All language subtitles for How The Universe Works S04E04 Dawn Of Life_ENG_Subtitles01

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There is an unbreakable bond
between life on Earth...

..and the stars above.

Everything we see up there and down
here is made from the same stuff...

..atoms.

The question is, how did these
atoms come together to make us?

And are we the only life
asking this question?

Everything we see in the universe is
made from the same building-blocks.

The universe is only made up
of a handful of basic ingredients -

hydrogen, helium,
lithium, carbon and so on.

All of these chemicals, in different
proportions, are what make us up,

and these same chemicals
in different proportions

make up everything.

The same chemicals
that form galaxies and stars,

do something amazing on Earth,
perhaps even unique...

..they become living things.

Organisms that can grow...

..reproduce and think.

We are bits of the universe
made conscious.

I think that's a...
It's a biological miracle.

You look out into the sky

and you know you're connected to
that somehow. It's pretty fantastic.

The story of life on Earth actually
began long before Earth even existed.

Immediately after the Big Bang,

the universe was
a vast cloud of hydrogen gas.

Pockets of the gas cloud
collapsed to form stars.

The stars turned hydrogen into
more complex atoms and molecules.

I don't think there's any
way you could make life

out of just hydrogen.

You need other compounds to give
you the more complex chemistry.

The start of life was really
the start of the first stars,

probably about half a billion
years after the Big Bang.

Deep inside the cores
of these early stars,

heat and pressure crushed hydrogen
atoms together so powerfully,

they fused...

..creating helium atoms
and releasing a burst of energy.

Over time, helium atoms
fused together, too,

creating carbon, nitrogen,
oxygen and even heavier atoms.

Over hundreds of millions of years,

ancient stars built up
all the elements

that make up our solar system today,
including the atoms in your body.

But in doing so, these stars
paid a catastrophic price.

Drained of energy, the ancient stars
collapsed and then exploded.

A supernova...

spreading their chemically
rich stardust across space.

The iron in your blood, the calcium
in your teeth, in your bones.

These were created
in a supernova explosion,

probably different stars
that blew up billions of years ago,

seeding the space
around them with this stuff.

We are the product of
not just one stellar explosion,

but many stellar explosions
and the atoms in our left hand

probably came from a different star
than our right hand.

The carbon, nitrogen, oxygen, iron,

all of that was
only created in stars.

And the only way
it could get here on Earth

is if those stars exploded

and that material was later
amalgamated in our solar system.

Blasted into space,

these complex atoms
pepper the clouds of gas

that then themselves
become the nurseries for new stars.

4.6 billion years ago,

one particular cloud began
to collapse under its own gravity...

..and the sun ignited.

Most of the ancient stardust
was sucked into the sun.

What little remained
went on to form the asteroids,

comets, planets
and even the plants and the animals

that inhabit the Earth today.

I actually think of myself
as a very complicated rock.

I am made of things like iron
and copper and manganese.

When you sit down on a mountainside
and you're there with the rock,

those are your cousins, too.

Thanks to the remnants
of ancient stars,

the Earth formed with all the atoms
needed to create both rocks and life.

But what is it that distinguishes
life from mere chemistry?

There are essentially three
main parts to a living organism.

You've got to have some metabolism

or some kind of system of chemical
reactions that powers your life.

You've got to have some kind
of bag or sack that walls you off,

your internal systems
from the outside environment.

And thirdly, you've got to store
some kind of blueprint,

some kind of
description of yourself.

Three things set life apart...

..a power source, a protective sack,

and the blueprints for
making duplicates of itself.

On Earth, every living thing
has the same kind of blueprint.

It's a chemical code called DNA.

DNA contains the instructions
for how to build the cell's engine,

using small molecules
called amino acids.

DNA also tells the cell
how to make lipids,

the fatty molecules that
form the protective sack,

and that's it.

The most basic form of life - a cell.

The chemistry set for
life is actually quite simple.

It's 20 amino acids,

it's a few nucleotide bases
for making DNA and RNA,

a few lipids and that's it.

Think of it as like a Lego kit.

Scientists wanted to
find out where the ingredients

for this simple
kit-of-life came from.

In the 1950s, chemist Stanley Miller
set up an experiment to find out.

He filled a series of flasks
with water vapour and volcanic gases

to recreate the early atmosphere
of the Earth.

And then he sent an electric spark
across the mixture

to simulate lightning.

The result
was a foul-smelling gunk...

..that included one of the three
basic building-blocks for life.

We find, produced in these
experiments, some amino acids.

Some of the same amino acids
that are produced in life.

Before Miller's experiment,
it was assumed

that this kind of organic material
could only be produced by biology,

which is why it was called organic.

Miller showed
that it's not biological,

it's occurring, we would expect,
lots of different places.

Because amino acids
were so easy to make,

scientists wondered
whether these same molecules

could have formed in the gas cloud
that made the sun even before
the Earth itself was born.

If the theory was right,
then asteroids,

the leftovers from this period
of planet-building,

might still contain
these ancient molecules today.

Proof arrived in the 1960s

when a space rock, older than the
Earth, fell on Murchison, Australia.

When you pick up pieces
of this meteorite, it just reeks.

It stinks of kind of organic,
volatile chemicals.

And when you analyse
what's in there,

we find there's
plenty of amino acids,

are the building-blocks
of proteins.

We find kind of fatty molecules

that make these envelopes, these
membranes around all of ourselves,

and incredibly,
we find the basis of DNA.

The Murchison meteorite proved

that the component parts
of a living cell are everywhere.

They were in the clouds of stardust
that formed the Earth...

..the atmosphere of
the early Earth made more.

And asteroids containing
organic building-blocks

continued to rain down for millions
of years after the crust cool.

The early Earth was steeped
in the building-blocks for life.

And how these building-blocks
come together...

..in just the right way
to form a cell...

..could be described as miraculous.

*

*

The Earth, four billion years ago.

There was land, sea
and a newly formed moon.

The moon was much nearer
than it is today.

Its close proximity
raised huge tides

that swept miles in land.

Volcanoes belch choking fumes
into the broiling-hot atmosphere...

..and asteroids and comets
rained down from space.

It was a time of no oxygen
in the atmosphere.

It was much hotter because
of the radioactive heating

left over from
the accretion of the Earth,

the impact heating left over
from the accretion of the Earth.

An incredibly alien place,

and not anything
like the Earth we see today.

And yet life arose there.

If we're going to search
for the origins of life on Earth,

we have to bear
those conditions in mind.

Similar conditions
exist on Earth today.

Scientists study them to understand
how life could have come to exist

on our hostile young planet.

The early Earth wouldn't have had
great continental land masses

like we see on the globe today,

but more like archipelagos
of volcanic islands.

You would have had these
enormous tides washing miles upland

and then receding back again.

And leaving behind them
something a lot like this landscape

we see here, with rock pools
of warm, steamy water.

Some scientists believe
life could have started

in these warm rock pools.

The building-blocks of life
was suspended in the water.

They would have concentrated together

as the water evaporated
in the strong sunlight,

forcing the molecules to interact.

At this geothermal site in Iceland,

a similar process concentrates
minerals into a thick, white paste.

One of the most
important kinds of chemicals

that might have been concentrated
down in these volcanic rock pools

on the early Earth for the origins
of life, are lipid molecules,
so fatty molecules.

And these are able to pull
off a very clever trick.

They naturally self-assemble.

On the early Earth,

individual lipid molecules
floated free in the oceans.

But trapped together in rock pools,

these fatty molecules
joined up to form bubbles.

And this is important
for the origin of life

because they form
the outside membrane

of all cells of all life on Earth.

And to show you what I mean,
I can use these fishing floats here.

Now, these fishing floats
have an end which hates water

and an end that loves water,
just like a lipid molecule.

Let's see what happens.

So no matter which way they go in,

they've all naturally orientated
themselves with one end sticking out

and one end staying in the water.

And we can see
they've clumped together.

The fatty molecules were drawn
to each other like oil droplets

on the surface of water
to form a thin membrane.

And whenever these waters
lapped against land,

the films would
have coated the inside

of the volcanic rocks
with oily bubbles.

This rock has got
a very spongy texture to it.

So if these lipid molecules
form naturally into these films

and bubbles and line the inside
of these vesicles in the rock,

you've essentially
built a protocell.

With the protocell in place,
the fatty sack would have been filled

with organic molecules
like amino acids,

from the concentrated soup
left behind in the rock pool.

Perhaps these simple
building-blocks joined together

to form proteins and DNA.

Maybe that was a great environment
to get things concentrated.

You had water,

but you had a chance for things
to sink together into shallow pools,

where molecules could
really be forced to interact.

Rock pools show us that it's possible

for the organic machinery
of cells to assemble.

But as a place
for the origin of life,

rock pools had a huge drawback.

Four billion years ago,

the sun's UV radiation

was up to 1,000 times
stronger than it is today.

This intense radiation
would have destroyed the DNA

that formed
in the shallow rock pools.

So in an effort to understand

how a cell could have come
together away from the sun...

..scientists took a closer look
at what a cell needs to work.

You can think of it
like an industrial city.

Tiny structures inside
the cell operate like factories.

They take in raw materials

and transform them
into more complex forms

such as the hardware
to build new cells.

And just like a city,

cells also need energy to keep
their industrial units running.

Some scientists believe that
the key to the origin of life

is hidden in the way
life gathers and uses energy.

It all comes down to energy.

Energy is what drives complexity
and development and technology.

We see it in human history.

It drove development and complexity
into the story of life.

Today, cells have complex biological
power stations built inside them.

These structures help
to drive chemical energy

in and out of the cell membrane.

And this chemical flow ultimately
provides the cell with power.

But the very first cell
wouldn't have had the luxury

of such a complex system
to generate power.

And the energy from the sun

would have been tainted
with lethal radiation.

So the quest to find
the place where life first arose,

lead scientists to search the Earth

for a shady spot with chemical
energy already moving through it.

In the 1970s, scientists embarked
on a daring submarine mission

to a long volcanic crack
on the bottom of the Pacific Ocean.

They discovered
tall chimney-like structures...

..belching hot volcanic water.

Incredibly, these structures
were covered with life.

What really blew people's minds

when we first discovered these
was the ecosystems.

Like oases of life
huddled around these black smokers

miles deep in the water in the sea

where the light of
the sun never shines.

Before these vents were discovered,

nobody knew that life
could exist without light.

But here were creatures
thriving on the chemical energy

jetting directly from the seabed.

Scientists began to wonder
if the same chemical energy

could have kick-started life...

..but there was a problem.

These vents that
were first discovered

were really too hot to
be the site for the origin of life.

In the year 2000,

scientists working 14km to the west
of the Mid-Atlantic Ridge

discovered a new,
much cooler type of vent.

They named them "alkaline vents",
after their unique chemistry.

What we find
with these alkaline vents,

we have this warm mineral-rich water
seeping out in the seabed

and then kind of mixing
and interacting with
the cold seawater around it,

is it deposits the solids and
kind of builds up these vast chimney
kind of towering-type structures.

The temperature inside
the towers was perfect

for organic molecules to assemble
into more complicated forms.

Scientists then searched
the vents for a source of energy

that could potentially
turn chemistry into biology.

Laurie Barge is part of a NASA team
that grows alkaline vents.

Now we're beginning
to test in the lab

what specifically could be happening
on vents on the early Earth.

We have to take into account the
conditions of the early atmosphere,

the early ocean,

the type of ocean crust
and reactions that would
have been occurring.

Laurie starts by injecting
alkaline fluids into a simulation

of an early Earth ocean.

The ocean here
contains dissolved iron

as it would have on the early Earth.

And then the chimney
that you're seeing

is the precipitate that forms

when you have two
contrasting solutions like this.

A delicate chimney builds up
inside the flask.

And because
this structure is alkaline,

it reacts with the
acidic water around it...

..drawing chemical energy
into the walls of the chimney.

And this chemical flow
is almost identical

to the one generated
by living cells today.

But energy and temperature
aren't the only features

these alkaline vents
share with living cells.

The curious thing
about these alkaline vents

is that the pockets and the pores
and the kind of channels and
tunnels we find riddling their way

throughout these structures,
these chimneys,
are about the same size as cells.

On the early Earth,

these tiny pockets would
have provided a warm crucible

for the three basic building-blocks
of life to come together.

Chemical energy flooding
through the chimney walls

may then have jump-started

the tiny metabolic engines
inside these protocells.

After millions of years,

the protocells could have developed
a way to make energy for themselves

and then broken free.

This could've been
the moment chemistry became life.

Alkaline vents are the leading theory
for the origins of life on Earth.

But the theory faces competition.

Some scientists believe
that life arrived on Earth

from another planet...

..and that our ancestors were aliens.

*

*

The Earth, four billion years ago.

The crust has cooled,

it's warm and wet.

The asteroids and comets
that brought water

and organic molecules to
the Earth are a distant memory.

Some scientists believe
that simple life may have taken hold

at the bottom of the sea,

but this may not be the life
that turned into us.

Because a radical theory
called panspermia

suggests that our ancestors
are about to arrive...

..from outer space.

A second wave of rocks
pummel the Earth,

and according to the theory,
they're carrying alien hitchhikers.

So panspermia is the idea that life
rose on some other planetary body,

or other environment,

and came to Earth
and was delivered by falling debris.

We don't know, but I think the idea

that panspermia may have played
a role must be considered,

because a lot of evidence
points us in that direction.

The story of how alien
hitchhikers arrived on Earth
starts 4.1 billion years ago...

..when the giant outer planets
flung Neptune off-course

and threw a belt
of comets and asteroids.

The giant planet sent a hail
of mountain-sized space rocks

towards the inner solar system
and the Earth.

It's called
the late heavy bombardment.

We're just orbiting the sun,
happy as can be,

and the outer planets are throwing
these gigantic objects at us,

and they just kept coming in and
kept coming in and kept coming in.

There were giant asteroids and
comets raining down on the Earth,

and occasionally even the oceans
would be set to boiling.

Even if simple life had
started in Earth's oceans,

it might not have
survived this onslaught...

..but the Earth wasn't
the only planet in the firing line.

Asteroids and comets also hit Mars...

..and back then,
it was a different planet.

Mars is smaller than the Earth,
it would have cooled more rapidly.

It could have had a thick
atmosphere and oceans of water

before the Earth did.

Ancient oceans would have
given Mars a head-start

in the race to foster life.

Perhaps by the time
the late heavy bombardment struck,

hardy bacteria had already
evolved on the Red Planet.

We've seen life on Earth

that are cryptoendolithic,
so they hide in those rocks.

And they survive the radiation
and the harsh environment

by hiding and thriving
inside of that surface.

A giant impact on
the surface of early Mars

could have thrown rocks filled
with bacteria high into space.

These are organisms pre-packaged,
ready to fly.

You could imagine some of them
trapped in a rock,

kicked off a planet, flying through
space thousands of years later,

landing on another world,
popping open and being able
to reproduce and grow.

So did a Martian rock
seed the Earth with life?

It's possible.

But only if the Martian hitchhikers

could survive
the long journey through space.

NASA engineer Moogega Cooper knows
exactly how hardy bacteria can be...

..because her job is to kill them
so that no super-bacteria from Earth

contaminates space missions
to other planets.

If we send a rover
and it's covered in bacteria,

it could potentially propagate
in that environment.

So we're kind of
like a bug inspector.

In the ideal case, we would like
for every piece of hardware

to be sterile.

The reason for this vigilance

is the freakish ability of bacteria
to survive in space.

Certain bacteria on Earth, when they
experience a stressful environment,

they start forming
what we call "spores".

And spores, if you imagine a seed,

has all of the genetic
information in the middle

and it's protected
by numerous layers of defence.

They really seal themselves up
in little spaceships,

and that would allow them
to survive in space.

You could take a spore,
put it in space,

bring it back
and it would still be viable.

Spores allow bacteria to
stay alive in a dormant state

for incredible lengths of time.

The record on Earth

is a spore that formed
before the age of the dinosaurs

and was recently resuscitated
after a 250-million-year sleep.

You know that spores
can survive in theory

for millions and millions of years.

But to actually see evidence
of a spore being revived

is pretty fantastic.

The final challenge
for the Martian hitchhikers

is to survive the impact
with Earth's surface.

Planetary scientists
simulate this violent event

with high-speed guns
loaded with rocks.

Not every bit of
the projectile is destroyed

and highly shocked in an impact.

When we do these experiments,

we often find little bits
of the projectile left over

in the impact chamber.

If there are bacteria living
in that portion of that rock,

they could potentially survive
the impact back onto the planet.

The science shows us
that panspermia is possible...

..but does it take us any closer
to understanding the origins of life?

The fundamental problem
with panspermia

is that it's just
removing one step of the problem

and putting it someplace else.

We don't know
how life originated on Earth,

now it's gonna originate on Mars.

But we don't know
how it originated on Mars,

so you still have
this basic problem,

and that is, how did life start?

A lot of people say, well,
panspermia shouldn't be considered

because it just moves
the question somewhere else.

But that may be important

cos then we'd say
that we need two planets

to create what we see on Earth.

One to get it started
and one to carry it on further.

At the moment, we don't know
whether life arrived from space

or rose up from
the oceans of the Earth.

All we know is that
the next stage of life's journey

is filled with danger...

..because before life can get clever,
it must face oblivion.

*

*

Our planet is filled with
a dazzling diversity of life.

Plant life and animal life...

..simple life...

..and complex,
intelligent life like us.

Yet every living thing on Earth

can trace its family tree
back to the same tiny cell

that lived billions of years ago.

All life on Earth is
related to each other.

We share 50% of our
DNA with a banana.

I mean, we feel like we're
pretty different from a banana,

but when you look at its core,
what its DNA looks like,

it's almost identical.

DNA is the operating system for life.

It stores the program that tells
cells how to grow complex structures,

how to generate energy,
and ultimately,

how to make an identical copy
of themselves.

When we look at life, we tend to
focus on what it's made out of it,

and that's important.

It's made out of amino acids
and molecules, et cetera.

But the key difference between
life and just simple chemistry

is the information content.

So using the computer words,
it's not the hardware

that's so amazing,
it's the software.

The greatest property of DNA
is its ability to change.

Over billions of years,
tiny mistakes in the structure of DNA

have led to the vast diversity
of life we see today.

These mutations can happen
when DNA gets damaged.

The missing section is normally
patched up with a perfect copy...

..but from time to time,

a different set of nucleotides
slot into place instead.

Sometimes there are
mismatches that occur,

and these mutations
are sometimes harmful,

but sometimes,
it could be a good thing.

Sometimes a random change might
make you process food better.

It might make your eyesight
a little bit better,

make you a slightly better hunter.

It might make you
a little bit taller

so you can see above the grass
a little bit better.

Those are advantageous changes
and they're random.

They don't happen very often,
but they do happen,

and that has led, basically,
to the way we are now.

Of all the mutations
that led to human life,

the most important
is also one of the earliest -

the jump from simple, single-celled
life to complex, multicellular life.

It's hard to imagine that
without multicellularity,

intelligence is possible.

You've got to have
a big enough organism

so that specialisation
is enough that some of the cells,

some of the fraction
of that organism,
can just focus on being a brain.

The jump from simple life
to complex life

began around 2.4 billion years ago...

..but what was the trigger
for this revolutionary change?

Scientists have boiled it down to
a single, game-changing mutation

called photosynthesis.

What happened was a mistake.

A mutation led to
a true superpower.

The first organism to
develop this superpower

is called cyanobacteria.

It was green and able to use sunlight
to create its own food supply.

For the first time, life had
its own internal energy source,

wherever you are, as long
as you have sunlight, you have food.

So you could cut
the umbilical cord and break free

and start to really branch out
into the environments of the Earth.

The cyanobacteria thrived.

But the waste product
of photosynthesis was oxygen,

a gas that was highly toxic
to almost all other primal life -

a weapon of mass destruction.

At that point, there wasn't
any free oxygen in the atmosphere.

This was the first time
this happened,

and as these things
evolved and flourished,

they started dumping this basic
poison into the atmosphere.

The oxygen killed off
most of the life on Earth...

..but the creatures that
survived evolved to use oxygen

and turbocharged their evolution.

Oxygen is so dangerous
cos it's so reactive,

but that makes it a very good fuel.

So the tiny percentage of life

that wasn't killed
by the poisonous gas oxygen,

all of a sudden could speed up,
it had a more efficient fuel to use.

And more energy means
more complex molecules,

more complex chemistry,
more complex biology,

and that meant that these creatures
could evolve more rapidly.

Boosted by oxygen,

some single-cells evolve to do
something they hadn't done before -

they joined forces.

Single-celled microorganisms
really were smart

when they knew to cluster together.

Because it allowed them
to have protection

and worked kind of as a community.

Different cells
within these communities

started to specialise
in different tasks.

Eventually, the communities started
to function as a single organism.

The stage was set
for the next superpower -

multicellular life.

But a second global
catastrophe was coming...

..because in the background,

cyanobacteria populations
were still exploding.

As they released
the oxygen as they grew,

it would have changed
the chemistry of the entire planet.

As oxygen filled the air,
it reacted with the early atmosphere,

removing greenhouse gases
such as methane.

The result was a rapid cooling
of the Earth's climate.

And this, we think,

would have tipped the climate
of the entire planet

to a very, very cold,
kind of glaciated world.

What we call the "Snowball Earth".

And it was probably the first
climate catastrophe that happened

after life originated on Earth.

Snowball Earth came very close
to wiping all life off the surface

of our planet.

But some creatures
must have made it through,

otherwise we wouldn't be here today.

Geothermal hot springs
like this one in Iceland

offer a clue as to how
our tiny ancestors

managed to survive this trial by ice.

This temperature's shooting up.
160, 170, 180...

..190...

..over 200 degrees Fahrenheit.
Now, that's very, very hot.

That's practically
the boiling point of the water,

and you can see it's kind of
churning away like cooking soup

or something in the kitchen at home.

The heat source
for hot springs like these

is buried deep within
the molten core of the Earth.

Radioactive metals sank here
during the formation of the Earth,

and they decayed, slowly
releasing heat into the rocks

that sit below the surface
of our planet.

Where the Earth's crust is thin,

rainwater can seep down
onto these hot rocks

and shoot back up
at near boiling point.

Warm pools like these

would have kept on bubbling
all the way through Snowball Earth.

What probably would have helped us
in that process and survival

would have been regions like this.

There would have been volcanic
activity and geothermal hot-spots.

And they would have
thawed out the ice,

and provided kind of
oases of warmth

where life has
an opportunity to cling on.

So maybe it was less
of a Snowball Earth,

and more of a kind of a slush-ball.

Maybe there were periods
and regions around the equator,

and around hot-spots,
where life was able to persist.

Snowball Earth lasts
for 200 million years.

Eventually, volcanoes released
enough greenhouse gases

for the climate to recover.

And the organisms that survived

inherited a warm, oxygenated world
perfect for multicellular life.

Multicellularity really booms,

and it seems to coincide
with a rise in oxygen.

Over the next 500 million years,
oxygen levels continued to rise...

..and life grew bigger
and more complex.

Most of the major animal groups
we see today evolved.

Fish turned into reptiles.

Reptiles turned into small mammals

and then primates.

Finally, just 200,000 years ago,
the first humans walked the Earth...

..beings with the capacity
for intelligent thought.

If we think of landmarks in
evolution, there aren't very many.

I would just have three.

The origin of life,

the rise of complex life
associated with oxygen,

and the rise of intelligence.

That's it. To me,
that's the story of life on Earth.

It started, it got complex,
then it got smart.

Now scientists are investigating

whether the same process of evolution
could have happened elsewhere.

I've become more and more confident
over the last few decades

that life is everywhere
in the universe.

Now, is there intelligent life?

That's a much more
difficult question.

One way to answer it

is to look at the key factors
that made our evolution possible,

and see if they exist elsewhere.

By studying the light
from distant dust clouds,

astronomers now know
that the building-blocks for life

are common throughout the galaxy.

And they've detected over
1,000 potential planetary homes

for life around nearby stars.

The stage for simple life,
at least, seems virtually infinite.

But for complex, multicellular
life, you need something else -

an oxygen-rich atmosphere.

Is there oxygen on these worlds?

That's the question I want
to live to see the answer to,

and if the answers for any of them
is yes, that's phenomenal.

That is really
an important milestone

in our understanding
of life in the universe.

NASA is developing
a new generation of telescopes

to find planets around nearby stars

and scan for
oxygen-rich atmospheres.

But a recent surprise result
from the planet next-door,

suggests oxygen-rich worlds may be
much more common than we thought.

I think we can do it right here.

Nina Lanza works with NASA
on the Mars Curiosity Rover.

She's interested
in a mysterious black glaze

that appears to be present
on both Mars and the Earth.

Great, thank you.

So what we're looking at here
is called rock varnish.

And this is a coating
on the surface of the rock

that is very high
in manganese oxides.

Living cells on Earth
contain manganese.

These dark deposits are
thought to have been formed

when this manganese
leached out of dead bacteria.

The manganese then reacted
with oxygen in the air

and became fixed to the rock.

Nina wanted to understand

the chemistry of
similar-looking stains on Mars.

So in 2014,

she requested the Mars Curiosity
Rover to fire at a set of dark rocks

with its chem-cam laser.

Wherever we zap the rock, it
vaporises a little bit of material.

And so if we keep shooting
the rock in that one place,

then we can find out

the composition through
the coating, if there is one.

There was this one sample
that had such a big peak

that we noticed it right away,

and we were like,
"This has to be a mistake."

We need to check our data to make
sure we haven't mis-calibrated it.

And absolutely not,

we looked at the raw data,
we recalibrated it,

and it was still
a huge amount of manganese.

The surprise result

suggests life may once
have thrived on Martian rocks

inside an oxygen-rich atmosphere.

Even if the manganese
came from another source,

the dark stains would have still
required atmospheric oxygen

to fix them to the rocks.

So finding a coating
like this on Mars,

or even just a layer made
of a similar composition,

opens up the possibility
that there was oxygen

in the Martian atmosphere
sometime in the past.

Mars lost its atmosphere
billions of years ago...

..but the possibility
it once had oxygen is significant.

Because if two planets
in the same solar system

can both have all the ingredients
needed to develop complex life...

..then the odds on their being
more intelligent life out there
look pretty good.

When we look at the story of life,

it seems like the universe
started off with hydrogen

and has now ended up
with intelligence, human beings.

Well, that's a wonderful story.

Are we the only chapter
in that book, though?

That's the question.

Whether or not there's
a person in some far away galaxy

having the same thoughts as I am,

I'm not sure.

It's hard to say no,
because this universe is so large.

We are a collection of atoms

that understands that
it's a collection of atoms.

That's amazing.

This is the universe knowing
that it's the universe.

I think it's really important that
we figure out how that's possible.

I actually have a bottle
of very nice champagne

chilling in my refrigerator.

I think we're gonna find
evidence of life on other planets

sometime in my lifetime.

I'm ready to celebrate.

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