Space's Deepest Secrets

The oceans define the Earth.

They're crucial to life.

In fact, without the oceans, there would be no life.

We once thought they were unique to our planet.

But we were wrong.

We've recently discovered oceans all over our solar system,

and they're very similar to our own.

Imagine this at the bottom of Enceladus' ocean.

Now, scientists are going on an epic journey

in search of new life in places

that never seemed possible.

Life has got this amazing ability to, you know,

just keep surprising us.

I want to get data back from a probe and be able to say,

"it's life, Jim, but not as we know it."

The hunt for oceans in space

marks the new dawn of an era

in the search for alien life.

captions paid for by Discovery communications.

Nearly two centuries ago,

Charles Darwin set out on a journey

across the world's oceans

to uncover the secrets of life.

What he came to understand was that the answer

to the mystery of where we came from lay beneath the hull

of his ship, the Beagle.

As he filled his notebooks with beautiful sketches

of the birds and animals he came across,

he began to formulate an idea

that life might actually have started in water.

Darwin's important for the whole story

of evolution of life and natural selection,

where we all came from,

how life ultimately started as well.

A lot of that goes back to Darwin.

He had ideas, not very well publicized ideas,

not in "the origin of species,"

but on how life started in a small, warm pond.

So Darwin had put his finger on the importance of water

and the origin and evolution of life very early on.

Water is so essential

that it's dictated where scientists look

in the search for life in our solar system.

Life needs water. You look at all life-forms on earth,

the one requirement they all have in common is water.

An ocean may be a good place to incubate life,

and, not surprisingly,

an ocean has got what life needs to survive.

Everywhere where we look on earth,

whether it's frozen or boiling hot,

wherever we find water, we find life.

Water is our working fluid.

You're mostly made up of water, I'm mostly made up of water.

The search criteria was simple,

to find life, first find a liquid ocean.

Only, beyond earth,

there didn't seem to appear to be any in our solar system.

There used to be the idea of the goldilocks zone,

where everything was just right

for water to be in the liquid stage

on the surface of a planet,

and earth was slap-bang in it.

Venus was too close to the sun,

too hot really for liquid water on the surface.

Mars, thought to be a little bit too far away.

But is finding liquid water

and life on Mars impossible?

We have been sending increasingly more complex

and sophisticated spacecraft

to the red planet for decades,

and we now know more about it than we ever did.

Unfortunately, all the scientific evidence

gathered so far points to Mars being dry, cold,

and seemingly lifeless.

But has it always been that way?

It's a question that's intrigued scientists

and astronomers like Geronimo villanueva for years.

Ironically, the search

for evidence of an ancient martian ocean

is being conducted from one of the driest places on earth...

the atacama desert in Chile.

So there's a strong relationship

between Mars and atacama because Mars is a very dry place,

and atacama is one of the driest places on the planet.

Actually, the relative humidity measured

by the Curiosity rover on Mars is practically the same

as we are right now here on this desert.

Fittingly, it's that lack of water

that makes the atacama the perfect place

to build one of the biggest telescopes in the world,

because water in the atmosphere here

would drastically limit the telescope's ability

to find water anywhere else.

Water and many other things

like organics are what we're looking for.

So we come to a place which devoid of those things,

like a desert.

So we don't get the contamination from those things

when we observe for the atmosphere.

So when you come to a place like this, you're looking for...

you're trying to look through the water in our own atmosphere.

What's immediately obvious to anyone

with even an ordinary telescope

is that there is water on Mars,

but today, it's frozen solid at the poles.

Yet the martian landscape looks strangely

as though it was carved and shaped by liquid water.

Planets show all this morphology,

geomorphology driven by water... a huge amount of water.

So the estimates of how much was on the planet

vary a lot because we didn't know.

I mean, we see all this carving, all these big valleys.

And so how much water was there was a big question.

Answering that question was pretty much impossible

until scientists got lucky in 1984 in another desert,

this time in the coldest place on earth...

Antarctica.

Here, they found a remarkable meteorite.

Analysis confirmed it was martian in origin

and that they had discovered the key

that would unlock the mystery of Mars' watery past.

So once we identify when in the history of our solar system

where it came, then say,

"okay, this rock is dated there and it comes from Mars."

So you have a good reference point

in time and in place of that rock.

Careful analysis revealed

that this meteorite was 4.5 billion years old.

The meteorite also carried crucial chemical information,

an isotopic signature fixed by the amount of water on Mars

4.5 billion years ago.

On its own, this signature was worthless.

But by measuring the amount of water on Mars today,

then comparing the signatures of recent rocks

against the ancient meteorite,

all would be revealed.

And that's where the huge telescope comes in.

It's so powerful,

it can detect water molecules on the surface of the planet.

Armed with a precise measurement

of the amount of water on Mars today,

Geronimo was able to make an astonishing calculation.

We extrapolated back in time,

and we infer that there was

almost seven times more water than is right now.

What happened, Mars... topographically speaking...

has very low plains in the north

and very high-altitude plains on the south.

So if you flow water,

it will tend to flow into the lower topography,

which is gonna be the northern plains.

So one of the things we did is, okay,

so we had this body of water,

and so what do we do with this?

So one trick, we said,

"okay, let's just throw it on the planet,

and let's see where it falls."

And I just did, like,

you know, follow the rivers and everything,

and it formed an ocean

on the northern plains of the planet.

4.5 billion years ago,

a martian ocean covered 19% of the planet

and was as deep as the mediterranean.

In fact, NASA's planetary models

reveal a Mars at its warmest,

complete with an earth-like atmosphere.

If you were in an alien space craft

randomly coming to earth, the chances

are better than even that you're gonna end up in water.

So bring a boat.

And it was the same on early Mars.

And that's a fundamental point,

that Mars was a water world.

It would have been better

to characterize it as a water world.

Whereas now, of course, it's a desert world.

But it's that water world that's interesting.

That's the world that may have had life,

and that's the world we want to investigate.

It even had waves.

The reduced gravity on Mars

meant that these waves

would have been twice as tall as those on earth,

a surfer's paradise.

But according to NASA's scientists,

most of the time,

you'd have to be pretty tough to catch a martian wave.

If we think back to early Mars,

we would expect it to be an earth-like environment...

if it had water and a thicker atmosphere and was warmer.

The one big difference, I think,

would be that it would be more like the arctic ocean.

It would be an ice-choked, ice-covered ocean.

So if you imagine standing on the north shore of Greenland

looking out at the ice packs moving,

I think you get a good imagination

of what early Mars might have looked like.

It may have been cold.

Mars is much further away from the sun than the Earth.