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Finding Life Beyond Earth -

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(generated from captions) NARRATOR: Are we alone
in the universe?

This age-old question is yielding
some provocative new answers.

Recent discoveries suggest
that the conditions for life

might be more prevalent
than ever imagined.

Science fiction didn't tell us
in any way, shape or form

what we're finding out now.

Missions to our neighbour Mars

are revealing evidence that water,
a key ingredient for life,

may be present.

Mars has lots of water.

Mars is an ice cube
covered with a layer of dirt.

And probes are finding the essential
chemical building blocks of life

in unexpected places.

Literally, the seeds of life

would've been delivered
to all the planets and their moons

in our solar system.

But what about the colder,
outer reaches of our solar system

and beyond?

Could life exist out here too?

New missions are revealing
strange worlds -

moons that could have vast oceans
concealed beneath miles of ice...

..landscapes littered with
hundreds of active volcanoes...

So now the zone where life
could possibly exist

has expanded out from Earth to the
outer reaches of the solar system.

..and places where jets erupt
hundreds of miles into space.

WOMAN: We could hold in our hands
evidence for extra-terrestrial life.

And the same epic forces
that gave birth to our solar system

are at work throughout the universe.

Tens of billions of planets

are estimated to be orbiting
other stars in our own galaxy alone.

Could there be
an Earth-like planet among them?

We will find habitable
worlds for sure,

if not this week or next month
or next year, sooner or later.

Finding Life Beyond Earth.

The possibility of life beyond Earth
is a tantalising idea...

..long prompting our species
to wonder

if there are other worlds
where life exists.

Now, as space technology advances,

the chances of finding it
are greater than ever.

I would love to find life
beyond Earth.

I'd like to think we could do that,

and I'd like to think we could do
that in the next several years.

The search focuses
on three key ingredients.

The first one is life's basic
chemical building blocks,

made from simple elements found
in the cloud of gas and dust

that gave birth
to all the planets and moons.

These chemicals
were possibly delivered

throughout the solar system
billions of years ago...

..by comets and asteroids.

They are compounds called organics,

containing carbon, oxygen,
hydrogen and nitrogen.

Next, life needs a liquid,
like water,

that allows these compounds
to mix and interact...

..and finally, an energy source,
like the sun,

to power the chemical reactions
that make life possible.

Scientists were once convinced

that all three ingredients
could only be found, if at all,

on planets that are at just
the right distance from the sun.

Too close and it's too hot.

Any further away than Mars
and it's too cold.

But now missions
to the outer solar system

are calling this assumption
into question.

This is Jupiter as seen
by the space probe 'Voyager 1',

launched decades ago
to explore the outer solar system.

Half a billion miles from the sun,

it seems unlikely that life could
exist out here in such extreme cold.

'Voyager' approaches Io,
one of Jupiter's more than 60 moons,

orbiting in the shadow
of the gas giant.

Io should be a frozen,
icy, barren world,

but 'Voyager' spots something
completely unexpected.

These actual images of Io's surface

reveal hundreds
of giant, active volcanoes.

Later probes
expose vast lakes of molten lava.

On Earth, volcanic activity
is driven by heat in the interior...

..but Io is so small

that it should have cooled down
billions of years ago.

There must be another source
of energy inside the moon.

The discovery of active volcanism
on Io

was one of the greatest discoveries
of planetary science.

By observing Earth's volcanoes

and studying the huge amount of data
gathered from Io,

Ashley Davies pictures what walking
on Io's surface would be like.

DAVIES: Walking across the surface
of Io,

it's a very, very hostile
environment.

It's either very, very cold

or it's very, very hot where there's
volcanic activity taking place.

And of course there's no atmosphere.

There'd be a bounce in your step,

because the gravity of Io
is about the same on the moon -

one-sixth of the Earth.

You could feel the crunch underfoot

as you head from one volcano to
another across these vast plains.

Well, here we are in the middle
of a vast lava-flow field.

It's dark. It's quite hot.

This is comprised of lava flows

that have erupted
from one of Io's many volcanoes,

like that one over there.

The probe 'New Horizons'
flies past Io.

It takes this photograph
of an enormous eruption

from a volcano called Tvashtar.

A vast plume of sulfur
shoots 200 miles into space.

These actual images reveal the plume

as it spreads out
and rains back to the surface.

On Io, we see these
large volcanic eruptions.

The gases that are
coming out of the lava

blast this material high into space,
into the vacuum of space.

It's very, very spectacular.

What could be generating
so much energy

in a moon that should be
frozen solid?

And where is the power coming from?

The key to understanding
Io's volcanic activity

is its parent planet, Jupiter.

Io orbits Jupiter in a slight
ellipse rather than a circle.

With every orbit,

Io experiences gravitational pushes
and pulls from Jupiter

and other moons.

When Io is closest
to the giant planet,

it is stretched
by more than 330 feet.

Over billions of years,

this has created an immense amount
of friction deep inside the moon.

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This continual flexing
of the satellite

is like bending a piece of metal -
it heats up.

And this is the ultimate source
of Io's volcanic energy

and its volcanic heart.

The powerful tidal force,

generated by the massive
gravitational pull of Jupiter,

creates an alternate
source of energy

far from the warmth of the sun,

a source of energy that could,
in principle, support life.

What's so important about Io

is that it moves our perceptions

away from a habitable zone
around the sun,

where energy is just derived
completely from the sun.

So now the zone where life
could possibly exist

has expanded out from Earth to the
outer reaches of the solar system.

But the chances of life
existing on Io itself are slim.

Even though it has an energy source

and could have the right
chemical building blocks,

possibly delivered by comets
and asteroids billions of years ago,

scientists have not yet detected
the third key ingredient -

a liquid like water.

But Io is not the only moon
circling Jupiter.

NASA's unmanned space probe
'Galileo'

flies by the next moon out...

..Europa.

It passed by Europa 12 times
and only 12 times.

Virtually everything we know about
Europa is from those 12 passes.

And each and every one of them
has excited us beyond belief.

Slightly smaller than our own moon,
Europa is covered with ice.

Data collected by 'Galileo'

shows that the surface
is -260 degrees Fahrenheit,

surely hostile to life.

But as the probe gets closer,
it takes these images.

A mysterious network of dark cracks
is etched into Europa's icy surface.

We see places where, very clearly,

the ice has cracked
and two sides have spread apart,

material has come up and frozen
in the middle to fill the gap.

In addition to the dark cracks,

the probe also reveals
vast jagged areas of ice

that appear to have melted,
broken apart

and frozen back together again.

There's something
very dramatic happening

to destroy
the existing surface there.

To an expert eye,
it's a familiar pattern.

Sea ice found on Earth
looks very similar.

Then 'Galileo' takes readings
of Europa's magnetic field.

These indicate an electric current
flowing inside,

consistent with an ocean
of salty liquid water.

It's very hard to get that pattern

without having an ocean
underneath the ice.

The magnetic field data
suggests that miles down,

beneath Europa's icy surface,

there is an ocean
that could be 60 miles deep.

This small moon could have
twice as much liquid water

as in all the oceans on Earth.

Something must be melting the moon
from deep inside.

And, again, the key is Jupiter.

The same gravitational forces
that flex Io's rocky interior,

turning it into an ocean of magma,

are melting Europa's ice to produce
its hidden ocean of liquid water

and creating the cracks
on the moon's icy surface.

The ice is creaking
and groaning around.

That generates a huge amount of
friction and a huge amount of heat.

But the question is, could anything
live in this cold, liquid ocean,

concealed beneath miles of ice,

where there is no energy
from the sun?

To find out, biologist Tim Shank
explores the oceans here on Earth

that most resemble
Europa's icy depths.

200 miles from the North Pole,
Tim sends robots to search for life,

12,000 feet beneath
the Arctic icesheets,

where the sunlight never reaches.

Exploring the deep Arctic Ocean

is not unlike exploring another
planetary body in our solar system.

You have to deal with
immense pressures, temperatures,

extremes where life might exist.

Here, volcanic activity
is pushing apart the sea floor.

Scientists believe that
something similar may be at work

under the ocean on Europa.

We believe it has a rocky core.

That rocky core is under
tidal forces and influences,

and it's flexing also,

just as the rest of the planet does.

And that heat has got to
go somewhere.

On the restless floor
of the Arctic Ocean,

Tim's robots discover evidence
of an extremely hostile environment.

Volcanic vents are spewing out water
that is super-heated to 700 degrees

and laden with toxic chemicals
like hydrogen sulfide.

Tim believes that vents like this

could also exist
on Europa's ocean floors.

And, clustered around the vents,
in pitch darkness,

Tim's team finds life.

We discovered new forms of life,

microbes that cover
miles of the sea floor there.

There's life
even in the coldest waters

in the deepest regions
of our polar oceans

that we didn't know about before.

Instead of using sunlight
to trigger vital reactions,

microbes like these

use sulfur, hydrogen and methane
as chemical sources of energy.

And the microbes form the basis
of an extensive food chain.

The discovery of life here raises
the possibility of life on Europa.

It's clear to me that the basic
components, the basic elements,

the chemical elements

There's nothing that
I can think of, no component,

that's missing
from the Europan ocean.

I would be surprised if we didn't
find life there, really.

With liquid water,

an energy source and the necessary
chemical building blocks,

perhaps delivered
by comets and asteroids,

Europa opens up the possibility

that life could exist
in places never imagined.

And so the moons,
as they go around the planets,

are generating heat, melting water,

creating under-ice-shell oceans

and producing a potential
environment for life.

That is a revolution
in our thinking.

But getting a probe
safely to the surface of Europa

to test these theories

is just one of the challenges

in looking for life
half a billion miles away.

You've got to build something

that can get through what is
surely kilometres of ice.

That's hard to do on Earth.

Then you've got to have something
that can swim.

It's going to happen.

I would love to live to see it,
but it's a tough one.

Europa isn't the only
intriguing place

this far out in the solar system.

Could similar conditions exist on
other moons orbiting other planets,

even further away from the sun?

One mission launched to find out
is the probe 'Cassini'.

It is heading
for the ringed planet, Saturn,

one billion miles from the sun.

Its mission - to explore Saturn,
find out how its vast rings formed,

and investigate
some of its more than 60 moons.

WOMAN: 'Cassini's' mission,
from the outset,

was to investigate everything
we could about the Saturn system.

It is a major exploratory
expedition.

'Cassini' gives scientists
their best view yet

of this mysterious planetary system.

'Cassini' was outfitted

with the most sophisticated suite
of scientific instruments

ever carried
into the outer solar system.

It has cameras, spectrometers.

It is really the farthest
robotic outpost

that humanity has ever established
around the sun.

Seven years after launch, 'Cassini'
finally enters orbit around Saturn.

These images reveal the rings
in unprecedented detail.

They stretch out across
hundreds of thousands of miles,

yet in places, they are just
tens of feet thick.

Using its instruments to analyse
wavelengths of reflected light,

'Cassini' confirms
these majestic rings

are made of billions of shining
particles of almost pure water ice.

They range in size from a grain
of dust to the size of a mountain.

After nearly eight months collecting
data of Saturn and its rings,

'Cassini' makes its way
to one of the closer moons.

This tiny ball of ice,
only 300 miles across, is Enceladus.

These 'Cassini' images
reveal a glistening white surface,

unlike any other of Saturn's moons.

It is carved with crevasses,

ridges

and cracks.

And stretching out
across the south pole,

'Cassini' photographs these strange
large cracks, seen here in blue,

four parallel fissures scientists
named the 'tiger stripes'.

They are 75 miles long
and hundreds of feet deep.

They look a lot like
fault lines on Earth.

Enceladus was a major focus
for the 'Cassini' mission.

It was clear that there had been
something going on on Enceladus

in the past.

The question was, was there anything
going on on Enceladus at present?

On another fly-by,

'Cassini's' thermal imaging sensors
reveal something unexpected.

At the south pole,

the tiger stripes should be colder
than the rest of the moon,

but they are radiating heat.

Though still a frigid -120 degrees,

the cracks are more than 200 degrees
warmer than most of the moon.

Then, as 'Cassini'
changes its orientation,

it sees Enceladus
silhouetted by the sun...

..and vast jets of ice
erupting into space.

These actual images

reveal the jets are blasting
hundreds of miles out

from the tiger stripes.

Carolyn and her team are stunned.

Never did we expect
that we were going to see something

like a whole forest of jets

shooting hundreds of kilometres
into the sky above Enceladus.

It was like nothing
we'd ever seen before.

Could Enceladus also have
an internal energy source

like Io and Europa?

Scientists believe that when
Enceladus orbits the massive Saturn,

friction from gravitational forces
causes it to heat up,

melting ice in the moon's interior
in the same way as on Europa.

They believe the jets
consist of liquid water,

vaporising and freezing as it meets
the cold vacuum of space.

They shoot upwards
at 1,200 miles per hour.

Enceladus is being flexed
as it's orbiting Saturn.

That's like flexing a paperclip.

It creates heat inside,

and we think the heat
maintains liquid under the surface.

Excited by this discovery,

the team programs 'Cassini'
to fly through the jets

and collect particles.

After several fly-throughs,

'Cassini's spectrometers detect,
in the jets,

some of the basic chemical
building blocks of life.

That was tremendously exciting
to find,

because not only do we think
there's liquid water there,

not only is there
an enormous amount of excess heat,

but we also have organic materials.

I mean, that's the trifecta
that we're looking for -

the three main ingredients
for a habitable zone.

But could this strange and alien
world actually support life?

Carolyn imagines what it would be
like to hunt for the answer

on the surface of Enceladus.

Walking on the surface of Enceladus,

as you approach
the tiger stripe fractures,

you would first encounter a region

that is continually
blanketed in snow.

The sky is inky black.

Walking is like floating,
has very little gravity.

If we had the sun at our back
we wouldn't see anything,

but if we put ourselves
in the right geometry,

looking in the direction of the sun,

then suddenly we see something

that I think would be
the greatest spectacle

that the solar system
has to offer...

..giant ghostly fountains

shooting skyward
fine, sparkly, icy crystals,

most of which
eventually fall back down

and coat the surface
in a blanket of snow.

If we are correct

that the jets of Enceladus
derive from pockets of liquid water,

in which life
might have gotten started,

a scoop full of Enceladan snow
might - just might -

contain the remains
of microscopic living organisms.

Since 'Cassini's instruments

cannot detect
the signatures of life itself,

there is no evidence yet

of microscopic organisms
in these jets...

..but the discovery

makes Enceladus a prime candidate
for future missions.

To me, it's like there's a sign
on Enceladus that says

"Free samples, take one."

We've just got to fly through
the plume and collect the stuff.

We don't have to drill.
We don't have to dig.

We don't have to scurry around
looking for it.

It's being ejected into space.

The discovery of a new energy source

and the possible oceans of liquid
water inside planetary moons

point to potential new footholds
for life in our solar system.

Meanwhile, discoveries here on Earth

are revealing that life
can withstand

an even wider variety of conditions
than previously thought.

Missions to extreme environments

are showing that microbes
can live in dry deserts...

..and thrive in lakes
full of poisonous arsenic.

Bacteria survive in slimy colonies
on cave walls,

dripping with sulfuric acid,

living off noxious
hydrogen sulfide gas.

And microbes flourish

in toxic rivers
of corrosive industrial waste.

We now know it's possible
for micro-organisms to exist

in these large acidic,
and even poisonous, regions.

The more we look
at the extreme habitats on Earth,

the more we find life there.

We're pushing back the limits of
where life can live, all the time,

through our own discoveries.

From freezing glaciers

to super-heated hot springs...

..from high deserts,
blasted by ultraviolet radiation...

..to deep mines miles underground...

..and ocean trenches
where sunlight never penetrates,

scientists are discovering that life
finds a way to adapt and thrive.

Life on Earth can exist
in many extreme environments,

and it can do
many remarkable things.

And we're learning more every day

about how flexible and remarkable
life on Earth really is.

So could environments
on other worlds,

previously thought
too harsh for life,

be worth a second look?

We've really got to
put ourselves out there,

in terms of thinking
what the possibilities are.

When we first started looking
for life on other worlds,

we were looking for
Earth-like conditions.

OK, well, we've got to have water,
got to have an energy source,

got to have carbon.

But to me, the number one question,
THE big question,

is, "Is there another type of life

"on another world somewhere
in our solar system?"

So Chris wants to know -
if life could develop in new ways,

perhaps even using
different kinds of chemistry,

then could even the most
inhospitable places

offer surprising new footholds
for life?

One such place
is one of Saturn's moons,

visited by the space probe
'Cassini',

Saturn's largest moon - Titan.

'Cassini' detects organic building
blocks in the atmosphere,

and the spacecraft's radar
reveals something mysterious

beneath clouds at the south pole.

It looks like a lake of water.

Further fly-bys reveal
it's just one of hundreds

scattered across
both the north and south poles.

It was exciting and mysterious
to see all these different lakes

and to try to understand
what's going on.

Titan is the first world,
other than the Earth,

known to have a liquid
on its surface.

But at -290 degrees,
this liquid can't be water.

Analysis of infra-red light,
reflected off the lakes,

reveals that they are filled

with super-chilled
liquid methane and ethane.

On Earth, these hydrocarbons
are gases we use as fuel.

Data now reveals
that methane on Titan

carves river valleys,

forms clouds,

and even falls as rain.

Liquid methane acts a lot like
water on Earth...

..but could it act the way
water does,

as an essential foundation for life,

allowing organic molecules
to dissolve, mix and interact?

It's a question astrobiologist
Chris McKay is investigating.

Our general theory of life,

based on one example on Earth,
is that we need a liquid.

Some people would argue that
that liquid has to be water.

Well, on Titan,
we can ask the question,

"Well, what about another liquid?

"Could some other liquid
besides water do the trick?"

For life to exist on Titan,

Chris believes one fundamental
process has to happen first,

a process that, according to
the most widely accepted theory,

took place on early Earth
and ultimately produced us.

In this scenario,
the raw ingredients of life,

organic molecules,

dissolved in water.

And once in this liquid,
they came together and reacted

to form bigger,
more complex molecules

that would eventually,
somehow, become living things.

For life to have a chance on Titan,

the building blocks would have to
dissolve in liquid methane.

Chris is now trying to find out
if this is possible.

He first has to replicate
the organic building blocks

that 'Cassini's' instruments
detected high in Titan's atmosphere.

Simulating an energy source,

Chris fires an electric spark that
hits gases inside the test tube

that are known to exist on Titan.

This creates organic molecules

similar to those
in Titan's atmosphere -

the brown residue
at the bottom of the tube.

And we trigger the same reactions
in the flask,

and, as a result,

we produce the same kind of solid
organic material in the flask

that is being produced
in Titan's atmosphere.

Then Chris re-creates
Titan's remarkable lakes.

He fills the test tube
with methane gas

and then cools it below -290 degrees
using liquid nitrogen.

Now the methane liquefies, just as
it does on Titan's frigid surface.

So, in the flask, we'll have
a miniature little lake,

a little puddle of liquid methane,

swirling around
in that organic material.

Will anything dissolve
in that organic material?

That's the question.

And will that, over time,
build up organic complexity?

Could it be the start of what
could be another type of life?

No-one knows exactly
how life gets started,

but the question
Chris is interested in is,

"Can organic compounds dissolve
in liquids like methane?"

If so, it would suggest that,
even at extremely cold temperatures,

the chemistry needed for life

could be possible in liquids
other than water.

We know that there's conditions
there that maintain liquid,

there's energy sources,
there's organic material,

there's nutrients,

there's an environment
that may be suitable for life.

But if there's life there, it's
going to be completely different

than anything we have on Earth.

Chris's experiment is one step

toward understanding whether
there could be life on Titan.

To me, the most exciting possibility
is that there's life on Titan.

Because then that would show
not just that life started twice,

but it started twice
in very different conditions.

It would show us
that life is a natural process

that's going to pop up
on many different worlds,

many different planets
around many different stars.

Titan,

Enceladus...

..Europa

and Io

show that, even within
our solar system,

there are places
where some scientists believe

life could potentially
gain a foothold.

Might be extreme life, might be life
that we've never seen before,

in terms of its structure
and its composition.

But we're now realising that those
environments could harbour life.

The three vital factors -

energy, liquids
and chemical building blocks -

are more widespread
than has ever been realised.

And if it's possible here,

then could the right conditions
also exist

beyond the boundaries
of our own solar system?

By understanding
our own solar system,

I believe we'll then be well on our
way to understanding the conditions

that could occur around other stars
and throughout our galaxy.

It really changes our view
of this universe.

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Is there, somewhere out there,
a star like our sun,

orbited by habitable planets
that are teeming with life?

There are billions of stars
just like our sun within our galaxy.

And the odds suggest

that tens of billions of planets
are orbiting around them.

If there is life out there,
can we find it?

Astronomer Mario Livio
is at the forefront of the search.

He's using the Hubble space
telescope to look deep into space

to where new stars, like our sun,
are bursting into life.

This is the Orion Nebula,
as seen by Hubble.

Here, 1,500 light years
beyond our solar system,

new stars are being born
inside a vast cloud of dust and gas.

So when we look at the Nebula now,

it's almost like looking
into a cave.

We see this hollow part

where gas and dust has been
blown away,

and inside
where these stars are being born.

And right inside,
among all the shining stars,

is what looks like
a small dark smudge.

In fact, it is a young sun

surrounded by a dense disc
of dust and gas,

more than 50 billion miles across.

This smudge represents
the dawn of a new solar system.

In this case,
we see the disc edge-on

and, therefore, the disk completely
obscures the light from the star.

And this is why
you don't see the star.

Other images show similar discs,

tilted to reveal the star
at the centre.

These spinning clouds of matter

may, one day,
form planets and moons,

as particles of dust, ice and gas
collide and clump together.

This is the same process

that is thought to have created
the planets of our solar system.

Hubble has revealed
that swirling discs like this

are extremely common.

The fact that we see these
very often

tells us that these raw materials
from which planets form

are very, very common,

and so that planetary systems form,
probably, around most stars.

But do these young solar systems
produce Earth-like planets

containing the right ingredients
needed to sustain life?

Astronomer Josh Eisner
wants to find out.

He has come to Mauna Kea, Hawaii,

to look at the clouds of gas
and dust in more detail.

We'd really like to understand,

"Are there building blocks
of life there?

"Are things that we associate
at least with life on our planet

"available for planet formation
around other stars?"

Analysing gas and tiny bits of dust
from hundreds of light years away

is no simple feat.

It requires instruments
of great sensitivity and precision -

the Keck telescopes.

14,000 feet up, on the summit
of a dormant volcano,

these twin telescopes are among
the most powerful on Earth.

Josh uses both of them together.

And with a spectroscope
to analyse infra-red light

emitted from inside
the early solar systems,

he can tell what they are made of.

We're actually trying to map
a detailed picture of the dust

and what that hot gas is made of.

Is there water vapour there
that might get incorporated

into an atmosphere one day

or into an ocean one day?

His findings are encouraging.

In some of the distant
solar systems,

Josh is detecting evidence
of carbon, oxygen and hydrogen -

three key elements needed to produce
the chemical building blocks

on which life depends.

Even more intriguing
is that, in some discs,

those ingredients

also appear to be at the right
distance from their stars

to form planets
with Earth-like qualities.

So much for theory.

The question is
do such planets actually exist?

Geoff Marcy is one astronomer trying
to directly answer that question.

He's a planet hunter -

scanning the heavens
for signs of planets

that may have already formed
around other stars

thousands of light years away
from our solar system.

It is actually quite a challenge
to find planets around other stars.

And the reason is very simple -
planets don't shine.

Planets are essentially dark.

By using advanced telescopes,

dedicated planet hunters like Geoff

have found ways
to overcome this challenge.

If you watch a star,

it ought to have the same brightness
all the time, 24/7,

but if there's a planet
orbiting that star,

when the planet crosses
in front of the star,

the planet will block
a little of the starlight,

and you'll see the star dim,
a tiny amount,

every time the planet crosses
in front, over and over,

in a repeated way.

And, marvellously, you can learn
the size of the planet,

because the bigger the planet is

the more light from the star
it blocks.

And so we learn an enormous amount
of information about these planets

just by watching stars dim.

Not surprisingly,

most of the planets
astronomers have found this way

are giant ones
that block a lot of starlight.

By also observing the gravitational
pull they have on their stars,

Geoff calculates that most of these
giant planets are made of gas

and are unlikely to be habitable.

But the Holy Grail is to find far
smaller rocky worlds, like Earth,

where the conditions for life
could exist.

The challenge of finding Earth-sized
planets is enormous.

When an Earth crosses
in front of a star,

it blocks only one-100th of 1%
of the light from the star.

The Kepler space telescope

is designed to detect
this subtle dimming.

Its mission -

to focus on one tiny spot of space
and scrutinise 150,000 stars

for signs of planets
the size of Earth.

Sensitive enough to detect
minute dips in a star's light,

Kepler is already producing
mountains of data,

and thousands of new planet
candidates are being discovered.

Kepler has now already discovered
a few planets

that have a diameter and a mass

that indicates clearly
the planet is rocky.

And so we now have,
for the first time in human history,

definite planets, out there among
the stars, that remind us of home.

These first rocky planets

are too close to their stars
to sustain life,

but the sheer number
of smaller planets being found

is transforming our view
of solar systems beyond our own.

We've learned that nature

the size of Jupiter and Saturn,

but nature makes even more
of the smaller planets

the size of Neptune,

and even more of the planets
the size of the Earth.

The number of planets

is sort of like the rocks
and pebbles you see on a beach.

There are a few big boulders,

there are many more rocks

and there are an uncountable number
of grains of sand

that represent the Earth-sized
planets we see in the cosmos.

Geoff believes
it's only a matter of time

before we find a habitable planet.

I suspect that this scene
we see here is one that reproduced,

billions of times over,

among the Earth-like planets,

the habitable planets
in our Milky Way galaxy.

But even if we find a world
just the right size

and in just the right place,

with oceans of liquid water,

could we detect life from a distance
of trillions of miles?

The James Webb space telescope
may be able to do just that.

Due to go into orbit
later this decade,

this new telescope is three times
more powerful than Hubble.

It will be able to analyse starlight

passing through the atmospheres
of the closest Earth-like worlds,

looking for the telltale signs
of life itself.

I think the chances are very good
that if you find a planet

with oxygen, methane,
carbon dioxide and nitrogen,

like our own Earth,

there's probably plant life on that
planet that is producing the oxygen.

As telescopes see farther

and spacecraft voyage
closer to distant worlds,

new discoveries are transforming
what we thought we knew

about our solar system
and our galaxy.

I am constantly awe-struck
by the data that's coming in

from our current fleet of missions.

Science fiction didn't tell us,
in any way, shape or form,

what we're finding out now.

Years from now, people are
going to look back on this

as being the golden age of
exploration in the solar system.

You can only go someplace
for the first time once, right?

And we're doing that now.

Scientists are finding
organic molecules,

the raw ingredients
that life needs to take hold,

in our solar system and beyond.

I think we'd be naive

to think that this chemistry
and life here on Earth

is the only place that
it's happening in the universe.

I mean, the fact is we've got
billions of galaxies,

you know, trillions
of star-forming environments

that probably have the same
chemistry going on.

The right conditions
that make a world habitable

could be more widespread
than ever imagined.

All of this leads us to think

that life should be an easy start

on another world.

And the same forces of nature
that forged life here

could be playing out
elsewhere in our galaxy.

A lovely exercise for everyone to do
is to look up into the night sky,

look at the twinkling lights
and realise that those stars,

by and large, all have planets.

And that's just our galaxy.

There are hundreds of billions
of galaxies out there

like our Milky Way,

and so the number of planets
in our universe

is a truly uncountable number.

So the race is now on to see if life
actually exists beyond Earth.

Will life first be discovered
on a moon such as Enceladus?

Will it be found
by an advanced telescope?

Or will it be found at all?

Whatever the answer, many believe
this is a turning point in history,

when we at last have the technology
and the know-how

to find out if there is life
beyond Earth.

Supertext Captions by
Red Bee Media Australia
Captions copyright SBS 2012