Nova (1974–…): Season 45, Episode 103 - NOVA Wonders: Are We Alone? - full transcript
What do you wonder about?
The unknown.
What our place
in the universe is.
Artificial intelligence.
Hello.
Look at this, what's this?
Animals.
An egg.
Your brain.
Life on a faraway planet.
"NOVA Wonders"... investigating
the biggest mysteries.
We have no idea
what's going on there.
These planets in the middle
we think are
in the habitable zone.
And making incredible
discoveries.
Trying to understand
their behavior, their life,
everything that goes on here.
Building an artificial
intelligence
is going to be the crowning
achievement of humanity.
We're three scientists
exploring the frontiers
of human knowledge.
I'm a neuroscientist
and I study
the biology of memory.
I'm a computer scientist
and I build technology
that can read human emotions.
And I'm a mathematician,
using big data to understand
our modern world.
And we're tackling
the biggest questions...
- Dark energy?
- Dark energy?
Of life...
There's all of these microbes,
and we just don't know
what they are.
And the cosmos.
♪♪
On this episode,
the hunt for alien life is on,
turning up mysterious clues.
The star loves attention.
And it makes everybody crazy.
That's not a planet.
So what is it?
What are the odds?
The ingredients for life
are everywhere.
The universe has
hundreds of billions of planets.
But does anything live there?
The chances of us finding life
is very high.
"NOVA Wonders"... "Are We Alone?"
Right now.
The planet Earth...
A ball of rock
about 8,000 miles in diameter.
We know there's a lot
going on here.
Almost eight billion people
call it home,
along with billions
of other species.
But is this the only place
where the action is?
Our sun is just one of
an estimated 300 billion stars
in the Milky Way.
And we think there are at least
100 billion other galaxies.
So what are the chances that
all the fun is only happening
right here in our tiny corner
of the universe?
♪♪
Today, astronomers and engineers
are building new tools
to probe our solar system
and our galaxy,
hunting for clues
of life beyond Earth.
What are they discovering?
I'm Rana el Kaliouby.
I'm André Fenton.
I'm Talithia Williams.
And in this episode,
"NOVA Wonders"...
"Are We Alone?"
And what will it take
to find out?
♪♪
A few years ago,
a group of amateur astronomers
discovered a mysterious star.
Located about
1,500 light years from Earth,
the star flickers erratically,
and no one knows why.
If a star dims
at regular intervals,
chances are it's caused
by an orbiting planet.
And typically it's only
by a fraction of one percent.
But the light from this star
is dimming by more, much more.
The thing about this star is the
light dims every now and again.
But it's being dimmed by 22%.
So that's not a planet...
That's much too much.
Even for a Jupiter-sized planet,
you don't get anywhere near
that kind of dimming,
so what is it?
Unlocking the star's secrets
becomes the quest
of Tabetha Boyajian,
a stellar astrophysicist.
Soon people are calling it
"Tabby's Star."
I worked with dozens
of other astronomers
for several years
trying to figure out
what could be causing
these strange fluctuations
in its light.
Is it caused by
an asteroid belt?
Or colliding planets?
So we had this
whole long list of ideas.
None of them worked.
Then, one of Tabby's colleagues
offers a possible idea,
a bit outside
the standard astronomy box.
When I showed him this star,
he said, "Wow, this is
really weird,
and we don't
have an explanation for it."
He said, "These things
all look like they could be
caused by some
artificial alien megastructure."
♪♪
An artificial
alien megastructure...
A giant structure built by a
hypothetical alien civilization
to harness the energy
from its own sun.
When the word gets out...
talk about the prospect
of an alien megastructure.
Evidence of alien life.
The strange light pattern makes
it seem more like a death star
planet rather than a star.
The star loves attention,
and it makes everybody crazy.
It is far-fetched.
To dim a star by so much,
an alien megastructure
would have to be at least
half as big as the star itself.
But when the theory
is first proposed,
astronomers can't rule it out.
The behavior of Tabby's Star
is quite weird.
Given that we have no idea
what's going on there,
I'm not too quick
to throw out theories.
Could this be
some alien megastructure?
We don't know.
Tabby and her team
will continue to study the star,
hoping to find more evidence.
For some people,
the idea that there's
a civilization out there
capable of building
a giant structure around its sun
would be a dream come true.
It's the same dream that fuels
our obsession with aliens,
whether they charm us...
I am Groot.
Frighten us...
seduce us...
Oh, no.
Or try to kill Tom Cruise.
Oh, man!
My God...
And it's not just the movies.
Even the Pentagon
recently admitted
that it secretly investigated
UFO sightings for years.
But what's the reality?
♪♪
Right now, as far as
technologically advanced life
goes, we have a sample size
of one...
Us.
In fact, when it comes
to any form of life,
whether it looks like this...
or this...
or this, the only examples
we know of are right here
on Earth.
And the truth is, if we found
even one other example
of this kind of life,
it would be
the biggest scientific discovery
in our lifetimes.
So where do we start to look?
♪♪
In 2009, NASA took a major step
in the hunt for life
beyond earth, launching
the Kepler space telescope
to track down signs
of earthlike planets
beyond our solar system.
♪♪
Up until then, astronomers
had found about 300 exoplanets.
But few were
anything like Earth.
Small, rocky planets like ours
are not easy to spot.
Planets are literally lost in
the glare of their parent stars.
The brightness difference,
the contrast between
a star like our sun and the
Earth that's right next to it
is ten billion to one.
So instead of hunting for light
reflecting off
a planet's surface,
the telescope focuses
on starlight.
What Kepler did was look in
a part of the Milky Way galaxy
where we had lots of stars
in a small field,
and it just took pictures
over and over again.
And, occasionally,
if those stars have planets,
then sometimes those planets
would come in front of the star.
As the planet comes around,
it's going to block
part of the star,
and that light won't get to you.
And so that constant level
that you see from the star
suddenly goes down just a bit.
So these momentary
dimmings of light
that repeat once every orbit
are indicative
of a planet orbiting a star.
Astrophysicists like
John Asher Johnson
and his team at Harvard
use Kepler data
to estimate
an orbiting planet's size
and distance from its star.
The dips are pretty deep, so it
must be a fairly large planet.
Deep dips in the star's light
mean the planet is really big,
or the star is really small.
The spacing between those,
what is it, like, a day or two?
And frequent dimming
means gravity has drawn it
close to the star,
making the planet really hot.
Feels pretty much like
a classic hot Jupiter.
A giant broiling
ball of gas like this
would not be a great spot
for life.
So the team looks for signals
that are more subtle.
Looking at this,
it doesn't look like much.
But it looks like there is some
kind of periodic signal there.
So what do we know?
We know the thing is small?
It's blocking out
less than a percent of the light
that we're receiving.
Something is causing the star
to dim ever so slightly,
and at longer intervals.
Could this be a small planet
closer to Earth's size?
And the distance from its sun
suggests temperatures
potentially
comfortable for life.
This is really interesting.
I mean, this exactly
the kind of thing
that we're looking for.
This could be a rocky planet
somewhere near
the habitable zone.
Yeah, this is really exciting.
Yeah.
The discoveries coming from
Kepler have been astounding...
Nearly 3,000 confirmed planets
so far.
The Kepler Space Telescope
blew open our understanding
of planets.
We have found lava worlds.
We've got planets
that are orbiting not one
but two stars.
We have found planets
that may be covered
entirely in liquid water.
And some of these planets
are Earth-sized,
with temperatures
potentially ripe for life.
Kepler allowed us
to see the sheer numbers
and the absolute commonness
of Earth-sized planets
throughout the galaxy.
And so the chances of us finding
life elsewhere, in my view,
is very high.
In fact, using the small sample
of sky observed by Kepler,
astronomers now estimate that
there are tens of billions
of planets in our galaxy
the same size and temperature
as Earth.
These planets could have liquid
water on their surfaces.
Their rocky cores could hold
the building blocks of life.
And their stars should provide
plenty of energy.
But does that mean that life
would thrive there?
Turns out that could depend
a lot on the star itself.
Planets are really at the mercy
of what happens to the stars
that they're orbiting around.
Dad, can you walk slower, maybe?
Jason Kalirai is
a stellar astrophysicist.
What are you guys excited
about seeing today?
I'm excited about seeing Saturn.
Saturn should look amazing...
An expert in
the behavior of stars,
he knows the profound influence
they can have
on orbiting planets.
So by studying those stars,
we can figure out
what kind of planets might be
most suitable for finding life.
All right, so here's
our main mirror.
Do you guys remember
what this is called?
The first mirror?
Primary mirror.
Oh, primary.
Jason's curiosity
about the cosmos started early.
As a young kid,
one of the things
that I found most exciting
was trying to figure out
how the universe works.
Countless times, I would be
in our backyard looking up
at the night sky, wondering what
part of the universe I'm seeing.
Jason had clear views of the sky
in British Columbia,
where he grew up.
His parents moved there from
Punjab, India, in the 1970s.
If they had stayed in India,
I would not be an astronomer.
That's just the way
the system is.
But in Canada, I could take
a liking to whatever I liked,
and as a very young kid,
I liked astronomy.
And when I wanted
to become an astronomer
and see that through,
there was nothing stopping me.
Today, he shares
his love of astronomy
with his twin daughters
Suriya and Mira.
Are there any people
on different planets?
So there's lots of stars
in the universe.
And so all of those stars
have planets around them.
So on one of those planets
right now there might be a dad
with his two daughters on a farm
looking up at the night sky,
asking the same question.
OMG!
I love showing my daughters
the night sky
through a telescope.
Is that Saturn?
Because you see
so much more out there that's
otherwise invisible to us.
Is that cool?
Yeah.
That instills that curiosity
to want to go
and find out those answers.
And with astronomy,
they'll never be satisfied,
because it'll always just
throw more questions at you.
♪♪
Jason pursues his questions
about the cosmos
at the Space Telescope Science
Institute in Maryland.
And when it comes to
the search for alien worlds,
he focuses on the kinds of stars
that might be friendliest
for life.
Because not all stars
are created equal.
When we look up
at the night sky,
we're seeing just
the brightest beacons of light.
It's not representative of
the true distribution of stars,
which contains many more
lower-mass stars...
Stars much smaller than the sun.
These low-mass stars,
sometimes called red dwarfs,
are smaller and cooler
than our sun.
And while our own sun will burn
out in about five billion years,
red dwarves could burn
for trillions of years.
Across the Milky Way galaxy,
red dwarves probably host
billions of planets,
many of them small and rocky,
like Earth.
So how likely is it these
planets host life?
One group of planets
just 40 light years away
has enticed scientists like
Jason... the TRAPPIST-1 System.
One of the biggest discoveries
in the last few years
was the discovery
of the TRAPPIST-1 System.
This is an incredible star.
TRAPPIST-1's seven planets
are all close to Earth-size,
and circle it in tight orbits,
like a condensed version
of our own solar system.
These planets
take a few days
to go around their star,
and they're only located
a couple million miles
from their star.
TRAPPIST-1's innermost planet
orbits its host star
every one and a half days.
It's 90 times closer
to the TRAPPIST-1 star
than our Earth is to the sun.
And so it's going to be
very hot on that planet.
Though not a lava world,
it's too hot for liquid water,
or for life as we know it.
The other end of the extreme,
We've got Planet H, which is
going to take about 20 days
going around
the TRAPPIST-1 System,
which is a huge amount of time,
given how faint
the TRAPPIST-1 star is.
And so it's going to be
very cold.
Any water here
is likely frozen solid.
But a few TRAPPIST-1 planets
seem to orbit
in the Goldilocks zone...
Just right, with temperatures
that could be similar
to those on Earth.
We think these
planets in the middle
are in the habitable zone.
Conditions are going to be
just right
where liquid water could exist.
When the discovery
was first announced,
hopes were high that some of
these planets might harbor life.
But Jason is more skeptical...
Not because of the planets,
but because of the star.
♪♪
Red dwarfs may be small and
cool, but they are also
more violent and volatile
than our sun.
These are generally
pretty active stars.
These exhibit a number
of solar flares
where there's material
that can impact a planet.
This material carries
enormous amounts of radiation,
many billions of
hydrogen bombs' worth...
Enough to destroy
the cells of any living thing
on a nearby planet.
Jason fears these
radioactive solar flares
could wipe out any life
that might arise
in the TRAPPIST-1 system.
It's actually unclear
whether or not
the conditions necessary
to sustain life
and the time that life needs
to develop are going to be
stable on these planets.
Jason isn't giving up on planets
that orbit red dwarfs,
but he does worry
that life there may be
so different from our own,
we might never recognize it.
I have no doubt
that planets that are
very different from Earth
and stars that are
very different from the sun
will still lead
to different types of life.
But we don't know
what we're looking for.
So the simplest experiment
is to try and find life
that resembles the life that
we understand well on Earth.
So can we find a twin...
An earth-like planet
orbiting a sun-like star?
Kepler tracked down a few,
but they're more than
a thousand light years away.
How can we find more,
and closer?
Luckily, a new detective
is joining the hunt...
NASA's transiting exoplanet
survey satellite, called TESS.
TESS will now do
a survey of all the nearby stars
so that we can find the very
closest planetary systems to us.
The telescope's four cameras
will observe some 200,000 stars,
many big and bright
like our sun.
TESS will take a snapshot,
and will image all the stars
along the strip of the sky,
and then it'll move on and do
the next set of stars,
and the next set of stars.
That's when there's going to be
this firehose
that's going to turn on.
All of a sudden,
we're going to get data
from all the closest stars.
Data that could translate into
thousands of nearby planets...
Including a lot like our own.
We could soon find ourselves
surrounded
by potentially habitable
neighbors.
But then what?
If we find a nearby twin,
could we ever know
if life exists there?
The very closest
potentially habitable planets
are a few light years away.
That's about 25 trillion miles!
Even if we built a spacecraft
that could travel
a million miles an hour,
it would take about
3,000 years to get there.
But even if we can't go there,
it might be possible
to find evidence of life
on a faraway planet
in effect by sniffing
its atmosphere.
♪♪
I mean, we'd all love
to find an alien.
We'll just be lucky
to find anything at all.
So at this point,
it doesn't matter what it is.
We just want to find
some sign of life.
MIT astronomer
Sara Seager thinks that sign
will come in the form of gases
in a planet's atmosphere
called biosignatures.
We call a gas a biosignature gas
if it's a gas
that's produced by life
that accumulates
in the planet atmosphere.
About two-and-a-half
billion years ago,
life on earth began pumping out
a powerful biosignature.
Colonies of bacteria
like these stromatolites
started producing oxygen,
like plants do today.
Now, our atmosphere
is roughly 20% oxygen...
A telltale sign of life.
But how could we ever study
a distant planet's atmosphere,
and detect what gases it holds?
If the planet and star
are fortuitously aligned,
that starlight can shine
through the planet atmosphere.
Different gases will absorb
starlight in different ways.
It turns out that each gas
has its own specific way
of interacting with light.
♪♪
We're all familiar
with glowing colored gases...
They're what light up
the neon signs of cities.
In this tube, for example,
there's mercury showing up
as a blue.
I can change that out
for another gas.
This one is helium.
It looks orange.
When Sara splits the light,
she can see even more detail.
Each gas has a unique
light signature.
These signatures could tell Sara
about the gases
in a planet's atmosphere... gases
that could be signs of life.
But to see them, she'll need
a very powerful telescope.
In 2020,
NASA plans to launch
the James Webb Space Telescope...
The most powerful
spaceborne telescope to date.
The James Webb Space Telescope
has a 21-foot gold mirror
so it can make exquisitely
sensitive measurements
of the atmospheric composition
of other planets.
It makes those measurements
with the help of a device
called a spectrometer,
which, like a prism,
divides light
into constituent colors.
This helps scientists like Sara
identify gases
surrounding a planet.
♪♪
We hope to see gases
like water vapor
on a small rocky planet,
which would indicate
liquid water oceans.
We'd like to see
methane and other gases.
And some of these
on their own or together
would help make the case
for life on another planet.
But even with those gases,
the case might be missing
a crucial piece of evidence.
Those are pieces of the puzzle,
but that puzzle will be
incomplete
until we detect oxygen.
Astrophysicist
Mercedes Lopez-Morales
wants to find oxygen
in another planet's atmosphere.
Remember, Earth got
most of its atmospheric oxygen
only after living creatures
started pumping it out.
But oxygen has a faint signal,
and might be difficult for
the James Webb Space Telescope
to spot on distant planets.
So Mercedes is pinning her hopes
for finding oxygen
on a new telescope being
constructed in a unlikely place.
Underneath the football stadium
at the University of Arizona,
scientists are turning
seven massive slabs of glass
into gigantic mirrors.
This is an 8.4 meter in diameter
mirror that is today
the largest one-piece mirror
that humans can build.
When completed, the mirrors,
each weighing 20 tons,
will travel to a mountain
in Chile, where they will be
assembled into
the giant Magellan telescope...
A mega-telescope expected to be
ten times stronger
than the Hubble Space Telescope.
That power will come from
the near-perfect shaping
and polishing
of seven mirrors
joined into one.
We need to polish this mirror
very, very finely.
Each mirror takes more than
three years to polish
to within 20 nanometers.
That's at least
1,000 times smaller
than the width of a human hair.
Every time I see
one of these mirrors
I see this big bucket
that is collecting light for me.
And the bigger the bucket,
the more light I can collect,
and the easier it will be
to detect oxygen
in an earth-like planet.
The giant Magellan telescope
is going to be
a game changer for us.
The GMT is scheduled
to start hunting for oxygen
on other planets
within the decade.
Technology moves very quickly.
I think we will find life
on another world.
We will find a signature
that's a smoking gun
for life on a nearby planet.
But could we find
more than a smoking gun?
While some alien hunters
set their hopes
on the next generation
of telescopes
to spot life from afar,
some explorers
are searching for E.T.
much closer to home.
Astrobiologist Kevin Hand
is hunting for life
in our own solar system.
But the aliens he dreams of
are very different
from the ones in the movies.
He's looking for a kind of life
that could thrive
in some of the harshest
places on earth.
♪♪
So here we are sitting on
a red-hot blister
on planet Earth, a volcano.
At Lassen Volcanic
National Park in California,
temperatures in these springs
rise to nearly
200 degrees Fahrenheit...
Deadly to most forms of life.
This particular
bubbling hot spring, of course,
does not look like
a good place for life.
It's not a good place
for me, this tree,
or any large creature.
And yet, if you look closely,
the pools are literally
teeming with life.
It's just very tiny...
Microbes.
What's amazing about microbes
is that they can survive
in a variety of different
harsh and extreme conditions.
For example, all of the green
that you see here,
these are microbes
that are doing photosynthesis,
thriving off of
energy from the sun.
♪♪
But not all microbes
need sunlight.
In this stream that's coming
from one of the hot springs,
we've got microbes
that are surviving
on all the compounds
dissolved in the water.
These microbes
don't need sunlight.
♪♪
Kevin thinks he might
find creatures like these
lurking not too far from Earth.
These are the kinds
of life forms
that we think could
potentially inhabit
the deep, dark oceans
of other worlds.
But what oceans?
None of the other planets
in our solar system
have liquid water oceans
on their surfaces.
So, astrobiologists like Kevin
are laying their bets
on two balls of ice that aren't
planets at all, but moons:
Enceladus, a moon of Saturn,
and Europa, a moon of Jupiter.
At first glance,
both appear to be barren.
But cracks on the surface
reveal activity below.
Extreme gravitational forces
created by their
massive parent planets
could be be causing the moons'
rocky cores to heat up.
And when you put together
heat and ice...
Because of frictional heating
of the ice against
the solid core,
you get the formation
of subsurface oceans.
Scientists now believe
that the ice on both moons
covers hidden oceans below,
with Europa holding more water
than all of Earth's oceans
combined.
And here, deep in the oceans
of these tiny moons,
could lie all the fundamental
ingredients of life.
If you have ocean water
coming into contact with rock
at elevated temperatures,
you'll get energy for life
that's not coming from the sun,
but from chemical reactions.
Worlds like Europa
and Enceladus,
where we've got good evidence
for vast, global,
liquid-water oceans
could be where a second
origin of life occurred.
Kevin thinks
there's a strong chance
that life could exist on Europa,
the larger of the two moons.
But how could you ever find it?
You wouldn't want
to go to Europa.
It'd be a beautiful view
of Jupiter,
but as soon as you stepped out
of your spacecraft, you'd die.
It's -280 degrees Fahrenheit,
there's no atmosphere,
and then the radiation
that would rain down onto you
would kill you within a matter
of tens of minutes.
Astronauts won't be attempting
to skate across Europa's
icy surface anytime soon.
So, NASA is studying ways
to send a robotic probe
nearly 400 million miles
to the bright moon
to hunt for traces of life...
But not before we know
what to look for.
If Europan sea creatures,
even microbes, existed,
and made their way
to the surface of the ice,
their cells...
And anything resembling DNA...
Would be heavily altered
by radiation.
But Kevin thinks we can hunt
for remnants of life
in the form of amino acids,
the building blocks of proteins.
So, if we found
amino acids in ice,
that could be
a pretty strong sign of life
within that ocean.
But how likely is it
that traces,
in the form of amino acids,
could survive on the surface
and be detected
by our spacecraft?
To figure that out,
Kevin and his team
are replicating some
of the conditions
on the icy moon right here
at NASA's Jet Propulsion
Laboratory in Pasadena.
In this latest test,
Kevin's molecular guinea pig
is glycine,
the simplest amino acid,
found in every
living thing on Earth.
We're mixing glycine
in with water
to kind of replicate what
could be in Europa's ocean,
were it to have life.
The mixture goes
into a stockpot,
a witch's brew
of water and salts.
Over three weeks,
Kevin pummels the glycine
with the sub-zero temperatures
and dangerously low pressure
you'd experience
on Europa's surface.
Finally, it's time to find out
if any glycine
survived the ordeal.
Okay, well, we've definitely
cooked up something
interesting in here.
If the amino acid
is completely destroyed,
the odds of finding
some sign of life
on Europa's surface
are slim to none.
It doesn't look like ice.
It looks like a very solid
but soft surface.
This is almost like
a creme brulee, I think.
Going in...
Ooh! Interesting.
Do you feel like there
was a... a tough crust?
No, no, it's very powdery.
Oh, look at that.
Hmm.
Kevin was expecting
a hard, icy shell,
but he's surprised to see
that the ingredients
have frozen into a thick powder.
You can see it's almost like
a layered, feathered material.
Now for the real test...
Kevin probes the ice with
a spectrometer,
using light
to seek out and measure
glycine's unique signature.
Can a simple amino acid...
A single building block
of life...
Withstand the harsh environment
of Europa's surface
and be detectable?
Get in nice and close
and we'll get
the maximum signal.
And like a beacon, it appears...
A small but clear
signal of glycine.
It means that if there is
microbial life
in the oceans of Europa,
we might be able to find
some of its building blocks
on the moon's icy surface.
Is this what the signal of life
on a distant world
might look like?
We just don't know.
The next thing to do
is launch a spacecraft
and go look for it
out there in the solar system.
Finding amino acids
on Europa's surface
would be encouraging,
but what we really
want to know is
what might be swimming
around in Europa's vast oceans?
Could there be microbes?
Like the ones that
dominated Earth's own oceans
for billions of years?
Or something more complex?
If we want to find out,
Then we need to send
a mission much deeper,
down through the ice and into
the pitch black oceans below.
But how do you prepare
for such an ambitious trip,
to a place unlike
anywhere on Earth?
♪♪
Engineer Bill Stone believes
he has the answer.
If you ask me
what is exploration,
it is the process
of putting your boot
in a place where no one
has ever been before.
Bill's "boot"
is an underwater vehicle
named Sunfish,
his prototype for
an ocean-exploring robot.
It might not look like much,
but if there's something
swimming around on Europa,
a miniature version
of this robot
could be the first to spot it.
It will be one of
the greatest intellectual feats
of humankind
if we pull this off.
NASA is studying
how to get to Europa's surface
in about 15 years.
Bill is planning for
a much more ambitious journey...
Fly a robotic lander
400 million miles to Europa
and land on the surface.
Bore through an ice cap
some ten to 15 miles thick,
then release an autonomous
underwater vehicle to explore
the mysterious ocean below.
Once you get through the ice,
Sunfish will go out
and map, explore,
and look for life.
This wouldn't be
the first robotic mission
in our solar system.
♪♪
Mars rovers have explored
the red planet
by following commands
that come from Earth,
34 million miles away.
That's not possible on Europa,
which is roughly three times
as distant as Mars.
The problem is there's
a two-hour delay
light travel time
between Europa and Earth,
so we can't sit there
and joystick something.
This robot must be able to think
and explore all on its own...
Or else it won't be able to see
much of the Europan ocean,
and the mission
to Jupiter's moon
could be a wasted opportunity.
Where would you like us
to position the robot?
To do that, it needs practice.
Here we go, heading east...
We're at Peacock Springs State
Park in northern Florida,
because there is
an underwater labyrinth, a maze.
The ground in
this part of Florida
is riddled with winding,
water-filled caves.
Can Bill's robot negotiate
this confusing environment
on his own?
A team of experienced
cave divers
tags along in case
the robot breaks down.
Other than that,
the robot is virtually alone,
using sonar to explore and map
its surroundings, inch by inch.
The robot doesn't know
anything about this cave,
and so it is learning
to explore as it goes.
So we're at 21, 33...
So, 240 points us
down the tunnel.
Things seem to be going well,
until, in one narrow cave,
Sunfish stops.
It suddenly seems confused.
It's drifting a lot.
It is.
What do you do
if something goes wrong?
What's your procedure?
All that has to
go into the code.
Zero, zero, 240-D...
A few lines of code
outline a new strategy:
back up and remap
from a different angle.
♪♪
This time, the robot succeeds.
♪♪
It's achieved the goal
and turning back.
This is a small step
that could one day
lead to giant leap in the search
for life beyond Earth.
If there's going
to be life on Europa,
there is no reason why we can't
have life somewhere else
in the universe.
Be the first validation
that we aren't the only ones.
So, from that standpoint,
it's going to shake
a lot of ground.
If we found evidence of life
on Europa,
even if it were just
a teeny, tiny microbe,
that would be huge!
All it needs is for one microbe,
that is life,
but not as we know it
to make the point
that it can't be that hard
to get going.
Just one microbe.
The importance of that
is to say, "Guess what?
"Biology's not very hard.
"It's an infection
in the universe, right?
It's all over the place."
If a galaxy oozing
with pond scum
doesn't seem too exciting,
then remember...
Over a few billions years,
these tiny creatures evolved
into all the plants and animals
that swim, crawl,
and fly around our planet,
including us.
So, could the same thing
happen somewhere else?
What do we think aliens that
evolved on another planet
would be like?
Flying saucers have
invaded our planet...
In lots of movies,
aliens look remarkably like us,
with two arms and legs...
Only you of Earth,
you and your women,
can give us life.
Get back or I'll fire.
You fool.
And, of course, those eyes.
From the standpoint
of Hollywood,
the aliens tend to be
these little gray guys
with big eyeballs,
and, you know,
no sense of humor,
and no clothes, by the way.
They seem very dispassionate.
They don't seem to get angry,
they don't seem
to have a lot of fun, either.
Come on down,
Mr. Ambassador.
Science fiction aliens usually
have something else in common
with us: intelligence.
But what are
the chances that life...
If it did arise elsewhere...
Would evolve into creatures
with big brains?
After all, aren't we the only
smart ones on this planet?
Come here.
Some biologists would say no...
Good job, buddy!
And they're not just talking
about our closest relatives.
From dolphins,
to birds,
to even the octopus...
A creature more closely related
to snails and clams than to us,
but smart enough to use tools
and open jars...
We're not the only animals
who've evolved
impressive brains.
Of course, none
of these creatures
will build a spaceship
anytime soon.
But for many scientists,
the idea that
we're the only technologically
advanced creatures
in the universe
seems a bit, well, presumptuous.
We used to think the earth
was the center of the universe,
that was wrong.
Then we thought the sun
was the center of the universe,
and that was wrong.
Then we thought our galaxy
was the center of the universe,
and that was wrong.
Every time we've thought we were
really special, we were wrong.
And so, the idea
that we're somehow special
in terms of being alive
or being intelligent,
I mean, that's
probably wrong, too.
I find it extremely hard
to believe that
in the vastness of our universe,
that a rocky planet that harbors
intelligent, sentient life
happened just once.
♪♪
Some scientists have spent
their entire careers
hunting the vast emptiness
of space,
trying to pick up a signal.
I always just took for granted
that there would be
other stars that would be suns
for other creatures,
and that just seemed to me
the natural way of the world.
More than three decades ago,
astronomer Jill Tarter
co-founded the SETI Institute,
dedicated to the search
for extraterrestrial intelligence.
It's been amazing
to be able to spend
a career on a question
that I'm fascinated with
and a question
that everybody else out there
is curious
to know the answer to.
She was the inspiration
for the character
Dr. Ellie Arroway
in Carl Sagan's book "Contact,"
which was adapted
to a feature film in 1997.
Today, SETI conducts searches
with the Allen Telescope Array,
a network of 42 radio telescopes
in Hat Creek, California.
The telescopes comb the skies
for radio waves,
which can carry signals
and information across
the great distances of space.
Radio waves are an excellent way
to communicate
because they cut through
the atmosphere of our earth
and also cut through
the space between the stars.
In fact, we've been sending out
our own radio waves since
the dawn of broadcasting,
about a century ago.
Good morning, honey.
If any aliens are listening,
their ideas about earthlings
could be based on
"The Dick Van Dyke Show."
I said, how's my old lady?
Well, I don't know,
I haven't spoken
to your mother lately,
but I'm fine.
The hope of SETI
is that some aliens
might also be broadcasting.
The idea is that
if life has sprung up
on some other worlds
and it's technological life,
in other words,
they've, you know,
they've learned
a little bit of physics,
they build some equipment,
this, that, and the other,
they could build
radio transmitters
that are sending
signals into space
that we could pick up here.
At Hat Creek, the telescopes
listen in on millions
of radio channels at a time,
looking for unique patterns
that could be
alien transmissions.
When something shows up
that we don't think
is interference,
something that
we've not seen before,
immediately we follow up
on that signal
to try and figure out
what it is,
and whether it's, in fact,
our technology
or potentially someone else's.
But unique signals are rare...
Just one or two a year.
And so far, even
the most promising ones
have turned out
to be human interference.
Still, the event
that SETI is waiting for
could happen any day.
Okay! Point source confirmed.
Whatever it is, it ain't local.
While Hollywood has fantasized
about this moment of discovery,
it's harder than it looks.
The Allen Telescope Array
can only listen
to a few hundred million
out of billions
of possible radio frequencies
at a time.
We haven't yet figured out
how to look at all the sky,
all the time,
at all frequencies,
but that's ultimately
what we want to do.
In fact, we've been listening
for nearly 60 years,
and so far... crickets.
But the fraction of stars
we've searched carefully
and the amount of time
we've been listening
are still both quite small.
So plenty of people
remain hopeful
that technologically advanced
civilizations are out there.
And that's why
the mysterious dimming
of one particular star
was, for some, so tantalizing.
♪♪
In 2015, astronomer
Tabetha Boyajian
and her colleagues
published their findings
about a very weird star.
According to data
from the Kepler Space Telescope,
Tabby's Star was dimming
at strange, irregular intervals,
sparking theories
about an enormous structure
built by a hypothetical
advanced alien civilization.
The buzz spurred more research.
Today, a worldwide network
of powerful
ground-based telescopes stare
at Tabby's Star
around the clock.
We can actually process the data
in near real-time,
and when we see something
start to happen, we can trigger
more intense observations
of what is passing in front of
the star at that time.
For a while,
the star was silent.
Then, suddenly, it started
dimming erratically again.
The ground-based telescopes
provide information
about the star
that Kepler couldn't see.
Not just the dimming
of the star,
but how those dips
in brightness appear
in different colored
wavelengths.
Something is happening
with our star here...
We sent off alerts via Twitter
and data of all sorts
started coming our way.
At this point,
it's like we're swimming
in data.
Tabby and her team
at Louisiana State
are looking for patterns
in the color data
that could tell them
what kind of material
is passing in front of the star.
Blue light and red light
will react differently
to material that's passing
in front of the star,
and you'll have
a different signature
in how far down these dips go.
Whatever is passing
in front of Tabby's Star
appears to be blocking
more blue light
than red and orange light.
But what would block out
more blue light?
Tabby has a theory:
space dust.
Dust scatters blue light
more than it does red light.
And so, that indicates
that there's some sort of dusty,
semi-opaque, you know, material
that's crossing
in front of the star
and blocking out the light.
It's got the signatures
of being dust, rather than...
it can't be some kind of
completely opaque object,
like a planet or
an alien megastructure.
That's right.
The culprit is likely
scattered dust,
and not a solid
alien megastructure.
But the mystery
is hardly solved.
What created
this giant cloud of dust?
Why is it centered
around Tabby's Star?
Astronomers will need more data
if they're ever going
to crack this one.
Nature is a lot more creative
than we are,
and you know,
we're just going to have to,
you know, really buckle down
and try and, and,
and figure this one out.
Tabby's Star is one
in a long line of mysteries
that at first raised hopes
for finding E.T.,
but later were revealed
to have solutions
unrelated to life.
For some, the lack
of firm evidence is troubling.
In 1950, physicist Enrico Fermi
went to lunch
with some colleagues
and asked a simple question:
"Where is everybody?"
If there are billions of
habitable planets out there,
and life is common...
Why haven't a bunch of aliens
already shown up
on our doorstep?
What could explain the silence?
For some, the quietness
of the cosmos
is evidence that
we really could be alone.
But many astronomers disagree.
The idea that there's
intelligent life out there
that has never
interacted with us
or that we've never seen it...
That, to me,
is not confusing at all.
I mean, I think that's
perfectly consistent.
You know, it's no different than
a child looking at an ant farm.
The child is not going to be
compelled to interact
with an individual ant
and more so, the ants
probably don't even know
that the child
is analyzing the ant farm.
And so there's very likely
intelligent civilizations
out there that
may be looking at us.
But what do they have to gain
from interacting with us?
We might be very
basic and insignificant
compared to them.
Or perhaps interstellar travel
is too challenging,
even for super-smart aliens.
Or maybe they did exist,
but ended up
destroying themselves.
♪♪
For many, the universe
is simply too large.
Too many stars,
with too many planets.
Too many potential homes
for creatures
that might start small,
but could, like us,
thrive and grow.
The universe is mind-boggling.
It's bigger than
what we humans can actually
wrap our consciousness around.
The universe has hundreds
of billions of planets
in hundreds of billions
of galaxies.
So it just seems like
when you roll the dice
many, many times, one of them
is going to luck out.
We live in a groundbreaking era.
We might be the first generation
that will be able to say
that there is life elsewhere
in the universe.
Our young people
have a much greater opportunity
to see themselves as earthlings.
But we also could find out that
to the best
of our ability to measure,
we really are alone.
If it turns out
that Earth is rare,
then that's all the more reason
to look after what we've got.
Because if we destroy ourselves,
the flame of mind
and the flame of culture
will be snuffed out for good.
I hope that we aren't
the only things out there.
There's gotta be something else.
You know, there's just
a lot of room up there.
It's hard to believe that
everything interesting
is down here.
It just never struck me
as a very reasonable
point of view.
Are we alone in the universe?
Not a chance.
♪♪
The unknown.
What our place
in the universe is.
Artificial intelligence.
Hello.
Look at this, what's this?
Animals.
An egg.
Your brain.
Life on a faraway planet.
"NOVA Wonders"... investigating
the biggest mysteries.
We have no idea
what's going on there.
These planets in the middle
we think are
in the habitable zone.
And making incredible
discoveries.
Trying to understand
their behavior, their life,
everything that goes on here.
Building an artificial
intelligence
is going to be the crowning
achievement of humanity.
We're three scientists
exploring the frontiers
of human knowledge.
I'm a neuroscientist
and I study
the biology of memory.
I'm a computer scientist
and I build technology
that can read human emotions.
And I'm a mathematician,
using big data to understand
our modern world.
And we're tackling
the biggest questions...
- Dark energy?
- Dark energy?
Of life...
There's all of these microbes,
and we just don't know
what they are.
And the cosmos.
♪♪
On this episode,
the hunt for alien life is on,
turning up mysterious clues.
The star loves attention.
And it makes everybody crazy.
That's not a planet.
So what is it?
What are the odds?
The ingredients for life
are everywhere.
The universe has
hundreds of billions of planets.
But does anything live there?
The chances of us finding life
is very high.
"NOVA Wonders"... "Are We Alone?"
Right now.
The planet Earth...
A ball of rock
about 8,000 miles in diameter.
We know there's a lot
going on here.
Almost eight billion people
call it home,
along with billions
of other species.
But is this the only place
where the action is?
Our sun is just one of
an estimated 300 billion stars
in the Milky Way.
And we think there are at least
100 billion other galaxies.
So what are the chances that
all the fun is only happening
right here in our tiny corner
of the universe?
♪♪
Today, astronomers and engineers
are building new tools
to probe our solar system
and our galaxy,
hunting for clues
of life beyond Earth.
What are they discovering?
I'm Rana el Kaliouby.
I'm André Fenton.
I'm Talithia Williams.
And in this episode,
"NOVA Wonders"...
"Are We Alone?"
And what will it take
to find out?
♪♪
A few years ago,
a group of amateur astronomers
discovered a mysterious star.
Located about
1,500 light years from Earth,
the star flickers erratically,
and no one knows why.
If a star dims
at regular intervals,
chances are it's caused
by an orbiting planet.
And typically it's only
by a fraction of one percent.
But the light from this star
is dimming by more, much more.
The thing about this star is the
light dims every now and again.
But it's being dimmed by 22%.
So that's not a planet...
That's much too much.
Even for a Jupiter-sized planet,
you don't get anywhere near
that kind of dimming,
so what is it?
Unlocking the star's secrets
becomes the quest
of Tabetha Boyajian,
a stellar astrophysicist.
Soon people are calling it
"Tabby's Star."
I worked with dozens
of other astronomers
for several years
trying to figure out
what could be causing
these strange fluctuations
in its light.
Is it caused by
an asteroid belt?
Or colliding planets?
So we had this
whole long list of ideas.
None of them worked.
Then, one of Tabby's colleagues
offers a possible idea,
a bit outside
the standard astronomy box.
When I showed him this star,
he said, "Wow, this is
really weird,
and we don't
have an explanation for it."
He said, "These things
all look like they could be
caused by some
artificial alien megastructure."
♪♪
An artificial
alien megastructure...
A giant structure built by a
hypothetical alien civilization
to harness the energy
from its own sun.
When the word gets out...
talk about the prospect
of an alien megastructure.
Evidence of alien life.
The strange light pattern makes
it seem more like a death star
planet rather than a star.
The star loves attention,
and it makes everybody crazy.
It is far-fetched.
To dim a star by so much,
an alien megastructure
would have to be at least
half as big as the star itself.
But when the theory
is first proposed,
astronomers can't rule it out.
The behavior of Tabby's Star
is quite weird.
Given that we have no idea
what's going on there,
I'm not too quick
to throw out theories.
Could this be
some alien megastructure?
We don't know.
Tabby and her team
will continue to study the star,
hoping to find more evidence.
For some people,
the idea that there's
a civilization out there
capable of building
a giant structure around its sun
would be a dream come true.
It's the same dream that fuels
our obsession with aliens,
whether they charm us...
I am Groot.
Frighten us...
seduce us...
Oh, no.
Or try to kill Tom Cruise.
Oh, man!
My God...
And it's not just the movies.
Even the Pentagon
recently admitted
that it secretly investigated
UFO sightings for years.
But what's the reality?
♪♪
Right now, as far as
technologically advanced life
goes, we have a sample size
of one...
Us.
In fact, when it comes
to any form of life,
whether it looks like this...
or this...
or this, the only examples
we know of are right here
on Earth.
And the truth is, if we found
even one other example
of this kind of life,
it would be
the biggest scientific discovery
in our lifetimes.
So where do we start to look?
♪♪
In 2009, NASA took a major step
in the hunt for life
beyond earth, launching
the Kepler space telescope
to track down signs
of earthlike planets
beyond our solar system.
♪♪
Up until then, astronomers
had found about 300 exoplanets.
But few were
anything like Earth.
Small, rocky planets like ours
are not easy to spot.
Planets are literally lost in
the glare of their parent stars.
The brightness difference,
the contrast between
a star like our sun and the
Earth that's right next to it
is ten billion to one.
So instead of hunting for light
reflecting off
a planet's surface,
the telescope focuses
on starlight.
What Kepler did was look in
a part of the Milky Way galaxy
where we had lots of stars
in a small field,
and it just took pictures
over and over again.
And, occasionally,
if those stars have planets,
then sometimes those planets
would come in front of the star.
As the planet comes around,
it's going to block
part of the star,
and that light won't get to you.
And so that constant level
that you see from the star
suddenly goes down just a bit.
So these momentary
dimmings of light
that repeat once every orbit
are indicative
of a planet orbiting a star.
Astrophysicists like
John Asher Johnson
and his team at Harvard
use Kepler data
to estimate
an orbiting planet's size
and distance from its star.
The dips are pretty deep, so it
must be a fairly large planet.
Deep dips in the star's light
mean the planet is really big,
or the star is really small.
The spacing between those,
what is it, like, a day or two?
And frequent dimming
means gravity has drawn it
close to the star,
making the planet really hot.
Feels pretty much like
a classic hot Jupiter.
A giant broiling
ball of gas like this
would not be a great spot
for life.
So the team looks for signals
that are more subtle.
Looking at this,
it doesn't look like much.
But it looks like there is some
kind of periodic signal there.
So what do we know?
We know the thing is small?
It's blocking out
less than a percent of the light
that we're receiving.
Something is causing the star
to dim ever so slightly,
and at longer intervals.
Could this be a small planet
closer to Earth's size?
And the distance from its sun
suggests temperatures
potentially
comfortable for life.
This is really interesting.
I mean, this exactly
the kind of thing
that we're looking for.
This could be a rocky planet
somewhere near
the habitable zone.
Yeah, this is really exciting.
Yeah.
The discoveries coming from
Kepler have been astounding...
Nearly 3,000 confirmed planets
so far.
The Kepler Space Telescope
blew open our understanding
of planets.
We have found lava worlds.
We've got planets
that are orbiting not one
but two stars.
We have found planets
that may be covered
entirely in liquid water.
And some of these planets
are Earth-sized,
with temperatures
potentially ripe for life.
Kepler allowed us
to see the sheer numbers
and the absolute commonness
of Earth-sized planets
throughout the galaxy.
And so the chances of us finding
life elsewhere, in my view,
is very high.
In fact, using the small sample
of sky observed by Kepler,
astronomers now estimate that
there are tens of billions
of planets in our galaxy
the same size and temperature
as Earth.
These planets could have liquid
water on their surfaces.
Their rocky cores could hold
the building blocks of life.
And their stars should provide
plenty of energy.
But does that mean that life
would thrive there?
Turns out that could depend
a lot on the star itself.
Planets are really at the mercy
of what happens to the stars
that they're orbiting around.
Dad, can you walk slower, maybe?
Jason Kalirai is
a stellar astrophysicist.
What are you guys excited
about seeing today?
I'm excited about seeing Saturn.
Saturn should look amazing...
An expert in
the behavior of stars,
he knows the profound influence
they can have
on orbiting planets.
So by studying those stars,
we can figure out
what kind of planets might be
most suitable for finding life.
All right, so here's
our main mirror.
Do you guys remember
what this is called?
The first mirror?
Primary mirror.
Oh, primary.
Jason's curiosity
about the cosmos started early.
As a young kid,
one of the things
that I found most exciting
was trying to figure out
how the universe works.
Countless times, I would be
in our backyard looking up
at the night sky, wondering what
part of the universe I'm seeing.
Jason had clear views of the sky
in British Columbia,
where he grew up.
His parents moved there from
Punjab, India, in the 1970s.
If they had stayed in India,
I would not be an astronomer.
That's just the way
the system is.
But in Canada, I could take
a liking to whatever I liked,
and as a very young kid,
I liked astronomy.
And when I wanted
to become an astronomer
and see that through,
there was nothing stopping me.
Today, he shares
his love of astronomy
with his twin daughters
Suriya and Mira.
Are there any people
on different planets?
So there's lots of stars
in the universe.
And so all of those stars
have planets around them.
So on one of those planets
right now there might be a dad
with his two daughters on a farm
looking up at the night sky,
asking the same question.
OMG!
I love showing my daughters
the night sky
through a telescope.
Is that Saturn?
Because you see
so much more out there that's
otherwise invisible to us.
Is that cool?
Yeah.
That instills that curiosity
to want to go
and find out those answers.
And with astronomy,
they'll never be satisfied,
because it'll always just
throw more questions at you.
♪♪
Jason pursues his questions
about the cosmos
at the Space Telescope Science
Institute in Maryland.
And when it comes to
the search for alien worlds,
he focuses on the kinds of stars
that might be friendliest
for life.
Because not all stars
are created equal.
When we look up
at the night sky,
we're seeing just
the brightest beacons of light.
It's not representative of
the true distribution of stars,
which contains many more
lower-mass stars...
Stars much smaller than the sun.
These low-mass stars,
sometimes called red dwarfs,
are smaller and cooler
than our sun.
And while our own sun will burn
out in about five billion years,
red dwarves could burn
for trillions of years.
Across the Milky Way galaxy,
red dwarves probably host
billions of planets,
many of them small and rocky,
like Earth.
So how likely is it these
planets host life?
One group of planets
just 40 light years away
has enticed scientists like
Jason... the TRAPPIST-1 System.
One of the biggest discoveries
in the last few years
was the discovery
of the TRAPPIST-1 System.
This is an incredible star.
TRAPPIST-1's seven planets
are all close to Earth-size,
and circle it in tight orbits,
like a condensed version
of our own solar system.
These planets
take a few days
to go around their star,
and they're only located
a couple million miles
from their star.
TRAPPIST-1's innermost planet
orbits its host star
every one and a half days.
It's 90 times closer
to the TRAPPIST-1 star
than our Earth is to the sun.
And so it's going to be
very hot on that planet.
Though not a lava world,
it's too hot for liquid water,
or for life as we know it.
The other end of the extreme,
We've got Planet H, which is
going to take about 20 days
going around
the TRAPPIST-1 System,
which is a huge amount of time,
given how faint
the TRAPPIST-1 star is.
And so it's going to be
very cold.
Any water here
is likely frozen solid.
But a few TRAPPIST-1 planets
seem to orbit
in the Goldilocks zone...
Just right, with temperatures
that could be similar
to those on Earth.
We think these
planets in the middle
are in the habitable zone.
Conditions are going to be
just right
where liquid water could exist.
When the discovery
was first announced,
hopes were high that some of
these planets might harbor life.
But Jason is more skeptical...
Not because of the planets,
but because of the star.
♪♪
Red dwarfs may be small and
cool, but they are also
more violent and volatile
than our sun.
These are generally
pretty active stars.
These exhibit a number
of solar flares
where there's material
that can impact a planet.
This material carries
enormous amounts of radiation,
many billions of
hydrogen bombs' worth...
Enough to destroy
the cells of any living thing
on a nearby planet.
Jason fears these
radioactive solar flares
could wipe out any life
that might arise
in the TRAPPIST-1 system.
It's actually unclear
whether or not
the conditions necessary
to sustain life
and the time that life needs
to develop are going to be
stable on these planets.
Jason isn't giving up on planets
that orbit red dwarfs,
but he does worry
that life there may be
so different from our own,
we might never recognize it.
I have no doubt
that planets that are
very different from Earth
and stars that are
very different from the sun
will still lead
to different types of life.
But we don't know
what we're looking for.
So the simplest experiment
is to try and find life
that resembles the life that
we understand well on Earth.
So can we find a twin...
An earth-like planet
orbiting a sun-like star?
Kepler tracked down a few,
but they're more than
a thousand light years away.
How can we find more,
and closer?
Luckily, a new detective
is joining the hunt...
NASA's transiting exoplanet
survey satellite, called TESS.
TESS will now do
a survey of all the nearby stars
so that we can find the very
closest planetary systems to us.
The telescope's four cameras
will observe some 200,000 stars,
many big and bright
like our sun.
TESS will take a snapshot,
and will image all the stars
along the strip of the sky,
and then it'll move on and do
the next set of stars,
and the next set of stars.
That's when there's going to be
this firehose
that's going to turn on.
All of a sudden,
we're going to get data
from all the closest stars.
Data that could translate into
thousands of nearby planets...
Including a lot like our own.
We could soon find ourselves
surrounded
by potentially habitable
neighbors.
But then what?
If we find a nearby twin,
could we ever know
if life exists there?
The very closest
potentially habitable planets
are a few light years away.
That's about 25 trillion miles!
Even if we built a spacecraft
that could travel
a million miles an hour,
it would take about
3,000 years to get there.
But even if we can't go there,
it might be possible
to find evidence of life
on a faraway planet
in effect by sniffing
its atmosphere.
♪♪
I mean, we'd all love
to find an alien.
We'll just be lucky
to find anything at all.
So at this point,
it doesn't matter what it is.
We just want to find
some sign of life.
MIT astronomer
Sara Seager thinks that sign
will come in the form of gases
in a planet's atmosphere
called biosignatures.
We call a gas a biosignature gas
if it's a gas
that's produced by life
that accumulates
in the planet atmosphere.
About two-and-a-half
billion years ago,
life on earth began pumping out
a powerful biosignature.
Colonies of bacteria
like these stromatolites
started producing oxygen,
like plants do today.
Now, our atmosphere
is roughly 20% oxygen...
A telltale sign of life.
But how could we ever study
a distant planet's atmosphere,
and detect what gases it holds?
If the planet and star
are fortuitously aligned,
that starlight can shine
through the planet atmosphere.
Different gases will absorb
starlight in different ways.
It turns out that each gas
has its own specific way
of interacting with light.
♪♪
We're all familiar
with glowing colored gases...
They're what light up
the neon signs of cities.
In this tube, for example,
there's mercury showing up
as a blue.
I can change that out
for another gas.
This one is helium.
It looks orange.
When Sara splits the light,
she can see even more detail.
Each gas has a unique
light signature.
These signatures could tell Sara
about the gases
in a planet's atmosphere... gases
that could be signs of life.
But to see them, she'll need
a very powerful telescope.
In 2020,
NASA plans to launch
the James Webb Space Telescope...
The most powerful
spaceborne telescope to date.
The James Webb Space Telescope
has a 21-foot gold mirror
so it can make exquisitely
sensitive measurements
of the atmospheric composition
of other planets.
It makes those measurements
with the help of a device
called a spectrometer,
which, like a prism,
divides light
into constituent colors.
This helps scientists like Sara
identify gases
surrounding a planet.
♪♪
We hope to see gases
like water vapor
on a small rocky planet,
which would indicate
liquid water oceans.
We'd like to see
methane and other gases.
And some of these
on their own or together
would help make the case
for life on another planet.
But even with those gases,
the case might be missing
a crucial piece of evidence.
Those are pieces of the puzzle,
but that puzzle will be
incomplete
until we detect oxygen.
Astrophysicist
Mercedes Lopez-Morales
wants to find oxygen
in another planet's atmosphere.
Remember, Earth got
most of its atmospheric oxygen
only after living creatures
started pumping it out.
But oxygen has a faint signal,
and might be difficult for
the James Webb Space Telescope
to spot on distant planets.
So Mercedes is pinning her hopes
for finding oxygen
on a new telescope being
constructed in a unlikely place.
Underneath the football stadium
at the University of Arizona,
scientists are turning
seven massive slabs of glass
into gigantic mirrors.
This is an 8.4 meter in diameter
mirror that is today
the largest one-piece mirror
that humans can build.
When completed, the mirrors,
each weighing 20 tons,
will travel to a mountain
in Chile, where they will be
assembled into
the giant Magellan telescope...
A mega-telescope expected to be
ten times stronger
than the Hubble Space Telescope.
That power will come from
the near-perfect shaping
and polishing
of seven mirrors
joined into one.
We need to polish this mirror
very, very finely.
Each mirror takes more than
three years to polish
to within 20 nanometers.
That's at least
1,000 times smaller
than the width of a human hair.
Every time I see
one of these mirrors
I see this big bucket
that is collecting light for me.
And the bigger the bucket,
the more light I can collect,
and the easier it will be
to detect oxygen
in an earth-like planet.
The giant Magellan telescope
is going to be
a game changer for us.
The GMT is scheduled
to start hunting for oxygen
on other planets
within the decade.
Technology moves very quickly.
I think we will find life
on another world.
We will find a signature
that's a smoking gun
for life on a nearby planet.
But could we find
more than a smoking gun?
While some alien hunters
set their hopes
on the next generation
of telescopes
to spot life from afar,
some explorers
are searching for E.T.
much closer to home.
Astrobiologist Kevin Hand
is hunting for life
in our own solar system.
But the aliens he dreams of
are very different
from the ones in the movies.
He's looking for a kind of life
that could thrive
in some of the harshest
places on earth.
♪♪
So here we are sitting on
a red-hot blister
on planet Earth, a volcano.
At Lassen Volcanic
National Park in California,
temperatures in these springs
rise to nearly
200 degrees Fahrenheit...
Deadly to most forms of life.
This particular
bubbling hot spring, of course,
does not look like
a good place for life.
It's not a good place
for me, this tree,
or any large creature.
And yet, if you look closely,
the pools are literally
teeming with life.
It's just very tiny...
Microbes.
What's amazing about microbes
is that they can survive
in a variety of different
harsh and extreme conditions.
For example, all of the green
that you see here,
these are microbes
that are doing photosynthesis,
thriving off of
energy from the sun.
♪♪
But not all microbes
need sunlight.
In this stream that's coming
from one of the hot springs,
we've got microbes
that are surviving
on all the compounds
dissolved in the water.
These microbes
don't need sunlight.
♪♪
Kevin thinks he might
find creatures like these
lurking not too far from Earth.
These are the kinds
of life forms
that we think could
potentially inhabit
the deep, dark oceans
of other worlds.
But what oceans?
None of the other planets
in our solar system
have liquid water oceans
on their surfaces.
So, astrobiologists like Kevin
are laying their bets
on two balls of ice that aren't
planets at all, but moons:
Enceladus, a moon of Saturn,
and Europa, a moon of Jupiter.
At first glance,
both appear to be barren.
But cracks on the surface
reveal activity below.
Extreme gravitational forces
created by their
massive parent planets
could be be causing the moons'
rocky cores to heat up.
And when you put together
heat and ice...
Because of frictional heating
of the ice against
the solid core,
you get the formation
of subsurface oceans.
Scientists now believe
that the ice on both moons
covers hidden oceans below,
with Europa holding more water
than all of Earth's oceans
combined.
And here, deep in the oceans
of these tiny moons,
could lie all the fundamental
ingredients of life.
If you have ocean water
coming into contact with rock
at elevated temperatures,
you'll get energy for life
that's not coming from the sun,
but from chemical reactions.
Worlds like Europa
and Enceladus,
where we've got good evidence
for vast, global,
liquid-water oceans
could be where a second
origin of life occurred.
Kevin thinks
there's a strong chance
that life could exist on Europa,
the larger of the two moons.
But how could you ever find it?
You wouldn't want
to go to Europa.
It'd be a beautiful view
of Jupiter,
but as soon as you stepped out
of your spacecraft, you'd die.
It's -280 degrees Fahrenheit,
there's no atmosphere,
and then the radiation
that would rain down onto you
would kill you within a matter
of tens of minutes.
Astronauts won't be attempting
to skate across Europa's
icy surface anytime soon.
So, NASA is studying ways
to send a robotic probe
nearly 400 million miles
to the bright moon
to hunt for traces of life...
But not before we know
what to look for.
If Europan sea creatures,
even microbes, existed,
and made their way
to the surface of the ice,
their cells...
And anything resembling DNA...
Would be heavily altered
by radiation.
But Kevin thinks we can hunt
for remnants of life
in the form of amino acids,
the building blocks of proteins.
So, if we found
amino acids in ice,
that could be
a pretty strong sign of life
within that ocean.
But how likely is it
that traces,
in the form of amino acids,
could survive on the surface
and be detected
by our spacecraft?
To figure that out,
Kevin and his team
are replicating some
of the conditions
on the icy moon right here
at NASA's Jet Propulsion
Laboratory in Pasadena.
In this latest test,
Kevin's molecular guinea pig
is glycine,
the simplest amino acid,
found in every
living thing on Earth.
We're mixing glycine
in with water
to kind of replicate what
could be in Europa's ocean,
were it to have life.
The mixture goes
into a stockpot,
a witch's brew
of water and salts.
Over three weeks,
Kevin pummels the glycine
with the sub-zero temperatures
and dangerously low pressure
you'd experience
on Europa's surface.
Finally, it's time to find out
if any glycine
survived the ordeal.
Okay, well, we've definitely
cooked up something
interesting in here.
If the amino acid
is completely destroyed,
the odds of finding
some sign of life
on Europa's surface
are slim to none.
It doesn't look like ice.
It looks like a very solid
but soft surface.
This is almost like
a creme brulee, I think.
Going in...
Ooh! Interesting.
Do you feel like there
was a... a tough crust?
No, no, it's very powdery.
Oh, look at that.
Hmm.
Kevin was expecting
a hard, icy shell,
but he's surprised to see
that the ingredients
have frozen into a thick powder.
You can see it's almost like
a layered, feathered material.
Now for the real test...
Kevin probes the ice with
a spectrometer,
using light
to seek out and measure
glycine's unique signature.
Can a simple amino acid...
A single building block
of life...
Withstand the harsh environment
of Europa's surface
and be detectable?
Get in nice and close
and we'll get
the maximum signal.
And like a beacon, it appears...
A small but clear
signal of glycine.
It means that if there is
microbial life
in the oceans of Europa,
we might be able to find
some of its building blocks
on the moon's icy surface.
Is this what the signal of life
on a distant world
might look like?
We just don't know.
The next thing to do
is launch a spacecraft
and go look for it
out there in the solar system.
Finding amino acids
on Europa's surface
would be encouraging,
but what we really
want to know is
what might be swimming
around in Europa's vast oceans?
Could there be microbes?
Like the ones that
dominated Earth's own oceans
for billions of years?
Or something more complex?
If we want to find out,
Then we need to send
a mission much deeper,
down through the ice and into
the pitch black oceans below.
But how do you prepare
for such an ambitious trip,
to a place unlike
anywhere on Earth?
♪♪
Engineer Bill Stone believes
he has the answer.
If you ask me
what is exploration,
it is the process
of putting your boot
in a place where no one
has ever been before.
Bill's "boot"
is an underwater vehicle
named Sunfish,
his prototype for
an ocean-exploring robot.
It might not look like much,
but if there's something
swimming around on Europa,
a miniature version
of this robot
could be the first to spot it.
It will be one of
the greatest intellectual feats
of humankind
if we pull this off.
NASA is studying
how to get to Europa's surface
in about 15 years.
Bill is planning for
a much more ambitious journey...
Fly a robotic lander
400 million miles to Europa
and land on the surface.
Bore through an ice cap
some ten to 15 miles thick,
then release an autonomous
underwater vehicle to explore
the mysterious ocean below.
Once you get through the ice,
Sunfish will go out
and map, explore,
and look for life.
This wouldn't be
the first robotic mission
in our solar system.
♪♪
Mars rovers have explored
the red planet
by following commands
that come from Earth,
34 million miles away.
That's not possible on Europa,
which is roughly three times
as distant as Mars.
The problem is there's
a two-hour delay
light travel time
between Europa and Earth,
so we can't sit there
and joystick something.
This robot must be able to think
and explore all on its own...
Or else it won't be able to see
much of the Europan ocean,
and the mission
to Jupiter's moon
could be a wasted opportunity.
Where would you like us
to position the robot?
To do that, it needs practice.
Here we go, heading east...
We're at Peacock Springs State
Park in northern Florida,
because there is
an underwater labyrinth, a maze.
The ground in
this part of Florida
is riddled with winding,
water-filled caves.
Can Bill's robot negotiate
this confusing environment
on his own?
A team of experienced
cave divers
tags along in case
the robot breaks down.
Other than that,
the robot is virtually alone,
using sonar to explore and map
its surroundings, inch by inch.
The robot doesn't know
anything about this cave,
and so it is learning
to explore as it goes.
So we're at 21, 33...
So, 240 points us
down the tunnel.
Things seem to be going well,
until, in one narrow cave,
Sunfish stops.
It suddenly seems confused.
It's drifting a lot.
It is.
What do you do
if something goes wrong?
What's your procedure?
All that has to
go into the code.
Zero, zero, 240-D...
A few lines of code
outline a new strategy:
back up and remap
from a different angle.
♪♪
This time, the robot succeeds.
♪♪
It's achieved the goal
and turning back.
This is a small step
that could one day
lead to giant leap in the search
for life beyond Earth.
If there's going
to be life on Europa,
there is no reason why we can't
have life somewhere else
in the universe.
Be the first validation
that we aren't the only ones.
So, from that standpoint,
it's going to shake
a lot of ground.
If we found evidence of life
on Europa,
even if it were just
a teeny, tiny microbe,
that would be huge!
All it needs is for one microbe,
that is life,
but not as we know it
to make the point
that it can't be that hard
to get going.
Just one microbe.
The importance of that
is to say, "Guess what?
"Biology's not very hard.
"It's an infection
in the universe, right?
It's all over the place."
If a galaxy oozing
with pond scum
doesn't seem too exciting,
then remember...
Over a few billions years,
these tiny creatures evolved
into all the plants and animals
that swim, crawl,
and fly around our planet,
including us.
So, could the same thing
happen somewhere else?
What do we think aliens that
evolved on another planet
would be like?
Flying saucers have
invaded our planet...
In lots of movies,
aliens look remarkably like us,
with two arms and legs...
Only you of Earth,
you and your women,
can give us life.
Get back or I'll fire.
You fool.
And, of course, those eyes.
From the standpoint
of Hollywood,
the aliens tend to be
these little gray guys
with big eyeballs,
and, you know,
no sense of humor,
and no clothes, by the way.
They seem very dispassionate.
They don't seem to get angry,
they don't seem
to have a lot of fun, either.
Come on down,
Mr. Ambassador.
Science fiction aliens usually
have something else in common
with us: intelligence.
But what are
the chances that life...
If it did arise elsewhere...
Would evolve into creatures
with big brains?
After all, aren't we the only
smart ones on this planet?
Come here.
Some biologists would say no...
Good job, buddy!
And they're not just talking
about our closest relatives.
From dolphins,
to birds,
to even the octopus...
A creature more closely related
to snails and clams than to us,
but smart enough to use tools
and open jars...
We're not the only animals
who've evolved
impressive brains.
Of course, none
of these creatures
will build a spaceship
anytime soon.
But for many scientists,
the idea that
we're the only technologically
advanced creatures
in the universe
seems a bit, well, presumptuous.
We used to think the earth
was the center of the universe,
that was wrong.
Then we thought the sun
was the center of the universe,
and that was wrong.
Then we thought our galaxy
was the center of the universe,
and that was wrong.
Every time we've thought we were
really special, we were wrong.
And so, the idea
that we're somehow special
in terms of being alive
or being intelligent,
I mean, that's
probably wrong, too.
I find it extremely hard
to believe that
in the vastness of our universe,
that a rocky planet that harbors
intelligent, sentient life
happened just once.
♪♪
Some scientists have spent
their entire careers
hunting the vast emptiness
of space,
trying to pick up a signal.
I always just took for granted
that there would be
other stars that would be suns
for other creatures,
and that just seemed to me
the natural way of the world.
More than three decades ago,
astronomer Jill Tarter
co-founded the SETI Institute,
dedicated to the search
for extraterrestrial intelligence.
It's been amazing
to be able to spend
a career on a question
that I'm fascinated with
and a question
that everybody else out there
is curious
to know the answer to.
She was the inspiration
for the character
Dr. Ellie Arroway
in Carl Sagan's book "Contact,"
which was adapted
to a feature film in 1997.
Today, SETI conducts searches
with the Allen Telescope Array,
a network of 42 radio telescopes
in Hat Creek, California.
The telescopes comb the skies
for radio waves,
which can carry signals
and information across
the great distances of space.
Radio waves are an excellent way
to communicate
because they cut through
the atmosphere of our earth
and also cut through
the space between the stars.
In fact, we've been sending out
our own radio waves since
the dawn of broadcasting,
about a century ago.
Good morning, honey.
If any aliens are listening,
their ideas about earthlings
could be based on
"The Dick Van Dyke Show."
I said, how's my old lady?
Well, I don't know,
I haven't spoken
to your mother lately,
but I'm fine.
The hope of SETI
is that some aliens
might also be broadcasting.
The idea is that
if life has sprung up
on some other worlds
and it's technological life,
in other words,
they've, you know,
they've learned
a little bit of physics,
they build some equipment,
this, that, and the other,
they could build
radio transmitters
that are sending
signals into space
that we could pick up here.
At Hat Creek, the telescopes
listen in on millions
of radio channels at a time,
looking for unique patterns
that could be
alien transmissions.
When something shows up
that we don't think
is interference,
something that
we've not seen before,
immediately we follow up
on that signal
to try and figure out
what it is,
and whether it's, in fact,
our technology
or potentially someone else's.
But unique signals are rare...
Just one or two a year.
And so far, even
the most promising ones
have turned out
to be human interference.
Still, the event
that SETI is waiting for
could happen any day.
Okay! Point source confirmed.
Whatever it is, it ain't local.
While Hollywood has fantasized
about this moment of discovery,
it's harder than it looks.
The Allen Telescope Array
can only listen
to a few hundred million
out of billions
of possible radio frequencies
at a time.
We haven't yet figured out
how to look at all the sky,
all the time,
at all frequencies,
but that's ultimately
what we want to do.
In fact, we've been listening
for nearly 60 years,
and so far... crickets.
But the fraction of stars
we've searched carefully
and the amount of time
we've been listening
are still both quite small.
So plenty of people
remain hopeful
that technologically advanced
civilizations are out there.
And that's why
the mysterious dimming
of one particular star
was, for some, so tantalizing.
♪♪
In 2015, astronomer
Tabetha Boyajian
and her colleagues
published their findings
about a very weird star.
According to data
from the Kepler Space Telescope,
Tabby's Star was dimming
at strange, irregular intervals,
sparking theories
about an enormous structure
built by a hypothetical
advanced alien civilization.
The buzz spurred more research.
Today, a worldwide network
of powerful
ground-based telescopes stare
at Tabby's Star
around the clock.
We can actually process the data
in near real-time,
and when we see something
start to happen, we can trigger
more intense observations
of what is passing in front of
the star at that time.
For a while,
the star was silent.
Then, suddenly, it started
dimming erratically again.
The ground-based telescopes
provide information
about the star
that Kepler couldn't see.
Not just the dimming
of the star,
but how those dips
in brightness appear
in different colored
wavelengths.
Something is happening
with our star here...
We sent off alerts via Twitter
and data of all sorts
started coming our way.
At this point,
it's like we're swimming
in data.
Tabby and her team
at Louisiana State
are looking for patterns
in the color data
that could tell them
what kind of material
is passing in front of the star.
Blue light and red light
will react differently
to material that's passing
in front of the star,
and you'll have
a different signature
in how far down these dips go.
Whatever is passing
in front of Tabby's Star
appears to be blocking
more blue light
than red and orange light.
But what would block out
more blue light?
Tabby has a theory:
space dust.
Dust scatters blue light
more than it does red light.
And so, that indicates
that there's some sort of dusty,
semi-opaque, you know, material
that's crossing
in front of the star
and blocking out the light.
It's got the signatures
of being dust, rather than...
it can't be some kind of
completely opaque object,
like a planet or
an alien megastructure.
That's right.
The culprit is likely
scattered dust,
and not a solid
alien megastructure.
But the mystery
is hardly solved.
What created
this giant cloud of dust?
Why is it centered
around Tabby's Star?
Astronomers will need more data
if they're ever going
to crack this one.
Nature is a lot more creative
than we are,
and you know,
we're just going to have to,
you know, really buckle down
and try and, and,
and figure this one out.
Tabby's Star is one
in a long line of mysteries
that at first raised hopes
for finding E.T.,
but later were revealed
to have solutions
unrelated to life.
For some, the lack
of firm evidence is troubling.
In 1950, physicist Enrico Fermi
went to lunch
with some colleagues
and asked a simple question:
"Where is everybody?"
If there are billions of
habitable planets out there,
and life is common...
Why haven't a bunch of aliens
already shown up
on our doorstep?
What could explain the silence?
For some, the quietness
of the cosmos
is evidence that
we really could be alone.
But many astronomers disagree.
The idea that there's
intelligent life out there
that has never
interacted with us
or that we've never seen it...
That, to me,
is not confusing at all.
I mean, I think that's
perfectly consistent.
You know, it's no different than
a child looking at an ant farm.
The child is not going to be
compelled to interact
with an individual ant
and more so, the ants
probably don't even know
that the child
is analyzing the ant farm.
And so there's very likely
intelligent civilizations
out there that
may be looking at us.
But what do they have to gain
from interacting with us?
We might be very
basic and insignificant
compared to them.
Or perhaps interstellar travel
is too challenging,
even for super-smart aliens.
Or maybe they did exist,
but ended up
destroying themselves.
♪♪
For many, the universe
is simply too large.
Too many stars,
with too many planets.
Too many potential homes
for creatures
that might start small,
but could, like us,
thrive and grow.
The universe is mind-boggling.
It's bigger than
what we humans can actually
wrap our consciousness around.
The universe has hundreds
of billions of planets
in hundreds of billions
of galaxies.
So it just seems like
when you roll the dice
many, many times, one of them
is going to luck out.
We live in a groundbreaking era.
We might be the first generation
that will be able to say
that there is life elsewhere
in the universe.
Our young people
have a much greater opportunity
to see themselves as earthlings.
But we also could find out that
to the best
of our ability to measure,
we really are alone.
If it turns out
that Earth is rare,
then that's all the more reason
to look after what we've got.
Because if we destroy ourselves,
the flame of mind
and the flame of culture
will be snuffed out for good.
I hope that we aren't
the only things out there.
There's gotta be something else.
You know, there's just
a lot of room up there.
It's hard to believe that
everything interesting
is down here.
It just never struck me
as a very reasonable
point of view.
Are we alone in the universe?
Not a chance.
♪♪