Nova (1974–…): Season 38, Episode 13 - Finding Life Beyond Earth: Are We Alone? - full transcript

Scientists are on the verge of answering one of the greatest questions in history: Are we alone? Finding Life Beyond Earth immerses audiences in the sights and sounds of alien worlds, while top astrobiologists explain how these pl...

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NARRATOR: Is Earth the only
planet of its kind in the universe?

Or is there somewhere
else like this out there?

Is there life beyond Earth?

The search for alien life

is one of humankind's greatest
technological challenges.

And scientists are seeking
new ways to find answers.

We're pushing the
boundary of information

of where life can exist

past the Earth and out
into the solar system.

NARRATOR: Leading the search
are sophisticated telescopes

that scan the sky

and an armada of robotic probes

exploring the outer reaches
of our solar system...

all revealing the planets,
moons, asteroids and comets

like never before.

WOMAN: We can go
places and see things

that there's no other way
we could have ever seen.

NARRATOR: The search reveals evidence
of strange and unexpected worlds--

places with lakes, storms and rain,

violent places driven
by powerful forces

deep underground.

Worlds that may have hidden oceans

hundreds of millions of miles
from the heat of the sun.

The pace of discovery, just
in the last couple of years,

is just mind-boggling.

NARRATOR: New missions are
helping to unlock the mysteries

of what makes a planet habitable,

raising the question of whether
the building blocks of life

are more prevalent than
previously imagined,

not just in our own solar system,

but possibly throughout our galaxy.

We now have for the first
time in human history

definite planets out
there among the stars

that remind us of home.

NARRATOR: "Finding
Life Beyond Earth,"

up now on NOVA.

Major funding for NOVA
is provided by the following:


And the Corporation
for Public Broadcasting.

And by:

Additional funding is provided
by Millicent Bell through:

NARRATOR: After a seven-year,
two-billion-mile voyage,

the spacecraft Cassini
enters orbit around Saturn.

Cassini heads towards the
largest of Saturn's 62 moons...


Bigger than the planet Mercury,

Titan is hidden by
a thick orange haze.

No one has ever seen its surface.

But a small probe named Huygens,
released by Cassini,

is about to change everything.

This mission will
challenge long-held notions

of where life could
exist beyond Earth.

These are the actual
images Huygens takes

as it breaks through
the clouds and haze.

Titan is a land of
mountains and valleys,

a place that looks
surprisingly like Earth.

Then, images reveal
something no one expects.

The surface is littered
with smooth rocks,

the type normally found
in river beds on Earth.

CHRIS McKAY: My response was shock.

We look out on the surface and
we see what looks like a desert

and at the same time,
the data from the probe

told us that the ground
around the site was wet.

NARRATOR: Hundreds
of miles overhead,

Cassini's radar
sweeps the surface.

The images show a landscape

covered with what appear
to be hundreds of lakes.

This one covers an area
of 6,000 square miles,

about the size of Lake
Ontario, one of the Great Lakes.

It's a surprising discovery.

It's the only world
other than the Earth

that has a liquid on its surface.

NARRATOR: But what
exactly is this liquid?

Titan is minus-290
degrees Fahrenheit.

If it's water, it
should be frozen solid.

Then, one of Cassini's
instruments analyzes

the infrared light
reflected off the lakes.

The readings are
consistent not with water

but with liquid methane and ethane,

substances that on Earth are
volatile, flammable gases.

The data from Cassini are
so detailed, scientists can imagine

what it would be like to stand
on this cold, distant world.

McKAY: Standing on
the surface of Titan,

you see Saturn just
sitting there in the sky,

big, huge, stationary object,

almost like a door
to another dimension.

Here we see lakes,
lakes of liquid methane.

And in the horizon,
we see mountains.

These are mountains made
of ice, made of water ice,

frozen so hard that
it acts like rocks.

And the features that we see in them

are carved by the liquid methane
that's forming these lakes.

Looking across the horizon on Titan,

you might see a thunderstorm
or a range of thunderstorms

coming at you.

We see rain coming down.

It's not drops like we're
familiar with on Earth.

This is methane instead of water.

It falls much more slowly
due to the low gravity

and the drops are bigger.

NARRATOR: So what are the implications
of finding a liquid flowing

on Titan's surface for a
scientist like Chris McKay?

McKAY: Liquid seemed
to be the key to life,

so maybe there's life
in that liquid on Titan,

little things swimming
in liquid methane,

being quite happy at these
low, cold temperatures.

NARRATOR: There is no evidence

that living things like
microbes exist in these lakes.

But if such evidence
were found here,

it would fundamentally
change perceptions

about life beyond Earth.

If life could evolve

on worlds as drastically different

as the Earth and Titan,

then perhaps life could
evolve in many other ways

on many different worlds.

NASA's director of planetary
science is Jim Green.

GREEN: One of the questions

that we all want to know,
I think, deep down inside,

is, "Are we alone?"

I mean, that's really fundamental.

NARRATOR: Jim is at the forefront
of a global effort to understand

whether the conditions for
life exist beyond our planet.

GREEN: We're pushing the boundary

of information of
where life can exist

past the Earth and out
into the solar system.

NARRATOR: So, where in our solar
system could life potentially exist?

Heading out from the sun,
the first planet is Mercury.

It's an extremely
hostile environment.

In March 2011, NASA's
Messenger probe becomes

the first spacecraft to orbit

this small ball of rock and iron.

These are some of the
first images sent back.

Three times closer to
the sun than Earth is,

Mercury bakes in 800-degree
heat on its side facing the sun,

while on the night side,

temperatures plummet to minus 290.

Mercury is the
ultimate desert world.

Life of any kind
here seems unlikely.

Mercury's closest neighbor,
Venus, is almost as hostile.

Though nearly twice
as far from the sun,

temperatures here
exceed 880 degrees.

Decades of observations
have revealed

a planet shrouded in carbon dioxide

and toxic clouds of sulfuric acid.

These radar images reveal
thousands of ancient volcanoes

on a surface hot
enough to melt lead.

And with an atmospheric
pressure that is 90 times greater

than on Earth,

it is hard to imagine that
anything could live down here.

But based on chemical
analysis of the atmosphere,

scientists believe that water
once flowed on Venus's surface.

If life ever did exist here,
evidence has yet to be found.

So what is it about Earth, the
third planet out from the sun,

that makes life possible?

The answer lies in
three key ingredients.

First, all life is made
up of organic molecules

consisting of carbon in
compounds that include nitrogen,

hydrogen and oxygen, among others.

Although organic molecules
aren't alive themselves,

they are the basic building
blocks of every living organism.

Life also needs a
liquid, like water.

In water, the basic organic
molecules can mix, interact

and become more complex.

The last ingredient is an
energy source like the sun

to power the chemical reactions

that drive all life, from
the smallest microbe...

to us.

When these three
ingredients came together

billions of years ago, life
found a way to take hold...

and today persists even in
the most extreme environments,

like here.

This is the Mojave Desert, Nevada.

It is one of the hottest,
driest places on our planet.

McKAY: This part of the desert
is particularly interesting to me,

because it's the driest part.

There's an axis of dryness here.

If we go either east or
west, it becomes wetter.

NARRATOR: Surprisingly, even here,
with only a foot of rainfall a year,

all three ingredients
for life are present.

The rocks provide just enough shade

to prevent water from
evaporating completely.

McKAY: Underneath the white rocks,

we can find the most amazing thing.

We see this layer of green.

This is bacteria.

The rock provides a little shelter.

It's a little wetter
and a little nicer

living under the rock than
it is in the soil around it.

In addition, the white
rocks are translucent.

Hold them up to the sun and
see light coming through.

These organisms are

here in the desert where
nothing else will grow.

So they're living in a
miniature little greenhouse.

NARRATOR: This place shows

that even in some of Earth's
most extreme environments,

under the right conditions,
life has a chance.

For scientists like Chris
McKay, the question is:

Is Earth the only planet

with the essential
conditions for life?

One way to know is to investigate

how planets like ours formed

to have these ingredients
in the first place.

That story starts
4.6 billion years ago,

with the birth of our solar system.

As a vast cloud of dust and
gas collapses in on itself,

pressures increase.

Temperatures at the center
rise to millions of degrees...

until energy from the early sun
blasts away some of the cloud.

This lights up the
young solar system,

revealing the beginnings of planets.

The mystery has always been

how did this spinning cloud of dust

become the massive
planets we see today?

SCOTT SANDFORD: How does one go from
microscopic grains to golf-ball size things,

and how do golf-ball
size things go from there

to ten-meter size things?

How do those go to
planetary embryos?

And there's a lot of steps in there

we don't quite understand.

NARRATOR: Many scientists believe

the answers are
hidden in asteroids...

the oldest rocks
in the solar system,

leftover debris from
its earliest days.

In 2003 the Japanese probe
Hayabusa sets out

on an audacious mission.

The goal: to land on an asteroid,

collect samples of dust and
then return them to Earth.

The target is asteroid Itokawa,

a third of a mile long
and speeding through space

at 56,000 miles per hour.

Landing on it would be like
trying to hit a speeding bullet

with another speeding bullet.

SANDFORD: Hayabusa
in Japanese

means falcon, and the idea was to do

like a falcon
grabs a rabbit--

swoop down, sort of
just touch the surface,

get your sample and go.

NARRATOR: In 2005, 180 million miles
from Earth, Hayabusa makes contact.

It stays just long
enough to grab a sample.

It will take five years

before Hayabusa
returns asteroid dust to Earth.

But in the meantime,
using lasers on board,

Hayabusa takes measurements
of Itokawa's size and mass.

These allow scientists

to determine the asteroid's
internal structure.

What they discover
could be a blueprint

for how planets like
Earth first formed.

SANDFORD: It's not one solid
lump of rock, but, in fact,

it consists of a
pile of smaller rocks,

of many sizes all the way from
houses down to dust grains.

NARRATOR: If we could see
inside asteroid Itokawa,

this is what it would look like:

a loose mixture of smaller asteroids

that are held together by gravity.

SANDFORD: Maybe 40% of the internal
volume of the asteroid is empty space.

You probably could just take
your hand and just go like this

and just push it down
into the asteroid.

NARRATOR: Is this the first step

in building rocky
planets like Earth?

GREEN: Asteroids are
just not lumps of rock.

These are the basic parts or
building blocks of planets.

NARRATOR: Over hundreds
of thousands of years,

asteroids like Itokawa
continue to collide,

growing bigger and hotter.

As their gravity increases,
they attract even more asteroids

until eventually,
as temperatures rise,

they become spheres of
rock with hot molten cores--


Computer simulations suggest
that within ten million years

of the solar system's birth,

up to a hundred protoplanets

ranging in size
from our moon to Mars

were orbiting close to the sun.

So why does the solar system
look so different today?

This is proto-Earth four-
and-a-half billion years ago.

Planetary geologist
Stephen Mojzsis believes

this world was very different
from the one we see today.

MOJZSIS: Looking at the surface
here, this landscape is dominated

by lava, black and
blasted by impacts.

Underfoot we find
mostly basaltic rock.

It is the frozen
product of molten rock.

These planetary surfaces
weren't molten boiling cauldrons.

But instead, for most
of their early histories,

they were solid and cool.

NARRATOR: The atmosphere
is thick with carbon dioxide

and laced with sulfuric acid,

the result of intense
volcanic activity.

MOJZSIS: The embryonic Earth
would have an atmosphere

denser than the one we have

and a sky yellow and red and
thoroughly unbreathable to us.

NARRATOR: How does this
toxic and inhospitable world

eventually become the
Earth we know today?

Ironically, it will
take a cataclysmic event

to create a planet
capable of harboring life.

A protoplanet the size of
Mars slams into early Earth.

The collision is so violent
it melts the surface,

creates an even larger planet,

and blasts molten rock back
into space that will coalesce

and eventually form our moon.

Earth isn't the only planet

that gets transformed
by giant impacts.

Over tens of millions of years,

all the protoplanets of
the early solar system

repeatedly collide,

becoming larger
bodies with each impact

in a destructive game
of planetary billiards.

This process eventually formed

the four rocky planets seen today:




and Mars.

SARAH STEWART: So the final
planets that we have today

are really the ones
that won the competition

in that some planets
were literally destroyed

or thrown out of the solar system

and others survived
to be here today.

NARRATOR: Sarah Stewart
is a planetary scientist.

She's trying to determine

how these impacts
created a habitable world.

There's some magic set of
conditions that has to occur

in a solar system to give
you an Earth-like planet.

NARRATOR: Figuring out what happens

when a massive planet the
size of Mars hits Earth

is no small feat.

It requires smashing things together

at extremely high velocities.

We want to simulate what happens

when materials strike the
Earth at very high speeds.

What we can do in the lab

is study little
pieces of the process

and, using the information we
gather from many experiments,

we build computer models

that try and recreate
the whole event.

NARRATOR: This requires a
special piece of hardware,

a 20-foot cannon that
uses an explosive charge

to fire projectiles at up
to 6,000 miles per hour.

At the other end is
a pressure chamber

and the target, representing
a planet like Earth,

wired up with precision sensors.

STEWART: We have
a 40-millimeter gun

that launches 100-gram
bullets into rocks or ices,

and we study what happens
as that shock wave travels

through the material.

NARRATOR: The gun is set to fire.


Each test measures the
temperatures and shock waves

generated in different materials

when they are slammed
into each other.

The results are fed
into computer models

of the final stages of
a planet's formation.

STEWART: Over the past few years,

we've realized how important

the last giant impact is to
the final state of a planet.

That last impact could
fundamentally change

major parts of the
planet, and that could lead

to something that's Earth-like

or something that's
more Mercury-like.

NARRATOR: Sarah's work, though
not yet conclusive, suggests

that giant impacts could
play a role in producing water

on a planet's surface.

Her results indicate the
collisions were so violent,

they could heat rock
to 2,700 degrees,

hot enough to release water

trapped deep beneath
the surfaces as steam.

Sarah believes this
may have happened

during Earth's final
catastrophic collision.

In its aftermath,

as the raging hot planet
cools over millions of years,

this steam condenses
and falls as rain,

covering the surface
with seas and oceans.

If this hypothesis is correct,

then several million
years after forming,

Earth has two of the three
ingredients needed for life:

water, and energy from the sun.

But what about organic molecules,

the chemical building
blocks of life?

How did they get to Earth?

Some scientists believe
the answer may lie

in the furthest reaches
of the solar system...

beyond Jupiter...



and even Neptune.

Here, three billion
miles from the sun,

is a vast ring of comets

and other debris
called the Kuiper Belt.

Like asteroids,

comets are remnants from
the dawn of the solar system,

but as well as rock,
they are also made of ices

that only freeze
this far from the sun.

Astrobiologist Danny Glavin
and his team think comets

are the key to understanding

how the final ingredients
necessary for life

arrived on Earth.

GLAVIN: The reason that comets
are so important to study

is that they really are
windows back in time.

These things formed four-
and-a-half billion years ago,

before the Earth even formed,

and so we're looking at the
chemistry in these objects

that was frozen in time.

NARRATOR: But analyzing
actual comet material

when the closest sample is more
than three billion miles away

is a major challenge.


icy comets occasionally
fly in closer to Earth.

As they approach the
sun, comets warm up

and the ice starts to vaporize,

spitting out tiny
particles of ice and dust.

GLAVIN: So when you're
looking at a comet in the sky,

what you're actually seeing
is predominantly the tail.

You don't see that
tiny rocky ice nucleus,

because it's being dominated

by the sublimation
of ices and rocks.

So you see that long
tail and the solar wind,

which is just dragging it
for millions of miles behind.

NASA ANNOUNCER: Zero and lift-off
of the Stardust spacecraft.

rocket blasts into space.

Onboard is the probe

ANNOUNCER: Gone through mach 1,
vehicle looks very good, burning nicely.

NARRATOR: The aim: to meet up
with a comet speeding through space

at nearly 60,000 miles per hour,

then, fly through the ice and dust

and bring some of it back to Earth.

240 million miles from Earth,

Stardust approaches
the comet named Wild 2.

It heads to the heart of the comet

and takes these images
of its solid icy nucleus.

The surface is broken and jagged,

and shooting out of it are
jets of dust and ice particles.

Astronomer John Spencer is an expert

on objects from the
outer solar system.

SPENCER: The cometary
surface is pretty treacherous.

We have crazy spires that may
be several hundred feet high.

We have overhangs,

we have upturned layers
where the surface really seems

to have been torn apart.

This is a very, very
bizarre landscape.

We have a surface
that is mostly black,

but scattered around within
that we have fresh ice.

We see a mostly black sky

because the atmosphere
is almost negligible.

That black sky is punctuated

by these geyser-like
jets of ice particles

that are shooting up at
supersonic velocities.

NARRATOR: These icy geysers
bombard Stardust.

These particles hit at
almost 14,000 miles per hour,

six times faster than
a speeding bullet.

NARRATOR: Stardust
survives intact

and on January 15, 2006,
the samples return to Earth.

GLAVIN: The samples fell
down on Utah and boom--

we had the first
comet sample materials

and there were astrobiologists
all over the Earth

that were, you know,
kind of screaming inside,

because we knew this
was our first chance

to actually analyze comet material.

scientists discover

over 1,000 grains of comet dust.

Glavin and his team analyze
this material for three years.

Then, they make an
incredible discovery.

In the dust from the comet

are traces of the
organic molecule glycine,

an integral part of living things.

Probably frozen into
the comet when it formed,

glycine consists of simple elements

found in the cloud of gas and dust

that gave birth to our solar system.

Now, glycine is an amino acid.

It's one of the
building blocks for life.

GLAVIN: These make life go.

They make up proteins and enzymes,

they catalyze all the
reactions in our bodies,

they're fundamental to life.

Without these we
could not exist at all.

NARRATOR: All life on Earth,
from these bacteria to us,

uses amino acids.

Glycine is special

because it's the most common
of the 20 amino acids needed

to make proteins, part of
the very fabric of life.

The discovery means that comets
could have been one source

of the organic materials
necessary for life on Earth.

We've proved that in fact
comets could have delivered

the raw ingredients of
life to the early Earth.

NARRATOR: But what
could cause comets

to fly in from the furthest
edges of the solar system,

slam into Earth and deliver
these organic compounds?

The clues to one possible process

lie back out in the Kuiper
Belt, the disk of icy objects

that orbits the sun at the
edge of our solar system.

HAL LEVISON: We expected
when we found the Kuiper Belt

that we would just see
objects in nice circular orbits

about the sun.

NARRATOR: But observations reveal
that the Kuiper Belt objects

are not orbiting as predicted.

Out here, it's chaotic.

When we look at the Kuiper
Belt, we see something that looks

like somebody took the
solar system, picked it up

and shook it real hard.

And that's what started us thinking

that something really
strange has happened there.

NARRATOR: Levison theorizes
that the reason for this mayhem

likely is connected with
the two largest planets

in the solar system.

Jupiter is so big it could
swallow more than 1,300 Earths,

and Saturn, with its
vast rings of ice,

is 95 times Earth's mass.

With their enormous size comes
an enormous gravitational pull.

LEVISON: Everything that we see

is a result of what
Jupiter and Saturn did.

NARRATOR: Levison wonders if
the chaos of the Kuiper Belt

could have resulted from
a planet smashing into it.

To find out, he runs a number
of computer simulations.

One model creates the
conditions in the Kuiper Belt

that we see today.

3.9 billion years ago, as
Jupiter circled the sun twice,

Saturn made one complete orbit.

Each time these orbits coincided,

there was a powerful
gravitational surge.

That pushed Saturn's
orbit further from the sun

and destabilized the orbits
of the two outermost planets,

Uranus and Neptune.

Jupiter and Saturn sort
of tugged each other,

and that drove the orbits
of Uranus and Neptune

absolutely nuts.

NARRATOR: Uranus and Neptune
are sent careening outwards

towards the Kuiper Belt.

Comets ranging in
size from a mile across

to objects the size of Pluto

are blasted out of their orbits
by the planetary invasion.

The disk went kaplooey.

Think of it as sort of a bowling
ball hitting bowling pins.

These things got scattered
all over the place.

NARRATOR: The end result is
a hundred-million-year period

when comets, kicked out
into the solar system

by Uranus and Neptune,

smash into anything in their path.

It's a period scientists call
"the late heavy bombardment."

Earth doesn't escape.

LEVISON: This was so violent

that probably every square
inch of the surface of the Earth

was hit by a comet during this time.

NARRATOR: This is one
theory that might explain

how massive amounts
of organic molecules,

the building blocks of life,
made their way to Earth.

Possible evidence of the late
heavy bombardment can be seen

on the surface of other planets
and moons in the solar system.

Impact craters.

Literally the seeds of
life, the amino acids

would have been delivered
to all the planets

and their moons in our solar system.

NARRATOR: So if life's building
blocks were delivered by comets

throughout the solar system,

could life also have sprung
up on worlds other than Earth?

It is unlikely that living
organisms exist today

on Venus or Mercury,

as space probes have found
no evidence on these planets

of the other vital ingredient
life needs: liquid water.

But what about Mars?

Organic compounds have
yet to be found here,

but scientists are
searching the planet

for the other preconditions of life.

There have been many missions
to Mars, and nearly all suggest

that water once
flowed on the surface.

These detailed images from
satellites orbiting Mars

reveal vast canyons
blasted out by epic floods

and valleys carved by raging rivers.

But the evidence indicates
that all this water disappeared

from the surface
billions of years ago

as Mars cooled down
and lost its atmosphere.

But on May 25, 2008,

a spacecraft called
Phoenix touches down

near Mars' north pole.

Digging a few inches down,

it exposes a white material

that vaporizes after a few days.

Soil analysis reveals
it is water ice.

We landed 68 degrees north, poof!

Just a few centimeters below the
ground there was a layer of ice.

NARRATOR: Satellites analyze
radar waves bouncing back

from both polar caps.

They reveal that beneath a
layer of frozen carbon dioxide

there is a lot of water ice.

If it all melted, it would
cover the whole planet

in an ocean more than 80 feet deep.

GREEN: When we look at Mars

and we see the
reservoirs of water there,

it's completely surprised us
in terms of the amount of water

and how much water is
actually trapped underground.

NARRATOR: The same satellites
orbiting Mars are discovering

that buried ice is also widespread

beneath the desert floors.

McKAY: When we look at Mars, we
see what looks like a desert world

with no water, but in fact,
Mars has lots of water--

it's ice.

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

NARRATOR: But this doesn't mean
that finding life here is imminent.

Ice doesn't melt the same way
on Mars as it does on Earth.

The atmospheric pressure here
is 150 times lower than ours.

It's impossible for
water to exist as a liquid

at the surface.

McKAY: Ice on Mars behaves
like dry ice does on Earth.

A piece of dry ice on Earth

goes directly from
the solid ice to vapor.

It doesn't form a liquid.

That's why we call it dry ice.

On Mars the pressure is so low

that water ice does the same thing.

NARRATOR: No liquid water
on the surface of Mars today

means that vital chemical
reactions cannot take place.

It seems impossible that
life could exist there.

But could it exist in
the buried ice itself?

An expedition to one of
the coldest places on Earth

is looking to answer that question.

These are the dry
valleys of the Antarctic,

one of the world's
most extreme deserts.

Here, beneath a layer of dry dirt,

is buried ice similar to Mars.

If life can exist here,
could it exist on Mars too?

We're doing in the Antarctic

exactly what we want to do on Mars.

We drill down into
this Mars-like soil,

we collect Mars-like ice,
and we look for what we hope

are Mars-like microorganisms.

NARRATOR: At the point
where the dirt meets the ice,

the team discovers a
thin film of liquid water.

And when they look at the
samples under a microscope,

to their surprise, there
is something moving.

We're finding at the
ice there is life,

which is quite remarkable.

NARRATOR: Microorganisms thrive
in this thin film of water,

but only for a short time.

McKAY: They spend most of the year

frozen and dormant,

and they're only active
for a few weeks each summer,

when temperatures get warm.

NARRATOR: On Mars, summer
temperatures at the equator

can reach 70 degrees.

Could the buried ice melt
here and create conditions

similar to those
found in the Antarctic?

McKAY: We may be able
to find conditions

where the ice is close
enough to the surface,

close enough to the equator that
even under today's conditions,

there's a small chance
of liquid water and life.

NARRATOR: If probes were to
find liquid water on Mars,

it would be an
extraordinary discovery,

but water alone does not equal life.

is a better match today

between conditions that we
know can support life on Earth

and conditions that we know
either exist or once existed

on other planets
within our solar system.

But that still begs the question,

what conditions are required

for life to emerge
in the first place?

How does this process of genesis,

life emerging from nonliving
material, take place?

Are the conditions that
once existed on Mars

adequate for that?

We don't know.

We simply don't know.

NARRATOR: So how could
scientists find out

if life is possible
below Mars' surface?

One recent discovery, still
open to debate, provides a clue.

Measuring wavelengths
of infrared light,

a NASA telescope on Earth
detects something mysterious

in Mars' atmosphere--
evidence of methane gas.

It's an intriguing find.

Some methane gas on Earth

is produced by geological
activity like mud volcanoes,

but most of the methane
found in our atmosphere

is a waste product
generated by microorganisms.

Methane has a very interesting
connection to life in many ways.

It could be a product of life.

It could be something that
life has made, evidence of life.

GREEN: Well, the
discovery of methane

was really one of the fabulous
discoveries that have come out

just in the last several years.

NARRATOR: New observations
by the Keck telescopes suggest

that certain areas on Mars
are releasing thousands of tons

of methane gas every year.

So where is the methane coming from?

It's seasonal.

We seem to have more methane emitted

during the summer season on Mars
than we do at any other time.

NARRATOR: There is
not enough data yet

to tell scientists what
is producing the methane.

But whatever the source,
it's a tantalizing clue

that could change our
understanding of Mars.

Methane could be biological,
which would be amazing,

or it would indicate

that there's some geological
process making methane,

which would also be amazing
because that would indicate

that Mars is an active world.

NARRATOR: To find out, NASA is
going back to the red planet.

This time, one of its
key missions is to search

for organic molecules, the
building blocks of life.

If we were to find
organic molecules on Mars

and confirmed that
they're actually from Mars

and not something we
brought along, wow!

That would be spectacular.

NARRATOR: If found, it might mean
that all three ingredients for life

are here, opening the possibility

that life could take hold.

Of course we're all human, right?

And we want certain things.

Nobody wants us to be alone, right?

But it's important in science
to maintain an open mind.

NARRATOR: To find organic molecules,

NASA is launching a Mars
rover the size of a compact car

named Curiosity.

GREEN: Curiosity will be

our first great chance, I believe,

to look for life on Mars.

NARRATOR: Curiosity holds

the most advanced set of
science instruments yet sent

to the planet.

It will zap, grind
and bake Martian rocks

and use spectroscopic analysis
to reveal if the samples contain

any of the chemical
ingredients for life.

It is not just a geologist,
it's an astrobiologist.

It can look at rocks and
everything else around it

in ways that we've never
looked at the material before.

NARRATOR: Even with an
advanced set of instruments,

finding organic molecules
will still be a challenge.

SQUYRES: It's going
to be a tricky problem.

There are lots of processes that
can destroy organic molecules.

Radiation from space
can destroy them.

Oxidizing compounds in
the Martian atmosphere

can destroy them.

So you're looking
for organic molecules

that have somehow been protected
from the Martian environment

for a while.

NARRATOR: And the bar is set even higher,
because Curiosity will search

for specific organic compounds

that are the product
of living things,

evidence that life
once existed here.

That's what Jennifer
Eigenbrode's experiment

is designed to uncover.

molecules tell a story

about where they came from
and what happened to them,

and that's the story that I'm
trying to uncover in Mars rocks.

GREEN: That experiment may very
well change our impression of Mars

as a lifeless body

and change it to harboring life.

NARRATOR: If Curiosity
turns up any evidence

that life once existed on Mars,

it will have enormous implications.

If right here in our own little
solar system life started twice,

then it would say that
life is just everywhere.

NARRATOR: Curiosity and
other missions may one day reveal

if life once existed
on places like Mars

and if it still exists today.

But even if scientists
ultimately conclude

that there is no life on
the planets closest to Earth,

it doesn't mean it's not out there.

Beyond Mars are other worlds
waiting to be explored...

The distant moons that orbit

the giant planets
Jupiter and Saturn...

Moons just as strange as
the orange-shrouded Titan...

One pockmarked with
hundreds of volcanoes...

Others glistening with ice and
covered in mysterious lines...

And one tiny moon etched
with deep fissures.

GREEN: We're now finding when
we look at these giant planets

and their moons

that they are almost like mini
solar systems in themselves.

NARRATOR: Probes are making
discoveries on these moons

that are changing our understanding

of where life can exist.

They're finding evidence
of new sources of energy,

hidden oceans of liquid water,

and organic molecules
blasting into space.

And far beyond these worlds,

scientists are exploring
entire new solar systems

around other stars.

GEOFF MARCY: Surely billions,

hundreds of billions of the
Earth-like planets out there

have the conditions
suitable for life.

NARRATOR: As scientists race
to explore these distant places

with more and more
advanced technologies,

they are finding that
the conditions for life

are not exclusive to Earth

and that the natural
forces set in motion here

might be active elsewhere
in our galaxy and beyond.

We now return to NOVA's
"Finding Life Beyond Earth."

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.

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

what we're finding out now.

NARRATOR: Missions to our neighbor
Mars are revealing evidence

that water, a key ingredient
for life, may be present.

CHRIS McKAY: Mars has lots of water.

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

NARRATOR: And probes are finding

the essential chemical
building blocks of life

in unexpected places.

the seeds of life

would have been delivered to
all the planets and their moons

in our solar system.

NARRATOR: 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.

the zone where life

could possibly exist has
expanded out from Earth

to the outer reaches
of the solar system.

NARRATOR: And places where jets
erupt hundreds of miles into space.

could hold in our hands

evidence for
extra-terrestrial life.

NARRATOR: 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?

GEOFF MARCY: We will find

habitable worlds for
sure, if not this week

or next month or next
year, sooner or later.

NARRATOR: Finding "Life Beyond
Earth," up now on NOVA.

Major funding for NOVA
is provided by the following:


And the Corporation
for Public Broadcasting.

And by:

Additional funding is provided
by Millicent Bell through:

NARRATOR: The possibility of life
beyond Earth is a tantalizing 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.

GREEN: I would love to find

life beyond Earth.

I'd like to think
that we could do that,

and I'd like to think
that we could do that

in the next several years.

NARRATOR: 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.

NARRATOR: 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.

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.

NARRATOR: 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.

DAVIES: 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.

NARRATOR: 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.

DAVIES: 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.

NARRATOR: 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.

DAVIES: 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.

NARRATOR: 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.

GREEN: 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.

NARRATOR: Slightly
smaller than our own moon,

Europa is covered with ice.

Data collected by
Galileo shows

that the surface is
minus-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.

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.

NARRATOR: 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.

SPENCER: There's something
very dramatic happening

to destroy the
existing surface there.

NARRATOR: 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.

NARRATOR: 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.

SPENCER: The ice is
creaking and groaning around.

That generates a huge
amount of friction

and a huge amount of heat.

NARRATOR: 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 ice sheets,

where the sunlight never reaches.

TIM SHANK: 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.

NARRATOR: Here, volcanic activity
is pushing apart the sea floor.

Scientists believe that
something similar may be at work

under the ocean on Europa.

GREEN: 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.

NARRATOR: 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.

SHANK: 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.

NARRATOR: 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.

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

the chemical elements that we
need for life are on Europa.

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.

NARRATOR: 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.

GREEN: 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.

NARRATOR: 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.

STEVE SQUYRES: You've got to build
something that can get through

what is surely kilometers 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.

NARRATOR: 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.

PORCO: Cassini's
mission from the outset

was to investigate everything
we could about the Saturn system.

It is a major
exploratory expedition.

NARRATOR: 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.

NARRATOR: 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 analyze
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.

PORCO: 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?

NARRATOR: On another flyby,
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
minus-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.

PORCO: Never did we expect that
we were going to see something

like a whole forest of jets
shooting hundreds of kilometers

into the sky above Enceladus.

It was like nothing
we'd ever seen before.

NARRATOR: 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,

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

They shoot upwards at
1,200 miles per hour.

PORCO: 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
the liquid under the surface.

NARRATOR: 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.

That's the trifecta
that we are looking for,

the three main ingredients
for a habitable zone.

NARRATOR: 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.

PORCO: 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,
it 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

this 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.

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 just gotta 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 injected into space.

NARRATOR: 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.

GREEN: We now know it's
possible for microorganisms

to exist in these large acidic
and even poisonous regions.

SHANK: 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.

NARRATOR: 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.

McKAY: 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.

NARRATOR: So, could
environments on other worlds

previously thought too harsh
for life be worth a second look?

GREEN: We've really
gotta put ourselves

out there in terms of thinking
what the possibilities are.

McKAY: When we first started looking

for life on other worlds,

we were looking for
Earth-like conditions.

"Okay, well, we 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?

NARRATOR: 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 flybys 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.

NARRATOR: Titan is the first
world other than the Earth

known to have a
liquid on its surface.

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

Analysis of infrared 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.

McKAY: Our general theory of life,

based on our 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?"

NARRATOR: 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.

NARRATOR: Then Chris recreates
Titan's remarkable lakes.

He fills the test
tube with methane gas

and then cools it
below minus-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?

NARRATOR: 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.

McKAY: 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.

NARRATOR: Chris's experiment
is one step toward understanding

whether there could
be life on Titan.

McKAY: 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's 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.

Enceladus, Europa, and Io

show that even within
our solar system

there are places where
some scientists believe

life could potentially
gain a foothold.

GREEN: 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 realizing

that those environments
could harbor life.

NARRATOR: The three
vital factors--

energy, liquids and
chemical building blocks--

are more widespread than
has ever been realized.

And if it's possible here,

then could the right
conditions also exist

beyond the boundaries
of our own solar system?

GREEN: 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.

NARRATOR: 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.

LIVIO: 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.

NARRATOR: 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 disk

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 disk
edge on, and therefore the disk

completely obscures
the light from the star,

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

NARRATOR: Other images
show similar disks

tilted to reveal the
star at the center.

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 disks 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.

NARRATOR: 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.

EISNER: We'd really
like to understand

are there building
blocks of life there?

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

available for planet
formation around other stars?

NARRATOR: Analyzing 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 analyze infrared light

emitted from inside
the early solar systems,

he can tell what they're made of.

EISNER: We're actually trying
to map a detailed picture

of the dust and what
that hot gas is made of.

Is there water vapor there

that might get incorporated
into an atmosphere one day,

or into an ocean one day?

NARRATOR: 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 disks

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.

NARRATOR: 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, marvelously, 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.

NARRATOR: Not surprisingly, most of
the planets astronomers have found

this way are giant ones that
block a lot of star light.

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.

MARCY: The challenge of finding

Earth-sized planets is enormous.

When an Earth crosses
in front of a star,

it blocks only one one
hundredth of one percent

of the light from the star.

NARRATOR: The Kepler space telescope

is designed to detect
this subtle dimming.

Its mission: to focus
on one tiny spot of space

and scrutinize 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.

MARCY: 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.

NARRATOR: 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.

MARCY: We've learned that nature

makes some large planets, 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.

NARRATOR: 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's reproduced

billions of times over
among the Earth-like planets,

the habitable planets,
in our Milky Way galaxy.

NARRATOR: 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 analyze 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, nitrogen,

like our own Earth,

there's probably plant
life on that planet

that is producing the oxygen.

NARRATOR: 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.

GREEN: I am constantly awestruck

by the data that's coming in
our current fleet of missions.

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

what we're finding out now.

SQUYRES: Years from now, people
are gonna 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.

NARRATOR: Scientists are
finding organic molecules,

the raw ingredients that
life needs to take hold,

in our solar system and beyond.

GLAVIN: I think we'd
be na?ve 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 that we've
got billions of galaxies,

you know, trillions of
star-forming environments

that probably have the
same chemistry going on.

NARRATOR: 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.

NARRATOR: 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 realize 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.

NARRATOR: 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.

The exploration continues
on NOVA's website,

where you can watch any part
of this program again,

take a tour of
the solar system,

find out how we can
detect distant planets

where life might be possible,

and dig deeper into space and
flight with expert interviews,

interactives, video
clips and more.

Follow NOVA on Facebook
and Twitter, and find us online

A 5,000-year-old man,
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MAN: This changes forever

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Now, investigators
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Will this unusual autopsy
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