Original subtitles

A host of factors have enabled

the emergence of life on our beautiful blue world.

None of which exist on our moon.

Indeed, to describe the lunar environment

as inhospitable would be an understatement.

So what will it take for us to live there?

(dramatic music)

Planet Earth is astonishingly well suited

to supporting life.

It is large enough to maintain an atmosphere,

which, in turn, means that it can support

liquid water on it's surface.

And thanks to that atmosphere, global temperatures

have never exceeded 60 degrees celsius.

Nor have they ever fallen below minus 90 degrees celsius.

The annual average is a comfy 15 degrees celsius.

Fortunately, the Earth has managed

to hang on to that atmosphere for over 3.8 billion years.

Thanks to it's swirling molten iron core.

That turns it into one huge magnet,

generating a massive magnetic field

that extends far out into space.

Without that magnetic field, the Earth's atmosphere

would have been stripped away long ago.

That, in turn, would have meant that

the surface of the Earth would have been exposed

to the full force of the sun's

blistering ultraviolet radiation.

And a constant stream of charged particles,

known as the solar wind.

The emergence of life as we know it

would have been impossible.

But our little sister moon enjoys

none of the benefits of earth.

It has no atmosphere.

It has almost no magnetic field.

And it's tiny.

In short, the moon is about as inhospitable

as it's possible to be.

On the moon, the sky is always jet black,

both by day and by night.

The lunar surface is subject to

dramatic extremes of temperature.

By day the temperature in direct sunlight

can reach over 120 degrees celsius.

By night the temperature can drop

to a distinctly frosty minus 153 celsius.

Even the concepts of day and night

are different on the moon.

A lunar day, and a lunar night, are both

a little over 14 and a half earth days long.

And for reasons that have to do with

the interaction of the earth's and the moon's

uneven gravity fields, that is almost

the same length of time that it takes

for the moon to orbit the earth.

They are locked together, which is why

we only ever see this, the near side of the moon,

and we never see the far side.

This was important when planning the Apollo missions.

The reason why Apollo missions were so short

was because they landed in the sunlight

and they took off while the sun was still there.

Should they have stayed past 14 days into the night time,

the temperatures plummet drastically.

On earth, you know, the air around us allows us

to cool machinery, whereas in space you don't have that.

So now I'm designing hardware that may have to operate

under conditions that would make the Arctic

look like a summer day.

And then turn around and have that

maybe operate in the sunlight,

where you're now at 100 degrees Fahrenheit,

during lunar daytime.

But the earth's atmosphere doesn't just

help to regulate temperatures at ground level,

it also protects us from the estimated 200 tons

of interplanetary dust and rocks

that plow into it's upper layers every day.

Fortunately most of these objects are very small.

And because of their extremely high speed,

they burn up in the atmosphere

long before they reach the ground.

It's a very different story on the moon.

With no atmosphere to slow them down,

meteorites of all shapes and sizes

are smashing into the lunar surface every day,

and have been doing so for 4.5 billion years.

The scars of these impacts are plain to see

in any image of the moon's face.

But look more closely, and the reality

becomes even more worrying.

Imagine taking a glass and smashing it.

You don't get nice rounded pieces.

You get these shards with very jagged edges.

And that's what the soil, or lunar regolith

is like on the moon.

It's extremely abrasive.

Also, it's been pummeled for millions of years

through asteroids and such.

So these small abrasive particles can

get into space suits and moving machinery and such,

and cause a lot of damage.

There's been anecdotal stories about

the Apollo astronauts' suits, the joints,

being highly abraded, such that if the Apollo missions

had actually gone more than three days,

that it might have been very difficult

for the suits to survive in that environment.

Mechanically it's very difficult to deal with.

It's very abrasive.

It's all broken up in small angular pieces.

The glass is very sharp, they have sharp little edges.

And that can cause moving parts to stop.

You can get silicosis of the lungs,

there's all kinds of problems you could have with that.

Currently, one solution to the problem

is to never let the dust get inside

the living quarters or the vehicles.

On this lunar rover, the space suits

are fixed to the shell of the cabin in such a way

that the astronaut enters and exits

their suit from the rear.

The backpack is, in effect, also the access hatch

into and out of the interior.

The suit, and more importantly, the dust on it,

never enters the cabin.

But not all of the hazards of lunar living

can be mitigated as simply.

The lack of an atmosphere, combined

with the moon's almost nonexistent magnetic field,

means that the lunar surface is also

bombarded with high energy particles

coming from all directions.

It's called cosmic background radiation.

These come from deep space.

You can't stop them.

They're gonna penetrate almost anything.

Right now the only way to deal with them

is to accept that hit, and hope

that you don't get a really bad hit from one.

A more difficult problem, but one that

you can deal with, are solar particle events.

These are the coronal mass ejections, CMEs,

where you have the sun throws out huge quantities

of highly energetic charged particles

that travel through space and will kill ya.

Effectively they're extremely high radiation.

The earth's magnetic field and atmosphere

shield humans from that.

But in space that's not there, so the radiation

from both our own sun as well as

this cosmic background radiation,

are significantly challenging aspects of designing hardware.

But, there's one potential health hazard

that can never be overcome.

Compared to earth, the moon is tiny.

It's diameter is only 27 percent of earth's.

It would fit neatly into the North Atlantic Basin.

And it's mass is just a little over one percent of earth's.

All of which leads to the fact that

the pull of gravity on the moon

is just under 17 percent of the gravity

on earth, about a sixth.

To date, 12 humans, all of them Apollo astronauts,

have spent an accumulated total

of just 80 hours on the moon's surface.

Long enough to collect some rocks,

drive around a bit in the world's most expensive car,

and plant a few flags.

But not long enough to assess the biological consequences

of living and working in one sixth g.

It's already clear that microgravity, or zero g,

takes a heavy toll on even short term visitors

to the space station.

From bone loss to impaired vision,

from red blood cell loss, to cardiovascular changes,

from fluid redistribution, to changes in coordination,

these are just a few of the physiological degradations

that astronauts have to endure, and try to counteract.

We know that there are physiological deterioration

in microgravity, and they have to

adopt countermeasures for that.

What we don't know is how the human body

responds to long periods of time

in one sixth gravity of the moon.

And that's a big question.

It may turn out to be

the biggest question of them all.

And it won't only apply to the moon.

Although bigger than the moon, gravity on Mars

is still only one third of earth's.

And no one yet knows whether future colonists

will be able to have children

in the fractional gravity of the moon or Mars.

What is known, is that during

the first few hours and days of development,

most animal embryos, including humans,

are exquisitely sensitive to the force of gravity.

But for the billions of years

that life has been evolving here on earth,

that gravity has been constant.

The future of mankind in space may depend

on whether our human biology will permit us

to survive, thrive, and colonize worlds

that are very different from our own.