Original subtitles

Mars.

The red planet.

Many scientists believe that the first person

to set foot on its surface is alive today.

Perhaps it's you.

If it is you, then welcome to your ultimate travel guide.

Using real images and data,

we will take you to some of the most jaw-dropping landscapes

discovered in our solar system

right here on Mars.

We don't have anything like this on earth.

Places that may change

the way you think about our own world...

Is there life beyond the earth?

This is probably one of the most profound questions

that's ever been asked by the human mind.

...on a journey that will test the endurance

of any traveler.

Traveling to Mars is not for the faint of heart.

At the dawn of the next golden age of exploration,

here's your quintessential guide to the martian frontier.

Oh, it's beautiful.

Have you ever dreamed about traveling out of this world?

My name is Mike Massimino,

and I turned that fantasy into a reality

when I space-walked to repair the Hubble space telescope.

Great job, Mike.

Now as we expand our knowledge of our solar system

from Mercury to the cosmic unknowns,

I want to take you on a personal journey to...

-- Captions by vitac -- www.Vitac.Com

captions paid for by discovery communications

welcome to "the planets."

I'm Mike Massimino.

Ever since my space missions,

I've thought about which planet in the solar system

I'd like to visit.

Hands down, it's Mars.

So far, humans have only touched down on our moon,

but that could change.

NASA is planning on sending its first astronaut to Mars

as soon as 2030,

but there's a whole lot more

we need to find out about our neighbor before we visit.

The red glow of Mars

is a constant feature in our night sky.

But it's only when viewed up close

that this rusty planet begins to reveal its secrets.

It promises to wow any visitor

who just traveled the seven months it would take

to get there from the earth by spaceship.

Other than our home planet,

there is no world we know in such detail.

That's thanks to the numerous satellites and rovers

we've sent there over the past 50 years.

And the landscapes they have looked down upon

tell astonishing stories.

Vast plains riddled with hundreds of thousands

of craters, deep canyons, and strange rock formations,

and views not seen anywhere on earth.

We've photographed every corner of the planet,

and plans are now under way to send the first humans to Mars.

But what does it take to get there?

How can we survive on the surface?

And where are the best places to explore?

For those ready for adventure,

the best place to start is a well-known martian landmark --

Gale crater,

a vast scar on the planet

and home to NASA's flagship rover, curiosity, since 2012.

The crater itself dwarfs any similar features here on earth.

Every day, curiosity sends back detailed images

from within the crater.

This is one of them.

And here, at the data science institute,

professor Sanjeev Gupta is part of the team studying them.

This is the crater rim over here.

This is 150 kilometers in diameter.

It's a really big feature.

And there, in this view over here,

what we can see is mount sharp.

That's 5 kilometers high.

That sits in the center of the crater, so it's really amazing

'cause you really get a sense of this mountain

that's sort of towering high above us.

That's a mountain over 93 miles across

and over 3 miles high.

But professor Gupta isn't simply enjoying the view.

Today, we know Mars as a dry, desolate world,

but some images suggest that wasn't always the case.

Gale crater was chosen as the landing site for curiosity

after a very lengthy selection process.

Orbiters had discovered evidence

that the rocks at the base of mount sharp --

so, the rocks that we can see over here --

had evidence for hydration.

Long before curiosity left earth,

satellite images like this

hinted there was more to this crater than meets the eye.

And what's beautiful in this image

is that you can see these canyons or valleys

carved into the crater rim,

and this is really suggestive

that water flowed down the crater rim

and eroded these canyons.

Secondly, we can see all these beautiful layers here

that form the base of mount sharp.

These layers are enriched in hydrated minerals.

So, those are minerals that contain water.

Curiosity's mission?

To follow the elusive trail of water on Mars.

So, essentially, the orbital images

provide us clues on where to go,

but we really need to be on the ground,

looking carefully at these rocks from a few meters away,

and that's why we send rovers to Mars.

Once the rover touched down,

it quickly began picking up more clues.

These are actually pebbles

that are a few centimeters in diameter.

What you can see when you look at the pebble outlines

is that they have rounded shapes.

So they've been, basically, rounded

during a transport process.

And they're too large

to be moved and rounded by wind processes,

and so the only way we can actually get this rounding

is by water flow.

I think it's irrefutable

that there was once water flowing at the surface on Mars,

based on the geological evidence.

But even with its smooth surface,

Gale crater wouldn't be the best landing site on Mars.

So the question remains, where should you first touch down?

This canyon is Valles Marineris,

named after the mariner 9, the NASA mission that discovered it.

The scale of the canyon is breathtaking.

It is like the Grand Canyon on earth, but supersized.

In places, its walls plunge 6 miles down,

a unique geological formation

not matched anywhere else on the planet.

And it's thanks to this geology that this vast canyon system

makes the ideal landing site for martian explorers.

Astrogeologist Dr. Jim rice is confident in this conclusion.

He's been involved in selecting Mars landing sites

for every NASA mission since Mars pathfinder in 1994.

You want something fairly flat, not too rocky, not too dusty.

And because we use parachutes to help slow us down

in the entry to the martian atmosphere,

we're gonna be lower in elevation.

And the views while landing would be jaw-dropping.

Valles Marineris is a great spot

because it's basically kind of like the Grand Canyon here.

It's like someone has taken --

a giant surgeon with a scalpel making an incision

and opened up the crust of the planet,

allowing you to see deeper down,

and deeper down in geology is further back in history.

It's this view inside the planet

that is the big draw for Dr. rice,

but for most of us, the epic scale alone

would be enticing enough.

Now, that canyon is 10 times longer

than the Grand Canyon here,

it's four times deeper, and about 12 times wider.

Another way to think about it is,

the vast expanse of this canyon system,

the length of it would be from New York City to Los Angeles.

So that truly is the grand canyon of the solar system.

Valles Marineris would provide the ultimate draw

for any martian visitor.

But it's not just the views that are attractive.

Touching down inside Valles Marineris

could help answer long-held questions

about the chasm's formation.

Images like this, taken from orbit,

give us some clues to its history.

Once theory is that ancient volcanoes

ripped apart the surface,

creating a rift that running water continued to carve.

But only by landing there can we gather the conclusive proof.

What you want to do as a geologist

is get to outcrop like we see right here,

a slab of rock you can get up and interrogate

and kind of taste, so to speak, with your instruments.

If you're a martian coming to earth, you'd probably come here,

because you'd get a good idea

of the geologic history of the earth

from the rim all the way down to the floor.

You know, most of these rocks

record oceans that came and went,

mountain chains that came and went,

deserts that came and went.

You know, on Mars, I think it'd be safe to say

you'd go back 3, 3 1/2, maybe even 4 billion years

at the floor of the canyon down there.

I'd go in a heartbeat.

Would you take the chance to travel to Mars?

Visiting the red planet is not just about sightseeing.

Once you get there, you'll have to survive

some of the harshest conditions in the entire solar system.

Years of hard work and planning

went into my missions to the Hubble space telescope,

but preparing to go to Mars is a whole other story.

There'll be ice-cold temperatures

and solar radiation coming at you from every angle.

So to meet these challenges,

scientists are coming up with some useful new tools

to help us survive.

Mars is a barren world,

with its water and atmosphere long lost to the hands of time.

For human space travelers,

it would be an absolutely inhospitable environment.

That is why researchers

have descended upon the volcanoes of Hawaii,

an environment on earth that closely matches Mars

in terms of landscape, at least.

They're trying to figure out how we can survive

on the desolate and hostile planet.

Michael lye and his team have designed a space suit

to simulate Mars missions here on Hawaii.

Once you land on Mars, you're basically living in a vacuum.

It's got an atmosphere, but not much.

And while you're there,

you won't be able to go outside and breathe naturally.

Temperature-wise, it's gonna be extremely cold many times.

And it's generally a pretty hostile environment --

solar flares, U.V. radiation, Alpha particles,

other kinds of radiation from the sun,

as well as cosmic radiation

that's coming from all over the solar system and beyond.

You have to wear a space suit

the entire time you're on the surface of Mars.

Temperatures on Mars can plummet

to below negative-195 degrees near the poles.

Containing virtually no oxygen,

the wispy atmosphere has a pressure of just 0.6%

of what can be found at sea level here on earth.

This is why space suits will be one of the critical components

for any future human missions.

So, you need something

to protect you from essentially exploding

or at least having your skin all stretched out

and the blood boiling and getting the bends,

things like that.

The way space suits are designed now,

they're mostly pressurized spacecraft.

Essentially, they're almost like a mini spaceship.

Oh, it's beautiful, Mike. It really is.

Martian visitors will require a full face helmet,

permanent oxygen supply, life support,

and electrical systems

just like astronauts on board the international space station.

But you'll have to look beyond your space suit

for safety and shelter.

The next location in our Mars travel guide

is one that could provide some much-needed refuge

for the weary traveler -- the Tharsis region,

home to some of the largest volcanoes in the solar system,

including Pavonis Mons.

This may not look like a typical home,

but buried just beneath the surface of this volcano

is a unique feature that offers protection from the elements,

and, remarkably, similar features

can be found right here on earth

if you know where to look for them.

We're out here on an A'a flow in Hawaii.

This lava flow originated towards the summit of Mauna Loa

and has flowed about 20 kilometers

towards the ocean here.

But what you don't see is that this lava flow

is covering a vast network of lava tubes that is now below us,

and that's what we want to get to.

Volcanoes are cool

'cause we find them all over the solar system.

Volcanism is a fundamental process

for shaping planetary bodies, for shaping moons,

so the more we can learn about it, the more we can understand

our solar system and our universe.

The surface of Pavonis Mons

is riddled with lava tubes like this,

natural caverns that formed

when the planet was still volcanically active.

NASA volcanologist Dr. Brent Garry

has dedicated his career to understanding these features.

As a lava flow is coming down,

these tube systems can form underneath a solid crust.

So you'll have a hard crust on the outside,

and the interior will be the lava,

the liquid rock flowing through it.

Think of the London underground.

It's like a subway system of lava going through there.

And as the lava drains out,

that's when we're left with these giant cavern systems

that we see here, that we're inside right now.

Today, Dr. Garry is using light detection

and ranging technology, or LiDAR,

to create a 3-d model of this lava tube in Hawaii.

What we're building with all the LiDAR scans

is a map of a lava tube.

LiDAR is an optimal system to use

because it doesn't need its own light source.

It can see in the dark.

Until we land on the red planet,

mapping lava tubes on earth is Dr. Garry's best chance

of understanding their martian equivalents.

This is a map created on one of his previous expeditions.

Here, we're flying through

one of the collapse pits,

and what we're capturing

is the shape, the dimensions,

the morphology of the whole entire lava-tube system.

But we're also capturing the details

of all the different textures

that are on the inside of the lava tube.

Traveling to Mars is not for the fainthearted.

You need to be prepared for a harsh, dynamic environment.

Micrometeorites rain down,

dust storms rage for weeks at a time,

and radiation levels are up to 250 times higher than on earth.

Lava tubes would provide much-needed sanctuary

for any travelers weary of the ferocious martian climate.

And for those willing to venture outside,

the lava tubes provide the perfect base

to explore the rest of the Tharsis region

and its staggering volcanoes.

Home to 12 volcanoes near the martian equator

and stretching across 2,500 miles,

the volcanoes here are record-breaking --

up to 100 times larger than anything on earth,

including the largest volcano in our solar system, Olympus Mons.

This would surely be one of the top tourist attractions

for any traveler visiting Mars.

No trip is complete without sharing these spectacular sights

with your family and friends,

but a postcard wouldn't make it home to earth.

Instead, scientists are coming up with cutting-edge technology

to make sure our loved ones

never miss a moment of our martian adventure.

Communication to mission control during space travel is vital.

And for me, it was also essential

to stay connected to my family.

It was on my second mission

that I sent the first tweet from space.

And as we prepare for future missions to Mars,

what about space texting?

Researchers are suggesting that we try that,

along with some other groundbreaking methods.

With so many stunning images,

it's easy to forget just how isolated Mars is from earth.

Intrepid travelers will need a way to keep in touch with home.

NASA engineer Dr. Kara Beaton is part of the team

investigating how future Mars explorers

will be able to communicate.

The shortest journey

that you would have for a Mars mission

is close to three years.

It's about six months of transit time there,

and then you need to wait for about a year or year and a half

on the surface before you can begin

your return journey back to earth.

Three years in isolation

with a very small crew of just a couple people

and limited communication with family and friends on earth

is a big challenge that NASA is currently looking into.

Today, Dr. Beaton and her colleagues

are testing prototype communications backpacks.

So, because of the very large distances

between earth and Mars --

anywhere from 35 million to 225 million miles --

there is a communication delay between someone talking on earth

to someone on Mars and vice versa.

So if I were to have a conversation with you

and I'm on Mars and you're on earth

and I speak over a voice comm loop,

it would take anywhere from 4 to 22 minutes to get to you,

and then, for you to respond,

it would take another 4 to 22 minutes

for me to hear that response.

By seeing how these sorts of delays

impact real fieldwork,

Dr. Beaton and her team are able to develop solutions.

So, we've come up with different techniques

for how to best communicate.

So, obviously, voice is one way,

and certainly, that's a viable option,

but we've also found that text-messaging is good

because that allows the crew members

to do something else on the side

while they're waiting to hear a response.

But in a real Mars mission,

how would you actually send and receive these messages?

To begin, you'll need one of these --

a nearly 230-foot radio telescope.

Richard Stephenson is a radio engineer

here at the Canberra deep space communication complex

in Australia.

The deep space network is capable

of sending and receiving high-frequency radio signals

billions of miles away,

even to the very edges of our solar system.

The deep space network has three complexes around the globe,

and they're spaced around about 120 degrees apart.

So, as the earth rotates, we can provide 24/7 coverage

to any of the missions that we're supporting.

These radio dishes are our eyes and ears on the planet,

and any information we get back from Mars

is received right here.

Well, this antenna --

deep space station 43 is our 70-meter antenna.

It's a very heavy-duty antenna.

We're looking at 4,000 tons of steerable metal.

So regardless of wind, weather, we can support the spacecraft

that need to communicate to earth.

As we prepare to send the first human explorers

to the red planet,

building up a martian communication infrastructure

is going to be key.

The deep space network's motto is

"don't leave earth without us."

We're the traffic control of the solar system.

Thanks to radio telescopes like these,

strategically positioned around the globe,

travelers to Mars won't be isolated from everyone

back on earth.

If you're one of them,

you'll be able to communicate with your loved ones every day,

waxing lyrical about the epic wonders you have seen.

These telescopes will be the sorting offices

for the most spectacular postcards in the universe.

Despite its stunning landscapes, Mars has a dark secret,

a history shrouded in mystery and destruction.

If we are ever going to plan future expeditions to Mars,

we've got to understand its violent past.

For the past 50 years, unmanned spacecraft and rovers

have gathered incredible images and data

about our elusive neighbor.

But even though Mars is the planet

that we know the most about,

there's still a lot to understand

before we consider living there.

This is Orcus Patera crater.

Nearly 250 miles long, it dwarfs any features nearby.

No one knows quite how this unusual teardrop crater

was formed.

The latest in a long line of mysteries,

it will provide an intriguing stop on any martian adventure.

Mars has a lot of craters.

Most of them are circular.

You can see these craters 40 or 50 kilometers across --

they tend to be circular.

But there are some that are not.

Now, if I were going to Mars,

the one I would like to go to the most is the whopper.

It looks like a whale.

In fact, it's called Orcus Patera.

"Orcus" means "whale."

So, there's something odd.

Look at all the other craters. They're round.

What formed this?

Coming down.

Until we go there ourselves,

our best shot at answering that question

is to re-create the impact here on earth,

and professor Peter Schultz has just the experiment.

Going back.

This is the NASA Ames vertical gun range,

a unique facility

that simulates high-speed celestial body impacts

on a small scale.

Today, professor Schultz

is trying to re-create the Orcus Patera crater.

This is a case of trying to simulate what happens

when you have a giant projectile --

an asteroid or even a moon -- collide with Mars.

So, we're gonna try that here.

The target sits

inside a large pressure- controlled impact chamber.

So, at the chamber,

we can control the atmospheric conditions.

And we have a projectile

that will be launched to go through this hole,

this launch tube,

maybe about eight times the velocity of a speeding bullet.

So now all we have to do is really lock and load.

Professor Schultz has rigged the gun

so that it fires at just 15 degrees from the horizontal,

simulating an oblique meteor strike.

With everything in place,

the final step is to fire the projectile.

Rolling.

Oh, good!

We got it, we got it, we got it, we got it.

Let me see, let me see, let me see.

5.60 kilometers per second.

Well done, sir.

Whoa!

It looks like it worked.

So, instead of getting a round crater,

we have an oblong crater,

and we have an oblong crater

that has multiple impacts downrange.

There's a really low rim here, high rim there, and a shelf.

And it requires a very low-angle impact,

and I think that's what's happened on Mars.

The crater is almost a mirror image of Orcus Patera,

scoured lengthways across the landscape.

And professor Schultz has a theory for how it was formed.

A moon going around Mars is in an orbit,

and eventually, that orbit decays,

gets closer and closer to Mars.

In fact, the moon Phobos going around Mars right now

will collide with Mars

in something like 28 million, maybe 30 million years.

So, when that happens,

it'll come in at an extremely low angle,

grazing, just like a spacecraft trying to come in for a landing,

except it's not gonna land so well.

It's gonna collide

and form a crater very similar to Orcus Patera.

Mars has two potato-shaped moons --

Phobos and Deimos.

But Peter's audacious thought

is that there was once another lost moon orbiting the planet.

The theory makes sense, but the jury remains out.

Situated close to some of Mars' largest volcanoes,

other scientists argue that volcanic forces

could have created the crater

by stretching and compressing the ground.

If we are to discover the crater's true origins,

we must go there ourselves,

because it's only by studying landscapes up close

that we can fully understand them.

Imagine standing atop the crater rim

rising a mile above the surrounding plains,

looking into the depths of the crater below.

What an incredible and enigmatic stop

on your adventure across Mars.

Just like preparing for a trip to a foreign land,

smart packing will be a must for Mars.

So what should you fill your suitcase with?

For starters, you may want to bring a winter coat.

Mars is nicknamed the red planet because of its crimson color.

But take a closer look,

and you'll see beautiful white swirls.

Learning more about these mysterious white ribbons

may unlock the secrets of how Mars formed

and where it's headed.

Your ultimate travel guide to Mars

includes marvelous canyons,

the most spectacular volcanoes in the solar system,

and even underground caves.

But there's no better place

to explore the mysterious martian landscapes

than at the southernmost reaches of the planet.

It may be well off the beaten track,

but the extra effort required to get there will be worthwhile.

This is Mars' Southern polar cap,

one of the coldest places on the planet.

Temperatures here can drop below minus-248 degrees Fahrenheit.

It's an icy destination

that planetary scientist Dr. Meg Schwamb

has long held a fascination.

So, we're standing on a dormant volcano

on the big island of Hawaii.

And so, this is where we have

some of the world-class telescopes

that are observing the night sky.

So, I'm really interested in the south pole of Mars,

and so how that can tell us more about Mars' past

and its current history.

On a clear night, the poles of Mars

can even be seen through small telescopes from here on earth.

Amateur images like these

show the bright ice caps against the red disk of the planet,

but their true wonder is only truly revealed

with images taken from orbit.

At over 248 miles wide and almost 2 miles thick,

the Southern polar cap is a freezing vision

of swirling white on an otherwise rusty-colored planet.

Though it may look much like the south pole on earth,

it has one crucial difference.

So, as you can see behind me,

there's some white dotting the surface,

and that's actually some snow left after

from one of our recent snowfalls.

But on Mars, in the south pole,

there isn't water ice that's exposed, or snow.

It actually snows carbon dioxide.

Often referred to as dry ice,

in the martian winter, this frozen carbon dioxide

blankets the Southern reaches of the planet.

Come spring, when it melts, it transforms straight into a gas,

dramatically changing the landscape

and creating a remarkable phenomenon.

So, what happens on the south pole of Mars

is that you have this layer of semitranslucent ice

on top of the dirt,

and when the sun comes up in the spring and summer,

the sunlight penetrates through down to that dirt layer

and heats up.

Because it's warm, the carbon dioxide ice in contact with it

starts to turn into gas.

And so now you have a layer of gas

trapped underneath a layer of ice.

The consequences of this thaw are quite spectacular.

So, when this gas is trapped underneath this ice sheet,

it breaks through in any way it can through the ice.

And when it gets to the surface, it creates these jets or geysers

on the surface of the south pole of Mars.

Gas is rushing out maybe a few meters --

not much further, we think.

But it brings up this dust and dirt from below that ice sheet.

If I was standing on the surface of Mars,

you'd see these sort of dark jets coming up,

and it's the local surface winds

that blow these material into these dark streaks.

And then, when there's no more carbon dioxide ice,

it disappears.

Seen from space,

this windblown dust creates breathtaking landscapes.

But these images aren't simply pretty.

They tell us about the martian climate, too.

If we can study how these geysers form, these jets,

and how the wind sort of blows these material,

we can learn more about the martian atmosphere.

This process is completely alien.

We don't have anything like this on earth.

These features disappear each year,

but they leave behind another wonder in their wake --

the real spiders from Mars.

If we look a little deeper into these images,

what we find, that when there's no carbon dioxide ice anymore,

the fans go away.

And what's left in many of these areas

are these kind of dendritic, like, spider-like features,

which actually has been informally dubbed spiders,

or aranea forms.

These erosion channels meet in a central pit

resembling the body and long legs of a spider,

legs that can stretch for hundreds of miles

and can take more than 1,000 martian years to grow.

Explorers lucky enough to stand at the south pole

during a martian summer

would gaze upon these alien spider-like features

stretching across the landscape.

They would be offered a taste of martian weather

and witness the dramatic proof

that Mars is far from the dead and unchanging planet

that many people assumed.

Mars' icy poles provide some respite

from the desert landscapes that cover most of the planet.

And the more adventurous traveler

may also choose to follow the elusive trail of liquid water

on the martian surface.

In doing so, they will uncover the hidden story

of ancient Mars.

Thanks to the curiosity rover,

we now know that Gale crater

was once the site of an ancient lake.

But where did all the water go?

And how did it shape the landscape we see today?

To see that, Dr. Gupta

needs to look at Gale crater 3.8 billion years ago,

just after it was formed by a meteor impact.

So, this is really cool here.

We've got an augmented reality sandbox,

and so what I'm doing now is, I'm creating the crater rim.

So, there would have been a mountain

in the center of the crater

formed during that impact process.

That forms the core of mount sharp.

When Gale crater first formed,

it's thought Mars had a much more substantial atmosphere,

making the planet warmer and, therefore, wetter than today.

And the water fell across the planet's surface

as rain and snow.

We've got rain forming on the crater rim

and then gushing out into the center of Gale crater

and building up.

As it poured down into the crater,

its water shaped many of the features we see today.

Imagine, if you have heavy rainfall,

rainfall over hundreds of years,

the landscape gets progressively eroded

and carves deep canyons and valleys.

The sediment eroded from those gullies

would have washed into Gale crater,

forming those river deposits that we can see so beautifully

in the images that curiosity takes.

And then the climate changed.

It lost its atmosphere and became arid and hyper-cold,

and all that water evaporated.

And we were left with a crater infilled with sediment.

The rusty, ancient surface of Mars

has enigmatic landscapes at every turn,

from towering sculpted peaks to hidden underground caverns.

And if you are one of the first explorers,

you will need to study every detail.

Each landmark holds its own clues to Mars' mysteries,

and there is no greater mystery

than whether life exists beyond the earth.

As a stranger from earth,

will you be greeted by martian life when you arrive?

When people meet me for the first time,

the question I get asked the most is,

"is there life somewhere else in the universe?"

And while I don't know for sure,

I love the possibility that life could exist on other planets.

So how do we find this life,

whether it be past, present, or future?

There's one scientist that says the proof is in the salt.

To stand a chance of finding life on Mars,

it's thought travelers will need

to journey to a region of the planet

unexplored by landers or rovers.

Perched in the remote Southern highlands,

Terra Sirenum is a land of cratered terrain

capped in crystalline mineral deposits.

It's thought that if we're going to find signs of local wildlife,

past or present, then this will be the best spot.

Of all the questions astrobiology asks,

probably its biggest one is, is there life beyond the earth?

When we're assessing whether a planet is habitable,

we're looking for some basic things.

We need some liquid water

for all those chemical reactions to happen in,

we need a source of energy, like sunlight or chemical energy,

and we also need some basic elements

like carbon and phosphorus.

All those things have to come together in one place

for life as we know it, at least, to be able to grow.

Before our first spacecraft arrived in the 1960s,

the idea of visitors to Mars

setting foot on a lush, living planet

seemed like a perfectly reasonable idea.

In the early history of Mars,

the planet would have looked quite a lot like early earth.

There would have been liquid water on the surface.

Maybe it would have been warmer.

Perhaps during that period of time,

it could have sustained biology.

But about 3 1/2 billion years ago, that water froze up,

and the planet become what we know today --

pretty much a desert world.

Because of that, it was never able

to sustain the sort of evolutionary development

that you can see around you here.

So we need to look in places on Mars and on earth

that could give primitive life a fighting chance.

There are two types of places.

We might look in briny, salty solutions.

Those brines could still be liquid

on the surface of Mars today.

And we're looking at ancient salt deposits.

In those salts,

maybe we might try and look for signs of past life.

With that in mind,

astrobiologists like professor Cockell

started searching for the perfect spot to hunt for life.

And in time, images taken from orbit

revealed more than 200 places in the Terra Sirenum region

where thick salt layers exist.

The Terra Sirenum region of Mars

has salt deposits from ancient ponds and lakes

that essentially evaporated --

the last remnants of liquid water on Mars.

And these salts in Terra Sirenum

could preserve or record the existence of life on Mars.

And to support this theory, professor Cockell

has been investigating some

of the most remote and inhospitable places on earth.

So, here we've got some samples from the Negev desert.

Microbes that live in those environments are very tolerant

of both high temperatures and extreme dryness.

And then, these microbes are from a lake in Canada

that has very high concentrations of sulfate,

similar to the sorts of salts that we find on Mars.

Finding living bacteria in places like this

tells Cockell and his team

that Mars-like environments here on earth can support life.

But that's only half the picture.

So, this is a sample from a very extreme environment.

It comes from a kilometer underground in a salt mine.

This is the sort of sample

you might be able to find in Terra Sirenum

if you dug down beneath the surface.

The question is, could these microbes

also survive under the conditions on present-day Mars?

We've subjected these microbes

to similar sorts of environments that you might find on Mars,

so no oxygen, very low amounts of energy,

very low concentrations of nutrients.

And in those sorts of environments,

these microbes can not only survive -- they can also grow.

What these results show us

is that some of these salty environments on Mars

may well have been habitable.

It may not look like much,

but this is the closest thing to life on Mars anyone has seen.

I often joke that if you send me to Terra Sirenum

with a microscope and a shovel,

I can tell you within a few hours

whether there's life on Mars.

Astrobiologists like professor Cockell

are building a case that the salt plains on Mars

are potentially habitable.

The inquisitive traveler prepared to dig deep

might just find some of the local wildlife

sheltered beneath the subsurface.

It would be the discovery of the century

and proof that life probably exist elsewhere

in the universe too,

and it would be the perfect end to an epic journey.