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...
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:
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 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
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, 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--
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 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.
(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 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.
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 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.
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 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."
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.
Major funding for NOVA
is provided by the following:
And...
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.
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
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.
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.
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,
a homicide victim,
preserved in ice since
the Stone Age.
MAN: This changes forever
what we think about the past.
Now, investigators
do the unthinkable
and defrost the Iceman.
Will this unusual autopsy
help solve the mystery
of the Iceman's murder?
Next time,
on a NOVA/National
Geographic special.
Major funding for
NOVA is provided by:
And...
And the Corporation
for Public Broadcasting
and by PBS viewers like you.
Additional funding is provided
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This NOVA program is
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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:
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 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
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, 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--
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 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.
(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 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.
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 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.
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 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."
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.
Major funding for NOVA
is provided by the following:
And...
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.
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
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.
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.
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.
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