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Our solar system is a savage place.

From the ice volcanoes of Saturn's moon Enceladus,

to the vast lava fields of Jupiter's Io,

to our own world, the Earth,

volcanoes destroy.

They also create.

It is literally true that, if there weren't volcanoes here,

we would not be here either.

Volcanoes shape and change our climate.

Volcanoes are the giver of life and, also, the takers of life.

Today's space probes and telescopes

reveal volcanoes on worlds we once thought dead.

Finding volcanoes on an object that's smaller than our own Moon

was a huge shock.

If volcanoes exist on other worlds,

could we find life there, too?

Planet Earth -- a jewel in the darkness of space.

Our home is timeless...

beautiful...

and incredibly violent.

Volcanoes are one of the most powerful natural phenomena

on the planet.

They create new land,

destroy the old.

They blast out gases that transform the air we breathe.

Deep in our oceans,

volcanic heat fuels strange new life.

Volcanoes help power the living Earth.

Now we search for signs of life on alien worlds.

We know life needs water.

We know it needs energy.

And that's where volcanoes come in --

they pump out vast amounts of energy.

Find volcanoes on other worlds,

and we might find life.

The search starts here --

the planet orbiting closest to Earth...

Venus, a world that appears very much like ours.

Venus and Earth are roughly the same mass.

They're roughly the same distance away from the Sun.

So they're kind of like twins.

3 billion years ago,

Earth and Venus were very similar...

...new land, new oceans, an atmosphere.

Both planets were perfect for life.

But on Venus, something went wrong.

Something made Venus

diverge radically from the history of the Earth.

Venus took a definite turn to the dark side a long time ago.

Venus is a hellhole, our evil twin.

Today, Venus' surface is like a furnace.

It's 900 degrees Fahrenheit on the surface.

It's hot enough to melt, actually, some metals,

so you wouldn't stand a chance.

Venus is a greenhouse world.

Its atmosphere is thick with carbon dioxide.

It traps heat from the Sun like a blanket.

These actual images of Venus' surface

reveal a barren, superheated wasteland.

Venus' thick blanket of CO2 killed the planet.

The CO2 came from volcanoes.

Orbiting space probes gave the first clues.

Radar punched through Venus' thick clouds...

...and revealed volcanic formations across the planet...

...like formations we also see right here on Earth --

the shield volcanoes of Hawaii.

Shield volcanoes get their name from their round, flat shape.

These volcanoes ooze.

But they ooze for thousands of years.

Once we were able to map the entire surface of Venus

using cloud-penetrating radar,

we started to study the landforms there,

and we saw a lot that was actually very familiar.

In particular, we saw giant shield volcanoes

that are very similar to the shield volcanoes here in Hawaii.

The radar images of Venus

were dead ringers for the shield volcanoes on Hawaii.

Sometime in the past, Venus had volcanoes.

For the first time, we had a picture of Venus revealed,

and, boy, were we shocked.

We found a scarred surface, a volcanic surface.

There are at least a thousand volcanoes that are very large

and maybe tens or even hundreds of thousands of smaller ones.

3/4 of Venus' surface is lava plains,

evidence of an ancient cataclysm.

This could have been a home for life.

Instead, it was engulfed by fire.

Volcanoes belched trillions of tons of carbon dioxide

into Venus' atmosphere.

Temperatures soared.

The seas boiled dry.

A runaway greenhouse process began.

On Earth, carbon dioxide

is able to absorb into the rocks.

It's able to absorb into the ocean.

But on Venus, you have no water,

and it's now so hot

the carbon dioxide can't even combine with the rocks.

So as carbon dioxide was released into the atmosphere

by volcanoes a long time ago,

over time, there was less and less of a method

to take it back out of the atmosphere.

If Venus ever had life,

volcanoes sterilized the entire world.

Earth remains the only living world we know of.

That may change.

This is the gas giant Jupiter,

its moons frozen and dead...

...or so we thought.

Look closer, and a mystery emerges...

...a cloud hanging over a cold and lifeless world.

On Venus,

volcanoes turned an earth-like world into a superheated hell.

Finding volcanoes on an earth-like world

was no surprise.

But spotting volcanoes on a moon was a shock.

In March 1979,

the Voyager 1 space probe

gave us our first close-up view of Jupiter's tiny moon Io...

...a world we once thought cold and dead.

And they saw something really weird.

They saw this arc next to the moon,

and it looked almost

as if like there was another moon behind it.

And we scratched our heads and said,

"Well, what could that be?

Everybody knows that io is dead, boring, uninteresting."

And then people realized, "Oh, my God.

It's a volcanic eruption."

We found that it's covered with volcanoes.

It is tremendously geologically active.

There are volcanoes erupting all the time.

And what they're erupting is a lot of sulfur,

and it gets very hot.

And sulfur, when it changes temperature, changes color.

It can be red or orange or yellow or black.

And so these pictures of the face of Io

make it look like a pizza

covered with different kinds of cheese and olives

where the little black spots are.

Io is not dead.

It's alive and kicking.

It has over 400 active volcanoes.

The largest, Pele, erupts from a gigantic lava lake.

It reaches nearly 250 miles into space.

If we could stand on the edge of that lava lake

and watch that plume shooting off into the blackness of space,

that would be an incredible sight.

Pele's eruptions are so huge because Io is so small.

There's nothing to hold the lava back --

virtually no atmosphere and very little gravity.

These vast eruptions

make Earth volcanoes look like firecrackers.

How can such a tiny moon be so volcanic?

The answer is Jupiter.

Just as the Moon raises tides in Earth's oceans,

Jupiter raises tides on Io --

tides of solid rock.

Io's orbit around Jupiter is not a circle.

Sometimes, it's closer.

Sometimes, farther away.

Jupiter gives Io a gravitational pounding.

And so, Jupiter's gravity

pulls on it a little bit harder and a little bit weaker.

And what happens is the moon stretches, like this.

It's called a tidal force.

And it doesn't stretch this much --

it's only a little bit.

But, in fact, it's enough to heat it up.

It's just friction.

It's the same way when you rub your hands together really fast,

they begin to feel warm.

Friction creates heat.

Jupiter's gravity

stretches and squeezes Io.

In every two-day orbit,

the ground rises and falls by nearly 300 feet.

This pummeling generates intense heat and gigantic pressure.

Wherever there's a weak part in the crust, the lava rushes out.

So the volcanism is on a planetary scale.

Unlike here on Earth,

where there are certain bits that are active

around the plates or in weak spots,

this is an entire moon that's one active hot spot.

Thanks to the incredible power of gravity,

Io is the most volcanically active world

in the solar system.

The volcanism on Io taught us something new.

It taught us that internal sources of energy

can drive volcanism

in a way that's different from that on Earth.

In outer space, tidal forces,

the differential squeezing of the moons of a gas giant,

can also create volcanic activity --

that was a game-changer.

Io is a lava world, superheated and violent.

It's hard to imagine anything surviving there.

Yet the volcanic principle here is the same as on Earth --

pressurized, superheated magma below the surface

blasts through fissures in the crust.

But not all volcanoes need magma.

They don't even need to be hot.

Travel out past Jupiter into the outer solar system,

and it gets cold -- really cold.

The distant moon Triton is so cold

that much of its tenuous atmosphere can freeze solid.

Yet there are volcanoes here --

volcanoes that may hold the secret of alien life.

We think of volcanoes as mountains of solid rock.

Deep beneath, rock is so hot and pressurized

that it bursts violently out as lava.

But not all volcanoes work this way.

There are volcanoes on other worlds

that don't use molten rock at all.

Right at the frontiers of the sun's planetary system,

Triton orbits the ice giant Neptune.

2 1/2 billion miles from the Sun,

the temperature is a frigid 390 degrees below zero.

When NASA's Voyager probe flew past,

it revealed a world covered mostly with frozen nitrogen ice.

But the probe found something else.

When Voyager flew by, it saw these black smudges,

and all of the smudges were going in one direction,

almost as if there was a wind

blowing dark material, dust, in one direction.

Signs of activity

on a world so cold, it freezes nitrogen --

volcanoes at almost 400 degrees below zero.

Forget molten rock.

Triton spews out a mixture of nitrogen and moon dust.

And the geyser not only has liquid nitrogen,

which is in a fluid form,

but, also, sort of dusty stuff that's lighter,

that can even go farther in the weak winds.

So you have this wonderful sort of double plume of an icy area

and then a darker, smudgy area,

basically made of dust, like moon dust.

Triton's surface is nitrogen ice.

Underneath, there are lakes of liquid nitrogen.

How?

Scientists believe it's because nitrogen ice lets light in,

but doesn't let heat out.

There's almost a bit of a greenhouse effect

going on on Triton,

that there's a layer of nitrogen ice that's transparent.

And just like a greenhouse here on Earth, when you have glass,

light can pass through it,

but then the heat is trapped by the glass.

The Sun shines through the surface

and warms the nitrogen beneath.

Just a few degrees

is all it takes to turn nitrogen ice into gas.

A temperature gradient, a change in that temperature --

that's what's important.

And that's enough to melt the nitrogen

underneath the surface on Triton

and have it burst through as a geyser.

This is a cryovolcano,

so cold that the material it erupts

would freeze water as hard as rock.

The solar system is more active than we ever imagined.

We have found weird eruptions on many planets and moons.

But so far, the only world

where volcanoes are linked to life is ours...

or so we thought.

This is Europa.

It orbits Jupiter nearly 500 million miles from the Sun,

a frozen 2,000-mile-wide rock-hard ball of ice.

From a distance, its surface looks smooth.

Up close, it's a different story.

Jupiter's enormous gravity gives Europa a pounding,

just like its neighbor, Io.

The surface heaves and flexes,

creating ridges and deep crevices.

When we first got close-up images of Jupiter's moon Europa,

they looked a little familiar,

and it turns out it looks like ice floes

that you see when you fly over the Arctic.

And it turns out it's the same thing.

Europa has a several-mile-thick shell of ice on its surface,

and beneath that is a global liquid ocean.

Magnetic readings suggest Europa has an ocean

that's a staggering 60 miles deep.

Jupiter's gravitational pounding

heats the rocky core and melts the ice above.

It's not unreasonable to think that, as the core

is being stretched by tides and heated up, possibly even molten,

there's some boundary

between a hot core and a liquid-water ocean.

On Earth,

underwater eruptions are surrounded by life.

The same could happen on Europa.

Here, the darkness is total...

the pressure -- a crushing 2,000 earth atmospheres.

A brutal world, but perhaps a cradle for life.

If life got off the ground here on Earth, why not on Europa?

All the ingredients are there --

an energy source -- volcanic activity --

a universal solvent -- liquid water --

a rich hydrocarbon chemistry.

We have this mixing bowl of ingredients

that happened on the Earth 3 1/2 billion years ago,

and we have similar conditions on Europa.

So some people are saying,

"If it happened here, why not there?"

Life on Europa would be hard, but not impossible.

On Earth, there is life at every extreme --

searing heat, crushing pressure, total darkness.

Alien life on Europa might look surprisingly similar.

If life exists under the ice cover of Europa,

they would be aquatic, but without eyes,

because there's no light to speak of.

They would probably use sonar

in order to make sense of their surroundings --

organisms that literally feed off the energy from the volcano.

On Europa, volcanoes could be the source of new life.

It's even possible that Europa is normal,

that this is how worlds with life generally are.

Earth could be the exception.

Think of it -- Europa could be a template

for billions of moons out there that have liquid oceans on them.

So, all of a sudden,

our horizons have expanded several billion times

by looking at the moons of Jupiter.

What a shock.

Our solar system alone has over 170 moons.

Multiply that across the Universe,

and that's a lot of places where life might take hold.

All it takes is liquid water and a source of energy.

Potentially, volcanoes provide both.

And they are everywhere.

This is Saturn, twice as far from the Sun as Jupiter.

Yet it, too, has volcanic moons.

And just like Jupiter's Europa, these moons could harbor life.

This is one of the strangest worlds

in our solar system -- Saturn --

a ring system 600,000 miles wide,

an amazing 62 moons,

and one with a secret.

Enceladus is one of Saturn's smaller, more distant moons.

And it's been known for a long time that it's covered in ice,

because it's very bright, very reflective.

But when the Cassini spacecraft went there,

it discovered something amazing.

The Cassini probe revealed something incredible --

not on the planet itself, but on Enceladus.

Backlit by the sun, a gigantic plume bursts out into space --

a sure sign of volcanic activity.

It was an amazing discovery,

and it helped answer a question

that has puzzled scientists for decades --

the mystery of Saturn's "E" ring.

Saturn's outermost ring is vast,

almost 200,000 miles across,

and it shouldn't exist.

The ice particles that make up most of the ring

are too far from Saturn to stay in orbit.

They constantly drift away into space.

Something replenishes the ring --

the ice volcanoes of Enceladus.

Those plumes

that are ejected from Enceladus' south pole --

it turns out that those are going into space.

And they're not just going away.

They're feeding a ring around Saturn, the "E" ring.

So this little moon

is giving something back to its parent planet.

Water blasts from Enceladus' volcanoes,

hits the vacuum of space,

and instantly freezes into tiny ice crystals,

creating the vast "E" ring.

One mystery solved.

Another replaces it.

What creates the volcanic plumes?

Cassini's cameras zoom in on the moon's south pole

and capture these huge chasms scarring the surface.

There are these wonderfully huge cracks

at the south pole of Enceladus,

and as Enceladus goes around Saturn,

these cracks open and shut as the tides go by.

Now, these cracks are huge.

They're hundreds of miles long.

And when they begin to open, you would have this big crevasse

opening at maybe 100 miles an hour down the length of that.

It'd be incredibly spectacular.

Huge gravitational forces

crack the surface open and closed at enormous speeds.

Like Europa and Io's orbits 'round Jupiter,

Enceladus' orbit 'round Saturn is elliptical.

This helps generate the heat to melt ice

and create oceans of water beneath the surface.

The conditions of the water

underneath Enceladus' surface

are absolutely perfect for life.

It's the right temperature.

It'd be a good pressure for life.

Liquid water would be just like seawater here on Earth.

And the chemistry of the water

we see shooting out of these vents

suggests that it is very similar -- there's salt.

There's organic material in it, as well.

So we've identified a place in the solar system

where there very well may be life right now.

Cassini has detected complex carbon molecules

in the ice plumes.

Combined with liquid water,

they suggest that just maybe life

could survive deep within this enigmatic moon.

Enceladus may not be alone.

Another of Saturn's moons might also harbor life --

Titan, one of the largest moons in our solar system,

the only moon with a thick atmosphere...

...a frozen world --

ice as hard as rock, lakes of liquid methane.

Yet here, too, we might find evidence of volcanoes

and the tantalizing prospect of alien life.

A raging inferno on the surface of Io,

eruptions of ice and nitrogen on Triton...

Volcanoes are one of the most destructive forces

in our Universe.

But out of annihilation comes the possibility of life,

even here on Saturn's mysterious moon Titan.

It's 3,000 miles across,

larger than the planet Mercury.

It's the only moon in our solar system

with a thick atmosphere.

There is weather here -- storms, winds, rain, even lakes --

all so cold that liquid methane takes the place of water.

And it's loaded with chemicals that life needs to survive.

Titan has turned out to be absolutely one

of the most interesting places in the solar system.

It's an active world.

It's the only moon with a thick atmosphere --

an atmosphere very much like Earth,

because it's mostly nitrogen,

and it turns out, an atmosphere loaded with organic molecules.

Methane gas high in Titan's atmosphere

reacts with sunlight

and creates the kind of chemicals life depends on.

But if sunlight converts methane into organics continuously,

why doesn't the methane run out?

The atmosphere's full of methane,

and yet we know methane

is being destroyed by sunlight on a short time scale,

so it shouldn't be there.

There needs to be a source of methane.

Something on Titan

pumps out a continuous supply of methane.

Cassini has detected what looks like a crater.

Its interior is as deep as the Grand Canyon.

Infrared cameras reveal different types

of materials surrounding the crater.

Scientists believe the green areas could be volcanic,

perhaps plains of lava ejected from Titan's interior.

If it exists,

lava Titan-style is a superchilled icy slush.

But compared to the rest of Titan,

even ice slush is scalding hot.

On Titan, the hot liquid spewing from volcanoes

might be ammonia or water.

Normally, those are frozen solid on the surface,

but if they're heated beneath the surface somehow,

they could erupt out.

On Titan, what comes out of volcanoes is methane and ethane,

and that's probably the reason

why we have this very thick cloud cover,

this orange haze around Titan.

This haze

probably came from outgassing from the volcanoes of Titan.

Even for volcanoes on a world as cold as Titan, you need heat.

That's what turns ice into liquid and generates eruptions.

On Titan, that heat has two sources.

Radioactive materials warm the interior.

And Saturn's huge gravity massages the moon,

just like Enceladus.

These two forces generate enough heat

to turn ice into water

and liquid methane to gas.

We think of volcanoes as being hot and ice as cold,

and yet if you're out on Titan,

where you're a billion miles from the Sun

and it's -- it's quite cold,

then those floes

of just-barely-above-freezing water ammonia ice --

they might be the hottest things around.

So "hot" is a relative term,

depending on where in the solar system you are.

Could volcanoes on Titan

give life a chance to survive here?

Life as we know it needs an atmosphere...

...a solid surface...

liquid water...

and the heat to drive chemical reactions.

On Titan, volcanoes could provide them all.

If you have a volcano on Titan, you'll have heat added to that,

and all of a sudden, you'll have liquid water

surrounded by organic material --

I mean, literally, anything you need for the start of life.

If life does exist on Titan,

it would be truly alien.

It would breathe hydrogen in place of oxygen,

perhaps swimming through lakes of liquid methane

at 300 degrees below zero.

Perhaps there are oceans of ethane.

Perhaps there are tide pools

and perhaps volcanic activity and hydrothermal activity.

Perhaps there are hot springs.

Perhaps volcanic heat

could generate enough to get life off the ground in Titan.

That's a speculation, but it can't be ruled out.

But we may not need to travel this far

to find signs of life.

We may find it on a volcanic world much closer to home...

...the red planet, Mars.

Volcanoes are everywhere

across the solar system.

Worlds like Io, Titan, and Triton

are complex, dynamic, and violent.

Once, we thought that Earth

was the only planet with volcanoes and with life.

Now we find volcanoes everywhere,

but we have yet to find alien life.

Volcanoes embody the sheer power of creation and destruction.

They go hand in hand.

It is literally true that, if there weren't volcanoes here,

we would not be here either.

In the caldrons of volcanoes is the origin of life.

Volcanoes create new landscapes,

seed the atmosphere with complex chemicals,

replace the old with the new.

If volcanoes are bound up with the processes of life,

then where is the life on other worlds?

Perhaps the answer originates in deep time,

when the solar system was young...

...on a young planet much like our own.

This is Mars.

3 billion years ago, it had active volcanoes.

One still remains --

the largest volcano in the solar system.

The cliffs leading to it are over 6 miles high.

Mount Everest would sit comfortably in their shadow,

and those are just the foothills.

This is the awe-inspiring Olympus Mons.

It covers an area the size of Arizona.

Its crater alone is 53 miles wide.

A goliath like this takes millions of years to build,

time that volcanoes here on Earth never get.

On Earth, the crust is always moving.

Deep below, a single hot spot

pushes magma through the surface,

building a new volcanic island.

But while the hot spot stays still, the surface is moving.

The new island moves away from the hot spot,

and a new volcanic island takes its place.

Mars is different.

The crust is locked solid.

On Mars, there's just none of that tectonic activity.

The crust is one big solid plate,

and so if there's a hot spot,

it just sits there and builds and builds and builds.

And you get a bigger and bigger and bigger volcano.

And that's why Olympus Mons is so huge.

Olympus Mons today

is a frozen relic of a distant, warmer past.

Mars' shrunken atmosphere

means that Olympus now reaches almost into space --

a true colossus, an extinct volcano on a dying world.

But Mars' ancient volcanic terrain

could, one day, harbor life again.

The evidence is right here on Earth.

On Hawaii, volcanoes

have created mysterious tunnels called lava tubes,

channels left behind

when torrents of molten rock surge into the sea.

But some are now empty,

and that offers us an opportunity.

Lava tubes are formed when you have an underground river

of hot basaltic lava, 2,000-degree magma, molten rock.

And picture it like a frozen river of water,

with the ice crust forming on the top.

It's the same thing,

only here, the crust is solid rock

and the river keeps flowing underneath and makes this cave,

this lava tube.

Extraordinary recent images

suggest Mars' volcanoes also may have created lava tubes.

Any planet with basaltic volcanism, any rocky planet,

will probably have lava tubes.

And now we've found a couple of them on Mars,

in places where there are skylights,

places where the roof has collapsed

and you can see from orbit right into those lava tubes.

If some tubes have collapsed,

perhaps many others are still intact,

the ancient relics of Mars' volcanic past.

Now, after lying dormant for perhaps millions of years,

these lava tubes could bring life back to the red planet.

That life will be us.

One of the challenges of living on Mars for future humans

will be the radiation environment.

And in particular, when there are solar storms,

the cosmic rays coming in can be deadly.

And having a storm shelter under some large mass of rock

is really the best way

to protect yourself from cosmic rays.

The tubes and caves of Mars' extinct volcanoes

might one day make a perfect home --

holding in air, shielding us from deadly radiation.

A long-dead volcano

could help fill a world with new life.

Volcanoes can destroy, but they can also create.

From the superheated vents of Europa's 60-mile-deep ocean

to the water volcanoes of Titan and the rock volcanoes of Earth,

vast geologic processes

shape our worlds, our imaginations,

and perhaps the very stuff of life.