Original subtitles

WILLIAM SHATNER: Massive asteroids

on a collision course with Earth,

deadly bursts of cosmic radiation

with the power to wipe out life as we know it,

and microscopic alien viruses that can invade our planet.

When we look up at the stars at night,

we see the peaceful, shining tapestry of the galaxy,

yet just out of sight

are cosmic dangers beyond our control,

each one able to end human civilization as we know it.

Can we prepare for the inevitable calamity

coming our way?

Or are we doomed to oblivion?

Well, that is what we'll try and find out.

♪ ♪

SHATNER: As this small industrial city in the Ural Mountains

begins its day,

a 66-foot-long asteroid suddenly streaks across the sky.

Within seconds of its arrival,

the giant rock abruptly explodes in the sky...

(car alarms wailing)

...18 and a half miles above the region...

...generating a superheated shock wave

that rips through the city.

DAVID J. THOLEN: When it entered the Earth's atmosphere,

this asteroid superheated the air

so rapidly that it created effectively a thunderclap,

or a sonic shock wave.

But this was so powerful that it shattered windows

throughout the city of Chelyabinsk.

1,600 people were injured by flying glass.

MICHAEL DENNIN: With Chelyabinsk,

we were pretty lucky 'cause it was in the atmosphere

that it really detonated.

But imagine if it had hit the surface,

this would've really caused huge amounts of damage.

SHATNER: Fortunately, no lives were lost

as a result of the airburst and shock wave

that created a blast radius over 60 miles wide.

The Chelyabinsk asteroid is a sobering reminder

that our planet is vulnerable to numerous dangers from space

that have the power to unleash incredible devastation

and obliterate life on Earth.

JASON WRIGHT: We think of Earth as a pretty safe place,

but there's actually quite a few things coming down

from outer space that might hurt life on Earth.

PAUL SUTTER: The Earth has suffered

innumerable cosmic catastrophes,

and this happens more commonly than you might think.

Any day now, a rock could come from outer space

and strike the Earth.

Any day now, a supernova could go off

and irradiate our atmosphere.

Any day now,

our Sun could blast off a coronal mass ejection

headed right in our direction.

So, even though we have it relatively safe,

any one of these dangers could strike at any moment.

SHATNER: The fact that we could suddenly be wiped out

in a cosmic cataclysm is profoundly unsettling.

But it also begs the question,

what is the most imminent threat to Earth's safety?

Well, if the explosion over Chelyabinsk

in 2013 is any indication,

the answer would seem to be killer asteroids.

WRIGHT: Asteroids are the leftovers of the formation

of all of the planets in the solar system.

When the Sun formed,

it had a disk of material around it

that formed lots of boulders and rocks.

Many of these came together to form the Earth,

Mars, Venus and even the cores of the giant planets,

but not all of the boulders and rocks got used up.

We know of over a million asteroids orbiting the Sun

that are in orbits

that sometimes come near the Earth.

And of those, there are several hundred

that are potentially the sorts of asteroids

that might hit the Earth one day.

SHATNER: Is a massive asteroid headed

for Earth at this very moment?

And if so, how catastrophic would it be

for life on our planet?

According to experts,

the answer can be found by examining a place

where such a devastating impact has happened before.

For many, the lush vegetation

and tropical climate of this region

makes it feel like paradise.

But when viewed from space,

the landscape tells a much different story.

Because if you look closely,

the faint outline of a 120-mile crater

can be seen stretching from the jungle

out into the Gulf of Mexico.

The crater is a scar left by a massive asteroid impact

that occurred 66 million years ago,

a disaster that is referred to as the Chicxulub Impact Event.

THOLEN: The Chicxulub asteroid was about ten kilometers in diameter.

It did produce a global catastrophe.

In fact, it wiped out an estimated 75%

of all species on the planet at that time.

It is believed to be responsible

for the extinction of the dinosaurs.

Because with that particular asteroid impact,

some of the finer materials,

the dust got injected up into the atmosphere,

where it can linger for months, if not years.

Now we've got dust

that's reflecting sunlight back out into space

rather than making it down to the ground.

You basically prevent plants from growing.

Once the plants die off, well, then the animals

that feed off the plants start dying off.

And the whole food chain gets disrupted.

That's one of the reasons why there would be

such massive loss of life

if an asteroid a kilometer or larger were to hit.

MICHIO KAKU: Because the object that hit the Yucatán of Mexico

wiped out the dinosaurs,

we want to know, could it happen again?

Is there an object out there in space with our name on it?

SHATNER: According to experts,

there are some 2,300 known asteroids

that are considered potentially hazardous.

Hopefully, we'll continue to dodge these galactic bullets,

but what if it's only a matter of time

before our luck runs out?

GRAHAM LAU: NASA's doing sky surveys

using telescopes and infrared and radar

and other ways to monitor

for these objects that are out there.

We have most of those identified and tracked.

But that's probably still only a small fraction

of what's really out there.

And if we didn't catch one of these things early enough,

that could really cause massive devastation

for life as we know it.

SHATNER: If another massive asteroid heads towards our planet,

are we simply doomed to extinction?

Or is there something we could do

to protect ourselves?

MISSION CONTROL: Three, two, one.

And liftoff.

SHATNER: At Vandenberg Space Force Base,

a Falcon 9 Heavy rocket blasts off,

carrying an experimental payload in space.

Known as the Double Asteroid Redirection Test-- or DART--

the spacecraft is bound for a tiny asteroid

named Dimorphos, located 6.8 million miles from Earth.

Its mission is to crash into the space rock at high speed

in an attempt to change its orbit.

LAU: The DART mission was

our very first attempt in space

to try out some method of asteroid deflection.

The idea was to see if we could redirect

an asteroid coming towards us,

to push it a little bit out of the way.

SHATNER: On September 26, 2022,

after ten long months of traveling through space,

DART finally arrived at Dimorphos

and successfully smashed into it at almost 15,000 miles per hour.

LAU: Hitting that asteroid was actually very difficult.

We had a spacecraft roughly the size of a school bus

that had to then hit a target 500 feet across.

Destroying such a target,

that's extremely difficult to do.

WRIGHT: NASA was hoping that all

of the momentum that it hit that asteroid with

would go into moving the asteroid out of the way,

and it was actually extremely successful,

much more than they thought.

And that's great news for protecting the Earth

because it means we don't have to hit them

as hard as we worried we might.

SHATNER: It's certainly a relief

that scientists have a plan in place

to help save us from giant killer asteroids.

But what about smaller rocks from space?

Could they also pose a threat to humanity?

Some scientists believe that tiny meteorites

are potentially just as lethal

because they could carry an alien virus

with deadly repercussions.

SHATNER: The danger Earth faces

from a massive, planet-killing asteroid

is both real and terrifying.

However, another chilling scenario

involving space rocks also exists.

Because at this very moment, Earth is being bombarded

with millions of micrometeorites.

And those seemingly harmless rocks

could be carrying the seeds of an extraterrestrial disease.

Every single day, material from space

constantly rains down onto the Earth,

somewhere around 100,000 pounds every day.

And we believe that it is possible for some sort of

alien viruses to hitch rides on micrometeoroids

and drift to the surface of our planet.

LAU: I think a lot of us in astrobiology,

we've been so excited for so long at possibly

finding definitive signs of alien life out there.

But one thing we don't talk about enough

is, what happens if there is a malicious pathogen

coming from space to our planet and infecting life

as we know it, or changing life as we know it?

SHATNER: Could an alien virus infect and perhaps destroy

life on Earth?

It sounds like a horrific scenario

out of a science fiction movie, and yet scientists claim

that the threat posed by an extraterrestrial plague

is very real.

There have been experiments in which microorganisms

have been flown to the International Space Station

and exposed to the hard vacuum and the radiation

and the temperature changes of deep space.

And many of those organisms survived.

So I think it is quite conceivable that material

raining down on the surface of the planet Earth

could carry biology in the form of viruses from

some other body in our solar system

or even from a distant star system.

SHATNER: Is there anything we can do to protect ourselves from

an extraterrestrial virus?

Perhaps a clue can be found by examining how humanity

has prepared for this threat before.

At Johnson Space Center, dozens of NASA scientists watch

with nervous anticipation

as the Apollo 11 Lunar Module descends onto the Moon.

But their concern is not only for a safe landing.

NASA is also extremely worried

that the astronauts may get infected

with alien microbes.

When Apollo 11 landed on the Moon,

there were still a lot of mysteries about

what they would actually find up there.

Because no one could be certain that there wasn't

some evil Moon plague up on the Moon that the astronauts

would bring back with them, the Apollo 11 crew was actually

quarantined for three weeks starting the moment

they closed the hatch after their Moon walk.

Being quarantined was easy during the return trip home

because there was nowhere to go.

But once they were back on Earth, this became a very

delicate dance of transporting them from the ocean

to Houston without exposing them to anything

or exposing what they might have to the world.

SHATNER: The Apollo 11 astronauts spent a total of

21 days in isolation after returning to Earth.

Fortunately, they emerged with a clean bill of health.

But they weren't the only ones NASA subjected

to a strict quarantine.

Nearly 50 pounds of Moon rocks were collected on the mission,

and this material was also rigorously tested

for alien pathogens.

Scientists did a bunch of experiments to make sure

that there was nothing alive

and nothing potentially disastrous

involved in those samples.

They actually injected crushed up rock into insects and mice

to make sure that if there was anything ingested

or something that entered a human's bloodstream,

it wouldn't have an adverse effect.

In the end, NASA scientists realized that there

was nothing nefarious up on the Moon.

There was no Moon plague that the astronauts were going

to bring back with them.

And everything was safe coming home.

SHATNER: It's comforting to know that NASA has procedures

in place to quarantine a virus that astronauts could

potentially bring back from space.

But what happens if our safety measures fail?

How would we handle the outbreak of an alien disease?

If an individual gets infected by an extraterrestrial

microorganism or virus, the next steps would be very critical.

That person would need to be isolated right away.

And hopefully that person is not exposed to the general public

because the unknown component of what is causing

the outbreak would be very difficult to handle right away.

Especially if it's not measurable by our science.

At that point, that's when the military would come in

to understand the nature of the outbreak, how fast it is,

and then would there be a way to contain it?

We haven't really dealt with this yet because it's

such a hypothetical case.

But are we ready for that worst-case scenario?

I'm not really sure we are.

SHATNER: Deadly plagues have ravaged our population

throughout human history.

So far, we've managed to survive all of the lethal outbreaks.

But if an alien disease ever spread across

our planet, would we be so lucky?

All life on Earth shares

some basic biochemistry in common.

We all use the same set of amino acids, we all use DNA,

we all use proteins.

But alien life may have a completely different set

of chemical rules that it uses to govern itself.

So an alien pathogen may try to get under our skin,

literally, and simply nothing happens because

we're playing by different rules.

On the other hand, if an alien pathogen finds

itself on the Earth, it could very quickly adapt

and evolve to our local environment

and hijack our DNA replication mechanisms.

Because it's-it's just how life works.

Life finds a way.

Could a virus from another planet invade Earth

and our bodies, making us its new host?

It's a distinct possibility.

But experts warn that we face an even graver danger.

One that's hit our planet in the past

and can strike again.

A blanket of deadly radiation

that's millions of years old.

SHATNER: When we gaze up at the stars, it's easy to forget

that the picturesque dots of light we see are actually...

massive balls of fire floating in space,

which burn at unimaginably high temperatures,

just like our own Sun.

One day, some of these stars will eventually die

in a giant explosion so bright,

it can momentarily outshine the entire galaxy.

It's a cataclysm that scientists refer to

as a supernova.

A supernova happens when

the nuclear fusion powering the star

is no longer strong enough to prevent gravity

from causing a massive collapse of all the matter in the star.

And the amount of energy released is incredibly intense

and happens in a very short time.

If you have a star somewhere around at least eight

to ten times more massive than our Sun,

when it dies,

the entire star rushes inward and bounces off of itself,

releasing a tremendous amount of energy in

one spectacular burst.

And so, when the largest stars in the universe die,

all that material from the star...

...swirls around and launches these beams

of radiation that appear to us as a gamma ray burst.

And gamma ray bursts represent some of the most

powerful explosions that can happen in the universe.

SHATNER: Could gamma rays that originate light years away

actually pose a threat to life here on Earth?

According to experts, the answer is yes.

Because unlike the normal types of solar radiation

that we experience every day,

gamma rays are often described as death beams from outer space.

Gamma rays are the most powerful form of light,

or electromagnetic radiation.

They're more powerful than ultraviolet light,

they're more powerful than X-rays.

They're all the way at the top

of the scale when it comes to energy light can have.

PYLE: Gamma rays are off the scale

in terms of dangerous radiation.

Even short exposure to gamma rays

can scramble your DNA.

Extended exposure to gamma rays are the absolute

top of the scale, and over time will basically liquefy you.

A gamma ray burst could easily destroy

not just one star but many stars in the process.

We're talking about the energy release that's comparable

to the Big Bang itself, the creation of the universe.

If a gamma ray burst were to happen in our vicinity,

not only would it affect our solar system,

it would probably wipe out

all the neighboring solar systems as well.

And so this is a threat that could affect

a good sector of the Milky Way galaxy itself.

SHATNER: While the hypothetical threat of

a dying star destroying our solar system

is terrifying to consider,

is there any evidence to suggest that

our planet has been hit by gamma rays before?

Curiously, the answer lies at the bottom of the ocean.

In the scientific journal Physical Review Letters,

a group of German physicists announce a remarkable discovery.

By analyzing deep-sea mineral deposits,

they are able to detect a rare iron isotope

not typically found on Earth.

Known as iron-60,

it is formed only in the explosion

of the most powerful supernovas,

and its presence on Earth proves that our planet

was once struck by gamma rays.

SUTTER: Not all gamma ray bursts

have happened billions of light-years away.

Some have happened much closer to home.

In fact, astronomers estimate that

about 2.6 million years ago,

there was a significant supernova burst

that may have led to what we call

the Pleistocene megafauna extinction,

which eliminated something like 30% of

all large animals living in the ocean at the time.

DENNIN: The best theory we have for the cause of

this gamma ray burst about 2.6 million years ago

is the death of a massive star that was 160 light-years away.

This sounds far away, but in cosmic scales,

it's actually quite close,

so that kind of gives you a sense of

the scale of this explosion.

SHATNER: When a gamma ray burst

wiped out a third of life in the oceans

2.6 million years ago,

mankind's early ancestors

were just beginning to learn how to use tools.

Scientists aren't sure how our species was able to survive,

but the event does raise an important question.

Are scientists aware of any star that is about to go supernova?

Surprisingly, there is one

that most people are already familiar with,

whether they know it or not.

One of the most famous constellations in the night sky

is known as Orion.

Orion consists of seven primary stars

in the shape of a mythical hunter,

but perhaps the most recognizable

is the reddish-orange star that forms its right shoulder.

It is a supergiant star named

Betelgeuse.

One of the stars in our Milky Way that's

a good candidate for going supernova

kind of soon is Betelgeuse.

The key for a star to go supernova

is when the nuclear fusion finally gives out

and isn't able to support the gravity.

And that's going to show up in various signatures

as you measure the light coming from the star.

And that's the type of behavior we're seeing with Betelgeuse.

SUTTER: Betelgeuse is about to go supernova any day now.

In fact,

because it's hundreds of light-years away,

it may have already gone supernova

and we're simply not gonna find out about it

until the light reaches us.

And then you have to deal with

the large-scale ecological collapse

that will follow it.

SHATNER: If Betelgeuse is, in fact, on the verge of going supernova,

then is there anything we can do

to protect ourselves from the deadly gamma rays

it would unleash?

SUTTER: The honest truth is

if a gamma ray burst were to strike us

or were to be headed in our direction,

there's nothing we can really do.

We wouldn't know it until it's too late.

Gamma ray bursts may be the most powerful explosions

in the known universe.

However, some scientists are concerned about a threat

that's much closer to home.

One where our oceans boil,

the atmosphere blows away,

and the Earth itself...

...dies.

SHATNER: Since the dawn of the space age,

Earth has often been referred to as The Blue Marble

because, when viewed from outer space,

it's clear that 70% of our planet is covered by water.

However, what cannot be seen with the naked eye

is that Earth is surrounded

by a magnetic field,

which is an invisible energy shield

that blocks damaging rays from the sun.

Without this protection,

all of our planet's life-sustaining water

would be in jeopardy.

Fortunately for us, and all life on Earth,

our magnetic field protects

our atmosphere from the sun's radiation.

But, more importantly for the Earth,

it keeps the liquid water on Earth's surface

instead of escaping to space.

The Earth's magnetic field

is our force field

that protects our planet

from the solar wind,

which is a stream of charged particles

constantly coming out of the sun.

KAKU: Without our magnetic field,

the solar wind then hits the planet,

and temperatures start heating up too much.

And, at that point, water boils away

and drifts into outer space.

So, it's a question of life and death.

SHATNER: The magnetic field has shielded Earth's water

for billions of years.

And while scientists have imagined

what would happen if we lost our protection,

is it really possible for

a planet's magnetic field to disappear?

According to experts, the answer is "yes,"

and evidence of this doomsday scenario

can be found on the dry and dusty surface

of Mars.

SUTTER: Mars had liquid water and a magnetic field

at the exact same time that

the Earth did billions of years ago.

And at the exact same time that

life was first arising on our planet,

and the conditions on Mars,

as far as we can tell, were exactly the same.

So this means Mars may have also been

a home for life.

Then the magnetic field of Mars shut down.

Without its magnetic field

that it had when it was very young,

Mars, with its low gravity,

was simply not able to hold on to its liquid surface water.

And so, Mars lost its oceans

and all of its water, which is why

today, it's a dry desert.

BEN McGEE: The Martian environment right now

is completely inhospitable.

It lets radiation right on in down to the surface.

It's ice cold.

I mean, these are extremes the likes of which

no human being,

or life as we know it, could survive.

SHATNER: If Mars once had a magnetic field and then lost it,

as scientists believe,

it begs the question

how did this occur?

And, more importantly,

could the same calamity ever happen

on Earth?

McGEE: The magnetic field

for a planet, as we understand it today,

is all related to a molten core.

Any planet can have a magnetic field if it has

a hot core and it's rotating.

It works like an electromagnet.

And that's why Earth has one.

Mars doesn't have a magnetic field today

because its core went cold.

SHANNON CURRY: One of the main theories on

why the magnetic field of Mars

effectively died was that

its core just stopped churning.

And we really don't understand enough about

the interior of Mars to know what the dynamics there were.

In fact, we barely understand it on Earth.

But Earth's dynamo could, in fact, stop.

WRIGHT: The Earth has changed a lot over its 4.5 billion year history.

We know today, though,

that as planets get older, they get cooler,

and the mechanisms that generate

their magnetic fields in their cores get weaker.

And over time, that, in principle,

could ultimately lead to the loss of Earth's water.

SHATNER: Could our planet become a barren,

lifeless world like Mars one day?

It's a disturbing possibility,

and what's even more terrifying, is that some experts think

it may already be happening.

Scientists from NASA make an unsettling announcement.

Using data collected by satellites,

they discovered a "dent" in the magnetic field

where it is actually

getting weaker.

CURRY: Earth is actually losing some of its

global magnetic field.

What's less clear is how much and how fast

that erosion is happening.

There are leading theories on why,

but the loss of Earth's magnetic field

would seriously impact life as we know it.

There would be huge shifts in radiation,

and, certainly, that can seriously disrupt

the entire balance of this system.

We would slowly lose our oceans,

and as things dried up,

it would become much more barren,

and possibly lifeless.

It would certainly have effects on human life.

KAKU: In the coming centuries, it'll probably go down to zero,

our magnetic field,

so we have to make sure that

the magnetic field of the Earth is preserved

so that we don't have an evaporation of the atmosphere

and the boiling of the oceans

like what happened on Mars.

We're talking about a tremendous danger

to the planet Earth.

It's unsettling to think that our bright blue Earth

could become as desolate and lifeless as the Red Planet.

But even if we avoid that fate,

astronomers fear that right now

we might be on a collision course

of galactic proportions.

SHATNER: A team of astronomers with the Canada-France

Brown Dwarf Survey project announce a remarkable discovery.

Using infrared telescopes, they are able to locate

a distant world 100 light-years from Earth.

But unlike every other planet

previously identified by scientists,

this one isn't orbiting around a star.

Instead, it is drifting alone through our galaxy.

It is the first-ever observation of a mysterious object

known as a rogue planet.

A rogue planet is a planet that is

not attached to any star.

It simply floats free throughout a galaxy.

♪ ♪

We think rogue planets happen

through the formation of solar systems.

When solar systems form, it's a chaotic mess

of planets that are crashing into each other

and interacting with each other,

and they can eject some of those planets

and send them flying out throughout the galaxy.

But on top of that,

they can have all sorts of wild and crazy motion

because they were ejected from solar systems

in all sorts of wild and crazy directions.

And so there could be a rogue planet headed at Earth.

SUTTER: It sounds preposterous to most people,

the idea that another planet could enter the solar system

and be the end of us.

But that doesn't mean that one can't come

hurtling out of the darkness.

And if one of them happened to come in

on a collision course with Earth,

that could be it.

SHATNER: Could a rogue planet actually drift

into our solar system and collide with Earth?

It may sound far-fetched,

but experts believe the impact would unleash

apocalyptic levels of destruction.

The result of us getting hit with another planet

would hypothetically be devastating.

Based on our best estimations,

if you actually had a titanic impact,

you're talking about a complete global reset for both worlds,

the likes of which no human being

or life as we know it could survive.

SHATNER: But is the threat of a collision with a rogue planet

an actual concern,

or are experts simply fearmongering?

As it turns out, scientists may be

on to something because, in fact,

the Earth has been hit by another planet before.

LAU: Earth has certainly gone through many periods

of bombardment of objects from space.

We had this early impact event

on our own planet,

roughly 100 million years after it formed,

when a Mars-size world that we call Theia

crashed into the Earth.

And in the process, it blew off a bunch of material

from our surface and made the moon.

SHATNER: According to experts, the impact with Theia

left the Earth in a fiery, molten state

for millions of years, inhospitable to all life.

But could it happen again?

Fortunately, experts do not currently believe

that there is a rogue planet on a collision course with Earth.

However, even the mere presence of a rogue planet

in our vicinity could have catastrophic implications.

Something like the mass of the Earth

passing through the inner solar system is--

we're barely gonna notice.

But something the mass of, say, Jupiter

passing through the inner solar system

will destabilize all of our orbits.

It might send our planets crashing into each other.

It will wreak havoc through pure gravity alone.

SHATNER: The notion that a rogue planet

simply passing through our solar system

could cause so much chaos is deeply unnerving.

And unlike a direct collision, there is a distinct possibility

that a rogue planet might wander into our neighborhood.

Because the sheer number of rogue planets

currently roaming our galaxy is mind-boggling.

WRIGHT: These rogue planets tend to be very difficult to find.

They're not orbiting a star, so they're very dark.

So it can be very tricky to figure out

how many of them there might be out there.

But we think that there are probably a few times

as many rogue planets as there are stars in the galaxy.

So that means there could be a trillion rogue planets

throughout the Milky Way.

SHATNER: A trillion rogue planets in our galaxy alone?

It's a disturbing notion.

But what's even more unsettling is that Earth itself

might one day become a rogue planet.

SUTTER: A rogue planet passing through the solar system

might destabilize Earth's orbit to such a degree

that we become ejected from our own solar system

and become a rogue planet.

This would be a game changer for humanity.

Because the vast majority of energy we receive

on the surface of our planet comes from the Sun,

the source of light, heat and warmth

and ultimately of life on the Earth.

And that would be cut off from us.

SHATNER: Could a rogue planet send the Earth careening out

into the cold depths of the Milky Way?

Perhaps, but many experts believe

the true threat to Earth isn't a rogue planet

but a different type of visitor

to our solar system

in the form of extraterrestrial invaders.

We officially inaugurate the newest branch

of our military.

This is a very big and important moment.

It's called the Space Force.

SHATNER: President Donald Trump signs

the National Defense Authorization Act,

creating the U.S. Space Force.

According to its official mission,

the Space Force is intended

to protect the United States' national interests

in outer space,

but some have wondered whether it may also have

a secret objective.

Could the Space Force have been created

to protect Earth from an alien invasion?

The government has a track record

of saying as little as possible about UFOs.

But there is an argument

that extraterrestrials may take the view

that it is logical to eliminate

any potential threat to their own existence,

and emerging civilizations like humanity

might be that threat.

So, there's a great logic

that governments should have a range of contingency plans

because this is going to be hugely impactful.

SHATNER: The idea of aliens invading Earth

has been a staple of pop culture since the early 20th century.

But is there any evidence

that the Space Force could actually mount

a successful defense against an extraterrestrial attack?

The U.S. Space Force created their own military organization.

And just like the Army has brigades,

the Air Force has wings,

the Space Force came up with these deltas.

And there's several different deltas,

with Delta 9 being the one that's been charged

with orbital warfare.

So actually engaging in warfare in orbit.

Delta 9 is focused exclusively on what we might do

in the event of something hostile

in space, orbital combat, essentially.

So, if something extraterrestrial

actually came into our airspace,

they have a detection system and an intercept system

that launches very fast

and physically smashes something out of the sky.

Right now, we have 44 interceptors.

So, in a way, we're prepared

for someone to try and kick down our door.

SHATNER: It's fascinating to know

that the U.S. military has systems in place

that could be used in the event of

an orbital invasion by aliens.

But would our current defense systems have

any hope of overcoming advanced alien technology?

TRIMBLE: The U.S. military has a pretty vast and diverse arsenal.

But when you're talking about alien spacecraft technology,

it's impossible to know if we have any weapons

available to us that would do us any good

in that kind of situation.

POPE: Civilizations with, maybe,

millions of years head start on us

probably have technology that could crack this planet open

like a nut if they wanted to.

This is an existential threat.

SHATNER: Is humanity able to defend itself

in the event of an extraterrestrial incursion?

Or are we doomed?

Let's hope we never find out.

But the fact is that an alien invasion

is just one of many dangers from space

that-- while they may seem remote--

are very real threats to Earth's existence.

We believe that the Earth is calm,

everything's okay.

Stuff happens in the universe, but it's far away.

But we have been hit by giant rocks

going tens of thousands of miles per hour.

We have been slammed by supernova.

That is going to happen to the Earth

again and again and again.

DENNIN: When you think about what would happen

that could wipe out the human race,

it does feel like we're always on the edge.

But I feel like

we keep moving to better and better understanding,

and we're gonna better and better protected.

At least if there is a mass extinction

and some things survive, I hope we're one of them.

It appears that the universe is far more chaotic

than we tend to think.

I mean, just look at all the planets around us.

They've been devastated by numerous disasters.

From killer asteroids and rogue planets

to deadly viruses and lethal radiation,

so far Earth has survived these dangers from space,

but will our luck run out?

For now, the answer remains...

unexplained.

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