Mars - A Traveller's Guide Horizon

Mars...

..the Red Planet.

Many scientists believe that the first person to set foot

on its surface is alive today.

Perhaps it's someone watching this film?

Perhaps it's you!

If it is you, then welcome to your traveller's guide...

..a guide in which we will show you where to land,

where to live, and, most importantly of all,

what to see and do while you're there...

..from towering volcanoes...

..to unfathomably large canyons...

..and mysterious features etched on the landscape.

We'll even take you deep underground.

Horizon has gathered together the world's leading experts on Mars.

I've been interested in space exploration since I was seven years old.

We asked each of them where would they go if they got the chance.

We don't have anything like this on Earth.

And what they would need to survive.

You need something to protect you from essentially exploding,

or at least having your skin all stretched out and the blood boiling.

Using real images and data,

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

discovered in our solar system...

Standing on the rim,

I wonder, "Could I pick up the rock that actually came from

"the object that formed this enormous feature?"

..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 traveller.

Travelling to Mars, the idea sounds romantic,

but, you know, the journey is not for the faint of heart.

At the dawn of the next golden age of exploration,

we'll take you to the Martian frontier.

I cannot wait for the day

I get to see people walk on Mars for the first time.

This is your traveller's guide to Mars.

The red glow of Mars

is an omnipresent feature of our night sky.

But it's only when viewed up close

that this rusty planet really begins to reveal its secrets.

It promises to wow any visitor

who's spent the past seven months onboard a spaceship

travelling to get there.

Other than our home planet, there is no world we know in such detail.

That's thanks to the numerous successful satellites and rovers

we've sent there over past 50 years.

And the landscapes they've looked down upon tell astonishing stories.

Vast plains, riddled with hundreds and thousands of craters.

Deep canyons and strange rock formations.

And scenery not seen anywhere on Earth.

We've photographed every corner of the planet

and plans are now underway 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?

We'll start with the Martian landmark we know best.

Gale Crater,

a vast scar on the planet

and home to NASA's flagship rover Curiosity since 2012.

Arguably the most ambitious explorer sent to the Red Planet so far.

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 remote here.

This is 150km in diameter, so a really big feature.

And there, in this view over here, what we can see is Mount Sharp.

That's 5km high.

That sits in the centre of the crater,

so it's really amazing here being able to look at this image

at such a scale because you really get a sense of this mountain

that's sort of towering high above us.

But Professor Gupta isn't simply enjoying the view.

Today, we know Mars is 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.

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 metres 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 centimetres 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 have been moved and rounded by wind processes,

and so the only way we can actually get this rounding is by water flow.

And I remember when this image first came up and we were all

huddled around a giant screen looking at this,

it actually took us a while to really hit home, oh, gosh,

actually, this is the first evidence

from on the ground of water flow on Mars.

This was just one in a long list of features Curiosity discovered

within the crater that are reminiscent of features

shaped by water here on Earth.

I think it's irrefutable that there was once water flowing

at the surface on Mars, based on the geological evidence.

Rovers haven't just shown us the surface of Mars in detail,

they've also shown us how difficult it is to land.

Spacecraft structures engineer Abbie Hutty

is responsible for making sure Europe's first rover, ExoMars,

stays in one piece.

Landing's always going to be one of the trickiest parts

of getting a mission to Mars safely.

It's very hard to predict

exactly what you're going to be dropping down through

because the wind speeds vary dramatically.

You get dust storms, which really change the atmospheric density.

And fundamentally, you don't have that much thickness of atmosphere

between entering it at the top and hitting the ground at the bottom,

so you've not got very much to actually slow yourself down.

When you first hit the top of Mars' atmosphere,

you are going so fast that really

all you can do is just hide behind a heat shield and hope for the best.

During atmospheric entry,

the lander will need to withstand

temperatures reaching up to 1750 Celsius.

So eventually you'll get to the point

where you can deploy a much larger parachute,

so you have a lot more acting to slow yourself down

and, at this point, you're going slow enough

that you don't really need this heat shield any more,

so you jettison your heat shield.

The next stage is you can fire retrorockets,

so they're rockets that fire in the direction of travel.

These retrorockets can bring it to a hover about a metre,

a metre and a half above the planet's surface,

and then you can drop that final metre down onto the surface,

until you're landing there on the surface of Mars.

This is an aluminium prototype.

But the final version of ExoMars will be made of carbon fibre,

an incredibly tough, lightweight material that is thermally stable -

all qualities needed for a safe landing and successful mission.

As with any really grand challenge like this,

there's so many different stages the rover has to go through successfully

for the whole mission to be declared a success.

I think the things that really are concerning are things that are

completely out of your hands.

So the rocket launch, it's one of those kind of split-second things

that it's either going to work or it's going to go up in flames.

And then the landing as well

is another really challenging aspect and that's where a lot of missions

have failed in the past,

so definitely, when you get that safe landing confirmed,

that's going to be a big relief.

Engineers like Abbie

will one day design vehicles to take the first human travellers to Mars.

But the question remains, where should you land?

Seven months after leaving Earth behind,

Martian visitors will be met with astounding views of the Red Planet

and vast landscapes calling out to be explored.

But the perfect spot may surprise you.

This is Valles Marineris, named after Mariner 9,

the NASA mission that discovered it.

The scale of the canyon is breathtaking.

It is like the Grand Canyon on Earth, but super-size.

In places, its walls plunge 10km 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 on Mars...

..as astro geologist Dr Jim Rice can testify to.

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 into the Martian atmosphere,

a little bit lower in elevation.

And the views would be breathtaking, too.

Valles Marineris is a great spot

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

it's like someone's taken a giant surgeon with a scalpel and made

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 ten 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,

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.

One theory is that ancient volcanoes ripped apart the surface,

creating a rift that running water continued to carve.

But it's only by landing there we can 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 that you can interrogate and taste, so to speak,

with your instruments.

If you were a Martian coming to Earth, you'd probably come here

because you get a good idea of the geological history of the Earth,

from the rim all the way down to the floor.

Most of these rocks record oceans that came and went,

mountain changes that came and went, deserts that came and went.

You know, on Mars, it would be safe to say you go back three,

three and half, maybe even four billion years

at the floor of the canyon down there.

I'd go in a heartbeat.

Like many of us, perhaps even you,

Dr Rice also dreams of walking on Mars.

I mean, on Mars, we don't know what there is to learn yet.

It's this open book waiting for us to go there and sample it

and to decipher the geological history.

In a canyon system like Valles Marineris,

the book is open right there for you.

You've just got to get there and start collecting samples.

Many think Valles Marineris is the perfect landing zone.

Not only are there last flat areas to touch down,

but it would also give a tantalising hint into Mars's geological past.

And, of course, stood at the edge of the grandest canyon

of the solar system, the view would be jaw-dropping.

So, now you know how to get there and where to land.

But travelling around Mars is not just about seeing the sights.

No guide would be complete without advice for visitors

on how to survive once they get there.

Mars is a barren world,

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

For humans, it would be an 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 working out how we can survive

on this desolate and hostile planet.

Michael Lye and his team have designed a spacesuit

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 going to be extremely cold at many times

and it's generally a pretty hostile environment.

Solar flares, UV 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 spacesuit the entire time

you're on the surface of Mars.

Temperatures on Mars can plummet below minus 126 degrees Celsius 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 spacesuits 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 stretched out

and the blood boiling and getting the bends, things like that.

The way spacesuits are designed now,

they're mostly pressurised spacecraft.

Essentially, they're almost like a mini spaceship.

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.

The microgravity environment aboard the Space Station

makes the 130-kilogram spacesuits effectively weightless.

The suit itself is a little bit top-heavy,

so it makes it a little hard to negotiate.

It's actually pretty comfortable walking,

even though it weighs quite a bit.

Unfortunately, this won't be the case on Mars.

Mars is a much smaller planet.

The gravity field on Mars is roughly about a third of Earth's gravity,

so if something weighs 150 pounds on Earth it would weigh about 50 pounds

in a Martian gravity field.

The volcano looks pretty impressive over the hill.

I'm just going to take a breather here for a moment.

We're going to be doing field tests all summer on this suit,

starting with short ones like today

and going onto longer duration ones

to get it ready for the HI-SEAS mission.

HI-SEAS stands for the Hawaii Space Exploration Analog And Simulation program.

Teams of researchers regularly enter this facility to simulate

a long duration planetary surface mission to Mars.

Hidden about 2,500 metres above sea level,

inhabitants are completely cut off from the outside world

for between four and 12 months at a time.

This is footage specially filmed by the teams.

It reveals the extent of the habitat.

There are sleeping quarters, a kitchen,

laboratory, bathroom, simulated air lock and work area.

Research into food, crew dynamics,

behaviours, roles and performance are all analysed.

But it's when researchers step outside the habitat on EVAs,

or extravehicular activities,

that this Martian simulation really comes to life.

Thanks to the research being conducted in places like this,

any future travellers will be prepared

to brave the harsh Martian environments.

But you'll also need a place to shelter, a place to call home.

And if you're really clever,

Mars has some peculiar geology that you could find astonishingly useful.

Our next location is one that could provide some much-needed refuge

for the weary traveller.

The flanks of the Pavonis Mons volcano.

It may not look like a home that you or I recognise,

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 20km, you know, 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.

That's what we want to get to.

Vulcanoes are cool cos 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 the lava flow is coming down,

these tube systems can form underneath a solid crust.

So, you 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, you know, 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 at understanding

their Martian equivalents.

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

Here we're flying through one of the collapsed 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.

Travelling to Mars is not for the faint-hearted.

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

Micro meteorites 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 travellers weary of the ferocious Martian climate,

but visitors needn't be entirely cut off from the outside world.

Behind me is a skylight

and that is an opening that goes into the lava tube.

We have satellites that are orbiting Mars right now

and they have these very powerful cameras

that can image the surface with extreme resolutions

that we can actually find and observe pits on Mars

that look just like the skylight.

The view outside would be dramatic, seeing the stars.

Maybe if you're lucky you could maybe see Phobos or Deimos,

the moons of Mars, transit past the skylight.

Trying to watch a Martian sunrise or Martian sunset,

that would be pretty cool to see.

If you're down there, it just gives you this little window to the outside world on the Red Planet.

This skylight on the western slopes of Pavonis Mons is a cavernous hole

about 35 metres wide and 30 metres deep.

Perhaps this will be the window that you will look out

from your subterranean refuge.

Maybe one day, you know,

we can have the technology to get us to these areas.

First we have to get to the surface, then we have to get inside these lava tube systems,

so it's definitely going to be a challenge

and we'll need some innovative engineering to get us into these tube systems.

Explorers staying in the Pavonis Mons lava tubes

would get much-needed respite from the relentless Martian climate...

..and escape from the radiation and fine dust

that coats much of the planet.

They may even get access to underground water resources.

Surely, a destination not to be missed.

But for those clamouring for more of the great outdoors,

the lava tubes provide the perfect base from which to explore the rest of the region.

Home to 12 vast volcanoes and stretching across 4,000km,

this is the Tharsis region.

The volcanoes here are record-breaking,

up to 100 times larger than anything on Earth.

The most spectacular of all is Olympus Mons,

the largest volcano in our solar system.

With so many stunning images,

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

Intrepid travellers 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 a 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 of 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 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 com loop,

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

and then for you to respond,

it would take another four to 22 minutes

for me to hear that response.

By seeing how these sorts of delays impact upon real fieldwork,

Dr Beaton and the 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 crewmembers 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 70-metre 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.

This antenna,

Deep Space Station 43, is our 70-metre antenna.

It's a very heavy-duty antenna.

We're looking at 4,000 tonnes 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.

It's going to be up to Richard and the deep space network team

to juggle communications with future Mars travellers

and, more importantly, prevent their spacecraft

from slamming into one another in a Martian traffic jam.

So today the team are testing how this might work.

Over there, on the work station,

John is just about to commence a Multiple Spacecraft Per Aperture.

RADIO CHATTER

Essentially, what we do is we point the antenna

right in the middle of Mars and, using the beam,

we can incorporate any spacecraft orbiting Mars.

John will be supporting four.

What makes it particularly difficult is they're all orbiters,

so we have to make sure that we capture them

as they come around Mars.

This is the first glimpse of the future of our Martian communications network,

the very same one that will support the first human travellers to the Red Planet.

In two years' time,

we start possibly launching humans beyond our atmosphere

and my ambition is to be able to talk to somebody

who is on a pathway to Mars.

Thanks to radio telescopes like these,

strategically positioned around the globe,

travellers to Mars needn't worry about being isolated

from everyone back on Earth.

If you're one of them, you'll be able to communicate

with your loved ones every day, if you want,

waxing lyrical about the epic wonders you have seen.

These telescopes will be the sorting offices of the most spectacular postcards in the universe.

With a plan for how to get there,

and armed with everything we need to survive,

we can now start to explore some of the mysteries of Mars.

This is Orcus Patera crater.

Nearly 400km long, it dwarfs any features nearby.

No-one quite knows how this unusual teardrop crater was formed.

The latest in a long line of mysteries,

it would prove an intriguing stop on any Martian adventure.

Mars has a lot of craters, yet most of them are circular.

You can see these craters, 40 or 50km across,

they tend to be circular, but there are some that are not.

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?

Until we go there ourselves,

our best shot at answering that question

is to recreate the impact here on Earth

and Professor Peter Schultz has just the experiment.

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 going to try to recreate the Orucs 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 trying going to try that here by impacting into sand.

The target sits inside a large pressure-controlled impact chamber.

So, with the chamber, we can control the atmosphere conditions

and we have a projectile that will be launched

to go through this hole, this launch tube,

and is going to hit right here where this laser is hitting,

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, all it takes now is to fire the projectile.

JP, are you ready?

We're good. Ready.

Yeah, ready to go.

It's charged.

Lights are green.

Here we go.

Rolling.

Oh! Sweet.

5.53 kilometres per second.

Well done.

To see if Professor Schultz has recreated Orcus Patera,

he needs to analyse the footage.

And now we watch the evolution of the plume...

and you can see this vapour, this plasma.

This is 6,000 Kelvin.

This is really hot. It's like the surface of the sun.

In this perspective, all this brightness here is because of the projectile

that has sheared off at the moment of impact and is impacting this

aluminium plate that's lying down on the surface.

At the same time, the crater is beginning to form.

Right now, the crater looks like it's a gash.

It begins as a gash.

But, as it progresses,

it begins to be circular.

The sand shows how an oblique meteor strike throws material

downstream of the impact, just like in Orcus Patera.

But it's not the perfect Mars analogue.

The fluid, loose nature of sand

means the original impact crater shape is not preserved.

Professor Schultz must repeat the experiment with a tougher target -

an aluminium block.

JP, are you ready?

-Ready.

-Get it to reset.

Rolling.

Oh, good! We got it, we got it, we got it.

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

6.0 kilometres per second.

Well done, sir.

Oh!

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 has 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 her 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, maybe 30 million years.

So, when that happens, it will come in at an extremely low angle,

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

except it's not going to land so well.

It's going to collide and form a crater very similar to Orcus Patera.

Mars has two small 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's 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.

We can look at the San Andreas Fault, it's right there.

But to understand how old it is,

and understand what's on both sides of the Fault,

you've got to be there.

I think we need to be on Mars.

Standing on the rim of Orcus Patera,

I'd probably find the entire history of the solar system

spread across the surface in different places.

I wonder, could I pick up a rock that actually came from the object

that formed this enormous feature?

Could it be an ancient moon on Mars?

Could it be just another big, giant asteroid?

This is the advantage of being there.

You identify the rock, you make a decision, your choice.

You look, you study.

It's different when you actually hold the sample

and that is the next step.

For now, Orcus Patera remains a mystery,

but what a beautiful mystery it is.

Imagine standing atop the crater rim,

rising 1,800 metres above the surrounding plains,

looking into the depths of the crater almost 2.5km below.

What an incredible and enigmatic stop on your adventure across Mars.

Our technology has allowed us to map Mars in unprecedented detail.

Some of the landscapes we discovered look eerily like those on Earth,

while others are completely alien.

And there is no better place to explore these strange,

ever-changing, mysterious 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's southern polar cap.

One of the coldest places on the planet,

temperatures here can drop below minus 120 Celsius.

It's an icy destination for which 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.

I'm a planetary astronomer and a planetary scientist,

and I study both using telescopes and spacecraft around planets,

studying what they're made of and how they formed,

both in our solar system and outside.

I'm really interested in the South Pole of Mars

and how that can tell us more about Mars's 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 disc of the planet,

but their wonder is only truly revealed with images taken from orbit.

Over 400km wide and 3km thick,

the southern polar cap is a freezing vision of swirling white

on an otherwise rust-coloured 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 one of our recent snowfalls.

But on Mars, on the South Pole,

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

it actually snows carbon dioxide.

Often referred to as dry ice, during 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 you have this layer

of semi-translucent 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 metres, not much further, we think.

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 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 blows these materials,

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 any more, the fans go away.

And what's left in many of these areas

are these kind of dendritic-like, spiderlike features,

which have been informally dubbed spiders.

These erosion channels meet in the central pit,

resembling the body and long legs of a spider -

legs that can stretch for hundreds of metres

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

I'd be really excited to be able to walk around

and see what these spiders look like on the surface in the summer,

and maybe even tentatively kind of explore there in the spring and summer,

when these carbon dioxide jets break through the surface,

creating these brilliant bands that we see on the service.

Explorers lucky enough to be stood at the South Pole during a Martian

summer would gaze upon these alien spiderlike 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 assume.

Mars's icy poles provide some respite from the desert landscapes

that cover most of the planet.

And the more adventurous traveller,

they 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 that 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.

There would have been a mountain in the centre 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 so wetter than today.

And the water fell across the planet's surface as rain and snow.

You see, now it's raining on the crest of that crater rim, and look at that.

We've got rain forming on the crater rim and then gushing out

into the centre of Gale Crater and building up.

As it poured down into the crater,

this 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 what happens is all that

rushing water erodes into the landscape

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.

Surprisingly, though,

it's not the dried river beds but the towering Mount Sharp

that provided the definitive proof of Gale Crater's watery past.

So we think that the basal parts of Mount Sharp

are actually the deposits of erosion of that crater rim.

They're recording that water story,

water erosion and deposition within Gale Crater over here.

Deposits that were exposed when the Martian climate eventually dried up.

So this is Gale Crater, in a wet and warm period,

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.

So imagine my hand here is actually wind erosion over millions of years,

progressively carving out the moat,

leaving Mount Sharp, this 5km high mountain, in the centre,

and the eroded crater rim to the sides.

The next generation of explorers stepping foot inside the crater

will build on the body of evidence collected by Curiosity

and paint in even more detail about Mars's past.

And just as Curiosity has done,

travellers visiting Gale Crater and Mount Sharp

will be able to explore a breathtaking landscape.

They'll gaze upon a vast mountain,

where it appears to have burst from the base of an impact crater,

but, more than that, they'll peer into an ancient watery world,

a world that has long since been lost to the winds.

The rusty, ancient surface of Mars has enigmatic landscapes at every turn...

..from towering sculpted peaks to hidden underground caverns.

And if you're one of the first explorers,

you will need to study every detail.

Each landmark holds its own clues to Mars's mysteries...

..and there is no greater mystery than whether life exists beyond the Earth.

To stand a chance of finding it on Mars,

travellers will need to journey to a region of the planet

hitherto unexplored by landers or rovers.

Perched in the removed 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...

..a theory that Professor Charles Cockell believes is entirely viable.

I'm an astrobiologist,

which means that I study life in extreme environments on the Earth

and then I use that to try and understand

whether there might be habitable conditions or even life elsewhere.

Of all the questions astrobiology asks, probably its biggest one is -

is there life beyond the Earth?

This is one of the most profound questions

that's ever been asked by the human mind.

The first step in looking for life on Mars

is figuring out where to look.

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

and maybe it could do, even today, deep underground.

But about three and a half billion years ago,

that water froze up and the planet became what we know today -

pretty much a desert world.

Because of that, it was never able to sustain the sort of evolutionary

developments that you can see around you here.

We would probably, if we were looking for life on Mars,

be looking for something quite primitive

that was able perhaps to take hold

in that early period of Martian history.

So we need to look in places on Mars

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 are looking at ancient salt deposits.

In those salts, maybe we might try and look for signs of past life.

So, 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.

If we want to test the hypothesis that Mars was habitable,

maybe even hosted life,

it's to places like these that we need to go.

Any 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.

We go to extreme environments around the world and we collect samples,

and what we want to do is try and isolate the microbes

that live in those samples and study their ability to survive in extremes.

So here we've got some examples 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 sulphate

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

Finding living bacteria in places like this tells Charles 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 kilometre underground in a salt mine.

This is a sort of sample you might be able to find in Terra Sirenum if you dug down beneath the surface.

You can collect these samples and you can culture microbes and have a look at them under the microscope.

The question is, could these microbes also survive under the conditions on the 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.

I think the simplest thing to do is to collect samples.

If you could grow something from a sample taken from Mars

and just look at your microbes under a microscope,

it would probably look a bit like this.

Astrobiologists like Professor Cockell are building a case

that the salt plains on Mars are potentially habitable.

The inquisitive traveller 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 prove that life probably exists elsewhere in the universe, too.

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

Mars, the Red Planet.

A world similar to ours in so many ways, yet also totally alien.

A world waiting to be explored.

Many scientists believe that the first person to set foot on its surface is alive today.

Someone, somewhere,

looking up into the night sky and glimpsing the small, rusty planet

may one day make the journey there.

They may even discover the first alien life.

Perhaps it's someone watching this film.

Perhaps it's you.