new suns.

And who knows?
In one of those young solar systems,

life could emerge.

Or could it already exist
somewhere out there?

Maybe even much closer to us.

Granted, our local planets
don't have the best conditions.

Mercury doesn't have an atmosphere.

It's way too hot on one side,
and way too cold on the other.

Venus has no water on the surface,

because it evaporates in the heat
of the crushing atmosphere.

Mars' atmosphere, on the other hand,
is too thin,

it can store neither warmth nor water.

And the four gas giants Jupiter, Saturn,
Uranus and Neptune,

they do not even have a surface.

But there are not just planets
that could host life,

there are also moons.

Our main planets have
over 100 of them in total,

and some of these are bigger
than the planet Mercury.

An impressive example is lo.

It orbits Jupiter at a distance of 250,000 miles

and is about the same size as our own moon.

On getting a closer look at Io,
you might describe it as a hell of a moon.

After all, the most distinctive structures
on its surface are volcanoes

and lava pools of gigantic dimensions.

There are seas of liquefied sulphur,

an element covering the whole planet
in various aggregate states,

from gaseous to liquid to solid.

This gives lo its colourful appearance.

Of all bodies in our solar system,
lo has the most active volcanoes.

The constant eruptions hurl scorching lava
up to 180 miles high.

Aside from the huge lava pools
that are up to 250 miles wide,

there are also rivers of lava,
that flow hundreds of miles.

Next to the burning heat of the lava,

the temperature instantly drops
to minus 200 degrees.

Extreme conditions like these can't exactly
be called life-friendly environments.

Our next stop in the vicinity appears
to be even colder.

We're closing in on Europa.

This moon is covered
with an ice crust 6 miles deep.

Europa has a very thin atmosphere,
mostly made up of oxygen.

The surface is very bright

and is among the smoothest
and youngest of all moons.

It features a network of chaotic ridges
and trenches which is visually striking.

These so-called Linea are strongly
reminiscent of ice fields on Earth.

Since the positions and alignments
of the Linea

cannot be explained by geological processes,

they are a clue to one of the biggest secrets
of our solar system.

Under Europa's icy crust lies
a huge ocean of liquid water.

This water interacts with the surface,
constantly renewing it,

and the Linea are created in the process.

Scientists are already thinking about a probe
that can drill its way through the ice

and dive into the water,

the element that spawned
the first life on Earth.

Two other important ingredients
are oxygen and warmth.

On the surface of Europa, the average
temperature is minus 240 degrees.

It is too far away from the sun
for any significant warmth to arrive here.

But the gravitation from Jupiter creates
tidal forces that heat up Europa's inside

and keep the water from freezing.

And there is oxygen, too,
released from the ice by cosmic radiation.

According to scientific estimates,

the waters here could be more oxygen-rich
than our earthly oceans.

So, in spite of all the cold on the surface,

Europa is indeed a hot contender
for alien life.

Still, this icy world seems
very different from our own.

There is one that is much more Earth-like,
namely the biggest of Saturn's moons.

Its size alone is impressive. In fact,
it's even bigger than the planet Mercury,

so it has been aptly named Titan.

Titan is the only known moon to
have a really dense atmosphere.

Consisting mainly of nitrogen
and rich in methane.

On the surface, temperatures are as low
as minus 275 degrees Fahrenheit.

Still, Titan has landscapes
that look a lot like those on Earth.

Along the equator lies a region called Xanadu,

which is about the size of Australia.

Here we find mountains of up to a mile high.

They are made of frozen water,
washed out by methane rain.

Due to the low temperatures,
this ice is as hard as rock.

There is no liquid water due to the cold,

instead, pools and even seas of methane
define the landscapes.

In contrast to the methane seas are
desert-like areas dominated by dunes.

These dunes are several hundred miles long
and up to 500 feet high.

They are made of organic materials that
dried out after raining onto Titan's surface.

With all these visual similarities to our Earth,
it's easy to imagine life here.

Because of the cold, it is impossible
for water-based life forms to exist,

but current data from Titan
has given us exciting clues.

Scientists speculate that there may
be methane-based organisms

that consume hydrogen
just in the way we consume oxygen.

No one knows what these creatures
could be like.

The course of action is clear, though.

We have to send more spacecraft,
probes and rovers out there

to look under every icy bit of rock.

Still, we have another interesting astral body
on our list that is mostly unexplored.

It's a dwarf planet, but it's much closer
than those in the Kuiper Belt.

There is another ring of asteroids located
between the orbits of Mars and Jupiter.

And, there, we find the icy world of Ceres.

The spacecraft Dawn will
be the first to visit here in 2015,

to provide detailed information.

But Ceres is also known
to be similar to Europa,

maybe it even has a subglacial ocean.

This is especially exciting, as even Earth
was once completely frozen over,

while life in the subglacial ocean
was retained.

There are many wonders to be found
out there, even in our own solar system.

So who can tell what the chances

of extraterrestrial life are
in the entire universe?

Look at this image.

At first glance, it seems to be a typical
snapshot of our night sky, with a lot of stars.

Actually, this isn't too far off.

The surprise is that the area we see here
is so small,

it's only a tenth the space the moon
takes up in our field of view.

And what we see shining
there aren't just stars.

No, all these little lights
are full-blown galaxies.

Just imagine that.

Behind a piece of our sky
about the size of a fingernail,

there are more than 10,000 galaxies.

Each galaxy contains
billions of solar systems,

so even if there is no other case
of intelligent life in our solar system,

what about the probability when we multiply
these chances by a trillion?

For now, we can only speculate,

and dream about the fascinating worlds
that could be waiting out there.

Out there in our universe.