1
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...
And the Corporation
for Public Broadcasting
and by PBS viewers like you.
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...
Titan.
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 201 1 ,
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
photosynthesizing
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, 1 80 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--
protoplanets.
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:
Mercury...
Venus...
Earth...
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 1 00-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.
(gunshot)
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...
Saturn...
Uranus...
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.
Fortunately,
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.
NARRATOR:
A Delta II rocket blasts
into space.
Onboard is the probe Stardust.
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 geyserlike jets
of ice particles
that are shooting up
at supersonic velocities.
NARRATOR:
These icy geysers
bombard Stardust.
These particles hit at almost
1 4,000 miles per hour,
six times faster
than a speeding bullet.
NARRATOR:
Stardust survives intact
and on January 1 5, 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.
NARRATOR:
Inside, 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 1 50 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.
STEVE SQUYRES:
There 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.
EIGENBRODE:
Organic 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 rightere 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.
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.
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.
DANNY GLAVIN:
Literally 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.
ASHLEY DAVIES:
So now 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.
CAROLYN PORCO:
We 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.
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
1 2 times and only 1 2 times.
Virtually everything we know
about Europa
is from those 1 2 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.
JOHN SPENCER:
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.
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
1 2,000 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-1 20 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.
NARRATOR:
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 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.
NARRATOR:
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.
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.
1 4,000 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 1 50,000 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 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 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.
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