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 on board 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,