Finding Life Beyond Earth Page #7

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in the middle to fill the gap.

NARRATOR:

In addition to the dark cracks,

the probe also reveals

vast jagged areas of ice

that appear to have melted,

broken apart,

and frozen back together again.

SPENCER:

There's something very

dramatic happening

to destroy the existing

surface there.

NARRATOR:

To an expert eye,

it's a familiar pattern.

Sea ice found on Earth

looks very similar.

Then Galileo takes readings

of Europa's magnetic field.

These indicate an electric

current flowing inside,

consistent with an ocean

of salty liquid water.

It's very hard

to get that pattern

without having an ocean

underneath the ice.

NARRATOR:

The magnetic field data

suggests that miles down,

beneath Europa's icy surface,

there is an ocean

that could be 60 miles deep.

This small moon could have

twice as much liquid water

as in all the oceans on Earth.

Something must be melting

the moon from deep inside.

And again, the key is Jupiter.

The same gravitational forces

that flex Io's rocky interior,

turning it

into an ocean of magma,

are melting Europa's ice

to produce its hidden ocean

of liquid water

and creating the cracks

on the moon's icy surface.

SPENCER:

The ice is creaking

and groaning around.

That generates a huge amount

of friction

and a huge amount of heat.

NARRATOR:

But the question is,

could anything live in this

cold, liquid ocean

concealed beneath miles of ice

where there is no energy

from the sun?

To find out, biologist Tim Shank

explores the oceans

here on Earth that most resemble

Europa's icy depths.

200 miles from the North Pole,

Tim sends robots to search

for life

1 2,000 feet beneath

the Arctic ice sheets,

where the sunlight

never reaches.

TIM SHANK:

Exploring the deep Arctic Ocean

is not unlike exploring

another planetary body

in our solar system.

You have to deal with immense

pressures, temperatures,

extremes where life might exist.

NARRATOR:

Here, volcanic activity is

pushing apart the sea floor.

Scientists believe that

something similar may be at work

under the ocean on Europa.

GREEN:

We believe it has a rocky core,

that rocky core is under tidal

forces and influences

and it's flexing also, just as

the rest of the planet does.

And that heat

has got to go somewhere.

NARRATOR:

On the restless floor

of the Arctic Ocean,

Tim's robots discover evidence

of an extremely hostile

environment.

Volcanic vents are spewing out

water

that is super-heated

to 700 degrees

and laden with toxic chemicals

like hydrogen sulfide.

Tim believes

that vents like this

could also exist on Europa's

ocean floors

and, clustered around the vents

in pitch darkness,

Tim's team finds life.

SHANK:

We discovered new forms of life,

microbes that cover miles

of the sea floor there.

There's life even

in the coldest waters

in the deepest regions

of our polar oceans

that we didn't know about

before.

NARRATOR:

Instead of using sunlight

to trigger vital reactions,

microbes like these use

sulfur, hydrogen, and methane

as chemical sources of energy.

And the microbes form the basis

of an extensive food chain.

The discovery of life here

raises the possibility

of life on Europa.

SHANK:

It's clear to me that the basic

components, the basic elements,

the chemical elements that we

need for life are on Europa.

There's nothing

that I can think of,

no component that's missing

from the Europan ocean.

I would be surprised if we

didn't find life there, really.

NARRATOR:

With liquid water,

an energy source,

and the necessary chemical

building blocks

perhaps delivered by comets

and asteroids,

Europa opens up the possibility

that life could exist

in places never imagined.

GREEN:

And so the moons,

as they go around the planets,

are generating heat,

melting water, creating--

under ice shell-- oceans

and producing a potential

environment for life.

That is a revolution

in our thinking.

NARRATOR:

But getting a probe safely

to the surface of Europa

to test these theories

is just one of the challenges

in looking for life

half a billion miles away.

STEVE SQUYRES:

You've got to build something

that can get through

what is surely

kilometers of ice.

That's hard to do on Earth.

Then you've got to have

something that can swim.

It's going to happen.

I would love to live to see it,

but it's a tough one.

NARRATOR:

Europa isn't the only

intriguing place

this far out

in the solar system.

Could similar conditions exist

on other moons

orbiting other planets even

further away from the sun?

One mission launched to find out

is the probe Cassini.

It is heading for the ringed

planet, Saturn,

one billion miles from the sun.

Its mission:

to explore Saturn, find out how

its vast rings formed,

and investigate some

of its more than 60 moons.

PORCO:

Cassini's mission

from the outset

was to investigate everything we

could about the Saturn system.

It is a major exploratory

expedition.

NARRATOR:

Cassini gives scientists

their best view yet

of this mysterious

planetary system.

Cassini was outfitted with

the most sophisticated suite

of scientific instruments

ever carried

into the outer solar system.

It has cameras, spectrometers.

It is really the farthest

robotic outpost

that humanity has ever

established around the sun.

NARRATOR:

Seven years after launch,

Cassini finally enters orbit

around Saturn.

These images reveal the rings

in unprecedented detail.

They stretch out across hundreds

of thousands of miles,

yet in places they are just

tens of feet thick.

Using its instruments to analyze

wavelengths of reflected light,

Cassini confirms

these majestic rings

are made of billions

of shining particles

of almost pure water ice.

They range in size

from a grain of dust

to the size of a mountain.

After nearly eight months

collecting data

of Saturn and its rings,

Cassini makes its way

to one of the closer moons.

This tiny ball of ice only

300 miles across is Enceladus.

These Cassini images reveal

a glistening white surface

unlike any other

of Saturn's moons.

It is carved with crevasses,

ridges, and cracks,

and stretching out across

the south pole,

Cassini photographs these

strange large cracks--

seen here in blue--

four parallel fissures

scientists named

the Tiger Stripes.

They are 75 miles long

and hundreds of feet deep.

They look a lot like

fault lines on Earth.

PORCO:

Enceladus was a major focus

for the Cassini mission.

It was clear that there had been

something going on on Enceladus

in the past.

The question was,

was there anything going on

on Enceladus at present?

NARRATOR:

On another flyby, Cassini's

thermal imaging sensors

reveal something unexpected.

At the south pole,

the Tiger Stripes

should be colder

than the rest of the moon,

but they are radiating heat.

Though still a frigid

minus-1 20 degrees,

the cracks are more

than 200 degrees warmer

than most of the moon.

Then, as Cassini

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