Cosmos: Possible Worlds - First Season

We are a long way from home, and from our time.

This was our Milky Way when the galaxy was young

and more fertile than it is today.

Back then, she birthed 30 times as many stars as she does now...

a firestorm of star creation.

It's a summer night, 11 billion years ago.

We're on the planet of another star,

one with an ideal view of the Milky Way galaxy's

chaotic stellar nursery.

Our own star was a child of the galaxy's later years,

and that may be one of the reasons we exist.

After the short-lived, more massive stars died out,

there was time...

another five billion years, for those dead stars to bequeath

their heavier elements to us.

These elements enriched and nurtured the formation

of the planets and moons of our solar system.

And we ourselves are made of that star stuff.

Those blazing pink clouds of hydrogen gas are the swaddling

of countless new-born stars.

See those bright blue splashes?

They're clusters of slightly older sibling stars.

Gravity's embrace will transform this amorphous

collection of gas and dust into the galaxy we call home today.

Our sun is born.

The star endows her surrounding worlds

with precious minerals, diamonds and green olivine...

a mineral that will play a major role in our story.

The stars make planets, moons and comets.

There's Jupiter, the firstborn world of our solar system.

These future planets and moons are awash with organic molecules...

the chemical building blocks of life.

This is their inheritance from the deaths of other stars.

Does the cosmos give rise to life as naturally

as it makes stars and worlds?

This is our voyage to the heart of that mystery.

Long, long ago, when our world was young,

there was a city at the bottom of the sea that covered the Earth.

It took tens of thousands of years to build this city,

but there was no life on this world back then.

So who built these submarine skyscrapers?

Nature did.

She made them with carbon dioxide and the same minerals

she uses to make seashells and pearls...

calcium carbonate.

But these soaring towers were nothing compared to what

happened beneath them.

We'll need to get 1,000 times smaller to see it.

Doesn't look like much, does it?

But just wait.

Our restless Mother Earth cracked open,

and cold sea water poured down into her hot rocky mantle,

getting richer in organic molecules and minerals,

including a green jewel called olivine.

This mix of water and minerals got so hot that it

shot out of her with great force.

The mixture became trapped in the pores of the carbonate

rocks that would later become her towers.

These pores were incubators, safe places where the organic

molecules could become more concentrated.

This is how we think that the rocks built life's first home.

It was the beginning, at least in our little

part of the cosmos, of an enduring collaboration

between the minerals of earth,

the rocks and life.

See those snaky cracks?

That's how this process got its name.

Serpentinization.

It's the evidence for the conversion of water and

carbon dioxide into hydrogen and methane...

the organic molecules that fueled this earthshaking event.

Those scientists who search for life on other worlds,

they used to say, "follow the water,"

because water is the most basic requirement for life.

Now, they also say, "follow the rocks,"

because serpentinization is so closely associated with

the processes that make life possible.

To witness the main event, we have to get even smaller.

At this scale, these caves look vast,

but they're actually the tiny pores in the mortar of the towers.

These jewels are the organic molecules which are,

like everything, including you and me, made of atoms.

In order to turn these inanimate jewels into jewelry,

the stuff of life, it takes energy.

We think it happened in a treasure cave like this one.

The energy came from the reaction between the alkaline

water trapped within the towers

and the acidic water of the ocean.

That ancient treasure chest filled with rings and

bracelets and necklaces,

longer and more complex molecules,

until the greatest treasure of all...

Life.

We think it was that chemical reaction that provided

the energy that powered the first cell.

That was the spark that electrified the building blocks of life

into something alive.

Over time, the towers decayed,

making it possible for the fledgling life within them

to escape and evolve.

What you've just seen is the most plausible scientific

creation myth we have today for the origin of life.

This hypothesis required the reunification

of four long separated scientific fields:

biology, chemistry, physics and geology.

We think life first took hold in the rocks.

And from day one, life was an escape artist,

always wanting to break free, to conquer new worlds.

Even the great big ocean couldn't contain it.

If that's the true story of how life got started,

it was long ago, back before the sky was blue,

before the moon spun away from us to where it is today.

Back when the planet was an ocean world,

with waters bloodred with iron.

Life would remake the world, the sea and the sky.

But life doesn't always act in its own best interest.

There came a day of reckoning,

when life nearly destroyed itself.

The Cosmic Calendar is a way for us to wrap our

heads around the vastness of time.

To grasp the history of the cosmos,

from the birth of our universe to this very moment,

we've compressed all of it into a single calendar year.

On this scale, every month represents about a billion years.

Every day represents nearly 40 million years.

That first day of the cosmic year began with the Big Bang,

almost 14 billion years ago.

Nothing really happened in our neck of the universe

until about three billion years later...

March 15 of the cosmic year,

when our Milky Way galaxy began to form.

Six billion years after that, our star, the Sun, was born.

It was August 31st on the Cosmic Calendar.

Jupiter and the other planets, including our own,

would soon follow.

This was our planet nearly four billion years ago...

September 21st on the Cosmic Calendar,

when we believe life began.

The atmosphere was a hydrocarbon smog.

No oxygen to breathe and no one to breathe it.

We've only recently begun to appreciate how powerfully

life has shaped the planet.

When we think about the ways life has changed Earth,

the first things that come to mind are the green expanses

of forests, and the sprawling cities.

But life began transforming the planet long before there

were any such things.

A billion years after that tiny glimmer at the bottom of the sea,

life had become a global phenomenon thanks to

a champion that to this day has never been vanquished.

I give you the cyanobacteria.

In business for 2.7 billion years,

cyanobacteria can make a living anywhere.

Fresh water, salt water, hot springs, salt mines...

makes no difference, it's all home to them.

Over the next 400 million years, the cyanobacteria...

taking in carbon dioxide and giving back oxygen,

turned the sky blue.

But the cyanobacteria didn't just change the sky,

they reached into the very rocks themselves

and changed them, too.

Oxygen rusted the iron,

working its magic on the minerals.

Of the 5,000 kinds of minerals on Earth,

3,500 of them arose as a result of the oxygen made by life.

But here comes that day of reckoning.

Cyanobacteria were the dominant life-form on this planet,

wreaking havoc wherever they went,

changing the landscape, the water and the skies.

This was 2.3 billion years ago,

or late October on the Cosmic Calendar.

But the cyanobacteria shared the planet with other beings:

The anaerobes, life-forms that had come of age before

cyanobacteria had begun to pollute the Earth with oxygen.

For the anaerobes, oxygen was poison,

but the cyanobacteria wouldn't stop loading up

the atmosphere with the stuff.

For the anaerobes, and nearly all of the other

life on Earth, it was an oxygen apocalypse.

The lone survivors among the anaerobes were those

who sought refuge at the bottom of the sea,

deep in the sediment where the oxygen could not reach them.

The cyanobacteria acted like oxygen-pumping machines.

They continued in overdrive, and 400 million years later,

they brought about an even more radical change to the planet.

Remember those serpentinized rocks at the bottom of the sea

that were cranking out hydrogen and methane?

Methane is a powerful greenhouse gas,

and back then it was the main thing keeping the planet warm.

But once again, the oxygen produced by life shook things up.

It gobbled up the methane, producing carbon dioxide,

a much less potent greenhouse gas...

meaning it was not as efficient at trapping heat

in Earth's atmosphere.

Earth's temperature began to plunge.

Life, the escape artist, busted out of the icy death grip

that entombed the planet.

The corpses of dead bacteria left behind a planetwide

reservoir of carbon dioxide.

Volcanoes pumped the carbon dioxide in huge quantities into the atmosphere,