Original subtitles

(dramatic techno music)

This is a vision of our future,

the fateful day in a far-flung corner of the universe,

when a probe from Earth

initiates the first descent onto an alien world,

looking for proof of life beyond our solar system.

(dramatic orchestral music)

There are no witnesses,

no cheering crowds in the control room.

(swooshing)

A decade or more will pass

before news finally reaches us,

back across the dark oceans of space.

But the seeds of this mission

are already being sowed today

by the first generation of scientists

bold enough to believe it could be possible.

When I look up in the sky and I see, not stars,

I see planetary systems.

We must understand that the journey to exoplanets

is not limited by the laws of physics.

(roaring)

They look to planets orbiting distant stars,

searching for an answer to the oldest human question.

Are we alone?

Is there life on other worlds?

And if not, why not, and if so, how?

This is the first generation in human history

where we have the technological ability

to actually go and answer that great question.

This is the story of humanity,

launched into the final frontier

by a new breed of adventurers, the planet hunters,

engineers, explorers and dreamers,

taking the first steps on an inter-stellar journey

they know that they will not complete.

That.

The journey of a future mission,

searching for a second genesis

among the stars.

A spacecraft that goes to another star,

to look for life, on a planet out there,

Earth-like, in the Goldilocks zone,

where liquid water could exist in great quantities.

And when will that process begin?

Ah, we are on the cusp of discovery.

(suspenseful music) (sonic tinkling)

(dramatic music)

(sonic hissing)

(dramatic music)

I am Artemis.

I am the mind of the mother ship.

I am the body that has traveled

to where human bodies can not go,

to an alien world 4.7 light years from Earth,

on a mission to solve the mystery:

is there life beyond our solar system?

(dramatic music)

I release my landing module into the atmosphere

of the exoplanet Minerva B.

(swooshing) (dramatic music)

Two centuries of human labor

and human hope

have brought me to this moment.

(sonic whirring)

And I am ready to touch down.

I am ready to explore.

I am ready to discover life.

(suspenseful music)

(mellow piano music)

Four and a half billion years ago,

in the nursery of the heavens,

a star was born,

a giant cloud of dust and gas,

distended and ballooned,

until under the burden of its gravity,

it collapsed upon itself,

swirled into a disk,

and forged a solar system from the dust.

That star was our sun.

(dramatic orchestral music)

Of the planets that were formed,

only one that we know of

gave rise to life.

(water rushing) (dramatic music)

But could our sun, our solar system,

our living Earth,

have produced the only genesis

among the stars?

(pensive orchestral music)

My intuition is that the universe is full of life.

There's no reason fundamentally,

it might not look like Earth,

with vegetation and animals.

Well, the question I'm interested in

is really the start of life.

And on Earth, we see for a long time,

life was just microbial, where all

the essential features of life were there.

Nothing new was invented

when life became trees and animals.

That's just morphological,

it's just window dressing.

To me, it's actually not very interesting at all.

Everything interesting with respect to biology

was present when there were no trees and no animals

and life was just microscopic.

The DNA was there, the amino acids were there,

all the biochemical machinery

that makes life life was there.

(lighthearted music)

Life is a miracle and an enigma,

even to those who've spent their own lives

trying to crack the code.

NASA planetary scientist Chris Mckay is one of them,

part of the generation of scientists

on a quest to find a second genesis beyond Earth.

The search for life began with a lot of optimism,

focused on Mars.

(suspenseful music)

Here was a planet that could have had a thick atmosphere,

could have had water in the recent past,

and in the popular literature, at least, still had water.

So, the search for life on Mars

really was thought to be easy.

In 1976, NASA's Viking mission

made the first-ever landing on the Martian surface,

looking for the life that had been hoped for.

Well, it turned out a lot harder.

Nature was guarding her secrets

much more closely than we imagined.

So then things basically went quiet

in the search for life.

And I think they were sparked again,

not on Mars, but in the outer solar system.

Three, two, one (blasting),

and liftoff of the Cassini spacecraft

on a billion-mile trek to Saturn.

In the final decades of the 20th century,

humanity launched a series of ambitious missions

to explore the outer solar system.

Standing by for Saturn rocket boosters.

All systems go at this time.

The discovery of liquid water

on the moons of Jupiter and Saturn,

in the misty plumes of Enceladus,

and the subterranean oceans of Europa and Ganymede

has opened a thrilling new chapter

in the search for a second genesis.

The impact of identifying a separate origin of life

on one of these worlds

would extend far beyond our solar system.

Finding life that's distinctly different,

that truly represents a second genesis of life,

well, that would tell us that the answer's not one,

it's two, in terms of life in the universe.

And going from one to two is huge

because in the scale of the universe,

the only numbers that make sense are

zero, one, and infinity.

And what we learn in our solar system

will then guide how we search for life beyond.

(upbeat music)

The renewed optimism

in the search for life within our solar system

emerged alongside the discovery that transformed

the way we see the universe.

In the early 2000s, NASA's Kepler telescope revealed

that every star in the galaxy, just like our sun,

is orbited by at least one planet.

And up to a quarter of these so-called exoplanets

are believed to be suitable for life.

(mellow music)

In a milky way (mumbles),

that means roughly 400 billion solar systems

and 80 billion potentially habitable worlds,

the odds of finding a second genesis

have never been better.

(mellow music)

[Jonathan Voiceover] The way I like to think of this

is that life will arise anywhere

where the conditions are right.

And the trick in that is

what constitutes the right conditions.

Planetary scientist Jonathan Lunine

is another veteran in the hunt for life beyond Earth.

(pensive orchestral music)

But what exactly is life?

And how does one search for it?

The basic essentials for life to begin and to exist

are liquid water,

organic molecules because carbon

is really the essential versatile element

that can combine with other elements

in many different ways to make the structures of life.

Free energy,

and minerals and nitrogen

to provide the other elements

that are required to keep the chemistry going,

to generate catalyst that generate more catalyst

and more structures, until we get to the complexity

of a primitive cell.

(water rushing)

Liquid water,

carbon molecules,

energy, minerals,

and the secret formula

that animates it all into a living cell.

(mellow music)

These ingredients, this recipe for life,

is what our scientists are hunting for

on other worlds.

(somber music) (sonic tinkling)

I deploy my spider bots

onto the Minervan surface.

I 3D-print a fleet of drones

and I let them fly.

(whirring)

With these eyes and these instruments,

I will taste, and touch, and see

this new world for the first time.

Will I find all that is hoped for?

(upbeat music)

Exoplanets are the new frontier

in the search for life beyond Earth.

But the prospect of exploring distant worlds

presents an expanding universe of rivers to cross

and mountains to climb.

How on earth can we prepare to explore planets

we know so little about?

(upbeat music)

Exoplanets present a real challenge

because there's so much uncertainty.

So, knowing whether or not you're going to find

a cliff face versus a desert,

versus an ocean, versus an ice tundra,

we may not know when we launch.

See, you gotta design your system

to survive and operate in all of those possible conditions.

At NASA's robotics headquarters

in Pasadena, California, around 100 young engineers

are busy reinventing the wheels

of the robots of old.

With plans, our exploration started with a

large robot that was very stable, very safe.

And now we're beginning to take more risk.

We're trying to get to new places,

trying to shrink down the size of the platform,

do more with less.

It's a pretty perfect ledge over there.

Yeah. Just the sort of thing

other robots can't fit into.

(bright orchestral music)

Some of our robots are designed

to climb up different surfaces.

So we have a claw-inspired robot

that uses sharp hooks to grab on to the rough surface,

kind of like an insect or a rock-climber

would scale up a cliff.

We also use electrostatics to stick to surfaces,

so this is by rubbing the balloon on your head

and it sticks to the wall.

(mellow music)

One of the key innovations

in the new breed of robotics is biomimicry,

using biological systems and processes

as the model for design.

To look for life, behave like life.

We have created a material

that has mechanical properties similar to that

you see in biological tissues.

We have already, with this system,

developed swimming robots.

There's a lot of work today in robots

that can go between dry surfaces and water-like surfaces.

Wherever we find water on Earth, we find life,

so we have a strategy that we've used on Mars

called follow the water.

I think we're gonna use that same strategy

when we visit an exoplanet.

(soft suspenseful music)

I follow the alluvial plain

of the retreating glacier.

My hydrometers detect increasing humidity.

(hissing)

(dripping)

I am on the scent of fresh water,

tracing its inevitable cause,

its branching channels

over wide flat plains,

consuming rock and mineral.

(water rippling)

Now growing brackish,

perhaps estuarine,

fresh water and sediments

meeting the insistent flow

of an incoming tide.

There is a river ocean system on Minerva B,

an ideal breeding ground for life.

(mellow music)

This is a place where there's life,

but it's not life as we're familiar with.

Here, life is pink and living in saturated salt.

It's not the kind of green things

we normally think of as life.

The salt ponds of San Francisco Bay

are a naturally occurring wetland,

reshaped by human industry

and colonized by trillions of colored microorganisms.

These are a type of halophilic archaea.

It's a particularly unusual type of microorganism.

It's extremophile, it requires high salt

and it (mumbles) in an environment

where only it can survive, so it dominates,

so where it grows, it grows well

and it's the king.

What these salty bugs have in common

with everything from oak trees to humans

is access to liquid water.

(splashing)

(upbeat music)

All life on Earth, in some sense, is fragile.

It's all tied to the availability

and the chemistry of water.

We tend to think all life on Earth

is expanded to all the corners of the Earth,

it's really, it's everywhere.

That's because water is everywhere on this planet.

This is a water planet.

And when we look beyond the Earth,

we realize that water is, in fact, rare.

The liquid state of water is rare

and life is not the all-conquering capability.

Life can only squeeze itself into those environments

where there's liquid water.

(waves crashing)

Water's interesting in that

if we look at carbon,

which is the next part of the recipe for life,

where water is liquid, carbon can be a solid,

a dissolved ion, or a gas,

all co-existing in the same place.

Carbon is an unusual element

in that it is capable of making

many, many different kinds of molecules.

There are literally millions of organic molecules known.

And water then becomes the milieu in which

all of the chemistry of carbon that leads to us

is gonna take place.

Carbon-based organic molecules,

like amino acids, are the building blocks of life,

combining in liquid water to form the structures

of every living cell.

On Earth today, these complex molecules are everywhere.

But where do they come from?

(suspenseful music)

On Earth, the problem we have

and the scenario of the origin of life

is that when the Earth formed around 4.5 billion years ago,

it had a turbulent period in a (mumbles),

with very intense meteor bombardment.

(ominous music)

It was an extremely hot environment,

which was not conducive to the emergence

of complex organic molecules.

(roaring) (crackling)

One of the ideas that emerged around this is,

could some of this organic matter have come from space?

(roaring)

In March 2004, the European Space Agency

launched the Rosetta spacecraft

on a hunt for the building blocks of life beyond Earth.

Its destination was 250 million miles away, and counting,

a moving target hurtling through space

at 37,000 miles per hour,

a lump of ice and dust the size of Mt. Fuji,

the comet, 67P.

Rosetta's mission was to land on it

and find out what it's made of.

From 2011 onwards, Nicola Altobelli

was Rosetta project scientist.

We think that comets, when they were formed,

remained somewhat frozen in a state

that has not changed for billions of years.

So the idea is, maybe they've incorporated

the organic material that was already present

in the molecular cloud from which the solar system evolved.

Because comets formed

in the icy outer regions,

they hold a frozen record of the solar system's birth.

And as the young Earth cooled

and oceans formed around four billion years ago,

some of those same comets

came crashing down to Earth.

So could it have been comets,

bearing the carbon-based organic molecules

from our solar system's birth,

that seeded life on Earth?

It was the task of Rosetta's landing module,

Philae, to find out.

(dramatic techno music)

The landing was a time of very strong emotions,

and it took place over a full day.

It was the 12th of November 2014.

(tense music)

In the morning, there was confirmation of the separation.

(mellow music)

The first image arrived,

taken by the lander when it was separating from Rosetta.

Then there were seven hours of waiting.

(suspenseful music)

Around 4:00 p.m.

came the confirmation of touchdown.

(clapping)

But the followup signals suggested

something wasn't right.

(speaking in foreign language)

The first panoramic images

that were taken of the surface

showed an orientation of the lander

which was not as it should have been.

And as the hours passed, we realized

that the anchor had failed.

(dramatic music)

Philae had bounced back into space,

then bounced a second time

before finally coming to rest

several hundred meters away.

(tense thumping music)

I remember someone saying,

"Philae dances a little zumba."

But we performed most of the scientific experiments

that were planned.

One can even say,

because it bounced in several places,

it allowed us to obtain data

from different areas of the comet.

And the orbiter perfectly fulfilled its mission.

(clapping)

The results were remarkable.

Philae detected 16 organic molecules

in just a tiny sample of dust

kicked up by the initial touchdown,

among them, some of the key building blocks

of life on Earth.

50% by mass of the dust particles

ejected by the comet is organic carbon-based material.

This organic material came from the molecular cloud

from which the solar system was born.

(dramatic music)

And thus, may have seeded Earth

with all this organic material.

The organic molecules necessary

for the emergence of life on Earth

were already present in space.

(dramatic music)

Rosetta demonstrated

that the building blocks of life on Earth

were created during the birth of our solar system.

(water rippling)

(twittering)

But what about beyond?

Could these same vital ingredients

be part of the birth of all stars?

Looking back at our own Earth

and why we have this breach in our biosphere,

well, I think it all started with having

all these organic material that we are made up of,

that that was delivered from space,

from comets, and from asteroids.

So we're thinking about the likelihood of life elsewhere.

We're pretty much thinking about the likelihood

of having that same scenario taking place.

In 2015, high on the arid mountains

of the Atacama Desert,

Professor Karen Oberg set out on a hunt

for the building blocks of life

in a birth cloud on an alien star system

with the help of a new telescope called ALMA.

ALMA consists of 66 individual telescopes

that's all working together.

It operates at millimeter wavelengths,

and millimeter wavelengths is

where we can detect molecules,

(mumbles) organic molecules that we are so interested in.

Oberg turned ALMA's gaze

towards the Taurus system and found a young star,

MWC 480, in the throes of labor,

girdled by a disk of gas and dust

from which planets were being born.

We see this dusting gas

that's surrounding these young stars.

And what's even more exciting,

we see that they often have little lanes

or tracks in them,

where it looks like planet formation

is going on right now.

After months of collecting

and analyzing the data,

Oberg announced the discovery

that blew the odds wide open

of finding a second genesis on other worlds.

In the disk of this alien solar system,

ALMA had detected some of the same organic molecules

that helped give rise to life on Earth.

We found three kinds of cyanides,

three molecules and the same chemical family,

and those three kinds of molecules

have also been found in our old solar system and comets.

The same organic molecules

with the same miraculous potential to create life

are out there among the stars.

(lighthearted orchestral music)

Chemistry is awesome.

It's the reason that we are alive

and that we're here in the first place.

So far it's only, you know, bond system,

apart from our solar system

where we have this chemical information.

But my intuition would be that it's gonna be very common.

This kind of chemistry is gonna be almost universal.

(plaintive orchestral music)

I scan for sights of geochemical activity.

I find a hydrothermal field of fumaroles

and hot springs.

On Earth, such conditions are rich

in carbon chemistry and minerals.

I find another mineral-rich water source upstream.

I identify complex molecular structure in solution.

(fast beat music) (sonic tinkling)

I extract a sample for analysis.

(fast beat music) (whirring)

And return it to the lander module.

(whirring) (fast beat music)

Could this be evidence of life?

(fast beat music)

(mellow piano music)

Let's get the samples here. Yeah.

Can stick another measurement.

The laws of chemistry and physics are universal.

So it's a given

that when we go to another Earth-like planet,

with water, with the sorts of minerals

that we have here in the iron core and atmosphere,

it's inevitable that this kind of simple chemistry

would have been present.

Okay, it's 15 degrees up here.

Let's see what this little guy has for us.

As long as there's a chance for energy

to interact with that mixture, things will happen.

Wow, look at that. One degree, keep going up.

The question that we are heading for right now,

how certain can we be

that that mix of simple chemistry

could take the next step in complexity

so life could begin?

In the hydrothermal fields

of Bumpass Hell, California,

all the ingredients of life are brought together:

water, carbon molecules, energy, minerals.

Be careful of the end not coming out.

Biologists David Deamer and Bruce Damer

believe this is the kind of environment

where life could get started on another world.

Bubbling pools, strange-colored rocks,

water of different pHs,

all kinds of flows and dynamics, steam rising,

it looks like nature's chemistry is set.

And it's an engine, an actual engine

for the beginning of a living system.

(suspenseful music)

Conditions like this

defined the early Earth.

Evidence of similar environments

has been found on Mars,

and researchers expect hydrothermal fields

to be a common feature of Earth-like exoplanets.

But how might nature's chemistry set

cook up the recipe of life?

(fast beat music)

Everything that's alive is, in fact, based on polymers.

Everybody knows the name, DNA, nucleic acid,

that's one of the polymers.

Proteins, these are amino acid polymers.

And that's basically the start of all life,

are those two polymers.

(upbeat techno music)

So what we're doing is taking small molecules,

the pieces of a polymer called monomers, in fact,

and we're exposing them to energy,

such as you see here at Bumpass Hell

and seeing where that energy is sufficient

to make those monomers link up,

one after another after another, to make a polymer.

And, in fact, if we can make a protein-like molecule,

and a nucleic acid-like molecule,

and put it into a little wrapper, a compartment,

we're underway, we call those protocells.

Each sample contains organic molecules,

or monomers, exposed to the mineral-rich steam

and heat energy of the fumarole

in an attempt to form a protocell.

We think that drying out, such as you see

all around us here at Bumpass hell,

water coming in and drying out,

coming in, drying out, that's a cycle.

We think that that cycle is very important

to drive the process by which polymers

are synthesized and then accumulate.

Let's go for it.

Failure.

Are you sure?

Yeah, there's nothing there.

The first experiment fails,

just as it would do many times

on an Earth-like exoplanet.

But if all the elements were present

in conditions such as this,

this experiment in life would repeat again and again.

Some of them got lot of liquid in.

One last try.

Given enough time, and keep in mind,

we have an inter-planet

with lots of volcanic land masses coming up,

with lots of puddles like this trying to

learn how to become alive, mostly is failures,

but it will only take a few successful protocells

that happen to be able to survive

and had learned how to make more than cells.

So go ahead and get them into the boxes.

And then?

(mellow orchestral music)

Is the universe made to make life?

This is a huge question that sort of

beyond the scope of perhaps humans

to be able to answer.

But what we can observe

is everything comes down to cycling.

It comes to rhythms,

and overlapping rhythms and patterns.

And it's almost as though if you get

the right cycling and patterning in a system,

it learns how to do that itself,

and how to lift itself into being.

And so, perhaps, that's the closest metaphor that we know

that the geology gave us that ability.

The moon going around the Earth gave us tides.

The rotation of the Earth gives us days and nights.

Rainfall into these hydrothermal fields

gives us geysers that are periodic.

And life still follows rhythmic patterns.

(mellow orchestral music)

That's the clue we have.

So, perhaps, it's the universal harmonic

that creates life.

(mellow orchestral music)

(upbeat music)

Most of us tend to think of things

as either alive or dead.

But the transition from not alive,

the inanimate state to the animate state,

is that transition only possible as a single step?

Or is it possible as a series of steps?

If it's possible as a series of steps,

then the intermediate stage would be partially alive.

Now you might say, "Well, come on.

"It's either alive or it's not."

Now I'd say, well, alive means it's got cells,

the cells are replicating,

the cells are doing this, that, and the other.

And you need all of that to be fully alive.

But the chance of getting that all in one go

seems a little bit remote.

So maybe we got one of the attributes early on,

and then it acquires another attribute, and another,

and eventually reaches the point where it is fully alive.

(mellow music)

Professor John Sutherland

is trying to retrace the steps in the origins of life,

in search of the processes that animate a cell into being.

Of course, a cell is more than just

the chemicals that comprise it,

because a cell has just died,

it is still the chemical that it has,

so there's something that energizes it,

that coordinates it,

and we don't know how to get that,

but that's the goal.

(mellow music)

So what we're doing here is putting the sample

into an apparatus in which it will be

irradiated by ultraviolet light.

(upbeat music)

In a series of experiments

that simulated the conditions of a young rocky planet,

Sutherland successfully achieved stage one,

producing the basic components of a cell,

lipids, proteins, sugars, and nucleic acids.

What we found is that you can make

all of the components for life,

under slightly different conditions.

When you first see it happen, it's like magic.

But it isn't magic, it's not as hard to make

as we originally thought.

(mellow orchestral music)

All the hardware of a cell

can be created from a single base molecule

that's widespread among the stars.

But what about the next step?

How is that hardware organized

and energized into life?

If the conditions are the same elsewhere,

what are the chances that you can get

some building blocks to life?

The chemistry of cells is unique in itself and organized.

So, one part of chemistry is actually controlling another,

and yet, somehow that's controlling the first one.

Chemists are used to controlling the chemistry themselves,

and the idea of letting things run

and go off of their own accord is something

that goes slightly against your chemical education.

How can chemists say, place, if you like,

with the experiment to just setting the system up

and then letting it go off its own accord?

(mysterious music)

Life is information that can reproduce itself.

Not hardware, it's genetic information.

That's the key to life.

It's the information and the DNA,

and the ability of the DNA

to express that information of proteins,

and propagate the information that way.

DNA is the blueprint

for all of life on Earth,

an instruction book for how to make

and maintain all living organisms.

Encoded in the twin coiling lines of a double helix

is the genetic information that tells life

to build a rose, or a leopard, or a blue whale.

If we find DNA on other worlds,

there's no doubt that there's been life there.

The characteristic molecules and life makes,

the genetic molecules that contain information,

like DNA, these molecules do not arise non-biologically.

They have to be built, the surest as,

if we find a skyscraper on Mars,

we know that it was built

and it's not just a random assemblage of rocks.

That's how we will find evidence of life.

(sonic tinkling)

My lander module prepares to uplink

the sample data from the hydrothermal field.

My optical communication transmits

via hybrid silicone laser at 12 gigabits per second.

I receive the signal and ingest the data for analysis.

Organic, polymeric, triple helix structure.

Some consistency with terrestrial forms,

and yet, unlike anything I've seen before,

a bio-molecule of alien life.

(suspenseful thumping music)

[Martin Voiceover] We have come to a place

deep in the outback of Australia,

looking for what we think is evidence

for the oldest life on Earth.

Astrobiologist Martin von Kranendonk

is traveling back in time,

to the dawn of life on Earth

over three and a half billion years ago,

conveniently recorded in the ancient rocks

of Australia's remote northwest.

At this time in early Earth,

it was a very different planet

to what we have today.

We would have had some shallow seas,

but those seas would have been green,

'cause they were rich in iron.

And if we look up at the sky,

the sky wouldn't have been the beautiful blue

that we see behind us here.

On early Earth, without oxygen,

the sky would have been orange.

We would have seen black continents of fresh basaltic lava.

(rumbling)

It would have been very active,

so there would've been faults and earthquakes,

and there would have been bubbling geysers

that were going off.

It was actually a very alien thing.

Yet this alien Earth

was already inhabited.

Colonizing the shores of the crater lakes

and the seas that washed the ancient (mumbles) land mass

was a living skin of slime.

But the bacterial communities

that left the clearest fossil (mumbles)

built up their homes in high-rise mountains.

So the really wonderful thing about this outcrop

is that we can look down

and see the sea floor so long ago.

And really, you get this incredible view of

the gentle undulations of the water

moving across the surface,

but then popping up through are these domes,

and cone shapes, all irregular,

different sizes, different shapes.

These distinctive bumps

are the fossilized dwellings

of the oldest living organisms on Earth.

It was here, over three and a half billion years ago,

that stromatolites first raised their heads

above the water of an ancient shore.

They can start to get a feel for life,

grab in a foothold, in the geological record.

And so this currently still is the oldest

semblance for life on Earth.

It's our great, great, great, great, great, great

grandmothers and grandfathers.

It's really the precursor to everything that came later.

All the green bushes and the trees,

that all started here.

(mellow orchestral music)

The prehistoric organisms

that built stromatolites were so successful

they ruled the Earth for up to three billion years.

Life finds a way,

and somehow, these crafty architects

found a way to organize water,

carbon molecules, minerals,

and energy into a living cell.

(pensive orchestral music)

Is this what we should be looking for on alien worlds?

(suspenseful music) (sonic tinkling)

My drones survey the dried up basin

of an inland sea.

But what's this?

A lone survivor on the arid plain?

Zerophite, succulent stem,

phycobilin-like pigments

to absorb the red dwarf sun.

A hybrid of terrestrial and aquatic species.

(pensive orchestral music)

Around 500 million years ago,

long since stromatolites first took root in the shallows,

Earth's oceans bloomed with animal life.

(lighthearted music)

It was a very different world

to the one that had made way for microbes,

with air to breathe now,

and a protective atmosphere

under a gentler sun.

We think microbial life

is gonna be very common,

that the conditions to produce microbial life

happen over and over and over

in many, many different planets,

but that animal life is only gonna be able to evolve

and then stick around for any length of time

when you have really stable conditions.

Professor Peter Ward

is one of the originators of the Rare Earth hypothesis,

the theory that a long-term habitability

of Earth or animal life

may be rare in the galaxy.

Habitability is really the ability

of a planet to have conditions

that can allow life, first to originate

and second, to stay alive.

(pensive music)

Habitable worlds can be just a short instant in time,

and then it changes and again is nasty.

So what to us made Earth rare

is the long-term habitability of the planet.

The fact that it has remained constant in temperature,

with the oxygen values we have,

that we don't have these extremes in climate,

that we've got this constancy,

that's the rarity of it.

(waves gently crashing) (sonic tinkling)

My drones detect a disturbance

in the electromagnetic field,

a network of forged metallic structures,

bearing the mark of industry.

This is not plants.

This is not animal.

But this is evidence of life.

(dramatic orchestral music)