Space's Deepest Secrets

Mars, our cosmic neighbor.

More spacecraft have been sent to Mars than any other planet.

One day, humans will visit, as well.

Humans should go to Mars, and we should do it quickly.

This rocky planet could almost be home.

Mars is very different than Earth,

but in many ways, it's like a long-lost brother.

Yet, Mars is an alien world.

Looking at Mars gives us some disturbing lessons

about the future of our own planet.

What lies ahead for the first human astronauts

to set foot on Mars?

To find out, we will strip the red planet...

We'll peel open its dusty surface...

And dive deep into its alien underworld,

revealing the secrets

that await the first human explorers on Mars.

captions paid for by discovery communications

Mars... it sits 142 million miles from the sun.

The average temperature is minus 80 degrees Fahrenheit.

Today, scientists are racing to reach the red planet.

In addition to the Mars missions currently in progress,

upcoming operations are intended to study Mars' atmosphere,

geology, and weather systems in more detail than ever before.

The ultimate goal...

To land the first human astronauts on Mars.

Eventually, humans have to leave planet Earth.

Mars is our first step outward.

I think that's going to be the key to our own survival

is going there and living on this planet,

and we'll be able to explore the rest

of the solar system from there.

Sending humans to Mars is really the next great challenge.

We will get there... It's just a matter of when.

Mars may be one of our closest planets,

but it is also home to some of the greatest

unsolved mysteries in the solar system.

Hidden inside...

A frozen world may hold the key to martian life.

Vast canyons that would stretch from New York to L.A.

Scar the surface.

Violent dust storms engulf the planet,

while some of the tallest volcanoes in the solar system

rise up from its plains.

These supervolcanoes hide an alien underworld.

Mars is a tantalizing destination

for human exploration.

When we first got to Mars, it just looked like

a cold, dry, dead planet, but the more we study it,

the more we learn that it's actually dynamic, alive.

Before NASA launches a manned mission,

they must confirm that Mars is habitable for humans.

So they've sent a scouting party...

The Mars Curiosity rover.

Curiosity touched down in August 2012.

It has roamed the martian surface ever since.

This 1-ton robot is the size of an SUV.

It uses its high-resolution cameras

and scientific instruments to uncover the secrets of Mars.

Here on Earth at NASA's jet propulsion laboratory,

Chris Roumeliotis is one of Curiosity's drivers.

Chris can't make mistakes with $2.5 billion worth of gear.

So he practices his skills on JPL's own little piece

of the red planet, the Mars yard.

We have all the rover drivers come up here,

and we test things to the limit so we see what happens.

Every maneuver that has been done on Mars

has essentially been tested in this Mars yard.

Chris uses a full-sized working model of Curiosity

to perfect his maneuvers.

If you ever try to drive your car over this...

Not gonna happen.

She can do it... no problem.

We actively try to avoid rocks like this, if we can.

But look how gracefully she goes over that rock...

Doesn't even drop.

Chris and his team have successfully driven Curiosity

over 12 miles and counting across the martian surface,

thanks to practice here in the Mars yard.

For humans to survive on Mars,

the first thing Curiosity must find is water.

Mars looks like a dry desert now...

But features in the landscape suggest

that Mars was once covered in liquid water.

Three layers of rocks lie beneath a top coating

of red dust.

The bottom rock layer is the oldest.

It's an ancient lake bed that contains compressed clays

and minerals once carried by water.

Next is a salty layer one mile deep.

When the water evaporated,

it left this salty residue behind, like a pan boiling dry.

On top lies a cold, dusty surface,

worn down and smoothed over by billions of years of wind.

Scientist Ashwin Vasavada leads the search for water on Mars.

We've been chasing evidence of liquid water on Mars

for decades.

Curiosity's discoveries are astonishing.

One of the first things we found with Curiosity

was rounded pebbles, about this size, rounded corners.

You don't see that naturally

without something grinding the rocks together,

and the action of the liquid water flowing in a stream,

grinding those rocks created this ancient stream bed.

This dry stream bed proves

that there was once liquid water on Mars.

We're really talking about water flowing maybe ankle-to-hip-deep.

You know, this is the first time we're really encountering,

you know, and holding in our hand,

so to speak, this evidence of a habitable environment.

But could Mars support humans today?

To find out, Ashwin needs to uncover

what happened to all the water.

One of the big mysteries about Mars

is that early in its history

is where we find all this evidence for flowing water,

lakes, maybe even an ocean.

What happened on Mars to create this dry environment

that we see today?

Scientists now believe that, 4 billion years ago,

oceans, lakes, and rivers covered the surface of Mars.

Deep inside, Mars had a hot core of flowing metal,

just like Earth.

Mars' molten core created a magnetic field

around the wet planet.

This shielded its atmosphere from the sun's radiation,

but, eventually, the core cooled

and stopped powering the magnetic field.

Without protection, Mars' water evaporated into space...

And Mars the water world became Mars the desert.

On the martian surface, Curiosity looks for proof of how

and when this happened.

The rocks may hold the secret to figuring out

how Mars evolved from that life-sustaining state

in its early history to where it is today.

Curiosity is a rover, but it's also a geochemical laboratory.

It's so big because we took these advanced

chemical instruments to Mars inside the rover,

and we feed those instruments with samples of rock and soil.

The rover now sits at the base of a 3-mile-high mountain,

mount sharp.

Its layers of rocks were laid down over billions of years.

They provide a record of the conditions on Mars

at different points in its past.

We really hope that whole geologic record

of Mars' environmental history

is preserved for us and that, just by driving through it,

we'll be driving through 3 billion,

4 billion years of Mars history.

- How's it going, Ashwin? - Hey. Good to see you.

Hey. Yeah.

So... Where we driving?

Yeah, we had some...

Chris and Ashwin use a 3-d landscape viewer

to plan Curiosity's routes toward mount sharp.

Here, we're doing an arc to the left to avoid a rock.

They see what the rover sees on Mars... accurate to an inch.

Pretty gnarly terrain.

A lot of rocks. Yeah.

But she needs to go very slow today.

Yeah, right. Because of...

The hazards, huh? The hazards, yeah.

Got it.

There's a 20-minute communication delay

between Earth and Mars, so Chris can't drive Curiosity live.

Instead, he sends a whole day of instructions

to the rover at once.

Everything that's done, in terms of operations,

has to go through this room.

It is the center of the universe for us and our spacecraft.

At JPL's mission control,

Chris hands over the list of commands.

How's it going? I think we're ready.

At the click of a button, tomorrow's maneuvers

head to Mars, guiding Curiosity

on the next leg of her groundbreaking journey.

NASA's missions prove that, at some point,

Mars was stripped of its water and atmosphere.

But was all of Mars' water lost to space?

Will future astronauts find any water

left hidden beneath Mars' desert surface?

And could they encounter martians already living there?

Within a generation, a human will set foot on Mars.

The first visitors will experience

a cold, barren terrain.

Curiosity confirmed there was once water on Mars.

Could human explorers still find water there today?

Mars is so cold that its atmosphere freezes.

Carbon dioxide snow covers the northern plains.

3 feet below this snowy crust lies an Earth-like secret...

A massive reservoir of frozen water over a mile deep.

These are Mars' ice caps.

If these ice caps melted, they would cover the planet

with over 60 feet of water.

They contain 100 times the water in the Great Lakes.

With this much water on the planet,

could there also be life?

Water is a precursor for life itself.

If there's water, there's a possibility of life.

So maybe the martians are not science fiction.